Energy source

References

1-Steam plant operation by Everett B Woodruf et al

2-HANDBOOK OF ENERGY ENGINEERING by Albert Thumann et al

3- RENEWABLE ENERGY A First Course by Robert Ehrlich

4-Energy source by B Viswanathan 2006

1st lecture

Energy is the property that must be transferred to an object in order to perform work on or to heat the object Energy is a conserved quantity the law of conservation of energy states that energy can be converted in form but not treated or destroyed The SI unit of energy is the joule which is the energy transferred to an object by the work of moving it a distance of 1 metre against a force of 1 newton

WHAT ARE THE UNITS OF ENERGY

The fact that energy exists in many forms is part of the reason why there are so many different units for this quantitymdashfor example calories and British thermal units (BTUs) are typically used for heat Joules ergs and foot-pounds for mechanical energy kilowatt-hours for electrical energy

and million electronVolts (MeV) for nuclear energy However since all these units describe the same fundamental entity there must be conversion factors relating them all To make matters more even confusing there are a whole host of separate units for the quantity power which refers to the rate at which energy is produced or consumed ie

1

Example 1

Suppose during a test of a nuclear reactor its power level is ramped up from zero to its rated power of 1000 MW over a 2 h period and then after running at full

2

power for 6 h it is ramped back down to zero over a 2 h period Calculate the total energy generated by the reactor during those 10 h

Solution

We shall assume here that during the time which the power is ramped up and down it varies linearly so that the power the reactor generates varies accordingly during the 10 h test as shown in Figure 12 Based on Equation 11 and the definition of the integral as the area under the powerndashtime curve the energy must equal the area of the trapezoid in Figure 12 or 8000 MWh (Table 12)

Table 12 Some Common Prefixes Used to Designate

Various Powers of 10 Terra (T) 1012

Giga (G) 10+9

Mega (M) 10+6

Kilo (k) 10+3

Milli (m) 10minus3

Micro (μ) 10minus6

3

Nano (n) 10minus9

Pico (p) 10minus12

Example 2

Example 1-2 A portable electric generator that is powered by diesel fuel produces 7 kWh of electricity during a single period of operation (A) What is the equivalent amount of energy measured in MJ (B) Suppose the fuel consumed had an energy content of 110 MJ If the device were 100 efficient how much electricity would it produce in wh

Solution

(A) 7 kWh times 36 MJkWh = 252 MJ

(B) 110 MJ36 MJkWh = 306 kWh

WHAT IS AN ENERGY SOURCE

Some energy sources are either stores (repositories) of energy such as coal oil or uranium typically chemical or nuclear that can be liberated for useful purposes Other energy (second source) sources are flows of energy through the natural environment that are present in varying degrees at particular times and places An example is wind or solar energy Consider the question of electricitymdashis it an energy source or not Electricity does exist in the natural environment in the extreme form of lightning and therefore it can be considered to fall into the second category In fact lightning lightning strike could be captured and stored (in a capacitor) and then later released for useful purposes Anyone watching a storm is likely to marvel at the awesome power of a lightning bolt which is indeed prodigiousmdash typically about 1 TW (1012 W) This amount is equal to the power output of a thousand 1000 MW nuclear reactorsmdashmore than exists in the

4

entire world Such a comparison may prompt the thought Great Why not harness lightning as an energy source The problem is not figuring out how to capture the lightning but rather that while the power is very high the energy lightning contains is quite small since a lightning bolt lasts such a short timemdasharound 30 μs = 3 times10minus5s so by Equation 11 the energy contained is around 1012 times 3 times10minus5 = 3 times107 J = 30MJ Thirty million joules may sound impressive but suppose we designed a ldquolightning catcherrdquo that managed to capture say 10 of this energy It would only be sufficient to light a 100 W light bulb for a time t = Ep = 3 times106 J100W = 3000 s which is just under an hourmdashhardly a useful energy source considering the likely expense involved What about electricity that humans createmdashcan it be thought of as an energy source Hardly Any electricity that we create requires energy input of an amount that is greater than that of the electricity itself since some energy will always be lost to the environment as heat Thus human-created electricity whether it be from batteries generators or solar panels is not an energy source itself but merely the product of whatever energy source that created it In the case of a generator it would be whatever gave rise to the mechanical energy forcing it to turn while in the case of a solar panel it would be the energy in the sunlight incident on the panel In order for an energy resource to be reliable it must first of all deliver the service that the consumer expects Secondly it must be available in the quantity desired when the consumer wishes to consume it (whether this is electricity from a wall outlet or gasoline dispensed from a filling station) Lastly the resource must be available at a price that is economically affordable

WHAT EXACTLY IS THE WORLDrsquoS ENERGY PROBLEM

1-All sources of energy have some environmental impact but as you

are aware the impacts of different sources vary considerably

2-The energy sources people worry the most about are fossil fuels (coal

oil and gas) as well as nuclear while the renewable (ldquogreenrdquo) energy

5

sources are considered much more benignmdasheven though they too have

some harmful impacts

3-Moreover the environmental impact of fossil

fuel and nuclear energy usage has gotten worse over time as the

human population has grown and the energy usage per capita has

also grownmdashan inevitable consequence of the rise in living standards

worldwide

Problems

1-How many kWh would a 1000 MW nuclear power plant generate in a

year

2-Consider a nuclear power plant whose power level is ramped up from

zero to a maximum 1000 MW and then back down to zero over a 10 h

period of time Assume that the power level varies as a quadratic function

of time during those 10 h Write an expression for the power as a

function of time and then find the total energy generated by the plant

during the 10 h period

3-Compare the direct costs to the consumer of using a succession of ten

100-W incandescent light bulbs with an efficiency to visible light of

5 a lifetime of 1000 h and a price of 50 cents with one compact

6

fluorescent lamp giving the same illumination at 22 efficiency a

lifetime of 10000 h and a price of $3 Assume a price of electricity

of 10 cents per kWh

2nd lecture

WHY HAS RENEWABLE ENERGY AND CONSERVATION BEEN NEGLECTED UNTIL FAIRLY RECENTLY

There are many reasons aside from simple inertia why moving away from fossil fuels and toward renewable energy has and will continue to be a challenge First the awareness of the environmental problems associated with fossil fuels has come very gradually and views on the seriousness of the threat posed by climate change vary considerably Moreover in times of economic uncertainty long-term environmental issues can easily take a backseat to more immediate concerns especially for homeowners

Second compared to fossil fuels there are problems with renewable sources which may be very dispersed intermittent and expensivemdash although the cost differential varies widely and often fails to take into account what economists refer to as ldquoexternalitiesrdquo ie costs incurred by society as a whole or the environment The intermittency poses special problems if the renewable source is used to generate electricity at large central power plants connected to the grid One can cope with this problem using various energy storage methods and upgrades to the electric power grid but of course both have costs see table 14

7

Example 2 Which Solar Panels Are Superior

Suppose that ten type A solar panels produced enough power for your electricity

needs had a lifetime of 30 years cost only $1000 but they had an efficiency of only 5 Five type B panels cost $5000 but they had an efficiency of 10 and lasted only 15 not 30 years Which panels should you buy

Solution

Obviously the more efficient panels would take up only half the area on your roof than the type A panels but who cares if they both met your needs The cost over a 30 year period would be $1000 for the type A panels but $10000 for the more efficient type B panels that produced the same amount of power (since they last

8

only half as long) so clearly you would opt for the less efficient choice in this case As a general rule as long as the fuel is free and there are no differences in labor or maintenance costs your primary consideration would almost always be based on cost per unit energy generated over some fixed period of timemdashusually the lifetime of the longer-lived alternative

Example 3 How the Usage of Wind Power to Offset Coal-Fired Plants Can Generate More Emissions Not Less

Suppose that a certain fraction of the power produced by a 500 MW coal

plant is offset by wind power Assume that when the coal plant runs at its

constant rated power it has an efficiency of 35 but that when it needs

to be ramped up and down to compensate for the wind power variations

its efficiency is reduced by according to e = 035 minus 000001p2 where p is

the amount of wind power Find the percentage increase in emissions that

results when 90 MW of the 500 MW is generated by wind power instead

of coal

Solution

In order to generate the full 500 MW by itself the coal plant requires 500035 = 1429 MW of heat flow from the coal If the wind power is 90 MW the efficiency of the coal plant is reduced to e = 035 minus 000001(90)2 = 0269 and the heat flow required to generate (500 minus 90) = 410 MW is therefore 410(0269) = 1524 MW The percentage increase in emissions is the same as the percentage increase in the heat flow to the coal plant ie 67

9

Problem 1 Using the data in Example 3 find the amount of wind power that could be used with a 500 MW coal-fired plant that would result in the least

amount of emissions

Fossil Fuels

Most fossil fuels which include coal oil and natural gas were formed from the remains of ancient life over the course of tens to hundreds of millions of yearsmdashhence the adjective fossil Today fossil fuels account for totally 85 of the worldrsquos primary energy usage with nuclear and hydropower comprising 8 and 3 and the renewable sources of geothermal solar tidal wind and wood waste amounting to a bit over 1 collectively An obvious question is what has made fossil fuels so attractive as an energy source in the past as well as today and why is it so difficult to move away from them despite the mounting evidence of the environmental problems they pose The answer is For example coal oil and gas have at least 200 times the energy per kilogram that is stored in a lead acid car battery Fossil fuels represent highly concentrated stores of energy compared to the much more dilute concentrations typical of renewablecheaply collected stored shipped and used where and when desired than most renewable energy sources

COAL

Composition of Coal Coal is a combustible sedimentary rock It differs from other kinds of rocks which are generally made of minerals and hence inorganic by definition Coal however is mostly carbon made

10

primarily from plant material and is therefore organic While carbon may be its primary component it does contain minor amounts of hydrocarbons like methane and inorganic mineral material that are considered impurities Coal does not have a specific chemical composition because the precise mixture of sulfur oxygen hydrogen nitrogen and other elements comprising it varies according to the particular rank or grade of coal and even within a grade For example for anthracite the highest and hardest rank of coal its composition includes 0ndash375 hydrogen 0ndash25 oxygen and up to around 16 sulfur Although the number of coal ranks depends on the classification system one system that is widely used is based on the four grades listed in Table 21

Coal is generally cheaper than oil whereas natural gas is more expensive The difference in price reflects the different costs of recovery storage and transport Nuclear fuel refined for use in nuclear electric power plants is less expensive than fossil fuels per unit of heating value

The energy believed to be present in the worldrsquos coal supply dwarfs all

other fossil fuels combined and it has been estimated at 29 times 1020 kJ most of which is not economically exploitable

11

Example Energy Content of Coal

An empirically determined formula for the energy content of coal based on the elemental abundances of carbon hydrogen oxygen and sulfur is

E = 337C + 1442(H minusO8) + 93S (21)

where E is in units of kJkg and the symbols stand for the mass percentages of the elements C H O and S Use Equation 21 and the information provided earlier about anthracite ie H = 0ndash375 O = 0ndash25 and S = 1 to estimate the highest value lowest value and average value of the energy content of anthracite assuming that no elements besides C H O and S are present

Solution

Based on the values of the constants in Equation 21 the maximum

energy density requires H be as high as possible and O is as low as possible and the minimum energy requires the opposite Thus using the data from Table 21 we have

12

As a check we note that these values are fairly close to those provided in

Table 21 for anthracite

Figure below shows energy consumption by the world in 2008

Figure hellip world consumption of energy 2008

13

Figure

3ed lecture

Electricity Generation from Coal

All three fossil fuels can be used for electricity generation but petroleum is used mostly in other sectors (petrochemicals and transportation fuels) and coal tends to be the dominant fossil fuel source for electricity generation There are many possible reasons however why a nation (such as Germany or Japan) might wish to use natural gas or even oil to generate electric power instead of coal even though coal in the past has been the cheaper alternativemdashignoring ldquoexternalrdquo (environmental) costs These reasons include concern for the environment and human health lack of abundant domestic coal reserves and greater ease of transport of oil and gas through existing pipelines or nearby ports

14

Figure 27 Basic components of a coal-fired power plant

15

Example

Total consumption of gas oil and coal in the United States in 2004 measured 238 426 and 240 EJ of energy content respectively

(A) Calculate the ratio of reserves to energy consumption for the United States for these three resources (B) Discuss the validity of this calculation

Solution

From Table 5-4 the total reserves for the United States are 195 115 and 6750 EJ respectively Therefore the ratios are 85 28 and 301 for the three fuels This calculation implies that at current rates without considering other circumstances the gas reserves will be consumed in 85 years and the oil reserves in 28 years while the coal reserves will last for more than three centuries

16

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Example 1

Suppose during a test of a nuclear reactor its power level is ramped up from zero to its rated power of 1000 MW over a 2 h period and then after running at full

2

power for 6 h it is ramped back down to zero over a 2 h period Calculate the total energy generated by the reactor during those 10 h

Solution

We shall assume here that during the time which the power is ramped up and down it varies linearly so that the power the reactor generates varies accordingly during the 10 h test as shown in Figure 12 Based on Equation 11 and the definition of the integral as the area under the powerndashtime curve the energy must equal the area of the trapezoid in Figure 12 or 8000 MWh (Table 12)

Table 12 Some Common Prefixes Used to Designate

Various Powers of 10 Terra (T) 1012

Giga (G) 10+9

Mega (M) 10+6

Kilo (k) 10+3

Milli (m) 10minus3

Micro (μ) 10minus6

3

Nano (n) 10minus9

Pico (p) 10minus12

Example 2

Example 1-2 A portable electric generator that is powered by diesel fuel produces 7 kWh of electricity during a single period of operation (A) What is the equivalent amount of energy measured in MJ (B) Suppose the fuel consumed had an energy content of 110 MJ If the device were 100 efficient how much electricity would it produce in wh

Solution

(A) 7 kWh times 36 MJkWh = 252 MJ

(B) 110 MJ36 MJkWh = 306 kWh

WHAT IS AN ENERGY SOURCE

Some energy sources are either stores (repositories) of energy such as coal oil or uranium typically chemical or nuclear that can be liberated for useful purposes Other energy (second source) sources are flows of energy through the natural environment that are present in varying degrees at particular times and places An example is wind or solar energy Consider the question of electricitymdashis it an energy source or not Electricity does exist in the natural environment in the extreme form of lightning and therefore it can be considered to fall into the second category In fact lightning lightning strike could be captured and stored (in a capacitor) and then later released for useful purposes Anyone watching a storm is likely to marvel at the awesome power of a lightning bolt which is indeed prodigiousmdash typically about 1 TW (1012 W) This amount is equal to the power output of a thousand 1000 MW nuclear reactorsmdashmore than exists in the

4

entire world Such a comparison may prompt the thought Great Why not harness lightning as an energy source The problem is not figuring out how to capture the lightning but rather that while the power is very high the energy lightning contains is quite small since a lightning bolt lasts such a short timemdasharound 30 μs = 3 times10minus5s so by Equation 11 the energy contained is around 1012 times 3 times10minus5 = 3 times107 J = 30MJ Thirty million joules may sound impressive but suppose we designed a ldquolightning catcherrdquo that managed to capture say 10 of this energy It would only be sufficient to light a 100 W light bulb for a time t = Ep = 3 times106 J100W = 3000 s which is just under an hourmdashhardly a useful energy source considering the likely expense involved What about electricity that humans createmdashcan it be thought of as an energy source Hardly Any electricity that we create requires energy input of an amount that is greater than that of the electricity itself since some energy will always be lost to the environment as heat Thus human-created electricity whether it be from batteries generators or solar panels is not an energy source itself but merely the product of whatever energy source that created it In the case of a generator it would be whatever gave rise to the mechanical energy forcing it to turn while in the case of a solar panel it would be the energy in the sunlight incident on the panel In order for an energy resource to be reliable it must first of all deliver the service that the consumer expects Secondly it must be available in the quantity desired when the consumer wishes to consume it (whether this is electricity from a wall outlet or gasoline dispensed from a filling station) Lastly the resource must be available at a price that is economically affordable

WHAT EXACTLY IS THE WORLDrsquoS ENERGY PROBLEM

1-All sources of energy have some environmental impact but as you

are aware the impacts of different sources vary considerably

2-The energy sources people worry the most about are fossil fuels (coal

oil and gas) as well as nuclear while the renewable (ldquogreenrdquo) energy

5

sources are considered much more benignmdasheven though they too have

some harmful impacts

3-Moreover the environmental impact of fossil

fuel and nuclear energy usage has gotten worse over time as the

human population has grown and the energy usage per capita has

also grownmdashan inevitable consequence of the rise in living standards

worldwide

Problems

1-How many kWh would a 1000 MW nuclear power plant generate in a

year

2-Consider a nuclear power plant whose power level is ramped up from

zero to a maximum 1000 MW and then back down to zero over a 10 h

period of time Assume that the power level varies as a quadratic function

of time during those 10 h Write an expression for the power as a

function of time and then find the total energy generated by the plant

during the 10 h period

3-Compare the direct costs to the consumer of using a succession of ten

100-W incandescent light bulbs with an efficiency to visible light of

5 a lifetime of 1000 h and a price of 50 cents with one compact

6

fluorescent lamp giving the same illumination at 22 efficiency a

lifetime of 10000 h and a price of $3 Assume a price of electricity

of 10 cents per kWh

2nd lecture

WHY HAS RENEWABLE ENERGY AND CONSERVATION BEEN NEGLECTED UNTIL FAIRLY RECENTLY

There are many reasons aside from simple inertia why moving away from fossil fuels and toward renewable energy has and will continue to be a challenge First the awareness of the environmental problems associated with fossil fuels has come very gradually and views on the seriousness of the threat posed by climate change vary considerably Moreover in times of economic uncertainty long-term environmental issues can easily take a backseat to more immediate concerns especially for homeowners

Second compared to fossil fuels there are problems with renewable sources which may be very dispersed intermittent and expensivemdash although the cost differential varies widely and often fails to take into account what economists refer to as ldquoexternalitiesrdquo ie costs incurred by society as a whole or the environment The intermittency poses special problems if the renewable source is used to generate electricity at large central power plants connected to the grid One can cope with this problem using various energy storage methods and upgrades to the electric power grid but of course both have costs see table 14

7

Example 2 Which Solar Panels Are Superior

Suppose that ten type A solar panels produced enough power for your electricity

needs had a lifetime of 30 years cost only $1000 but they had an efficiency of only 5 Five type B panels cost $5000 but they had an efficiency of 10 and lasted only 15 not 30 years Which panels should you buy

Solution

Obviously the more efficient panels would take up only half the area on your roof than the type A panels but who cares if they both met your needs The cost over a 30 year period would be $1000 for the type A panels but $10000 for the more efficient type B panels that produced the same amount of power (since they last

8

only half as long) so clearly you would opt for the less efficient choice in this case As a general rule as long as the fuel is free and there are no differences in labor or maintenance costs your primary consideration would almost always be based on cost per unit energy generated over some fixed period of timemdashusually the lifetime of the longer-lived alternative

Example 3 How the Usage of Wind Power to Offset Coal-Fired Plants Can Generate More Emissions Not Less

Suppose that a certain fraction of the power produced by a 500 MW coal

plant is offset by wind power Assume that when the coal plant runs at its

constant rated power it has an efficiency of 35 but that when it needs

to be ramped up and down to compensate for the wind power variations

its efficiency is reduced by according to e = 035 minus 000001p2 where p is

the amount of wind power Find the percentage increase in emissions that

results when 90 MW of the 500 MW is generated by wind power instead

of coal

Solution

In order to generate the full 500 MW by itself the coal plant requires 500035 = 1429 MW of heat flow from the coal If the wind power is 90 MW the efficiency of the coal plant is reduced to e = 035 minus 000001(90)2 = 0269 and the heat flow required to generate (500 minus 90) = 410 MW is therefore 410(0269) = 1524 MW The percentage increase in emissions is the same as the percentage increase in the heat flow to the coal plant ie 67

9

Problem 1 Using the data in Example 3 find the amount of wind power that could be used with a 500 MW coal-fired plant that would result in the least

amount of emissions

Fossil Fuels

Most fossil fuels which include coal oil and natural gas were formed from the remains of ancient life over the course of tens to hundreds of millions of yearsmdashhence the adjective fossil Today fossil fuels account for totally 85 of the worldrsquos primary energy usage with nuclear and hydropower comprising 8 and 3 and the renewable sources of geothermal solar tidal wind and wood waste amounting to a bit over 1 collectively An obvious question is what has made fossil fuels so attractive as an energy source in the past as well as today and why is it so difficult to move away from them despite the mounting evidence of the environmental problems they pose The answer is For example coal oil and gas have at least 200 times the energy per kilogram that is stored in a lead acid car battery Fossil fuels represent highly concentrated stores of energy compared to the much more dilute concentrations typical of renewablecheaply collected stored shipped and used where and when desired than most renewable energy sources

COAL

Composition of Coal Coal is a combustible sedimentary rock It differs from other kinds of rocks which are generally made of minerals and hence inorganic by definition Coal however is mostly carbon made

10

primarily from plant material and is therefore organic While carbon may be its primary component it does contain minor amounts of hydrocarbons like methane and inorganic mineral material that are considered impurities Coal does not have a specific chemical composition because the precise mixture of sulfur oxygen hydrogen nitrogen and other elements comprising it varies according to the particular rank or grade of coal and even within a grade For example for anthracite the highest and hardest rank of coal its composition includes 0ndash375 hydrogen 0ndash25 oxygen and up to around 16 sulfur Although the number of coal ranks depends on the classification system one system that is widely used is based on the four grades listed in Table 21

Coal is generally cheaper than oil whereas natural gas is more expensive The difference in price reflects the different costs of recovery storage and transport Nuclear fuel refined for use in nuclear electric power plants is less expensive than fossil fuels per unit of heating value

The energy believed to be present in the worldrsquos coal supply dwarfs all

other fossil fuels combined and it has been estimated at 29 times 1020 kJ most of which is not economically exploitable

11

Example Energy Content of Coal

An empirically determined formula for the energy content of coal based on the elemental abundances of carbon hydrogen oxygen and sulfur is

E = 337C + 1442(H minusO8) + 93S (21)

where E is in units of kJkg and the symbols stand for the mass percentages of the elements C H O and S Use Equation 21 and the information provided earlier about anthracite ie H = 0ndash375 O = 0ndash25 and S = 1 to estimate the highest value lowest value and average value of the energy content of anthracite assuming that no elements besides C H O and S are present

Solution

Based on the values of the constants in Equation 21 the maximum

energy density requires H be as high as possible and O is as low as possible and the minimum energy requires the opposite Thus using the data from Table 21 we have

12

As a check we note that these values are fairly close to those provided in

Table 21 for anthracite

Figure below shows energy consumption by the world in 2008

Figure hellip world consumption of energy 2008

13

Figure

3ed lecture

Electricity Generation from Coal

All three fossil fuels can be used for electricity generation but petroleum is used mostly in other sectors (petrochemicals and transportation fuels) and coal tends to be the dominant fossil fuel source for electricity generation There are many possible reasons however why a nation (such as Germany or Japan) might wish to use natural gas or even oil to generate electric power instead of coal even though coal in the past has been the cheaper alternativemdashignoring ldquoexternalrdquo (environmental) costs These reasons include concern for the environment and human health lack of abundant domestic coal reserves and greater ease of transport of oil and gas through existing pipelines or nearby ports

14

Figure 27 Basic components of a coal-fired power plant

15

Example

Total consumption of gas oil and coal in the United States in 2004 measured 238 426 and 240 EJ of energy content respectively

(A) Calculate the ratio of reserves to energy consumption for the United States for these three resources (B) Discuss the validity of this calculation

Solution

From Table 5-4 the total reserves for the United States are 195 115 and 6750 EJ respectively Therefore the ratios are 85 28 and 301 for the three fuels This calculation implies that at current rates without considering other circumstances the gas reserves will be consumed in 85 years and the oil reserves in 28 years while the coal reserves will last for more than three centuries

16

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

power for 6 h it is ramped back down to zero over a 2 h period Calculate the total energy generated by the reactor during those 10 h

Solution

We shall assume here that during the time which the power is ramped up and down it varies linearly so that the power the reactor generates varies accordingly during the 10 h test as shown in Figure 12 Based on Equation 11 and the definition of the integral as the area under the powerndashtime curve the energy must equal the area of the trapezoid in Figure 12 or 8000 MWh (Table 12)

Table 12 Some Common Prefixes Used to Designate

Various Powers of 10 Terra (T) 1012

Giga (G) 10+9

Mega (M) 10+6

Kilo (k) 10+3

Milli (m) 10minus3

Micro (μ) 10minus6

3

Nano (n) 10minus9

Pico (p) 10minus12

Example 2

Example 1-2 A portable electric generator that is powered by diesel fuel produces 7 kWh of electricity during a single period of operation (A) What is the equivalent amount of energy measured in MJ (B) Suppose the fuel consumed had an energy content of 110 MJ If the device were 100 efficient how much electricity would it produce in wh

Solution

(A) 7 kWh times 36 MJkWh = 252 MJ

(B) 110 MJ36 MJkWh = 306 kWh

WHAT IS AN ENERGY SOURCE

Some energy sources are either stores (repositories) of energy such as coal oil or uranium typically chemical or nuclear that can be liberated for useful purposes Other energy (second source) sources are flows of energy through the natural environment that are present in varying degrees at particular times and places An example is wind or solar energy Consider the question of electricitymdashis it an energy source or not Electricity does exist in the natural environment in the extreme form of lightning and therefore it can be considered to fall into the second category In fact lightning lightning strike could be captured and stored (in a capacitor) and then later released for useful purposes Anyone watching a storm is likely to marvel at the awesome power of a lightning bolt which is indeed prodigiousmdash typically about 1 TW (1012 W) This amount is equal to the power output of a thousand 1000 MW nuclear reactorsmdashmore than exists in the

4

entire world Such a comparison may prompt the thought Great Why not harness lightning as an energy source The problem is not figuring out how to capture the lightning but rather that while the power is very high the energy lightning contains is quite small since a lightning bolt lasts such a short timemdasharound 30 μs = 3 times10minus5s so by Equation 11 the energy contained is around 1012 times 3 times10minus5 = 3 times107 J = 30MJ Thirty million joules may sound impressive but suppose we designed a ldquolightning catcherrdquo that managed to capture say 10 of this energy It would only be sufficient to light a 100 W light bulb for a time t = Ep = 3 times106 J100W = 3000 s which is just under an hourmdashhardly a useful energy source considering the likely expense involved What about electricity that humans createmdashcan it be thought of as an energy source Hardly Any electricity that we create requires energy input of an amount that is greater than that of the electricity itself since some energy will always be lost to the environment as heat Thus human-created electricity whether it be from batteries generators or solar panels is not an energy source itself but merely the product of whatever energy source that created it In the case of a generator it would be whatever gave rise to the mechanical energy forcing it to turn while in the case of a solar panel it would be the energy in the sunlight incident on the panel In order for an energy resource to be reliable it must first of all deliver the service that the consumer expects Secondly it must be available in the quantity desired when the consumer wishes to consume it (whether this is electricity from a wall outlet or gasoline dispensed from a filling station) Lastly the resource must be available at a price that is economically affordable

WHAT EXACTLY IS THE WORLDrsquoS ENERGY PROBLEM

1-All sources of energy have some environmental impact but as you

are aware the impacts of different sources vary considerably

2-The energy sources people worry the most about are fossil fuels (coal

oil and gas) as well as nuclear while the renewable (ldquogreenrdquo) energy

5

sources are considered much more benignmdasheven though they too have

some harmful impacts

3-Moreover the environmental impact of fossil

fuel and nuclear energy usage has gotten worse over time as the

human population has grown and the energy usage per capita has

also grownmdashan inevitable consequence of the rise in living standards

worldwide

Problems

1-How many kWh would a 1000 MW nuclear power plant generate in a

year

2-Consider a nuclear power plant whose power level is ramped up from

zero to a maximum 1000 MW and then back down to zero over a 10 h

period of time Assume that the power level varies as a quadratic function

of time during those 10 h Write an expression for the power as a

function of time and then find the total energy generated by the plant

during the 10 h period

3-Compare the direct costs to the consumer of using a succession of ten

100-W incandescent light bulbs with an efficiency to visible light of

5 a lifetime of 1000 h and a price of 50 cents with one compact

6

fluorescent lamp giving the same illumination at 22 efficiency a

lifetime of 10000 h and a price of $3 Assume a price of electricity

of 10 cents per kWh

2nd lecture

WHY HAS RENEWABLE ENERGY AND CONSERVATION BEEN NEGLECTED UNTIL FAIRLY RECENTLY

There are many reasons aside from simple inertia why moving away from fossil fuels and toward renewable energy has and will continue to be a challenge First the awareness of the environmental problems associated with fossil fuels has come very gradually and views on the seriousness of the threat posed by climate change vary considerably Moreover in times of economic uncertainty long-term environmental issues can easily take a backseat to more immediate concerns especially for homeowners

Second compared to fossil fuels there are problems with renewable sources which may be very dispersed intermittent and expensivemdash although the cost differential varies widely and often fails to take into account what economists refer to as ldquoexternalitiesrdquo ie costs incurred by society as a whole or the environment The intermittency poses special problems if the renewable source is used to generate electricity at large central power plants connected to the grid One can cope with this problem using various energy storage methods and upgrades to the electric power grid but of course both have costs see table 14

7

Example 2 Which Solar Panels Are Superior

Suppose that ten type A solar panels produced enough power for your electricity

needs had a lifetime of 30 years cost only $1000 but they had an efficiency of only 5 Five type B panels cost $5000 but they had an efficiency of 10 and lasted only 15 not 30 years Which panels should you buy

Solution

Obviously the more efficient panels would take up only half the area on your roof than the type A panels but who cares if they both met your needs The cost over a 30 year period would be $1000 for the type A panels but $10000 for the more efficient type B panels that produced the same amount of power (since they last

8

only half as long) so clearly you would opt for the less efficient choice in this case As a general rule as long as the fuel is free and there are no differences in labor or maintenance costs your primary consideration would almost always be based on cost per unit energy generated over some fixed period of timemdashusually the lifetime of the longer-lived alternative

Example 3 How the Usage of Wind Power to Offset Coal-Fired Plants Can Generate More Emissions Not Less

Suppose that a certain fraction of the power produced by a 500 MW coal

plant is offset by wind power Assume that when the coal plant runs at its

constant rated power it has an efficiency of 35 but that when it needs

to be ramped up and down to compensate for the wind power variations

its efficiency is reduced by according to e = 035 minus 000001p2 where p is

the amount of wind power Find the percentage increase in emissions that

results when 90 MW of the 500 MW is generated by wind power instead

of coal

Solution

In order to generate the full 500 MW by itself the coal plant requires 500035 = 1429 MW of heat flow from the coal If the wind power is 90 MW the efficiency of the coal plant is reduced to e = 035 minus 000001(90)2 = 0269 and the heat flow required to generate (500 minus 90) = 410 MW is therefore 410(0269) = 1524 MW The percentage increase in emissions is the same as the percentage increase in the heat flow to the coal plant ie 67

9

Problem 1 Using the data in Example 3 find the amount of wind power that could be used with a 500 MW coal-fired plant that would result in the least

amount of emissions

Fossil Fuels

Most fossil fuels which include coal oil and natural gas were formed from the remains of ancient life over the course of tens to hundreds of millions of yearsmdashhence the adjective fossil Today fossil fuels account for totally 85 of the worldrsquos primary energy usage with nuclear and hydropower comprising 8 and 3 and the renewable sources of geothermal solar tidal wind and wood waste amounting to a bit over 1 collectively An obvious question is what has made fossil fuels so attractive as an energy source in the past as well as today and why is it so difficult to move away from them despite the mounting evidence of the environmental problems they pose The answer is For example coal oil and gas have at least 200 times the energy per kilogram that is stored in a lead acid car battery Fossil fuels represent highly concentrated stores of energy compared to the much more dilute concentrations typical of renewablecheaply collected stored shipped and used where and when desired than most renewable energy sources

COAL

Composition of Coal Coal is a combustible sedimentary rock It differs from other kinds of rocks which are generally made of minerals and hence inorganic by definition Coal however is mostly carbon made

10

primarily from plant material and is therefore organic While carbon may be its primary component it does contain minor amounts of hydrocarbons like methane and inorganic mineral material that are considered impurities Coal does not have a specific chemical composition because the precise mixture of sulfur oxygen hydrogen nitrogen and other elements comprising it varies according to the particular rank or grade of coal and even within a grade For example for anthracite the highest and hardest rank of coal its composition includes 0ndash375 hydrogen 0ndash25 oxygen and up to around 16 sulfur Although the number of coal ranks depends on the classification system one system that is widely used is based on the four grades listed in Table 21

Coal is generally cheaper than oil whereas natural gas is more expensive The difference in price reflects the different costs of recovery storage and transport Nuclear fuel refined for use in nuclear electric power plants is less expensive than fossil fuels per unit of heating value

The energy believed to be present in the worldrsquos coal supply dwarfs all

other fossil fuels combined and it has been estimated at 29 times 1020 kJ most of which is not economically exploitable

11

Example Energy Content of Coal

An empirically determined formula for the energy content of coal based on the elemental abundances of carbon hydrogen oxygen and sulfur is

E = 337C + 1442(H minusO8) + 93S (21)

where E is in units of kJkg and the symbols stand for the mass percentages of the elements C H O and S Use Equation 21 and the information provided earlier about anthracite ie H = 0ndash375 O = 0ndash25 and S = 1 to estimate the highest value lowest value and average value of the energy content of anthracite assuming that no elements besides C H O and S are present

Solution

Based on the values of the constants in Equation 21 the maximum

energy density requires H be as high as possible and O is as low as possible and the minimum energy requires the opposite Thus using the data from Table 21 we have

12

As a check we note that these values are fairly close to those provided in

Table 21 for anthracite

Figure below shows energy consumption by the world in 2008

Figure hellip world consumption of energy 2008

13

Figure

3ed lecture

Electricity Generation from Coal

All three fossil fuels can be used for electricity generation but petroleum is used mostly in other sectors (petrochemicals and transportation fuels) and coal tends to be the dominant fossil fuel source for electricity generation There are many possible reasons however why a nation (such as Germany or Japan) might wish to use natural gas or even oil to generate electric power instead of coal even though coal in the past has been the cheaper alternativemdashignoring ldquoexternalrdquo (environmental) costs These reasons include concern for the environment and human health lack of abundant domestic coal reserves and greater ease of transport of oil and gas through existing pipelines or nearby ports

14

Figure 27 Basic components of a coal-fired power plant

15

Example

Total consumption of gas oil and coal in the United States in 2004 measured 238 426 and 240 EJ of energy content respectively

(A) Calculate the ratio of reserves to energy consumption for the United States for these three resources (B) Discuss the validity of this calculation

Solution

From Table 5-4 the total reserves for the United States are 195 115 and 6750 EJ respectively Therefore the ratios are 85 28 and 301 for the three fuels This calculation implies that at current rates without considering other circumstances the gas reserves will be consumed in 85 years and the oil reserves in 28 years while the coal reserves will last for more than three centuries

16

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Nano (n) 10minus9

Pico (p) 10minus12

Example 2

Example 1-2 A portable electric generator that is powered by diesel fuel produces 7 kWh of electricity during a single period of operation (A) What is the equivalent amount of energy measured in MJ (B) Suppose the fuel consumed had an energy content of 110 MJ If the device were 100 efficient how much electricity would it produce in wh

Solution

(A) 7 kWh times 36 MJkWh = 252 MJ

(B) 110 MJ36 MJkWh = 306 kWh

WHAT IS AN ENERGY SOURCE

Some energy sources are either stores (repositories) of energy such as coal oil or uranium typically chemical or nuclear that can be liberated for useful purposes Other energy (second source) sources are flows of energy through the natural environment that are present in varying degrees at particular times and places An example is wind or solar energy Consider the question of electricitymdashis it an energy source or not Electricity does exist in the natural environment in the extreme form of lightning and therefore it can be considered to fall into the second category In fact lightning lightning strike could be captured and stored (in a capacitor) and then later released for useful purposes Anyone watching a storm is likely to marvel at the awesome power of a lightning bolt which is indeed prodigiousmdash typically about 1 TW (1012 W) This amount is equal to the power output of a thousand 1000 MW nuclear reactorsmdashmore than exists in the

4

entire world Such a comparison may prompt the thought Great Why not harness lightning as an energy source The problem is not figuring out how to capture the lightning but rather that while the power is very high the energy lightning contains is quite small since a lightning bolt lasts such a short timemdasharound 30 μs = 3 times10minus5s so by Equation 11 the energy contained is around 1012 times 3 times10minus5 = 3 times107 J = 30MJ Thirty million joules may sound impressive but suppose we designed a ldquolightning catcherrdquo that managed to capture say 10 of this energy It would only be sufficient to light a 100 W light bulb for a time t = Ep = 3 times106 J100W = 3000 s which is just under an hourmdashhardly a useful energy source considering the likely expense involved What about electricity that humans createmdashcan it be thought of as an energy source Hardly Any electricity that we create requires energy input of an amount that is greater than that of the electricity itself since some energy will always be lost to the environment as heat Thus human-created electricity whether it be from batteries generators or solar panels is not an energy source itself but merely the product of whatever energy source that created it In the case of a generator it would be whatever gave rise to the mechanical energy forcing it to turn while in the case of a solar panel it would be the energy in the sunlight incident on the panel In order for an energy resource to be reliable it must first of all deliver the service that the consumer expects Secondly it must be available in the quantity desired when the consumer wishes to consume it (whether this is electricity from a wall outlet or gasoline dispensed from a filling station) Lastly the resource must be available at a price that is economically affordable

WHAT EXACTLY IS THE WORLDrsquoS ENERGY PROBLEM

1-All sources of energy have some environmental impact but as you

are aware the impacts of different sources vary considerably

2-The energy sources people worry the most about are fossil fuels (coal

oil and gas) as well as nuclear while the renewable (ldquogreenrdquo) energy

5

sources are considered much more benignmdasheven though they too have

some harmful impacts

3-Moreover the environmental impact of fossil

fuel and nuclear energy usage has gotten worse over time as the

human population has grown and the energy usage per capita has

also grownmdashan inevitable consequence of the rise in living standards

worldwide

Problems

1-How many kWh would a 1000 MW nuclear power plant generate in a

year

2-Consider a nuclear power plant whose power level is ramped up from

zero to a maximum 1000 MW and then back down to zero over a 10 h

period of time Assume that the power level varies as a quadratic function

of time during those 10 h Write an expression for the power as a

function of time and then find the total energy generated by the plant

during the 10 h period

3-Compare the direct costs to the consumer of using a succession of ten

100-W incandescent light bulbs with an efficiency to visible light of

5 a lifetime of 1000 h and a price of 50 cents with one compact

6

fluorescent lamp giving the same illumination at 22 efficiency a

lifetime of 10000 h and a price of $3 Assume a price of electricity

of 10 cents per kWh

2nd lecture

WHY HAS RENEWABLE ENERGY AND CONSERVATION BEEN NEGLECTED UNTIL FAIRLY RECENTLY

There are many reasons aside from simple inertia why moving away from fossil fuels and toward renewable energy has and will continue to be a challenge First the awareness of the environmental problems associated with fossil fuels has come very gradually and views on the seriousness of the threat posed by climate change vary considerably Moreover in times of economic uncertainty long-term environmental issues can easily take a backseat to more immediate concerns especially for homeowners

Second compared to fossil fuels there are problems with renewable sources which may be very dispersed intermittent and expensivemdash although the cost differential varies widely and often fails to take into account what economists refer to as ldquoexternalitiesrdquo ie costs incurred by society as a whole or the environment The intermittency poses special problems if the renewable source is used to generate electricity at large central power plants connected to the grid One can cope with this problem using various energy storage methods and upgrades to the electric power grid but of course both have costs see table 14

7

Example 2 Which Solar Panels Are Superior

Suppose that ten type A solar panels produced enough power for your electricity

needs had a lifetime of 30 years cost only $1000 but they had an efficiency of only 5 Five type B panels cost $5000 but they had an efficiency of 10 and lasted only 15 not 30 years Which panels should you buy

Solution

Obviously the more efficient panels would take up only half the area on your roof than the type A panels but who cares if they both met your needs The cost over a 30 year period would be $1000 for the type A panels but $10000 for the more efficient type B panels that produced the same amount of power (since they last

8

only half as long) so clearly you would opt for the less efficient choice in this case As a general rule as long as the fuel is free and there are no differences in labor or maintenance costs your primary consideration would almost always be based on cost per unit energy generated over some fixed period of timemdashusually the lifetime of the longer-lived alternative

Example 3 How the Usage of Wind Power to Offset Coal-Fired Plants Can Generate More Emissions Not Less

Suppose that a certain fraction of the power produced by a 500 MW coal

plant is offset by wind power Assume that when the coal plant runs at its

constant rated power it has an efficiency of 35 but that when it needs

to be ramped up and down to compensate for the wind power variations

its efficiency is reduced by according to e = 035 minus 000001p2 where p is

the amount of wind power Find the percentage increase in emissions that

results when 90 MW of the 500 MW is generated by wind power instead

of coal

Solution

In order to generate the full 500 MW by itself the coal plant requires 500035 = 1429 MW of heat flow from the coal If the wind power is 90 MW the efficiency of the coal plant is reduced to e = 035 minus 000001(90)2 = 0269 and the heat flow required to generate (500 minus 90) = 410 MW is therefore 410(0269) = 1524 MW The percentage increase in emissions is the same as the percentage increase in the heat flow to the coal plant ie 67

9

Problem 1 Using the data in Example 3 find the amount of wind power that could be used with a 500 MW coal-fired plant that would result in the least

amount of emissions

Fossil Fuels

Most fossil fuels which include coal oil and natural gas were formed from the remains of ancient life over the course of tens to hundreds of millions of yearsmdashhence the adjective fossil Today fossil fuels account for totally 85 of the worldrsquos primary energy usage with nuclear and hydropower comprising 8 and 3 and the renewable sources of geothermal solar tidal wind and wood waste amounting to a bit over 1 collectively An obvious question is what has made fossil fuels so attractive as an energy source in the past as well as today and why is it so difficult to move away from them despite the mounting evidence of the environmental problems they pose The answer is For example coal oil and gas have at least 200 times the energy per kilogram that is stored in a lead acid car battery Fossil fuels represent highly concentrated stores of energy compared to the much more dilute concentrations typical of renewablecheaply collected stored shipped and used where and when desired than most renewable energy sources

COAL

Composition of Coal Coal is a combustible sedimentary rock It differs from other kinds of rocks which are generally made of minerals and hence inorganic by definition Coal however is mostly carbon made

10

primarily from plant material and is therefore organic While carbon may be its primary component it does contain minor amounts of hydrocarbons like methane and inorganic mineral material that are considered impurities Coal does not have a specific chemical composition because the precise mixture of sulfur oxygen hydrogen nitrogen and other elements comprising it varies according to the particular rank or grade of coal and even within a grade For example for anthracite the highest and hardest rank of coal its composition includes 0ndash375 hydrogen 0ndash25 oxygen and up to around 16 sulfur Although the number of coal ranks depends on the classification system one system that is widely used is based on the four grades listed in Table 21

Coal is generally cheaper than oil whereas natural gas is more expensive The difference in price reflects the different costs of recovery storage and transport Nuclear fuel refined for use in nuclear electric power plants is less expensive than fossil fuels per unit of heating value

The energy believed to be present in the worldrsquos coal supply dwarfs all

other fossil fuels combined and it has been estimated at 29 times 1020 kJ most of which is not economically exploitable

11

Example Energy Content of Coal

An empirically determined formula for the energy content of coal based on the elemental abundances of carbon hydrogen oxygen and sulfur is

E = 337C + 1442(H minusO8) + 93S (21)

where E is in units of kJkg and the symbols stand for the mass percentages of the elements C H O and S Use Equation 21 and the information provided earlier about anthracite ie H = 0ndash375 O = 0ndash25 and S = 1 to estimate the highest value lowest value and average value of the energy content of anthracite assuming that no elements besides C H O and S are present

Solution

Based on the values of the constants in Equation 21 the maximum

energy density requires H be as high as possible and O is as low as possible and the minimum energy requires the opposite Thus using the data from Table 21 we have

12

As a check we note that these values are fairly close to those provided in

Table 21 for anthracite

Figure below shows energy consumption by the world in 2008

Figure hellip world consumption of energy 2008

13

Figure

3ed lecture

Electricity Generation from Coal

All three fossil fuels can be used for electricity generation but petroleum is used mostly in other sectors (petrochemicals and transportation fuels) and coal tends to be the dominant fossil fuel source for electricity generation There are many possible reasons however why a nation (such as Germany or Japan) might wish to use natural gas or even oil to generate electric power instead of coal even though coal in the past has been the cheaper alternativemdashignoring ldquoexternalrdquo (environmental) costs These reasons include concern for the environment and human health lack of abundant domestic coal reserves and greater ease of transport of oil and gas through existing pipelines or nearby ports

14

Figure 27 Basic components of a coal-fired power plant

15

Example

Total consumption of gas oil and coal in the United States in 2004 measured 238 426 and 240 EJ of energy content respectively

(A) Calculate the ratio of reserves to energy consumption for the United States for these three resources (B) Discuss the validity of this calculation

Solution

From Table 5-4 the total reserves for the United States are 195 115 and 6750 EJ respectively Therefore the ratios are 85 28 and 301 for the three fuels This calculation implies that at current rates without considering other circumstances the gas reserves will be consumed in 85 years and the oil reserves in 28 years while the coal reserves will last for more than three centuries

16

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

entire world Such a comparison may prompt the thought Great Why not harness lightning as an energy source The problem is not figuring out how to capture the lightning but rather that while the power is very high the energy lightning contains is quite small since a lightning bolt lasts such a short timemdasharound 30 μs = 3 times10minus5s so by Equation 11 the energy contained is around 1012 times 3 times10minus5 = 3 times107 J = 30MJ Thirty million joules may sound impressive but suppose we designed a ldquolightning catcherrdquo that managed to capture say 10 of this energy It would only be sufficient to light a 100 W light bulb for a time t = Ep = 3 times106 J100W = 3000 s which is just under an hourmdashhardly a useful energy source considering the likely expense involved What about electricity that humans createmdashcan it be thought of as an energy source Hardly Any electricity that we create requires energy input of an amount that is greater than that of the electricity itself since some energy will always be lost to the environment as heat Thus human-created electricity whether it be from batteries generators or solar panels is not an energy source itself but merely the product of whatever energy source that created it In the case of a generator it would be whatever gave rise to the mechanical energy forcing it to turn while in the case of a solar panel it would be the energy in the sunlight incident on the panel In order for an energy resource to be reliable it must first of all deliver the service that the consumer expects Secondly it must be available in the quantity desired when the consumer wishes to consume it (whether this is electricity from a wall outlet or gasoline dispensed from a filling station) Lastly the resource must be available at a price that is economically affordable

WHAT EXACTLY IS THE WORLDrsquoS ENERGY PROBLEM

1-All sources of energy have some environmental impact but as you

are aware the impacts of different sources vary considerably

2-The energy sources people worry the most about are fossil fuels (coal

oil and gas) as well as nuclear while the renewable (ldquogreenrdquo) energy

5

sources are considered much more benignmdasheven though they too have

some harmful impacts

3-Moreover the environmental impact of fossil

fuel and nuclear energy usage has gotten worse over time as the

human population has grown and the energy usage per capita has

also grownmdashan inevitable consequence of the rise in living standards

worldwide

Problems

1-How many kWh would a 1000 MW nuclear power plant generate in a

year

2-Consider a nuclear power plant whose power level is ramped up from

zero to a maximum 1000 MW and then back down to zero over a 10 h

period of time Assume that the power level varies as a quadratic function

of time during those 10 h Write an expression for the power as a

function of time and then find the total energy generated by the plant

during the 10 h period

3-Compare the direct costs to the consumer of using a succession of ten

100-W incandescent light bulbs with an efficiency to visible light of

5 a lifetime of 1000 h and a price of 50 cents with one compact

6

fluorescent lamp giving the same illumination at 22 efficiency a

lifetime of 10000 h and a price of $3 Assume a price of electricity

of 10 cents per kWh

2nd lecture

WHY HAS RENEWABLE ENERGY AND CONSERVATION BEEN NEGLECTED UNTIL FAIRLY RECENTLY

There are many reasons aside from simple inertia why moving away from fossil fuels and toward renewable energy has and will continue to be a challenge First the awareness of the environmental problems associated with fossil fuels has come very gradually and views on the seriousness of the threat posed by climate change vary considerably Moreover in times of economic uncertainty long-term environmental issues can easily take a backseat to more immediate concerns especially for homeowners

Second compared to fossil fuels there are problems with renewable sources which may be very dispersed intermittent and expensivemdash although the cost differential varies widely and often fails to take into account what economists refer to as ldquoexternalitiesrdquo ie costs incurred by society as a whole or the environment The intermittency poses special problems if the renewable source is used to generate electricity at large central power plants connected to the grid One can cope with this problem using various energy storage methods and upgrades to the electric power grid but of course both have costs see table 14

7

Example 2 Which Solar Panels Are Superior

Suppose that ten type A solar panels produced enough power for your electricity

needs had a lifetime of 30 years cost only $1000 but they had an efficiency of only 5 Five type B panels cost $5000 but they had an efficiency of 10 and lasted only 15 not 30 years Which panels should you buy

Solution

Obviously the more efficient panels would take up only half the area on your roof than the type A panels but who cares if they both met your needs The cost over a 30 year period would be $1000 for the type A panels but $10000 for the more efficient type B panels that produced the same amount of power (since they last

8

only half as long) so clearly you would opt for the less efficient choice in this case As a general rule as long as the fuel is free and there are no differences in labor or maintenance costs your primary consideration would almost always be based on cost per unit energy generated over some fixed period of timemdashusually the lifetime of the longer-lived alternative

Example 3 How the Usage of Wind Power to Offset Coal-Fired Plants Can Generate More Emissions Not Less

Suppose that a certain fraction of the power produced by a 500 MW coal

plant is offset by wind power Assume that when the coal plant runs at its

constant rated power it has an efficiency of 35 but that when it needs

to be ramped up and down to compensate for the wind power variations

its efficiency is reduced by according to e = 035 minus 000001p2 where p is

the amount of wind power Find the percentage increase in emissions that

results when 90 MW of the 500 MW is generated by wind power instead

of coal

Solution

In order to generate the full 500 MW by itself the coal plant requires 500035 = 1429 MW of heat flow from the coal If the wind power is 90 MW the efficiency of the coal plant is reduced to e = 035 minus 000001(90)2 = 0269 and the heat flow required to generate (500 minus 90) = 410 MW is therefore 410(0269) = 1524 MW The percentage increase in emissions is the same as the percentage increase in the heat flow to the coal plant ie 67

9

Problem 1 Using the data in Example 3 find the amount of wind power that could be used with a 500 MW coal-fired plant that would result in the least

amount of emissions

Fossil Fuels

Most fossil fuels which include coal oil and natural gas were formed from the remains of ancient life over the course of tens to hundreds of millions of yearsmdashhence the adjective fossil Today fossil fuels account for totally 85 of the worldrsquos primary energy usage with nuclear and hydropower comprising 8 and 3 and the renewable sources of geothermal solar tidal wind and wood waste amounting to a bit over 1 collectively An obvious question is what has made fossil fuels so attractive as an energy source in the past as well as today and why is it so difficult to move away from them despite the mounting evidence of the environmental problems they pose The answer is For example coal oil and gas have at least 200 times the energy per kilogram that is stored in a lead acid car battery Fossil fuels represent highly concentrated stores of energy compared to the much more dilute concentrations typical of renewablecheaply collected stored shipped and used where and when desired than most renewable energy sources

COAL

Composition of Coal Coal is a combustible sedimentary rock It differs from other kinds of rocks which are generally made of minerals and hence inorganic by definition Coal however is mostly carbon made

10

primarily from plant material and is therefore organic While carbon may be its primary component it does contain minor amounts of hydrocarbons like methane and inorganic mineral material that are considered impurities Coal does not have a specific chemical composition because the precise mixture of sulfur oxygen hydrogen nitrogen and other elements comprising it varies according to the particular rank or grade of coal and even within a grade For example for anthracite the highest and hardest rank of coal its composition includes 0ndash375 hydrogen 0ndash25 oxygen and up to around 16 sulfur Although the number of coal ranks depends on the classification system one system that is widely used is based on the four grades listed in Table 21

Coal is generally cheaper than oil whereas natural gas is more expensive The difference in price reflects the different costs of recovery storage and transport Nuclear fuel refined for use in nuclear electric power plants is less expensive than fossil fuels per unit of heating value

The energy believed to be present in the worldrsquos coal supply dwarfs all

other fossil fuels combined and it has been estimated at 29 times 1020 kJ most of which is not economically exploitable

11

Example Energy Content of Coal

An empirically determined formula for the energy content of coal based on the elemental abundances of carbon hydrogen oxygen and sulfur is

E = 337C + 1442(H minusO8) + 93S (21)

where E is in units of kJkg and the symbols stand for the mass percentages of the elements C H O and S Use Equation 21 and the information provided earlier about anthracite ie H = 0ndash375 O = 0ndash25 and S = 1 to estimate the highest value lowest value and average value of the energy content of anthracite assuming that no elements besides C H O and S are present

Solution

Based on the values of the constants in Equation 21 the maximum

energy density requires H be as high as possible and O is as low as possible and the minimum energy requires the opposite Thus using the data from Table 21 we have

12

As a check we note that these values are fairly close to those provided in

Table 21 for anthracite

Figure below shows energy consumption by the world in 2008

Figure hellip world consumption of energy 2008

13

Figure

3ed lecture

Electricity Generation from Coal

All three fossil fuels can be used for electricity generation but petroleum is used mostly in other sectors (petrochemicals and transportation fuels) and coal tends to be the dominant fossil fuel source for electricity generation There are many possible reasons however why a nation (such as Germany or Japan) might wish to use natural gas or even oil to generate electric power instead of coal even though coal in the past has been the cheaper alternativemdashignoring ldquoexternalrdquo (environmental) costs These reasons include concern for the environment and human health lack of abundant domestic coal reserves and greater ease of transport of oil and gas through existing pipelines or nearby ports

14

Figure 27 Basic components of a coal-fired power plant

15

Example

Total consumption of gas oil and coal in the United States in 2004 measured 238 426 and 240 EJ of energy content respectively

(A) Calculate the ratio of reserves to energy consumption for the United States for these three resources (B) Discuss the validity of this calculation

Solution

From Table 5-4 the total reserves for the United States are 195 115 and 6750 EJ respectively Therefore the ratios are 85 28 and 301 for the three fuels This calculation implies that at current rates without considering other circumstances the gas reserves will be consumed in 85 years and the oil reserves in 28 years while the coal reserves will last for more than three centuries

16

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

sources are considered much more benignmdasheven though they too have

some harmful impacts

3-Moreover the environmental impact of fossil

fuel and nuclear energy usage has gotten worse over time as the

human population has grown and the energy usage per capita has

also grownmdashan inevitable consequence of the rise in living standards

worldwide

Problems

1-How many kWh would a 1000 MW nuclear power plant generate in a

year

2-Consider a nuclear power plant whose power level is ramped up from

zero to a maximum 1000 MW and then back down to zero over a 10 h

period of time Assume that the power level varies as a quadratic function

of time during those 10 h Write an expression for the power as a

function of time and then find the total energy generated by the plant

during the 10 h period

3-Compare the direct costs to the consumer of using a succession of ten

100-W incandescent light bulbs with an efficiency to visible light of

5 a lifetime of 1000 h and a price of 50 cents with one compact

6

fluorescent lamp giving the same illumination at 22 efficiency a

lifetime of 10000 h and a price of $3 Assume a price of electricity

of 10 cents per kWh

2nd lecture

WHY HAS RENEWABLE ENERGY AND CONSERVATION BEEN NEGLECTED UNTIL FAIRLY RECENTLY

There are many reasons aside from simple inertia why moving away from fossil fuels and toward renewable energy has and will continue to be a challenge First the awareness of the environmental problems associated with fossil fuels has come very gradually and views on the seriousness of the threat posed by climate change vary considerably Moreover in times of economic uncertainty long-term environmental issues can easily take a backseat to more immediate concerns especially for homeowners

Second compared to fossil fuels there are problems with renewable sources which may be very dispersed intermittent and expensivemdash although the cost differential varies widely and often fails to take into account what economists refer to as ldquoexternalitiesrdquo ie costs incurred by society as a whole or the environment The intermittency poses special problems if the renewable source is used to generate electricity at large central power plants connected to the grid One can cope with this problem using various energy storage methods and upgrades to the electric power grid but of course both have costs see table 14

7

Example 2 Which Solar Panels Are Superior

Suppose that ten type A solar panels produced enough power for your electricity

needs had a lifetime of 30 years cost only $1000 but they had an efficiency of only 5 Five type B panels cost $5000 but they had an efficiency of 10 and lasted only 15 not 30 years Which panels should you buy

Solution

Obviously the more efficient panels would take up only half the area on your roof than the type A panels but who cares if they both met your needs The cost over a 30 year period would be $1000 for the type A panels but $10000 for the more efficient type B panels that produced the same amount of power (since they last

8

only half as long) so clearly you would opt for the less efficient choice in this case As a general rule as long as the fuel is free and there are no differences in labor or maintenance costs your primary consideration would almost always be based on cost per unit energy generated over some fixed period of timemdashusually the lifetime of the longer-lived alternative

Example 3 How the Usage of Wind Power to Offset Coal-Fired Plants Can Generate More Emissions Not Less

Suppose that a certain fraction of the power produced by a 500 MW coal

plant is offset by wind power Assume that when the coal plant runs at its

constant rated power it has an efficiency of 35 but that when it needs

to be ramped up and down to compensate for the wind power variations

its efficiency is reduced by according to e = 035 minus 000001p2 where p is

the amount of wind power Find the percentage increase in emissions that

results when 90 MW of the 500 MW is generated by wind power instead

of coal

Solution

In order to generate the full 500 MW by itself the coal plant requires 500035 = 1429 MW of heat flow from the coal If the wind power is 90 MW the efficiency of the coal plant is reduced to e = 035 minus 000001(90)2 = 0269 and the heat flow required to generate (500 minus 90) = 410 MW is therefore 410(0269) = 1524 MW The percentage increase in emissions is the same as the percentage increase in the heat flow to the coal plant ie 67

9

Problem 1 Using the data in Example 3 find the amount of wind power that could be used with a 500 MW coal-fired plant that would result in the least

amount of emissions

Fossil Fuels

Most fossil fuels which include coal oil and natural gas were formed from the remains of ancient life over the course of tens to hundreds of millions of yearsmdashhence the adjective fossil Today fossil fuels account for totally 85 of the worldrsquos primary energy usage with nuclear and hydropower comprising 8 and 3 and the renewable sources of geothermal solar tidal wind and wood waste amounting to a bit over 1 collectively An obvious question is what has made fossil fuels so attractive as an energy source in the past as well as today and why is it so difficult to move away from them despite the mounting evidence of the environmental problems they pose The answer is For example coal oil and gas have at least 200 times the energy per kilogram that is stored in a lead acid car battery Fossil fuels represent highly concentrated stores of energy compared to the much more dilute concentrations typical of renewablecheaply collected stored shipped and used where and when desired than most renewable energy sources

COAL

Composition of Coal Coal is a combustible sedimentary rock It differs from other kinds of rocks which are generally made of minerals and hence inorganic by definition Coal however is mostly carbon made

10

primarily from plant material and is therefore organic While carbon may be its primary component it does contain minor amounts of hydrocarbons like methane and inorganic mineral material that are considered impurities Coal does not have a specific chemical composition because the precise mixture of sulfur oxygen hydrogen nitrogen and other elements comprising it varies according to the particular rank or grade of coal and even within a grade For example for anthracite the highest and hardest rank of coal its composition includes 0ndash375 hydrogen 0ndash25 oxygen and up to around 16 sulfur Although the number of coal ranks depends on the classification system one system that is widely used is based on the four grades listed in Table 21

Coal is generally cheaper than oil whereas natural gas is more expensive The difference in price reflects the different costs of recovery storage and transport Nuclear fuel refined for use in nuclear electric power plants is less expensive than fossil fuels per unit of heating value

The energy believed to be present in the worldrsquos coal supply dwarfs all

other fossil fuels combined and it has been estimated at 29 times 1020 kJ most of which is not economically exploitable

11

Example Energy Content of Coal

An empirically determined formula for the energy content of coal based on the elemental abundances of carbon hydrogen oxygen and sulfur is

E = 337C + 1442(H minusO8) + 93S (21)

where E is in units of kJkg and the symbols stand for the mass percentages of the elements C H O and S Use Equation 21 and the information provided earlier about anthracite ie H = 0ndash375 O = 0ndash25 and S = 1 to estimate the highest value lowest value and average value of the energy content of anthracite assuming that no elements besides C H O and S are present

Solution

Based on the values of the constants in Equation 21 the maximum

energy density requires H be as high as possible and O is as low as possible and the minimum energy requires the opposite Thus using the data from Table 21 we have

12

As a check we note that these values are fairly close to those provided in

Table 21 for anthracite

Figure below shows energy consumption by the world in 2008

Figure hellip world consumption of energy 2008

13

Figure

3ed lecture

Electricity Generation from Coal

All three fossil fuels can be used for electricity generation but petroleum is used mostly in other sectors (petrochemicals and transportation fuels) and coal tends to be the dominant fossil fuel source for electricity generation There are many possible reasons however why a nation (such as Germany or Japan) might wish to use natural gas or even oil to generate electric power instead of coal even though coal in the past has been the cheaper alternativemdashignoring ldquoexternalrdquo (environmental) costs These reasons include concern for the environment and human health lack of abundant domestic coal reserves and greater ease of transport of oil and gas through existing pipelines or nearby ports

14

Figure 27 Basic components of a coal-fired power plant

15

Example

Total consumption of gas oil and coal in the United States in 2004 measured 238 426 and 240 EJ of energy content respectively

(A) Calculate the ratio of reserves to energy consumption for the United States for these three resources (B) Discuss the validity of this calculation

Solution

From Table 5-4 the total reserves for the United States are 195 115 and 6750 EJ respectively Therefore the ratios are 85 28 and 301 for the three fuels This calculation implies that at current rates without considering other circumstances the gas reserves will be consumed in 85 years and the oil reserves in 28 years while the coal reserves will last for more than three centuries

16

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

fluorescent lamp giving the same illumination at 22 efficiency a

lifetime of 10000 h and a price of $3 Assume a price of electricity

of 10 cents per kWh

2nd lecture

WHY HAS RENEWABLE ENERGY AND CONSERVATION BEEN NEGLECTED UNTIL FAIRLY RECENTLY

There are many reasons aside from simple inertia why moving away from fossil fuels and toward renewable energy has and will continue to be a challenge First the awareness of the environmental problems associated with fossil fuels has come very gradually and views on the seriousness of the threat posed by climate change vary considerably Moreover in times of economic uncertainty long-term environmental issues can easily take a backseat to more immediate concerns especially for homeowners

Second compared to fossil fuels there are problems with renewable sources which may be very dispersed intermittent and expensivemdash although the cost differential varies widely and often fails to take into account what economists refer to as ldquoexternalitiesrdquo ie costs incurred by society as a whole or the environment The intermittency poses special problems if the renewable source is used to generate electricity at large central power plants connected to the grid One can cope with this problem using various energy storage methods and upgrades to the electric power grid but of course both have costs see table 14

7

Example 2 Which Solar Panels Are Superior

Suppose that ten type A solar panels produced enough power for your electricity

needs had a lifetime of 30 years cost only $1000 but they had an efficiency of only 5 Five type B panels cost $5000 but they had an efficiency of 10 and lasted only 15 not 30 years Which panels should you buy

Solution

Obviously the more efficient panels would take up only half the area on your roof than the type A panels but who cares if they both met your needs The cost over a 30 year period would be $1000 for the type A panels but $10000 for the more efficient type B panels that produced the same amount of power (since they last

8

only half as long) so clearly you would opt for the less efficient choice in this case As a general rule as long as the fuel is free and there are no differences in labor or maintenance costs your primary consideration would almost always be based on cost per unit energy generated over some fixed period of timemdashusually the lifetime of the longer-lived alternative

Example 3 How the Usage of Wind Power to Offset Coal-Fired Plants Can Generate More Emissions Not Less

Suppose that a certain fraction of the power produced by a 500 MW coal

plant is offset by wind power Assume that when the coal plant runs at its

constant rated power it has an efficiency of 35 but that when it needs

to be ramped up and down to compensate for the wind power variations

its efficiency is reduced by according to e = 035 minus 000001p2 where p is

the amount of wind power Find the percentage increase in emissions that

results when 90 MW of the 500 MW is generated by wind power instead

of coal

Solution

In order to generate the full 500 MW by itself the coal plant requires 500035 = 1429 MW of heat flow from the coal If the wind power is 90 MW the efficiency of the coal plant is reduced to e = 035 minus 000001(90)2 = 0269 and the heat flow required to generate (500 minus 90) = 410 MW is therefore 410(0269) = 1524 MW The percentage increase in emissions is the same as the percentage increase in the heat flow to the coal plant ie 67

9

Problem 1 Using the data in Example 3 find the amount of wind power that could be used with a 500 MW coal-fired plant that would result in the least

amount of emissions

Fossil Fuels

Most fossil fuels which include coal oil and natural gas were formed from the remains of ancient life over the course of tens to hundreds of millions of yearsmdashhence the adjective fossil Today fossil fuels account for totally 85 of the worldrsquos primary energy usage with nuclear and hydropower comprising 8 and 3 and the renewable sources of geothermal solar tidal wind and wood waste amounting to a bit over 1 collectively An obvious question is what has made fossil fuels so attractive as an energy source in the past as well as today and why is it so difficult to move away from them despite the mounting evidence of the environmental problems they pose The answer is For example coal oil and gas have at least 200 times the energy per kilogram that is stored in a lead acid car battery Fossil fuels represent highly concentrated stores of energy compared to the much more dilute concentrations typical of renewablecheaply collected stored shipped and used where and when desired than most renewable energy sources

COAL

Composition of Coal Coal is a combustible sedimentary rock It differs from other kinds of rocks which are generally made of minerals and hence inorganic by definition Coal however is mostly carbon made

10

primarily from plant material and is therefore organic While carbon may be its primary component it does contain minor amounts of hydrocarbons like methane and inorganic mineral material that are considered impurities Coal does not have a specific chemical composition because the precise mixture of sulfur oxygen hydrogen nitrogen and other elements comprising it varies according to the particular rank or grade of coal and even within a grade For example for anthracite the highest and hardest rank of coal its composition includes 0ndash375 hydrogen 0ndash25 oxygen and up to around 16 sulfur Although the number of coal ranks depends on the classification system one system that is widely used is based on the four grades listed in Table 21

Coal is generally cheaper than oil whereas natural gas is more expensive The difference in price reflects the different costs of recovery storage and transport Nuclear fuel refined for use in nuclear electric power plants is less expensive than fossil fuels per unit of heating value

The energy believed to be present in the worldrsquos coal supply dwarfs all

other fossil fuels combined and it has been estimated at 29 times 1020 kJ most of which is not economically exploitable

11

Example Energy Content of Coal

An empirically determined formula for the energy content of coal based on the elemental abundances of carbon hydrogen oxygen and sulfur is

E = 337C + 1442(H minusO8) + 93S (21)

where E is in units of kJkg and the symbols stand for the mass percentages of the elements C H O and S Use Equation 21 and the information provided earlier about anthracite ie H = 0ndash375 O = 0ndash25 and S = 1 to estimate the highest value lowest value and average value of the energy content of anthracite assuming that no elements besides C H O and S are present

Solution

Based on the values of the constants in Equation 21 the maximum

energy density requires H be as high as possible and O is as low as possible and the minimum energy requires the opposite Thus using the data from Table 21 we have

12

As a check we note that these values are fairly close to those provided in

Table 21 for anthracite

Figure below shows energy consumption by the world in 2008

Figure hellip world consumption of energy 2008

13

Figure

3ed lecture

Electricity Generation from Coal

All three fossil fuels can be used for electricity generation but petroleum is used mostly in other sectors (petrochemicals and transportation fuels) and coal tends to be the dominant fossil fuel source for electricity generation There are many possible reasons however why a nation (such as Germany or Japan) might wish to use natural gas or even oil to generate electric power instead of coal even though coal in the past has been the cheaper alternativemdashignoring ldquoexternalrdquo (environmental) costs These reasons include concern for the environment and human health lack of abundant domestic coal reserves and greater ease of transport of oil and gas through existing pipelines or nearby ports

14

Figure 27 Basic components of a coal-fired power plant

15

Example

Total consumption of gas oil and coal in the United States in 2004 measured 238 426 and 240 EJ of energy content respectively

(A) Calculate the ratio of reserves to energy consumption for the United States for these three resources (B) Discuss the validity of this calculation

Solution

From Table 5-4 the total reserves for the United States are 195 115 and 6750 EJ respectively Therefore the ratios are 85 28 and 301 for the three fuels This calculation implies that at current rates without considering other circumstances the gas reserves will be consumed in 85 years and the oil reserves in 28 years while the coal reserves will last for more than three centuries

16

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Example 2 Which Solar Panels Are Superior

Suppose that ten type A solar panels produced enough power for your electricity

needs had a lifetime of 30 years cost only $1000 but they had an efficiency of only 5 Five type B panels cost $5000 but they had an efficiency of 10 and lasted only 15 not 30 years Which panels should you buy

Solution

Obviously the more efficient panels would take up only half the area on your roof than the type A panels but who cares if they both met your needs The cost over a 30 year period would be $1000 for the type A panels but $10000 for the more efficient type B panels that produced the same amount of power (since they last

8

only half as long) so clearly you would opt for the less efficient choice in this case As a general rule as long as the fuel is free and there are no differences in labor or maintenance costs your primary consideration would almost always be based on cost per unit energy generated over some fixed period of timemdashusually the lifetime of the longer-lived alternative

Example 3 How the Usage of Wind Power to Offset Coal-Fired Plants Can Generate More Emissions Not Less

Suppose that a certain fraction of the power produced by a 500 MW coal

plant is offset by wind power Assume that when the coal plant runs at its

constant rated power it has an efficiency of 35 but that when it needs

to be ramped up and down to compensate for the wind power variations

its efficiency is reduced by according to e = 035 minus 000001p2 where p is

the amount of wind power Find the percentage increase in emissions that

results when 90 MW of the 500 MW is generated by wind power instead

of coal

Solution

In order to generate the full 500 MW by itself the coal plant requires 500035 = 1429 MW of heat flow from the coal If the wind power is 90 MW the efficiency of the coal plant is reduced to e = 035 minus 000001(90)2 = 0269 and the heat flow required to generate (500 minus 90) = 410 MW is therefore 410(0269) = 1524 MW The percentage increase in emissions is the same as the percentage increase in the heat flow to the coal plant ie 67

9

Problem 1 Using the data in Example 3 find the amount of wind power that could be used with a 500 MW coal-fired plant that would result in the least

amount of emissions

Fossil Fuels

Most fossil fuels which include coal oil and natural gas were formed from the remains of ancient life over the course of tens to hundreds of millions of yearsmdashhence the adjective fossil Today fossil fuels account for totally 85 of the worldrsquos primary energy usage with nuclear and hydropower comprising 8 and 3 and the renewable sources of geothermal solar tidal wind and wood waste amounting to a bit over 1 collectively An obvious question is what has made fossil fuels so attractive as an energy source in the past as well as today and why is it so difficult to move away from them despite the mounting evidence of the environmental problems they pose The answer is For example coal oil and gas have at least 200 times the energy per kilogram that is stored in a lead acid car battery Fossil fuels represent highly concentrated stores of energy compared to the much more dilute concentrations typical of renewablecheaply collected stored shipped and used where and when desired than most renewable energy sources

COAL

Composition of Coal Coal is a combustible sedimentary rock It differs from other kinds of rocks which are generally made of minerals and hence inorganic by definition Coal however is mostly carbon made

10

primarily from plant material and is therefore organic While carbon may be its primary component it does contain minor amounts of hydrocarbons like methane and inorganic mineral material that are considered impurities Coal does not have a specific chemical composition because the precise mixture of sulfur oxygen hydrogen nitrogen and other elements comprising it varies according to the particular rank or grade of coal and even within a grade For example for anthracite the highest and hardest rank of coal its composition includes 0ndash375 hydrogen 0ndash25 oxygen and up to around 16 sulfur Although the number of coal ranks depends on the classification system one system that is widely used is based on the four grades listed in Table 21

Coal is generally cheaper than oil whereas natural gas is more expensive The difference in price reflects the different costs of recovery storage and transport Nuclear fuel refined for use in nuclear electric power plants is less expensive than fossil fuels per unit of heating value

The energy believed to be present in the worldrsquos coal supply dwarfs all

other fossil fuels combined and it has been estimated at 29 times 1020 kJ most of which is not economically exploitable

11

Example Energy Content of Coal

An empirically determined formula for the energy content of coal based on the elemental abundances of carbon hydrogen oxygen and sulfur is

E = 337C + 1442(H minusO8) + 93S (21)

where E is in units of kJkg and the symbols stand for the mass percentages of the elements C H O and S Use Equation 21 and the information provided earlier about anthracite ie H = 0ndash375 O = 0ndash25 and S = 1 to estimate the highest value lowest value and average value of the energy content of anthracite assuming that no elements besides C H O and S are present

Solution

Based on the values of the constants in Equation 21 the maximum

energy density requires H be as high as possible and O is as low as possible and the minimum energy requires the opposite Thus using the data from Table 21 we have

12

As a check we note that these values are fairly close to those provided in

Table 21 for anthracite

Figure below shows energy consumption by the world in 2008

Figure hellip world consumption of energy 2008

13

Figure

3ed lecture

Electricity Generation from Coal

All three fossil fuels can be used for electricity generation but petroleum is used mostly in other sectors (petrochemicals and transportation fuels) and coal tends to be the dominant fossil fuel source for electricity generation There are many possible reasons however why a nation (such as Germany or Japan) might wish to use natural gas or even oil to generate electric power instead of coal even though coal in the past has been the cheaper alternativemdashignoring ldquoexternalrdquo (environmental) costs These reasons include concern for the environment and human health lack of abundant domestic coal reserves and greater ease of transport of oil and gas through existing pipelines or nearby ports

14

Figure 27 Basic components of a coal-fired power plant

15

Example

Total consumption of gas oil and coal in the United States in 2004 measured 238 426 and 240 EJ of energy content respectively

(A) Calculate the ratio of reserves to energy consumption for the United States for these three resources (B) Discuss the validity of this calculation

Solution

From Table 5-4 the total reserves for the United States are 195 115 and 6750 EJ respectively Therefore the ratios are 85 28 and 301 for the three fuels This calculation implies that at current rates without considering other circumstances the gas reserves will be consumed in 85 years and the oil reserves in 28 years while the coal reserves will last for more than three centuries

16

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

only half as long) so clearly you would opt for the less efficient choice in this case As a general rule as long as the fuel is free and there are no differences in labor or maintenance costs your primary consideration would almost always be based on cost per unit energy generated over some fixed period of timemdashusually the lifetime of the longer-lived alternative

Example 3 How the Usage of Wind Power to Offset Coal-Fired Plants Can Generate More Emissions Not Less

Suppose that a certain fraction of the power produced by a 500 MW coal

plant is offset by wind power Assume that when the coal plant runs at its

constant rated power it has an efficiency of 35 but that when it needs

to be ramped up and down to compensate for the wind power variations

its efficiency is reduced by according to e = 035 minus 000001p2 where p is

the amount of wind power Find the percentage increase in emissions that

results when 90 MW of the 500 MW is generated by wind power instead

of coal

Solution

In order to generate the full 500 MW by itself the coal plant requires 500035 = 1429 MW of heat flow from the coal If the wind power is 90 MW the efficiency of the coal plant is reduced to e = 035 minus 000001(90)2 = 0269 and the heat flow required to generate (500 minus 90) = 410 MW is therefore 410(0269) = 1524 MW The percentage increase in emissions is the same as the percentage increase in the heat flow to the coal plant ie 67

9

Problem 1 Using the data in Example 3 find the amount of wind power that could be used with a 500 MW coal-fired plant that would result in the least

amount of emissions

Fossil Fuels

Most fossil fuels which include coal oil and natural gas were formed from the remains of ancient life over the course of tens to hundreds of millions of yearsmdashhence the adjective fossil Today fossil fuels account for totally 85 of the worldrsquos primary energy usage with nuclear and hydropower comprising 8 and 3 and the renewable sources of geothermal solar tidal wind and wood waste amounting to a bit over 1 collectively An obvious question is what has made fossil fuels so attractive as an energy source in the past as well as today and why is it so difficult to move away from them despite the mounting evidence of the environmental problems they pose The answer is For example coal oil and gas have at least 200 times the energy per kilogram that is stored in a lead acid car battery Fossil fuels represent highly concentrated stores of energy compared to the much more dilute concentrations typical of renewablecheaply collected stored shipped and used where and when desired than most renewable energy sources

COAL

Composition of Coal Coal is a combustible sedimentary rock It differs from other kinds of rocks which are generally made of minerals and hence inorganic by definition Coal however is mostly carbon made

10

primarily from plant material and is therefore organic While carbon may be its primary component it does contain minor amounts of hydrocarbons like methane and inorganic mineral material that are considered impurities Coal does not have a specific chemical composition because the precise mixture of sulfur oxygen hydrogen nitrogen and other elements comprising it varies according to the particular rank or grade of coal and even within a grade For example for anthracite the highest and hardest rank of coal its composition includes 0ndash375 hydrogen 0ndash25 oxygen and up to around 16 sulfur Although the number of coal ranks depends on the classification system one system that is widely used is based on the four grades listed in Table 21

Coal is generally cheaper than oil whereas natural gas is more expensive The difference in price reflects the different costs of recovery storage and transport Nuclear fuel refined for use in nuclear electric power plants is less expensive than fossil fuels per unit of heating value

The energy believed to be present in the worldrsquos coal supply dwarfs all

other fossil fuels combined and it has been estimated at 29 times 1020 kJ most of which is not economically exploitable

11

Example Energy Content of Coal

An empirically determined formula for the energy content of coal based on the elemental abundances of carbon hydrogen oxygen and sulfur is

E = 337C + 1442(H minusO8) + 93S (21)

where E is in units of kJkg and the symbols stand for the mass percentages of the elements C H O and S Use Equation 21 and the information provided earlier about anthracite ie H = 0ndash375 O = 0ndash25 and S = 1 to estimate the highest value lowest value and average value of the energy content of anthracite assuming that no elements besides C H O and S are present

Solution

Based on the values of the constants in Equation 21 the maximum

energy density requires H be as high as possible and O is as low as possible and the minimum energy requires the opposite Thus using the data from Table 21 we have

12

As a check we note that these values are fairly close to those provided in

Table 21 for anthracite

Figure below shows energy consumption by the world in 2008

Figure hellip world consumption of energy 2008

13

Figure

3ed lecture

Electricity Generation from Coal

All three fossil fuels can be used for electricity generation but petroleum is used mostly in other sectors (petrochemicals and transportation fuels) and coal tends to be the dominant fossil fuel source for electricity generation There are many possible reasons however why a nation (such as Germany or Japan) might wish to use natural gas or even oil to generate electric power instead of coal even though coal in the past has been the cheaper alternativemdashignoring ldquoexternalrdquo (environmental) costs These reasons include concern for the environment and human health lack of abundant domestic coal reserves and greater ease of transport of oil and gas through existing pipelines or nearby ports

14

Figure 27 Basic components of a coal-fired power plant

15

Example

Total consumption of gas oil and coal in the United States in 2004 measured 238 426 and 240 EJ of energy content respectively

(A) Calculate the ratio of reserves to energy consumption for the United States for these three resources (B) Discuss the validity of this calculation

Solution

From Table 5-4 the total reserves for the United States are 195 115 and 6750 EJ respectively Therefore the ratios are 85 28 and 301 for the three fuels This calculation implies that at current rates without considering other circumstances the gas reserves will be consumed in 85 years and the oil reserves in 28 years while the coal reserves will last for more than three centuries

16

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Problem 1 Using the data in Example 3 find the amount of wind power that could be used with a 500 MW coal-fired plant that would result in the least

amount of emissions

Fossil Fuels

Most fossil fuels which include coal oil and natural gas were formed from the remains of ancient life over the course of tens to hundreds of millions of yearsmdashhence the adjective fossil Today fossil fuels account for totally 85 of the worldrsquos primary energy usage with nuclear and hydropower comprising 8 and 3 and the renewable sources of geothermal solar tidal wind and wood waste amounting to a bit over 1 collectively An obvious question is what has made fossil fuels so attractive as an energy source in the past as well as today and why is it so difficult to move away from them despite the mounting evidence of the environmental problems they pose The answer is For example coal oil and gas have at least 200 times the energy per kilogram that is stored in a lead acid car battery Fossil fuels represent highly concentrated stores of energy compared to the much more dilute concentrations typical of renewablecheaply collected stored shipped and used where and when desired than most renewable energy sources

COAL

Composition of Coal Coal is a combustible sedimentary rock It differs from other kinds of rocks which are generally made of minerals and hence inorganic by definition Coal however is mostly carbon made

10

primarily from plant material and is therefore organic While carbon may be its primary component it does contain minor amounts of hydrocarbons like methane and inorganic mineral material that are considered impurities Coal does not have a specific chemical composition because the precise mixture of sulfur oxygen hydrogen nitrogen and other elements comprising it varies according to the particular rank or grade of coal and even within a grade For example for anthracite the highest and hardest rank of coal its composition includes 0ndash375 hydrogen 0ndash25 oxygen and up to around 16 sulfur Although the number of coal ranks depends on the classification system one system that is widely used is based on the four grades listed in Table 21

Coal is generally cheaper than oil whereas natural gas is more expensive The difference in price reflects the different costs of recovery storage and transport Nuclear fuel refined for use in nuclear electric power plants is less expensive than fossil fuels per unit of heating value

The energy believed to be present in the worldrsquos coal supply dwarfs all

other fossil fuels combined and it has been estimated at 29 times 1020 kJ most of which is not economically exploitable

11

Example Energy Content of Coal

An empirically determined formula for the energy content of coal based on the elemental abundances of carbon hydrogen oxygen and sulfur is

E = 337C + 1442(H minusO8) + 93S (21)

where E is in units of kJkg and the symbols stand for the mass percentages of the elements C H O and S Use Equation 21 and the information provided earlier about anthracite ie H = 0ndash375 O = 0ndash25 and S = 1 to estimate the highest value lowest value and average value of the energy content of anthracite assuming that no elements besides C H O and S are present

Solution

Based on the values of the constants in Equation 21 the maximum

energy density requires H be as high as possible and O is as low as possible and the minimum energy requires the opposite Thus using the data from Table 21 we have

12

As a check we note that these values are fairly close to those provided in

Table 21 for anthracite

Figure below shows energy consumption by the world in 2008

Figure hellip world consumption of energy 2008

13

Figure

3ed lecture

Electricity Generation from Coal

All three fossil fuels can be used for electricity generation but petroleum is used mostly in other sectors (petrochemicals and transportation fuels) and coal tends to be the dominant fossil fuel source for electricity generation There are many possible reasons however why a nation (such as Germany or Japan) might wish to use natural gas or even oil to generate electric power instead of coal even though coal in the past has been the cheaper alternativemdashignoring ldquoexternalrdquo (environmental) costs These reasons include concern for the environment and human health lack of abundant domestic coal reserves and greater ease of transport of oil and gas through existing pipelines or nearby ports

14

Figure 27 Basic components of a coal-fired power plant

15

Example

Total consumption of gas oil and coal in the United States in 2004 measured 238 426 and 240 EJ of energy content respectively

(A) Calculate the ratio of reserves to energy consumption for the United States for these three resources (B) Discuss the validity of this calculation

Solution

From Table 5-4 the total reserves for the United States are 195 115 and 6750 EJ respectively Therefore the ratios are 85 28 and 301 for the three fuels This calculation implies that at current rates without considering other circumstances the gas reserves will be consumed in 85 years and the oil reserves in 28 years while the coal reserves will last for more than three centuries

16

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

primarily from plant material and is therefore organic While carbon may be its primary component it does contain minor amounts of hydrocarbons like methane and inorganic mineral material that are considered impurities Coal does not have a specific chemical composition because the precise mixture of sulfur oxygen hydrogen nitrogen and other elements comprising it varies according to the particular rank or grade of coal and even within a grade For example for anthracite the highest and hardest rank of coal its composition includes 0ndash375 hydrogen 0ndash25 oxygen and up to around 16 sulfur Although the number of coal ranks depends on the classification system one system that is widely used is based on the four grades listed in Table 21

Coal is generally cheaper than oil whereas natural gas is more expensive The difference in price reflects the different costs of recovery storage and transport Nuclear fuel refined for use in nuclear electric power plants is less expensive than fossil fuels per unit of heating value

The energy believed to be present in the worldrsquos coal supply dwarfs all

other fossil fuels combined and it has been estimated at 29 times 1020 kJ most of which is not economically exploitable

11

Example Energy Content of Coal

An empirically determined formula for the energy content of coal based on the elemental abundances of carbon hydrogen oxygen and sulfur is

E = 337C + 1442(H minusO8) + 93S (21)

where E is in units of kJkg and the symbols stand for the mass percentages of the elements C H O and S Use Equation 21 and the information provided earlier about anthracite ie H = 0ndash375 O = 0ndash25 and S = 1 to estimate the highest value lowest value and average value of the energy content of anthracite assuming that no elements besides C H O and S are present

Solution

Based on the values of the constants in Equation 21 the maximum

energy density requires H be as high as possible and O is as low as possible and the minimum energy requires the opposite Thus using the data from Table 21 we have

12

As a check we note that these values are fairly close to those provided in

Table 21 for anthracite

Figure below shows energy consumption by the world in 2008

Figure hellip world consumption of energy 2008

13

Figure

3ed lecture

Electricity Generation from Coal

All three fossil fuels can be used for electricity generation but petroleum is used mostly in other sectors (petrochemicals and transportation fuels) and coal tends to be the dominant fossil fuel source for electricity generation There are many possible reasons however why a nation (such as Germany or Japan) might wish to use natural gas or even oil to generate electric power instead of coal even though coal in the past has been the cheaper alternativemdashignoring ldquoexternalrdquo (environmental) costs These reasons include concern for the environment and human health lack of abundant domestic coal reserves and greater ease of transport of oil and gas through existing pipelines or nearby ports

14

Figure 27 Basic components of a coal-fired power plant

15

Example

Total consumption of gas oil and coal in the United States in 2004 measured 238 426 and 240 EJ of energy content respectively

(A) Calculate the ratio of reserves to energy consumption for the United States for these three resources (B) Discuss the validity of this calculation

Solution

From Table 5-4 the total reserves for the United States are 195 115 and 6750 EJ respectively Therefore the ratios are 85 28 and 301 for the three fuels This calculation implies that at current rates without considering other circumstances the gas reserves will be consumed in 85 years and the oil reserves in 28 years while the coal reserves will last for more than three centuries

16

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Example Energy Content of Coal

An empirically determined formula for the energy content of coal based on the elemental abundances of carbon hydrogen oxygen and sulfur is

E = 337C + 1442(H minusO8) + 93S (21)

where E is in units of kJkg and the symbols stand for the mass percentages of the elements C H O and S Use Equation 21 and the information provided earlier about anthracite ie H = 0ndash375 O = 0ndash25 and S = 1 to estimate the highest value lowest value and average value of the energy content of anthracite assuming that no elements besides C H O and S are present

Solution

Based on the values of the constants in Equation 21 the maximum

energy density requires H be as high as possible and O is as low as possible and the minimum energy requires the opposite Thus using the data from Table 21 we have

12

As a check we note that these values are fairly close to those provided in

Table 21 for anthracite

Figure below shows energy consumption by the world in 2008

Figure hellip world consumption of energy 2008

13

Figure

3ed lecture

Electricity Generation from Coal

All three fossil fuels can be used for electricity generation but petroleum is used mostly in other sectors (petrochemicals and transportation fuels) and coal tends to be the dominant fossil fuel source for electricity generation There are many possible reasons however why a nation (such as Germany or Japan) might wish to use natural gas or even oil to generate electric power instead of coal even though coal in the past has been the cheaper alternativemdashignoring ldquoexternalrdquo (environmental) costs These reasons include concern for the environment and human health lack of abundant domestic coal reserves and greater ease of transport of oil and gas through existing pipelines or nearby ports

14

Figure 27 Basic components of a coal-fired power plant

15

Example

Total consumption of gas oil and coal in the United States in 2004 measured 238 426 and 240 EJ of energy content respectively

(A) Calculate the ratio of reserves to energy consumption for the United States for these three resources (B) Discuss the validity of this calculation

Solution

From Table 5-4 the total reserves for the United States are 195 115 and 6750 EJ respectively Therefore the ratios are 85 28 and 301 for the three fuels This calculation implies that at current rates without considering other circumstances the gas reserves will be consumed in 85 years and the oil reserves in 28 years while the coal reserves will last for more than three centuries

16

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

As a check we note that these values are fairly close to those provided in

Table 21 for anthracite

Figure below shows energy consumption by the world in 2008

Figure hellip world consumption of energy 2008

13

Figure

3ed lecture

Electricity Generation from Coal

All three fossil fuels can be used for electricity generation but petroleum is used mostly in other sectors (petrochemicals and transportation fuels) and coal tends to be the dominant fossil fuel source for electricity generation There are many possible reasons however why a nation (such as Germany or Japan) might wish to use natural gas or even oil to generate electric power instead of coal even though coal in the past has been the cheaper alternativemdashignoring ldquoexternalrdquo (environmental) costs These reasons include concern for the environment and human health lack of abundant domestic coal reserves and greater ease of transport of oil and gas through existing pipelines or nearby ports

14

Figure 27 Basic components of a coal-fired power plant

15

Example

Total consumption of gas oil and coal in the United States in 2004 measured 238 426 and 240 EJ of energy content respectively

(A) Calculate the ratio of reserves to energy consumption for the United States for these three resources (B) Discuss the validity of this calculation

Solution

From Table 5-4 the total reserves for the United States are 195 115 and 6750 EJ respectively Therefore the ratios are 85 28 and 301 for the three fuels This calculation implies that at current rates without considering other circumstances the gas reserves will be consumed in 85 years and the oil reserves in 28 years while the coal reserves will last for more than three centuries

16

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Figure

3ed lecture

Electricity Generation from Coal

All three fossil fuels can be used for electricity generation but petroleum is used mostly in other sectors (petrochemicals and transportation fuels) and coal tends to be the dominant fossil fuel source for electricity generation There are many possible reasons however why a nation (such as Germany or Japan) might wish to use natural gas or even oil to generate electric power instead of coal even though coal in the past has been the cheaper alternativemdashignoring ldquoexternalrdquo (environmental) costs These reasons include concern for the environment and human health lack of abundant domestic coal reserves and greater ease of transport of oil and gas through existing pipelines or nearby ports

14

Figure 27 Basic components of a coal-fired power plant

15

Example

Total consumption of gas oil and coal in the United States in 2004 measured 238 426 and 240 EJ of energy content respectively

(A) Calculate the ratio of reserves to energy consumption for the United States for these three resources (B) Discuss the validity of this calculation

Solution

From Table 5-4 the total reserves for the United States are 195 115 and 6750 EJ respectively Therefore the ratios are 85 28 and 301 for the three fuels This calculation implies that at current rates without considering other circumstances the gas reserves will be consumed in 85 years and the oil reserves in 28 years while the coal reserves will last for more than three centuries

16

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Figure 27 Basic components of a coal-fired power plant

15

Example

Total consumption of gas oil and coal in the United States in 2004 measured 238 426 and 240 EJ of energy content respectively

(A) Calculate the ratio of reserves to energy consumption for the United States for these three resources (B) Discuss the validity of this calculation

Solution

From Table 5-4 the total reserves for the United States are 195 115 and 6750 EJ respectively Therefore the ratios are 85 28 and 301 for the three fuels This calculation implies that at current rates without considering other circumstances the gas reserves will be consumed in 85 years and the oil reserves in 28 years while the coal reserves will last for more than three centuries

16

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Example

Total consumption of gas oil and coal in the United States in 2004 measured 238 426 and 240 EJ of energy content respectively

(A) Calculate the ratio of reserves to energy consumption for the United States for these three resources (B) Discuss the validity of this calculation

Solution

From Table 5-4 the total reserves for the United States are 195 115 and 6750 EJ respectively Therefore the ratios are 85 28 and 301 for the three fuels This calculation implies that at current rates without considering other circumstances the gas reserves will be consumed in 85 years and the oil reserves in 28 years while the coal reserves will last for more than three centuries

16

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Question

can you represent the above figure in any heat cycle (eg Carnothellipetc) How

Apart from steam-powered locomotives powered by coal transportation fuels are generally either liquids or gases A gaseous fuel syngasrdquo(short for synthetic gas which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor The syngas reaction known as coal gasification is

Coal +O2 + H2O=H2 + CO

Although syngas can be used on its own as a transportation fuel its energy content is only about half that of natural gas so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells The conversion to a liquid akin to gasoline or diesel can be done through the FischerndashTropsch (FndashT) process which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons The process is still being used by South Africa today to make synthetic gasoline from coalmdasha process that accounts for 30 of their fuel needs In most other nations production of synthetic fuels usually starts from natural gas

17

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

rather than coalmdashthis currently being the more economical alternativeHow In fact one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015

Atmospheric Emissions from Coal Power Plants

Coal-fired power plants are prodigious emitters of pollution although newer plants using ldquoscrubbersrdquo to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions Nevertheless as can be seen from Table 22 coal is still the dirtiest of the fossil fuels For example compared to gas-fired power plants coal plants emit 1200 times more particulates and nearly double the CO2 Is that reasonable

PETROLEUM AND NATURAL GAS

Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules Its elemental composition includes 83ndash87 carbon 10ndash14 hydrogen 0ndash6 sulfur and under 2 nitrogen and

18

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

oxygen Natural gas is a gaseous hydrocarbon primarily methane CH4 with up to 20 higher hydrocarbons primarily ethane

API Gravity

The gravity of crude oil determines its price commercially It is generally

expressed as API gravity defined as

API = (1415SG)-1315 60F

Table below is a classification of crude

Products of oil

1-Liquefied Petroleum Gas (LPG)

19

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation They include thane ethylene propane propylene normal butane butylene isobutane and isobutylene For convenience of transportation these gases are liquefied through pressurization

2 Gasoline

Gasoline is classified by octane ratings (conventional oxygenated and

reformulated) into three grades Regular Midgrade and Premium

-Regular gasoline Gasoline having an antiknock index ie octane

rating greater than or equal to 85 and less than 88

- Mid-grade gasoline Gasoline having octane rating greater than or

equal to 88 and less than or equal to 90

-Premium gasoline Gasoline having octane rating greater than 90

Premium and regular grade motor gasoline are used depending on the

octane rating In addition aviation gasoline which is a complex mixture

of relatively volatile hydrocarbons is blended with additives to form suitable fuel for aviation engines

3Kerosene

Kerosene is a light petroleum distillate that is used in space heaters cook stoves and water heaters and which is suitable for use as a light

20

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

source Kerosene has a maximum distillation temperature of 204 C (400F) at the 10 recovery point a final boiling point of 300 C (572 F) and a minimum flash point of 378 C (100 F) The two grades are recognized by ASTM Specification D3699 A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10 recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655

21

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Figure

4Jet Fuel

This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units

5 Diesel Fuel

The quality of diesel fuels can be expressed as cetane number or cetane index The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality Diesel fuel includes No1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines trucks and buses No 2 diesel has 40 cetane number Railroad diesel fuels are similar to the heavier automotive diesel fuels but have higher boiling ranges upto 400 C (750 F) and lower cetane numbers (CN = 30)

6 Fuel Oil

The fuel oils are mainly used in space heating and thus the market is

quite high specially in cold climates No 1 fuel oil is similar to kerosene

22

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

and No 2 fuel oil is very similar to No 2 diesel fuel Heavier grades of

No 3 and 4 are also available

7 Residual Fuel Oil

It is mainly composed of vacuum residue Critical specifications are viscosity and sulphur content Low sulphur residues are in more demand in the market

8 Lube Oil

Lubricants are based on the viscosity index Paraffinic and naphthenic

lubricants have a finished viscosity index of more than 75

9 Asphalt

Asphalt is an important product in the construction industry and comprises upto 20 of products It can be produced only from crude containing asphaltenic material

10 Petroleum Coke

Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes Fuel grade coke contains about 85 carbon and 4 hydrogen The balance is made up of sulphur nitrogen oxygen vanadium and nickel

23

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Example 1

You have a natural gas furnace in your home that used 81300 cubic feet of natural gas for heating last winter Your neighbor has a furnace that burns heating oil that used 584 gallons of heating oil last winter You can convert the natural gas and heating oil consumption data into Btu to determine which home used more energy for heating

Natural gas 81300 cubic feet (your home) x 1032 Btu per cubic foot = 83901600 Btu

Heating oil 584 gallons (neighbors home) x 138500 Btu per gallon = 80884000 Btu

Result You used more energy to heat your home

Example 2

You need a new furnace for your home and you are comparing heating systems that use natural gas with systems that use heating oil One factor to consider is the cost of the fuels You can compare the price of the fuels on an equal basis by dividing the price per unit of the fuels by the Btu content of the fuels in million Btu per unit to get the price in dollars per million Btu

Natural gas $1040 per thousand cubic feet divide 1032 million Btu per thousand cubic feet = $1008 per million Btu

Example

Calculate the energy released from combusting CH4 per kilogram of CO2 released to the atmosphere in units of MJkg CO2

24

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Solution

In order to solve for MJkg CO2 recall that the molecular mass of an atom of carbon is 12 that of oxygen is 16 and that of hydrogen is 1 Therefore the mass of a kilogram-mole of each of these elements is 12 kg 16 kg and 1 kg respectively The mass of a kilogram-mole of CH4 is therefore 16 kg and the mass of a kilogram-mole of CO2 is 44 kg so the amount of energy released per unit of CO2 emitted to the atmosphere is 50 MJkg times (1644) = 182 MJkg CO2Repeating this calculation for gasoline gives 161 MJkg CO2 and for coal gives 818 MJkg CO2

Production or Extraction of Petroleum

The first stage in the extraction of crude oil is to drill a well into the underground reservoir

1-Primary oil recovery

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure Gaseous fuels or natural gas are usually present which also supply needed underground pressure In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing This is called primary oil recovery Usually only about 20 of the oil in a reservoir can be extracted this way

2-Secondary oil recovery

25

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Over the lifetime of the well the pressure will fall and at some point there will be insufficient underground pressure to force the oil to the surface If economical and it often is the remaining oil in the well is extracted using secondary oil recovery methods Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs Sometimes pumps such as beam pumps and electrical submersible pumps are used to bring the oil to the surface Other secondary recovery techniques increase the reservoirrsquos pressure by water injection natural gas re-injection and gas lift which injects air carbon dioxide or some other gas into the reservoir Together primary and secondary recovery allow 25 to 35 of the reservoirrsquos oil to be recovered

3 Tertiary oil recovery

Tertiary oil recovery reduces the oilrsquos viscosity to increase oil production Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production but only when the oil can still be extracted profitably This depends on the cost of the extraction method and the current price of crude oil When prices are high previously unprofitable wells are brought back into production and when they are low production is curtailed Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract

1048707 Steam injection is the most common form of TEOR and is often done with a cogeneration plant In this type of cogeneration plant a gas turbine is used to generate electricity and the waste heat is used to produce steam which is then injected into the reservoir

26

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

1048707 In-situ burning is another form of TEOR but instead of steam some of the oil is burned to heat the surrounding oil

1048707 Occasionally detergents are also used to decrease oil viscosity

Tertiary recovery allows another 5 to 15 of the reservoirrsquos oil to be recovered

Some properties of oils should be looked from the following

1-pour point

The pour point is defined as the lowest temperature at which the sample will flow It indicates how easy or difficult it is to pump the oil especially in cold weather It also indicates the aromaticity or the paraffinity of the crude oil or the fraction A lower pour point means that the paraffin content is low

2-Viscosity

The resistance to flow or the pumpability of the crude oil or petroleum

fraction is indicated by the viscosity More viscous oils create a greater

pressure drop when they flow in pipes

3-Freezing Point

Petroleum fractions are mostly liquids at ambient conditions However heavy oils contain heavy compounds such as waxes or asphaltenes These compounds tend to solidify at low temperatures thus restricting flow The freezing point is the temperature at which the hydrocarbon liquid solidifies at atmospheric pressure It is one of the important

27

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

property specifications for kerosene and jet fuels due to the very low temperatures encountered at high altitudes in jet planes

4-Aniline Point

The lowest temperature at which an equal volume mixture of the petroleum

oil and aniline are miscible is the aniline point

5-Octane number

An octane number is a measure of the knocking tendency of gasoline fuels in spark ignition engines The ability of a fuel to resist auto-ignition during compression and prior to the spark ignition gives it a high octane number

6-Cetane Number

The cetane number measures the ability for auto ignition and is essentially the opposite of the octane number The cetane number is the percentage of pure cetane (n-hexadecane) in a blend of cetane and alpha methyl naphthalene which matches the ignition quality of a diesel fuel sample

7-Smoke Point

The smoke point is a test measures the burning qualities of kerosene and jet

28

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

fuel It is defined as the maximum height in mm of a smokeless flame of

fuel

8-Water Salt and Sediment

Crude oil contains small amounts of water mineral salts and sediments Most of the salts are dissolved in the water and the remainder is present in the oil as fine crystals Chlorides of magnesium calcium and sodium are the most common salts The presence of salts causes problems in processing such as corrosion erosion and plugging of equipment and catalyst deactivation Sediments are solid material that are not soluble in the hydrocarbon or water and can be comprised of sand drilling mud rock or minerals coming from erosion of metal pipes tanks and equipment

9-Molecular Weight

Most crude oils and petroleum fractions have average molecular weights

from 100 to 500

Example showing the yield and the waste

29

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Kerogen or shale oil has been proposed as a potential liquid fuel source The ultimate analysis of a typical 1-ton sample of raw shale is given below

Raw shale constituent Percentage

Ash 657

CO2 189

Organic carbon 124

H2 18

N2 04

Sulfur 06

H2O 02

Using these percentages determine (1) the dry and ash less gravimetric analysis of the shale

Solution

1 Mass fraction where lbm mixt = lbm total ndash lbm H2O ndash lbm ash

30

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

The values of API can be corrected to another temperature using the following formula

APIdeg 60 = [0002 (60 minus observeddegF) + 1] times [observed APIdeg]

Another useful property of the fuel is the higher heating value HHV which can be estimated for some products as below Also some value can be found from tables

31

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Fuel oil HHV = 43380 + 93 (API - 10) kJkg

Kerosene HHV = 42890 + 93 (API - 10) kJkg

Gasoline HHV = 42612 + 93 (API - 10) kJkg

Heavy cracked fuel HHV = 41042 + 126 times API kJkg

Or

Example

The specific gravity of 2 diesel fuel measured at 60degF is found to be

325 API For conditions of 75degF calculate (a) the specific gravity API (b) the density of the fuel lbmft3 (c) the higher heating value of the fuel (d) the

higher heating value from given data ( Appendix) and (e) the heating value using given Figures

Solution

1 Specific gravity

32

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

2-density of fuel from data below with API = 335 SG=0857

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

5 from figure below with API of 335

33

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

34

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Another Empirical equations such as DuLongs formula can be used to predict a higher heating value of solid fuels when an ultimate analysis is known

35

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

Worked example

Assume that the following table gives the mass fractions to the referred components as follows

Then the HHV according to Dulongrsquos formulaIs

=3064 kJkg

Further questions

New lect

Electrochemical Source

36

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37

3 HHV from data below

Approximately=

4 from the equation concerning fuel oil

37