6 natural gas

7/31/2019 6 Natural Gas

1/40

NATURAL GASFROM PRODUCTION TO PROFIT


2/40

WHAT IS NATURAL GAS?

Natural Gas is one of the cleanest, safestand one of the most useful fuel sources

available.

Natural Gas is a combustible mixture of

hydrocarbon gases usually found togetherwith petroleum (associated) or by itself(non-associated)


3/40


Typical Composition of Natural Gas (wet)

Methane CH4 70-90%

Ethane C2H6 Propane C3H8 0-20% Butane C4H10 Carbon Dioxide CO2 0-8% Oxygen O2 0-0.2% Nitrogen N2 0-5% Hydrogen Sulphide H

2

S 0-5% Rare gases Ar, He, Ne, Xe trace

Natural gas is considered 'dry' when it is almost pure methane,having had most of the other commonly associated hydrocarbonsremoved. When other hydrocarbons are present, the natural gasis 'wet'.


4/40


Dried Natural Gas is primarily pure Methane, which combust as:

CH4[g] + 2 O2[g] -> CO2[g] + 2 H2O[l] + 802 kJ

In more familiar units this is equivalent to 191 kilocalories per 16grams of methane. This is a little more than the 150 calories in acan of Coke.

The heat of combustion of one mole of octane is 5508.9 KJ

Unlike Petroleum Fuels which are complex mixtures of

hydrocarbons producing complicated and potentially harmfulproducts of combustion, Natural Gas produces almost exclusivelyCarbon Dioxide and Water.

This makes Natural Gas one of the cleanest burning fuelsavailable.


5/40



6/40

HOW IS NATURAL GASMEASURED?

Natural gas can be measured in a number of different ways.

Production and distribution companies commonly measure natural gas in

thousands of cubic feet (Mcf), millions of cubic feet (MMcf), billions ofcubic feet (Bcf), or trillions of cubic feet (Tcf). Ie. The volume it takes upat normal temperatures and pressures

Natural gas is also commonly measured and expressed in British thermalunits (Btu).

One Btu is the amount of natural gas that will produce enough energy toheat one pound of water by one degree at normal pressure.

One cubic foot of natural gas contains about 1,027 Btus.


7/40

HOW IS NATURAL GAS FORMED?

Natural Gas is formed when petroleum is cracked under hightemperatures and pressures occurring naturally under the earthscrust.

The deeper under the earth's crust, the higher the temperature.

At low temperatures (shallower deposits), more oil is producedrelative to natural gas.

At higher temperatures, however, more natural gas is created, as

opposed to oil.

That is why natural gas is usually associated with oil in depositsthat are 1 to 2 miles below the earth's crust.

Deeper deposits, very far underground, usually contain primarilynatural gas, and in many cases, pure methane.


8/40

HISTORY OF NATURAL GAS

In ancient times, lightning strikes ignitednatural gas seepages, resulting in the

burning bush phenomenon located inmany ancient places of worship such asDelphi in Greece.

The Chinese were the first to use naturalgas as a fuel, transporting it via bamboopipelines where it was used to purify saltwater (distillation)


9/40


The British were the first to us Natural Gascommercially in 1785 as a fuel source forlighting roadways.

This practice continued until the invention ofthe light bulb in the late 1800s, when theuse of natural gas fell out of favor.

In 1885, Robert Bunsen invented the BunsenBurner, which was capable of effectivelymixing Natural Gas and Air to produce a veryhot clean burning blue flame.


10/40


The invention of the Bunsen Burner revolutionized theuse of Natural Gas as a fuel.

However, due to limitations in pipelines, Natural Gasusage was limited to the location of the source of thegas.

In most cases, Natural Gas was considered anuisance gas since it was difficult to transport and itsuses were limited.

The practice of flaring Natural Gas was common atmost oil wells, and where wells produced mostlyNatural Gas, their production was halted.


11/40


The technological advances of WWII lead tonew welding techniques and more reliablepipeline networks.

This lead to Natural Gas usage increasingexponentially for heating and energy uses.

However, Natural Gas could only be usedwhere reliable pipelines were present. This restricted its usage globally.


12/40


The process of liquefying natural gas, firstinvented by Conoco Philips in 1969,revolutionized shipping the fuel.

And for the first time made Natural Gasavailable to countries with limited quantitiesor none of the fuel.

The majority of the worlds Natural Gas aretransported via liquefaction and re-gasification.


13/40

USES OF NATURAL GAS

Natural Gas has many uses as outlinedbelow:


14/40

USES OF NATURAL GAS

RESIDENTAL & COMMERCIAL

Natural Gas is used by over 52% of UShomes for heating. Highly efficient naturalgas furnaces are used to provideresidential heating.

Natural Gas is the primary source ofcommercial heating and 13% ofcommercial Air Conditioning.


15/40

USES OF NATURAL GAS

POWER GENERATION

Various technologies exist for the generationof power from Natural Gas; Steam Generation Centralized Turbines Combined Cycle Units

Gas Fired Turbines Gas Fired Reciprocating Engines Microturbines Fuel Cells


16/40

USES OF NATURAL GAS

TRANSPORTATION

Natural Gas in the form of Compressed Natural Gas is an

increasing source of vehicle fuel.

Engines designed to use Natural Gas exclusively are as efficientas gasoline engines, but produce the lowest possible emissions.

Vehicles that have been converted from Gasoline to Natural Gasor are dual in nature are less efficient.

Fleet vehicles such as buses and trucks more commonly use CNG. Natural Gas vehicles are safer than their gasoline counterparts. In

the case of an accident, CNG will dissipate in air, thus reducingthe possibility of fires.


17/40

USES OF NATURAL GAS

INDUSTRIAL Natural Gas has many industrial uses including:

Heating Cooling Incineration Drying and dehumidification Power Glass melting Metal pre-heating Feedstock in Methanol Manufacture


18/40

NATURAL GAS PRODUCTION

Natural Gas comes from three (3) types of wells:

Oil Wells associated - free or dissolved Gas Wells non-associated Condensate Wells associated

Natural Gas in its raw form contains a mixture of

Light Hydrocarbons as well as Water, HydrogenSulfide and Rare Gases

These impurities must be removed.


19/40


The processing of Natural Gas consists of4 steps

Removal of Oil and Condensate

Removal of Hydrogen Sulphide and

Carbon Dioxide

Removal of Water

Separation of Natural Gas Liquids (NGL)


20/40


REMOVAL OF OIL AND CONDENSATE

The first step in the separation

process involves settling in tanks

at atmospheric pressure.


21/40


Gas is dissolved in Oil at high pressures.By settling at atmospheric pressure, gas

naturally evolves from the oil similar toopening a soft drink bottle.

The gas is collected at the top of thevessel, and the oil is collected at thebottom.


22/40


REMOVAL OF H2S AND CO2

Natural Gas containing >5.7mg/m3 H2S is considered sour.

H2S and other acid gases are removed using the AmineProcess or Girdler Process

This is called Sweetening

Monoethanolamine (MEA) or Diethanolamine (DEA) have astrong affinity for sulfur compounds and acid gases.

The sour gas is flowed through a column containing MEA orDEA.


23/40


The reaction occurring is:

This reaction is reversible, and the amine can beregenerated with the H2S recovered.

Amine absorbs H2S and CO2 at 35-50oC, and

releases H2S and CO2 115-126oC

SHRNHSHRNH22222 .)(2

3222222.)(2 COHRNHOHCORNH


24/40


A typical Amine Treater
http://en.wikipedia.org/wiki/File:AmineTreating.png


25/40


Hydrogen Sulfide removed from Natural Gas via the AmineScrubbers is converted to elemental Sulfur using the ClausProcess

This is a 2 step process:

Thermal Step. The H2S is partially oxidized with air at hightemperatures (1000-1400 deg C). Sulfur is formed, but some H2Sremains unreacted, and some SO2 is made.

Catalytic Step. The remaining H2S is reacted with the SO2 atlower temperatures (about 200-350 deg C) over a catalyst tomake more sulfur.

2H2S + SO2 ==> 3S + 2H2O

Elemental Sulfur is sold as a by-product of the process.


26/40


WATER REMOVAL

Water is removed from he natural GasStream by the use of two processes:

Glycol Dehydration Solid-desiccant dehydration


27/40


Glycol Dehydration

Tri-ethylene Glycol is

mixed with the wet gas.

The Glycol absorbs waterfrom the gas leaving drygas and wet glycol.

The wet glycol is re-generatedby boiling off water andreturned to the process.


28/40


Solid-Desiccant Dehydration

This involves the use of 2columns filled with granular

alumina or silica.

Heated Gas flows through

One of the columns while

The other is regenerated.


29/40


Low Temperature Separator (LTX).

Separation of liquids from Natural Gas can be

achieved by the use of a Low TemperatureSeparator (LTX).

In the LTX Separator, the Natural Gas stream ismaintained at pressures up to 800psi and

temperatures as low as -4oC.

The Natural Gas stream enters a cycloneexpansion valve at a tangent and at about400psi.


30/40


The movement from high pressure to lowpressure at a high speed (close to sound)results in temperature drops down to -18oC.

This is called the Joule-Thompson Process

At this temperature, condensable liquids are

removed by low temperature distillation

The process however is not cool enough toremove ethane and propane from the NaturalGas.


31/40


The separation principle is based on the BP of thehydrocarbons present in Natural Gas.

Name Formula M.P (oC) B.P (oC) State

@25oC

methane CH4 -183 -164 gas ethane C2H6 -183 -89 gas propane C3H8 -190 -42 gas butane C4H10 -138 -0.5 gas pentane C5H12 -130 36 gas

Only by cooling the gas to -91oC, can Methane beseparated from most other components.

This is done later on when NGL are removed.


32/40


NATURAL GAS LIQUID (NGL) REMOVAL

NGLs are valuable products when separated

into its base components such as Ethane,Propane, Butane etc.

They must be first separated from theNatural Gas Stream. Two Processes are used:

The Absorption Process

The Cryogenic Expansion Process


33/40


The Absorption Process

The Natural Gas is contacted with a lean absorption

oil with mw=150 in a counter flow process column.

NGLs are absorbed into the Oil leaving almost puremethane in the gas stream.

The Oil, now called Rich Oil is distilled to remove theNGLs, and returned into the absorption system.

The NGLs are processed.


34/40



35/40


36/40



37/40


Cryogenic Expansion Process


38/40


Liquification of Natural GasNatural Gas is cooled to -160C until it liquefies. LNG is stored in

Cryogenic Tanks and transported in Cryogenic Sea Vessels or LNGCarriers to all parts of the world.

LNG is re-gasified at the port of entry and distributed in pipelines to itspoint of use.

The Liquefaction process is typically achieved by using one of the 2processes:

1. Phillips Optimized Cascade RefrigerationProcess (Propane, Ethane, Methane)

2. APCI Process Propane cooled Multi-componentRefrigeration. (C3-MR)

These two processes account for up to 85% LNG Plants.


39/40



40/40


APCI LNG Liquefaction Process

6 natural gas

Documents