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Internship Report

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Jamshoro Power Company Limited, Jamshoro

Internship Report

By

Mahmood Ali Korai

(12EL92)

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Introduction To Power Generating Station:

Power House also known as Power Station is a place where electricity is produced. Power House

can be classified on the basis of the source from which the electricity is produced i.e. The Hydro

Power Plant (in which the electricity is produced for the water stored by dam), Thermal Power

Plant (in which the electricity is produced from the heat which is produced from of combustion

fossil fuel, garbage or by using geothermal energy, and biomass), Solar Power Plant (in which the

electricity is produced by striking of sunlight on photovoltaic cell), Windmill Power (in which the

electricity is produced by wind) and Nuclear Power Plant (in which the electricity is produced

from nuclear fission).

In each type of power plant, the way of producing electricity is different and their cost of

installation, operational, and maintenance cost also vary. Electricity is produced by hydro power

plant is the cheapest and the electricity which is produced by thermal power station (burning

fossil fuel) is very costly.

Such a type of power plant is installed in an area where availability of resource is available. In

simple words, you cannot install a windmill power where is no wind. There is a great abundance

of water in northern areas of Pakistan, so hydro power plants are installed and in southern areas

of Pakistan, only thermal power stations are installed namely HUBCO, Hub; GUDDU Power Plant,

Guddu; JPCL, Jamshoro; GTPS Kotri and also Bin Qasim Power Plant, Karachi which is owned by

KESC (Karachi Electric Supply Company) now known as K-Electric (Karachi Electric). It must also

be noted that thermal power stations are not only installed in southern areas but all over

Pakistan.

Thermal power station are usually located near a river or lake because large quantity of cooling

water is needed to condense steam as it exhausts from turbines. Therefore Thermal Power

Station Jamshoro is also located near to the right bank of Indus River. The Power Station comprises

of four units having total capacity of 850 MW. Unit No.1; 250 MW is installed by Mitsui Ship Holding Co.

Japan only runs on HSD (High Speed Diesel) oil, whereas Units 2, 3 and 4 of 200 MW are installed by a

Chinese company each are dual fuel i.e. Gas/HSD oil.

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The efficiency of thermal generating station is very low because of the inherent of low efficiency

of turbines. The maximum efficiency of any turbine that converts heat energy into mechanical

energy is given by the equation

ŋ = �1 −�2

�1� × 100

where

ŋ = efficiency of the machine

T1 = Temperature of the gas entering the turbine [K]

T2 = Temperature of the gas leaving turbine [K]

In thermal power station the gas is steam quotient T2/T1 should be small as possible. However

temperature cannot be lower than ambient temperature, which is usually about 20 oC. As a result

T2 cannot be less than

�2 = 273 + 20 = 293�

This means that to obtain higher efficiencies, T2 should be as high as possible. The problem is

that we cannot use temperature above those steel and other metals can safely withstand,

bearing in mind the corresponding high steam pressure. It turns out that the highest feasible

temperature T1 about 550 oC or 540 oC. As a result

�1 = 550 + 273 = 823�

It follows that the maximum possible efficiency of a turbine can be given as at different

temperatures;

T1 = 293:293+25; T2 = 273 + 540; efficiency = (1-(T1./T2))*100; [T1' efficiency'] Temperature Efficiency 293.0000 63.9606 294.0000 63.8376 295.0000 63.7146 296.0000 63.5916 297.0000 63.4686 298.0000 63.3456 299.0000 63.2226 300.0000 63.0996 301.0000 62.9766 302.0000 62.8536 303.0000 62.7306 304.0000 62.6076 305.0000 62.4846 306.0000 62.3616

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307.0000 62.2386 308.0000 62.1156 309.0000 61.9926 310.0000 61.8696 311.0000 61.7466 312.0000 61.6236 313.0000 61.5006 314.0000 61.3776 315.0000 61.2546 316.0000 61.1316 317.0000 61.0086 318.0000 60.8856 Due to other losses, some of the most efficient steam turbines have efficiencies of 35 %. This means that the 65 % of thermal energy is lost during the thermal to mechanical conversion process. The enormous loss of heat and how to dispose of it represents one of the major aspect of a thermal generating station. With the combined cycle, the efficiency of power plant can be improved up to 75-85 %.In combined cycle power plants (CCPPs) a gas turbine generator generates electricity while the waste heat from the gas turbine is used to make steam to generate additional electricity via a steam turbine. In other words: The output heat of the gas turbine flue gas is utilized to generate steam by passing it through a heat recovery steam generator (HRSG), so it can be used as input heat to the steam turbine power plant. This combination of two power generation cycles enhances the efficiency of the plant. While the electrical efficiency of a simple cycle plant power plant without waste heat utilization typically ranges between 25% and 40%, a CCPP can achieve electrical efficiencies of 60% and more. Supplementary firing further enhances the overall efficiency.

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Makeup of a Thermal Generating Station Pumping Plant:

As the name suggests, the job of pumping plant is to pump the water from one place to another. It usually

pumps water from river or lake for thermal generating station. A thermal generating station needs a huge

amount of water to produce the steam and to condense it after striking on turbine. In Jamshoro Power

House, water is pumped from Indus River with the help of heavy duty motors to pump water.

Water Treatment Plant:

After pumping plant, water goes to water treatment plant where it is filtered and all its impurities are

removed. The boiling point of water contacting impurity is higher than distilled water i.e. 100 oC. The

boiling point of impure water may rise to 102 oC and melting point of water may decrease to -2 oC. So, it’s

clear if boiling of water will increase, we will have to use more energy (more fuel we will have to burn) to

convert the water into steam. Because of impurities, they can also corrode the pipes, turbine and other

equipment and will also reduce their life and hence of power plant. The ph of water is kept a little greater

than 7.0 which is the neutral point. It means that water is kept basic.

After filtration plant, water goes to boiler [1] or steam generator. There are many types of boiler.

Water tube boiler is very commonly used. Boiler acts as furnace, transferring heat from burning

fuel to row upon row of water tubes S1, which entirely surround the flames. Water is kept

circulating through tubes by a pump P1.

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A drum [2] containing water and steam. Under high pressure produces the steam required by the

turbines. The pressure is kept high because at low pressure boiling point of water decreases and

at high pressure boiling point of water increases. It also receives the water delivered by boiler

feed pump P3. Steam races towards HP (high pressure) turbine after having passed through

superheater S2. The superheater composed of a series of tubes surrounding the flames, raise the

steam temperature about 200 oC. This increase in temperature ensure that steam is absolutely

dry and raise the overall efficiency of the station.

The low, medium, and high pressure turbine possess a series of blades mounted in the driver

shaft. The steam is deflected by the blades, producing a powerful torque. These blades are made

of special steel to withstand the high temperature and intense centrifugal forces. The HP, MP, and

LP turbines are coupled together to drive a common generator. In Jamshoro Power House, HP

turbines drive one generator while MP and LP drive two different generator. A HP turbine [3]

converts thermal energy into mechanical energy by letting the steam expand as it moves through

turbine blades. The temperature and pressure at the output of the turbine, therefore, less than

at the input. In order to raise thermal efficiency and to prevent permanent condensation, the

steam passes through a reheater S3, composed of a third set of heated tubes.

The MP (medium pressure) turbine or IP (Intermediate pressure) turbine [4] is similar to the high

pressure turbine, except that it is bigger that the steam may expand still more.

The LP (low pressure) turbine [5] is composed of two identical left hand and right hand sections.

The turbine sections remove the remaining available energy from the steam. The figure of LP

turbine is given below;

The steam flowing out of LP expands into an almost perfect vacuum created by the condenser.

The condenser [6] causes the steam to condense by letting it flow over cooling pipes S4. Cold water

from an outside source, such as filtration plant, flows through the pipes, thus carrying away the

heat. It is the condensing steam that creates the vacuum.

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A condensate pump P2 removes the lukewarm condensate steam and drives it through a reheater

[7] towards a feedwater pump [8].

The reheater [7] is a heat exchanger. It receives the hot steam, bled off from HP turbine, to raise

the temperature of feed water.

The burners [9] supply and control the amount of gas, oil or coal injected into the boiler. Heavy

bunker oil is preheated and injected as an atomized jet to improve the surface contact (and

combustion) with surrounding air.

A FDF [10] (forced draft fan) furnishes the enormous quantities of air needed for combustion.

An IDF [11] (induced draft fan) carries gases and other products of combustion toward cleansing

apparatus and from there to the stack and the outside air.

Generator G, mechanically coupled with all turbines, convert the mechanical energy into electrical

energy.

There is also two other equipment that are not shown in figure is i.e. de-aerator and economizer.

Deaerator

Deaerator is used to remove the dissolved oxygen as well as other non-condensable gases from feedwater

which can react with metallic equipment and form oxides. Consequently it will corrode them and reduce

the life of a power station. Dissolved carbon dioxide combines with water to form carbonic acid that

causes further corrosion. Most deaerators are designed to remove oxygen down to levels of 7 ppb by

weight (0.005 cm³/L) or less as well as essentially eliminating carbon dioxide.

There are two basic types of deaerators, the tray-type and the spray-type.

http://en.wikipedia.org/wiki/Carbon_dioxide

http://en.wikipedia.org/wiki/Carbonic_acid

http://en.wikipedia.org/wiki/Parts_per_billion

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The tray-type (also called the cascade-type) includes a vertical domed deaeration section

mounted on top of a horizontal cylindrical vessel which serves as the deaerated boiler

feedwater storage tank.

The spray-type consists only of a horizontal (or vertical) cylindrical vessel which serves as both

the deaeration section and the boiler feedwater storage tank.

Economizer:

An economiser is a mechanical device which is used as a heat exchanger by preheating a fluid to reduce

energy consumption. In a steam boiler, it is a heat ex-changer device that heats up fluids or recovers

residual heat from the combustion product i.e. flue gases in thermal power plant before being released

through the chimney. Flue gases are the combustion exhaust gases produced at power plants consist of

mostly nitrogen, carbon dioxide, water vapour, soot carbon monoxide etc.

Cooling Tower:

The Jamshoro Power House is located far away from Indus River. When steam comes from turbine, then

it is condensed by condenser. Hence, the temperature of condenser increases. So, we will have to cool

condenser, on way or another. In the case of thermal generating station, the warm cooling water flowing

out of the condenser is pipes to the top of a cooling tower where it is broken into small droplets. As the

droplets fall towards upon reservoir below, evaporation takes place and the droplets are chilled. The cool

water is pumped from the reservoir and recirculated through the condenser, where it again removes heat

from condensing steam. The cycle then repeats. Approximately 2 % of the cooling water that flows

through the condenser is lost by evaporation. This loss can be made up by Indus River.

Thermal Power Station and the Environment:

The products of combustion of thermal generating station are an interesting subject of concern, due to

their impact on the environment. Carbon dioxide, sulfur dioxide, and water are the main products of

combustion when oil, gas or coil are burned. Carbon dioxide and water produce no immediate

environmental effects, but sulfur dioxide creates substance that give rise to acid rain. Dust and fly ash are

other pollutants that may reach the atmosphere. Natural gas produces only water and carbon dioxide.

This explains, why gas is used rather than (oil or coal), when atmospheric pollution must be reduced to

minimum. But, the carbon dioxide is a greenhouse which is playing an active role in global warming and

increasing the temperature of earth atmosphere. Because of global warming, glaciers are melting

dramatically and raising the sea level and causing flood in the rivers.

http://www.electrical4u.com/steam-boiler-working-principle-and-types-of-boiler/

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Here is the data of a power plant for the better understanding of a power generating station that how it

works. This data may vary from one generating station to another.

Electrical Data Number of generator: 4

Power per generator: 660 MW

Speed: 3000 rev/min

Voltage: 23,000 V

Frequency: 50 Hzphase: 3

Mechanical Data Number of steam turbines: 4

Number of condensers: 4

Number of boilers: 4

Steam flow per turbine: 560 kg/s

Steam temperature: 540 oC

Steam pressure: 16.55 MPa

Cooling water per condenser: 21,000 kg/s

Coal consumption per boiler: 51.5 kg/s

Dust capture by cleaning system: 28 kg/s

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