8. Thermal Power Plants

8/10/2019 8. Thermal Power Plants

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THERMAL POWER PLANT


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TYPES OF THERMAL POWER PLANT

1. Boiler-Turbine Cycle

2. Diesel engine type

2. Gas turbine cycle


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BOILER-TURBINE CYCLE


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SURFACE CONDENSER


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WATER COOLED CONDENSER

Basically it condenses the low pressure/temp steam at the

exhaust of turbine to convert steam into water at the same

pressure and temp. In Indian condition, the pressure and temp.

of steam at condenser inlet is approx. 680 mmHg and 45 degC.

It consists of a shell and bundles of tubes inside. Water will be

passed through the tubes and steam falls directly on the tube

surface.

Water in circulation in the condenser of a 100 MW turbine will

be approx.20,000 cum/hr(20 million litres/hr).

A cooling tower will be necessary for cooling the hot water

leaving the condenser so that the same water can be circulated

to condenser through a set of pumps.


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AIRCOOLED CONDENSER


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It is a variation to the conventional water cooled condenser.

Instead of using water, here atmospheric air through a set of

fans will be impinged on the tube surface.

One major difference is that here steam will be passed through

the tubes and cooling medium, air will be passed over the tube

surface.

Here there is no necessity of cooling tower as in the case of

water cooled condenser.

This is most suitable for project sites where water availability is

scarce.

AIR COOLED CONDENSER


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STEAM JET EJECTOR


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STEAM JET EJECTOR

Steam jet ejectors are a reliable and economical means for

producing vacuum. The primary advantages of the ejector design are

its low initial cost, lack of moving parts, and simplicity of operation.

The conventional steam jet ejector has four basic parts; the steam

chest, the nozzle(s), the mixing chamber and the diffuser.

A high pressure motivating fluid (steam) enters and expands

through the converging-diverging nozzle.

The suction fluid enters and mixes with the motivating fluid in the

mixing chamber . Both are then recompressed through the diffuser .


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DEAERATOR SPRAY TYPE


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DEAERATOR PRINCIPLE

The removal of dissolved gases from boiler feedwater is an essential

process in a steam system. The presence of dissolved oxygen in

feedwater causes rapid localized corrosion in boiler tubes.

Carbon dioxide will dissolve in water, resulting in low pH levels and

the production of corrosive carbonic acid. Low pH levels in feedwater

causes severe acid attack throughout the boiler system.

While dissolved gases and low pH levels in the feedwater can be

controlled or removed by the addition of chemicals, it is more

economical and thermally efficient to remove these gases

mechanically.

This mechanical process is known as deaeration and will increase the

life of a steam system dramatically.


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DEAERATOR PRINCIPLE

The feedwater is sprayed in thin films into a steam atmosphere

allowing it to become quickly heated to saturation.

Spraying feedwater in thin films increases the surface area of the

liquid in contact with the steam, which, in turn, provides more rapid

oxygen removal and lower gas concentrations.

This process reduces the solubility of all dissolved gases and

removes it from the feedwater.

The liberated gases are then vented from the deaerator.


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AIR PREHEATER


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REGENERATIVE AIR PREHEATER

(TRI SECTOR)


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REGENERATIVE AIRHEATER


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REGENERATIVE AIRPREHEATER

In regenerative type the heating medium flows through a closely

packed matrix to raise its temperature and then air is passed

through the matrix to pick up the heat.

Either the matrix or the hoods are rotated to achieve this and hence

there is slight leakage through sealing arrangements at the moving

surfaces.


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ELECTROSTATIC PRECIPITATOR


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ELECTROSTATIC PRECIPITATOR WORKING

PRINCIPLE

An electrostatic precipitator is air pollution control device used toseparate solid particulate matter from a contaminated fluegas

stream.

Contaminated fluegas flows into an ESP chamber and is ionized by

electron emitting electrodes; also known as the corona chamber.

ESP essentially consists of a number of emitting electrodes and

collecting surfaces between which the gas carrying entrained solid

or liquid particles flows.


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ELECTROSTATIC PRECIPITATOR

WORKING PRINCIPLE

A unidirectional high potential field is set up between them through

the use of high voltage direct current. The emitting electrodes are at

high tension negative, while the collecting surfaces are at ground

potential. Ionisation of the gas takes place.

The ions formed attach themselves to the solid or liquid particles

entrained

Accumulate particulate matter is removed from the collection plates

at periodic intervals by rapping or hitting the plates with rappers

(mallets type hammers).

Heavy particles fall to the base of the ESP where hoppers hold the

removed particles for disposal.


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FUNCTION OF ESP


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FUNCTION OF ESP


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RAPPING OF THE COLLECTING ELECTRODES


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BOILERS


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BOILER TYPES AND CLASSIFICATIONS

WATER TUBE BOILER

Water flow through tubes

Water Tubes surrounded by hot

gas

Application

Used for Power Plants

Used for high pressure high

capacity steam boiler


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TRAVELLING GRATE BOILER


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BASIS OF FBC TECHNOLOGY BUBBLING BED TYPE


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FBC TECHNOLOGY

FLUIDIZED BED COMBUSTION (FBC) BOILER


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FLUIDIZED BED COMBUSTION (FBC) BOILER

Further, increase in velocity gives

rise to bubble formation, vigorous

turbulence and rapid mixing and

the bed is said to be fluidized.

Coal is fed continuously in to a hot

air agitated refractory sand bed, the

coal will burn rapidly and the bed

attains a uniform temperature

When an evenly distributed air or gas is passed upward through a finely

divided bed of solid particles such as sand supported on a fine mesh, the

particles are undisturbed at low velocity. As air velocity is graduallyincreased, a stage is reached when the individual particles are suspended in

the air stream

Fluidized Bed Combustion


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TYPES OF FLUIDIZED BED COMBUSTION SYSTEM

There are three basic types of fluidized bed combustion boilers:

1. Atmospheric Fluidized Bed Combustion System (AFBC)

2. Circulating Fluidized Bed Combustion system (CFBC)


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SCHEMATIC DIAGRAM OF AFBC


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FLUIDISED BED COMBUSTION

The 3 Ts as required for complete combustion which is satisfied byfluidised bed combustion boiler are as follows:

Time

Temperature

Turbulence

Turbulence is promoted by fluidisation making the entire mass of

solids behave much like a liquid

Improved mixing generates heat at a substantially lower and more

uniformly distributed temperature typically 800 to 9000

C


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ATMOSPHERIC FLUIDIZED BED COMBUSTION

(AFBC)

In AFBC, coal is crushed to a size of 110 mm depending on the

rank of coal, type of fuel feed and fed into the combustion chamber.

The atmospheric air, which acts as both the fluidization air and

combustion air, is delivered at a pressure and flows through the bed

after being preheated by the exhaust flue gases.

The velocity of fluidizing air is in the range of 1.2 to 3.7 m /sec.

The rate at which air is blown through the bed determines the

amount of fuel that can be reacted.


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ATMOSPHERIC FLUIDIZED BED COMBUSTION(AFBC)

Almost all AFBC/ bubbling bed boilers use in-bed evaporator tubes

in the bed of limestone, sand and fuel for extracting the heat from

the bed to maintain the bed temperature.

The bed depth is usually 0.9 m to 1.5 m deep and the pressure drop

averages about 1 inch of water per inch of bed depth.

Very little material leaves the bubbling bedonly about 2 to 4 kg of

solids are recycled per ton of fuel burned.

The combustion gases pass over the super heater sections of the

boiler, flow past the economizer, the dust collectors and the air

preheaters before being exhausted to atmosphere.


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CIRCULATING BED BOILER


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CIRCULATING FLUIDISED BED COMBUSTION

(CFBC)

Circulating Fluidised Bed Combustion (CFBC) technology has

evolved from conventional bubbling bed combustion as a means to

overcome some of the drawbacks associated with conventional

bubbling bed combustion .

This CFBC technology utilizes the fluidized bed principle in which

crushed (612 mm size) fuel and limestone are injected into the

furnace or combustor.

The particles are suspended in a stream of upwardly flowing air (60-

70% of the total air), which enters the bottom of the furnace through

air distribution nozzles.

The fluidising velocity in circulating beds ranges from 3.7 to 9

m/sec. The balance of combustion air is admitted above the bottom

of the furnace as secondary air.


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CIRCULATING FLUIDISED BED COMBUSTION

(CFBC)

Similar to Pulverized Coal (PC) firing, the controlling parameters in

the CFB combustion process are temperature, residence time and

turbulence.

For large units, the taller furnace characteristics of CFBC boiler

offers better space utilization, greater fuel particle and sorbent

residence time for efficient combustion and SO2 capture, and easier

application of staged combustion techniques for NOx control than

AFBC generators.


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POWER PLANT CYCLE WITH CFBC BOILER


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TECHNOLOGY


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Overview of Pressurized fluidized bed boiler


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Overview of Pressurized fluidized bed boiler


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PULVERISED FUEL FIRED BOILER


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PULVERISED FUEL FIRED BOILER

PULVERIZED FUEL BOILER


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PULVERIZED FUEL BOILER

Tangential firing

Coal is pulverised to a fine powder, so that less than 2% is +300 microns,

and 70-75% is below 75 microns.

Coal is blown with part of the combustion air into the boiler plant through

a series of burner nozzles.

Combustion takes place at

temperatures from 1300-1700C

Particle residence time in the boiler is

typically 2-5 seconds

One of the most popular system for

firing pulverized coal is the tangential

firing using four burners corner to

corner to create a fire ball at the

center of the furnace. See Figure


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TYPES OF PULVERISERS

Slow speed millsThese mills will be rotating between 15 to 25

rpm depending on the mill size. E.g. Drum mills or Tube mills or

Ball mills

Medium speed mills- These mills will be rotating between 50 to

100 rpm. E.g. Vertical shaft mills, Bowl mills, Ball & Race mills,

Roller mills etc.,

High Speed millsThese are directly coupled to the driving motor

and run at 750 to 1000 rpm. E.g., Hammer or Beater mill


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DRUM MILLS

The mill drum carrying the ball charge rotates on the antifriction

bearings.

Rawcoal is fed to the drum through the inlet elbow and gets crushed

to powder inside the mill drum.

The ball charge and the coal are carried to a certain height inside

the drum and allowed to fall down.

Due to the impact of balls on coal particles and due to attrition as

the particles slide over each other and also over the liners, the coal

get crushed.

Hot flue gases are used for drying and transporting the pulverisedcoal from the mill to the classifier.

The coarser particles are returned by the classifier for further

grinding.


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BALL MILLS

BALL & RACE MILL


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BALL MILLS

Coal fed from the top and fall in the center of the mill table and

passess through the grinding elements which consists of hollow

steel balls carried between two grinding rings.

Upper ring is stationary and applies pressure to the balls from

pneumatic loading cylinders containing pressurised inert gas.

The bottom ring rotates and inturn rotates the balls and in this

process coal trapped in between the grinding elements get

pulverised.

Hot primary air is fed to the mill which carries the finely ground coal

to the classifier.


grinding

BOWL MILL


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BOWL MILL

Coal is fed from the bunkers by drag link feeder.

The coal falls on the mill grinding table and is carried under the

spring loaded, free running grinding rolls, which reduce the coal to

pulverised fuel of the required fineness.

Hot primary air is fed to the mill which carries the finely ground coal

to the classifier. These passages surround the lower part of the mill.


grinding

HAMMER MILL


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HAMMER MILLS

Coal fed to the mill is crushed by the impact against the armour

plates and by attrition.

The hot air supplied dries the coal in the mill and transports the

coal powder to the classifier.


grinding.


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DRUM

EVAPORATOR

SUPER HEATERPANEL

GAS FLOW

RADIAT

ION

STEAM

ECONOMISER

AFTERBURNINGCHAMBER

TYPICAL CROSS SECTION OF WASTE HEAT RECOVERY BOILER


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LIST OF WHRB PROJECT REFERENCE EXECUTED BY DASTURCO


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Sl.

No.

Name of the Client Capacity Commissioned in

the year

1. Prakash Industries Ltd,

Champa, Chhattisgarh2 x 7.5MW TG set &

1 x 50 tph WHRB.

(150,000 Tons/annum Sponge Iron

production)

1991

2. Orissa Sponge Iron Ltd,

Palaspanga, Orissa

1 x 10MW TG set &

1 x 46 tph WHRB(120,000 Tons/annum Sponge Iron

production)

1997

3. Tata Sponge Iron Ltd,

Joda, Orissa

1 x 7.5MW TG set &

1 x 35 tph WHRB

(110,000 Tons/annum Sponge Iron

production)

2001

4. Bellary Steels and Alloys

Ltd, Bellary, Karnataka

1 x 12MW TG set,

2 x 12 tph WHRB &

1 x 40 tph FBC

(2 x 30,000 Tons/annum Sponge

Iron production)

1996 (Project

implementation

partly completed in

1996. Presentlyunder HOLD)


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Sl.

No.Name of the Client Capacity Commissioned in

the year

8. Vandana Global Ltd,

Raipur

1 x 33MW TG set

1 x 55 tph WHRB

2 x 90 tph AFBC boiler

(1 x 150,000 Tons/annum &

1 x 60,000 Tons/annum

Sponge Iron Kiln

Project

commissioned in

September 2007

9. Abhijeet Infrastructure

Ltd, Raipur (Jayaswals

NECO Group)

1 x 15MW CPP

1 x 39 tph WHRB

1 x 33 tph AFBC boiler

(1 x 1,15,500 tons/annum

Sponge Iron Kiln)

Commissioned in

April 2007

10. Corporate Ispat Alloys Ltd,

Raipur (Jayaswals NECO

Group)

1 x 15MW CPP

1 x 56 tph WHRB

(1 x 1,65,000 tons/annum

Sponge Iron Kiln)

Project

Commissioned in

August 2007.



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Sl.

No.Name of the Client Capacity Commissioned in

the year

11. Surana Industries Ltd,

Chennai

1 x 35MW

4 x 10.5 tph WHRB

1 X 110 tph AFBC boiler

(4 x 100 tpd Sponge Iron Kiln)

Project activities in

progress. Scheduled

for commissioning in

December 2008.

12. Janki Corp Ltd, Bellary 1 x 15MW CPP

6 x 100 tpd;

6 x 10.5 tph WHRB

Project under

execution


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DIESEL GENERATOR POWER PLANT

Diesel Engine


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DIESEL ENGINE SYSTEMS


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DIESEL ENGINE SYSTEMS

This system provides

process heat or steam

from engine exhaust.

The engine jacket

cooling water heat

exchanger and lube oil

cooler may also be

used to provide hot

water or hot air.

RECIPROCATING ENGINE BASED COGENERATION SYSTEM WITH UNFIRED

WHRB


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WHRB


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GAS TURBINE CYCLE

1. Using conventional fuels like Natural Gas, Diesel oil& Naphtha

2. Integrated gasification combined cycle (IGCC)

GAS TURBINE COMBINED CYCLE


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GAS TURBINE


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GAS TURBINE

The fuel is burnt in a pressurized combustion chamber using

combustion air supplied by a compressor that is integral with thegas turbine.

Gases enter the turbine at a temperature range of 900 to 1000oC

and leave at 400 to 500 oC.

Hot pressurized gases are used to turn a series of turbine blades,

and the shaft on which they are mounted, to produce mechanical

energy.

The available mechanical energy can be applied in the following

ways:

to produce electricity with a generator (most applications);

to drive pumps, compressors, blowers, etc.

SOME GAS TURBINE BASED POWER PLANTS


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Power station Agency/Promoter StateInstalled

capacity (MW)

Faridabad CCGT NTPC Haryana 430

Anta GT NTPC Rajasthan 413

Auraiya GT NTPC Uttar pradesh 652

Dadri GT NTPC Uttarpradesh 817

Kawas GT NTPC Gujarat 644

Gandhar GT NTPC Gujarat 648

Kayakulam GT NTPC Kerala 350Urban GT MSEB Maharastra 672.0

Vijeswaram GTAndhra pradesh gas

power corporation

Andhraprades

h272.3

Valuthur GT TNEB TamilNadu 2 x 95.0

Jegurupadu GT GVK Industries Gujarat 235.4

Kondapalli GT Lanco KondapalliAndhraprades

h350

P.Nallur CCGTPPN power generating

companyTamilNadu 330.5

Jegurupadu GT Extn GVK IndustriesAndhraprades

h230


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INTEGRATED GASIFICATION

COMBINED CYCLE (IGCC)

INTEGRATED GASIFICATION



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GASIFIER


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GASIFIER


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LIST OF GE INSTALLATIONS

Project Power , MW Gas Turbine Main fuel - back

up fuel

Coal IGCC Experience

Coolwater 120 107E Coal

SUV Vresova 350 209E Coal

SVZ 70 1x106B Coal

Wabash 250 107FA Coal/Pet Coke

Tampa Polk 250 107FA Coal

Refinery IGCC Experience

Frontier 40 6B Pet Coke

Shell Pernis 120 206B Oil

Sarlux 550 3x109E Vis breaker tar

Motiva 180 2-6FA Pet Coke

Exxon Singapore 173 2-6FA Oil

Nexen/Opti 160 2-7EA Asphaltene


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LIST OF ANSALDO INSTALLATIONS

Project Power,MW GasTurbine Main fuel - backup fuel

Enil power

Ferrera

255 MW 1 x

V94.2K

77% Tar syngas +

13% Natural gas

Backup fuel -

natural gas

ISAB Priolo 2 x 250MW

2 xV94.2K

100% Tar syngasBackup fuel - fuel

oil

POWER PLANT BASIC VARIANT


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Utility Power Plant : It will generate and supply only Electric power.

Mostly owned by SEBs, PSU, IPPs

Cogeneration Power Plant:

Simultaneous generation of Electric power and low/medium

pressure & temperature steam.

Most ideal for process industries wherein both electric

power (for driving electric motors) and steam for heating

process fluids will be required.



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Captive Power Plant (CPP) : It refers to power plant set up by an

Industry for its own consumption.

Depending upon the type of Industry, CPP will be designed either as

an utility power plant or cogeneration plant.

The boilers will be designed for firing by-product fuels if anyavailable in the plant along with conventional fuels. (Eg.Blast

furnace gas and coke oven gas in steel plant; dolochar in sponge

iron plant; bagasse in sugar plant)

In some cases, the hot waste gases generated in the plant will be

used for producing steam (eg. waste gas from Sponge iron kiln, coke

oven)

BACKPRESSURE STEAM TURBINE BASED COGENERATION SYSTEM


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EXTRACTION-CUM-CONDENSING STEAM TURBINE BASEDCOGENERATION SYSTEM


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GAS TURBINE BASED COGENERATION SYSTEM WITH SUPPLEMENTARYFIRED WHRB


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RECIPROCATING ENGINE BASED COGENERATION SYSTEM WITH

UNFIRED WHRB


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UNFIRED WHRB

Documents

8. Thermal Power Plants