IJAET OCT-DEC,2010 ARTICLE 1.pdf

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International Journal of Advanced Engineering Technology E-ISSN 0976-3945

IJAET/Vol.I/ Issue III/Oct.-Dec.,2010/1-12

Research Article

THERMODYNAMIC ANALYSIS OF GANDHINAGAR

THERMAL POWER STATIONaProf. Alpesh V. Mehta*,bMr.Manish Maisuria, cMr.Mahashi Patel

Address for Correspondence

aAsst.Prefessor, G.H.Patel College Of Engineering And Technology, V.V.Nagarb,c

Students, G.H.Patel College Of Engineering And Technology,

[email protected],[email protected]

ABSTRACT

Energy and environment both are core for human comfort and peripheral for global survival now-a-days.

Modern economic pressure demands re-examination of the existing power generating plants for various options

for their techno-economical and efficient operations. This paper presents a detailed energy study based on the

first law analysis of the coal fired thermal power station namely Gandhinagar Thermal Power Station (GTPS).In this paper, a detailed energy study is shown for 210MW, Unit-4 of coal fired thermal power plant atGandhinagar Thermal Power Station (GTPS) to evaluate the plant and subsystem{feed water heaters(high

pressure and low pressure),etc} efficiencies. The boiler efficiency is calculated using indirect method after

estimating the various heat losses in the boilers. It highlights the positive features of this power plant as well as

brings out areas where further detailing and corrective measures are required for efficient utilization of the

sources available in the plant. Energy analysis is used to evaluate the overall thermal efficiency of the plant bycomputing the individual efficiency of the boiler (86.84%), steam turbine (43.5%), and generator (98%). The

overall efficiency of the plant (Unit-4) appears to be 37.01%.

KEY WORDS: Power generating plant, boiler, steam turbine, first law analysis.

1. INTRODUCTION

Power consumption per capital indicates the

industrial and economical growth of the

country and thereby represents the living

standard of the people of the same. The whole

world is in grip of electrical energy crisis and

pollution due to the power plants. The overall

power scene in India shows heavy shortages in

almost all the states. The government of India

has advocated Energy for all by the year

2012. Even though the Indian power sector is

at the forth place of the power production in

the world. The significant role of thermal

power station in Indias power generation

scenario can be gauged from the truth that they

supply about 66% of the total installed

capacity. Some of the available options are to

evaluate overall and individual component

efficiencies and to identify and assess

thermodynamic losses, thereby improving the

energy efficiencies of the system. Energy like

many other commodities should be evaluated

and the conventional energy analysis, based on

the first law of thermodynamics, evaluates

energy mainly on the quality.

Very careful analysis of the problem and

proper planning and execution is necessary to

solve the power crisis in India. So in this

paper, a detailed energy study is shown for

210MW, Unit-4 of coal fired thermal power

plant at Gandhinagar Thermal Power Station

(GTPS) to evaluate the plant and

subsystem{feed water heaters(high pressure

and low pressure),etc} efficiencies. The first

law analysis is used to assess the overall plant

performance. In operation and maintenance of

a power plant, the feed water heaters are

practically neglected compared with other


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components. Efficient and reliable service

from feed water heaters requires more care in

both operations and maintenance than care that

has been taken for nay other components of

power plant.

1.1Literature Review

Power plant is an assembly of a system, where

electricity is being generated by using

different mechanical and electrical equipment

and different processes. The basic components

of the plants are steam generator {Steam

generator is a complex integration of boiler

along-with accessories (furnace, super heater,

re-heater, boiler, economizer & air pre-heater

etc.) and various auxiliaries such as pulverizer,

burners, fans, stokers, dust collector and

precipitators, ash-handling equipment &

chimney.}, steam turbine, steam condenser

and feed water pump.

1.2The Principle types of Power Plants

The Principle types of Power Plants are as

below:

1. Steam Plants using coal, oil or nuclear

fission.

2. Internal combustion engine Plant.

3. Gas turbine Plant.

4.

Hydroelectric Plant.In steam power plant coal or oil is used as a

fuel for generation of high pressure and high

temperature steam. In the boilers / the steam

generators steam is produced and then utilised

to drive the steam turbines which are coupled

to generator to get electricity. The furnace may

employee grate burning of solid fuel,

pulverised fuel in burner or furnace oil in oil

burners. The Plant may content server with

saving devices such as super-heaters,

economiser, air preheater, reheaters, steam

traps etc. which effect on overall efficiency of

coal or oil fired thermal power plants. The

equipment for firing of fuel into furnace and

handling of fuel and ash are other important

aspects of plant study. One should also focus

on auxiliary equipments and need of

condensing exhausting steam, water treatment,

water cooling, dust removal, Draft control, etc.

In Nuclear stations heat is produce in a reactor

which replaces the convectional boiler.

1.3 Classification of steam generator or

boiler

Classification of steam generator or boilers

can be made in different ways. From the point

of view of application, they can be;

a) Utility steam generator ,b) Industrial steam

generator, c)Marine steam generator.

1.3.1 Utility steam generator

Utility steam generator is those used by

utilities for electric-power generating plants.

Depending on whether the pressure of steam is

below or above the critical pressure (221.2

bar), that can be either subcritical or

supercritical units. The subcritical steam

generators are water tube drum type and theyusually operate at between 130-180bar steam

pressure. The supercritical steam generators

are drum less once-through tube and operate at

240 bar pressure. Majority of the utility steam

generators are of the 170-180 bar water tube-

drum variety, which produce superheated at

about 540-5800C with one or two stages of

reheating.

1.3.2 Industrial steam generators


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Industrial steam generators are those used in

process industries like sugar, paper, and jute

and so on, and institution like hospital,

commercial and residential building

complexes. They are smaller in size. They

operate pressures ranging 5 to 105 bar with

steam capacities up to 125 kg/s.

1.3.3 Marine steam generators

Marine steam generators are used in many

marine ships and ocean liners driven by steam

turbines. They are usually oil-fire. They

produce superheated steam at about 60-65 bar

and 5400C.

1.3About power plant

The Rankine cycle is the basic cycle for

operation of steam power plant. Thermal

power station means a factory for conversion

of chemical energy of fuel into electrical

energy. Coal fired units produce electricity by

the burning coal in a boiler to heat water to

produce steam. The steam, at tremendous

pressure, flow into a turbine, which rotates

armature of generator to produce the

electricity. The steam is condensate and

converted back into water, and the returned to

the boiler to complete the closed cycle.

The basic requirements of thermal power plantare:

Raw material should be available

continuously, generated energy should be

utilized properly and qualified staff should be

available as per requirement and proper

provision of removal of ash and other by-

products during power generation.

Basic points to be considered during site

selection are as follows:

Type and cost of the land, availability of fuel,

transportation facility, service water facility,

availability of staff, near to the load centre, ash

disposal facility, away from residential area.

2. About Gandhinagar Power Plant

Gujarat State Electricity Corporation Limited

(GSECL) was incorporated in August 1993

and is registered under the Companies Act,

1956 with the objectives to initiate a process

of restructuring of Power Sector and to

mobilize resources from the market for adding

to the generating capacity of the State and

improving the quality and cost of existing

generation. The Company was promoted by

erstwhile Gujarat Electricity Board (GEB) as it

is wholly owned subsidiary in the context of

liberalization and as a part of efforts towards

restructuring of the Power Sector. The

operations of GSECL were limited to Power

Stations units Gandhinagar Thermal Power

Station, Wanakbori Thermal Power Station,

Utran GBPS & Dhuvaran Combined Cycle

Power Plant (CCPP) till the complete

unbundling of erstwhile GEB was undertaken

upto 31st March 2005. The Gandhinagar

Thermal Power Station is located at

Gandhinagar, the capital of Gujarat nearAhmedabad. It is a Coal Based Power

Station. It is on the bank of Sabarmati River.

There are two units of 120 MW each (Unit no.

1 & 2), three units of 210 MW each (Unit no.

3, 4 & 5) with a total installed capacity of 870

MW. All the above units are of BHEL make.

Commissioning dates of unit no. 1 to 5 are

13.03.1977, 10.04.1977, 20.03.1990,

20.07.1991 and 17.03.1998 respectively.


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Based on the data available in table 1, table 2

and table 3 for Gandhinagar Thermal Power

Station, we have done a) Energy analysis, b)

Boiler losses calculations, c) Turbine

efficiency, and d) Effectiveness of heaters.

Table 1: Boiler Specifications

Unit-3 &4 Unit-5

Actual value

Particular

Design

valueUnit-3 Unit-4

Design value Actual

value

Load(MW) 210 150 180 210 210

Type Radiant Reheat, Natural

Circulation,

Radiant Reheat, Natural

Circulation,

Capacity(T/hr) 690 480 520 690 662

Feed water temp(0C) 247 165 232 245.6 241

Steam at boiler outlet(Kg/cm2)

SH 155 135 153 155 147.3

RH 38.1 26 33 36.11 34.14

Steam temp at Boiler outlet(0C)

SH 540 540 540 540 541

RH 540 530 540 540 542

Fuel used coal coal

Efficiency (%) 85.77 82.91 81.79 85.77 81.83

Table 2: Turbine specification

Unit-3 &4 Unit-5

Actual value

Particular

Design

value Unit-3 Unit-4

Design

value

Actual value

Capacity(MW) 2x 210MW 1x 210MW

No. of stages of cylinder 690 480 520 690 662

HP turbine 25 25

IP turbine 20+20 20+20

LP turbine 8+8 8+8

Critical Speed 600 to 300

Exhaust temp(0C) 45-55 54 52 44-57 40.2

Efficiency 43.24 37.22 47.71 43.24 41.37

Table 3: Coal specification

Particular Unit-3 &4 Unit-5


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Actual valueDesign

value Unit-3 Unit-4

Design

value

Actual value

Type Bituminous Bituminous

Caloric value(Kcal/Kg) 3800 3000Ash content (%) 35 42

Volatile matter (%) 23 23

Sulphur content (%) 1 0.5

Quality required (MT/hr) 139.5 94.63 109.5 177 125.77

Storage capacity (MT) 300000 222003

3. Result analysis and discussion

Energy is conserved in every device or process

i.e. in balance; it can be neither produced nor

consumed. Energy entering with fuel,

electricity, flowing streams of matter, and so

on can be accounted for in the products and by

products. Energy cannot be destroyed. Energy

analysis is based on the first law of

thermodynamics and it is the measured of

quality only.

The data for boiler operation and turbine

operation of unit-4 of GTPS at full load were

observed and relevant parameters have been

estimated.

Using these data and compiled value, First law

analysis (energy analysis) is carried out for the

given thermal power plant.

The performance of a plant is evaluated by

calculating the overall efficiency of unit by

using the individual efficiencies of boiler,

turbine and generator.

The 210 MW units taken for analysis is to

consider being having the following system:

SYSTEM 1 : Boiler system.

SYSTEM 2 : Steam cycle.

SYSTEM 3 : Cooling water system.

SYSTEM 1 (Boiler system) consists of the

following components and is shown in

figure1; Combustor, Heat exchangers.

Figure 1 Folw of fluids on boiler

SYSTEM 2 (Steam cycle) consists of the

following components and is shown in

figure2; Turbine, Condenser(C), Feed Water

Heater (FWH), Pump (P)


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SYSTEM 3 (Cooling Water System) consists

of the following components; Circulating

water pumps, Fans.

The performance of a plant is evaluated bycalculating the individual efficiencies of the

boiler, turbine and generator. The efficiency of

the boiler is evaluated by indirect method. In

the indirect method the input is assumed to be

100% and the various losses encountered in

the boiler are calculated and subtracted from

100. The various losses in the boiler are;

Energy losses due to the exhaust gases ,

Energy losses due to unburn carbon ,Energy

losses due to incomplete combustion Energy

losses due to moisture in fuel ,Energy losses

due to hydrogen in fuel , Energy losses due to

moisture coming with air supplied ,Energylosses due to ash and slag, Energy losses due

to radiation loss.

The boiler efficiency is calculated, using the

indirect method after estimating the various

heat losses in the boiler. Table 4 represent the

reading taken for the boiler and coal mill.

Based on the data available in table 4 , the

calculations are made for boiler losses and the

results are shown in table 5.

Figure 2: Steam cycle

Figure 3: Energy Balance of Steam Generator

Table 4: Data for boiler and coal mills


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Content Unit Value

Load MW 210.36

Coal flow rate T/hr 140.35

Steam flow rate T/hr 593.37FW inlet temp.

0C 232

Mills

Mill power KW 900

Total air flow T/hr 690.2

Relative humidity % 60.42

Absolute humidity (Kg water/kg dry air) Kg 0.0195

Dry bulb temp.0C 30

Wet bulb temp. 0C 27

FD fan discharge temp0C 37.9

APH inlet gas temp0C 299

APH outlet gas temp0C 157.9

Oxygen in APH inlet % 4

Oxygen in APH outlet % 4.3

CO2in APH inlet % 14.8

CO2in APH outlet % 14.5

Nitrogen in APH inlet % 14.5

Combustibles in bottom ash % 6.6

Combustibles in fly ash % 0.7

Table 5: Result obtained for boiler and coal mills

Types of losses KJ/kg %

Energy losses due to the exhaust gas(Q2) 2501.1 5.29

Energy losses due to unburn carbon(Q3) 250.98 0.52

Energy losses due to incomplete combustion. (Q4) 2209.2 4.64

Energy losses due to moisture in fuel. (Q5) 237.80 0.40

Energy losses due to hydrogen in fuel. (Q6) 143.0 0.29

Energy losses due to moisture coming with air supplied. (Q7) 601.48 1.21

Energy losses due to ash and slag. (Q8) 384.65 0.81

Total losses 6328.21 13.16


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Chart 1 Energy Balance of Steam Generator

From the chart1, it is clear that losses Energy

losses due to the exhaust gas are more

compared to all boiler losses. Which is

5.2%.the next highest is losses due to

incomplete combustion, which is 3.4%. The

lowest losses occur in boiler due to moisture in

air, which is 0.14%. Due to these energy losses

boiler efficiency is decrease 13.16%.

Table no 6 represent the data available for the turbine.

Content Parameter Unit Reading

Load L MW 210.36

Turbine inlet steam flow MS T/hr 593.37

Super heater steam pressure PSH Kg /cm2

149.36

Super heater steam temp. TSH0C 532.92

Hot Re-heater steam pressure PHRH Kg /cm2 35.09

Hot Re-heater steam temp THRH0C 534.81

Cold Re-heater steam pressure PCRH Kg /cm2 34.81

Cold Re-heater steam temp TCRH0C 335.45

Feed Water pressure before Economiser PFW Kg /cm2 174.66

Feed Water temp. before Economiser TFW0C 241.09

Enthalpy of super heater steam HS KJ/Kg 3549.97

Enthalpy of Hot Re-heater steam HHRH KJ/Kg 3561.4

Enthalpy of Cold Re-heater steam HCRH KJ/Kg 3104.1

Enthalpy of feed water HFW KJ/Kg 1009.4


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From the available data for the turbine,

following calculations are made to calculate

the turbine efficiency.

Turbine inlet steam flow = 593.37 T/hr =164.825 kg/s.

Heat input to turbine

= {turbine inlet steam flow X (SH enthalpy-

FW enthalpy)} +{HRH steam flow X (HRH

enthalpy CRH enthalpy)

= {164.825 X (3549.97 1009.4)} + {140.1 X

(3561.4 3104.1)}

= 482817.18 KJ/Kg

Turbine efficiency = power generation/ heat

input to turbine= {210.36 X 103/ 482817.18}

= 43.5%

Superheater temperature 532.920C and

pressure 149.36 Kg/cm2. That means that

quality of steam is rich. Reheater temperature

534.810C it is nearly superheater temperature

532.920C so, we can say that reheater is good

condition. Feed water temperature is 241.090C

it is nearby 2500C that is desirable. Due to

turbine losses, we get turbine efficiency is

very low which is 43.5%.

Generator efficiency is taken as 98%

So the overall efficiency

= (boiler efficiency X turbine efficiency X

generator efficiency)= (0.8684 X 0.435 X 0.98)

= 37.01%

Due to the turbine efficiency and boiler

efficiency, we get overall efficiency is

37.01%. It is very low.

Overall heat rate = (1 / overall efficiency)

= 2.701 KJ/S

The efficiency of the turbine is determined

estimating the net heat input to turbine and

electrical power plant from the generator in

terms of heat values. Thus turbine efficiency

obtained is 43.5%.

The generator efficiency is taken as 98%.

Then the overall efficiency is estimated as

37.01%.

The above results are shown in the table no 7

shown below:

Table .7 Different efficiencies of power plant Chart 2 Compression of Energy Efficiencies

Component Efficiency (%)

Boiler 86.84%

Turbine 43.5%

Generator 98.0%

Overall efficiency 37.01%


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Table 8: Represents the observation taken for the high pressure feed water heater (HPH)

cascaded backward and effectiveness of heaters to be found.

Contents Unit

Load MW 210.36FW flow t/hr 593.87

HPH 5 shell pressure Kg/cm2

36

HPH 6 shell pressure Kg/cm2 16

FW temperature HPH 5 IN0C 163.7

FW temperature HPH 5 OUT0C 200.7

FW temperature HPH 6 OUT 0C 244

Enthalpy of drain water from HPH 5 KJ/Kg 2757

Enthalpy of drain water from HPH 5 KJ/Kg 2598.62

Figure 4 Flow diagram of HP Heater

Effectiveness of heater

= (FW Temp rise)/ (Tsat tempTFW temp)

Effectiveness of HPH6 = (243-200.7)/(244.2-

200.7) =0.97

Effectiveness of HPH5= (200.7 163.7) /

(201.1 163.7) =0.98

Net heat grain to feed water and actual heat

gained by feed water is respectively 3600

KJ/Kg and 4131.17 KJ/Kg. That shows that

system is perfect. Effectiveness of the heater

HPH6 and HPH5 is 0.97 and 0.98 that is

nearly 100%. In general, the total losses =

13.16% , Boiler efficiency = 100 13.26 =

86.84%, Turbine efficiency = 43.5% ,HP

heater effectiveness HPH5 and HPH6 are 0.98

and 0.97.


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CONCLUSION

From the energy analysis made for the unit-4,

210MW of the GTPS the following

conclusion are drawn:. It is seen that boiler efficiency is

highest, which is 86.84% and the heat

losses are only 13.16%.

Out of all the boiler losses, the highest

heat losses 5.29% occurs due to the

exhaust gas.

The turbine efficiency is very less and

is estimated as 43.5% Because of the

several turbine losses like ; Losses in

regulating valve, Nozzle friction

losses , Blade friction losses , Disc

friction losses , Partial admission

losses , Gland leakage losses, Cary

over losses.

From the thermodynamic analysis

using first law of thermodynamics, we

can conclude that, energy analysis

evaluates the plant quantitatively. The

power plant overall efficiency is

37.01%.

The effectiveness of HP heater

working in good condition should

have an effectiveness of 0.85. The

performance of HPH6 and HPH5 are

in good conditions as their

effectiveness 0.97 and 0.98.

6. ACKNOWLEDGMENTS

We are very much thankful to peoples of

Gandhinagar thermal power plant for

providing sufficient data for plant. We are also

thankful to those who help directly or

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IJAET OCT-DEC,2010 ARTICLE 1.pdf