Flue Gas Calculations

7
8/20/2019 Flue Gas Calculations http://slidepdf.com/reader/full/flue-gas-calculations 1/7 Journal of Scientific Indu stria l Research Vol. 63, Fe hru ary 2004, pp. 156- 1 62 Impact of Indian and imported coal on Indian thermal power plants A Chandra and H Chandra Ce ntre for E nergy Studies, Indi a n ln st itut e o f Technology, Delhi , Hau z Kh as, New De lhi 11001 6 Received : 23 May 2003 ; accepted: 30 October 2003 Energy efticiency a nd en v iro nmen t analysis have bee n performed for coa l based thermal powe r plants s ilU ated i n Delhi f or Indian a nd im p o rted coal from Australia a nd America. In our s tud y, it h as been found th at it i s better to use import e d C <11 in Indi an ther mal power plants , wi th advanta ges li ke, le ss amou nt of coal feed , low CO) em issio n , a nd less am o unt of parti c ul a te ge nerati on. The effect of per celll excess air o n particulate genera te d a nd co ll ection efficie ncy of e lec t rostatic prec ipit ator (ES P ) is a lso ana lyzed , and it is found th a t as th e pa r t icu late g enerated ( before discharge) is l ess for imported coal. on e may lise less e ffic ie nt ESP in thermal power pla nts . K ey w ords: Impact, In dian and i mported coal, Coa l , Indian Therma l P ower Plants , Thermal Powe r Pl ants 1 Introduction Th e power ge ne ra tion in Indi a ha s registered re ma rk ab l e grow th s in ce it ga in ed ind e pend e nc e in I947( r ef. I). Power ge nerat i on in cr eased from 1 362 MW in 1 947 to abo ut 1049 J7 MW in 2002( r ef. 2), Thermal power plants and hydro-sectors are the major power producer in Indi a. The majo r portion of power demand in Indi a i s met by thermal power plants du e to availability of fo ssil fue l s (coa l, o il , and gas). Around 72 per ce nt of t ot al in sta ll ed capacity i s met by thermal powe r plant s a nd 25-30 per ce nt is met by hyd ro e lec tri c powe r ge nerati on, while th e r est accounts f or o th er so ur ces of power ge ne rati on. Among th e co nv entional means of power ge neration , foss il fuel fir ed thermal power pl ant s are very si gnifi can t in the en er gy sce nario of Indi a H . Fossi l fuels (coa l, oil, a nd gas) is goi ng to r e main th e primary so urce of e ne rgy in Indi a in sp it e of atte mp ts to harn ess hyd e l, nu c l ea r, and renewable so urces of e nergy. In the sp he re of fossi I fuels, India is not ve ry well placed with r efe re nc e to resources of o il and imp o rt of o il is very expe ns i ve . However th e s ituation with re s p ect to coa l r es e rv es i s co mparativ e ly be tt e r, as it contributes 84 pe r cent of the rm al power ge nerat ion while, gas and oil contribute to 1 3 and 3 pe r ce nt of th e rm a l power ge ne rat ion , res pecti ve l / ) · t2 *Autho r for correspo nde nc e E-mai l cha ndr a 0 ces. i d .erne . in In India the demand of e l ec tri c ity is a lway s more than the s upply a nd the coal r ese rv es in India is in better condition than other fo ss i I fuels , thus th e power production i s tot a lly de pe ndant on the co al, which is re s pon si ble to a la rge ex te nt , in po llutin g ou r environment. Environmental probl ems associat ed with thermal powe r plants start wilh t ran s port at io n of coal f rom min e, feeding it to boi l e r , a nd th e e mi ss ion of flue gasesl.\ Now adays the e nvironmental problems of e nergy use are rel ated with e nvironmental cost, which have been risin g, rei nfo rc in g the effect of increase d mon e ta ry costs in creating in ce nti ves for incre as ing th e efficiency with which e ne r gy is used 1 4 . Th e e nergy eff ici e ncy a nd e nvironmental pollution of therma l power pl ant are de pendent up on the fuel use d for comb us tion in furnace of bo il er. Since coa l r ese rves in India is in bette r situation , thu s it is worthwhile s tudying the impact of coal qu a lity in thermal powe r plants. Howeve r th e coa l found in India is characterized by low calorific va lu e and high ash content. As a result , for getting a un it amount s of e lec tricity, large amount of pollutan ts ar e ge ne rated. It is desirable to ha ve a good qual ity of coa l for powe r ge ne ration, as it re duces the ge ne rat ed/ unit of e lectricity. Th e problem i s a nal yzed in the present st udy by considering good quality of coa l obtained from overseas. Th e work re ported he re exa min es the impac t of coal qu a lity in thermal powe r plant situated

Transcript of Flue Gas Calculations

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Journal

of Scientific

Industrial

Research

Vol.

63, Fe hruary

2004

, pp. 156- 162

Impact of Indian and imported coal on Indian thermal power plants

A Chandra  and H Chandra

Ce ntre for Energy Studies, Indi an lnstitute o f Technology, Delhi , Hauz Khas, New Delhi 11001 6

Received : 23 May 2003 ; accepted: 30 October 2003

En

ergy efticie

ncy and

env

iro

nm

en t analysis have b

ee

n

performed

for

coa

l

based

thermal

powe

r plants s ilUated in Delhi f

or

Indian and imported coal from Australia and America. In o

ur

stud y, it has been found that it is better to u

se

imported C <11 in Indi an

ther mal power plants , wi th advantages li ke, less amou nt of coal feed , low CO)

em

ission, and less

amo

unt

of

partic ul ate ge nerati on.

The

effect of per celll excess air on particulate genera ted and co ll ection efficiency of elec trostatic prec ipitator (ES P) is a lso ana lyzed ,

and it is found that as

th

e particu late g

enerated

(before discharge) is less for imported coal. on e may lise l

ess

e ffic ie

nt

ESP in thermal

power

plants .

Keywords: Impact, Indian and imported coal, Coa l, Indian Therma l Power Plants , Thermal Power Pl ants

1 Introduction

Th e power generation in Indi a ha s registered

re ma

rk

ab le grow th sin ce

it

ga in ed independe

nc

e in

I

947(

ref. I). Power ge nerat ion increased from 1362

MW

in

1947 to abo ut 10

49

J7 MW

in

2002(ref. 2), Thermal

power plants and hydro-sectors are the major power

producer in

Indi

a. The majo r portion of power demand in

Indi

a is

met

by thermal power plants du e to availability of

fo

ss

il

fuels (coal, o

il

, a

nd

gas).

Around 72

per ce nt of

total

in

sta lled capacity is met by thermal powe r plants

a

nd

25-30 per ce

nt

is met by hyd ro electric power

ge

ne

rati

on, while

th

e rest accounts for o

th

er

so ur

ces of

power ge nera

ti

on. Among the

co nv

entional means of

power

ge

neration, foss il fuel fired thermal power pla

nt

s

are very signifi can t

in

the ener

gy

sce nario of Indi a

H

.

Fossi l fuels (coal, oil, and gas) is goi ng to remain

th e primary source

of

energy in India

in

sp ite

of

atte mpts to harn ess hydel, nu clea r, and renewable

sources

of

energy. In the sphere

of

fossi I fuels, India

is

not ve ry well placed with refe renc e to resources of

o il and import

of

o il is very expensive . However th e

s

ituation with re spect to

coa

l rese rv es is

comparative

ly

better,

as

it contributes 84 per cent

of

the

rm

al power generat

ion

while, gas and oil contribute

to

13 and 3 per cent

of

th erm al power generation,

respecti ve l/ )· t2

*

Author for

correspo

ndence

E-mai l cha ndra 0 ces. i d .erne

 .

in

In India the demand

of

elec tri city is always more

than the supply and the coal rese

rv

es

in

India is

in

better condition than other fossi Ifuels, thus

th

e power

production is totally dependant on the coal, which is

respon si ble to a large ex te nt , in po llutin g ou r

environment. Environmental probl ems associated

with thermal power plants start wilh transportation

of coal from mine, feeding it to boi ler, and th e

emi

ss

ion

of

flue gasesl.\ Nowadays the environmental

problems

of

energy use are rel ated with environmental

cost, which have been rising, rei nforc

in

g the effect

of

increased monetary costs

in

creating

in

centi ves for

increasing

th

e efficiency with which energy is used 14 .

Th

e e nergy

eff

ici e ncy a nd e

nvironmental

pollution

of

thermal power pl ant are dependent up on

the fuel used for combustion in furnace

of

bo iler.

Since coal reserves

in

India is

in

better situation, thus

it is worthwhile studying the impact of coal quality

in

thermal power plants. However

th

e coa l found

in

India

is

characterized

by

low calorific va

lu

e and high

ash content. As a result , for getting a un

it

amounts of

electricity, large amount

of

pollutants are generated.

It is desirable to have a good qual ity

of

coal for powe r

generation, as it reduces the generated/unit

of electricity. The problem is analyzed in the present

study by considering good quality

of

coal obtained

from overseas. The work reported here examines the

impact

of

coal quality in thermal power plant situated

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CHAN

DR

A CHA OR

A: IMP

ACT OF INDI AN IMPORTED COAL 0 INDI AN TH ERM AL POWER PLANTS

157

in

Delhi , with res pec t to energy e ffi ciency and

env

ir

onmental pollution for Indian coa l and coa l

imported from

Au

strali a and Ame

ri

c

a.

2

aterials and ethods

For a

nal

ysis of polluta

nt

e

mi

ssion and ener

gy

efficiency, data have been co llected from

th

e power

plant loca ted

in

Delhi. Thi s power stati on is

th

e

Badarpur Thermal Power Station (BTPS

  ,

Badarpur,

New Delhi. BTPS is coal-fired

th

ermal power pl a

nt

under National Therm al Power Corp ora

ti

on (NTPC),

an ap

ex

body

in

India for power produc

ti

on. Analysis

of

th

e BTPS is perfo

rm

ed and

th

en

in thi

s power

pl

a

nt

th

e coal

is

repl aced from differe

nt

mines of India and

imported coal from Au strali a a

nd

Ameri ca.

2.1 Collection

of

Data

Data co llec ted

arc

as fo

ll

ows:

2.

1.1

Technical Data of

13TPS

Fo

ll

owin

a

data have bee n co

ll

ec ted from BTPS :

b

(a) Co

al

Co mpos iti on- As the co mpos iti on of coa l

va ri es eve ry day, so the co al co mpos iti on is

g iven by the ave ra

ge

va lu e of

pr

o

ximat

e and

ultimate analys is of the co al used for producing

heat in plant.

( i)

Pr

ox

imat

e

an

a l

ys

is ( pe r ce nt by m

  s s -

Moist

ur

e = 2.8 1, Ash = 45.25, Volatile matter

(

VM

)

=

16 .54, F i

xe

d

ca

rbon (F

C)

=

3

5.40

,

Calorific va lu e

(C

V) = 3995 .3 75 kcal/kg

(

ii

) Ultimate or total ana lys is (per ce nt by m  ss -

Ash

=

46.56,

Ca

rbon (C )

=

39.8 1, Hy

droge

n

(H)

=

3.3 5, Sulphur (S)

=

0.50, Nit rogen (N)

=

0.78,

Oxyge

n 0) = Remainder.

(b) Coal Feed

(i) Co al

so

urce is Jharia Coa l Fie ld s, Dhanbad,

Jharkhand

,

India

.

( ii )

Th

e

coa

l f

ee

d fo r ea ch unit is g iven

in

Table I .

U

nilnu

Firs l

Secund

Third

Fuurth

Fifth

Tulal

Tahle I- Coa l feed for each unil ofBTPS

Coa l feed lid

1664

1692

1640

31

93

3036

225

(c) Capac

it

y o f P

owe

r

Pr

od uc

ti

on

of Eac

h U

ni

t

Capac ities of first, second , and third unit s are

100 MW

eac

h. A ll th

ese

th ree unit s a re

co nnec ted to one chimney.

Ca

pac

iti

es

of

fourth ,

and fifth units

ar

e 2 10

MW

each and the

se

two

are

co

nnec ted to second c

himn

ey.

Thu

s, total

p

owe

r produced by BTPS is 720 MW.

(d) For Fourth Unit of BT PS- Emis sion rate of

total fl y ash vari

es

bet

wee

n 1

50

to

700

m

gl

Nm

  . Capac ity o f fourth unit is 2 10 MW .

Ave rage flue

gas

fl

ow

rate vari

es be

tween 1

60

Nm

 

s

to 2 15 Nm 

s

at I

SS e

2.1.2 Indian Cnal Quality

Th

e

co

al quality o f

diff

erent

coa

l fi e

ld

s from

In

d ia is

g iven in Table 2( re f. 15   . Indi a has

70

bt rese rve o f coa l;

amounting to almos t 7 per

ce

nt of the g loba l res erves.

Signifi cantl

y,

86.4

per

ce

nt

of

coa

l r

es e

rv

es

in In d ia

li

e

within eas

il

y ex plo itabl e depth of 600 m. Th e Ind ian coa l

is of mostly sub-bituminous rank, fo

ll

owed by bitumin ous

and li gnite (brow n coal  . Unlike coa ls o f Austra li a and

Ame

ri

ca, Indi an

coa

ls h

ave

a rather

hi

gh per

ce

nt

age

of

as h, rang

in

g between 20-40 pe r ce nt and sulphur co ntent

is

ge

nera

ll

y l

ess

than 0 .6 per

ce

nt

1/1

.

2.1.3

Imported

Coal

Quality

C hina and So uth Asi a a re both projec ted to in crease

the ir de

mand

for

coa

l by more than 3

pe

r ce ntly d

ur

ing

the projec

ti

on pe ri od. Coal demand in South As ia w ill

co

ntinue to be dominated by Indi a. C hina and Ind ia w ill

therefore exert more influen

ce

on

As

ian

coa

l produc ti on

and

inte rn ational

co

al trade.

In

India the future leve l o f

co al pr

oduc

ti

on will prima ril y d

epe

nd on th e ava il ab ility

of finance to ex pand produc

ti

on capac it

y, was

hing plants,

and infras truc ture . Th e problem is not one of res e rves ,

but the rate at which

pr

oduc

ti

on

capac it

y

ca

n be ex panded

and

it

s loca ti on re lati ve to po tential

co

nsumer

s.

Currently,

Indi

a s co

al produc

ti

on and transpo rta ti on ca pac ity is not

ex panding rapidly enough to sa ti sfy domes tic coa l demand.

Therefore, Indi a is currently importing coa l from Austra

li

a

and Ame ri ca. Austra

li

a has 7 7 bt of demonstrated ill sitll

coa l res ou rces 1(,. Au s tra lia is the fourth la rges t

coa

l

produ

ce

r in the world , that

pr

odu

ce

d

26

5 .5 mt

of

black

coa

l in 200 I (ref. 17 ). It ex ported 73 pe r ce nt of thi s

produ ction ( 193.8 mt) , makin g Aus tra li a the wor ld  s

lar

ges

t coa l exporter (a pos ition it has he

ld

s

in ce

I

Cl86 ,

accounting for around 30 per ce nt of wo rld trade. As ia

account s for almos t 80 per ce nt of Aus

tralia

 s coa l expo rls

with the top

four

markets be

in

g

Jap

an (47 per

ce

nt), Korea

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158

J SCI INO RES VOL

63

FEI3RUARY

2004

Tahle

In

dian coa l quality (per ce

nt

by we ig

ht

)

Coa l fi eld

C H S N

0

Ash fr acti on Moisturc CV (kc allkg)

Fly ash fraction

Ra

ni

ga

nj

, Wcst Bcnga l

60.2 4.2 0.3 7.1 22.9 3.5

42 :: O 82

Giri dih. Jharkhan d

5 0 ~

3.8 0.5

1.3

5.9 34

3.7 4058 8.U

E 1St Flokaro, Jharkhand 6 1

4. 1 0.49 1.53 7.2 2 1

4 _ 6 ~

4300

XX.58

Wcs t Fl okaro . Jlwrkhand 52.3

3.3

0.4 1

1. 23

4.9

36

U\6 4098

7lJ .6

S ngrau

li

, M P ;

111

d UP

39.27

2.8

055

o.n 9. 18 39 8.28

3 ~ 5

78.25

" m ha, CG

42.93

2.XOlJ 0.4 1.06 8. 5 6.30 1 3997

lJO

Wardha Va lley, Maharas

ht

ra

46.4 2.9

0.4 1 1. 16 lJ .3

32 7.83

402(}

X

X.58

TaJc har, O ri ss;1 40.56

2.76

(UX

0.93 9 40 6.37 39 10

90.5

Tahle 3 - Impo rtcd coa l qu alit y (per ce

nt

hy weight )

CO;ll

ty pc

c:

J /

S

N 0

Alistra l

i;lI1

coa l

70

4.X 0.5

1.

7 6. 3

American coal

Pcnnsy lvania

77.4

5.2 2.4 1.4 5

Ohi o

64.2 5

I .X

1.3

8.9

West Virginia

70

5. 1

1 2

1.5 12.9

KClll llck y

70.9

5. 1 2.3

I

'i 8. 1

Illinois

73.7

5.

1

?

.

1.6 7.4

( 13 per cent

).

Taiwan (8 per cent ) and India (7 per cent

).

Accordin g to

Au

stralia 's black co

al ex

po

rt

of year

2001

-

2002, India imported 1.4 mt of coal while total exp ort to

Asia is 83.7 Mt (re

f.

17) . The US is a maj or player in th e

int ernati onal st ea m coa l marke t. Co ns

id

erable excess

produ cti on and ex port capac it y ex ists

in

th e US, and thi s

e ffec

ti

ve ly pla

ces

a

limit

on th e ex tent to whi c h

i

nt

ernationall y traded co

al

pri ces can rise. The relatively

high price level at which th e

US

produ cers enter th e exp ort

ma

rk

e t. prov

id

es some she lter for th e deve lopme

nt

of new

capac ity in oth er

ex

pensive reg ions such a

s,

Lati n

Ame

ri

ca, lnd onc sia, and China . The imported co

al

quality

ha s been anal yzed in

th

e study and is given in Tabl e 3.

The relevant dat a has bee n co ll ec ted from relevant

SOLI rces 17·   I .

The comp a

ri

son of Table 2 and 3 regarding

th

e co

al

quality shows th at th e In dian variety o f coa ls gives less

c

al

orific value

(v

aryin g be tw een 3852 to 4300 kcallkg),

and

hi

gh ash

n t ~

(v

ary

in

g between

21

to 40 per cent);

whi le impo

rt

ed qualit y of coal is ha v

in

g hi gh calorific

v

al

ue (vary in g hetween 6300 to 7800 kcallkg), a

nd at

th e

same time hav in g low as h f

ra

c

ti

ons (varyin g between 7. 5

to 15 pe rcent ). Thu s,

fo

r ge tting the same amount of energy

the amount of co

al

bu

rn

ed in th e case of impo

rt

ed co

al

will be less and so is th e fl y ash generation. Thus th e O

Ash fracti on

Moist llre C V (kca /kg)

Fl y frac

ti

on

14.4 2.3 WlJO

70

7.5

1. 1 7728

55

16 2.8 6378

5 1

1.

2 7522

.'iX

9.8 2.3 7022

(

) }

7.9

2 7330

55.5

generated/ unit of ener

gy

in

th

e case or

im

po

rt

ed co

al

w

ill

be less, and fl y ash generated will also be le ss, requiring

the sma ller ESP for fl y ash co llec ti on. For Indian coa l

th

e

reverse

is th

e case

,i

.e., larger amount of coa l burned and

hence more CO" genera

ti

on, more

fl

y ,I

sh

to co

ll

ect, and

larger the s ize o f ESP.

2.2

Ma

thematical Model ing

Analysi s o f vari olls data co llected for power pl a

nt

s is

based on certain we ll establi shed relati onshi ps

  '

-('"" .

(a) Relations for

Energ

y Analysis"  '

Overall e

ffi

ciency of coa l based the rm al po\ve r plant

is

(per cent)

={ (Outpu t powe r)/(Input powe r)} x 100, ( I)

where, Input power

=

Coal feed x Cal or ihc value (CV)

of coal

(2)

(h)

Quick Comhustion Relationships

.'''''''''

Alth ough some of carbon and su lp hur may remain

unburned (less than or equal to 4 per however its

ex

act estimate are

di ffi

cLlI to mak

e, th

erefo

re

here

wc

have

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CHANDRA CHANDRA:

IMPA

CT OF INDIAN IMPORTED COAL

ON

INDIAN THERMAL POWER PLANTS

15

9

assumed 100 per cent combus

ti

on of carbon and sulphur

2:

Volume of CO

2

emitted =

u

1

=

(22.4  00). CII2) Nm

3

1

kg

of

coal

(3)

where C is c

arbon In per cent

by

weight

of

coa

l

composition.

Volume of emitted in Nm  /s = u

1

x coal feed

(kg

of coa l/s), ... (4)

Volume of

S0

2emitted =

u

2

=

(22.4  00) .(S/32)

Nm  /kg of coa l ,

. (5)

where S is s

ulphur

In

per

ce

nt by

weight of coa

l

compos

iti

on.

Volume of SO] emitted

in Nm  /s

=

u]

x coal feed

(kg of

coa l/s . (6)

Mass of gas produced/s =

w

=

111. PVIRT) , .

(7)

Vo lume of N2emitted =

y

= 0.79 A

ll +

[(Nx22.4) I

(28x I00)] (

10

)

Volume of

flu

e gases = V  = Nm  /kg of fuel,

. . . (

II

)

Combustion of coal requires excess air, so let n per cent

of

excess air

is

required, then ,

Volume of

flu

e gas

in Nm   l kg

of coa l = V = V

  +

II A

l

.

.. ..( 12)

Flue gas flow rate

in Nm

 /s = Vx Coa l feed .

.. . ( 13)

Inl

et Dust Concentrat ion = (Power capacity x Fly ash

fract i

on

x Coal feed

t/h/MW)

x Ash fraction x

10

(

) I

(F

lu

e gas flow rate x 3600)

g/N m  . . .

(

14)

In

Indian

, thermal p

owe

r plants E le

ctrostati

c

Precipitators (ESPs) are

Ll

sed to control

th

e particulate

emission . The co

ll

ection efficiency of ESP

(Tn

is given

where,

P

= atmospheric pressure( Pasca l) , = molecular as   :

weight of gas (kg/kg mol),

V=

vo

lume of gas

(N m  /s , R

= universa l gas constant

(J/kg mo l-K ), T= temperature ( K

).

Theo retica l air required =A I = {(22.4 x 4 .76)/IOO).

{(CI 12)+(H/4)- (0/32)+(S/32)) Nm

  /kg of coa l,

.. .(8)

where C, H,

°

nd S are ca rbon, hydrogen , oxygen, and

sulphur in per cent by weight of coal composition.

Volume of mo is tu re produced = =

22.4

  00).

{( H/

2

+

(Mil 8) }

Nm

  /kg of coal, .

. .

(9)

where H, and M are hydrogen, and moisture

in

per cent

by weight of coa l compos

iti

on.

= I-I (outlet dust concentrat ion)1

(inlet dust concentrati on)}

. . . ( 15)

Central Pollution Control Board (CPC B) set;

th

e o

utl

et

dust concentration from ESPs of th ermal power plants in

India, which

is

0.150

g/N m  .

3 Results

nd

Discussion

The data

of

th

e th ermal power plants , as give n in

section 2.1.1, is ana lyzed

in

terms of energy efficiency

and environment; and

th

e results are g

iv

cn

in

Table 4.

From Table 4,

it

is evident that the particu late generated

(before

di

scharge)

is

more than CPCB standards . CO

2

emission per unit of power output is more than S0 2

emission. The energy efficiency of BTPS for coa l feed of

11225 tid (or 0.6495

t/h/MW )

is 33.025 per ce

nt.

Analysis is ca

rri

ed out for BTPS with dif

fe

rc

nt

Indian

Table 4 - Environmental ami energy

an

alysis

or

BTPS with Jharia coal fie

ld

Therma l Power Plant Environmental Energy Efficiency

Analysis

Particulate generated SO, e

mis

sion

(p

er cent)

CO, emission

gIN

m ) before discharge

t/h/MW)

(t/h/MW)

Badarpur Thermal

Power Stalion (BTPS) 0.949665 99.305

0.006505

n

025

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C HA

ND

RA

&

C

HANDRA:

IMPACT

OF INDIAN & IMPORTED COAL ON INDIAN THERM

AL

POWER

PLA

TS 16

1

101

-

C

100

0

0

0

Q

99

VI

w

0

9

"--<>-- 8TPS I Jhar ia

co . , field I

>-

"-

j

~ P n n s

l v n i

"

97

96

95

v

0

94

93

40

50

60

70

eo 90 10

0

110

PtrClnt fxcell oir

Fi gure 5 - Vari a

ti

on of

co

ll

ec ti

on c

fl icie

n

cy of

ESP with res pect to

per ce nl excess air used for

co

mbustion in BTPS Pl ant

50 , 75 and 100 per cent, respec tive ly .

From

Figure 4, it

is

evident that Indian

coa

ls are

mor

e polluting with respec t

to the dust emiss ion to e

nvironm

ent.

It

is

du

e to the fact

th

at the

(l.s

h fraction of Indian coa l (varying betwee n 21 to

40

per

cent)

is

mo r

e than the

imported coal

(varying

betw

ee

n 7.5 to 15 per cent) . In imported coal American

coa

l is better than

Australian co a

l.

As

the

particu

late

generated

is hi

gh for Indian

coa

l therefore it is must to

co ntrol it before discharging into atmosphere with the help

of

pollution co ntrol d

ev

ices, e.g., e l

ec

trostatic

prec

ipitators

(ES Ps). Large ES Ps are required in order to mee t the

stipulated emiss ions standards, which will incr

ease

the

ca pital cost and maintenance cos t of power plant and hence

hi

gher value or obtaining power.

Form Figure

4,

it

is also

ev

id

ent that the inlet

dust

co

nce ntration

decr

eases

as the

per

cent excess

a ir increases. It is due to the fact that after

co mbu stion the mass of the particulate

is

same but due to

excess air used for co mbu stion its density d

ec

reases.

From Figure 4, it is ev ide

nt

that th e inl et

du

st

co

ncentration is

hi

gh for

BTPS

(Jharia coal field) while

low for Pe nn

sy

lvani a

co a

l. In

order

to m

ee

t

CPCB

e mi ss ion s tandard

of

0 . 150 g

/N m

J; th e variation of

co

ll

ec tion effi ciency

of

ES P with respect to per cent excess

air, Figure is drawn . Fo rm Figure 5, it

is

ev ident that

w

il

en the per cent

excess

air is

mor

e then

th

e

collect

ion

effic ien

cy

d

ec

r

eases

, and as

th

e inlet

dust concentration

fo r Pennsy lvania coa l is low

co

mpared with Jharia coal,

therefo re

th

e co llec tion

ef fi

c iency for Pennsy lvania coal

is low. From Eq. ( 15 ), it may be observed that

th

e co

ll

ec tion

effic iency depends upon inlet

dust concentration

only,

be

ca

use

th

e outlet dust

co

ncentrat ion is fixed by

CPCB.

ow when inlet du

st co

nce ntration decreases then the

co

ll

ec

ti

on e ffi c iency 01' ESP also dec reases. The inlet dust

_101

c

1 0

99

.

...

91

"0

97

>-

c

96

9S

c

'4

93

92

"

'

0

D

'c

. :.g

a

."

'

;;;

w

0

ID

ID

a

I

a

O

.t

Difftrent coal f

i lds

~

n

' SOpetCint

~

n

Sptr

cenl

O

n. 1 ptr

nt

a

'2

>-

0

:.c

>

c

;

'

Figure 6 - Co

ll

ec tion ef fici ency of ES P for BTPS anJ

diff

erent

coal fields used in BTPS with variatio n of per ce nt

exc

ess

ai

r (n)

concentration

of

the Pennsylvania coal is lower than Jharia

coa l, because the ash fract ion of Penns ylvan ia coal (7 .5

per

cent)

is

lower than

]h

a

ri

a

coa

l

(46.56

per ce

nt

).

Th e

\ inlet

dust co

ncentration also depends up on the

fl

ue gas

flow rate, whic h depends upon the per ce nt excess ai r,

and as the per cent excess air incr

eases

, flu e gas fl ow rate

increases, and the inlet dust concentration decreases.

Figure 6 shows the co llec tion effic iency of ESP for

BTPS and various coa l

fi

e ld s used in BTPS wit h variation

of per

cent

excess a ir.

From

Figure 6, it is evident that th e

required coll

ec

tion ef ficiency of ES P is l

ow

for impo

rt

ed

coal than Indian coa l, as imported coa l ha s low inlet dust

co

nc e ntrati o n . And as th e inl e t

dust co

n

ce ntrati

on

decreases then the co llec

ti

on ef fic iency als o dec rea ses,

b

eca

use

the

outlet

dust

co

n

ce

ntra

ti

on rema

in

co

nstant by

the standards fixed by

CPCB. Th

e inlet dust co ncentration

a l

so depend

s upon the flue gas flow rate, which depends

upon

the per cent

excess

a ir used for co mbu sti on.

4 Conclusions

In this study the suit ability

of

Indian

coa

l and impo

rt

ed

coa

l from Australia and

Am

erica for Indian

th

ermal power

plant is assessed with respect to en

er

gy effic iency and

environment analys is.

It

is

es tim ated that am ollnt or

coal feed is required in

th

e

case of

imported coa l (to ge t

the same energy ef fic iency) to generate the same

am

ount

of

e l

ec

tricity, as

it

has hi gh calorific value. Also

th

e CO,

emission and particulate gene rated (before di scharge) is

lower for imp

or

ted coa l than Indi an coa l. As

th

e particulate

generated are less for imp orted coa l thu s we can use less

ef ficient ESPs to co ntrol particulate. Th e SO , e

mi

ssion is

hi

gh in the case of imported coa l, which I; ight require

f

lu

e gas desulphuri sa

ti

on treatmcnt

in

so mc cases. One

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J SCI IND RES VOL

63

FEBRUARY 2004

has to

do

more

detailed analysis in

order to

ge

t overall

cos t of ge nerating e l

ec

tricity for each case.

Acknowledgement

The authors acknowledge support provided by the

Illana

ge

ment ofThennal Power Plant r

ega

rding collection

of

data

and

power

plant visit.

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