Journal of Scientific & Industria l Research Vol. 63, Fehruary 2004, pp. 156- 162

Impact of Indian and imported coal on Indian thermal power plants

A Chandra' and H Chandra

Centre for Energy Studies, Indi an lnstitute of Technology, Delhi , Hauz Khas, New Delhi 11001 6

Received : 23 May 2003 ; accepted: 30 October 2003

Energy efticiency and environmen t analysis have been performed for coal based thermal power plants s ilUated in Delhi for Indian and imported coal from Australia and America. In our study, it has been found that it is better to use imported C0

CHAN DR A & CHA OR A: IMPACT OF INDI AN & IMPORTED COAL 0 INDI AN TH ERM AL POWER PLANTS 157

in Delhi , with respect to energy e ffi c iency and environmental pollution for Indian coal and coal imported from Australi a and America.

2 Materials and Methods For anal ys is of pollutant emiss ion and energy

efficiency, data have been co ll ected from the power plant located in Delhi . Thi s power stati on is the Badarpur Thermal Power Station (BTPS), Badarpur, New Delhi. BTPS is coal-fired thermal power pl ant under National Thermal Power Corporation (NTPC), an apex body in India fo r power production. Analysis of the BTPS is performed and then in thi s power plant the coal is repl aced from different mines of India and imported coal from Australi a and Ameri ca.

2.1 Collection of Data Data collec ted arc as fo ll ows:

2.1.1 Technical Data of 13TPS Fo ll owin a data have been co llected from BTPS : b

(a) Coal Compositi on- As the compos ition of coal va ries every day, so the coal co mpos iti on is g iven by the average va lue of proximate and ultimate analys is of the coal used for producing heat in pl ant.

( i) Prox imate an a lys is ( pe r cent by mass)-Moisture = 2.8 1, Ash = 45.25, Vo latile matte r (VM ) = 16.54, F ixed carbo n (FC) = 35.40, Calorific value (CV) = 3995 .375 kcal/kg

( ii ) Ultimate or tota l ana lys is (per cent by mass)-Ash = 46.5 6, Carbon (C ) = 39.8 1, Hydrogen (H) = 3.35, Sulphur (S) = 0.50, Nit rogen (N ) = 0.78, Oxygen (0) = Rema inder.

(b) Coal Feed (i) Coal source is Jhari a Coal Fie ld s, Dhanbad,

Jharkhand , India . ( ii ) The coa l feed fo r each unit is g iven in Table I .

Unilnu. Firs l Secund Third Fuurth Fifth Tulal

Tahle I- Coal feed for each unil ofBTPS Coal feed ( lid)

1664 1692 1640 3193 3036 11 225

(c) Capac ity of Power Produc ti on of Each Uni t-Capac iti es of first, second , and third units are 100 MW eac h. A ll th ese three unit s a re connected to one chimney. Capac ities of fourth , and fifth units are 2 1 0 MW each and these two are connected to second chimney. Thus, tota l power produced by BTPS is 720 MW.

(d) For Fourth Unit o f BTPS- Emission rate of tota l fl y ash varies between 150 to 700 mgl Nm' . Capac ity o f fo urth unit is 2 10 MW. Average flue gas flow rate vari es between 160 Nm

' Is to 2 15 Nm' Is at ISS lie.

2.1.2 Indian Cnal Quality The coal quality o f diffe rent coal fi e lds from Ind ia is

g iven in Table 2( ref. 15). Indi a has 70 bt reserve o f coal; amounting to a lmost 7 per cent o f the g loba l reserves. Signifi cantl y, 86.4 per cent of coa l reserves in Ind ia lie within eas il y ex pl o itable depth of 600 m. The Ind ian coa l is o f mostly sub-bituminous rank, fo ll owed by bituminous and li gnite (brown coal ). Unlike coa ls o f Austra li a and America, Indi an coals have a rather hi g h per centage of ash, rang ing between 20-40 per cent and sul phur content is generall y less than 0 .6 per cent 1/1 .

2.1.3 Imported Coal Quality C hina and South Asi a a re both projected to increase

the ir demand for coal by more than 3 per cently during the projection peri od. Coal demand in South As ia w ill continue to be dominated by Indi a. C hina and Ind ia w ill therefore exert more influence on As ian coal produc ti on and inte rnational coal trade. In India the future leve l o f coal production will primaril y depend o n the ava il ab ility o f finan ce to expand producti on capac ity, washing plants, and infrastruc ture . The proble m is not one o f reserves , but the rate at which producti on capac ity can be ex panded and its locati on re lati ve to potenti al consumers. Currentl y, India's coal producti on and transpo rtati on capac ity is not expanding rapidly enough to sati sfy domesti c coal demand. Therefore, Indi a is currently importing coa l from Austra li a and America. Austra li a has 77 bt o f demonstrated ill sitll coa l resources 1(,. Aus tra lia is the fo urth la rges t coa l producer in the world , that produced 265 .5 mt of black coa l in 200 I (ref. 17). It ex po rted 73 pe r cent of thi s producti o n ( 193.8 mt) , makin g Austra li a the wor ld 's largest coa l exporte r (a positi on it has he ld s ince I Cl86), accounting for a round 30 per cent of world trade. As ia accounts for almost 80 per cent of Australia's coal expo rls with the top four markets be ing Japan (47 per cent), Korea

158 J SCI INO RES VOL 63 FEI3RUARY 2004

Tah le 2- Indian coa l quality (per cent by weight )

Coal fi eld C H S N 0 Ash fraction Moisturc CV (kcallkg) Fly ash frac tion

Raniganj , Wcst Bcnga l 60.2 4.2 0.3 U~ 7.1 22.9 3.5 42!::O 82 Giri dih. Jharkh and 50.~ 3.8 0.5 1.3 5.9 34 3.7 4058 8.U E 1St Fl okaro, Jharkhand 6 1 4. 1 0.49 1.53 7.2 2 1 4_6~ 4300 XX.58 Wcst 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 ;111d UP 39.27 2.8 055 o.n 9. 18 39 8.28 3~50 78.25 " m ha, CG 42.93 2.XOlJ 0.4 1.06 8.5 3~ 6.30 1 3997 lJO Wardha Vall ey, Maharasht ra 46.4 2.9 0.4 1 1. 16 lJ .3 32 7.83 402(} XX.58 TaJchar, Ori ss;1 40.56 2.76 (UX 0.93 9 40 6.37 39 10 90.5

Tahle 3 - Importcd coa l qu alit y (per cent hy weight )

CO;ll ty pc c: J--/ S N 0

Alistra li;lI1 coa l 70 4.X 0.5 1.7 6. 3

American coal Pcnnsy lvan ia 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 Australia 's black coal ex port of year 2001 -2002, India import ed 1.4 mt of coal while total export to Asia is 83.7 Mt (ref. 17) . The US is a major player in the internati onal st ea m coa l market. Considerabl e excess producti on and ex port capac it y ex ists in the US, and thi s e ffec ti ve ly places a limit on th e ex tent to whi c h internati onall y traded coal pri ces can ri se. The re latively high price level at which the US producers enter the export market. prov ides some shelter for the development of new capac ity in other l es ~; ex pensi ve regions such as, Lati n America, lndonc-sia, and China . The imported coal quality has been anal yzed in the study and is given in Table 3. The relevant dat a has bee n co ll ec ted from re levant SO LI rces 17 " I .

The co mpari son of Tab le 2 and 3 rega rding the coal quality shows that the Indian variety of coa ls gives less cal orific value (varying between 3852 to 4300 kcallkg), and hi gh ash content~ (v aryin g between 21 to 40 per cent); whi le imported quality of coal is having high ca lorific val ue (varyin g hetween 6300 to 7800 kca llkg), and at the same time hav ing low as h fracti ons (varying between 7.5 to 15 per cent ). Thu s, fo r ge tting the same amount of energy the amount of coal burned in the case of imported coal will be less and so is the fl y ash generati on. Thus th e CO~

Ash fracti on Moist llre C V (kca!/kg) Fl y ; : ~ h frac ti on

14.4 2.3 WlJO 70

7.5 1. 1 7728 55 16 2.8 6378 5 1 ~. I 1.2 7522 .'iX 9.8 2.3 7022 ()(} 7.9 2 7330 55.5

generated/ unit of energy in the case o r im po rted coal will be less, and fl y ash generated will also be less, requiring the sma ll er ESP for fl y ash co llecti on. For Indi an coa l the reverse is the case ,i .e., larger amount of coa l burned and hence more CO" generati on, more fl y ,Ish to co ll ec t, and larger the size of ESP.

2.2 Ma thematical Model ing Analysi s of vari olls data co ll ected for power pl ants is

based on certain well establi shed relati onshi ps"'-'('"" .

(a ) Relations for Energy Analysis""'" Overall effi ciency of coa l based thermal po\ver plant

is (per cent)

={ (Outpu t power)/(Input power)} x 100, ... ( I)

where, Input power = Coal feed x Cal or ihc value (CV) of coal

... (2)

(h) Quick Comhustion Relationships.''''''''' Although some of carbon and sulphur may remain

unburned (l ess than or equal to 4 per c(~ nt ). however it s exact estimate are di ffi cLlI! to make, therefore here wc have

~

CHANDRA & CHANDRA: IMPACT OF INDIAN & IMPORTED COAL ON INDIAN THERMAL POWER PLANTS 159

assumed 100 per cent combusti on of carbon and sulphur2:1 Volume of CO2 emitted = u 1 = (22.411 00).(CII2) Nm31 kg of coal, ... (3)

where C is carbon In per cent by weight of coa l composition.

Volume of CO~ emitted in Nm' /s = u 1 x coal feed (kg of coa l/s) , ... (4)

Volume of S02 emitted = u 2 = (22.411 00) .(S/32) Nm'/kg of coa l , . .. (5)

where S is sulphur 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 N2 emitted = y = 0 .79 All + [(Nx22.4) I (28x I00)] ( 10)

Volume of flue gases = VII = U I +U2+~+Y Nm'/kg of fuel, . . . ( II )

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

Volume of flue gas in Nm' l kg of coa l = V = VII + II All. .. .. ( 12)

Flue gas flow rate in Nm'/s = V x Coa l feed . .. . ( 13)

Inlet Dust Concentrat ion = (Power capacity x Fly ash fract ion x Coal feed (t/h/MW) x Ash fraction x 10(') I (Flue gas flow rate x 3600) g/N m' . . . ( 14)

In Indian , thermal powe r plants E lectrostati c Precipitators (ESPs) are Ll sed to control the particulate emission . The collection efficiency of ES P (Tn is given

where, P = atmospheric pressure(Pascal) , 111 = mo lecular as' : weight of gas (kg/kg mol) ,

V= vo lume of gas (Nm.1/s) , R = uni versa l gas constant (J/kg mol-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 coal,

.. . (8)

where C, H, and S are carbon, hydrogen , oxygen, and sulphur in per cent by weight of coal composition.

Volume of mo is ture produced = ~ = (22.411 00). {( H/2) + (Mil 8) } Nm'/kg of coal , . .. (9)

where H, and M are hydrogen , and moisture in per cent by weight of coal compos ition.

11 = I-I (outlet dust concentrat ion)1 (inlet dust concentrati on)} . . . ( 15)

Central Pollution Control Board (CPCB) set; the outlet dust concentration from ESPs of therma l power plants in India, which is 0.150 g/N m' .

3 Results and Discussion The data of the thermal power plants , as given in

section 2.1.1, is ana lyzed in terms of energy efficiency and environment; and the results are g ivcn 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 S02 emission. The energy efficiency of BTPS for coa l feed of 11225 tid (or 0.6495 t/h/MW ) is 33.025 per cent.

Analysis is carried out for BTPS with diffe rcnt Indian

Table 4 - Environmental ami energy analysis or BTPS with Jharia coal fie ld

Thermal Power Plant Environmental Energy Efficiency Analysis Particulate generated SO, emission (per cent)

CO, emission (gIN m ' ) before discharge (t/h/MW) (t/h/MW)

Badarpur Thermal Power Stalion (BTPS) 0.949665 99.305 0.006505 .n025

I ()() J SCI INO RES VOL 6] FEBRUARY 2004

O. &

0.7

~ ~ 0. 6 ~

~ 0.5

~ 0. 4 ~ - ';;: C wo '"

0 Co -,; ' ~v ~ ~ ox

'" co co c >< :.> ... ~ :; 0 ~ c

'" "" ; ~ ~ >< Difftr l nt coaU iJlds 0..

figurc 1- Coal fced requircd from diffcrent coal fic lds whcn uscd in BTPS

..

"

7. V-

I/. I/:

I/: 7- I

., /: ' ~ H /: . / v: V % ~ "

'" c ~ 0 2,.. ~ ' ~' ~ 0 - ~ " ... '" " ~~ ~ " -,; ~ ~~ ~o co c 0 .. ~ .. 0 0 0 ;i W o :..

'" ~ > -;;.

'" '" co c

'" ... ~v

u; -<

Oiffer.nt coa l f itlds

; "/

j "/

Figure ]-SO~ emiss ion from I3TPS and di ffcrcnt con i fields uscd in BTPS

and imported coa ls. The amount of different va rieties of coa l required fo r getting a MW of power is shown in Figure I. Once the coal feed required is calcul ated then with the help of environmental analys is methodology we can get CO" SO, emission and particu late generated (be fore d i s~harge-) from the power station for different coal fi e lds. The results are shown in Figures 2-4. As per epeE norms the particulate emitted in environment should not exceed 0. 150 g/Nm o, then we can calcu late the effici efl'Cy of ESPs fo r var ious coa l fi elds. F igure I shows the coa l feed required from vari ous coa l fi e lds when these coa ls are replaced in BTPS fo r same energy output. From Figure I, it is ev ident that minimum amount of coal feed is required fo r the imported coa l than the Indian coa l. It is due to the fac t that the ca lorifi c va lu e of imported coal is hi gh compared to the Indian coa l thereby to generate the same quant ity of steam (electrici ty) we have to burn less quantity or coa l. Figure 2 shows the CO2 emi ss ion from BTPS and d ifferent coa l used in this power pl ant. From Figure 2, it is evident that CO2 emi ssion fro m imported coal is less

1.6

1 .

:. 1.2 >: "- 1.0 -"

~ - 0,8 c .

~ .~ 0.6

cf" 0 . u

0.2

0,0

~ ~ ~ 7. / ~ V /: ~ V / V ~ ~ ~ / ~ ~ '/ V ~ ~ ~ / ~ V / I V /. c 0

'" 0,.. ;; ~- '0 : 0.. c -" . ~ 0 ; . ,.. 0 -"~ '"

... :;; ~ d 0 ~ " = ~ ,\ ~ : ~ L .. '" '" ~ ~ ';: ~ ~ '" 0 - C 0 ;;: . c ~! ~> -;v ~ ~ 0 '" '" c '" ~ ~ c ox '"

-< "'- ; >< -Differen t coo l f i. lds

Figurc 2- C01 emi ssion fro 'li BTPS and dilfc- rcl1 t coal fi clds usefi in BTPS

70.----------------------------- ----------~ '1 60 "-

c 50

'" i 40 ~ 30 ~ 20

~ 10

'"

c 0.. 0

'" ... "g IXl '"

~ . .

--." ~o ~" .~ 0 .. ::-: c; Wo '"

co c

j ~: 2 'w Vi

Diff,rln' coo.l 1i . \ds

~ n:: SO per (~ nt ~ n:z:75pucent

O ne 100 per ( t nt

0 c ,..

0 ~ ~ ~ ;;: ~ 0 c

c . ; ~ ><

Figure 4--lnlct dust conccntration (bcforc discharge) from BTPS and differcnt roa l fie lds w ith variat ion or per cent

exccss air (n) uscd for combustion

than Indian coa l. Figure 3 shows the SO~ emi ss ion fro m BTPS and

different coa ls used in this power plant. From Figu re 3, it is ev ident that SO~ emi ss ion from imported coa l is higher than Indian coal. It is due to the fact that the sulphur content of Indian coal is generall y less than 0.6 pCT cent, and from Table 2, it is ev ident that the sulphur con tent of Indian coa l va ries from 0.3 to 0.55 per cent. The sulphur content of American coal is varying between 1.2 to 2.4 per cent , which is more than Indian coa l; therefore for American coal SOl emiss ion is too hi gh co mpared to Indian coa l. The su lphur content of the Australi an COLl i is with in the range of Indian coa l, therefore SO~ emi ss ion is low, and it is in the range of Indian coa l.

Figure 4 shows the in let du st concentration (before discharge) to any pollution control device fo r BTPS and different coa l used in thi s power plant. In order to gel complete combusti on in boiler the amount or ai r should be more than sto ic hi ometri c ra ti o. The inl et du s t concentrati on is ca lculated for three cases or excess air.

,

C HA NDRA & 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.nnsy lv.ni. "

97 ..

96 ..

~ 95 v ..

0 94 ~

93 40 50 60 70 eo 90 100 110

PtrClnt fxcell oir

Fi gure 5 - Vari ation of co ll ection c fliciency of ESP with respect to per cenl excess air used for combustion in BTPS Plant

50, 75 and 100 per cent, respective ly. From Figure 4 , it is evident that Indian coals are more polluting with respect to the dust emiss ion to environment. It is due to the fact that the (l.s h fraction of Indian coal (varying between 21 to 40 per cent) is more than the imported coal (varying between 7.5 to 15 per cent) . In imported coal American coa l is better than Australian coal. As the particu late generated is hi gh for Indian coal therefore it is must to control it before discharging into atmosphere with the help of pollution control dev ices, e.g., e lectrostatic precipitators (ES Ps). Large ESPs are required in order to meet the stipulated e mi ss ions standards, which will increase the capital cost and maintenance cost of power plant and hence higher value o r obtaining power. Form Figure 4 , it is also ev ident that the inle t dust concentration decreases as the per cent excess a ir increases. It is due to the fact that after combu stion the mass of the particulate is same but due to excess air used for combu stion its dens ity decreases.

From Figure 4, it is ev ide nt that the inl e t du st concentration is high for BTPS (Jharia coal field) while low for Pe nn sy lv ani a coa l. In order to meet CPCB e mi ss ion s tandard of 0 . 150 g/NmJ; the variation of co llection effi ciency of ES P with respect to per cent excess air, Figure 5 is drawn . Form Figure 5, it is ev ident that wilen the per cent excess air is more then the collection effic iency decreases, and as the inlet dust concentration fo r Pennsy lvania coa l is low compared with Jharia coal, therefore the collection effi c iency for Pennsy lvania coal is low. From Eq. ( 15), it may be observed that the co llection effic iency depends upon inle t dust concentration only, because the outlet dust concentrat ion is fixed by CPCB.

ow when inlet dust concentration decreases then the co llecti on e ffi c ie ncy 01' ESP also decreases . The inlet dust

_101 c

~ 100 .. 99 D. ...

::: 91 "0 97 >-c 96 ..

9S

c '4 ~ 93 ~ 92 "

'" "[ ~ ~ 0 -~

.t v; Difftrent coal fi,lds

~ n '" SOpetCint . ~ n .7Sptr cenl O n. 100 ptr '.nt

a '2

>-.~ 0 ~

:.c "> ~ ~ 0 c ;' '"

Figure 6 - Collection effici ency of ES P for BTPS anJ different coal fields used in BTPS with variati o n of per cent

excess ai r (n) concentration of the Pennsylvania coal is lower than Jharia coal, because the ash fract ion of Pennsylvan ia coal (7 .5 per cent) is lower than ]haria coal (46.56 per cent ). The

\ inlet dust concentration also depends up on the fl ue gas flow rate, whic h depends upon the per cent excess ai r, and as the per cent excess air increases, flue gas fl ow rate increases, and the inle t dust concentration dec reases.

Figure 6 shows the collection e ffi c iency of ESP for BTPS and various coal fi e lds used in BTPS with variati on of per cent excess air. From Figure 6, it is evident that the required collection efficie ncy of ES P is low for imported coal than Indian coal, as imported coal has low inl et dust co nce ntrati o n . And as th e inl e t dust co nce ntrati on decreases then the co llection effic iency also dec reases, because the outlet dust concentration re ma in constant by the standards fixed by CPCB. The inl et dust concentrat ion a lso depends upon the flue gas flow rate, which depends upon the per cent excess a ir used for combu sti on.

4 Conclusions In this study the suitability of Indian coa l and imported

coal from Australia and America for Indian thermal power plant is assessed with respect to energy e ffic iency and environment analys is. It is es timated that l e s .~ amollnt or coal feed is required in the case of imported coa l (to get the same energy effic iency) to generate the same amount of e lectricity, as it has high calorific value. Also the CO, emission and particulate gene rated (before di scharge) is lower for imported coal than Indi an coal. As the particulate generated are less for imported coal thu s we can use less efficient ESPs to control particulate. The SO, e mi ss ion is high in the case of imported coa l, which I; ight require f lue gas desulphuri sati on treatmcnt in so mc cases. One

J SCI IND RES VOL 63 FEBRUARY 2004

has to do more detailed analysis in order to get overall cos t of generating e lectricity for each case. Acknowledgement

The authors acknowledge support provided by the Illanagement ofThennal Power Plant regarding collection of" data and power plant visit.

References I Sinha Subrato, Environmental guidelincs for powcr plants in India

and other nations, t ;lIvimll Qllal Mallug. (2()(JI) 57-61.) . :2 IJOIt 'I' r Lilll'. 6 (9) (2002) 70-71. .\ Chandra A, Kaushik S C & Chandra H. Encrgy effi ciency and

mitigation of pollutants in thermal powcr plams. Illdiall.! Ai,. Po /llIl COJl!rol . 3 ( I ) (20m ) 15-2 1.

4 Chandra A & Chandra 1-1. Environmental man:tgcmcnt for clean power generati on of thermal powcr plant s: an Indian perspective, IlI iIillll .! Air Po/lllI COlllml. 3 ( I ) (2003) 22-36.

'i ChanJra A. Chandra 1-1 & Sarita Soni , In vest igation of particu late cont ro l intherm