4P42 Section:

Reference:

Title:

1 .I

76

Alliance Technologies Corporation, Evaluation of Significant Anthropogenic Sources of Radiatively Important Trace Gases, U. S. Environmental Protection Agency, Office of Research and Development, Research Triangle Park, NC,

1990.

PB91-1277f3 I

Evaluation of Significant Anthropogenic Sources of Radiatively Important Trace Gases

w 9A

Alliance Technologies Corp., Chapel Hill, NC

Prepared for:

Environmental Protection Agency, Research Triangle Park, NC

Nov 90

Coal cosrbumtion produces omissions of several greenhouse gases,

including Cq, NO,. methane and other hydrocarbonm.

boilorm contributo an estimated 16 percent of tho global anthropogenic CO, omimmionm and about 12 percent of global NO, omimsiona.

rplmsion. o t tho.. tvo gases from coal-fired utility boilers are estimated

Coal-fired utility

The combined

to contributo .bout 10 prcent tO the total 0.timat.d global radiative

forcing ammoclatod with anthropogenic mourcem.

01-1 .piamions of Cq and NO, from utility boiler. are clearly

m1qnltieant.

to country. Thum, it i m nocemmary to characterize the variations to

dovolop ropromontativo global emimmionm emtinutam. ?or oxample, emiasiona

ot Cq aro ralatd to tho type and quality of cor1 umod in a given country (1.0.. -1 rank and carbon contont).

mignltierntly from country to country, .cnLmmionm of Cq almo vary.

Vurthormore. tho emimmionm of both species vary from country

Sinco coal quality varier

Tblm chapor B - r k O S tho romultm of AEIRL's initial effort to dmlop country-mpreitlc aimmion factor. for coal-firod utility boilers. Uhmro rrimDion f a C t O r D could not bo dovolopd duo to a lack of data or for

0ch.r roa.on8. tho armam roqulrinq additional study are identified.

m r a l as-. ot coal-tirod olectric parer mysterna influence carbon

dlma16. -1maiMm. T h . momt mignificant Of these aro the overall

3-1

I

efficiency of the generating station and distribution system and the fuel

quality (coal heating value and carbon content). A more afficlent power and electrical distrlbutlon system consumes less fossil fuel to produce a given mount of electricity and thus, reduces greenhouse gas emissions. For eruoplm, the 1986 overall efficiency for electric utilities in India is

estlmatod to bo 20.4 percent, while that for the Federal Republic of

Germany is 36.6 percent (OECD, 1987). Such efficiency differences produce

significant variations from country to country for carbon-based greenhouse

gaees emitted from power stations. Key variables which affect overall

efficiency include the following:

boiler type and vintage fuel quality use of plant auxiliaries and emissions controla turbine and generator efficiency transformer/transmission line losses operational procedures maintenance

Although data for all of these factors are not available on a

Country-specific basis, fossil fuel energy consurnptlon data and electricity generation data are available for many countries and can be uaed to estimate generating mtation efficiency (referred to here as the busbar efficiency) and transmlssion line lOsOeS (EIA, 1987a; EIA, 1987bj OECD,

19881 OECD, 19871 OECD, 1989).

Carbon dioxide emissions are ale0 affected by variatione in fuel heating value and carbon content. Emiselone of Cq are proportional to the fuel carbon content and inversely proportional to :he heating value of the fuel (a higher heating value requires less fuel consumption for a given mount of energy production). types. with lignite or brown Coals tending to have lower carbon content and

heating value than harder coals such as mubbltuminous, bitwinous and

anthracite.

Fuel properties vary for different coal

Country-specific coal consumption lnformatlon by typ. can bm

3-2

used to m m t h t e coal carbon content and hmating valumm for uno in calculating Cq mimmion factor..

D-- 0. COVYTILY-SPEEI?IC CBR8OBl DIOXIDE DIISSION ?ACZOM

Carbon dioxide .mimaion factors wore calculated by simplo maae balance

assumin9 that a11 the carbon in the coal i m converted to Cq (except a

small portion which im asaumed to remain in the fly amh). The emission

factor. are in unit. of mass of carbon per unit of mnergy produced at the Cencm U n o of thm p w m r plant (rmfmrrmd to am buabar mnmrgy). In general,

am carbon contmnt incrmamms, thm .mlmaion factor incrmammm, and am coal hmating valum incrmammm, tho mmimmion Zactor decrmamma.

mignificant influencm on'thm mimaionm of Cq from coal-firmd mlmctric utllltioa. Thmmm two factor. are: (1) thm ovmrall mnmrgy mfficimncy and ( 2 ) tho coal quality. Thm ovmrall enmrgy mfficimncy factor takmm into

account thm mfflcloncy amaoclat.6 with tho gmnmration atation itmolf and

tho lomamm aamoclatod with thm mlmctrlcity tranamimmion/dLmtribution lymt.O. Thm fuol quality factor takom into account thm mxtmnt to which

coal Carbon eontmnt and hmating valua affmct Cq emimaiona. factor. arm dlmcumm.6 in thm following pagmm.

Am prmvioumly dimcummed, tuo factor. havm bomn ldentffimd am having a

Theam two

Ovmrall orurgy officlmncy for coal-firmd poumr planta varimm algnlfle~ntly from country to country. Xmthtmm of thm ovmrall mnergy convermloa efflclmny of coal-flr.6 utility boilmrm on country-mprzific

barnla (m nndod eo omebatm plant fuel roquir..wntm bamod on mnorgy demand

omtbatom. In addltlon, an matbate of currmnt plant efflcimncy im needed to foruaoc r l m m l a umlnq rlmalonm -1. mince thr currmnt officier.cy

loru tho bmahurk f r o which future clungma in mnergy dficimncy are omtlmatd .nb ramurd.

3-3

Y I !

.>.----. .. . . . .. .., . I

I I R

Overall energy efficiency c ~ l b. 08tbAt.d basod on data Available for coal conoumption by electric utilitios and energy production from electric utilities, taking into account lomoee through tran.miaoLon 1Fn.m (U.N. I

1984; U.N., 1981;'YRI, 1986; OEQ), 1987).

Overall I Net Coal x A x 1OQ Off iciency

(*) Total coal rnergy Connumod

where A - (100 - Transmission Line Xnss).

overall officiency thus reprements the efficiency of the conversion Of coal energy into electricity delivered to tho end-user.

transmiamion lines may be omitted from the above equation to yield a

calculatod busbat efficiency.

0CpLtt.d depending on the t m of .missions calculation being performed (i..., entimating omismions basod on electricity consumed by the end user,

or olectricity producod at the busbar).

analysis are in torms of anergy produced at tho busbar, and have been calculatod using tho appropriate busbar efficienciem. Transmission line

lomses ere roportod separately.

Loases through

Tran.mission l i i e lossss can bo included or

Emission factors prssented in this

Country-mpocific busbar efficioncies and transmission line losses are

presontod in Table 3-1 along with koy data used in their derivation. Ovorall officioncios for countries marked with an asterisk ( * ) Ln

Table 3-1 w r o determinod by making aevoral assumptions as indicated in the table. In sevoral camem, the busbar efficiency for coal plants could not

k calculatod due to inadequate data. available in s o w cases. If tho busbar efficiency for all fossil fuels

(coal, oil, and 0.0) was available for a particular country, these data worm usod in 1iou of information specifically for coal plants. No

significant difioronces were notod k t w e n the busbar officiency for all

fuel. urd that for Coal plants for those few countties where both data

i t a w r o available. This may bo because coal is tho predominant fuel

Transmission l i n e losses were

3-4

ueod by oloctric utilitioe. Tr.n.miaaion U n o loemem, if availablo, were

appliod to tho busbu rfficiency to generato tho ovorall eLLiciency of coal plant. (coal onorgy to delivorod ond-umer olectricity). If buubar

officionciom could not be esth8att.d using sum actual data, values were

Assigned basad on estimates for a neighboring country. u e noted in T a b l e 3-1.

These exceptions

Emissions of Cq from cuabuatlon 80urcee generally depond on the amount of cubon ontoring the procoes as fuol cubon and the mount leaving thm syetan oither in the flue gases (a, a, and hydrocarbons) or as ash.

This ovaluation assumes almost complete combustion of fuel carbon to Cq.

Approrimately 1 percent of tho original fixed cubon in coal 18 retained in

aah on combustion (Rotty and Xuland, 1984). Thereforo, it Le assumed that 99 porcent of tho fuol carbon is roloamed in tho Cq emissions after combustion and tho omieeion factor is dotermLned accordingly.

Neglecting the effecte of boilor officioncy and fuel carbon retained

am ash, the general expremmion used to calculato Cq emission factors for coal cornburtion procesees La:

whore XI- - Carbon Dioxide Bmieeion ?actor (mass Cq p r unit energy into

mcq - locular Weight of Cq (44 g/mole) mc - Molecular Weight of C (12 g/mole) \c I Carbon Content of Puel (mamm C per mame fuel) Hv Heating Value of Ne1 (unit energy per m e # fuel)

the plant)

3-5

i

. . . . . . . . . . . . . .

'.?

- t e

- ~ - - - O o o O O O O 0 0 0 0 0 0 0 ????? d d d d d d d d d d d d d d d d d d d O O O O O

.., ,

. .-

... ... .. ...... .

The carbon content and heating value vary with coal type or rank. In

general, as a coal ages and hardens (progressing from low rank lignite to

nigher rank bituminous and anthracite coals), the carbon content and

heating value increase.

coal mines are presented in Table 3-2. Analyses of various coal types sampled from U.S.

Although country-specific data for coal carbon content were not

available, coal consumption data for the majority of coal-consuming

Countries generally are available for several coal types (e.g., hard coal

and brown coal or lignite). either in mass units or in coal energy units, and may often be givon simultaneously in bath unit mass and u n i t energy for a given time period.

When both fonds of data are available, heating values can be calculated as follows:

The consumption data available are provided

Coal Heating Value - -1 Cons umMion I unit eneravl Coal Consumption (unit mass)

Alternatively, heating values of particular coal types, as consumed,

are availablo on a country-specific basis for countries listed in

Table 3-3. Several countries for which coal heating value data are

unavailable are not major coal consumers, and omitting them should not

affect the results of this analysis significantly.

In contrast to coal heating values, Country-specific coal carbon

content data are less readily available. drawn between carkm content and heating value from the coal data presented

in Table 3-2. Coal carbon content versus heating value is plotted in

ligure 3-1 for the various coal types. including lignite, subbituminous, bituminous and anthracite. Carbon content is linearly proportional to

heating value for lignite, subbituminous and bituminous coals (tc = 2.27 x

However, a relationship can be

3-8

T W 3-2. CBARACCJZRISTICS O? COAL DURINO PR00RXSSLVE STAOES OF TRNWOIUIATIO~?'

Porcent Eeathg Valum luml Classification Loc.lity Carbon BlV/lb TJ/1000T

Peat

Lignite

Lignite

Subbituminous C

Subbituminous B

Subbltuminoum A

Bitumlnoum High High Volatile C

BitUl8LnOuB High Volatile B

Situminoum High Volatile A

Bituminous H o d i u m Volatile

situminoum Volatile

Semi Anthracite

~thracito

Xeta-anthracite

Minnesota

North Dakota

Texae

Wyoming

Wyoming

Wyoming

Colorado

Illinois

Pennaylvania

Weet Virginia

Weet Virginia

Arkansas

Pennaylvania

Rhodo Island

52.2

64.7

64.1

61.7',

67.3

73.1

79.5

86.4

85.4

76.4

76.8

82.4

9057

11038

11084

10598

12096

12902

13063

13388

14396

15178

15000

13142

12737

11624

21.05

25.65

15.76

24.63

28.11

29.99

30.36

31.11

33.46

35.27

34.86

30.54

29.60

27.01

'Analysim im on dry basie. 'Source: Combustion Engineering, 1957.

3-9

MI * 5.0285; r - 0.994). since anthracite apparontly contains a higher mount of fixed carbon relative to the other coal typos.

Tho relationship for anthracite is less clear,

Coal carbon contents used in this uralyais w e r e dorivod from tho relationships ahown in Pipure 3-1 using country-specific calculated or

reported heating valuos determined as dsecribod earlier. Tor anthracito, an averago carbon content of 78.5 porcent WA. used for a11 heating valuss

(generally 25-30 TJ/lOOOT).

Available data for coal consumption typically deltneate hard and soft coal and do not distinguish anthracite from other coal typos.

study, hard coal is asmunod to include higher rank coals (bituminous to anthracito) while soft coal is assumed to include lower rank coals (brown

and lignite). The International Energy Annual (BIA, 1987a) publishes

'Rankings of Coal- Producing Countries,' which gives an approximato m o u n t of anthracite producsd as comparsd to total hard coal production ( i . ~ . , tho

fraction of a11 hard coal produced which is represented by anthracite) f o r major coal-producing countrios. Although these data refer to coal

production as opposed to coal consumption, Lt w a s assumed that the

anthracito portion of hard coal remains approximately tho samo from production to consumption for a given country. Countrioe which produce no

anthracito (and are thus not includod in thm rankings) are assumed to burn

no anthracite as fuel. be bituminous and subbituminous coals. account that exports could contain anthracite1 therefore, tho results prosentod here could rofleot mor. or Loss anthracite coal than a given country actually conmuma.

In this

tho balanco of tho hard coal reported is assumed to This analysim doom not tako into

Carbon dioxide omission factors were calculated using the reported and ostiautod amounts of different coal typos consumed by a country's utility

sector, tho estimated heating value of the coal consumed, and the estimated

carbon contmnt.

omission factore for oach coal typey The calculation was based on a veighted average of the

3-10

C0V)ITllY SOURC6

Auatralia Japan South Korea Hong Kong Now Zealand

India Thailand

Coloebla )(.xico Philippine. Chile Argentina

Singapore

Poland

Paki8t.n

8elgium

USSR South Africa Braril

Economic Commission for Asia and the Pacific. Electric Power in Asia and the Pacific, 1981- 1982, United Nations, 1984.

United Nations. Profiles 1986. New York, 1988.

Energy Balances and Electricity

Economic C&ission for Europ., United Nations. The Annual Bulletin of Electric Energy Statistics for Europe, 1986. 1987.

United Nationas 1986 Energy Statiatics Yearbook, 1988.

3-11

m

m m

+

I I I I I I I I

L if m P

Q

% 3

0 a r( :

Y II 9 Y 8 0 U

3-12

whora 1.- -

EYCc7,HC - Z?CQ,AC - epcq,ec I

A - B - c =

A * B + C

Yalqhtmd Country-mpacific Carbon Dioxide Eminmion Factor 8aued on Dlffarent Types of Coal Conmumed (omlmsionm par unit onarqy input)

tpimsion Factor for Hard Coal

1CmLssion Sactor for AnthracLta Coal

mimsLon pactor for B r m cual hard coal (bituminous, mubbituminous) consumad anthracita COn8umed brown coal (llpnita) consumed

Taktnq into account the busbar anergy efficiency estimated as described

earlier, M d tho f u e l carbon retained as ash, the emission factor can be

calculatad am described below:

whera L?CO,* - country-apaciffc auimsion factor for co, (amiasions per unit. of onarqy producod)

off - buabar afficiancy for coal-firod utility plants ?or oach country includod hora, transmission U n a loamom can be added to ond-us. anarqy danund (0.0. . Oloctricity d-nd by industry) to yield the

anorgy raquired at th. foncalino of powor plants in .a 9iv.n country. thlm d a n d for coal plants La multiplied by E?-*, tha omissions from

coal-firad p o t plant0 within that country u a asthatad. tha country-spclfic Cq r{.smLon factors in grama of Cq roported as carbon par Qlqajoulo O f onorqy produead.

prtinont to .mission factor Cal.:UlatiOnS for asch country. listed Ln Tablas 3-4 urd 3-5 arm rankad from larqest coal producer to smallost for which data war'. wallable.

When

Table 3-4 lists

Tabla 3-5 prasenta tho data

The countries

3-13

biamion frctorm lor NO. vary .ignllLcantly lrm country to country. Tor oxamplm, 8ovoral w8torn Luropman countrir8 as w L 1 88 Japan have

rolativrly mtringont control rrguirmmmntm (i.o., riph otlic~mcy

~oloctivo catalytic reduction control.) uhilo much l08. mtringmnt control

requiremantm u o .ppployod in tho Unitod statom, Mexico, and pury othor

largo countriem (Wq, controls in thmmm countrim. uo typically limited to

tho unm of lor to modoratm officioncy c-umtion modification*. much am low

NO, burnerr, multi-.tag. combu.tion, flu. gam rmclrculation, reduced air

prohmat, reburning, or reduced oxcoam air). a..Ociat.d with these combu.tLon and po8t-combu8tion control., NO, .mimaion. arm affoctod by the qonmral boilmr doaiqn, which may also vary qlobally. ?or oxmplo, tangontially-fired boilor. omit mignificantly loss

NO, per unit fuel input than do cyclone and wall-flrod unit..

In additiop to tho infl~onco

?inally, NO, anismion8 aro affocted by other factor8 auch as operating practice., uhich may a1.o vary aubmtantially lroln on. country to another.

A boiler operating at full capacity will omlt mor0 NO, per unit fuel input

than on. operating at a reduced load. Hwevor, 8ince operating practices

are difficult to characterize frm country to country, goneral assumptions would have to bo made. Since many variables affecting country-specific NO,

emission factors are not quantifiable with the currently available data,

NO, emissions are discussed Ln detail, but country-specific emission

factors have not been developed.

COUNTRY-SPECITIC NITROOEN OXIDE ~ I S S I O W ?ACTORS

Uncontrolled emission factors for are published in the Compilation

of Air P o l l u t M t Emission Factors (comonly referred to as AP-42) on a mass

of pollutant per mass Coal bani8 for eeveral different boiler

configurations a# ehom in Table 3-6. Theee emission factors represent

UIIIP) 8TA- OY A X E R I U u*IQ OF SovIR S ~ X A L X B Z ~ I c s cJ$III (JIAIILUIO) L BoDio royo CIIUUXI, m.IuL IUHIIILIC OF u*xm I(1Y;Ww INDIA mLAm YHlM m 1 C A C B W CEKOcnAIIC RtPUBLIC CANADA AUSTRALIA CZLCHOSLOVhKIA SPAIN Y U G O I I U V I A JAPAN ?ma ROMANIA D E N W ITALY GRtECP HUNGARY KOREA, SOLlTii (REPUBLIC OF) HONG KONG 8 E U I U H ISRAEL BRAZIL NETHERLANDS FINLAND THAILAND INDONESIA ZIMBABWE COLOHBIA AUSTRIA nEXIC0 PORTUGAL PHILIPPINES CHILE

IRELAND TURKEY

noRocc0

74761 87831 88165 67931 72334 95416 81073 75769 88118 78696 76659 86880 83413 99140 61305 78169 95618 63960 67992

108092 125805

79590 62126 73735

67152 62085 44620

N o heating value.

60456 N o heating value. N o heating value.

105330 79458 66575 68916 73492 66567

70992 N o heating value.

N o heating value.

(continued)

3-15

.. 'LABLC 3-4. COW7SY-SPCCI?IC CARBON DIOXIDE m I S S I O N ?ACTORS

?OR UTILITY --FIRLO BOX- (continued)

NEW ZEALAND SWEDEN BOTSWANA hRGENTlNA U T A SWITZERLAND C LIECHTeNSTEIN NIGER PAKISTAN

B U W NETHERLANDS ANTILLES AND ARUBA LUXEXBOURG NORWAY m w 1 NIGERIA SINGAPORE

78486 63618

62973 91224

No heating value.

No heating value. No heating value.

159003

No heating value. NO heating value.

92980 52303

No heating value. No heating value.

69013

maximum NO, emissions, neglecting any reductions due to combustion or post-

combustion controls or the use of alternative operating practices.

regarding coal type and heat content can be used, together with the overall

efficiency factors presented in Table 3-1, to convert these uncontrolled AP-42

factors from a unlt mass to a unit energy basis. However, emission factors

vary depeqding on boiler configuration, so it is necessary to obtain

information regarding the population of bciler configurations that exist in

each country in order to use the data in Table 3-6 to estimate country-specific

NO, emission Zactors.

Information

D&ta are readily available for boiler configurations used in the United

However, estimates based on the 0.9. population of technologies may States.

not account for differences in NO, emissions due to different boiler types and

emlasion control atrategies employed by other countries. In addltlon to plant design, country-specific emission factors will also be affected by general

opa.-%tlng practices (e.9.. operating boilers at lema than Cull capaclty or at reduced combustion air rates). Again, data for Na, reductions due to genetal

3-16

..

operating practices are readily available for the United States, but may not be applicable to other countries. To obtain comprehensive country-specific data at this time requires a level of research which goes beyond the scope of this

Study. Literature searches were conducted and experts contacted, but a

Complete set of country-specific boiler population data was not readily

available.

The literature reviews and contacts made did yield some country-specific

information which could be useful in future efforts to develop country-specific emis8ion factors. These data are summarized here. First, it is clear that NO, emission8 are regulated and controlled in several western European countries and in Japan, the United States and Canada.

potentially siynificant countries producing NO, emissions from utilities are

presented in Table 3-7.

employed depend on various emissions standards established for the countries

shown.

high-efficiency post-combustion controls for NOx emissions.

requiring poSt-CombUEtiOn controls are identified in Table 3-8.

Regulations for many of the most

The extent and efficiency of control technologies

Of the countries listed in Table 3-7, only a few require the use of Countries

Data presented i n Tables 3-7 and 3-8 were obtained from reports prepared by IEA Coal Research in London. (Vernon, 16-88, A full report on NO, emissions

regulatione and controls is currently toing prepared by I M . should contain infornution on boiler configurations and NO, emissions control technologies employed by most western European countries, Japan, the United States, and Canada. Based upon this information from IEA Coal Research, it is

likely that these data will enable calculation of NO, emission factors for

these countries. However, information for Eastern Bloc countries and

developing nations i8 not as readily available. invostigations that countries not covered in their analysis generally 30 not

omploy combustion and post-combustion control teChnologie8 for NO, reduction.

Thus, only infornution doscribing goners1 boiler design and operating practices for theso countries i s necessary for ostiolation of country-specific NO,

emission factors.

This report

It was assumed based on IEA's

3-17

E!

n n I

3-19

Pfmmion Pactor Iirteg Configuration ko/W */ton

/'

Pulvorirod ' C o a l - P i r d Dry Bottom - Hall-Fired

\ /

/ 7 . 5 15 \ Dry Bottom -\ Tangential-Fired

wet Bottom \ //,/ Cyclone hrnace

34

37

Spreader Stoker 7 14

3.25 1.5 /

Underf&d Stoker '~ 4.15 9.5

Handfired Pnitm 1.5 3

\ /' 'AF-42 u n u a l , September 1985, T~U. ~ 1 - I .

'~ Yuturo offort. mhould be diractod toward &thering additional information

with rempect to coUntry-mpocifLc coal-fired boiler types currently in use. Thomo data, along with the NO, omimmionn controls and regulations report being propared by IEA, mhould .nablo a complote mmt of country-apecific NO, emission factor. to bo emtimated for major coal-conmuming countriem.

. ..

3-20

.. .

, . w. - 1989 Barton.. Carl.2%World Bank, p.r#onai 'cauuunication with' David Zincaannan, Alliance TOchnOl&leB Corporation, 8ePtember 1989. ' .!l.t.; .'%,i.

Triangle Park,.?WC. *Proceeding. o f Third U. S. - Dutch 1nt;rnatioal 8rmwsium _ _ 'on At~BphEri8~'brOne.,Research and Ita Policy ~mplicationo, Nijmegen. . .. . .. . . Nstherland~."May"?-l3, . . 1988. : .- . . . . . . ,. ..

g concentrations of Atmosphegic nothane, 1979-1983, PhD-

her Oreen&u,u.e Qases and Aerosols in and Ecosvsta,'Ed. B. Bolin. John

,*;

. , . . . . . .: " I

,. ~... HiiginBon, ode., Internatioiai '8olid wastes and Public

I. .-.

Brown, hater R., Christopher Flavin, and Colin Norman. -t - W O a . Worldwatch Papet No. 32. The Worldwatch Institute. Washington, DC. SepttSmber 1979.

n e Future of thg

. 1 '

Brown, L.R., an'r Pamela Shaw. to a Sustghnable soci&y . Worldwatch Paper 40. March, 1982.

tien and Chandler, Wlllilm U. Bartrpr Pr-itvt Kev to Protes -. Worldwatch Paper No. 63. The Worldwatch Institute. Washington, DC. , January '198s.

e8 and Calc ulated Release Chemical Manufacturer's Association. Boduction. sal 1986. Qf CFC-11 and CFC - 12 Thrn uah 19 84. Washington, D.C.

cicerone, R . J . , and R.S. Oremland. Biogeochemical Aspects of Atmospheric Methane. -tal CYChQ voi. 2. NO. 4. 1988. p. 299-327.

10-1

w. Mlk/EIA- Washington, D.C.

VOl. IV. 1987.

pood and Agricultural Organization. -tion Yearbook. vol. 39. Rome, Italy, 1987.

10-2

... ..I' ,- : . I . . .. ,- . . .

__

..

nsional' Uodel.

.. . . . . . . ...... 8 . .. Irani, U.C. IC m, Methane mission &om U.S. coal ULnOS, A Survey. Pittoburgh, PA, 1972.

Isakeen, I.S.A., P. 'stordal, Ozone Perturbations by Enh~ncad"f.evels of CPCs, NP, and q: . .A Two-Dimensional Diabetio Circulation study. ,Inoludinp

...... I L . .> . . . .

'' "',

concentration of q, ' . on , '"m, clt and NO,, a, 398, 271-285, 1987.

Isaksen, 'I.S.A., Unive

Isakaen, I.&, Univerdty of Oslo, Personal Comunication,. Decemhe; 19Bgb.

, . . A* .. ,*?,.. . : : . w A r * , , ? .

y of Oslo, Personal Communication;"October 1989'. I . . . . . :,?i<y _. . . . .

-..& .<,r.;:*:<

1 communication, 1989.

,. i: . -3 ,r**'.. . c , : ..

Sinks, and Seamonal Cycles of Atmosphmric Ueth 88: 5131-5144. 1984.

Source of Uethane in China: Ric. ?iddo,. Biopaa Pits, Cattle, Urban Areas, and Wetlands.

1. Ncrrrman, Ed. U.8. Department of Enerqy, 1990.

Kim, A.Q. Data, w a u of , 1977.

Estimating Uethane Content Of Bituminoue Coalbeds from Adeorption

10-3

. -

, , . .I ;:. ).:.

. , . i.

. . ' ; t h e Tro~ i sphoro t Olobal and Roglonal Budpots. 88(C15)~10,785-10~.r.r807. . . 1983. ....

. , -. * .......

. .* :k5*>:.> -i ,ti,* '- . ..<; ',y,. . . . ~..*;-.,>&~+.+:,.+,*: .. *... .. ,Xotor Vohlclo. Xanufacturer'. :Association of t h e United State.. Inc. U t e an4

Oak Ridgo National Laboratory. m t s of world Deve on 8

Appondlcos. ORNL/Sub/86-22033/1/V2. 1986.

.>-'D&&it'.'. :,1g88. ?:.. . . . . . . . . ..... . .I' . . . . . . . . . . ...... .. : . .

I

10-4 . .

....,. &... ... ... I-. ....

. . .. .. an &&r~~kaon'&ic Cooperation _* ind . Davolopmnt,.

ria, ?rance, 1988, . .

I s Handbppk . Sixth Edition. Robort H. Percy, Don W. aceen, James O.'-Maloney, Eds., McGraw H i l l Book Company, NOW York. -",1984.

B. .,SPA-600/7-90-010 (NTIS PB90-216433). 0.8. Envi romenta l Protection 12: Agency, ' A i r and Enorgy Engineering Research Laboratory, Rosoarch Triangle

Park, NC, May 1990.

Press, P.,..and ,R. .Siever, -. 2nd ed i t ion , p. 294-295, W i l l Freeman and

.. , .- .

an Francisco, CA, 1978. , :we*. ,.?.*I' , 2. . ,

'; V., R J ' C i c e r o n e , H.B. Singh, and J.T. K i e h l . .r: 4 .. ..~ *_, IC. I .'

Trace Oas Trends .. and Their Potential Role I n Climate Change. gournal of OR- . 90(D3): 6547- .. ,

" I n s t i t u t e of Hineral Resource.

. ,., . . . , . , , . :..l..

." ' . Reavir, J.L., ;tr. U-Cover Coal: New H i n i n a Methods and t h e En vironm- Research, Kansas oeoiopicai survey, The

.',sReVelle, The Environment --Xeauee and Choices for 8 ocietv,

Univetsity of KanSaD, Laurence, Kansas. 1974.

4nd Bar t l e t t , Publishers, Boston, 1986.

bed Uethane Resources in w e d M ethqa(l_gesources of t h e

$:<. . .

I -, odited by C.E. Rlqhtmlre, O.T. Eddy and J.M. Kirr, American

. ~. .~~ . ,~ .~ .~ , I :i..j < ,. _cI/.. . .. ; Rohdsi :~ann ing?3~F ' Canparison of t h e Contributions of Var ious o ~ s o a t o t h e

a r a e n h o u s d ~ ~ s f f o c t . ~ I ~ vo i 248. June 6, 1990, pp. i z i7- iz ig .

Rotty, R.M. and 0. Marland. '.Production of ~q From Pornmil -01 Burning by h a 1 Typw. . I n s t i t u t e f o r Energy Analysis, Oak Ridgo Asmociated Wnivorsitios. Oak Ridge, TN. 1984.

. . .

10-s

-

i?,

>e', .PA-6001 1-89-02 lA e ..... .- .;-..,- .

0.8. tnvirontmntal Protection Agency, A l r and taorgy tnqlnosrlnq ;, Rosearch .~ .. ,c_:,.

ory,~Re~br~h Trianqlo P u k e NC. N o * . r a b . t -1989 L :~-.w,!;... -* L I. ,

. . . n of Coal Petroloqy urd Coal QIanletry, for D.o .~ . 1981. .... . < , . w ,.:. . . 8cs, inqtneetm. aaa hianion rutea ircm Solid fill;,-.. n.mo to

.,&,$+.&Allen Gertdnr U.8. Znviromntal Protection Agen flce of ,Solid .Waete, ..$A ,;.

....... . . ~ 19ov.mb.r 17, .1986.,- :

:'+,- .~.. .?..- . ...... I So&, W. .Contribution of b1ologic;l procenses .in the atm0nphera.h --, eds. X.J. Xlug 'And C.A. Roddy. ;pp. 468-411. Nnerican Soclety for. robiology, Washington,

oba

. . . . . . . .

fel-Pachorn, R. Conrad, and W I. . 1984. Smlnalone frClp~RiCi Paddle., C h e r n u '

. . . . . ill +iuw .. s.:..-... , . . ..

Seinfald, J.H.i Wrbhn Air Pollution: State of the Sclence, w, 243, 745-752, 1989.

Shareof, O.S., W.A. Butler, L A . Bravo, and H.B. Stockton. &- .': EPA-450f2-88-003A. (NTIS 3888-225792). U.S. Envlronmental Protection Agency,

office of A i r Quality Planninq and standard.. R.rearch Trlangle Iark, NC.

e I r Vo-c--.

. . :, .:. .*k.:g" v ...

82 ...? Inventory of Global Xethane Sources and Their of G- . "?87(C2): 1305-1312.

ne Control - It's a Gasl, -, 19ovember/December,

Cicerone, Poaalble Pertur to Atmospheric co, , 91, 10853-10864, 1986.

Thompaon, A.M., R.W. Stewart. H.A. Ovenn, and J.A. H e w h e , Senaitivity of Tropospherlc OXidAntS to Olobal Chemical and Climate Change, -, 22, 1988. ~

Thompnon, A.X., Qoddard/NASb Per*Onal Cminunicatlon vlth author, September 14, 1989.

* . .

. . Ti@aot, E. and D.H. Welts, , Springer- Verlaq, Beclln, West Oermany, 1918.

Trabalka, J.R. aditor. and the 010 bal Carb on 0.5 . DOE/ER-0239. 1985.

10-6

...... ,:. .I ~ .... .. "_l _ . ....

.f:; '. . , 2. ... ri;4r. .... i f ' ,

United N8tiOnS. t h e P-. United NAtiOns Xconwlo Comisslon for AB18 and t h e PaCifLO. . NOW York, i

7 ,. 1984. .., ....... . ....-. ,,- ..*CITY' ..,..

Unitod. . Natlons Pubfloatlons. .Now Xork, 1988.

, i % 3 , > .

i

" . . . . . ,_ , .. .......... '-l*m?.... ...

.' Unitod N A t i O n s , ,rod.. Agricul tural Organization. or ?ood and. FA0 Envi

, I t a l y , 1980. ;;-, .. -._. i

i1 Develoopnent Organisation. i i Austria. 1986.

U.S. Department of Commmrce, Bureau of Census. w-. No. UA28P(86)-1. VI&-

;..United States Departwnt of Energy. Energy InformatLon Administration. Coal :;Data: A Reference. -DOE/EIA-0064(80), 1980.

'

. . . . : ,

5 5.;. . .:&&++, ;. . . L

i 0.8. Depattment of Energy, mrw -aLe s and t h e -, DOE/BH-0077,, Offico 0f.Environmental analyst^, Washington, DC, 1988. . .

0.8. Environmsntal Pratootion Agency. Standard.. of VOC i n oae Pr-

.. -. I .,. '$.3>. ::. .k& :

O f f i c e of A i r Quality Planning and

A# EPA-450/3-82-924a (NTIS P884-

. . .Ar.. - , . : . . , , - 2 . 5

..., <:. .-.. .?.""! - , ~ . . . . 1.

ion ~e-. o f i i e a of A i r i

A i r P-e X: I i !

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.~ I Motor Vehiclo Emiorion . . . . . . .:... L&oratory,..hn Arbor, MI. S e p t b e ' 198). i Vernon, J.L. f o r Coal - , m m o : A i r ! m. London, I J L I M Coal Research. IAAcR/11, August 1988.

. . .

Vosilind, P. -me, and Alan 6- ' R i m o r . -mince * -, 1981 . i ~ . :~ , . -o~ ; . '~ ;~~: ; . . . .. .r-.:.. ;. . - , . . :>4 ~ . ,.!~) 1'

: Walsh, Xichael P., - b 1987 S s

R e c o v w .. :. , :

. . . . . . . . ..: . ' . . , . .

i i 1 1 1987.

10-7

. . . I .

. . <.,!.,. . I . . .. , ,'- ' . . . -.. . . , . . .. . . . .

.. . . $ . : . .

. . . ..

. . . . . . .. . ... .. . . . . , . .. /

The Welatieaship of Carbon Dioxide Emissions with Coal Rank and Sulfur Content

Richard A. Winschel Consolidation Coal Company

Library, Pennsylvania

Carbon dioxide emissions, on an equivalent energy basis, were calculated for 504 North American coals to explore the effects of coal rank and sulfur content on COz emissions. The data set included coals ranging in rank from lignite through low-volatile bituminous from 15 U.S. s ta tes and Alberta, Canada. Carbon dioxide emissions were calculated from the carbon con- tent and gross calorific value of each coal. T h e lowest COz emissions are calculated for the high-volatile bituminous coals (198 to 211 Ibs COJ MMBtu) and the highest for lignites and subbituminous coals (209 to 224 Ibs COz/MMBtu). The lower COz emissions from the high-volatile bitumi- nous coals result in par t from their generally higher sulfur content. Howev- er, even at equivalent sulfur contents t he high-volatile bituminous coals give lower COz emissions than the lower-rank coals. On average, the lower- rank coals produce 5 percent more COz upon combustion than the high- volatile bituminous coals, o n the basis of gross calorific value. T h i s differ- ence increases to 9 percent on the basis of estimated net calorific value. The net calorific value is better indicator of power plant energy production than the gross calorific value. The difference in CO2 emissions resulting from the use of high-volatile bituminous coals and lower-rank coals is of the same order of magnitude as reductions expected from near-term combustion efficiency improvements. These results a re useful to those interested in current and future COP emissions resulting from coal combustion.

have been demonstrated as a result of hardware retrofits and on-line moni-

Pressurized fluidized-bed com- bustor retrofits are projected to reduce heat rates by 1,000 BtukWh (10 per- cent improvement).2 Integrated coal gasification combined cycle plants are expected to show heat rates of about 8,950 BtukWh (15 percent improve- mentL2

This paper provides a collection of data that shows that the combustion of different coals results in differences in C02 emissions of the same order of magnitude as those being sought through near-term design improve- ments, and that most of those differ- ences are related to coal rank.

The approach taken was to calculate the COz emissions of 504 North Ameri- can coals on the basis of gross calorific value, to estimate the COz emission of those coals on the basis of net calorific value and finally to observe the rela- tionship of sulfur content and C02 emissions.

There is growingscientificand political concern about carbon dioxide (C02) emissions resulting from the combus- tion of fossil fuels and the potential effects of those emissions on future global climate. Strategies for reducing the COz emissions from fossil fuel com- bustion include.reducing end-use ener- gy demand (conservation), improving the efficiency of engines and generators and shifting the mix of fossil fuels con- sumed. Natural gas generates the low- est C02 emissions per unit of energy output of all available fossil fuels. How- ever, the other major fossil fuels, coal and petroleum, will continue to supply the bulk of the United States' and the world's energy needs for the foresee- able future because of available re- sources and infra$tructure and relative economics. Coal currently supplies about one-fourth of the total U S . ener- PY demand and over one-half of the

' U.S. electrical generation demand. Coal account9 for about 80 percent of the COz emissiona from the US. utility power generation fuel-use sector and

June 1990

I ' 1

I Volume 40, No. 6

about half of the COZ emissions from the U S . industrial sect0r.l All fuels in these two sectors account for about 35 percent and 25 percent, respectively, of total US. C02 emissions and less than 8 percent and 6 percent, respectively, of the world-wide total.'

Power plant design improvements that would increase the thermal effi- ciency of electricity generation from coal are currently being sought. Any improvement in thermal efficiency will reduce C 0 2 emissions by a nearly equivalent amount. Most coal-fired electric generating plants have heat rates of about 10,000 BtukWh (34 per- cent thermal efficiency). Heat rate re- ductions t o below 6,000 Btu/kWh (nearly 60 percent thermal efficiency) are projected for an integrated coal gas- ification-fuel cell power plant,2 though the technology to provide such a high heat rate in a commercial plant will not be available for some time. Near-term improvements in heat rate are possible. For example, heat rate improvements of 100 to 300 BtukWh (1 to 3 percent)

Experlmental Methods

Analyses

All analyses were performed between 1976 and 1989. Almost all were per- formed by the Research and Develop- ment Department of Consolidation Coal Company (Consol). In most cases, proximate and ultimate analyses were performed with Leco MAC-400, CHN- 600 and SC-32 instruments and gross calorific values were determined with a Parr 1261 calorimeter. However. the earliest data in the set were obtained by modified. versions of s tandard ASTM methods.

Data Set

An original data set 'of analyses of 619 North American coals was com- piled from the archives of Conaolida- tion Coal Company. The analytical data included carbon, hydrogen, ash - Cowrighl1990-Air k Wnate Management h i a t i o n

861

and total sulfur contents and gross cal- orific value, all reported on a dry basis, and the coal identifications. Inspection of the data set revealed that 15 carbon or calorific value determinations were probably unreliable. In most of those cases, the moisture- and ash-free (MAF) carbon content appeared un- reasonable when compared to other samples taken from the same mine or from the same seam a t a nearby loca- tion. Most of these 15 analyses were performed prior to 1983. Those 15 sets of data (3 percent of the original set) were removed from further consider- ation. leaving a final data set of 504 analyses. A summary of the final data set appears in Table I.

The data set includes 504 coals rang- ing in apparent rank from lignite through low-volatile bituminous coal. Strick rank determinations such as ASTM D - 3 W were not performed. Ap, parent ranks were assigned on the basis of one or more of three methods: 1) the known rank of coals from the same mine or from the same seam a t nearby locations; 2) the dry-basis ultimate and proximate analyses and calorific value of the sample; and 3) reference to infor- mation supplied in K e y ~ t o n e . ~ The 504 coal samples were taken from 15 US. states and one Canadian province that, when combined, produce the vast ma- jority of North American coal. All sam- ples were commercially produced dur- ing routine mining operations except for the two Mississippi lignites and 11 of the West Virginia high-volatile bitu- minous coals, which are exploration samples. The samples include run-of- mine coals and various cleaned or sized preparation plant products. Ranges of

225 - - .I 2 2 0 .I - :

215

z : 2 1 0 .

2 0 5 0 .I

e 2 0 0 i

various properties of the coals in the data set appear in Table I.

Calculations

Calculated carbon dioxide (CO,) emissions were referenced to gross cal- orific value on a pounds COz per mil- lion British thermal units (lbs C o d MMBtu) basis as:

Ibs CO, MMBtu (gross) .

X 36,640 (1) - 90 Carbon -

gross calorific value where % carbon is from the ultimate

r'l I rr.7 r

analysis and gross calorific value is a- pressed in Btu/lh, both on a dry b-, The constant, 36,640, is simply the g!;;, tio of the molecular weight of C0;Ctij; the atomic weight of carbon, multiplied,! by the ratio of lo6 to 100 percent. ;, simplifying assumption that all car&i; converts to COz during combusti&Z$ The gross calorific value was chosen:t6; calculate CO2 emissions in this's because of ita general availab gross calorific value is determin constant volume and with water condensed state. The net calor ue, which is determined a t co pressure and with water in the

:Id;,

Inherent in this calculation is 9& ,@e.+

Table I. Data set of North American coals. ?%,4aq

S I el a! 0 e! dt ir 81

tl P

11

vi

n

CI

m

m 1

C

b n

P

0

S

v

\1

II

S 1 i I I.

( c

C

1

, I

1 c

I

1 I t

I 1

1

I I

date, is a better measurement of the wergy supplied by coal when it is used as a fuel.6 Though the net calorific val- ue is a better indicator of power plant energy production, it is not routinely determined for commercial coal trad- ing purposes.fi The net calorific value is always lower than the gross calorific value. The difference is proportional to the amount of water in the combustion products, whether that water is coal moisture or water of combustion, and is thus proportional to the total hydrogen content of the as-burned coal.

Actual moisture determinations, which are required to calculate net cal- orific values from dry-basis analyses, were not available in the data base. Therefore, a moisture value was as- signed to each coal for this purpose. Carbon, hydrogen, and gross calorific values were converted to an as-received basis through the use of the assigned moisture value. Net calorific values were calculated as: Net calorific value

= gross calorific value - %H X 92.04 (2)

where calorific values are in Btuhb and all values are on an as-received basis. The constant is the product of the ASTM correction factor of -1030 Btul Ib of water7 and the ratio of the molecu- lar weight of water to the atomic weight of hydrogen. divided by 100 percent. CO, emissions were referenced to net calorific values as:

lbs CO, MMBtu (net)

= X 36,640 (3) net calorific value

where net calorific value is expressed as Btuflb and all values are on an as-re- ceived basis. The constant, 36,640, is the same as used in Equation 1.

Results and Dlscusslon

COI Emlsslonr Based on Ororis Calorlflc Values

Calculated COa emissions are plot- ted in Figure I on a MMBtu (gross) hasis as a function of MAF carbon con- tent for the 504 coal-sample data set. The abscissa in Figure 1, MAF carbon, is a rank indicator, and generally in- creases with rank. ASTM coal rank classifications' consist of discrete points, e.g., subB, hvAb, Ivb, etc. The use of MAF carbon permits presenta- tion of the data as a function of a con- tinuous variable. For the entire data set, calculated COz emissions on a gross calorific value basis range from 198 to 224 Ibs COdMMBtu (gross), a differ- ence of 26 IbS COdMMBtu or about 13 percent. The individual data points in

June 1990 Volume 40. NO. 6

Figure 1 are keyed such that low-rank (lignite and subbituminous), medium- rank (high-volatile bituminous) and high-rank (low- and medium-volatile bituminous) coals are distinguishable. The lowest COz emissions are calculat- ed for the high-volatile bituminous coals (198 to 211, average = 204 Ibs C O m M B t u ) . The low- and medium- volatile bituminous coals give interme- diate calculated CO2 emissions (205 to 214, average = 210 lbs COz/MMBtu) and the lignites and subbituminous coals give the highest calculated COz emissions (209 to 224, average = 215 Ibs C02/MMBtu). Thus, on average, the lower-rank coals produce 5 percent more CO, upon combustion than the high-volatile bituminous coals on a gross calorific value hasis. No anthra- cites were included in the data base. However, as coal rank increases beyond low-volatile bituminous, calorific value tends to decrease though carbon con- tent continues to inc rea~e .~ Therefore, anthracites would be expected to have COz emissions even greater than the medium- and low-volatile bituminous coals.

The ASTM specifications for repeat- ability and reproducibility of the gross calorific value are 50 and 100 Btuflb, respe~tively.g~'~ In the hypothetical case of a coal having 68 percent dry carbon and having a dry gross calorific value of 11,500 B t d b , errors at the ASTM repeatability and reproducibili- ty limits would result in errors of 1 and 2 lbs C O a M B t u , respectively. An er- ror a t the ASTM repeatability limit of carbon content, 0.3 percent," would also give an error of 1 Ib COdMMBtu in calculated CO2 emissions. In the case of a coal having 78 percent dry carbon and a dry gross calorific value of 14,000 Btuflb, the Same errors in measure-

ment would produce slightly lower er- rors in calculated COX emissions. Thus, calculated CO2 emissions should be re- producible to within about 2 Ibs C o d MMBtu.

c02 Emlsslons Based on Net Calorlflc Values

The energy usable to a power plant from the combustion of fuels is more closely related to the net calorific value of the fuel than to the gross calorific value.6 The former is determined a t constant pressure and with all mois- ture, including moisture from combus- tion, in the vapor state, whereas the latter is determined a t constant volume and all moisture in the condensed state.' ASTM Method D-121' cites a correction-factor of -1030 Btuhb of water to convert the gross calorific val- ue to the net calorific value. Since most lignites and subbituminous coals con- tain much more moisture (20 to 30 per- cent or more) than higher rank coals, the difference between low-rank and bituminous coals in COn emissions for an equivalent net energy output will be somewhat greater than that calculated on the basis of the gross calorific value.

For the calculation of the net calorif- ic value from the gross calorific value, moisture contents or as-received total hydrogen contents are required. Since the archival data base included neither value, net calorific values were estimat- ed by assigning an estimated moisture content to each coal. Two estimating approaches were taken.

First, moisture contents were as- signed to six representative coals from the data base on the basis of informa- tion supplied in Keystones with refer- ence to the known specific sources of the coals. Assigned moisture values and

2 5 0

245

= 240

5 235

2 3 0

225 . 2 2 0

- - 0

D -

- -

2 215 - 2 1 0

0

e 205

- . - 2 0 0

195 65 7 0 7 5 80 8 5 90 9 5

% CARBON W A F

F~gura 2. CoI emlsslms (calculated on me basls 01 me sstlmlec net calorlllc value) 88 a tunctlon of MAF carban MnBnt. Symbols LU In Flgwe 1.

863

Table 11. COI emissions from representative coals calculated from gross and estimated net calorific values. 77 1

Ibs COdMMBtu, COz emksiom,A zr) based on relative #

U.S. Apparent Gross cal. moisture, Btufib, Grosseal. Netcal. to hvAb I

state Seam rank C,% H, 90 value, Btufib %as redd 89 rec'd value value -.I I'

ND Coteau IigA 63.2 4.2 10,653 37.9 5.985 217.5 240.4 1.07 1 . ~ 4 ' 1; WY UpperLower subC 67.2 4.5 11,724 29.8 7,633 210.1 226.5 1.03 i.cj-,,fi

-%d, IL Illinois 6 hvCb 69.9 4.8 12,631 10.0 10,871 202.6 211.9 1.00 I.M., i WV Mired. mvb 82.6 4.9 14,584 2.3 13,788 207.4 214.4 1.02 .i.m! .. VA Pocahontas3 Ivb 86.2 4.4 14,992 1.6 14,335 210.8 216.9 1.04 i.m'*f

Coal description Analysis, dry basis Assigned Net cal. value

Wyodak

WV Pithburgh hvAb 77.9 5.3 14,021 2.7 13,142 203.5 211.2 1.00 1.00 &

:t

"Mixture of Upper Eagle. Middle Eagle, No. 2 gas seams

%'L l-.. 632\

authentic analytical data which were used to estimate the net calorific values of the six coals appear in Table 11. Ta- ble ll includes a comparison of COz emissions calculated on the basis of both gross and net calorific values for those coals. On a gross calorific value basis, the subbituminous coal and l i g nite give COP emissions that are 3 per- cent and I percent, respectively, great- er than the high-volatile bituminous coals. On a net calorific value basis, the difference increases to I percent and 14 percent, respectively.

The second approach taken was to assign a single moisture content to all coals in the data base of a single rank. The moisture values assigned were as follows: lignite, 30 percent; subbitu- minous, 20 percent; high-volatile bitu- minous, 6 percent; medium-volatile bi- tuminous, 3 percent; low-volatile bitu- minous 2 percent. The values are compromises designed to best fit the entire data set. For example, within the high-volatile bituminous rank, 3 per- cent is a better estimate for the Appala- chian coals and 10 percent is a better estimate for the Illinois basin coals; however, a single estimate of 6 percent was chosen. The values assigned are reasonable compromises in light of typical moisture contents of specific coals5 and typical moisture contents of the various ranks of coal.12 Carbon di- oxide emissions based on estimated net calorific values are plotted in Figure 2 as a function of MAF carbon content. Net COz emissions in Ibs C O a M B t u ranged from 206 to 242, a difference of about 18 percent. Specific values were 206 to 219 (average = 212) for the high- volatile bituminous coals, 223 to 243 (average = 231) for the low-rank coals and 212 to 221 (average = 216) for the higher-rank coals. Thus, on average, the lower-rank coals produce 9 percent more COz upon combustion than the high-volatile bituminous coals on a net calorific value basis.

!

Relatlonshlp Between Sulfur Content and C02 Emlselons

I As the data in Figures 1 and 2 show, the high-volatile bituminous coals as a

864 I

group produce significantly less COz than the lower-rank coals. On average, the difference is 5 percent (gross basis) or 9 percent (net basis). As noted earli- er, the data set consists almost entirely of commercially produced coals. Many commercially produced North Ameri- can high-volatile bituminous coals have relatively high sulfur contents. The calculated CO2 emissions from high sulfur coals are somewhat de- pressed from their sulfur component. In essence, a greater proportion of the total energy of high sulfur coals is pro- duced by burning sulfur and a lower proportion of it is produced by burning carbon. Emission control devices that limit the sulfur dioxide so produced can consume as much as 3 percent of a plant's generated power.'3

To evaluate the imoortance of this effect, calculated COz emissions were dotted as a function of sulfur content. Figure 3 shows the COz emissions on a gross calorific value basis. As shown in Figure 3, the high-volatile bituminous coals as a group have lower calculated COz emissions than the lower-rank coals, even a t equivalent sulfur con- tents, e&, a t 0.9 percent sulfur. How-

tuminous coals, calc sions decrease with content. A linear re data yielded the

The regression line ure 3. Extrapolation o intercept of the regr

in the data set. T cient of determina cating that sulfur about half the var

and composition and hydrogen, ni

0 1 2

Z SULFUR (dry1

Fbure3. co~smlulau(calw~tatedanmebaaisolmeprmscalaiiicvaiut)a.a lundmof wllw Conlent. Reweulan 11- lw hvb coals. Symbols 88 In F lwe 1.

J. Air Waste Manage. A d

2 2 5

1 9 5 '

hen and oxygen concentrations un- doubtedly also contribute to the vari- ance. Some insight in this area can be gained from the semi-empirical equa- tions provided by Given et aLL4 and Mott and Spoonerlh and the related discussions, and the empirical equa- tions provided by Neavel e t a1.IG and Mason and Gandhil7 concerning the calculation of calorificvalues from ulti- mate analysis data.

Figure 4 is a similar plot of the data on the basis of the estimated net calo- rific value. On this basis, the separation between the bituminous and lower- rank coals is increased. Interestingly, the high-volatile and higher-rank bitu- minous coal populations merge to form a single group in Figure 4. A linear re- gression of the bituminous coal data yielded the following equation with a correlation-coefficient ( r ) of 0.73

lbs CO, MMBtu (net) = 216.3 - 1.695 X %sulfur (dry basis) The regression line is shown in Fig-

ure 4. The intercept indicates that a hypothetical sulfur-free bituminous coal would be expected to give a calcu- lated GO2 emission (net calorific value basis) of 216 lbs COflMBtu. which is considerably lower than the lowest val- ue calculated for all the lower-rank coals in the data base.

Acknowledgment

Most of the analyses used in this study were performed under the direc- tion of Mr. L. W. Rosendale of Consol Fi&D.

Reterences I. ECS Updofe. Electric Power Research

Institute, No. 16, Fall 1989. 2. AFPS Deuelopmenfs. Electric Power

Researeh!nstitute, No. 3, Winter 1989. 8. “Proceedinm: 1988 EPRI Heat-Rate ~~

lmprovem<nt Conference.” Electric Power Kesearch Institute. EPRI Report Nn GS-fifi35. J a n u m 1990. _ _ ..

4. “Standard &si%&m of coals by rank,” in 1988 Annual Book of ASTM Sfondards, Val. 05 .05, ASTM D-388. American Society of Testing and Mate- rials. Philadelohia. 1988. D. 182.

5. ii%3 Keysfpnk Cod Indistry Manual, Maraw-Hill, New York, 1983.

2 5 0

2 4 5

= 240

5 2 3 5

2 3 0

3 2 2 5 . 2 2 0

2 1 5

2 1 0 0

’ 2 0 5

200

1 9 5

0

s

.(

0 1 2 3 4 5

% SULFUR (dry1

C02 emisdons (calculated on h basis of me estimated ne1 cBlorific value) as a Flpure 1. l~nctlon OI sulfur content. Rsgrerslon line lor all bltumlnous coals. Symbols as in Figure 1.

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15. R. A. Mott. C. E. Spwner, “The calorif- 7. “Standard definitions of terms relatin

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9. “Standard test method for gross calorif- -far calculatini the calorific ;due of cod icvalueofcoalandc6ke by theadiabatic and coal cham: development, tests, and bomb calorimeter,” in 1988 Annual uses,” Fuel Process. Technol. 7: 11 Book of ASTM Standards. Val. 05.05, (1983). ASTM D-2015, American Society of Testine and Materials, Philadelphia,

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11. “Standard test methods for carbon and hydrogen in the analysis Sam le of coal

The author is with Consolidation D-3178, American of Testing , c0., Research ~ ~ ~ ~ l ~ ~ ~ ~ ~ ~ ,

4000 Brownsville Road, Library, PA 15129. This paper was submitted for peer review on October 13,1989. The revised manuscript was received March 14,1990.

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13. k%?&).&nfueLs Technology, p. 4, Feb. ruary 12,1990.

June 1990 Volume 40. NO. 6