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Man

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Lump coal derived soot formation and gasanalysis during pyrolysis from fixed bed

Q C Wang1 and Y H Luo2

The objectives of this work are to study lump coal derived soot formation and related gaseous

emissions during the pyrolysis process in a fixed bed A laboratory scale movable fixed bed a

water cooled soot collection system and an electric reactor have been designed and employed in

the process Three kinds of coals sized at 3ndash5 mm have been pyrolysed in the experiments The

ash content of the soot samples on the filter has been tested and analysed by using inductively

coupled plasma atomic emission spectrometer The tar and soot have been separated by

dissolving the samples in dichloromethane and the yields of soot have been determined The

compositions of gases from the exit have been determined by gas chromatograph mass

spectrometer The results show that more tar has been converted to soot at higher temperatures

and some of the saturated aliphatic hydrocarbons are condensed and polymerised to aromatic

hydrocarbons More tar has been converted to soot at longer residence times and some of the

unsaturated aliphatic hydrocarbons are reformed to saturated aliphatic hydrocarbons No small

molecular compound exists at longer residence time With high volatiles coal it is easier to form

soot which releases more aromatic hydrocarbons

Keywords Lump coal Pyrolysis Soot formation Fixed bed GCMS

IntroductionSmall submicron carbonaceous particles known as sootare commonly observed in pyrolysis and combustionprocess of hydrocarbons and coals Soot does greatharm to peoplersquos health because of the carcinogeniceffect The presence of soot in air also leads to visibilityreduction and global temperature change1 At the sametime sootrsquos being suspended in flames is important tocombustion systems because it will significantly enhanceradiative heat transfer2ndash4

Based on experimental study in simple hydrocarbonflames it is found that soot is usually formed whenexperimental conditions are sufficiently rich fuel to allowcondensation or polymerisation reactions4ndash7 Besidessoot formation has also been observed in manypulverised coal utilisation processes including coalgasification and combustion In a conventional pul-verised coal combustion boiler the polycyclic aromatichydrocarbons (PAH) have been believed to be theprecursor of coal derived soot These tar molecules arelarger and more chemically diverse than the simplehydrocarbon fuels generally used for soot formationstudies4 Nenniger8 Wornat9 and Chen10 et al studiedthe soot yields from pulverised coal in the pyrolysis

process They indicated that the sum of tar plus sootremained constant increases in soot yields coincidedwith decreases in tar yields Ma2 researched sootformation in presence of oxygen containing speciesand revealed that the soot yields obtained were muchlower than those obtained in inert condition

However few relevant investigations on lump coalderived soot formation in fixed bed have been made InChina the total installed capacity of the industrialboilers in the industrial and service sectors is more than126106 t h21 and more than 4006106 t lump coalshave been consumed a year11 In these industrial boilersstoker firing is the dominating combustion style Thecombustion mode of lump coal is different from that ofpulverised coal because of poor mixing between volatilesof coal and air and pyrolysis reaction exists in localareas in the hearth of stoker fired boiler The study onsoot formation in pyrolysis process in local areas ofstoker fired boiler is significant and necessary in terms ofits environmental impact The present work funded byShanghai Environmental Protection Bureau in China isto study the soot formation and correlative gasesemission regularity in stoker fired boiler

Experimental

Experimental apparatusIn order to study conveniently the soot formationregularity in a stoker fired boiler a fixed bed reactorhas been designed avoiding the expensive and difficultwork in the large scale equipment The lump coal

1Shanghai Institute of Technology No 120 Caobao Road ShanghaiChina2Institute of Thermal Engineering Shanghai Jiao Tong University No 800Dongchuan Road Shanghai China

Corresponding author email qingcheng_wangyahoocom

2009 Energy InstitutePublished by Maney on behalf of the InstituteReceived 2 January 2008 accepted 26 July 2008DOI 101179014426008X370979 Journal of the Energy Institute 2009 VOL 82 NO 1 19

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pyrolysis experiments were conducted in an electricallyheated reactor to simulate the coal pyrolysis on the gratein the hearth of stoker fired boilers It was configured toprovide a simulation of the fuel bed pyrolysis regime in acoal fired mass burning stoker A 12 mm thick fuel bedcomposed of lump coals was heated in a batch

experimental process In this configuration the coal inthe fixed bed was heated in a transient mode to provide aLagrangian simulation of the time temperature andenvironmental history experienced by small section ofcoal which is in the fuel bed in a large travelling gratestoker In this way the pyrolysis processes that occursimultaneously in a full scale unit can be simulated in thefixed bed12ndash14 Figure 1 is an illustration of this facilitybuilt at the Shanghai Jiaotong University (ShanghaiChina) after extensive discussions

There were three parts to the experimental apparatusthe most important parts were the electrically heatedreactor and two section temperature control equipmentsoot collection and the coal supply system

The electrically heated reactor consisted of acylindrical Alundum tube heated by a siliconndashcarbonpole The temperature in the tube could be controlledby regulating the electric current and voltage of thetwo section temperature control equipment andcontrolled by either one or two sections dependingon the experimental objectives The temperature rangein the reactor was 15ndash1500uC The diameter of thecylindrical tube was 45 mm and the height of theinvariable temperature tube section was 300 mm Afixed bed was in the tube supported by coal supplysystem

1 lifter equipment 2 argon inlet 3 corundum tube 4 fixed bed 5 heating facility 6 thermometer 7 two section heat-ing control equipment 8 refractory wall 9 water cooled tube 10 filter 11 flue gas flowmeter 12 valve 13 gas sam-pling 14 vacuum pump 14 argon flowmeter

1 Diagramatic illustration of lump coal pyrolysis equipment

2 Soot and tar percentage v pyrolysis temperature

(Shenmu coal)

Table 1 Ultimate and proximate analysis of Shenmu Datong and Zibo coal in China

Proximate analysis Ultimate analysis

Mar Aar Var Vdaf FCar Car Har Sar Nar Oar

Shenmu 1213 565 2936 3570 5286 6522 444 017 137 1102Datong 842 1628 2498 3317 5032 6167 399 072 128 764Zibo 285 2095 2979 3910 4641 6297 412 063 124 724

Wang and Luo Lump coal derived soot formation and gas analysis

20 Journal of the Energy Institute 2009 VOL 82 NO 1

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The gases from the tube reactor flowed through awater cooled 30 mm diameter tube in which aglass fibre or polycarbonate filter with 005 mm porediameters was fixed so the gases went through the filterand the aerosol samples were collected on the filter4 Theglass fibre filters were Whatman made in England Avacuum pump and valve were set for sustaining stablepressure in the tube and a port was provided to samplethe gases

The fixed bed was a 44 mm diameter and plate shaperefractory Thirty-two holes were arranged in thebottom of the fixed bed and the diameters of holeswere 2 mm A moveable refractory rod was employed tosupport the fixed bed and a larger diameter stainlesstube was connected to the base of the reactor by boltsThe different heights of the fixed bed in the reactordepend on the position of the moveable refractory poleand thus the residence time of gases in the reactor couldbe adjusted

Experimental methodsThree influencing factors temperature residence time ofgases and type of coal were considered for thisexperiment

In the experimental facility described in Fig 1temperature was adjusted to appointed value accordingto temperature in stoker fired boiler first Second thelump coals were introduced onto the bed outside of thereactor A batch of coal particles was 7 g The coal wasclassified with sieves by its diameter and particlesranging in size from 3 to 5 mm were employed The

selected coals were three kinds of coals widely used inindustrial boiler in China and ultimate and proximateanalysis data of these coals are shown in Table 1 Thirdthe bed with coals were sent to the hearth from thebottom of the reactor supported and fixed by the coalsupply system (Fig 1) The volatiles were released andexpanded away from the coal particles Argon flowsmeasured with a rotameter were brought to the reactorfrom the bottom of the reactor immediately at the sametime the vacuum pump was turned on The variation ofargon amount was necessary for the case of differenttemperature in the reactor in order to achieve theprojected residence time of gases After 1 min the fluegases could be extracted with an injector for gaschromatograph mass spectrometer (GCMS) analysisThe GCMS (QP2010NC Shimadzu Japan) wasemployed for all measurements with a PLOT-Q chro-matograph column coupled to a MS engine with anionisation energy of 70 eV in the electron impact modeCompounds were separated on a 30 m6032 mm idcolumn coated with a 20 mm film The initial columntemperature was 35uC which was increased at10uC min21 to 200uC The filter papers with soot aerosolsamples were weighed by electronic balance to obtainthe amount of aerosol samples generated during certaina period of time The filter with soot aerosol mixturecould be scraped The contents of ash could also becomputed according to the element contents tested byinductively coupled plasma atomic emission spectro-meter (PE400 Perkin Elmer Wellesley MA USA)All ash components are oxides chlorides and other

3 Total ion chromatogram of gases products from coal pyrolysis with temperature variation peaks are identified in

Table 2

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 21

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Wang and Luo Lump coal derived soot formation and gas analysis

22 Journal of the Energy Institute 2009 VOL 82 NO 1

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compounds have been ignored because of its smallcontents In the end the tar and soot were separated indichloromethane by dissolving the sample The amountof tarsoot sample that did not dissolve was referred toas soot while the amount that dissolved was referred toas tar

Results and discussionMany factors that impact soot formation in stoker firedboiler have been studied in this fixed bed such astemperature residence time of gases and coal type Theresults of these experiments are given below

Effects of temperatureTemperature is a critical parameter in soot formationThe higher temperature the easier the volatiles arereleased from the coal surface Large PAH (sootprecursors) start to form soot at about 1300 K forhydrocarbon flames and for a complicated compoundlike coal the incipient temperature for soot precursorformation can be as low as 1100 K15 The soot aerosolsamples changed from viscous to solid particles as thetemperature increased so the sample viscosity serves asa rough visual measure of the extent of soot formationFigure 2 shows mass per cent of soot or tar ( daf) as itchanges with temperature increase The yields of sootare increased and the yields of tar are decreased withincreasing temperature It shows that a high temperatureis helpful for the release of volatiles and soot formationIt can also be concluded that the sum of tar plus soot

remains approximately constant that is increases insoot yields coincides with decreases in tar yields in thesame experimental condition This conclusion is con-sistent with Nenniger8 Wornat9 and Chenrsquos10 view-points in pulverised coal pyrolysis

The compositions of sample gases under experimen-tal conditions where the residence time of gases is176 s and the Shenmu coal is selected have beenexamined by GCMS and analysed Figure 3 shows thetotal ion chromatogram (TIC) of gases products frompyrolysis with temperature increase Correspondingcompounds identified and relative concentrations arelisted in Table 2 These compounds identified contain2-methyl pentane 12-dichloro ethane 3-methyl pen-tane benzene cyclohexane 223-trimethyl butane24-dimethyl hexane 3-methyl hexane heptane andtoluene in all experimental conditions Benzenetoluene 24-dimethyl hexane 3-methyl hexane hep-tane and 12-dichloro ethane are dominant compo-nents Besides there are many small molecules such asethane and ethylene from the volatiles of coals or fromthe decomposed polymer being formed at the tempera-ture of 1600 K It can be seen that the amount ofsaturated aliphatic hydrocarbons is decreased and theamount of aromatic hydrocarbons is increased with thetemperature increase by computing the contents ofthese compounds It may be caused by saturatedaliphatic hydrocarbons which have undergone con-densation or polymerisation reactions and beenconverted to aromatic hydrocarbons

4 Total ion chromatogram of gases products from coal pyrolysis with variation of gases residence time peaks are iden-

tified in Table 3

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 23

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Wang and Luo Lump coal derived soot formation and gas analysis

24 Journal of the Energy Institute 2009 VOL 82 NO 1

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Effects of gases residence timeResidence time of gases is also a factor in sootformation The residence time has been altered byregulating the position of fixed bed in the reactor and theinlet gas velocity Figure 2 represents the mass percentof soot or tar ( daf) change with extension of gasesresidence time (in vertical direction) at different tem-perature The yields of soot are higher at longerresidence time on the whole and the change regularityof tar yields is contrary with extension of gases residencetime It shows that tar is more readily converted to sootin longer residence time of gases

The composition of sample gases at a temperature of1600 K and with Shenmu coal selected has also beeninspected by GCMS and analysed Figure 4 shows theTIC of gases products from pyrolysis with extension ofgases residence time Corresponding compounds identi-fied and relative contents are listed in Table 3 Thesecompounds identified contain 2-methyl pentane 12-dichloro ethane 3-methyl pentane hexane benzene223-trimethyl butane 24-dimethyl hexane 3-methylhexane and heptane in all experimental conditionsBenzene 24-dimethyl hexane 3-methyl hexane heptaneand 12-dichloro ethane are dominant componentsamong them Besides there are many small moleculessuch as ethane and ethylene from the volatiles of coalsor from the decomposed segment of polymer beingseparated at earlier time when the residence time of gasesis 152 or 176 s whereas no small molecules aredetected when the residence time of gases is 200 s It canalso be observed that amount of unsaturated aliphatichydrocarbons are decreased and amount of saturatedaliphatic hydrocarbons are increased with extension ofgases residence time by computing the contents of thesecompounds The result can be interpreted by that partsof unsaturated aliphatic hydrocarbons have been con-verted to saturated aliphatic hydrocarbons by reason ofchemical bond reforming

Effects of coal typeFrom the proximate analysis of the three kinds of coalsshown in Table 1 volatile contents of dry ash free coals(including Datong Shenmu and Zibo) are 3317 3570and 3910 respectively At the same heating rates

5 Yields of soot and tar v coal type (T51600 K

t5176 s)

6 Total ion chromatogram of gases products from coal pyrolysis with coal type variation peaks are identified in Table 4

Wang and Luo Lump coal derived soot formation and gas analysis

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0 2

9C

yclo

penta

ne

meth

yl-

422 6

83

0 4

4C

yclo

penta

ne

meth

yl-

522 7

83

0 6

33-H

exanone

22

-dim

eth

yl-

522 7

83

1 1

9H

exane

623 1

58

33 9

4B

enzene

623 1

75

44 0

7B

enzene

723 6

83

0 3

6C

yclo

hexane

723 4

25

0 1

2S

ilane

tetr

am

ehty

l-8

25 6

33

0 1

3B

uta

ne

22

3-t

rim

eth

yl-

823 6

75

0 5

Cyclo

hexane

925 8

08

0 5

2P

enta

ne

24

-dim

eth

yl-

925 8

25

3 1

5B

uta

ne

22

3-t

rim

eth

yl-

10

26 9

83

0 1

9C

yclo

penta

ne

13

-dim

eth

yl-

trans

10

26 9

83

1 9

8P

enta

ne

33

-dim

eth

yl-

11

27 3

25

3 2

7H

exane

24

-dim

eth

yl-

11

27 3

42

8 1

1H

exane

24

-dim

eth

yl-

12

27 5

92

2 9

2H

exane

3-m

eth

yl-

12

27 5

92

6 4

3H

exane

3-m

eth

yl-

13

28 9

1 5

7H

ep

tane

13

28 9

3 5

Hep

tane

14

30 2

10 7

3Tolu

ene

14

29 1

58

0 3

6C

yclo

hexane

meth

yl-

Dato

ng

coal(e

arlie

rsep

ara

ted

mole

cule

s)

15

29 7

58

1 4

o-X

yle

ne

15 2

50 0

22-B

uty

ned

ioic

acid

16

30 2

17

16 4

8Tolu

ene

28 9

58

37 5

3W

ate

rS

henm

ucoal(e

arlie

rsep

ara

ted

mole

cule

s)

Zib

ocoal

14 3

33

3 3

7M

eth

ylA

lcohol

122 0

25

1 0

7P

enta

ne

2-m

eth

yl-

24 4

25

0 1

9Fura

n

2-b

uty

ltetr

ahyd

ro-

222 1

83

8 1

4E

thane

12

-dic

hlo

ro-

36 5

58

0 5

0B

enzene

1-m

eth

yl-4-

322 2

92

0 7

9P

enta

ne

3-m

eth

yl-

46 7

25

0 1

3(E

)-1-P

henyl-1-b

ute

ne

422 6

83

0 6

5C

yclo

penta

ne

meth

yl-

56 7

58

0 1

5E

thyle

ne

522 7

92

0 8

53-H

exanone

22

-dim

eth

yl-

66 8

25

0 1

1E

thane

623 1

58

53 0

2B

enzene

76 9

17

0 0

5N

eop

enta

ne

723 6

83

1 0

7C

yclo

hexane

87 1

42

0 0

2C

arb

onic

dih

yd

razid

e8

26 9

0 5

6P

enta

ne

33

-dim

eth

yl-

97 2

33

0 1

0W

ate

r9

27 3

42

6 9

9H

exane

24

-dim

eth

yl-

10

7 2

58

0 0

512

-Oxath

iola

ne

10

27 5

92

6 1

8H

exane

3-m

eth

yl-

11

7 3

17

0 2

6S

ilane

11

28 9

2 0

2H

ep

tane

12

7 5

08

0 0

2Fura

n

2-b

uty

ltetr

ahyd

ro-

12

30 2

17

18 6

6Tolu

ene

Dato

ng

coal

Wang and Luo Lump coal derived soot formation and gas analysis

26 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

more volatiles are released from the high volatiles coalThe experimental condition is that the residence time ofgases is 176 s and the temperature in the reactor is1600 K Figure 5 describes the mass percent of soot ortar ( daf ) from different coals The soot yields derivedfrom Datong Shenmu and Zibo coal are increased inthat order The reason may be that there are morevolatiles in the reactor from high volatile coals in thesame conditions and the volatiles are easier to form sootdue to the oxygen scarcity

The composition of sample gases have also beentested by GCMS and analysed Figure 6 shows the TICof gases products from pyrolysis process with coal typevariation The compounds identified and relative con-tents are listed in Table 4 These compounds contain 2-methyl pentane 12-dichloro ethane 3-methyl pentanecyclopentane benzene cyclohexane 24-dimethyl hex-ane 3-methyl hexane heptane and toluene under allexperimental conditions Benzene toluene 24-dimethylhexane 3-methyl hexane heptane and 12-dichloroethane are the dominant components Besides thereare many small molecules such as ethane and ethylenefrom the volatiles of Shenmu coal or from thedecomposed segment of polymer being separated atearlier time and water vapour has been detected fromthe volatiles of Datong coal being separated at earliertime The aromatic hydrocarbon gases from Zibo coalpyrolysis is the highest The reason may be that thevolatiles content (daf) of Zibo Shenmu and Datong coaldecreased in that order Another reason is that thecomponents of gases relate to the microstructure of thecoals

ConclusionsSoot formation from lump coal has been studied duringthe pyrolysis process in a fixed bed Based on theexperimental study of the soot formation and relatedgases emission in the experimental facility theseconclusions can be drawn

1 Yields of soot are increased and yields of tar aredecreased that is more tars have been converted tosoot with temperature increase The relative contents ofsaturated aliphatic hydrocarbons are decreased andthose of aromatic hydrocarbons are increased becauseof condensation and polymerisation reactions withtemperature increase

2 More tars have been converted to soot with longergas residence time The relative contents of unsaturatedaliphatic hydrocarbons are decreased and those ofsaturated aliphatic hydrocarbon are increased becauseof reforming with longer residence time and no smallmolecules exists at longer residence time of gases

3 More soot is formed in the pyrolysis of highvolatile (Zibo) coal and more aromatic hydrocarbonsare released in high volatiles (Zibo) coal pyrolysisprocess under the same conditions

Acknowledgement

The authors thank Shanghai Environmental ProtectionBureau in China for its financial support (Huhuanke05-14)

References1 B L He Q Song C H Chen and X C Xu Proc 5th Asia-Pacific

Conf on lsquoCombustionrsquo Nanjing China November 2003 South-

eastern University 1ndash5

2 J L Ma T H Fletcher and B W Webb Proc 8th Int Conf on

lsquoCoal sciencersquo Oviedo Spain September 1995 International

Energy Agency 869ndash872

3 H F Zhang lsquoNitrogen evolution and soot formation during

secondary coal pyrolysisrsquo PhD thesis Brigham Young University

Provo UT USA 2001

4 T H Fletcher J L Ma J R Rigby A L Brown and B W

Webb Prog Energy Combust Sci 1997 23 283ndash301

5 E J Lee K C Oh and H D Shin Fuel 2005 84 543ndash550

6 F Inal G Tayfur T R Melton and S M Senkan Fuel 2003 82

1477ndash1490

7 I M Aksit and J B Moss Fuel 2005 84 239ndash245

8 R D Nenniger lsquoAerosols produced from coal pyrolysisrsquo MSc

thesis Massachusetts Institute of Technology Cambridge MA

USA 1986

9 M J Wornat A F Sarofim and J P Longwell Energy Fuel 1987

1 431ndash437

10 J C Chen lsquoEffect of secondary reactions on product distribution

and nitrogen evolution from rapid coal pyrolysisrsquo PhD thesis

Stanford University Palo Alto CA USA 1991

11 M J Tan and J X Mao Proc Conf on lsquoAdvanced technologies

of industrial boilers in USndashChinarsquo Beijing China June 2004

Power Engineer Institute 1ndash17

12 D Sun and S Choi Combust Flame 2000 121 167ndash180

13 N Ford M J Cooke and M D Pettit Inst Energy 1992 65 137ndash

143

14 G P Staley F W Bradshaw C S Carrel D W Pershing and G

B Martin Combust Flame 1985 59 197ndash211

15 M S Solum A F Sarofim R J Pugmire T H Fletcher and H

Zhang Energy Fuels 2001 15 961ndash971

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 27

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

pyrolysis experiments were conducted in an electricallyheated reactor to simulate the coal pyrolysis on the gratein the hearth of stoker fired boilers It was configured toprovide a simulation of the fuel bed pyrolysis regime in acoal fired mass burning stoker A 12 mm thick fuel bedcomposed of lump coals was heated in a batch

experimental process In this configuration the coal inthe fixed bed was heated in a transient mode to provide aLagrangian simulation of the time temperature andenvironmental history experienced by small section ofcoal which is in the fuel bed in a large travelling gratestoker In this way the pyrolysis processes that occursimultaneously in a full scale unit can be simulated in thefixed bed12ndash14 Figure 1 is an illustration of this facilitybuilt at the Shanghai Jiaotong University (ShanghaiChina) after extensive discussions

There were three parts to the experimental apparatusthe most important parts were the electrically heatedreactor and two section temperature control equipmentsoot collection and the coal supply system

The electrically heated reactor consisted of acylindrical Alundum tube heated by a siliconndashcarbonpole The temperature in the tube could be controlledby regulating the electric current and voltage of thetwo section temperature control equipment andcontrolled by either one or two sections dependingon the experimental objectives The temperature rangein the reactor was 15ndash1500uC The diameter of thecylindrical tube was 45 mm and the height of theinvariable temperature tube section was 300 mm Afixed bed was in the tube supported by coal supplysystem

1 lifter equipment 2 argon inlet 3 corundum tube 4 fixed bed 5 heating facility 6 thermometer 7 two section heat-ing control equipment 8 refractory wall 9 water cooled tube 10 filter 11 flue gas flowmeter 12 valve 13 gas sam-pling 14 vacuum pump 14 argon flowmeter

1 Diagramatic illustration of lump coal pyrolysis equipment

2 Soot and tar percentage v pyrolysis temperature

(Shenmu coal)

Table 1 Ultimate and proximate analysis of Shenmu Datong and Zibo coal in China

Proximate analysis Ultimate analysis

Mar Aar Var Vdaf FCar Car Har Sar Nar Oar

Shenmu 1213 565 2936 3570 5286 6522 444 017 137 1102Datong 842 1628 2498 3317 5032 6167 399 072 128 764Zibo 285 2095 2979 3910 4641 6297 412 063 124 724

Wang and Luo Lump coal derived soot formation and gas analysis

20 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

The gases from the tube reactor flowed through awater cooled 30 mm diameter tube in which aglass fibre or polycarbonate filter with 005 mm porediameters was fixed so the gases went through the filterand the aerosol samples were collected on the filter4 Theglass fibre filters were Whatman made in England Avacuum pump and valve were set for sustaining stablepressure in the tube and a port was provided to samplethe gases

The fixed bed was a 44 mm diameter and plate shaperefractory Thirty-two holes were arranged in thebottom of the fixed bed and the diameters of holeswere 2 mm A moveable refractory rod was employed tosupport the fixed bed and a larger diameter stainlesstube was connected to the base of the reactor by boltsThe different heights of the fixed bed in the reactordepend on the position of the moveable refractory poleand thus the residence time of gases in the reactor couldbe adjusted

Experimental methodsThree influencing factors temperature residence time ofgases and type of coal were considered for thisexperiment

In the experimental facility described in Fig 1temperature was adjusted to appointed value accordingto temperature in stoker fired boiler first Second thelump coals were introduced onto the bed outside of thereactor A batch of coal particles was 7 g The coal wasclassified with sieves by its diameter and particlesranging in size from 3 to 5 mm were employed The

selected coals were three kinds of coals widely used inindustrial boiler in China and ultimate and proximateanalysis data of these coals are shown in Table 1 Thirdthe bed with coals were sent to the hearth from thebottom of the reactor supported and fixed by the coalsupply system (Fig 1) The volatiles were released andexpanded away from the coal particles Argon flowsmeasured with a rotameter were brought to the reactorfrom the bottom of the reactor immediately at the sametime the vacuum pump was turned on The variation ofargon amount was necessary for the case of differenttemperature in the reactor in order to achieve theprojected residence time of gases After 1 min the fluegases could be extracted with an injector for gaschromatograph mass spectrometer (GCMS) analysisThe GCMS (QP2010NC Shimadzu Japan) wasemployed for all measurements with a PLOT-Q chro-matograph column coupled to a MS engine with anionisation energy of 70 eV in the electron impact modeCompounds were separated on a 30 m6032 mm idcolumn coated with a 20 mm film The initial columntemperature was 35uC which was increased at10uC min21 to 200uC The filter papers with soot aerosolsamples were weighed by electronic balance to obtainthe amount of aerosol samples generated during certaina period of time The filter with soot aerosol mixturecould be scraped The contents of ash could also becomputed according to the element contents tested byinductively coupled plasma atomic emission spectro-meter (PE400 Perkin Elmer Wellesley MA USA)All ash components are oxides chlorides and other

3 Total ion chromatogram of gases products from coal pyrolysis with temperature variation peaks are identified in

Table 2

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 21

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Ta

ble

2Id

en

tifi

ca

tio

na

nd

rela

tiv

ec

on

ten

tso

fc

om

po

un

ds

rele

as

ed

fro

mc

oa

lp

yro

lys

isw

ith

tem

pe

ratu

rev

ari

ati

on

Peak

nu

mb

er

Rete

nti

on

tim

e

min

Reta

tive

co

nte

nt

C

om

po

un

dn

am

eP

eak

nu

mb

er

Rete

nti

on

tim

e

min

Reta

tive

co

nte

nt

C

om

po

un

dn

am

e

T5

1100

K2

22 1

83

4 6

9E

thane

12

-dic

hlo

ro-

121 2

3 5

9B

uta

ne

22

-dim

eth

yl-

322 2

92

1P

enta

ne

3-m

eth

yl-

222 0

25

9 7

6P

enta

ne

2-m

eth

yl-

422 6

83

0 4

4C

yclo

penta

ne

meth

yl-

322 1

83

2 6

1E

thane

12

-dic

hlo

ro-

522 7

83

1 1

9H

exane

422 2

92

6 8

8P

enta

ne

3-m

eth

yl-

623 1

75

44 0

7B

enzene

522 7

92

7 2

2H

exane

723 4

25

0 1

2S

ilane

tetr

am

ehty

l-6

23 1

67

43 8

8B

enzene

823 6

75

0 5

Cyclo

hexane

723 6

75

1 2

5C

yclo

hexane

925 8

25

3 1

5B

uta

ne

22

3-t

rim

eth

yl-

825 8

17

7 8

1B

uta

ne

22

3-t

rim

eth

yl-

10

26 9

83

1 9

8P

enta

ne

33

-dim

eth

yl-

927 3

42

8 6

7P

enta

ne

24

-dim

eth

yl-

11

27 3

42

8 1

1H

exane

24

-dim

eth

yl-

10

27 5

92

3 9

8H

exane

3-m

eth

yl-

12

27 5

92

6 4

3H

exane

3-m

eth

yl-

11

28 9

2 1

2H

ep

tane

13

28 9

3 5

Hep

tane

12

30 0

17

0 5

8Tetr

achlo

roeth

yle

ne

14

29 1

58

0 3

6C

yclo

hexane

meth

yl-

13

30 2

17

1 6

5Tolu

ene

15

29 7

58

1 4

o-X

yle

ne

T5

1400

K16

30 2

17

16 4

8Tolu

ene

122 0

33

0 6

8P

enta

ne

2-m

eth

yl-

T5

1600

K(e

arlie

rsep

ara

ted

mole

cule

s)

222 1

92

4 4

7E

thane

12

-dic

hlo

ro-

14 3

33

3 3

7M

eth

ylA

lcohol

322 3

0 9

Penta

ne

3-m

eth

yl-

24 4

25

0 1

9Fura

n

2-b

uty

ltetr

ahyd

ro-

422 6

75

0 5

9C

yclo

penta

ne

meth

yl-

36 5

58

0 5

0B

enzene

1-m

eth

yl-4-

522 7

92

0 9

53-H

exanone

22

-dim

eth

yl-

46 7

25

0 1

3(E

)-1-P

henyl-1-b

ute

ne

623 1

83

38 4

2B

enzene

56 7

58

0 1

5E

thyle

ne

723 7

1 7

8C

yclo

hexane

66 8

25

0 1

1E

thane

825 8

17

1 8

5B

uta

ne

22

3-t

rim

eth

yl-

76 9

17

0 0

5N

eop

enta

ne

927 3

42

8 5

7H

exane

24

-dim

eth

yl-

87 1

42

0 0

2C

arb

onic

dih

yd

razid

e10

27 6

08

9 0

8H

exane

3-m

eth

yl-

97 2

33

0 1

0W

ate

r11

28 9

08

4 5

1H

ep

tane

10

7 2

58

0 0

512

-Oxath

iola

ne

12

30 2

33

27 8

9Tolu

ene

11

7 3

17

0 2

6S

ilane

T5

1600

K12

7 5

08

0 0

2Fura

n

2-b

uty

ltetr

ahyd

ro-

122 0

17

1 6

3P

enta

ne

2-m

eth

yl-

Wang and Luo Lump coal derived soot formation and gas analysis

22 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

compounds have been ignored because of its smallcontents In the end the tar and soot were separated indichloromethane by dissolving the sample The amountof tarsoot sample that did not dissolve was referred toas soot while the amount that dissolved was referred toas tar

Results and discussionMany factors that impact soot formation in stoker firedboiler have been studied in this fixed bed such astemperature residence time of gases and coal type Theresults of these experiments are given below

Effects of temperatureTemperature is a critical parameter in soot formationThe higher temperature the easier the volatiles arereleased from the coal surface Large PAH (sootprecursors) start to form soot at about 1300 K forhydrocarbon flames and for a complicated compoundlike coal the incipient temperature for soot precursorformation can be as low as 1100 K15 The soot aerosolsamples changed from viscous to solid particles as thetemperature increased so the sample viscosity serves asa rough visual measure of the extent of soot formationFigure 2 shows mass per cent of soot or tar ( daf) as itchanges with temperature increase The yields of sootare increased and the yields of tar are decreased withincreasing temperature It shows that a high temperatureis helpful for the release of volatiles and soot formationIt can also be concluded that the sum of tar plus soot

remains approximately constant that is increases insoot yields coincides with decreases in tar yields in thesame experimental condition This conclusion is con-sistent with Nenniger8 Wornat9 and Chenrsquos10 view-points in pulverised coal pyrolysis

The compositions of sample gases under experimen-tal conditions where the residence time of gases is176 s and the Shenmu coal is selected have beenexamined by GCMS and analysed Figure 3 shows thetotal ion chromatogram (TIC) of gases products frompyrolysis with temperature increase Correspondingcompounds identified and relative concentrations arelisted in Table 2 These compounds identified contain2-methyl pentane 12-dichloro ethane 3-methyl pen-tane benzene cyclohexane 223-trimethyl butane24-dimethyl hexane 3-methyl hexane heptane andtoluene in all experimental conditions Benzenetoluene 24-dimethyl hexane 3-methyl hexane hep-tane and 12-dichloro ethane are dominant compo-nents Besides there are many small molecules such asethane and ethylene from the volatiles of coals or fromthe decomposed polymer being formed at the tempera-ture of 1600 K It can be seen that the amount ofsaturated aliphatic hydrocarbons is decreased and theamount of aromatic hydrocarbons is increased with thetemperature increase by computing the contents ofthese compounds It may be caused by saturatedaliphatic hydrocarbons which have undergone con-densation or polymerisation reactions and beenconverted to aromatic hydrocarbons

4 Total ion chromatogram of gases products from coal pyrolysis with variation of gases residence time peaks are iden-

tified in Table 3

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 23

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Ta

ble

3Id

en

tifi

ca

tio

na

nd

rela

tiv

ec

on

ten

tso

fc

om

po

un

ds

rele

as

ed

fro

mc

oa

lp

yro

lys

isw

ith

va

ria

tio

no

fg

as

es

res

ide

nc

eti

me

Peak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

eP

eak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

e

t51 5

2s

11

27 3

42

8 1

1H

exane

24

-dim

eth

yl-

122 0

33

0 8

6P

enta

ne

2-m

eth

yl-

12

27 5

92

6 4

3H

exane

3-m

eth

yl-

222 1

92

6 8

Eth

ane

12

-dic

hlo

ro-

13

28 9

3 5

Hep

tane

322 3

17

0 9

Penta

ne

3-m

eth

yl-

14

29 1

58

0 3

6C

yclo

hexane

meth

yl-

422 6

92

0 4

6C

yclo

penta

ne

meth

yl-

15

29 7

58

1 4

o-X

yle

ne

522 8

08

1 6

53-H

exanone

22

-dim

eth

yl-

16

30 2

17

16 4

8Tolu

ene

623 1

83

53 4

3B

enzene

t51 7

6s

(earlie

rsep

ara

ted

mole

cule

s)

723 6

92

1 5

3C

yclo

hexane

14 3

33

3 3

7M

eth

ylA

lcohol

825 8

25

2 5

9B

uta

ne

22

3-t

rim

eth

yl-

24 4

25

0 1

9Fura

n

2-b

uty

ltetr

ahyd

ro-

927 3

59 3

9H

exane

24

-dim

eth

yl-

36 5

58

0 5

0B

enzene

1-m

eth

yl-4-

10

27 6

08

6 4

Hexane

3-m

eth

yl-

46 7

25

0 1

3(E

)-1-P

henyl-1-b

ute

ne

11

28 9

3 4

9H

ep

tane

56 7

58

0 1

5E

thyle

ne

12

30 2

511 4

1Tolu

ene

66 8

25

0 1

1E

thane

t51 5

2s

(earlie

rsep

ara

ted

mole

cule

s)

76 9

17

0 0

5N

eop

enta

ne

14 3

333

0 3

2N

eop

enta

ne

87 1

42

0 0

2C

arb

onic

dih

yd

razid

e2

4 4

25

0 0

7A

cete

ne

97 2

33

0 1

0W

ate

r3

4 4

67

0 2

Eth

ane

11

1-t

rifluoro

-10

7 2

58

0 0

512

-Oxath

iola

ne

44 5

0 0

9S

ilane

tetr

am

eth

yl-

11

7 3

17

0 2

6S

ilane

54 5

42

0 1

Sili

cane

hyd

rid

e12

7 5

08

0 0

2Fura

n

2-b

uty

ltetr

ahyd

ro-

64 5

83

0 1

24

-Penta

ned

ione

t52 0

0s

74 6

92

0 2

1M

eth

anol

121 8

83

32 0

6S

tyre

ne

t51 7

6s

222 0

25

16 2

1P

enta

ne

2-m

eth

yl-

122 0

17

1 6

3P

enta

ne

2-m

eth

yl-

322 1

92

6 0

4E

thane

12

-dic

hlo

ro-

222 1

83

4 6

9E

thane

12

-dic

hlo

ro-

422 2

92

8 9

9P

enta

ne

3-m

eth

yl-

322 2

92

1P

enta

ne

3-m

eth

yl-

522 7

92

4 8

5H

exane

422 6

83

0 4

4C

yclo

penta

ne

meth

yl-

623 1

75

18 9

1B

enzene

522 7

83

1 1

9H

exane

725 6

33

1 0

4B

uta

ne

22

3-t

rim

eth

yl-

623 1

75

44 0

7B

enzene

825 8

17

0 7

9B

uta

ne

22

33

-tetr

am

eth

yl-

723 4

25

0 1

2S

ilane

tetr

am

ehty

l-9

27 3

33

5 9

Hexane

24

-dim

eth

yl-

823 6

75

0 5

Cyclo

hexane

10

27 6

4 3

4H

exane

3-m

eth

yl-

925 8

25

3 1

5B

uta

ne

22

3-t

rim

eth

yl-

11

28 9

0 8

7H

ep

tane

10

26 9

83

1 9

8P

enta

ne

33

-dim

eth

yl-

Wang and Luo Lump coal derived soot formation and gas analysis

24 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Effects of gases residence timeResidence time of gases is also a factor in sootformation The residence time has been altered byregulating the position of fixed bed in the reactor and theinlet gas velocity Figure 2 represents the mass percentof soot or tar ( daf) change with extension of gasesresidence time (in vertical direction) at different tem-perature The yields of soot are higher at longerresidence time on the whole and the change regularityof tar yields is contrary with extension of gases residencetime It shows that tar is more readily converted to sootin longer residence time of gases

The composition of sample gases at a temperature of1600 K and with Shenmu coal selected has also beeninspected by GCMS and analysed Figure 4 shows theTIC of gases products from pyrolysis with extension ofgases residence time Corresponding compounds identi-fied and relative contents are listed in Table 3 Thesecompounds identified contain 2-methyl pentane 12-dichloro ethane 3-methyl pentane hexane benzene223-trimethyl butane 24-dimethyl hexane 3-methylhexane and heptane in all experimental conditionsBenzene 24-dimethyl hexane 3-methyl hexane heptaneand 12-dichloro ethane are dominant componentsamong them Besides there are many small moleculessuch as ethane and ethylene from the volatiles of coalsor from the decomposed segment of polymer beingseparated at earlier time when the residence time of gasesis 152 or 176 s whereas no small molecules aredetected when the residence time of gases is 200 s It canalso be observed that amount of unsaturated aliphatichydrocarbons are decreased and amount of saturatedaliphatic hydrocarbons are increased with extension ofgases residence time by computing the contents of thesecompounds The result can be interpreted by that partsof unsaturated aliphatic hydrocarbons have been con-verted to saturated aliphatic hydrocarbons by reason ofchemical bond reforming

Effects of coal typeFrom the proximate analysis of the three kinds of coalsshown in Table 1 volatile contents of dry ash free coals(including Datong Shenmu and Zibo) are 3317 3570and 3910 respectively At the same heating rates

5 Yields of soot and tar v coal type (T51600 K

t5176 s)

6 Total ion chromatogram of gases products from coal pyrolysis with coal type variation peaks are identified in Table 4

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 25

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Ta

ble

4Id

en

tifi

ca

tio

na

nd

rela

tiv

ec

on

ten

tso

fc

om

po

un

ds

rele

as

ed

fro

mc

oa

lp

yro

lys

isw

ith

co

al

typ

ev

ari

ati

on

Peak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

eP

eak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

e

Shenm

ucoal

122 0

17

0 5

9P

enta

ne

2-m

eth

yl-

122 0

17

1 6

3P

enta

ne

2-m

eth

yl-

222 1

75

7 0

8E

thane

12

-dic

hlo

ro-

222 1

83

4 6

9E

thane

12

-dic

hlo

ro-

322 3

0 2

3P

enta

ne

3-m

eth

yl-

322 2

92

1P

enta

ne

3-m

eth

yl-

422 6

92

0 2

9C

yclo

penta

ne

meth

yl-

422 6

83

0 4

4C

yclo

penta

ne

meth

yl-

522 7

83

0 6

33-H

exanone

22

-dim

eth

yl-

522 7

83

1 1

9H

exane

623 1

58

33 9

4B

enzene

623 1

75

44 0

7B

enzene

723 6

83

0 3

6C

yclo

hexane

723 4

25

0 1

2S

ilane

tetr

am

ehty

l-8

25 6

33

0 1

3B

uta

ne

22

3-t

rim

eth

yl-

823 6

75

0 5

Cyclo

hexane

925 8

08

0 5

2P

enta

ne

24

-dim

eth

yl-

925 8

25

3 1

5B

uta

ne

22

3-t

rim

eth

yl-

10

26 9

83

0 1

9C

yclo

penta

ne

13

-dim

eth

yl-

trans

10

26 9

83

1 9

8P

enta

ne

33

-dim

eth

yl-

11

27 3

25

3 2

7H

exane

24

-dim

eth

yl-

11

27 3

42

8 1

1H

exane

24

-dim

eth

yl-

12

27 5

92

2 9

2H

exane

3-m

eth

yl-

12

27 5

92

6 4

3H

exane

3-m

eth

yl-

13

28 9

1 5

7H

ep

tane

13

28 9

3 5

Hep

tane

14

30 2

10 7

3Tolu

ene

14

29 1

58

0 3

6C

yclo

hexane

meth

yl-

Dato

ng

coal(e

arlie

rsep

ara

ted

mole

cule

s)

15

29 7

58

1 4

o-X

yle

ne

15 2

50 0

22-B

uty

ned

ioic

acid

16

30 2

17

16 4

8Tolu

ene

28 9

58

37 5

3W

ate

rS

henm

ucoal(e

arlie

rsep

ara

ted

mole

cule

s)

Zib

ocoal

14 3

33

3 3

7M

eth

ylA

lcohol

122 0

25

1 0

7P

enta

ne

2-m

eth

yl-

24 4

25

0 1

9Fura

n

2-b

uty

ltetr

ahyd

ro-

222 1

83

8 1

4E

thane

12

-dic

hlo

ro-

36 5

58

0 5

0B

enzene

1-m

eth

yl-4-

322 2

92

0 7

9P

enta

ne

3-m

eth

yl-

46 7

25

0 1

3(E

)-1-P

henyl-1-b

ute

ne

422 6

83

0 6

5C

yclo

penta

ne

meth

yl-

56 7

58

0 1

5E

thyle

ne

522 7

92

0 8

53-H

exanone

22

-dim

eth

yl-

66 8

25

0 1

1E

thane

623 1

58

53 0

2B

enzene

76 9

17

0 0

5N

eop

enta

ne

723 6

83

1 0

7C

yclo

hexane

87 1

42

0 0

2C

arb

onic

dih

yd

razid

e8

26 9

0 5

6P

enta

ne

33

-dim

eth

yl-

97 2

33

0 1

0W

ate

r9

27 3

42

6 9

9H

exane

24

-dim

eth

yl-

10

7 2

58

0 0

512

-Oxath

iola

ne

10

27 5

92

6 1

8H

exane

3-m

eth

yl-

11

7 3

17

0 2

6S

ilane

11

28 9

2 0

2H

ep

tane

12

7 5

08

0 0

2Fura

n

2-b

uty

ltetr

ahyd

ro-

12

30 2

17

18 6

6Tolu

ene

Dato

ng

coal

Wang and Luo Lump coal derived soot formation and gas analysis

26 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

more volatiles are released from the high volatiles coalThe experimental condition is that the residence time ofgases is 176 s and the temperature in the reactor is1600 K Figure 5 describes the mass percent of soot ortar ( daf ) from different coals The soot yields derivedfrom Datong Shenmu and Zibo coal are increased inthat order The reason may be that there are morevolatiles in the reactor from high volatile coals in thesame conditions and the volatiles are easier to form sootdue to the oxygen scarcity

The composition of sample gases have also beentested by GCMS and analysed Figure 6 shows the TICof gases products from pyrolysis process with coal typevariation The compounds identified and relative con-tents are listed in Table 4 These compounds contain 2-methyl pentane 12-dichloro ethane 3-methyl pentanecyclopentane benzene cyclohexane 24-dimethyl hex-ane 3-methyl hexane heptane and toluene under allexperimental conditions Benzene toluene 24-dimethylhexane 3-methyl hexane heptane and 12-dichloroethane are the dominant components Besides thereare many small molecules such as ethane and ethylenefrom the volatiles of Shenmu coal or from thedecomposed segment of polymer being separated atearlier time and water vapour has been detected fromthe volatiles of Datong coal being separated at earliertime The aromatic hydrocarbon gases from Zibo coalpyrolysis is the highest The reason may be that thevolatiles content (daf) of Zibo Shenmu and Datong coaldecreased in that order Another reason is that thecomponents of gases relate to the microstructure of thecoals

ConclusionsSoot formation from lump coal has been studied duringthe pyrolysis process in a fixed bed Based on theexperimental study of the soot formation and relatedgases emission in the experimental facility theseconclusions can be drawn

1 Yields of soot are increased and yields of tar aredecreased that is more tars have been converted tosoot with temperature increase The relative contents ofsaturated aliphatic hydrocarbons are decreased andthose of aromatic hydrocarbons are increased becauseof condensation and polymerisation reactions withtemperature increase

2 More tars have been converted to soot with longergas residence time The relative contents of unsaturatedaliphatic hydrocarbons are decreased and those ofsaturated aliphatic hydrocarbon are increased becauseof reforming with longer residence time and no smallmolecules exists at longer residence time of gases

3 More soot is formed in the pyrolysis of highvolatile (Zibo) coal and more aromatic hydrocarbonsare released in high volatiles (Zibo) coal pyrolysisprocess under the same conditions

Acknowledgement

The authors thank Shanghai Environmental ProtectionBureau in China for its financial support (Huhuanke05-14)

References1 B L He Q Song C H Chen and X C Xu Proc 5th Asia-Pacific

Conf on lsquoCombustionrsquo Nanjing China November 2003 South-

eastern University 1ndash5

2 J L Ma T H Fletcher and B W Webb Proc 8th Int Conf on

lsquoCoal sciencersquo Oviedo Spain September 1995 International

Energy Agency 869ndash872

3 H F Zhang lsquoNitrogen evolution and soot formation during

secondary coal pyrolysisrsquo PhD thesis Brigham Young University

Provo UT USA 2001

4 T H Fletcher J L Ma J R Rigby A L Brown and B W

Webb Prog Energy Combust Sci 1997 23 283ndash301

5 E J Lee K C Oh and H D Shin Fuel 2005 84 543ndash550

6 F Inal G Tayfur T R Melton and S M Senkan Fuel 2003 82

1477ndash1490

7 I M Aksit and J B Moss Fuel 2005 84 239ndash245

8 R D Nenniger lsquoAerosols produced from coal pyrolysisrsquo MSc

thesis Massachusetts Institute of Technology Cambridge MA

USA 1986

9 M J Wornat A F Sarofim and J P Longwell Energy Fuel 1987

1 431ndash437

10 J C Chen lsquoEffect of secondary reactions on product distribution

and nitrogen evolution from rapid coal pyrolysisrsquo PhD thesis

Stanford University Palo Alto CA USA 1991

11 M J Tan and J X Mao Proc Conf on lsquoAdvanced technologies

of industrial boilers in USndashChinarsquo Beijing China June 2004

Power Engineer Institute 1ndash17

12 D Sun and S Choi Combust Flame 2000 121 167ndash180

13 N Ford M J Cooke and M D Pettit Inst Energy 1992 65 137ndash

143

14 G P Staley F W Bradshaw C S Carrel D W Pershing and G

B Martin Combust Flame 1985 59 197ndash211

15 M S Solum A F Sarofim R J Pugmire T H Fletcher and H

Zhang Energy Fuels 2001 15 961ndash971

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 27

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

The gases from the tube reactor flowed through awater cooled 30 mm diameter tube in which aglass fibre or polycarbonate filter with 005 mm porediameters was fixed so the gases went through the filterand the aerosol samples were collected on the filter4 Theglass fibre filters were Whatman made in England Avacuum pump and valve were set for sustaining stablepressure in the tube and a port was provided to samplethe gases

The fixed bed was a 44 mm diameter and plate shaperefractory Thirty-two holes were arranged in thebottom of the fixed bed and the diameters of holeswere 2 mm A moveable refractory rod was employed tosupport the fixed bed and a larger diameter stainlesstube was connected to the base of the reactor by boltsThe different heights of the fixed bed in the reactordepend on the position of the moveable refractory poleand thus the residence time of gases in the reactor couldbe adjusted

Experimental methodsThree influencing factors temperature residence time ofgases and type of coal were considered for thisexperiment

In the experimental facility described in Fig 1temperature was adjusted to appointed value accordingto temperature in stoker fired boiler first Second thelump coals were introduced onto the bed outside of thereactor A batch of coal particles was 7 g The coal wasclassified with sieves by its diameter and particlesranging in size from 3 to 5 mm were employed The

selected coals were three kinds of coals widely used inindustrial boiler in China and ultimate and proximateanalysis data of these coals are shown in Table 1 Thirdthe bed with coals were sent to the hearth from thebottom of the reactor supported and fixed by the coalsupply system (Fig 1) The volatiles were released andexpanded away from the coal particles Argon flowsmeasured with a rotameter were brought to the reactorfrom the bottom of the reactor immediately at the sametime the vacuum pump was turned on The variation ofargon amount was necessary for the case of differenttemperature in the reactor in order to achieve theprojected residence time of gases After 1 min the fluegases could be extracted with an injector for gaschromatograph mass spectrometer (GCMS) analysisThe GCMS (QP2010NC Shimadzu Japan) wasemployed for all measurements with a PLOT-Q chro-matograph column coupled to a MS engine with anionisation energy of 70 eV in the electron impact modeCompounds were separated on a 30 m6032 mm idcolumn coated with a 20 mm film The initial columntemperature was 35uC which was increased at10uC min21 to 200uC The filter papers with soot aerosolsamples were weighed by electronic balance to obtainthe amount of aerosol samples generated during certaina period of time The filter with soot aerosol mixturecould be scraped The contents of ash could also becomputed according to the element contents tested byinductively coupled plasma atomic emission spectro-meter (PE400 Perkin Elmer Wellesley MA USA)All ash components are oxides chlorides and other

3 Total ion chromatogram of gases products from coal pyrolysis with temperature variation peaks are identified in

Table 2

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 21

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Ta

ble

2Id

en

tifi

ca

tio

na

nd

rela

tiv

ec

on

ten

tso

fc

om

po

un

ds

rele

as

ed

fro

mc

oa

lp

yro

lys

isw

ith

tem

pe

ratu

rev

ari

ati

on

Peak

nu

mb

er

Rete

nti

on

tim

e

min

Reta

tive

co

nte

nt

C

om

po

un

dn

am

eP

eak

nu

mb

er

Rete

nti

on

tim

e

min

Reta

tive

co

nte

nt

C

om

po

un

dn

am

e

T5

1100

K2

22 1

83

4 6

9E

thane

12

-dic

hlo

ro-

121 2

3 5

9B

uta

ne

22

-dim

eth

yl-

322 2

92

1P

enta

ne

3-m

eth

yl-

222 0

25

9 7

6P

enta

ne

2-m

eth

yl-

422 6

83

0 4

4C

yclo

penta

ne

meth

yl-

322 1

83

2 6

1E

thane

12

-dic

hlo

ro-

522 7

83

1 1

9H

exane

422 2

92

6 8

8P

enta

ne

3-m

eth

yl-

623 1

75

44 0

7B

enzene

522 7

92

7 2

2H

exane

723 4

25

0 1

2S

ilane

tetr

am

ehty

l-6

23 1

67

43 8

8B

enzene

823 6

75

0 5

Cyclo

hexane

723 6

75

1 2

5C

yclo

hexane

925 8

25

3 1

5B

uta

ne

22

3-t

rim

eth

yl-

825 8

17

7 8

1B

uta

ne

22

3-t

rim

eth

yl-

10

26 9

83

1 9

8P

enta

ne

33

-dim

eth

yl-

927 3

42

8 6

7P

enta

ne

24

-dim

eth

yl-

11

27 3

42

8 1

1H

exane

24

-dim

eth

yl-

10

27 5

92

3 9

8H

exane

3-m

eth

yl-

12

27 5

92

6 4

3H

exane

3-m

eth

yl-

11

28 9

2 1

2H

ep

tane

13

28 9

3 5

Hep

tane

12

30 0

17

0 5

8Tetr

achlo

roeth

yle

ne

14

29 1

58

0 3

6C

yclo

hexane

meth

yl-

13

30 2

17

1 6

5Tolu

ene

15

29 7

58

1 4

o-X

yle

ne

T5

1400

K16

30 2

17

16 4

8Tolu

ene

122 0

33

0 6

8P

enta

ne

2-m

eth

yl-

T5

1600

K(e

arlie

rsep

ara

ted

mole

cule

s)

222 1

92

4 4

7E

thane

12

-dic

hlo

ro-

14 3

33

3 3

7M

eth

ylA

lcohol

322 3

0 9

Penta

ne

3-m

eth

yl-

24 4

25

0 1

9Fura

n

2-b

uty

ltetr

ahyd

ro-

422 6

75

0 5

9C

yclo

penta

ne

meth

yl-

36 5

58

0 5

0B

enzene

1-m

eth

yl-4-

522 7

92

0 9

53-H

exanone

22

-dim

eth

yl-

46 7

25

0 1

3(E

)-1-P

henyl-1-b

ute

ne

623 1

83

38 4

2B

enzene

56 7

58

0 1

5E

thyle

ne

723 7

1 7

8C

yclo

hexane

66 8

25

0 1

1E

thane

825 8

17

1 8

5B

uta

ne

22

3-t

rim

eth

yl-

76 9

17

0 0

5N

eop

enta

ne

927 3

42

8 5

7H

exane

24

-dim

eth

yl-

87 1

42

0 0

2C

arb

onic

dih

yd

razid

e10

27 6

08

9 0

8H

exane

3-m

eth

yl-

97 2

33

0 1

0W

ate

r11

28 9

08

4 5

1H

ep

tane

10

7 2

58

0 0

512

-Oxath

iola

ne

12

30 2

33

27 8

9Tolu

ene

11

7 3

17

0 2

6S

ilane

T5

1600

K12

7 5

08

0 0

2Fura

n

2-b

uty

ltetr

ahyd

ro-

122 0

17

1 6

3P

enta

ne

2-m

eth

yl-

Wang and Luo Lump coal derived soot formation and gas analysis

22 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

compounds have been ignored because of its smallcontents In the end the tar and soot were separated indichloromethane by dissolving the sample The amountof tarsoot sample that did not dissolve was referred toas soot while the amount that dissolved was referred toas tar

Results and discussionMany factors that impact soot formation in stoker firedboiler have been studied in this fixed bed such astemperature residence time of gases and coal type Theresults of these experiments are given below

Effects of temperatureTemperature is a critical parameter in soot formationThe higher temperature the easier the volatiles arereleased from the coal surface Large PAH (sootprecursors) start to form soot at about 1300 K forhydrocarbon flames and for a complicated compoundlike coal the incipient temperature for soot precursorformation can be as low as 1100 K15 The soot aerosolsamples changed from viscous to solid particles as thetemperature increased so the sample viscosity serves asa rough visual measure of the extent of soot formationFigure 2 shows mass per cent of soot or tar ( daf) as itchanges with temperature increase The yields of sootare increased and the yields of tar are decreased withincreasing temperature It shows that a high temperatureis helpful for the release of volatiles and soot formationIt can also be concluded that the sum of tar plus soot

remains approximately constant that is increases insoot yields coincides with decreases in tar yields in thesame experimental condition This conclusion is con-sistent with Nenniger8 Wornat9 and Chenrsquos10 view-points in pulverised coal pyrolysis

The compositions of sample gases under experimen-tal conditions where the residence time of gases is176 s and the Shenmu coal is selected have beenexamined by GCMS and analysed Figure 3 shows thetotal ion chromatogram (TIC) of gases products frompyrolysis with temperature increase Correspondingcompounds identified and relative concentrations arelisted in Table 2 These compounds identified contain2-methyl pentane 12-dichloro ethane 3-methyl pen-tane benzene cyclohexane 223-trimethyl butane24-dimethyl hexane 3-methyl hexane heptane andtoluene in all experimental conditions Benzenetoluene 24-dimethyl hexane 3-methyl hexane hep-tane and 12-dichloro ethane are dominant compo-nents Besides there are many small molecules such asethane and ethylene from the volatiles of coals or fromthe decomposed polymer being formed at the tempera-ture of 1600 K It can be seen that the amount ofsaturated aliphatic hydrocarbons is decreased and theamount of aromatic hydrocarbons is increased with thetemperature increase by computing the contents ofthese compounds It may be caused by saturatedaliphatic hydrocarbons which have undergone con-densation or polymerisation reactions and beenconverted to aromatic hydrocarbons

4 Total ion chromatogram of gases products from coal pyrolysis with variation of gases residence time peaks are iden-

tified in Table 3

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 23

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Ta

ble

3Id

en

tifi

ca

tio

na

nd

rela

tiv

ec

on

ten

tso

fc

om

po

un

ds

rele

as

ed

fro

mc

oa

lp

yro

lys

isw

ith

va

ria

tio

no

fg

as

es

res

ide

nc

eti

me

Peak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

eP

eak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

e

t51 5

2s

11

27 3

42

8 1

1H

exane

24

-dim

eth

yl-

122 0

33

0 8

6P

enta

ne

2-m

eth

yl-

12

27 5

92

6 4

3H

exane

3-m

eth

yl-

222 1

92

6 8

Eth

ane

12

-dic

hlo

ro-

13

28 9

3 5

Hep

tane

322 3

17

0 9

Penta

ne

3-m

eth

yl-

14

29 1

58

0 3

6C

yclo

hexane

meth

yl-

422 6

92

0 4

6C

yclo

penta

ne

meth

yl-

15

29 7

58

1 4

o-X

yle

ne

522 8

08

1 6

53-H

exanone

22

-dim

eth

yl-

16

30 2

17

16 4

8Tolu

ene

623 1

83

53 4

3B

enzene

t51 7

6s

(earlie

rsep

ara

ted

mole

cule

s)

723 6

92

1 5

3C

yclo

hexane

14 3

33

3 3

7M

eth

ylA

lcohol

825 8

25

2 5

9B

uta

ne

22

3-t

rim

eth

yl-

24 4

25

0 1

9Fura

n

2-b

uty

ltetr

ahyd

ro-

927 3

59 3

9H

exane

24

-dim

eth

yl-

36 5

58

0 5

0B

enzene

1-m

eth

yl-4-

10

27 6

08

6 4

Hexane

3-m

eth

yl-

46 7

25

0 1

3(E

)-1-P

henyl-1-b

ute

ne

11

28 9

3 4

9H

ep

tane

56 7

58

0 1

5E

thyle

ne

12

30 2

511 4

1Tolu

ene

66 8

25

0 1

1E

thane

t51 5

2s

(earlie

rsep

ara

ted

mole

cule

s)

76 9

17

0 0

5N

eop

enta

ne

14 3

333

0 3

2N

eop

enta

ne

87 1

42

0 0

2C

arb

onic

dih

yd

razid

e2

4 4

25

0 0

7A

cete

ne

97 2

33

0 1

0W

ate

r3

4 4

67

0 2

Eth

ane

11

1-t

rifluoro

-10

7 2

58

0 0

512

-Oxath

iola

ne

44 5

0 0

9S

ilane

tetr

am

eth

yl-

11

7 3

17

0 2

6S

ilane

54 5

42

0 1

Sili

cane

hyd

rid

e12

7 5

08

0 0

2Fura

n

2-b

uty

ltetr

ahyd

ro-

64 5

83

0 1

24

-Penta

ned

ione

t52 0

0s

74 6

92

0 2

1M

eth

anol

121 8

83

32 0

6S

tyre

ne

t51 7

6s

222 0

25

16 2

1P

enta

ne

2-m

eth

yl-

122 0

17

1 6

3P

enta

ne

2-m

eth

yl-

322 1

92

6 0

4E

thane

12

-dic

hlo

ro-

222 1

83

4 6

9E

thane

12

-dic

hlo

ro-

422 2

92

8 9

9P

enta

ne

3-m

eth

yl-

322 2

92

1P

enta

ne

3-m

eth

yl-

522 7

92

4 8

5H

exane

422 6

83

0 4

4C

yclo

penta

ne

meth

yl-

623 1

75

18 9

1B

enzene

522 7

83

1 1

9H

exane

725 6

33

1 0

4B

uta

ne

22

3-t

rim

eth

yl-

623 1

75

44 0

7B

enzene

825 8

17

0 7

9B

uta

ne

22

33

-tetr

am

eth

yl-

723 4

25

0 1

2S

ilane

tetr

am

ehty

l-9

27 3

33

5 9

Hexane

24

-dim

eth

yl-

823 6

75

0 5

Cyclo

hexane

10

27 6

4 3

4H

exane

3-m

eth

yl-

925 8

25

3 1

5B

uta

ne

22

3-t

rim

eth

yl-

11

28 9

0 8

7H

ep

tane

10

26 9

83

1 9

8P

enta

ne

33

-dim

eth

yl-

Wang and Luo Lump coal derived soot formation and gas analysis

24 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Effects of gases residence timeResidence time of gases is also a factor in sootformation The residence time has been altered byregulating the position of fixed bed in the reactor and theinlet gas velocity Figure 2 represents the mass percentof soot or tar ( daf) change with extension of gasesresidence time (in vertical direction) at different tem-perature The yields of soot are higher at longerresidence time on the whole and the change regularityof tar yields is contrary with extension of gases residencetime It shows that tar is more readily converted to sootin longer residence time of gases

The composition of sample gases at a temperature of1600 K and with Shenmu coal selected has also beeninspected by GCMS and analysed Figure 4 shows theTIC of gases products from pyrolysis with extension ofgases residence time Corresponding compounds identi-fied and relative contents are listed in Table 3 Thesecompounds identified contain 2-methyl pentane 12-dichloro ethane 3-methyl pentane hexane benzene223-trimethyl butane 24-dimethyl hexane 3-methylhexane and heptane in all experimental conditionsBenzene 24-dimethyl hexane 3-methyl hexane heptaneand 12-dichloro ethane are dominant componentsamong them Besides there are many small moleculessuch as ethane and ethylene from the volatiles of coalsor from the decomposed segment of polymer beingseparated at earlier time when the residence time of gasesis 152 or 176 s whereas no small molecules aredetected when the residence time of gases is 200 s It canalso be observed that amount of unsaturated aliphatichydrocarbons are decreased and amount of saturatedaliphatic hydrocarbons are increased with extension ofgases residence time by computing the contents of thesecompounds The result can be interpreted by that partsof unsaturated aliphatic hydrocarbons have been con-verted to saturated aliphatic hydrocarbons by reason ofchemical bond reforming

Effects of coal typeFrom the proximate analysis of the three kinds of coalsshown in Table 1 volatile contents of dry ash free coals(including Datong Shenmu and Zibo) are 3317 3570and 3910 respectively At the same heating rates

5 Yields of soot and tar v coal type (T51600 K

t5176 s)

6 Total ion chromatogram of gases products from coal pyrolysis with coal type variation peaks are identified in Table 4

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 25

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Ta

ble

4Id

en

tifi

ca

tio

na

nd

rela

tiv

ec

on

ten

tso

fc

om

po

un

ds

rele

as

ed

fro

mc

oa

lp

yro

lys

isw

ith

co

al

typ

ev

ari

ati

on

Peak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

eP

eak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

e

Shenm

ucoal

122 0

17

0 5

9P

enta

ne

2-m

eth

yl-

122 0

17

1 6

3P

enta

ne

2-m

eth

yl-

222 1

75

7 0

8E

thane

12

-dic

hlo

ro-

222 1

83

4 6

9E

thane

12

-dic

hlo

ro-

322 3

0 2

3P

enta

ne

3-m

eth

yl-

322 2

92

1P

enta

ne

3-m

eth

yl-

422 6

92

0 2

9C

yclo

penta

ne

meth

yl-

422 6

83

0 4

4C

yclo

penta

ne

meth

yl-

522 7

83

0 6

33-H

exanone

22

-dim

eth

yl-

522 7

83

1 1

9H

exane

623 1

58

33 9

4B

enzene

623 1

75

44 0

7B

enzene

723 6

83

0 3

6C

yclo

hexane

723 4

25

0 1

2S

ilane

tetr

am

ehty

l-8

25 6

33

0 1

3B

uta

ne

22

3-t

rim

eth

yl-

823 6

75

0 5

Cyclo

hexane

925 8

08

0 5

2P

enta

ne

24

-dim

eth

yl-

925 8

25

3 1

5B

uta

ne

22

3-t

rim

eth

yl-

10

26 9

83

0 1

9C

yclo

penta

ne

13

-dim

eth

yl-

trans

10

26 9

83

1 9

8P

enta

ne

33

-dim

eth

yl-

11

27 3

25

3 2

7H

exane

24

-dim

eth

yl-

11

27 3

42

8 1

1H

exane

24

-dim

eth

yl-

12

27 5

92

2 9

2H

exane

3-m

eth

yl-

12

27 5

92

6 4

3H

exane

3-m

eth

yl-

13

28 9

1 5

7H

ep

tane

13

28 9

3 5

Hep

tane

14

30 2

10 7

3Tolu

ene

14

29 1

58

0 3

6C

yclo

hexane

meth

yl-

Dato

ng

coal(e

arlie

rsep

ara

ted

mole

cule

s)

15

29 7

58

1 4

o-X

yle

ne

15 2

50 0

22-B

uty

ned

ioic

acid

16

30 2

17

16 4

8Tolu

ene

28 9

58

37 5

3W

ate

rS

henm

ucoal(e

arlie

rsep

ara

ted

mole

cule

s)

Zib

ocoal

14 3

33

3 3

7M

eth

ylA

lcohol

122 0

25

1 0

7P

enta

ne

2-m

eth

yl-

24 4

25

0 1

9Fura

n

2-b

uty

ltetr

ahyd

ro-

222 1

83

8 1

4E

thane

12

-dic

hlo

ro-

36 5

58

0 5

0B

enzene

1-m

eth

yl-4-

322 2

92

0 7

9P

enta

ne

3-m

eth

yl-

46 7

25

0 1

3(E

)-1-P

henyl-1-b

ute

ne

422 6

83

0 6

5C

yclo

penta

ne

meth

yl-

56 7

58

0 1

5E

thyle

ne

522 7

92

0 8

53-H

exanone

22

-dim

eth

yl-

66 8

25

0 1

1E

thane

623 1

58

53 0

2B

enzene

76 9

17

0 0

5N

eop

enta

ne

723 6

83

1 0

7C

yclo

hexane

87 1

42

0 0

2C

arb

onic

dih

yd

razid

e8

26 9

0 5

6P

enta

ne

33

-dim

eth

yl-

97 2

33

0 1

0W

ate

r9

27 3

42

6 9

9H

exane

24

-dim

eth

yl-

10

7 2

58

0 0

512

-Oxath

iola

ne

10

27 5

92

6 1

8H

exane

3-m

eth

yl-

11

7 3

17

0 2

6S

ilane

11

28 9

2 0

2H

ep

tane

12

7 5

08

0 0

2Fura

n

2-b

uty

ltetr

ahyd

ro-

12

30 2

17

18 6

6Tolu

ene

Dato

ng

coal

Wang and Luo Lump coal derived soot formation and gas analysis

26 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

more volatiles are released from the high volatiles coalThe experimental condition is that the residence time ofgases is 176 s and the temperature in the reactor is1600 K Figure 5 describes the mass percent of soot ortar ( daf ) from different coals The soot yields derivedfrom Datong Shenmu and Zibo coal are increased inthat order The reason may be that there are morevolatiles in the reactor from high volatile coals in thesame conditions and the volatiles are easier to form sootdue to the oxygen scarcity

The composition of sample gases have also beentested by GCMS and analysed Figure 6 shows the TICof gases products from pyrolysis process with coal typevariation The compounds identified and relative con-tents are listed in Table 4 These compounds contain 2-methyl pentane 12-dichloro ethane 3-methyl pentanecyclopentane benzene cyclohexane 24-dimethyl hex-ane 3-methyl hexane heptane and toluene under allexperimental conditions Benzene toluene 24-dimethylhexane 3-methyl hexane heptane and 12-dichloroethane are the dominant components Besides thereare many small molecules such as ethane and ethylenefrom the volatiles of Shenmu coal or from thedecomposed segment of polymer being separated atearlier time and water vapour has been detected fromthe volatiles of Datong coal being separated at earliertime The aromatic hydrocarbon gases from Zibo coalpyrolysis is the highest The reason may be that thevolatiles content (daf) of Zibo Shenmu and Datong coaldecreased in that order Another reason is that thecomponents of gases relate to the microstructure of thecoals

ConclusionsSoot formation from lump coal has been studied duringthe pyrolysis process in a fixed bed Based on theexperimental study of the soot formation and relatedgases emission in the experimental facility theseconclusions can be drawn

1 Yields of soot are increased and yields of tar aredecreased that is more tars have been converted tosoot with temperature increase The relative contents ofsaturated aliphatic hydrocarbons are decreased andthose of aromatic hydrocarbons are increased becauseof condensation and polymerisation reactions withtemperature increase

2 More tars have been converted to soot with longergas residence time The relative contents of unsaturatedaliphatic hydrocarbons are decreased and those ofsaturated aliphatic hydrocarbon are increased becauseof reforming with longer residence time and no smallmolecules exists at longer residence time of gases

3 More soot is formed in the pyrolysis of highvolatile (Zibo) coal and more aromatic hydrocarbonsare released in high volatiles (Zibo) coal pyrolysisprocess under the same conditions

Acknowledgement

The authors thank Shanghai Environmental ProtectionBureau in China for its financial support (Huhuanke05-14)

References1 B L He Q Song C H Chen and X C Xu Proc 5th Asia-Pacific

Conf on lsquoCombustionrsquo Nanjing China November 2003 South-

eastern University 1ndash5

2 J L Ma T H Fletcher and B W Webb Proc 8th Int Conf on

lsquoCoal sciencersquo Oviedo Spain September 1995 International

Energy Agency 869ndash872

3 H F Zhang lsquoNitrogen evolution and soot formation during

secondary coal pyrolysisrsquo PhD thesis Brigham Young University

Provo UT USA 2001

4 T H Fletcher J L Ma J R Rigby A L Brown and B W

Webb Prog Energy Combust Sci 1997 23 283ndash301

5 E J Lee K C Oh and H D Shin Fuel 2005 84 543ndash550

6 F Inal G Tayfur T R Melton and S M Senkan Fuel 2003 82

1477ndash1490

7 I M Aksit and J B Moss Fuel 2005 84 239ndash245

8 R D Nenniger lsquoAerosols produced from coal pyrolysisrsquo MSc

thesis Massachusetts Institute of Technology Cambridge MA

USA 1986

9 M J Wornat A F Sarofim and J P Longwell Energy Fuel 1987

1 431ndash437

10 J C Chen lsquoEffect of secondary reactions on product distribution

and nitrogen evolution from rapid coal pyrolysisrsquo PhD thesis

Stanford University Palo Alto CA USA 1991

11 M J Tan and J X Mao Proc Conf on lsquoAdvanced technologies

of industrial boilers in USndashChinarsquo Beijing China June 2004

Power Engineer Institute 1ndash17

12 D Sun and S Choi Combust Flame 2000 121 167ndash180

13 N Ford M J Cooke and M D Pettit Inst Energy 1992 65 137ndash

143

14 G P Staley F W Bradshaw C S Carrel D W Pershing and G

B Martin Combust Flame 1985 59 197ndash211

15 M S Solum A F Sarofim R J Pugmire T H Fletcher and H

Zhang Energy Fuels 2001 15 961ndash971

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 27

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Ta

ble

2Id

en

tifi

ca

tio

na

nd

rela

tiv

ec

on

ten

tso

fc

om

po

un

ds

rele

as

ed

fro

mc

oa

lp

yro

lys

isw

ith

tem

pe

ratu

rev

ari

ati

on

Peak

nu

mb

er

Rete

nti

on

tim

e

min

Reta

tive

co

nte

nt

C

om

po

un

dn

am

eP

eak

nu

mb

er

Rete

nti

on

tim

e

min

Reta

tive

co

nte

nt

C

om

po

un

dn

am

e

T5

1100

K2

22 1

83

4 6

9E

thane

12

-dic

hlo

ro-

121 2

3 5

9B

uta

ne

22

-dim

eth

yl-

322 2

92

1P

enta

ne

3-m

eth

yl-

222 0

25

9 7

6P

enta

ne

2-m

eth

yl-

422 6

83

0 4

4C

yclo

penta

ne

meth

yl-

322 1

83

2 6

1E

thane

12

-dic

hlo

ro-

522 7

83

1 1

9H

exane

422 2

92

6 8

8P

enta

ne

3-m

eth

yl-

623 1

75

44 0

7B

enzene

522 7

92

7 2

2H

exane

723 4

25

0 1

2S

ilane

tetr

am

ehty

l-6

23 1

67

43 8

8B

enzene

823 6

75

0 5

Cyclo

hexane

723 6

75

1 2

5C

yclo

hexane

925 8

25

3 1

5B

uta

ne

22

3-t

rim

eth

yl-

825 8

17

7 8

1B

uta

ne

22

3-t

rim

eth

yl-

10

26 9

83

1 9

8P

enta

ne

33

-dim

eth

yl-

927 3

42

8 6

7P

enta

ne

24

-dim

eth

yl-

11

27 3

42

8 1

1H

exane

24

-dim

eth

yl-

10

27 5

92

3 9

8H

exane

3-m

eth

yl-

12

27 5

92

6 4

3H

exane

3-m

eth

yl-

11

28 9

2 1

2H

ep

tane

13

28 9

3 5

Hep

tane

12

30 0

17

0 5

8Tetr

achlo

roeth

yle

ne

14

29 1

58

0 3

6C

yclo

hexane

meth

yl-

13

30 2

17

1 6

5Tolu

ene

15

29 7

58

1 4

o-X

yle

ne

T5

1400

K16

30 2

17

16 4

8Tolu

ene

122 0

33

0 6

8P

enta

ne

2-m

eth

yl-

T5

1600

K(e

arlie

rsep

ara

ted

mole

cule

s)

222 1

92

4 4

7E

thane

12

-dic

hlo

ro-

14 3

33

3 3

7M

eth

ylA

lcohol

322 3

0 9

Penta

ne

3-m

eth

yl-

24 4

25

0 1

9Fura

n

2-b

uty

ltetr

ahyd

ro-

422 6

75

0 5

9C

yclo

penta

ne

meth

yl-

36 5

58

0 5

0B

enzene

1-m

eth

yl-4-

522 7

92

0 9

53-H

exanone

22

-dim

eth

yl-

46 7

25

0 1

3(E

)-1-P

henyl-1-b

ute

ne

623 1

83

38 4

2B

enzene

56 7

58

0 1

5E

thyle

ne

723 7

1 7

8C

yclo

hexane

66 8

25

0 1

1E

thane

825 8

17

1 8

5B

uta

ne

22

3-t

rim

eth

yl-

76 9

17

0 0

5N

eop

enta

ne

927 3

42

8 5

7H

exane

24

-dim

eth

yl-

87 1

42

0 0

2C

arb

onic

dih

yd

razid

e10

27 6

08

9 0

8H

exane

3-m

eth

yl-

97 2

33

0 1

0W

ate

r11

28 9

08

4 5

1H

ep

tane

10

7 2

58

0 0

512

-Oxath

iola

ne

12

30 2

33

27 8

9Tolu

ene

11

7 3

17

0 2

6S

ilane

T5

1600

K12

7 5

08

0 0

2Fura

n

2-b

uty

ltetr

ahyd

ro-

122 0

17

1 6

3P

enta

ne

2-m

eth

yl-

Wang and Luo Lump coal derived soot formation and gas analysis

22 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

compounds have been ignored because of its smallcontents In the end the tar and soot were separated indichloromethane by dissolving the sample The amountof tarsoot sample that did not dissolve was referred toas soot while the amount that dissolved was referred toas tar

Results and discussionMany factors that impact soot formation in stoker firedboiler have been studied in this fixed bed such astemperature residence time of gases and coal type Theresults of these experiments are given below

Effects of temperatureTemperature is a critical parameter in soot formationThe higher temperature the easier the volatiles arereleased from the coal surface Large PAH (sootprecursors) start to form soot at about 1300 K forhydrocarbon flames and for a complicated compoundlike coal the incipient temperature for soot precursorformation can be as low as 1100 K15 The soot aerosolsamples changed from viscous to solid particles as thetemperature increased so the sample viscosity serves asa rough visual measure of the extent of soot formationFigure 2 shows mass per cent of soot or tar ( daf) as itchanges with temperature increase The yields of sootare increased and the yields of tar are decreased withincreasing temperature It shows that a high temperatureis helpful for the release of volatiles and soot formationIt can also be concluded that the sum of tar plus soot

remains approximately constant that is increases insoot yields coincides with decreases in tar yields in thesame experimental condition This conclusion is con-sistent with Nenniger8 Wornat9 and Chenrsquos10 view-points in pulverised coal pyrolysis

The compositions of sample gases under experimen-tal conditions where the residence time of gases is176 s and the Shenmu coal is selected have beenexamined by GCMS and analysed Figure 3 shows thetotal ion chromatogram (TIC) of gases products frompyrolysis with temperature increase Correspondingcompounds identified and relative concentrations arelisted in Table 2 These compounds identified contain2-methyl pentane 12-dichloro ethane 3-methyl pen-tane benzene cyclohexane 223-trimethyl butane24-dimethyl hexane 3-methyl hexane heptane andtoluene in all experimental conditions Benzenetoluene 24-dimethyl hexane 3-methyl hexane hep-tane and 12-dichloro ethane are dominant compo-nents Besides there are many small molecules such asethane and ethylene from the volatiles of coals or fromthe decomposed polymer being formed at the tempera-ture of 1600 K It can be seen that the amount ofsaturated aliphatic hydrocarbons is decreased and theamount of aromatic hydrocarbons is increased with thetemperature increase by computing the contents ofthese compounds It may be caused by saturatedaliphatic hydrocarbons which have undergone con-densation or polymerisation reactions and beenconverted to aromatic hydrocarbons

4 Total ion chromatogram of gases products from coal pyrolysis with variation of gases residence time peaks are iden-

tified in Table 3

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 23

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Ta

ble

3Id

en

tifi

ca

tio

na

nd

rela

tiv

ec

on

ten

tso

fc

om

po

un

ds

rele

as

ed

fro

mc

oa

lp

yro

lys

isw

ith

va

ria

tio

no

fg

as

es

res

ide

nc

eti

me

Peak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

eP

eak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

e

t51 5

2s

11

27 3

42

8 1

1H

exane

24

-dim

eth

yl-

122 0

33

0 8

6P

enta

ne

2-m

eth

yl-

12

27 5

92

6 4

3H

exane

3-m

eth

yl-

222 1

92

6 8

Eth

ane

12

-dic

hlo

ro-

13

28 9

3 5

Hep

tane

322 3

17

0 9

Penta

ne

3-m

eth

yl-

14

29 1

58

0 3

6C

yclo

hexane

meth

yl-

422 6

92

0 4

6C

yclo

penta

ne

meth

yl-

15

29 7

58

1 4

o-X

yle

ne

522 8

08

1 6

53-H

exanone

22

-dim

eth

yl-

16

30 2

17

16 4

8Tolu

ene

623 1

83

53 4

3B

enzene

t51 7

6s

(earlie

rsep

ara

ted

mole

cule

s)

723 6

92

1 5

3C

yclo

hexane

14 3

33

3 3

7M

eth

ylA

lcohol

825 8

25

2 5

9B

uta

ne

22

3-t

rim

eth

yl-

24 4

25

0 1

9Fura

n

2-b

uty

ltetr

ahyd

ro-

927 3

59 3

9H

exane

24

-dim

eth

yl-

36 5

58

0 5

0B

enzene

1-m

eth

yl-4-

10

27 6

08

6 4

Hexane

3-m

eth

yl-

46 7

25

0 1

3(E

)-1-P

henyl-1-b

ute

ne

11

28 9

3 4

9H

ep

tane

56 7

58

0 1

5E

thyle

ne

12

30 2

511 4

1Tolu

ene

66 8

25

0 1

1E

thane

t51 5

2s

(earlie

rsep

ara

ted

mole

cule

s)

76 9

17

0 0

5N

eop

enta

ne

14 3

333

0 3

2N

eop

enta

ne

87 1

42

0 0

2C

arb

onic

dih

yd

razid

e2

4 4

25

0 0

7A

cete

ne

97 2

33

0 1

0W

ate

r3

4 4

67

0 2

Eth

ane

11

1-t

rifluoro

-10

7 2

58

0 0

512

-Oxath

iola

ne

44 5

0 0

9S

ilane

tetr

am

eth

yl-

11

7 3

17

0 2

6S

ilane

54 5

42

0 1

Sili

cane

hyd

rid

e12

7 5

08

0 0

2Fura

n

2-b

uty

ltetr

ahyd

ro-

64 5

83

0 1

24

-Penta

ned

ione

t52 0

0s

74 6

92

0 2

1M

eth

anol

121 8

83

32 0

6S

tyre

ne

t51 7

6s

222 0

25

16 2

1P

enta

ne

2-m

eth

yl-

122 0

17

1 6

3P

enta

ne

2-m

eth

yl-

322 1

92

6 0

4E

thane

12

-dic

hlo

ro-

222 1

83

4 6

9E

thane

12

-dic

hlo

ro-

422 2

92

8 9

9P

enta

ne

3-m

eth

yl-

322 2

92

1P

enta

ne

3-m

eth

yl-

522 7

92

4 8

5H

exane

422 6

83

0 4

4C

yclo

penta

ne

meth

yl-

623 1

75

18 9

1B

enzene

522 7

83

1 1

9H

exane

725 6

33

1 0

4B

uta

ne

22

3-t

rim

eth

yl-

623 1

75

44 0

7B

enzene

825 8

17

0 7

9B

uta

ne

22

33

-tetr

am

eth

yl-

723 4

25

0 1

2S

ilane

tetr

am

ehty

l-9

27 3

33

5 9

Hexane

24

-dim

eth

yl-

823 6

75

0 5

Cyclo

hexane

10

27 6

4 3

4H

exane

3-m

eth

yl-

925 8

25

3 1

5B

uta

ne

22

3-t

rim

eth

yl-

11

28 9

0 8

7H

ep

tane

10

26 9

83

1 9

8P

enta

ne

33

-dim

eth

yl-

Wang and Luo Lump coal derived soot formation and gas analysis

24 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Effects of gases residence timeResidence time of gases is also a factor in sootformation The residence time has been altered byregulating the position of fixed bed in the reactor and theinlet gas velocity Figure 2 represents the mass percentof soot or tar ( daf) change with extension of gasesresidence time (in vertical direction) at different tem-perature The yields of soot are higher at longerresidence time on the whole and the change regularityof tar yields is contrary with extension of gases residencetime It shows that tar is more readily converted to sootin longer residence time of gases

The composition of sample gases at a temperature of1600 K and with Shenmu coal selected has also beeninspected by GCMS and analysed Figure 4 shows theTIC of gases products from pyrolysis with extension ofgases residence time Corresponding compounds identi-fied and relative contents are listed in Table 3 Thesecompounds identified contain 2-methyl pentane 12-dichloro ethane 3-methyl pentane hexane benzene223-trimethyl butane 24-dimethyl hexane 3-methylhexane and heptane in all experimental conditionsBenzene 24-dimethyl hexane 3-methyl hexane heptaneand 12-dichloro ethane are dominant componentsamong them Besides there are many small moleculessuch as ethane and ethylene from the volatiles of coalsor from the decomposed segment of polymer beingseparated at earlier time when the residence time of gasesis 152 or 176 s whereas no small molecules aredetected when the residence time of gases is 200 s It canalso be observed that amount of unsaturated aliphatichydrocarbons are decreased and amount of saturatedaliphatic hydrocarbons are increased with extension ofgases residence time by computing the contents of thesecompounds The result can be interpreted by that partsof unsaturated aliphatic hydrocarbons have been con-verted to saturated aliphatic hydrocarbons by reason ofchemical bond reforming

Effects of coal typeFrom the proximate analysis of the three kinds of coalsshown in Table 1 volatile contents of dry ash free coals(including Datong Shenmu and Zibo) are 3317 3570and 3910 respectively At the same heating rates

5 Yields of soot and tar v coal type (T51600 K

t5176 s)

6 Total ion chromatogram of gases products from coal pyrolysis with coal type variation peaks are identified in Table 4

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 25

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Ta

ble

4Id

en

tifi

ca

tio

na

nd

rela

tiv

ec

on

ten

tso

fc

om

po

un

ds

rele

as

ed

fro

mc

oa

lp

yro

lys

isw

ith

co

al

typ

ev

ari

ati

on

Peak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

eP

eak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

e

Shenm

ucoal

122 0

17

0 5

9P

enta

ne

2-m

eth

yl-

122 0

17

1 6

3P

enta

ne

2-m

eth

yl-

222 1

75

7 0

8E

thane

12

-dic

hlo

ro-

222 1

83

4 6

9E

thane

12

-dic

hlo

ro-

322 3

0 2

3P

enta

ne

3-m

eth

yl-

322 2

92

1P

enta

ne

3-m

eth

yl-

422 6

92

0 2

9C

yclo

penta

ne

meth

yl-

422 6

83

0 4

4C

yclo

penta

ne

meth

yl-

522 7

83

0 6

33-H

exanone

22

-dim

eth

yl-

522 7

83

1 1

9H

exane

623 1

58

33 9

4B

enzene

623 1

75

44 0

7B

enzene

723 6

83

0 3

6C

yclo

hexane

723 4

25

0 1

2S

ilane

tetr

am

ehty

l-8

25 6

33

0 1

3B

uta

ne

22

3-t

rim

eth

yl-

823 6

75

0 5

Cyclo

hexane

925 8

08

0 5

2P

enta

ne

24

-dim

eth

yl-

925 8

25

3 1

5B

uta

ne

22

3-t

rim

eth

yl-

10

26 9

83

0 1

9C

yclo

penta

ne

13

-dim

eth

yl-

trans

10

26 9

83

1 9

8P

enta

ne

33

-dim

eth

yl-

11

27 3

25

3 2

7H

exane

24

-dim

eth

yl-

11

27 3

42

8 1

1H

exane

24

-dim

eth

yl-

12

27 5

92

2 9

2H

exane

3-m

eth

yl-

12

27 5

92

6 4

3H

exane

3-m

eth

yl-

13

28 9

1 5

7H

ep

tane

13

28 9

3 5

Hep

tane

14

30 2

10 7

3Tolu

ene

14

29 1

58

0 3

6C

yclo

hexane

meth

yl-

Dato

ng

coal(e

arlie

rsep

ara

ted

mole

cule

s)

15

29 7

58

1 4

o-X

yle

ne

15 2

50 0

22-B

uty

ned

ioic

acid

16

30 2

17

16 4

8Tolu

ene

28 9

58

37 5

3W

ate

rS

henm

ucoal(e

arlie

rsep

ara

ted

mole

cule

s)

Zib

ocoal

14 3

33

3 3

7M

eth

ylA

lcohol

122 0

25

1 0

7P

enta

ne

2-m

eth

yl-

24 4

25

0 1

9Fura

n

2-b

uty

ltetr

ahyd

ro-

222 1

83

8 1

4E

thane

12

-dic

hlo

ro-

36 5

58

0 5

0B

enzene

1-m

eth

yl-4-

322 2

92

0 7

9P

enta

ne

3-m

eth

yl-

46 7

25

0 1

3(E

)-1-P

henyl-1-b

ute

ne

422 6

83

0 6

5C

yclo

penta

ne

meth

yl-

56 7

58

0 1

5E

thyle

ne

522 7

92

0 8

53-H

exanone

22

-dim

eth

yl-

66 8

25

0 1

1E

thane

623 1

58

53 0

2B

enzene

76 9

17

0 0

5N

eop

enta

ne

723 6

83

1 0

7C

yclo

hexane

87 1

42

0 0

2C

arb

onic

dih

yd

razid

e8

26 9

0 5

6P

enta

ne

33

-dim

eth

yl-

97 2

33

0 1

0W

ate

r9

27 3

42

6 9

9H

exane

24

-dim

eth

yl-

10

7 2

58

0 0

512

-Oxath

iola

ne

10

27 5

92

6 1

8H

exane

3-m

eth

yl-

11

7 3

17

0 2

6S

ilane

11

28 9

2 0

2H

ep

tane

12

7 5

08

0 0

2Fura

n

2-b

uty

ltetr

ahyd

ro-

12

30 2

17

18 6

6Tolu

ene

Dato

ng

coal

Wang and Luo Lump coal derived soot formation and gas analysis

26 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

more volatiles are released from the high volatiles coalThe experimental condition is that the residence time ofgases is 176 s and the temperature in the reactor is1600 K Figure 5 describes the mass percent of soot ortar ( daf ) from different coals The soot yields derivedfrom Datong Shenmu and Zibo coal are increased inthat order The reason may be that there are morevolatiles in the reactor from high volatile coals in thesame conditions and the volatiles are easier to form sootdue to the oxygen scarcity

The composition of sample gases have also beentested by GCMS and analysed Figure 6 shows the TICof gases products from pyrolysis process with coal typevariation The compounds identified and relative con-tents are listed in Table 4 These compounds contain 2-methyl pentane 12-dichloro ethane 3-methyl pentanecyclopentane benzene cyclohexane 24-dimethyl hex-ane 3-methyl hexane heptane and toluene under allexperimental conditions Benzene toluene 24-dimethylhexane 3-methyl hexane heptane and 12-dichloroethane are the dominant components Besides thereare many small molecules such as ethane and ethylenefrom the volatiles of Shenmu coal or from thedecomposed segment of polymer being separated atearlier time and water vapour has been detected fromthe volatiles of Datong coal being separated at earliertime The aromatic hydrocarbon gases from Zibo coalpyrolysis is the highest The reason may be that thevolatiles content (daf) of Zibo Shenmu and Datong coaldecreased in that order Another reason is that thecomponents of gases relate to the microstructure of thecoals

ConclusionsSoot formation from lump coal has been studied duringthe pyrolysis process in a fixed bed Based on theexperimental study of the soot formation and relatedgases emission in the experimental facility theseconclusions can be drawn

1 Yields of soot are increased and yields of tar aredecreased that is more tars have been converted tosoot with temperature increase The relative contents ofsaturated aliphatic hydrocarbons are decreased andthose of aromatic hydrocarbons are increased becauseof condensation and polymerisation reactions withtemperature increase

2 More tars have been converted to soot with longergas residence time The relative contents of unsaturatedaliphatic hydrocarbons are decreased and those ofsaturated aliphatic hydrocarbon are increased becauseof reforming with longer residence time and no smallmolecules exists at longer residence time of gases

3 More soot is formed in the pyrolysis of highvolatile (Zibo) coal and more aromatic hydrocarbonsare released in high volatiles (Zibo) coal pyrolysisprocess under the same conditions

Acknowledgement

The authors thank Shanghai Environmental ProtectionBureau in China for its financial support (Huhuanke05-14)

References1 B L He Q Song C H Chen and X C Xu Proc 5th Asia-Pacific

Conf on lsquoCombustionrsquo Nanjing China November 2003 South-

eastern University 1ndash5

2 J L Ma T H Fletcher and B W Webb Proc 8th Int Conf on

lsquoCoal sciencersquo Oviedo Spain September 1995 International

Energy Agency 869ndash872

3 H F Zhang lsquoNitrogen evolution and soot formation during

secondary coal pyrolysisrsquo PhD thesis Brigham Young University

Provo UT USA 2001

4 T H Fletcher J L Ma J R Rigby A L Brown and B W

Webb Prog Energy Combust Sci 1997 23 283ndash301

5 E J Lee K C Oh and H D Shin Fuel 2005 84 543ndash550

6 F Inal G Tayfur T R Melton and S M Senkan Fuel 2003 82

1477ndash1490

7 I M Aksit and J B Moss Fuel 2005 84 239ndash245

8 R D Nenniger lsquoAerosols produced from coal pyrolysisrsquo MSc

thesis Massachusetts Institute of Technology Cambridge MA

USA 1986

9 M J Wornat A F Sarofim and J P Longwell Energy Fuel 1987

1 431ndash437

10 J C Chen lsquoEffect of secondary reactions on product distribution

and nitrogen evolution from rapid coal pyrolysisrsquo PhD thesis

Stanford University Palo Alto CA USA 1991

11 M J Tan and J X Mao Proc Conf on lsquoAdvanced technologies

of industrial boilers in USndashChinarsquo Beijing China June 2004

Power Engineer Institute 1ndash17

12 D Sun and S Choi Combust Flame 2000 121 167ndash180

13 N Ford M J Cooke and M D Pettit Inst Energy 1992 65 137ndash

143

14 G P Staley F W Bradshaw C S Carrel D W Pershing and G

B Martin Combust Flame 1985 59 197ndash211

15 M S Solum A F Sarofim R J Pugmire T H Fletcher and H

Zhang Energy Fuels 2001 15 961ndash971

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 27

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

compounds have been ignored because of its smallcontents In the end the tar and soot were separated indichloromethane by dissolving the sample The amountof tarsoot sample that did not dissolve was referred toas soot while the amount that dissolved was referred toas tar

Results and discussionMany factors that impact soot formation in stoker firedboiler have been studied in this fixed bed such astemperature residence time of gases and coal type Theresults of these experiments are given below

Effects of temperatureTemperature is a critical parameter in soot formationThe higher temperature the easier the volatiles arereleased from the coal surface Large PAH (sootprecursors) start to form soot at about 1300 K forhydrocarbon flames and for a complicated compoundlike coal the incipient temperature for soot precursorformation can be as low as 1100 K15 The soot aerosolsamples changed from viscous to solid particles as thetemperature increased so the sample viscosity serves asa rough visual measure of the extent of soot formationFigure 2 shows mass per cent of soot or tar ( daf) as itchanges with temperature increase The yields of sootare increased and the yields of tar are decreased withincreasing temperature It shows that a high temperatureis helpful for the release of volatiles and soot formationIt can also be concluded that the sum of tar plus soot

remains approximately constant that is increases insoot yields coincides with decreases in tar yields in thesame experimental condition This conclusion is con-sistent with Nenniger8 Wornat9 and Chenrsquos10 view-points in pulverised coal pyrolysis

The compositions of sample gases under experimen-tal conditions where the residence time of gases is176 s and the Shenmu coal is selected have beenexamined by GCMS and analysed Figure 3 shows thetotal ion chromatogram (TIC) of gases products frompyrolysis with temperature increase Correspondingcompounds identified and relative concentrations arelisted in Table 2 These compounds identified contain2-methyl pentane 12-dichloro ethane 3-methyl pen-tane benzene cyclohexane 223-trimethyl butane24-dimethyl hexane 3-methyl hexane heptane andtoluene in all experimental conditions Benzenetoluene 24-dimethyl hexane 3-methyl hexane hep-tane and 12-dichloro ethane are dominant compo-nents Besides there are many small molecules such asethane and ethylene from the volatiles of coals or fromthe decomposed polymer being formed at the tempera-ture of 1600 K It can be seen that the amount ofsaturated aliphatic hydrocarbons is decreased and theamount of aromatic hydrocarbons is increased with thetemperature increase by computing the contents ofthese compounds It may be caused by saturatedaliphatic hydrocarbons which have undergone con-densation or polymerisation reactions and beenconverted to aromatic hydrocarbons

4 Total ion chromatogram of gases products from coal pyrolysis with variation of gases residence time peaks are iden-

tified in Table 3

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 23

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Ta

ble

3Id

en

tifi

ca

tio

na

nd

rela

tiv

ec

on

ten

tso

fc

om

po

un

ds

rele

as

ed

fro

mc

oa

lp

yro

lys

isw

ith

va

ria

tio

no

fg

as

es

res

ide

nc

eti

me

Peak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

eP

eak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

e

t51 5

2s

11

27 3

42

8 1

1H

exane

24

-dim

eth

yl-

122 0

33

0 8

6P

enta

ne

2-m

eth

yl-

12

27 5

92

6 4

3H

exane

3-m

eth

yl-

222 1

92

6 8

Eth

ane

12

-dic

hlo

ro-

13

28 9

3 5

Hep

tane

322 3

17

0 9

Penta

ne

3-m

eth

yl-

14

29 1

58

0 3

6C

yclo

hexane

meth

yl-

422 6

92

0 4

6C

yclo

penta

ne

meth

yl-

15

29 7

58

1 4

o-X

yle

ne

522 8

08

1 6

53-H

exanone

22

-dim

eth

yl-

16

30 2

17

16 4

8Tolu

ene

623 1

83

53 4

3B

enzene

t51 7

6s

(earlie

rsep

ara

ted

mole

cule

s)

723 6

92

1 5

3C

yclo

hexane

14 3

33

3 3

7M

eth

ylA

lcohol

825 8

25

2 5

9B

uta

ne

22

3-t

rim

eth

yl-

24 4

25

0 1

9Fura

n

2-b

uty

ltetr

ahyd

ro-

927 3

59 3

9H

exane

24

-dim

eth

yl-

36 5

58

0 5

0B

enzene

1-m

eth

yl-4-

10

27 6

08

6 4

Hexane

3-m

eth

yl-

46 7

25

0 1

3(E

)-1-P

henyl-1-b

ute

ne

11

28 9

3 4

9H

ep

tane

56 7

58

0 1

5E

thyle

ne

12

30 2

511 4

1Tolu

ene

66 8

25

0 1

1E

thane

t51 5

2s

(earlie

rsep

ara

ted

mole

cule

s)

76 9

17

0 0

5N

eop

enta

ne

14 3

333

0 3

2N

eop

enta

ne

87 1

42

0 0

2C

arb

onic

dih

yd

razid

e2

4 4

25

0 0

7A

cete

ne

97 2

33

0 1

0W

ate

r3

4 4

67

0 2

Eth

ane

11

1-t

rifluoro

-10

7 2

58

0 0

512

-Oxath

iola

ne

44 5

0 0

9S

ilane

tetr

am

eth

yl-

11

7 3

17

0 2

6S

ilane

54 5

42

0 1

Sili

cane

hyd

rid

e12

7 5

08

0 0

2Fura

n

2-b

uty

ltetr

ahyd

ro-

64 5

83

0 1

24

-Penta

ned

ione

t52 0

0s

74 6

92

0 2

1M

eth

anol

121 8

83

32 0

6S

tyre

ne

t51 7

6s

222 0

25

16 2

1P

enta

ne

2-m

eth

yl-

122 0

17

1 6

3P

enta

ne

2-m

eth

yl-

322 1

92

6 0

4E

thane

12

-dic

hlo

ro-

222 1

83

4 6

9E

thane

12

-dic

hlo

ro-

422 2

92

8 9

9P

enta

ne

3-m

eth

yl-

322 2

92

1P

enta

ne

3-m

eth

yl-

522 7

92

4 8

5H

exane

422 6

83

0 4

4C

yclo

penta

ne

meth

yl-

623 1

75

18 9

1B

enzene

522 7

83

1 1

9H

exane

725 6

33

1 0

4B

uta

ne

22

3-t

rim

eth

yl-

623 1

75

44 0

7B

enzene

825 8

17

0 7

9B

uta

ne

22

33

-tetr

am

eth

yl-

723 4

25

0 1

2S

ilane

tetr

am

ehty

l-9

27 3

33

5 9

Hexane

24

-dim

eth

yl-

823 6

75

0 5

Cyclo

hexane

10

27 6

4 3

4H

exane

3-m

eth

yl-

925 8

25

3 1

5B

uta

ne

22

3-t

rim

eth

yl-

11

28 9

0 8

7H

ep

tane

10

26 9

83

1 9

8P

enta

ne

33

-dim

eth

yl-

Wang and Luo Lump coal derived soot formation and gas analysis

24 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Effects of gases residence timeResidence time of gases is also a factor in sootformation The residence time has been altered byregulating the position of fixed bed in the reactor and theinlet gas velocity Figure 2 represents the mass percentof soot or tar ( daf) change with extension of gasesresidence time (in vertical direction) at different tem-perature The yields of soot are higher at longerresidence time on the whole and the change regularityof tar yields is contrary with extension of gases residencetime It shows that tar is more readily converted to sootin longer residence time of gases

The composition of sample gases at a temperature of1600 K and with Shenmu coal selected has also beeninspected by GCMS and analysed Figure 4 shows theTIC of gases products from pyrolysis with extension ofgases residence time Corresponding compounds identi-fied and relative contents are listed in Table 3 Thesecompounds identified contain 2-methyl pentane 12-dichloro ethane 3-methyl pentane hexane benzene223-trimethyl butane 24-dimethyl hexane 3-methylhexane and heptane in all experimental conditionsBenzene 24-dimethyl hexane 3-methyl hexane heptaneand 12-dichloro ethane are dominant componentsamong them Besides there are many small moleculessuch as ethane and ethylene from the volatiles of coalsor from the decomposed segment of polymer beingseparated at earlier time when the residence time of gasesis 152 or 176 s whereas no small molecules aredetected when the residence time of gases is 200 s It canalso be observed that amount of unsaturated aliphatichydrocarbons are decreased and amount of saturatedaliphatic hydrocarbons are increased with extension ofgases residence time by computing the contents of thesecompounds The result can be interpreted by that partsof unsaturated aliphatic hydrocarbons have been con-verted to saturated aliphatic hydrocarbons by reason ofchemical bond reforming

Effects of coal typeFrom the proximate analysis of the three kinds of coalsshown in Table 1 volatile contents of dry ash free coals(including Datong Shenmu and Zibo) are 3317 3570and 3910 respectively At the same heating rates

5 Yields of soot and tar v coal type (T51600 K

t5176 s)

6 Total ion chromatogram of gases products from coal pyrolysis with coal type variation peaks are identified in Table 4

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 25

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Ta

ble

4Id

en

tifi

ca

tio

na

nd

rela

tiv

ec

on

ten

tso

fc

om

po

un

ds

rele

as

ed

fro

mc

oa

lp

yro

lys

isw

ith

co

al

typ

ev

ari

ati

on

Peak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

eP

eak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

e

Shenm

ucoal

122 0

17

0 5

9P

enta

ne

2-m

eth

yl-

122 0

17

1 6

3P

enta

ne

2-m

eth

yl-

222 1

75

7 0

8E

thane

12

-dic

hlo

ro-

222 1

83

4 6

9E

thane

12

-dic

hlo

ro-

322 3

0 2

3P

enta

ne

3-m

eth

yl-

322 2

92

1P

enta

ne

3-m

eth

yl-

422 6

92

0 2

9C

yclo

penta

ne

meth

yl-

422 6

83

0 4

4C

yclo

penta

ne

meth

yl-

522 7

83

0 6

33-H

exanone

22

-dim

eth

yl-

522 7

83

1 1

9H

exane

623 1

58

33 9

4B

enzene

623 1

75

44 0

7B

enzene

723 6

83

0 3

6C

yclo

hexane

723 4

25

0 1

2S

ilane

tetr

am

ehty

l-8

25 6

33

0 1

3B

uta

ne

22

3-t

rim

eth

yl-

823 6

75

0 5

Cyclo

hexane

925 8

08

0 5

2P

enta

ne

24

-dim

eth

yl-

925 8

25

3 1

5B

uta

ne

22

3-t

rim

eth

yl-

10

26 9

83

0 1

9C

yclo

penta

ne

13

-dim

eth

yl-

trans

10

26 9

83

1 9

8P

enta

ne

33

-dim

eth

yl-

11

27 3

25

3 2

7H

exane

24

-dim

eth

yl-

11

27 3

42

8 1

1H

exane

24

-dim

eth

yl-

12

27 5

92

2 9

2H

exane

3-m

eth

yl-

12

27 5

92

6 4

3H

exane

3-m

eth

yl-

13

28 9

1 5

7H

ep

tane

13

28 9

3 5

Hep

tane

14

30 2

10 7

3Tolu

ene

14

29 1

58

0 3

6C

yclo

hexane

meth

yl-

Dato

ng

coal(e

arlie

rsep

ara

ted

mole

cule

s)

15

29 7

58

1 4

o-X

yle

ne

15 2

50 0

22-B

uty

ned

ioic

acid

16

30 2

17

16 4

8Tolu

ene

28 9

58

37 5

3W

ate

rS

henm

ucoal(e

arlie

rsep

ara

ted

mole

cule

s)

Zib

ocoal

14 3

33

3 3

7M

eth

ylA

lcohol

122 0

25

1 0

7P

enta

ne

2-m

eth

yl-

24 4

25

0 1

9Fura

n

2-b

uty

ltetr

ahyd

ro-

222 1

83

8 1

4E

thane

12

-dic

hlo

ro-

36 5

58

0 5

0B

enzene

1-m

eth

yl-4-

322 2

92

0 7

9P

enta

ne

3-m

eth

yl-

46 7

25

0 1

3(E

)-1-P

henyl-1-b

ute

ne

422 6

83

0 6

5C

yclo

penta

ne

meth

yl-

56 7

58

0 1

5E

thyle

ne

522 7

92

0 8

53-H

exanone

22

-dim

eth

yl-

66 8

25

0 1

1E

thane

623 1

58

53 0

2B

enzene

76 9

17

0 0

5N

eop

enta

ne

723 6

83

1 0

7C

yclo

hexane

87 1

42

0 0

2C

arb

onic

dih

yd

razid

e8

26 9

0 5

6P

enta

ne

33

-dim

eth

yl-

97 2

33

0 1

0W

ate

r9

27 3

42

6 9

9H

exane

24

-dim

eth

yl-

10

7 2

58

0 0

512

-Oxath

iola

ne

10

27 5

92

6 1

8H

exane

3-m

eth

yl-

11

7 3

17

0 2

6S

ilane

11

28 9

2 0

2H

ep

tane

12

7 5

08

0 0

2Fura

n

2-b

uty

ltetr

ahyd

ro-

12

30 2

17

18 6

6Tolu

ene

Dato

ng

coal

Wang and Luo Lump coal derived soot formation and gas analysis

26 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

more volatiles are released from the high volatiles coalThe experimental condition is that the residence time ofgases is 176 s and the temperature in the reactor is1600 K Figure 5 describes the mass percent of soot ortar ( daf ) from different coals The soot yields derivedfrom Datong Shenmu and Zibo coal are increased inthat order The reason may be that there are morevolatiles in the reactor from high volatile coals in thesame conditions and the volatiles are easier to form sootdue to the oxygen scarcity

The composition of sample gases have also beentested by GCMS and analysed Figure 6 shows the TICof gases products from pyrolysis process with coal typevariation The compounds identified and relative con-tents are listed in Table 4 These compounds contain 2-methyl pentane 12-dichloro ethane 3-methyl pentanecyclopentane benzene cyclohexane 24-dimethyl hex-ane 3-methyl hexane heptane and toluene under allexperimental conditions Benzene toluene 24-dimethylhexane 3-methyl hexane heptane and 12-dichloroethane are the dominant components Besides thereare many small molecules such as ethane and ethylenefrom the volatiles of Shenmu coal or from thedecomposed segment of polymer being separated atearlier time and water vapour has been detected fromthe volatiles of Datong coal being separated at earliertime The aromatic hydrocarbon gases from Zibo coalpyrolysis is the highest The reason may be that thevolatiles content (daf) of Zibo Shenmu and Datong coaldecreased in that order Another reason is that thecomponents of gases relate to the microstructure of thecoals

ConclusionsSoot formation from lump coal has been studied duringthe pyrolysis process in a fixed bed Based on theexperimental study of the soot formation and relatedgases emission in the experimental facility theseconclusions can be drawn

1 Yields of soot are increased and yields of tar aredecreased that is more tars have been converted tosoot with temperature increase The relative contents ofsaturated aliphatic hydrocarbons are decreased andthose of aromatic hydrocarbons are increased becauseof condensation and polymerisation reactions withtemperature increase

2 More tars have been converted to soot with longergas residence time The relative contents of unsaturatedaliphatic hydrocarbons are decreased and those ofsaturated aliphatic hydrocarbon are increased becauseof reforming with longer residence time and no smallmolecules exists at longer residence time of gases

3 More soot is formed in the pyrolysis of highvolatile (Zibo) coal and more aromatic hydrocarbonsare released in high volatiles (Zibo) coal pyrolysisprocess under the same conditions

Acknowledgement

The authors thank Shanghai Environmental ProtectionBureau in China for its financial support (Huhuanke05-14)

References1 B L He Q Song C H Chen and X C Xu Proc 5th Asia-Pacific

Conf on lsquoCombustionrsquo Nanjing China November 2003 South-

eastern University 1ndash5

2 J L Ma T H Fletcher and B W Webb Proc 8th Int Conf on

lsquoCoal sciencersquo Oviedo Spain September 1995 International

Energy Agency 869ndash872

3 H F Zhang lsquoNitrogen evolution and soot formation during

secondary coal pyrolysisrsquo PhD thesis Brigham Young University

Provo UT USA 2001

4 T H Fletcher J L Ma J R Rigby A L Brown and B W

Webb Prog Energy Combust Sci 1997 23 283ndash301

5 E J Lee K C Oh and H D Shin Fuel 2005 84 543ndash550

6 F Inal G Tayfur T R Melton and S M Senkan Fuel 2003 82

1477ndash1490

7 I M Aksit and J B Moss Fuel 2005 84 239ndash245

8 R D Nenniger lsquoAerosols produced from coal pyrolysisrsquo MSc

thesis Massachusetts Institute of Technology Cambridge MA

USA 1986

9 M J Wornat A F Sarofim and J P Longwell Energy Fuel 1987

1 431ndash437

10 J C Chen lsquoEffect of secondary reactions on product distribution

and nitrogen evolution from rapid coal pyrolysisrsquo PhD thesis

Stanford University Palo Alto CA USA 1991

11 M J Tan and J X Mao Proc Conf on lsquoAdvanced technologies

of industrial boilers in USndashChinarsquo Beijing China June 2004

Power Engineer Institute 1ndash17

12 D Sun and S Choi Combust Flame 2000 121 167ndash180

13 N Ford M J Cooke and M D Pettit Inst Energy 1992 65 137ndash

143

14 G P Staley F W Bradshaw C S Carrel D W Pershing and G

B Martin Combust Flame 1985 59 197ndash211

15 M S Solum A F Sarofim R J Pugmire T H Fletcher and H

Zhang Energy Fuels 2001 15 961ndash971

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 27

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Ta

ble

3Id

en

tifi

ca

tio

na

nd

rela

tiv

ec

on

ten

tso

fc

om

po

un

ds

rele

as

ed

fro

mc

oa

lp

yro

lys

isw

ith

va

ria

tio

no

fg

as

es

res

ide

nc

eti

me

Peak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

eP

eak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

e

t51 5

2s

11

27 3

42

8 1

1H

exane

24

-dim

eth

yl-

122 0

33

0 8

6P

enta

ne

2-m

eth

yl-

12

27 5

92

6 4

3H

exane

3-m

eth

yl-

222 1

92

6 8

Eth

ane

12

-dic

hlo

ro-

13

28 9

3 5

Hep

tane

322 3

17

0 9

Penta

ne

3-m

eth

yl-

14

29 1

58

0 3

6C

yclo

hexane

meth

yl-

422 6

92

0 4

6C

yclo

penta

ne

meth

yl-

15

29 7

58

1 4

o-X

yle

ne

522 8

08

1 6

53-H

exanone

22

-dim

eth

yl-

16

30 2

17

16 4

8Tolu

ene

623 1

83

53 4

3B

enzene

t51 7

6s

(earlie

rsep

ara

ted

mole

cule

s)

723 6

92

1 5

3C

yclo

hexane

14 3

33

3 3

7M

eth

ylA

lcohol

825 8

25

2 5

9B

uta

ne

22

3-t

rim

eth

yl-

24 4

25

0 1

9Fura

n

2-b

uty

ltetr

ahyd

ro-

927 3

59 3

9H

exane

24

-dim

eth

yl-

36 5

58

0 5

0B

enzene

1-m

eth

yl-4-

10

27 6

08

6 4

Hexane

3-m

eth

yl-

46 7

25

0 1

3(E

)-1-P

henyl-1-b

ute

ne

11

28 9

3 4

9H

ep

tane

56 7

58

0 1

5E

thyle

ne

12

30 2

511 4

1Tolu

ene

66 8

25

0 1

1E

thane

t51 5

2s

(earlie

rsep

ara

ted

mole

cule

s)

76 9

17

0 0

5N

eop

enta

ne

14 3

333

0 3

2N

eop

enta

ne

87 1

42

0 0

2C

arb

onic

dih

yd

razid

e2

4 4

25

0 0

7A

cete

ne

97 2

33

0 1

0W

ate

r3

4 4

67

0 2

Eth

ane

11

1-t

rifluoro

-10

7 2

58

0 0

512

-Oxath

iola

ne

44 5

0 0

9S

ilane

tetr

am

eth

yl-

11

7 3

17

0 2

6S

ilane

54 5

42

0 1

Sili

cane

hyd

rid

e12

7 5

08

0 0

2Fura

n

2-b

uty

ltetr

ahyd

ro-

64 5

83

0 1

24

-Penta

ned

ione

t52 0

0s

74 6

92

0 2

1M

eth

anol

121 8

83

32 0

6S

tyre

ne

t51 7

6s

222 0

25

16 2

1P

enta

ne

2-m

eth

yl-

122 0

17

1 6

3P

enta

ne

2-m

eth

yl-

322 1

92

6 0

4E

thane

12

-dic

hlo

ro-

222 1

83

4 6

9E

thane

12

-dic

hlo

ro-

422 2

92

8 9

9P

enta

ne

3-m

eth

yl-

322 2

92

1P

enta

ne

3-m

eth

yl-

522 7

92

4 8

5H

exane

422 6

83

0 4

4C

yclo

penta

ne

meth

yl-

623 1

75

18 9

1B

enzene

522 7

83

1 1

9H

exane

725 6

33

1 0

4B

uta

ne

22

3-t

rim

eth

yl-

623 1

75

44 0

7B

enzene

825 8

17

0 7

9B

uta

ne

22

33

-tetr

am

eth

yl-

723 4

25

0 1

2S

ilane

tetr

am

ehty

l-9

27 3

33

5 9

Hexane

24

-dim

eth

yl-

823 6

75

0 5

Cyclo

hexane

10

27 6

4 3

4H

exane

3-m

eth

yl-

925 8

25

3 1

5B

uta

ne

22

3-t

rim

eth

yl-

11

28 9

0 8

7H

ep

tane

10

26 9

83

1 9

8P

enta

ne

33

-dim

eth

yl-

Wang and Luo Lump coal derived soot formation and gas analysis

24 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Effects of gases residence timeResidence time of gases is also a factor in sootformation The residence time has been altered byregulating the position of fixed bed in the reactor and theinlet gas velocity Figure 2 represents the mass percentof soot or tar ( daf) change with extension of gasesresidence time (in vertical direction) at different tem-perature The yields of soot are higher at longerresidence time on the whole and the change regularityof tar yields is contrary with extension of gases residencetime It shows that tar is more readily converted to sootin longer residence time of gases

The composition of sample gases at a temperature of1600 K and with Shenmu coal selected has also beeninspected by GCMS and analysed Figure 4 shows theTIC of gases products from pyrolysis with extension ofgases residence time Corresponding compounds identi-fied and relative contents are listed in Table 3 Thesecompounds identified contain 2-methyl pentane 12-dichloro ethane 3-methyl pentane hexane benzene223-trimethyl butane 24-dimethyl hexane 3-methylhexane and heptane in all experimental conditionsBenzene 24-dimethyl hexane 3-methyl hexane heptaneand 12-dichloro ethane are dominant componentsamong them Besides there are many small moleculessuch as ethane and ethylene from the volatiles of coalsor from the decomposed segment of polymer beingseparated at earlier time when the residence time of gasesis 152 or 176 s whereas no small molecules aredetected when the residence time of gases is 200 s It canalso be observed that amount of unsaturated aliphatichydrocarbons are decreased and amount of saturatedaliphatic hydrocarbons are increased with extension ofgases residence time by computing the contents of thesecompounds The result can be interpreted by that partsof unsaturated aliphatic hydrocarbons have been con-verted to saturated aliphatic hydrocarbons by reason ofchemical bond reforming

Effects of coal typeFrom the proximate analysis of the three kinds of coalsshown in Table 1 volatile contents of dry ash free coals(including Datong Shenmu and Zibo) are 3317 3570and 3910 respectively At the same heating rates

5 Yields of soot and tar v coal type (T51600 K

t5176 s)

6 Total ion chromatogram of gases products from coal pyrolysis with coal type variation peaks are identified in Table 4

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 25

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Ta

ble

4Id

en

tifi

ca

tio

na

nd

rela

tiv

ec

on

ten

tso

fc

om

po

un

ds

rele

as

ed

fro

mc

oa

lp

yro

lys

isw

ith

co

al

typ

ev

ari

ati

on

Peak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

eP

eak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

e

Shenm

ucoal

122 0

17

0 5

9P

enta

ne

2-m

eth

yl-

122 0

17

1 6

3P

enta

ne

2-m

eth

yl-

222 1

75

7 0

8E

thane

12

-dic

hlo

ro-

222 1

83

4 6

9E

thane

12

-dic

hlo

ro-

322 3

0 2

3P

enta

ne

3-m

eth

yl-

322 2

92

1P

enta

ne

3-m

eth

yl-

422 6

92

0 2

9C

yclo

penta

ne

meth

yl-

422 6

83

0 4

4C

yclo

penta

ne

meth

yl-

522 7

83

0 6

33-H

exanone

22

-dim

eth

yl-

522 7

83

1 1

9H

exane

623 1

58

33 9

4B

enzene

623 1

75

44 0

7B

enzene

723 6

83

0 3

6C

yclo

hexane

723 4

25

0 1

2S

ilane

tetr

am

ehty

l-8

25 6

33

0 1

3B

uta

ne

22

3-t

rim

eth

yl-

823 6

75

0 5

Cyclo

hexane

925 8

08

0 5

2P

enta

ne

24

-dim

eth

yl-

925 8

25

3 1

5B

uta

ne

22

3-t

rim

eth

yl-

10

26 9

83

0 1

9C

yclo

penta

ne

13

-dim

eth

yl-

trans

10

26 9

83

1 9

8P

enta

ne

33

-dim

eth

yl-

11

27 3

25

3 2

7H

exane

24

-dim

eth

yl-

11

27 3

42

8 1

1H

exane

24

-dim

eth

yl-

12

27 5

92

2 9

2H

exane

3-m

eth

yl-

12

27 5

92

6 4

3H

exane

3-m

eth

yl-

13

28 9

1 5

7H

ep

tane

13

28 9

3 5

Hep

tane

14

30 2

10 7

3Tolu

ene

14

29 1

58

0 3

6C

yclo

hexane

meth

yl-

Dato

ng

coal(e

arlie

rsep

ara

ted

mole

cule

s)

15

29 7

58

1 4

o-X

yle

ne

15 2

50 0

22-B

uty

ned

ioic

acid

16

30 2

17

16 4

8Tolu

ene

28 9

58

37 5

3W

ate

rS

henm

ucoal(e

arlie

rsep

ara

ted

mole

cule

s)

Zib

ocoal

14 3

33

3 3

7M

eth

ylA

lcohol

122 0

25

1 0

7P

enta

ne

2-m

eth

yl-

24 4

25

0 1

9Fura

n

2-b

uty

ltetr

ahyd

ro-

222 1

83

8 1

4E

thane

12

-dic

hlo

ro-

36 5

58

0 5

0B

enzene

1-m

eth

yl-4-

322 2

92

0 7

9P

enta

ne

3-m

eth

yl-

46 7

25

0 1

3(E

)-1-P

henyl-1-b

ute

ne

422 6

83

0 6

5C

yclo

penta

ne

meth

yl-

56 7

58

0 1

5E

thyle

ne

522 7

92

0 8

53-H

exanone

22

-dim

eth

yl-

66 8

25

0 1

1E

thane

623 1

58

53 0

2B

enzene

76 9

17

0 0

5N

eop

enta

ne

723 6

83

1 0

7C

yclo

hexane

87 1

42

0 0

2C

arb

onic

dih

yd

razid

e8

26 9

0 5

6P

enta

ne

33

-dim

eth

yl-

97 2

33

0 1

0W

ate

r9

27 3

42

6 9

9H

exane

24

-dim

eth

yl-

10

7 2

58

0 0

512

-Oxath

iola

ne

10

27 5

92

6 1

8H

exane

3-m

eth

yl-

11

7 3

17

0 2

6S

ilane

11

28 9

2 0

2H

ep

tane

12

7 5

08

0 0

2Fura

n

2-b

uty

ltetr

ahyd

ro-

12

30 2

17

18 6

6Tolu

ene

Dato

ng

coal

Wang and Luo Lump coal derived soot formation and gas analysis

26 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

more volatiles are released from the high volatiles coalThe experimental condition is that the residence time ofgases is 176 s and the temperature in the reactor is1600 K Figure 5 describes the mass percent of soot ortar ( daf ) from different coals The soot yields derivedfrom Datong Shenmu and Zibo coal are increased inthat order The reason may be that there are morevolatiles in the reactor from high volatile coals in thesame conditions and the volatiles are easier to form sootdue to the oxygen scarcity

The composition of sample gases have also beentested by GCMS and analysed Figure 6 shows the TICof gases products from pyrolysis process with coal typevariation The compounds identified and relative con-tents are listed in Table 4 These compounds contain 2-methyl pentane 12-dichloro ethane 3-methyl pentanecyclopentane benzene cyclohexane 24-dimethyl hex-ane 3-methyl hexane heptane and toluene under allexperimental conditions Benzene toluene 24-dimethylhexane 3-methyl hexane heptane and 12-dichloroethane are the dominant components Besides thereare many small molecules such as ethane and ethylenefrom the volatiles of Shenmu coal or from thedecomposed segment of polymer being separated atearlier time and water vapour has been detected fromthe volatiles of Datong coal being separated at earliertime The aromatic hydrocarbon gases from Zibo coalpyrolysis is the highest The reason may be that thevolatiles content (daf) of Zibo Shenmu and Datong coaldecreased in that order Another reason is that thecomponents of gases relate to the microstructure of thecoals

ConclusionsSoot formation from lump coal has been studied duringthe pyrolysis process in a fixed bed Based on theexperimental study of the soot formation and relatedgases emission in the experimental facility theseconclusions can be drawn

1 Yields of soot are increased and yields of tar aredecreased that is more tars have been converted tosoot with temperature increase The relative contents ofsaturated aliphatic hydrocarbons are decreased andthose of aromatic hydrocarbons are increased becauseof condensation and polymerisation reactions withtemperature increase

2 More tars have been converted to soot with longergas residence time The relative contents of unsaturatedaliphatic hydrocarbons are decreased and those ofsaturated aliphatic hydrocarbon are increased becauseof reforming with longer residence time and no smallmolecules exists at longer residence time of gases

3 More soot is formed in the pyrolysis of highvolatile (Zibo) coal and more aromatic hydrocarbonsare released in high volatiles (Zibo) coal pyrolysisprocess under the same conditions

Acknowledgement

The authors thank Shanghai Environmental ProtectionBureau in China for its financial support (Huhuanke05-14)

References1 B L He Q Song C H Chen and X C Xu Proc 5th Asia-Pacific

Conf on lsquoCombustionrsquo Nanjing China November 2003 South-

eastern University 1ndash5

2 J L Ma T H Fletcher and B W Webb Proc 8th Int Conf on

lsquoCoal sciencersquo Oviedo Spain September 1995 International

Energy Agency 869ndash872

3 H F Zhang lsquoNitrogen evolution and soot formation during

secondary coal pyrolysisrsquo PhD thesis Brigham Young University

Provo UT USA 2001

4 T H Fletcher J L Ma J R Rigby A L Brown and B W

Webb Prog Energy Combust Sci 1997 23 283ndash301

5 E J Lee K C Oh and H D Shin Fuel 2005 84 543ndash550

6 F Inal G Tayfur T R Melton and S M Senkan Fuel 2003 82

1477ndash1490

7 I M Aksit and J B Moss Fuel 2005 84 239ndash245

8 R D Nenniger lsquoAerosols produced from coal pyrolysisrsquo MSc

thesis Massachusetts Institute of Technology Cambridge MA

USA 1986

9 M J Wornat A F Sarofim and J P Longwell Energy Fuel 1987

1 431ndash437

10 J C Chen lsquoEffect of secondary reactions on product distribution

and nitrogen evolution from rapid coal pyrolysisrsquo PhD thesis

Stanford University Palo Alto CA USA 1991

11 M J Tan and J X Mao Proc Conf on lsquoAdvanced technologies

of industrial boilers in USndashChinarsquo Beijing China June 2004

Power Engineer Institute 1ndash17

12 D Sun and S Choi Combust Flame 2000 121 167ndash180

13 N Ford M J Cooke and M D Pettit Inst Energy 1992 65 137ndash

143

14 G P Staley F W Bradshaw C S Carrel D W Pershing and G

B Martin Combust Flame 1985 59 197ndash211

15 M S Solum A F Sarofim R J Pugmire T H Fletcher and H

Zhang Energy Fuels 2001 15 961ndash971

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 27

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Effects of gases residence timeResidence time of gases is also a factor in sootformation The residence time has been altered byregulating the position of fixed bed in the reactor and theinlet gas velocity Figure 2 represents the mass percentof soot or tar ( daf) change with extension of gasesresidence time (in vertical direction) at different tem-perature The yields of soot are higher at longerresidence time on the whole and the change regularityof tar yields is contrary with extension of gases residencetime It shows that tar is more readily converted to sootin longer residence time of gases

The composition of sample gases at a temperature of1600 K and with Shenmu coal selected has also beeninspected by GCMS and analysed Figure 4 shows theTIC of gases products from pyrolysis with extension ofgases residence time Corresponding compounds identi-fied and relative contents are listed in Table 3 Thesecompounds identified contain 2-methyl pentane 12-dichloro ethane 3-methyl pentane hexane benzene223-trimethyl butane 24-dimethyl hexane 3-methylhexane and heptane in all experimental conditionsBenzene 24-dimethyl hexane 3-methyl hexane heptaneand 12-dichloro ethane are dominant componentsamong them Besides there are many small moleculessuch as ethane and ethylene from the volatiles of coalsor from the decomposed segment of polymer beingseparated at earlier time when the residence time of gasesis 152 or 176 s whereas no small molecules aredetected when the residence time of gases is 200 s It canalso be observed that amount of unsaturated aliphatichydrocarbons are decreased and amount of saturatedaliphatic hydrocarbons are increased with extension ofgases residence time by computing the contents of thesecompounds The result can be interpreted by that partsof unsaturated aliphatic hydrocarbons have been con-verted to saturated aliphatic hydrocarbons by reason ofchemical bond reforming

Effects of coal typeFrom the proximate analysis of the three kinds of coalsshown in Table 1 volatile contents of dry ash free coals(including Datong Shenmu and Zibo) are 3317 3570and 3910 respectively At the same heating rates

5 Yields of soot and tar v coal type (T51600 K

t5176 s)

6 Total ion chromatogram of gases products from coal pyrolysis with coal type variation peaks are identified in Table 4

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 25

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Ta

ble

4Id

en

tifi

ca

tio

na

nd

rela

tiv

ec

on

ten

tso

fc

om

po

un

ds

rele

as

ed

fro

mc

oa

lp

yro

lys

isw

ith

co

al

typ

ev

ari

ati

on

Peak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

eP

eak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

e

Shenm

ucoal

122 0

17

0 5

9P

enta

ne

2-m

eth

yl-

122 0

17

1 6

3P

enta

ne

2-m

eth

yl-

222 1

75

7 0

8E

thane

12

-dic

hlo

ro-

222 1

83

4 6

9E

thane

12

-dic

hlo

ro-

322 3

0 2

3P

enta

ne

3-m

eth

yl-

322 2

92

1P

enta

ne

3-m

eth

yl-

422 6

92

0 2

9C

yclo

penta

ne

meth

yl-

422 6

83

0 4

4C

yclo

penta

ne

meth

yl-

522 7

83

0 6

33-H

exanone

22

-dim

eth

yl-

522 7

83

1 1

9H

exane

623 1

58

33 9

4B

enzene

623 1

75

44 0

7B

enzene

723 6

83

0 3

6C

yclo

hexane

723 4

25

0 1

2S

ilane

tetr

am

ehty

l-8

25 6

33

0 1

3B

uta

ne

22

3-t

rim

eth

yl-

823 6

75

0 5

Cyclo

hexane

925 8

08

0 5

2P

enta

ne

24

-dim

eth

yl-

925 8

25

3 1

5B

uta

ne

22

3-t

rim

eth

yl-

10

26 9

83

0 1

9C

yclo

penta

ne

13

-dim

eth

yl-

trans

10

26 9

83

1 9

8P

enta

ne

33

-dim

eth

yl-

11

27 3

25

3 2

7H

exane

24

-dim

eth

yl-

11

27 3

42

8 1

1H

exane

24

-dim

eth

yl-

12

27 5

92

2 9

2H

exane

3-m

eth

yl-

12

27 5

92

6 4

3H

exane

3-m

eth

yl-

13

28 9

1 5

7H

ep

tane

13

28 9

3 5

Hep

tane

14

30 2

10 7

3Tolu

ene

14

29 1

58

0 3

6C

yclo

hexane

meth

yl-

Dato

ng

coal(e

arlie

rsep

ara

ted

mole

cule

s)

15

29 7

58

1 4

o-X

yle

ne

15 2

50 0

22-B

uty

ned

ioic

acid

16

30 2

17

16 4

8Tolu

ene

28 9

58

37 5

3W

ate

rS

henm

ucoal(e

arlie

rsep

ara

ted

mole

cule

s)

Zib

ocoal

14 3

33

3 3

7M

eth

ylA

lcohol

122 0

25

1 0

7P

enta

ne

2-m

eth

yl-

24 4

25

0 1

9Fura

n

2-b

uty

ltetr

ahyd

ro-

222 1

83

8 1

4E

thane

12

-dic

hlo

ro-

36 5

58

0 5

0B

enzene

1-m

eth

yl-4-

322 2

92

0 7

9P

enta

ne

3-m

eth

yl-

46 7

25

0 1

3(E

)-1-P

henyl-1-b

ute

ne

422 6

83

0 6

5C

yclo

penta

ne

meth

yl-

56 7

58

0 1

5E

thyle

ne

522 7

92

0 8

53-H

exanone

22

-dim

eth

yl-

66 8

25

0 1

1E

thane

623 1

58

53 0

2B

enzene

76 9

17

0 0

5N

eop

enta

ne

723 6

83

1 0

7C

yclo

hexane

87 1

42

0 0

2C

arb

onic

dih

yd

razid

e8

26 9

0 5

6P

enta

ne

33

-dim

eth

yl-

97 2

33

0 1

0W

ate

r9

27 3

42

6 9

9H

exane

24

-dim

eth

yl-

10

7 2

58

0 0

512

-Oxath

iola

ne

10

27 5

92

6 1

8H

exane

3-m

eth

yl-

11

7 3

17

0 2

6S

ilane

11

28 9

2 0

2H

ep

tane

12

7 5

08

0 0

2Fura

n

2-b

uty

ltetr

ahyd

ro-

12

30 2

17

18 6

6Tolu

ene

Dato

ng

coal

Wang and Luo Lump coal derived soot formation and gas analysis

26 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

more volatiles are released from the high volatiles coalThe experimental condition is that the residence time ofgases is 176 s and the temperature in the reactor is1600 K Figure 5 describes the mass percent of soot ortar ( daf ) from different coals The soot yields derivedfrom Datong Shenmu and Zibo coal are increased inthat order The reason may be that there are morevolatiles in the reactor from high volatile coals in thesame conditions and the volatiles are easier to form sootdue to the oxygen scarcity

The composition of sample gases have also beentested by GCMS and analysed Figure 6 shows the TICof gases products from pyrolysis process with coal typevariation The compounds identified and relative con-tents are listed in Table 4 These compounds contain 2-methyl pentane 12-dichloro ethane 3-methyl pentanecyclopentane benzene cyclohexane 24-dimethyl hex-ane 3-methyl hexane heptane and toluene under allexperimental conditions Benzene toluene 24-dimethylhexane 3-methyl hexane heptane and 12-dichloroethane are the dominant components Besides thereare many small molecules such as ethane and ethylenefrom the volatiles of Shenmu coal or from thedecomposed segment of polymer being separated atearlier time and water vapour has been detected fromthe volatiles of Datong coal being separated at earliertime The aromatic hydrocarbon gases from Zibo coalpyrolysis is the highest The reason may be that thevolatiles content (daf) of Zibo Shenmu and Datong coaldecreased in that order Another reason is that thecomponents of gases relate to the microstructure of thecoals

ConclusionsSoot formation from lump coal has been studied duringthe pyrolysis process in a fixed bed Based on theexperimental study of the soot formation and relatedgases emission in the experimental facility theseconclusions can be drawn

1 Yields of soot are increased and yields of tar aredecreased that is more tars have been converted tosoot with temperature increase The relative contents ofsaturated aliphatic hydrocarbons are decreased andthose of aromatic hydrocarbons are increased becauseof condensation and polymerisation reactions withtemperature increase

2 More tars have been converted to soot with longergas residence time The relative contents of unsaturatedaliphatic hydrocarbons are decreased and those ofsaturated aliphatic hydrocarbon are increased becauseof reforming with longer residence time and no smallmolecules exists at longer residence time of gases

3 More soot is formed in the pyrolysis of highvolatile (Zibo) coal and more aromatic hydrocarbonsare released in high volatiles (Zibo) coal pyrolysisprocess under the same conditions

Acknowledgement

The authors thank Shanghai Environmental ProtectionBureau in China for its financial support (Huhuanke05-14)

References1 B L He Q Song C H Chen and X C Xu Proc 5th Asia-Pacific

Conf on lsquoCombustionrsquo Nanjing China November 2003 South-

eastern University 1ndash5

2 J L Ma T H Fletcher and B W Webb Proc 8th Int Conf on

lsquoCoal sciencersquo Oviedo Spain September 1995 International

Energy Agency 869ndash872

3 H F Zhang lsquoNitrogen evolution and soot formation during

secondary coal pyrolysisrsquo PhD thesis Brigham Young University

Provo UT USA 2001

4 T H Fletcher J L Ma J R Rigby A L Brown and B W

Webb Prog Energy Combust Sci 1997 23 283ndash301

5 E J Lee K C Oh and H D Shin Fuel 2005 84 543ndash550

6 F Inal G Tayfur T R Melton and S M Senkan Fuel 2003 82

1477ndash1490

7 I M Aksit and J B Moss Fuel 2005 84 239ndash245

8 R D Nenniger lsquoAerosols produced from coal pyrolysisrsquo MSc

thesis Massachusetts Institute of Technology Cambridge MA

USA 1986

9 M J Wornat A F Sarofim and J P Longwell Energy Fuel 1987

1 431ndash437

10 J C Chen lsquoEffect of secondary reactions on product distribution

and nitrogen evolution from rapid coal pyrolysisrsquo PhD thesis

Stanford University Palo Alto CA USA 1991

11 M J Tan and J X Mao Proc Conf on lsquoAdvanced technologies

of industrial boilers in USndashChinarsquo Beijing China June 2004

Power Engineer Institute 1ndash17

12 D Sun and S Choi Combust Flame 2000 121 167ndash180

13 N Ford M J Cooke and M D Pettit Inst Energy 1992 65 137ndash

143

14 G P Staley F W Bradshaw C S Carrel D W Pershing and G

B Martin Combust Flame 1985 59 197ndash211

15 M S Solum A F Sarofim R J Pugmire T H Fletcher and H

Zhang Energy Fuels 2001 15 961ndash971

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 27

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

Ta

ble

4Id

en

tifi

ca

tio

na

nd

rela

tiv

ec

on

ten

tso

fc

om

po

un

ds

rele

as

ed

fro

mc

oa

lp

yro

lys

isw

ith

co

al

typ

ev

ari

ati

on

Peak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

eP

eak

nu

mb

er

Rete

nti

on

tim

e

min

Rela

tive

co

nte

nt

C

om

po

un

dn

am

e

Shenm

ucoal

122 0

17

0 5

9P

enta

ne

2-m

eth

yl-

122 0

17

1 6

3P

enta

ne

2-m

eth

yl-

222 1

75

7 0

8E

thane

12

-dic

hlo

ro-

222 1

83

4 6

9E

thane

12

-dic

hlo

ro-

322 3

0 2

3P

enta

ne

3-m

eth

yl-

322 2

92

1P

enta

ne

3-m

eth

yl-

422 6

92

0 2

9C

yclo

penta

ne

meth

yl-

422 6

83

0 4

4C

yclo

penta

ne

meth

yl-

522 7

83

0 6

33-H

exanone

22

-dim

eth

yl-

522 7

83

1 1

9H

exane

623 1

58

33 9

4B

enzene

623 1

75

44 0

7B

enzene

723 6

83

0 3

6C

yclo

hexane

723 4

25

0 1

2S

ilane

tetr

am

ehty

l-8

25 6

33

0 1

3B

uta

ne

22

3-t

rim

eth

yl-

823 6

75

0 5

Cyclo

hexane

925 8

08

0 5

2P

enta

ne

24

-dim

eth

yl-

925 8

25

3 1

5B

uta

ne

22

3-t

rim

eth

yl-

10

26 9

83

0 1

9C

yclo

penta

ne

13

-dim

eth

yl-

trans

10

26 9

83

1 9

8P

enta

ne

33

-dim

eth

yl-

11

27 3

25

3 2

7H

exane

24

-dim

eth

yl-

11

27 3

42

8 1

1H

exane

24

-dim

eth

yl-

12

27 5

92

2 9

2H

exane

3-m

eth

yl-

12

27 5

92

6 4

3H

exane

3-m

eth

yl-

13

28 9

1 5

7H

ep

tane

13

28 9

3 5

Hep

tane

14

30 2

10 7

3Tolu

ene

14

29 1

58

0 3

6C

yclo

hexane

meth

yl-

Dato

ng

coal(e

arlie

rsep

ara

ted

mole

cule

s)

15

29 7

58

1 4

o-X

yle

ne

15 2

50 0

22-B

uty

ned

ioic

acid

16

30 2

17

16 4

8Tolu

ene

28 9

58

37 5

3W

ate

rS

henm

ucoal(e

arlie

rsep

ara

ted

mole

cule

s)

Zib

ocoal

14 3

33

3 3

7M

eth

ylA

lcohol

122 0

25

1 0

7P

enta

ne

2-m

eth

yl-

24 4

25

0 1

9Fura

n

2-b

uty

ltetr

ahyd

ro-

222 1

83

8 1

4E

thane

12

-dic

hlo

ro-

36 5

58

0 5

0B

enzene

1-m

eth

yl-4-

322 2

92

0 7

9P

enta

ne

3-m

eth

yl-

46 7

25

0 1

3(E

)-1-P

henyl-1-b

ute

ne

422 6

83

0 6

5C

yclo

penta

ne

meth

yl-

56 7

58

0 1

5E

thyle

ne

522 7

92

0 8

53-H

exanone

22

-dim

eth

yl-

66 8

25

0 1

1E

thane

623 1

58

53 0

2B

enzene

76 9

17

0 0

5N

eop

enta

ne

723 6

83

1 0

7C

yclo

hexane

87 1

42

0 0

2C

arb

onic

dih

yd

razid

e8

26 9

0 5

6P

enta

ne

33

-dim

eth

yl-

97 2

33

0 1

0W

ate

r9

27 3

42

6 9

9H

exane

24

-dim

eth

yl-

10

7 2

58

0 0

512

-Oxath

iola

ne

10

27 5

92

6 1

8H

exane

3-m

eth

yl-

11

7 3

17

0 2

6S

ilane

11

28 9

2 0

2H

ep

tane

12

7 5

08

0 0

2Fura

n

2-b

uty

ltetr

ahyd

ro-

12

30 2

17

18 6

6Tolu

ene

Dato

ng

coal

Wang and Luo Lump coal derived soot formation and gas analysis

26 Journal of the Energy Institute 2009 VOL 82 NO 1

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

more volatiles are released from the high volatiles coalThe experimental condition is that the residence time ofgases is 176 s and the temperature in the reactor is1600 K Figure 5 describes the mass percent of soot ortar ( daf ) from different coals The soot yields derivedfrom Datong Shenmu and Zibo coal are increased inthat order The reason may be that there are morevolatiles in the reactor from high volatile coals in thesame conditions and the volatiles are easier to form sootdue to the oxygen scarcity

The composition of sample gases have also beentested by GCMS and analysed Figure 6 shows the TICof gases products from pyrolysis process with coal typevariation The compounds identified and relative con-tents are listed in Table 4 These compounds contain 2-methyl pentane 12-dichloro ethane 3-methyl pentanecyclopentane benzene cyclohexane 24-dimethyl hex-ane 3-methyl hexane heptane and toluene under allexperimental conditions Benzene toluene 24-dimethylhexane 3-methyl hexane heptane and 12-dichloroethane are the dominant components Besides thereare many small molecules such as ethane and ethylenefrom the volatiles of Shenmu coal or from thedecomposed segment of polymer being separated atearlier time and water vapour has been detected fromthe volatiles of Datong coal being separated at earliertime The aromatic hydrocarbon gases from Zibo coalpyrolysis is the highest The reason may be that thevolatiles content (daf) of Zibo Shenmu and Datong coaldecreased in that order Another reason is that thecomponents of gases relate to the microstructure of thecoals

ConclusionsSoot formation from lump coal has been studied duringthe pyrolysis process in a fixed bed Based on theexperimental study of the soot formation and relatedgases emission in the experimental facility theseconclusions can be drawn

1 Yields of soot are increased and yields of tar aredecreased that is more tars have been converted tosoot with temperature increase The relative contents ofsaturated aliphatic hydrocarbons are decreased andthose of aromatic hydrocarbons are increased becauseof condensation and polymerisation reactions withtemperature increase

2 More tars have been converted to soot with longergas residence time The relative contents of unsaturatedaliphatic hydrocarbons are decreased and those ofsaturated aliphatic hydrocarbon are increased becauseof reforming with longer residence time and no smallmolecules exists at longer residence time of gases

3 More soot is formed in the pyrolysis of highvolatile (Zibo) coal and more aromatic hydrocarbonsare released in high volatiles (Zibo) coal pyrolysisprocess under the same conditions

Acknowledgement

The authors thank Shanghai Environmental ProtectionBureau in China for its financial support (Huhuanke05-14)

References1 B L He Q Song C H Chen and X C Xu Proc 5th Asia-Pacific

Conf on lsquoCombustionrsquo Nanjing China November 2003 South-

eastern University 1ndash5

2 J L Ma T H Fletcher and B W Webb Proc 8th Int Conf on

lsquoCoal sciencersquo Oviedo Spain September 1995 International

Energy Agency 869ndash872

3 H F Zhang lsquoNitrogen evolution and soot formation during

secondary coal pyrolysisrsquo PhD thesis Brigham Young University

Provo UT USA 2001

4 T H Fletcher J L Ma J R Rigby A L Brown and B W

Webb Prog Energy Combust Sci 1997 23 283ndash301

5 E J Lee K C Oh and H D Shin Fuel 2005 84 543ndash550

6 F Inal G Tayfur T R Melton and S M Senkan Fuel 2003 82

1477ndash1490

7 I M Aksit and J B Moss Fuel 2005 84 239ndash245

8 R D Nenniger lsquoAerosols produced from coal pyrolysisrsquo MSc

thesis Massachusetts Institute of Technology Cambridge MA

USA 1986

9 M J Wornat A F Sarofim and J P Longwell Energy Fuel 1987

1 431ndash437

10 J C Chen lsquoEffect of secondary reactions on product distribution

and nitrogen evolution from rapid coal pyrolysisrsquo PhD thesis

Stanford University Palo Alto CA USA 1991

11 M J Tan and J X Mao Proc Conf on lsquoAdvanced technologies

of industrial boilers in USndashChinarsquo Beijing China June 2004

Power Engineer Institute 1ndash17

12 D Sun and S Choi Combust Flame 2000 121 167ndash180

13 N Ford M J Cooke and M D Pettit Inst Energy 1992 65 137ndash

143

14 G P Staley F W Bradshaw C S Carrel D W Pershing and G

B Martin Combust Flame 1985 59 197ndash211

15 M S Solum A F Sarofim R J Pugmire T H Fletcher and H

Zhang Energy Fuels 2001 15 961ndash971

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 27

Pub

lishe

d by

Man

ey P

ublis

hing

(c)

Ene

rgy

Inst

itute

more volatiles are released from the high volatiles coalThe experimental condition is that the residence time ofgases is 176 s and the temperature in the reactor is1600 K Figure 5 describes the mass percent of soot ortar ( daf ) from different coals The soot yields derivedfrom Datong Shenmu and Zibo coal are increased inthat order The reason may be that there are morevolatiles in the reactor from high volatile coals in thesame conditions and the volatiles are easier to form sootdue to the oxygen scarcity

The composition of sample gases have also beentested by GCMS and analysed Figure 6 shows the TICof gases products from pyrolysis process with coal typevariation The compounds identified and relative con-tents are listed in Table 4 These compounds contain 2-methyl pentane 12-dichloro ethane 3-methyl pentanecyclopentane benzene cyclohexane 24-dimethyl hex-ane 3-methyl hexane heptane and toluene under allexperimental conditions Benzene toluene 24-dimethylhexane 3-methyl hexane heptane and 12-dichloroethane are the dominant components Besides thereare many small molecules such as ethane and ethylenefrom the volatiles of Shenmu coal or from thedecomposed segment of polymer being separated atearlier time and water vapour has been detected fromthe volatiles of Datong coal being separated at earliertime The aromatic hydrocarbon gases from Zibo coalpyrolysis is the highest The reason may be that thevolatiles content (daf) of Zibo Shenmu and Datong coaldecreased in that order Another reason is that thecomponents of gases relate to the microstructure of thecoals

ConclusionsSoot formation from lump coal has been studied duringthe pyrolysis process in a fixed bed Based on theexperimental study of the soot formation and relatedgases emission in the experimental facility theseconclusions can be drawn

1 Yields of soot are increased and yields of tar aredecreased that is more tars have been converted tosoot with temperature increase The relative contents ofsaturated aliphatic hydrocarbons are decreased andthose of aromatic hydrocarbons are increased becauseof condensation and polymerisation reactions withtemperature increase

2 More tars have been converted to soot with longergas residence time The relative contents of unsaturatedaliphatic hydrocarbons are decreased and those ofsaturated aliphatic hydrocarbon are increased becauseof reforming with longer residence time and no smallmolecules exists at longer residence time of gases

3 More soot is formed in the pyrolysis of highvolatile (Zibo) coal and more aromatic hydrocarbonsare released in high volatiles (Zibo) coal pyrolysisprocess under the same conditions

Acknowledgement

The authors thank Shanghai Environmental ProtectionBureau in China for its financial support (Huhuanke05-14)

References1 B L He Q Song C H Chen and X C Xu Proc 5th Asia-Pacific

Conf on lsquoCombustionrsquo Nanjing China November 2003 South-

eastern University 1ndash5

2 J L Ma T H Fletcher and B W Webb Proc 8th Int Conf on

lsquoCoal sciencersquo Oviedo Spain September 1995 International

Energy Agency 869ndash872

3 H F Zhang lsquoNitrogen evolution and soot formation during

secondary coal pyrolysisrsquo PhD thesis Brigham Young University

Provo UT USA 2001

4 T H Fletcher J L Ma J R Rigby A L Brown and B W

Webb Prog Energy Combust Sci 1997 23 283ndash301

5 E J Lee K C Oh and H D Shin Fuel 2005 84 543ndash550

6 F Inal G Tayfur T R Melton and S M Senkan Fuel 2003 82

1477ndash1490

7 I M Aksit and J B Moss Fuel 2005 84 239ndash245

8 R D Nenniger lsquoAerosols produced from coal pyrolysisrsquo MSc

thesis Massachusetts Institute of Technology Cambridge MA

USA 1986

9 M J Wornat A F Sarofim and J P Longwell Energy Fuel 1987

1 431ndash437

10 J C Chen lsquoEffect of secondary reactions on product distribution

and nitrogen evolution from rapid coal pyrolysisrsquo PhD thesis

Stanford University Palo Alto CA USA 1991

11 M J Tan and J X Mao Proc Conf on lsquoAdvanced technologies

of industrial boilers in USndashChinarsquo Beijing China June 2004

Power Engineer Institute 1ndash17

12 D Sun and S Choi Combust Flame 2000 121 167ndash180

13 N Ford M J Cooke and M D Pettit Inst Energy 1992 65 137ndash

143

14 G P Staley F W Bradshaw C S Carrel D W Pershing and G

B Martin Combust Flame 1985 59 197ndash211

15 M S Solum A F Sarofim R J Pugmire T H Fletcher and H

Zhang Energy Fuels 2001 15 961ndash971

Wang and Luo Lump coal derived soot formation and gas analysis

Journal of the Energy Institute 2009 VOL 82 NO 1 27