Pub
lishe
d by
Man
ey P
ublis
hing
(c)
Ene
rgy
Inst
itute
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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Man
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(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
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Man
ey P
ublis
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(c)
Ene
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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
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Ta
ble
2Id
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ilane
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l-6
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yclo
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925 8
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24
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22
-dim
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46 7
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ne
623 1
83
38 4
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56 7
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723 7
1 7
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yclo
hexane
66 8
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thane
825 8
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3-t
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76 9
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927 3
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24
-dim
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arb
onic
dih
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razid
e10
27 6
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97 2
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0 1
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r11
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ne
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27 8
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ene
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ilane
T5
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K12
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n
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uty
ltetr
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ro-
122 0
17
1 6
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2-m
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yl-
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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Ene
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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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Inst
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Ta
ble
3Id
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3-m
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Eth
ane
12
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ro-
13
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3 5
Hep
tane
322 3
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Penta
ne
3-m
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yclo
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meth
yl-
422 6
92
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6C
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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
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24
-dim
eth
yl-
36 5
58
0 5
0B
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1-m
eth
yl-4-
10
27 6
08
6 4
Hexane
3-m
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yl-
46 7
25
0 1
3(E
)-1-P
henyl-1-b
ute
ne
11
28 9
3 4
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tane
56 7
58
0 1
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12
30 2
511 4
1Tolu
ene
66 8
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2s
(earlie
rsep
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cule
s)
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17
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333
0 3
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42
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arb
onic
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4 4
25
0 0
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33
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r3
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0 2
Eth
ane
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1-t
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-10
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58
0 0
512
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ne
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0 0
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tetr
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yl-
11
7 3
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54 5
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Sili
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hyd
rid
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322 2
92
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522 7
92
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5H
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422 6
83
0 4
4C
yclo
penta
ne
meth
yl-
623 1
75
18 9
1B
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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
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825 8
17
0 7
9B
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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
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11
28 9
0 8
7H
ep
tane
10
26 9
83
1 9
8P
enta
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33
-dim
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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
Journal of the Energy Institute 2009 VOL 82 NO 1 25
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ublis
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Ene
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Inst
itute
Ta
ble
4Id
en
tifi
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Peak
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Rela
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Rete
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Rela
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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
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
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