Tar yield and composition from poultry litter gasification in a fluidised bed reactor

14 Pages·2017·1.38 MB·English

by  Alen Horvat

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Tar yield and composition from poultry litter
ce. gasification in a fluidised bed reactor: effects of
n
M. d Lice Citethis:RSCAdv.,2019,9,13283 equivalence ratio, temperature and limestone
0:10 AUnporte addition†
23 1:1n 3.0 Alen Horvat, *a Daya Shankar Pandey, ab Marzena Kwapinska, ac
on 3/4/20Attributio BLuacrbPa.raL.BM. M. Reallboo,auA,lbeertWoitGoo´ldmKewz-aBpainrsekai, adaLnyddiJaaEm.eFrsyJd.aL,eahey a
ed ns Air gasification of poultry litter was experimentally investigated in a laboratory scale bubbling fluidised bed
do
2019. DownloaCreative Comm tgapanaarspd.iefiA8ren0re.0xoGaff(cid:1)ma-Csliii,nfinaecensadsttioohtlenihdeetepffashedtascdstwietoioeafrndethsocoeforeplniqmtdiuoueincvsattemolednneeacthteboalredtamntwidooeas(dspEhRewe)mirtiinhpcltopthhyreeeesdrpsauoninrugeleoturryosdifenli0trgt.e1tsor8il–iocq0nau.a4stnha1n,teidftyeymaietsalpdrtehcareaontbdmuerpcedoobmumenaptdwtoesesriiheatinelo.anT7v0hioei0srf
0 April nder a tmhaicnrostgyarsenceh,rowmhaetroegasralpighhyt.eTrostpaletcairesyiesuldcshwaesrebienntzheeneranangdeftroolmuen15e.7wteore30m.7egatsoutarletadrkbgypomulteryanlitstero(dfryoann-dlinaseh
n 3d u freebasis)(cid:3)1.Thesevaluesareconsideredlowwithrespecttothefeedstockswithahigherorganicfraction.It
d onse also needs to be noted that the yields of benzene and toluene were measured by on-line micro gas
ee
cle. Publisharticle is lic cyoihffer-lodlimnweahttoeegrcerhaanpsihqpyuo,euasl.ttrBeycyhlvintatierqyruineognwthhitieschEoRwin,nhpeosruhenlotrtwylyeldditteealirvnebrilnsecnhrdiegeahdseinwrgtitahrtavlriamlyueieeslstdocnooevmesprhaotrhweededEtoRacrroeamdnugmcetoitonenlsytienedmt.opItnlaolyttheader
Artihis presence of limestone, polycyclic aromatic hydrocarbons (PAHs), heterocyclic compounds, toluene and
ss T benzeneshowedatendencytoreduceovertheERrangetested.SincetheERalsoplaysacrucialroleintar
e
c reduction, the reduction in tar cannot be unambiguously attributed to calcined limestone/lime (CaCO/
c 3
A
n CaO).Increasingthetemperaturewasshowntobeeffectiveforreducingthetotaltaryieldbuttheamounts
e
Op of polycyclic aromatic hydrocarbons increased. However, no definitive correlation could be established
between limestone/lime catalytic activity for tar reduction and elevated gasification temperature, because
therewasnopossibilitytostudytheireffectsseparately.Thechemicalcompositionofthetararisingfrom
poultry litter is distinctive compared with conventional lignocellulosic fuels linked to the fact that poultry
Received4thApril2019 litterhasahighernitrogencontent(z6.5%w/w(dryandashfreebasis)).Nitrogen-containinghydrocarbons
Accepted13thApril2019
such as pyridine, 2-methylpyridine, 2-methyl-1H-pyrrole and benzonitrile were identified in significant
DOI:10.1039/c9ra02548k amounts. This study has demonstrated that poultry litter gasified in a bubbling fluidised bed yielded
rsc.li/rsc-advances aproductgaswithrelativelylowtarcontentwhileitscompositionreflectsthechemicalnatureofthefeedstock.
1. Introduction also predicted a growth rate of about 1% a year. Even though
intensivelivestockproductionhasbecomeamoreeconomically
According to the AVEC annual report 2016,1 the European viable option compared to traditional farming practices, such
Union is the world's leading supplier of poultry meat with an industrialisedproductionfacesissuesassociatedwithitsenvi-
annual production of 13.6 million tonnes in 2015. The report ronmentalimpact duetothe accumulationoflargequantities
aCarbolea Research Group, Department of Chemical Sciences, Bernal Institute, dChemicalandEnvironmentalEngineeringDepartment,EscuelaT´ecnicaSuperiorde
UniversityofLimerick,Limerick,V94T9PX,Ireland.E-mail:[email protected]; Ingenier´ıa,UniversityofSeville,CaminodelosDescubrimientoss/n,41092Seville,
[email protected] Spain
bSchool of Engineering and the Built Environment, Anglia Ruskin University, eEnergyResearchCentreoftheNetherlands(ECN),Biomass&EnergyEfficiency,
Chelmsford,Essex,CM11SQ,UK Petten,TheNetherlands
cTechnologyCentreforBiorening&Biofuels,UniversityofLimerick,Limerick,V94 †Electronicsupplementaryinformation(ESI)available:Taryieldsgraphically
T9PX,Ireland presented(Fig.2–6)inthispaperarealsotabulatedandgiveninnumerical
form.SeeDOI:10.1039/c9ra02548k
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of waste with estimates of 1.4 billion tonnes per annum2 of indole. The composition ofthe tarfrom poultry litter gasica-
manure in EU states. The increasing popularity of free range tion is expected to reect the high nitrogen and low lignin
andorganicfarmingsupportedbyEuropeanDirectives2007/43/ contentinthefeedstock.Theformationanddecompositionof
EC and 1999/74/EC requires poultry farmers to comply with poultrylittertarisfurtherdiscussedintheSection3.
minimum animal welfare standards which results in an Itiswellknownthattarcanbedecomposedcatalyticallywith
increasedvolumeofpoultrylitterduetoutilisationofbedding limestone/lime which is an inexpensive, abundant and natu-
material (i.e. wood shavings, straw and hay). Poultry litter is rallyoccurringnon-toxicmaterial.12,13Additionally,ithasbeen
a heterogeneous fuel composed of bedding material, excreta, reportedthatCa-basedadditivesenhancepyrolysisconversion
e. wastefeedandfeathers.Comparedtoconventionallignocellu- rates.14Anactivationenergyof46kJmol(cid:3)1fortarcrackingover
nc losicfeedstocks,poultrylitterisrecognisedasalowvaluefuel acalcineddolomite(CaO–MgO)and77kJmol(cid:3)1overaninert
e
c
M. d Li due to its relatively high moisture and ash content. It is also bedofsilicasandwasreportedbyDelgadoetal.15Inregardsto
23 1:10:10 An 3.0 Unporte 2ap0o1tsTao4hsusperiacurevmeecs.oe3fnthtneEuuptrraoitephnetfasonrsCucoocmmhbmausisstsniioointnroo(gEfeUnp)o,rueplgthruoylsalptitihoteonrronauons.d5ao9nn2d/- tccgaaaorrtoabdmloynticitaciatgtebaaetlryidoot.cinckT,shaSebciymtaiuvpeitalthlysoseirttnsogawcloma.1nr2odcdsltueedslttaeterdadrtrchtehoadmetuccpcatoailotucaninnl/ydretesdicfooCvraamecOrtiinavsight.yoxweIondsf
on 3/4/20Attributio facaidarvmlasncucateliedlisianantcidionnweriodafteoltyrhsaeopefpnplieoerduglytt.reyCcholinmttoeblrougcsyutirworneitnhrtelsymebvaeeirninaslgtchuosememdmofeosrrt- HcraoownwtCreavaseCtr,O,aC3,amwOuhccicohhnsvilesorwstsoerisnlroteowdtuhtchetaicotanirtbrioastnceaothneasdsidfboeerrmeednCnoaobCtsOetorv,oewdcchfueornr.
d s 3
ademon electricitygenerationandashrecoveryintheUK,theUSAand theCO2partialpressureishigherthanthatoftheequilibrium
Downloe Com gTahseiNeedthineralanudisd.i4sRedecbeendtlgyapsoiueltrr5y,6laisttwerelhlaassbineeansxuecdc/mesosfvuinllgy p90re0s(cid:1)sCurCeaaOtwthaescparrobcoesnsatteedmtpoeCraatCuOre3.oTnelsytisfhthaevepasrhtoiawlnprtehsasturaet
2019. Creativ bcoendtgeanstioefr.7elTehmeesentsstusduiecshhaasvepchonoscpluhdoerdouthsatandudeptoottahsesihuimgh, oanfdCOM2ewdiansah16igdheemrothnastnra1t0e0dkthPaat. tOhnetchaelcointhateironharnedac,tVioanlvetrridge-
0 April nder a pwohuelntrygalsititeerdisinpraoneuitdoisperdovboekdegsaisniteerrin.gToanadvoaidggtlhoemseerpatrioobn- gtieornshaats8a5l7so(cid:1)Cbeuenndoebrstehreve5d0a%ttCemO2peartmatuosrepshbereelo.wRa8p5i7d(cid:1)cCa.lWcinitah-
d on 3nsed u dleumrisnlgiminedsutosntrei/allimscea(lCeaCuOid3i/sCeadOb)ehdavceombebeunsatidodne8dantodtlhaebobread- ereqsupielicbtrituomgapsairtciaatliopnresthsuereCOth2atyiceoldulidsbuenlaibkleelytotorerveearcshe tthhee
ee
cle. Publisharticle is lic atosryTaasrcgaieslenaebruiyci-dpir(suoendduspbceetcdoifgtcah)seirtmecraamtliognaa6scicoofcupantoituoinnltgrpyrflooitcrteesras.lelsdoreganneidc acraatmnlcgioensap5thi0oe0nr–e7p0Cr0oOc2(cid:1)eCsiss.foBreremldeyainksegedtCafarl.oO17m.foWCuhanCidleOo3utetisntthstahitneintaeinmpeuprtereraartCguoOrne2
Artihis compounds in the product gas excluding benzene and lighter atmosphereandatemperaturerangeof600–800(cid:1)Cresultedin
Access T gparosevoiduess ahysdtraoncdaarrbdoinsesd.9 dAelthnoituiognh ofCEtaNr/,TSin p15ra4c3t9ic,e2t0ar06is9 CCOO22raedlseoarspetoiocncufrorremdiantgthCeaCteOm3.peInratthueressaambeovCeO8250at(cid:1)mCo.sphere
n dened by restrictions of sampling, the identication and Saw and Pang13 tested the extent of tar reduction with 0%,
e
Op quanticationmethodsappliedaswellasthenalapplication 50%and100%limeasthebedmaterial.Thetotaltarconcen-
of the product gas or syngas. For example, the solid phase tration (sum of all tar compounds) decreased exponentially
adsorption (SPA) sampling method combined with gas chro- from5.0to0.7gNm(cid:3)3asthelimeloadingincreasedfrom0%to
matography (GC) detection provides accurate results for 100%. A signicant reduction was also observed for all the
phenolic and 2–5 rings polycyclic aromatic tar compounds. individual tar compounds studied. Tar reduction with lime
However, measurement reliability drops remarkably when loadingismostlikelyduetothesteamreformingoftarinthe
eitherlight volatile compounds (i.e. benzene) or6+ring poly- presenceofCaO.Thesteamreformingreactionsofthephenol,
cyclic aromatic tar compounds are to be quantied. Tar is cresolsandtolueneareshownineqn(1)–(4).
a black viscous material potentially giving rise to system mal-
function if condensation occurs. In practice, tar needs to be C6H5OH+5H2O46CO+8H2 (1)
removed for applications other than direct burning of the
productgas.10Tarfrompoultrylittergasicationinauidised (CH3)C6H4OH+13H2O47CO2+17H2 (2)
bedreactorhasnotbeenreportedtodate.Although,ithasbeen
C7H8+7H2O47CO+11H2 (3)
established that a large portion of the nitrogen present in
poultry litter is converted into NH3 and HCN during uidised C7H8+14H2O47CO2+18H2 (4)
bedgasication6itisexpectedthatthehighnitrogencontentin
poultry litter would also deliver a wide variety of nitrogen- EnhancedproductionofH mayhaveanegativeeffectonthe
2
containing compounds in the tar. Jaramillo-Arango et al.11 tarsteamreformingratebecauseH decreasesthecatalyticactivity
2
investigatedthecompositionofpyrolysisoilfromuidisedbed of CaO due to the adsorption of H onto its active sites, dimin-
2
tests employing nitrogen rich sewage sludge. They found ishing the available sites for tar adsorption.13 Likewise CaO can
notable amounts of aliphatic acetamide, single aromatic ring reactwithothergasicationproducts(i.e.H O,H Sandchar/coke)
2 2
speciessuchaspyridine,pyrimidine,pyrrole,anilineandben- thatmaydeteriorateitscatalyticactivityfortarreduction.15,17–19
zonitrile as well as two ring structures such as quinoline and
13284 | RSCAdv.,2019,9,13283–13296 Thisjournalis©TheRoyalSocietyofChemistry2019
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Inthispaper,anexperimentalstudytocharacterisetheyield EnergyResearchCentreofTheNetherlands(ECN).Experiments
and composition of tar in the gas during poultry litter gasi- wereperformedatdifferenttemperatures(700,750and800(cid:1)C)
cation in a laboratory scale uidised bed reactor is presented. andatdifferentERsbetween0.18and0.41byadjustingtheair
The objectives of this study are to investigate the effect of (a) and N ow rate while maintaining the total ow at 12
2
equivalenceratio(ER),(b)limestoneaddition(blendedwiththe dm3min(cid:3)1(Table2).Alongwiththatanefforthasbeenmadeto
poultry litter) and (c) reactor temperature, on tar yield and its maintain a constant feedstock feed rate. The downstream
composition.Somebasicdataregardingoveralltaryieldswere sectionsofthereactoruptothecoldlterwereinsulatedand
publishedbyPandeyetal.,6inacomplementarypublicationto maintained at 400 (cid:1)C in order to avoid tar condensation. Tar
e. thepresentwork.However,adetailedtaranalysisispresented samplesweretakenthroughaSPAsamplingportlocatedaer
nc here,includingthechangeoftarcompositionwiththeprocess thehotlter.Silicasandwithaparticlesizebetween0.25and
e
c
23 1:10:10 AM. n 3.0 Unported Li vac2ao.rmdiaipsboclMeuussn.sadioAstnnperreaosidnaednlitttshiionenaatnehlvedokpleurymtoidoaunsepctteochgftaoson.dfitrtsohgeenp-rceosnetnatinwinogrktaisr bpa0dt.ere5iedno0vsnimmio,tuia1mest.se2(eromikxfapgel1e.a4orTn2ifmo2pfreaaaenvrnstothdisicdl2sae6ianls2indic0zyaetkiosnogafrnme0udd.(cid:3)e3un3w1ccreameesstmohpifnee)tacarrctoniicsvddukeumlbyocueufwldlkbaaetsaaedtnuddtsahaegaesdgbhlbsaooefsmrglotuiehmntree--
on 3/4/20Attributio 2D.e1taiMledatdeerisaclrsiptionofpoultrylittercollection,preparationand nccooinnngdstuaocnftteedtahcrihnouesgxuphceohruimtatewhneatytaeltshdtsaa.tyT.thhGeeamsiuinicdiamitsiuionmngerxeupgieidmriismeinergenmvtsealowinceiertdey
ded ons characterisation including detailed chemical composition of wasaround0.097ms(cid:3)1at20(cid:1)C,calculatedaccordingtoWen
am
Downloe Com athseumpomualtrryyoflirtetelervaansthincfaonrmbateiofnouisnpdreeslesnetwehdehreer.6e.HThoweebvuelrk, ganasdiYcua'tsiocnorcroenladtiitoionn.2s0 lEaasctehdtaebstouutnadnerhtaokuern. Satteathdyesstpaeteciweads
2019. Creativ adepnasrittiycloefstihzeepbaerttwiaelelynd0r.i7edanpdou2l.t8rymlimtt.erTwheasli3m6e0sktognme(cid:3)u3s,ewditinh fueseudailnlyg.reTahcehednawlit3h0inmtihnewersret3d0edmicinateadetroctohmemtaernscaimngplfiunegl
0 April nder a twhiitshsatupdayrwticalsessuipzepliinedthbeyRrahneginekoaflk0.G9–m1b.2Hm(Bmri.loUnlt,iGmeartmeaannyd) achnrdomanaatolygsriaspohf(pmeGrCm)a(nVeanritagna,sCePs-4u9s0in0g).aRneleovna-nlitneinmfoircmroatigoans
n 3d u proximateproperties,chemicalcompositionaswellasheating comprising schematic diagram of gasier, technical data and
d onse valueofthepoultrylitterarereportedinTable1.Thecontentof operatingconditionsoftheexperimentalsetupwaspreviously
ee
cle. Publisharticle is lic aconxneddtevncoatlaritbnioletnhmewfaautsteelcrawlcacosunlctaaetnlecdtuflbaroytemsdub1by0tr0da%icfft.ienLrgeikntechwee.isme,otihsteuroex,ygaesnh pTouraebtsleuens2ti.neIdgtibosynwlPoyarntphdoemuylterenyttialoiltn.t6ienarg,ndtwhhaaritleeteastletsssot1sc,o2fnraocnmisde3l5ywoteourte1lic4naerwdrieeirnde
Artihis conductedwithpoultrylitterblendedwith8%w/woflimestone.
ss T 2.2 Experimentalfacility
e
c
Ac Thegasicationexperimentswereconductedusingalaboratory
en scale air-blown bubbling uidised bed gasier located at the 2.3 Tarmeasurementmethods
p
O The detailed description of the SPA tar sampling method,
extraction and chromatographic analysis of tar is provided
elsewhere.21Briey,SPAcartridgeswereassembledbypacking
Table1 Chemicalcharacteristicofpoultrylitter6
500 mg of aminopropyl silica sorbent. The sampling volume
Proximateanalysis(%w/w) was adjusted to 100 ml of dry product gas. For each experi-
Moisture(a.r.) 22.10 mental condition duplicate SPA samples were taken. Aer
Volatilematter(d.b.) 73.65(cid:5)0.02 sampling the cartridges were shipped to the University of
Ash(d.b.) 17.55(cid:5)0.06 Limerick – Ireland where the tar compounds were extracted
Fixedcarbona(d.b.) 8.81(cid:5)0.02
LHV(MJkg(cid:3)1)(a.r.) 13.53(cid:5)0.41 from the sorbent with 3 (cid:4) 600 ml of dichloromethane. tert-
Butylcyclohexane and 4-ethoxy phenol were added as internal
Ultimateanalysis(d.a.f.)(%w/w) standards to the extracted tar solutions. An Agilent 7890A GC
N 6.48(cid:5)0.01 coupled with a triple-axis MSD 5975C was used for identica-
C 54.70(cid:5)0.37 tionofthemostabundanttarcompounds.AThermoScientic
H 6.43(cid:5)0.07
S 0.90(cid:5)0.03 Trace 1310 GC with a ame ionisation detector (GC-FID) was
Cl 0.70(cid:5)0.02 usedfortarquantication.Calibrationcurvesnaphthalene/tert-
Oa 30.79(cid:5)0.25 butylcyclohexane and phenol/4-ethoxy phenol were applied to
quantify the aromatic and phenolic tar, respectively. The FID
Chemicalcomposition(d.b.)(wt%)
detector was deemed more accurate than the MSD for tar
Hemicellulose 11.72
quantication based on a statistical comparison of both
Cellulose 12.88
Lignin 14.16 methods.21Benzeneandtolueneconcentrationsweremeasured
Extractivesb 39.21 alongwiththeotherpermanentgasesusingon-linemGC(Var-
aCalculatedbydifference,a.r.–asreceived,d.b.–drybasis,d.a.f.–dry ian,CP-4900). Theiryieldsarepresentedasanaverageoffour
andashfreebasis.bContainingwaterandethanolextractives. successivemeasurementsconductedatthree-minuteintervals.
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Table2 Summaryofoperatingconditionsaduringthefluidisedbedgasificationofpoultrylitter6
Testnumber 1 2 3 5 6 7 9 10 11 13 14
Feedstocktype Poultrylitter Poultrylitterwith8%w/w Poultrylitterwith8%w/w Poultrylitter
limestone limestone with8%w/w
limestone
Poultrylitterfeedrate,kg 0.66 0.49 0.61 0.57
h(cid:3)1(a.r.)
Limestone,kgh(cid:3)1 0.0 0.04 0.05 0.05
e. Throughput,kgh(cid:3)1m(cid:3)2 155 113 141 132
enc Temperatureofgasier,(cid:1)C 700 700 750 800
c
M. d Li Tmeemdipuemra,tu(cid:1)Creofgasifying 160 160 160 160
0:10 AUnporte EAqiruivoawlernactee,rdatmio3,mERin((cid:3)(cid:3)1) 60.18 70..222 100.30 70.29 80..535 100.41 70.23 80..528 100.33 70.25 80..530
23 1:1n 3.0 Ndmitr3omgeinn(cid:3)1owrate, 6 4.8 2 5 3.5 2 5 3.5 2 5 3.5
on 3/4/20Attributio FSdulmupi3edrmisiicnniag(cid:3)l1mgaesdviuelmocitoywbarasteed, 102.21 102.24 102.24 102.22 102.21 102.20 102.24 102.23 102.23 102.25 102.24
d s onthetotalproductgas
wnloadeCommon yaiLeladt,ermins(cid:3)th1e(Tmg)anuscriptthesetestsarealsoreferredtoascampaignECNPt.III.
Doe
2019. Creativ
d on 30 April nsed under a t(dhreyTapandrroyadsiheulcfdrteseg-adar.ase.f.ew)(cid:3)xh1perinnesosserliddgehortntodaeemvliiamatsiisonnbastaesoiasfnabysidogimtlauratskiosgnpfoeeueffltdreycrltiattoteefr cppooromsdspiuboclutengrdaessas(oif.rneo.mcuonudsltedyrreb1ne0egthtateorkrgeblpeaontuizlvt[reayl]ylaitntleotrhw(rda.atc.afe.r)n(cid:3)ce1o)snuatmelonmntgiinngwtiuhthpe
hece occur,22 or when the oxygen to nitrogen ratio is reduced to previously mentioned losses during the analysis delay. Table 3
Article. Publishis article is li raakedrgsepjpuoaeusllcsttrtofyottlaroitbtletourhwlae(det.erafde.fE.e)iR(cid:3)dn.1s2tt3hoeTneckaaEr,bSlywIe†ihe.fliTduleasnbdyauairelemaldtpeesnrdetpsyareileenlsstdeteusnddpteigredersasepaonshftiegctdaalralysmwbgitutahtr cdcwouuemrclrltepeandsatrdiesnistffu2rede0rpy1e)ne2aut(tspEaioCbnsiNgtlisttPyhatme.fIr)spo,aml2imn01gteh3ttrre(eeEseatCtemrNxigpePenbtrt.uiImoIt)fdeatnihnfftedaeSlr2ePc0nAa1tm5sfape(mEeadCipgsNlnteossPc.ctkS.oIPIanIAs--
cess T product gas(cid:3)3 are more useful for developers and operatatrorsdorfy tar samples from campaigns ECN Pt.I and ECN Pt.II were
Ac downstreamapplicationssuchastarmitigationtechnologiesor extracted on-site immediately aer the sampling, while as
n
e usingtheproductgasininternalcombustionengine. mentionedpreviously,therewasadelaybeforetheextractionstep
p
O
TotaltarinthispaperreferstoGCdetectabletarsampledby of ECN Pt.III samples. SPA tar yields measured during experi-
SPAinclusiveoftarcompoundsfromstyrene(Mz104gmol(cid:3)1) mental campaigns ECN Pt.I and ECN Pt.II were signicantly
tobenz[a]anthracene(Mz228gmol(cid:3)1)aswellasbenzeneand higher25comparedwiththoseinthecurrentstudy.Repeatability
toluene measured by on-line micro GC instrument. The reason was estimated using an open access excel spreadsheet26 model
whytotaltardoesnotincludelighttarcompounds(i.e.socalled implementingcalculationssimilartothoseintheTAPPIstandard
BTEX–Benzene,Toluene,Ethylbenzene,Xylene)sampledbySPA T1200,“InterlaboratoryEvaluationofTestMethodstoDetermine
is due to delay between sampling and extraction of the SPA TAPPI Repeatability and Reproducibility”.27 In short, coefficient
cartridges.AsreportedpreviouslybyHorvatetal.24asignicant ofvarianceiscalculatedforSPAreplicatesofeachexperimental
portionofthevolatilecompoundssuchasbenzene,tolueneand condition.Soderivedcoefficientsofvariancearethencombined
xylene are lost during transport resulting in their quantitative intoaveragecovariancewhichenablesexpressionofrepeatability
underestimation as well as poor measurement repeatability. inpercentage.Higher values inTable 3 indicate poor measure-
Instead, benzene and toluene measured by on-line mGC is mentagreementbetweenreplicates.
combinedwithSPAsampledtartosumupfortotaltar.Although,
accordingtoCEN/TS15439,20069benzeneisexcludedfromthe
denition of tar, in the present work it is presented as a tar Table 3 Measurement repeatability of total SPA tar, phenol and
naphthalenecalculatedforthreeexperimentalcampaignsa
compound since its aromatic chemical structure is more char-
acteristic of tar species than permanent gases. The results of
TotalSPAtar Phenol Naphthalene Ref.
poultry litter tar sampled by SPA arepresented in duplicate for
each gasication condition to show the repeatability of the ECNPt.I 9 11 15 Horvatetal.25
measurements and the random errors associated with uctua- ECNPt.II 13 11 9 Horvatetal.25
ECNPt.III 68 66 71 Currentstudy
tions in the feeding rate. It is evident from Table 3 that the
measurement repeatability in this study is mediocre. One aRepeatabilityisexpressedin(%).
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2.4 Limestone/limecharacterisationmethods containing hydrocarbons arising from proteins retain their
monomerstructureorderivefromreformingreactionsbetween
Limestone samples were analysed by the thermal gravimetric
permanent gases (i.e. NO , NH , HCN) and the condensable
analyser (TGA). The elemental composition of limestone (C, x 3
fraction (i.e. tar) in the product gas. Nitrogen-containing
H, N and S) was determined by a Vario EL cube elemental
compoundsarenormallynotreportedintherelevantgasica-
analyser. To reduce the uncertainties involved in measure-
tion literature since insignicant amounts are generated from
ments, elemental analyses were performed in triplicates.
conventional lignocellulosic feedstock. Fig. 1 shows the struc-
Results are presented on as received basis. Prior to analysis
tural formulae of the nitrogen-containing compounds identi-
limestonegrainsweremanuallyseparatedfromthebedcontent
e. (i.e. char, ash and silica sand). PerkinElmer's Pyris 1 TGA was edinthisstudy.
c
n The formation of nitrogen-containing hydrocarbons in the
e employed to test the degree of calcination of the limestone.
c
M. d Li Approximately 20 mg of limestone grain was placed into an pyrolysisprocesshasbeeninvestigatedbyDignacetal.30Inthe
23 1:10:10 An 3.0 Unporte atcuhmlnued3mrearmintaeiancop(cid:3)afa1r2.nb0oTwn(cid:1)hiCtedhimoosuaximtinda(cid:3)ee1lpitudeunmradgnpeederrwaaotawnusrirthaerteoepagtroeeofndg2rpf0arumocrmmgew33am0sotiwonpr(cid:3)e9ar19tf.e5oro(cid:1)mCfe2ad0t pacdonyenrrdoitvlaiaynistndiaviotneelgsesdtfhoreyordtmihvroaefctripaevyrsebrhsoowvlnyeessgri.eseTtaodhbfeeltaeealscautpnethyidnroiaedrm-sicnoaoentn,ttgrpaiyibtnhrurietoneolgdet,hptberheorentnezpiiotynrnrsoiidgtarienninldee-
on 3/4/20Attributio 3. Results and discussion pfarneopdmtiidtspeysdr,eorwliyvistaihstivotehfsewphbeereennzyflooanrlmaitnreiidlneeb-ydcoecnryictvalaiitsniavitneisognppdrrooubtreianibnglsy.pyfPoryorrmlryoselides
d s
deon ofproteinscontainingtheaminoacidsproline,hydroxyproline,
2019. DownloaCreative Comm olTfirrthodteemerridgciaonensnwitvihecniaecttdhiioottnnahareilsycloidegmliunsttpoieocndeuc.ltnlTiuvdhlesoelysacirdcoeimfffuppeerroelesssn,iettsnipoftreenodcmoiifncttaaaTlrrlayfcbroiolnmemtp4eporiosmniutsilttohorneyf goodlfreyirpgciiivinngameatitvaeeennsfdtrsoogmsrluiugctwiahnmaasatitsececaffhrceolieodmdr,obapbunhetddycldfloe.iunaTltgdhheemarlpssar,otoewbtrehieaiinlplesyaritnonhdleypswocishuallpsottrrreoyodpfliuehtectyedtlsrl.
0 April nder a npoituroltgreynli-tctoenrtdaeinriivnegshfryodmrotchaerbaonnims.aMlfoesetdo,fetxhcerentaitarongdefneainthtehres Pinouthlteryfoerxmcraettiaoanlsoofcnointrtoaginens-ncoitnrotagienninthgahtypdorsosciabrlbyopnlasyassainrodlie-
n 3d u ratherthanfromthebeddingmaterial.Thisnitrogenischem- catedbyInoueetal.31whoanalysedtheproductsofliquefaction
d onse ically incorporated into protein molecules and urea.28,29 It is of ammonia and cellulose. Brebu and Spiridon32 investigated
ee
cle. Publisharticle is lic ibmseelditeuhveyelpdtoytrhtihdaetinthhe,ieg2ph-mreleesvetehnlycloe-1foHnf-isptirygorngrioelnceaiannntdtahmbeeonfuuzneoltns(iptorofiulpelytirrniydtlihinteete,tra2)r-. tcfhohreimcktaehtnieorfnmeaoatflhaedrroesmgcroaantditcaatpiinoyirnnrogolekfserasanhtdeinepppyrroiwdtoeinoinel,sstahonutdmhaeatnatrmibhiunatoieradcatinhddes
Artihis However, the question remains as to whether nitrogen- in the protein of keratin. The majority of the nitrogen-
ss T containing hydrocarbons were found in the aqueous phase of
cce Table4 Identifiedtarcompoundswiththeretentiontimeandclas- thepyrolysiscondensatewhichneedstobetakenintoaccount
n A sificationaccordingtoMilneetal.33 in the development of tar cleaning and waste water treatment
e
p
O technologies.
Retentiontime
Tarcompound (min) Targroup EightindividualtarcompoundssampledbytheSPAmethod
(designated by * in Table 4) are presented quantitatively in
Benzene 4.65 Secondary Fig. 2–6. Pyridine and benzonitrile represent nitrogen-
Pyridine* 7.15 Secondary
containing hydrocarbons while phenolic hydrocarbons mainly
Toluene 7.90 Secondary
containphenolandcresols.Itshouldbenotedthattwoisomers
2-Methylpyridine 8.25 Secondary
2-Methyl-1H-pyrrole 9.81 Secondary of cresol are summed and presented as a single quantity.
Ethylbenzene 11.38 Secondary Indene, naphthalene, acenaphthylene and phenanthrene are
p-Xylene 11.68 Secondary representativesofPAHs.
Styrene 12.49 Secondary
Benzonitrile* 15.85 Secondary
Phenol* 16.15 Secondary
Indene* 17.81 Secondary
o/m/p-Cresol* 18.25 Secondary
o/m/p-Cresol* 18.92 Secondary
1,2-Dihydronaphthalene 21.10 Secondary
Naphthalene* 22.18 Tertiary-PAH
Acenaphthylene* 29.36 Tertiary-PAH
2,4A-Dihydrouorene 32.14 Secondary
Fluorene 32.57 Tertiary-PAH
Phenanthrene* 36.80 Tertiary-PAH
1-Methylphenanthrene 38.84 Tertiary-alkyl
4-Methylphenanthrene 39.22 Tertiary-alkyl
Pyrene 41.48 Tertiary-PAH
11H-Benzo[b]uorene 41.86 Tertiary-PAH
Benzo[a]anthracene 45.85 Tertiary-PAH Fig.1 Nitrogen-containingcompoundsfoundinpoultrylittertar.
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Table 5 includes the yields of principal permanent gases totaltaryieldsintherangeof40–45g kg (cid:3)1
totaltar drywoodsawdust
expressed in g kg (cid:3)1. Although the yields of whileconductingthetestsundersimilarERconditionstothose
gas poultry litter (d.a.f.)
permanent gases are not the main focus of the present work, reportedhere.Thetarsamplingsetupemployedwasacombi-
these data aim to support discussion on tar yield and nation of dry and wet cold trapping Horvat et al.25 measured
composition. totaltarbetween14–34g kg (cid:3)1fromrawand
totaltar biomass(d.a.f.)
Thescaleonthey-axisiskeptthesameinallgraphsinorder torreed Miscanthus x giganteus respectively using the same
tosimplifycomparisonoftaryields.Theresultsindicatethattar experimental reactorasbeingusedforthisstudy. Inthat case
yields from poultry litter gasication are lower than from tarcompoundsinthemolecularweightrangefrombenzeneto
e. feedstocks with a higher organic fraction. This was corrobo- benzo[k]uoranthene were sampled by means of the SPA
nc rated by only mild coloration of the white aminopropyl silica method.Comparedtothepoultrylitter,bothrawandtorreed
e
c
M. d Li sorbentwhichtypicallyturnsdarkyellowwhenproductgaswith Miscanthus x giganteus have lower ash contents of 2.8 and
23 1:10:10 An 3.0 Unporte alhuitgihgendhiignthtoacratoshcnheotenvcnteoetrnny(ttTesnpaisbetclsaeianm1dc)p.clloLoemwidg.npoLiornogsiwaitsniotikocnntfaoorlfawtcpnatoriotuyonlite,brlyiednlsaitpcttaeaarrnrtwipcbhrueeilccaahurttrhrlsoiaobwsr- 4r3e..21spewEcttff%iveecltyao.nfdeqhuiigvhaleerncleigrnaitnioocnontaternytielodfan2d1coamndpo4si3tiownt%– ,
d on 3/4/20s Attributio gcpeihvleliunnlgoolssreisaaenndtdohPheAimgHhisceercllatunoltoasalels.G3o4C,35bdeHeotfewocretmvaeberld,esfmtraoramllaenrcdeqluPluaAlnHotsisetiethasnaondf wFraiignth.goe2ubitenltciwmlueedesnetso0n.t1oe8taaadlndtdaitri0o.yn3ie0ldats7a0n0d(cid:1)Cco,mwipthosoiutitoanddoivteiornthoeftEhRe
deon hemicellulose.36 An ash content of 17.55 wt% (dry basis) in
am limestonetothepoultrylitter.Itisevidentthattotaltaraswell
Downloe Com ppoarutlitcruylalirtttehreicsonrecgeanrtdraetdioansohfieglhembeunttsitssuccohmapsoCsait,iMong,aAnld,Fien, ainscrneiatsroegweinthatnhdeEoRx.ySguenchcaonnotabisneirnvgatitoanr icsoimnpdoisuangdresemsleignhtttloy
30 April 2019. under a Creativ piZpnnrlace,ylsuMeeddnnet6aebwderhoninilzceehFniinegex.aht2hni–bed6ittt(oo1ctla5uat.l7aelntytaeotricm3r0teea.da7rsurgucetrtodietouadlnctbt.ai3ryo7knoTgnhap-coelutiniltvtoreiyttmyaliltctieoctraru(ordld.Gay.ihfCe.)al(cid:3).dv1Iest) teathamifenupirelneol.sgyuiTntlhatgsreypwcroooembossedpenortsvueaendwdddbsauywsdKtie,itnchproeeisanahsncietruaetoaefsstithnaoeglt.la2lE3laRatnanrwddahHwnildhaenekoapextiyengspgteirnneatgwcaotlha.n3es9-
d on nsed imseawsourrtehdbmyeonnt-iloinnienmgictrhoatGCifarbeesnuzbetnraectaenddfrotmolutheneetotyaielltdasr temperature at 700 and 800 (cid:1)C, respectively. However, more
hece recentlyHorvatetal.25foundthatatconstanttemperature,the
cle. Publisarticle is li f3pr.ro1emvtioopu1os0ul.yl3t2r4ygtthloitatattleotra,nrt-hkligenpeyoiumeltlGrdyColitfmtetreoat(das.lua.trf.ae)(cid:3)rm1w.eonItutslhdgaidsvreboepceotnnosrbiedepetowraretbeelnde cEfroRonmhsiadsaerrgeelrdaatsfiosvyrelcyboilmoitmtplaearsiimss.opnTahdcteusoeentotthhthreeeyeiireasltdbuiodliriteycsto2om3,2s5pt,u3o9dsihytaitohvneeeobfffeeteacnrt
ess Arti This hAdigdhietironbaelnlyzeBnreagaendet taoll.u38ensheoqwueadnttihtaietsScPoAmspaamripnlgingtoisSPfaAr. oTfheERcosnecpeanrtartaetliyofnroomf PtAhHe tceommppeorautnudreseinffetchtisonstutadryeivnoclruetaiosens.
cc superior for quantication of BTEX compounds compared to
A withincreasingER.Theyieldsforbenzeneandtolueneincrease
en traditional cold trapping. Therefore, comparing the total tar slightlyandthenlevel-offatanERof0.3.Similartothetotaltar,
Op yield from the relevant literature is complicated due to differ-
theyieldofproductgasesincreaseswithER.AthigherERmore
ences in dening tar, sampling conditions, analytical instru-
oxygenisavailableforcharconversionintoproductgasaswell
mentcalibrationandreportedunits.Kinoshitaetal.23reported
as reacting with permanent gases and tar. Therefore, as
Table5 Yieldsaofpermanentgasesduringfluidisedbedgasificationofpoultrylitter
Testnumber 1 2 3 5 6 7 9 10 11 13 14
Feedstocktype Poultrylitter Poultrylitterwith8%w/w Poultrylitterwith8%w/w Poultrylitterwith
limestone limestone 8%w/wlimestone
Temperatureofgasier,(cid:1)C 700 700 750 800
Equivalenceratio,ER((cid:3)) 0.18 0.22 0.30 0.29 0.35 0.41 0.23 0.28 0.33 0.25 0.30
Permanentgasyield,
g kg (cid:3)1
gas poultrylitter(d.a.f.)
H 14.2 25.5 26.4 15.7 13.9 6.2 24.3 21.7 20.5 27.8 22.2
2
CH 28.7 44.5 42.9 39.6 34.7 29.1 50.8 43.1 41.6 53.6 45.5
4
CO 145.5 259.5 294.5 191.1 187.4 150.2 274.9 264.3 255.6 336.2 258.2
CO 483.2 636.7 749.2 733.1 813.1 844.8 656.8 687.3 762.7 743.6 770.7
2
C H 24.4 35.4 34.6 35.0 31.5 29.5 47.6 42.4 40.8 52.9 44.8
2 4
C H 5.6 9.5 9.6 7.5 7.0 5.3 6.6 6.2 6.1 4.1 3.7
2 6
C H 0.4 0.5 0.4 0.6 0.6 0.6 0.8 0.8 0.6 0.8 0.5
2 2
H S 1.5 2.3 2.1 1.9 2.4 1.1 0.9 1.2 1.1 0.8 1.0
2
Sum 703.7 1014.0 1159.8 1024.6 1090.6 1067.0 1062.7 1067.0 1129.0 1219.8 1146.4
aValuescalculatedbasedondatafromref.6.
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ss T
e
c
c
n A expected an increase in product gas yield and carbon conver- whetherthedifferenceintaryieldsisduesolelytotheeffectof
pe sion(from49.1%atERof0.18toover70%atERof0.22and0.3) limestone. The only gasication conditions allowing direct
O
wasobserved.However,thiswasaccompaniedbyanincreasein evaluation of the effect of limestone are ER 0.30; T 700 (cid:1)C;
tar yield. Poultry litter comprise a very high fraction of extrac- without limestone addition and ER 0.29; T 700 (cid:1)C; with lime-
tives(40%onadrybasis,Table1)buttheirexactcompositionis stoneaddition,respectively.Therewas5%lessoftotaltarfrom
notknown.Literatureinformationontheextractivefractionin thetestwithoutlimestoneaddition.Thedifferencebetweenthe
poultry litter is scarce. It is not known to what extend these yieldsofindividualtarcompoundsvarybetween–9and21.3%
extractivescontributetoeithertheproductgasortaryields. takingthetestwithoutlimestoneadditionasareferencevalue.
Thesendingsshownosignicanteffectoflimestoneaddition
3.2 Effectofequivalenceratioontaryieldandcomposition- on the tar yield and its composition at the lowest gasication
withlimestoneaddition temperature. Permanent gases measurements actually reveal
higher yields of H , CH , CO in the test without limestone
Fig. 3 presents tar yields for the experiments undertaken 2 4
betweenanERof0.29and0.41,atagasicationtemperatureof addition, while the concentration of CO2 was similar for both
700 (cid:1)C using poultry litter blended with limestone (8% w/w). scenarios. Correlation exist between the yields of permanent
gases and carbon conversion efficiency which appears to be
Fig.2and 3showdata forthesametemperature, butthe ERs
correspond to two different ranges (0.18–0.30 vs. 0.29–0.41). 81.8%inthetestwithoutlimestoneadditionand70.8%inthe
DifferencesintheERderivefromdailyvariationsoffuelfeeding test with limestone addition. Although it has been found that
rate,despiteeffortsbeingmadetomaintainaconstantfeeding alkaline earth metal oxides (CaO/MgO) employed in steam
gasicationincreasetheyieldsofpermanentgases(H ,CO )by
rate throughout the experimental campaign. Due to the 2 2
promotingthedecompositionreactionsoftarandlighthydro-
agglomerationissueassociatedwiththerawpoultrylitter,itwas
carbon13,40,41 it seems this phenomena did not occur in gasi-
decidedtoaddlimestone(CaCO ),howevernoadjustmentwas
3 cationtestat700(cid:1)C.Therecouldbetwopotentialreasonsfor
madetothecalibrationofthefeedingsystem.Sincetherangeof
ERdiffersforboththelimestoneblendedandrawpoultrylitter, low catalytic activity of limestone: limited calcination at low
temperatureandadsorptionofsulphur.Inordertounderstand
itis notpossibletodrawunambiguous conclusionsregarding
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Article. Publishis article is li Fig.3 Equivalenceratioprofileforthetaryieldsatreactortemperatureof700(cid:1)Cwithlimestoneaddition.
ss T
e
c
c
n A thetransformationoflimestoneduringgasicationtestsaddi- total tar and yields of individual tar species show the same
pe tionalcharacterisationoflimestonegrains separatedfromthe trend.Benzeneandtoluenealsofollowadecreasingtrendasthe
O
bed aer tests was carried out. These results are discussed in other SPA sampled tar compounds do, although toluene does
detailinSection3.4andtheyshowthatat700(cid:1)Climestonewas notseemtobenotablyaffectedovertheERrangetested.There
onlypartiallycalcined,thereforeinactivetowardstarreduction. areatleasttwofactorswhichcouldhavecauseddecreaseoftar:
According to Florin and Harris42 calcination of limestone higher content of reactive oxygen (higher ER) and presence of
forming catalytically active lime does take place in an inert limestone whose calcination degree increased with tempera-
atmosphere at 700 (cid:1)C. In an atmosphere containing CO the ture.FromthedataavailableinTable5anincreaseinERresults
2
carbonation/calcination reactions shi to higher temperature inareductionofbothH andCOconcentrationandanincrease
2
comparingtoinertatmospherebecauseofreversiblenatureof inCO intheproductgasduetocombustionofthevolatilesand
2
the calcination reaction at an equilibrium condition.17 Lime char.Despiteitshigherconcentration,itseemsthattheCO did
2
alteration can also occur in the presence of gaseous H S not impact on the catalytic ability of the lime due to carbon-
2
(Table5)formingCaS.43Directevidenceofcatalyticdeactivation izationintolimestoneoverthetimeframeoftheexperimentsat
oflimebyH Shasnotbeenfoundintheliterature,butcatalyst 750and800(cid:1)C.Thermalgravimetricanalysisoflimestone/lime
2
poisoningcausedbysulphurhasbeenreportedpreviously.44,45 aergasicationrevealedthatthedegreeofinsitucalcination
The sulphur content inthe recovered limestone/lime aer the wassignicantly higherat750 and 800 (cid:1)C.Moreover, over 10-
gasicationat700(cid:1)Cincreased3timescomparedtotheunused folds higher sulphur content was observed in the recovered
limestone (Table 6) proving chemical interaction between H S limestone/limefromthegasicationexperimentscomparedto
2
andthelimestone/lime. the unused limestone. Despite high sulphur adsorption, no
InFig.3areductionintotaltarisobservedoverthetestedER clear evidence of reduced catalytic tar reduction capacity of
range when poultry litter was blended with the limestone. limestone/limewasfoundduringthegasication.
SimilartrendsareobservedinFig.4and5showingdecreasing Delgado et al.40 and Simell et al.12 reported rapid catalytic
totaltarovertherangeofERtestedatgasicationtemperatures deactivationoflimestone/limeasaresultofcokedepositionon
of750and800(cid:1)C,respectively.Itisworthemphasizingthatthe thesurfaceofactivesites.Theauthorsalsostatedthatbothwet
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ss T
Acce (steam) and dry (CO2) gasication eliminate coke from the unambiguously attributed to the calcined limestone/lime
n surfacewhichcouldexplaintheincreasedcatalyticactivitywith because oxygen content, ER, could play a crucial role in tar
e
Op increasing ER. Wet and dry gasication reactions are strongly reductionaswell.
endothermic. Therefore, they are more likely to play a crucial
roleinthetestsat750and800(cid:1)Cthanat700(cid:1)C.Moreover,at
3.3 Effectoftemperatureontaryieldandcomposition-with
higher ER more oxygen is available to oxidise any deposited
coke. It is not clear how the oxygen itself affects the redox limestoneaddition
equilibrium of limestone/lime. Of relevance to the present InFig.2–4theyieldsofphenols(from0.11to1.22g kg
tar poultry
work, Campoy et al.46 conducted gasication tests in an air (cid:3)1)andbenzonitrile(from0.10to0.61g kg
litter(d.a.f.) tar poultrylitter
blown bubbling uidised bed reactor using wood pellets as (cid:3)1) are relatively high at low gasication temperatures
(d.a.f.)
a fuel. Ote, a silicate subvolcanic rock was compared to between700and750(cid:1)C.However,at800(cid:1)Conlybetween0.02
calcinedlimestoneoveranERrangebetween0.23and0.36.The and 0.27 g kg (cid:3)1, of phenols and benzonitrile
tar poultry litter (d.a.f.)
yieldsofgravimetrictardecreasedonlyatanERabove0.3while are observed due to their conversion via demethylation, dehy-
employing silicate rock. On the other hand, the addition of dration47 and denitrication reactions.48 Reforming mecha-
calcinedlimestoneresulted ina slightdecrease ofgravimetric nisms using model compounds such as pyridine, pyrrole and
tarovertheentireERrangetested.However,notablevariations indole have been studied in the context of thermochemical
havebeenfoundbetweensilicaterocktestsandthetestswith conversionofcoal.48,49Liuetal.48measuredNH andHCNasthe
3
added calcined limestone. Gravimetric tar quantities between maingaseousproductsfromconversionofnitrogen-containing
40and50gtarkgwood(d.a.f.)(cid:3)1resultedfromsilicaterock,while hydrocarbons. Gasication of indole was carried out in super-
between25and30gtarkgwood(d.a.f.)(cid:3)1weremeasuredaerthe critical water and the authors concluded that one portion of
additionofcalcinedlimestone. indole converted directly into aromatic compounds without
In a nutshell, there are indications that catalytic tar reduc- nitrogenbyreleasingammonia,whileanotherportionofindole
tion took place when the gasication tests were performed at was converted into nitrogen-containing aromatic compounds
750 and 800 (cid:1)C. However, tar reduction cannot be such as aniline, o-toluidine and 9-nitroso-9H-carbazole. Zhao
etal.49pyrolysedpyridineandpyrroleat600–1200(cid:1)Cinaow
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ss T
e
c
c
A reactor.H andHCNweremeasuredinordertodeterminethe that if benzene and toluene are excluded, the total SPA tar
n 2
pe thermal stability of pyridine and pyrrole. The results showed summedfromstyrenetobenz[a]anthraceneshowsasignicant
O
thatthethermalstabilityofpyridineisgreatersincesignicant reductionwithincreasingtemperature.
production of HCN was observed at 825 (cid:1)C while pyrrole According to Delgado et al.40 higher reaction temperature
generated notable amounts of HCN at 775 (cid:1)C. A thermal favours catalytic activity of lime for tar destruction in the
degradation (i.e. ring-opening) mechanism was proposed for temperature range of 780–880 (cid:1)C in a uidised bed biomass
both nitrogen-containing hydrocarbons studied. The pyridine gasier.Although, the authorsalso observed catalystdeactiva-
ringundergoesaseriesoffreeradicalreactionsresultinginH tion due to coke formation and adsorption on the active sites
2
andanaliphatic$R–CN.Ontheotherhand,itisassumedthat regenerationoflimebycokeremovalwaseffectivelyachievedby
pyrroleundergoesdirectringopening,thereforereforminginto steamanddry(CO )gasication.Fig.6indicatesthatcatalytic
2
an aliphatic R–CN without passing through free radical activity of limestone/lime promoted by elevated temperature
reactions. couldhavereducedheterocyclictar(i.e.phenols,benzonitrile),
Fig. 6 presents the total tar yields and quantities of ten toluene and indene, while no reduction effect is observed for
individualtarspecieswithrespecttogasicationtemperatureat benzeneandPAHs.Similarquantitativecurvesofindividualtar
anERof0.29(cid:5)0.01.Theyieldoftotaltaroverthetemperature compoundspresentedinFig.6werepreviouslyattributedsolely
rangetestedremainssteadywhichisconsideredasanatypical to the temperature effect.23,25 Saw and Pang13 investigated the
observationwithrespecttoearlierliteraturendings.Depend- inuence of lime loading on the tar yields in a dual uidised
ing on the range of temperature tested and the tar sampling bed steam gasier operated at 710–750 (cid:1)C. They observed
methodemployedtheyieldsoftotaltareitherdecreased22,50,51or catalytically driven reduction of tar including tar species in
exhibited the peak yield at around 750 (cid:1)C followed by classes from C2 to C5 according to ECN classication.52
a decrease.25,33,52 Steady total tar yields are attributed to the However,benzenewasnotincludedintheirstudy.Simelletal.12
prevailingeffectofhighbenzeneconcentrationswhichincrease tested calcined carbonated rock for its catalytic reforming
with temperature over less abundant and diminishing species potencyusingbenzene,tolueneandnaphthaleneasmodeltar
such as benzonitrile, phenols and indene. It should be noted compounds.Theorderofreformingtoluene>naphthalene[
13292 | RSCAdv.,2019,9,13283–13296 Thisjournalis©TheRoyalSocietyofChemistry2019