DSpace at VNU: Fast pyrolysis of palm kernel cake using a fluidized bed reactor: Design of experiment and characteristics of bio-oil

Fast pyrolysis of palm kernel cake using a fluidized bed reactor: Design ofa Department of Chemical Engineering, Ho Chi Minh City University of Technology, 268 Ly Thuong Kiet, District 10

Fast pyrolysis of palm kernel cake using a fluidized bed reactor: Design of

a Department of Chemical Engineering, Ho Chi Minh City University of Technology, 268 Ly Thuong Kiet, District 10, Ho Chi Minh City, Vietnam

b

Department of Chemical Engineering, Kyung Hee University, 1 Seocheon-dong Giheung-gu, Yongin, Gyeonggi-do 446-701, Republic of Korea

c

Department of Chemical Engineering, Kangwon National University, 1 Joongang-ro, Samcheok, Gangwon-do 245-711, Republic of Korea

1 Introduction

Among oils and fats, palm oil is currently produced at the

highestvolumeworldwide[1].Accompanyingthepalmoil,palm

kernel cake, an undesirable by-product primarily composed of

mannan(cellulose-likebiopolymer[2,3]),isalsoproduced.Dueto

itsabundance,numerousattemptstoconvertthiswastebiomass

intoenergyorfuelbydirectburning,pyrolyzing,orgasifyinghave

beencarried out Of allthe products obtained fromprocessing

palm kernel cake, bio-oil is preferable Since bio-oil currently

receivesmuchinterestasan alternativetotheshrinking

fossil-basedfuelreserves,muchefforthasbeenspenttofindaneffective

andeconomicallyfeasibletechnologytoobtainashighabio-oil

yieldaspossible.Fastpyrolysisusingafluidizedbedreactorcan

achieverelativelyhighyieldsandisconsidered oneofthemost

efficientapproachestoacquirethehighestyieldofbio-oil

Inordertoyieldhigheramountsofoil,thefluidizedbedreactor

mustbeoperatedataresidencetimeoflessthanonesecond[4]

However, this does not mean that if the residence time is

extremely short,the bio-oil yield will increase significantly In

thecaseofaveryshortresidencetime,entrainmentofbiomass

mayoccurduringthepyrolysisprocess,thuscausing lossofthe

feedstock.Anappropriate flowrateofthefluidizinggascan be

calculatedfromtheresidencetimebasedon theinverse propor-tionalitybetweenresidencetimeandflowrate.Withtheresidence timerequirementoflessthanonesecondpreviouslymentioned,the operating flowrateofthe fluidizinggasshouldbechangedtoa specificrangeatwhichthefluidizedconditioncanoccurwithout entrainment.Inadditiontotheresidencetime,thebio-oilyieldis alsostronglyaffectedbythepyrolysistemperature.Thefeedstock willdecomposetoproducemoregasandliquidproductsathigher pyrolysistemperatures.Atlowtemperaturesbelow2508C,mostof thecomponentsinbiomassdonotdegrade.Whenthetemperature

is in the range of 250–5208C, the pyrolysis process will occur efficientlyduetothedecompositionofhemicellulose,cellulose,and lignin, as reported in literature [4,5] Many studies have also reportedthat thistemperaturerangeis preferabletoobtainthe highestbio-oilyield[6].Oncethetemperatureexceeds5208C,the secondary cracking reaction of bio-oil will occur, leading to a reducedproductyield[7]

Sincepyrolysisisathermalprocess,heattransferplaysacritical roleinthefluidizedbedtechnology.Theparticlesizeandfeedrateof thefeedstockarethetwofactorsdirectlyaffectingtheheattransfer

Toenhancethesupplyofenergyfromthereactortodeepinsidethe biomassparticles,asmallparticlesizeismoredesirable.However, the biomassparticlesizeshould becarefullyselected forusein fluidizationbecauseasmallparticlesizewillfacilitateentrainment Thefeedrateofthefeedstocknotonlyaffectstheheattransfer,but alsothepressuredropinfluidizedbedreactor.Inpractice,thefeed rateofthefeedstockmayaffecttheinitialheightofmaterialinthe reactor, resulting in the pressure drop as well as fluidization behavior(smooth,particulate,bubblingoraggregative)[8]

A R T I C L E I N F O

Article history:

Received 31 May 2012

Accepted 16 July 2012

Available online 24 July 2012

Keywords:

Fast pyrolysis

Palm kernel cake (PKC)

Central composite rotatable design (CCRD)

Optimization

A B S T R A C T

Inthisstudy,thecentralcompositerotatabledesign(CCRD)wasemployedtoinvestigatetheeffectsof thefeedstockfeedrate,biomassparticlesize,pyrolysistemperature,andresidencetimeonthefast pyrolysisofpalmkernelcake.Amathematicalmodelfortheliquidproductyieldwasdevelopedand appliedtoobtainamaximumyieldof49.5wt%.TheGC–MSanalysesofthebio-oilsatthetwodifferent temperaturesof 400 and 5008Cshowed that theywere acomplex mixture composed ofmostly oxygenatedcompounds including b-D-allose, derivativesof furanand phenol, and aconsiderable amountoffattyacids

ß2012TheKoreanSocietyofIndustrialandEngineeringChemistry.PublishedbyElsevierB.V.Allrights

reserved

* Corresponding author Tel.: +82 31 201 2492; fax: +82 31 202 1946.

** Corresponding author Tel.: +82 33 570 6544; fax: +82 33 570 6535.

E-mail addresses: jkim21@khu.ac.kr (J Kim), sskim2008@kangwon.ac.kr

(S.-S Kim).

ContentslistsavailableatSciVerseScienceDirect

j o urna l hom e pa ge :ww w e l s e v i e r c om/ l o ca t e / j i e c

1226-086X/$ – see front matter ß 2012 The Korean Society of Industrial and Engineering Chemistry Published by Elsevier B.V All rights reserved.

Finally, there are at least four operating parameters which

influencethefastpyrolysisusingafluidizedbedreactor.Although

manyresearchershavestudiedtheinfluenceoftheparameterson

thebio-oilyieldexperimentallyandnumerically,itisnoteasyto

obtaintheoptimumconditionforhigheryieldofbio-oilwithout

scanningalltheparameters

Therefore,inthisresearch,anexperimentaldesigntechnique

referred to as central composite rotatable design (CCRD)was

utilized to organize the experimental runs This experiment

designprocedure is commonly used forplanningexperiments

bothinthelaboratoryandinindustry[9].Followingthisdesign

closely,asecond-orderregressionequationdescribingtheeffects

appropriatealgorithmwas thenused to obtain the optimized

conditions

2 Experimentalsections

2.1 Palmkernelcake

The raw palm kernel cake received from Green Ocean Co

(Malaysia)wasgroundwithaknifemillandthenexposedtoairfor

24h.Thepreparedsamplewasthensievedtoobtainthedesirable

particlesizeforeachexperiment.Beforebeingusedasafeedstock

forthefast pyrolysis experiments,all the samples were dried

again at 808C for 24h in a dryer They were subsequently

preservedinaclosedbagpriortotheexperiment.Theweightof

theremainingpalmoilwasquantifiedbasedonthedifferenceof

theweightsoftherawsamplebeforeandafterwashinginpure

acetonewheretheweightoftheremainingsamplewasassumed

tobepalmoil

2.2 Fluidizedbedreactor Thefastpyrolysisofthepalmkernelcakewasconductedina fluidized bed reactor, as schematicallydescribed in Fig 1 The pyrolysis reactor, cyclone, and two condensers used in this researchweremadeofPyrexglass Thereactorhada diameter

of3.6cmwithaheightof20cm Inordertoavoidtheproduct condensing on thewallof thecyclone and pipeline, thewhole apparatuswascarefullycoveredbyaheat-insulatingmaterial.For thepurposeofapplyingvariousbiomassparticlesizesforthefast pyrolysis and maintaining the fluidized condition more stably anotherexitfromthereactor,inadditiontotheusualproductexit fromthereactortothecyclone(way1),toasolidcollectingbottle (way2)wasalsodesigned.Thepresenceofway2washelpfulfor drawingthecharoutofthereactorwhenalargeparticlesizeand smallflowrateoffluidizinggas(atwhichtheentrainmentofsolid productdoes notoccur)wereusedand successfullyresultedin balancingtheinputandoutputmaterialsduringtheprocess Foreachrun,100gofasamplewasplacedinthefeedhopper.In addition,thereactorwasalsochargedwith15gofsilicasandin rangeof250–300mmasapyrolysismedium.When thefurnace

controller) was switched on at a prescribed value (from 10 to

15L/min,dependingontheresidencetime)toallowthefluidizing gas(N2)toenterthereactor.Theequipmentsetupwasfirstrun without feeding biomass for 30min until the flow rate of the fluidizinggasandfurnacetemperaturebecamestable

Subsequent-ly, the controller of screw feeder was turned on to push thefeedstocktothereactoratanaccuratefeedrate.Afterpyrolysis, thesmallsizedsolidproductwasblownoutandseparatedatthe cyclone,whilethelargersizedparticlesweredrawnouttothebottle belowthereactor.Afterpassingthroughthecyclone,themixtureof

twocondensers,whichusedachillerwithcoolantat208C.Mostof

theliquidproductwascondensedandcollectedintwo-neckflasks,

whiletheothernon-condensablecompoundswereretainedatthe

cottonfilterlocatedattheendofequipment

Theweightofliquidproduct,Wliquid,isdefinedastheweight

differenceofthetwocondensersandthecottonfilterbeforeand

after pyrolysis The liquid yield of the fast pyrolysiswas then

calculatedbasedontheequationshownbelow,

Liquidyieldðwt%Þ¼ Wliquid

Wbiomass

100%

whereWbiomass isthe weightof thebiomass feedstock usedin

experiments

2.3 Productanalysis

Thebio-oilwasfirstdissolvedinpureacetoneandthenanalyzed

byGC–MS.TheGC–MSanalysisofpyrolyzingoilwas performed

usinganAgilentTechnologies7890AGCequippedwithanAgilent

Technologies 19091S-433 column (30m0.25mm0.25mm)

andamassspectrometer(AgilentTechnologies5975C).Thecarrier

gaswasheliumataflowrateof1mL/min.Thecolumntemperature

wasinitiallyheldat408Cfor5min,thengraduallyincreasedto

2808Cat108C/min,andfinallymaintainedat2808Cfor10min.The

injector and detectortemperatures were setat 250and 2808C,

respectively

The ashcontent of thebio-oil was determinedusing ASTM

E1755-01(2001)[10].TheelementalanalysesforC,H,O,N,andS

werecarriedoutusinganautomaticelementalanalyzer(EA,Flash

EA1112,CEInstruments).Thewatercontentwasanalyzedusinga

methodpreviouslyreportedintheliterature[11].When1.0gof

anhydrousCaCl2wasaddedintoasolutionof10mLofacetone

containing water, the exothermic energy led to an increased

temperatureofthesolutionwhichdependsonthewatercontent

Basedonthisprinciple,acalibrationcurveshowingthe

relation-ship between thewater contentand the temperaturerise was

constructed.Usingthiscalibratingcurve,itwaseasytocalculate

thewatercontentexistinginthepyrolyzingliquidproduct

2.4 Experimentaldesign

Experimentaldesignreferstotheprocessofplanning,

design-ing, and analyzing experiments so that valid and objective

conclusions can be efficiently made [12,13] In practice, the

second-order design referred to as central composite rotatable

design (CCRD) is commonly employed, especially in chemical

engineering[9]

Forthedesign,amatrixofcodedvariables(X)isinitiallysetup

toplantheexperiments.Thenumberofrowsinthismatrixorthe

totalexperimentstorun(n)dependsonthefactor(k)accordingto

thefollowingexpression:

n¼2kþ2kþno¼njþnaþno

wherenois thenumber ofreplicated experiment atthecenter

point.Therefore,thenumberofexperimentalrunsincludesnj=2k

experimentsatthecorepoints(X=1),na=2kexperimentsatthe

axialpoints(X=a=2k/4),andnoexperimentsatthecenterpoint

(X=0)

Corresponding to each set of variables in this matrix,

the response value from the experiments can be obtained

Subsequently, the experimental data are fit to a polynomial

mathematicalmodelofsecondorder,asshownbelow

Y¼boþXk

i¼1

biXiþXk i¼1

Xk

j > i

bijXiXjþXk

i¼1

whereXiandXjarethecodedvariablesfromtheactualxi,andxj

variables,respectively.Yrepresentstheresponsevaluefromthe experimentwhileboisthevalueofthefittedresponseatthecenter pointof thedesign bi,bii,andbijarethelinear,quadratic, and interactionterms,respectively.Thecodedvariablewasachieved fromtheactualvariablebasedonthefollowingexpression[14]:

Xi¼xix

o i

where

xo

i is the midpoint value of the actual variable xi ðxo

i ¼

½xmax

i þxmin

i =2Þ,Dxiistheintervalvalueoftheactualvariablexi

ðDxo

i ¼½xmax

i þxmin

i =2Þ,andxmax

i ;xmin

i arethehighandlowlevels

oftheactualvariable,respectively

Alltheregressioncoefficients(bo,bi,bii,bij)werecalculatedas follows:

bo¼a1

Xn u¼1

Yua2

Xk i¼1

Xn u¼1

X2

bi¼a3

Xn u¼1

bi j¼a4

Xnj u¼1

bii¼a5

Xn u¼1

X2

iuYuþa6

Xk i¼1

Xn u¼1

X2

iuYua7

Xn u¼1

wherea1,a2,a3,a4,a5,a6,anda7areconstantsdeterminedfrom literature[14].Incaseofexperimentwithfourfactors,a1,a2,a3,a4,

a5,a6,anda7are0.1428,0.0357,0.0417,0.0625,0.0312,0.0037, and0.0357respectively

Once all the regression coefficients were determined, their statisticalsignificancewasthenestimated.Aregressioncoefficient

isstatisticallysignificantifitsabsolutevalueishigherthanthe confidence interval Finally, theobtained regression modelwas thencheckedforalackoffitbycalculatingtheFRvalue.IfFR<FT

(FT:tabularvalueoftheFisher-criterion),theregressionequationis consideredtobeadequate

3 Resultsanddiscussion

parameters.Thecodedvaluesweredesignatedby1(minimum),

0(center),+1(maximum),a,and+a.Theselectionoflevelsfor each factor was based on previous pyrolysis reports of other biomassusingafluidizedbedreactor.Theinvestigated tempera-turerangewasfrom400to5008Csincethebiomasscontaining hemicellulose, cellulose,andligniniseffectively decomposedin thistemperaturerange,asreportedbyDemirbasandArin[5].The residencetime,whichwasintherangeof0.6–0.9s,waslimitedby thefactthatthepyrolysisonlyeffectivelyyieldsahighbio-oilyield

iftheresidencetimeislessthan1s[4].Thebiomassparticlesize rangeselectedwas300–600mminordertomakethescrewfeeder operatewell.Becausepalmkernelcakecontainsresidualpalmoil

at an amount of up to 10.7wt% (determined by the acetone washing methodpreviously mentioned),it willbe stickyifthe particlesizeistoosmall.Dependingonthesizeofthereactor,a feed ratein therangeof 160–300g/hwasappropriate.Table 2

designmatrix.Theobtainedliquidyieldforeachconditioninthis

table was presented in form of the average value of

two-experimentrunvaluesandplus/minusthestandarderror

3.1 Checkingthefittedmodels

Eqs.(3)–(6)andtheF-testoftheobtainedmodels.Thesignificance

ofeachregressioncoefficientwasalsoverifiedandispresentedin

coefficient by its standard error A coefficient was considered

significantifthemagnitudeofitst-testvaluewaslargerthanthe

standardt-distributionatacertainconfidence.Inthisstudy,a95%

confidencewasselected.Alargetvalueimpliesthatthecoefficient

ismuchgreaterthanitsstandarderror.Ascanbeseeninthet-test

valuesfortheliquidyieldinTable3,mostofthecoefficientswere

significant,exceptfortheb14andb33coefficient.Therefore,these

twocoefficientscanbeeliminatedfromtheregressionequationof

theliquidyield

Subsequently,theF-testvalueoftheregressionmodelwasalso

calculated.TheobtainedF-testvaluewassmallerthantheF-value

fromthestandardF-distributionwithaconfidenceof99% This meansthattheregressionequationwasadequate.Thisadequacy can be revealed by the relationship between the actual and predictedvaluesoftheliquidyield.Itclearlyshowsthatthemodel successfullycorrelatestheprocessparameterstotheliquidyield withacorrelationcoefficientofR2=0.99

Finally,thepredictiveresponseequationcontainingallofthe significantcoefficientswasdetermined,asshownbelow

Incodedunits:

3.2 Effectofoperatingparametersonthefastpyrolysisperformance Fromtheregressionequation,itcanbeseenthattherearethree types of effects of the variables on the response value: main, squared,andinteractioneffectscorrespondingtothebi,bii,andbij

coefficients,respectively.Asforthemaineffects,themagnitudesof thet-testwereobtainedintheorderasfollows:b2(59.06)>b3

(30.6)>b1(16.3)>b4(4.3).Itisalsoknownthatthehigherthe t-testvalueofacoefficient,themoresignificanttheeffectofthe coefficient.Therefore,it canbeconcludedthattheX2(pyrolysis temperature)andX3(residencetime)variableswerethetwomost important factors havingthe strongest effects on the response value.Theorderofthesignificanteffectontheresponsevaluecan

Table 2

Experimental design matrix and response values.

Run X 1 X 2 X 3 X 4 Liquid yield (%) Run X 1 X 2 X 3 X 4 Liquid yield (%) Experiment at core point Experiment at axial point

1 1 1 1 1 30.0  1.5 17 2 0 0 0 40.0  1.5

3 1 1 1 1 43.6  1.5 19 0 2 0 0 13.0  0.6

5 1 1 1 1 44.0  2.0 21 0 0 2 0 40.2  0.5

9 1 1 1 1 32.3  1.3 Experiment at center point

Table 1

Factor variation intervals.

Residence time, x 3 s 0.45 0.6 0.75 0.9 1.05 0.15

Particle size, x 4 mm 150 300 450 600 750 150

Yliq¼45:711:697X1þ6:142X2þ3:182X3þ0:446X4þ2:906X1X2þ1:794X1X3

4:069X2X3þ1:044X2X40:894X3X42:277X25:285X20:33X2 (7)

Inuncoded(actual)units:

Yliq¼529:1790:31x1þ2:177x2þ243:574x30:017x4þ8:3104x1x2þ0:171x1x3

0:543x2x3þ1:392104x2x40:040x3x44:647104x2

2:114103x2

1:467105x2

(8)

be arranged as follows: X2>X3>X1>X4 Since there are four

factorswhich affectedthepyrolysisprocess, itis impossible to

presentalltheeffectsonthesame3Dgraph.Asaresult,twofactors

wereheldconstant,whiletheotherswerevariedleadingtothe3D

graphsshowninFigs.2–4

Indeed, pyrolysis is a cracking reaction to break a high

molecular weight hydrocarbon chain into smaller compounds

Pyrolysisisalwaysanendothermicprocess.Consequently,when

thepyrolysistemperatureincreases,theproductyieldincreases

However,itshouldbenotedthatifthetemperatureexceedsthe

valueatwhichtheproductsdecompose,theobtainedproductyield

decreases.Therefore,itwasfoundthattheliquidyieldincreases

withpyrolysistemperatureuntilthedecompositiontemperature

is achieved, after which the yield decreases with increasing

temperature

Intheexperimentsconductedatalowtemperatureof4008C,

thereceivingenergymaynotbeenoughtocompletelydecompose

thebiomass,asshowninFig.2.Iftheresidencetimewasdecreased

byincreasingtheflowrateofthefluidizinggas,moreandmore

reactor.Whenfeedstockispushedoutofthereactor,thebiomass

conversionis obviouslynotcomplete,thusleadingtoa reduced liquidyield.Atthehightemperatureof5008C,thebiomasscanbe completelydecomposed.Hence,iftheresidencetimeisdecreased (ortheflowrateofthefluidizinggasisincreased),theproductcan

bepushedoutofthereactorasquickaspossibleinordertoavoid decompositionofthebio-oil,whichthereforeresultsinincreasing theliquidyield

Fig.3showsthatthefeedratehasmoreeffectonliquidyield thantheparticlesize.Atacertainpyrolysistemperature,residence time and particle size, the increase of feed rate results in morebiomassaccumulatedinsidethereactor.Consequently,the efficiencyoftheheattransferinsidethereactorislowered,leading

to incomplete decomposition of the biomass Therefore, it is observedthathigherliquidyieldisobtainedatthelowerfeedrate

On thecontrary,theeffectofparticlesizeonliquidyield isnot noticeable.Withincreasingtheparticlesizefrom300to600mm, theliquidyieldincreaseslessthan5%

Fig 3 Liquid yield at a pyrolysis temperature of 400 8C and a residence time of 0.9 s.

m

Table 3

Statistical significance of regression coefficients.

Coefficient t-test Significance

F R 3.32

F T 7.87

+ = significant;  = insignificant; degree of freedom f = 6, t-student (0.05) (6) = 2.45.

a

F T : referenced in [9]

m

Fig 4 showstheeffect oftemperature andfeed rate on the

liquid yield at the residence time of 0.9s and particle size of

600mm.Bothtemperatureandfeedrateinfluencesignificantlyon

theliquidyieldinformofasecond-orderpolynomial.Fig.4also

showsthattheliquidyieldisinverselyproportionaltopyrolysis

temperature.Incontrast,theliquidyieldrisestoamaximumand

thendecreaseswithincreasingthefeedratefrom160to300g/h

3.3 Optimizationofoperatingparameters

The analysis of the response surface from the mathematic

model of liquid yield yielded the stationary point (X1=0.149,

X2=0.597,X3=0.356,andX4=1.139)atwhichthederivativeof

theequationiszeroand islocatedoutsidethesurveyedregion

Therefore,theoptimalresponsevaluesmaybedeterminedatone

oftheboundariesoftheinvestigatedvariableranges[9].Inorderto

specifytheoptimalresponsevalues,atrialanderroralgorithmwas

applied for the equation of the liquid yield in coded units A

procedureusing Matlab wassetupas a looptosearch for the

conditioninthesurveyedrange atwhichtheresponsefunction

achievedthehighestvalue

Onceobtained,theoptimalcondition(X1=0.1,X2=1,X3=1,

and X4=1) was then converted into the respective uncoded

(actual)units using theformulas shown in Eq.(2) Finally, the

optimalvaluesofthefeedrate,pyrolysistemperature,residence

time,andparticlesizewerefoundtobe225g/h,5008C,0.6s,and

600mm,respectively,correspondingtothehighestliquidyieldof

49.5wt%

Inordertochecktheaccordancewiththeregressionmodel,the

experimentatoptimalconditionwasalsoperformed.Theliquid

yield obtained was 50.31.4% This result shows that the

experimentwaswellfittedwiththemodel

3.4 Characteristicsofpyrolyzingliquidproduct

Thephysicalpropertiesofbio-oilareusefulintheevaluationof

treatment technology and the selection of process equipment

directlyaffectstheapplicationandefficiencyofbio-oil.Theliquid

productobtainedfromexperimentrunattemperatureof5008C,

feedrateof300g/h,particlesizeof300mm,andresidencetimeof

0.6swasusedforcharacteristicanalysis,includingashandwater

contents,density,andamountsofcarbon,hydrogen,oxygen,and

nitrogen.TheresultsareshowninTable4.Ascanbeseeninthis

table,theashcontentiszero,whichsuggeststhatthisbio-oilhas

obviousadvantagesasacleanfueloil.Thedataalsoshowthatthe

watercontent, aproduct of thedehydrationreaction occurring

duringthepyrolysis[15],wasratherconsistentandintherangeof

15–30%,asreportedbyCzernikandBridgwater[15]

From the elemental analysis results, the heating value was

obtainedusingtheformulashownbelow[16],

HHVðMJ=kgÞ ¼ f33:5½Cþ142:3½H15:4½O14:5½Ng102 (9)

where [C], [H], [O], and [N] are the contents (wt%) of carbon,

hydrogen, oxygen, and nitrogen, respectively The calculated

heating value is just 13.9MJ/kg, which is rather small in

comparison with other conventional fuels such as petroleum

(43MJ/kg),LPG (45.75MJ/kg),or kerosene (41MJ/kg) [16] The

reasonforthisresultismainlyduetothehighcontentofoxygen

andnitrogenremaininginthebio-oil.Infact,itcanbeobserved

fromformula(9)thattheheatingvaluedecreaseswithincreasesof

boththeoxygenandnitrogencontents.Theoxygencanexistinthe

formofwateroroxygenatedcompoundssuchasketones,phenols,

andesters.Duetothehighoxygencontent,challengesremainin

the further utilization of the bio-oil as a fuel oil Therefore,

additionalupgradingincludingdeoxygenationisnecessary

frompyrolysisexperimentsattemperaturesof400and5008Cat thesamefeedrate(300g/h),particlesize(300mm),andresidence time(0.6s).Accordingtothedata,thedetectablecomponentsof the bio-oil were acetic acid, ketones, derivatives of furan, phenolics, esters, b-D-allose, and fatty acids As reported by Yaman[17],thebio-oilfrompyrolysisoflignocellulosicbiomass was largely composed of alcohols, aldehydes, ketones, organic aicds,ester,phenolics,andlevoglucosan

Obviously,itcanberealizedthatthereexistssomedifferences

intheproductdistributionobtainedinthisstudyandthatofother researchers.Themostnoticeabledifferencewasthepresenceofb -D-allose(aC3epimerofglucose[18])atanamountofuptoaround 20% while some compounds such as alcohols, aldehydes, and phenolicswerepresentatsmallerquantities.Theseresultscanbe explainedbythedifferencesinthebiomasscompositions.Indeed,

(C6H12O6) units (C2 epimer of glucose [18]) Basically, when a polymeristhermallydecomposed,itschainiscrackedtorelease lowermolecular compoundsincludingmonomer,dimer,trimer, tetramer,oligomer,andsomeothercompoundsdependingonthe reactionconditions.Duringthiscrackingprocess,varioustypesof reactionsmayoccursuchastranspositionofC,H,orcleavageofthe C–Clinkage[19].Foramonomer,theremaybea changeinthe molecular structure compared to its initial structure unit

Table 5 GC–MS analysis of bio-oil obtained from pyrolysis of palm kernel cake at the optimal conditions.

N o Compound 400 8C 500 8C

Area (%) Area (%)

1 Acetic acid 11.6 5.0

2 1-hydroxy-2-propanone 7.83 3.1

4 4-hydroxy-4-methyl-2-pentanone 0 3.0

5 2-Furanmethanol 10.3 5.0

6 2 (5H)-Furananone 4.04 0

7 1, 2-cyclopentanedione 2.03 0

8 2-furancarboxaldehyde, 5-methyl- 1.34 0

10 2-furancarboxylic acid, hydrazide 1.91 0

11 Benzenecarboxylic acid 0 2.9

13 1, 2-benzenediol 2.51 2.7

14 2, 3-o-acetonemannosan 3.05 2.8

15 b-D-allose 19.23 23.2

16 Dodecanoic acid 3.77 11.2

17 Tetradecanoic acid 0.88 3.6

18 Hexadecanoic acid 0 1.5

19 6-octadecenoic acid (Z) 0 2.6

20 1, 2-benzenedicarboxylic acid, bis (2-ethylhexyl) ester

9.34 14.9

Table 4 Physical and chemical properties of pyrolytic oil obtained from an experiment at

500 8C.

Ash content (%) free Water content (%) 12.1 Elemental analysis (%)

Empirical formula C 12.25 H 35.13 O 14.87 N Heating value (MJ/kg) 13.9

moleculesofb-D-alloseand mannose,itcan beseen thattheir

structuresarerathersimilarandhavethesamemolecularformula

Therefore,it canbeconcludedthatb-D-allose wastheproduct

obtainedfromthedecompositionof mannancomponentin the

palmkernelcake

Apartfromb-D-allose, a considerableamountof fattyacids

werealsodetectedinthepyrolyzedbio-oilofPKCmainlyincluding

dodecanoicandtetradecanoicacid.AsreportedbyDemirbas[20],

oilsderivingfromplantsarebuiltupwithtriglyceridemolecules

Whenthismoleculeisdecomposedunderthermalconditions,the

threebranchesmakingthestructureofthemoleculearerandomly

cleavedtogeneratefattyacidsandothersmallermolecules.Based

onthisresult,thefattyacidscanbeattributedtothepyrolysisof

theremainingpalmoilintherawbiomassfeedstock

Moreover,ascanbeseeninTable5,theaceticacid,

1-hydroxy-2-propanone, and 2-furanmethanol contents decreased with

increasedpyrolysis temperature.This meansthat the pyrolysis

processpreferablyproducedthesecompoundsatlower

tempera-tures In contrast,thecontents of two majorcompounds,b

-D-alloseand1,2-benzenedicarboxylicacid,bis(2-ethylhexyl)ester,

increased proportionally to the pyrolysis temperature As

explainedpreviously,b-D-alloseisaproductofmannan

decom-position.Therefore,itscontentonlyincreasesifthedegradation

reactionofmannanoccursmorecompletely.Inaddition,whenthe

pyrolysistemperatureincreased,thecrackingreactionof

triglyc-eride was also favored to produce fatty acids, as reported by

Demirbas[20].Asaresult,itwasfoundthatthecontentofeach

fattyacidincreasedwithincreasingpyrolysistemperature

4 Conclusions

The fast pyrolysis of palm kernel cake was conducted by

applyingthecentralcompositerotatabledesigninafluidizedbed

reactorovera rangeofvariables asfollows:afeedrateof160–

300g/h,apyrolysistemperatureof400–5008C,aresidencetimeof

0.6–0.9s, and a particle size of 300–600mm The results

demonstratedthat theexperimentaldata werewellfittedwith

asecond-orderregressionequation.Therefore,theeffectsofthe

fouroperatingparametersonthefastpyrolysiswereelucidated Theorderofsignificanceofeachoperatingparameterfactorwas obtained as follows: pyrolysis temperature>residence time

->feedrate>particlesize.Thehighestliquidyieldachievedwas 49.5wt% at a feed rate of 225g/h, a pyrolysis temperature of

5008C,aresidencetimeof0.6s,andaparticlesizeof600mm The pyrolysis was conducted at temperatures of 400 and

5008Candtheobtainedproductsweresubsequentlyanalyzedin ordertodeterminethereactioncharacteristics.Thepyrolyticoil contained a considerable amount of oxygen, which led to a reduced heating value This bio-oil largely contained 1, 2-benzenedicarboxylicacid-bis(2-ethylhexyl)ester,b-D-allose, andfattyacids

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