KineticModelofBiomassPyrolysisBasedonThree-componentIndependentParallelFirst-orderReactions

Thepyrolysisbehavioroftwokindsoftypicalbiomass(pinewoodandcottonstalk)wasstudiedinnitrogenatmosphereatvariousheatingratesbythermogravimetricanalysis(TGA).Thepyrolysisprocesscanbedividedintothreestagesevolutionofmoisture(<200℃),devolatilization(200~400℃)andcarbonization(>400℃).ThecomparisonofDTGcurvesoftwobiomassmaterialsshowthatthehigherthehemicellulosecontentofbiomass,themoreevidenttheshoulderpeakofDTGcurve.Theweightlossprocessoftwomaterialswassimulatedbythekineticmodelassumingcellulose,hemicelluloseandligninpyrolyzingindependentlyandinparallel,obeyingfirst-orderreactions.Thepyrolysiskineticparameterscorrespondingtothethreecomponentswereestimatedbythenonlinearleastsquarealgorithm.Theresultsshowthattheirfittingcurvesareingoodagreementwiththeexperimentaldata.Theiractivationenergyvaluesforpinewoodandcottonstalkareintherangeof188~215,90~102,29~49and187~214,95~101,30~38kJ/mol,respectively.Thecorrespondingpre-exponentialfactorsareintherangeof1.8′1015~2.0′1016,1.6′107~7.1′108,9.3′101~1.5′103and1.2′1015~6.7′1017,1.2′108~1.4′109,1.4′102~4.6′102min-1,respectively.Inaddition,theactivationenergyofcelluloseandligninincreasedandtheircontributionstovolatiletendedtofall,whereastheactivationenergyofhemicellulosedecreasedanditscontributiontovolatiletendedtorisewithincreasingofheatingrate.