oxidation of metals Oxidation behavior of biomass chars.doc

oxidation of metals Oxidation behavior of biomass chars Fuel83(2004)1495–1503 www.fuel? Oxidationbehaviorofbiomasschars:pectinandPopulusdeltoides Hong-ShigShim1,MohammadR.Hajaligol*,VickiL.Baliga PhilipMorrisUSA,ResearchCenter,P.O.Box26583,Richmond,VA23261,USA Received14May2003;revised25November2003;accepted25November2003;availableonline5March2004 Abstract Biomasscharsofpectinandcottonwood(Populusdeltoides)werepreparedbyusingaheatingrateofabout18C/s,peakpyrolysistemperaturesof400?008C,andresidencetimesof10?0minatpeaktemperatures.Charsampleswerepyrolyzedinaheliumatmosphereusingathermogravimetricanalyzer(TGA).OxidationreactivitymeasurementsofthesamecharsamplesintheTGAwerecollectedafterconvertingtheheliumatmospheretoanoxygencontainingatmosphere.Reactivitiesweremeasuredusinganisothermalmethodatvariousreactiontemperaturesfrom400to7008Candoxygenconcentrationsof2?1%.Oxidationkineticparameterssuchasapparentreactionorderandapparentactivationenergieswereobtained.Scanningelectronmicroscopy(SEM)wasemployedtostudymorphologicalandstructuraldevelopmentinthecharsamplesasafunctionofheattreatmenttemperature.AninterestingmorphologicaldevelopmentonthesurfaceofthecharwasobservedbySEM,whichshowedevolutionofvesicleformationandwhiskergrowthasheattreatmenttemperaturesincreased.Itsimplicationoncharreactivityisdiscussed.Preliminaryresultsshoweddecreasingreactivitywithincreasingpeakheattreatmenttemperatures.Charreactivitywasaffectedmorebytheheattreatmenttemperaturethanbytheholdtimes(10?0min). q2004ElsevierLtd.Allrightsreserved. Keywords:Populusdeltoides;Pectin;Pyrolysis;Biomass;Char;Oxidation 1.Introduction Modelingofbiomasscombustionrequiresinformation onbothbiomasspyrolysisandcharoxidationprocesses.To understandtheseprocesses,itisimportanttounderstandthe effectofpyrolysisconditions,suchasheattreatment temperature(HTT),holdtimeatapeaktemperature,and heatingrateandtheeffectsofcarbonburnoutconversion levelsoncharoxidationreactivityandoxidationkinetics. Consideringthecomplexityandhe