Variation of the pore structure of coal chars during gasification

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1、Carbon41(2003)507523VariationoftheporestructureofcoalcharsduringgasificationBoFeng,SureshK.Bhatia*DepartmentofChemicalEngineering,TheUniversityofQueensland,St.Lucia,QLD4072,AustraliaReceived16March2002;receivedinrevisedform10October2002;accepted11October2002AbstractThevariationoftheporestructureofsev

2、eralcoalcharsduringgasificationinairandcarbondioxidewasstudiedbyargonadsorptionat87KandCOadsorptionat273K.Itisfoundthatthesurfaceareaandvolumeofthesmallpores(,10A)do˚2notchangewithcarbonconversionwhenthecoalcharisgasifiedinair,whilethoseofthelargerpores(1020A,2050A,˚˚502500A)increasewithincreaseofcarb

3、onconversion.HoweverinCOgasification,alltheporesindifferentsizeranges˚2increaseinsurfaceareaandvolumewithincreaseofcarbonconversion.Simultaneously,thereactionratenormalizedbythesurfaceareaofthepores.10Aforairgasificationisconstantoverawiderangeofconversion(˚.20%),whileforCO2gasificationsimilarresultsar

4、eobtainedusingthetotalsurfacearea.However,intheearlystagesofgasification(,20%)thenormalizedreactionrateismuchhigherthanthatinthelaterstageofgasification,duetoexistenceofmoreinaccessibleporesinthebeginningofgasification.Theinaccessibilityofthemicroporestoadsorptionatlowandambienttemperaturesisconfirmedby

5、themeasurementoftheheliumdensityofthecoalchars.Therandomporemodelcanfittheexperimentaldatawellandthefittedstructuralparametersmatchthoseobtainedbyphysicalgasadsorptionforcoalcharswithoutclosedpores.Ó2002ElsevierScienceLtd.Allrightsreserved.Keywords:A.Coal,char;B.Gasification;C.Modeling;D.Porosity,Surfa

6、ceareas1.Introduction(TSA)[1316],suggestingtheratioofthereactingsurfaceareaandtheTSAisconstantduringgasification.Thegasificationrateofcoalchar/carboninoxygen,Incontrasttherehavebeennumerousreportsthatthecarbondioxideandsteamiswellknowntobegovernedbytotalsurfaceareadoesnotnormalizethereactionrateitsstr

7、ucture.Thereactiongaspenetratestheparticleandsuccessfully(e.g.[17,18]).Otherworksuggeststhatattacksthecarbonatomsandtheproductgasthendiffusesmicroporesmightnotbefullyutilizedduringgasificationoutthroug