挥发分-半焦交互反应对生物质热解半焦特性的影响
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摘要
挥发分-半焦交互作用是生物质热化学利用过程普遍存在的现象。为了解析交互反应对生物质热解半焦特性的影响,利用一阶固定床/流化床反应器及快速热裂解仪进行实验。针对挥发分-半焦交互反应,对碱金属和碱土金属(AAEM)元素的析出特性展开了研究,同时分析了交互反应对生物质热解半焦反应活性的影响。结果表明在700~900℃范围内,交互反应的存在使得热解成焦率较无交互反应下有所提高。热解过程中交互反应导致了单价K元素析出量增加,对二价Ca/Mg元素的析出影响较小。挥发分-半焦交互反应的存在使得半焦反应活性对温度的敏感度降低,随温度的升高其反应速率的下降幅度变缓。
The volatile-char interaction is a common phenomenon during the biomass pyrolysis. In order to study the effect of volatile-char interaction on pyrolysis biochar, the one-stage fluided bed/fixed bed reactor and Py were used in the experiment. The AAEM analysis was carried out with/without the volatile-char interaction. The effect of volatile-char interaction on pyrolysis biochar reactivity was analyzed. The results showed that with increasing pyrolysis temperature from 700℃ to 900℃, the pyrolysis char yield was increased due to the volatile-char interaction as compared with the weak interaction. In the process of pyrolysis, the increase of precipitation of K was caused by the volatile-char interaction. The migration and precipitation characteristics of Ca/Mg elements did not have a significant change. The biochar sensitivity to temperature was reduced by volatile-char interaction and the reactivity of biochar was decreased with increasing temperature.
The volatile-char interaction is a common phenomenon during the biomass pyrolysis. In order to study the effect of volatile-char interaction on pyrolysis biochar, the one-stage fluided bed/fixed bed reactor and Py were used in the experiment. The AAEM analysis was carried out with/without the volatile-char interaction. The effect of volatile-char interaction on pyrolysis biochar reactivity was analyzed. The results showed that with increasing pyrolysis temperature from 700℃ to 900℃, the pyrolysis char yield was increased due to the volatile-char interaction as compared with the weak interaction. In the process of pyrolysis, the increase of precipitation of K was caused by the volatile-char interaction. The migration and precipitation characteristics of Ca/Mg elements did not have a significant change. The biochar sensitivity to temperature was reduced by volatile-char interaction and the reactivity of biochar was decreased with increasing temperature.
引文
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[18]ZHANG S.Effects of volatile-char interactions on char structure and reactivity during the gasification of low rank fuels[D].Melbourne:Monash University,2010.
[2]LI C Z.Importance of volatile-char interactions during the pyrolysis and gasification of low-rank fuels—a review[J].Fuel,2013,112(3):609-623.
[3]谢克昌.煤的结构和反应性[M].北京:科学出版社,2002:222.XIE K C.Coal Structure and Its Reactivity[M].Beijing:Science Press,2002:222.
[4]ZHANG S,MIN Z,TAY H L,et al.Effects of volatile-char interactions on the evolution of char structure during the gasification of Victorian brown coal in steam[J].Fuel,2011,90(4):1529-1535.
[5]ZHANG S,MIN Z,TAY H L,et al.Effects of volatile-char interactions on the evolution of char structure during the gasification of Victorian brown coal in steam[J].Fuel,2011,90(4):1529-1535.
[6]SONG Y,WANG Y,HU X,et al.Effects of volatile-char interactions on in-situ destruction of nascent tar during the pyrolysis and gasification of biomass(Ⅱ):Roles of steam[J].Fuel,2015,143(15):555-562.
[7]SONG Y,WANG Y,HU X,et al.Effects of volatile-char interactions on in-situ destruction of nascent tar during the pyrolysis and gasification of biomass(Ⅰ):Roles of nascent char[J].Fuel,2014,122(122):60-66.
[8]KEOWN D M,HAYASHI J I,LI C Z.Effects of volatile-char interactions on the volatilisation of alkali and alkaline earth metallic species during the pyrolysis of biomass[J].Fuel,2008,87(7):1187-1194.
[9]ASADULLAH M,ZHANG S,MIN Z,et al.Effects of biomass char structure on its gasification reactivity[J].Bioresource Technology,2010,101(20):7935-7943.
[10]QUYN D M,WU H,BHATTACHARYA S P,et al.Volatilisation and catalytic effects of alkali and alkaline earth metallic species during the pyrolysis and gasification of Victorian brown coal(Ⅱ):Effects of chemical form and valence[J].Fuel,2002,81(2):151-158.
[11]SCHAFER H N S.Chapter 7—Functional groups and ion exchange properties//The Science of Victorian Brown Coal[M].Elsevier,1991:323-357.
[12]TOMITA A,OHTSUKA Y.Chapter 5—Gasification and combustion of brown coal//Advances in the Science of Victorian Brown Coal[M].Elsevier,2004:223-285.
[13]SATHE C,YANYUAN PANG A,LI C Z.Effects of heating rate and ion-exchangeable cations on the pyrolysis yields from a Victorian brown coal[J].Energy&Fuels,1999,13(3):748-755.
[14]LI C Z,SATHE C,KERSHAW J R,et al.Fates and roles of alkali and alkaline earth metals during the pyrolysis of a Victorian brown coal[J].Fuel,2000,79(s 3/4):427-438.
[15]WU H,HAYASHI J I,CHIBA T,et al.Effects of volatile-char interactions on the reactivity of chars from the pyrolysis of brown coals[J].J.Am.Chem.Soc.,1932,6(4):1600-1602.
[16]ZHANG S,LUO Y,LI C,et al.Changes in char reactivity due to char-oxygen and char-steam reactions using Victorian brown coal in a fixed-bed reactor[J].Chinese Journal of Chemical Engineering,2015,23(1):321-325.
[17]LI C Z.Some recent advances in the understanding of the pyrolysis and gasification behaviour of Victorian brown coal[J].Fuel,2007,86(12/13):1664-1683.
[18]ZHANG S.Effects of volatile-char interactions on char structure and reactivity during the gasification of low rank fuels[D].Melbourne:Monash University,2010.