棉秆半焦与载镍橄榄石固-固化学链反应动力学研究

Kinetics of solid-solid reaction between cotton char and Ni/olivine in chemical looping gasification

本实验利用微型流化床反应分析仪(MFBRA)研究了棉秆半焦(CSC)与载镍橄榄石(Ni/olivine)的固-固化学链反应特性,利用模型拟合法在等温条件下对29种模型函数进行拟合计算,从中选取了最优的三种模型,计算出棉秆半焦和载氧体的固-固反应动力学。结果表明,CO和CO_2是CSC与Ni/olivine反应的主要气体产物,固-固反应过程中,先析出CO后再析出CO_2,CSC并不会完全转换成CO_2,产气中CO的浓度比CO_2大;随着反应温度的升高,产气中CO和CO_2的浓度和产率增加。CO、CO_2和CSC利用三种不同模型函数计算出来的活化能平均值分别为27.5、46.4和69.8 kJ/mol。利用热重研究了CSC和Ni/olivine非等温反应特性及动力学,结果表明,CSC和Ni/olivine的反应从750℃开始,在890℃时反应速率达到了峰值,非等温反应活化能为72.05 kJ/mol,这与MFBRA等温动力学活化能基本相似,说明生物质化学链气化过程中,半焦和镍基载氧体的固-固反应较容易发生。

Direct solid-solid reaction characteristics of cotton stalk char(CSC)and nickel loaded olivine(Ni/olivine)were studied using micro-fluidized bed reaction analyzer(MFBRA).Model fitting method was used to fit 29 model functions under isothermal conditions.Three optimal models were selected to calculate kinetics of the solid-solid reaction of cotton char and oxygen carries.The results show that CO and CO2 are main gas products of CSC and Ni/olivine.CO is first and then CO2 is evolved during the reaction.CSC does not completely convert into CO2,and concentration of CO is higher than that of CO2.With increasing reaction temperature,concentration and yield of CO and CO2 in the product gas increase obviously.The average activation energies for CO,CO2 and CSC are 27.5,46.4 and 69.8 kJ/mol,respectively.The non-isothermal reaction characteristics and kinetics of CSC and Ni/olivine were studied by thermogravimetric analyzer(TGA).The results show that reaction of CSC and Ni/olivine starts at 750℃,and reached the peak at 890℃.The activation energy of non-isothermal reaction is 72.05 kJ/mol,which is in accordance with the result of MFBRA.It indicates that the solid-solid reaction between char and nickelbased oxygen carrier easily occurs in during chemical looping gasification of biomass.