Abstract:

The influence of two typical alkali and alkaline earth metal (AAEM),sodium and magnesium,on the gas releasing kinetics during rice husk high-temperature pyrolysis was investigated in a micro-fluidized bed reactor (MFBRA).Reaction kinetics for generating four main gases (H₂,CO,CH₄ and CO₂) was deduced based on universal integral method.Results indicated that different gas components had different times to start and end the gas releasing process,indicating different evolution routes and mechanics for generating these gas species.The conversion rate of four gases could be promoted at higher temperature or with the presence of AAEM.The gas releasing process was calculated by linear fitting method based on typical gas-solid reaction models and the most probable mechanism functions of four gas components were obtained at different conditions.The kinetic parameters of gaseous products calculated by most probable mechanism functions indicated that the resulting apparent activation energies for four gases decreased in presence of sodium and magnesium.Particularly,the effect of the two metal irons on the formation of CO was more obvious compared with the other gas species.From this study,the influence of two metal ions on biomass pyrolysis characteristics was confirmed on the basis of the variation of the activation energy.

Key words: micro-fluidized bed, pyrolysis, sodium, magnesium, kinetics, biomass

摘要：

通过微型流化床反应分析仪（MFBRA）研究两种典型碱金属和碱土金属（AAEM）钠与镁对稻壳热解气体生成动力学的影响，并采用模型积分法求解出4种主要气体组分（H₂、CO、CH₄与CO₂）的生成动力学参数。结果表明：不同气体组分具有不同的开始与终止释放时间，说明4种气体对应不同的生成路径和机理，高温条件和添加钠、镁离子均会提高气体生成的反应速率。采用典型气固反应动力学模型对气体生成过程进行了拟合求解，获取了气体组分在不同条件下的最概然机理函数。通过最概然机理函数求得了4种气体生成动力学参数，对比发现钠离子与镁离子降低了H₂、CO、CH₄与CO₂生成反应的表观活化能，其中CO受钠离子和镁离子的影响最为显著，进而从活化能角度证实了两种金属离子对于生物质热解特性的影响。

关键词: 微型流化床, 热解, 钠离子, 镁离子, 动力学, 生物质