玉米芯半焦CO_2等温气化特性及动力学

Gasification characteristics and kinetics of corncob char with CO_2 by using isothermal thermogravimetry

为研究玉米芯半焦在CO2气氛中的气化特性,采用等温热重法考察了5、40、100℃/min热解升温速率和800～1000℃反应温度对气化反应活性影响的程度。结果表明,随着热解升温速率的提高,半焦气化的总反应速率有所提高,完成反应所需要的时间相应减少。反应温度对整个气化过程有着重要的影响。随着温度的升高,反应速率明显加快,反应时间显著缩短。通过扫描电镜观察了不同热解升温速率下半焦的表面形态,表明热解升温速率越高,半焦表面的孔径越大,孔结构越发达。对比分析可知,反应温度比热解升温速率对气化过程有着更加重要的影响。最后用混合反应模型求取了动力学参数,玉米芯半焦CO2等温气化的平均表观活化能为98.7kJ/mol,指前因子为519176min-1。该研究结果将有助于深入理解生物质气化的反应机理,为气化装置的设计提供参考依据。

In order to research gasification characteristics of corncob char with CO2,the reactivity and kinetics were investigated by isothermal thermogravimetry（TG） at 800–1 000℃ with pyrolysis heating rates of 5,40,100℃/min. The results showed that the char reaction activity increased and the whole reaction time was relatively shortened with raising the heating rate. On the other hand,the reaction temperature had a remarkable effect on the corncob char gasification. With increasing the gasification temperature,the reaction rate speeded up distinctly and the reaction time became short evidently. Scanning electron microscopy（SEM） was employed to observe the corncob char structure. The results indicated that the faster the pyrolysis heating rate was,the bigger the hole on the char would be,and also the more abundant the pore structure was. It can be concluded that the reaction temperature has a greater influence on the gasification process than the pyrolysis heating rate. Finally,the mixed reaction model was used to calculate kinetic parameters,so the average activation energy of isothermal gasification of corncob char with CO2 was 98.7 kJ/mol and the pre-exponential factor was 519 176 min-1. The study can help to understand the reaction mechanism of biomass gaisification and provide reference for the design of gasification equipment.