微型流化床中不同CO_(2)分压下煤焦气化反应动力学研究

Study on gasification reaction kinetics of coal char under different CO_(2) partial pressures at micro fluidized bed reaction analyzer

利用新开发的微型流化床反应分析仪(MFBRA)开展了煤焦-CO_(2)等温气化反应实验,考察了气化剂分压对半焦气化反应特性的影响,并与热重分析仪(TGA)中的气化反应行为和动力学进行了对比。结果表明,与TGA相比,相同条件下,MFBRA测定的反应速率更高,利用等转化率法计算得到的活化能偏大,这主要是由于MFBRA中均匀的温度分布、高传热速率及对气-固反应扩散的有效抑制。分析MFBRA中气化剂分压影响发现,高气化剂分压下,半焦具有更高的反应速率和更短的气化反应完成时间,且CO_(2)分压大于20%时,分压对气化反应的影响有限。总体而言,各气化剂分压下半焦气化反应在不同转化率下的活化能分布均匀,这进一步说明MFBRA内低气体扩散在半焦气化反应行为测定和动力学求算准确性方面的优势,求得的数据更贴近实际情况。

A newly-developed micro fluidized bed reaction analyzer(MFBRA)was adopted to test the isothermal reaction behavior of coal char gasification with CO_(2) and the effect of partial pressure of gasification agent on the gasification reaction characteristics of char was investigated.Meanwhile,the above experiments were compared with the gasification reaction behavior and kinetics in the thermogravimetric analyzer(TGA).The results show that compared with TGA,the reaction rate measured by MFBRA is higher and the activation energy calculated by equal conversion method is larger under the same conditions,which is mainly due to the uniform temperature distribution,high heat transfer rate and effective inhibition of gas-solid reaction diffusion in MFBRA.By analyzing the effect of partial pressure of gasification agent in MFBRA,it is found that under the high gasification agent partial pressure,the char has higher reaction rate and shorter gasification reaction completion time.For the CO_(2) partial pressure above 20%,its impact becomes not very obvious.Totally,the activation energy distribution of the char gasification reaction at different conversion rates is uniform under the partial pressure of each gasification agent.The results further demonstrates the advantages of low gas diffusion in MFBRA in the measurement of reaction behavior of the char gasification and the accuracy of kinetic calculation,and the calculated data from MFBRA are more close to the actual situation.