松木屑颗粒热解过程中的热/质传递规律  

Rule of heat and mass transfer during the pyrolysis process of pine sawdust particles

作　　者：薛小慧 袁梦丽 宋云彩[1] 冯杰[1] XUE Xiaohui;YUAN Mengli;SONG Yuncai;FENG Jie(State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology,Taiyuan 030024,Shanxi,China)

机构地区：[1]太原理工大学省部共建煤基能源清洁高效利用国家重点实验室,山西太原030024

出　　处：《化工进展》2022年第12期6245-6254,共10页Chemical Industry and Engineering Progress

基　　金：国家重点研发计划(2019YFC1906802)。

摘　　要：为探索在固定床反应器中有机固废颗粒热解过程中的热量、质量传递机理,本研究从颗粒尺度上对有机固废松木屑颗粒热解过程建模分析,模型中考虑了焦油的二次裂解反应及挥发分在颗粒孔隙中的质量、动量传递过程,并采用达西定律模拟了挥发分在颗粒孔隙内的流动现象,对颗粒热解过程的吸热反应以及挥发分逸出时的对流换热对颗粒温度的影响进行考察。基于两步反应动力学模型,探讨了不同颗粒尺寸、热解温度对有机固废松木屑颗粒热解过程的影响。结果表明,热解吸热反应和挥发分的对流换热阻碍了热量向颗粒中心的传递,延长了颗粒达到均温的时间;松木屑颗粒热解时,颗粒内会存在明显的温度梯度,在颗粒表面主要受化学反应动力学限制,在颗粒内部则主要受热量传递过程限制。此外,热解温度越低,粒径越大,颗粒内部的传热阻力越大。松木屑颗粒完全热解所需时间会随着颗粒粒径的增大而增加,但当颗粒粒径在10mm以上时,随着颗粒粒径的增大,颗粒完全热解所需时间的增量要大于10mm以下颗粒。To explore the mechanism of heat and mass transfer during the pyrolysis process of organic solid waste particles in a fixed-bed reactor, the pyrolysis of organic solid waste, pine sawdust chosen as raw materials, was simulated and analyzed at the particle scale. The secondary cracking reaction of tar,the mass and momentum transfer of volatile in the pores of particles were considered. Additionally, the flow phenomenon of volatile in the particles was simulated by Darcy’s law. The effects of endothermic reaction and convective heat transfer on particle temperature during particle pyrolysis were also considered. Based on the model of two-step reaction kinetic, the effects of different particle sizes and pyrolysis temperature on the pyrolysis of organic solid waste particles were discussed. The results showed that the endothermic reaction and the convective heat transfer of volatile hindered heat transfer to particle center and prolonged the time for the particles to reach the average temperature. During pine sawdust particles pyrolysis, there was a significant temperature gradient inside the particles. The rate-control step for the pyrolysis of the particles surface was the chemical reaction kinetics while that inside the particles was heat transfer. Additionally, the results showed that the lower pyrolysis temperature was and the larger the particle size was, the more significant the heat transfer resistance was inside the particle. The time required for complete pyrolysis of pine wood chips particles would rise with the increase of particle size,but when particle size was above 10mm, the increment of time required for complete pyrolysis of pine sawdust was greater than that of particles below 10mm.

关 键 词：有机固废热解 传热 传质 数值模拟 

分 类 号：TQ021[化学工程]