多区循环反应器中丙烯气相聚合的模拟分析

摘要

多区循环反应器是一种新型的丙烯气相聚合反应装置,聚合过程模型化研究对理解与剖析这一新型反应器具有指导意义.基于气固二相流在提升管和下降管中平推流模型,结合丙烯聚合反应动力学,建立了多区循环反应器中丙烯气相聚合的过程模型.模拟结果与Fabiano模型进行比较,验证了其可靠性;考察了反应器关键操作参数循环比对单体在反应器内的空间分布以及聚丙烯相对分子质量的影响;分析了提升管与下降管中单体浓度、氢气浓度和聚合物单程停留时间的参数敏感性.结果表明:增大循环比和减小聚合物颗粒在下降管中单程停留时间,聚合物平均相对分子质量都会降低;提升管中丙烯浓度、氢气浓度对平均相对分子质量影响小于下降管中,聚合物平均相对分子质量对下降管中的氢气浓度最为敏感.%Multizone circulating reactor is a new propylene gas-phase polymerization reactor.Modeling of propylene gas-phase polymerization in this reactor is instructive to understand and analyze this new reactor.With propylene homopolymerization kinetics mechanism, the multizone circulating reactor model was developed based on the assumption that riser model and downer model are plug-flow model.The result from the proposed model was compared with Fabiano's model and they were in good agreement with each other, which proved the accuracy of the model.The effect of recycling ratio as the key parameter on the monomer concentration in the reactor and relative molecular mass of polypropylene was investigated.Moreover, the parameter sensitivity analysis of propylene concentration, hydrogen concentration and the ratio of residence time in the riser and the downer were performed.The simulation results indicate that the effect of propylene concentration and hydrogen concentration in the riser on polymer average relative molecular mass is less than that in the downer.Polymer average relative molecular mass is the most sensitive to the hydrogen concentration in the downer.