EPS聚合反应釜内混合过程的数值模拟

Numerical Simulation of Mixing Process in EPS Polymerization Reactor

可发性聚苯乙烯(EPS)的黏度较高,聚合搅拌反应釜作为EPS生产的核心装置,釜内物料的流动状态对产品质量有很大的影响,所以选择合适的搅拌器显得非常重要。文章采用CFD方法分别模拟了Rushton涡轮桨、三叶后弯桨和三叶PTU桨应用于反应釜时的混合过程。选用多重参考系法(MRF)及标准k-ε模型,分开求解了速度场和浓度场,分区讨论了不同桨型的混合特性。模拟结果表明:釜内流型对混合过程有决定性的的影响,Rushton桨以径向流动和周向流动为主,而三叶后弯桨和PTU桨以轴向流动和周向流动为主。从混合时间上看,除了液面监测点外,其它监测点的结果都是三叶后弯桨的混合时间最短。综合比较来看,三叶后弯桨的流场特性比较适合EPS聚合反应的高粘工况,混合效率相对较高。

The viscosity of expandable polystyrene （EPS） is relatively high. Polymerization mixing Reactor is the key devices of the production of EPS and the flow field in the vessel has a great effect on the quality of products, so itg very important to choose the appropriate agitator. In this study, the flow fields generated by a three-bladed backswept agitator, three-bladed PTU agitator and six-bladed Rushton turbine were simulated separately by using the CFD. A multiple reference frame （MRF） approach and standard k-turbulent model were used to predict the velocity and concentration profiles separately, and the mixing characteristics of three agitators were compared. The results show that flow field in the vessel has a critical influence on the mixing process, the flow field of Rushton turbine was dominated by radial and circumferential flow, and the other two agitators were controlled by axial and circumferential flow. In addition to the monitoring near the liquid-level, the mixing time of three-bladed backswept agitator is the shortest. The flow field characteristics of three-bladed backswept agitator are more appropriate for the high viscosity condition of EPS polymerization, and the mixing efficiency is relatively better. [ Ch ,5 fig. 11 ref. ]