甲醇制烯烃流化床反应器的模拟与分析

采用流化床两相模型描述甲醇制烯烃(MTO)过程,采用拉格朗日颗粒跟踪方法模拟催化剂上的积炭与反应,考察了相间传质、催化剂停留时间及返混对MTO过程的影响。结果表明,湍动流化床相间传质速率小于催化反应速率,是MTO过程的速率控制步骤;强化传质和延长催化剂停留时间都能显著提高催化剂的积炭量,有利于提高乙烯与丙烯的选择性;而减小催化剂返混或采用多级串连操作对反应选择性的改善作用不大,采用气固多级逆流操作反而会导致选择性显著下降。

Simulation of Fluidized Bed Reactor for Methanol to Olefins (MTO) Process

The two-phase model was employed to simulate the fluidized bed reactor for the continuous methanol to olefins(MTO) process over SAPO-34 catalyst.Followed by Lagrangian method,the MTO reactions and the coke accumulation on the SAPO-34 catalyst particles were investigated in detail,including the effects of the mass transfer rate,the catalyst residence time and the back-mixing of the catalyst particles on the MTO process.The results show that,the rate of the inter-phase mass transfer is much slower than the rate of the MTO chemical reaction,and the mass transfer is the controlling step in the fluidized bed MTO process.Increasing mass transfer rate or catalyst residence time,the coke accumulation on the catalyst will be promoted,which will also result in increasing the selectivity of ethylene and propylene.However,reducing the catalyst back-mixing or employing the multi-stage bed,the olefins products’ distribution is affected only a little.And the option of counter-current multi-stage bed even leads to a remarkable decrease of the selectivity of ethylene and propylene.