甲醇制烯烃多级串联流化床反应器模拟

Simulation of multi-fluidized-bed in series for methanol to olefins

甲醇制烯烃(MTO)是现代煤化工发展的新技术,合理的甲醇制烯烃反应器操作模式可以有效提高催化剂的效率和低碳烯烃选择性。采用在工业SAPO34催化剂上实验得到的反应与失活动力学和流化床动态两相模型,结合颗粒停留时间分布模型,对MTO单一流化床反应器、二级串联及三级串联反应器进行了模拟,考察了催化剂停留时间、气固并流和气固逆流对甲醇制烯烃反应的影响。模拟结果表明:采用多级串联反应器有利于减小颗粒的返混,使出口积炭量分布更加均匀,催化剂寿命延长;二级气固逆流操作可以提高低碳烯烃选择性及出口催化剂积炭量,催化剂单位生产能力比单级反应器提高24.4%;三级串联、气固逆流反应器可以充分利用各级反应器的不同功能,使总的低碳烯烃选择性提高到79.36%(质量分数),比单级反应器提高1%,同时单位催化剂单程生产能力比单级提高31.1%。

Methanol to olefins （MTO） is a new technology of modern coal-to-chemicals industry. The catalyst performance and selectivity of light olefin in the MTO process can be remarkably improved by well-designed reactor operating mode. The simulation of MTO reaction in a single, two and three fluidized-bed connected in series was carried out by using the reaction and deactivation kinetics experimentally obtained on the commercial SAPO-34 catalyst, combined with fluidized-bed dynamic two-phase model and particle residence time model. The effects of catalyst residence time, gas-solid cocurrent and countercurrent flow on the MTO performance were investigated. The simulation results show that the catalyst coke content and selectivity of the light olefin depend on the catalyst residence time. The multi-bed in series operating mode will reduce the particle back-mixing, which results in a more uniform coke distribution and a longer catalyst lifetime. For the gas-solid countercurrent flow of two reactors in series, the second reactor is used to pre-coke the catalysts before entering into the first reactor and therefore the light olefin selectivity and the total coke content are increased. The catalyst production capacity of one pass is increased by 24.4% compared with that of single reactor mode. Three reactors connected in series mode can fully utilize the different functions of each reactor for pre-coking, MTO reaction and post-coking, bring about a 1% increase in the selectivity of the light olefin and a 31.1% increase in the catalyst production capacity when compared with the single reactor.