甲醇制烯烃装置脱甲烷和丙烯回收控制的模拟优化

针对某公司180万t/a（以甲醇进料计）甲醇制烯烃（MTO）装置运行中能耗高的问题，用Aspen Plus软件对该装置的脱甲烷塔（T 202）和丙烯回收单元进行了模拟和灵敏度分析，确定了简单可行的优化改造方案。结果表明:T 202、丙烯回收单元精馏塔（T 205）的灵敏板分别为第9，第85块塔板，其灵敏板的运行参数与相应产品控制组分变化呈现一一对应关系，均可反映并指导相应塔釜及其产品质量的操控；用流经冷却器（E 201）的碳四洗液加热T 202的进料至0 ℃，不仅可使其乙烯产品满足质量分数不小于99.95%的质量控制要求，而且可降低再沸器和冷凝器的能耗，节省丙烯冷却剂费用402.6万元/a；当T 205和T 206丙烯回收单元两精馏塔的操控压力分别降至1.674，1.600 MPa时，不仅T 206的回流比可降为12.3，并可将T 205塔底丙烷产品中含丙烯质量分数降至0.2%，减少丙烯损失量约为70 kg/h，同时相应减少冷凝器循环水、再沸器急冷水的消耗量分别为62.9，18.9 t/h。

Simulation and optimization of demethanization and propylene recovery control in methanol to olefins unit

Aiming at the problem of high energy consumption in the operation of the methanol-to-olefin （MTO） unit with the processing capacity of 1.8 Mt/a（basing on methanol feed）， Aspen Plus software was used to simulate and analyze the sensitivity of the demethanizer（T 202） and the propylene recovery unit， and a simple and feasible optimization scheme was worked out. The results showed that: the sensitive plate of T 202 and the rectification tower（T 205） of propylene recovery unit was the 9th， 85th plate， respectively， and the operation parameters of the sensitive plate were in one-to-one correspondence with the changes of the control components of the corresponding target products， which could reflect and guide the operation of T 202， T 205 and the relevant product quality control. It not only made its ethylene product meet the quality control requirements（mass fraction not less than 99.95%） by heating T 202 feed to 0 ℃ with the C4 washing liquid flowing through the cooler E 201， but also reduced the energy consumption of reboiler and condenser， saving the cost of propylene coolant of 4.026 million Yuan/a. When the control pressure of both rectifying columns T 205 and T 206 of the propylene recovery unit was reduced to 1.674，1.600 MPa， respectively， not only the reflux ratio of T 206 decreased to 12.3， but also the mass fraction of propylene in the bottom propane product of T 205 could be reduced to 0.2%， and the loss of propylene can be reduced by about 70 kg/h， meanwhile， the consumptions of the circulating water for condenser and the quench water for reboiler could be reduced by 62.9， 18.9 t/h， respectively.