苯-甲苯双效精馏的优化计算

建立了苯－ 甲苯单塔精馏的ＭＥＳＨ 方程组，采用分割技术用计算机进行迭代求解，得到了塔内各理论板的气液流量、温度和浓度分布及塔顶和塔底热负荷，并计算了该过程的热力学效率为１３ ．９７ ％ 。在此基础上，提出了苯－ 甲苯的并流型双效精馏流程，并对该流程进行了工艺分析，确定了高压塔塔顶采出量及回流比为两个塔的协调变量。在规定各塔压和高压塔塔底流量的条件下，以综合效益为优化目标，以两塔的回流比为决策变量，采用一维定步长搜索给出决策变量改进值的方法进行优化计算，确定了双效精馏流程的工艺操作条件。优化计算结果表明，高压塔压力为３４ ．３４ Ｎ／ｃｍ ２ ，回流比为１ ．１ ，低压塔压力为常压，回流比为３ ．２ 的双效精馏比单塔精馏可节约供热量３２ ％ ，节约蒸汽用量２８ ％ ，且双效精馏过程的热力学效率可提高４ ．３９ ％ ，是一种非常有效的节能措施

Optimization Calculation of Binary Distillation Column for Benzene-Toluene

The MESH equation system of one-column distillation process for benzene-toluene was established. With computer iteration calculation method, the distributions of gas flow, liquid flow, temperature, concentration on each theoritical bed and the heat loads on the top and bottom of tower were obtained. The calculated thermodynamic efficiency for one-column distillation process is 13.97%. Based on the simulation results, a binary distillation column was proposed in this paper, an analysis for the process was performed and the correlation variables between the two towers, the top flow rate from the high pressure tower and its reflux, were determined. Under the conditions that the tower pressure and bottom flow rate from the high pressure tower were given, taking comprehensive benefit as optimizing object, reflux ratio between two columns as decision variable, the optimization calculation was performed with one-dimension fixed step search method and the operating conditions for the binary distillation column were determined. The optimization results show that compared with the one-column distillation process, the binary distillation column with the operating pressure 34.34 N/cm 2 and reflux 1.1 in high pressure tower and mormal pressure and reflux ration 3.2 in low pressure tower can save energy by 32%,save steam consumption by 28%, increase thermodynamic efficiency by 4.39%. The binary distillation column has been confirmed to be an effective energy saving one.