耦合变压精馏分离甲醇-丙酸甲酯共沸体系的工艺模拟和优化

Process simulation and optimization of the separation of a methanol-methyl propionate azeotropic system by coupled pressure swing distillation

在丙酸甲酯和正丙醇酯交换法生产丙酸丙酯的过程中,反应精馏塔的塔顶会产生大量的丙酸甲酯和甲醇共沸物,可通过分离的手段使其中的丙酸甲酯循环使用。提出耦合变压精馏工艺,选用非随机(局部)双液体模型方程(NRTL)热力学模型,利用Aspen Plus V10.0对工艺流程进行模拟研究。以塔釜产品纯度为约束变量,高压塔塔釜能耗最低为优化目标,分别对理论板数、进料位置、回流比等参数进行优化,优化后的两塔最优工艺参数如下:常压塔理论板数31,回流比2.5,进料位置第9块塔板,循环物料进料位置第14块塔板;高压塔操作压力500 kPa,理论板数21,进料位置第13块塔板,回流比3.3。分离效果可达到甲醇质量分数99.95%,丙酸甲酯质量分数99.94%。与传统变压精馏相比,本文的耦合变压精馏可节省能耗48.8%。

In the process of transesterification of methyl propionate and n-propanol to produce n-propyl propionate, a large number of azeotropes of methyl propionate and methanol are produced at the top of the reactive distillation column, and methyl propionate needs to be recycled by separation. A coupled variable pressure distillation process has been proposed to achieve this,and Aspen Plus process simulation software has been used to design and simulate the process using the NRTL thermodynamic model. Taking the purity of the tower kettle product as the constraint variable and the energy consumption of the high-pressure tower reboiler as the optimization target, the theoretical plate number, feed position and reflux ratio were optimized. The optimized parameters were as follows: number of theoretical plate for the atmospheric pressure column=31, mass reflux ratio=2.5, feed at position 9, feed plate position of circulating materials at position 14;for the high pressure column, operating pressure=500 kPa, number of theoretical plates=21, feed at position 13, reflux ratio=3.3. Under these conditions, high purity-methanol(99.95 wt%) and methyl propionate(99.94 wt%) were obtained. Compared with the traditional variable pressure distillation, the coupled variable pressure distillation process can reduce energy consumption by 48.8%.