苯、甲苯、二甲苯作为重要的基础化工原料，目前主要来源于石油裂解，而我国富煤少油，同时煤基甲醇产能过剩，因此需积极发展煤基甲醇制芳烃（MTA）生产工艺，对石油制芳烃进行补充，同时在“双碳”背景下，加强节能减排。MTA工艺流程主要分为4部分，即甲醇芳构化单元、芳烃-非芳烃分离单元、芳烃分离单元和非芳烃分离单元。根据不同物质及操作条件对MTA各单元选取了不同物性方法，分别为PRMHV2、UNIFAC、SRK、PENG-NOB，并修正其反应动力学参数，使模拟结果与试验结果基本一致。在此基础上，利用Aspen Plus对MTA工艺进行全流程模拟，通过灵敏度分析，优化了反应器、萃取精馏塔、甲苯提纯精馏塔的操作条件，最后采用变压精馏、完全热耦合精馏方法完成节能改造，并利用Aspen Energy Analyzer对工艺流程进行换热网络优化。结果表明，优化得到的反应器最佳反应条件为470 ℃，催化剂用量为7 000 kg，萃取精馏塔的最佳萃取剂用量为10 000 kg/h，甲苯提纯精馏塔的塔板数量为59，进料位置为29，回流比为3。节能改造后，变压精馏节约能耗43%，CO2排放量降低227.3 kg/h；完全热耦合精馏节约能耗56.26%，CO2排放量降低185.5 kg/h。经换热网络优化，MTA工艺节约能耗52.82%，即36.34 MW，减少CO2排放量64.40%，即6 282 kg/h。最终主产物的模拟结果为：纯度97.89%的苯产量397.28 kg/h，纯度99.99% 的甲苯产量2 772.81 kg/h，纯度99.99%的二甲苯产量5 486.49 kg/h。利用化工流程模拟软件对MTA工艺进行操作条件优化及节能改造，为实现MTA工艺工业化提供了参考意义，同时符合我国节能减排要求。

As important basic chemical materials, benzene, toluene and xylene are currently mainly derived from petroleum cracking. China is rich in coal and less in oil with an overcapacity of coal-based methanol. Therefore, it is necessary to develop coal-based methanol to aromatics (MTA) production technology and to save energy and reduce CO2 emissions. The MTA process flow was divided into four parts, namely methanol aromatization unit, aromatics/non-aromatics separation unit, aromatics separation unit and non-aromatics separation unit. Different physical property methods were selected for each unit according to different materials and operating conditions, namely PRMHV2, UNIFAC, SRK, PENG-NOB. The kinetic parameters were modified, so that the simulation results were basically consistent with the experimental results. On this basis, the MTA process was simulated by Aspen Plus. Sensitivity analysis was used to optimize the reactor, the extractive distillation tower and the toluene purification and rectification tower. Pressure swing rectification and complete thermal coupling rectification were used to carry out energy-saving transformation of the process. At last, the Aspen Energy Analyzer was used to optimize the heat exchange network of the process. The results show that the optimal reaction temperature of the reactor is 470 ℃, the catalyst dosage is 7 000 kg, the optimum extractant dosage of the extractive distillation column is 10 000 kg/h, and the number of trays of the toluene purification and rectification column is 59, the feed position is 29, and the reflux ratio is 3. After the energy-saving renovation, the pressure swing rectification saves 43% of energy and reduces CO2 emission by 227.3 kg/h; the completely thermally coupled rectification saves 56.26% of energy, reduces CO2 emission by 185.5 kg/h. After the optimization of the heat exchange network, the MTA process saves 52.82% of energy, namely 36.34 MW, and reduces 64.40% of CO2 emissions, namely 6 282 kg/h. The final simulated main products are benzene, toluene, xylene with purity of 97.89%, 99.99% and 99.99% respectively, and output of 397.28, 2 772.81 and 5 486.49 kg/h, respectively. The use of chemical process simulation software to optimize the operating conditions and energy-saving transformation of the MTA process provides a reference for the realization of the industrialization of the MTA process, and meets the requirements of energy conservation and emission reduction in China.

0 引言

1 MTA工艺模拟的模型设计

   1.1 工艺流程

   1.2 物性方法的确定

   1.3 反应动力学参数的确定

2 MTA工艺的模拟优化

   2.1 反应器的优化

   2.2 萃取精馏塔的优化

   2.3 甲苯提纯精馏塔的优化

   2.4 模拟结果

3 MTA工艺换热网络综合利用与优化

   3.1 变压精馏

   3.2 完全热耦合精馏塔

   3.3 全流程换热网络设计

4 结论