Abstract:

The UNIQUAC thermodynamic model parameters of dimethyl carbonate (DMC) -water (H₂O) mixture was corrected by regressing the literature data with Aspen Plus software. Based on this model, the separation principle of the ternary mixture by extractive distillation with water as extractant was analyzed. The reverse extraction distillation process extractive distillation process was designed according to the triangular phase diagram and the material composition. The results showed that taking advantage of the partial miscibility of DMC-water, the ternary mixture of DMC-methanol-water could be separated by three-column distillation when using water as extractant, while avoiding the formation of DMC-methanol binary azeotrope. Although DMC had a higher boiling point than methanol, DMC and a small amount of water were distilled from the top of the column, while methanol and most of the water were obtained from the bottom of the column. And the pressure swing distillation process was designed under the same separation requirements for comparison. Through the simulation and optimization of the two distillation process parameters, it was found that the total condensing load and total heating load of the extractive distillation process were 888.7kW and 898.2kW, respectively, and its total energy consumption was saved by 47.2% compared with the pressure swing distillation process. The total annual cost (TAC) of the extractive distillation process was 48.8% lower than that of the pressure swing distillation process.

Key words: extraction distillation, separation, azeotrope, dimethyl carbonate, methanol, water

摘要：

运用Aspen Plus软件回归文献数据校正了碳酸二甲酯（DMC）-水（H₂O）混合物的UNIQUAC热力学模型参数，并以该模型为基础分析了水作为萃取剂萃取精馏分离DMC-甲醇（CH₃OH）-水三元混合物的分离原理，结合混合组分的三角相图和物料组成设计了反向萃取精馏工艺，发现选用水为萃取剂可以利用DMC-水的部分互溶特性，通过三塔精馏即可分离DMC-甲醇-水三元混合物，沸点较高的DMC和少量水由塔顶馏出，而沸点较低的甲醇和大部分水由塔底采出，避免了DMC-甲醇二元共沸物的形成。同时，在相同分离要求下设计了变压精馏工艺，通过对两个精馏工艺参数模拟优化，发现萃取精馏工艺的总冷凝负荷和总加热负荷分别为888.7kW和898.2kW，其总能耗较变压精馏工艺节约了47.2%，萃取精馏工艺的年总费用（TAC）比变压精馏工艺下降了48.8%。

关键词: 萃取精馏, 分离, 共沸物, 碳酸二甲酯, 甲醇, 水