变压精馏分离甲醇-乙酸甲酯-乙酸乙酯物系中甲醇的模拟分析与优化

Simulation analysis and optimization of methanol separation in methanol-methyl acetate-ethyl acetate system by pressure-swing distillation

常压下甲醇、乙酸甲酯和乙酸乙酯会形成多种共沸物,采用普通精馏难以分离。通过分析剩余曲线图,确定可以采用双塔变压精馏对甲醇-乙酸甲酯-乙酸乙酯混合物系进行分离,在低压塔中得到纯甲醇产品。利用Aspen Plus软件进行了模拟,以820 kPa(方案一)或650 kPa(方案二)作为高压塔的压力,170 kPa作为低压塔的压力,以年度总费用(TAC)为目标函数,对比发现方案一的经济性最优。以此为基础,进一步提出了双效热集成变压精馏工艺,利用高压塔塔顶蒸汽的潜热为低压塔的再沸器提供热量。与普通变压精馏工艺相比,新工艺节约蒸汽36.3%,节约循环水40.3%。

Methanol, methyl acetate and ethyl acetate can form several azeotropes under normal pressure, which are difficult to separate by ordinary distillation. By analyzing the residual curve, it is determined that the ternary system(methanol-methyl acetateethyl acetate) can be separated by double tower variable pressure distillation, and pure methanol product can be obtained in the lowpressure tower. Aspen Plus software was used for simulation of the ternary system separation, and 820 kPa(scheme I) or 650 kPa(scheme II) was used as the pressure of the high-pressure tower, 170 kPa was used as the pressure of the low-pressure tower. With the annual total cost(TAC) as the objective function, the economy of the two schemes was compared, it is found that the scheme I is optimal. On this basis, the dual effect thermal integrated pressure swing distillation process was proposed, which uses the latent heat of the overhead steam of the high-pressure tower to provide heat to the reboiler of the low-pressure tower. Compared with the ordinary pressure swing distillation process, the new process can save 36.3% steam consumption and 40.3% circulating water consumption.