萃取精馏与变压精馏分离甲醇/乙酸异丙酯工艺优化及节能

Optimization and energy-saving for methanol+isopropyl acetate separation by extractive distillation and pressure swing distillation

基于甲醇/乙酸异丙酯的二元共沸性质分析,探究萃取精馏和变压精馏工艺分离该共沸物的可行性,以年总费用最小作为经济评价指标、CO2排放量作为环境评价指标,采用序贯迭代法,经Aspen Plus对上述2种工艺开展模拟优化及节能研究。首先,基于无限稀释相对挥发度筛选萃取精馏的萃取剂,考察操作压力、萃取剂流量、理论板数和进料位置等因素对萃取精馏工艺年总费用的影响;其次,基于能量集成、公用工程费用最低原则确定了变压精馏工艺的操作压力,考察理论板数、进料位置与回流比等因素对变压精馏年总费用的影响;最后,对2种分离工艺进行综合对比。研究结果表明:双塔萃取精馏或变压精馏工艺均能高效地实现甲醇和乙酸异丙酯共沸物的分离。热集成变压精馏分离工艺由于热集成使得年总费用比常规变压精馏工艺的年总费用降低47.2%,二氧化碳排放量减少42.5%,这主要是因为热量集成使再沸器负荷降低,操作费用节省。与热集成变压精馏分离工艺相比,萃取精馏分离工艺的总设备折旧费和总操作费用均显著降低,萃取精馏工艺年总费用降低61.3%,且CO2排放量减少68.1%,故萃取精馏工艺更适合甲醇和乙酸异丙酯的分离。

The feasibility and energy-saving for the methanol and isopropyl acetate separation were studied by extractive distillation and pressure swing distillation owing to the characteristics of the binary azeotropic properties.The minimization of the total annual cost was used as the economic evaluation index,and the CO2 emission was used as the environmental evaluation index.The above two techniques were simulated and optimized by Aspen Plus via taking sequential iterative optimization procedure.Firstly,the extractant of extractive distillation was selected based on the relative volatility of infinite dilution,and the influences of the factors such as operating pressure,extractant flow rate,theoretical stages and feed position on the total annual cost were investigated.Secondly,based on the energy integration and the minimum cost of public work,the operating pressure of the pressure swing distillation was determined,and the effects of theoretical stages,feed location and reflux ratio on the total annual cost were analyzed.Finally,a comprehensive comparison of the two separation techniques were carried out.The results show that the azeotrope of methanol and isopropyl acetate can be both efficiently separated by extractive distillation and pressure swing distillation.Heat integration in pressure swing distillation leads to 47.2%reduction in the total annual cost and 42.5%reduction in CO2 emission as compared to the conventional pressure swing distillation,which is mainly owning to the reduction in reboiler load and the saving in operating cost.Compared with the heat integrated pressure swing distillation,the total equipment depreciation cost and operating cost of the extractive distillation have been both significantly reduced.The total annual cost required for the extractive distillation is 61.3%less than that of heat integrated pressure swing distillation,and the CO2 emissions have been reduced by 68.1%.Therefore,the extractive distillation is more suitable for the separation of methanol and isopropyl acetate.