渗透汽化-热泵精馏工艺分离DMC-MeOH共沸物

Separation of DMC-MeOH azeotrope by PV-heat pump distillation process

碳酸二甲酯(DMC)-甲醇(MeOH)共沸物分离存在能耗高、能源利用效率低的问题.渗透汽化(PV)作为液-液分离技术,不受汽-液平衡限制,广泛用于共沸物体系的分离.传统的PV过程需要外部提供热量来维持恒定的原料侧温度;同时,渗透侧需要外部提供冷量来冷凝收集,降低了能源利用效率.本研究设计开发了PV-热泵精馏工艺,用聚二甲基硅氧烷(PDMS)/聚偏氟乙烯(PVDF)复合膜分离DMC-MeOH共沸物体系,用热泵进行热集成,并将模拟结果与文献报道的萃取精馏、变压精馏和传统PV-精馏等过程进行比较.结果表明,在常压、共沸点进料、PV单元渗透液与进料质量流量的比值(stage-cut)为0.3时,PV-热泵精馏工艺节能效果较好,与有热集成的变压精馏相比,可降低能耗约47%,能效提高90%.本研究设计的PV-热泵精馏工艺为共沸物的分离提供了一个新的发展方向.

The separation of dimethyl carbonate(DMC)-methanol(MeOH)azeotropes has the characteristics of high energy consumption and low energy efficiency.As a liquid-liquid separation technology,pervaporation is not limited by vapor-liquid equilibrium and is widely used in the separation of azeotropic systems.Conventional pervaporation processes require an external energy supply to maintain a constant residual liquid temperature.Besides,the permeation side requires external cooling to condense collection,reducing energy efficiency.In this study,a coupled membrane-heat pump distillation process was designed and developed,in which the DMC-MeOH azeotrope system was separated by polydimethylsiloxane(PDMS)/polyvinylidene fluoride(PVDF)composite membrane,the energy integration optimization was performed with a heat pump,and the simulation results were compared with the extracted distillation,pressure swing rectification and conventional membrane-rectification processes reported in the literatures.The results show that the PV-heat pump distillation process has a good energy-saving effect when the atmospheric pressure,azeotrope feed and the stage cut of PV unit is 0.3.Compared with the pressure swing distillation with heat integration,the energy consumption can be reduced by about 47%and the energy efficiency can be increased by 90%.The membrane-heat pump distillation process designed in this study provides a new development direction for the separation of azeotropes.