甲醇-醋酸乙烯变压精馏工艺的研究与模拟

Study and Simulation on Pressure-swing Distillation Process for Azeotrope of Methanol and Vinyl Acetate

甲醇-醋酸乙烯属于共沸物体系,目前分离方法主要有共沸精馏、萃取精馏、变压精馏等操作。与共沸精馏、萃取精馏相比,变压精馏具有工艺简单、无需引入第三组分及通过热耦合降低能耗等优点。在验证了NRTL对甲醇-醋酸乙烯模拟计算精确可靠的基础上,采用Aspen Plus软件对其进行分析,确认该体系属于压力敏感体系,提出了甲醇-醋酸乙烯变压精馏工艺流程。利用灵敏度分析工具分析了理论塔板数、进料位置、回流比及侧采位置等工艺参数对该工艺分离效果的影响,优化后的工艺参数为：减压塔28块理论板,进料位置为第12块板,回流比为0.6;加压塔27块理论板,进料位置为第14块板,回流比为0.575,侧采位置为第23块板。模拟计算结果表明,变压精馏可以有效分离甲醇-醋酸乙烯,甲醇质量分数可达99.89%,醋酸乙烯产品质量分数可达99.61%,与原萃取精馏工艺相比,该工艺可节省蒸汽9.07t/h,可减少废水20.75t/h。

Methanol-vinyl acetate is an azeotrope.At present,the separation methods for azeotrope mainly include azeotropic distillation,extractive distillation and pressure-swing distillation.Compared with azeotropic dis-tillation and extractive distillation,pressure-swing distillation has advantages of simple process,no need to introduce a third component and lower energy consumption via thermal coupling.NRTL model is verified to be accurate and reliable in simulating methanol-vinyl acetate.On this basis,Aspen Plus is used to analyze the methanol-vinyl acetate and confirm that this azeotrope is pressure sensitive,and pressure-swing distillation process is proposed for methanol-vinyl acetate.Sensitivity analysis tool is used to analyze the impacts of pro-cess parameters such as theoretical plates,feeding position,reflux ratio and side-draw position on the separation effect.After optimization,the parameters for vacuum tower are 28 theoretical plates,feeding position on the12 thplate and a reflux ratio of 0.6,and the parameters for pressurized tower are 27 theoretical plates,feeding position on the 14 thplate,a reflux ratio of 0.575 and side-draw position on the 23 rdplate.The simulation results show that methanol can be effectively separated from vinyl acetate by pressure-swing distillation,the mass fraction of methanol can reach 99.89% and the mass fraction of vinyl acetate can reach 99.61%.Com-pared with the original extractive distillation process,this process can save the steam by 9.07 t/h and reduce the wastewater by 20.75 t/h.