Technological Researches for Separation of Methanol and Water by Multi-Effect Distillation

Because of the high energy consumption for separation of methanol-water in mono-column distillation processes, multi-effect distillation processes including two-tower, three-tower and four-tower were proposed.Simulations of multi-effect concurrent and countercurrent distillation treating different mass concentration methanol were performed by ASPEN PLUS software in which RADFRAC block and WILSON physical property set were used.The optimum operation conditions (including the pressure distributions) were determined on the basis of the minimum energy consumption and the variable of the distillate, which is tower's methanol vapor.Moreover, the columns' parameters and areas of the heater exchangers were also calculated by hydraulic block of ASPEN PLUS.The results show that the three-effect concurrent distillation is the best separation technology in response to the objective function of the ratio of multi-effect distillation expenditures to mono-column expenditures.Results show that the three-effect concurrent distillation can save energy consumption by 57.8%, 57.5% and 58.0% respectively, compared with mono-column distillation when treating 70%, 80% and 85% mass concentration methanol.