多效精馏分离甲醇-水体系的工艺研究

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

关键词:  甲醇-水  多效顺流精馏  多效逆流精馏  能耗

Key words:  methanol-water  three-effect concurrent distillation  three-effect countercurrent distillation  energy consumption

摘要:

针对传统甲醇回收工艺的高能耗问题,本文提出了分离甲醇-水体系的双效、三效和四效精馏工艺流程。利用ASPEN PLUS化工模拟软件中的RADFRAC模块和WILSON热力学计算模型,系统模拟了多效顺流、多效逆流分离不同甲醇浓度的工艺。以能耗最低为目标函数、各塔顶甲醇蒸出量为决策变量,确定了各种回收工艺的最佳条件(包括塔压分布)。利用ASPEN PLUS软件中的流体力学计算模块,计算出各塔的设备参数,包括附属冷换设备的面积。并以多效精馏与单塔精馏总费用的相对值最低为目标函数,确定分离甲醇-水体系的最佳方案为三效顺流精馏工艺。研究结果表明,该工艺与单塔工艺相比,处理浓度分别为70%、80%和85%的甲醇物料时,节能分别为57.8%、57.5%和58.0%。

Abstract:

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.