The Design And Optimization Of Membrane Process For Chloromethane Recovery From The Vent Gas Of Organic Silicon

Chloromethane,widely used for production of organic silicon,is also an important raw materials used for synthesis of methyl chlorosilane,a kind of organic silicon monomer. During the production of organic silicon,the vent gas leaving rectification or compression condensation separation process contains about 25～30 wt%chloromethane,which not only wastes the resources,but also contaminates the environment.It is helpful to obtain huge economic profit and protect environment by recovering chloromethane in the vent gas.In order to recover chloromethane in the vent gas,membrane-rectification integrated process and membrane-compression-condensation integrated process were designed in this study.And all the membrane integrated process was simulated and optimized by UniSim Design software. According to the results of the simulation,the optimum membrane integrated process was determined.According to the characteristics of the vent gas which originated from rectification and non-condensable gas which originated from compression condensation separation process during the production of organic silicon,membrane-rectification integrated process and membrane-compression-condensation integrated process were designed,respectively.For the former,two kinds of membrane-rectification integrated process were proposed.In order to evaluate and optimize the two kinds of membrane-rectification integrated process,the chloromethane rectification system was simulated by UniSim Design at first.From the fact that the simulation results coincide with the design values,it is concluded that the simulation is reliable and accurate as well as the thermodynamic method is suitable for the chloromethane system.Then,two kinds of membrane-rectification integrated process were simulated and optimized on the basis of simulation of chloromethane rectification system.Finally,the optimum membrane areas were determined.For the first membrane-rectification integrated process,the optimum membrane area was chosen 30 m~2.Correspondingly,the value added of economic profit can be obtained as much as 1.84 million RMB each year and chloromethane concentration in the vent gas can be reduced to 9.0 wt%.For the second membrane-rectification integrated process,the optimum membrane area was chosen 150 m~2. Correspondingly,the value added of economic profit can be obtained as much as 3.00 million RMB each year and chloromethane concentration in the vent gas can be reduced to 7.2 wt%. Therefore,it is indicated that membrane-rectification integrated process can obtain the huge economic profit and good environmental benefit.However,compared between the two kinds of membrane-rectification integrated process,the second one is much better.Hence,the second membrane-rectification integrated process was chosen.For the latter,membrane-compression-condensation integrated process was designed to recover chloromethane in non-condensable gas which originated from compression condensation separation process during the production of organic silicon.In order to optimize its economic profit,the process was also simulated by UniSim Design.Under the optimum conditions,the value added of economic profit of membrane-compression-condensation integrated process can be obtained as much as nearly 4 million RMB each year and chloromethane concentration in non-condensable gas can be reduced to 10.1 wt%.At the same time,effects of parameters such as membrane module price,chloromethane price and membrane performance on economic profit were studied.Moreover,taking into account of the operation load and margin,an alternative scheme of membrane process for chloromethane recovery was designed as well.Under the optimum conditions,membrane area of the alternative scheme was chosen 120m~2 and pressure in permeation was chosen 150kPa.Then, the optimal economic profit can be obtained as much as 3.08 million RMB each year.What's more,chloromethane concentration in non-condensable gas can be reduced to 6.0 wt%.The results indicate that the alternative scheme of membrane process for chloromethane recovery can be obtained huge economic profit and good environmental benefit as well.