Comparison And Optimization Of The Improved Recovery Processes Of Chloromethane From The Vent Gas

Chloromethane was an important raw material used for synthesis of methyl chlorosilane, one kind of the organic silicon monomer, which accounted for a large proportion of the synthesis cost. In the organic silicon production process, the masas fraction of the chloromethane in the vent gas was about 20-30 wt%, this part of the vent gas was not taken to effectively deal with, but directly transported to the downstream process for incineration, which resulted in serious wastage of resource. In order to reduce the wastage of the resource and increase economic profit, it was necessary to recover chloromethane from the vent gas. In this paper, based on rectification and compression condensation separation processes, two kinds of chloromethane vent gas were taken for further recycling, and the processes were simulated and optimized by UniSim Design software.In this paper, the raw materials in the rectification system were the proposed recycling gas and liquid, and three methods were coupled with the rectification process for the chloromethane recovery, including condensation, membrane separation and absorption, spectively. After simulated and optimized, three recovery processes were compared by economic profit increasing. The mass fractions of chloromethane in the gas were reduced from 27.0 wt% to 6.4 wt%,6.9 wt%,4.3 wt% after treated by the three designed processes, with the economic profit increasing 2.72,2.83,2.43 million yuan/year, respectively. From the aspect of economic profit, the membrane separation method was the optimal one in comparison to the other two methods, for it could achieve the highest enhancement in economic profit by lower consumption and less investment, which meeted the demand of the chloromethane treatment.The raw material in the compression condensation separation process was the crude single tower outlet gas from the production of organic silicon, and the membrane separation method was coupled with the compression condensation process for the chloromethane recovery. The recovery process was simulated and optimized, and the optimal parameter was also achieved finally.The mass fraction of chloromethane in the gas was reduced from 19.5 wt% to 8.5 wt% after treated by the designed process, with the economic profit increasing 0.69 million yuan/year.The condensation-vapor membrane process was transformed from static process to dynamic process. After the key parameters of traditional equipments, such as mixer, compressor and so on, were specialized and the the model of membrane separator was restructured, the key parameters of dynamic process were analyzed by changed the flow rate of the raw material. When the flow rate of the raw material was changed, for the traditional equipments, compared with the time that the fluctuations of the key parameter curves got stabilized to need, the time that downstream equipments needed is longer than that of upstream equipments needed, and the fluctuations that the downstream equipments parameters got were more obvious. The fluctuation trends of the key parameter curves were all consistent with the controlling principles of the key parameters. For membrane separator, as a new kind of separator equipment, the fluctuation trend of the mass fraction of chloromethane was the same as the fluctuation trend that the flow rate curve showed, but did not showed significant delay and lag. Compared with the other traditional devices, membrane seperation showed more excellent operation and work stability.