Optimization And Control Strategy Of Distillation Separation Processes For Organosilicon Crude Monomer

The preparation of organosilicon material has a very high requirement on the purity of organosilicon monomer.However,when the direct method is used in the current industry to prepare organosilicon crude monomer,the main products,dichlorodimethylsilane and methyl silicochloroform are usually affected by other methyl chlorosilane and high and low boiling components,resulting in lower product quality and higher separation energy consumption.In this study,a new separation sequence of organosilicon crude monomer is proposed based on the relationship between the number of component vaporization and energy consumption.In order to solve the problem of high energy consumption in the process of distillation,the energy saving processes of distillation using steam recompression and heat integration are further investigated.Based on the stability of the process and the purity standard,the main variables affecting the purity of the product and their variation rules are studied,and the optimal control structure is designed.First,a new distillation process which separates light components first and then heavy components(Light Split distillation process)is proposed according to the traditional distillation process.Based on the root mean square deviation and the average absolute deviation models,WILSON is selected as the thermodynamic model.Taking the total annual cost and gas emissions as the objective function,the traditional distillation process and the Light Split distillation process are improved by multiobjective optimization based on the nondominated sorting genetic algorithm II.Furthermore,based on the results of exergy analysis and heat exchange network analysis,the heat matching between cold and heat flows is carried out to achieve the optimization of energy.Results show that the total annual cost and gas emissions of the improved distillation process are reduced by more than 50% compared with the basic distillation process.The total annual cost and gas emissions of the improved Light Split distillation process are reduced by 13.28% and 4.47% compared with the improved traditional distillation process,respectively.Comprehensive consideration,the improved Light Split distillation process has excellent economic and environmental performance.Secondly,in order to further investigate the impact of pressure adjustment on the energy-saving process of organosilicon crude monomer distillation.Two heat integration enhancement schemes,which are heat integrated distillation process and vapor recompression assisted heat integrated distillation process,are designed.The results show that the key to reducing energy consumption lies on the energy saving of dichlorodimethylsilane and methyl silicochloroform separation column.Hence,the pressure-regulating heat integrated distillation process and the vapor recompression assisted pressure-regulating heat integrated distillation process are proposed.The pressure of ichlorodimethylsilane and methyl silicochloroform separation column is increased to make better use of overhead steam to exchange heat for other columns in the pressure-regulating heat integrated distillation process and vapor recompression assisted pressure-regulating heat integrated distillation process.The results show the gas emissions and total annual cost of the four improved energy-saving schemes are reduced significantly.The vapor recompression assisted pressure-regulating heat integrated distillation process has the best environmental and economic performance,with total annual cost reduced by 44.46% and gas emissions reduced by 70.96%compared with the traditional distillation process.Finally,the dynamic control of the distillation separation process of organosilicon crude monomer is studied.The temperature-sensitive stage of the distillation column is selected according to the slope criterion method.A control structure composed of a value selector and reflux ratio and temperature is designed,after trying a reboiler or reflux ratio to control the stage temperature with poor results.It can ensure that the purity of the product meets the industrial separation requirements when disturbed by±10% feed flow and composition.At present,the main problem in the production of organosilicon in industry is the high energy consumption for the separation of crude monomers.By exploring the new sequence separation process of crude organosilicon monomer and studying the energysaving optimization and control strategy of the separation process,it is found that the Light Split distillation process has the advantages of low cost and less gas emissions compared with the traditional process.The developed the vapor recompression assisted pressure-regulating heat integrated distillation process has significant effect in solving the problem of high energy consumption.This provides some guidance for solving the problems of difficult separation process,high energy consumption and poor controllability of complex mixtures in the production of organosilicon monomer.