Study On Energy-saving Process Optimization Of Dichloroethane Production From Ethylene Process

As an early plastic variety,polyvinyl chloride is widely used in various fields of national economy.Vinyl chloride（VCM）is a monomer for the preparation of polyvinyl chloride and its copolymer,and 1,2-dichloroethane（EDC）is an important raw material for the preparation of VCM.The preparation of EDC by ethylene oxychlorination is recognized as a technically and economically reasonable method in the world.Ethylene,HCl and oxygen undergo oxychlorination in the presence of ferric chloride catalyst to produce 1,2-dichloroethane（EDC）.The generated crude EDC is refined to extract pure EDC for subsequent cracking.This paper mainly studies the energy-saving of EDC production and refining process.In the process of producing EDC by oxychlorination,firstly,the reactor temperature and pressure are analyzed,and the optimal control range of temperature and pressure is determined according to the oxychlorination reaction conditions.Then,under constant pressure,the generation of by-products is reduced by changing the reactor temperature;Because different feed ratios will lead to different EDC yields,change the feed ratio and calculate the EDC conversion by measuring the EDC content in the tail gas,so as to determine the feed ratio with the highest yield;Because the oxychlorination reaction is exothermic,the removal of reaction heat is the key step to control the reaction temperature.In this paper,the heat is recycled,and the steam generated by the steam drum is used to supply the steam pipe network.For the refining of EDC,a conventional four tower process is constructed,including dehydration tower,light removal tower,heavy removal tower and recovery tower.The process is optimized by sequential iteration method with the minimum annual total cost（TAC）as the optimization objective to obtain the optimal process and the corresponding operating parameters of each tower.Based on the four tower process,an integrated process with side line is established.The light removal tower is coupled with the dehydration tower as a side line tower,and the subsequent heavy removal tower and recovery tower remain unchanged.Similarly,the whole process is optimized by sequential iteration method to obtain the optimal process flow and operating parameters.Comparing the TAC of the two processes,the results show that the TAC of the integrated process with side line is reduced by 22% compared with the traditional four tower process,and the heat load is reduced by 25.8 year-on-year,which has more economic and energy-saving advantages.Taking the optimized integrated process with side line as the research object,its dynamic control is studied.Finally,the control scheme of double temperature control +component controller is proposed.The results of flow and composition disturbance show that the control scheme can deal with various disturbances well,the purity of each component can almost stabilize to the target value,and the stabilization time is short.,It shows that the control scheme is effective.To sum up,the energy-saving research on the process of preparing EDC by ethylene oxychlorination in this paper can greatly reduce the production cost and improve the energy utilization rate,which is of positive significance for the industrial production of factories,practicing green chemical industry and building a beautiful China.