| Vinyl acetate(VAC)is an important organic chemical raw material,widely used in synthetic fiber,plastics and paint industries.In the process of producing VAC by the ethylene method,crude VAC containing unreacted synthesis gas and by-products is obtained,which needs to be separated and purified to obtain refined VAC products,which are then used for the subsequent production of polyvinyl alcohol(PVA).This study gives a feasible solution to the rectification and separation problems of ethylene acetate production in a factory,and then uses Aspen Plus commercial software to complete the simulation and optimization of the new process plan to obtain the best operating parameters of each tower.On this basis,the energy-saving configuration scheme of the separation process was further designed and developed.The specific research contents are as follows:(1)Due to the lack of VAC-ethyl acetate(EtOAc)interaction parameters in Aspen Plus,this study first selected the VLE data provided in the literature,and then based on three thermodynamic methods(NRTL,WILSON,UNIQUAC)completed the fitting regression of the VLE data of the system and obtained the corresponding model parameters,and then the reliability of the selected literature data was determined by the thermodynamic consistency test.It was found that the deviation of the UNIQUAC model is the smallest,which is most suitable as a physical method for subsequent process simulation.(2)In view of the separation problem of vinyl acetate-methyl acetate-ethyl acetate,the following solutions are proposed:1)Increase the pre-water separation tower and pickling tower.The top steam of the pre-water separation tower is condensed and layered to remove part of the water after condensation,reducing the water content of the feed of the first rectification tower,thereby reducing the reboiling of the first rectification tower heat load.2)Increase the secondary column of the first rectification tower,extract ethyl acetate from the side of the first rectification tower,and send it to the secondary tower,the ethyl acetate and vinyl acetate are effectively separated,and the ethyl acetate content of the vinyl acetate product is reduced.3)Adding the secondary column of the second rectification column and the secondary column of the fourth rectification column,the effective separation of methyl acetate and vinyl acetate has greatly reduced the content of methyl acetate in vinyl acetate products.Through simulation optimization,the appropriate process parameters of each rectification tower of the improved rectification process flow were obtained.The simulated vinyl acetate product had a mass fraction of 99.985%,with an impurity content of ethyl acetate of 130 ppm and methyl acetate content of 8.22 ppm.The investment cost of the new process is estimated,and the cost investment is 3.8446 million yuan each year,and the economic benefit is 6.341 million yuan/year,which can provide a theoretical basis for the production transformation of the enterprise.(3)In view of the high energy consumption of the VAC rectification process,further design and development of the energy-saving enhancement scheme of the process:1)Condensate flash evaporation device and an adjustable booster heat pump are used to achieve energy recovery of high-pressure steam condensate,the amount of steam recovered is about 1253.79 kg/hr.2)The new energy-saving technologies of tower-box liquid flash heat pump distillation are adopted for the second rectification tower and the third rectification,respectively,and the best operating parameters are obtained through simulation optimization,The results of economic analysis show that the heat integration enhancement program has saved operating costs of approximately RMB 7.604 million per year,which has helped to promote the improvement of the company's quality and efficiency as well as energy conservation and consumption reduction. |
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