Study On Simulation And Optimization Of Extractive Dividing Wall Column For Separating Ethanol-dimethyl Carbonate

In order to explore a novel process of high efficiency and energy saving for separating binary azeotrope ethanol-dimethyl carbonate(DMC),the method of extractive dividing wall column is adopted to separate the system,and the sepearation process is studied by simulating and optimizing.The major contents and results show as below:Firstly,Aspen Plus software is used to establish five kinds of extractive distillation processes for separating ethanol-DMC,and these processes are conventional double-column extractive distillation,single-column extractive distillation with side outlet,extractive dividing wall column(EDWC),extractive dividing wall column with side-rectifying(EDWC-SR)and extractive dividing wall column with side-stripper(EDWC-SS).Afterwards,the self-made sensitivity analysis software is adopted to optimize and design these processes preliminarily.The results show that only double-column process and EDWC-SR process can satisfy the requirement of separation which the purity of ethanol and DMC is not less than 0.996(mole fraction,the same below)and 0.989,respectively,and the recovery rate is not less than 0.996 and 0.989,respectively.Under the same requirement and task of separating,EDWC-SR process is saved up to 11.61%of the reboiler duty when compared with double-column process.Secondly,in order to find a high efficient algorithm to solve the optimization problem of complex distillation system.According to these disadvantages of weak local search,slow convergence velocity and low convergence precision,an improved cuckoo search algorithm(SDCS)is proposed by introducing two strategies,including selective elimination and decision domain.The test results show that the comprehensive performance of SDCS is superior to CS and the cuckoo search algorithm based on gauss perturbation(GCS).Thirdly,taking the minimum total annual cost as the objective function,the optimization model of EDWC-SR process and the double-column process are established to separate ethanol-DMC.Afterwards,the SDCS algorithm is used to solve these optimization models.The results show that when the same separation task is completed,EDWC-SR process is a highly efficient new process which can save 14.50%of the annual operation cost,reduce 9.63%of the annual depreciation charge for equipment and save 13.53%of TAC,compared to conventional double-column extractive distillation process.Finally,using the methods of profile analysis and exergy analysis to explore coupling principle and energy conservation principle of EDWC-SR based on the optimization of the EDWC-SR process.The results show that EDWC-SR ably couples the extractive distillation column and extraction solvent recovery column of double-column process in a column,and EDWC-SR process can weaken the back-mixing phenomenon of distillation process is the essential reason for energy saving,and the thermodynamic efficiency of EDWC-SR process is 10.09%,increasing by 3.3 percent at the side of double-column process whose thermodynamic efficiency is 6.79%.Namely,EDWC-SR process has higher energy efficiency and saves more energy than double-column process.The following conclusions can be obtained from the above research.SDCS algorithm is a quick and efficient method which can be used to control the Aspen Plus software,optimize and design EDWC-SR process.It is primarily validated that EDWC-SR process is a good economic benefits and high energy utilization effect new technology,which has good prospects for industrial application.