Simulation And Optimization Of Separation For Methanol/Ethanol-tetrahydrofuran With Extractive Distillation

The formation of minimum azeotrope makes the separation of methanol/ethanoland THF difficult through common distillation. In view of the applicability ofextractive distillation in separation of azeotrope in industry, the research ofoptimization and improvement focused on extracitive distillation separatingmethanol-THF and ethanol-THF is carried out in this article with advanced chemicalengineering software to simulate.Vapor-Liquid equilibrium data were obtained with the block Flash2. Foursubstances were preselected as solvent, that is DMSO, DMF, NMP and EG. The mostsutable solvents for extractive distillation of methanol-THF and ethanol-THF werefinally ascertained as DMSO and EG respectively. The effect of solvent/mixture ratioon the relative votility of methanol/ethanol-THF was also studied.Simulation and optimization of extracitive distillation separating methanol-THFand ethanol-THF were carried out applying UNIQUAC model. The effect of refluxratio, solvent/feed flow ratio and solvent feed temperature on distillate concentrationand heatduties of reboilers were investigated. The results show that reflux ratio andsolvent flow are main factors affecting separating efficiency of extractive distillation.Based on the modle of cost, the capital investment and energy cost in the total annualcost (TAC) were analysed，by which the most effective factors affecting on TACwere determined as reflux ratio, solvent/feed flow ratio and the number of tray. Theoptimized process parameters were determined, and the distribution curves ofconcentration, temperature and vapor or liquid flow were analysised focused on theoptimized extractive distillation flowsheet, which reflects the rationality of theoptimized process. The optimization of processes with varied feed composition were also conducted, the general law of variation of process operation parameters werepatial determined by analysising and comparing the most optimized process ofseparating mixture with different feed composition.In order to reduce the energy cost of solvent recovery column, the improvedscheme of operating at lower pressure for the column was proposed on the basis oftraditional process. The three-column extractive distillation scheme for theethanol-THF system with low composition of THF was invented, which lowers TACof the separation process obviously compared to the traditional two-column scheme.