Azeotropic Characteristics Of Methanol/Ethanol-tetrahydrofuran Systems And Optimization Of Pressure-swing Distillation Process

The separation of methanol-THF and ethanol-THF systems usingpressure-swing distillation is studied in this article.The selection of operating pressure of the two columns is based on theazeotropic characteristics of tetrahydrofuran-alcohol system. Based on the modle ofcost, the optimized process operation parameters and capital parameters weredetermined on the basis of analysising capital investment and energy cost in the totalannual cost (TAC)The optimization and improvement focused on pressure-swing distillationseparating methanol-THF and ethanol-THF is carried out in this article usingadvanced chemical engineering software (Aspen Plus). Simulation and optimizationof pressure-swing distillation separating methanol-THF and ethanol-THF werecarried out applying UNIQUAC model. The impact of feed location, reflux ratio andnumber of stages on TAC was studied in this paper. Furthermore, the separationprocess of mixture with different composition is also optimized and the resultsshows that the feasible sequence of high and low pressure of two columns in thepressure-swing distillation process and the suitable heat integration scheme are bothdetermined by the feed composition.Reflux ratio and solvent flow are main factors affecting separating efficiency ofextractive distillation. Firstly, the variation of distillate concentration with refluxratio and solvent/feed flow ratio as well as the effect of solvent feed temperature onseparating efficiency were investigated. The distribution curves of concentration,temperature and vapor or liquid flow were analysised focused on the optimized extractive distillation flowsheet, which reflects the rationality of the optimizedprocess. The optimization of processes with varied feed composition were alsoconducted, the general law of variation of process operation parameters were patialdetermined by analysising and comparing the most optimized process of separatingmixture 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.In this paper, the simulation and optimization of the separation process oftetrahydrofuran-alcohol systems contribute to the similar separation process in theindustrial process. The study of this paper is of guiding significance for the design ofthe separation process of similar systems.