Energy-saving Research Of Separating Ternary Azeotropic Mixtures Via Pressure Swing Distillation Process

It is popularly among researchers for pressure-awing distillation to separate azeotropic mixture without adding entrainers.However,the high energy consumption of the process is acutely a difficulty,which can be solved by heat-pump technology with its property,and more and more people have investigated it in-depth.Though there are many papers about heat pump-assisted pressure-swing distillation,the related mixtures are mainly binary azeotropes and the analysis for heat-pump process is not rigorous.Hence,in this study,the discussion of heat-pump applied in triple-column pressure-swing distillation will be presented and the systematic analysis of heat pump process will be given.In this paper,the pressure-swing distillation process is selected to separate the ternary mixtures.The feasibility of the separation method and the determination of the separation sequence are based on the analysis of the ternary diagram of the mixture.Then the better conventional process is selected as the basic process and the heat-pump technology is used as the main energy-saving means to carry out energy-saving research for the conventional triple-column pressure-swing distillation process.In the separation system of water/acetonitrile/isopropanol,compared with the conventional process,the annual cost and total energy consumption of the optimal process of triple-heat-pump-assisted triplecolumn pressure-swing distillation process decreased by 57.59% and71.4%,respectively.In the separation and energy saving process of the dioxane/water/acetonitrile ternary azeotropic system,the processes with heat-pump technology are better than the conventional one in terms of cost and energy consumption,especially the triple-heat-pump-assisted process with splitting arrangement is the best.Compared to the conventional pressure-swing distillation,the annual cost and energy consumption of the best process have been reduced by 45.83% and 65.82%,respectively.The research results show that the application of heat-pump technology makes full use of the latent heat of the overheads in the distillations,especially in the processes with triple-heat-pump,which utilizes the latent heat of all columns,and successfully replaces the steam of the hot utility requirement,which is the heat source of the liquid streams from the bottom of columns.The energy consumption in the process is reduced to the greatest extent,the emission of exhaust gas and the operating cost are decreased,so that the thermal efficiency of the process is maximized,and its excellent energy-saving effect is fully demonstrated.