Study On The Separation Of Isopropanol-Water System

Isopropanol is a commonly used organic solvent in chemical industry.Accordingly the isopropanol-water mixture is an unavoidable waste especially in the pharmaceutical industry.Therefore recycling large amounts of isopropanol can not only reduce the solvent cost but also reduce the environment pollution.Azeotropic distillation and extractive distillation have been used to separate isopropanol-water system.Both could easily achieve industrialization,but their energy consumption is high.So far,there is nearly no specific research about the comparison between two process.Practically it is of great significance to choose a separation process that can achieve the production requirement and meet the needs of energy saving at the same time.Therefore,this paper studied the energy consumption of azeotropic distillation and extractive distillation for the separation of isopropanol–water mixture.Cyclohexane,with low toxicity,was selected as an entrainer in the azeotropic distillation process,which could form ternary azeotrope with isopropanol and water which contained more water than the original mixture.On the other hand,diethylene glycol,a cheap and easy to get organic solvent,was selected as the extractive solvent.It can seriously affect the relative volatility of isopropanol–water and make isopropanol–water more easily to separate.Moreover,the two processes were simulated using Aspen Plus.This paper took the energy consumption as the objective function and optimized the two processes using the same method.Firstly,the single factor analysis was used to optimize the operating parameters of each process.And then two central composite design experiments with the results of the single factor optimization were performed.Consequently the response surface method(RSM)results showed that there were mutualinfluences among the operating parameters in each process.Generally the mathematical models fitted out by RSM have a high fitting degree,which could well predict the experimental value.The results showed that the minimum energy consumption of the two processes was 1008.35 kW and 907.22 kW,respectively.The heat duty and cold duty of extractive distillation process respectively reduced 10.03% and 35.35% than the azeotropic distillation process.Through the economic accounting,it was found that the cost of extractive distillation was lower in all aspects.Specifically the cost of the equipment reduced 20.63%,the energy consumption reduced 12.14%,and the TAC reduced 12.52%.