Separation of azeotropic mixture by extractive distillation and pressure-swing distillation:computer simulation and economic optimization

Abstract

The Separation of Di-n-propyl ether and n-propyl alcohol is difficult because the highly non-ideal vapour-liquid equilibrium forms a azeotrope. It is very difficult to separate the azeotropic mixture by ordinary processes of distillation. The most common methods for separating the azeotropic mixture are pressure swing distillation and extractive distillation process. Pressure swing distillation is a better process for the case where the azeotropic composition changes significantly with the change in pressure whereas the extractive distillation process is effective only if we are able to find a suitable solvent. This thesis equates these two different process to separate the mixture consisting of 50-50 mole % of di-n-propyl ether and n-propyl alcohol by means of a practical case of a industry. We have studied and simulated these two separate alternatives of the mixture for the case of a plant to treat 12000 Tm/year of the original mixture. The simulation is carried out satisfactorily by means of a package of commercial software i.e. Aspen Plus using the thermodynamic model UNIQUAC with the help of other parameters obtained. Aspen plus is a very important tool for the simulation of various processes with different thermodynamic models. In the result we have calculated different parameters required such as number of plates, feed plate etc. We have also calculated the amount of heat required for the reboiler and the cooling required in the condensers. We have also calculated the reflux ratio and the graph between the reflux ratio and the no. of stages is plotted. We have also simulated the stream results required for the valves and the mixer. The pump efficiency electricity required and the pressure drop across the pump has also been accounted.