Study On The New Operation Of Batch Extractive Distillation

Batch extractive distillation (BED) is used to separate azeotrope andthe mixture of which the relative volatility is close to 1.0. Thecomponents to be separated must have different affinities for the solventso that an enough increase in relative volatility can make the separationfeasible and economical. Being suitable for small-scale production andeconomical mode, BED is a promising separation technology in chemicaland pharmaceutical industry. In this paper, a new mode of batch extractive distillation with thesolvent recovery by an equilibrium distillation still was proposed. Theliquid containing the solvent didn't flow into the reboiler, but into theequilibrium distillation still where only the vapor phase flowed into thereboiler and the solvent was kept in the equilibrium distillation still. Theexperiment of the separation of ethanol-water using glycol as solvent wascarried out and the result showed that the temperature in batch extractivedistillation still increased gently and the operation of solvent recoverywas simple and effective while comparing with the operation ofconventional batch extractive distillation (CBED). This paper provided a simplified mode to simulate batch extractivedistillation, in which two approximate methods were proposed. Asimplified vapor-liquid equilibrium relation and the average relativevolatility of ethanol-water under a given ratios of the solvent to thesystem were used in the mode. Simulation of CBED ofethanol-water-glycol system using the simplified model was carried out.The simulation result showed acceptable agreement with the experimentdata in the paper.