Study On The Intensification Of Batch Extractive Distillation

In this paper, the progress of batch extractive distillation were summaried. Selection and design of extractive solvents(named solvent,the same as follow), different configuration for extractive distillation column, operation policies and effect of operating parameters on separation were presented.Then the advance in the simulation of batch extractive distillation and batch extractive distillation were also described. The current disadvantages and the problems to be solved for the batch extractive distillation were pointed out.The selection of extractive solvent is the key problem for extractive distillation. A number of extractive solvents for separation of benzene-cyclohexane, n-hexane - ethyl acetate and ethyl acetate-ethanol were examined respectively in a VLE experiment apparatus. The integrated properties of sing solvent and mixed solvent were investigated , The expermental results showed that the binary mixed solvents and the ternary mixed solvents are better than the single solvent,and they are have a good solution to the contradictory problem of selectivity and solubility of the single solvent, so that the choice of the extractive would increased .Considering molecular electrostatic force, the inductive capacity, the dispersion force, the hydrogen bond and the association, the experimental data were correlated with the modified MDUNIFAC model. It was found that the prediction by modified MDUNIFAC model conformed by experiments is a rapid, accurate approach for selection for extractive distillation.Vacuum batch extractive distillation process for separating close boiling and azeotropic mixtures was simulated, the mathematical model is a group of stiff equations and resolved by two point implicit method.The experimental results agree well with the simulation.The effect of operating parameters such as reflux ratio , theoretical plates, operation pressure and solvent feed rate on the separation process were analogged by the constant molar holdup model. All these features were illustrated by the increase of the reflux ratio and flow rate of the solvents or decreasing of operation pressure, and resulting the increase of the concentration of product at the top of the column. A model for discussing minimum amount of intermediate cut was set up and solved with the four order Runge Kuta method.