Study On Batch Extractive Distillation With A Middle Vessel

The solvent selection and batch extractive distillation with a middle vessel (BEDM) were studied by theoretical analysis and experiment.Solvent selection is the key problem for extractive distillation. A solubility parameter method for solvent selection was set up by Scatchard-Hildebrand theory. The effective solvents for extractive distillation can be selected by solubility parameters using such a theory. The range of solubility parameters for effective solvent can be calculated by our equation. This theory can be used to systems which the solutes and solvents cannot form hydrogen bond. Both single solvent and mixed solvent can be selected by such a theory.Another method for solvent selection is group contribution method, proposed by analyzing UNIFAC equation. The solvent selectivity was divided into two parts: the partial combinatory solvent selectivity and the residue solvent selectivity. The combinatory solvent selectivity was studied by function analysis and the conditions which combinatory solvent selection was great than 1 were derived. The residue solvent selectivity was studied by analyzing the interaction parameter table composed by the interaction parameters for the groups in solutes and solvent. The interaction parameter table was divided into four parts. The part composed by the interaction parameters of the groups in solutes had no effect to residue solvent selectivity, but the other three parts had great effect to residue solvent selectivity. The general UNIFACinteraction parameter table can be used to select solvent. If v_k', which is the value ofthe number of group k in solute 1 minus the number of group k in solute 2, is great than zero, the groups in the same line or column with group k which has a high interaction value can be selected as candidate group for solvent, and vice versa. The candidate groups can form solvent molecular according to molecular structure rule. The solubility of solvent and solutes was also studied. The solubility can be judged by infinite dilution activity coefficient.