Study On Batch Extractive Distillation For High Purity Methanol

High purity methanol has been widely used in the fields of medicament, electronics and so on, and the demand quantity is continuously rising. At present, domestic high purity methanol is low-grade, preparation technology is not yet mature. However, much high purity methanol will also depend on imports. Preparation of high purity methanol with high added value by purifying industrial methanol adapts to the situation of our country and has high research value. It utilizes the abundant raw materials of methanol and the modern purification techniques that have been rapidly developing in recent years. Due to methanol can form azeotropic with a variety of solvents, batch extractive distillation is used for the preparation of high purity methanol in this paper.Firstly, the fuzzy comprehensive evaluation method was used for solvent selection. Several solvents were compared and DMSO was chosen as the separation solvent for the preparation of high purity methanol; Secondly, constant-molar-holdup model of batch extractive distillation was proposed and solved by the quasi-steady approach. The simulation includes two cases: solvent feeding one-off and solvent feeding continuously. Effects of such parametrers as theoretical plates stages, solvent ratio, reflux ratio on recovery fraction of high purity methanol was researched. The simulating results show that the mode that solvent feeding continuously is better than feeding one-off. When the composition of raw material is 98%, and the average purity specification of product in top of column is above 99.9%, the suitable number of theoretical plates is 35, solvent ratio is 0.3, the reflux ratio of slop cut withdrawal and product phase respectively is 8 and 5. Accordingly, the single recovery fraction of high purity methanol can reach 60%. Subsequently, the corresponding experiments were carried out. The purity of product was reflected by values of ultraviolet transmission and content of water. The suitable operating condition that the experimental results educed coincides with the calculated results. Finally, the optimum conditions of the batch extractive distillation for high purity methanol were determined.