Extractive Distillation Separation Process And Optimization Study For The Preparation Of Anhydrous Ethanol

Absolute ethanol has a wide range of uses in the medical,chemical,pharmaceutical and other industries,and it involves a large amount of low-concentration ethanol or ethanol waste in the production and application.Recycling ethanol can not only reduce the purchase cost of raw material ethanol to bring the economic benefits,but also reduce environmental pollution and waste of resources.Therefore,it is very meaningful to study the purification and recycling of ethanol.In this paper,based on the extractive rectification separation method,the ethanol solution was separated and purified to prepare absolute ethanol.Firstly,the theoretical plate numbers of rectification unit were experimentally determined to be 9;only 94.67wt%ethanol solution can be obtained by the ordinary rectification experiment on the ethanol aqueous solution.The effect of the main operating parameters?such as feed position,raw material concentration,solvent ratio,etc.?of glycol on the separation process was studied;under the conditions of reflux ratio 2,ethanol concentration 90wt%,ethanol feed position 5,extractant feed position 1 and solvent ratio 2.1,absolute ethanol with 99.97%mass fraction can be obtained at the top of the tower.The extraction rectification process was simulated and optimized by Aspen Plus,and the optimum conditions were obtained as follows:the feed concentration of ethanol was90 wt%,the feed position of raw material was 10 plate,the feed position of extractant was 3 plate,the solvent ratio was 1.5,and the ethanol concentration at the top of the tower was 99.93 wt%.The three-tower?two ordinary rectification towers,one extractive rectification tower?process and process conditions for separating phosphoric acid-ethanol-water solution were developed and optimized.The three-tower process was improved to a process consisting of one evaporator,one extractive rectification tower and one rectification towers,and under the optimum process conditions,the effective separation of phosphoric acid and ethanol could be achieved by improving the process to obtain the higher concentration of phosphoric acid and absolute ethanol:the concentration and yield of phosphoric acid?H₃PO₄?could respectively reach 85.24 wt%and 99.99%,the concentration and yield of ethanol could respectively reach 99.05 wt%and 94.47%,and the extractant could be recycled.Finally,in order to optimize the separation process from packed rectification tower equipment,the commercial software ICEM CFD was used to establish a three-dimensional model of the tower equipment.The Euler model of multiphase flow in Fluent was applied to simulate the gas-liquid-solid three-phase flow and gas-liquid two-phase flow in the packed rectification tower used in the experiment,and the pressure distribution and velocity vector distribution of different sections in the tower were obtained,which the simulation results could directly reflect the velocity distribution and pressure drop of the fluid in the packed rectification tower and could provide a reference for the optimization of packed rectification tower equipment.