Experimental Studies Of High Gravity Salt Distillation For Separating Ethanol-water

Separation operation of azeotrope is an important research direction of distillation unit. Ordinary distillation method can not break through the "bottleneck", so it is necessary to use special rectification means to separate the mixture. Salt distillation aims to achieve the purpose of separation of high concentration by adding the extraction agent, which breaks the original system’ of the vapor liquid equilibrium.The ethanol water system is a typical azeotrope system.What’s more, in the present environmental protection under the background of low energy consumption, high concentrations of ethanol used as clean fuel has good prospects. This paper is a study of the strengthening process of the high gravity technology used in salt distillation, separation of ethanol water system to investigate the separation effect and mass transfer performance.The study has built a continuous extractive distillation process for multistage high gravity equipment filled with star packing and wire packing. On the basis of stable operation, comparing insoluble salt with soluble salt (dissolved salt content 5-25g/L),the effects of super gravity factor 20.9～130.6, feed ethanol concentration 15-45wt%, feed flow rate 20～45L/h and reflux ratio 1.0～4.0 on the separation efficiency of ethanol water system were investigated. The experimental results show that the effect of soluble salts is mainly reflected in the low purity of the raw material:the quality concentration of the product is improved, as well as the enhancement of the mass transfer effect and the improvement of the recovery rate. While the former is restricted by the constant boiling point, the lifting effect is limited, and the recovery rate is more significant. When the concentration of the raw material is relatively low, the RPB does not break the boiling point, but the mass transfer performance is improved, which is close to the constant boiling point.For separation effect:it increases firstly with the high gravity factor and feed flow rate and then decreases; it also increases with the increase of reflux ratio, soluble salt content and concentration of the raw material. The influence degree of each factor on the top product quality concentration varies from largely to weakly:the concentration of raw material, the feed rate, the amount of dissolved salt, reflux ratio, and the super gravity factor; For the mass transfer effect:with the increase of the super gravity factor, the flow rate and the reflux ratio of the raw material, NTP increases at first and then decreases. And NTP goes up with the increase of the salt content and the concentration of the raw material. The influence degree of each factor on NTP is from large to small:feed flow rate, feed concentration, dissolved salt content, super gravity factor, reflux ratio.The experimental conditions of breaking the constant boiling point of ethanol water were studied by increasing the concentration of the feed liquid and the amount of dissolved salt.When the feed concentration is more than or equal to 93.0% and other experimental conditions are set as:super gravity factor 83.6094, reflux ratio 3.5, feed flow 10L/h, dissolved salt 20g/L, product quality concentration over the atmospheric pressure without salt ethanol water azeotropic composition (95.60%). Other experimental conditions for a certain time, the quality of raw liquid concentration of 92%, the amount of soluble salt of 30g/L will break through the constant boiling point.In the application of the research, the recovery of ethanol solvent in the process of pectin production was studied. Under the optimum operating conditions, the separation effect is good (93.6%), And separation cost is low (Salt recycling,0.45yuan/L). and also ecovery has been improved.The comprehensive research results can be found:the height of mass transfer unit is 9.3-36.1mm. Visible use of RPB for salt distillation does enhance the mass transfer performance. The application of the technology of separating ethanol and water from the mixture of the super gravity salt distillation technology has the advantages of improving the operation safety, strengthening the process and improving the efficiency of the energy saving.