Study On The Vapor-liquid Equilibrium Mechanism Of Ternary Azeotrope Vacuum Distillation

Vapor-liquid equilibrium(VLE)theory can effectively explain the process of vacuum distillation separation and purification of crude metals.In the process of separating and purifying crude metals by vacuum distillation technology,azeotropic phenomena will occur.Related theoretical studies have not been reported.This subject carried out experimental verification and theoretical prediction of the azeotropic phenomenon of vacuum distillation of crude metals.The research work is as follows:Correlating the parameters of the Wilson equation,the saturated vapor pressure equation and the enthalpy of evaporation of pure metals,a method for predicting the azeotropy of binary alloys different from the VLE phase diagram is proposed.In addition,four sets of binary systems are selected for verification,and the results show that this method is reliable.This method is also used to predict the azeotrope of the tin-based binary alloy under vacuum distillation at 10 Pa,Al-Sn,Cu-Sn and Ti-Sn were azeotropic.The VLE phase diagram was used to predict the azeotropic composition of the Cu-Sn binary alloy under vacuum distillation at 5 Pa.Combined with the calculation results,the vacuum distillation experiment was carried out under the corresponding conditions and the experimental value was consistent with the predicted value.The Euler prediction-Newton correction method was used to calculate the azeotropic composition of Cu-Sn,Al-Sn,Ti-Sn,Al-Cu and Pb-Bi binary system under vacuum distillation at 10 Pa.The VLE theory was used to calculate the VLE phase diagram and the isothermal crosssectional diagram of the Ga-Sn-Zn,Cu-Pb-Sn and Al-Cu-Sn to determine the law of volatilization of the vacuum distillation alloy.And it obtained the interaction relationships of the new binary metal in the binary azeotropic system with the original binary azeotropic system.Based on the experiments and theoretical predictions of the binary azeotropic system,the azeotropic phenomenon in the vacuum distillation process of the ternary system was analyzed and discussed.Correlation of material balance and VLE theory to calculate the content of Ga-Sn-Zn,Cu-Pb-Sn and Al-Cu-Sn in the liquid and vapor phases when VLE is reached at different temperatures of 10 Pa.Studying the azeotrope of alloy vacuum distillation can complete the VLE theory of alloy vacuum distillation and provide guidance for the experiment of vacuum distillation to separate crude metals.