Experimental Study On The Vapor-liquid Equilibrium Of Copper-based Ternary Alloy Vacuum Distillation

With the wide application of copper's excellent performance in various industrial sectors,the shortage of copper mineral resources and the accumulation of a large amount of copper-containing waste have been caused.Effective recycling and utilization of copper secondary resources is of great significance for reducing mineral consumption and environmental pollution.Vacuum metallurgy technology is widely used in the recovery of secondary resources and the separation and purification of metals by the advantages of its high efficiency,pollution-free and high metal recovery.However,vacuum distillation technology may encounter the formation of azeotropy alloys when separating crude copper,so that impurities cannot be separated effectively.The research content of this paper is as follows:Based on the vapor-liquid phase equilibrium?VLE?theory,the activity of components of Cu-Bi,Cu-Sb and Cu-Sn binary alloys was predicted by the Wilson equation.It was extended to Cu-Bi-Sb and Cu-Bi-Sn ternary alloys to calculate the activity of components.The VLE phase diagrams of Cu-Bi,Cu-Sb,Cu-Sn and Cu-Bi-Sb,Cu-Bi-Sn systems were predicted by activity coefficient method.The positions of the azeotropes of copper-based binary and ternary alloys were predicted according to the theories of VLE and azeotropy.The vapor-liquid equilibrium experiments for the copper-based binary and ternary systems in vacuum distillation process were studied and the VLE data were meaured at pressure of 10 Pa.The correlation between the experimental data and the VLE phase diagram shows that the predicted VLE phase diagram of Cu-Bi binary alloy is in good agreement with the experimental data.The Cu-Bi alloy could be separated well by vacuum distillation.A single distillation could collect relatively pure Cu in the liquid phase and Bi in the vapor phase.The predicted VLE phase diagram of Cu-Sb binary alloy is inconsistent with the trend of experimental data with the change of temperature.The main reason is that there is a strong interaction between Cu and Sb.The formation of the metallic compound Cu₃Sb prevents Sb from volatilizing and prevents vacuum distillation from completely removing Sb from the crude copper.The Cu-Sn alloy could not be separated well under 10 Pa and the experimental data are close to the predicted position of azeotropy at 1689 K.The Bi in Cu-Bi-Sb ternary alloy could be removed by vacuum distillation,Cu and Sb could not be completely separated in the liquid residue,which is consistent with the result of the Cu-Sb binary alloy.For the Cu-Bi-Sn system,Bi was completely volatilized into the vapor phase.There is a very small amount of Sn in the vapor phase,Cu and Sn remain in the liquid phase to form azeotropy.The theoretical predictions of the location of azeotrope are consistent with the experimental results.It indicates that the predicted method of the VLE and the position of azeotrope of copper-based alloys in this work could be used to predict the separation and design process for crude metal in vacuum distillation.