Study On Vacuum Distillation Separation Of Tin - Antimony Alloy

In view of the problem as low removal efficiency of antimony in the process of vacuum distillation of Sn-Pb-Sb alloy, the investigation on vacuum distillation of Sn-Sb alloy was performed. This thesis focused on the volatilization law of components of Sn-Sb alloy in vacuum distillation. The feasibility of deep removal of Sb from Sn-Sb alloy was determined by using theoretical prediction. Meanwhile, the volatilization rates of Sn, Sb, and Sn-Sb alloy were measured experimentally in various temperatures and pressures. On the basis of preceding research, the distributions of the components of Sn-Sb alloy in vacuum distillation were investigated experimentally. Furthermore, the optimum conditions of vacuum distillation of Sn-Sb alloy were obtained by using response surface method. Here are the main conclusions:(1) The boiling point and the saturated vapor pressures of Sn and Sb, the separation coefficient and the vapor-liquid phase equilibrium of Sn-Sb alloy were calculated, which confirms that Sn-Sb alloy can be completely separated by vacuum distillation in the view of thermodynamics.(2) The volatilization rates of Sn, Sb, and Sn-Sb alloy (Sn51.3%-Sb48.7%) were measured over the temperature range 1000-1400℃, under the pressure of 5-90 Pa. The relationship between the maximun volatilization rate of Sn and temperature, and the relation of the critical pressure and temperature are as follows, lgωSn-max*=510.35/T-3.5075, Pc=102.28-89314/T. The relationship between the maximum volatilization rate of Sb and temperature, and the relation of the critical pressure and temperature are as follows, lgωSb-max*=-2624/T-0.0449, Pc=58.36-50787/T. The relationship between the maximum volatilization rates of the component of Sn-Sb alloy and temperature are as follows, lgωSn-max=-4641/T+0.3580; lgωSb-max=-3044/T+0.2644. Following from preceding results, there exists some interaction between the components of Sn-Sb alloy, viz. the existence of Sb will increase the volatilization rate of Sn, instead, the volatilization of Sb was suppressed. While the temperature rising up to 1400℃, there is no effect on the volatilization of Sb.(3) The effects of distillation temperature, feeding materials (thickness of raw materials) and soaking time on the content of Sn in liquid phase and the direct yield of Sn were investigated by using single factor experiments. Based on the single factor experiments, the separation process of Sn-Sb alloy in vacuum distillation was optimized by the response surface method. After the optimized design, two mathematical regression models of between the content of Sn in liquid phase and the direct yield of Sn and factors were obtained. The analysis of variance (ANOVA) results show that these models are in good agreement with the experimental data. The optimum process conditions were determined through above models. The optimum process conditions were distillation temperature,1258℃; feeding materials, 137g; soaking time,46min. The content of Sn in liquid phase and the direct yield of Sn were 99.43% and 91.22% from the confirmation test under the optimum conditions.