铅锑合金共沸及气液相平衡研究

Study on Azeotropic and Vapor-Liquid Equilibrium of Pb-Sb Alloy

根据气液相平衡理论设计了测定合金气液相平衡的试验设备并测定了铅锑合金气液相平衡数据。测定结果证实了铅锑合金存在共沸现象,共沸现象发生在铅锑合金中锑摩尔含量为10%~20%。采用分子相互作用体积模型计算了铅锑合金的活度组元的系数,平均相对偏差和平均标准偏差分别为±0.08%和±0.005,证明该模型适用于计算铅锑合金活度系数。结合气液相平衡理论,应用该模型计算并绘制了铅锑合金气液相平衡相图(T-x-y图),计算结果并没有出现共沸现象并且与试验结果偏差很大。通过分析可知,纯金属的饱和蒸气压的准确性、金属挥发时分子形式、液态金属原子间结合力、液态金属表面张力和黏度等都会影响合金气液相平衡的计算结果,而目前的气液相平衡理论都没有考虑这些因素。本研究指出,下一步合金气液相平衡研究工作的重点是从试验角度测定纯金属的饱和蒸气压,在此基础上结合原子间结合力和分子挥发状态发展目前的气液相平衡理论,使其适用于计算共沸合金体系,从而更好地指导真空蒸馏。

Based on theory of vapor-liquid equilibrium,an experimental equipment was designed to measure vapor-liquid equilibrium data of Pb-Sb alloy.The results show that azeotropic phenomena exists in Pb-Sb alloy,which occur between 10%and 20%of molar content of antimony in Pb-Sb alloys.Activity component coefficients of Pb-Sb alloys are calculated by molecular interaction volume model.Average relative deviation and average standard deviation are±0.08%and±0.005,respectively,which proves that molecular interaction volume model is suitable for calculating activity component coefficients of Pb-Sb alloys.Vapor-liquid equilibrium phase diagrams(T-x-y diagrams)of Pb-Sb alloys are calculated and plotted by molecular interaction volume model combined with vapor-liquid equilibrium theory.The results show that there is no azeotropy and there is a big deviation from experimental results.The results show that accuracy of saturated vapor pressure of pure metals,molecular form of metal volatilization,bonding force between atoms of liquid metals,surface tension and viscosity of liquid metals all affect calculation results of vapor-liquid equilibrium of alloys,which are not taken into account in current vapor-liquid equilibrium theory.It is pointed out that in this study the next step in study of vapor-liquid equilibrium of alloys is to measure saturated vapor pressure of pure metals from experimental point of view.Based on this,the present vapor-liquid equilibrium theory is developed by combining interatomic binding force and molecular volatilization state so that to be used to calculate azeotropic alloys system and serve vacuum distillation better.