Measurement and effect of volatilization kinetic parameters in the production of high-purity zinc by vacuum distillation

Abstract

Vacuum distillation is commonly used for preparing high-purity zinc. However, the pressure of the experimental equipment must be below 1 Pa. Therefore, careful control over the accuracy of the equipment and vacuum system is required. In addition, there is a lack of information concerning the volatilization kinetic parameters for Zn, which makes it difficult to control the temperature and time parameters for the production of high-purity Zn. To solve these issues, the change in the mass of Zn and its evaporation rate (ω) at different temperatures (T) and pressures (P) was measured in real time using the vacuum differential-weight method. Using fitting, mathematical models for ω-T, ω-P, and ω-P-T were obtained, and, thus, other volatilization kinetic parameters, such as the evaporation coefficient and critical pressure, could be derived. The results showed that the critical pressure of Zn with respect to temperature was linear. Crucially, using the optimized parameters, high-purity Zn (6N8) was produced. Thus, this study provides volatilization kinetic parameters for the vacuum distillation of Zn and acts as a reference for improving the technological conditions and equipment production parameters used in Zn vacuum metallurgy.