Bubble point measurement and high pressure distillation column design for the environmentally benign separation of zirconium from hafnium for nuclear power reactor

Abstract

We examined the feasible separation of ZrCl₄ and HfCl₄ through high pressure distillation as environmentally benign separation for structural material of nuclear power reactor. The bubble point pressures of ZrCl₄ and HfCl₄ mixtures were determined experimentally by using an invariable volume equilibrium cell at high pressure and temperature condition range of 2.3–5.6 MPa and 440–490 °C. The experimental bubble point pressure data were correlated with Peng-Robinson equation of state with a good agreement. Based on the vapor-liquid equilibrium properties evaluated from the experimental data, the feasibility of high pressure distillation process for the separation of ZrCl₄ and HfCl₄ was investigated with its main design condition through rigorous simulation using a commercial process simulator, ASPEN Hysys. An enhanced distillation configuration was also proposed to improve energy efficiency in the distillation process. The result showed that a heat-pump assisted distillation with a partial bottom flash could be a promising option for commercial separation of ZrCl₄ and HfCl₄ by taking into account of both energy and environmental advantages.