Separation and recycling of chloride salts from electrolytic titanium powders by vacuum distillation

Abstract Molten salt electrolysis is an important and low-cost method to prepare titanium powders. The separation and recycling of chloride salts from electrolytic titanium powder(ETP) is quite crucial for the purpose of improving the quality and reducing production cost. In this study, a novel process was developed to remove and recycle the chloride salts impurities (e.g., NaCl, KCl) in ETP by using vacuum distillation. The saturated vapor pressures of components in ETP were theoretically analyzed to predict the system pressure and temperature conditions during distillation process. It shows that the vaporization of the mixture of NaCl–KCl salt strengthens upon increasing the temperature. The volatilization behavior of NaCl-KCl salt and the effects of system pressure, distillation temperature and holding time on the separation were investigated using a lab scale vertical vacuum distillation furnace. Experimental studies indicates that the chlorine impurity content in purified titanium powder can be maintained at a percentage of below 0.04 wt. % under the optimal experimental condition of 850 °C, 3.5–4 h, and 0.1–1 Pa. These results demonstrate that the chloride salts can be efficiently separated and recycled from ETP in an environmentally-friendly manner by using vacuum distillation. The process comparison and evaluation show that the vacuum distillation post-treatment is a method without the generation of waste acid and wastewater, and the titanium powder with a low oxygen impurity can be produced.