Purification of crude titanium powder produced by metallothermic reduction by acid leaching

Abstract

The CSIR is developing a process to produce commercially pure (CP) Grade 4 titanium metal powder via direct metallothermic reduction of TiCl4. Crude titanium produced by this method is inevitably contaminated with unreacted reducing metal and titanium subchlorides occluded in halide salt. For the product to meet stringent titanium industry quality requirements, the concentration of impurities must be held to acceptably low levels. Acid leaching was identified as a suitable method for purifying the crude reduction mass, due to the solubility of the by-products and the potential for cost-saving provided by this method compared to vacuum distillation. However, purification by leaching poses drawbacks such as high oxygen impurity concentrations in the product, due to the dissolution of subchlorides in water to form insoluble hydroxides and oxychlorides that concentrate on the surface of the titanium powder. The crude titanium was leached under different conditions using water and 1 M and 0.035 M hydrochloric acid at a temperature below 50°C. The 1 M acid leach yielded a product with the lowest oxygen content, demonstrating that when the pH of the media and temperature are controlled, the drawbacks associated with acid leaching can be overcome and the process used successfully for downstream purification of the crude product.