Investigation of Molten Salt Phase Formation during Alkali Roasting of Titaniferous Minerals with Sodium and Potassium Hydroxide

摘要

Current processes for beneficiation of titaniferous minerals are energy-intensive and produce significant waste. The benefit of alkali roasting over existing process is that it minimises waste. Previous studies on liquid phase formation during alkali roasting of titaniferous minerals were based on the use of Na_2CO_3, whereas this study focuses on oxidative roasting of titaniferous minerals with either NaOH or KOH, using different alkali to mineral ratios. Phase equilibria of the Na/K-Fe-Ti-O system are calculated the results compared to observed results. This work attempts to characterise the alkali-rich liquid phase formed during roasting and determine its impact on alkali titanate and alkali ferrite separation, as it has been found that Ti-K-Fe-O and Ti -Na-Fe-O ternary phases can be present. The presence of the liquid phase at the reaction interface adversely affects the oxygen diffusion during roasting, which has consequences on the products formed.