Influence of Temperature on Reaction Mechanism of Ilmenite Ore Smelting for Titanium Production

Abstract

The carbothermic smelting reduction process of ilmenite ore at high temperature was investigated by thermodynamic calculations in conjunction with smelting experiments. Based on thermodynamic calculations, conducting the smelting process at a higher temperature was recommended to achieve a larger amount of FeO reduction, i.e., higher Ti-enrichment, as less precipitate and thus large amounts of a liquid slag were predicted. However, even though the reduction of FeO in ilmenite ore at the initial stage seemed to be faster as the temperature increased, no significant difference in the TiO₂ or FeO concentration was observed after the reaction was complete, regardless of the temperature. This was caused by the precipitation of pseudobrookite due to the local depletion of FeO during reaction at higher temperatures, by which further reduction reaction was prohibited. The apparent rate constant increased with increasing temperature and the activation energy of the reduction process was estimated to be 144 kJ/mol, from which it was concluded that the reduction reaction of FeO in ilmenite slag by carbonaceous reductant was generally controlled through the mass transfer in the slag phase. Additionally, the formation of TiC also occurred in the iron bath. At 1923 K (1650 °C), approx. 20 pct more TiC was generated as compared to TiC formation at 1823 K (1550 °C), which also prevented further reduction of Fe at higher temperatures.