The relationship between FeO and Ti2O3 in ilmenite smelter slags

Smelting is used to upgrade ilmenite (FeO.TO2) to high-titania slags which serve as feedstocks for TiO2 pigment manufacture. During smelting, partial reduction of FeO to liquid iron, and of TiO2 to Ti2O3, occurs. Lower FeO levels in the solidified slag correlate with higher Ti2O3, Since some pigment manufacturers limit the allowable Ti2O3 level in the slag, the origin of this relationship is of interest. Ilmenite smelter slag compositions from the literature were examined to test possible origins of the FeO-Ti2O3 relationship. Available equilibrium data indicated that the relationship does not follow equilibrium, nor is there likely to be a simple kinetic cause. It is concluded that a phase-chemistry effect causes the relationship to follow closely that required by the stoichiometric M3O5 phase, the major component of solidified slag.