Effects of Preoxidation of Titania-Ferrous Ore on the Ore Structure and Reduction Behavior

Abstract

The paper examined an effect of preoxidation of titania-ferrous ore (New Zealand ironsand) on the ore structure and reduction by carbon monoxide.
The major phase in ironsand is titanomagnetite, Fe₃O₄-Fe₂TiO₄ solid solution, with spinel cubic structure. In the non-isothermal preoxidation titanomagnetite was oxidized to cubic maghemite and then transformed to rhombohedral titanohematite, Fe₂O₃-FeTiO₃ solid solution. Isothermal preoxidation of the ironsand at 1 273 K transformed titanomagnetite to titanohematite and partly to pseudobrookite (Fe₂TiO₅), however, complete oxidation of Fe²⁺ to Fe³⁺ in titanomagnetite was not achieved in the experimental condition.
The reduction of the titania-ferrous ore was investigated in non-isothermal and isothermal experiments using 75vol%CO-25vol%Ar gas mixtures in a laboratory fixed bed reactor. Samples in the course of reduction were characterized using XRD and EPMA. Preoxidation increased the rate of ironsand reduction.