Effects of preoxidation of titania-ferrous ore on the ore structure and reduction behavior

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.