8th International Congress on Science and Technology of Ironmaking - ICSTI 2018

New Zealand ironsand is an unconventional titaniferous ore (typically ~8% TiO2 by mass) which is commercially utilised to produce DRI, and as a blending component within BF sinters. Oxidative sintering of this titanomagnetite sand enables high-strength porous pellets to be formed, and such pre-oxidation is known to significantly enhance the gas-solid reduction rate compared to unoxidised ironsand. This is attributed to the increase in available surface area which results from cracking of individual grains during oxidation. However, the fate of titanium during oxidation has not been extensively studied, despite titanium playing an important role in the overall kinetics and yield of subsequent direct-reduction processes. In this work we report a detailed study of the evolution of titanium-bearing phases during the controlled oxidation of NZ ironsand pellets. Samples were oxidised in air at temperatures between 800 °C and 1300 °C, and then characterised using FEG-SEM, EDS, EBSD and XRD. Electron microscopy shows localised regions of titanium enrichment within the oxidised grains, and we observe the emergence of pseudo-brookite and ilmenite phases during the oxidation process. Our results indicate that titanium is highly mobile within individual oxidised grains, and that the final phase composition is strongly affected by both oxidising temperature and time.