Morphological changes accompanying the partial reduction/re-oxidation cycles applied to an iron ore

This paper is concerned with ironmaking and its purpose is to gain insight into the effect of the partial reduction/re-oxidation process during sinter making in the resultant ore reducibility. Morphological changes experienced by hematite iron ores during thermal-chemical treatment of hematite-to-magnetite partial reduction, followed by magnetite-to-hematite re-oxidation, were observed by scanning electron microscopy and surface-area measurements. It was verified that during the partial reduction step, a considerable increase in the surface area occurs, arising from the generation of pores and cracks. During the re-oxidation step, another significant increase in surface area also occurs, resulting from the nucleation and growth of numerous globules of hematite at the surface of grains. This feature is associated with the iron-ore sintering process and may contribute to improving the sinter reducibility during the subsequent iron-making process. Hematite composition: 1.03wt%SiO₂, 0.04wt%FeO, 98.2wt% Fe₂O₃, 0.53wt% Al₂O₃, 0.03wt% MnO, 0.05wt% Na₂O, 0.02wt% K₂O, 0.05wt% CaO, and 0.10wt%MgO.