Whether magnetization roasting requires complete phase reconstruction of iron minerals: A study of phase transition and microstructure evolution

Abstract

Previous magnetization roasting studies usually pursued whole phase reconstruction of iron minerals. This research innovatively proposed a surface magnetization roasting technology requiring only partial phase reconstitution of hematite to decrease carbon emissions. Two hematite samples with narrow particle size distributions (45–74 μm and 74–150 μm) were adopted to better control the magnetite layer thickness. The optimal magnetic separation index was obtained when the relative thickness of the magnetite layer was only approximately 0.3000 and the magnetite content in the roasted product was only about 40%. The remaining hematite still needed a long time to be reduced to magnetite. The hematite on the particle surface was preferentially reduced to magnetite. The surface magnetite can provide magnetic force during the magnetic separation process to recover the roasted particles. The efficient iron recovery was realized through surface magnetization roasting, which only required partial reduction of hematite, consuming less energy and reductant.