Interaction Between Mineral Phases in a Hematite Iron Ore and Fluxing Materials During Sintering

The interaction between mineral phases in two commercial iron ores and flux materials (CaO, MgO, SiO₂, and Al₂O₃) was studied under 0.5 kPa O₂ partial pressure while heating to different temperatures. CaO was the most effective flux for liquid phase generation during sintering. For a hematite ore with few gangue components (Ore A), the formation of an initial liquid phase commenced at ~ 1275 °C, with the liquid volume increasing dramatically as temperature increased to 1300 °C. For a goethite containing hematite ore (Ore B), the formation of an initial liquid phase through interaction between goethite and CaO was observed when heating to 1225 °C, with the majority of goethite transformed to liquid at 1250 °C. The porous morphology of sintered goethite and finely distributed quartz results in a high reactivity with CaO. The initial liquid phase penetrated into the pores within the hematite matrix, promoting assimilation and by 1300 °C, all hematite in Ore B was dissolved. The hematite/martite phase in Ore B was much easier to assimilate than that in Ore A due to the presence of goethite. MgO diffused into hematite ore grains by solid-state diffusion and formed a solid solution (Fe, Mg)O∙Fe₂O₃ without the formation of a liquid phase. The reaction layer formed by MgO diffusion was limited to approx. 60 μm at 1300 °C. The porous morphology in goethite facilitated MgO diffusion. However, the cavities and cracks caused by goethite dehydration significantly restricted solid phase diffusion of Mg²⁺. There was no observed interaction between Al₂O₃ and SiO₂ with Ores A and B when heated to 1300 °C.