In Situ Microscale Observation of FeOx–SiO₂ Interfacial Reaction

Promoting the interfacial reaction between iron oxide (FeOx) particles generated from concentrate and silica-flux in the reaction shaft is essential to make the slag with good flowability and ensure matte separation in the settler of the flash furnace. The interfacial reaction of micro-meter-order-sized FeOx particles in contact with silica-flux was observed using high-temperature microscopy, and the slag formation behavior was successfully observed directly with this system. The main product of FeS oxidation is Fe₃O₄ in the flash furnace operation condition, and the reaction temperature between Fe₃O₄ and SiO₂ is considerably higher than the typical melt temperature in the settler. On the other hand, when FeS coexisted with Fe₃O₄, the reaction temperature with SiO₂ was significantly lowered. It was shown that the coexistence of FeS with Fe₃O₄ and SiO₂ is the key to the removal of Fe₃O₄ and the formation of FeOx–SiO₂ slag in the reaction shaft. The effect of the particle size, the composition of silica-flux, and the partial pressure of O₂ on the reaction were also investigated in this study. It was shown that the observation method reported here has the potential for obtaining the reaction kinetics of interfacial slag formation reactions.