Fundamentals of reduction of CaO·Fe2O3 in CO/CO2 gas at 1000°C

Calcium ferrite is the most basic bonding phase in sinter and the matrix of Silico-ferrites of calcium and aluminium (SFCA). In order to better understand the fundamentals of the reduction of CaO·Fe2O3, CaO·Fe2O3 samples were prepared by solid-state sintering and reduced by CO/CO2 mixture gas at 1000°C. Then, the equilibrium phase and morphology were tested by XRD and SEM-EDS. The experimental results indicated that (1) As CO/(CO + CO2) = 20%, CaO·Fe2O3 was reduced to CaO·FeO·Fe2O3 and 2CaO·Fe2O3. (2) As CO/(CO + CO2) = 40%, CaO·FeO·Fe2O3 was reduced to CaO·3FeO·Fe2O3 and 2CaO·Fe2O3, the equilibrium phases were CaO·3FeO·Fe2O3 and 2CaO·Fe2O3. (3) As CO/(CO + CO2) = 60%, CaO·3FeO·Fe2O3 was reduced to FeO and 2CaO·Fe2O3, and 2CaO·Fe2O3 was still the stable phase. (4) As CO/(CO + CO2) = 80%, FeO was reduced to metallic Fe, and 2CaO·Fe2O3 was reduced to metallic Fe and CaO. The finding from this work may be used as a theoretical foundation for the research of the reduction of SFCA.