A further investigation on the MnO2-Fe2O3 system roasted under CO-CO2 atmosphere

Abstract

Investigations on the MnO2-Fe2O3 system roasted in air has been reported in our previous work. This study further investigated the MnO2-Fe2O3 system roasted under CO-CO2 atmosphere. Extensive investigations were concentrated on the reduction of simplex iron oxides or manganese oxides, and little attention were paid on the reduction of MnO2-Fe2O3 system regarding to interactive reactions between them. In this work, it was found that spinel-type MnxFe3−xO4 with high magnetism formed easily under CO-CO2 atmosphere. The reduction and thermodynamic analyses of pure MnFe2O4 were also researched to better understand the reduction behaviors of MnO2-Fe2O3 system. Phase study showed that a series of Mn-Fe composite oxides, including MnxFe3−xO4 and (MnO)y(FeO)1−y, generated during the reduction of MnO2-Fe2O3 system. MnxFe3−xO4 was readily generated under CO content of 2.5–25 vol% at 1000 °C. With further increase of CO content, MnxFe3−xO4 was reduced to (MnO)y(FeO)1−y and then to MnO and metallic iron. Reduction of manganese oxides, iron oxides and manganese ferrites happened concurrently during the reduction of MnO2-Fe2O3 system. And the reduction of MnO2, Fe2O3, Fe3O4 and MnFe2O4 were compared by TG and thermodynamic analyses. In addition, the morphology evolution and magnetism change of the MnO2-Fe2O3 system reduced under different CO contents were also studied.