REDUCTION OF Fe AND Ni IN Fe-Ni-O SYSTEMS

The reduction behaviors of Fe-Ni-O compounds/systems (NiO, Fe2O3, NiFe2O4, Fe2O3 + NiO and Fe2O3 + Ni) were studied using H-2 and activated carbon C as reducing agents, and the mechanism of NiFe2O4 reduction was analyzed. With H-2 as reductant, these systems showed lower starting reaction temperatures and lower reaction rates. The differences of reaction rates among the different samples were small compared to those using C as reductant. With C as reductant, the reduction of the Fe2O3 + NiO system was much more facile compared to NiFe2O4, Fe2O3 + Ni, and pure Fe2O3. The heat released from the initial reduction of NiO by CO led to a higher temperature, which was more favorable for the further reduction of the Fe2O3 + NiO system. In both cases, NiFe2O4 appeared to be more difficult to reduce, as it required a higher starting temperature and exhibited a lower reaction rate and lower final reduction degree. Additionally, the data suggested that with increasing temperature, the products for the reduction of NiFe2O4 appeared in the order NiFe2O4 -> Fe3O4 + NiO -> Fe3O4 + Ni -> FeO + FexNiy -> FexNiy+ Fe (FemCn). Based on this data, kinetic information about the H-2 reduction for the five compounds/systems, such as apparent activation energy and reaction mechanism, was obtained.