Reduction kinetics for Fe2O3/NiO-doped compound in a methane atmosphere

The reduction characteristics of a Fe2O3/NiO-doped compound in a methane (CH4) atmosphere were investigated at 1050-1200 degrees C using isothermal thermogravimetric analysis (TGA). Isothermal kinetic reduction curves show two obvious stages in the process of methane reduction, corresponding to an initial stage (Fe2O3 -> FeO) and a final stage (FeO -> Fe). The kinetic investigation indicated the activation energies of the two stages for pure Fe2O3 were 54 and 99 kJ/mol. With the addition of NiO, the reduction rate of the two stages was discussed. The results indicated that NiO had a promoting effect on the initial stage of reduction due to the formation of trevorite [NiFe2O4]. Kamacite [Fe Ni] was observed in the reduction roasted ore, and it can be attributed mainly to the reaction of Fe + Ni = [Fe Ni] at high temperature. Based on the analyses, the reaction rate at the final stage decreased with addition of NiO, and the value of activation energy of the reduction process was increased to 112 kJ/mol, resulting in a reduction rate-determining step of solid-state diffusion. (C) 2017 Elsevier B.V. All rights reserved.