Reduction and oxidation kinetics of different phases of iron oxides

The redox properties and kinetic parameters of three different phases of as-received iron ores such as γ-FeOOH, Fe₂O₃, and Fe₃O₄ were investigated using isothermal experiments for reduction and oxidation reaction using hydrogen and H₂O, respectively, to investigate the possibility for chemical looping process to produce pure hydrogen. Among the selected kinetic equations of three different iron oxide ores for the reduction at 800 °C and oxidation in the temperature ranges 700-850 °C, three-dimensional diffusion kinetic model such as Jander equation was well fitted with the experimental redox reactions of the three different iron ores. The calculated activation energies of iron ores with a main phase of γ-FeOOH, Fe₂O₃, and Fe₃O₄, for the oxidation reaction with H₂O, were found to be around 21.5, 48.9, and 11.0 kJ/mol, respectively. The smaller activation energy and larger oxidation rate were observed on the Fe₃O₄-phase iron ore owing to its large reduction rate and stable particle size maintenance even under high temperature redox reactions, and it is suitable for the further application to chemical looping process.