Effect of Water Vapor on the Hydrogen Reduction of Iron Ore Oxides: Formulation of Appropriate Rate Equation
摘要
In this work, results on the iron oxide reduction by hydrogen under varying H2/H2O partial pressures have been analyzed to formulate a rate equation that directly incorporates the thermodynamically consistent effect of water vapor on the reaction kinetics. Additionally, the effect of water vapor has been investigated at different phases of the reduction process. The experimental data were analyzed by the use of the Avrami–Erofeev nucleation-and-growth rate equation (and also the volume contraction model, just for comparison), from which the intrinsic kinetic parameters for the reduction of iron oxides under a mixture of hydrogen and water vapor have been determined. The findings indicate that the presence of water vapor in the hydrogen reduction of iron oxide significantly impacts the chemical driving force relative to the reaction equilibrium. The activation energy values for the hydrogen reduction of various phases of iron oxides ranged from 32.1 to 37.2 kJ mol−1 in the range of 1023 K to 1373 K, while the Avrami parameter of 1.4 represented the data satisfactorily. The reaction order with respect to hydrogen and water vapor partial pressures were unity. It is noted that for the kinetics analysis of the reaction of fine iron oxide particles the Avrami–Erofeev nucleation-and-growth model is best justified based on the reaction mechanism, unlike other statistical correlations.