Reduction Kinetics of Pre-Oxidized Ilmenite Pellets by H2-H2O Gas Mixtures

The reduction behavior of pelletized and pre-oxidized ilmenite is investigated in H2-H2O atmospheres containing between 0 and 7% H2O and at temperatures between 983 and 1183 K (710 and 910 °C). The reduction mechanism occurs in two stages wherein the rapid reduction of trivalent to divalent iron cations is followed by the slower metallization of iron. Both temperature and gas composition are critical to achieving high reaction rates; within the range of conditions studied, the driving force for metallization has a significant effect on the reduction rate. Based on the experimental data and thermodynamic calculations, a model is established to predict the progress of the reduction as a function of temperature, gas composition and time. The application of this model at variable temperatures permits the determination of the activation energy Ea = 51 kJ/mol for the metallization reaction.