Complete Reduction of Ilmenite by CO in Chemical Looping CombustionMultistep Kinetic Model Approach

The complete reduction behavior of iron oxide to iron in ilmenite ore was studied thermogravimetrically in the temperature range of 900–1100 °C by 30% CO concentration over 200 min. The rate of reduction curves moved from deceleratory to sigmoidal-shape (knee shape) behavior after about one-third of conversion. Analysis of data reveals that the reduction of ilmenite ore occurs by three independent parallel reduction steps, namely, Fe2O3 → Fe3O4, Fe3O4 → FeO, and FeO → Fe. The conversion data have been correlated for the first time using a multistep kinetic model derived from the Johnson–Mehl–Avrami approach. The apparent activation energies of these three steps have been estimated to be 46.32, 63.14, and 46.07 kJ/mol. The model is able to predict reduction data of complete conversion of ilmenite ore.