Isothermal and non-isothermal reduction kinetics of iron ore oxygen carrier by CO: Modelistic and model-free approaches

The reduction of iron oxides has significant potential in the development of abating CO2 emissions since hematite is a noteworthy oxygen carrier in Chemical Looping Combustion (CLC). This work aimed to investigate the reduction kinetics of an iron ore oxygen carrier from Menteş (Turkey) using thermogravimetry (TG). By the cooperative utilization of modelistic and model free kinetic techniques on both isothermal and nonisothermal data, the kinetics of the gas-solid reaction between the ore and CO was comprehensively revealed. The reduction was determined to composed of 3 stages; first includes the “hematite to magnetite” transition which can be represented by zero-order contradiction model (F0), while the second and the third stages include the transformations of “magnetite to wustite”, and “wustite to metallic iron” respectively. The two-dimensional contradiction (R2) and unimolecular decay (F1) models were found to represent the experimental data belong to the second and the third stages best. The obtained activation energy values concentrated around 40–65 kJ/mol interval throughout the reaction as the mean of all used methods.