Constitutive Model and Experimental Verification of Kinetics of Non-isothermal Hydrogen Reduction of Ilmenite: A Case Study on Kahnuj Ilmenite

In this study, the reduction kinetics of ilmenite concentrate from a domestic mine (Kahnuj, Kerman, Iran) in pure hydrogen in the temperature range of 500 °C to 1100 °C was investigated. From the non-isothermal reduction results corresponding kinetic parameters for the as-received and pre-oxidized concentrates were calculated using the Coats-Redfern method. The reduction process in both raw and pre-oxidized ilmenite, at 800 °C was controlled by diffusion through the product layer. The kinetic analysis for ilmenite pre-oxidized at 1000 °C indicated that the reduction process followed a chemical reaction and nucleation and growth mechanism. The samples pre-oxidized at 800 °C and 1000 °C exhibited higher mass loss values and reduction degrees compared to the raw ilmenite. The promoting effect of pre-oxidation on the reduction of ilmenite is attributed to the phase changes in pre-oxidized ilmenite and the porous structure created during the reduction process after the pre-oxidation process. X-ray diffraction (XRD) patterns confirmed the presence of pseudorutile, rutile, and hematite after oxidation at 800 °C, and pseudobrookite and rutile were stable phases after oxidation at 1000 °C.