Investigation on the kinetics of hematite reduction reaction under different atmosphere systems in the process of hydrogen-based mineral phase transformation

Mineral phase transformation technology is an effective method for utilizing refractory iron ores. However, traditional CO-based processes generate significant CO₂ emissions, conflicting with the steel industry's low-carbon goals. Using H₂ and NH₃ as reducing agents offers a promising, carbon-free alternative, but studies on hematite reduction kinetics in different atmospheres remain limited. This study compares the hematite reduction kinetics in H₂, NH₃, and CO, utilizing XRD, SEM and BET to investigate phase transformation and microstructural evolution. Results show that reduction in H₂ and NH₃ follows the 3D diffusion model, with activation energies of 35.82 kJ·mol⁻¹ (H₂) and 100.69 kJ·mol⁻¹ (NH₃), respectively. In CO, the reaction follows the Avrami-Erofeev model with an activation energy of 18.97 kJ·mol⁻¹. The reduction rate is highest in H₂, with the largest specific surface area and pore volume of the product, followed by CO. H₂ and NH₃ can effectively reduce hematite, offering environmental advantages over CO.