Hydrogen-based direct reduction of vanadium-titanium magnetite raw ore: Process optimization and mechanism insights

Abstract

The conventional processing of vanadium-titanium magnetite (VTM) has been associated with substantial CO₂ emissions and inefficient resource utilization, raising significant sustainability concerns. This study introduced a hydrogen-based direct reduction method for processing VTM raw ore without the need for a beneficiation process. Through thermodynamic analysis and experimental validation, we demonstrated the feasibility of this novel approach, achieving a remarkable metallization degree of iron up to 92.6 % at 1120 °C. Additionally, this method effectively enriched iron and titanium, yielding recovery efficiencies of 91.0 % for iron and 58.4 % for titanium via wet grinding and magnetic separation. The reduction process of VTM followed a stepwise reaction mechanism, characterized by distinct pathways for titanium and iron. The conversion sequences were as follows: Fe₂TiO₅ → Fe₂TiO₄ → FeTiO₃ → FeTi₂O₅ → TiO₂ → Ti_xO_y for titanium and Fe₂O₃ → Fe₃O₄ → FeTiO₃ → Fe + FeTi₂O₅ → Fe for iron. Notably, the conversion of FeTiO₃ to Fe emerged as the rate-limiting step, with an apparent activation energy of 75.56 kJ·mol⁻¹. These findings underscore the potential of hydrogen-based reduction as a sustainable and resource-efficient pathway for VTM processing, significantly contributing to reducing the environmental impact of metallurgical practices.