Thermodynamic and Experimental Analysis of the Selective Reduction of Iron by Hydrogen from the Kergetas Iron–Manganese Ore

Thermodynamic modeling combined with experimental reduction tests was conducted to investigate the selective reduction behavior of iron-manganese ore using hydrogen gas at 800–900 °C. The results reveal that hydrogen reduction at a flow rate of 0.5 L/min promotes the stepwise transformation of iron oxides (Fe2O3 → Fe3O4 → FeO → Fe), accompanied by the decomposition of the intermediate spinel phase Fe2MnO4, resulting in the formation of metallic iron. In contrast, the reduction of MnO to metallic manganese is thermodynamically unfavorable (ΔG > 0), limiting the extent of manganese reduction. Experimental findings confirm the formation of metallic iron inclusions enriched in Fe, while manganese predominantly remains in the form of MnO and silicate-associated oxides. X-ray diffraction analysis of reduced samples shows a decrease in Fe3O4 and Fe2MnO4 phases with increasing reduction degree and indicates the growth of metallic Fe particles with rising temperature. These results demonstrate that hydrogen enables controlled and selective reduction of iron with minimal manganese conversion, providing a promising route for subsequent efficient magnetic separation of metallic and oxide phases following reduction roasting.