Near-zero carbon iron powder from high‑phosphorus oolitic pellets via hydrogen reduction-electromagnetic iron phase reconstruction - magnetic separation

Abstract

To overcome the limitations of conventional carbothermic reduction—specifically its high carbon footprint and the inefficient treatment of finely disseminated iron minerals in high‑phosphorus oolitic iron ore (HPOIO)—this study introduces an innovative process combining hydrogen reduction, electromagnetic induction heating, and magnetic separation. Under optimized reduction conditions (950 °C, 90 min, 10 L/min H₂ flow), the oxidized pellets attained a metallization degree of 85.56 %. A profound microstructural transformation was achieved via electromagnetic induction heating at 1350 °C for 30 min, which resulted in an approximately 16-fold increase in the average equivalent circular diameter of the metallic iron grains, from an initial 1.19 μm to a final 19.03 μm. This microstructural evolution, driven by recrystallization and phase rearrangement, converted finely dispersed iron phases into coarse vermicular and massive aggregates, markedly improving slag–metal separation. The efficacy of the induction treatment was demonstrated by a substantial upgrade in the magnetic concentrate. This was evidenced by an elevation of the iron grade to 91.18 % from an initial 59.57 %, a concomitant drop in phosphorus content to 0.09 % from 0.26 %, and a resultant surge in dephosphorization efficiency to 79.77 % from 12.14 %. The integrated approach demonstrates a viable near-zero-carbon route for converting HPOIO into high-grade, low-phosphorus iron powder via hydrogen-based direct reduction and precisely controlled iron phase reconstruction.