Hydrogen-based suspension roasting for efficient utilization of high-phosphorus oolitic hematite: Selective reduction mechanism and metallization behavior

• Hydrogen suspension selective reduction enables low-carbon use of refractory oolitic hematite. • Selective reduction produced 80% metallized products under optimized conditions. • Multi-scale analyses revealed mineral phase transformations and reduction mechanism. • Detailed characterization of mineral composition and intergrowth relationships in optimal products. High-phosphorus oolitic hematite is a typical refractory iron ore whose complex oolitic structure hinders efficient utilization. In this study, a hydrogen-based suspension roasting technology was employed to achieve selective direct reduction of this ore in an efficient and environmentally friendly manner. The effects of reduction temperature, hydrogen concentration, and time on metallization were systematically investigated, while the phase transformation and microstructural evolution of the reduced products were characterized using Brunauer–Emmett–Teller (BET) surface area analysis, electron probe microanalysis (EPMA), Mineral Liberation Analysis (MLA), XRD and SEM-EDS. Under optimized conditions (800 °C, 60% H 2 , 25 min), the metallization degree reached 80.22%. The reduced products consisted mainly of metallic iron, apatite, and Fe–Si–Al–O amorphous residues, with a dense intergrowth structure suitable for electric furnace smelting. Apatite remained stable during the entire process, ensuring selective reduction of hematite, while temperatures above 700 °C promoted fayalite formation and encapsulation of oxides, limiting further improvement in metallization. These results highlight hydrogen-based suspension roasting as a promising pathway for the efficient, green, and sustainable utilization of high-phosphorus oolitic hematite, contributing to clean and low-carbon ironmaking.