Study of Kinetics and Mechanism of Hydrogen Plasma Reduction Process in Low-Grade Iron Ores for Sustainable Steel Production

Steelmaking currently emits about 2.1 tons of CO2 per ton of steel produced, making up 8% of global emissions; at the same time, good-quality iron ore is becoming scarce to utilise through traditional carbon intensive processing routes. Hydrogen Plasma Smelting Reduction (HPSR) offers a cleaner alternative, using hydrogen plasma to reduce and melt iron ore in one step without any CO2 emissions. This study compares the reduction behaviour of high-grade Carajás ore and low-grade Tubarão ore under HPSR, using XRD, SEM-EDS, and Thermo-Calc to track phase changes and Fe recovery. Hematite quickly converts to FeO and fayalite (Fe2SiO4), and then to metallic iron, but higher SiO2 content increases fayalite formation, trapping iron in the slag-this effect is stronger in Tubarão ore, while Carajás ore shows better reducibility due to fewer impurities. At the end, we found that some part of the metallic Fe actually forms from fayalite reduction; at the same time, mass balance calculations highlight the reproducibility in the process. SEM-EDS reveals trapped metallic Fe within unreduced oxide regions, likely due to rapid cooling limiting iron droplet coalescence. These findings highlight fayalite formation as a key challenge for recovering iron from low-grade ores, and future work will focus on improving fayalite reduction and understanding scale-up feasibility for HPSR.

Séminaire organisé par le département SI2M.