Scientific Advances & Plasma Process Mechanism
ROC has uncovered the chemical and phase transformation pathways in iron ore reduction via lean hydrogen plasmas. Experiments show that a 10% H2 in Ar mix generates highly reducing plasmas in conventional EAFs. The process involves:
• Filling the EAF with Ar-10%H2 gas;
• Igniting an arc between the electrode and the material;
• Electron collisions dissociate H2 into reactive species (H, H⁺);
• At arc-material interfaces (T ≈ 2000°C), plasma species enable fast, simultaneous smelting and reduction of iron ores (melting point ≈1600°C).
This uses standard EAFs with minimal modification and demonstrates that impurities (Si, P, Ca) can be evaporated, allowing processing of low-grade ores, especially those rich in phosphorus, a major steel contaminant.
Red Mud Valorization: A Breakthrough
One of ROC’s most groundbreaking results, published in Nature, is the reduction of red mud via hydrogen plasma. Red mud is a hazardous by-product of aluminium production, with ~4 billion tons stored globally and <3% recycled. Conventional iron recovery methods from red mud rely on C-based reductants and costly treatments (roasting, milling, wet separation), which emit CO2.
ROC demonstrated a simple one-step process: dried red mud (e.g. 40% Fe2O₃) is reduced in hydrogen plasma, yielding pure metallic iron and an inert slag rich in TiO2. No carbon, no pre-treatment, no CO2. This enables a sustainable solution for red mud while producing high-quality iron and titanium feedstocks. It also links two major industries—steel and aluminium—through a shared recycling pathway.
Cu-Contaminated Scrap Recycling
Another advance is Cu removal from steel scrap. Copper is detrimental to mechanical properties, and today’s solution—dilution with pure iron—is resource-intensive. ROC showed that scrap contaminated with Cu can be co-processed with iron ore in an EAF under inert Ar plasma. Cu preferentially evaporates and is captured via electrostatic filters. The resulting melt is Cu-free, enabling simultaneous production of fresh iron and scrap recycling in one step.
The most important results have been published in high-reputed peer-reviewed journals:
1. Jovičević-Klug, M.*, Souza Filho, I. R.*, Springer, H., Adam, C., Raabe, D. Green steel from red mud through climate-neutral hydrogen plasma reduction (2024). Nature, 625, 703-709. * equal contribution
2. Büyükuslu, K. Ö., Aota, L., Raabe, D., Springer, H. Souza Filho, I. R. Mechanisms and elemental partitioning during simultaneous dephosphorization and reduction of Fe-OP melts by hydrogen plasma (2024). Acta Materialia, 277, 120221.
3. Souza Filho, I. R., Kwiatkowski da Silva, A., Büyükuslu, Ö. K., Raabe, D., Springer, H. Sustainable Ironmaking Toward a Future Circular Steel Economy: Exploiting a Critical Oxygen Concentration for Metallurgical Cu Removal from Scrap‐Based Melts (2024). Steel Research International, 95 (5) 2300785.
4. Souza Filho, I. R., Springer, H., Ma, Y., Mahajan, A.; Da Silva, C. C., Kulse, M., Raabe, D. (2022). Green steel at its crossroads: Hybrid hydrogen-based reduction of iron ores. Journal of Cleaner Production, 340, 130805.
5. Souza Filho, I. R., Ma, Y., Kulse, M., Ponge, D., Gault, B., Springer, H., & Raabe, D. (2021). Sustainable steel through hydrogen plasma reduction of iron ore: Process, kinetics, microstructure, chemistry. Acta Materialia, 213, 116971.
