Periodic Reporting for period 1 - ROC (Reducing Iron Oxides without Carbon by using Hydrogen-Plasma)
Reporting period: 2022-09-01 to 2025-02-28
ROC’s Mission and Breakthroughs in Sustainable Ironmaking
ROC is laying the scientific foundations for scalable, energy- and feedstock-efficient technologies to reduce iron from ores and scrap, enabling a hydrogen-plasma-based revolution in steelmaking. This transformative approach could reduce CO2 emissions from the steel industry by up to 80%, addressing the largest single industrial source of CO2 emissions and offering a major lever in fighting global warming. As emphasized by the IPCC, urgent decarbonization is possible—and ROC is showing how.
Two Main Research Strands
I. Late-Stage Direct Reduction & Hybrid Operation:
The final step of hydrogen-based reduction (wüstite to iron) is slow. ROC studies how to accelerate this via control of oxide microstructure, particle size, and chemistry, or by completing the final stage in a hydrogen-based plasma reactor. The “hybrid” approach performs initial reduction in a direct reduction furnace (DRF) and finishes in an electric arc furnace (EAF). It is sensible because:
(a) All reduced sponge iron must be melted in an EAF anyway;
(b) EAFs can run on renewable electricity;
(c) Completing only the final reduction in the EAF requires minimal hydrogen partial pressures and moderate retrofits.
II. Hydrogen-Plasma-Based Reduction:
ROC also investigates how hydrogen plasma can achieve rapid and efficient reduction with minimal modifications to conventional EAFs. The project explores:
(a) Fe-carrier feedstocks (scrap, partially reduced ores/pellets, hematite, magnetite, fines);
(b) Plasma gases (H2, NH₃, Ar, N2) and inert blends;
(c) Gangue contaminant tolerance;
(d) Retained oxides;
(e) Slag behavior;
(f) Plasma and arc properties (power, frequency, shape);
(g) Reduction kinetics at lowest H2 use;
(h) Plasma-driven O-removal via vapor pressure and stirring;
(i) Hybrid processing (H2-based DR + plasma);
(j) Electrode types (graphite vs. alternative).
Technology & Context
Ironmaking is the largest industrial CO2 emitter. To decarbonize, carbon must be replaced with hydrogen. ROC focuses on maximizing hydrogen efficiency, vital due to its limited availability and cost. Outcomes depend on oxide structure, gas composition, gangue elements, and electrode types.
Traditional steelmaking (~2.1 t CO2/t steel) vs.:
• Scrap-based (~0.3–0.6 t CO2/t);
• Fully hydrogen-based DR + graphite EAF (~0.7 t CO2/t);
• Pure H-based DR alone (~0.05–0.2 t CO2/t);
• Green H2 + clean electricity + non-graphite EAF: near-zero CO2.
With 1.86 billion tons of steel made yearly and rising demand, this is the most impactful industrial decarbonization route, potentially cutting 3.5–4 Gt of CO2 annually. ROC targets the core scientific mechanisms to unlock this future.
ROC is laying the scientific foundations for scalable, energy- and feedstock-efficient technologies to reduce iron from ores and scrap, enabling a hydrogen-plasma-based revolution in steelmaking. This transformative approach could reduce CO2 emissions from the steel industry by up to 80%, addressing the largest single industrial source of CO2 emissions and offering a major lever in fighting global warming. As emphasized by the IPCC, urgent decarbonization is possible—and ROC is showing how.
Two Main Research Strands
I. Late-Stage Direct Reduction & Hybrid Operation:
The final step of hydrogen-based reduction (wüstite to iron) is slow. ROC studies how to accelerate this via control of oxide microstructure, particle size, and chemistry, or by completing the final stage in a hydrogen-based plasma reactor. The “hybrid” approach performs initial reduction in a direct reduction furnace (DRF) and finishes in an electric arc furnace (EAF). It is sensible because:
(a) All reduced sponge iron must be melted in an EAF anyway;
(b) EAFs can run on renewable electricity;
(c) Completing only the final reduction in the EAF requires minimal hydrogen partial pressures and moderate retrofits.
II. Hydrogen-Plasma-Based Reduction:
ROC also investigates how hydrogen plasma can achieve rapid and efficient reduction with minimal modifications to conventional EAFs. The project explores:
(a) Fe-carrier feedstocks (scrap, partially reduced ores/pellets, hematite, magnetite, fines);
(b) Plasma gases (H2, NH₃, Ar, N2) and inert blends;
(c) Gangue contaminant tolerance;
(d) Retained oxides;
(e) Slag behavior;
(f) Plasma and arc properties (power, frequency, shape);
(g) Reduction kinetics at lowest H2 use;
(h) Plasma-driven O-removal via vapor pressure and stirring;
(i) Hybrid processing (H2-based DR + plasma);
(j) Electrode types (graphite vs. alternative).
Technology & Context
Ironmaking is the largest industrial CO2 emitter. To decarbonize, carbon must be replaced with hydrogen. ROC focuses on maximizing hydrogen efficiency, vital due to its limited availability and cost. Outcomes depend on oxide structure, gas composition, gangue elements, and electrode types.
Traditional steelmaking (~2.1 t CO2/t steel) vs.:
• Scrap-based (~0.3–0.6 t CO2/t);
• Fully hydrogen-based DR + graphite EAF (~0.7 t CO2/t);
• Pure H-based DR alone (~0.05–0.2 t CO2/t);
• Green H2 + clean electricity + non-graphite EAF: near-zero CO2.
With 1.86 billion tons of steel made yearly and rising demand, this is the most impactful industrial decarbonization route, potentially cutting 3.5–4 Gt of CO2 annually. ROC targets the core scientific mechanisms to unlock this future.
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.
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.
The findings of ROC go beyond the current state-of-the-art in green steelmaking. Its hydrogen plasma technology not only decarbonizes iron ore reduction but also offers circular pathways for processing industrial waste like red mud and Cu-contaminated scrap. These breakthroughs, rooted in accessible and existing infrastructure, make ROC a cornerstone for next-generation metallurgical processes.