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| Direct reduction | |
|---|---|
| Name | Direct reduction |
| Other names | DR, sponge iron, DRI |
| Industry | Steelmaking |
| First developed | 1930s |
| Major proponents | Midrex Corporation, Hüttenes-Albertus, Salzgitter AG |
| Applications | Blast furnace, Electric arc furnace, Steel industry |
Direct reduction is a metallurgical process that converts iron ore into metallic iron at temperatures below the melting point of iron by removing oxygen from iron oxides using gaseous or solid reductants. The method produces products such as sponge iron and direct reduced iron that feed steelmaking routes including Electric arc furnace and blast-furnace pathways. Direct reduction plays a strategic role in national industrial policies, energy transitions, and international trade among resource-rich and industrialized nations.
Direct reduction yields metallic iron through solid-state chemical reactions between iron oxides and reductants in shaft furnaces, rotary kilns, fluidized beds, or shaft reactors. Major process families include gas-based processes promoted by Midrex Corporation and coal-based routes exemplified by Corex-adjacent technologies and historical processes developed by Hirohisa Sato and groups at Kobe Steel. Outputs—commonly termed sponge iron, direct reduced iron (DRI), or hot briquetted iron (HBI)—serve as feedstock for Electric arc furnaces, Basic oxygen furnaces, and specialized smelting units. Key industrial actors include ArcelorMittal, Tata Steel, Posco, and state-owned enterprises in India, Brazil, and Saudi Arabia.
Early experimentation with solid-state ironmaking dates to the late 19th and early 20th centuries with inventors in Germany and Sweden exploring direct-reduction kilns. Systematic development accelerated during the 1930s and 1940s with processes piloted by Krupp and researchers affiliated with Thyssen. Post‑World War II reconstruction and rising demand for decentralized steel supply stimulated adoption of gas-based technologies in the 1960s led by Midrex Corporation and the Hylsa consortium. From the 1970s through the 1990s, expansions in India driven by Rashtriya Ispat Nigam Limited and Tata Steel favored coal-based/direct-smelting variants, while the 2000s saw growth in Gulf states with companies such as Emirates Steel investing in HBI production. Recent innovation integrates renewable hydrogen research promoted by institutions like Fraunhofer Society and demonstration projects by corporations including SSAB and Hybrit partners.
Gas-based shaft furnaces, typified by the Midrex process and the HYL process, use reformed natural gas or synthesis gas to generate carbon monoxide and hydrogen that reduce iron oxides in countercurrent flow. Coal-based routes include rotary kiln systems and fluidized-bed technologies developed by Eramet and historical implementations by Kobe Steel. Smelting reduction concepts such as Corex and Finex combine coal gasification and smelting in integrated units, reducing reliance on coke and traditional blast-furnace charge. Hot briquetting produces HBI for transport and storage, with equipment supplied by companies like Danieli and SMS Group. Process control relies on instrumentation from Emerson Electric and automation platforms integrated by firms such as Siemens.
Feedstock quality spans iron ore lump, sinter, pellets, and concentrates produced by miners including Vale S.A., Anglo American, BHP, and Rio Tinto. Pellets from Pelletizing plants and sinter from plants owned by NMDC are common inputs. Gas-based reduction employs reformed natural gas derived from suppliers like Gazprom and QatarEnergy, while coal or metallurgical coke is used in coal-based systems with major coal suppliers including Peabody Energy. Emerging reductants involve low‑carbon hydrogen produced by electrolyzers from companies such as Nel ASA and ITM Power, and biogenic fuels promoted by research at Rothamsted Research and demonstration projects in partnership with SSAB and LKAB.
Direct reduction yields sponge iron, DRI, and HBI with metallurgical properties tailored for downstream processes. Sponge iron is commonly used as a charge in Electric arc furnaces run by steelmakers like Nucor and Gerdau, while HBI serves export markets and integrated plants operated by POSCO and ArcelorMittal. Specialty grades feed stainless steelmaking at producers such as Outokumpu and Aperam. DRI chemistry influences alloying, refractory selection, and secondary metallurgy practiced at facilities including Thyssenkrupp and Voestalpine.
Direct reduction alters emissions profiles relative to blast furnaces: gas-based routes emit less CO2 per tonne of iron than traditional coke-based smelting when using natural gas, benefiting from suppliers like QatarEnergy and regional policies in Norway and United Arab Emirates. Coal-based and smelting routes still generate significant CO2, shaping policy debates in jurisdictions such as India and China. Lifecycle assessments by research groups at Imperial College London and MIT compare greenhouse gas intensity, while projects like Hybrit and initiatives at European Commission level aim to decarbonize via hydrogen and CCS technologies developed in collaboration with Equinor and TotalEnergies. Economic drivers include ore and energy prices set by markets influenced by OPEC and commodity firms Glencore, affecting competitiveness and trade patterns among exporting countries like Australia and Brazil.
Operational risks encompass high-temperature environments, gas handling hazards, and dust explosion risks in shipment of DRI/HBI, managed through standards from American Society of Mechanical Engineers and International Organization for Standardization. Hydrogen integration introduces flammability and embrittlement concerns addressed by engineering teams at Linde plc and Air Products and Chemicals. Occupational health oversight by agencies such as Occupational Safety and Health Administration and European Agency for Safety and Health at Work guides protective measures. Continuity of supply and geopolitical factors—illustrated by events involving Russia and global LNG trade—affect feedstock security and operational resilience.