Key Technologies for Low-Carbon Iron and Steel Metallurgy: Research Progress and Future Directions

Abstract

Steel production remains difficult to decarbonize because high-temperature heat supply, iron-oxide reduction and melting are still closely coupled to coke, coal and natural gas. With the blast furnace-basic oxygen furnace (BF-BOF) route continuing to dominate global output, the transition requires more than substitution of a single fuel; reductants, heat sources, metallic feedstocks and energy supply must be reconfigured together. Here we review the key reactions and engineering boundaries of low-carbon iron and steel metallurgy, including hydrogen-enriched blast furnaces with top-gas recycling, hydrogen-based direct reduction in shaft furnaces and fluidized beds, DRI-EAF and DRI-ESF routes, electrochemical ironmaking, hydrogen plasma metallurgy, and carbon capture, utilization and storage (CCUS). Particular attention is given to temperature-dependent phase transformations, gas-solid mass transfer and pellet sticking during hydrogen reduction; defluidization in fine-ore fluidized beds; downstream melting of high-gangue DRI; residual elements in EAF feedstocks and carbonaceous-material consumption during slag foaming; and the energy penalties and accounting boundaries associated with CO₂ capture. Hydrogen-based direct reduction and electrochemical routes offer substantial potential for deep decarbonization, but their system-level advantage depends on low-carbon hydrogen, electricity carbon intensity, ore quality and the downstream melting route. For the existing BF-BOF fleet, hydrogen enrichment, top-gas recycling and CCUS provide more immediate, although inherently bounded, mitigation options. Future comparisons should use consistent whole-chain boundaries spanning ore preparation, energy supply, reduction, melting and resource circulation, and should report direct and indirect emissions, energy demand, feedstock adaptability and product quality on the same basis.