Decarbonization Strategies in Ironmaking Processes

The iron and steel sector is among the most carbon-intensive industries, accounting for roughly 7 % of global CO₂ emissions. Traditional blast furnace routes rely on coke and coal as both reducing agents and energy sources. Decarbonization pathways focus on lowering fossil carbon input, capturing residual CO₂ and integrating renewable energy. Key strategies include partial or full oxygen enrichment in blast furnaces, top gas recycling to reuse uncombusted CO and H₂, direct reduction of iron ore with hydrogen, carbon capture and storage (CCS) or utilisation, and power-to-gas (PtG) schemes that convert excess renewable electricity into hydrogen or synthetic methane. Electrolysis and magnetic separation can pre-treat feedstocks, while electric arc furnaces (EAFs) powered by low-carbon electricity enable greater scrap utilisation. Techno-economic assessments highlight trade-offs between capital costs, operational complexity and market carbon prices. Life-cycle analysis underlines the need for system integration: coupling hydrogen generation or PtG plants with ironmaking can achieve CO₂ reductions in excess of 30 %, while novel smelting reactors promise near-zero emissions in the medium term. Policy frameworks, carbon trading and green steel certification are crucial to de-risk investments and accelerate deployment at steel-making hubs worldwide.

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Recent studies have provided concrete evaluations of emerging process configurations. An economic analysis of an integrated steel plant compared conventional blast furnaces with oxygen-enriched blast furnaces equipped for top gas recycling. It found that oxygen blast furnaces with top gas recycling, even without capture, deliver significant CO₂ abatement and superior net present value under current carbon trading schemes. Full commercial viability, however, often requires a moderate carbon price or further efficiency gains.

Investigations into a full oxygen blast furnace combined with a carbon metabolism model demonstrated that complete recycling of furnace top gas can reduce coke rates from 270 to 207 kg per tonne of hot metal and lower direct process emissions to under 0.1 t CO₂ per tonne of charge. As replacements of traditional furnaces increase, direct combustion and process emissions fall to exceptionally low levels, underscoring the potential of oxygen-only ironmaking loops.

Power-to-gas integration has also been analysed through modelling sixteen PtG configurations for blast furnaces. The most promising concept uses treated blast furnace gas to synthesise methane, replacing a portion of coal or coke and avoiding up to 21 % of CO₂ emissions. Energy penalties range from 10 to 21 MJ per kilogramme of CO₂ avoided, and practical limits on electrical self-sufficiency are imposed by flame temperature constraints and electrolyser capacity. These findings guide optimisation of PtG scale and integration pathways.

Decarbonization Strategies in Ironmaking Processes publication trend

The graph below shows the total number of articles in decarbonization strategies in ironmaking processes across all publications each year (not limited to Nature Index journals).

Technical terms

Blast furnace: A tall shaft furnace in which iron ore is reduced to molten iron by coke and preheated air (or oxygen) in a counter-current process.

Top gas recycling: The process of cleaning and re-injecting furnace off-gas rich in CO and H₂ into the blast furnace to reduce overall fuel consumption and emissions.

Oxygen blast furnace: A variant of the blast furnace that uses high-purity oxygen instead of air to lower nitrogen dilution and enhance thermal efficiency.

Power-to-gas (PtG): The conversion of surplus renewable electricity into hydrogen (via electrolysis) or synthetic methane (via methanation) for industrial integration.

Carbon capture and storage (CCS): Technologies that separate CO₂ from industrial flue gases and transport it to geological formations for long-term storage or utilisation.

References

1. Economic Analysis of an Integrated Steel Plant Equipped with a Blast Furnace or Oxygen Blast Furnace. Sustainability (2023).
2. Limits on the integration of power to gas with blast furnace ironmaking. Journal of Cleaner Production (2022).
3. Effect of applying a full oxygen blast furnace on carbon emissions based on a carbon metabolism calculation model. High Temperature Materials and Processes (2024).