Wenwen Liu, Renjie Zhang, Haokun Li, Yuanhong Qi
Under China's "carbon peaking before 2030 and carbon neutrality before 2060" targets, the low-carbon transformation of the ironmaking stage-which contributes approximately 70% of the CO2 emitted per ton of steel in the dominant blast furnace-basic oxygen furnace (BF-BOF) route-is decisive for decarbonizing the steel industry. In contrast to earlier reviews that describe individual technologies in isolation, this review provides a structured, cross-technology synthesis: the main routes are classified into short-/medium-term low-carbon blast furnace technologies (hydrogen-rich carbon-recycling oxygen blast furnace, hydrogen-rich injection, biomass char injection and ultimate energy-efficiency measures) and medium-/long-term non-blast furnace technologies (hydrogen-based shaft furnace direct reduction, smelting reduction, rotary hearth furnace, fluidized-bed reduction and electric smelting reduction) and are then compared on a common set of quantitative indicators-CO2 mitigation, specific energy and hydrogen demand, technology readiness level (TRL) and relative cost. On this basis, emerging hydrogen-based flash ironmaking, developed from the interdisciplinary integration of "iron and steel-non-ferrous metallurgy-hydrogen metallurgy-plasma", is critically assessed, with a clear separation between laboratory/pilot feasibility and industrial readiness. We conclude that low-carbon blast furnace technologies, owing to low retrofit cost and high maturity, will dominate near-term mitigation, whereas hydrogen-based shaft furnaces and, in the longer term, hydrogen-based flash ironmaking define the pathway toward near-zero-carbon ironmaking-conditional on the availability of green hydrogen and low-carbon electricity and on overcoming key engineering barriers.