Material and exergy-driven comparative assessment of hydrogen-rich fuels injection in blast furnaces: Feasibility envelope and carbon reduction

To address the urgent need for decarbonization in ironmaking, this study investigates the sustainable co-injection of hydrogen-rich fuels, including hydrogen (H₂), coke oven gas (COG), and natural gas (NG) with pulverized coal into blast furnaces. Based on a comprehensive mass-energy-exergy balance model incorporating the Rist operation line, a systematic evaluation model has been developed. This model enables synergistic assessment of technical indicators, CO₂ emission reduction, and optimization of the matching relationship among hydrogen-rich fuels, pulverized coal, and oxygen enrichment ratio at a critical raceway adiabatic flame temperature (RAFT) of 2050 °C and reasonable top gas temperature. Under optimal operating conditions, the maximum injection rates for H₂, COG, and NG are determined to be 165, 97, and 85 m³/THM, respectively, while the maximum carbon reduction amount with pulverized coal and H₂ co-injection reaches 9.03 %. In comparison to a traditional blast furnace, the input exergy of pulverized coal for H₂, COG, and NG co-injection decreases by 7.11, 8.98 and 12.47 %, whereas the output exergy of blast furnace gas (BFG) increases by 20.29, 17.28 and 24.41 %, respectively. Furthermore, hydrogen-rich blast furnaces exhibit favorable performance in terms of energy efficiency and thermodynamic perfection degree. However, maintaining a constant RAFT in hydrogen-rich blast furnaces requires higher exergy input. This study provides a quantitative framework for optimizing the hydrogen-rich fuels injection in blast furnaces, establishing decarbonization roadmaps for achieving low-carbon ironmaking.