Impact of Scrap and Hydrogen-Based Direct Reduced Iron Ratios on Energy Demand, Emissions, and Oxygen Management in Green Steelmaking

Steel production contributes significantly to global emissions, making its decarbonization essential. Electrified steelmaking based on electric arc furnaces (EAF) using hydrogen-based direct reduced iron (H2-DRI) and scrap is a promising pathway. This study analyzes how the H2-DRI:scrap ratio affects electricity demand, CO2 emissions, slag formation, and oxygen management. To address limitations of approaches based on aggregated data and linear scaling assumptions, a detailed bottom-up mass and energy balance model is developed, explicitly resolving process interactions between electrolysis, direct reduction, and EAF steelmaking. Eight H2-DRI:scrap ratios ranging from 0:100 to 100:0 are evaluated. Electricity demand increases from 1.1 GJ/tSteel (0.31 MWh/tSteel) for scrap-based operation to 13.9 GJ/tSteel (3.86 MWh/tSteel) for fully H2-based production, largely driven by hydrogen generation. Consequently, emissions strongly depend on electricity carbon intensity, with reductions of up to 95% under renewable supply. Electrolytic oxygen can fully cover process demand at ~10–13% H2-DRI, enabling system integration benefits. A sensitivity analysis evaluates the influence of key process parameters on electricity demand, CO2 emissions, and oxygen management, demonstrating the robustness of the proposed modelling approach.