Thermodynamic Assessment of Gangue Content in Hydrogen-Direct Reduced Iron Smelting in Electric Smelting Furnaces: Part 1

Electric smelting furnace (ESF)-based smelting of direct reduced iron (DRI), followed by refining in either a basic oxygen furnace (BOF) or an electric arc furnace (EAF) is increasingly recognized as a promising pathway for low-emission iron and steel production. In this study, three hydrogen-based DRIs produced from low-grade Australian iron ores were evaluated using FactSage® thermodynamic modeling to investigate the effects of gangue content in DRI production and key operating parameters on smelting performance. As Part 1 of the two-part study, hot metal chemistry, carbon consumption to reach the target carbon content of hot metal, and specific energy consumption (SEC) are discussed. Base operating conditions for the model were set at a slag basicity of 1.1, a dissolved carbon content of 3.5 wt% in hot metal, and a smelting temperature of 1500 °C, unless otherwise specified. The results showed that 94–95 wt% Fe and acceptable impurity levels in hot metal at 1500 °C, with silicon ([Si]) generally within 0.3–0.5 wt%, were achieved in the hot metal from ESF, which is suitable for normal BOF operations. Fe and Si levels were unaffected by variations in metallization ratio and DRI–scrap ratio. Hot metal chemistry, carbon consumption, and SEC were strongly influenced by key operational parameters. Carbon consumption generally increased with higher temperature and carbon content in hot metal but decreased with higher metallization ratio, Al2O3/SiO2 mass ratio, gangue content, and DRI–scrap ratio. The SEC followed similar trends. Overall, this study provides valuable insights for defining a suitable operating window to optimize process efficiency while producing hot metal of the desired quality for subsequent BOF/EAF operations.