An enabling model for analyzing the carburization process in a carbon-neutral electric smelting furnace (ESF)

Electric smelting furnaces (ESFs) are an emerging low-carbon ironmaking technology that can process direct reduced iron (DRI) produced using H 2 or H 2 -rich reducing gases and accommodate DRI from different iron ore grades. However, the resulting molten iron is carbon-deficient, making controlled carburization essential to achieve the carbon level required for downstream steelmaking. Despite its industrial importance, the carburization mechanisms remain poorly understood. This study develops an interface-resolved hybrid VOF model that captures multiphase flow, heat and mass transfer, and chemical reactions among slag, metal, gas, and discrete solids, droplets, and bubbles. The model combines algebraic phase transport with geometric interface reconstruction to quantify the evolving interfacial contact areas governing reaction kinetics. It also incorporates a stable source term redistribution method and a time-scaling approach for long-term carbon dissolution. Model predictions agree well with published experimental data for both FeO reduction and iron carburization, including the evolution of gas bubbles, iron droplets, and dissolved carbon. The simulation results reveal that CO/CO 2 bubble generation promotes FeO reduction by enlarging the gas–slag interface but limits carbon dissolution by shrouding carbon particles immersed in slag, thereby reducing direct contact with iron droplets. In contrast, immersing carbon particles in the iron bath can achieve the desired carbon level, with contact time playing a critical role. When carbon particles are placed on the slag surface, coalesced iron droplets remain in contact with them, further demonstrating that effective carbon–iron contact promotes carburization. This study provides an enabling tool for analyzing and controlling carburization in ESFs.