Mechanism and optimization conditions of direct reduced iron melting process: A study based on numerical simulation and experimental validation

In this investigation, the melting characteristics of Direct Reduced Iron (DRI) within a steel bath are analyzed, targeting the critical issue of enhancing efficiency and reducing energy consumption in steelmaking. A CFD model integrating the enthalpy–porosity formulation with the Volume of Fluid (VOF) scheme was utilized to describe the melting characteristics of DRI. The results indicate that the melting process of high-carbon DRI in a low-carbon molten pool is influenced by heat exchange, carbon diffusion, and changes in the liquidus temperature. This gives rise to a gradual sequence: the surface first develops a solidification shell, then DRI melts while steel infiltrates, and finally the shell thickens inward before complete melting takes place. In contrast, the melting of low-carbon DRI in a high-carbon molten pool shows a sequential melting of the solidification shell and DRI. Simulations of the effects of molten pool temperature, carbon content, and DRI preheating temperature reveal that increasing preheating to 700 K shortens DRI melting time by 17.56%. Raising the molten pool temperature significantly reduces the solidification shell duration, with the melting time at 1923 K reduced to 2.61 s. Increasing the carbon fraction in both the molten pool and DRI contributes to a reduction in melting time. At a carbon content of 2.0%, the melting time is shortened to 0.91 s. Carbon content above 2.0% has minimal impact on the solid-phase melting rate. In practical production, appropriate molten pool and DRI parameters can be selected based on specific requirements to optimize melting efficiency and reduce energy consumption.