Dynamic Process Modeling of Electric Arc Furnace Steelmaking Using Direct Reduced Iron Charges: Focusing on Dephosphorization

The use of direct reduced iron (DRI) in electric arc furnace (EAF) steelmaking has grown in popularity, yet dephosphorization, as a special concern because of high phosphorous levels, is yet to be fully understood. Here, a dynamic process model, accounting for phosphorus behavior under the circumstance of a continuous charge of raw materials and semi-continuous flushing slag in an industrial DRI-charged EAF, is developed and verified to predict trajectories of steel and slag phosphorus levels and slag chemistry in real time based on process conditions. The model is then employed to evaluate dephosphorization in a wide range of DRI phosphorus levels and process conditions. It is found that dephosphorization in industrial DRI-charged EAFs does not occur in equilibrium, with the phosphorus partition range of 20~70, compared to 130~170 for equilibrium conditions. For the phosphorus content in DRI, ranging from 0.02 wt.% to 0.2 wt.%, a dephosphorization ratio of more than 81% can be achieved at a slag basicity of 2.3. Dephosphorization is likely easily achieved even at a relatively low slag basicity of 1.5~1.7 when DRI containing phosphorus levels as high as ~0.1 wt.% is used, attaining a dephosphorization ratio of more than 70%. The current model can serve as a valuable tool, providing a knowledge base to assist in the design, operation, and optimization of DRI-charged EAF practices.