Modelling Investigation of Gas–Slag–Metal Flow Interactions in Top-Blown Basic Oxygen Furnace

Basic oxygen furnace (BOF) steelmaking is a major steelmaking route, involving complex high-temperature reacting flow inside the reactor. The impurity removal of liquid steel is governed by multiphase flow and interfacial interactions, resolving the transient internal behaviours of gas–slag–metal systems is essential for understanding hydrodynamic conditions relevant to impurity removal. In this study, a transient multiphase BOF model is developed to quantify velocity fields, phase distribution, evolution of interfacial behaviours, and the time lag between converter opening and internal flow response. The results show that all phases exhibit velocity fluctuations, with average velocities of 1.49 m/s (gas), 0.17 m/s (metal), 0.21 m/s (slag), and 0.38 m/s (mixture) for the basic case. Mixture motion correlates more strongly with slag flow rather than with metal flow, whilst domain-scale velocity fluctuations are strongly correlated with gas flow. Rapid interfacial reconfiguration occurs within the first ~1s of cavity formation, followed by relative stabilisation. The slag–metal interfacial area is approximately 3 times larger than that of the gas–metal interface and increases with increasing slag thickness. In addition, under the present non-reacting hydrodynamic conditions, the simulated gas-transport delay between in-furnace flow response and BOF-opening gas signal is approximately 2.0 to 2.5s. These results provide model-based hydrodynamic indicators of flow–interface coupling in BOF steelmaking and may support future studies of impurity-control mechanisms.