Blowing Number-Dominated Multiphase Splashing Behavior and Protective Wall Film Evolution in BOF Slag Splashing Protection Based on Gas-Slag-Steel Coupled Model

Slag splashing protection is the dominant technology for extending refractory lining service life and enhancing production efficiency in basic oxygen furnace (BOF) steelmaking. However, the intrinsic mechanism of gas-slag-steel multiphase coupled splashing remains poorly understood, and existing numerical methods suffer from prohibitive computational costs and inaccurate characterization of interfacial momentum transfer and multiphase interactions. This study establishes a fully coupled three-dimensional numerical model integrating Volume of Fluid (VOF)–Discrete Particle Method (DPM) bidirectional phase transition, adaptive mesh refinement (AMR), and Eulerian Wall Film Model (EWFM), and the multiphase flow simulation in this study adopts constant thermophysical parameters of molten steel and slag at the industrial splashing temperature of 1650 °C. Taking the Blowing Number (NB) as the core similarity criterion, a 1:10 scaled geometric model of a 50-ton industrial BOF is employed to systematically investigate the regulatory effects of top-blowing flow rate, lance height, and NB on droplet splashing behavior and wall liquid film evolution. The model is validated against mercury-glycerol cold model experimental data, with a relative error of less than 3% in total splashing mass prediction. Results demonstrate that increasing NB significantly enhances splashing intensity. Under optimal conditions (200 mm lance height, 11.76 Nm3/h flow rate, NB = 9.30), the wall liquid film fully covers the middle-upper furnace wall with a uniform thickness of 0.8–1.2 mm. NB dominates jet momentum distribution: high NB forms a deep-penetrating four-lobed impact cavity, remarkably improving droplet axial momentum and residence time. Molten steel droplets concentrate at 3–4 mm, while slag droplets shift to 2–4 mm at high flow rates of 11.76 Nm3/h, with maximum slag droplet production at NB = 6.99. This work provides reliable theoretical support for industrial BOF slag-splashing process optimization.