Multiphase jet–bath hydrodynamics and centroid sloshing in side-blown nonferrous smelting furnaces

Side-blown gas-injection reactors are widely used in industrial processes, such as electroplating-sludge treatment, partial nitrification, smelting, and solid waste treatment. However, the coupled effects of lance design and activation pattern on jet-driven mixing and bath sloshing remain unclear. In this study, a multiphase computational framework based on the volume of fluid combined with a realizable k–ε turbulence model is established to resolve gas–slag–metal flow in a side-blown furnace, and its predictions are benchmarked against experimental measurements. Results indicate that the penetration depth of the side-blown jet is limited, producing a central dead zone in the molten bath that constrains reaction efficiency and effective furnace width. The residual kinetic energy of bubbles reaching the free surface is identified as the primary driver of slag spattering. Under a fixed total gas flow, increasing the lance diameter strengthens bath agitation but exacerbates molten splashing. Opposed blowing suppresses bubble coalescence, enlarges the gas-melt interfacial area, and improves momentum-transfer efficiency. The enhanced slag circulation further strengthens bath sloshing, as reflected by the increased centroid displacement and the higher dominant frequency and amplitude of the rotational sloshing wave. Specifically, the dominant sloshing frequency is about 18.4% higher than that of paired staggered blowing. This stronger hydrodynamic response not only improves mixing but also increases the mechanical loading on the furnace support structure. Overall, these results provide the theoretical support for optimizing the side-blown system with consideration of both process intensification and structural reliability.