Molten Bath Flow Characteristics and Metallurgical Performance of Bottom Injection in a 300 t Basic Oxygen Furnace

Efficient lime utilization and dephosphorization in basic oxygen furnace (BOF) steelmaking require a bottom-blowing regime that disperses injected lime powder without forming a penetrating gas column. This study optimized the bottom-blowing flow rate for O2–CO2–CaO powder injection in a 300 t BOF by combining a 1:7 water-model experiment, three-phase volume-of-fluid computational fluid dynamics (CFD), and industrial trials. The industrial process used an O2–CO2 carrier-gas mixture with a volumetric ratio of 50:50 to convey CaO powder. The water model showed that bath homogenization time first decreased and then increased with flow rate, reaching a minimum of 35.90 s at 1350 Nm3/h. The simulations predicted dispersed bubble flow at 1200–1350 Nm3/h, a transitional regime at 1450 Nm3/h, and a fully developed gas column at 1500 Nm3/h. At 1350 Nm3/h, the gas–liquid interfacial area reached 5.624 m2 and the low-velocity-zone fraction decreased to 0.04%. Industrial implementation reduced lime consumption from 9.28 to 7.57kg/t, lowered endpoint phosphorus from 0.037% to 0.029%, increased the lime dissolution ratio from 0.52 to 0.68, and decreased total iron in the endpoint slag from 24.7% to 22.9%. By correlating flue gas behavior with hydrodynamic parameters from CFD simulations and industrial metallurgical performance, this study confirms that the bottom-blown gas process is favorable under the investigated converter conditions.