Fluid flow and surface waves in the BOF

Physical modeling of the basic oxygen furnace (BOF) was undertaken with the objective of developing an overall flow pattern within the vessel as a function of fluid flow dynamics/vessel geometry interaction. The four-fold symmetry of the lance tip enabled the application of a quadrant sector model of the bath. This simplified the flow to the effect of an individual nozzle. A scale of one-sixth was chosen on the basis of the bath depth and required flow rates. The multi-phase system of the BOF involving supersonic gas jets, molten iron and slag, and the interaction between these, ensure that there is no single model in which all facets of similarity may be satisfied simultaneously This is the major problem in modeling the BOF. The existence of surface waves that dominate bath behavior was demonstrated. Such waves may be present throughout the processing cycle, continuing even after the blow has stopped. The period of the radially directed surface waves was independent of the mode of excitation, typically 0.9 seconds. This suggests that the natural frequency depends on the size and geometry of the vessel, as has been found with waves in other vessels. There is a wave inherent in the process - the splash generated from within the cavity by interaction with the jet. Combined, these two phenomena led to a gushing motion at the vessel wall. The gushing appeared similar to the plunging mechanism associated with a breaking wave. This gushing motion was minimized at lower lance heights.