Analysis of Vortex Stability During the BOF Tapping Process

The present work discusses the numerical simulation of the tapping process to validate the earlier postulates related to the influence of BOF vessel shape on vortex formation. Numerical experiments were conducted by varying the initial filling flow rates (FR 40 and 20 lpm), dwell times (DT 90 and 30 seconds), nozzle diameters (ND 2.14 and 1.04 cm), and initial liquid height (LH 14 and 11 cm). It was earlier reported that the vortex formation is mainly dependent on the nozzle diameter and the stability of the vortex relay on the residual motion in the draining liquids. The present numerical study provides insight into the vortex stability and elucidates the role of residual motion in the draining liquids under different process conditions. The delay in vortex formation for the case of higher residual motion is due to a delay in acceleration and alignment of angular momentum at the nozzle axis vicinity. Further, it is also observed from the numerical experiments that the vertical velocity component's magnitude exceeds the curl velocity's horizontal velocity component to establish the stable vortex. The findings of simulated results are in good agreement with the experimental results reported earlier. It also supports the theory of controlling the vortex formation in BOF vessels (by tilting front/back) without using an external device, such as a dart, a device to arrest the slag entering the ladle at the tapping end.