Mathematical modeling on the fluid flow during RH degassing process

Abstract

A mathematical model combining VOF and DPM has been developed to investigate the effect of the lift force and the bubble size on the fluid flow in the RH process. The effect of the type of gas blowing was also discussed. The calculated results were validated against the experimental data from water modeling using a particle image velocimetry technique (PIV). In the current model, the interfacial behavior between the molten steel and the gas phase, and the motion of argon bubbles can be captured and tracked simultaneously. The results indicated that the speed of the molten steel and the recirculation rate increased with increasing the lift force. In order to accurately simulate the fluid flow in the RH process, the optimum lift coefficient was 0.1. However, an inverse tendency was obtained for the bubble size. With the bubble size increasing, the gas volume fraction in the up-leg snorkel changed from a double-peak distribution to a single-peak distribution, which weakened the interaction between the molten steel and gas bubbles and decreased the recirculate rate. To improve the recirculate rate and good stirring, small size gas bubbles should be adopted. In addition, the symmetrical flow of the molten steel in the down-leg snorkel was converted into a rotating flow pattern when increasing gas flow rates in one nozzle or two nozzles. Meanwhile, the recirculate rate decreased and the slag entrainment at the free surface might occur. Therefore, it was of great importance to ensure an equal gas flow rate in each nozzle in actual operations.