Formation of Free Surface Vortex in the Steelmaking Process (Dual Tapping Hole System in a Converter)

Abstract

During the tapping after BOF, slag may carry over due to the formation of free surface vortex. It should be avoided because it would result in not only severe deterioration of the quality of steel but also considerable losses in productivity. In this study, dual tapping hole system is suggested to prevent the vortex formation near tapping hole. Water model experiments and numerical simulation are conducted in order to test feasibility of the dual tapping hole system. Both water model experiments and numerical simulation should similar tendencies that the dual tapping hole system is promising to prevent the vortex formation. Experimental results showed that the free surface vortex formation is highly related to the initial conditions such as tangential velocity, size of the tapping nozzle and shape or configuration of the nozzle. Also by simulation, flow characteristics are checked. Vortex canceling effect between nozzles is observed. Since free surface vortex is rotating phenomena, this effect decreases the vorticity and results in suppressing the vortex. Also, there is a critical value of tangential velocity to generate a free surface vortex and critical height according to the nozzle size and type.