Enhancement of mass transfer in converter by improving the flow of slag and molten steel

Abstract

In top blowing steelmaking, the impact behavior of the supersonic oxygen jet significantly affects the emulsification of slag–metal and the reaction rate in the molten bath. To enhance the mass transfer rate, a swirl-type oxygen lance is proposed. The mass transfer processes between slag and molten steel in the converter during the swirl-type oxygen lance blowing process are investigated. A mixing index Im is proposed to assess the slag–metal mixing degree, and the effects of operating parameters on mass transfer rate and mixing index are discussed. The results demonstrate that compared to the traditional oxygen lance, the swirl-type oxygen lance enhances the stirring intensity of the jet on the molten bath, resulting in a 5.1%–13.0% increase in the mass transfer rate. When the swirl-type oxygen lance is under the condition of H = 45de, the mixing index is the lowest (4.52) and the volumetric mass transfer coefficient is the highest (1.92 × 10−3 m3/s). The energy transferred from the jet to the molten bath can be enhanced by an increase in the flow rate or operation pressure, thereby decreasing the mixing index and increasing the volumetric mass transfer coefficient. Finally, a criterion number equation (Sh = 5.78 × 10−3Re0.43Sc0.33) for the involved mass transfer processes is established, which indicates that increasing the velocity of the slag and molten steel is more effective in enhancing the mass transfer rate than adjusting the liquid phase components in practical steelmaking.