Concept of dynamic foaming index and its application to control of slag foaming in electric arc furnace steelmaking

Abstract

To sustain a foam in steelmaking processes, two basic requirements should be fulfilled, i.e. appropriate physical properties of the slag such as high viscosity, low density, and low superficial tension, and the generation of sufficient reaction gas. To date, foaming indexes have been focused on the physical properties of refining slags. In the present paper a dynamic foaming index (DFI) that involves both above requirements is proposed, using a kinetic model of the electric arc furnace process to calculate the generation rate of reaction gas, mainly CO. When the arc distortion, as affected by electrode submergence in the foam, is compared with the DFI, calculated via the kinetic model, it is observed that both parameters follow very similar trends. This finding indicates the feasibility of knowing the foaming conditions of a heat in advance, or of using the kinetic model online to control the foaming phenomena. Furthermore, experimental results relating to dynamic behaviour of the slag chemistry are well simulated using the kinetic model. To take into account the effect of size distribution of carbon particles injected into the slag to reduce FeO, a Monte Carlo simulation has been integrated into the process simulator, allowing a more realistic prediction of the current steelmaking process.