An investigation into the slag clearing phenomenon

Abstract

The phenomenon of slag layer clearing from the surface of a melt by a top-blown gas jet was assessed both experimentally and theoretically. The effects of gas jet dynamic state and simulated-slag properties on the area cleared of slag were examined using experiments at room temperature. A theoretical model based on a force balance of pushing and resistant actions was proposed and assessed with the experimental results. For extremely thin simulated-slag layers only the surface tension and drag force terms are significant, so this permitted an evaluation of the total drag from experimental observation. For thicker layers, the total frictional drag, the gravitational force, the surface tension force and the inertia force of the gas wall jet are all of the same order of magnitude. The total drag force was split into its liquid-side and gas-side components using gas-phase mass transfer data and the j-factor analogy. Of the two drag forces, that due to circulation of liquid beneath the slag layer is by far the larger, but further research would be required to predict the slag-free area in real high-temperature smelting processes.