Numerical And Experimental Investigation Of Top Submerged Gas Injection System

Abstract

The injection of gas into a liquid bath has been widely practiced in the metallurgical industry for smelting and refining operations and has been successfully used for increasing mixing and minimizing temperature and composition inhomogenities. However, due to the complexity of the flow structure involved in the gas injection system, together with the limitation of most measurement techniques, a complete understanding of the hydrodynamics of the gas injection process is lacking. In this paper Ausmelt top submerged lancing system was investigated experimentally and numerically. The fluid flow phenomena resulted from the swirl and non-swirl top injection into a liquid bath was experimentally investigated with the aid of air-water physical model and laser Doppler anemometry (LDA) to gain understanding of the mixing processes. The effects of swirl injection, submergence levels and injection rates on the gas-liquid interaction were investigated. The results indicated that the swirl gas injection promoted high liquid velocities and better mixing in the tank. When two-thirds of the lance was submerged better mixing and high liquid velocities resulted for both injection rates. The assumption of isotropic turbulence was also investigated. It was found that the assumption of isotropic turbulence may hold only outside the plume region. In the numerical part of the study CFX was used to model the flow field. The Eulerian-Eulerian two phase model was used. In this model the drag force, lift force and turbulence dispersion force were taken into account for the interface between gas and liquid. Comparison of flow behaviour between the numerical predictions and experimental findings showed good similarities of the flow patterns and velocity magnitudes. Transactions on Modelling and Simulation vol 30, © 2001 WIT Press, www.witpress.com, ISSN 1743-355X