Circulating Flow and Mixing Time in a Molten Metal Bath with Inert Gas Injection

Abstract

Mixing characteristics in a molten metal bath are analyzed for inert gas injection through a nozzle at the center of the vessel bottom. It is postulated that the bath consists of two zones: bubble plume zone where gas-liquid mixtures flow upward and annular zone where liquid flows downward. The analysis is made by setting up a steady-state energy balance for the liquid phase. The liquid velocity in the plume zone, the liquid circulating flow rate and the mixing time are calculated under various injecting conditions and correlated as simple functions of gas-flow rate, liquid depth and cross sections of both the plume zone and the vessel. It is found that the cross section of the plume zone has a significant influence on the circulating flow. Large cross section of the plume zone is desirable for mixing in the bath. The calculated results of circulating flow rate and mixing time agree with experimental results obtained previously.