Effect of background melt flow and interface distortion on the stability of Hall--Héroult cells

H. Sun¹ - O. Zikanov² - B. A. Finlayson¹

¹ Dept. of Chemical Engineering, University of Washington, Seattle, WA 98125
² Dept. of Mechanical Engineering, University of Michigan-Dearborn, 4901 Evergreen Road, Dearborn, MI 48128-1491

Abstract
We use the method of linear stability analysis to study the effect of background melt flows and interface deformation on the stability characteristics of Hall--Héroult reduction cells. The linearized perturbation equations are based on a two-dimensional shallow water model. Two kinds of background states are investigated, one with a strong interface deformation and negligible melt flow, and another with strong vortical flows in aluminum and cryolite but a practically flat interface. It is found that the interface deformation with the length scale of the order of the cell size has a strong destabilizing effect. We also confirm earlier predictions that the unstable interfacial wave becomes wall-limited as the electromagnetic instability parameter increases. Tables 3, Figs 5, Refs 18.