Alumina distribution in point-fed Hall-Heroult cells

We compute alumina concentrations in point-fed Hall cells using a finite physical element, finite difference method. Time-independent oxide distributions are obtained from the balance between consumption and supply of alumina, and presented as contour maps. The same tool can be used to fit velocity fields and turbulent diffusivities to experimental tracer data. Applying established theories for sediment transport, we also calculate sludge movements and sludge distributions. A new theory for the back feeding mechanism is suggested, originating in the hydrodynamic lifting force on sludge particles caused by the horizontally moving metal. A fluid mechanical analysis supports observations that the bath is convectively coupled to the metal. The dispersion of oxide in aluminium cells would then be affected by metal movements, since our oxide distribution model shows that convection is important in transporting oxide to all parts of the pot. Originally conceived for the New Soderberg concept at Elkem Aluminium ANS, the program is now being applied to prebake pots as well.