The Effect of Detaching Bubbles on Aluminum-Cryolite Interfaces: An Experimental and Numerical Investigation

Because of gas-induced flow in commercial aluminum reduction cells, deformations of the cryolite-aluminum interface will appear close to the side channel of the cell. In the present work, the dynamic nature of this phenomena is studied both in experiments and with help of a numerical model in the commercial computational fluid dynamics (CFD) code, FLUENT. Experiments are conducted in a full scale, two dimensional oil-water half-anode model, quantifying interfacial deformations over various operating conditions. Besides data on interfacial deformations, the experiments confirm previously published data on bubble motion under inclined anodes. The oil-water model is studied further with a three-fluid CFD model by means of a transient volume of fluid method. The model presented is verified and validated against experimentally measured data, yielding promising results. The CFD model is generalized further to realistic parameters for the Hall-Heroult cell. Averaged results from the transient model are compared with steady state calculations, showing good agreement. Average deformations up to 20 mm are observed under normal operating conditions. The transient approach shows that the dynamic behavior of the aluminum-cryolite interface is significant and is the same magnitude of the average deformations.