Sideledge Facing Metal in Aluminium Electrolysis Cells: Preliminary Modelling Study of Bath Film Formation

Abstract

For design and operation of highly efficient aluminium electrolysis cells, knowledge concerning side ledge formation and heat loss through the sides is indispensable. Measurement of ledge profiles and heat fluxes seems to concur with theoretical models only by including a thin film of bath located at the metal-sidewall interface. A transient CFD (Computational Fluid Flow) model including metal circulation is made for these initial studies of how bath film develops. The model includes two liquids (bath and metal) with a bath layer initially sitting at the lowest two cm below the metal, before it proceeds upwards along the side wall by gravitation and surface tension. A parameter study was conducted with surface tension, bath film properties, and metal flow as parameters. It is shown that metal flow has a considerable impact on the film formation rate. The modelled bath film behaviour is in accordance with theoretical considerations.