TOWARDS A PROPER UNDERSTANDING OF SIDELEDGE FACING THE METAL IN ALUMINIUM CELLS?

摘要

Existing calculation models and hypotheses concerning the sideledge facing the metal in aluminium electrolysis cells are critically examined. It can be concluded that the commonly used "heat transmittance theory" for heat flow and growth of ledge is not correct, although the existence of the sideledge can probably only be explained by the presence of a bath film between metal and sideledge. Most likely, the bath film is maintained by a source of liquid bath at the bottom of the cell, and the film is alumina-saturated at a temperature close to the metal temperature. An alternative conceptual model for the formation of sideledge facing the metal is briefly outlined. According to the model, formation and removal of sideledge at the metal level will be very slow, and the dynamic behaviour can not be directly related to the superheat or to the heat transfer coefficient.