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Erschienen in:
2016 | OriginalPaper | Buchkapitel
Model for Excessive Cathode Wear By a “Carbon Pump” at the Cell Bottom
verfasst von : Asbjørn Solheim, Kati Tschöpe
Erschienen in: Light Metals 2013
Verlag: Springer International Publishing
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The lifetime of aluminium electrolysis cells is limited by cathode wear, which takes place mainly at the periphery of the cathode. In the present paper it is suggested that excessive wear is due to electrochemical formation and dissociation of aluminium carbide in bath-filled pores within a carbide layer present at the bottom of the cell. The relationship between current and voltage in the pore was established using the Stefan-Maxwell equations on a structure model of the bath, in combination with the calculated reversible voltage and the ohmic voltage drop. A general “wear equation” was derived, describing the relationship between voltage drop along the pore, the thickness and porosity of the carbide layer, and the cryolite ratio. The voltage drop across aluminium carbide layers with different properties is discussed. The model shows that the wear rate will be nearly proportional with the local current density, which is in agreement with practical observations.