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Comparing the MHD cell stability of an aluminium reduction cell at
different metal pad height and ledge thickness


M. Dupuis
GéniSim Inc.
3111 Alger St.
Jonquière, Québec, Canada G7S 2M9


V. Bojarevics
University of Greenwich, School of Computing and Mathematics
Park Row
London, SE10 9LS, UK

ABSTRACT

It is well known that horizontal current density in the metal pad contributes
greatly to the generation of MHD driven bath-metal interface wave.

It is possible to compute very accurately the metal pad current density using a
very detailed finite element model [1], but a MHD model must be compatible to this
level of mesh refinement and to recalculate the current distribution at each time step,
including the full busbar supply system.

The accuracy of the instability prediction of the cell depends on the accuracy of
the metal pad current density calculation.

This study presents the comparison of the metal pad current density calculation of
the detailed finite element model and the MHD-Valdis model for different metal pad
heights and ledge thickness. It also presents the corresponding cell MHD stability
predictions.

INTRODUCTION

As it has been discussed previously [2,3], there are many aspects of the cell
design and operation that will have an impact on the metal pad current density field. For
example: the metal pad height, the ledge thickness, the cathode block/collector bar(s)
connection design, the cathode block carbon grade, the busbar design, etc.

It has also been demonstrated in [4] that the intensity of the stationary metal pad
current density field has an impact on the cell stability in a very similar way as the