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Conclusions

MHD-Valdis non-linear cell stability analysis software was
successfully updated to be able to take into account the impact of
having a non perfectly horizontal cathode surface.

For the 500 kA demonstration cell, the non-linear cell stability
analysis results show that vertical potshell displacement and hence
the cathode block top surface displacement do affect the cell
stability in a negative way.

This preliminary study suggests that with a 20 cm average metal
pad thickness, a 17 meters long 500 kA cell, that was predicted to
be relatively stable with a flat bottom metal pad, is getting very
close to the cell instability threshold when the metal pad has a 4.5
cm maximum vertical bottom displacement.

In that context, one can judge of the importance of using counter
measures like forced air cooling on the potshell walls in order to
prevent such an excessive vertical potshell displacement, for
example, on the AP50 potshell [2].

References

1. M. Dupuis, V. Bojarevics and D. Richard, "MHD and pot

mechanical design of a 740 kA cell" Aluminium 82, (2006) 5,
442-446.

2. M. Dupuis & D. Richard, "Study of the Thermally-induced

Shell Deformation of High Amperage Hall-Héroult Cells", in
Proceedings of COM, (2005), 35-47.

3. M. Dupuis, "Thermo-Electric Design of a 740 kA Cell, is there

a Size Limit?" Aluminium 81, (2005) 4, 324-327.

4. J. Chaffy, B. Langon and M. Leroy, "Device for connection

between very high intensity electrolysis cells for the production
of aluminium comprising a supply circuit for correcting the
magnetic field", United States patent, (1987), number:
4,713,161.

5. D. Richard, P. Goulet, M. Dupuis and M. Fafard. "Thermo-

Chemo-Mechanical Modeling of a Hall-Héroult Cell Thermal
Bake-out', in Proceedings of TMS Light Metals (2006), 669-
674.

6. D. Richard, P. Goulet, M. Dupuis J. Bédard and M. Fafard.

"Thermo-Electro-Mechanical Modeling of a Hall-Héroult Cell
Coke-Bed Preheating", in Proceedings of COM, (2006), 525-
542.

7. M. Dupuis and V. Bojarevics, "Comparing the MHD cell

stability of an aluminium reduction cell at different metal pad
height and ledge thickness", in Proceedings of COM, (2006),
479-497.

8. V. Bojarevics and K. Pericleous, "Comparison of MHD Models

for Aluminium Reduction Cells", in Proceedings of TMS Light
Metals

(2006), 347-352.