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Mathematical modeling of aluminium reduction cell potshell: Improvements and applications
Inproved "half empty shell" potshell model
Finally, the "half empty shell" potshell model has also been improved by decoupling the 2D potshell mesh from the
3D lining mesh and by completely refining the 2D potshell mesh. Furthermore, the 3D side lining mesh has been
decoupled from the 3D cathode panel mesh as it is assumed that only the cathode panel is affected by sodium
swelling. As it was the case for the "almost empty shell" potshell model, contact pair elements are used to reconnect
the three decoupled model parts.
The "half empty shell" model has been further improved by also taking into account the cathode panel thermal
expansion which was not considered in the model version presented in [1]. When the thermal expansion is one order
of magnitude greater than the thermal expansion, it may be justified to neglect the latter in the analysis, but when the
sodium chemical expansion is 1% or less, this simplification is no longer acceptable. So in the "half empty shell"
model presented here, the pure thermal expansion problem is solved first (see results in figure 10). Then, the
transient sodium diffusion and its stress level related expansion is added as presented in [1]. The final predicted
potshell and lining displacements are presented in figure 11 for the combined design retrofit case. Figure 12 presents
only the lateral displacement confirming the results obtained with the "almost empty shell" potshell model for the
second retrofit idea. Figure 13 presents only the vertical displacement confirming the results obtained with the
"empty shell" and the "almost empty shell" potshell models for the first retrofit idea. Notice that even if the potshell
itself is not deflecting vertically, the cathode panel still does. The gain of cell stability between the standard design
presented in [1] and the retrofitted design presented here can be analyzed using MHD-Valdis as demonstrated in
[11].
Conclusions
Redeveloped thermo-chimio-mechanical models [2,3,4,and 5] presented at the 2010 TMS conference [1] have been
improved adding up to date ANSYS® contact elements technology into them. Furthermore, two innovative retrofit
design proposals have been successfully tested using them, demonstrating their ability to be use as efficient design
analysis tools. Those models are now available to the hole aluminium industry through GeniSim Inc.
References
[1] M. Dupuis, "Mathematical modelling of aluminum reduction cell potshell deformation", Light Metals, TMS,
(2010), to be published.
[2] M. Dupuis, G. V. Asadi, C. M. Read, A. M. Kobos and A. Jakubowski. "Cathode shell stress modeling", Light
Metals, TMS, (1991), 427-430.
[3] M. Dupuis, G. V. Asadi, C. M. Read and I. Tabsh, "Hall-Héroult cell, cathode modelling; impact of sodium
swelling on the loading forces", Proceedings of the 31st Conference of Metallurgists, CIM, (1992), 115-130.
[4] G. V. Asadi, M. Dupuis and I. Tabsh, "Shell design technique considering the sodium swelling phenomena of
carbon cathode blocks", Proceedings of the 32nd Conference of Metallurgists, CIM, (1993), 125-130.
[5] C. M. Read, A. M. Kobos, M. Dupuis, G. V. Asadi and K. P. Misegades, "Modelling of aluminium production
processes with CRAY supercomputers", Supercomputing Symposium '90, (1990).
[6] M. Dupuis, "Development of a 3D transient thermo-electric cathode panel erosion model of an aluminum
reduction cell", Proceedings of the 39th Conference of Metallurgists, CIM, (2000), 169-178.
[7] M. Dupuis and D. Richard, "Study of the thermally-induced shell deformation of high amperage Hall-Héroult
cells", Proceedings of the 44th Conference of Metallurgists, CIM, (2005), 35-47.
[8] M. Dupuis, "Towards the development od a 3D full cell and external busbars thermo-electric model",
Proceedings of the 41th Conference of Metallurgists, CIM, (2002), 25-39.