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Impact of the solidification rate on the chemical composition of frozen cryolite bath

Poncsák Sándor, Kiss Lazlo I., Guérard Sébastien et Bilodeau Jean-François. (2017). Impact of the solidification rate on the chemical composition of frozen cryolite bath. Metals, 7, (3), p. 97.

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URL officielle: http://dx.doi.org/doi:10.3390/met7030097

Résumé

Solidification of cryolite (Na3AlF6)-based bath takes place at different rates along the sideledge, and around alumina rafts and new anodes. The solidification rate has a significant impact on the structure and the chemical composition that determine the thermal conductivity and thus the thickness of sideledge, or the duration of the existence of the temporary frozen bath layers in other cases. Unfortunately, samples that can be collected in industrial cells are formed under unknown, spatially and temporally varying conditions. For this reason, frozen bath samples were created under different heat flux conditions in a well-controlled laboratory environment using the so-called cold finger technique. The samples were analyzed by X-ray Diffractometer (XRD) and Scanning Electron Microscope (SEM) in Back Scattering (BS) mode in order to obtain spatial distribution of chemical composition. Results were correlated with structural analysis. XRD confirmed our earlier hypothesis of recrystallization of cryolite to chiolite under medium heat flux regime. Lower α-alumina, and higher γ-alumina content in the samples obtained with very high heating rate suggest that fast cooling reduces α–γ conversion. In accordance with the expectation, SEM-BS revealed significant variation of the Na/Al ratio in the transient sample

Type de document:Article publié dans une revue avec comité d'évaluation
Volume:7
Numéro:3
Pages:p. 97
Version évaluée par les pairs:Oui
Date:2017
Sujets:Sciences naturelles et génie > Génie > Génie des matériaux et génie métallurgique
Département, module, service et unité de recherche:Départements et modules > Département des sciences appliquées > Module d'ingénierie
Mots-clés:aluminum electrolysis, frozen ledge, cold finger, chemical composition, cooling rate, électrolyse en aluminium, rebord congelé, doigts froids, composition chimique, taux de refroidissement
Déposé le:11 sept. 2017 17:55
Dernière modification:11 sept. 2017 17:55
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