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On the analysis of ionic mass transfer in the electrolytic bath of an aluminum reduction cell
Author(s) -
Ariana Mohsen,
Désilets Martin,
Proulx Pierre
Publication year - 2014
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.22047
Subject(s) - electrolyte , electrolysis , ion , electrochemistry , diffusion , mass transfer , chemistry , ionic bonding , electric field , electrode , current density , analytical chemistry (journal) , diffusion current , electrolytic cell , chemical physics , thermodynamics , current (fluid) , chromatography , physics , organic chemistry , quantum mechanics
An electrolyte typically used in an aluminum electrolysis cell is composed of different ions moving in the electromagnetic field generated by the high intensity current needed for the industrial application. The flux of these ions has an important impact on the functional parameters of the cell, like current efficiency. In this study, the transient behaviour of these ions in the NaF‐AlF 3 ‐Al 2 O 3 mixture is modelled using a numerical finite element method. The electric potential field equation governed by electrochemical reaction kinetics at electrodes is solved to obtain the electric potential field, current density, and consequently heat generation in the cell. Subsequently, the concentration field is solved for ionic species in the bath. The results indicate formation of a high concentration gradient of electroactive ions like Al 2 OF 6 2− and AlF 4 − at the corresponding reacting electrodes with time and diffusion as the main mechanism for these ions transfer. It is found that from the early stages of the 3 minute simulation of the electrochemical process, the difference between bulk concentration and surface concentration of electroactive ions remains constant. Moreover, the results indicate that although the flux of electroactive species is dominated by diffusion, especially for larger times, migration is the controlling mechanism of transport for the electroinactive ions.