Studies of Perfluorocarbon Formation on Anodes in Cryolite Melts

Kjos, Ole Sigmund; Aarhaug, Thor Anders; Skybakmoen, Egil; Solheim, Asbjørn

doi:10.1007/978-3-319-48179-1_106

Cited by 5 publications

(2 citation statements)

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“…A large part of During aluminium electrolysis oxide ions from the dissolution of alumina in cryolite are discharged electrolytically and form CO 2 on the carbon anode, made from coke and a pitch binder, whilst aluminium metal is formed on the cathode. Some studies show that CO is also formed at the anode, especially at low current densities [3,4], and other gases including the perfluorocarbon gases CF 4 and C 2 F 6 are formed at higher anode potentials during anode effect [5][6][7][8][9]. Gas bubbles are thought to nucleate at specific sites on the anode surface by (non-classical) heterogeneous nucleation [10,11], and grow spherically or semi-spherically, before detaching and moving to coalesce with other bubbles.…”

Section: Introductionmentioning

confidence: 99%

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Bubble Evolution and Anode Surface Properties in Aluminium Electrolysis

Thorne

Sommerseth

Ratvik

et al. 2015

J. Electrochem. Soc.

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One significant contribution to the anodic potential during aluminium electrolysis is the formation of CO 2 bubbles that screen the anode surface. This effect creates an additional ohmic resistance as well as an increased reaction overpotential, hyperpolarisation, as the effective surface area decreases. This work aims to improve the understanding of how anode properties -including isotropy at the optical domain level, wettability (towards electrolyte), surface roughness and porosity -affect bubble 2 evolution. Pilot anodes, made with single source coke types varying in isotropy, were used to study bubble evolution by electrochemical methods. In order to retain bubbles during experiments, anodes were designed to have only horizontal surface area.Bubble formation and release were monitored at different current densities, and were tracked by measuring the oscillations in anode potential and series resistance. Anodes made from different cokes were found to have different bubble evolution properties, possibly due to variation in the density of nucleation sites at the surface of each anode and varying anode-electrolyte wettability.

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Section: Introductionmentioning

confidence: 99%

“…crucible and aluminium reference electrode contained in a boron nitride casing as described in [7]. Error bars show one standard deviation, where n = 6 for graphite and n = 3 for the industrial coke-based anodes.…”

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confidence: 99%