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Qian, Kun; Chen, Z. D.; Chen, J. J. J.

doi:10.1023/a:1003447913204

Cited by 63 publications

(20 citation statements)

References 1 publication

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“…On small anodes this process is sequential, but with intermediate size or industrial anodes, typical behaviour is less periodic and multiple bubbles are released [13]. Previously, bubbles have been monitored through direct visual/X-ray observation [14][15][16], bath height fluctuation [3], current interruption and/or associated resistance [3,4,17,18] and potential oscillation [19][20][21][22]. Most studies suggest that bubble layer thickness is around 5 mm in both laboratory [3,12,16,23] and industrial [3,14,16,24] cells, although there is some variation reported [25,26].…”

Section: Introductionmentioning

confidence: 99%

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%

Bubble Evolution and Anode Surface Properties in Aluminium Electrolysis

Thorne

Sommerseth

Ratvik

et al. 2015

J. Electrochem. Soc.

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“…Their error was less than 4%. Quian et al [11] investigated the incremental resistance caused by the presence of the bubbles produced by an airwater model and by a water electrolysis cell with their above mentioned electrochemical method. At a given current density, the electrical resistance caused by the bubbles in the electrolysis cell was always greater than for the air-water model.…”

Section: List Of Symbolsmentioning

confidence: 99%

“…These correlations do not take into account the size distribution of the bubbles and the interaction between them as well as the dynamic nature of the bubble layer. A lot of work has also been reported on laboratory experiments [7][8][9][10][11][12]. Although these small-scale electrochemical models are very useful to study the role of the small bubbles, their anode sizes are generally too small to represent the real size distribution and the fluctuating behaviour of bubbles.…”

Section: Introductionmentioning

confidence: 99%

Mathematical model to evaluate the ohmic resistance caused by the presence of a large number of bubbles in Hall-Héroult cells

2007

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Bubbles play an important role in the productivity of an electrolysis cell. They induce flow in the cell and increase the overvoltage, which is still two times greater than the thermodynamic voltage. Their contribution to the total electrical resistance of the electrolyte must be known for several reasons such as the energy efficiency and control. A computationally efficient mathematical model has been proposed that computes the total resistance of the electrolyte by using the concept of parallel-connected current tubes. The resistance of the individual current tubes has been determined earlier by the solution of the Laplace equation around the bubbles by the finite element method. Both electrical resistance models take into account the morphology (position, size and shape of each bubble) of the bubble layer. The current-tube model has been compared to the solutions obtained by a finite element method (FEM) for several real and hypothetical situations, using a large number of bubbles. The agreement between the results obtained by the proposed model and the FEM is very good. The difference between the two approaches is around 5% for a covering factor of 50%.

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“…The volume of gas was obtained by measuring the rise of the electrolyte level, as done by Solheim and Thonstad [7]. As pointed out by Quian et al [8], this measurement method may introduce an error since the bubbles outside the interpolar region are included in the total accumulated gas. Nevertheless the typical covering factor measured was about 45%.…”

Section: Introductionmentioning

confidence: 99%

The influence of bubble shape and the thickness of the wetting film on the incremental electrical resistance caused by the presence of a single bubble in Hall-Héroult cells

2006

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Bubbles play an important role in the transport phenomena existing in an electrolysis cell. They increase the total ohmic resistance of the electrolyte but their contribution is still not well quantified. During their movement under the anode, the bubbles are separated from the solid by the so-called wetting film, that is by a thin liquid layer. In order to develop a mathematical model to compute the increment of the electrical resistance of the electrolyte due to the presence of several bubbles under the anode, the effects of the bubble shape and the thickness of the wetting film for a single bubble must be quantified a priori. In this first paper, these effects are computed using the finite element method (FEM). The results have shown that the influence of the bubble shape and that of the wetting film is small, about 5% and 2%, respectively.

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Cited by 63 publications

References 1 publication

Bubble Evolution and Anode Surface Properties in Aluminium Electrolysis

Bubble Evolution and Anode Surface Properties in Aluminium Electrolysis

Mathematical model to evaluate the ohmic resistance caused by the presence of a large number of bubbles in Hall-Héroult cells

The influence of bubble shape and the thickness of the wetting film on the incremental electrical resistance caused by the presence of a single bubble in Hall-Héroult cells

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