Abstract
The relationship between the content of sodium in the metal in aluminium production cells and the current efficiency (CE) was analysed, using available theory and experimental data. The sodium concentration as well as the CE varies with the bath composition (the bath ratio) and the cathodic overvoltage . The mentioned parameters are all functions of the same type of ratio between the activities of sodium fluoride and aluminium fluoride, thus enabling an internally consistent and quantitative description. The “ideal” relationships between the sodium concentration in the metal, the CE, and the cathodic overvoltage are illustrated. It is suggested that the sodium content in the metal can indeed be used as an indicator of the cell performance. However, it is necessary to use adequate sampling and analysis techniques. The exact cell conditions during sampling should be taken into account as well, such as the bath composition and the overfeeding/underfeeding cycle.
References
A.T. Tabereaux, The role of sodium in aluminium electrolysis: a possible indicator of cell performance, in Light Metals (1996), pp. 319–326
P.V. Polyakov, V.Y. Buzunov, Y.G. Mikheev, V.G. Putintsev, Movement of metal-electrolyte interface in aluminium reduction cells by Marangoni effect. Tsvet. Met. 34(3), 29–31 (1993)
T. Müftüoglu, B. Rasch, S. Rolseth, A. Solheim, J. Thonstad, Effect of anode-cathode distance on the current efficiency in aluminium cells. Part II: Interfacial waves and stirring in laboratory cells. Aluminium 64(3), 284–288 (1988)
W.H. Tingle, J. Petit, W.B. Frank, Sodium content of aluminium in equilibrium with NaF-AlF3 Melts. Aluminium 57, 286–288 (1981)
V. Danielik, private communication
V. Danielik, P. Fellner, Content of sodium and lithium in aluminium in equilibrium with cryolite melts. Experimental data and thermodynamic model. Chem. Papers 52(4), 195–198 (1998)
J. Thonstad, S. Rolseth, J. Rødseth, O. Lund, J. Tonheim, V. Danielik, P. Fellner, J. Hives, The content of sodium in aluminium in laboratory and in industrial cells, in Light Metals (2001), pp. 441–448
K. Yoshida, E.W. Dewing, Activities in NaF-AlF3 melts saturated with Al2O3. Met. Trans. 3, 683–686 (1963)
R. Keller, J.W. Burgman, P.J. Sides, Electrochemical reactions in the Hall-Heroult cathode, in Light Metals (1988), pp. 629–631
A. Solheim, Å. Sterten, Activity of alumina in the system NaF-AlF3-Al2O3 at NaF/AlF3 molar ratios ranging from 1.4 to 3, in Light Metals (1999), pp. 445–452
Å. Sterten, I. Mæland, Thermodynamics of molten mixtures of Na3AlF6-Al2O3 and NaF-AlF3. Acta Chem. Scand. A 39, 241–257 (1985)
Å. Sterten, K. Hamberg, I. Mæland, Activities and phase diagram data of NaF-AlF3-Al2O3 mixtures derived from electromotive force and cryoscopic measurements. Standard thermodynamic data of β-Al2O3(s), Na3AlF6(s), Na5Al3F14(s) and NaAlF4(l). Acta Chem. Scand. A 36, 329–344 (1982)
NIST-JANAF Thermochemical Tables, http://kinetics.nist.gov/janaf/
J. Thonstad, S. Rolseth, On the cathodic overvoltage on aluminium in cryolite-alumina melts. Electrochim. Acta 23(3), 223–241 (1978)
J. Thonstad, P. Fellner, G.M. Haarberg, J. Hives, H. Kvande, Å. Sterten, Aluminium Electrolysis. Fundamentals of the Hall-Héroult Process, 3rd edn. (Aluminium-Verlag Marketing & Kommunikation, GmbH, Düsseldorf, 2001)
Å. Sterten, P.A. Solli, An electrochemical current efficiency model for aluminium electrolysis cells. J. Appl. Electrochem. 26, 187–193 (1996)
P.A. Solli, T. Eggen, E. Skybakmoen, Å. Sterten, Current efficiency in Hall-Héroult cells: experimental and modelling studies. J. Appl. Electrochem. 27, 939–946 (1997)
A. Solheim, H. Gudbrandsen, K.S. Osen, J. Kvello, Current efficiency in laboratory aluminium cells. Paper presented at the 33rd international ICSOBA conference, Dubai, United Arab Emirates, 29 November–1 December 2015 (Travaux No. 44, 625–634)
A. Solheim, Current Efficiency in Aluminium Reduction Cells: Theories, Models, Concepts, and Speculations, in Light Metals 2014 (2014), pp. 753–758
A. Solheim, S. Rolseth, E. Skybakmoen, L. Støen, Å. Sterten, T. Støre, Liquidus temperatures for primary crystallization of cryolite in molten salt systems of interest for the aluminium electrolysis. Met. Trans. B 27B, 739–744 (1996)
Acknowledgements
The present work was supported by the project “Sustainable Production and Recycling of Metals” (SUPREME), financed by the Research Council of Norway and Hydro Aluminium, Boliden, Glencore, and Permascand. The author would like to thank Dr. Per Arinn Solli, Hydro Aluminium, for the inspiration to initiate this work.
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2017 The Minerals, Metals & Materials Society
About this paper
Cite this paper
Solheim, A. (2017). Sodium in Aluminium as a Cell Performance Indicator: A Quantitative Framework. In: Ratvik, A. (eds) Light Metals 2017. The Minerals, Metals & Materials Series. Springer, Cham. https://doi.org/10.1007/978-3-319-51541-0_78
Download citation
DOI: https://doi.org/10.1007/978-3-319-51541-0_78
Published:
Publisher Name: Springer, Cham
Print ISBN: 978-3-319-51540-3
Online ISBN: 978-3-319-51541-0
eBook Packages: Chemistry and Materials ScienceChemistry and Material Science (R0)