Abstract
Anode impurities are the major source of sulfur in aluminum electrolysis. Sulfur in anodes is mainly found as organic compounds. Alumina also introduces small quantities of sulfur, typically in the form of sulfates. The scarcity and cost of low-sulfur raw materials and the possibility of sulfur removal from the cell by means of flue gas may make high-sulfur content anodes a viable option. However, some anode impurities are known to affect current efficiency in aluminum production and caution must be exercised. The effect of increased sulfur content in the aluminum electrolysis electrolyte must be studied. This paper explores the effect of increased sulfur concentration in the electrolyte on current efficiency in a laboratory cell. Sodium sulfate was added to the electrolyte as a source of sulfur at regular time intervals to maintain a constant sulfur concentration. Current efficiency decreased by 1.1 pct per each 100 mg/kg (ppm) increase in sulfur concentration in the electrolyte.
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Acknowledgments
This work was supported by Alcoa Fjarðaál, HRV Engineering, SINTEF, and NTNU. Authors would like to thank Ms. Anne Tofte for her invaluable contribution to this work. Authors would also like to express endless gratitude to Dr. Andrei Manolescu, Dr. Arne P. Ratvik, Dr. Thor A. Aarhaug, Dr. Ole S. Kjos, Mr. Asbjørn Solheim, and Dr. Marketa Valterova for their comments and suggestions.
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Manuscript submitted July 8, 2015.
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Meirbekova, R., Haarberg, G.M., Thonstad, J. et al. Influence of Sulfur Species on Current Efficiency in the Aluminum Smelting Process. Metall Mater Trans B 47, 1309–1314 (2016). https://doi.org/10.1007/s11663-016-0595-z
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DOI: https://doi.org/10.1007/s11663-016-0595-z