Skip to main content

Mass- and Heat Transfer During Dissolution of Alumina

  • Conference paper
  • First Online:
Light Metals 2020

Part of the book series: The Minerals, Metals & Materials Series ((MMMS))

Abstract

Dissolution of alumina in industrial aluminium cells is a complicated process, not least because it involves formation of agglomerates, and it involves mass- and heat transfer phenomena taking place simultaneously. In the present study, the diffusion coefficient of alumina in cryolitic melts was measured using a rotating alumina disc. It was found that the temperature dependence of the diffusion coefficient is relatively large. The enthalpies for heating of alumina, conversion, and dissolution are summarised. The addition of 1 wt% alumina causes adiabatic cooling of typically 10–12 °C in a normal industrial bath. The dissolution can be regarded as being purely mass transfer controlled, since the heat required for dissolution only brings about 1 °C temperature drop from the bath bulk to the alumina surface. The bath at the alumina surface is saturated in alumina and has a lower liquidus temperature than the bulk. Alumina dissolution can, therefore, take place in a supercooled bath.

This is a preview of subscription content, log in via an institution to check access.

Access this chapter

Subscribe and save

Springer+ Basic
EUR 32.99 /Month
  • Get 10 units per month
  • Download Article/Chapter or eBook
  • 1 Unit = 1 Article or 1 Chapter
  • Cancel anytime
Subscribe now

Buy Now

Chapter
USD 29.95
Price excludes VAT (USA)
  • Available as PDF
  • Read on any device
  • Instant download
  • Own it forever
eBook
USD 429.00
Price excludes VAT (USA)
  • Available as EPUB and PDF
  • Read on any device
  • Instant download
  • Own it forever
Softcover Book
USD 549.99
Price excludes VAT (USA)
  • Compact, lightweight edition
  • Dispatched in 3 to 5 business days
  • Free shipping worldwide - see info
Hardcover Book
USD 549.99
Price excludes VAT (USA)
  • Durable hardcover edition
  • Dispatched in 3 to 5 business days
  • Free shipping worldwide - see info

Tax calculation will be finalised at checkout

Purchases are for personal use only

Institutional subscriptions

Similar content being viewed by others

References

  1. S.E. Gylver, N.H. Omdahl, A.K. Prytz, A.J. Meyer, L.P. Lossius, and K.E. Einarsrud: Alumina Feeding and Raft Formation: Raft Collection and Process Parameters, Light Metals 2019, 659–666.

    Google Scholar 

  2. N.P. Østbø: Evolution of Alpha Phase Alumina in Agglomerates upon Addition to Cryolitic Melts, PhD Thesis, Norwegian University of Science and Technology (2002).

    Google Scholar 

  3. K. Grjotheim, C. Krohn, M. Malinovsky, K. Matiasovsky, and J. Thonstad: Aluminium Electrolysis. Fundamentals of the Hall-Héroult Process, 2nd Edition, Aluminium-Verlag, Düsseldorf, 1982, p. 122.

    Google Scholar 

  4. J. Gerlach, U. Hennig und H.-D. Pöthsch: Zur Auflösungskinetik von Aluminiumoxid in Kryolithschmelzen mit Zusätzen von Al2O3, AlF3, CaF2, LiF oder MgF2, Erzmetall 31 496–504 (1978).

    Google Scholar 

  5. E.J. Frazer and J. Thonstad: Alumina Solubility and Diffusion Coefficient of the Dissolved Alumina Species in Low-Temperature Fluoride Electrolytes, Met. Mater. Trans. B B41(3) 543–548 (2010).

    Google Scholar 

  6. V.G. Levich: Physicochemical Hydrodynamics (English translation). Prentice Hall, Englewood Cliffs, N. J., 1962.

    Google Scholar 

  7. A. Solheim: The Density of Molten NaF-LiF-AlF3-CaF2-Al2O3 in Aluminium Electrolysis, Aluminum Transactions 2 (1) 161–168 (2000).

    Google Scholar 

  8. T. Herzberg, K. Tørklep, and H.A. Øye: Viscosity of Molten NaF-AlF3-Al2O3-CaF2 Mixtures, Light Metals 1980, 159–170.

    Google Scholar 

  9. E. Skybakmoen, A. Solheim, and Å. Sterten: Alumina Solubility in Molten Salt Systems of Interest for Aluminium Electrolysis and Related Phase Diagram Data, Met. Trans. B 28B 81–86 (1997).

    Google Scholar 

  10. G.J. Janz and N.P. Bansal: Diffusion Coefficients in Single and Multi-Component Salt Systems, J. Phys. Chem. Ref. Data 11(3) (1982).

    Google Scholar 

  11. J. Thonstad: Chronopotentiometry Measurements on Graphite Anodes in Cryolite-Alumina Melts, Electrochim. Acta, 14 127–134 (1969).

    Google Scholar 

  12. R. Ødegård, S. Rønning, S. Rolseth, and J. Thonstad: On Alumina Phase Transformation and Crust Formation in Aluminum Cells, Light Metals 1984, 695–709.

    Google Scholar 

  13. NIST-JANAF Thermochemical Tables, http://kinetics.nist.gov/janaf/.

  14. J.L. Holm: Thermodynamic Properties of Molten Cryolite and Other Fluoride Mixtures, Thesis, Institutt for uorganisk kjemi, NTH, Norway, 1971.

    Google Scholar 

  15. A. Solheim and Å. Sterten: Activity of Alumina in the System NaF-AlF3-Al2O3 at NaF/AlF3 Molar Ratios Ranging from 1.4 to 3, Light Metals 1999, 445–452.

    Google Scholar 

  16. V.A. Khoklov, E.A. Filatov, A. Solheim, and J. Thonstad: Thermal Conductivity in Cryolitic Melts - New Data and Its Influence on Heat Transfer in Aluminium Cells, Light Metals 1998, 501–506.

    Google Scholar 

  17. A. Solheim, S. Rolseth, E. Skybakmoen, L. Støen, Å. Sterten, and 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).

    Google Scholar 

  18. W.E. Haupin: The Liquidus Enigma, Light Metals 1992, 477–480.

    Google Scholar 

  19. J. Thonstad, A. Solheim, S. Rolseth, and O. Skar: The Dissolution of Alumina in Cryolite Melts, Light Metals 1988, 655–661.

    Google Scholar 

  20. Y. Yang, B. Gao, Z. Wang, Z. Shi, and X. Hu: Study on the Dissolution of Alumina in Cryolite Electrolyte Using the See-Through Cell, Light Metals 2015, 583–588.

    Google Scholar 

Download references

Acknowledgements

The present work was mainly supported by SFI Metal Production, which is a Centre for Research-based Innovation financed by the Research Council of Norway and several end-users, among them Hydro Aluminium and Alcoa. Permission to publish the results is gratefully acknowledged.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Asbjørn Solheim .

Editor information

Editors and Affiliations

Rights and permissions

Reprints and permissions

Copyright information

© 2020 The Minerals, Metals & Materials Society

About this paper

Check for updates. Verify currency and authenticity via CrossMark

Cite this paper

Solheim, A., Skybakmoen, E. (2020). Mass- and Heat Transfer During Dissolution of Alumina. In: Tomsett, A. (eds) Light Metals 2020. The Minerals, Metals & Materials Series. Springer, Cham. https://doi.org/10.1007/978-3-030-36408-3_90

Download citation

Publish with us

Policies and ethics