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Metallurgical and Materials Transactions B

, Volume 49, Issue 5, pp 2809–2820 | Cite as

Balancing Sodium Impurities in Alumina for Improved Properties

  • Hasini WijayaratneEmail author
  • Margaret Hyland
  • Grant McIntosh
  • Linus Perander
  • James Metson
Article
  • 115 Downloads

Abstract

As there are direct and indirect impacts of feed material purity on the aluminum production process and metal grade, there is a high demand on the so-called pure smelter grade alumina (SGA)—the main feedstock for aluminum production. In this work, impurities within the precursor gibbsite used for SGA production and SGA are studied using NanoSIMS and XPS with a focus on sodium—the most abundant impurity. Although the industry trend is towards minimizing sodium due to the well-known negative impacts on the process, high sodium is also correlated with relatively attrition-resistant calcined products. Here, we show that this relationship is indirect and arises from sodium’s role in inhibiting α-alumina formation. Alpha alumina formation in SGA has previously been demonstrated to induce a macro-porous and therefore attrition-prone microstructure. Sodium distribution within the precursor gibbsite and its migration during the calcination process are proposed to be most likely responsible for the spatial distribution of α-alumina within the calcined product grain. This in turn determines the behavior of the product during its transportation and handling (i.e., attrition). Therefore, tolerance of a certain amount of sodium within the precursor material does demonstrate a net benefit while balancing its negative impacts on the process.

Notes

Acknowledgments

The authors would like to acknowledge the generous support of Outotec GmbH. The assistance of Dr. Paul Guagliardo and Professor Matt Kilburn at UWA for NanoSIMS data collection and Reece Oosterbeek for XPS data collection are also acknowledged.

Supplementary material

11663_2018_1310_MOESM1_ESM.docx (11 kb)
Supplementary material 1 (DOCX 11 kb)

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Copyright information

© The Minerals, Metals & Materials Society and ASM International 2018

Authors and Affiliations

  • Hasini Wijayaratne
    • 1
    Email author
  • Margaret Hyland
    • 1
  • Grant McIntosh
    • 1
  • Linus Perander
    • 2
  • James Metson
    • 1
  1. 1.Light Metals Research CentreUniversity of Auckland, NewmarketAucklandNew Zealand
  2. 2.Outotec GmbHOberurselGermany

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