Beneficiation Strategies for Removal of Silica and Alumina from Low-Grade Hematite-Goethite Iron Ores

ABSTRACT

As higher-grade ores become depleted, there will be a greater focus on developing suitable beneficiation strategies to treat low-grade hematite-goethite ores containing higher levels of impurities such as silica and alumina. The processes selected to reduce impurity levels of these lower-grade iron ores will depend on the ore mineralogy and a thorough understanding of the separation process dynamics. The major concentration methods that may be applied to upgrade lower-grade lump iron ores include magnetic separation, wet and dry heavy media separation, and air-pulsed jigging. The technologies applicable to beneficiating iron ore fines include wet and dry gravity and magnetic separation, flotation, and roasting followed by magnetic separation. A commercial flowsheet is expected to involve the implementation of several of these separation technologies. Here the performance of different separation technologies, their testing methodologies, and difficulties in removing silica and alumina from low-grade iron ores are reviewed.

KEYWORDS:

• Iron ore beneficiation
• low-grade iron ore
• impurity removal
• gravity concentration
• magnetic separation
• flotation
• magnetizing roast

Acknowledgments

This work has been conducted over a number of years and involved discussions with a number of current and former CSIRO colleagues. In particular, we would like to thank Dr Ralph Holmes for critically reviewing earlier versions. Minor sections of this work were presented at Iron Ore 2021 (Nunna et al. 2021b), but the work therein has been significantly expanded upon. A number of references have been given in this paper to Iron ore: Mineralogy, processing and environmental sustainability, ed. L. Lu. Cambridge: Woodhead Publishing. A second edition of this book is in production and the appropriate chapters in it also should be consulted. We would also like to thank the reviewers for their thoughtful comments and efforts toward improving our manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).