Effect of impurity oxides on CWF (CaFe₃O₅) formation in lime magnetite pellets – part I: thermodynamic assessments and experimental investigations

ABSTRACT

Lime magnetite pellets (LMPs) containing CWF phase (CaFe₃O₅) provide potential feed materials for ironmaking. In this paper, the effects of typical impurity oxides inherent to magnetite ores such as Al₂O₃, MgO and SiO₂ on the formation of CWF in LMPs have been investigated. The thermodynamics of the Ca–Fe–O–X systems (X = Al, Mg or Si) were assessed followed by time-series experiments using natural and synthetic materials. The X-Ray Diffraction (XRD) results indicated a significant decrease in CWF percentage by over 45 wt-% and 18 wt-% with the addition of 5 wt-% SiO₂ and 2 wt-% Al₂O₃, respectively due to the formation of α’ Ca₂SiO₄ and Ca₂(Al, Fe)₂O₅ phases. A 5 wt-% decrease in CWF amount was observed for 2 wt-% MgO added LMPs. In summary, the presence of impurity oxides limits the formation of CWF, which may affect the suitability of LMPs for industrial application.

KEYWORDS:

• Lime magnetite pellets (LMPs)
• Ca–Fe–O–Al system
• Ca–Fe–O–Si system
• Ca–Fe–O–Mg system
• CWF phase (CaFe₃O₅)
• Ca₂(Al, Fe)₂O₅)
• Ca₂SiO₄
• XRD
• Rietveld QPA

Acknowledgements

The authors wish to thank Swinburne University of Technology for providing financial support for this research and Dr. Matthew Glenn (CSIRO Mineral Resources) for assistance with scanning electron microscopy. Dr. Nick Wilson (CSIRO Mineral Resources) is thanked for assistance with the EPMA measurements.

Disclosure statement

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

Additional information

Funding

This work was supported by Swinburne University of Technology: [Grant Number HDR Publication Award].