Microwave reduction of Black Thor chromite ore

ABSTRACT

Black Thor chromite ore from the Ring of Fire deposit in Northern Ontario was carbothermically reduced in a microwave system to produce a ferrochromium alloy. The as-received ore contained 43.0% Cr₂O₃, 19.9% Fe₂O₃, 14.5% MgO, 13.4% Al₂O_3, and 7.0% SiO₂. Activated charcoal was utilised as the reducing agent. First, thermogravimetric analysis/differential thermal analysis (TGA/DTA) and permittivity studies were carried out in order to determine the relationship between the reduction process and the microwave susceptibility. Second, microwave reduction experiments were performed on the chromite ore. The variables investigated were; the amount of carbon, processing time, input power, and type of atmosphere. A maximum chromium grade of 76.1% and a chromium metallisation of 82.7% were obtained for a processing time of 20 min, a power input of 800 W and a carbon addition of 15% in an argon atmosphere.

RÉSUMÉ

On a traité par réduction carbothermique le minerai de chromite de Black Thor provenant du dépôt de l’Anneau de Feu au nord de l’Ontario, dans un système à micro-ondes, afin de produire un alliage de ferrochrome. Le minerai brut contenait 43.0% de Cr₂O₃, 19.9% de Fe₂O₃, 14.5% de MgO, 13.4% d’Al₂O₃ et 7.0% de SiO₂. On a utilisé du charbon actif comme agent réducteur. Premièrement, on a effectué des études de TGA/DTA et de permittivité afin de déterminer la relation entre le procédé de réduction et la susceptibilité aux micro-ondes. Deuxièmement, on a réalisé des expériences de réduction par micro-ondes avec le minerai de chromite. Les variables examinées incluaient la quantité de carbone, la durée de traitement, la puissance d’entrée et le type d’atmosphère. On a obtenu une nuance maximale de chrome de 76.1% et une métallisation du chrome de 82.7% avec une durée de traitement de 20 min, une puissance d’entrée de 800 W et une addition de carbone de 15% dans une atmosphère d’argon.

KEYWORDS:

• Chromite
• microwave
• reduction
• carbothermic
• ferrochromium

Acknowledgements

The Natural Sciences and Engineering Research Council of Canada (NSERC) is acknowledged for supporting this research. The authors would like to thank Noront Resources for providing the chromite ore. Microwave Properties North (MPN) is thanked for the permittivity measurements.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Kristian Mackowiak did his B.A.Sc. and M.A.Sc. in the Robert M. Buchan Department of Mining at Queen's University. His Master's thesis was on the microwave reduction of Black Thor chromite ore. He is currently doing a Ph.D. at the University of British Columbia. His research interests include new pyrometallurgical processes and process modelling.

Chris Pickles did his Ph.D. in the Department of Metallurgy and Materials Science at the University of Toronto. He is currently a professor in the Robert M. Buchan Department of Mining at Queen's University. His major interests are related to environmental and energy concerns in extractive metallurgy.