Investigation of the reduction roasting of saprolite ores in the Caron process: effect of sulphur addition

ABSTRACT

Laboratory studies have been undertaken to determine the mechanisms and kinetics of reactions occurring during the reduction roasting of saprolite ores with 1 wt% elemental sulphur addition. The reduction was undertaken using a 15%H₂/85%N₂ gas mixture at temperatures between 400 and 800°C; nickel was recovered by subsequent leaching in an ammoniacial aqueous solution. The effect of sulphur on dehydroxylation, reduction and sintering was investigated. Improvements in nickel recoveries were obtained when 1 wt% S was added to the nickel-bearing serpentine ore prior to the reduction roasting. Characterisation of the reduced and leached ore samples indicated that this improved Ni recovery with S addition is due to the formation of a leachable nickel sulphide phase, and the suppression of sintering and recrystallisation of the olivine phase formed at high reduction temperatures.

KEYWORDS:

• Saprolite
• serpentine
• sulphur
• reduction roasting
• ferronickel alloy
• nickel sulphide
• leaching
• recovery

Acknowledgements

The authors would like to acknowledge financial support for this research from the Australian Research Council Linkage program and our industry sponsor, QN Yabulu, Townsville, Queensland, Australia. Particular thanks are due to John Fittock, QN for his invaluable assistance in obtaining mineral samples for the research, and for providing valuable insight into the principles and industrial operation of the Caron process used at QNI. Thanks also to the staff of The University of Queensland’s Centre for Microanalysis and Microscopy (CMM) for their support for sample analysis undertaken in the Centre.

Disclosure statement

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

Additional information

Funding

The authors would like to acknowledge financial support for this research from the Australian Research Council Linkage program and our industry sponsor, QN Yabulu, Townsville, Queensland, Australia.