M. A. Rhamdhani

Nickel laterite Part 2 – thermodynamic analysis of phase transformations occurring during reduction roasting

Abstract Thermodynamic and phase transformation analyses of nickel laterite ores processed in industry have been carried out. The nickel in the laterite ores is principally associated with Fe rich goethite and serpentine particles. The thermodynamic analysis suggests that the nickel recovery from the Fe rich matrix is limited by equilibrium. The nickel recovery from the single phase serpentine/olivine appears to be higher for particles with Mg/Fe molar ratio <8. The nickel partitioning to the alloy phase is sensitive to the change of temperature and oxygen partial pressure both in the case of reduction roasting of Fe rich goethite and serpentine. It has also been shown in the current study that the optimum conditions for high nickel recovery from the Fe rich goethite and serpentine are different.

Nickel laterite Part 1 – microstructure and phase characterisations during reduction roasting and leaching

Abstract Detailed microstructure and phase characterisations of processed nickel laterite ore feed, reduced ore and leached ore have been carried out using scanning electron microscope, synchrotron X-ray powder diffraction and electron probe X-ray microanalysis as a part of study aimed to increase Ni recovery from the laterite ores. The majority of the nickel in the ore feed were found to be associated with fine grained goethite (Fe rich matrix of limonite composite) and serpentine particles. These phases were transformed to magnetite and olivine respectively upon reduction roasting. Nanosize metallic particles were also observed on the free surface of limonite composite particles following reduction roasting. Upon leaching, >90% of the nickel in the Fe rich matrix was leached out, while <50% was removed from the olivine and its composites. The characterisation results from this study were used to assist the analysis of thermodynamic and phase changes during reduction roasting and leaching described in Part 2 of the paper.