Advances in research on nickel production through the Caron Process

New environmental and chemical policy regulations require further optimisation of current nickel production processes. This paper outlines recent fundamental research in support of improvements in nickel production process through the Caron Process. The research focuses on two major areas: (i) reduction roasting of nickel laterite, and (ii) reduction of basic nickel carbonate (BNC) and NiO to nickel. Nickel in laterite is associated with Fe-rich goethite and serpentine/olivine particles. Results indicate that the nickel recoveries from the limonite ores correspond closely to values predicted by thermodynamic modelling; nickel recoveries from serpentine ores are however significantly lower than these chemical equilibrium values. The nickel recovery from serpentine/olivine appears to be higher for particles with Mg to Fe mol ratio of lower than 8. In relation to the reduction of BNC and NiO, the change of phase, product surface, internal microstructures taking place during reduction/oxidation of BNC at 110oC to 900oC; as well as the kinetics and microstructure transformation mechanism during reduction of synthetic NiO at 400oC to 1000oC have been studied. A clear link has been established between the rates of reduction, the nickel product morphology, and the reaction mechanisms occurring at the Ni-NiO interface. A change in the reduction behaviour was observed between 600 and 800oC depending on the hydrogen partial pressures and reduction time. The phenomena affecting the final-product microstructure were identified as follows: (1) chemical changes, i.e. decomposition, reduction and oxidation reactions; (2) NiO and Ni recrystallisation and grain growth; (3) NiO and Ni sintering and densification; and (4) agglomeration of the NiO and Ni particles