Enhancing nickel grade and recovery with counter-current washing of the concentrated bubbly-zone of a single stage REFLUX™ Flotation Cell

• Published in: Minerals engineering 2024-01, Vol.206, p.108506, Article 108506
• Main Authors: Wang, Peipei, Yvon, Meolla, Parkes, Siân, Galvin, Kevin P.
• Format: Article
• Language: English
• Subjects: Bias flux; Counter-current washing; Nickel; Performance ratio; REFLUX™ Flotation Cell; Selectivity
• ISSN: 0892-6875
• DOI: 10.1016/j.mineng.2023.108506

•RFC™ offers a significant hydrodynamic advantage over conventional flotation.•Nickel recovery and silica rejection were investigated at different bias fluxes.•The selectivity of nickel to the silica was 121 at the highest bias flux.•Hydrophilic gangue rejection increased significantly as the bias flux increased.•The performance ratio was at least 6 and would exceed 10-fold for a higher upgrade. The recovery and concentration of the nickel sulphide mineral, pentlandite, present several challenges due to its relatively slow flotation, leading to excessive hydrophilic gangue minerals in the concentrate. The REFLUX™ Flotation Cell (RFC™) offers the potential for a significant hydrodynamic advantage over conventional flotation. Much of this advantage is due to the replacement of the pulp and froth phases with a concentrated bubbly zone, which in turn supports more intense counter-current washing by permitting a powerful and effective positive bias flux. Thus, the aim of this study was to investigate the nickel recovery and silica rejection in the RFC™, by applying a wide range of positive bias fluxes. The focus was on a single stage of separation in the RFC™ using a feed flux of 0.63 cm/s at a feed nickel grade of 2.1%. At the lowest bias flux of 0.1 cm/s, a nickel grade of 7.5% was obtained at a single stage recovery of 70.2%. By increasing the bias flux to 0.42 cm/s, the grade increased to 9.7% but the recovery fell to 64.9%. With an extreme bias flux of 1.04 cm/s, the grade reached 12.3%, while the recovery fell to 54.7%. The selectivity, given by the nickel recovery relative to the silica recovery, was estimated to be 121 at the highest bias flux, declining sharply with a reduction in the bias flux. The performance ratio proposed by Parkes et al (2022) was quantified by comparing the RFC™ performance with the batch kinetic results from a mechanical cell, the product grade being ∼7%. The performance ratio was based on the experiment at the lowest bias flux used in the RFC™, and found to be at least 6, meaning the RFC™ footprint would be reduced by a factor of ∼6 for a similar product grade. Based on the higher product grades achieved in the RFC™ using the higher positive bias fluxes, the performance ratio would likely exceed 10-fold given the need for the mechanical cell concentrate to undergo at least one further stage of flotation.