• Preserve natural pulp chemistry wherever possible by floating the slurry soon after collection, ensuring the integrity and representativeness of the sample. Plant samples representative of the regrind cyclone underflow stream were subjected to batch flotation testing using a JKTech 5 L bottom‑driven laboratory flotation cell. The agitation speed was maintained at a minimum of 1,200 rpm to ensure adequate suspension of coarse particles. Collectors (Potassium Amyl Xanthate and Aerophine 3418A) and frother (IF50) were added according to the specific test conditions. Staged concentrates were collected and submitted for chemical analysis. Laboratory batch flotation test results indicated that gold recoveries ranged between 20– 60%, while copper recoveries ranged between 45–70%. The copper grade–recovery relationships presented in Figure 5 demonstrate that copper concentrate grades exceeding 20% Cu were achievable in most tests. Figure 2 - Laboratory flash flotation test work 3.3 Pilot scale flash flotation test work The encouraging findings from the laboratory test program and mineralogical characterisation supported the decision to progress to pilot‑scale testing to further evaluate the viability of flash flotation technology at Ernest Henry Operations. The primary objective of the pilot campaign was to determine whether flash flotation could improve gold recovery while maintaining overall copper grade and recovery. In addition, the pilot program enabled the collection of kinetic data from the flash flotation unit, providing essential inputs for mathematical modelling of the Ernest Henry Operations flotation circuit. A pilot‑scale flash flotation unit supplied by Metso was installed at ground level adjacent to the Ernest Henry Operations regrind circuit (Figure 3). The Metso SkimAir® (SK0.25) pilot unit has a processing capacity of approximately 0.25 t/h of dry solids. Spear samplers, designed to extract a representative and unbiased slurry feed of 0.15–0.6 m³/h from a flanged regrind cyclone underflow pipe, delivered the sample to the flash cell by gravity via a 1‑inch hose.
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