622 A two‑week pilot program was conducted by the Ernest Henry Operations onsite metallurgy team in September 2023 under the specified test conditions shown in Table 1. Operational variables included residence time, air rate, collector dosage, and lime dosage. Slurry was fed into the cell by gravity, and the tail ball valve was manually adjusted until the slurry level in the cell reached the target operating point and a steady state was achieved. For each test, steady state was maintained for approximately 10 minutes before sampling commenced. Feed flow rate, pulp chemistry, and reagent additions were measured and recorded manually, while air rate was monitored using a regulator. Samples of the concentrate and tailings streams were collected in labelled buckets for processing. These samples were analysed for percent solids and chemical assays, including Cu, Au, Ag, S, As, F, and U. Table 1 – Range of pilot-scale test variables Residence time Superficial gas velocity 3418A pH (min) (cm/s) (g/t) Min - max 1.6-8.7 0.25-1.12 0.19-17 7.8-11.9 It was observed that increasing collector dosage resulted in higher mass recovery, which in turn increased both gold and copper recoveries. However, these improvements were achieved at the expense of concentrate grade, with dilution effects most pronounced for copper. For the remaining tests, mass pull was constrained to 3–6% and pH was maintained between 11.5 and 11.9 to ensure adequate pyrite depression and to achieve an acceptable copper concentrate grade. The relationship between gold and copper recovery obtained from the pilot tests is presented in Figure 4, where triangular data points represent tests for which the copper concentrate grade met or exceeded the 20% Cu threshold. Figure 4 – Gold and copper recovery from pilot testing 3.4 Flotation survey campaign A full flotation circuit sampling survey was conducted during the SK0.25 pilot campaign to collect data for the development of a flotation model in JKSimFloat. Representative samples of feed, concentrate, and tailings streams were taken throughout the circuit every 30 minutes, with a total of four sampling rounds completed during the survey. A diagram illustrating the sampling locations is provided in Figure 5. Hot flotation tests were also performed on the flotation feed, cleaner feed, flash feed and regrind cyclone feed to obtain kinetic information of the ore being processed across various sections of the circuit. Additional hot flotation tests were conducted on the rougher tails and cleaner tails streams. The kinetic data generated from these tests provided essential inputs for the development of the flotation model.
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