adjustments to the cleaner circuit were required to maintain concentrate grade. While operating the SK240 more aggressively improved both copper and gold recoveries, this improvement came at the expense of reduced concentrate grade—particularly copper grade. In addition, Coombs and Ma (2025) suggested that, given the relatively high liberation of pyrite in the SK concentrate, diverting this stream to the third cleaner stage may offer benefits, although it could also lead to some loss of gold. An ON/OFF trial was initiated to evaluate this option; however, this work is ongoing, and results are not yet available at the time of this publication. 6.3 Additional froth crowding Identified during the initial feasibility study and confirmed through subsequent surveys and observations, the diversion of 4 tph of cleaner feed to SK concentrate generally resulted in reduced froth carry rates (FCRs) in the cleaner circuit. Efforts to increase crowding and improve mass‑pull distribution within the cleaner circuit are ongoing. 7. CONCLUSIONS Flash flotation has been shown to be an effective solution for addressing gold losses associated with recirculating loads in the regrind circuit at Ernest Henry Operations. A thorough, systematic, step by step, approach used by the Ernest Henry Operations Metallurgy Team, which consisted of mineralogy diagnosis, laboratory testing, pilot plant trial and flotation modelling has proven to be effective in identification of the drivers for the losses and finding a suitable solution. The installation of a Metso SkimAir® SK240 flash flotation cell on the regrind cyclone underflow successfully recovered coarser, fast-floating valuable particles prior to further grinding, leading to statistically significant improvements in overall gold recovery while maintaining copper grade and recovery. Post-commissioning plant data show a gold recovery uplift of 1.06–1.99% and a modest improvement in copper recovery at 90% confidence. Ongoing optimisation work indicates further potential to enhance recovery through operating strategy. This case study highlights the value of a considered, methodical approach to circuit modification and confirms flash flotation as a low-risk, high-impact opportunity for unlocking value in mature copper–gold concentrators.
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