618 FLASH FLOTATION IN ERNEST HENRY’S REGRIND CIRCUIT – A CASE STUDY IN ADDING VALUE THROUGH A CONSIDERED AND METHODICAL APPROACH *T.K. Nguyen1, E.S. Brodie2, L.T. Killer3, R.E. Bown4, G. Binks5 1JKTech Pty. Ltd., Brisbane, Australia, (*Presenting author: t.nguyen@jktech.com.au) 2,3,4,5Evolution Mining, Australia ABSTRACT Surveys undertaken at Evolution Mining’s Ernest Henry Operations concentrator revealed an accumulation of gold in the flotation regrind circuit, evident in elevated gold grades of 25-50g/t in the recirculating load. This resulted in overgrinding, smearing, and degradation of these particles, exacerbating gold losses in the cleaner circuit. Opportunities to recover this gold with flash flotation technology were initially explored through lab-scale testing, which soon progressed to pilot-scale testing. Further derisking was undertaken by simulating the impact of a flash flotation unit upon overall circuit performance in JKSimFloat. It was important to ensure that the installation of the unit would not adversely impact copper grade or recovery, as copper remains the primary source of revenue at Ernest Henry Operations. Simulation results suggested that a flash flotation unit would not be detrimental to concentrate grades or copper recoveries but would increase gold recovery by at least 1-2%. A flash flotation cell (Metso SkimAir® SK240) was installed and commissioned in early 2025. Analysis of plant data to-date has indicated improved gold recoveries due to the removal of gold-bearing particles from the regrind circuit via the flash flotation cell. This has equated to an overall plant recovery uplift of 1.06-1.99% for gold and 0.52% for copper at 90% confidence. Modelling and simulations using JKSimFloat were used to identify opportunities to further optimise gold and copper recovery post-commissioning. These suggested that further increases in recoveries can be achieved with changes in operating strategies around the flash and cleaner cells, such as running the flash cell at shallow froth depth and thereby increasing the mass recovery while pulling harder from the cleaner cells. KEYWORDS World Mining Congress, Ernest Henry Operations, JKSimFloat, JKTech, Flash Flotation, Regrind, Gold 1. INTRODUCTION Evolution Mining’s Ernest Henry Operations is a large‑scale copper–gold–silver operation located in regional Queensland, Australia. With a processing capacity of 8.5 Mtpa and a mine life extending at least to 2040, Ernest Henry Operations is a long‑life asset with substantial growth potential. The deposit, hosted within a hydrothermal breccia, contains magnetite, quartz, biotite, chalcopyrite, pyrite, fluorite, gold, molybdenite, uraniferous minerals, and potassic feldspar. Additional gangue minerals include chlorite, calcite, dolomite, barite, apatite, muscovite, garnet, scapolite, sphene, rutile, and tourmaline (Ryan, 1998). Chalcopyrite is the main copper‑bearing mineral and, together with pyrite, represents the only significant sulphide phases. Sulphides constitute approximately 1–20% of the breccia matrix and occur as fine‑ to medium‑grained disseminations commonly associated with magnetite. Gold occurs predominantly (>98%) as native gold–electrum (65–95 wt% Au), with minor contributions from sylvanite and sulphide‑hosted gold. Gold precipitation is interpreted to have been closely associated with, but preceded some of the chalcopyrite deposition, as evidenced by the lower gold‑to‑copper ratios in late‑stage chalcopyrite‑rich veins. Although arsenic, fluorine, and uranium minerals are present, their concentrations
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