total circuit specific-energy and SAG mill specific-energy, based on ore hardness properties and the calculated SAG mill feed F80 (linked to the alteration domains). The specific energy is used to determine plant throughput for a given SAG milling and ball milling power. The throughput forecast model was calibrated and then validated using historical production data (March 2019 – September 2019 for calibration September 2019 –February 2020 for validation) and was supported by the mathematical process models developed during the optimization project. Despite limitations in ore characterization data available at the time, the model predicts throughput quite well on a weekly and monthly basis, with errors of 11% and 3.5%, respectively, at the 95% confidence level. Further improvements in model accuracy are expected with additional ore characterization. Accurate throughput forecast models are useful production tools that can assist in improving production reliability and strategic planning to maximize profit over the life-of-mine (LOM). 4. IMPLEMENTATION STATUS Chinalco has commenced implementation which is ongoing as some recommendations take longer to implement in a production environment. A summary of recommendations and implementation status for the Phase II grinding line and flotation circuit is provided in Table 2 and Table 3. Table 2 Summary List of Opportunities and their Status of Implementation for Phase II Grinding Circuit Opportunity Actions Benefits Implementation Status, % Maintain higher SAG mill speed more consistently. Maintain SAG mill speed at 76% C.S. Increase power draw and throughput ~ 6% - some coarsening of product size. Implemented. Increase and maintain ball mill ball charge. Increase and maintain the ball mill ball charge at 35 %vol and operate consistently at mill speeds of about 75 – 76% C.S. Increase power draw (~7%) and reduce P80 to mitigate the coarsening of grinding product size expected at higher throughput. Able to maintain ball mill ball charge at 33%vol. Include finer grinding media Change ball make-up from solely 3” balls to a 25/75 mix of 3”and 2.5” balls. Improve breakage efficiency. Implementing a 60/40 mix of 3”/2.5” balls. Currently running a test with high chrome balls at ball mill #3. Increase slurry residence time in ball mill. Reduce water addition to cyclone underflow. Improve grinding efficiency. Reduce P80 by about 10 µm and improve the current operating work index. Implemented but difficulty controlling the water addition. Shift load from the constrained SAG mill to the ball mill. Redirecting the crushed pebbles to the ball mill. Additional 7% increase in throughput - some coarsening of grinding product P80 (~ 13 - 18 µm). Planned to be implemented in 2028. Improve cyclone performance Maintain the current cyclone feed percent solids (~ 55%) and pressure (~ 90 kPa). To achieve good cyclone classification efficiency. In progress. Currently, it reducing the vortex diameters from 300 to 270 mm and increasing feed percent solids to cyclones from 55 to 62% for improve the circuit efficiency and copper recovery. Improve SAG mill performance. Implement curve discharge design at both SAG mills. • Increase throughput above 3%. Implemented: • New curved design is installed in March 2026. • Implemented: Currently running with 14 grates of 65 mm, and 4 65/70 mm. Reduce slot opening • Increase residence time at SAG mill, reducing slot opening from 65/70 to 65 mm. Increase the service life of the grates to match the shell service life. Increase the feed head outer plate thickness to match service life of grates. Table 3 Summary List of Opportunities and their Status of Implementation for Flotation Circuit Opportunity Actions Benefits Implementation Status, % Quick-Win Opportunities Reducing load in downstream cleaner bulk circuit (Sim A) By-pass first rougher cell concentrate of Phase II to bulk conc. thickener. Reduce the load on cleaner bulk circuit. ~1.3% increase in overall Cu recovery. Under Review.
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