and Phase II). Phase I comprises a 40’×26’ SAG mill (28 MW), two pebble crushers and two 28’×44’ ball mills (22 MW each). Phase II, commenced operations in 2020 and comprises a 36’×17’ SAG mill (13.5 MW), one pebble crusher and one 28’×44’ ball mill (22 MW). The target product size for both grinding lines is 80% passing (P80) 195 µm. The grinding product feeds the bulk flotation circuit. Bulk flotation consists of two rougher lines (Phase I and II), which are fed separately by each grinding line, respectively. The rougher concentrate is combined before feeding the bulk cleaner circuit. If the copper concentrate grade exceeds 20% Cu, concentrate from the first cell of the bulk cleaner circuit is bypassed to the final product stream. The remaining bulk cleaner cells' concentrates are sent to a bulk concentrate thickener, then to the regrind circuit, and finally cleaned in the cleaner circuit to produce the final concentrate. Figure 1 shows a simplified flowsheet of the Toromocho circuit. Figure 1 – Toromocho Simplified Comminution and Flotation Circuit Flowsheet (Phase I and Phase II) Toromocho commenced operations in 2013 (with Phase I) and was designed to process a nominal throughput of 5,250 tph. However, the ore hardness values used for plant design are significantly softer than those encountered during operation. This resulted in higher specific energy consumption, negatively impacting plant throughput and preventing the operation from reaching its design capacity. In response to the higher specific energy consumption, Toromocho adopted a proactive improvement strategy rather than accepting the limitations imposed by the original design. Feed size has a significant impact on the performance and capacity of comminution circuits. Therefore, the initial focus was drill and blast optimization tailored to feed ore characteristics (rock structure and strength) to produce finer ROM fragmentation and, consequently, a finer SAG mill feed. This was followed by the extension of optimization efforts downstream to ensure that the comminution circuit could fully capture the benefits of the improved feed size distribution. The structured drill and blast optimization program was developed and implemented at Toromocho in 2017. Key ROM fragmentation indicators including P80 and fines content (% passing 1 inch and % passing ½ inch) and show sustained improvement over time. The ROM P80
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