757 dosage—was explicitly recognized and addressed through comparative and statistically robust evaluation frameworks. Rather than relying on direct absolute before and after comparisons, the authors of the original studies adopted normalized, parallel line methodologies that allowed the upgraded and baseline circuits to be evaluated relative to one another, thereby isolating the effect of the froth launder upgrade. Across the three sites, metallurgical performance was assessed using composite samples collected over extended operating periods (typically 12-hour shift composites over 2+ months or stabilized survey campaigns), with metal recoveries calculated from mass balanced assays. Data screening criteria were applied to exclude non-representative operating conditions, ensuring that the statistical analysis reflected steady-state plant operation. The significance of the observed recovery gains—primarily for copper and molybdenum—was then tested using conventional two sample t-tests, with confidence levels ranging from approximately 90% to greater than 99%, depending on the case and metal considered. These analyses consistently demonstrated that the measured recovery improvements associated with launder upgrades were statistically significant and unlikely to be attributable to random process variability alone. Given the review nature of the present paper, detailed descriptions of sampling protocols, data filtering, assay balancing, and statistical test results are not reiterated here. Readers interested in the full statistical methodology, assumptions, and numerical outputs are encouraged to consult the case studies references, where these aspects are presented comprehensively and transparently for each individual installation. 4.3 Launder Retrofit Effect on Copper Recovery According to the results from the case studies, the center launder upgrade significantly increases copper recovery. As mentioned earlier, all three case studies—Constancia, Kennecott Copperton, and Bagdad—are operating with a similar Cu-Mo ore type. In all cases, the improvements in copper recovery were consistent and the gained results represent statistically significant net recovery gains of copper. These consistent results indicate the high potential for copper recovery with the center launder retrofit, thereby increasing the profitability of the operation. To further understand the impact of center launder retrofit in Bagdad’s rougher circuit, the size-bysize analysis was conducted to calculate the achieved copper recovery. From two similar lines, A and B, the last three out of six flotation cells of line A were upgraded with a center launder upgrade. Measurements from each line were taken using down-to-bank sampling during a one-month process survey, and the collected samples were analyzed by size and balanced using HSC® Software. The results are presented in Fig. 7 (Liu et al. 2022).
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