The impact of center launder upgrade on operating parameters, like airflow rates and froth bed depths has also been investigated. Measurements showed that after the retrofit, similar gas velocities (Jg) were achieved with reduced airflow rates. The reduction in airflow rates is expected to lower the energy consumption of the blower, thereby promoting more sustainable metals processing. On the other hand, the froth bed thickness in upgraded cells is considered to be higher due to smaller froth surface areas, which has been enhanced process control. (Bermudez et al. 2022) 3. EVALUATION OF CENTER LAUNDER UPGRADE INSTALLATIONS Center launder installations have been successfully implemented in various operations, including Hudbay Constancia, Kennecott Copperton, Bagdad, Red Chris, and New Afton Mine, to address current operational challenges. In all these cases, the existing launder models were upgraded to enhance the recovery of valuable minerals and improve operational parameters by shortening the froth transport distance and decreasing the froth surface area. The results from these cases show up to a 68% decrease in froth surface area (FSA) and an 83% decrease in froth transport distance (FTD) (Metso 2021), which have been proven to correlate with higher recovery of valuable metals (Liu et al. 2022). The metallurgical recovery evaluation was conducted for the Constancia, Kennecott, and Bagdad operations, yielding highly consistent results. In each case, the difference in recovery between the upgraded and baseline configurations was measured over the evaluation period, highlighting changes in recovery rates. The direct comparison of a given line performance before and after modification is challenging due to natural variability in ore type, head grade, flotation feed particle size, tonnage, and reagent dosage. However, since these changes affect both flotation lines equally, a statistical evaluation comparing the performance of one line relative to the other before and after the launder upgrade is feasible. Performance was assessed using chemical assays of 12-hour shift composite samples collected by automated on-line sampling devices from both lines. Instead of focusing only on measuring recovery improvements, the studies of Red Chris, New Afton, and Kennecott examined the effect of center launders on operational flexibility, process controllability, and reduction in operational airflow rates. The consistency of the results was demonstrated by improvements in decreased operational airflow rates, increased froth bed thickness, and enhanced stability of the froth surface area (Metso 2021; Bermudez et al. 2022; Seaman et al. 2021). The smaller froth surface area notably increased froth crowding and successfully eliminated all stagnant froth zones within the cell (Seaman et al. 2021). 4. DISCUSSION Based on the studied case examples, the installation of the center launder upgrade has proven to be a highly efficient way to enhance the recovery of copper and other valuable minerals, as well as to improve operational parameters. It has also been highlighted that installing center launder upgrades may positively affect flotation decarbonization by decreasing the energy intensity of the flotation cell.
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