Flotation circuit improvements at the Sarcheshmeh copper mine

Abstract

The flotation circuit of the Sarcheshmeh copper mine, which processes 41 000 t day^-1 of ore at 0·9% Cu, consists of rougher, cleaning and re-cleaning stages. To study the stage recovery of copper, one of the eight identical flotation banks was selected for sampling. It was observed that 17% of copper goes to the tailings and the lowest copper recovery was for particles coarser than 105 μ m. The third 5-cell rougher unit of this bank not only did not recover an appreciable amount of copper but also decreased the concentrate grade. The grade of the last five cells was lower than the feed grade suggesting that mixing of the concentrates of the three units was not beneficial. To alleviate the problem, the concentrate of the first 4-cell unit was directed to the cleaners’ feed box (i.e. by-passing the re-grind mill). This increased the overall copper recovery by 1·7%. Also, rather than the current practice of adding the reagents only at the feed tank (i.e. 100-0-0%), various combinations of stage addition were examined. It was found that a 75-25-0% addition regimen could increase the total copper recovery by 1·3%. At the re-cleaning stage in order to increase the final copper concentrate grade, a froth washing system was used. To ease the maintenance of the system, a shower type system was installed. The optimum wash water superficial flow-rate was found to be 0·06 cm s^-1. Continuous sampling of the re-cleaners with and without wash water over a period of 2 months showed an increase of 1·5% in the final copper concentrate grade at constant overall copper recovery.