Flotation improvements at Placer Dome's Campbell mine

Conventional crushing and grinding is followed by gravity concentration to recover free milling gold. Refractory gold, finely disseminated within the pyrite and arsenopyrite matrix, is recovered by flotation followed by press ure oxidation, cyanidation, and cementation. Non-refractory gold is recover ed by cyanidation/CIP processing. A comprehensive test program aimed at improving flotation recovery was init ialed in June 1995. Plant testing indicated that flotation tails value coul d be significantly reduced using mechanical flotation cells. Based on these test results a flotation circuit that incorporates one of the three existi ng flotation columns followed by mechanical scavenging and cleaning was dev eloped. Detailed engineering was completed in September 1996 Construction s tarted in February 1997, and was completed in three months at a cost of $3. 2 million. An on-stream X-ray analyzer was installed to provide real-time a rsenic and iron analyses and inferred sulphur value on some of the flotatio n streams. The new flotation circuit proved to be an instant success. Flotation tails values were reduced by 27%. Final tails solids and solution was reduced fro m 0.035 to 0.023 oz/ton, and 0.0014 to 0.0006 oz/ton Au, respectively, Base d on a mill throughput of 1620 stpd, this decrease in tails value will resu lt in an increased gold production of 7500 ounces per year. The payback for the project is estimated to be around one year. This paper describes the evolution of the project from bench scale testing to commissioning. Also, the operational and economic impacts on down stream processing are highlighted.