Start-up and Operation of Placer Dome’s Campbell Mine Gold Pressure Oxidation Plant

The Campbell gold operation of Placer Dome Inc. produces an arsenopyrite-sulfide concentrate that must be treated by roasting, biooxidation or pressure oxidation to obtain high gold recoveries. Pressure oxidation is a proven process that also meets Ontario's stringent environmental regulations. A comparison of biooxidation and pressure oxidation was completed early in 1990. Placer Dome selected pressure oxidation as the preferred process to replace the roaster. The commercial plant design was based on technology supplied by Sherritt Gordon. In July of 1991, the existing roaster operation was shut down and a new pressure oxidation plant was commissioned. The Campbell Red Lake Mine, in Balmertown in northwestern Ontario, is the first plant in Canada to use Sherritt Gordon's pressure oxidation technology to recover gold from a refractory ore body. A similar process has been used at Sao Bento in Brazil since 1986. The Porgera complex in Papua New Guinea also uses Sherritt's technology. At the Campbell Mine, gold occurs as either free gold or is encapsulated with sulfide minerals, mainly arsenopyrite, pyrite and pyrrhotite. These sulfide species are recovered from the ore by crushing and grinding to 80% -75. µm (200 mesh), followed by flotation. About 40% of the gold in the ore is recovered by gravity separation. The remainder reports to the ground slurry feed to flotation. The flotation concentrate averages about 55 to 60 t/d (60 to 66 stpd). A typical analysis is shown in Table 1. Before the installation of the pressure oxidation plant, the flotation concentrate was treated in a two-stage, fluid bed roasting circuit. Roaster off-gases passed through two parallel sets of cyclones, followed by electrostatic precipitators. Arsenic trioxide was captured in a four-chamber baghouse before the gas was discharged to a stack. The arsenic trioxide was sold or conveyed to an underground storage vault. The roasted calcine was fed to a gravity separation circuit and then subjected to cyanide leaching. Gold was recovered from the filtered leach solution in a Merrill-Crowe zinc precipitation circuit.