The Cerro Vanguardia mine is an AngloGold Limited operationin southern Argentina that includes multiple open pits and a hybridMerrill-Crowe and CIL circuit to recover gold and silver from oxide ore.Operations were commissioned at the site in 1998, which included aplant in the metallurgical circuit to recover cyanide from mill tailings. Thecyanide recovery plant was initially configured to process tailings slurryand achieved greater than 90% cyanide recovery from tailings containingabout 600 to 800 mg/L WAD cyanide (as CN). The cyanide recovery circuitwas operated in this manner for approximately eight months, duringwhich time the consumption of sulphuric acid and sodium hydroxide wasrelatively high, leading to high rates of scale formation in the acidificationtank and stripping towers. In July 1999, several piping changes weremade in the cyanide recovery system to permit its operation with clearsolution, which reduced the sulphuric acid consumption and eliminatedscale formation in process equipment. The cyanide recovery systemcurrently operates with a two-stage counter-current decantation (CCD)circuit which provides clear solution for processing in the cyanide recoveryplant. The cyanide recovery efficiency now averages about 90% to92% from solution containing about 350 mg/L WAD cyanide (as CN).Recovered sodium cyanide now accounts for about two-thirds of the totalcyanide added to the leaching circuit. This paper presents a descriptionof the cyanide recovery plant and details regarding its current operatingefficiency.
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