Pressure oxidation was selected over a hybrid process that combines bio-leaching and pressure oxidation. The decision reflects the company’s intention to increase platinum, palladium and gold recoveries.
The company expects to recover 71.4% of the platinum and palladium and 72.4% of the gold, along with 92.2% of the copper, 71.4% of the nickel and 42.6% of the cobalt.
The NorthMet deposit, formerly known as Dunka Road, contains more than 800 million tonnes of mineralized material averaging 0.43% copper, 0.12% nickel, 0.0096% cobalt and 0.14 gram platinum, plus 0.39 gram palladium and 0.088 gram gold per tonne.
On a daily basis, PolyMet will process 50,000 tonnes of ore, grinding the material to produce as much as 1,200 tonnes of flotation concentrate.
Concentrates will be pressure-leached in autoclaves at 220C. Platinum, palladium and gold will then be recovered from the leach solution, whereas solvent extraction-electrowinning will be used to recover base metals — first copper as London Metal Exchange-grade cathode, followed by nickel cathode and cobalt sulphide.
Capital costs could run as high as US$500 million. Cash operating costs are expected to exceed US$8 per tonne, translating into US33 cents per lb. on a copper-equivalent basis, using metal prices of US65 cents per lb. copper, US$2.45 per lb. nickel, US$10 per lb. cobalt, US$350 per oz. platinum, US$330 per oz. palladium and US$265 per oz. gold.
PolyMet intends to confirm these estimates in a prefeasibility study.
Be the first to comment on "PolyMet chooses process"