Pilot plant demonstration of the Platsol process for the treatment of the NorthMet copper-nickel-PGM deposit

摘要

PolyMet Mining is developing the NorthMet property near Duluth, MN. Laboratory investigations have led to the development of the Platsol process to dissolve in one step the base metals (copper and nickel) as well as the gold and platinum group metals (PGM). To complete the prefeasibility study, a fully integrated, 10-day pilot plant trial was undertaken. The trial consisted of high-temperature (>220 deg C or >428 deg F) pressure oxidation in the presence of 5 to 10 g/L chloride (the Platsol process). This was folio wed by solid/liquid separation gold plus PGM recovery from solution, conventional copper solvent extractions/electrowinning (SX/EW) and recycling of the copper raffinate to the autoclave. The concentrate tested during the trial period was a NorthMet bulk flotation concentrate. It assayed 14.7 percent Cu, 3.05 percent Ni, 0.14 percent Co, 26.7 percent S, 1.4 g/t (0.041 oz/st) Au, 2.2 g/t (0.064 oz/st) Pt and 9.9 g/t (0.289 oz/st) Pd. Laboratory results were confirmed and, with minor adjustments of the laboratory Platsol conditions, the following leach extractions were obtained during the pilot plant trial: 99.6 percent Cu, 98.9 percent Ni, 96 percent Co, 94.6 percent Pd, 96 percent Pt and 89.4 percent Au.