Abstract
Vale Base Metals operates the Long Harbour Refinery using a novel hydrometallurgical process** to produce high purity electrolytic nickel, cobalt, and copper, from the nickel sulphide concentrate produced at the mining operation at Voisey’s Bay. The process is based on controlled partial oxidation of sulphide sulphur to sulphate using oxygen at moderately elevated temperature and pressure, sufficient to achieve high pay-metal extractions. Impurities are subsequently removed from the product pressure leach solution, copper and cobalt are separated from the nickel by solvent extraction, resulting in a high-nickel solution from which nickel metal is produced by electrowinning at high current efficiency. Heat generated from the exothermic oxidation of sulphide concentrate in the pressure vessels is recovered for heating the process buildings. The combination of low-energy intensive hydrometallurgy technology, energy recovery and utilization as well as the use of hydroelectric power for the plant results in very low carbon footprint of the metals produced. This paper will review the low carbon footprint features of the process and ongoing initiatives to reduce it even further, including electrification of a boiler used to produce process steam.
** Derek Kerfoot was the key driver for the research and development of the novel Pressure Oxidative Leach (POL) with direct nickel electrowinning process, ultimately commercialized at Long Harbour. Through a combination of deep hydrometallurgy knowledge, wide industry experience, persistence and perseverance, he helped turn a vision into reality.