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VANCOUVER — Twenty years after Diamond Fields Resources discovered nickel in at Voisey’s Bay in Labrador and eight years after Vale (NYSE: VALE) predecessor Inco started mining, work is now wrapping up on a state-of-the-art hydrometallurgical facility that will process the mine’s rich nickel–copper–cobalt ore without smelting it.
Vale has been sending ore from its open-pit Voisey’s Bay mine to its smelters in Sudbury, Ont., and Thompson, Man. Starting early next year those long hauls will be over, replaced by shipments to a new facility in Long Harbour, 100 km west of St. John’s, N.L. — keeping a promise made to the provincial government that Voisey’s Bay ore or its equivalent would be refined in-province.
Cutting back on haulage is just one advantage. More important is the new facility design, which represents the first time hydromet technology will be used on a large scale to produce nickel.
Hydrometallurgy uses water, oxygen, solvents and high pressure to dissolve a metal from its ore, or from a concentrate or intermediate product, such as matte (the product of smelting). Mines around the world have used hydrometallurgy for years to extract zinc and copper from sulphidic ores, but Vale–Inco was the first to figure out how to adapt the process to nickel sulphides.
The nickel industry generally processes sulphide ores by first smelting to produce matte and then using hydrometallurgical techniques to refine the matte into high-purity nickel, copper and cobalt. The new hydromet process at Long Harbour skips the smelting step, using hydrometallurgy to extract nickel, copper and cobalt directly.
The ore is crushed, ground and concentrated in a conventional manner. Then the finely ground sulphide concentrate is exposed to oxygen and sulphuric acid in a pressurized vessel to produce a nickel–cobalt–copper solution. Several more chemical processes remove impurities and separate the three metals, at which point electrolysis transforms the nickel concentrate into nearly pure nickel.
The new process offers a host of benefits. From an economic perspective, power bills will be lower compared with a smelter-refinery, and more of the ore’s contained cobalt — which is a valuable by-product — can be recovered.
Environmentally, the major difference is that the hydromet process produces solid-waste products, as opposed to the air emissions from smelting. Smelting is based on burning off unwanted sulphides, which creates sulphur dioxide. With hydrometallurgy sulphides are transformed into elemental sulphur, which go into the neutralized tailings alongside iron oxide, gypsum, and other gangue minerals.
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