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.
Vale tested the novel technology extensively before committing to it. First the major tested each step of the process at a laboratory scale. Next Vale developed a mini-pilot plant in its lab to ensure the steps were connected in a continuous process. This mini-pilot plant ran from 2003 to mid-2005.
Finally, Vale built a hydrometallurgical demonstration plant in the town of Argentia, N.L., to confirm the lab-scale results could be replicated in larger scale. The plant began processing Voisey’s Bay ore in late 2005 and operated until mid-2008. With positive results from the pilot plant in hand, in November 2008, Vale made a firm decision to use hydromet technology in the Long Harbour facility.
Construction for the US$2.8-billion facility got underway in Long Harbour in April 2009. The task was divided into two phases: construction and commissioning. Vale met its goal for completing the first phase when Long Harbour achieved “construction mechanical completion” on Oct. 30, one day ahead of target.
In July, with construction 86% complete, Vale launched a worker-incentive program to help get the job done on time. Known as the “Long Harbour Completion Challenge,” the program offered pay raises for getting tasks completed on or ahead of schedule. The raises initially ran as high as $5 an hour, but were set to jump retroactively to $10 an hour if Long Harbour was completed before Oct. 30.
With the goal achieved, workers will now get their extra pay as bonuses, which helps, as many have since been laid off. The number of tradespeople at the site peaked at just over 6,000 during construction, but commissioning will require only 1,500 workers. During regular operations the site would employ 500 people.
Voisey’s Bay is a fly-in, fly-out operation that started operating in late 2005, after a $950-million build. The mine feeds 6,000 tonnes of ore per day into a concentrator that produces a copper concentrate and a nickel–cobalt–copper concentrate.
At present the operation has an estimated mine life of 30 years, but Vale is optimistic that further exploration will delineate new reserves and extend the mine’s lifespan. Provided those exploration efforts go as expected, in 2018 Vale will start developing an underground component at Voisey’s Bay. The underground mine would boost the mine’s workforce from 450 to 800 people, and the concentrator would be expanded to accommodate the increased ore output.