Lateritic nickel ore for the Refinery is imported from mine sites in New Caledonia, Indonesia and the Philippines. Lateritic ore is formed by rainwater flowing through rock near the surface and weathering it over a considerable period of time. The highest grade lateritic ore forms in tropical and sub-tropical climates where nickel rich rocks called peridotites are found at the surface. There are two predominant types of lateritic ore — limonitic and saprolitic. Limonitic, the uppermost layer, is the best feed for Queensland Nickel’s Refinery.
The Refining Process
Click here to view a diagram of the refinery process.
Ore is transported from an ore handling facility at the Port of Townsville to the Refinery by rail. On arrival at the refinery the ore is removed from the rail wagons by a rotary tippler. From the tippler the ore is conveyed to a radial stacker from which the ore is trucked to solar drying stock piles. The ore is reclaimed and moved along a conveyer system and fed to three rotary driers to remove moisture. The dry ore is fed into ball mills, where it is ground to a fine powder.
After the grinding process, the fine ore is mixed with fuel oil reductant and fed into 12 multi-hearth furnaces where the nickel and cobalt compounds are reduced at very high temperatures to reactive metals. The hot ore is cooled then leached in an ammonium carbonate solution and the nickel and cobalt dissolve into soluble amines. The nickel and cobalt amines are separated from the waste products by progressively washing in fresh ammonia solution in eight thickeners. Waste materials are pumped to and stored in the tailings dams.
Nickel is separated from the cobalt by the ammoniacal solvent extraction (ASX) process. The ASX technology was developed at the Refinery and installed in 1989. This process, which carries international patents, has significantly improved the original separation process and has enabled the production of near-pure nickel and cobalt products.
Nickel carbonate is precipitated from solution by boiling off ammonia. By calcining the carbonate at 1200°C it is converted to nickel oxide. The nickel oxide is then converted to metal at 1000°C in a hydrogen atmosphere.
Most of the output from the refinery is in the form of nickel metal compacts, which are in the shape of 3cm high by 3cm wide cylinders. These are packed in containers for export to international customers.
Cobalt, the other valuable product of the Refinery, is separated from the metal-laden ammonia solution as cobalt sulphide. Cobalt sulphide is then processed further in the cobalt plant to produce value-added cobalt products.