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While it was rigorously testing a customized use of hydrometallurgical technology to assure commercial viability for its mammoth nickel-mining project, Vale Canada Ltd. was also testing a comprehensive effluent treatment program that incorporates new high-rate softening and clarification technology to help protect the environment.
International mining company, Vale, is nearing completion of its US$3.7-billion nickel processing plant at Long Harbour, on Newfoundland’s Placentia Bay. The Brazilian mining company’s wholly owned subsidiary, Vale Canada Limited, formerly known as Vale Inco, is directing the construction of the processing plant, which began in April 2009.
Start-up of the plant is scheduled for August 2013. Once fully operational, it is expected to annually produce 50,000 metric tons of nickel, 4,700 metric tons of copper, and 2,500 metric tons of cobalt.
The mined ore will first undergo a concentrating process at the Voisey’s Bay mine site in Labrador before it is transported by ship to the processing plant at Long Harbour. By processing ore concentrate at the plant, Vale anticipates achieving higher metal recoveries while also eliminating the time and expense of shipping to Ontario or Manitoba for refining.
The processing plant will use an innovative hydrometallurgical (hydromet) processing technology researched and developed by Vale in Canada. Although several Canadian operations use hydrometallurgical processes, Vale has tailored this processing technology specifically to treat the nickel-cobalt-copper sulphide deposits at Voisey’s Bay. The overall flow sheet, patented by Vale in 2000, results in an efficient and cost effective integrated process that makes high quality finished metals.
Hydromet Technology Commercially Viable
Because Vale had never used hydromet processing technology on the type of ore present at Voisey’s Bay, the company invested $200-million on a 10-year R&D feasibility program to test the technical, economic, and environmental viability of the process.
Hydromet testing was conducted in three stages. The first involved bench-scale testing, which proved that each separate chemical process worked individually at laboratory scale. The second stage featured the operation of a 1:10,000 scale pilot plant at the company’s Mississauga, Ontario, research centre. The third stage involved the design, construction and operation of a 1:100 scale demonstration plant in Argentia, Newfoundland
The objective there was to confirm technical and economic viability and to assist engineers in the selection of the most appropriate construction materials and specification of major equipment.
Results at the Argentia demonstration plant confirmed to Vale that the technology would be technically, commercially and environmentally viable for this project. Use of the water-based hydromet technology will enable the plant to process the nickel concentrate directly to metal products without first having to smelt the concentrate. It also will allow Vale to process higher yields of the nickel and valuable cobalt, both of which are lost to a great extent in traditional smelting processes.
Water Supply & Treatment Challenges
With water being a crucial resource in all steps of the process, Vale was also challenged with determining how to effectively manage water usage and treatment to meet the process and potable water needs of the facility as well as regulatory and environmental discharge requirements. Following performance testing of a proprietary water treatment technology at the 1:100 scale demonstration plant, Vale contracted Veolia Water Solutions & Technologies to design, supply and manufacture a complete effluent treatment package for the facility’s process effluent prior to discharge into the environment.
Vale also contracted Veolia for a water treatment plant to provide process and potable water for the entire complex.
The processing plant’s raw water treatment plant will include ACTIFLO® sand-ballasted clarification, a proven high-rate settling process that combines the advantages of ballasted flocculation and lamella clarification. The ACTIFLO process operates with microsand as a seed for floc formation. The microsand provides surface area that enhances flocculation and also acts as a ballast to aid rapid settlement, resulting in a high-rate settling process with a very small footprint.
For treating the facility’s process effluent water, the treatment system will include the ACTIFLO Softening process, a new technology developed by VWS Canada initially for pilot testing at Vale’s Argentia Demonstration Plant.
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