February 2008

Thetford Branch visits Nichromet

By P. Laroche

From left: Normand Ouellet, Normand Cimon, Caroline Chouinard, Alain Boucher, Charles Gagné, Laury Gauthier, Roger Paré, David Lemieux, Bertrand Dubreuil, and Steve Marchand

Last November 14, more than 50 members of the CIM Thetford Mines Branch visited (most for the first time) the Nichromet Extraction facilities in Black Lake. This pilot plant is housed in a building of the old British Canadian Asbestos Mine #1 in Black Lake; it is dedicated to the extraction of nickel and other substances contained in the serpentine tailings of the regional chrysotile asbestos mines.

The company vice president, Jean-Marc Lalancette, first briefly explained the extraction process: dissolving the serpentine with hydrochloric acid. This expensive acid is produced onsite by a chemical reaction between sulphuric acid, a low-cost and fairly common acid, and potassium chloride imported from western Canada. The reaction produces a by-product — potassium sulphate — which can be sold as fertilizer.

According to Lalancette, the nickel extraction process takes place at atmospheric pressure and at a temperature not exceeding 150 degrees Celsius; investment and operating costs are thus lower than the conventional pyrometallurgical process (high temperature to melt the concentrates) or the conventional high-pressure hydrometallurgical process (requiring very expensive autoclaves or reactors).

Upper management and team leaders (David Lemieux, Bertrand Dubreuil, François Larouche and Caroline Chouinard) then guided small groups of participants through the plant to explain in detail the operations taking place in three rooms: one room is reserved for the mechanical processing of serpentine tailings (grinding and sieving); a second is reserved for the production of hydrochloric acid; and in the last, the serpentine tailings are attacked by the acid, producing nickel chloride, a green liquid that can be sold to metallic nickel producers.

The pilot plant can currently treat serpentine tailings at a rate of 1.0 tonnes per hour. The next step will be to build an intermediate size plant with a 15-tonne per hour capacity. This will require an investment of $50 to 60 million and could create about 50 jobs in our region.

The participants were impressed with the advanced stage of the Nichromet process in the eventual recovery of useful substances in the Thetford Mines tailings.

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