The production process begins with the arrival of anodes—large plates of impure copper weighing 340 kg each. The anodes come from multiple Glencore smelters, including the Horne Smelter in Rouyn-Noranda, Quebec. This copper has to be processed to purify it and to recover the precious metals and by-products of value it contains.
The anodes are first weighed, sampled, and conditioned to meet our requirements.
The anodes, together with sheets of stainless steel (mother blanks), are submerged in electrolyte baths. An electrical current is then applied. Copper detaches from the anodes and is deposited on the stainless-steel plates to form cathodes. The anodes remain in the tanks for 21 days, while the stainless-steel plates are replaced every 7 days.
Four products result from this refining cycle:
- Pure copper in the form of cathodes
- Spent anodes
- Impurities dissolved in the electrolyte
- Anode slime—a mixture of precious metals and insoluble elements that settle to the bottom of the tank
The cathodes are moved along to the stripping machines where they are washed, separated from the stainless-steel plates, sampled, weighed, and packaged. They are then shipped to our customers by truck, train, or boat.
The spent anodes are melted down in a remelt furnace and cast into the shape of new anodes. They are then returned to the refining process so that no raw materials are lost.
The impurities dissolved in the electrolyte are sent through three purification processes where antimony and bismuth are removed, and nickel is recovered for sale.
Anode slime consists of precious metals such as gold, silver, platinum, and palladium, but also by-products like tellurium and selenium. The slime is directed to the precious metals and by-products line where a variety of separation processes are used to recover the finished products, ready for sale on the market.
Anode slime is first treated in autoclaves—pressurized tanks where copper, nickel, and tellurium are dissolved with acid and oxygen. Tellurium is then converted into tellurium dioxide and shipped to our customers.
The slime is them dried and melted in a converter to separate the precious metals from impurities like selenium. The molten metal alloy is cast into bars called Doré anodes. Selenium is recovered in powder form and sold on the market.
The Doré anodes are then processed in the separation plants using electrorefining and hydrometallurgy. The silver and gold contained in the anodes are produced separately in the form of sand, then melted and cast into ingots of high purity silver and gold. The platinum and palladium are transformed into a concentrate that is shipped to other refineries for subsequent conversion.