From concentrate to finished product
Copper refining steps at Horne Smelter
Our recycling system enables us to recover almost all the precious metals and copper contained in the approximately 110,000 metric tonnes of recycled materials received annually. When the materials arrive at the plant, they are cross-checked to ensure that they are in conformance with our authorizations. The recycled materials are then sampled, sorted, and shredded according to their size, nature, and content, then forwarded to the Noranda reactor. The approximately 740,000 metric tonnes of copper concentrate and other copper- and precious-metal-containing materials, along with the recycled materials, are sampled and sent via conveyors to the reactor.
Fusion occurs in the reactor where the concentrate and melt are heated to a temperature of 1,200°C. When it reaches a copper content of 70%, the matte is transferred to the Noranda converter. Oxygen enrichment from the air used in the process generates enough heat to virtually eliminate the need for fuel.
The Noranda converter was commissioned in 1997 and operates on a batch basis. It transforms the reactor matte to raise the copper content to 98%. The copper thus produced is transferred to the converters for another transformation step.
The concentrator receives the slag produced by the reactor and Noranda converter. After crushing, it is reduced to fine particles in the grinders, then pumped to the flotation cells. The copper is recovered by mechanically separating it from its impurities.
The sulfuric acid plant consists of three sections: in the first, wet gasses are cleaned, cooled, and dried; in the second (dry gasses), sulfurous anhydride is converted into sulfuric anhydride, which is absorbed in the third and final section (strong acid) to produce sulfuric acid. Over 640,000 metric tonnes of acid are produced annually.
Copper from the Noranda converter is transferred to the converters, where most of the impurities are removed through oxidation and slagging.
Natural gas is used to remove the excess oxygen in the copper from the converters. This copper is rendered 99.1% pure and is cast into 340 kg anodes.
The copper anodes are transported by rail car or truck to the CCR Refinery in Montréal-Est for a final transformation stage. There, the copper will be purified to 99.99% and sold on the market.
Steps in copper electrorefining and anode slime treatment at the CCR Refinery
Copper is received in the form of anodes with a purity of about 99%. These plates will act as electrodes in the refining process. They are placed in an electrolyte—a bath composed of conducting elements that dissolve the copper and separate it from its impurities, which fall to the bottom of the tank. Through electroplating, copper is deposited on cathodes to obtain a new plate with a maximal level of purity. By the nature of the process, a fraction of the anode remains undissolved and is melted down (in the anode furnace) to be recast into new anodes.
In the course of the refining process, some impurities dissolve and mix into the electrolyte bath, which is periodically purified to continue to produce 99.99% pure copper cathodes. Impurities that are not dissolved in the electrolyte form an anode slime containing precious metals and other elements.
CCR Refinery has the equipment and expertise to process anode slime—not only what is produced in house, but also slime from other companies that are less well equipped. The slime is put into a rotary converter to separate the remaining impurities and to produce Doré anodes containing mainly precious metals.
Doré anodes are then treated in the silver refinery, where high quality (over 99.99% pure) silver ingots are produced. As with the copper, the anode slime is recovered and forwarded to the gold refinery. Through a variety of hydrometallurgical processes, high quality gold ingots (over 99.99% pure), as well as platinum/palladium concentrate, are produced and sold on the market.