From concentrate to finished product
The raw material needed to produce copper anodes and cathodes are concentrates, most of which are in powder form, obtained by crushing and grinding ore. At Horne Smelter, we also add recycled materials to our process.
After receiving these materials at our Rouyn-Noranda smelter, the concentrates and recycled materials go through various stages of processing to arrive at the finished product, 99.1% pure copper anodes. These anodes, sent to the CCR Refinery in Montréal-Est, then undergo an electrorefining process to turn them into cathodes. In this step, the anodic sludge is treated to recover several precious metals and products. This processing chain yields 99.99% pure cathodes for markets.
Copper refining steps at Horne Smelter
When the materials arrive at the plant, they are cross-checked to ensure that they are in conformance with our authorizations. After sampling, sorting and shredding, the batches of recycled materials are sent mainly to the Noranda reactor, depending on their size, nature and content. 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 tons 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.