Smelting and Refining

Smelters

The smelters use a chemical reduction process to produce copper metal from the concentrated ore shipped from the mineral processing plant. The smelting itself is conducted in a furnace with temperatures exceeding 1000°C. This kind of process also needs a reducing agent, often in the form of carbon, to reduce the oxidation state of the ore.

Molten Copper in ChileCarbon helps remove sulphur from the ore, but as most ores are impure it is also necessary to use a flux (for example iron oxide) to be able to remove the rock gangue as slag. The slag would then float to the surface with most of the impurities leaving a heavier sulphide matte beneath with most of the valuable metal. The slag is removed and the matte is sent to a converter for further oxidation in two stages, iron oxidation and copper oxidation. The final result is called blister or copper anode and has a purity of around 95 % copper metal.

Refiners

The copper anode is transported to a refiner which typically uses an electrolysis process to further “refine” the copper. The electrolytic process uses either a copper or steel plate anode or blister as an anode and a pure, thin copper metal sheet as the cathode. The solution in which this process takes place is often an acidic solution of copper sulphate. When current is turned on in the process, copper dissolves from the anode and deposits on the cathode and leaves the impurities in the solution. The final product is now typically around 99.99% pure copper metal and ready for the copper markets.

 

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