How a copper smelter works

A basic flowsheet of smelting and refining can be found below [1, 2]:

In a first step, smelting takes place in different types of furnaces depending on the raw materials and the process technology. An upper layer of slag and a lower one of matte, which has a copper content of approximately 55% form in the furnace.

The copper matte is tapped into a converter furnace where iron and other impurities, together with sulphur, are separated out. The converter is also charged with scrap metal and, in some cases, black
copper – an intermediate product from the recycling of electronics. The result is known as blister copper, which has a copper content of 97-98 per cent.

The blister copper is then processed in an anode furnace to reduce its oxygen content. This increases
the purity level to 98-99 per cent and the copper is then cast to form anodes.

The anodes are placed in tanks with steel cathode plates. In the subsequent electrolytic refining process,
copper migrates from anodes to cathodes, which ultimately have a copper content of 99.99 per cent or
higher. 

Cathode cannot be easily processed and will be melted to be cast into wire rod, billets or cakes, the "first uses of cathode":

• Wire rod is the term used to describe coils of copper of 6 to 35 mm diameter (typically 8 mm) which provide the starting stock for wiredrawing. This is the most important first use of cathode, representing  60% of all copper used (when including alloys).
• Cakes (or slabs) are used when flat plate, sheet, strip and foil are required. They are now mostly cast continuously, which gives an improvement of pieceweight, yield and quality over the earlier static casting methods. Copper is commonly hot rolled from a thickness of 150 mm down to about 9 mm and cold rolled thereafter.
• Billets, usually about 250–350 mm diameter, are cast for subsequent extrusion to rod and bar. Normally these are cut to no more than 750 mm in length to fit the extrusion chamber and this controls the maximum pieceweight which may be made. Extrusions are usually subsequently drawn to the required finished sizes by one or more passes through drawblocks.

A smelter that processes secondary raw materials operates in a similar flow. In practice, smelters will often use a mix of primary and secondary materials. The following schematic helps to visualise the main inputs & outputs for the smelting & refining process. 

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Last update: August 12, 2021

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References

[1] Langner, Bernd E. 2011. Understanding Copper: Technologies, Markets, Business. Page 109. Accessed July 27, 2021.

[2] New Boliden. Metals for Modern Life. Pages 16-17. Accessed July 27, 2021.