What is the role of Smelters and Refiners?
Smelters
Smelting is a form of extractive metallurgy that is used to produce a metal from its concentrated ore by use of the chemical reduction process. The process uses a chemical reducing agent, often carbon and heat to change the oxidation state of the metal ore. The carbon or carbon monoxide derived from it removes sulphur from the ore to leave the metal. As most ores are impure, it is often necessary to use flux to remove the accompanying rock gangue as slag. The copper sulphides were smelted using the formation of two liquids in a furnace, one an oxide slag containing most of the impurity elements, and the other a sulfide matte containing the valuable metal sulfide and some impurities. The slag floats on top of the heavier matte, and is removed and discarded or recycled. The sulfide matte, which settles near the bottom of the furnace bath is removed then sent to the converter, for further oxidation. Here the matte is "converted" to oxidize iron in the first stage, and oxidized copper in the second stage. Now the copper is above 95% pure and is known as blister or copper anode, at which stage it is prepared for further purification in the refining process
Refiners
Refining consists of purifying an impure material such as copper anode. The most common refining processes are via electrolysis. The purest copper is obtained by an electrolytic process, undertaken using a slab of impure copper anode and a thin sheet of pure copper as the cathode. The electrolyte is an acidic solution of copper sulphate. By passing electricity through the cell, copper is dissolved from the anode and deposited on the cathode. However impurities either remain in solution or collect as an insoluble sludge. The final copper metal cathode is required to metal exchange specifications which 99.99% level of purity.
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