Fire Refining

The objective of fire refining is to increase the purity of the blister copper from the stage before (conversion) by eliminating the oxygen (about 0.5%) and the sulfur (about 0.02%) that the blister copper still contains. The process, which takes place in three refining furnaces, consists in oxidizing the sulfur with pressurized air blown in through a 22-mm tuyere. This process, called “oxidation”, generates copper oxide, which is later reduced in what is called “the reduction stage” by blowing natural gas in through the same tuyere. The furnace runs at a temperature of roughly 1,250 °C.