The whole refining process starts with low copper scrap. This includes ashes, drosses and dusts with copper contents of about 15 to 60 percent. Apart from that we also use alloy scrap like brass and (red) bronze with copper contents ranging from 60 to 80 percent.
After inspecting the materials used for refining we smelt them. It depends on the type of refining required if we use the anode furnace, converter, shaft furnace or smelting furnace for that process.,Scrap with low copper content like copper iron material and shredded copper gets into the shaft furnace, where the pyrometallurgical refining process begins. The scrap gets smelted and cleaned at around 1.200°C.
After the pyrometallurgical refining process the molten metal from the shaft furnace has a copper content of about 75 percent. This molten metal also called black copper gets further processed in the converter. Together with copper alloys like brasses and (red) bronze it gets processed to lead, tin and zinc as mixed oxides using oxygen.
The next step in the copper refining process takes place in the anode furnace. The copper content is already at 96% after the shaft furnace. To further improve the purity the material gets mixed with sheet, pipe and wire scrap in the anode furnace. The end result of this step is molten metal with a copper content of about 99%, which is cast into anode plates.
Right after that, the anode plates get into the hydrometallurgical refining process. In this process the copper gets refined using electromechanical processes. Therefore we hang the anode plates in a sulfuric acid solution of copper sulfate where the copper gets seperated from the anode using stainless steel sheets as cathodes under the influence of electric current. This leads to a copper content of more than 99.99 percent.
