Pretreatment of Scrap Copper
Copper electric wire encased in insulation
The copper electric wire is of very high purity but encased in insulation which must be removed. This can be removed from the wire by striping it off in the normal manner you would use when rewiring a plug. It can also be removed by chopping up the wire and the cable into small pieces. These are fed into shakers and mesh screens where most of the insulation will come away from the wire. Various types of plastic insulation can also be segregated for recycling, both methods being highly automated and efficient at insulation removal and separation from the copper wire. Following these processes, the copper wire is then washed in a diluted acid mix to remove any lacquer or impurities.
Copper windings in electric motors, generators and starters
The removal of copper from electric motor windings is very labor intensive and time consuming, however, an innovative method is under research where the windings are subjected to very low temperatures. This makes the copper wire brittle, enabling it to be broken away from the winding frames in small pieces before it is washed in a light acid mix to remove lacquer.
Copper piping and tanks
Copper piping and tanks are immersed in a light acid bath, then washed in water. They may also be flattened after this stage.
Components made from copper alloys such as brass, bronze and nickel make up a high percentage of recycled copper. The components are immersed in light acid, washed with water and segregated into their separate categories according to their alloyed metals of tin, lead and zinc. They remain in this state for transportation to the recycling furnaces.
Recycling of copper alloys is carried out in a furnace, where the alloys are added to pure copper ingots to achieve grade of copper with certain required properties.
Where there are too many trace elements in the alloys, they are melted separately, usually in an electric furnace, where the minor trace elements are removed from the molten metal, before pouring into ingots.
Copper alloy can also be recycled by adding more pure copper, thus diluting the alloyed metals to an acceptable level.
Copper shavings from machine operations
Cuttings and swarf from machining copper will be contaminated with coolant oil, which is removed by immersion in a light acid bath after which it is washed in water.
Shredding and compacting
Once all the scrap copper has been recovered and treated, it is shredded and compacted into bales. These bales, along with the copper alloy components, are shipped to a copper smelter or remelting facility.