Equipment manufacturer Bunting’s electrostatic separator was launched earlier in 2020, and enhances the ability of companies to recover fine metals such as copper wire. In this project, the feed material is fine material from air-extraction post-shredding; a mix normally classified as waste, despite the valuable metal content. Previous attempts to recover the metal constituent, including fine copper wire, had been unsuccessful. Prior to ordering the equipment, controlled tests conducted at Bunting’s centre in Redditch determined that a three-stage separation process would enable high levels of metal recovery and purity.
On site, between one and two tonnes per hour of the metal mix initially passes through the metal separation module before the final stage of electrostatic separation. The metal separation module consists of a ferrite drum magnet, vibratory feeder and high-intensity rare earth roll separator. The ferrite drum magnet removes strong magnetic metal, with the remaining mix passing on to the vibratory feeder. This regulates and presents an even layer of material on to the belt of the rare earth roll separator.
The rare earth roll separator has a thin belt feeding material on to a head pulley constructed from high-strength neodymium rare earth magnets. As material passes over the head roll, weakly-magnetic metals are attracted to the radial high-intensity field and held on the belt and then deposited underneath. A strategically-placed splitter enables the separation of the attracted metals (including fragmented stainless steel) from other non-magnetic materials (such as fine copper wire and aluminium).
This non-magnetic metal mix passes onto the third separation stage to recover fine copper wire at a feed rate of approximately one tonne per hour. The electrostatic separator exploits the difference in electrical conductivity between various materials in a feed material. This enables the recovery of metals such as fine copper wire. In this project, the recovered copper wire has a purity of +95%.
Developing new metal separation processes, such as this three-stage system, is vitally important to reduce the amount of metal lost to waste and of unrecyclable material sent to landfill. There is also significant financial gain, with increased metal recovery and reduced disposal costs.