Vital Metal Recovery in MRFs

Metal recovery and recycling from waste is not new, with evidence of such activity in Roman times.  In materials recycling facilities (MRFs), metal recovery provides a vital financial lifeline.  Bunting assists waste management companies and MRF designers in maximising metal recovery whilst maintaining high purity levels.  On average, there is 8% metal in waste being handled in MRFs in the UK.

Bunting is one of the world’s leading designers and manufacturers of magnetic separators, eddy current separators, metal detectors and electrostatic separators, with globally located manufacturing facilities.

The recovery of ferrous metals, such as steel food and beverage cans, commonly occurs early in the MRF.  Overband Magnets, placed across or in-line with the conveyor transporting the waste, magnetically attract the ferrous metal before automatically transporting the recovered metal into a collection area.  Low throughput MRFs commonly use Permanent Overband Magnets, with larger volume plants installing larger Electro Overband Magnets such as the ElectroMax. 

The remaining mix of non-magnetic material contains non-ferrous metals, which are predominantly aluminium beverage cans.  High in value and demand, aluminium cans provide a good financial return when supplied with the optimum purity specification.  Installed after picking in many MRFs, the Eddy Current Separator uses strong magnetic forces to propel aluminium cans off a conveyor transporting the mixed waste and into a separate collection area or onto another conveyor.

An Eddy Current Separator is a dual pulley conveyor system, where the non-metallic rotor cover houses an independently rotating high-speed magnetic rotor.  Separation occurs when a non-ferrous metal particle (e.g. aluminium) is conveyed into the magnetic zone.  The non-ferrous metal particle is exposed to rapidly changing magnetic polarity.  This induces ‘eddy currents’ into the particle generating an electrical current (Fleming’s left-hand rule) that subsequently creates its own magnetic field.  The two magnetic fields oppose each other (i.e. North vs North pole repulsion), causing the repulsion of the non-ferrous metal particle and change in trajectory.  The measured positioning of a splitter enables the separation of non-ferrous metals from non-metallic material due to the altered and unaltered material trajectories.

At the Parry & Evans pre-sorted domestic refuse recycling site in Deeside, UK, the combination of the Bunting Overband Magnet, Drum Magnet, and Eddy Current Separator recover approximately 800 kg/hr of metal.  A vital financial benefit to ensure the recycling operation remains viable.