4th of 5 Misconceptions About Eddy Current Separation
This is the 4th in a short series of blogs discussing misconceptions about Eddy Current Separation. Eddy Current Separators are used extensively throughout the recycling industry to separate non-ferrous metal (e.g. aluminium beverage cans, shredded aluminium and copper etc) from non-metallic materials.
All Ferrous Metal Need to be Removed
Despite the Eddy Current Separator being a separation system based on magnetic principles, there is often a question about whether it should be used to also remove ferrous metals.
In its simplest form, the Eddy Current Separator is a conveyor with a magnetic rotor acting as a magnetic head pulley. Due to the laws of physics, the Magnetic Rotor will attract ferrous metal and so could be used to separate magnetically susceptible materials. However, there are some limitations:
- With Eddy Current Separators that have Concentric Magnetic Rotors (ie the magnetic rotor spins uniformly within an outer non-magnetic shell), it can be difficult to discharge magnetic material from the belt. Due to the high speed rotating magnetic field, magnetic material that has not been discharged and remains vibrating at the bottom of the rotor can get hot and, when the conveyor belt stops, can burn through the plastic of the belt. This can then damage the shell and the magnetic rotor;
- The Eccentric Magnetic Rotor design is more forgiving as the rotor sits in a corner quadrant of the non-metallic shell and so magnetic material leaves the magnetic field as it is pulley around by the conveyor. This ferrous metal is discharged underneath and often into the non-metallic fraction;
Successful metal recovery and separation is achieved by focusing on specific materials at key points in the process and this means removing as much ferrous metal prior to the Eddy Current Separator as possible. This then leaves the Eddy Current to focus on separating non-ferrous metals from non-metallic materials.
Typically ferrous metals are removed and recovered prior to the Eddy Current Separators with:
Other blogs in this series on Misconceptions about Eddy Current Separation include:
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