An eddy current separator (ECS) is a machine that uses a powerful

magnetic field A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...

to separate

non-ferrous metal In metallurgy, non-ferrous metals are metals or alloys that do not contain iron ( allotropes of iron, ferrite, and so on) in appreciable amounts. Generally more costly than ferrous metals, non-ferrous metals are used because of desirable pro ...

s from an input waste or ore stream. The device makes use of eddy currents to effect the separation. Non-ferrous metals typically separated by an ECS include aluminum, copper and die-cast metals. In

waste sorting Waste sorting is the process by which waste is separated into different elements. Waste sorting can occur manually at the household and collected through curbside collection schemes, or automatically separated in materials recovery facilities ...

single-stream recycling Single-stream (also known as “fully commingled” or "single-sort") recycling refers to a system in which all paper fibers, plastics, metals, and other containers are mixed in a collection truck, instead of being sorted by the depositor into se ...

at materials recovery facilities, ECS is used after the waste has passed through some arrangement of magnets to remove

ferrous metals Ferrous metallurgy is the metallurgy of iron and its alloys. The earliest surviving prehistoric iron artifacts, from the 4th millennium BC in Egypt, were made from meteoritic iron-nickel. It is not known when or where the smelting of iron from ...

. Eddy current separators are typically used at the end of the waste material stream, since ferrous metals will become heated when exposed to an eddy current field, leading to potential damage to the eddy current separator. In mining, ECS is sometimes used to separate metals from mined ore.

Technique

The eddy current separator is applied to a

conveyor belt A conveyor belt is the carrying medium of a belt conveyor system (often shortened to a belt conveyor). A belt conveyor system consists of two or more pulleys (sometimes referred to as drums), with a closed loop of carrying medium—the conveyor b ...

carrying a layer of mixed waste. At the end of the conveyor belt is an eddy current rotor. Non-ferrous metals caught in the eddy current end up in a product bin, while other material falls off the belt due to gravity. Eddy current separators may use a rotating drum with

permanent magnets Permanent may refer to: Art and entertainment * ''Permanent'' (film), a 2017 American film * ''Permanent'' (Joy Division album) * "Permanent" (song), by David Cook *"Permanent", a song by Alex Lahey from '' The Answer Is Always Yes'', 2023 Other ...

, or may use an

electromagnet An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire (likely copper) wound into a electromagnetic coil, coil. A current through the wire creates a magnetic ...

depending on the type of separator.

History

for a device using eddy currents to separate non-ferrous metals from non-metals was granted to William Benson and Thomas Falconer of Eriez Magnetics in 1969.W.H. Benson et al., Electrodynamics Separator (1969)

References

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Recycling Waste treatment technology