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

magnetic field A magnetic field is a vector 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 its own velocity and to ...

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 proper ...

s from an input waste or ore stream. The device makes use of

eddy current Eddy currents (also called Foucault's currents) are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday's law of induction or by the relative motion of a conductor in a mag ...

s to effect the separation. Non-ferrous metals typically separated by an ECS include aluminum, copper and die-cast metals. In waste processing, ECS is used after all

ferrous metals In chemistry, the adjective Ferrous indicates a compound that contains iron(II), meaning iron in its +2 oxidation state, possibly as the divalent cation Fe2+. It is opposed to "ferric" or iron(III), meaning iron in its +3 oxidation state, such as ...

have been removed previously by some arrangement of magnets. 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 belt conveyor). A belt conveyor system is one of many types of conveyor systems. A belt conveyor system consists of two or more pulleys (sometimes referred to ...

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, or may use an electromagnet 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

{{Reflist Recycling Waste treatment technology