Superconducting discs as permanent magnets for magnetic separation

Magnetic separation is used widely in the mineral processing industry to concentrate and recover valuable minerals. Superconducting discs offer the opportunity to produce stronger magnetic forces than are available from conventional permanent magnets. Permanent magnets have been used to provide fields and field gradients for drum separators in which magnetic forces are used to hold magnetisable mineral particles against the surface of a rotating drum against gravity in such a way that they are spatially separated from less magnetisable particles and for 'open gradient' separators in which the particles are separated, by deflection with magnetic forces, from a falling stream of mixed particles, the 'falling curtain' technique or by guiding them on a belt moving over a magnetized rotor. Calculations of the field distribution within superconducting discs by the authors have provided a basis for the examination of their use in magnetic separation. A number of configurations of discs are discussed in relation to magnetic separator performance.