Magnetic Separation Using Superconducting Bulk Magnets

Our objective was to apply superconducting bulk magnets to a magnetic separation technique. A pair of Sm123 bulk superconductors were magnetized by the “IMRA” method and arranged opposite each other with a gap of 20mm. The maximum flux density at the surface of the magnetic poles containing the bulk magnets and at the center of the gap of the poles was 2.26T and 1.76T, respectively. We set up a magnetic separator by placing a pipe between the magnetic poles of face-to-face superconducting bulk magnets and conducted experiments for two types of magnetic separation: high gradient magnetic separation (HGMS) with the use of a stainless steel filter, and open gradient magnetic separation (OGMS) without filters. The former uses separation filters composed of ferromagnetic wires stuffed into a glass pipe, and therefore a high gradient magnetic field is generated near the wires. The latter does not use filters. The separation ratio is investigated by the experiments using water mixed with fine powder of Fe3O4 and the performance of about 100% is achieved in HGMS.