Eddy Current Separation of Nonferrous Metals Using a Variable-Frequency Electromagnet

Abstract

We present a novel technique for sorting nonferrous metal scrap by using eddy current separation. However, rather than vary the magnetic field with a spinning rotary drum, our system utilizes a fixed electromagnet excited by an alternating electric current. The technique requires no moving parts other than a feeding mechanism and has the capacity to operate at excitation frequencies up to 50 kHz and beyond. Sorting results are demonstrated using various combinations of metal spheres, which resulted in nearly perfect performance in terms of grade and recovery. We also demonstrate sorting of aluminum alloys from other aluminum alloys, with consistent grade and recovery between 85–95 %.