Design and application of a longitudinal field Aubert permanent magnet composed of identically-shaped blocks for large-scale Magnetic Separation

•Economic, portable permanent magnet providing a longitudinal magnetic field for cylindrical separation devices.•Analytic calculation method of the magnetic flux density for the design of large-scale devices.•Magnetic field enhancement by a second annular structure that surrounds the inner magnet.•Suitable to take the place of heavy and expensive electromagnets.

Magnetic Separation processes such as magnetically enhanced centrifugation (MEC) or magnetic cake filtration, usually require cost-intensive and heavy electromagnets. Permanent cylindrical magnets providing a comparable longitudinal magnetic field may be more advantageous for these applications both in terms of cost and weight. In this publication we propose the use of Aubert magnets. As they may be composed of identically-shaped magnet blocks, the investment costs and running expenses are very low. We analyze the magnetic field in the central bore of an Aubert magnet both by analytic calculations based on a dipole model and by FEM (finite element method) and compare the results to our measured data on such a device. We find very good agreement with an extended dipole model and suggest our analytic method even for the design of large-scale devices. Finally, the pros and cons of both types of magnetic devices are discussed.