Drum magnetic separator

Magnetic separators introduction

By creating an environment comprimizing a magnetic force (Fm), a gravitational force (Fg) and a drag force (Fd) magnetic particles can be separated from nonmagnetic particles by Magnetic separators.

Magnetic separation – Magnetic attraction force (Fm)
Fm = V x X x H x grad H
V = particle volume (determined by process)
X = magnetic susceptibility (see table below)
H = magnetic field (created by the magnet system design) in mT
(milliTesla) or kG (kiloGauss) 1 kG = 100 mT = 0.1 T
grad H = Magnetic field gradient (created by the magnet system design) in mT/m

Magnetic field and magnetic gradient are equally important factors for creating the magnet attraction force.

Magnetic separation – Competing forces

    • Gravitational force (Fg) is determined by particle size and density.
    • Drag force (hydrodynamic, aerodynamic), Fd, is determined by particle size, shape, fluid density, viscosity, turbidity and velocity.
    • Centripetal force (Fc).
    • Adhesion
    • Electrostatic forces etc.

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Introduction of Magnetic Separation

Dry low-intensity magnetic separation is confined mainly to the concentration of coarse sands which are strongly magnetic, the process being known as cobbing, and often being carried out in drum separators. Below the 0.5 cm size range, dry separation tends to be replaced by wet methods, which produce much less dust loss and usually a cleaner product. Low-intensity wet separation is now widely used for purifying the magnetic medium in the dense medium separation process, as well as for the concentration of ferromagnetic sands.
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