Abstract: Magnetic separations are made by feeding material to a magnetic separator having elongated ferromagnetic bodies that are disposed parallel to each other with spaces therebetween, the bodies being disposed at an angle to the magnetic field direction. The magnetic particles are deflected away, while the nonmagnetic particles pass through the spaces between the ferromagnetic bodies. In one embodiment, the separator includes a magnetic circuit including an array of elongated ferromagnetic bodies, parallel to each other with spaces therebetween, and on the same side of a common tangential plane that is positioned substantially perpendicular to the direction of the field created by the magnetic system and at an acute angle to the direction of particle feed towards the ferromagnetic bodies.

Abstract: A flowable mixture of particles is separated in accordance with the magnetic susceptibilities of the particles by feeding the mixture into a magnetic field in such a manner that the mixture is urged by a non-magnetic force, e.g., gravity, towards the locus at which the magnetic energy gradient H.differential.H/.differential.X of the field is at a maximum. The magnetic energy gradient defines a magnetic barrier along the locus of its maximum magnitude which exerts a magnetic force on the particles in opposition to the non-magnetic feeding force. Particles having a magnetic susceptibility lower than that value at which the force exerted by the magnetic barrier balances the non-magnetic feeding force pass through the barrier, whereas particles of greater magnetic susceptibility are prevented from crossing from one side of the barrier to the other side and may thereafter be recovered separately from the less susceptible particles.

Abstract: Particles suspended in a fluid carrier are differentially separated by, first, grading the particles into fractions of equal settling rates and, second, separating the equal-settling particles of each fraction according to the magnetic susceptibilities of the particles. The particulate sample to be separated is passed through a two-path parallel flow system. In one path, the sample is selectively graded, by elutriation, into equal-settling fractions. Each such fraction then flows directly to the second path, where it crosses a magnetic field at a velocity proportional to its settling rate. Such proportionality between settling rate and flow velocity provides a residence time which ensures that the degree of deflection, in response to gravitational and magnetic forces, required for separate recovery of magnetic particles, on the one hand, and non-magnetic particles, on the other hand, will be attained within the active length of the magnetic field.