Method of, and a magnetic separator for, separating magnetizable particles from a fluid

A magnetic separator for separating magnetisable particles from a fluid, said separator comprising:

• (a) a chain of separating chambers for receiving the fluid, each separating chamber having an inlet at a top region thereof and a closable outlet in a bottom region thereof wherein the fluid flows through the chamber from the inlet to the outlet in a first direction;
• (b) a respective fluid-permeable mass of magnetisable material disposed within each separating chamber;
• (c) magnet means for establishing a magnetic field in a separating zone, the magnet means comprising pole pieces the faces of which are oriented in planes, normals to which are parallel to a second direction perpendicular to the first direction;
• (d) means for passing the chain of separating chambers continuously through the separating zone in a third direction, the third direction being perpendicular to the first and second directions;
• (e) filling means for introducing fluid containing magnetisable particles into each separating chamber so as to immerse at least a portion of the associated mass of magnetisable material;
• (f) means for removing magnetisable particles from the mass of magnetisable material disposed within each separating chamber by flushing further fluid through the mass of magnetisable material, after the separating chamber has passed out of the separating zone;
• and
• (g) valve means connected to the outlet of each separating chamber and means for controlling the valve means, each of the valve means having a first position, for preventing flow through the outlet, wherein the valve means is in the first position during filling of the chamber with fluid containing magnetisable particles and for a finite period of time after filling and after entry of the separating chamber into the separating zone, whereby the fluid and magnetisable particles are held substantially stationary in the chamber for the finite period of time;
• a second position, for allowing flow through the outlet at a relatively slow rate, wherein when the valve means is in the second position the fluid is drained from the separating chamber as the chamber passes through the separating zone after the said finite period of time;
• and a third position, for allowing flow through the outlet at a relatively high rate, wherein the valve means is in the third position while the further fluid is flushed through the magnetisable material after the separating chamber has passed out of the separating zone, the valve means thereafter being returned to its first position.