Method and apparatus for magnetic separation of particles in a fluid carrier

A method for separating a mixture of diverse-size particles in accordance with the magnetic susceptibilities of the particles, comprising:

• flowing a fluid carrier upward through a first flow path in opposition to the settlement of the particles suspended therein due to gravity;
• adjusting the upward rate of flow of the fluid carrier in said first path by one or more intervals to select from said mixture one or more fractions of substantially uniform settling rates in the fluid carrier;
• flowing each of said one or more fractions suspended in the fluid carrier from the first flow path to a second flow path;
• establishing a magnetic field extending over at least a portion of said second flow path;
• and
• in response to said one or more flow interval adjustments in the first flow path, adjusting the fluid flow rate through the second flow path so as to pass each of said one or more fractions through the magnetic field at a velocity proportional to the settling rate of the fraction in the first flow path, thereby to enable separation of said fractions into relatively magnetic and relatively nonmagnetic portions within the active length of the field, said adjustments of the second path flow rate being such as to maintain the ratio of the velocity at which each fraction is passed through the magnetic field to the settling velocity of said each fraction in the first flow path at a substantially constant value.

Apparatus for separating a mixture of diverse-size particles in accordance with the magnetic susceptibilities of the particles, comprising:

• a source of fluid carrier;
• means defining a first flow path communicating with the fluid source for flowing the fluid carrier upward in opposition to the settlement therein due to gravity of said mixture of diverse-size particles;
• means for adjusting the upward rate of flow of the fluid carrier in said first flow path to select from said mixture a fraction of particles of a substantially uniform settling rate in the fluid carrier;
• means defining a second flow path communicating with the fluid source and with the first flow path for receiving said fraction suspended in the fluid carrier;
• means for applying opposing magnetic and nonmagnetic forces to said fraction over at least a portion of the second flow path;
• and
• means responsive to said flow adjustment in the first flow path for passing said fraction through said portion of the second flow path at a velocity proportionally related to the settling rate of the fraction in the first flow path such that the residence time of the fraction in said portion of the second flow path is sufficient to enable the separation therein of the fraction into relatively magnetic and relatively nonmagnetic portions by said opposing forces.

Apparatus for separating a mixture of diverse-size particles in accordance with the magnetic susceptibilities of the parties, comprising:

• a source of fluid carrier:
• means defining a first flow path communicating with the fluid source for flowing the fluid carrier upward in opposition to the settlement therein due to gravity of said mixture of diverse-size particles;
• means for adjusting the upward rate of flow of the fluid carrier in said first path by one or more intervals to select from said mixture one or more fractions of particles of substantially uniform settling rates in the fluid carrier, said flow adjustment means further including means for monitoring the flow of particles settling out of the first flow path and, in response thereto, for adjusting the upward flow rate through the first flow path to provide a desired particle flow density therefrom;
• means for establishing a magnetic field;
• and
• means defining a second flow path communicating with the first flow path for receiving said one or more fractions suspended in the fluid carrier and, in response to said one or more flow interval adjustments in the first flow path, for passing each of said one or more fractions through said magnetic field at a velocity proportional to the settling rate of said each fraction in the first flow path, thereby to enable separation of said fractions into relatively magnetic and relatively nonmagnetic portions within the active length of the field.