Apparatus and methods for separating particles

A method for classifying a mixture of fine and coarse particles in a fluid stream, wherein fine particles have a size or density below a predetermined cut size and coarse particles have a size or density above the cut size, the method comprising the steps of:

• (a) providing a particle separation assembly comprising:
• (i) a housing comprising an inlet, an interior chamber, a coarse particle outlet, and a fine particle outlet;
• and
• (ii) a boundary layer momentum transfer device comprising a plurality of disks stacked in spaced, parallel relation in the interior chamber and rotatable about a disk axis, the disks having respective central openings cooperatively defining a plenum having a closed axial end and an opposing open axial end, wherein the plenum communicates with spaces defined between each adjacent disk;
• (b) creating a decreasing pressure gradient from the disk spaces to the plenum to establish a fine particle flow path through the inlet of the housing, the interior chamber, the disk spaces, the plenum, the open axial end of the plenum, and the fine particle outlet;
• (c) flowing a particle-laden fluid stream through the inlet of the housing into the interior chamber;
• (d) adjusting a tangential velocity component of the fluid stream to promote uniform dispersion of particles in the fluid stream as the fluid stream flows around and toward the disks;
• and
• (e) rotating the disks to eject coarse particles away from the disks, whereby fine particles are permitted to continue along the fine particle flow path to the fine particle outlet.