Abstract: Raw coal, in slurry form, is fed to a dense media cyclone, entering tangentially into the cyclone. Three major forces act on the solid particles as they travel radially and helically inside the cyclone body, forcing the heavier particles toward the wall of the body and the lighter particles toward the center. As the lighter particles near the frustoconical portion of the cyclone body, their velocity vector changes horizontally, causing them to exit the cyclone through the adjustable vortex finder. The heavier particles exit the opposite end through the apex, of which the diameter may be changed by interchangeable apex inserts. Adjusting the vortex finder and diameter of the apex allows the selection of a desired cut size and gravity of the particles. The attributes of the cyclones allow for a separation of coal from ash and sulfur in the 28.times.325 mesh size fraction.