Patent ID: 7857247

Claim:
A milling apparatus comprising a radially symmetrical sleeve having an axial passageway with an upstream inlet and a downstream outlet, a radially symmetrical rotor located within the sleeve, either or both of the rotor and sleeve being rotatable relative to the other, the diameter of the rotor being less than the diameter of the sleeve at each axial position to define an annular passageway between the rotor and sleeve, one or both of the surfaces of the rotor and sleeve having formations adapted to increase the surface area encountered by particles in a fluid flow from the inlet to the outlet, wherein the rotor and the sleeve are frustoconical, the diameter of the inlet being smaller than the diameter of the outlet, and wherein the rotor carries an array of indentations, the array comprising a plurality of adjacent circular arrays, the arrays being arranged in axially offset configuration such that corresponding portions of adjacent arrays do not coincide.