Abstract: Improved grinding in a re-entrant jet comminuting and classifying mill is provided by directing the gaseous jet streams emitted from the nozzles in the annular peripheral wall of the mill's vortex chamber at a relatively acute angle to the radius of the chamber and also at an acute angle to the central axis of the chamber whereby the jet streams merge at a tangent circle that is substantially within the midpoint of the radius of the chamber and axially spaced from the plane of the nozzles in a direction remote from the axial outlet of the mill. The mill is provided with axial feed.

Abstract: Apparatus for comminuting materials to extremely fine size includes a circulating stream jet mill and a discrete but functionally interconnected and interdependent rotating anvil-jet impact mill. New material is injected into the impact mill against a rotor, and the partly comminuted material is transferred to the jet mill with vortex feed into the jet mill. Uncomminuted material in the jet mill is reinjected into the impact mill. The two mills transfer the material back and forth until the particles are comminuted, classified, and removed from the jet mill. The anvil-jet mill is provided with stationary anvils and support for turning the rotor at increased velocity.