Comminution of pulverulent material by fluid energy

A fluid energy mill for grinding pulverulent material comprising a vessel having a closed bottom providing a grinding zone at one end, outlet means at the other end, and a generally cylindrical core zone having an axis disposed generally centrally within said vessel between said grinding zone and said outlet means, and an annular peripheral zone surrounding said generally cylindrical core zone, a plurality of circumferentially-spaced ejector nozzles for injecting fluid carrier medium into said grinding zone in a direction between a radius to said central zone axis and a direction perpendicular to said radius, all of said nozzles being disposed in said grinding zone to inject a primary flow of fluid carrier medium into said vessel through said grinding zone, said nozzles cooperating with said closed bottom and said outlet means so as to generate an axially-flowing vortex within said central zone, said vessel having transverse wall means at the other end spaced from said grinding zone to intercept the axially-flowing vortex and deflect at least a first portion of the medium therein outwardly into the peripheral zone, the fluid medium being deflected into said peripheral zone flowing oppositely as a secondary flow and being introduced into said primary flow issuing from said nozzles to thereby effect a recirculation of the fluid carrier medium within said vessel, and feed means to introduce pulverulent material into said circulating flow of fluid carrier medium, so that the material is introduced into said primary flow for fluid energy grinding thereof, said outlet means at the remote end of said vortex operable to withdraw a second portion of said fluid medium and with it a fraction of the pulverulent material which has been reduced in mass below a predetermined limit in said grinding zone.