Improved impact plate grinding mill having reduced milling gas consumption

A method of milling a powder in a mill comprising a powder inlet to introduce powder material into a gas, a first jet nozzle for supplying said gas, a first venturi axially in-line with said first jet nozzle and spaced therefrom by said powder inlet, an impact mill surface mounted at a reflective angle to the axis of said first jet nozzle and said first venturi for altering the direction of flow of said powder material entrained in said gas, a second jet nozzle for a gas spaced from said impact mill surface and having a longitudinal axis transverse to the direction of the altered flow downstream from said impact mill surface, cylindrical chamber having a circumferential wall and having outlets for exhaust gas and powder material and feeding means extending through said circumferential wall comprising a second venturi axially in line with said second jet nozzle to introduce powder material into said cylindrical chamber which comprises passing a gas through said first jet and said first venturi while feeding a powder to be ground through said powder inlet to be entrained by said gas to impact on said impact mill surface and to be reflected therefrom, feeding a gas to said second jet nozzle and through said second venturi into said cylindrical chamber and to entrain powder material reflected from said impact mill surface and separating the milled powder from said gas and discharging said separated milled powder and said gas separately from said chamber.