Jet mill

The principle of jet milling in a dynamic slurry is illustrated in the figure below. It shows a stream of compressed air entering the grinding chamber and accelerating the particles.

The initial velocities of the particles are very small. After acceleration, they reach supersonic speed in the axis of the chamber. Optimum optimal conditions occur when the air pressure in the nozzle area is both high enough to entrain enough particles and not too high so that the amount of mass does not inhibit the stream velocity. The highest speed of the maximum number of particles at the point of collision determines the optimal productivity of the mill.

The feed material enters the mill by gravity through the diagonal inlet pipe (feed). As a consequence, the particles fall into the grinding chamber, in which compressed air nozzles are placed alternately. Air nozzles deliver directed, clean compressed air. The grains of the material are subjected to a force accelerating them to high speeds.

The accelerated particles collide in the axis of the chamber and are ground to a small size. The decompression of the air stream lifts the particles to the top of the mill equipped with an aerodynamic size classifier. The fine grains are sucked out of the device, while the coarse fraction falls into the grinding chamber for reprocessing. The fine grains flow with the air between the impeller blades and then are ejected through the spiral outlet together with the main stream (product). They are separated from the air by means of a cyclone or filter.