Powder mill AFG

talcopposed jetvertical

Fluidised bed opposed jet mill for manufacturing powders with a steep particle size distribution and sharp top size limitation in the range < 5 µm to 200 µm. Grinding nozzles arranged around the periphery of the grinding chamber Classifying wheel(s) arranged horizontally in the classifier top section Cool and contamination-free grinding Cleaning made easy by the hinge-back and removable classifier top section and the inspection deck in the mill housing Principle of operation During expansion, the energy contained in the compressed gas in the form of heat is converted to kinetic energy. The speed of sound is initially a natural limit for the exit velocity. But by using Laval nozzles, the exit velocity can be increased to above the speed of sound. Laval nozzles are characterised by their hourglass shape, which widens downstream of the narrowest cross-sectional point, the nozzle throat. The length of the divergent part of the nozzle is adapted to suit the operating pressure. Compressed air of 20°C and 6 bar overpressure is frequently used as the grinding gas, and delivers nozzle exit speeds of around 500 m/s. As a result of drawing in gas and product from the fluidised bed, the speed of the gas jets sinks extremely rapidly after exiting the nozzles. Comminution is a result of interparticle collision in the jets of air and also in the core area, i.e. the point where the opposing jets intersect.