Contrary to a traditional mechanical mill, a jet mill uses a high-pressure process gas (usually compressed air or nitrogen) as milling energy.
Particle-to-particle collision is what reduces the powder size. No mechanical crushing is involved.
The most important part of a Jet Mill is the grinding chamber. If is fitted with a series of calibrated nozzles that distributes the process gas inside (at high pressure, high speed and obviously at a high kinetic energy).
The powder, forced into the chamber by an injector and a venturi system, is moved by the internal high-pressure gas at almost supersonic speeds. The combination of high speed, centrifugal and centripetal effects crush the particles. The resulting fine particles are selected by a classifier ad leave the jet mill, moved by the same process gas into a separating cyclone or other collecting systems. Then, the exhaust gas can be filtered by a HEPA filter.
Thanks to jet milling, particle size can be reduced down to 3µm and with very minimal heat generation
