Inertial separators: basic principles

Inertial separators concentrate or collect particles by changing the direction of motion of the flowing gas, in such a way that the particle trajectories cross over the gas steamlines and the particles are either concentrated into a small part of the gas flow or are separated by impingement onto a surface. By far the most widely used type of inertial separator is the cyclone, in which the gas undergoes some kind of vortex motion so that the gas acceleration is centripetal; the particles, therefore, move centrifugally towards the outside of the cyclone. Almost all practical cyclones induce the vortex motion ‘passively’, by appropriate design of the gas flow channel so that the device has no moving parts. Some rotating devices — perhaps more properly called ‘gas centrifuges’ — have been proposed but have seen very limited application.