The Secondary-air-flow dust separators use a secondary fan to skim off a layer off gas prior to his exit which concentrates the uncollected particles. The gas is returned to a position close to the wall of the inlet, where the movement of the larger particles encourage the collection of the recirculated smaller particles.
The injection of this secondary air flow increase also the speed of the cyclone which increase the separation efficiency. This configuration also eliminate the need of gravity force to move the separated particulate downward which allow an horizontal installation of the cyclone separator.