Reverse-flow cyclone can be subdivided in two category : tangential inlet and axial inlet.
In a reverse-flow cyclone with tangential inlet, the dirty gas enters at the top of the cyclone and is given a spinning motion because of its tangential entry. Particles are forced to the wall by centrifugal force and then fall down the wall due to gravity. At the bottom of the cyclone the gas flow reverses to form an inner core that leaves at the top of the unit.
In a reverse-flow cyclone with axial-inlet cyclone, the inlet gas is introduced down the axis of the cyclone, with centrifugal motion being imparted by permanent curved blades at the top. Particles are forced to the wall by centrifugal force and then fall down the wall due to gravity. At the bottom of the cyclone the gas flow reverses to form an inner core that leaves at the top of the unit.
The reverse-flow cyclones can be arranged as a single cyclone separator or as similar cyclone separators in parallel (the multicyclone).
Parallel-cyclone separators, also called Multiple-cyclone separators, consist of a number of small-diameter cyclones dust collector, operating in parallel and having a common gas inlet and outlet. They operate on the same principle as single cyclone separators—creating an outer downward vortex and an ascending inner vortex.
Multiple-cyclone separators remove more dust than single cyclone separators because the individual cyclones have a greater length and smaller diameter. The longer length provides longer residence time while the smaller diameter creates greater centrifugal force. These two factors result in better separation of dust particulates. The pressure drop of multiple-cyclone separators collectors is higher than that of single-cyclone separators, requiring more energy to clean the same amount of air.