Investigation of the flow pattern in different dust outlet geometries of a gas cyclone by laser Doppler anemometry

The separation process in a gas cyclone can be divided in three determining steps: (1) the movement of the particles in the cyclone chamber towards the cyclone wall due to centrifugal force, (2) agglomeration of particles at the wall and in the dust bin and (3) separation of the particles and/or agglomerates in the bin. For many years the dust outlet has been considered to be very important for the separation process. However, the actual geometry of the dust outlet was rarely investigated. Tests performed by the authors prove that different dust outlet geometries have significantly different separation efficiencies. Laser Doppler anemometry measurements in a cyclone equipped with three different dust outlet geometries show that both the gas flow in the dust outlet and the gas flow within the lower part of the cyclone change. By examining the different flows within the different dust outlet geometries the influence of the geometry on the separation efficiency can be explained. The best dust outlet of a cyclone is a downcomer tube, due to the "additional" separation process which takes place within it. (C) 2003 Elsevier B.V. All rights reserved.