Improving the removal efficiency of industrial-scale cyclones for particles smaller than five micrometre

A new approach has been adopted to reduce the dust emission from gas cyclones by using the strong swirl present in the vortex finder of the cyclone. Preliminary calculations of the flow pattern in the vortex finder using computational fluid dynamics (CFD) indicate that it is possible to collect a certain fraction of the escaped particles utilizing the swirl present. The collection of the particles occurs in a so-called 'Post Cyclone' (PoC) in which the diameter of the vortex finder is broadened slightly. The particles in the effluent air from the cyclone enter the PoC region through a narrow slit where they are collected in a bleed stream. Different mechanisms such as impact on walls and agglomeration aid in the collection. Initial experiments performed with a cyclone of dimensions greater than the usual laboratory range (diameter = 0.4 m) indicate a reduction in emission of particles of 1-3 mu m by around 30%. Experiments were conducted with different configurations of the PoC and also under different operating conditions in order to characterize the system. Flow patterns and collection efficiencies for the cyclone and the PoC, both individually and in combination, were calculated by CFD and compared with experimental data. (C) 1998 Elsevier Science B.V.