IMPROVING THE REMOVAL EFFICIENCY OF INDUSTRIAL-SCALE CYCLONES FOR PARTICLES SMALLER THAN 5 MICROMETER

A new approach has been adopted to reduce the dust emission from gas c yclones by using the strong swirl present in the vortex finder of the cyclone. Preliminary calculations of the flow pattern in the vortex fi nder using computational fluid dynamics (CFD) indicate that it is poss ible to collect a certain fraction of the escaped particles utilizing the swirl present. The collection of the particles occurs in a so-call ed '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 i n a bleed stream. Different mechanisms such as impact on walls and agg lomeration aid in the collection. Initial experiments performed with a cyclone of dimensions greater than the usual laboratory range (diamet er = 0.4 m) indicate a reduction in emission of particles of 1-3 mu m by around 30%. Experiments were conducted with different configuration s of the PoC and also under different operating conditions in order to characterize the system. Flow patterns and collection efficiencies fo r the cyclone and the PoC, both individually and in combination, were calculated by CFD and compared with experimental data. (C) 1998 Elsevi er Science B.V.