Experimental Research On Cyclone Efficiency Based On Equivalent Settling Velocity Particle Diameter

Cyclone separators are widely applied in gas-solid separation.The conventional characterization methods of grade efficiencies assume that the particles are spherical or characterize the non-spherical particles by equivalent volume diameter.This makes it difficult to characterize the grade efficiencies of non-spherical particles and apply the results.This dissertation focuses on the characterization of performance of cyclones based on equivalent settling velocity particle diameter.Firstly,four kinds of particles: coal fly ash,silica,talcum and barite,are selected to be measured by centrifugal settling particle size analyzer and laser particle size analyzer to obtain the particle diameter distribution based on different equivalent methods.The performance experiments of coal fly ash and silica are carried out on the PV cyclone separator(D=300mm)to show the grade efficiency based on different equivalent diameter.Then the equivalent settling velocity diameter,which reflects the influence of particle size,particle density and shape of particle,is put forward to characterize the grade efficiency.The results show that the efficiencies of different kinds of particles which have the same equivalent settling velocity diameter are equal under the same operating conditions.Then,this theory is verified by the repeated experiments carried out with talcum and barite.It means that the equivalent settling velocity diameter is satisfactory to feature the separation ability of particles.The diameter of cylinder and the structure of inlet and outlet of the separator are changed to conduct other comparative experiments to verify the new characterization method of grade efficiencies.The results show that the grade efficiency curves based on the equivalent settling velocity diameter of different kinds of particles are still coincident in the same operating conditions;and there are significant differences in grade efficiency curves based on equivalent settling velocity diameter for different separators,which shows that this characterization method of grade efficiency can characterize the performance of different separators accurately.Finally,two corrections are proposed for the equilibrium orbit model: one is to characterize the particle size by the equivalent sedimentation diameter to include the influence of the particle shape on the resistance coefficient;the other is to modify the additional friction coefficient between the cyclone wall and the dust layer near the wall with the packing density and the angle of repose.The modified equilibrium orbital model can predict the separation efficiency of non-spherical particles more accurately.