Effect of apex cone shape and local fluid flow control method on fine particle classification of gas-cyclone

The purpose of this report is to study the effects of apex cone shape and local fluid flow control method on particle separation performance of gas-cyclones. New type of dry cyclone with the movable apex cone which is covered with special shaped ring indicated cut size movement from 2 to 40 μm.By use of the apex cone at the inlet of dust box, it is possible to decrease the fluid velocity component in the dust box and to reduce the re-entrainment of particles from the dust box. The cut size indicated the minimum value for the specific height of the apex cone. The optimum apex cone height was found for each inlet velocity.It is found that the optimum apex cone angle is 70 deg. The minimum 50% cut size was obtained by use of this apex cone angle. From the flow visualization method by use of soap foam, the upward flow and downward flow coexisted on the surface of this special apex cone. The clear interface between upward flow and downward flow was detected on the apex cone angle of 70 deg.The effect of secondary flow injection method on particle separation was also examined. It is found that particle collection efficiency increased with an increased secondary flow rate and number of secondary flow injection in the upper cylindrical part of the cyclone. The new optimum injection method was proposed in this study. The particle separation performance and flow visualization results qualitatively supported the 3-dimensional CFD simulation based on the direct method.

► The effect of apex cone in gas-cyclone is to decrease the cut size and to increase particle collection efficiency.
► The 50% cut size shows a minimum value for the specific value of apex cone height and cone angle.
► The 50% cut size decreases as the additional flow rate into the upper cylindrical part increases.