There exists a rotating top ash ring in the cyclone separator annular space due to the action of the secondary vortex,which will not only affect the separation efficiency but also cause erosion and wear.Using a PV type cyclone separator(barrel diameter D=160 mm)made of Plexiglas,spent acrylonitrile catalyst and iron ore powder,experiments were conducted at the inlet gas velocity(vin)of 12-20 m/s and the inlet particle mass concentration(Cin)of 10-100 g/m3,and then the flow characteristics of the top ash ring were investigated by a high-speed camera.The experimental results show that the top ash ring falls off periodically;the falling-off period is related to the inlet gas velocity and inlet particle mass concentration,which increases with the increase of inlet gas velocity and decreases with the increase of inlet particle mass concentration.To further analyze the formation mechanism of the top ash ring,the gas-phase flow field in annular space is simulated by Fluent.The simulated results show that the entrainment of particles by secondary vortices has led to the formation of top ash ring,and the ash particles aggregation will cause the periodic falling-off of the top ash ring.Relying on the simulation analysis,a prediction mode based on criterion number correlations was established for the falling-off period of the top ash ring.
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