CPFD Simulation On Cyclone Separator Performance And Flow Field Under Abnormal Operating Conditions

Cyclone separator is a core fluidized bed component with versatile large-scale applications in industries not limited to petroleum and petrochemicals.Cyclone separators are perpetually faced with air leakage problem which in turns adversely affects its operational performance in terms of reduction in separation efficiency and an increase in pressure drop.This leak is often caused by the inevitable prolong operation periods,the nature of the fluidized medium,the abrasion between the particles and the wall,the stress cracking at the weld seam,among others..Based on the existing experimental data,this study establishes a three-dimensional model of a 180° volute inlet.With the aid of computational particle fluid dynamics(CPFD)simulation method using the large commercial software Barracuda,the flow and separation characteristics of the cyclone at different leakage positions as well as at different leakage areas are investigated extensively.Firstly,the simulation results under normal operating conditions are compared with the previous experimental data to obtain a suitable grid number and drag model,and thereafter the operating parameters are tuned to further study the leakage of the cyclone separator at different positions(inlet,cone,ash bucket).In turn,the total efficiency,separation efficiency,pressure drop and flow field changes are compared with the normal state.For cyclones under normal operating conditions,the CPFD model predicts that:(1)the separation efficiency of the cyclone separator increases with the increase of the inlet gas velocity,and the simulation results are in good agreement with the experimental data.(2)the pressure drop also increases with the increase of the inlet gas velocity,this however does not agree well with the experimental data,which could be linked to the improper use of the turbulence model.(3)the tangential and axial velocities on different axial sections are distributed symmetrically about the geometric center.Basically,the tangential velocity is a typical internal and external vortex distribution,and the axial velocity refers to a standard combination of up and down flow.The CPFD simulation of cyclone under the abnormal states generate the following findings:(1)with a constant leakage area(at inlet,cone,ash bucket),the pressure drop of the cyclone separator increases with the increase in equivalent velocity,this implies that the amount of leakage and the separation efficiency decreases significantly,especially for the fine particles;(2)for the effect of air leakage on the flow field of the cyclone separator: when the air leakage area is the same(at inlet,cone,ash bucket),the tangential and axial velocities of the cyclone separator both decrease with the increase of the equivalent velocity,the distribution pattern changes,and the symmetry decreases.Consequently,the flow field is disturbed,and the eccentricity becomes very serious.(3)comparing the influence of the air leakage at the inlet,cone and ash bucket on the separation and flow characteristics of the cyclone separator,it is evident that the effect of the air leakage at the ash hoper on the performance indicators(cyclone separator’s separation efficiency,pressure drop and flow field)is the largest while the effect at the inlet is the least pronounced,the impact at the cone weighs in between the cone and that of the inlet.