Numerical Simulation Analysis Of The Split-type Third Stage Cyclone Separator In FCC

Cyclone separator as an important gas-solid separation equipment has been used in many industries such as petrochemical,coal-fired power generation and environmental protection.The split-type third stage cyclone separator is characterized by several small cyclone separators with simple structure suspended on the central tube and collection chamber,which greatly reduces the difficulty of manufacturing,construction and installation.The separation efficiency and the ability to separate small particle size can also meet the dust particle size control index at the inlet of the flue gas turbine.In order to better understand the gas-solid flow mechanism in Thesplit-type third stage cyclone separator,this paper uses computational fluid dynamics software to perform numerical simulation of the split-type third stage cyclone separator,and obtains the corresponding internal flow field through the appropriate solution model and the setting of boundary conditions.After analyzing the law of internal flow field,the separation efficiency and pressure loss under different working conditions and structures were simulated,hoping to obtain an optimized structure with low pressure loss and high separation efficiency that is more suitable for working conditions.Firstly,the gas phase flow field is simulated by RSM turbulence model suitable for cyclone separator,and the corresponding velocity,pressure distribution cloud map,velocity vector distribution map and trace map can be obtained.All of these can give us a deep understanding of the gas-phase flow field inside the cyclone separator,so we know the double-layer rotating flow inside the cyclone separator,and we can also see the track of the internal swirling flow swaying in the center.Secondly,DPM model was added to the flow field of the gas phase,that is,sparse catalyst particles were added to the gas phase flow field of the cyclone separator through the fluid-solid coupling.The existence of apical ash ring was found by the distribution of particles.According to the movement path of particles,I get the action mode of the gas phase flow in the cyclone separator on particles with different particle sizes.For example,the movement trajectory of particles with small particle size cannot move along the wall surface,but rotates downward on the cylinder with smaller radius,which is easy to escape from the ascending pipe under the influence of the draft.According to the final state of particle motion,the method of calculating the separation efficiency is obtained.After that,the effects of different operating parameters(inlet velocity and temperature)on gas phase flow,particle separation efficiency and pressure loss in the third-stage cyclone separator are analyzed.It is concluded that the higher the inlet velocity,the lower the temperature,the greater the corresponding pressure loss,and the higher the corresponding separation efficiency.Finally,we studied the separation efficiency and pressure drop of the small cyclone separator connected with the central tube,and found that the separation efficiency of the third-stage cyclone separator significantly decreased after the combination.After changing the elbow Angle at the junction of the center tube and the small rotation,it is found that when the elbow Angle is 45°,the pressure loss caused by the corresponding model is the least,and the separation efficiency is the highest.When the number of small cyclone separators in the Split-type third stage cyclone separator is changed,it is found that when the number of small cyclone separators reaches 8,the better the separation effect is,but the higher the pressure loss is.The diameter of the center tube also has a great influence on the Split-type third stage cyclone separator.The smaller the diameter,the better the separation effect,but the greater the pressure drop.