Research on Structure Optimization and Internal flow of Cyclone in Catalytic Cracking Device

The third stage cyclone (TTS) in the catalytic cracking device is the pivotal part to separate and recover catalyst particles, and it can ensure the normal operation of follow-up process. Internal flow patterns in it are particularly important for the selection and use of the equipment. In this paper, the structure parameters of the PV third stage cyclone of 2.8 million tons/year catalytic cracking device in a chemical plant are determined. Simulation of the turbulent 3D flow has been done with Reynolds stress model (RSM) and discrete phase model (DPM). Velocity and pressure drop patterns in the cyclone, effects of the inlet duct dimension on the separation performance and pressure drop, and the motion and separation efficiency of different diameter particles were analyzed. The results indicate that the flow field inside the cyclone forms a typical Rankin vortex flow pattern, and simulated pressure drops agree well with experimental results, which validates the numerical simulation method. When the inlet area is unchanged, the separation efficiencies first increase and then decrease with the increase of inlet height, and the optimal ratio of inlet height to cyclone's body diameter is 0.58. The migration trajectory of small particles have great randomness, and they are easy to escape from the vortex finder affected by the gas flow. The large particles rotate along the relatively large diameter and can be separated well. These results can provide the reference for the flow mechanism analysis and the industrial application of TTS.