The Reynolds stress model was used to simulate gas-solids flow field of built-in fourth stage separation cyclone system in FCCU. Cross flow existed at the bottom of the dust hopper in the cyclone separator

which was not favorable for particle discharge. Although blowdown on the top of the dust storage tank could help separator discharge

it also increased the chance of particles escaping from the balance tube

lowering separation efficiency. The movement trajectory of particles in the system included trapped in the dust hopper of the dust storage tank

escaping from the vortex finder and the balance tube. In order to reduce particles escaping from the balance tube

adding a cone baffle in the dust storage tank could be an effective way. Particle concentration was higher at the top of the annular space and the bottom of the dust hopper

causing wall wear out. The built-in fourth stage separation cyclone system had an advantage of resolving catalyst loss.