FCC Regenerator flow model

Abstract

Catalyst flow patterns in FCC cross-flow and swirl-type dense-bed regenerators affect regenerator efficiency. A two-dimensional, pseudo-homogeneous flow model describing such flow patterns is developed. The predicted catalyst flow patterns for swirl regenerators indicate catalyst bypassing and recirculating zones. More severe bypassing is predicted for cross-flow regenerators, the severity of bypassing increases with increasing Reynolds number. The calculated flow patterns are combined with a radial mixing-cell model to account for radial mixing in fluidized beds. Radial mixing rates in commercial size regenerators counteract somewhat the effect of bypassing. Model calculations coupling coke burning kinetics with the flow model, however, show that bypassing leads to non-uniform coke levels and oxygen breakthrough. This modeling technology is used to optimize FCC regenerator operation.