CFD modeling of mass transfer and stripping efficiency in FCCU strippers



This article presents an experimental and computational study of mass transfer characteristics and stripping efficiency of bubbling fluidized beds within FCCU strippers. The hydrodynamic and mass transfer characteristics are investigated experimentally. Based on the granular kinetics theory, a two-fluid CFD model coupled with a modified Gidaspow drag model and an empirical mass transfer model has been developed and verified against the experimental results. The overall trend of the time-averaged bed density, concentration of tracer and stripping efficiency at various superficial gas velocities were in reasonable agreement with the experimental data. It was found that stripping efficiency depends strongly on the operating conditions as well as on the internal configuration of the strippers. Increasing superficial gas velocity increases stripping efficiency. Internal baffles improve break-up and redistribution of bubbles and enhance the gas-solids contacting remarkably, showing a benefit for the mass transfer in the V-baffled stripper. © 2008 American Institute of Chemical Engineers AIChE J, 2008