Abstract

The refining industry trend toward increased throughput of heavier feeds, accompanied by increased catalyst circulation rates in the fluid catalytic cracking (FCC) unit, has created flow problems in the FCC stripper. This has reduced stripper efficiency, leading to loss of valuable product to the regenerator. This adversely affects the FCC unit heat balance in some cases, requiring the catalyst circulation rate to be reduced, thereby limiting the flow of feed to the unit. Research on FCC strippers published in the open literature is scarce. The purpose of the present study is to model the hydrodynamics of a cold flow, laboratory scale FCC stripper using computational fluid dynamics (CFD). Simulations were performed using the two-fluid CFD code MFIX (www.mfix.org) for operating conditions of gas superficial velocities between 0.1 and 0.33 m/s and solid circulation fluxes ranging between 28 and 90 kg/m²s. A 2-D cold-flow annular FCC stripper was simulated since this study is a first step in modeling stripper hydrodynamics. The simulations were in good qualitative and quantitative agreement with the limited cold-flow stripper hydrodynamic data published in the open literature. The model was also shown to predict the onset of flooding in the baffled stripper, and the addition of downcomers to the baffles widened the stable operating envelope.

Recommended Citation

McKeen, Tim and Pugsley, Todd S. (2003) "Simulation of Cold Flow FCC Stripper Hydrodynamics at Small Scale Using Computational Fluid Dynamics," International Journal of Chemical Reactor Engineering: Vol. 1: A18.
Available at: http://www.bepress.com/ijcre/vol1/A18

Related Files

Fig2a.avi (5390 kB)
AVI animation of baffled stripper in Fig. 2a (0.18 m/s, 28 kg/(m2s))
Fig2b.avi (4728 kB)
AVI animation of non-baffled stripper in Fig. 2b (0.18 m/s, 28 kg/(m2s))
Fig3a.avi (6142 kB)
AVI animation of baffled stripper in Fig. 3a (0.33 m/s, 28 kg/(m2s))
Fig3b.avi (4414 kB)
AVI animation of baffled stripper in Fig. 3b (0.10 m/s, 28 kg/(m2s))
Fig4a.avi (5492 kB)
AVI animation of baffled stripper in Fig. 4a (0.18 m/s, 58 kg/(m2s))
Fig4b.avi (5492 kB)
AVI animation of baffled stripper with downcomers in Fig. 4b (0.18 m/s, 58 kg/(m2s))
Fig11a.avi (9178 kB)
AVI animation of baffled stripper showing flooding at 0.18 m/s, 85 kg/(m2s)
Fig11b.avi (8900 kB)
AVI animation of baffled stripper with downcomers showing mitigation of flooding at 0.18 m/s, 90 kg/(m2s)