Cold Modelling of an Internally Circulating Fluidized Bed Membrane Reactor

A novel fluidized bed membrane reactor with internal catalyst circulation is being developed for the production of high-purity H2 from an autothermal reformer. In order to provide guidance to pilot reactor testing, a cold model was built to study the influence of reactor configuration on hydrodynamics and catalyst circulation. It was found that catalyst circulation was reproducible, but that parallel non-communicating flow channels could lead to flow instability. Solids circulation was found to be adequate for design of the autothermal reformer.

Simulation of Cold Flow FCC Stripper Hydrodynamics at Small Scale Using Computational Fluid Dynamics

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.