(360g) Effectiveness Factor Phenomena for the Transition between PBR (Packed Bed Reactor) and MR (Membrane Reactor) Via Coupled Heat and Mass Transfer

Authors: 
Karagoz, S., UCLA
Tstosis, T., University of Southern California
Manousiouthakis, V., University of California Los Angeles, Los Angeles
The study of multiphase transport/reaction phenomena is, of course, of interest to a wide range of separation and reactor applications involving of simultaneous heat, momentum, and multi-component mass transport. The most marked characteristic of such multiphase systems is their nonlinear nature, which requires the quantification of a multiple-coupled set of nonlinear differential equations for the problem solutions that entails a complex set of technical challenges. For reactors, including the MR studied here, accounting for all such phenomena dictates the use of the so-called heterogeneous models rather than the simplified pseudo-homogeneous models that have, to date, dominated the MR modeling literature. This work focuses on the multi-scale modeling of a membrane reactor (MR within which the water gas shift (WGS) reaction is carried out. The work assesses the MR’s effectiveness in transforming, coal-derived syngas into two streams, one rich in hydrogen and the other rich in carbon dioxide. It is shown that significant variation of the catalyst pellet effectiveness factor occurs along the reactors’ axial direction, and that catalyst pellets of the same diameter exhibit different effectiveness factors within the PBR and MR environments. The effect of catalyst solid thermal conductivity on temperature gradients within the catalytic pellet, and the effect of sweeping gas pressure/temperature on the MR’s behavior, are both quantified. Adiabatic and wall-isothermal operation are shown to exhibit significant differences from each other for both PBR and MR reactors.