Chemical Engineering Science, Vol.66, No.9, 2001-2007, 2011
From bubbling to turbulent fluidization: Advanced onset of regime transition in micro-fluidized beds
Membrane fluidized bed reactors have been proposed and demonstrated as an effective reactor concept for ultrapure hydrogen production with integrated carbon dioxide capture. Recent experimental studies have shown that the hydrogen permeation rate through the membranes and the mass transfer rate from the bubble phase to the emulsion phase are the two main limiting factors in this type of reactors. To this end, we propose the concept of a micro membrane fluidized bed reactor (MMFBR) as a possible method to remove those two limitations. The idea of the MMFBR is that a significantly larger membrane area per unit reactor volume can be accommodated, there by removing the limitation of the hydrogen permeation rate through the membranes. Furthermore, we numerically show with discrete particle simulations that the onset of turbulent fluidization is advanced significantly in a MMFBR, which allows the bed to be operated at the turbulent fluidization regime at a relatively low gas velocity. This is quite beneficial, since it provides a gentler environment for the membranes, and indicates a significant attenuation or possible removal of mass transfer limitations due to the well-known excellent mass transfer characteristic of turbulent fluidization. (C) 2011 Elsevier Ltd. All rights reserved.
Keywords:Powder technology;Regime transition;Fluidization;Membrane fluidized beds;Particulate processes;Multiphase flow