A Two‐Fluid model study of hydrogen production via water gas shift in fluidized bed membrane reactors

Abstract

Fluidized bed membrane reactors have been proposed as a promising reactor concept for the production of ultra-pure hydrogen via Water Gas Shift (WGS). High-flux thin-film dense palladium-based membranes are used to selectively extract hydrogen from the reaction medium, which shifts the thermodynamic equilibrium towards the products’ side, increasing the conversion. A Two-Fluid Model (TFM) has been used to investigate the effect of hydrogen extraction via perm-selective membranes on the WGS reaction rates in the fluidized bed. A thorough TFM verification study was performed, which showed that the model is able to accurately predict the concentration profiles for various types of nth order and equilibrium chemical reactions. Also, the implementation of the WGS reaction rate in the TFM was checked. The results have shown a clear positive effect of the hydrogen permeation on the WGS reaction rates, both for vertically and horizontally immersed membranes. In systems with horizontally immersed membranes, gas pockets that contain a very small amount of catalyst develop underneath the membrane tube, resulting in reduced local reaction rates. Densified zones on top of the membrane tube show increased local reaction rates. Mass transfer limitations from the emulsion phase to the membrane surface is the most pronounced effect that reduces the overall reactor performance. The developed model allows further investigating different configurations and operation modes to further optimize the reactor’s performance.