(567a) Comparative Study of a Hybrid Adsorptive-Membrane Reactor (HAMR) with a Membrane Reactor/Adsorptive Reactor Sequence

Reactive separation processes such as membrane reactors (MRs) and absorptive reactors (ARs) have been attracting renewed interest for industrial applications. We have been studying a novel process that combines the MR and AR functions and which shows good promise for application in the efficient ultra-pure hydrogen production with simultaneous CO₂ recovery and capture.. Two system configurations are being investigated: One (known as the Hybrid Adsorptive-Membrane Reactor or HAMR) in which the membrane, adsorbent and catalyst are all housed in the same unit; and another in which the MR and the AR are separate but coupled units (known as the MR-AR system). The aim of this study is to perform a comparative numerical study between the HAMR and the combined MR-AR system, in which the MR is followed by an adsorptive reactor (AR), for the case-study of the water gas shift (WGS) reaction process for hydrogen production and carbon dioxide capture.

The HAMR is a dynamically-operated process, which typically employs one or multiple tubular membranes. The HAMR’s reaction section, surrounding the membrane tubes, contains catalyst and adsorbent material that accelerates reaction kinetics via the adsorption of one (or several) of the reaction products. The HAMR’s permeation section consists of the membrane tubes which physically remove some of the other reaction products from the reacting mixture, further accelerating reaction kinetics. The HAMR is, typically, operated in reaction and regeneration modes, since the adsorbent meterial reaches its adsorption capacity after a period of operation, and thus needs to be regenerated.

The MR-AR configuration (with the AR following the MR) provides significant added flexibility for the application, for which in addition to efficient hydrogen production CO₂ recovery and purity are also important key drivers. In the MR, a membrane that is selective to hydrogen is used to enhance the WGS reaction rate, and to potentially overcome equilibrium conversion limitations imposed by thermodynamics. The MR system is composed of a reaction zone packed with catalyst pellets, and a permeation zone, where the reaction products permeate. The AR contains both catalyst and adsorbent in a fixed-bed configuration for simultaneous reaction and separation. The combined MR-AR as with the HAMR is a dynamically operated process.

In the study, the velocity and species concentration profiles along the reactors’ lengths are captured by momentum/species transport models accounting for convection/reaction /diffusion mechanisms. The model’s equations are solved using Finite Element Method (FEM). The rigorous Maxwell-Stefan and dusty gas models are applied to describe mass diffusion fluxes. The developed model is used to intensify the Water Gas Shift Reactor (WGSR) Process. Then parametric studies of the HAMR and combined system are carried out, so as to identify maximum intensification designs. These studies include a broad range of operating conditions and parameters (e.g., reactor operating temperature, catalyst and adsorbent weight to feed flowrate ratios, and others).