Modeling and simulation of the fluid dynamic and performance of the Pd-based membrane by CFD for hydrogen separation

In this paper, the capability of the Computational Fluid Dynamics (CFD) approach to reliably predict the fluid dynamic and the separation performance of Pd membranes modules for gas mixture separation is evaluated. In this approach, the flow fields of the pressure and velocity for the gas mixture and the species concentration distribution in the selected three-dimensional domains are obtained by the simultaneous, numerical solution of continuity, momentum, and species transport (especially, the gas-through-gas diffusion term derived from the Stefan–Maxwell formulation) equations. Therefore, the calculation of the hydrogen permeation depends on the local determination of the mass transfer resistance caused by the gas phase and membrane, which is modeled as a permeable surface of known characteristics. The applicability of the model to properly predict the separation process under a wide range of pressures, feed flow rates, temperatures, and gas mixtures compositions is assessed through a strict comparison with experimental data. Moreover, in this work, the influence of the inhibitor species on the module performance, which is obtained by implementing the CFD model, is discussed. The results of the simulation showed that increasing the pressure on the feed side increases the molar fraction of hydrogen gas and the feed inlet flow on the shell side, and the hydrogen permeation through the membrane in the tube side. Comparison of simulation results with laboratory data showed good agreement. The model was obtained with an error of less than 3% at 450K and below 6% for 475K and 500K.