Concentration polarization distribution along Pd-based membrane reactors: A modelling approach applied to Water-Gas Shift

In this work, an improved membrane characterization, computational fluid dynamic (CFD) simulations of inert particle beds, and simulations of a membrane reactor for Water Gas Shift (WGS) are coupled together to evaluate the concentration polarization distribution along Pd-based membrane reactors. To perform this investigation, first a 3.6 mm-thick Pd75Ag25-membrane is characterized using experimental data from the literature as input to an improved approach allowing the non-ideality of internal diffusion to be quantitatively evaluated as a function of hydrogen partial pressure. Then, CFD simulations of a particle bed composed of regular arrays of mono-disperse spherical particles are carried out, showing that the velocity field between particles and membranes contributes to enhance the mass transfer towards the membrane surface. Finally, after validating a 1D-1D reactor model by literature experimental data in terms of both conversion and recovery index vs. feed pressure, simulations of concentration polarization coefficient (CPC) profiles along the reactor are performed. These profiles allow a clearly identification of the reactor zones where polarization is higher, providing useful information to minimize the polarization influence on reactor performances.