On concentration polarization in fluidized bed membrane reactors

A numerical study on concentration polarization in 3D cylindrical fluidized beds with vertically immersed membranes

“…The TFM used in the present work has previously already been verified by checking the pressure drop over a packed bed [33], and validated by comparing the hydrogen flux and bubble sizes to experimental results [4,34]. Furthermore, the component mass balances have been verified with the analytical solution of Ogata and Banks [35] and the Fourier solutions for two-sided diffusion.…”

“…In practice, membranes are generally inserted lengthwise in fluidized bed reactors, which is referred to as vertically immersed membranes in this work. In previous research, Helmi et al [4] have found that when feeding binary H 2 /N 2 gas mixtures, the mixing even in fluidized beds with state-of-the-art, high-flux, vertically immersed palladium membranes is still insufficient to completely prevent mass transfer limitations from the bulk of the bed to the membrane surface, also known as concentration polarization [5]. They have quantified the concentration polarization with Cartesian 2D Two-Fluid Model (TFM) simulations and experiments, considering a single membrane in a small fluidized bed.…”

“…Extracting a large amount of gas from a fluidized bed via porous walls can even alter the flow pattern of the solids, as shown by De Jong et al [30] and Dang et al [31]. However, Helmi et al [4] have shown that selective extraction of hydrogen via a supported palladium-based membrane only has a small effect on the bed hydrodynamics.…”

“…The simulation domain size is similar to a realistic laboratory scale fluidized bed membrane reactor. The values for the membrane flux data, reactor pressure, hydrogen mole fraction at the inlet, reactor temperature and dispersion coefficient were obtained from the work by Helmi et al [4]. The membrane permeation flux data was obtained for a 5 µm thick dense Pd/Ag thin film onto a ceramic support.…”

Latest Developments in Membrane (Bio)Reactors

“…On the other hand, fluidized bed reactors are also used to decrease the mass transfer limitation, where mixing is induced by catalyst particles circulation inside the reactor [35,36]. As a direct consequence, the temperature profiles are also virtually uniform throughout the bed.…”