On concentration polarization in fluidized bed membrane reactors

A. Helmi, R.J.W. Voncken, A.J. Raijmakers, I. Roghair, F. Gallucci, M. van Sint Annaland

Research output: Contribution to journalArticleAcademicpeer-review

6 Citations (Scopus)

Abstract

Palladium-based membrane-assisted fluidized bed reactors have been proposed for the production of ultra-pure hydrogen at small scales. Due to the improved heat and mass transfer characteristics inside such reactors, it is commonly believed that they can outperform packed bed membrane reactor configurations. It has been widely shown that the performance of packed bed membrane reactors can suffer from serious mass transfer limitations from the bulk of the catalyst bed to the surface of the membranes (concentration polarization) when using modern highly permeable membranes. The extent of concentration polarization in fluidized bed membrane reactors has not yet been researched in detail. In this work, we have quantified the concentration polarization effect inside fluidized bed membrane reactors with immersed vertical membranes with high hydrogen fluxes. A Two-Fluid Model (TFM) was used to quantify the extent of concentration polarization and to visualize the concentration profiles near the membrane. The concentration profiles were simplified to a mass transfer boundary layer (typically 1 cm in thickness), which was implemented in a 1D fluidized bed membrane reactor model to account for the concentration polarization effects. Predictions by the TFM and the extended 1D model showed very good agreement with experimental hydrogen flux data. The experiments and models show that concentration polarization can reduce the hydrogen flux by a factor of 3 even at low H2 concentrations in the feed (10%), which confirms that concentration polarization can also significantly affect the performance of fluidized bed membrane reactors when integrating highly permeable membranes, but to a somewhat lesser extent than packed bed membrane reactors. The extraction of hydrogen also affects the gas velocity and solids hold-up profiles in the fluidized bed.

LanguageEnglish
Pages464-478
Number of pages15
JournalChemical Engineering Journal
Volume332
Early online date2017
DOIs
StatePublished - 15 Jan 2018

Fingerprint

Fluidized beds
polarization
Polarization
membrane
Membranes
Hydrogen
hydrogen
Packed beds
mass transfer
Mass transfer
Fluxes
reactor
Fluids
fluid
palladium
Palladium
heat transfer
Boundary layers
boundary layer
Gases

Keywords

  • Concentration polarization
  • Fluidized bed
  • Pd membrane
  • TFM

Cite this

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On concentration polarization in fluidized bed membrane reactors. / Helmi, A.; Voncken, R.J.W.; Raijmakers, A.J.; Roghair, I.; Gallucci, F.; van Sint Annaland, M.

In: Chemical Engineering Journal, Vol. 332, 15.01.2018, p. 464-478.

Research output: Contribution to journalArticleAcademicpeer-review

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AU - Helmi,A.

AU - Voncken,R.J.W.

AU - Raijmakers,A.J.

AU - Roghair,I.

AU - Gallucci,F.

AU - van Sint Annaland,M.

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