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

Voncken, R.J.W.; Roghair, I.; Annaland, Martin van Sint

doi:10.1016/j.ces.2019.05.010

Cited by 10 publications

(9 citation statements)

References 36 publications

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“…Voncken et al and Helmi et al reported that near the bottom of the membrane, concentration polarization disappeared more quickly, but evident concentration polarization was still observed at zones nearby the bottom end of membrane tube in this work. The major reason for this distinct observation was that our membrane tube was installed nearby the reactor inlet where hydrogen was produced quickly by reforming reactions, whereas no chemical reactions had been involved in their studies. , The average CPC along tube membrane during MA-SE-SRCOG at specified operation conditions was estimated to be ∼0.13. Variation of CPC along with operation conditions would be studied further in the following discussion.…”

Section: Resultscontrasting

confidence: 42%

Section: Resultsmentioning

confidence: 96%

“…As can be seen from Figure S2, around the top end of the membrane, most of the concentration polarization has disappeared within about 0.5–1 cm distance away from the membrane, ,, leading to a CPC approximate to zero. Voncken et al and Helmi et al reported that near the bottom of the membrane, concentration polarization disappeared more quickly, but evident concentration polarization was still observed at zones nearby the bottom end of membrane tube in this work. The major reason for this distinct observation was that our membrane tube was installed nearby the reactor inlet where hydrogen was produced quickly by reforming reactions, whereas no chemical reactions had been involved in their studies. , The average CPC along tube membrane during MA-SE-SRCOG at specified operation conditions was estimated to be ∼0.13.…”

Section: Resultsmentioning

confidence: 96%

“…Hydrogen separation in a fixed bed ,, or fluidized bed membrane reactor, ,, without chemical reactions being involved, has been extensively studied used varieties of simulation models. Chen et al numerically studied hydrogen permeation in a dense palladium membrane tube, with hydrogen permeation across the membrane being treated as a source–sink pair of species transport equation and momentum conservation equation.…”

Section: Introductionmentioning

confidence: 99%

“…Chen et al numerically studied hydrogen permeation in a dense palladium membrane tube, with hydrogen permeation across the membrane being treated as a source–sink pair of species transport equation and momentum conservation equation. Yang et al and Voncken et al , investigated the hydrogen extraction (from H 2 /N 2 mixture in bed) thorough vertically immersed membrane tubes in a FBMR under the Euler–Euler framework. The concentration polarization effects and mass transfer resistance were well explored.…”

Section: Introductionmentioning

confidence: 99%

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Comprehensive Modeling of Sorption-Enhanced Steam Reforming of Coke Oven Gas in a Fluidized Bed Membrane Reactor

et al. 2020

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Integration of membrane hydrogen separation and carbon dioxide capture with fuel steam reforming efficiently promoted hydrogen production and feedstock conversion. In this study, catalytic steam reforming of coke oven gas in a sorption-enhanced fluidized bed membrane reactor (MA-SE-SRCOG) was simulated using a reactive three-fluid model under the Euler framework. The numerical studies provided insights into details about interactions of multiscale subprocesses, including hydrogen permeation, carbon dioxide adsorption, catalytic reforming, and multiphase flow dynamics, during MA-SE-SRCOG. Concentration polarization caused by hydrogen separation was also examined. Meanwhile, impacts of several operating parameters, such as reaction pressure, steam concentration, membrane position, and reactor scale, on the performance of MA-SE-SRCOG were evaluated in terms of CH4 conversion, CO selectivity, hydrogen recovery factor, and CO2 fix factor. The simulation results demonstrated that membrane hydrogen separation and carbon dioxide adsorption promoted reforming kinetics and reactant conversions in the fast reaction zone, and also extended the reactive zone, thus efficiently improving the overall reforming efficiencies. Fast CO2 adsorption kinetics showed more profound enhancements on reducing CO selectivity compared to membrane separation, which instead had greater potential to facilitate high CH4 conversion when membrane effectiveness (a parameter representing impacts of membrane area, layer thickness and composite on permeation rates) was sufficiently large, particularly at high operation pressures. With membrane effectiveness increasing from 1 to 5, a CH4 conversion of 91.3% was achieved by MA-SE-SRCOG at 0.33 MPa and 560 °C, while the H2 permeation flux was augmented from 0.077 mol/(m2·s) to 0.192 mol/(m2·s). However, the increase of membrane effectiveness would cause more serious H2 concentration polarization in FBMR, which inhibited the effective H2 separation rates, so membrane effectiveness >10 has been observed to not remarkably benefit CH4 conversion and H2 production further. High S/C (>6) enhanced the occurrence of larger bubbles, and decreased the driving force (hydrogen partial pressure) for hydrogen permeation, both of which degraded the reforming performances and reduced yield of high purity H2. The more closely membrane units were installed to the fast reaction zone, the larger the enhancements of membrane expected to exert on COG-steam reforming reactions. With the given dimensions of the membrane tube, the decrease of reactor diameter helped to decrease concentration polarization, so higher CH4 conversion and H2 separation factors were achieved.

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