On the hydrodynamics of membrane assisted fluidized bed reactors using X-ray analysis

Helmi, Arash; Wagner, Evert C.; Gallucci, Fausto; Annaland, Martin van Sint; Ommen, J. Ruud van; Mudde, Robert F.

doi:10.1016/j.cep.2017.05.006

Cited by 14 publications

(7 citation statements)

References 22 publications

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“…To achieve interesting hydrogen recoveries from a fluidized bed membrane reactor, multiple membranes are required. Even though there have already been experimental hydrodynamic studies on cylindrical fluidized beds with vertically immersed membranes [37], the effect of the membranes on the fluidization behavior remains difficult to be quantified, and simulations are required to visualize and quantify concentration polarization effects. CFD simulations are limited by the number of grid cells in the system, so only cases with a small number of membranes can be simulated.…”

Section: Interaction Between Membranes and Hydrogen Recoveriesmentioning

confidence: 99%

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

Voncken

Roghair

Annaland

2019

Chemical Engineering Science

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Section: Interaction Between Membranes and Hydrogen Recoveriesmentioning

confidence: 99%

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

Voncken

Roghair

Annaland

2019

Chemical Engineering Science

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“…Using the workstation, it was possible to trigger the X-ray source and read out the signals from the detector plate. Further details on the X-ray setup and the measurement technique can be found in Mudde et al (2008) , Maurer et al (2015) , and Helmi et al (2017) . The X-ray images are recorded at 61 Hz during approximately 1 minute, which corresponds to 3700 images.…”

Section: X-ray Imagingmentioning

confidence: 99%

Void fraction measurements in partial cavitation regimes by X-ray computed tomography

Jahangir

Wagner

Mudde

et al. 2019

International Journal of Multiphase Flow

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Cavitation is a complicated multiphase phenomenon, where the production of vapor cavities leads to an opaque flow. Exploring the internal structures of the cavitating flows is one of the most significant challenges in this field of study. While it is not possible to visualize the interior of the cavity with visible light, we use X-ray computed tomography to obtain the time-averaged void fraction distribution in an axisymmetric converging-diverging nozzle ('venturi'). This technique is based on the amount of energy absorbed by the material, which in turn depends on its density and thickness. Using this technique, two different partial cavitation mechanisms are examined: the re-entrant jet mechanism and the bubbly shock mechanism. 3D reconstruction of the X-ray images is used (i) to differentiate between vapor and liquid phase, (ii) to obtain radial geometric features of the flow, and (iii) to quantify the local void fraction. The void fraction downstream of the venturi in the bubbly shock mechanism is found to be more than twice compared to the re-entrant jet mechanism. The results show the presence of intense cavitation at the walls of the venturi. Moreover, the vapor phase mixes with the liquid phase downstream of the venturi, resulting in cloud-like cavitation.

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“…On the other hand, Wassie et al experimentally demonstrated that a stable densified zone in the bed consisted of only smaller particles when the gas was extracted via flat vertical membranes placed at the back of the column; this was especially noticeable at high extraction rates. No densified layers were observed during the gas extraction when Geldart B‐type particles (400–600 μm) were used as the bed material in experiments carried out by Helmi et al When flat membranes were installed, both a reduction and a slight increase in the average bubble size were observed during the gas extraction from the fluidized bed. In addition, most available studies on the hydrodynamics of FBMR have been carried out at room temperature .…”

Section: Introductionmentioning

confidence: 99%

“…No densified layers were observed during the gas extraction when Geldart B‐type particles (400–600 μm) were used as the bed material in experiments carried out by Helmi et al When flat membranes were installed, both a reduction and a slight increase in the average bubble size were observed during the gas extraction from the fluidized bed. In addition, most available studies on the hydrodynamics of FBMR have been carried out at room temperature . The characteristics of the bubble phase or emulsion phase in FBMR have been investigated using experimental techniques such as particle image velocimetry, digital image analysis, electrical capacity, magnetic resonance tomography, and optical fiber detection .…”

Section: Introductionmentioning

confidence: 99%

Effect of gas extraction on the hydrodynamics in a fluidized bed membrane reactor at elevated temperatures

Xiao

Chun

Chen

et al. 2019

Asia-Pacific J Chem Eng

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This study describes experimental explorations on the effects of gas extraction on hydrodynamics in a pilot-scalegas fluidized bed membrane reactor (FBMR) at high temperatures. Differential pressure signals were measured at different vertical intervals in bed and were then characterized by multiscale resolution and power spectra analysis. The experimental results showed that the relative amplitude of σ r (σ/x av ) of pressure signal tended todecrease with the increase of gas extraction fraction.At room temperature, 20% gas extraction caused defluidization at an inlet velocity of 2U mf . However, athigh temperatures the gas extraction simultaneously decreased the magnitude of the low-frequency components and the numbers of the medium-to small-sized structures, mainly due to the decreased number of small-sized structures and the integration of bubbles. This effect of gas extraction increased with increase of gas extraction fraction and slightly decreased at higher inlet gas velocities. At elevated temperatures, the D6 sub-signals (0.781~1.562Hz) possessed the highest wavelet energy distribution percentage of the pressure signals, which meant that the medium-to small-sized bubbles dominated the gas-solid flow dynamics. Gas extraction was observed to enhance the dominance of the D6 scale components..

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On the hydrodynamics of membrane assisted fluidized bed reactors using X-ray analysis

Cited by 14 publications

References 22 publications

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

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

Void fraction measurements in partial cavitation regimes by X-ray computed tomography

Effect of gas extraction on the hydrodynamics in a fluidized bed membrane reactor at elevated temperatures

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