Local time-averaged gas holdup in fluidized bed reactor using gamma ray computed tomography technique (CT)

Efhaima, Abdelsalam; Al‐Dahhan, Muthanna H.

doi:10.1007/s40090-015-0048-6

Cited by 19 publications

(21 citation statements)

References 14 publications

(18 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…certain area of the pixel, and when conducting an azimuthal average for the linear attenuation in the wall region, it will count peripherally for all these kinds of variation that will provide such differences in the wall region of the phantom (see Figure 9 and Figure 10). These obtained results in terms of reconstructed linear attenuation coefficient distributions and their diametrical profiles achieved this high accuracy for the first time as compared to other previous studies [46,48,69] that scanned the same phantom. Also, these past studies were unable to reproduce the geometry of the phantom and capture the small thickness of the phantom wall and this was due to using an empty phantom as a reference scan in their studies.…”

Section: Validation Of Ct Scanningsupporting

confidence: 68%

Overcoming the gamma‐ray computed tomography data processing pitfalls for bubble column equipped with vertical internal tubes

et al. 2018

Self Cite

View full text Add to dashboard Cite

This study identifies and addresses some major pitfalls that are involved in the visualization and quantification of the gas‐liquid distributions and their profiles in a bubble column with internals using the gamma‐ray computed tomography (CT) technique. Some of these pitfalls encountered in the scanning of bubble columns with internals are using an improper reference scan, and applying the same experimental scanning procedure and mathematical relationships for estimating the gas holdup in the column without internals to the column with internals. The experimental results revealed that the selection of the inappropriate reference scan for CT experiments would significantly affect the reconstructed linear attenuation coefficient values and consequently the gas holdup results. Additionally, the reconstructed linear attenuation values showed good agreement with theoretical values when considering air as reference scans. However, disagreement is observed when using the empty column with internals as a reference scan. Moreover, it was found that using the proper reference scan eliminated the errors not only for the reconstructed linear attenuation coefficients but also for the gas holdup values near the wall region. Furthermore, the CT technique was capable of capturing the small thickness (5 mm) of the wall for phantom and bubble columns as well as the internals when the air was used as the reference scan. Finally, a new methodology has been implemented to exclude the internals from the cross‐sectional images, and the azimuthally averaged gas holdup profiles to provide accurate and reliable results for comparison and validation purposes for the bubble column with internals.

show abstract

Section: Validation Of Ct Scanningsupporting

confidence: 68%

Overcoming the gamma‐ray computed tomography data processing pitfalls for bubble column equipped with vertical internal tubes

et al. 2018

Self Cite

View full text Add to dashboard Cite

show abstract

“…The superficial gas velocities used were 1.5–3

U_{m f}

, where the

U_{m f}

is the minimum fluidization velocity. These gas velocities covered the bubbling and turbulent flow regime based on the previous work performed in our laboratory . The static bed height above the distributor was kept constant at H/D = 2 for the two columns.…”

Section: Methodsmentioning

confidence: 99%

“…These gas velocities covered the bubbling and turbulent flow regime based on the previous work performed in our laboratory. [21,[38][39][40] The static bed height above the distributor was kept constant at H/D ¼ 2 for the two columns. RPT technique was implemented on the bed height of H/D ¼ 0.1À2.2 above the gas distributor for the 14 cm diameter column and of H/D ¼ 0.05-2.5 above the gas distributor for 44 cm diameter column as illustrated in Figure 1.…”

Section: Methodsmentioning

confidence: 99%

Bed diameter effect on the hydrodynamics of gas‐solid fluidized beds via radioactive particle tracking (RPT) technique

Efhaima

Al‐Dahhan

2017

Can J Chem Eng

Self Cite

View full text Add to dashboard Cite

The hydrodynamics observed in large‐scale gas‐solid fluidized bed reactors are different from those observed in smaller scale beds. In this study, the effect of bed diameter on the hydrodynamics of gas‐solid fluidized bed reactors has been investigated in two bubbling fluidized beds of 44 cm and 14 cm in diameter using an advanced non‐invasive radioactive particle tracking (RPT) technique. Compressed air at room temperature was used as the gas phase, and the solid was glass beads with a particle size of 210 μm (Geldart‐B) and density of 2.5 g · cm−3. Particle velocity field, Reynolds stresses, normal stresses, turbulent kinetic energy, and axial and radial eddy diffusivities were measured in two beds at gas velocities of 1.5 Umf, 2 Umf, and 3 Umf. Experimental results showed that the bed scales have a significant effect on some of these hydrodynamic parameters where the magnitude of solids velocity is much higher in the larger bed and the solids mixing and diffusion of particles are increased by increasing the column diameter.

show abstract

“…The cross‐section of the bed is divided into 80 × 80 square pixels. More details on both the hardware and the software used in this technique and the related post‐data processing have been described by Varma, Varma et al, Bhusarapu, Bhusarapu et al, and Efhaima . The measured time averaged cross‐sectional distribution of gas and solids holdups have been used to estimate the radial profiles of the holdups at the designated axial levels mentioned above.…”

Section: Measurement Techniquesmentioning

confidence: 99%

Assessment of scale‐up dimensionless groups methodology of gas‐solid fluidized beds using advanced non‐invasive measurement techniques (CT and RPT)

Efhaima

Al‐Dahhan

2017

Can J Chem Eng

Self Cite

View full text Add to dashboard Cite

The most common scale‐up methodology for gas‐solid fluidized bed reactors that has been reported in the literature is based on matching the dimensionless groups. This scale‐up methodology in the literature has been validated by only measuring global hydrodynamic parameters (overall holdups and pressure drop, etc.) without details. Therefore, in this work, we have applied advanced non‐invasive measurement techniques, gamma‐ray computed tomography (CT) and radioactive particle tracking (RPT) techniques, for the first time to evaluate such scale‐up methodology by measuring local hydrodynamic parameters. The results obtained demonstrate that the reported set of the dimensionless groups are not adequate in capturing all the interplay phenomena for achieving similarity in the local hydrodynamic parameters when the proposed set of dimensionless groups has been matched using two sizes of fluidized beds of 0.14 m and 0.44 m and sets of operating conditions. This finding confirms that the local measurements of the hydrodynamic parameters are essential for detailed assessment of scale‐up methodologies.

show abstract

Local time-averaged gas holdup in fluidized bed reactor using gamma ray computed tomography technique (CT)

Cited by 19 publications

References 14 publications

Overcoming the gamma‐ray computed tomography data processing pitfalls for bubble column equipped with vertical internal tubes

Overcoming the gamma‐ray computed tomography data processing pitfalls for bubble column equipped with vertical internal tubes

Bed diameter effect on the hydrodynamics of gas‐solid fluidized beds via radioactive particle tracking (RPT) technique

Assessment of scale‐up dimensionless groups methodology of gas‐solid fluidized beds using advanced non‐invasive measurement techniques (CT and RPT)

Contact Info

Product

Resources

About