Tomographic diagnosis of gas maldistribution in gas–solid fluidized beds

Patel, A.; Waje, S. S.; Thorat, Bhaskar N.; Mujumdar, Arun S.

doi:10.1016/j.powtec.2007.10.019

Cited by 32 publications

(19 citation statements)

References 21 publications

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“…Patel et al (2008) used GRT to determine the gas maldistribution of a gas-solid fluidized bed drier and how the gas maldistribution was affected by various parameters, such as particle size, particle density, and superficial gas velocity. Results showed that GRT was a reliable technique that provided a good estimation of the gas maldistribution with a good spatial resolution (Patel et al, 2008).…”

Section: Noninvasive Techniquesmentioning

confidence: 99%

Bed height and material density effects on fluidized bed hydrodynamics

Escudero

Heindel

2011

Chemical Engineering Science

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Section: Noninvasive Techniquesmentioning

confidence: 99%

Bed height and material density effects on fluidized bed hydrodynamics

Escudero

Heindel

2011

Chemical Engineering Science

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“…Invasive and noninvasive methods can be employed, however, noninvasive observation techniques are more reliable [11]. Techniques such as electrical capacitance [12], X-ray absorption [13], c-ray absorption [14], or positron emission tomography [15] utilize field measurements (i.e., capacitance, absorption, transmission, etc.) to quantify local property variations.…”

Section: Introductionmentioning

confidence: 99%

Comparisons of Annular Hydrodynamic Structures in 3D Fluidized Beds Using X-Ray Computed Tomography Imaging

Drake

Heindel

2012

Journal of Fluids Engineering

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Fluidized beds are common equipment in many process industries. Knowledge of the hydrodynamics within a fluidized bed on the local scale is important for the improvement of scale-up and process efficiencies. This knowledge is lacking due to limited observational technologies at the local scale. This paper uses X-ray computed tomography (CT) imaging to describe the local time-average gas holdup differences of annular hydrodynamic structures that arise through axisymmetric annular flow in a 10.2 cm and 15.2 cm diameter cold flow fluidized bed. The aeration scheme used is similar to that provided by a porous plate and hydrodynamic results can be directly compared. Geldart type B glass bead, ground walnut shell, and crushed corncob particles were studied at various superficial gas velocities. Assuming axisymmetry, the local 3D timeaverage gas holdup data acquired through X-ray CT imaging was averaged over concentric annuli, resulting in a 2D annular and time-average gas holdup map. These gas holdup maps show that four different types of annular hydrodynamic structures occur in the fluidized beds of this study: zones of (1) aeration jetting, (2) bubble coalescence, (3) bubble rise, and (4) particle shear. Changes in the superficial gas velocities, bed diameters, and bed material densities display changes in these zones. The 2D gas holdup maps provide a benchmark that can be used by computational fluid dynamic (CFD) users for the direct comparisons of 2D models, assuming axisymmetric annular flow.Keywords annular flow, fluidized bed, gas holdup, hydrodynamic structure, X-ray computed tomography Fluidized beds are common equipment in many process industries. Knowledge of the hydrodynamics within a fluidized bed on the local scale is important for the improvement of scale-up and process efficiencies. This knowledge is lacking due to limited observational technologies at the local scale. This paper uses X-ray computed tomography (CT) imaging to describe the local time-average gas holdup differences of annular hydrodynamic structures that arise through axisymmetric annular flow in a 10.2 cm and 15.2 cm diameter cold flow fluidized bed. The aeration scheme used is similar to that provided by a porous plate and hydrodynamic results can be directly compared. Geldart type B glass bead, ground walnut shell, and crushed corncob particles were studied at various superficial gas velocities. Assuming axisymmetry, the local 3D time-average gas holdup data acquired through X-ray CT imaging was averaged over concentric annuli, resulting in a 2D annular and time-average gas holdup map. These gas holdup maps show that four different types of annular hydrodynamic structures occur in the fluidized beds of this study: zones of (1) aeration jetting, (2) bubble coalescence, (3) bubble rise, and (4) particle shear. Changes in the superficial gas velocities, bed diameters, and bed material densities display changes in these zones. The 2D gas holdup maps provide a benchmark that can be used by computational fluid dynamic (CFD) users fo...

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“…The quality of fluidization can be described in terms of the uniformity of distribution of the fluidizing gas (Patel et al 2008). Several measurement techniques have been utilised in the past to investigate the quality of fluidization or the gas maldistribution in a fluidized bed.…”

Section: Introductionmentioning

confidence: 99%

“…These techniques include pressure probe measurements (Saxena et al 1993, Lin andWey 2004), temperature probe measurements (Saxena et al 1993), γ-ray tomog- 2004) is modified from its original form and was used to describe good or bad bed behaviour in terms of the pressure fluctuations in the bed. The fluidization index can also be related to the maldistribution factor, χ, used in the work done by Patel et al (2008) and Loser (1999). The maldistribution factor can be defined for pixilated solid fraction images and is defined as…”

Section: Introductionmentioning

confidence: 99%

“…where n denotes the number of pixels in the particular image (tomogram), α i is the solid fraction of a particular pixel and α is the solid fraction of the entire image or reactor cross-section (Patel et al 2008). Alternatively pressure frequency and magnitude have been used to A pressure probe is usually located at the bed wall and according to Saxena et al (1993) the probe will only register damped pressure fluctuations that reaches the bed wall.…”

Section: Introductionmentioning

confidence: 99%

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