Models for prediction of hydrodynamic characteristics of gas–solid tapered and mini-tapered fluidized beds

Khani, Mohammad Hassan

doi:10.1016/j.powtec.2010.09.018

Cited by 33 publications

(25 citation statements)

References 13 publications

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“…The flow regimes change from fixed beds to partially, fully, transition, and turbulently fluidized beds with an increase in the fluid velocity . In some other studies, the first three regimes were also observed. , In the case of the partial fluidization regime, a central fully fluidized region coexists with a peripheral unfluidized region. ,− The fraction of this unfluidized region decreases with the gas velocity at a given taper angle. ,, The reason for this core–peripheral flow structure is the motion of bubbles. The bubbles prefer to pass through the bed center rather than the bed periphery.…”

Section: Introductionmentioning

confidence: 85%

“…12 In some other studies, the first three regimes were also observed. 16,18 In the case of the partial fluidization regime, a central fully fluidized region coexists with a peripheral unfluidized region. 7,19−21 The fraction of this unfluidized region decreases with the gas velocity at a given taper angle.…”

Section: Introductionmentioning

confidence: 99%

“…The hydrodynamics of tapered fluidized beds controls the heat and mass transfer and reaction kinetics. The crucial parameters governing their hydrodynamics are maximum bed pressure drop, Δ P max , minimum fluidization velocity, U mf , the minimum velocity of full fluidization, U mff , along with the ratio of bed expansion, R . − It was found that the former three parameters increase with the rise in the mean particle diameter, initial bed height, and taper angle . It was observed that the rise in gas velocity and the fall in the taper angle, particle size, particle density, and initial bed height causes the ratio of bed expansion to increase .…”

Section: Introductionmentioning

confidence: 99%

“…It was observed that the rise in gas velocity and the fall in the taper angle, particle size, particle density, and initial bed height causes the ratio of bed expansion to increase . The empirical correlations are also developed to predict these main hydrodynamic parameters. − The first three hydrodynamic parameters are obtained from the bed pressure drop versus fluid velocity profiles.…”

Section: Introductionmentioning

confidence: 99%

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Experimental Study of Bubble Behavior in a Two-Dimensional Gas–Solid Tapered Fluidized Bed

Sahoo

Sarkar

2021

Ind. Eng. Chem. Res.

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The hydrodynamics of tapered fluidized beds is significantly different from the columnar beds due to the variation of the cross-sectional area along the height. The hydrodynamic behavior in tapered beds was studied experimentally using an image analysis method. The peripheral unfluidized region was quantified through the overlapping of binary images. Further, the effect of the taper angle and air velocity on the bubble size, shape, fraction, and rise velocity, along with the bed expansion ratio and the unfluidized region, was investigated. A new method is proposed to obtain expanded bed height from an image. The time-averaged bed expansion ratio and bubble fraction increase with the air velocity and decrease with the taper angle, while a reverse trend is observed for the mean unfluidized area fraction. Correlations are proposed for predicting the bubble fraction, bed expansion ratio, and unfluidized area fraction. An operating regime map is also proposed based on the unfluidized region.

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Section: Introductionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Experimental Study of Bubble Behavior in a Two-Dimensional Gas–Solid Tapered Fluidized Bed

Sahoo

Sarkar

2021

Ind. Eng. Chem. Res.

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“…△P is magnified when the approach air velocity is increased (16). In addition, F d and F b will also increase, causing the pellet bed to expand and bed voidage to increase (17). The reduced resistance to the air flow will help to set the pellets in motion.…”

Section: Pellet Flow Patternsmentioning

confidence: 99%

A Feasibility Study on Pellet Coating Using a High-Speed Quasi-continuous Coater

et al. 2012

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Abstract. Pellet coating is traditionally carried out using the Wurster coater. This study investigated the feasibility of pellet coating in a newly developed coater built with a unique airflow system, the Supercell™ coater (GEA Pharma Systems, UK). A full factorial design study was carried out to evaluate the influences of the spray rate of the coating dispersion, batch size of the pellet load, pellet size fraction and plenum pressure of the fluidizing air on the color coating of pellets in the Supercell™ coater. Results showed that pellets could be successfully coated using the Supercell™ coater. Higher plenum pressures and lower spray rates were found to minimize pellet agglomeration during coating. Although coating efficiencies were comparable amongst the different pellet size fractions, larger batch sizes of pellets were coated with higher efficiencies. Process optimization was carried out for each pellet size fraction and a large batch size (120 g) in combination with a high plenum pressure (1,500 mm WC) were deemed optimal. Optimal spray rates differed according to pellet size fraction and a lower spray rate was required for smaller pellets. Pellet flow patterns observed during coating were dependent on the pressure drop across the fluidized load. A 'swirling' pellet flow pattern was generally observed at coating conditions which led to optimal outcomes.

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Numerical simulation of homogeneous fluidization behaviour of Geldart Group A particles in gas tapered fluidized beds

2022

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A two-dimensional gas-solid tapered fluidized bed at laboratory-scale in a homogenous fluidization regime is simulated using the computational fluid dynamics (CFD) software COMSOL 5.4. The Eulerian-Eulerian (EE) hydrodynamic model is used to predict the minimum fluidization velocity, minimum bubbling velocity, bed height, and solid volume fraction of alumina particles (in Geldart Group A) in the bed with different tapered angles.The effects of static bed heights on the minimum fluidization velocity of tapered beds are investigated. The highest minimum fluidization velocity is 6 mm/s with a static height of 11 mm and a tapered angle of 12 . The bed height is increased with increasing superficial air velocity. At a given air velocity, the minimum bed height is obtained at a 12 tapered angle. A decrease in solid volume fraction is also observed upon an increase in the superficial air velocity. The CFD results show an almost uniform solid concentration over the bed height. The homogenous or non-bubbling regime appears in a wider range of critical velocity at a 12 tapered angle. In the case of a 0 tapered angle, the results of this study and the discrete element method computational fluid dynamics (DEM-CFD) simulation exhibit a good match. In the case of 6 and 12 tapered angles, the proposed model leads to good predictions based on the theory of homogenous fluidization of Geldart Group A. This research introduces a rapid and cost-effective approach for the better design and operation of a tapered fluidized bed in large scales.

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Models for prediction of hydrodynamic characteristics of gas–solid tapered and mini-tapered fluidized beds

Cited by 33 publications

References 13 publications

Experimental Study of Bubble Behavior in a Two-Dimensional Gas–Solid Tapered Fluidized Bed

Experimental Study of Bubble Behavior in a Two-Dimensional Gas–Solid Tapered Fluidized Bed

A Feasibility Study on Pellet Coating Using a High-Speed Quasi-continuous Coater

Numerical simulation of homogeneous fluidization behaviour of Geldart Group A particles in gas tapered fluidized beds

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