Minimum fluidization velocities for gas–solid 2D beds

Caicedo, Guadalupe Ramos; Ruı́z, Mónica Garcı́a; Marqués, Juan J. Prieto; Soler, Jesús Guardiola

doi:10.1016/s0255-2701(02)00005-3

Cited by 47 publications

(24 citation statements)

References 8 publications

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“…One of the most important parameters to characterize fluidized bed 1 Corresponding Author: David Escudero (drescude@iastate.edu) 47 conditions is the mm1mum fluidization velocity (Umr) [1], which is related to the drag force needed to attain solid suspension in the gas phase. The minimum fluidization velocity also constitutes a reference for evaluating fluidization intensity when the bed is operated at higher gas velocities [2].…”

Section: Introductionmentioning

confidence: 99%

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Acoustic Field Effects on Minimum Fluidization Velocity in a 3D Fluidized Bed

Escudero

Heindel

2012

Volume 2: Fora

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Fluidized beds are used in a variety of process industries because they provide uniform temperature distributions, low pressure drops, and high heat/mass rates. Minimum fluidization velocity is an important factor in understanding the hydrodynamic behavior of fluidized beds, and this characteristic may be modified through high frequency (sound) vibrations. The effects caused by sound wave frequency on the minimum fluidization velocity in a 3D fluidized bed are investigated in this study. Experiments are carried out in a 10.2 cm ID cold flow fluidized bed filled with glass beads with material density of 2600 kg/m 3 , and particles sizes ranging between 212-600 μm. In this study, four different bed height-to-diameter ratios are examined: H/D = 0.5, 1, 1.5, and 2. Moreover, the sound frequency of the loudspeaker used as the acoustic source ranges between 50-200 Hz, with a sound pressure level fixed at 110 dB. Results show that the minimum fluidization velocity is influenced by the frequency change. As the frequency increases, the minimum fluidization velocity decreases until a specific frequency is reached, beyond which the minimum fluidization velocity increases. Thus, acoustic fields provide an improvement in the ease of fluidization of these particles. ABSTRACT Fluidized beds are used in a variety of process industries because they provide uniform temperature distributions, low pressure drops, and high heat/mass rates. Minimum fluidization velocity is an important factor in understanding the hydrodynamic behavior of fluidized beds, and this characteristic may be modified through high frequency (sound) vibrations. The effects caused by sound wave frequency on the minimum fluidization velocity in a 3D fluidized bed are investigated in this study. Experiments are carried out in a 10.2 em ID cold flow fluidized bed filled with glass beads with material density of 2600 kg/m 3 , and particles sizes ranging between 212-600 J.lm. In this study, four different bed height-todiameter ratios are examined: HID = 0.5, 1, 1.5, and 2. Moreover, the sound frequency of the loudspeaker used as the acoustic source ranges between 50-200 Hz, with a sound pressure level fixed at 110 dB. Results show that the minimum fluidization velocity is influenced by the frequency change. As the frequency increases, the minimum fluidization velocity decreases until a specific frequency is reached, beyond which the minimum fluidization velocity increases. Thus, acoustic fields provide an improvement in the ease of fluidization of these particles.

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Section: Introductionmentioning

confidence: 99%

“…Ramos et al [1] studied the minimum fluidization velocity for gas-solid 2D fluidized beds. They used a rectangular bed (1 x0.2x0.012 m) filled with glass beads of three different diameters (160-250, 250-400, and 490-700 !lm) and various bed heights (2, 4, 8, 16, 20, 40, and 60 em).…”

Section: Introductionmentioning

confidence: 99%

Acoustic Field Effects on Minimum Fluidization Velocity in a 3D Fluidized Bed

Escudero

Heindel

2012

Volume 2: Fora

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“…Ramos Caicedo et al [27] fluidized glass ballotoni (density ρ s = 2550 kg/m 3 particle size d p = 250 − 400 μm) and demonstrated that the minimum fluidization velocity in 2D fluidized beds was dependent on the thickness and height of the bed. Thus, significant differences in the U mf (up to 500%) were detected when the bed height was varied from h = 8 cm to h = 60 cm (bed thickness t = 6 mm).…”

Section: Introductionmentioning

confidence: 99%

“…Thus, significant differences in the U mf (up to 500%) were detected when the bed height was varied from h = 8 cm to h = 60 cm (bed thickness t = 6 mm). Ramos Caicedo et al [27] proposed a correlation for the extrapolation of the U mf in 2D fluidized beds to the U mf of a 3D bed; however, the constant in the proposed correlation was dependent on the particle size. Thus, the correlation could not be used when different experimental conditions were applied.…”

Section: Introductionmentioning

confidence: 99%

On the minimum fluidization velocity in 2D fluidized beds

et al. 2011

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a b s t r a c tIn the present study, a new correlation for the determination of the minimum fluidization velocity in 2D fluidized beds was developed. The proposed correlation was based on the experimental results obtained in 2D fluidized beds with different particle sizes, bed thicknesses and bed heights. Thus, the proposed correlation depends only on the nondimensional variable t/d p , where t is the bed thickness and d p is the particle size. The proposed correlation was compared with other experimental results that can be found in the literature, and two different trends were observed. Namely, one set of experimental results was in accordance with the proposed correlation, while the other set deviated from the theoretical results. In particular, the minimum fluidization velocities of the experimental results were greater than the predicted values of the proposed correlation. In view of the differences in the experimental conditions, the observed discrepancies may be attributed to the effects of electrostatic charge and particle shape. In addition, the experimental fluidization defluidization curves were compared to the theoretical results of Jackson's model, and the parameters were fitted to the experimental data. However, Jackson's model is based on a 1D bed; thus, general parameters could not be obtained for a bed with a fixed particle size and thickness due to the two dimensional voidage distribution in the bed and bed cohesion effects, which are a result of electrostatic forces and are not considered in Jackson's model.

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“…Hence, we decided to investigate how the choice of bed depth value affects the numerical prediction of In the literature, the effect of the bed thickness has mainly been studied with respect to the minimum fluidization velocity. It was observed that the latter increases as the bed thickness decreases (Caicedo et al, 2002;Kathuria & Saxena, 1987;Sanchez-Delgado et al, 2011;Saxena & Vadivel, 1988). This is because, as the bed depth reduces, the effect of wall friction becomes more pronounced, limiting the movement of the particles.…”

Section: Dem Simulationsmentioning

confidence: 97%

Lateral solid mixing in gas-fluidized beds: CFD and DEM studies

Oke

Wachem

Mazzei

2016

Chemical Engineering Research and Design

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We investigated lateral solid mixing in gas-fluidized beds using CFD and DEM. We ran 3D CFD simulations, comparing the results with those formerly obtained in 2D CFD simulations. We observed that the frictional stress model affects the numerical results. This was also observed in 2D simulations, but in 3D simulations the effect is less pronounced. The 3D simulations described the lateral solid mixing process more accurately than the 2D simulations, simulation dimensionality being an important factor. To analyse further the role of frictional stress models, we ran 3D DEM simulations, employing the soft-sphere approach to model the particle-particle contact forces. The simulation results agreed reasonably well with the empirical data, but their accuracy depended on the values used for the collision parameters; also, the 3D CFD simulations matched the empirical data more closely.Altogether, we concluded that the simulation dimensionality plays the dominant role in predicting lateral solid mixing accurately.

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Minimum fluidization velocities for gas–solid 2D beds

Cited by 47 publications

References 8 publications

Acoustic Field Effects on Minimum Fluidization Velocity in a 3D Fluidized Bed

Acoustic Field Effects on Minimum Fluidization Velocity in a 3D Fluidized Bed

On the minimum fluidization velocity in 2D fluidized beds

Lateral solid mixing in gas-fluidized beds: CFD and DEM studies

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