Effect of vertical vibration and particle size on the solids hold-up and mean bubble behavior in a pseudo-2D fluidized bed

Abstract

The solids hold-up and mean bubble behavior in a vertically-vibrated fluidized bed are experimentally studied in the present work by means of Digital Image Analysis (DIA) for four different powders with Geldart classifications A, B and A/B. The bed has a small thickness (i.e. pseudo-2D bed) and operates in bubbling regime subject to a wide range of gas superficial velocities, vibration frequencies and vibration amplitudes.Mean parameters of the bed and the bubbles, such as solids hold-up, bubble fraction, bubble number density and bubble diameter and velocity, are characterized here by averaging the results over time and space. The results reveal that vibration of the bed promotes a confinement of the bubble path to the central section of the bed. This bubble confinement is more intense for the smallest particles tested and for high vibration strengths and creates two different bubble regimes in the bed. In particular, close to the distributor, the bubble velocity decreases when increasing the vibration amplitude of the bed vessel because bubbles are smaller and less confined, and they behave like isolated bubbles. The behavior of bubbles changes when they are far from the distributor, where the interaction between bubbles becomes greater due to their bigger size and the confinement of bubbles induced by vibration. This confinement promotes coalescence of bubbles.It is shown that consideration of these two different regimes of bubble dynamics allows to shed light on understanding the apparently contradictory results encountered in the literature regarding bubble behavior in bubbling vibrated fluidized beds.

Investigation of Bubble Behavior in Gas‐Solid Fluidized Beds with Different Gas Distributors

“…The simulation results of the bubble diameter along the bed column were compared with the experimental data reported by Cano‐Pleite et al 27 who investigated the bubble behavior in a vertically vibrated pseudo‐2D fluidized bed by means of digital image analysis. The used experimental data are the results obtained under the same operating conditions such as superficial velocity, particle diameter, bed height, no vibration etc.…”

“…The bubbles tend to coalesce easily because the bubbles above the gas distributor are closer to each other for case 1 and larger for case 4. Consequently, the bubble velocity becomes higher due to both the acceleration of the trailing bubble prior to coalescence with the leading bubble of the upper position and the larger bubble formed by merging 13, 27.…”

Characteristics of Vibrating Fluidization and Transportation for Al2O3 Powder

“…There is much research on vibrating fluidized powder beds [ 19 , 20 , 21 , 22 , 23 , 24 ]. These studies have investigated the flow pattern [ 20 , 24 ] and flow characteristics [ 19 , 20 , 21 , 22 , 23 , 24 ] to the particulate materials of micron- and nano-size when the vibrating amplitude, frequency, and fluidized air velocity are changed.…”

“…There is much research on vibrating fluidized powder beds [ 19 , 20 , 21 , 22 , 23 , 24 ]. These studies have investigated the flow pattern [ 20 , 24 ] and flow characteristics [ 19 , 20 , 21 , 22 , 23 , 24 ] to the particulate materials of micron- and nano-size when the vibrating amplitude, frequency, and fluidized air velocity are changed. Regarding the particle dispersion in the vibrated powder bed, there is also an experimental study of the release of dust from cohesive powder by vibrating fluidization [ 25 , 26 ].…”

Vibration augmentation of the solids volume dragged by the wake of a bubble rising in a fluidized bed

“…Among the different experimental techniques aimed at characterizing the bed and bubble behavior in VFBs, Digital Image Analysis (DIA) is one of the most used, not only in VFBs but also in conventional fluidized beds [5,[8][9][10][11][12][13][14][15][16][17][18]. Conventional DIA can be combined with Particle Image Velocimetry (PIV) techniques to characterize the motion of particles in the bed.…”