Bubble Behaviors of Large Cohesive Particles in a 2D Fluidized Bed

Abstract

Fluidization hydrodynamics is greatly influenced by interparticle cohesive forces. In this paper, we study the bubbling behaviors of cohesive Geldart B particles in a 2D fluidized bed, using the “polymer coating” approach to introduce cohesive force. The effect of cohesive force on bubbles can be differentiated into two regimes: (i) by increasing the cohesive force within a low level, the bubble number increases, while the bubble fraction and bubble diameter decrease; (ii) when the force is large enough to cause the particles to adhere to the side walls of the bed, the bubble numbers and the bed expansion sharply decrease. With the increasing cohesive force, the bubble shape changes from roughly circular shape, to oblong shape, leading to the “short pass” of fluidizing gas through the bed. Finally, we analyzed the switching frequency and standard deviation of local pixel values to characterize the bubble dynamics.

Fluidization dynamics of cohesive Geldart B particles. Part I: X-ray tomography analysis

“…And then, the bubble size in turn increases [34]. Our early work also observed similar trends in a 2D fluidized bed [35]. The rising velocity and passage frequency of bubbles under different cohesive forces were also studied [36].…”

CFD–DEM simulations of wet particles fluidization with a new evolution model for liquid bridge

“…Furthermore, the measured bubble volume is apparently larger in a wet bed. Ma et al 49 pointed out that F I G U R E 1 0 Effects of liquid bridge evolution model on bubble behavior in a wet bed (liquid property: Λ = 0.8 wt% and μ l = 5 mPa s)…”

“…The bubble fraction was found to increase with the superficial gas velocity when the gas enters uniformly. 49 According to the discussions in Sections 4.1 and 4.2, U 0 was set to be 0.5 m/s for the dry bed and 0.6 m/s for the wet bed for Λ = 0.8 wt% and μ l = 5 mPa s. Therefore, the effects of background gas velocity might overweigh the effects of the inter-particle cohesive force, causing an enlarged bubble in a wet bed.…”

Analysis of the effect of small amounts of liquid on gas–solid fluidization using CFD‐DEM simulations

“…The hydrodynamics of granular flows and fluidized beds can be influenced significantly by interparticle forces, arising from van der Waals interactions, electrostatics, small amounts of liquid, or sticky surface coatings . Adding small amounts of liquid to granular flows and fluidized beds is necessary in a variety of processes, particularly in the energy and pharmaceuticals industries .…”