Bubble behavior in corrugated‐wall bubbling fluidized beds—Experiments and CFD simulations

Abstract

A new concept to harness bubble dynamics in bubbling fluidization of Geldart D particles was proposed. Various geometrical declinations of a cold‐prototype corrugated‐wall bubbling fluidized bed were compared at different flow rates (Ug) to conventional flat‐wall fluidized bed using high‐speed digital image analysis. Hydrodynamic studies were carried out to appraise the effect of triangular‐shaped wall corrugation on incipient fluidization, bubble coalescence (size and frequency), bubble rise velocity, and pressure drop. Bubble size and rise velocity in corrugated‐wall beds were appreciably lower, at given Ug/Umb, than in flat‐wall beds with equal flow cross‐sectional areas and initial bed heights. The decrease (increase) in size (frequency) of bubbles during their rise was sustained by their periodic breakups while protruding through the necks between corrugated plates. Euler‐Euler transient full three‐dimensional computational fluid dynamic simulations helped shape an understanding of the impact of corrugation geometry on lowering the minimum bubbling fluidization and improving gas distribution. © 2011 American Institute of Chemical Engineers AIChE J, 2012

Effect of vertical internals on the pressure drop in a gas‐solid fluidized bed

“…[5] Various methods have been used to overcome the drawbacks of the gas-solid fluidized beds, and these include using a secondary fluidizing medium, [1] implementing mechanical stirrers [9] and baffled promoters, [6,10] operating in multistage units, [4] vibration of the bed and modification of the bed geometry, [4,8] using different types and configurations of internals, [5,11] and the use of corrugated walls in the bubbling fluidized bed. [12][13][14][15] Khan Wardag and Larachi and Khan Wardag et al have proven [12][13][14][15] that the implementation of corrugated walls inside the bubbling fluidized beds has several advantages such as improving gas distribution and heat transfer, promoting solids mixing and bubble size reduction, repelling the transition to bubbling, and smoothing out gas disengagement. Among all of the above, various kinds of methods are used to enhance the fluidization quality and to minimize the problems associated with the operating of the gas-solid fluidized beds.…”

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

“…Cohesive force may exist in the fluidized beds with different forms, such as van der Waals force, − electrostatic force, , liquid bridge force, − and particle bridge force. , Basically, the existing studies on fluidized beds with cohesive particles mainly focus on: (i) the transition of fluidization behaviors between different groups according to Geldart classification; − (ii) collapse and expansion behaviors of the bed; − (iii) minimum fluidization, particle motion and bubbling characteristics. − Out of the many characteristics of the fluidization hydrodynamics, the bubble behaviors strongly influence the particle motion and mass transfer , in addition to being affected by the interaction between particles. − A detailed understanding of the bubble behaviors is helpful for improving and optimizing the operation of fluidized beds with cohesive particles.…”

Bubble–wall interaction for asymmetric injection of jets in solid–gas fluidized bed

“…It is well established in flow of bubbles in viscous fluid that the containing wall greatly affects the velocity (Collins, 1967), shape elongation and wake formation (Bhaga and Weber, 1981). Wardag and Larachi (2012) have used corrugated wall for the fluidized container to show its impact on bubble size and distribution. The wall has also been shown to affect the minimum fluidisation velocity (Saxena and Vadivel, 1988 Glicksman and McAndrews (1985) experimentally studied the effect of bed thickness on the hydrodynamics of large particles in fluidized beds and concluded that the two-dimensional beds exhibit larger bubbles, higher bubble voidage, higher bubble flow rate than their three dimensional counterpart for similar bed height and superficial velocity.…”