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

Abstract

• X-ray tomography was used to reconstruct 3D bubbles in a bubbling bed. • The inter-particle cohesive force facilitates the coalescence of bubbles in the bed. • The fluidization fails as the whole bed slugging under large cohesive force.

Fluidization dynamics of cohesive Geldart B particles. Part II: Pressure fluctuation analysis

“…Similar trends were also observed by Zhang et al [58]. As the bed temperature increases below 35°C, a tiny increase of σ p is observed, indicating a slight increase in the bubble size, which agrees well with the companion work (Part I) [18]. When the temperature exceeds 35°C, σ p sharply increases then decreases for the measurement heights of 30 mm, 110 mm and 190 mm while rises monotonically for 270 mm.…”

“…6(c) and (d)), implying that the size of normal bubbles considerably rises in the vicinity of bed surface. It is worth pointing out that our companion work (Part I) reported different behaviors that the average size of 'bubbles' near the bed surface changes slowly with the cohesive force [18]. The difference may be attributable to the presence of gas slugs (its definition has been given in Part I) under strong cohesive force, because X-ray tomography used in Part I captures both normal bubbles and gas slugs.…”

“…The geometric construction of the experimental apparatus and the preparation of cohesive particles have been introduced in the companion work (Part I) [18]. This paper mainly focuses on how to measure and analyze the pressure fluctuation signals.…”

“…liquid content [13], liquid distribution [14,15] and liquid migration between free particles and agglomerates [16,17], have been widely investigated. In the companion work, we reported bubbling dynamics of cohesive Geldart B particles by means of multi-source X-ray tomography analysis [18]. The inter-particle cohesive force was found to facilitate bubble coalescence, leading to an increase in bubble size and decrease in bubble numbers.…”

“…Obviously, for a better understanding and more targeted optimization of the fluidization dynamics of cohesive particulate systems it is of prime importance to know the inner details of such transition process. Besides that, the companion work (Part I) has reported that the defluidization pattern of the bed under strong cohesive force is whole-bed slugging [18]. Nevertheless, the cause of slugging and the approach for repressing such slugging is still unknown.…”