Raining of particles from an emulsion-gas interface in a fluidized bed

Lim, K. S. ; Khakhar, D. V. ; Chen, Z. ; Agarwal, P. K. (1997) Raining of particles from an emulsion-gas interface in a fluidized bed Chemical Engineering Communications, 161 (1). pp. 205-229. ISSN 0098-6445

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Related URL: http://dx.doi.org/10.1080/00986449708936627


This paper deals with the raining of particles from an interface between a dense fluidized phase and a gas phase with the fluidized phase uppermost. Such interfaces occur at the upper surfaces of gas bubbles and slugs in fluidized beds. Particle rain in these cases would enhance contact between gas and particles within the bubbles and slugs. The rise velocities of single square-nosed slugs injected in incipiently fluidized beds of different diameters were measured. Relatively small columns of internal diameters of 0.0125, 0.019 and 0.0254 m were employed in the experiments; In such beds, square-nosed slugs are formed which span the entire cross-section of the beds and rise entirely due to raining of particles from their top surfaces. Since the upper surface of such slugs is flat, their motion can be analyzed using the one-dimensional hydrodynamic theory. Glass ballotini and sand of different sizes were used as bed particles. Comparison of theory and experiment has enabled the determination of the dimensionless gradient diffusivity characterizing the motion of particles induced by a gradient in the void fraction. The results confirm the scaling proposed by Batchelor (1988). The use of the calculated gradient diffusivity in the criterion for stability of a gas fluidized bed predicts the systems under consideration to be always unstable.

Item Type:Article
Source:Copyright of this article belongs to Taylor and Francis Ltd.
Keywords:Particle Rain; Square-nosed Slug; Slug Rise Velocity; Fluidized Bed; Hydrodynamic Model
ID Code:17508
Deposited On:16 Nov 2010 09:40
Last Modified:17 May 2016 02:08

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