Abstract
Localized fluidization within a granular packing along an almost cylindrical chimney is observed when an upward fluid-flow, injected through a small port diameter, exceeds a critical flow-rate. Once this threshold reached, a fluidized area is first initiated in the close vicinity of the injection hole before gradually growing upward to the top surface of the granular layer. In this work, we present an experimental investigation specifically dedicated to the kinetics of chimney fluidization in an immersed granular bed. Two different transient regimes are identified depending on whether the expansion of the fluidized area is rather fast and regular, reaching the final chimney state typically in less than 10 seconds, or, on the contrary, slow and very progressively accelerated, giving rise to transient duration up to 1 hour or even more. Some systematic investigations allow to propose several empirical scaling relations for the kinetics of chimney fluidization in the fast regular regime.
Highlights
Many industrial processes rely on particle bed fluidization, induced in most cases by a uniform fluid flow [1]
A more systematic investigation was carried out to study the kinetics of fluidized area expansion, including the dependencies with the different control parameters, and to propose some empirical scaling relations
Q − 1 −n Qc where Qc appears as a critical flow rate while the exponent n remains between 1 and 0.5
Summary
Many industrial processes rely on particle bed fluidization, induced in most cases by a uniform fluid flow [1]. A systematic analysis of the fluidized area expansion with time was undertaken, based on the measurement of the total duration of the transient phase which allows distinguishing between a slow and very progressively accelerated transient regime and a faster and regular one. In this later regime, a more systematic investigation was carried out to study the kinetics of fluidized area expansion, including the dependencies with the different control parameters, and to propose some empirical scaling relations
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