Scale-up of bottom-bed dynamics and axial solids-distribution in circulating fluidized beds of Geldart-B particles

J.C. Schouten, R.C. Zijerveld, C.M. Bleek, van den

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26 Citations (Scopus)

Abstract

In this paper it is shown that the gas flow pattern in the dense bottom-bed of circulating fluidized beds, operated with Geldart-B type of solids, exhibits three different types of dynamic behavior, dependent on the width of the riser and on the aspect ratio of the dense bottom-bed. These types of dynamic behavior are defined as: (a) ‘exploding bubble with wall effect’ in risers with a diameter smaller than 0.7 m and with a bed aspect ratio smaller than 3.5; (b) ‘exploding bubble without wall effect’ in risers with a diameter larger than 0.7 m and with a bed aspect ratio smaller than 3.5; (c) ‘circulating slugging’ in narrow risers at bed aspect ratios larger than 5. The term ‘wall effect’ indicates that the wall of the riser imposes limitations to the growth of the exploding bubbles and to the solids flow in the dense bottom-bed. Non-dimensional correlations are presented, for each of these types of dynamic behavior, for the Kolmogorov entropy, quantifying the dynamic flow behavior, and for the decay-parameter a, describing the decay of the solids volume fraction in the splash zone above the bottom-bed. These correlations were developed using pressure fluctuation and time-averaged pressure-drop data that were measured in five CFB risers varying in size from 0.083 m ID to 1.2×0.8 m using the same type of Geldart-B sand.
Original languageEnglish
Pages (from-to)2103-2112
JournalChemical Engineering Science
Volume54
Issue number13-14
DOIs
Publication statusPublished - 1999

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