Jc. Schouten et al., Scale-up of bottom-bed dynamics and axial solids-distribution in circulating fluidized beds of Geldart-B particles, CHEM ENG SC, 54(13-14), 1999, pp. 2103-2112
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, exh
ibits 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 d
ynamic 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 small
er than 3.5; (b)'exploding bubble without wall effect' in risers with a dia
meter larger than 0.7 m and with a bed aspect ratio smaller than 3.5; (c)'c
irculating slugging' in narrow risers at bed aspect ratios larger than 5. T
he term 'wall effect' indicates that the wall of the riser imposes limitati
ons to the growth of the exploding bubbles and to the solids flow in the de
nse bottom-bed. Non-dimensional correlations are presented, for each of the
se types of dynamic behavior, for the Kolmogorov entropy, quantifying the d
ynamic flow behavior, and for the decay-parameter a, describing the decay o
f the solids volume fraction in the splash zone above the bottom-bed. These
correlations were developed using pressure fluctuation and time-averaged p
ressure-drop data that were measured in five CFB risers varying in size fro
m 0.083 m LD to 1.2 x 0.8 m using the same type of Geldart-B sand. (C) 1999
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