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Channels and chains of bubbles in gas fluidized beds
Author(s) -
Botterill J. S. M.,
Bloore P. D.
Publication year - 1963
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.5450410306
Subject(s) - fluidization , pressure drop , mechanics , disturbance (geology) , bubble , fluidized bed , flow (mathematics) , materials science , volume (thermodynamics) , drop (telecommunication) , geology , thermodynamics , physics , geomorphology , telecommunications , computer science
Abstract The disturbance caused by the development of channels and chains of bubbles through gas fluidized beds has been studied using a local gas injection technique. The average disturbance formed was measured using a γ‐radiation absorption technique supplemented by pressure drop and bed expansion measurements. The channels or close chains of bubbles were found to persist through the bed to a height dependent on bed conditions and the energy of the gas flow through the disturbance. The disturbance then degenerated into larger bubbles which tended to coalesce, grow and become more widely separated. The rate of increase of disturbance diameter was inversely proportional to the square of the estimated gas flow velocity through the disturbance. Bubble spacing increased through the upper elements of the disturbance. It was concluded that the resistance to flow of escape gas through this part of the chain was increased and that this caused an increase in gas residence time corresponding to the observed increase in resident void volume in the upper elements of the disturbance. The channel or close chain of bubbles provided a low resistance path by which gas readily escaped. In shallow beds at incipient fluidization the path readily reached through to the bed surface and reactant gasses may largely bypass the bed under these conditions and the bed cease to be fluidized.