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Dominant flow structures in gas–liquid–solid fluidized beds
Author(s) -
ArjmandiTash Omid,
Zarghami Reza
Publication year - 2015
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.22143
Subject(s) - flatness (cosmology) , mechanics , fluidization , skewness , bubble , standard deviation , fluidized bed , materials science , slugging , low frequency , range (aeronautics) , flow (mathematics) , analytical chemistry (journal) , chemistry , thermodynamics , chromatography , physics , mathematics , composite material , statistics , cosmology , quantum mechanics , astronomy
Effective time series analysis techniques in time and frequency domains were applied to characterize three‐phase fluidization under a wide range of gas and liquid velocities. The experiments were carried out in a laboratory scale fluidized bed, operated under ambient conditions. Standard deviation of pressure fluctuations successfully detected four distinct regimes, namely compacted bed, agitated bed, coalesced and discrete bubble regimes (or discrete and dispersed bubble regimes at extremely low gas velocities). A minimum in skewness and average cycle frequency and a maximum in flatness indicated a minimum deviation from larger structures of the bed. A transition between macro and finer structures occurred during agitated bed regime and accordingly, minimum liquid fluidization velocity was perceived by skewness, flatness, and average cycle frequency analyses. The results showed that at very low liquid velocities in the compacted bed regime, the power spectrum at lower frequencies slightly increased with increasing liquid velocity. This results in the consecutive appearance of single bubbles of low frequencies. With further increase in the liquid velocity at agitated bed regime the power spectrum at lower frequencies gradually decreased. At higher liquid velocities near U Lmf , the peak dominant frequency is transmitted from low frequency ranges of 2 Hz to the higher frequency of about 10 Hz.