Premium
Effect of vibration on agglomerate particulate fluidization
Author(s) -
Valverde Jose Manuel,
Castellanos Antonio
Publication year - 2006
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.10769
Subject(s) - agglomerate , fluidization , particle size , fluidized bed , mechanics , materials science , particulates , acceleration , coalescence (physics) , vibration , particle (ecology) , chemistry , composite material , thermodynamics , physics , classical mechanics , geology , oceanography , organic chemistry , quantum mechanics , astrobiology
Agglomerate particulate fluidization (APF), consisting of uniform bubbleless fluidization of agglomerated fine particles, has been observed in some fluidized beds of fine and ultrafine powders. Experiments performed in centrifugal fluidized beds (CFB) and vibrofluidized beds (VFB) show that the quality of fluidization is improved by increased effective acceleration. The Richardson‐Zaki modified equation is used, and a proposed criterion for agglomerate size is presented in order to predict the effect of the increase of gravitational acceleration on the APF bed. Following, model predictions are compared with experimental data on VFB of xerographic toners (particle size ≈ 10μ m) displaying APF in a wide interval of gas velocities. It is seen that the agglomerate size and agglomerate volume fraction ϕ* decrease as the effective acceleration is increased. The agreement with the model predictions is good, but at some critical acceleration visible bubbling is stimulated. At bubbling stimulation ϕ* is close to the value of ϕ* at the onset of bubbling in the absence of external vibrations when the gas velocity is increased up to the minimum bubbling velocity. This result indicates that the agglomerate size cannot be decreased indefinitely since at some critical point the concentration and size of local voids can be higher enough to yield the irreversible coalescence of voids into large bubbles. Particle agglomeration is, therefore, essential at some extent to the uniform fluidized state observed for fine particles. © 2006 American Institute of Chemical Engineers AIChE J, 2006