The influence of the frequency of acoustic waves on sound-assisted fluidization of beds of fine particles

Abstract Sound-assisted fluidization of nonfluent 0.5–45 μm catalyst particles has been studied with a 145 mm i.d. column. Different amounts of solids of weight W ranging from 1 to 3 kg have been charged in the column. A loudspeaker generated an acoustic field, above the bed, with a sound pressure level SPL (referred to 20 μPa) varying from 110 to 140 dB and a frequency f varying from 30 to 1000 Hz. The improvement of the quality of fluidization obtained with certain combinations of W , SPL and f has been attributed to the breakup of clusters originally forming the bed into subclusters. For given W and SPL, the ranges of frequency within which channel-free homogeneous fluidization could be obtained have been determined, and within these ranges the kinds of curves for sizes of subclusters d s as a function of the frequency have been outlined. The nonmonotonic form of these curves could not be explained by means of the original sound-assisted fluidization model, which assumes a rigid cluster-subcluster structure. The existence of elastic forces between clusters and subclusters, assumed by the cluster/subcluster oscillators model, yields theoretical d s versus f curves with the same trend as those from experiments.

[1]  Kan-ich Suzuki,et al.  CHARACTERISTICS OF VIBRO-FLUIDIZED BED FOR DRYING OF WETTED AND AGGLOMERATED PARTICLES , 1980 .

[2]  Leonard Meirovitch,et al.  Elements Of Vibration Analysis , 1986 .

[3]  J. Visser,et al.  Van der Waals and other cohesive forces affecting powder fluidization , 1989 .

[4]  O. R. Walton,et al.  A single-particle friction cell for measuring contact frictional properties of granular materials , 1991 .

[5]  O. Levenspiel,et al.  The uses of magnetic fields in the processing of solids , 1983 .

[6]  Riccardo Chirone,et al.  Bubble-free fluidization of a cohesive powder in an acoustic field , 1993 .

[7]  G. Donsì,et al.  Cohesive forces between particles of fluid-bed catalysts , 1976 .

[8]  R. Chirone,et al.  Sound-assisted aeration of beds of cohesive solids , 1994 .

[9]  L. Massimilla,et al.  The structure of bubble-free gas fluidized beds of fine fluid cracking catalyst particles , 1972 .

[10]  L. Fan,et al.  Performance of a rotating fluidized bed , 1984 .

[11]  Alex C. Hoffmann,et al.  The effect of vibration on the fluidization behaviour of some cohesive powders , 1994 .

[12]  G. Donsì,et al.  The influence of bed moisture on fluidization characteristics of fine powders , 1979 .

[13]  S. Ergun.  Fluid flow through packed columns , 1952 .

[14]  W. Flügge.  Handbook of Engineering Mechanics , 1962 .

[15]  R. D. Morse.  Sonic Energy in Granular Solid Fluidization , 1955 .

[16]  Ye-Mon Chen,et al.  Fundamentals of a centrifugal fluidized bed , 1987 .

[17]  J. Beeckmans,et al.  Solids mixing kinetics and segregation in a vibrostabilized fluid bed , 1987 .

[18]  J. Arnaldos,et al.  Magnetically stabilized fluidization: modelling and application to mixtures , 1985 .