Fluidization characteristics in micro-scale fluidized beds with acoustic intensification

In a micro-scale fluidized bed (MFB) with inner diameter of 4.3 mm, the effects of adding acoustic field on the minimum fluidization velocity and fluidization quality of quartz and FCC catalyst particles were investigated. The experiment results show that the sound field added can improve the fluidization quality of the MFB; especially for quartz sand particles of 51 μm, adding sound field can disrupt channeling and stabilize the fluidization. The stronger the sound pressure applied, the more evident the improvement of the fluidization quality in the MFB, and the minimum fluidization velocity decreases monotonously with the increase of the sound pressure level. Under the same applied sound field, the decrease range of the minimum fluidization velocity in MFB is bigger than that in fluidized bed with bigger size dimension. It was found that the minimum fluidization velocities of FCC (83 μm) and three kinds of quartz sand particles (51, 67 and 83μm) have their minimum value when the applied sound frequencies are 140, 90, 90 and 140 Hz, respectively. With the assistance of acoustic wave added, the minimum fluidization velocities in micro-scale fluidized beds with inner diameters of 4.3, 5.5, 10.5 and 15.5 mm can be decreased by 9%~21%. For the MFBs, the smaller the inner diameter, the bigger the bed voidage, the more beneficial the realization of the intensification by externally added sound field and the bigger the decrease range of the minimum fluidization velocity.