Study On Fluidization Characteristics Of SiO₂ Nano-particles In A Sound-assisted Fluidized Bed

The fluidized techniques of nano-particles are gaining increasing importance along with the great application of particles to the manufacture industry. But the fluidization of nano-particles easily results in channeling and poor fluidized behavior as a consequence of strong particle-to-particle cohesiveness. So various techniques have been proposed to improve the quality of fluidization of nano-particles. Especially, the sound-assisted fluidization of nano-particles is researched in this work. A two dimensional bed which cross section is 130×10mm² and a three dimensional bed which ID is 130mm are designed to study the effects of sound wave frequency and sound pressure level on the fluidization of the nano-particles. The SiO₂ nano-particles have been fluidized in the beds. The experimental results prove that the quality of fluidization of particles is dramatically improved by the application of acoustic field of appropriate SPLs, and the air bubbles grow bigger in the sound (when SPL up to 138 dB, the air bubbles become slugging fluidization in the two dimensional bed). There are cracks , channels in the two dimensional bed and the three dimensional bed, and pistons in the three dimensional bed without sound. However, cracks, channels or pistons are disappear with sound. Especially the minimum fluidization velocity and the size of agglomerations have minimum values when the frequency of sound waves is 120Hz and they will decrease as the sound pressure level increases. A good quality of fluidization can exist in a greater ranges of frequency of sound when the SPL is higher. The theoretical calculations are accordant with the experimental results in the three dimensional bed and it shows that the theoretical model can successfully describe the influence of the acoustic field on fluidization of the particles by Liang etc.