粒径及声场对SiO2超细颗粒流化行为的影响

采用内径为56 mm的玻璃管流化床，考察了平均粒径分别为5~10 nm(1#), 0.5 mm(2#)及10 mm(3#)的SiO2超细颗粒在无声场及声场存在下的流化行为. 无声场时，1#和2#颗粒可在较高的气速下形成稳定聚团，单位质量颗粒团间作用力与原生颗粒相比显著下降，因而可实现稳定的聚团流化，3#颗粒因颗粒间粘性力较大，无法实现稳定流化. 40~60 Hz的声场对3种超细颗粒的流化行为均可起到一定的改善作用，在此频率范围外，声场的作用不明显. 提高声压级，可以使1#和2#颗粒团发生一定程度的破碎，聚团尺寸减小，最小流化速度降低. 在实验范围内，添加声场无法使3#颗粒实现稳定流化.

Influences of Particle Size and Acoustic Field on Fluidization of SiO2 Ultrafine Particles

Fluidization behavior of three kinds of SiO2 powder with different sizes and influence of acoustic field were investigated in a 56 mm i.d. glass tube fluidized bed. The average diameters of the three kinds of powder were 5~10 nm (sample 1#), 0.5 mm (sample 2#) and 10 mm (sample 3#), respectively. The particles of samples 1# and 2# could form stable agglomerates under high gas velocity, thus the cohesive force of unit mass was decreased and stable fluidization achieved. However, no stable agglomerates were observed during fluidization of 3# particle sample, which was never fluidized stably. Sound wave could improve the fluidization behavior within a given range of sound frequencies (40~60 Hz) for all the three kinds of powder. The sizes of agglomerates decreased and the minimum fluidization velocities reduced with increasing sound pressure level for 1# and 2# particle samples. Whereas 3# particle sample could never be fluidized smoothly even under sound energy action.