超细颗粒在声场流化床中的流化特性

Fluidization Characteristics of Ultrafine Particles in a Sound-field Fluidized Bed

在内径为130mm的声场流化床中,以原生纳米级SiO2超细颗粒为物料,在声压水平为0～140dB、声波频率为0～500Hz范围内系统地考察了声波对超细颗粒流化特性的影响.结果表明:当声波频率为100～150Hz、声压大于130dB时,声波可以有效地消除节涌、抑制沟流、降低临界流化速度,显著地改善纳米SiO2颗粒的流化质量.在频率一定的情况下,声压越高,超细颗粒的临界流化速度越低,流化质量越好.当频率低于100Hz或高于150Hz时,随着频率的进一步降低或增加,超细颗粒的临界流化速度都增大,甚至又出现节涌和沟流,声波的效果减弱甚至消失.

Under different sound pressure levels, frequencies and weights of bed material, the fluidization characteristics and phenomena of SiO2 ultrafine powder, original nano-particle, were investigated in a transparent column with the 130 mm ID. The sound wave generated by a loudspeaker located above the bed had a sound pressure level SPL varying from 0 to 140 dB and frequency f varying from 0 to 500 Hz. It was found that the acoustic field could restrain channels, reduce minimum fluidization velocities, and improve the quality of fluidization dramatically at the sound frequencies of 100-150 Hz and the sound pressure level greater than 130 dB. Under the above sound wave frequency range, the minimum fluidization velocity umf will decrease when the SPL is increased. However, the improving effect of acoustic field on the quality of fluidization will be weakened, and even disappear when the sound frequency is lower than 100 Hz or greater than 150 Hz.