Experimental investigation on the bubble characteristics in a gas-solid sound-assisted separation fluidized bed

Bubble characteristic is one of the most important parameters affecting back-mixing/circulation and mixing/segregation processes of the particles, and this characteristic may be modified through sound vibrations. The effects of the acoustic field on the bubbles number, size and frequency were systematically investigated in a sound pressure level range of 110–130 dB at the frequencies of 110–170 Hz. Results show that the most pronounced inhibition effect of the acoustic on the bubble size was achieved in the frequency range of 120–130 Hz. Independently of how the sound pressure level and sound frequency were adjusted, the bubble size inhibition index decreased first and then increased along the bed height. As the sound pressure level increased to 130 dB, the number of large bubbles (>2 cm) almost disappeared. At the sound frequency of 130 Hz, the ratio of the bubble frequency in the presence of the sound field to that in the absence of the sound field was less than 1. A bubble size distribution prediction model was established to make up for the lack of information on bubble growth prediction in sound-assisted fluidized beds, and the error of the bubble size distribution model was found to be within 17 %.