Characterization of pressure fluctuation signals in an acoustic bubbling fluidized bed

The pressure fluctuation of the fluid catalytic cracking (FCC) particles was described using a pressure transducer probe in an acoustic bubbling fluidized bed. The effect of sound frequency and sound pressure level on the pressure fluctuation was researched in this work. The results showed that the minimum fluidization velocity has a minimum value when the frequency of sound waves was 150 Hz, and decreased as the sound pressure level was increased at the same sound frequency. On the basis of discrete wavelet transform, an original signal was resolved into six detailed scale signals. It was found that the scalograms obtained by wavelet transform provide both the localization of scale and time, and make it possible to identify the status of the bed such as the passage of bubbles. The results indicated that the dominant frequency decreased with increasing sound frequency from 50 to 150 Hz, and further increased with increasing sound frequency from 150 to 500 Hz. The dominant frequency has a minimum value at a sound frequency of 150 Hz. (C) 2011 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.