Monitoring particle fluidization in a fluidized bed granulator with an acoustic emission sensor

A high-frequency (140 kHz) acoustic emission (AE) sensor with narrow-band receptors was developed and applied in monitoring the particle fluidization in a fluidized bed granulator. In particle fluidization processes, the impact and the friction of the fluidized particles on the wall of fluidized beds produce AE waves. By calibrating an AE sensor at various fluidization conditions with several uniform, spherical granules, the measurement of mean AE amplitudes can be used to monitor fluidization phenomena. It was found that there are direct correlations between the mean AE amplitude, dimensionless excess gas velocity, and dimensionless bed height. The AE sensor can be applied to detect the onset of unstable fluidization due to the increase of moisture content in the fluidized bed.