Study of the Power Spectrum of Acoustic Emission (AE) by Accelerometers in Fluidized Beds

Power spectrums of acoustic emission (AE) on the walls of fluidized beds were calculated, to investigate the particle movement in the bed. It is determined that the main frequency of the AE power spectrum can be related to the average Landau−Lifshitz collision time of particles impacting on the walls of the bed. A frequency model was proposed to examine the effect of superficial velocity, the size and density of particles, and the elastic modulus of the materials. The influence of chunk formation on the structure of AE power spectrum was shown to be significant. A very good agreement of frequency was observed between the AE measurement and the model prediction in a fluidized bed both for cold mode in laboratory scale and hot mode in plant scale. The AE spectrum can be used to monitor the particle average size and chunk formation successfully.