Conditional monitoring of moisture content in a fluidized bed dryer by the acoustic emission signature

Wetted rice particles were dried in a fluidized bed and the corresponding passive acoustic emissions signals (AES) were recorded at a given frequency to study the drying phenomena and bed hydrodynamic changes as well. The results show that the end time of the constant rate zone and the end of the falling rate can be determined from the variation of standard deviation and kurtosis of AES, respectively. Frequency domain analysis was also used to quantify the moisture content of solids. For this end, the original signal was decomposed into ten sub-signals, and it was found that the energy of the 4th sub-signal can be correlated with the moisture content. The results show that the acoustic emission measurement is applicable as a practical method for on-line condition monitoring of drying process in fluidized bed dryers.