COMPARISON BETWEEN PRESSURE FLUCTUATIONS AND PASSIVE ACOUSTIC EMISSIONS IN MONITORING OF FLUIDIZED BED DRYER

Wetted rice particles were dried in a fluidized bed in two independent series of experiments for monitoring of the fluidization status of the dryer. In the first series of the experiments, air at ambient conditions with superficial velocity of 1.1 ms−1 was used for drying and the corresponding passive acoustic emissions signals (AES) were recorded at a given frequency. In the second series of experiments, absolute pressure fluctuations were measured at similar conditions. Ability of both passive acoustic emission and pressure fluctuation measurements for monitoring gradual process changes was assessed by frequency domain analysis. With the aim of increased focus on signals, the original signals were decomposed into ten sub-signals and it was found that energy of the 4th and 7th sub-signals can be correlated with the moisture content in acoustic and pressure measurement, respectively. The results showed that both methods are applicable for on-line condition monitoring and determining the end time of drying process while AES is more sensitive to changes of the moisture.

Keywords:

fluidized bed dryer , online monitoring , acoustic emission , pressure fluctuations