Dynamics of Pressure Fluctuation in a Bubbling Fluidized Bed at High Temperature

Abstract

Dynamic behaviors were investigated using ashes of three sizes in an 82-mm-i.d. stainless steel fluidized bed at temperatures up to 1000 °C. Pressure fluctuation signals were analyzed using power spectral density function (PSDF) analysis, chaos analysis, and wavelet analysis. The major frequency of the pressure fluctuation signals is in the range from 20 to 80 Hz in the fixed state, whereas the major frequency ranges from 1 to 9 Hz in the fluidized state. The correlation dimension and Kolmogorov entropy are zero in the fixed state, and then they increase with increasing fluidization number in the transition region. Finally, these two exponents vary little with changing fluidization gas velocity in the fully fluidized state. Through a wavelet transform, the fluctuating pressure signals of the bed can be decomposed into approximations and details at different resolutions. The number of peaks in the five-detail signal represents the bubble formation frequency, which is in agreement with the major frequency obtained from a PSDF analysis of the pressure signals.