Stochastic analysis of bubble and particle motions in a 2-D three-phase reactor.

Abstract

The bubble and particle frequencies in a 2-D gas-liquid-solid three-phase reactor were measured with a novel optical transmittance probe using a narrow laser beam. The signals for the gas and solid phases were extracted separately based on the differences in the shape and voltage level of the signals. The power spectral densities of the extracted time series data for both phases were then calculated. All the power spectra were found to exhibit a continuous spectrum and exponential decay in the high-frequency region. Comparison between the power spectra of both phases indicates that these can be classified into three frequency regions: the low frequency region where most of the peaks were found to be common to both the gas and solid phases and no component intrinsic to the solid phase was found; the frequency region between 10 and 35 Hz where the components intrinsic to each of the gas and solid phases were found; and the region above 35 Hz where the components intrinsic to the solid phase were only observed. No significant change of the power spectrum intrinsic to the gas phase was observed with the gas velocity, whereas the component of the power spectrum of the solid phase, especially in the high-frequency region, showed a dependence on the gas velocity. These results indicate that although bubble rising motion affects the dominant frequency of the solid phase, the bubble dynamics were almost independent of the local solid flow structure.