| Summary: | 碩士 === 國立臺灣大學 === 化學工程學研究所 === 93 === Abstract
In order to understand the effect of bed heights and probe locations on standard deviation of pressure fluctuations have been measured by a absolute pressure and differential pressure method in a bubbling fluidized bed of 0.1m i.d. and height of 1.8 m and, with respect to variations in gas velocity. Air was used as fluidizing gas and fluid catalytic cracking (FCC) catalyst particles and glass bead particles (Geldart’s group A particles) as bed material. The result showed that the variance of pressure fluctuations for Geldart’s group A particles was a practically linear function of the gas velocity. Thus, more consistent value of Umb was determined by using absolute pressure probes (20cm,30cm) and differential pressure probes (10cm-20cm,20cm-30cm) in this study.
The cross-correlation function was used to process the signal from probes each separated by a gap are suitable for calculation of the bubble residence time and bubble rising velocity in this study. The value of Ub was found to be nearly independent of bed heights for glass bead particles but to increase with increasing static bed height for FCC particles. In this study, Bubbles near the surface of the bubbling fluidized bed rose faster in the centre than the wall.
The dominant frequency was found to be nearly independent of probe locations with absolute pressure probes but to decrease with increasing air velocity and static bed height at absolute, differential pressure probes (plenum-10cm, plenum-20cm…). The dominant frequency decreased with increasing heights of probe locations at differential pressure probes (plenum-10cm, plenum-20cm…) for low gas velocity, but it did not change at high gas velocity.
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