Hydrodynamics in a Gas-Solids Fluidized Bed Using X-ray Fluoroscopy and Pressure Fluctuation Measurements

ABSTRACT

In this work, non-intrusive techniques were used to characterize the hydrodynamics in a gas-solids bubbling fluidized bed using polyethylene powder and glass beads of comparable mean diameter (dp = 360 µm) but different density. X-ray fluoroscopy measurements and pressure fluctuations were performed on a pseudo 2-dimensional gas-solids fluidized bed. Bubble properties were captured from X-ray fluoroscopy measurements. Similarities and differences of flow behavior of the two particle systems were revealed from comparison of bubble properties. Bubble properities normally varied similary with operating conditions for the two particle systems, while bubble sizes for the glass beads system are larger than those for the polyethylene system. Wavelet analysis of pressure fluctuations was applied to investigate the gas and solids phase flow behavior. Multi-scale flow behavior was extracted from the standard deviation of the decomposed coefficient series. Flow behavior due to particles and bubbles of different sizes were captured at different decomposition levels of pressure fluctuations, which is difficult to know from analysis of the original signal. Results extracted from X-ray fluoroscopy and pressure fluctuation measurements were consistent, suggesting that conventional pressure fluctuation measurements can be effectively used for investigation of the bubbling behavior.

A full version of this paper is available on Wiley Online.