Bed nonhomogeneity in turbulent gas-solid fluidization

Bed dynamic behavior in a gas‐solid fluidization system is measured in real time using ECT based on the NNMOIRT recently developed. The ECT results reveal the time‐averaged and transient characteristics of the bubble/void phase and the emulsion phase, which is of value to the verification of the 3‐D computation codes with real physical systems. In the turbulent regime, the time‐averaged solids holdup distribution exhibits radial symmetry, which is not the case for the bubbling regime. The standard deviations of the fluctuations of the cross‐sectional, averaged bubble/void phase fraction, and the cross‐sectional, averaged solids holdups in the bubble/void phase and in the emulsion phase, all peak at the transition velocity from the bubbling to the turbulent regimes Uc. The addition of 10% fine particles decreases the solids holdup in the emulsion phase due to the breakup of large bubbles. The ECT study indicates that optical fiber probe measurement of the bubble/void phase fraction may yield significantly different results depending on the threshold level selected for the measured solids holdup distribution. The bubble/void phase fraction measured by the optical fiber probe does not vary with bed temperature up to 400°C; the emulsion phase voidage is observed to increase as the bed temperature increases.