Characterizing and Modeling the Hydrodynamics of Shallow Spouted Beds

The hydrodynamics of shallow, conical spouted beds of heavy particles were experimentally studied to determine how they differ from previous spouted bed reports in the literature. Key experimental measurements included minimum spouting velocity, time-average and time-varying (dynamic) pressure drop, time-average fountain height and time-average gas velocity profile in the bed. New correlations were developed for minimum spouting velocity, time-average pressure drop and fountain height based on the experimental data. The time-average gas velocity profile measurements confirmed that the beds in the present study exhibited gas flow features that were at least qualitatively similar to those previously reported for other experimental conical spouted beds and predicted by detailed computational fluid dynamics models.

At least some of the major features of the observed spouted bed pulsation behavior appear to be captured by a simple zone-based model of ordinary differential equations. The equations are derived from time-differential mass and momentum balances over 4 spatial zones: entrainment, spout, fountain, and annulus. The dynamic behavior of the model is dominated by the entrainment zone, which includes the effects of 3 key processes: 1) Granular particle flow from the annulus into the area immediately above the gas inlet; 2) Radial leakage of gas outward from the inlet zone in response to the inward flowing particles and; 3) Upward flow of the main part of the inlet gas and subsequent particle entrainment in response to the gas-particle drag. Recommendations are made for further improvements to the model.