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UBC Theses and Dissertations

Spouted bed and spout-fluid bed hydrodynamics in a 0.91 m diameter vessel He, Yan-Long


Experiments were conducted in a 0.91 m diameter half-cylindrical spouted bed/spout-fiuid bed column equipped with a 60° conical base and semi-circular inlet orifice diameters of 76 to 140 mm. Three particulate solid materials were studied: 3.25 mm polystyrene, 4.72 mm brown beans and 6.71 mm green peas. Beds with static depths of 0.55 to 2.60 m were contacted with air, both in the standard spouted bed and the spout-fluid bed mode. The dependent hydrodynamic parameters studied included minimum spouting velocity, maximum spoutable bed height, spout shape and diameter, fountain height, dead zone dimensions, overall bed pressure drop, fluid distribution in the annulus, longitudinal and radial pressure profiles in the annulus, and regime maps for the spout-fluid bed. Correlations for minimum spouting velocity developed on smaller vessels generally gave poor predictions for the large diameter vessel employed in this work and failed to predict the observed dependence of U[formula omitted]₈ on the static bed height. The empirical correlation due to McNab (1972) was found to predict the average spout diameter very well for standard spouted beds, while the correlation due to Hadzisdmajlovic et al. (1983) gave a reasonable prediction for spout-fluid beds. Substantial dead zone regions where particles were stagnant were observed in the lower portion of the vessel. The Littman et al. (1977) equation overestimated the maximum spoutable bed height, while the McNab and Bridgwater (1977) equation gave a value which appeared to be far too high. The observed fountains were extremely dilute, and their heights always exceeded the corresponding static bed heights for the conditions studied. The Epstein and Levine (1978) equation gave good estimates of overall bed pressure drop. The longitudinal fluid velocity in the annulus was well predicted by the modified Lefroy-Davidson (1969) equation due to Epstein et al. (1978) and was reasonably predicted by the Mamuro-Hattori (1968) model in the cylindrical portion. However, both equations gave poor predictions in the conical base portion. In the conical base section, the Rovero et al. (1983) equation predicted the correct trend, but consistently overestimated U[formula omitted] by a considerable margin. Both the Epstein and Levine (1978) equation and the Lefroy and Davidson (1969) equation were found to be in good agreement with the experimental longitudinal pressure profiles. The radial distribution of pressure in the annulus for any bed level was observed to be nearly constant when there was auxiliary flow. A computer model based on the Ergun equation gave useful qualitative predictions of the fluid flow distribution in the annulus. Four fairly distinct flow regimes were delineated in this work for cases where there were auxiliary air flow: (1) spouting-with-aeration; (2) spout-fluidization; (3) submerged jets, slugs and bubbles in fluidized bed, and (4) packed bed. The minimum total fluid flowrate for spouting-with-aeration always exceeded the minimum spouting flowrate, but was smaller than the minimum fluidization flowrate. The minimum total fluid flowrate for spout-fluidization was found to be equal to the minimum fluidization flowrate.

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