The effect of a change in pressure drop in a distributor on the fluidizing characteristics in a tapered bed was investigated by measuring the pressure drop in the bed and the volume mean diameter of the bubbles. These measurements indicated that the volume mean diameter of the bubbles could be estimated with the magnitude of pressure fluctuation in the bed. In addition, a larger pressure drop in gas distributors was found to result in a smaller pressure fluctuation in the beds. Finally, the magnitude of the pressure fluctuation and the averaged pressure drop were found to be the important indices to characterize the fluidizing state of the powder beds.

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The granulation of an organic powdered material in a tapered-fluidized bed has been studied experimentally and theoretically. The size and density of granules were measured under various conditions, and the effect of change in the fluidizing characteristics on these physical properties of granules were examined. As a result of this study, it was found that the factors dominating the physical properties of the granules were air velocity, the moisture content of the powdered material and the magnitude of the pressure fluctuation reflecting the size of the bubbles in the bed. From the theoretical consideration of the mechanism of granulation in the tapered bed, a granulation index consisting of these factors was newly proposed, and this index was found to be useful in expressing the physical properties of the granule in terms of a single factor.

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A new method has been developed to measure and evaluate the operational powder characteristics for fine particle processing based on the reentrainment phenomena. Experiments on particle reentrainment were carried out by use of an accelerated air flow for 21 different test powders. Both the reentrainment fluxes, which were measured by an electrostatic method, and the average air velocities were automatically sampled in a computer. The sampled data were processed to give the reentrainment profiles as a function of the average air velocity. The cumulative reentrainment efficiencies were also obtained and represented by a function of the wall shear stress.
It was found that fine particles having tendencies to form large aggregates were reentrained mainly in the early stage of the measurement where the flow velocity was as low as 5m·s^-1. Also, the mass ratio of the reentrained large aggregates to the total particles was well applied to obtain the information on the particle-particle or particle-wall interactions. On the other hand, the cumulative reentrainment efficiency-curves would be applied to determine the operational conditions controlling the amount of adhered particles in various aerosol processes.

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