Although spouted bed with a draft tube is widely used in pharmaceutical particle coating to modify the release characteristics of various medicines, the coating condition and pharmaceutical formulation are determined based mostly on experiences and experiments. In the present work, we theoretically analyzed the coating process of a spouted bed with a draft tube by calculating particle trajectories in the draft tube and impaction efficiencies of sprayed mists onto a particle and obtained the coating efficiency. Furthermore, experiments were carried out to measure the coating efficiencies in a laboratory model of spouted bed. As a result, it was found that the number of seed particles in the draft tube was the most important parameter in determining the coating efficiency, suggesting that the coating efficiency can be raised by increasing the number concentration of seed particles.

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This investigation was undertaken to evaluate the control performance of a vortex orifice air distributor in transient behavior of agglomeration and dispersion of particles in a laboratory-scale conical fluidized bed granulation. A two-fluid nozzle for spraying a binder solution or a fine particle suspension into the bed was installed at the center of the distributor. When the binder solution was sprayed into the bed, the degree of agglomeration, which is defined as mass ratio of agglomerated particles to the total mass, was controlled by the air injection nozzle torque generated within the vortex orifice. The degree of agglomeration in spraying fine particle suspension drastically decreased when compared to spraying the binder solution. The attrition loss increased with air injection nozzle torque and decreased with an increase in the binder mass per unit surface area of fine particles.

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Two-dimensional fluidized beds of glass and polystyrene beads were investigated from the view point of image analysis. Images of a two-dimensional fluidized bed were recorded by a digital video camera at 1/30-second intervals and the fractal dimension of a contour image was quantitatively determined by using the cover method. The fractal dimension fluctuates with time, corresponding to the birth, growth and collapse of bubbles in the fluidized bed. Fifty percent value and standard deviation of fractal dimension distribution increase with non-dimensional air velocity. The 50% value is correlated with a standard deviation of fractal dimension.

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An apparatus for continuously separating specific plastic from plastic mixtures was devised. The apparatus consisted of a triboelectric section and an electrostatic separating section according to their polarities. Various plastic sheets were frictionally electrified in the first fluidized bed and then introduced into the second fluidized bed where plastic sheets were blown off into the electrostatic separation unit. The recovery of plastics was more than 70% for polyvinyl chloride, and 80% for other plastic sheets. The purity of recovered plastics was more than 90% for polyvinyl chloride, and 70% for other plastic sheets. The separation performance of a continuous flow apparatus was slightly lower than that of batch operation.

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