A novel rotating coil-shaped spiral gas-solid contacting device was proposed. Cold models of the spiral structure were made by combining 180° elbows of half-hexagonal shape using ID 24 mm transparent plastic tube. A 5-cycle spiral model was continuously driven by a motor to transport particles, and the pressure drop in the solid bed during gas feed was measured when the rotation was stopped. This pressure drop was compared with that in a vertical packed bed of the same diameter (24 mm). The height of the vertical packed bed that gave the same pressure drop as the solid bed in the spiral was defined as the “equivalent bed height for pressure drop.” The equivalent bed height for pressure drop was lower than that expected from the total volume of solids in the spiral assuming straight packed bed. This result is attributable to gas passing by way of shortcuts formed in the spiral. A simplified model of gas flow distribution in the packed bed within the spiral was proposed. The model with a parameter obtained by use of the 5-cycle model agreed with the results obtained using the 1.5-cycle model with wider range of gas flow rate than 5-cycle model. Thus this model is expected to be useful to estimate the gas-solid contact within the spiral. Also, a 1.5-cycle model was used to visually observe the flow pattern and mixing of particles in the spiral. A circulating flow pattern of particle movement was observed when the spiral was rotated. In spite of the shortcut gas flow, uniform solid conversion is expected because of good mixing of particles in the spiral.

We previously developed a method to fabricate spherical millicasules on a superamphiphobic surface. The procedure includes formation of spherical droplets of a liquid with dissolved ingredients on the surface and solidification of the droplets. The purpose of this study was to fabricate spherical millicapsules from highly viscous slurry consisting of solid particles as the ingredient and a liquid monomer. The high viscosity inhibited formation of spherical droplets of the slurry on the surface. We added dichloromethane, which is highly volatile, a good solvent for the ingredient, and miscible with the monomer, to obtain a homogeneous solution. The solution formed spherical droplets on the surface, leading to successful fabrication of spherical millicapsules by polymerization of the monomer after evaporation of dichloromethane. We showed that the ingredient could be encapsulated with high efficiency. Further, the release rate of the ingredient could be controlled by coating the capsules with the polymer prepared by polymerization of the monomer.