Drying characteristics of slurry in a fluidized bed of inert particles （average diameter＝0.12 mm） under reduced pressure were examined. A mixture of distilled water and fly ash （median diameter＝5μm） was used as （model） slurry.
To obtain the dry dispersed powder continuously, feed rate of slurry （water flow rate） must be equal to the evaporation rate in the fluidized bed, i.e., the maximum evaporation rate when the water flow rate is equal to the evaporation rate exists. As the powder content in slurry increased, the drying rate became lower. The drying rate was higher as the pressure in the drying chamber decreased, and the temperature in the fluidized bed became lower as the drying rate increased. From these, it was found that the low temperature drying with high drying rate was possible in the fluidized bed of inert particles under the reduced pressure.

View full abstract

Here we quantitatively evaluated the mixing performance of a tailor-made microreactor with central-collision type through the iodide/iodate chemical test reaction, and applied the microreactor to the synthesis of zeolitic imidazolate framework-8 （ZIF-8）, which is a subclass of porous coordination polymers （PCPs） or metal organic frameworks （MOFs）. The chemical test reaction demonstrated excellent mixing performance of the microreactor with a characteristic mixing time shorter than 1 millisecond, which is approximately 100 times faster than those of a batch reactor and a millimeter-sized Y-shaped mixer. Taking advantage of the rapid and uniform mixing, the microreactor successfully produced ZIF-8 particles with high reproducibility by simply mixing aqueous solutions of zinc nitrate and 2-methylimidazole. The synthesis at room temperature resulted in ZIF-8 particles with chamfered cube shape, while a lower temperature of 5℃ produced raspberry-type spherical particles. We confirmed that prepared ZIF-8 particles have BET surface area of ～1500 m²/g and exhibit the gate adsorption behavior caused by the structural transition of the ZIF-8 framework.

View full abstract

This study is related to the development of a new continuous manufacturing system for the solid powder cosmetics. This system is combined the wet powder dispersion process by an annular type medium stirring mill and the successive drying process by a flash type dryer.
The impact energy of beads was calculated from a distinct element method （DEM） simulation. The impact energy increases with an increase in rotational speed of the stirring mill. In addition, this tendency is quite similar to the concentration of ferrous ion generated by wear in ion-exchange water. The other optimal operating conditions were determined by experiment. A fluorescent observation revealed that the medium stirring mill was efficient for achieving the homogeneous dispersion of powder and oil. We also investigated various drying systems, and finally found that the dry powders obtained by the flash type dryer could keep the constant particle size distribution in slurry before drying.

View full abstract

In order to clarify the atmospheric corrosion process of steel in different exposure environments, various methods such as exposure test, salt spray test, accelerated corrosion test, combined wet-dry cyclic corrosion test have been used. Our group has proposed that the rust formation by atmospheric corrosion in thin film water and/or adsorbed water on the steels regards as the reaction of metal ions eluted from steel and anions generated by dissolution of corrosive gasses such as NaCl, SO_x and NO_x. Therefore, simulating study using the artificial iron rust particles is effective to understand the rust formation process on the steels. In this review, influence of cations and anions on the structure, composition and morphology of artificially synthesized iron rust particles was described centering on our researches.

View full abstract