Particle separation by selective wet agglomeration was investigated for a suspension with particle concentration of 10-40vol%. The suspension consisted of calcium carbonate particles and soda lime glass particles, with median diameters of 9.2μm and 18.6μm respectively. Dodecane was used as a bridging liquid. The fluidity of suspension decreased with an increase in particle concentration, and the wet agglomeration process was affected by the fluidity of the suspension. However, the influence of fluidity on particle separation efficiency was small. The particle separation efficiency by selective wet agglomeration became high at a high particle concentration, and the maximum separation efficiency of 0.93 was attained at the particle concentration of 40vol%. By surface treatment of suspended particles and bridging liquid droplets, the particle separation efficiency markedly changed due to the change in adhesion tension.

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This study provides fundamental knowledge on the centrifugal classification of liquid-borne particles. It is found that the cut size of a centrifugal separator decreases as the rotational speed increases and the liquid flow rate decreases. Comparing our experimental data with the theory, they agree with each other in the case of a high liquid flow rate. However, the difference between them is significant in the case of a low liquid flow rate. This is because dead spaces are generated in the centrifugal separator at the low liquid flow rate. The computer simulation of fluid flow in the centrifugal separator shows a decrease in velocity near the wall at a low liquid flow rate, suggesting the possibility of formation of dead spaces.

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Pressure drop of a long packed granular bed is usually calculated by using the air velocity at the mid-length of bed because a decrease in pressure towards the bed outlet brings the expansion of air and therefore an increase in air flow velocity. However, for a long bed consisting of small particles with a low voidage at a high air velocity, the air pressure decreases so significantly that the prediction of pressure drop with the air velocity at the mid-length of the bed is no longer applicable. Consequently, the pressure drop has to be calculated in an integral manner by considering the air velocity increase across the bed. The present work estimated the error between the pressure drop predicted with the mid-length air velocity and that in an integral manner for various lengths of bed. As a result, it is shown that the pressure drops at various air velocities can be readily predicted when the pressure ratio at two locations in the bed is known at a given air velocity.

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Control of chemical contaminant has become of great importance in addition to particle contamination in a clean room for manufacturing semiconductors, liquid crystal device and other electronics devices. In particular, acid gases, base gases, hydrocarbon gases, boron and phosphor could damage electrical properties of these devices. Therefore, the reduction of contaminant concentration in clean room air is required. In this paper, constitute materials for a clean room newly developed as countermeasure for chemical contamination are introduced. Then, their analysis and evaluation methods for chemical contamination are also described.

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The photolytic degradations of photolabile solid drugs are very complex and therefore difficult to quantitatively analyze the results because they are typical topochemical reactions differing from those in aqueous media. In this article, based on the results of several works performed by the authors, some essential and important problems and factors (e. g., effects of temerature, humidity, irradiation wavelength and intensity of light source, particle size, crystal forms) for rational evaluation of photostability of these drugs are presented and extensively discussed.

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