Solubilities of high-boiling components in supercritical fluid are reviewed from the point of view of process design. The authors described the solid-gas equilibria for binary systems, entrainer effects, supercritical fluid + two solid components for ternary systems. Furthermore, a prediction method by using an equation of state and molecular simulation was shown to calculate the solubilities of high-boiling components and the entrainer effects. Finally, the distinction for pressure dependence of the solubilities of high-boiling compounds between solid-gas and liquid-gas equilibria was discussed.

View full abstract

The relationships between the plate height HETP and the linear mobile phase velocity u in supercritical fluid chromatography (SFC) were investigated over a wide range of experimental conditions (pressure p = 8. 5 ∼ 15 MPa, temperature T = 35 ∼ 45°C) with carbon dioxide as the mobile phase. When the HETP - u curves were converted into the dimensionless variables h = HETP/d_p and ν = ud_p/D_m, the curves were similar regardless of the pressure, the temperature and the state of the mobile phase. The distribution coefficient K decreased with increasing T and/or p. The K values were correlated to the mobile phase density. A linear increase of the pressure was applied to elute the sample from the column. The result was simulated by a chromatography model with the isobar chromatography data. These results have shown that the separation behavior of SFC at low sample loadings can be predicted by ordinary liquid chromatography models. Further research should be done for the prediction of the separation behavior at overloaded conditions.

View full abstract

Practical use of supercritical fluid such as C0₂ as an extraction medium has been known; e. q., C0₂ is applied to the extraction process of food additives on the industrial scale. Furthermore, many other advantages have been sutudied recently in a wide area. In this paper, the novel process of direct hydration reaction of n-butene under supercritical condition is reviewed.

View full abstract

The possibilities of the practical application of the supercritical carbon dioxide for the organic syntheses have been discussed based upon the recent experimental results obtained at author's laboratory, focusing on the "unusual phenomena", i. e., the acceleration of reaction rates, the shift of equiliblium constants, or the selectivity of reaction products which were used to be induced near the critical points (Tc & Pc).

View full abstract

The generation of high pressure in water associated with the tangential impact of a solid body is reviewed, and the possible application of the transient or unsteady behaviors of fluid motion including the water jet technology is suggested.

View full abstract

The characteristics of a water jet emerging from the nozzle into an infinite space filled with air is described in this paper. The water jet is characterized by the maximum velocity and pressure decay in the jet axis, velocity and pressure distribution, jet spreading width and core length. Especially, the core length of jet can be estimated as a basic factor for the characteristics of a water jet.

View full abstract

The mechanism of fracture of solid materials is considered for the water jet in air, the abrasive jet which is a water jet including abrasives, the underwater cavitating jet and the supersonic air jet. It is emphasized that the users should take note of each fracture mechanism in their applications, because the mechanism is quite different among the jets mentioned above.

View full abstract

High purity synthetic diamond crystals (type IIa) grown by the temperature gradient method with impurities less than 0. 1 ppm were studied on the crystal defects and residual strains in details by polarizing microscopy, double-crystal X-ray rocking curve measurement, X-ray topography and Raman spectroscopy. The results indicated that the synthetic type IIa diamonds had less crystal defects and lower residual strain than natural diamonds or synthetic type I b diamonds did. Furthermore it was found that some of dislocations in the synthetic type IIa diamond could be removed and the crystal quality of the diamonds could be improved by using strain-free and low defect crystals for the seeds.

View full abstract

It was shown that strain meters at observation stations in Kobe did not satisfactorily function during periods including the occurrence time of the 1995 Kobe earthquake, while present stress meters are incapable of continuous recording. Here we propose a new stress meter for earthquake surveillance which continuously records the accurate value of stress. The probe for measuring stress is a coil of manganin wire having pressure-sensitive resistivity which is confined within a thin vessel filled with liquid Such vessels are buried underground in groups of 6 with different orientations to record the 6 components of stress. Extra values of stress caused by burying the vessels can be subtracted from the observed data. Thus the absolute values of underground stress are obtained.

View full abstract

The full knowledge of the state of stress in the earth' s crust is indispensable for earthquake prediction research. Today, the crustal stress is measured only intermittently at limited sites by several methods, but not continuously. There are some difficulties in measuring the crustal stress (and not strain) continuously and monitoring its variation with time. The main reason is the fundamental lack of any effective method, because we have to know quantitatively the anisotropic deformation of the measuring device due to anisotropic crustal stress. A comment is presented on a proposed method for continuous stress measurement by a stress meter composed of a disk-shaped pressure vessel filled with liquid.

View full abstract