A new system was developed to mix viscoelastic fluid. To prevent fluid from creeping up the impeller shaft by the Weissenberg effect, the impeller was stopped, and the vessel was rotated, with periodic reversal of the direction of rotation. The impeller used was an anchor type that scraped the fluid from near the vessel wall. Viscoelastic fluid with the very large apparent viscosity of silicone rubber could be mixed efficiently with this system.

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A new home base (HB) type impeller with 3S performance (simple, speedy and stable) was developed based on the streak line visualization method (Kato et al., 2015b). The characteristics of mixing performance and power consumption were evaluated with a view to practical use in industrial processes. It was found that the power number could be estimated by the correlation formula for a paddle impeller by taking into consideration the impeller position. No isolated mixing region of doughnut-ring form was observed in the mixing vessel with HB impeller over a wide range of Reynolds number by using decolorization method.

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The collision of particles having diameter ranging from 20 to 300µm in a gas with a wall was studied both experimentally and theoretically. The effect of the particle diameter on the incident and rebound velocities was quantitatively examined by using images captured by a high-speed microscope camera. The incident velocities calculated using a model that takes into account the increase in fluid resistance near a wall surface, i.e., the lubrication effect, were in good agreement with the results obtained experimentally. Smaller particles had lower velocities owing to the increase in the ratio of fluid resistance to particle inertia. Experiments conducted by varying the incident velocity and particle density further indicated that the coefficients of restitution decrease with the decrease in the Stokes number.

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The vibrating conveyor is a machine with an obliquely oscillating trough that induces the saltation of particles. It is widely used for the transport of solid materials in industry. However, basic studies on the adhesive forces and fluid resistance that act on the particles have been neglected, and there have been few reports detailing the vibratory conveying of fine particles. This review summarizes the latest experimental and theoretical results on the behavior of fine particles on a two-dimensional oscillating plate. When a sufficiently high intensity of two-dimensional vibrations is applied to particles adhering to a plate, the particles become detached and bounce repeatedly. The external force in the tangential direction of the plate induces particle rolling, which decreases the particle-plate interaction force; as a result, even a relatively small external force will allow the particle to become detached from the plate. Furthermore, coarse single particles are transported by the repeated larger bounces with both forward and backward motions. On the other hand, fine particles can easily form agglomerated particles with low restitution and bounce slightly but only forward. Consequently, the transport velocity of agglomerated particles is greater than that of coarse single particles. These phenomena can be explained with a theoretical probability model and numerical simulation of the particle trajectory.

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Supercritical fluid extraction with a rectification process was developed with a view to separating nobiletin from citrus peels. With CO₂–ethanol extraction-rectification systems, nobiletin with carotenoids were recovered from top of the rectification tower, while chlorophylls were recovered from the bottom of the tower. With CO₂–ethanol–water systems, nobiletin was recovered from top of the rectification tower, while carotenoids and chlorophylls were recovered from bottom of the tower and separated from each other. Rectification conditions for separation of nobiletin from extracts were optimized by taking into consideration the phase separation of CO₂–ethanol–water systems.

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Electrochemical separation of carbon dioxide from simulated flue gas was investigated using an anion exchange membrane. Carbon dioxide reacts with hydroxide ions to produce hydrogen carbonate and carbonate ions at the cathode. These ions migrate to the anode, where they are converted to carbon dioxide gas and oxygen. Extensive experiments under various conditions of anode humidification and electrode composition demonstrated the possibility of the separation. Transport numbers of hydrogen carbonate and carbonate ions were obtained. The voltage required for separation was around 2.0 V/cell, the reduction of which remains to be solved.

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Electrochemical separation of oxygen from air using an anion exchange membrane is investigated. When oxygen contained gas is supplied to the cathode at the ambient temperature and pressure, hydroxide ion will be formed reacting with water and migrates to the anode to produce pure oxygen. We confirmed the hydroxide ion selectivity of the membrane through membrane potential measurement and electrolysis experiments. Oxygen is produced at electrochemically equivalent rate at the anode. Rate determining steps are charge transfer for both formation and decomposition of hydroxide ion. But about 2.0 V is required for 1000 A·m^－2 current density. Adding alkali to the cathode decreased the cell resistance significantly.

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Constant-rate and constant-pressure microfiltration experiments were carried out using dilute colloids of binary mixtures of polystyrene latex particles with two different sizes and the microfiltration membranes, making them essentially impermeable to larger particles but permeable to smaller particles, and both filtration behaviors were examined. In addition to the measurement of the rejection of smaller particles with the progress of filtration, the pressure rising and flux decline behaviors were measured in constant-rate and constant-pressure filtration experiments, respectively. As suggested by the plots based on the characteristic filtration form for the blocking filtration laws, in each case of constant-rate and constant-pressure filtration, the filter cake comprised of larger particles initially formed, and subsequently smaller particles were trapped in the pores of the filter cake of larger particles. Eventually, a binary cake of both larger and smaller particles grew up, indicating a much higher specific cake resistance than that of larger particles alone. The capture of smaller particles was accelerated by the decrease in the filtration rate in constant-rate filtration and the decrease in the filtration pressure in constant-pressure filtration, and this contributed to the remarkable increase in the filtration resistance. The logistic growth equation was used to describe the variation of the rejection of smaller particles during the course of filtration. A generalized filtration equation applicable to both constant-rate and constant-pressure filtration processes was proposed with the use of the logistic growth equation in consideration of the total cake resistance represented by adding the increased cake resistance caused by the capture of smaller particles to the sum of the cake resistance of larger particles alone and the membrane resistance. The validity of the model presented here was confirmed by the fact that the calculations based on the model were in relatively good agreement with the experimental data of filtration behaviors obtained under various experimental conditions.

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The thermo-physical properties of magnetic fluid (solvent, water; nano-particulates, magnetite) were elucidated in order to examine its temperature dependency in the presence and absence of a magnetic field. Heat transfer by natural convection was also investigated around a horizontal thin wire, which was heated uniformly in the presence and absence of a magnetic field in order to estimate the heat transfer characteristics. Various thermal properties of the magnetic fluid and their temperature dependency were clarified in the present research. It was also found that the heat transfer coefficient coincides well with the conventional heat-transfer correlation of natural convection heat transfer around a horizontal heated thin wire by applying the values of thermo-physical properties obtained in the present measurement.

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A study was performed to clarify the mechanisms of limestone dissolution in sulfuric and sulfurous acids, which is important in the wet method of flue gas desulfurization. The mass-transfer characteristics of a benzoic acid plate of fixed area were first tested in a dissolution vessel, and then the dissolution rates of limestone plates in sulfuric acid, sulfurous acid, and gypsum-saturated sulfuric acid were measured and correlated with various factors such as agitation speed in the vessel. The results obtained for sulfuric acid were as follows: the dissolution rate of limestone is controlled by the diffusion in the film formed on the solid surface, of which the diffused component is dissolved limestone in region I (C_H2SO4<2×10^－2 mol·m^－3), sulfuric acid in region II (2×10^－2<C_H2SO4 <5 mol·m^－3), and dissolved gypsum from the surface of deposited gypsum on the limestone surface in region III (5<C_H2SO4 <100 mol·m^－3). In the case of sulfurous acid, no deposit on the limestone surface that would affect the dissolution rate was observed, and the rate was found to be controlled by the diffusion of sulfurous acid. Finally, the dissolution rate in sulfuric acid saturated with gypsum was found to be controlled by the diffusion of sulfuric acid in region I and region II.

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Due to the advance of the distributed control systems in the chemical industry, the number of alarms per operator has increased drastically. A poor alarm system might cause sequential alarms, which are triggered in succession by a single root cause in a chemical plant. In this paper, we propose a method for identifying sequential alarms hidden in plant operation data by using dot matrix analysis. Dot matrix analysis is one of the sequence alignment methods for identifying similar regions in a pair of DNA or RNA sequences. The proposed method first converts plant operation data recorded in a distributed control system into a single alarm sequence by putting alarms in order of occurrence time. Next, regions similar to each other in the alarm sequence are identified. Finally, the identified regions, which are assumed to be sequential alarms, are classified into sets of similar sequential alarms in accordance with the similarities between them. The method was applied to simulated plant operation data of an azeotropic distillation column. The results showed that the method is able to correctly identify sequential alarms in plant operation data. Classifying sequential alarms into small numbers of groups with this method effectively reduces unimportant sequential alarms in industrial chemical plants.

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To investigate the fate of boron and selenium in low-rank coals during coal combustion, the effects of the dust collector and wet-flue gas desulfurization (FGD) conditions on the distributions of B and Se have been studied with a lab-scale pulverized combustor equipped with an FGD unit. Although the residence time of fly ash (FA) from the furnace inlet to the dust filter does not affect B distribution, the proportion of Se condensed onto the FA increases with increase in the residence time. Further, the proportion of B transferred into the bottom ash (BA) during the combustion of high ash-containing coal is greater than that during the combustion of middle-level ash-containing coal. On the other hand, the amounts of B condensed onto the FA are equal for the two types of coals examined. This result shows that the B distribution during coal combustion strongly depends on the coal type. No such coal type dependence is observed in the case of Se, because almost all of the Se in raw coal transfers into the gas phase during coal combustion, resulting in a very low amount of Se in BA. Examination of the effect of flue gas temperature on B distribution reveals that the gaseous B produced during coal combustion does not condense onto the FA as FA-B in the temperature range of 90–400°C. On the other hand, the amount of gaseous Se decreases with decrease in the flue gas temperature, and gaseous Se condenses onto the FA. We hypothesize that the ash composition in the FA and/or the sulfur content in the flue gas (Ca/S or Fe/S) may affect Se distribution, because the condensation behavior of Se onto the FA is quite different between for high-ash and high-sulfur-containing coals. In addition, it is found that over 90% of the gaseous Se can be removed at a flue gas temperature of 90°C. In the FGD test, almost all of the gaseous B or Se passing through the dust filter is trapped in the FGD solution, and the residual gaseous B or Se transfers into gypsum. The pH or temperature of the FGD solution does not affect B and Se distributions in the FGD unit. It is found that the gaseous B or Se formed during the combustion of pulverized coal can be removed via the flue gas and FGD unit.

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