Single stage polymerizations proposed for producing micron-sized polymer particles in aqueous media by Konno et al. (Konno et al., 1997; Konno and Orihara, 2000) are conducted to study the effect of agitation on particle size distribution. These polymerizations employed cationic and anionic surfactants or an amphoteric surfactant that were added to the system during reaction. Polymer yield and particle size distribution were emasured in the polymerizations of styrene initiated with K₂S₂O₈ in a reactor with different impellers in a range of impeller speed. Experimental results for the different impellers suggest that short mixing time is required for producing large particles with high monodispersity. It is shown that polymerization employing an amphoteric surfactant can produce micron-sized particles with higher monodispersity than polymerization employing cationic and anionic surfactants. In the former polymerization, large particles with high monodispersity were formed at low impeller speed.

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The structure of isolated mixing regions was observed in a stirred vessel with the aid of flow-visualization technique. Two toroidal regions were clearly formed respectively above and below the turbine impeller in the range less than Re = 100. Under the condition of this experiment, these regions remained visible for a couple of hours. Under the nearly same rotational condition, a set of three stable filaments surrounding the torus was found in the case of the six-bladed turbine, while a set of four filaments was found in the case of the four-bladed turbine. The velocity fluctuation of flow caused by the rotating turbine blades can be regarded as periodical perturbations for the secondary circulating flow. Hence it can be considered that these structures depend on periodical perturbations caused by the rotating turbine blades. In order to observe the inside structure of ring-doughnut-shaped core regions, the unsteady rotation procedure was applied. Another set of filaments was observed inside the core. It has been found that the isolated mixing regions have complex multi-structures consisting of various KAM tori.

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Measurement of mass transfer rate was carried out in an agitated vessel with gas sparging. The performance of mass transfer of several commonly used impellers (i.e. Lightnin A315 and A310, 45° pitched blade turbine, concave blade turbine, Rushton turbine, and Rushton turbine with holes) were examined systematically under the same fluid and tank conditions. A dynamic gassing-out method was used to measure the mass transfer rate of oxygen from gas to the de-ionised water. The variation of the dissolved oxygen concentration of the water was measured by a polarographic dissolved oxygen probe (ORION PCM800). The present data shows reasonable agreement with that in previous publications such as those of Linek et al. (1987), Hickman (1988), Warmoeskerken and Smith (1989), Martin et al. (1994), and Chen and Chen (1999). All the data collected here shows that van’t Riet’s (1979) expression, i.e.: k_La = α(P/V)^0.4U_s^0.5 represents reasonably, well (to within ± 30%) the correlation of k_La with specific power P/V and superficial gas velocity U_s. However, the present data seem to indicate that the radial flow impellers provide slightly higher (17%) mass transfer rate than the axial flow impellers.

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Eulerian approach is developed in order to determine the flow pattern and the concentration field in dense solid-liquid suspension in an industrial vessel. These numerical simulations are a very practical aid to understand and design the solid-liquid processes. The knowledge of solid distribution is useful for numerous processes, including crystallization, where vessel performance is closely linked to the solid phase distribution. The calculations are performed using the FLUENT commercial package. The crystallizer studied is used for alumina production. The predicted solid distributions in this crystallizer are compared with experimental solid distribution for several rotational speeds and mean concentrations. The agreement is remarkable. The behaviour of this dense solid-liquid system is studied.

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Addition of fine α-alumina powder as a seed by up to 50 wt% to a gibbsite (Al(OH)₃) powder sample enables it to reduce its α-transformation temperature from about 1360 to 1090°C. Intensive mixing of the sample with 50 wt% seed using a planetary mill lessens the α-transformation temperature further down to around 910°C. A similar trend can be seen in the boehmite sample. The intensive mixing (grinding) of these samples by the planetary mill is accompanied with their size reduction, dispersing fine particles that play a significant role to reduce the α-transformation temperature in the calcination stage.

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Power consumption and gas-liquid mass transfer volumetric coefficient in a mechanically agitated vessel with wire-gauze impeller were measured over a wide range of Reynolds number. The power consumption of the wire-gauze impeller did not decrease so much with aeration and was almost independent of the gas flow rate in the turbulent flow region, contrast to that of conventional impellers such as turbine and paddle. The agitation power correlation of the wire-gauze impeller was proposed in the operating condition of the gross circulation of the gas back into the impeller. The mass transfer volumetric coefficient was empirically correlated with both the physical properties of liquid and the agitation and aeration power input per unit liquid volume in the same manner as that by Nishikawa et al. (1981b), where it depended on the void fraction of the wire-gauze blade.

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A liquid-gas-solid system has been studied at higher solids concentration (up to 40% by wt) and gas flow rates (up to 2 vvm) than previously. Two different radial flow impellers (Scaba 6SRGT and a standard Rushton turbine) and a six-bladed mixed flow impeller with pitch angle of 45°, either in its downward (6MFD) or upward pumping (6MFU) mode were used. Power input, mixing time, the speed to achieve complete suspension of the solids (ungassed and gassed) as well as the amount of suspended solids and the height of the liquid-solid interface were measured. In addition, a new technique for measuring the amount of suspended solids in two-phase systems was extended successfully to three phases. When compared to the situation without solids, the mixing time, t_m, in the solid-liquid case at the higher solid concentrations was much greater, as previously reported, but for the three-phase case, the increase was relatively small, especially with the Scaba and 6MFU impellers. In general, the power and speed required to suspend the solids increased with increasing solids concentration but once suspended, with the Scaba and the 6MFU impellers, even the highest solids concentration and gas flow rates only required a very small further increase. It has recently been proposed (Pantula and Ahmed, 1997) that by maintaining constant agitator torque on gassing, solids suspension would be sustained. The present work showed this to be broadly valid for the 6SRGT and the 6MFU but not for the Rushton and the 6MFD impellers. Overall, the most stable impeller, requiring the least specific energy dissipation rate for solids suspension and gas dispersion under the most demanding conditions, was the 6MFU.

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The distribution of pressure over the leading and trailing faces of blades on a Rushton turbine was investigated using both experimental and computational methods. Pressures on mechanical impeller blades are of interest for several reasons, including calculation of power input to the tank, assessment of the mechanical design of the impeller, and predicting the gas entrainment rate for impellers in gas-liquid systems. Experimental measurements of pressure on the surfaces of the impeller blades in a rotating Rushton turbine have been made using a hollow blade fitted with pressure tappings and connected to an external pressure cell. Pressures on the trailing face show a pattern indicative of roll vortex formation and detachment. Pressures are used to calculate the power number, which compares fairly well with power according to a torque meter. Fluid flow in the laboratory tank was simulated using computational fluid dynamics (CFD), using a Multiple Frames of Reference method to account for impeller motion. Since the region of interest represents a small fraction of total tank volume, a second simulation was carried out in which better grid resolution was obtained by restricting the computational domain to a zone surrounding a single impeller blade. Pressures on the impeller blades are predicted by the CFD simulations and both methods show reasonable agreement compared with the experimental measurements, with some improvement using the second method. The CFD results were also used to calculate power, and both CFD methods show good agreement with measurements from a torque meter. The study shows that CFD can provide a very useful tool for the analysis of impeller blade design and process issues related to pressure in the impeller region.

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Particle concentration distribution in seven phases in stirred tank is simulated on the basis of information in three dimensional flow field, as obtained by numerical solution of the flow equations (CFD), using the well known κ-ε model. A model for simulation of multi-phase flow field was developed based on the commercial CFD program of CFX4.2. The volume fraction distribution of different sizes of particle was studied by the simulation results. Local particle size distributions in suspension are studied as a function of agitation intensity and distance from the bottom of the tank by the use of CFD. For this purpose a multiple phase approach was used. There, the different particle size classes are taken as separate computational phases. Six classes of particle sizes were used in the simulation. The continuous phase was water. The six solid phases were composed of particle sizes of 50, 100, 300, 500, 700 and 900 μm. The particle density was 2600 kg/m³, different stirrer speeds were used with multiple phase flow. Further, expressions were developed and added in the program which enable the local particle size distributions to be calculated. Computed suspension densities were verified with existing experimental data in the literature.

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The size distribution function of particles that present as droplets in liquid-liquid mixing, bubbles in gas-liquid mixing, crystals in crystallization, and crushed materials in crushing, is examined based on consideration of the balance of the external and the internal force/energy of the particle, and from the viewpoint of information entropy. Then, a new size distribution function (PSF), which is the product of the original size distribution function and the realizable probability function of the size of particles, is presented. The same formula style as that of newly presented PSF can be derived also by balancing the external energy calculated from the energy spectrum density distribution function (ESF) for the turbulent flow field and the internal force/energy of particles. Additionally, it is clarified that the size distribution of eddies in the turbulent flow can be deduced from the same viewpoint by considering that a large eddy is segmented by external force/energy and the style of the distribution is isomorphic with that of ESF. In addition, the usefulness of newly presented PSF is clarified by fitting it to the data generated by the traditional three common unimodal PSF; Rosin-Rammler, Normal and Log-Normal size distribution functions. The main advantages of the newly presented PSF are that it is defined based on a clear physical background and that, for all practical purposes, it can replace the three common PSF. Therefore, this newly presented PSF provides a means of presenting and comparing the different size distribution patterns in terms of a single mathematical expression.

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The performance of two new dispersing tools (Deflo and Sevin turbines) were tested for the preparation of highly pigmented solids slurries. Their power consumption and dispersing efficiency are compared against the performance of the classical Cowles sawtooth turbine. The experiments are carried out with kaolin clays at solid concentration up to 72 wt.%. The influence of powder feeding rate on the slurry preparation is also investigated. Although the classical Cowles disperser is able to promote good slurry dispersion, the power consumption is significant due to the high rotational speed required to maintain a sufficient circulation in the tank. The Deflo and Sevin turbines give the same results for the dispersion quality, but the power consumption is greater with the Deflo turbine, which makes the Sevin impeller a very promising technology for high solids slurry preparation.

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A novel ultra high velocity jet device was used to form fine drops of an organic phase in a continuous aqueous stream. Experiments were carried out for different operating conditions including number of passes through the orifice and pressure drops across it. Computational fluid dynamics (CFD) was used to map the transient continuous phase jet velocity and the associated energy dissipation rate. The results were verified using a high-speed photographic technique. The CFD predictions of the maximum energy dissipation rate at the jet orifice was combined with a population balance equation to predict the evolution of drop size distributions as a function of the number of passes through the orifice (residence time) and the operating pressure. The results compared well with the experimental data giving confidence in the theoretical predictions.

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Among others, the maximum power consumption in a fermentation broth is one of the most decisive engineering parameters to characterize culture conditions and to scale-up bioprocesses, especially with filamentous microorganisms. Based on the fact that maximum drop diameter in coalescence inhibited two-phase dispersing processes is solely dependent on maximum power consumption, no matter which dispersing machine is used, drop sizes were measured in shaking bioreactors and the ratios between maximum and specific power consumption were calculated. In agreement with two different simplifying theoretical considerations relatively small ratios are obtained. It is concluded that the power consumption in shaking bioreactors is much more evenly distributed than in stirred tank fermentors. As the specific power consumptions in both types of bioreactors are of the same order of magnitude, shaking bioreactors create much lower levels of hydromechanical stress to microorganisms and dispersed phases.

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The turbulent field in a dilute suspension of solid particles, agitated by a pitched-blade turbine pumping downwards in an agitated tank, is investigated experimentally. A three-dimensional phase-Doppler anemometer is used to measure local, instantaneous, three-dimensional velocities of the fluid and of the suspended particles. A shaft encoding technique is used to resolve the turbulent fluctuations from the periodic velocity fluctuation due to the impeller blades, and to provide a more detailed information about the variations in flow and particle concentration. The solid particles diverge from the flow especially below the agitator close to the tip where the strongest turbulence is found. Periodic fluctuations in the particle concentration relate to the variations found in the mean velocity and in the fluctuating velocity.

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To examine the gas dispersion mechanism around a disk turbine impeller, the cavity structures behind impeller blade were studied from the range of a vortex cavity and a clinging cavity to a large cavity. An approach named the “minimum pressure point connecting method” was developed and it was adopted to depict the locus and conformation of the trailing vortex, while the shape of the large cavity was obtained through the experimental observation. The variations in the calculated pressure, deformation rate and shear stress along the axis of the trailing vortex were illustrated. The bubble sizes and bubble size distributions were measured at various locations around different type cavities to discuss how the gas entering the impeller is dispersed. For the vortex cavity and clinging cavity, the largest values of the forces related to gas dispersion, such as deformation rate and shear stress, always appear at the cavity tail, which indicates that most of the total gas passing through the impeller was dispersed at the tail of the cavity. From the results obtained from bubble size measurements, it is found that for the vortex or clinging cavities, approximately 60% of the total gas is dispersed at the cavity tail, and about 15% of the total gas is dispersed at the circumference of the cavity. However, for a large cavity, more than 80% of the total gas is dispersed at the cavity tail and almost no gas is torn at the edge of a large cavity, which indicates the diminution of the intense rotary motion of a large cavity.

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Measures of mixture homogeneity and their links with mixing time measurements were discussed. The statistical foundations of homogeneity measures for different scales of scrutiny were presented, followed by the differential mixing model application to defining conditions of physical similarity for macromixing. Selected variable effects on mixing time were studied by means of the CFD analysis. The conclusions drawn from this study can help understand importance of some process parameters. Reasons for a broader discussion on standard experimental procedures were also specified.

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Crystalline 3C-SiC films were grown on Si substrate whose surface has been modified with SiN_x by NH₃ nitridation and their qualities were examined. The growth rate of 3C-SiC film increased with the increase of tetramethysilane (TMS) partial pressure. The growth reaction of 3C-SiC film was the 1st order with respect to TMS partial pressure. When SiC films were grown on pure Si surface, voids were observed in the silicon side of the SiC/Si interface. But void-free SiC films with a flat and smooth film/substrate interface were grown on 60-min nitrided Si surfaces. Crystal quality of 3C-SiC grown on the nitrided Si substrate was better than that on pure Si. The growth mechanism of 3C-SiC films on the nitrided Si substrate was discussed in detail in this work.

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Nano-sized semiconductor CdS covered with a carboxyl group was prepared in an aqueous solution and demonstrated to be applicable as a fluorescent probe. Amino-modified latex beads or those mixed with CdS without surface modification could not detect any luminescence. On the other hand, those attached to the CdS with carboxyl group were distinct the fluorescent images. It suggests that the carboxyl group capped CdS particle can be used as a fluorescent probe.

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The ellipsometry was applied to estimate the thicknesses of the adsorption layer of water on the surfaces of single crystals of silicon, Si(001) and Si(111) at a constant temperature of 20°C. Water molecules adsorb more strongly on Si(111) than on Si(001) in the monolayer regime, whereas the opposit is the case for the bilayer regime. The water adsorbed on Si(111) in the submonolayer regime does not desorb even when the vapor pressure of water is lowered down to 0.1 Pa, resulting in a strong hysteresis behavior. In contrast, water desorbs readily from Si(001) when the water vapor pressure is lowered. The ab initio molecular orbital (MO) calculations with cluster models of the surfaces Si(111) and Si(001) were carried out to elucidate the characteristics of the adsorption of water observed by the ellipsometry. The calculations were executed for the physical adsorption and dissociative adsorption of water on Si(111) and Si(001) in the monolayer regime, and the physical adsorption of water on the dissociative-adsorbed sites in the bilayer regime. The results from the ab initio MO calculations were qualitatively consistent with the experimental ones.

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A negative resist was spin-coated on the surface of a 50-μm thick copper film, and was solidified as a protection film. A palladium layer was then electrodeposited on the other uncovered surface. After removing the protection film, the resist was again spin-coated on the copper surface, and a pattern of microslits was transferred by photolithography. After development, the microslits were electrolytically etched out. Thus a palladium membrane of 5 mm in diameter was formed as an assemblage of thin layers formed in the microslits. The palladium membranes prepared were characterized by SEM observation, as well as by permeation measurements for hydrogen and nitrogen at 573-873 K. The palladium membrane, which was 3 μm in thickness and formed on a polished copper film, showed separation factor of hydrogen to nitrogen of 120 at 873 K.

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Associated with sustainable technology, in this paper, we have developed a prototype system for evaluating life cycle engineering of chemical products. For this purpose, giving a whole framework on the G2 software known as a graphical development environment of intelligent system, we have built a product life cycle model as one of its element technologies. Practically it is described as an object-oriented model having a hierarchical structure like IDEF0 model. Furthermore, due to the interdisciplinary nature of the problem-solving, highlighting an importance to facilitate a continuous improvement and to employ distributed information technologies, we also engage in developing a few related element technologies. Through a case study associated with the farm sheets, we have revealed that the developed system can analyze easily various kinds of life cycle scenarios just by giving certain values via a graphical user interface, and support strategic decision making on the life cycle engineering of chemical products.

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Two telomers containing amino end-group are synthesized and attached covalently to peroxidase by using coupling agents. When the enzyme is modified with a telomer having polystyrene as a main chain, it dissolves in organic solvents and exhibits catalytic activity in water-immiscible solvent. The catalytic activity increases as the polarity of the solvents decreases. The enzyme modified with a telomer having poly-N-isopropylacrylamide chain varies its solubility drastically from water-soluble to water-insoluble at a certain temperature, being accompanied by change in the catalytic activity. The solubility variation is reversible against temperature change and allows the catalytic activity to be controlled reversibly.

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