Studies on emulsification, have hitter to dealt mainly with droplets of micrometer size. Very few reports concern emulsification into droplets of sub-micrometer size, though recently a few studies have been reported on emulsification by means of high-pressure homogenizers which can prepare such emulsions. In the present work, oil in water (o/w) emulsions composed of droplets of sub-micrometer size were produced by means of a high pressure wet-type jet mill, and the relation of mean droplet size to operating variables was discussed. Furthermore, the time dependency of droplet size was discussed on the basis of a kinetic model. The drop size distribution (volume basis) showed a log-normal distribution. As the number of passages increased, the drop size distribution became bimodal, due to the increase of extremely fine droplets. When the number of passages was unity, Sauter mean diameter (d32) increased with increasing dispersion phase fraction, but the geometric standard deviation remained unchanged. For the present experimental conditions, the maximum droplet diameter (dmax) based on droplet number was expressed in the form of dmax=1.76d32. At low surfactant concentrations and low dispersion phase fractions, d32 was proportional to the applied pressure raised to the power of ca. -O.6. The drop size distribution exhibited the time-dependence because of the coalescence of droplets. The process of coalescence was judged to be described by a second-order process consisting of a rapid coalescence process and a slow coalescence process. The slow coalescence process was realized under the conditions of high processing pressure, high surfactant concentration, low dispersed phase fraction and large number of passages. It was also found that the coalescence rate constant increased with increasing dispersed phase fraction and decreased with increasing surfactant concentration.
A three-dimensional void distribution in an air-water bubble column was measured with an electric conductivity probe. Sensitivity analyses of closure relations for interfacial momentum transfer terms and an eddy viscosity coefficient were conducted by using an (N+2)-field model proposed in our previous study. Comparison of measured and predicted void distributions revealed that: (1) a bubblesize-dependent lift coefficient model and classification of bubbles into several groups by size are prerequisite for the accurate prediction of heterogeneous bubbly flow, (2) the effects of virtual mass and eddy viscosity coefficients on numerical predictions are negligible, (3) the inclusion of a shear-induced turbulence model results in the overestimation of turbulence kinetic energy, and (4) further efforts are required for modeling the effects of bubble-induced turbulence on the turbulent dispersion force and the drag reduction caused by the wakes behind a cluster of large bubbles.
High temperature air jets are used widely in the fields of drying, sintering, powder treatment, sterilization and others, but the velocity and temperature fields and their relation have not been sufficiently clarified. The main purpose of this study is to improve the performance of surface fusing, or globular forming, systems of thermoplastic fine particles. First, the flow and thermal characteristics and their relation of high temperature air jet from a pipe nozzle were clarified by measuring the mean and fluctuating velocity and temperature profiles. In order to control the jet diffusion in the radial direction, a ring nozzle with a ring-shaped contraction near the nozzle exit was used and its flow and thermal characteristics were determined. Next, the effect of nozzle shape on the performance of the globular forming was examined, and the ring nozzle was shown to be suitable.
The mechanism of alkylation in the synthesis of zotepine, a commercial anti-psychotic drug, was studied. The alkylation of 2-chloro-10,11-dihydro-dibenzo[b,f]thiepin-11-one (CT) was carried out in a solvent containing potassium carbonate as a base. Examination of the reaction field and reaction rate suggested that the deprotonation and succeeding alkylation of CT took place on the surface of potassium carbonate, and the rate-controlling step for the reaction was determined to be the deprotonation of CT on the surface of potassium carbonate. In addition, the overall reaction rate increased as the particle size of potassium carbonate decreased. Measurements of particle size distributions of potassium carbonate revealed that the addition of water to the solution was effective for fracturing potassium carbonate particles of 250 to 420 µm and thereby enhancing the reaction rate. The overall reaction progress was well expressed by taking account of the increase in the surface area of potassium carbonate due to fracturing in the expression for the overall reaction rate.
Vamicamide hydrochloride has four hydrates (A, B, C and D forms). The powder characteristics and crystallization behavior of each hydrate were investigated. The C-form has good filterability and lower risk of dust explosion than other hydrates. Accordingly, the C-form was selected, and its crystallization conditions were examined. The C-form is the most stable form with lowest solubility among hydrates, but in the absence of seeding the D-form was crystallized and then transformed to the C-form via solvent-mediated transformation. Furthermore, the D-form was crystallized during cooling and became mixed in the product. To prevent crystallization of the D-form, its supersolubility was determined. The manufacturing process of the C-form was established by operating without exceeding the supersolubility of the D-form. Based on these results, a scale-up experiment was performed with a 1,500–1 crystallization vessel. The control of hydrates on a 1,500–l scale was successfully achieved, and the C-form was crystallized selectively without involving the D-form.
To reduce the stiction between a magnetic disk and a flying slider carrying a magnetic head in a hard disk drive, the slider was subjected to surface treatment. Namely, the slider was dipped in 1 mass% FAS solution (2-(heptadecafluorooctyl)-ethyltrimethoxysilane) and heated to 393 K (i.e., a dipping/heating process). The mineral-oil contact angle on the slider after this treatment was 72 degrees. A read/write test was performed with the treated slider, and the stiction force on the treated slider was found to be decreased by about 80%, compared with that of an untreated slider. This result confirmed that the surface treatment effectively reduces stiction. Moreover, by irradiating the slider surface with ultraviolet light before the dipping/heating process, the contact angle was increased to about 80 degrees. It is also confirmed that ultraviolet light irradiation effectively reduces the stiction between the slider and disk.
A mathematical model was proposed that gave the polymer content profile in convective dried porous material wetted with polymer solution. The model equations were simple and practical. Convective drying experiments were performed by using a glass particle layer wetted with aqueous polyvinyl alcohol solution or styrene-butadiene rubber latex, and polymer content profiles in dried samples were measured. Agreement between the calculated and the measured results was satisfactory.
To improve the rate of gas-blow drainage of wet pulp in pulp molding, we tried steam-blow drainage of the wet pulp in the mold instead of air. In this procedure, the temperature of water in the pulp is increased rapidly to the saturated steam temperature, due to the conductivity of condensation of steam, and the viscosity and surface tension of the water are greatly decreased. As a result, we obtained a high efficiency of gas-blow drainage. Additionally, we have proposed an equation for the rate of drainage which depends on the temperature and the time in the state where the temperature, the pressure and the values of properties are changing.
To clarify the flocculation and dispersion behavior of α-Al2O3 particles in aqueous solution, α-Al2O3 particles were added to various polyacrylic acid solutions differing in molecular weight, and added amount of polyacrylic acid, and pH. Median diameter, flow property, surface sedimentation rate, sedimentation volume, turbidity and zeta potential were measured for the α-Al2O3 particles in suspension. The effect of polyacrylic acid on the dispersion of α-Al2O3 particles and its mechanism were considered from the viewpoint of molecular length and dissolved state of the polyacrylic acid. Physical properties such as median diameter, shear stress, surface sedimentation rate and turbidity are suitable for judgment of the flocculation and dispersion behavior of fine particles. The flocculation and dispersion vary with the molecular weight and added amount of polyacrylic acid. In the case of polyacrylic acid with molecular weight under 20,000, Al2O3 particles are flocculated at low concentrations of polyacrylic acid but dispersed in high concentrations. When polyacrylic acid with molecular weight of 450,000 is added to the Al2O3 suspensions, Al2O3 particles are flocculated over the whole range of polymer concentrations. The effects of pH on the dissolved state of polyacrylic acid and the flocculation/dispersion behavior of Al2O3 are also clarified.
A new method using powder simulation was proposed to predict the optimum mechanical conditions of ceramic granules, which clarifies the relation between the mechanical characteristics and compression behavior of the granules. The tri-axial compression of granules was simulated by the three-dimensional particle element method (PEM) in order to obtain Young's modulus and strain-hardening rate of the granule bed, which are important mechanical characteristics for stress analysis in the compact by the finite element method (FEM). The relation between deviatoric stress and strain obtained by the simulation agreed well with that by the experiment. Young's modulus and the strain-hardening rate were expressed as a function of minor principal stress and strain, which were determined from the deviatric stress and strain diagrams, and stress analysis in the compression of granules was performed by FEM using these values of the mechanical characteristic. In the analysis, the granular bed was treated as compressible elasto-plastic material. It thus became possible to examine the relation between the mechanical characteristics of single granules and the stress distribution in the compact by these two simulations, and the result of such examination for single granules having arbitrary mechanical characteristics gives useful information for the granule design to obtain homogeneous green compacts.
The spring-back of compacts was quantitatively related with granule properties by a new mechanical analysis using the powder simulation to restrain the spring-back that occurs in compression of granules. First, it was confirmed experimentally that the mechanical properties of single granules varied with slurry conditions and affected the properties of compression and the spring-back of compacts. The compression and spring-back behavior of granules was simulated by the finite element method (FEM) considering the mechanical properties of single granules. The validity of proposed method was confirmed by the fairly good agreement of the simulated stress-strain curve and spring-back rate with the experimental results. Based on the results of simulation for granules having arbitrary mechanical properties, it was found that granules that undergo re-arrangement in the early stage of compression, transmit stress homogeneously in the middle stage, and undergo large plastic deformation in the last stage produce homogeneous compacts and restrain the spring-back of green compacts. The procedure proposed here offers useful information to design granules that restrain the spring-back of green compacts.
We have evaluated a transdermal delivery system containing prednisolone by in vitro/in vivo/in silico experiments. An in vitro study using hairless mouse skin showed that the steady-state rate of the drug penetration across the skin with polyoxyethylated oleyl ether (POE) and isopropyl myristate (IPM) as enhancer was 444-fold greater than that without enhancer. The plasma concentration after the application of transdermal prednisolone delivery system with POE and IPM was also measured using rats in vivo. The transdermal application showed an initial transient absorption process for 2 h after application and thereafter a constant concentration level of drugs was maintained for about 9 h. Moreover, the plasma concentration after the application of the transdermal prednisolone delivery system to the central abdominal skin of rats was simulated using the skin permeation parameters determined from the in vitro experiment. The simulated profiles agreed with the in vivo experiment.
Electroflotation of chlorinated organic compounds from wastewater using a soluble aluminum electrode was examined in the presence of surfactant added as a collector. The effects of the kind and concentration of surfactant, power consumption, and pH on removal of 2,4,5 trichlorophenoxyacetate (2,4,5-T) and 2,4,6 trichlorophenol (2,4,6 TCP) were examined experimentally. Cationic surfactants such as cetyltrimethylammonium bromide and trimethylstearylammonium chloride were shown to be effective to remove chlorinated organic compound. The final fraction of cationic surfactants remaining decreased below about 5 percent. The kinetics of flotation observed experimentally to follow a firstorder rate equation. As the concentration of cationic surfactants increased, the kinetic constant increased and the final fraction of chlorinated organic compounds remaining decreased. The kinetic constant increased with increasing power consumption, and reached a maximum value at approximately pH 9.
Treatments for detoxification of polychlorinated biphenyls are accelerating globally. We have developed an environmentally sound chemical detoxification plant for polychlorinated biphenyls using a combination of photochemical dechlorination (P.C.D.) and catalytic dechlorination (C.D.). First, a rate equation was modeled based on the results of experiments on P.C.D. On the other hand the C.D. by use of palladium carbon catalyst (Pd/C) was considered to remain chlorines at the ortho positions of PCB rings and therefore to be unsuitable for the degradation of PCB homologues such as tetrachlorobiphenyls and pentachlorobiphenyls. Additionally, for an initial concentration of PCB of more than 1,000 ppm, the crystallization of NaCl, one of the by-products was considered to inhibit the homogeneous dispersion of particles of catalyst in the solvent (isopropyl alcohol). Performance tests with the combined system were done, and finally a rate constant of 0.132 min−1 was obtained, which was greater than the target value of 0.102 min− 1 for this reaction. In conclusion the validity of this combined system for commercial-scale plants was confirmed.
Chloride volatilization characteristics of Cu, Pb, and Zn from MSW (Municipal Solid Waste) molten fly ash were studied using spent hydrochloric acid as a chlorinating agent. Experiments were carried out by using MSW molten fly ashes and model ashes to investigate the effect of Ca (Ca(OH)2) contained in the ashes on the chloride volatilization of heavy metals. When Ca-free model ash soaked with hydrochloric acid was heated at 1,123 K, more than 96% of Cu, Pb, and Zn were volatilized. However, the volatilization of these metals decreased with an increase in Ca(OH)2 content in the model ash. The volatilization behaviors of Cu, Pb and Zn in the model ash mixed with CaCl2 were almost the same as those in the model ash soaked with hydrochloric acid. It was considered that CaCl2 formed by the reaction of Ca(OH)2 and hydrochloric acid was responsible for the chloride volatilization of heavy metals. When the molten fly ash treated with a 20% excess molar concentration of hydrochloric acid over the Ca and heavy metals was heated at 1,123 K, more than 99 % of Pb and Zn were volatilized, irrespective of the kind of molten fly ash. The volatilization of Cu was also increased from 10–20% to 35–60% by heating the molten fly ash to 1,123 K, after soaking with hydrochloric acid. However, it was found that Cu was difficult to volatilize from the molten fly ash with a high Ca-content. SEM/EDS observation of the treated fly ash indicated that the surface of the fly ash was covered with CaCl2 melt in the heating process. It is considered that CaCl2 melt prevents the volatilization of CuCl2, which has a low vapor pressure at this temperature.
A method for determination of the amount of solid particles reaching the wall of a coal gasifier was developed in order to predict the adhesion phenomena of particles to the furnace wall. In this study, experimental measurements of the rate of arrival (adhesion) at the wall of particles flowing in a straight tube were compared with our numerical results. The experimental arrival rate could be represented numerically by analyzing the simplified two-fluid model. In this study, a system having a thermal gradient in the flow field near the wall was numerically analyzed using this simplified two-fluid model, and it was confirmed by comparing the calculated result with the result of Direct Numerical Simulation that the thermophoretic force increased the amount of solid particles reaching the wall.
To improve the performance and safety of a polymer electrolyte fuel cell (PEFC), five kinds of separators (parallel, two serpentine and two semi-serpentine) were evaluated from the viewpoint of state of gas flow, uniformity of current density and temperature, reduction of pressure loss, and exhaustibility of stay water by using the PEFC reaction and flow analysis model proposed by authors. In the case of the parallel separator, flow rate and current density distributions were not uniform, and exhaustibility of the stay water was low. In the case of the serpentine separators, the pressure drop was large. On the other hand, the semi-serpentine separators, which combine parallel and serpentine separators, showed the most uniform temperature distribution and were thus concluded to be the best type of those examined in the present study.
Three kinds of lignin were added to CWMs of Taiheiyou and Horonai coals and their dispersing abilities were evaluated from the change in viscosity of the CWMs. All three lignins markedly decreased the viscosity of both CWMs. Their addition at ca. 6.0 mg/g-coal was found to be optimal, because the viscosity reached minimum at this value. The maximum coal concentration in the practically applicable CWMs, whose viscosity has to be below 1,000 mPa·s, increased from 58.25 to 65.71 wt% for Taiheiyou coal and from 59.20 to 67.31 wt% for Horonai coal. Irrespective of the kind of lignin, the amount adsorbed on coal particles reached saturation at 6.0 mg/g-coal, which agreed with the optimal amount for addition to the CWMs. The ζ-potential of coal particles was influenced only by sulfonated lignin among the three lignins. From these results, lignin was considered to disperse coal particles mainly through its steric repulsion effect. Co-addition of lignin with the commercial dispersant PSSNa was examined from an economic point of view, but it was found not to be effective, because lignin might be adsorbed preferentially on coal particles and hinder the adsorption of PSSNa.
In our previous paper, we reported a hydrogen peroxide sensor that used crude particles of MnO2 immobilized in a polyvinyl chloride membrane attached on top of a dissolved oxygen sensor (Nagata et al., 2000). In this study we used MnO2 particles of under 400 mesh for the sensor preparation. With this sensor, the effects of the coexistence of oxidizing substances and of various water preparations on the steady-state sensor response, Rs, were investigated. The results were as follows. 1) The use of fine MnO2 particles of under 400 mesh improved the sensor sensitivity for H2O2 in distilled water to more than twice that of the sensor reported previously. The temperature dependency increased about 10% per 10 K as the temperature increased from 288 to 308 K, with the sensitivity at 298 K as 100%. 2) Rs values for oxidizing substances dissolved in distilled water were negligibly small. The coexistence of oxidizing substances with H2O2 in distilled water affected Rs values by less than 4%. For H2O2 dissolved in tap water, NaClO aqueous solution, or chlorine water, the Rs values were 4 to 11% lower than that for the distilled water solution of H2O2. For seawater solution of H202, the Rs values were almost equal to that of the distilled water solution of H2O2.