The influences of magnetic particle-particle interactions on orientational distributions and viscosity of a semi-dense dispersion composed of rod-like particles with a magnetic moment magnetized normal to the particle axis were investigated. In addition, the influences of the magnetic field strength, shear rate, and random forces on the orientational distribution and rheological properties were clarified. The mean field approximation was applied to take into account magnetic interactions between rod-like particles. The basic equation of the orientational distribution function was derived from the balance of torques and solved by the numerical analysis method. The results obtained are summarized as follows. For a strong magnetic field, the rotational motion of the rod-like particle is restricted in a plane normal to the shearing plane because the magnetic moment of the particle is restricted in the magnetic field direction. When a very strong magnetic interaction exists between particles, the magnetic moment is strongly restricted in the magnetic field direction, so that the particles tend to incline in the flow direction with the magnetic moment aligned with the magnetic field. For a strong shear flow, the directional characteristic of rod-like particles is enhanced, and this leads to a more significant one-peak-type distribution of the orientational distribution function. Magnetic interactions between particles do not contribute to the viscosity because the mean-field vector has only a component in the direction of the magnetic field.
An experimental study was carried out on the volume of the cavity formed behind impeller blades in aerated agitated vessels with highly viscous liquids. Two Rushton turbine impellers with different sizes were used to measure the volume of the “stable cavity” that remained behind impeller blades after stopping aeration. Agitation power was also measured under the condition of stable cavity formation and compared with that required for normal operation of an aerated agitated vessel. From the results, the relationships between the volume of the cavity formed in the normal operation and that of the stable cavity were considered. Stable cavity volumes were measured over wide ranges of agitation speed and test liquid viscosity. The results were discussed in terms of the forces acting on the cavity, and correlation equations for the cavity volume were derived for both laminar and turbulent flow regions.
Many difficulties have been encountered in safe and efficient abatement of the many varieties of VOCs (volatile organic compounds) present in large volume and low concentration in effluent gas. The authors propose the utilization of a VOC concentrator operating on the thermal swing adsorption of a honeycomb rotor adsorbent of hydrophobic zeolite. As a design and operation guide to industrial practice, discussion covers selection of appropriate honeycomb rotors, rotor dimensions and fluid velocity, flow rate ratio of process zone to regeneration zone, and optimum rotation speed. A new hydrophobic zeolite rotor was developed by reducing the silica sol binder by half to avoid the deterioration of performance due to accumulation of high boiling point VOCs. The amount of VOCs adsorbed by the deteriorated rotor was reached up to 90% of that of the virgin rotor by regeneration at high temperature of 300°C. Seal structure was also improved to allow long-term operation with high-temperature regeneration, and thus a high- performance VOC concentrator incorporating the new honeycomb rotor was put into operation.
To analyze the effect of the maldistribution of vapor and liquid flows among tube units of an internally heat-integrated distillation column (HIDiC) on its separation performance, a simulator was developed with an equilibrium stage model. The simulation study indicated that the maldistribution of vapor and liquid flows among tube units would influence the top product specification. From the simulation results, the acceptable difference between the maximum and the minimum liquid flow rates was determined to be less than 3%. The design strategy for the high performance liquid distributor for the pilot-scale HIDiC with seven tube units was discussed. The distribution system developed was validated by experiments. Furthermore, the distributor was applied to the pilot HIDiC. Since there is no temperature distribution between tube units, the distributor seems to achieve a maldistribution rate of less than 2.5%.
Gold was selectively separated and recovered by means of aggregation and precipitation using astringent persimmon extract which contains a large amount of persimmon tannin, a kind of polyphenol. Quantitative recovery of gold was achieved in the concentration range of HCl lower than 0.5 mol·dm−3. The XRD analysis and the observation by digital micrograph of the gel after filtration supported the formation of gold particle during recovery process. High selectivity of the persimmon extract is attributable to the reduction of Au(III) to elemental form.
Control of the turbidity and concentration of free residual chlorine is of growing importance in the purification and disinfection of pool water. In general, suspended solids are removed from pool water by cycle filtration, and disinfectant is injected into pool water intermittently, depending on the concentration of free residual chlorine. In this study, various types of program swimming, in which a given number of people swam at a scheduled time, was performed in a heated indoor pool equipped with a sand filter and disinfection system using sodium hypochlorite. The variations over time of the turbidity, the concentration of free residual chlorine in pool water, and the dosage of disinfectant were measured. The variation of the turbidity over time was well evaluated using the quantity of turbid material secreted outwardly per man-hour, on the basis of the modified Muroya equation, in which the removal characteristics of turbid material by the filter were taken into account. The calculated results accorded well with the measured turbidity. Moreover, the chlorine consumption needed to maintain a consistent level of free residual chlorine in pool water was calculated on the assumption that the consumption consists of two parts: a part caused by swimmers and a part that was proportional to the concentration of free residual chlorine in pool water. As a result, the variation of the consumption of free residual chlorine was well evaluated. These results serve as a basis for the design and operation of a swimming pool.
A counter-diffusion chemical vapor deposition method using siloxanes (hexamethyldisiloxane (HMDS), 1,3-divinyltetramethyldisiloxane (DVTMDS), 1,3-dioctyltetramethyldisiloxane (DOTMDS)) as silica precursors was employed to prepare composite silica membranes, showing stable hydrogen permselectivity at high temperature. The membrane prepared with HMDS showed a H2 permeance of 1.2×10−6 mol·m−2·s−1·Pa−1 and a H2/N2 ideal selectivity of 550 at 873 K, and 1.0×10−6 mol·m−2·s−1·Pa−1 and 590 at 1073 K. The H2 permeance was about one order of magnitude larger than that of the conventional silica membrane prepared with tetramethylorthosilicate (TMOS) as a silica precursor. It was found that the H2 permeance of the HMDS silica membrane initially decreased about 8% and was then maintained for 200 h at 773 K, whereas that of the TMOS silica membrane decreased gradually. Hydrothermal stability test was also carried out in a stream of nitrogen including steam at 773 K. Though an initial 26% drop in the H2 permeance was observed, the change afterwards was small during a 20-h test. It was shown that the use of a precursor having the siloxane structure was effective in preparing silica membranes with high temperature durability.
A Langmuir-Hinshelwood type kinetic model of ethyleneimine (EI) formation by vapor phase dehydration of monoethanolamine over an acid-base catalyst was derived. By using this model, the extraordinary behavior of this reaction was explained as follows: EI formation reaction was restricted by equilibrium, but side reactions were not restricted. When monoethanolamine was converted at a level higher than the equilibrium of the main reaction, EI selectivity was theoretically restricted. A reaction process was designed by use of this model, and a reduced pressure process without carrier gas was proposed.
Ultrasonic emulsion polymerization, which allows low surfactant concentration and absence of any chemical initiator, is advantageous from the viewpoint of green sustainable chemistry. In this study, polymerization of styrene under unsteady indirect ultrasonic irradiation was investigated. The position of the reactor was changed in two steps depending on the progress of the polymerization. In the first step, the reactor was set at the position where the induction period was short. On the other hand, in the second step, the reactor was set at the position where the effect of degradation of the polymer was small. The effects of the irradiation time in the first step and position of the reactor in the second step on the molecular weight distribution were studied. The proposed dynamic process operational method by changing irradiation conditions with the progress of the polymerization is efficient for intensification of emulsion polymerization process.
The pure and fine silica particles are widely used in the semiconductor industries. In our previous paper, the authors have demonstrated that production of fine silica powder is possible by gas phase hydrolysis of tetramethoxysilane (TEMS). In this paper, we report the effect of the shape of reactor and operational condition, such as mixing condition and temperature on conversion of the reaction and properties especially particle diameter of produced silica fine particles. The different shapes of reactors named as Type 1, Type 2, and Type 3, were tested. In Type1, H2O and TEMS were introduced cocurrently and heated in the reactor. On the other hand, in Types 2 and 3, TEMS introduced from the top was vigorously mixed, at relatively upper and rather vicinity of the center parts respectively, with heated H2O introduced from the bottom through the center part of the reactor. Thus TEMS is mixed with more heated water in case of Types 2 and 3 than Type 1. Type 3 has a shorter water introduction pipe and TEMS and H2O are mixed at higher temperature than Type 2. The average diameters were decreased as the order of Type 1, Type 2 and Type 3. It was demonstrated that smaller fine particles were produced by rapid heating of TEMS under coexistence of water vapor. Under the condition, only nucleation reaction is expected to be accelerated, by suppressing particle growth through heterogeneous reaction. The mixture condition of the gas leading to the heating condition of TEMS with water vapor could be changed by changing the shape of reactor, which resulted in the change in averaged diameter of the produced silica particles.
The author's previous drying characteristic model for planes with Fickian mass transfer was modified by taking into consideration the sensible heat and the penetration period. A new drying characteristic model incorporating the acceleration effect of the mass transfer caused by drying stress was proposed on the basis of the modified model. The drying characteristic model may be modified easily for a new material and be suitable as a general drying model for multiple materials. Performance of the new model was examined by comparing the results with experimental results and simulated results obtained with a Fick-type diffusion equation for polyvinylalcohol aqueous solution film in a previous study. Drying rate curves calculated with the new model showed quantitative agreement both with the previous experimental results and with the simulated results that had not agreed with the experimental ones. Results calculated with the new model for an imaginary gel film showed qualitative agreement with experimental results for gelatin gel film obtained in another previous study. A large difference between the simulated drying rate with and without the acceleration effect by the new model for a coated layer thickness of factory production level was found during the final stage of drying process.
Most architectural waste wood contains preservative-treated material, and one of the most popular preservatives is CCA, which contains chromium, copper and arsenic oxide. This work was conducted to examine the gasification characteristics of charcoal derived from CCA-treated waste wood for production of fuel gas from architectural waste wood. Charcoal from CCA-treated wood was gasified by using a thermobalance-type reactor under CO2 atmosphere, and the behavior of chromium, copper and arsenic during carbonization and gasification, and the influence of these components on gasification of the charcoal were examined. The experimental results revealed that the metals included in the CCA reagent, particularly copper, decreased the activation energies for CO2 gasification of the charcoal. During carbonization and gasification, it was confirmed that the arsenic were escaped from the wood and charcoal, while the copper and chrome ware completely concentrated in the gasification residual ash.
Fundamental research was conducted on the recovery, separation and purification of indium from spent liquid crystal display panels containing a small amount of indium. Acid leaching tests suggested that effective extraction can be achieved by using hydrochloric acid, with nearly the same efficiency as aqua regia. Solvent extraction tests suggested that indium can be effectively extracted with trialkylphosphine oxide compounds from concentrated hydrochloric acid. High porous XRD-7 resins impregnated with Cyanex 923 and Aliquat 336 were prepared to examine their adsorption behaviors from hydrochloric acid for all metal ions contained in the spent panels. The two types of resins were packed in two columns, through which model hydrochloric acid solution containing the same concentrations of metal ions as those in the leach liquor was passed. In the first column, in which the resin impregnated with Aliquat 336 was packed, the major impurities, iron, tin and zinc, were removed. In the second column in which the resin impregnated with Cyanex 923 was packed, indium was selectively adsorbed. The loaded indium was eluted with dilute sulfuric acid and was enriched more than 10 times composed with the feed solution.
Lead-free glasses with a low melting temperature (lower than 600°C) and good chemical durability are desirable for the sealing process in the ceramic and electronic industries. In our previous studies, the quaternary systems (41.8 mol% V2O5–3.1 mol% ZnO–17.6 mol% BaO–37.5 mol% TeO2 or 53.0 mol% V2O5–4.0 mol% ZnO–22.4 mol% BaO–20.6 mol% P2O5) were confirmed to have excellent sealing and thermal properties. In this study, we carried out a thermal-shock test, a pressure-resistance test, and a continuous lighting test for evaluating the practical application. These lead-free glasses exhibited excellent performance and properties as a substitute for the commercial lead sealing glass.
To develop an efficient recovery process of zinc from molten fly ashes, the release of zinc from the ashes was investigated during heat treatment with and without the addition of polyvinyl chloride or carbon. Change in the form of zinc in the ashes with temperature was clarified by sequential leaching analysis. Two kinds of molten fly ash obtained from different melting processes were used which contained ZnO or ZnCO3 as the major zinc component, respectively. In the case of PVC addition, formation of zinc chloride was identified in the ZnO-based sample from 573 K, and volatilization of zinc was observed from 873 K. In the ZnCO3-based sample, the volatilization of zinc was accelerated from the melting point of CaCl2, while zinc chloride was not observed in the solid phase. When carbon added to the ashes, remarkable volatilization of zinc was observed from the boiling point of ZnCl2, and the extent of zinc release depended on the chlorine content of the ashes.
To develop the newly dry-processing technology for reconverted resources fluorine as fluorite contained in waste chlorofluorocarbon (R22), the reaction characteristics of steam decomposition gases of chlorofluorocarbon with air and calcium carbonate were investigated. The gas–solid reaction of the chlorofluorocarbon decomposition gases, in which the HF concentration of about 30% and HCl concentration of about 15%, and calcium carbonate, of which grain size is 1–2 mm, was conducted at the temperature of 200°C and SV of 1860 h−1. It was found that HF concentration contained in the off-gas from fixed-bed reaction furnace before HF break-through time was very as low as less than 1000 ppm, on the other hand HCl concentration becomes high with the range of 10–15%. This result shows that fluorine is alternatively absorbed by calcium carbonate in a fixed-bed reaction furnace. Moreover, the fluorite purity of the sample by which the reaction progressed comparatively into the fixed-bed reaction furnace became about 94%. Also, we demonstrated that the calcium chloride generated by reacting chlorine and calcium carbonate in the lower part of the fixed-bed furnace replaces calcium fluoride gradually with advance of a reaction time. From these results, the implement ability of the dry-type reconverted resources technology of waste chlorofluorocarbon can be verified.
Waste incineration fly ash could be successfully recycled into calcium phosphate hydrogel, a type of fast proton conductor. Various properties of the intermediate and calcium phosphate hydrogel from incineration fly ash were characterized and compared with those from calcium carbonate reagent. It was found that the intermediate from the incineration ash, calcium phosphate glass has lower strength than that from calcium carbonate reagent. The electrical conductivity of amorphous and crystallized hydrogel obtained from any raw material increases exponentially with increasing temperature. However, the amorphous hydrogel from incineration ash shows higher electrical conductivity than that from the reagent. On the other hand, the crystallized hydrogel from incineration ash has lower electrical conductivity and lower crystallinity than that from the reagent. Moreover, the difference in electrical conductivity between these crystallized hydrogels decreases with temperature. These experimental results suggest that the incineration fly ash is a useful calcium source for the synthesis of calcium phosphate hydrogel.
In this study, we used iron powder and hydrogen peroxide, and investigated the kinetics of decomposition of TCE by the Fenton's reaction. As a result, the decomposition of TCE with iron powder was found to occur after some introduction period, which is not observed for that with ferrous iron. Excepting the period, the decomposition rate was found to be analyzes as the first order reaction. The obtained first reaction constants are found to be proportional to the iron powder concentration, but the reaction order to hydrogen peroxide changed with the range of its concentration. At its relatively high concentration of hydrogen peroxide, the reaction order for the concentration of hydrogen peroxide became negative.