We have investigated the influences of longitudinal external magnetic field strength and area fraction of particles on microstructures of quasi-two-dimensional monolayers composed of ferromagnetic nanoparticles by means of Monte Carlo simulation. The microstructures of the monolayers obtained in simulations were analyzed in terms of the radial distribution and orientational distribution functions. The results obtained are summarized as follows. For a small area fraction of particles, the formation of a chain-like structure is prevented by the orientation of the magnetic moment in the direction of the magnetic field, so that a gas-like microstructure appears for a sufficiently strong magnetic field. For a large area fraction of particles, the chain-like structures are still formed even when a relatively strong magnetic field is applied. For a very strong magnetic field, a liquid-like microstructure appears, and the chain-like structures disappear.
Activity coefficient equations such as the NRTL equation are widely used for examining solvent recycling processes where distillation separation is used. However, many activity coefficient parameters of aqueous systems have not been determined. Because aqueous systems can form two liquid phases according to the conditions, experimental determination is not necessarily easy. This study aims to determine activity coefficient parameters of two liquid systems. First, because a vapor hold-up compensable ebulliometer was unable to measure a heterogeneous system, it was modified. Next, the boiling points of three binary systems, namely, 2-propanol+water and 2-butanol+water, which show heterogeneous azeotropic systems, and water+n-pentyl acetate, which is not reported in available vapor–liquid equilibria data and is not a homogeneous system, were determined in a range of 40.00 to 98.66 kPa. Experimental boiling point data were satisfactorily correlated using the NRTL equation. For the 2-butanol+water system, for which vapor–liquid equilibria and solubility data are available, boiling point data were correlated using the vapor–liquid equilibria and solubility data. Compared with using only the boiling point data, the solubility data determined were closer to the measured values. It was postulated that the NRTL parameter of the water+n-pentyl acetate system as measured was useful because measured data have not yet been reported for vapor–liquid equilibria.
The effect of a binary solvent with high and low boiling points on the film formation in ink-jet printing of a polymer solution was studied experimentally. The principal reason that the binary solvent prevents the formation of a ring-stain is that the low boiling solvent evaporates quickly, resulting in an increase in the solution viscosity at the pinning of the contact line. The experimental results revealed that this increase in viscosity is caused by Marangoni convection due to the concentration profile of the solvents on the free surface. Based on this finding, experiments with a single-solvent droplet showed that ring-stain formation can be suppressed by increasing the initial solute concentration. With the binary solvent, it becomes possible to impact fluids of even higher viscosity on the surface by increasing the evaporation of the low boiling solvent. Furthermore, the atmospheric temperature and the gap between the nozzle and the surface affect the viscosity at impact at which the ring stain is eliminated.
We experimentally studied the motion and shape of single rising bubbles in superpurified water. We developed an apparatus, which was equipped with a measurement system of both resistance and TOC value of water, in order to maintain water purity by monitoring it during the experiment. We investigated the critical Reynolds number over which the rising bubble motion changed from rectilinear motion to zigzag or spiral motion. In the case of Re=650, the bubble reached the terminal velocity at the height of 40 mm and the onset of transition to zigzag or spiral motion was observed at the height of 140 mm. On the other hand, in the case of Re=700, both the terminal velocity and onset of transition were observed at the approximately same height; hence the critical Reynolds number was unable to be uniquely determined. The height of the onset of transition increased with the decrease in Reynolds number. We also compared experimental results of both the terminal rise velocities and drag coefficients with those obtained theoretically for ellipsoidal bubble in the limit of potential flow theory. For smaller bubbles, experimental values of the terminal velocities and drag coefficients showed good agreement with those obtained theoretically. For larger bubbles, however, the deferences between experimental and theoretical values in the terminal velocities and drag coefficients became prominent. Finally we quantitatively evaluated the bubble shapes by expanding them in terms of Legendre's polynomials and proposed the new correlations of the aspect ratio with either Weber number or Eotvos number.
The behavior in an electric field of fine particles present in aqueous solution was measured in order to apply the results to the classification of fine particles. The sample particles used were spherical polystyrene particles with average diameters of 0.03, 0.1, 1.0, 4.3 and 9.6 μm. Electrophoretic mobility and zeta potential of the particles were measured based on the principle of the laser Doppler effect. The electrophoretic mobility was found to increase with increasing pH and temperature of suspensions, and to vary with electrolyte concentration and particle size. The electrophoretic retardation effect and relaxation effect were considered to explain the behavior of fine particles in an electric field by applying the electro-kinetic theory of Wiersema et al. The forces acting on particles in an electric field are considered to be electrical force, friction force and other forces like relaxation effect and electrophoretic retardation effect which appear in ionic behavior. We found that the particle moving velocity depends on the particle size. When the particle size is less than 1 μm, the velocity increases with increasing the particle size. On the other hand, the velocity deceases with increasing in particle size when the particle size is larger than 1 μm. These phenomena can be explained by the forces acting on the fine particles in the electric field. The behavior can be applied to classification of fine particles.
In the semiconductor manufacturing process, mixtures of hydrofruoric acid, nitric acid and other acids are often used as washing or etching solutions for silicon wafers. In our previous paper, the salt effect on vapor-liquid equilibrium of nitric acid-water systems was measured, and a distillation method for separation of nitric acid from acid mixture was been presented. This study presents the distillation treatment of hydrofluoric acid with use of the salt effect on the vapor-liquid equilibrium for acid aqueous solutions and acid mixtures. The vapor–liquid equilibrium of hydrofluoric acid-salt systems (fluorite, potassium nitrate, cesium nitrate) was measured using apparatus made of PFE (perfluoro alkyl vinyl ether). Cesium nitrate showed a salting-out effect on the vapor–liquid equilibrium of the hydrofluoric acid-water system. Fluorite and potassium nitrate showed a salting-in effect on the hydrofluoric acid-water system. Separation of hydrofluoric acid from an acid mixture containing nitric acid and hydrofluoric acid was tested by the simple distillation treatment using the salt effect of cesium nitrate (45 wt%). Acid mixture of nitric acid (5.0 mol/dm3) and hydrofluoric acid (5.0 mol/dm3) was prepared as sample solution for distillation test. The concentration of nitric acid in the first distillate decreased from 5.0 mol/dm3 to 1.13 mol/dm3, and the concentration of hydrofluoric acid increased to 5.41 mol/dm3. This first distillate was further distilled without addition of salt. The concentrations of hydrofluoric acid and nitric acid in the second distillate were 7.21 mol/dm3 and 0.46 mol/dm3, respectively. It was thus found that the salt effect on vapor–liquid equilibrium of acid mixtures was effective for the recycling of acids from acid mixture wastes.
Experiments to separate copper, nickel, zinc and cobalt were carried out on an unmodified Vycor porous glass-packed column using pyridine-2,6-dicarboxylic acid (PDCA) as an eluent. The retention volumes of zinc and cobalt had the maximal values around pH 3, because the concentrations of hydrogen ion and PDCA anion are both low. Copper, nickel and zinc were eluted in order with a large stability constant of PDCA complex which included these metals as a central metal. On the other hand, cobalt was eluted the last without following this rule. It was considered that cobalt ion was oxidized to change into the trivalent cation in the column. These four metals were completely separated in 150 min under the conditions of eluent pH of 3.0, PDCA concentration of 0.05 mol/m3 and column length of 150 mm; and in 60 min under the conditions of eluent pH of 2.5, PDCA concentration of 0.15 mol/m3 and column length of 300 mm. Thus it was shown that an unmodified Vycor porous glass-packed column could be used to separate divalent transition metals.
Dust collection by an annulus granular bed filter consisting of a double packed column, having large diameter granules outside an inner tube with multiple holes in the wall for dust gas in-flow, and small diameter granules inside the outer tube with multiple holes for gas out-flow, was carried out experimentally to examine a new functional filtration method. The filter granules and fines used were glass beads and fly ash, respectively. The same high collection efficiency as a single packed bed of small granules of 1 mm diameter, but lower pressure loss of less than one-half could be attained with the double packed column with a suitable combination of granule diameters of 3 mm and 1 mm. The dust collection model proposed previously was also fairly applicable to represent the experimental results and was considered to be useful for designing the functional annulus granular filter.
To improve the CO2-reforming performance of TiO2 photocatalyst, various metals were supported by means of photodeposition on coated TiO2 film prepared by sol-gel and dip-coating method, and CO2-reforming performance of such coated TiO2 film was evaluated. When Pd was supported on the surface of coated TiO2 film on Cu tube, the effect of the supported metal was not fully realized, because the coated TiO2 film was separated from the Cu tube by embrittlement in the process of supporting the metal. When the coated TiO2 film was prepared by dissolving TiO2 powder with the supported metal in TiO2 sol solution, the CO2-reforming performance of coated TiO2 film with Pd supported on TiO2 powder was the highest among coated TiO2 films with Cu, Pd or Pt supported on TiO2 powder. The performance of reforming a gaseous mixture of CO2 and H2O into CO and hydrocarbon was promoted by decreasing firing time from 420 s to 180 s irrespective of supported metal type. With the aid of supported metal, the concentration of produced CO, the intermediate in the production of CH4, increased with the concentration of produced CH4, resulting in improved CO2-reforming performance of coated TiO2 film.
This paper presents a mechanistic study of low-temperature (300–600°C) steam reforming of poor biogas using dielectric barrier discharge and catalyst-bed hybrid reactor. Although excited species produced by high-energy electron impact are responsible for the synergistic effect between non-thermal plasma and catalyst-bed, heat generated by non-thermal plasma also accelerates catalytic methane reforming at low temperatures: when discharge power was excess in supply, catalyst-bed temperature significantly increased and synergistic effect due to radical production was no longer anticipated. In order to distinguish their respective contributions to the synergistic effect, we analyzed the overall methane-reforming rate based on power law kinetics (r=k [CH4]α [H2O]β). The forward reaction rate constant (k) was analyzed by means of Arrhenius plots with respect to catalyst-bed temperature measured by infrared camera. Reaction orders for methane (α) and water-vapor (β) were experimentally determined from the initial conversion rate of methane, showing both α and β were clearly increased in the presence of non-thermal plasma. Activation energy in the reaction-dominant regime (<450°C) was approximately 100 kJ·mol−1 regardless of non-thermal plasma: reaction pathways seem to be essentially unchanged by the non-thermal plasma. On the other hand, pre-exponential factors increased by a factor of ten by applying non-thermal plasma. The sticking probability of excited molecules to the catalyst surface is expected to increase, which in turn accelerates the dissociative chemisorption of excited methane on the catalyst. The result also implies that excited water-vapor may have an ability to prohibit solid carbon deposition. Although methane dehydrogenation is the rate-determining step, activation of water-vapor is beneficial to maintain catalyst activity with minimum steam/carbon ratio.
This paper presents a reliability analysis using “sensuous level of incidence” for estimating the probability of accidents in chemical plants. The effects of measures to prevent accidents caused by human error are estimated quantitatively in the calculation based on the fault tree analysis. Here, the sensuous level of incidence is introduced as a sensitive variable because the frequent probability of a primary event connected with an accident tends to be not precise at present. By the analysis of plant accidents in an abnormal state, it is clarified that use of the sensuous level of incidence is effective for evaluateing the effects of preventive measures for accidents.
A solid oxide fuel cell (SOFC) hybrid cycle power plant system is expected to be a higher efficiency energy system than a conventional gas turbine combined cycle system (GTCC). The optimal design and operational conditions of a SOFC-GTCC hybrid system were derived by using static principle models. Results showed that the electrical efficiency of a 100 MW pressurized topping cycle system can be more than 70% on the basis of high heating value. On the other hand, the electrical efficiency of the SOFC-GTCC hybrid system minimizing the life cycle cost decreased to 67%, because the initial cost of SOFC is much higher than that of GTCC. The SOFC-GTCC system showed robustness to load changes during operation when it was designed through a multi-period optimization.
The conditions of the air layer on a solid–liquid surface in a reactor were investigated at 1 G and under microgravity to reduce the aeration power required in a gas–liquid dispersion system under microgravity. Air adhered to the water–repellent surface in a static liquid under microgravity. The adhesion conditions were determined by the Capillary number and the Froude number. Feeding air in a low centrifugal force field under microgravity created the air layer on the water–repellent surface.
Spray-drying with a two-fluid nozzle was used to produce composite particles consisting of silica or titania nanocolloids and template particles (polystyrene latex: PSL). Template particles were then removed from the composite particles by heating or washing with organic solvent to yield respectively porous SiO2 and TiO2 particles. The average size and standard deviation of particles prepared by spray-drying with the two-fluid nozzle were 1.31 μm and 1.59 respectively. When the size of template particles was varied in the rage of 100–400 nm, porous particles were synthesized with template particles of 200 nm or smaller, while hollow particles were obtained with template particles of 300 nm or larger. In addition, polyethylene glycol (PEG) porous particles could be obtained by the same method.
To level the electric load and increase the efficiency of cold heat production, a new cold heat storage-heat utilization air conditioning system incorporating PCM13 (phase-change material with a melting temperature of 13°C) in a conventional VCRM (vapor compression refrigerating machine) was proposed. In this system, the cold heat is stored in PCM13 during the VCRM operation in the night-time. Subsequently, the cold heat stored in PCM13 is released for use as a coolant in the VCRM condenser in the case of high COP (coefficient of performance) during daytime. Energy savings of the proposed system were compared with the conventional cold heat production system with ice in terms of the cooling load of a standard office and a residence in summer in Tokyo. This comparison was based on estimation of COP of VCRM from p-h diagram of hydrofluorocarbon refrigerant, R134a. As a result, the energy saving of the proposed system, compared with the ice thermal storage in terms of power input of cold heat of 5°C, was 13% and 11% for a standard office and a residence, respectively. The higher energy saving obtained for a standard office was attributed to the fact that the cooling load is distributed over day-time in the office, while in the residence, it is highest at night-time. Finally, when ice was replaceed with PCM13 in a conventional ice thermal storage, the energy consumption was reduced by 47% and 49% for a standard office and a residence, respectively. However, the temperature of cold heat supplied was 18°C, which was too high to dehumidify the air in the air-conditioning process.
Catalysis by CaO/SiO2 composite (silica-supported calcium oxide) was studied for production of biodiesel, which has attracted interest as a means to reduce greenhouse gas emissions. The catalyst composite was prepared by carbonation of Ca(OH)2 in an aqueous suspension including the silica support, followed by calcination in an argon gas flow. In the carbonation, the silica support could be coated with CaCO3 as precursor of the active material below 18°C. Above 30°C, the precipitated CaCO3 did not coat the silica support at all. The precursor composite with an appreciable core-shell structure prepared below 18°C was subjected to calicimation at 900°C, then the catalytic activity of the composite was fesfecl in the transesterification of soybean oil with methanol at its refluxing temperature. However, the testing reaction was not catalyzed. Since all CaCO3 particles were converted into calcium silicate after the calcination due to reaction with the silica support, CaO as the active material could not survive on the surface of the composite sample. Such the catalytic deactivation was overcome by increasing of the amount of CaCO3 particles on the surface of the silica support. This operation provided CaO survivors on the surface of the improved catalyst composite obtained after the calcination, and the transestrification of soybean oil was approximately completed in 3 h over the improved catalyst composite. The improved catalyst composite was as active in the test reaction as fine particles of bulk CaO.
To develop highly efficient adsorbents for water vapor that may be applicable in an adsorption heat pump (AHP), KOH chemical activation was applied to containing added melanine, in an attempt to keep as many hydrophilic functional groups as possible on te activated carbon. As a result, it was found that simple addition of melamine did not increase the number of hydrophilic functional groups. However, when phenol resin with chemically bound melamine was employed, the attachment of nitrogen on the active carbon was observed. Further, the number of hydrophilic functional groups was found to increase. Finally, the amount of water vapor adsorbed on the active carbon manufacutred was found to be 1.7 times higher than that adsorbed on silica gel, in the relative water vapor pressure range of an AHP in a closed system.
This study aimed to obtain fundamental data for developing efficient recovery process of valuable metals from various molten fly ashes produced from melting furnaces. Release behavior and chemical form change of zinc were investigated during chlorination of ashes. Chemical forms of zinc in ash were classified into four groups, oxide and carbonate, silicate and aluminosilicate, ferrite, and sulfide by chemical leaching and XRD analyses. In molten fly ash M and B produced from coke bed and fluidized bed–gasification melting furnaces, 93% and 60% of zinc existed in the form of oxide or carbonate, respectively. Ash B contained ferrite, silicate, aluminosilicate, and sulfide as the remainder. A drastic change of zinc form distribution was observed for ash B after heat treatment at 1073 K, while zinc was hardly released from the solid phase of ashes M and B. When the ashes were heated with polyvinyl chloride, zinc oxide and aluminosilicate reacted to give a volatile compound. Zinc ferrite reacted with calcium carbonate and was stabilized into the solid phase as zinc oxide. Carbon addition was effective for volatilization of all zinc forms, including zinc silicate and zinc sulfide.