KAGAKU KOGAKU RONBUNSHU
Online ISSN : 1349-9203
Print ISSN : 0386-216X
ISSN-L : 0386-216X
Volume 25 , Issue 6
Showing 1-37 articles out of 37 articles from the selected issue
  • AKINORI TAKAMI, TOSHIYA KOBAYASHI, HIDEAKI KURITA, SEIICHIRO KODA
    1999 Volume 25 Issue 6 Pages 827-831
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Irradiation of the second harmonics of Nd : YAG laser (532 nm) to gold nano-particles dispersed in gelatin for 5 min changed the diameter of the particles from 10 to 3 nm. At the same time the particles were dispersed more homogeneously after irradiation. Size change was observed with the fluence of more than 90 mJ cm-2. The particles were dispersed more homogeneously when the number of pulse irradiation increased. Due to the breaking up of the particles, the number density of the particles per unit volume increased 10 times more than that before irradiation.
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  • BING SUN, MASAYUKI SATO
    1999 Volume 25 Issue 6 Pages 832-836
    Published: November 10, 1999
    Released: February 19, 2010
    JOURNALS FREE ACCESS
    The characteristic of active species formation in aqueous phase is investigated by applying a high voltage pulse to needle-plate electrode configuration. Radicals (·OH, ·O, ·H) were detected by analyzing emission spectra from the discharge channel. It is found that the radical formation is slightly delayed (1μs is in the order of magnitude, depending on rising time of the applied pulse) from the peak of the applied voltage. Formation of radicals is also influenced by pulse wave shape such as half width and peak voltage, and oxygen gas bubbling into the discharge region. Hydrogen peroxide is formed by the pulsed discharge where the formation rate is larger in the case with oxygen gas bubbling than that of no bubbling.
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  • HISAMICHI ARUGA, HIDEO NISHIUMI, KOUICHI SATO
    1999 Volume 25 Issue 6 Pages 837-841
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Experiments on photo-decomposition of CFC-115 bubbled in an alkaline alcoholic solution were carried out in a photochemical reactor irradiated by a 32 W low-pressure mercury-vapor lamp. It was found that initial decomposition rate of CFC-115 was governed by a chain reaction, and the reaction rate increased with partial pressure of CFC-115, was independent of sodium hydroxide concentration, and proportional to the square root of the light intensity. Based on this, a radical reaction mechanism of initial photo-decomposition is proposed.
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  • TAKUO SUGAWARA, TOSHIAKI KAWASHIMA, JUNJI SAKURADA, KATSUYASU SUGAWARA
    1999 Volume 25 Issue 6 Pages 842-848
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    By utilizing a batch-recycle photoreaction system, decomposition characteristics of formic acid and hydrogen peroxide are precisely examined in the course of 254-nm light irradiation of dilute, aqueous formic acid solution added with hydrogen peroxide. Irrespective of the initial concentration level of hydrogen peroxide, its decreasing rate is low, while formic acid remains in the presense of oxygen. The decomposition rate of formic acid is proportional to the irradiation intensity and to the 0.5 th order of hydrogen peroxide concentration. The effect of formic acid concentration is low.
    The observed results are simulated with a photoreaction model which incorporates a group of elementary steps. The reaction rate constant of the photo-initiation step is firstly determined for the autophotolysis of hydrogen peroxide. To evaluate the oxidative decomposition kinetics of formic acid, a model is then developed which includes subtraction of the hydrogen atom from formic acid molecule by a hydroxyl radical and reproduction of hydrogen peroxide through addition of oxygen to the formic-acid derivedradical.The present reaction model simulates the decomposition characteristics of formicacid and the unique concentration change of hydrogen peroxide fairly well.
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  • EIKO OBUCHI, MASAYUKI HASHIMURA, KATSUYUKI NAKANO
    1999 Volume 25 Issue 6 Pages 849-853
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    A titania coating solution was prepared by dissolving amorphous titania powders in 31 % hydrogen peroxide solution. Transparent titania thin films were prepared by dip-coating them on glass plates. The titania film was found to be uniform in thickness, when prepared using this solution with viscosity of 1 mPa·s. The refractive index of the film was estimated to be d = 2.3, which is slightly lower than that of pure anatase powders (d=2.5). The film thickness was found to be directly proportional to the withdrawal speed of V2/3. It was also found that the absorption edge of the UV-vis spectra shifts to a longer wavelength with increasing film thickness. Film thickness was easily estimated from the value of the wavelength at the absorption edge.
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  • TOSHIYUKI YOKOTA, HERI PURWOTO, YASUYUKI TAKAHATA, TETSUO KATSUYAMA
    1999 Volume 25 Issue 6 Pages 854-860
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Light intensity profiles in an annular photoreactor with gas-solid-in-liquid dispersions are measured by means of a newly designed photo-probe which shows a uniform sensitivity to scattered light rays from any directions. The light scattering intensity profiles are approximated by a modified equation which includes two model parameters as a weight coefficient and an effective attenuation coefficient in the light intensity profile equation based on a diffused line light source model for an annular photoreactor with a homogeneous phase. The functional relations between the two parameters, and gas-holdup and solid particles concentration are determined to satisfy the measured profiles. The modified equation can estimate the light absorption rate due to the dispersed solid particles in the reactor. The rate shows a maximum value for the optimum solid concentration with a certain gas hold-up.
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  • JUNICHIRO OTOMO, TOKURO EBUKURO, YOSHITO OSHIMA, SEIICHIRO KODA
    1999 Volume 25 Issue 6 Pages 861-867
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Photo-oxidation reactions in a mixture of C2H6/O2/CO2 are investigated with KrF excimer laser irradiation. The main initial products are acetaldehyde and ethanol. The reaction is induced by onephoton absorption of O2 which yields to O2 (A'3 Δu). It is considered that C2H6 reacts principally withO2 (A') to generate oxidation products. The solvent density effects on the light absorption process of O2 and its subsequent quenching processes are discussed.
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  • MOTOAKI ADACHI, CHAN SOO KIM, TAE OH KIM, KIKUO OKUYAMA
    1999 Volume 25 Issue 6 Pages 868-872
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Effects of NO2 gas on the particle formation inSO2/H2O/Air mixture by a-ray radiolysis are studied experimentally. When NO2 gas is added to the SO2/H2O/Air mixture, particle number concentrations increase and the charged-particle fractions of newly borne particles are higher than 0.85. These results suggest that HNO3 is not produced by the reaction between NO2 and OH radical and the particle generation is not reduced by the production of HNO3. In order to elucidate whether HNO3 is produced or not, NH3 gas is added to NO2/H2O/Air mixture. Particles appear upon the addition of NH3, but they are not generated in its absence. All particles generated upon the addition of NH3 have a charge. It is found from the results that particles are formed by the ion-induced nucleation in the NH3/NO2/H2O/Air mixture, but not by the homogeneous nucleation of NH4NO3 produced by the reaction between HNO3 and NH3. The above results suggest that particle generation in the NO2/SO2/H2O/Air mixture by a-ray radiolysis is caused by ion-induced nucleation following the ion-molecule reactions, but HNO3 is not produced by the reaction of NO2 and OH radical.
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  • YUSUKE TAJIMA, HISAYOSHI ARAI, KAZUO TAKEUCHI
    1999 Volume 25 Issue 6 Pages 873-877
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Polycondensation of furan derivative by singlet oxygen, which is generated using the sensitizer such as fullerene C60, is applied to the crosslinking of polymers. A polymer having furan units in the side chains was synthesized by the polymerization of furfrylmethacrylate with 2, 2'-azobis (isobutyronitrile). A 1, 1, 2, 2-tetrachloroethane solution of the polymer was exposed to visible light in the presence of several sensitizers. The solution turned to a gel after several hours and then solidified completely. Photochemical studies and quantum calculations reveal the predominant of fullerene in photocrosslink-ing of the polymer.
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  • MOTOAKI ADACHI, TOSHIYUKI FUJIMOTO, KOICHI NAKASO, TAE OH KIM, KIKUO O ...
    1999 Volume 25 Issue 6 Pages 878-883
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Two different ionization CVD reactors where the surface corona discharger is used as the ion source, are developed and film preparation by a tetraethoxysilane/ozone atmospheric pressure CVD is arrempted. In the close-type reactor where the discharger is close to the substrate, discontinuous films where thickness changes alternately and extremely from zero to a few microns in the distance of millimeter order are formed probably due to the charge of ions accumulated on the surface of Si wafer. In the separate-type reactor where the discharger is distant from the substrate, films with uniform thickness are formed, and the film growth rate is 1.3-1.5 times higher than that without discharge. The separate-type reactor prepared films with strong flow-like shape under conditions where films without flow-like shape are formed in the common reactor. Nanometer-sized particles of 20-100 nm in diameter, which have been generally generated without discharge, are not detected in the ionization CVD reactor.
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  • HITOSHI FUNAYAMA, MITSURU KUROSAWA, YUJI YAMAKOSHI, KATSUYASU SUGAWARA ...
    1999 Volume 25 Issue 6 Pages 884-886
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Photocatalytic degradation of polychlorinated biphenyls (PCBs) in a plate-type batch recycle photoreactor using a TiO2 thin film is experimentally examined in an acetonitrile/H2O system.
    The concentrations of higher chlorinated biphenyls, hexa-, hepta-and octa-CBs, degrease regularly with irradiation time ; those of lower chlorinated biphenyls, tetra-and penta-CBs, increase in the initial period, and then decrease slowly. It is suggested that some series reactions occur from higher chlorinated biphenyls to lower ones. Based on the analysis of mass fragmentograms, various PCBs decomposition/ production reactions are found to occur. The extend of dechlorination rate of total PCBs from tetrato octa-CBs is approximately 35 % after 12 hours of irradiation through providing oxygen gas.
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  • KAZUTAKA TAKATA, HISAYOSHI ITO, MASAHIKO KIKUCHI, YUKIMICHI OKAMOTO
    1999 Volume 25 Issue 6 Pages 887-892
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    A helical ribbon impeller without a shaft is considered to be effective not only to reduce the stagnant region around the shaft but also actually to prevent polymer growing at the surface of the shaft. Chemical process industries demand truly effective mixing impellers which overcome conventional impellers such as those with a shaft that have problems in actual operation. In this study, a new type of helical ribbon impeller, which consists of frame and blades, is supported by computational fluid dynamics studies, which are useful to analyze the effects of ribbon and frame dimensions on flow and mixing characteristics. Also the difference between the conventional ribbon impeller and the new type impeller are examined.
    The results of the computations show that the flow pattern of the new impeller largely depends on the ribbon and frame dimensions, and that a set of optimum dimensions can minimize the mixing time. In particular, the frame not only contributes a mechanical strength but also changes the mixing pattern formed by the ribbon blades to effectively shorten the mixing time. The computational results also show that the new impeller has a flow pattern quite different from that produced by the conventional ribbon, and that the new impeller's mixing time is reduced to approximately a half of the conventional ribbon's.
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  • WENFA Ll, KEN TSUDA, HIDEMITSU HOJO
    1999 Volume 25 Issue 6 Pages 893-897
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    The corrosion behaviors of HNO3 absorption tower (diameter : 2.6 m and2.0 m, height : 15 m, thickness of wall : 20 mm) made of rigid PVC are discussed. The specimens were cut from the outside, middle and inner layers of the tower wall, then the creep rupture strength, tensile strength, flexural strength and impact strength were measured, and alsoIR analyses were made. From theIR analyses, the absorption peaks of-OH and> C= O groups were caused in the outside layer and inner layer and the absorption by>C=O and nitro groups was recognized. The corrosion depths of outside andinner layer were estimated to be 250 and 500 μm respectively by theIR absorption peak of barium stearate used as a stabilizer.
    As a result, it is found that PVC is quite suitable as a substitute material of stainless steel used for HNO3 production equipment.
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  • TADAHIRO HAGITA, TERUO ONO, HIDEKAZU YOSHIZAWA, YOSHIMITSU UEMURA, YAS ...
    1999 Volume 25 Issue 6 Pages 898-903
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Spray etching characteristics of 42 Alloy with a fine-slit resist pattern were investigated bychanging the width of photo-resist aperture, etchant temperatures (90°C) and spraying pressures (6 atm). Both the etch rate and factor decreased with decreasing the width of photo-resist aperture. High etchant temperatures gave high etch rates. However, high etchant temperatures were not always effective in etch factor. Activation energies were 28.4 kJ/mol and 31.2 kJ/mol when slit patterns were parallel to and perpendicular to the rolling direction of 42 Alloy, respectively. High spraying pressures improved both the etch rate and factor by the strong blow of etchant droplets. By increasing both the etchant concentration and the spraying pressure, high accuracy and high efficiency were achieved even for the high temperature etching processes.
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  • TAKASHI SASAKI, SHIGEHIKO YAMAMOTO, IORI HASHIMOTO
    1999 Volume 25 Issue 6 Pages 904-913
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    (1) In a paper machine, optimizing control of the basis weight profile based on a process model does not achieve long term continuous running. We have made manual operation of the machine by expert operators into a control algorithm by using membership functions in fuzzy theory, and succeeded in improving the saw tooth profile that is not able to be improved by optimizing control.
    (2) We have developed an algorithm that defines membership functions of expert fuzzy control using the process interference by slice bolt manipulation. This algorithm makes it possible to apply easily this expert fuzzy control to any type of paper machine.
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  • MOTOHIRO KONDOH, MICHIHIKO HAMAI, MASATAKA YAMAGUCHI, SHIGEKATSU MORI
    1999 Volume 25 Issue 6 Pages 914-920
    Published: November 10, 1999
    Released: February 19, 2010
    JOURNALS FREE ACCESS
    With the aim of achieving highly efficient waste power generation through combustion in the fluidized bed and by utilizing RDF (Refuse Derived Fuel) as an energy resource, a mixed fuel of RDF and coal was burned and a running test for energy recovery was conducted, using an internal-circulation-type fluidized bed boiler designed for sole combustion of coal with a maximum steam generation rate of 70. 6 t/h. Evaluation was then made with a focus on the characteristics of emissions and on heat recovery, and we concluded that waste power generation using RDF has become a practicality. From the results of this test, there seemed to be a possibility that, when burning RDF and coal together, NO goes through a generation mechanism that was different from the one that took place when burning coal alone because of the influence of combustion at the freeboard part, the influence of the composition of RDF, interactions with CO, hydrogen chloride, and other gases that are generated during combustion. It is also found that there was a strong relationship between the concentration of dioxins and that of hydrogen chloride that is generated during mixed combustion of RDF and coal. Another finding is that it is highly possible that the calcium compound added to RDF during manufacture contributes to a reduction in the concentration of hydrogen chloride and that of dioxin emissions.
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  • MOTOHIRO KONDOH, MICHIHIKO HAMAI, MASATAKA YAMAGUCHI, SHIGEKATSU MORI
    1999 Volume 25 Issue 6 Pages 921-928
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    With the aim of contributing to more extensive use of Refuse Derived Fuel, an industrial internal-circulation-type fluidized bed boiler with a steam-generation capacity of 70 t/h was operated to observe the generating behavior of dioxins during incineration and the impact of hydrogen chloride, carbon monoxide, and copper compounds on dioxin emission. In this test, Refuse Derived Fuel and coal were incinerated with, while paying special attention to the combustion characteristics when incinerating coal alone in the fluidized bed. It is found that the generating pattern of dioxins is strongly dependent on the composition of Refuse Derived Fuel. The composition of Refuse Derived Fuel also affecs the increase in dioxins generated through synthesis. It is also found that the concentration of dioxins emissions had a strong correlation with the concentration of hydrogen chloride and that of carbon monoxide. Re-synthesizing rate is strongly affected by the concentration of copper chloride in the ash produced during incineration.
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  • YUJI TATEMOTO, YOSHIYUKI BANDO, KEIJI YASUDA, MASAAKI NAKAMURA, MUNEO ...
    1999 Volume 25 Issue 6 Pages 929-934
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    The effect of hard layer due to thermal denaturation on the drying characteristics was examined experimentally and theoretically. The hot air drying of multi-layer sample, which consisted of Thermally Hardening Material (THM) and Thermally Stable Particle (TSP) layers, was performed. In the theoretical calculation, the formation of hard layer was expressed as the resistance to heat and mass transfers. The calculated results were compared with the experimental data.
    The period when the evaporation rate at the interface between THM and TSP layers governs the drying is observed, and the decrement degree of drying rate and the increment degree of sampletemperature become small. During the period, the drying rate becomes lower as THM layer becomes thicker. In the case of relatively low temperature of drying gas, the effect of evaporation at the interface on drying rate becomes small. To obtain the short drying time, it is important that no THM layer exists near the surface.
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  • TOMOYUKI IMAI, TOSHIKI MATSUI, TASUKU NAKAI
    1999 Volume 25 Issue 6 Pages 935-939
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Combustion experiments with polyethylene (PE) and PE-added goethite or hematite in various fractions were carried out using a combustion apparatus of fixed-bed semi-batch type. As a result, it is confirmed that benzene is formed during combustion for PE and PE-added hematite, while it is not formed for PE-added goethite. Furthermore, measurements of apparent activation energy in combustion are performed, and the oxidation mechanism of PE-added iron oxides is also studied.
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  • TAKEHIKO MORIYA, HEIJI ENOMOTO
    1999 Volume 25 Issue 6 Pages 940-946
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    High density polyethylene was hydrothermally cracked in supercritical water using 2H216O and 1H218O as tracers. The objective was to reveal the participation of molecules of supercritical water in the decomposition of polyethylene. It is found that hydrogen atoms from the supercritical water are donated to produce cracked oils, and the oxygen atoms are donated to the gases and aqueous phase products. With an increase in the water fill rate, more hydrogen atom from the supercritical water are transferred to the oils.
    A mechanism of hydrogen participation in cracking polyethylene is proposed, namely that lower 1-alkenes (propylene, etc.) decomposed from polyethylene are hydrated to produce secondary alcohols (2-propanol, etc.), which are then oxidized into ketones (2-propanone, etc.) and active hydrogen atoms are liberated. These hydrogen atoms are further donated to produce decomposition products.
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  • TAKASHI SASAKI, MITSUHIRO MATSUDA, SHIGEHIKO YAMAMOTO, IORI HASHIMOTO
    1999 Volume 25 Issue 6 Pages 947-954
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    We have analyzed theoretically the virtual slice-bolt corresponding optimizing control of basis weight profile in paper machines that was previously devised by the authors. It has the following features :
    (1) Optimizing control of basis weight profile in slice-bolt position generates a saw tooth profile between slice bolts, and does not satisfy quality demand in actual plants.
    (2) We have devised a virtual slice bolt corresponding profile that is obtained by averaging the basis weight raw profile not only on the position at each slice bolt but also on the intermediate point between the slice bolts. We have applied a virtual slice bolt corresponding optimizing control that minimizes the square sum of the profile errors and succeeded in satisfying the quality demand of actual plants sufficiently.
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  • DAIQING ZHAO, HIROSHI YAMASHITA, TSUYOSHI YAMAMOTO, TOMOHIKO FURUHATA, ...
    1999 Volume 25 Issue 6 Pages 955-960
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    In the steam-injected combustion field where the Prompt mechanism controls NOx formation, a decrease in flame temperature physically affects the NOx reduction. In addition, it is anticipated that the changes of concentrations of active radicals (CH, OH, H, etc.) due to steam addition bring about a chemical kinetic effect on the NOx reduction.
    In order to investigate the chemical reaction effect of steam addition on NOx reduction, we carried out numerical calculations of counterflow diffusion flame using detailed chemical kinetics, where the maximum flame temperature were adjusted to the same value by varying the initial temperatures. Under the same maximum flame temperature, the NO emission index decreases with increasing amount of steam addition, and the concentration and mass production rate of CH, HCN and N, etc., related to NOx formation also decrease when steam is added. Consequently, we clarify chemical kinetic effect of steam addition on NOx reduction.
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  • FUJIO WATANABE, TOMOYA UEKI, DAISAKU KATO, HITOKI MATSUDA, MASANOBU HA ...
    1999 Volume 25 Issue 6 Pages 961-965
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    For reducing environmental discharge of NOx below 1 ppm, the authors propose a minimum NOx emission system comprised of an absorption process that can concentrate low level NOx coupled with a de-NOx;low level NO;adsorption;active carbon;temperature swing adsorption process. Adsorption of NO, especially in the range 0.5-20 ppm, for various adsorbents are studied with adsorption at ambient temperature and with desorption at 353 K. Phenol resin based active carbon is found to have excellent adsorption characteristics and can achieve almost zero emission of NO. It can reach a maximum adsorptivity of 2.5 × 10-3m-3·kg under the presence of O2 for the initial gas concentration of 15 ppm NO. When desorbed at 353 K, NO concentration in the desorbed gas is about five times higher than that of the initial gas. It is concluded that the temperature swing adsorption process is quite appropriate for enrichment of low level NO. Although CO2 has no adverse effect on the adsorption characteristics, water vapor exerts considerable deleterious effect. Thus it is required to remove water vapor before processing.
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  • HISAO INAMI, MITSUKO SAITO, MASAFUMI MOCHIZUKI, TAKASHI AKEHATA
    1999 Volume 25 Issue 6 Pages 966-972
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    With a view to obtaining better gasification performance, pyrolytic gasification of polyethylene (HDPE) by partial combustion was carried out in a porous alumina fluidized bed with a conical gas distributor and the effects of operating conditions on gasification products were studied experimentally. To clarify the gasification process, the alumina particles were taken out of the column during the run and substances forming on the alumina particles were imaged by SEM and analyzed by using a mass spectrometer.
    The product gas is of higher heat value than that in a fluidized bed with a perforated plate gas distributor because the product gas includs many C3-5 of hydrocarbons with a conical gas distributor under the optimum conditions of air ratio of 0.2 to 0.3, and bed height/column diameter ratio of 1.0 to 1.5. The amount of carbonaceous substances retained in the alumina particles with a conical gas distributor is 20 to 30% of those with a perforated plate gas distributor, while mass spectra show that carbonaceous substances with a conical gas distributor are 300 to 1, 000 of molecular weight, and they are heavier than those with a perforated plate gas distributor.
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  • YOSUKE YAMAMOTO, KUNIO SHINOHARA
    1999 Volume 25 Issue 6 Pages 973-978
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Mono-dispersed silica particles were prepared with a tube flow reactor. To prevent effects of residence time distribution, nitrogen gas was introduced to separate the reaction fluid into segments.
    Then, TEOS monomer was added twice along the reaction tube path to increase the growth rate of particles. As a result, silica fine particles of narrow size range can continuously be produced in the tube reactor.
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  • TAKAJI INAMURO, MASATO YOSHINO, FUMIMARU OGINO
    1999 Volume 25 Issue 6 Pages 979-986
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Unsteady fluid flows in a three-dimensional porous structure consisting of spherical bodies at relatively high Reynolds numbers are numerically investigated by using the lattice Boltzmann method with the fifteen-velocity model. When the Reynolds number, defined by the superficial velocity and the equivalent diameter of the body, is higher than about 80, unsteady vortices appear behind the bodies and the flow fields become time-dependent. The characteristics of the transition from laminar to turbulent flow are studied by calculating the velocity fluctuations, the power spectra, and the turbulence intensity at three different points in the structure. It is found that the Reynolds numbers where the velocity fluctuation begins and the transition from laminar to turbulent flow occurs depend on the positions in the structure.
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  • KUNIHIRO FUKUI, HIDETO YOSHIDA, HIRONORI SAKAGUCHI, MITSUHIRO ARITA
    1999 Volume 25 Issue 6 Pages 987-992
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    We investigate the effect of fly ash particle size on the synthesis of zeolites from coal fly ash, and propose and formulate the formation mechanism of zeolite.
    It is found that the treatment time for the zeolites to synthesize decreases with decreasing feed fly ash particle size. When the feed size is small, both phillipsite and hydroxysodalite are synthesized by hydrothermal treatment with NaOH solution. Only phillipsite is synthesized when large fly ash particles are used. The zeolite from the fly ash having 2.1 p.m mass median diameter indicates the maximum NH 4+-adsorption capacity.
    The change in liquid ion concentrations calculated by the newly proposed model agrees with the experimental results. It is assumed that dissoluble silica is contained by about twice the mass of dissoluble alumina in the large fly ash particles, while in the case of small ones, they are almost equal.
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  • TAKAFUMI SATO, SHUTARO KUROSAWA, TADAFUMI ADSCHIRI, KUNIO ARAI
    1999 Volume 25 Issue 6 Pages 993-997
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    A series of experiments for the measurement of non-catalytic water-gas shift reaction (CO + H2O→CO2+ H2) rate was conducted in supercritical water at temperatures of 380 to 440°C and pressures of10 to 30 MPa using a flow-type apparatus. At 380 °C, the reaction rate first gradually decreases to a minimum at around the critical point, and then increas with increasing water density. The results at 400°C, however, indicate that the reaction rate order is zero with respect to water density. The rate constantfor the water-gas shift reaction is correlated with a global reaction model, that can reproduce the experimental data of CO conversion at 380-440 °C and 1030 MPa.
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  • MANABU KANO, KOJI NAGAO, HIROMU OHNO, SHINJI HASEBE, IORI HASHIMOTO
    1999 Volume 25 Issue 6 Pages 998-1003
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    For process monitoring, principal component analysis (PCA) has been widely used. Since PCA is able to capture the correlation among variables, PC-based monitoring outperforms traditional statistical process control methods, such as the Shewhart chart. Nevertheless, PC-based monitoring cannot detect changes in the correlation while the indices monitored are within their control limits. In order to detect such changes in the correlation, a new monitoring method is proposed. In the proposed method, PCA is applied to data within a predefined time-window, and the change of direction of each principal component is calculated at each step. This method is thus termed Moving PCA (MPCA), as PCA is applied on-line by moving the time-window. The fault detection performance of the proposed monitoring method and the traditional PC-based method is compared using simulated data. It is found that the proposed monitoring method using MPCA functions better than the traditional PC-based method in many cases.
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  • MANABU KANO, HIROMU OHNO, SHINJI HASEBE, IORI HASHIMOTO
    1999 Volume 25 Issue 6 Pages 1004-1009
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    For process monitoring, principal component analysis (PCA) has been widely used. Since PCA can describe the correlation among variables, PC-based monitoring outperforms traditional statistical process control methods, such as the Shewhart chart. Nevertheless, PC-based monitoring cannot detect changes in the correlation while the indices monitored are within their control limits. In the present work, a new monitoring method based on distributions of data is proposed, noting that distributions of data reflect the corresponding operational conditions. In order to quantitatively evaluate differences between two data sets, dissimilarity is defined and calculated by applying PCA to transformed-data matrices. The proposed monitoring method and the traditional PC-based method are compared using simulated data. The results of this study clearly indicate the advantage of the proposed method.
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  • MASAHIRO HOMMA, YOSHIO NAKANO
    1999 Volume 25 Issue 6 Pages 1010-1014
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    This paper describes a method to chemically form a platinum thin layer on the surface of on electro-driven polymer gel membrane for quick bending. Nafion membranes are selected as the polymer gel membrane. To obtain the Pt thin layer of the lower resistance on the Nafion membrane, [Pt (NH3) 4] Cl2 solution is impregnated into the Nafion membranes and then the Nafion membranes are dipped into 0.02 M NaBH4 solution under pH = 9, 293 K to form a Pt thin layer on the membrane surfaces. Subsequently, the Pt thin layer growth on the treated Nafion membrane is performed by two methods (1) and (2). (1) Pt thin layer growth was carried out in the solution of [Pt (NH3) 4] Cl2 and hydrazine mixture under pH =10 and 313 K. The resistance of Pt layer decreased with decreasing the concentration of hydrazine. (2) Pt layer growth on the Nafion membrane impregnating 1 M hydrazine was carried out in the [Pt (NH3) 4] Cl2 solution under pH =10 and 333 K. The resistance of the Pt layer also decreases with increasing concentration of [Pt (NH3) 4] Cl2. The bending rate of polymer gel/platinum composite membrane increases remarkably with decreasing resistance of the Pt thin layer formed by both plating methods (1) and (2). Comparing method (1) with method (2), the Pt thin layer plated on the treated Nafion membrane by method (2) has much lower resistance than that plated by method (1). These results will provide some important information in designing the electro-driven polymer gel/platinum composite membranes.
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  • DAIGO SHIROTA, MITSUO KAMIWANO, MEGURU KAMINOYAMA, KAZUHIKO NISHI, KAZ ...
    1999 Volume 25 Issue 6 Pages 1015-1023
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    For an improved understanding of liquid-liquid contactor with agitation, it is very important to accumulate data about the droplet size distribution at all locations in the stirred tank. However, there are few methods to precisely and rapidly measure droplet diameter in the tank. In particular, no reliable method has been developed yet to apply to high droplet concentration, which is often utilized in industry. In this study, a real-time high speed image processing system, which was originally developed by the authors, is utilized as the measuring technique for droplet size distribution. The authors improved the experimental apparatus for droplet size measurement, and investigated the conditions with no coalescence and breakup of the sampled droplet. It was shown that various droplet diameter distributions, in some liquid-liquid systems where physical properties were different, were able to be measured. It took less than 0.7 s with error less than 6 % to perform each run, in which about 500 droplets were measured. The dependency of droplet size distribution and specific surface area on impeller revolutional rate, sampling location and droplet concentration were precisely measured. It is also shown that this image processing system is able to detect droplets in a droplet.
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  • YOSHIMI SEIDA, YOSHIO NAKANO
    1999 Volume 25 Issue 6 Pages 1024-1026
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Adsorption and desorption of a hydrophobic organic molecule onto N-isopropylacrylamide gel (thermosensitive polymer gel) undergoing hydrophobic-hydrophilic balance change were performed. The time courses of the adsorption (desorption) under a variety of heating (cooling) rates are elucidated, from which the adsorption mechanism of the hydrophobic organic molecule onto the gel is analyzed kinetically using theoretical models of adsorption process including rate determining step. The rate of adsorption is controlled by film diffusion of the adsorbate. Adsorption occurs on the surface of the gel.
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  • KUNIHIKO SHIRAHATA, TADAHIRO MURAKATA (AITA), SHIMIO SATO
    1999 Volume 25 Issue 6 Pages 1027-1029
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Primary alcohols with different alkyl chain length were emulsified with an anionic surfactant SDS and electrolyzed indirectly by using a redox couple I+/I- as a mediator to be converted into esters. For all the alcohols, ester yield shows maximum against surfactant concentration. The yield increases moresignificantly for hydrophobic alcohols having a longer alkyl chain.
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  • TAKUYA OYASHIKI, NAOKI NODA, HITOSHI TAKAMI, YOSHINORI ITAYA, HITOKI M ...
    1999 Volume 25 Issue 6 Pages 1030-1032
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Waste liquid incineration using a triple coaxial tube burner in a riser with upper stream is proposed. The effect of hold up of FCC particles on NOx concentration in the burnt gas and conversion of nitrogen in the model waste liquid into NOx is experimentally studied.
    The experimental results show that the region in which NOx is generated is almost independent of the existence of the particles. However, a rise in the hold up of the particles reduces NOx emission in the exhaust gas. The behavior of the NOx emission can be summarized by applying Fenimore's correlation.
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  • YOSHITOMO HANAKUMA, JUNZOU YAMAMOTO
    1999 Volume 25 Issue 6 Pages 1033-1036
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    The performance of signal analysis for fault detection in a pump is examined in this study. Eight types of signal analysis ; power spectrum, absolute magnitude, phase spectrum, cepstrum, auto-correlation, histrum, atractor and wavelet method are used in this study. The actual result indicates that power spectrum, absolute magnitude, auto-correlation, atractor and wavelet method are effective for fault detection in this pump.
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  • TOSHIRO TSUJI, TOMOKO CHIBA, TOSHIHARU SHIBATA, OSAMU UEMAKI, HIRONORI ...
    1999 Volume 25 Issue 6 Pages 1037-1039
    Published: November 10, 1999
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    A flow regime map for a two-dimensional spouted bed is constructed from the experimental conditions that cause the fixed bed, spouted bed, bubbling fluidized bed and slugging bed. The map is compared to the one that is made from the simulations using P-TAK, a general-purpose simulation code of gas and particle flow by the discrete element method.
    Both maps coincide very well, indicating that the discrete element method has big potential for predicting critical flow conditions such as the minimum spouting velocity or the maximum spoutable bed height.
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