KAGAKU KOGAKU RONBUNSHU
Online ISSN : 1349-9203
Print ISSN : 0386-216X
ISSN-L : 0386-216X
Volume 34 , Issue 3
Showing 1-14 articles out of 14 articles from the selected issue
Transport Phenomena and Fluid Engineering
  • Takako Shiba, Yoshiro Inoue
    Type: Research Paper
    Subject area: Transport Phenomena and Fluid Engineering
    2008 Volume 34 Issue 3 Pages 313-320
    Published: May 20, 2008
    Released: June 15, 2008
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    Mixedness and mixing ability are two kinds of quantitative indexes to evaluate fluid mixing. Mixedness is an index of spatial distribution uniformity of particular species in fluid. On the other hand, mixing ability is an index of kinematic intensity of mixing fluid motion. In this study, the new quantitative index to express kinematic mixing ability is proposed based on an information measure corresponding to a relative entropy, known as Kullback-Leibler information. The regions essentially dominating the fluid mixing motion strongly depend on the geometric structure of Birkhoff pattern on a Poincaré section, In this pattern, there are a chaotic sea and many islands enclosed by KAM curves. The new mixing ability proposed in this paper accurately expresses the potential mixing ability intrinsic to the flow field. In other word, this index coincides with the potential mixing ability predicted from Birkhoff pattern. Furthermore, there is an advantage that this index hardly depends on the number of virtual test particles used in this calculating procedure.
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Particle Engineering
  • Daisuke Nishiura, Atsuko Shimosaka, Yoshiyuki Shirakawa, Jusuke Hidaka
    Type: Research Paper
    Subject area: Particle Engineering
    2008 Volume 34 Issue 3 Pages 321-330
    Published: May 20, 2008
    Released: June 15, 2008
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    A method to simulate the drying behavior of suspensions containing fine solid particles was developed to obtain information on the control of structure in a dried particle packing bed. The method is a combination of the discrete element method for analyzing particle behavior and the constrained interpolation profile method for analyzing gas–liquid multiphase flow. Interaction forces between fine particles such as mechanical contact, cohesion, Van der Waals and electrostatic forces caused by the double electric layer and the interaction between particles and fluid such as lubricant, Brownian force and surface tension acting on the floating particles on a liquid surface were taken into consideration as forces acting on the suspended fine particles during drying of suspensions. Drying behaviors of suspensions on a flat substrate were simulated under various dispersion conditions of fine particles and various drying rates to confirm the reliability of the developed simulation method. The particle arrangement at the top surface of the particle packing bed obtained by simulation was in good agreement with the experimental one. The relationship between the behavior of fine particles during drying of suspensions and the structure in the dried particle packing bed was investigated microscopically using the developed simulation method. The particle arrangement in the first particle layer deposited on a substrate greatly affects the particle packing structure. The increase of contact force between particles with increasing of drying rate leads to disorder of particle the packing structure.
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Separation Engineering
  • Hideki Yamamoto, Daisei Kumamura, Chika Nagano, Fumiko Takeuchi, Makik ...
    Type: Research Paper
    Subject area: Separation Engineering
    2008 Volume 34 Issue 3 Pages 331-338
    Published: May 20, 2008
    Released: June 15, 2008
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    Food wastes discharged from beer breweries are mainly composed of malt and hop. The nutritional value of malt is quite high and, consequently, it is recycled as feed for domestic animals; however, the nutritional value of hop as feed is not so high. A new utilization method for hop waste is therefore required. In the previous paper, it has been found that Procyanidin, a polymer composed of catechins, was abundantly contained in hop bract part and hop itself.
    This research deals with the extraction of total polyphenols, catechins, and procyanidin-B2 from hop bract part using some pure solvents and aqueous solutions under the various extraction conditions.
    In this experiment, water, methanol, ethanol, 1-propanol, acetone and their aqueous solutions were used as solvent for polyphenol extraction.
    The magnitude of extracted amount of polyphenols from hop bract part were water>methanol>acetone>ethanol>1-propanol. In the case of aqueous solutions (methanol–water, ethanol–water, acetone–water systems), it is found that there is the optimal concentration for polyphenol extraction. The amount of extracted polyphenols at the concentration of 40 vol% (about 0.2 mol%) for methanol–water system shows the maximum value. Similar tendencies at 50 vol% for ethanol–water system and at 40 vol% for acetone–water system are obtained.
    In order to evaluate the separabiliy of polyphenols containing in hop bract part, Hildebrand's solubility parameter (δH) and Hansen's solubility parameters (δd, δp, δh) for the polyphenols and solvents were calculated by the method of Fedors and van Klevelen. When solubility parameter difference between solvent and solute is smaller, the amount of extracted polyphenols shows higher values. Furthermore, the 3-dimensional plots and the triangular diagrams of Hansen's three parameters give similar tendency on the separability of polyphenols with Hildebrand's parameter, and it was found that their diagrams could be applied to the prediction of optimum concentration for the polyphenol extraction.
    This research shows that Hansen's solubility parameters could be used for choosing good solvent and solvent mixture for separation of polyphenols from hop bract part.
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  • Takumi Shibukawa, Katsunori Matsuno, Yuichi Ohira, Eiji Obata
    Type: Note
    Subject area: Separation Engineering
    2008 Volume 34 Issue 3 Pages 339-343
    Published: May 20, 2008
    Released: June 15, 2008
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    To inhibit nitrate synthesis during the absorption process of nitrogen dioxide, we experimentally examined the effects of the initial pH, ionic strength, and reductant on the absorption rate, absorption efficiency, and selectivity. In this experiment, we fed a mixed gas, which contained nitrogen dioxide, through a bubble-column batch-type absorbing apparatus, and measured the concentrations of nitrite and nitrate in the absorbing solution. The results indicate that the higher the initial pH and ionic strength of the absorbing solution, the greater the absorption rate, and thereby, the greater the suppression of nitrate synthesis. Furthermore, adding sodium sulfite to the absorbing solution resulted in an abundance of the nitrite.
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Thermal Engineering
  • Toshimitsu Asotani, Toru Yamashita, Hiroaki Tominaga, Yoshinori Itaya, ...
    Type: Research Paper
    Subject area: Thermal Engineering
    2008 Volume 34 Issue 3 Pages 344-350
    Published: May 20, 2008
    Released: June 15, 2008
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    A radiative heat transfer model for pulverized coal combustion was developed. The monochromatic extinction of pulverized coal particles dispersed in liquid paraffin wax was measured spectroscopically by using FT-IR. The effects of absorption and scattering could be expressed by the extinction efficiency, which was calculated from electromagnetic theory. The extinction efficiency was applied to the developed radiative heat transfer model. To evaluate the accuracy of the developed radiative transfer model, radiative heat transfer and combustion analyses of a turbulent pulverized coal-fired furnace (coal feed 6 kg·hr−1) were carried out. Calculations were performed for three cases: without radiative heat transfer, with the radiative heat transfer model in which the particle emissivity is assumed to be a function of unburned carbon, and with the developed radiative heat transfer model. The influence of radiative heat transfer appeared particularly as differences in the ignition position and the relaxation of the temperature gradient around the flame zone, because the preheating effect of coal particles near the burner nozzle is enhanced by the absorption of radiation energy propagated from the combustion area. The calculated temperatures agreed with measurements when the developed radiative heat transfer model was applied. This proves the accuracy of the developed radiative heat transfer model in which the extinction coefficient is used to express the radiative properties of pulverized coal clouds.
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Chemical Reaction Engineering
  • Takami Kai, Kei-ich Toriyama, Takeshige Takahashi, Mitsuyuki Nakajima
    Type: Research Paper
    Subject area: Chemical Reaction Engineering
    2008 Volume 34 Issue 3 Pages 351-357
    Published: May 20, 2008
    Released: June 15, 2008
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    A large decrease in fluidization quality was observed in the reactions involving the decrease in gas volume due to reactions. The upper part of the emulsion phase was defluidized and this part was lifted up through the column like a moving piston. The cause was the decrease in the gas velocity in the emulsion phase. The calculation showed that the gas drag force became small not enough to balance with gravitational force and buoyancy force acting on particles in the emulsion phase even when the gas flow from bubble to the emulsion phase was considered. In the present study, internals were used to prevent the defluidization and to improve the fluidization quality. The effects of the position and number of plates were studied. The horizontal metal sieves enhanced the fluidization quality. It was difficult to destroy the defluidized part moving through the column by the metal sieves installed in the upper part of the bed. However, the metal sieves successfully prevented the generation of the defluidized part when they were installed in the lower part of the bed.
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  • Yasushi Sugawara, Katsuyasu Sugawara, Takuo Sugawara
    Type: Research Paper
    Subject area: Chemical Reaction Engineering
    2008 Volume 34 Issue 3 Pages 358-366
    Published: May 20, 2008
    Released: June 15, 2008
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    In order to establish an efficient inactivation process of aerobic bacteria, yeast, and mold contained in a solution discharged from a soaking germination process in producing germination brown rice, the germs were inactivated in a photocatalytic reactor where a laminated catalyst was prepared by coating and drying emulsion of commercial photocatalyst on a stainless steel plate. A combination process of filtering with the diatomaceous earth produced in Akita Prefecture and photocatalytic reaction was also evaluated for the effective inactivation of the germs.
    A prototype of laminated photocatalyst with blacklight lamps was effective for inactivation of aerobic bacteria, yeast, and mold contained in a solution discharged from a soaking germination process. Inactivation rates of the germs were affected by distance between blacklight lamp and photocatalyst surface (r2) and thickness of solution layer (l); their rates tended to be lower as l became larger than 3×10−3 m even under the thin layer zone. By applying suction filter with the diatomaceous aid to sample solution, ca. 90% of aerobic bacteria and 100% of yeast and mold were removed. A combination of diatomaceous filter and photocatalysis proved to be efficient for inactivation of aerobic bacteria.
    To kinetically formulate the rate of inactivation for germs by a laminated photocatalyst, a single-hit with multitarget model with the light intensity on the photocatalyst surface I, estimated by the radial light model, was applicable only under thin liquid-layer conditions, while introduction of the effective light intensity Ieff proved to represent observed results well by adopting a single set of target number m and inactivation efficiency η for the inactivation of aerobic bacteria under various values of r2 and l irrespective of filtering or unfiltering of sample solution. The value of Ieff/I became smaller as l got bigger, and it was nearly identical irrespective of filtering or unfiltering of sample solution. The values of Ieff obtained for the aerobic bacteria also gave good relationship to the observed results for yeast and mold; the values of target number and inactivation efficiency were almost the same as the ones for aerobic bacteria.
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Process Systems Engineering and Safety
  • Koji Kawano, Shinji Hasebe
    Type: Research Paper
    Subject area: Process Systems Engineering and Safety
    2008 Volume 34 Issue 3 Pages 367-375
    Published: May 20, 2008
    Released: June 15, 2008
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    In a batch process, the processing time changes according to various unforeseen factors. The delay of pre-assigned schedule lowers productivity and acts as a trigger for operational faults. Thus, the delay should be recovered within a reasonable time period. In the proposed system, several delay recovery strategies are defined in advance, and for each strategy the maximum reduction time and its cost are assigned to each processing stage. Then, the problem of finding the revised schedule is formulated as the problem of optimizing the recovery cost under the constraint of the number of batches within which the schedule should be recovered. A progress control support system using the proposed optimization method has been developed. When the delay of the operation occurs, the proposed system graphically indicates the operations where the processing times should be shortened. The effectiveness of the developed system was evaluated by applying the system to several test problems.
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  • Yoshiyasu Sakakura, Masaru Noda, Hirokazu Nishitani
    Type: Research Paper
    Subject area: Process Systems Engineering and Safety
    2008 Volume 34 Issue 3 Pages 376-382
    Published: May 20, 2008
    Released: June 15, 2008
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    This paper presents a new coordination method of multiple model predictive controllers (MPCs) for the chemical process. In this control scheme, multiple MPCs are implemented in the control system and they run in parallel. The input to the controlled process is calculated by an affine combination of these MPC outputs. Each coordination function is made by using the soft-max function. We applied this method to temperature control for a continuous stirred tank reactor (CSTR). The simulation result showed that the proposed method provides better control performance than individual MPCs. We also compared this method with an MPC with a scheduling rule of the Q–R weights.
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Materials Engineering and Interfacial Phenomena
  • Sachi Honjo, Masaaki Yokota, Norihito Doki, Kenji Shimizu
    Type: Research Paper
    Subject area: Materials Engineering and Interfacial Phenomena
    2008 Volume 34 Issue 3 Pages 383-387
    Published: May 20, 2008
    Released: June 15, 2008
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    2,2′:6′,2″-Terpyridine (terpy) is interesting photophysical molecule which exhibits long-lived phosphorescence. And more long-lived phosphorescence is expected in a solid state. Until now, two crystal structures were reported for terpy. However, details of photophysical properties of the crystals were seldom discussed. We show new method for controlling the two polymorph of terpy using magnetic-field and possibility for the development of magnetic-tunable organic phosphorescent materials is discussed.
    Under normal conditions, the orthorhombic crystals were obtained. Under magnetic field above 5 T, however, the monoclinic crystals were precipitated. The monoclinic crystals exhibited room temperature phosphorescence. The lifetime of phosphorescence was increased with increasing magnet intensity.
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Energy
  • Takashi Komiya, Tetsuya Ochiai, Tatsuya Morimoto, Hirokazu Oda
    Type: Research Paper
    Subject area: Energy
    2008 Volume 34 Issue 3 Pages 388-395
    Published: May 20, 2008
    Released: June 15, 2008
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    The behavior of closed pores in coal chars during pyrolysis and gasification was analyzed in terms of gas adsorption, XRD and helium density. Closed pore volume of coking coal chars was larger than that of non-coking coal chars. The coking probably influences the generation of closed pores during pyrolysis. Also, the higher pyrolysis temperature caused the increase of closed pore volumes. It seems that micropores were closed by development of a stacking structure of graphite crystal layers with increasing pyrolysis temperature.
    Closed pore volume rapidly decreased, and specific surface area rapidly increased at an initial stage of char gasification for both coal and model samples(phenol resin and PVC pitch). This suggests that the opening of closed pores is a factor in the increase of specific surface area in the initial reaction.
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Environment
  • Masahiro Katoh, Tatsuya Yamazaki, Naoko Kikuchi, Yoshie Okada, Takushi ...
    Type: Research Paper
    Subject area: Environment
    2008 Volume 34 Issue 3 Pages 396-401
    Published: May 20, 2008
    Released: June 15, 2008
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    The conversion of bio-ethanol (ethanol: 77.4%, water: 19.6% and trace) derived from corn into hydrocarbons over HZSM-5 zeolites was studied. The reaction behaviors for formation of gaseous olefins and aromatics at WHSV=26 h−1 at 573–773 K were discussed by comparing with those of pure ethanol and 80% ethanol aqueous solution. The main products in the bio-ethanol conversion were ethylene or diethyl ether, and C3–C5 hydrocarbons and aromatics were also produced. The selectivity of olefins formation in C3–C4 hydrocarbons was depends on the reaction temperature. The yields of C3–C4 olefins increase with the rise of reaction temperature. The formation of them from bio-ethanol needs higher temperature than that from ethanol, and the decline of activity for bio-ethanol conversion was observed faster than that for a pure ethanol and an ethanol/water solution. The reason was explained by the strong acid site of HZSM-5 was poisoned by impurities in bio-ethanol such as sulfur. The content of aromatics was the largest at 648 K, but it decreased at 673 K. The order of amounts of aromatics produced were from pure ethanol>bio-ethanol>ethanol/water solution. The coexistence of water depressed the amount of aromatics, but the active sites changed by impurities in bio-ethanol promoted the formation of aromatics.
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  • Hidemasa Kakigami, Gen Inoue, Yousuke Matsukuma, Masaki Minemoto, Akin ...
    Type: Research Paper
    Subject area: Environment
    2008 Volume 34 Issue 3 Pages 402-409
    Published: May 20, 2008
    Released: June 15, 2008
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    Carbon dioxide (CO2) included in exhaust gas from heat power plants is the chief cause of global warming. In the present study, the numerical simulations of CO2 recovery systems for the exhaust gas were conducted in order to decide optimal values of 5 operation conditions for actual plant. Optimization was conducted by augmented Lagrangian method.
    For example, for actual plant (flow rate of flue gas: 70000 m3 (STP)·h−1), the optimal operation conditions were calculated, in which required consumption energy was minimum within the term that CO2 recovery rate was 60% and CO2 concentration of recovery gas was about 90%. And it was confirmed that 3 different conditions given as initial operation condition converged same optimal conditions. In the optimal condition, required consumption energy that is sum of energy consumed by heater and blower was 835 kJ·kg−1, CO2 recovery rate was 60% and CO2 concentration of recovery gas was 92%. This required energy was 5% less than that in previous work (Matsukuma et al., 2007), and from this fact we think optimization by this method is effective.
    Furthermore, from the result of previous work (Matsukuma et al., 2007), it was suggested that recovery performance was better when the purge process of the system was removed. However we confirmed that the present system including purge process has better performance by the present optimization method.
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  • Shingo Yamada, Yuta Naito, Takashi Yamamoto, Yukio Noma, Masaaki Hosom ...
    Type: Note
    Subject area: Environment
    2008 Volume 34 Issue 3 Pages 410-414
    Published: May 20, 2008
    Released: June 15, 2008
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    Perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA), persistent organic pollutants, were photodegraded by ultra-violet light irradiation in water, alkaline 2-propanol (IPA), water including H2O2 and water including both H2O2 and Fe2+, and the photodegradability in each condition was compared. F and SO42− were generated with the PFOS decomposition and F was generated with the PFOA decomposition. The degradation ratio of PFOS was lower than that of PFOA in each condition. The photodegradability of PFOS and PFOA depended on the sample condition. Effective degradation was observed in alkaline IPA for PFOS, and in water for PFOA. Added H2O2 increased the photodegradability of PFOS. With the photo-Fenton reaction, although the degradation ratio of PFOA reached to 100%, that of PFOS was only 28.6%.The C–F bond dissociation in PFOA molecular progressed slowly in water, however the process was accelerated under photo-Fenton condition. In PFOS, on the other hand, C–F bond dissociation was suppressed to progress under photo-Fenton condition.
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