JOURNAL OF CHEMICAL ENGINEERING OF JAPAN
Online ISSN : 1881-1299
Print ISSN : 0021-9592
32 巻, 6 号
選択された号の論文の17件中1~17を表示しています
Transport Phenomena, Fluid Mechanics and Mixing
  • Mohamed Nabil Noui-Mehidi, Naoto Ohmura, Kunio Kataoka, Abdelaziz Sale ...
    2000 年 32 巻 6 号 p. 732-741
    発行日: 2000年
    公開日: 2004/04/28
    ジャーナル 認証あり
    This work is concerned with a numerical study of the laminar flow of a viscous fluid between two coaxial cones, with the inner one rotating on which a constant axial flow is imposed. The two cones have the same apex angle value, so that the gap width between them is constant. Two configurations of the same volume are studied: (i) divergent flow passage (Div) and (ii) convergent flow passage (Cov), which represents geometrically the reverse case of (i). Analysis with the aid of the boundary layer assumptions is carried out by the use of an implicit finite difference method. A coordinate transformation is applied to the governing equations in order to remove the explicit effect of the apex angle from the calculation process for both cases, so that the boundary conditions can be simplified. The swirl characteristics are studied in both configurations with regard to the same inlet flux and the same rotation speed of the inner cone. The competition between centrifugal and axially-transporting effects in both cases is discussed. As a result, it is found that the swirl increases in Div from the entrance for a fixed value of the apex angle, while the swirl evolution in Cov depends strongly on the apex angle value.
  • Manabu Iguchi, Yukio Terauchi
    1999 年 32 巻 6 号 p. 789-795
    発行日: 1999年
    公開日: 2004/04/28
    ジャーナル 認証あり
    The effect of parallel flow of water on the frequency of bubble formation from a single-hole nozzle placed in a vertical pipe is investigated under terrestrial gravity (1-g) and micro-gravity (μ-g) conditions. The parallel flow means that the water flow in the pipe is parallel to the air flow emitted from the nozzle. The micro-gravity conditions were realized using the drop tower of the Japan Microgravity Center (JAMIC). A force balance equation based on a one-stage model was introduced to predict the frequency of bubble formation under the two gravity conditions. The predicted value could approximate the measured value regardless of the gravity level when the frequency of bubble formation, fB, was relatively low. When the one-stage model was valid, the buoyancy force, surface tension force and drag force acting on the bubble just before detachment from the nozzle tip almost balanced under the terrestrial gravity (1-g) conditions, while the latter two forces balanced under micro-gravity (μ-g) conditions.
  • Chul Am Kim, Jun Hee Sung, Hyoung J. Choi, Chong Bo Kim, Wongi Chun, M ...
    1999 年 32 巻 6 号 p. 803-811
    発行日: 1999年
    公開日: 2004/04/28
    ジャーナル 認証あり
    Polymer induced turbulent drag reduction in a rotating disk apparatus was investigated using four different molecular weights of nonionic poly(ethylene oxide) (PEO) in synthetic seawater for potential application to cold water piping in the Ocean Thermal Energy Conversion (OTEC) system. The linear correlation between polymer concentration (C) and C/DR for different molecular weights of PEO and a universal correlation are obtained. In addition, to measuring the drag reduction efficiency change during the operation period, the drag reduction behavior is measured as a function of time, and the results obtained from this experiment are then correlated with Brostow’s equation for polymer degradation. From this study, the drag reduction effect induced by polymer additives is found to be applicable to the OTEC plant to reduce the pumping energy cost.
  • R. P. Chhabra
    1999 年 32 巻 6 号 p. 812-816
    発行日: 1999年
    公開日: 2004/04/28
    ジャーナル 認証あり
    Based on the integral momentum and energy balance equations, the laminar boundary layer heat transfer is studied between a plane surface and a power law medium. The analysis presented herein encompasses both types of boundary conditions imposed on the surface, i.e., constant temperature and constant heat flux. Analytical expressions have been developed for the local values of heat transfer coefficients. The approximate results presented herein are in good agreement with the previously available scant results.
Catalysis, Kinetics and Reactor Design
  • Leonila C. Abella, Pag-asa D. Gaspillo, Hajime Itoh, Shigeo Goto
    1999 年 32 巻 6 号 p. 742-746
    発行日: 1999年
    公開日: 2004/04/28
    ジャーナル 認証あり
    A system of tert-butyl alcohol can be effectively provided for a chemical heat pump cycle to upgrade low-temperature waste heat energy. This study focuses on an important part of the cycle, an endothermic reaction, specifically the liquid-phase dehydration of tert-butyl alcohol to produce isobutene and water below 373 K.
    Dehydration is carried out in a reactive distillation column with a catalyst-bed filled with Amberlyst 15 for various reduced pressures and feed flowrates. The use of reactive distillation facilitates complete conversion of the dehydration of tert-butyl alcohol by avoiding strong inhibition of water in this reaction.
    Experimental results are compared with the results simulated by using an ASPEN PLUS Process Simulator.
  • Jun-Hun Kim, Byung-Seok Choi, Jongheop Yi
    1999 年 32 巻 6 号 p. 760-769
    発行日: 1999年
    公開日: 2004/04/28
    ジャーナル 認証あり
    Methane Steam Reforming (MSR) is a catalytic process in which methane is reacted with steam to produce hydrogen and carbon dioxide gases. Many experimental and simulation studies have been assumed to be under isothermal conditions using a packed-bed inert membrane reactor (PBIMR). However, the flow fields inside the reactor are complex and a temperature gradient also occurs because of the catalyst particles packed in the reactor. This study suggests a new model considering heat transfer at the reactor wall and pressure drop inside the reactor. The model applies to the MSR reaction using PBIMR with a stainless steel reactor supported by a palladium membrane and packed-bed type reactor. Results are compared with the published experimental and simulation results. The simulation results suggested in the study shows better agreement than the simple model with constant temperature assumption, for both cases of palladium membrane and packed-bed type reactor. In addition, the effects of H2O/CH4, flow rate of sweep gas and particle diameter of catalyst on the methane conversion are investigated. In all cases, the proposed heat transfer model reveals better agreement with the published experimental data than that of the isothermal model.
  • Hideo Tajima, Takashi Niitsu, Hakuai Inoue
    1999 年 32 巻 6 号 p. 776-782
    発行日: 1999年
    公開日: 2004/04/28
    ジャーナル 認証あり
    Thiamine is a primary catalyst of carbohydrate production from a simple chemical. As the best immobilization method, we succeeded in immobilization of thiamine on a cation exchange resin, and formaldehyde polymerization with the immobilized catalyst. The desorption and decomposition of the immobilized thiamine can be suppressed in an organic solvent and by using the cation-exchange resin in the sodium ion form. The main product is 1, 3-dihydroxyacetone in all reaction under our conditions. The effect of the base concentration and the diffusion in the particle on the reaction rate are not observed under our conditions. Formaldehyde polymerization with the thiamine immobilized resin in 1, 4-dioxane proved to be able to express the equation, –d [formaldehyde]/dt = k [thiamine] [formaldehyde]. The activation energy of the reaction can be estimated to be approximately 82 kJ mol–1.
Materials and Devices
  • Tadahiro Murakata (Aita), Keita Takekoshi, Shimio Sato
    1999 年 32 巻 6 号 p. 825-829
    発行日: 1999年
    公開日: 2004/04/28
    ジャーナル 認証あり
    An ITO electrode was coated with layers of TiO2 by using a sol-gel method. The coated electrodes were calcined to change pore and crystal structure of the TiO2 layer. For these electrodes, cyclic voltammetry and spectro-electrochemical measurements were carried out in the absence of a substrate and in the presence of ethyl viologen as a substrate. Significant differences in electrochemical properties were found between the calcined and uncalcined electrodes. When a negative potential was applied to the uncalcined electrode, Ti3+ was formed in its TiO2 layer. The uncalcined electrode reduced irreversibly ethyl viologen while the calcined one did reversibly. These behaviors are discussed on the basis of the porosity and electronic structure of the TiO2 layer.
Separations
  • Aynur Senol
    1999 年 32 巻 6 号 p. 717-731
    発行日: 1999年
    公開日: 2004/04/28
    ジャーナル 認証あり
    Distribution of formic, levulinic and acetic acids between water and Alamine 336, a mixture of tertiary aliphatic amines, dissolved in various (proton-donating and -accepting, polar and nonpolar) diluents, as well as a comparison with the extraction equilibria of pure diluent alone are studied at 25°C. The influence of the acid structure over distribution is evaluated through comparing the extractabilities of five acids containing different functional groups, namely, formic, levulinic, acetic, valeric and nicotinic acids. The results were correlated using a modified linear solvation energy relation (LSER) and various versions of the mass action law, namely, a chemical modeling approach and a modified version of the Langmuir equilibrium model comprising one or two acid-amine complex formations. Details underlying some aspects of selection of an appropriate algorithm for fitting the data are discussed. Finally, the reliability of the proposed extraction models is analyzed statistically on the basis of the overall loading factor of amine, Zt, using a log-ratio objective function.
Particle Technology and Fluidization
  • Junya Kano, Hiroshi Mio, Fumio Saito, Mitsuo Tanjo
    1999 年 32 巻 6 号 p. 747-751
    発行日: 1999年
    公開日: 2004/04/28
    ジャーナル 認証あり
    Dry grinding of gibbsite is conducted using tumbling ball mills with different diameters from 7.8 to 19.9 cm in order to investigate the effect of mill diameter on the size reduction rate of the sample, in correlation with the ball impact energy simulated on the basis of the Particle Element Method. The size reduction rate increases with an increase in the rotational speed of the mill. Subsequently, it rapidly falls over about 90% of the critical rotational speed. The size reduction rate reaches a maximum value at about 90% of the critical rotational speed, and the maximum value becomes large as the mill diameter increases. The same trend is seen in the relation between the specific impact energy of balls and the rotational speed of the mill, and the size reduction rate is proportional to the specific impact energy regardless of the mill scale. Therefore, the size reduction rate of gibbsite in tumbling ball mills scaled-up can be fairly estimated by simulating the specific impact energy of balls.
  • Keigo Nagata, Tomoaki Tadama, Kazuo Murase, Yoshiyuki Bando, Masaaki N ...
    1999 年 32 巻 6 号 p. 816-820
    発行日: 1999年
    公開日: 2004/04/28
    ジャーナル 認証あり
    The particle dynamics in a gas-solid contactor with inclined baffle plates forming a zig-zag path have been numerically simulated by a two-fluid model. In this contactor, solid particles slide down along the baffle plates and are fluidized at the openings between the wall and the edge of the baffle plates by the upflowing gas. Thus this structure is called a “moving-fluidized bed.” In the present two-fluid model, both the gas and particles are considered to be in continuum and fully interpenetrating and their behavior are described in terms of four hydrodynamic equations; conservation equations of mass and momentum for the respective phases.
    The computer simulated porosity distributions in a two-dimensional moving-fluidized bed show that the gas bubbles appear in the fluidized bed region at the opening for the gas velocity exceeding a critical value. The average diameter of the bubbles and the distribution of the particle velocity along the baffle plate have been calculated. These results are in good agreement with the experimental results.
  • Hitoshi Takase, Mitsuhiro Mabari
    1999 年 32 巻 6 号 p. 821-825
    発行日: 1999年
    公開日: 2004/04/28
    ジャーナル 認証あり
    In wet spherical agglomeration, rapid progress in the agglomeration process occurs at an almost definite elapsed time after the beginning of the agglomeration operation according to the agglomeration conditions. This rapid progress in the agglomeration process is called “phase inversion, ” and at this point the power number of the impeller agitating the suspension in the agglomeration tank is also known to increase rapidly.
    In this paper, we report our experimental investigation of the cause of the increase in the power number of the agitating impeller at phase inversion of wet spherical agglomeration of coal. The power number after phase inversion is 1.3–1.5 times that before phase inversion. At phase inversion, the agglomerate diameter increases rapidly, and the bulk volume of the agglomerates in the suspension also increases. The increase in these values greatly influences the increase in the power number at phase inversion.
Process Systems Engineering
  • Cheng-Liang Chen, Hsiao-Ping Huang, Chung-Tyan Hsieh
    1999 年 32 巻 6 号 p. 783-788
    発行日: 1999年
    公開日: 2004/04/28
    ジャーナル 認証あり
    A simple PI/PID controller tuning formula is presented in this article, where the maximum closed-loop amplitude ratio in the frequency domain is set to +2 dB, a value recommended by Luyben (1990) for considering performance robustness. A first-order-plus-dead-time (FOPDT) model or a second-order-plus-dead-time (SOPDT) model is first identified for process dynamics. The PI/PID settings for the FOPDT/SOPDT models are then derived based on the internal model control (IMC) principle. The robustness parameter left for adjusting in the IMC tuning is determined according to the specified value of maximum closed-loop magnitude. Several testing processes with an extensive variety of dynamic characteristics are used, demonstrating the effectiveness and robustness of the proposed tuning method on typical processes.
  • Emrod Elisante, Masatoshi Yoshida, Shigeru Matsumoto
    1999 年 32 巻 6 号 p. 796-802
    発行日: 1999年
    公開日: 2004/04/28
    ジャーナル 認証あり
    This work details an IMC-based pole placement controller tuning procedure for a multi-loop SISO system in the presence of model uncertainty. For a given uncertainty level, selection of the IMC low-pass filter parameter is done using Kalman filter poles and open-loop poles as respective lower and upper limits. Tuning is facilitated using a convex tuning parameter, which depends on both the structured singular value μ as a quantitative performance measure and closed-loop behaviour like overshoots and manipulated variable move sizes as qualitative measures. The method is applied here to a distributed parameter system using model control, but can be generally applied for any multi-loop SISO system using a state estimator. Using simulation studies it is shown that the ambiguity encountered during selection of the IMC filter constant is significantly reduced.
Biochemical, Food and Medical
Safety, Environment and Energy
  • Yoshiyuki Bando, Tatsuyoshi Kato, Keiji Yasuda, Yukio Sakurai, Masaaki ...
    1999 年 32 巻 6 号 p. 770-775
    発行日: 1999年
    公開日: 2004/04/28
    ジャーナル 認証あり
    For enhancement of removals of nitrogen and phosphorus in wastewater treatment using activated sludge, two different types of bubble columns with a draft tube are proposed. One is a bubble column with a relatively small and short draft tube, and the other is a column with a long draft tube whose upper end is located a little above the liquid surface at aeration. In both columns, the annulus between column and draft tube is anaerobic. Using these two columns in addition to the standard bubble column without a draft tube, wastewater treatment experiments are performed. It is found that the proposed columns have higher removals of nitrogen and phosphorus than those of standard one. The liquid circulation flow rate in the column and the gas-liquid mass transfer volumetric coefficient are measured. By using these data and the oxygen consumption rate of activated sludge, the distribution of dissolved oxygen concentration in column is calculated. Based on the calculated results of dissolved oxygen distribution, the contribution of anaerobic region volume to the removals is examined. Independently of column type, the removals of nitrogen and phosphorus have maximum values when the volume fraction of anaerobic region is 40–60%.
  • Takeshi Sako, Tsutomu Sugeta, Katsuto Otake, Chiyoshi Kamizawa, Makoto ...
    1999 年 32 巻 6 号 p. 830-832
    発行日: 1999年
    公開日: 2004/04/28
    ジャーナル 認証あり
    Polychlorinated biphenyls (PCBs) were made harmless using supercritical water hydrolysis with an alkali catalyst such as sodium hydroxide. PCBs over a wide concentration range from 2wt% in transformer oil to pure state were dechlorinated to biphenyl and, in some parts, decomposed to phenol, gases and other small molecules at 30 MPa, 653–723 K, and 20–100 min of reaction time. Furthermore no dioxins were detected in both gaseous and liquid products. Supercritical water hydrolysis has advantages as follows: (1) it dechlorinates pure PCBs rapidly and completely, (2) it realizes the selective dechlorination of dilute PCBs in transformer oil without thermal deterioration of the oil, and (3) it can reduce corrosion problems by neutralizing the product of hydrogen chloride.
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