JOURNAL OF CHEMICAL ENGINEERING OF JAPAN
Online ISSN : 1881-1299
Print ISSN : 0021-9592
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Volume 29, Issue 1
Displaying 1-33 of 33 articles from this issue
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Original Papers
  • Three-Dimensional Simulation of Polymer Melt Flow in a Coat-Hanger Die
    Su Yeon Na, Do Hyum Kim
    1996 Volume 29 Issue 1 Pages 1-11
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.1
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    The power-law fluid of polymer melts in a coat-hanger die is modded three-dimensionally and simulated using finite element method. In order to get an optimum coat-hanger die, design equation devioped perviously based on one-dimensional flow model in manifold and slot is employed. From the calculated flow rate distributions, the optimum process condition for maximum flow rate uniformity can be determind. The optimum conditions were mainly dependent on the manifold angle and power-law index of polymer melt. The effects of disturbances of power-law index, die width, slot thickness, and manifold angle from the optimum values are investigated thoroughly. Results show that any departure of process conditions from optimum value decreases flow rate uniformity. The effect of land length is also analyzed. Manifold angle is a primary factor governing uniformity of residence time distribution. Two-dimensional analysis is also conducted and its results are compared with those of three-dimensional to show that application of two-dimensinal model using lubrication approximation in the region of manifold is subject to critical error.
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  • New Invariant Asymmetric Mixing Rules
    Ming-Ler Lee, In-Tung Liu
    1996 Volume 29 Issue 1 Pages 12-19
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.12
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    New invariant asymmmetric mixing rules were developed which obeyed the boundary condition of the second virial coefficient. These mixing rules were incorporated into the PRSV (Peng-Robinson-Stryjek-Vera) equation of state and applied to vapor-liquid equilibrium (VLE) calculations with emphasis on aqueous mixtures. The new mixing rules could improve VLE calculations for binary aqueous systems while an asymmetric interaction constant (l12) and temperature-dependent q12 were used. The new model reasonably predicts the VLE behavior for several aqueous weak electrolyte systems and is generally better than the API-Sour model at elevated temperature applications.
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  • Gas Holdup and Volumetric Liquid-Phase Mass Transfer Coefficient in a Spout-Fluid Bed
    Mohammed Zohdi Anabtawi, Ghaleb Ali Ibrahim
    1996 Volume 29 Issue 1 Pages 20-24
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.20
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    The effects of gas velocity, liquid velocity and nozzle diameter on the gas holdup and the volumetric liquid phase mass transfer coefficient, kLa, were studied a experimentally in a spout-fluid bed by absorption of oxygen in air into tap water. Gas holdup was found to increase with increasing gas velocity and to decrease with increasing liquid velocity and not to depend on nozzle diameter. kLa was found to increase with increasing gas velocity and liquid velocity and to decrease with increasing nozzle diameter. kLa was found to be strongly dependent on the liquid velocity. Two correlations for gas holdup and kLa in spout-fluid bed were presented with maximum deviation of 8% and 7% respectively.
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  • Spray Pyrolysis in a Circulating Fluidized Bed
    Seiichi Deguchi, Hitoki Matsuda, Masanobu Hasatani, Bernd Hirschberg, ...
    1996 Volume 29 Issue 1 Pages 25-28
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.25
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    In order to prepare fine metal-oxide particles and circulating fluidized particles coated with metal compounds, experimental investigations were carried out to study spray pyrolysis using the superior heat transfer characteristics of a circulating fluidized bed (CFB). Quartz sand particles of three different size ranges were used as circulating fluidized particles in the CFB loop, and a nickel-acetate solution was injected as droplets into the CFB riser.
    It was recognized that the size distribution of the prepared particles was considerably affected by the size of circulating fluidized particles. Increasing the circulating fluidized particle size was found to lead to larger nickel-oxide particles. It was shown that the concentration of the injected nickel-acetate solution had no influence on the geometric characteristics of the prepared nickel-oxide particles.
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  • The Uni-Axial Compression of Solid-Liquid Materials Under Constant Rate of Strain
    Serge Rebouillat, Henry G. Schwartzberg, Dominique Leclerc
    1996 Volume 29 Issue 1 Pages 29-36
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.29
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    A multi-mode compression cell has been developed to study the compression behavior of relatively thin layers of biological materials. By a line of reasoning similar to that previously used in advanced soil mechanics, a theory is proposed for the case corresponding to the expression of these materials under constant rate of deformation. In this theory the samples are assumed to be linear materials having a constant coefficient of compressibility, –(dv/dPs). Providing that fairly thin layers were compressed under relatively slow rate of deformation, this theory was also found to be sufficiently accurate in the case of non-linear materials. The ratio of the measured fluid pressure at the no-flow surface versus the total stress, Pf1/P1 seems to be a useful parameter to establish the validity limits of the proposed theory. The rate of deformation also influences the compression characteristics of the sample, such as the modified coefficient of consolidation. Its impact caries considerably with the sample considered and the Pf1/P1 ratio.
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  • Evaluation of Co-Immobilized Lactobacillus delbrueckii with Porous Particles for Lactic Acid Production
    Henian Wang, Minoru Seki, Shintaro Furusaki
    1996 Volume 29 Issue 1 Pages 37-43
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.37
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    Lactic acid production using co-immobilized L. delbrueckii with porous particles has been studied. The effect of co-immobilization with porous particles was verified by measuring the variations of both overall production rate of lactic acid and effective diffusion coefficient in the co-immobilized gel. The effective diffusion coefficient decreased with increasing cell concentration in the co-immobillized gel. However, in the high cell density regimes, the effective diffusion coefficient in co-immobilized gel was higher than that without co-immobilized porous particles. The optimal volume fraction of porous particles in the co-immobilizing gel beads was estimated experimentally at about 10%(v/v). An approximately 30% increase of the overall production rate was obtained compared to the control culture. Mathematical analysis showed that by co-immobilizing cells with porous particles, the steady-state concentration profiles of proton and undissociated lactic acid changed favorably inside the gel beads. The result indicates that co-immobilioation with porous particles is a useful method to improve fermentation efficiency in processes using immobilized cells.
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  • Effect of Secondary Air Injection on Bed-to-Wall Heat Trasfer in a Circulating Fluidized Bed
    Yong Jun Cho, Won Namkung, Sang Done Kim, Sunwon Park, Pyung-Tchai Kim
    1996 Volume 29 Issue 1 Pages 44-50
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.44
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    The effects of secondary air ratio (0–50%) and injection types (radial or tangential) on the bed-to-wall heat transfer coefficient have been determined in a circulating fluidized bed (0.1 m-I.D. × 5.3 m-high). The bed-to-wall heat transfer coefficient increases with increasing particle suspension density. The heat transfer coefficient by gas convection increases, but the overall convective heat transfer coefficient decreases with increasing the radial injection of secondary air. The convective heat transfer coefficient increases, but the particle convective component decreases with the tangential secondary air injection. A model, based on the model of Basu (1990), is proposed to predict the bed-to-wall heat transfer coefficients in a circulating fluidized bed (CFB) with the tangential secondary air injection system.
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  • A New Perspective for the Mixing of Yield Stress Fluids with Anchor Impellers
    F. Bertrand, P. A. Tanguy, E. Brito-De La Fuente
    1996 Volume 29 Issue 1 Pages 51-58
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.51
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    The mixing of yield stress fluids with an anchor impeller is investigated numerically in the laminar regime using a three-dimensional finite element method. First, it is shown that the flow behavior is strongly influenced by the level of viscoplasticity and that mixing is rather inefficient in such a case. Next, correlations of the power number versus the Reynolds number are presented for different values of the Bingham number. In particular, it is established that the Metzner-Otto concept remains valid for fluid exhibiting a yield stress and that the Metzner and Otto constant (Ks) varies slightly over a wide range of Bingham numbers (Bi ≤ 75M). Finally, the 25-year old experimental findings of Nagata are reviewed and clarified.
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  • Removal of Iodine and Methyl Iodide in Gas by Wetted-Wall Reactor Based on Selective Electron Attachment
    Noriaki Sano, Toshiki Nagamoto, Hajime Tamon, Morio Okazaki
    1996 Volume 29 Issue 1 Pages 59-64
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.59
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    An electron attachment reaction, which produces a negative ion by the collision between an electron and a gas molecule, can be applied to gas purification because this reaction has a very high selectivity depending on the electron energy, the structure of the gas molecules and its electron affinity. In this study, a “wetted-wall reactor” using corona discharge was proposed and experiments involving removal of dilute iodine and methyl iodide from nitrogen were conducted. A deposition-type reactor using the discharge, which had been previously proposed by the authors, showed removal limitations of iodine and methyl iodide. On the other hand, in the removal of iodine by the wetted-wall reactor, negative ions produced by electron attachment were absorbed into the liquid film on the anode resulting in the change of chemical species in the liquid so that gas absorption increased to raise the removal efficiency. Since iodine produced by the dissociative electron attachment of methyl iodide inhibited the removal of methyl iodide, it was effective to prevent the formation of iodine in the reactor for pursuing high removal efficiency of methyl iodide. In the removal of methyl iodide by the wetted-wall reactor, the reaction byproduct, iodine, was not produced in the reactor, and the removal efficiency became high compared with the deposition-type reactor.
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  • Dynamic Analysis on Constant Pressure Filtration of Power Law Slurry
    Kuo-Jen Hwang, Wei-Ming Lu
    1996 Volume 29 Issue 1 Pages 65-74
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.65
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    The mechanism of cake formation in constant pressure filtration of power law slurry is studied. By analyzing the forces exerted on the depositing particles, the critial friction angles, θc, are estimated under various conditions. The lowest value of θc is found when the frictional drag and the interparticle force are of the same order of magnitude. The packing structure of particles on the cake surface has been simulated, and the results indicate that a more compact cake will be obtaind if a power law slurry with smaller n is filtered. A numerical program besed upon the continuity equation and the Rabinowitsch-Mooney equation is also designed to estimate the variations of local cake properties during a course of constant pressure filtration. The calculated results of cake porosity and specific filration resistance agree very well with the experimental data.
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  • Analysis of Velocity and Temperature Fields of Molten Metal in DC Electric Arc Furnace
    Hidekazu Kurimoto, Harendra Nath Mondal, Toshiya Morisue
    1996 Volume 29 Issue 1 Pages 75-81
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.75
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    Recently some small scale industries have started using DC electric arc furnace to recycle scrap materials, however modelling and simulation data are very limited in the literature. Therefore, it appears that a numerical simulation could provide many important components for predicting suitable operating conditions, better design and efficient control of the process. With this objective, a numerical simulation model is developed under certain simplifying assumptions. A SIMPLER algorithm is used to solve the model equations.
    Computed results show that the circulating patterns and the patterns of increasing the temperature of the melt are significantly affected by the change in bottom electrode diameter and these calculated results present very important information. For example, a furnace can be designed in such a way that the melt temperature can be increased uniformly throughout the bath which is very important for making homogeneous alloys. It is also found that the effect of natural convection on melt circulation is negligible, that is, circulation is totally controlled by the electromagnetic force field. In addition to the flow field data, data obtained from the electromagnetic field computations are also presented.
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  • Solvent Extraction of Vanadium(IV) from Sulfuric Acid Solution by Bis(2,4,4-Trimethylpentyl)Phosphinic Acid in Exxsol D80
    Pingwei Zhang, Katsutoshi Inoue, Kazuharu Yoshizuka, Hiromi Tsuyama
    1996 Volume 29 Issue 1 Pages 82-87
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.82
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    The distribution equilibrium of vanadium(IV) between solution of bis(2,4,4-tri-methylpentyl)phosphinic acid (BTMPPA, HR) dissolved in EXXSOL D80 and weakly acidic sulfate solution was investigated as functions of the concentration of extractant, vanadyl ion, hydrogen ion and sulfate ion in the aqueous phase.
    The stoichiornetry and the chemical structure of the extracted species of vanadium(IV) were determined on the basis of slope analysis and IR spectra. The extraction reaction proceeds according to a cation exchange mechanism, in which vanadyl ion VO2+ replaces hydrogen ions of P-O-H and coordinates with oxygens in P=O in the BTMPPA and forms the complex VOR2·2HR with a possible structure containing eight-membered chelating rings.
    Temperature dependence of the extraction equilibrium constants was examined to estimate the apparent thermodynamic functions of extraction reaction (ΔH, ΔS and ΔG).
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  • An Efficient Method for Solving Two-Point Boundary Value Problems with Extremely High Accuracy
    Fumihide Shiraishi, Satoshi Fujiwara
    1996 Volume 29 Issue 1 Pages 88-94
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.88
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    A novel numerical method for solving two-point boundary value problems is presented. This method utilizes a recasting technique for transformation of fundamental differential equations into S-system (synergistic and saturable system) canonical form that consists of a set of simultaneous first-order differential equations, an efficient computational algorithm that was proposed to numerically solve the S-system differential equations, and the shooting method. A two-point boundary value problem associated with an immobilized enzyme reaction was investigated as a model system, and it was found that the accuracy of numerical solutions obtained by the proposed method was almost the same as the accuracy of the computer. Another advantage of the proposed method is that it enables one to write a generalized computer program for two-point boundary value problems. With such a program, the user can solve different types of two-point boundary value problems by just imputing S-system parameters that are obtained by recasting their fundamental differential equations.
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  • Model for Geometry of Surfactant Assemblies in the Oil-Rich Phase of Winsor II Microemulsions
    Akihisa Shioi, Makoto Harada
    1996 Volume 29 Issue 1 Pages 95-104
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.95
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    A model for the relationship between W/O-aggregate geometries and molecular species constituting the aggregates was proposed. The microemulsion phase in equilibrium with an excess aqueous phase was discussed. We restricted the surfactants to ionic ones in which head groups electrostatically interact with each other. The hydrophobic groups were modelled by the density distribution of the chain segments within the surfactant tails in the hydrophobic layer coating the aggregate. The interaction between the hydrophobic groups of surfactants was incorporated based on the excluded volume interaction of the segments. On this basis, we analytically expressed the chemical potential of the surfactants in terms of microscopic parameters characterizing the nature of the surfactants. Following the thermodynamical equilibrium condition, the surfactant systems were classified into four types: systems forming spherical aggregates, systems forming cylindrical aggregates, to form aqueous micelles or O/W aggregates and to form no small aggregates. The domain for the four types were drawn on the maps, of which abscissa and ordinate represent the strength of the electrostatic interaction and the length-ratio of the hydrophilic/hydrophobic layers, respectively. The packing of the segments within the hydrophobic tails played a key role to determine the aggregates geometry. The predictions by the present model were qualitatively consistent with some experimental observations.
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  • Experimental and Theoretical Studies on Drying of Food Materials
    Kanathipan Buvanasundaram, Nobumasa Mukai, Takao Tsukada, Mitsunori Ho ...
    1996 Volume 29 Issue 1 Pages 105-111
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.105
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    A mathematical model was developed to predict heat and moisture transfer, drying-induced stresses and the material shrinkage of viscoelastic food materials during drying. Potato starch was selected as the model food material and physical and material properties such as moisture diffusivity, thermal conductivity, and viscoelastic properties were measured as a function of temperature and moisture concentration. To verify the numerical model, results of the drying experiments were compared with the numerically ohtained results and were found to be in good agreement with each other.
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  • Study of Carbonation Reactions of Ca-Mg Oxides for High Temperature Energy Storage and Heat Transformation
    Kyaw Kyaw, Michito Kanamori, Hitoki Matsuda, Masanobu Hasatani
    1996 Volume 29 Issue 1 Pages 112-118
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.112
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    Storing and temperature upgrading of heat energy at 773 K by means of a CaO-CO2 reaction seems very attractive. One way of storing the reaction product CO2 gas is in the form of an other carbonate by letting it react with a metal oxide, such as MgO or ZnO. Two metal oxides, MgO and (CaMg)O2 were selected for CO2 storage, with the CaO-CO2 energy storage system as CaO-CO2-MgO and CaO-CO2-CaMgO2 systems, and studies on CaO-CO2, MgO-CO2 and CaMgO2-CO2 reactions over the temperature range 773–1073 K were carried out. As the CaO-CO2 system is used not only for storing the heat energy but is also expected to perform as a heat transformer, verification of the temperature upgrading ability is made by means of a lab-scale adiabatic reactor. Pseudo-steady state temperature and pressure existed during the experiments, which correspond quite well with Haul’s equilibrium dissociation values of CaCO3, illustrating that upgraded temperatures of above 1273 K can be achieved by adjusting the carbonating CO2 gas pressure to around 500 kPa.
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  • Applicability of Carbonation/Decarbonation Reactions to High-Temperature Thermal Energy Storage and Temperature Upgrading
    Kyaw Kyaw, Hitoki Matsuda, Masanobu Hasatani
    1996 Volume 29 Issue 1 Pages 119-125
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.119
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    Storing thermal energy by thermochemical means seems very attractive since large amounts of energy can be stored per unit mass, and such systems can function as a heat pumps. For storing high temperature heat energy such as concentrated solar energy at 773 K, various candidate chemical reactions have been evaluated in terms of energy storage density, turning temperature, toxicity, corrosiveness, and other factors. The dissociation reaction of CaCO3 is found to be very promising. Three methods for storing the dissociation product CO2 gas; (i) storing as a compressed gas, (ii) letting the CO2 gas react with a metal oxide and storing it in the form of another carbonate, and (iii) adsorbing with an appropriate adsorbent and storing as an adsorbed gas; have been proposed and the respective thermal operating efficiencies at various upgraded temperatures are evaluated. The CaO-CO2 metal oxide system seems very effective for temperature upgrading around 1273 K and the CaO-CO2-compressor system seems suitable for storing and delivering heat energy at the same temperature. Whether the efficiency of the CaO-CO2-Adsorbent system is comparable to one of the other two systems or not greatly depends upon the adsorptivity of the adsorbent.
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  • Enhancement in Extraction Rates by Addition of Organic Acids to Aqueous Phase in Solvent Extraction of Rare Earth Metals in Presence of Diethylenetriamine-Pentaacetic Acid
    Hideto Matsuyama, Abdul Azis, Mamoru Fujita, Masaaki Teramoto
    1996 Volume 29 Issue 1 Pages 126-133
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.126
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    It is well known that the selectivity of rare earth metals by solvent extraction is increased by the addition of a chelating agent such as diethylenetriaminepentaacetic acid (DTPA) in the aqueous phase. One of the disadvantages of this method is the decrease in extraction rates due to complexation in the aqueous phase. In this paper, further addition of organic acids to the aqueous phase was examined for the purpose of enhancing the extraction rates in solvent extraction with DTPA. The addition of several kind of organic acids such as formic acid, acetic acid, malonic acid, lactic acid and citric acid was investigated for a Er/Y separation system. A remarkable enhancement in extraction rates was observed with a slight decrease in the selectivity by the addition of citric acid or lactic acid. Extraction rates in the presence of both DTPA and citric acid increased with the increase in citric acid concentration and with the increase in proton concentration. A 150 times enhancement in extraction rates was found in the low proton concentration condition. In order to analyze the extraction rates and selectivities obtained, mass transfer equations were presented by considering both the dissociation reaction of rare earth metal-DTPA complexes and the complex formation between rare earth metal and organic acid in the aqueous phase. The experimental data were analyzed by these equations.
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  • Development and Mixing Characteristics of Folding Anchor Impeller for Round-Bottomed Flask
    Toshio Nomura, Yongfu He, Koji Takahashi
    1996 Volume 29 Issue 1 Pages 134-138
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.134
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    A folding anchor impeller was developed for a round-bottomed flask with a small neck, which is frequently used for research and development of new materials and technologies in the laboratories of industries and universities. The power consumption and mixing time were measured over a wide range of Reynolds number and compared with those obtained for two traditional types of impellers for relatively high viscous liquids in a round-bottomed flask and those calculated for a helical ribbon impeller set in a cylindrical vessel. It was found that the power correlation developed for paddle impellers in a spherical agitated vessel was also applicable for data obtained for the folding anchor impeller. The power consumption for the folding anchor impeller was much higher than those of two traditional impellers, but almost the same with that for a double helical ribbon impeller. On the other hand, the mixing time for the folding anchor impeller was less than one-fifth those obtained for two traditional impellers, and it was comparable to that calculated for a helical ribbon impeller according to the correlation. Consequently, the folding anchor impeller needs the lowest mean energy dissipation rate to attain the same mixing time among the impellers considered in this work.
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  • FTIR Study of Adsorption on Silica Gel for Organic Solvents Diluted in Supercritical Carbon Dioxide
    Do WON Jin, Kiyoshi Onose, Hiroaki Furukawa, Tomoshige Nitta, Katsuhik ...
    1996 Volume 29 Issue 1 Pages 139-145
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.139
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    Physical adsorption on a silica gel (pore size of 80 nm, particle size of 10 μm) has been studied for binary mixtures of methanol, acetone, and triethylamine diluted in supercritical CO2 by use of a FTIR transmission technique. Measurements were made at 313.2 K and pressures up to 15 MPa. Vibrational frequencies of hydroxyl groups on the silica gel surface shift downward due to the hydrogen-bond formation with organic substances. As the pressure increases from 0.1 MPa, the integral absorbance of the hydrogen-bonded OH groups interacting with methanol or acetone increases at first, and reaches a maximum at a pressure below the critical pressure of CO2, and then the intensity decreases gradually with increasing pressure. Furthermore, both spectra of hydrogen-bonded OH groups of silica and C=O group of acetone show a slight frequency downshift with increasing pressure. On the other hand, the integral absorbance for triethylamine in CO2 is almost constant from 0.1 to 15 MPa, indicating that most of the surface OH groups are covered by triethylamine molecules.
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  • Sorption Kinetics of Citric Acid from Aqueous Solutions by Macroporous Resins Containing a Tertiary Amine
    Ruey-Shin Juang, Tzung-Chiang Chou
    1996 Volume 29 Issue 1 Pages 146-151
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.146
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    The rates for the sorption of citric acid from relatively concentrated aqueous solutions (0.05–0.2 mol/dm3) with macroporous resins containing tri-n-octylamine (TOA) were measured in finite bath. Experiments were carried out as functions of citric acid concentration in the aqueous phase, TOA concentration in the resin phase, and temperature. It was shown that the kinetic data could be well described by the Elvoich equation. Rate equations for the sorption processes were obtained and the activation energy was also determined.
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  • Drying of Microparticle Slurry and Salt-Water Solution by a Powder-Particle Spouted Bed
    Qimin Guo, S. Hikida, Y. Takahashi, N. Nakagawa, K. Kato
    1996 Volume 29 Issue 1 Pages 152-158
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.152
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    Adhesion and agglomeration between fine particles and coarse particles are very strong for fine particles under several microns in diameter. The powder-particle spouted bed (P-PSB) was developed as a new type of dryer for continuous drying of microparticles under several microns in diameter. The powder-particle spouted bed dryer is a cone-bottomed fluidized bed without a gas distributor. Coarse particles were loaded into the dryer and the hot gas was fed to it from the cone-bottom so that coarse particles were fluidized violently, and a microparticle slurry and a salt-water solution were continuously fed to it.
    Continuous drying of a microparticle slurry and a salt-water solution were carried out by using the powder-particle spouted bed, and the drying characteristics were investigated. The moisture content of the microparticles dried by this process from the submicroparticle (under 1 μm in diameter) slurry and the salt-water solution were nearly equal to their equilibrium moisture content over the range of the experiment. When the drying efficiency was above 60%, agglomerates were observed in the bed. The relative humidity of the outlet gas and the drying efficiency can be calculated by mass and heat balances across the bed.
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  • Calculation of Surface Tensions of Polar Mixtures with a Simplified Gradient Theory Model
    You-Xiang Zuo, Erling H. Stenby
    1996 Volume 29 Issue 1 Pages 159-165
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.159
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    In this work, assuming that the number densities of each component in a mixture across the interface between the coexisting vapor and liquid phases are linearly distributed, we developed a simplified gradient theory (SGT) model for computing surface tensions. With this model, it is not required to solve the time-consuming density profile equations of the gradient theory model. The SRK EOS was applied to calculate the properties of the homogeneous fluid. First, the SGT model was used to predict surface tensions of 34 binary mixtures with an overall average absolute deviation of 3.46%. The results show good agreement between the predicted and experimental surface tensions. Next, the SGT model was applied to correlate surface tensions of binary mixtures containing alcohols, water or/and glycerol by application of one and two adjustable parameters and satisfactory results were obtained. Finally, the SGT model was used to predict surface tensions of a ternary mixture with reasonable accuracy.
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  • Crystallization Fouling of Calcium Sulfate Dihydrate on Heat-Transfer Surfaces
    Hidetoshi Mori, Masaaki Nakamura, Shigeki Toyama
    1996 Volume 29 Issue 1 Pages 166-173
    Published: 1996
    Released on J-STAGE: March 17, 2005
    DOIhttps://doi.org/10.1252/jcej.29.166
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    The present paper deals with the fouling process of calcium sulfate dihydrate on heat transfer surfaces. The crystallization of calcium sulfate showed typical asymptotic fouling curves, the asymptotic value of which was greatly influenced by the surface temperature and fluid velocity. The fouling mechanism was discussed with a generalized fouling model and proved to be surface process controlled, where the activation energy was 6.2 × 104 J/mol.
    The availability of mechanical cleaning against the formed scale was quantitatively evaluated by applying the particle abrasion method. The removal test verified that the removing rate per unit particle concentration decreased in an inverse proportion to the overall particle load, to the power of 0.8, and that it was affected by the fluid velocity. The observed final residual fouling resistance decreased asymptotically with an increase in particle concentration. The suitable concentration of the abrasive particles for mild cleaning was markedly low as compared with the operating condition of the fluidized bed heat exchanger.
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Prompt Paper
Short Communications
Letter to The Editor
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