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Volume 31 (1998)
- Issue 6 Pages 897-
- Issue 5 Pages 677-
- Issue 4 Pages 499-
- Issue 3 Pages 313-
- Issue 2 Pages 171-
- Issue 1 Pages 1-
Volume 31, Issue 2
Displaying 1-22 of 22 articles from this issue
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Transport Phenomena, Fluid Mechanics and Mixing
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Weiguang Yao, Koji Takahashi, Kiyohito Koyama1998 Volume 31 Issue 2 Pages 220-227
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSA theoretical tool for the optimum design of a mixer, and visualization and quantification of mixing performance, is presented. Visualization of the mixing performance is based on the kinematic theory of mixing rate proposed by Ottino, and it gives a map of the distribution of local mixing efficiency which illustrates the local mixing information throughout the flow domains. As application examples of the visualization technique, the mixing mechanisms of Couette flow and circulating flow are illustrated and explained, then the geometry optimization of a common pin mixing section used for screw extruders is carried out. The quantification of mixing performance is obtained by tracking and accumulating the local mixing histories of a number of particles to discriminate the mixing ability among several mixers with similar configurations. The influence of the height of a pin in a cavity on mixing is investigated using this approach. The results show that with an increase in the height of the pins, the mixing ability also increases. However, when h changes from 3/4H to 9/10H, an inflection occurs. The results also show that only if these particles are evenly distributed throughout the flow domains will the calculated values of mixing ability in different initial locations start to agree. This tool appears to be generally applicable to mixers but requires knowledge of the velocity field.View full abstractDownload PDF (3667K) -
Shinji Hayashi, Yutaka Hisaeda, Hideyuki Aoki, Takatoshi Miura, Tomohi ...1998 Volume 31 Issue 2 Pages 244-252
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSA three-dimensional spray combustion simulation of a carbon black furnace is developed in order to predict the reaction behavior and yield of carbon black. The effect of the raw-fuel flow rate on the soot formation reaction is examined.
The experimental furnace used in this study was one fifth the scale of a commercial plant. The light oil (LO) was fed as a fuel and the heavy oil (HO) as a raw-fuel. Both oils were derived from coal tar. Calculated gas temperature, pressure, gas species, and soot yields are compared with experimental data. The following results are obtained;
1)An increase of the raw-fuel rate makes the gas temperature lower near the spray nozzles by its latent heat. The high temperature region caused by the heat of incomplete combustion shifts toward the downstream side of the furnace.
2)Simulated results show the consumption of oxygen and formation of hydrogen and CO in a few milliseconds, and they are in good agreement with the experimental data.
3)It is also found that both acetylene and methane are formed in the furnace. As the raw-fuel flow rate increases, their maximum concentrations become higher and the positions of their maximum concentrations move toward the downstream side of the furnace.
4)The soot yield increases as the raw-fuel flow rate increases. The calculated soot yields are in good agreement with the experimental data.View full abstractDownload PDF (1496K) -
Keiko Fujioka, Shin-ichi Kato, Yushi Hirata1998 Volume 31 Issue 2 Pages 266-272
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSAn experimental method has been developed to measure the effective thermal conductivity of a bed consisting of CaCl2 reactive particles accompanying the variations of thermophysical properties with the progress of gas-solid reactions. Using this method, measurements have been performed for the beds in CaCl2/CH3NH2, CaCl2/CH3OH and CaCl2/NH3 reaction systems. The effective thermal conductivity of the reactive bed, which was reduced to less than one half of that of the initial anhydrous CaCl2 bed, increased with the absorption and decreased with the desorption of the reactive gas. Corresponding to the variations of effective thermal conductivity, the void fraction varied during the reaction cycles. The relation between the effective thermal conductivity and the void fraction inside the particle indicates that the main cause of the reduction in the effective thermal conductivity is attributed to a decrease in the thermal conductivity of the solid product.View full abstractDownload PDF (1307K) -
Takafumi Shimada, Setsuo Omoto, Masami Kondo, Keiji Fujikawa1998 Volume 31 Issue 2 Pages 273-276
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSIn many polymer manufacturing processes, mass transfer operations between a high viscosity liquid and gases are applied, but mass transfer rates have been explained only using kLa. We measured kL for molten polystyrene and corn syrups by using a rotating cylinder with surface renewal action in which surface area was known. As a result, it is proved that (1) kL between gases and high viscosity liquids are expressed by Hibgie’s penetration theory, and (2) diffusivities are obtained from measurements of kL in corn syrup-CO2 and glycerine-CO2 systems.View full abstractDownload PDF (497K) -
Jane S. R. Coimbra, Fabiane Mojola, Antonio J. A. Meirelles1998 Volume 31 Issue 2 Pages 277-280
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSDispersed phase hold-up and characteristic velocity in a perforated rotating disc contactor were studied using an aqueous two-phase system composed by polyethylene glycol 6000 and dibasic potassium phosphate. The geometrical and operational variables were flow free area of discs, rotating speed and volume flow ratio. Flow free area of discs showed small influence on the hold-up values. It was also observed the increase of the hold-up on the rotating speeds and phase flow ratios.View full abstractDownload PDF (536K) -
Fukuji Yamashita1998 Volume 31 Issue 2 Pages 285-288
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSThe effect of clear liquid height and gas inlet height on gas holdup in a 0.16-m I.D. bubble column is theoretically and experimentally studied. From the gas balance in the bubble column, a three-region model is derived to express the effect of clear liquid height on gas holdup in the bubble column. This model can satisfactorily express the effect of the clear liquid height.
The gas holdup decreases with increasing gas inlet height because of the decrease in effective clear liquid height. The effect of gas inlet height was well expressed by the three-region model using the effective clear liquid height.
The meaning of different values of the critical clear liquid height in the previous works is explained by the three-region model.View full abstractDownload PDF (492K) -
Fukuji Yamashita1998 Volume 31 Issue 2 Pages 289-294
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSThe effect of kind of gas sparger, outer diameter Do and length Ld of draft tube, lower clearance, superficial gas velocity and clear liquid height HL on gas holdup εG in a 0.16 m I.D. bubble column with a draft tube for gas dispersion into the annulus and for an air-water system was experimentally studied.
εG depended on the kind of gas sparger in the range of φ ≤ 0.713, but hardly depends on them at φ = 0.875. φ is the ratio of (Do/DT) and DT is the inner diameter of the bubble column.
At a given HL and in the range of φ ≤ 0.713, εG hardly depends on φ and Ld. But εG decreases clearly with increasing Ld at φ = 0.875.
εG decreases with increasing HL. The effect of HL is well expressed by the modified three-region model.
The experimental data for εG is correlated.View full abstractDownload PDF (643K) -
Takao Ohmori, Takashi Amemiya, Jun-ichi Kawahara, Kunio Kamiya, Tomohi ...1998 Volume 31 Issue 2 Pages 302-305
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSThe diffusion coefficients of potassium chloride (KCl) in shrunken polyacrylamide gels were measured as a function of volume fraction of polymer in the gel, φ. The gel samples were first produced under a given condition and then shrunk in methanol-water mixtures to change the volume fractions in the gels. The partition coefficients of both KCl and methanol in the gel were also determined. As a result, the ratio of diffusion coefficient in gel to that in solution, which is an index exhibiting the degree of reduction in the diffusion rate for the shrunken gel, is found to well correlate with φs/(1 – φ).View full abstractDownload PDF (580K)
Catalysis, Kinetics and Reactor Design
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Hakan Uygur, Süheyda Atalay, Tunç Ö. Savasçi1998 Volume 31 Issue 2 Pages 178-186
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSA study was made of kinetic parameters of methylacetylene (MA) and propadiene (PD) selective hydrogenation in liquid phase. C3 cut, produced by naphtha steam cracking, contains 93.5 wt% propylene, 3.5 wt% propane, 2.5 wt% MAPD and lighter hydrocarbons. MA and PD are unwanted for the propylene conversion processes in the downstream plants and are removed by converting them to propylene itself. For this purpose, a palladium based commercial catalyst was used in a lab scale trickle-bed reactor, in the temperature range of 20–50°C and in the WHSV range of 70–110 h–1, at 2.53 MPa. It was found that MAPD conversion to propylene decreases as temperature and WHSV increase. In the reaction mixture, propylene itself also reacts to give propane. However, propylene conversion remains nearly constant in different WHSV and temperature values. Rate equations for MA, PD and propylene conversions were obtained by using experimental results. Kinetic parameters were calculated by taking into consideration external and internal mass transfer resistances.View full abstractDownload PDF (1047K) -
Ying-Hwa Hwang, Chun-I Lin1998 Volume 31 Issue 2 Pages 214-219
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSThe reaction between titanium pellet and flowing nitrogen under 1 atm over the temperature range 973 to 1373 K was investigated by thermogravimetric analysis system, scanning electron microscope and X-ray diffractometer. α-Ti → TiN0.3 → TiN0.5 → TiN was found to be the sequence of transformation of solid sample. Experimental results indicated that the reaction rate could be increased by increasing the gas flow rate, nitrogen concentration or reaction temperature. The rate was also found to be increased by decreasing the thickness of titanium pellet. The smaller the titanium grain, the faster the reaction. The effect of forming pressure of pellet on the reaction rate was found to be insignificant. Effects of additives such as Al, B, Fe, Si, TiN and Y2O3 were found to be negative on the reaction rate. Empirical expression of conversion of titanium has been determined.View full abstractDownload PDF (1244K)
Separations
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Motonobu Goto, Bhupesh C. Roy, Akio Kodama, Tsutomu Hirose1998 Volume 31 Issue 2 Pages 171-177
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSExtraction or leaching of solute from natural solid material is a mass transfer process involving dissolution or release of solutes from a solid matrix. Interaction between the solute and solid matrix often influences the supercritical fluid extraction process. A model accounting for the solute-solid interaction as well as mass transfer is developed. The BET equation is used to incorporate the interaction and the solubility of solutes into the local equilibrium in the model. Experimental data for the supercritical extraction of essential oil and cuticular wax from peppermint leaves are successfully analyzed by the model. The effects of parameters on the extraction behavior are demonstrated to illustrate the concept of the model.View full abstractDownload PDF (1041K) -
Katsuyuki Kubota, Tooru Nishikawa, Shinya Hayashi, Hironobu Imakoma1998 Volume 31 Issue 2 Pages 187-194
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSFinely crushed and sized quartz particles were floatated in a supporting electrolyte, KNO3, both continuously and countercurrently by using a bench scale flotation column. This work is a continuation of previous work. Quartz particles were flotated by making them hydrophobic through using a cationic surfactant, a collector, and n-dodecyltrimethyl ammonium bromide. To reexamine the continuous and dispersed phase concentration profiles and removabilities, this work employs the traditional free settling and sedimentation model equations which involve a collision and attachment probability constant between a bubble and the particles. Here, in view of previous work, eddy diffusion of the particles is not taken into consideration in the model equations.
Experimentally, it could be deduced that a fraction of the particles lifted by the bubbles up to the froth/slurry (pulp) interface return to the slurry phase to be flotated again.
Incorporating this fraction, newly defined in this work, and the above probability constant into the model equations, they were solved numerically to reexamine the observed particle concentration profiles and the particle removabilities. As a result, the removabilities are supported by the model equations with a mean error of –18.4% and a maximum error of –35% even though data scattering was in part large.
A series of the experiments were conducted to investigate how gas flow rate and collector concentration affect the apparent rate constant. As a result variations of the rate constant do not contradict those concluded by a number of previous studies of column floatation.View full abstractDownload PDF (1054K) -
Luis A. Guzman, Kouji Maeda, Shouji Hirota1998 Volume 31 Issue 2 Pages 295-297
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSThe effects of Pb(II) on potassium dihydrogen phosphate (KDP) single crystal have been observed. It is found that the growth of the {100} face of KDP crystal is suppressed under traces of Pb(II), and that no tapering for KDP crystal by Pb(II) is observed. The hourglass pattern in KDP single crystal appears under traces of Pb(II). When measuring the distribution of Pb(II) between solution and prism-section crystal or pyramid-section crystals, the concentration of Pb(II) in both section crystals is higher than that in solution. Moreover, the concentration of Pb(II) in prism-section crystal is higher than that in pyramid-section crystal.View full abstractDownload PDF (1015K)
Particle Technology and Fluidizaion
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Guangwen Xu, Kousuke Nomura, Yunru Bai, Guogang Sun, Nobuyoshi Nakagaw ...1998 Volume 31 Issue 2 Pages 236-243
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSThe characteristics of pressure in gas/solids fluidization is measured with respect to the heterogeneous structure typified as lateral core/annulus segregation and local two-phase coexistence. Experiments are carried out in two circulating fluidized bed risers with bed diameters of 0.09 m and 0.15 m, respectively. Particles FCC (Geldart A) and silica sand (Geldart B) are used in the experiment, and are fluidized by air. It is found that the dynamic changes of the particle-rich dense phase (clusters or emulsion) and the fluid-rich dilute phase (broth or bubbles), as well as the alternations between these two distinct phases, can create a serious imbalance of instantaneous pressures among different radial locations at a same bed height. However, only a subtle time-mean pressure difference can be detected between the bed wall and the bed center with the higher pressure residing on the bed wall. It is observed that this wall-to-axis pressure difference is less than 30 Pa in a typical fast fluidized bed, while it reaches at most about 150 Pa for usual bubbling fluidization. The intra-phase pressures in both the dense phase and the dilute phase are also demonstrated to be subject to a dynamic variation other than a particular relation.View full abstractDownload PDF (1305K) -
Koji Kuramoto, Katsutoshi Tanaka, Atsushi Tsutsumi, Kunio Yoshida, Tad ...1998 Volume 31 Issue 2 Pages 258-265
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSMacroscopic flow structure of circulating liquid-solid fluidized beds (CLSFB) is investigated over a wide range of liquid velocities and circulating solid mass fluxes. Two kinds of glass ballotini, having respective mean diameters of 93 μm and 182 μm, were employed as a bed material, which always exhibit particulate fluidization in a batch operation. From systematic measurements of static pressures in the CLSFB riser at various liquid velocities and circulating solid mass fluxes it is found that the axial distribution of solid holdup is always uniform throughout the riser. The liquid-solid slip velocity is found to become appreciably higher than that in batch liquid-solid fluidized beds. From visual observation, it is found that particles tend to form aggregates with irregular shapes at liquid velocity higher than the particle terminal velocity, indicating the transition of fluidization state from particulate to aggregative. The change of the fluidization states with the operating conditions is quantitatively characterized by a power spectral density distribution and a fractal dimension of local voidage fluctuation obtained from an image analysis of photographs taken through the riser wall for the different fluidization regimes. The results clearly indicated that the formation of larger scale aggregates takes place at a liquid velocity appreciably higher than the particle terminal velocity leading to a slight decrease of complexity in the microscopic spatial distribution of bed voidage.View full abstractDownload PDF (1808K) -
Yoshimitsu Uemura, Sumio Nezu, Naoki Hamakawa, Kazuya Ijichi, Yoshihir ...1998 Volume 31 Issue 2 Pages 298-301
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSA reactor consisting of a high-velocity fluidized bed reactor with circulating ceramic particles as a thermal medium is proposed to produce hollow inorganic microspheres (so-called Shirasu balloons) from a volcanic glass, Shirasu. Using the reactor, Shirasu balloon production was investigated. Shirasu balloons of 25 μm in average diameter were successfully produced. This is the first work producing Shirasu balloons using a high-velocity fluidized bed reactor.View full abstractDownload PDF (879K)
Biochemical, Food and Medical
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Takaharu Sakiyama, Toshihisa Toyomasu, Asuka Nagata, Koreyoshi Imamura ...1998 Volume 31 Issue 2 Pages 208-213
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSAdsorption and desorption behavior of bovine serum albumin (BSA) and gelatin on the surface of stainless steel particles are studied. The amount of BSA adsorbed increases significantly with temperature above 60°C whereas that of gelatin decreases slightly with increasing temperature. Results of adsorption experiments with S-carboxymethylated BSA show that the thermal aggregation of BSA molecules at the surface through intermolecular thiol-disulfide interchange reactions plays an important role in the adsorption of BSA at elevated temperatures. Furthermore, the initial desorption rate constants and residual amounts of the two proteins during caustic and enzymatic cleanings of the fouled particles are compared under various conditions. As a result, a large difference is found in the temperature dependence of the initial desorption rate constant in caustic cleaning, suggesting different modes of adsorption of the proteins.View full abstractDownload PDF (910K)
Safety, Environment and Energy
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Kouichi Miura, Taisuke Maki1998 Volume 31 Issue 2 Pages 228-235
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSRecently one of the authors has presented a method (method I) to estimate both the distribution curve of the activation energy, f(E), and the frequency factor, k0, in the so called distributed activation energy model (DAEM) from three sets of experimental data obtained at different heating rates. No a priori assumptions are made for the functional forms of f(E) and k0. The k0 vs. E relationships obtained by this method for pyrolysis of 19 coals are found to be grouped into three groups, depending on coal rank. Utilizing the result, a simple method (method II) for estimating the f(E) curve is presented for analyzing the pyrolysis reaction of coal. The k0 vs. E relationship can be converted to the relationship between E and temperature, T, for a selected constant heating rate, a. Establishing the E vs. T relationship, we can easily estimate the f(E) curve from a single weight loss curve measured at the heating rate of a. The f(E) curve obtained by the simple method is rather close to the f(E) curve estimated by method I. The difference of the peak E values of f(E) curves estimated by both methods is always less then 15 kJ/mol. The f(E) curve estimated by the simple method is utilized well for predicting the weight change under different heating profiles.View full abstractDownload PDF (1015K) -
Yoichi Mitsuma, Hisashi Yamauchi, Tsutomu Hirose1998 Volume 31 Issue 2 Pages 253-257
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSCeramic paper sheets were formed into a honeycomb rotor with inorganic adhesive and it was calcined at about 500°C. The honeycomb adsorbent was impregnated with high-silica zeolite powder by a chemical reaction being dipped into a solution that contains zeolite powder and silica sol as an inorganic binder of the zeolite powder. After dried and finished, it was set in a SUS tube with insulation spacer and installed in testing equipment.
VOC vapor, butylacetate, was generated and directed to the honeycomb adsorbent, laden in the feed air stream, to conduct the adsorption and desorption efficiency test of the honeycomb adsorbent for this VOC. The test was done in a cyclic manner by feeding the air stream to the honeycomb adsorbent (adsorption process), and reversing the direction of the stream which was heated up (desorption process), with sequential damper arrangement and with scheduled periodic time control.
The result was compared with the one obtained by the conventional rotary test runs of the honeycomb adsorbent and was evaluated for a new trial of efficiency prediction method.View full abstractDownload PDF (754K) -
Kyaw Kyaw, Mitsuhiro Kubota, Fujio Watanabe, Hitoki Matsuda, Masanobu ...1998 Volume 31 Issue 2 Pages 281-284
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSIn view of its potential application to high temperature heat energy storage, carbonation of CaO with various CO2 pressures is investigated in the temperature range 873–1173 K by using a thermogravimetric analyzer under atmospheric conditions. For a given temperature, although the reaction takes place for a partial pressure of CO2, P, higher than the equilibrium CO2 pressure of CaCO3, Pe, the reaction rate shows a slight increase with increasing P. On the other hand, for a given P, the rate increases rapidly with increasing temperature from 973 to 1023 K, above which it decreases gradually. By applying a grain model and assuming the presence of a reaction intermediate, a possible reaction rate equation has been developed.View full abstractDownload PDF (466K)
General Research
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Kunihiko Koike, Goichi Inoue, Masanori Suzuki, Junji Saida, Ikuo Komat ...1998 Volume 31 Issue 2 Pages 195-200
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSExperimental and theoretical studies have been made on the nature of concentrated ozone. We proved that ozone with concentrations above 50 vol% can produce a passivated layer on the surface of stainless steel, which is considerably inactive to ozone decomposition. The ozone decomposition rate is strongly dependent on temperature, concentration and pressure. We also determined the activation energy and order of reaction for the decomposition. Moreover, our results reveal that N2, Ar and He have no effects on ozone decomposition, while CH4 and H2 act as catalysts and CO reacts with ozone under ordinary temperature and pressure conditions.View full abstractDownload PDF (842K) -
Ming Song, B. M. Li, A. Steiff, P.-M. Weinspach1998 Volume 31 Issue 2 Pages 201-207
Published: 1998
Released on J-STAGE: April 26, 2004
JOURNAL RESTRICTED ACCESSBased on the analysis of dynamic breakup process of particles in particulate systems, a direct stochastic simulation method is proposed in this paper, which is applicable for general population balances with particle breakup. The detailed algorithm is presented. There are two important steps in algorithm: 1. to determine whether a particle breaks up, using the breakup frequency function; 2. to determine the volume of daughter particles for one breakup, using the probability distribution function of daughter particles after the breakup of a mother particle. A calculation example of turbulent liquid-liquid dispersion is given to predict the development of particle size distribution. The calculation results are in very good agreement with the analytical solution from Das (1996).View full abstractDownload PDF (828K)
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