All issues
Predecessor
Volume 31, Issue 1
Displaying 1-14 of 14 articles from this issue
- |<
- <
- 1
- >
- >|
Transport Phenomena and Fluid Engineering
-
Hiroshi Ohmori, Yasuyuki Ishii, Atushi Shono, Kazumi Satoh2005 Volume 31 Issue 1 Pages 1-6
Published: 2005
Released on J-STAGE: February 25, 2005
JOURNAL RESTRICTED ACCESSA new type of mechanically agitated gas-liquid contactor is proposed. In this contactor, bubble breakup is assigned to a sparger with larger ring diameter than impeller diameter, and circulation of gas-liquid mixture to an axial impeller with high discharge performance.
The performance was evaluated by measuring the rate of oxygen absorption into tap water and CMC aqueous solutions (viscosity 10–70 mPa·s), the gas holdup and the power consumption in comparison with the conventional type.
The new type of contactor prevents the concentration of aeration gas around the impeller and the formation of stable cavities in viscous liquid, resulting in the efficient discharge of gas-liquid mixture from the impeller. As a result, the performance of gas absorption, especially into viscous liquids, was improved. The relative contribution of aeration power to KLa became larger than that of agitation power in contrast to the conventional type. KLa increased with decreasing diameter of the sparger holes under the same superficial gas velocity, but no effects of the number of sparger holes were found.View full abstractDownload PDF (617K) -
Kae Fujita, Toshiro Miyahara2005 Volume 31 Issue 1 Pages 7-14
Published: 2005
Released on J-STAGE: February 25, 2005
JOURNAL RESTRICTED ACCESSExperiments were performed to study the stability of cellular foam for the purpose of foam breakage in chemical reactors and bioreactors. The growth and collapse process of cellular foam formed from four kinds of nonionic surfactant aqueous solutions with different Hydrophile-Lipophile-Balance (HLB) values were observed in a standard bubble column. As a result, three types of foam growth process and two types of foam collapse process were found. Furthermore, the critical film thickness at the time of the burst of the cellular foam was obtained by using the thinning equation of liquid film proposed by Hartland and Barber (1974) and Barber and Hartland (1975). The critical film thickness obtained was correlated with surface viscosity and HLB, which are physical properties at gas–liquid interface, in addition to density, viscosity and surface tension of liquid.View full abstractDownload PDF (735K) -
Naoki Shimada, Akio Tomiyama2005 Volume 31 Issue 1 Pages 15-24
Published: 2005
Released on J-STAGE: February 25, 2005
JOURNAL RESTRICTED ACCESSAn (N+2)-field model proposed in our previous study was modified so as to be applicable to compressible two-phase flows by taking into account the dependence of phase densities on temperature and pressure. Then, a numerical method for solving the modified (N+2)-field model was developed. The main feature of the proposed method is that the numerical stability is not determined by the Courant–Friedrichs–Levy condition but by the Courant condition, and therefore, stable numerical solutions can be obtained with a time step Δt much larger than the one used in a standard numerical method for solving compressible two-phase flows.
The verification of the proposed method was carried out through three sample calculations, i.e., simulations of an adiabatic air-water bubbly flow in a vertical duct of 10 m in length, an air-water bubbly flow in a uniformly heated duct of 10 m in length and a bubbly flow in a large bubble column. As a result, it was confirmed that (a) the proposed method accurately predicts the effects of pressure and temperature on phase densities and volumetric fluxes and (b) a simulation of a compressible bubbly flow in a practical bubble column can be performed with Δt satisfying the Courant condition.View full abstractDownload PDF (920K)
Particle Engineering
-
Yasumitsu Tanaka, Shu Saeki, Qiwu Zhang, Fumio Saito2005 Volume 31 Issue 1 Pages 25-30
Published: 2005
Released on J-STAGE: February 25, 2005
JOURNAL RESTRICTED ACCESSA novel mechanochemical (MC) method was examined for dechlorinating and recycling waste recording media tape. In this treatment, the tape was ground with CaO powder to decompose the constituent PVC. The ground sample was then washed with water to dissolve soluble chloride compounds formed during the MC treatment and filtered. The filtrated contained mainly calcium ions (Ca2+) besides the metals such as Co and Fe derived from the recording media, and thus it can be added to liquid containing phosphate ions (PO43−) to synthesize hydroxyapatite. The solid residue of filtration can be used for thermal recycling, because it does not contain any chlorine, and it has almost the same calorific value as RDF (refuse-derived fuel). Thus, the proposed MC method would be suitable for environmentally friendly treatment of waste recording media and their recycling.View full abstractDownload PDF (400K) -
Ryusei Ito, Manabu Nishimura, Boris Golman, Kunio Shinohara, Tadashi F ...2005 Volume 31 Issue 1 Pages 31-34
Published: 2005
Released on J-STAGE: February 25, 2005
JOURNAL RESTRICTED ACCESSThe dissolution rate of medical tablets has hitherto been measured by repeating dissolution tests, which require considerable time to get experimental confirmation of dissolution characteristics. Thus, it has not been investigated from the viewpoint of prescription of the dissolution rate. In this paper, the effects of tablet compaction and primary-particle properties on the dissolution rate were studied experimentally and quantitatively. It was found that the dissolution rate increased with increasing voidage of the tablet, increasing shape index of primary particles, decreasing active component and with decreasing specific surface diameter. The effect of shape index should, therefore, be considered by constructing a new dissolution model, because it is of an equal level to the effect of the specific surface diameter.View full abstractDownload PDF (419K)
Separation Engineering
-
Masatoshi Yoshida, Yuji Homura, Yoshiyuki Yamashita, Shigeru Matsumoto2005 Volume 31 Issue 1 Pages 35-40
Published: 2005
Released on J-STAGE: February 25, 2005
JOURNAL RESTRICTED ACCESSThis paper presents a new non-isothermal chromatographic process for the continuous separation of a multicomponent gaseous mixture. The process involves continuous cyclic operation of temperature swing adsorption (TSA) process in a single column by moving a properly controlled temperature profile along the column. This process can be considered as a combination of TSA and gas chromatography. The usefulness of proposed process was demonstrated by experiments with a laboratory-scale column for separation of dilute ethylene and carbon dioxide in nitrogen carrier gas. The experimental results were well explained by numerical simulations.View full abstractDownload PDF (463K) -
Shuji Himeno, Atsushi Nakazawa, Toshiya Komatsu, Shoichi Fujita, Hirom ...2005 Volume 31 Issue 1 Pages 41-50
Published: 2005
Released on J-STAGE: February 25, 2005
JOURNAL RESTRICTED ACCESSEffective utilization of biogas can contribute to the reduction of greenhouse gasses and the promotion of recycling. However, further development of gas storage technology is required. In this study, focused on adsorption storage technology and evaluated the storage density of biogas taking into account of temperature rise of the activated carbon. First, methane and carbon dioxide adsorption isotherms of various activated carbons were determined and analyzed by the Toth equation and the extended Toth equation. Secondly, binary adsorption equilibria of methane and carbon dioxide were measured and analyzed with IAST (ideal adsorbed solution theory). The amount adsorbed of the digestion gas from an institution and that predicted by IAST for digestion gas of the same composition were in good agreement, demonstrating that IAST is able predict the storage capacity of digestion gas. Finally, the adsorption storage density of digestion gas taking into account of the influence of adsorption heat was calculated by adiabatic approximation, and a temperature rise of 32 K for storage of digestion gas at 0.7 MPa in activated carbon A. However, storage capability was 10 (0.5 MPa) to 16 (0.2 MPa) times higher than the conventional compressed storage at same pressure. Furthermore, the temperature rise predicted by the proposed method agreed within 3 K with the temperature rise measured with the pilot-scale equipment.View full abstractDownload PDF (740K)
Chemical Reaction Engineering
-
Toshinori Kojima, Shinpei Komiya, Sigeyuki Uemiya2005 Volume 31 Issue 1 Pages 51-55
Published: 2005
Released on J-STAGE: February 25, 2005
JOURNAL RESTRICTED ACCESSIn electronics processes, downsizing of various electronic parts and the increase in load of semiconductor elements cause increase in heat production. Therefore, AlN with high thermal conductivity, radiativity, and expansibility similar to Si is utilized as semiconductor packaging materials. For this purpose, highly purified AlN is required, as the desired properties of AlN are rapidly lost with the increase in concentration of impurities. In recent years, AlN is manufactured by the direct nitriding and the carbothermal reduction methods. However, these methods have the problems of high reaction temperature (1500°C) and difficulties in continuous operation. In the present study, we synthesized AlN fine powder by direct nitriding method in a fluidized bed. The present process is expected to allow the continuous production of AlN fine powder with high conversion rate at relatively low temperature, because fluidized bed method gives excellent heat exchange; Al material is melted and distributed in the bed. To find suitable operation conditions for efficient continuous synthesis of AlN in a fluidized bed with bed materials of AlN, various operational conditions were tested. It was demonstrated high purity AlN could be produced without containing unreacted Al at relatively low temperature (1200°C). However, part of the product was obtained not as fine powder but as agglomerates.View full abstractDownload PDF (749K) -
Effects of Coal Grade and Gasification Conditions on the Pore Characteristic Parameter of Coal CharsTatsuya Morimoto, Tetsuya Ochiai, Kazumasa Arakita, Tomohiko Kametani, ...2005 Volume 31 Issue 1 Pages 56-61
Published: 2005
Released on J-STAGE: February 25, 2005
JOURNAL RESTRICTED ACCESSThis work focused on effects of coal grades and the conditions of CO2 gasification of coal chars, namely, reaction temperature and conversion rate, on the dimensionless parameter Ψ in the random pore model (RPM). The parameter Ψ was calculated from true density, N2-BET surface area and pore length of partially gasified chars at various rates of conversion. For coals with lower carbon content (<C80%), Ψ decreased with carbon conversion only in the initial stage, but did not change significantly at higher conversions. For coals with >C80%, a drastic decrease was observed at the beginning of gasification, and the minimum of Ψ was obtained at around a conversion of X=0.5. This significant decrease was alleviated at a higher gasification temperature. The Ψ variation represented above is probably related with the opening of closed pores during gasification.View full abstractDownload PDF (467K)
Energy
-
Mizue Saho, Tsutomu Nakazato, Kazumasa Kobayashi, Nobuyoshi Nakagawa2005 Volume 31 Issue 1 Pages 62-67
Published: 2005
Released on J-STAGE: February 25, 2005
JOURNAL FREE ACCESSA direct methanol fuel cell (DMFC) was operated at different phases of methanol feeding, i.e., a liquid phase, a gas phase with 90% relative humidity (RH) and a gas–liquid mixed two-phase with 130% RH, at 353 K and the atmospheric pressure, and the i–V performances of the cell were compared. For the gas phase flow, the ohmic cell resistance became larger than that of the gas flow, suggesting a deficiency in the water content of the membrane. For the liquid phase and the two-phase flows, the same performance was obtained. Also, the overvoltage characteristic of the liquid phase feed was very similar to that of the gas phase when the methanol activities were almost the same. These findings suggested that the anodic overvoltage and the reaction mechanism are not affected by the state of the feed of methanol as long as the methanol activity is the same. Some difference was found in fluctuation characteristics, the frequency and the amplitude, of current density at a constant cell voltage among those states of the feed phase. This was attributed to the effect of mass transfer of CO2.View full abstractDownload PDF (635K) -
Ryokichi Hamaguchi, Yuki Nishimura, Yousuke Matsukuma, Masaki Minemoto ...2005 Volume 31 Issue 1 Pages 68-73
Published: 2005
Released on J-STAGE: February 25, 2005
JOURNAL RESTRICTED ACCESSA system for recovery of methane hydrate from the deep ocean floor has not been established. As one possible recovery system, a gas-lift system was investigated. Experiments were performed with a gas-lift system of 5 m height and 100 mm in diameter to determine the relationship between injected gas quantity and pumped water quantity. Vertical flow in the gas-lift pipe was calculated with a compressible one-dimensional two-fluid model to analyze flow in the recovery pipe of methane hydrate from the deep ocean floor. Basic equations were mass conservation equations and motion conservation equations of each phase, the relation of volume fractions and the state equation of the gas phase. The calculation showed that the power requirement of the gas-lift system is 0.5 to 4% of power generated from recovered methane gas, and that optimal gas injection depths exist. Thus, the gas-lift system can be economically effective the recovery of methane hydrate from the deep ocean floor.View full abstractDownload PDF (484K)
Environment
-
Junji Shibata, Norihiro Murayama, Mitsuaki Tanabe, Hideki Yamamoto2005 Volume 31 Issue 1 Pages 74-79
Published: 2005
Released on J-STAGE: February 25, 2005
JOURNAL RESTRICTED ACCESSHydrotalcite, an inorganic anion exchanger with a layered structure comprising complex hydroxides, was synthesized using aluminum dross and MgCl2 waste solution discharged from an aluminum regeneration process as raw materials. Various physical properties of the product, such as crystal structure, surface texture, thermogravimetric change, pH buffer action and phosphate removal ability were investigated.
Hydrotalcite was synthesized from aluminum dross and MgCl2 waste solution by co-precipitation of complex hydroxides of Al and Mg. Traces of SiO2, Al2O3, Fe2O3 etc. remained as impurities in the reaction product. The interlayer distance of the obtained hydrotalcite is about 0.3 nm. Hydrotalcite changes to Mg–Al complex oxides by calcination at 773 K for 3 h, and hydrotalcite can be regenerated by rehydration. The physical properties of hydrotalcite obtained from the wastes are almost the same as those of hydrotalcite prepared from fresh reagents. The obtained hydrotalcite has both pH buffer action and phosphate removal ability.View full abstractDownload PDF (599K) -
Shoji Kagawa, Keisuke Suzuki, Lei Hosaka2005 Volume 31 Issue 1 Pages 80-83
Published: 2005
Released on J-STAGE: February 25, 2005
JOURNAL RESTRICTED ACCESSActivated carbon was produced from cigarette butts. Water contained in the raw materials influenced its activation. When the water content in the cigarette butts was 200%, increasing temperature at the rate of 5 K/min and, holding at the carbonization and activation temperature of 1173 K for 1 h produced activated carbon with a specific surface area of about 556 m2/g. The activated carbon had mesopores of 4 nm in diameter showed adsorption capacities of 522 mg/g for iodine and 58 cm3/g for methylene blue.View full abstractDownload PDF (264K)
General Research and Others
-
Yuichi Ohira, Jun Amanai, Yoshikazu Kuga, Kiyoshi Idogawa, Eiji Obata, ...2005 Volume 31 Issue 1 Pages 84-88
Published: 2005
Released on J-STAGE: February 25, 2005
JOURNAL RESTRICTED ACCESSThe effects of surface tension and bubble diameter on the bubble breakage time in water and ethanol solutions were experimentally investigated on the ground and under microgravity. Bubble breakage times increase as the bubble diameter increases and as the surface tension decreases. The calculated results from the correlation equation were consistent with the data measured on the ground and under microgravity.View full abstractDownload PDF (391K)
- |<
- <
- 1
- >
- >|