Online ISSN : 1349-9203
Print ISSN : 0386-216X
ISSN-L : 0386-216X
Volume 8 , Issue 1
Showing 1-15 articles out of 15 articles from the selected issue
  • Minoru Kumagai, Hiroshi Imai
    1982 Volume 8 Issue 1 Pages 1-6
    Published: January 10, 1982
    Released: February 19, 2010
    The gas entrainment rate of an impinging water jet was measured by using a straight circular nozzle with a length-to-diameter ratio of 50. The gas entrainment curve, which is the plot of volume flow rate of entrained gas against water jet velocity, consists of four regions : I) initial entrainment region, II) low jet velocity region, III) transition region, IV) high jet velocity region. The three critical jet velocities that show the transition of the slope of the gas entrainment curve were correlated as Reynolds numbers with nozzle diameter (D), jet length (Lj) and jet discharge angle (α).
    The gas entrainment rates in regions I and II were expressed respectively by the following equations.
    Region I : G=1.15×10-7V3.6D-0.17D4.8Lj0.28sin0.21 α
    Region II : G=1.9×10-3V1.7D1.0Lj0.35sin-0.8 α
    For region IV, two distinct experimental correlations were obtained, depending upon the jet length-to-nozzle diameter ratio, as follows.
    Lj/D>70 : G=3.0×10-4 (ριD2V2) · (Lj/D) 0.35·sin-0.3α
    Lj/D>70 : G=5.4×10-5 (ριD2V2) · (Lj/D) 0.75·sin-0.2α
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  • Naohiro Shiragami, Ichiro Inoue
    1982 Volume 8 Issue 1 Pages 7-12
    Published: January 10, 1982
    Released: November 12, 2009
    The laminar secondary flow in square bends was studied by the flow visualization technique.
    Axial and secondary velocities were measured by using the hydrogen bubble method, and it was observed that the position of maximum axial velocity moved along the plane of symmetry away from the center of curvature.
    To express quantitatively the secondary flow which characterizes the bend flow, the intensity of secondary flow is newly defined as the circulation, and its axial distribution was obtained experimentally.
    The intensity of secondary flow was related to the deflection angle from the bend inlet, the radius of curvature and the Dean number. It was found that the circulation has its maximum value near the bend inlet and almost disappears at the bend outlet.
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  • Toshiro Miyahara, Yorishige Matsuba, Teruo Takahashi
    1982 Volume 8 Issue 1 Pages 13-17
    Published: January 10, 1982
    Released: November 12, 2009
    An empirical approach was used to investigate the size of bubbles generated from perforated plates. Previous reports have shown that the size of bubbles formed at single circular holes is affected remarkably by chamber volume. The effect of chamber volume, however, becomes small with increasing number of holes and is not noticed at a number greater than about 15. The size of bubbles generated from perforated plates in the range where chamber volume has no effect shows different behavior at the critical ratio of pitch to hole diameter P/do of about 8. Empirical equations of the size of bubbles for each range are given.
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  • Toshiro Miyahara, Noriyuki Haga, Teruo Takahashi
    1982 Volume 8 Issue 1 Pages 18-24
    Published: January 10, 1982
    Released: November 12, 2009
    Bubble formation from an orifice at high gas injection rates was experimentally studied. At high gas injection rates, coalescence between growing and detached bubbles occurs. The coalescence is repeated approximately twice and the cycle of coalescence goes to completion. Coalescence between detached bubbles and the orifice becomes more or less continuous at very high gas injection rates; that is, a gas jet column is formed. The critical points for transition to the occurrence of coalescence and gas jet column are correlated by empirical equations.
    The size of the non-coalesced first bubble formed at high gas injection rates is studied theoretically, based on the two-stage model obtained by authors previously by considering the force due to gas momentum through a hole, and a comparison with measurements is made.
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  • Koichi Yamada, Tadatsune Fukunaga, Takuo Harato
    1982 Volume 8 Issue 1 Pages 25-31
    Published: January 10, 1982
    Released: November 12, 2009
    To develop a process for SO2 removal from waste gas by red mud slurry as a waste obtained from the Bayer process, equilibrium is measured for SO2-containing gas, and the slurry and absorption rate is also measured in semi-batchwise bubble-column gas absorption system.
    Johnstone's equilibrium equation for SO2-Na2SO3 solution turns out to be applicable for the system of SO2-red mud slurry.
    Oxidation of the red mud accelerates SO2 absorption.
    To select an absorber for an SO2 removal plant using red mud slurry, pilot plant tests at 1, 300 Nm3/hr were performed using a spray absorber, TCA and a perforated-plate absorber.
    1) Spray absorber : The efficiency of SO2 removal (Mass transfer coefficient KGa) is high enough to be applied to the plant. However, long term operation cannot be expected because of high wearing rate of spray nozzle.
    2) TCA : The efficiency of SO2 removal per tray (Murphree tray efficiency) is 0.50.6 at a gas velocity of 1.53.0m /s. The continuous operating time is limited to about 4 months by the wearing of ball in the absorber.
    3) Perforated plate absorber without downcomers : Stable operation can be obtained in the gas velocity range of 1.02.5 m/s. The efficiency of SO2 removal per tray is 0.40.6 and is higher than that using TCA at the same pressure loss.
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  • Koichi Yamada, Takuo Harato
    1982 Volume 8 Issue 1 Pages 32-38
    Published: January 10, 1982
    Released: November 12, 2009
    Using a pilot plant (1, 000 Nm3/h) of SO2 removal by red mud slurry, operating conditions and behavior of boiler dust and SO3 were investigated. The method of solving scaling trouble and the scale-up concept of perforated plate absorber were studied.
    90% of SO2 in boiler-waste gas is removed at a utilization rate of 60% Na2O in solid phase. Stable SO2 removal is attained by change of waste gas feed rate. Submicroscopic dust cannot be removed in the absorber.
    Scale formation of Ca-compounds depends on pH value of red mud slurry.
    The results obtained from the pilot plant agree well with those of an actual plant (220, 000 Nm3/H).
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  • Chikao Arai, Kikuo Yamazaki, Yoshiki Sano
    1982 Volume 8 Issue 1 Pages 39-44
    Published: January 10, 1982
    Released: November 12, 2009
    A simple calculation method is proposed for estimating pore volume distribution of porous material by adsorption isotherms. It is shown that the pore volume, Vi, can be calculated by the following equation :
    Vi=Rc, ivi-i-1Σj=1Mi, jVj)
    where Δvi is adsorption volume increment, and Rc, i, Mi, j are coefficients which depend on pore radius and thickness of the multimolecular layer. Values of these coefficients were evaluated from t-curve of nitrogen adsorption by using a cylindrical pore model.
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  • Masanobu Hasatani, Megumu Yuzawa, Norio Arai
    1982 Volume 8 Issue 1 Pages 45-50
    Published: January 10, 1982
    Released: November 12, 2009
    Reactivity (chemical reaction rate and reaction equilibrium) of CaO with SO2 was studied experimentally by means of a thermal gravimetric analyzer (TGA). Experiments were conducted for various kinds of limestone particles with dp=5-294 μm in a range of temperatures from 600 to 1, 200°C.
    Overall reaction rates were compared with theoretical results calculated on the basis of the existing Grain Model.
    For micro-fine particles (5 μm), the ultimate conversion of sulfation, X, reaches 1.0 on CaSO4/CaO basis in the range of temperatures from 750 to 1, 000°C but the X-values are always lower than 1.0 at temperatures of above 1, 000°C or below 750°C.
    The overall reaction rates over reaction temperatures of interest in the present study can be treated as chemical reaction controlling by introducing the modified conversion normalized by using X.
    The effects of pore diffusion on the overall reaction rates become increasingly significant with increase in particle diameter dp, particularly above values of about 20 μm.
    All these experimental trends can be well explained by the proposed theoretical analysis within the range of the present experimental conditions.
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  • Shigeaki Kasaoka, Yusaku Sakata, Shigeru Kayano
    1982 Volume 8 Issue 1 Pages 51-58
    Published: January 10, 1982
    Released: November 12, 2009
    For the purpose of developing a low-temperature gasification process for coal char, the catalytic effects of impregnated alkaline earth metal (Mg, Ca, Sr, Ba) and coupled Ba+Fe compounds on gasification rate with steam and/or carbon dioxide were investigated and compared with those of a porous pure carbon (PPC) prepared from thermal decomposition of Saran resin. The experiments were carried out by using a thermobalance under an atmospheric pressure of 600900°C.
    The following results were obtained : 1) A simple expression, f=1-exp (-aθb), with two parameters, a and b, simulated very closely both the sigmoidal (b>1) and the non-sigmoidal (1 ≥b>0) rate curves shown by fractional gasification (f) vs. gasifying time (°Cθ). 2) The catalytic effect for steam gasification of PPC was evaluated with rate constant at f=0.5. The order was Ba (17) >Sr (10) >Ca (1.6) _??_Mg (1.2) _??_non-additive (1). Activation energy of 51 kcal/mol for PPC (non-additive) was reduced to 37 kcal/mol with Ba-addition. 3) Ba-additive was effective for producing hydrogen-rich gas. Scheme of Ba-compounds for steam gasification of PPC was thought to be composed of catalytic gasification and CO-shift reaction, both based on the reaction cycles between Ba (OH) 2 and BaCO3. 4) Addition of Ba-compound over three coal chars also increased the steam gasification rate to 2 to 7 times at 900°C, and the composition of gas produced was in the order H2>CO2>CO. Coupling Ba-compound with Fe-compound, the effect of Ba was predominant for gasification of coal chars and PPC. 5) Since fairly good activity was comfirmed even after H2S treatment of PPC with Ba and Ba+Fe, a hybrid effect of both gasification and desulfurization was expected for Ba-additive.
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  • Tsutao Otake, Setsuji Tone, Isao Komasawa, Masao Kawashima
    1982 Volume 8 Issue 1 Pages 59-64
    Published: January 10, 1982
    Released: November 12, 2009
    Photochemical decomposition of alkaline solution of potassium ferro- and ferricyanide was carried out, using a low-pressure mercury lamp immersed in the reactant solution.
    The complex could be completely decomposed to cyanide ion and ferric hydroxide when the fine particles of the ferric hydroxide formed were removed from the solution by circulating the solution through a Mn-zeolite adsorption column.
    The decomposition process was confirmed to proceed in two steps as follows.
    Fe (CN) 63-, Fe (CN) 64-→ [Fe (CN) 5H2O] 3-→Fe (OH) 3
    The rates of both the first and second steps were found to be zero-order with respect to the concentration of the species. Both rates were independent of reaction temperature, but varied with the pH value and the light quanta absorbed by the solution.
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  • Tsutao Otake, Setsuji Tone, Shinji Ogawa
    1982 Volume 8 Issue 1 Pages 65-72
    Published: January 10, 1982
    Released: November 12, 2009
    An experimental study was performed on the flow pattern and gas hold-up in a bubble column with liquid jet ejector as the gas distributor.
    At the spouting state under the condition of high liquid flow rate, two different flow regions existed in the column : the spouting section and the calm section. The spouting section was the lower region in the column and heavy liquid circulation existed there. The calm section was the upper region and constituted the uniform bubble flow regime. The border between the two sections was defined as the critical height which gave the variation point of the static pressure gradient, and was nearly three times the column diameter.
    As liquid flow rate increased, gas hold-up in each section greatly increased and was influenced by the liquid characteristics concerning bubble coalescence. Empirical correlations of gas hold-up in each section were obtained by using Weber number based on the liquid velocity through the throat.
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  • Isamu Kashiki, Akira Suzuki, Keishi Gotoh
    1982 Volume 8 Issue 1 Pages 73-78
    Published: January 10, 1982
    Released: November 12, 2009
    A new type of flocculant is synthesized by the polycondensation of piperazine and ethylene bromide. Despite its low molecular weight (M=3, 240), the flocculant becomes large colloidal particles in water by association of the molecules. For the clarification of kaolin and quartz-sand suspensions, the new type of flocculant is compared with two commercial water-soluble polymer flocculants : noninoic Kurifloc PN141 and cationic Accofloc C100. For kaolin suspensions, the new flocculant requires a high dosage compared with the two commercial ones. For quartz-sand suspensions, the new flocculant is still effective, but the commercial ones do not work.
    The experimental results are discussed by use of the DLVO theory.
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  • Naoya Yoshioka, Yuji Yoshimura, Shoichiro Goto, Seiji Hanatani
    1982 Volume 8 Issue 1 Pages 79-85
    Published: January 10, 1982
    Released: November 12, 2009
    Initial filter coefficients, which express the collection efficiencies of suspended particles in clean deep-bed filters, were estimated by trajectory calculations using Kuwabara's flow model in fibrous deep bed.
    These calculated initial filter coefficients were correlated with five dimensionless groups as in granular deep-bed filtration, i.e. modified adhesion group, modified gravity group, interception parameter, Kuwabara's flow model parameter and retardation group for van der Waals attraction force, under conditions where double-layer repulsion forces between suspended particles and fibers were negligible and the adhesion efficiency was untiy.
    In particular, these values could be estimated approximately by semiempirical correction equations under conditions where the effects of gravity settling on filtration efficiencies were negligible.
    And, the more dominant the double-layer repulsion forces were against van der Waals attraction forces, as in granular deep-bed filtration, the more decreases in initial filter coefficients were observed.
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  • Eiji O'shima, Masato Tanaka
    1982 Volume 8 Issue 1 Pages 86-90
    Published: January 10, 1982
    Released: November 12, 2009
    For the purpose of investigating the mechanism of coalescence and breakup of liquid droplets in the process of suspension polymerization of styrene, a dual-step operation where bulk polymerization is carried out up to a certain conversion as preliminary step prior to suspension polymerization was investigated. It was found that a narrower droplet size distribution is obtained by this operation with increase of conversion attained in the bulk polymerization step.
    The following empirical equation was obtained to represent the rates of coalescence and breakup of droplets as a function of impeller speed and physical properties of droplets :
    It was, furthermore, found that the final particle size distribution of polymer is determined within a reaction time of 5 hours or about 0.8 conversion.
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  • Ikuho Yamada, Setsuro Hiraoka, Hirotsugu Sugimoto, Shigekatsu Mori, Na ...
    1982 Volume 8 Issue 1 Pages 91-108
    Published: January 10, 1982
    Released: February 19, 2010
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