KAGAKU KOGAKU RONBUNSHU
Online ISSN : 1349-9203
Print ISSN : 0386-216X
ISSN-L : 0386-216X
Volume 12 , Issue 6
Showing 1-16 articles out of 16 articles from the selected issue
  • Toshio Kawaguchi, Toshihisa Wakasugi
    1986 Volume 12 Issue 6 Pages 627-634
    Published: November 10, 1986
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Optimum operating conditions of vinyl acetate synthesis from acetylene were studied from the viewpoint of active carbon-supported zinc acetate catalyst consumption and by-product ratio of impurities to vinyl acetate by use of two fluidized bed reactors. Both had a diameter of 3.28 m and a vinyl acetate production capacity of 50 tons/day. The by-product ratio of impurities was affected by reaction conditions, but the quantities of reactants to impurities were small as yield. As for catalyst consumption, it was seemed better to raise the reaction temperature gradually with deteriorating catalyst activity in a similar operation to that of a fixed-bed reactor.
    But, considering operational stability, by-products, utility consumption and catalyst consumption, the operating method using a combination of reactor temperatures, which means that the new catalyst is fed to the reactor at lower temperature and the discharging catalyst from this reactor is fed to the reactor at higher temperature, is the optimum method.
    It is found that the optimum operating conditions are SV 100 1/h, MR 2.5, 447 K lower reactor temperature and 463 K higher reactor temperature, and the unit consumption of the new catalyst is calculated as 6.7 l/ton vinyl acetate. This value agrees with the actual results of the commercially operating process.
    Download PDF (1095K)
  • Hiroshi Yamamoto, Ryoji Utsumi, Akira Kushida
    1986 Volume 12 Issue 6 Pages 635-639
    Published: November 10, 1986
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    The aperture size in a screen of plain dutch weaves which a sphere was passed through was studied. It was shown that the particles would be screened by two areas in the weaves, that is, the opening area between two wefts on the surface and an inner area like a triangle which was made of a warp and two wefts. The triangle area was studied by geometrical calculation and compared with experiments in practical screening by glass beads and sand. The experimental results were investigated on the basis original size distribution, the number distribution of screened oversize and undersize, and the cut size on the partial separation efficiency curve. It was concluded that the calculated aperture size agreed with experimental results.
    Download PDF (1993K)
  • Ikuru Toyoda, Satoru Kato, Junjiro Kawasaki
    1986 Volume 12 Issue 6 Pages 640-646
    Published: November 10, 1986
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Bicomponent Adsorption of carbon dioxide and ethylene contained in an inert nitrogen stream by a fixed bed of synthetic zeolite 4A was studied.
    The adsorption equilibrium obtained for the single component carbon dioxide was correlated well by a Langmuir-Freundlich-type equation rather than the Langmuir equation, while the equilibrium data for ethylene were expressed well by the Langmuir equation. The extended Langmuir-Freundlich-type equation was modified on the basis of a concept that synthetic zeolite 4A has two kinds of adsorption sites, and was further modified empirically to account for interactions between the two adsorptive components. The adsorption equilibrium data obtained for the bicomponent system were correlated well by this modified, extended Langmuir-Freundlich-type equation. Fixed bed breakthrough curves were simulated by use of the equation along with the so-called linear-driving-force approximation for the intraparticle diffusion equations. The breakthrough curves calculated for both adsorbates agreed well with those measured under various operating conditions.
    Download PDF (1161K)
  • Masaaki Izumi, Toshiharu Shinmura, Yoshiaki Isobe, Norio Yamakawa, Shi ...
    1986 Volume 12 Issue 6 Pages 647-653
    Published: November 10, 1986
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Heat transfer during drop and filmwise condensation was measured on the rough surfaces of copper pieces which were scratched horizontally with sand paper of various grades and set in a vertical position, over a wide range of subcooled temperature Δt.
    By observation, there was typical dropwise condensation in the lower range of Δt, although the shape of drops was flatter than that on a smooth surface and the dynamics of drops showed irregular motion like stopping or shifting.
    Experimental data showed that the values of heat flux and the sweeping frequency decreased with increasing surface roughness. This was considered to be due to the increase of drag force on the motion of the drops.
    The transient and filmwise condensation which appear in the higher range of Δt occurred easily compared with that on the smooth surface, because of the increase of wettability and drag force on the rough surface. The heat flux values became very much lower and showed different values under the condition that the subcooled temperature was increased and decreased. One could easily reproduce this hysteresis phenomenon on the rough surface.
    Download PDF (5097K)
  • Osamu Miyatake, Hiroyuki Iwashita
    1986 Volume 12 Issue 6 Pages 654-660
    Published: November 10, 1986
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    This paper deals with the laminar-flow heat transfer to a fluid flowing axially between a triangular arrangement of heated cylinders with a uniform wall temperature.
    The finite-difference form of the energy equation is solved to obtain the axial variation of temperature distribution by means of a forward-marching, implicit method with iteration, and typical results for the local Nusselt number Nuloc and the logarithmic mean Nusselt number Nulm are presented graphically for the local Graetz number Gzloc or the Graetz number Gz up to 105 and spacing-to-diameter ratios σ of 1.0 to 4.0.
    From the numerical solutions, approximate expressions of Nuloc and Nulm are derived as
    Nu loc=9.26 (1+0.0022Gzloc1.46) 1/4, Nulm=9.26 (1+0.0179Gz1.46) 1/4for 1.0≤σ<1.1
    Nuloc= {f2(σ)+g2 (σ) Gzloc2/3} 1/2, Nulm= {f2(σ)+ (3/2) 2g2 (σ) Gz2/3} 1/2for 1.1≤σ≤4.0
    where
    f (σ) =8.92 1+2.82(σ-1) / 1+6.86(σ-1)5/3, g(σ)=2.34 1+24(σ-1) / {1+36.5(σ-1)5/4} (2√3σ2-π) 1/3
    Download PDF (939K)
  • Masahiro Niwa, Haruhiko Ohya, Kenichi Katauke, Youichi Negishi, Yoshio ...
    1986 Volume 12 Issue 6 Pages 661-667
    Published: November 10, 1986
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Piezodialysis concentration of aqueous ethanol solutions containing sucrose was carried out using four composite membranes and cellulose acetate (CA) membrane.
    The concentration ratio of EtOH using CA membrane shows the largest value of 2.24.
    The ethanol permeation flux is found to be proportional to the volume permeation flux of solution.
    The concentration of ethanol inside the membrane was calculated and found larger than that of bulk solutions, assuming the mechanism of membrane flux can be expressed by Spiegler Kedem's transport model.
    The distribution coefficients of EtOH in symmetrical CA membrane were measured and found to increase with addition of sucrose and with decrease of water content in membranes and was almost equal to the calculated value.
    Download PDF (1008K)
  • Mikio Takemoto, Junichi Nagata
    1986 Volume 12 Issue 6 Pages 668-674
    Published: November 10, 1986
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    The effects of atmosphere and fluid flow on the SCC susceptibility of AISI type 304 stainless steel in 35 wt % magnesium chloride solution were studied.
    1) Dissolved oxygen in the corrodent is absolutely necessary for SCC to occur in 35wt% MgCl2 solution with pH of 3.8 to 4.4. The bubbling of air accelerated the SCC to a great extent compared to that in stagnant solution open to atmosphere.
    2) The fluid flow was found to decrease the time to crack initiation to a great extent in laminar flow, but to have no discernible effect in turbulent flow. The critical Re number at which repassivation could occur apparently increased with increasing temperature of corrodent.
    Download PDF (5661K)
  • Mikio Takemoto, Junichi Nagata
    1986 Volume 12 Issue 6 Pages 675-680
    Published: November 10, 1986
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Thermal stress corrosion cracking tests of a vertical stainless steel tube (AISI 304) under natural convective heat transfer, where the tube was heated on the inside and cooled on the outside with stagnant corrodent (35wt% MgCl2), was studied. The results obtained are as follows;
    1) Stress corrosion cracking under natural convection was associated with corrosion pits which were blocked up with corrosion product, and it propagated in the axial direction of the vertical tube. The time to crack initiation under natural convection was almost equal to the time to crack under flowing condition at average temperature of thermal boundary layer.
    2) The time to pit formation did not show distinct dependency on either heating surface temperature or thermal stresses. The incubation time from pit formation to crack initiation, however, showed an Arrhenius-type temperature dependency, and its activation energy was equal to that in acidified 42wt% MgCl2 solution. The heat transfer might accelerate the change of solution to lower pH in the corrosion pits so that the corrosion rate was controlled by the activated reaction of hydrogen charging.
    Download PDF (5850K)
  • Mikio Takemoto, Junichi Nagata
    1986 Volume 12 Issue 6 Pages 681-687
    Published: November 10, 1986
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Thermal stress corrosion cracking of stainless steel tube (AISI 304) under forced convective heat transfer was studied in 35wt% MgCl2 solution. The results obtained are as follows :
    1) Corrosion pits were observed within a very short period after the beginning of the SCC test, and SCC was initiated at the bottom of corrosion pits which were blocked up with corrosion product. The time to crack initiation under forced convective heat transfer was shorter than that under other any test condition used in a series of these studies.
    2) Under constant surface temperature and thermal stress, the time to pit formation decreased, but the incubation period from pit formation to crack initiation increased with increasing Reynolds number in turbulent flow. The SCC susceptibility was affected by both wall temperature and physical conditions of fluid such as temperature and flow velocity. Further study is necessary to clarify the physical meaning of the incubation period.
    Download PDF (11975K)
  • Toshiro Murase, Eiji Iritani, Jun Hyung Cho, Mompei Shirato
    1986 Volume 12 Issue 6 Pages 688-693
    Published: November 10, 1986
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Filter cake dewatering in a horizontal plate filter is achieved by using hydraulic expression in a specially designed chamber with an impermeable membrane. The expression mechanism due to a change in the filtrate flow pattern is studied under constant-pressure conditions. A method is presented for analyzing the dehydration rate on the basis of Terzaghi's model for two-dimensional consolidation.
    The change in the filtrate flow pattern, which occurs after cake formation is completed, necessarily causes a change in the hydraulic pressure and compressive pressure distribution through the cake, thus leading to consolidation of the cake. The average moisture content of the compressed cake at the end of the operation is quite close to the final average moisture content obtained by the mechanical expression, since the impermeable membrane assists in compressing the cake. The expression rate heavily depends on the applied pressure and the thickness and radius of the filter chamber.
    The experimental results of the expression rate for slurry material of Korean kaolin agree well with predictions based on the compression-permeability cell data.
    Download PDF (858K)
  • Chiaki Igarashi, Hiroaki Sato, Hidetomo Suzuki
    1986 Volume 12 Issue 6 Pages 694-700
    Published: November 10, 1986
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    The effect of adsorption of polyelectrolyte on dewatering characteristics was investigated for night soil treatment sludge.
    The results obtained were as follows.
    1) Under an apparently saturated condition, the adsorbed weight of polyelectrolyte per unit weight of suspended solid (Xw*) was constant for polyelectrolytes of low-molecular weight, but it came to decrease with increasing molecular weight for those of higher molecular weight.
    2) Under the apparently saturated condition, the adsorbed charge of polyelectrolyte per unit weight of suspended solid showed a similar dependency on the molecular weight to Xw*.
    3) Dewatering characteristics with high-molecular weight polyelectrolyte was optimum at break point, i.e., a polyelectrolyte dosage above which residual polyelectrolyte was observed in centrifugally separated water. At the break point a large number of sites, to which cationic polyelectrolyte molecules could adsorb, remained on the suspended solid surface.
    4) Dewatering by using both a low-molecular weight cationic polyelectrolyte and a high-molecular weight anionic polyelectrolyte in series was optimum at the break point dosages for each polyelectrolyte. The more a sludge which was treated with a cationic polyelectrolyte amount less than the break point dosage had adsorbed cationic charge, the lower the moisture ratio became for the dewatered cake.
    Download PDF (2979K)
  • Yoshiyuki Bando, Makoto Nishimura, Michio Kuraishi, Tukasa Kasuga
    1986 Volume 12 Issue 6 Pages 701-706
    Published: November 10, 1986
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    The collection efficiency of the “Volume Heat Trap” type solar collector can be improved by suppressing the natural convection within the layer. This improvement is thought to be attained by partitioning the working fluid layer with transparent plates and making the zone of the natural convection small.
    In the present study, to examine the collection characteristics of the “Volume Heat Trap” type multilayer solar collector, the temperature distribution and the collection efficiency of collectors with one and two layers were measured under various flow rates of the working fluid. A theoretical analysis, taking the natural convection into consideration, was performed. The experimental data and the calculated results were compared and the effects of various parameters were studied.
    It was clear that the multilayer solar collector is efficient for suppression of the natural convection within the layer. It was also found that an optimum number of partitions exists for each operation condition.
    Download PDF (894K)
  • Hiroshi Yoshida, Hiroshi Yukawa
    1986 Volume 12 Issue 6 Pages 707-713
    Published: November 10, 1986
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    The electroosmotic dewatering mechanism for compressible sludge under the condition of constant electric current is theoretically analyzed and a basic equation is presented. The variations of water content and electric potential difference distributions in the sludge with time can be estimated by solving the equation numerically. The analytical solutions of these distributions are compared with experimental results obtained by using gelatinous bentonite sludge. The variations of applied voltage, dewatered volume, sludge bed height and average water content in the sludge are calculated from the basic equation and these results are also compared with the experimental results. It is proved that the equation obtained theoretically is reasonable for the estimation of the electroosmotic dewatering process under constant electric current.
    Download PDF (1262K)
  • Morihiro Yasuda, Saburo Yasukawa, Taro Sekine
    1986 Volume 12 Issue 6 Pages 714-720
    Published: November 10, 1986
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Electrochemical characteristics of a concentric cylindrical fluidized-bed electrode (CFBE) with copper-coated glass particles (diameter 2.9 mm) were studied by using the electrodeposition of copper from aqueous sulfuric acid containing 0.1 mol ·dm-3 of CuSO4. Three electrolyzers of different sizes were used in the experiments. The diameters of their external and internal cylinders were 7 cm and 0.9 cm in cell A, 7 cm and 2.2 cm in cell B and 4.2 cm and 0.9 cm in cell C.
    The apparent current densities, jW, at the working electrode in the CFBE were calculated by using the standard electrode surface area that was the sum of the working electrode area corresponding to the surface area of the diaphragm and the surface area of total particles included in the volume expressed by a product of the diaphragm area and the fluidized-bed thickness. The current-potential curves (jWW curves) at the working electrode surface in the CFBE were made by plotting the apparent current densities, jW. Also, the current-potential curves (jKK curves) of the CFBE were expressed by using apparent current densities, jK, of the CFBE, that is, jW (rW/rK), where rW/rK was the ratio of the radius, rW, of the working electrode to the radius, rK, of the middle point of the width of the K-th compartment in the CFBE, and jW-K was an apparent current density estimated by using ηK instead of ηW in jWW curves. The total reaction current estimated by using these curves and the local overpotentials agreed with the experimental values of cell currents within an error of 2-5 %.
    Download PDF (1137K)
  • Yosuke Kawashima, Shingo Ito, Satoru Iuchi
    1986 Volume 12 Issue 6 Pages 721-725
    Published: November 10, 1986
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    The heat transfer characteristics in the region downstream from a rectangular mixing junction with an oblique branch were obtained experimentally, and the effect of the confluent flow on heat transfer was investigated. Experiments were carried out for cross-sectional area ratios of 1.0 and 2.0 and branch angles of 50°, 70°, 90°, 110° and 130° at test section Reynolds numbers of 29, 900 and 40, 000.
    It was shown that the average axial Nusselt numbers, normalized by the value for a flow rate ratio of 1.0, could be expressed as a function of the contraction coefficient evaluated from the two-dimensional flow pattern in a mixing junction with an oblique branch, which was solved numerically by using a k-ε turbulence model.
    Download PDF (830K)
  • Yasuo Kato, Nobuyuki Hidaka, Hiroshi Kamimura, Naotsugu Ito, Kiyoshi N ...
    1986 Volume 12 Issue 6 Pages 726-746
    Published: November 10, 1986
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Download PDF (6071K)
feedback
Top