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991.
A multistage, mechanically stirred column absorber has been designed and built with a modular construction, based on preliminary experiments with a test column. The column has been characterized as a gas-liquid contactor by its gas holdup, gas and liquid axial dispersion, mixing times, oxygen transfer coefficients and power consumptions, determined as a function of gas velocity, liquid velocity and impeller speed for one and two impellers per stage.Gassed power was correlated with ungassed power, gas rate and impeller speed. The gas phase axial mixing was essentially plug flow and the liquid phase axial mixing varied between 5 and 12 equivalent stages.Oxygen transfer coefficients were correlated with power consumptions and aeration rates by the equation KLa γ (P/V)asg)b. The oxygen transfer coefficients with single stiffer stages were 25% above those for the double stirrer stages for equal power consumption and gas rates. Except for the low aeration and high power consumption extremes, the column showed superior oxygen transfer performance. in comparison to tubular loop and tank fermenters.  相似文献   
992.
The design of multistage fluidized beds for heat exchange necessitates the solution of the mass and energy balance equations combined with the equilibrium relations for each stage. This paper presents a novel way of applying well known methodology to a different technology, one where it has not been widely applied.

In the present work a McCabe-Thiele type of graphical approach is presented for both counter-current and cross-current contacting multiple fluidized beds. The necessary equations for a multistage calciner are developed and the application of the proposed method is demonstrated. Generalized fluidized bed efficiency for counter-current and cross-current multiple fluidized bed is presented.  相似文献   
993.
Yttria-containing tetragonal zirconia polycrystals with low thermal stability showed plastic deformation with a maximum bending strain of 0.8% due to the stress-induced tetragonal to monoclinic transformation. The strain rate depended on applied stress and temperature. The temperature at which the transformation rate is maximum increases with increasing applied stress. Changes in microstructure and crystallographic structure after plastic deformation were examined by transmission electron microscopy and X-ray analyses. The mechanism of plastic deformation is discussed in relation to the tetragonal to monoclinic transformation.  相似文献   
994.
The effect of 2,2′-oxydiethanol (diethylene glycol, DEG) content (ranging from 2 to 15 mol %) and of the annealing temperature (in the range from 100 to 260°C) on the density, calorimetric, dynamic- and static-mechanical and small angle X-ray scattering (SAXS) behavior of undrawn and drawn samples (granules, films, and bristles) of poly(ethylene terephthalate) (PET) has been studied. The known dependences on the annealing temperature are confirmed. Some discrepancies with earlier investigations of the dependences on the DEG content are established: constant values for the SAXS intensity and long spacing, for the lamellar thickness and for the volume fraction crystallinity ac. These discrepancies are explained by the variation of the glass transition temperature (Tg) and melting temperature (Tm) of the materials with different DEG contents. The previous hypothesis of the segregation of the comonomer (DEG) units into the amorphous regions is confirmed.  相似文献   
995.
Optical inspection is a potentially powerful and practical tool to collect information on polymer blend morphology for on-line quality and process control. This paper describes two approaches for the characterization of polymer blend materials by multiple light scattering. A quantitative evaluation of spectral turbidimetry (scattering of transmitted light) is presented and an adaptation of this technique for monitoring particle size, independent of the volume fraction is demonstrated. Such a procedure is applicable to materials in film form. A different approach is presented for the analysis of nearly spherical particles in optically thick samples: the diffuse reflection pattern surrounding the position of incidence of a focused light beam on the surface of the turbid medium is scanned by a single side imaging system. A spectral pseudo-transmittance signal processing technique provides particle size information again independent of the volume fraction: Both techniques have been tested using well characterized polystyrene microspheres suspended in water as well as poly(methyl) (methacrylate)/polystyrene polymer blends.  相似文献   
996.
Conclusions Out of all the experimental bonding agents used in the production of unfired magnesite and magnesite-chromite refractories: SDW; MgSO4,· 7H2O; MgSO4·7H2O + H3BO3; (NaPO3)n, the greatest strength on heating is provided by the addition of 2% (NaPO3)n.An addition of boric acid to the refractories using the MgSO4,·7H2O bonding agent helps to strengthen the refractories in the 500–900°C interval; at a higher temperature the refractories with the magnesium sulfate plus boric acid bonding have no advantages in their strength properties over the articles with the magnesium sulfate bonding agent only.The magnesite-chromite articles with the chemical bonding agent have better strength in the 1000–1400°C interval than the magnesite articles. This is explained by the spinelformation reactions which occur at these temperatures.On the basis of these studies (NaPO3)n and also MgSO4,· 7H2O with an addition of H3BO3 can be recommended as chemical bonding agents for unfired magnesite-chromite refractories.Translated from Ogneupory, No. 1, pp. 48–52, January, 1979.  相似文献   
997.
The slag resistance of refractory concretes prepared from mechanically activated aluminosiliceous binding suspensions is investigated. The composition of the binding part of vibration-cast refractory mixtures strongly affects their slag resistance. A good effect is obtained by introducing finely milled corundum-, zircon- and chromium-containing additives. The concretes were tested in the lining of a heating well and in the lining of the doors of the charging gates of open-hearth furnaces.Translated from Ogneupory, No. 2, pp. 28 – 30, February, 1996.  相似文献   
998.
H. Mitomo  K. Nakazato  I. Kuriyama 《Polymer》1978,19(12):1427-1432
Nylon-6,6 — a typical polyamide — was annealed in the swollen state in glycerol to promote the partial melting of the polymer crystal. The recrystallization or lamellar thickening of nylon-6,6 crystal following partial melting was easily induced by this annealing, and the lamellar thickness of the crystal increased stepwise by 12 monomer unit length with increasing annealing temperature or annealing time. In addition, another distinct layer-thickening mechanism was observed which led to approximately doubling (and frequently quadrupling) the straight stem length of the lamellar crystal for all samples annealed under adequate conditions. New melting endotherms corresponding to these layer thicknesses (range of long spacings 140–180Å) were obtained by differential scanning calorimetry (d.s.c.) at temperatures ranging from 270° to 282°C. The mechanism of lamellar thickening is discussed with reference to the experimental results.  相似文献   
999.
This paper presents a transient axial dispersion model for an isothermal, catalytic fluidized bed reactor, which is frequently employed in synthetic production processes including coal gasification and liquefaction. A non-linear chemical reaction is considered to occur in the reactor. This model of a fluidized bed reactor takes into account the axial dispersion in the three phases, bubble, cloud-wake and emulsion. The physical properties along the axial coordinate are invariant in the model. Transient characteristics of the gas reactant, and the length of the transient period have been examined based on the model. The model compares favorably with experimental data in the steady state condition.  相似文献   
1000.
Cocurrent and countercurrent absorption and desorption of CO2 in water was investigated in tall bubble columns (length 440 and 720 cm, diameter 15 and 20 cm, respectively). Operating conditions were applied which provided for high interphase mass transfer rates. Under these circumstances the relative gas holdup varies considerably with axial position whereas the mean bubble diameter measured at two points was found to be approximately constant. The measured data permit the calculation of local values of interfacial areas, superficial gas velocities, and frequency factors for bubble coalescence and break up. A dispersion model which takes into account the hydrostatic head and a variable gas velocity was applied to describe the measured concentration profiles in both phases. If increased mass transfer coefficients at the column bottom and measured local values of the hold up were used a striking agreement between experimental and predicted profiles could be obtained. The findings lead to a more sophisticated picture of the complex behaviour of gas-liquid dispersions at high interphase mass transfer rates.  相似文献   
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