Metal hydride powders were fixed in resin forms of two different shapes, a cylinder and a film. The pressure-composition-temperature (PCT) characteristics and the durability to the hydriding/dehydriding cycles were tested. The PACT characteristics were found to show a similar trend to that of untreated powders, except for a slight decrease in hydration capacity and a slight increase in the pressure hysteresis. The hydration rate increased with increase in metal hydride content and was not much different from that of powders of samples with a high content of metal hydride. Further, from SEM observation it was confirmed that the metal powders were well fixed in the resin matrix in spite of the breakdown of the powders themselves after several repetitive operations. Little damage was observed to the base resin with repetition. It is concluded that the metal-hydride fixation tested in this work is applicable as a new functional method with durability.
For the reduction of hematite by solid carbon a new model has been derived, taking into consideration both the rate enhancement and rate degradation effects observed during the reduction. The model helped in evaluating the rate constant as a function of fractional conversion. Calcium lignosulfonate catalyst introduced into the matrix of industrial coke increased the reduction rate of hematite considerably. Kinetic parameters derived using a simple model for catalyzed and noncatalyzed reductions indicated that the catalyst mainly increased the number of active sites during the reduction.
The effects of column dimensions, gas velocity and properties of the liquid and the gel particles on gas holdup εG and volumetric liquid-phase mass transfer coefficient kLa in a gel-suspended bubble column with a draught tube and a conical bottom were studied experimentally in a liquid-solid batch operation. The presence of suspended gel particles in the column reduces values of εG and kLa, and the degree of reductions due to addition of gel particles to the column increases with increasing gel-particle concentration. Based on these observations, empirical equations of εG and kLa applicable to columns of 0.14–0.3 m diameter are proposed.
Performance of a pervaporation membrane consisting of polyacrylonitrile hollow fiber with a thin ionized cross-linking chitosan layer, developed for dehydration from aqueous organic mixture, was evaluated at the scale of a 6 m2 module under various conditions of feed composition (95–99.8 wt%), temperature (40–75°C) and pressure (0.1–1.8 kPa). The data indicate high performance of the module in both permeation rate and separation factor, 0.6 kg/(m2·h) and 5000 respectively at an ethanol concentration of 95 wt%. It was also shown that the permeation rates vary in proportion to the mole fraction of water in the feed to the power of 1.3, while the separation factor was almost constant in the range of ethanol concentration from 95 to 99.5 wt%. Under an operating pressure lower than the partial vapor pressure of water in the feed, the temperature dependence of the permeation rate follows the Arrhenius equation with an activation energy of 54 kJ/mol independently of the operating pressure.
To solve some problems of conventional experimental analyses of coal liquefaction, other workers have proposed a method utilizing an autoclave equipped with sampling cells with which reacting coal pastes can be sampled as such. They have not showed how to apply the method accurately, however, nor its effectiveness in comparison with conventional analyses. In this work an accurate procedure for applying the method was developed and efficiency was demonstrated. Some of the experimental findings by application of the procedure developed were as follows: (1) the real product distribution under liquefaction conditions was obtainable, while the conventional analyses gave only an apparent product distribution under ambient conditions; (2) the coal slurry holdup was reduced because of considerable conversion of the slurry into gaseous products with the progress of liquefaction.
Based on graph theory and the concept of degree of vertex, a new reachable vector method for network decomposition is proposed in this paper. It differs from the traditional tearing algorithms which first find maximal cyclical nets and elementary cycles, and then tear elementary cycles to get a set of cut streams that break all cycles in the flow of information. In the proposed method the initial precedence sequence of vertex is formulated by introducing the conception of the degree of vertex, which serves as a reasonable primary structure for further adjustment. Then a reachable vector is presented instead of the reachable matrix to adjudge the position of vertices. With this new method a set of torn streams and calculation sequence of the process considered are obtained directly, and it is simple and easy to understand and program. Ten test problems are examined, and the new tearing algorithm finds the minimum number of tears for all ten problems. It indicates the effectiveness of the proposed method in the process decomposition.
An enantioselective membrane was prepared by introducing an amino acid condensate with glutaraldehyde into a polysulfone membrane matrix. The optical resolution of phenylalanine from aqueous racemate solutions was examined under the concentration and pressure gradients across the membrane respectively. The membrane was permeable with respect to D-phenylalanine in preference to L-phenylalanine, and the separation factor was 1.25 to 4.10. The solute fluxes were analyzed on the basis of a permeation model consisting of both diffusing flow and viscous flow. Using the solute fluxes of D- and L-amino acids, the separation factor could be successfully expressed by the solute permeability of amino acid and the volume flux.
Local controllability of jet impingement heat transfer was investigated by immersing an array of circular cylinders within a slot jet. Heat transfer on the central stagnation line was augmented most effectively due to the acceleration and surface-renewal effects when the cylinder array was placed from four to six cylinder diameters upstream of the heat transfer surface in a ‘passing’ arrangement. The maximal point of heat transfer was shifted, without attenuation, to half the cylinder pitch off the jet axis on both sides by a ‘blocking’ arrangement whereas the central stagnation-line heat transfer was suppressed very much due to the blocking effect. The mechanism for augmentation of the stagnation-line heat transfer was explained successfully by the surface-renewal model proposed.
The application of KCl to the catalytic gasification of higher-rank coal char was investigated. K-exchanged brown coal was prepared from KCl using an ion-exchange method. The K-loaded coal was physically mixed with a higher-rank coal. The mixture was gasified in steam with a thermobalance. The effects of the mixing pattern and the caking property of higher-rank coal on the catalytic effectiveness of K-excbanged coal were examined. The catalytic effectiveness of physical mixing of K-loaded brown coal was compared with that of physical mixing of Ni-loaded brown coal. Rate enhancement by physical mixing of K-exchanged Yallourn coal was almost independent of both the caking property of higher-rank coal and the chemical state of potassium catalyst before mixing. Direct contact between K-exchanged coal and higher-rank coal was required for this catalytic coal gasification system. EPMA analysis showed that potassium catalyst easily transferred from Yallourn coal to higher-rank coal char surface, whereas no transfer of Ni catalyst was observed. Potassium was a highly suitable catalyst for catalytic gasification by the physical mixing method.
The effects of equipment dimensions and gas dispersion on the flow characteristics of a bubble column with perforated draft tube were experimentally examined. Gas was dispersed into the inner section of the draft tube or into the annular section between the column and the draft tube. Under various combinations of column diameter and diameter and length of the draft tube, the flow pattern was observed and the liquid mixing time, gas holdup and specific gas-liquid interfacial area were measured. In either gas dispersion, gas and liquid radially flowed through holes in the draft tube, and large bubbles were subdivided into small ones. Gas dispersion into the inner section was more effective in shortening the liquid mixing time. The liquid mixing time was shortened by increasing the ratio of height/column diameter, and was most shortened at a diameter ratio of draft tube/column of about 0.6. Gas dispersion into the annular section was effective in increasing the gas holdup and the interfacial area. The interfacial area was also increased by decreasing the characteristic length of the gas dispersion section.
Reliable polarization characteristics of noble metal or oxide electrodes in contact with solid oxide electrolyte are quite important. To obtain such characteristics, we fixed sputtered platinum electrodes on yttria stabilized-zirconia (YSZ) electrolyte by covering the electrode with a porous ceramic layer. As a result of the fixation, the Pt film was kept stable and the resistance of the electrodes was very small. Electrode impedance and potential-current curves were measured on the fixed electrodes. The effect of the oxygen partial pressure, PO2, on the electrode resistance, Ri, which was obtained from the impedance plots, was represented as Ri ∝ PO2–1 at high temperature and low oxygen partial pressure, and as Ri ∝ PO21/4 at low temperature and high oxygen partial pressure. Furthermore, effects of the thickness of the Pt film and the ceramic layer on the polarization characteristics were examined. The cathodic current increased as the Pt thickness decreased. The anodic current increased as the ceramic layer thickness decreased.
Effects of magnetic fields on natural and Marangoni convections in a two-dimensional rectangular open boat were studied numerically. Convective velocities in magnetic fields depend on the Marangoni number, the Grashof number, physical properties, direction of the applied magnetic field and strength of magnetic field. For suppression of natural convection, either a horizontal (perpendicular to gravity) or a vertical (parallel to gravity) magnetic fields is effective. For suppression of Marangoni convection, the vertical magnetic field is more effective than the horizontal magnetic field.
For the purpose of removing carbon dioxide from flue gases a novel operation, “permabsorption”, a hybrid operation of membrane permeation and gas absorption was proposed. Permeability of a non-porous hollow-fiber (HF) membrane made of polydimethylsiloxane for PUre CO2 and O2 was obtained in this simple-operation mode, the observed values being in reasonable agreement with literature values. High permselectivity can be attained by using an appropriate absorbent liquid. In the permabsorption of CO2 using alkaline solution, the permeation rate could be expressed by a model based on membrane permeation with gas absorption. The performance of a multiple-HFs module was comparable to that of a packed column. This result implies that the permabsorption method provides the possibility of operation at lower liquid flow rate than in packed columns and, therefore, of energy-saving CO2 removal from flue gases.
Information about the particle impact on mixer geometry is very important in understanding the secondary nucleation in crystallization, but has rarely been investigated. In this work, a method of measuring the rate of particle-impeller impaction was developed. Using this method, the effects of impeller speed, particle properties and solid concentration on the rate and position of impaction were studied. It was found that the rate of impaction depends strongly on each experimental condition studied in this work. The preponderant position where particle-impeller impaction occurred was usually at the outer bottom corner of the blade.
As a method for making liquid chromatography a continuous operation, a simulated moving-bed adsorber has been applied. This method is applicable only to two-component mixtures. Hence a new process for multi-component separation by combining multiple liquid chromatography columns was proposed. Its applicability was confirmed partly by experiments with a single column in the process and partly by simulation of the separation of dimethyl phthalate, diethyl phthalate, and di-n-butyl phthalate. The results showed that a mixture of more than three components can be separated and refined by use of this process. The values of distribution coefficient and overall mass transfer coefficient for each component required for the simulation were obtained from impulse response experiments, using the same column.
For the 6″ silicon CZ system, effects of a funnel-shaped radiation shield on the temperature profiles in the melt and crystal, the melt/crystal interface shape and also the distribution of the thermal stresses were investigated theoretically by the finite element analysis based on the conduction-dominated model. It is found that a funnel-shaped radiation shield can make the melt/crystal interface less convex to the crystal (relatively flatter), providing a higher pull rate and smaller thermal stresses in the crystal compared with other radiation shield geometries, such as a doughnut (torus) shape. Also, the principal operating conditions in the CZ system, such as the crucible temperature, can be changed widely by selecting the emissivity and/or thickness of the shield.
The microbial retainment process in porous support particles in a fluidized-bed wastewater treatment reactor was investigated. The behavior of retained and suspended microbes differed in three reactors, each containing particles of a different pore size. To analyze this phenomenon, a model was proposed which includes the growth of both retained and suspended microbes, the capture of suspended microbes by the porous particles and the detachment of retained microbes. It was found that the specific capture rate of suspended microbes was larger in particles of smaller pore size and that detachment had occurred in particles of larger pore size.