A transient response method using the isotope replacement technique was used to verify “pseudo-liquid phase” behavior of 12-tungstophosphoric acid and to investigate the solubility and mobility of polar substances such as alcohols and ethers. The relationship between the concentration of labeled molecules in gas phase and that in bulk phase can reasonably be assumed as linear in this technique, regardless of intrinsic non-linear relationships of diffusion and absorption. It was found that the polar molecules can be absorbed into the bulk phase of catalyst under these experimental conditions. The small values of effective diffusivities, which are on the order of 10–10 m2s–1, are observed to be close to that in liquid-filled pores. The amount of absorbed molecules of alcohols, determined by polarity, tend to have a unique stoichiometry corresponding to the number of protons in H3PW12O40, and the mobility depends on either polarity or molecular size.
A new random-walk model was developed to assess light energy absorbed by a photosynthetic microorganism. The model had two parameters, which were determined from transmittance through an algae suspension obtained by opalescent plate spectrophotometry. The validity of the proposed model was confirmed by comparing experimental data of light absorption in a Chlorella ellipsoidea suspension with the computation results of a Monte Carlo simulation, and by comparing light intensities passed through the suspension by a Reinecke’s salt actinometer with those predicted by the random-walk model.
The chemometrics approach has been applied to the analysis of the combined effects of temperature, light intensity and CO2 concentration on the growth rate of the blue-green alga Anacystis nidulans. The strategy for the experiments is based on an extended factorial design. A statistically significant interaction is found between temperature and light intensity. Optimal conditions for maximal growth rate can be predicted by multiple regression analysis and its reliability has been confirmed by experiments. At the optimal growth condition the photosynthetic nature of A. nidulans was examined. The results suggest the importance of the utilization of these cells in the logarithmic growth phase for the purpose of CO2 fixation.
Heat transfer between vertical electronic boards was studied. Each electronic board consisted of a printed writing plate with 81 or 162 electronic resistance devices attached. Temperature distribution on the writing plate and temperature and gas velocity distributions between the boards were measured with thermocouples and a laser doppler velocimeter (LDV). Those distributions were affected by electric power supplied, distance between the boards and open ratios at the top and bottom of the shelf. The average Nusselt number and average Reynolds number for the electronic boards were obtained. These values were calculated from empirical equations obtained with the flat vertical parallel plates with suitable modification. To calculate the temperature distribution and axial gas velocity distribution between the boards, fundamental equations were solved numerically with suitable boundary conditions. The calculated temperature and axial gas distributions approximately agreed with experimental values.
Ionic transport in a continuous Donnan dialyzer with two parallel-plate channels was studied for a bi-ionic exchange system. A theoretical model of the system was formulated on the basis of diffusion equations in terms of diffusion, migration and convection of each ion. Theoretical solutions were obtained by numerical calculations using a finite-difference technique. Simultaneously, continuous Donnan dialytic experiments with a cation-exchange membrane were conducted for the K+–H+ and Ca2+–H+ exchange systems. The validity of the model and the numerical calculations was confirmed by comparison with experimental results for mean dialytic rates. The numerical calculation also provided distributions of ionic concentrations in both the channels and the membrane, and the electric potential in the channels. An effectiveness factor was introduced to investigate the proportion of the mass transfer resistance in the membrane phase or the liquid phase to its overall value. The influence of Reynolds number, channel height and valence of counter-ion on the mean dialytic rates and on the effectiveness factor was also discussed.
Clarification filtration experiments are conducted under constant pressure, using a filter cloth and very dilute suspensions prepared by suspending diatomaceous earth in a power-law fluid comprising aqueous sodium polyacrylate. To analyze the clarification filtration process, a stochastic model that describes particle capture in a filtration process has been coupled with the conventional blocking filtration laws. Four types of blocking filtration equations are derived, including complete blocking, intermediate blocking, and standard blocking equations. The intermediate blocking law can be applied when the particle size is larger than the pore size or is almost the same as the pore size. In contrast, the standard blocking law can be applied when the particle size is considerably smaller than the pore size. In addition, the effects of the solid concentration in the feed suspension and of the applied filtration pressure on the clarification filtration characteristics are delineated.
A new unsteady-state method for measuring simultaneously the thermal dilfusivity and the thermal conductivity of liquids is presented. The method utilizes the principle of the Laplace transform and has the advantage of measuring these two properties under arbitrary heating or cooling conditions imposed on the test liquid, where unidirectional heat flow and a uniform temperature profile at the initial stage are conditions of testing. A measuring theory is developed for a measuring system wherein test liquid is intruded between a pair of flat reference samples whose properties are known. The characteristics and measuring errors of the method are discussed. An apparatus in which low-expansion borosilicate glass is used as the reference sample is made on an experimental basis. The method is verified by measuring both the thermal diffusivity and the thermal conductivity of water, toluene and NaCl solution.
Growth behavior of ammonium sulfate secondary nuclei originated from a seed crystal in a stirred-tank crystallizer was investigated using a Coulter Counter. From the time dependence of the cumulative curves it appeared that the particles can be divided according to growth behavior into two groups. Particles larger than 40 μm grow fast, independently of size (group I), and particles less than 20–30 μm grow at a rate 1–2 orders lower than that of group I (group II). It was also suggested that the secondary nucleation mechanisms of groups I and II are different, and that of group I may be initial breeding. It was observed that for a portion of the group II particles the growth rate increases abruptly during the crystallization. Dissolution rates of group I particles obtained from the cumulative curves were consistent with the values calculated by the mass transfer rates equation, but those of group II were largely lower than the calculated values. The difference in growth behavior between groups I and II was attributed neither to Gibbs–Thomson effect nor to mass transfer rate changes with particle size, but to the difference in the contribution of surface kinetic process. It was found that the growth process of large ammonium sulfate crystals (group I) is much more controlled by volume diffusion than are those of other salts such as potassium sulfate.
An ultrasonic measurement method was applied to obtain information about the properties of cake formed on the membrane in microfiltration of suspensions of yeast. The microfiltration was carried out at low applied pressure in order to assess that the cake formed was incompressible. A spherically concave transducer made of piezoelectric films of a vinylidene fluoride-trifluoroethylene copolymer was adopted. The surface shape of the cake was found not to be flat by the reflection technique. An on-line method of measuring cake thickness was developed by using the transmission technique, and the results showed good agreement with data reported elsewhere.
A mixed oxide catalyst was prepared from a binary hydrogen storage alloy, Mg2Cu, and its activity and selectivity were compared with those of conventional CuCrO catalyst. The catalyst’s activity was stable for the synthesis of C18 alcohol by gas-phase hydrogenolysis of methyl oleate in a continuous-flow reactor at 553 K under atmospheric pressure. Considerable amounts of unsaturated alcohol were produced together with saturated alcohol. From a kinetic study the rate equation was formulated for each alcohol. From XRD analysis, active sites are thought to be copper species on MgO support.
A theoretical study of asymptotic solutions (constant-pattern solutions) of fixed-bed hydriding processes is presented for systems with finite longitudinal dispersion in a bed and finite resistances to mass transfer. A closed form of the solutions is obtained under conditions where a metal hydride has a plateau pressure on its equilibrium isotherm. If the equilibrium isotherm does not intersect a straight line connecting two points of an influent condition and an initial one of the bed on an x–ym diagram, a single asymptotic mass transfer zone propagates through the bed. On the other hand, if the isotherm does intersect the line, a twin asymptotic mass transfer zone propagates. Then a plateau zone is formed between the two zones. Application to a titanium hydride bed demonstrates the usefulness of the analytical results on the basis of the asymptotic solutions.
This paper presents a dynamic model which includes axial dispersion and interphase mass transfer for a simulated countercurrent adsorption separation process, together with a numerical technique based on the method of orthogonal collocation for the solution of the governing partial differential equations. It is shown that the experimental transient behavior may be predicted by modeling the system in terms of an equivalent true countercurrent process provided that the inherent limitation of this approach is noted. This approach nonetheless provides a handy tool for predicting the time required for the system to approach quasi-steady state.
When a two-layer system consisting of water (upper layer) and an aqueous solution (lower layer) is heated from one side and cooled from the opposite side, convection begins in each layer and a sharp horizontal interface is formed by two flows circulating in opposite directions. The heat transfer soon appears to become approximately steady, but the mass transfer remains unsteady. When the concentration difference becomes small and the interface unstable, phenomena such as wavering of the interface and a large interface slope are observed. The fluid near the wall finally streams into the other layer and the two-layer system changes into a one-layer system. For a typical two-layer convection in the present study, the temperature was high at the top of a layer and low at the bottom of the layer. The concentration gradient was sharp at the interface. The concentration in a layer was almost uniform. The average concentration in the upper layer increased linearly with time.
For the organic compound cimetidine, which has seven polymorphic forms, the growth rates of form A (metastable) and B (stable) and the solvent-mediated phase transition rates from A to B were measured in 2-propanol solvent. At high supersaturation ratio (SC,A = 3.6), with form-A seed, agglomerated crystals of form A were obtained without an induction period. With form-B seed, by contrast, form A nucleated heterogeneously on B seed’s surface and then grew to single-like crystals after the induction period. At low supersaturation ratio (SA ≤ 1.3, SB ≤ 1.7), the growth rate of form A was higher than that of form B at the same supersaturation ratio, Si, based on their respective solubilities, but at the same solute concentration this tendency was reversed. At SA = 1.0, a solvent-mediated phase transition took place, being controlled by the growth rate of form B. The growth rates of both forms at low supersaturation were proportional to the surface area of crystal and (Si – 1)2.
Bubbling, jetting and spouting as gas discharge modes at a single nozzle in a two-dimensional gas-fluidized bed with Group B particles were investigated by means of visual observation and spectral analysis of pressure fluctuations in the grid region. A bubble plume was observed with a frequency of bubble formation in the range 2–7 Hz. Empirical equations predicting the transitions of gas discharge modes were obtained. The flow regimes of gas discharge modes were mapped by using two parameters, the static bed height-to-nozzle diameter ratio and a modified two-phase Froude number.
Experimental and theoretical studies were made of the separation efficiency of an air cyclone separator. The results of numerical calculations of three-dimensional Navier–Stokes equations indicate that the flow field changes with circumferential angle. The upward and downward velocity components merge strongly near the entrance of the dust box. Large particles are collected on the upper wall, small particles on the conical wall. It is also confirmed that particles with small inertia enter the dust box first, but finally exit from the cyclone because of the upward velocity component. The experimental partial separation efficiencies obtained agree well with the numerical calculations when the data are rearranged according to the particle inertia parameter.
The formation of ordered and disordered cakes of monodispersed PSL particles by constant-pressure filtration is investigated. It is found that ordering occurs under the condition where the transition of a dispersed phase of particles to an ordered one, like the Alder transition, takes place above the cake surface, and that common cakes are composed of both disordered and ordered domains with specific cake resistances of 0.9 × 1013 and 1.5 × 1013 m/kg respectively. An equation for a constant-pressure filtration in which the dependence of the cake structure on the flow rate is taken into account is proposed and is found to be successfully applicable to cakes composed of ordered and disordered domains.
The distribution and dissociation equilibria of a representative phase-transfer catalyst, tricaprylmethylammonium chloride (Aliquat 336; Q+Cl–), were measured for the systems of n-butyl acetate–water, toluene–water, n-butyl acetate–aqueous NaCl solutions and toluene–aqueous NaOH solutions. The evaluated distribution coefficients of Q+Cl– and the OH–-substituted derivative (Q+OH–) were correlated as a function of the ionic concentrations in the aqueous phases. The dissociation constants of Q+Cl– and Q+OH– in the aqueous phase could be regarded as being identical. The diffusivities of Q+Cl– in water and in n-butyl acetate, and the ionic diffusivity of Q+ in the aqueous phase were measured. The aqueous-phase mass transfer of Q+Cl– could be quantitatively explained as that with an instantaneous reversible dissociation reaction.