The recirculating flow characteristics in a confined space with axisymmetric sudden expansion followed by a conical contraction section were measured by means of an electrochemical method. Integral scales of space correlation in both longitudinal and circumferential directions were obtained. Also, the recirculating velocity of a large eddy was determined from the measurement of space-time correlation. Experimental results confirmed that there exists a large recirculating eddy near the wall of test chambers.
To investigate the mechanism of extracting organic acids from water by amine, the extraction equilibria of the ternary systems of tri-n-octylamine (TOA), water, and each of four lower carboxylic acids were measured at 30°C. The experiments show that the distribution ratio of an organic acid strongly depends on the kind of acid when the concentration in the aqueous phase is very low. An extraction model where both association and physical distribution are taken into consideration has been proposed. By this model the experimental data can be explained well, while the association mechanism of the model is estimated from the excess volumes of TOA/organic acid binary mixtures. The model suggests that the 1:1 complex between amine and an organic acid strongly contributes to the distribution and selectivity of the acid in the region of very low concentration.
This paper presents the heat trap and heat storage characteristics of an optically semitransparent-material packed-bed solar air heater, which may have two advantages over conventional flat-plate solar air heaters: (1) it has accelerative effects on the heat transfer rate due to increases in the apparent optical depth of the air layer and in the heat transfer area, and (2) the packed-bed material itself can be used as a heat storage material. When glass beads are packed in the air channel of an air heater as a semitransparent material, a heat storage effect as well as 1.2–1.5 times higher heat-trap efficiency than in the absence of packing or where the packing is an opaque material like porcelain beads result. It is also indicated that packing with a glass tubes bundle will increase the pressure drop considerably less than will packing with glass beads. From these results, it is likely that the proposed solar air heater has good enough heat trap and heat storage characteristics for development as a new type of solar air heater with high efficiency. In addition, the experimental results can be predicted well by a theoretical model describing transient, two-dimensional, combined convective and radiative heat transfer.
We developed an effective process for separating the positional isomers α- and β-naphthyl sulfates, in which a separator carries out the selective hydrolysis of β-naphthyl sulfate into β-naphthol, catalyzed by sulfatase from Helix pomatia, and extraction of the resulting product by an organic solvent. Separator performance was analyzed theoretically on the basis of the purity and the recovery of each isomer. The analysis elucidated the best separator type, the activity of the membrane-bound sulfatase and the operational conditions for efficient separation of the isomers. Mixtures of various feed compositions were separated by use of a model separator with a porous cellulose membrane of 102 cm2 area in which sulfatase was immobilized by albumin and glutaraldehyde, and decanol was used as a sweep liquid. The experimental results of the purity and the recovery of each set of isomers agreed well with the theoretical predictions.
Axial mixing in the continuous phase and the mass transfer characteristics of a new spray column with four rod electrodes were examined in a range of applied voltages up to 23 kV using a system of water drops in cyclohexane. Iodine was used as a transfer solute for measuring the mass transfer rate and as a tracer for measuring liquid mixing in the continuous phase. The axial dispersion coefficients under applied voltages showed lower values than that in the absence of applied voltage. The extraction efficiencies were increased by about 50 percent for applied voltages of up to 23 kV. It is concluded that these significant enhancement of mass transfer were due to the increased frequency of coalescence and redispersion of the drops.
Generally, chemical processes behave nonlinearly. But existing well-developed controller design techniques are based on linearized models of nonlinear processes. The neglected nonlinear effects affect the stability of control systems. Robustness degree, a new measure for robust control, is introduced and studied from the engineering point of view. The concept of robustness degree, proposed by applying the semigroup theory of functional analysis, can play a role in analysis and design of control systems. It is a sufficient and quantitative measure of the margin of stability within which certain nonlinear functions and modelling errors can be tolerated. Robustness degree of an open-loop or closed-loop system is linked with system matrix measure as an estimation that is straightforward and easy to calculate. A chemical reactor is studied as an example of robust control system design by this approach.
The distribution ratios of copper(II) ion between an aqueous solution containing a copper salt in the presence of nitrate, chloride or sulfate and an organic phase containing 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproine) in 1,2-dichloroethane (DCE) were measured as a fundamental study for establishing the liquid membrane system. The difference in distribution ratio between nitrate and sulfate used in large excess was applied to drive the uphill transport of copper ion. The liquid membrane process consisted of the DCE solvent containing bathocuproine as a transport carrier and the two aqueous copper ion solutions containing a large excess of nitrate and sulfate ions. In this process, reproducible rate data were obtained by using a liquid-film holder in which the liquid membrane was maintained at constant pressure between two sheets of hydrophilic filter to prevent its leakage. The transport rate was examined by the quasi-steady model based on the three mass transfer steps involving a series of formation and dissociation of the copper-bathocuproine ion-pair with nitrate anion that take place instantaneously and reversibly at both interfaces of the liquid membrane. As a result, it became clear that copper ion was concentrated by the extraction through one hydrophilic filter, the diffusion of ion-pair across the liquid membrane and the back-extraction through the opposite filter accompanying the pseudo-first order equilibrium reaction for the complexation of copper with sulfate ion.
A new, efficient model reduction method for multistage distillation columns is proposed by combining the orthogonal collocation method and the two-part modular concept. To assess the performance of the proposed method, numerical simulation was performed for two distillation examples—the high-purity freon 11–12 binary system and the nonideal ethanol–1-propanol–water ternary system— and the results were compared with those obtained by the methods of existing collocation as well as rigorous equation solving. It was shown that the proposed method reduces the computing time by about 40% with accuracy comparable to that of the rigorous methods. Furthermore, while the existing collocation method could not properly reproduce the sharp changes of variables in the vicinity of the feed stage, the proposed method could successfully reproduce them as well.
Nickel/alumina catalysts were prepared by the deposition of nickel chloride vapor on spherical alumina (3.5 mm diameter) followed by reduction. This paper describes the effects of preparation conditions (deposition time and deposition temperature) on the nickel content, the nickel concentration profile, and the nickel particle diameter. The nickel content increased with increasing deposition time of nickel chloride vapor, and decreased with increasing deposition temperature. The average nickel particle diameters were observed by TEM, and were not affected substantially by deposition time or deposition temperature. They ranged from 500 to 650 nm. The intraparticle penetration of nickel proceeded with increasing deposition time. The activation energy of acetylene hydrogenation was about 50 kJ·mol–1, regardless of the preparation method, which involves gas phase method and impregnation method. The activity per unit surface area of nickel showed the following order: vapor deposition nickel/alumina > gas phase reduction nickel ≅ impregnated nickel/alumina.
Amylase (Dabiase K-27) was immobilized covalently on enteric coating polymers that were reversibly soluble-insoluble (S-IS) depending on pH. Among several immobilized amylase preparations, the amylase immobilized on Eudragit L (Dabiase-Eudragit: D-E) showed good response of solubility to pH change without decrease in activity. The specific activity per amount of enzyme protein of D-E for raw starch was more than 85% that of the native enzyme. In the hydrolysis reaction of raw starch, changing the pH of the reaction medium at an appropriate interval allows the insoluble D-E and the reaction product, glucose, to be repeatedly separated. By the hydrolysis method with repeated removal of the reaction inhibitor, glucose, the time required for converting a high-concentration raw starch to glucose was significantly reduced. The reaction method using the reversibly S-IS enzyme is a promising procedure for repeatedly utilizing the enzyme in a heterogeneous reaction system containing raw starch as a substrate.
The Brinkman model, previously extended to the concentrated region of monodisperse flocculated solid–liquid system, is used here with respect to polydisperse flocculated system. This model can describe fluid flow relative to a swarm of flocs of uniform permeability over a wide concentration range, and can be used to estimate the concentration dependence of permeability. For checking the model, permeability determination by the constant-rate expression method, floc solidosity (packing fraction) estimation by gravitational drainage of floc bed, and floc size analysis by a photographic method were performed for polydisperse flocculated Korean kaolin. The agreement between theoretical and experimental characteristics of flocculated Korean kaolin was satisfactory. It is also shown that the empirical Tambo–Watanabe floc density function can be theoretically derived from the model, and is closely related to the separation kinetics of flocculated dispersion.
Filtration characteristics of power-law non-Newtonian fluids–solids mixtures are investigated by use of a specially designed filter having a hole at the top of the filter chamber. On the basis of the principle of sudden reduction in filtration area of the cake surface, a method is developed for determining such overall filtration characteristics as the ratio m of wet to dry cake mass and the average specific filtration resistance γav for power-law fluids. Analytical equations are derived for correlating the overall filtration characteristics with the point or local values in filter cake. The compression-permeability characteristics, which are essential to the theoretical analysis of the mechanism of filtration within compressible filter cake, are evaluated on the basis of the overall filtration characteristics obtained under various filtration pressure conditions. It is shown that the results obtained from the newly developed non-Newtonian filtration technique are in good agreement with those obtained from conventional C-P (compression-permeability) cell measurements and Newtonian filtration experiments.
Using a newly synthesized surfactant, a kinetic study of copper extraction by liquid surfactant membranes containing anti-2-hydroxy-5-nonylbenzophenone oxime was carried out in a stirred tank, along with studies of the extraction equilibrium of copper with the extractant organic solution containing the surfactant and adsorption equilibrium of the surfactant between the organic and aqueous solutions at 303 K. The extraction rate by liquid surfactant membranes was analyzed by an interfacial reaction model between the carrier adjacent to the interface and the 1:1 copper chelate complex adsorbed at the interface. Furthermore, the change of extent of copper extracted with time was simulated by use of the constants of adsorption equilibrium and the interfacial reaction rate obtained from the analysis.
To investigate the effect of anionic surfactants on the extraction rate of copper with a liquid surfactant membrane containing LIX65N and a nonionic surfactant, three kinds of oil-soluble anionic surfactants were prepared: phosphoric, sulfonic and carboxylic acid surfactants having two oleyl chains. Phosphoric and sulfonic acid surfactants accelerated the extraction rate in a stirred tank where the interfacial reaction between copper and the extractant was the rate-determining step, but the carboxylic acid surfactant did not show the acceleration effect. It is considered that the acceleration effect is caused by an electrostatic interaction between copper ion and the anionic surfactants at the interface.
Plant hairy roots from horseradish, carrots, etc. transformed by the soil bacterium Agrobacterium rhizogenes showed active growth in the phytohormone-free Murashige–Skoog medium with sucrose as a carbon source. Reticulate polyurethane foam was an appropriate support for the immobilization of hairy root cells. The hairy roots of 11 kg-dry cells·m–3 (110 kg-fresh cells·m–3) were obtained in a 31-d culture in an air-lift column bioreactor with immobilized horseradish cells. A linear relationship was observed between the dry cell mass grown and medium conductivity decrease for hairy root cultures. Thus, it was possible to monitor cell mass concentration during the hairy root culture by on-line measurement of conductivity in the bioreactor system.
In viable animal cells, fluorescein diacetate is hydrolyzed to fluorescein (a fluorescent compound) which is retained in the cells. Fluorescein was effectively extracted from the cells by treatment with hypotonic phosphate buffer (1 mmol·dm–3, pH 7.4) and the extract showed a fluorescent peak at excitation and emission wavelengths of 496.5 and 515 nm, respectively. A linear relationship was confirmed between the viable cell concentrations based on fluorometry and microscopy. Animal cell growth could be successfully monitored based on fluorometry for suspension and microcarrier cultures of animal cells.