A preparative separation method with dynamic equilibrium gradient is proposed. The equilibrium gradient is generated by counteracting chromatographic and electrophoretic forces in the column. The electrophoretic force has a gradient along the column due to the pH gradient induced by applied voltage. Protein continuously introduced in the column is separated and concentrated at an equilibrium point. Experiments were carried out with human hemoglobin, which was purified and concentrated in the column. A stable accumulation zone was formed in the column. A theoretical model was developed to simulate the concentration profile of the protein in the column. An equation to evaluate the position of the accumulation zone was derived. The method was found to be a promising approach to preparative separation.
Experimental approaches were taken to examine heat and mass transfer in evaporation of the methanol–2-propanol and the methanol–water systems into dry air by a cocurrent vertical flat-plate wetted-wall column over wide ranges of gas and liquid flow rates and liquid concentrations. The observed gas-phase sensible heat fluxes are compared with a theoretical analysis of heat transfer in a laminar boundary layer under high mass flux with finite tangential surface velocity. The effect of evaporative mass injection, tangential surface velocity and interactions between diffusion fluxes on the observed gas-phase diffusion fluxes are discussed. The observed diffusion fluxes are compared with a theoretical analysis of ternary mass transfer in a laminar boundary layer by taking into account the effect of interactions between diffusion fluxes under high mass flux with finite tangential surface velocity.
The effect of vibration on forced convection mass transfer from spheres, discs and cylinders was investigated experimentally by use of the electrochemical method. It is found that the effect of vibration on the mass transfer rate is well correlated in terms of the energy dissipation ratio calculated from the fluid drag acting on the vibrating bodies.
Solid-phase mixing time was measured in a 0.2 m i.d. three-phase sparged reactor using a radioactive tracer technique. Air and water formed the gas and liquid phases. Spherical glass beads with an average size of 58, 92.5, 250, 600, 900, 1300 and 2100 microns were used as the solid phase. Glass particles were coated with radioactive gold and used as a tracer. The superficial gas velocity was varied in the range of 0.07–0.366 m/s and the solid loading was varied in the range of 0–10 vol.%. The effect of physical properties such as surface tension, liquid viscosity and the presence of electrolyte on solid phase mixing was investigated. A mathematical model has been developed which successfully correlates data on mixing time.
Particle holdup and axial pressure drop in a fast fluidized bed were measured. In a fast fluidized bed, there is a dense region of particles in the lower part of the bed and a dilute region of particles in the upper part of the bed. The height of the inflection point between the dense region of particles and the dilute region of particles was determined by an axial pressure drop profile. Its location was affected by the superficial gas velocity, the circulation rate of particles and the particle Reynolds number. An empirical equation for the location of the inflection point was obtained. Particle holdup in a fast fluidized bed was affected by superficial gas velocity, circulation rate of particles, particle Reynolds number, tube diameter, location of the inflection point and axial distance from the distributor. An empirical equation for particle holdup in a fast fluidized bed was obtained.
Residence time distributions of gas phase in bubble columns were obtained by excluding end effects from observed responses to pulse inputs of tracer, using Fourier transforms. Based on the behavior of the residence time distributions, a gas-phase mixing model was proposed in which bubble swarm was assumed to be composed of two bubble groups, one in the core (or central) region and the other in the annular (or peripheral) region of the column. As a result, it was found that about 80% of all the bubbles are rising in the core region and that gas-phase mixing is more intensive in the core region than in the annular region. Axial dispersion coefficients in each bubble group were correlated empirically.
The kinetics of the reduction of NiO pellet by H2–CO mixture is investigated in the temperature range from 873 to 1073 K where carbon deposition takes place simultaneously. To determine the respective rates of NiO reduction and carbon deposition, the weight change of the pellet and concentrations of CO2, H2O and CH4 in the exit gas were measured as a function of time. The reduction rate of NiO increases with increasing hydrogen content of the reducing gas. Carbon deposition occurs at the highest rate for a gas composition of 25% H2 and 75% CO. The reduction rate increases and the rate of carbon deposition decreases with increasing temperature. A reaction model in which the reduction, carbon deposition, methanation and the water gas shift reaction are taken into consideration is proposed. In the model it is assumed that the reduction proceeds according to the unreacted shrinking-core model and that the other reactions take place in the Ni layer. The experimental results agree closely with those calculated by using kinetic parameters obtained in previous studies.
Tubular fouling by coke deposition on its inner wall has restricted the development of a high-conversion furnace for residual oil. Such a furnace is desirable from the viewpoint of economics and operability. The proposed tubular fouling model well represents the complex phenomena of tubular fouling of a residue conversion furnace by modeling a sedimentation of coke precursor and its reaction into coking material in and out the boundary film. The model was developed from the experimental data of a bench unit which was specially equipped to generate a high linear velocity and conversion at the same time, and was verified by data collected in a commercial unit.
The solubilities of m-xylene and nonane vapors in polystyrene and of ethylbenzene and nonane vapors in polybutadiene were measured with a sorption apparatus in the temperature range from 130 to 175°C and 80 to 130°C, respectively. A new expression for the free-volume term derived previously was coupled with UNIFAC to predict activities of hydrocarbons in polymer solutions. In this study, the UNIFAC-FV model has been reexamined and the parameters in the free volume term have been revised. The parameters in the UNIFAC-FV model can be calculated by the group contribution. The model was applied to predict solubilities, activities, or mass-fraction Henry constants for the systems studied here and published in the literature. From comparison of experiment with calculation it is found that the present UNIFAC-FV model can give fairly good predictions of such equilibrium properties of organic vapors in polymers on the basis of a knowledge of molecular structure alone.
To establish an evaluation system of coals for CWM, attempts were made with twenty kinds of coal from various countries and locations to study the relations of the rank of coal as bulk material to viscosity characteristics in CWM, in addition to surface-chemical properties such as water vapor adsorption and zeta potential. Various parameters of viscosity described in Fig. 2-b, such as φ0, α and φ1000, show almost the same tendency of reaching a constant level above about 85% carbon content in coal (Fig. 12 Curve a)—an outstanding feature of viscosity characteristics. The same tendencies were also observed in zeta potential, quantities of adsorption of water on coal surface, φAD, and of water occluded within aggregates of coal particles, φOC. The results on various parameters are rather scattered, and it is presumed necessary to study coal not only as bulk material but also on the basis of surface chemistry.
The kinetic mechanism was elucidated for metal extraction with hydroxyoximes. The reaction of the 1:2 metal–chelating agent complex formation determines the rate of copper extraction with the chelating agents, which are surface-active and less soluble in the aqueous phase. It is found from the results about the diluent’s effect on the rate that this complex is formed at the interface through the reactions between the adsorbed 1:1 complex and the chelating agent dissolved in the aqueous phase, and also between the adsorbed chelating agent and the 1:1 complex in the aqueous phase. The overall rate constant of this interfacial reaction can be related to the pKa value of the chelating agent. The 1:1 complex formation in the stagnant film of the aqueous phase controls the rate of copper extraction with the chelating agent, which is surface-inactive and soluble in the aqueous phase. The catalysis of α-hydroxyoxime in the copper extraction with β-hydroxyoxime is caused by the fast reaction between the 1:1 copper–β-hydroxyoxime complex adsorbed at the interface and the α-hydroxyoxime dissolved in the aqueous phase. The question of increasing the rate of extraction is examined by focusing on the physical properties, the partition coefficient of the chelating agent between the aqueous and the organic phases, and the surface activity of the chelating agent. Modification of the substitutional group in the hydroxyoximes is also examined as a means of increasing the rate.
Dynamic polyion complex membrane (PIC-DM) was formed by depositing a mixture of two oppositely charged polyions, sodium polyacrylate and polyethylene imine. The effect of composition on solute rejection by the PIC-DM formed was investigated. The rejection curve of the PIC-DM shifted to the higher-molecular weight side with increase of the charge amount of excess polyion in the mixture. The membrane structure evaluated from the solute rejection property was analyzed successfully by dual pore sizes model. The pore sizes and their number fractions were related to the ratio of charge of the polyions.
Extraction and stripping of copper with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester dissolved in n-heptane were carried out at 303 K in both a stirred transfer cell and a membrane extractor using a hollow fiber, along with a study of the interfacial adsorption equilibria of extractant and copper complex between aqueous and organic solutions. These results obtained by use of both the stirred transfer cell and the membrane extractor were explained by a diffusion model with interfacial reaction.
This paper describes the use of flexibility analysis with uncertain parameters involved in linear models. Due to the presence of various judgments of value in large-scale systems, the previous formulation developed under single-objective optimization is revised by use of the minimum aspiration level, which plays an important role in multiobjective optimization. An improved algorithm to compute the flexibility index in an iterative manner is also presented. The proposed approach is applied to a post-optimal analysis of the dynamic allocation planning of an electric power system. Such consideration is shown to be of special importance in increasing reliability at the planning stage of problem-solving in uncertain systems.
An understanding of the expansion phenomena of compressed materials is essential to improving the technique of forming by expression in ceramics industries and other processes. In this study, a slurry of Korean kaolin–Solka floc mixture was used as experimental material. The slurry was consolidated in a compression cell at constant pressure, resulting in a semisolid material with uniform void ratio. The expansion process of such a homogeneous material was investigated experimentally and theoretically under the condition in which the compression pressure was released momentarily and the material was saturated with liquid during expansion. Expansion of a homogeneous material is very similar to consolidation of a semisolid material, and can be analyzed well by use of the Terzaghi–Voigt combined model, although the expansion proceeds considerably more slowly than does consolidation under the same change of compression pressure. It is found that the ratio of secondary deformation to total deformation in expansion is much larger than that in consolidation.
The extraction rate of molybdenum with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester dissolved in n-heptane was measured at 303 K by using a membrane extractor made of a hollow fiber. The results were explained by a diffusion model with interfacial reaction, taking account of the laminar velocity distributions of the aqueous and organic solutions in the membrane extractor. In the region of high pH, the extraction rate was interpreted by taking account of both the cationic and nonionic species of molybdenum as the reacting species.