The hydrodynamic behavior of binary solids circulating fluidized beds was examined in terms of axial distributions of apparent solid holdup as well as of fine and coarse solid holdups. Experiments were carried out in two circulating fluidized beds of 3 m in height and 97 mm and 150 mm in diameter, using FCC catalysts with a mean diameter of 69.7 μm as the fine particles and 321-μm silica sand and 633-μm activated alumna as coarse particles. The influences of gas velocity, solids circulation rate, loading ratio of coarse particles and bed diameter on the axial distributions of apparent holdup and of fine and coarse particles holdups were investigated. Comparisons were made of the axial distributions of solids holdups both in the presence and absence of coarse particles. It was found that the addition of coarse (or dense) particles results in a significant variation in both the apparent and the fine particles holdups. In addition, the nonuniformity of the axial solid holdup distribution was found to vary with increasing loading ratio of coarse particles.

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In a process of flue gas desulfurization by use of dry limestone, the smaller the particle size of the limestone, the higher is the SO₂ conversion expected. In a powder-particle fluidized bed (PPFB) fine particles less than 40 μm in diameter fed into the bed are fluidized with coarse particles. But only the fine particles are entrained from the bed, and their residence time in the bed is remarkably long. In this study, PPFB, was applied to a desulfurization process. SO₂ conversion from a model gas was investigated with a laboratory-scale PPFB, and the effect of the operating conditions on SO₂ conversion was examined. SO₂ conversion was affected by reaction temperature, Ca/S ratio, particle size of limestone and static bed height. When the temperature was about 1073 K, SO₂ conversion reached its maximum. 100% of SO₂ conversion was obtained at Ca/S = 3 in the temperature range between 1073 K and 1223 K.

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The effect of water content in a dolomite sample on the grinclability and change in the crystalline structure during grinding were studied by using a planetary ball mill. The size reduction of the dolomite sample proceeds in the presence of water more than 10 mass%, while, below this content the specific surface area of ground product indicates a downward trend in prolonged grinding after showing an increase at the initial stage. The phase transformation from calcite to aragonite takes place during the grinding of dolomite samples containing over 10 mass% of water, while dry grinding of the sample only decreases the peak intensity of the original X-ray diffraction patterns. DTA reveals that the temperature at decomposition of magnesium carbonate shifts towards the lower-temperature side with the progress of grinding.

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The heterogeneous phase transition of four organic vapors and water vapor on a cold substrate was studied by either slowly cooling a substrate or by accumulating vapor under reduced-pressure conditions. At low vapor pressures a solid condensate formed directly on the substrate. At higher vapor pressures, liquid condensate usually appeared first, followed either by1) subsequent formation of solid crystals independently from the liquid phase (subsequent solidification) or 2) rapid freezing of the liquid condensate (subsequent freezing). Subsequent freezing occurred in a wider temperature range than did the subsequent solidification. A new phase transition model is proposed, based on the equilibrium phase diagram and the measured relationship between critical vapor pressure and temperature for solid condensate formation. The proposed model explains the experimental results quite well. Liquid condensate always forms at critical supersaturation ratios close to unity. The critical vapor pressure and temperature at the boundary separating the formation of the solid condensate from formation of the liquid condensate, as determined by the proposed model, agrees well with the experimentally determined values.

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Air-impregnated alginate and ovalbumin gels were prepared as model systems for porous foods, and their effective thermal conductivity was measured at 30–70°C by a steady-state method. The effective thermal conductivity of the air-impregnated gels increased with temperature more greatly than that of gels containing no air bubbles. For effective thermal conductivity of air-impregnated gels, a theoretical model which included latent heat transport accompanied by water vapor diffusion in addition to heat conduction was presented and was compared with experimental data. The model gave a good approximation to the experimental data up to 50°C. At higher temperature, however, the model overestimated the effective thermal conductivity, especially for gels of high porosity.

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A novel combustor based on controlled chemical-looping reactions without flame differs from the traditional combustor, in which the fuel is in direct contact with air. It allows CO₂ to be easily recovered and promises advanced-level thermal efficiency for power generation. Promising results of laboratory experiments with the novel combustor are presented here. We found that NiO particles mixed with YSZ (yttria-stabilized zirconia) have very good properties with respect to oxidation rate, conversion, and physical strength. Especially, the rate of oxidation of Ni particles is increased significantly. The effects of YSZ content in the particle, the reaction temperature, the particle size, and the water vapor concentration were examined by studying the kinetic behavior of reactions. These promising results revealed high potential for applying chemical-looping combustion in a power-generation plant.

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Reactive distillation for the production of methyl tert-butyl ether (MTBE) from methanol (MeOH) and tert-butyl alcohol (TBA) using two types of catalysts, ion exchange resin and heteropoly acid (HPA), has been studied. The reaction was performed in the liquid phase and at the boiling point of the reactant mixture under atmospheric pressure. The reactive distillation was examined with and without pervaporation. An azeotropic mixture of XTBE and MeOH was obtained as a top product. HPA showed higher selectivity than did ion exchange resin. It was found that the pervaporation might be effective in removing water.

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An improved basket reactor, equipped with a specially designed catalyst basket assembly to determine the exact starting time of reaction in batchwise experiments, was developed. The reactor was proved to be useful in experiments even under high temperature and pressure. Using this reactor, kinetic studies of liquid-phase hydrogenation of 1-methylnaphthalene were carried out as a model reaction of regeneration of hydrogen donor solvent for coal liquefaction and hydrotreating of polyaromatic sources of gas oil, in the range of 583–643 K temperature and 3.1–7.7 MPa hydrogen partial pressure over a commercial Co-Mo/γ-Al₂O₃ catalyst. To establish kinetic equations, the reaction equilibrium for conversion of 1-methylnaphthalene to methyltetralins was measured. Langmuir-Hinshelwood type kinetic equations, based on surface reaction between dual adsorption sites of hydrogen and reactants, fairly represented the effects of temperature and hydrogen partial pressure on the yields.

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Micellar-enhanced ultrafiltration has been carried out to investigate the separation of phenol from an aqueous stream via hollow fiber membranes. First, phenol is solubilized into the micelles of cationic surfactant such as hexadecyltrimethylammonium chloride (CTAC) and hexadecylpyridinium chloride (CPC), and then the micellar solution is treated continuously through an ultrafiltration membrane module. In the present study we examine the effects of retentate concentration, molecular weight cut-offs, molar ratios of surfactant to phenol and other operating conditions on the rejection efficiency. The results show that the concentration of phenol in the permeate rapidly decreases as the surfactant aggregates to form micelles beyond its critical micelle concentration. Further, the rejection of phenol and surfactant by the membrane is enhanced when the operating condition is favorable to formation of a gel layer at the surface of the membrane which provides the presieving effect. Formation of a gel layer becomes pronounced when either the flux ratio of permeate to retentate or the micelle concentration in the feed increases.

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Solute permeability and reflection coefficients (σ) through hollow-fiber membranes were measured for cellulose and poly(methyl metharrylate) (PMMA) membranes. The dialysis apparatus used was a U-type hollow fiber unit which was loosely bundled and set in a perfectly mixed reservoir with dialyzate flowing perpendicularly to the hollow fibers. Mass transfer resistance across the boundary layer outside the fibers was small at low flow velocity, so solute permeability could be measured accurately. The mass transfer correlation obtained was

Sh = 0.38Re_out^0.72Sc^1/3

Ultrafiltration experiments were performed for the case of flow within the fibers, in order to determine actual rejections and σ values. The relationship between σ and the molecular weights of polyethylene glycols (PEGs) in the cellulose membrane approached that of inulin and other solutes when the amount of hydrated molecules of water to PEG units was taken into account. Negative σ values were observed in PMMA membrane for PEGs #1000–#6000.

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Focusing on CO₂ fixation and α-linolenic acid (ALA) production, photoautotrophic cultivation of the hot-spring alga Cyanidium caldarium was investigated using Allen’s medium under a 5% CO₂-enriched atmosphere. Although the growth rate was maximum at ca. 40°C, the optimum cultivation conditions (temperature, H⁺ concentration in the medium and light intensity) for ALA production were found to be 30°C, pH 2.0–4.0 and ca. 10,000 lux respectively. Simulation of a chemostat cultivation at these optimum conditions showed that the rates of CO₂ fixation and of ALA production could reach 0.75 kg- CO₂/(kg-cells·d) and 5.44 g-ALA/(kg-cells·d), respectively, in the exponential phase. This rate of CO₂ fixation corresponded to 0.030 kg-CO₂/(m³·h) at a cell concentration of 0.96 kg/m³. This activity of C. caldarium for CO₂ fixation was comparable to that of blue-green algae and was 10 to 100 times greater than that of green plants. Thus, C. caldarium was shown to be useful for the fixation of CO₂.

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The restricted umbrella sampling method proposed by Shing and Gubbins was applied to calculate the solubilities of hexamethylbenzene and those of phenanthrene in supercritical carbon dioxide. It was also used to calculate solubility enhancements of phenanthrene by the addition of octane in supercritical carbon dioxide. The Lennard–Jones (12–6) potential was used as the intermolecular potential and the Lorentz–Berthelot mixing rule was adopted for unlike molecular pairs. The solubilities of phenanthrene and those of hexamethylbenzene in supercritical carbon dioxide were calculated quantitatively by introducing only a binary interaction parameter between unlike molecules. Furthermore, the entrainer effects calculated by the Monte Carlo simulation show good agreement with the experimental data.

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The liquid surfactant membrane has advantages superior to those of other types of liquid membranes, but its biggest bottleneck lies in the demulsification process for separating the stripping solution from the organic phase containing surfactant and carrier. This paper is concerned with the electrostatic coalescence of the W/O emulsion stabilized with surfactant in an a.c. high-voltage current applied between two insulated flat electrodes. Effects of the dispersed phase hold-up, the applied voltage and the frequency on the phase separation rate were studied.
The separation rate was larger for lower initial hold-up of the dispersed phase. When the initial hold-up was less than 40%, the coagulation stage preceded the coalescence stage and the separation rate decreased. The separation rate increased approximately with the second order of the applied voltage. It also increased with frequency and tended to become constant at frequencies in the range of 1000 to 2000 Hz. The water content of the separated oil phase decreased with increase in frequency.

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Numerical computations were carried out for liquid encapsulated Czochralski bulk flow for the modeled fluid of glycerol (model for melt) and silicon oil (model for encapsulated fluid) which were employed for temperature and flow visualization. Axi-symmetric cylindrical model equations were derived and numerically solved for stable cyclic solutions to be consistent with the flow visualization experiments to confirm the present computational system. Afterward, actual physical properties for GaAs and B₂O₃ were employed for more realistic numerical simulation and oscillatory convection was found for Gr_m/Re_m² values less than 10.

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The T–x–y data for binary mixtures composed of methyl acetate + (1-chloropentane or 1-chlorohexane) and ethyl acetate + (1-chloropentane or 1-chlorohexane) have been measured ebulliometrically at 101.32 kPa using a dynamic method. In thermodynamic calculations using these data, the vapor phase was considered to be non-ideal, and the four systems studied exhibit positive deviations from Raoult’s law. The activity coefficients and vapor phase compositions have been compared with those predicted by using UNIFAC and ASOG models.

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In protein ultratiltration, solution environment factors such as pH and solvent density are important in controlling the filtration flux. Also, the properties of the filter cake of macromolecular solutes formed on the membrane surface play a vital role in determining the filtration flux in ultratiltration. On the basis of the sedimentation velocity technique and the high-speed sedimentation equilibrium technique using an analytical ultracentrifuge, the influence of the protein solution pH on the time variation of the filtration flux in unstirred dead-end ultrafiltration was accurately described. It was clearly demonstrated that the low filtration flux around the isoelectric point is mainly due to the build-up of compact filter cake, which causes a large hydraulic flow resistance. Furthermore, it was shown that the solvent density ρ has a large effect on the dynamically balanced filtration rate in upward ultrafiltration just as it does on the sedimentation coefficient in ultracentrifugation.

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A scheduling method that incorporates the design of multipurpose batch plants is developed. The scheduling consists of two interactive sub-problems: production scheduling and constrained resources scheduling, and on-site work is one of the typical constrained resources. In the design of these plants, the optimal schedule should be made within a short time, and cyclic scheduling according to the cycle production is appropriate. An IP (Integer Programming) model is suitable for such short-term scheduling, and the scheduling method is developed on the basis of the previous IP model for production scheduling. To make the optimal schedule, the allocation and sequence of tasks of on-site work should be optimized in relation with the production scheduling. In this study, the required properties of the on-site work scheduling in design is considered, and this sub-problem is converted into an assignment problem. The on-site work is defined in linear constraints with integer variables describing the task assignments. Moreover, the on-site work is newly defined in the production scheduling, and these definitions are related by the introduced integer variables. Finally, the effectiveness of the developed scheduling method is demonstrated by an example problem.

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Studies have been made of mass-transfer characteristics of a novel operation mode of the liquid membrane. In this operation, feed and recovery sides were partitioned by a hydrophobic porous membrane, and a membrane solution was forced to flow with a feed or recovery solution within each flow channel. The membrane solution moves through the pores of the porous membrane freely, and the solute extracted within the feed-side channel was transferred across the porous partition membrane by the bulk motion of the membrane solution as well as by diffusion, i.e., the organic phase acts as a bulk liquid membrane. By decreasing the depth of flow channels, a large specific interfacial area can be obtained, which becomes an advantage in practical use. It was shown that this operation mode has possibilities of fast separation and concentration in comparison with operation in a supported liquid membrane. To evaluate the contribution of bulk motion of the membrane solution across the porous membrane, a transfer coefficient of membrane based on a model for the present mode is introduced and correlated with organic phase velocity. Experimental results for circulating membrane solution between the feed-side and the recovery-side channels suggest that efficient concentration of solute can be achieved in this operation mode.

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A mass transfer model for deionization by mixed cation and anion exchange resins is presented in this paper. This model is based on ion exchange and neutralization reactions and is composed by considering ionic valence, diffusion resistances in both resin and liquid phases and mixed volume fraction of the resins. A simplified form of the above model is also shown for deionization by the mixed resin as adsorption of a salt.
The calculated results for a batch system were studied and it was found that: 1) pH value of the solution showed complicated behavior in the course of deionization, even though equal-normality mixed resins were used. Its behavior was greatly affected by the mixed-resin volume fraction and the initial concentration of a salt; 2) both strict and simplified models were compared, and it was found that the neutralization reaction has a large effect on the deionization rate.

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It is attempted to make an advanced model for the flow of water without solid particles in a hollow-fiber membrane module for plasma separation including the tubular shell part, considering that part is similar to a packed column. On the basis of the model, distribution of pressure and flow rate in hollow-fibers and in the tubular shell are estimated. The availability of the model is confirmed by comparing the estimated distribution with results of measurement of the pressure loss in the shell and that in a hollow-fiber. Furthermore, the probability of reflux is confirmed and the position of reflux is estimated based on the model.

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The sorption equilibria of glutamic acid (Glu), methionine (Met), and lysine (Lys) on a cation-exchange membrane, SELEMION-CMV, and an anion-exchange membrane, SELEMION-AMV, have been investigated over a wide range of pH. The cation-exchange membrane showed increasing selectivity from solutions containing HCl in the order Glu, Lys, and Met, but showed only very slight sorption of Met and Glu from NaCl solutions. With anion-exchange membrane, the sorption from NaCl solution increased in the order Lys, Met, and Glu as pH increased from 8 to 11. The dependence of amino acid ionic form on pH provides a qualitative explanation of those results. A quantitative selectivity coefficient model was then determined, based on the solution and ion-exchange equilibria for each amino acid, and was found to simulate experimental results quite successfully, thereby proving that amino acids are stoichiornetrically sorbed by ion-exchange membranes.

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In a photo-autotrophic microalgae culture, a linear functional relation between a specific growth rate and a light energy absorption rate has been adopted. However, this relation does not always hold for a wide range of variation of a specific light-absorption rate. Therefore, in this paper we have proposed a new model for growth kinetics as follows:

μ = k(ξ – a)^(1/n)

k = α exp(–βI_o)

where μ is a specific growth rate, ξ is a specific light absorption rate and I_o is an incident light intensity, and a, n, α, β are constants. The model was verified by experimental data obtained from a Chlorella ellipsoidea photo-aututrophic culture.

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The extraction of Chromobacterium viscosum lipase and α-chymotrypsin from aqueous solution, and hydrolysis catalyzed by these enzymes were carried out in AOT/Span 60 and in AOT/Tween 85 mixed reverse micellar systems. Span 60 was likely to be solubilized in the water pool of AOT micelles without any change in micellar shape, while Tween 85 brought about an elongation of the micellar shape. The extracted fraction of the α-chymotrypsin at pH 6 was decreased by the addition of Span 60 or Tween 85, owing to the dilution of negative charge density of micelles. However, the extracted fraction of the lipase was increased by the addition of Tween 85, which seemed to act as an affinity ligand. The activity of α-chymotrypsin was improved by the addition of Span 60 or Tween 85, which decreases the electrostatic and hydrophobic interaction with AOT molecules. The activity of the lipase was significantly improved by the addition of Tween 85, especially in the higher range of water content, and the bell-shaped dependence of the activity on the water content disappeared. The lipase activity was maximum when the molar ratio of AOT to Tween 85 was 3:2–4:1.

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Solubilization of β-galactosidase into AOT/isooctane reverse micelles was achieved by the injection method while holding its activity. The observed activity in reverse micelles was influenced by the water content Wo. Two peaks in the initial activity were observed, at Wo = 10 and 45. Enzyme stability increased with Wo value. The activity and the stability of β-galactosidase in reverse micelles are interpreted by the solubilization mechanism of proteins, considering micelle size distribution. Selective back-extraction of solubilized β-galactosidase from the micellar phase into a new aqueous phase was achieved by using 0.1 M KCl aqueous solution with high activity yield. The separation of β-galactosidase from E. coli cells was also successfully carried out by the present method where the solubilization of the crude extracts into reverse micelles by the injection method was followed by the next selective back-extraction from the reverse micelles. Enzyme was purified four-fold over the initial crude extract with high activity yield.

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