Ovalbumin solution, which is known to form a gel layer on membrane surfaces, was filtrated in a cross-flow mode using ceramic microfiltration membranes. The influences of pH and ionic strength of the ovalbumin solution on the properties of the gel layer and membrane permeability were studied. At a pH near the isoelectric point of the ovalbumin solution, both the permeate flux and ovalbumin rejection showed the lowest value. The cohesion force acting among ovalbumin molecules became strongest because the electrostatic repulsion force among the molecules was weakened, and then the gel layer was tightly adsorbed onto the membrane surface. Therefore, the membrane permeate flux obtained at the pH of the isoelectric point was smaller than that obtained at the other pH. The ovalbumin rejection increased at the other pH, except for the isoelectric point, because of the electrostatic repulsion of the ovalbumin gel layer formed on the membrane surface. The influence of electric charge was also recognized in the case of the filtration of sodium L-glutamate solution using the ovalbumin gel layer. When the ovalbumin solution was filtered with a high ionic strength, the permeate flux and the ovalbumin rejection were almost constant, independent of the solution pH. The molecular weight cut-off values of the ovalbumin gel layer were about 200,000–300,000 as self-rejecting dynamic membranes. The specific resistance of the ovalbumin gel layer obtained in dead-end filtration increased in pH near the isoelectric point and with increasing ionic strength of the feed solution. This tendency of the specific resistances was in good agreement with the behavior of the permeate flux of the ovalbumin solution.
In this work the attention was focused on the use of SorbalitTM, a mixture of impregnated activated carbon and Ca(OH)2, for adsorption of mercuric chloride from flue gas of municipal solid waste incinerators. The study was performed in an apparatus at laboratory scale in which simulated flue gas at a given temperature and HgCl2 concentration flowed through a fixed bed of adsorbent material. The experimental results showed that the adsorbate loading at saturation depends on temperature in an unusual fashion: the saturation adsorbate loading decreases with T for 70° ≤ T ≤ 150°C, but then increases for 150° ≤ T ≤ 250°C. This result was interpreted by assuming that for T ≤ 150°C a process of physical adsorption takes place, while for T ≥ 150°C the results fall in a “transition zone” between physical adsorption and chemical adsorption. The Langmuir parameters were evaluated for the “low” temperature results, and the differential equations modeling the adsorption phenomenon were integrated, leading to the evaluation of a kinetic parameter describing the breakthrough curves experimentally determined.
The ejection rate of overflow generated by air-lift pump at reduced pressure has been studied under various operating conditions, namely, top pressure, gas flow rate, nozzle submergence, riser diameter and lift ratio. Slow motion moveis were taken to decide the levels of the experimental parameters. The decrease of top pressure and the incerase of nozzle submergence have the same effect as the increase of gas flow rate on the ejection rate of overflow. The ejection rate of overflow increased as top pressure decreased, nozzle submergence increased, gas flow rate increased, lift ratio decreased and/or riser diameter decreased. The churn-turbulent flow is predominant on flow regime.
In a microalgal culture under illuminated conditions, the production rate of cells depends on the distribution of light intensity and growth rate of cells. The relationship between fight transmittance through culture liquid and cell concentration was estimated from experimental data using a green alga, Chlorella sp. UK001. In batch cultures of this alga, the optimum conditions for the growth were temperature of 30°C and pH of 5.7. Under these conditions, the value of specific growth rate of the alga increased with the increase in incident light intensity (I0) up to 130 W m–2, and it decreased when I0 was over 130 W m–2. Continuous cultures of the alga in a rectangular reactor were performed at I0 = 55.8 and 71.4 W m–2. The dilution rates maximizing the production rate of cells existed for the respective values of I0. The production rates of cells in these cultures were calculated considering the distribution of light intensity in the reactor. The calculated results could successfully describe the experimental data at different dilution rates, and when I0 = 55.8 and 71.4 W m–2, the production rates of cells indicated maxima at dilution rates of 0.0218 and 0.0220 h–1, respectively.
Forced convection is sometimes employed in the cooling of electronic equipment operating at high heat dissipation rates. The heated electronic components are usually arranged evenly on the vertical circuit boards. To analyze the heat transfer of such electronic equipment, the forced convective heat transfer between two vertical parallel electronic circuit boards (ECBs) was investigated. The local heat transfer coefficient from the board was affected by the Reynolds number, the distance between the boards, and the distance from the channel entrance. Two empirical equations for calculating local Nusselt numbers for the heat transfer in a channel between vertical electronic boards were obtained. One was for an ECB surface with components, another was for its rear surface without components, and the range of Reynolds numbers was from 1500 to 9000.
A heat transfer analysis of a convective air cooled electronic circuit board (ECB) in a vertical electronic circuit boards channel was carried out. To validate the model and the algorithms used in the computations, experimental tests were performed on dummy ECBs. Temperature distribution on an axial ECB and axial temperature distribution of air were measured with thermocouples. The temperature measurements were in good agreement with the computed value. As a working example, the temperature distributions of air flow and the vertical circuit boards with evenly arranged electronic components cooled by forced convective heat transfer were simulated, and typical results were reported and discussed. It is clear that, such a computer program for the thermal analysis of electronic circuit boards is effective and enables the user to choose any arbitrary arrangement of components on the ECB as well as different values of all design parameters. The program can serve as a powerful tool either for checking the performance of an existing ECB or for sensitivity analysis in designing the packaging of new electronic circuit boards.
Filtration behaviors in the unsteady-state phase of crossflow filtration of broths of Bacillus subtilis, Escherichia coli, and Lactobacillus delbrueckii, which are rod-shaped, were studied from the viewpoint of the changes in the specific resistance and in the structure of the microbial cake formed on the membrane surface. The permeation flux followed the cake filtration law at the initial stage of the crossflow filtration of the broths of B. subtilis and E. coli, where the cells deposited randomly on the membrane. In the case of the crossflow filtration of a L. delbrueckii broth, the period of random deposition was shorter. The specific resistance for the cake formed at the initial stage agreed with that measured in dead-end filtration. Then, the specific resistance started to increase in comparison with that measured in dead-end filtration due to shear-induced arrangement of the cells. The extent of the increase in specific resistance became higher and the time taken to start the cell arrangement became shorter with increasing circulation flow rate. The increase in specific resistance due to the shear-induced arrangement was more appreciable in the crossflow filtration of the broth of L. delbrueckii than that of B. subtilis and E. coli. The average permeation flux was increased considerably by applying periodical backwashing with appropriate time intervals. The permeation flux was well predicted by the cake filtration law, since the cells deposited in a way similar to that for dead-end filtration during a sufficiently short period of crossflow filtration in a backwashing mode.
Selective separation of concanavalin A (Con A) using alkylglucoside (AGn) as an affinity ligand was achieved by two different methods in reverse micellar systems. The first method used the sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/butanol/iso-octane system, in which Con A was extracted effectively when AGn was added to the system but was not extracted at all without AGn. Selective extraction was attained in three steps. In the first step, reverse micelles composed of AOT and alcohol without AGn were used. Proteins extractable to these reverse micelles were removed from the aqueous phase. In the second extraction step, Con A was selectively extracted to the reverse micellar phase with AGn. Backward extraction was successfully performed using buffer solutions containing glucose. The problem of this method was the precipitation of Con A at the liquid/liquid interface presumably due to the denaturation of Con A by AOT. The second method used the reverse micellar system composed of tetra-oxyethylenedecylether. This reverse micellar system had no ability to extract water-soluble proteins without an affinity ligand, whereas Con A could be extracted selectively with high overall efficiency when AGn was added to the system. Rapid backward extraction was performed using a buffer solution containing glucose or methyl-α-glucoside by adding ethanol or butanol.
A new identification method using the second order plus time delay model for the automatic tuning of the PID controller and a simple and explicit tuning method are proposed. We present a relay feedback test combined with a P controller to identify the process using the second order plus time delay model. Thus, the difficulty to determine the initial proportional gain is overcome. Since the proposed identification method uses the second order plus time delay model to identify the prodess, it can incorporate more various processes such as underdamped and high order processes than the identification method using the first order plus time delay model. In addition, a simple and explicit tuning relation for the second order plus time delay model is proposed in this paper. This tuning relation shows almost the same performance as the optimal tuning parameters. The proposed method needs no numerical technique and shows good performances in both simulation and experimental study.
The characteristics of a new type of batch distillation column called the “complex batch distillation column” are examined. In the complex column, the feed is supplied to the middle of the column, and the light and heavy components are withdrawn from the top and the bottom at the same time. The liquid on the feed tray is recycled to the feed tank so as to accumulate the intermediate component in the tank. The complex column is convenient for removing light and heavy impurities from raw materials since the impurities can be withdrawn simultaneously from the top and the bottom. The complex column is similar to a combined system of ordinary and stripping batch distillation columns where the condenser of the stripping column is heat-integrated with the reboiler of the ordinary column. Therefore, it can be expected that separation can be executed effectively compared with the ordinary column. In this paper, by analyzing the differences between ordinary and stripping batch distillation columns, the conditions at which the complex column works effectively compared with an ordinary batch distillation column, are clarified.
In this study, we investigated the kinetics of the substitution reaction of hexachlorocyclotriphosphazene, (NPCl2)3, with phenol to synthesize the partially substituted (phenoxy) chlorocyclotriphosphazenes, N3P3Cl6-i(OC6H5)i, i = 1–6 by phase-transfer catalysis (PTC) in an organic phase/alkaline solution. A mathematical model was developed for solving the kinetics parameters for a longer series reaction. The kinetic data of this reaction closely corresponded to a second-order equation by a combined model proposed. The reaction system was controlled by both chemical kinetics and mass transfer effects. Also, the technique of phase-transfer catalysis significantly enhanced the reaction rate. In this reaction, the steric hindrance effect plays a crucial role.
The recovering rate of CH4 from CH4-hydrate soaked in liquid CO2 was measured at 274–277 K and 4–5 MPa. The fugacity of CH4 in liquid CO2 was kept below its initial hydrate forming fugacity, while that of CO2 was much higher than the initial forming fugacity of CO2-hydrate. The CH4-recovering rate in liquid CO2 was much lower than that in gaseous N2 which dose not make hydrate under the conditions. The composition of the hydrate measured at the end of the experiment indicated that the formation of CO2-hydrate consumed all the H2O molecules which had been encaging the recovered CH4. The observed phenomena was described by a mathematical model based on nonequilibrium thermodynamics for use in feasibility studies.
The effects of chemical composition of alginate (i.e., M/ G ratio) and gelling agents on the effective diffusivity DE of oxygen, nitrate and glucose were investigated for preparation of an immobilization matrix to entrap denitrifier. The ratio of DE of oxygen to DW in water for Ba-alginate gel was the lowest among Ca-, Sr- and Ba-alginate gels, and the value was only about one half. With increasing M/G ratios above about 0.5, the value of DE of nitrate or glucose of alginate gels tended to decrease. Ba-alginate gel with M/G ratios below 0.5 was found to be suitable for immobilization of denitrifier. The effects of bulk dissolved oxygen (DO) concentration on the denitrification activity of the immobilized denitrifier was investigated. At DO concentrations up to about 2.5 mg/l, the immobilized denitrifier in Ba-alginate gel had almost the same activity to that under anoxic conditions. In addition, denitrification activity under oxic conditions was highest at a cell loading of about 3 g/l, and increased with increasing bead radius.