We photographed the flow patterns of a liquid film on a large rotating substrate (650 × 830 mm). Two kinds of flow patterns were observed: turbulent-transition flow and fingering flow spread out in the radial direction. To determine the factors that affect the onset point (i.e., the “onset radius”) of the fingering flow pattern, we measured the effects of viscosity of the liquid, the flow rate of the liquid from the nozzle, and the angular velocity of the substrate on the fingering flow pattern. Moreover, we devised a new equation based on dimensional analysis for predicting the onset radius of the fingering flow pattern. It was found that the predicted onset radius agreed well with the measured one; thus, it is concluded that the equation can successfully predict operating conditions of a liquid to produce a uniform film flow.
A prediction of drop coalescence behavior based on HLB (Hydrophile-Lipophile Balance) of extractants has been examined for liquid-liquid systems using industrial extractants. With a video camera, time course of coalescence was observed for droplets formed at the top of adjacent nozzles in water. Drop coalescence behavior in a liquid-liquid system has been monitored for ten systems containing industrial extractants, e.g. PC88A (2-ethylhexyl-phosphonic acid mono-2-ethylhexyl ester), D2EHPA (di(2-ethylhexyl)phosphoric acid), TBP (tri-n-butyl phosphate), MIBK (methylisobutyl ketone), LIX84I (2-hydroxy-5-nonylacetophenone oxime), LIX860IC (5-dodecylsalicylaldoxime), TOA (trioctylamine), Et2CO (diethylketone), BA (benzoylacetone) and TOPO (tri-n-octylphosphine oxide). Investigated parameters are the concentration and HLB of the extractants. Similar experiments were conducted with surfactants, SPAN systems for which HLB values are known. Average times needed for coalescence for the extractants are compared with those for the surfactants. Average times needed for coalescence decrease with the increase in the extractants concentration and HLB values of the extractants. HLB of the extractants works as one controlling factor for drop coalescence.
Methane decomposition was investigated experimentally with the capacitively coupled rf discharge. Glow discharge was generated from the low temperature capacitively coupled radio frequency (rf) plasma and was used for activating methane to make free radicals without catalysts. Operating variables in the experiment were reaction pressure, feed flow rate, and total input power. The gaseous reaction products were mainly hydrogen, ethane, propane and ethylene. When the input power increased, the density of hydrogen increased and the unsaturated groups of C2 and C3 began to form. The surface-phase polymerization reactions occurred inside the discharge tube wall. A mathematical model was derived using collision theory and diffusion effect of reaction products. From the result of the mathematical modeling, the simple mathematical relation of the methane conversion was obtained, and it was the function of specific input energy only. As the results of sensitivity analysis, the conversion of methane could be determined from the input flow rate and the electrical input power without measuring reaction temperature.
Silica-supported cobalt catalyst was studied for hydroformylation of 1-hexene. The influence of pore size of the silica support was investigated. It was found that cobalt catalyst supported on silica with appropriate pore size, about 6-10 nm, was active for the reaction with very high selectivity to oxygenates. The smaller the pore size and the higher the surface area of the silica support, the higher metal dispersion and the smaller the cobalt particle size. But, in turn, the reducibility of the supported cobalt was lower. The cobalt catalyst supported on silica with small pore size seemed to be more stable during the reaction due to the interaction between cobalt particles and the support. Although there might be homogeneous reaction on the dissolved cobalt species, the activity was mainly from the heterogeneous hydroformylation of 1-hexene.
This research has explored the effect of adding potassium to nickel supported on γ-alumina in the selective hydrogenation of 1,3-butadiene. The catalysts containing 15 wt% Ni and varying amounts of K ((K/Ni+K)atomic = 0.2-0.6) were prepared by impregnation and characterized by temperature-programmed reduction (TPR), chemisorption of H2, X-ray photoelectron spectroscopy (XPS) and X-ray absorbance near edge structure (XANES) spectroscopy. Activity and product selectivities were tested for hydrogenation of 1,3-butadiene in the temperature range of 373-673 K. The catalytic activity for the hydrogenation of 1,3-butadiene is closely related to the specific surface area of nickel metal and the crystal structure of the oxide, from which the metal was formed by reduction. The addition of potassium increased the 1-butene selectivity due to the modification of the electron density of Ni metal. It has been established that the addition of K modified the electron density of Ni metal, and this result is ascertained by a shift of the Ni binding energy in XPS measurement and Ni absorption edge in XANES spectra.
The performance of a plate fin type reactor with anodized alumina catalyst for methanol decomposition was prepared and evaluated. The measured temperature difference between heating oil and reaction gas was as small as 3°C and under, and it was smaller than the calculated value using the overall heat transfer coefficient obtained by inert gas and reaction heat. The response of reaction against the change of the gas flow rate and the change of the heating oil temperature were so quick that the gas temperature in the reactor and the gas flow rate of the outlet of the reactor became constant within 1 minute. The excellent thermal performance of the plate fin type reactor with the anodized alumina catalyst was demonstrated.
Effects of catalyst amount, membrane tube diameter, and permeation rate on porous membrane reactor performance were investigated through experiments and simulations. Porous Vycor glass membrane reactors were used in the experiment. To study the effect of catalyst amount, permeation side of a membrane reactor was filled with the same catalyst as that used in the feed side, i.e. 0.5 wt% Pt/Al2O3. The Ω, that is, a volume fraction of a catalyst in the permeation side was varied from 0% to 100%. It was observed that overall conversion increases with the Ω value. To study the effect of membrane tube diameter on the performance of a modified porous membrane reactor (MPMR), experiment and simulation using different membrane tube diameters were conducted. The results show that there are optimum membrane tube diameter to achieve maximum conversion. It also reveals that in an MPMR, membrane surface area and ratio of VT/VS are more important than membrane thickness. In order to study the effect of permeation rate, some simulations were conducted. The results show that permeation rate significantly affects the performance of porous membrane reactors. By designing appropriate parameters, it is possible to achieve high purity organic product in the permeation side of MPMR.
The objective of this work is to propose a calculational model for the surface-diffusion based Pressure Swing Adsorption. The assumptions inherent in the model are that the PSA column behaves as a series of stirred cells and then on the application of Fick's law in each cell the transfer of sorbed species in a particle is calculated; in the depressurization period the column pressure is assumed to decrease in a step-wise manner and the intraparticle species mass transfer is evaluated for each constant pressure step. The calculational results for a benzene-activated carbon system show little desorption taking place in the depressurization stage.
The extraction equilibrium of zinc in ammonium chloride medium with CYANEX 923 (phosphine oxides mixture) in Solvesso 100 has been investigated. The distribution coefficient of zinc was independent of the equilibrium pH; this independence being attributable to a solvation extraction mechanism. Slope analysis for the system using dilute zinc solution reveals that two moles of CYANEX 923 react with one mol of zinc. The stoichiometric factor of water in the extraction reaction is found to be 2, whereas experimental data indicated that two chloride ions are involved for each metal extracted. The extraction reaction is exothermic (ΔH° = −42.0 kJ mol-1).
A calculational model is proposed for the pore-diffusion based PSA. In principle the model is identical with that of the previous work on the surface-diffusion based PSA, except for the diffusion coefficient being inversely proportional to pressure. From the calculation for a methane-activated carbon system it is found that the increase in the intraparticle diffusion coefficient in the depressurization stage increases desorption, but a considerable desorption still occurs in the purge stage. In this work we also show that the maximal discharge of sorbate mass increases when the depressurization is accomplished in a short time. The process consisted of the adsorption, depressurization and purge stages is compared with the process having only the adsorption and purge stages in terms of the discharge of sorbate mass and the volume of gas leaving the column bottom.
The performance characteristics of a horizontal column equipped with 36 non-woven fabric elements that could be rotated in a direction normal to the column-sectional area were evaluated. Separation efficiency and pressure drop were measured under atmospheric pressure at total reflux, using the cyclohexane-heptane system. The stable operation range for a horizontal orientation was limited to the restricted region of the F-factor. However, separation efficiency, which was expressed in terms of HETP (height equivalent to a theoretical plate), at inclinations of 5 and 10 degrees was found to be approximately equal to that for a brush packing system with a horizontal orientation described in a previous work. Particularly, HETP values at a 5 degree inclination ranged from 0.078 to 0.16 m when the F-factor ranged from 0.07 to 0.27 m/s(kg/m3)1/2 at rotation speeds of 50 to 200 rpm. The pressure drop at inclinations of 5 and 10 degrees was larger than that for the brush packing system oriented horizontally by a factor of between 2.5 and 4.
In this work the performance of an industrial hydrogen plant is improved by multi-objective optimization using an adaptation of the nondominated sorting genetic algorithm (NSGA). The heat flux profile on the steam reformer tubes is treated as a decision variable, yielding optimal heat flux profiles for each Pareto solution. The optimization problem has been considered both as a two and three-objective problem. For a fixed feed rate of methane to the unit, simultaneous maximization of product hydrogen and export steam flow rates are considered as the two objectives. The results are better than those obtained in an earlier work by Rajesh et al. (2001), with flue gas temperature in place of the heat flux profile as a decision variable. Minimization of reformer duty was chosen to be the third objective. More useful information is available for the optimal operation by hydrogen plants from three-objective optimization, even though computational time for two and three objectives is comparable.
We have been studying the use of multiple channel electroencephalogram (EEG) data to infer a human's thinking state. As a result, we have confirmed off-line thinking state estimation to be effective, in experimental studies on simulator training during malfunctions and mathematics problem solving. In this research, we developed a real-time system that monitors a human's thinking state on the basis of off-line results. First, an artificial neural network (ANN) model and a linear regression model were compared to determine which was more appropriate for real-time use. The ANN model was adopted because of its ease of handling and higher accuracy in thinking state estimation. Then, a prototype real-time thinking state monitoring (RTSM) system with the ANN model was developed and its effectiveness was evaluated experimentally via mathematics problem solving. Finally, we discuss a conception of plant operations with RTSM.
Temperature control of a gas-phase polyolefin reactor is prone to be unstable when operating conditions and/or catalyst are changed. Using a simple first principles model, it is shown that the dominant dynamics of the open-loop can be expressed by a second order transfer function, with which the number of unstable poles varies from zero to two depending on operating conditions. The frequency domain analysis shows that these changes in the process dynamics primarily affect the process phase and cause the closed-loop instability. Thus, PID temperature controller is retuned so as to increase phase margin. A practical retuning method of a PID temperature controller, which can be performed at the onset of closed-loop instability, is developed and its effectiveness is demonstrated through simulations.
In this paper, a fault tolerant controller design method is proposed. It assures the integrity against actuator and sensor faults. While some controller design methods to assure integrity have been proposed, they assumed that the plant was stable. The proposed method in this paper assures the integrity even for unstable plants. To avoid making the controller too conservative, the possibility of the failure is limited to one actuator or one sensor. In addition to the integrity, the quadratic control performance is given to the design problem. Therefore, the fastest controller, which assures integrity, can be designed.
A chemical heat transport system using methanol decomposition and synthesis was analyzed using a process simulator. The most of the required electric energy was that of the compressor and the heat loss was caused mainly by the recovery process of the unreacted methanol from the decomposed gas. As pressure of methanol decomposition became higher, the heat loss increased, but the power of compressor was reduced and the heat transport efficiency became higher. A plate fin type reactor for methanol decomposition was prepared and tested, which showed that the conversion of methanol decomposition decreased with increasing pressure. The result of the experiment was applied to the process simulation and it was found that the heat transport efficiency scarcely changed with the pressure of the reactor in the conversion range from 40 to 80%. At higher conversion than 80%, the efficiency increased with increasing pressure, and at lower conversion than 40%, the efficiency decreased with increasing pressure.
The characteristics of calcification in biocomposite are studied by adopting the molecular-level approaches such as X-ray, NMR, Zeta potential and analysis of secondary structure of organic matrix. The compositional and conformational features of organic matrix have a great influence on the structural properties (crystallite size, surface charge, stability, binding state, and polymorphic change). On the other hand, in synthetic calcium salts, the noticeable properties are not shown. From these results, the organic matrix by controlling specific peptide blocks is another key point for understanding of manifold morphology and superior biocomposite properties.
Photosterilization of Escherichia coli cells was investigated using TiO2 particles in the presence of ferric ion as an electron acceptor. Deactivation of the cells was recognized in the reaction mixture containing ferric ion at the initial concentration of CFe3, 0 = 1, 30 and 100 × 10-3 mol/m3 and the cell deactivation did not occur in the absence of ferric ion. The apparent sterilization rate constant, k', was determined from the photoreaction tests conducted under the varied conditions of average light intensity (Iobs = 0-22 W/m2) and TiO2 concentration (CTO = 0-0.1 kg/m3). A proportional relation was obtained between the values of k' and Iobs with the slope of k'/ Iobs = 3.8 × 10-5 m2/J at CTO = 0.01 kg/m3, while the value of k'/ Iobs increased with an increase in TiO2 concentration depicting a saturated profile up to CTO = 0.1 kg/m3 at Iobs = 8, 13 and 22 W/m2. This relation between the values of k'/ Iobs and CTO could be kinetically explained by considering the photoreactions of ferric and ferrous ions and the adsorption of TiO2 particles onto E. coli cells in the reaction mixture.
In the photoautotrophic cultures of pak-bung hairy roots, the elongation rate of apical meristems (growing points, GPs) was examined using the root segments with varied lengths located under incident light intensities of I = 1.0, 3.3 and 11 W/m2. It was found that there were minimum root lengths for the elongation of GPs, the values of which were 5.0 × 10-2, 4.0 × 10-2 and 2.0 × 10-2 m at I = 1.0, 3.3 and 11 W/m2, respectively. Concerning the root segments with lengths more than these minimum values, the elongation rates of GPs increased with increasing root length and light intensity under the examined conditions. It was recognized that the addition of photosynthesis inhibitor, 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea (5.0 × 10-4 mol/m3), to the medium caused the reduction in the elongation rate of GPs and the enlargement in minimum root length for the elongation. Carbon balance in the hairy roots was calculated from the CO2 fixation rate considering the distribution of chlorophyll content along with root length and carbon amount to meet the increase in root mass through the elongation. As a result, a minimum carbon requirement was estimated to be approximately 9.4 × 10-2 mol-carbon/(h·kg-DW) for the elongation of the hairy roots irrespective of the examined culture conditions.
Nicotiana tabacum cells were immobilized in the Ca-alginate gel beads coated with the cell-free gel film and then cultivated in the flask. The effects of the coating film thickness on intraparticle cell growth and cell leakage were investigated. The beads with the coating film of a desired thickness can be prepared by controlling the amount of free Ca2+ in the core beads. The optimum thickness for preventing cell leakage without inhibiting intraparticle cell growth was determined. The productivity of the phenolics, which was one of the secondary metabolites of tobacco cells, for the immobilization cultures was compared with that for the suspension culture. The phenolics production and release to the medium seemed to be promoted by the immobilization. The immobilization culture using the coated beads was very effective in promoting the extracellular productivity of the phenolics as well as preventing cell leakage. The immobilization method was applied to the culture system using an airlift bioreactor with a draft tube. Cell leakage was completely prevented throughout the 25-day cultivation without inhibiting cell growth.
Graft copolymerization of ethyleneglycol dimethacrylate and merthacrylic acid onto cellulosic membrane was performed in the presence and absence of theophylline as the template for imprinting the copolymer molecularly. The effect of the presence of the template on the diffusive permeability of the grafted membrane was estimated by batch-wise dialysis of creatinine. The permeability of the theophylline-imprinted membrane was increased by the presence of theophylline, but was virtually unaffected by caffeine, which is an analogue of theophylline. The permeability of the non-imprinted grafted membrane decreased in the presence of theophylline or caffeine without discrimination. These results indicate that the diffusive permeability of the cellulosic membrane grafted with molecularly imprinted copolymer discriminates between the template and its analogue.