The lattice Boltzmann method for multicomponent immiscible fluid is applied to the simulations of wetting dynamics in micro channels. The wetting condition is introduced with the wetting potential which gives free energy on the wetting wall. To confirm the validity of the model, the static contact angle of a droplet onto a wetting wall is calculated and compared with Young’s equation. Then, the flow behavior near the interface in hydrophilic and hydrophobic channels is investigated and compared to the experimental results. Finally, the method is applied to the flow in micro channels with heterogeneous and hydrophilic wetting walls. It is found that the interface is advanced only by the capillary force and that different interfacial disorders appear due to the heterogeneousness of the wetting potential of the wall.
By utilizing the optical Schlieren method, Marangoni convection produced in different gas–liquid mass transfer processes was observed and recorded. Different liquid solvent mixtures were selected to investigate the flow patterns of the Marangoni convection as well as the driven mechanism of the surface tension gradient. Unordered flow patterns were observed frequently in experiments, and it is different from ordinary orderly Marangoni flow patterns such as regular roll and cellular flow patterns. Qualitative analysis of flow patterns in mass transfer was made through the Schlieren images observed, and in consequence a scaling analysis was made to discuss the relationship between the Marangoni effect and the unusual mass transfer performance. By combining the Marangoni hydraulic boundary condition with the penetration theory of mass transfer, the Marangoni number characterizing the intensity of Marangoni effect enters the conventional mass transfer correlation. The quantitative result successfully explains these different correlations between Sh and Ma obtained in mass transfer processes accompanied by the Marangoni effect.
A numerical analysis for a flow induced by the Rushton disc turbine was done by a finite element method. As flows in the vessel depend on the geometry of the impellers and the vessels, unstructured mesh was used in order to consider their geometries accurately. Moreover, elements used were a hybrid composed of tetrahedral and prism, which could be resolved boundary layer near the impeller and the shaft. Turbulence models used were k–ε and k–ω models and their governing equations were also discretized by the Characteristic-Galerkin method that includes stabilizing terms as well as the momentum equation. Calculated results were compared with the experimental result. The doubleloop pattern in the r–z cross-section could be reproduced by both turbulence models, though with stronger circulation patterns. It was found that the k–ω model could reproduce the Rankin’s vortex qualitatively, while the k–ε model could not even qualitatively.
For operability improvement in a fully thermally coupled distillation column (FTCDC), a new configuration of a separated main column system was proposed and its performance was examined with an industrial BTX fractionation process. The main column of an original FTCDC was divided into two sections, and the three sections including a prefractionator and the two main columns were operated at different pressures resulting in easy vapor transfer between the sections. The section pressure can be independently manipulated according to product volatility. In addition, the separate adjustment of liquid flow at the sections makes the control of product specification easier than that of the original FTCDC as exhibited in the simulation study of a step response test.
In order to clarify the kinetics of the synergistic extraction of gallium with the mixed extractant of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPNA) and 5-chloro-8-quinolinol, the initial extraction rate of gallium with the mixed extractant was measured using a stirred transfer cell. Based on the knowledge of the extraction mechanism of gallium with EHPNA or 5-chloro-8-quinolinol alone and the synergistic extraction equilibrium of gallium with the mixed extractant, the synergistic extraction mechanism of gallium with the mixed extractant of EHPNA and 5-chloro-8-quinolinol was clarified. The experimental data were well explained by the model presented in this article without any adjustable parameters.
A new type of filter press which is capable of dewatering slurry by filtration, squeezing and drying in a single chamber is developed. In the drying process, a filter cake is heated by steam via thin diaphragms while vacuuming the chamber. The basic performance of filter press is investigated using the slurry of magnesium carbonate which forms an incompressible filter cake. As a result, it is found that a thinner diaphragm is effective for significantly reducing the drying time, altering the temperature evolution of the cake as well as the time-change in the water content. Since new filter press utilizes a single chamber for filtration, squeezing and drying, there is no need for cake discharge into a dryer, which prevents the dust generation as well as the cake contamination.
To simulate thermal behavior in suspension polymerization, the equations of mass and energy balances based on the kinetics of the free radical polymerization were used by incorporating an overall heat transfer coefficient as a function of reaction conversion to the energy balance equation. In the experiments of batch-suspension polymerization of styrene, variations of reaction temperature during polymerization were measured for various reaction conditions of a monomer (styrene) and an initiator, ratios ranging 2–3 wt%. As the results of the simulation with the above equations, theoretical reaction temperature profiles were in good agreement with experimentally measured temperature, especially for the runaway reaction. Also, it was found that initial overall heat transfer was very sensitive to the runaway reaction during suspension polymerization of polystyrene.
This study focuses on the reaction characteristics of active hydrocarbon species mainly composed of methine radicals and active hydrogen species mainly composed of hydrogen radicals, to both of which methane as a raw material is converted by microwave irradiation to create plasma that comes into contact with the Pt/Al2O3 catalysis field. The results indicate that when 4 chemical species, i.e., active hydrocarbon species, active hydrogen species, acetylene molecules (produced by coupling of the active species) and hydrogen molecules are supplied to the solid catalyst, an increase in catalyst surface temperature facilitates apparent hydrogenation on the surface of the catalyst and thereby increases the yields of ethylene and ethane. It also appears that addition of hydrogen molecules to microwave-irradiated methane causes significant hydrogenation at 500 K or lower.
In this study, the effect of gold-added silver catalyst supported on high surface area alumina on the ethylene epoxidation activity was investigated. An addition of Au with a small amount was found to create Au–Ag bimetallic which favors the ethylene epoxidation reaction. Gold as a diluting agent on silver surface resulting in destroying multiple Ag sites which favor atomic oxygen adsorption. As a result, adding gold simply creates new adsorption sites for molecular oxygen which is responsible for the ethylene epoxidation reaction. However, at high gold loadings of Ag/Al2O3 catalyst, the formation of Au–Ag alloys was found resulting in decreasing the ethylene epoxidation activity since the Au–Ag alloy favors a complete oxidation reaction. For the ethylene epoxidation reaction, the optimum Ag to Au ratio was 13.18 wt% to 0.63 wt% in the optimum temperature range of 510–520 K.
Hydrolysis of dimethyl terephthalate (DMT) to produce terephthalic acid (TPA) was studied using a batch reactor. Zink acetate was used as a catalyst to promote the reaction rate. We found that the reaction consists of two reactions: from DMT to mono methyl terephthalate (MMT) and then MMT to TPA. The first reaction is relatively fast and irreversible while the second reaction is relatively slow and reversible. A kinetic equilibrium constant for the second reaction decreases with reaction temperature. A kinetic model consisting of the two reactions for the hydrolysis fitted well with the experimental data.
In order to examine the characteristics of a concentrator using ultrasonic atomization, an ethanol aqueous solution was used and ultrasonic atomization concentration was performed under various conditions such as different ultrasonic conditions, liquid mixing methods and vessel diameters. The flow rate of accompanied liquid had a maximum against the initial liquid height, and the optimum initial liquid height decreased with increasing ultrasonic frequency. The flow rate of accompanied alcohol increased with increasing net electric power to a transducer, but was hardly affected by the ultrasonic frequency. In the case of mechanical agitation, as the revolution speed of a stirrer was faster, the flow rate of accompanied liquid increased but the alcohol content in accompanied liquid decreased. As a result, the revolution speed had no significant influence on the flow rate of accompanied alcohol. When the gas was sparged into liquid for liquid mixing, with increasing gas velocity, both the flow rate and the alcohol content of accompanied liquid became higher with increasing gas velocity, and the flow rate of accompanied alcohol increased. From these results, the liquid mixing by the sparging gas was found to be effective for the enhancement in performance of ultrasonic concentration. At the relatively high net electric power to an ultrasonic transducer, the flow rate of accompanied liquid increased with increasing vessel diameter, but the alcohol content in accompanied liquid was hardly affected by the vessel diameter.
The control strategy of a reactive distillation column for the production of methanol and n-butyl acetate by transesterification of methyl acetate and n-butanol is investigated. The keys of controlling the column, in which the reaction is kinetically controlled, are (1) to maintain the quality of two products, (2) to maintain the correct stoichiometric balance between the feeds, (3) to account for possible changes in control objective when throughput rate changes. Proper pairing of controlled and manipulated variables chosen for these three objectives was determined by using steady-state analysis. The top temperature is controlled by manipulating a reflux flow to maintain the top product quality. The bottom product quality is maintained by a feed ratio plus bottom temperature control scheme using a control valve installed on the n-butanol feed-line as a manipulated variable. The bottom n-butanol composition is controlled by manipulating the reboiler duty to maintain stoichiometric balance. Simulations show that such a control scheme can provide adequate control of the system, while a more intuitive scheme of controlling the bottom product quality with reboiler duty and maintaining stoichiometric balance using a reactant feed flow does not work.
The production and low-temperature application of cyanobacterial carbonic anhydrase that catalyzes the reversible hydration between CO2 and HCO3– has been studied. The genes encoding carbonic anhydrase was isolated from the cyanobacterium Anabaena sp. strain PCC7120 that performs a photosynthesis in a wide range of temperature and even at around 288 K, and functionally expressed it in Escherichia coli Origami B(DE3) using an expression vector pET15b. The specific activity reached 528 WA (Wilbur–Anderson units per mg of protein) at 298 K, which was 2.5 times higher than that at 310 K. Addition of this recombinant carbonic anhydrase to the aerated culture of the cyanobacterium Synechococcus sp. strain PCC7942/1 at 293 K increased the carbon dioxide fixation rate 1.9 fold to that without its addition.
Transdermal delivery is preferable for some drugs to oral administration or intravenous injection. Macromolecules such as peptide drugs, however, little penetrate through the skin. In this paper, we have studied the effect of the molecular weight of penetrants on the diffusion across the skin, under the influence of the electric field applied. Since large molecular drugs used in this study hardly penetrated through the intact skin with the whole stratum corneum, the model drugs permeated through the viable skin without stratum corneum completely more than 100 times greater than through the intact skin. This finding implies that the stratum corneum is the major diffusional barrier. In addition, the diffusion coefficients of the compounds across viable skin were inversely proportional to the molecular weight with the exponent of 0.38 (D ∝ (M.W.)–0.38), suggesting a similar trend in the aqueous medium. The flux of vitamin B12 (M.W. = 1.4 × 103) increased appreciably during iontophoresis application, and the fluxes were proportional to the current density applied. However, FITC-Dextrans with the average molecular weight of 4.4 × 103 to 19 × 103 increased negligibly during iontophoresis, while skin pretreatment by iontophoresis appreciably increased the penetration. After the removal of the electric field, FITC-Dextrans continuously penetrated at a higher level.
Nitrogen oxides (NO + NO2) in most practical exhaust gases is mainly composed of NO. The injection of ozone, produced by dielectric barrier discharge, into the exhaust gas gives rise to rapid oxidation of NO into NO2. Once NO is converted into NO2, it can readily be reduced to N2 by a reducing agent in the next step. Sodium sulfide (Na2S) used as the reducing agent can also remove SO2 effectively, which makes it possible to treat NOx and SO2 simultaneously. The present two-step process through an ozonizing chamber and an absorber containing a reducing agent solution was able to remove about 95% of the NOxand 100% of the SO2, initially contained in the simulated exhaust gas. The formation of H2S from sodium sulfide was able to be suppressed by a basic reagent. The use of NaOH and CaCO3, together with the reducing agent not only prevented H2S from forming, but also cut down on the consumption of the reducing agent.
A graphical method for calculating the number of non-ideal plates of a binary distillation column has been developed. The method assumes complete mixing plates of the vapor and liquid phases. The composition of the low boiling point component in the exit vapor from a plate is not in equilibrium with that in the exit liquid from the plate. Other than these, the same assumptions adopted by McCabe-Thiele’s graphical calculation method for an ideal number of plates are used. Equations of lines containing the mass transfer coefficients as parameters are deduced from the mass balances of the low boiling point component and total mass, and the number of non-ideal plates are successfully calculated by repeated drawings of the equations. The method is also applicable for the calculation of the number of non-ideal plates for a counter current extraction operation under certain conditions.