The tangential velocity near the side wall of a fully turbulent agitated vessel without baffles uD was estimated based on the tangential velocity at the radial distance of the impeller tip far above and below the impeller. Comparison of the estimated tangential velocity and the observed tangential velocity yielded the simple relation. The simple relationship between momentum and heat transfer at the vessel wall was derived.
Control of physicochemical structure of fine particles based on the self-organization attracts a great interest. In particular, complicated geometry and ordered distribution of chemical elements formed by reaction-diffusion kinetics will be quite useful to develop a novel process for the particle technology. In this work, diffusion-limited growth of solid solution (Ba, Sr)SO4 was investigated. The cations diffused into gelatin from the end of a gel column, and the anion SO42– also diffused into the gel from the opposite end. Various kinds of particles with fine and complicated structures and with peculiar chemical distribution were obtained. The characteristics depended not only on the physicochemical properties of gelatin but also on the location of the particle growth. Particle structures changed by the reaction time with the complicated process. All of the characteristics were able to be understood by an assumption: the dependencies of the diffusion rates of the cations on the physicochemical properties of gelatin may be different from each other, which results in the complicated behavior of the particle growth. We were able to show a possibility to accomplish a single new process based on the reaction-diffusion process in order to obtain fine particles with novel characteristics.
The nucleation and growth process of the polystyrene particles prepared by soap-free emulsion polymerization at the reaction temperature of 70°C are observed by dynamic light scattering (DLS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Here, the use of a cationic initiator enables us to synthesize the positively charged polystyrene, which then adsorbs electrostatically on the negatively charged mica plate with molecular scale smoothness. As a result, the followings are found. 1. In the nucleation process, the monomers are polymerized by initiators and form polymers, and the polymers are coagulated and probably make micelle-like embryos, and then nuclei are generated. The nuclei absorb monomers in the bulk to form particles, such that the surfaces of the formed particles increase hydrophobicity. The hydrophobic particles are coagulated by their hydrophobic attractions. Through these processes, mono-dispersed particles are formed. 2. In the growth of the mono-dispersed particles, they absorb the monomers in the bulk and swelling, and then become extremely soft. As the reaction time increases, the rigidity of the particles changes from soft to hard by their polymerization. In the present experimental system, polymeric materials are not born in the bulk continuously because of a small amount of initiators. That is why the growth by their deposition to the particle surface, so called hetero coagulation, can not be expected.
The separation characteristics of a rotating probability screen having non-blinding and variable sieve openings are theoretically investigated to improve the separation accuracy. The partial separation efficiency of this screen is estimated based on the probability of particle passage through the openings. The separation particle size depends on the rotational velocity of the screen and the included angle of separation rods. As the rotational velocity of the screen increases, the separation accuracy deteriorates. By applying multi-deck screen, the separation accuracy is improved to a sufficient level for practical application.
In an electrolytic reduction process developed to treat spent oxide fuels, alkali and alkaline earth metals (AM and AEM) are dissolved in a molten salt. The dissolution characteristics of AM and AEM are used to selectively separate them from the spent oxide fuel by using a porous MgO filter and, accordingly, to reduce the heat load and the radioactivity from a metal product of the electrolytic reduction process. In this work, the concentration changes of Cs, Sr, and Ba in molten LiCl were measured and the mass transfer behavior was correlated with a diffusion model. The effects of the Li2O concentration on the mass transfer were investigated and the applicability of the porous MgO filter for the selective separation was demonstrated by analyzing the chemicals in the molten salt phase and in the filter.
The effects of the direction of the vertical and horizontal magnetic fields on L-alanine crystal growth were investigated. It was found that the direction of the magnetic fields (either vertical or horizontal for gravity) changed the morphology of L-alanine crystals. The growth of (011) and (120) faces of L-alanine crystal at 5 T in a vertical or horizontal magnetic field was relatively inhibited compared with those at 0 T. On the other hand, in a horizontal magnetic field, when the direction of the c-axis of the seed crystal was set vertically to that of both magnetic and gravitational fields, the growth of (011) and (120) faces of L-alanine crystal was relatively promoted at 5 T compared with those at 0 T. We considered that the difference in the growth environment was caused by magnetic orientation of the crystals and buoyancy-driven convection.
Phase-change slurry is a promising fluid for a district heating and cooling system. In this work, hydrodynamics and heat transfer characteristics of drag reducing trimethylolethane (TME: CH3C(CH2OH)3) solution and suspension by cationic surfactant were studied. Oleyl bishydroxyethyl methyl ammonium chloride (trade name: Ethoquad O/12) was used as the surfactant, while sodium salicylate (NaSal) as counter-ion. Two kinds of experiments were conducted, namely pressure drop/friction factor and heat transfer measurements. From friction factor measurements, it is found that surfactant can induce drag reduction (DR) in TME solution/suspension. It is also found that TME molecule reduces the DR capability. From heat transfer measurement, it is found that surfactant induces heat transfer reduction (HTR) in TME solution and suspension. It is also revealed that Colburn analogy cannot be applied for TME suspension or drag-reducing TME solution and suspension. By using a correction factor for the Colburn analogy, application of the analogy for the drag-reducing TME solution is improved. At low velocity, HTR is higher than the DR, but at high velocity (just before DR is lost) both HTR and DR are nearly the same.
The phase-transfer catalyzed reaction of o-phenylene diamine and carbon disulfide to synthesize 2-mercaptobenzimidazole (MBI) in a gas/alkaline solution of KOH two-phase medium was carried out in a semi-continuous reactor. Tributylamine of competitive price was employed as the catalyst to promote the reaction rate. The reaction is also enhanced by the addition of KOH to the reaction mixture. Gas-phase carbon disulfide of higher temperature is continuously introduced to the reactor for the reaction. The main advantage of the present system is that the reaction is carried out at relatively high temperature in the semi-continuous reactor. Carbon disulfide first dissolves in the organic phase and reacts with tertiary amine in the organic-phase solution to produce an active intermediate (R3N–CS2). Then, this active intermediate further reacts with o-phenylene diamine to produce the desired product MBI. Based on the experimental observation, a reaction mechanism is proposed. A kinetic model which considered the two-step reaction was developed. A pseudo first order rate law is sufficient to describe the reaction. The effect of the reaction conditions, such as: the amount of tributylamine (TBA), agitation speed, initial concentration of carbon disulfide, flow rate of gas phase, amount of o-phenylene diamine and temperature, on the conversion and the apparent rate constant are investigated in detail.
As Murphree plate efficiency becomes lower than 70%, bifurcation with output multiplicity against organic reflux flow rate was found in the simulation of a reactive distillation process for the production of EtAc. Conceptual design of this RD process at an MPE of 60% is thus studied in details. The temperature and composition profiles corresponding to different MPEs are presented, and the open-loop stability of these steady-states is investigated. It is then found that to use a reflux ratio, instead of the reflux flow rate, as a manipulation variable can avoid the occurrence of such output multiplicity. This result is useful in guiding the selection of manipulation variable to design the process as well as the control for the production of EtAc using reactive distillation.
In this paper, the static and dynamic influences of pressure distribution are examined on an ideal heat-integrated distillation column. In the aspect of process design, pressure distribution is found to have an effect upon the thermodynamic efficiency and it appears beneficial to explore an optimum pressure distribution during process development. From the viewpoint of process operation, the dynamics of pressure distribution may give rise to a severe deterioration on process controllability. Therefore, it should be taken into account in control system design for an ideal HIDiC.
Microporous activated anthracite was produced from waste anthracite powders by the conventional steam activation. The activated anthracite was also treated by supercritical water reaction (SWR) by using distilled water and hydrogen peroxide solution as a liquid medium for SWR treatment. It was found that SWR treatment can improve the mesoporosity of the activated anthracite though the micropore volume was reduced by the treatment. In liquid-phase adsorption and supercritical water regeneration studies, phenol and organic dye RED 31 were selected as the representative adsorbates. The adsorption and regeneration characteristics of activated anthracite were compared with those of a commercial activated carbon. The results indicate that the activated anthracite prepared showed comparable phenol adsorption capacity but significantly lower dye adsorption capacity than the commercial one. However, supercritical water regeneration efficiency was remarkably high. The first/second regeneration efficiencies of commercial activated carbon and activated anthracite exhausted with phenol were 55/55 and 65/65%, respectively, and in the case of RED 31, 78/79 and 338/317%, respectively, with losses of activated carbon less than 4% per regeneration. Because of little loss of activated carbon during successive regenerations, this SWR regeneration method was suitable for regenerating spent activated carbon or anthracite.
An air–oil and oil–water interface detector composed of bent plastic optical fiber, photodiode, light emitting diode (LED) and five analog electric circuits was developed and the sensor system was applied to measurement of the oil layer thickness of kitchen wastewater in a grease trap (oil separator for industrial kitchen wastewater). The raw output voltage of the developed sensor system depends on the refractive indexes of the air, soybean oil and tap water. When the sensitive part of the sensor passes through the oil layer, the air–oil and oil–water interfaces can be detected by the peak of the first derivative data calculated from the output voltage of the sensor system. The optimal sampling interval of the output voltage and the optimal movement speed of the sensor are between 100 and 400 ms and over 2.56 mm/s, respectively. The detection limit of oil layer thickness is approximately 3 mm at a 100 ms sampling interval and 2.56 mm/s movement speed. To evaluate the developed sensor system, the thickness of the oil layer in the actual wastewater was measured. Good agreement between the conventional analysis value obtained by a hexane extraction method and the calculated value obtained by the developed sensor was observed. The developed plastic optical fiber sensor system is useful to measure the amount of the floating oil (oil layer thickness) in a grease trap installed in the stream of the wastewater discharged from an industrial kitchen, and the sensor materials are very cheap. A sensing system for detecting the interface of the various materials can be constructed because the refractive index of the materials may be detectable by the developed sensor.
We report here an experiment for the chemical reaction engineering laboratory. The reaction between sodium hydroxide and ethyl acetate is conducted isothermally in a tubular reactor under isothermal, laminar flow, conditions. Steady-state reactor performance is followed at different space times and Reynolds numbers. Analysis of reactor performance is easily followed by direct sampling and titration. Comparisons between theory and experiment are in reasonably good agreement. The experiment demonstrates how concepts in transport phenomena, introduced early in the chemical engineering curriculum, are related to reactor engineering.
Self-cleaning window glasses based on TiO2 photocatalysis are becoming popular products, and the importance of quantitative measure of glass contamination is increasing in order to evaluate its self-cleaning performance. Contaminated glass samples were rated for visual impression of dirtiness. Then the dirtiness ratings were compared with transmittance, haze value, change in lightness, change in color, intensity average of digital photograph, standard deviation of intensity of digital photograph. It was found that the last parameter gives the best correlation with the dirtiness rating.