Outstanding Paper Awards Subcommittee of Kagaku Kogaku Ronbunshu has assessed the 74 papers published in 2005, corresponding to volume 31, and selected the candidates of the award. As a result, the editorial board finally selected the three papers for Kagaku Kogaku Ronbunshu Paper Awards of 2005; those are the papers on “effects of flow phases of methanol on the performance of the direct methanol fuel cell”, “the assessment of micro-mixing of wet particles”, and “the development of a novel static micromixer”.
Solid–liquid mixing is a common industrial operation conducted in processes, such as slurry preparation, polymerization, and crystallization. Thus, many studies have investigated the just suspension speed, solid concentration distribution and solid–liquid mass transfer. However, most were done for single impeller systems and few for multi-stage impeller ones. In this study, we examined the suspension of solid particles in a vessel equipped with dual traditional impellers. The combination of the impellers and the optimal installed position were investigated. As a result, it was found that the optimal combination of traditional impellers is one of a pitched paddle pumping down in the lower position and a pitched paddle pumping up in the upper one, and that the optimal clearance of dual impellers is equal to vessel diameter.
Two-dimensional computer simulation was done to simulate the cross sectional view of non-woven fibrous filter, assuming that each fiber is arranged randomly and in parallel without overlapping other fibers. The distribution of the diameter of the inscribed circle drawn in the space formed by three adjacent fibers (D) and the distribution of thedistance between two fibers (L) were obtained by the Monte Carlo method. These size distributions evaluated by computer simulation were compared with the actual pore size distributions measured by the differential flow method (DFM) and microscopic observation of the cross sectional view of stainless steel fibrous filters. The following results were obtained, (1) The size distributions of D and L approximately followed the gamma (Γ) distribution, (2) The distribution of pore size measured by DFM (Df) and by microscopic observation (LM) followed the log-normal distribution within the limit range of distribution, but the size distribution of Df also followed the Γ distribution, (3) The relationship between the porosity of the filter (ε) and the median size of Df closely agreed with that of ε vs. D, (4) The relationship between ε and the mean flow pore size measured by DFM closely agreed with that of ε vs. the mean value of D at Γ distribution, (5) The maximum value of Df measured by bubble point test closely agreed with the maximum value of D and L at any porosity, (6) The relationship between ε and the median size of LM approximately agreed with that of ε vs. the median size of L.
Low-concentration solvent included in exhaust gas is the chief cause of environmental pollution such as photochemical smog and odor nuisance. In the present study, numerical simulations of a rotor-type solvent recovery system were conducted in order to decide the optimal operation conditions for the actual plant. The dependence of the rotation speed, bed height and adsorption angle on the recovery rate, concentration rate and consumption energy was calculated. From these simulations, the following optimal operation conditions were obtained. 1) The optimal size of actual plant (flow rate of flue gas: 53000 m3 (STP)·h−1) are height of 0.8 m, adsorption angle of 300°, heating zone angle of 30°and purge zone angle of 30°. 2) The optimal operation conditions are desorption gas flow rate of 15000 m3 (STP)·h−1, desorption gas temperature of 453 K and rotation speed of 14 rph. Furthermore, the optimal performance of the proposed system can be maintained by means of a simple feedback control, even though the flow rate of flue gas changes. These results could be helpful guidance for system optimization of the rotor-type solvent recovery system.
Biosorption of Cd2+ and Pb2+ onto sphagnum peat moss was investigated. The mole numbers and acid dissociation constants of metal-binding sites (carboxyl and phenolic hydroxyl groups) were determined by potentiometric titration. The Cd2+ and Pb2+ adsorption data were analyzed using two different adsorption models. The models were based on the acid dissociation reactions of acidic sites and the monodentate or bidentate binding reactions of bivalent metal ions to acidic sites. The results showed that the biosorption of bivalent metal ions onto peat moss followed the bidentate adsorption model. The number of acidic sites of peat moss was about 1.5 mmol·g−1, so that the saturated adsorption amount of bivalent metal ions was 0.75 mmol·g−1. It was also shown that the adsorption process of Cd2+ and Pb2+ followed pseudo-second-order kinetics.
Carbon-fiber cloths were installed in a latent heat thermal energy storage (LHTES) tank to expand the heat transfer area, and the characteristics of the energy charge and discharge processes were compared with the results for carbon-fiber brushes previously reported. In the charge process, carbon-fiber cloths with a volume of 0.27% of the tank volume exhibited better thermal performance than carbon-fiber brushes with a volume of 1.3%. In the discharge process, their thermal performances were the same. The thermal performance of the cloths was accordingly superior to the brushes. When the discharge characteristics were evaluated in terms of the overall fin efficiency, that of carbon-fiber cloths under the present conditions was twice as high as that without carbon fibers. An increase in volume fraction of carbon fibers resulted in higher efficiency, which reached 0.9 only at 1 vol.% of carbon fibers.
In numerical simulation of spray combustion using kerosene, the validity of using water in spray experiments to determine the size distribution of spray droplets and the effect of the size distribution on the calculated spray combustion characteristics were investigated. The effect of parcel number on the combustion behavior was also discussed. A 20 wt% ethanol solution was used as a substitute for kerosene because its physical properties are similar to those of kerosene. Although the droplet diameters of water spray are larger than those of ethanol solution spray, the difference has little influence on combustion characteristics. The calculated temperature distribution using a small number of parcels (=450) is similar to that using a large number of parcels (=450,000), but they differ in the upstream region. Recently, further reduction of NOx and soot emission is required. Therefore, to predict NOx and soot concentration more accurately, it is important to calculate the exact temperature distribution especially in the upstream. The calculated results indicate that a parcel number of at least 4500 is needed to carry out accurate spray combustion calculation when a pneumatic atomizer is used in the combustor.
To develop new organic PCMs for use in hot water supply, an attempt was made to adjust the melting temperature as well as the latent heat, by adding polyalcohol to erythritol, which has a melting temperature of 119°C and a latent heat of 340 kJ/kg. The present study employed seven different polyalcohols: trimethylolethane, trimethylolpropane, 2-ethyl-2-methyl-1,3-propanediol, pinacol, dithioerythritol, xylitol and sorbitol. Thermophysical properties of latent heat and melting temperature of the binary mixtures of erythritol and polyalcohol were measured by means of a DSC. The data on the melting temperature and the latent heat were compared with those obtained by ideal enthalpy change in fusion of a binary mixture and thermodynamic equilibrium equation between a liquid and solid phase, respectively. As a result, the latent heat of erythritol–polyalcohol mixtures could be estimated by the sum of latent heat of each component within a mean square error of 13%, in accordance with the weight ratio of erythritol and polyalcohol. Further, the melting temperature of a new organic PCM could be predicted within an error of 7% by an expression for the ideal solubility of a solid solute in a liquid solvent that takes into account the activity coefficient of the solution.
We previously showed that some glycol-ether aqueous solutions possess unique characteristics of phase-transition and oil solubility. Utilizing these characteristics, we have developed and reported a unique cleaning process with non-distilled type regeneration of detergent liquid and non-waste water, where 35 wt% GE (diethylene-glycol-diethyl-ether) aqueous solution was used as detergent liquid. In this study we constructed a more powerful and effective cleaning process adopting 90 wt% GE aqueous solution as detergent liquid, by means of a cascade-wise sequence of three different states, in which different phases and solubilities are realized respectively. Furthermore, we confirmed that the time required to convert between the homogeneous phase and two phases and to separate oily dirt from oil-resolved homogeneous detergent liquid is within the time allowed in practice.
Activated coke was manufactured by using wood biomass in a fluidized bed reactor for adsorption of H2S in a gasification process. In the previous paper, activated coke was produced from wood biomass in a fixed bed reactor. It was found that the activated coke produced showed good performance in H2S adsorption. In this study, a fluidized bed reactor was employed for the development of mass production equipment. The activated coke produced in a fluidized bed reactor was found to have comparably good the H2S adsorption ability to that produced in a fixed bed reactor.
Three activation methods, CO2 activation, steam activation and KOH activation, were used to activate beer lees charcoal manufactured from beer lees discharged by a brewery. Liquid-phase adsorption properties of phenol, methylene blue, 1,2-dichloroethane and 1,2-dichloropropane by the resulting activated charcoal were examined. The amounts of phenol and methylene blue adsorbed were found to increase in the order CO2 activated charcoal<steam activated charcoal<KOH activated charcoal. This order coincides with the order of their pore volume of the charcoals. Phenol was adsorbed in a larger amount than methylene blue on all charcoals, probably because of its smaller molecular size. The same order of performance was found for the adsorption of 1,2-dichloroethane and 1,2-dichloropropane: CO2 activated charcoal<steam activated charcoal<KOH activated charcoal. The amount of 1,2-dichloropropane adsorbed was twice that of 1,2-dichloroethane, even though they have similar molecular sizes. This is thought to be due to higher solubility of 1,2-dichloroethane in water, which would reflect its higher affinity for water molecules and make it more difficult to be captured by adsorbent.
The extraction and decomposition characteristics of an organo-chlorine herbicide (4-chloro-2-methyl phenoxy) acetic acid (MCPA) absorbed on kaolin as a model soil were investigated by means of ultrasonic irradiation. It was found that a higher extraction ratio of MCPA from the model soil was obtained in a shorter time by irradiation of ultrasound of 500 kHz frequency and 21 W power, compared with the case where the ultrasound was not applied. From the experiments of ultrasonic irradiation on the slurry of MCPA-containing model soil, it was found that the concentration of MCPA extracted from the soil increased with time to attain a maximum value, then decreased with further exposure to ultrasonic irradiation. With the progress of ultrasonic decomposition of MCPA and the reaction intermediates, the concentration of Cl− released from these organo-chlorides was increased in the extract. On the other hand, it was found that the degree of ultrasonic decomposition of MCPA absorbed on kaolin was lower than that of MCPA in water. The lower decomposition efficiency of MCPA absorbed on kaolin was thought to be attributable to the presence of mass transfer resistance of kaolin particles for MCPA extraction, as well as the attenuation of ultrasound waves owing to an excessive amount of kaolin particles in the slurry.
We investigated the effects of nitrate decomposition temperature on thermolysis of magnesite. Experiments using mixtures of magnesite and nitrates with different decomposition temperatures revealed that the magnesite decomposition rate depended upon the decomposition temperature of nitrates. Among nitrate compounds tested, magnesium nitrate hexahydrate showed the greatest effect on the thermolysis of magnesite.