When a time periodic perturbation is added to a laminar steady flow, fluid mixing effect is sometimes extremely enhanced. In order to clarify the reason, numerical simulations of fluid mixing were conducted for two 2-dimensional and one 3-dimensional flow systems. As a result, it was revealed that for perturbation of constant amplitude the best mixing effect was obtained when the period ratio Tave/Tp was approximately equal to the golden number where Tave is the mean circulation period of the unperturbed flow and Tp the perturbation period. In addition, the validity of this golden ratio condition for the convective fluid mixing was confirmed in two experiments of the 2-dimensional and the 3-dimensional flows. This phenomenon is due to the fact that the two flows related by the golden period ratio hardly synchronize with each other, and as a result, the streakline acting as the template of fluid mixing distributes uniformly in the fluid mixing region.
To evaluate the performance of a new water circulating system (rate of evaporation, 40 kg/h) in a washing process for radiation-contaminated soil, decontamination by water washing and water circulating tests of the system were conducted in Fukushima with soil contaminated with over 570,000 Bq/kg of radioactivity. The results were as follows. (1) Condensation water with low contamination and low content of impurities was produced by the water-circulating machine, and the recovery rate of water from filtrate was 86–88%. (2) The concentrated solution contained 77–100% of fission products in soil washing water together with impurities.
To evaluate the performance of field-portable (360 mm D×360 mm H×800 mm W) and fixed-mount (1,880 mm D×2,140 mm H×9,085 mm W) filter presses for soil consolidation and volume reduction in the radiation-contaminated soil washing process, radiation assessment was conducted with soil from Fukushima contaminated with over 570,000 Bq/kg of radioactivity. The results were as follows. (1) During soil consolidation, the maximum core dose in the field-portable and fixed-mount types was evaluated respectively as 196 µSv/h and 60 µSv/h at the distance of 1 m from the core. (2) From these results, the maximum exposure dose in ordinary maintenance and inspection was evaluated as 48.1 mSv, exceeding the radiation protection guide level, and thus measures to reduce radiation exposure are required particularly in ordinary maintenance.
We have examined the extraction selectivity towards various metals of N-dodecylaniline, which has an aromatic secondary amine moiety, a weaker base than an aliphatic secondary amine. The selectivity of N-dodecylaniline in toluene for extraction from hydrochloric acid solution was examined by a batchwise method at 300 K, and Pt(IV), Pd(II) and Au(III) were found to be quantitatively extracted, while base metals were not extracted. Therefore, N-dodecylaniline as an extractant was found to be a highly selective for Pt(IV), Pd(II) and Au(III) over base metals. In the extraction of Pt(IV), it was suggested that different platinum complexes were extracted at low and high concentrations of hydrochloric acid. Pt(IV) was found to be extracted by the following extraction reactions from hydrochloric acid solution. Back extraction of the extracted Pt(IV) from the loaded organic phase was examined using various stripping agents, of which aqueous thiourea and thiourea containing HCl were found to be effective.
2-Dodecylsulfanylmethyl-5-hydroxy-pyran-4-one (DSHP) containing a pyrone moiety as a ligand was synthesized in order to develop a highly selective extractant for In(III) and Ga(III). The extraction selectivity of various metal ions from 1 mol dm3 (=M) aqueous ammonium nitrate solution was examined for DSHP in toluene. Considering selective recovery of In(III) and Ga(III) from a residue of zinc refining and bauxite, In(III) and Ga(III) were selectively extracted over Zn(II) with DSHP, while Ga(III) was selectively extracted over Al(III) at low pH. This indicates that DSHP can be applied to selective separation of Ga(III) from bauxite. It was found that In(III) and Ga(III) were extracted with DSHP according to the following reaction: . The extracted complex was crystallized for analysis by 1H-NMR. The extraction equilibrium constants for In(III) and Ga(III) with DSHP were determined to be 2.16 [-] and 3.59×102 [-], respectively. Moreover, the back extraction of In(III) and Ga(III) from the loaded organic phase was examined using various stripping agents. In(III) and Ga(III) extracted with DSHP were effectively stripped using HCl.
Supercritical fluid extraction with a rectification process was developed with a view to separation of trace components from natural materials. Fundamental experiments for separation of 7-hydroxyflavone from anthracene were carried out in a newly developed apparatus at a pressure of 12 MPa. When the respective temperatures of supercritical CO2+ethanol extraction and rectification were controlled at 333 K and 353 K, and with a feed ethanol concentration of 12 mol% and a CO2 flow rate of 1.4 L/min, only anthracene was recovered from the top of the rectifier. Rectification conditions were optimized by selecting a low feed ethanol concentration and by taking into consideration the phase separation of CO2-ethanol systems.
A heat storage system without an evaporator promises high-density heat storage and a high rate of heat output since the solid-liquid product that is formed will itself be transferred as a heat medium to an object that requires heat. In this study, we compared the characteristics of this system using solid CaCl2, CaBr2, or LiBr with liquid H2O as reactants for the storage system. The exothermic heat produced for each reaction was measured and a relationship between the equivalence ratio and the reaction heat was observed. Heat values of 622, 534, and 481 kJ/L were obtained for CaBr2/H2O, LiBr2/H2O, and CaCl2/H2O, respectively. CaBr2 has the highest solubility and heat storage density of the three materials, as well as the highest heat value. The rate of heat output using CaBr2/H2O reached 10 kW/L 10 s after the reaction was initiated, and thus CaBr2 is considered the most effective material for this system.
A biogas upgrading process was developed to achieve both high CH4 concentration and high CH4 recovery from biogas. First, we built process that can achieve both 95% CH4 concentration and 98% CH4 recovery by using DDR-type zeolite membranes with reduced pressure on the permeate side. Second, we showed that both 98% CH4 concentration and 98% CH4 recovery can be achieved by using a process combining a DDR-type zeolite membrane and a polyimide hollow fiber membrane. Finally, we clarified that this biogas upgrading system has long-term stability. The results show that a membrane separation system using a DDR-type zeolite membrane can be operated with lower environmental-impact and higher CH4 recovery than other biogas upgrading technologies.
In this study, program management was applied to the framework of R & D management to create an Agile Program Management Model that can achieve an integrated and agile adaptation to changing circumstances in multiple projects. The effectiveness of the model was evaluated by a case study of chemical engineering research.