Based on the idea that eutectic formation is an useful technology for controlling the melting points of latent heat storage materials over a wide temperature range, precise experimental studies were carried out on the inevitability of eutectic composition of salt hydrate mixtures. Phase diagrams were developed from heating curves of two pseudo-binary systems, Ni(NO3)2·6H2O–CoCl2·6H2O and NiCl2·6H2O–Co(NO3)2·6H2O. The melting points of individual hydrates were 53.5, 53.0, 51.5 and 53.5°C, respectively. In the two binary systems, similar simple eutectic formations were recognized under the same conditions of 30°C and equimolar composition. The crystal compositions in the systems changed depending on the binary mixing ratio. At the same time, new crystal phases that were not attributed to either of original salt hexahydrates were also generated, and the contents of the new phases became maximum at the eutectic points. The two eutectics generated were found to have the same crystal composition as each other as analyzed by X-ray powder diffraction patterns. Consequently, it was concluded that the eutectics were formed through the mutually equivalent exchange of dissociated ions. Further, the inevitability of those compositions was determined as the mixing ratio at which the mutually equivalent exchange might be maintained for all dissociated ions.
The effect of salt addition on the supercooling properties of erythritol was investigated in an attempt to create a novel sugar alcohol type of latent heat storage material that has high thermal storage density and remains in a supercooled state at room temperature. The mechanism of the effect was also examined. Various cationic and anionic species having different valences were each added to erythritol, and their effects on supercooling properties were evaluated with crystallization temperature and supercooling retention time as indices. The supercooling retention mechanism was also investigated focused on the interaction between erythritol and each additive by NMR (Nuclear Magnetic Resonance) spectroscopy. It was found that erythritol additives containing monovalent anions are effective as supercooling stabilizers, and additives containing divalent anions are effective as supercooling inhibitors. It was also found that cationic species have a smaller influence than anionic species. Additives that include the acetate ion were found to be a capable of maintaining erythritol in a supercooled state at room temperature, and the improvement of supercooling retention was considered to be due to the interaction between the hydroxy group of erythritol and the acetate ion.
As a method for efficiently recovering marine organisms, which is expected as a resource for next generation biofuels, crystallizing concentration which can be considered as application of melt crystallization was studied. An operation of forming an ice phase from the outer wall surface to the central portion in the crystallizer was carried out by a cooling jacket with circulating solution. As the operation conditions, the stirring rotation number, the cooling temperature, and the freezing rate were varied to clarify the influence on the concentration ratio of Chaetoceros gracilis in the solution, the dilution ratio of Chaetoceros gracilis in ice, and the solid-liquid distribution coefficient of Chaetoceros gracilis measured experimentally in this study. Furthermore, it is suggested that the solid-liquid distribution coefficients are correlated by two kinds of solid-liquid distribution coefficients models, and concentration by high-speed freezing is also efficient as a result of comparison of the two models.
Solid-state polymorphic transitions of organic compound crystals occur during mechano-chemical processing in a planetary ball mill, but the kinds of mechanical energies that influence these transitions are not known. This study examined the solid-state polymorphic transitions from γ-glycine (Gly) crystals to α-Gly ones by collision, friction, and compression energies in order to elucidate the mechanisms involved. When friction and compression energies were applied to γ-Gly crystals, the solid-state polymorphic transitions to α-Gly crystals were observed. The changes in the transition ratios from γ-Gly to α-Gly crystals with time were analyzed by use of Avrami’s equation, and the solid-state polymorphic transitions were found to be controlled by the phase boundary in the case of friction energy and by diffusion in the case of compression energy. Collision energy alone did not cause solid-state polymorphic transitions, but the combination of collision and friction energies caused the transitions. From the analysis of the changes in transition ratios with time, the solid-state polymorphic transitions are thought to occur initially by nucleation of α-Gly crystals within the γ-Gly crystals, and then by crystal growth of the α-Gly nuclei.
The change in zeta potential of CaCO3 crystal during reactive crystallization was studied. In the reactive crystallization with Ca(OH)2 solution and CO2 gas, the zeta potential had a positive value, suggesting that Ca2+ was adsorbed on the surface of crystal. In the early stage of the reaction, the zeta potential of CaCO3 crystal was about +70 mV and decreased during the reaction. At the neutralization point, the zeta potential showed a minimum value of about +15 mV, after which it increased slowly. This dynamic change in the zeta potential during the reaction may reflect the change in the equilibrium between ions in the mother liquor and those on the crystal surface. To confirm this assumption, the zeta potential of the crystal sampled at the neutralization point was measured in mother liquors with various ionic compositions. The results showed that the change in zeta potential of the crystal reflects the change in the equilibrium at the crystal surface. The same measurement was conducted in the reaction with in the presence of polyacrylate acid (PAA) as polymeric additive. The zeta potential had a negative value, which suggests that PAA was adsorbed on the surface of crystal, and showed a dynamic change during the reaction. These results demonstrated that the change in zeta potential during the crystallization process reflects the change in the equilibrium between ions in the mother liquor and those on the crystal surface, information which will be useful for controlling crystallization processes.
Electroless plating has several advantages over electroplating, such as uniformity of the plated layer, corrosion resistance, and applicability to an electrically non-conductive surface. In this study, to study the effect of high pressure on both the plating rate and the surface structure of the plated layer prepared by electroless nickel–phosphorus plating, we changed the pressure applied to the plating bath in the range from 0 to 400 MPa. As a result, we confirmed the reproducibility of the plating rate under the same plating conditions. It was found that the plating rate increased significantly when the applied pressure was increased from 0 to higher than 20 MPa but gradually decreased with further increase in pressure.
The just-suspension speed NJS in agitated vessels was estimated by using CFD simulation with the Euler-Euler granular model. Empirical correlations as developed by Zweitering are available for predicting NJS, but the parameter S, which is dependent on the geometry of a tank, is required to estimate NJS from the Zwietering correlation. The just-suspension speeds from both the correlation and CFD were investigated and found to be consistent with each other. The parameter S is often unavailable for a variety of agitated vessels, and just-suspension speeds from experimental measurement and CFD have been found to be adequately consistent for such cases.
A model was proposed for calculating the size distribution of particles produced in a stirred-type continuous crystallizer. The model takes into account the process of particle growth due to precipitation on particles and the collision and coagulation between particles. The coagulation efficiency of particles was defined in terms of kinetic energy based on the relative velocity of particles and binding energy based on the precipitation rate. Using this model, it was possible to reproduce the differences in size distribution of particles produced under varying conditions of impeller shape, rotation speed, and tank scale in an actual crystallizer.
The applicability to the screening of crystallization solvents of solubility values estimated by the COSMO-RS (COnductor -like Screening MOdel for Realistic Solvents) method was investigated. The tendencies of estimated and experimental solubility were found to be consistent. When the enthalpy of fusion and melting point were obtained from differential scanning calorimetry (DSC), the minimum error of estimation was about 25%. In comparison, when enthalpy of fusion was calculated from the experimental solubility in a given solvent, the minimum error was reduced to 9%. Thus, it was judged that estimation of solubility by the COSMO-RS method can contribute greatly to the selection of crystallization solvents and the development of crystallization processes.
Low-quality waste oils and fats such as the oily content of trap grease offer an alternative to fossil fuel oil, but they are not fully utilized since they contain saturated fatty acids (SFAs) and saturated triglycerides (STGs), which have relatively high melting points. For practical use of the oily content, it is necessary to remove the components that are solid at room temperature. In this study, we measured the liquidus curves of systems comprising an SFA (stearic acid, palmitic acid, or myristic acid) or an STG (tristearin, tripalmitin, or trimyristin) plus fuel oil A by differential scanning calorimetry. At the same mass fraction of the solid component, the STG plus fuel oil A systems had higher liquidus temperatures than the SFA plus fuel oil A systems with the same fatty acid chains. In both of the SFA plus fuel oil A systems and the STG plus fuel oil A systems, the system in which the solid component had a longer carbon chain had a higher liquidus temperature. On the assumption that fuel oil A is a pseudo-pure component, we proposed two simple methods for predicting liquidus temperature, from the ideal solution approximation and the Dortmund-UNIFAC model, and evaluated their prediction performance by comparing the experimental liquidus curves and the calculated results.
Experiments on aeration from a bubble diffuser pipe having five aeration holes were carried out to investigate the effects of the azimuthal angle of the holes and liquid viscosity on flows inside and outside the pipe. The azimuthal angle was varied by rotating the pipe. When the azimuthal angle of the hole exceeded a certain angle, the liquid height inside the pipe was fixed just below the holes at any liquid viscosity, which resulted in preventing of the formation of liquid slugs inside the pipe. Hence, uniform aeration was realized just by rotating the pipe. The downstream gas flow rates from holes were slightly higher than those upstream, which is due to the pressure recovery in the direction of the stream.
Our group has developed a new powder manufacturing process that employs the spray-drying of emulsion consisting of nanoparticle-dispersed aqueous solutions and carbon dioxide. The method has high productivity and controllability of powder size by using high Re number turbulent field and the Joule–Thomson effect caused by the adiabatic expansion of CO2. However, the dispersion state of the emulsion in high Re number turbulent flow field and the effect of aggregation in the spray process are unclear. In this study, a visualization cell was developed, and the C/W emulsion was observed by using high speed camera in a high Re number turbulent field. It was confirmed that the emulsion drops do not aggregate in the high Re number turbulent field even though no surfactant was used. Moreover, it was suggested that the fine particles contained in the emulsion were preserved intact in the dried powder particles.
The performance of steam generators to generate high-temperature steam using waste heat from industrial processes was investigated. Two types of steam generators were constructed. One is a bench-scale cylindrical generator having similar structure to the laboratory-scale reactor used in the authors’ previous research. The other is a scaled-up generator whose flow passage area is extended to store a large amount of adsorbent for further scale-up on practical application. Temperature measurements in the bench-scale generator in the atmospheric steam generation process showed that a high-temperature region is formed above the water level due to adsorption of water vapor, while a low-temperature region below saturation temperature is formed below the water level. The mass of steam generated per unit mass of adsorbent increased with increasing energy supplied from the regeneration air and approached an asymptotic value depending on the temperature of the regeneration air. The mass of steam generated per unit mass of adsorbent increased with decreasing heat capacity of the generator.
Denatured soluble proteins (DSP), or hydrothermal soluble proteins (peptides) were treated at hydrothermal conditions and their characteristics (foaming property, antioxidant activity and hypotensive effect) were evaluated. To enhance the yield of DSP, base additives and microwave heating were found to be effective. The maximum yield of DSP at 190°C by microwave heating in the presence of base additive for 1 h was 80% based on the original amount of protein in a defatted soybean. The peak of molecular weight distribution of DSP by GPC was around 10 kDa. The foaming capacity and foaming stability of DSP were higher than that of alkali soluble (60°C, 30 min, pH 8 NaOH solution) soybean protein. Antioxidant activity (AA) was 63% and that of commercially available soluble protein isolated (SPI) was 64%. AA is closely related to the order of amino acid polymerized (such as histidine, proline and hydrophobic amino acid) and thus DSP probably consisted of histidine and proline in its structure. Hypotensive effect of DSP was measured by angiotensin converting enzyme (ACE) inhibition effect and was found to be positive while IC50 of DSP was 0.66 mg/L compared with 3.3 mg/L of SPI and thus DSP is superior to SPI in view of hypertensive effect.
This paper describes the analysis of lanthanum nickel oxide (LaNiO3) formation process during heating of a precursor prepared via a mechanochemical (MC) route. To study the effect of the MC treatment on the solid-state reaction of the precursor, two kinds of precursor were prepared: one was a simple mixture of lanthanum hydroxide (La(OH)3), nickel hydroxide (Ni(OH)2), and sodium chloride (NaCl); the other was the mixture obtained by mechanochemical treatment of the simple mixture in a high-energy planetary ball mill. The MC-treated precursor consisted mainly of La(OH)3, Ni(OH)2, and NaCl, as did the simple mixture. However, the MC-treated precursor contained relatively low crystalline components and was well mixed compared with the simple mixture. After the heat treatment, LaNiO3 was obtained from both precursors through three steps of endothermic solid-state reactions. The mechanochemical treatment suppressed the formation of relatively stable hexagonal lanthanum oxycarbonate (La2O2CO3) phase as the intermediate, resulting in the formation of high crystallinity LaNiO3 at relatively low temperature.