At present, a model has been developed for predicting solubility of solid solutes in supercritical carbon dioxide with a single modifier addition systems. First, we accumulated a total of 960 solubility data sets for 24 organic solutes using ethanol, methanol, acetone, and ethyl acetate as a modifier, and then developed a solubility correlation model. In the development thereof, a Dimensionless Solubility (pDS) model (Ota et al., 2018), which is a solubility estimation model of a solid solute in a supercritical carbon dioxide pure solvent constructed by the authors previously, was adopted as the basic part, and the solubility promoting effect of the modifier addition systems was newly formulated as an m-pDS model (pDS for a single modifier addition systems) using the Hansen solubility parameter for expressing solute-modifier interactions.

The high-pressure vapor–liquid equilibria of a CO₂–ethanol–water system was measured using a flow-type device at temperatures of 313–353 K and a pressure of 8 MPa. With the obtained vapor–liquid equilibria data and the data of a previous report (Sato et al., 2019), the applicability of a correlation method using the van der Waals one fluid (vdW1) mixing rule and Wong–Sandler (WS) mixing rule in the Peng–Robinson equation of state was confirmed. From an estimation made using the temperature-dependent approximation formula of fitting parameters determined by the correlation, the applicability of both the vdW1 mixing rule and WS mixing rule to CO₂–ethanol–water systems was suggested.

The mixing performance of new impellers HR320 and HR320S, which were developed with the purpose of improving the mixing efficiency of low viscosity fluids, was evaluated by measuring power consumption and mixing time. The required stirring powers of HR320 and HR320S were correlated by correcting the parameter for the turbulence term in the correlation equation of the pitched paddle impeller. According to the measurement of mixing time by the decolorization method, more favorable mixing performances were obtained from HR320 and HR320S under turbulent flow conditions compared to the propeller, pitched paddle, and HR100.

The present study synthesizes, as high-volume absorbants targeting boron, hydrogels having polyols in side chains from polyethyleneimine, lactones having four hydroxyl groups, and a crosslinking agent. Adsorption of boron on the hydrogels prepared from gluconolactone reached equilibrium within 3 h when charging a 100 mg/L boron solution. The amount of boron adsorbed in a solution ranging from pH 4 to 8 exceeded 13 mg/g-drygel, which was about 1.5 times the adsorption amount of existing chelate resin. The adsorption isotherm of boron on the hydrogel follows the Langmuir equation, exhibiting maximum adsorption capacity of the hydrogel was 17.2 mg/g-drygel. Furthermore, it was elucidated that hydrogel of higher cross-linking could be used repeatedly for boron adsorption without loss of its capacity by regeneration.

A novel rotating coil-shaped spiral gas–solid contacting device was proposed. A five-cycle spiral was formed by connecting JIS 50^A size 180° long elbows made of stainless steel, which is 10.6 times in size by volume compared to a small-scale (JIS 20^A size) device used in previous research. This spiral was continuously driven by a motor to transport particles. The external surface was heated by flexible heaters and the particle transport rate and heat transfer rate from the wall to particles were measured. Regarding the particles, in addition to the spherical particles used in previous research, non-spherical crushed stones were employed. A solid packing model which takes account of angle of repose was proposed to estimate the volume of the bed and the surface area to which solids contacted. The estimated solid volume fraction in the spiral agreed with the experimental results. An empirical equation of the heat transfer coefficent which had been determined using the previous smaller scale model agreed for the most part with the heat transfer coefficient from the wall to particles. The heat transfer coefficient was estimated based on Packet-renewal model. The discrepancy between the experimental results and model results suggested that the solid-lean layer near the wall affected heat transfer resistance.

Disodium hydrogen phosphate dodecahydrate is a latent heat storage material which is expected to be applied to indoor air conditioning and floor heating. However, because the dodecahydrate melt in the heat storage state does not nucleate easily even if it is cooled to a temperature below its melting point, it makes difficult to operate the latent heat storage system to release the stored heat at its melting point. In order to solve this supercooling problem, generally, nucleating agents are added. But, in spite of the many studies on the development of the agent thus far, their nucleation promoting abilities were still insufficient. In the present study, with the aim of extracting the physical properties necessary for functioning as a nucleating agent, the added reagents were fixed to sodium salts and the strength of their promoting abilities was investigated by thermal cycle experiments. As a result of examining the relationship between the strength of the promoting ability quantified by defining as a supercooling ratio and the acid dissociation constant of the anion, in the anion having a higher dissociation constant compared with the mono-hydrogen phosphoric ion constituting the dodecahydrate, it was found that the anion having a larger number of the dissociation constant exhibited a stronger promoting ability. In addition, as a mechanism for the appearance of the promoting effect, it was considered that the ionic environment in the dodecahydrate melt was destabilized due to the basic action of added anions, and the energy barrier for the nucleation was reduced.