University of the Ryukyus · Faculty of Engineering · 教授

Research keywordsクラスレートハイドレートの物理化学とエンジニアリング

This is a public-data preview. Personalized fit, contact angles, and saved workflows require sign-in.

• Eutectic crystallization of cyclopentane clathrate hydrate and calcium sulfate: Implications for seawater desalination2025 · The eutectic crystallization of cyclopentane clathrate hydrate and solid calcium sulfate was performed to reduce the amount of calcium sulfate in concentrated seawater for the development of seawater desalination and salt production technology. The experiments were performed in terms of eutectic conditions and dynamics of eutectic crystallization. From the eutectic condition measurements, it was found that the eutectic temperature is 280.1 K, and the eutectic concentration corresponds to a mass fraction of 0.002 of calcium sulfate. In the eutectic crystallization experiments, the remaining unreacted solution was analyzed. An increase in the water-to-hydrate conversion ratio led to an increase in the reduction ratio of calcium sulfate; it was found that an average water-to-hydrate conversion ratio of 14 % yielded an average reduction ratio of calcium sulfate of 18 %. Based on these results, a conceptual design for a methodology was presented combining reverse osmosis, multi-stage clathrate hydrate-based seawater desalination, multi-stage clathrate hydrate-based seawater desalination with calcium sulfate reduction, and clathrate hydrate-based seawater desalination and salt production.
• Dynamics and morphology of CO 2 hydrate crystals formed in highly concentrated sodium chloride aqueous solution2025 · Clathrate-hydrate-based desalination would surpass reverse osmosis membrane technology in terms of the water recovery ratio and energy consumption on an industrial scale. For engineering practice, comprehension of hydrate crystal growth and morphology is essential because these kinetics affect the efficiency of the hydrate formation and dewatering process. We measured the three-phase equilibrium conditions of CO#D2#DR + NaCl aqueous solution with a mass fraction of 0.20. The equilibrium temperature at 2.1 MPa was determined to be 265.9 K. We observed crystal growth and the morphology of the CO#D2#DR hydrate in the same system at various subcooling temperatures under 2.1 MPa. Dendritic and polyhedral crystals were observed at large and small subcooling temperatures. The crystal growth rate was higher at large subcooling temperatures in the same system. At a given subcooling temperature, the growth rate in NaCl aqueous solution was obviously lower than in pure water under a given driving force of crystal growth. We discussed this difference in the aspects of viscosity, CO#D2#DR solubility, and thermal conductivity. These observations indicate that both hydrate formation rate and dewatering efficiency depend on subcooling temperature and are in a trade-off relation. The results would facilitate the optimization of the operation conditions of hydrate-based desalination plants.
• Eutectic conditions of carbon dioxide clathrate hydrate and sodium Chloride: Implications for zero liquid discharge seawater desalination2025 · The eutectic temperature, pressure, and concentration conditions of carbon dioxide clathrate hydrate and sodium chloride dihydrate were measured to advance clathrate hydrate-based seawater desalination and salt production technology that enables seawater desalination through zero liquid discharge. The measured eutectic conditions were within the temperature range of 256.2 K ≤ Teu ≤ 263.5 K, the pressure range of 0.91 MPa ≤ peu ≤ 2.70 MPa, and the concentration range, expressed as the mass fraction of sodium chloride, of 0.235 ≤ wm,eu ≤ 0.242. These eutectic conditions correspond to the four-phase equilibrium of a saturated sodium chloride aqueous solution, carbon dioxide clathrate hydrate, carbon dioxide gas, and sodium chloride dihydrate, as well as the five-phase equilibrium of a saturated sodium chloride aqueous solution, carbon dioxide clathrate hydrate, carbon dioxide gas, liquid carbon dioxide, and sodium chloride dihydrate. Based on the measured eutectic conditions, implications for implementing clathrate hydrate-based seawater desalination and salt production were presented, including a conceptual design for a methodology involving reverse osmosis, multi-stage clathrate hydrate-based seawater desalination, and clathrate hydrate-based seawater desalination and salt production.
• Thermophysical Properties of Clathrate Hydrates with Various Guests for Novel Technologies: A Review2024 · Thermophysical properties relevant to clathrate hydrate-based technologies were reviewed. Clathrate hydrates are solids composed of water and guests. The clathrate hydrate-based technologies considered in this study were as follows: carbon capture, utilization, and sequestration; natural gas storage and transportation; ozone storage and transportation; carbon dioxide clathrate hydrate as food; desalination and salt production; separation of tritiated water; cold thermal energy storage; and heat pumps and heat engines. The review was based on the experimentally measured data. The reviewed thermophysical properties were phase equilibrium conditions, formation/decomposition enthalpy, heat capacity, thermal conductivity, interfacial tension, and density. The phase equilibrium conditions determine the operating conditions for the clathrate hydrate-based technologies. The formation/decomposition enthalpy, heat capacity, and thermal conductivity relate to the thermal energy exchange during hydrate formation/decomposition. The interfacial tension is a key parameter when considering the multiphase flow composed of water and guests. The density influences the behavior of clathrate hydrates within the reactor. The relevance between these properties and the clathrate hydrate-based technologies was discussed. The methods correlating the phase equilibrium conditions were also compared in terms of applicability and usefulness. It was revealed that the suitability of the model, which is based on the Clausius–Clapeyron equation or statistical thermodynamic modeling, depends on the purpose of the correlation. Future perspectives of the thermophysical properties of clathrate hydrates were also discussed.

• ハイドレート法による海水淡水化と製塩および石膏回収のゼロ・エミッション技術2022 · 基盤研究(C)
• クラスレートハイドレート法による海水淡水化/製塩ハイブリッドシステムの開発2019 · 若手研究
• クラスレートハイドレート法による海水淡水化技術の開発2017 · 若手研究(B)
• 氷点下温度域におけるクラスレート水和物 －相平衡条件測定と結晶構造解析ー2010 · 特別研究員奨励費

• Official profile