Yasuda Keita

写真a

Title

Professor

Researcher Number(JSPS Kakenhi)

60760163

Date of Birth

1984

Laboratory Address

1 Senbaru,Nishihara,Okinawa

Mail Address

E-mail address

Laboratory Phone number

+81-98-895-8613
To the head of this page.▲

Current Affiliation Organization 【 display / non-display 】

  • Duty   University of the Ryukyus   Faculty of Engineering   School of Engineering_Energy and Environment Program   Professor  

  • Charge of Lecture   University of the Ryukyus   Graduate School of Engineering and Science   Mechanical Systems Engineering   Professor  

  • Charge of Lecture   University of the Ryukyus   Graduate School of Engineering and Science   Material,Structural and Energy Engineering   Professor  

To the head of this page.▲

University 【 display / non-display 】

  • 2003.04
    -
    2007.03

    Keio University   Faculty of Science and Engineering   Department of Mechanical Engineering   Graduated

To the head of this page.▲

Graduate School 【 display / non-display 】

  • 2007.04
    -
    2009.03

    Keio University  Graduate School, Division of Science and Engineering  School of Science for Open and Environmental Systems  Master's Course  Completed

  • 2009.04
    -
    2015.03

    Keio University  Graduate School, Division of Science and Engineering  School of Science for Open and Environmental Systems  Doctor's Course  Completed

To the head of this page.▲

Academic degree 【 display / non-display 】

  • Keio University -  Ph.D. in Engineering

To the head of this page.▲

External Career 【 display / non-display 】

  • 2009.04
    -
    2010.03

     

  • 2010.04
    -
    2012.03

     

  • 2010.05
    -
    2010.10

    Visiting Scholar in Colorado School of Mines  

  • 2015.04
    -
    2017.03

    University of the Ryukyus, Faculty of Engineering, Department of Mechanical Systems Engineering, Instructor  

  • 2017.04
    -
    2022.05

    University of the Ryukyus, Faculty of Engineering, School of Engineering, Energy and Environment Program, Instructor  

display all >>

To the head of this page.▲

Research Interests 【 display / non-display 】

  • Physical Chemistry and Engineering of Clathrate Hydrates

To the head of this page.▲

Research Areas 【 display / non-display 】

  • Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Thermal engineering

To the head of this page.▲

Thesis 【 display / non-display 】

  • 氷点下温度域におけるクラスレートハイドレートの相平衡条件と結晶構造

    2015.03

To the head of this page.▲

Published Papers 【 display / non-display 】

  • Eutectic crystallization of cyclopentane clathrate hydrate and calcium sulfate: Implications for seawater desalination

    Yuta Agatsuma, Mion Orita, Yukari Sukegawa, Kouki Mekaru, Rinnosuke Tamaki, Ryo Ohmura, Keita Yasuda

    Journal of Environmental Chemical Engineering ( Elsevier )  13 ( 5 ) 118029   2025.10 [ Peer Review Accepted ]

    Type of publication: Research paper (scientific journal)

    　View Summary

    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 CO2 hydrate crystals formed in highly concentrated sodium chloride aqueous solution

    Ryonosuke Kasai, Leo Kamiya, Keita Yasuda, Ryo Ohmura

    ACS Sustainable Resource Management ( ACS Publications )  2 ( 9 ) 1769 - 1775   2025.09 [ Peer Review Accepted ]

    Type of publication: Research paper (scientific journal)

    　View Summary

    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.

  • Clathrate Hydrate-Based Carbon Capture: A Laboratory Experiment

    Keita Yasuda, Mion Orita

    Journal of Chemical Education ( ACS Publications )  102   4102 - 4108   2025.08 [ Peer Review Accepted ]

    Type of publication: Research paper (scientific journal)

    　View Summary

    Clathrate hydrate-based carbon dioxide separation technology was applied to a laboratory experiment using a mixed gas of carbon dioxide and nitrogen. From October 2022 to August 2024, this experiment was offered to 16 groups comprising 109 second- and third-year undergraduate students. The experiment was also conducted in a high school lecture involving a total of 16 participants. To ensure safety, a glass pressure vessel enclosed in a polycarbonate casing was used at a maximum pressure of 1.5 MPa. Under low temperatures and high pressures, carbon dioxide and nitrogen reacted with a tetra-n-butylammonium aqueous solution to form clathrate hydrates, which preferentially incorporate carbon dioxide. By measuring the gas composition before and after hydrate formation, it was confirmed that carbon dioxide was consumed, thereby lowering its fraction. Based on the measured temperature, pressure, and gas-phase composition data, students tackled exercise problems requiring them to calculate the composition within the clathrate hydrates by applying the equation of state to the gas phase before and after clathrate hydrate formation. Assessment was based on written reports. An analysis employing The Revised Taxonomy verified that the experiment covered a broad spectrum of both Knowledge and Cognitive Process domains. Consequently, many students reached the learning objectives, resulting in a 93% pass rate with an average passing score of 86 out of 100.

  • Eutectic conditions of carbon dioxide clathrate hydrate and sodium Chloride: Implications for zero liquid discharge seawater desalination

    Akari Gibo, Seiya Nakao, Ryo Ohmura, Keita Yasuda

    Journal of Industrial and Engineering Chemistry ( Elsevier )  147   512 - 521   2025.07 [ Peer Review Accepted ]

    Type of publication: Research paper (scientific journal)

    　View Summary

    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 Review

    Keita Yasuda, Ryo Ohmura

    International Journal of Thermophysics ( Springer Nature )  45   139   2024.10 [ Peer Review Accepted ]

    Type of publication: Research paper (scientific journal)

    　View Summary

    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.

display all >>

To the head of this page.▲

Other Papers 【 display / non-display 】

  • Phase Equilibrium Conditions in Carbon Dioxide + Cyclopentane Double Clathrate Hydrate Forming System for Development of Seawater Desalination Technology

    Hideya Suzuki, Kouki Mekaru, Takuto Miyagi, Ayaka Mishima, Isami Uehara, Keita Yasuda

    2024 6th International Conference on Resources and Environmental Research     XG6002-A   2024.12  [Refereed]

     

  • Phase Equilibrium Condition Measurements for Dual-Functional Technology of Clathrate Hydrate-Based Seawater Desalination and Carbon Capture

    Toshikazu Sasaki, Kouki Mekaru, Toru Kubonaka, Shosei Morizumi, Keita Yasuda

    2024 6th International Conference on Resources and Environmental Research     XG6004-A   2024.12  [Refereed]

     

  • Interfacial Tension Measurements in Carbon Dioxide and Seawater System: An Implication for Clathrate Hydrate-Based Seawater Desalination

    Shun Tsunekawa, Suzuna Yamaguchi, Kazuma Ishikawa, Ayushman Tripathi, Keita Yasuda

    2024 6th International Conference on Resources and Environmental Research     XG6003-A   2024.12  [Refereed]

     

  • Phase Equilibrium Conditions in Cyclopentane Clathrate Hydrate Forming Systems Coexisting with Sodium Chloride Aqueous Solutions

    Toshikazu Sasaki, Keitatsu Kamochi, Ayushman Tripathi, Masanao Taoka, Ryo Ohmura, Keita Yasuda

    The 12th International Conference on Separation Science and Technology     109   2023.11  [Refereed]

     

  • Relative Density of Carbon Dioxide Clathrate Hydrate and Sodium Chloride Aqueous Solution: Implications for Desalination Processes

    Shun Tsunekawa, Akari Gibo, Toshiyuki Tanaka, Sayaka Shiraishi, Ryo Ohmura, Keita Yasuda

    The 12th International Conference on Separation Science and Technology     109   2023.11  [Refereed]

     

display all >>

To the head of this page.▲

SDGs 【 display / non-display 】

  • 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

To the head of this page.▲