Development of prediction method of equilibrium conditions for clathrate hydrate

2019 Fiscal Year Final Research Report

• Project/Area Number: 15H02222
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Thermal engineering
• Research Institution: Keio University
• Principal Investigator: Kenji Yasuoka 慶應義塾大学, 理工学部(矢上), 教授 (40306874)
• Project Period (FY): 2015-04-01 – 2020-03-31
• Keywords: クラスレート水和物 / 分子動力学シミュレーション / モンテカルロシミュレーション / 充填率 / 平衡条件

Outline of Final Research Achievements

To develop prediction methods of three-phase equilibrium conditions of methane hydrate by molecular simulations, we examined the use of NVT (isometric-isothermal) molecular dynamics (MD) simulations. NVT MD simulations of coexisting solid hydrate, liquid water, and vapor methane phases were performed at four different temperatures. We found that the calculated equilibrium pressures tended to be higher than those reported by previous simulation studies using the same water model. The deviations of equilibrium conditions from previous simulation studies are mainly attributable to the employed calculation methods of pressure and Lennard-Jones interactions. Isobaric-isothermal Gibbs ensemble Monte Carlo simulations of methane hydrates in equilibrium with bulk methane are performed to calculate large and small cage occupancies. The simulations provide comprehensive predictions of large and small cage occupancies for temperatures and pressures. We also performed hydrogen hydrate system.

Free Research Field

熱工学

Academic Significance and Societal Importance of the Research Achievements

分子動力学シミュレーションによってクラスレート水和物の相平衡状態を求める方法が提案された．この方法を用いることにより様々なクラスレート水和物の相平衡状態を求めることできる．また，本方法を発展させることにより固体・液体・気体の３相平衡状態を求めることができるようになる．また，ギブスアンサンブル・モンテカルロシミュレーションにより充填率を求めることができるようになり，様々なクラスレート水和物の充填率を計算できるようになった．