SCI和EI收录∣中国化工学会会刊

Chinese Journal of Chemical Engineering ›› 2024, Vol. 73 ›› Issue (9): 1-14.DOI: 10.1016/j.cjche.2024.04.022

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Microscopic experimental study on the effects of NaCl concentration on the self-preservation effect of methane hydrates under 268.15 K

Yu-Jie Zhu1, Yu-Zhou Chen1, Yan Xie2, Jin-Rong Zhong3, Xiao-Hui Wang1, Peng Xiao1, Yi-Fei Sun1, Chang-Yu Sun1, Guang-Jin Chen1   

  1. 1. State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China;
    2. Research Centre of Ecology &Environment for Coastal Area and Deep Sea, Guangdong University of Technology, Guangzhou 510006, China;
    3. School of Chemistry and Food Engineering, Changsha University of Science and Technology, Changsha 410114, China
  • Received:2023-12-22 Revised:2024-04-10 Accepted:2024-04-15 Online:2024-05-28 Published:2024-11-21
  • Contact: Xiao-Hui Wang,E-mail:xh.wang@cup.edu.cn;Chang-Yu Sun,E-mail:cysun@cup.edu.cn
  • Supported by:
    The financial support received from the Basic Research Program of Qinghai Province (2023-ZJ-703), the National Natural Science Foundation of China (22178379, 42206223), and the National Key Research and Development Program of China (2021YFC2800902) is gratefully acknowledged.

Microscopic experimental study on the effects of NaCl concentration on the self-preservation effect of methane hydrates under 268.15 K

Yu-Jie Zhu1, Yu-Zhou Chen1, Yan Xie2, Jin-Rong Zhong3, Xiao-Hui Wang1, Peng Xiao1, Yi-Fei Sun1, Chang-Yu Sun1, Guang-Jin Chen1   

  1. 1. State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China;
    2. Research Centre of Ecology &Environment for Coastal Area and Deep Sea, Guangdong University of Technology, Guangzhou 510006, China;
    3. School of Chemistry and Food Engineering, Changsha University of Science and Technology, Changsha 410114, China
  • 通讯作者: Xiao-Hui Wang,E-mail:xh.wang@cup.edu.cn;Chang-Yu Sun,E-mail:cysun@cup.edu.cn
  • 基金资助:
    The financial support received from the Basic Research Program of Qinghai Province (2023-ZJ-703), the National Natural Science Foundation of China (22178379, 42206223), and the National Key Research and Development Program of China (2021YFC2800902) is gratefully acknowledged.

Abstract: It is known that salt ions are abundant in the natural environment where natural gas hydrates are located; thus, it is essential to investigate the self-preservation effect of salt ions on methane hydrates. The dissociation behaviors of gas hydrates formed from various NaCl concentration solutions in a quartz sand system at 268.15 K were investigated to reveal the microscopic mechanism of the self-preservation effect under different salt concentrations. Results showed that as the salt concentration rises, the initial rate of hydrate decomposition quickens. Methane hydrate hardly shows self-preservation ability in the 3.35% (mass) NaCl and seawater systems at 268.15 K. Combined the morphology of hydrate observed by the confocal microscope with results obtained from in situ Raman spectroscopy, it was found that during the initial decomposition stage of gas hydrate below the ice point, gas hydrate firstly converts into liquid water and gas molecules, then turns from water to solid ice rather than directly transforming into solid ice and gas molecules. The presence of salt ions interferes with the ability of liquid water to condense into solid ice. The results of this study provide an important guide for the mechanism and application of the self-preservation effect on the storage and transport of gas and the exploitation of natural gas hydrates.

Key words: Gas hydrate, Self-preservation, Salinity, In situ Raman spectroscopy, Endothermic behavior, Dissociation

摘要: It is known that salt ions are abundant in the natural environment where natural gas hydrates are located; thus, it is essential to investigate the self-preservation effect of salt ions on methane hydrates. The dissociation behaviors of gas hydrates formed from various NaCl concentration solutions in a quartz sand system at 268.15 K were investigated to reveal the microscopic mechanism of the self-preservation effect under different salt concentrations. Results showed that as the salt concentration rises, the initial rate of hydrate decomposition quickens. Methane hydrate hardly shows self-preservation ability in the 3.35% (mass) NaCl and seawater systems at 268.15 K. Combined the morphology of hydrate observed by the confocal microscope with results obtained from in situ Raman spectroscopy, it was found that during the initial decomposition stage of gas hydrate below the ice point, gas hydrate firstly converts into liquid water and gas molecules, then turns from water to solid ice rather than directly transforming into solid ice and gas molecules. The presence of salt ions interferes with the ability of liquid water to condense into solid ice. The results of this study provide an important guide for the mechanism and application of the self-preservation effect on the storage and transport of gas and the exploitation of natural gas hydrates.

关键词: Gas hydrate, Self-preservation, Salinity, In situ Raman spectroscopy, Endothermic behavior, Dissociation