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A Uniaxial Compression Experiment with CO2-Bearing Coal Using a Visualized and Constant-Volume Gas-Solid Coupling Test System
Published on: June 12, 2019
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Raman Spectroscopy Study on Ternary Model Coal Mine Methane Hydrates
Chuanhai Liu1,2, Qiang Wu1,2, Baoyong Zhang1,2
1School of Safety Engineering, Heilongjiang University of Science and Technology, Harbin 150022, China.
ACS Omega
|May 31, 2021
Summary
This study reveals how methane, ethane, and nitrogen in coal mine methane hydrates influence their structure and composition. Ethane dominates hydrate composition, while methane increasingly occupies small cavities as its concentration rises.
Area of Science:
- Geochemistry
- Materials Science
- Chemical Engineering
Background:
- Coal mine methane (CMM) hydrates are significant in energy storage and geological processes.
- Understanding CMM hydrate microfeatures is crucial for managing gas resources and mitigating risks.
Purpose of the Study:
- To investigate the microfeatures of synthesized coal mine methane hydrates using Raman spectroscopy.
- To analyze the impact of varying CH4/C2H6/N2 gas compositions on hydrate structure and guest occupancy.
Main Methods:
- Synthesis of CMM hydrates in a transparent high-pressure cell at 275.15 K and 5 MPa.
- Raman spectroscopy analysis to determine hydrate structure (Structure I) and guest molecule behavior.
- Calculation of cavity occupancies, hydrate guest compositions, and hydration numbers.
Main Results:
- Raman spectra confirmed all synthesized hydrates are Structure I.
- Large cavity occupancy by C2H6 decreased from 85.12% to 79.32%, while small cavity occupancy by CH4 increased from 73.75% to 96.42%.
- CH4 competed with C2H6 for large cavities, with N2 occupancy remaining below 1.2%.
Conclusions:
- The study presents the molecular formulas for three CMM hydrate compositions based on guest distribution and hydration numbers.
- Findings provide insights into the complex microstructural behavior of CMM hydrates under pressure.
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