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Study on Coal Wettability under Different Gas Environments Based on the Adsorption Energy
Nan Ding1,2, Leilei Si1,2, Jianping Wei1,2
1School of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan 454003, China.
ACS Omega
|June 26, 2023
Summary
Gas adsorption in coal reduces water wettability, impacting coal seam water injection safety. Higher gas pressure and stronger gas adsorption capacity significantly increase the coal-water contact angle, hindering effective water injection.
Area of Science:
- Earth Sciences
- Materials Science
- Chemical Engineering
Background:
- Coal seam water injection is crucial for preventing gas outbursts and coal dust disasters.
- Adsorbed gas in coal negatively affects coal-water wetting, a critical factor in water injection efficiency.
- Understanding coal-water wetting under high-pressure adsorbed gas conditions is essential for safe mining.
Purpose of the Study:
- To experimentally investigate the mechanism of coal-water contact angle under various gas environments.
- To analyze coal-water adsorption mechanisms in a pre-absorbed gas environment.
- To provide theoretical support for enhancing coal seam water injection effectiveness.
Main Methods:
- Experimental investigation of coal-water contact angle under different gas environments (CO2, N2, He).
- Molecular dynamics simulation to analyze coal-water adsorption mechanisms.
- Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and 13C NMR for material characterization.
Main Results:
- Contact angle increased most significantly in CO2 (17.62°), followed by N2 (10.21°) and He (8.89°).
- Water adsorption capacity decreased with increasing gas pressure, lowering coal surface free energy and stabilizing coal structure.
- Adsorbed gas occupies primary adsorption sites, competing with water molecules and reducing coal wettability.
Conclusions:
- Increased gas pressure and stronger gas adsorption capacity enhance coal-gas interaction, reducing coal wettability.
- Competitive adsorption between gas and water molecules is more pronounced with stronger gas adsorption.
- Findings offer theoretical insights for optimizing coal seam water injection by addressing gas interference.
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