Molecular simulation of CO2/N2 injection on CH4 adsorption and diffusion
Ziwen Li1, Hongqing Hu2, Yinji Wang2
1College of Safety and Emergency Management Engineering, Taiyuan University of Technology, Taiyuan, 030024, People's Republic of China. liziwen@tyut.edu.cn.
Scientific Reports
|September 6, 2024
Summary
Molecular simulation reveals that injecting nitrogen (N₂) and carbon dioxide (CO₂) affects methane (CH₄) adsorption and diffusion in coal. CO₂ significantly inhibits CH₄ adsorption, while N₂/CO₂ mixtures enhance CH₄ diffusion for efficient extraction.
Area of Science:
- Earth and Environmental Sciences
- Chemical Engineering
- Materials Science
Background:
- Coalbed methane (CBM) is a vital clean energy source, crucial for energy conservation and emission reduction.
- Efficient CBM extraction is essential for maximizing its environmental and economic benefits.
- Understanding gas interactions within coal seams is key to optimizing CBM recovery.
Purpose of the Study:
- To investigate the impact of nitrogen (N₂) and carbon dioxide (CO₂) injection on methane (CH₄) adsorption and diffusion in coal.
- To evaluate how different gas injection methods influence the efficiency of CBM extraction.
- To provide a scientific basis for enhancing CBM development strategies.
Main Methods:
- Utilized molecular simulation techniques to model gas-molecule interactions within coal.
- Analyzed adsorption isotherms and diffusion coefficients under varying temperature and pressure conditions.
- Examined the effects of single-gas (N₂, CO₂) and mixed-gas (N₂ + CO₂) injection scenarios.
Main Results:
- Gas adsorption in coal is inversely related to temperature and directly related to pressure.
- Adsorption affinity follows the order: CO₂ > CH₄ > N₂.
- CO₂ and N₂ injection significantly inhibit CH₄ adsorption, with CO₂ showing a stronger effect. Mixed injection maximized this inhibition.
- Mixed N₂ + CO₂ injection enhanced CH₄ diffusion more effectively than individual gas injections.
- N₂ injection increased coal porosity, while CO₂ and mixed gas injection decreased it, with CO₂ having a more pronounced effect.
Conclusions:
- Gas injection strategies profoundly impact CBM adsorption and diffusion dynamics.
- CO₂ injection is effective in suppressing CH₄ adsorption, potentially aiding CBM recovery.
- Mixed N₂ + CO₂ injection offers a dual benefit of enhanced CH₄ diffusion and moderated porosity reduction.
- Molecular simulation provides valuable insights for optimizing CBM extraction technologies.
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