The effect of carbon dioxide treatment on micro-crack propagation of bituminous coals
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ORIGINAL ARTICLE
The effect of carbon dioxide treatment on micro-crack propagation of bituminous coals Jie Zhu . Di Tang . Tangsha Shao . Qi Wang . Jun Tang . Wei Sun
Received: 27 May 2020 / Accepted: 17 September 2020 Ó Springer Nature Switzerland AG 2020
Abstract With the development of carbon dioxide sequestration, the influence of carbon dioxide on coal properties has been paid more and more attention by experts and scholars. Scanning electron microscopy was employed to observe the three-point bending characteristics of bituminous coals treated with or without carbon dioxide gas. The experimental results showed that the carbon dioxide gas treatment had obvious effects on the micro-crack propagation of the coal samples. With the carbon dioxide gas treatment, the bending strength, bending modulus and fracture toughness of the coal samples decreased, and the brittleness of the coal materials tended to be alleviated. The influence of the carbon dioxide gas treatment on the brittleness of the coal samples could be estimated by means of the bending energy index a, which is the ratio of the post-peak and pre-peak bending energy. The experimental results also indicated that the fracture lengths and fractal dimensions increased for coals that underwent the carbon dioxide gas treatment. Keywords Carbon dioxide treatment Scanning electron microscope Mechanical properties Crack propagation Coal
J. Zhu (&) D. Tang T. Shao Q. Wang J. Tang W. Sun School of Mechanics and Civil Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China e-mail: [email protected]
1 Article Highlights 1. The three-point bending mechanical characteristics of coal samples were measured under SEM observation. 2. The energy accumulation and dissipation of coal samples were analyzed to evaluate the change of coal brittleness with carbon dioxide gas treatment. 3. The fractal dimensions and lengths of the main fractures of coals were calculated to quantify the effect of carbon dioxide gas on coal crack propagation.
2 Introduction As one of the greenhouse gases, carbon dioxide affects the global climate to a large extent. Geological sequestration is an effective method for reducing anthropogenic atmospheric CO2 emissions (Lackner 2003; Perera et al. 2011). Compared with the large carbon dioxide storage space, researchers focus more on the safety after storage, which is mainly reflected by the impact of carbon dioxide on the storage site in contact with it and the impact of carbon dioxide leakage on the surrounding environment (Hega 2015; Soltanian and Dai 2017). Coal has numerous pores and can absorb carbon dioxide gas, so deep un-minable coal seams are considered ideal places for carbon dioxide storage. CO2 storage in coalbeds can also
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Geomech. Geophys. Geo-energ. Geo-resour. (2020)6:55
enhance the recovery of coalbed methane. However, the injection of carbon dioxide will cause an expansion of the coal matrix, resulting in changes in the mechanical properties of coal, which
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