Pore structure evolution and oxidation characteristic change of coal treated with liquid carbon dioxide and liquid nitrogen

Haihui Xin, Wenjiang Tian, Banghao Zhou, Xu-yao Qi, Jianfeng Li, Jinfeng Wu and De-ming Wang

Energy, 2023, vol. 268, issue C

Abstract: Coal fire is the major hazard to energy security and the environment in the world. Liquid CO2 and liquid N2 are widely used in coal mines. However, the spontaneous combustion tendency and re-ignition of coal which is dealt with liquid CO2 and liquid N2 remain unclear. To solve the problem, this paper studied the pore and oxidation property changes in coal treated by liquid carbon dioxide and liquid nitrogen, applying SEM, isothermal adsorption and thermogravimetric experiments. The results showed that the matrix of coal soaked by liquid CO2 and liquid N2 is shrunk due to cold condition in the context of low temperature (236 K, 77 K). The pore and crack are grown with the increase of total pore volume and specific surface area, which result in increased the oxygen absorption capacity, especially when being soaked by liquid N2. It can be explained liquid CO2 mainly promotes the increase of mesopores in 3.5 nm – 4 nm. Because of the low temperature of liquid N2, new micropores are formed in 0.45 nm–0.55 nm and mesopores in 2 nm–4 nm are increased. After coal is soaked by liquid CO2 and liquid N2, the pore surface becomes rougher and the pore structure for liquid N2 tends to be more complex. Pore evolution promotes oxygen absorption by the coal, which results in the decrease of characteristic temperatures in coal oxidation and combustion stages. After coal is soaked in liquid CO2 and liquid N2, the oxidation and combustion intensity of coal has increased and the average apparent activation energy of oxidation has dropped by 9.65%–11.33% and 15.10%–17.62% respectively, which indicates that their tendency of spontaneous combustion and reignition increases. In all, this study reveals the evolution of pore structure and changes in oxidation property of coal soaked by liquid CO2 and liquid N2, focusing on providing more information for effectively controlling coal spontaneous combustion after using liquid CO2 and liquid N2.

Keywords: Pore structure evolution; Oxidation characteristic; Liquid CO2 and liquid N2; Coal spontaneous combustion (search for similar items in EconPapers)
Date: 2023
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (13)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:268:y:2023:i:c:s0360544223000683

DOI: 10.1016/j.energy.2023.126674

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