Oxidative combustion law of water-soaked coal under oxygen-lean condition

ABSTRACT

Residual coal is easily submerged and damaged by groundwater. In the course of mining underlying coal seam, coal belonging to the overlying gob area tends to spontaneously combust during draining water. To explore the effect of micro-functional group transformation in immersed coal on the coal spontaneous combustion (CSC) traits during the low-temperature oxidation process (LTO), the migrant law of special functional groups under varying oxygen concentration (C_o) of immersed coal was discussed by infrared spectroscopy. The endothermal and exothermal properties of the function group inside of coal were studied via thermal analysis. It is shown that the higher C_o, the more oxygenic function groups on the soaked, and by contrasted with the C_o of 18% the 14% has a small increase and the chain length is shortened. The temperature increment together with the C_o content determines the functional group content, the pyrolysis process produces some function group. The lower the C_o, endothermic coefficient decreases and endothermic temperature increases, the higher the ignition temperature of coal oxy-combustion, the lower the total heat release. And the speed of the oxygen-absorbing weight gain and the conversion of the functional group would be improved followed by the burnout temperature rising. Below 14% C_o, the oxidative combustion process will be greatly inhibited. Those findings complement a theoretical basis for preventing long-term water-soaked coal oxidative spontaneous combusting in shallow buried coal seams.

KEYWORDS:

• Coal spontaneous combustion
• water immersion
• oxygen concentration
• FTIR
• TG-DSC

Acknowledgements

The authors wish to acknowledge gratefully the financial support of the research funding provided by the National Natural Science Foundation of China (Nos. 52174163 & 51874131&51474106).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The work was supported by the National Natural Science Foundation of China [52174163, 51874131,51474106].

Notes on contributors

Yun-Chuan Bu

Yun-Chuan Bu is currently pursuing a Ph.D degree in Safety Science and Engineering from University of Science and Technology Beijing. His research interests include mechanism and control methods of coal spontaneous combustion.

Hui-Yong Niu

Hui-Yong Niu is a professor of the University of Science and Technology Beijing. His research interests are centered on the areas of mine fire prevention theory and technology, mine disaster rescue and accident investigation and analysis technology.

Hai-Yan Wang

Hai-Yan Wang is a professor of the University of Science and Technology Beijing. His research interests are centered on the areas of mine safety engineering, mine fire prevention and control.

Qi Fu

Qi Fu is a professor of the Hunan University of Science and Technology. His research interests are centered on the areas of wireless sensor networks, ad hoc networks and internet of things applications.

Meng Tao

Meng Tao is currently pursuing a master’s degree in Safety Science and Engineering from University of Science and Technology Beijing. Her research interests include detection and control of coal spontaneous combustion.

Tian Qiu

Tian Qiu is currently pursuing a Ph.D. at Beijing University of Chemical Technology. Her research interests include research on cross-scale mechanics of advanced materials and structures.