Study on the Re-ignition Characteristics of High-Temperature Oxidization & Water Immersion Long-Flame Coal at Different Heating Rates

ABSTRACT

The water immersion residual coal tend to happen spontaneous combustion accidents after mining the coal seam. For exploring the oxidative re-ignition properties of high-temperature oxidized water-impregnated long-flame coal, the thermal evolution law toward each pre-oxidized coal soaked in water under varying heating rates (R_h) (5, 10, 15°C/min) has been analyzed by thermogravimetric differential scanning calorimetry (TG-DSC). The findings are as follows: the DTG at the critical temperature (T₁) and maximum weight loss temperature (T₅) increases, the activation energy (E) decreases, and the heat output increases (maximum 6391J/g) with the rising R_h. The violent oxidated reaction process of coal samples has been delayed as the R_h was 10°C/min. The water-immersed coal sample (I₂₀₀) contains more free water on the surface, and the maximum (0.45 mW/mg) and total (178.8 J/g) heat absorption of are higher. Oxidation at 200°C and soaking in water (O₂₀₀I₂₀₀) reduced the ignition point temperature (minimum 399°C) and E (minimum 18.5 kJ/mol), and increased the total heat release (maximum 323 J/g) making it easier to oxidize and re-ignite. Under the same R_h, the oxidation and combustion traits of each pre-oxidized water-immersed coal (PWIC) remained unchanged. Reducing the R_h can effectively prevent spontaneous combustion of high-temperature oxidized water-soaked coal in shallow-buried and short-distance coal seams in northwest of China.

KEYWORDS:

• Coal spontaneous combustion
• Water immersion
• High temperature pre-oxidation
• r_h
• 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]; National Natural Science Foundation of China [51874131]; National Natural Science Foundation of China [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.

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.