Study on Spontaneous Combustion Characteristics of Waste Coal Gangue Hill

ABSTRACT

In order to provide theoretical guidance for controlling spontaneous combustion in coal gangue hills, this study investigated the characteristic of spontaneous combustion. The variations of temperature at different depths were obtained through arranging temperature measurement boreholes in the coal gangue hill and observing for 30 days. The results show that the temperature at a depth of 2.5 m of the coal gangue hill was significantly higher than the temperature at other depths and had the fastest increase. The coal gangue at the depth of 2.5 m gradually developed into the fire source of spontaneous combustion. Due to the continuous heating by the heat generated at the depth of 2.5 m and the sufficient conditions of oxygen supply and heat storage, the coal gangue at the depth of 1.5 m was ignited. The spreading trend of spontaneous combustion was from the fire source (2.5 m deep) to the outside of the gangue hill (1.5 m deep). Through analyzing the variations of free radical in coal gangue oxidation, the study found that the free radical concentration and g factor of coal gangue increased slowly before 200 °C, but after then they began to increase rapidly. By measuring the free radical parameters of coal gangue at different depths, it was found that the coal gangue at the depth of 2.5 m contained the highest free radical concentration and g factor, which indicated that it had the strongest reaction activity. Therefore, in the treatment of spontaneous combustion of coal gangue hills, it is necessary to carry out fixed-point grouting at the depth of 2.5 m.

KEYWORDS:

• Coal gangue hills
• spontaneous combustion
• temperature measurement by drilling
• free radical reaction

Acknowledgments

This work was supported by “Double First Rate” Independent Innovation Project of CUMT (2018ZZCX05). The authors would like to thank the editors for their careful review of this paper.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Highlights

1. Interpretation of coal gangue oxidation by free radical reaction.

2. The law of spontaneous combustion spreading from the fire source to the outside of waste dump is obtained.

3. When the oxidation temperature is higher than 200 °C, the coal gangue changes from slow oxidation to rapid oxidation.

Additional information

Funding

This work was supported by the “Double First Rate” Independent Innovation Project of CUMT [2018ZZCX05].