Numerical Simulation Study on Coal Spontaneous Combustion: Effect of Porosity Distribution

ABSTRACT

The non-uniform distribution of coal porosity has a considerable impact on coal spontaneous combustion (CSC) characteristics. In this study, a one-step global coal oxidation numerical model which took into account the thermal buoyancy and the generation and consumption of multi-component substances was established. The movement of the hot spot and the evolution characteristics of reactants during CSC were researched on. The results suggest that in the early stage of coal self-heating, the hot spots are generated in the high-porosity areas. As coal oxidation intensifies, the hot spots move to the air supply positions. Different coal porosity distributions result in different thermal runaway times, and the coal samples are prone to thermal runaway when the high-porosity areas are near the air supply positions. Resultantly, the movement path of the hot point becomes longer, leading to a larger reduction of average density. Meanwhile, the corresponding thermal runaway and the drastic change in oxygen mole fractions occur later, and the drastic change in thermal runaway is more likely to lag behind that in the oxygen mole fraction. Compared with the gradually changing porosity distribution, the abruptly changing porosity distribution tends to hinder the development of coal oxidation perpendicular to the sudden change cross-section.

KEYWORDS:

• Coal spontaneous combustion
• porosity
• numerical simulation
• hot spot
• lag behind

Acknowledgments

This study was supported by National Key R&D Program of China (2018YFC0807900), National Natural Science Foundation of China (Grant Nos. 51974235, 51774233) and Natural Science Foundation of Shaanxi Province (Grant Nos. 2018JZ5007).

Authors’ contributions

Xiaokun Chen: Conceptualization, Supervision, Validation.

Xueqiang Shi: Methodology, Writing- Original draft preparation, Writing - review & editing.

Yutao Zhang: Writing - review & editing.

Yuanbo Zhang: Investigation.

Qian Ma: Investigation.

Data availability

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Compliance with ethical standards

Competing interests The authors declare that they have no competing interests.

Disclosure statement

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

Additional information

Funding

This study was supported by National Key R&D Program of China (2018YFC0807900), National Natural Science Foundation of China (Grant Nos. 51974235, 51774233) and Natural Science Foundation of Shaanxi Province (Grant Nos. 2018JZ5007);National Science Foundation of China [51774233,51974235];Natural Science Basic Research Program of Shaanxi [2018JZ5007];