Evaluation of lignite combustion characteristics and gas explosion risks under different air volumes

ABSTRACT

Coal spontaneous combustion (CSC), when not properly controlled during the process of closure, is extremely prone to secondary disasters-gas explosion. Thus, to prevent gas explosion accidents, it is important to understand the characteristics of the coal combustion gas generation law under different air volumes. This study utilized a tube furnace temperature-programmed experimental system to investigate the generation law in a few gas samples. The results demonstrated that oxygen concentration is inversely related to CO and C₂H₄ gas concentration and that coal spontaneous combustion can be divided into four stages: a slow oxidation stage (20–146.4°C), an accelerated oxidation stage (146.4–225.7°C), a speedup-ignition temperature stage (225.7–363.7°C) and a combustion stage (363.7–534.5°C). At Stage 2, the CO and C₂H₄ concentration increased rapidly whereas the O₂ concentration decreased. Moreover, Stage 4 was the most dangerous stage of gas explosion, because CO generation reached its peak value. A decrease in the air volume resulted in the following: prolonged contact time between coal and oxygen, advancement of the initial formation temperature of gases, increase in oxygen consumption, enhancement of the production of index gases CO and C₂H₄, reduction in the lower limit of gas explosion, and increase in explosion risk areas.

Abbreviations

CSC: coal spontaneous combustion; RA: Rui’an Coal Mine

KEYWORDS:

• Air volume
• apparition temperature
• indicator gas concentration
• gas explosion hazard
• lignite combustion

Acknowledgments

This work was financially supported by the Youth Project of Liaoning Provincial Education Department (No. LJ2019QL002), the National Natural Science Foundation of China (Grant No. 51274115), and the National Key R&D Program of China (No. 2018YFC0807900). These supports are gratefully acknowledged. The authors are grateful to the reviewers for discerning comments on this paper.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China[51274115]; the National Key R&D Program of China[2018YFC080790]; the Youth Project of Liaoning Provincial Education Department[LJ2019QL002].

Notes on contributors

Gang Bai

Gang Bai is a lecturer at College of Safety Science and Engineering, Liaoning Technical University. His main research direction is mine fire prevention and mine gas prevention.

Xueming Li

Xueming Li is a doctoral student at College of Safety Science and Engineering, Liaoning Technical University. Her main research direction is the mechanism of coal spontaneous combustion and mine fire prevention.

Xihua Zhou

Xihua Zhou is a professor at College of Safety Science and Engineering, Liaoning Technical University. His main research direction is mine fire prevention.

Jiren Wang

Jiren Wang is a professor at College of Safety Science and Engineering, Liaoning Technical University. His main research direction is mine fire prevention.

Jianshe Linghu

Jianshe Linghu is a professor level senior engineer at Yangquan Coal Industry (group) Co.,Ltd. His research interests include fire prevention theory and technology.