Characterization of the Products of Explosions of Varying Concentrations of Coal Dust

ABSTRACT

Coal dust explosions using various concentrations of dust were performed and the gaseous and solid explosion products were analyzed. The explosion severity parameters P_m and (dP/dt)_m were found to initially increase and then decrease with increasing dust concentration, while combustion time, t_c, exhibited the opposite trend. The value of t_c was also found to exhibit a linear correlation with both P_m and (dP/dt)_m. Volatile matter and fixed carbon were the major components of each explosion and were significantly reduced in residues. CO, CO₂ and CH₄ were the major gas components and were present at different levels depending on the dust concentration. Micropores and mesopores played an important role in the explosion process. The data show that an explosion involving a low dust concentration is dominated by heterogeneous combustion, while homogeneous combustion is the primary process when employing worst-case and high concentrations.

KEYWORDS:

• Coal dust explosion
• gas products
• homogeneous reaction
• pore structure

Highlights

The coal dust explosion using different concentrations was conducted in 20 L spherical device. With the aid of different analysis methods, the characterization of explosion products was studied and also provided a new perspective for the understanding of explosion mechanism.

1. For characteristic explosion parameters, it can be seen that there is a good linear correlation between t_c, P_m and (dP/dt)_m, with both exhibiting negative correlations and the effect of the effect of t_c on (dP/dt)_m is more significant.

2. According to proximate analysis, we found that the high consumption rates of both the volatile matter and fixed carbon at the worst-case concentration suggest that they had a synergistic relationship in the present study.

3. According to quantitative determination of gaseous products, it can identify that the toxic and harmful gases produced by coal dust explosion are composed of CO, CO₂ and CH₄.Based on the coal pyrolysis and volume fraction of residual gases, it can be concluded that, at low dust concentrations, CH₄ and CO₂ are primarily formed in stage I via the pyrolysis of a small quantity of coal particles; at the worst-case and high concentrations, the production of hydrocarbon is concentrated in II and relatively low during stage III.

4. The analysis of pore structure of solid products indicated that the precipitation and combustion of the volatile matter occur in the micropores and mesopores (2 nm < d < 10 nm). Combined with the aggregation of the solid explosion products, such microscopic structural variations provide useful information with regard to determining the explosion source.

5. The coal dust explosion mechanisms associated with different concentrations can be categorized into two regimes. At low concentrations, the combustion during an explosion is dominated by heterogeneous processes. With increases in the dust concentration, homogeneous combustion begins to play a dominant role, leading to the release of a large amount of heat that promotes continuous combustion.

Acknowledgments

This work is supported by National Natural Science Foundation of China［No.51174200］, Outstanding and Innovative Team Building Project of China University of Mining and Technology, ［2014ZY001］and Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions［PAPD］. The authors are grateful to all the coal mines mentioned in the paper for providing experimental coal samples.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [No. 51174200].