Study of the Abnormal CO-Exceedance Phenomenon in the Tailgate Corner of a Low Metamorphic Coal Seam
Abstract
:1. Introduction
2. Background
2.1. Working Face Overview
2.2. CO Monitoring
2.3. CO Multi-Source Analysis
2.4. Low-Temperature Oxidation Analysis of Goaf
2.4.1. Residual Coal
2.4.2. Caving Condition
2.4.3. Air Leakage
3. CO-Exceedance Mechanism Study
3.1. Experiment
3.2. Simulation of CO-Production Mechanism in Goaf Based on CFD
3.2.1. Research on O2 Distribution in Goaf
3.2.2. Study of the CO-Production-Rate Distribution in the Goaf
4. Discussion
4.1. The CO-Early-Warning Limit for CSC in the Tailgate Corner
4.2. Further Key Scientific Problems
4.2.1. Combined Oxidation Mechanism Research
4.2.2. Index Gases Migration Law of CSC under Combined Oxidation in Goaf
5. Conclusions
- (1)
- Based on field measurements, the abnormal CO-exceedance area of the 1305-working face are systematically investigated. The results show that during the normal mining period of the working face and without any signs of CSC in the goaf, the CO exceedance accounts for about 43% of the support range of the working face, the tailgate is frequently in the CO exceedance state, and the CO concentration in the tailgate corner reaches 4.8 times that of the specified limit. Factors, such as the large amount of residual coal in the goaf, the large degree of fragmentation, complex air-leakage channels, and difficult collapses at the air inlet side, provide opportunities for ambient-temperature oxidation of residual coal in the goaf.
- (2)
- The ambient-temperature-oxidation experiment for lignite shows that when the ambient O2 concentration is ≥7.7%, the coal sample can react strongly with O2 and release a large amount of CO, and the production rate of CO is closely related to the ambient-O2 concentration, showing a quadratic function fitting relationship. The study of the CO-production mechanism in the goaf based on CFD shows that under ambient-temperature-oxidation conditions, the average CO-production rate of the dissipation zone in the 1305 goaf is 10 times that of the oxidation zone, and the CO-output proportion is 4.7. The dissipation zone plays a decisive role in the continuous exceedance of CO concentration in the tailgate corner.
- (3)
- The early-warning-limit model of CO in the tailgate corner for CSC of low-metamorphic coal seams is established, and the early-warning limit is 163 ppm. When the CO concentration in the tailgate corner exceeds 163 ppm, CSC will occur in the 1305 goaf.
- (4)
- The key scientific problems to ensure CSC safety of low-metamorphic coal seam are discussed. Research on the combined oxidation mechanism and the index-gases-migration law of CSC under the combined oxidation condition in low-metamorphic coal goaf is urgently required.
Author Contributions
Funding
Conflicts of Interest
References
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Mad (%) | Vad (%) | Aad (%) | Fcad (%) | Q (MJ/kg) |
13.63 | 35.34 | 6.17 | 44.86 | 26.55 |
C (%) | H (%) | O (%) | S (%) | N (%) |
74.36 | 4.67 | 18.61 | 1.04 | 0.15 |
Name | Boundary Type | Name | Boundary Type |
---|---|---|---|
Solver | Pressure-based | Viscous model | Standard k-ε |
MG | Velocity inlet | Species model | Species transport |
TG | Outflow | Other faces | Standard wall |
Initialization | Standard |
Zone | Nodes | Otal Production Rate/(cm3/m3·s) | Average Production Rate/(cm3/m3·s) | Comparison of Average Release Rate |
---|---|---|---|---|
Dissipation | 6674 | 648.939 | 0.097234 | Dissipation:Oxidation = 10:1 |
Oxidation | 2491/9853 | 95.125 | 0.009654 |
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Li, L.; Ren, T.; Zhong, X.; Wang, J. Study of the Abnormal CO-Exceedance Phenomenon in the Tailgate Corner of a Low Metamorphic Coal Seam. Energies 2022, 15, 5380. https://0-doi-org.brum.beds.ac.uk/10.3390/en15155380
Li L, Ren T, Zhong X, Wang J. Study of the Abnormal CO-Exceedance Phenomenon in the Tailgate Corner of a Low Metamorphic Coal Seam. Energies. 2022; 15(15):5380. https://0-doi-org.brum.beds.ac.uk/10.3390/en15155380
Chicago/Turabian StyleLi, Lei, Ting Ren, Xiaoxing Zhong, and Jiantao Wang. 2022. "Study of the Abnormal CO-Exceedance Phenomenon in the Tailgate Corner of a Low Metamorphic Coal Seam" Energies 15, no. 15: 5380. https://0-doi-org.brum.beds.ac.uk/10.3390/en15155380