The most common method for monitoring the processes of spontaneous combustion of coal in the mines is the analysis of the composition of the mine atmosphere to detect gases released from coal when the temperature rises. Carbon monoxide and hydrogen are usually used as the main indicators. In recent years, nitrogen is widely used to prevent and extinguish the underground fires. It reduces the oxygen concentration in the fire area and can affect the indicator gases release. To study this effect, the samples of coal with a fraction of 1–3 mm, and the samples of coal dust with a particle size of 0.2–0.4 mm were used. Nitrogen with an admixture of oxygen was supplied to the heated samples. Studies showed that the carbon monoxide and hydrogen are released from the coal dust much more intensively than from the coal. Therefore, high concentrations of these indicator gases may point to the spontaneous combustion of the coal dust. As the proportion of oxygen in the mixture with nitrogen decreases, the release of carbon monoxide and hydrogen from the heated samples of coal and coal dust decreases. This can make it difficult to assess the state of spontaneous combustion foci in an inert environment.
To determine the coal temperature when nitrogen with different oxygen content is supplied, the ratio of carbon monoxide and hydrogen concentrations can be used. In the coal dust it turns out to be the same as in the coal only at 3 % oxygen content. With an increase in the oxygen concentration, this ratio for the coal dust changes significantly. This fact can be used for the identification of fire foci.
2. Semenova S.A., Patrakov Y.F., Majorov A.E. Assessment of the likelihood of underground coal oxidation and self-ignition: A review. Koks i khimiya = Coke and Chemistry. 2020. № 5. pp. 12–21. (In Russ.).
3. Akbarov T.G., Israilov M.A., Makhmudov D.R. Analysis and prevention of spontaneous combustion of Angren coal. Gornyy informatsionno-analiticheskiy byulleten (nauchno-tekhnicheskiy zhurnal) = Mining Informational and Analytical Bulletin (Scientific and Technical Journal). 2021. № 1. pp. 170–177. (In Russ.). DOI: 10.25018/0236-1493-2021-1-0-170-177
4. Zhang Y., Liu Y., Shi X., Yang C., Wang W., Li Y. Risk evaluation of coal spontaneous combustion on the basis of auto-ignition temperature. Fuel. 2018. Vol. 233. pp. 68–76. DOI: 10.1016/J.FUEL.2018.06.052
5. Liang Y., Zhang J., Wang L., Luo H., Ren T. Forecasting spontaneous combustion of coal in underground coal mines by index gases: A review. Journal of Loss Prevention in the Process Industries. 2019. Vol. 57. pp. 208–222. DOI: 10.1016/J.JLP.2018.12.003
6. Snopek L., Adamus A., Sancer J. Research on indicator gases of brown coal spontaneous heating. Journal of Mines, Metals and Fuels. 2012. Vol. 60. pp. 193–196.
7. Wen H., Yu Z., Fan S., Zhai X., Liu W. Prediction of spontaneous combustion potential of coal in the gob area using CO extreme concentration: A case study. Combustion Science and Technology. 2017. Vol. 189. Iss. 10. pp. 1713–1727. DOI: 10.1080/00102202.2017.1327430
8. Skochinskiy A.A., Ogievskiy V.M. Mine fires. Moscow: Izd-vo «Gornoe delo» OOO «Kimmeriyskiy tsentr», 2011. 375 p. (In Russ.).
9. Xie J., Xue S., Cheng W., Wang G. Early detection of spontaneous combustion of coal in underground coal mines with development of an ethylene enriching system. International Journal of Coal Geology. 2011. Vol. 85. Iss. 1. pp. 123–127. DOI: 10.1016/j.coal.2010.10.007
10. Portola V.A., Taylakov O.V., Lee Khi Un, Sobolev V.V., Bobrovnikova A.A. Detection, location and assessment of underground fires using radon anomalies on the day surface. Ugol = Russian Coal Journal. 2021. № 5. pp. 47–52. (In Russ.). DOI: 10.18796/0041-5790-2021-5-47-52
11. Sin S.A., Portola V.A., Igishev V.G. Improving safety and nitrogen injection efficiency to prevent spontaneous combustion of coal in coal mine goaf. Ugol = Russian Coal Journal. 2019. № 2. pp. 11–14. (In Russ.). DOI: 10.18796/0041-5790-2019-2-11-14
12. Kovrizhin O.I., Kolyada A.Yu., Kalinichenko N.A. Use of the gaseous nitrogen during elimination of underground fires. Nauchnyy vestnik NIIGD «Respirator» = Scientific Bulletin of the NIIGD «Respirator». 2020. № 3 (57). pp. 37–44. (In Russ.).
13. Si J., Cheng G., Zhu J. Optimisation of multisource injection of carbon dioxide into goafs based on orthogonal test and fuzzy comprehensive theory. Heliyon. 2019. Vol. 5. Iss. 5. e01607. DOI: 10.1016/j.heliyon.2019.e01607
14. Portola V.A. Danger of Coal Dust Self-Ignition. Bezopasnost truda v promyshlennosti = Occupational Safety in Industry. 2015. № 6. pp. 36–39. (In Russ.).