Investigation into Role of Intrinsic Factors in
the Spontaneous Heating of Coals

Abstract

Coal mine fire is a major problem in India and also worldwide has been a great fear both for the industry and researchers in this field. Most mine fires start very small area by spontaneous heating and gradually enlarge in size, thereby, causing loss of coal, life and also the property, environmental pollution due to emission of gases, damage of machinery present inside the mine, a lots of smoke comes out from the mine, increase of temperature inside the mine and ventilation problems. Therefore, the determination of susceptibility of coals to spontaneous heating and their classification is essential to plan the production activities and optimise coal mine production within the incubation period for proper working. The spontaneous heating of coal may define as, when coal is exposed to air, it absorbs oxygen from air at the exposed surfaces. Some fraction of the exposed coal substance absorbs free oxygen at a faster rate than others and the oxidation process results in the formation of gases, (mainly CO, CO2), water vapour along with the evolution of some heat during the chemical reaction. The oxidation process of coal takes place even at ambient temperatures.
EXPERIMENTAL INVESTIGATION
The project deals with the proximate analysis and susceptibility indices analysis of several of coal with the spontaneous heating tendency of coal according to the standardised procedure. For this project, 19 coal samples were collected from South Eastern Coalfields Limited (SECL), Bharat coaking coal Limited (BCCL), central coalfields Limited (CCL), North Eastern Coalfields Ltd (NEC), Eastern coalfields Ltd (ECL) of Coal India Limited and Jindal. The intrinsic properties as well as susceptibility indices of the coal samples were determined by following experimental techniques:
 Proximate analysis
 Calorific value
 Wet oxidation potential
 Differential thermal analysis

The project deals with correlation analysis of various parameters determined by experimental techniques like proximate analysis and spontaneous indices.
Table 1 Results of proximate analysis, characteristic temperature and EMF value
Sl. No. Sample M (%) A (%) VM (%) FC (%) Tc (0C) EMF (mV)
1. BCCL-1 1.495 13.455 22.155 62.895 249.58 21.5
2. BCCL-2 1.845 20.19 21.62 56.245 255.72 33.7
3. BCCL-3 1.94 23.59 24.555 49.915 257.30 50.8
4. BCCL-4 3.095 18.975 24.81 53.12 227.37 79.5
5. CCL-1 1.945 28.685 20.425 48.945 252.11 47
6. CCL-2 1.84 25.56 24.035 48.565 244.08 42.5
7. CCL-3 2.24 43.13 22.135 32.494 244.70 44.6
8. CCL-4 2.29 36.415 19.41 41.885 253.04 66.5
9. JSPL-1 10.83 33.48 23.25 32.44 166.74 149.2
10. JSPL-2 6.39 50.12 19.41 24.08 205.05 153.2
11. JSPL-3 11.84 11.38 31.9 44.88 190.33 142
12. NEC-1 6.05 2.29 41.72 49.94 211.34 114.8
13. NEC-2 7.29 3.8505 26.943 61.916 211.82 138
14. ECL-1 5.441 34.58 23.064 31.474 186.49 162.9
15. SECL-1 4.852 16.9 21.846 56.402 183.84 149
16. SECL-2 6.691 24.425 23.097 46.787 182.73 146.7
17. SECL-3 4.947 8.986 23.605 62.48 190.59 147.3
18. SECL-4 8.316 15.127 18.247 58.31 174.14 150.5
19. SECL5 5.244 8.529 22.314 63.91 173.23 158.3



CONCLUSION
From the experimental investigation it was found that the coal samples from SECL were very highly susceptible to spontaneous heating, whereas the samples from BCCL and CCL were found to less susceptible to spontaneous heating. It is hoped that the outcome of the project work will help the practicing field engineers to plan their workings in advance so that spontaneous heating of coal leading to mine fires can be avoided.
REFERENCES
Banerjee, S.C. Spontaneous Combustion of Coal and Mine Fires, Oxford & IBH Publishing Co, 1985, Pp. (1-40).
Ramlu M. A. 2007, “mine disasters and mine rescue”, 2nd edition, chapter-1, “mine fires” Pp. (2-15).