Page 374 - Advanced Mine Ventilation

21
Spontaneous Combustion of Coal

Chapter Outline

21.1 Spontaneous Combustion of Coal 346
21.1.1 Adiabatic Heating Oven 346
21.1.2 Crossing-Point Temperature Index 352
21.1.3 Oxygen Absorption Index 353
21.2 Detection of Spontaneous Combustion 354
21.2.1 Physical Indicators of Spontaneous Combustion 354
21.2.2 Gas Analysis for Detection of Spontaneous Combustion 354
21.2.2.1 CO/CO 2 Ratio 355
21.2.2.2 Graham Ratio 355
21.2.2.3 Young’s Ratio 356
21.2.2.4 JoneseTrickett Ratio 356
21.3 Mine Design for Coal Seams Liable to Spontaneous Combustion 357
21.3.1 Mine Development 357
21.3.1.1 Roadways and Pillar Size 358
21.3.1.2 Direction of Mains 358
21.3.1.3 Roof Supports in the Airway 358
21.3.1.4 Premining Infusion of Coal With Silicate Gel to Reduce Permeability 358
21.3.2 Secondary Extraction 358
21.3.2.1 Pillar Extraction by Continuous Miners 359
21.3.2.2 Longwall Mining 359
21.3.3 Mine Ventilation and Methane Control on Longwall Faces 359
21.3.4 Inertization 360
21.3.4.1 Self-Inertization 360
21.3.4.2 Induced Inertization 361
Problems 361
References 361

Because coal is not only a combustible material but also liable to spontaneous combus-
tion, mine fire is a clear and present danger in all coal mines. As coal is exposed to
ventilation air, it begins a slow oxidation process that produces heat. Mostly such
produced heat is dissipated by large volumes of circulating air but there are cases
where air supply is limited and the oxidation process continues to raise the coal
temperature until it catches fire. There are many other sources of fire in the mines.
Table 21.1 lists the major sources recorded over a 10-year period (1990e99) in US
coal mines.
Mine explosions (not listed) are another cause of mine fire. They are rare but have
the greatest fatalities. Mobile electrical equipment is being replaced by diesel-powered

Advanced Mine Ventilation. https://doi.org/10.1016/B978-0-08-100457-9.00021-3
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