prevention and control of spontaneous combustion - Mining and

6 Control of spontaneous combustion
6.1 Underground Mines
6.1.1 Containment
Mitchaylov 46 in his book suggests several rules for controlling a spontaneous combustion, as
described below.
Spontaneous Combustion Rule 1. To stop a heating, stop airflows. If this cannot be done,
maintain oxygen below the critical concentration. Rule 1 is generally attempted after the damage
has been done. Before that, note that all of the reactions produced heat. This leads to:
Spontaneous Combustion Rule 2. To prevent spontaneous heating from going over to
combustion, the velocity of the airflow must be great enough to remove heat as fast or faster
than it is being produced. The likelihood of spontaneous combustion increases with an increase
in the pressure differential across materials prone to spontaneous combustion.
Spontaneous Combustion Rule 3. The likelihood of spontaneous combustion increases with an
increase in resistance to airflow. Associated with this is the most important of all spontaneous
combustion rules, particularly when attempting to stop reactions by zero-pressure differential.
Spontaneous Combustion Rule 4. The likelihood of spontaneous combustion increases with an
increase in the pressure differential across the mass of broken coal, carbonaceous shale, or
wood. The pressure differential results from interrelationships between path resistance and
quantity of airflow; the latter depends on the mine fan(s) and ventilation networks. In deep
mines, abandoned mines, and some sealed areas of active mines, pressure differentials and
airflows are developed by differences in elevations, barometric pressures, gases and
temperatures.
Spontaneous Combustion Rule 5. The likelihood of spontaneous combustion increases with an
increase in depth.
Fuel-rich fires
The definition of a fuel-rich fire is one in which gases and tars in the atmosphere downstream
from the flames are increasing and exceed the quantity that could be reacted by the available
oxygen supply. This occurs when:
a) temperatures are hot enough to continue pulling-out gases and tars from the wood or coal,
and
b) the oxygen concentration is less than required to sustain flaming.
Control of a fuel-rich fire is difficult and dangerous. The measures include:
• Reacting promptly
• Removing downstream fuels
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