Geology Reference
In-Depth Information
16.5. Controlling
Abandoned Mine
Fires
Excavation of the fire zone at
the Calamity Hollow Fire in
Pennsylvania.
Photo: US Bureau of Mines, 1982.
Introduction
A
fire requires three elements, fuel, oxygen, and energy. To extinguish a fire at least one of these elements must be
removed (Figure 16.5.1.). Fuel is removed when it is consumed or when it is physically separated from the burning
mass. Oxygen removal depends on either the introduction of an inert atmosphere or on the isolation of the fire zone
from sources of fresh air. Heat removal, the cooling of all fuel below the reignition point, can be accomplished by
moving a heat-absorbing agent (usually an inert gas or water) through the mine. Given the limitations of conventional
fire-control methods, the Bureau of Mines developed and tested several new extinguishment methods.
Burnout Control
T
he Bureau of Mines developed and patented (Chaiken, 1983) Burnout Control, a technique that can control fires
in abandoned coal mines and waste banks, and also extract the thermal energy represented by such coal fires
(Chaiken,1980). The technique involves complete combustion of the coal in place while maintaining control of the
resulting heat and fumes. The thermal energy produced and brought to the surface as high temperature flue gas (up
to 1000°C) can be 20 times the equivalent thermal energy required to operate the Burnout Control system.
During Burnout Control (Figure 16.5.2.), the burning waste bank or coal mine is placed under negative pressure
relative to the atmosphere. Air flows into the underground combustion zones through natural fractures, crevices, pores
in the ground, and/or through specially drilled air inlet boreholes. An exhaust ventilation system consists of a large
borehole, which acts as a combustion manifold, and a fan which draws hot gases from the fire zone, pulling them out
at a single point. In Burnout Control, the affected mine or refuse bank will be at negative pressure, relative to ambient;
hence, fumes will be emitted to the atmosphere only at the fan exhaust point. The accumulation of all the fumes
allows postburn incineration of the exhaust to insure complete combustion to carbon dioxide and water. If needed,
flue gas scrubber treatment can also be applied to remove air pollutants such as sulfur dioxide and particulates.
The heat of combustion of the burning coal will appear as sensible heat in the exhaust at temperatures as high as
1000°C. This heat is recoverable for producing steam and/or electricity. The complete burnout of carbonaceous
material and pyrites in a mine or waste bank will permanently solve the environmental problems of an active fire.
Calamity Hollow
Burnout Control had two limited field trials during its development. The first was a 4-month controlled burn of a
shallow, abandoned coal-mine fire in a confined area of the Pittsburgh seam, the Calamity Hollow Mine Fire
Project (Irani et al., 1983; Chaiken et al., 1984; Dalverny et al., 1984; Soroka et al., 1986; Chaiken et al., 1989).
