Geology Reference
In-Depth Information
2.4. Coal Mining and Coal
Fires
Abandoned illegal mining and
small-scale coal coking operation
along a coal outcrop in the state of
West Bengal, India.
Photo by Stanley R. Michalski, 1994.
Discovery and Investigation
N o single mining technique can claim responsibility for causing coal-mine fires. In the underground methods of
coal mining, coal fires can be initiated by accident or, given the proper conditions, by spontaneous combustion. A
successful recovery from a fire in an active mine is possible only if fire abatement methods are quickly
implemented. In surface mining, fires may be minimized since, theoretically, all the coal is removed which
precludes a fire. In some regions of the world where subbituminous and lignite coals are highly susceptible to
spontaneous combustion, surface mining cannot be successfully carried to completion if procedures are not in place
to deal with the spontaneous eruption of fire that is caused by exposing these coal seams to the atmosphere (Blazek,
2001).
Many technologies are available to determine the location, extent, and rate of spread of coal fires both underground
and on the ground surface. Some of these technologies include satellite imagery, airborne thermal infrared imagery
(TIR), and historical geologic and mining data and reports. Drilling programs can sample overburden and coal and
provide an access to the mine to monitor fire conditions with temperature and gas sampling equipment and to
conduct ventilation studies.
Monitoring
A network of monitoring devices in an active mine can provide an early warning and location of an impending fire,
help isolate an existing fire, and provide a means of evaluating the effectiveness of fire abatement measures.
Monitoring gases that accumulate in active underground workings provides an early warning of spontaneous
combustion.
Existing fires in underground mines, where access to the workings is prohibited, can be located and monitored
through a network of boreholes drilled to mine level and equipped with appropriate gas- and temperature-sensing
devices. Such equipment can be used to determine the intensity, the rate, and direction in which a fire progresses.
These boreholes drilled to mine level can normally be left in place for monitoring over the longer term to monitor
the effectiveness of abatement measures.
Airborne TIR is a process where a low flying aircraft, flying in the predawn hours, scans the ground surface with
an on-board thermal infrared scanner. The method is most often used to diagnose the surface extent of underground
burning over large areas of abandoned mined lands. The TIR product is a pictorial representation on a photographic
medium of temperature differences between objects at the ground surface. TIR primarily highlights the area where
heated gases escape or vent at the ground surface. These vents or
may be distant from the actual source
of underground burning in a mine. Properly interpreted in the context of the local geology and mine plans, the
hot spots
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