Geology Reference
In-Depth Information
Surface
Fresh air
Crevices
Smoke and
fumes
Abandoned
mine entries
Subsidence
area
Rider coals
and shales
Abandoned
mine opening
Airflow
Pillars
Combustion
zones
Figure 1.2.2. Wasted-coal fire in an abandoned mine showing emission of smoke and fumes through cracks and
fractures and intake of fresh air through openings and overburden. From Kim and Chaiken 1993, p. 3.
Figure 1.2.3. Glenburn anthracite waste bank at Shamokin, Pennsylvania. From Kim and Chaiken 1993, p. 5.
Surface disposal of coal waste, from mines, and from preparation plants, is also a source of wasted-coal fires
(McNay, 1971). Approximately 25% of the coal removed from the mine in the United States was rejected
and disposed of on the surface (Doyle, 1976). Over the past 200 years, over three billion tons of refuse has
accumulated in 3000
5000 active and abandoned waste piles and impoundments in the eastern coalfields
alone. It has been estimated that a billion m
3
of anthracite waste has been disposed of in surface piles in the
anthracite region (Figure 1.2.3). The refuse consists of waste coal, slate, carbonaceous shales, pyritic shales,
and clay associated with the coal seam. The combustible content of this material averages between 2000 and
6000 Btu/lb. Material with a combustible content above 1500 Btu/lb will support combustion (Chaiken, 1980;
Kim, 1995).
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In anthracite mines and in some western mines, the dip or pitch of the beds also influences the propagation of fires.
On steep pitches, differences in temperature and elevation are sufficient to control the circulation of air and fumes.
The movement of hot gases can transfer heat to other areas of a mine. The distance between coal beds and their
connection by fractures or tunnels determines the transfer of heat between beds and the possibility of propagation
of a fire from the source bed to adjacent beds (White, 1973).
The rank of a coal is also a factor in the incidence of coal fires. Generally, lower rank coals tend to be more
susceptible to spontaneous combustion. Although lignites and subbituminous coals are more prone to spontaneous
