Geology Reference
In-Depth Information
Figure 5.1.4. Fires extinguished by first spraying with water and then with a bitumen compound at high pressure
to seal fissures and prevent air ingress (operated by two specially trained fire fighters). Reproduced with permission
of Taylor & Francis. From Bell and Donnelly 2006; photo by Donnelly 2000.
Examples of Spontaneous Combustion and Coal Fires
C ase studies of spontaneous combustion are based on observations made by the authors. Some of these are
published in more detail in Bell and Donnelly (2002, 2006). They include the following:
￿
Witbank coalfield, South Africa
￿
Singrauli coalfield, India
￿
Cerrejón coalfield, Colombia
￿
Yorkshire coalfield, Barnsley, England
￿
Nottinghamshire coalfield, Shirebrook, England.
Spontaneous Combustion in the Witbank Coalfield, South Africa
Coal mining by the pillar and stall method took place at Middelberg Steam Colliery, in the Witbank coalfield, South
Africa, in the early 1900s. Mining occurred there until about 1947, when the mine was abandoned, apart from the
localized and temporary reopening of the mine in the early 1980s. The coal was extracted at a relatively shallow
depth of approximately 20 m and the height of the mine was 2.5 m. Following closure of the mine, coal fires were
observed from the mine workings and these continue to the present, burning for at least 65 years over an area of
150
-
200 ha (Bullock and Bell, 1997) (Figure 5.1.5).
Steam and noxious gases were and are emitted from the mine via ground fissures and crown holes. These
were induced by the collapse of support pillars, possibly exacerbated by pillar robbing which took place
from the 1930s to 1947 (Bullock and Bell, 1997). Attempts to extinguish the coal fires in the past included
the excavation of cut-off trenches backfilled with an inert material ahead of the burn zones, water injection,
and controlled explosions to collapse the workings and cut off air flow. However, none of these methods
have been completely successful. The ground fissures and crown holes continue to permit the flow of air into
the workings and so help promote the oxidation of coal and combustion. Collapse of some pillars may have
been as caused by pillar robbing which may have took place in the final stages of mine abandonment. The
burning and subsequent collapse of the remnant coal pillars leads to the generation of additional fissures,
allowing the ingress of air currents in the collapsed workings. A combination of collapsed mine workings,
ground fissures and crown holes, and high volatile coal containing pyrite all seem to promote spontaneous
combustion (Bell and Donnelly, 2006).
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