2. The term "Coal fire" refers to a burning or smoldering
coal seam, coal storage pile or coal waste pile. Two
major causes have been identified for coal fires:
Natural causes:
coal seam or dust can be exposed by the erosion or a
subsidence event, strike by lightning or ignite by a
wildfire.
Human causes:
friction, electricity or oxygen can ignite coal peat or
dust during regular extraction, illegal mining,
transportation.
Introduction
6. 'spontaneous combustion' means that coal can
start to burn without any recognizable outer
influence.
Spontaneous combustion depends, amongst others:
on coal type
temperature
availability of oxygen
exposure to surface
thickness of coal seam
Spontaneous combustion
7. Based on barometric pressure, underground coal fire
development
Stage I: Cracks and fissures allow air to enter the
ground and reach abandoned mine workings or
sealed-off areas. Breathing starts as a result of
changing barometric pressure and residual coal is
supplied with sufficient
oxygen to ignite.
The process of
spontaneous combustion
has begun.
9. Stage II: Once sufficient draught has been created
by the spreading fire, areas of exclusive in- and out-
breathing develop. A continuous air circulation loop
forms that enables the fire to progress steadily
10. DETECTION OF SPONTANEOUS
COMBUSTION
Chemical Indication / Fire Ratios
The composites of gas concentration have been suggested
to assist in the interpretation of fire gases.
Some of these are as follows:
Graham's ratio [C0]/402
Willet's ratio CO2/[excess N2 + CO2 + combustibles]
As a thumb rule it can be taken that
• 0.4% or less indicates normal value
• 0.5% ___ necessity for a thorough a checkup
• 1% ____existence of heating
• 2% ____ serious heating approaches active fire
• 3% and above _____ action fire with certainty
11. CONTROL OF SPONTANEOUS COMBUSTION
three types of gases which have already been used
to fight mine fires.
a) Carbon dioxide b) inert gases c)Nitrogen
Inorganic Inhibitors
magnesium chloride, cadmium chloride &
trisodium
Sealant
Mica, rubber, bitumen
High Pressure Foam
12. Smoking Hills in Canada’s Northwest Territories
Cause: Auto-ignition of a lignite deposit
Starting date: Discovered in 1926 but probably started
burning centuries ago
Amplitude: Over time the sulfur dioxide from the smoke
has acidified the tundra biome of the whole area
-hundreds of hectares
13. Anna Waste Dump, Aachen Anthracite Coal Field,
Alsdorf, germany.
•Cause: Self ignition certainly due to high pressures of a high
grade coal waste dump
•Starting date: 1850
•Amplitude: 42 hectares
14. CAUSES OF DISASTER IN COAL MINE
1. Explosion
2. Roof fall
3. Fire
•presence of explosive mixture
Firedamp alone
Coal dust alone
•suitable source of ignition
•presence of explosive mixture
Firedamp alone
Coal dust alone
•suitable source of ignition
(I) Accidental fire
(II)Spontaneous heating
15. (||) Spontaneous Heating:
Coal undergoes slow oxidation on exposure to air at
ambient temperatures with the evolution of heat, gases
and moisture.
The heat generated, if not dissipated, gives rise to an
increase the temperature of the coal which in turn
increases the rate of oxidation.
• The higher the inherent moisture, the higher the heating
tendency.
• The lower the ash content, the higher the heating
tendency.
• The higher the oxygen content in the coal, the higher the
heating tendency.
16. Oaks Colliery explosion is the deadliest coal mine disaster in
the United Kingdom after the disaster at Senghenyd Colliery.
The disaster took place on 12 December 1866 at the Oaks
Colliery, South Yorkshire
17. The Courrieres mine disaster in France, with a total death
toll of 1,099, is the deadliest coal mining disaster in history.
The coal mining catastrophe occurred on 10 March 1906
due to a massive explosion sparked by an underground fire
in one of the pits of the Courrieres Colliery
18. The Senghenydd Colliery disaster is the worst ever mining
tragedy in the United Kingdom. The disaster, also known as
the Senghenydd Explosion, occurred at the Universal
Colliery in Senghenydd, Wales, on 14 October 1913
19. Impact on atmospheric environment
Release of carbon dioxide, a greenhouse gas, is one of
the major cause to climate change and global warming,
according to the IPCC.
Coal is the largest contributor to the human-made
increase of CO2 in the atmosphere.
According to Guan et al., coal fires in northern China
discharge into the atmosphere each year:
490,200 t of carbon monoxide (CO),
514,700 t of sulfur dioxide (SO2),
300,000 t of nitrogen dioxide (NO2),
112,000 t of dust,
as well as other harmful gases such as carbon dioxide
(CO2) and hydrogen sulfide (H2S).
20. Impact on soil environment
Soil moisture and air have a great impact on plant
growth. Coal fires change the physico-chemical
properties of soil. Yellow burned soil is omnipresent
in coal fire areas
Soil becomes fragile and prone to crumbling, with
very low organic matter content and only small
numbers of microorganisms
21. Impact on human health
Coal tar is a respiratory carcinogen identified by the
International Cancer Research Institution of the
World Health Organization.
Arsenic contained in coal fire discharge can cause
chronic intoxication with after-effects such as
pigment deficiency, over-pigmentation, and skin
cancer.
22. Coal fire mitigation
• Trench cutting and filling with incombustible
materials;
• Surface sealing with soil (soil with high water-
retaining capacity);
• Creation of water pools on the surface, water
circulation under pressure, flooding of fire areas;
• Inert gas and/or foam infusion;
• Cementing and grouting, flushing with bentonite
and/or fly ash;
It was found that a 10 cm layer of bentonite can
reduce air permeation by up to 90 %.
23. Opencast mining- a blazing fire
at the gallery mouth.
The chemicals ultimately used in Shatabdi
Opencast Mine were phosphoric acid, boric
acid, sodium chloride, sodium silicate,
Diammonium phosphate (DAP), and silica gel
in varying proportions.
1.A water admix with phosphoric acid (0.05 to
0.10 %) was sprayed onto the flames. They die
down within 5 to 7 min.
24. DAP (0.03 to 0.1 %) was sprayed with a fog fighter.
After spraying, temperatures in the debris dropped
from 450 to 60 °C and below within 10 to 12 h
overlying rock strata, they fell from 250 to 80°C
within fifteen to twenty days
Silica gel, a mixture of sodium silicate and DAP,
was applied afterwards to form an impervious
coating on the coal surface and thus reduce the risk
of re-ignition.
26. A more-controlled version of a natural coal seam fire
produces primarily hydrogen and CO2, with lesser
amounts of carbon monoxide, methane, and trace
amounts of other gases
syngas and can be combusted directly to produce
heat
greatly reduce the impacts associated with coal
mining, coal dust, and the emissions of sulfur
dioxide and nitrous oxides
Groundwater Contamination- leach out into
surrounding groundwater.
27. Conclusion
India coal mining industry strive
toward zero disaster
proper Vigilance
Environmental tele-monitoring in fire
prone areas.
