Detection and prevention of spontaneous combustion

“DETECTION AND PREVENTION OF
SPONTANEOUS COMBUSTION”
GOVERNMENT ENGINEERING COLLEGE- BHUJ
PREPAREDBY:
SUJITSURENDRAN
KATARIYAPRASHANTRAMESHBHAI
SAROJRAJRAMNARESH

“DETECTION AND PREVENTION OF SPONTANEOUS COMBUSTION”
A PROJECT REPORT
Submitted by
1. SUJIT SURENDRAN (100150122039)
2. KATARIYA PRASHANT RAMESHBHAI
(100150122095)
3. SAROJ RAJ RAMNARESH
(100150122033)
UNDER THE GUIDENCE OF C.H.THAKER
In fulfilment for the award of the degree of
BACHELOR OF ENGINEERING
in
MINING DEPARTMENT

Fires in coal mines can be categorised into two groups, Viz. –
A) Fires resulting from spontaneous combustion of coal
and
B) Open fires – which are accidental in nature and are
caused because of ignition of combustion materials.
Here, in this paper we are going to discuss for –
group A) kind of fires – its detection, prevention techniques and newly
developed ideas which can bring about a revolutionary change in the face

WHAT IS SPONTANEOUS COMBUSTION ???
SPONTANEOUS COMBUSTION OF COAL
DEFINED AS THE PROCESS OF “SELF-
HEATING” RESULTING EVENTUALLY IN ITS
IGNITION WITHOUT THE APPLICATION OF
EXTERNAL HEAT.
MAINLY CO, CO2, WATER VAPOR
ALONG WITH THE EVOLUTION OF HEAT
DURING THE CHEMICAL REACTION. THE
PROCESS TAKES PLACE AT NORMAL
TEMPERATURE, BUT IT IS SLOW AND THE
HEAT EVOLVED IS NOT PERCEPTIBLE AS IT
IS CARRIED AWAY BY AIR UNLESS AIR IS
STAGNANT.

How spontaneous combustion leads to fire?
OXIDATION OF COAL (FUEL) AND HENCE –
PRODUCTION OF HEAT
IF HEAT NOT DISSIPATED, TEMPERATURE
OF COAL INCREASES
IF HEAT NOT DISSIPATED, TEMPERATURE
OF COAL INCREASES
FIRE

MYTH & FACT ABOUT SPONTANEOUS COMBUSTION
FACT : “Coal is a macro-molecule” which has many different
components, each with their own reactivity
It shows that coal contains a wide range of functional groups
including those containing purely carbon and hydrogen as well
as many including oxygen, such as aldehyde, alcohol, ketone,
ether, ester, carboxylic acid. These latter functional groups are
much more reactive than the pure hydrocarbon groups.
(Kalema and Gavalas, 1987).
CONVENTIONALLY : Spontaneous combustion is thought of as simply coal reacting with
oxygen to form carbon dioxide and carbon monoxide which reduces the coal to a simple
uniform molecule, which of course it is not.

AN EXAMPLE SHALL CLEAR OUR DOUBTS REGARDING COAL AND ITS
SPONTANEOUS HEATING. . . . .
Consider the oxidation of methane to
carbon dioxide.
2CH4 + O2 = 2CH3OH
CH3OH + O2 = CH2O + H2O
2CH2O + O2 = 2HCOOH
2HCOOH + O2 = 2CO2 + 2H2O
ACTIVATION
ENERGY
REQUIRED
DECREASES
From the given reaction series, the latter coals in
the reaction chain will generate more heat when
they react with oxygen.Figure 1.3 Coal Model (Wells and Smoot 1991)

HOW ACTIVATION ENERGY EFFECTS THE SUSCEPTIBILITY OF
SPONTANEOUS COMBUSTION?
Basic Principle - “The activation energy required to break aromatic
hydrocarbon bonds is even higher than for aliphatic hydrocarbon bonds.”
 High rank coals are low in oxygen content and have few reactive functional
groups, they are the most aromatic. Therefore generally they are not
highly prone to spontaneous combustion and produce the most heat
when burnt.
 Low rank coals, contain more oxygen than high rank coals, and have
significant concentrations of oxygenated functional groups. These are
generally more reactive and prone to spontaneous combustion but do not
generate as much heat when burnt.

Factors Responsible for Spontaneous Combustion
A. Seam Factors :
1. Rank 7. Bacteria
2. Temperature 8. The effect of previous oxidation
3. Available air 9. Physical properties
4. Particle size 10. Heating due to earth movement
5. Moisture 11. Bacteria
6. Sulphur 12. Other minerals

(contd.)
B. Geological factors:
1. Seam thickness 5. Coal outbursts
2. Seam gradient 6. Friability
3. Caving characteristics 7. Depth of cover
4. Faulting

(contd.)
C. Mining Factors:
1. Mining methods 9. Multi-seam working
2. Rate of advance 10. Coal losses
3. Pillar conditions 11. Main roads
4. Roof condition 12. Worked out areas
5. Crushing 13. Heat from machines
6. Packing 14. Stowing
7. Effect of timber 15. Ventilating pressure
8. Leakage 16. Change in humidity

THEORIES ON SPONTANEOUS COMBUSTION
Pyrite theory:
Heating of coal can be caused by iron pyrites (when present in considerable proportion)
and in finely powdered and dispersed state in the presence of moisture.
The reaction of iron pyrites with oxygen and moisture is exothermic yields products of
greater volume than the original pyrite thus opening more pore area for oxygen. The
reaction can be given as -
Fe S2+ 702+ 16 H2O = 2 H2SO4+ 2 Fe S04.7 H2O + 316 kcal
Fe S2+ 15/4 O2+ 9/2 H2O = Fe O.OH + 2 H2SO4
The equations indicate that both oxygen and moisture, two prime weathering agents,
contribute to pyrite alteration and the sulphuric acid is formed as a by-product of the
alteration.

THEORIES OF SPONTANEOUS COMBUSTION(contd.)
Bacterial theory:
Different evidences showed that bacteria were capable of living on coal and in some cases
such bacteria caused a slight rise in temperature of the coal.
Graham observed that sterilized coal oxidized at the same rate as the un sterilized coal
and concluded that mechanism of oxidation did not include bacterial activity.
Finally, Fuchs however concluded that bacteria could cause only a slight heating which
may not play any significant role. There is no conclusive proof to authenticate or discard
this theory.

THEORIES ON SPONTANEOUS COMBUSTION(contd.)
 Phenol theory:
Experiments have shown that phenolic hydroxyls and poly phenols oxidize faster
than many other groups. This theory is interesting because it offers a method of
determining liability of coal to spontaneous heating.
 Electro-chemical theory:
It explains auto-oxidation of coals as oxidation-reduction processes In micro galvanic
cells formed by the coal components.
 Coal-oxygen complex theory:
Oxidation of coal is believed to be initiated at native radical sight. Formation of
peroxyl radical and hydro peroxides is commonly to be thought to be they mechanism
by which oxygen and moisture are initially in corporate into organic matrix. These
species may react, rearrange or decomposed to form wide range of oxygen functionality
in the matrix or gaseous product.

THEORIES ON SPONTANEOUS COMBUSTION(contd.)
Humidity theory:
Quantity of heat liberated by atmospheric oxidation of coal is much less than the quantity of heat
required removing water from the coal. Thus it can be concluded that if the evaporation of water can
be induced at the seat of heating, then the temperature of heating would decrease. Mukherjee and
Lahiri (1957) proposed the following mechanism of the reaction between water and coal at 100°C.
(Brackets indicate chemisorptions):
H2O - (H) (OH) - (H2) (0) -- (H2) +02
C + 0 --- (CO) --- CO
(CO) + (0) --- (CO2) --- CO2
When it is recalled that water is an oxidation product of low temperature oxidation of coal, the
above scheme well explains other possible sources of CO and CO2 in low temperature reaction
between coal and oxygen.

Summary of problems due to spontaneous combustion
 The problems due to spontaneous combustion of coal can be categorized according to
the method of working adopted i.e.
(1) Underground,
(2) Opencast
(1) Underground:
The universal problem due to spontaneous combustion in an underground mine is fire or
precisely “coal seam fire”. Coal seam fires can be divided into,
 near-surface fires, in which seams extend to the surface and the oxygen required for
their ignition comes from the atmosphere, and
 Fires in deep underground mines, where the oxygen comes from the ventilation.

(contd.)
 Subsidence Induced due spontaneous combustion occur due to ignition the coal closer to the
surface or entrance. The smoldering fire can spread through the seam, creating subsidence that
may open further seams to oxygen and spawn future wildfires when the fire breaks to the
surface.
Example: JCF is prone to subsidence and
formation of pot holes or cracks reaching up to
surface. Around 34.97 sq. km. area of the JCF is
under subsidence.

(contd.)
(2) Opencast /Surface:
Fire in overburden is are noticeable in many quarries in Jharia, Raniganj, West Bokarao (Kedla –
Jharkhand) and other coalfields.
 Such dumps are on cracked surface of a goaf area the heat travels to underground through
cracks resulting in ignition of coal left in underground during depillaring.
 Stockpiles are prone to spontaneous combustion especially when large quantities are stored for
extended periods.
 Slope failures induced by spontaneous combustion Example, Singrauli Coalfields.

(contd.)
(3) Other Problems:
 Uncontrollable fire in of coal storage in the power plant and during coal transport.
 Spontaneous heating can result into catastrophic in damage to power plant equipments.
ENVIRONMENT IMPACT AND ECONOMIC LOSS:
 Greenhouse gas emissions (CO2 and CH4) from low temperature oxidation and spontaneous
combustion in coal mines.
 Land acquisition as become the greatest challenge to BCCL and other subsidiaries of CIL post
Jharia fires.
 India has to bear the loss of 453 million tons of coal which is locked up in 70 fires in the
Jharkhand due to spontaneous heating.

HISTORY OF SPONTANEOUS COMBUSTION IN INDIA
 “History of coal mines fires due to spontaneous heating can be traced back to
the year 1865, when the first fire was reported in Raniganj Coalfields.”
 Critical-investigations reveal that fires due to –
“Endogenous cause” i.e., spontaneous heating, are more severe than “Exogenous”
one. Further it is observed that the occurrence of spontaneous heating in
underground workings got reduced considerably in 1969 to 1972, 'thereafter start
in- creasing giving the peak maxima in 1977

Dangerous occurrences due to spontaneous heating between 1960
and 1974
Sl.
No.
Cause 1975 ‘76 ‘77 ‘78 ‘79 ‘80 ‘81 ‘82 ‘83 ‘84 ‘85 ‘86 ‘87 ‘88 ‘89 ‘90
1. Spontaneous
Heating
Underground
18 17 23 12 14 18 8 8 19 13 19 19 19 12 9 14
2. Spontaneous
Heating
Surface
19 19 12 2 0 4 - 3 3 1 5 1 1 1 - -
3. Spontaneous
Heating O.C
Workings
1 2 5 1 2 - 1 2 2 2 3 2 2 1 2 -
TOTAL 38 38 40 15 16 22 9 13 24 16 27 22 22 14 11 14

Sr.
No.
Cause 1960 ‘61 ‘62 ‘63 ‘64 ‘65 ‘66 ‘67 ‘68 ‘69 ‘70 ‘71 ‘72 ‘73 ‘74
1. Spontaneous
Heating
Underground
9 5 10 12 8 10 10 11 10 8 6 3 6 11 11
2. Spontaneous
Heating
Surface
10 22 11 22 26 10 19 9 14 9 13 11 16 17 20
3. Spontaneous
Heating O.C
Workings
3 6 2 3 7 2 4 2 1 4 1 4 3 1 1
TOTAL 22 33 23 37 41 22 33 22 25 21 20 18 25 29 32
Dangerous occurrences due to spontaneous heating between 1975
and 1990

SLOPE FAILURES AT SINGRAULI DUE TO SPONTANEOUS HEATING
Date of Failure Description of Events
10 February 1997 A slope failure affected the lower section of the steepest part of the dragline dumps,
to a height of 48 m. The total height of the tip before failure was inclined at 54’ .
The rotational slide was 140 m wide and the coal underwent translational shift by 5 m
Along the floor of the seam, in the dip direction. The collapsed material accumulated
Up to 15 m in the mined out section of the workings.
28 May 1997 A slope failure affected the lower 52 m of the dump material. The total height of the tip
Before failure was 82 m and was inclined at 51’. The width of the slide was 51 m, and
The tip material accumulated 18 m into the workings.
3 October 1997 The total pre-slide dump height was 106 m and the overall slope was 48’, steeping to
76’ in the lower 50m of the slope. Failure affected the dragline dump 50 m high and
220 m long. The collapsed material accumulated on the floor of the mine where the
Turra seam was being extracted. The coal pillar underwent translational shift by 7 m towards the high wall
face.
19 September 1998 A slope failure involved the failure of a 94 m high, 47’, dragline tip. This created a scar 75 m high and 250 m
long and caused the down-dip translational shift of the coal pillar by 65 m, stopping just short of the high
wall.

DETECTION AND PREVENTION
OF SPONTANEOUS
COMBUSTION

Detection Methods:
1 Principal Techniques:
 By Physical Indications
 By Chemical Indications
1) PHYSICAL INDICATIONS
The different odors at different stages can alarm about spontaneous heating
 At initial stage we find faint haze, moisture deposition on roof, side and timber and
smells like “gob-stink”
 “Petrol like odor” at intermediate stage.
 “Fire stink” at last stage approaching ignition.

Detection Methods (contd.)
Keeping systematic records of dry and wet bulb
temperatures may also alarm about spontaneous
combustion.
A Whirling Hygrometer
Drawbacks:
 The odors may be interrupted by
• Decay of wood in warm damp places,
• Tarred brattice cloth,
• Lubricating oil.
 Strata temperature in deep mines can and
percolation of ground water can result in high
dry and wet bulb temperatures(as observed
during training in Moonidih Colliery).

Detection methods (contd.)
2) Chemical Indications
The method includes detection by collection and interpretation of mine
samples. Graham's Ratio is most conventionally used which detects spontaneous
heating by “oxygen deficiency ratio” .
Graham’s Ratio = 𝐶𝑂 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑 / 𝑂𝑥𝑦𝑔𝑒𝑛 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑑
0.1 -0.5% is normal to the coal mine
1% indicate existence of spontaneous heating
2% indicates heating in advanced stage approaching active fire.
3% or more indicates active fire.

Detection methods (contd.)
Drawbacks:
 It can’t be always assumed that
oxygen is consumed due to
oxidation.
 The use of the fresh air nitrogen
concentration of 79.02% includes
argon (Ar) in the amount. Use of
this equation is only valid for
samples where the initial gas has
the same oxygen to nitrogen
ratio as fresh air.Dragger Multigas detector for detection of
percentages of CO and CO2

Other Techniques and Work by CMRI
1) Tele monitoring system :
This system essentially comprises of temperature sensors, toxic and
combustible gas analyzers placed in underground workplace environment and
other fire prone areas and connected to the pit top computer through a data
acquisition system.
IMPEMENTED IN :
 Kotadih Colliery (ECL) & New Manjari Colliery (WCL).
 In reopening a sealed of area at VK7 incline, SCCL this system worked
successfully.

Other Techniques and Work by CMRI (contd.)
2) Thermal Oxidation Of Coal –CMRI
 It is a laboratory technique suggested
by CMRI which uses thermo-
decompositional analysis of coal
sample.
 The coal sample is kept in a reaction
vessel and temperature of which is
measured by thermocouple and
regulated with a programmable
temperature controller. Air samples
are collected through water
displacement methods and interpreted
with a chromatograph at every 20ºC.Apparatus For thermal oxidation of coal

Prevention Methods
1) Control measures to reduce or eliminate oxygen from the process:
i. Sealing of the fire
If the fire is inaccessible, e.g. in a goaf area and there are chances
of spontaneous combustion, it has to be sealed off. The stoppings are
constructed to seal a fire area are of the following types depending
upon the purpose they serve
1. Preparatory Stoppings
2. Emergency stopping or temporary stopping
3. Permanent Stoppings.
ii. Dozing over
This can done to douse fire in opencast mine.

Prevention Methods (contd.)
iii. Cladding of the high wall.
Cladding refers to Covering of the highwall or the overburden surface
with a layer of inert material, usually sand or soft soil excavated during the
removal of overburden.
2) Control measure to reduce the temperature and hence the reaction rate:
i. Water Flushing with bitumen.
Water is flooded in worked out area in
u/g mines where there is propensity of
heating. If the area to be doused is
large it can cause “gas explosions”.

ii. Nitrogen Injection :  The mine we visited during our vocational
training (Moonidih Colliery –BCCL) had faced
spontaneous heating in F1 longwall caving panel
of XVI combined seam was detected in August
1993 in, a degree III gassy mine. The ratio of
goaf-volume and quantity of N2 pumped was
1:1.65. N2 injection helped in salvaging the
longwall equipment.
 N2 flushing has a drawback that the cost of liquid
N2 is high. In 1982, during the firefighting
operations at Laikdih deep colliery, the cost of N2
gas was estimated at $ 11,628 per million m3 and
this cost rose to $ 18,605 per million m3 in 1986.
Nitrogen Injection in u/g mine

3) Removal of the fuel:
Excavation of hot or burning material. This is possible if the igniting materials are not
spread in a wide area.
Work done by CMRI :
 Development techniques for immediate halting of advancing fire by “gel infusion
through coal massive;
 Development of high expansion foam and its application technology for combating
mine fires in the mine roadways;
 Development of fire protective coating material for preventing spontaneous heating
in coal mines ;

 Development of pressure balancing techniques for controlling fire in
underground coal mines;
 Development of fire gallery model for studying the different conditions
which take part in occurrence of fire;
 Material development research like grouting material, remote sealing,
inhibitors for controlling for controlling and preventing fire.

Future Prospects
Our work in next semester

Future Prospects
Use of Radioactivity For early detection of Spontaneous
Heating
Use of Infra-red techniques for detection.
Use of remote sensing for monitoring fires in surface ,
subsurface fires and subsidence induced by spontaneous
heating.
Colloid injection and other better techniques that can prove
better than nitrogen and water injection.

Detection and prevention of spontaneous combustion

Detection and prevention of spontaneous combustion

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