Chapter 135
Published : PROCEEDINGS OF THE 7TH INTERNATIONAL MINE VENTILATION
CONGRESS, June 17-22, Crakow, Poland
CONTROL OF FIRE IN A LONGWALL PANEL UNDER SHALLOW COVER WITH
CHAMBER METHOD OF VENTILATION AND HIGH PRESSURE HIGH STABILITY
NITROGEN FOAM - A CASE STUDY
N. Sahay
Scientist
Central Mining Research Institute,
Dhanbad, India
B.C. Bhowmick
N.K. Varma
S.K. Ray
S.M. Verma
Scientist
Central Mining Research Institute,
Dhanbad, India
P.K. Mandal
General Manager
Jhanjra Area
Eastern Coalfields Limited, India
ABSTRACT
Fire in a powered support longwall panel (AW 1 ) in RVIIA seam of 1 & 2 Incline mine of Jhanjra Project in Raniganj
Coalfields, India was successfully brought under control using a novel ventilation technique and infusion of high
pressure high stability nitrogen foam from surface through boreholes. A few years ago in 1994, a similar fire in
Kottadih colliery about 10 km away from this mine was successfully tackled with pressure balancing and infusion of
gaseous and liquid nitrogen from PSA type nitrogen generator and LN2 from tanker/reservoir (1). Due to complex geomining situations at AW1 panel the above method had to be supplemented by Chamber method of ventilation and
infusion of high pressure high stability nitrogen foam.
The panel had to be sealed three times within a period of six months due to recurrence of fire after reopening. Finally,
Chamber method of ventilation was adopted for making the pressure of affected panel positive with respect to
surface atmosphere and caved & sealed longwall panel (W1) in RVII seam which was about 40 m above the fire
affected panel. Further high pressure high stability nitrogen foam procured from TECHNOVENT Czech Republic
was injected through a number of boreholes in a systematic manner. For this purpose a foam generator of 9.6 m3/ min
capacity coupled with trolley mounted PSA type nitrogen generator of 300 Nm 3/h capacity was put into service.
Foaming agent having an expansion factor of 80 - 160 times and foam stability of about 72 hours was used. In
addition to above, to meet any emergency situation LN2 in tanker and a reservoir filled with LN2 were kept in
readiness. Above measures supported by thorough monitoring of status of fire by drawing gas samples from goaf
through a number of boreholes and its analysis in the field laboratory ultimately led to control of fire in the panel.
The panel is running smoothly with an average production of about 3000 tonnes of coal per day.
The paper briefly discusses the genesis of the problem, chronological order of the events and action taken, results
obtained, principle & practices of Chamber method of ventilation and high pressure high stability nitrogen foam
technology coupled with a trolley mounted PSA type nitrogen generator.
The method seems to be promising and cost effective for controlling fire in a running longwall panel with complex
geo-mining conditions. This technique is general enough for successful application in other mine under similar
situation.
KEYWORDS
Longwall technology, nitrogen infusion, chamber method of ventilation, dynamic balancing of pressure, sealed off
area, foam infusion, goaf
INTRODUCTION
In 21st century powered support longwall technology
has bright future in Indian coal mines. It has been
successfully adopted in 1 & 2 Incline mine, Jhanjra
Area of Raniganj Coalfields about 200 km from
Kolkata, India. The mine has the reputation of
successful completion of 10 (ten) longwall panels at
972
PROCEEDINGS OF THE 7TH INTERNATIONAL MINE VENTILATION CONGRESS
shallow depth (about 40 m). The success at Jhanjra
brightened the prospect of Longwall technology in
Indian coal mine. However, fire in AW1 longwall panel,
RVIIA seam not only crippled the Jhanjra mine by
bringing all production activities to a halt but also had a
much greater suppressive impact in the entire mining
industry of the country as the story of Longwall
technology in the country seemed to be leading to a sad
end. It was, therefore, imperative to pool the collective
wisdom and expertise of CMRI and mine management
to work out innovative measures to tackle this fire,
reopen the sealed off panel to save the costly equipment
like powered support, shearer, AFC etc. and resume
production at an early date.
A similar type of fire in a longwall panel of Kottadih
colliery(1), a neighbouring mine about 10 km from
Jhanjra project was successfully controlled by
application of pressure balancing and nitrogen infusion.
However, the difficult geo-mining conditions at Jhanjra,
explained later in the paper, made the fire problem more
complicated and the technique of pressure balancing
with nitrogen infusion was found effective in
controlling fire in the longwall panel as long as it
remained sealed. However, on reopening the panel the
fire would erupt again.
It was obvious that an improved technique of fire
control was needed for this mine which led to
introduction of chamber method of ventilation along
with high pressure nitrogen foam technology that
ultimately proved successful in keeping the fire under
control not only when the panel was sealed but also
when the panel was reopened and put under normal
operation. The paper briefly deals with the problem,
various measures taken to control the fire, their impact
on status of fire and highlight the important lessons
learnt which would be beneficial to other mines.
In RVII seam a manual section is in operation and ten
longwall panels have already been successfully
completed, whereas in RVIIA seam developments by
Road header machine in east and west sides of the
property are in progress and one longwall panel (AW 1)
in west side of the mine has just started. Layout of
panels and developments in RVII and RVIIA seams are
shown in Figure 1. Entries into the mine are through
Incline 1 & 2 and ‘D’ shaft sunk upto RVII seam. No 1
& 2 Incline mine was producing about 3500 tonnes of
coal per day deploying 1200 personnel before the onset
of fire in AW1 panel.
INCLINE 1
INCLINE 2
MANUEL DIST
1D 2D
W4
AW2
AW2
AE1
AW1
AE1
W1
D
S
D Shaft
PARTICULARS OF THE MINE
RVII seam circuit
RVIIA seam circuit
Jhanjra Area extends to about 12 Sq km which is
encircled by faults with throws varying from 10 to 30
m. Jhanjra block has nine viable seams with total
extractable reserves of 212 million tonnes of coal. It is
being extracted by two mines viz 1&2 Inclined mine
and Main Industrial Complex. Depth of the seams varies
from 38 to 380 m. Details of thickness and depth of the
five top seams are given in Table below:
S.No
1.
2.
3.
4.
5.
Seam number
RVII
RVIIA
RVI
RV
RIV
Thickness, m
1.27 - 4.23
0.45 - 4.11
2.15 - 5.60
2.90 - 6.64
3.75 - 11.27
Depth, m
76
109
201
231
257
The seams are degree II gassy. In Incline 1 & 2 mine
workings are spread in two seams viz. RVII and RVIIA.
Figure 1. Schematic diagram of 1 & 2 Incline mine,
Jhanjra area
Ventilation circuit
General Ventilation layout of the mine is shown in
Figure 1. The mine is being ventilated by an Axial flow
fan (make - Voltas, Model - VF 2500) installed at
Incline No 1. The fresh air reaches the mine through
Incline No. 2 and Shaft ‘D’ situated at extreme
boundary of the property. Development of the mine is
between these openings viz. No 2 Incline and ‘D’ shaft
along RVII and RVII A seams. No 1 dip having
conveyor belt installations all along its length is
connected with incline no. 1 serving the purpose of
main return airways and transportation of coal of the
total mine. The air flowing down through incline no. 2
is mostly utilised for ventilation of workings of RVII
CONTROL OF FIRE IN A LONGWALL PANEL UNDER SHALLOW COVER
HISTORY OF FIRE IN THE MINE
Presence of CO to the extent of 80 PPM was noticed
in the tail gate during extraction of W1 panel in 1990 91 which ultimately vanished after 400 m progress of
the face. The measure taken was only dozing on the
surface above W1 panel .
115.0 m
BH 1
C
B
BH 4
B
A
B
BH 12
BH 3
B
BH 2
C
BH 13
BH 5
BH 11
C
Figure 2: Conceptual model of the goaf
Figure 2. Conceptual of the goaf
BH 14
Installation Chamber
Some details of AW1 panel
AW1 longwall panel with single entries, retreat and
U-system of ventilation is the first panel in RVIIA
seam. This panel is located below the caved and sealed
longwall panels W1 & W2 in RVII seam. Details of the
panel are given below.
 Name of the Panel
:
AW1
 Name of seam
:
RVIIA
 Seam Thickness
:
3.2 m
 Length of panel
:
850 m
 Depth from surface
:
97 m
 Parting between RVII :
40 m
& RVIIA seams
 Length of face
:
120 m
 No. of chocks
:
82
 Chock resistance
:
(4 × 550) tonnes
 Distance of installations chamber between :
40 m
AW1 & W1 panels
 Date of Starting of
:
08.06.1999
the panel
Thickness of RVIIA seam at installation chamber is
3.2 m, but due to limitation in support resistance (4 x
550 tonnes) only 2.4 m height of the seam could be
extracted along the floor. About 0.8 m thick coal layer
along the roof was left in the goaf. After progress of 40
m of the face it was observed that there was no periodic
weighting and goaf was not even half filled.
Apprehending the danger of air blast, Induced blasting
was resorted to after every 10.0 m mark to fill up the
goaf. After 40.5 m progress of the face local fall
occurred on 27.7.99 and as a result the goaf was filled to
about 90%. Main fall occurred after 80.5 m progress of
the face on 18.8.99. After occurrence of main fall water
from upper seam goaf started percolating down at the
rate of about 200 GPM, although a borehole was drilled
earlier from lower seam to upper seam for dewatering
purpose.
On 28.8.99 traces of CO gas at top gate of AW 1 panel
in RVIIA seam was noticed after ocurrence of main fall
which increased gradually to 400 PPM even after
further progress of the face by 30 m. Finally, the panel
was sealed on 8.9.99 by erecting stoppings at top and
bottom gates. At this juncture CMRI was called for
scientific support for assessment of status of fire and
extinguishment of fire quickly.
A team of scientists of CMRI visited the mine. Details
of investigations2 carried out by the authors, approaches
adopted for control of fire and result obtained are
discussed briefly phase wise in the following
paragraphs.
The entire period of fighting the fire are divided into
eight phases. List of the action taken and their results
with observation are furnished in Table 1.
From the account of action taken to control fire during
the first seven phases of fire fighting operation and their
results it is clear that:
1. The conventional model of packing of longwall goaf
viz. free zone, critical zone and compact zone as
propounded by various authors (3) are not applicable in
this mine.
2. Location of seat of fire was not known.
3. Heat could not be dissipated even after keeping the
panel in sealed condition more than 90 days and
maintaining its temperature below 10°C by pouring
LN2 through different boreholes.
4. Requirement of Nitrogen gas is very high to control
fire in open longwall panel due to uncontrolled
leakage of air .
5. Rate of emission of CO increased rapidly within a few
days after getting an indication of its presence in the
face.
Finally, during 8th phase of fire fighting operation a
new model for packing of goaf in this situation
considering:
 bolted roof of top & bottom gate,
 panel located below caved panel of upper seam,
 shape of the goaf being almost square.
was conceived. Conceptual model alogwith location of
bore holes is shown in Figure 2.
Face
seam and developments of RVIIA seam whereas air
entering through ‘D’ shaft is used for ventilation of
isolation stoppings of sealed Longwall Panel of RVII
seam and Longwall panel AW1 of RVIIA seam. Air
enters through ‘D’ shaft into RVIIA seam flows along
shaft level, 1 L north sump, 0 dip and reaches to bottom
gate of AW1 longwall panel. Return air of AW1 flows
along top gate, 0 rise and joins the main return flowing
along 1st rise and No 1 incline.
973
974
PROCEEDINGS OF THE 7TH INTERNATIONAL MINE VENTILATION CONGRESS
Table 1. Summary of results of action taken during different phases of controlling fire with observations
Ph.
No
Period
No of
days/ panel
condition
I
01.09.99
to
10.09.99
9
Sealed
II
11.09.99
to
12.09.99
2
Opened
III
13.09.99
to
27.09.99
14
Sealed
IV
27.09.99
to
09.10.99
V
10.09.99
to
28.11.99
14
Sealed
29.11.99
to
08.12.99
10
Opened
VI
VII
9.12.99
to
13.03.99
12
Opened
94
Sealed
Bore
Hole
available
Action taken
1, 2 & 3 Injection of LN2 through
BH Nos. 1, 2 & 3
-do-
-
Injection of LN2 through
1, 2, 3 boreholes and Dynamic
& 4 balancing of pressure
around AW1 panel
Chamber
method
of
ventilation and Injection
of LN2 through BH4
Dynamic
balancing
1, 2, 3, around
AW1
and
4 & 5 Injection of LN2 through
bore-holes.
Chamber
method
of
ventilation and Injection
-do- of LN2 through BH4 & 5
-do-
Dynamic balancing of
pressure and Injection of
LN2 through boreholes
selected on the basis of
O2 in the borehole.
Further LN2 inj. rate was
controlled so as to keep
the goaf only slightly
positive with respect to
atmosphere
In the Figure the zone marked A is considered well
compacted through which no or little leakage of air is
possible. Hence it is not very risky from heating point of
view. The area marked B is only partially compacted
which may allow slight leakage of air. The area under C
is by far least compacted zone allowing leakage of air
which may lead to spontaneous heating The crushing
along the boundary of this zone may further enhance the
chances of heating. On the basis of this model a few
additional bore holes viz. 11, 12, 13 & 14 were drilled
in zone C to facilitate inertisation and plugging this
highly sensitive area by injection of high pressure high
stability nitrogen foam.
IDENTIFICATION OF LOCATION OF SEAT OF FIRE
To deal with fire identification of its location is very
important. However, in most cases identification of
Goaf environment at
end of the Day
O2 % CO Tem.
0C
ppm
12
Nil
26
19
400
-
1.9
30
26
-
1400
-
1.9
Nil
26
-
2200
-
Amount
of LN2
flushed,
ltrs.
51,123
Observations
Environment of goaf
behind stoppings and bore
holes i.e. only closed to
the face could be assessed
Ventilation of the face
could not be controlled
because face was abot
90% filled with water
Environment of total goaf
was monitored by using
1,05,915 number of bore holes
67,046
Ventilation sys-tem was
disturbed on 7.10.99 and
LN2 supply was intrupted.
Environment of total goaf
was monitored by using
2,31,965 number of bore holes
35,427
Chamber
method
of
ventilation
could
be
maintained upto 5.12.99
Environment of total goaf
was monitored by using
number of bore holes and
consumption of LN2 was
reduced
0.2
Nil
<10
1,74,097
exact location of seat of fire is rather difficult. In case of
fire in AW1 panel, due to geo-mining condition the
problem become very complex. As per example the fire
could be in the same (RVIIA) or in the upper
seam(RVII). Fire in RVIIA seam may be due to:
 Spontaneous heating in the heap of broken coal lying
in the goaf.
 Non dissipation of heat generated during induced
blasting in the panel.
 Delay in main fall allowing free path for air in the
goaf.
But the possibility of heating in the upper seam
(RVII) also could not be ruled out due to following
reasons:
1. The W1 panel in RVII seam having a history of fire is
just above the AW1 panel with a parting of only 40.0
m. Toxic gases and even smoke due to fire in this
panel may easily leak to AW1 panel giving false
indication of fire in the bottom seam.
CONTROL OF FIRE IN A LONGWALL PANEL UNDER SHALLOW COVER
The System requires
1. Ventilation Survey data in the mine
2. Conversion of an area into Chamber by closing cross
connections.
3. Axial flow fan of desired capacity.
4. Two regulators of variable aperture, R1 & R2 as
shown in Figure 3.
The function of R1 is to create pressure difference
across the face to achieve optimum flow of air at the
face and minimum leakage of air into goaf. Similarly R2
is to raise the pressure of the chamber to desired level so
that goaf pressure is slightly positive with respect to
atmosphere.
Before finalising the design of the arrangement for
implementation of Chamber method of ventilation a
limited ventilation survey was carried out in the mine
from the mouth of Incline 2 to bottom gate of AW 1
panel along intake via drift. Results showed that the
cumulative pressure drop upto bottom gate was 120 Pa.
Accordingly, design of chamber method of ventilation
was worked out and implemented around AW1 panel.
In this system of ventilation a chamber is formed by
closing cross cut connections between 0 rise and 1st rise
as shown in Figure 3.
0 Rise
1 Rise
R2
Top Gate
BH 5
R1
Goaf
Bottom Gate
X
D
Keeping the above arguments in mind following
strategies were worked out to control the fire and its
quick suppression if it gets aggravated again after
reopening on 14.03.2000.
1. Reduction in air leakage into goaf either from bottom gate
side or from upper seam or surface with adequate air
quantity at the face. Monitoring of status of fire through
boreholes by maintaining pressure of the boreholes
slightly positive by adoption of a ventilation arrangement
called Chamber method of ventilation, which has been
discussed in later chapter in the paper.
2. Plugging of air path from top and bottom gate sides
particularly along the barrier and create N2 bank in the
floor of the goaf. For this purpose High pressure high
stability Nitrogen foam technology comprising foam
generating machines and foaming agent from M/s
Technovent PTY Ltd, Czech Republic was used. Another
foaming solution from M/s Control system, Kolkata,
India was also used when the foaming agent from Czech
was exhausted. Details of high pressure high stability
foam technology has been discussed in the later chapters.
3. To keep good environment at face safe and to maintain
CO level within permissible limit even when
concentration of CO in the goaf became high, air from
Chamber method of ventilation
It is a ventilation arrangement which is superimposed
on the main ventilation system to neutralise or reduce
the cumulative pressure drop from desired area in the
mine measured from surface. In case of a longwall panel
at shallow depth or in multi seam working air leakage
may take place in uncontrolled manner, depending upon
size of cracks & fissures and suction pressure created by
the fan. Continuos feeding of air either through bottom
gate or surface in a place where rate of dissipation of
heat is poor, may result in onset of spontaneous heating
in the goaf. To overcome this problem Chamber method
of ventilation may be adopted with benefit.
D
ACTION TAKEN DURING 8th PHASE
goaf was discharged to atmosphere through boreholes
close to the zone of high CO concentration.
D
2. Leakage of air through surface cracks to the goaf due
to suction pressure created by the main fan may lead
to heating.
3. Huge amount of coal lying on the floor in the panels
and its possible oxidation after dewatering of the goaf.
Further, the panels W1 , W2 , W3 & W4 in RVII seam
may be inter connected and migration of CO from any one
of the panels to AW1 panel is possible. Presence of air
leakage path from surface through cracks to any segment
of the four panels stated earlier may extend upto AW1
panel and seat of fire may be any where in this path.
Considering the possibilities and situations mentioned
above in both the seams it was very difficult to decide
the exact location of seat of fire.
To locate the seat of fire further investigations were
carried out with particular emphasis on following.
1. Study of concentration gradient of CO in RVII &
RVIIA seams. All boreholes samples results
showed that CO concentration was always higher in
bottom seam than in top seam clearly indicating that
location of fire was in bottom seam.
2. Study of pressure gradient along the panels in both the
seams indicated favourable condition for flow of CO
from lower to upper seam. The concentration of CO is
lower in upper seam than that in lower seam is again a
clear indication of existence of fire in the lower seam.
The above analysis more or less confirmed that
location of seat of fire was in AW 1 panel. Exact
location of fire could be established only after
assessment of results of foam infusion through different
bore holes, discussed in later chapters.
975
Auxiliary Ventilation System
1 L North
Chamber fan
‘D’ Shaft
Figure 33.
: Layout
of Chamber
system around
AW1 Panel, RVIIA
seam
Figure
Layount
ofventilation
Chamber
ventilation
system
around AW1 Panel, RCIIA seam
976
PROCEEDINGS OF THE 7TH INTERNATIONAL MINE VENTILATION CONGRESS
The chamber comprises top and bottom gates, 0 rise
and the face. A forcing fan of suitable capacity is
installed at 1L north on intake side of the chamber. The
specification of the fan is worked out on the basis of
requirement of the air quantity in the chamber
considering pressure of the chamber to be maintained
slightly higher with respect to atmosphere and to create
pressure difference sufficient for optimum airflow rate
at the face with minimum leakage of air into goaf. In
this system there are two regulators namely R1 and R2
in 0 rise. Results of performance studies of chamber
ventilation system are furnished below:
 Fan make
:
Voltas
 Fan type
:
PV-160
 Fan pressure
:
314.0 Pa
 Air quantity handled by fan
:
41 m3/s
 Pressure of chamber measured at :
(+) 98.0 Pa
top gate
 Pressure drop across R1
:
8.0 pa
 Air quantity at face
:
6.70 m3/s
 Air quantity at R1
:
20.0 m3/s
 Pressure of borehole No5
:
(+) 20.0 Pa
 Air quantity at bottom gate
:
7.43 m3/s
 Leakage of air into goaf
:
0.76 m3/s
 Pressure developed by main fan :
785.0 pa
 Air quantity handled by main fan :
90.0 m3/s
High pressure nitrogen foam
Injection of N2 in liquid or gaseous form through
borehole may not yield the desired result in open goaf
because during injection, pressure at the bottom of
borehole is high and N2 comes out from the goaf in a
very short time following low resistance path, possibly
along the roof. To reduce the requirement of Nitrogen
and for plugging leakage path, injection of high pressure
nitrogen foam was found very effective in controlling
fire in AW1 longwall panel. Details of the foam
technology are given in reference (4).
Foam was generated with 3% solution of foaming
agent using a Foam generator connected to a trolly
mounted PSA type nitrogen generator having a capacity
of 300 Nm3/hr at 98% purity. The arrangement is shown
in Figure 4.
The efficacy of this technology depends upon
 Location of borehole used for infusion of foam.
 Amount of foam injection
To find the best results of foam injection, foam was
injected through different bore holes located in different
zones of the goaf. It has been stated earlier that on the
basis of compaction, the goaf may be divided into three
zones viz., A, B and C. A is compact zone, B is critical
zone and C is free from roof fall. From Figure 2 it can
be seen that bore holes No 1, 2, 3, 4 & 11 are all located
in zone C and bore hole No 5 lies in zone B. Effect of
foam injection through different bore holes are
discussed below:
Case I : Injection of foam through BH No. 1
Nitrogen foam generated from 3% solution of
foaming agent with 98% pure N2 from PSA type
nitrogen generator was injected through BH No. 1. 100
Kg of foaming agent which is equivalent to 200 m3 of
foam was used. Environment inside goaf was monitored
through boreholes by multi gas analyser. Results are
furnished in Table below.
Date
15.3.2k
BH
NO.
1
3
4
AFC,
U/G
Time
hrs.
12.20
13.15
12.05
13.10
CO2,
%
5.59
3.03
2.64
1.37
O 2,
%
4.49
7.26
12.6
17.2
CO,
ppm
Nil
Trace
Nil
Nil
The table revealed that O2 % in BH 1 is 4.49% where
as O2 % in BH 4 is 12.60%. Hence injection of foam
through BH-1 does not plug air space which is extended
up to installation chamber. Hence injection through
BH-1 alone was not very effective.
Figure 4. Arrangements for injection of foam through
boreholes
Case II: Injection of foam through BH Nos. 1 &2
On 17.3.2k foam was injected through Borehole Nos.
1 & 2. Foam generated from 100 Kg of foaming agent
was injected into goaf through BH-1 and 300 Kg of
CONTROL OF FIRE IN A LONGWALL PANEL UNDER SHALLOW COVER
foam in similar concentration was injected through BH
2. Environmental condition of goaf was monitored
through B H No. 1 & 4. Results are given below.
Date
17.3.2k
BH
NO
1
4
Time
hrs.
21.00
21.10
O2,
%
3.97
16.9
CO,
ppm
Nil
38
From the result it is clear that percentage of O2 in BH
4 is increasing even after injection of foam through BH
1 & 2. It clearly indicated that injection of foam
through these boreholes was also not very effective.
of gas concentration seat of fire appears to be around
BH 11 in AW1 panel, RVIIA seam and probably it is
between BH11 and installation chamber. To investigate
this problem further drilling of three boreholes around
BH 11 connecting to installation chamber of AW1 panel
were proposed. Boreholes viz., 12, 13 & 14 were drilled
near junction of installation chamber of AW1 panel and
top gate as shown in Figure 2 and gas sample drawn
through these boreholes were analysed. Results are
furnished in table below:
Date
26.3.2k
Case III: Injection of foam through BH Nos. 4, 5&11
On 18.03.2k foam generated from solution of 150 Kg,
75 Kg and 150 Kg was injected through borehole Nos.
4, 5 & 11 respectively and environmental condition of
goaf was monitored before and after injection. The
results are furnished in table below.
Date
18.3.2k
19.3.2k
20.3.2k
BH
Time O2, %
CO,
Face
NO.
hrs.
ppm
1
05.40
9.0
Nil
Nil
5
05.45
12.9
62
Nil
11
06.20
13.6
110
Nil
1
10.15
10
Nil
Nil
11
10.30
13.8
110
Nil
2
10.40
16.9
13
Nil
No communication through borehole No.
4, 5 & 11 after foaming
1
23.30
1.5
8
Nil
2
23.45
17.8
19
Nil
5
00.00
17.0
133
18
From the table it can be seen that O2 concentration is
high through out the goaf except near borehole No.1.
Case IV : Injection of foam and LN2 through BH No. 11
On 21.3.2k, foam infusion was done through Bore
hole No 11 200 Kg of foaming agent was used. Further,
10 K litres of LN2 was injected through borehole No. 5
and environmental condition of goaf was monitored
through boreholes. Results of the monitoring are
furnished in table below.
Date
22.3.2k
BH
NO.
2
4
11
O2, %
7.7
12.1
6.8
CO, ppm
21
0
1200
The table reveales that CO in BH 11 is 1200 ppm and
it was gradually rising even after injection through
different boreholes in different quantity. From the study
977
01.4.2k
BH
NO
12
13
5
13
14
Time
hrs.
10.00
10.30
18.30
18.45
18.50
O2,
%
4
11.2
7.5
5.27
4.52
CO,
ppm
201
1200
10800
10375
10900
From the above results location of fire was confirmed
to be in the installation chamber of AW1 panel in top
gate side between borehole No. 13 and 14.
Discharging CO into atmosphere through borehole
When CO at face increased from permissible limit,
pressure of the chamber was increased by closing
regulator R2 underground and boreholes 5, 2 & 3 were
opened to allow discharge of goaf air to atmosphere.
However, care was taken to see that fresh air from
longwall face did not leak into goaf. For this purpose
LN2 injection through borehole No 12 & 13 at the same
rate of air discharge was maintained. This measure
proved effective.
Control of fire
After confirmation of location of fire, Indian protein
foam was injected through boreholes No. 12,13&14
alternately. Foam generated from 200 to 800 kg of
protein base foaming chemical of Indian origin
(procured from M/s Control system, Kolkata) was
injected daily using trolly mounted PSA type nitrogen
generator at the rate between 200 to 220Nm3/hr and
purity 98%. This was supplemented with injection of
about 150 liters/h of LN2 infusion through nearest to
aforesaid borehole. Further, as stated earlier chamber
method of ventilation was adopted around AW1 panel
to make the chamber slightly positive with respect to
atmosphere as well as the W1 & W2 panel in RVII
seam and provided air quantity at face in the range of
6.0 to 12.0 m3/s at the pressure drop across the panel
between 80 and 210 Pa. Environmental condition of the
goaf was monitored by air sampling through borehole
no. 1, 2, 3 & 5. Results of all these measures were very
encouraging as can be seen from the Figure5. Fire was
brought under control. The panel was finally reopened
on 14th march 2000. Since then it is running smoothly
and producing about 3000 tonnes of coal per day.
978
PROCEEDINGS OF THE 7TH INTERNATIONAL MINE VENTILATION CONGRESS
12000
1000
Injection of foam & LN2 through
BH Nos. 1, 2, 4 & 11
Nitrogen Foam, Kg
900
Injection of foam & LN2 through
BH Nos. 12, 13 & 14
10000
800
CO
700
8000
CO, ppm
LN2, ltr/hr
6000
600
500
400
4000
300
200
2000
100
Series1
Series2
5/6/00
5/4/00
5/2/00
4/30/00
4/28/00
4/26/00
4/24/00
4/21/00
4/15/00
4/13/00
4/9/00
4/11/00
4/7/00
4/3/00
4/1/00
3/28/00
3/26/00
3/23/00
3/21/00
3/18/00
3/15/00
0
3/13/00
0
Series3
Figure 5 : Variation of CO in the goaf of AW1 panel of 1 & 2 Incline with injection of
LN2 & Nitrogen foam
Figure 5. Variation of CO in the goaf of AW1 panel of 1 & 2 Incline with injection of LN 2& Nitrogen foam
CONCLUSIONS & RECOMMENDATIONS
Conclusions that emerged during dealing with fire in
AW 1 panel are as below:
1. Reduction in air leakage into goaf either from bottom
gate side or from upper seam or surface even when
adequate air quantity flows through the face by
Application of Chamber method of ventilation around
AW1 panel was very effective in control of fire.
2. Monitoring of status of fire through boreholes by
maintaining pressure of the boreholes slightly positive
and analysing the air samples by Multi-gas Analyser
provided an accurate status of the fire affected area and
helped in locating the actual seat of fire.
3. Plugging of air path from top and bottom gate side
particularly along the barrier and creation of N2 bank in
the floor of the goaf by injection of high pressure high
stability N2 foam was found effective in
eliminating/reducing leakage of air to seat of fire.
4. Method to check flow of CO from seat of fire to face
by discharging of CO in the atmosphere through
boreholes when concentration of CO at the face is
exceeding the permissible limit was found quite
effective however, it must be worked out and executed
carefully and the amount of goaf air discharged must be
replaced by infusion of same amount of N2 into goaf
through bore hole.
Finally, after the advancement of the face to about
240 m, fire was brought under complete control. The
face is progressing smoothly and producing about 3000
tonnes of coal per day.
ACKNOWLEDGMENT
The authors express their sincere thanks to Director,
Central Mining Research Institute, Dhanbad for
granting permission to publish this paper, members of
Ventilation & Special Projects Discipline of CMRI and
Mine management for sincere cooperation in field
investigations and execution of the measures in
controlling fire. Further special thanks to Sri A. Ansari
of CMRI for field investigation and compilation of data.
Thanks are also due to Dr. V.Voracek., Czech Republic,
for valuable suggestions during Injection of foam.
The opinion express in this paper are those of authors
and not necessarily of CMRI.
REFERENCES
Bhowmick, B.C., Sahay, N., Ahamad, I. and Verma,
S.M.,
2000,
“Significant
improvement
in
effectiveness of nitrogen infusion technology for
control of fire by dynamic balancing of pressure - a
case study of powered support longwall face”, The
Canadian Mining and Metallurgical Bulletin, Vol. 93,
No. 1038, March, pp. 74-80
CMRI report on “Quick control of spontaneous heating
and early reopening of aw 1 longwall panel in 1 & 2
incline mine, jhanjra area, ECL”, 2000
McPherson, M. J., 1993, Subsurface ventilation and
environmental engineering. Chapman & Hall, London
Voracek V., 1994, “Usage of nitrogen foam for both
prevention and suppression of spontaneous
combustion of coal in Ostrava-Karvina coalfields”,
Proceeding of Workshop on Occupational safety and
environment protection in underground coal mining
Industry, Sczyrk, poland, October