Transcript The Positive Pressure Chamber Austar Coal Mine & Joncris

Austar Coal Mine
The Positive
Pressure Chamber
Austar Coal Mine & Joncris Sentinel
Services
Proactive:
- Spontaneous & Combustible Gas Management
- Seal Design
What are we up against?
Our Challenge
• Understand and Manage Spontaneous
Combustion and Flammable Atmospheres
in Active and Sealed Goaves
• Utilise Proactive rather than Reactive Risk
Management
• Eliminate the Hazard rather than accept
the inevitable and use Reactive
Management to reduce, control or contain
the potential Catastrophic Consequences
The Oxidation Process
Temperature vs Time
Serious Incident
Serious Incident
Tube Bundle Monitor CO Readings
C O in P P M in th e U p c a s t S h a ft @ P t 1
120
100
80
60
40
20
0
27-D ec
26-D ec
25-D ec
24-D ec
23-D ec
22-D ec
21-D ec
20-D ec
19-D ec
18-D ec
17-D ec
16-D ec
15-D ec
14-D ec
13-D ec
12-D ec
11-D ec
10-D ec
9-D ec
8-D ec
7-D ec
6-D ec
5-D ec
4-D ec
3-D ec
2-D ec
1-D ec
CO
Serious Incident
CO Readings – Air Free Basis Analysis
A ir F re e C O in P P M in th e U p c a s t S h a ft @ P t 1
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
27-D ec
26-D ec
25-D ec
24-D ec
23-D ec
22-D ec
21-D ec
20-D ec
19-D ec
18-D ec
17-D ec
16-D ec
15-D ec
14-D ec
13-D ec
12-D ec
11-D ec
10-D ec
9-D ec
8-D ec
7-D ec
6-D ec
5-D ec
4-D ec
3-D ec
2-D ec
1-D ec
AF C O
Serious Incident – CO Make
Tailgate
CO Make Ltrs/min
120000
100000
80000
60000
40000
20000
0
23-Dec
24-Dec
25-Dec
26-Dec
27-Dec
28-Dec
29-Dec
Serious Incident – Ratios
Tailgate
Grahams Ratio / Index of Carbon Monoxide
50
45
40
35
30
25
20
15
10
5
0
23-Dec
24-Dec
25-Dec
26-Dec
27-Dec
28-Dec
29-Dec
Serious Incident – Gas
Tailgate
Total Combustibles %
25
20
15
10
5
0
23-Dec
24-Dec
25-Dec
26-Dec
27-Dec
28-Dec
29-Dec
Inertisation Attempt - GAG
The GAG Jet Engine Inertisation
Sealing the Mine
Re-Entry Controls
Gas Monitoring
C o n tro ls - G as M onitoring
X
X
X
X
X
Re-Entry Experience
Gas Levels
18% 02
0.3% CO2
0 ppm CO
Tube bundle and
borehole readings
12% 02
4% CO2
7000 ppm CO
0.5% CH4
6% 02
4% CO2
0 ppm CO
3.5% CH4
Typical Gas analysis
during re-entry :
6% 02
5% CO2
0 ppm CO
2% CH4
3% 02
5% CO2
0 ppm CO
7% CH4
3% 02
6% CO2
1000 ppm CO
4% CH4
Re-Entry Experience
The Physical Toll
CM Buried in SL5MG
Poly Pipe
melted
MG Travel road:
cables,poly pipe,
O2 Rescuers
melted
Conveyor Road
flooded at 6c/t
Coked roof coal
Charred Conveyor
Belt
Secondary Fire
and Roof Fall
Found
Limit of
Exploration
Fall of Ground in
6c/t
Major Damage Found
D.JOLLIFFE
Austar Coal Mine
Austar Coal Mine Complex
Top Coal Caving
Ventilation Network
25m3/s
R
t
as
a ll le
B Ho m
4
43
R
140m3/s
ft
ha UC
3m
sedhole
isu
D ast 2m
all 4 5
B
R
C
le
T o
H H
le m
ab 56
4
80m3/s
70m3/s
S
44
3.
le
be Ho
T u le
m
d .7
un 35
4
p
le
om Ho
le
C
m HT Ho
ft
ir
e l 2O
A 48
h a /C s H
le m
4
S D D ie n ic ,
ab 1
C 45 4.
e
m
3m
o lc 5 5
S
45
4 r
a te e n
g
eW
D it ro5 m
N 5
& 4
B
70m3/s
2 0 0 M A IN S
1 01 Panel
35m3/s
2
0
1
n
el
LEG EN D
V E N T IL A T IO N D E V IC E L E G E N D
Pa
35m3/s
R
1 02 Panel
D
Problem – Leaking Seals
Combustion & Flammable Mixtures in Goaf Areas
Celsius
40.00 30.00
29.50
29.00
Spot 2
25.10
28.50
Spot 3
22.82
28.00
27.50
27.00
26.50
26.00
25.50
25.00
24.50
24.00
23.50
23.00
22.50
22.00
21.50
21.00
FACT:
1. All underground
mine seals leak &
breathe
2. Sealed and Active
Goaves = High
Risk
Spot 1
25.53
Area 1
Max. Avg. Min.
25.80 23.28 21.74
Effects of Leaking Seals
Effects of Leaking Seals
Conventional Thinking
• Airflow past Seals is governed by the well known relationship:
P=RQn
• Q = Quantity (measured in m3/s varies from Q2 to Q depending on
the nature of the flow - laminar or turbulent)
• R = Resistance (measured in Gauls varies from 50,000 to 200
depending on Seal Integrity and more importantly the integrity of the
roof, floor and sides - rarely do we see this in the higher quartile)
• P = Pressure (measured in Pascals varies depending on Mine
Ventilation Pressure; Diurnal and Synoptic Barometric Pressure
variations with the latter having the largest impact)
• Seals erected pumped or sprayed during Diurnal Barometric Lows
will not be as effective as those erected during Higher barometric
pressure (try patching a leaking bicycle tyre with bubble gum)
• We as an industry continue with the old outdated Strategy and
spend Megabucks trying to increase Resistance
• This is re-active risk management and doomed to failure
Solution to Leaking Seals
- Positive Pressure Chamber Concept
Oxygen Leakage into
Sealed Area
Oxygen Leakage into
Chamber
NITROGEN INJECTION POINT
x
x
PRESSURE BALANCE CHAMBER
Oxygen Leakage into
Sealed Area
NORMAL:
1. Oxygen flow through seal
2. Potential for spontaneous
combustion or explosive
mix of gases
Reduced Oxygen Leakage into
Sealed Area
BALANCE CHAMBER:
1. Oxygen flow through chamber
2. Potential for spontaneous
combustion or explosive mix
of gases
x
x
x
x
NIL Oxygen
Leakage into
Chamber or Goaf
x
x
POSITIVE PRESSURE CHAMBER
POSITIVE
PRESSURE CHAMBER
POSITIVE PRESSURE
CHAMBER:
1. Nitrogen injected into the
chamber
2. Positive pressure
maintained within the
chamber
3. IMPOSSIBLE FOR OXYGEN
TO FLOW THROUGH
CHAMBER
Positive Pressure Effects
• Dramatic reduction in combustible (explosive) gases.
• Inert and safe goaf (unable to promote spontaneous combustion).
• NIL oxygen ingress through the chamber.
Positive Pressure Chamber
70m3/hr Nitrogen Inertisation Unit
Nitrogen Injection Location
20PSI Structural Seal
5PSI Flexible Seal
Positive Pressure System
Nitrogen
Injection Sites
1936m3/hr Nitrogen
Plant. Sufficient to
maintain positive
pressure across 24
different Positive
Pressure Chambers.
Sealing Effectiveness – TG End
Sealing Effectiveness – MG End
Implementation
 World First Innovation
 Eliminated one of the biggest risks to the mine
 Simple and safe
 Reliable & low maintenance (>99% availability)
 Proven:
– First trial September 2005 (70m3/hr)
– System has been running since September 2006 (1936m3/hr)
 Positive Pressure Chamber System Costs (large 1936m3/hr Unit):
– Infrastructure = $250,000 (including reticulation).
– Leasing and running = $0.07 per m3 of Nitrogen.
– Annual costs ~$1.2 million (continuous use at full capacity)
 Set the benchmark for managing risk of combustion / explosive
atmospheres in underground coal mining & Panel Sealing.
 Australia and world wide application and interest
Risk Management
Current Mining Practice - Reactive
•
Build a seal
•
Seal leaks or breathes
resulting in oxygen
ingress through or around
the seal
•
Monitor for changes in the
potential explosive
atmosphere or for signs
of spontaneous
combustion
•
React to explosive
atmosphere or heating
– IF POSSIBLE!!
SEAL
LEAKAGE
SPONTANEOUS COMBUSTION
OR EXPLOSION
Risk Management
The Pressure Balance Chamber System - Proactive
•
Build a chamber
•
Inject Nitrogen into
chamber (+’ve pressure)
Eliminate Oxygen ingress
into the goaf
Encourage nitrogen
ingress into the goaf
•
•
•
CHAMBER
Inert goaf which:
1. Eliminates risk of
spontaneous
combustion (heat)
2. Eliminates risk of
explosive atmosphere
SPONTANEOUS COMBUSTION
OR EXPLOSION
Significance
COAL
DUST
TRANSPORT
STRATA
INRUSH
OUTBURST
SPONTANEOUS
COMBUSTION
FIRE &
EXPLOSION
• There are seven (7) prescribed MAJOR HAZARDS for an underground coal mine.
• The Positive Pressure Chamber has effectively ELIMINATED one of these seven
MAJOR HAZARDS.
And put a few holes in another one.
In Summary
The Positive Pressure Chamber
History does not
need to repeat itself.