The Positive Pressure Chamber

Austar Coal Mine & Joncris Sentinel Services

Austar Coal Mine

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

CO in PPM in the Upcast Shaft @ Pt 1

0

20

40

60

80

100

120

1-D

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2-D

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3-D

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4-D

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23-D

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24-D

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25-D

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26-D

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27-D

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CO

Serious Incident CO Readings – Air Free Basis Analysis

Air Free CO in PPM in the Upcast Shaft @ Pt 1

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

1-D

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2-D

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3-D

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4-D

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5-D

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6-D

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27-D

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AF CO

Serious Incident – CO Make

TailgateCO Make Ltrs/min

0

20000

40000

60000

80000

100000

120000

23-Dec 24-Dec 25-Dec 26-Dec 27-Dec 28-Dec 29-Dec

Serious Incident – Ratios

TailgateGrahams Ratio / Index of Carbon Monoxide

0

5

10

15

20

25

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50

23-Dec 24-Dec 25-Dec 26-Dec 27-Dec 28-Dec 29-Dec

Serious Incident – Gas

Tailgate Total Combustibles %

0

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25

23-Dec 24-Dec 25-Dec 26-Dec 27-Dec 28-Dec 29-Dec

Inertisation Attempt - GAG

The GAG Jet Engine Inertisation The GAG Jet Engine Inertisation

Sealing the Mine

Re-Entry Controls Gas Monitoring

BB Mains Return Monitor

ALARM: 10 ppm

CH

CO

4 ALARM: 0.5%

Monitor 10

O

CH

CO

CO

GAS

30%

19%

3%

50ppm

2 21%

2.5%

30ppm

4

L1

20%2

L2

ISG Gas Monitoring

Gas Monitoring System

1 : 4000

D.J OLLIFFE

5/1/04

Controls - Gas Monitoring

XX

X

XX

Re-Entry Experience Gas Levels

Pitfire/RECOVERYstages1:5000

19/2/04

D.J OLLI FFE

TCN-0800-SL4-PF0040-Stage 10 RecoveryStage 10 Recovery of Mine

A L L I A N C E

18% 02 0.3% CO20 ppm CO

3% 02 6% CO21000 ppm CO4% CH4

3% 02 5% CO20 ppm CO7% CH4

6% 02 5% CO20 ppm CO2% CH4

6% 02 4% CO20 ppm CO3.5% CH4

12% 02 4% CO27000 ppm CO0.5% CH4

Typical Gas analysis during re-entry :

Tube bundle and borehole readings

18% 02 0.3% CO20 ppm CO

Typical Gas analysis during re-entry :

Tube bundle and borehole readings

Re-Entry Experience The Physical Toll

Pitfire/RECOVERYstages1:5000

19/2/04

D.J OLLI FFE

TCN-0800-SL4-PF0040-Stage 10 RecoveryStage 10 Recovery of Mine

A L L I A N C E

Poly Pipe melted

MG Travel road: cables,poly pipe, O2 Rescuers melted

Coked roof coal

Charred Conveyor Belt Limit of

Exploration

Major Damage Found

Secondary Fire and Roof Fall Found

Fall of Ground in 6c/t

Conveyor Road flooded at 6c/t

CM Buried in SL5MG

Austar Coal Mine

Austar Coal Mine Complex

Top Coal Caving

Ventilation Network

101 Panel

200 MAINS

102 Panel

DD

VENTILATION DEVICE LEGEND LEGEND

80m3/s

25m3/s

35m3/s

70m3/s

70m3/s

140m3/s

35m3/s

Problem – Leaking Seals Combustion & Flammable Mixtures in Goaf Areas

T h e r m o t e k n i x VisIR 9:05:55 AM 16/08/2005 e : 1.00 Bg : 25.0°C

10.00

40.00

20.00

30.00Celsius

20.50

21.00

21.50

22.00

22.50

23.00

23.50

24.00

24.50

25.00

25.50

26.00

26.50

27.00

27.50

28.00

28.50

29.00

29.50

Spot 125.53

Spot 225.10

Spot 322.82

Area 1Max. Avg. Min.25.80 23.28 21.74

FACT:

1. All underground mine seals leak & breathe

2. Sealed and Active Goaves = High Risk

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

NORMAL:

1. Oxygen flow through seal2. Potential for spontaneous

combustion or explosive mix of gases

Oxygen Leakage into Chamber

8/

D.JOLLIFFE

1:4000

PROPOSED VENTILATION STAGE 1

VEN0501/1

TIER 1

NITROGEN INJ ECTION POINT

POSITIVE PRESSURE CHAMBER

Oxygen Leakage into Sealed Area

Oxygen Leakage into Sealed Area

PRESSURE BALANCE CHAMBER

Reduced Oxygen Leakage into Sealed Area POSITIVE PRESSURE CHAMBER

NIL Oxygen Leakage into Chamber or Goaf

x x

x x

x x

x x

BALANCE CHAMBER:

1. Oxygen flow through chamber2. Potential for spontaneous

combustion or explosive mix of gases

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 ManagementCurrent Mining Practice - Reactive

• Monitor for changes in the potential explosive atmosphere or for signs of spontaneous combustion

SPONTANEOUS COMBUSTION OR

EXPLOSION

SEAL • Build a seal

• React to explosive atmosphere or heating – IF POSSIBLE!!

• Seal leaks or breathes resulting in oxygen ingress through or around the seal

LEAKAGE

Risk Management

CHAMBER The Pressure Balance Chamber System - Proactive• Build a chamber

• Eliminate Oxygen ingress into the goaf

• Inject Nitrogen into chamber (+’ve pressure)

• Encourage nitrogen ingress into the goaf

• Inert goaf which:

2. Eliminates risk of explosive atmosphere

1. Eliminates risk of spontaneous combustion (heat)

SPONTANEOUS COMBUSTION OR

EXPLOSION

Significance

• There are seven (7) prescribed MAJOR HAZARDS for an underground coal mine.

TRANSPORTINRUSH

FIRE & EXPLOSION

SPONTANEOUS COMBUSTION

COAL DUST

OUTBURSTSTRATA

• 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.