1. Austar Coal Mine
The Positive Pressure Chamber Austar Coal Mine & Joncris Sentinel Services
Proactive: - Spontaneous & Combustible Gas Management - Seal Design

2. What are we up against?

3. 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

4. The Oxidation Process Temperature vs Time

5. Serious Incident

6. Serious Incident Tube Bundle Monitor CO Readings

7. Serious Incident CO Readings – Air Free Basis Analysis

8. Serious Incident – CO Make

9. Serious Incident – Ratios

10. Serious Incident – Gas

11. Inertisation Attempt - GAG
The GAG Jet Engine Inertisation

12. Sealing the Mine

13. Re-Entry Controls Gas Monitoring

14. Re-Entry Experience Gas Levels
18% 02
0.3% CO2
0 ppm CO
3% 02
6% CO2
1000 ppm CO
4% CH4
5% CO2
7% CH4
6% 02
2% CH4
4% CO2
3.5% CH4
12% 02
7000 ppm CO
0.5% CH4
Typical Gas analysis during re-entry :
Tube bundle and borehole readings

15. Re-Entry Experience The Physical Toll
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

16. Austar Coal Mine

17. Austar Coal Mine Complex

18. Top Coal Caving

19. Ventilation Network
80m3/s
25m3/s
35m3/s
70m3/s
140m3/s

20. Problem – Leaking Seals Combustion & Flammable Mixtures in Goaf Areas
FACT:
All underground mine seals leak & breathe
Sealed and Active Goaves = High Risk

21. Effects of Leaking Seals

22. Effects of Leaking Seals

23. 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

24. Solution to Leaking Seals - Positive Pressure Chamber Concept
NORMAL:
Oxygen flow through seal
Potential for spontaneous combustion or explosive mix of gases
BALANCE CHAMBER:
Oxygen flow through chamber
Potential for spontaneous combustion or explosive mix of gases
POSITIVE PRESSURE CHAMBER:
Nitrogen injected into the chamber
Positive pressure maintained within the chamber
IMPOSSIBLE FOR OXYGEN TO FLOW THROUGH CHAMBER

25. Positive Pressure Effects
Dramatic reduction in combustible (explosive) gases.
Inert and safe goaf (unable to promote spontaneous combustion).
NIL oxygen ingress through the chamber.

26. Positive Pressure Chamber
70m3/hr Nitrogen Inertisation Unit
Nitrogen Injection Location PSI Structural Seal PSI Flexible Seal

27. Positive Pressure System
Nitrogen Injection Sites
1936m3/hr Nitrogen Plant. Sufficient to maintain positive pressure across 24 different Positive Pressure Chambers.

28. Sealing Effectiveness – TG End

29. Sealing Effectiveness – MG End

30. $ 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

31. SPONTANEOUS COMBUSTION OR EXPLOSION
Risk Management
Current Mining Practice - Reactive
SEAL
Build a seal
Seal leaks or breathes resulting in oxygen ingress through or around the seal
LEAKAGE
React to explosive atmosphere or heating – IF POSSIBLE!!
Monitor for changes in the potential explosive atmosphere or for signs of spontaneous combustion
A goaf is the area in underground coal mining which has had the coal extracted and is abandoned, left to collapse and sealed off. The areas are sealed off to preventt:
people from entering,
gases from escaping,
the ingress of oxygen and providing conditions for spontaneous combustion or an explosive mixture of gases.
The seals used to prevent this are designed, manufactured, erected and maintained to strict standards.
However,
FACT: a flow path exists across all of these seals and that they “breathe in and out”. This is caused by pressure differentials across the seals. Alternately, flows through the coal around the seals.
RISK: oxygen is able to enter the sealed off area providing conditions suitable for spontaneous combustion, explosive mixture of gases and the potential for an explosion.
● Conventional ventilation strategies only focus on high-resistance seals which does not prevent the flow of oxygen.
SPONTANEOUS COMBUSTION OR EXPLOSION

32. SPONTANEOUS COMBUSTION OR EXPLOSION
Risk Management
The Pressure Balance Chamber System - Proactive
CHAMBER
Build a chamber
Inject Nitrogen into chamber (+’ve pressure)
1. Eliminates risk of spontaneous combustion (heat)
Eliminate Oxygen ingress into the goaf
Encourage nitrogen ingress into the goaf
2. Eliminates risk of explosive atmosphere
Inert goaf which:
The positive pressure chamber system eliminates two sides of the fire triangle.
This is achieved by eliminating the oxygen from entering the goaf and forming an explosive mixture of gases or conditions for accelarted oxidation of the remaining coal to occur.
This in turn prevents the coal from heating and supplying the heat source.
SPONTANEOUS COMBUSTION OR EXPLOSION

33. Significance
COAL DUST
TRANSPORT
SPONTANEOUS COMBUSTION
INRUSH
And put a few holes in another one.
The Positive Pressure Chamber has effectively ELIMINATED one of these seven MAJOR HAZARDS.
STRATA
OUTBURST
FIRE & EXPLOSION
A goaf is the area in underground coal mining which has had the coal extracted and is abandoned, left to collapse and sealed off. The areas are sealed off to prevent:
people from entering,
gases from escaping,
the ingress of oxygen and providing conditions for spontaneous combustion or an explosive mixture of gases.
The seals used to prevent this are designed, manufactured, erected and maintained to strict standards.
However,
FACT: a flow path exists across all of these seals and that they “breathe in and out”. This is caused by pressure differentials across the seals. Alternately, flows through the coal around the seals.
RISK: oxygen is able to enter the sealed off area providing conditions suitable for spontaneous combustion, explosive mixture of gases and the potential for an explosion.
● Conventional ventilation strategies only focus on high-resistance seals which does not prevent the flow of oxygen.
There are seven (7) prescribed MAJOR HAZARDS for an underground coal mine.

34. History does not need to repeat itself.
In Summary
The Positive Pressure Chamber
History does not
need to repeat itself.
World First Innovation
Ingress of O2 eliminated
Oxidation halted
Fire / explosive zone neutralised
Risk eliminated