The Positive Pressure Chamber Austar Coal Mine

1
The Positive Pressure ChamberAustar Coal Mine
Joncris Sentinel Services
Austar Coal Mine
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
15
Re-Entry Experience The Physical Toll
16
Austar Coal Mine
17
Austar Coal Mine Complex
18
Top Coal Caving
19
Ventilation Network
20
Problem Leaking Seals Combustion
Flammable Mixtures in Goaf Areas
21
Effects of Leaking Seals
22
Effects of Leaking Seals
23
Conventional Thinking

• Airflow past Seals is governed by the well known
  relationship PRQn
• 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• We as an industry continue with the old outdated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 20PSI
Structural Seal 5PSI
Flexible Seal
27
Positive Pressure System
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
31
Risk Management
Current Mining Practice - Reactive
SPONTANEOUS COMBUSTION OR EXPLOSION
32
Risk Management
The Pressure Balance Chamber System - Proactive

• Build a chamber

• Eliminate Oxygen ingress into the goaf

• Inert goaf which

33
Significance
COAL DUST
TRANSPORT
SPONTANEOUS COMBUSTION
INRUSH
FIRE EXPLOSION
OUTBURST
STRATA

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

34
In Summary
The Positive Pressure Chamber