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The Role Of Gas Monitoring In The Prevention And Treatment Of Mine Fires

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The Role Of Gas Monitoring In The Prevention And Treatment Of Mine Fires Darren Brady Manager, OHECC Simtars Department of Mines and Energy Queensland s Coal Mine ... – PowerPoint PPT presentation

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Title: The Role Of Gas Monitoring In The Prevention And Treatment Of Mine Fires


1
The Role Of Gas Monitoring In The Prevention And
Treatment Of Mine Fires
Darren Brady Manager, OHECC Simtars Depart
ment of Mines and Energy
2
Queenslands underground coal industry, as a
whole, has arguably the best gas monitoring
systems in the world. Each mine utilises real
time, tube bundle and onsite ultra fast gas
chromatograph systems.
3
(No Transcript)
4
Queenslands Coal Mine Explosions
  • YEAR MINE LIVES LOST TYPE OF EXPLOSION
  • 1921 Mount Mulligan 75 Gas and dust
  • 1928 Redbank 4 Gas
  • 1936 Hart's Aberdare 4 Gas
  • 1945 Ebbw Vale No 3 4 Gas
  • 1954 Aberdare Extended 2 Gas
  • 1972 Box Flat 17 Gas and dust
  • 1975 Kianga No 1 13 Gas and dust
  • 1986 Moura No 4 12 Gas and dust
  • 1994 Moura No 2 11 Gas

5
  • These systems are the result of nearly 20 years
    of ongoing development and follow recommendations
    from inquiries into explosions at underground
    coal mines in Queensland and subsequent changes
    to mining legislation.

6
  • Queenslands mining legislation has specific
    requirements for mine gas monitoring but there is
    no requirement for all three techniques.

7
  • Industry has however recognised the need for all
    three and adopted this as a standard, resulting
    in mines generating over sixty thousand gas
    results each day.

8
  • Dedicated software packages have been developed
    to assist in the interpretation of the large
    volume of results generated.
  • Automated monitoring systems are programmed to
    alarm for gas concentrations, gas ratios and
    explosibility.

9
Early Detection
  • Early detection of a problem is the key to
    successfully dealing with it!
  • Early detection can only be achieved if routine
    monitoring is being conducted, otherwise how do
    we know if something has changed?

10
Why Three Techniques?
  • Must consider what hazard we are trying to detect
    and manage.
  • Each technique will only address particular
    hazards.
  • All hazards addressed when a combination of
    systems is used.

3?
11
Real Time Monitoring
  • Real time sensor systems (telemetric systems) are
    ideal for telling us what is happening now.
  • Sensors are exposed to the harsh underground
    environment which is not ideal for precise
    analytical measurements.
  • Looking to detect step changes, such as the onset
    of a fire, a sudden increase in a seam gas in the
    general body or reduction in oxygen.

12
Real Time Monitoring
  • Limited measuring ranges
  • CO often only capable of being measured up to
    50ppm
  • CH4 to 5
  • CO2 to several percent.
  • In a major incident these sensors may quickly
    reach full scale and be unable to return a true
    indication of the concentrations.

13
Real Time Monitoring
  • Require the presence of oxygen to work and are
    therefore unsuitable for monitoring areas of low
    oxygen concentration such as sealed or non
    ventilated goaves.

14
Tube Bundle
  • Very good analytical equipment is available and
    can be housed in dedicated air conditioned rooms
    on the surface with the samples dried and passed
    through particulate filters prior to entering the
    analyser.
  • Suited to long term trending.
  • Most systems measure O2, CH4, CO2 and CO.

15
Tube Bundle
  • To get this improved stability and analytical
    capability, the immediate availability of the
    results is sacrificed.

16
Tube Bundle
  • Depending on the number of tubes in the system
    and the programmed sampling sequence, each point
    may only be analysed once every thirty to sixty
    minutes.
  • Because the samples need to be drawn to the
    surface for analysis the data being generated can
    be from samples collected from over an hour
    before.
  • not suitable for the instantaneous detection of
    an incident such as a fire

17
Tube Bundle
  • Best technique for long term trending of CO, and
  • CO Make because it can measure CO down to 1ppm
    and has long term stability and frequent sampling.

18
Tube Bundle
  • Best system for automated monitoring of
    explosibility of an area, so long as a fire or
    heating doesnt exist.

19
Tube Bundle
  • Only CO presents problems with measuring range
  • -most systems can only measure to 1000ppm.

20
Maintenance
  • Too often the maintenance of the tubes is
    overlooked.
  • Monthly leak testing identified in Australian
    Standard AS2290.3 Electrical equipment for coal
    mines Maintenance and overhaul Part 3
    Maintenance of gas detecting and monitoring
    equipment. is often not performed or not done as
    stated by the standard.
  • Following the standard an approximate draw time
    can be calculated as well as tube integrity
    tests.
  • Knowing draw times of each tube is critical to
    adequately assess what is happening and how long
    ago it actually happened in an emergency
    situation.

21
Gas Chromatography
  • Expands analysis to include gases crucial in the
    interpretation of spontaneous combustion events,
    particularly ethylene and hydrogen.

22
Gas Chromatography
  • Provides a complete analysis of the gases
    expected underground.
  • During a significant spontaneous combustion
    event, fire or following an explosion, only
    technique capable of accurately determining the
    explosibility of the underground environment.

23
Gas Chromatography
  • The ultrafast gas chromatographs allow the
    analysis of most the components expected
    underground in approximately 2 minutes.
  • The number of routine samples analysed has
    increased significantly allowing the mine to
    build a comprehensive background knowledge of the
    normal background composition of particular areas
    underground.
  • This increased sampling and analysis regime has
    also increased the chances of identifying any
    deviation from what is normal and allows early
    intervention to deal with any problems identified.

24
Gas Chromatography
  • Increased speed of analysis is invaluable during
    emergency situations, particularly when assessing
    the underground atmosphere for re-entry or during
    re-entry by mines rescue teams.
  • GC is onsite and can be operated by mine
    personnel.
  • No delay in determining the status underground
    while waiting for external providers to arrive or
    transporting samples away from site for
    laboratory analysis.

25
Comparison of Techniques
  • Real time sensors and tube bundle monitoring are
    at fixed locations, resulting in consistent
    automated sampling/measurement.
  • Much more data is collected by real time and tube
    bundle.
  • Samples collected underground for GC analysis,
    can show variations in results and trends
    attributed to not collecting samples from exactly
    the same locations, or poor sampling techniques.

26
Comparison of Techniques
  • Differences in the concentrations measured using
    the different techniques complicate the
    application of preset trigger levels.
  • Data for trends should only be generated by one
    technique and not an accumulation of results from
    different techniques.
  • Trends from different techniques should indicate
    the same pattern.
  • These measurement differences may be related to
    the techniques themselves or sometimes to
    calibration gases used for each technique.

27
Realtime vs Tube Bundle Oxygen
28
Realtime vs Tube Bundle Methane
29
Realtime vs Tube Bundle Carbon Monoxide
30
Tube Bundle vs GC Carbon Dioxide
31
Tube Bundle vs GC Oxygen
32
Tube Bundle vs GC Methane
33
Tube Bundle vs GC Carbon Monoxide
34
TARPS
  • Mines determine gas levels that they think should
    not be exceeded. Often these numbers are based on
    historical data collected from the monitoring
    systems.
  • To handle the large volumes of measurements made
    gas monitoring software has been developed that
    will automatically trigger a visual and audible
    alarm if one of the preset levels is exceeded.
  • Alarm set points can be different for every
    sample point.
  • These alarms activate what are known as Trigger
    Action Response Plans (TARPS) that have
    predetermined actions to follow.
  • These actions have been formulated to ensure that
    appropriate actions are taken to ensure the
    safety of workers and maintain control of the
    mine.

35
TARPS
  • Alarms can be generated from absolute
    concentrations, gas ratios or explosibility.
  • Most useful as an early warning, not as an alert
    to an emergency or a need to evacuate the mine.
  • When alerted early enough theres time to take
    remedial action to fix the problem.
  • Continual automated gas monitoring provides the
    best chance for early detection.

36
TARPS
  • The frequency and scope of monitoring is often
    included in the TARPS to ensure that the
    situation is not escalating or that the control
    measures are being effective.
  • It must be noted that if inertisation is one of
    the control measures called for in the TARPS, any
    monitoring to determine the effectiveness of the
    control must be done from a location indicative
    of the affected area and not just at the point of
    entry of the inertisation gas, otherwise
    assessment of the situation may not be indicative
    of the true state.

37
Assessment of Flammability
  • Complete analysis by GC of atmospheres generated
    during coal fires or heatings is critical
  • Its the only option to obtain an accurate
    assessment of the flammability status of the
    underground environment because of percent levels
    of carbon monoxide and hydrogen .
  • Failure to do so can lead to wrongly assessing
    the atmosphere to be inert, when in fact it could
    be explosive or fuel rich.

38
Explosibility
  • Gas Mix 1.26 H2, 10.45 O2, 78.85 N2, 3.93
    CH4, 1.82 CO, 3.66 CO2, 130ppm C2H4, 179ppm C2H6

39
Explosibility
  • Gas Mix 2.90 H2, 7.51 O2, 78.45 N2, 1.38
    CH4, 2.02 CO, 6.67 CO2, 480ppm C2H4, 1082ppm
    C2H6

40
Explosibility
  • Gas Mix 6.48 H2, 0 O2, 73.17 N2, 1.99 CH4,
    2.33 CO, 15.07 CO2, 1152ppm C2H4, 774ppm C2H6

41
Conclusions
  • As beneficial as they are, it must be remembered
    that monitoring systems on their own are not
    going to provide a successful solution to gas
    monitoring. Success depends on systems, processes
    and training built around the hardware and the
    way these systems are used.

42
Conclusions
  • An effective gas monitoring system includes real
    time sensors, a tube bundle system and a gas
    chromatograph.

43
Conclusions
  • Monitoring on its own will never prevent a mine
    fire or put it out if it starts. What it does
    offer is a means of identifying a problem early
    and subsequently an opportunity to take
    appropriate controlling actions.
  • The earlier a problem is identified the better
    the chance of successfully dealing with the
    problem.
  • The best chance of getting an early warning is by
    continual monitoring.

44
Conclusions
  • The successful application of mine monitoring
    systems requires the setting of appropriate
    alarms that trigger effective remedial actions.

45
Conclusions
  • The mine must implement effective maintenance and
    calibration procedures to ensure reliable ongoing
    operation of the mine gas monitoring systems if
    they rely on them for an early warning or in fact
    use results to assess any control measures they
    might implement during an event.
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