Booster fan applications for sections in longwall and room-and-pillar mining

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Booster fan applications for sections in longwall
and room-and-pillar mining
Christopher Pritchard MS PE Acting Team
Lead Ventilation Group Fires and Explosions
Branch Spokane, WA
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Acknowledgement

• Thanks to Co-Authors
• Anu Martikainen PhD
• Andrew Wala PhD
• Garrett Frey
• Gerrit Goodman PhD

3
Introduction

• Background
• Short development modeling
• Long development modeling
• Small mine field testing
• Large mine field testing
• Discussion and Conclusions

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Background

• Booster fan use in US coal mines
• 30 CFR 75.302
• Each coal mine shall be ventilated by one or
  more main mine fans. Booster fans shall not be
  installed underground to assist main mine fans
  except in anthracite mines. In anthracite mines,
  booster fans installed in the main air current or
  a split of the main air current may be used
  provided their use is approved in the ventilation
  plan.
• 2006 Technical Study Panel recommendation
• that booster fans be examined as one of the
  potential available tools to assist main surface
  fans, reduce leakage, and provide more air to
  ventilate working areas

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Proposed Study

• NIOSH Project in response to Technical Stugy
  Panel
• Modeling of booster fan installations in
• Short panel development systems lt 1000m
• Long panel development systems 3000m
• Perform field studies in
• Small mine Bruceton research coal mine
• Large mine Wyoming trona mine with longwall
  and development panels
• MNM Class III Gassy Mine
• Similar layout and equipment to coal mining

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Short development model scenarios

• No. of Entries Description
• 2 Intake / Return
• 3 Intake central, belt, and return outside
• 4 Belt and intake central, outside return
  entries (fishtail)
• 5 Dual return left, belt/track central, intake
  outside right
• Utilized Ventgraph to simulate a single booster
  fan operation
• Booster locations (a) first Xcut inby portal or
  (b) Mid-way to face
• Installed in (a) belt, (b) travelway or (c)
  return

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Illustration Small Mine Development Model
4Fishtail VentilationBooster Mid-Panel
Travelway
Main Fan
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Small development results

• Outby locations generally minimize recirculation
• Inby locations recirculate more air with
  increasing pressure, necessitating increased
  vigilance
• Belt installations are not practical (as
  expected) and were eliminated from further
  modeling
• Boosters increase airflow, but not always system
  efficiency
• Even small networks require effort to correctly
  locate booster fans due to system sensitivity
  from small pressure changes
• Small developments are good place to start
  modeling to understand booster fans

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Extended 3,000m development model scenarios

• 1. base case modelmain fan only
• 2. four boosters, two intake and two return
  (shown)
• 3. single outby intake booster
• 4. single inby intake booster
• 5. two offset boostersoutby intake and inby
  return
• 6. two boostersoutby intake and outby return

Main Fan
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Discussion - modeling

• 3,000-m longwall extended developments show
  that booster fans operating at lower pressures,
  around 125 Pa, can improve system efficiency with
  minimal recirculation.
• In some applications, multiple booster fan
  systems show improved results, although benefits
  must be balanced with the associated issues of
  ventilation system complication and management.
• Recirculation was less than 2.5 of booster fan
  airflow in all extended development system
  models, except for the inby intake booster fan
  which, at 18, is consistent with results from
  the small mine development system models.
• A well-designed system minimizes pressure
  differentials, stopping leakage, and
  recirculation through appropriate booster fan
  location and pressure management.
• Extended development system models showed that
  booster fans can increase face airflow and,
  through careful placement and pressure
  management, can control pressure differentials
  to minimize recirculation.

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Booster Fan Testing at the Bruceton Experimental
(small) Mine
Booster Inby
Booster fan with VFD
Booster Outby
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Bruceton small mine results

• Confirmed small mine modeling results
• Inby booster systems are more prone to
  recirculation
• In both cases, airflow in neutral entries
  ultimately reversed as booster fan pressure
  increased
• With increasing pressure, the booster fan caused
  recirculation outby the fan and reversal of
  neutral airflow
• Airflow at the face increases with higher inby
  booster fan pressure, often containing a
  recirculated air component

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Field Work at large room and pillar longwall mine
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Booster fan test area

• Booster Fan 125 HP w/VFD in Belt Drift

• Airflow / Pressure Differentials

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Test results large room and pillar longwall mine

• Ventilation airflow efficiency and panel/submain
  recirculation percentages rose with booster fan
  airflow
• Booster fan test panel circuit recirculation was
  high outby the fan, with most of additional panel
  airflow leaking back into the intake
• Recirculation caused by return airway restriction
  outby
• Test and model airflows and pressures showed good
  correlation, but existing mine model needs
  updated
• Modeling of leakage during normal and booster fan
  operation was not equivalent. Stopping resistance
  value is different depending on return or intake
  direction.

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Discussion field work

• Booster pressures over 500 Pa greatly increased
  test panel airflows (2.6 to 4.3 times), caused
  high localized recirculation with minimal effects
  on nearby panel airflows, and produced good
  correlation with pretest modeling.
• As booster fan pressures increase, efficiency can
  decrease due to overriding of main fan or
  localized ventilation capacity.
• Balancing is easier during modeling when the mine
  is in a static condition, and much more
  complicated in the dynamic conditions of
  day-to-day operation.

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Conclusions

• Booster fans have yielded favorable results in US
  metal and non-metal mines and international coal
  mines over many years and under different
  conditions.
• When installed and operated correctly to minimize
  recirculation, and by utilizing the improved
  technology of network modeling, ventilation
  system monitoring and control, booster fans can
  be an effective tool to increase airflow in
  underground coal mines.
• Studies of short and extended coal mine
  development systems in conjunction with small and
  large in-mine tests show that booster fans can be
  used to increase face airflow.

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Conclusions continued

• Outby locations minimize recirculation, and
  multiple booster fan installations may be used to
  balance leakage and recirculation effects.
• In coal mine applications, safety is enhanced by
  pressurizing the intake entry with an outby
  booster fan to prevent the potential influx of
  belt entry contaminants and to minimize
  recirculation.
• Multiple booster fans installations may add
  safety and efficiency benefits, but also
  complicate the ventilation system.
• Mine environments continually change, requiring
  constant vigilance should booster fans be
  installed.

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Where are we?

• Remember?
• 2006 Technical Study Panel recommendation
• That booster fans be examined as one of the
  potential available tools to assist main surface
  fans, reduce leakage, and provide more air to
  ventilate working areas
• Answer
• Yes - with appropriate precautions, booster fans
  can be used to accomplish the above goals.

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Thank you! Questions?May 2nd, 40th Anniversary
of Sunshine Fire
Questions or Comments? CPritchard_at_cdc.gov 509-354-
8021