DUST CONTROL IN ROOM AND PILLAR COAL MINING USING IMPROVED SCRUBBERS AND IMPROVED SPRAY CONFIGURATIO

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DUST CONTROL IN ROOM AND PILLAR COAL MINING USING
IMPROVED SCRUBBERS AND IMPROVED SPRAY
CONFIGURATIONS
Mine Ventilation Symposium - 2008 Reno, NV

• Y. P. Chugh1, A. S. Patwardhan2,1, H. G. Gurley1
  R. C. Carty3
• 1Department of Mining and Mineral Resources
  Engineering
• Southern Illinois University at Carbondale
• 2Rio Tinto Minerals, Boron Operations
• 3Illinois Clean Coal Institute, Carterville, IL

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ACKNOWLEDGEMENTS

• Illinois Department of Commerce and Economic
  Opportunity
• Illinois Clean Coal Institute
• Illinois Mining Companies
• Joy Mining Machinery
• Spray Systems Inc.
• Mine Safety and Health Administration
• NIOSH
• Coal Research Center, SIUC

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OUTLINE

• Background
• Sources and distribution of dust around a CM
• Sampling and Data Analysis methods
• Modified Scrubbers Improved Spray Systems
• Conclusions

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BACKGROUND

• Increased productivity (2.5 to 4.0 tons/man-hour
  over past decade) higher dust
• Further productivity gains needed for reducing
  production cost
• Productivity gains may be dust constrained
• Potential tightening of regulations Allowable
  dust exposure reduction from 2 to 1 mg/m3 will
  result in only 37 mining units remaining in
  compliance
• Health and safety of workforce

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Sources of Dust around a CM
PLAN VIEW
ELEVATION VIEW
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ConceptualDust Profiles

• Highest concentration at the face.
• Respirable dust fraction increases away from
  face as coarse dust settles.
• Respirable dust fraction highest at roof level
  due to cutting of rock and coal.
• Therefore, scrubber suction inlets should be
  located close to roof level.

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CFD Modeling

• CFD modeling of a CM in Room-and-Pillar Entry.
• Aerodynamic conditions in the face area provide
  invaluable insights into analyzing the problem of
  occupational dust exposures.
• Though modeling requires refinement, it is clear
  that improvements in line-curtain management
  practices are necessary to reduce dust exposures
  to occupations and to dilute methane
  concentrations.

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Model 3 (Mid-Plane)
Tight Line Curtain
Very Low Air Velocities at Face
Miner Operator Location Very Sensitive
Recirculation Zone Ram Car Operator Breathing
Zone
Experimentally Validated Airflows
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Model 8 (Mid-Plane)
15-ft Advance Tight LC
Ample room for Miner Operator to stay in Fresh Air
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Dust Sampling
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Sampling Layout
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Dust Data Transformations

• Dust Concentrations Corrected for
• Intake Dust Concentration
• Line Curtain Airflow
• LOXC Airflow
• Production
• Cut Dimensions
• Delays
• Data Screening
• /- 2 SD Outliers
• Post-Hoc comparisons between cut types

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Modified Scrubbers Improved Spray Systems
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Develop an Innovative Spray System For Continuous
Miners

• Proven principles
• Have multiple check points when you are fighting
  a large, smart army.
• Surround the enemy to efficiently use resources
  and minimize enemy escape at each check point.
• Utilize different tactics to deal with enemy left
  at each check point.

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Modify Spray Configuration around a Miner -
Principles

• Control the dust as close to the generation point
  as possible.
• Cutting face, In the pan, at conveyor
  discharge and Scrubber inlets must be
  emphasized.

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Unmodified Scrubber
Unmodified Horizontal Spray
Only Screen (30 Layer)
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Modified Scrubber
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Expanded Metal Screen Covers on Suction Inlets
Expanded metal screens keep out the coarsest coal
particles being sucked into the scrubber
Right Side Suction
Left Side Suction
Side suctions improve suction of respirable dust
concentrated at higher levels into the scrubber.
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Unmodified Versus Modified Miner Comparison
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Key Concepts Utilized for Spray System Design

• Prevent dust generation, and minimize generated
  dust from becoming airborne by increasing water
  at the cutting bits, and cutting face, with
  appropriate spatial distribution of sprays.
• Wet and surround the airborne dust to allow the
  scrubber to capture it.
• Further wet the airborne dust escaping the
  scrubber inlets area before it enters the area
  behind the miner and the last open crosscut.
• Maximize the residence time in the face area to
  improve wetting of coal dust.
• Detailed spray system discussion curtailed due to
  Intellectual Property reasons.

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Mining Conditions During Sampling (Rounds I-III)
Very Comparable Conditions
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Summarized Results (Graphical)
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Realized Improvements in Dust Control
High variance in standard spray sampling and very
high diluting LOXC air flow makes confidence
level determination difficult.
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Results at Another Mine (Round IV)
Statistically Significant Difference _at_ 0.10
significance
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Results at Another Mine (Round V)
Statistically Significant Difference _at_ 0.10
significance
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Summary Results
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Summary

• Approximately 25-40 reduction in dust has been
  documented using the modified spray and scrubber
  systems.
• These improvements have been statistically
  validated.
• Higher improvements would have been possible if
  higher water pressures (120 psi) were available.
• Results may improve even further if improved face
  ventilation practices are followed.

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THANK YOU !