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DUST CONTROL IN ROOM AND PILLAR COAL MINING USING IMPROVED SCRUBBERS AND IMPROVED SPRAY CONFIGURATIONS PowerPoint Presentation
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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. Chugh 1 , A. S. Patwardhan 2,1 , H. G. Gurley 1 & R. C. Carty 3 1 Department of Mining and Mineral Resources Engineering

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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

acknowledgements
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
outline
OUTLINE
  • Background
  • Sources and distribution of dust around a CM
  • Sampling and Data Analysis methods
  • Modified Scrubbers & Improved Spray Systems
  • Conclusions
background
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
sources of dust around a cm
Sources of Dust around a CM

PLAN VIEW

ELEVATION VIEW

conceptual dust profiles

0

Distance (m)

FACE

Distance (feet)

0

FACE

A

% Respirable

Total Dust Conc.

A

Dust Conc. (mg/m3)

Plan View

Plan View

B

0

Roof Level

% Respirable Dust

Total Dust Conc.

Heightfrom floor

Floor Level

B

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.
cfd modeling
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.
model 3 mid plane
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

model 8 mid plane
Model 8 (Mid-Plane)

15-ft Advance

Tight LC

Ample room for Miner Operator to stay in Fresh Air

sampling layout

Straight Cut - Deep

~30’

2

10’-40’

41’

1

Intake Air

3

19’

Return Air

Ram Car In

4

Curtains

Ram Car Out

Sampling Layout
dust data transformations
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
develop an innovative spray system for continuous miners
Develop an Innovative Spray System For Continuous Miners

Provenprinciples:

  • 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.
modify spray configuration around a miner principles
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.
unmodified scrubber
Unmodified Scrubber

Unmodified Horizontal Spray

Only Screen (30 Layer)

modified scrubber

Sprays

Sprays

First 10-layer filter

Second 10-layer filter

Modified Scrubber
expanded metal screen covers on suction inlets
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.

key concepts utilized for spray system design
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.

realized improvements in dust control
Realized Improvements in Dust Control

High variance in standard spray sampling and very high diluting LOXC air flow makes confidence level determination difficult.

results at another mine round iv
Results at Another Mine (Round IV)

* Statistically Significant Difference @ 0.10 significance

results at another mine round v
Results at Another Mine (Round V)

* Statistically Significant Difference @ 0.10 significance

summary
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.