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

1. 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

2. 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

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

4. 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

5. Sources of Dust around a CM PLAN VIEW ELEVATION VIEW

6. 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.

7. 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.

8. 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

9. Model 8 (Mid-Plane) 15-ft Advance Tight LC Ample room for Miner Operator to stay in Fresh Air

10. Dust Sampling

11. 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

12. 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

13. Modified Scrubbers & Improved Spray Systems

14. 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.

15. 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.

16. Unmodified Scrubber Unmodified Horizontal Spray Only Screen (30 Layer)

17. Sprays Sprays First 10-layer filter Second 10-layer filter Modified Scrubber

18. 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.

19. Unmodified Versus Modified Miner Comparison

20. 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.

21. Mining Conditions During Sampling (Rounds I-III) Very Comparable Conditions

22. Summarized Results (Graphical)

23. Realized Improvements in Dust Control High variance in standard spray sampling and very high diluting LOXC air flow makes confidence level determination difficult.

24. Results at Another Mine (Round IV) * Statistically Significant Difference @ 0.10 significance

25. Results at Another Mine (Round V) * Statistically Significant Difference @ 0.10 significance

26. Summary Results

27. 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.

28. THANK YOU !