Handbook for Methane Control in Mining
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IC 9486 Information Circular/2006 TM Handbook for Methane Control in Mining Department of Health and Human Services Centers for Disease Control and Prevention National Institute for Occupational Safety and Health Information Circular 9486 Handbook for Methane Control in Mining By Fred N. Kissell, Ph.D. DEPARTMENT OF HEALTH AND HUMAN SERVICES Centers for Disease Control and Prevention National Institute for Occupational Safety and Health Pittsburgh Research Laboratory Pittsburgh, PA June 2006 ORDERING INFORMATION Copies of National Institute for Occupational Safety and Health (NIOSH) documents and information about occupational safety and health are available from NIOSH–Publications Dissemination 4676 Columbia Parkway Cincinnati, OH 45226–1998 FAX: 513–533–8573 Telephone: 1–800–35–NIOSH (1–800–356–4674) e-mail: [email protected] Website: www.cdc.gov/niosh This document is in the public domain and may be freely copied or reprinted. ————————————————————— Disclaimer: Mention of any company or product does not constitute endorsement by the National Institute for Occupational Safety and Health (NIOSH). In addition, citations to Web sites external to NIOSH do not constitute NIOSH endorsement of the sponsoring organizations or their programs or products. Furthermore, NIOSH is not responsible for the content of these Web sites. DHHS (NIOSH) Publication No. 2006–127 CONTENTS Page About this handbook ......................................................................... 1 Acknowledgments ........................................................................... 1 Chapter 1.—Facts about methane that are important to mine safety, by F. N. Kissell ........................ 3 Chapter 2.—Sampling for methane in mines and tunnels, by F. N. Kissell ............................... 27 Chapter 3.—Methane control at continuous miner sections, by F. N. Kissell, C. D. Taylor, and G. V. R. Goodman ........................................................................ 37 Chapter 4.—Preventing methane ignitions at longwall faces, by F. N. Kissell and A. B. Cecala .............. 55 Chapter 5.—Bleeder systems in underground coal mines, by J. E. Urosek, W. J. Francart, and D. A. Beiter ..... 63 Chapter 6.—Coal seam degasification, by P. C. Thakur ............................................. 77 Chapter 7.—Managing excess gas emissions associated with coal mine geologic features, by J. P. Ulery ....... 97 Chapter 8.—Forecasting gas emissions for coal mine safety applications, by C. O. Karacan and W. P. Diamond.......................................................................... 113 Chapter 9.—Control of methane during coal mine shaft excavation and filling, by F. N. Kissell ............. 127 Chapter 10.—Methane control in highwall mining, by J. C. Volkwein and F. N. Kissell ................... 135 Chapter 11.—Control of methane in coal silos, by F. N. Kissell ...................................... 141 Chapter 12.—Explosion hazards of coal dust in the presence of methane, by K. L. Cashdollar and M. J. Sapko . 147 Chapter 13.—Methane control in metal/nonmetal mines, by H. J. Head and F. N. Kissell .................. 151 Chapter 14.—Preventing methane gas explosions during tunnel construction, by F. N. Kissell .............. 169 Index.................................................................................... 181 ILLUSTRATIONS 1–1. Depiction of methane being diluted into a moving air stream ..................................... 4 1–2. Methane explosibility diagram ............................................................ 5 1–3. Effect of elevated pressure on methane explosibility limits ...................................... 6 1–4. Estimated methane content of coal versus depth and rank ...................................... 10 1–5. Original gas content of mined coal versus mine emission ....................................... 11 1–6. Methane layering with roof, side, and floor sources ........................................... 14 1–7. Recirculation in a heading ............................................................... 15 1–8. Dust scrubber recirculation .............................................................. 15 1–9. Ignitions per year per gate road ........................................................... 18 1–10. Relative frequency of occurrence of major and minor gas and dust explosions ...................... 20 2–1. Depiction of methane being diluted into a moving air stream .................................... 29 2–2. Methane profile map from a simulated continuous miner face ................................... 32 2–3. Recorder chart from a machine-mounted methane monitor ...................................... 33 3–1. Recorder chart from a machine-mounted methane monitor ...................................... 37 3–2. Peak average methane emissions for several U.S. coalbeds ..................................... 38 3–3. Ventilation setback distance ............................................................. 39 3–4. Methane dilution capacity for exhaust line curtain at setbacks of 10 ft and 20 ft ..................... 39 3–5. Spray fan system on a continuous miner .................................................... 40 3–6. Methane dilution capacity of the spray fan system ............................................ 41 3–7. Dust scrubber used in conjunction with blowing ventilation ..................................... 42 3–8. Methane dilution capacity from MSHA scrubber tests ......................................... 42 3–9. Test configuration used by Thimons et al. ................................................... 43 3–10. Dust scrubber used with exhaust ventilation ................................................. 45 3–11. Graph showing that performance of a spray fan depends on water pressure ......................... 47 3–12. Effect of bit wear on frictional ignition ..................................................... 49 4–1. Increased methane liberation during coal bumps .............................................. 56 4–2. Modified shearer-clearer system .......................................................... 56 4–3. Methane concentration at shearer during tail-to-head pass ...................................... 57 4–4. Plan view of walkway and gob curtains .................................................... 57 4–5. Walkway curtain at support No. 3 forces air over the shearer .................................... 58 ILLUSTRATIONS—Continued Page 4–6. Upwind-pointing venturi spray creates eddy zone and methane buildup ........................... 58 4–7. L-shaped wing curtain, which can cause methane buildup ...................................... 59 4–8. Anti-ignition back spray ................................................................ 60 4–9. Best methane monitor location ........................................................... 61 5–1. Simplified illustration of a wrap-around bleeder system for a longwall panel ....................... 64 5–2. Simplified illustration of a flow-through system with bleeder entries .............................. 65 6–1. Gas content of coal versus gas pressure for some U.S. coals .................................... 80 6–2. Generalized optimum point for methane drainage ............................................. 81 6–3. Simplified illustration of a typical longwall panel layout in a U.S. coal mine ....................... 82 6–4. Limits of the gas emission space .......................................................... 82 6–5. Longwall panel methane drainage ......................................................... 83 6–6. Premining methane drainage from surface .................................................. 84 6–7. Methane drainage by the packed cavity method .............................................. 86 6–8. Partially filled longwall gob ............................................................. 87 6–9. Methane drainage with cross-measure boreholes ............................................. 87 6–10. Methane drainage by the superjacent method ................................................ 89 6–11. Simplified illustration of methane drainage by vertical gob wells ................................. 89 6–12. Underground methane pipe installation ..................................................... 91 6–13. Surface installation for horizontal drainage boreholes ......................................... 92 7–1. Methane drainage scenarios for paleochannels ............................................... 99 7–2. Methane drainage of a normal fault from the “footwall” side ................................... 102 7–3. Methane drainage of a normal fault from the “hanging” wall side ............................... 102 7–4. Methane drainage of a reverse fault from the “hanging” wall side ............................... 103 7–5. Methane drainage of a reverse fault from the “footwall” side ................................... 103 7–6. Typical clay vein acting as a barrier to gas migration ......................................... 104 7–7. Methane drainage of a clay vein gas barrier ................................................ 105 7–8. Hypothetical gas cell formed by clay veins ................................................. 106 8–1. Methane content as a function of depth and coal rank ........................................ 115 8–2. Gas content versus depth and coal rank, Black Warrior basin, Alabama .......................... 115 8–3. PFG/FGK method to predict gas emissions in a previously disturbed zone ........................ 120 8–4. Gas pressure