Prediction of Longwall Methane Emissions: An Evaluation of the Influence of Mining Practices on missions and Methane Control Syst +' *iJ, srnvrr@a U.S. DEPARTMENT OF HEALTH UMAN SERVICES Public Health Service Centers for D~seaseControl and Prevent~on Narional Irist~tutefor Occupational Safety and Health CENTERSAND FL< PREVENTION [, ~ASECONTROL 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 45226-1 998 Fax: 513-533-8573 Telephone: 1-800-35-NIOSH (1-800-3 56-4674) E-mail: pubstaft @cdc.gov Web site: www.cdc.gov/niosh This document is the public domain and may bepeely copied or reprinted. Disclaimer: Mention of any company or product does not constitute endorsement by NIOSH. DHHS (NIOSH) Publication No. 99-150 October 1999 Report of Investigations 9649 Prediction of Longwall Methane Emissions: An Evaluation of the Influence of Mining Practices on Gas Emissions and Methane Control Systems William P. Diamond and Fred Garcia U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service Centers for Disease Control and Prevention National Institute for Occupational Safety and Health Pittsburgh Research Laboratory Pittsburgh, PA 1 PiughRemarch Laboratory Library #( International Standard Serial Number ISSN 1066-5552 CONTENTS Page Abstract ...................................................................................... 1 Introduction ................................................................................... 2 Study area ..................................................................................... 2 Instrumentation and monitoring strategy ............................................................. 2 Longwall pass methane emission data ............................................................... 5 VP-1 Mine study results ....................................................................... 5 VP-3 Mine study results ....................................................................... 11 Prediction of methane emissions for 305-m (1.000.ft) longwall faces ...................................... 18 VP-1Mine .................................................................................. 18 VP-3Mine .................................................................................. 18 Bleeder system methane flow rates ................................................................. 19 VP-1 Mine .................................................................................. 19 VP-3Mine .................................................................................. 20 Methanedrainage ............................................................................... 22 Horizontal boreholes: VP- 1 Mine study panel ...................................................... 22 Horizontal boreholes: VP-3 Mine study panel ...................................................... 24 Gob gas ventholes: VP-I Mine study panel ........................................................ 26 Gob gas ventholes: VP-3 Mine study panel ........................................................ 27 Discussionofresults ............................................................................. 29 Variation in longwall pass methane emission levels .................................................. 29 Significance of ventilation and gas drainage for methane control ....................................... 30 Summary ..................................................................................... 31 Acknowledgments .............................................................................. 32 References .................................................................................... 32 ILLUSTRATIONS MapoftheVPMinecomplex ................................................................. 3 Map of VP-1 and VP-3 Mine study areas ........................................................ 4 Plan view of longwall face divided into equal-length segments for analysis and prediction of methane emission trends .................................................................................. 4 Longwall face methane emissions for the baseline and days 1 and 2. VP-I Mine ......................... 6 Average methane emissions by pass segment. VP- I Mine ........................................... 7 Average daily methane emissions. all passes with data basis. VP-1 Mine ............................... 8 Methane emissions associated with floor gas bleeder. pass 8. day 2. VP-I Mine ......................... 9 Methane emissions and delays. pass 5. day 2. VP-1 Mine ........................................... 9 Longwall face methane emissions for days 3-5. VP-I Mine ......................................... 10 Longwall face methane emission intervals exhibiting a possible "staircase" effect. day 1. VP-1 Mine ......... 10 Longwall face methane emission intervals exhibiting a possible "staircase" effect. day 4. VP-1 Mine ......... 11 Longwall face methane emissions for the baseline and day 1. VP-3 Mine .............................. 12 Longwall face methane emissions for days 2 and 3. VP-3 Mine ...................................... 12 Average methane emissions by pass segment. VP-3 Mine ........................................... 13 Average daily methane emissions. all passes with data basis. VP-3 Mine ............................... 14 Longwall face methane emission intervals exhibiting a possible "staircase" effect. day 1. VP-3 Mine ......... 14 Longwall face methane emission intervals exhibiting a possible "staircase" effect. days 2 and 3. VP-3 Mine ... 15 Methane emissions. pass 3. day 1. VP-3 Mine .................................................... 16 Methane emissions. pass 7. day 1. VP-3 Mine .................................................... 17 Methane emissions. pass 5. day 2. VP-3 Mine .................................................... 17 Methane emissions. pass 10. day 3. VP-3 Mine ................................................... 18 Methane emission prediction curves for 305-m (1.000-ft) longwall faces. VP-I and VP-3 Mines ............ 19 Page Detailed map of VP- 1 Mine study area .......................................................... 20 Methane flows and emissions during mining of the VP-1 Mine study site .............................. 21 Methane flows and emissions during mining of the VP-3 Mine study site .............................. 21 Detailed map of VP-3 Mine study area .......................................................... 22 Location of horizontal methane drainage boreholes. VP-1 Mine study panel ............................ 23 Horizontal methane drainage borehole production. VP-1 Mine study panel .............................. 24 Location of horizontal methane drainage boreholes. VP-3 Mine study panel ............................ 25 Horizontal methane drainage borehole production. VP-3 Mine study panel ............................. 25 Daily total gob gas venthole methane production. VP-1 Mine study panel .............................. 26 Cumulative gob gas venthole methane production. VP-I Mine study panel ............................. 27 Daily total gob gas venthole methane production. VP-3 Mine study panel .............................. 28 Cumulative gob gas venthole methane production. VP-3 Mine study panel ............................. 28 TABLES Average longwall pass methane emission summary. VP-1 Mine ...................................... 6 Average direction of pass mining and delay time summary. VP-1 Mine ................................ 8 Average longwall pass mining and delay time summary. VP-1 Mine .................................. 8 Average daily longwall pass methane emission summary. all passes with data basis. VP-1 Mine ............ 9 Average longwall pass methane emission summary. VP-3 Mine ...................................... 13 Average daily longwall pass methane emission summary. all passes with data basis. VP-3 Mine ............ 13 Average longwall pass mining and delay time summary. VP-3 Mine .................................. 16 Average direction of pass mining and delay time summary. VP-3 Mine ................................ 16 Bleeder system methane flows during VP-1 and VP-3 Mine emission studies ........................... 19 Horizontal borehole methane production. VP-1 and VP-3 Mines ..................................... 24 Gob gas venthole methane production. VP-1 and VP-3 Mines ....................................... 27 Ventilation system and borehole methane flows during VP-1 and VP-3 Mine emission studies .............. 30 UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT cfm cubic foot (feet) per minute m3/mo cubic meter (s) per month cm3/g cubic centimeter(s) per gram m3/sec cubic meter(s) per second ft foot (feet) min minute(s) ft3/st cubic foot (feet) per short ton MMcf million cubic feet h r hour(s) MMcfd million cubic feet per day m meter(s) MMcfImo million cubic feet per month m3 cubic meter(s) YO percent m3/d cubic meter(s) per day PREDICTION OF LONGWALL METHANE EMISSIONS: AN EVALUATION OF THE INFLUENCE OF MINING PRACTICES ON GAS EMISSIONS AND METHANE CONTROL SYSTEMS By William P. ~iamond'and Fred Garcia2 ABSTRACT As part of its mine safety and health research program, the National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory, has been investigating the geologic and mining factors influencing methane gas emissions associated with longwall