Handbook for Methane Control in Mining - AMMSA

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89Figure 6–10.—Methane drainage by the superjacent method.Figure 6–11.—Simplified illustration of methane drainage by vertical gob wells. Ventilationcontrols are not shown.
90Early experiences with this method of gob degasification have been described by Moore et al.[1976] for the Lower Kittanning Seam, by Moore and Zabetakis [1972] for the Pocahontas Seam,and by Davis and Krickovic [1973] and Mazza and Mlinar [1977] for the Pittsburgh Seam.Many gob degasification boreholes produce naturally when the longwall face intersects them,but vacuum pumps are often added to further improve the flow and, in some cases, to prevent thereversal of flow. The capture ratios vary from 30% to 80% depending on the number and size ofgob wells per panel and the size of vacuum pumps.A summary of methane capture ratios for the abovementioned postmining methane drainagetechniques is presented in Table 6–3. Although each technique offers high capture efficiency insome cases, it is the author’s experience that vertical gob wells, if properly designed, offer themost universal application with consistently high capture ratios. In addition, this technique is anatural outgrowth of the premining degasification technique using vertical frac wells. These fracwells can be converted easily into postmining gob wells with minimal additional expense.HOW TO TRANSPORT GAS IN UNDERGROUND MINESIn-mine horizontal drilling and cross-measure boreholes drilled to degas longwall gobs producelarge volumes of gas. This gas must be conducted out of the mine without being allowed to mixwith the mine ventilation air. The U.S. coal industry, working with the Mine Safety and HealthAdministration (MSHA), has developed general 7 guidelines for installing and operating undergroundmethane pipelines, as follows:1. Underground methane pipeline will be made of well-designed plastic or steel, as detailed inFigure 6–12.a. All underground steel pipelines will be 3½- to 8½-in O.D. schedule 40 pipes joinedtogether with threaded couplings. These pipes will be made up tightly using a goodgrade of thread lubricant. Mill collars will be broken out, doped, and remade.A flange connection will be used every 10 joints (approximately 210 ft apart) so thata section of the pipeline can be removed without cutting the line if one or more jointsneed to be replaced later.b. All underground plastic line will be 3- to 6-in high-density polyethylene pipe. Plasticflange adapters will be fusion bonded to the pipe ends in fresh air. Steel flangebackup rings installed prior to fusion bonding will be used to connect plastic to plasticand plastic to steel.2. The entire length of pipeline between the bottom of the venthole and the well head will bepressure tested to 1.25 times the shut-in pressure of the borehole or 90 psi, whichever is greater.3. Pipeline will be generally laid in the return airway and will not be buried. Whenever thepipeline must cross a fresh air entry, it will be conducted through a steel line.7 The specifics will vary from mine to mine.
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TMIC 9486Information Circular/2006H
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ORDERING INFORMATIONCopies of Natio
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ILLUSTRATIONS—ContinuedPage4-6. U
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HANDBOOK FOR METHANE CONTROL IN MIN
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4Below 5%, called the lower explosi
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6reduced pressure, except at very l
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8Static electricity. Protection aga
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10Figure 1-4.—Estimated methane c
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12LAYERING OF METHANE AT THE MINE R
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14good eyesight. 24methane level.Ot
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16a material balance indicated that
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18As an example, assume that themet
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20Figure 1-10.—Relative frequency
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22Davies AW, Isaac AK, Cook PM [200
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24Margerson SNA, Robinson H, Wilkin
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CHAPTER 2.—SAMPLING FOR METHANE I
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29USING PORTABLE METHANE DETECTORST
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Out-of-range gas concentrations in
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Figure 2-3.—Recorder chart from a
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35Industrial Scientific Corp. [2004
Page 43 and 44: 38peaks, not the overallmethane lev
Page 45 and 46: 40hung on J-hook assemblies, which
Page 47 and 48: 42Methane dilution effectiveness.Th
Page 49 and 50: 44found that effective scrubber ope
Page 51 and 52: 46When the scrubber exhaust is not
Page 53 and 54: 48Methane monitors are usually moun
Page 55 and 56: 50to use radial bits instead of con
Page 57 and 58: 52Mott ML, Chuhta EJ [1991]. Face v
Page 59 and 60: 54Service, Centers for Disease Cont
Page 61 and 62: 56Methane accumulationsaround thesh
Page 63 and 64: 58corner and by 43% at supportNo. 4
Page 65 and 66: 60When using water sprays to reduce
Page 67 and 68: 62Cecala AB, Zimmer JA, Thimons ED
Page 69 and 70: 64DESIGNING BLEEDER SYSTEMSAs part
Page 71 and 72: 66Caved area characteristics. The c
Page 73 and 74: 68then move this gas into the activ
Page 75 and 76: 70perform tests to determine whethe
Page 77 and 78: 72A major purpose of the bleeder sy
Page 79 and 80: 74• Inlets to the pillared area n
Page 81 and 82: 76REFERENCESCFR. Code of federal re
Page 83 and 84: 78Methane is released into each min
Page 85 and 86: 80Figure 6-1.—Gas content of coal
Page 87 and 88: 82Figure 6-3.—Simplified illustra
Page 89 and 90: 842. In-mine inclined or vertical b
Page 91 and 92: 861. Packed cavity method and its v
Page 93: 88Table 6-3.—Methane capture rati
Page 97 and 98: 9211. At the surface installation (
Page 99 and 100: 94• Estimated cost for moderately
Page 101 and 102: 96Thakur PC [1981]. Methane control
Page 103 and 104: 98Anomalous, unanticipated methane
Page 105 and 106: 100Vertical methane drainage boreho
Page 107 and 108: 102Figure 7-2 shows a mine entry ap
Page 109 and 110: 104obvious solution to this problem
Page 111 and 112: 106Figure 7-8.—Hypothetical gas c
Page 113 and 114: 108Lama and Bodziony [1998] compile
Page 115 and 116: 110In-mine methane drainage systems
Page 117 and 118: 112Iannacchione AT, Ulery JP, Hyman
Page 119 and 120: 114More sophisticated reservoir eng
Page 121 and 122: 116coal lithotype on gas content is
Page 123 and 124: 118FORECASTING REMAINING GAS-IN-PLA
Page 125 and 126: 120⎛ y⎞⎜⎛⎞ ⎛ ⎞= ⎜
Page 127 and 128: 122emissions. The geometry and size
Page 129 and 130: 124Reservoir models require a subst
Page 131 and 132: 126King GR, Ertekin T [1989a]. A su
Page 133 and 134: 128an area of 314 ft 2 would requir
Page 135 and 136: 130In the case of the abovementione
Page 137 and 138: 132FILLING SHAFTS AT CLOSED MINESFi
Page 139 and 140: 134Hinderfeld G [1995]. Ventilation
Page 141 and 142: 136To calculate the effectiveinert,
Page 143 and 144: 138exhaust. The remaining diesel ex
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140required only 4 min. As a result
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142Figure 11-1.—Desorption test a
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144enclosed in a tunnel-like struct
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146Kolada RJ [1985]. Investigation
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148air in a 6-ft by 9-ft by 6.5-ft
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150represents flammable mixtures. F
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152• In Eastern Europe, petroleum
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154Category II applies to domal sal
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1562. Monitoring for gas and taking
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158These mines typically have large
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160Dave Graham is the safety and he
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162Figure 13-2.—Examples of metha
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164REFERENCESAndrews JN [1987]. Nob
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166APPENDIX A.—ONTARIO OCCUPATION
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169CHAPTER 14.—PREVENTING METHANE
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Ways to confirm the presence of gas
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173The tunnel face is usually venti
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175Figure 14-5.—TBM ventilation s
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face. While one of these elements a
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179ELIMINATING IGNITION SOURCESElec
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181INDEXAAbnormally gassy faces....
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183NNatural ventilation, coal silos
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Delivering on the Nation’s Promis
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Handbook for Methane Control in Mining - AMMSA

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