Handbook for Methane Control in Mining - AMMSA

182GGas accumulation, longwall...............................56–58Gas blowers ..........................................................107Gas content of coal ........................................114, 116Gas detector.............................................................27Gas emission from coal in silos.............................141Gas emission sources, longwall...............................55Gas from bumps, longwall.......................................55Gas-in-place...........................................................116Gas mixtures, explosive range...................................3Gas outbursts .........................................................107Gas readings ............................................................29Gassiness of coal seams...........................................79Gilsonite mines......................................................153Gob curtain, longwall ..............................................57HHeadgate cutout, longwall .......................................57Heat of combustion sensors...............................13, 27High-volume scrubbers............................................47Higher air velocity, effect of..............................12, 17Highly gassy coal seams..........................................79Highwall mining ...........................................135–140auger removal ...................................................140inert gas quantity ..............................................138oxygen concentration........................................139purging..............................................................139starter hole ........................................................139Horizontal boreholes, degasification .......................83Human factors .......................................................179Hydrofracing, degasification ...................................84IIgneous intrusions..................................................106Ignition ....................................................................59Ignition of methane by—adiabatic compression...........................................7hot solids...............................................................6lightning................................................................8sliding friction.......................................................7static electricity.....................................................8thermite sparking ..................................................7Ignition sources in metal/nonmetal mines .............158Indirect method......................................................114Inert gas .............................................................4, 135Inert gas generator .................................................137Infrared absorption, sampling..................................28Inlets to pillared areas..............................................74Instruments to measure methane .............................27JJoints......................................................................103LLarge cross-sectional entries....................................18Layering number......................................................12Layering of methane................................................12Le Chatelier’s law......................................................5Lightning ...................................................................8Lower explosive limit............................................3, 5Lower flammable limit ..........................................3, 5L-shaped wing curtain, longwalls............................59MMachine-mounted methane monitors ......................28Metal and nonmetal mines, methane in .........151–167actions to take ...................................................156Australia ...........................................................152Canada ..............................................................152difference from coal mines ...............................155estimating the hazard ........................................161Europe...............................................................152ignition sources.................................................158Scandinavia.......................................................151South Africa, Republic of.................................152starting a new mine...........................................161United Kingdom ...............................................152Methaneexplosions..........................................................78origins................................................................77Methane and coal dust mixtures, explosibility ......149Methane capture ratios, degasification ..............83–90Methane content, coal seams ...................................79Methane detection..............................................47–48Methane detectorscalibration of.......................................................33dust-clogged heads .............................................33machine-mounted ...............................................28portable.........................................................27–28sensor head response ..........................................32where to take readings ..................................29–30Methane dilution by scrubbers...........................42, 45Methane dilution capacity of scrubbers...................39Methane drainage techniques ..................................83Methane emission peaks..........................................37Methane ignition......................................................59Methane layers.........................................................12Methane monitor, longwall......................................60Methane pipeline, degasification .............................90Methane stored in coal...............................................8Mildly gassy coal seams ..........................................79Mine emissions......................................................119Mixing into air, methane .....................................4, 17Modeling techniques, methane reservoirs .............124Moderately gassy coal seams...................................79Modified shearer-clearer..........................................56