Page 206 - Advances In Productive, Safe, and Responsible Coal Mining

Coal mine methane: Control, utilization, and abatement 185

On the other hand, methane is an important source of hydrogen and some organic
chemicals. Methane reacts with steam at high temperatures to yield carbon monoxide
and hydrogen; the latter is used in the manufacture of ammonia for fertilizers and
explosives. In the chemical industry, methane is a raw material for the manufacture
of methanol (CH 3 OH), formaldehyde (CH 2 O), nitromethane (CH 3 NO 2 ), chloroform
(CH 3 Cl), carbon tetrachloride (CCl 4 ), and some freons. The incomplete combustion of
methane yields carbon black, which is widely used as a reinforcing agent in rubber, the
principal component of automobile tires.
As a whole, methane is not a bad gas in and of itself, but mankind is pushing more
quantities of it into the atmosphere than ever before. Understanding where it comes
from and developing technologies to mitigate adverse effects will play an important
role in maintaining the Earth’s climate for the future. Therefore, modern technologies
need to be developed and employed to remove fugitive CMM from underground coal
mines and to use it in profitable and practical ways. Beside various other industrial
uses, CMM can potentially be utilized as a clean energy source supplied directly to
neighboring communities as town gas or used to generate electricity at electric power
plants built adjacent to mines.

10.3 Methane emission control in coal mines

CMM emissions into mine workings essentially result from pressure differences
between gases trapped in the coal seam and the atmosphere of the mine. In the past
century, much effort has been expended to control CMM emission in underground
coal mines. The earliest attempts were to control CMM accumulations in active work-
ings by mixing it with air and ventilating it to the outlet roadway or tailgate. In recent
years, efforts have mainly focused on coal seam degasification and gas drainage sys-
tems to collect CMM from active coal mines at the surface or in advance of mining
underground. These efforts have led to using CMM to supplement mine ventilation
systems and other commercial uses.
Mechanization and increasing productivity, especially in longwall coal mining,
have led to greater volumes of CMM emissions. In longwall mining, it is necessary
to control CMM emissions at the face area, at T-junctions, and along gate roadways
and rooms. In this respect, having knowledge of geological and mining conditions
such as coal rank, gassiness of the coal seam and rock formations, productivity of
the coal mine, mining method, depth of mining, and rate of advancement can be an
enormous help in controlling excess gas emissions and consequently preventing disas-
ters and explosions. It is important to mention that achieving and maintaining these
high levels of productivity requires proper control of CMM.
Methane in coal mines will always be a hazard, but the risk of explosion has been
greatly minimized by increased safety regulations, sensitive gas detectors, improved
ventilation, and methane drainage systems. Considerable research has gone into effec-
tively and commercially controlling CMM in underground coal mines. The main tech-
nique used for controlling CMM concentrations is ventilation; however, other
emission control measures such as horizontal and crossmeasure (inclined) boreholes,