Page 208 - Advances In Productive, Safe, and Responsible Coal Mining

Coal mine methane: Control, utilization, and abatement 187

Fig. 10.2 Ventilation setback distance in exhaust systems near a continuous miner [4].

certain locations in the ventilation system. As an example, the United States Mine
Safety and Health Administration (MSHA) has regulations requiring exhaust systems
to have a maximum setback distance of 3m (10ft) to prevent CMM concentration at
the face (Fig. 10.2).
The productivity and safety of longwall mining can far exceed that of room-and-
pillar mining; however, total CMM emissions per volume extracted by shearers in
longwall panels are generally higher than those for continuous miners in room-
and-pillar mines [10]. Therefore, wide mine faces and high production rates charac-
teristics of longwall mining present unique ventilation problems. For this reason, a
number of supplemental operations such as degasification and drainage systems are
designed to reduce the amount of CMM emitted at the face during longwall mining.

10.3.2 Degasification/drainage control measures
Mine ventilation is not the only method of CMM control in underground mining, par-
ticularly in very deep or gassy mines. In fact, using a ventilation system alone to con-
trol CMM emissions in deep or gassy mines would be prohibitively expensive, and it is
necessary to supplement the ventilation system with a degasification system con-
sisting of a network of underground and/or surface boreholes. A methane drainage
system is unavoidable when the ventilation system cannot dilute CMM emissions
to a level below statutory limits. In such cases where explosive CMM levels are likely,
CMM can be drained prior to, during, and even after mining operations in order to
mitigate unwanted disasters within the mine. These systems have the added benefit
of reducing environmental concerns with regard to GHGs.
Coal mine degasification was originally developed to improve worker safety in
mines. However, apart from alleviating environmental concerns and enabling produc-
tivity improvements, capturing CMM has many economical benefits that can justify