PURPOSE:  Reduce or eliminate hazardous frictional ignitions at coal mine working faces through improved face ventilation and enhanced positioning of machine-mounted methane monitors.

RESEARCH SUMMARY:  Large volumes of methane can be released at the mining face during coal extraction. When the lower explosive limit (LEL) is exceeded, this methane-air mixture is capable of being ignited if it contacts hot cutting bits on a mining machine. These frictional ignitions can injure, sometimes fatally, those working in the vicinity. To prevent frictional ignitions, an adequate quantity of fresh air must be provided to the mining face to dilute methane below the LEL. In addition, continuous methane monitoring is essential to assure that the LEL has not been exceeded.

To determine the effectiveness that different ventilation techniques have on diluting and carrying-off methane emissions at the mining face, researchers are conducting ventilation studies in a full-scale coal mine face gallery. Three-axis ultrasonic anemometers are placed at predetermined locations to measure airflow speed and direction. Results have shown that variables, such as air quantity and entry width, can affect airflow patterns and methane concentrations near the face. Presently, research is being performed to more accurately define the relationship of face air velocities and methane levels.

Studies are also evaluating the relationship between air velocities and the accurate detection of methane at typical machine-mounted methane sensor locations. Preliminary results have shown that these methane-sampling locations are not ideal. Research will determine the practicality of moving the machine-mounted continuous monitor to different locations on the machine. This work will determine which locations provide; 1) a more accurate indication of true methane concentrations, and 2) the fastest response-times to changing face methane levels. Ideally, the results will optimize the location of the monitor, minimizing the potential for methane ignitions at the face.

Research products will provide guidelines for improving face airflow and controlling face methane levels with the goal being to reduce or eliminate methane ignitions at the working face. To enhance face worker safety, it is imperative that advancements in face ventilation and methanometer placement be reviewed, accepted, and incorporated into the mining industry’s face ventilation plans. To promote these findings a research-derived transfer of technology will be provided to MSHA, private industry, labor organizations, and miners. These outputs will be in the form of written publications and both formal and informal presentations.