Credit: West Virginia University
Despite longwall mining being an efficient way of extracting coal, it produces dangerous methane gas that has the potential to lead to explosions in underground mines. Researchers from West Virginia University are combatting this issue by developing an improved methane monitoring network to increase the safety of longwall mines.
Derek Johnson, associate professor of mechanical and aerospace engineering in the Statler College, explained that methane gas becomes explosive when it can be found at a volume of five to 15 percent in the air, but the danger increases when the effects of methane and coal dust combine in the mine. Even if methane is found at only one to two percent in the air, it can lead to delays in the production of mining.
Longwall mining is a mining technique capable of fully extracting large panels of coal. As a longwall miner advances along a panel, the roof behind the miner’s path is allowed to collapse, according to Science Direct.
“Currently, mines use a single shearer mounted methane sensor and intermittent measurements with handheld units,” Johnson said. “A refined network of sensors will enable a proactive response to rising trends which will hopefully improve not only safety – but also productivity.”
Johnson, along with Nigel Clark, George B. Berry chair emeritus of engineering and research professor, received a second grant from the Alpha Foundation to build upon the researchers previous findings to further develop and refine a second generation of the methane watchdog system, a cost-effective, multi-nodal network of methane sensors distributed across the longwall face that serves to measure methane in longwall coal mining operations.
“During the first program, we evaluated two, low-cost methane sensors and identified their strengths and weaknesses,” Johnson said. “We also focused on the use of 3D printed water powered ejectors as an inherently safe method to provide the motive force for sampling methane from various locations. This method enabled the sample to be transported to central nodes for concentration measurements.”
Johnson said the second generation of the methane watchdog system will focus on improving six key areas, such as improving sensor technology, conducting scaled demonstrations and adding additional technology as needed will be addressed prior to deployment in active mines.
“After the key areas are addressed, the general goal is for the multi-nodal network of sensors to monitor and alert miners of elevated methane before they would have to walk into the area and take a measurement with a handheld system,” Johnson said. “The system will provide an alarm at one percent methane and can shut down equipment at one and a half or two percent methane in air.”
The team reached out to an industry partner to obtain a state-of-the-art dual infrared sensor that could be integrated to replace the previous two sensor approach. Johnson explained that if successful, the physical system would be redesigned to ensure that system response is maintained or improved.
Alongside Johnson and Clark, Graduate Research Assistant Amber Barr will be using computational fluid dynamics modeling, 3D printing, and experiments to develop an improved water ejector within the laboratory. These results will help predict operation with higher water pressures that may be available in the mines.