The use of infrared spectroscopy to determine methane emission rates from coals at atmospheric pressures

In this study, we present a laboratory method for determining CH4 emissions from coal particles into 1 atmosphere of nitrogen and air using the infrared signature of CH4. The sensitivity of infrared allows detection of methane even at the sub-10 ppm level, allowing extended measurements of emission rates to be made. Using this method, the release rate of CH4 from 7 coal samples with different maceral composition and rank into 1 atm dry N2 was monitored over 5 days. The results were compared with those determined in a manometric system. The initial rate of gas release from coals, defined as the inverse of time at which 63.2% of the overall gas released at 25 h is emitted, were found to be slightly greater into 1 atm N2 than those in a manometric system. The overall emission of CH4 was also generally faster into N2 than in the manometric system. The emission rate increased with decreasing mean particle size and varied as r-2 over the size range (0.1-1.0 mm) investigated. Emission of CH4 into 1 atm air envir...