The use of infrared spectroscopy to determine methane emission rates from coals at atmospheric pressures
American Chemical Society
School of Engineering
In this study, we present a laboratory method for determining CH4 emissions from coal particles into 1 atm of nitrogen and air using the infrared signature of CH4. The sensitivity of infrared allows for the 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 compositions and ranks into 1 atm dry N2 was monitored over 5 days. The results were compared with those determined in a manometric system. The initial rates 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 environment was tested for three different coals and found to be identical with that into 1 atm N2, indicating that the presence of oxygen had no effects on the CH4 emission from the coals. The method and the results presented in this study may lead to a better fundamental understanding of emission from coal during handling and as a result assist in the development of models for predicting this emission.