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 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 N-2 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 N-2 than those in a manometric system. The overall emission of CH4 was also generally faster into N-2 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 N-2, 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.