Emission Characteristics of Higher-Molecular-Weight Gases During the Oxidation of Bituminous Coals

To explore the application prospects of higher-molecular-weight gases (HMWGs) in forecasting coal spontaneous combustion (CSC), the emission characteristics of HMWGs during the oxidation of seven bituminous coals with different degrees of metamorphism were studied using gas chromatography. By analyzing the gas samples released from the oxidation of experimental samples, a total of 20 HMWGs with hydrocarbons as the main component was detected. The concentration of HMWGs changed regularly during the oxidation of experimental samples. The concentrations of most representative hydrocarbon gases increased significantly with increasing temperature but plateaued or even decreased when the temperature exceeded about 210 degrees C. The relationship between HMWG production and the metamorphic degree indicators was nonlinear. The volatile matter content and vitrinite reflectance of coal cannot be used directly to evaluate HMWG production. The initial appearance temperatures of HMWGs during the oxidation of different coal samples also varied. The accuracy of CSC forecasting technology can be significantly improved if HMWGs are used as complementary index gases to forecast the different development stages of bituminous CSC.