Effect of greenhouse gases emissions from coal spontaneous combustion under different inerting conditions in the quenching process

Coal spontaneous combustion (CSC) is one of the main sources of greenhouse gases (GHGs) emission. In order to understand the GHGs emissions law of the heating and quenching processes in the coal low-temperature oxidation stage, three kinds of coal samples with different degrees of metamorphism were selected to investigate the influence of particle size and oxygen concentration on GHGs emissions. Compared with the heating process, the greenhouse effect of CSC under different inerting conditions was determined. The results showed that the CO2 and CH4 were the mainly GHGs in the initial stage of the coal oxidation, which were emitted from the oxidation and desorption of coal, while the particle size of coal displayed the opposite effect on GHGs. By comparison with the heating process, the average emission factor and total emission of CO2 of 1/3 JM, the average emission factor and total emission of CH4 of HM with 21% O-2 were higher in the quenching process. Meanwhile, with the decrease in oxygen concentration, the emission rate, average emission factor and total emission of GHGs decreased, and the greenhouse effect of CSC became weaker. Among them, the highest inerting rates of GHGs of HM, 1/3 JM and WYM reached 81.5%, 64.8% and 77.7%, respectively. In addition, the oxygen concentration was linearly positively correlated with the total emissions of CO2 and CH4, and conformed to the quadratic polynomial function with the equivalent CO2 emission factor. However, due to the strong displacement effect of N-2, the emission rate, average emission factor and total emission of CH4 of WYM and 1/3 JM with 0% O-2 were higher than those with 7% O-2, and it is shown that inert gases can weaken the coal oxidation, diminished GHGs emissions, reduced the greenhouse effect of CSC on the environment, and enhanced the desorption of gases in coal. The research results have important practical significance for improving the incomplete emissions of GHGs in the low-temperature oxidation process, and evaluating the emission reduction effect of CSC prevention.

Automated summary

Coal spontaneous combustion (CSC) is a significant source of greenhouse gas emissions. This study investigated the emissions of greenhouse gases during the heating and quenching processes in the low-temperature oxidation stage of different types of coal samples. The results showed that CO2 and CH4 were the main greenhouse gases emitted during the initial stage of coal oxidation. The particle size of coal had an opposite effect on greenhouse gas emissions. The emissions of CO2 and CH4 were higher in the quenching process compared to the heating process. Lower oxygen concentration reduced greenhouse gas emissions and weakened the greenhouse effect of CSC. Inert gases could weaken coal oxidation, reduce greenhouse gas emissions, and enhance gas desorption in coal.