Type of the study: Original research article relationship between temperature rise characteristics and the emission of carbon oxides during the spontaneous combustion latency of coal

Abstract

The emission of carbon oxides during the spontaneous combustion latency of coal poses a severe challenge to the ecological and geological environmental protection of mining areas. Owing to the insidious nature of latency, the oxidative characteristics during this stage have rarely been studied. This study investigated the relationship between temperature rise characteristics and the emission of carbon oxides under different coal samples, initial temperatures, and particle sizes. The results indicated that the formation of carbon oxides correlated with the temperature rise characteristics during latency. Time-dependent carbon oxide formation followed an exponential function y=aexp(xb)+c. The metamorphic degree and initial temperature of the coal had a significant impact on the CO2/CO ratio and the particle size was independent of the ratio. In addition, in-situ Fourier transform infrared reflection experiments on four coal samples revealed that the hydroxyl, aliphatic hydrocarbon methyl, and methylene groups are key active groups in carbon oxide formation during latency, providing the original heat source for coal oxidation. The carbonyl and carboxyl groups acted as reactants and products and their content varied irregularly during oxidation. These results improve the understanding of CO and CO2 emissions from coal oxidation during spontaneous combustion latency and will aid early prevention of coal spontaneous combustion.