Thermal kinetics of nitrogen inhibiting spontaneous combustion of secondary oxidation coal and extinguishing effects

摘要

Spontaneous combustion of secondary oxidation coal seriously affects the safety of goaf in coal mine. To investigate the effect of nitrogen on secondary oxidation coal, thermal analysis and temperature-programmed methods were adopted to explore the thermal behavior and extinguishing ability. The combustion process was divided into the heating process and extinguishing process. Simultaneous thermal analyses performing connected with a Fourier transform infrared spectroscopy analyzer, were applied to the heating process. A temperature-programmed system was employed for extinguishing process. The results demonstrated that nitrogen concentration inhibited the oxidized decomposition and solid-phase reaction. As the nitrogen concentration increased, characteristic temperatures were delayed, and the activation energy of the secondary oxidation coal combustion stage elevated from 138.6 to 158.6 kJ/mol. The nitrogen concentration had little effect on the product H2O, CO, and CO2, while change of the nitrogen concentration mainly inhibited the generation of oxygen-containing functional groups and decomposition of aliphatic hydrocarbons. When the nitrogen concentration increased to 50% during the extinguishing process, the time required for the temperature to decrease from 400 to 30 degrees C was 39.0% shorter than that during natural extinction, and CO disappeared 42.1% faster. Reaction kinetics were used to analyze the fire extinguishing process of secondary oxidation coal and its spontaneous combustion. The heating process is conducive to determining the combustion characteristics of secondary oxidation coal. The extinguishing process experiments can monitor the changes after extinguishing the spontaneous combustion of coal in a closed fire zone.