An novel experimental study on the thermorunaway behavior and kinetic characteristics of oxidation coal in a low temperature reoxidation process

The coal spontaneous combustion is a great threat to the coal seam mining, personal safety and ecological environment. The coal spontaneous combustion in the underground goaf refers to a reoxidation process of oxidation coal. In this paper, the coal thermorunaway behavior is introduced in the low-temperature oxidation stage as a potential early-warning index for the spontaneous combustion prevention. A novel test platform using mesh basket is employed to reveal the kinetic characteristics of oxidation ordos lignite. Experimental results show that the thermorunaway temperature of ordos lignite is about 135 degrees C. The coal structure collapse occurs together with a plummet in the coal sample mass. As the coal oxidation level rises, the thermorunaway temperature and maximum mass gradient pose an advance rule, and the 80 degrees C oxidation coal creates a higher mass gradient than 40 degrees C and 60 degrees C. The oxidation coals possess more mesopore and macropore with the total specific surface area decline by 37.9% from raw coal to 80 degrees C oxidation coal. The coal hardness exhibits a reduction as the oxidation level rises that promotes the structure collapse. The peak area of -CH2 and -CH accounts for 65.3% in 60 degrees C oxidation coal and -CH3 plays a dominated role for 80 degrees C oxidation coal thermorunaway.