Classification of Spontaneous Combustion Hazard Levels of Coal with Different Metamorphism Degrees

Abstract

ABSTRACT Coal spontaneous combustion is the main disaster affecting the safety production of mines, and efficient early warning is the key to controlling coal spontaneous combustion disasters. In order to construct an early warning system for spontaneous combustion disasters of coal with different degrees of metamorphism, the programmed-temperature control experiment was conducted to obtain the change curve of the volume fraction of the index gases of the low, medium and high degrees of metamorphosis, and then the Logistic function is used to fit the volume fraction and temperature of the index gases, and the mathematical model of the index gas and temperature of the index gases with different degrees of metamorphism is obtained, and the inflection point temperature is determined, and finally the spontaneous combustion hazard level of the coal is divided in combination with the initial temperature of the index gases. The results show that the changes of coal sample index gases and characteristic temperatures with different degrees of metamorphism are different; the initial appearance temperature of CO is about 30°C, while the initial appearance temperature of C2H4 and C2H2 is positively correlated with the degree of metamorphism, and the initial appearance temperature is 117°C (low), 123°C (medium) and 137°C (high) for C2H4, 291°C (low), 297°C (medium) and 297°C (high) for C2H2; For the same marker gas, the inflection point temperature increases with the degree of metamorphism, indicating that the higher the degree of metamorphosis, the less likely it is to oxidize at the beginning; According to the variation characteristics of coal spontaneous combustion, based on the initial emergence temperature of CO and C2H4 and CO inflection point temperature, coal spontaneous combustion is divided into five states: safe, low risk, medium risk, high risk and catastrophic state, and the energy level transition map between each state indicates that the energy required to transition from safe state to low risk and high risk state is the largest. Once the high-risk state is crossed, it does not require higher energy to maintain the continuous development of spontaneous combustion of coal and evolve into a catastrophic state. The classification of coal spontaneous combustion hazard levels with different degrees of metamorphism can provide prior data and form effective support for intelligent early warning of coal spontaneous combustion.