A study on the prediction method of coal spontaneous combustion development period based on critical temperature

Prediction of the development and evolution process of coal spontaneous combustion is of great significance to its prevention and control. Through the testing of different metamorphic degrees coal programmed heating characteristics and the infrared functional groups, the critical temperatures of the coalification process were analyzed and a method to predict the period of spontaneous combustion was established according to the characteristic of the critical temperature change. What can be inferred from this research is that the critical temperature of activation energy of coal in programmed heating experiments can characterize the nature of coal at low temperature and the macrocritical temperature point can be obtained from the characteristics of the activation energy change during the low-temperature period. The critical point of coal functional groups in terms of its micro changes is similar to its macro changes, the absorption intensity of the characteristic peak shows a general increasing trend, with an initial decline and then increase, followed by a decrease and a subsequent increase. In the high-temperature combustion process, the activation energy is not constant and changes from a negative value to 0, then the activation energy changes to a positive value, and finally goes down to a negative value. Therefore, the prediction of development period of spontaneous combustion can be achieved through the critical temperature of activation energy which acts as the critical temperature in high-temperature combustion process, and the prediction of low-temperature oxidation process is based on the critical temperature of activation energy in programmed heating process and the macro critical temperature of absorption intensity of coal functional groups.