Abstract: To find out the reason for the sudden rise of the oxidation temperature in coal spontaneous combustion process, and provide theoretical basis for the prevention and control of spontaneous combustion in coal mines, the adiabatic testing method and programmed temperature rising method were used in this paper, to study the temperature rising, oxygen consumption, gas production (CO and CO2) characteristics of lignite in Baizao coal mine during the oxidation process. It is indicated that the oxidation of lignite has the subsection characteristic, and can be divided into two stages , that is, slow oxidation process during the low temperature and fast oxidation during the high temperature. The functional groups variation law during the whole oxidation process was tested by in-situ FTIR. The results show that the reaction of OH leads to the subsection characteristic of lignite during oxidation process, and the endothermic reaction of OH is the main reason why the heat is difficult to accumulate in the low temperature stage. Once OH is depleted, heat begins to accumulate and the temperature of coal rises immediately.

Key words: subsection characteristic, spontaneous combustion of coal, lignite, oxidation process, functional groups