Characteristics and critical parameters of coal spontaneous combustion at low temperature stage based on CPT method

Coalmine fire caused by coal spontaneous combustion is one of the main disasters in coalmines. The cross- ing-point temperature (CPT) method is an experimental technique to test the propensity of coal to spontaneous com- bustion and the characteristic parameters of temperature increase. A Temperature-Programmed System ( TPS) was used to develop the oxidation tests of the bituminous coal under various flow and oxidation conditions for temperatures at low temperatures (such as the volume fraction of oxygen in air at inlet are 20. 65% ,17. 80% ,13. 62% ,10. 49% , 5. 00% and 3. 00% respectively). Based on the present analysis of temperature increase rate of coal,the temperature differences between oven and coal,and the characteristics of oxygen consumption,furthermore,considering the heat generation rate of coal during the procedure of the Temperature-Programmed tests,the four stages of coal oxidation at low temperature were identified:(I) initial heating with no reaction,(II) a endothermic period,(III) an unsteady ex- othermic period and (IV) a steady period. Moreover,according to the normalization of the energy conservation equation of the coal spontaneous combustion during the tests,the temperature differences of the oven and the coal samples were dominated by the parameters of ατ and (B-1)ατ separately at the stages I & IV. Also,there must be parameter B larger than 1 as the CPTs occur at stage III. The theoretical results remains the same as the experimental ones.