Preoptimal analysis of phase characteristic indicators in the entire process of coal spontaneous combustion

To accurately predict the development degree of coal spontaneous combustion (CSC), the CSC process was investigated using a programmed high-temperature-heating experimental system, and the variation law of index gas concentration in the holistic process of CSC and oxidation is formulated. Additionally, the accuracy of the experimental system was evaluated using experimental design for thermal analysis, and the correlation between gas index and apparent activation energy was determined using grey correlation analysis. The results indicated the following. In the critical temperature stage (0-100 degrees C), phi(CO)/phi(CO2) should serve as the main index and C2H4 should serve as the auxiliary index; in the crack-active-speedup temperature stage (100-260 degrees C), CO and phi(C2H4)/phi(C2H6) should serve as the main index and R-1, the Graham index, and phi(C2H4)/phi(CH4) should serve as auxiliary indexes; in the speedup-ignition temperature stage (260-370 degrees C), R-2 and the Graham index should serve as main indexes and f(CO)/f(CO2), C2H4, and R1 should serve as auxiliary indexes; in the ignition temperature (370-500 C), R-3 should serve as the main index and R-2, the Graham index and C2H4 should serve as auxiliary indexes. Among them, the grey correlation degrees among the Graham index, Grignard fire coefficient, and apparent activation energy were the highest, reaching 0.91.