Thermokinetic characteristics of coal spontaneous combustion based on thermogravimetric analysis.

• Mechanisms causing mass variation of combusting coal were separated and evaluated. • Contributions of different mechanisms to mass variation of coal were researched. • Transformation of the kinetic mode in spontaneous coal combustion was explored. • Kinetic compensation effect of variations in E a and A was investigated. Coal spontaneous combustion (CSC) is a severe threat to coal mining operations. Using thermogravimetric experiments, the contributions of different mechanisms to the mass variation during CSC were analysed. Furthermore, the kinetic mode and kinetic compensation processes were investigated. Among the different mechanisms of coal–oxygen reaction, solid-phase combustion contributes least to mass loss; for coals of high rank, gas-phase combustion makes the greatest contribution. Oxidative decomposition contributes most for coals of low rank. Furthermore, the kinetic mode governing CSC is three-dimensional diffusion in the mass gain stage and changes to random nucleation and subsequent growth in the mass loss stage. The apparent activation energy reaches its maximum near the ignition temperature and indicates a kinetic compensation effect with the pre-exponential factor in each stage. These findings are crucial for understanding the processes involved in CSC. [ABSTRACT FROM AUTHOR]