Dynamic behaviours on oxidation heat release of key active groups for coal with different degrees of metamorphism.

• Correlation between gas products and active groups is determined for CDDM. • Relationship between active groups and exothermic is characterized for CDDM. • Evolution difference of active groups is explored for CDDM. • Oxidizing ability of active groups determine macroscopic characteristics of coal. The exothermic kinetic properties of the oxidation of key active groups are closely related to the coal with different degrees of metamorphism (CDDM) in the low-temperature oxidation of coal. To study the dynamic characteristics of oxidative exotherm of the key active groups for the CDDM, and reveal the macroscopic and microscopic interrelationships, the CDDM were selected and analyzed through temperature-programmed testing system, microcalorimetry experimental system, and in-situ Fourier transform infrared spectrometer experimental system. The results indicated that the carbonyl groups were oxidized to produce CO and CO 2 at an increased rate in the accelerated oxidation stage. In the vigorous oxidation stage, the accumulation of heat accelerated the conversion of methyl and methylene groups to carbonyl groups, and promoted the oxidation reaction. At the same temperature conditions, the total production of CO and CO 2 released from a coal with a high degree of metamorphism is lower. The key preventing the low-temperature oxidation is obstructing the reaction progression of the accelerated oxidation stage and the carbonyl groups, which are the key stage and active groups respectively. [ABSTRACT FROM AUTHOR]