Evolution patterns of coal micro-structure in environments with different temperatures and oxygen conditions

摘要

Before mining, a deep coal seam exists in a state with a high formation temperature and high stress. After mining, the coal body is exposed to oxygen, and the oxidation reaction results in significant changes in the micro-structure of the oxidized coal body. To understand the change process, in this paper, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy are employed to test a coal body subjected to flow of hot gas. The evolution patterns of the coal oxidation micro-structure under different temperatures and oxygen conditions are compared and analysed. The results show that in an environment with oxygen, as the temperature increases, the stacking height (L-c) of the coal macromolecular lattice follows an overall increasing trend and has a self-repair capability. During oxidation, the spatial arrangement of the evolution of the coal molecular structure is reversible. In an environment without oxygen, the hydroxyl (-OH) peak height and peak area exceed those of an environment with oxygen, which suggests that the -OH group facilitates coal oxidation. Coal functional groups under high-temperature fracture polymerize constantly, and oxidation produces new functional groups.