Product characteristics and functional group changes of spontaneous combustion during different stages of metamorphic coal
The characteristic of coal molecular structure is the basis for studying the process of coal oxidation and spontaneous combustion and the mechanism of coal spontaneous combustion,the change law of middling coal molecu-lar structure in the process of coal low-temperature oxidation is the fundamental way to explain the cause of coal spon-taneous combustion,which is of great significance to the study of coal spontaneous combustion characteristics.Taking Yannan lignite,Hongyang coking coal and Nanyangpo anthracite as the research objects,the temperature pro-grammed system was used to test the law of gas product formation during low temperature oxidation of coal.The micro-structure characteristics of coal with different metamorphic degrees were analyzed by Fourier transform infrared spec-troscopy(FTIR).The influence of temperature on the surface functional groups of coal molecules was explored.The intrinsic properties of coal spontaneous combustion were revealed and characterized from macro and microscopic.The results shows that:the amount of gas products increased with the increase of temperature,the molecular structure of coal was broken and aromatic nucleus condensation was carried out in the process of coal oxidation at low tempera-ture.With the deepening of coal metamorphism,the amount of gas products decreased,the content of oxygen-contai-ning functional groups on the surface of coal molecules decreased,the activity decreased,and the spontaneous com-bustion ability of coal weakened.With the increase of temperature,the methyl and methylene groups on coal molecu-lar surface increased as a whole,the hydroxyl groups decreased at first,then increased and then decreased,and the carboxyl and carbonyl groups increased.
coal spontaneous combustionproduct characteristicsfunctional groupprogrammed heating experi-mentinfrared spectroscopyaromatic nucleusamount of gas product