Study on correlation between coal spontaneous combustion characteristic temperature and physical and chemical characteristic parameters

WAN Cheng; ZHANG Binbin; LI Dailin; LIU Yin; CHEN Yanfeng; GUO Jun; WU Yunfei

doi:10.13347/j.cnki.mkaq.20240846

Abstract：The fine division of coal spontaneous combustion characteristic stage is the premise for the establishment of early warn-ing system of coal fire disaster.The physical and chemical properties of coal and their variation laws are the key to determine the characteristic temperature and divide the spontaneous combustion stages.In order to explore the correlation between the characterist-ic temperature of coal spontaneous combustion and the physical and chemical properties,the long flame coal samples of Chenjiagou Coal Mine in Gansu Province were selected to prepare oxidized coal at different temperature conditions(40℃,60℃,80℃,100℃,120℃,140℃,160℃,180℃,200℃).Industrial analysis,scanning electron microscopy(SEM),energy dispersive X-ray spectro-scopy(EDS),X-ray diffraction(XRD)and infrared spectroscopy(FTIR)were carried out to study the changes of physical and chem-ical parameters of coal samples with temperature in different oxidation stages.The characteristic temperature of coal spontaneous combustion in Chenjiagou coal sample was determined.Combined with the grey correlation analysis method,the correlation between the key physical and chemical parameters and coal temperature was further clarified.The results show that the spontaneous combus-tion process of coal samples in Chenjiagou Mine can be divided into three stages according to the characteristic temperature,namely,the critical stage(40-80℃),the pyrolysis stage(80-120℃)and the fission stage(140-180℃).The physical and chemical structure parameters of coal have different effects on the change of characteristic temperature in the process of coal spontaneous combustion.The correlation degree of hydroxyl group and methylene group in the micro group of coal sample to the characteristic temperature stage is high,and the correlation degree is 0.675 3 and 0.692 6 respectively.In the critical and pyrolysis stages,the surface active structure of coal body is physically and chemically adsorbed with oxygen molecules.The hydroxyl group first reacts with oxygen to store heat.As the temperature increases,a small amount of side chain breaks,resulting in an increase in the content of methylene.The hydroxyl group is also continuously consumed due to other functional groups.The reaction continues to generate.In the pyrolys-is stage,the free water in the coal evaporates,the bound water begins to evaporate,the intramolecular association hydrogen bond is accelerated,the porosity of the coal becomes larger,the gas adsorption capacity is enhanced,the reactivity of various functional groups with oxygen is improved,and the coal spontaneous combustion process is accelerated.In addition,the stacking height and lamellar diameter are related to the volume,surface morphology and stability of coal accumulation.The stacking height and lamellar diameter always have a high correlation degree(0.668 9)between the initial stage of coal spontaneous combustion process and the characteristic temperature stage.