Study On Spontaneous Combustion Characteristics Of Coal Based On Thermal Dynamics Analysis

Coal is a complex organic macromolecular structure composed of various functional groups and chemical bonds,so that its spontaneous combustion process involves a series of complex physical and chemical reactions.In order to reveal the characteristics of physical and chemical reactions,a series of thermodynamic theories and experimental researches have been carried out around the characteristics of coal spontaneous combustion.The coal quality analysis,apparent morphology and surface pore structure characteristics were studied by proximate and ultimate analysis,scanning electron microscopy and specific surface area and pore analysis instruments.The results show that the coalification degree of Inner Mongolia Erdos coal,Shaanxi Shenmu coal and Shanxi Datong coal decreases in turn,and the main pore volume is micropores and transition pores;study also shows that the higher the degree of coalification,the larger the proportion of corresponding micropores.Based on the thermodynamic analysis method,in order to better study the spontaneous combustion characteristics of coal,this paper summarizes the single scan rate method commonly used in the field of coal scpontaneous combustion(Coats-Redfern,Achar,universal equation,Mac Callum-Tanner,Madhusudanan-Krishnan-Ninan And non-isothermal TG-DSC method)and multiple scan rate method(Flynn-Wall-Ozawa,Kissinger-Akahira-Sunose,Starink and Friedman method).The theoretical basis,advantages and disadvantages of each method are summarized.This paper selected coal from ordos,Inner Mongolia and used each method to deduce the stage of oxygen absorption and weight gain.It is confirmed that Starink method is the best thermodynamic analysis method.Based on the apparent activation energy,it is concluded that the higher the degree of coal carbonization is,the lower the content of active material is,the more energy is needed for the oxidation reaction,the greater the activation energy is,and the less spontaneous the coal sample is.The release characteristics of CO₂,CO and H₂O gas during coal heating process were analyzed by thermogravimetry-infrared spectroscopy.The results show that with the increase of coalification degree,the release of CO₂ gradually increases,the release of CO gradually decreases,and H₂O is mainly produced in two stages below 200?and200-600?.Fourier transform infrared spectrometer is used to analyze the difference of functional groups among different coal,and the spectrum is divided into three regions to compare the differences of functional groups with different coalification degrees.The results show that the higher the coal rank,the aromatic hydroxyl,cyclic hydroxyl,ether oxygen and methyl content gradually increase,The ratio of methylene to methyl and the content of carboxyl,alcoholic hydroxyl and self-associated hydroxyl gradually decreased;using XPS full spectrum scanning,the surface elements and relative contents of the three coal samples were analyzed.The results show that with the increase of coal rank,the content of C-C/C-H functional groups also gradually increases,and the contents of C-O,C=O and O=C-O gradually decrease.