Study on the whole process and gas products of coaloxygen complex reactionbased on TG/DSC/MS technology

In response to study the stage division, heat change and product formation path of coaloxygen complex reaction by DSC curve, there are some scientific problems, such as lack of systematic definition and description, and insufficient indepth TG and DSC coupling relationship, etc., the combined technology of TG/DSC/MS was used to test and analyze the whole process of coaloxygen complex reaction at different heating rates in inert gas and air atmosphere. The experimental results show that the coaloxygen complex reaction process can be divided into the heat absorption stage of water evaporation and gas desorption, the exothermic stage of chemical adsorption and slow reaction, the exothermic stage of coal pyrolysis to generate reaction groups, and the exothermic stage of volatile matter and fixed carbon combustion based on DSC curve. By drawing and comparing the characteristic temperature, it was found that the division of coaloxygen compound stage based on TG division method and DSC division method has a high degree of overlap and consistency, which proves the feasibility and correctness of DSC division method. The temperature range, products, reaction course and reaction mechanism of the corresponding stages were defined by using the theory of coalmine fire science, thermal analysis dynamics and coal chemistry theory. The multichannel, reaction path and formation mechanism of methane, ethylene, carbon monoxide and carbon dioxide were clarified by the mass spectrometry analysis of ionic flow intensity of gas products and the modeling analysis of Chem 3D software on the basis of the fragment unit of coal molecular structure. It was obtained that the generation trends of CH4 and C2H4 are similar in the process of coaloxygen complex reaction. And the peak temperature of ion current intensity curve is basically the same (135 ℃). The escape curve of CO2 is parabola, and the escape peak appears at 560 ℃. It was found that the ionic current intensity curve of CO gas has bimodal characteristic, and the characteristic temperatures corresponding to double peak are 530 ℃ and 609 ℃, respectively. The research results can provide a theoretical support and positive influence for clarifying the whole process of coaloxygen complex reaction, classification of coal spontaneous combustion and early warning.