Study On Reburning Characteristics Of Coal Pyrolysis Residue

The widespread phenomenon of coal spontaneous combustion has made reignition frequent and serious when the closed working face is opened.The current research on the coal reignition only stays in the experimental analysis of secondary coal oxidation and fire-fighting technologies.The studies on the combustion characteristics of unburned zone coal masses affected by high-temperature in goafs have not been investigated.Therefore,this paper makes use of thermogravimetric and infrared measurements to analyze the pyrolysis residual structure and mass characteristics as well as oxidation and heat release characteristics of three typical spontaneous combustion coal samples.The results show that the coal affected by high temperature is more prone to spontaneous combusting and the intensity is greater.It provides a theoretical basis for the study of residual structural oxidation mechanism of coal pyrolysis and the coal fire prevention and control technology.Main contents are as the following:(1)The thermal analyses of coal samples under different temperatures were carried out by a synchronous thermal analyzer.Meanwhile,the characteristic parameters of the residual structure under different pyrolysis degrees were investigated to determine its quality and phase characteristics.The results show that with the increase of pyrolysis temperature,the maximum precipitation rate of volatile matter and the loss of volatile dispersion increase,the constant temperature loss of volatile matter increases first and then decreases,while the mass of the residual combustible component decreases.The trend of these characteristic parameters exhibits obvious turning point at 450 °C,which proves that the critical temperature of the three coal samples in the thermal decomposition stage is near 450 °C,and the change of the reaction content causes the parameters changing.(2)The FTIR in-situ test system was used to test the coal and pyrolysis residues of three types of coal samples.Quantitative analysis of experimental infrared spectra was performed based on quantum chemical methods to calculate the percentage of radicals in different coal samples.It turned out that the pyrolysis reaction mainly affected hydroxyl,aliphatic hydrocarbon and aromatic hydrocarbon.The pyrolysis temperature increasing resulted in the hydroxyl and aliphatic hydrocarbon content decreasing in coal and the aromatic hydrocarbon content increasing.(3)The pyrolysis residue of different coal samples were subjected to an oxidation experiment at a programmed temperature and the oxidation heat flux simultaneously measured to analyze the characteristic parameters of coal oxidation and the change of the heat release with the degree of pyrolysis.The results show that the temperature of the ignition point of the coal sample decreases first and then rises with the degree of pyrolysis increasing.The combustion intensity,the centralized combustion level,and the heat of oxidation increase.That is,the coal pyrolysis residue is easer to be spontaneous ignited and has higher combustion intensity as well as more exothermic combustion.