Abstract
Coal is the foundation of Chinese energy and economic structure, and the unsealing of coal mine fires would cause a great risk of coal re-ignition. The uniaxial compression equipped with a temperature-programmed (UCTP) device was built to explore the influence of pressure-bearing state on the re-ignition characteristics of residual coal. The Scanning Electron Microscope (SEM), Synchronous Thermal Analyzer (STA) and Fourier Transform Infrared Absorption Spectrometer (FTIR) was applied to investigate the microscopic structure and thermal effect of the coal samples. Moreover, the microscopic effect of uniaxial stress on coal re-ignition was revealed, and the re-ignition mechanism was also obtained. As the uniaxial stress increases, the number, depth and length of the fractures in the pretreated coal increase, and the filling material increases. The application of uniaxial stress causes the thermal conductivity to change periodically, which enhances the heat transfer inhibition effect of nitrogen and prolongs the oxidation exothermic stage. The content of oxygen-containing functional groups has a high correlation with apparent activation energy, and coal samples at 6 MPa are more likely to re-ignition when the fire zone is unsealed. Uniaxial stress controls the re-ignition mechanism by changing the structure of fractures and pores. The side chains and functional groups in the coal structure are easier to break under thermal-stress coupling. The higher the ·OH content, the more difficult it is to re-ignition. The research results have laid a solid theoretical foundation for the safe unsealing of coal field fire areas, tightened the common bond between the actual industry and the experimental theory in the closed fire area, and provided theoretical guidance for preventing coal re-ignition.
Influence Mechanism of Nitrogen Injection Into Closed Fire Zone On the Re-Ignition For Residual Coal in Goaf
