Measurement and Numerical Simulation of Coal Spontaneous Combustion in Goaf under Y-type Ventilation Mode

Abstract

In the process of advancing the working face, the temperature rise and oxidation characteristics of residual coal in goaf and the prediction of index gas are of great significance to mine fire prevention and safety production. Based on the coal spontaneous combustion test, the oxygen consumption and heat release characteristics of coal spontaneous combustion were analyzed by taking coal samples at the working face and carrying out temperature-programmed experiments in the laboratory. The characteristic temperature and index gas of coal spontaneous combustion were determined as the judgment bases of “three zones” of spontaneous combustion in goaf, and the influencing factors of coal spontaneous combustion in goaf under Y-type ventilation were analyzed. Based on the test results, the changes of gas composition in goaf during the advancing of the W1310 working face were monitored. According to the actual situation of the W1310 working face in the Gaohe energy mine of Lu’an group, the multifield three-dimensional numerical simulation calculation and analysis of gas composition in goaf were carried out, and the distribution of oxygen concentration field in goaf under different air volume ratios of machine roadway and air roadway was studied. Through the analysis of the parameters of porous media in the goaf, combined with the actual situation, the user-defined function was compiled for the key parameters such as porosity, viscous resistance coefficient, and inertial resistance coefficient of porous media in the goaf. The three-dimensional seepage field, gas concentration field, oxygen concentration field, and pressure field of the gas components in goaf during the advancement of the goaf working face were simulated. The comparison of the numerical simulation results with the field-measured results shows good agreement. In order to consider safety, the numerical simulation results with a wide oxidation temperature rise zone are used for linear regression, and the regression equation is used to dynamically determine the O 2 concentration at a point away from the goaf and to determine the “three-zone” state of the point, which is of great significance to guide the progress of the working face and safe production.

Study on the Effect of Pore Evolution on the Coal Spontaneous Combustion Characteristics in Goaf

“…The coal and rock in the region between the loose and compacted zones are in a transitional state, and the wind flow in this region is transitioning from turbulent to laminar flow [17,18]. The conventional Darcy's law only applies to laminar movement in the central and deeper parts of goaf, where wind movement is dominated by gas viscous forces [19,20]. However, the turbulence state in the loose zone is more complicated and, in addition to the gas viscous force, the movement of the wind flow in this region is also affected by the medium resistance of the coal and rock, the pressure difference, the gas density and other factors.…”

Study on Nitrogen Injection Fire Prevention and Extinguishing Technology in Spontaneous Combustion Gob Based on Gob-Side Entry Retaining

“…Chai conducted a temperature-programmed experiment on coal and improved the prediction index gas system of SC, suggesting that CO and C 2 H 4 can be used as warning indicators for suspended solids in the gob. The scope of the “three zones” of spontaneous combustion can be comprehensively determined by the oxygen concentration, air leakage velocity, and temperature in the gob. , Through the coal spontaneous combustion experiment, Gui et al developed a method to determine the “three zones” of a gob using O 2 concentration through regression analysis. Dai prevented residual coal spontaneous combustion accidents using a fire prevention system comprising pressure equalization, gas monitoring, and nitrogen injection.…”

Exploring the Effect of Low-Temperature Oxidation on the Petrophysical Characteristics of Coal

“…Coal is still the main fossil energy even under the general trend of carbon neutrality. − However, due to the poor thermal conductivity of coal, − it easily causes heat accumulation, which evolves coal spontaneous combustion (CSC), resulting in the waste of resources. − Therefore, it becomes highly necessary to study how the pore fissure characteristics do an impact on CSC from the perspective of structure …”