Hazardous Area Reconstruction and Law Analysis of Coal Spontaneous Combustion and Gas Coupling Disasters in Goaf Based on DEM-CFD

The harmful gas in the sealed fire area of a small coal mine rushes into the mining face of the lower coal seam, which restricts the efficient promotion of the working face. In this paper, based on the evolution law of caving coal rock dilatation coefficient, the characteristics of the heterogeneous distribution of permeability and voidage in goaf were obtained, and the mathematical model of gas migration in goaf is constructed. The numerical solution of gas migration in goaf under the sealed fire area of a small coal mine was realized by using the Free and Porous Media Flow module and the Transport of Dilute Matter in Porous Media module in COMSOL Multiphysics, and the corresponding measure was proposed. The results show that the fresh air flows into the goaf from both the inlet air roadway and the working face and then flows out from the upper corner. Driven by the air flow, the CO in the overlying sealed fire area of a small coal mine flows out from the upper corner of the working face, resulting in the CO overlimit. Due to the influence of air leakage and the CO overlimit in the working face, low oxygen occurs in the working face. According to the characteristics of gas emission, balanced pressure ventilation technology is proposed to control the low oxygen in the working face and the CO overlimit in the upper corner. It is found that the balanced pressure ventilation obviously increases the pressure of the working face, reduces the pressure difference between the two ends of the working face by 45.7−26.7%, and decreases the air leakage to the goaf in the upper corner of the inlet air roadway. The field application shows that the problems of low oxygen in the working face and a CO overlimit in the upper corner are effectively solved.

Section: Mathematical Model Of Gas Migration In Goafmentioning

confidence: 99%

Simulation on Harmful Gas Control by Balanced Pressure Ventilation in the Fully Mechanized Caving Face under Sealed Fire Area of Small Coal Mine

Fan,

Sun,

Yang

et al. 2024

“…In this study, the simulation of airflow and CO diffusion characteristics in a dead-end tunnel is carried out using finite element software (ANSYS FLUENT) . First, a mathematical model that reflects the actual situation needs to be selected .…”

Section: Mathematical and Physical Modelsmentioning

confidence: 99%

Diffusion Characteristics of Airflow and CO in the Dead-End Tunnel with Different Ventilation Parameters after Tunneling Blasting

Wang,

Xue,

Xiao

et al. 2023

After tunnel blasting, a large amount of CO will be produced and accumulated in the dead-end tunnel. If the ventilation discharge is not proper and the entry time into the dead-end tunnel is not appropriate, then it can cause workers to suffer from poisoning, hypoxia, and suffocation. Therefore, to understand the airflow and diffusion characteristics of CO in the dead-end tunnel after excavation and improve the working environment quality of the heading excavation tunnel, this paper uses numerical simulation and on-site verification to study the influence of different ventilation parameters on the airflow and CO diffusion characteristics in the dead-end tunnel after excavation and blasting. The research results show that the higher the air velocity of the duct, the smaller the distance between the duct and the working face, and the higher the hanging height of the duct, the easier it is for CO to be discharged from the dead-end tunnel. The larger the distance between the duct and the side wall, the more vortices there are in the dead-end tunnel and the more difficult it is to discharge CO from the tunnel. This study provides theoretical guidance for the research of the migration law of CO after tunnel blasting and has important value for ensuring a safe working environment and clean production in tunnel excavation.

“…7 Ma et al 8 studied the distribution of oxygen concentration in adjacent goafs by the numerical simulation method and determined the risk zone of spontaneous combustion in adjacent goafs. Zou et al 9 employed the method of combining PFC3D and FLUENT to simulate and analyze the distribution law of oxygen and gas concentration in goaf. Yuan et al 10 adopted the obtained experimental data to simulate the oxidation and temperature rise process of different coal samples in the longwall goaf with three-dimensional CFD and studied the influence of the coal surface area and reaction heat on the natural heat release process.…”

Section: Introductionmentioning

confidence: 99%

Study on Multifield Migration and Evolution Law of the Oxidation Heating Process of Coal Spontaneous Combustion in Dynamic Goaf

Lei

Jiang

Bao³

et al. 2023

To study the dynamic evolution law of the oxidation heating process of coal spontaneous combustion in the goaf during the advancing process of the working face, a dynamic model of oxidation heating of coal spontaneous combustion in the goaf was established on the basis of deformed geometry. Through numerical simulation research, the evolution and migration laws of seepage field, oxygen concentration field, temperature field, and high-temperature area of coal spontaneous combustion in the goaf during the advancement of the working face was obtained. The results indicate that the distribution of the bulking coefficient, porosity, and permeability of the falling coal and rock mass in the goaf is nonuniform. They are relatively large in the area near the working face and the inlet and return airway and remain relatively unchanged with the advancement of the working face, but they are constantly decreasing in the location of the gob in the middle and deep. The oxygen concentration in the goaf presents an asymmetrical distribution. The oxygen concentration distribution area on the inlet side is wider than that on the return air side. At the same depth of the goaf, the oxygen concentration gradually decreases from the inlet side to the return air side; after the advancement distance exceeds 200 m, the air leakage in the goaf basically disappears, and the oxygen concentration decreases to zero. The high-temperature area of coal spontaneous combustion oxidation in the goaf was mainly concentrated on the air inlet side and extended toward the return air side. The advancing speed has a significant effect on the oxidation heating process of coal spontaneous combustion in the dynamic goaf. Under the same propulsion distance, when the advancing speed is 6 m/day, the highest temperature in the goaf is about 40 °C, and when the advancing speed is 2 m/day, the highest temperature in the goaf is as high as 120 °C. The smaller the advancing speed, the higher the heating rate of the goaf and the closer the high-temperature area to the working surface. The higher the advancing speed, the lower the temperature of the high-temperature point of the goaf and the greater the depth of the high-temperature point of the high temperature area; when the advancing speed is 2 m/day, the highest temperature point in the goaf is 70 m away from the working face, whereas when the advancing speed is 6 m/day, it reaches 174.6 m.