Numerical simulation study on the influence of air leakage on oxygen concentration in goafs of fully mechanized caving mining with shallow buried and large mining height

Abstract

In order to reveal the influence of air leakage on oxygen concentration in goafs of fully mechanized caving mining with a shallow buried and high mining height, the air leakage of No.122108 working face in Caojiatan coal mine in different seasons was tested by the SF6 tracer gas test method. Based on the result of the air leakage test, the “three zones” of spontaneous combustion in the goaf were simulated using Ansys Fluent fluid dynamics software, and the simulated result was compared with that of the field test. The result shows that the vertical air leakage of the working face is serious, the wind speed is high, and the air leakage rate is up to 86.96%. The air leakage rate is higher in winter and lower in summer. The air leakage intensity decreases from the air inlet side to the air return side through the middle of the goaf. The range of the oxidation heating zone of the goaf is 98–245 m on the air inlet side and 33–96 m on the air return side. The numerical simulation result is well consistent with the field test data. The research conclusion can guide fire prevention and the extinguishing of No.122108 working face and lay a foundation for the prevention and control of spontaneous fire in goafs of fully mechanized caving mining with a shallow buried and high mining height.

Mitigating Coal Spontaneous Combustion Risk within Goaf of Gob-Side Entry Retaining by Roof Cutting: Investigation of Air Leakage Characteristics and Effective Plugging Techniques

“…Note: A is the pre-exponential factor; C is the oxygen concentration; E a is the activation energy; R is a gas constant; T is the temperature of the coal sample; q is the porosity of floating coal. [27,40] (1) Conservation of mass equation:…”

Effects of CO2 injection factors on preventing spontaneous coal combustion in coal mine gobs: a simulation approach

“…Therefore, the residual coal in the gob is exposed to continuous O 2 and has the possibility of spontaneous combustion. The hazardous areas of self-ignition in the gob depend on many factors, such as air leakage, thickness of residual coal, and the advanced rate of the working face (Zhu and Wen, 2023). Normally, the "three zones" (the cooling zone, oxidation zone, and suffocation zone) in the gob are determined based on the distribution of O 2 concentration in the gob area (Ma et al, 2020).…”

“…Therefore, many technical solutions were presented to prevent coal from spontaneous combustion and inhibit coal fire, which normally focus on two aspects: isolating coal active sites from O 2 and cooling the temperature (Dou et al, 2022). The present strategies can be broadly classified as uniform pressure ventilation (Lu et al, 2017), grouting (Zhang et al, 2018), spray inhibitors (Lu et al, 2020;Sun et al, 2022), pumping inert gas (Zhu and Wen, 2023), and injecting gel foam or gel (Lu et al, 2018;Lu et al, 2021;Han et al, 2022;Huang et al, 2022). CO 2 is an inert gas and can dilute the O 2 concentration and protect the coal from heat release.…”