Effect of gas extraction on mitigating low-oxygen conditions in upper corners and its impact on coal spontaneous combustion in goaf
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摘要:
气体抽排技术作为治理浅埋煤层工作面上隅角低氧现象的有效措施，其应用过程中存在采空区漏风量增加可能导致煤自燃风险升高的问题。以中煤平朔集团有限公司井工一矿19112工作面为研究对象，在典型浅埋煤层工作面上隅角低氧致因分析基础上，构建了采空区流−固−化多场耦合数学模型，采用计算流体动力学（CFD）数值模拟方法分析了90，120，240，360 m3/min气体抽排流量下上隅角低氧治理效果与采空区煤自燃风险程度。研究结果表明：① 上隅角低氧现象是由煤层处于CO2−N2带且惰性气体下泄、采空区遗煤低温氧化、采空区与地表形成贯通裂隙发育通道及工作面U型负压通风方式等因素共同作用形成的。② 当气体抽排流量提升至360 m3/min时，上隅角区域O2体积分数显著提升，低氧现象得到有效控制。③ 低氧范围宽度与气体抽排流量呈二次函数拟合关系。④ 在上隅角安装抽排通风机进行抽排时虽然会使采空区氧化带宽度有一定程度增加，但其最大宽度（53.8 m）仍远低于理论采空区氧化带宽度安全阈值（604.8 m），表明气体抽排技术在有效治理低氧的同时，不会显著增加采空区煤自燃风险。
Abstract:Gas extraction technology, as an effective measure to mitigate oxygen deficiency in upper corners of shallow coal seam working faces, may lead to an increased risk of coal spontaneous combustion due to elevated air leakage in the goaf during its application. Working face 19112 of No.1 mine at China Coal Pingshuo Group Co., Ltd. was taken as the research object. A coupled fluid-solid-chemical mathematical model of the goaf was constructed based on an analysis of the causes of low-oxygen phenomena in the upper corner of the typical shallow coal seam working face. The Computational Fluid Dynamics (CFD) numerical simulation method was employed to analyze the effectiveness of gas extraction at flow rates of 90, 120, 240, and 360 m3/min in mitigating low-oxygen conditions in the upper corner while assessing associated spontaneous combustion risks in the goaf. The findings indicated that: ① the low-oxygen phenomenon in the upper corner primarily resulted from multiple factors, such as the coal seam location within the CO2-N2 zone with downward migration of inert gases, low-temperature oxidation of residual coal in the goaf, formation of interconnected fracture channels between the goaf and the surface, and the U-shaped negative pressure ventilation method in the working face. ② When the gas extraction flow rate reached 360 m3/min, the O2 volume fraction in the upper corner region significantly rose, effectively controlling the hypoxic conditions. ③ A quadratic function relationship was identified between the width of the low-oxygen zone and gas extraction flow rate. ④ Although installing extraction ventilators in the upper corner for gas extraction may moderately increase the width of the oxidation zone in the goaf, its maximum width (53.8 m) remained far below the theoretical safety threshold (604.8 m), suggesting that gas extraction technology effectively mitigated low-oxygen conditions without significantly increasing coal spontaneous combustion risks.
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Keywords:
- upper corner /
- low-oxygen phenomenon /
- gas extraction /
- goaf /
- coal spontaneous combustion
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图 3 数值模拟与现场测试结果对比
Figure 3. Comparison between numerical simulation and on-site testing results
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图 5 上隅角O2浓度分布云图
Figure 5. Contour plot of O2 concentration distribution in upper corner
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图 6 上隅角附近区域O2浓度分布切片云图
Figure 6. Sliced contour plots of O2 concentration distribution near upper corner
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图 7 上隅角低氧范围宽度随气体抽排流量变化特征
Figure 7. Variation of width of low-oxygen area in upper corner with gas extraction flow rate
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图 8 采空区整体O2浓度分布云图
Figure 8. Overall contour plot of O2 concentration distribution in goaf
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图 9 不同气体抽排流量下采空区氧化带宽度
Figure 9. Width of oxidation zone in goaf under different gas extraction flow rates
表 1 数值模拟参数
Table 1 Numerical simulation parameters
参数 值 参数 值 Kp,max 1.25 b1 −10 Kp,min 1.1 b2 0 m0/（kg·s−1） 0.033 3 mc/（kg·s−1） 0.133 4 A/s−1 9 590 mn/（kg·s−1） 1.5 $ j $ 0.61 dp/m 0.15 T/K 293.15 
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表 2 采空区氧化带最大宽度确定关键点位置信息
Table 2 Key point location information for determining maximum width of oxidation zone in goaf
上隅角抽排
流量/（m3·min−1）坐标/m 关键点 M1 M2 P1 P2 P3 0 X −75.5 −112.0 31.0 −61.5 −86.5 Y 143.5 143.5 0 8.3 5.1 90 X −70.2 143.5 10.5 −56.3 −109.0 Y 143.5 −124.0 0 8.7 4.2 120 X −75.8 −121.5 10.2 −54.8 −94.8 Y 143. 5 143.5 0 7.8 3.8 240 X 240.0 143. 5 3.8 −61.2 −92.6 Y −76.2 −123.8 0 8.0 5.0 360 X −80.0 −124.0 0 −61.4 −104.0 Y 143.5 143.5 0 7.8 4.1
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