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首页> 外文期刊>International Journal of Heat and Mass Transfer >Predicting fugitive gas emissions from gob-to-face in longwall coal mines: Coupled analytical and numerical modeling
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Predicting fugitive gas emissions from gob-to-face in longwall coal mines: Coupled analytical and numerical modeling

机译：预测长壁煤矿采空工作面产生的逃逸性瓦斯排放：耦合分析和数值模拟

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Understanding gas emission and transport from the gob to the active working face in longwall coal mines is necessary for mine ventilation and gas control planning and optimization. We document a mine-wide ventilation pressure and flow rate survey (p-Q survey) to establish a ventilation network model - including methane gas concentrations recorded at selected face locations. We propose an analytical pressure gradient model to evaluate gob gas emission and its interaction with the ventilation system. This model combines viscous energy losses along a tortuous gas flow path within the gob materials with kinetic energy losses at irregular cross-sections. A numerical gas emission model was also established to predict gas emission rates at the longwall face and to dynamically determine the gas emission rate from the compacted gob. Field monitoring indicates that steady methane concentrations increase monotoni-cally and almost linearly from headgate to tailgate. The average methane emission rates are estimated as 0.0061 m~3/s, 0.0044 m~3/s and 0.00215 m~3/s for wide, intermediate-width and narrow panels. A numerical network model of the mine was validated then calibrated against the field methane monitoring results at our partner mine. We observe that gob compaction and related porosity reduction significantly affects gas emission rate. An eleven-fold increase in stress (1.70-18.68 MPa) results in a nonlinear decrease in porosity of only ~75% (from 0.368 to 0.093) but a 56-fold reduction on gas emission rate (compared to the maximum transient gas emission rate). The mine-wide ventilation system is especially sensitive to methane emission rates - a 50% increase in emission rate (from 0.00455 m~3/s to 0.00637 m~3/s) clearly impacts concentrations in the return branches. Peak methane concentration at related branches increase 39.7%, from 2.24% to 3.13% with the potential to trigger elevated methane alarms. These results can ultimately provide the data for analyzing the interactions between the caved gob and the ventilation system and define mitigation strategies to minimize gas concentrations and hazard.
机译：了解长壁煤矿从采空区到工作面的瓦斯涌出和运输，对于煤矿通风和瓦斯控制规划和优化是必不可少的。我们记录了整个矿井范围内的通风压力和流量调查（p-Q调查），以建立通风网络模型-包括在选定工作面位置记录的甲烷气体浓度。我们提出了一种分析压力梯度模型来评估采空区瓦斯的排放及其与通风系统的相互作用。该模型将沿料料内部曲折气体流动路径的粘性能量损失与不规则横截面处的动能损失结合在一起。还建立了一个数值气体排放模型，以预测长壁工作面的气体排放率并从压实的料滴中动态确定气体排放率。现场监测表明，稳定的甲烷浓度从后挡板到后挡板单调递增，并且几乎呈线性增加。宽，中宽度和窄面板的平均甲烷排放速率估计为0.0061 m〜3 / s，0.0044 m〜3 / s和0.00215 m〜3 / s。验证了该矿山的数字网络模型，然后针对我们合作伙伴矿山的甲烷监测结果进行了校准。我们观察到，料滴压实和相关的孔隙度降低会显着影响气体排放速率。应力（1.70-18.68 MPa）增大11倍导致孔隙率非线性降低仅〜75％（从0.368降低至0.093），但气体排放率降低了56倍（与最大瞬态气体排放率相比） ）。整个矿井的通风系统对甲烷排放速率特别敏感-排放速率增加50％（从0.00455 m〜3 / s增加到0.00637 m〜3 / s）显然会影响返回分支的浓度。相关分支机构的甲烷峰值浓度从2.24％增至3.13％，增幅为39.7％，有可能触发更高的甲烷警报。这些结果最终可以提供数据来分析带孔采空区与通风系统之间的相互作用，并定义缓解策略，以最大程度地减少气体浓度和危害。

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