高地温矿井采空区煤自燃O_(2)浓度场分布研究

Study on the distribution of O_(2) concentration field of coal spontaneous combustion in high ground temperature goaf

针对采用理论分析及实验研究的方法研究高地温对采空区煤自燃的影响难以全面反映采空区煤自燃O_(2)浓度场分布情况的问题,采用Fluent数值模拟软件对高地温矿井采空区及进风侧、回风侧和采空区中段O_(2)浓度场分布规律进行了研究。结果表明:①在通风量相同情况下,温度从24.8℃升高到40℃时,O_(2)随着风流向整个采空区渗入,O_(2)浓度随采空区深度增加而减小;在温度相同情况下,当风量从1800 m^(3)/min增大到2700 m^(3)/min时,采空区漏风范围大幅度提升,采空区O_(2)浓度场变化明显,O_(2)几乎充满整个采空区,并且高浓度O_(2)存在范围增大,此时由于热量积聚导致采空区温度升高,采空区内部遗煤温度也持续增加,煤氧复合作用加快,遗煤自燃的可能性增大。②随着采空区距工作面距离增大,O_(2)浓度减小,进风侧O_(2)浓度大于回风侧O_(2)浓度,表明进风侧煤自燃危险性大于回风侧。③随着采空区深度增加,进风侧与采空区中段O_(2)体积分数持续减小,曲线斜率呈先增大后减小趋势;回风侧O_(2)体积分数随采空区深度增加呈减小趋势;大量高浓度O_(2)存在于采空区150 m之前,整个采空区进风侧与采空区中段煤自燃危险性均大于回风侧。④当温度为40℃、通风量为2700 m^(3)/min时,氧化带最大宽度为131 m,将该最大宽度视为开采最大理论宽度,进一步计算安全推进速度,可为煤矿开采提供理论依据。

It is difficult to fully reflect the distribution of O_(2) concentration field of coal spontaneous combustion in goaf by using theoretical analysis and experimental research methods to study the impact of high ground temperature on coal spontaneous combustion in goaf.Fluent numerical simulation software is used to analyze the distribution law of O_(2) concentration field in the inlet air side,return air side and the middle section of the high ground temperature goaf.The results are listed as follows.①When the temperature increases from 24.8℃to 40℃with the same ventilation volume,O_(2) flows into the whole goaf with the wind,and the O_(2) concentration decreases with the increase of goaf depth.When the air volume increases from 1800 m^(3)/min to 2700 m^(3)/min with the same temperature,the air leakage range in goaf increases significantly,the O_(2) concentration field in goaf changes obviously,and O_(2) almost fills the whole goaf.Moreover,the existence range of high concentration O_(2) increases,then the temperature of goaf increases due to heat accumulation,and the temperature of the residual coal inside goaf also continues to increase,the coal-oxygen reaction accelerates,and the possibility of spontaneous combustion of the residual coal increases.②As the distance between goaf and the working face increases,the O_(2) concentration decreases.The O_(2) concentration on the inlet air side is greater than the O_(2) concentration on the return air side,indicating that the risk of coal spontaneous combustion on the inlet air side is greater than that on the return air side.③As the depth of goaf increases,the volume fraction of O_(2) on the inlet air side and the middle section of goaf continues to decrease,and the slope of the curve increases first and then decreases.The volume fraction of O_(2) on the return air side decreases with the increase of goaf depth.A large amount of high concentration O_(2) exists before 150 m of goaf,and the risks of coal spontaneous combustion in the inlet air side and the middle section of the whole goaf are greater than in the return air side.④When the temperature is 40℃and the ventilation volume is 2700 m^(3)/min,the maximum width of the oxidation zone is 126 m.This maximum width is regarded as the maximum theoretical width of mining.Further calculation of the safe advancing speed can provide a theoretical basis for coal mining.