松散煤体自然发火过程氡析出及运移规律

Law of radon precipitation and migration in loose coal during spontaneous combustion process

火源精准探测一直是煤火灾害防治方向的世界性难题,而同位素测氡是火源精准探测的主要研究方法。为了解采空区火源位置分布及发火情况,基于煤自然发火实验台研究松散煤体发火过程中氡析出及运移规律。为减小测氡过程对自然发火实验影响,设计局部气体循环系统,控制实验取气量,获得松散煤体自然发火过程中氡活度浓度沿轴线分布规律;通过数据筛选及统计分析,获得同一温度条件下氡活度浓度沿轴线分布规律;根据氡活度浓度分布理论,推导实验台轴线方向氡分布方程;基于同一温度条件下氡活度浓度沿轴线分布规律及氡分布方程,获得松散煤体自然发火过程中氡的运移规律,确定真实反映氡析出与煤温关系的节点位置;通过松散煤体单元划分及氡析出理论分析,推导松散煤体氡析出随发火时间的对应关系;基于实验分析和理论推导,获得氡析出与发火时间的变化规律。结果表明:松散煤堆自然发火过程中,沿轴线方向松散煤体内氡运移主要以渗流为主,当Tmax<50℃时,渗流影响范围为0<L<175cm,其中L为与进风口的距离;当Tmax≥50℃时,渗流影响范围减小为0<L<125cm,多种运移方式耦合作用范围为125<L<175cm,可为采空区发火位置判断提供依据;在一定温度范围内,氡析出随煤温升高呈指数增长,且存在临界温度值,可为松散煤体发火程度判断提供依据。

The accurate detection of fire source has always been a worldwide problem in coal fire disaster prevention,and the isotope measurement is the main research method for the accurate detection of fire source.In order to understand the location distribution of the fire source and the degree of ignition in the goaf,this paper studied the radon precipitation and migration laws in the ignition process of loose coal based on the coal spontaneous combustion laboratory.To reduce the influence of radon measurement process on spontaneous combustion experiment,a local gas circulation system was designed to control the amount of gas taken in the experiment and obtain the distribution law of radon activity concentration along the axis in the spontaneous combustion process of loose coal.Through data screening and statistical analysis ,the distribution law of radon activity concentration along the axis was obtained under the same temperature condition.According to the distribution theory of radon activity concentration,the distribution equation of radon in the direction of the axis of the experimental platform was deduced.Based on the distribution law of radon activity concentration along the axis and the distribution equation of radon under the same temperature condition,the migration law of radon in the process of spontaneous combustion of loose coal was obtained,and the node position that truly reflects the relationship between radon precipitation and coal temperature was determined.Corresponding relationship between the precipitation of radon from loose coal and the ignition time was established by loose coal element division and radon exhalation theoretical analysis .Based on experimental analysis and theoretical derivation,the variation law of radon precipitation and ignition time was obtained.The results show that during the spontaneous combustion of loose coal piles,the migration of radon in the direction of the axis is mainly dominated by seepage.When T max <50 ℃,the influence range of seepage is 0< L <175 cm,where L is the distance from the air inlet.It can provide a basis for judging the location of fire in the goaf.When T max ≥50 ℃,the influence range of seepage decreases to 0< L <125 cm,and the coupling range of multiple migration modes is 125< L <175 cm.It can provide a basis for determining the location of the fire in the goaf.Within a certain temperature range,radon precipitation increases exponentially with the rise of coal temperature,and there is a critical temperature value,which can provide a basis for judging the degree of ignition of loose coal.