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

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 under-stand the location distribution of the fire source and the degree of ignition in the goaf,this paper studied the radon pre-cipitation 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 ac-tivity concentration along the axis in the spontaneous combustion process of loose coal. Through data screening and sta-tistical analysis,the distribution law of radon activity concentration along the axis was obtained under the same tem-perature condition. According to the distribution theory of radon activity concentration,the distribution equation of ra-don in the direction of the axis of the experimental platform was deduced. Based on the distribution law of radon activi-ty concentration along the axis and the distribution equation of radon under the same temperature condition,the migra-tion 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 Tmax