Study On The Law Of Radon Exhalation In The Heating Process Of Coal Oxidation And Sponstaneous Combustion

Precise detection of fire sources has been a worldwide problem in coal mine fire control engineering.Isotope measurement technique is widely used for precise detection of fire sources,but its actual detection depth is less than 500m.In recent years,with the increasing mining depth of mine in China(>700m),the geological structure of coal seam is becoming more and more complex and the influence of mining is drastic,the radon measurement technology on the surface can not be satisfied,especially in the deep mechanized coal caving face,there will be continuous loose coal piles left behind in the gob area,and the spontaneous combustion phenomenon will be more serious.Therefore,in order to accurately detect the location of fire sources in the goaf,it is necessary to study the law of radon exhalation and migration in loose coal firing process.In this paper,the main factors affecting radon exhalation in underground coal mines are analyzed by analyzing the influencing factors of underground radon exhalation and combining with the environmental conditions of underground coal mines.By means of field detection,theoretical analysis and experimental research,the relationship between radon exhalation and the degree of ignition and the relationship between radon migration and the position of high temperature point is studied by temperature programmed device and self-ignition experiment stand.Through the analysis of the environmental conditions in the goaf,the main factors influencing the radon exhalation were determined,and the experimental conditions were determined for the study.The general equation of radon propagation in loose coal piles was obtained by the theory of radon exhalation and transmission dynamics analysis of homogeneous crushing medium.Based on the temperature rising experiment,a local gas circulation system is designed to study the relationship between radon,indicator gas and coal temperature.The relationship between radon concentration and coal temperature was compared and analyzed.Through the theoretical analysis of radon accumulation,the relationship of radon accumulation with time is deduced.Based on the temperature programmed device,a closed cycle system is designed to study the relationship between the accumulation of radon and the time,to obtain the time of radon concentration balance.According to the actual conditions,the general equation of radon migration is simplified.Combined with self-ignition experiment stand,the local gas circulation system is designed to obtain the distribution of radon concentration and movement in the axis of the experimental bench,which provides the basis for the prediction of the firing position of the loose coal pile.Through the radon exhalation,migration rule and local coal sample microscopic analysis,the radon exhalation law in the natural ignition process is studied,which provides a basis for the location judgment of high temperature points.The results show that during the process of oxidative heating,the radon exhalation increases first and then tends to stabilize,and there are obvious temperature mutation points,which can be used as an early prediction index of natural ignition.In the spontaneous combustion process of loose coal piles,the migration along the axial direction is mainly seepage and diffusion.With the increase of coal temperature,the scope of seepage and diffusion changes,and the migration law of radon changes.Based on this rule,it can provide the basis for determining the location of the fire in the goaf and the position of the high temperature point.