Study On Spontaneous Combustion Characteristics Of Coal Under Thermal Radiation

In the process of coal mining,coal spontaneous combustion has always threatened the safety of mine production.As the mining depth and intensity of mines increase,the disasters caused by spontaneous combustion of coal are often more serious in the presence of gas.In the mine fire area,burning gas can easily ignite coal.Thermal radiation,as the main form of heat transfer in gas combustion,greatly affects the process of gas combustion and igniting coal.Therefore,research on the characteristics and critical conditions of thermal radiation ignited coal is helpful to explore the way of gas combustion ignited coal,to a certain extent,to reduce the risk of coal spontaneous combustion and gas explosion in underground coal mines,and to ensure safe production in coal mines.This paper designs and builds an experimental platform for testing coal sample combustion characteristics under thermal radiation.The experimental platform includes a heat flow control system,a data acquisition system and a sample processing device.Through the experimental platform,under three heat flow intensities(11.52kW/m2,8.15kW/m2,5.68kW/m2)and two different distances(8cm,12cm),four different particle sizes(30-60,60-100,100-120,120-180 mesh)the radiation characteristics of Dongtan gas coal samples.The response mechanism of coal samples with different radiation intensities,different radiation distances and different particle sizes to thermal radiation was studied.Visual representation of the apparent morphology of coal at different stages of oxidative combustion under the action of radiation.The change characteristics of characteristic temperature and mass loss rate in the process of coal oxidation and combustion were tested,and the coal heating model under thermal radiation conditions was verified.The critical time and space conditions for coal ignited by radiation have been preliminarily determined.Studies have shown that the intensity of heat flow,the particle size of the coal sample and the relative distance between the fire source and the coal sample are all important factors that affect coal by thermal radiation.When the intensity of heat flow is stable,changing any variable may directly affect Combustion characteristics of coal samples.In this paper,based on the heating characteristics of coal samples,the coal sample combustion process under thermal radiation conditions is divided into three stages:air area heating,coal body heat storage,and coal combustion.The study found that as the heat flow intensity increases,the residence time of the coal sample at the highest temperature becomes shorter,and the heating rate increases;under the same thermal radiation condition,as the particle size of the coal sample decreases,the coal sample heating rate gradually increases,and The heat period becomes shorter,the surface of coal samples becomes more dry and cracked,and coal samples with small particle diameters have a stronger ability to absorb thermal radiation;the reduction of the relative distance between the radiant heat source and the coal sample will result in more intense oxidation and combustion.The time for the weight loss is significantly shortened,the overall weight loss rate increases and the duration at the peak becomes shorter.The coal sample with a particle size of 0.975mm at the two relative distances will not ignite spontaneously when the heat flow intensity is less than 5.68kW/m2.According to the test results of thermal radiation characteristics,the coal combustion results under thermal radiation conditions are divided into ignition zone and non-ignitable zone,and the critical conditions for thermal radiation to ignite coal are preliminarily determined.This study has a significant on the coupling of gas and coal spontaneous combustion.This research has important theoretical and practical significance for coal mine disaster prevention.