Research On The Evolution Law Of High Temperature Region Of Loose Coal Body Under The Action Of Lateral Wind Flow On The Surface

Coal spontaneous combustion occurs frequently in the process of coal mining and transportation,which greatly hinders the sustainable development of the coal industry.The spontaneous combustion of coal in the process of open-vehicle transportation not only affects the normal order of railway transportation,but even endangers the safety of workers.Therefore,in order to study the problem of high temperature spread during open-vehicle transportation of coal in this paper,a similar simulation device is built,and the research on the influence of surface transverse air flow on the spread of high temperature in coal and gas distribution is carried out,which provides a certain theoretical basis for the prevention and control of coal fires during open-vehicle transportation.Based on the similar principle,this paper independently designs a high-temperature evolution simulation experimental device for open-vehicle transportation,and selects the coal sample that is easy to spontaneously combust as the research object.Under the condition of static no wind and surface transverse wind flow(1m/s and 2m/s),the dynamic distribution law of the temperature and gas inside the coal body when the high temperature area of 300℃appears in the box is simulated.The results show that the lateral wind flow on the surface accelerates the horizontal and vertical spread of high temperature in the coal body,the time for the downward spread of high temperature in the wind flow lm/s experiment is 0.3 times earlier,and the wind flow 2m/s is 0.5 times earlier.Under the condition of no wind flow,the temperature inside the loose coal body is finally stabilized at 420±20℃;under the influence of wind flow,the temperature of the coal fire area inside the box increases by 120±20℃.During the no-air flow experiment,affected by factors such as voids and heat transfer,the high temperature inside the coal body spreads downward in a nonlinear movement law.The high temperature point inside the coal body moves from the middle to the direction of the wind flow by the effect of lateral wind flow on the surface.By analyzing the distribution characteristics of the gas inside the coal body,it is found that the surface transverse air flow accelerates the consumption of O2 inside the coal body and shortens the time for CO and CO2 to reach their peaks.When the surface temperature change is small,the surface CO and CO2 gases fluctuate within a certain range,and the greater the wind flow,the higher the fluctuation range.Meanwhile,the fluctuation range of surface CO and CO2 concentrations in the no-wind experiment was 0.25 to 0.35%,and the coal fire area above 400℃has appeared in a large area in the box.The distribution law of O2 inside the box is opposite to the change trend of coal temperature.The gas generated inside the coal will move to the upper seam coal sample under the influence of thermal buoyancy and thermal diffusion,resulting in a higher gas concentration in the upper layer.