Study On The Law Of Gas Accumulation In Coal Mine Fire Area Based On Changes Of Atmospheric Pressure

After a mine fire occurs,If the ignition time is not effectively controlled within a certain period of time,the fire area will be closed.Even a closed fire zone can not be considered as a complete extinction of its internal fire source,closed fire zone the biggest threat is the mixing and detonation of explosive gases in the zone.Changes in surface atmospheric pressure will cause pressure difference inside and outside the closed wall,because the firewall is not tightly sealed,resulting in fresh air leakage into the fire area and increase the oxygen content in the area or gas outflow in the area causing poisoning,similar to "breathing" phenomenon.The "breathing" phenomenon will also be affected by the change of atmospheric pressure during the opening of fire zones.Firstly,this paper analyzes the types and characteristics of fire combustion,and then analyzes the mechanism and relationship between fire combustion and its characteristics.According to the characteristics of mine fire,the classification of gas components in mine fire area is analyzed.By introducing the concepts of throttling effect and buoyancy effect,the influence of different types of roadway fire on air flow in mine is analyzed.Based on the theory of mine ventilation,the relationship among total pressure,static pressure and dynamic pressure under different ventilation modes is analyzed,and the relationship between surface atmospheric pressure and mine static pressure is analyzed.Based on the field measured data,the relationship between the pressure in the fire zone and the atmospheric pressure is analyzed.Based on the theory of gas seepage,the mathematical models of atmospheric pressure,goaf gas and free zone gas emission are derived respectively.In view of the danger of gas emission and explosion,the causes of gas explosion caused by the change of atmospheric pressure are expounded.Finally,combined with the mechanism of surface atmospheric pressure on gas migration in coal mine fire area,the influence of atmospheric pressure on coal mine fire area closure and fire area opening is analyzed theoretically.Combining with the actual situation of the mine,the physical model of the closed fire zone is established by Geometry,and the setting of the fire flow field is treated appropriately.The turbulence model,the dynamic control equation and the solving method for the fire simulation are expounded,and the appropriate mathematical model,the boundary condition and the initial strip are selected according to the actual situation.And the calculation of natural wind pressure in mines.Fluent software is used to simulate the gas accumulation and gas migration in coal mine fire area under the change of surface atmospheric pressure.CFD-Post is used to postprocess the simulation results,and the gas concentration field and temperature field in coal mine fire area under different atmospheric pressure are analyzed.At the same time,the change of gas state in the process of opening the fire area is analyzed when the atmospheric pressure changes.Finally,the influence of surface atmospheric pressure change on gas accumulation in coal mine fire area is summarized.According to the analysis results,some measures and suggestions are put forward for the management of coal mine fire area,the management of fire wall and the opening of fire area.Finally,it provides a theoretical basis for the management of coal mine fire area and the selection of opening time,and improves the safety of fire area management and opening.