Study Of Impact On Gas Migration In Fire Zone Closed For Closing Coal Fire Area

Mine fire is one of the five major disasters seriously endangering the safety of coal production, it has characteristics such as breaking out suddenly,fire developing rapidly, rescuing hardly and so on.When it is difficult to extinguish the mine fire directly,casing fire lasted more than two hours, in order to control the development of the fire, it needs to close the fire zone at both ends of the district, and then take measures to extinguish fire such as injecting inert gas, injecting slurry,injecting water,etc. However, it may occurs gas explosion in fire zone during or after conducting a closing process,due to merry disorders and other reasons,casing fire rescue failed.There are there orders to close a fire zone,namely "fist air inlet side then air return side","first air return side then air inlet side" and closing simultaneously.Factors which affect merry flow in closed fire zone such as mechanical pressure and fire pressure change variously when closing fire zone using different orders.Based on the combustion characteristics of coal fires and theory of smoke stream flowing,it analyses the source and composition of the gas in fire zone; and as oxygen for example,it describes gas concentration changes in the characteristics of the fire zone by deriving formulas.Respectively,it describes the transportation of smoke and the combustible of the gas layers in closed fire zone under normal ventilation conditions and after closing the fire area by using formulas; it lists five forms of gas emission and migration and four merry disorders that may occur in the fire zone during mine fire, and describes the characteristics of them respectively.It analyses how closure order affects the gas migration in fire zone;it studies the coupling of mechanical pressure and thermal pressure,and analyses how the changes of pressure in fire area affects the gas migration in fire zone the region by deriving formulas. In this paper, it establishes a three-dimensional physical model of fire roadway by using "Gambit",and sets up fire flow field model properly,describes the equations which control the flowing of gas in fire zone;and it selects the turbulence models of fire simulation,develops boundary conditions and initial conditions for numerical simulation of the closed fire zone.And then it completes three-dimensional numerical simulations of gas migration in closed fire zone under different closure orders by using Fluent software. According to the simulation results,it analyzes the migration law of gas in closed fire zone during and after conducting a closing process for different closure orders. By analyzing the temperature, gas concentration and oxygen concentration in the fire zone under different conditions of fire zone closing, getting the risks of gas explosions in the fire zone,discussing the security of three closure orders.According to the analysis results,it puts forward some suggestions for the choice of the closure order,the construction of the firewalls and the arrangements of the fire zone.It finally provides a theoretical basis for choice of closure order,improving the safety of fire disaster relief.