Numerical Simulation Research On Goaf Fire-prevention By Nitrogen Injection Based On Partial-W Type Ventilation In Duanwang Mine

The comprehensive control of spontaneous combustion in goaf and gas disaster are always the key and difficult points during the mine production process.Duanwang mine in Shouyang Shanxi province use ventilation pattern of "partial-W,two intakes one return" to control gas concentration of workface's upper corner,while the flow field of goaf is complex under the ventilation pattern,and which will have an effect on spontaneous combustion in goaf,so that CFD software is used to make numerical simulation and carry out research on fire preventing and extinguishing problem of using reasonable nitrogen injection volumes based on coal seams susceptible to spontaneous combustion in goaf.According to the actual data of 150405 face in Duanwang mine,the 3D physical model of goaf with an angle of 6 is built;while caving goaf is heterogeneous,so that the porosity distribution is built as per "O-ring type" mode,it also considers the gravity;meanwhile,the coal sample oxygen consumption rate is got by the coal sample closed oxygen consumption experiment and inhomogeneous oxygen consumption source term could be set as per the result.The paper compare the simulation result with the actual data,as a result,the two are coincide with each other and it show the reliability of experiment.Through simulation to analyze gas extraction intensity's influence on spontaneous combustion of remaining coal,the simulation results show that with gas extraction intensity increasing,the highest gas concentration becomes lower,the width of oxidizing zone has the tendency to reduce in belt-roadway side,while in rail-roadway side,it has the tendency to increase,and the actual gas extraction intensity 82m3/nin can meet field needs;150405 Workface's optimal nitrogen injection location is between 40m and 60m distance from workface on the goaf belt-roadway side;then according to maximal oxidized zone width which guarantee the remaining coal do not self-ignite,the lowest limit value nitrogen injection volume could be determined.The partial-W type is a emerging ventilation pattern for controlling gas exceeding the limit of high production and efficiency face,the paper provides theoretical support and assistant analysis for safety production of coal seams susceptible to spontaneous combustion,to make sure at the moment that gas does not be exceeded,the spontaneous combustion of remaining coal could be prevented effectively.