Numerical Study On The Evolution Of Methane Explosion Limits During Fire Zone Sealing

Thermal explosion hazard of coal mine gas explosion threaten safety production of mine.And Methane explosion may easily happen in the process of fire sealing.The gas field and temperature filed in the goaf were changed during sealing.Meanwhile,the methane explosibility varied in the sealing.So,focusing on the thermal disasters in the process of sealing mine fire area is the key of mine disasters.And the related research in the combustion state,the explosibility of mixture gas and spatial and temporal distribution of methane explosibility in the goaf was studied.The combustion state varied during sealing.The fire dams were built in the intake airway and return airway at the same time.The ventilation quantity line decreased and the resistance index changes with the sealing time increasing.The oxygen concentration is less than 16% when the ventilation quantity is less than 65%⁷0%.The combustions state varied from complete combustion to fuel enriched combustion.The gases are the productions of fuel-enriched combustion.Based on the heat balance of methane combustion,the heat balance model proposed,which is applied to open system,semi-closed system and closed system.The methane explosion limit model was proposed.And the methane explosion limit with the single gas influenced was shown.The CO₂ increases the lower methane explosion limit.And the upper explosion limit was decreased with.However,The CO increases the lower methane explosion limit.The multicomponent smokes（the mixture gases of CO and CO₂）during sealing changes the methane explosion limits.The lower explosion limit is sensitive to the variation of CO concentration.And the upper explosion limit is sensitive to the variation of CO₂ concentration.With analyzing the methane explosibility in the process of sealing,the position and time of methane explosion in the goaf was shown.Based on finite element model,the process of sealing was analyzed with FLUENT software.The methane explosion limit was influenced by the multicomponent smokes（the mixture gases of CO and CO₂）.The zone with methane explosibility risk was located at area near fire location and returnside in the goaf.And the area near fire location is with high risk area.Meanwhile,the inflammable gas is within the explosion limits and is with highest explosion risk,when the ventilation quantity is less than 7.5%¹2.5%.