Experimental Study On High Efficiency Inerting And Optimization Of Inert Gas Compounds In Goaf

Mine fires have always been a serious hazard in mining.According to statistics,more than 56%of coal seams have a tendency to spontaneous combustion in China.The fires caused by spontaneous combustion of coal account for 94%of the total number of fires in the mine,and about 60%of them occurred in the goaf.Injection of N₂ or CO₂ is the commonly used measure for fire prevention in the goaf.On the basis of injection of an inert gas or synergistic injection,the inerting effect of premixed inert gas instead of CO₂ in conditions of same goaf and injections was studied with different wind speed of coal mining face,inclination and ventilation of goaf,and pipeline buried by an experimental platform that follows similar principles.The main research content and the main conclusions are listed below:（1）Inerting effect of N₂ and CO₂in conditions of different wind speed of coal mining face,inclination and ventilation of goaf,and pipeline buried:（1）As the wind speed at the coal mining face increases,the inerting effect of N₂ and CO₂ gradually weakens in nearly horizontal goaf,which is the obvious area that cannot be inerted by CO₂on the floor;（2）The optimization of the pipeline buried is not obvious to improve the inerting effect in condition of wind speed at the coal mining face has obvious interference to the flow of inert gas in the goaf;（3）the inerting effect of CO₂ is greatly reduced by gravity in the gently inclined goaf.（2）On the basis of insufficiency of CO₂,the inerting effect of CO₂replace by premixed gas with N₂ proportion of 50%,60%,70%,and 80%was studied:（1）The effect of premixed inert gas with 70%N₂ is the best in the nearly horizontal goaf,and the average O₂ concentration is reduced to 6.4%in the area,which is 9.7%when CO₂is injected.The effect of premixed inert gas with 80%N₂ is the best in the gently inclined goaf with upward ventilation,and the average O₂ concentration is reduced to8.4%in the area,which is 12.1%when CO₂ is injected.Moreover,there is on area that cannot be inerted by premixed inert gas in these two conditions.（2）The effect of premixed inert gas with 70%N₂ is the best in the gently inclined goaf with downward ventilation,and the average O₂ concentration is reduced to 11.2%in the area,which is15.1%when CO₂ is injected.However,the premixed gas with only N₂ proportion of60%and 70%has no blind zone of inert gas.（3）On the basis of insufficiency of an inert gas,the inerting effect of asynchronous synergistic injection was studied in gently inclined goaf,which injects premixed inert gas at the upper part of goaf first and then N₂ at the lower part of goaf:（1）Compared with the synchronous synergistic injection,which injects premixed inert gas at the upper part of goaf and N₂at the lower part of goaf at the same time,the asynchronous synergistic injection is better.（2）The principle that the inerting effect is enhanced by asynchronous synergistic injection is the displacement and mixing of premixed inert gas and N₂in the cracks of the floor.（3）On the basis of premixed inert gas that N₂ accounts for 50%-80%,the greater the density difference with premixed inert gas is,the more N₂is mixed,and the closer outlet and direction of movement of and premixed inert gas is,the stronger N₂ is displaced.（4）Due to the synergistic effect of leakage air and N₂ weakens the displacement effect of premixed inert gas on N₂ in gently inclined goaf with upward ventilation,N₂ is more fully mixed with premixed inert gas and the weaker the displacement effect is,the better the N₂is mixed.（5）The N₂ ratio of 50%in the premixed gas is always the best effect on decrease of O₂concentration in gently inclined goaf with upward or down ventilation,which is reduced to 4.4%and 9.7%respectively.This thesis includes 27 figures,44 tables and 80 references.