| In coal mine production,gas disasters are often the biggest cause of accidents.Therefore,the source of gas and its prevention technology are also the top priorities of mine safety production.Based on the analysis and summary of predecessors on the gas source in the goaf and the gas treatment technology at the upper corner of the working face,this article aims at the stop of production and the stop of the working face caused by the excessive gas in the upper corner of the 1202 fully-mechanized working face in Yixing Coal Industry No.1 mining area.For gas sources in the goaf,we use on-site sampling,analysis and testing and other technical means,use the stable hydrocarbon isotope separation method and propose a gas source calculation model in the goaf to predict the contribution rate of each adjacent coal seam and this coal seam to the gas in the 1202 goaf.According to the prediction results of separate sources,the gas source separation control measures in the goaf were proposed,and the FLUENT simulation software was used to simulate different gas control methods in the goaf.After comprehensive consideration,it was decided to adopt the upper corner buried pipe drainage gas control method to solve the above problems.Corner gas overrun problem.The following results were mainly achieved during the research process:(1)The source of mixed gas in goaf of 1202 fully-mechanized mining face was quantitatively analyzed by using stable carbon and hydrogen isotopic markers,and the calculation model of gas source separation was proposed.(2)The single-day and single-month forecast results showed that the 2~#coal seam in the goaf of 1202 fully mechanized mining face accounts for the largest proportion of gas sources,reaching about 52.72%.The average gas contribution rate of 2~#coal seam and 3~#coal seam was24.53%and 16.52%,respectively,while the gas contribution rate of 1~#coal seam had little fluctuations and stabilized at about 6.24%.Therefore,the 1202 gas prevention and control are the focus of the 2~#coal seam under,and 2+3~#coal seam auxiliary prevention and control.(3)Based on the study of the goaf porous media theory system,a mathematical model of gas flow between the goaf and the working face was established.The different methods of gas drainage in the goaf of 1202 working face were used to simulate and analyze the gas migration inside the goaf by using the FLUENT numerical simulation software.The results showed that under the condition of buried pipe,the gas concentration in the upper corner is reduced by 28%compared with that without extraction,and the gas concentration in the corner of the working face is reduced to 0.45%.When the simulated buried pipe was lengthened and the high-position borehole is jointly arranged,the gas concentration in the deep area of the goaf can be greatly weakened.After extraction,the gas concentration reduced by 45%,and the gas concentration in the corner of the working face reduced to 0.35%.(4)The field drainage test results showed that during the drainage period,the average gas concentration in the upper corner decreased to 0.40%,the extraction pure quantity was stabilized at about 8.03m~3/min,the suction negative pressure was maintained at about 12.37k Pa,and the average gas concentration in the upper corner and the return air roadway decreases to 0.48%and 0.31%respectively,which is basically consistent with the simulation results.Although the use of buried pipe drainage can effectively reduce the gas concentration in the upper corner and reach the safety level of production,according to the simulation results,it is suggested to adopt the combined arrangement of buried pipe and high-level borehole to effectively control gas fundamentally. |
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