Research On The Theory And Applicatiaon Of Gas Control By Microorganism In The Coal Seam

As the depth of mine excavation goes further, the ground stress is continuouslyincreasing but the permeability coefficient of coal seam reduce. It leads to the difficultyof gas extraction or emission. More time, manpower or resources are needed todischarge gas and the effect is not very obvious.Therefore, mining conditions are moreand more complicated and the coal and gas outburst accident become more and morefrequent. Especially Chongqing area, the gas content and pressure is on the increasethese years, the outburst scale continuously aggravate and coal and gas extensiveoutburst replace the former basically gas outburst. The major means of pre-draining ishard to meet the current state, the long-term drainage remains below standards. The rootof these phenomena is the low permeability.Though tests of coal hole and fracture, thereare mainly micropore compared with macropore in Chongqing area. Total volume of thepores is large while the volume of interconnected pores is small, and the coals wouldmanifest pressure and water sensibility, all these are positive for storage of gas butnegative for moving of gas.Traditional methods of gas control mainly which base onavoiding, driving, elimination are not very ideal for realizing the goal of safe mining.Meanwhile, the cost of gas purification for low concentration gas is so high that theproduce benefit after purification is far below the cost of energy and fund demanded. Somost of the mines at home and abroad discharge the low concentration coal mine gasinto the atmosphere directly, that would cause bad influence on the ecologicalenvironment.From the view of microorganisms, this paper jumps out of the traditional gasmanagement ideas and studys on making use of microbial technology to deal with coalseam gas. By the using of methane oxidation bacteria, the gas could be controlledsimplely and safely, and the coat will be low,too. This technology will reduce the directdischarging of gas and the amount of accidents of gas explosion or asphyxia.This paper studys the enrichment, isolation, identification, gene analysis andsuitable growth conditions of methanotrophs, and its property of the oxidation ofmethane are verified through laboratory experiences. Then the feasibility test on theground and field experiment underground were conducted. The results of theexperiments showed that degrading coal seam gas by methanotrophs was rational.（1） Analyzed the diversity and mechanism of methane oxidation of methanotrophs, and introduced the characteristics and functions of the four main enzymes.（2） Collected five soil samples and observed in NMS culture medium, and foundthat methanotrophs collected form the water environment of paddy field was of thehighest efficiency of methane degradation and enrichmen. The highestone kind ofmethanotrophs was named M02-019.（3） The gram observation,16S rDNA of PCR amplification and sequence analysisexperiments showed M02belonged to the fungus of degradation or decomposition ofmethane, and made sure that the strain M02-019is in the same branch ofMethylophilus.（4） Negative control experiment, experiment of conservation of mass and smallamplification experiment were conducted, and the results showed that M02was of havehigh activity of degrading methane.（5） Studied the growth conditions of mass culture. The experimental resultsshowed that the growth cycle for this bacterial strain was12days, and its growthentered the logarithmic phase from the third day after inoculation. Using methane andmethanol together as the carbon source of strain growth was best, and it was not easy todye bacteria. It would grow better when using nitrocellulose nitrogen and a smallamount of amino nitrogen together as the nitrogen source of strain. The optimumgrowth temperature for M02-019was30℃and optimum PH was6.5, Fe²⁺concentration was0.4mg/L and Cu²⁺concentration was0.03mg/L.（6） Analyzed the main reason for the gas outburst of the coal seam, and thechemical composition, aperture structure, pore configuration and the permeability of thecoal mass were tested. The results showed that both pressure-sensitive effect and watersensitivity effect exist in the coal seam. After analyzing the relationship between the lowpermeability and them, the methods were put forward in order to increase thepermeability. The study of injecting fluid into the coal seam indicated that the way ofinjection was feasible and the performance of injection depended on the pressure andtime of injection, as well as the wettability of coal seam.（7） Before field experiment underground, the feasibility test on the ground wasconducted through HCA-1type device of high pressure capacity method for gasadsorption. By the comparison of the effect of injecting water and microbial culturesolution, the feasibility of gas control by microbial culture solution was testified, andfurther experiment underground could be conducted. Through the observation andanalysis of underground experiment, the methanotrophs remarkably weakened the dynamic phenomenon of gas and reduced the gas concentration of return air, gas content,gas pressure and the index of K1of the two experimental sites in different degree. Thegas concentration of return air of the two experimental sites respectively reduced by22.54%and77.23%, the gas content reduced by39.67%and13.45%, the gas pressurereduced by76%and18%, and the index of K1reduced by62.8%and26.88%.（8） Whether the feasibility test on the ground or field experiment underground, theeffect were obvious. Meantime, this microbiological method is simple and practicablefor gas control; therefore this technique is of the great industrial value.