Law And Prevention Research Of Coal Spontaneous Combustion Inducing Gas Burning Or Explosion In Goaf

Gas burning is one of multiple accident in coalmine goaf. With the increase ofmining depth, gas emission and ground temperature are increased continuously. Thismakes gas burning induced by coal spontaneous combustion become an importantform. Due to the lack of gas burning law and prevention research under the conditionof spontaneous combustion, it has certain blindness to prevent gas burning frominducing by spontaneous combustion in field. Therefore, this paper focused onresearching the law and prevention of coal spontaneous combustion inducing gasburning in goaf. The result is beneficial to decrease the occurrence of gas burning ingoaf.In order to control coal spontaneous combustion inducing gas burning in goaf,law of spontaneous combustion and gas emission in stope was studied based on minepressure theory. On the basis of analyzing stress distribution in stope, stress “threeareas” is gradually formed in strike and tendency of stope during coal mining isobtained. This results in the formation of overlying strata caving “three zones” invertical direction and O-ring recompaction area in caving zone of goaf. The stratacaving law leads to “U” type air leakage before becoming a square of goaf and “M”type air leakage after becoming a square of goaf. Easy self-ignition area is dividedinto the vicinity of coalpillar, fault and large gangue. Based on the gas emission ofstope, effective means of decreasing spontaneous combustion inducing gas burning,controlling air leakage and residual coal distribution, are proposed.On the basis of analyzing spontaneous combustion igniting gas theory,experiment platform of high temperature coal igniting gas was designed andconstructed and experiment of high temperature coal inducing gas burning wascompleted. Closed space gas change law during coal warming was studied underdifferent heating power, different initial CH₄concentration and different heat sourcedepth. The results showed O₂concentration decreases, N₂concentration increases firstand then decreases and other gas concentration increases with the increase of closedspace coal warming. In the high temperature stage, O₂concentration increases, N₂concentration increases first and then decreases and other gas concentration decreaseswith the increase of heating power. O₂concentration decreases first and then increases,CH₄concentration increases and other gas concentration decreases with the increaseof initial CH₄concentration. O₂concentration increases, N₂concentration decreases first and then increases and other gas concentration decreases with the increase of heatsource depth. Relation between closed space gas concentration and explosion limitduring coal warming process was analyzed by Matlab. The result shows closed spacegas concentration is greater than its explosion limit and easily loses explosiveness inmany conditions. Advancing oxidation area of coalpillar, top coal and upper adjacentcoal seams is easy to ignite gas during crushing or caving in goaf was proposed bycombining with spontaneous combustion form in field.In order to obtain gas burning law of different spatial characteristic in uppercorner, gas burning experiment of free space, filling gangue, gas package and faninterference was devised based on gas burning experiment platform. Burning processand temperature were recorded by high-speed camera and temperature measuringsystem. Burning process of CH₄burning under different conditions was analyzed. Theresult shows the burning speed of7.8%and21%gas concentration under free space isslower. Low and high concentration gas burning are possible to occur is proposed.Gas of filling gangue is not easy to ignite. But the burning speed and strength becomestronger after being ignited and burning is easy to become explosion. When gaspackage is ignited, explosive destructiveness is increased because of the superpositionof combustion wave. Gas is not easy to ignite under fan interference. But the burningspeed becomes quicker and is easy to spread in gangue inside. This increases thedifficulty of putting out gas burning. Relation of gas burning time and condition wasanalyzed. The result shows gas burning speed of initial moment in free space is a fewto a few hundred centimeters per second. Qualitative analysis of gas burningtemperature under different conditions was done and gas burning spread process wasproved.Prevention research of coal spontaneous combustion inducing gas burning infield was completed in order to ensure6135test face smoothly mining. Machine-lanecoalpillar and upper adjacent coal seam were the area of spontaneous combustionigniting gas in this face was proved by gas and temperature observation. According tothe "Y" type ventilation, the quantitative calculation model of air leakage in face wasestablished based on model hypothesis and continuous quantitative stable release SF6.Air leakage test was done and the result shows air leakage volume in lower corner ismore large and the air leakage rate is-23.35%. Based on numerical simulationtechnology, range of spontaneous combustion “there zones” and gas explosionconcentration was acquired in6135goaf. The region where gas was frequently ignited by coal spontaneous combustion in this face was obtained. According to the dangerzone of coal spontaneous combustion, the fire prevention and extinguishing measuressuch as pre-injecting inhibitor, three-phase foam and liquid CO₂were proposed. Theresult shows pre-injecting inhibitor can prevent60coal from spontaneous combustionand large perfusion three-phase foam and liquid CO₂can control machine-lanespontaneous combustion point. Measures made the face smoothly mining andrecovery and good economic benefits were achieved.