Research About The Spontaneous Combustion Mechanism And "Three Zone" Surveying Of Chahasu No.3 Coal Goaf

For Chahasu No.3 coal seam belongs to the easy spontaneous combustion of coal seam, and the shortest spontaneous combustion period is 39 days. Chahasu coal mine is a large mining height fully mechanized coal mining face, the spontaneous combustion of coal seam is the main reason for the safety production of large mining height. As the last working face, part of the 31303 working face roof has broken under great pressure, which greatly increase the possibility of the coal goaf spontaneous combustion. According to the site situation of Chahasu 31303 working face, a research has been taken to study the spontaneous combustion mechanism and the main conclusion as follows:1.The internal cause of coal spontaneous combustion in goaf is analyzed,then testing sulfur, water, coal maceral and macerals of the coal sample, the test results show that the high content of the lens group is the leading factor of the spontaneous combustion; From the aspect of ignition point, absorbed oxygen, this paper has made the thermogravimetric analysis and static absorbed oxygen test,arrived at the kindling point relatively low and oxygen intake relatively large,testing results and experimental results show that the 3 coal seam is easy to spontaneous combustion.2. Through the goaf buried beam tube and thermocouple in 31303 working face, this paper has made a real-time monitoring about the air and temperature change in the 31303 working face goaf and according to monitoring data divide the goaf into “three zone. The heat dissipation zone in the air taken side with a width of 150.5-182 m, suffocation zone 220.6-274.6m and the heat dissipation zone in the air return side with a width of 163.7-212 m, suffocation zone 258.3-261 m. According to the thermocouple monitoring data, it is concluded that the temperature change is relatively large in the mined out area, which is 3 to 10 days after exploitation, in the range of 30 to 130 m,mining of coal oxidation and concentrated in the rear of the working face in the area, the area of nitrogen injection, grouting and other measures should be concentrated in this area, so as to improve fire prevention measures of pertinence and effectiveness.3. Using FLUENT software,and according to the actual situation of the 31303 working face, a computational physics model is established. The distribution of "three zones" in the goaf of 31303 working face was simulated. In order to study the variation law of the "three zone" in Goaf, the operating conditions of different air supply were simulated. At the same time, under the condition of closed condition, the distribution of the "three zone" in goaf under different air flow field and oxygen concentration field was simulated. According to the research, the spontaneous combustion zone will move to the depth of goaf and the spontaneous combustion area will become larger when the wind become strong. In the meantime, the leakage of the connection roadway brings more air to the coal deep and increase the content of oxygen, greatly increasing the possibility of spontaneous combustion.Through the research about the spontaneous combustion mechanism and “three zone” surveying of Chahasu No.3 coal goaf, this paper has made a foundation for the work of fireproofing and guarantee of safety mining work.