| The “Three Zones” of spontaneous combustion in goaf of working face reflects the oxidation characteristics of residual coal in goaf.Through testing the scope of the“Three Zones” of spontaneous combustion,the minimum safe advancing speed can be confirmed,which provides a basis for the design of anti-fire measures of nitrogen injection and grouting in goaf.Usually measuring “Three Zones” of spontaneous combustion in a goaf is only once in a mining area or working face.However,the normal rate advanceing at the working face could decrease when hitting a fault.When coal thickness changes,the amount of coal left in goaf changes with it.These factors must affect the oxidation and spontaneous combustion of coal in goaf.Therefore,the“Three Zones” of spontaneous combustion in goaf are dynamically changed during the working face advancing.There were few researches about it at home and abroad.In this thesis,the dynamic “Three Zones” of spontaneous combustion in goaf based on distributed optical fiber temperature measurement system was studied,and a dynamic division method of “Three Zones” based on coal temperature change index was established,which had been applied in 7401 working face of Zouzhuang Coal Mine,Anhui Shenyuan Coal Chemical Co.,LTD.This thesis analyzed the influence of fault,seam thickness and advancing speed on the “Three Zones” of spontaneous combustion in goaf,which grasped the variation law of the “Three Zones” of spontaneous combustion in goaf during mining.This provided a reliable basis for the development of fire prevention measures in goaf,to ensure the safety of mine production.The main research achievements of this thesis are as follows:Firstly,the static “Three Zones” of spontaneous combustion test was carried out in 7401 working face by traditional method.The temperature probe and gas sampling pipe were laid in the machine and wind roadway of the working face,and the measurement was carried out for more than 20 days.The temperature and gas concentration of coal in goaf were collected and analyzed.The oxygen concentration of 18% and 6% was taken as the dividing point to divide the “Three Zones”,and calculate the minimum safe advancing speed.The scope of “Three Zones” is as follows:the maximum width of divergent zone is 19 m,and the maximum width of oxidation zone is 44.2 m.Secondly,through the static “Three Zones” of spontaneous combustion test,a method for dividing “Three Zones” based on the change of coal temperature in goaf was studied.by analysing the change and correlation between the oxygen concentration and the temperature of abandoned coal in goaf,the coal temperature rise value when the oxygen concentration drops from 21% to 18% and the highest coal temperature when the oxygen concentration drops to 6% are determined as the temperature index value to divide the “Three Zones” of spontaneous combustion.Thus,the method of dividing the “Three Zones” of spontaneous combustion in goaf based on coal temperature is established.Then distributed optical fiber temperature measuring system was arranged in 7401 working face of Zouzhuang Coal mine.The system mainly consists of optical fiber,laser controller,laser,wavelength division multiplexer,computer and so on.The temperature measuring host machine was arranged at the entrance of 7401 machine roadway.Two optical fibers are respectively drawn from the host machine.One leads to the corner of machine roadway into the goaf,and the other leads to the corner of wind roadway into the goaf.The temperature measurement system can monitor the temperature of 7401 working face in real time during mining,and the data was transmitted to the ground computer through communication cable.This thesis selected the temperature measurement data from January to August2022.According to the coal temperature variation and the classification standard of“Three Zones” of spontaneous combustion,the variation of “Three Zones” in the goaf of the working face during this period was analyzed.The results showed that the width of “Three Zones” of spontaneous combustion in the working face had changed in different degrees.The minimum width and maximum width of the dispersing zone at the side of the machine roadway are 12 m and 54 m,and the minimum width and maximum width of the oxidation zone are 22 m and 66 m.The minimum width and maximum width of the dispersing zone at the side of the wind roadway are 24 m and102 m,The minimum width and maximum width of the oxidation zone are 28 m is 66 m.Further analysis shows that the variation of the “Three Zones” of spontaneous combustion in goaf is mainly affected by the thickness of coal seam,geological conditions and advancing speed.When the thickness of coal seam is larger,the geological conditions are simpler and the advancing speed is faster,the width of the“Three Zones” of spontaneous combustion in goaf of 7401 working face is smaller.When the coal seam is thinner and the geological conditions are complicated,the dispersing zone and the oxidation zone width increase.When the advancing speed slows down or stops due to equipment maintenance and other reasons,the range of oxidation zone increases.Finally,this thesis analyzed the shortcomings of the existing fire prevention measures of nitrogen injection and grouting in 7401 working face.Combined with the monitoring results of dynamic “Three Zones” during mining,it was proposed that the nitrogen injection and grouting measures should be changed with the change of oxidation zone location,so as to prevent coal spontaneous combustion in goaf more effectively.This thesis contains 72 figures,26 tables and 115 references. |
