Comprehensive treatment of spontaneous combustion

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The application of fully mechanized top coal caving technology has found a new way to mine 15 # coal in Yangquan coal industry group to achieve high yield and efficiency. However, due to the bulkiness of the fully mechanized mining equipment, it takes a long time to install and remove it, especially the removal of the support, which takes at least one month from the completion of the pulling track to the removal of the support. The coal seam of Yangquan No. 5 coal mine belongs to class I spontaneous combustion coal seam, and the shortest ignition period is only 10 days. Therefore, when the working face is demolished, the floating coal at the top of the goaf and support is very easy to ignite naturally. It is difficult to find the location of the ignition point and take corresponding measures for these parts, which has been plagued by the normal demolition of the working face. Therefore, it is necessary to analyze the causes of natural ignition during the demolition of fully mechanized top coal caving face in order to take corresponding measures

1 overview of mine

No. 5 mine of Yangquan coal industry group is a high gassy mine, and the relative emission of gas is 59.95m3/t. The mine is designed to adopt zonal ventilation. Due to the poor geological conditions of the mine, only the northwest wing is produced at present. If there are special requirements for the use of the main inclined shaft, auxiliary vertical shaft and waste discharge shaft, we can propose to our company that the South air shaft should be used for air intake and the double shaft should be used for air return. The main ventilator in Sanggou should be used for the ventilation of the whole mine. At present, there are only two fully mechanized mining teams, three tunneling teams and three development teams in the whole mine. The air inflow of the whole mine is 10630 m3/min, the air return is 10731 m3/min, and the negative pressure is 3480 PA. Minmetals mainly mines 15# coal seams, with an average thickness of 7m, an inclination of 3 °~ 10 °, and an average of 6 °. The coal seams have different degrees of softness and hardness. Most of the softest silty particles are medium hard, with developed joint bedding and complex structure. The coal seams contain 2 ~ 3 layers of gangue. The main gangue layer is distributed 0.7m in the middle and upper part of the coal seams, mainly mudstone and sandy mudstone. The coal rock type is mainly bright, and the coal seams are easy to be broken, while improving the product quality; However, after cooling and crushing at the hopper, it is mostly massive with more pores and large surface area

2 spontaneous combustion condition

coal seam 15# of Minmetals is a class I spontaneous combustion coal seam, and the shortest ignition period is 10 days. Most working faces have been burned since it was put into operation. There were 5 times of ignition in tunneling and 29 times of ignition in mining, of which 18 times were on fire in 8110 working face during the frame removal, especially during the frame removal in fully mechanized top coal caving face. In particular, it is difficult to find the location of the ignition point above the support and the goaf, and corresponding measures cannot be taken. The most serious problem is the 8110 working face, which has been ignited for 18 times from the beginning of the frame pulling machine head to the end of the frame removal

3 analysis of the causes of coal spontaneous combustion during the frame removal of fully mechanized top coal caving face

through the summary and analysis of the characteristics of coal seam spontaneous combustion during the frame removal of several working faces, the main causes of spontaneous combustion during the frame removal of fully mechanized top coal caving face are as follows

(1) the recovery rate of fully mechanized face is low. A large amount of floating coal is mixed in the gangue from the roof, which is not easy to be compacted behind the support, and the air leakage passes slowly, which provides sufficient oxygen for natural ignition and increases the opportunity of coal and oxygen combination

(2) it takes a long time to remove the frame and close it. It takes at least one month from the erection to the dismantling of the support. During this period, the support is not advanced, the floating coal in the goaf is oxidized slowly, and the accumulated heat cannot be taken away by the wind in time. The temperature of the coal body gradually rises, providing sufficient conditions for natural ignition

(3) gob leakage "he pointed out that the wind is relatively strict, reducing the labor intensity of operators; Heavy. During the frame removal, the ventilation system is damaged, the air leakage in the goaf increases, and the air volume will flow from the air inlet corner to the air return along the goaf. Thus, "three belts" are formed behind the support: "heat dissipation belt, oxidation belt and suffocation belt", as shown in Figure 1. The range of "three zones" has a considerable relationship with the air volume of the working face. The larger the air volume, the more air leakage, and the wider the area of the oxidation zone, the easier it is to catch fire

(4) the coal is soft: there are many voids in the floating coal, and the air will enter these voids when the air leakage passes through the goaf, so that the surface of the coal and the oxygen in the air are slowly oxidized to generate heat. This part of heat is not easy to be taken away by the wind. Thus, the heat will accumulate and the coal temperature will rise. When the critical temperature is exceeded, the rise of coal temperature accelerates sharply, and finally leads to spontaneous combustion of coal seams

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