Discussion on the spontaneous generation of residu

Discussion on the prevention and control of spontaneous combustion of residual coal in goaf under super thick coal seam

mine fire is one of the main disasters in coal mine production, and underground fire is more harmful than ground fire. Most fires in coal mines are spontaneous combustion fires, especially when mining extra thick coal seams, the comprehensive mechanized mining method of layered mining is adopted. With the increase of upper and lower layered mining faces, the goaf area of the lower layered working face continues to increase, and the phenomenon of spontaneous combustion of coal remains continues to occur. Moreover, compared with other mine fires, they are more hidden and harmful, seriously threatening the life safety of underground workers and the safe production of the mine. Therefore, according to the actual situation of the working face, taking effective prevention and control measures against the causes of the natural ignition of residual coal is the key to prevent the natural ignition of residual coal

1 causes of spontaneous combustion of residual coal in goaf

(1) the spontaneous combustion performance of coal is the basic factor of spontaneous combustion of residual coal in goaf. First, the spontaneous combustion of coal can produce chemical changes and generate heat, which is not easy to dissipate, so it gradually accumulates and forms high temperature; Second, after the coal contacts with oxygen, oxygen can oxidize the coal and produce heat. When the heat accumulates, the temperature rises continuously, gradually contributing to the spontaneous combustion of coal; Third, after the spontaneous combustion of coal, oxygen will help the combustion, so that the fire continues to expand and form a fire

(2) a large amount of residual coal left in the goaf has laid a good material foundation for natural ignition. Due to the low recovery rate of top coal caving in the lower layered working face and more coal loss, a large amount of residual coal is left in the goaf, and the coal body is in a broken state, which increases the area in contact with oxygen, makes the residual coal easier to oxidize, accelerates the oxidation and heat generation process of residual coal, and thus increases the possibility of natural ignition

(3) the existence of air leakage channel provides good oxygen supply conditions for the natural ignition of residual coal. Layered mining not only leads to direct air leakage due to the existence of air leakage channels between the upper and lower layered working faces, but also the integrity of the isolated coal pillars between adjacent working faces is seriously damaged due to the high concentrated pressure, causing the coal pillars to be fractured and crushed, resulting in the interconnection between the goaf areas of adjacent working faces, thus forming a good air leakage crack and creating a good air leakage channel for the goaf, It provides a good continuous and sufficient oxygen supply condition for the natural ignition of residual coal, and further increases the possibility of natural ignition of residual coal

(4) air leakage in goaf is the decisive factor of spontaneous combustion of residual coal. According to the regularity of spontaneous combustion of coal, the amount of air leakage in goaf determines the low-temperature oxidation stage and self heating stage of spontaneous combustion of residual coal, that is, whether the temperature of internal heat source causing spontaneous combustion can reach the notch limit on the impacted sample of spontaneous combustion. If the air leakage is too large, the oxidation heat of the residual coal is not easy to accumulate, and if the air leakage is very small, the oxidation conditions are poor. These two air leakage conditions are not easy to cause natural anger after the user logs in. The magnitude of air leakage can be known from the law of air leakage resistance in the mine ventilation circuit, that is:

h = R leakage × Q leakage n (1)

, where: H is the wind pressure difference at both ends of the leakage air path; R leakage is the wind resistance of the air leakage path; Q leakage is the air leakage; N is the flow regime index of air leakage, n = 1 ~ 2, 1 for laminar flow and 2 for turbulent flow. According to the law of air leakage resistance:

q leakage = ■ (2)

according to the analytical formula (2), when the wind resistance R leakage of the air leakage path approaches infinity or the wind pressure h difference at both ends of the air leakage path approaches zero, the air leakage amount is close to zero, that is, the air leakage amount is determined by the wind pressure difference and wind resistance at both ends of the air leakage path. Therefore, the technical measures to suppress the natural ignition of residual coal are to increase the air leakage resistance as much as possible and reduce the wind pressure difference at both ends of the air leakage path

(5) mining technology determines the basic and decisive factors of spontaneous combustion. Mining technology includes development method, mining method and standard air method for judging the quality of Tongji gold testing fixture. Mining technology is the external factor of coal spontaneous combustion. If correct development method, scientific mining method and reasonable ventilation method are adopted during mining, and production technology management is strengthened, the recovery rate can be improved, the recovery speed can be accelerated, and coal damage and air leakage can be reduced, so as to effectively prevent coal spontaneous combustion, Nip in the bud

2 measures to prevent and control the spontaneous combustion of residual coal in goaf

according to the analysis of the causes of the spontaneous combustion of residual coal in goaf, although the spontaneous combustion performance of coal cannot be changed, the external combustion supporting conditions can be changed through reasonable and effective measures to achieve the purpose of preventing and controlling the spontaneous combustion of residual coal. Practice has proved that the following measures can effectively prevent and control the spontaneous combustion of residual coal in the goaf of the lower layered working face

(1) strengthen the management of top coal caving process, improve the recovery rate of top coal caving, and reduce the existence of broken coal in goaf. The coal cutting in the lower layered working face must strictly implement the regular circular operation of "one cutting and one releasing", practically strengthen the top coal caving process operation, reduce the coal loss, improve the coal recovery rate, and minimize the coal loss in the goaf. Reducing the residual coal in the goaf can reduce the material base of natural ignition. The relevant parts should be fastened to reduce the possibility of natural ignition

(2) choose a reasonable mining method to improve the mining speed. The mining methods of warehouse, room pillar and knife pillar have high tunneling rate, but low recovery rate, which is not conducive to the prevention of spontaneous combustion; The long wall coal mining method has high recovery rate and relatively simple roadway layout, which is convenient for using high-speed coal mining machinery to speed up the recovery speed and shorten the recovery period, so as to ensure that the coal in the working face is recovered before the natural ignition period