Prevention of coal seam spontaneous combustion in

Prevention and control technology of coal seam spontaneous combustion in Yankuang comprehensive mechanized top coal caving face

the situation of coal seam spontaneous combustion in China is serious. According to statistics, about 56% of the state-owned key coal mines have the risk of coal seam spontaneous combustion, and the spontaneous combustion in the mining of extra thick coal seams is more serious. In recent years, with the test and promotion of fully mechanized top coal caving technology in extra thick coal seams in China, the output and efficiency of coal have been greatly improved. The daily output of raw coal is as high as 10000-16000 tons, the daily output value is more than 2million yuan, the working face equipment investment is 40-50 million yuan, and the mine with an annual output of 5million tons can basically realize one mine, so it is particularly important to ensure the safe production of the working face. However, the mining intensity of this mining method is high, there are many residual coal left in the goaf, the caving height is high, and the air leakage is serious, resulting in a series of problems such as fire, gas, dust and so on, which are difficult to solve. According to statistics, although it still has a smooth appearance, more than 50% of the fully mechanized top coal caving faces in China's coal mines have the risk of spontaneous combustion, which seriously threatens the safety production of the mine. Therefore, the research of fire prevention and extinguishing technology is also one of the keys to the safety production of fully mechanized top coal caving face

1. Overview of coal seam spontaneous combustion prevention and control technology in China

1.1 fire prevention and suppression technology

in the 1950s, China began to study and promote yellow mud grouting fire prevention and suppression technology in coal mines, studied chemical inhibitor fire prevention, pressure equalizing ventilation, high expansion foam fire suppression and other technologies in the 1980s and 1990s, studied coal mine spontaneous combustion prediction system, inert gas fire prevention and suppression, fast and efficient air leakage blocking, belt conveyor fire prevention and control and other technologies, And gradually form a comprehensive fire prevention and extinguishing technology suitable for ordinary coal mining method and high-yield and high-efficiency coal mining method. At present, the fire prevention and control technical measures adopted during the coal mining period in China generally include inerting, flame retardation, plugging, cooling and comprehensive prevention and control technologies, which work together to achieve the purpose of fire prevention and suppression

1.1 we can basically do it 1. Inerting fire prevention and extinguishing technology

inerting technology mainly refers to the technology of sending inert gas into the area to be treated to inhibit coal spontaneous combustion. It is mainly used in closed areas caused by external fires or coal spontaneous combustion fires. China has developed fuel type D inert gas generating devices with poor gas resistance, gloss and transparency, and equipped with China's coal mine rescue team, which has become an important equipment for fire fighting and disaster relief. In addition, bgp-200 type high expansion foaming machine and yzwp-180 type inert foam generator have been developed

in recent years, nitrogen injection fire prevention and extinguishing technology has been rapidly promoted and applied in coal mines in China. In addition to some coal mines using cryogenic fixed nitrogen generating units and pipe transportation downhole nitrogen injection system, some coal mines began to be equipped with ground mobile carbon molecular sieve pressure swing adsorption nitrogen generating units (bxnd-500, KYZD-800), underground mobile pressure swing adsorption nitrogen generating units (jxzd-400), membrane separation nitrogen generating units (kmds-600), etc. newly developed in recent years. After the width of the three zones of oxidation, spontaneous combustion and asphyxiation in the goaf is determined by the continuous monitoring and measurement of the beam tube monitoring system, nitrogen is continuously injected into the spontaneous combustion zone of the goaf with buried pipes or drilling, and the spontaneous combustion zone is inerted to achieve the purpose of fire prevention. In extinguishing the tunnel fire, after building a temporary enclosure, inject nitrogen into the enclosed area to reduce the gas oxygen concentration in the fire area to less than 10% to extinguish the open fire, and to 1% - 2% to extinguish the fire quickly. For the fire source with large combustion depth, the amount of nitrogen injection should reach 2-3 times the volume of the fire area

1.1.2 fire prevention and extinguishing technology of flame retardant substances

fire prevention and extinguishing technology of flame retardant substances mainly refers to sending some flame retardant substances into the area to be treated, so as to achieve the purpose of fire prevention and extinguishing. In addition to the yellow mud slurry that has been used as a conventional fire prevention and extinguishing measure, the fly ash, shale slurry, tailings slurry of coal preparation plant, inhibitor and inhibitor slurry developed in recent years have been widely used

1.1.3 air leakage prevention and fire extinguishing technology

after the working face is pushed, the roadway connected with the goaf is closed in time, the filling isolation zone beside the trough roadway of the coal pillar working face that is not included in the national key special plan, and the air leakage is blocked by grouting to isolate the coal pillar cracks are all air leakage prevention and fire extinguishing. In recent years, China has studied the double material high water quick setting filling and hydraulic quick grouting equipment, and carried out the test of filling the isolation zone beside the trough roadway in the non pillar working face, which has been successful. Kbj-100/5, kbj-50/3 quick setting pulverized coal slurry equipment and grouting process have also been developed. The slurry transportation distance is up to 800m, which is used for the construction of permanent sealing, coal wall cracks, grouting and cementation in high caving areas of roadways, etc. The equipment and materials can also be used for rapid construction of closures

1.1.4 air flow stability, control and disaster relief command technology in disaster period

the research on air flow stability and air flow control in fire period in China is still in the stage of establishing physical and mathematical models for ventilation path solution and disaster air flow simulation, and has not reached the practical stage. In recent years, the research on disaster relief expert system has also been carried out, trying to integrate the technical experience of many fire prevention and suppression experts into artificial intelligence through computer software to form a disaster relief expert decision-making system, so as to quickly select disaster relief plans in case of fires and avoid one sidedness of human factors. Due to the heavy workload and difficulty of this research, there is no formal product world yet. Automatic fire monitoring damper and automatic fire water curtain are also the contents of development and research, and have reached the practical stage