Residual coal secondary mining working face coal spontaneous combustion prevention and control method

Abstract

The invention provides a coal spontaneous combustion prevention and control method for a residual coal re-mining working face, and belongs to the technical field of residual coal spontaneous combustion prevention and control. Determining a relation equation f (sigma) of roof pressure Fs and broken coal rock sample seepage through methods such as an experiment, and determining a pressure threshold value sigma t through a seepage threshold value; dividing an easy-to-leak area of the goaf according to the pressure threshold sigma t; different control measures are adopted according to different divided areas; temperature measuring optical fibers and beam tubes are laid in the two roadways in the on-site mining process to verify the fire preventing and extinguishing effect in the goaf, and feedback adjustment is conducted. The method not only has high pertinence to the air leakage area of the goaf, but also innovatively provides a coal spontaneous combustion prevention and control method guided from the mine pressure rule aspect.

Description

Technical Field

[0001] The invention relates to the field of residual coal spontaneous combustion prevention and control, and in particular to a method for preventing and controlling coal spontaneous combustion in a residual coal re-mining working face. Background Art

[0002] Since the introduction of comprehensive caving mining technology, it has gradually matured after more than ten years of exploration. However, due to the limitations of previous technology and equipment, a large number of coal pillars were left over from the early mining. According to incomplete statistics, the abandoned coal resources in the country are about 1.2 trillion tons, and the recoverable reserves are about 40.3 billion tons. The resource reserves are huge. The re-mining of abandoned coal will increase my country's recoverable reserves by 30%. Among them, the abandoned resources of thick coal seams are more widely distributed. The re-mining of abandoned coal in the goaf has effectively improved the coal recovery rate and made full use of coal resources. However, due to the complex geological conditions, there are many loose abandoned coal in the re-mining area, the roof is severely damaged and irregularly distributed, which also aggravates the spontaneous combustion of the abandoned coal on the re-mining face, seriously threatening the safe re-mining of the working face. Therefore, it is urgent to study the prevention and control methods of coal spontaneous combustion in the re-mining working face of residual coal. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preventing and controlling coal spontaneous combustion in a residual coal re-mining working face, which can improve the safety factor of coal mining operations and provide a theoretical reference for fire prevention and extinguishing projects in similar re-mining working faces.

[0004] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is specifically as follows:

[0005] A method for preventing and controlling spontaneous combustion of coal in a residual coal re-mining working face, comprising the following methods:

[0006] S1. Collect rock data of residual coal mining working face, broken coal rock samples and mining plan;

[0007] S2. The roof pressure F is obtained through the seepage test s The relationship equation f(σ) with the seepage of broken coal rock samples is used to determine the pressure threshold σ through the seepage threshold t , when the top plate pressure F s ≤Pressure threshold σ t It is determined to be a goaf area prone to air leakage;

[0008] S3. Establish a physical similarity model of the re-mining working face, bury pressure boxes in the goaf and the direct bottom, monitor the pressure distribution law inside the goaf during the mining process of the working face, and calculate the pressure according to the pressure threshold σ t Divide the goaf area prone to air leakage, establish the residual coal re-mining working face through COMSO numerical simulation to determine the nitrogen injection diffusion range;

[0009] S4. Determine the location of nitrogen injection drilling according to the air leakage area in the goaf and the diffusion range of nitrogen injection. s ≤Pressure threshold σt The geometric ratio determines the air leakage area in the goaf, thereby determining the location of the nitrogen injection drilling hole. According to the roof pressure F in the physical similarity model, s The timing of nitrogen injection is determined by the relationship with the advance distance of the working face;

[0010] S5. Bury a steel pipe in the goaf, bury a nitrogen injection pipeline in the steel pipe, and use the nitrogen injection pipeline to pressurize liquid nitrogen into the air leakage-prone area of ​​the goaf in the re-mining working face;

[0011] S6. During on-site mining, temperature measuring optical fibers and bundle tubes are laid inside the goaf to verify the fire prevention and extinguishing effects.

[0012] Preferably, the rock formation data of the residual coal re-mining working face include rock formation thickness, inclination, strength, and also include the inclined length, advancement length and daily advance of the re-mining working face.

[0013] Preferably, the drilling hole spacing is less than or equal to the liquid nitrogen diffusion radius, and the nitrogen injection work is completed before the air leakage zone in the goaf with increased roof pressure disappears.

[0014] Preferably, the pressure box is pre-buried at the direct bottom of the goaf, with the pressure box spacing in the goaf being less than 20m, and in the direct bottom less than 5m away from the coal seam.

[0015] Preferably, the nitrogen injection amount is calculated according to the calculation method in MT / T701-1997 standard.

[0016] Preferably, the bundle pipes are laid in three routes in the two lanes respectively, and the bundle pipe openings are arranged in the goaf at 30m, 50m and 80m, and are extended according to the needs of mining at the working face, and samples are analyzed once a day.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This method proposes a method for preventing and controlling coal spontaneous combustion in residual coal re-mining working faces by guiding the law of mine pressure manifestation according to the relationship between mine pressure and air leakage channels, calculates the nitrogen injection position and timing, and blocks the air leakage-prone areas in the goaf in a targeted manner by pre-burying grouting pipelines in the goaf, completes fire prevention and extinguishing work before the residual coal spontaneously ignites, ensures the smooth progress of the coal mining working face, improves the safety factor of coal mining operations, and provides theoretical reference for similar fire prevention and extinguishing projects in re-mining working faces. This design method is simple and easy to implement, has strong technical innovation, is easy to operate, has high economy and practicality, and has broad application prospects. The principle described is similar to the principle. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0019] Figure 1A flow chart of a method for preventing and controlling spontaneous combustion of coal in a residual coal re-mining working face provided by an embodiment of the present invention.

[0020] Figure 2 A schematic diagram of the on-site application of a method for preventing and controlling spontaneous combustion of coal in a residual coal re-mining working face provided by an embodiment of the present invention.

[0021] Figure 3 A method for preventing and controlling spontaneous combustion of coal in a residual coal re-mining working face provided in an embodiment of the present invention physically simulates the pressure curve of the goaf.

[0022] Figure 4 A COMSO numerical simulation cloud diagram of a method for preventing and controlling spontaneous combustion of coal in a residual coal re-mining working face provided by an embodiment of the present invention.

[0023] In the figure, 1-return air lane; 2-transport lane; 3-bundle tube; 4-temperature measuring optical fiber; 5-air leakage prone area; 6-liquid nitrogen diffusion range; 7-nitrogen injection pipeline. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Of course, the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0025] Taking a mine as an example, the specific implementation steps are as follows:

[0026] The F301 re-mining working face of a certain mine is arranged between the original 301 and 302 working faces. The return air lane 1 and transport lane 2 are arranged in the goaf of the original 301 and 302 working faces respectively. The original 301 and 302 working faces were mined 15 years ago. The main mining is the #3 coal seam, the residual thickness of the coal seam is about 5m, the working face advancement length is 700m, the daily advance is 5.0m / d, the face length is about 200m, and the comprehensive mechanized top coal caving mining process is adopted. The roof is managed by the full caving method. The coal seam inclination is 2~15°, with an average of 9°. The coal seam of the F301 working face has good coal quality, which is low in ash, low in sulfur, extra-low in phosphorus, and high in calorific value. The coal seam hardness coefficient f=1~2 is medium hard coal.

[0027] This embodiment provides a method for preventing and controlling coal spontaneous combustion in a residual coal re-mining working face, comprising the following steps:

[0028] (1) Collect rock data, broken coal samples and mining plan of F301 residual coal mining face, mainly including rock thickness, inclination, strength, broken coal samples, inclination length, advancement length and daily advance of mining face;

[0029] (2) The roof pressure F is obtained through the seepage test s The relationship equation f(σ) with the seepage of broken coal rock samples is used to determine the pressure threshold σ through the seepage thresholdt =5.4MPa, when the top plate pressure F s ≤Pressure threshold σ t It is determined to be a goaf area prone to air leakage 5;

[0030] (3) A physical similarity model of the re-mining working face was established with a geometric ratio of 200:1, a 50-meter coal pillar was left, and the model length was 4 meters. Pressure boxes were buried directly at the bottom of the goaf to monitor the pressure distribution law inside the goaf during the mining process of the working face. The spacing between the pressure boxes was 10 cm. The law of mine pressure in the goaf is as follows: Figure 3 As shown, according to the pressure threshold σ t Divide the goaf into the air leakage zone 5. Taking the 1# measuring point as an example, after the working face advances, the first air leakage zone is formed, which is 5cm away from the cut. The residual coal re-mining working face is established through COMSO numerical simulation to determine that the liquid nitrogen diffusion range 6 is 55m.

[0031] (4) The position of nitrogen injection pipeline 7 is determined according to the air leakage area in the goaf and the diffusion range of nitrogen injection. The roof pressure F in the physical similarity model is s ≤Pressure threshold σ t The geometric ratio determines that the first goaf area prone to air leakage is 10m away from the cut hole, so the nitrogen injection drilling position is determined to be 35m away from the cut hole, with a spacing of 50m. According to the roof pressure F in the physical similarity model, s The timing of nitrogen injection is determined by the relationship with the advancement distance of the working face. In the physical simulation, the mine pressure in the first air leakage zone decreases after 70cm is pushed. Therefore, in the real working face, the first air leakage zone has a tendency to spontaneously combust after 140m is advanced. The daily advance of the working face is 5.0m / d, which means that the first air leakage zone needs to be treated with nitrogen injection within 28 days of advancement.

[0032] (5) Steel pipes are buried in the goaf, and nitrogen injection pipelines are buried in the steel pipes. Liquid nitrogen is injected into the goaf of the re-mining working face in a targeted manner. The gas content cloud diagram of the goaf before and after grouting is as follows: Figure 4 As shown, the analysis shows that the gas content in the goaf has been greatly reduced overall, and there is basically no risk of spontaneous combustion of coal in the goaf;

[0033] (6) During the on-site mining process, the temperature measuring optical fiber 4 and the bundle tube 3 were laid inside the goaf to verify the fire prevention and extinguishing effect. The CO concentration was finally stabilized below 0.20‰, and the application effect was good.

[0034] This method is not only highly targeted at areas prone to air leakage in goafs, but also innovatively proposes a method to guide the prevention and control of coal spontaneous combustion from the perspective of mine pressure laws.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preventing and controlling spontaneous combustion of coal in a residual coal re-mining working face, characterized in that: The following steps are involved: S1. Collect rock data of residual coal mining face, broken coal rock samples and mining plan; S2. The roof pressure F is obtained through the seepage test s The relationship equation f(σ) with the seepage of broken coal rock samples is used to determine the pressure threshold σ through the seepage threshold t , when the top plate pressure F s ≤Pressure threshold σ t It is determined to be a goaf area prone to air leakage; S3. Establish a physical similarity model of the re-mining working face, bury pressure boxes in the goaf and the direct bottom, monitor the pressure distribution law inside the goaf during the mining process of the working face, and calculate the pressure according to the pressure threshold σ t Divide the goaf area prone to air leakage, establish the residual coal re-mining working face through COMSO numerical simulation to determine the nitrogen injection diffusion range; S4. Determine the location of nitrogen injection drilling according to the air leakage area in the goaf and the diffusion range of nitrogen injection. s ≤Pressure threshold σ t The geometric ratio determines the air leakage area in the goaf, thereby determining the location of the nitrogen injection drilling hole. According to the roof pressure F in the physical similarity model, s The relationship with the distance of advancement of the working face determines the timing of nitrogen injection; S5. Bury a steel pipe in the goaf, bury a nitrogen injection pipeline in the steel pipe, and use the nitrogen injection pipeline to pressurize liquid nitrogen into the air leakage-prone area of ​​the goaf in the re-mining working face; S6. During on-site mining, temperature measuring optical fibers and bundle tubes are laid inside the goaf to verify the fire prevention and extinguishing effects.

2. A method for preventing and controlling spontaneous combustion of coal in a residual coal re-mining working face according to claim 1, characterized in that: The rock formation data of the residual coal re-mining working face include rock formation thickness, inclination, strength, as well as the inclined length, advancement length and daily advance of the re-mining working face.

3. The method for preventing and controlling spontaneous combustion of coal in a residual coal re-mining working face according to claim 1 is characterized in that: The drilling hole spacing is less than or equal to the liquid nitrogen diffusion radius, and the nitrogen injection work is completed before the air leakage zone in the goaf area where the roof pressure increases disappears.

4. The method for preventing and controlling spontaneous combustion of coal in a residual coal re-mining working face according to claim 1 is characterized in that: The pressure box is pre-buried at the direct bottom of the goaf, with the pressure box spacing less than 20m, and in the direct bottom less than 5m away from the coal seam.

5. The method for preventing and controlling spontaneous combustion of coal in a residual coal re-mining working face according to claim 1 is characterized in that: The nitrogen injection amount is calculated according to the calculation method in MT / T701-1997 standard.

6. The method for preventing and controlling spontaneous combustion of coal in a residual coal re-mining working face according to claim 1, characterized in that: The bundle pipes are laid in three lines in the two lanes, and the bundle pipe openings are arranged in the goaf at 30m, 50m and 80m. They are extended according to the needs of working face recovery, and sampling and analysis are carried out once a day.

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