Coal spontaneous combustion prevention and treatment method for residual coal repeated mining working face

Abstract

The application provides a coal spontaneous combustion prevention and treatment method for residual coal recovery working face, and belongs to the technical field of residual coal spontaneous combustion prevention and treatment. s Determine the pressure threshold value sigma through the seepage threshold value and the seepage relationship equation f(sigma) of the crushed coal rock sample t ; according to the pressure threshold value sigma t , the goaf easy air leakage area is divided; different control measures are adopted according to different division areas; the temperature measuring optical fiber and the beam tube are laid in the two lanes in the mining process to verify and feedback the adjustment of the internal fire prevention and extinguishing effect of the goaf. The method not only has strong pertinence to the goaf easy air leakage area, but also innovatively proposes a coal spontaneous combustion prevention and treatment method guided from the mine pressure law.

Description

Technical Field

[0001] This invention relates to the field of prevention and control of spontaneous combustion of residual coal, and in particular to a method for preventing spontaneous combustion of coal in a residual coal mining face. Background Technology

[0002] Since the introduction of fully mechanized longwall mining technology, it has gradually matured after more than a decade of exploration. However, due to limitations in previous technology and equipment, a large amount of coal pillars have been left behind in the early stages of mining. According to incomplete statistics, the national abandoned coal resource reserves are about 120 billion tons, with recoverable reserves of about 40.3 billion tons. The resource reserves are huge, and the remining of abandoned coal will increase my country's recoverable reserves by 30%. Among them, abandoned resources in thick coal seams are widely distributed. The remining of abandoned coal in goaf areas has effectively improved the coal extraction rate and made full use of coal resources. However, due to the influence of complex geological conditions, there is a lot of loose abandoned coal in the remining area, and the roof is severely damaged and irregularly distributed. This also exacerbates the spontaneous combustion of abandoned coal in the remining face, which seriously threatens the safe remining of the working face. Therefore, research on methods to prevent spontaneous combustion of coal in the remining working face is imminent. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preventing spontaneous combustion of coal in residual coal mining faces. This method can improve the safety factor of coal mining operations and provide theoretical reference for fire prevention and extinguishing projects in similar mining faces.

[0004] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0005] A method for preventing spontaneous combustion of coal in a residual coal mining face includes the following steps:

[0006] S1. Collect data on rock strata, broken coal and rock samples, and mining plans for the residual coal mining face;

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

[0008] S3. Establish a physical similarity model of the re-mining face, pre-embed pressure cells in the goaf and immediate bottom, monitor the pressure distribution pattern inside the goaf during the mining process, and base the model on the pressure threshold σ. t The goaf is divided into areas prone to air leakage, and the nitrogen diffusion range is determined by establishing a residual coal re-mining face through COMSOL numerical simulation.

[0009] S4. Determine the location of nitrogen injection boreholes based on the air leakage-prone areas and nitrogen diffusion range in the goaf, using the roof pressure F in the physical similarity model. s ≤ Pressure threshold σt The geometric ratio is used to determine the air leakage areas in the goaf, thereby determining the location of nitrogen injection boreholes, based on the roof pressure F in the physical similarity model. s The timing of nitrogen injection is determined by its relationship with the advance distance of the working face;

[0010] S5. Lay steel pipes into the goaf area, and lay nitrogen injection pipelines inside the steel pipes. Use the nitrogen injection pipelines to inject liquid nitrogen into the goaf area of ​​the re-mining face that is prone to air leakage.

[0011] S6. During the on-site mining process, temperature-measuring optical fibers and bundled tubes were laid inside the goaf to verify the fire prevention and extinguishing effect.

[0012] Preferably, the rock strata data of the residual coal re-mining face includes rock strata thickness, dip angle, and strength, as well as the inclined length, advancing length, and daily advance of the re-mining face.

[0013] Preferably, the borehole spacing is less than or equal to the liquid nitrogen diffusion radius, and the nitrogen injection work is completed before the easily leaky area in the goaf where the roof pressure increases disappears.

[0014] Preferably, the pressure box is pre-embedded in the direct bottom of the goaf, with the spacing between pressure boxes 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 the MT / T701-1997 standard.

[0016] Preferably, the bundled tubes are laid in three routes in the two roadways respectively, with the tube openings arranged in the goaf at 30m, 50m and 80m intervals. The extension is carried out according to the mining needs of the working face, and sampling and analysis are performed once a day.

[0017] Compared with existing technologies, the beneficial effects of this invention are as follows: This method proposes a method for preventing spontaneous combustion of coal in residual coal mining faces by guiding the understanding of mine pressure manifestation patterns based on the relationship between mine pressure and air leakage channels. It calculates the nitrogen injection location and timing, and targets air leakage-prone areas in the goaf by pre-burying grouting pipelines. This completes fire prevention and extinguishing work before the residual coal spontaneously combusts, ensuring the smooth operation of the coal mining face, improving the safety factor of coal mining operations, and providing theoretical reference for similar fire prevention and extinguishing projects in re-mining faces. This design method is simple and easy to implement, technologically innovative, convenient to operate, highly economical and practical, and has a very broad application prospect. The description is based on the principle. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0019] Figure 1A flowchart illustrating a method for preventing spontaneous combustion of coal in a residual coal mining face, provided as an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram illustrating the field application of a method for preventing spontaneous combustion of coal in a residual coal mining face, as provided in an embodiment of the present invention.

[0021] Figure 3 The pressure curve of the goaf is simulated using physical similarity to a method for preventing spontaneous combustion of coal in a residual coal mining face, which is provided in an embodiment of the present invention.

[0022] Figure 4 COMSOL numerical simulation cloud map of a method for preventing spontaneous combustion of coal in a residual coal mining face provided in an embodiment of the present invention.

[0023] In the diagram, 1-return airway; 2-transportation airway; 3-bundle tube; 4-temperature measuring fiber optic cable; 5-area prone to air leakage; 6-liquid nitrogen diffusion range; 7-nitrogen injection pipeline. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Of course, the specific embodiments described herein are merely illustrative and not intended to limit the invention.

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

[0026] The F301 longwall face in a certain mine is located between the original 301 and 302 longwall faces. Return airway 1 and transport airway 2 are located in the goaf areas of the original 301 and 302 longwall faces, respectively. The original 301 and 302 longwall faces were completely mined 15 years ago. The main mining seam is #3, with a residual thickness of approximately 5m. The working face advance length is 700m, with a daily advance of 5.0m / d and a face length of approximately 200m. It employs a fully mechanized top-coal caving mining process, with the roof managed by the caving method. The coal seam dip angle is 2–15°, averaging 9°. The coal seam in the F301 longwall face has good coal quality, being a low-ash, low-sulfur, ultra-low-phosphorus, and high-calorific-value coal seam with a hardness coefficient f = 1–2, classifying it as medium-hard coal.

[0027] This embodiment provides a method for preventing spontaneous combustion of coal in a residual coal mining face, including the following steps:

[0028] (1) Collect strata data, broken coal and rock samples and mining plan for F301 residual coal mining face, including strata thickness, dip angle, strength, broken coal and rock samples, inclined length, advancing length and daily advance of mining face, etc.

[0029] (2) The top plate pressure F was obtained through seepage test. s The relationship equation f(σ) with the seepage flow of fractured coal and rock samples is used to determine the pressure threshold σ through the seepage threshold.t =5.4MPa, when the top plate pressure F s ≤ Pressure threshold σ t It was determined that area 5 was prone to air leakage in the goaf.

[0030] (3) Establish a physical similarity model of the mining face with a geometric ratio of 200:1, leaving a 50m coal pillar. The model length is 4m. Pre-embed pressure boxes in the goaf directly below the goaf to monitor the pressure distribution within the goaf during the mining process. The pressure box spacing is 10cm. The goaf pressure manifestation pattern is as follows: Figure 3 As shown, based on the pressure threshold σ t 5. Taking the No. 1 measuring point as an example, after the working face advances, the first air leakage zone is formed. At this time, the distance from the cut is 5cm. The liquid nitrogen diffusion range 6 is determined to be 55m by establishing the residual coal re-mining working face through COMSOL numerical simulation.

[0031] (4) Determine the location of nitrogen injection pipeline 7 based on the air leakage-prone areas and nitrogen diffusion range of the goaf, and use the roof pressure F in the physical similarity model. s ≤ Pressure threshold σ t Based on the geometric ratio, the first easily leaky air zone in the goaf was determined to be 10m away from the cut-in point. Therefore, the location of the nitrogen injection borehole was determined to be 35m away from the cut-in point, with a spacing of 50m. This was based on the roof pressure F in the physical similarity model. s The timing of nitrogen injection is determined by the relationship between the working face advance distance and the nitrogen injection time. In the physical simulation, the mine pressure in the first easily leaky area decreases after advancing 70cm. Therefore, in the actual working face, the first easily leaky area has a tendency to spontaneous combustion after advancing 140m. The daily advance of the working face is 5.0m / d, which means that the first easily leaky area needs to be treated with nitrogen injection within 28 days of advancing.

[0032] (5) Steel pipes are laid into the goaf area, and nitrogen injection pipelines are installed inside the steel pipes. Liquid nitrogen is then injected into the easily leaky areas of the goaf area of ​​the re-mining face using the nitrogen injection pipelines. The gas content cloud map of the goaf area before and after grouting is shown in the figure. Figure 4 As shown in the figure, the analysis shows that the overall gas content in the goaf has decreased significantly, and there is basically no risk of spontaneous combustion of coal in the goaf.

[0033] (6) During the on-site mining process, temperature measuring optical fiber 4 and bundle tube 3 were laid inside the goaf to verify the fire prevention and extinguishing effect. The CO concentration was eventually 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 goaf areas, but also innovatively proposes a method for preventing spontaneous combustion of coal based on the laws of mine pressure.

[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 principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preventing spontaneous combustion of coal in a residual coal mining face, characterized in that, Includes the following steps: S1. Collect data on rock strata, broken coal and rock samples, and mining plans for the residual coal mining face; S2. The roof pressure F is obtained through seepage test. s The relationship equation f(σ) with the seepage flow of fractured coal and rock samples is used to determine the pressure threshold σ through the seepage threshold. t When the pressure F on the top plate s ≤ Pressure threshold σ t It was determined to be a goaf area prone to air leakage; S3. Establish a physical similarity model of the re-mining face, pre-embed pressure cells in the goaf and immediate bottom, monitor the pressure distribution pattern inside the goaf during the mining process, and base the model on the pressure threshold σ. t The goaf is divided into areas prone to air leakage, and the nitrogen diffusion range is determined by establishing a residual coal re-mining face through COMSOL numerical simulation. S4. Determine the location of nitrogen injection boreholes based on the air leakage-prone areas and nitrogen diffusion range in the goaf, using the roof pressure F in the physical similarity model. s ≤ Pressure threshold σ t The geometric ratio is used to determine the air leakage areas in the goaf, thereby determining the location of nitrogen injection boreholes, based on the roof pressure F in the physical similarity model. s The timing of nitrogen injection is determined by its relationship with the advance distance of the working face; S5. Lay steel pipes into the goaf area, and lay nitrogen injection pipelines inside the steel pipes. Use the nitrogen injection pipelines to inject liquid nitrogen into the goaf area of ​​the re-mining face that is prone to air leakage. S6. During the on-site mining process, temperature-measuring optical fibers and bundled tubes were laid inside the goaf to verify the fire prevention and extinguishing effect. The rock strata data for the residual coal re-mining face includes the rock strata thickness, dip angle, and strength, as well as the inclined length, advancing length, and daily advance of the re-mining face; The borehole spacing should be less than or equal to the liquid nitrogen diffusion radius, and nitrogen injection should be completed before the easily leaky areas in the goaf where the roof pressure increases disappear.

2. The method for preventing spontaneous combustion of coal in a residual coal mining face according to claim 1, characterized in that, The pressure boxes are pre-embedded in the direct bottom of the goaf, with a spacing of less than 20m between the pressure boxes, and are located in the direct bottom less than 5m away from the coal seam.

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

4. The method for preventing spontaneous combustion of coal in a residual coal mining face according to claim 1, characterized in that, The bundled tubes are laid in three routes in the two roadways respectively, with the tube openings arranged in the goaf at 30m, 50m and 80m. The extension is carried out according to the mining needs of the working face, and sampling and analysis are performed once a day.

Images