Goaf carbon sequestration and fire preventing and extinguishing method

Abstract

The invention discloses a goaf carbon sequestration and fire preventing and extinguishing method, and belongs to the technical field of mine engineering and carbon sequestration. Comprising the following steps: stoping along the periphery of a working face, and mining the working face towards a main roadway. A mining area is constructed in a working face after mining is completed through a flexible formwork material, a CO2 storage space with the periphery closed and a goaf are constructed on the inner side, and an inflation pipeline and a grouting pipeline are reserved. Filling materials are injected into the goaf through the grouting pipeline, and CO2 is injected into the CO2 storage space through the inflation pipeline. And when the filling material accounts for 90% of the volume of the goaf, injection is stopped, and a monitoring valve is installed on the inflation pipeline. If it is monitored that the CO concentration rises and tends to be on fire, the monitoring valve is automatically opened, CO2 is released, the CO concentration is reduced, and meanwhile the filling material expands to make up the space. According to the method, various requirements of the goaf are comprehensively considered, and an effective solution is provided for sustainable treatment of the goaf.

Description

Technical Field

[0001] The present invention belongs to the technical fields of mine engineering and carbon sequestration, and particularly relates to a method for carbon sequestration and fire prevention in goafs. Background Art

[0002] The energy structure dominated by coal and the continuous high-intensity development mode have played an important role in promoting rapid economic development, but have also caused prominent problems such as a large accumulation of solid waste in mining areas, damage to the ecosystem, and an increase in greenhouse gas emissions. At the same time, problems such as surface subsidence and vegetation damage caused by coal mining have severely degraded the functions of the mining area ecosystem and significantly reduced biodiversity. More severely, the carbon dioxide emissions generated by coal combustion have become one of the main contributors to global warming. These problems are intertwined and affect each other, and have become the key bottleneck restricting the green and low-carbon development of the coal industry. In this context, the innovative development of technologies integrating carbon dioxide capture, utilization, and storage (CCUS) has become an urgent need to promote the green transformation of the industry. Summary of the Invention

[0003] In view of the above technical problems, the present invention proposes a method for carbon sequestration and fire prevention in goafs. By transforming the goaf and injecting slurry for carbon fixation, the purposes of carbon sequestration and fire prevention are achieved, which has the characteristics of low cost, easy operation, and good environmental protection.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A method for carbon sequestration and fire prevention based on the coordination of goaf closed transformation and grouting filling, comprising the following steps:

[0006] Step 1: First, conduct mining along the perimeter of the working face, and then mine the working face towards the main roadway. Use flexible mold materials to construct a mining area within the mined working face, and use flexible mold bags to construct a CO2 storage space and a goaf that are airtight on all sides inside the mining area. At the same time, reserve an inflation pipeline on the CO2 storage space and a grouting pipeline on the goaf.

[0007] Step 2: Inject the filling material into the goaf through the grouting pipeline, and at the same time inject CO2 into the CO2 storage space through the inflation pipeline.

[0008] Step 3: When the filling material occupies 90% of the volume of the goaf, stop injecting the filling material and the CO2, and install a monitoring valve on the inflation pipeline.

[0009] Step 4: When the monitoring valve detects an increase in CO concentration indicating a fire tendency, the monitoring valve automatically opens to release CO2 to reduce the CO concentration, thereby achieving the purpose of fire prevention and extinguishment. At the same time, the flexible mold material expands to fill the space after CO2 is released;

[0010] Step 5: Regularly monitor and maintain the gob area after filling.

[0011] In the present invention, the coal pillars around the working face are first mined. When mining the working face towards the main roadway, a mining area is constructed with flexible mold material at the rear. And flexible mold bags are used to construct a CO2 storage space and a gob area with sealed surroundings inside the mining area. At the same time, an inflation pipeline is reserved on the CO2 storage space, and a grouting pipeline is reserved in the gob area. Then, a special filling material made from coal-based solid waste is injected into the gob area for filling, and at the same time, CO2 is injected into the reserved CO2 storage space through the inflation pipeline. When 90% of the gob area is filled, the inflation stops, and a monitoring valve is installed on the inflation pipeline. When the CO concentration is detected to increase, the monitoring valve automatically opens to release CO2 to reduce the CO concentration to a safe range, and then the valve closes to achieve the effect of fire prevention and extinguishment. Finally, multi-technology monitoring and maintenance are carried out on the filled gob area to ensure safety and stability, meeting the requirements of carbon storage and fire prevention and extinguishment in the gob area, providing guarantee for coal mine safety, and providing new development ideas for the construction of green and low-carbon mines. During the carbon storage process, a storage unit is used to store CO2 to prevent its escape, thereby achieving the goal of carbon storage. In terms of fire prevention and extinguishment, when the monitoring valve detects an increase in CO concentration, the monitoring valve automatically opens to release CO2 to reduce the CO concentration to a safe range, and then the valve automatically closes to achieve the effect of fire prevention / extinguishment, effectively suppressing the occurrence of spontaneous combustion in the gob area. This not only guarantees the safety of coal mine production, but also helps to maintain the stable environment of the gob area, further promoting the realization of carbon storage and other related goals.

[0012] Further, the specific operation steps for constructing the CO2 storage space include: when mining the working face towards the main roadway, every 40 m forward, a mining area with a length of 30 m and close to the wall surface is constructed with flexible mold material at the rear.

[0013] Further, the flexible mold material is made by injecting polyurethane foam into the flexible mold bag; the injection amount of the polyurethane foam is 60% of the volume of the flexible mold bag.

[0014] Further, the polyurethane foam is composed of a polyether polyol composition, an isocyanate component, and a composite stabilizer component mixed in a mass ratio of 120∶90∶3.5.

[0015] Furthermore, the polyether polyol composition is prepared by compounding polyether 3030 and polyether DL2000 at a mass ratio of 100:20; and / or,

[0016] The isocyanate component is prepared by compounding PM-200 and TDI-80 at a mass ratio of 85:5; and / or,

[0017] The composite stabilizer component is prepared by compounding silicone oil L-580, cell opener B-8680, antioxidant 1135, UV-531, and delayed catalyst C225 at a mass ratio of 1.5:0.65:0.55:0.35:0.2.

[0018] The high durability elasticity of the present invention stems from the precise molecular structure of polyether polyol and polyfunctional isocyanate. The aromatic ring rigid skeleton provided by PM-200 and the flexible aromatic isocyanate structure introduced by TDI-80 jointly construct a microphase-separated block hard segment network to achieve stress absorption and dissipation functions. In the composite stabilization system, silicone oil L-580 and cell opener B-8680 synergistically regulate the cell structure to construct a three-dimensional interconnected cell system with an open cell rate of 88% ± 2%, enabling stress to be multi-dimensionally conducted along the Plateau boundary direction. Antioxidant 1135 and ultraviolet absorber UV-531 synergistically form a dual stabilization mechanism of free radical capture - ultraviolet shielding to effectively inhibit the degradation reaction induced by thermal oxygen and light. Delayed catalyst C225 ensures uniform distribution of crosslinking density during the polymerization reaction. The isocyanate index is controlled at 0.88 - 0.92 to form a moderately crosslinked molecular network, enabling the material to achieve reversible deformation recovery through hydrogen bond recombination (bond energy is about 12 kJ / mol) and intrasegmental bond angle adjustment (from about 30° to 120°) under dynamic load. At the same time, the hard segment glass transition temperature (Tg ≈ -25°C) and the soft segment glass transition temperature (Tg ≈ -50°C) act synergistically to effectively inhibit crack initiation and propagation, significantly improving the permanent elasticity and fatigue resistance of the foam material.

[0019] Furthermore, the length of the flexible mold bag is within ±15 cm of the roadway height.

[0020] Furthermore, the raw materials of the filling material include coal gangue, fly ash, and cement, and the water-cement ratio is 0.4.

[0021] Furthermore, by mass percentage, the raw materials of the filling material include 40% coal gangue, 10% fly ash, and 50% cement.

[0022] Furthermore, the filling material meets the following indicators: slump is 180 - 220 mm; bleeding rate is less than 5%; early strength is 10 - 15 MPa; later strength is 20 - 30 MPa.

[0023] Further, the monitoring includes underground CO concentration monitoring, seismic wave monitoring, internal displacement monitoring of the filling body, and ground gas monitoring.

[0024] Compared with the prior art, the present invention has the following advantages and technical effects:

[0025] The present invention comprehensively considers various requirements of the goaf, and provides an effective solution for the sustainable treatment of the goaf through innovative methods and reasonable material applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0027] Figure 1 is the process flow chart of Embodiment 1 of the present invention;

[0028] Figure 2 is the pre-mining display diagram of Embodiment 1 of the present invention;

[0029] Figure 3 is the goaf sealing effect flow chart of Embodiment 1 of the present invention;

[0030] Figure 4 is the goaf sealing effect schematic diagram of Embodiment 1 of the present invention;

[0031] Figure 5 is the schematic diagram of the swelling effect of the flexible mold material in the goaf of Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation to the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0033] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described in this invention, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0035] Without departing from the scope or spirit of the present invention, various modifications and variations can be made to the specific embodiments of the specification of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0036] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0037] Due to the characteristics of large quantity, wide distribution and low space utilization rate of coal mine gob areas, they show significant advantages as CO2 geological storage sites. This enclosed space can safely inject the captured CO2 into the abandoned gob area by controlling the injection flow rate and pressure, and utilize its natural sealing characteristics to form a stable storage layer to achieve reliable physical storage. At the same time, CO2 storage technology physically stores CO2 by constructing a CO2 storage space. In view of the coordinated requirements of goaf spontaneous combustion prevention and control and carbon storage, it is urgent to construct a "space transformation - carbon storage - fire prevention" trinity technology system. This innovative solution can not only simultaneously achieve the goals of goaf safety management and carbon storage, but also isolate oxygen through the physical storage layer to inhibit coal spontaneous combustion, providing double guarantees for coal mine safety production and opening up a new path for the construction of green mines.

[0038] As Figure 1 shown, an embodiment of the present invention provides a method for carbon storage and fire prevention and extinguishing based on the coordination of goaf closed transformation and grouting filling, including the following steps:

[0039] Step 1: First, carry out mining along the perimeter of the working face, and then mine the working face towards the main roadway. Use flexible mold materials to construct a mined area within the mined working face, and use flexible mold bags to construct a CO2 storage space and a goaf that are airtight on all sides inside the mined area. At the same time, reserve an inflation pipeline on the CO2 storage space and a grouting pipeline on the goaf.

[0040] Step 2: Inject the filling material into the goaf through the grouting pipeline, and at the same time inject CO2 into the CO2 storage space through the inflation pipeline.

[0041] Step 3: When the filling material occupies 90% of the volume of the goaf, stop injecting the filling material and the CO2, and install a monitoring valve on the inflation pipeline;

[0042] Step 4: When the monitoring valve detects that the CO concentration increases and there is a tendency to catch fire, the monitoring valve automatically opens to release CO2 to reduce the CO concentration, thereby achieving the purpose of fire prevention and extinguishing. At the same time, the flexible mold material expands to fill the space left by the release of CO2.

[0043] Step 5: Regularly monitor and maintain the goaf after filling.

[0044] In some feasible schemes, in step one, the specific operational steps for constructing the CO2 storage space include: when mining the working face in the direction of the main tunnel, every 40m forward, a mining area 30m long and close to the wall is constructed at the rear with flexible mold materials.

[0045] The mining method is: use continuous mining machine to mine the coal pillars of the working face, and then mine the working face towards the main tunnel.

[0046] The order of constructing the mining area is: first use wooden strips to enclose the approximate outline, then hang a flexible mold bag on it, then fill it with polyurethane foam to expand it to form an enclosed space, and finally fix it to the wooden strips with wire.

[0047] When polyurethane foam is injected into the flexible mold bag, it is necessary to use wooden strips to build temporary support and ensure a certain airtightness. The polyurethane foam used should have good sealing, light weight, heat insulation and sound insulation, convenient construction, strong corrosion resistance, poor high temperature resistance, and a certain elasticity. The polyurethane foam that can be used in the following embodiments of the present invention is prepared in the following way.

[0048] The process of injecting the polyurethane foam into the flexible mold bag to make the flexible mold material is as follows:

[0049] (1) polyether 3030 and polyether DL2000 were mixed in a mass ratio of 100:20, and stirred at 1000 rpm for 60 seconds using an electric stirrer to obtain a polyether polyol composition;

[0050] PM-200 and TDI-80 are mixed in a mass ratio of 85:5 to obtain an isocyanate component;

[0051] Silicone oil L-580, pore opening agent B-8680, antioxidant 1135, UV-531, and delayed catalyst C225 were compounded in a mass ratio of 1.5:0.65:0.55:0.35:0.2, and stirred at 1000 rpm for 30 seconds using an electric stirrer until a light yellow viscous liquid was formed, thereby obtaining a composite stabilizer component;

[0052] Mix the polyether polyol composition, isocyanate component and composite stabilizer component in a mass ratio of 120:90:3.5, and stir with an electric mixer at 1000 rpm for 30 s to obtain the polyurethane foam.

[0053] (2) Use an injection pump to inject the mixed polyurethane foam into the suspended flexible mold bag through the injection port (the injection volume is 60% of the volume of the flexible mold bag), and ensure that the injection port is well sealed to avoid liquid leakage.

[0054] The specific installation process of the flexible mold bag is as follows: First, select a suitable flexible mold bag according to the height of the roadway, and its length should be not less than the roadway height ±15 cm; Second, hang the flexible mold bag from the position where grouting starts, and ensure that the flexible mold bag touches the bottom completely (if the bottom of the roadway is uneven, it needs to be leveled before construction); Finally, use expansion screws with hooks and wire to connect the lugs above the mold bag to the roof, and ensure that the first steel ring of the flexible mold bag is close to the roof to reduce the waste of the length of the flexible mold bag.

[0055] In some feasible solutions, in step two, the composition of the filling material can be adjusted to a reasonable and appropriate ratio according to the different conditions of different mines. In the present invention, the raw materials of the multi-component alkaline filling material include coal gangue, fly ash and cement, and the water-cement ratio is 0.4. By mass percentage, the raw materials of the filling material include: 40% coal gangue, 10% fly ash, and 50% cement. The filling material meets the following indicators: slump is 180 - 220 mm; bleeding rate is less than 5%; early strength is 10 - 15 MPa; later strength is 20 - 30 MPa. These indicators are not absolute, and in actual application, they need to be adjusted and determined in combination with specific coal mine geological conditions, filling technology, safety requirements, etc.

[0056] Exemplarily, the water in the filling material is generally tap water or treated mine water. Ensure that the water does not contain impurities that have an adverse effect on the performance of the filling material.

[0057] The mixing equipment used can be a forced mixer. Ensure that the mixing equipment can fully mix various raw materials to achieve a uniform effect.

[0058] During the preparation process of the filling material, first put the solid materials into the mixer, then add cement and fly ash, stir evenly, slowly add water, and continue to stir at the same time to make the materials fully moistened and mixed.

[0059] The principle of the fire prevention and extinguishing effect is: when the monitoring valve detects an increase in the CO concentration, the monitoring valve automatically opens and releases CO2, thereby reducing the CO concentration. When the CO concentration drops to the safe range, the valve closes to achieve the fire prevention and extinguishing effect, and this method effectively inhibits the occurrence of spontaneous combustion in the goaf.

[0060] In some feasible solutions, the monitoring includes CO concentration monitoring, seismic wave monitoring, internal displacement monitoring of the filling body, and ground gas monitoring. It should be noted that the monitoring of all indicators can be carried out using conventional monitoring equipment, which is not the inventive point of the present invention and will not be elaborated.

[0061] Seismic wave imaging and monitoring: Three-dimensional seismic imaging can be used to detect structural changes in the storage area. By analyzing seismic wave reflection and refraction data, the morphology and density changes of the storage area after injecting carbon dioxide can be monitored to evaluate its stability.

[0062] Ground gas monitoring: By deploying sensors on the ground, the leakage of carbon dioxide is monitored. If carbon dioxide leaks in the storage area, abnormal changes will occur in the ground gas concentration.

[0063] Internal displacement monitoring of the filling body: If it is monitored that local deformation or damage occurs in the filling body, reinforcement treatment should be carried out in a timely manner. Methods such as grouting, bolt support, and shotcrete can be used to enhance the stability of the filling body.

[0064] All raw materials used in the present invention are obtained by purchasing on the market.

[0065] The technical solution of the present invention will be further described below through embodiments.

[0066] The present invention provides a method for carbon sequestration and fire prevention / extinguishing by reforming the goaf and injecting grout for carbon sequestration. The goaf is closed and reformed, and CO2 sequestration and filling are carried out for carbon sequestration and fire prevention / extinguishing in the goaf, including specific processes and steps as Figures 1 - 5 shown. The method will be mainly introduced below with reference to the schematic diagram.

[0067] In the following embodiments of the present invention, the composition of the filling material is limited to:

[0068] Gangue: Ground fine by a jaw crusher and a planetary ball mill, with an average particle size of 0.045 mm;

[0069] Fly ash: S95 mineral powder;

[0070] Cement: Portland cement with a strength grade of 42.5 is used;

[0071] Example 1

[0072] Step 1: Preparation of the flexible mold material:

[0073] (1) Mix polyether 3030 and polyether DL2000 in a mass ratio of 100:20, and stir with an electric mixer at 1000 rpm for 60 s to obtain a polyether polyol composition;

[0074] Mix PM-200 and TDI-80 in a mass ratio of 85:5 to obtain an isocyanate component;

[0075] Compound silicone oil L-580, blowing agent B-8680, antioxidant 1135, UV-531, and delayed catalyst C225 in a mass ratio of 1.5:0.65:0.55:0.35:0.2, and use an electric stirrer to stir at 1000 rpm for 30 s until a light yellow viscous liquid is formed, thus obtaining a composite stabilizer component;

[0076] Mix the polyether polyol composition, isocyanate component, and composite stabilizer component in a mass ratio of 120:90:3.5, and use an electric stirrer to stir at 1000 rpm for 30 s to obtain polyurethane foam;

[0077] (2) Use an injection pump to inject the mixed polyurethane foam into a suspended flexible mold bag through the injection port (the injection volume is 60% of the volume of the flexible mold bag), and ensure that the injection port is well sealed to avoid liquid leakage, thus obtaining a flexible mold material;

[0078] Step two: As Figure 2 shown, first conduct coal mining along the perimeter of the working face, then use a continuous miner to mine the coal pillars of the working face, and then mine the working face towards the main roadway. When advancing 40 m each time, use the flexible mold material to construct a mining area with a length of 30 m close to the wall surface at the rear, and use flexible mold bags to construct a CO2 storage space and a goaf that are airtight all around inside the mining area. At the same time, reserve an inflation pipeline (using a DN50 high-density polyethylene (HDPE) pipeline) on the CO2 storage space, and reserve a grouting pipeline (using a DN200 high-density polyethylene (HDPE) pipeline) in the goaf (as Figure 3 shown);

[0079] Step three: Preparation of the filling material: Mix 40% coal gangue, 10% fly ash, and 50% cement to prepare the filling material, and add water to control the water-cement ratio to 0.4;

[0080] Step four: Inject the filling material into the goaf through the grouting pipeline, and at the same time inject CO2 into the CO2 storage space through the inflation pipeline;

[0081] Step five: When the filling material occupies 90% of the volume of the goaf, stop injecting the filling material and CO2, and install a monitoring valve on the inflation pipeline;

[0082] Step six: Repeat operation steps two to five until the working face is completely mined. The length of the working face is 140 m, and a total of 4 mining areas are established (as Figure 4 shown);

[0083] Step 7: When the monitoring valve detects an increase in CO concentration indicating a fire tendency, the monitoring valve automatically opens to release CO2 to reduce the CO concentration, thereby achieving the purpose of fire prevention and extinguishing. At the same time, the flexible mold material expands to fill the space after the release of CO2 (as Figure 5 shown);

[0084] Step 8: Regularly monitor and maintain the gob area after filling.

[0085] Performance test of flexible mold material:

[0086] 1. Conventional material (CM) group: Use commercially available general-purpose polyurethane raw materials (black material: white material = 1:1 mass ratio),

[0087] Black material: isocyanate;

[0088] White material: polyol mixture;

[0089] Mix the black material and white material in a mass ratio of 1:1, and use an electric stirrer to mix at a speed of 1500 r / min for 20 s. After mixing, immediately pour it into a standard mold (100*100*25 mm).

[0090] 2. Flexible mold material (PM) group in Example 1: Prepared according to the formula in Example 1, and immediately pour it into a standard mold (100*100*25 mm) after preparation.

[0091] 3. Place the molds containing PM and CM on a horizontal workbench, keep them static and foaming for about 3 - 5 minutes to complete expansion. Place them at room temperature (25°C) for 24 hours; then put them into a constant temperature oven and treat them at 60°C for 12 hours to ensure complete cross-linking reaction.

[0092] The test items are as follows:

[0093] 1) Density: Take 3 foam samples from each group, measure the size with a vernier caliper, weigh the mass with an electronic balance, and calculate the volume density.

[0094] 2) Compression deformation rate: Take a 25-mm-thick sample block, compress it by 50% and keep it for 22 hours, release it for 30 minutes and then measure the height, and calculate the permanent deformation rate.

[0095] 3) Short-term hot air aging: Put the sample into a 120°C air oven and treat it for 8 h, cool it and then repeat compressing it by 50%, and calculate the recovery height change rate = (recovery height after aging / original height) × 100%.

[0096] 4) Quasi-dynamic compression fatigue: Manually compress and release the sample 10 times, compress it by 50% each time and keep it for 10 s, measure the release height each time, and record the growth trend of residual deformation.

[0097] 5) Cell structure (SEM analysis): After the sample was cryo-cut and sputter-coated with gold, the cell morphology (pore size, porosity, collapsed structure) was observed using SEM to evaluate the uniformity and integrity of the cell structure.

[0098] 6) Compression modulus: The sample block was compressed at a rate of 5 mm / min using a universal material testing machine, and the stress-strain slope in the 0-10% strain section was recorded to calculate the initial compression modulus.

[0099] Table 1

[0100] Test items PM group CM group Density (kg / m³) 50.3 50.7 Compression deformation rate (%) 30.1 39.5 Deformation retention rate after hot air aging (%) 85.2 68.4 Estimation of compression residual deformation (%) 6.5 16.2 Cell structure (SEM analysis) Uniform open pores, honeycomb-like, no collapse Collapse exists, many closed pores, uneven pore diameters Peak compression modulus (kPa) 32.5 25.9

[0101] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for carbon sequestration and fire prevention in goaf, characterized in that, The following steps are involved: Step 1: First, carry out mining along the periphery of the working face, then mine the working face in the direction of the main tunnel, construct a mining area in the mining-completed working face with flexible mold materials, and use flexible mold bags to construct a closed CO2 storage space and goaf area inside the mining area, and at the same time, reserve an inflation pipe on the CO2 storage space, and reserve a grouting pipe in the goaf; Step 2: injecting the filling material into the goaf through the grouting pipe, and injecting CO2 into the CO2 storage space through the inflation pipe; Step 3: When the filling material occupies 90% of the volume of the goaf, stop injecting the filling material and the CO2, and install a monitoring valve on the inflation pipeline; Step 4: When the monitoring valve detects that the CO concentration increases and there is a tendency to catch fire, the monitoring valve automatically opens to release CO2 to reduce the CO concentration, thereby achieving the purpose of fire prevention and extinguishing. At the same time, the flexible mold material expands to fill the space left by the release of CO2. Step 5: Regularly monitor and maintain the goaf after filling.

2. The goaf carbon sequestration and fire prevention method according to claim 1, characterized in that The specific operation steps of constructing the CO2 storage space include: when mining the working face in the direction of the main tunnel, every time you advance 40m, use flexible mold materials to construct a mining area with a length of 30m and close to the wall at the rear.

3. The goaf carbon sequestration and fire prevention method according to claim 2, wherein, The flexible mold material is made by injecting polyurethane foam into a flexible mold bag; the amount of polyurethane foam injected is 60% of the volume of the flexible mold bag.

4. The goaf carbon sequestration and fire prevention method according to claim 3, characterized in that, The polyurethane foam is prepared by mixing a polyether polyol composition, an isocyanate component and a composite stabilizer component in a mass ratio of 120:90:3.

5.

5. The goaf carbon sequestration and fire prevention method according to claim 4, characterized in that, The polyether polyol composition is prepared by compounding polyether 3030 and polyether DL2000 in a mass ratio of 100:20; and / or, The isocyanate component is prepared by compounding PM-200 and TDI-80 in a mass ratio of 85:5; and / or, The composite stabilizer component is prepared by compounding silicone oil, a pore opening agent, an antioxidant, UV-531 and a delayed catalyst in a mass ratio of 1.5:0.65:0.55:0.35:0.

2.

6. The goaf carbon sequestration and fire prevention method according to claim 1, characterized in that, The length of the flexible mold bag is the lane height ±15cm.

7. The gob carbon sequestration and fire prevention method according to claim 1, characterized in that, The raw materials of the filling material include coal gangue, fly ash and cement, and the water-cement ratio is 0.

4.

8. The goaf carbon sequestration and fire prevention method according to claim 7, characterized in that, Calculated by mass percentage, the raw materials of the filling material include 40% coal gangue, 10% fly ash and 50% cement.

9. The goaf carbon sequestration and fire prevention method according to claim 7, characterized in that, The filling material meets the following indicators: slump of 180-220 mm; water seepage rate of less than 5%; early strength of 10-15 MPa; and late strength of 20-30 MPa.

10. The goaf carbon sequestration and fire prevention method according to claim 1, characterized in that, The monitoring includes underground CO concentration monitoring, seismic wave monitoring, filling body internal displacement monitoring and ground gas monitoring.

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