A method for carbon sequestration and fire prevention in goaf

Abstract

The present invention discloses a method for carbon sequestration and fire prevention in goafs, which belongs to the field of mining engineering and carbon sequestration technology. The method comprises the following steps: first, mining along the four sides of the working face, and then mining the working face in the direction of the main tunnel. A mining area is constructed with a flexible mold material within the mined working face, and a CO2 storage space and goaf area with airtight surroundings are constructed inside, with inflation pipes and grouting pipes reserved. Filling material is injected into the goaf through the grouting pipe, and CO2 is injected into the CO2 storage space through the inflation pipe. When the filling material occupies 90% of the volume of the goaf, the injection is stopped, and a monitoring valve is installed on the inflation pipe. If it is detected that the CO concentration is increased and there is a tendency to ignite, the monitoring valve automatically opens, releasing CO2 to reduce the CO concentration, and at the same time the filling material expands to fill the space. This method comprehensively considers the various needs of goafs and provides an effective solution for the sustainable management of goafs.

Description

Technical Field

[0001] The present invention belongs to the technical field of mining engineering and carbon sequestration, and in particular relates to a method for carbon sequestration and fire prevention in a goaf. Background Art

[0002] While a coal-dominated energy structure and sustained high-intensity development model have played a significant role in driving rapid economic development, they have also led to significant problems such as the massive accumulation of solid waste in mining areas, ecosystem damage, and increased greenhouse gas emissions. Furthermore, coal mining-induced surface subsidence and vegetation destruction have severely degraded ecosystem functions in mining areas and significantly reduced biodiversity. More seriously, carbon dioxide emissions from coal combustion have become a major contributor to global warming. These intertwined and mutually reinforcing issues have become a key bottleneck restricting the green and low-carbon development of the coal industry. Against this backdrop, the innovative development of CO2 capture, utilization, and storage (CCUS) technologies has become an urgent need to promote the industry's green transformation. Summary of the Invention

[0003] To address the above technical issues, the present invention proposes a method for carbon sequestration and fire prevention in goafs. This method achieves the purpose of carbon sequestration and fire prevention by modifying the goaf and injecting carbon into it. The method is low-cost, easy to operate, and environmentally friendly.

[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 goaf sealing and transformation-grouting filling synergy, comprising the following steps:

[0006] Step 1: First, carry out mining along the perimeter of the working face, then mine the working face towards the main tunnel. Use flexible mold materials to construct a mining area within the mined working face, and use flexible mold bags to construct a sealed CO2 storage space and goaf inside the mining area. At the same time, reserve an inflation pipe in the CO2 storage space and a grouting pipe in the goaf.

[0007] Step 2: injecting filling material into the goaf through the grouting pipe, and injecting CO2 into the CO2 storage space through the inflation pipe;

[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 that the CO concentration is increasing and there is a tendency for 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 CO2 release.

[0010] Step 5: Regularly monitor and maintain the filled goaf.

[0011] The present invention first mines the coal pillars around the working face. When mining the working face toward the main tunnel, a mining area is constructed at the rear with flexible mold materials, and a CO2 storage space and goaf that are sealed all around are constructed inside the mining area with flexible mold bags. At the same time, an inflation pipe is reserved on the CO2 storage space, and a grouting pipe is reserved in the goaf. Special filling materials made of coal-based solid waste are then injected into the goaf for filling. At the same time, CO2 is injected into the reserved CO2 storage space through the inflation pipe. When the goaf is filled to 90%, inflation is stopped, and a monitoring valve is installed on the inflation pipe. When the CO concentration is detected to be increased, the monitoring valve automatically opens and releases CO2 to reduce the CO concentration to a safe range. The valve is then closed to achieve the effect of fire prevention and extinguishing. Finally, the filled goaf is monitored and maintained with multiple technologies to ensure safety and stability, and to achieve the requirements of carbon sequestration, fire prevention and fire extinguishing in the goaf, thereby providing protection for coal mine safety and providing a new development idea for the construction of green and low-carbon mines. During the carbon sequestration process, CO2 is stored in a sequestration unit to prevent its escape, thereby achieving the goal of carbon sequestration. Regarding fire prevention and extinguishing, when a monitoring valve detects an increase in CO2 concentration, it automatically opens, releasing CO2 to reduce the CO concentration to a safe range. The valve then automatically closes, achieving both fire prevention and extinguishing effects and effectively suppressing spontaneous combustion in the goaf. This not only ensures coal mine safety but also helps maintain a stable environment in the goaf, further promoting the achievement of carbon sequestration and other related goals.

[0012] Furthermore, the specific operation steps for constructing the CO2 storage space include: when mining the working face in the direction of the main tunnel, every time 40 meters are advanced, a mining area with a length of 30 meters and close to the wall is constructed at the rear using flexible mold materials.

[0013] Furthermore, 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.

[0014] Furthermore, 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.

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

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

[0017] The composite stabilizer component is prepared by compounding silicone oil L-580, pore opener 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.

[0018] The high-durability elasticity described in the present invention originates from the precise molecular structure of polyether polyol and multifunctional isocyanate. The rigid aromatic ring skeleton provided by PM-200 and the flexible aromatic isocyanate structure introduced by TDI-80 jointly construct a microphase-separated block hard segment network, realizing stress absorption and dissipation functions. In the composite stabilization system, silicone oil L-580 and cell opener B-8680 synergistically regulate the foam structure to construct a three-dimensional interconnected foam system with an opening rate of 88%±2%, so that stress can be multi-dimensionally transmitted along the plateau boundary direction. Antioxidant 1135 and ultraviolet absorber UV-531 synergistically form a dual stabilization mechanism of free radical capture and ultraviolet shielding, effectively inhibiting degradation reactions triggered by thermal oxygen and light. Delay catalyst C225 ensures uniform crosslinking density distribution during the polymerization reaction. The isocyanate index is controlled at 0.88-0.92, forming a moderately cross-linked molecular network, which enables the material to achieve reversible deformation recovery under dynamic load through hydrogen bond reorganization (bond energy of approximately 12 kJ / mol) and adjustment of intra-chain bond angles (approximately 30° to 120°); at the same time, the hard segment glass transition temperature (T_g ≈ -25°C) and the soft segment glass transition temperature (T_g ≈ -50°C) work synergistically to effectively inhibit crack initiation and propagation, significantly improving the long-lasting elasticity and fatigue resistance of the foam material.

[0019] Furthermore, the length of the flexible mold bag is within ±15 cm of the lane 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, in terms of 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 of 180-220 mm; water bleeding rate of less than 5%; early strength of 10-15 MPa; and late strength of 20-30 MPa.

[0023] Furthermore, the monitoring includes underground CO concentration monitoring, seismic wave monitoring, filling body internal displacement monitoring and surface 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 needs of goafs and provides an effective solution for the sustainable management of goafs through innovative methods and reasonable material utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0027] Figure 1 This is a process flow chart of Example 1 of the present invention;

[0028] Figure 2 This is a diagram showing the early stage of mining in Example 1 of the present invention;

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

[0030] Figure 4 This is a schematic diagram of the sealing effect of the goaf in Example 1 of the present invention;

[0031] Figure 5 This is a schematic diagram of the expansion effect of the flexible mold material in the goaf according to Example 1 of the present invention. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0034] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0035] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0036] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] Coal mine goafs, due to their large number, widespread distribution, and low spatial utilization, offer significant advantages as geological CO2 storage sites. This confined space can safely inject captured CO2 into abandoned goafs by controlling the injection flow and pressure, leveraging its natural sealing properties to form a stable storage layer for reliable physical storage. At the same time, CO2 storage technology physically stores CO2 by constructing a CO2 storage space. To address the coordinated needs of goaf spontaneous combustion prevention and control and carbon sequestration, a three-in-one technical system of "space transformation-carbon sequestration-fire prevention and control" is urgently needed. This innovative solution not only simultaneously achieves the goals of goaf safety management and carbon sequestration, but also inhibits coal spontaneous combustion by isolating oxygen through a physical sealing layer, providing dual protection for coal mine safety production while opening up a new path for green mine construction.

[0038] like Figure 1 As shown, an embodiment of the present invention provides a method for carbon sequestration and fire prevention based on goaf sealing and transformation-grouting filling synergy, including the following steps:

[0039] Step 1: First, carry out mining along the perimeter of the working face, then mine the working face towards the main tunnel. Use flexible mold materials to construct a mining area within the mined working face, and use flexible mold bags to construct a sealed CO2 storage space and goaf inside the mining area. At the same time, reserve an inflation pipe in the CO2 storage space and a grouting pipe in the goaf.

[0040] Step 2: injecting filling material into the goaf through the grouting pipe, and injecting CO2 into the CO2 storage space through the inflation pipe;

[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 is increasing and there is a tendency for 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 CO2 release.

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

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

[0045] The mining method is: use a continuous miner to mine the coal pillars on 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 injecting polyurethane foam into a flexible mold bag, it's necessary to use wooden strips to create a temporary support and ensure a certain degree of airtightness. The polyurethane foam used should have good sealing properties, be lightweight, provide thermal and sound insulation, be easy to install, be highly corrosion-resistant, have poor high-temperature resistance, and possess a certain degree of elasticity. The polyurethane foam used in the following examples of the present invention is prepared in the following manner.

[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 opener B-8680, antioxidant 1135, UV-531, and delay 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] The polyether polyol composition, the isocyanate component and the composite stabilizer component were mixed in a mass ratio of 120:90:3.5, and stirred at 1000 rpm for 30 seconds using an electric stirrer to obtain a polyurethane foam;

[0053] (2) Use an injection pump to inject the mixed polyurethane foam into the hanging 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 leakage.

[0054] The specific installation process of the flexible formwork bag is as follows: first, select a suitable flexible formwork bag according to the height of the tunnel, and its length should be no less than ±15cm of the tunnel height; second, hang the flexible formwork bag from the position where grouting is to be started, and ensure that the flexible formwork bag is completely connected to the bottom (if the bottom of the tunnel is uneven, the bottom needs to be shoveled before construction); finally, use expansion screws with hooks and iron wire to connect the lifting ears above the formwork bag to the top plate, and ensure that the first steel ring of the flexible formwork bag is close to the top plate to reduce the waste of the flexible formwork bag length.

[0055] In some feasible solutions, in step 2, 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-alkaline filling material include coal gangue, fly ash and cement, and the water-cement ratio is 0.4. In terms of 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 of 180-220mm; water seepage rate of less than 5%; early strength of 10-15MPa; late strength of 20-30MPa. 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 processes, safety requirements, etc.

[0056] For example, the water in the filling material is generally tap water or treated mine water, and it is ensured that the water does not contain impurities that may adversely affect the performance of the filling material.

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

[0058] During the preparation of the filling material, solid materials are first put into a mixer, then cement and fly ash are added and stirred evenly, water is slowly added while continuing to stir to fully wet and mix the materials.

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

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

[0061] Seismic imaging and monitoring: 3D seismic imaging can be used to detect structural changes in storage areas. By analyzing seismic wave reflection and refraction data, changes in the storage area's morphology and density after CO2 injection can be monitored, allowing for assessment of its stability.

[0062] Ground gas monitoring: Sensors are deployed on the ground to monitor CO2 leakage. If CO2 leaks from the storage area, the ground gas concentration will change abnormally.

[0063] Internal displacement monitoring of the filling: If monitoring reveals local deformation or damage to the filling, reinforcement should be carried out promptly. Grouting, anchor support, and shotcrete can be used to enhance the stability of the filling.

[0064] The raw materials used in the present invention are all purchased from the market.

[0065] The technical solution of the present invention is further illustrated by the following examples.

[0066] The present invention provides a method for achieving carbon sequestration and fire prevention by transforming the goaf and grouting carbon fixation, sealing and transforming the goaf, and performing CO2 sequestration and filling for carbon sequestration and fire prevention / extinguishing in the goaf, including specific processes and steps such as Figure 1-Figure 5 As shown, the following is a detailed introduction to this method with reference to the schematic diagram.

[0067] The composition of the filling material in the following embodiments of the present invention is defined as follows:

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

[0069] Fly ash: S95 mineral powder;

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

[0071] Example 1

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

[0073] (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;

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

[0075] Silicone oil L-580, pore opener B-8680, antioxidant 1135, UV-531, and delay 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;

[0076] The polyether polyol composition, the isocyanate component and the composite stabilizer component were mixed in a mass ratio of 120:90:3.5, and stirred at 1000 rpm for 30 seconds using an electric stirrer to obtain a polyurethane foam;

[0077] (2) Use a syringe pump to inject the mixed polyurethane foam into the hanging flexible mold bag through the injection port (the injection amount is 60% of the volume of the flexible mold bag), ensuring that the injection port is well sealed to avoid leakage, and obtain the flexible mold material;

[0078] Step 2: If Figure 2 As shown, first, mining is carried out along the periphery of the working face, then a continuous miner is used to mine the coal pillars of the working face, and then the working face is mined in the direction of the main tunnel. Every time 40m is advanced, a 30m long mining area close to the wall is constructed at the rear with flexible mold materials, and a closed CO2 storage space and goaf are constructed inside the mining area with flexible mold bags. At the same time, an inflation pipe (DN50 high-density polyethylene (HDPE) pipe) is reserved on the CO2 storage space, and a grouting pipe (DN200 high-density polyethylene (HDPE) pipe) is reserved in the goaf (as shown in FIG. Figure 3 shown);

[0079] Step 3: Preparation of filling material: 40% coal gangue, 10% fly ash, and 50% cement are mixed to prepare the filling material, and water is added to control the water-cement ratio to 0.4;

[0080] Step 4: Inject the filling material into the goaf through the grouting pipe, and inject CO2 into the CO2 storage space through the inflation pipe;

[0081] Step 5: 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 6: Repeat steps 2 to 5 until the working face is mined out. The working face is 140m long and a total of 4 mining areas are established (such as Figure 4 shown);

[0083] Step 7: When the monitoring valve detects that the CO concentration is increasing and there is a tendency to ignite, the monitoring valve automatically opens and releases CO2 to reduce the concentration of CO, 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 (such as Figure 5 shown);

[0084] Step 8: Regularly monitor and maintain the filled goaf.

[0085] Flexible mold material performance test:

[0086] 1. Conventional material (CM) group: using 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] The black material and the white material were mixed in a mass ratio of 1:1, and mixed with an electric stirrer at a speed of 1500 r / min for 20 s. After mixing, they were immediately poured into a standard mold (100*100*25 mm).

[0090] 2. The flexible mold material (PM) group in Example 1 was prepared according to the formula in Example 1 and immediately poured into a standard mold (100*100*25 mm) after preparation.

[0091] 3. Place the mold containing the PM and CM on a horizontal workbench and allow it to foam for approximately 3-5 minutes to complete expansion. Leave it at room temperature (25°C) for 24 hours. Then, place it in a constant temperature oven at 60°C for 12 hours to ensure complete crosslinking.

[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 bulk density.

[0094] 2) Compression set rate: Take a 25mm thick sample, compress it to 50%, hold it for 22 hours, release it for 30 minutes, and then measure the height again to calculate the permanent set rate.

[0095] 3) Short-term aging in hot air: Place the sample in an air oven at 120°C for 8 hours, then repeat the compression by 50% after cooling. Calculate the recovery height change rate = (recovery height after aging / original height) × 100%.

[0096] 4) Quasi-dynamic compression fatigue: The sample was manually compressed and released 10 times, with each compression of 50% held for 10 seconds. The release height was measured each time, and the growth trend of the residual deformation was recorded.

[0097] 5) Cell structure (SEM analysis): The samples were freeze-cut and then gold-sprayed. The cell morphology (pore size, porosity, and collapsed structure) was observed using SEM to evaluate the uniformity and integrity of the cell structure.

[0098] 6) Compression modulus: The specimen was compressed at a rate of 5 mm / min using a universal testing machine. The stress-strain slope in the 0-10% strain range was recorded and the initial compression modulus was calculated.

[0099] Table 1

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

[0101] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection 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 perimeter of the working face, then mine the working face towards the main tunnel. Use flexible mold materials to construct a mining area within the mined working face, and use flexible mold bags to construct a sealed CO2 storage space and goaf inside the mining area. At the same time, reserve an inflation pipe in the CO2 storage space and a grouting pipe in the goaf. Step 2: injecting 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 is increasing and there is a tendency for 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 CO2 release. Step 5: Regularly monitor and maintain the filled goaf; The specific operation steps of constructing the CO2 storage space include: when mining the working face in the direction of the main tunnel, every 40 meters of advance, a 30-meter-long mining area close to the wall is constructed at the rear with flexible mold materials; 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.

2. The method for carbon sequestration and fire prevention in goaf according to claim 1, 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.

3. The method for carbon sequestration and fire prevention in goaf according to claim 2, 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.

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

5. The method for carbon sequestration and fire prevention in goaf 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.

6. The method for carbon sequestration and fire prevention in goaf according to claim 5, characterized in that: Calculated by mass percentage, the raw materials of the filling material include 40% coal gangue, 10% fly ash and 50% cement.

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

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

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