Method for storing carbon dioxide based on space of deep goaf of thick loose layer

Abstract

The application discloses a carbon dioxide storage method based on thick loose layer deep goaf space, and the storage method comprises the following steps: selecting a grouting hole design hole position, drilling and constructing a grouting hole at the grouting hole design hole position; filling cement-based composite slurry and aggregate filling material slurry into a goaf through grouting to form a curtain wall in the goaf and block the grouting hole; selecting a CO2 injection hole design hole position, drilling and injecting a CO2 injection hole at the CO2 injection hole design hole position; injecting CO2 into the goaf through the CO2 injection hole by using an injection device; and blocking the injection hole after the injection is completed. The carbon dioxide storage method based on thick loose layer deep goaf space has the advantages that the goaf is closed by using a curtain wall, the goaf is used for storing CO2, the storage effect is good, the storage cost is low, the carbon neutralization target is positively played, the resource utilization of abandoned mines is realized, the CO2 can be extracted and used again when needed, and economic benefits are created.

Description

Technical Field

[0001] This invention relates to the field of carbon sequestration technology, and in particular to a method for storing carbon dioxide in the space of deep goaf areas in thick loose layers. Background Technology

[0002] With the rapid development of the global economy, the demand for energy is constantly expanding, leading to the overexploitation of traditional fossil fuels and causing serious environmental problems. The overuse of traditional fossil fuels such as coal and oil has severely impacted the ecological environment, with carbon dioxide emissions continuously increasing and threatening human survival. In addition to taking proactive measures to reduce emissions and improving the Earth's terrestrial systems' capacity to absorb carbon dioxide, the anthropogenic disposal of already generated carbon dioxide has become a focus of attention in recent years.

[0003] China has a long history of coal mining, and to date, a large number of mines have been abandoned due to resource depletion. Abandoned coal mines contain large areas of goaf collapse, as well as abandoned roadways and chambers. Therefore, by adjusting the sealing pressure and taking appropriate sealing measures according to the conditions of the mining area, a considerable amount of carbon dioxide sequestration capacity can be obtained. This is an easily achievable geological carbon dioxide sequestration technology in the short term. Among related technologies, the sealing of abandoned mines is difficult, resulting in poor carbon dioxide sequestration effects and a high risk of leakage. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, embodiments of the present invention propose a carbon dioxide storage method based on the space of a deep goaf in a thick loose layer, which has a good CO2 sequestration effect.

[0006] The carbon dioxide storage method based on the deep goaf space of thick loose layers in this invention includes:

[0007] Based on the mine excavation data, determine the location of the roadway. On both sides of the working face, 10-20m above the goaf, select the design position of the grouting hole and drill the grouting hole at the design position.

[0008] Cement-based composite grout and aggregate filling grout are injected into the goaf through the grouting holes to construct a curtain wall in the goaf. After the grouting is completed, the grouting holes are sealed to form a closed space in the goaf.

[0009] Investigate the distribution characteristics of voids in the goaf area. Based on the investigation results, select the design location of CO2 injection holes within the range of the ground surface above the sealed space of the goaf area and the curtain wall. Drill and construct CO2 injection holes at the design location of CO2 injection holes. Install hole opening connectors at the opening of the CO2 injection holes.

[0010] The injection process parameters are determined based on the sealing conditions and the characteristics of different forms of CO2. CO2 is injected into the sealed space of the goaf through the CO2 injection hole using an injection device. After the injection is completed, the valve of the hole connector is closed.

[0011] This invention discloses a carbon dioxide storage method based on the space of a deep, loosely layered goaf. The method utilizes a curtain wall to enclose the goaf, thereby storing CO2 within the goaf. It achieves good storage efficiency, stores a large volume of CO2, and employs an environmentally friendly and efficient storage technology. The storage process does not generate additional CO2 or other pollution. Furthermore, the storage cost is low, playing a positive role in achieving carbon neutrality goals, realizing the resource utilization of abandoned mines, and allowing for the extraction and reuse of CO2 when needed, thus generating economic benefits.

[0012] In some embodiments, the drilling method for grouting holes includes:

[0013] The first grouting hole section was drilled into the loose overburden layer, and the first grouting hole section penetrated the loose overburden layer and entered the stable bedrock layer;

[0014] After the first grouting hole section is drilled, a protective sleeve is installed inside the first grouting hole section.

[0015] Based on the first grouting section, continue drilling the second grouting section into the stable bedrock layer to the goaf or the roadway floor.

[0016] In some embodiments, when the roof of the goaf or roadway has not collapsed, the second grouting hole section is drilled into the roof of the goaf or roadway.

[0017] When the roof of the goaf has collapsed, the second grouting section is drilled into the floor of the goaf or roadway.

[0018] In some embodiments, a method for constructing a curtain wall within the goaf includes:

[0019] The cement-based composite grout and the aggregate filling grout are prepared according to the specified ratio;

[0020] For large-cavity goaf areas or roadways that have not collapsed, first inject the aggregate filling grout, and then pressure inject the cement-based composite grout. For small-fracture goaf areas or roadways that have collapsed, directly inject the cement-based composite grout.

[0021] After grouting is completed, high-concentration cement mortar is used to seal the opening of the grouting hole.

[0022] In some embodiments, the cement-based composite slurry is a volume-expanding cement fly ash slurry, wherein desulfurization ash or an expanding agent is added to the volume-expanding cement fly ash slurry.

[0023] In some embodiments, the drilling method for CO2 injection holes includes:

[0024] The first injection hole section was drilled into the loose overburden layer, and the first injection hole section penetrated the loose overburden layer and entered the stable bedrock layer;

[0025] After the first injection hole section is completed, the second injection hole section will continue to be drilled into the goaf on the stable bedrock layer, based on the first injection hole section.

[0026] After the second grouting section is drilled, the grouting inner pipe is installed in the first and second grouting sections.

[0027] In some embodiments, when the roof of the goaf has not collapsed or has not collapsed sufficiently, a single row of CO2 injection holes is provided along the direction of the working face.

[0028] When the roof of the goaf has collapsed, multiple rows of CO2 injection holes are set along the working face.

[0029] In some embodiments, when the roof of the goaf has collapsed, the CO2 injection holes should be arranged in the non-central area of ​​the goaf.

[0030] In some embodiments, the CO2 infusion method includes:

[0031] Safety valves, pressure relief valves, and pressure monitoring devices are installed on the gas pipelines, and pressure relief valves and pressure monitoring devices are installed at the orifice of the CO2 injection hole.

[0032] When injecting gaseous CO2, the first injection device is used to inject CO2 into the goaf at a pressure of 5-10 MPa. When injecting liquid CO2, the second injection device is used to inject CO2 into the goaf at a pressure of 10-15 MPa.

[0033] After CO2 injection is completed, close the valve of the orifice connector.

[0034] In some embodiments, the orifice connector is provided with a removable valve.

[0035] The first injection device includes a liquefaction station and an injection pump, wherein the liquefaction station, the injection pump and the orifice connector are connected in sequence via a gas transmission pipeline;

[0036] The second injection device includes an air storage chamber and an air compressor, wherein the air storage chamber, the air compressor and the orifice connector are connected in sequence via an air supply pipeline. Attached Figure Description

[0037] Figure 1 This is a flowchart of a carbon dioxide storage method based on the space of a deep goaf in a thick loose layer, according to an embodiment of the present invention.

[0038] Figure 2 This is a plan view of the grouting hole layout in the carbon dioxide storage method of this invention.

[0039] Figure 3 This is a flowchart of the CO2 injection process for the carbon dioxide storage method according to an embodiment of the present invention.

[0040] Figure 4 This is a schematic diagram of the CO2 injection hole in the carbon dioxide storage method of this invention.

[0041] Figure 5 This is a schematic diagram of the second filling device for the carbon dioxide storage method according to an embodiment of the present invention.

[0042] Figure 6 This is a schematic diagram showing the planar distribution characteristics of voids in the goaf.

[0043] Figure label:

[0044] 1. Loose overburden; 2. Stable bedrock; 3. Key layer; 4. Goaf; 5. Roadway; 6. Coal pillar; 7. Floor; 8. Grouting hole; 9. CO2 injection hole; 10. Inner grouting pipe; 11. Orifice connector; 12. Liquefaction station; 13. Injection pump; 14. Gas storage tank; 15. Air compressor. Detailed Implementation

[0045] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0046] The following describes, with reference to the accompanying drawings, a method for storing carbon dioxide in a deep goaf area 4 of a thick loose layer according to an embodiment of the present invention.

[0047] like Figures 1-5 As shown, the carbon dioxide storage method based on the space of a deep goaf in a thick loose layer according to an embodiment of the present invention includes the following steps:

[0048] S1. Determine the location of the roadway based on the mine excavation data, select the design position of the grouting hole, and drill the grouting hole at the design position.

[0049] S2. Inject cement-based composite grout and aggregate filling grout into the goaf 4 through the grouting holes to construct a curtain wall in the goaf 4. After the grouting is completed, seal the grouting holes to form a closed space in the goaf.

[0050] S3. Investigate the void distribution characteristics of goaf 4. Based on the investigation results, select the design position of CO2 injection hole 9 within the range corresponding to the curtain wall above the sealed space of goaf 4. Drill and construct CO2 injection hole 9 at the design position of CO2 injection hole 9. Install the hole opening connector at the hole opening of CO2 injection hole.

[0051] S4. Determine the injection process parameters based on the sealing conditions and the characteristics of different forms of CO2. Use the injection device to inject CO2 into the sealed space of the goaf 4 through the CO2 injection hole 9. After the injection is completed, close the valve of the hole connector 11. When CO2 is needed, the valve can be opened again to extract CO2 from the goaf 4.

[0052] When a thick loose layer exists in the overlying strata of goaf 4, the thick loose layer can provide a good upper sealing layer, which is a natural favorable condition for constructing a sealed storage space. After curtain grouting, a sealed space can be formed in goaf 4, which can effectively seal CO2 and prevent CO2 leakage. At the same time, when a thick loose layer exists in the deep coal seam working face, it can prevent the development of water-conducting fracture zones in the overlying strata of goaf 4 to the surface. The construction of the grouting curtain wall is feasible, and the grouting filling cost is relatively low.

[0053] The carbon dioxide storage method based on the space of a deep goaf 4 in a thick loose layer according to embodiments of the present invention utilizes a curtain wall to seal the goaf 4 and utilizes the goaf 4 to seal CO2. The sealing effect is good, the volume of CO2 sealed is large, the sealing technology is environmentally friendly and efficient, the sealing process does not generate additional CO2 or other pollution, and the sealing cost is low. It plays a positive role in achieving the carbon neutrality goal, realizes the resource utilization of abandoned mines, and can also extract CO2 again for reuse when needed, creating economic benefits.

[0054] In some embodiments, the drilling method for grouting holes includes the following steps:

[0055] Drill the first grouting hole section into the loose overburden 1. The diameter of the hole should not be less than 150 mm. The first grouting hole section penetrates the loose overburden 1 and enters the stable bedrock layer 2.

[0056] After drilling is completed, a metal casing is installed in the first grouting section, and a casing is poured with cement mortar.

[0057] Based on the first grouting section, continue drilling the second grouting section on the stable bedrock layer 2 and the key layer 3 to the goaf 4 or the roadway floor.

[0058] Because the soil in the thick loose layer is loose, it is prone to borehole collapse. Therefore, it is necessary to install a protective casing to prevent borehole collapse. The first grouting section uses mud slurry wall protection and positive circulation drilling, while the second grouting section uses clean water drilling. The diameter of the second grouting section is smaller than that of the first grouting section, and the diameter of the second grouting section is above 89mm.

[0059] It should be noted that abandoned mines lack maintenance, and the roof of goaf 4 or roadway may collapse. When the roof of goaf 4 or roadway has not collapsed or has not collapsed sufficiently, drilling can be stopped when the second grouting hole section reaches the roof of roadway 5. When the roof of goaf 4 or roadway has collapsed sufficiently, the second grouting hole section needs to be drilled to the bottom 7 of goaf 4 or roadway 5. This setup can ensure good sealing of goaf 4 after grouting.

[0060] In some embodiments, the method for constructing a curtain wall within the goaf 4 includes the following steps:

[0061] Prepare cement-based composite grout and aggregate filling grout according to the specified ratio;

[0062] For large void goaf 4 or non-collapsed roadway 5, first inject aggregate filling grout, then pressure grout cement-based composite grout. For small fracture goaf 4 or collapsed roadway 5, directly inject cement-based composite grout.

[0063] After grouting is completed, high-concentration cement mortar is used to seal the opening of the grouting hole.

[0064] When preparing the grout, the water-to-solid ratio is generally between 1.1:1 and 1:1.3. The grout concentration should not be too low to avoid excessive volume shrinkage after setting. For curtain filling, the uniaxial compressive strength of the grout-bonded specimens does not need to be too high, exceeding 1 MPa is sufficient; therefore, the cement admixture ratio does not need to be too high. Cement-based composite grout can use cement-fly ash grout, with a cement:fly ash mass ratio between 1:9 and 3:7. For aggregate-filled grout, the cement:fly ash:recycled solid waste mass ratio is (1-3):(9-7):(6-25).

[0065] Preferably, for large-cavity goaf areas 4 or uncollapsed roadways 5, aggregate filling grout is injected first, followed by cement-fly ash grout. For small-fracture goaf areas 4 or collapsed roadways 5, cement-fly ash grout is injected directly.

[0066] In some embodiments, the cement-based composite slurry is a volume-expanding cement fly ash slurry, which contains a certain proportion of desulfurization ash or an expanding agent.

[0067] It should be noted that the traditional grouting or curtain grouting for goaf 4 filling is mainly cement-based granular grout. This type of grout has significant condensation and water separation characteristics, resulting in some residual voids in the grouting target area. For the coal mining subsidence area treatment industry, a filling coefficient of 85% or higher is sufficient to meet national standards. However, for CO2 storage and utilization, denser grouting and filling of the voids in the goaf 4 target area is necessary to achieve good storage results. Therefore, from a technical perspective, a new grouting process method different from traditional grouting techniques is required. The carbon dioxide storage method in this embodiment of the invention improves the grouting filling rate by adding desulfurization ash or cement expansion agent to the cement fly ash grout.

[0068] Adding a certain proportion of desulfurized ash to cement-fly ash slurry can cause the slurry aggregate to expand, and in severe cases, it can lead to cracking and disintegration of the aggregate, significantly reducing its strength and posing serious quality risks. Therefore, this practice is prohibited in the field of coal mining subsidence area remediation. However, in the field of CO2 sequestration and utilization, the expansion characteristics of slurry prepared with desulfurized ash can be utilized to improve the filling rate of the curtain zone and enhance the curtain sealing effect.

[0069] Tests have shown that desulfurization ash can cause a volume expansion rate of 5%-50% in grout samples. A well-designed proportion of desulfurization ash can effectively control the expansion rate of the grout aggregate. Experiments have verified that when the aggregate rate of the grout samples does not exceed 20%, the strength loss is less than 50%, and the strength can still exceed 1 MPa, meeting the requirements for CO2 sequestration and utilization grouting filling technology. Furthermore, desulfurization ash also acts as a retarder, extending the setting time of the cement-based grout, increasing the flow time of the grout, expanding the diffusion range of the grout, and improving the grouting filling rate.

[0070] The mechanism of volume expansion and retarded setting of desulfurization ash is as follows:

[0071] (1) The high free CaO content in fly ash causes volume expansion.

[0072] (2) High SO3 content generates high-sulfur hydrated calcium sulfoaluminate, which increases in volume by about 1.5 times.

[0073] (3) Retarding effect: Desulfurization ash contains CaSO3, CaSO4, Ca(OH)2 and CaO. CaSO3 and CaSO4 have obvious retarding effects on cement. The retarding effect of CaSO3 is stronger than that of dihydrate gypsum, which prolongs the setting time of cement-based slurry.

[0074] Adding an expansive agent to cement-fly ash grout effectively inhibits the shrinkage characteristics of cement-based grout, resulting in a grout aggregate volume expansion rate of approximately 5%. The dosage of the expansive agent is generally 2-10% of the cement weight, and can be adjusted according to the expected expansion rate. Furthermore, the addition of the expansive agent improves the fluidity of the grout, helping to expand its diffusion range and increase the grouting filling rate.

[0075] The method for drilling CO2 injection holes 9 is similar to the method for drilling grouting holes, and specifically includes the following steps:

[0076] The first injection hole section is drilled into the loose overburden 1, and the first injection hole section penetrates the loose overburden 1 and enters the stable bedrock layer 2;

[0077] After the first grouting section is completed, the second grouting section will continue to be drilled on the stable bedrock layer 2 and the key layer 3 to the goaf 4.

[0078] After the second grouting section is drilled, the grouting inner pipe 10 is installed in the first and second grouting sections. The grouting inner pipe 10 is a circular perforated pipe. The strata in the goaf are relatively broken, and the inner pipe is made of seamless steel pipe.

[0079] like Figure 3 and Figure 4 As shown, when the roof of the goaf 4 or the roadway has not collapsed or has not fully collapsed, a single row of CO2 injection holes 9 is set along the direction of the working face; when the roof of the goaf 4 or the roadway has collapsed, multiple rows of CO2 injection holes 9 are set along the direction of the working face. The spacing between the rows of holes can be determined comprehensively based on geological conditions, mining methods, and shutdown time. For the thick loose layer goaf 4, multi-branch directional drilling can be used, with branch holes drilled at the bottom of the CO2 injection holes 9 to reduce drilling costs.

[0080] When the roof of goaf 4 or the roadway has collapsed, CO2 injection holes 9 should be opened in the non-central area of ​​goaf 4. The specific location is determined based on the distribution characteristics of the remaining voids in the goaf. For goaf 4 where the roof of the fully mechanized mining face has fully collapsed, when laying boreholes, attention should be paid to the spatial distribution characteristics of the remaining voids in goaf 4. Based on the "O"-shaped ring theory, the porosity and permeability of the collapsed rock mass in goaf 4 are distributed in a concave shape in the horizontal direction. The porosity and permeability are larger near the roadways 5 on both sides of goaf 4 and smaller in the middle. Therefore, boreholes should not be laid in the exact center of the working face in the dip direction, but rather on both sides of goaf 4. Figure 6 As shown, CO2 injection holes should be arranged in area A or area B.

[0081] In some embodiments, the CO2 infusion method includes the following steps:

[0082] To ensure the safety of high-pressure injection construction, safety valves, pressure relief valves, and pressure monitoring devices are installed on the gas pipeline, and pressure relief valves and pressure monitoring devices are installed at the orifice of CO2 injection hole 9.

[0083] When injecting gaseous CO2, the first injection device is used to inject CO2 into the goaf 4 at a pressure of 5-10 MPa, generally not exceeding 5-10 MPa. When injecting liquid CO2, the second injection device is used to inject CO2 into the goaf 4 at a pressure of 10-15 MPa. The specific injection pressure is determined based on the depth of the goaf and the injection test, and generally should not exceed 10-15 MPa.

[0084] After CO2 injection is completed, close the valve of orifice connector 11.

[0085] It should be noted that before injecting CO2, the injection process parameters should be set reasonably according to the critical temperature and pressure characteristics of CO2.

[0086] When injecting gaseous CO2, the injection pressure should be no less than 5 MPa, and ideally between 5 and 10 MPa, to improve the flow characteristics of the CO2 gas. In domestic mines with a burial depth of 500-1000m, the formation temperature is generally between 25-40℃, which is exactly within the critical temperature range of CO2. When injecting liquid CO2, a centrifugal injection pump (13) is used for high-pressure injection, with an injection pressure of around 10-15 MPa. The injection pressure should not be too high, as excessive pressure can cause formation fracturing and create new fractures. For coalfield formations, which are generally sedimentary rocks such as mudstone and sandstone with low tensile strength, the injection pressure should not exceed 15 MPa.

[0087] In some embodiments, an orifice connector 11 is provided at the orifice of the CO2 injection hole 9. The orifice connector 11 is provided with a detachable valve. One end of the orifice connector 11 is connected to the orifice of the CO2 injection hole 9, and the other end is connected to the injection device. The orifice connector 11 serves to change the diameter and seal. The injection inner tube 10 is a seamless steel pipe with threads. The orifice connector 11 is a short steel pipe with threads. The side wall opening of the orifice connector 11 is welded with threads, and the threads are connected to the detachable valve.

[0088] The orifice connector 11 serves as a connection between the CO2 surface injection pipe and the in-hole injection pipe, facilitating the quick replacement of valves and pipes of different specifications.

[0089] Specifically, such as Figure 3 As shown, the first injection device includes a liquefaction station 12 and an injection pump 13. The liquefaction station 12, the injection pump 13 and the orifice connector 11 are connected in sequence through a gas transmission pipeline. The liquefaction station 12 can prepare CO2 from external CO2 under high pressure. The liquid CO2 is then injected into the CO2 injection hole 9 through the injection pump 13.

[0090] like Figure 5 As shown, the second injection device includes a gas storage chamber 14 and an air compressor 15. The gas storage chamber 14, the air compressor 15 and the orifice connector 11 are connected in sequence through a gas transmission pipeline. The gas storage chamber 14 can store CO2 supplied from the outside and then inject it into the CO2 injection hole 9 through the air compressor 15.

[0091] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0092] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0093] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0094] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0095] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0096] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A method for carbon dioxide storage based on the space of a deep goaf in a thick loose layer, characterized in that, include: Based on the mine excavation data, determine the location of the roadway. On both sides of the working face, 10-20m above the goaf, select the design position of the grouting hole and drill the grouting hole at the design position. Cement-based composite grout and aggregate filling grout are injected into the goaf through the grouting holes to construct a curtain wall in the goaf. After the grouting is completed, the grouting holes are sealed to form a closed space in the goaf. Investigate the distribution characteristics of voids in the goaf area. Based on the investigation results, select the design location of CO2 injection holes within the range of the ground surface above the sealed space of the goaf area and the curtain wall. Drill and construct CO2 injection holes at the design location of CO2 injection holes. Install hole opening connectors at the opening of the CO2 injection holes. The injection process parameters are determined based on the sealing conditions and the characteristics of different forms of CO2. CO2 is injected into the sealed space of the goaf through the CO2 injection hole using the injection device. After the injection is completed, the valve of the hole connector is closed. The drilling methods for grouting holes include: Drill the first grouting hole section into the loose overburden layer. The diameter of the hole is not less than 150 mm. The first grouting hole section penetrates the loose overburden layer and enters the stable bedrock layer. After the first grouting hole section is drilled, a protective sleeve is installed inside the first grouting hole section. Based on the first grouting section, continue drilling the second grouting section into the stable bedrock layer to the goaf or the bottom of the roadway; The first grouting section uses mud wall protection and positive circulation drilling, while the second grouting section uses clean water drilling. The diameter of the second grouting section is smaller than that of the first grouting section, and the diameter of the second grouting section is above 89mm. When the roof of the goaf or roadway has not collapsed, the second grouting hole section is drilled into the roof of the goaf or roadway. When the roof of the goaf has collapsed, the second grouting section is drilled into the floor of the goaf or roadway. The method for constructing a curtain wall within the goaf includes: The cement-based composite slurry and the aggregate filling slurry are prepared according to the specified ratio. When preparing the slurry, the water-to-solid ratio is in the range of 1.1:1 to 1:1.

3. The cement-based composite slurry uses cement-fly ash slurry with a cement:fly ash mass ratio between 1:9 and 3:7; for aggregate filling slurry, the cement:fly ash:recycled solid waste aggregate mass ratio is 1:9:

25. For large-cavity goaf areas or roadways that have not collapsed, first inject the aggregate filling grout, and then pressure inject the cement-based composite grout. For small-fracture goaf areas or roadways that have collapsed, directly inject the cement-based composite grout. After grouting is completed, high-concentration cement mortar is used to seal the opening of the grouting hole; The cement-based composite slurry is a volume-expanding cement fly ash slurry, and the volume-expanding cement fly ash slurry contains desulfurization ash or an expanding agent. The drilling methods for CO2 injection holes include: The first injection hole section was drilled into the loose overburden layer, and the first injection hole section penetrated the loose overburden layer and entered the stable bedrock layer; After the first injection hole section is completed, the second injection hole section will continue to be drilled into the goaf on the stable bedrock layer, based on the first injection hole section. After the second grouting hole section is drilled, the grouting inner pipe is installed in the first grouting hole section and the second grouting hole section. When the roof of the goaf has not collapsed or has not collapsed sufficiently, a single row of CO2 injection holes shall be set along the direction of the working face. When the roof of the goaf has collapsed, multiple rows of CO2 injection holes are set along the working face; When the roof of the goaf has collapsed, the CO2 injection holes are arranged in the non-central area of ​​the goaf.

2. The carbon dioxide storage method according to claim 1, characterized in that, CO2 infusion methods include: Safety valves, pressure relief valves, and pressure monitoring devices are installed on the gas pipelines, and pressure relief valves and pressure monitoring devices are installed at the orifice of the CO2 injection hole. When injecting gaseous CO2, the first injection device is used to inject CO2 into the goaf at a pressure of 5-10 MPa. When injecting liquid CO2, the second injection device is used to inject CO2 into the goaf at a pressure of 10-15 MPa. After CO2 injection is completed, close the valve of the orifice connector.

3. The carbon dioxide storage method according to claim 2, characterized in that, The orifice connector is equipped with a detachable valve. The first injection device includes a liquefaction station and an injection pump, wherein the liquefaction station, the injection pump and the orifice connector are connected in sequence via a gas transmission pipeline; The second injection device includes an air storage chamber and an air compressor, wherein the air storage chamber, the air compressor and the orifice connector are connected in sequence via an air supply pipeline.

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