Mineralization grouting method for reinforcing sequestration of carbon dioxide

Abstract

The invention provides a mineralization grouting method for reinforcing sequestration of carbon dioxide, and belongs to the technical field of underground goaf grouting filling, the working process comprises the steps that supercritical CO2, micro-nano filler and calcium-containing solid waste are jointly mixed and mixed into slurry, the slurry is injected into a goaf, part of CO2 is turned into a gaseous state to escape in the state of being lower than the supercritical pressure of CO2, and then the CO2 is discharged; bubble cores are formed on the surface of the micro-nano filler, and uniformly distributed micropores are formed in a stone body after the slurry is solidified. Due to the fact that the micropores can seal gaseous CO2, the carbon sequestration amount of the slurry per cubic meter can reach 150-350 kg, and the carbon sequestration capacity of the slurry is higher than the carbon sequestration capacity of a common grouting material. The technological method is easy to operate, supercritical CO2 reacts with the slurry, a large amount of CO2 in the shallow goaf is stored, the solid waste material is used for grouting, meanwhile, the carbon sequestration amount of the slurry is increased, and the grouting cost is saved.

Description

Technical Field

[0001] The present invention belongs to the technical field of underground gob grouting and filling, and specifically discloses a mineralized grouting method for strengthening the sequestration of carbon dioxide. Background Art

[0002] At present, coal occupies a dominant position in China's energy structure and has long been the main energy supply. However, this also brings many problems: large-scale continuous coal mining has led to large areas of underground goafs, unbalanced rock strata, and frequent ground collapses; in the use process, coal combustion not only releases a large amount of CO2, exacerbating the greenhouse effect, but also generates a large amount of coal-based solid waste. Limited by technology and cost, it is difficult to effectively treat these solid wastes. A large amount of stockpiling not only wastes land resources, but also easily pollutes the surrounding soil and water bodies due to percolation, and the CO2 emissions aggravate the greenhouse effect. It is urgent to explore effective treatment paths. The coal-based solid waste CO2 mineralized grouting technology can not only reduce the ground collapse caused by the goaf, but also fix CO2 and reduce the stockpiling of solid wastes. The existing CO2 mineralized grouting technologies are mainly divided into two categories. One is to introduce CO2 into the goaf where the slurry has been injected and use the carbonation reaction between CO2 and the slurry to sequester CO2. The other is to introduce CO2 during the slurry production process so that the slurry reacts fully with CO2 and then grouting is carried out. However, due to the lack of stirring conditions or the relatively small solubility of CO2 under normal temperature and pressure in the above two methods, the actual amount of CO2 that can be fixed per cubic meter of slurry in grouting practice is about 20 - 120 kg. In a coal-electricity integrated plant, in addition to the filling requirement, there are also a large amount of solid wastes and CO2 waste gases that need to be treated. The above technologies cannot completely consume CO2.

[0003] In order to achieve large-scale and stable storage of CO2, supercritical CO2 is widely used. Chinese patent CN117868760A discloses a water treatment method for storing carbon dioxide in sandstone fracture aquifers. After collecting CO2, temperature control and pressurization are performed to obtain supercritical CO2, which is then injected into the sandstone fracture aquifers in the deep strata. The temperature and pressure conditions of the deep strata keep CO2 in a supercritical state. Supercritical CO2 is dissolved in water in large quantities to produce carbonate ions, which react with calcium and magnesium ions in the slurry to form a carbonation reaction to store CO2 in large quantities. On the other hand, unreacted supercritical CO2 continues to be stored underground in a supercritical state, which improves the grouting reinforcement effect while expanding the storage volume of CO2. Chinese patent CN114575800A discloses a method for deep in-situ supercritical storage of flue gas. After the flue gas generated by the power plant is pressurized to a supercritical state, it is also injected into the storage layer in the deep stratum along the wellbore and then sealed layer by layer. While storing CO2, the cost of CO2 transportation and shipment is saved. In practical application, the supercritical CO2 grouting storage technology needs to maintain a temperature of >31.1℃ and a pressure of >7.38MPa, which often requires the grouting depth to be at least 800m underground, but this condition does not exist in shallow goafs. Supercritical CO2 grouting storage technology is not applicable to shallow goafs or coal mine cavities because CO2 will escape in large quantities, resulting in large cavities in the grouting material or its stone body, which seriously reduces the mechanical properties of the stone body, such as compressive strength.

[0004] In short, the depth of goaf is generally tens to hundreds of meters. The temperature and pressure at this depth cannot keep CO2 in a supercritical state. During mineralization grouting in shallower goafs, supercritical CO2 will escape due to changes in pressure and temperature. Not only will the amount of carbon fixation be reduced, but the stone body will also no longer be stable, making it impossible to achieve the purpose of simultaneously absorbing solid waste and CO2 tail gas during grouting to fill the goaf. Summary of the invention

[0005] In view of the above technical problems, the present invention provides a mineralization grouting method for strengthening the storage of carbon dioxide. When using supercritical CO2 and solid waste slurry for mineralization grouting, the method uses a micro-nano filler that is compatible with CO2 gas as a multiphase interface to stimulate the escaped CO2 to form fine bubbles on the surface of the micro-nano filler, thereby forming a uniformly distributed group of tiny bubbles. This method can avoid the gas from agglomerating into large bubbles due to the large amount of CO2 escaping, and cause large bubble cavities to appear inside the grouting material stone body. Since this method can form uniformly distributed tiny bubbles, the internal structure of the grouting material stone body will not be seriously damaged, and sufficient mechanical properties can be maintained, so that a large amount of CO2 can be fixed and stored while filling the goaf.

[0006] The above-mentioned mineralization grouting method for enhanced carbon dioxide storage comprises the following steps:

[0007] S1. By mass fraction, mix 50% - 80% of fly ash or coal gangue, 10% - 40% of carbide slag, 8% - 15% of alkaline solid waste, and 2% - 10% of micro-nano fillers to obtain a solid mixture.

[0008] S2. After pressurizing CO2, transport it to a gas storage tank, control the temperature and pressure of the gas storage tank to make the CO2 in the gas storage tank reach the supercritical state with a temperature > 31.1°C and a pressure > 7.38 MPa.

[0009] S3. Under the state of temperature > 31.1°C and pressure > 7.38 MPa, mix and stir supercritical CO2 with the solid mixture and water. The mass ratio of water to solid is 0.6:1 - 0.9:1, and the mass ratio of supercritical CO2 to the solid mixture is 1:1 - 1:2. After mixing and stirring, a slurry is obtained.

[0010] S4. Inject the slurry into the shallow underground mined - out area through a high - pressure pipeline. Part of the supercritical CO2 changes back to the gaseous state and escapes, forming micron - sized bubbles on the surface of the micro - nano fillers, thus forming a uniformly distributed micron - sized bubble group in the slurry. After the initial setting of the slurry, a micron - sized closed - pore group structure is formed in the stone body. The gaseous CO2 is accommodated through the micron - sized closed - pore group structure in the stone body, forming a foam - like stone body that locks the gaseous CO2.

[0011] In step S1, the alkaline solid waste includes one or more of red mud, steel slag, magnesium slag, and desulfurization ash, and the micro - nano fillers include one or more of silica powder, gypsum powder, ultra - fine calcium carbonate, and polymer microspheres.

[0012] In step S4, the slurry is obtained after mixing and stirring for 10 min - 3 h.

[0013] In step S4, inject the slurry into the shallow underground mined - out area within 800 m underground. The initial setting time is 5 - 7 h, and a foam - like stone body that locks the gaseous CO2 is formed after 7 d - 28 d.

[0014] Specifically, in step S1, mix 60% of fly ash, 20% of carbide slag, 15% of red mud, and 5% of silica powder to obtain a solid mixture.

[0015] In step S3, the mass ratio of water to solid is 0.6:1, and the mass ratio of supercritical CO2 to the solid mixture is 1:1.5. The slurry is obtained after mixing and stirring for 3 h.

[0016] In step S4, the initial setting time is 5 h.

[0017] Specifically, in step S1, mix 50% of fly ash, 30% of carbide slag, 10% of magnesium slag, and 10% of gypsum powder to obtain a solid mixture.

[0018] In step S3, the mass ratio of water to solid is 0.8:1, and the mass ratio of supercritical CO2 to the solid mixture is 1:1. After mixing and stirring for 1 h, a slurry is obtained.

[0019] In step S4, the initial setting time is 6 h.

[0020] Specifically, in step S1, 80% fly ash, 10% carbide slag, 8% desulfurized ash, and 2% ultrafine calcium carbonate are mixed to obtain a solid mixture.

[0021] In step S3, the mass ratio of water to solid is 0.9:1, and the mass ratio of supercritical CO2 to the solid mixture is 1:2. After mixing and stirring for 10 min, a slurry is obtained.

[0022] In step S4, the initial setting time is 7 h.

[0023] Specifically, in step S1, 50% coal gangue, 40% carbide slag, 8% steel slag, and 2% SiO2@PS microspheres are mixed to obtain a solid mixture.

[0024] In step S3, the mass ratio of water to solid is 0.7:1, and the mass ratio of supercritical CO2 to the solid mixture is 1:1. After mixing and stirring for 2 h, a slurry is obtained.

[0025] In step S4, the initial setting time is 6.5 h.

[0026] Compared with the prior art, the present invention has the following beneficial effects.

[0027] (1) The process method of the present invention is easy to operate. By using supercritical CO2 to react with the slurry, a large amount of CO2 can be sequestered in the shallow goaf, and while injecting the slurry with solid waste materials, the carbon sequestration amount of the slurry is increased. The solubility of CO2 in the supercritical state is 5-10 times that at normal temperature and pressure. Reacting supercritical CO2 with the slurry accelerates the dissolution of CO2, thereby accelerating the carbonation reaction process with calcium and magnesium ions in the slurry and increasing the fixed amount of dissolved CO2.

[0028] (2) In the past, large-scale sequestration of supercritical CO2 usually required injecting slurries into deep formations to ensure the temperature and pressure conditions required for supercritical CO2. However, this invention has no strict requirements for the grouting depth. Due to the addition of micro-nano fillers in the slurry, even when supercritical CO2 returns to the gaseous state and escapes after shallow grouting, the micro-nano fillers can reduce the surface energy required to form its bubbles, making it easier for the gas to aggregate on the particle surface to form small bubble nuclei, and then form uniformly distributed micron-sized bubbles in the slurry. After the slurry solidifies, micropores with a diameter of 100μm - 500μm are formed, and these micropores have the ability to continue to adsorb and accommodate CO2, enabling each cubic meter of slurry to fix and accommodate 150 - 350 kg of CO2, which is higher than the carbon sequestration capacity of 20 - 120 kg / m 3 of most grouting materials in conventional application environments.

[0029] (3) The compressive strength of the foam-like solid formed by this invention reaches 5 - 15 MPa after 28 days, meeting the compressive strength requirements of grouting materials for goafs.

[0030] (4) The CO2 in this invention can be sourced from the waste gas generated by power plants and other industries, and the grouting raw materials can be sourced from the solid waste of coal mines or coal power plants. For coal-electricity integrated mining areas, materials can be obtained locally, and waste recycling can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0032] Figure 1 Process flow chart of the mineralization grouting method for enhanced carbon dioxide sequestration;

[0033] Figure 2 Experimental device diagram of the mineralization grouting method for enhanced carbon dioxide sequestration;

[0034] Figure 3 Microscopic picture of the stone body.

[0035] In the figure: 1 - CO2 collection device; 2 - booster pump; 3 - supercritical CO2 storage tank; 4 - liquid volume control valve; 5 - high-temperature and high-pressure reaction kettle; 6 - grouting pump; 7 - high-pressure pipeline; 8 - temperature monitoring mechanism; 9 - pressure monitoring mechanism; 10 - rock mass; 11 - stone body. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work belong to the scope of protection of the present invention.

[0037] This embodiment provides a method for mineralized grouting to enhance the sequestration of carbon dioxide. The experimental raw materials include circulating fluidized bed fly ash (CFBA, sourced from a thermal power company), desulfurized ash (sourced from a thermal power company), carbide slag (CS, sourced from a chemical company), red mud (RM, sourced from an aluminum plant), magnesium slag, gypsum powder, silicon dioxide powder, and ultrafine calcium carbonate, all of which are commercially available.

[0038] The chemical compositions of some of the experimental raw materials are shown in Table 1.

[0039] Table 1 Chemical Compositions of Some Raw Materials

[0040]

[0041] The experimental device used includes a CO2 collection device 1, a booster pump 2, a supercritical CO2 storage tank 3, a liquid flow control valve 4, a high-temperature and high-pressure reactor 5, a grouting pump 6, and a high-pressure pipeline 7 connected in sequence. The high-temperature and high-pressure reactor 5 is equipped with a temperature monitoring mechanism 8 and a pressure monitoring mechanism 9.

[0042] The above method for mineralized grouting to enhance the sequestration of carbon dioxide includes the following steps:

[0043] S1, by mass fraction, mix 50% - 80% of fly ash or coal gangue, 10% - 40% of carbide slag, 8% - 15% of alkaline solid waste, and 2% - 10% of micro-nano fillers to obtain a solid mixture.

[0044] S2, after pressurizing CO2, transport it to the gas storage tank, control the temperature and pressure of the gas storage tank to make the CO2 in the gas storage tank reach a supercritical state with a temperature > 31.1°C and a pressure > 7.38 MPa.

[0045] S3, under the condition of a temperature > 31.1°C and a pressure > 7.38 MPa, mix and stir supercritical CO2 with the solid mixture and water. The mass ratio of water to solid is 0.6:1 - 0.9:1, and the mass ratio of supercritical CO2 to the solid mixture is 1:1 - 1:2. After mixing and stirring for 10 min - 3 h, a slurry is obtained.

[0046] In step S4, the slurry is injected into the shallow mined - out area within 800 m underground through a high - pressure pipeline. Part of the supercritical CO₂ re - turns to the gaseous state and escapes, forming micron - sized bubbles on the surface of the micro - nano filler, thus forming a uniformly distributed micron - sized bubble group in the slurry. After the slurry initial - sets in 5 - 7 h, a micron - sized closed - pore group structure is formed in the stone body. The gaseous CO₂ is accommodated through the micron - sized closed - pore group structure in the stone body, and a foam - like stone body locking the gaseous CO₂ is formed after 7 d - 28 d.

[0047] In step S1, the alkaline solid waste includes one or more of red mud, steel slag, magnesium slag, and desulfurization ash, and the micro - nano filler includes one or more of silicon dioxide powder, gypsum powder, ultrafine calcium carbonate, and polymer microspheres.

[0048] Four groups of experiments were carried out in this embodiment, and the raw material ratios of the four groups of experiments are shown in Table 2.

[0049] Table 2 Raw material ratios of the experiments

[0050]

[0051] The operation steps of experimental group 1 are as follows:

[0052] S1, by mass fraction, 60% fly ash, 20% carbide slag, 15% alkaline solid waste, and 5% micro - nano filler are mixed to obtain a solid mixture. The alkaline solid waste is red mud, and the micro - nano filler is silicon dioxide powder;

[0053] S2, CO₂ is pressurized and then transported to a gas storage tank. The temperature and pressure of the gas storage tank are controlled so that the inside of the gas storage tank reaches the supercritical state of CO₂ with a temperature > 31.1 °C and a pressure > 7.38 MPa;

[0054] S3, in the state of temperature > 31.1 °C and pressure > 7.38 MPa, the supercritical CO₂ is mixed and stirred with the solid mixture and water. The mass ratio of water to solid is 0.6:1, and the mass ratio of supercritical CO₂ to the solid mixture is 1:1.5. After mixing and stirring for 3 h, a slurry is obtained;

[0055] S4, the slurry is injected into the shallow mined - out area within 800 m underground through a high - pressure pipeline. Part of the supercritical CO₂ re - turns to the gaseous state and escapes, forming micron - sized bubbles on the surface of the micro - nano filler, thus forming a uniformly distributed micron - sized bubble group in the slurry. After the slurry initial - sets in 5 h, a micron - sized closed - pore group structure is formed in the stone body. The gaseous CO₂ is accommodated through the micron - sized closed - pore group structure in the stone body, and a foam - like stone body locking the gaseous CO₂ is formed after 7 d - 28 d.

[0056] The operation steps of experimental group 2 are as follows:

[0057] S1. By mass fraction, mix 50% fly ash, 30% carbide slag, 10% alkaline solid waste, and 10% micro-nano filler to obtain a solid mixture. The alkaline solid waste is magnesium slag, and the micro-nano filler is gypsum powder;

[0058] S2. After pressurizing CO2, transport it to a gas storage tank, and control the temperature and pressure of the gas storage tank to make the CO2 in the gas storage tank reach the supercritical state with a temperature > 31.1 °C and a pressure > 7.38 MPa;

[0059] S3. Under the state of temperature > 31.1 °C and pressure > 7.38 MPa, mix and stir supercritical CO2 with the solid mixture and water. The mass ratio of water to solid is 0.8:1, and the mass ratio of supercritical CO2 to the solid mixture is 1:1. After mixing and stirring for 1 h, a slurry is obtained;

[0060] S4. Inject the slurry into the shallow goaf within 800 m underground through a high-pressure pipeline. Part of the supercritical CO2 re-becomes gaseous and escapes, forming micron-sized bubbles on the surface of the micro-nano filler, thus forming a uniformly distributed micron-sized bubble group in the slurry. After the slurry initial sets in 6 h, a micron-sized closed pore group structure is formed in the stone body. The gaseous CO2 is accommodated through the micron-sized closed pore group structure in the stone body, and a foamy stone body locking gaseous CO2 is formed after 7 d - 28 d.

[0061] The operating steps of Experimental Group 3 are as follows:

[0062] S1. By mass fraction, mix 80% fly ash, 10% carbide slag, 8% alkaline solid waste, and 2% micro-nano filler to obtain a solid mixture. The alkaline solid waste is desulfurization ash, and the micro-nano filler is ultrafine calcium carbonate;

[0063] S2. After pressurizing CO2, transport it to a gas storage tank, and control the temperature and pressure of the gas storage tank to make the CO2 in the gas storage tank reach the supercritical state with a temperature > 31.1 °C and a pressure > 7.38 MPa;

[0064] S3. Under the state of temperature > 31.1 °C and pressure > 7.38 MPa, mix and stir supercritical CO2 with the solid mixture and water. The mass ratio of water to solid is 0.9:1, and the mass ratio of supercritical CO2 to the solid mixture is 1:2. After mixing and stirring for 10 min, a slurry is obtained;

[0065] S4. Inject the slurry into the shallow mined - out area within 800 m underground through a high - pressure pipeline. Part of the supercritical CO₂ reverts to a gaseous state and escapes, forming micron - sized bubbles on the surface of the micro - nano filler, thus forming a uniformly distributed micron - sized bubble group in the slurry. After the slurry initial - sets in 7 h, a micron - sized closed - pore group structure is formed in the stone body. The gaseous CO₂ is accommodated through the micron - sized closed - pore group structure in the stone body, and a foamed stone body locking the gaseous CO₂ is formed after 7 d - 28 d.

[0066] The operating steps of experimental group 4 are described as follows:

[0067] S1. Mix 50% coal gangue, 40% carbide slag, 8% alkaline solid waste, and 2% micro - nano filler by mass fraction to obtain a solid mixture. The alkaline solid waste is steel slag, and the micro - nano filler is SiO₂@PS microspheres.

[0068] S2. After pressurizing CO₂, transport it to a gas storage tank, and control the temperature and pressure of the gas storage tank to make the CO₂ in the gas storage tank reach the supercritical state with a temperature > 31.1 °C and a pressure > 7.38 MPa.

[0069] S3. Under the state of temperature > 31.1 °C and pressure > 7.38 MPa, mix and stir the supercritical CO₂ with the solid mixture and water. The mass ratio of water to solid is 0.7:1, and the mass ratio of supercritical CO₂ to the solid mixture is 1:1. After mixing and stirring for 2 h, a slurry is obtained.

[0070] S4. Inject the slurry into the shallow mined - out area within 800 m underground through a high - pressure pipeline. Part of the supercritical CO₂ reverts to a gaseous state and escapes, forming micron - sized bubbles on the surface of the micro - nano filler, thus forming a uniformly distributed micron - sized bubble group in the slurry. After the slurry initial - sets in 6.5 h, a micron - sized closed - pore group structure is formed in the stone body. The gaseous CO₂ is accommodated through the micron - sized closed - pore group structure in the stone body, and a foamed stone body locking the gaseous CO₂ is formed after 7 d - 28 d.

[0071] Perform performance tests on the slurries of the four groups of experiments. The compressive strength is measured by a YAW - 200B type microcomputer - controlled constant - stress testing machine, the initial setting time is measured by an SK09989 type Vicat apparatus, and the average pore diameter is measured by industrial CT and a microscope. The results are shown in Table 3.

[0072] Table 3 Slurry Performance Test

[0073]

[0074] The CO2 foam stone body realizes CO2 sequestration and utilization through two aspects: the mineralization reaction of solid waste-based materials and microbubble carbon storage. On the one hand, solid waste materials can carry out mineralization reactions with CO2 and have excellent carbon sequestration ability. On the other hand, the pores of the CO2 foam stone body have a certain carbon storage capacity, and the amount of CO2 stored in the micropores can be calculated by the pore volume.

[0075] Therefore, M 固碳量 = M 矿化反应固碳量 + M 微孔容纳CO2量

[0076] The carbon sequestration amount of the mineralization reaction is determined by TG / DTG analysis: Model: TGA-5500), Test conditions: Temperature range 42 - 1000 °C, Test atmosphere: N2 atmosphere, Heating rate: 10 °C / min. By analyzing the mass loss of the sample, the composition of the sample is analyzed according to the principle that different substances have different decomposition temperatures.

[0077] In the DTG curve of the thermogravimetric test of the stone body, four relatively obvious weight loss peaks appear between 100 °C - 380 °C, 380 °C - 470 °C, 470 °C - 700 °C and 700 °C - 900 °C, which are the weight loss peaks of C-S-H, CH, CaCO3 and C-S-H respectively, that is, CaCO3 will decompose between 470 °C - 700 °C. By calculating the weight loss rate of the blank group and the supercritical carbonization group at this temperature, the amount of CO2 fixed by the carbonization reaction can be obtained.

[0078] The porosity is determined by industrial CT: Industrial CT (GE Vtomex) is used to measure the porosity of the foam stone body under different conditions. Test conditions: Scanning voltage: 60 kv, Current: 80 μA, Resolution: 1.3 μm.

[0079] Taking experimental group 1 as an example, the specific calculation process is as follows:

[0080] M 矿化反应固碳量 = Weight loss rate × Dry density of the stone body = 36% × 969.3 kg / m 3 = 348.948 kg / m 3 ≈ 348.95 kg / m 3

[0081] M 微孔容纳CO2量 = Pore volume × ρ, where ρ is the density of CO2, Pore volume = Porosity × 1 m 3

[0082] Therefore, M 微孔容纳CO2量 = 50% × 1 m 3 × 1.997 kg / m 3 = 0.9985 ≈ 1 kg / m 3

[0083] Therefore, M 固碳量 = 348.95 kg / m 3 + 1 kg / m 3 = 349.95 kg / m 3 .

[0084] The weight loss rate and pore volume were measured according to the above method, and the results are shown in Table 4. The density of CO2 is calculated as 1.997 kg / m 3 .

[0085] Table 4 Determination of Carbon Sequestration Capacity

[0086]

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A mineralization grouting method for enhanced carbon dioxide storage, characterized in that: The steps include: S1, mixing 50% to 80% of fly ash or coal gangue, 10% to 40% of carbide slag, 8% to 15% of alkaline solid waste, and 2% to 10% of micro-nano filler according to mass fraction to obtain a solid mixture; S2, transporting the CO2 to the gas storage tank after pressurization, and controlling the temperature and pressure of the gas storage tank to make the CO2 in the gas storage tank reach a supercritical state with a temperature > 31.1°C and a pressure > 7.38MPa; S3, under the condition of temperature>31.1°C and pressure>7.38MPa, supercritical CO2 is mixed with solid mixture and water, the water-solid mass ratio is 0.6:1-0.9:1, the mass ratio of supercritical CO2 to solid mixture is 1:1-1:2, and slurry is obtained after mixing and stirring; S4, injecting the slurry into the shallow underground goaf through a high-pressure pipeline, part of the supercritical CO2 turns back into gas and escapes, forming micron-sized bubbles on the surface of the micro-nano filler, thereby forming a uniformly distributed micron-sized bubble group in the slurry, and after the initial coagulation of the slurry, a micron-sized closed-pore group structure is formed in the stone body, and the CO2 is accommodated by the micron-sized closed-pore group structure in the stone body, forming a foamy stone body that locks the gaseous CO2.

2. The mineralization grouting method for enhanced carbon dioxide storage according to claim 1, characterized in that: In step S1, the alkaline solid waste includes one or more of red mud, steel slag, magnesium slag, and desulfurization ash, and the micro-nano filler includes one or more of silicon dioxide powder, gypsum powder, ultrafine calcium carbonate, and polymer microspheres.

3. The mineralization grouting method for enhanced carbon dioxide storage according to claim 2, characterized in that: In step S4, the mixture is mixed and stirred for 10 min to 3 h to obtain a slurry.

4. The mineralization grouting method for enhanced carbon dioxide storage according to claim 3, characterized in that: In step S4, the slurry is injected into the shallow goaf within 800m underground through a high-pressure pipeline. The initial setting time is 5 to 7 hours, and a foamy stone body that locks the gaseous CO2 is formed after 7 to 28 days.

5. The mineralization grouting method for enhanced carbon dioxide storage according to claim 4, characterized in that: In step S1, 60% of fly ash, 20% of carbide slag, 15% of red mud, and 5% of silicon dioxide powder are mixed to obtain a solid mixture; In step S3, the water-solid mass ratio is 0.6:1, the mass ratio of supercritical CO2 to solid mixture is 1:1.5, and the slurry is obtained after mixing and stirring for 3 hours; In step S4, the initial setting time is 5 hours.

6. The mineralization grouting method for enhanced carbon dioxide storage according to claim 4, characterized in that: In step S1, 50% of fly ash, 30% of carbide slag, 10% of magnesium slag, and 10% of gypsum powder are mixed to obtain a solid mixture; In step S3, the water-solid mass ratio is 0.8:1, the mass ratio of supercritical CO2 to solid mixture is 1:1, and the slurry is obtained after mixing and stirring for 1 hour; In step S4, the initial setting time is 6 hours.

7. The method for mineralization grouting for enhanced storage of carbon dioxide according to claim 4, characterized in that: In step S1, 80% of fly ash, 10% of carbide slag, 8% of desulfurization ash, and 2% of ultrafine calcium carbonate are mixed to obtain a solid mixture; In step S3, the water-solid mass ratio is 0.9:1, the mass ratio of supercritical CO2 to solid mixture is 1:2, and the slurry is obtained after mixing and stirring for 10 minutes; In step S4, the initial setting time is 7 hours.

8. The mineralization grouting method for enhanced carbon dioxide storage according to claim 4, characterized in that: In step S1, 50% of coal gangue, 10% of carbide slag, 8% of steel slag, and 2% of SiO2@PS microspheres are mixed to obtain a solid mixture; In step S3, the water-solid mass ratio is 0.7:1, the mass ratio of supercritical CO2 to solid mixture is 1:1, and the slurry is obtained after mixing and stirring for 2 hours; In step S4, the initial setting time is 6.5 hours.

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