Mine structural carbon storage unit construction method based on carbon mineralization synergistic filling technology

Abstract

The invention provides a mine structural carbon storage unit construction method based on a carbon mineralization synergetic filling technology, and belongs to the technical field of mineral engineering and comprehensive utilization of resources, and the mine structural carbon storage unit construction method comprises the following steps: mixing a solid waste powder raw material with a regulating agent solution, introducing industrial waste gas containing CO2, and carrying out a carbon mineralization reaction to obtain mixed slurry; mixing a carbon mineralization solid product obtained by solid-liquid separation with tailings, water and a cementing material to obtain filling slurry; and after the filling slurry is conveyed to the underground goaf through a pipeline and filling is completed, the mine structural carbon storage unit is formed through maintenance and curing. The carbon mineralization reaction is coupled with mine filling, so that CO2 is fixedly sealed in a filling body microstructure in a stable carbonate form for a long time, a carbon storage unit with a bearing function is formed, the carbon emission of a mining system is reduced from the source, and the safety and stability of an underground space are improved.

Description

Technical Field

[0001] This invention belongs to the field of mining engineering and comprehensive resource utilization technology, specifically relating to a method for constructing structural carbon storage units in mines based on carbon mineralization synergistic filling technology. Background Technology

[0002] With the advancement of global climate governance, the mining industry, as an energy and resource-intensive sector, involves significant energy consumption and greenhouse gas emissions throughout its entire process (exploration, mining, transportation, tailings treatment, and related primary processing). Simultaneously, large amounts of solid waste, such as tailings, waste rock, and metallurgical slag, continue to accumulate, resulting in both resource waste and ecological risks. Therefore, it is urgent to promote the transformation of the mining industry from a high-carbon-emission sector to one with potential carbon sequestration functions.

[0003] Backfilling mining is considered an important path to achieving green and low-carbon mining. Related processes include using tailings and other solid waste as raw materials, mixing and preparing slurry, and backfilling them into underground goaf areas. This can control ground pressure, improve recovery rates, and help reduce and recycle solid waste. However, existing backfilling systems are highly dependent on cement in the cementing material stage, and cement production is a significant source of CO2 emissions, creating a contradiction of "treating waste with waste but leading to high carbon emissions."

[0004] It is worth noting that metallurgical slag and ultrabasic tailings rich in calcium and magnesium minerals in solid waste have high carbon mineralization potential. They can react with CO2 to generate thermodynamically stable carbonate minerals, achieving long-term solidification and forming reaction products with certain cementation and structural strength. Based on this, in recent years, relevant technical paths for introducing the carbon mineralization process into mine backfilling systems have been gradually developed. Among the existing technologies, the methods related to carbon mineralization backfilling can be mainly summarized into the following three categories: First, after the backfilling in the goaf or roadway is completed, CO2 is injected underground to cause in-situ carbonization reaction in the backfill body; second, CO2 is introduced into the slurry preparation process or aqueous system during the backfill material preparation stage; and third, materials with carbon fixation function are prepared through chemical leaching-remineralization.

[0005] However, the aforementioned technical approaches generally suffer from a high degree of coupling between the reaction stage and the filling system: downhole gas injection requires complex closed-loop and piping systems, resulting in high construction risks and costs; while introducing CO2 into the slurry or aqueous system can easily lead to a sudden drop in pH, inhibiting cement hydration and thus affecting the final strength and stability of the filling body. Furthermore, in these approaches, carbon mineralization often acts indiscriminately on the entire slurry or spatial system, making it difficult to precisely control the carbon sequestration process. In addition, for technical approaches using chemical leaching-remineralization, carbon mineralization typically requires dissolving, migrating, and reprecipitating the calcium and magnesium active components in solid waste. This process often involves multiple chemical treatments and solid-liquid separation operations, making the process relatively complex, with high requirements for reagent consumption and process control, and presenting challenges for continuous engineering and large-scale application.

[0006] Therefore, how to achieve efficient carbon mineralization treatment with solid waste particles as the main reactant without relying on underground gas injection, directly introducing CO2 during the filling and slurry preparation stage, and without dissolving, migrating, and re-precipitating the active components of solid waste, and then stably introducing it into the mine filling system to construct a structural carbon storage unit in the mine that combines engineering bearing capacity and long-term carbon sequestration capability, still needs further research and solutions. Summary of the Invention

[0007] This invention provides a method for constructing a structural carbon storage unit in a mine based on carbon mineralization synergistic filling technology. The method includes: before filling the mine with slurry, using solid waste particles as the main reactant, placing them and a regulator solution in an independent carbon mineralization reactor. Then, CO2 gas is introduced to perform rapid carbon mineralization treatment, obtaining a modified carbon mineralization product. This modified carbon mineralization product is then introduced into the mine filling system, ultimately forming a structural carbon storage unit that combines engineering load-bearing capacity with long-term carbon sequestration capability.

[0008] This invention limits carbon mineralization to the cementitious phase, or introduces carbon-mineralized reactive solid waste as part of the cementitious system into the backfill material, so that CO2 is mainly sequestered in the cementitious phase and its related reaction products. Because the cementitious phase accounts for a relatively low proportion in the backfill, the overall carbon storage capacity is relatively limited, but its dependence on aggregate type is low, making it suitable for engineering applications in mines lacking ultrabasic tailings resources.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for constructing structural carbon storage units in mines based on carbon mineralization synergistic filling technology includes the following steps:

[0011] S1. Solid waste pretreatment: Solid waste is crushed and ground to obtain powder raw materials.

[0012] S2. Preparation of regulator solution: Add regulator to water and stir thoroughly until completely dissolved to obtain regulator solution, which is used to adjust the carbon mineralization reaction environment.

[0013] S3. Rapid carbon mineralization treatment: The powder raw material obtained in S1 is mixed with the regulator solution obtained in S2, injected into the rapid carbon mineralization device and CO2-containing industrial waste gas is introduced to carry out the carbon mineralization reaction and obtain a mixed slurry.

[0014] S4. Solid-liquid separation of carbon mineralized slurry: Solid-liquid separation is performed on the mixed slurry obtained in S3 to obtain carbon mineralized solid products, which are used for the preparation of subsequent filling materials.

[0015] S5. Preparation of backfill material: The carbon mineralization solid products obtained in S4 are mixed with tailings, water, and cementing materials, and stirred evenly to obtain backfill slurry. The carbon mineralization solid product particles, as a component of the backfill system, synergistically participate in the cementation and formation of the load-bearing structure.

[0016] S6. Filling slurry transportation: The filling slurry obtained in S5 is transported to the underground goaf area through pipelines via the filling station.

[0017] S7. Formation of structural carbon storage units in mines: After the filling slurry described in S6 is injected into the goaf and filling is completed, it is cured and solidified to form a structural carbon storage unit in mines with mechanical bearing capacity and long-term carbon sequestration capability.

[0018] Specifically, in step S1, the particle size of the powder raw material after crushing and grinding is 50-400 mesh. If the powder raw material particles are too coarse, carbon mineralization reaction will not easily occur; if they are too fine, they will easily become muddy, which is not conducive to the subsequent formation of structural carbon storage units in the mine.

[0019] Specifically, in step S1, the solid waste is preferably solid waste with carbon mineralization activity, that is, rich in alkaline or Ca / Mg active phases that can react with CO2, such as calcium oxide / calcium hydroxide, magnesium oxide / magnesium hydroxide, CSH / CASH gel, hydrotalcite-like (LDH) phase, calcium silicate, calcium aluminate, calcium ferroaluminate, calcium sulfoaluminate and calcium fluoroaluminate, as well as magnesium silicate minerals such as olivine and serpentine. The sources may also include cement kiln dust, lime kiln ash, carbide slag, waste concrete sand powder generated during the crushing or screening of waste concrete, steel slag by-products generated during steelmaking, bottom ash or fly ash from waste incineration, and industrial solid red mud and magnesium silicate tailings generated during the extraction of alumina in the aluminum industry.

[0020] When solid waste originates from waste concrete, its mineral composition typically includes various cement hydration products, including but not limited to: hydrated calcium silicate gel, hydrated calcium aluminosilicate gel, hydrated calcium aluminate, hydrated calcium sulfoaluminate, hydrated calcium ferrite, hydrated calcium aluminoferrite, and hydrated calcium fluoroaluminate. Under carbon mineralization conditions, these hydration products can participate in the formation of structural carbon storage units as reactive phases or potential cementing components.

[0021] Specifically, in step S2, the regulator is used to adjust the alkalinity and ionic environment of the system, promote carbonate nucleation and growth, and improve dispersion rheology. It can be selected from one or more of the following types of substances: alkalinity regulators (selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, sodium silicate, potassium silicate), nucleation promoters and crystal form regulators (selected from ammonia, ammonium nitrate, ammonium chloride, calcium chloride, magnesium chloride, magnesium sulfate, aluminum hydroxide, fine calcium carbonate / magnesium carbonate seed crystals), dispersion rheology regulators (selected from sodium chloride, potassium chloride, sodium hexametaphosphate, lignin sulfonate dispersants, polycarboxylate water-reducing agents, polyacrylamide, polyacrylic acid), organic additives (selected from triethanolamine, alkanolamines, organosilicon defoamers), and catalytic / biosynergistic agents (selected from carbonic anhydrase or its biomimetic catalysts). The regulator can be selected and combined according to the properties of the solid waste and the reaction requirements. Its role is not limited to mediating the mineral carbonization process, but also can actively regulate the reaction pathway, reaction kinetics, and product morphology.

[0022] Specifically, in step S2, the molar concentration of the regulator solution is 0.001~1.0 mol / L.

[0023] Specifically, in step S3, the solid waste powder raw material processed in S1 is mixed with the regulator solution obtained in S2 in a set ratio to form a multiphase mixed system with solid waste particles as the main reactant, and then injected into a rapid carbon mineralization device with stirring and aeration functions. In the device, a stable stirring-shearing field is formed by mechanical stirring, shearing or turning, so that the solid waste particles can fully contact the regulator solution without significant dissolution and migration. At the same time, industrial waste gas containing CO2 is introduced. Under the gas-liquid-solid multiphase interface conditions, CO2 and the alkaline active components in the solid waste particles undergo an in-situ carbon mineralization reaction.

[0024] Specifically, in step S3, the carbon mineralization device is a carbon mineralization reactor with stirring function, capable of forming a stable stirring-shear field within the reaction chamber. This reaction chamber can be integrated into a device that applies mechanical shear force, or it can be an external container structure connected to it. Examples of suitable force-applying devices include atmosphere mills with aeration function and stirred tanks. To meet reaction kinetic requirements, the mechanical stirring speed during operation is preferably controlled within the range of 100~2000 rpm.

[0025] Specifically, in step S3, the liquid-to-solid weight ratio is 0.2:1 to 30:1, preferably 1:1 to 10:1. The liquid is a regulator solution, and the solid is solid waste powder raw material. If too much regulator solution is added, it increases the burden on subsequent solid-liquid separation and introduces excessive ions into the structural carbon storage unit of the mine; if too little seawater is added, the solid waste cannot fully undergo carbon mineralization.

[0026] Specifically, in step S3, the carbon mineralization temperature is 20~100 ℃, preferably 20~60 ℃, and the mineralization time is 10~60 min.

[0027] Specifically, in step S3, the carbonizing gas used is various industrial tail gas containing CO2, with the volume percentage of CO2 in the industrial tail gas being ≥5%. Sources may include, but are not limited to, mining, steel industry, cement industry, power industry, chemical industry, non-ferrous metal products industry, glass industry, and ceramics industry, or any combination of the above industries. The carbonizing gas may also be selected from flue gas from coal-fired or gas-fired power plants, tail gas from lime kilns / limestone roasting, and tail gas from oil refining and petrochemical plants (including tail gas from hydrogenation, reforming, cracking, and catalytic cracking regenerators). The industrial exhaust gas can be derived from the following sources: CO2 byproducts of the ammonia / urea conversion-decarbonization unit; CO2-rich tail gas from the natural gas and syngas deacidification section; tail gas from alcohol and other bio-fermentation processes; flue gas from biomass boilers and waste incineration generator sets; tail gas from alkali recovery furnaces and lime kilns in the paper industry; tail gas from non-ferrous metal smelting and roasting processes; and CO2 obtained through carbon capture devices (including direct air capture, DAC). It can also be gas obtained from the gasification of food-grade or industrial-grade liquid CO2, or any combination of the above sources. The gas flow rate is 0.05~2.0 L / min / g solids. This means that for every gram of solid waste, the industrial exhaust gas flow rate is 0.05~2.0 L per minute.

[0028] Specifically, in step S4, the mixed slurry obtained in S3 undergoes solid-liquid separation to adjust the water content of the system and obtain carbon mineralization solid products suitable for engineering applications. The solid-liquid separation is not aimed at separating or extracting reaction products, but rather at removing excess liquid phase while maintaining the overall structure of the solid waste particles and the carbon mineralization modified state, so that the resulting carbon mineralization solid products can be directly used as filling components. Preferably, the water content of the dehydrated mixture is 10-20 wt%.

[0029] Specifically, in step S4, the solid-liquid separation can be achieved by setting up a pre-concentration unit (such as a thickener or hydrocyclone) before entering the dewatering equipment; the dewatering equipment can further include a belt vacuum filter, a drum / disc vacuum filter, a diaphragm filter press, a horizontal screw / tripod / disc centrifuge, etc. Flocculants can be added if necessary to improve separation efficiency. The filtrate obtained from dewatering can be reused in the aforementioned steps (such as S2 and / or S3) to achieve water recycling; to reduce scaling and corrosion, corrosion-resistant and wear-resistant materials are preferred, and backwashing and periodic cleaning measures are implemented.

[0030] Specifically, in step S5, the cementitious materials include, but are not limited to: silicate cement and clinker, aluminate cement and clinker, sulfoaluminate cement and clinker, ferroaluminate cement and clinker, fluoroaluminate cement and clinker, as well as other industrial waste residues or cements that are optionally composed of calcium silicate, calcium aluminate, calcium aluminosilicate or calcium sulfoaluminate as the main minerals, and various cementitious materials composed of waste.

[0031] Specifically, in step S5, the weight ratio of the solid products after carbon mineralization treatment, tailings, and cementitious materials is (10~30):(50~70):(5~20). If the amount of solid products added is too large, the compressive strength of the carbon storage unit will be insufficient, and it will not be able to control the ground pressure in the goaf; if the amount added is too small, the proportion of cementitious materials will increase, and the filling cost will increase. Conventional filling materials include cementitious materials (usually cement) and tailings. If the amount of tailings added is too large, the proportion of cementitious materials will be reduced accordingly, the strength of the filling body will not meet the requirements, and it will not be able to achieve the purpose of engineering support; if the amount of tailings added is too small, it will lead to an increase in filling costs.

[0032] Specifically, in step S5, the solid mass percentage of the filling slurry is 60-80%.

[0033] The technical difficulty of this invention lies in:

[0034] Under the actual constraints of mine backfilling projects, it is necessary to achieve efficient carbon mineralization of solid waste without relying on underground gas injection systems or directly introducing CO2 during the backfilling slurry preparation stage, while simultaneously meeting the comprehensive requirements of the backfill body for early strength, long-term load-bearing stability, and engineering adaptability.

[0035] In existing technologies, one type of method involves injecting CO2 into the goaf or roadway to achieve in-situ carbonization. This method requires a complex underground sealing and piping system, and has high requirements for construction organization and operational safety. Another type of method introduces CO2 into the filling slurry or aqueous system during the slurry preparation or mixing stage, which easily leads to a decrease in the system pH and inhibits the cement hydration reaction, thereby affecting the final strength and stability of the filling body. Both of these methods highly couple the carbon mineralization reaction with the filling system, making it difficult to achieve efficient and stable carbon sequestration while ensuring engineering controllability.

[0036] In addition, some technical approaches employ chemical leaching-remineralization, which dissolves and migrates active components such as calcium and magnesium in solid waste, reacting them with CO2 in a liquid system to generate carbonates or a gelled phase. These methods primarily target ionic species during the reaction, and the mineralization products often exist as independently formed carbonate phases. These need to be prepared and metered separately before being introduced into the system. The original particle structure and framework of the solid waste are weakened or reconstructed, making it difficult to directly apply them to mine backfilling projects while maintaining the solid waste particles as the main filling material and structural framework.

[0037] Therefore, the key technical challenge that this invention needs to address is how to achieve controllable carbon mineralization treatment with solid waste particles as the main reactant without adopting any of the above-mentioned technical approaches, while maintaining the overall structure and engineering properties of solid waste particles, and enabling the mineralized solid products to directly participate in the formation of the filling system, synergistically play a cementing and load-bearing role, and ultimately construct a structural carbon storage unit that has both engineering load-bearing function and long-term carbon sequestration capability.

[0038] Technical Mechanism Explanation:

[0039] From the perspective of reaction mechanism, this invention combines the carbon mineralization process with the formation process of the cementitious phase in the filling system, so that CO2 is stably sealed in the carbon mineralization reaction with solid waste particles as the main reaction body, while generating or activating reaction products that can participate in the cementation reaction, thereby constructing a mine structural carbon storage unit that has both engineering bearing function and long-term carbon sealing capability.

[0040] During rapid carbon mineralization, alkaline active components such as calcium and magnesium contained in solid waste particles react in situ with CO2, causing CO2 to be encapsulated in the solid particles and their surface structure in the form of thermodynamically stable carbonates. Simultaneously, the silicate structure undergoes depolymerization and rearrangement in the carbon mineralization environment, generating a silica gel phase with high pozzolanic activity. This silica gel can further participate in hydration reactions during subsequent filling material preparation and curing, synergistically acting with cement hydration products or other cementitious phases, thereby contributing to the densification of the filling structure and the improvement of its mechanical properties.

[0041] Therefore, this invention essentially provides a construction path for a gelling material that also has carbon dioxide sequestration capabilities. Based on this mechanism, any solid waste that has carbonization reaction potential and can form stable reaction products or active gel phases under carbon mineralization conditions can be used as one of the raw materials in the technical solution of this invention, without being strictly limited by its specific source or mineral composition.

[0042] The beneficial effects of this invention are as follows:

[0043] 1) Simplified downhole support and reduced risk: There is no need to lay complex downhole pipelines and closed gas injection systems, nor is CO2 introduced into the slurry, avoiding the adverse effects of sudden pH drops on the strength of the filling body, making construction and operation safer and more reliable.

[0044] 2) Structural carbon storage: The carbon mineralization reaction is coupled with mine backfilling, so that CO2 is permanently sealed in the microstructure of the backfill in the form of stable carbonate, forming a carbon storage unit with load-bearing function, reducing carbon emissions of the mining system from the source and improving the safety and stability of underground space.

[0045] 3) High-value application of solid waste: It is compatible with multi-source solid waste such as steel slag, waste concrete sand powder, incineration ash, and red mud. The carbon mineralization products and cementitious phase work together to form a dense structure and interface, which significantly improves strength and durability. It also has the advantages of reducing the amount of primary cementitious materials and being easy to integrate with existing filling processes. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a flowchart illustrating the overall process flow of the method of the present invention.

[0048] Figure 2 This is a thermogravimetric analysis diagram of the structural carbon storage unit in Example 1. Detailed Implementation

[0049] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0050] Example 1

[0051] S1: Solid waste pretreatment involves crushing, grinding, and sieving converter steel slag to a particle size of 200 mesh to obtain steel slag powder.

[0052] S2: Regulator Preparation

[0053] Sodium carbonate was dissolved in water to prepare a 0.20 mol / L sodium carbonate solution. The solution was stirred until completely dissolved to obtain the regulator solution.

[0054] S3: Rapid carbon mineralization treatment

[0055] The steel slag powder obtained in S1 was mixed with the regulator solution obtained in S2 at a liquid-to-solid mass ratio of 3:1. The mixture was then injected into a rapid carbonization reactor. CO2-containing flue gas was introduced at 800 rpm for 15 min for carbonization. The CO2 volume percentage in the flue gas was 15%, and the gas flow rate was 0.2 L / min / g solid. Continuous stirring and stable gas supply were maintained during the reaction.

[0056] S4: Solid-liquid separation of carbon mineralization slurry

[0057] After carbonization, the slurry obtained in S3 is dehydrated to obtain a carbon mineralized solid product with a water content of about 15%; the filtrate obtained from the separation is collected for reuse in S2 (water and a small amount of sodium carbonate are added if necessary to maintain solution stability).

[0058] S5: Preparation of filling materials

[0059] The carbon mineralization solid products obtained from S4, tailings, and cement are mixed at a mass ratio of 30:60:10. Water is added to adjust the solid content to about 70%, and the mixture is stirred evenly to form a filling slurry.

[0060] S6: Filler slurry conveying

[0061] The filling slurry obtained from S5 is transported to the underground goaf area through pipelines via the filling station, and the filling operation is completed according to the design zones and layers.

[0062] S7: Formation of structural carbon storage units

[0063] After filling, natural / wet curing is carried out according to site conditions to solidify and form a structural carbon storage unit with load-bearing capacity and long-term carbon sequestration capability. Samples can be taken to conduct CO2 sequestration and mechanical property tests, and the results can be recorded for evaluation.

[0064] Example 2

[0065] S1: Solid waste pretreatment involves drying the red mud to a surface-dry state, crushing and grinding it, and then sieving it to an 80-mesh particle size to obtain red mud powder.

[0066] S2: Regulator Preparation

[0067] A 0.20 mol / L ammonium nitrate solution was prepared using water as a solvent and stirred until completely dissolved to obtain a regulator solution.

[0068] S3: Rapid carbon mineralization treatment

[0069] The red mud powder obtained in S1 was mixed with the regulator solution obtained in S2 at a liquid-to-solid mass ratio of 3:1, and then injected into a rapid carbon mineralization reactor. CO2-containing flue gas was introduced for 10 min at 30 ℃ and 1000 rpm. The CO2 volume percentage in the flue gas was 15%, and the gas flow rate was 0.3 L / min / g solid. Continuous stirring and stable gas supply were maintained during the reaction.

[0070] S4: Solid-liquid separation of carbon mineralization slurry

[0071] After carbonization, the slurry obtained from S3 is filtered and dehydrated to obtain carbon mineralized solid product (the filter cake has an apparent water content of about 15%). The filtrate obtained from the separation is collected and reused in S2 as a solvent and ion source. If necessary, ammonium nitrate is added to maintain the solution concentration at 0.20 mol / L.

[0072] S5: Preparation of filling materials

[0073] The carbon mineralization solid products obtained from S4, tailings, and cement are mixed at a mass ratio of 20:70:10. Water is added to adjust the solid content to about 68%, and the mixture is stirred evenly to form a filling slurry.

[0074] S6: Filler slurry conveying

[0075] The filling slurry obtained from S5 is transported to the underground goaf area through pipelines via the filling station, and filling is completed in zones and layers according to the design.

[0076] S7: Formation of structural carbon storage units

[0077] After filling, natural / wet curing is carried out according to site conditions to solidify and form a structural carbon storage unit with load-bearing capacity and long-term carbon sequestration capability. Samples can be taken to conduct CO2 sequestration and mechanical property tests, and the results can be recorded for evaluation.

[0078] Example 3

[0079] S1: Solid waste pretreatment involves crushing, grinding, and sieving waste concrete blocks to a 200-mesh particle size to obtain concrete powder.

[0080] S2: Regulator Preparation

[0081] A 0.15 mol / L magnesium chloride solution was prepared using water as a solvent and stirred until completely dissolved to obtain a regulator solution.

[0082] S3: Rapid carbon mineralization treatment

[0083] The concrete powder obtained in S1 was mixed with the regulator solution obtained in S2 at a liquid-to-solid mass ratio of 2:1. The mixture was then injected into a rapid carbon mineralization reactor. CO2-containing flue gas was introduced at 1200 rpm for 30 min, with a CO2 volume percentage of 15% and a gas flow rate of 0.25 L / min / g solid. Continuous stirring and stable gas supply were maintained during the reaction.

[0084] S4: Solid-liquid separation of carbon mineralization slurry

[0085] After carbonization, the slurry obtained in S3 is dehydrated to obtain a carbon mineralized solid product with a water content of about 15%; the filtrate obtained from the separation is collected for reuse in S2 (water and a small amount of magnesium chloride are added if necessary to maintain solution stability).

[0086] S5: Preparation of filling materials

[0087] The carbon mineralization solid products obtained from S4, tailings, and cement are mixed in a mass ratio of 15:70:15. Water is added to adjust the solid content to about 72%, and the mixture is stirred evenly to form a filling slurry.

[0088] S6: Filler slurry conveying

[0089] The filling slurry obtained from S5 is transported to the underground goaf area through pipelines via the filling station, and filling is completed in zones and layers according to the design.

[0090] S7: Formation of structural carbon storage units

[0091] After filling, natural / wet curing is carried out according to site conditions to solidify and form a structural carbon storage unit with load-bearing capacity and long-term carbon sequestration capability. Samples can be taken to conduct CO2 sequestration and mechanical property tests, and the results can be recorded for evaluation.

[0092] Example 4

[0093] S1: Solid waste pretreatment

[0094] Converter slag, a product of the steelmaking process, was selected as a solid waste raw material. The slag was naturally aged, then crushed, ground, and sieved to approximately 200 mesh size.

[0095] S2: Regulator Preparation

[0096] A triethanolamine (TEA) aqueous solution with a molar concentration of 0.05 mol / L was prepared using water as a solvent and added to it, which served as the regulator solution.

[0097] Steps S3 to S7 are the same as in Example 1.

[0098] Comparative Example 1

[0099] To verify the role of the regulator in the carbon mineralization co-filling process, while keeping the process route, raw material type, process parameters and operating conditions of Example 1 unchanged, only the regulator solution used in step S2 of Example 1 was replaced with pure water, and the other steps were the same as in Example 1.

[0100] Specifically, in step S2, no regulator is added, and only pure water is used as the liquid medium to mix with the solid waste; the operating conditions, parameter settings and implementation methods of steps S1 and S3 to S7 are the same as those in Example 1.

[0101] Comparative Example 2

[0102] To verify the proportion of carbon mineralization solid products added, while keeping the process route, raw material types, process parameters and operating conditions unchanged except for step S5 in Example 1, only the mass ratio of each component in step S5 was changed.

[0103] Specifically, in step S5, the mass ratio of carbon mineralization solid products, tailings and cement is adjusted to 20:60:20, and the remaining steps are the same as in Example 1.

[0104] Comparative Example 3

[0105] To verify the tailings addition ratio, while keeping the process route, raw material types, process parameters and operating conditions unchanged except for step S5 in Example 1, only the mass ratio of each component in step S5 was changed.

[0106] Specifically, in step S5, the mass ratio of carbon mineralization solid products, tailings and cement is adjusted to 20:70:10, and the remaining steps are the same as in Example 1.

[0107] Comparative Example 4

[0108] To verify the proportion of cementitious material added, while keeping the process route, raw material types, process parameters and operating conditions unchanged except for step S5 in Example 1, only the mass ratio of each component in step S5 was changed.

[0109] Specifically, in step S5, the mass ratio of carbon mineralization solid products, tailings and cement is adjusted to 20:60:20, and the remaining steps are the same as in Example 1.

[0110] It should be noted that "Step S6, Filling Slurry Delivery" and "Step S7, Structural Carbon Storage Unit Formation" are process steps geared towards industrial applications and were not implemented in actual underground goaf environments due to laboratory limitations. In the laboratory research phase, this invention injected the filling slurry obtained in Step S4 into a prefabricated cylindrical mold (50 mm bottom diameter, 100 mm height) and cured it in a standard curing chamber at a temperature of 20℃±2℃ and a relative humidity ≥95%. Equivalent verification was performed on the above steps, thus verifying the feasibility and technical effects of the invention at the laboratory level.

[0111] The structural carbon storage units obtained in the examples and comparative examples were tested for compressive strength and carbon sequestration capacity. The results are shown in Table 1.

[0112] Table 1 Compressive strength and carbon sequestration capacity of structural carbon storage units

[0113]

[0114] As can be seen from Table 1, the structural carbon storage units prepared in each embodiment all achieved the relevant technical requirements for mine backfilling engineering after 28 days of curing, and also showed a significant carbon sequestration capacity. This indicates that the carbon mineralization synergistic backfilling technology can realize the transformation of traditional backfill bodies into structural carbon storage units that have both mechanical bearing capacity and long-term carbon sequestration capacity.

[0115] In contrast, the compressive strength and carbon sequestration of each comparative sample decreased to varying degrees after the removal of the regulator or adjustment of the carbon mineralization solid products, tailings, and cementitious material ratios. However, their compressive strength still met the basic support requirements of mine backfilling projects. These results further demonstrate that the introduction of regulators and the rational matching of component ratios are beneficial for further improving the carbon sequestration capacity and overall performance of the backfill body while meeting engineering support requirements.

[0116] Thermogravimetric analysis was performed on the structural carbon storage unit obtained in Example 1, and the results are as follows: Figure 2 As shown, the sample experienced significant weight loss in the 500-800 °C range, corresponding to the thermal decomposition of calcium carbonate. This indicates the formation of a stable carbonate phase in the filler, thus demonstrating its excellent carbon sequestration effect. Based on the process pathway of this invention, it can be further determined that the aforementioned carbonate phase originates from solid waste raw materials that have undergone carbon mineralization treatment, rather than simply being added as inert filler. During the subsequent preparation and curing of the filler material, the carbon-mineralized solid waste can synergistically interact with cement hydration products and other cementitious phases to participate in the formation of the filler's cementitious structure.

[0117] Therefore, the above thermogravimetric analysis results, from the perspective of material composition and reaction products, show that the solid waste raw materials used in this invention not only exist as physical filling components in the structural carbon storage unit, but also participate in the construction of the load-bearing structure as a component of the cementation system, so that the stable solidification process of CO2 and the mechanical load-bearing function of the filling body are intrinsically coupled, thereby forming a structural carbon storage unit with both engineering support and long-term carbon sequestration capabilities.

[0118] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for constructing structural carbon storage units in mines based on carbon mineralization synergistic filling technology, characterized in that, Includes the following steps: S1. Solid waste pretreatment: Solid waste is crushed and ground to obtain powder raw materials; S2. Prepare the regulator solution: Add the regulator to water and stir thoroughly until completely dissolved to obtain the regulator solution; S3. Rapid carbon mineralization treatment: The powder raw material obtained in S1 is mixed with the regulator solution obtained in S2, injected into the rapid carbon mineralization device and CO2-containing industrial waste gas is introduced to carry out the carbon mineralization reaction and obtain a mixed slurry. S4. Solid-liquid separation of carbon mineralization slurry: Solid-liquid separation is performed on the mixed slurry obtained in S3 to obtain carbon mineralization solid products; S5. Preparation of backfill material: The carbon mineralization solid product obtained in S4 is mixed with tailings, water and cementing material, and stirred evenly to obtain backfill slurry; S6. Filling slurry transportation: The filling slurry obtained in S5 is transported to the underground goaf area through pipelines via the filling station; S7. Formation of structural carbon storage units in mines: After the filling slurry described in S6 is injected into the goaf and filling is completed, it is cured and solidified to form structural carbon storage units in mines.

2. The method for constructing structural carbon storage units in mines based on carbon mineralization synergistic filling technology according to claim 1, characterized in that, In step S1, the solid waste is a solid waste with carbon mineralization activity, which is rich in alkaline or Ca / Mg active phases that can react with CO2.

3. The method for constructing structural carbon storage units in mines based on carbon mineralization synergistic filling technology according to claim 2, characterized in that, In step S1, the solid waste is selected from one or more of the following substances: calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, CSH gel, CASH gel, hydrotalcite-like material, calcium silicate, calcium aluminate, calcium aluminoferrite, calcium sulfoaluminate, calcium fluoroaluminate, magnesium silicate minerals, waste concrete sand powder, steel slag, waste incineration bottom ash or fly ash, red mud, and magnesium-rich silicate tailings.

4. The method for constructing structural carbon storage units in mines based on carbon mineralization synergistic filling technology according to claim 1, characterized in that, In step S2, the regulator is selected from one or more of the following substances: sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, sodium silicate, potassium silicate, ammonia, ammonium nitrate, ammonium chloride, calcium chloride, magnesium chloride, magnesium sulfate, aluminum hydroxide, fine calcium carbonate, magnesium carbonate seed crystals, sodium chloride, potassium chloride, sodium hexametaphosphate, lignin sulfonate dispersant, polycarboxylate water-reducing agent, polyacrylamide, polyacrylic acid, triethanolamine, alkanolamines, organosilicon defoamers, carbonic anhydrase or its biomimetic catalyst.

5. The method for constructing structural carbon storage units in mines based on carbon mineralization synergistic filling technology according to claim 1, characterized in that, In step S2, the molar concentration of the regulator solution is 0.001~1.0 mol / L.

6. The method for constructing structural carbon storage units in mines based on carbon mineralization synergistic filling technology according to claim 1, characterized in that, In step S3, the liquid-to-solid weight ratio is 0.2:1 to 30:1, preferably 1:1 to 10:

1.

7. The method for constructing structural carbon storage units in mines based on carbon mineralization synergistic filling technology according to claim 1, characterized in that, In step S3, the carbon mineralization temperature is 20~100 ℃, preferably 20~60 ℃, and the mineralization time is 10~60 min.

8. The method for constructing structural carbon storage units in mines based on carbon mineralization synergistic filling technology according to claim 1, characterized in that, In step S3, the carbonizing gas used is industrial tail gas containing CO2, and the volume percentage of CO2 in the industrial tail gas is ≥5%; And / or, the ventilation rate of industrial exhaust gas is 0.05~2.0 L / min / g solids.

9. The method for constructing structural carbon storage units in mines based on carbon mineralization synergistic filling technology according to claim 1, characterized in that, In step S5, the cementitious material is selected from one or more of the following substances: silicate cement and clinker, aluminate cement and clinker, sulfoaluminate cement and clinker, ferroaluminate cement and clinker, fluoroaluminate cement and clinker, and other industrial waste residues or cements that are optionally composed of calcium silicate, calcium aluminate, calcium aluminosilicate or calcium sulfoaluminate as the main minerals, as well as various cementitious materials composed of waste.

10. The method for constructing structural carbon storage units in mines based on carbon mineralization synergistic filling technology according to claim 1, characterized in that, In step S5, the weight ratio of the solid product after carbon mineralization treatment, tailings, and cementitious material is (10~30):(50~70):(5~20).

Images