Mine goaf filling cementing material based on multi-source coal-based solid waste and preparation method thereof

Abstract

The application discloses a kind of based on multi-source coal-based solid waste mine goaf filling cementing material and preparation method, belong to mine filling material technical field.The present application at least two of coal gangue, fly ash, desulfurization gypsum, coal slime, gasification slag, furnace bottom slag are raw material, after grinding, screening pretreatment and mixed with water glass to make cementing material slurry, CO2 is introduced into the inside of slurry under continuous stirring to carry out in-situ carbon sequestration mineralization reaction, then is transported to mine goaf solidification forming, and the filling cementing material is prepared.The present application breaks through the limitation of single coal-based solid waste resource utilization, solves the technical problems that existing CO2 mineralization is difficult to be in-situ coupled with mobile cementing slurry, cannot realize large solid waste disposal, goaf safe filling and CO2 storage efficient cooperation.The obtained material has low cost, good stability, can realize CO2 permanent storage, is suitable for coal mine goaf treatment, and has multiple benefits of solid waste resource disposal, carbon sequestration and carbon reduction, mine safety management.

Description

Technical Field

[0001] This invention belongs to the field of mine backfilling materials technology, specifically relating to a cementitious material for backfilling goaf areas in mines based on multi-source coal-based solid waste and its preparation method. Background Technology

[0002] Ordos, as one of the country's important energy bases, generates a large amount of coal-based solid waste during coal mining and utilization, including coal gangue, fly ash, desulfurization gypsum, coal slime, and gasification slag. The historical stockpile of this type of solid waste is enormous. Long-term accumulation not only occupies land, but the heavy metal ions it contains can easily seep into the ground under rainwater erosion, causing serious ecological damage and threatening the ecological security barrier of the middle and lower reaches of the Yellow River and northern China. After coal mining, unfilled goaf areas are formed underground, which can easily trigger geological disasters such as roof collapse and surface subsidence, resulting in waste of land resources and threatening life and property safety. Currently, the most effective way to manage goaf areas is to prepare a cementitious slurry, which is then transported or pumped into the goaf area. After the slurry solidifies, it forms a filling body with a certain strength to ensure the safety and stability of the mine goaf area.

[0003] The coal industry is both an energy producer and a major source of carbon emissions. The large-scale stockpiling of coal-based solid waste, the significant pressure of managing goaf areas, and substantial CO2 emissions have become key bottlenecks restricting the green and sustainable development of the coal industry. In 2022, global energy-related CO2 emissions reached 36.8 billion tons, of which coal-related CO2 emissions accounted for 17.7 billion tons. In my country's energy consumption structure, coal accounts for a high proportion, and coal development and utilization contribute approximately 80% of the country's total carbon emissions. Reducing carbon emissions from coal development is a pressing technological direction for the industry.

[0004] Coal-based solid waste refers to byproducts generated during coal mining, processing, and combustion. It mainly includes high-quality coal-based solid waste such as fly ash and desulfurization gypsum, as well as low-quality coal-based solid waste such as coal gangue, bottom ash, gasification slag, and coal slime. As of 2024, the cumulative accumulated amount of coal-based solid waste in my country exceeded tens of billions of tons, and continues to grow at a rate of 1.8 billion tons per year.

[0005] Existing research indicates that the compressive strength of backfill materials prepared from multi-source coal-based solid waste is influenced by various factors. The effects of slurry concentration, gasification slag content, and desulfurization gypsum content on strength gradually increase with increasing curing age, while the effects of fly ash content and bottom ash content on strength show a trend of first increasing and then decreasing with increasing curing age. Related technologies clarify the feasibility of using coal-based solid waste for backfilling mining from five dimensions: economic, technical, environmental, policy, and spatial. A co-treatment technology for coal-based solid waste and high-salt wastewater ("solid-liquid") is proposed, using high-salt wastewater instead of ordinary water and additives such as early-strength agents, and solid waste cementitious materials instead of cement materials. The coal-based solid waste and high-salt wastewater are mixed to form a backfill paste, which is then pumped into the underground space of the coal mine for backfilling disposal.

[0006] Carbon sequestration is the process by which CO2 reacts with alkaline or neutral metal components to form mineral carbonates. Compared with other carbon sequestration methods, it has significant advantages, and the carbonate products generated by mineralization are stable, enabling permanent CO2 sequestration. Existing research shows that under mineralization reaction times of 1–2 hours, the carbon sequestration rate of cement paste typically fluctuates between 5% and 15%, mainly affected by the water-to-solid ratio, temperature, and pressure.

[0007] Related studies investigated the CO2 mineralization and carbon sequestration performance, as well as compressive and flexural mechanical properties, of different Portland cement concretes under ambient temperature, 0.5 MPa, and 2 hours of mineralization. The carbon sequestration rate, based on cement mass, was approximately 9%–16%, and the compressive strength after 2 hours of mineralization exceeded the strength after 7 days of hydration. Microstructural studies showed that calcium hydroxide and calcium silicate preferentially participated in the reaction during mineralization, while the CSH component reacted relatively slowly. Studies on fly ash mineralization showed that increasing the mineralization reaction pressure and temperature effectively improved the CO2 absorption characteristics and carbon sequestration performance of fly ash.

[0008] Although existing technologies have conducted extensive research on the resource utilization and CO2 mineralization of coal-based solid waste, there are still significant shortcomings: First, existing coal-based solid waste utilization mainly focuses on single solid waste or conventional cementitious systems, lacking multi-source coal-based solid waste synergistic utilization schemes; second, traditional CO2 mineralization is mostly targeted at cement-based materials or solid materials, failing to achieve in-situ synchronous carbon sequestration and mineralization under cementitious slurry systems; and third, it is difficult to efficiently couple the disposal of bulk solid waste, safe backfilling of goaf areas, and CO2 sequestration, failing to meet the actual needs of green mining and low-carbon development in mines. Summary of the Invention

[0009] In view of this, the purpose of this invention is to provide a cementitious material for filling goaf areas in mines based on multi-source coal-based solid waste and its preparation method, so as to solve the technical problems in the prior art, such as insufficient utilization of coal-based solid waste resources, difficulty in in-situ coupling of CO2 mineralization with cementitious slurry, inability to achieve large-scale solid waste disposal, and efficient synergy between safe filling of goaf areas and CO2 sequestration, so as to meet the actual needs of green mining and low-carbon development in mines.

[0010] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0011] This invention discloses a method for preparing a cementitious material for filling goaf areas in mines based on multi-source coal-based solid waste, comprising the following steps: S1, selecting multi-source coal-based solid waste and pretreating it; S2, mixing and stirring the pretreated multi-source coal-based solid waste with an alkali activator to prepare a cementitious material slurry; S3, during the continuous stirring of the cementitious material slurry, introducing CO2 gas into the slurry to allow CO2 to fully contact the slurry and undergo a carbonization reaction, thereby obtaining a carbonization mineralization cementitious material; S4, transporting the carbonization mineralization cementitious material to the goaf area in the mine for solidification and molding to obtain a goaf filling cementitious material.

[0012] This invention adopts an integrated process of pretreatment, alkali-activated slurry preparation, in-situ simultaneous carbon fixation and mineralization, and goaf solidification and molding. The process is simple and coherent, which can realize the large-scale disposal and resource utilization of multi-source coal-based solid waste, as well as the in-situ carbon fixation and mineralization under the gelling slurry system. It organically combines solid waste disposal, goaf treatment and CO2 sequestration, effectively making up for the shortcomings of existing technologies that are difficult to efficiently coordinate and couple.

[0013] Furthermore, in step S1, the multi-source coal-based solid waste includes at least two of the following: coal gangue, fly ash, desulfurization gypsum, coal slime, gasification slag, and bottom ash.

[0014] By using at least two types of coal-based solid waste in combination, the complementary and synergistic cementing advantages of different solid waste components can be fully utilized, overcoming the limitations of existing single solid waste utilization models and the low resource utilization efficiency. This expands the types and scale of solid waste disposal in mining areas, improves the overall utilization rate of solid waste, and alleviates the land occupation and ecological environmental pollution problems caused by long-term solid waste storage.

[0015] Furthermore, in step S1, the pretreatment includes grinding and screening the multi-source coal-based solid waste in sequence.

[0016] By grinding and sieving to control and homogenize the particle size of solid waste, the activity and dispersion uniformity of material particles can be optimized, the reaction between solid waste and alkali activator can be fully promoted, the stability of cementitious slurry can be improved, and the carbon mineralization reaction can be carried out uniformly and fully, providing a good material basis for the stable solidification and molding of filling bodies.

[0017] Furthermore, in step S2, the alkaline activator is water glass.

[0018] Water glass can effectively activate the potential cementitious activity of multi-source coal-based solid waste, without the need to add large amounts of traditional auxiliary materials such as cement and early strength agents, simplifying the preparation system, reducing material costs, and adapting to the application needs of large-scale mine backfilling projects.

[0019] Furthermore, in step S3, the carbon fixation and mineralization reaction is carried out in a carbon fixation and mineralization reaction device, which can continuously stir the cementitious slurry while introducing CO2 gas.

[0020] The use of a dedicated reaction device that can simultaneously stir and ventilate ensures that CO2 and fluid cementitious slurry are in full and uniform contact, enabling simultaneous in-situ pulping and carbon sequestration. This overcomes the shortcomings of insufficient and uneven mineralization of traditional solid and cement-based materials, significantly improving mineralization efficiency and carbon sequestration stability.

[0021] The present invention also discloses a cementitious material for filling goaf in mines based on multi-source coal-based solid waste, which is prepared by the preparation method disclosed in the present invention.

[0022] The filling cementitious material prepared by the above process has both stable curing support performance and reliable carbon fixation capacity. It can not only meet the filling and reinforcement needs of goaf areas, effectively prevent geological disasters such as roof collapse and surface subsidence, and ensure mine safety, but also realize the resource utilization of large-scale coal-based solid waste, which is in line with the concept of green mine construction and low-carbon development.

[0023] Furthermore, the filling cementitious material sequesters CO2 through a carbon fixation and mineralization reaction.

[0024] This filling cementitious material can stably generate and seal carbonate products through mineralization reactions, achieving permanent CO2 storage, effectively reducing carbon emissions in the coal development process, and helping the coal industry achieve green and low-carbon transformation.

[0025] Existing CO2 mineralization technologies are mostly applied to cement-based materials or solid powders, making them difficult to directly apply to fluid cementitious slurry systems. It is generally believed in the art that introducing CO2 during the cementitious slurry stage easily leads to premature carbonization, inhibited hydration, and deterioration of mechanical properties. This understanding of the technology has also limited the technical motivation to apply CO2 mineralization to cementitious slurry systems. This invention overcomes these limitations by introducing CO2 in situ into the cementitious slurry under continuous stirring to achieve controllable carbon fixation and mineralization. This avoids premature localized carbonization interference and improves problems such as uneven reaction and insufficient system stability, resulting in superior mineralization effects and material properties. It solves the technical challenge of simultaneously implementing carbon fixation and mineralization in cementitious slurry systems.

[0026] The advantages of this invention compared to the prior art are as follows:

[0027] (1) This invention pre-treats multi-source coal-based solid waste and then uses an alkaline activator to make slurry, realizing the synergistic resource utilization of multiple types of coal-based solid waste. It breaks through the limitations of the single solid waste utilization mode of the existing technology and can dispose of large quantities of coal-based solid waste such as coal gangue, fly ash, and gasification slag on a large scale, effectively alleviating the land occupation and ecological pollution problems caused by solid waste stockpiling.

[0028] (2) In this invention, CO2 is introduced simultaneously during the continuous stirring of the cementitious slurry to carry out in-situ carbon fixation and mineralization. This is different from the traditional mineralization method for cement-based or solid materials. It realizes the integrated operation of slurry preparation, stirring and carbon fixation and mineralization, with sufficient gas-liquid contact and good mineralization uniformity. It greatly improves the stability of CO2 storage and realizes permanent CO2 storage, which meets the technical needs of carbon reduction and green development in the coal industry.

[0029] (3) This invention highly couples solid waste resource utilization, goaf treatment and CO2 mineralization and storage. The process is simple and coherent, and does not rely on high-salt wastewater and a large amount of cement, early strength agent and other auxiliary materials. The preparation cost is low. The cementitious material can be stably solidified and formed in the goaf, effectively preventing geological disasters and ensuring mine safety. It realizes the synergistic unity of solid waste disposal, goaf treatment and carbon sequestration, and meets the actual needs of green mining and low-carbon development.

[0030] The following detailed description of the present invention, in conjunction with the embodiments shown in the accompanying drawings, discloses the cementitious material for filling goaf areas in mines based on multi-source coal-based solid waste and its preparation method. Attached Figure Description

[0031] Figure 1 This is a flowchart of the steps in the preparation method of the filling cementitious material for mine goaf based on multi-source coal-based solid waste of the present invention;

[0032] Figure 2 The figures show the dynamic strain-vibration time history curves of the filling cementitious material under different confining pressures, where Figures a, b, and c are the dynamic strain-vibration time history curves under confining pressures of 10 kPa, 20 kPa, and 30 kPa, respectively; the different shades in each figure correspond to loading conditions with dynamic stress ratios of 15%, 20%, and 30%, respectively.

[0033] Figure 3 A bar chart showing the pore size distribution of the filling cementitious material of the present invention under the first set of modulus conditions;

[0034] Figure 4 A bar chart showing the pore size distribution of the filling cementitious material of the present invention under the second set of modulus conditions;

[0035] Figure 5 A bar chart showing the pore size distribution of the filling cementitious material of the present invention under the third group of modulus conditions;

[0036] Figure 6 This is a bar chart showing the pore size distribution of the filling cementitious material of the present invention under the fourth group of modulus conditions. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with embodiments of this invention. Obviously, the described embodiments are one embodiment of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0038] Addressing the issues of large stockpiles of multi-source coal-based solid waste, significant land occupation, and ecological pollution risks in the Ordos mining area, underground goafs formed by coal mining are prone to geological disasters such as roof collapse and surface subsidence, adversely affecting mine safety and regional ecological protection. Furthermore, existing technologies suffer from low levels of synergistic utilization of multi-source coal-based solid waste and a lack of in-situ synchronous carbon sequestration technology for cementitious slurries, making it difficult to achieve efficient coupling of solid waste disposal, goaf safety management, and carbon dioxide sequestration. Therefore, this invention provides a method for preparing a mine goaf filling cementitious material based on multi-source coal-based solid waste. By optimizing the proportions of multi-source coal-based solid waste raw materials and controlling the carbon dioxide sequestration process parameters, a high-performance, cost-effective mine filling cementitious material with carbon sequestration and emission reduction functions is prepared. This invention verifies and optimizes the entire technical solution through systematic raw material characterization, proportion optimization, mineralization mechanism analysis, macroscopic mechanical testing, and microscopic structure testing, achieving a synergistic unity of mine solid waste resource utilization, goaf safety management, and permanent carbon dioxide sequestration.

[0039] In the implementation of this invention, sample preparation and performance testing are completed using supporting material preparation equipment, mechanical property testing equipment, microstructure characterization equipment, and environmental simulation equipment. The material preparation equipment is used for coal-based solid waste pretreatment and cementitious slurry mixing; the mechanical property testing equipment includes a servo universal testing machine and a dynamic triaxial apparatus; the microstructure characterization equipment includes a nuclear magnetic resonance spectrometer, a CT scanner, a scanning electron microscope, and an X-ray diffractometer; and the environmental simulation equipment uses a freeze-thaw cycler for performance testing under environmental conditions. This complete set of equipment supports the implementation of research work such as raw material characterization, proportioning and screening, carbon sequestration and mineralization, mechanical property testing, and microstructure analysis, ensuring the repeatability of the technical solution and the reliability of the experimental data.

[0040] like Figure 1As shown, the present invention provides a method for preparing a cementitious material for filling goaf areas in mines based on multi-source coal-based solid waste, which mainly includes the following steps: S1, selecting multi-source coal-based solid waste and pretreating it; S2, mixing and stirring the pretreated multi-source coal-based solid waste with an alkali activator to prepare a uniform and stable cementitious material slurry; S3, simultaneously introducing CO2 gas during the continuous stirring of the cementitious material slurry to allow CO2 to fully contact the fluid slurry and undergo an in-situ carbon fixation and mineralization reaction, thereby preparing a carbon fixation and mineralization cementitious material; S4, transporting the prepared carbon fixation and mineralization cementitious material to the goaf area of ​​the mine for solidification and molding, ultimately forming a stable cementitious material for filling goaf areas in mines.

[0041] This invention adopts an integrated preparation process that includes pretreatment, alkali-activated slurry preparation, in-situ simultaneous carbon fixation and mineralization, and solidification and molding of goaf areas. The process flow is simple and coherent, and can simultaneously realize the large-scale disposal of multi-source coal-based solid waste, safe filling and treatment of goaf areas, and carbon dioxide resource storage, effectively making up for the shortcomings of existing technologies in achieving efficient coupling of the three.

[0042] In the implementation of this invention, the multi-source coal-based solid waste selected in step S1 includes at least two of the following: coal gangue, fly ash, desulfurization gypsum, coal slime, gasification slag, and bottom ash. By using a combination of various types of coal-based solid waste, the component differences and activity advantages of different solid wastes can be fully utilized to form a complementary and synergistic cementing system. This improves the problems of low utilization rate, limited cementing performance, and limited resource utilization scale of traditional single solid wastes, broadens the types and volume of solid waste disposal in mining areas, and alleviates the problems of land occupation, rainwater leaching pollution, and regional ecological damage caused by long-term stockpiling of coal-based solid wastes from the source.

[0043] The pretreatment process in step S1 mainly includes grinding and screening the raw coal-based solid waste sequentially. Mechanical grinding and particle size screening achieve homogenization and control of the solid waste particles, optimizing their activity and dispersion uniformity, promoting the full reaction between the active components and the alkali activator, improving the overall uniformity and stability of the cementitious slurry, ensuring the uniform and sufficient subsequent carbon sequestration reaction, and providing a reliable material basis for the overall solidification and stable operation of the filling body.

[0044] In the implementation of this invention, the alkali activator used in step S2 is water glass. Water glass can effectively activate the potential cementitious activity of multi-source coal-based solid waste, without the need for large amounts of traditional auxiliary materials such as cement and early-strength agents, simplifying the preparation system of cementitious materials, reducing the overall cost of backfill materials, and meeting the actual application needs of large-scale, large-volume goaf backfilling projects in the Ordos mining area.

[0045] In the implementation of this invention, the carbon sequestration reaction in step S3 is completed entirely within a dedicated carbon sequestration reaction device. This device enables integrated operation of continuous stirring of the cementitious material slurry and simultaneous introduction of CO2 gas. Traditional solid waste mineralization technologies often rely on reactors to mineralize solid waste separately, depending solely on crushing and screening to increase the solid-gas contact area, resulting in low mineralization efficiency and uneven reaction. This invention directly introduces CO2 gas into a dynamically stirred liquid slurry system, allowing CO2 to achieve full and uniform contact and reaction with the slurry.

[0046] The synchronous stirring and gas injection mineralization method adopted in this invention has certain innovative advantages: On the one hand, the introduced CO2 can react with the pore water inside the slurry to generate carbonic acid, reduce the pH value of the slurry system, accelerate the precipitation of calcium ions inside the system through the acidification environment, shorten the setting and hardening time of the cementitious material, and promote the steady development of the early strength of the filling material; on the other hand, the rapid setting and hardening of the slurry can reduce the segregation and stratification of the filling slurry during the filling process in the goaf, ensure the uniformity of the filling material composition, facilitate the rapid roof connection and dense filling of the goaf, and improve the mineralization reaction effect and the overall filling and treatment quality of the goaf.

[0047] To clarify the influence of raw material ratios and process parameters on material properties, this invention conducted systematic raw material characterization and ratio optimization experiments. Using SEM and XRD testing methods, this invention systematically analyzed the physicochemical and active component characteristics of various coal-based solid wastes, including coal gangue, fly ash, gasification slag, and desulfurization gypsum, clarifying the cementitious activity basis of different solid wastes. Based on this, pretreated various coal-based solid wastes were compounded with water glass in different proportions. Through orthogonal experiments on unconfined compressive strength, the optimal raw material ratio suitable for mine backfilling conditions was selected.

[0048] This invention relies on a dedicated carbon sequestration and mineralization reaction device to regulate key process parameters such as CO2 concentration, reaction pressure, curing temperature, and mineralization reaction time. It systematically explores the influence of each parameter on the rheology, setting time, mineralization reaction efficiency, reaction rate, and mineralization product type of the cementitious slurry, sorts out the complete carbon sequestration and mineralization reaction evolution path, and clarifies the intrinsic reaction mechanism of CO2 participating in the carbon sequestration and mineralization of multi-source coal-based solid waste cementing system.

[0049] This invention clarifies the correlation between carbon sequestration processes and material properties through multi-dimensional performance testing. Unconfined compressive strength tests and nuclear magnetic resonance microscopic tests are conducted on filling cementitious materials prepared under different carbon sequestration process conditions to systematically characterize the macroscopic mechanical strength and internal pore structure characteristics of the materials. The influence of different mineralization parameters on the comprehensive service performance of the filling materials is explored, and optimal carbon sequestration process conditions suitable for mining area engineering applications are obtained. An intrinsic correlation model is established between the composition of multi-source coal-based solid waste raw materials, carbon sequestration processes, microstructure, and macroscopic mechanical properties, enabling reasonable control of material properties.

[0050] like Figure 2 The figure shows the dynamic strain-vibration time history curves of the filling cementitious material of this invention under different confining pressure conditions. This invention simulates complex stress conditions in mining goaf areas with different burial depths and mining disturbance intensities through dynamic triaxial cyclic loading tests. Three sets of confining pressure conditions were set: TS1 (10 kPa), TS2 (20 kPa), and TS3 (30 kPa), and cyclic dynamic loads with gradient dynamic stress ratios of 15%, 20%, and 30% were applied to obtain the variation law of dynamic strain of the material with the number of loading vibrations. The test results show that under cyclic disturbances with different confining pressure levels and different dynamic load amplitudes, the dynamic strain of the filling cementitious material of this invention increases gradually, and the cumulative plastic deformation remains at a low level. The material exhibits good dynamic stability and resistance to mining disturbance, can adapt to the complex stress environment of the goaf, ensures the overall structural stability of the filling body, and reduces the risk of geological disasters such as deformation, collapse, and surface subsidence of the surrounding rock in the goaf.

[0051] like Figures 3 to 6 The figure shows a bar chart of the pore size distribution of the filling cementitious material of the present invention under different modulus conditions. The horizontal axis of each bar chart represents the pore type, specifically including gel pores, capillary pores, and harmful pores, while the vertical axis represents the percentage of the corresponding pore type. The present invention characterizes the microstructure of the filling material under different modulus conditions using nuclear magnetic resonance (NMR) testing. The test results show that the filling cementitious materials prepared under all experimental conditions have gel pores as the main pore structure, with relatively low proportions of capillary pores and harmful pores. By precisely controlling the modulus parameters, the pore distribution characteristics of the material can be optimized in a targeted manner, increasing the proportion of harmless gel pores and reducing the content of harmful pores. This microstructure characteristic can improve the overall compactness and impermeability of the filling cementitious material, reduce internal erosion channels for moisture and harmful media, and ensure the mechanical stability and long-term service performance of the filling material in complex mining environments.

[0052] The filling cementitious material prepared by this invention can stably generate carbonate products through carbon sequestration and mineralization reactions, achieving permanent CO2 sequestration and reducing carbon emissions throughout the coal mining process. Compared with traditional coal-based solid waste filling materials, this invention innovatively constructs an integrated technical system of multi-source solid waste synergistic cementation and in-situ synchronous carbon sequestration and mineralization of slurry, improving the technical limitations of traditional solid mineralization and single solid waste utilization. Simultaneously, this invention specifically designs a carbon sequestration and mineralization reaction device adapted to liquid slurry systems, enabling simultaneous slurry preparation and mixing with carbon sequestration and mineralization, improving mineralization reaction efficiency and carbon sequestration stability.

[0053] In summary, this invention is suitable for the current industrial status and ecological governance needs of the Ordos large-scale coal base. It can absorb existing and newly added coal-based solid waste in the mining area on a large scale, alleviating the ecological pollution problems caused by solid waste accumulation. It can improve the safety and stability of the goaf through high-quality backfilling and support, ensuring safe production in the mine. It can realize the permanent storage of carbon dioxide resources through in-situ mineralization reaction, helping the coal mining industry to achieve green and low-carbon transformation. It can meet the actual needs of ecological governance and low-carbon technology development in the coal industry, and has good engineering practicality and prospects for promotion and application.

[0054] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0055] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment includes only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a cementitious material for filling goaf areas in mines based on multi-source coal-based solid waste, characterized in that, Includes the following steps: S1, Select multi-source coal-based solid waste and pre-treat the multi-source coal-based solid waste; S2, mix the pretreated multi-source coal-based solid waste with an alkaline activator to make a cementitious slurry; S3, During the continuous stirring of the cementitious material slurry, CO2 gas is introduced into the slurry so that CO2 can fully contact the slurry and undergo a carbon fixation and mineralization reaction to obtain a carbon fixation and mineralization cementitious material. S4, the carbon-fixing mineralized cementitious material is transported to the goaf area of ​​the mine for solidification and molding to obtain the goaf filling cementitious material.

2. The preparation method according to claim 1, characterized in that, In step S1, the multi-source coal-based solid waste includes at least two of the following: coal gangue, fly ash, desulfurization gypsum, coal slime, gasification slag, and bottom ash.

3. The preparation method according to claim 1, characterized in that, In step S1, the pretreatment includes grinding and screening the multi-source coal-based solid waste in sequence.

4. The preparation method according to claim 1, characterized in that, In step S2, the alkaline activator is water glass.

5. The preparation method according to claim 1, characterized in that, In step S3, the carbon fixation and mineralization reaction is carried out in a carbon fixation and mineralization reaction device, which can continuously stir the cementitious material slurry while introducing CO2 gas.

6. A cementitious material for filling goaf areas in mines based on multi-source coal-based solid waste, characterized in that, It is prepared by any one of claims 1 to 5.

7. The mine goaf filling cementitious material based on multi-source coal-based solid waste according to claim 6, characterized in that, The filling cementitious material seals in CO2 through a carbon fixation mineralization reaction.

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