Solid waste filling method based on MICP technology and carbon dioxide mineralization cooperation

Abstract

The application discloses a solid waste filling method based on MICP technology and carbon dioxide mineralization cooperation, and the gangue aggregate is treated by microbial infiltration; CO2 is introduced into the alkaline solid waste for carbonation treatment, thereby reducing the alkalinity of the alkaline solid waste and absorbing and solidifying CO2; the aggregate modified by the microorganism is fully mixed with the mineralized solid waste slurry according to a reasonable ratio to form a filling slurry with stable performance. After the slurry is injected into a goaf, calcium carbonate is induced to form calcium carbonate crystals by using the MICP technology, thereby effectively filling the internal pores of the material and enhancing the compactness and certain mechanical properties of the grouting body. The method can simultaneously and efficiently solve the treatment problems of solid wastes such as coal gangue and fly ash, realize large-scale storage of CO2, provide the goaf with a filling body with excellent mechanical properties, enhance the surface corrosion resistance and improve the bonding performance with surrounding rocks.

Description

Technical Field

[0001] This invention belongs to the field of underground backfilling and solid waste resource utilization technology, and relates to a solid waste backfilling method based on MICP technology and carbon dioxide mineralization synergy. Background Technology

[0002] During coal mining, large-scale goaf areas formed underground are prone to inducing surface subsidence, rock strata movement, and even geological disasters, seriously threatening the ecological environment and safe production of mining areas. At the same time, the large amounts of solid waste generated during coal mining and utilization also face significant treatment pressure. Using alkaline solid wastes such as coal gangue and fly ash to mineralize and seal carbon dioxide in goaf areas can simultaneously achieve synergistic underground treatment of alkaline solid waste and carbon sequestration. However, the interfacial bonding between gangue backfill and fly ash is poor, easily leading to peeling and internal damage, affecting the long-term stability of the backfill, and the carbon dioxide sequestration efficiency is relatively low. Microbial induced calcium carbonate precipitation (MICP) technology is an emerging green technology that utilizes microbial metabolites to combine calcium ions and carbonate ions to form calcium carbonate precipitate. This technology has been explored for applications in soil reinforcement, seepage prevention, and dust control. Combining MIP technology with traditional gangue-fly ash backfilling systems, leveraging microbial mineralization to enhance interparticle bonding, improve overall material performance, and increase CO2 fixation efficiency will generate significant technical, economic, and ecological value. Summary of the Invention

[0003] The purpose of this invention is to provide a solid waste backfilling method based on MIP technology and carbon dioxide mineralization synergy. This method can simultaneously and efficiently solve the treatment problems of solid wastes such as coal gangue and fly ash, realize large-scale CO2 sequestration, and provide backfill materials with excellent mechanical properties for goaf areas, enhancing surface corrosion resistance and improving adhesion to surrounding rock.

[0004] The technical solution adopted in this invention is a solid waste backfilling method based on MIP technology and carbon dioxide mineralization synergy. The specific operation steps are as follows: Step 1: Prepare microbial mineralization solution, mix and impregnate crushed gangue with microbial mineralization solution, cultivate and promote microbial growth, and then prepare microbial mineralized aggregate; Step 2: Prepare CO2 mineralized solid waste slurry; prepare a uniform slurry by mixing alkaline coal-based solid waste such as fly ash and gasification slag with water in a stirring reaction system, and then introduce CO2 gas to react and obtain CO2 mineralized solid waste slurry.

[0005] Step 3: Mix the microbial mineralized aggregate prepared in Step 1 and the CO2 mineralized solid waste slurry prepared in Step 2 in a certain proportion to prepare microbial modified filling slurry. Step 4: Microbial modified filling slurry is injected into the goaf using a slurry filling method to achieve synergistic filling and treatment of coal-based solid waste and CO2. At the same time, microbial mineralization induces calcium carbonate precipitation to fill pores, improves grouting strength, and seals CO2.

[0006] The invention is further characterized in that, Step 1 is as follows: Step 1.1: Prepare microbial culture solution and mineralization induction solution; Step 1.1.1, Preparation of microbial inoculum: Bacillus pasteurellii was selected as the strain to provide nucleation sites on the surface of gangue aggregate. The microbial inoculum was obtained by activation and dilution, and the OD600 value was controlled above 1.0.

[0007] Step 1.1.2: Preparation of mineralization induction solution: The solution contains urea at a concentration of 0.5-1 mol / L and calcium chloride at a concentration of 0.5-1.0 mol / L, with a molar ratio of urea to calcium source of 1.1-1.2:1. A 1.0 mol / L mineralization induction solution is prepared using deionized water and filtered through a 0.22 μm filter membrane for sterilization. Step 1.2: Crushing of gangue aggregate: First, coarse crushing is performed using a primary crusher to break the gangue to a particle size of less than 30 mm; then, fine crushing is performed using a secondary crusher to obtain gangue aggregate with a particle size of less than 3 mm. Step 1.3: Mix and impregnate the gangue aggregate with microbial inoculum and mineralization induction liquid at a mass ratio of 1:0.5-1:1 for 1-4 hours. After impregnation, filter the supernatant to obtain microbial mineralized gangue aggregate.

[0008] Step 2 is as follows: Step 2.1: Prepare alkaline solid waste slurry: The alkaline solid waste should be a mixture of fly ash and gasification slag with high calcium oxide and magnesium oxide content. Steel slag can be used as an additive to further increase the calcium oxide content. The mass ratio of fly ash to gasification slag is 7~8:2~3. The alkaline solid waste and water are mixed in a stirred reactor at a solid-liquid mass ratio of 1:2~3. The stirring speed is 300-500 rpm, and the stirring time is 2 minutes, until a uniform slurry is formed with no visible particles. Step 2.2, CO2 mineralization treatment: After the slurry in step 2.1 is stirred evenly, CO2-containing gas (the source of CO2 gas is industrial flue gas from a coal-fired power plant) is introduced into the slurry; when introducing CO2 gas, the stirring speed is maintained at 300-500 rpm, the mineralization reaction temperature is room temperature, and the inlet pressure is 0.2-0.5 MPa; the mineralization reaction time is set to 1-2 hours or the pH of the slurry decreases from the initial value to 7.

[0009] Step 3 is as follows: After the CO2 mineralized solid waste slurry prepared in step 2 is allowed to stand for 1 hour, part of the supernatant is filtered off; the microbial mineralized aggregate and the CO2 mineralized solid waste slurry are mixed at a mass ratio of 1:1~3. Step 4 is as follows: The microbial modified filling slurry is pumped by an integrated mixing and pumping machine and transported to the goaf through pipelines. The slurry flow rate is controlled at 1-2 m / s for the co-filling treatment of CO2 and coal-based solid waste. The filling body utilizes the microbial mineralization effect to continuously consume and absorb CO2 from the CO2 mineralized solid waste slurry and the external CO2, forming calcium carbonate precipitate to fill the pores of gangue.

[0010] The beneficial effects of this invention are: This invention provides a solid waste backfilling method based on synergistic microbial infiltration (MICP) technology and carbon dioxide mineralization. Microbial infiltration of gangue aggregate improves its surface cohesiveness. Simultaneously, CO2 is introduced into the alkaline solid waste for carbonation, reducing its alkalinity while absorbing and solidifying the CO2. Subsequently, the microbially modified aggregate is thoroughly mixed with the mineralized solid waste slurry in a suitable ratio to form a stable backfill slurry. After the slurry is injected into the goaf, MIP technology induces the formation of calcium carbonate, further generating calcium carbonate crystals that effectively fill the internal pores of the material, enhancing the density and mechanical properties of the grout. This method not only significantly improves the overall performance of the backfill material but also achieves the synergistic underground disposal and resource utilization of solid waste such as gangue and CO2, possessing both environmental benefits and engineering application value. Attached Figure Description

[0011] Figure 1 This is a process flow diagram of the solid waste backfilling method based on MICP technology and carbon dioxide mineralization synergy of the present invention. Detailed Implementation

[0012] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0013] Example 1 The solid waste backfilling method based on MICP technology and carbon dioxide mineralization synergy of the present invention, such as Figure 1 As shown, the specific operation steps are as follows: Step 1: Preparation of microbial mineralized aggregate Step 1.1: Prepare microbial culture and mineralization induction solution.

[0014] Step 1.1.1, Preparation of microbial culture. Pasteurella multocida was selected as the inoculum, and the microbial culture was obtained through activation and dilution, with the OD600 value controlled above 1.0.

[0015] Step 1.1.2: Preparation of the mineralization induction solution. The solution contains urea at a concentration of 0.5-1 mol / L and calcium chloride at a concentration of 0.5-1.0 mol / L, with the preferred molar ratio of urea to calcium source being 1.1:1 to 1.2:1. A 1.0 mol / L microbial solution is prepared using deionized water and filtered through a 0.22 μm filter membrane for sterilization. The mineralization induction solution should be prepared fresh and used immediately to avoid urea hydrolysis.

[0016] Step 1.2: Gangue Aggregate Crushing. For coal gangue, it is first coarsely crushed using a primary crusher to reduce the particle size to less than 30mm. Then, it is finely crushed using a secondary crusher to obtain gangue aggregate with a particle size of less than 3mm. Step 1.3: Mixing and Impregnation. Mix the gangue aggregate with the microbial inoculum and mineralization induction solution at a mass ratio (kg / L) of 1:0.5-1:1, and impregnate for 1-4 hours. After impregnation, filter the supernatant to obtain microbially mineralized gangue aggregate.

[0017] Step 2: Preparation of CO2 mineralized solid waste slurry Step 2.1: Preparation of Alkaline Solid Waste Slurry. Alkaline solid waste includes fly ash, gasification slag, etc. The mixing ratio of solid waste is: 70-80% fly ash and 20-30% gasification slag (by mass). The solid waste and water are mixed in a stirred reactor at a solid-liquid ratio of 1:2 to 1:3 (by mass). The stirring speed is 300-500 rpm, and the stirring time is 2 minutes, until a homogeneous slurry is formed with no visible particles.

[0018] Step 2.2, CO2 mineralization treatment. After the slurry in Step 2.1 is stirred evenly, CO2-containing gas is introduced into the slurry. The gas source is flue gas from a coal-fired power plant. During gas introduction, the stirring speed is maintained at 300-500 rpm, the mineralization reaction temperature is room temperature, and the inlet pressure is 0.2-0.5 MPa. The mineralization reaction time is set to 1-2 hours or until the slurry pH decreases from its initial value to 7.

[0019] Step 3: Preparation of Microbially Modified Filling Slurry. First, the microbial mineralized aggregate prepared in Step 1 is filtered to remove the supernatant, ensuring only surface water remains on the aggregate. The CO2 mineralized solid waste slurry prepared in Step 2 is allowed to stand for 1 hour, after which a portion of the supernatant is filtered off to reduce the water-cement ratio and increase the slurry concentration as a pretreatment. Next, the treated microbial mineralized aggregate and CO2 mineralized solid waste slurry are mixed at a ratio of 1:1 to 1:3. Water is obtained from the filtered supernatant to ensure the slurry's fluidity meets pumping requirements.

[0020] Step 4: The slurry is pumped using an integrated mixing and pumping machine and transported to the goaf via pipeline with a diameter of 100mm. The slurry flow rate is controlled at 1-2m / s to prevent sedimentation and blockage. This process involves co-filling with CO2 and coal-based solid waste. The filling material utilizes microbial mineralization to continuously consume and absorb CO2 from the CO2-mineralized solid waste slurry and external CO2, forming calcium carbonate precipitates that fill the pores of the gangue. Simultaneously, this improves the interfacial adhesion between the gangue and the cementing material, thereby increasing the material strength.

[0021] Example 2 This invention relates to a solid waste backfilling method based on MICP technology and synergistic carbon dioxide mineralization, comprising the following steps: Step 1: Prepare microbial mineralization solution. After crushing the gangue to 3mm, mix and impregnate it with the microbial mineralization solution, and incubate for 4 hours to promote microbial growth, thus preparing microbial mineralized aggregate. Step 2: Prepare CO2 mineralization solid waste slurry. Mix alkaline coal-based solid waste such as fly ash and gasification slag with water at a solid-liquid mass ratio of 1:3. Make a uniform slurry in a stirring reaction system, and then introduce CO2 gas for stirring and mineralization treatment.

[0022] Step 3: Mix the microbial mineralized aggregate prepared in Step 1 and the CO2 mineralized solid waste slurry prepared in Step 2 at a mass ratio of 1:2 to prepare a microbial modified filling slurry with excellent fluidity and low bleeding rate.

[0023] Step 4: Microbial modified filling slurry is injected into the goaf using a slurry filling method to achieve synergistic filling and treatment of coal-based solid waste and CO2. At the same time, microbial mineralization induces calcium carbonate precipitation to fill pores, improves grouting strength, and seals CO2.

[0024] Example 3 The solid waste backfilling method based on MIP technology and carbon dioxide mineralization synergy of the present invention has the following specific operation steps: Step 1: Preparation of microbial mineralized aggregate Step 1.1: Prepare microbial culture and mineralization induction solution.

[0025] Step 1.1.1, Preparation of microbial culture: Pasteurella multocida was selected as the strain, and microbial culture was obtained by activation and dilution, with the OD600 value controlled above 1.0.

[0026] Step 1.1.2, Preparation of Mineralization Induction Solution: The solution contains 0.8 mol / L urea and 1.0 mol / L calcium chloride, with a molar ratio of urea to calcium source of 1.1:1. A 1.0 mol / L microbial solution is prepared using deionized water and filtered through a 0.22 μm filter membrane for sterilization. The mineralization induction solution should be prepared fresh and used immediately to avoid urea hydrolysis. Step 1.2, Gangue Aggregate Crushing: For coal gangue, it is first coarsely crushed by a primary crusher to break the gangue to a particle size of less than 30mm. Then it is finely crushed by a secondary crusher to obtain gangue aggregate with a particle size of less than 3mm. Step 1.3, Mixing and Impregnation: Mix the gangue aggregate with the microbial inoculum and mineralization induction solution at a mass ratio (kg / L) of 1:0.5:1, and impregnate for 3 hours. After impregnation, filter the supernatant to obtain microbially mineralized gangue aggregate; Step 2: Preparation of CO2 mineralized solid waste slurry Step 2.1, Preparation of Alkaline Solid Waste Slurry: Alkaline solid waste includes fly ash, gasification slag, etc. The mixing ratio of solid waste is: 75% fly ash and 25% gasification slag (by mass). Alkaline solid waste and water are mixed in a stirred reactor at a solid-liquid ratio of 1:2 (by mass). The stirring speed is 500 rpm, and the stirring time is 2 minutes, until a uniform slurry is formed with no visible particles. Step 2.2, CO2 mineralization treatment: After the slurry in Step 2.1 is stirred evenly, CO2-containing gas is introduced into the slurry. The gas source is flue gas from a coal-fired power plant. During gas introduction, the stirring speed is maintained at 300 rpm, the mineralization reaction temperature is room temperature, and the inlet pressure is 0.3 MPa; the mineralization reaction time is set to 1 hour.

[0027] Step 3: Preparation of Microbially Modified Filling Slurry. First, the microbial mineralized aggregate prepared in Step 1 is filtered to remove the supernatant, ensuring only surface water remains on the aggregate. The CO2 mineralized solid waste slurry prepared in Step 2 is allowed to stand for 1 hour, after which a portion of the supernatant is filtered off to reduce the water-cement ratio and increase the slurry concentration through pretreatment. Next, the treated microbial mineralized aggregate and CO2 mineralized solid waste slurry are mixed 1:1. Water is obtained from the filtered supernatant to ensure the slurry's fluidity meets pumping requirements.

[0028] Step 4: The slurry is pumped using an integrated mixing and pumping machine and transported to the goaf via pipeline with a diameter of 100mm. The slurry flow rate is controlled at 1m / s to prevent sedimentation and blockage. This process involves co-filling with CO2 and coal-based solid waste. The filling material utilizes microbial mineralization to continuously consume and absorb CO2 from the CO2-mineralized solid waste slurry and external CO2, forming calcium carbonate precipitates that fill the pores of the gangue. Simultaneously, it improves the interfacial adhesion between the gangue and the cementing material, thereby increasing the material strength.

[0029] Example 4 The solid waste backfilling method based on MIP technology and carbon dioxide mineralization synergy of the present invention has the following specific operation steps: Step 1: Preparation of microbial mineralized aggregate Step 1.1: Prepare microbial culture and mineralization induction solution.

[0030] Step 1.1.1, Preparation of microbial culture. Pasteurella multocida was selected as the inoculum, and the microbial culture was obtained through activation and dilution, with the OD600 value controlled above 1.0.

[0031] Step 1.1.2: Preparation of the mineralization induction solution. The solution contains 1 mol / L urea and 0.5 mol / L calcium chloride, with a preferred molar ratio of urea to calcium source of 1.2:1. A 1.0 mol / L microbial solution is prepared using deionized water and filtered through a 0.22 μm filter membrane for sterilization. The mineralization induction solution should be prepared fresh and used immediately to avoid urea hydrolysis.

[0032] Step 1.2: Gangue Aggregate Crushing. For coal gangue, it is first coarsely crushed using a primary crusher to reduce the particle size to less than 30mm. Then, it is finely crushed using a secondary crusher to obtain gangue aggregate with a particle size of less than 3mm. Step 1.3: Mixing and Impregnation. Mix the gangue aggregate with the microbial inoculum and mineralization induction solution at a mass ratio (kg / L) of 1:1:1 and impregnate for 2 hours. After impregnation, filter the supernatant to obtain microbially mineralized gangue aggregate.

[0033] Step 2: Preparation of CO2 mineralized solid waste slurry Step 2.1, Preparation of Alkaline Solid Waste Slurry: Alkaline solid waste includes fly ash, gasification slag, etc. The mixing ratio of solid waste is: 80% fly ash and 20% gasification slag (by mass). Solid waste and water are mixed in a stirred reactor at a solid-liquid ratio of 1:3 (by mass). The stirring speed is 500 rpm, and the stirring time is 2 minutes, until a uniform slurry is formed with no visible particles.

[0034] Step 2.2, CO2 mineralization treatment: After the slurry in Step 2.1 is stirred evenly, CO2-containing gas is introduced into the slurry; the gas source is flue gas from a coal-fired power plant. During gas introduction, the stirring speed is maintained at 300 rpm, the mineralization reaction temperature is room temperature, and the inlet pressure is 0.5 MPa. The mineralization reaction causes the pH of the slurry to decrease from its initial value to 7.

[0035] Step 3: Preparation of Microbially Modified Filling Slurry: First, the supernatant of the microbial mineralized aggregate prepared in Step 1 is filtered off, ensuring that only the surface of the aggregate is wetted. The CO2 mineralized solid waste slurry prepared in Step 2 is allowed to stand for 1 hour, after which a portion of the supernatant is filtered off to reduce the water-cement ratio and increase the slurry concentration as a pretreatment. Next, the treated microbial mineralized aggregate and CO2 mineralized solid waste slurry are mixed at a 1:3 ratio. Water is obtained from the filtered supernatant to ensure the slurry's fluidity meets pumping requirements.

[0036] Step 4: The slurry is pumped using an integrated mixing and pumping machine and transported to the goaf via pipeline with a diameter of 100mm. The slurry flow rate is controlled at 2m / s to prevent sedimentation and blockage. This process involves co-filling with CO2 and coal-based solid waste. The filling material utilizes microbial mineralization to continuously consume and absorb CO2 from the CO2-mineralized solid waste slurry and external CO2, forming calcium carbonate precipitates that fill the pores of the gangue. Simultaneously, this improves the interfacial adhesion between the gangue and the cementing material, thereby increasing the material strength.

[0037] Example 5 The solid waste backfilling method based on MIP technology and carbon dioxide mineralization synergy of the present invention has the following specific operation steps: Step 1: Preparation of microbial mineralized aggregate Step 1.1: Prepare microbial culture and mineralization induction solution.

[0038] Step 1.1.1, Preparation of microbial culture. Pasteurella multocida was selected as the inoculum, and the microbial culture was obtained through activation and dilution, with the OD600 value controlled above 1.0.

[0039] Step 1.1.2: Preparation of the mineralization induction solution. The solution contains 0.6 mol / L urea and 0.8 mol / L calcium chloride, with a preferred molar ratio of urea to calcium source of 1.1:1. A 1.0 mol / L microbial solution is prepared using deionized water and filtered through a 0.22 μm filter membrane for sterilization. The mineralization induction solution should be prepared fresh and used immediately to avoid urea hydrolysis.

[0040] Step 1.2: Gangue Aggregate Crushing. For coal gangue, it is first coarsely crushed using a primary crusher to reduce the particle size to less than 30mm. Then, it is finely crushed using a secondary crusher to obtain gangue aggregate with a particle size of less than 3mm. Step 1.3: Mixing and Impregnation. Mix the gangue aggregate with the microbial inoculum and mineralization induction solution at a mass ratio (kg / L) of 1:0.8:1, and impregnate for 3 hours. After impregnation, filter the supernatant to obtain microbially mineralized gangue aggregate.

[0041] Step 2: Preparation of CO2 mineralized solid waste slurry Step 2.1: Preparation of Alkaline Solid Waste Slurry. Alkaline solid waste includes fly ash, gasification slag, etc. The mixing ratio of solid waste is: 70% fly ash and 30% gasification slag (by mass). Solid waste and water are mixed in a stirred reactor at a solid-liquid ratio of 1:3 (by mass). The stirring speed is 400 rpm, and the stirring time is 2 minutes, until a homogeneous slurry is formed with no visible particles.

[0042] Step 2.2, CO2 mineralization treatment. After the slurry in Step 2.1 is stirred evenly, CO2-containing gas is introduced into the slurry. The gas source is flue gas from a coal-fired power plant. During gas introduction, the stirring speed is maintained at 500 rpm, the mineralization reaction temperature is room temperature, and the inlet pressure is 0.3 MPa. The mineralization reaction time is set to 2 hours.

[0043] Step 3: Preparation of Microbially Modified Filling Slurry. First, the microbial mineralized aggregate prepared in Step 1 is filtered to remove the supernatant, ensuring only surface water remains on the aggregate. The CO2 mineralized solid waste slurry prepared in Step 2 is allowed to stand for 1 hour, after which a portion of the supernatant is filtered off to reduce the water-cement ratio and increase the slurry concentration through pretreatment. Next, the treated microbial mineralized aggregate and CO2 mineralized solid waste slurry are mixed at a 1:2 ratio. Water is obtained from the filtered supernatant to ensure the slurry's fluidity meets pumping requirements.

[0044] Step 4: The slurry is pumped using an integrated mixing and pumping machine and transported to the goaf via pipeline with a diameter of 100mm. The slurry flow rate is controlled at 1m / s to prevent sedimentation and blockage. This process involves co-filling with CO2 and coal-based solid waste. The filling material utilizes microbial mineralization to continuously consume and absorb CO2 from the CO2-mineralized solid waste slurry and external CO2, forming calcium carbonate precipitates that fill the pores of the gangue. Simultaneously, it improves the interfacial adhesion between the gangue and the cementing material, thereby increasing the material strength.

[0045] Example 6 The solid waste backfilling method based on MIP technology and carbon dioxide mineralization synergy of the present invention has the following specific operation steps: Step 1: Preparation of microbial mineralized aggregate Step 1.1: Prepare microbial culture and mineralization induction solution.

[0046] Step 1.1.1, Preparation of microbial culture. Pasteurella multocida was selected as the inoculum, and the microbial culture was obtained through activation and dilution, with the OD600 value controlled above 1.0.

[0047] Step 1.1.2: Preparation of the mineralization induction solution. The solution contains 0.8 mol / L urea and 0.5 mol / L calcium chloride, with a preferred molar ratio of urea to calcium source of 1.2:1. A 1.0 mol / L microbial solution is prepared using deionized water and filtered through a 0.22 μm filter membrane for sterilization. The mineralization induction solution should be prepared fresh and used immediately to avoid urea hydrolysis.

[0048] Step 1.2: Gangue Aggregate Crushing. For coal gangue, it is first coarsely crushed using a primary crusher to reduce the particle size to less than 30mm. Then, it is finely crushed using a secondary crusher to obtain gangue aggregate with a particle size of less than 3mm. Step 1.3: Mixing and Impregnation. Mix the gangue aggregate with the microbial inoculum and mineralization induction solution at a mass ratio (kg / L) of 1:0.7:1, and impregnate for 2 hours. After impregnation, filter the supernatant to obtain microbially mineralized gangue aggregate.

[0049] Step 2: Preparation of CO2 mineralized solid waste slurry Step 2.1: Preparation of Alkaline Solid Waste Slurry. Alkaline solid waste includes fly ash, gasification slag, etc. The mixing ratio of solid waste is: 70% fly ash and 30% gasification slag (by mass). Solid waste and water are mixed in a stirred reactor at a solid-liquid ratio of 1:2 (by mass). The stirring speed is 400 rpm, and the stirring time is 2 minutes, until a homogeneous slurry is formed with no visible particles.

[0050] Step 2.2, CO2 mineralization treatment. After the slurry in Step 2.1 is stirred evenly, CO2-containing gas is introduced into the slurry. The gas source is flue gas from a coal-fired power plant. During gas introduction, the stirring speed is maintained at 400 rpm, the mineralization reaction temperature is room temperature, and the inlet pressure is 0.4 MPa. The mineralization reaction time is set to 2 hours.

[0051] Step 3: Preparation of Microbially Modified Filling Slurry. First, the microbial mineralized aggregate prepared in Step 1 is filtered to remove the supernatant, ensuring only surface water remains on the aggregate. The CO2 mineralized solid waste slurry prepared in Step 2 is allowed to stand for 1 hour, after which a portion of the supernatant is filtered off to reduce the water-cement ratio and increase the slurry concentration through pretreatment. Next, the treated microbial mineralized aggregate and CO2 mineralized solid waste slurry are mixed at a 1:2 ratio. Water is obtained from the filtered supernatant to ensure the slurry's fluidity meets pumping requirements.

[0052] Step 4: The slurry is pumped using an integrated mixing and pumping machine and transported to the goaf via pipeline with a diameter of 100mm. The slurry flow rate is controlled at 1.5m / s to prevent sedimentation and blockage. This process involves co-filling with CO2 and coal-based solid waste. The filling material utilizes microbial mineralization to continuously consume and absorb CO2 from the CO2-mineralized solid waste slurry and external CO2, forming calcium carbonate precipitates that fill the pores of the gangue. Simultaneously, this improves the interfacial adhesion between the gangue and the cementing material, thereby increasing the material strength.

Claims

1. A solid waste backfilling method based on MIP technology and synergistic carbon dioxide mineralization, characterized in that, The specific steps are as follows: Step 1: Prepare microbial mineralization solution, mix and impregnate crushed gangue with microbial mineralization solution, cultivate and promote microbial growth, and then prepare microbial mineralized aggregate; Step 1.1: Prepare microbial culture solution and mineralization induction solution; Step 1.1.1, Preparation of microbial culture: Pasteurella multocida was selected as the strain, and microbial culture was obtained by activation and dilution, with the OD600 value controlled above 1.0; Step 1.1.2, Preparation of mineralization induction solution: The solution contains urea at a concentration of 0.5-1 mol / L and calcium chloride at a concentration of 0.5-1.0 mol / L, with a molar ratio of urea to calcium source of 1.1-1.2:1; a mineralization induction solution of 1.0 mol / L is prepared using deionized water and filtered through a 0.22 μm filter membrane for sterilization; Step 1.2: Crush the gangue aggregate. First, coarsely crush it using a primary crusher to break the gangue to a particle size of less than 30mm; then, finely crush it using a secondary crusher to obtain gangue aggregate with a particle size of less than 3mm. Step 1.3: Mix and impregnate the gangue aggregate with microbial inoculum and mineralization induction liquid at a mass ratio of 1:0.5-1:1 for 1-4 hours. After impregnation, filter the supernatant to obtain microbial mineralized gangue aggregate. Step 2: Prepare CO2 mineralized solid waste slurry; Step 2.1: Prepare alkaline solid waste slurry: Alkaline solid waste includes a mixture of fly ash and gasification slag; the mass ratio of fly ash to gasification slag is 7~8:2~3; alkaline solid waste and water are mixed in a stirred reactor at a solid-liquid mass ratio of 1:2~3; the stirring speed is 300-500 rpm and the stirring time is 2 minutes until a uniform slurry is formed with no visible particles. Step 2.2, CO2 mineralization treatment: After the slurry in step 2.1 is stirred evenly, CO2-containing gas is introduced into the slurry; when introducing CO2 gas, the stirring speed is maintained at 300-500 rpm, the mineralization reaction temperature is room temperature, and the inlet pressure is 0.2-0.5 MPa; Step 3: Mix the microbial mineralized aggregate prepared in Step 1 and the CO2 mineralized solid waste slurry prepared in Step 2 in a certain proportion to prepare microbial modified filling slurry; Step 3 is detailed as follows: After the CO2 mineralized solid waste slurry prepared in step 2 is allowed to stand for 1 hour, part of the supernatant is filtered off; the microbial mineralized aggregate and the CO2 mineralized solid waste slurry are mixed at a mass ratio of 1:1~3. Step 4: Microbial modified filling slurry is injected into the goaf using a slurry filling method to achieve synergistic filling and treatment of coal-based solid waste and CO2. At the same time, microbial mineralization induces calcium carbonate precipitation to fill pores, improves grouting strength, and seals CO2.

2. The solid waste backfilling method based on MICP technology and carbon dioxide mineralization synergy according to claim 1, characterized in that, The source of the CO2 gas is industrial flue gas from a coal-fired power plant.

3. The solid waste backfilling method based on MICP technology and carbon dioxide mineralization synergy according to claim 1, characterized in that, Step 4 is as follows: Microbial modified backfill slurry is pumped by an integrated mixing and pumping machine and transported to the goaf through pipelines. The slurry flow rate is controlled at 1-2 m / s for the co-filling and treatment of CO2 and coal-based solid waste. The backfill body utilizes the microbial mineralization process to continuously consume and absorb CO2 from the CO2 mineralized solid waste slurry and the external CO2, forming calcium carbonate precipitate to fill the pores of gangue.

4. The solid waste backfilling method based on MICP technology and synergistic carbon dioxide mineralization according to claim 1, characterized in that, In step 2.2, the mineralization reaction time is set to 1-2 hours or the slurry pH decreases from the initial value to 7.

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