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

Abstract

The invention discloses a solid waste filling method based on cooperation of an MICP technology and carbon dioxide mineralization. Gangue aggregate is treated through microbial infiltration; cO2 is introduced into the alkaline solid waste for carbonation treatment, so that the alkalinity of the alkaline solid waste is reduced, and CO2 is absorbed and cured; the microbe modified aggregate and the mineralized solid waste slurry are fully mixed according to a reasonable ratio to form the filling slurry with stable performance. After the slurry is injected into the goaf, calcium carbonate is formed through induction of the MICP technology, calcium carbonate crystals are further generated, internal pores of the material are effectively filled, and the compactness and certain mechanical performance of the grouting body are enhanced. The method can synchronously and efficiently solve the problem of treatment of solid wastes such as coal gangue and fly ash, realizes large-scale storage of CO2, provides a filling body with excellent mechanical properties for a goaf, enhances the surface corrosion resistance and improves the bonding property with surrounding rock.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of underground backfilling and solid waste resource utilization, and relates to a solid waste filling method based on MICP technology and carbon dioxide mineralization cooperation. BACKGROUND

[0002] In the process of coal mining, large-scale goaf formed underground is easy to induce surface subsidence, rock movement and even geological disasters, which seriously threatens the ecological environment and safety production in the mining area. At the same time, a large amount of solid waste such as coal gangue and fly ash is also facing great treatment pressure in the process of coal mining and utilization. Using coal gangue, fly ash and other alkaline solid waste to mineralize and store carbon dioxide to fill the goaf can realize the cooperative underground treatment of alkaline solid waste and carbon storage. However, the interface bonding performance between the gangue filling body and the fly ash is poor, which is easy to cause peeling and internal damage, affecting the long-term stability of the filling body, and the carbon dioxide storage efficiency is low. The microbial induced carbonate precipitation (MICP) technology is a new green technology that can combine calcium ions and carbonate ions to generate calcium carbonate precipitation by using microbial metabolites. This technology has been explored for soil reinforcement, dust prevention and other fields. If the MICP technology is combined with the traditional gangue-fly ash filling system, the microbial mineralization can be used to enhance the inter-particle bonding, improve the overall performance of the material and improve the CO2 fixation efficiency, which will produce significant technical, economic and ecological value. SUMMARY

[0003] The purpose of the present application is to provide a solid waste filling method based on MICP technology and carbon dioxide mineralization cooperation, which can simultaneously and efficiently solve the treatment problems of solid waste such as coal gangue and fly ash, realize large-scale storage of CO2, and provide a filling body with excellent mechanical properties for the goaf, enhance the surface corrosion resistance and improve the bonding performance with surrounding rock.

[0004] The technical scheme adopted by the present application is: a solid waste filling method based on MICP technology and carbon dioxide mineralization cooperation, the specific operation steps are as follows: Step 1: Prepare a microbial mineralization liquid, mix and soak the crushed gangue with the microbial mineralization liquid, cultivate and promote the growth of microorganisms, and then prepare a microbial mineralization aggregate; Step 2: Prepare a CO2 mineralized solid waste slurry; mix and react the alkaline coal-based solid waste such as fly ash and gasified slag with water in a stirring reaction system to form a uniform slurry, then introduce CO2 gas to react, and obtain a 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 proportion to prepare a microbial modified filling slurry; Step 4: The microbial modified filling slurry is injected into the goaf in a slurry filling manner to realize the collaborative filling treatment of coal-based solid waste and CO2, and at the same time, the microbial mineralization is used to induce calcium carbonate precipitation to fill pores, improve the grouting strength, and store CO2.

[0006] The application also has the characteristics that, Step 1 is specifically as follows: Step 1.1, microbial bacteria liquid and mineralization induction liquid are prepared; Step 1.1.1, microbial bacteria liquid preparation: Pasteuria agardhi is selected as the strain to provide nucleation sites on the surface of the gangue aggregate, and the microbial bacteria liquid is obtained by activation and dilution, and the OD600 value is controlled to be greater than 1.0.

[0007] Step 1.1.2, mineralization induction liquid preparation: the solution contains urea with a concentration of 0.5-1 mol / L and calcium chloride with a concentration of 0.5-1.0 mol / L, and the molar ratio of urea to calcium source is 1.1~1.2:1; 1.0 mol / L mineralization induction liquid is prepared by using deionized water, and bacteria are removed by filtering through a 0.22 μm filter membrane. Step 1.3, the gangue aggregate is mixed with the microbial bacteria liquid and the mineralization induction liquid at a mass ratio of 1:0.5-1:1, and is soaked for 1~4h, and after soaking, the supernatant is filtered to obtain the microbial mineralized gangue aggregate.

[0008] Step 2 is specifically as follows: Step 2.1, alkaline solid waste slurry is configured: the alkaline solid waste is a mixture of calcium oxide, fly ash with high magnesium oxide content, and gasification slag, and steel slag can be further added as an additive to increase the content of calcium oxide; the mass ratio of fly ash and gasification slag is 7~8:2~3; the alkaline solid waste is mixed with water in a solid-liquid ratio of 1:2~3 in a stirring reaction kettle. The stirring speed is 300-500 rpm, and the stirring time is 2 minutes, until a uniform slurry is formed without visible particles; Step 2.2, CO2 mineralization treatment: after the slurry in step 2.1 is stirred uniformly, CO2-containing gas (CO2 gas source is industrial flue gas from a coal-fired power plant) is introduced into the slurry; when the CO2 gas is introduced, 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 1-2h or the pH of the slurry is reduced from the initial value to 7.

[0009] Step 3 is specifically 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). Mix the solid waste and water in a stirred reactor at a solid-liquid ratio of 1:2 to 1:3 (by mass). Stir at 300-500 rpm for 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 reduce the particle size to 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). The 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 method for solid waste filling based on MICP technology and carbon dioxide mineralization synergy, characterized in that, The specific operation steps are as follows: Step 1: Prepare the microbial mineralization liquid, soak the gangue after crushing with the microbial mineralization liquid, cultivate to promote the growth of microorganisms, and then prepare the microbial mineralized aggregate; Step 2: Prepare CO2 mineralized solid waste slurry; Step 3: Mix the microbial mineralized aggregate prepared in step 1 and the CO2 mineralized solid waste slurry prepared in step 2 according to the proportion to prepare the microbial modified filling slurry; Step 4: The microbial modified filling slurry is injected into the goaf by slurry filling method to realize the cooperative filling treatment of coal-based solid waste and CO2, and at the same time, the microbial mineralization is used to induce calcium carbonate precipitation to fill the pores, improve the grouting strength and store CO2.

2. The method according to claim 1, characterized in that, Step 1 is as follows: Step 1.1, prepare microbial liquid and mineralization induction liquid; Step 1.2, crush the gangue aggregate, first coarsely crush the gangue to a particle size of less than 30mm by a primary crusher, and then finely crush the gangue by a secondary crusher to obtain a gangue aggregate with a particle size of less than 3mm; Step 1.3, mix the gangue aggregate with the microbial liquid and the mineralization induction liquid according to the mass ratio of 1:0.5-1:1, soak for 1-4h, and filter the supernatant to obtain the microbial mineralized gangue aggregate after soaking.

3. The method according to claim 1, characterized in that, Step 1.1 is as follows: Step 1.1.1, microbial liquid preparation: select Pasteuria bactrocida as the strain, obtain the microbial liquid by activation and dilution, and control the OD600 value to be above 1.0; Step 1.1.2, mineralization induction liquid preparation: the solution contains urea with a concentration of 0.5-1mol / L and calcium chloride with a concentration of 0.5-1.0mol / L, the molar ratio of urea to calcium source is 1.1-1.2:1; 1.0mol / L mineralization induction liquid is prepared by using deionized water, and bacteria are removed by filtering through a 0.22μm filter membrane.

4. The method of claim 3, wherein, Step 2 is as follows: Step 2.1, configure the alkaline solid waste slurry: the 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; the alkaline solid waste is mixed with water in a solid-liquid ratio of 1:2-3 in a stirring reactor; the stirring speed is 300-500rpm, and the stirring time is 2 minutes until a uniform slurry is formed without visible particles; Step 2.2, CO2 mineralization treatment: after the slurry in step 2.1 is stirred uniformly, CO2-containing gas is introduced into the slurry; when the CO2 gas is introduced, the stirring speed is maintained at 300-500rpm, the mineralization reaction temperature is room temperature, and the inlet gas pressure is 0.2-0.5Mpa.

5. The method of claim 1, wherein the method is characterized by, The CO2 gas source is the industrial flue gas of a coal-fired power plant.

6. The method of claim 5, wherein the method is characterized by, Step 3 is as follows: After the CO2 mineralized solid waste slurry prepared in step 2 is placed for 1 hour, part of the supernatant is filtered off; the microbial mineralized aggregate and the CO2 mineralized solid waste slurry are mixed according to the mass ratio of 1:1-3.

7. The method of claim 6, wherein the method is characterized by, Step 4 is as follows: The microbially modified filling slurry is pumped by the stirring and pumping integrated machine and transported to the goaf through the pipeline, the slurry flow rate is controlled at 1-2 m / s, and the CO2 and coal-based solid waste are disposed by filling; the filling body utilizes the microbial mineralization to continuously consume and absorb the CO2 in the CO2 mineralized solid waste slurry and the external CO2, and forms calcium carbonate precipitation to fill the gangue pores.

8. The method of claim 4, wherein the method is characterized by, In step 2.2, the mineralization reaction time is set to 1-2 h or the slurry pH decreases from the initial value to 7.

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