Full-tailing filling body enhanced carbon sequestration method based on bubble regulation and control

Abstract

The invention discloses a full-tailing filling body enhanced carbon sequestration method based on bubble regulation and control, and belongs to the technical field of mine filling materials, and the method comprises the following steps: uniformly stirring raw materials; then carrying out ultrasonic treatment in cooperation with double-frequency ultrasonic waves to obtain full-tailing mixed slurry; and the full-tailing mixed slurry is subjected to pouring, damp-heat curing and carbon dioxide atmosphere curing, and the full-tailing filling body is obtained. Wherein except water, the raw materials comprise the following components in percentage by mass: 80% of tailings, 12% of cement, 2%-5% of nano SiO2, 1%-3% of nano ZrO2, 0.05%-1% of hydroxypropyl methyl cellulose, 0.1%-0.5% of an air entraining agent and 0.5%-1.5% of nano MgO; the air entraining agent is obtained by compounding an anionic surfactant and a protein natural foaming agent. According to the method, stable bubbles are formed through the synergistic effect of the air entraining agent / foam stabilizer, the nano ZrO2 is combined to enhance the interface and the nano SiO2 is combined to optimize the pore connectivity, and the nano MgO active component is supplemented, so that the synergistic improvement of high strength, high air permeability and efficient carbon sequestration of the filling material is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of mine filling materials, and particularly relates to a method for enhancing carbon sequestration of full tailings filling body based on bubble regulation. BACKGROUND

[0002] The full tailings filling body is a kind of full tailings filling material, which is mainly composed of full tailings (i.e. all fine particle waste remaining after beneficiation) generated in the beneficiation process of the mine and cementing material (such as cement). By backfilling this filling body into the mined-out area or ore pillar, efficient utilization of mine resources, reduction of surface subsidence and improvement of mine safety can be achieved. Although the traditional full tailings filling body (with cement as the cementing agent) has certain mechanical strength, it still has the following problems:

[0003] 1. High density and poor air permeability: the filling body has low porosity and insufficient connectivity, which hinders the diffusion and adsorption of CO2;

[0004] In the field of full tailings paste filling carbon sequestration, the microstructure characteristics of the filling body have a key influence on the diffusion and adsorption process of CO2. It is found through research that the filling body has the significant characteristic of low porosity, with a small number of internal pores and insufficient connectivity between these pores. This microstructure state greatly hinders the diffusion path of CO2 in the filling body, making it difficult for CO2 molecules to freely shuttle inside the filling body and effectively reach the active sites where adsorption can occur, thereby seriously hindering the adsorption process of CO2 and greatly limiting the carbon sequestration efficiency and effect of the full tailings paste filling carbon sequestration technology.

[0005] 2. Low carbon sequestration efficiency: the existing filling material has limited chemical adsorption and mineralization capacity for CO2;

[0006] In the full tailings paste filling carbon sequestration technology system, carbon sequestration efficiency is a key indicator for measuring the practical application value of the technology. From the micro mechanism, when the full tailings paste filling material interacts with CO2, it mainly relies on chemical adsorption and mineralization reaction to achieve carbon sequestration. The existing material itself has obvious limitations in chemical adsorption capacity for CO2. On the one hand, the number of active sites on the material surface for adsorbing CO2 molecules is limited, resulting in a small amount of CO2 that can be adsorbed per unit time; on the other hand, the chemical composition and crystal structure characteristics of the material determine that its activity in chemical reaction with CO2 is not high, making the chemical adsorption process difficult to proceed efficiently. In terms of mineralization capacity, it is also not good. The mineralization process is essentially a chemical reaction between CO2 and certain components in the material to generate stable carbonate minerals. In the existing filling material, the content of components that can effectively participate in the mineralization reaction is insufficient, and the reaction kinetics conditions are not good, resulting in a slow mineralization reaction rate and difficulty in converting a large amount of CO2 into stable mineralization products in a short period of time.

[0007] 3. Strength vs. air permeability: Increasing porosity generally leads to a decrease in mechanical properties.

[0008] In the practical application and research process of the full tailings paste filling carbon sequestration technology, the contradiction between strength and air permeability becomes a key factor hindering the further optimization and development of the technology. From the perspective of material microstructure, the performance of the full tailings paste filling body is largely dependent on its internal pore structure. In order to improve the adsorption and diffusion capacity of CO2 of the filling body, i.e. to improve its air permeability, it is usually necessary to increase the porosity. However, when the porosity increases, the mechanical properties of the filling body will decrease significantly. Increasing the porosity means that more voids are introduced into the filling body structure, which reduces the effective contact area between particles, weakening the friction and engagement force between particles. At the same time, the role of cementing material in supporting the filling body structure is also dispersed due to the increase in pores, and it is difficult to effectively transfer and bear the load as effectively as in the low porosity state. SUMMARY

[0009] In view of the above technical problems, the present application provides a full tailings filling body enhanced carbon sequestration method based on bubble regulation. The method significantly improves the CO2 permeation and adsorption capacity while maintaining high strength, achieving the dual benefits of mine waste utilization and carbon sequestration.

[0010] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0011] A full tailings filling body enhanced carbon sequestration method based on bubble regulation, comprising the following steps:

[0012] stirring the raw materials uniformly; then performing ultrasonic treatment with double-frequency ultrasonic waves to obtain a full tailings mixed slurry;

[0013] casting, wet heat curing and carbon dioxide atmosphere curing the full tailings mixed slurry to obtain the full tailings filling body (i.e. full tailings filling material);

[0014] Among them, in addition to water, the raw materials include, by mass percentage:

[0015] 80% tailings, 12% cement, 2% to 5% nano-SiO2, 1% to 3% nano-ZrO2, 0.05% to 1% hydroxypropyl methyl cellulose, 0.1% to 0.5% air entraining agent and 0.5% to 1.5% nano-MgO;

[0016] Among them, the air entraining agent is a compound of anionic surfactant and protein-based natural foaming agent.

[0017] Beneficial effects: The hydroxypropyl methyl cellulose (HPMC) defined in the application and nano-SiO2 synergistically act as a foam stabilizer. HPMC forms a tough protective film on the bubble surface, and nano-SiO2 fills the gaps in the HPMC film by virtue of its high specific surface area and activity, further strengthening the compactness of the film. The synergistic effect of the two extends the bubble half-life to more than 48 hours, effectively preventing bubble rupture during the subsequent pouring process, providing a stable carrier for successful carbon dioxide storage. In addition, nano-SiO2 not only plays a role in stabilizing the foam, but also reacts with the cement hydration products to form C-S-H gel. These gels fill the microcracks in the setting paste, effectively improving the microstructure of the paste and improving the pore connectivity, which is beneficial to the uniform distribution and storage of carbon dioxide in the paste. That is, the present application builds a stable bubble network through the synergistic effect of air entraining agents / foam stabilizers, combines nano-ZrO2 to enhance the interface and nano-SiO2 to optimize the pore connectivity, and adds nano-MgO as an active component, to achieve the synergistic improvement of high strength, high air permeability and high carbon sequestration of the filling material.

[0018] Optionally, the particle size of nano-SiO2 is 20-50 nm.

[0019] Optionally, the mass ratio of the anionic surfactant and the protein-based natural foaming agent is 1:1-2.

[0020] Beneficial effects: The present application selects anionic surfactants (such as sodium dodecyl sulfate) and protein-based natural foaming agents to construct a composite foaming system. Among them, sodium dodecyl sulfate has a high surface tension reduction effect and can quickly produce a large number of bubbles; the protein-based natural foaming agent enhances the stability of the bubbles due to its unique molecular structure. Under the condition of the above optimal compounding ratio defined in the present application, the initial bubble diameter (particle size) can be precisely controlled to be within 200 μm during the stirring process. Such a particle size range can not only ensure the uniform distribution of bubbles in the setting paste, but also, by virtue of the high specific surface area after solidification, improve the CO2 adsorption and mineralization efficiency while simultaneously enhancing the mechanical properties of the filling body.

[0021] Further, the anionic surfactant is sodium dodecyl sulfate; and the protein-based natural foaming agent is whey protein or soy protein.

[0022] Optionally, the particle size of nano-ZrO2 is 30-50 nm.

[0023] Beneficial effects: Nano-ZrO2 with a particle size of 30-50 nm can form a rigid shell on the bubble interface through electrostatic adsorption. This rigid shell not only enhances the stability of the bubbles, but also significantly improves the mechanical properties of the entire filling body.

[0024] Optionally, the average particle size of the nano-MgO is 40 nm.

[0025] Beneficial effects: The nano-MgO has good chemical activity and can react with carbon dioxide to form magnesite (MgCO3). In the filling system, the carbonation reaction of Ca(OH)2 and the carbonation reaction of MgO and Ca(OH)2 are mutually synergistic. Specifically, the reaction of MgO and carbon dioxide increases the adsorption sites of the system for carbon dioxide, and the carbonation reaction of Ca(OH)2 further enriches the reaction path. The synergistic effect of the two makes the CO2 adsorption capacity of the filling body reach 15-25 kg / m 3 , significantly improves the carbon dioxide sequestration efficiency, and meets the demand for efficient carbon dioxide sequestration.

[0026] Optionally, the specific steps of the whole tailings filling body enhanced carbon sequestration method based on bubble regulation are as follows:

[0027] According to the above mass percentage, the tailings, cement, nano-ZrO2, nano-SiO2 and nano-MgO are weighed, dry mixed and stirred to obtain a whole tailings mixture;

[0028] Water is added to the whole tailings mixture at a total solid (except water, the rest of the raw materials are solids) mass of 20% to 35%, and air entraining agent and hydroxypropyl methyl cellulose are added in sequence while stirring to perform wet mixing and stirring;

[0029] After stirring, double-frequency ultrasonic pulse ultrasonic treatment is performed for a duration of 2 min to eliminate large bubbles and ensure that the particle size of the bubbles is within a reasonable range (0-200 μm), thereby obtaining a whole tailings mixed slurry;

[0030] The whole tailings mixed slurry is sequentially poured, wet heat cured and carbon dioxide atmosphere cured to obtain the whole tailings filling material.

[0031] Optionally, the whole tailings mixture slurry has a viscosity of 0.75-1.0 Pa·s and a yield stress of 100-130 Pa.

[0032] The curing temperature during the wet heat curing process is controlled to be 25-30℃.

[0033] Beneficial effect: When the viscosity and yield stress of the slurry are too low, most of the bubbles in the slurry will float up and escape from the slurry, so that a suitable pore structure with a proper aperture cannot be formed in the slurry; when the viscosity is too high, a small amount of large-sized bubbles in the slurry cannot escape from the slurry, forming a pore structure with a diameter greater than 200 μm, which is not conducive to the increase in the mechanical strength of the filling body. In addition, the curing temperature will also affect the formation of the pore structure; when the temperature is less than 25℃, the setting time of the slurry becomes longer, and the strength grows slowly, which is not conducive to the safety of mining; when the temperature is higher than 30℃, the shrinkage of the pores of the filling slurry increases, and pores with a diameter greater than 200 μm are easily generated, thereby deteriorating the mechanical strength of the filling body.

[0034] Optionally, the rotating speed of the wet mixing and stirring is 100-300 rpm.

[0035] Beneficial effect: The rotating speed will affect the fusion and crushing of the bubbles, so it is necessary to accurately control the stirring speed during the preparation of the composite foaming system. Within the stirring speed range of 100-300 rpm defined in the present application, the overlarge bubbles can be broken into small bubbles, and a pore structure within a reasonable range (0-200 μm) can be formed, which reduces the amount of material used while improving the air permeability of the filling body and dominating the gas diffusion in the subsequent carbon dioxide storage process, so as to ensure that the carbon dioxide can be quickly and uniformly distributed in the entire system.

[0036] Optionally, the dual-frequency ultrasonic wave is 20 kHz+100 kHz, and the pulse ultrasonic wave treatment is working for 5 s and pausing for 2 s, and the duration is 2 min.

[0037] Beneficial effect: The ultrasonic wave treatment can produce an impact wave through the synergistic effect of the cavitation effect and the mechanical vibration, which can directly crush the overlarge bubbles (diameter >200 μm) in the slurry to break them into bubbles within a reasonable range (0-200 μm); the dual-frequency ultrasonic wave of 20 kHz+100 kHz in combination with the pulse ultrasonic wave treatment can break the overlarge bubbles while retaining the bubbles within a beneficial range (0-200 μm), and the pulse mode (5 s on / 2 s off) can avoid local overheating to cause the collapse of the pores, so as to realize the optimization of the pores by removing the poor ones and retaining the good ones.

[0038] Optionally, the standing time after pouring is 30 min.

[0039] Beneficial effects: During the 30min standing period after pouring, the pores of different diameters form a uniform distribution of pore structure inside the filling body, among which the large pores (100-200μm) form a macroscopic channel network, which significantly improves the permeability of the filling body through the connected pore structure, providing an efficient path for the rapid diffusion and transmission of CO2. At the same time, the presence of large pores can absorb the dynamic impact of external load and disperse stress concentration, thereby enhancing the dynamic mechanical strength of the filling body; the mesopores (10-100μm) are blocked by the colloidal network formed by tailings fine particles and nano-SiO2, and finally form a honeycomb structure. This structure provides more contact interfaces for CO2 adsorption by increasing the internal surface area, effectively enhancing the binding capacity of CO2 and the filling body; the micropores (<10μm) are wrapped by nano-ZrO2 and C-S-H gel to form stable nano-scale micropore groups. These micropores maintain the continuity of the skeleton structure of the filling body through filling and wrapping, ensuring the CO2 storage function while greatly improving the compressive strength of the system due to the uniform stress on the surface of the spherical structure of the nano-scale micropores, ensuring that the filling body has good static mechanical properties.

[0040] Optionally, the conditions during the wet heat curing process are:

[0041] Curing for 24h under the condition of 25-30℃ and relative humidity RH≥90%.

[0042] Beneficial effects: After pouring, first wet heat curing is carried out. The filling body is cured in an environment with a temperature of 25-30℃ and a relative humidity of ≥90% for 24 hours. During this stage, the high temperature can accelerate the cement hydration reaction process to form a dense matrix, reduce large voids and improve the compressive strength of the filling body, while the high humidity environment can prevent the filling body from being excessively dry due to rapid water evaporation. Adequate water helps to maintain the water film in the pores and maintain the stability of the pore structure, preventing pore collapse and providing a stable physical structure foundation for subsequent CO2 storage.

[0043] Optionally, the conditions during the CO2 atmosphere curing process are:

[0044] Curing for 6h under the condition of CO2 concentration of 20% (the rest is air) and pressure of 0.2MPa.

[0045] Beneficial effect: After the end of the wet heat curing, enter the CO2 atmosphere curing stage. Put the filling body into the environment with 20% carbon dioxide concentration and 0.2 MPa pressure for 6 hours. Among them, the higher carbon dioxide concentration and pressure can significantly accelerate the carbonation reaction rate, make the nano-MgO and Ca(OH)2 fully react with carbon dioxide, and further improve the carbon dioxide fixation amount. At the same time, the stable structure formed by the early wet heat curing can effectively resist the structural stress changes caused by the carbonation reaction in this stage, ensure that the pore structure is not damaged, so as to realize efficient carbon dioxide sequestration.

[0046] Compared with the prior art, the present application has the following advantages and technical effects:

[0047] 1. The present application provides a kind of based on bubble regulation can increase the carbon sequestration of full tailings filling material and its preparation method, by bubble regulation technology, paste filling technology is combined with carbon dioxide mineralization sequestration, makes the mine solid waste with a large amount of metal elements and carbon dioxide fully adsorbed and mineralized, and is prepared into mineralized filling slurry, is filled into underground goaf. This not only helps to improve the mechanical properties of filling body and improve its pore structure, but also promotes the realization of "strength-rheology-cost-environmental protection" multi-objective coordinated development of paste filling;

[0048] 2. Compared with the filling paste prepared by the current ordinary carbon sequestration method, the full tailings filling material prepared by the method of the present application has 10% to 15% improvement in 28-day compressive strength; Permeability coefficient increases by 2 to 3 orders of magnitude (up to 10 -6 m / s level), which is beneficial to the diffusion of CO2 in the filling body and facilitates the progress of CO2 adsorption; CO2 sequestration rate increases by 3-5 times, i.e. has a large amount of CO2 mineralization sequestration, which can realize large-scale mineralization sequestration of CO2 in mines;

[0049] 3. Under the condition of ensuring the strength of the filling material, the amount of cementing material in the present application is reduced by 10% to 20%, which reduces the cost of preparing filling paste (filling material). BRIEF DESCRIPTION OF DRAWINGS

[0050] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of the present application illustrated in the drawings and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0051] Figure 1 Schematic diagram of bubble-nanoparticle composite structure in the full tailings filling material prepared for Example 1;

[0052] Figure 2 Microscopic electron microscope image of three-level pore structure in the full tailings filling material prepared for Example 1;

[0053] Figure 3 The CO2permeation-absorption synergistic mechanism diagram for full tailings filling material. DETAILED DESCRIPTION

[0054] Various exemplary embodiments of the present application will now be described in detail, which should be considered to be illustrative of certain aspects, features and embodiments of the present application, but not a limitation thereof.

[0055] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. In addition, where particular ranges of values are given, understand that each intervening value, to the upper or lower limit of the ranges is also specifically included. Each smaller range that falls within the broader ranges is also specifically included in the present application. The upper and lower limits of these smaller ranges can independently be included or excluded in the range.

[0056] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In case of conflict, the present specification will control.

[0057] Various modifications and changes can be made to the specific embodiments of the present application described herein without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those of ordinary skill in the art from the description and examples presented herein. The description and examples are illustrative of the application and are not intended to limit the scope of the application.

[0058] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" or the like are open-ended and do not exclude additional, unrecited elements or method steps.

[0059] The raw materials used in the present application are all commercially available. The nano-ZrO2 sample has an average particle size of 50 nm; the nano-SiO2 sample has an average particle size of 100 nm; the cement is PO42.5 ordinary portland cement; the nano-MgO sample has an average particle size of 40 nm; and the whey protein is purchased from the company of Milkline.

[0060] The technical solutions of the present application are further described below through examples.

[0061] Example 1

[0062] A method for enhancing permeability and carbon fixation of a full tailings filling body based on bubble control specifically comprises the following steps:

[0063] Step 1: Preparation of materials and equipment

[0064] Prepare filling equipment for preparing filling paste (filling material), and prepare raw materials for preparing filling paste in advance according to the formula. In addition to water, the formula includes the following raw materials in weight percentage:

[0065] Tailings 80%, PO42.5 cement 12%, nano-SiO2 3.5%, nano-ZrO2 2.5%, hydroxypropyl methylcellulose (HPMC) 0.3%, air-entraining agent (sodium lauryl sulfate and whey protein in a mass ratio of 1:2) 0.5% and nano-MgO 1.2%; the tailings need to be screened (passed through a 100-mesh sieve) and pre-treated to remove impurities;

[0066] Step 2: Preparation of paste filling materials

[0067] S1: Add weighed tailings, cement, nano-ZrO2, nano-SiO2 and nano-MgO into a blender and dry mix them at a stirring speed of 100 rpm for 3 minutes to obtain a full tailings mixture, ensuring that all solid raw materials are evenly mixed to form a nanoparticle-coarse aggregate bridge structure, which provides mechanical support points for bubbles;

[0068] S2: Add water to the above-mentioned tailings mixture and stir at a solid-to-liquid ratio of 8:2. During stirring, add an air-entraining agent and HPMC sequentially. After adding the air-entraining agent, stir at 250 rpm to introduce uniform and stable microbubbles, improve the material's pore structure, and enhance its impermeability and durability. The addition of HPMC further enhances the material's cohesiveness and water retention, making it easier to handle during construction. The entire mixing process should last no less than 10 minutes.

[0069] S3: After the stirring is completed, the full tailings filling material is subjected to ultrasonic treatment, with dual-frequency ultrasonic (20kHz+100kHz) pulsed ultrasonic treatment (working for 5s and pausing for 2s) for 2 minutes to eliminate excessive bubbles and ensure that the bubble particle size is within a reasonable range (0-200μm); and a full tailings mixed slurry is obtained;

[0070] Step 3: Sample pouring and curing

[0071] Pour the mixed filling material into the mold and let it stand for 30 minutes to allow bubbles of different pore sizes to be evenly distributed;

[0072] The cast sample is first steam cured at 25°C in an environment with RH≥90% for 24h to promote the hydration reaction of cement and the early strength development of the material; then, a mixed gas containing 20vol.% CO2 is introduced, and the pressurized curing is carried out at 35°C and 0.2MPa for 6h to obtain the full tailings filling body (i.e. full tailings filling material). In this process, CO2 reacts with the components in the material to generate carbonates and other substances, which not only enhances the compressive strength of the material, but also increases the adsorption amount of CO2 of the filling material, realizes a certain degree of carbon sequestration, and has environmental benefits.

[0073] Figure 1 The schematic diagram of the bubble-nanoparticle composite structure in the full tailings filling material prepared for Example 1; as can be seen from the figure, the surface of the bubbles generated by the air entraining agent is covered with a HPMC protective film, and the nanoparticles (SiO2, ZrO2, MgO) are anchored at the film interface by electrostatic adsorption to play a bubble stabilizing role.

[0074] Figure 2 The microelectronic microscope graph of the three-level pore structure in the full tailings filling material prepared for Example 1; as can be seen from the figure, the three-level pore structure (large pores adsorb energy and transmit carbon, honeycomb pores adsorb CO2, and micropores strengthen mechanics to seal and store carbon) realizes the dual optimization of the mechanical properties of the filling body and the efficient fixation of CO2.

[0075] Figure 3 The CO2 penetration-adsorption synergistic mechanism diagram of the full tailings filling material; as can be seen from the figure, the pore structure provides channels and spaces for CO2 penetration and adsorption, helping CO2 to penetrate into the interior; at the same time, the calcium ions and magnesium ions in the material react with the adsorbed CO2 to generate CaCO3, MgCO3 and other substances, through the dual action of the adsorption and accommodation of CO2 by the pores and the mineralization reaction of calcium and magnesium ions, the efficient fixation of CO2 is realized, and the performance of the filling body is synergistically improved.

[0076] Example 2

[0077] A full tailings filling body transparence and carbon fixation method based on bubble regulation, specifically comprising the following steps:

[0078] Step 1, preparation of materials and equipment

[0079] Prepare the filling equipment for preparing the filling paste (filling material), and prepare the raw materials for preparing the filling paste according to the formula, except water, the formula includes the following raw materials in weight percentage:

[0080] Tailings 80%, Portland cement 12%, nano-SiO2 4.3%, nano-ZrO2 3%, hydroxypropyl methylcellulose (HPMC) 0.1%, air entraining agent (mass ratio of sodium dodecyl sulfate to whey protein is 1:2) 0.1%, and nano-MgO 0.5%; wherein the tailings need to be screened and pretreated to ensure that the particle size range of the tailings is <0.15 mm and impurities are removed;

[0081] Step two, preparation of paste filling material

[0082] S1: The weighed tailings, cement, nano-ZrO2, nano-SiO2, and nano-MgO were sequentially added to a blender in order, and dry mixing was performed, wherein the stirring speed was 100 rpm, and the stirring time was 3 min, to ensure uniform mixing of the various solid raw materials. After stirring, a full tailings mixture was obtained;

[0083] S2: Water was added to the full tailings mixture in an amount of 30% of the total mass of the solid raw materials, and air entraining agent and HPMC were sequentially added during stirring. After the addition of the air entraining agent, high-speed stirring was performed at 250 rpm to introduce uniform and stable micro-bubbles, improve the pore structure of the material, and improve the impermeability and durability of the material. The addition of HPMC further enhances the cohesiveness and water retention of the material, making it easier to operate during construction. The total mixing time was 10 min.

[0084] S3: After stirring was completed, the full tailings filling material was subjected to ultrasonic treatment. Double-frequency ultrasonic waves (20 kHz + 100 kHz) were used for pulsed ultrasonic treatment (working for 5 s and pausing for 2 s), with a duration of 2 min, to eliminate large bubbles and ensure that the bubble size was within a reasonable range (0-200 μm);

[0085] Step three, sample pouring and curing

[0086] The stirred filling material was poured into a mold. After pouring, it was allowed to stand for 30 min to ensure uniform distribution of bubbles of different diameters.

[0087] The poured sample was first subjected to steam curing at 25°C in an environment with a relative humidity RH≥90% for 24 h to promote the hydration reaction of the cement and the early strength development of the material. Subsequently, a mixed gas containing 20 vol.% CO2 was introduced, and the sample was subjected to pressurized curing at 35°C and 0.2 MPa for 6 h. During this process, CO2 reacted with the components in the material to form carbonates and other substances, which not only enhanced the compressive strength of the material but also increased the adsorption capacity of the filling material for CO2, achieving a certain degree of carbon sequestration and having environmental benefits.

[0088] Example 3

[0089] A method for increasing the permeability and carbon sequestration of a full tailings filling body based on bubble regulation, specifically comprising the following steps:

[0090] Step one, preparation of materials and equipment

[0091] Prepare the filling equipment for the preparation of the filling paste (filling material), and prepare the raw materials for the preparation of the filling paste according to the formula, in addition to water, the formula includes the following raw materials in weight percentage:

[0092] 80% tailings, 12% P042.5 cement, 2.7% nano-SiO2, 3% nano-ZrO2, 0.3% hydroxypropyl methyl cellulose (HPMC), 0.5% air entraining agent (mass ratio of sodium dodecyl sulfate and whey protein is 1:2), and 1.5% nano-MgO; wherein the tailings need to be screened (through a 100 mesh screen) and pretreated to ensure that the particle size range of the tailings is <0.15mm, and impurities are removed to ensure the stability of the particle size and composition;

[0093] Step two, preparation of paste filling material

[0094] S1: sequentially add the weighed tailings, cement, nano-ZrO2, nano-SiO2 and nano-MgO into the mixer in order, dry mix, wherein the stirring speed is 100 rpm, the stirring time is 3 min, and ensure that the various solid raw materials are uniformly mixed, and the full tailings mixture is obtained after stirring;

[0095] S2: add 30% solid water to the above full tailings mixture, and sequentially add air entraining agent and HPMC during stirring; wherein, after adding the air entraining agent, stir at a high speed of 250 rpm to introduce uniform and stable micro-bubbles, improve the pore structure of the material, and improve the impermeability and durability of the material; the addition of HPMC further enhances the adhesion and water retention of the material, making the material easier to operate during construction. The entire mixing time is 10 min;

[0096] S3: after stirring, the full tailings filling material is treated by ultrasonic waves, double-frequency ultrasonic waves (20kHz+100kHz) pulse ultrasonic treatment (work for 5s, pause for 2s), the duration is 2min, to eliminate large bubbles and ensure that the particle size of the bubbles is within a reasonable range (0-200μm);

[0097] Step three, sample pouring and curing

[0098] Pour the stirred filling material obtained in step two into the mold; after pouring, stand for 30 min to make the bubbles of different pore sizes uniformly distributed;

[0099] After the completion of the pouring process, the curing phase is entered immediately. The poured sample is placed in an environment with a temperature of 25°C and a relative humidity RH≥90% for steam curing for 24 hours. In such a hot and humid environment, the hydration reaction of cement can be greatly promoted. Various components in the cement undergo a series of complex chemical reactions with water to generate a large amount of hydration products, which gradually fill the pores inside the material, making the structure of the material more dense, thereby promoting the rapid development of the early strength of the material.

[0100] Subsequently, the CO2 pressurized curing phase is entered. The steam-cured sample is introduced into a mixed gas environment containing 20 vol.% CO2, and pressurized curing is carried out for 6 hours at a temperature of 35°C and a pressure of 0.2 MPa. In this process, CO2 reacts chemically with various components in the material. The generated carbonates and other substances fill the pores inside the material, enhancing the compressive strength of the material; and also increase the adsorption amount of CO2 in the filling material, achieving a certain degree of carbon sequestration. The carbon sequestration process reduces the emission of greenhouse gases, while also improving the performance of the material.

[0101] Comparative Example 1 (ordinary carbon sequestration method)

[0102] A carbon sequestration method of a filling material, comprising the following steps:

[0103] Step one, preparation of materials and equipment

[0104] Prepare the filling equipment for preparing the filling paste (filling material), and prepare the raw materials for preparing the filling paste according to the formula, except water, the formula includes the following weight percentage of raw materials:

[0105] 60% tailings, 20% PO42.5 cement, 10% CO2 suspension, 10% magnesium oxide powder (average particle size 1 μm); wherein the tailings need to be screened and pretreated to ensure that there are no impurities in the tailings and the particle size is <0.15 mm;

[0106] The CO2 suspension is made by introducing 25 cm 3 of CO2 per liter of saturated Mg(OH)2 solution;

[0107] Step two, preparation of paste filling material

[0108] S1: The weighed tailings, cement and magnesium oxide powder are added to the mixer and dry mixed, the stirring time is 3 min, to ensure uniform mixing of various solid raw materials, and the full tailings mixture is obtained after stirring;

[0109] S2: Add water to the above-mentioned whole tailings mixture and stir it according to a solid-liquid mass ratio of 4:1 (wherein, in the solid-liquid ratio, the solid is the sum of all other raw materials except the CO2 suspension), and add the CO2 suspension during the stirring process; the stirring speed is 200 rpm, and the stirring and mixing time is 10 minutes, and the whole tailings mixture obtained after stirring is as homogeneous as possible;

[0110] Step 3: Sample pouring and curing

[0111] Pour the mixed filling material into the mold;

[0112] The cast samples were steam-cured for 24 hours at 25°C and relative humidity RH ≥ 90% to promote the hydration reaction of the cement and the early strength development of the material; a certain degree of carbon sequestration was achieved, which has environmental benefits.

[0113] Comparative Example 2

[0114] The difference from Example 1 is that no nano-SiO2 is added to the raw materials, and other raw material compositions and preparation conditions are the same as in Example 1.

[0115] Comparative Example 3

[0116] The difference from Example 1 is that HPMC is not added to the raw materials, and other raw material compositions and preparation conditions are the same as in Example 1.

[0117] Comparative Example 4

[0118] The difference from Example 1 is that no nano-MgO is added to the raw materials, and other raw material compositions and preparation conditions are the same as in Example 1.

[0119] Performance testing and verification

[0120] After the curing is completed, the compressive strength, permeability coefficient, CO2 adsorption capacity, CO2 adsorption rate and CO2 storage rate of the filling material are tested in accordance with relevant standards.

[0121] The compressive strength test of the sample was carried out in accordance with the "Test Method for Cement Mortar Strength" (GB / T17671-2021).

[0122] Darcy's law can be used to describe the migration of gas in the filling body, and the gas permeability coefficient is:

[0123]

[0124] Where: P is the absolute pressure of the reactor (Pa); q is the gas inlet flow rate (m 3 / s); g is the acceleration due to gravity; ρ a is the gas density (kg / m 3 ); A is the cross-sectional area of ​​the specimen (m2 ) ; P atm is the ambient atmospheric pressure (Pa).

[0125] To determine the CO2 adsorption amount of the sample, a double flow meter system was used for dynamic monitoring, using two flow meters to monitor and record the instantaneous CO2 consumption, temperature and absolute pressure (AP), one at the reactor inlet and one at the reactor outlet. The inlet flow meter records the total CO2 flow (L / min) and the cumulative volume (L) into the mold, and the outlet flow meter synchronously records the corresponding parameters of the exhaust gas after the reaction. The total amount of adsorbed CO2 is accurately quantified by the cumulative CO2 volume difference between the inlet and outlet. The calculation formula is

[0126]

[0127] In the formula, L1 and L2 are the cumulative volumes of the inlet flow meter and the inlet flow meter, respectively.

[0128] To determine the CO2 adsorption rate of the sample during carbonation curing, based on the dual mechanism of physical adsorption and chemical reaction during the carbonation process of the sample, a function model of the carbon sequestration amount with time evolution is established:

[0129]

[0130]

[0131] In the formula: Q (t) is the carbon sequestration amount per unit volume of the sample at time t (kg / m 3 ) ; is the porosity of the sample at time t (0-1), is the initial porosity (0-1) ; γ is the pore clogging rate (day -1 ) ; τ (t) is the tortuosity of the sample at time t (τ≥1) ; τ0 is the initial tortuosity (τ≥1) ; λ is the densification coefficient of carbonation products (day -1 / (kg / m 2 ) ) ; A is the physical adsorption capacity coefficient (kg / m 3 ) ; α is the physical adsorption rate constant (day -1 ) ; B is the chemical adsorption capacity coefficient (kg / m 3 ) ; k0 is the intrinsic reaction constant (day -1 ) ; E is the carbonation reaction activation energy (kJ / mol) ; R is the gas constant; T is the absolute temperature (K) ; β is the chemical reaction rate adjustment factor.

[0132] Then the adsorption rate of CO2 is:

[0133]

[0134] wherein: V is the carbon dioxide adsorption rate (m / s); 3

[0135] The instantaneous adsorption rate of CO2 is:

[0136]

[0137] To determine the CO2 storage rate of the sample after carbonization curing, the dried sample is crushed and heated in a temperature range of 20-1000℃ using a TG209 F3 type thermal gravimetric analyzer (TGA). The heating process is carried out in an inert gas N2 atmosphere. The mass loss of the tested sample between 600-950℃ is taken as the CO2 storage rate, and the calculation formula is:

[0138]

[0139] wherein, M1 and M2 are the mass of the lightweight aggregate sample at 600 and 950℃, respectively; M dry is the dry mass of the sample.

[0140] Table 1: The corresponding effect data of the filling materials prepared in Examples 1-3 and Comparative Examples 1-4 at 28d

[0141]

[0142]

[0143] Conclusion: From the data in Table 1, it can be seen that compared with the filling paste prepared by the current ordinary carbon sequestration method (Comparative Example 1), the full tailings filling material prepared by the method of the present application has a 10%-15% increase in 28-day compressive strength; the permeability coefficient is increased by 2-3 orders of magnitude (up to 10 -6 m / s level), which is beneficial to the diffusion of CO2 in the filling body and facilitates the progress of CO2 adsorption; the CO2 storage rate is increased by 3-5 times, i.e., it has a large CO2 mineralization storage capacity, which can realize large-scale mineralization of CO2 in mines.

[0144] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements easily thought of by those skilled in the art within the technical scope disclosed by the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.​

Claims

1. A method for enhancing carbon fixation of full tailings filling based on bubble control, characterized in that: The following steps are involved: The raw materials are stirred evenly; then ultrasonic treatment is performed with a dual-frequency ultrasonic wave to obtain a full tailings mixed slurry; The whole tailings mixed slurry is poured, subjected to wet heat curing and carbon dioxide atmosphere curing to obtain the whole tailings filling body; Wherein, excluding water, the raw materials include, by mass percentage: Tailings 80%, cement 12%, nano-SiO2 2% to 5%, nano-ZrO2 1% to 3%, hydroxypropyl methylcellulose 0.05% to 1%, air entraining agent 0.1% to 0.5% and nano-MgO 0.5% to 1.5%; The air entraining agent is obtained by compounding an anionic surfactant and a protein-based natural foaming agent.

2. The method for enhancing carbon fixation of full tailings filling based on bubble control according to claim 1, characterized in that: The mass ratio of the anionic surfactant to the protein-based natural foaming agent is 1:(1-2).

3. The method for enhancing carbon fixation of full tailings filling based on bubble control according to claim 2, characterized in that: The anionic surfactant is sodium lauryl sulfate; The protein-based natural foaming agent is whey protein or soy protein.

4. The method for enhancing carbon fixation of full tailings filling based on bubble control according to claim 1, characterized in that: The particle size of the nano ZrO2 is 30 to 50 nm.

5. The method for enhancing carbon fixation of full tailings filling based on bubble control according to claim 1, characterized in that: The average particle size of the nano-MgO is 40 nm.

6. The method for enhancing carbon fixation of full tailings filling based on bubble control according to claim 1, characterized in that: The particle size of the nano-SiO2 is 20nm to 50nm.

7. The method for enhancing carbon fixation of full tailings filling based on bubble control according to claim 1, characterized in that: The specific steps of the method for enhancing carbon fixation of full tailings filling body based on bubble control are as follows: Add the tailings, cement, nano ZrO2, nano SiO2 and nano MgO into a mixer in order according to mass percentage and dry mix them to obtain a full tailings mixture; Adding water to the whole tailings mixture, and sequentially adding an air entraining agent and hydroxypropyl methylcellulose while stirring to perform wet mixing; then performing ultrasonic treatment with a dual-frequency ultrasonic wave to obtain a whole tailings mixed slurry; The whole tailings mixed slurry is poured, subjected to wet heat curing and carbon dioxide atmosphere curing to obtain the whole tailings filling body.

8. The method for enhancing carbon fixation of full tailings filling based on bubble control according to claim 7, characterized in that: The rotation speed of the wet mixing is 100-300 rpm.

9. The method for enhancing carbon fixation of full tailings filling based on bubble control according to claim 7, characterized in that: The dual-frequency ultrasonic parameters are 20kHz+100kHz; the pulse mode is working for 5s and pausing for 2s.

10. The method for enhancing carbon fixation of full tailings filling based on bubble control according to claim 7, characterized in that: The viscosity of the whole tailings mixed slurry is 0.75-1.0 Pa·s, and the yield stress is 100-130 Pa; The temperature during the moist heat curing process is 25-30°C.

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