Amino acid mediated coal-based solid waste negative carbon filling material and preparation method thereof

Abstract

The invention relates to an amino acid-mediated coal-based solid waste negative carbon filling material and a preparation method thereof, and the method comprises the following steps: adding an amino acid aqueous solution as a fly ash activator and fly ash into a first-section mineralization reaction kettle, introducing CO2 to carry out mineralization reaction, separating slurry obtained by the first-section mineralization reaction to obtain fly ash mineralization residues, and adding the fly ash mineralization residues into the first-section mineralization reaction kettle; the filtrate is recovered to the first-section mineralization reaction kettle for cyclic utilization; adding the coal ash mineralization residues, coal gangue, cement, NaOH, glucose and water into a second-stage mineralization reaction kettle, and introducing CO2 gas for mineralization reaction to obtain the negative carbon filling material. The negative carbon filling material with high carbon sequestration amount and high solid waste mixing amount is prepared through two-stage mineralization reaction, and the material has good fluidity before solidification and certain compressive strength after solidification, and can meet the use requirements of mine filling; wherein the amino acid solution can play a role in leaching Ca < 2 + > / Mg < 2 + > ions in the fly ash, the transfer of protons and CO2 is enhanced, and the carbon sequestration effect is remarkable.

Description

Technical Field

[0001] This invention relates to the field of mine management and carbon dioxide sequestration technology, specifically to an amino acid-mediated coal-based solid waste negative carbon backfill material and its preparation method. Background Technology

[0002] Utilizing coal-based solid waste (fly ash, coal gangue) to prepare negative carbon backfill materials and applying them to backfilling coal mine goaf areas is a technological approach with multiple significant advantages and strategic importance.

[0003] Current research on the preparation of negative carbon backfill materials for mines using coal-based solid waste is quite extensive. Patent publication number CN120004565A discloses a mineralized CO2-sequestering cemented backfill mortar material for mines and its preparation method. This method uses carbonic anhydrase-producing microorganisms, aggregates, calcium source solution, and nano-zinc oxide as raw materials, which can effectively increase carbon dioxide sequestration to meet low-carbon and carbon reduction requirements, and significantly accelerate CO2 hydration to HCO3-. - / CO3 2- The reaction rate is increased, thereby promoting the CO2 hydration reaction and subsequent gelation, and improving the environmental protection and low-carbon performance of the material.

[0004] Patent CN119951390A discloses a method for preparing solid carbon energy-absorbing paste fillers based on supercritical carbon dioxide (SC-CO2) foaming. The method first involves crushing and grinding coal-based solid waste raw materials, then mixing them with mixing water at a speed below 60 r / min to form a coal-based solid waste slurry. During the mixing process, supercritical CO2 is continuously injected until a set pressure is reached, allowing it to penetrate the slurry and form a mixture of supercritical CO2 and the slurry. This mixture is then stirred by a turbine to form the base slurry for the foam paste filler. This base slurry is held at high temperature and pressure in a high-temperature, high-pressure mixer for 10-30 minutes, followed by rapid depressurization, ultimately forming a large quantity of coal-based solid waste foam paste fillers with supercritical CO2 as the foam nucleus, completing the foaming process. The resulting filler exhibits low density, good thermal insulation performance, and a controllable cell structure.

[0005] Patent CN119954474A discloses a backfill material based on multi-component solid waste, its preparation method, and its application. The material consists of the following solid components by mass percentage: 10%-20% artificial granite slag, 0%-20% fly ash, 10%-20% phosphogypsum, with the balance being calcined kaolin and calcium carbide slag, and the mass ratio of calcined kaolin to calcium carbide slag being 1.6:1. This invention significantly improves the utilization rate of bulk industrial solid wastes such as phosphogypsum, calcium carbide slag, and fly ash, alleviating the land occupation and environmental pollution problems caused by their large-scale stockpiling; it also ensures that the material still has excellent compressive strength under high solid waste content conditions, making it suitable for various application scenarios such as mine backfilling.

[0006] However, the aforementioned research on the preparation of mine backfill materials from coal-based solid waste has problems such as low carbon sequestration, complex processes, and high costs. Summary of the Invention

[0007] The purpose of this invention is to provide an amino acid-mediated coal-based solid waste negative carbon backfill material and its preparation method. The method is simple, the amino acid aqueous solution used as a fly ash activator can be recycled and reused, reducing costs, and the prepared backfill material can increase the carbon fixation capacity.

[0008] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0009] A method for preparing an amino acid-mediated coal-based solid waste negative carbon backfill material includes the following steps:

[0010] S1. Prepare an amino acid aqueous solution of 1-3% by mass as an activator for fly ash; add a certain volume of amino acid aqueous solution to a first-stage mineralization reactor, then add fly ash according to a certain solid-liquid ratio, stir at room temperature, and mix thoroughly before use;

[0011] S2. CO2 gas is introduced into the first-stage mineralization reactor to initiate a mineralization reaction. After the reaction, the slurry in the first-stage mineralization reactor is transported to the solid-liquid separation unit through a pipeline.

[0012] S3. The fly ash mineralization residue and filtrate are separated by a plate and frame filter press. Most of the amino acids are still retained in the filtrate. The filtrate is recycled back to step S1.

[0013] S4. Add the fly ash mineralization residue obtained in step S3 to the second-stage mineralization reactor in a certain proportion, along with coal gangue, cement, NaOH, and glucose. Add a certain amount of water in a certain liquid-solid ratio. Stir at room temperature until all materials in the second-stage mineralization reactor are fully mixed and ready for use.

[0014] S5. CO2 gas is introduced into the two-stage mineralization reactor to carry out the two-stage mineralization reaction and obtain negative carbon filling material.

[0015] Preferably, in step S1, the particle size of the fly ash after pretreatment is less than 0.075 mm; in step S4, the particle size of the coal gangue after pretreatment is 2-5 mm.

[0016] Preferably, in step S1, the solid-liquid ratio is 100-500 g / L, the stirring speed of the first-stage mineralization reactor is 600 rpm, and the stirring time is 5 min.

[0017] Preferably, in step S1, the amino acid is one of glycine, aspartic acid, glutamic acid, and alanine.

[0018] Preferably, in step S2, the mineralization reaction pressure is 0.5–2 MPa and the mineralization reaction time is 20 min.

[0019] Preferably, in step S4, the proportions of each material in the two-stage mineralization reactor are as follows: fly ash mineralization residue 30-40 wt%, coal gangue 40-50 wt%, cement 16-19 wt%, NaOH 1-3 wt%, and glucose 0.1-0.5 wt%.

[0020] Preferably, in step S4, the liquid-to-solid ratio is 0.3 L / kg, the stirring speed of the two-stage mineralization reactor is 600 rpm, and the stirring time is 5 min.

[0021] Preferably, in step S5, the pressure of the second-stage mineralization reaction is 0.5–2 MPa, and the mineralization reaction time is 20 min.

[0022] Preferably, in steps S2 and S5, the CO2 comes from a carbon capture device in a coal-fired power plant and has a purity higher than 98%.

[0023] To achieve the above-mentioned objectives, the present invention also provides an amino acid-mediated coal-based solid waste negative carbon backfill material prepared by the above-described preparation method.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) This invention first employs a wet direct mineralization method, simultaneously adding fly ash and a low-concentration amino acid solution (<3%) to the reactor. After stirring in the reactor for 5 minutes to ensure uniform mixing of the amino acid solution and fly ash, CO2 or industrial flue gas is then introduced into the reactor to allow the leached Ca to precipitate. 2+ The precipitate forms calcium carbonate and regenerates amino acids. Amino acids activate the mineralization reaction of calcium-containing minerals in fly ash, significantly increasing the CO2 absorption capacity of fly ash. Simultaneously, amino acids play a proton transfer role in the reaction process and are theoretically not consumed. The calcium in solid waste... 2+ Dissolution and CO2 mineralization occur simultaneously; amino acids have extremely low toxicity, are easily biodegradable, and leave very low residues in negative carbon filling materials, causing no environmental pollution; after the reaction, solid-liquid separation equipment is used to separate fly ash filter residue and filtrate, and more than 90% of amino acids can be recovered from the filtrate, significantly reducing carbon fixation costs, and the obtained filtrate can be recycled.

[0026] (2) In this invention, fly ash filter residue and crushed coal gangue are mixed in a certain proportion, and a small amount of cement is added as a binder, sodium hydroxide as an alkali activator and glucose as a retarder to further absorb CO2, so that the prepared filling material has high fluidity before solidification, is easy to fill, and has a certain strength after solidification, which can prevent the collapse of the goaf in the mine; the addition of retarder can delay the solidification time of the slurry, which is beneficial to the transportation of negative carbon filling material. Attached Figure Description

[0027] Figure 1 This is a flowchart of the preparation process of the present invention;

[0028] Figure 2 This is a schematic diagram of the solidified appearance of the negative carbon filling material prepared in Example 6 of the present invention. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to specific embodiments.

[0030] Example 1

[0031] like Figure 1 As shown, a method for preparing an amino acid-mediated coal-based solid waste negative carbon backfill material includes the following steps:

[0032] S1. Prepare a 1% glycine aqueous solution by mass percentage and place it in a reaction vessel. Add fly ash to the reaction vessel at a solid-liquid ratio of 100 g / L. The reaction temperature is room temperature, and the stirring speed of the reaction vessel is 600 rpm. Stir continuously for 5 minutes to ensure that the amino acid aqueous solution and fly ash are fully mixed.

[0033] S2. CO2 gas is introduced into the first-stage mineralization reactor to initiate a mineralization reaction. The CO2 pressure inside the reactor is maintained at 0.5 MPa. After the reaction lasts for 20 minutes, the slurry in the first-stage mineralization reactor is transported to the solid-liquid separation unit through a pipeline.

[0034] S3. The fly ash mineralization residue and filtrate are separated by a plate and frame filter press. Most of the amino acids are still retained in the filtrate. The filtrate is recycled back to step S1.

[0035] S4. Add the fly ash mineralization residue obtained in step S3 to the secondary mineralization reactor in a certain proportion, along with coal gangue, cement, NaOH, and glucose. Add a certain amount of water at a liquid-to-solid ratio of 0.3 L / kg. Stir continuously at 600 rpm for 5 minutes at room temperature until all materials in the secondary mineralization reactor are fully mixed and ready for use. The proportions of each material in the secondary mineralization reactor are as follows: fly ash mineralization residue 30 wt%, coal gangue 50 wt%, cement 18.9 wt%, NaOH 1 wt%, and glucose 0.1 wt%.

[0036] S5. CO2 gas is introduced into the second-stage mineralization reactor to maintain the CO2 pressure inside the reactor at 0.5 MPa. The reaction is stopped after 20 minutes to obtain negative carbon filling material. The negative carbon filling material is transported to the outside through pipelines and then transported to the downhole filling area by a filling pump. The data on carbon fixation and compressive strength in this embodiment are shown in Table 1.

[0037] Example 2

[0038] The difference between this embodiment and Embodiment 1 is that: the amino acid used in step S1 is aspartic acid; in step S4, the proportions of each material in the two-stage mineralization reactor are: fly ash mineralization residue 40 wt%, coal gangue 40 wt%, cement 18.9 wt%, NaOH 1 wt%, and glucose 0.1 wt%; all other steps remain the same as in Embodiment 1. The data on carbon fixation and compressive strength of this embodiment are shown in Table 1.

[0039] Example 3

[0040] The difference between this embodiment and Embodiment 1 is that: the amino acid used in step S1 is glutamic acid; in step S4, the proportions of each material in the two-stage mineralization reactor are: fly ash mineralization residue 30 wt%, coal gangue 50 wt%, cement 16.9 wt%, NaOH 3 wt%, and glucose 0.1 wt%; all other steps remain the same as in Embodiment 1. The data on carbon fixation and compressive strength of this embodiment are shown in Table 1.

[0041] Example 4

[0042] The difference between this embodiment and Embodiment 1 is that: the amino acid used in step S1 is alanine; in step S4, the proportions of each material in the two-stage mineralization reactor are: fly ash mineralization residue 40 wt%, coal gangue 40 wt%, cement 16.5 wt%, NaOH 3 wt%, and glucose 0.5 wt%; all other steps remain the same as in Embodiment 1. The data on carbon fixation and compressive strength of this embodiment are shown in Table 1.

[0043] Example 5

[0044] The difference between this embodiment and Embodiment 1 is that the concentration of glycine used in step S1 is increased to 3 wt%; in step S4, the proportions of each material in the two-stage mineralization reactor are: fly ash mineralization residue 40 wt%, coal gangue 40 wt%, cement 18.9 wt%, NaOH 1 wt%, and glucose 0.1 wt%; all other steps remain the same as in Embodiment 1. The data on carbon fixation and compressive strength of this embodiment are shown in Table 1.

[0045] Example 6

[0046] The difference between this embodiment and Embodiment 1 is that: in step S1, the mineralization reaction pressure is increased to 2 MPa, and the stirring speed of the reactor is increased to 500 rpm; in step S4, the proportions of each material in the two-stage mineralization reactor are: fly ash mineralization residue 40 wt%, coal gangue 40 wt%, cement 17 wt%, NaOH 2.9 wt%, and glucose 0.1 wt%; all other steps remain the same as in Embodiment 1. The data on carbon fixation and compressive strength of this embodiment are shown in Table 1.

[0047] Example 7

[0048] The difference between this embodiment and Embodiment 1 is that: in step S1, the glycine concentration is increased to 3 wt%, and the stirring speed of the reactor is increased to 500 rpm; in step S4, the proportions of each material in the two-stage mineralization reactor are: fly ash mineralization residue 40 wt%, coal gangue 40 wt%, cement 18.5 wt%, NaOH 1 wt%, and glucose 0.5 wt%; all other steps remain the same as in Embodiment 1. The carbon fixation amount and compressive strength data of this embodiment are shown in Table 1.

[0049] Table 1 Carbon fixation content and compressive strength

[0050]

[0051] As shown in Table 1, adding amino acids can effectively increase the carbon fixation of fly ash. The carbon fixation of fly ash is related to the amount of amino acids added and the solid-liquid ratio. When the amount of amino acids added is 3wt% and the solid-liquid ratio is 100g / L, the carbon fixation reaches its maximum of 64.54g / kg. The carbon fixation of the secondary mineralization of the filling material is related to the proportion of coal gangue, cement, and sodium hydroxide. The carbon fixation increases with the increase of the proportion of the above materials. The compressive strength of the material after solidification is related to the proportion of coal gangue, cement, sodium hydroxide, and glucose. Among them, increasing the proportion of coal gangue, cement, and sodium hydroxide can increase the strength of the material after solidification, while increasing the proportion of glucose will decrease the strength. Under the optimal ratio, the carbon fixation of the secondary mineralization is 29.78g / kg, and the compressive strength is 8.07MPa. After conversion, each ton of solid waste has a combined carbon fixation of 69.50kg, which shows a significant carbon fixation effect. The filling material prepared in Example 5 is as follows: Figure 2 As shown.

[0052] In summary, this invention utilizes fly ash and coal gangue as main raw materials, amino acid aqueous solution as an activator, cement as a binder, glucose as a retarder, and NaOH as an alkali activator to prepare a negative carbon backfill material with high carbon fixation and high solid waste content through a two-stage mineralization reaction. This material exhibits good fluidity before solidification and a certain compressive strength after solidification, meeting the requirements for mine backfilling. The amino acid solution can neutralize the calcium in fly ash...2+ / Mg 2+ Ion leaching enhances proton and CO2 transfer, resulting in significant carbon fixation.

Claims

1. A method for preparing an amino acid-mediated coal-based solid waste negative carbon backfill material, characterized in that, Includes the following steps: S1. Prepare an amino acid aqueous solution of 1-3% by mass as an activator for fly ash; add a certain volume of amino acid aqueous solution to a first-stage mineralization reactor, then add fly ash according to a certain solid-liquid ratio, stir at room temperature, and mix thoroughly before use; S2. CO2 is introduced into the first-stage mineralization reactor to carry out a mineralization reaction. After the reaction, the slurry in the first-stage mineralization reactor is transported to the solid-liquid separation unit through a pipeline. S3. The fly ash mineralization residue and filtrate are separated by a plate and frame filter press. Most of the amino acids are still retained in the filtrate. The filtrate is recycled back to step S1. S4. Add the fly ash mineralization residue obtained in step S3 to the second-stage mineralization reactor in a certain proportion, along with coal gangue, cement, NaOH, and glucose. Add a certain amount of water in a certain liquid-solid ratio. Stir at room temperature until all materials in the second-stage mineralization reactor are fully mixed and ready for use. S5. CO2 is introduced into the two-stage mineralization reactor to carry out the two-stage mineralization reaction and obtain negative carbon filling material.

2. The method for preparing an amino acid-mediated coal-based solid waste negative carbon backfill material according to claim 1, characterized in that, In step S1, the particle size of the fly ash after pretreatment is less than 0.075 mm; in step S4, the particle size of the coal gangue after pretreatment is 2-5 mm.

3. A method for preparing an amino acid-mediated coal-based solid waste negative carbon backfill material according to claim 1 or 2, characterized in that, In step S1, the solid-liquid ratio is 100-500 g / L, the stirring speed of the first-stage mineralization reactor is 600 rpm, and the stirring time is 5 min.

4. A method for preparing an amino acid-mediated coal-based solid waste negative carbon backfill material according to claim 1 or 2, characterized in that, In step S1, the amino acid is one of glycine, aspartic acid, glutamic acid, and alanine.

5. A method for preparing an amino acid-mediated coal-based solid waste negative carbon backfill material according to claim 1 or 2, characterized in that, In step S2, the mineralization reaction pressure is 0.5–2 MPa and the mineralization reaction time is 20 min.

6. A method for preparing an amino acid-mediated coal-based solid waste negative carbon backfill material according to claim 1 or 2, characterized in that, In step S4, the proportions of each material in the two-stage mineralization reactor are as follows: fly ash mineralization residue 30-40 wt%, coal gangue 40-50 wt%, cement 16-19 wt%, NaOH 1-3 wt%, and glucose 0.1-0.5 wt%.

7. A method for preparing an amino acid-mediated coal-based solid waste negative carbon backfill material according to claim 1 or 2, characterized in that, In step S4, the liquid-to-solid ratio is 0.3 L / kg, the stirring speed of the two-stage mineralization reactor is 600 rpm, and the stirring time is 5 min.

8. A method for preparing an amino acid-mediated coal-based solid waste negative carbon backfill material according to claim 1 or 2, characterized in that, In step S5, the pressure of the second-stage mineralization reaction is 0.5–2 MPa, and the mineralization reaction time is 20 min.

9. A method for preparing an amino acid-mediated coal-based solid waste negative carbon backfill material according to claim 1 or 2, characterized in that, In steps S2 and S5, the CO2 comes from the carbon capture device of a coal-fired power plant and has a purity of over 98%.

10. An amino acid-mediated coal-based solid waste negative carbon backfill material prepared by the preparation method of any one of claims 1-9.

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