Penetrability-adjustable high-porosity gangue-based filling material, preparation method and application thereof

Abstract

This invention discloses a permeability-adjustable high-porosity gangue-based backfill material, its preparation method, and its application, belonging to the field of coal-based solid waste resource utilization and carbon sequestration. The permeability-adjustable high-porosity gangue-based backfill material, by mass, comprises the following components: 70-80 parts coal gangue aggregate, 30-40 parts activated coal gangue powder, 25-40 parts alkaline activator, 1-3 parts foaming agent, 0.5-2 parts polypropylene fiber, and 5-15 parts water. This invention, by adjusting the dosage of foaming agent and polypropylene fiber, can control the permeability of the backfill material, promoting the migration and diffusion of CO2 gas in the pores and solving the problem of low CO2 sequestration efficiency caused by pore closure. Using gangue with a particle size of 10-15 mm as coarse aggregate, and through a surface spraying process of the binder, the prepared backfill material exhibits high porosity and excellent mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of coal-based solid waste resource utilization and carbon sequestration, and specifically relates to a permeability-adjustable high-porosity gangue-based backfill material, its preparation method, and its application. Background Technology

[0002] In the process of coal development and utilization, the discharge of solid waste such as gangue seriously restricts the efficient production and coordinated development of the ecological environment in mining areas. On-site backfilling of gangue underground can directly fill the underground goaf after crushing and processing the gangue solid waste. This method is one of the key technologies for the disposal and utilization of gangue solid waste in mining areas. However, the traditional gangue backfilling method currently faces some problems: First, the gangue output of the mine accounts for about 15%-20% of the raw coal output. Direct backfilling is limited by the output and is prone to gangue shortage. Second, the gangue needs to be compacted multiple times when directly transported to the goaf for backfilling, which affects the coal mining speed. In addition, the traditional backfilling process is difficult to coordinate and control the porosity and permeability of the backfilling material. The unreasonable particle size distribution of gangue is prone to causing the pore structure to be closed, which not only affects the permeability of the backfill body, but also limits its application potential in CO2 sequestration.

[0003] Currently, research on carbon fixation filling materials is still in its early stages. Existing technologies generally suffer from problems such as low carbon fixation efficiency and uncontrollable material permeability, making it difficult to achieve long-term storage. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a permeability-adjustable high-porosity gangue-based backfill material, its preparation method, and its applications. The method involves activating coal gangue powder with an alkali activator, adding coal gangue aggregate, and preparing the backfill material using a foaming agent and polypropylene fibers. This allows for flexible adjustment of the permeability in the backfill material, achieving large-scale gangue disposal and CO2 sequestration. The backfill material of this invention exhibits adjustable permeability, high porosity, excellent mechanical properties, and good carbon sequestration performance.

[0005] One of the technical solutions provided by this invention:

[0006] A permeability-adjustable high-porosity gangue-based backfill material, comprising the following components by weight: 70-80 parts coal gangue aggregate, 30-40 parts activated coal gangue powder, 25-40 parts alkaline activator, 1-3 parts foaming agent, 0.5-2 parts polypropylene fiber, and 5-15 parts water.

[0007] Furthermore, the coal gangue aggregate has a particle size of 10-15mm to form a supporting skeleton structure and provide basic load-bearing capacity.

[0008] Furthermore, the activated coal gangue powder is obtained by crushing, calcining, and mechanically and chemically modifying coal gangue. The specific preparation method includes the following steps: calcining the crushed coal gangue powder; adding a chemical modifier to the calcined coal gangue powder, mixing it evenly, and then ball milling it to prepare the activated coal gangue powder.

[0009] Furthermore, the calcination temperature is 800℃ and the time is 1h; and / or, the mass ratio of the chemical modifier to the coal gangue powder is (3-9):30; and / or, the ball milling speed is 520rpm and the ball milling time is 3h; the particle size of the coal gangue powder is 0.2mm-1mm.

[0010] Calcination can catalyze the transformation of kaolinite inside coal gangue into metakaolinite, thereby stimulating the activity of coal gangue.

[0011] Furthermore, the chemical modifier is composed of calcium sulfate and sodium sulfate in a mass ratio of (2-6):(1-3).

[0012] Appropriate amounts of sulfate can enhance the formation of CSH gel, and a higher proportion of calcium sulfate results in the production of more ettringite, which is beneficial for strength development.

[0013] Furthermore, the alkaline activator includes at least one of sodium hydroxide and sodium silicate.

[0014] Furthermore, the mass ratio of sodium hydroxide to sodium silicate in the alkaline activator is (2-10):(15-20).

[0015] Furthermore, the foaming agent is composed of sodium fatty alcohol polyoxyethylene ether sulfate and dodecyl dimethylamine oxide in a mass ratio of (5-8):(1-2).

[0016] The second technical solution provided by this invention:

[0017] The preparation method of the above-mentioned permeability-adjustable high-porosity gangue-based backfill material includes the following steps:

[0018] Weigh the raw materials according to the mass fraction, mix the alkaline activator and water, let stand, then add the foaming agent, activated coal gangue powder and polypropylene fiber in sequence, mix and stir to obtain a permeability adjustable binder material; spray the permeability adjustable binder material evenly onto the surface of coal gangue aggregate, put it into a mold to solidify and harden, and prepare the permeability adjustable high porosity gangue-based filling material.

[0019] Furthermore, the coal gangue aggregate needs to be washed and dried before spraying.

[0020] The third technical solution provided by this invention:

[0021] A method for carbon sequestration in coal mining using the aforementioned adjustable-permeability high-porosity gangue-based backfill material involves filling the goaf with the adjustable-permeability high-porosity gangue-based backfill material using a backfilling hydraulic support, while simultaneously laying a CO2 gas delivery pipeline on the roof to seal CO2 through the adjustable-permeability high-porosity gangue-based backfill material.

[0022] Furthermore, the CO2 injection pressure is 0.1-0.3 MPa, and the pipeline spacing is 0.5-1 m.

[0023] This invention proposes using alkali activator to activate coal gangue powder as a binder, and using foaming agent and polypropylene fiber to control the permeability of the binder. Coal gangue with a particle size of 10-15mm is used as aggregate. The resulting gangue-based backfill material has high porosity, adjustable permeability, excellent mechanical properties, and good CO2 sequestration effect, aiming to provide a new material and sequestration method for the utilization of gangue solid waste, green backfilling, and CO2 sequestration.

[0024] Compared with the prior art, the present invention has the following advantages and technical effects:

[0025] (1) This invention uses gangue as raw material, realizing the large-scale disposal and graded utilization of gangue solid waste, which is green, economical and environmentally friendly.

[0026] (2) By adjusting the amount of foaming agent and polypropylene fiber, the permeability of the filling material can be controlled, promoting the migration and diffusion of CO2 gas in the pores and solving the problem of low CO2 storage efficiency caused by pore closure.

[0027] (3) Using gangue with a particle size of 10-15mm as coarse aggregate, the filling material prepared by the surface spraying process of the binder has high porosity and excellent mechanical properties. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a sample image of the high-porosity gangue-based filling material with adjustable permeability prepared according to the present invention. Detailed Implementation

[0030] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0031] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0032] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0033] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0034] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0035] This invention provides a method for preparing a permeability-adjustable high-porosity gangue-based backfill material, comprising the following steps:

[0036] S1. Coal gangue is successively crushed, calcined, and mechanically and chemically modified to obtain activated coal gangue powder;

[0037] S2. Mix the alkaline activator with water and stir for 30-60 minutes, let stand for 12-24 hours, then add the foaming agent, the activated coal gangue powder prepared in S1, and the polypropylene fiber in sequence, mix and stir for 10-30 minutes to obtain a permeability adjustable cohesive material.

[0038] S3. The permeability-adjustable binder material prepared in S2 is uniformly sprayed onto the coal gangue aggregate, and after being placed in a mold and solidified, a permeability-adjustable high-porosity coal-based solid waste filling material is prepared.

[0039] In a preferred embodiment of the present invention, the coal gangue aggregate has a particle size of 10-15 mm to form a supporting skeleton structure and provide basic load-bearing capacity.

[0040] In some preferred embodiments of the present invention, in step S1, the coal gangue is crushed to a particle size of 0.2 mm-1 mm; the calcination temperature is 800 °C and the time is 1 h, which can catalyze the conversion of kaolinite to metakaolinite and activate the activity of coal gangue; the chemical modifier used in the mechanochemical modification is composed of calcium sulfate and sodium sulfate in a mass ratio of (2-6):(1-3); an appropriate amount of sulfate will increase the formation of CSH gel, and when the proportion of calcium sulfate is higher, more ettringite is produced, which helps to develop strength; in the mechanochemical modification, 3-9 parts of chemical modifier are mixed with 30-40 parts of coal gangue powder and stirred for 3-5 min; poured into a ball mill, the ball milling speed is set to 520 rpm, and after ball milling for 3 h, activated coal gangue powder is obtained, which further increases the specific surface area of ​​coal gangue powder and fully activates its activity.

[0041] In some preferred embodiments of the present invention, in step S2, the alkali activator includes at least one of sodium hydroxide and sodium silicate; preferably, the mass ratio of sodium hydroxide to sodium silicate in the alkali activator is (2-10):(15-20), both of which are widely available and low in cost, and the condensation time can be flexibly controlled by adjusting the modulus.

[0042] In some preferred embodiments of the present invention, in step S2, the foaming agent is a mixture of AE2S (sodium fatty alcohol polyoxyethylene ether sulfate) and OA-12 (dodecyl dimethylamine oxide) in a mass ratio of (5-8):(1-2). This ratio results in a low foam decay rate and maintains stability under high temperature and high salt conditions.

[0043] Figure 1 This is a sample image of the high-porosity gangue-based filling material with adjustable permeability prepared according to the present invention.

[0044] The high-porosity gangue-based backfill material prepared by this invention has a porosity of 31% to 34%, a 28-day compressive strength ≥ 25 MPa, and a gas permeability of 13D to 16D.

[0045] This invention also provides a method for carbon sequestration using the aforementioned adjustable-permeability, high-porosity gangue-based backfill material. The method involves using a backfilling hydraulic support to fill the goaf with the adjustable-permeability, high-porosity gangue-based backfill material, while simultaneously laying a CO2 gas delivery pipeline in the roof. The CO2 is then sealed using the adjustable-permeability, high-porosity gangue-based backfill material. This invention provides a carbon sequestration backfilling mining method that flexibly adjusts the porosity of the backfill material, enabling large-scale gangue disposal and CO2 sequestration.

[0046] In some preferred embodiments, the CO2 injection pressure is 0.1-0.3 MPa and the pipeline spacing is 0.5-1 m; for example, the CO2 injection pressure is 0.2 MPa and the pipeline spacing is 0.5 m.

[0047] In the embodiments of this invention, unless otherwise specified, "parts" refers to "parts by mass".

[0048] In the embodiments of the present invention, the coal gangue aggregate used is washed with water for 10-20 minutes before spraying and then dried in a drying oven at 60°C for 12 hours.

[0049] Example 1

[0050] Thirty parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800℃ for 1 hour. Two parts of calcium sulfate, one part of sodium sulfate, and the calcined coal gangue powder were ball-milled together at 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of alkaline activator (sodium hydroxide to sodium silicate mass ratio of 7:18), one part of foaming agent (AE2S to OA-12 mass ratio of 6:1), 0.5 parts of polypropylene fiber, and 10 parts of water were mixed and stirred for 20 minutes to obtain a permeability-adjustable binder. The binder was evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size of 10-15 mm), placed in a mold, and allowed to solidify and harden to prepare a permeability-adjustable high-porosity gangue-based filling material.

[0051] Example 2

[0052] Thirty parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800℃ for 1 hour. Four parts of calcium sulfate, two parts of sodium sulfate, and the calcined coal gangue powder were ball-milled together at 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of alkaline activator (sodium hydroxide to sodium silicate mass ratio of 7:18), two parts of foaming agent (AE2S to OA-12 mass ratio of 6:1), one part of polypropylene fiber, and 10 parts of water were mixed and stirred for 20 minutes to obtain a permeability-adjustable binder. The binder was evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size of 10-15 mm), placed in a mold, and allowed to solidify and harden to prepare a permeability-adjustable high-porosity gangue-based filling material.

[0053] Example 3

[0054] Thirty parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800℃ for 1 hour. Six parts of calcium sulfate, three parts of sodium sulfate, and the calcined coal gangue powder were ball-milled together at 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of alkaline activator (sodium hydroxide to sodium silicate mass ratio of 7:18), 3 parts of foaming agent (AE2S to OA-12 mass ratio of 6:1), 1.5 parts of polypropylene fiber, and 10 parts of water were mixed and stirred for 20 minutes to obtain a permeability-adjustable binder. The binder was evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size of 10-15 mm), placed in a mold, and allowed to solidify and harden to prepare a permeability-adjustable high-porosity gangue-based filling material.

[0055] Example 4

[0056] 35 parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800℃ for 1 hour. 6 parts of calcium sulfate, 3 parts of sodium sulfate, and the calcined coal gangue powder were ball-milled together at 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 25 parts of alkaline activator (sodium hydroxide to sodium silicate mass ratio of 2:20), 3 parts of foaming agent (AE2S to OA-12 mass ratio of 5:2), 2 parts of polypropylene fiber, and 5 parts of water were mixed and stirred for 20 minutes to obtain a permeability-adjustable binder. The binder was evenly sprayed onto the surface of 70 parts of coal gangue aggregate (particle size of 10-15 mm), placed in a mold, and allowed to solidify and harden to prepare a permeability-adjustable high-porosity gangue-based filling material.

[0057] Example 5

[0058] Forty parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800℃ for 1 hour. Six parts of calcium sulfate, three parts of sodium sulfate, and the calcined coal gangue powder were ball-milled together at 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 40 parts of alkaline activator (sodium hydroxide to sodium silicate mass ratio of 10:15), three parts of foaming agent (AE2S to OA-12 mass ratio of 8:1), two parts of polypropylene fiber, and 15 parts of water were mixed and stirred for 20 minutes to obtain a permeability-adjustable binder. The binder was evenly sprayed onto the surface of 80 parts of coal gangue aggregate (particle size of 10-15 mm), placed in a mold, and allowed to solidify and harden to prepare a permeability-adjustable high-porosity gangue-based filling material.

[0059] Comparative Example 1

[0060] In this comparative example, cement was used as the binder, and the specific preparation method is as follows:

[0061] Mix 30 parts cement with 10 parts water and stir for 20 minutes to obtain a binder. Spray the binder evenly onto 75 parts coal gangue aggregate, fill it into a mold, and after it sets and hardens, obtain a high-porosity coal-based solid waste filling material.

[0062] Comparative Example 2

[0063] This comparative example is the same as Example 1, except that no foaming agent or polypropylene fiber was used. The specific preparation method is as follows:

[0064] Thirty parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800℃ for 1 hour. Two parts of calcium sulfate, one part of sodium sulfate, and the calcined coal gangue powder were ball-milled together at a speed of 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of alkaline activator (sodium hydroxide to sodium silicate mass ratio of 7:18), and 10 parts of water were mixed and stirred for 20 minutes to obtain a binder. The binder was evenly sprayed onto the surface of 75 parts of coal gangue aggregate, placed in a mold, and allowed to solidify and harden to obtain a high-porosity coal-based solid waste filling material.

[0065] Comparative Example 3

[0066] This comparative example is the same as Example 1, except that no foaming agent was used. The specific preparation method is as follows:

[0067] Thirty parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800℃ for 1 hour. Two parts of calcium sulfate, one part of sodium sulfate, and the calcined coal gangue powder were ball-milled together at a speed of 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of alkaline activator (sodium hydroxide to sodium silicate mass ratio of 7:18), 0.5 parts of polypropylene fiber, and 10 parts of water were mixed and stirred for 20 minutes to obtain a binder material. The binder material was evenly sprayed onto the surface of 75 parts of coal gangue aggregate, placed in a mold, and allowed to solidify and harden to obtain a high-porosity coal-based solid waste filling material.

[0068] Comparative Example 4

[0069] This comparative example is the same as Example 1, except that polypropylene fiber was not used. The specific preparation method is as follows:

[0070] 30 parts of coal gangue were crushed and sieved to a particle size of 0.2mm-1mm, and calcined at 800℃ for 1 hour. 2 parts of calcium sulfate, 1 part of sodium sulfate, and the calcined coal gangue powder were ball-milled together at 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of alkaline activator (sodium hydroxide to sodium silicate mass ratio of 7:18), 1 part of foaming agent (AE2S to OA-12 mass ratio of 6:1), and 10 parts of water were mixed and stirred for 20 minutes to obtain a binder. The binder was evenly sprayed onto the surface of 75 parts of coal gangue aggregate, placed in a mold, and allowed to solidify and harden to obtain a high-porosity coal-based solid waste filling material.

[0071] Comparative Example 5

[0072] This comparative example is the same as Example 1, except that urea or similar substances are used to replace the alkali activator. The aim is to demonstrate the effect of the alkali activator on the permeability of high-porosity gangue-based backfill materials. The specific preparation method is as follows:

[0073] 30 parts of coal gangue were crushed and sieved to a particle size of 0.2mm-1mm, and calcined at 800℃ for 1 hour. 2 parts of calcium sulfate, 1 part of sodium sulfate, and the calcined coal gangue powder were ball-milled together at 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of urea, 1 part of foaming agent (AE2S to OA-12 in a mass ratio of 6:1), 0.5 parts of polypropylene fiber, and 10 parts of water were mixed and stirred for 20 minutes to obtain a binder material. The binder material was evenly sprayed onto the surface of 75 parts of coal gangue aggregate, placed in a mold, and allowed to solidify and harden to obtain a high-porosity coal-based solid waste filling material.

[0074] Comparative Example 6

[0075] Same as Example 1, except that the particle size of the coal gangue aggregate used is 0.5-1 mm, and the specific preparation method is as follows:

[0076] Thirty parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800℃ for 1 hour. Two parts of calcium sulfate, one part of sodium sulfate, and the calcined coal gangue powder were ball-milled together at 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of alkaline activator (sodium hydroxide to sodium silicate mass ratio of 7:18), one part of foaming agent (AE2S to OA-12 mass ratio of 6:1), 0.5 parts of polypropylene fiber, and 10 parts of water were mixed and stirred for 20 minutes to obtain a permeability-adjustable binder. The binder was evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size of 0.5-1 mm), placed in a mold, and allowed to solidify and harden to prepare a permeability-adjustable high-porosity gangue-based filling material.

[0077] Comparative Example 7

[0078] Same as Example 1, except that the particle size of the coal gangue aggregate used is 30-40mm, and the specific preparation method is as follows:

[0079] Thirty parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800℃ for 1 hour. Two parts of calcium sulfate, one part of sodium sulfate, and the calcined coal gangue powder were ball-milled together at 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of alkaline activator (sodium hydroxide to sodium silicate mass ratio of 7:18), one part of foaming agent (AE2S to OA-12 mass ratio of 6:1), 0.5 parts of polypropylene fiber, and 10 parts of water were mixed and stirred for 20 minutes to obtain a permeability-adjustable binder. The binder was evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size of 30-40 mm), placed in a mold, and allowed to solidify and harden to prepare a permeability-adjustable high-porosity gangue-based filling material.

[0080] Comparative Example 8

[0081] Same as Example 1, except that the amount of foaming agent added is 0.5 parts, and the specific preparation method is as follows:

[0082] Thirty parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800℃ for 1 hour. Two parts of calcium sulfate, one part of sodium sulfate, and the calcined coal gangue powder were ball-milled together at 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of alkaline activator (sodium hydroxide to sodium silicate mass ratio of 7:18), 0.5 parts of foaming agent (AE2S to OA-12 mass ratio of 6:1), 0.5 parts of polypropylene fiber, and 10 parts of water were mixed and stirred for 20 minutes to obtain a permeability-adjustable binder. The binder was evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size of 10-15 mm), placed in a mold, and allowed to solidify and harden to prepare a permeability-adjustable high-porosity gangue-based filling material.

[0083] Comparative Example 9

[0084] Same as Example 1, except that the amount of foaming agent added is 10 parts, and the specific preparation method is as follows:

[0085] Thirty parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800℃ for 1 hour. Two parts of calcium sulfate, one part of sodium sulfate, and the calcined coal gangue powder were ball-milled together at 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of alkaline activator (sodium hydroxide to sodium silicate mass ratio of 7:18), 10 parts of foaming agent (AE2S to OA-12 mass ratio of 6:1), 0.5 parts of polypropylene fiber, and 10 parts of water were mixed and stirred for 20 minutes to obtain a permeability-adjustable binder. The binder was evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size of 10-15 mm), placed in a mold, and allowed to solidify and harden to prepare a permeability-adjustable high-porosity gangue-based filling material.

[0086] Comparative Example 10

[0087] Same as Example 1, except that the amount of polypropylene fiber added is 0.1 parts, and the specific preparation method is as follows:

[0088] Thirty parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800℃ for 1 hour. Two parts of calcium sulfate, one part of sodium sulfate, and the calcined coal gangue powder were ball-milled together at 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of alkaline activator (sodium hydroxide to sodium silicate mass ratio of 7:18), one part of foaming agent (AE2S to OA-12 mass ratio of 6:1), 0.1 parts of polypropylene fiber, and 10 parts of water were mixed and stirred for 20 minutes to obtain a permeability-adjustable binder. The binder was evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size of 10-15 mm), placed in a mold, and allowed to solidify and harden to prepare a permeability-adjustable high-porosity gangue-based filling material.

[0089] Comparative Example 11

[0090] Same as Example 1, except that the amount of polypropylene fiber added is 10 parts. The specific preparation method is as follows:

[0091] Thirty parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800℃ for 1 hour. Two parts of calcium sulfate, one part of sodium sulfate, and the calcined coal gangue powder were ball-milled together at 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of alkaline activator (sodium hydroxide to sodium silicate mass ratio of 7:18), one part of foaming agent (AE2S to OA-12 mass ratio of 6:1), 10 parts of polypropylene fiber, and 10 parts of water were mixed and stirred for 20 minutes to obtain a permeability-adjustable binder. The binder was evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size of 10-15 mm), placed in a mold, and allowed to solidify and harden to prepare a permeability-adjustable high-porosity gangue-based filling material.

[0092] Performance testing

[0093] To test the porosity, mechanical properties, and permeability of the filling materials, the filling materials prepared in Examples 1-5 and Comparative Examples 1-11 were cured and subjected to corresponding tests, as detailed below:

[0094] The samples were poured into a cubic mold with dimensions of 70*70*70mm and a cylindrical mold with dimensions of Φ100mm×H50mm, respectively. The cubic samples were used to test porosity and compressive strength, while the cylindrical samples were used to test gas permeability. The samples were vibrated on a vibrator for 1 minute, demolded after 1 day, and placed in a curing chamber at 25℃ and 95% humidity for 28 days to obtain the specimens.

[0095] A partially cured sample (28 days old) was completely immersed in water for 24 hours, and its mass in water was determined using a hydrostatic balance as W1. The sample was then dried in a 45°C drying oven to a constant weight, and W2 was measured in air. Porosity P v The calculation formula is as follows:

[0096]

[0097] In the formula: P v W1 is the porosity (%); W2 is the dry mass in air (g); W3 is the mass in water (g). w The density of water is in g / cm³. 3 V is the sample volume, in cm. 3 .

[0098] Some specimens were tested using a WAW-1000D servo hydraulic universal testing machine. The uniaxial compressive strength of the specimens was tested according to the national standard GB / T17671-2021. Each specimen was tested three times and the average value was taken.

[0099] The cylindrical specimen was placed in the holder, and a confining pressure was applied to seal it. An inlet pressure of 2 MPa was applied. After the pressure stabilized, the CO2 flow rate per unit time at the other end of the specimen was obtained. The permeability K of the specimen was calculated using Darcy's law.

[0100]

[0101] In the formula: K is the gas permeability, D; Q is the gas flow rate, cm. 3 / s; μ is the gas viscosity, cP; L is the sample length, cm; A is the sample cross-sectional area, cm². 2 P1 is the inlet pressure, MPa; P2 is the outlet pressure, MPa.

[0102] The porosity, 28-day compressive strength and gas permeability of the test blocks obtained from each comparative example and embodiment were tested, and the results are shown in Table 1.

[0103] Table 1

[0104]

[0105]

[0106] As can be seen from Comparative Examples 1-11 and Examples 1-5, the porosity of Comparative Example 1 with added cement, Comparative Example 2 without added foaming agent and polypropylene fiber, Comparative Example 3 without added foaming agent, and Comparative Example 4 without added polypropylene fiber are all lower than that of the gangue cemented high-porosity filling material prepared using the permeability adjustable binder. The compressive strength is not much different, but the gas permeability is the most different. The gas permeability of Example 3 is 250% and 177% higher than that of Comparative Example 1 and Comparative Example 2, respectively, and the gas permeability of Example 1 is 226% and 158% higher than that of Comparative Example 1 and Comparative Example 2, respectively.

[0107] Compared with Example 1, the coal gangue aggregate used in Comparative Example 6 had too small a particle size, the coal gangue aggregate used in Comparative Example 7 had too large a particle size, the foaming agent added in Comparative Example 8 was too small, the foaming agent added in Comparative Example 9 was too large, the polypropylene fiber added in Comparative Example 10 was too small, and the polypropylene fiber added in Comparative Example 11 was too large. The porosity, 28-day compressive strength, and gas permeability measured in the above comparative examples were all lower than those in Example 1. This indicates that the high-porosity gangue-based filling material prepared by the present invention has high porosity and permeability while maintaining excellent mechanical properties. As can be seen from Comparative Example 5 and Examples 1-5, after using urea to replace the alkali activator, the 28-day compressive strength was significantly reduced, and it was reduced by 61% compared with Examples 3 and 1. This indicates that the alkali activator has a better activation effect on the coal gangue powder.

[0108] A comparison of Examples 1 to 5 reveals that the gas permeability of the filling material fluctuates with changes in the dosage of foaming agent and polypropylene fiber, indicating that the foaming agent and polypropylene fiber can effectively regulate the permeability of the material.

[0109] Application Example 1

[0110] 1. The adjustable permeability high-porosity gangue-based backfill material prepared in Example 1 is filled into the goaf using a backfilling hydraulic support for coal mining to construct a high-porosity backfill body to support the overlying strata.

[0111] 2. Lay CO2 gas delivery pipelines on the roof slab, and use a gas pressure pump to deliver CO2 gas to the filling area. The CO2 injection pressure is 0.2 MPa, and the pipeline spacing is 0.5 m.

[0112] The formula for calculating the CO2 sequestration capacity is as follows:

[0113]

[0114] Where: CO2 Uptake CO2 sequestration amount, %; The density of CO2 gas is kg / m³. 3 v1 represents the CO2 injection volume displayed when the CO2 flow meter remains constant, in meters. 3 ;v0 is the initial volume displayed by the flow meter, in m 3 m represents the mass of the adjustable permeability high-porosity gangue-based backfill material, in kg.

[0115] CO2 is calculated using the above formula. Uptake The percentage was 24.46%. When CO2 gas is injected into high-porosity coal-based solid waste backfill material, the high porosity and high permeability of the material promote the migration and diffusion of CO2 gas in the pores, achieving both physical and chemical sequestration of CO2. This not only realizes the large-scale treatment and utilization of gangue solid waste, but also effectively sequesters CO2, showing good prospects for widespread application.

[0116] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A permeability-adjustable high-porosity gangue-based backfill material, characterized in that, The raw materials, by weight, include the following components: 70-80 parts coal gangue aggregate, 30-40 parts activated coal gangue powder, 25-40 parts alkaline activator, 1-3 parts foaming agent, 0.5-2 parts polypropylene fiber, and 5-15 parts water. The particle size of the coal gangue aggregate is 10-15 mm; The preparation method of the permeability-adjustable high-porosity gangue-based backfill material includes the following steps: Weigh the raw materials according to the mass fraction, mix the alkaline activator and water, let stand, then add the foaming agent, activated coal gangue powder and polypropylene fiber in sequence, mix and stir to obtain a permeability adjustable cohesive material. The adjustable permeability binder is uniformly sprayed onto the surface of coal gangue aggregate, placed in a mold, and allowed to solidify and harden to prepare the adjustable permeability high porosity gangue-based filling material.

2. The adjustable permeability high-porosity gangue-based backfill material according to claim 1, characterized in that, The method for preparing the activated coal gangue powder includes the following steps: calcining the crushed coal gangue powder; adding a chemical modifier to the calcined coal gangue powder, mixing it evenly, and then ball milling it to prepare the activated coal gangue powder.

3. The adjustable permeability high-porosity gangue-based backfill material according to claim 2, characterized in that, The calcination temperature is 800℃ and the time is 1h; and / or, the mass ratio of the chemical modifier to the coal gangue powder is (3-9):30; and / or, the ball milling speed is 520rpm and the ball milling time is 3h.

4. The adjustable permeability high-porosity gangue-based backfill material according to claim 2, characterized in that, The chemical modifier is composed of calcium sulfate and sodium sulfate in a mass ratio of (2-6):(1-3).

5. The adjustable permeability high-porosity gangue-based backfill material according to claim 1, characterized in that, The alkaline activator includes sodium hydroxide and sodium silicate.

6. The adjustable permeability high-porosity gangue-based backfill material according to claim 5, characterized in that, The mass ratio of sodium hydroxide to sodium silicate in the alkaline activator is (2-10):(15-20).

7. The adjustable permeability high-porosity gangue-based backfill material according to claim 1, characterized in that, The foaming agent is composed of sodium fatty alcohol polyoxyethylene ether sulfate and dodecyl dimethylamine oxide in a mass ratio of (5-8):(1-2).

8. A method for carbon sequestration in coal mining using the adjustable permeability high-porosity gangue-based backfill material according to any one of claims 1-7, characterized in that, The adjustable permeability high-porosity gangue-based backfill material is filled into the goaf using a backfilling hydraulic support. At the same time, a CO2 gas transmission pipeline is laid on the roof to seal the CO2 through the adjustable permeability high-porosity gangue-based backfill material.

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