Permeability-adjustable high-porosity gangue-based filling material as well as preparation method and application thereof

Abstract

The invention discloses a permeability-adjustable high-porosity gangue-based filling material as well as a preparation method and application of the permeability-adjustable high-porosity gangue-based filling material, and belongs to the field of coal-based solid waste resource utilization and carbon sequestration. The raw materials comprise the following components: 70-80 parts of coal gangue aggregate, 30-40 parts of activated coal gangue powder, 25-40 parts of an alkaline activator, 1-3 parts of a foaming agent, 0.5-2 parts of polypropylene fiber and 5-15 parts of water. The permeability of the filling material can be regulated and controlled by regulating and controlling the mixing amount of the foaming agent and the polypropylene fiber, migration and diffusion of CO2 gas in pores are promoted, and the problem of low CO2 storage efficiency caused by pore sealing is solved; gangue with the particle size of 10-15 mm is adopted as coarse aggregate, and the filling material prepared through a binding material surface spraying process is high in porosity and excellent in mechanical property.

Description

Technical Field

[0001] The present invention belongs to the field of coal-based solid waste resource utilization and carbon sequestration, and particularly relates to a high-porosity gangue-based filling material with adjustable permeability, a preparation method thereof, and an application thereof. Background Art

[0002] During the development and utilization of coal, the emission of solid waste such as gangue seriously restricts the efficient production and coordinated development of the ecological environment in mining areas. The on-site filling of gangue underground can directly fill the gangue solid waste into the underground goaf after crushing and processing. This method is one of the key technologies for the disposal and utilization of gangue solid waste in mining areas. However, the current traditional gangue filling method faces some problems: First, the gangue production in mines accounts for about 15%-20% of the raw coal production. Direct filling is easily subject to production restrictions and may lead to a shortage of gangue; second, the gangue needs to be transported directly to the goaf for filling and needs to be compacted multiple times, which affects the speed of coal mining; in addition, the traditional filling process is difficult to coordinately control the porosity and permeability of the filling material. The unreasonable particle size grading of the gangue may easily cause the pore structure to be closed, which not only affects the permeability of the filling body, but also limits its application potential in CO2 storage.

[0003] At present, the research on carbon-fixing filling materials is still in its infancy. Existing technologies generally have problems such as low carbon fixation efficiency and uncontrollable material permeability, making it difficult to achieve long-term sealing. Summary of the Invention

[0004] To address the shortcomings of the existing technology, the present invention provides a highly porous gangue-based filling material with adjustable permeability, as well as its preparation method and application. By activating gangue powder with an alkaline activator, adding gangue aggregate, and preparing the filling material using a foaming agent and polypropylene fiber, the filling material achieves flexible permeability adjustment, enabling large-scale gangue disposal and CO2 storage. The filling material of the present invention exhibits adjustable permeability, high porosity, excellent mechanical properties, and good carbon sequestration.

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

[0006] A high-porosity gangue-based filling material with adjustable permeability comprises the following raw materials, calculated by weight: 70-80 parts of gangue aggregate, 30-40 parts of activated gangue powder, 25-40 parts of alkaline activator, 1-3 parts of foaming agent, 0.5-2 parts of polypropylene fiber and 5-15 parts of water.

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

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

[0009] Furthermore, the calcination temperature is 800°C and the time is 1 hour; 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 520 rpm and the ball milling time is 3 hours; the particle size of the coal gangue powder is 0.2 mm-1 mm.

[0010] Calcination can catalyze the transformation of kaolinite inside the gangue into metakaolinite and stimulate the activity of the 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 addition of sulfate will enhance the formation of CSH gel, and when the calcium sulfate ratio is higher, more ettringite is produced, which helps the 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 dimethyl amine oxide in a mass ratio of (5-8): (1-2).

[0016] The second technical solution provided by the present invention is:

[0017] The method for preparing the above-mentioned permeability-adjustable high-porosity gangue-based filling material comprises the following steps:

[0018] The raw materials are weighed according to their mass parts, an alkaline activator and water are mixed and stirred, and then allowed to stand. Then, a foaming agent, activated coal gangue powder and polypropylene fiber are added in sequence, mixed and stirred to obtain a permeability-adjustable adhesive material; the permeability-adjustable adhesive material is evenly sprayed onto the surface of the coal gangue aggregate, placed in a mold to solidify, and prepared to obtain the permeability-adjustable high-porosity gangue-based filling material.

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

[0020] The third technical solution provided by the present invention is:

[0021] A method for carbon fixation in coal mining using the above-mentioned permeability-adjustable high-porosity gangue-based filling material, wherein the permeability-adjustable high-porosity gangue-based filling material is filled into the goaf using a filling mining hydraulic support, and a CO2 gas transmission pipeline is laid on the roof, and CO2 is sealed by the permeability-adjustable high-porosity gangue-based filling material.

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

[0023] The present invention proposes to use an alkaline activator to activate coal gangue powder as a cohesive material, use a foaming agent and polypropylene fiber to regulate the permeability of the cohesive material, and use coal gangue with a particle size of 10-15 mm as aggregate. The prepared gangue-based filling material has large porosity, adjustable permeability, excellent mechanical properties and good CO2 storage effect, in order to provide a new material and storage method for gangue solid waste utilization, green filling and CO2 storage.

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

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

[0026] (2) The present invention can adjust the permeability of the filling material by regulating the dosage of the foaming agent and the polypropylene fiber, thereby 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) Gangue with a particle size of 10-15 mm is used as coarse aggregate. Through the surface spraying process of the adhesive material, the filling material prepared has high porosity and excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 This is a sample of the permeability-adjustable high-porosity gangue-based filling material prepared by the present invention. DETAILED DESCRIPTION

[0030] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting 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 terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0032] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0033] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

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

[0035] An embodiment of the present invention provides a method for preparing a high-porosity gangue-based filling material with adjustable permeability, comprising the following steps:

[0036] S1. The gangue is sequentially crushed, calcined and mechanochemically modified to obtain activated gangue powder;

[0037] S2. The alkaline activator is mixed with water for 30-60min, allowed to stand for 12-24h, and then the foaming agent, activated gangue powder prepared in S1, polypropylene fiber are added, mixed and stirred for 10-30min to obtain a permeability-adjustable adhesive material;

[0038] S3. The permeability-adjustable adhesive material prepared in S2 is evenly 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 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 to 1 mm; the calcination temperature is 800° C. and the time is 1 hour, which can catalyze the conversion of kaolinite to metakaolinite and stimulate the activity of the 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 can enhance the formation of CSH gel, and when the calcium sulfate ratio is higher, more ettringite is produced, which helps to develop strength; in the mechanochemical modification, 3-9 parts of the chemical modifier are mixed with 30-40 parts of coal gangue powder and stirred for 3-5 minutes; the mixture is poured into a ball mill, the ball mill speed is set to 520 rpm, and the activated coal gangue powder is obtained after ball milling for 3 hours, further increasing the specific surface area of ​​the coal gangue powder and fully stimulating 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 coagulation 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 dimethyl amine oxide), and the mass ratio of the two is (5-8): (1-2). Under this ratio, the foam decay rate is low and it can maintain stability under high temperature and high salt conditions.

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

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

[0045] An embodiment of the present invention also provides a method for carbon sequestration using the above-mentioned high-porosity, permeability-adjustable gangue-based filling material. The method involves using a filling mining hydraulic support to fill the goaf with the high-porosity, permeability-adjustable gangue-based filling material. A CO2 gas pipeline is simultaneously laid in the roof, and the CO2 is sequestered using the high-porosity, permeability-adjustable gangue-based filling material. This invention provides a carbon sequestration and filling mining method that allows for flexible adjustment of the porosity of the filling material, enables large-scale gangue disposal, and sequesters CO2.

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

[0047] In the embodiments of the present invention, “parts” refer to “parts by mass” unless otherwise specified.

[0048] The gangue aggregate used in the embodiment of the present invention was washed with water for 10-20 minutes before spraying and dried in a drying oven at a temperature of 60° C. for 12 hours.

[0049] Example 1

[0050] 30 parts of coal gangue are crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800°C for 1 hour. 2 parts of calcium sulfate, 1 part of sodium sulfate and the calcined coal gangue powder are ball-milled together at a ball milling speed of 520 rpm for 3 hours to obtain activated coal gangue powder; the activated coal gangue powder, 30 parts of an alkaline activator (the mass ratio of sodium hydroxide to sodium silicate is 7:18), 1 part of a foaming agent (the mass ratio of AE2S to OA-12 is 6:1), 0.5 parts of polypropylene fiber and 10 parts of water are mixed and stirred for 20 minutes to obtain a permeability-adjustable adhesive material; the adhesive material is evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size is 10-15 mm), placed in a mold and solidified to prepare a high-porosity gangue-based filling material with adjustable permeability.

[0051] Example 2

[0052] 30 parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800°C for 1 hour. 4 parts of calcium sulfate, 2 parts of sodium sulfate and the calcined coal gangue powder were ball-milled together at a ball milling speed of 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of an alkaline activator (the mass ratio of sodium hydroxide to sodium silicate is 7:18), 2 parts of a foaming agent (the mass ratio of AE2S to OA-12 is 6:1), 1 part of polypropylene fiber and 10 parts of water were mixed and stirred for 20 minutes to obtain a permeability-adjustable adhesive material. The adhesive material was evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size is 10-15 mm), placed in a mold and solidified to prepare a high-porosity gangue-based filling material with adjustable permeability.

[0053] Example 3

[0054] 30 parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800°C for 1 hour. 6 parts of calcium sulfate, 3 parts of sodium sulfate and the calcined coal gangue powder were ball-milled together at a ball milling speed of 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of an alkaline activator (the mass ratio of sodium hydroxide to sodium silicate is 7:18), 3 parts of a foaming agent (the mass ratio of AE2S to OA-12 is 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 adhesive material. The adhesive material was evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size is 10-15 mm), placed in a mold and solidified to prepare a high-porosity gangue-based filling material with adjustable permeability.

[0055] Example 4

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

[0057] Example 5

[0058] 40 parts of coal gangue are crushed and sieved to a particle size of 0.2 mm to 1 mm, and calcined at 800°C for 1 hour. 6 parts of calcium sulfate, 3 parts of sodium sulfate and the calcined coal gangue powder are ball-milled together at a ball milling speed of 520 rpm for 3 hours to obtain activated coal gangue powder; the activated coal gangue powder, 40 parts of an alkaline activator (the mass ratio of sodium hydroxide to sodium silicate is 10:15), 3 parts of a foaming agent (the mass ratio of AE2S to OA-12 is 8:1), 2 parts of polypropylene fiber and 15 parts of water are mixed and stirred for 20 minutes to obtain a permeability-adjustable adhesive material; the adhesive material is evenly sprayed onto the surface of 80 parts of coal gangue aggregate (particle size is 10-15 mm), placed in a mold and solidified to prepare a high-porosity gangue-based filling material with adjustable permeability.

[0059] Comparative Example 1

[0060] The cementing material of this comparative example is cement, and the specific preparation method is as follows:

[0061] 30 parts of cement and 10 parts of water were mixed and stirred for 20 minutes to obtain a cohesive material, which was evenly sprayed into 75 parts of coal gangue aggregate, placed in a mold and solidified to 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 and polypropylene fiber are used. The specific preparation method is as follows:

[0064] 30 parts of coal gangue were crushed and sieved to a particle size of 0.2mm-1mm, and calcined at 800℃ for 1h. 2 parts of calcium sulfate, 1 part of sodium sulfate and the calcined coal gangue powder were ball-milled together at a ball milling speed of 520rpm for 3h to obtain activated coal gangue powder; the activated coal gangue powder, 30 parts of alkaline activator (the mass ratio of sodium hydroxide to sodium silicate is 7:18) and 10 parts of water were mixed and stirred for 20min to obtain a cohesive material; the cohesive material was evenly sprayed onto the surface of 75 parts of coal gangue aggregate, placed in a mold and solidified 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 is used. The specific preparation method is as follows:

[0067] 30 parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800°C for 1 hour. 2 parts of calcium sulfate, 1 part of sodium sulfate and the calcined coal gangue powder were ball-milled together at a ball milling speed of 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of an alkaline activator (the mass ratio of sodium hydroxide to sodium silicate is 7:18), 0.5 parts of polypropylene fiber and 10 parts of water were mixed and stirred for 20 minutes to obtain a cohesive material. The cohesive material was evenly sprayed onto the surface of 75 parts of coal gangue aggregate, placed in a mold and solidified 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 is not used. The specific preparation method is as follows:

[0070] 30 parts of coal gangue were crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800°C for 1 hour. 2 parts of calcium sulfate, 1 part of sodium sulfate and the calcined coal gangue powder were ball-milled together at a ball milling speed of 520 rpm for 3 hours to obtain activated coal gangue powder. The activated coal gangue powder, 30 parts of an alkaline activator (the mass ratio of sodium hydroxide to sodium silicate is 7:18), 1 part of a foaming agent (the mass ratio of AE2S to OA-12 is 6:1) and 10 parts of water were mixed and stirred for 20 minutes to obtain a cohesive material. The cohesive material was evenly sprayed onto the surface of 75 parts of coal gangue aggregate, placed in a mold and solidified 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 the like is used as a substitute for the alkaline activator. This is intended to demonstrate the effect of the alkaline activator on the permeability of the high-porosity gangue-based filling material. The specific preparation method is as follows:

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

[0074] Comparative Example 6

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

[0076] 30 parts of coal gangue are crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800°C for 1 hour. 2 parts of calcium sulfate, 1 part of sodium sulfate and the calcined coal gangue powder are ball-milled together at a ball milling speed of 520 rpm for 3 hours to obtain activated coal gangue powder; the activated coal gangue powder, 30 parts of an alkaline activator (the mass ratio of sodium hydroxide to sodium silicate is 7:18), 1 part of a foaming agent (the mass ratio of AE2S to OA-12 is 6:1), 0.5 parts of polypropylene fiber and 10 parts of water are mixed and stirred for 20 minutes to obtain a permeability-adjustable adhesive material; the adhesive material is evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size is 0.5-1 mm), placed in a mold and solidified to prepare a high-porosity gangue-based filling material with adjustable permeability.

[0077] Comparative Example 7

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

[0079] 30 parts of coal gangue are crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800°C for 1 hour. 2 parts of calcium sulfate, 1 part of sodium sulfate and the calcined coal gangue powder are ball-milled together at a ball milling speed of 520 rpm for 3 hours to obtain activated coal gangue powder; the activated coal gangue powder, 30 parts of an alkaline activator (the mass ratio of sodium hydroxide to sodium silicate is 7:18), 1 part of a foaming agent (the mass ratio of AE2S to OA-12 is 6:1), 0.5 parts of polypropylene fiber and 10 parts of water are mixed and stirred for 20 minutes to obtain a permeability-adjustable adhesive material; the adhesive material is evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size is 30-40 mm), placed in a mold and solidified to prepare a high-porosity gangue-based filling material with adjustable permeability.

[0080] Comparative Example 8

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

[0082] 30 parts of coal gangue are crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800°C for 1 hour. 2 parts of calcium sulfate, 1 part of sodium sulfate and the calcined coal gangue powder are ball-milled together at a ball milling speed of 520 rpm for 3 hours to obtain activated coal gangue powder; the activated coal gangue powder, 30 parts of an alkaline activator (the mass ratio of sodium hydroxide to sodium silicate is 7:18), 0.5 parts of a foaming agent (the mass ratio of AE2S to OA-12 is 6:1), 0.5 parts of polypropylene fiber and 10 parts of water are mixed and stirred for 20 minutes to obtain a permeability-adjustable adhesive material; the adhesive material is evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size is 10-15 mm), placed in a mold and solidified to prepare a high-porosity gangue-based filling material with adjustable permeability.

[0083] Comparative Example 9

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

[0085] 30 parts of coal gangue are crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800°C for 1 hour. 2 parts of calcium sulfate, 1 part of sodium sulfate and the calcined coal gangue powder are ball-milled together at a ball milling speed of 520 rpm for 3 hours to obtain activated coal gangue powder; the activated coal gangue powder, 30 parts of an alkaline activator (the mass ratio of sodium hydroxide to sodium silicate is 7:18), 10 parts of a foaming agent (the mass ratio of AE2S to OA-12 is 6:1), 0.5 parts of polypropylene fiber and 10 parts of water are mixed and stirred for 20 minutes to obtain a permeability-adjustable adhesive material; the adhesive material is evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size is 10-15 mm), placed in a mold and solidified to prepare a high-porosity gangue-based filling material with adjustable permeability.

[0086] Comparative Example 10

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

[0088] 30 parts of coal gangue are crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800°C for 1 hour. 2 parts of calcium sulfate, 1 part of sodium sulfate and the calcined coal gangue powder are ball-milled together at a ball milling speed of 520 rpm for 3 hours to obtain activated coal gangue powder; the activated coal gangue powder, 30 parts of an alkaline activator (the mass ratio of sodium hydroxide to sodium silicate is 7:18), 1 part of a foaming agent (the mass ratio of AE2S to OA-12 is 6:1), 0.1 part of polypropylene fiber and 10 parts of water are mixed and stirred for 20 minutes to obtain a permeability-adjustable adhesive material; the adhesive material is evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size is 10-15 mm), placed in a mold and solidified to prepare a high-porosity gangue-based filling material with adjustable permeability.

[0089] Comparative Example 11

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

[0091] 30 parts of coal gangue are crushed and sieved to a particle size of 0.2 mm-1 mm, and calcined at 800°C for 1 hour. 2 parts of calcium sulfate, 1 part of sodium sulfate and the calcined coal gangue powder are ball-milled together at a ball milling speed of 520 rpm for 3 hours to obtain activated coal gangue powder; the activated coal gangue powder, 30 parts of an alkaline activator (the mass ratio of sodium hydroxide to sodium silicate is 7:18), 1 part of a foaming agent (the mass ratio of AE2S to OA-12 is 6:1), 10 parts of polypropylene fiber and 10 parts of water are mixed and stirred for 20 minutes to obtain a permeability-adjustable adhesive material; the adhesive material is evenly sprayed onto the surface of 75 parts of coal gangue aggregate (particle size is 10-15 mm), placed in a mold and solidified to prepare a high-porosity gangue-based filling material with adjustable permeability.

[0092] Performance test

[0093] In order to detect the porosity, mechanical characteristics and permeability of the filling materials, the filling materials prepared in Examples 1-5 and Comparative Examples 1-11 were cured and tested accordingly, as follows:

[0094] The samples were poured into a 70*70*70mm cubic mold and a 100mm Φ×50mm H cylindrical mold, respectively. The cubic sample was used to test porosity and compressive strength, while the cylindrical sample was used to test gas permeability. The samples were shaken on a vibrator for 1 minute. After 1 day, the samples were removed from the molds and placed in a curing chamber at 25°C and 95% humidity for 28 days to obtain the test pieces.

[0095] Take a sample that has been partially cured for 28 days and immerse it completely in water for 24 hours. Use a hydrostatic balance to measure its mass in water as W1. Then dry the sample in a drying oven at 45°C to a constant weight, and measure W2 in air. Porosity P v The calculation formula is as follows:

[0096]

[0097] Where: P v is the porosity, %; W1 is the dry mass in air, g; W2 is the mass in water, g, ρ w is the water density, g / cm 3 , V is the sample volume, cm 3 .

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

[0099] Place the cylindrical specimen in a holder, apply confining pressure and seal it, and apply an inlet pressure of 2 MPa. After the pressure stabilizes, obtain the CO2 flow rate per unit time at the other end of the specimen, and calculate the permeability K of the specimen using Darcy's law:

[0100]

[0101] Where: K is gas permeability, D; Q is gas flow, cm 3 / s; μ is the gas viscosity, cP; L is the sample length, cm; A is the sample cross-sectional area, cm 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 in each comparative example and embodiment were tested. The results are shown in Table 1.

[0103] Table 1

[0104]

[0105]

[0106] It can be seen from Comparative Examples 1-11 and Examples 1-5 that 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 by using permeability-adjustable adhesive material, the compressive strength is not much different, and the gas permeability is the largest difference. The gas permeability of Example 3 is increased by 250% and 177% compared with that of Comparative Example 1 and Comparative Example 2, respectively, and the gas permeability of Example 1 is increased by 226% and 158% compared with that of Comparative Example 1 and Comparative Example 2, respectively.

[0107] Compared with Example 1, the particle size of the coal gangue aggregate used in Comparative Example 6 is too small, the particle size of the coal gangue aggregate used in Comparative Example 7 is too large, the foaming agent added in Comparative Example 8 is too little, the foaming agent added in Comparative Example 9 is too large, the polypropylene fiber added in Comparative Example 10 is too little, and the polypropylene fiber added in Comparative Example 11 is too much. The porosity, 28-day compressive strength and gas permeability measured in the above comparative examples are all less than those in Example 1, which shows that the high-porosity gangue-based filling material prepared by the present invention has high porosity and permeability while maintaining excellent mechanical properties; it can be seen from Comparative Example 5 and Examples 1-5 that after using urea instead of the alkaline activator, the 28 compressive strength is significantly reduced, which is 61% lower than that in Example 3 and Example 1, which shows that the use of an alkaline activator has a better effect on stimulating the activity of coal gangue powder.

[0108] From the comparison of Examples 1 to 5, it can be found that as the dosage of the foaming agent and the polypropylene fiber changes, the gas permeability of the filling material fluctuates, indicating that the foaming agent and the polypropylene fiber can effectively regulate the permeability of the material.

[0109] Application Example 1

[0110] 1. Using a filling coal mining hydraulic support, the high-porosity gangue-based filling material with adjustable permeability prepared in Example 1 is filled into the goaf to construct a high-porosity filling body to support the overlying rock strata;

[0111] 2. Lay the CO2 gas transmission pipeline on the roof and transport the CO2 gas to the filling area through a gas pressure pump. The CO2 injection pressure is 0.2MPa and the pipeline layout spacing is 0.5m;

[0112] The calculation formula for CO2 storage capacity is as follows:

[0113]

[0114] Where: CO2 Uptake is the CO2 storage capacity, %; is the density of CO2 gas, kg / m 3 ; v1 is the CO2 injection volume displayed when the CO2 flow meter remains unchanged, m 3 ; v0 initial volume displayed by the flow meter, m 3 ; m is the mass of the high-porosity gangue-based filling material with adjustable permeability, kg.

[0115] CO2 is calculated by the above formula Uptake The injection of CO2 into highly porous coal-based solid waste filling materials, due to the material's high porosity and permeability, facilitates its migration and diffusion within the pores, achieving both physical and chemical sequestration of the CO2. This not only enables the large-scale disposal and utilization of gangue solid waste but also effectively seals the CO2, promising promising prospects for widespread adoption.

[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 changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A high-porosity gangue-based filling material with adjustable permeability, characterized in that: The raw materials include the following components in parts by mass: 70-80 parts of coal gangue aggregate, 30-40 parts of activated coal gangue powder, 25-40 parts of alkaline activator, 1-3 parts of foaming agent, 0.5-2 parts of polypropylene fiber and 5-15 parts of water.

2. The permeability-adjustable high-porosity gangue-based filling material according to claim 1, characterized in that: The particle size of the coal gangue aggregate is 10-15 mm.

3. The permeability-adjustable high-porosity gangue-based filling material according to claim 1, characterized in that: The preparation method of the activated coal gangue powder comprises the following steps: calcining the coal gangue powder obtained by crushing; adding a chemical modifier to the calcined coal gangue powder, mixing and then ball milling to prepare the activated coal gangue powder.

4. The permeability-adjustable high-porosity gangue-based filling material according to claim 3, characterized in that: The calcination temperature is 800° C. and the calcination time is 1 hour; 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 520 rpm and the ball milling time is 3 hours.

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

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

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

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

9. The method for preparing the high-porosity gangue-based filling material with adjustable permeability according to any one of claims 1 to 8, characterized in that: The following steps are involved: Weigh the raw materials according to parts by mass, mix the alkaline activator and water, stir, and let it stand, then add the foaming agent, activated coal gangue powder, and polypropylene fiber in sequence, mix and stir to obtain a permeability-adjustable adhesive material; The permeability-adjustable adhesive material is evenly sprayed onto the surface of the coal gangue aggregate, placed in a mold for solidification and hardening, and the permeability-adjustable high-porosity coal gangue-based filling material is prepared.

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

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