Coal mine paste filling material and preparation method thereof

Abstract

The invention discloses a coal mine paste filling material and a preparation method thereof, and relates to the technical field of coal mine filling. The coal mine paste filling material is prepared from the following raw material components in parts by mass: 20 to 25 parts of mineral slag, 12 to 15 parts of furnace slag, 8 to 10 parts of carbide slag, 8 to 10 parts of steel slag, 5 to 6 parts of desulfurized gypsum, 5 to 6 parts of polyaspartic acid, 8 to 12 parts of aluminum phosphate, 5 parts of sodium hydroxide and 20 to 45 parts of water. According to the coal mine paste filling material and the preparation method thereof, the industrial waste residues are fully utilized as main raw materials, the preparation process not only realizes resource utilization of the industrial waste residues, but also remarkably improves the performance of the coal mine paste filling material through reasonable modification treatment and design of the composite material, meanwhile, the preparation process pays attention to environmental friendliness and economic feasibility, and the coal mine paste filling material has wide application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mine filling, in particular to a coal mine paste filling material and a preparation method thereof. Background Art

[0002] With the continuous development of coal resources, traditional coal mining methods face numerous challenges, such as surface subsidence, water resource depletion, and environmental pollution. To address these issues, coal mine backfill mining technology has emerged. This technology injects specialized backfill materials into the goaf to support the roof, reduce ground subsidence, and prevent damage to groundwater systems. In recent years, with increasing environmental awareness and technological advancements, the research and application of backfill materials has received increasing attention.

[0003] Early filling materials commonly used were primarily slurries composed of cement, sand, and gravel. While these materials offer high strength and durability, their production is energy-intensive, generates significant carbon emissions, and is relatively expensive. Furthermore, cement-based materials are prone to segregation during transportation and pumping, resulting in uneven filling. Using industrial waste residues, such as fly ash, to prepare filling materials has become an environmentally friendly option. However, due to its inherently low reactivity, fly ash alone struggles to achieve ideal mechanical properties. Furthermore, excessive fly ash addition can reduce the fluidity and stability of the paste.

[0004] In view of the problems existing in traditional filling materials, researchers have begun to explore new filling material systems. These materials usually use natural minerals or industrial by-products as the main ingredients, and combine advanced modification technology and optimized formula design to make up for their respective defects, thereby achieving higher overall performance. Summary of the Invention

[0005] The purpose of the present invention is to provide a coal mine paste filling material and a preparation method thereof, so as to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above object, the present invention provides the following solutions: The present invention provides a coal mine paste filling material, which comprises the following raw material components in parts by mass: 20-25 parts of slag, 12-15 parts of furnace slag, 8-10 parts of carbide slag, 8-10 parts of steel slag, 5-6 parts of desulfurized gypsum, 5-6 parts of polyaspartic acid, 8-12 parts of aluminum phosphate, 5-7 parts of sodium hydroxide and 20-45 parts of water.

[0007] The filling material with the raw material ratio of the present invention can achieve high mechanical properties and durability requirements while ensuring good construction performance.

[0008] The present invention also provides a method for preparing the above-mentioned coal mine paste filling material, comprising the following steps: (1) Immerse slag, blast furnace slag, and carbide slag in acetic acid solution to obtain modified silicate minerals; calcine steel slag at 800 - 1000 °C to obtain calcined steel slag; (2) Mix the modified silicate minerals with the calcined steel slag, then add a mixture of polycarbonate and polyacrylamide, and carry out a blending reaction at 150 - 180 °C, and then cool to room temperature; (3) Add an aqueous solution of polyaspartic acid to the reaction system of step (2); wherein, the aqueous solution of polyaspartic acid is obtained by dissolving polyaspartic acid in water with a partial raw material ratio; (4) Add desulfurized gypsum and aluminum phosphate to the system of step (3), and add sodium hydroxide and the remaining raw material ratio of water, and stir to obtain the coal mine paste filling material.

[0009] As a further preference of the present invention, the mass ratio of polycarbonate to polyacrylamide is 1 - 2:2 - 3.

[0010] As a further preference of the present invention, the blending reaction time is 5 - 8 min.

[0011] As a further preference of the present invention, in step (2), cool to room temperature at a cooling rate of 8 - 12 °C / min.

[0012] As a further preference of the present invention, the total mass of polycarbonate and polyacrylamide is 20 - 25% of the total mass of modified silicate minerals and steel slag.

[0013] The present invention further provides the application of the above coal mine paste filling material or the coal mine paste filling material prepared by the above preparation method in the backfill of coal mine goafs.

[0014] The preparation process of the present invention makes full use of industrial waste residues (such as slag, blast furnace slag, carbide slag, steel slag) as the main raw materials, realizes the resource utilization of waste, reduces environmental pollution, lightens the environmental burden, and by treating and mixing waste residues from different sources (slag, blast furnace slag, carbide slag, steel slag), gives full play to the advantages of each component and improves the overall performance of the material.

[0015] The present invention immerses slag, blast furnace slag, and carbide slag in acetic acid solution to obtain modified silicate minerals, enhancing their activity and reactivity, which is beneficial to the subsequent reactions. Calcining steel slag at 800 - 1000 °C not only removes impurities but also improves its structure and chemical properties, making it more suitable for the composite modification of subsequent mixing and blending reactions.

[0016] The present invention adds polycarbonate and polyacrylamide for blending reaction to form a composite material with excellent mechanical properties and rheological properties, which is suitable for the needs of coal mine paste filling. In addition, the blending reaction at 150-180°C can effectively avoid the damage of high temperature to the polymer material, and also ensure the effective combination of slag and steel slag.

[0017] The raw material component polyaspartic acid of the present invention is a highly efficient dispersant and chelating agent, which can effectively improve the fluidity and stability of the material while enhancing its environmental friendliness; the desulfurized gypsum can further provide good gelling properties, and the aluminum phosphate enhances the durability and compressive strength of the material. The combined effect makes the filling material have better comprehensive performance.

[0018] During the entire preparation process of the filling material of the present invention, the temperature is controlled within a reasonable range, thereby avoiding excessive energy consumption and reducing production costs. In addition, the use of environmentally friendly reagents such as acetic acid solution and polyaspartic acid reduces the emission of harmful substances, thus meeting the requirements of green environmental protection.

[0019] The present invention discloses the following technical effects: 1. The coal mine paste filling material of the present invention has excellent flow properties and can be smoothly pumped without adding additional admixtures. While ensuring sufficient fluidity, it can still maintain good cohesion and avoid the occurrence of stratification, which greatly facilitates construction operations in complex environments under goaf areas and improves work efficiency.

[0020] 2. The filling material of the present invention exhibits high compressive strength at an early stage and can effectively prevent crack expansion even when subjected to large loads or deformation, thereby ensuring the safety and durability of the structure while demonstrating excellent load-bearing capacity.

[0021] 3. The filling material of the present invention has long-term stability and will not show obvious signs of deterioration even after long-term exposure to the natural environment.

[0022] 4. The present invention adheres to the concept of green development, selects natural minerals as the main raw materials, strictly controls the emission of harmful substances, meets environmental protection requirements, and is conducive to promoting resource recycling and sustainable development.

[0023] 5. This invention maximizes economic and social benefits while ensuring safe production in mines, and is a filling material solution with great potential. DETAILED DESCRIPTION

[0024] 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.

[0025] It should be understood that the terms used in this invention are only for describing specific embodiments and are not intended to limit the invention. Additionally, for the 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. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in this invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0026] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0027] Without departing from the scope or spirit of this invention, various improvements and changes can be made to the specific embodiments of the specification of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the specification of this invention are obvious to those skilled in the art. The specification and examples of this invention are merely exemplary.

[0028] Regarding "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to. Examples

[0029] This example provides a coal mine filling material, and the mass ratio of raw materials is as follows: 23 parts of slag, 14 parts of furnace slag, 8 parts of carbide slag, 9 parts of steel slag, 5 parts of desulfurized gypsum, 6 parts of polyaspartic acid, 10 parts of aluminum phosphate, 5 parts of sodium hydroxide, and 35 parts of water.

[0030] The preparation steps are as follows: (1) Soak the slag, furnace slag, and carbide slag in an acetic acid solution with a mass concentration of 30% for 40 min to obtain modified silicate minerals; calcine the steel slag at 850 °C to obtain the calcined steel slag; (2) Mix the modified silicate minerals with the calcined steel slag, then add a mixture of polycarbonate and polyacrylamide with a mass ratio of 1:2, carry out a blending reaction at 180 °C for 5 min, and then cool to room temperature at a cooling rate of 10 °C / min; wherein, the total mass of polycarbonate and polyacrylamide is 20% of the total mass of the modified silicate minerals and the calcined steel slag.

[0031] (3) Add the aqueous solution of polyaspartic acid to the reaction system in step (2), and stir; wherein, the aqueous solution of polyaspartic acid is obtained by dissolving polyaspartic acid in water with a mass ratio of half of the raw material ratio. (4) Add desulfurized gypsum and aluminum phosphate to the system in step (3), and add sodium hydroxide and water with the remaining mass ratio of raw materials, and stir to obtain the coal mine paste filling material. Example

[0032] This example provides a coal mine filling material, and the mass ratio of raw materials is as follows: 20 parts of slag, 15 parts of furnace slag, 8 parts of carbide slag, 10 parts of steel slag, 5 parts of desulfurized gypsum, 5 parts of polyaspartic acid, 10 parts of aluminum phosphate, 6 parts of sodium hydroxide, and 25 parts of water.

[0033] The preparation steps are as follows: (1) Immerse the slag, furnace slag, and carbide slag in acetic acid solution with a mass concentration of 35% for 45 min to obtain modified silicate minerals; calcine the steel slag at 1000 °C to obtain the calcined steel slag. (2) Mix the modified silicate minerals with the calcined steel slag, then add a mixture of polycarbonate and polyacrylamide with a mass ratio of 2:3, carry out a blending reaction at 150 °C for 6 min, and then cool to room temperature at a cooling rate of 8 °C / min; wherein, the total mass of polycarbonate and polyacrylamide is 25% of the total mass of the modified silicate minerals and the calcined steel slag.

[0034] (3) Add the aqueous solution of polyaspartic acid to the reaction system in step (2), and stir; wherein, the aqueous solution of polyaspartic acid is obtained by dissolving polyaspartic acid in water with a mass ratio of half of the raw material ratio. (4) Add desulfurized gypsum and aluminum phosphate to the system in step (3), and add sodium hydroxide and water with the remaining mass ratio of raw materials, and stir to obtain the coal mine paste filling material. Example

[0035] This example provides a coal mine filling material, and the mass ratio of raw materials is as follows: 22 parts of slag, 12 parts of furnace slag, 8 parts of carbide slag, 10 parts of steel slag, 5 parts of desulfurized gypsum, 5 parts of polyaspartic acid, 12 parts of aluminum phosphate, 7 parts of sodium hydroxide, and 35 parts of water.

[0036] The preparation steps are as follows: (1) Immerse the slag, furnace slag, and carbide slag in acetic acid solution with a mass concentration of 28% for 30 min to obtain modified silicate minerals; calcine the steel slag at 800 °C to obtain the calcined steel slag. (2) Mix the modified silicate mineral with the calcined steel slag, then add a mixture of polycarbonate and polyacrylamide with a mass ratio of 1:3, carry out a blending reaction at 180 °C for 5 min, and then cool to room temperature at a cooling rate of 8 °C / min; wherein, the total mass of polycarbonate and polyacrylamide is 22% of the total mass of the modified silicate mineral and the calcined steel slag.

[0037] (3) Add the aqueous solution of polyaspartic acid to the reaction system of step (2) and stir; wherein, the aqueous solution of polyaspartic acid is obtained by dissolving polyaspartic acid in half of the mass portion of water. (4) Add desulfurized gypsum and aluminum phosphate to the system of step (3), and add sodium hydroxide and the remaining mass portion of water, and stir to obtain a coal mine paste filling material. Example

[0038] This example provides a coal mine filling material, and the raw material mass portion ratio is as follows: 25 parts of slag, 12 parts of furnace slag, 8 parts of carbide slag, 8 parts of steel slag, 6 parts of desulfurized gypsum, 5 parts of polyaspartic acid, 10 parts of aluminum phosphate, 6 parts of sodium hydroxide, and 40 parts of water.

[0039] The preparation steps are as follows: (1) Immerse the slag, furnace slag, and carbide slag in an acetic acid solution with a mass concentration of 30% for 35 min to obtain a modified silicate mineral; calcine the steel slag at 900 °C to obtain the calcined steel slag. (2) Mix the modified silicate mineral with the calcined steel slag, then add a mixture of polycarbonate and polyacrylamide with a mass ratio of 2:3, carry out a blending reaction at 150 °C for 5 min, and then cool to room temperature at a cooling rate of 8 °C / min; wherein, the total mass of polycarbonate and polyacrylamide is 25% of the total mass of the modified silicate mineral and the calcined steel slag.

[0040] (3) Add the aqueous solution of polyaspartic acid to the reaction system of step (2) and stir; wherein, the aqueous solution of polyaspartic acid is obtained by dissolving the polyaspartic acid in half of the mass portion of water. (4) Add desulfurized gypsum and aluminum phosphate to the system of step (3), and add sodium hydroxide and the remaining mass portion of water, and stir to obtain a coal mine paste filling material.

[0041] The difference from Example 1 is only that polyacrylamide is replaced with an equal mass of polycarbonate.

[0042] The difference from Example 1 is only that the mixing reaction process in step (2) is not carried out. (1) Soak slag, blast furnace slag and carbide slag in acetic acid solution with a mass concentration of 30% for 40 min to obtain modified silicate minerals; calcine steel slag at 850 °C to obtain calcined steel slag; (2) Add an aqueous solution of polyaspartic acid to the reaction system in step (1) and stir; wherein, the aqueous solution of polyaspartic acid is obtained by dissolving polyaspartic acid in water with a mass ratio of half; (3) Add desulfurized gypsum and aluminum phosphate to the system in step (2), and add sodium hydroxide and water with the remaining raw material ratio, and stir to obtain a paste filling material for coal mines.

[0043] The difference from Example 1 is only that polyaspartic acid is replaced with polyacrylic acid of equal mass.

[0044] 1. Fluidity test Refer to "Standard Test Method for Properties of Ordinary Concrete Mixtures" (GB / T 50080-2016), and evaluate the fluidity by measuring the settlement depth of the paste under a standard cone according to the penetrometer method.

[0045] The penetrometer results of the paste filling materials prepared in Examples 1-4 and Comparative Examples 1-3 are shown in Table 1: Table 1 Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Penetration (mm) 35 37 36 35 33 32 33 2. Density test Refer to "Standard Test Methods for Geotechnical Engineering" (GB / T 50123-2019), and measure the wet density and dry density of the filling material according to the unit weight determination method to understand the mass distribution per unit volume.

[0046] The wet density and dry density data of the paste filling materials prepared in Examples 1-4 and Comparative Examples 1-3 are shown in Table 2.

[0047] Table 2 Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Wet density (g / cm³) 1.81 1.86 1.79 1.85 1.70 1.63 1.66 Dry density (g / cm³) 1.52 1.55 1.53 1.56 1.41 1.38 1.44 3. Compressive strength test Refer to "Standard Test Methods for Physical and Mechanical Properties of Concrete" (GB / T 50081-2019), prepare standard specimens with dimensions of 100 mm × 100 mm × 100 mm, apply axial load on a press until failure, record the maximum bearing capacity, and calculate the compressive strength value.

[0048] The compressive strength results of the paste filling materials prepared in Examples 1-4 and Comparative Examples 1-3 at different ages under standard curing are shown in Table 3.

[0049] Table 3 7-day compressive strength (MPa) 28-day compressive strength (MPa) Example 1 5.9 10.2 Example 2 5.8 10.8 Example 3 5.6 9.8 Example 4 5.8 10.7 Comparative Example 1 3.5 5.9 Comparative Example 2 3.2 6.2 Comparative Example 3 3.3 5.7 4. Elastic modulus test Refer to the "Standard Test Methods for Physical and Mechanical Properties of Concrete" (GB / T 50081-2019), conduct uniaxial compression tests, and obtain the elastic moduli of various materials after 7 days of curing. The results are shown in Table 4.

[0050] Table 4 4. Acid and alkali corrosion resistance test Refer to the "Standard Test Methods for Long-Term Performance and Durability of Ordinary Concrete" (GB / T 50082-2009), immerse the paste filling material specimens in sulfuric acid solution with pH = 2 or sodium hydroxide solution with pH = 12 respectively. After 7 days of immersion, take them out, clean and dry, compare the mass change and appearance damage degree before and after, and evaluate their corrosion resistance. The results are shown in Table  5.

[0051] Table 5 Mass loss rate after soaking in sulfuric acid solution with pH = 2 for 7 days (%) Swelling and disintegration conditions after soaking in sodium hydroxide solution with pH = 12 for 7 days Example 1 1.56 No obvious swelling or disintegration Example 2 1.53 No obvious swelling or disintegration Example 3 1.49 No obvious swelling or disintegration Example 4 1.51 No obvious swelling or disintegration Comparative Example 1 2.68 No obvious swelling or disintegration Comparative Example 2 2.45 No obvious swelling or disintegration Comparative Example 3 2.52 No obvious swelling or disintegration The mass loss rate of the coal mine filling material of the present invention after being immersed in sulfuric acid solution with pH = 2 for 7 days is less than 2%, and there is no obvious expansion or disintegration phenomenon after being immersed in sodium hydroxide solution with pH = 12 for 7 days.

[0052] 5. Leaching toxicity test: According to the "Leaching Method for Leaching Toxicity of Solid Wastes" standard, simulate the groundwater environment, measure the concentration of harmful substances released by the paste filling material during the leaching process, and evaluate its potential pollution risk to the surrounding water bodies. The results show that the leaching concentrations of heavy metal ions in the filling materials of each example and comparative example are all lower than the limits specified in GB 18598-2019, and no organic pollutants are detected.

[0053] 6. Accelerated aging test: According to the "Standard Test Methods for Long-Term Performance and Durability of Ordinary Concrete" (GB / T 50082-2009), under the simulated extreme climate conditions (-20°C to +60°C cycle), after 1000 freeze-thaw cycles, the compressive strength retention rates of each filling material are shown in Table 6.

[0054] Table 6 The preparation process of the present invention not only realizes the resource utilization of industrial waste residues, but also significantly improves the performance of coal mine paste filling materials through reasonable modification treatment and composite material design. At the same time, the preparation process pays attention to environmental friendliness and economic feasibility, and has broad application prospects.

[0055] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention should fall within the protection scope determined by the claims of the present invention.

Claims

1. A paste filling material for coal mines, characterized in that, Comprising the following raw material components by mass parts: 20-25 parts of slag, 12-15 parts of furnace slag, 8-10 parts of carbide slag, 8-10 parts of steel slag, 5-6 parts of desulfurized gypsum, 5-6 parts of polyaspartic acid, 8-12 parts of aluminum phosphate, 5-7 parts of sodium hydroxide, and 20-45 parts of water.

2. The preparation method of the coal mine paste filling material according to claim 1, characterized in that Comprising the following steps: (1) Soaking slag, furnace slag, and carbide slag in acetic acid solution to obtain modified silicate minerals; calcining steel slag at 800-1000 °C to obtain calcined steel slag; (2) Blending reaction: Mixing the modified silicate minerals with the calcined steel slag, then adding a mixture of polycarbonate and polyacrylamide, and carrying out a blending reaction at 150-180 °C, and then cooling to room temperature; (3) Adding an aqueous solution of polyaspartic acid to the reaction system in step (2); wherein, the aqueous solution of polyaspartic acid is obtained by dissolving the polyaspartic acid in water with a partial raw material ratio; (4) Adding desulfurized gypsum and aluminum phosphate to the system in step (3), and adding sodium hydroxide and the remaining raw material ratio of water, and stirring to obtain the coal mine paste filling material.

3. The preparation method according to claim 2, characterized in that, The mass ratio of the polycarbonate to the polyacrylamide is 1-2:2-3.

4. The preparation method according to claim 2, wherein The time of the blending reaction is 5-8 min.

5. The preparation method according to claim 2, wherein In step (2), the temperature is cooled to room temperature at a cooling rate of 8-12 °C / min.

6. The preparation method according to claim 2, characterized in that, The total mass of the polycarbonate and the polyacrylamide is 20-25% of the total mass of the modified silicate minerals and the steel slag.

7. Application of the coal mine paste filling material according to claim 1 or the coal mine paste filling material prepared by the preparation method according to any one of claims 2-6 in backfilling of coal mine gob areas.