High-water backfilling material based on red mud aluminum extraction residue and preparation method and application thereof

Abstract

The application provides a high-water backfilling material based on red mud aluminum extraction residue and a preparation method and application thereof. The high-water backfilling material comprises the following components in parts by mass: red mud aluminum extraction residue 155-192 parts, cementing auxiliary material 5-28 parts, mine solid waste 7-22 parts, alkali-reducing cementing component 4-15 parts, retarder 1-5 parts, expanding agent 0.5-6.8 parts and mixing water 12-33 parts. The content of the red mud aluminum extraction residue in the high-water backfilling material is as high as 70% or more, which can greatly reduce the solid waste storage of an aluminum oxide production enterprise, and simultaneously cooperatively absorbs the mine solid waste, thereby realizing bidirectional resource utilization of metallurgical solid waste and mine solid waste. The high-water backfilling material can be directly used for red mud storage yard excavation and mine goaf backfilling, thereby achieving the purpose of in-situ absorption of industrial solid waste.

Description

Technical Field

[0001] This invention belongs to the field of industrial solid waste resource utilization technology, specifically relating to a high-water-content refill material based on red mud aluminum extraction slag, its preparation method and application. Background Technology

[0002] Red mud is a highly alkaline waste residue discharged after alumina production in the aluminum industry. It is both a solid waste and a secondary resource that can be comprehensively utilized. Currently, the research and utilization of red mud mainly involves the extraction of valuable elements (iron, aluminum, titanium, scandium, etc.), the production of building materials, and the manufacturing of functional materials. Bayer process red mud has a high aluminum and sodium content, and the extraction of aluminum and sodium can achieve resource recovery and utilization. The main methods for aluminum recovery from red mud include acid leaching, sintering, calcification-carbonization, and biological methods, among which the sintering method is the most mature. The waste residue generated after recovering aluminum and sodium components is called red mud aluminum extraction slag, which is mainly composed of dicalcium silicate. The amount of slag produced is 0.8-1.2 times that of the original red mud, which increases the amount of waste residue stockpiled.

[0003] However, there is currently a lack of large-scale utilization solutions for red mud aluminum extraction slag in China. Due to the lack of effective disposal methods, the red mud aluminum extraction slag can only continue to be stockpiled, further exacerbating the solid waste disposal pressure on enterprises. The long-term stockpiling of red mud aluminum extraction slag not only occupies land, but the continuous leaching of its residual alkali also poses a long-term pollution risk to the surrounding environment. Summary of the Invention

[0004] The purpose of this invention is to provide a high-water-content refill material based on red mud aluminum extraction slag, which can at least solve some of the defects existing in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A high-water-content backfill material based on red mud aluminum extraction slag comprises the following components by mass: 155-192 parts of red mud aluminum extraction slag, 5-28 parts of cementing auxiliary materials, 7-22 parts of mine solid waste, 4-15 parts of alkali-reducing cementing components, 1-5 parts of retarder, 0.5-6.8 parts of expansion agent, and 12-33 parts of mixing water.

[0007] Furthermore, the red mud aluminum extraction slag is the original waste residue from the red mud dry sintering aluminum extraction process, with a water content of 70-90%, and its chemical composition includes SiO2 mass percentage ≥15%, CaO mass percentage ≥45%, and Na2O mass percentage ≥2.0%.

[0008] Furthermore, the cementitious auxiliary material is one or more of ordinary silicate cement, aluminate cement, blast furnace slag powder, water-quenched steel slag powder, metakaolin and molybdenum tailings, and the fineness of the cementitious auxiliary material is greater than 325 mesh.

[0009] Furthermore, the solid waste from the mine is one or more of the following: limestone ore, granite tailings, coal gangue, and iron tailings.

[0010] Furthermore, the alkali-reducing cementing component is sodium silicate water glass with a modulus of 1.0 to 1.8.

[0011] Furthermore, the retarder is one or more of fluorogypsum and phosphogypsum.

[0012] Furthermore, the expanding agent is one or more of lightly calcined magnesium oxide, calcium carbide sludge, and magnesium slag.

[0013] In addition, the present invention also provides a method for preparing the above-mentioned high-water refill material based on red mud aluminum extraction slag, comprising the following steps:

[0014] S1. Add the designed quality of red mud aluminum extraction slag to the mixing device; S2. Grind the mine solid waste;

[0015] S3. Add the designed mass of cementitious auxiliary materials, finely ground mine solid waste, alkali-reducing cementitious components, retarder, expanding agent and mixing water to the stirring device.

[0016] S4. Stir and mix until uniform to obtain high-water backfill material.

[0017] Furthermore, in S2, the particle size of the finely ground mine solid waste is ≤2.5mm.

[0018] This invention also provides the application of the above-mentioned high-water backfill material based on red mud aluminum extraction slag in backfilling of mined-out areas, backfilling of open-pit storage areas, and remediation of old goaf areas.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] (1) The red mud aluminum extraction slag in the high water content of the red mud aluminum extraction slag provided by this invention is as high as 70% or more, which can significantly reduce the amount of solid waste stockpiled by alumina production enterprises, and at the same time, it can synergistically dispose of mine solid waste, realizing the two-way resource utilization of metallurgical solid waste and mine solid waste.

[0021] (2) The high-moisture backfill material prepared by the present invention has an initial setting time of 4.5 to 7 hours, a final setting time of 6.5 to 10 hours, an expansion of 225 to 265 mm, a 7-day uniaxial compressive strength of 6.5 to 10 MPa, a 28-day uniaxial compressive strength of 16 to 22 MPa, and a bleeding rate of 1.5 to 2.4%, which meets the technical requirements of mine backfilling projects. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] This invention provides a high-water refill material based on red mud aluminum extraction slag, comprising the following components by mass: 155-192 parts of red mud aluminum extraction slag, 5-28 parts of cementing auxiliary materials, 7-22 parts of mining solid waste, 4-15 parts of alkali-reducing cementing components, 1-5 parts of retarder, 0.5-6.8 parts of expansion agent, and 12-33 parts of mixing water.

[0024] Among them, red mud aluminum extraction slag is the original waste residue of the red mud dry sintering aluminum extraction process. Its moisture content is 70-90%, and its chemical composition has the following mass percentages: SiO2 ≥15%, CaO ≥45%, and Na2O ≥2.0%.

[0025] This invention utilizes the high alkalinity of red mud aluminum extraction slag. The soluble alkalis such as Na2O remaining in the red mud aluminum extraction slag dissolve in the slurry system and release a large amount of OH-. - This creates a highly alkaline environment, which effectively breaks down the glassy network structure in cementing auxiliaries (such as blast furnace slag powder and metakaolin), promoting the breaking and recombination of Si-O and Al-O bonds, thereby stimulating their potential hydraulic cementing activity. Simultaneously, the alkali-reducing cementing component introduced into the system (high-modulus sodium silicate water glass) reacts with free alkali to generate cementing products such as hydrated calcium silicate (CSH), significantly enhancing the early strength of the system and solidifying free Na⁺ in a bound state within the products, further reducing the risk of alkali leaching from the backfill material. Therefore, this invention transforms the high alkalinity of red mud aluminum extraction slag from a traditionally perceived "environmental burden" into a "chemical driving force," utilizing its in-situ stimulating cementing reaction to achieve high-strength cementing and solidification without the need for adding large amounts of industrial alkali activators.

[0026] This invention also utilizes the high moisture content of red mud aluminum extraction slag, which has a moisture content of 70-90%. The slurry itself has excellent fluidity and pumpability. Unlike existing technologies that require dehydration and drying of red mud, this invention directly uses the original high-moisture-content red mud aluminum extraction slag as the "liquid phase carrier" and "premixed slurry" in the formulation. The large amount of water it carries directly serves as the mixing water required by the system. While meeting the requirements for material fluidity and spreadability, it eliminates the need to add a large amount of external water source. This not only realizes the in-situ resource utilization of water in the waste residue, but also greatly simplifies the production process, eliminates the dehydration and drying steps, and significantly reduces energy consumption and process costs, making the material preparation more economical and engineering feasible.

[0027] Its mechanism of action lies in the fact that the high water content of red mud aluminum extraction slag provides the liquid medium required for ion migration and reaction, ensuring that the alkali-activated reaction can proceed fully and uniformly; while the high alkalinity provides the necessary kinetic conditions for the hydration of cementitious auxiliary materials, and the NASH / CASH gel in the liquid phase enables the components to quickly bond into a whole; at the same time, the introduction of the retarder component precisely controls the potentially excessively rapid coagulation process in the high alkaline environment, the expansion agent compensates for the later shrinkage, and the mine solid waste serves as a skeleton support to enhance the strength of the system. The resulting formulation as a whole constitutes a self-activated, self-supplying, controllable coagulation, and volume-stable synergistic working system, realizing the efficient, low-cost, and large-scale disposal of red mud aluminum extraction slag, a specific solid waste.

[0028] Optionally, the cementitious auxiliary material is one or more of ordinary Portland cement, aluminate cement, blast furnace slag powder, water-quenched steel slag powder, metakaolin, and molybdenum tailings, and the fineness of the cementitious auxiliary material is greater than 325 mesh. The mine solid waste is one or more of limestone ore, granite tailings, coal gangue, and iron tailings. The alkali-reducing cementing component is commercially available sodium silicate water glass, and the modulus is controlled by mixing sodium silicate nonahydrate with high-modulus water glass, with a modulus of 1.0 to 1.8. The retarder is one or more of fluorogypsum and phosphogypsum. The expanding agent is one or more of lightly calcined magnesia, calcium carbide sludge, and magnesium slag.

[0029] The preparation process and performance of the high-moisture refill material based on red mud aluminate extraction slag of the present invention are illustrated below through specific embodiments. The red mud aluminate extraction slag used in the following embodiments is the original waste residue produced by the dry sintering aluminate extraction process of Bayer red mud, and its chemical composition is shown in Table 1.

[0030] Table 1:

[0031]

[0032] Example 1:

[0033] This embodiment provides a high-water refill material based on red mud aluminum extraction slag, comprising the following components by mass: 178 parts red mud aluminum extraction slag, 10.5 parts blast furnace slag powder, 18 parts coal gangue, 8 parts sodium silicate water glass with a modulus of 1.2, 2 parts fluorogypsum, 3.2 parts magnesium slag, and 22 parts mixing water.

[0034] The high-water backfill preparation process in this embodiment is as follows: 1) Raw red mud aluminum extraction slag is added to a horizontal ribbon mixer via pipeline transportation. The motor power of the horizontal ribbon mixer is 12kW, the single mixing volume is 500kg, and the mixing tank volume is 8m³. 3 2) Grind the coal gangue using a roller mill. The roller mill parameters are as follows: roller diameter 300mm, working roller gap 10mm, maximum feed particle size 40mm, and pre-crushing capacity 400kg / h. 3) Add blast furnace slag powder, ground coal gangue, fluorogypsum, and magnesium slag to the horizontal ribbon mixer according to the above proportions. Add sodium silicate water glass to the mixing water, pre-mix it, and then add it to the horizontal ribbon mixer. 4) Start the horizontal ribbon mixer and run it for 8 minutes to obtain high-moisture backfill material. This high-moisture backfill material can be directly used for grouting backfilling.

[0035] To evaluate the mechanical properties and long-term volume stability of the high-water backfill material in this embodiment, the basic performance of the high-water backfill material obtained in the above steps was tested in accordance with the "Technical Standard for Backfilling Engineering of Metal and Non-metal Mines" (GB / T 51450-2022) and the "Technical Standard for Backfilling Engineering of Flowable Filler" (T / CMEA32-2023). The test results are shown in Table 2.

[0036] Example 2:

[0037] This embodiment provides a high-water-content backfill material based on red mud aluminum extraction slag, comprising the following components by mass: 165 parts red mud aluminum extraction slag, 5 parts metakaolin, 14 parts water-quenched steel slag powder, 20 parts coal gangue, 12 parts sodium silicate water glass with a modulus of 1.0, 2.5 parts fluorogypsum, 1.9 parts magnesium slag, and 16 parts mixing water.

[0038] The high-water backfill preparation process in this embodiment is as follows: 1) Raw red mud aluminum extraction slag is added to a horizontal ribbon mixer via pipeline transportation. The motor power of the horizontal ribbon mixer is 10kW, the single mixing volume is 400kg, and the mixing tank volume is 6.5m³. 32) Grind the coal gangue using a roller mill. The roller mill parameters are as follows: roller diameter 300mm, working roller gap 12mm, maximum feed particle size 40mm, and pre-crushing capacity 450kg / h. 3) Add metakaolin, water-quenched steel slag powder, ground coal gangue, fluorogypsum, and magnesium slag to the horizontal ribbon mixer according to the above proportions. Add sodium silicate water glass to the mixing water, pre-mix it, and then add it to the horizontal ribbon mixer. 4) Start the horizontal ribbon mixer and run it for 6.5 minutes to obtain high-moisture backfill material. This high-moisture backfill material can be directly used for grouting backfilling.

[0039] To evaluate the mechanical properties and long-term volume stability of the high-water backfill material in this embodiment, the basic performance of the high-water backfill material obtained in the above steps was tested in accordance with the "Technical Standard for Backfilling Engineering of Metal and Non-metal Mines" (GB / T 51450-2022) and the "Technical Standard for Backfilling Engineering of Flowable Filler" (T / CMEA32-2023). The test results are shown in Table 2.

[0040] Example 3:

[0041] This embodiment provides a high-water-content backfill material based on red mud aluminum extraction slag, comprising the following components by mass: 180 parts red mud aluminum extraction slag, 2.5 parts blast furnace slag powder, 18 parts water-quenched steel slag powder, 16 parts granite tailings, 5 parts sodium silicate water glass with a modulus of 1.6, 3.5 parts fluorogypsum, 4.2 parts magnesium slag, and 30 parts mixing water.

[0042] The high-water backfill preparation process in this embodiment is as follows: 1) Raw red mud aluminum extraction slag is added to a horizontal ribbon mixer via pipeline transportation. The motor power of the horizontal ribbon mixer is 15kW, the single mixing volume is 600kg, and the mixing tank volume is 9m³. 3 2) Grind the granite tailings using a roller mill. The roller mill parameters are as follows: roller diameter 400mm, working roller gap 8mm, maximum feed particle size 40mm, and pre-crushing capacity 600kg / h. 3) Add blast furnace slag powder, water-quenched steel slag powder, ground granite tailings, fluorogypsum, and magnesium slag to the horizontal ribbon mixer according to the above proportions. Add sodium silicate water glass to the mixing water, pre-mix it, and then add it to the horizontal ribbon mixer. 4) Start the horizontal ribbon mixer and run it for 10 minutes to obtain high-water backfill material. This high-water backfill material can be directly used for grouting backfilling.

[0043] To evaluate the mechanical properties and long-term volume stability of the high-water backfill material in this embodiment, the basic performance of the high-water backfill material obtained in the above steps was tested in accordance with the "Technical Standard for Backfilling Engineering of Metal and Non-metal Mines" (GB / T 51450-2022) and the "Technical Standard for Backfilling Engineering of Flowable Filler" (T / CMEA32-2023). The test results are shown in Table 2.

[0044] Example 4:

[0045] This embodiment provides a high-water refill material based on red mud aluminum extraction slag, comprising the following components by mass: 180 parts red mud aluminum extraction slag, 2 parts blast furnace slag powder, 3 parts aluminate cement, 16 parts molybdenum tailings, 20 parts iron tailings, 9 parts sodium silicate water glass with a modulus of 1.2, 3.2 parts fluorogypsum, 2.8 parts magnesium slag, and 21 parts mixing water.

[0046] The high-water backfill preparation process in this embodiment is as follows: 1) Raw red mud aluminum extraction slag is added to a horizontal ribbon mixer via pipeline transportation. The motor power of the horizontal ribbon mixer is 12kW, the single mixing capacity is 400kg, and the mixing tank volume is 6.5m³. 3 2) Grind the iron tailings using a roller mill. The roller mill parameters are as follows: roller diameter 500mm, working roller gap 10mm, maximum feed particle size 40mm, and pre-crushing capacity 500kg / h. 3) Add blast furnace slag powder, aluminate cement, molybdenum tailings, ground iron tailings, fluorogypsum, and magnesium slag to the horizontal ribbon mixer according to the above proportions. Add sodium silicate water glass to the mixing water, pre-mix it, and then add it to the horizontal ribbon mixer. 4) Start the horizontal ribbon mixer and run it for 8 minutes to obtain high-moisture backfill material. This high-moisture backfill material can be directly used for grouting and backfilling operations.

[0047] To evaluate the mechanical properties and long-term volume stability of the high-water backfill material in this embodiment, the basic performance of the high-water backfill material obtained in the above steps was tested in accordance with the "Technical Standard for Backfilling Engineering of Metal and Non-metal Mines" (GB / T 51450-2022) and the "Technical Standard for Backfilling Engineering of Flowable Filler" (T / CMEA32-2023). The test results are shown in Table 2.

[0048] Table 2:

[0049]

[0050] As shown in Table 2, the high-moisture backfill materials prepared in each embodiment of the present invention all exhibit good workability and mechanical properties. The initial setting time is between 4.5 and 7 hours, and the final setting time is between 6.5 and 10 hours, meeting the requirements for setting time under different construction conditions. The spread is between 225 and 265 mm, indicating good fluidity and pumpability. The 7-day compressive strength reaches 6.5–10 MPa, and the 28-day compressive strength reaches 16–22 MPa, meeting the strength requirements for backfill bodies in mine backfilling projects. The bleeding rate is controlled between 1.5% and 2.4%, indicating good water retention and homogeneity.

[0051] Comparative Example 1:

[0052] This comparative example uses the same formula and preparation method as Example 1, except that the red mud aluminum extraction slag is replaced with an equal mass of Bayer red mud that has not been treated by the dry sintering aluminum extraction process.

[0053] The material performance tests of this comparative example show that the initial setting time is 10h, the final setting time is 13.5h, the spread is 248mm, the uniaxial compressive strength and flexural strength at 7d and 28d are 3.5MPa and 6MPa, respectively, and the bleeding rate is 5.2%.

[0054] Compared with Example 1, the setting time of this comparative example was significantly prolonged (final setting time increased from 7.5h to 13.5h), severely affecting construction efficiency; the compressive strength was significantly reduced (28-day strength decreased from 19MPa to 6MPa); and the bleeding rate increased significantly (from 1.8% to 5.2%), indicating poor water retention and a tendency for segregation and stratification. The comparative results show that the Bayer process red mud without aluminum extraction treatment has a fundamentally different phase composition and chemical activity compared to red mud aluminum extraction slag, and cannot effectively participate in the alkali-activated gelation reaction, thus making it difficult to obtain satisfactory engineering performance.

[0055] Comparative Example 2:

[0056] This comparative example uses the same formula and preparation method as Example 1, the only difference being that the red mud aluminum extraction slag is replaced with an equal mass of red mud aluminum extraction slag that has undergone water washing and dealkalization treatment.

[0057] The material performance tests of the comparative example showed that the initial setting time was 15.5 h, the final setting time was 18.5 h, the spread was 263 mm, the uniaxial compressive strength and flexural strength at 7 days and 28 days were 2.7 MPa and 5.1 MPa, respectively, and the bleeding rate was 4.5%.

[0058] Compared with Example 1, the setting time of this comparative example was significantly prolonged (final setting time increased from 7.5 h to 18.5 h), the compressive strength was significantly reduced (28-day strength decreased from 19 MPa to 5.1 MPa), the water bleeding rate was significantly increased (from 1.8% to 4.5%), and the water retention and homogeneity of the system were significantly worse. The comparative results show that the highly alkaline environment provided by the red mud aluminum extraction slag is the core driving force for activating the hydration activity of the cementing auxiliary materials. After water washing and dealkalization, a large amount of soluble Na2O and other alkaline components in the red mud aluminum extraction slag are removed, the pH value of the system is significantly reduced, and the glassy network structure in the cementing auxiliary materials (such as blast furnace slag powder) cannot be effectively broken. The hydration reaction is difficult to start or the degree of reaction is extremely low, so sufficient cementing strength cannot be formed.

[0059] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A high-water-content refill material based on red mud aluminum extraction slag, characterized in that, It includes the following components by mass: 155-192 parts of red mud aluminum extraction slag, 5-28 parts of cementing auxiliary materials, 7-22 parts of mine solid waste, 4-15 parts of alkali-reducing cementing components, 1-5 parts of retarder, 0.5-6.8 parts of expansion agent, and 12-33 parts of mixing water.

2. The high-water refill material based on red mud aluminum extraction slag as described in claim 1, characterized in that, The red mud aluminum extraction slag is the original waste residue from the red mud dry sintering aluminum extraction process. Its moisture content is 70-90%, and its chemical composition has the following mass percentages: SiO2 ≥ 15%, CaO ≥ 45%, and Na2O ≥ 2.0%.

3. The high-water refill material based on red mud aluminum extraction slag as described in claim 1, characterized in that, The cementitious auxiliary material is one or more of ordinary silicate cement, aluminate cement, blast furnace slag powder, water-quenched steel slag powder, metakaolin and molybdenum tailings, and the fineness of the cementitious auxiliary material is greater than 325 mesh.

4. The high-water refill material based on red mud aluminum extraction slag as described in claim 1, characterized in that, The solid waste from the mine is one or more of the following: limestone ore, granite tailings, coal gangue, and iron tailings.

5. The high-water refill material based on red mud aluminum extraction slag as described in claim 1, characterized in that, The alkali-reducing cementing component is sodium silicate water glass with a modulus of 1.0 to 1.

8.

6. The high-water refill material based on red mud aluminum extraction slag as described in claim 1, characterized in that, The retarder is one or more of fluorogypsum and phosphogypsum.

7. The high-water refill material based on red mud aluminum extraction slag as described in claim 1, characterized in that, The expanding agent is one or more of lightly calcined magnesium oxide, calcium carbide sludge, and magnesium slag.

8. A method for preparing a high-moisture backfill material based on red mud aluminum extraction slag as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Add the designed quality of red mud aluminum extraction slag to the mixing device; S2. Grind the mine solid waste; S3. Add the designed mass of cementitious auxiliary materials, finely ground mine solid waste, alkali-reducing cementitious components, retarder, expanding agent and mixing water to the stirring device. S4. Stir and mix until uniform to obtain high-water backfill material.

9. The preparation method according to claim 8, characterized in that, In S2, the particle size of the finely ground mine solid waste is ≤2.5mm.

10. The application of the high-water backfill material based on red mud aluminum extraction slag as described in any one of claims 1-7 in backfilling of mined-out areas, backfilling of open-pit storage areas, and remediation of old goaf areas.

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