Filling material for improving filling strength of low-concentration fine-fraction iron tailings and preparation method of filling material

Abstract

The invention relates to the technical field of underground filling of metal mines, in particular to a filling material for improving the filling strength of low-concentration fine-fraction iron tailings and a preparation method of the filling material. The invention discloses a filling material for improving the filling strength of low-concentration fine-fraction iron tailings. The filling material is prepared from the following raw materials in parts by weight: 4500-5400 parts of fine-fraction wet-based iron tailing slurry, 500-600 parts of a cementing material, 5-6 parts of an exciting agent, 5-6 parts of a reinforcing agent A and 5-6 parts of a reinforcing agent B, according to the method, the iron tailing slurry with high water content and high fine silt content is directly used as a main raw material, a composite gelling system is constructed by adopting a particle-plant fiber composite enhancement technology, and the strength of the filling material is remarkably improved through a physical and chemical synergistic effect. According to the method, an expensive tailing deep dehydration link is omitted, the use amount of the cementing material is remarkably reduced while the utilization rate of the wet-based fine-fraction tailings is greatly increased (up to 90% or above), and the method has the advantages of simple process, low cost, high strength and the like, and is easy to realize industrial application.

Description

Technical Field

[0001] This invention relates to the field of underground backfilling technology in metal mines, specifically to a backfilling material and its preparation method for improving the backfilling strength of low-concentration fine-grained iron tailings. Background Technology

[0002] Iron tailings are solid waste generated after iron ore beneficiation. Their storage not only occupies a large amount of land but also causes environmental pollution and safety hazards. Backfilling mining is a green mining technology that backfills tailings into underground goaf areas, effectively solving the above problems and controlling ground pressure.

[0003] However, with the continuous mining of iron ore resources, the grade of the feed ore has decreased and the grinding fineness has increased, resulting in a significant increase in the content of fine particles (below 38μm) in the tailings. These fine-particle tailings usually exist in a wet matrix with high water content, and are characterized by small particles, large specific surface area, strong water retention, and difficulty in dewatering. When used directly in traditional cemented backfilling, the following prominent problems exist: (1) The strength of the backfill material is low. The high content of fine-particle tailings will lead to a large increase in water demand. The high water-cement ratio will severely dilute the cementitious material, making it difficult to form a dense structure, resulting in extremely low final strength. (2) The consumption of cementitious materials is large. In order to achieve the design strength, it is necessary to significantly increase the amount of cement and other cementitious materials, resulting in high backfilling costs. (3) The dewatering efficiency is low and the settling is slow. Fine-particle tailings will clog the filter cloth or dewatering holes, prolonging the dewatering time and affecting the mining cycle operation.

[0004] Currently, the main method for treating fine-grained tailings is to perform deep dewatering (such as using high-efficiency thickeners and filter presses) to reduce their moisture content, but the investment and operating costs of such equipment are extremely high. Therefore, developing a method that does not rely on deep dewatering and directly and efficiently utilizes a high proportion of fine-grained wet-based iron tailings to prepare high-strength backfill materials is of great significance for reducing backfilling costs and promoting the resource utilization of tailings. Summary of the Invention

[0005] To address the above-mentioned technical problems, the purpose of this invention is to overcome the shortcomings of existing technologies and provide a simple and low-cost backfill material for improving the backfill strength of low-concentration fine-grained iron tailings, as well as its preparation method. This method can directly utilize fine-grained tailings with high moisture content, and through chemical activation and particle-plant fiber composite reinforcement technology, significantly improve the early and late strength of the backfill material, while greatly reducing the amount of cementitious material used.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A backfill material for improving the backfill strength of low-concentration fine-grained iron tailings is prepared from the following raw materials in parts by weight: 4500-5400 parts of fine-grained wet-based iron tailings slurry, 500-600 parts of cementitious material, 5-6 parts of activator, 5-6 parts of reinforcing agent A, and 5-6 parts of reinforcing agent B.

[0007] The filling material uses 60% fine-grained wet-based iron tailings slurry as the basic raw material. Through the synergistic strengthening effect of two reinforcing agents, the compressive strength of the filling material is effectively improved, realizing the comprehensive utilization of fine-grained iron tailings.

[0008] Preferably, in the fine-grained wet-based iron tailings slurry, the mass concentration of fine-grained wet-based iron tailings powder is 60%, and in the fine-grained wet-based iron tailings powder, the proportion of particles with a particle size of less than 38 μm is ≥60%, the proportion of particles with a particle size between 38 and 74 μm is 30%, the proportion of particles with a particle size of more than 74 μm is ≤10%, and the moisture content of the fine-grained wet-based iron tailings powder is 40 ± 0.5%.

[0009] Preferably, the cementitious material is composed of ordinary Portland cement and slag powder in a mass ratio of 1:1 to 3, wherein the slag powder is S95 grade slag powder.

[0010] Preferably, the activator is anhydrous sodium sulfate.

[0011] Preferably, the reinforcing agent A is a plant fiber with a length of 10-20 mm and a diameter of 25-35 μm. More preferably, the plant fiber is selected from cotton fiber or hemp fiber.

[0012] Preferably, the reinforcing agent B is nano-silica with a particle size of 10-30 nm, a purity of ≥ 99%, and a specific surface area greater than 150 m² / g.

[0013] A method for preparing a backfill material to improve the backfill strength of low-concentration fine-grained iron tailings includes the following steps: (1) Fine-grained wet-based iron tailings slurry is added to cementitious materials for the first stage of mixing to form a filling slurry; (2) Add activator, reinforcing agent A and reinforcing agent B to the filling slurry and stir in the second stage to obtain the filling material.

[0014] Preferably, in step (1), the stirring speed of the first stage is 100-200 rpm and the stirring time is 60-1200 s.

[0015] Preferably, in step (2), the stirring speed of the second stage is 300-500 rpm and the stirring time is 60-600 s.

[0016] Preferably, the fine-grained wet-based iron tailings slurry is prepared by the following method: a fine-grained wet-based iron tailings slurry with a mass concentration of 60% is obtained by using a vertical sand bin or a deep cone thickener.

[0017] The beneficial effects of this invention are as follows: (1) This application uses fine-grained wet iron tailings slurry with high water content, high fine mud content and mass concentration of about 60% as the main raw material. On the one hand, it makes efficient use of fine-grained iron tailings, and on the other hand, it saves production costs by eliminating the expensive deep dewatering process of tailings and reduces wastewater discharge.

[0018] (2) This application adopts particle-plant fiber composite reinforcement technology, which cleverly integrates the "rigid skeleton" effect of nano silica particles and the "flexible bonding" effect of plant fibers to construct a composite cementing system. The compressive strength of the filling material prepared in this application at 28 days is 23% higher than that of the single reinforcing agent, realizing the synergistic optimization of macroscopic mechanical properties and microstructural characteristics.

[0019] (3) This invention significantly improves the utilization rate of wet-based fine-grained tailings (to over 90%) while significantly reducing the amount of cementitious materials used (over 20-30%). While achieving the same or even higher filling strength, the cost of the filling materials in this invention is significantly reduced, resulting in significant economic benefits. Furthermore, this invention also has the advantages of simple process, low cost, and high strength, making it easy to implement in industrial applications. Detailed Implementation

[0020] The present application will now be described in detail with reference to embodiments. The various examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will understand that modifications and variations can be made to the present application without departing from the scope or spirit of the present application. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention should fall within the scope of protection of the embodiments of the present invention.

[0021] A backfill material for improving the backfill strength of low-concentration fine-grained iron tailings is prepared from the following raw materials in parts by weight: The fine-grained wet-based iron tailings slurry contains 4500–5400 parts. The fine-grained wet-based iron tailings powder has a mass concentration of 60%. Of the fine-grained wet-based iron tailings powder, particles smaller than 38 μm account for ≥60%, particles between 38 and 74 μm account for 30%, and particles larger than 74 μm account for ≤10%. The moisture content of the fine-grained wet-based iron tailings powder is 40 ± 0.5%. 500-600 parts of cementitious material, which is composed of ordinary Portland cement and slag powder in a mass ratio of 1:1-3. The slag powder is S95 grade slag powder. 5-6 parts of activator, the activator being anhydrous sodium sulfate; Reinforcing agent A: 5-6 parts. Reinforcing agent A is plant fiber with a length of 10-20 mm and a diameter of 25-35 μm. The plant fiber is selected from cotton or hemp fiber. 5-6 parts of reinforcing agent B; reinforcing agent B is nano-silica with a particle size of 10-30 nm, a purity of ≥ 99%, and a specific surface area greater than 150 m² / g.

[0022] A method for preparing a backfill material to improve the backfill strength of low-concentration fine-grained iron tailings includes the following steps: (1) Add fine-grained wet-based iron tailings slurry to cementitious materials for the first stage of stirring to form a filling slurry; the stirring speed of the first stage is 100-200 rpm and the stirring time is 60-1200s; the fine-grained wet-based iron tailings slurry is prepared by the following method: using a vertical sand bin or deep cone thickener, the underflow mass concentration of the fine-grained iron tailings slurry is increased to 60% to obtain a fine-grained wet-based iron tailings slurry with a mass concentration of 60%.

[0023] (2) Add activator, reinforcing agent A and reinforcing agent B to the filling slurry and carry out the second stage of stirring to obtain the filling material; the stirring speed of the second stage is 300-500 rpm and the stirring time is 60-600s.

[0024] Example 1 A method for preparing a backfill material to improve the backfill strength of low-concentration fine-grained iron tailings includes the following steps: (1) Prepare the following ingredients: 700g of fine-grained wet-based iron tailings slurry, with a fine-grained wet-based iron tailings mass concentration of 60%. A mass concentration of 60% is chosen to ensure pumpability and stability while also being technically mature and economically feasible. Particles with a diameter of less than 38μm account for 60%, particles with a diameter between 38 and 74μm account for 30%, and the remaining particles have a diameter >74μm. The moisture content of the fine-grained wet-based iron tailings powder is 40%. The fine-grained wet-based iron tailings slurry is prepared using the following method: a vertical sand silo or deep cone thickener is used to increase the underflow mass concentration of the fine-grained iron tailings slurry to 60%, thus obtaining a fine-grained wet-based iron tailings slurry with a mass concentration of 60%. 70g of cementitious material, which is composed of ordinary Portland cement and slag powder in a mass ratio of 1:1 to 3. The slag powder is S95 grade slag powder. Activator (anhydrous sodium sulfate) 3g; Reinforcing agent A (plant cotton fiber) 7g, the cotton fiber length is 10-10mm and the diameter is 25-35μm; 7g of reinforcing agent B (nano silica), the particle size of nano silica is 10-30 nm, the purity of nano silica is ≥ 99%, and the specific surface area is greater than 150 m² / g.

[0025] (2) Add fine-grained wet-based iron tailings slurry and cementitious material to the mixer and stir at 150 rpm for 300 s to form filling slurry.

[0026] (3) Add an activator to the above filling slurry and stir at 400 rpm for 150 s. Then, add reinforcing agent A (plant fiber) and stir at 400 rpm for 60 s until uniform. Finally, add reinforcing agent B (nano silica) and stir at 400 rpm for 60 s to obtain uniform fine-grained iron tailings filling material.

[0027] The above-mentioned fine-grained iron tailings backfill material was poured into a mold and cured for 3 days, 7 days and 28 days under standard curing conditions of 20±2℃ and 95% humidity. The uniaxial compressive strength was then measured, and the results are shown in Table 1.

[0028] Comparative Example 1 A method for preparing a backfill material to improve the backfill strength of low-concentration fine-grained iron tailings includes the following steps: (1) Prepare the following ingredients: 700g of fine-grained wet-based iron tailings slurry was prepared using the same method as in Example 1.

[0029] 70g of cementitious material, including 14g of PO 42.5 cement and 56g of S95 grade slag powder; Activator (anhydrous sodium sulfate) 3g; The preparation and testing methods in this embodiment are the same as in Embodiment 1, and the results are shown in Table 1.

[0030] Comparative Example 2 A method for preparing a backfill material to improve the backfill strength of low-concentration fine-grained iron tailings includes the following steps: (1) Prepare the following ingredients: 700g of fine-grained wet-based iron tailings slurry; 70g of cementitious material, including 14g of PO 42.5 cement and 56g of S95 grade slag powder; Activator (sodium sulfate) 3g; Reinforcing agent A (cotton fiber) 7g; The preparation and testing methods in this embodiment are the same as in Embodiment 1, and the results are shown in Table 1.

[0031] Comparative Example 3 A method for preparing a backfill material to improve the backfill strength of low-concentration fine-grained iron tailings includes the following steps: (1) Prepare the following ingredients: 700g of fine-grained wet-based iron tailings slurry; 70g of cementitious material, including 14g of PO 42.5 cement and 56g of S95 grade slag powder; Activator (sodium sulfate) 3g; Enhancer B (nano silica) 7g; The preparation and testing methods in this embodiment are the same as in Embodiment 1, and the results are shown in Table 1.

[0032] Comparative Example 4 700g of fine-grained wet-based iron tailings slurry from the same source as in Example 1 was used with a traditional backfilling formula: 70g of PO 42.5 cement, with the same concentration as the slurry in Example 1 (approximately 60%). After mixing, the slurry was cured under the same conditions and its compressive strength was tested. The results are shown in Table 1.

[0033] Table 1 Performance characterization results of the examples and comparative examples As shown in Table 1, using the method of the present invention (Example 1), with the same amount of cementitious material, the strength at all ages of the group without cementitious materials (Comparative Example 1) is significantly higher than that of the group without cementitious materials (Comparative Example 2). Compared with Comparative Examples 2 and 3, Example 1 demonstrates that the two cementitious materials have a synergistic effect on the compressive strength of fine-grained wet-based iron tailings backfill materials. Using the method of the present invention (Example 1), with the same amount of cementitious material, the strength at all ages of the material is significantly higher than that of the traditional method (Comparative Example 4), while ensuring fluidity and effectively controlling bleeding, thus ensuring good pipeline transportation capacity. This fully demonstrates that the present invention has significant advantages in improving the strength of low-concentration fine-grained iron tailings backfill materials and reducing the amount of cementitious material used.

[0034] This invention directly utilizes fine-grained wet-based iron tailings slurry with high water content, eliminating the expensive deep dewatering process. It also innovatively introduces nano-silica and plant fibers for synergistic physical and chemical enhancement, successfully achieving the goals of significantly improving the strength of the filling material, reducing the amount of cementing material by 20-30%, and achieving a tailings utilization rate of over 90%. At the same time, it has both cost and environmental advantages.

[0035] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0036] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A backfill material for improving the backfill strength of low-concentration fine-grained iron tailings, characterized in that, It is prepared from the following raw materials by weight: 4500-5400 parts of fine-grained wet-based iron tailings slurry, 500-600 parts of cementitious material, 5-6 parts of activator, 5-6 parts of reinforcing agent A, and 5-6 parts of reinforcing agent B.

2. The backfill material for improving the backfill strength of low-concentration fine-grained iron tailings according to claim 1, characterized in that, In the fine-grained wet-based iron tailings slurry, the mass concentration of fine-grained wet-based iron tailings powder is 60%. Among the fine-grained wet-based iron tailings powder, the proportion of particles with a diameter less than 38 μm is ≥60%, the proportion of particles with a diameter between 38 and 74 μm is 30%, the proportion of particles with a diameter greater than 74 μm is ≤10%, and the moisture content of the fine-grained wet-based iron tailings powder is 40 ± 0.5%.

3. The backfill material for improving the backfill strength of low-concentration fine-grained iron tailings according to claim 1, characterized in that, The cementitious material is composed of ordinary Portland cement and slag powder in a mass ratio of 1:1 to 3, and the slag powder is S95 grade slag powder.

4. The backfill material for improving the backfill strength of low-concentration fine-grained iron tailings according to claim 1, characterized in that, The activator is anhydrous sodium sulfate.

5. The backfill material for improving the backfill strength of low-concentration fine-grained iron tailings according to claim 1, characterized in that, The reinforcing agent A is a plant fiber with a length of 10-20 mm and a diameter of 25-35 μm.

6. The backfill material for improving the backfill strength of low-concentration fine-grained iron tailings according to claim 1, characterized in that, The reinforcing agent B is nano-silica with a particle size of 10-30 nm, a purity of ≥ 99%, and a specific surface area greater than 150 m² / g.

7. A method for preparing a backfill material for improving the backfill strength of low-concentration fine-grained iron tailings as described in any one of claims 1 to 6, characterized in that, Includes the following steps: (1) The fine-grained wet-based iron tailings slurry is mixed with cementitious materials in the first stage to form a filling slurry; (2) Add activator, reinforcing agent A and reinforcing agent B to the filling slurry and stir in the second stage to obtain the filling material.

8. The method for preparing the backfill material for improving the backfill strength of low-concentration fine-grained iron tailings according to claim 7, characterized in that, In step (1), the stirring speed of the first stage is 100-200 rpm and the stirring time is 60-1200 s.

9. The method for preparing the backfill material for improving the backfill strength of low-concentration fine-grained iron tailings according to claim 7, characterized in that, In step (2), the stirring speed of the second stage is 300-500 rpm and the stirring time is 60-600s.

10. The method for preparing the backfill material for improving the backfill strength of low-concentration fine-grained iron tailings according to claim 7, characterized in that, The fine-grained wet-based iron tailings slurry is prepared by the following method: a fine-grained wet-based iron tailings slurry with a mass concentration of 60% is obtained by using a vertical sand bin or a deep cone thickener.

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