Method for preparing cementitious materials for mine backfilling using iron tailings from suspension roasting

Abstract

This invention discloses a method for preparing a cementitious material for mine backfilling using suspended roasted iron ore tailings. The cementitious material is composed of the following components, with the following mass percentages at 100%: suspended roasted iron ore tailings 24%–35%, composite powder 63.5%–74.7%, and activator 0.3%–1.5%. The composite powder is a mixture of slag powder, desulfurized gypsum, and cement in a specific ratio. The activator is a mixture of sodium ethylsilicate, sodium sulfate, sodium lignosulfonate, and triethanolamine in a specific ratio. Using this cementitious material to solidify fine-grained iron tailings can yield backfill with a compressive strength exceeding 2.6 MPa, fully meeting the requirements of underground backfilling processes. This method is simple, safe, and pollution-free in tailings treatment, realizing the resource utilization of suspended roasted iron ore tailings and providing a new approach for its resource utilization.

Description

Technical Field

[0001] This invention belongs to the technical field of preparation of cementitious materials for tailings backfilling, and in particular relates to a method for preparing mine backfilling cementitious materials using iron tailings from suspension roasting. Background Technology

[0002] Currently, most cementitious materials used in mines are made from cement clinker, slag, gypsum, and other activators, resulting in high costs. For example, Chinese patent (CN201510166877) utilizes blast furnace water-quenched slag, fly ash, cement clinker, lime, and gypsum in a specific ratio to prepare a novel cementitious agent for tailings consolidation and discharge. While the strength of the filling body meets requirements, the raw material cost of this method is high. For ordinary tailings-based cementitious materials, due to the low activity of tailings themselves, high-temperature thermal activation or chemical treatment is usually required to produce cementitious materials, leading to high costs and difficulty in industrialization. For instance, Chinese patent (CN2020107722659) discloses a tailings-based cementitious material and its preparation method, which involves drying the tailings and then sequentially subjecting them to mechanical ball milling activation, thermal activation, and chemical activation treatment to obtain the tailings-based cementitious material. Although the properties of the cementitious material obtained by this method can meet the requirements of the downhole filling process, its thermal activation process requires a high temperature of 300-1000℃, which not only consumes a lot of energy but also causes a lot of pollution.

[0003] The vast majority of iron ore in my country is refractory iron ore, and suspension roasting magnetic separation technology is a new technology for processing refractory iron ore. Compared with traditional strong magnetic and flotation technologies, suspension roasting magnetic separation technology can significantly improve concentrate grade and metal recovery rate, thus having a very broad application prospect. This technology has been industrially applied at the Jiuquan Iron and Steel Group's concentrator and has achieved good technical and economic indicators. Currently, the suspension roasting magnetic separation production line at Hainan Iron Mine has also been built and is undergoing production commissioning. With the large-scale promotion and application of suspension roasting magnetic separation technology in the future, a large amount of suspension roasting magnetic separation iron tailings will inevitably be generated. If these tailings are not rationally utilized, they will not only occupy a large amount of storage land but also have a serious impact on the ecological environment. Because the industrial application of suspension roasting magnetic separation technology is relatively recent, there is very little research on the resource utilization of suspension roasting iron tailings, and there are basically no publicly disclosed related technology patents.

[0004] Because suspended roasted iron tailings are not only fine-grained (typically below 74 micrometers) but also undergo high-temperature roasting, they generally possess a certain degree of activity and have the potential to be used as raw materials for cementitious materials in mine backfilling. Based on the above considerations, this invention prepares a novel cementitious material for mine backfilling by mechanically grinding and chemically activating suspended roasted iron tailings. This achieves both the resource utilization of suspended roasted iron tailings and reduces the production cost of cementitious materials. Summary of the Invention

[0005] The purpose of this invention is to address the technical challenges of large-volume production, difficult disposal, and challenging resource utilization of existing suspended roasted iron tailings by providing a method for preparing cementitious materials for mine backfilling using suspended roasted iron tailings.

[0006] To achieve the above-mentioned objectives of the present invention, the method for preparing cementitious materials for mine backfilling using suspension roasting iron tailings adopts the following technical solution.

[0007] The cementitious material for mine backfilling is composed of the following components, with the total mass percentage of each component at 100% being: 24%–35% suspension roasted iron tailings, 63.5%–74.7% composite powder, and 0.3%–1.5% activator. The composite powder is composed of slag powder, desulfurized gypsum, and cement mixed in a specific ratio. The activator is composed of sodium ethylsilicate, sodium sulfate, sodium lignosulfonate, and triethanolamine mixed in a specific ratio.

[0008] Furthermore, the aforementioned suspension roasting iron tailings are powdered materials that have been crushed and ground to a fineness of -38 micrometers or more (90% or more). Generally, the suspension roasting iron tailings are first naturally dried, then crushed to -2mm in two stages using a jaw crusher and a roller crusher, and then the crushed product is dry-ground to a fineness of -38 micrometers or more using a ball mill.

[0009] Furthermore, the total mass percentage of each component in the composite powder when the total mass is 100% is as follows: 40%–60% slag powder, 20%–30% desulfurized gypsum, and 20%–30% cement.

[0010] Furthermore, the slag powder is of grade S105 with a specific surface area ≥700 μm. 2 / kg; the desulfurized gypsum is an industrial grade, with a β-hemihydrate gypsum content >70%, a residue of <5% on a 0.2mm square-hole sieve, an initial setting time >5min, a final setting time <25min, and a 2-hour compressive strength ≥6MPa; the cement is 42.5 # Ordinary silicate cement.

[0011] Furthermore, the total mass percentage of each component in the activator at 100% is as follows: sodium ethylsilicate 30%–35%, sodium sulfate 30%–35%, sodium lignosulfonate 30%–35%, and triethanolamine 3%–10%. The sodium ethylsilicate, sodium sulfate, sodium lignosulfonate, and triethanolamine are mixed in the specified proportions and then dry-milled using a ball mill until a fineness of -38 micrometers or higher is achieved (over 90%). The sodium ethylsilicate, sodium sulfate, sodium lignosulfonate, and triethanolamine are all industrial grade, with an effective component content >90%.

[0012] The principle behind this invention, which uses high-temperature roasted iron ore tailings as a raw material for preparing cementitious materials for mine backfilling, is as follows: After high-temperature suspension roasting of refractory iron ore, the high-temperature roasted iron ore tailings discharged after grinding and magnetic separation to recover iron minerals have characteristics similar to volcanic ash, containing high levels of active components such as active silica and active alumina. These active components readily react with calcium hydroxide in the backfill tailings to generate reaction products such as hydrated calcium silicate, hydrated calcium aluminate, or hydrated calcium sulfoaluminate, thereby significantly improving the strength of the backfill. Therefore, high-temperature roasted iron ore tailings can be used as a raw material for preparing cementitious materials for mine backfilling.

[0013] Compared with existing technologies, the method of preparing cementitious materials for mine backfilling using iron tailings by suspension roasting in this invention has the following advantages:

[0014] (1) Using suspended roasted iron tailings as raw material for cementitious materials for mine backfilling is the first time that mine tailings have been used as raw material for cementitious materials for mine backfilling. This not only expands the source of raw materials for cementitious materials, but also significantly reduces the production cost of cementitious materials. At the same time, it realizes the resource utilization of suspended roasted iron tailings and reduces the land occupation and environmental hazards of suspended roasted iron tailings storage.

[0015] (2) The main raw materials of the cementitious material prepared by the method of the present invention, namely slag powder and desulfurized gypsum, are industrial by-products with wide availability and low price.

[0016] (3) The method of the present invention uses mechanical grinding and a combination of chemical activators to further activate the activity of suspension roasting iron tailings, so that the resulting cementitious material can be used as a cementing agent for fine-grained tailings, and the performance of the cemented body meets the requirements of normal filling.

[0017] (4) The production process of the gelling material prepared by the method of the present invention does not require high temperature, only grinding and mixing. The production process is simple, environmentally friendly and requires less investment.

[0018] (5) Compared with the cementing agents for fine-grained tailings cementing and backfilling sold on the market, the production cost (including raw material cost) is reduced by more than 30%. Detailed Implementation

[0019] To describe the present invention, the method for preparing a cementitious material for mine backfilling using iron tailings by suspension roasting is further described in detail below with reference to embodiments. However, the present invention is not limited to the embodiments.

[0020] The iron ore tailings used in the method of this invention are those discharged after suspension roasting iron ore beneficiation at a domestic specular hematite mine. This specular hematite ore is a difficult-to-beneficiate iron ore and cannot be separated or enriched using conventional physical beneficiation methods; it requires magnetic roasting (suspension roasting) for separation. In the embodiments, the specific implementation steps of the method for preparing mine backfill cementitious materials using suspension roasting iron ore tailings are as follows:

[0021] (1) After the suspended roasted iron tailings are naturally dried, they are crushed to -2mm in two stages using a jaw crusher and a roller crusher. Then, the crushed product is dry-ground to a fineness of -38 microns or more using a ball mill for later use.

[0022] (2) The slag powder, desulfurized gypsum, and cement were mixed according to the proportions shown in Table 1 to obtain three composite powders with different proportions, which were then set aside. The slag powder was of grade S105 with a specific surface area ≥700 μm. 2 / kg; the desulfurized gypsum is an industrial grade, with a β-hemihydrate gypsum content >70%, a residue of <5% on a 0.2mm square-hole sieve, an initial setting time >5min, a final setting time <25min, and a 2-hour compressive strength ≥6MPa; the cement is 42.5 # Ordinary Portland cement;

[0023] (3) Sodium ethylsilicate, sodium sulfate, sodium lignosulfonate, and triethanolamine were mixed according to the proportions described in Table 2, and then dry-milled using a ball mill until the fineness was -38 micrometers or more (over 90%), yielding three different ratios of activators for later use. The sodium ethylsilicate, sodium sulfate, sodium lignosulfonate, and triethanolamine mentioned above are all industrial products with an effective ingredient content >90%.

[0024] (4) The suspended roasted iron tailings, composite powder and activator obtained in steps (1)(2)(3) are mixed in the proportions shown in Table 3 to obtain three different proportions of cementitious materials for mine filling.

[0025] Table 1. Composite powder formulations (mass percentage) used in the method of this invention.

[0026]

[0027] Table 2. Activator formulations (mass percentage) used in the method of this invention.

[0028]

[0029] Table 3. Formulation (mass percentage) of the cementitious material for mine backfilling prepared by the method of the present invention.

[0030]

[0031] In the embodiments, the cementing material for mine backfilling prepared by the method of the present invention was used to conduct cementation tests on two types of fine-grained iron tailings from different mines in China. One type was magnetite tailings, the particle size distribution of which is shown in Table 4, with a -0.076mm content of 90.61%; the other type was hematite tailings, the particle size distribution of which is shown in Table 5, with a -0.076mm content of 95.50%. Both types of tailings in the embodiments are fine-grained tailings that are difficult to cement for backfilling.

[0032] Table 4. Particle size composition analysis of tailings from a magnetite mine (%)

[0033]

[0034]

[0035] Table 5. Particle size composition analysis of tailings from a hematite mine (%)

[0036]

[0037] The three proportions of cementitious materials prepared by the method of this invention, as well as the comparative example—the patented product "A Cementitious Agent for Cemented Backfilling of Fine-Particle Tailings" (Patent No.: ZL201610106411.8)—were mixed with the hematite or magnetite tailings described in step 1 at a cement-sand ratio of 1:6, and then water was added to adjust the solid mass concentration to 60% for the backfill slurry. The slurry was poured into triple specimens of 70.7mm × 70.7mm × 70.7mm, and the specimens were placed in a standard cement curing box and cured at a constant temperature (20℃) and constant humidity (90%). After one day, the specimens were demolded and cured until the specified age. The compressive strength of the cemented backfill at different curing ages was tested using an automatic pressure tester. The test results are shown in Tables 6 and 7. Experiments show that the three different proportions of cementing materials prepared using the method of this invention can achieve the filling performance requirements of 3-day strength greater than 0.5 MPa, 7-day strength greater than 1.0 MPa, and 28-day strength greater than 2.5 MPa when cementing two types of iron tailings. Moreover, the compressive strength at the same time is better than that of the comparative patented product "a cementing agent for fine-particle tailings cementing and filling", while the cost is less than 70% of that of the comparative example, achieving unexpected technical results.

[0038] Table 6. Strength (MPa) of cemented backfill material from a fine-grained magnetite tailings

[0039]

[0040] Table 7. Strength (MPa) of cemented backfill material from a fine-grained hematite tailings.

[0041]

Claims

1. A method for preparing a cementitious material for mine backfilling using iron tailings from suspension roasting, characterized in that: The aforementioned cementitious material for mine backfilling is composed of the following components, with the total raw material components comprising the following mass percentages when the total weight is 100%: Suspension roasting of iron tailings: 24%–35%; Composite powder content: 63.5%–74.7%; Activator 0.3%–1.5%; The composite powder is prepared by mixing slag powder, desulfurized gypsum and cement in a certain proportion; the activator is prepared by mixing sodium ethylsilicate, sodium sulfate, sodium lignosulfonate and triethanolamine in a certain proportion.

2. The method for preparing a cementitious material for mine backfilling using iron tailings from suspension roasting as described in claim 1, characterized in that: The iron tailings from the suspension roasting process are powders that have been crushed and ground to a fineness of -38 micrometers or more, accounting for more than 90%.

3. The method for preparing a cementitious material for mine backfilling using iron tailings from suspension roasting as described in claim 1, characterized in that... The total mass percentage of the components in the composite powder, when calculated as 100%, is as follows: Slag powder 40%–60%; Desulfurized gypsum 20%–30%; Cement 20%–30%.

4. The method for preparing a cementitious material for mine backfilling using iron tailings from suspension roasting as described in claim 3, characterized in that: The slag powder is of grade S105 with a specific surface area ≥700 μm. 2 / kg; the desulfurized gypsum is an industrial grade, with a β-hemihydrate gypsum content >70%, a residue of <5% on a 0.2mm square-hole sieve, an initial setting time >5min, a final setting time <25min, and a 2-hour compressive strength ≥6MPa; the cement is 42.5 # Ordinary silicate cement.

5. The method for preparing a cementitious material for mine backfilling using iron tailings from suspension roasting as described in claim 1, characterized in that... The components of the activator, when totaled at 100%, have the following mass percentages: Sodium ethylsilicate 30%–35%; Sodium sulfate 30%–35%; Sodium lignosulfonate 30%–35%; Triethanolamine 3%–10%.

6. The method for preparing a cementitious material for mine backfilling using iron tailings from suspension roasting as described in claim 5, characterized in that: The sodium ethyl silicate, sodium sulfate, sodium lignosulfonate, and triethanolamine are mixed in a certain proportion and then dry-milled in a ball mill until the fineness is -38 micrometers or more (over 90%).

7. The method for preparing a cementitious material for mine backfilling using iron tailings from suspension roasting as described in claim 2, characterized in that: The total mass percentage of each component in the composite powder when the total mass is 100% is as follows: 40%–60% slag powder, 20%–30% desulfurized gypsum, and 20%–30% cement. The slag powder is of grade S105 with a specific surface area ≥700 μm. 2 / kg; the desulfurized gypsum is an industrial grade, with a β-hemihydrate gypsum content >70%, a residue of <5% on a 0.2mm square-hole sieve, an initial setting time >5min, a final setting time <25min, and a 2-hour compressive strength ≥6MPa; the cement is 42.5 # Ordinary Portland cement; The activator comprises the following components in 100% mass percentage: sodium ethylsilicate 30%–35%, sodium sulfate 30%–35%, sodium lignosulfonate 30%–35%, and triethanolamine 3%–10%. The sodium ethylsilicate, sodium sulfate, sodium lignosulfonate, and triethanolamine are mixed in the specified proportions and then dry-milled using a ball mill until a fineness of -38 micrometers or higher is achieved (over 90%). Sodium ethylsilicate, sodium sulfate, sodium lignosulfonate, and triethanolamine are all industrial grade products with an effective ingredient content >90%.

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