A method for preparing active filling material for mine cementation based on superfine lead-zinc tailings and a mine cementation filling material

Abstract

This invention belongs to the field of solid waste resource utilization and mine cemented backfilling, specifically involving a method for preparing active filler for mine cementing based on ultrafine lead-zinc tailings and a mine cemented backfilling material. The method includes the following steps: (1) mixing coking desulfurization ash, alkali slag powder and water to obtain a premixed solution; (2) adding slag powder and composite activating agent to the premixed solution and mixing to obtain a pre-activated active filler; (3) adding lead-zinc tailings and water to the pre-activated active filler and stirring. This invention utilizes the synergistic effect of ternary solid waste to solve the cementing problem of ultrafine tailings, resulting in high solid waste utilization, excellent mechanical properties of the backfill, and low cost, making it suitable for the field of mine cemented backfilling.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization and mine cemented backfilling, specifically involving a method for preparing active filler for mine cementing based on ultrafine lead-zinc tailings and a mine cemented backfilling material. Background Technology

[0002] In the lead-zinc ore beneficiation industry, a large amount of tailings rich in ultrafine particles are generated, with a very high proportion of particles smaller than 20μm or even 10μm in diameter, resulting in severe mudification. When such tailings are used to prepare cemented mine backfill materials, significant challenges are faced. First, the huge specific surface area of ​​ultrafine particles allows them to trap a large amount of water, leading to a significant increase in the water-to-solid ratio of the backfill slurry. Second, these particles tightly bind cement particles, hindering water penetration and ion exchange, severely inhibiting the normal hydration of silicate cement, and causing a significant decrease in the early and later strength of the backfill. Third, ultrafine particles easily form a dense structure, making slurry dewatering difficult, and due to the large water demand, severe bleeding occurs, making it difficult to form a uniform backfill. In addition, to ensure the strength of the backfill, traditional processes require the addition of large amounts of cement, significantly increasing backfill costs. At the same time, the long-term stability of heavy metals remaining in lead-zinc tailings is affected by both the strength of the solidified body and environmental chemical conditions, posing a potential leaching risk.

[0003] Meanwhile, coking desulfurization ash, an industrial solid waste generated from coke oven gas desulfurization, also faces challenges in resource utilization. The main component of this solid waste is sodium sulfate (Na2SO4 content greater than 60%), along with small amounts of carbonates, sulfites, unburned carbon, and trace heavy metals. Currently, its resource utilization pathways are extremely limited: on the one hand, due to its high salt content and complex composition, it is difficult to purify through economic means, making it unsuitable for high-value-added applications and resulting in low direct utilization value; on the other hand, landfilling of high-salt coking desulfurization ash may lead to soil salinization and groundwater pollution, and landfill disposal is subject to numerous restrictions under increasingly stringent environmental regulations; furthermore, when used directly in cement or concrete as an admixture or additive, the high sodium sulfate content may cause early overexpansion (formation of ettringite), later strength reduction, or potential sulfate erosion risks, and the carbon content may also adversely affect the product's color and performance. Although existing technologies attempt to use coking desulfurization ash as a component of filling cementitious materials, they are mostly limited to simply replacing part of the cement or simply mixing it with other materials. They have not designed a special cementitious system activation strategy for the special cementing difficulties of ultrafine tailings, and have failed to fully utilize the synergistic effect between Na2SO4 (which is both a sulfur source and an early strength activator) in coking desulfurization ash and the potential activity of slag. They lack an economical, efficient, and core method that can "unlock" the inhibition effect of ultrafine particles.

[0004] In existing technologies addressing the aforementioned problems, all solutions have significant drawbacks: simply increasing cement usage leads to excessively high costs; using special cements (such as sulfoaluminate cement) is not only costly but also offers limited improvement in the encapsulation effect of ultrafine particles; adding chemical activators (such as strong alkali NaOH and water glass) can activate the potential cementing activity of slag, but the cost of purely chemical reagents is high, and the strong alkalinity may increase the risk of heavy metal leaching and deteriorate workability; physical desliming or pretreatment of tailings is costly and difficult to apply on a large scale; existing patents or research involving coking desulfurization ash mostly focus on its use as a single admixture or simple compounding with fly ash, without designing a specific cementing system activation strategy for the inhibitory characteristics of ultrafine tailings, thus failing to effectively solve the cementation problem of ultrafine lead-zinc tailings.

[0005] Therefore, based on this, the technical solution of the present invention is proposed. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for preparing active filler for mine cementation based on ultrafine lead-zinc tailings. This method utilizes sodium sulfate, the main effective component in coking desulfurization ash, as a highly efficient activator. Combined with raw materials such as slag powder and alkali slag powder, the mixture undergoes pre-mixing and moderate activation reactions before being added to the tailings, forming a pre-activated "highly active cementing nucleus." This significantly improves the cementing efficiency of the cementing system for ultrafine lead-zinc tailings particles, overcomes the encapsulation and inhibition effect of ultrafine particles, and ultimately obtains a mine cemented filler with excellent mechanical properties, low cost, and environmental friendliness, achieving large-scale disposal of solid waste.

[0007] The present invention provides a method for preparing active filler for mine cementation based on ultrafine lead-zinc tailings, the method comprising the following steps: (1) Mix coking desulfurization ash, alkali residue powder and water to obtain a premixed solution; (2) Add slag powder and composite activator to the premixed solution and mix to obtain pre-activated active filler; (3) Add lead-zinc tailings and water to the pre-activated active filler and stir.

[0008] Preferably, based on dry weight parts: 5-20 parts coking desulfurization ash, 5-15 parts alkali slag powder, 45-70 parts slag powder, and 0-5 parts composite activator.

[0009] Preferably, the main component of the coking desulfurization ash is Na2SO4, and the Na2SO4 content is ≥60wt%; the specific surface area of ​​the coking desulfurization ash is ≥350m². 2 / kg; And / or, the slag powder is S95 or S105 grade granulated blast furnace slag powder conforming to national standards; And / or, the alkaline residue powder is chlor-alkali white mud with a specific surface area ≥300m². 2 / kg; the alkaline residue powder contains Ca(OH)2 ≥ 30wt%, Cl - ≤5wt%; And / or, the lead-zinc tailings are dry-discharged or concentrated tailings, wherein particles with a diameter ≤20μm account for ≥30wt%; And / or, the composite activating agent comprises alkali metal carbonates and / or activated aluminosilicate powders; the alkali metal carbonates are sodium carbonate or potassium carbonate; the activated aluminosilicate powders are metakaolin or silica fume; And / or, the water is industrial water or wastewater from a treatment plant.

[0010] Preferably, in step (1), the water added is 15-30 wt% of the total dry weight of coking desulfurization ash, alkali slag powder and slag powder.

[0011] Preferably, in step (1), the mixing speed is 500-550 r / min and the mixing time is 3-5 min.

[0012] Preferably, in step (2), the mixing speed is 500-550 r / min and the mixing time is 5-8 min.

[0013] Preferably, in step (3), the mass ratio of the pre-activated active filler to the lead-zinc tailings is 1:6-12 on a dry basis.

[0014] Preferably, in step (3), after adding water, the final concentration of the material is 65-75 wt%.

[0015] Preferably, in step (3), the stirring time is 5-8 minutes.

[0016] Based on the same technical concept, another aspect of the present invention is to provide a mine cemented backfill material prepared by the above method.

[0017] To facilitate understanding of this invention, the preparation process and related principles of this invention are explained below: Step (1) involves premixing and dissolving the coking desulfurization ash and alkali residue powder. These are then added to a portion of the slurry water and thoroughly mixed under stirring conditions. The Ca(OH)₂ in the alkali residue powder dissolves rapidly, providing a high concentration of OH⁻. - and Ca 2+ The presence of ions causes the pH of the system to rise sharply to above 12. Na₂SO₄ (and other soluble salts) in the coking desulfurization ash is effectively dissolved by a saturated Ca(OH)₂ solution, forming a solution containing high concentrations of Na₂SO₄. + SO4 2- The solution environment of ions.

[0018] Step (2) involves slag activation and synergistic reaction. Slag powder and composite activating aid are added to the above-mentioned coking desulfurization ash / alkali slag powder slurry and continuously stirred. In a strongly alkaline (OH) environment... - ) and sulfate-rich salts (SO4) 2- Under certain conditions, the glassy network of slag powder is rapidly depolymerized by Ca(OH)2, releasing Ca2+. 2+ SiO4 4- AlO2 - Plasma. Dissolved AlO2 - (or monopolymer Al(OH)4) - ) quickly with Ca 2+ SO4 2- The combined process continues, generating more ettringite (AFt) crystals and forming a continuous network structure. The dissolved SiO4... 4- In Ca 2+ In the presence of these substances, a preliminary CSH gel begins to form. CaCO3 in the alkali slag acts as micro-aggregate and crystal nuclei, facilitating the growth of hydration products on its surface. A composite activating agent (alkali metal carbonate) further enhances the initial alkalinity of the system, accelerating activation; activated aluminosilicate micropowder provides additional reactants and optimizes the microstructure. This step allows the coking desulfurization ash, alkali slag, and mineral powder to fully pre-react before the addition of tailings, forming a slurry or moist powder "active filler" containing highly active cementitious precursors (activated slag, ettringite crystal nuclei). The beneficial effects of this invention are as follows: 1. Innovative pretreatment solves core problems: The "active filler pretreatment" process is adopted, which utilizes the strong alkaline environment of Na2SO4 and alkali slag powder in coking desulfurization ash to pre-activate slag powder to form highly active cementitious precursors (AFt crystal nuclei, activated slag particles), thereby solving the problem of encapsulation and inhibition of ultrafine lead-zinc tailings particles from the root and ensuring the normal hydration of the cementation system.

[0019] 2. Enhanced efficiency of ternary solid waste co-processing: Constructing coking desulfurization ash (providing SO4) 2- ), alkali residue powder (providing OH) - Ca 2+ And fix Cl - The system combines three components: slag powder (which provides Si and Al active sources), slag powder (which provides Si and Al active sources), and slag powder (which provides Si and Al active sources). These three components complement each other and are indispensable. At the same time, the system can dispose of three types of industrial solid waste on a large scale, reducing the environmental risks and treatment costs of solid waste landfill.

[0020] 3. Significantly reduce the overall cost of backfilling: Industrial solid waste is used to replace traditional cement as the main cementing material, which greatly reduces the amount of cement used; and low-cost water resources such as wastewater from the concentrator can be used to reduce the raw material and operating costs of cemented backfilling in mines.

[0021] 4. Comprehensive upgrade of mechanical properties: For ultrafine lead-zinc tailings with a particle size ≤20μm and a proportion ≥30wt%, the 7-day compressive strength of the filling body is increased by 50%-120%, and the 28-day compressive strength is increased by 30%-100%, fully meeting the strength requirements of mine filling projects.

[0022] 5. Optimization of construction and service performance: The pre-activated gelling precursor shortens the final setting time of the filling body by 20%-40%, accelerates the early (1-3d) strength development, and is conducive to speeding up the mining cycle; at the same time, it improves the dewatering performance of the slurry, reduces bleeding, and forms a uniform and stable filling body structure. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] Example 1 This embodiment provides a method for preparing active fillers for mine bonding based on ultrafine lead-zinc tailings, the method comprising the following steps: (1) Raw material screening and preparation: Select raw materials with Na2SO4 content ≥60wt% and specific surface area ≥350m². 2 20 kg of coking desulfurization ash per kg; Select Ca(OH)₂ ≥ 30 wt%, Cl - ≤5wt%, specific surface area ≥300m² 2 15 kg of chlor-alkali white mud-type alkaline slag powder; 63 kg of S95 grade granulated blast furnace slag powder conforming to national standards; 2 kg of metakaolin; and lead-zinc tailings with a particle size ≤20μm and a particle size ≥30wt% after dry discharge treatment for later use.

[0025] (2) Preparation of premixed solution: Coking desulfurization ash, alkali slag powder and industrial water (30wt% of the total dry weight of coking desulfurization ash, alkali slag powder and slag powder) are added to the stirring equipment in sequence. The stirring speed is adjusted to 500r / min and the mixture is continuously mixed for 3min. The slurry is observed to thicken, and the premixed solution is obtained.

[0026] (3) Preparation of pre-activated active filler: Keep the stirring speed constant at 500 r / min, slowly add slag powder and metakaolin to the premixed solution, and continue mixing for 5 min to obtain pre-activated active filler.

[0027] (4) Preparation of cemented filling material: According to the dry basis mass ratio of pre-activated active filler to lead-zinc tailings of 1:8, add spare lead-zinc tailings to the pre-activated active filler, add an appropriate amount of industrial water, adjust the final material concentration to 68wt%, keep stirring for 5min, and make the material evenly mixed.

[0028] (5) Molding and curing: The prepared cemented filling material is injected into the standard test mold and cured at room temperature and pressure until the specified age.

[0029] The final performance is as follows: extension 150mm, 3d compressive strength 1.8MPa, 7d compressive strength 3.8MPa, and 28d compressive strength 4.6MPa.

[0030] Example 2 This embodiment provides a method for preparing active fillers for mine bonding based on ultrafine lead-zinc tailings, the method comprising the following steps: (1) Raw material screening and preparation: Select raw materials with Na2SO4 content ≥60wt% and specific surface area ≥350m². 2 30 kg of coking desulfurization ash per kg; Select Ca(OH)₂ ≥ 30 wt%, Cl - ≤5wt%, specific surface area ≥300m² 2 20 kg of chlor-alkali white mud-type alkaline slag powder per kg; 50 kg of S105 grade granulated blast furnace slag powder conforming to national standards; lead-zinc tailings with a particle size ≤20μm and a particle size ≥30wt% after concentration treatment; and recycled water from the beneficiation plant as mixing water.

[0031] (2) Preparation of premixed solution: Coking desulfurization ash, alkali slag powder and industrial water (30wt% of the total dry weight of coking desulfurization ash, alkali slag powder and slag powder) are added to the stirring equipment in sequence. The stirring speed is adjusted to 500r / min and the mixture is continuously mixed for 3min. The slurry is observed to thicken, and the premixed solution is obtained.

[0032] (3) Preparation of pre-activated active filler: Maintain a stirring speed of 500 r / min, add slag powder to the premixed solution at a uniform speed, and continue mixing for 5 min to complete the slag activation and synergistic reaction, and obtain the pre-activated active filler.

[0033] (4) Preparation of cemented filling material: Add spare lead-zinc tailings to the pre-activated active filler at a dry basis mass ratio of 1:10, add the beneficiation plant return water to adjust the final material concentration to 68wt%, and continue stirring for 8min to ensure uniform mixing of materials.

[0034] (5) Molding and curing: Inject the slurry into the standard test mold and cure it under natural curing conditions until the specified age.

[0035] The final performance is as follows: extension 170mm, 3d compressive strength 1.4MPa, 7d compressive strength 2.6MPa, and 28d compressive strength 3.2MPa.

[0036] Example 3 This embodiment provides a method for preparing active fillers for mine bonding based on ultrafine lead-zinc tailings, the method comprising the following steps: (1) Raw material screening and preparation: Select raw materials with Na2SO4 content ≥60wt% and specific surface area ≥350m². 2 15 kg of coking desulfurization ash per kg; Select Ca(OH)₂ ≥ 30 wt%, Cl - ≤5wt%, specific surface area ≥300m² 2 10 kg of chlor-alkali white mud-type alkaline slag powder per kg; 70 kg of S105 grade granulated blast furnace slag powder conforming to national standards; 2 kg of potassium carbonate (K2CO3) and 3 kg of metakaolin; lead-zinc tailings with a particle size ≤20μm and a particle size ≥30wt% after dry discharge treatment for later use; industrial water is used as mixing water.

[0037] (2) Preparation of premixed solution: Coking desulfurization ash, alkali slag powder and industrial water (30wt% of the total dry weight of coking desulfurization ash, alkali slag powder and slag powder) are added to the stirring equipment in sequence. The stirring speed is adjusted to 500r / min and the mixture is continuously mixed for 3min. The slurry is observed to thicken, and the premixed solution is obtained.

[0038] (3) Preparation of pre-activated active filler: Keep the stirring speed at 500 r / min, first add potassium carbonate to the premixed solution and stir for 1 min, then add slag powder and metakaolin, and continue mixing for 4 min (total mixing time 5 min) to obtain pre-activated active filler.

[0039] (4) Preparation of cemented filling material: According to the dry basis mass ratio of pre-activated active filler to lead-zinc tailings of 1:8, add spare lead-zinc tailings to the pre-activated active filler, add industrial water to adjust the final material concentration to 68wt%, and stir continuously for 7min to ensure that the material is fully cemented.

[0040] (5) Molding and curing: The prepared slurry is injected into the standard mold and cured at room temperature until the specified age.

[0041] The final performance is as follows: extension 145mm, 3d compressive strength 2.1MPa, 7d compressive strength 4.2MPa, and 28d compressive strength 5.5MPa.

[0042] Comparative Example 1 Comparative Example 1 used the same raw materials as Example 1. The preparation method was to mix all raw materials (coking desulfurization ash, alkali slag powder, slag powder, metakaolin, lead-zinc tailings, and water) at one time to make a slurry with the same solid content / slump. The strength properties were measured as follows: 3-day compressive strength 1.17 MPa, 7-day compressive strength 2.47 MPa, and 28-day compressive strength 2.85 MPa.

[0043] Comparative Example 2 Comparative Example 2 used the same raw materials as Example 2. The preparation method was to mix all raw materials (coking desulfurization ash, alkali slag powder, slag powder, lead-zinc tailings, and water) at one time to make a slurry with the same solid content / slump. The strength properties were measured as follows: 3-day compressive strength 0.6 MPa, 7-day compressive strength 1.1 MPa, and 28-day compressive strength 1.44 MPa.

[0044] Comparative Example 3 Comparative Example 3 used the same raw materials as Example 3. The preparation method was to mix all raw materials (coking desulfurization ash, alkali slag powder, slag powder, potassium carbonate, metakaolin, lead-zinc tailings, and water) at one time to make a slurry with the same solid content / slump. The strength properties were measured as follows: 3-day compressive strength 1.36 MPa, 7-day compressive strength 2.73 MPa, and 28-day compressive strength 3.57 MPa.

[0045] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing active filler for mine cementation based on ultrafine lead-zinc tailings, characterized in that, The method includes the following steps: (1) Mix coking desulfurization ash, alkali residue powder and water to obtain a premixed solution; (2) Add slag powder and composite activator to the premixed solution and mix to obtain pre-activated active filler; (3) Add lead-zinc tailings and water to the pre-activated active filler and stir.

2. The method for preparing active filler for mine cementation based on ultrafine lead-zinc tailings according to claim 1, characterized in that, Based on dry weight parts: 5-20 parts coking desulfurization ash, 5-15 parts alkali slag powder, 45-70 parts slag powder, and 0-5 parts composite activator.

3. The method for preparing active filler for mine cementation based on ultrafine lead-zinc tailings according to claim 1, characterized in that, The main component of the coking desulfurization ash is Na2SO4, and the content of the Na2SO4 is ≥60wt%; the specific surface area of the coking desulfurization ash is ≥350m 2 / kg. And / or, the slag powder is S95 or S105 grade granulated blast furnace slag powder conforming to national standards; And / or, the alkaline residue powder is chlor-alkali white mud with a specific surface area ≥300m². 2 / kg; the alkaline residue powder contains Ca(OH)2 ≥ 30wt%, Cl - ≤5wt%; And / or, the lead-zinc tailings are dry-discharged or concentrated tailings, wherein particles with a diameter ≤20μm account for ≥30wt%; And / or, the composite activating agent comprises alkali metal carbonates and / or activated aluminosilicate powders; the alkali metal carbonates are sodium carbonate or potassium carbonate; the activated aluminosilicate powders are metakaolin or silica fume; And / or, the water is industrial water or wastewater from a treatment plant.

4. The method for preparing active filler for mine cementation based on ultrafine lead-zinc tailings according to claim 1, characterized in that, In step (1), the water added is 15-30 wt% of the total dry weight of coking desulfurization ash, alkali slag powder and slag powder.

5. The method for preparing active filler for mine cementation based on ultrafine lead-zinc tailings according to claim 1, characterized in that, In step (1), the mixing speed is 500-550 r / min and the mixing time is 3-5 min.

6. The method for preparing active filler for mine cementation based on ultrafine lead-zinc tailings according to claim 1, characterized in that, In step (2), the mixing speed is 500-550 r / min and the mixing time is 5-8 min.

7. The method for preparing active filler for mine cementation based on ultrafine lead-zinc tailings according to claim 1, characterized in that, In step (3), the mass ratio of the pre-activated active filler to the lead-zinc tailings is 1:6-12 on a dry basis.

8. The method for preparing active filler for mine cementation based on ultrafine lead-zinc tailings according to claim 1, characterized in that, In step (3), after adding water, the final concentration of the material is 65-75 wt%.

9. The method for preparing active filler for mine cementation based on ultrafine lead-zinc tailings according to claim 1, characterized in that, In step (3), the stirring time is 5-8 minutes.

10. The mine cemented backfill material prepared by the method according to any one of claims 1-9.