Mine filling solidified powder based on chemical solid waste and preparation method thereof

Abstract

This invention discloses a mine filling solid powder based on chemical solid waste, its preparation method, and its application. The raw materials include slag powder, anhydrous gypsum, quicklime, wollastonite fiber, low-crosslinked sodium polyacrylate, modified starch adhesive, and calcium stearate. The preparation method includes raw material mixing, crushing and screening, and packaging. In use, the low-crosslinked sodium polyacrylate first absorbs water and swells, while other inorganic fillers hydrate to form hydrated calcium silicate gel and ettringite, which serve as filling and support. Through material innovation and process optimization, this invention successfully solves the two core pain points of existing mine filling solid powders: high cost and insufficient early strength, making it an ideal choice for a new generation of solid powders.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, and more particularly to mine filling solid powder based on chemical solid waste and its preparation method. Background Technology

[0002] Mine filling solids are a type of powdered cementitious material made primarily from industrial waste such as slag, steel slag, and fly ash.

[0003] While existing mine filling solid binders (mainly including cement-based materials, metallurgical slag-based materials, composite cementitious materials, etc.) are widely used, they still have some significant drawbacks, mainly in the following aspects: High costs are a major factor, as cement (especially ordinary Portland cement) is typically the main component of the cost of cementitious powder. Cement prices are highly susceptible to market fluctuations, and its production involves high energy consumption and significant carbon emissions. Transportation costs from cement plants or specialized manufacturers to the mine site, especially in remote mines, account for a large proportion of the overall cost.

[0004] Low early strength and long setting time result in slow early strength development of the filler, requiring a longer curing time to reach the strength required for safe mining (such as self-supporting strength and load-bearing strength), which directly affects the stope circulation speed and the overall production efficiency of the mine. Long setting time may cause the slurry to bleed and segregate in the stope, affecting the uniformity and final strength of the filler.

[0005] Therefore, the current direction of research into novel solid adhesive powders is to develop a product that can gel rapidly while maintaining or lowering the overall cost compared to existing solid adhesive powders. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a mine filling solid powder based on chemical solid waste, its preparation method, and its application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention first proposes a mine filling solid powder based on chemical solid waste, comprising the following raw materials: 55-65 parts of slag powder; 10-15 parts anhydrous gypsum; 8-12 parts quicklime; 3-5 parts wollastonite fiber; 1-1.6 parts of low-crosslinked sodium polyacrylate; 2-4 parts of modified starch gum; 0.3-0.8 parts of calcium stearate; The preparation process of the low-crosslinked sodium polyacrylate includes the following steps: Cyclohexane and Span 80 were added to the reactor and stirred at 200 rpm. The temperature was raised to 60°C. After 30 min, acrylic acid and N,N'-methylenebisacrylamide were slowly added. The mixture was neutralized to pH 7 using a 30% NaOH solution and stirred for 1 h. The temperature was raised to 70°C, and a 10% potassium persulfate aqueous solution was added. The mixture was kept at this temperature for 2 h and then naturally cooled to 40°C. The mixture was filtered, and the solid was washed three times with ethanol to obtain wet low-crosslinked sodium polyacrylate. The wet low-crosslinked sodium polyacrylate was fed into a fluidized bed, and the air inlet was set to 80°C. The mixture was dried for 90 min until the water content was 5 ppm. The mixture was then sprayed with a 0.01% calcium stearate ethanol solution and passed through an 80-120 mesh sieve to obtain a white powder, which is the dried low-crosslinked sodium polyacrylate powder, SAP.

[0008] Acrylic acid (AA) is polymerized under the action of an initiator (potassium persulfate) and a crosslinking agent (N,N'-methylenebisacrylamide, MBA). The carboxyl groups of acrylic acid react with NaOH to form sodium acrylate. Preferably, in the preparation process of the low-crosslinked sodium polyacrylate, the mass ratio of cyclohexane, Span 80, acrylic acid, N,N'-methylenebisacrylamide, potassium persulfate aqueous solution, and calcium stearate ethanol solution is 40:1:6:0.01:0.5:1.

[0009] Low-crosslinked sodium polyacrylate has a lower crosslinking point density, fewer connection points between polymer chains, a looser crosslinking network structure, and a higher degree of freedom of molecular chains. Therefore, it can quickly swell into a soft hydrogel after contact with water. Sodium polyacrylate with a higher degree of crosslinking has higher swelling and water retention. The degree of crosslinking of low crosslinked sodium polyacrylate is 0.07%-0.09% (corresponding to an MBA:AA mass ratio of 0.014-0.018:6), and the crosslinking agent accounts for only 0.17%, ensuring that the connection points between molecular chains are sparse, which meets the "low crosslinking" design.

[0010] Cross-linked polymers swell in good solvents by absorbing solvent, but they cannot dissolve indefinitely. The degree of swelling is limited by the cross-linking density; the higher the degree of cross-linking, the smaller the swelling. Therefore, the cross-linking density can be calculated using the swelling method: [The text then describes a process involving a known dry mass (m)]. dry The cross-linked polymer sample is immersed in a good solvent until swelling equilibrium is reached (mass no longer changes).

[0011] Remove the sample, quickly wipe off any excess solvent from the surface, and weigh the swollen mass (m). swell ).

[0012] Calculate the swelling ratio (Q) or degree of swelling: Mass swelling ratio Q m =m swell / m dry； Volume swelling ratio Qv ≈Q m ×(ρ polymer / ρ solvent (Assuming the volumes are additive, and ρ is the density), the swelling ratio is correlated with the crosslinking density using the Flory-Rehner equation: The number of effective crosslinking points per unit volume (mol / m³) 3 ), that is, crosslinking density (positively correlated with the degree of crosslinking).

[0013] 2,m : Volume fraction of polymer in the swollen gel at swelling equilibrium ( 2,m ≈1 / Q v ).

[0014] x: Flory-Huggins polymer-solvent interaction parameter.

[0015] V s Molar volume of solvent (m³) 3 / mol).

[0016] This invention also proposes a method for preparing the mine filling solid powder based on chemical solid waste, comprising the following steps: Add pretreated slag powder and wollastonite fiber to the high-speed mixer, start the mixer, and set the speed to 300 rpm; After 5 minutes, add quicklime and anhydrous gypsum, and continue stirring at 400 rpm for 10 minutes. Use cooling water circulation to control the temperature to ≤35℃. Add SAP slowly at 200 rpm, add modified starch glue and calcium stearate after 5 minutes; after 15 minutes, discharge the material, pass it through a 40-mesh vibrating screen, crush the material on the screen again and add it back in, and package it under nitrogen protection. After packaging, the product is obtained: mine filling solid powder based on chemical solid waste.

[0017] Preferably, the preparation of the pretreated slag powder includes the following steps: Take water-quenched blast furnace slag, dry it at 105℃ for 12 hours until the moisture content is ≤1ppm; put it into an air jet mill and pulverize it to D50=3-5μm under nitrogen atmosphere; seal it in packaging and store it in a desiccator. The composition of CaO is 38-46%, Al2O3 is 7-15%, SiO2 is 28-36%, and the mass ratio of CaO to SiO2 is 1.0-1.3.

[0018] Preferably, the preparation of the modified starch adhesive includes the following steps: Hydroxypropyl oxidized starch and deionized water were added to a jacketed stirring vessel and gelatinized at 90°C for 30 minutes until the viscosity reached ≥5000 cP. The mixture was then spray-dried with an inlet air temperature of 180°C and an outlet air temperature of 80°C. The mixture was then pulverized and passed through a 100-mesh sieve to obtain modified starch glue, which was then sealed for later use.

[0019] Preferably, in the preparation process of the modified starch adhesive, the mass ratio of hydroxypropyl oxidized starch to deionized water is 3:10.

[0020] During use, quicklime rapidly hydrates, producing Ca(OH)2, which is exothermic and provides an alkaline environment. Anhydrous gypsum then hydrates (CaSO4). Slag powder (containing CaO·Al2O3·SiO2 glass) depolymerizes under the alkaline activation of Ca(OH)2, releasing Ca 2+ [SiO4] 4- [AlO4] 5- Plasma.

[0021] A hydrated calcium silicate (Ca-Si-H) gel is formed within the system: And ettringite (AFt): At the same time, the SAP water-absorbing and swelling physical cross-linking network absorbs water, reduces bleeding, and provides internal moisture; the wollastonite fiber surface Ca 2+ It participates in hydration and enhances interfacial bonding; gelatinized starch slowly degrades in an alkaline environment, releasing gluconic acid, which acts as a retarder.

[0022] Compared with the prior art, the beneficial effects of the present invention are: This invention abandons traditional cement and uses chemical solid waste slag powder and anhydrous gypsum as the core cementing components, which can be sourced locally, avoid long-distance transportation of cement, and reduce the cost of use.

[0023] This invention utilizes quicklime (CaO) to synergistically excite the system, accelerating the dissociation and ion dissolution of the slag glass, providing a strongly alkaline environment (pH > 12), breaking the Si-O-Si and Al-O-Al bonds in the slag, releasing active SiO2 and Al2O3, promoting the formation of the cementitious phase, and thus rapidly forming an early high-strength skeleton, reducing downtime waiting time.

[0024] In summary, this invention achieves efficient gelation of solid waste resources through synergistic alkali activation (Ca(OH)2) and sulfate activation (gypsum), while optimizing construction performance by utilizing polymer additives. In other words, through material innovation and process optimization, it successfully solves the two core pain points of existing mine filling solid adhesive powder: high cost and insufficient early strength. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0026] The purity and manufacturers of the various drugs used in the experiment are shown in Table 1. Table 1. Raw Material Drug Information Example 1:

[0027] Add 55 kg of pretreated slag powder and 3 kg of wollastonite fiber to the high-speed mixer, start the mixer, and set the speed to 300 rpm. After 5 minutes, add 12 kg of quicklime and 15 kg of anhydrous gypsum, and continue stirring at 400 rpm for 10 minutes. The temperature is controlled to be ≤35℃ by circulating cooling water. At 200 rpm, slowly add 1 kg of SAP, and after 5 minutes add 4 kg of modified starch glue and 0.3 kg of calcium stearate; after 15 minutes, discharge the material, pass it through a 40-mesh vibrating screen, crush the material on the screen again and add it back in, and package it under nitrogen protection. After packaging, the product is obtained: mine filling solid powder based on chemical solid waste. Example 2

[0028] Add 55 kg of pretreated slag powder and 3 kg of wollastonite fiber to the high-speed mixer, start the mixer, and set the speed to 300 rpm. After 5 minutes, add 12 kg of quicklime and 15 kg of anhydrous gypsum, and continue stirring at 400 rpm for 10 minutes. The temperature is controlled to be ≤35℃ by circulating cooling water. At 200 rpm, slowly add 1 kg of SAP, and after 5 minutes add 4 kg of modified starch glue and 0.3 kg of calcium stearate; after 15 minutes, discharge the material, pass it through a 40-mesh vibrating screen, crush the material on the screen again and add it back in, and package it under nitrogen protection. After packaging, the product is obtained: mine filling solid powder based on chemical solid waste. Example 3

[0029] Add 55 kg of pretreated slag powder and 3 kg of wollastonite fiber to the high-speed mixer, start the mixer, and set the speed to 300 rpm. After 5 minutes, add 12 kg of quicklime and 15 kg of anhydrous gypsum, and continue stirring at 400 rpm for 10 minutes. The temperature is controlled to be ≤35℃ by circulating cooling water. At 200 rpm, slowly add 1 kg of SAP, and after 5 minutes add 4 kg of modified starch glue and 0.3 kg of calcium stearate; after 15 minutes, discharge the material, pass it through a 40-mesh vibrating screen, crush the material on the screen again and add it back in, and package it under nitrogen protection. After packaging, the product is obtained: mine filling solid powder based on chemical solid waste.

[0030] Based on this, the following design was also created: Comparative Example 1: Same formulation and experimental method as Example 2, but with insufficient quicklime added; Comparative Example 2: The formulation and experimental method were the same as in Example 2, but an excess of quicklime was added; Comparative Example 3: Same formulation and experimental method as Example 2, but with insufficient SPA added; Comparative Example 4: Same formulation and experimental method as Example 2, but with the addition of excessive SPA; Comparative Example 5: Same formulation and experimental method as Example 2, but with insufficient addition of modified starch gum; Comparative Example 6: The formulation and experimental method were the same as in Example 2, but an excessive amount of modified starch gum was added; The specific formula is shown in Table 2: Table 2. Formulation of Mine Filling Solid Powder Based on Chemical Solid Waste According to GB / T 1345-2005 "Test Method for Fineness of Cement", GB / T 2419-2005 "Determination of Flowability of Cement Mortar", JGJ / T 70-2009 "Test Method for Basic Performance of Building Mortar", GB / T 1346-2011 "Test Method for Standard Consistency Water Requirement, Setting Time and Soundness of Cement", GB / T 17671-2021 "Test Method for Strength of Cement Mortar", and GB / T 50082-2009 "Test Method for Long-Term Performance and Durability of Ordinary Concrete", the present invention was tested for fineness, flowability, bleeding rate, setting time, strength development, and durability. The test data for each performance are summarized in Table 3. Table 3. Test data of various properties of the adhesive powder Data analysis shows that: Comparative Example 1 used 2 kg of quicklime, which was insufficient to activate the system, resulting in a 28-day strength of 5.3 MPa. Comparative Example 2 used 20 kg of quicklime, which was too alkaline, resulting in an initial setting time of only 1.5 hours, posing a risk of rapid setting in actual use. Comparative Example 3 had only 0.5 kg of SPA, which was insufficient in water retention and had a water exudation rate of 23.8%, which was much higher than the ≤9% of the Example; Comparative Example 4 had 5 kg of SPA, which absorbed too much water and had too low fluidity. Comparative Example 5 had no starch adhesive, resulting in poor bonding, increased water bleeding, and significantly increased freeze-thaw losses. Comparative Example 6 had 10 kg of starch adhesive, which easily agglomerated, deteriorated in fineness, and thus hindered slag hydration, with a final setting time of 11 hours.

[0031] In summary, the solid binder powder of the present invention is not as mechanically strong as the solid binder powder based on barium sulfide iron aluminate cement (3-day compressive strength 16MPa), but it far exceeds the strength standard of the Shanxi Provincial Group Standard (7-day compressive strength 15MPa), and can meet the needs of mine filling operations. Considering its performance, including setting time, mechanical strength and overall cost, it is an ideal choice for the new generation of solid binder powder.

[0032] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A mine filling solid powder based on chemical solid waste, characterized in that, Including the following parts by weight of raw materials: 55-65 parts of slag powder; 10-15 parts anhydrous gypsum; 8-12 parts quicklime; 3-5 parts wollastonite fiber; 1-1.6 parts of low-crosslinked sodium polyacrylate; 2-4 parts of modified starch gum; 0.3-0.8 parts of calcium stearate; The preparation process of the low-crosslinked sodium polyacrylate includes the following steps: Cyclohexane and Span 80 were added to the reactor and stirred at 200 rpm. The temperature was raised to 60°C. After 30 min, acrylic acid and N,N'-methylenebisacrylamide were slowly added. The mixture was neutralized to pH 7 using a 30% NaOH solution and stirred for 1 h. The temperature was raised to 70°C, and a 10% potassium persulfate aqueous solution was added. The mixture was kept at this temperature for 2 h and then naturally cooled to 40°C. The mixture was filtered, and the solid was washed three times with ethanol to obtain wet low-crosslinked sodium polyacrylate. The wet low-crosslinked sodium polyacrylate was fed into a fluidized bed, and the air inlet was set to 80°C. The mixture was dried for 90 min until the water content was 5 ppm. The mixture was then sprayed with a 0.01% calcium stearate ethanol solution and passed through an 80-120 mesh sieve to obtain a white powder, which is the dried low-crosslinked sodium polyacrylate powder, SAP.

2. The mine filling solid powder based on chemical solid waste according to claim 1, characterized in that, In the preparation process of the low crosslinked sodium polyacrylate, the mass ratio of cyclohexane, Span 80, acrylic acid, N,N'-methylenebisacrylamide, potassium persulfate aqueous solution, and calcium stearate ethanol solution is 40:1:6:0.01:0.5:

1.

3. The method for preparing mine filling solid powder based on chemical solid waste as described in any one of claims 1-2, characterized in that, Includes the following steps: Add pretreated slag powder and wollastonite fiber to the high-speed mixer, start the mixer, and set the speed to 300 rpm; After 5 minutes, add quicklime and anhydrous gypsum, and continue stirring at 400 rpm for 10 minutes. Use cooling water circulation to control the temperature to ≤35℃. Add SAP slowly at 200 rpm, add modified starch glue and calcium stearate after 5 minutes; after 15 minutes, discharge the material, pass it through a 40-mesh vibrating screen, crush the material on the screen again and add it back in, and package it under nitrogen protection. After packaging, the product is obtained: mine filling solid powder based on chemical solid waste.

4. The method for preparing mine filling solid powder based on chemical solid waste according to claim 3, characterized in that, The preparation of the pretreated slag powder includes the following steps: Take water-quenched blast furnace slag, dry it at 105℃ for 12 hours until the moisture content is ≤1ppm; put it into an air jet mill and pulverize it to D50=3-5μm under nitrogen atmosphere; seal it in packaging and store it in a desiccator. The composition of CaO is 38-46%, Al2O3 is 7-15%, SiO2 is 28-36%, and the mass ratio of CaO to SiO2 is 1.0-1.

3.

5. The method for preparing mine filling solid powder based on chemical solid waste according to claim 3, characterized in that, The preparation of the modified starch adhesive includes the following steps: Hydroxypropyl oxidized starch and deionized water were added to a jacketed stirring vessel and gelatinized at 90°C for 30 minutes until the viscosity reached ≥5000 cP. The mixture was then spray-dried with an inlet air temperature of 180°C and an outlet air temperature of 80°C. The mixture was then pulverized and passed through a 100-mesh sieve to obtain modified starch glue, which was then sealed for later use.

6. The method for preparing mine filling solid powder based on chemical solid waste according to claim 3, characterized in that, In the preparation of the modified starch adhesive, the mass ratio of hydroxypropyl oxidized starch to deionized water is 3:10.

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