Preparation method of multi-source solid waste-based gel

Abstract

The present application belongs to the technical field of solid waste material preparation, and aims to solve the problem of poor solid waste synergistic effect and weak compactness of existing solid waste-based gel. A preparation method of multi-source solid waste-based gel is provided, comprising the following steps: preparing modified sodium polyacrylate; performing surface chemical modification on multi-source solid waste powder in a container by a silane coupling agent modification liquid to obtain modified multi-source solid waste powder; stirring and mixing the modified multi-source solid waste powder with deionized water to obtain a multi-source solid waste composite gel material; mixing and stirring the modified sodium polyacrylate with the multi-source solid waste composite gel material to a gel state, and adding a sodium hydroxide solution for neutralization to obtain a solid waste-based composite gel; after hydrothermal strengthening treatment of the solid waste-based composite gel, immersing the solid waste-based composite gel in a CaCl2 solution, taking out the solid waste-based composite gel for drying treatment, and obtaining a multi-source solid waste-based gel. The method can overcome the defects of traditional inorganic gel, such as easy cracking and pulverization, and make the gel have excellent water retention.

Description

Technical Field

[0001] This invention belongs to the field of solid waste material preparation technology, specifically relating to a method for preparing multi-source solid waste-based gel. Background Technology

[0002] With the rapid development of coal mining technology and the increasing number of coal mines, the risk of spontaneous combustion of coal is growing, seriously affecting the safety of coal mining. Spontaneous combustion of coal not only causes a large waste of resources, but also triggers secondary disasters such as gas explosions and coal dust explosions.

[0003] Gels, due to their excellent oxygen barrier properties, permeability, and water retention, have become commonly used materials for preventing and extinguishing spontaneous combustion of coal. Fire prevention and extinguishing materials include both fire-resistant materials and fire-extinguishing materials. Currently, gels are mainly divided into inorganic gels and organic gels. Inorganic gels are low in cost but have poor water retention and are prone to water loss and cracking at high temperatures. Organic gels have good water retention but are generally more expensive, and their molecular chains are easily broken at high temperatures, damaging the gel network.

[0004] Solid waste materials are not only low-cost and have good environmental benefits, but their inherent active silica-alumina and calcium-based components also give them the potential to become gels. However, existing solid waste-based gels still suffer from problems such as poor synergistic effects with solid waste and weak density, making it difficult to meet the diverse performance requirements of gels in the complex environment of coal mines. Summary of the Invention

[0005] In order to address the problems of poor synergistic effect of solid waste and weak compactness in existing solid waste-based gels, which make it difficult to meet the different performance requirements of gels in the complex environment of coal mines, this invention provides a method for preparing multi-source solid waste-based gels.

[0006] This invention is achieved using the following technical solution: a method for preparing a multi-source solid waste-based gel, comprising the following steps: Modified sodium polyacrylate was prepared. The modified sodium polyacrylate was a graft copolymer obtained by amination of sodium polyacrylate with 3-aminopropyltriethoxysilane and then graft polymerization with hydroxyethyl methacrylate monomer containing active double bonds. The raw materials of multi-source solid waste are dried, ground and screened to obtain multi-source solid waste powder. The raw materials of multi-source solid waste include granulated blast furnace slag, desulfurized gypsum and carbide slag. The multi-source solid waste powder includes slag powder, desulfurized gypsum powder and carbide slag powder. Slag powder, desulfurized gypsum powder, and carbide slag powder are fed into a container using a layered feeding method. The surface of the multi-source solid waste powder in the container is chemically modified by a silane coupling agent modification liquid. The modification liquid on the upper layer of the container is then removed by centrifugation to obtain the modified multi-source solid waste powder. The modified multi-source solid waste powder is then mixed with deionized water to obtain a multi-source solid waste composite cementitious material. Modified sodium polyacrylate was mixed with multi-source solid waste composite cementitious material and stirred until a gel state was reached. Sodium hydroxide solution was then added for neutralization to obtain a solid waste-based composite gel. The solid waste-based composite gel was placed in a closed reactor for hydrothermal intensification treatment, and then immersed in CaCl2 solution to introduce Ca through ion exchange. 2+ The solid waste-based composite gel was removed from the CaCl2 solution and dried to obtain a multi-source solid waste-based gel.

[0007] Preferably, the process for preparing modified sodium polyacrylate includes the following steps: S11: Sodium polyacrylate and 3-aminopropyltriethoxysilane are added to anhydrous toluene at a first molar ratio and refluxed under nitrogen atmosphere. The reflux reaction is used to cause the carboxyl anions on the sodium polyacrylate polymer chain to undergo an amidation reaction with the amino group of 3-aminopropyltriethoxysilane, thereby introducing an amino group into the sodium polyacrylate polymer chain. The product of the reflux reaction is filtered, washed and dried to obtain amino-functionalized sodium polyacrylate. S12: Hydroxyethyl methacrylate and 2-isocyanate ethyl methacrylate are mixed at a second molar ratio, and dibutyltin dilaurate is used as a catalyst. The mixture is stirred under nitrogen atmosphere. The stirring reaction is used to allow the isocyanate of 2-isocyanate ethyl methacrylate to undergo an addition reaction with the hydroxyl group of hydroxyethyl methacrylate, to obtain a product containing polymerizable double bonds. The product containing polymerizable double bonds is purified by column chromatography to obtain hydroxyethyl methacrylate monomer containing active double bonds. S13: Dissolve amino-functionalized sodium polyacrylate in N,N-dimethylformamide solution, use 2,2'-azobisisobutyronitrile as initiator, and in a constant temperature oil bath under nitrogen atmosphere, dropwise add a mixture of hydroxyethyl methacrylate monomer containing active double bonds and N,N'-methylenebisacrylamide into the reaction system of amino-functionalized sodium polyacrylate and N,N-dimethylformamide, so that amino-functionalized sodium polyacrylate and hydroxyethyl methacrylate monomer containing active double bonds undergo graft polymerization reaction; S14: After the graft polymerization reaction is completed, potassium sulfate and tetraethylenepentamine are added to the graft polymerization reaction system to initiate secondary crosslinking of the unreacted amino-functionalized sodium polyacrylate with hydroxyethyl methacrylate monomer containing active double bonds; after cooling the graft polymerization reaction system, anhydrous ethanol is used to precipitate the product of the graft polymerization reaction, and after washing, filtering, drying and grinding, modified sodium polyacrylate is obtained.

[0008] Preferably, in the process of preparing modified sodium polyacrylate, the first molar ratio is the molar ratio of 3-aminopropyltriethoxysilane to the carboxyl group in sodium polyacrylate, which is 0.1:1; the second molar ratio is the molar ratio of 2-isocyanate methacrylate to the hydroxyl group in hydroxyethyl methacrylate, which is 0.2:1; the molar ratio of potassium sulfate to tetraethylenepentamine added to the graft polymerization reaction system is 1:1.5; the concentration of N,N-dimethylformamide solution is 5%; the mass of 2,2'-azobisisobutyronitrile is 0.5% of the total mass of amino-functionalized sodium polyacrylate and hydroxyethyl methacrylate monomer containing active double bonds; and the mass of N,N'-methylenebisacrylamide is 0.11% of the mass of hydroxyethyl methacrylate monomer containing active double bonds.

[0009] Preferably, in the process of obtaining multi-source solid waste powder, granulated blast furnace slag is dried, ground, and sieved to obtain slag powder, and desulfurized gypsum and carbide slag are dried, crushed, ground, and sieved to obtain desulfurized gypsum powder and carbide slag powder, respectively. The slag powder and carbide slag powder are both sealed and stored. The granulated blast furnace slag is S95 granulated blast furnace slag, and the carbide slag is taken from the by-product of the acetylene production process. The particle size of the slag powder and carbide slag powder does not exceed 75μm, and the particle size of the desulfurized gypsum powder does not exceed 0.5mm.

[0010] Preferably, the steps for obtaining multi-source solid waste composite cementitious materials include: S31: Weigh out slag powder, desulfurized gypsum powder and carbide slag powder according to the preset mass ratio. Pour the slag powder into the bottom and top layers of the container in two separate batches. Pour the carbide slag powder and desulfurized gypsum powder into the middle layer of the container in sequence. S32: Subsequently, anhydrous ethanol and silane coupling agent are added to the container to prepare a modification solution. After ultrasonic dispersion, the silane coupling agent molecules are wetted, adsorbed and initially hydrolyzed on the surface of the multi-source solid waste powder. The upper layer of modification solution is then removed by centrifugation to obtain the modified multi-source solid waste powder. After drying and multiple sieving, the modified multi-source solid waste powder is obtained. S33: Mix the modified multi-source solid waste powder with deionized water until a uniform, dry powder-free, and visible layered white slurry suspension is formed. The white slurry suspension is the multi-source solid waste composite cementitious material.

[0011] Preferably, in the step of obtaining the multi-source solid waste composite cementitious material, after the mixing and stirring are completed, the slurry in the container is lifted with a glass rod to check whether the slurry meets the conditions of uniform adhesion and fluidity when poured, with no water separation; if it does not meet the conditions, the mixing and stirring time is extended and the state of the slurry is checked again until it meets the requirements, and the multi-source solid waste composite cementitious material is obtained.

[0012] Preferably, the step of obtaining multi-source solid waste-based gel includes: S41: Modified sodium polyacrylate is mixed with multi-source solid waste composite cementitious material and stirred until gel state is reached, so that the modified sodium polyacrylate polymer chain extends and forms a dynamic ionic cross-linking network with the multivalent metal ions in the multi-source solid waste composite cementitious material, and is entangled with the particles and preliminary hydrolysis products in the multi-source solid waste composite cementitious material. S42: Add a 30% sodium hydroxide solution to neutralize and adjust the pH value to 7-8 to obtain a solid waste-based composite gel; S43: The solid waste-based composite gel is placed in a closed reactor for hydrothermal enhancement treatment; S44: The hydrothermally enhanced solid waste-based composite gel is immersed in a 10% CaCl2 solution, so that the Ca in the CaCl2 solution... 2+ Na in solid waste-based composite gel + Ion exchange occurs, forming Ca 2+ Crosslinking point; S45: The solid waste-based composite gel was removed from the CaCl2 solution and dried to obtain a multi-source solid waste-based gel.

[0013] Compared with the prior art, the beneficial effects of the present invention are: This invention modifies sodium polyacrylate by grafting it with hydroxyethyl methacrylate and then uses a silane coupling agent to chemically modify the surface of three solid waste powders. This allows the carboxyl anions in the modified sodium polyacrylate to react with the CaO dissolved from the three solid waste powders. 2+ Al 3+ Ionic crosslinking points are formed, and hydrogen bonds are established between the hydroxyl groups on the grafted side chains and the surfaces of the three solid waste powders. By adjusting the pH to weakly alkaline, the interaction between the dissociation of carboxyl groups on the modified sodium polyacrylate polymer chain and the amino groups modified on the surfaces of the three solid waste powders is enhanced, thereby establishing a multi-level, strongly bonded organic-inorganic interpenetrating network structure.

[0014] This structure effectively overcomes the defects of traditional inorganic gels, such as easy drying and cracking, and powdering. At the same time, it enables the gel to have excellent water retention properties, which can lock water in the gel network for a long time. This provides a continuous and efficient heat absorption and cooling effect throughout the coal oxidation heating process, solving the problem that conventional water-containing materials fail rapidly at high temperatures due to easy water evaporation.

[0015] In this invention, the proportions of three solid waste powders—slag powder, desulfurized gypsum powder, and carbide slag powder—can be adjusted to design the gelation time, permeability, and water loss rate of the multi-source solid waste-based gel according to different underground fire prevention needs. This application converts difficult-to-dispose-of industrial solid waste into high-performance fire prevention and extinguishing materials, which not only significantly reduces the cost of fire prevention and extinguishing materials but also enables the resource utilization of various solid wastes, demonstrating excellent economic benefits and environmental value. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of the method of the present invention; Figure 2 The graph shows the changes in water loss rate of the multi-source solid waste-based gels prepared in Examples 1 to 3 at different time points; Figure 3 A graph showing the change in oxygen consumption rate of coal samples treated with gel based on coking coal and multi-source solid waste. Figure 4 A graph showing the changes in CO production rate of coal samples treated with gel based on coking coal and multi-source solid waste. Figure 5 Characteristic temperature diagrams of coal samples treated with coking coal and multi-source solid waste-based gel during the heating process; Figure 6 The exothermic characteristic curves of coal samples treated with gel based on multi-source solid waste during the heating process are shown. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings. 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 implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] It should be noted that the structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should fall within the scope of the technical content disclosed in the present invention. It should be noted that in this specification, relational terms such as "first" and "second" are only used to distinguish one entity from several other entities, and do not necessarily require or imply any actual relationship or order between these entities.

[0020] Example 1: like Figure 1 As shown, this embodiment provides a method for preparing multi-source solid waste-based gels, including the following steps: S1: Preparation of modified sodium polyacrylate, which is a graft copolymer obtained by amination of sodium polyacrylate with 3-aminopropyltriethoxysilane and then graft polymerization with hydroxyethyl methacrylate monomer containing active double bonds.

[0021] The process of preparing modified sodium polyacrylate specifically includes the following steps: S11: Place vacuum-dried sodium polyacrylate (PAAS) into a three-necked flask equipped with a condenser and a nitrogen inlet tube. Add 3-aminopropyltriethoxysilane (APTES) and the carboxyl groups of sodium polyacrylate to the three-necked flask at a molar ratio of 0.1:1. Add anhydrous toluene at a mass equal to 10 times that of sodium polyacrylate. Heat to 80°C under nitrogen atmosphere and reflux for 12 hours. During the reflux reaction, the -COO groups on the sodium polyacrylate polymer chains... - The carboxyl anion undergoes an amidation reaction with the amino group of 3-aminopropyltriethoxysilane, introducing an amino group onto the sodium polyacrylate polymer chain. After the reflux reaction is complete, the solid product in the three-necked flask is filtered out, and unreacted reagents and byproducts are removed by thorough washing with toluene and anhydrous ethanol. The product is then dried in a vacuum drying oven at 60°C to constant weight to obtain amino-functionalized sodium polyacrylate (PAAS-NH2).

[0022] S12: Hydroxyethyl methacrylate (HEMA) was placed in a three-necked flask equipped with a condenser and a nitrogen inlet tube. Iethyl methacrylate-2-isocyanate (IEM) was mixed with the hydroxyl groups in hydroxyethyl methacrylate at a molar ratio of 0.2:1, and a trace amount of dibutyltin dilaurate was added dropwise as a catalyst. Under nitrogen atmosphere, an electronic stirrer was used at 300 rpm for 6 hours to allow the -NCO (isocyanate) group of 2-isocyanate to fully react with the -OH (hydroxyl) group of hydroxyethyl methacrylate, yielding a product (HEMA-IEM) with polymerizable double bonds at the ends. The product was then purified by column chromatography to obtain high-purity hydroxyethyl methacrylate monomer containing active double bonds.

[0023] S13: Take the amino-functionalized sodium polyacrylate prepared in S11 and dissolve it in a beaker containing a 5% N,N-dimethylformamide (DMF) solution. Add 2,2'-azobisisobutyronitrile (AIBN) as an initiator, with the mass of 2,2'-azobisisobutyronitrile being 0.5% of the total mass of the amino-functionalized sodium polyacrylate and the hydroxyethyl methacrylate monomer containing the active double bond. Place the beaker in a 70℃ constant temperature oil bath under nitrogen atmosphere. Mix the hydroxyethyl methacrylate monomer containing the active double bond prepared in S12 with N,N'-methylenebisacrylamide (MBA), with the mass of N,N'-methylenebisacrylamide being 0.11% of the mass of the hydroxyethyl methacrylate monomer containing the active double bond. Use a constant pressure dropping funnel to collect the mixed solution. The solution of amino-functionalized sodium polyacrylate was stirred using an electric stirrer (500 rpm) while the mixed solution in the constant pressure dropping funnel was slowly added dropwise into the solution of amino-functionalized sodium polyacrylate. The amino-functionalized sodium polyacrylate underwent a graft polymerization reaction with hydroxyethyl methacrylate monomer containing active double bonds.

[0024] S14: After the graft polymerization reaction has proceeded sufficiently, potassium sulfate and tetraethylenepentamine in a molar ratio of 1:1.5 are added sequentially to the graft polymerization reaction system. The system is then allowed to stand in a constant temperature oil bath at 70°C for 2 hours. This further initiates the cross-linking of unreacted active sites of the amino-functionalized sodium polyacrylate with the remaining hydroxyethyl methacrylate monomer containing active double bonds on the outer layer of the already formed cross-linked network. The reaction system is then cooled to room temperature and vigorously stirred using an electronic stirrer (800 rpm). Simultaneously, 5 times the volume of anhydrous ethanol is slowly poured into a beaker. Based on the characteristic that modified sodium polyacrylate is insoluble in ethanol, the product of the graft polymerization reaction is rapidly precipitated. The product is thoroughly washed and filtered 3-5 times with a 3:1 volume ratio of ethanol to water, dried in a vacuum drying oven at 60°C to constant weight, and then ground to obtain modified sodium polyacrylate.

[0025] S2: Dry, grind and screen the multi-source solid waste raw materials to obtain multi-source solid waste powder that meets the particle size requirements. The multi-source solid waste raw materials include granulated blast furnace slag, desulfurized gypsum and carbide slag. The multi-source solid waste powder includes slag powder, desulfurized gypsum powder and carbide slag powder.

[0026] The specific process for obtaining multi-source solid waste powder that meets the particle size requirements is as follows: S21: Granulated blast furnace slag is selected from S95 granulated blast furnace slag, where S95 is a quality grade designation. The granulated blast furnace slag is placed in a vacuum drying oven and dried to constant weight at 105±5℃, ensuring no residual free or adsorbed water remains. The dried granulated blast furnace slag is then ground using a planetary ball mill. The grinding media is zirconia balls, with a mass ratio of zirconia balls to granulated blast furnace slag of 3:1, a rotation speed of 350 rpm, and a grinding time of 60 minutes. Finally, all the granulated blast furnace slag powder is placed in a 200-mesh standard vibrating screen for multiple sieves, controlling the slag powder particle size to not exceed 75μm. The resulting slag powder is stored in open glass bottles, sealed with a sealing film, and stored in a desiccator.

[0027] S22: Calcium carbide slag is a byproduct of acetylene production, primarily composed of calcium hydroxide, initially in a slurry-like wet state. It is placed in a vacuum drying oven at 80±5℃ and dried at normal pressure for 36 hours, turning it over every 6 hours to ensure uniform moisture evaporation. After drying, it is initially crushed using a jaw crusher to achieve a particle size below 5mm, and then ground using a planetary ball mill with zirconia balls as the grinding media. The mass ratio of zirconia balls to calcium carbide slag is set at 3:1, the rotation speed is set at 350 rpm, and grinding lasts for 60 minutes. After grinding, it is sieved multiple times using a 200-mesh standard vibrating screen to obtain calcium carbide slag powder with a particle size not exceeding 75μm. This powder is then stored in sealed bags, air removed, and sealed for preservation.

[0028] S23: Spread the desulfurized gypsum evenly on a tray and dry it in a vacuum drying oven at 180℃ for 2 hours to remove some of the water of crystallization, gradually transforming the desulfurized gypsum into hemihydrate gypsum. This allows for rapid crystallization during hydration, effectively improving the strength of the gel. The dried desulfurized gypsum is initially crushed by a jaw crusher, and then finely ground using a planetary ball mill at a speed of 300 rpm. The mill is stopped every 10 minutes, and the lid is opened until the temperature drops below 50℃. This process is repeated three times to obtain desulfurized gypsum powder. The powder is then sieved multiple times using a 35-mesh standard sieve to obtain desulfurized gypsum powder with a particle size not exceeding 0.5 mm.

[0029] S3: Slag powder, desulfurized gypsum powder and carbide slag powder are fed into a container in layers. The surface of the multi-source solid waste powder in the container is chemically modified by a silane coupling agent modification liquid. The modification liquid on the upper layer of the container is then removed by centrifugation to obtain the modified multi-source solid waste powder. The modified multi-source solid waste powder is mixed with deionized water to obtain a multi-source solid waste composite cementitious material.

[0030] The specific steps to obtain multi-source solid waste composite cementitious materials include: S31: Take the slag powder, desulfurized gypsum powder and carbide slag powder prepared in S2. According to the determined mass ratio, use an electronic analytical balance with a calibrated accuracy of 0.01g to weigh 8g of slag powder, 1.6g of desulfurized gypsum powder and 0.8g of carbide slag powder respectively. Prepare a 250mL beaker. Pour 30% of the slag powder evenly into the bottom of the beaker, then pour all the carbide slag powder and desulfurized gypsum powder into the beaker in sequence. Finally, cover the remaining 70% of the slag powder on the top layer to reduce raw material loss and dust dispersion during the mixing process.

[0031] S32: Add anhydrous ethanol to a beaker at a volume of 5 times that of the multi-source solid waste powder to prepare a 5% silane coupling agent (KH-550) modification solution. Then, slowly pour the solution into the beaker containing the multi-source solid waste powder. Use an ultrasonic generator to ultrasonically disperse the powder for 20 minutes. The cavitation effect generated by the ultrasound breaks up the powder aggregation, allowing the silane coupling agent molecules to be fully wetted, adsorbed, and initially hydrolyzed on the surface of the multi-source solid waste powder. After ultrasonic dispersion, use a cantilevered electronic stirrer (550 rpm) to centrifuge the solution and multi-source solid waste powder for 5-10 minutes to remove the upper layer of modification solution from the beaker. Place the modified multi-source solid waste powder in an 80℃ vacuum drying oven to constant weight. After drying, sieve multiple times using a 200-mesh standard sieve to obtain loose, dry, modified multi-source solid waste powder.

[0032] S33: Place the beaker containing the modified multi-source solid waste powder on a thermostatic magnetic stirrer. Slowly and evenly pour 100 mL of deionized water along the inner wall of the beaker. Turn on the magnetic stirrer during the pouring process, setting the speed to 300 rpm to prevent localized clumping of the powder. After all the deionized water has been added, adjust the speed to 500 rpm and stir for 10 minutes. After mixing, use a glass rod to lift the slurry in the container and check if the slurry meets the conditions of uniform adhesion, fluid consistency when poured, and no obvious water separation. If not, extend the mixing time and check the slurry state again until it meets the requirements, obtaining the multi-source solid waste composite cementitious material. The multi-source solid waste composite cementitious material is a uniform, white, slurry-like suspension without dry powder or visible stratification.

[0033] S4: Modified sodium polyacrylate is mixed with multi-source solid waste composite cementitious material and stirred until a gel state is reached. Sodium hydroxide solution is added for neutralization to obtain solid waste-based composite gel. The solid waste-based composite gel is placed in a closed reactor for hydrothermal intensification treatment, and then the solid waste-based composite gel is immersed in CaCl2 solution to introduce Ca through ion exchange. 2+ The solid waste-based composite gel was removed from the CaCl2 solution and dried to obtain a multi-source solid waste-based gel.

[0034] In this embodiment, the specific steps for obtaining the multi-source solid waste-based gel include: S41: Slowly and evenly add 3.5g of modified sodium polyacrylate to the multi-source solid waste cementitious material. During the addition of the modified sodium polyacrylate, turn on the cantilevered electronic stirrer at a speed of 500 rpm. During stirring, the modified sodium polyacrylate polymer chains fully extend under the action of the shear field, and its -COO... - Groups and Ca in multi-source solid waste cementitious materials 2+ (Calcium ions), Al 3+ Multivalent metal ions such as aluminum ions form a dynamic ionic cross-linking network; at the same time, polymer chains interpenetrate with particles and preliminary hydrolysis products in multi-source solid waste cementitious materials through entanglement until the multi-source solid waste cementitious materials and modified sodium polyacrylate are uniformly mixed and present a gel state.

[0035] S42: Add a 30% sodium hydroxide solution to neutralize and adjust the pH value to 7-8 to obtain a solid waste-based composite gel; S43: The obtained solid waste-based composite gel was placed in a closed reactor and subjected to hydrothermal enhancement treatment at 100℃ for 3 hours. S44: The hydrothermally enhanced solid waste-based composite gel is immersed in a 10% CaCl2 (calcium chloride) solution, so that the CaCl2 solution contains Ca... 2+ Na in solid waste-based composite gel + Sodium ions undergo ion exchange to form more stable Ca. 2+ Crosslinking point.

[0036] S45: The solid waste-based composite gel was removed from the CaCl2 solution and dried in a vacuum drying oven at 60℃ to constant weight to obtain a multi-source solid waste-based gel. This gel isolates oxygen through a dense and stable organic-inorganic interpenetrating network structure and continuously absorbs heat by utilizing the locked-in moisture, thereby achieving the effect of inhibiting spontaneous combustion of coal.

[0037] Example 2: The difference between Example 2 and Example 1 is that in step S31, the weight of the slag powder is 6g, the weight of the desulfurized gypsum powder is 1.2g, and the weight of the carbide slag powder is 0.6g.

[0038] Example 3: The difference between Example 3 and Example 1 is that in step S31, the weight of the slag powder is 4g, the weight of the desulfurized gypsum powder is 0.4g, and the weight of the carbide slag powder is 0.8g.

[0039] The following is a verification of the multi-source solid waste-based gels prepared by the preparation method of one of Examples 1 to 3.

[0040] Table 1 shows the gel times of the multi-source solid waste-based gels prepared in Examples 1 to 3.

[0041] Table 1 As can be seen from Table 1, the multi-source solid waste-based gel prepared in Example 1 has the shortest gelation time, indicating that its solidification reaction rate is the fastest and it is suitable for underground mining areas that require rapid sealing and plugging.

[0042] Take an appropriate amount of coal and crush it into particles with a diameter of 1-2 cm. Place the crushed coal particles evenly into a funnel, place the funnel on a funnel stand, and place a beaker below it. Weigh 200 g of the prepared multi-source solid waste-based gel and pour it evenly onto the crushed coal in the funnel. After the multi-source solid waste-based gel has stabilized, weigh the mass of the multi-source solid waste-based gel in the beaker and calculate the permeability of the multi-source solid waste-based gel. The calculation formula is as follows: In the formula, The permeability of multi-source solid waste-based gel; The mass of the multi-source solid waste-based gel in the beaker; The initial mass of the multi-source solid waste-based gel is 200g in this example.

[0043] The permeability of the multi-source solid waste-based gels prepared in Examples 1 to 3 is shown in Table 2.

[0044] Table 2 As can be seen from Table 2, the multi-source solid waste-based gel prepared in Example 3 has the highest permeability, indicating that the multi-source solid waste-based gel at this ratio has good fluidity and can reach deeper into the coal body. It is suitable for deep penetration and filling in areas with well-developed internal fracture networks, complex air leakage channels, and loose coal and rock accumulation.

[0045] Weigh 2g of multi-source solid waste-based gel and place it in a 120-mesh nylon mesh bag, recording the mass of the gel in this state. Suspend the nylon mesh bag containing the multi-source solid waste-based gel in a vacuum drying oven at a constant temperature of 60℃. Remove the gel at a predetermined time point and quickly place it in a desiccator to cool for 3 minutes. Record the mass of the gel in this state and calculate its water loss rate using the following formula: In the formula, The water loss rate of multi-source solid waste-based gel; The mass of multi-source solid waste-based gels before a certain time period. The mass of multi-source solid waste-based gel after a certain period of time.

[0046] from Figure 2The results show that the water loss rate of the three multi-source solid waste-based gels was less than 20% within 24 hours, indicating that the three multi-source solid waste-based gels can maintain structural moisture for a long time and effectively isolate oxygen to inhibit spontaneous combustion of coal. Among them, the multi-source solid waste-based gel prepared in Example 2 had the lowest water loss rate, and the synergistic reaction of the three solid wastes was more complete under this ratio. The calcium silicate hydrate (CSH) gel generated by the hydration of slag powder and calcium carbide slag powder and the ettringite (AFt crystals) generated by the reaction of desulfurized gypsum powder, together with the polymer chains of modified sodium polyacrylate, form a denser organic-inorganic interpenetrating network with a more uniform distribution of cross-linking points, which strongly locks in moisture. This ratio is suitable for high-temperature environments and underground areas that require long-term moisture retention and sealing.

[0047] To test the inhibitory effect of multi-source solid waste-based gel on coal spontaneous combustion, coking coal was selected as the original coal sample. The coal was first mechanically crushed and the surface oxide layer removed, then ground using a ball mill. The resulting coal powder was sieved through a 200-mesh screen and placed in a vacuum drying oven at 60±1℃ for 24 hours to dehydrate. Multi-source solid waste-based gel prepared in Examples 1 to 3 was added to a portion of the coal powder to create three types of inhibited coal samples, while the remaining untreated coal powder served as the original coal sample.

[0048] The inhibitory effect of multi-source solid waste-based gel on the oxidation process of coking coal was analyzed using temperature-programmed gas chromatography-mass spectrometry (GC-GC) to assess both oxygen consumption rate and CO2 production rate. The oxygen consumption rate and CO2 production rate of the coal samples treated with multi-source solid waste-based gel are shown below. Figure 3 and Figure 4 As shown.

[0049] from Figure 3 and Figure 4 It can be seen that the oxygen consumption rate and CO generation rate of the coal samples treated with the multi-source solid waste gel prepared in Examples 1 to 3 are lower than those of the coking coal itself. When the temperature reaches 180℃, the oxygen consumption rate and CO generation rate of the coal samples treated with the multi-source solid waste gel are more significantly inhibited.

[0050] The coal samples treated with the multi-source solid waste-based gel prepared in Examples 1 to 3 showed that the final oxygen consumption rate was reduced by 37.7%, 40.7%, and 34.6% compared to the oxygen consumption rate of the coking coal itself, respectively, and the final CO production rate was reduced by 49.6%, 56.7%, and 42.8% compared to the CO production rate of the coking coal itself. This indicates that the multi-source solid waste-based gel can effectively inhibit the process of coal-oxygen complex reaction and has a good inhibitory effect on coal spontaneous combustion.

[0051] Thermogravimetric-Differential Scanning Calorimetry (TG-DSC) was used to test the changes in characteristic temperature and exothermic properties of different coal samples during the heating process. Figure 5 and Figure 6 As shown. The experiment involved six characteristic temperature points: The temperature at which the maximum water loss rate is reached. This is the drying temperature. The temperature at which thermal decomposition occurs. The ignition point temperature, The temperature at which the maximum rate of thermal weight loss occurs. This refers to the burnout temperature.

[0052] Based on the characteristic temperature points determined above, the reaction process of coal sample from low-temperature oxidation to the end of the combustion reaction is divided into 5 stages: moisture evaporation and gas desorption weight loss stage ( ), oxygen inhalation weight gain stage ( ), slow weightlessness phase ( ), combustion weightlessness stage ( ), burnout stage ( ).

[0053] pass Figure 5 and Figure 6 The characteristic temperature points and exothermic parameters of different coal samples were obtained to characterize the thermal effect of multi-source solid waste-based gel in inhibiting coal spontaneous combustion. Table 3 shows the characteristic temperature points of different coal samples, and Table 4 shows the exothermic parameters of different coal samples.

[0054] Table 3 As can be seen from Table 3, the characteristic temperature points of the coal samples treated with multi-source solid waste-based gel all showed a significant hysteresis effect compared with the characteristic temperature points of the coking coal itself, indicating that the multi-source solid waste-based gel prepared in this invention can enhance the thermal stability of coal and effectively inhibit the coal-oxygen complex reaction.

[0055] Table 4 As shown in Table 4, the inflection point temperature of the coal samples treated with the multi-source solid waste-based gel exhibited a significant lag compared to that of the coking coal itself, indicating that the multi-source solid waste-based gel effectively delayed the initial stage of the coal oxidation exothermic reaction. Simultaneously, the inflection point exothermic power, maximum exothermic power, and heat release of the coal samples treated with the multi-source solid waste-based gel were all lower than those of the coking coal itself. This indicates that the multi-source solid waste-based gel effectively suppressed the intensity of the coal oxidation reaction, thus weakening the heat release process of the coal.

[0056] The above description is merely a preferred 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 scope of the technology 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 a multi-source solid waste-based gel, characterized in that, Includes the following steps: Modified sodium polyacrylate was prepared. The modified sodium polyacrylate was a graft copolymer obtained by amination of sodium polyacrylate with 3-aminopropyltriethoxysilane and then graft polymerization with hydroxyethyl methacrylate monomer containing active double bonds. The raw materials of multi-source solid waste are dried, ground and screened to obtain multi-source solid waste powder. The raw materials of multi-source solid waste include granulated blast furnace slag, desulfurized gypsum and carbide slag. The multi-source solid waste powder includes slag powder, desulfurized gypsum powder and carbide slag powder. Slag powder, desulfurized gypsum powder, and carbide slag powder are fed into a container using a layered feeding method. The surface of the multi-source solid waste powder in the container is chemically modified by a silane coupling agent modification liquid. The modification liquid on the upper layer of the container is then removed by centrifugation to obtain the modified multi-source solid waste powder. The modified multi-source solid waste powder is then mixed with deionized water to obtain a multi-source solid waste composite cementitious material. Modified sodium polyacrylate was mixed with multi-source solid waste composite cementitious material and stirred until a gel state was reached. Sodium hydroxide solution was then added for neutralization to obtain a solid waste-based composite gel. The solid waste-based composite gel was placed in a closed reactor for hydrothermal intensification treatment, and then immersed in CaCl2 solution to introduce Ca through ion exchange. 2+ The solid waste-based composite gel was removed from the CaCl2 solution and dried to obtain a multi-source solid waste-based gel.

2. The method for preparing a multi-source solid waste-based gel according to claim 1, characterized in that: The process for preparing modified sodium polyacrylate includes the following steps: S11: Sodium polyacrylate and 3-aminopropyltriethoxysilane are added to anhydrous toluene at a first molar ratio and refluxed under nitrogen atmosphere. The reflux reaction is used to cause the carboxyl anions on the sodium polyacrylate polymer chain to undergo an amidation reaction with the amino group of 3-aminopropyltriethoxysilane, thereby introducing an amino group into the sodium polyacrylate polymer chain. The product of the reflux reaction is filtered, washed and dried to obtain amino-functionalized sodium polyacrylate. S12: Hydroxyethyl methacrylate and 2-isocyanate ethyl methacrylate are mixed at a second molar ratio, and dibutyltin dilaurate is used as a catalyst. The mixture is stirred under nitrogen atmosphere. The stirring reaction is used to allow the isocyanate of 2-isocyanate ethyl methacrylate to undergo an addition reaction with the hydroxyl group of hydroxyethyl methacrylate, to obtain a product containing polymerizable double bonds. The product containing polymerizable double bonds is purified by column chromatography to obtain hydroxyethyl methacrylate monomer containing active double bonds. S13: Dissolve amino-functionalized sodium polyacrylate in N,N-dimethylformamide solution, use 2,2'-azobisisobutyronitrile as initiator, and in a constant temperature oil bath under nitrogen atmosphere, dropwise add a mixture of hydroxyethyl methacrylate monomer containing active double bonds and N,N'-methylenebisacrylamide into the reaction system of amino-functionalized sodium polyacrylate and N,N-dimethylformamide, so that amino-functionalized sodium polyacrylate and hydroxyethyl methacrylate monomer containing active double bonds undergo graft polymerization reaction; S14: After the graft polymerization reaction is completed, potassium sulfate and tetraethylenepentamine are added to the graft polymerization reaction system to initiate the secondary crosslinking of the unreacted amino-functionalized sodium polyacrylate with the hydroxyethyl methacrylate monomer containing active double bonds; after cooling the graft polymerization reaction system, anhydrous ethanol is used to precipitate the product of the graft polymerization reaction, and after washing, filtering, drying and grinding, modified sodium polyacrylate is obtained.

3. The method for preparing a multi-source solid waste-based gel according to claim 2, characterized in that: In the preparation of modified sodium polyacrylate, the first molar ratio is the molar ratio of 3-aminopropyltriethoxysilane to the carboxyl group in sodium polyacrylate, which is 0.1:1; the second molar ratio is the molar ratio of 2-isocyanate methacrylate to the hydroxyl group in hydroxyethyl methacrylate, which is 0.2:1; the molar ratio of potassium sulfate to tetraethylenepentamine added to the graft polymerization reaction system is 1:1.5; the concentration of N,N-dimethylformamide solution is 5%; the mass of 2,2'-azobisisobutyronitrile is 0.5% of the total mass of amino-functionalized sodium polyacrylate and hydroxyethyl methacrylate monomer containing active double bonds; and the mass of N,N'-methylenebisacrylamide is 0.11% of the mass of hydroxyethyl methacrylate monomer containing active double bonds.

4. The method for preparing a multi-source solid waste-based gel according to claim 1, characterized in that: In the process of obtaining multi-source solid waste powder, granulated blast furnace slag is dried, ground, and sieved to obtain slag powder. Desulfurized gypsum and calcium carbide slag are dried, crushed, ground, and sieved to obtain desulfurized gypsum powder and calcium carbide slag powder, respectively. Both slag powder and calcium carbide slag powder are sealed and stored. The granulated blast furnace slag is S95 granulated blast furnace slag, and the calcium carbide slag is taken from the by-product of acetylene production. The particle size of slag powder and calcium carbide slag powder does not exceed 75μm, and the particle size of desulfurized gypsum powder does not exceed 0.5mm.

5. The method for preparing a multi-source solid waste-based gel according to claim 1, characterized in that: The steps to obtain multi-source solid waste composite cementitious materials include: S31: Weigh out slag powder, desulfurized gypsum powder and carbide slag powder according to the preset mass ratio. Pour the slag powder into the bottom and top layers of the container in two separate batches. Pour the carbide slag powder and desulfurized gypsum powder into the middle layer of the container in sequence. S32: Subsequently, anhydrous ethanol and silane coupling agent are added to the container to prepare a modification solution. After ultrasonic dispersion, the silane coupling agent molecules are wetted, adsorbed and initially hydrolyzed on the surface of the multi-source solid waste powder. The upper layer of modification solution is then removed by centrifugation to obtain the modified multi-source solid waste powder. After drying and multiple sieving, the modified multi-source solid waste powder is obtained. S33: Mix the modified multi-source solid waste powder with deionized water until a uniform, dry powder-free, and visible layered white slurry suspension is formed. The white slurry suspension is the multi-source solid waste composite cementitious material.

6. The method for preparing a multi-source solid waste-based gel according to claim 5, characterized in that: In the process of obtaining multi-source solid waste composite cementitious material, after mixing and stirring, the slurry in the container is lifted with a glass rod to check whether the slurry meets the conditions of uniform adhesion, fluid state when poured, and no water separation. If it does not meet the conditions, the mixing and stirring time is extended and the state of the slurry is checked again until it meets the requirements, and the multi-source solid waste composite cementitious material is obtained.

7. The method for preparing a multi-source solid waste-based gel according to claim 1, characterized in that: The steps to obtain multi-source solid waste-based gels include: S41: Modified sodium polyacrylate is mixed with multi-source solid waste composite cementitious material and stirred until gel state is reached, so that the modified sodium polyacrylate polymer chain extends and forms an ion cross-linking network with the multivalent metal ions in the multi-source solid waste composite cementitious material, and is entangled with the particles and preliminary hydrolysis products in the multi-source solid waste composite cementitious material. S42: Add a 30% sodium hydroxide solution to neutralize and adjust the pH value to 7-8 to obtain a solid waste-based composite gel; S43: The solid waste-based composite gel is placed in a closed reactor for hydrothermal enhancement treatment; S44: The hydrothermally enhanced solid waste-based composite gel is immersed in a 10% CaCl2 solution, so that the Ca in the CaCl2 solution... 2+ Na in solid waste-based composite gel + Ion exchange occurs, forming Ca 2+ Crosslinking point; S45: The solid waste-based composite gel was removed from the CaCl2 solution and dried to obtain a multi-source solid waste-based gel.

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