Coal gangue microwave-chemical synergistic activation method and activated coal gangue

Abstract

The invention discloses a coal gangue microwave-chemical synergistic activation method and activated coal gangue, the coal gangue microwave-chemical synergistic activation method comprises the following steps: (1) crushing coal gangue to obtain a crushed product; (2) mixing the crushed product with a composite activator, and performing microwave treatment to obtain an activated product; the composite activating agent comprises waste alkali liquor, fly ash aluminum extraction residues and water glass; and (3) drying, cooling and grinding the activated product to obtain the activated coal gangue. The microwave-chemical synergistic activation method for the coal gangue is high in activation efficiency, efficient destruction of crystal lattices of coal gangue minerals is achieved through the synergistic effect of microwaves and the composite activating agent, the activation time is shortened, the silicon-aluminum dissolution rate is increased, the silicon dissolution rate reaches 80% or above, the aluminum dissolution rate reaches 70% or above, the problem that single chemical activation is low in efficiency is solved, and the method is suitable for industrial production. And the obtained activated coal gangue product has high activity.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment, and particularly relates to a method for the resource utilization of coal gangue and the activation of coal gangue. Background Technology

[0002] Coal gangue is a major solid waste generated during coal mining, washing, and processing, accounting for approximately 15%-20% of total coal production. Statistics show that my country's cumulative coal gangue stockpile exceeds 7 billion tons, with an annual increase of about 300-500 million tons. The long-term accumulation of large quantities of coal gangue not only occupies land resources but also poses a significant challenge to the green development of the coal industry by causing soil, water, and air pollution through leaching and dust generation. However, coal gangue is rich in active components such as silicon (SiO2, 40%-60%) and aluminum (Al2O3, 15%-30%), and its mineral composition is mainly kaolinite and quartz, possessing the potential to be transformed into cementitious materials through activation. If the silicon and aluminum components in coal gangue can be efficiently activated, they can replace a portion of cement clinker in building materials, achieving the circular economy goal of "replacing materials with waste."

[0003] Traditional activation methods for coal gangue mainly include thermal activation and chemical activation. Thermal activation typically requires high temperatures of 800-1000℃, resulting in extremely high energy consumption. Furthermore, the high temperature process may cause some mineral crystal structures to become overly stable, hindering the subsequent dissolution of silicon and aluminum components. While chemical activation can improve the silicon and aluminum dissolution rate to some extent, it suffers from low activation efficiency and high cost of required chemical reagents. Microwave activation technology offers advantages such as rapid, bulk heating, and selective heating; however, current activator designs are relatively limited, failing to fully utilize the specific interactions between the microwave field and the material components, leaving room for improvement in activation efficiency. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a microwave-chemical synergistic activation method for coal gangue with high activation efficiency and activated coal gangue. The method significantly improves the activation efficiency and product performance of coal gangue by optimizing the activator formulation and introducing microwaves.

[0005] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0006] A microwave-chemical synergistic activation method for coal gangue includes the following steps: (1) The coal gangue is crushed to obtain the crushed product, and the crushed product is screened to 80-200 mesh; (2) The crushed product and the composite activator are mixed and microwave-treated to obtain the activated product; the composite activator includes waste alkaline solution, fly ash aluminum extraction residue and water glass; (3) The activated product is dried, cooled and ground to obtain activated coal gangue.

[0007] In the above-mentioned microwave-chemical synergistic activation method for coal gangue, preferably, the mass ratio of waste alkaline solution, fly ash aluminum extraction residue, and water glass in the composite activator is 10-30:30-50:30-50.

[0008] In the above-mentioned microwave-chemical synergistic activation method for coal gangue, preferably, the amount of the composite activator is 10%-30% of the mass of the crushed product.

[0009] In this invention, the synergistic effect of microwaves and a composite activator is beneficial to improving the activation efficiency of coal gangue. The composite activator contains Ca²⁺ provided by fly ash aluminum extraction residue. + This composite activator promotes CASH gel formation, efficiently disrupts mineral crystal lattices with waste alkaline solution, and replenishes active silicon. Under microwave action, the three substances synergistically shorten activation time and increase silicon-aluminum dissolution rate, solving the problem of low efficiency with single chemical activation. The resulting activated coal gangue product exhibits high activity. The composition of the composite activator requires determining the proportions of each component and the total dosage based on their mechanisms of action and the composition of the coal gangue to ensure activation efficiency. Research shows that controlling the mass ratio of waste alkaline solution, fly ash aluminum extraction residue, and water glass to 10-30:30-50:30-50, and using the composite activator at 10%-30% of the crushed coal gangue mass, ensures activation efficiency without wasting raw materials.

[0010] In the aforementioned microwave-chemical synergistic activation method for coal gangue, preferably, a portion of the waste alkaline solution is replaced by alkaline solution recycled from waste lithium batteries. This recycled alkaline solution contains lithium ions and alkaline solution; the mass concentration of alkali in the waste alkaline solution is 8%-15%. By using alkaline solution recycled from waste lithium batteries to replace part of the waste alkaline solution, lithium ions can be introduced into the alkaline solution system. Lithium ions have a small ionic radius and high charge density. During the microwave activation stage, the strong polarization effect of lithium ions helps to more efficiently break the Al-O bonds in the coal gangue minerals within the microwave field. Furthermore, in the subsequent gelation application stage, lithium ions can specifically catalyze the hydration reaction of the aluminum-containing active phase and compress the particle double layer, thereby synergistically endowing the final building material with significant early strength characteristics. This is beneficial for applying this activated coal gangue to applications requiring early strength. The introduction of alkaline solution recycled from waste lithium batteries must ensure that the mass concentration of the waste alkaline solution is not too low. The amount of alkaline solution used in the recycling of waste lithium batteries should not be too high, generally not exceeding 30% of the mass of the waste alkaline solution.

[0011] In the aforementioned microwave-chemical synergistic activation method for coal gangue, preferably, the fly ash aluminum extraction residue has a particle size of 150-200 mesh and contains 20%-30% CaO and 15%-20% Al2O3 by mass. The fly ash aluminum extraction residue is mainly used to provide active calcium oxide, and its particle size control is beneficial to its effectiveness. The source of the fly ash aluminum extraction residue is not critical, as long as the above conditions are met.

[0012] In the above-mentioned microwave-chemical synergistic activation method for coal gangue, preferably, the water glass is partially or completely replaced by solid sodium silicate pentahydrate, and the solid sodium silicate pentahydrate adopts a coating structure. The coated sodium silicate includes a core layer and a shell layer, the core layer is solid sodium silicate pentahydrate, and the shell layer is fly ash aluminum extraction residue in the composite activator. To better utilize the composite activator, this invention further optimizes the addition form of water glass by employing coated sodium silicate, which offers at least the following advantages: 1. By using solid pentahydrate sodium silicate instead of water glass, solid pentahydrate sodium silicate exhibits strong microwave absorption due to its crystal water and ionic bonds. In a microwave field, solid pentahydrate sodium silicate undergoes rapid selective heating, resulting in "explosive dissolution," instantly forming a localized ultra-high concentration micro-region of active silicate ions around the coal gangue particles. This instantaneous high concentration gradient significantly increases the probability of collision and reaction between silicate ions and the fresh surface of the coal gangue after microwave dissociation, thereby significantly improving silicon utilization efficiency and the early gel phase formation rate. In contrast, uniformly distributed water glass solutions cannot form this dynamic concentration gradient conducive to rapid reactions. 2. When solid sodium silicate pentahydrate is added to waste alkaline solution, it may dissolve, which does not match the aluminum release peak in the early stage of coal gangue activation, thus failing to achieve the above-mentioned effects. This invention adopts a coating structure to achieve delayed dissolution. The fly ash aluminum extraction residue acts as a shell layer, serving as a physical barrier to delay the initiation time of water molecule penetration and solid sodium silicate pentahydrate dissolution, achieving delayed release of active silicon source. At the same time, it matches the dissolution kinetics of active aluminum in coal gangue during microwave process, thereby maximizing the probability of silicon-aluminum encounter reaction and improving activation efficiency. 3. The fly ash aluminum extraction residue acts as a shell layer, which itself dissolves and releases active calcium oxide, directly encountering the internal active silicon. This "core-shell" structure itself forms a gradient reaction micro-region of "silicon-aluminum-calcium-alkali-alkali" at the microscopic level, which is extremely conducive to the rapid in-situ formation of gel. These early-formed gels can act as crystal nuclei, accelerating the gelation process of the entire system. 4. The solid sodium silicate pentahydrate core layer and the fly ash aluminization residue shell layer have different microwave absorption characteristics. In a microwave field, the heating rates of the shell layers may differ, generating internal thermal stress. This differential thermal expansion may cause the coating layer to "burst" from the inside, producing a "micro-burst" effect. This physical effect not only promotes the release of the solid sodium silicate pentahydrate core layer but also further pulverizes the fly ash aluminization residue shell layer and surrounding coal gangue particles, greatly increasing the reaction interface. In a more preferred embodiment, the water glass portion is replaced by coated sodium silicate, for example, using coated sodium silicate to replace 60% of the water glass, to avoid affecting the mixing uniformity of the composite activator. Overall, replacing part or all of the water glass with coated sodium silicate is beneficial to improving the activation efficiency of coal gangue.

[0013] In the aforementioned microwave-chemical synergistic activation method for coal gangue, preferably, ferrite powder is added to the shell layer, with the ferrite powder accounting for 5%-10% of the shell layer by mass, and the particle size of the ferrite powder being less than 10 μm. Fly ash aluminum extraction residue, used as the shell layer, has limited microwave absorption capacity and relatively uniform heating. This invention, by introducing ferrite powder and uniformly doping it into the shell layer, is equivalent to implanting countless micro-heating points within the shell layer. In the microwave field, these ferrite micro-points are preferentially and intensely heated, forming localized high-temperature zones. This targeted heating causes the shell layer to be directionally heated from the inside, generating stronger internal thermal stress. By controlling the amount of ferrite powder added, the timing of shell layer destruction can be controlled, allowing the shell layer to first develop porosity, thus achieving orderly dissolution of the core layer. The addition of the aforementioned ferrite powder should not be excessive, otherwise the shell layer will be destroyed prematurely. Furthermore, the ferrite powder will partially dissolve under the action of strong alkali and microwaves, releasing Fe. 2+ / Fe 3+ Fe 3+ It can enter the CASH gel structure and partially replace Al. 3+ This process forms more complex CAFSH gels, which typically exhibit higher chemical stability and strength. Undissolved nano-ferrite particles can also serve as nanofillers, enhancing the density of the gel matrix. The aforementioned ferrite powder can also be made from industrial waste powder to reduce raw material costs.

[0014] In the aforementioned microwave-chemical synergistic activation method for coal gangue, preferably, the preparation method of the coated sodium silicate includes the following steps: using a dry mechanical fusion coating method, dry fly ash aluminizing residue is mixed with ferrite powder, and a liquid binder is added for further mixing to form a viscous composite powder; then solid sodium silicate pentahydrate particles are added, and under shearing action, the viscous composite powder coats the surface of the solid sodium silicate pentahydrate particles; finally, drying and curing are performed; the liquid binder is a lignin sulfonate solution, and the amount of the liquid binder is 1%-2% of the total mass of the fly ash aluminizing residue and ferrite powder. In the preparation of this coated sodium silicate, the amount of fly ash aluminizing residue can be all of the fly ash aluminizing residue in the composite activator or part of the fly ash aluminizing residue in the composite activator, with the remaining fly ash aluminizing residue still added directly in powder form.

[0015] In the aforementioned microwave-chemical synergistic activation method for coal gangue, preferably, the microwave power is controlled at 595W-1.1kW and the treatment time is 12-20min. Under the microwave action of the above process parameters, the rapid heating characteristic of microwaves, combined with the synergistic effect of the composite activator components, can efficiently destroy the mineral lattice of coal gangue and promote the formation of active silicon-aluminum phase.

[0016] As a general technical concept, this invention also provides activated coal gangue prepared by the above-mentioned microwave-chemical synergistic activation method. The activated coal gangue can be widely used in building materials such as cement, concrete, mortar, and geopolymers, replacing part or all of the cement. This not only reduces production costs but also improves the workability, mechanical properties, and durability of the materials. For example, in cement production, activated coal gangue products replace 10%-30% of cement clinker; in concrete preparation, it replaces 15%-25% of cement; in mortar preparation, it replaces 10%-20% of cement; and in geopolymer preparation, it replaces all cementitious materials.

[0017] Compared with the prior art, the advantages of the present invention are as follows: 1. The microwave-chemical synergistic activation method for coal gangue of the present invention utilizes the rapid heating characteristics of microwaves, which greatly reduces the reaction temperature and significantly reduces energy consumption compared with traditional thermal activation methods, thus achieving the goal of energy saving.

[0018] 2. The microwave-chemical synergistic activation method for coal gangue of the present invention has high activation efficiency. Through the synergistic effect of microwave and composite activator, the mineral lattice of coal gangue is efficiently destroyed, the activation time is shortened, and the silicon and aluminum dissolution rate is increased. The silicon dissolution rate reaches more than 80%, and the aluminum dissolution rate reaches more than 70%. This solves the problem of low efficiency of single chemical activation, and the activated coal gangue product obtained has high activity.

[0019] 3. The microwave-chemical synergistic activation method for coal gangue of the present invention uses industrial waste such as waste alkaline solution and fly ash aluminum extraction residue as part of the activator, which further expands the solid waste disposal path, not only reduces the activation cost, but also realizes the resource utilization of waste, reduces environmental pollution, and meets the requirements of sustainable development.

[0020] 4. The microwave-chemical synergistic activation method of coal gangue of the present invention has prepared activated coal gangue, realizing the resource utilization of coal gangue. The activated product has high pozzolanic activity. Using it as a cement substitute can help reduce the amount of cement used, and provides a new type of efficient, energy-saving and environmentally friendly cementitious material for the field of building materials.

[0021] 5. The microwave-chemical synergistic activation method for coal gangue of the present invention is simple to operate and the process parameters are easy to control, which can meet the needs of large-scale industrial production and provide a feasible technical solution for the comprehensive utilization of coal gangue. Detailed Implementation

[0022] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0023] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0024] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0025] The coal gangue used in the following examples and comparative examples is Datong coal gangue from Shanxi Province, crushed and screened to 150 mesh, containing 45% SiO2 and 18% Al2O3; the waste alkaline solution is industrial waste alkaline solution with a NaOH mass concentration of 10%; the fly ash aluminum extraction residue is a by-product of the fly ash aluminum extraction process, screened to 180 mesh, containing 25% CaO and 18% Al2O3; and the water glass is an aqueous solution of sodium silicate with a modulus of 3.1.

[0026] Example 1: A microwave-chemical synergistic activation method for coal gangue includes the following steps: (1) The coal gangue is crushed to obtain the crushed product, and the crushed product is screened to 150 mesh; (2) Preparation of composite activator: by mass percentage, the composite activator includes 20% waste alkaline solution, 40% fly ash aluminum extraction residue and 40% water glass; (3) Mix the crushed product and the composite activator at a mass ratio of 100:20, stir evenly, and microwave treat to obtain the activated product. The microwave power is 800W and the treatment time is 18min. (4) The activated product is dried, cooled and ground to obtain activated coal gangue.

[0027] Traditional thermal activation processes, operating at 800-1000℃ for 2-4 hours, typically achieve SiO2 leaching rates of 45%-60% and Al2O3 leaching rates of 35%-50%, with energy consumption of 1.2-2.0 kWh / kg. The activation method in this embodiment yields activated coal gangue with SiO2 leaching rates reaching 82% and Al2O3 leaching rates reaching 72%, with a processing energy consumption of approximately 0.56 kWh / kg, significantly superior to traditional thermal activation processes.

[0028] The C35 concrete prepared by replacing 20% ​​of cement with activated coal gangue in this embodiment has a 1-day compressive strength of 5.8 MPa and a 28-day compressive strength of 53 MPa.

[0029] Example 2: A microwave-chemical synergistic activation method for coal gangue includes the following steps: (1) The coal gangue is crushed to obtain the crushed product, and the crushed product is screened to 150 mesh; (2) Preparation of composite activator: by mass percentage, the composite activator includes 30% waste alkaline solution, 30% fly ash aluminum extraction residue and 40% water glass; (3) Mix the crushed product and the composite activator at a mass ratio of 100:15, stir evenly, and microwave treat to obtain the activated product. The microwave power is 600W and the treatment time is 20min. (4) The activated product is dried, cooled and ground to obtain activated coal gangue.

[0030] The activated coal gangue obtained by the activation method in this embodiment has a SiO2 leaching rate of 81% and an Al2O3 leaching rate of 71%, with a processing energy consumption of approximately 0.44 kWh / kg.

[0031] The C35 concrete prepared by replacing 20% ​​of cement with activated coal gangue in this embodiment has a 1-day compressive strength of 5.5 MPa and a 28-day compressive strength of 51 MPa.

[0032] Example 3: A microwave-chemical synergistic activation method for coal gangue includes the following steps: (1) The coal gangue is crushed to obtain the crushed product, and the crushed product is screened to 150 mesh; (2) Preparation of composite activator: by mass percentage, the composite activator includes 10% waste alkaline solution, 45% fly ash aluminum extraction residue and 45% water glass; (3) Mix the crushed product and the composite activator at a mass ratio of 100:30, stir evenly, and microwave treat to obtain the activated product. The microwave power is 1000W and the treatment time is 12min. (4) The activated product is dried, cooled and ground to obtain activated coal gangue.

[0033] The activated coal gangue obtained by the activation method in this embodiment has a SiO2 leaching rate of 84% and an Al2O3 leaching rate of 74%, with a processing energy consumption of approximately 0.42 kWh / kg.

[0034] The C35 concrete prepared by replacing 20% ​​of cement with activated coal gangue in this embodiment has a 1-day compressive strength of 6.0 MPa and a 28-day compressive strength of 54 MPa.

[0035] Example 4: A microwave-chemical synergistic activation method for coal gangue includes the following steps: (1) The coal gangue is crushed to obtain the crushed product, and the crushed product is screened to 150 mesh; (2) Preparation of composite activator: By mass percentage, the composite activator includes 16% waste alkaline solution, 4% alkaline solution recycled from waste lithium batteries (adjusted to the same alkalinity as the waste alkaline solution, with a lithium ion content of about 1.0%), 40% fly ash aluminum extraction residue and 40% water glass. (3) Mix the crushed product and the composite activator at a mass ratio of 100:20, stir evenly, and microwave treat to obtain the activated product. The microwave power is 800W and the treatment time is 18min. (4) The activated product is dried, cooled and ground to obtain activated coal gangue.

[0036] The activated coal gangue obtained by the activation method in this embodiment has a SiO2 leaching rate of 83% and an Al2O3 leaching rate of 75%.

[0037] The C35 concrete prepared by replacing 20% ​​of cement with activated coal gangue in this embodiment has a 1-day compressive strength of 6.5 MPa and a 28-day compressive strength of 55 MPa.

[0038] Example 5: A microwave-chemical synergistic activation method for coal gangue includes the following steps: (1) The coal gangue is crushed to obtain the crushed product, and the crushed product is screened to 150 mesh; (2) Preparation of composite activator: By mass percentage, the composite activator includes 20% waste alkaline solution, 40% fly ash aluminum extraction residue, 20% water glass and 20% solid sodium silicate pentahydrate, and the solid sodium silicate pentahydrate is added in a coating structure. The coated sodium silicate includes a core layer and a shell layer. The core layer is solid sodium silicate pentahydrate and the shell layer is fly ash aluminum extraction residue (half of the aforementioned 40% fly ash aluminum extraction residue is used to prepare the shell layer, and the rest is added as powder). The preparation method of the coated sodium silicate includes the following steps: using a dry mechanical fusion coating method, 20% fly ash aluminum extraction residue is added to 1% of its mass of lignin sulfonate solution and mixed to form a viscous composite powder; then solid sodium silicate pentahydrate particles are added, and under shearing action, the viscous composite powder is coated on the surface of the solid sodium silicate pentahydrate particles; finally, drying and curing are performed to obtain coated sodium silicate. (3) Mix the crushed product and the composite activator at a mass ratio of 100:20, stir evenly, and microwave treat to obtain the activated product. The microwave power is 800W and the treatment time is 14min. (4) The activated product is dried, cooled and ground to obtain activated coal gangue.

[0039] The activated coal gangue obtained by the activation method in this embodiment has a SiO2 leaching rate of 85% and an Al2O3 leaching rate of 74%, with a processing energy consumption of approximately 0.38 kWh / kg.

[0040] The C35 concrete prepared by replacing 20% ​​of cement with activated coal gangue in this embodiment has a 1-day compressive strength of 6.2 MPa and a 28-day compressive strength of 56 MPa.

[0041] Example 6: A microwave-chemical synergistic activation method for coal gangue includes the following steps: (1) The coal gangue is crushed to obtain the crushed product, and the crushed product is screened to 150 mesh; (2) Preparation of composite activator: By mass percentage, the composite activator includes 20% waste alkaline solution, 40% fly ash aluminum extraction residue, 10% water glass and 30% solid sodium silicate pentahydrate, and the solid sodium silicate pentahydrate is added in a coating structure. The coated sodium silicate includes a core layer and a shell layer. The core layer is solid sodium silicate pentahydrate and the shell layer is fly ash aluminum extraction residue (30% of the aforementioned 40% fly ash aluminum extraction residue is used to prepare the shell layer, and the rest is added as powder). The preparation method of the coated sodium silicate includes the following steps: using a dry mechanical fusion coating method, 30% fly ash aluminum extraction residue is added to 1.5% of its mass of lignin sulfonate solution and mixed to form a viscous composite powder; then solid sodium silicate pentahydrate particles are added, and under shearing action, the viscous composite powder is coated on the surface of the solid sodium silicate pentahydrate particles; finally, drying and curing are performed to obtain coated sodium silicate. (3) Mix the crushed product and the composite activator at a mass ratio of 100:20, stir evenly, and microwave treat to obtain the activated product. The microwave power is 800W and the treatment time is 14min. (4) The activated product is dried, cooled and ground to obtain activated coal gangue.

[0042] The activated coal gangue obtained by the activation method in this embodiment has a SiO2 leaching rate of 86% and an Al2O3 leaching rate of 77%, with a processing energy consumption of approximately 0.38 kWh / kg.

[0043] The C35 concrete prepared by replacing 20% ​​of cement with activated coal gangue in this embodiment has a 1-day compressive strength of 6.3 MPa and a 28-day compressive strength of 57 MPa.

[0044] Example 7: A microwave-chemical synergistic activation method for coal gangue includes the following steps: (1) The coal gangue is crushed to obtain the crushed product, and the crushed product is screened to 150 mesh; (2) Preparation of composite activator: By mass percentage, the composite activator includes 20% waste alkaline solution, 40% fly ash aluminum extraction residue, 20% water glass, and 20% solid sodium silicate pentahydrate. The solid sodium silicate pentahydrate is added in a coated structure. The coated sodium silicate includes a core layer and a shell layer. The core layer is solid sodium silicate pentahydrate, and the shell layer is fly ash aluminum extraction residue (half of the aforementioned 40% fly ash aluminum extraction residue is used to prepare the shell layer). 5% of its mass is added to the shell layer. Ferrite powder (particle size less than 10 μm); the preparation method of this coated sodium silicate includes the following steps: using a dry mechanical fusion coating method, 20% of fly ash aluminum extraction residue and ferrite powder are dry mixed, and then 1% of its mass of lignin sulfonate solution is added and mixed further to form a viscous composite powder; then solid sodium silicate pentahydrate particles are added, and under shearing action, the viscous composite powder is coated on the surface of the solid sodium silicate pentahydrate particles; finally, drying and curing are performed to obtain coated sodium silicate; (3) Mix the crushed product and the composite activator at a mass ratio of 100:20, stir evenly, and microwave treat to obtain the activated product. The microwave power is 800W and the treatment time is 12min. (4) The activated product is dried, cooled and ground to obtain activated coal gangue.

[0045] The activated coal gangue obtained by the activation method in this embodiment has a SiO2 leaching rate of 86% and an Al2O3 leaching rate of 78%, with a processing energy consumption of approximately 0.35 kWh / kg.

[0046] The C35 concrete prepared by replacing 20% ​​of cement with activated coal gangue in this embodiment has a 1-day compressive strength of 6.4 MPa and a 28-day compressive strength of 59 MPa.

[0047] Comparative Example 1: A microwave-chemical synergistic activation method for coal gangue includes the following steps: (1) The coal gangue is crushed to obtain the crushed product, and the crushed product is screened to 150 mesh; (2) Preparation of composite activator: by mass percentage, the composite activator includes 40% waste alkaline solution and 60% water glass; (3) Mix the crushed product and the composite activator at a mass ratio of 100:20, stir evenly, and microwave treat to obtain the activated product. The microwave power is 800W and the treatment time is 18min. (4) The activated product is dried, cooled and ground to obtain activated coal gangue.

[0048] The activated coal gangue obtained by the activation method in this comparative example achieved a SiO2 leaching rate of 78% and an Al2O3 leaching rate of 60%, with a processing energy consumption of approximately 0.55 kWh / kg.

[0049] The C35 concrete prepared by replacing 20% ​​of the cement with activated coal gangue in this comparative example had a 1-day compressive strength of 4.0 MPa and a 28-day compressive strength of 42 MPa.

[0050] Comparative Example 2: A microwave-chemical synergistic activation method for coal gangue includes the following steps: (1) The coal gangue is crushed to obtain the crushed product, and the crushed product is screened to 150 mesh; (2) Preparation of composite activator: by mass percentage, the composite activator includes 40% waste alkaline solution and 60% fly ash aluminum extraction residue; (3) Mix the crushed product and the composite activator at a mass ratio of 100:20, stir evenly, and microwave treat to obtain the activated product. The microwave power is 800W and the treatment time is 18min. (4) The activated product is dried, cooled and ground to obtain activated coal gangue.

[0051] The activated coal gangue obtained by the activation method in this comparative example achieved a SiO2 leaching rate of 70% and an Al2O3 leaching rate of 61%, with a processing energy consumption of approximately 0.56 kWh / kg.

[0052] The C35 concrete prepared by replacing 20% ​​of cement with activated coal gangue in this comparative example had a 1-day compressive strength of 4.2 MPa and a 28-day compressive strength of 43 MPa.

[0053] Comparative Example 3: A microwave-chemical synergistic activation method for coal gangue includes the following steps: (1) The coal gangue is crushed to obtain the crushed product, and the crushed product is screened to 150 mesh; (2) The crushed product and waste alkaline solution are mixed at a mass ratio of 100:20, stirred evenly, and microwaved to obtain the activated product. The microwave power is 800W and the treatment time is 18min. (3) The activated product is dried, cooled and ground to obtain activated coal gangue.

[0054] The activated coal gangue obtained by the activation method in this comparative example achieved a SiO2 leaching rate of 65% and an Al2O3 leaching rate of 54%, with a processing energy consumption of approximately 0.55 kWh / kg.

[0055] The C35 concrete prepared by replacing 20% ​​of cement with activated coal gangue in this comparative example had a 1-day compressive strength of 3.5 MPa and a 28-day compressive strength of 38 MPa.

[0056] Comparative Example 4: A microwave-chemical synergistic activation method for coal gangue is proposed, which adopts traditional thermal activation. The coal gangue is from the same batch as in Example 1, crushed to 80 mesh, and then roasted in a muffle furnace at 800°C for 2 hours without adding a composite activator.

[0057] The activation method used in this comparative example yielded activated coal gangue with a SiO2 leaching rate of 61% and an Al2O3 leaching rate of 49%, with a processing energy consumption of approximately 1.80 kWh / kg. This result indicates poor activation performance of coal gangue and a significantly increased energy consumption.

[0058] The C35 concrete prepared by replacing 20% ​​of cement with activated coal gangue in this comparative example had a 1-day compressive strength of 3.3 MPa and a 28-day compressive strength of 37 MPa.

Claims

1. A microwave-chemical synergistic activation method for coal gangue, characterized in that, Includes the following steps: (1) The coal gangue is crushed to obtain the crushed product; (2) The crushed product and the composite activator are mixed and microwave-treated to obtain the activated product; the composite activator includes waste alkaline solution, fly ash aluminum extraction residue and water glass; (3) The activated product is dried, cooled and ground to obtain activated coal gangue.

2. The microwave-chemical synergistic activation method for coal gangue according to claim 1, characterized in that, In the composite activator, the mass ratio of waste alkaline solution, fly ash aluminum extraction residue and water glass is 10-30:30-50:30-50.

3. The microwave-chemical synergistic activation method for coal gangue according to claim 1, characterized in that, The amount of the composite activator is 10%-30% of the mass of the crushed product.

4. The microwave-chemical synergistic activation method for coal gangue according to claim 1, characterized in that, The waste alkaline solution is partially replaced by alkaline solution recycled from waste lithium batteries, which contains lithium ions and alkaline solution; the mass concentration of alkali in the waste alkaline solution is 8%-15%.

5. The microwave-chemical synergistic activation method for coal gangue according to claim 1, characterized in that, The fly ash aluminum extraction residue has a particle size of 150-200 mesh and contains 20%-30% CaO and 15%-20% Al2O3 by mass.

6. The microwave-chemical synergistic activation method for coal gangue according to claim 1, characterized in that, The water glass is partially or entirely replaced by solid sodium silicate pentahydrate, and the solid sodium silicate pentahydrate adopts a coating structure. The coated sodium silicate includes a core layer and a shell layer. The core layer is solid sodium silicate pentahydrate, and the shell layer is fly ash aluminum extraction residue in the composite activator.

7. The microwave-chemical synergistic activation method for coal gangue according to claim 6, characterized in that, Ferrite powder is also added to the shell layer, and the ferrite powder accounts for 5%-10% of the mass of the shell layer, and the particle size of the ferrite powder is less than 10μm.

8. The microwave-chemical synergistic activation method for coal gangue according to claim 7, characterized in that, The preparation method of the coated sodium silicate includes the following steps: using a dry mechanical fusion coating method, dry fly ash aluminum extraction residue and ferrite powder are dry mixed, and a liquid binder is added to continue mixing to form a viscous composite powder; then solid sodium silicate pentahydrate particles are added, and under shearing action, the viscous composite powder is coated on the surface of the solid sodium silicate pentahydrate particles; finally, drying and curing are performed; the liquid binder is a lignin sulfonate solution, and the amount of the liquid binder is 1%-2% of the total mass of the fly ash aluminum extraction residue and ferrite powder.

9. The microwave-chemical synergistic activation method for coal gangue according to claim 1, characterized in that, During microwave processing, the microwave power is controlled at 595W-1.1kW, and the processing time is 12-20min.

10. Activated coal gangue prepared by the microwave-chemical synergistic activation method according to any one of claims 1-9.