Method for preparing coal-based artificial stone through segmented microwave activation-gradient hot pressing

Abstract

The invention discloses a method for preparing coal-based artificial stone through segmented microwave activation-gradient hot pressing, and relates to the technical field of preparation of artificial stone through coal-based polymers. The preparation method comprises the following steps: uniformly mixing fly ash, coal gangue, an alkaline activator and metakaolin; and then carrying out primary pre-pressing, gradient hot-pressing pretreatment and segmented microwave activation to obtain the coal-based artificial stone. According to the method, gradient hot-pressing pretreatment and segmented microwave activation are combined in stages, the resource utilization rate of the coal-based solid waste is effectively increased, and meanwhile, the artificial stone material with high compressive strength and good durability is prepared.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing coal-based artificial stone by using segmented microwave activation-gradient hot pressing, belonging to the technical field of coal-based polymer preparation of artificial stone. BACKGROUND

[0002] Artificial stone is a composite material composed of natural stone particles, mineral powder and high molecular resin through polymerization process. Its mechanical properties can be optimized to exceed the standard of natural stone. Artificial stone meets the demand of diversified materials in the construction and environmental protection industries due to its advantages over natural stone. Dedan Duan et al. prepared a kind of artificial stone based on solid waste with high strength and low density by hot pressing method using circulating fluidized bed fly ash, calcium carbide slag and flue gas desulfurization gypsum as raw materials. However, the production energy consumption will increase significantly due to the need to maintain high temperature and high pressure environment during the preparation process. Sheng Jiang et al. improved the pozzolanic activity of Yellow River silt by calcination pretreatment, which facilitated the improvement of the compressive strength of artificial stone in the subsequent alkali activation and pressure molding. However, secondary addition of fly ash is required in the later stage to meet the compressive strength requirements in river revetment, flood control and other engineering projects. The addition of mineral fillers in the production of polymer composites helps to improve mechanical resistance. Anastasios et al. added various contents of fly ash powder and found that the mechanical resistance increased with the increase of ash content. Xu Li and Yang Wenbin et al. invented a method for preparing artificial stone using fly ash as raw material with acrylic resin as adhesive and various additives, thereby obtaining a dark-colored fly ash artificial stone with high compressive strength, wear resistance, low water absorption and low deformation. However, the initiators and accelerators used are peroxide and aniline, which may have toxicity or environmental problems.

[0003] At the same time, the annual production of fly ash from the thermal power industry has increased significantly to 900 million tons, with a historical cumulative stockpile of more than 3 billion tons. The large amount of coal-based solid waste stockpiling not only causes inefficient occupation of land resources, but also causes complex pollution problems in soil, water and air environment. The geopolymeric material preparation system based on alkali activation technology can activate the active silica and alumina components in coal-based solid waste to prepare a new type of cementing material with early strength development characteristics, excellent durability and economic feasibility. The preparation of high compressive strength geopolymer grouting material using coal gangue and fly ash as raw materials for building industry consumables is beneficial to improve the utilization rate of coal-based solid waste and meets the strategic demand of circular economy development.

[0004] Geopolymer is an inorganic cementitious material formed by alkali-activated silicate, which is the latest alternative of cementitious material with low carbon footprint. It is considered as an important development direction of new green building materials due to its low energy consumption (30%-50% of traditional cement), high strength, high temperature resistance, corrosion resistance and low carbon characteristics. However, the raw materials of existing geopolymer mainly depend on kaolin, metakaolin or slag, which has high cost and is limited by regional resources, making it difficult to be widely promoted. It is of great significance to develop a coal-based solid waste-based geopolymer block preparation technology with high content, low energy consumption and controllable performance, which can promote solid waste resource utilization and low-carbon building materials.

[0005] Mullite crystal phase has become a key reinforcing phase for building high-end functional artificial stone, and plays an irreplaceable supporting role in improving the overall service performance of artificial stone. The essence of mullite crystal phase formation lies in the regulation and optimization of the microstructure of artificial stone, which is specifically manifested in the introduction of a crystal network structure with high strength and high chemical stability, thereby effectively overcoming the core performance defects of ordinary artificial stone such as low strength, insufficient high temperature resistance, weak chemical corrosion resistance and easy deformation. From the application scene, whether in the field of civil decoration or in the field of industrial scale, mullite crystal phase can significantly improve the service life, safety and environmental adaptability of artificial stone. SUMMARY

[0006] In view of the shortcomings of the prior art, the present application provides a method for preparing coal-based artificial stone by using segmented microwave activation-gradient heat pressing, which solves the problems of high carbon emission, low solid waste utilization rate, high process energy consumption and insufficient product performance of traditional building materials through multi-dimensional technology, and provides a sustainable development path for the building materials industry.

[0007] A method for preparing coal-based artificial stone by using segmented microwave activation-gradient heat pressing, comprising the following steps: S1. Mix fly ash, coal gangue, alkaline activator and metakaolin uniformly; S2. Ball mill and sieve the mixed material obtained in S1 to obtain a mixture; S3. Pre-press the mixture in a mold, then perform heat pressing pretreatment, adjust the initial pressure to 5-10 MPa, heat to 350-400℃ at a rate of 5-10℃ / min in the first stage, and then keep the temperature constant for 15-20 minutes; in the second stage, heat to 600-700℃ at a rate of 5-10℃ / min, adjust the pressure to 15-20 MPa, and then keep the temperature constant for 30-60 minutes after reaching the set temperature, and then cool to 200-250℃ and take out; S4. The material obtained in step S3 is transferred to a microwave device, heated to 400-500℃ at a power of 1.5-2.5kW and maintained for 5-10min, then the microwave power is increased to 10-15KW, heated to 900-1000℃ at a rate of 15-20℃ / min, and the activation time is 15-20min; after natural cooling, the material is demolded to obtain the coal-based artificial stone.

[0008] In step S3 of the present application, the material is cooled to 200-250℃ and then transferred to a microwave device for microwave treatment, which can avoid the generation of cracks in the material due to direct cooling to room temperature and subsequent microwave treatment, which affects the network structure of the geopolymer.

[0009] Principle of the present application: Firstly, grinding to 10-50μm is beneficial to the activation of the geopolymer precursor; then, slightly pre-pressing the material in a hot-pressing pretreated mold is to make the material preliminarily flat and avoid excessive local voids during subsequent hot pressing; gradient hot pressing can help the residual gas to gradually escape from the gap between the material particles, avoiding the formation of bubbles due to the sealing of the gas in the green body, and avoiding the interference of the subsequent reaction with the formation of mullite crystal phase. Slow heating in the first stage can slowly release the gas, promote the preliminary reaction of the alkaline activator with the silicon-aluminum component, and discharge the free water in the material, while forming a preliminary loose skeleton for the green body, laying a foundation for subsequent densification; heating to 600-700℃ in the second stage can avoid excessive decomposition of the geopolymer, and constant temperature maintenance under pressure can promote the further condensation and densification of the geopolymer, ultimately promoting the formation of more active mullite precursor from the aluminum-silicon component. Therefore, the coal-based artificial stone production method of the present application realizes the preliminary densification and uniform distribution of the particles under low temperature and low pressure conditions through the process technology of gradient hot pressing pretreatment, pre-removal of impurities and unstable components, which facilitates the uniform transfer of subsequent microwave irradiation energy, avoids local overheating, and ensures the purity of mullite formation.

[0010] The coal-based artificial stone production method further adopts the process technology of segmented microwave activation treatment after gradient hot pressing pretreatment. The "internal heating" characteristic of microwave can be directed to the aluminum-silicon-oxygen precursor inside the green body, inducing the formation of mullite crystal phase and making the mullite crystal phase grow and shape quickly. After the first stage of hot pressing treatment, the material is quickly transferred to the microwave device at a temperature of 200-250℃, avoiding the generation of cracks in the material due to the temperature difference between the inside and outside, and avoiding the influence of the temperature difference on the activity of the precursor; in the second stage, the microwave power is further increased to ensure uniform heating of the material, and the high-temperature microwave energy drives the mullite precursor to convert into mullite crystal phase; finally, the green body is naturally cooled with the equipment, and slow cooling can avoid the generation of lattice defects in the mullite crystal phase due to thermal shock, ensuring the stability of the crystal phase structure.

[0011] As a preferred embodiment of the present application, the mass ratio of the fly ash, coal gangue, alkaline activator and metakaolin is 40-60:30-50:8-15:5-10.

[0012] As a preferred embodiment of the present application, the alkaline activator is NaOH and Na2SiO3, with a mass ratio of 1:2.5, and the modulus of Na2SiO3 is 2.4.

[0013] As a preferred embodiment of the present application, the rotation speed of the ball milling is 400-600 r / min, the time is 30-60 min, and the screening is 100 meshes.

[0014] As a preferred embodiment of the present application, the pressure of the pre-pressing is 1-2 MPa, and the time is 10-15 s.

[0015] The present application has the following beneficial effects: The present application forms a dense skeleton through the technology of hot-pressing pretreatment and segmented microwave activation, and the microstructure shows a more developed geopolymer matrix, combined with the precise induction of mullite crystal phase generation by microwave activation, so that the compressive strength of the artificial stone reaches 100-120 MPa, which is more than 30% higher than that of traditional geopolymer materials.

[0016] The present application forms a composite structure of geopolymer matrix + mullite crystal phase through the technology of hot-pressing pretreatment and segmented microwave activation, which comprehensively improves the performance of the artificial stone product, greatly improves the compressive strength, bending strength and wear resistance of the artificial stone, and makes it exhibit excellent high-temperature resistance and strong resistance to corrosive media, solving the defects of ordinary geopolymer artificial stone such as softening and cracking at high temperature.

[0017] (3) Microwave activation can improve the activity of the material's volcanic ash, reduce the temperature by 30-40% compared to traditional sintering process, reduce energy consumption by 40%-50%, shorten the total production cycle by 20%-40%, and meet the "green and low-carbon" trend.

[0018] (4) The proportion of coal-based solid waste in the raw material is ≥80%, which is more than 50% higher than that of traditional artificial stone, and meets the requirements of comprehensive utilization of bulk solid waste.

[0019] (5) The use of coal-based solid waste to produce geopolymerization as a cementing material for preparing artificial stone reduces the carbon footprint and reduces carbon dioxide emissions.

[0020] (6) The present application uses segmented microwave activation and gradient hot-pressing to prepare coal-based artificial stone, which achieves the following performance range: compressive strength 100-120 MPa; bending strength 15-20 MPa; dry density 2000-2400 kg / m 3 ; dry shrinkage value ≤0.5 mm / m. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a process flow chart of the preparation of coal-based artificial stone by the segmented microwave activation-gradient hot pressing method of the present application. DETAILED DESCRIPTION

[0022] The technical solutions provided by the present application will be described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present application.

[0023] A method for preparing coal-based artificial stone by the segmented microwave activation-gradient hot pressing method, specifically comprising the following steps: (1) 40 parts by weight of coal gangue with a particle size of ≤5 mm, 50 parts by weight of fly ash (particle size ≤5 mm), 10 parts by weight of an alkaline activator (the mass ratio of NaOH to Na2SiO3 is 1:2.5, and the modulus of Na2SiO3 is 2.4), and 8 parts by weight of metakaolin are mixed. After mixing the raw materials, they are put into a ball mill at a speed of 500 r / min for 45 min of grinding. After grinding, they are passed through a 100-mesh sieve to obtain a mixture with a particle size of 10-40 μm.

[0024] (2) The mixture is placed in a high-temperature-resistant graphite strip mold with a size of 600 mm x 300 mm x 300 mm, and pre-pressed at 2 MPa for 10 s.

[0025] (3) After pre-pressing, the material and the mold are placed together in a hot pressing device for gradient hot pressing pretreatment. In the first stage, the pressure is set to 8 MPa, and the temperature is raised to 380℃ at a rate of 8℃ / min, and kept constant for 18 min. After constant temperature, the pressure is adjusted to 18 MPa in the second stage, and the temperature is raised to 650℃ at a rate of 8℃ / min, and kept constant for 45 min.

[0026] (4) The hot pressing equipment is turned off, and after the material is slowly cooled to 250℃ with the equipment, the material and the mold are quickly transferred together to a microwave device for microwave activation.

[0027] (5) In the first stage, the power of the microwave device is set to 2.0 kW, and the temperature is raised to 450℃ at a rate of 12℃ / min, and kept constant for 8 min. After constant temperature, the power is adjusted to 12 kW in the second stage, and the temperature is raised to 950℃ at a rate of 20℃ / min, and kept constant for 18 min.

[0028] (6) After microwave activation, the instrument is turned off, and the material is naturally cooled to ambient temperature in the mold with the instrument.

[0029] After the material is cooled, it is taken out of the equipment, demolded, polished, and coated with a layer of hydrophobic coating, which is a nano-silicon dioxide coating or a fluorine-containing resin coating. Example 2

[0030] A method for preparing coal-based artificial stone by segmented microwave activation-gradient hot pressing specifically includes the following steps: (1) 50 parts by weight of coal gangue with a particle size ≤ 5 mm, 40 parts by weight of fly ash (particle size ≤ 5 mm), 12 parts by weight of alkaline activator (mass ratio of NaOH to Na2SiO3 is 1:2.5, modulus of Na2SiO3 is 2.4), and 10 parts by weight of metakaolin. After mixing the raw materials, put them into a ball mill at a speed of 600 r / min and crush them for 60 min. After crushing, pass them through a 100 mesh sieve to obtain a mixture with a particle size of 10-35 μm.

[0031] (2) Place the mixture into a high-temperature resistant graphite strip mold with specifications of 600mm×300mm×300mm and pre-press it with 1MPa for 15s.

[0032] (3) After the pre-pressing is completed, the material and the mold are placed together in the hot press device for gradient hot pressing pretreatment. The pressure is set to 10MPa in the first stage, and the temperature is increased to 400℃ at 10℃ / min and held for 20min. After the temperature is held, the pressure is adjusted to 20MPa in the second stage, and the temperature is increased to 700℃ at 10℃ / min and held for 60min.

[0033] Turn off the hot press equipment and wait for the material to cool slowly to 230°C. Then, quickly transfer the material and the mold together to the microwave device for microwave activation.

[0034] In the first stage, the power of the microwave device was set to 2.5kW, and the temperature was increased to 500℃ at a rate of 15℃ / min, and held for 10 minutes. After the temperature was held, in the second stage, the power was adjusted to 15kW, and the temperature was increased to 1000℃ at a rate of 18℃ / min, and held for 20 minutes.

[0035] After microwave activation, the instrument is turned off, and the material is allowed to cool naturally to ambient temperature within the mold.

[0036] After the material cools, it is removed from the equipment, demolded, polished, and coated with a hydrophobic coating, which is either a nano-silica coating or a fluorinated resin coating. Example 3

[0037] A method for preparing coal-based artificial stone by segmented microwave activation-gradient hot pressing specifically includes the following steps: (1) 30 parts by weight of coal gangue with a particle size ≤ 5 mm, 60 parts by weight of fly ash (particle size ≤ 5 mm), 8 parts by weight of alkaline activator (mass ratio of NaOH to Na2SiO3 is 1:2.5, modulus of Na2SiO3 is 2.4), and 5 parts by weight of metakaolin. After mixing the raw materials, put them into a ball mill at a speed of 400 r / min and crush them for 30 min. After crushing, pass them through a 100 mesh sieve to obtain a mixture with a particle size of 10-50 μm.

[0038] (2) Place the mixture into a high-temperature resistant graphite strip mold with specifications of 600mm×300mm×300mm and pre-press it with 1.5MPa for 15s.

[0039] (3) After the pre-pressing is completed, the material and the mold are placed together in the hot press device for gradient hot pressing pretreatment. The pressure is set to 5MPa in the first stage, and the temperature is increased to 350℃ at 5℃ / min and held for 15min. After the temperature is held, the pressure is adjusted to 15MPa in the second stage, and the temperature is increased to 600℃ at 5℃ / min and held for 30min.

[0040] (4) Turn off the hot press equipment and wait for the material to cool slowly to 220°C. Then, quickly transfer the material and the mold to the microwave device for microwave activation.

[0041] (5) In the first stage, the power of the microwave device is set to 1.5kW, and the temperature is increased to 400℃ at 10℃ / min and held for 5min. After the temperature is held, the power is adjusted to 10kW in the second stage, and the temperature is increased to 900℃ at 15℃ / min and held for 15min.

[0042] (6) After microwave activation, turn off the instrument and let the material cool naturally to ambient temperature in the mold.

[0043] (7) After the material is cooled, it is taken out of the equipment, demolded, polished, and coated with a hydrophobic coating. The hydrophobic coating is a nano-silica coating or a fluorinated resin coating.

[0044] Comparative Example 1 A method for preparing coal-based artificial stone by segmented microwave activation-gradient hot pressing specifically includes the following steps: (1) 40 parts by weight of coal gangue with a particle size ≤ 5 mm, 50 parts by weight of fly ash (particle size ≤ 5 mm), 10 parts by weight of alkaline activator (mass ratio of NaOH to Na2SiO3 is 1:2.5, modulus of Na2SiO3 is 2.4) and 8 parts by weight of metakaolin were mixed. After mixing, the raw materials were put into a ball mill at a speed of 500 r / min and rolled for 45 min. After rolling, the mixture was passed through a 100 mesh sieve to obtain a mixture with a particle size of 10-40 μm.

[0045] (2) Place the mixture into a high-temperature resistant graphite strip mold with specifications of 600mm×300mm×300mm and pre-press it with 2MPa for 10s.

[0046] (3) After the pre-pressing is completed, the material and the mold are placed together in the hot press device for hot pressing pretreatment. The pressure is 18MPa, the temperature is increased to 650℃ at 8℃ / min, and the temperature is kept constant for 63min.

[0047] (4) Turn off the hot press equipment and wait for the material to cool slowly to 250°C. Then quickly transfer the material and the mold to the microwave device for microwave activation.

[0048] (5) In the first stage, the power of the microwave device is set to 2.0kW, and the temperature is increased to 450℃ at 12℃ / min and held for 8min. After the temperature is held, the power is adjusted to 12kW in the second stage, and the temperature is increased to 950℃ at 20℃ / min and held for 18min.

[0049] (6) After microwave activation, turn off the instrument and let the material cool naturally to ambient temperature in the mold.

[0050] After the material cools, it is removed from the equipment, demolded, polished, and coated with a hydrophobic coating, which is either a nano-silica coating or a fluorinated resin coating.

[0051] Comparative Example 2 A method for preparing coal-based artificial stone by segmented microwave activation-gradient hot pressing specifically includes the following steps: (1) 40 parts by weight of coal gangue with a particle size ≤ 5 mm, 50 parts by weight of fly ash (particle size ≤ 5 mm), 10 parts by weight of alkaline activator (mass ratio of NaOH to Na2SiO3 is 1:2.5, modulus of Na2SiO3 is 2.4) and 8 parts by weight of metakaolin were mixed. After mixing, the raw materials were put into a ball mill at a speed of 500 r / min and rolled for 45 min. After rolling, the mixture was passed through a 100 mesh sieve to obtain a mixture with a particle size of 10-40 μm.

[0052] (2) Place the mixture into a high-temperature resistant graphite strip mold with specifications of 600mm×300mm×300mm and pre-press it with 2MPa for 10s.

[0053] (3) After the pre-pressing is completed, the material and the mold are placed together in the hot press device for gradient hot pressing pretreatment. The pressure is set to 8MPa in the first stage, and the temperature is increased to 380℃ at 8℃ / min and held for 18min. After the temperature is held, the pressure is adjusted to 18MPa in the second stage, and the temperature is increased to 650℃ at 8℃ / min and held for 45min.

[0054] (4) Turn off the hot press equipment and wait for the material to cool slowly to 250°C. Then quickly transfer the material and the mold to the microwave device for microwave activation.

[0055] (5) The power of the microwave device is set to 12kW, and the temperature is increased to 950℃ at 12℃ / min and held for 36min.

[0056] (6) After microwave activation, turn off the instrument and let the material cool naturally to ambient temperature in the mold.

[0057] After the material cools, it is removed from the equipment, demolded, polished, and coated with a hydrophobic coating, which is either a nano-silica coating or a fluorinated resin coating.

[0058] Comparative Example 3 A method for preparing coal-based artificial stone by segmented microwave activation-gradient hot pressing specifically includes the following steps: (1) 40 parts by weight of coal gangue with a particle size ≤ 5 mm, 50 parts by weight of fly ash (particle size ≤ 5 mm), 10 parts by weight of alkaline activator (mass ratio of NaOH to Na2SiO3 is 1:2.5, modulus of Na2SiO3 is 2.4) and 8 parts by weight of metakaolin were mixed. After mixing, the raw materials were put into a ball mill at a speed of 500 r / min and rolled for 45 min. After rolling, the mixture was passed through a 100 mesh sieve to obtain a mixture with a particle size of 10-40 μm.

[0059] (2) Place the mixture into a high-temperature resistant graphite strip mold with specifications of 600mm×300mm×300mm and pre-press it with 2MPa for 10s.

[0060] (3) After the pre-pressing is completed, the material and the mold are placed together in the hot press device for hot pressing pretreatment. The pressure is 18MPa, the temperature is increased to 650℃ at 8℃ / min, and the temperature is kept constant for 63min.

[0061] (4) Turn off the hot press equipment and wait for the material to cool slowly to 250°C. Then quickly transfer the material and the mold to the microwave device for microwave activation.

[0062] (5) The power of the microwave device is set to 12kW, and the temperature is increased to 950℃ at 12℃ / min and held for 36min.

[0063] (6) After microwave activation, turn off the instrument and let the material cool naturally to ambient temperature in the mold.

[0064] After the material cools, it is removed from the equipment, demolded, polished, and coated with a hydrophobic coating, which is either a nano-silica coating or a fluorinated resin coating.

[0065] After the specimens prepared in Examples 1-3 and Comparative Examples 1-3 were molded, performance tests were conducted according to the requirements of GB / T 9966.1-2020 "Test Methods for Natural Stone": standard cubic specimens of 400mm×200mm×200mm were cut in layers along the central area, dried in an oven to constant weight, and their dry density and compressive strength were measured. The raw material composition and test results of each formulation are detailed in Table 1.

[0066] Table 1. Raw material composition and test results

[0067] This invention discloses a method for preparing coal-based artificial stone using fly ash and coal gangue as main raw materials. Through a synergistic treatment of gradient hot pressing pretreatment and segmented microwave activation, a mullite crystalline phase with excellent properties is formed, thereby optimizing the material's performance. Furthermore, the utilization rate of industrial solid waste exceeds 80%, demonstrating significant environmental and economic benefits. Test results show that the finished artificial stone meets the standard of GB / T 9966.1-2020 "Test Methods for Natural Stone," and its drying shrinkage value is superior to that of ordinary concrete.

[0068] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing coal-based artificial stone using segmented microwave activation-gradient hot pressing, characterized in that: Includes the following steps: S1. Mix fly ash, coal gangue, alkaline activator and metakaolin evenly; S2. The mixture obtained in S1 is ball-milled and sieved to obtain a mixture. S3. Place the mixture into the mold for pre-compression, and then perform hot pressing pretreatment. Adjust the initial pressure to 5-10 MPa. In the first stage, heat the mixture to 350-400℃ at 5-10℃ / min and then keep it at that temperature for 15-20 minutes. The second stage involves heating the temperature to 600-700℃ at a rate of 5-10℃ / min, adjusting the pressure to 15-20MPa, and then maintaining the temperature at a constant temperature for 30-60 minutes. Finally, the temperature is cooled to 200-250℃ and removed. S4. Transfer the material obtained in step S3 into a microwave device, heat it to 400-500°C with a power of 1.5–2.5kW and hold for 5–10 minutes, then increase the microwave power to 10–15kW and heat it to 900-1000°C at a rate of 15–20°C / min for 15–20 minutes; after natural cooling, demold to obtain coal-based artificial stone.

2. The method for preparing coal-based artificial stone using segmented microwave activation-gradient hot pressing according to claim 1, characterized in that: The mass ratio of fly ash, coal gangue, alkaline activator, and metakaolin is 40-60:30-50:8-15:5-10.

3. The method for preparing coal-based artificial stone using segmented microwave activation-gradient hot pressing according to claim 1, characterized in that: The alkaline activator is NaOH and Na2SiO3, with a mass ratio of NaOH to Na2SiO3 of 1:2.5 and a modulus of Na2SiO3 of 2.

4.

4. The method for preparing coal-based artificial stone using segmented microwave activation-gradient hot pressing according to claim 1, characterized in that: The ball milling speed is 400-600 r / min, the time is 30-60 min, and the sieve is 100 mesh.

5. The method for preparing coal-based artificial stone using segmented microwave activation-gradient hot pressing according to claim 1, characterized in that: The pre-compression pressure is 1-2 MPa, and the time is 10-15 s.

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