Lightweight nanometer heat insulation plate and calcium carbide furnace

Abstract

The application relates to a light nano heat insulation plate and a calcium carbide furnace, and relates to the technical field of calcium carbide furnace heat insulation protection. The light nano heat insulation plate is composed of the following components and mass fractions: nano ceramic material, light refractory aggregate, high-temperature binder, anti-cracking fiber and beta-silicon carbide. The nano ceramic material comprises alumina and silicon oxide; the light refractory aggregate comprises alpha-silicon carbide and hollow floating beads; the high-temperature binder comprises aluminum dihydrogen phosphate and silica sol; and the anti-cracking fiber comprises aluminum silicate whiskers and carbon fibers. The preparation method of the light nano heat insulation plate comprises the following steps: dry material preparation, mixed material dispersion, mold pressing, and drying and baking. The light nano heat insulation plate provided in the application has good anti-cracking performance on the basis of ensuring that the light nano heat insulation plate has mechanical strength and high-temperature insulation effect, can meet the high-temperature working condition requirements when applied to the calcium carbide furnace, and can further guarantee stable operation of the equipment.

Description

Technical Field

[0001] This invention relates to the field of heat insulation and protection technology for calcium carbide furnaces, and in particular to a lightweight nano-insulation board and a calcium carbide furnace. Background Technology

[0002] During the operation of high-temperature industrial equipment, heat insulation panels, as key protective components, play a crucial role in blocking high-temperature transmission and protecting the equipment body and internal components. Insulation performance is one of the core requirements for the application of heat insulation panels in high-temperature, energized equipment such as calcium carbide furnaces. As a typical high-temperature, energized reaction device, the calcium carbide furnace maintains a high-temperature radiation level of thousands of degrees Celsius within its furnace cavity for extended periods, and its internal electrodes, contact elements, and other components operate under electrical current. Therefore, the heat insulation panels for calcium carbide furnaces must rely on high-performance insulating materials to effectively block high temperatures while preventing short circuits, circulating water leaks, and other safety accidents caused by the splashing of molten coke particles within the furnace cavity, thus ensuring the long-term stable operation of the equipment.

[0003] In the existing technology, the insulation materials used in the heat insulation protection plates for calcium carbide furnaces have the following problems: some insulation materials have acceptable heat insulation performance, but poor insulation stability. They are prone to performance degradation under long-term high-temperature environments, leading to insulation failure of the protection plate; some materials have a certain insulation strength, but insufficient mechanical strength. They are easily damaged under equipment vibration or external impact, destroying the overall structure of the heat insulation protection plate. This causes the calcium carbide furnace equipment to frequently experience faults such as short circuit breakdown, water leakage and furnace shutdown, which not only seriously affects the continuity of production, but also greatly increases equipment maintenance costs and safety hazards.

[0004] To address the aforementioned issues, Chinese invention patent application CN113981445A, published on January 28, 2022, proposes a protective insulating material suitable for calcium carbide furnaces. This material is prepared from nano-ceramic materials that provide insulation and enhance the mechanical strength of structural materials, sodium silicate (a liquid substance that helps strengthen the structural strength of the nano-ceramic materials and provides high-temperature resistance), and alumina and iron oxide (both with high-temperature resistance). This preparation process improves the curing efficiency of the protective insulating material in the entire mold, thereby avoiding furnace shutdowns and the need to replace protective equipment due to short circuits or water leaks.

[0005] However, the inventors discovered that because the insulating material in the above solution relies solely on sodium silicate as a binder, it is quite brittle after curing and lacks the necessary toughness and stress adjustment capabilities. Under the conditions of high-temperature radiation and temperature cycling in a calcium carbide furnace, the thermal expansion coefficients of the insulating material and the heat insulation substrate are difficult to match. Furthermore, internal stress is easily left behind during the preparation process. The release of internal stress during subsequent use will directly cause the material to crack, thereby damaging the overall structural integrity of the heat insulation board and ultimately causing its heat insulation and insulation functions to fail simultaneously. Summary of the Invention

[0006] To address the problem of cracking in the protective materials of calcium carbide furnaces, which leads to the failure of heat insulation and electrical insulation, this invention provides a lightweight nano-insulation board and a calcium carbide furnace.

[0007] In a first aspect, the present invention provides a lightweight nano-insulation board, which adopts the following technical solution: A lightweight nano-insulation board comprises the following components and parts by weight: 25-35 parts of nano-ceramic material, 40-50 parts of lightweight refractory aggregate, 10-15 parts of high-temperature binder, 5-10 parts of crack-resistant fiber, and 3-8 parts of β-silicon carbide. The nano-ceramic material includes alumina and silicon oxide, wherein the mass ratio of alumina to silicon oxide is 3 to 5:1. The lightweight refractory aggregate comprises α-silicon carbide and hollow cenospheres, wherein the mass ratio of α-silicon carbide to hollow cenospheres is 2 to 3:1; The high-temperature binder includes aluminum dihydrogen phosphate and silica sol, wherein the mass ratio of aluminum dihydrogen phosphate to silica sol is 2 to 3:1. The crack-resistant fiber comprises aluminum silicate whiskers and carbon fibers, with a mass ratio of aluminum silicate whiskers to carbon fibers of 4 to 6:1.

[0008] By adopting the above technical solutions, a three-dimensional interwoven network of aluminum silicate whiskers and carbon fibers in crack-resistant fibers is formed to bridge pores and disperse stress, thereby inhibiting crack initiation and propagation. α-silicon carbide and hollow cenospheres in lightweight refractory aggregates are used to regulate the material's thermal expansion coefficient, while β-silicon carbide refines grains and alleviates high-temperature shrinkage. The composite bonding system of aluminum dihydrogen phosphate and silica sol improves interfacial bonding, reducing the risk of cracking at its source. Nano-ceramic materials and hollow cenospheres construct a continuous and dense inorganic insulating structure, with all components resistant to high temperatures and not decomposing, ensuring stable insulation under high-temperature conditions. In terms of mechanical strength, lightweight refractory aggregates construct a rigid skeleton, nano-ceramic materials fill and densify the structure, β-silicon carbide strengthens the interface, and composite binders and crack-resistant fibers provide synergistic reinforcement, solving the problem of high brittleness in inorganic materials and further ensuring impact resistance during installation and use.

[0009] Overall, while ensuring that the lightweight nano-insulation board has mechanical strength and high-temperature insulation effect, it achieves good crack resistance and meets the working conditions of the calcium carbide furnace.

[0010] Optionally, the lightweight nano-insulation board further includes 0.5 to 1.5 parts of esterified cross-linked modified starch; The preparation method of the esterified cross-linked modified starch is as follows: take 100 parts of starch by mass, add 3-5 parts of sodium trimetaphosphate and 2-4 parts of acetic anhydride in sequence, stir and react for 2-3 hours under the conditions of pH 8-9 and temperature 45-55℃. After the reaction is completed, filter and wash until neutral, then dry at 80-90℃ and sieve to obtain the esterified cross-linked modified starch.

[0011] By adopting the above technical solution, esterified cross-linked modified starch is made hydrophilic and hydrophobic, reducing interparticle friction and improving the flowability and plasticity of the mixture. This allows the material to fully fill the mold during compression molding, reducing pores and stress concentration points. The cross-linked network formed by its molecular chains can act as a flexible bridge inside the material, absorbing external forces and thermal stress, buffering thermal expansion stress at high temperatures, and reducing cracking caused by thermal shock. At the same time, the hydroxyl groups of starch molecules form hydrogen bonds with inorganic components, enhancing the interfacial bonding force between components, preventing component detachment, and slowly decomposing during calcination to form micropores, buffering thermal expansion stress, and ensuring molding quality and crack resistance durability.

[0012] Optionally, the lightweight nano-insulation board further includes 0.8 to 1.2 parts of boron composite glass; the boron composite glass includes 35 to 45 parts of boric acid, 40 to 50 parts of quartz, 10 to 15 parts of alumina, and 5 to 8 parts of zirconium oxide; The boron composite glass is prepared by mixing boric acid, quartz, alumina and zirconium oxide evenly, melting them at 1200-1300℃, then atomizing them under high pressure, and finally sieving them to obtain the boron composite glass.

[0013] By adopting the above technical solution, boron composite glass melts during calcination to form a low-viscosity glass phase, which fills the micropores and inter-component gaps inside the material, achieving high-temperature self-healing and improving the material's density and thermal insulation effect. The glassy cementing layer formed after the molten glass phase cools firmly bonds the inorganic components, and the presence of alumina and zirconium oxide in the glass phase enhances its high-temperature resistance and hardness, preventing a decrease in bonding strength at high temperatures and ensuring the mechanical strength of the insulation board under high-temperature conditions. At the same time, the coefficient of thermal expansion of boron composite glass is between that of nano-ceramic materials and lightweight refractory aggregates, which can act as a buffer phase to coordinate differences in thermal expansion, reduce internal stress caused by uneven thermal expansion and contraction, further reduce the risk of high-temperature cracking, and ensure the structural stability of the material under 1000 degrees Celsius conditions.

[0014] Optionally, the boron composite glass is a modified boron composite glass; the preparation method of the modified boron composite glass is as follows: Add 0.5–1.5 parts of γ-methacryloxypropyltrimethoxysilane to 100 parts of boron composite glass, stir at 200–300 r / min for 15–20 min, dry at 100–120 °C for 2–3 h, and cool to room temperature to obtain modified boron composite glass.

[0015] By adopting the above technical solution, boron composite glass is modified with γ-methacryloxypropyltrimethoxysilane (KH-570). The siloxane groups of the silane coupling agent are chemically bonded to the hydroxyl groups on the surface of the boron composite glass. The organic functional groups interact with the molecular chains of modified starch or the organic groups on the surface of inorganic components to construct an inorganic-organic transition layer, which enhances the interfacial bonding force and avoids the formation of gaps due to glass phase detachment at high temperatures. The modified boron composite glass has enhanced synergistic deformation ability with the matrix, can better buffer thermal stress, inhibit crack initiation and propagation at the interface, and prolong crack resistance. At the same time, the silane modification layer can protect the surface of the boron composite glass, prevent adverse reactions with other components at high temperatures, maintain its densification and bonding strengthening effect, and ensure long-term stability of high-temperature performance.

[0016] Optionally, the nano-ceramic material further includes α-silicon carbide, wherein the mass ratio of α-silicon carbide to alumina and silicon oxide is 0.4–0.9:3–5:1.

[0017] By adopting the above technical solution, α-silicon carbide is introduced into the nano-ceramic material. α-silicon carbide has a higher thermal conductivity than alumina and silicon oxide, improving the internal thermal uniformity of the material, avoiding cracking caused by excessive local thermal stress, and ensuring uniform temperature distribution during calcination, thus improving molding quality. α-silicon carbide has high hardness and forms a nano-ceramic composite phase with alumina and silicon oxide, refining the grains and enhancing the hardness and compressive strength of the nano-ceramic material. At the same time, it forms a homologous synergistic effect with α-silicon carbide in lightweight refractory aggregates, strengthening the bonding force between the skeleton and the filler. Furthermore, the introduction of α-silicon carbide does not change the inorganic insulating nature of the nano-ceramic material, ensuring stable insulation performance at high temperatures.

[0018] Optionally, the aluminum silicate whiskers are modified aluminum silicate whiskers; the method for preparing the modified aluminum silicate whiskers is as follows: Aluminum silicate whiskers are mixed with γ-methacryloxypropyltrimethoxysilane at a mass ratio of 100:0.5-1.5, stirred at 200-300 r / min for 15-20 min, dried at 100-120℃ for 2-3 h, and cooled to room temperature to obtain modified aluminum silicate whiskers.

[0019] By adopting the above technical solution, γ-methacryloxypropyltrimethoxysilane (KH-570) forms a modified layer on the surface of whiskers, realizing the dual effects of inorganic groups and hydroxyl groups on the whisker surface, and organic groups and binder and modified starch functional groups. This enhances the interfacial bonding force, ensures efficient stress transfer to the whiskers, and fully utilizes their anti-cracking function of bridging cracks and absorbing stress. The modified whiskers have better dispersion, thus forming a more uniform three-dimensional network and avoiding local stress concentration caused by agglomeration. At the same time, the silane modified layer can protect the whisker surface, prevent oxidation or adverse reactions during high-temperature calcination, maintain its high aspect ratio and structural integrity, ensure long-term anti-cracking effect under high-temperature conditions, and improve the service life of the material.

[0020] Secondly, the present invention provides a method for preparing the lightweight nano-insulation plate described in the first aspect, employing the following technical solution: A method for preparing a lightweight nano-insulation panel includes the following steps: Dry material preparation: Take nano-ceramic materials, lightweight refractory aggregates and β-silicon carbide according to the mass fraction, mix them evenly, and then process them by air jet milling to a particle size of 100-200 mesh to obtain dry material; Dispersion of the mixture: Add a high-temperature binder to the dry material and stir at 300-500 r / min for 10-15 min until it becomes a paste. Then add the crack-resistant fiber and stir at 200-300 r / min for 16-20 min to obtain the mixture. Compression molding: Pour the mixture into the mold and use a step-by-step compression molding process. First, pre-press at 5-8 MPa for 2-3 minutes, then increase to 15-20 MPa and hold for 5-10 minutes. Drying and calcination: After molding, dry at 110-120℃ for 12-16 hours, then calcin at 800-900℃ for 2-3 hours, and demold after cooling to room temperature to obtain a lightweight nano heat insulation board.

[0021] By adopting the above technical solutions, the dry material is pulverized to 100-200 mesh and mixed evenly through airflow, ensuring that the particle size of each component is matched and the dispersion is uniform, reducing internal defects; the step-by-step mixing process ensures that the high-temperature binder and the dry material are fully integrated to form a paste-like mixture, while avoiding excessive breakage of the crack-resistant fibers and ensuring the construction of the fiber network structure; the step-by-step pressure molding first pre-presses to degas and then high-pressure compacts to reduce residual stress and porosity, and improve density and structural uniformity; drying at 110-120℃ removes moisture and calcining at 800-900℃ promotes the curing of the binder and the stable bonding of the components, allowing functional components such as β-silicon carbide to fully play their role, ensuring the material's mechanical strength, crack resistance and high-temperature stability.

[0022] Optionally, in the dry material preparation step, at least one of esterified cross-linked modified starch, boron composite glass, and modified boron composite glass is added in parts by mass, and mixed evenly with nano-ceramic materials, lightweight refractory aggregates, and β-silicon carbide, and then subjected to air jet milling treatment.

[0023] By adopting the above technical solution, esterified cross-linked modified starch, boron composite glass, modified boron composite glass and base dry materials are mixed together and air-jet pulverized to ensure uniform dispersion of functional components, avoid local concentration imbalance, and give full play to their role in improving formability, enhancing high-temperature stability and optimizing interfacial bonding. The functional components are added in the dry material stage to ensure that they undergo air-jet pulverization, stirring dispersion, molding and calcination processes simultaneously with other components. This ensures that the modified starch plays a molding auxiliary role, and the boron composite glass melts and fills the pores during calcination, avoiding process interruption or component separation caused by subsequent additions, and ensuring the continuity and stability of the preparation process.

[0024] Thirdly, the present invention provides a calcium carbide furnace, which adopts the following technical solution: A calcium carbide furnace includes a furnace body, a furnace opening, and a furnace cover; the furnace body includes furnace iron sheet, a refractory brick layer, and a heat insulation layer, wherein the heat insulation layer is the lightweight nano heat insulation board described in the first aspect, or the lightweight nano heat insulation board prepared by the preparation method described in the second aspect; the lightweight nano heat insulation board is laid between the refractory brick layer and the furnace iron sheet.

[0025] By adopting the above technical solution, lightweight nano-insulation boards are laid between the refractory brick layer and the furnace iron sheet to form a composite protective structure. The refractory bricks block high-temperature radiation, while the insulation boards provide efficient insulation to protect the furnace body. Their insulation properties block current conduction and prevent short-circuit breakdown. The crack resistance of the insulation boards withstands the vibration and temperature fluctuations during the operation of the calcium carbide furnace, and their mechanical strength ensures that they do not fall off or break, maintaining the integrity of the protective structure. At the same time, the lightweight nature of the insulation boards reduces the load on the furnace body, and the efficient insulation and heat insulation reduce equipment aging, prevent water leakage and furnace shutdown, improve the continuity of calcium carbide furnace operation, and reduce maintenance costs.

[0026] In summary, the present invention has at least one of the following beneficial technical effects: 1. By using lightweight refractory aggregates to construct a rigid skeleton and filling it with nano-ceramic materials to achieve densification, mechanical strength and impact resistance are ensured. At the same time, the nano-ceramic materials and hollow cenospheres form a continuous and dense inorganic insulating structure to ensure high-temperature insulation stability. Through the three-dimensional interwoven network of crack-resistant fibers, the thermal expansion regulation of composite aggregates, the refinement of β-silicon carbide grains, and the interface optimization of the composite bonding system, high-efficiency crack resistance is achieved, making it suitable for the harsh working conditions of calcium carbide furnaces.

[0027] 2. By using esterified cross-linked modified starch, the friction between particles is reduced, and the porosity and stress concentration points are decreased; the cross-linked network formed by its molecular chains buffers the thermal expansion stress under high temperature and reduces cracking caused by thermal shock; at the same time, the hydroxyl groups of starch molecules form hydrogen bonds with inorganic components, which enhances the interfacial bonding force between components, prevents component detachment, buffers thermal expansion stress, and ensures molding quality and crack resistance durability.

[0028] 3. By using composite glass, the density and thermal insulation effect of the material are improved, ensuring the structural stability of the material under 1000 degrees Celsius conditions; KH-570 modified boron composite glass is used to improve the interfacial bonding force and prevent the glass phase from falling off and causing gaps at high temperatures; the modified boron composite glass can better buffer thermal stress, inhibit the initiation and propagation of cracks at the interface, and extend the crack resistance durability.

[0029] 4. By using modified aluminum silicate whiskers, the interfacial bonding force is enhanced, ensuring that stress is efficiently transferred to the whiskers and giving full play to their anti-cracking function of bridging cracks and absorbing stress; at the same time, the silane-modified layer can protect the surface of the whiskers, avoid oxidation or adverse reactions during high-temperature calcination, and improve the service life of the material. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the embodiments.

[0031] Unless otherwise specified, the experimental methods used in the embodiments of this application are conventional methods, and the materials used are commercially available unless otherwise specified.

[0032] Example 1: This example discloses a lightweight nano-insulation board and a calcium carbide furnace.

[0033] (1) A lightweight nano-insulation board, the composition of which includes: 25 parts of nano-ceramic material, 50 parts of lightweight refractory aggregate, 10 parts of high-temperature binder, 10 parts of crack-resistant fiber, and 3 parts of β-silicon carbide by mass. The nano-ceramic material includes alumina and silicon oxide, wherein the mass ratio of alumina to silicon oxide is 4:1. The lightweight refractory aggregate comprises α-silicon carbide and hollow cenospheres, wherein the mass ratio of α-silicon carbide to hollow cenospheres is 2.5:1. The high-temperature binder includes aluminum dihydrogen phosphate and silica sol, wherein the mass ratio of aluminum dihydrogen phosphate to silica sol is 2.5:1; The crack-resistant fiber comprises aluminum silicate whiskers and carbon fibers, with a mass ratio of aluminum silicate whiskers to carbon fibers of 5:1.

[0034] (2) The preparation method of the above-mentioned lightweight nano-insulation plate includes the following steps: Dry material preparation: Weigh the nano-ceramic material, lightweight refractory aggregate, and β-silicon carbide according to the mass proportions in the above formula, put them into a three-dimensional mixer and mix for 30 minutes, then send them into an air jet mill for pulverization, and control the output particle size to be 150±50 mesh to obtain dry material; Mixture dispersion: Transfer the dry material into a mixer, add the high-temperature binder, and stir at 400 r / min for 12 min until a uniform paste is formed. Then add the crack-resistant fiber and stir at 250 r / min for 18 min to obtain the mixture, ensuring that the fiber is uniformly dispersed without agglomeration. Compression molding: Pour the mixture into a mold with dimensions of 500mm×500mm×20mm, and use a step-by-step compression molding process. First, pre-press at 6MPa for 2.5min, then increase to 18MPa and hold for 8min to ensure the material is compacted and obtain the blank. Drying and calcining: The shaped blank is placed in a drying oven and dried at 115℃ for 14 hours to remove moisture; then it is transferred to a calcining furnace and heated to 850℃ at a heating rate of 5℃ / min, and calcined at 850℃ for 2.5 hours. After naturally cooling to room temperature, it is demolded to obtain a lightweight nano-insulation board.

[0035] The lightweight nano-insulation board prepared above, with a thickness of 50 mm, is laid between the refractory brick layer and the furnace iron sheet. The joints of the insulation board are sealed with high-temperature sealant, such as silica sol.

[0036] In this embodiment, ① alumina: α-Al₂O₃ crystal form, purity ≥99.5%; ② silicon dioxide: silicon dioxide, purity ≥99.8%; ③ α-silicon carbide: purity ≥98.5%; ④ hollow cenospheres: particle size ≥70±30 mesh; ⑤ aluminum dihydrogen phosphate: viscous liquid, solid content 52.5±2.5%, viscosity 800 mPa·s (25℃); ⑥ silica sol: colloid, solid content 30%, viscosity 15 mPa·s (25℃); ⑦ aluminum silicate whiskers (Al₂O₃·SiO₂): Al₂O₃ 62.5±2.5wt%, SiO₂ 37.5±2.5wt%, aspect ratio 20:1, diameter 1μm, length 20μm; ⑧ carbon fiber: polyacrylonitrile-based carbon fiber (polyacrylonitrile-based T300), diameter 8μm, length 3mm; ⑨ β-silicon carbide: purity ≥99.0%.

[0037] (3) Performance index testing The following indicators were tested on the prepared lightweight nano-insulation board: ① Crack resistance: thermal shock resistance, flexural strength, fracture toughness, and volume stability; ② Insulation performance: volume resistivity; ③ Mechanical strength performance: compressive strength and flexural strength; ④ Thermal insulation performance: thermal conductivity.

[0038] Thermal shock resistance (cycles): Verify the crack resistance of the insulation board under thermal expansion and contraction; the test is conducted in accordance with GB / T 30873-2014 "Test Method for Thermal Shock Resistance of Refractory Materials - Water Quenching Method"; the test method is as follows: prepare a sample with a diameter of φ50mm×50mm, place the sample in a high-temperature furnace and heat it to 1000℃, hold it until it is thermally stable, then quickly remove it and quench it in room temperature water. After cooling to room temperature, observe whether there are cracks or peeling on the sample surface; repeat the above hot and cold cycle operation until visible cracks or peeling appear on the sample, and record the number of cycles, which is the thermal shock resistance index. Flexural strength and fracture toughness (MPa·m) 1 / 2 The value reflects the ability of the insulation board to resist crack initiation and propagation. The higher the value, the better the material's resistance to cracking and brittle fracture. The test is conducted in accordance with GB / T 3002-2017 "Test Method for Bending Strength of Refractory Materials". The test method is as follows: Prepare a single-sided notched beam specimen of 25mm×25mm×125mm with a notch depth of 12.5mm. The test is conducted on a material testing machine using the three-point bending method with a loading speed of 0.5mm / min. Record the maximum load when the specimen breaks and calculate the fracture toughness value. Volumetric stability (%): Reflects the dimensional stability of the insulation board under high-temperature use, expressed as linear shrinkage rate (-), with a negative sign indicating shrinkage. The smaller the value, the smaller the dimensional change of the material at high temperatures, the better the high-temperature stability, and the less likely it is to crack due to internal stress caused by thermal expansion and contraction. The test is conducted in accordance with GB / T 5988-2020 "Test Method for Volumetric Stability of Refractory Materials". The test method is as follows: Prepare a 100mm×100mm×100mm sample and measure the reference dimensions of the length, width, and height of the sample at room temperature; place the sample in a high-temperature furnace and heat it to 1000℃ at a rate of 5℃ / min, hold it at that temperature for 3 hours, and then cool it to room temperature with the furnace. Measure the corresponding dimensions of the sample again. Volume resistivity (Ω·m): Reflects the material's ability to impede current conduction and verifies the insulation stability of the insulation board. The higher the value, the better the insulation performance. The test is conducted in accordance with GB / T 20623-2006 "Test Method for Conductivity of Refractory Materials". The test method is as follows: Prepare a sheet sample with a diameter of 50 mm and a thickness of 5 mm. Place the sample in a high-temperature insulation test furnace, heat it to 1000℃ and hold it until thermally stable. Use a high-temperature resistant electrode to connect the sample to a high-resistivity meter to measure and calculate the volume resistivity. Compressive strength (MPa): Reflects the ability of the insulation board to resist compressive loads, providing basic mechanical support for crack resistance; the test is conducted in accordance with GB / T 3001-2017 "Test Method for High Temperature Compressive Strength of Refractory Materials"; the test method is as follows: prepare a cubic specimen of 40mm×40mm×40mm, put the specimen into a high temperature compressive strength test furnace, heat it to 1000℃ and hold it for 30min, and perform a pressure test at a loading rate of 2.0MPa / s, and calculate the compressive strength; Flexural strength (MPa): Reflects the bending stress of the insulation board in the furnace body and verifies its ability to resist bending deformation and cracking; the test is conducted in accordance with GB / T 3002-2017 "Test Method for Bending Strength of Refractory Materials"; the test method is as follows: prepare strip specimens of 25mm×25mm×125mm, put the specimens into a high-temperature bending test furnace, heat to 1000℃ and hold for 30min, with a loading speed of 0.5mm / min, and calculate the high-temperature residual flexural strength; Thermal conductivity (W / (m·K)): Verifies the insulation capacity of the insulation board; the lower the value, the better the insulation effect. The test is conducted in accordance with GB / T 10295-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Insulation Materials by Heat Flow Meter Method". The test method is as follows: Prepare a sheet sample with a diameter of 50 mm and a thickness of 5 mm. Using the heat flow meter method, place the sample in a high-temperature thermal conductivity test furnace, set the hot surface temperature to 1000℃ and the cold surface temperature to room temperature, establish a steady-state heat conduction system, measure the heat flux density and temperature gradient, and calculate the thermal conductivity.

[0039] Example 2: This example discloses a lightweight nano-insulation board and a calcium carbide furnace.

[0040] A lightweight nano-insulation board comprises the following components by weight: 35 parts of nano-ceramic material, 40 parts of lightweight refractory aggregate, 15 parts of high-temperature binder, 5 parts of crack-resistant fiber, and 8 parts of β-silicon carbide. The nano-ceramic material includes alumina and silicon oxide, wherein the mass ratio of alumina to silicon oxide is 4:1. The lightweight refractory aggregate comprises α-silicon carbide and hollow cenospheres, wherein the mass ratio of α-silicon carbide to hollow cenospheres is 2.5:1. The high-temperature binder includes aluminum dihydrogen phosphate and silica sol, wherein the mass ratio of aluminum dihydrogen phosphate to silica sol is 2.5:1; The crack-resistant fiber comprises aluminum silicate whiskers and carbon fibers, with a mass ratio of aluminum silicate whiskers to carbon fibers of 5:1; otherwise, it is the same as in Example 1.

[0041] Example 3: This example discloses a lightweight nano-insulation board and a calcium carbide furnace.

[0042] A lightweight nano-insulation board comprises the following components by weight: 30 parts nano-ceramic material, 45 parts lightweight refractory aggregate, 12.5 parts high-temperature binder, 7.5 parts crack-resistant fiber, and 5.5 parts β-silicon carbide. The nano-ceramic material includes alumina and silicon oxide, wherein the mass ratio of alumina to silicon oxide is 4:1. The lightweight refractory aggregate comprises α-silicon carbide and hollow cenospheres, wherein the mass ratio of α-silicon carbide to hollow cenospheres is 2.5:1. The high-temperature binder includes aluminum dihydrogen phosphate and silica sol, wherein the mass ratio of aluminum dihydrogen phosphate to silica sol is 2.5:1; The crack-resistant fiber comprises aluminum silicate whiskers and carbon fibers, with a mass ratio of aluminum silicate whiskers to carbon fibers of 5:1; otherwise, it is the same as in Example 1.

[0043] The test results of Examples 1-3 are shown in Table 1: Table 1: Test Results of Examples 1-3 Thermal shock resistance (secondary) 39 40 38 <![CDATA[Flexural strength fracture toughness (MPa·m 1 / 2 )]]> 4.12 4.38 4.22 Volume stability (%) -0.21 -0.25 -0.22 Volume resistivity (Ω·m) <![CDATA[1.8×10 12 ]]> <![CDATA[2.0×10 12 ]]> <![CDATA[1.9×10 12 ]]> Compressive strength (MPa) 42.2 40.1 41.6 Flexural strength (MPa) 9.3 8.9 9.2 Thermal conductivity (W / (m·K)) 0.082 0.083 0.080 Based on the test data from Examples 1-3, it can be seen that the addition of lightweight refractory aggregate and crack-resistant fiber in Example 1 is relatively high, resulting in better flexural strength, compressive strength, and volume stability. Example 2 increases the addition ratio of nano-ceramic materials, high-temperature binders, and β-silicon carbide, thus exhibiting the best performance in flexural strength, fracture toughness, and volume resistivity. The proportions of each component in Example 3 are between those of Examples 1 and 2, resulting in a more balanced formulation, the lowest thermal conductivity, and the best thermal insulation effect. Overall, the performance of all three examples meets the application requirements.

[0044] Example 4: This example discloses a lightweight nano-insulation board and a calcium carbide furnace.

[0045] In this embodiment, the lightweight nano-insulation board also includes 1.0 part of esterified cross-linked modified starch; A lightweight nano-insulation board comprises the following components by weight: 30 parts of nano-ceramic material, 45 parts of lightweight refractory aggregate, 12.5 parts of high-temperature binder, 7.5 parts of crack-resistant fiber, 5.5 parts of β-silicon carbide, and 1.0 part of esterified cross-linked modified starch. The preparation method of esterified cross-linked modified starch is as follows: Weigh 100 parts of starch by mass, add deionized water to prepare starch milk with a mass fraction of 30%, add 4 parts of sodium trimetaphosphate and 3 parts of acetic anhydride in sequence, adjust the pH to 8.5 with 5wt% sodium hydroxide solution, place in a water bath at 50℃ and stir for 2.5h. After the reaction is completed, filter and collect the precipitate, wash with water 3 times until neutral, dry in an oven at 85℃ for 6h, pulverize and pass through a 200-mesh sieve to obtain esterified cross-linked modified starch; Among them, ① Starch: Industrial grade corn starch, starch content ≥98%, gelatinization temperature 65±3℃; ② Sodium trimetaphosphate: Sodium trimetaphosphate content ≥90%, phosphorus pentoxide content ≥68%; ③ Acetic anhydride: Content ≥98%; In the preparation method of lightweight nano-insulation board, in the dry material preparation step, esterified cross-linked modified starch is added according to the mass fraction, and mixed evenly with nano-ceramic materials, lightweight refractory aggregates and β-silicon carbide, and then subjected to air jet milling treatment. Everything else is the same as in Example 3.

[0046] Example 5: This example discloses a lightweight nano-insulation board and a calcium carbide furnace.

[0047] In this embodiment, the lightweight nano-insulation board further includes 1.0 part of boron composite glass; the boron composite glass includes 40 parts of boric acid, 45 parts of quartz, 12 parts of alumina, and 6 parts of zirconium oxide; A lightweight nano-insulation board comprises the following components by weight: 30 parts of nano-ceramic material, 45 parts of lightweight refractory aggregate, 12.5 parts of high-temperature binder, 7.5 parts of crack-resistant fiber, 5.5 parts of β-silicon carbide, 1.0 part of esterified cross-linked modified starch, and 1.0 part of boron composite glass. The preparation method of the boron composite glass is as follows: weigh boric acid, quartz, alumina, and zirconium oxide according to the mass fraction, put them into a ball mill, use alumina balls as the grinding medium, the ball-to-material ratio is 5:1, grind at 200 r / min for 2 hours, mix evenly, melt at 1250℃ for 3 hours, and stir once every 30 minutes during the process to ensure uniform melting; after melting, pour the melt into a high-pressure atomization device, atomize it with 0.8 MPa compressed air to make powder, collect the powder and pass it through a 300-mesh sieve, the material under the sieve is the boron composite glass; Among them, ① boric acid: purity ≥99.5%, powder, moisture content ≤0.5%; ② quartz: amorphous quartz powder or low crystallinity quartz powder can be selected. In this embodiment, amorphous quartz powder is selected, with purity ≥99.0% and particle size 200±100 mesh; ③ alumina: γ-Al2O3, purity ≥99.0% and particle size 250±50 mesh; ④ zirconium oxide: monoclinic zirconium oxide (m-ZrO2) or tetragonal zirconium oxide (t-ZrO2) can be selected. In this embodiment, m-ZrO2 is selected, with purity ≥99.0% and particle size 250±50 mesh. In the preparation method of lightweight nano-insulation board, in the dry material preparation step, boron composite glass is added according to the mass fraction, and mixed evenly with nano-ceramic materials, lightweight refractory aggregates, β-silicon carbide and esterified cross-linked modified starch, and then subjected to airflow pulverization treatment. Everything else is the same as in Example 4.

[0048] Example 6: This example discloses a lightweight nano-insulation board and a calcium carbide furnace.

[0049] In this embodiment, the lightweight nano-insulation board also includes 1.0 part of modified boron composite glass; A lightweight nano-insulation board comprises the following components by weight: 30 parts of nano-ceramic material, 45 parts of lightweight refractory aggregate, 12.5 parts of high-temperature binder, 7.5 parts of crack-resistant fiber, 5.5 parts of β-silicon carbide, 1.0 part of esterified cross-linked modified starch, and 1.0 part of modified boron composite glass. The modified boron composite glass is prepared as follows: boron composite glass is prepared according to the method in Example 5. 1.0 part of γ-methacryloyloxypropyltrimethoxysilane (KH-570) is added to 100 parts of boron composite glass, stirred at 250 r / min for 18 min, dried in an oven at 110℃ for 2.5 h, cooled to room temperature, pulverized and passed through a 200-mesh sieve. The material passing through the sieve is the modified boron composite glass. In the preparation method of lightweight nano-insulation board, in the dry material preparation step, modified boron composite glass is added according to the mass fraction, and mixed evenly with nano-ceramic materials, lightweight refractory aggregates, β-silicon carbide and esterified cross-linked modified starch, and then subjected to airflow pulverization treatment. Among them, ①KH-570: purity ≥98.0%; Everything else is the same as in Example 5.

[0050] The test results of Examples 4-6 are shown in Table 2: Table 2: Test Results of Examples 4-6 Thermal shock resistance (secondary) 42 44 47 <![CDATA[Flexural strength fracture toughness (MPa·m 1 / 2 )]]> 4.78 5.12 5.42 Volume stability (%) -0.19 -0.17 -0.15 Volume resistivity (Ω·m) <![CDATA[2.1×10 12 ]]> <![CDATA[2.2×10 12 ]]> <![CDATA[2.3×10 12 <!-- 8 -->]]> Compressive strength (MPa) 43.5 48.3 51.8 Flexural strength (MPa) 9.4 9.6 9.9 Thermal conductivity (W / (m·K)) 0.079 0.078 0.077 By comparing Example 4 with Example 3, it can be seen that Example 4, based on Example 3, added esterified cross-linked modified starch. Compared with Example 3, all properties were significantly optimized. The reason is that esterified cross-linked modified starch has good dispersibility and molding effect, which effectively improves the uniformity of dry material mixing, reduces agglomeration defects and pores inside the green body, and forms a trace carbon skeleton during high-temperature drying and calcination, which strengthens the bonding force between particles, increases the density of the material, and thus simultaneously optimizes the mechanical properties, crack resistance, insulation properties and thermal insulation properties of the material.

[0051] By comparing Example 5 with Example 4, it can be seen that Example 5 adds boron composite glass to the basis of Example 4, and the performance is continuously improved. During the firing process, boron composite glass forms a low melting point glass phase, which can fill the tiny pores inside the material, strengthen the particle interface bonding, and improve the high-temperature sintering density of the material. At the same time, the oxide components in boron composite glass can also enhance the heat radiation shielding effect, reduce heat conduction, and further optimize the thermal insulation performance and high-temperature stability of the material.

[0052] By comparing Example 6 with Example 5, it can be seen that the modified boron composite glass used in Example 6 has optimized performance indicators compared to Example 5. After the boron composite glass is modified by KH-570 silane coupling agent, the interfacial compatibility between the boron composite glass and inorganic matrices such as nano-ceramic materials and lightweight refractory aggregates can be improved, reducing interfacial defects, making stress transmission more uniform, effectively inhibiting the initiation and propagation of cracks, and further improving the density and high-temperature stability of the material, thus achieving a steady improvement in performance.

[0053] Example 7: This example discloses a lightweight nano-insulation board and a calcium carbide furnace.

[0054] In this embodiment, the nano-ceramic material comprises α-silicon carbide, alumina, and silicon oxide, wherein the mass ratio of α-silicon carbide, alumina, and silicon oxide is 0.6:4:1. During the preparation of the lightweight nano-insulation board, the mass fraction of nano-ceramic materials remains constant. Everything else is the same as in Example 6.

[0055] Example 8: This example discloses a lightweight nano-insulation board and a calcium carbide furnace.

[0056] In this embodiment, the aluminum silicate whiskers are modified aluminum silicate whiskers; the preparation method of the modified aluminum silicate whiskers is as follows: Take 100 parts of aluminum silicate whiskers, add 1.2 parts of γ-methacryloxypropyltrimethoxysilane and mix. Stir at 250 r / min for 18 min, then dry in an oven at 110 ℃ for 2.5 h and cool to room temperature to obtain modified aluminum silicate whiskers. In the preparation of lightweight nano-insulation board, the mass fraction of crack-resistant fiber remains unchanged, only the aluminum silicate whiskers are replaced by modified aluminum silicate whiskers in the composition; Everything else is the same as in Example 7.

[0057] The test results of Examples 7-8 are shown in Table 3: Table 3: Test Results of Examples 7-8 Thermal shock resistance (secondary) 49 52 <![CDATA[Flexural strength fracture toughness (MPa·m 1 / 2 )]]> 5.56 5.82 Volume stability (%) -0.13 -0.10 Volume resistivity (Ω·m) <![CDATA[2.5×10 12 ]]> <![CDATA[2.6×10 12 ]]> Compressive strength (MPa) 53.5 56.8 Flexural strength (MPa) 10.3 10.8 Thermal conductivity (W / (m·K)) 0.076 0.075 By comparing Example 7 with Example 6, it can be seen that Example 7 changed the composition of the nano-ceramic material by adding α-silicon carbide, which improved the overall performance. This is because α-silicon carbide has excellent high-temperature strength, thermal stability and heat radiation shielding ability. When combined with alumina and silicon oxide to form a multiphase ceramic, it can improve the high-temperature performance of the nano-ceramic material, reduce high-temperature burn-off and volume shrinkage, and thus improve the overall mechanical properties, crack resistance, insulation properties and thermal insulation properties of the material.

[0058] By comparing Example 8 with Example 7, it can be seen that Example 8 uses modified aluminum silicate whiskers, and its performance is the best compared with the previous examples. The surface activity of the KH-570 modified aluminum silicate whiskers is improved, and the bonding with the matrix material is tighter, thereby giving full play to the toughening and crack-resistant effect of the fibers, inhibiting the initiation and propagation of cracks, improving the thermal shock resistance and fracture toughness of the material, and further improving the internal pore structure of the material, reducing heat conduction, and achieving the improvement of thermal insulation performance and mechanical properties.

[0059] Comparative Example 1: This comparative example discloses a lightweight nano-insulation board and a calcium carbide furnace.

[0060] In this comparative example, the lightweight nano-insulation board does not contain crack-resistant fibers. A lightweight nano-insulation board comprises the following components by weight: 30 parts of nano-ceramic material, 45 parts of lightweight refractory aggregate, 12.5 parts of high-temperature binder, and 5.5 parts of β-silicon carbide. No crack-resistant fibers are added during the preparation of the lightweight nano-insulation board; Everything else is the same as in Example 3.

[0061] Comparative Example 2: This comparative example discloses a lightweight nano-insulation board and a calcium carbide furnace.

[0062] In this comparative example, the lightweight nano-insulation panel does not contain β-silicon carbide. A lightweight nano-insulation board comprises the following components by weight: 30 parts nano-ceramic material, 45 parts lightweight refractory aggregate, 12.5 parts high-temperature binder, and 7.5 parts crack-resistant fiber. No β-silicon carbide is added during the preparation of the lightweight nano-insulation board; Everything else is the same as in Example 3.

[0063] Comparative Example 3: This comparative example discloses a lightweight nano-insulation board and a calcium carbide furnace.

[0064] In this comparative example, the lightweight nano-insulation board does not contain lightweight refractory aggregates. A lightweight nano-insulation board comprises the following components by weight: 30 parts nano-ceramic material, 12.5 parts high-temperature binder, 7.5 parts crack-resistant fiber, and 5.5 parts β-silicon carbide; No lightweight refractory aggregates are added during the preparation of the lightweight nano-insulation board; Everything else is the same as in Example 3.

[0065] The test results of comparative examples 1-3 are shown in Table 4: Table 4: Test Results of Comparative Examples 1-3 Thermal shock resistance (secondary) 12 22 25 <![CDATA[Flexural strength fracture toughness (MPa·m 1 / 2 )]]> 1.21 3.18 2.12 Volume stability (%) -0.45 -0.36 -0.46 Volume resistivity (Ω·m) <![CDATA[0.9×10 12 ]]> <![CDATA[1.4×10 12 ]]> <![CDATA[1.1×10 12 ]]> Compressive strength (MPa) 20.3 28.6 24.1 Flexural strength (MPa) 5.6 6.9 7.2 Thermal conductivity (W / (m·K)) 0.087 0.093 0.110 By comparing Comparative Example 1 and Example 3, it can be seen that Comparative Example 1, without the addition of crack-resistant fibers, showed a deterioration in all properties compared to Example 3. Crack-resistant fibers (alumina silicate whiskers and carbon fibers) are the main components for crack resistance and toughening of the material. Without them, the material lacks the crack-resistant and toughening effect of fibers, making it prone to cracking under high-temperature conditions and causing rapid crack propagation. This leads to a significant decrease in the material's thermal shock resistance, fracture toughness, and mechanical strength. At the same time, the internal pore structure is destroyed, and the insulation and thermal insulation properties also deteriorate.

[0066] By comparing Comparative Example 2 and Example 3, it can be seen that Comparative Example 2, without the addition of β-silicon carbide, suffers from performance degradation. β-silicon carbide has excellent high-temperature strength, thermal stability, and heat radiation shielding ability. Its addition can strengthen the internal structure of the material, improve high-temperature stability and mechanical properties, reduce heat radiation conduction, and optimize thermal insulation performance. Without it, the high-temperature structural stability of the material decreases, the interface bonding weakens, cracks are more likely to occur, and the heat radiation shielding effect is weakened, resulting in varying degrees of degradation in all properties.

[0067] By comparing Comparative Example 3 and Example 3, it can be seen that Comparative Example 3, which did not add lightweight refractory aggregate, showed a more significant deterioration in overall performance compared to Example 3. Lightweight refractory aggregate (α-silicon carbide and hollow cenospheres) is an important component that reflects the material's lightweight, heat insulation, and high-temperature stability. Its absence increases the material's density, destroys its internal pore structure, and reduces its heat insulation performance. At the same time, the material's high-temperature strength and structural stability decrease, and its volume shrinkage increases, resulting in deterioration in thermal shock resistance, mechanical properties, and insulation performance, which fails to meet the requirements for use in insulation boards for calcium carbide furnaces.

[0068] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A lightweight nano-insulation board, characterized in that, The composition and mass fractions include: 25-35 parts of nano-ceramic material, 40-50 parts of lightweight refractory aggregate, 10-15 parts of high-temperature binder, 5-10 parts of crack-resistant fiber, and 3-8 parts of β-silicon carbide. The nano-ceramic material includes alumina and silicon oxide, wherein the mass ratio of alumina to silicon oxide is 3 to 5:

1. The lightweight refractory aggregate comprises α-silicon carbide and hollow cenospheres, wherein the mass ratio of α-silicon carbide to hollow cenospheres is 2 to 3:1; The high-temperature binder includes aluminum dihydrogen phosphate and silica sol, wherein the mass ratio of aluminum dihydrogen phosphate to silica sol is 2 to 3:

1. The crack-resistant fiber comprises aluminum silicate whiskers and carbon fibers, with a mass ratio of aluminum silicate whiskers to carbon fibers of 4 to 6:

1.

2. The lightweight nano-insulation board according to claim 1, characterized in that, It also includes 0.5 to 1.5 parts of esterified cross-linked modified starch; The preparation method of the esterified cross-linked modified starch is as follows: take 100 parts of starch by mass, add 3-5 parts of sodium trimetaphosphate and 2-4 parts of acetic anhydride in sequence, stir and react for 2-3 hours under the conditions of pH 8-9 and temperature 45-55℃. After the reaction is completed, filter and wash until neutral, then dry at 80-90℃ and sieve to obtain the esterified cross-linked modified starch.

3. The lightweight nano-insulation board according to claim 1, characterized in that, It also includes 0.8 to 1.2 parts of boron composite glass; the boron composite glass includes 35 to 45 parts of boric acid, 40 to 50 parts of quartz, 10 to 15 parts of alumina, and 5 to 8 parts of zirconium oxide; The boron composite glass is prepared by mixing boric acid, quartz, alumina and zirconium oxide evenly, melting them at 1200-1300℃, then atomizing them under high pressure, and finally sieving them to obtain the boron composite glass.

4. The lightweight nano-insulation board according to claim 3, characterized in that, The boron composite glass is a modified boron composite glass; the preparation method of the modified boron composite glass is as follows: Add 0.5–1.5 parts of γ-methacryloxypropyltrimethoxysilane to 100 parts of boron composite glass, stir at 200–300 r / min for 15–20 min, dry at 100–120 °C for 2–3 h, and cool to room temperature to obtain modified boron composite glass.

5. The lightweight nano-insulation board according to claim 1, characterized in that, The nano-ceramic material further includes α-silicon carbide, wherein the mass ratio of α-silicon carbide to alumina and silicon oxide is 0.4–0.9:3–5:

1.

6. The lightweight nano-insulation board according to any one of claims 1-5, characterized in that, The aluminum silicate whiskers are modified aluminum silicate whiskers; the preparation method of the modified aluminum silicate whiskers is as follows: Aluminum silicate whiskers are mixed with γ-methacryloxypropyltrimethoxysilane at a mass ratio of 100:0.5-1.5, stirred at 200-300 r / min for 15-20 min, dried at 100-120℃ for 2-3 h, and cooled to room temperature to obtain modified aluminum silicate whiskers.

7. A method for preparing a lightweight nano-insulation panel according to any one of claims 1-6, characterized in that, Includes the following steps: Dry material preparation: Take nano-ceramic materials, lightweight refractory aggregates and β-silicon carbide according to the mass fraction, mix them evenly, and then process them by air jet milling to a particle size of 100-200 mesh to obtain dry material; Dispersion of the mixture: Add a high-temperature binder to the dry material and stir at 300-500 r / min for 10-15 min until it becomes a paste. Then add the crack-resistant fiber and stir at 200-300 r / min for 16-20 min to obtain the mixture. Compression molding: Pour the mixture into the mold and use a step-by-step compression molding process. First, pre-press at 5-8 MPa for 2-3 minutes, then increase to 15-20 MPa and hold for 5-10 minutes. Drying and calcination: After molding, dry at 110-120℃ for 12-16 hours, then calcin at 800-900℃ for 2-3 hours, and demold after cooling to room temperature to obtain a lightweight nano heat insulation board.

8. The method for preparing the lightweight nano-insulation plate according to claim 7, characterized in that, In the dry material preparation step, at least one of esterified cross-linked modified starch, boron composite glass, and modified boron composite glass is added in parts by mass. After being mixed evenly with nano-ceramic materials, lightweight refractory aggregates, and β-silicon carbide, the mixture is then subjected to air jet milling.

9. A calcium carbide furnace, comprising a furnace body, a furnace opening, and a furnace cover; characterized in that, The furnace body includes furnace iron sheet, refractory brick layer and heat insulation layer, wherein the heat insulation layer is the lightweight nano heat insulation board as described in any one of claims 1-6, or the lightweight nano heat insulation board prepared by the preparation method described in claim 7 or 8; the lightweight nano heat insulation board is laid between the refractory brick layer and the furnace iron sheet.