A high-temperature-resistant fiber insulation block and a preparation method and application thereof

Abstract

The application relates to the technical field of high-temperature refractory materials, in particular to a high-temperature-resistant fiber heat-insulating block and a preparation method thereof. The heat-insulating block is prepared by mixing polycrystalline mullite fibers, aluminum oxide fibers, hematite powder, vanadium-iron slag, zirconium oxide micropowder and a specific binder system, forming, drying and high-temperature reaction sintering in a protective atmosphere. The heat-insulating block of the application solves the technical problems of large brittleness, poor thermal shock resistance and insufficient long-term structural stability at 1250-1350 DEG C of traditional fiber materials by generating a high-melting-point cermet phase (such as FeSi) in situ during sintering, and simultaneously endows the material with higher toughness and heat resistance.

Description

Technical Field

[0001] This application relates to the field of high-temperature refractory materials technology, and more specifically, it relates to a high-temperature resistant fiber insulation block and its preparation method. Background Technology

[0002] Thermal insulation materials are used in high-temperature industrial equipment such as electromagnetic heating furnaces, resistance heating furnaces, and various fuel heating furnaces. Currently, the main thermal insulation material is aluminum silicate fiber blocks. However, as the application requirements for thermal insulation materials become increasingly stringent, they can no longer meet the application requirements in the high-temperature range of 1250-1350℃, which seriously affects the normal operation of the equipment and shortens its lifespan.

[0003] When aluminum silicate fiber modules in related technologies are exposed to the following problems for extended periods within the critical high-temperature range of 1250-1350℃:

[0004] 1) Insufficient thermal stability, specifically manifested as excessive shrinkage of the heating wire (usually >3.5%), leading to changes in structural dimensions and sealing failure;

[0005] 2) It has weak resistance to wind erosion and is easily pulverized and peeled off under the scouring of high-speed airflow or flames;

[0006] 3) Poor chemical stability, especially when facing most acid and base chemicals other than hydrofluoric acid, phosphoric acid, and concentrated alkali, its structure is easily corroded and its performance deteriorates sharply.

[0007] Therefore, some literature reports attempts to improve refractoriness by increasing alumina content or introducing zircon sand. However, these solutions often suffer from mismatched material systems or improper process control, failing to simultaneously achieve high-temperature structural stability, erosion resistance, and chemical stability. During long-term thermal cycling, they still face problems such as fiber crystallization, weakened interfacial bonding, and thermal stress cracking. Therefore, this paper presents a high-temperature resistant fiber insulation block that can systematically solve the above problems, along with its preparation method and applications. Summary of the Invention

[0008] To address the shortcomings of the existing technology, this application provides a high-temperature resistant fiber insulation block, its preparation method, and its application. Through unique material formulation design and optimized preparation process, this insulation block can be used stably for a long time at high temperatures of 1250-1350℃, and has low heating shrinkage, high resistance to wind speed erosion, and excellent chemical stability.

[0009] In the first aspect, this application provides a high-temperature resistant fiber insulation block, which adopts the following technical solution:

[0010] A high-temperature resistant fiber insulation block is prepared by sintering a mixture of matrix raw materials and binder. The weight percentages of the components in the raw materials are as follows:

[0011] Matrix materials: 20-40wt% polycrystalline mullite fiber, 8-12wt% alumina fiber, 8-12wt% hematite powder, 4-8wt% vanadium iron slag, 2-6wt% zirconium oxide;

[0012] Binder: 6-10 wt% yttrium silica sol, 5-8 wt% aluminum dihydrogen phosphate, 3-5 wt% high-purity silica micro powder, with deionized water as the balance.

[0013] Preferably, the polycrystalline mullite fiber has an Al2O3 content ≥72%, a SiO2 content ≥27%, and a fiber length of 5-20 mm.

[0014] Preferably, the alumina fiber has an Al2O3 content of ≥80% and a fiber diameter of 3-10μm.

[0015] Preferably, the hematite powder contains ≥68% Fe2O3 and has a particle size range of 800-1250 mesh.

[0016] Preferably, the vanadium-iron slag has a V2O5 content of 10-15% and a particle size range of 800-1250 mesh.

[0017] Preferably, the zirconium oxide micropowder has a particle size of 1-3 μm and is partially yttrium-stabilized zirconium oxide.

[0018] Preferably, the molar ratio of Y2O3 to SiO2 in the yttrium silica sol is 1:2 to 1:4, the solid content of the composite oxide is ≥25%, and the particle size is 10-30 nm.

[0019] Preferably, the high-purity silica micro powder has a particle size of 0.1-0.5 μm and a SiO2 content of ≥99%.

[0020] Secondly, this application provides a method for preparing a high-temperature resistant fiber insulation block, which adopts the following technical solution:

[0021] A method for preparing a high-temperature resistant fiber insulation block includes the following steps:

[0022] a) Weigh out the polycrystalline mullite fiber, alumina fiber, hematite powder, vanadium iron slag, and zirconium oxide powder according to the corresponding proportions, and dry mix them evenly;

[0023] b) Then mix yttrium silica sol, aluminum dihydrogen phosphate, high-purity silica micro powder and deionized water to prepare a binder solution;

[0024] c) Mix the dry mixture from step a) with the binder solution from step b) and stir to form a uniform slurry;

[0025] d) The slurry is injected into the mold, and after vacuum filtration, dehydration, and shaping, it is demolded;

[0026] e) Dry the shaped preform at 100-120℃ for 2-4 hours;

[0027] f) Place the dried blank in a sintering furnace, introduce nitrogen or argon into the furnace as a protective atmosphere, and then raise the temperature to 1350-1450℃ at a rate of 3-5℃ / min, and sinter at this temperature for 2-6 hours. After sintering, cool the blank to room temperature with the furnace to obtain the high-temperature resistant fiber insulation block.

[0028] Thirdly, this application provides a high-temperature resistant fiber insulation block for use as an insulation material in electromagnetic heating furnaces, resistance heating furnaces or fuel heating furnaces, which is suitable for long-term use in high-temperature environments of 1250℃-1350℃.

[0029] In summary, this application has the following beneficial effects:

[0030] 1) The rare earth-reinforced metal ceramic iron-rich high-temperature resistant fiber insulation block in this application achieves the synergistic effect of grain boundary stabilization and strengthening, crack bridging and toughening and high-temperature deformation suppression through the ternary synergistic strengthening mechanism of rare earth silicate intercrystalline phase, metal ceramic toughening phase and high-purity fiber skeleton, thereby ensuring its structural stability, thermal shock resistance and mechanical strength in long-term high temperature environment of 1250-1350℃.

[0031] 2) The insulation block prepared by the method in this application benefits from the rare earth silicate intercrystalline phase, the metal ceramic tough phase and the high-purity fiber skeleton and the precise control of the process. The resulting product has a dense and uniform microstructure, stable and reliable performance, and has both extremely low high-temperature creep and long-term durability. Moreover, the consistency of each production batch is good, and the industrial application value and market prospects are extremely significant.

[0032] 3) The insulation block in this application, compared with traditional aluminum silicate fiber blocks or improved materials using conventional silica sol, can effectively meet the harsh application requirements of equipment such as electromagnetic heating furnaces and high-temperature industrial kilns under extreme temperature and severe thermal cycling conditions. Its excellent comprehensive high-temperature performance, ultra-long service life and wide adaptability to complex environments are significantly better than traditional solutions, providing key material support for improving the reliability of high-end high-temperature equipment and reducing the cost of the entire life cycle. Detailed Implementation

[0033] The following detailed description of this application is based on the embodiments. Except for some specifications that are explicitly limited, the raw materials used in this application are all commercially available common materials.

[0034] Performance testing

[0035] The insulation blocks prepared in each embodiment and comparative example were selected as test objects, and their heating linear shrinkage rate, room temperature compressive strength, thermal conductivity, wind speed erosion resistance and chemical stability were tested respectively. The specific test methods and reference standards are as follows:

[0036] 1) Heating line shrinkage rate: Refer to GB / T 17911-2006, measured after heat preservation at 1500℃ for 24h. This is an accelerated aging test, so the application environment is higher than 1250–1350℃.

[0037] 2) Room temperature compressive strength: Tested according to GB / T 5072-2008 standard;

[0038] 3) Thermal conductivity: Tested at 1000℃ according to GB / T 10297-2015 standard;

[0039] 4) Resistance to wind speed erosion: A high-speed airflow jet device was used to continuously impact the sample surface with a wind speed of 50 m / s for 1 hour, and the surface damage was observed.

[0040] 5) Chemical stability: The obtained heating block samples were immersed in 10% HCl and 10% NaOH solutions for 24 hours respectively, and the mass loss rate was measured.

[0041] Examples 1-5

[0042] A high-temperature resistant fiber insulation block is prepared by sintering a mixture of matrix raw materials and binder. Table 1 shows the components and their corresponding weights (g) of the raw materials per 100g:

[0043] Table 1: Detailed list of components in Examples 1-5

[0044]

[0045] And it was prepared by the following method:

[0046] a) First, weigh out the polycrystalline mullite fiber, alumina fiber, hematite powder, vanadium iron slag, and zirconium oxide powder according to the corresponding proportions in the table above, and dry mix them evenly.

[0047] The polycrystalline mullite fiber has an Al2O3 content of ≥72%, a SiO2 content of ≥27%, and an average fiber length of 10mm.

[0048] The alumina fiber has an Al2O3 content of ≥80% and an average fiber diameter of 5μm;

[0049] The hematite powder contains ≥68% Fe2O3 and has an average particle size of 1000 mesh.

[0050] The vanadium-iron slag contains 10% V2O5 and has an average particle size of 1000 mesh.

[0051] The average particle size of the zirconia micro powder is 2 μm, and the proportion of yttrium-stabilized zirconia is 30%.

[0052] b) Then, according to the corresponding proportions in the table above, mix yttrium silica sol, aluminum dihydrogen phosphate, high-purity silica micro powder and deionized water to prepare a binder solution;

[0053] The molar ratio of Y₂O₃ to SiO₂ in yttrium silica sol is 1:2;

[0054] Its composite oxide solid content is ≥25%, the average particle size of the colloidal particles is 20nm, the average particle size of the high-purity silica micro powder is 0.2μm, and the SiO2 content is ≥99%;

[0055] c) Mix the dry mix from step a) with the binder solution from step b) and stir to form a uniform slurry;

[0056] d) The slurry is injected into the mold, and after vacuum filtration, dehydration, and shaping, it is demolded;

[0057] e) Dry the shaped preform at 120°C for 3 hours;

[0058] f) Place the dried blank in a sintering furnace, introduce nitrogen or argon into the furnace as a protective atmosphere, and then heat it to 1380°C at a rate of 4°C / min, and sinter it at this temperature for 4 hours. After sintering, cool it to room temperature with the furnace to obtain the high-temperature resistant fiber insulation block.

[0059] Comparative Example 1

[0060] A fiber insulation block, which differs from Example 1 in that it is replaced by an equal amount of commercially available aluminosilicate fiber blocks, wherein the aluminosilicate fiber blocks contain 45% Al2O3.

[0061] Comparative Example 2

[0062] A fiber insulation block differs from Example 1 in that hematite powder and vanadium slag are not added to the matrix raw materials, and the missing weight is replaced by an equal amount of polycrystalline mullite fiber.

[0063] Comparative Example 3

[0064] A fiber insulation block differs from Example 1 in that no zirconium oxide micropowder is added to the matrix raw material, and the missing weight is replaced by an equal amount of polycrystalline mullite fiber.

[0065] Comparative Example 4

[0066] A fiber insulation block differs from Example 1 in that vanadium-iron slag is not added to the matrix raw material, and the missing weight is replaced by an equal amount of kaolin.

[0067] Comparative Example 5

[0068] A fiber insulation block differs from Example 1 in that the yttrium silica sol in the binder is replaced by an equal amount of silica sol, wherein the silica sol has a SiO2 content of approximately 30% and a pH value of 9-10.

[0069] The high-temperature resistant fiber insulation blocks prepared in Examples 1-5 and Comparative Examples 1-5 were selected as test objects, and their heating linear shrinkage rate, room temperature compressive strength, thermal conductivity, wind speed erosion resistance and chemical stability were tested respectively. The test results are recorded in Table 2.

[0070] Table 2: Performance test results of Examples 1-5 and Comparative Examples 1-5

[0071]

[0072] As can be seen from the table above, the high-temperature resistant fiber insulation blocks prepared in Examples 1-5 all exhibit excellent high-temperature structural stability, thermal shock resistance, and chemical stability, making them suitable for high-temperature industrial environments of 1250-1350℃. In contrast, the performance of Comparative Examples 1-5 is significantly deteriorated, as detailed below:

[0073] As can be seen from the heating line shrinkage rates of Examples 1-5, the overall heating line shrinkage rate is ≤1.7%, and that of Examples 2, 4, and 5 is even ≤1.3%, which is much smaller than that of Comparative Examples 1-5 (2.5-4.5%). This indicates that the insulation block of this application has stable structural dimensions at high temperatures.

[0074] The reason for this is that the high-temperature skeleton formed by polycrystalline mullite fibers and alumina fibers, as well as the rare earth silicate intercrystalline phase and metal ceramic phase (such as FeSi) formed during the sintering process of the yttrium silica sol and aluminum dihydrogen phosphate binder system, effectively inhibit grain boundary migration and volume shrinkage.

[0075] As can be seen from the room temperature compressive strength of Examples 1-5, the overall compressive strength is in the range of 1.1-1.6 MPa, which is higher than that of Comparative Examples 1-5 (0.6-1.0 MPa), especially Examples 4 and 5. The reason for this is that the increased proportion of yttrium silica sol and aluminum dihydrogen phosphate in the binder further strengthens the grain boundary bonding and the toughness of the metal-ceramic phase, resulting in improved strength.

[0076] As can be seen from the thermal conductivity of Examples 1-5, the overall thermal conductivity is 0.18-0.21 W / m·K, which is lower than that of Comparative Examples 1-5 (0.22-0.30 W / m·K). The reason for this is that the uniform distribution of the fiber network and the thermal uniformity of the metal-ceramic phase reduce the heat flow path and improve the thermal insulation performance.

[0077] As can be seen from the wind speed erosion resistance of Examples 1-5, Examples 1, 2, 4, and 5 performed "intact", Example 3 showed "slight wear", while Comparative Examples 1-5 all showed varying degrees of damage (such as peeling and cracking). The reason for this is that the metal-ceramic phase generated in situ from hematite powder and vanadium iron slag enhanced the toughness and interfacial bonding of the material, resisting the erosion of high-speed airflow.

[0078] The chemical stability of Examples 1-5 shows that the overall mass loss rate in acid and alkaline solutions is less than 1.5%, while that in Comparative Examples 1-5 is as high as 1.5-7.8%. The reason for this is that the rare earth silicate phase formed by yttrium silica sol has excellent corrosion resistance, and the high-purity silica micropowder fills the micropores, reducing the chemical erosion path.

[0079] Further analysis of the performance defects in Comparative Examples 1-5 leads to the following conclusions:

[0080] Comparative Example 1 (commercially available aluminosilicate fiber): All properties were poor, with a heating wire shrinkage rate as high as 4.5%, a compressive strength of only 0.6 MPa, and low chemical stability. This is because traditional aluminosilicate fibers have a low alumina content (45%), lacking high-temperature stability and a metal-ceramic toughening mechanism.

[0081] Comparative Example 2 (without hematite powder and vanadium-iron slag): The heating shrinkage rate (3.2%) and compressive strength (0.8 MPa) were both poor, and edge cracking occurred in the resistance to wind erosion. This is because the lack of iron-rich components prevents the in-situ formation of the metal-ceramic phase, resulting in insufficient toughness and thermal stress concentration.

[0082] Comparative Example 3 (without zirconia): The heating shrinkage (2.8%) and compressive strength (0.9 MPa) were improved but still inferior to the Example, and the wind speed erosion resistance showed significant wear. This is because the phase transformation toughening effect of zirconia was missing, and the propagation of microcracks was not effectively suppressed.

[0083] Comparative Example 4 (vanadium-free iron slag, replaced by kaolin): Performance was similar to Comparative Example 2, with a heating shrinkage rate of 2.9%, compressive strength of 0.7 MPa, and poor chemical stability (HCl: 3.5%, NaOH: 4.1%). This is because kaolin introduces impurity phases, disrupting the formation of the cermet, and the strengthening effect of vanadium is lost.

[0084] Comparative Example 5 (Ordinary silica sol instead of yttrium silica sol): The heating wire shrinkage (2.5%) and compressive strength (1.0 MPa) were better than the other comparative examples, but still not as good as the examples. The reason is that ordinary silica sol lacks Y2O3, which prevents the formation of rare earth silicate intercrystalline phases, resulting in insufficient grain boundary stability.

[0085] In summary, the superior performance of the insulation block in this application stems from the combination of rigidity and flexibility and multi-scale synergistic toughening, specifically reflected in the following aspects:

[0086] 1) Metal ceramic toughening phase: FeSi and other metal ceramic phases are generated in situ by reacting hematite powder and vanadium iron slag with silicon micro powder during sintering. These phases act as "steel bars" to provide macroscopic toughness and thermal stress buffer.

[0087] 2) Rare earth silicate intercrystalline phases: Y2O3 in yttrium silica sol forms rare earth silicates with SiO2, which strengthens grain boundaries and inhibits high-temperature creep and crack propagation;

[0088] 3) Fiber skeleton and zirconia toughening: Polycrystalline mullite fibers and alumina fibers form a three-dimensional network, which, combined with the phase transformation toughening of zirconia, absorbs energy at the micro-nano scale and prevents brittle fracture.

[0089] 4) Optimization of binder system: Aluminum dihydrogen phosphate and high-purity silica micro powder form an AlPO4 glass phase at low temperature, which promotes densification and improves the interfacial bonding strength;

[0090] In Examples 4 and 5, the grain boundary stability and compactness were further enhanced by increasing the proportion of binder, thus achieving optimal performance.

[0091] In summary, the insulation block of this application systematically solves the problems of structural stability, corrosion resistance and chemical stability of traditional materials at high temperatures through material system design and process control, making it suitable for harsh high-temperature industrial environments.

[0092] Examples 6-10

[0093] A high-temperature resistant fiber insulation block, prepared by sintering a mixture of matrix raw materials and binder, differs from Example 1 in that the specifications of its components are different, as detailed in Table 3:

[0094] Table 3: Specifications of each component in Examples 6-10

[0095]

[0096] The high-temperature resistant fiber insulation blocks prepared in Examples 6-10 above were selected as test objects, and their heating linear shrinkage rate, room temperature compressive strength, thermal conductivity, wind speed erosion resistance and chemical stability were tested respectively. The test results are recorded in Table 4.

[0097] Table 4: Performance Test Results of Examples 6-10

[0098]

[0099] As can be seen from the table above, the high-temperature resistant fiber insulation blocks prepared in Examples 6-10 exhibit excellent performance in all aspects, outperforming Comparative Examples 1-5 overall, and comparable to those in Examples 1-5, with only slight fluctuations in a few indicators due to adjustments in raw material specifications. Specific analysis is as follows:

[0100] In Example 6, due to the increase in fiber length to 20 mm, the heating wire shrinkage rate was comparable to that of Example 1 (1.5%), and the compressive strength was slightly increased to 1.3 MPa, indicating that the longer fiber helps to strengthen the skeleton support; the thermal conductivity increased slightly to 0.21 W / m·K, which may be related to the looser fiber arrangement.

[0101] In Example 7, due to the finer particle size of hematite and vanadium slag, the heating shrinkage rate was slightly reduced to 1.4%, while the compressive strength remained at 1.2 MPa, indicating that fine particles are beneficial for sintering densification; the wind speed erosion resistance and chemical stability remained "intact" and the loss rate was low.

[0102] In Example 8, due to the finer zirconium particle size and increased yttrium stability, the heating shrinkage rate increased slightly to 1.6%, but the compressive strength increased to 1.4 MPa, indicating that fine-grained zirconium oxide is more likely to participate in grain boundary strengthening; the wind speed erosion resistance was "slight wear", which may be related to local stress concentration.

[0103] Example 9 shows that the Y2O3:SiO2 molar ratio in the yttrium silica sol was adjusted to 1:4, and its performance was basically the same as that in Example 6. This indicates that within a specific ratio range, yttrium silica sol can still effectively form a stable rare earth silicate intercrystalline phase and maintain its original performance.

[0104] In Example 10, due to the finer particle size, the heating linear shrinkage rate decreased slightly to 1.4%, and the thermal conductivity increased slightly to 0.21 W / m·K, indicating that the finer particles had a better filling effect, but may slightly affect the heat conduction path.

[0105] In summary, despite adjustments to the specifications of each component (such as fiber length, powder particle size, and sol-gel molar ratio), the overall performance of the resulting insulation block remains excellent, with a heating linear shrinkage rate ≤1.6%, room temperature compressive strength ≥1.2MPa, thermal conductivity ≤0.21 W / m·K, and wind speed erosion resistance essentially "intact," while the chemical stability loss rate is all below 1.5%.

[0106] This demonstrates that the material system described in this application has good process adaptability and stability, and can still ensure the reliability and consistency of product performance even when the raw material specifications fluctuate slightly, further supporting the rationality and feasibility of the scope described in the claims.

[0107] It should also be noted that the processing conditions of the high-temperature resistant fiber insulation block in this application are only based on the typical example listed in Example 1. Within the preferred range, those skilled in the art can adjust the operating temperature and other conditions according to actual operation, and the changes in various performances can be expected, so they will not be elaborated further.

[0108] The above are all modifications that can be made to this embodiment without contributing any inventive step, or solutions that clearly constitute technical teaching, after reading this specification. However, as long as they are within the scope of the claims of this application, they should be protected by patent law.

Claims

1. A high-temperature resistant fiber insulation block, characterized in that, It is prepared by sintering a mixture of matrix raw materials and binder. The weight percentages of each component in the raw materials are as follows: Matrix materials: 20-40wt% polycrystalline mullite fiber, 8-12wt% alumina fiber, 8-12wt% hematite powder, 4-8wt% vanadium iron slag, 2-6wt% zirconium oxide; Binder: 6-10 wt% yttrium silica sol, 5-8 wt% aluminum dihydrogen phosphate, 3-5 wt% high-purity silica micro powder, with deionized water as the balance.

2. The high-temperature resistant fiber insulation block according to claim 1, characterized in that, The polycrystalline mullite fiber has an Al2O3 content ≥72%, a SiO2 content ≥27%, and a fiber length of 5-20 mm.

3. The high-temperature resistant fiber insulation block according to claim 1, characterized in that, The alumina fiber has an Al2O3 content of ≥80% and a fiber diameter of 3-10μm.

4. The high-temperature resistant fiber insulation block according to claim 1, characterized in that, The hematite powder contains ≥68% Fe2O3 and has a particle size range of 800-1250 mesh.

5. The high-temperature resistant fiber insulation block according to claim 1, characterized in that, The vanadium-iron slag contains 10-15% V2O5 and has a particle size range of 800-1250 mesh.

6. The high-temperature resistant fiber insulation block according to claim 1, characterized in that, The zirconium oxide has a particle size of 1-3 μm and is partially yttrium-stabilized zirconium oxide.

7. The high-temperature resistant fiber insulation block according to claim 1, characterized in that, The molar ratio of Y2O3 to SiO2 in the yttrium silica sol is 1:2 to 1:4, the solid content of the composite oxide is ≥25%, and the particle size is 10-30nm.

8. The high-temperature resistant fiber insulation block according to claim 1, characterized in that, The high-purity silica micro powder has a particle size of 0.1-0.5μm and a SiO2 content of ≥99%.

9. A method for preparing the high-temperature resistant fiber insulation block according to any one of claims 1-8, characterized in that, Includes the following steps: a) Weigh out the polycrystalline mullite fiber, alumina fiber, hematite powder, vanadium iron slag, and zirconium oxide according to the corresponding proportions, and dry mix them evenly; b) Then mix yttrium silica sol, aluminum dihydrogen phosphate, high-purity silica micro powder and deionized water to prepare a binder solution; c) Mix the dry mixture from step a) with the binder solution from step b) and stir to form a uniform slurry; d) The slurry is injected into the mold, and after vacuum filtration, dehydration, and shaping, it is demolded; e) Dry the shaped preform at 100-120℃ for 2-4 hours; f) Place the dried blank in a sintering furnace, introduce nitrogen or argon into the furnace as a protective atmosphere, and then raise the temperature to 1350-1450℃ at a rate of 3-5℃ / min, and sinter at this temperature for 2-6 hours. After sintering, cool the blank to room temperature with the furnace to obtain the high-temperature resistant fiber insulation block.

10. The application of the high-temperature resistant fiber insulation block according to any one of claims 1-8 as an insulation material in an electromagnetic heating furnace, a resistance heating furnace, or a fuel heating furnace, characterized in that, It is suitable for long-term use in high-temperature environments of 1250℃-1350℃.

Images