Method for preparing heat-insulating ceramic tile by using aluminum oxide fiberboard waste

Abstract

The invention provides a heat-insulating ceramic tile prepared from aluminum oxide fiberboard waste. The heat-insulating ceramic tile is prepared from the following raw materials in parts by weight: 40-60 parts of modified aluminum oxide fiberboard waste, 15-25 parts of clay, 10-20 parts of expanded perlite, 5-15 parts of boehmite, 5-10 parts of hollow glass beads, 3-8 parts of a sintering aid, 1-3 parts of a plasticizer and 5-10 parts of water, the modified aluminum oxide fiberboard waste is waste aluminum oxide fiberboard broken particles treated by silica sol, and the particle size is 0.5-2 mm; the modified alumina fiberboard waste comprises the following chemical components: 82-84% of Al2O3, 14-17% of SiO2 and 1-3% of ignition loss. The preparation method disclosed by the invention is low in cost, feasible in process and environment-friendly, recycling of the waste aluminum oxide fiberboard is realized, and the prepared heat-insulating ceramic tile has the characteristics of low heat conductivity coefficient, high mechanical strength, good high-temperature resistance and the like, and can be widely applied to the fields of heat-insulating liners of industrial kilns and the like.

Description

Technical Field

[0001] This invention belongs to the field of solid waste recycling and ceramic materials technology, specifically relating to a method for preparing thermal insulation ceramic bricks using alumina fiberboard waste. Background Technology

[0002] Alumina fiberboard, as a high-performance refractory and thermal insulation material, is widely used in the linings of high-temperature kilns in industries such as metallurgy, petrochemicals, and ceramics due to its high temperature resistance, low thermal conductivity, and good chemical stability. However, these fiberboards generate a large amount of solid waste when they reach the end of their service life or during equipment maintenance and replacement. Currently, the main methods for disposing of these waste alumina fiberboards are stockpiling or landfilling. This not only occupies a large amount of land resources, but also, because the fiber material is difficult to degrade naturally, it results in a significant waste of resources and potential environmental risks.

[0003] On the other hand, with the increasing demands for energy conservation in high-temperature resistant ceramic bricks, the market demand for high-performance thermal insulation refractory ceramics is growing. Traditional thermal insulation ceramic bricks are mostly prepared using processes such as adding pore-forming agents, foaming, or gel casting. Although they have a certain thermal insulation effect, they often suffer from problems such as insufficient strength, limited thermal insulation performance, or high cost. For example, some lightweight alumina bricks produced from pure raw materials have excellent performance, but the high cost of raw materials limits their large-scale application.

[0004] In recent years, some studies have attempted to utilize various waste materials to prepare refractory materials, but research on the preparation of high-performance insulating bricks from waste alumina fiberboard for high added value is still insufficient. Current technologies typically use simply crushed waste refractory materials as aggregate, failing to fully utilize their microstructure and performance advantages. Waste alumina fiberboard itself possesses a rich three-dimensional network structure and inherent high-temperature resistance. If it can be used as one of the main raw materials, and its porous insulating structure can be preserved or reconstructed through reasonable formula design and process control, it is possible to "turn waste into treasure" and produce high-value insulating products. Therefore, developing a highly efficient resource utilization technology for waste alumina fiberboard is not only of great environmental significance, but can also bring significant economic benefits. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing heat-insulating ceramic bricks using waste alumina fiberboard. This method is low-cost, feasible, and environmentally friendly, realizing the recycling of waste alumina fiberboard. Moreover, the heat-insulating ceramic bricks prepared have the characteristics of low thermal conductivity, high mechanical strength, and good high-temperature resistance, and can be widely used in the field of heat insulation lining of industrial kilns.

[0006] This invention is achieved through the following technical solution: A thermal insulation ceramic brick prepared from alumina fiberboard waste comprises the following raw materials in parts by weight: 40-60 parts modified alumina fiberboard waste, 15-25 parts clay, 10-20 parts expanded perlite, 5-15 parts boehmite, 5-10 parts hollow glass microspheres, 3-8 parts sintering aid, 1-3 parts plasticizer, and 5-10 parts water. The modified alumina fiberboard waste is composed of crushed particles of waste alumina fiberboard treated with silica sol, with a particle size of 0.5-2 mm. The modified alumina fiberboard waste has the following chemical composition: Al2O3 82-84%, SiO2 14-17%, and loss on ignition 1-3%.

[0007] Furthermore, the raw materials for the thermal insulation ceramic bricks also include wear-resistant reinforcing agents.

[0008] Furthermore, the mass ratio of wear-resistant reinforcing agent to modified alumina fiberboard waste is 1:18-20.

[0009] Specifically, the wear-resistant reinforcing agent is selected from silicon carbide micro powder.

[0010] Furthermore, the sintering aid is selected from at least one of silica powder and p-alumina.

[0011] Furthermore, the plasticizer is selected from at least one of polyethylene glycol and carboxymethyl cellulose.

[0012] A method for preparing thermally insulating ceramic bricks using alumina fiberboard waste as described above includes the following steps: a) Weigh each raw material according to the above-mentioned weight proportions and pre-treat it; b) Dry mix the modified alumina fiberboard waste from the above raw materials with clay, then add boehmite, expanded perlite, hollow glass microspheres and sintering aid in sequence and continue dry mixing. Finally, dissolve the plasticizer in water to make an aqueous solution and add it to the dry mixture for wet mixing to obtain the billet. c) The blank is subjected to a binding process, and then filled into a mold and pressed to form a brick blank; d) The brick blanks are dried in sections to reduce the moisture content to less than 3%, and then sintered using a stepped heating curve and cooled in the furnace to obtain insulating ceramic bricks.

[0013] Furthermore, the pretreatment includes crushing and heat-treating the waste alumina fiberboard, immersing it in a silica sol aqueous solution, removing it, drying and curing it to obtain modified alumina fiberboard waste.

[0014] Furthermore, the heat treatment temperature is 400-600℃, and the time is 0.5-2h; And / or, the soaking time is 10-30 min; And / or, the curing temperature is 100-150℃.

[0015] Furthermore, the concentration of the silica sol aqueous solution is 5-15%.

[0016] Specifically, the waste alumina fiberboard is first crushed and heated at 400-600℃ for 0.5-2 hours to remove any organic wetting agents or impurities that may be attached to the surface. Then, it is immersed in a 5-15% silica sol aqueous solution for 10-30 minutes, removed, and dried and cured at 100-150℃. This process can form a nano-coating rich in active SiO2 on the fiber surface.

[0017] Furthermore, the pretreatment includes drying, pulverizing, and passing the clay, expanded perlite, boehmite, hollow glass microspheres, and sintering aids through a 200-mesh sieve for later use. Further, the preparation method of the silica sol aqueous solution is as follows: Tetraethyl orthosilicate, ethanol and water are mixed in a mass ratio of 2-10:1-9:1-9, hydrochloric acid is added to adjust the pH to 1-3, and the mixture is magnetically stirred for 2 hours to obtain a silica sol aqueous solution with a concentration of 5-15%.

[0018] Specifically, the silica sol-modified alumina fiberboard particles exhibit high surface activity, enabling them to more effectively react with the active alumina (γ-Al2O3) produced by the decomposition of boehmite (γ-AlOOH) during sintering, forming a strong "rivet"-like connection at the fiber-matrix interface. The three-dimensional network structure of the modified alumina fibers also interweaves and composites with the open voids of expanded perlite and the closed voids of hollow glass microspheres, constructing a multi-level composite thermal insulation structure of "fiber skeleton - microporous matrix - closed-cell filler," thus optimizing thermal and mechanical properties. Clay acts as a binder and plasticizer, ensuring the molding performance of the green body.

[0019] Furthermore, in step b), the total dry mixing time is not less than 25 minutes; the wet mixing time is 20 minutes.

[0020] Further, in step c), the conditions for the material treatment are: room temperature and relative humidity ≥85%; And / or, the pressing pressure is 20-30 MPa, and the holding time is 30-60 s.

[0021] Specifically, the billet is left to stand in a room temperature and high humidity environment for 18-36 hours to ensure uniform moisture distribution and improve the plasticity of the billet.

[0022] Further, in step d), the segmented drying is as follows: first drying at 40-50℃ for 12-15 hours, then raising the temperature to 80-110℃ for drying, so that the moisture content is less than 3%; The sintering conditions for the stepped heating curve are as follows: First stage: from room temperature to 600℃, with a heating rate of 1-3℃ / min; Second stage: 600℃ to 1600-1800℃, heating rate is 2-5℃ / min, holding time is 2-4h; Third stage: Cool to 600℃ at a rate of 3-5℃ / min.

[0023] The beneficial effects of this invention are: 1. This invention uses waste alumina fiberboard as the main raw material to prepare heat-insulating ceramic bricks, realizing a high-value-added recycling model for waste refractory materials, consuming a large amount of solid waste, reducing production costs, and reducing the environmental pressure caused by the mining of natural raw materials and the disposal of waste.

[0024] 2. This invention solves the industry problem of weak interfacial bonding between waste and new matrix by surface modification of alumina fiberboard waste. By introducing components such as boehmite, hollow glass microspheres and expanded perlite, a multi-level composite thermal insulation structure is constructed with waste alumina fibers. The thermal conductivity of the prepared thermal insulation ceramic brick can be as low as 0.20-0.25 W / (m·K), and the compressive strength can reach 20-28 MPa. The performance indicators are superior to many traditional thermal insulation bricks.

[0025] 3. The proprietary process flow of this invention effectively controls product shrinkage and ensures the stability of product performance; the equipment used are all conventional ceramic or refractory material production equipment, which are easy to upgrade and promote on existing production lines and have good industrialization prospects.

[0026] 4. The thermal insulation ceramic bricks of the present invention can be used not only as low-temperature thermal insulation bricks, but also as thermal insulation linings for industrial high-temperature kilns, with a wide range of applications. Attached Figure Description

[0027] Figure 1 Design drawing for the use of insulating ceramic bricks made from alumina fiberboard waste in high-temperature sintering furnaces; Figure 2 This is a process flow diagram for preparing the thermal insulation ceramic bricks of the present invention; Figure 3 Comparison of the thermal insulation effects of the thermal insulation ceramic bricks prepared in this invention and thermal insulation bricks from other manufacturers when used in the structure of high-temperature sintering furnace doors.

[0028] In the picture, 1 is a thermal insulation ceramic tile; 2 is a heat-insulating brick. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1 Waste alumina fiberboard was crushed, heat-treated at 550℃ for 1 hour, immersed in a 12% silica sol aqueous solution for 20 minutes, removed, and dried and cured in an oven at 120℃ to obtain modified alumina fiberboard waste.

[0031] By weight: 55 parts modified alumina fiberboard waste, 18 parts clay, 15 parts expanded perlite, 12 parts boehmite, 8 parts hollow glass microspheres, 6 parts silicon micropowder, 3 parts silicon carbide micropowder, 2 parts polyethylene glycol, and 10 parts water. Modified alumina fiberboard waste was dry-mixed with clay for 10 minutes, then boehmite, expanded perlite, hollow glass microspheres, silica powder, and silicon carbide powder were added, and the mixture was dry-mixed for another 15 minutes. Finally, polyethylene glycol was dissolved in water to make an aqueous solution, which was added to the dry mixture and wet-mixed for 20 minutes to obtain a blank. The blank was then left to stand for 28 hours at room temperature and relative humidity ≥85%, and then filled into a mold and pressed into shape at a pressure of 28 MPa to obtain a brick blank. The brick blank was dried in stages: first, it was slowly dried at 50℃ for 15 hours, and then the temperature was raised to 105℃ to be thoroughly dried until the moisture content was <2.5%. The dried brick blank was then placed in a kiln for step-by-step sintering: from room temperature to 600℃ at a heating rate of 2℃ / min; from 600℃ to 1700℃ at a heating rate of 3℃ / min, with a holding time of 3 hours; and finally, it was cooled to 600℃ at a rate of 4℃ / min and then cooled with the furnace to obtain an insulating ceramic brick.

[0032] Example 2 Waste alumina fiberboard was crushed, heat-treated at 550℃ for 1 hour, immersed in a 12% silica sol aqueous solution for 20 minutes, removed, and dried and cured in a 120℃ oven to obtain modified alumina fiberboard waste for later use.

[0033] By weight: 50 parts modified alumina fiberboard waste, 18 parts clay, 12 parts expanded perlite, 12 parts boehmite, 6 parts hollow glass microspheres, 6 parts p-alumina, 1.5 parts carboxymethyl cellulose, and 5 parts water. Modified alumina fiberboard waste was dry-mixed with clay for 10 minutes, then boehmite, expanded perlite, hollow glass microspheres, and p-alumina were added, and dry-mixed for another 15 minutes. Finally, carboxymethyl cellulose was dissolved in water to make an aqueous solution, which was added to the dry mixture and wet-mixed for 20 minutes to obtain a blank. The blank was then left to stand for 28 hours in an environment with a relative humidity of ≥85%, and then filled into a mold and pressed into shape at a pressing pressure of 28 MPa to obtain a brick blank. The brick blank was dried in stages: first, it was slowly dried at 50℃ for 15 hours, and then the temperature was raised to 105℃ to be thoroughly dried until the moisture content was <2.5%. The dried brick blank was then placed in a kiln for step-by-step heating curve sintering: from room temperature to 600℃ at a heating rate of 2℃ / min; from 600℃ to 1680℃ at a heating rate of 3℃ / min, with a holding time of 3 hours; and finally, it was cooled to 600℃ at a rate of 4℃ / min and then cooled with the furnace to obtain an insulating ceramic brick.

[0034] Example 3 Waste alumina fiberboard was crushed, heat-treated at 550℃ for 1 hour, immersed in a 12% silica sol aqueous solution for 20 minutes, removed, and dried and cured in a 120℃ oven to obtain modified alumina fiberboard waste for later use.

[0035] By weight: 45 parts modified alumina fiberboard waste, 22 parts clay, 18 parts expanded perlite, 8 parts boehmite, 9 parts hollow glass microspheres, 4 parts silica powder, 2.5 parts polyethylene glycol, and 5 parts water. Modified alumina fiberboard waste was dry-mixed with clay for 10 minutes, then boehmite, expanded perlite, hollow glass microspheres, and p-alumina were added, and dry-mixed for another 15 minutes. Finally, polyethylene glycol was dissolved in water to make an aqueous solution, which was added to the dry mixture and wet-mixed for 20 minutes to obtain a blank. The blank was then left to stand for 28 hours in an environment with a relative humidity of ≥85%, and then filled into a mold and pressed into shape at a pressure of 28 MPa to obtain a brick blank. The brick blank was dried in stages: first, it was slowly dried at 50℃ for 15 hours, and then the temperature was raised to 105℃ to be thoroughly dried until the moisture content was <2.5%. The dried brick blank was then placed in a kiln for step-by-step sintering: from room temperature to 600℃ at a heating rate of 2℃ / min; from 600℃ to 1650℃ at a heating rate of 3℃ / min, with a holding time of 3 hours; and finally, it was cooled to 600℃ at a rate of 4℃ / min and then cooled with the furnace to obtain an insulating ceramic brick.

[0036] Example 1 The performance of the thermal insulation ceramic bricks obtained in Examples 1-3 was tested, and the test results are shown in Table 1.

[0037] Table 1 Performance test results of thermal insulation ceramic bricks in each embodiment

[0038] Table 2 Comparison of performance indicators between thermal insulation ceramic bricks and existing thermal insulation bricks

[0039] As shown in Table 2, the thermal insulation ceramic bricks of the present invention have lower thermal conductivity and higher compressive strength compared with traditional thermal insulation bricks and foam thermal insulation bricks made by adding pore-forming agents. Furthermore, the thermal insulation ceramic bricks prepared using alumina fiberboard waste as the main raw material have lower raw material costs and higher environmental benefits.

[0040] Example 2 The thermal insulation effect of the thermal insulation ceramic bricks of this invention and other manufacturers' thermal insulation bricks used in the structure of high-temperature sintering furnace doors was tested.

[0041] The 290mm thick insulating ceramic brick 1 of this invention was used in the furnace door structure of furnace #9, and the 290mm thick insulating brick 2 from other manufacturers was used in the furnace door structure of furnace #1. The temperature of the upper, middle and lower parts of the outer side of the furnace door of furnace #9 and furnace #1 was measured at a high temperature of 1710℃, and the results are shown in Table 3.

[0042] Table 3: Temperature at three locations on the outer side of the doors of Furnace No. 9 and Furnace No. 1 (upper, middle, and lower parts)

[0043] The test data of the above-mentioned heat-insulating ceramic bricks used in the furnace door structure of high-temperature sintering furnaces show that the heat-insulating ceramic bricks prepared by our company through the secondary processing of waste alumina fiberboard have a thermal conductivity temperature that is 30-40℃ lower than that of heat-insulating bricks from other manufacturers on the market under the same conditions. The experiment proves that the heat-insulating ceramic bricks prepared by the present invention using waste alumina fiberboard have a low thermal conductivity, better heat insulation effect, and superior overall performance.

[0044] In summary, this invention provides an effective way to utilize waste alumina fiberboard. The resulting thermal insulation ceramic bricks exhibit excellent performance, are technologically feasible, and offer significant economic, environmental, and social benefits. By surface modification of waste alumina fiberboard, introducing components such as boehmite, hollow glass microspheres, and expanded perlite, a multi-level composite thermal insulation structure is constructed with the waste alumina fibers. Combined with a specialized process, the thermal insulation ceramic bricks produced can achieve a thermal conductivity as low as 0.20-0.25 W / (m·K) and a compressive strength of 20-28 MPa, outperforming many traditional thermal insulation bricks. The equipment used in this invention consists of conventional ceramic or refractory material production equipment, making it easy to upgrade and promote on existing production lines. The resulting thermal insulation ceramic bricks can be used not only as low-temperature thermal insulation bricks but also as thermal insulation linings for high-temperature industrial kilns, demonstrating a wide range of applications.

[0045] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A type of heat-insulating ceramic brick prepared from alumina fiberboard waste, characterized in that, The raw materials include the following parts by weight: 40-60 parts of modified alumina fiberboard waste, 15-25 parts of clay, 10-20 parts of expanded perlite, 5-15 parts of boehmite, 5-10 parts of hollow glass microspheres, 3-8 parts of sintering aid, 1-3 parts of plasticizer, and 5-10 parts of water. The modified alumina fiberboard waste is composed of crushed particles of waste alumina fiberboard treated with silica sol, with a particle size of 0.5-2 mm. The modified alumina fiberboard waste has the following chemical composition: Al2O3 82-84%, SiO2 14-17%, and loss on ignition 1-3%.

2. The thermal insulation ceramic brick prepared from alumina fiberboard waste according to claim 1, characterized in that, The raw materials for the thermal insulation ceramic bricks also include wear-resistant reinforcing agents, and the mass ratio of the wear-resistant reinforcing agents to modified alumina fiberboard waste is 1:18-20.

3. The thermal insulation ceramic brick prepared from alumina fiberboard waste according to claim 1, characterized in that, The sintering aid is selected from at least one of silica powder and p-alumina.

4. The thermal insulation ceramic brick prepared from alumina fiberboard waste according to claim 1, characterized in that, The plasticizer is selected from at least one of polyethylene glycol and carboxymethyl cellulose.

5. The method for preparing thermally insulating ceramic bricks using alumina fiberboard waste according to any one of claims 1-4, comprising the following steps: a) Weigh each raw material according to the above-mentioned weight proportions and pre-treat it; b) Dry mix the modified alumina fiberboard waste from the above raw materials with clay, then add boehmite, expanded perlite, hollow glass microspheres and sintering aid in sequence and continue dry mixing. Finally, dissolve the plasticizer in water to make an aqueous solution and add it to the dry mixture for wet mixing to obtain the billet. c) The blank is subjected to a binding process, and then filled into a mold and pressed to form a brick blank; d) The brick blanks are dried in sections to reduce the moisture content to less than 3%, and then sintered using a stepped heating curve and cooled in the furnace to obtain insulating ceramic bricks.

6. The method for preparing thermally insulating ceramic bricks using alumina fiberboard waste according to claim 5, characterized in that, The pretreatment includes crushing and heat-treating the waste alumina fiberboard, immersing it in a silica sol aqueous solution, removing it, drying and curing it to obtain modified alumina fiberboard waste.

7. The method for preparing thermally insulating ceramic bricks using alumina fiberboard waste according to claim 6, characterized in that, The heat treatment is performed at a temperature of 400-600℃ for a time of 0.5-2 hours. And / or, the soaking time is 10-30 min; And / or, the curing temperature is 100-150℃.

8. The method for preparing thermally insulating ceramic bricks using alumina fiberboard waste according to claim 5, characterized in that, In step b), the total dry mixing time is not less than 25 minutes; the wet mixing time is 20 minutes.

9. The method for preparing thermally insulating ceramic bricks using alumina fiberboard waste according to claim 5, characterized in that, In step c), the conditions for the material conditioning process are: room temperature and relative humidity ≥85%; And / or, the pressing pressure is 20-30 MPa, and the holding time is 30-60 s.

10. The method for preparing thermally insulating ceramic bricks using alumina fiberboard waste according to claim 5, characterized in that, In step d), the sintering conditions for the stepped heating curve are as follows: First stage: from room temperature to 600℃, with a heating rate of 1-3℃ / min; Second stage: 600℃ to 1600-1800℃, heating rate is 2-5℃ / min, holding time is 2-4h; Third stage: Cool to 600℃ at a rate of 3-5℃ / min.

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