Low-cost alumina fiber rigid heat insulation product as well as preparation method and application thereof

Abstract

The invention discloses a low-cost alumina fiber rigid heat-insulating product as well as a preparation method and application thereof. The low-cost alumina fiber rigid heat-insulating product is prepared by freezing, vacuum drying and sintering a green body prepared from alumina fiber slurry, the alumina fiber slurry is prepared from the following components: 3Al2O3. B2O3. 2SiO2 sol, alumina fiber cotton and cation modified starch; in the 3Al2O3. B2O3. 2SiO2 sol, the total mass fraction of the inorganic colloid particles is 20 to 40 percent. According to the invention, the inorganic SBA sol in a specific composition range is adopted as the binder, and the alumina fiber product is prepared by adopting a freezing gel injection process, so that the prepared alumina fiber rigid heat-insulating product has low cost and good high-temperature dimensional stability and heat-insulating effect, and meets the application requirements in the field of heat preservation and heat insulation of high-temperature kilns.

Description

Technical Field

[0001] The present invention relates to the technical field of rigid thermal insulation products, and in particular to a low-cost alumina fiber rigid thermal insulation product and a preparation method and application thereof. Background Art

[0002] High temperature resistant ceramic fiber products are widely used in the field of high temperature furnace insulation. For example, Unifrax produces and Fiber module, produced by ICI Alumina fiber is used as raw material, and a rigid insulation product is prepared through a process of blanking and sintering. Zircar Zirconia Company of the United States prepares sintered alumina / zirconia fiber high-temperature insulation products (US Patent 3861947) based on alumina fiber and zirconia fiber prepared in US Patent 3385915.

[0003] Due to the rapid industrialization of domestic alumina fibers in recent years, the price of products has gradually decreased, and its cost-effectiveness advantage is obvious. In addition, for most industrial kiln lining application scenarios, the thermal shock resistance and thermal shrinkage resistance of alumina fiber products have met the requirements for civilian use. However, at present, most of the fiber modules produced by domestic enterprises contain polymer low-temperature adhesives, and various technical indicators are far behind those of foreign advanced products. Therefore, it is of great practical significance to develop high-performance, low-cost ceramic fiber rigid fireproof insulation products that can meet the application of domestic steel smelting furnaces, electrolytic aluminum high-temperature furnaces, glass melting furnaces, cement kilns and other series of high-temperature thermal equipment. Summary of the invention

[0004] The present invention aims to overcome the above-mentioned problems existing in the ceramic fiber rigid fireproof insulation products in the prior art, and provides a low-cost alumina fiber rigid insulation product and a preparation method and application thereof. An inorganic SBA sol in a specific composition range is used as a binder, and a cryogel injection molding process is adopted to prepare the alumina fiber product. The prepared alumina fiber rigid insulation product has low cost and good high-temperature dimensional stability and thermal insulation effect, and meets the application requirements in the field of high-temperature kiln thermal insulation.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a low-cost alumina fiber rigid insulation product, characterized in that it is made by freezing, vacuum drying and sintering a green body made of alumina fiber slurry; the components of the alumina fiber slurry include 3Al2O3 in a mass ratio of 100 to 300:1:0.02:1 to 15 2 O 3 ·B 2 O 3 ·2SiO2 Sol, alumina fiber cotton, cationic modified starch and infrared sunscreen; 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 In the sol, the total mass fraction of the inorganic colloidal particles is 20 to 40%.

[0006] PJGielisse et al. first systematically studied Figure 1 Al 2 O 3 -B 2 O 3 -SiO 2 Phase diagram of ternary oxide system (PJ Gielisse and WRFoster, "Quaterly Progress Report 931-8", the Ohio State University Research Foundation, p.6, October 1961). Later, 3M Company of the United States further studied the ternary oxide system and developed two high-performance ceramic fibers, Nextel-312 and Nextel-440. GE Company used SBA-10 ternary oxide high-temperature adhesive in the development of REI-Mullite mullite fiber rigid insulation tiles. In addition, Corning Glass Company of the United States also conducted in-depth research on this ternary system when developing borosilicate glass and microcrystalline glass products. In short, in Al 2 O 3 -SiO 2 The introduction of boron oxide into the binary ceramic system is beneficial to the system maintaining the glass phase or inhibiting the grain growth rate within a wide range of composition and temperature, and has a significant effect on improving the temperature resistance of the product. 2 O 3 -B 2 O 3 -SiO 2 The ternary sol (SBA sol) was used as an inorganic binder, and its composition ratio was further studied. It was found that 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 The sol has excellent anti-crystallization ability, which can make the alumina fiber rigid insulation products have good high-temperature dimensional stability.

[0007] At the same time, the present invention adopts a cryogel injection process and utilizes the principle of thermally induced phase separation (TIPS). The colloidal particles in the SBA sol will be tightly attached to the fiber surface and the intersections between fibers, and it is easy to form sintered nodes with higher mechanical properties during the subsequent sintering process. When the traditional sol-gel-drying-sintering process is used to prepare rigid insulation products, the sintering aid used tends to self-sinter, so that the sintering agent ceramic particles after sintering remain in the pores formed by the overlap between ceramic fibers; while the cryogel injection process of the present invention, due to the effect of TIPS during the freezing process, the ternary oxide colloidal particles of the sintering aid are mostly condensed on the fiber surface and the intersections between fibers, so the prepared rigid insulation tile has a high porosity and excellent mechanical properties, further improving its insulation performance. During the vacuum drying process, the cationic modified starch in the alumina fiber slurry undergoes gelatinization and dehydration, so that as a low-temperature adhesive, it can provide sufficient mechanical properties to the dry blank and prevent large-sized blanks from cracking and being damaged during the transfer process.

[0008] Preferably, the beating degree of the alumina fiber slurry is 35-45°SR.

[0009] Preferably, the alumina fiber cotton has a length of 2 to 8 mm and a diameter of 1 to 15 μm.

[0010] As a preferred embodiment, the alumina fiber cotton is produced by Luyang Energy Conservation Co., Ltd. Alumina fiber cotton, polycrystalline mullite fiber cotton, aluminum silicate fiber cotton; Shanghai Rongrong's 85-15 type alumina wool, 72-28 type alumina wool, 99 type alumina wool; Shandong Dongheng Guoxian New Materials Co., Ltd. produced 72F, 72M, 85, 95M, 95N type alumina staple fibers; ICI company One or more of alumina fiber wool.

[0011] As preferably, the 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 The B-10 isotope is used in the sol. Since the B-10 isotope has a large neutron absorption area, the boron-containing fiber products prepared by controlling the abundance of the B-10 isotope in the SBA sol have potential uses in nuclear power plant safety protection and nuclear radiation protection.

[0012] Preferably, the infrared sunscreen is selected from one or more of silicon carbide powder, rutile titanium dioxide, boron carbide powder, zirconium oxide powder, zircon powder, etc. In order to further improve the performance of low-cost ceramic fiber rigid fireproof insulation products, the present invention also adds an infrared sunscreen, which can suppress high-temperature infrared radiation and thus reduce thermal conductivity.

[0013] Preferably, when the low-cost alumina fiber rigid insulation product is applied to high-temperature scenes, the particle size of the infrared sunscreen agent has certain requirements, which can be specifically designed according to the following rules: According to Wien's displacement law, the wavelength λ at which the energy density of infrared rays radiated outward by a high-temperature black body or gray body heat source is at its maximum value * and the heat source temperature T satisfies (λ * / m)×(T / K)=b=0.002897. The particle size of the infrared shading agent should be slightly larger than λ according to D50. * (T) When the particle size of the infrared sunscreen agent is too small (such as <1 μm), the infrared radiation from the heat source directly penetrates the heat insulation layer and cannot shield the infrared heat radiation.

[0014] In a second aspect, the present invention provides a method for preparing the above-mentioned low-cost alumina fiber rigid insulation product, comprising the following steps: (1) Preparation of 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol; (2) The obtained 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 The sol is used as a dispersion medium, and alumina fiber cotton, cationic modified starch and infrared sunscreen are added into the dispersion medium, and the alumina fiber slurry is obtained after beating; (3) forming a green body from the obtained alumina fiber slurry; (4) freezing the obtained green body; (5) vacuum drying the frozen green body; (6) Sintering the vacuum-dried green body to obtain the low-cost alumina fiber rigid thermal insulation product.

[0015] Preferably, in step (1), 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 The preparation method of the sol is: mixing aluminum subacetate stabilized by boric acid, alkaline silica sol stabilized by ammonium and water to obtain the 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol; Or Al(NO 3 )3 、Al(OC 3 H 7 ) 3 、Si(OC 2 H 5 ) 4 , B(OCH 3 ) 3 Add water according to the stoichiometric ratio, adjust the pH value of the sol to 3-4 with concentrated nitric acid, and obtain the 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol.

[0016] Preferably, in the ammonium stabilized alkaline silica sol, SiO 2 The content is 35-45wt%; the mass ratio of boric acid-stabilized aluminum subacetate, ammonium-stabilized alkaline silica sol and water is 210-215:400:85-90.

[0017] Preferably, during freezing in step (4), the blank is placed in liquid nitrogen for freezing for 10 to 30 minutes.

[0018] Preferably, the vacuum degree during vacuum drying in step (5) is -0.08 to -0.1 MPa, and the vacuum drying time is 24 to 48 hours.

[0019] Preferably, the sintering method in step (6) is: heating from room temperature to 500-600°C at a rate of 2-4°C / min, and keeping warm for 20-40 minutes; then heating to 1100-1300°C at a rate of 1.5-2°C / min, keeping warm for 2-6 hours, and naturally cooling to room temperature to obtain the low-cost alumina fiber rigid insulation product.

[0020] In a third aspect, the present invention provides an application of the above-mentioned low-cost alumina fiber rigid insulation product, which is used as a thermal insulation material in a high-temperature kiln.

[0021] Preferably, the high temperature kiln includes a steel smelting furnace, an electrolytic aluminum high temperature furnace, a glass melting furnace, and a cement kiln.

[0022] Therefore, the present invention has the following beneficial effects: (1) SBA sol is used as an inorganic binder. SBA sol prepared in an appropriate proportion has excellent anti-crystallization ability, which can make alumina fiber rigid insulation products have good high-temperature dimensional stability; (2) Using the frozen gel casting process and the principle of thermally induced phase separation, the colloidal particles in the SBA sol will be tightly attached to the fiber surface and the intersections between fibers. The prepared rigid insulation tile has a high through-porosity and excellent mechanical properties, further improving its insulation performance; (3) Cationic modified starch is added to the alumina fiber slurry. During the vacuum drying process, the starch is gelatinized and dehydrated, so that it can act as a low-temperature adhesive to provide sufficient mechanical properties to the dry blank and prevent cracks and damage to the large-sized blank during the transfer process; (4) Adding an infrared sunscreen as one of the raw materials can be used to suppress high-temperature infrared radiation and thus reduce thermal conductivity; (5) It is made of alumina fiber cotton as raw material, which has low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It's Al 2 O 3 -B 2 O 3 -SiO 2 Phase diagram of ternary oxide system.

[0024] Figure 2 This is the SEM image of the alumina fiber rigid insulation product in Example 2.

[0025] Figure 3 This is the EDS image of the alumina fiber rigid insulation product in Example 2.

[0026] Figure 4 This is the SEM image of the alumina fiber rigid insulation product in Example 3.

[0027] Figure 5 This is the EDS graph of the alumina fiber rigid insulation product in Example 3. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0029] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are conventional methods in the art.

[0030] Overall embodiment: A method for preparing a low-cost alumina fiber rigid insulation product comprises the following steps: (1) Preparation of 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol: 3Al2 O 3 ·B 2 O 3 ·2SiO 2 In the sol, the total mass fraction of inorganic colloidal particles is 20-40%; (2) The obtained 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol is used as a dispersion medium, and alumina fiber cotton, cationic modified starch and infrared sunscreen are added into the dispersion medium to obtain alumina fiber slurry after beating; 3Al in the alumina fiber slurry 2 O 3 ·B 2 O 3 ·2SiO 2 The mass ratio of the sol, the alumina fiber cotton cationic modified starch and the infrared sunscreen agent is 100-300:1:0.02:1-15; (3) forming a green body from the obtained alumina fiber slurry; (4) freezing the obtained green body; (5) vacuum drying the frozen green body; (6) Sintering the vacuum-dried green body to obtain the low-cost alumina fiber rigid thermal insulation product.

[0031] As a specific embodiment, in step (1), 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 The preparation method of the sol is as follows: boric acid-stabilized aluminum subacetate (Al(OH) 2 (CH 3 COO)·1 / 3H 3 BO 3 , CAS No. 7360-44-3), ammonium stabilized alkaline silica sol and water are mixed, and the mass ratio of boric acid stabilized aluminum subacetate, ammonium stabilized alkaline silica sol and water is 210-215:400:85-90 to obtain the 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol; preferably, the manufacturer of boric acid-stabilized aluminum subacetate is Niacet Corporation of the United States; ammonium stabilized alkaline silica sol Na + Content ≤5ppm, SiO 2Content 40wt%, pH=10, particle size 10-12nm, manufacturer Hebei Jiashi Hongwei Technology Co., Ltd.

[0032] As a specific embodiment, in step (1), 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 The preparation method of sol is as follows: Al(NO 3 ) 3 、Al(OC 3 H 7 ) 3 、Si(OC 2 H 5 ) 4 , B(OCH 3 ) 3 Add water according to the stoichiometric ratio, adjust the pH value of the sol to 3-4 with concentrated nitric acid, and obtain the Al 2 O 3 -B 2 O 3 -SiO 2 Ternary sol.

[0033] As a specific implementation, the beating degree of the alumina fiber slurry in step (2) is 35-45°SR.

[0034] As a specific implementation, the alumina fiber cotton described in step (2) has a length of 2 to 8 mm and a diameter of 1 to 15 μm.

[0035] As a specific embodiment, the alumina fiber cotton used in step (2) is selected from Luyang Energy Conservation Co., Ltd. Alumina fiber cotton, polycrystalline mullite fiber cotton, aluminum silicate fiber cotton; Shanghai Rongrong's 85-15 type alumina wool, 72-28 type alumina wool, 99 type alumina wool; Shandong Dongheng Guoxian New Materials Co., Ltd. produced 72F, 72M, 85, 95M, 95N type alumina staple fibers; ICI company One or more of alumina fiber wool.

[0036] As a specific embodiment, the 3A1 2 O 3 ·B 2 O 3 ·2SiO 2 B-10 isotope is used in the sol; for example, a series of B-10 isotope chemicals produced by Anhui Anboqiao New Material Technology Co., Ltd. are used.

[0037] As a specific implementation, the infrared sunscreen agent described in step (2) is selected from one or more of silicon carbide powder, rutile titanium dioxide, boron carbide powder, zirconium oxide powder, zircon powder, etc.

[0038] As a specific implementation method, in step (3), a plate-shaped blank with a width of 0.6 m and a thickness of 10 mm or 20 mm is continuously prepared according to the method disclosed in the invention patent CN117733988A; Or according to the method disclosed in the invention patent CN118024393A, a large-sized semi-cylindrical blank is made by imitating the papermaking process of the intangible cultural heritage of Xuan paper; Or according to the method disclosed in the invention patent CN108252163B or CN117342880B, a small-sized spherical crown or conical cylindrical blank is made; Alternatively, the alumina fiber slurry is added into a centrifugal filter, and most of the water in the alumina fiber slurry is separated out through the principle of a spin-drying barrel. The alumina fibers are retained on the inner surface of the filter to form a conical wet blank.

[0039] As a specific implementation, during the freezing in step (4), the blank is placed in liquid nitrogen for freezing for 10 to 30 minutes.

[0040] As a specific implementation manner, the vacuum degree during vacuum drying in step (5) is -0.08 to -0.1 MPa, and the vacuum drying time is 24 to 48 hours.

[0041] As a specific implementation method, the sintering method in step (6) is: heating from room temperature to 500-600°C at a rate of 2-4°C / min, and keeping warm for 20-40 minutes; then heating to 1200-1600°C at a rate of 1.5-2°C / min, keeping warm for 2-6 hours, and naturally cooling to room temperature to obtain the low-cost alumina fiber rigid insulation product.

[0042] Embodiment 1: A method for preparing a low-cost alumina fiber rigid insulation product comprises the following steps: (1) Preparation of 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol: Al(NO 3 ) 3 、Al(OC 3 H 7 ) 3 、Si(OC 2 H 5 ) 4 , B(OCH 3 )3 Add water according to the stoichiometric ratio to make the Al in the sol 2 O 3 , B 2 O 3 and SiO 2 The total mass fraction of inorganic colloidal particles is 30wt%; concentrated nitric acid is added to water to adjust the pH value of the sol to 3.5 to obtain 30wt% 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol; (2) The obtained 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol was used as the dispersion medium, and alumina fiber cotton (Luyang Energy Conservation Co., Ltd., Alumina fiber cotton), cationic modified starch and silicon carbide powder with a particle size of 2 to 5 μm, start a fiber beating machine, and perform wet pulping until the beating degree reaches 40°SR to end the beating to obtain alumina fiber slurry; 30wt% 3Al in the alumina fiber slurry 2 O 3 ·B 2 O 3 ·2SiO 2 The mass ratio of sol, alumina fiber cotton, cationic modified starch and silicon carbide powder is 199:1:0.02:2; (3) According to the method S2 in Example 1 of the invention patent CN117733988A, the obtained alumina fiber slurry is used to continuously prepare a plate-shaped wet blank with a width of 0.6 m and a thickness of 10 mm; (4) The obtained wet blank is fixed in a positioning tool, and then the entire tool is quickly placed in a Dewar flask filled with liquid nitrogen and frozen for 20 minutes, so that the ternary oxide colloidal particles in the wet blank are separated from the water, thereby being enriched at the fiber intersection and the fiber surface to obtain a frozen blank; (5) placing the obtained frozen dough into a vacuum drying oven and vacuum drying it at a vacuum degree of -0.09 MPa for 24 h; (6) The vacuum-dried green body is placed in a muffle furnace for sintering; the sintering method is: heating from room temperature to 550°C at a rate of 3°C / min, keeping warm for 30 minutes, degumming, and removing starch; then heating to 1400°C at a rate of 2°C / min, keeping warm for 4 hours, and naturally cooling to room temperature before taking out the product from the furnace to obtain the low-cost alumina fiber rigid insulation product.

[0043] Embodiment 2: A method for preparing a low-cost alumina fiber rigid insulation product comprises the following steps: (1) Preparation of 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol: Boric acid stabilized aluminum subacetate (Al(OH) 2 (CH 3 COO)·1 / 3H 3 BO 3 , CAS No. 7360-44-3, Niacet Corporation, USA), ammonium stabilized high purity alkaline silica sol (Na + Content ≤5ppm, SiO 2 Content 40wt%, pH = 10, particle size 10-12nm, Hebei Jiashi Hongwei Technology Co., Ltd.) and water are mixed in a mass ratio of 211:400:86 to obtain 30wt% 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol; (2) The obtained 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol was used as a dispersion medium, and alumina fiber cotton (Shanghai Rongrong New Materials Co., Ltd., 72-28 type alumina cotton), cationic modified starch and silicon carbide powder with a particle size of 2 to 5 μm were added to the dispersion medium, and a fiber beating machine was started to perform wet pulping until the beating degree reached 40°SR, and the beating was stopped to obtain an alumina fiber slurry; 30wt% of 3Al in the alumina fiber slurry 2 O 3 ·B 2 O 3 ·2SiO 2 The mass ratio of sol, alumina fiber cotton, cationic modified starch and silicon carbide powder is 199:1:0.02:2; (3) Adding the alumina fiber slurry into the centrifugal filter, separating most of the water in the alumina fiber slurry through the principle of the spin-drying bucket, and retaining the alumina fibers on the inner surface of the filter to form a conical wet blank with a bottom diameter of 0.6 m and a height of 0.5 m; (4) The obtained wet blank is fixed in a positioning tool, and then the entire tool is quickly placed in a Dewar flask filled with liquid nitrogen and frozen for 20 minutes, so that the ternary oxide colloidal particles in the wet blank are separated from the water, thereby being enriched at the fiber intersection and the fiber surface to obtain a frozen blank; (5) placing the obtained frozen dough into a vacuum drying oven and vacuum drying it at a vacuum degree of -0.09 MPa for 24 h; (6) The vacuum-dried green body is placed in a muffle furnace for sintering; the sintering method is: heating from room temperature to 550°C at a rate of 3°C / min, keeping the temperature for 30 minutes, degumming, and removing starch; then heating to 1400°C at a rate of 2°C / min, keeping the temperature for 4 hours, and taking out the product from the furnace after naturally cooling to room temperature to obtain the low-cost alumina fiber rigid insulation product, whose SEM and EDS images are as follows Figure 2 and Figure 3 as shown in .

[0044] Embodiment 3: A method for preparing a low-cost alumina fiber rigid insulation product comprises the following steps: (1) Preparation of 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol: Al(NO 3 ) 3 、Al(OC 3 H 7 ) 3 、Si(OC 2 H 5 ) 4 , B(OCH 3 ) 3 Add water according to the stoichiometric ratio to make the Al in the sol 2 O 3 , B 2 O 3 and SiO 2 The total mass fraction of inorganic colloidal particles is 30wt%; concentrated nitric acid is added to water to adjust the pH value of the sol to 3.5 to obtain 30wt% 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol; (2) The obtained 3Al 2 O 3 ·B 2 O 3 ·2SiO 2Sol was used as a dispersion medium, and alumina fiber cotton (Shanghai Rongrong New Materials Co., Ltd., 85-15 type alumina cotton) and cationic modified starch and silicon carbide powder with a particle size of 2 to 5 μm were added to the dispersion medium, and a fiber beating machine was started to perform wet pulping until the beating degree reached 40°SR, and the beating was stopped to obtain an alumina fiber slurry; 30wt% of 3Al in the alumina fiber slurry 2 O 3 ·B 2 O 3 ·2SiO 2 The mass ratio of sol, alumina fiber cotton, cationic modified starch and silicon carbide powder is 199:1:0.02:2; (3) According to the methods S3 to S5 in Example 1 of the invention patent CN118024393A, the obtained alumina fiber slurry is used to make a large-sized semi-cylindrical wet blank with a bottom radius of 0.3 m and a height of 0.6 m; (4) The obtained wet blank is fixed in a positioning tool, and then the entire tool is quickly placed in a Dewar flask filled with liquid nitrogen and frozen for 20 minutes, so that the ternary oxide colloidal particles in the wet blank are separated from the water, thereby being enriched at the fiber intersection and the fiber surface to obtain a frozen blank; (5) placing the obtained frozen dough into a vacuum drying oven and vacuum drying it at a vacuum degree of -0.09 MPa for 24 h; (6) The vacuum-dried green body is placed in a muffle furnace for sintering; the sintering method is: heating from room temperature to 550°C at a rate of 3°C / min, keeping the temperature for 30 minutes, degumming, and removing starch; then heating to 1400°C at a rate of 2°C / min, keeping the temperature for 4 hours, and taking out the product from the furnace after naturally cooling to room temperature to obtain the low-cost alumina fiber rigid insulation product, whose SEM and EDS images are as follows Figure 4 and Figure 5 as shown in .

[0045] Embodiment 4: A method for preparing a low-cost alumina fiber rigid insulation product comprises the following steps: (1) Preparation of 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol: Al(NO 3 ) 3 、Al(OC 3 H 7 ) 3 、Si(OC 2 H 5 ) 4 , B(OCH 3 ) 3Add water according to the stoichiometric ratio to make the Al in the sol 2 O 3 , B 2 O 3 and SiO 2 The total mass fraction of inorganic colloidal particles is 30wt%; concentrated nitric acid is added to water to adjust the pH value of the sol to 3.5 to obtain 30wt% 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol; (2) The obtained 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol is used as the dispersion medium, and alumina fiber cotton (ICI company) is added into the dispersion medium. Alumina fiber cotton), cationic modified starch and silicon carbide powder with a particle size of 2 to 5 μm, start a fiber beating machine, and perform wet pulping until the beating degree reaches 40°SR to end the beating to obtain alumina fiber slurry; 30wt% 3Al in the alumina fiber slurry 2 O 3 ·B 2 O 3 ·2SiO 2 The mass ratio of sol, alumina fiber cotton, cationic modified starch and silicon carbide powder is 199:1:0.02:2; (3) According to the method in the invention patent CN108252163B, the obtained alumina fiber slurry is used to make a spherical crown-shaped wet blank with a diameter of 0.5 m; (4) The obtained wet blank is fixed in a positioning tool, and then the entire tool is quickly placed in a Dewar flask filled with liquid nitrogen and frozen for 5 minutes, so that the ternary oxide colloidal particles in the wet blank are phase-separated from water, thereby being enriched at the fiber intersection and fiber surface to obtain a frozen blank; (5) placing the obtained frozen dough into a vacuum drying oven and vacuum drying it at a vacuum degree of -0.09 MPa for 24 h; (6) The vacuum-dried green body is placed in a muffle furnace for sintering; the sintering method is: heating from room temperature to 550°C at a rate of 3°C / min, keeping warm for 30 minutes, degumming, and removing starch; then heating to 1400°C at a rate of 2°C / min, keeping warm for 4 hours, and naturally cooling to room temperature before taking out the product from the furnace to obtain the low-cost alumina fiber rigid insulation product.

[0046] Comparative Example 1 (changing the composition range of SBA sol): The difference between Comparative Example 1 and Example 1 is that the ternary sol used is Al 2 O 3 , B 2 O 3 、SiO 2 The molar ratio of 3:0.5:1 is 3Al 2 O 3 0.5B 2 O 3 ·SiO 2 Sol, and the rest are the same as in Example 1.

[0047] Comparative Example 2 (freezing gel injection molding process is not adopted): A method for preparing a low-cost alumina fiber rigid insulation product comprises the following steps: (1) Using water as the dispersion medium, add alumina fiber cotton (Luyang Energy Conservation Co., Ltd., alumina fiber cotton), cationic modified starch and silicon carbide powder with a particle size of 2 to 5 μm, start a fiber beating machine, and perform wet pulping until the beating degree reaches 40°SR, and then the beating is terminated to obtain alumina fiber slurry; the mass ratio of water, alumina fiber cotton, cationic modified starch and silicon carbide powder in the alumina fiber slurry is 199:1:0.02:2; (2) According to the method S2 in Example 1 of the invention patent CN117733988A, the obtained alumina fiber slurry is used to continuously prepare a plate-shaped wet blank with a width of 0.6 m and a thickness of 10 mm; (3) drying the wet blank at 100° C. for 24 hours to obtain a fiber blank; (4) Preparation of 3Al 2 O 3 ·B 2 O 3 ·2SiO 2 Sol: Al(NO 3 ) 3 、Al(OC 3 H 7 ) 3 、Si(OC 2 H 5 ) 4 , B(OCH 3 ) 3 Add water according to the stoichiometric ratio to make the Al in the sol 2 O 3 , B 2 O 3 and SiO 2 The total mass fraction of inorganic colloidal particles is 30wt%; concentrated nitric acid is added to water to adjust the pH value of the sol to 3.5 to obtain 30wt% 3Al2 O 3 ·B 2 O 3 ·2SiO 2 Sol; (5) placing the fiber blank obtained in step (3) into a mold, uniformly injecting the sol obtained in step (4) to fully impregnate the fiber blank with the sol, and then allowing the fiber blank to stand for gel aging; (6) drying the gel and the aged body in an oven at 80° C. for 48 h; (7) The dried green body is placed in a muffle furnace for sintering; the sintering method is: heating from room temperature to 550°C at a rate of 3°C / min, keeping warm for 30 minutes, degumming, and removing starch; then heating to 1200°C at a rate of 2°C / min, keeping warm for 4 hours, and taking out the product from the furnace after naturally cooling to room temperature, thereby obtaining the low-cost alumina fiber rigid insulation product.

[0048] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that the alumina fiber wool is replaced by ceramic fiber wool, wherein the ceramic fiber wool includes quartz fiber wool and alumina fiber wool in a mass ratio of 1:0.2, and the rest is the same as in Example 1.

[0049] According to the method of GB / T 17911-2018, the refractoriness, high temperature linear shrinkage, high temperature thermal conductivity, bending strength and other properties of the alumina fiber rigid insulation products prepared in the above embodiments and comparative examples were characterized, and the results are shown in Table 1.

[0050] Table 1: Performance test results of alumina fiber rigid insulation products.

[0051] As can be seen from Table 1, the alumina fiber rigid insulation products prepared by the method of the present invention in Examples 1 to 4 have good insulation performance and high-temperature dimensional stability. In Comparative Example 1, the composition of the SBA sol is not within the scope of the present invention, and the boron oxide content is too low, resulting in a decrease in refractoriness. In Comparative Example 2, the cryogel injection molding process of the present invention is not used, but the traditional sol-gel-drying-sintering process is used to prepare alumina fiber rigid insulation products. Since the colloidal particles in the SBA sol cannot be tightly attached to the fiber surface and the intersections between fibers, the mechanical properties are reduced. In Comparative Example 3, the product made of ceramic fiber wool mixed with quartz fiber wool and alumina fiber wool has reduced mechanical properties and thermal insulation properties compared with those in the examples.

Claims

1. A low-cost alumina fiber rigid insulation product, characterized in that: The green body is made of alumina fiber slurry, and then subjected to freezing, vacuum drying and sintering; The components of the alumina fiber slurry include 3Al2O3·B2O3·2SiO2 sol, alumina fiber cotton, cationic modified starch and infrared sunscreen agent in a mass ratio of 100~300:1:0.02:1~15; In 3Al2O3·B2O3·2SiO2 sol, the total mass fraction of inorganic colloidal particles is 20~40%.

2. The low-cost alumina fiber rigid insulation product according to claim 1 is characterized in that: The beating degree of the alumina fiber slurry is 35-45︒SR; the length of the alumina fiber cotton is 2-8mm and the diameter is 1-15μm.

3. The low-cost alumina fiber rigid insulation product according to claim 1 is characterized in that: The 3Al2O3·B2O3·2SiO2 sol uses B-10 isotope.

4. The low-cost alumina fiber rigid insulation product according to claim 1 is characterized in that: The infrared sunscreen is selected from one or more of silicon carbide powder, rutile titanium dioxide, boron carbide powder, zirconium oxide powder and zircon powder.

5. A method for preparing a low-cost alumina fiber rigid insulation product as claimed in any one of claims 1 to 4, characterized in that: The steps include: (1) Preparation of 3Al2O3·B2O3·2SiO2 sol; (2) using the obtained 3Al2O3·B2O3·2SiO2 sol as a dispersion medium, adding alumina fiber cotton, cationic modified starch and infrared sunscreen agent into the dispersion medium, and beating to obtain alumina fiber slurry; (3) forming a green body from the obtained alumina fiber slurry; (4) freezing the obtained green body; (5) vacuum drying the frozen green body; (6) Sintering the vacuum-dried green body to obtain the low-cost alumina fiber rigid thermal insulation product.

6. The method for preparing a low-cost alumina fiber rigid insulation product according to claim 5, characterized in that: The preparation method of the 3Al2O3·B2O3·2SiO2 sol in step (1) is as follows: boric acid-stabilized aluminum subacetate, ammonium-stabilized alkaline silica sol and water are mixed to obtain the 3Al2O3·B2O3·2SiO2 sol; the content of SiO2 in the ammonium-stabilized alkaline silica sol is 35-45wt%; the mass ratio of boric acid-stabilized aluminum subacetate, ammonium-stabilized alkaline silica sol and water is 210-215:400:85-90; Alternatively, Al(NO3)3, Al(OC3H7)3, Si(OC2H5)4, and B(OCH3)3 are added into water in a stoichiometric ratio, and the pH value of the sol is adjusted to 3-4 with concentrated nitric acid to obtain the 3Al2O3·B2O3·2SiO2 sol.

7. The method for preparing a low-cost alumina fiber rigid thermal insulation product according to claim 5, characterized in that: During the freezing step (4), the green body is placed in liquid nitrogen for freezing for 10 to 30 minutes.

8. The method for preparing a low-cost alumina fiber rigid thermal insulation product according to claim 5, characterized in that: The vacuum degree during vacuum drying in step (5) is -0.08 to -0.1 MPa, and the vacuum drying time is 24 to 48 hours.

9. The method for preparing a low-cost alumina fiber rigid thermal insulation product according to claim 5, characterized in that: The sintering method in step (6) is: heating from room temperature to 500-600°C at a rate of 2-4°C / min, and keeping warm for 20-40 minutes; then heating to 1200-1600°C at a rate of 1.5-2°C / min, keeping warm for 2-6 hours, and naturally cooling to room temperature to obtain the low-cost alumina fiber rigid insulation product.

10. An application of a low-cost alumina fiber rigid thermal insulation product as claimed in any one of claims 1 to 4 or a low-cost alumina fiber rigid thermal insulation product prepared by the preparation method as claimed in any one of claims 5 to 9, characterized in that: Used as thermal insulation material in high temperature kilns.

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