High-temperature-resistant and acid-corrosion-resistant modified silicon carbide ceramic filter brick and preparation method thereof

Abstract

The application discloses a modified silicon carbide ceramic filter brick resistant to high temperature and acid corrosion and a preparation method thereof, and belongs to the field of high-temperature gas purification materials. The ceramic filter brick is composed of a base body and an anticorrosion coating. The base body raw material comprises SiC aggregate, Sialon generating powder, yttrium stabilized zirconium (YSZ) short fibers, a pore forming agent and a binder. The preparation method is as follows: the mixed green body is subjected to high-temperature nitriding reaction sintering to obtain a high-strength SiC porous base body; then, yttrium silicon composite sol is used for impregnation, and the surface is subjected to calcination to form a yttrium disilicate anticorrosion coating. The application improves the thermal shock resistance of the material by using the YSZ fibers, and the erosion of alkali metal vapor and acid gas is isolated by the yttrium disilicate coating, so that the service life under extreme working conditions is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature gas purification and separation materials, and specifically relates to a modified silicon carbide-based ceramic filter brick and its preparation method that can be used in environments containing acidic gases (HCl, SOx) and alkali metal vapors at temperatures above 1000℃. Background Technology

[0002] In modern chemical engineering, waste incineration, biomass power generation, and waste treatment, the high-temperature flue gas generated during these processes not only contains a large amount of dust but also often includes high concentrations of acidic gases (such as HCl and SOx) and alkali metal vapors (such as chlorides or sulfates of Na and K). Efficient dust removal from these high-temperature gases is crucial for energy conservation, emission reduction, and the protection of downstream equipment.

[0003] Currently, the filter bricks widely used in industry (such as mullite, cordierite, or ordinary silicon carbide filter bricks with clay and glass phases as binders) are typically suitable for temperatures around 700℃. When the operating temperature is increased to 1000℃ or above, existing filter bricks have the following defects: 1. When subjected to drastic temperature fluctuations at 1000℃, thermal stress cracks are easily generated, leading to filter brick fracture and failure. 2. At high temperatures of 1000℃, gaseous alkali metals and acidic gases will rapidly react chemically with traditional silicate or oxide ceramics to generate low-melting-point eutectics (such as glass phases), causing blockage of filter brick pores, surface peeling, and even structural collapse.

[0004] To address these issues, researchers have proposed several solutions. For example, to improve the mechanical properties and chemical stability of silicon carbide ceramics at high temperatures, nitrides are used instead of traditional oxide-binding phases. Sialon, a solid solution of the Si-Al-ON quaternary system, is widely studied for its excellent high-temperature strength, hardness, thermal shock resistance, and chemical inertness, and is used in the manufacture of refractory materials, cutting tools, and structural ceramics. However, despite the good corrosion resistance of the sialon-binding phase itself, its corrosion resistance remains insufficient under extreme combined environments above 1000°C, strong acidic atmospheres, and high concentrations of alkali metal vapors. Studies have shown that high-temperature alkali metal vapors (especially KCl and NaCl) can still react with sialon and SiC, forming a low-melting-point alkali-alumina-silicate glass phase on the material surface, causing slow dissolution and pore blockage.

[0005] To further improve the corrosion resistance of ceramic materials, surface coating technology is a common solution. For example, Chinese patent CN105418164A discloses a method for preparing silicon carbide ceramic kiln furniture with a yttrium-stabilized zirconia coating. This patent improves the oxidation resistance and chemical stability of the kiln furniture by preparing a layer of yttrium-stabilized zirconia (YSZ) coating on the surface of a dense silicon carbide kiln furniture. However, while dense kiln furniture is suitable, porous filter bricks, whose core function is to allow gas to pass through and filter dust, have limited ability to resist alkali metal vapor corrosion and will still react with SiO2 and alkali metal salts in the flue gas.

[0006] To address the aforementioned issues, there is an urgent need to develop a filter brick that can maintain its mechanical properties at medium and high temperatures (>1000℃) and resist extremely harsh corrosive environments (resistance to alkali metal and acid gas corrosion). Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a composite filter brick and its preparation process that is stable at 1000℃ and can be used stably in environments with high concentrations of HCl, SOx and alkali metal vapors. This invention utilizes YSZ fibers to improve the thermal shock resistance of the material and isolates the corrosion of alkali metal vapors and acidic gases through a coating, thereby extending its service life.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] Filter brick matrix formulation, by weight percentage:

[0010] Silicon carbide (SiC) aggregate: 50%~65%;

[0011] Sialon powder: 15%~30%;

[0012] Yttrium-stabilized zirconia short fibers: 5%~10%;

[0013] Pore-forming agent: 5%~15%;

[0014] High-temperature adhesive: 2%~5%.

[0015] The sum of the mass percentages of the above components is 100%.

[0016] Furthermore, the Sialon powder is produced by mixing silicon powder, aluminum nitride, and aluminum oxide in a certain proportion, and generating the Sialon bonding phase in situ during nitriding sintering.

[0017] Sialon powder, by mass percentage: silicon metal powder (Si): 50%~60% (median particle size D50 < 10μm, purity ≥ 99%), alumina powder (Al2O3): 25%~35% (using α-Al2O3 micro powder, particle size < 5μm); aluminum nitride powder (AlN): 10%~20% (particle size < 2μm).

[0018] Furthermore, the preferred silicon carbide (SiC) aggregate is coarse aggregate (accounting for 35%~45% of the total): with a particle size of 200~500μm; and fine powder aggregate (accounting for 15%-20% of the total): with a particle size of 10~45μm.

[0019] Furthermore, the pore-forming agent is modified starch or PMMA microspheres.

[0020] Furthermore, the high-temperature adhesive is polyvinyl alcohol (PVA).

[0021] Furthermore, the source of the yttrium-stabilized zirconia short fibers is ZircarZirconiaZYBF-1 from the United States.

[0022] The preparation method is as follows:

[0023] (1) Mixing and molding: The silicon carbide aggregate, Sialon powder, YSZ short fiber, pore-forming agent and high-temperature binder are dry-mixed evenly, and water is added for kneading. The filter brick green body is obtained by vacuum extrusion molding or machine pressing. The amount of water used is 12% to 18% of the total mass of the dry mixture.

[0024] (2) After drying the green blank, heat it to 450℃~550℃ at a rate of 1~2℃ / min and hold it for 4~6 hours. Then place it in a furnace filled with high-purity nitrogen (N2) at 0.1~0.2MPa and heat it to 1450℃-1550℃ at a certain heating rate, and hold it for 4-8 hours. During this stage, silicon powder, AlN, Al2O3 react with N2 to generate the Sialon phase in situ, which tightly binds the SiC aggregate to form a high-strength porous matrix.

[0025] (3) Coating preparation: Soluble yttrium salts (such as yttrium nitrate [Y(NO3)3]) and tetraethyl orthosilicate (TEOS) are mixed in anhydrous ethanol at a molar ratio of Y:Si = 1:1. The pH value is adjusted to 2.5~3.5, stirred, and allowed to stand for aging to obtain yttrium-silicon composite sol. The porous substrate is placed in a vacuum impregnation tank, and the vacuum is drawn to below -0.09MPa. The above composite sol is then injected, and then the pressure is restored to normal to allow the sol to enter the interior of the filter brick.

[0026] (4) Take out the impregnated filter bricks, rotate them at a low speed of 200~300r / min for 3~5 minutes, dry them, put them in an air furnace, heat them at a rate of 2~3℃ / min to 1100℃-1200℃ and calcine them for 2~4 hours to obtain modified silicon carbide ceramic filter bricks.

[0027] Preferably, step (3) involves adjusting the pH using dilute nitric acid or citric acid. The soluble yttrium salt is yttrium nitrate or yttrium acetate.

[0028] Furthermore, the application of modified silicon carbide ceramic filter bricks resistant to high temperature and acid corrosion in high-temperature gas purification and separation.

[0029] The high-temperature gas is high-temperature flue gas containing acidic gases and alkali metal vapors, generated during the incineration of waste or hazardous waste.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] (1) To address the problem that existing ordinary silicon carbide filter bricks easily react with alkali metal vapors (Na, K) and acidic gases (HCl, SOx) in flue gas at high temperatures above 1000℃, generating a low-melting-point glassy phase that causes the filter bricks to collapse, this invention generates a yttrium pyrosilicate (Y2Si2O7) coating in situ within the filter brick pores. This coating can isolate the corrosive medium from contact with the internal substrate. Experimental results show that after continuous exposure to a high-concentration acid-base mixed gas at 1000℃ for 500 hours, the filter bricks maintain their temperature, exhibiting extremely strong resistance to strong corrosion.

[0032] (2) This invention controls the pH value of the yttrium silicon composite sol between 2.5 and 3.5, which makes the sol flow well and able to penetrate into the pores of the filter brick. After calcination, a coating is formed on the pore wall, and the apparent porosity of the finished filter brick is as high as 38% or more, with low gas penetration resistance.

[0033] (3) During the start-up, shutdown, or dust removal of industrial equipment, the temperature often fluctuates drastically, which can easily cause ceramic filter bricks to crack and break due to thermal expansion and contraction. This invention uses Sialon powder as a binder, which has strong bonding force, and adds yttrium-stabilized zirconia (YSZ) short fibers. When thermal stress is generated inside the filter brick, the YSZ short fibers effectively prevent the cracks from expanding further. After 50 cycles of thermal cycling from 1100℃ to 20℃, the compressive strength retention rate of the filter brick of this invention is as high as 94% or more, solving the problem of high brittleness and easy breakage of traditional rigid ceramic filter bricks. Attached Figure Description

[0034] Figure 1 The X-ray diffraction (XRD) pattern of the modified silicon carbide ceramic filter brick coating prepared in Example 1 of this invention.

[0035] Figure 2 A photograph of the honeycomb modified silicon carbide ceramic filter brick prepared in Example 2 of the present invention. Detailed Implementation

[0036] The yttrium-stabilized zirconia short fibers are sourced from ZircarZirconiaZYBF-1 in the United States.

[0037] Example 1

[0038] (1) Weigh 49 kg of SiC particles with a particle size of 300~400 μm, 21 kg of SiC fine powder with a particle size of 15~30 μm, 18 kg of Sialon powder (including 10 kg of silicon powder, 5 kg of Al2O3, and 3 kg of AlN), and 8 kg of YSZ short fibers. Add 10 kg of PMMA microspheres as a pore-forming agent, 3 kg of PVA dry powder, and 16 kg of deionized water for mixing. Extrude the mixture using a vacuum extruder to form a honeycomb porous filter brick.

[0039] (2) The green body is dried at 100℃ for 24 hours. The dried green body is placed in a sintering furnace and heated to 500℃ at a rate of 1~2℃ / min and held for 4 hours. Then, a vacuum is drawn and the temperature is raised to 1500℃ at a rate of 4℃ / min under a nitrogen atmosphere of 0.1MPa and held for 6 hours. After cooling, a porous matrix is ​​obtained.

[0040] (3) Measure 200 mL of 0.5 mol / L yttrium nitrate aqueous solution (containing 0.1 mol yttrium) and mix it with 20.8 g of tetraethyl orthosilicate (TEOS) (at a molar ratio of Y:Si = 1:1) in 500 mL of anhydrous ethanol. Add citric acid as a complexing agent, adjust the pH to 3.0, stir at room temperature for 1 hour, and let it stand for 24 hours to obtain a composite sol. Place the porous matrix in a vacuum impregnation tank, evacuate to -0.09 MPa, and then inject the composite sol until the matrix is ​​submerged; restore to normal pressure and maintain impregnation for 30 minutes.

[0041] (4) Take out the impregnated filter bricks and rotate them at a low speed of 200~300r / min for 3~5 minutes. Then dry them at 120℃ for 6 hours. After drying, put them into an air muffle furnace and calcine them at 1150℃ for 3 hours at a rate of 2~3℃ / min to allow the sol to react in situ and densify, thus obtaining modified silicon carbide ceramic bricks.

[0042] Appendix Figure 1 The image shows the X-ray diffraction (XRD) pattern of the modified silicon carbide ceramic filter brick coating prepared in Example 1 of this invention. Figure 1As shown, in addition to the strong diffraction peaks belonging to the main crystalline phase 3C-SiC of the matrix observed near 2θ = 35.6°, 41.4°, 60.0°, and 71.8°, and the diffraction peaks belonging to the β-Sialon bonding phase near 33.4° and 36.0°, obvious diffraction peaks belonging to the coating phase also appeared in the spectrum. Specifically, characteristic diffraction peaks corresponding to β-Y2Si2O7 appeared at 2θ = 29.5°, 31.2°, 34.1°, and 48.5°, with sharp peak shapes and no obvious amorphous silica dispersion peaks. This proves that the yttrium silicate coating was successfully formed on the surface of a porous silicon carbide substrate after impregnation with the weakly acidic composite sol and calcination.

[0043] Example 2

[0044] (1) Weigh out: 40 kg of coarse SiC particles with a particle size of 300~400 μm and 15 kg of fine SiC powder with a particle size of 15-30 μm; 25 kg of Sialon powder (which includes 14 kg of metallic silicon powder, 7 kg of α-Al2O3 micro powder, and 4 kg of AlN powder); 10 kg of YSZ short fibers; 8 kg of modified starch as a pore-forming agent; and 2 kg of PVA powder as a high-temperature binder. After mixing the above dry materials evenly, add water (15 kg) accounting for 15% of the total weight of the dry materials and knead thoroughly. Extrude the mixture through a vacuum extruder to form a honeycomb porous filter brick.

[0045] (2) The green body was dried at 100℃ for 24 hours. The dried green body was placed in a sintering furnace and heated to 500℃ at a rate of 1~2℃ / min and held for 5 hours. Then, a vacuum was drawn and the temperature was increased to 1480℃ at a rate of 5℃ / min under a nitrogen atmosphere of 0.1MPa and held for 8 hours for reaction sintering. After cooling, a porous matrix was obtained.

[0046] (3) Measure 200 mL of 0.5 mol / L yttrium nitrate aqueous solution (containing 0.1 mol yttrium) and 24.96 g of tetraethyl orthosilicate (TEOS) in a molar ratio of Y:Si = 1:1.2 and dissolve in 500 mL of anhydrous ethanol. Add citric acid to adjust the pH to 3.0. Stir at room temperature for 1 hour and let stand for 24 hours to obtain a composite sol. Place the porous matrix in a vacuum impregnation tank and evacuate to -0.09 MPa. Then, inject the composite sol until the matrix is ​​submerged. Return to normal pressure and maintain impregnation for 35 minutes.

[0047] (4) Take out the impregnated filter bricks, rotate them at a low speed of 200~300r / min for 3~5 minutes, dry them at 120℃ for 6 hours, and then put them into a muffle furnace. In an air atmosphere, heat them to 1200℃ at 3℃ / min and calcine them for 2 hours to obtain modified silicon carbide ceramic bricks.

[0048] Example 3:

[0049] (1) Weigh out: 45 kg of coarse SiC particles with a particle size of 300~400 μm and 20 kg of fine SiC powder with a particle size of 15-30 μm; 20 kg of Sialon powder (including 12 kg of metallic silicon powder, 5 kg of α-Al2O3 micro powder, and 3 kg of AlN powder); 6 kg of YSZ short fibers; 14 kg of PMMA microspheres as a pore-forming agent; and 5 kg of PVA powder as a high-temperature binder. Mix with 16 kg of deionized water. Extrude into honeycomb porous filter bricks using a vacuum extruder.

[0050] (2) The green body is dried at 100℃ for 24 hours. The dried green body is placed in a sintering furnace and heated to 550℃ at a rate of 1~2℃ / min and held for 4 hours. Then, a vacuum is drawn and the temperature is raised to 1550℃ at a rate of 4℃ / min under a nitrogen atmosphere of 0.1MPa and held for 4 hours. After cooling, a high-strength porous matrix is ​​obtained.

[0051] (3) Measure 200 mL of 0.5 mol / L yttrium nitrate aqueous solution (containing 0.1 mol yttrium) and mix it with 20.8 g of tetraethyl orthosilicate (TEOS) at a molar ratio of Y:Si = 1:1. Dissolve the mixture in 500 mL of anhydrous ethanol, adjust the pH to 2.5 with dilute nitric acid, stir at room temperature for 1 hour, and let it stand for 24 hours to obtain a composite sol. Place the porous matrix in a vacuum impregnation tank, evacuate to -0.09 MPa, and then inject the composite sol until the matrix is ​​submerged; restore to normal pressure and maintain impregnation for 30 minutes.

[0052] (4) Take out the impregnated filter bricks, rotate them at a low speed of 200~300r / min for 3~5 minutes, dry them at 120℃ for 6 hours, put them into a muffle furnace, and then calcine them in an air furnace at 1100℃ for 4 hours to obtain modified silicon carbide ceramic bricks.

[0053] Example 4

[0054] The difference between Example 4 and Example 1 is that, based on the formulation of Example 1, the amount of YSZ short fiber is reduced from 8 kg (about 8%) to 2 kg (about 2%), and the remaining 6 kg is replaced with SiC coarse aggregate. Other operations are the same as in Example 1.

[0055] Example 5

[0056] The difference between Example 5 and Example 1 is that, based on the formulation of Example 1, the amount of YSZ short fiber is increased from 8 kg to 15 kg (accounting for about 15%), and 7 kg of SiC coarse aggregate is reduced. Other operations are the same as in Example 1.

[0057] Comparative Example 1:

[0058] The difference between Comparative Example 1 and Example 1 is that 18 kg of Sialon powder was replaced with an equal mass of 18 kg of α-Al₂O₃ micro powder. The remaining components and processes remained unchanged.

[0059] Comparative Example 2

[0060] The difference between Comparative Example 2 and Example 1 is that 18 kg of Sialon powder was replaced with an equal mass of 18 kg of AlN powder. The remaining components and processes remained unchanged.

[0061] Comparative Example 3

[0062] Comparative Example 3 differs from Example 1 in that 8 kg of YSZ short fibers were replaced with an equal mass of 8 kg of mullite fibers. All other formulations and processes are identical to those in Example 1.

[0063] Comparative Example 4: Compared to Example 1, the substrate preparation for Comparative Example 4 was exactly the same as in Example 1. The difference was that in the coating preparation step, the mixed sol of yttrium nitrate [Y(NO3)3] and silica sol was replaced with pure silica sol (prepared by hydrolysis of tetraethyl orthosilicate TEOS only). The remaining operations were the same as in Example 1.

[0064] Comparative Example 5

[0065] Comparative Example 5 differs from Example 1 in that the substrate preparation follows exactly the same procedure as in Example 1. In the coating preparation step, a pure YSZ coating is used. All other processes remain unchanged.

[0066] Comparative Example 6

[0067] The difference between Comparative Example 6 and Example 1 is that the filter brick substrate was prepared according to steps (1) and (2) of Example 1, and then no subsequent coating treatment was performed. Other operations were the same as in Example 1.

[0068] Comparative Example 7

[0069] The difference between Comparative Example 7 and Example 1 is that yttrium nitrate and tetraethyl orthosilicate (TEOS) were mixed at a molar ratio of Y:Si = 1:3, while the other operations were the same as in Example 1.

[0070] Comparative Example 8

[0071] The difference between Comparative Example 8 and Example 1 is that yttrium nitrate and tetraethyl orthosilicate (TEOS) were mixed at a molar ratio of Y:Si = 3:1, while the other operations were the same as in Example 1.

[0072] Comparative Example 9

[0073] The difference between Comparative Example 9 and Example 1 is that the pH in step (3) is adjusted to 5.0, while the other operations are the same as in Example 1.

[0074] Table 1

[0075]

[0076] Comparative Examples 1 and 2 failed due to cracking during the thermal shock test, so no subsequent high-temperature corrosion test was conducted.

[0077] Compressive strength: Tested using a universal testing machine in accordance with GB / T8489-2006 standard.

[0078] Apparent porosity: The apparent porosity (%) of the final filter brick product after coating impregnation and calcination was tested using a mercury porosimeter (MIP).

[0079] Initial air permeability resistance: At room temperature (25℃), the filter brick sample was placed in a wind tunnel test bench, and the oncoming wind speed was set to 2m / min. The pressure drop (Pa) of the gas before and after passing through the filter brick was measured using a micro differential pressure gauge. The lower the resistance, the smoother the filtered airflow.

[0080] Thermal shock stability: The sample was heated to 1100℃ and held at that temperature for 30 minutes, then rapidly immersed in 20℃ cold air (wind speed 10m / s) to cool to room temperature. This constitutes one thermal cycle. After 50 cycles, the remaining compressive strength was tested, and the strength retention rate was calculated.

[0081] High-temperature corrosion resistance testing: Simulated high-temperature flue gas with the following composition: N2 (carrier gas); 5% O2; 10% HCl; 2000 ppm SO2, and alkali metal vapor with a concentration of approximately 500 ppm was generated by heating a NaCl / KCl mixed salt (molar ratio 1:1). The mixture was continuously exposed at 1000℃ for 500 hours. The weight change rate before and after corrosion was recorded (negative values ​​represent matrix erosion and dissolution, positive values ​​represent trace oxidation or salt deposition), and the increase in air permeability resistance after 500 hours of corrosion.

[0082] Corrosion resistance analysis: After 500 hours of corrosion by high-concentration alkali metals and acidic gases at 1000℃, the uncoated Comparative Example 6 was severely corroded, with a weight decrease of 14.2%, and the generated alkali metal silicate glass phase blocked the pores (resistance increased by 300%). Comparative Example 4, using a pure silica sol coating, suffered from collapse and blockage due to the easy reaction of free SiO2 with alkali metals; while Comparative Example 5, using a conventional YSZ coating, showed insufficient acid and alkali resistance. The filter bricks prepared in Examples 1-3 effectively isolated the corrosive media at high temperatures, with almost no weight change and a resistance increase rate controlled within 8%. Comparative Examples 7 and 8 demonstrated the necessity of limiting the Y:Si molar ratio to 1:1~1:1.2. Excess silicon reduces corrosion resistance; excessive yttrium causes microscopic peeling of the coating during thermal shock.

[0083] In Comparative Example 9, adjusting the pH of the sol to 5.0 directly caused the apparent porosity of the filter brick to drop sharply to 25.4%, and the initial air permeability resistance to rise to 1250 Pa (loss of filtration function). This indicates that pH 2.5~3.5 is an important condition for ensuring the permeability of the sol.

[0084] As shown in Examples 4 and 5, when the proportion of YSZ short fibers is less than 5%, the toughening effect is insufficient, and the strength retention rate after thermal shock decreases to 68.7%. Conversely, an excessively high proportion (15% in Example 5) leads to a decrease in the initial density of the matrix and a lower initial strength. Comparative Example 3 uses conventional mullite fibers, which are prone to phase transformation degradation under high-temperature alkaline atmospheres, resulting in a loss of toughening effect. This invention uses 5% to 10% YSZ short fibers, combining initial strength with thermal shock stability.

[0085] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A modified silicon carbide ceramic filter brick resistant to high temperature and acid corrosion, characterized in that, Including porous ceramic substrate and anti-corrosion coating; The formulation for preparing the porous ceramic matrix comprises, by mass percentage, the following components: Silicon carbide aggregate: 50%~65%; Sialon powder: 15%~30%; Yttrium-stabilized zirconia (YSZ) short fibers: 5%~10%; Pore-forming agent: 5%~15%; High-temperature adhesive: 2%~5%; The anti-corrosion coating is obtained by vacuum impregnation of a yttrium-silicon composite sol with a yttrium to Si molar ratio of 1:1 to 1:1.2, followed by calcination.

2. The modified silicon carbide ceramic filter brick resistant to high temperature and acid corrosion according to claim 1, characterized in that, The components of the Sialon powder, by mass percentage, include: 50%~60% silicon metal powder, 25%~35% α-alumina powder, and 10%~20% aluminum nitride powder.

3. The modified silicon carbide ceramic filter brick resistant to high temperature and acid corrosion according to claim 1, characterized in that, The silicon carbide (SiC) aggregate consists of coarse particles and fine powder, wherein the coarse particles have a particle size of 200~500 μm and account for 35%~45% of the total weight of the matrix formulation; the fine powder has a particle size of 10~45 μm and accounts for 15%~20% of the total weight of the matrix formulation.

4. The modified silicon carbide ceramic filter brick resistant to high temperature and acid corrosion according to claim 1, characterized in that, The length of the yttrium-stabilized zirconia (YSZ) short fibers is 2-5 mm.

5. The modified silicon carbide ceramic filter brick resistant to high temperature and acid corrosion according to claim 1, characterized in that, The pore-forming agent is polymethyl methacrylate (PMMA) microspheres or modified starch; the high-temperature binder is polyvinyl alcohol (PVA).

6. The method for preparing the high-temperature resistant and acid-corrosion resistant modified silicon carbide ceramic filter brick according to any one of claims 1-5, characterized in that: (1) The silicon carbide aggregate, Sialon powder, YSZ short fiber, pore-forming agent and high-temperature binder are dry mixed evenly, water is added for kneading, and the mixture is extruded or machine-pressed and dried to obtain a porous filter brick green body. (2) The dried green body is placed in a sintering furnace and heated to 450℃~550℃ at a rate of 1~2℃ / min and held for 4~6 hours. Then it is placed in a nitrogen atmosphere and heated to 1450℃~1550℃ and held for 4~8 hours to obtain a porous matrix. (3) Mix soluble yttrium salt and tetraethyl orthosilicate in anhydrous ethanol, control the molar ratio of yttrium to silicon to be 1:1 ~ 1:1.2, and add an acid regulator to control the pH value of the system to be 2.5~3.

5. Stir and let stand for aging to obtain yttrium-silicon composite sol; put the porous matrix obtained in step (2) into a vacuum impregnation tank, evacuate to below -0.09MPa, inject the above composite sol, and then restore normal pressure to allow the sol to enter the interior of the filter brick; (4) Take out the impregnated filter bricks, rotate them at a low speed of 200~300 r / min for 3~5 minutes, dry them, place them in an air atmosphere, and calcine them at a rate of 2~3 ℃ / min to 1100℃~1200℃ for 2~4 hours to obtain modified silicon carbide ceramic filter bricks.

7. The method for preparing the high-temperature resistant and acid-corrosion-resistant modified silicon carbide ceramic filter brick according to claim 6, characterized in that: In step (3), the soluble yttrium salt is yttrium nitrate or yttrium acetate.

8. The method for preparing the high-temperature and acid-corrosion-resistant modified silicon carbide ceramic filter brick according to claim 6, characterized in that: The acid regulator is dilute nitric acid or citric acid.

9. The application of the modified silicon carbide ceramic filter brick with high temperature and acid corrosion resistance according to any one of claims 1-5 in high temperature gas purification and separation.

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