A method for preparing a foam ceramic filter by using all components and large amount of waste chrome corundum

Abstract

The application provides a method for preparing a foamed ceramic filter from waste chrome corundum with full components and a large amount of utilization, and relates to the field of foamed ceramics. The method comprises the following steps: grinding waste chrome corundum, and then screening the waste chrome corundum through a 200-mesh screen to obtain coarse particles and fine particles; mixing first raw materials, granulating, and then performing first sintering, first cooling and first crushing to obtain first powder; mixing second raw materials, performing second sintering, second cooling and second crushing to obtain second powder; mixing the first powder and the second powder, performing third sintering, third cooling and third crushing to obtain third powder; mixing the third powder and water to obtain slurry, impregnating the slurry with soft polyurethane foam as a carrier, and then performing pressing and drying to obtain a blank; and performing fourth sintering and fourth cooling on the blank to obtain a foamed ceramic filter. The method provided by the application can use waste chrome corundum with full components and in a large amount, and effectively improves the utilization rate of waste chrome corundum.

Description

Technical Field

[0001] This application relates to the field of foam ceramics, and more particularly to a method for preparing foam ceramic filters using waste chromium corundum with a large amount of all components. Background Technology

[0002] The main mineral composition of chromium corundum is α-Al₂O₃-Cr₂O₃ solid solution. Refractory materials prepared from chromium corundum can be used as linings for glass kilns, cover bricks for glass drawing slurry flow channels, and back linings for molten iron pretreatment devices, waste incinerators, and pressurized coal-water slurry gasifiers. Waste chromium corundum mainly comes from waste refractory materials in the above-mentioned scenarios.

[0003] The main raw material for foam ceramics is alumina. Waste chromium corundum contains a large amount of alumina. Therefore, recycling waste chromium corundum to prepare foam ceramics is one way to reuse it as a resource.

[0004] The main application of alumina foam ceramics is in the preparation of foam ceramic filters for filtering molten aluminum. However, when using waste chromium corundum as a raw material to prepare foam ceramic filters for filtering molten aluminum, there are many problems, such as poor filtration effect, easy introduction of impurities such as chromium, and inability to use waste chromium corundum as a raw material in large quantities throughout the entire process.

[0005] Therefore, it is necessary to study a method to utilize waste chromium corundum with large amounts of all components to prepare foam ceramic filters with good filtration effect and without introducing impurities. Summary of the Invention

[0006] The purpose of this application is to provide a method for preparing foam ceramic filters using waste chromium corundum with a large amount of all components, so as to solve the above-mentioned problems.

[0007] To achieve the above objectives, this application adopts the following technical solution:

[0008] A method for preparing foam ceramic filters using waste chromium corundum with high dosage of all components includes:

[0009] Waste chromium corundum is ground and then sieved through a 200-mesh sieve to obtain coarse and fine particles;

[0010] The first raw material is mixed, granulated, and then subjected to a first sintering, followed by a first cooling and a first pulverization to obtain a first powder. The first raw material, calculated based on its total mass of 100%, includes: 60-80% coarse particles, 5-10% silica powder, 1-5% zirconium oxide powder, 1-5% alumina powder, 1-5% polyethylene glycol, and 10-15% polyoxymethylene dimethyl ether. The first sintering temperature is 800-1000℃.

[0011] It should be noted that polyethylene glycol (PEG) acts as a medium between coarse particles and silica powder, zirconium oxide powder, and alumina powder. Granulation on this basis can avoid the defect caused by the coarse particles' inability to react uniformly with other raw materials during sintering. This defect would prevent the first powder from fully utilizing the complex phase containing lanthanum and cerium elements generated during mixing and sintering with the second powder, ultimately leading to a large amount of impurities such as chromium from the coarse particles entering the molten aluminum and contaminating it. Polyoxymethylene dimethyl ether (DMMn, where n is generally 2-6) acts as a solvent, facilitating the granulation of other components, enhancing the aforementioned effects of PEG, and preventing PEG residue after sintering. The first sintering temperature should not be too high, as excessively high temperatures increase the difficulty of pulverization and reduce the uniformity of the first powder.

[0012] In addition, the particle size of coarse particles is generally between 100-200 mesh. The particle size of the granulated particles is generally 5-10 mm.

[0013] Optionally, the first raw material, calculated based on its total mass (100%), can have the following amounts: coarse particles (60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80% or between 60% and 80%); silica powder (5%, 6%, 7%, 8%, 9%, 10% or between 5% and 10%); and zirconium oxide powder (1%, 2%, 3%, 4%). The amount of alumina powder can be any value between 1%, 2%, 3%, 4%, 5%, or 1-5%, the amount of polyethylene glycol can be any value between 1%, 2%, 3%, 4%, 5%, or 1-5%, and the amount of polyoxymethylene dimethyl ether can be any value between 10%, 11%, 12%, 13%, 14%, 15%, or 10-15%. The first sintering temperature can be any value between 800℃, 850℃, 900℃, 950℃, 1000℃, or 800-1000℃.

[0014] The second raw material is mixed, subjected to a second sintering, followed by a second cooling and a second pulverization to obtain a second powder; the second raw material, calculated based on its total mass of 100%, includes: 95-98% fine particles, 1-3% lanthanum oxide, and 1-3% cerium oxide; the second sintering temperature is 1000-1200℃;

[0015] If the second sintering temperature is too low, lanthanum oxide and cerium oxide will not be able to function properly; if the temperature is too high, energy consumption will increase, the difficulty of pulverization will increase, and the uniformity of the first powder will deteriorate.

[0016] Optionally, the second raw material, calculated based on its total mass of 100%, can have the following parameters: the amount of fine particles can be any value between 95%, 96%, 97%, 98%, or 95-98%; the amount of lanthanum oxide can be any value between 1%, 2%, 3%, or 1-3%; the amount of cerium oxide can be any value between 1%, 2%, 3%, or 1-3%; and the second sintering temperature can be any value between 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, or 1000-1200℃.

[0017] The first powder and the second powder are mixed, subjected to a third sintering, followed by a third cooling and a third pulverization to obtain a third powder. The third sintering includes: sintering at 1200℃ for 1-2 hours, then rapidly cooling to room temperature within 10 minutes, then heating to 600℃ for 0.5-1 hours and holding for 1-2 hours; then heating to 1000℃ for 4-6 hours and holding for 12-24 hours; and then heating to 1600℃ for 1-2 hours and holding for 1-2 hours.

[0018] In the third sintering process, 1200℃ is used for pre-sintering, followed by rapid cooling and then programmed temperature rise sintering. This process allows for the re-merging of coarse and fine particles after separate treatment, achieving full utilization of all components. At the same time, it improves the uniformity of the material and avoids local defects and cracking in the product.

[0019] The first, second, and third sintering processes effectively increase the maximum operating temperature of the resulting ceramic filter.

[0020] The third powder is mixed with water to obtain a slurry, which is then impregnated with a soft polyurethane foam carrier, and then pressed and dried to obtain a blank.

[0021] The blank is subjected to a fourth sintering and a fourth cooling to obtain a foam ceramic filter; the fourth sintering temperature is 1200-1400℃.

[0022] Optionally, the fourth sintering temperature can be any value between 1200℃, 1250℃, 1300℃, 1350℃, 1400℃ or 1200-1400℃.

[0023] Preferably, the mass ratio of the first powder to the second powder is 1:(1-3).

[0024] Optionally, the mass ratio of the first powder to the second powder can be any value between 1:1, 1:2, 1:3 or 1:(1-3).

[0025] Preferably, the first cooling, the second cooling, and the third cooling are all natural cooling.

[0026] Preferably, the particle size of the first powder, the second powder, and the third powder is independently less than or equal to 200 mesh.

[0027] Preferably, the solid content of the slurry is 50-80 wt%.

[0028] Optionally, the solid content of the slurry can be any value between 50wt%, 60wt%, 70wt%, 80wt%, or 50-80wt%.

[0029] Preferably, the flexible polyurethane foam has a pore size of 10-50 PPI.

[0030] Optionally, the pore size of the flexible polyurethane foam can be any value between 10 PPI, 20 PPI, 30 PPI, 40 PPI, 50 PPI, or 10-50 PPI.

[0031] Preferably, the drying temperature is between room temperature and 100°C.

[0032] Optionally, the drying temperature can be any value between room temperature, 30, 40, 50, 60, 70, 80, 90, 100, or room temperature to 100°C.

[0033] Preferably, the first sintering, the second sintering, and the third sintering are all carried out in an air atmosphere.

[0034] Preferably, the sintering times for the first, second, and fourth sintering processes are each 1-2 hours.

[0035] Preferably, the fourth cooling rate is 100-200℃ / h.

[0036] The cooling rate should not be too fast, otherwise it will cause the foam ceramic filter structure to become unstable or even crack.

[0037] Optionally, the times for the first sintering, the second sintering, and the fourth sintering can each be independently set to any value between 1h, 1.5h, 2h, or 1-2h, and the fourth cooling rate can be set to any value between 100℃ / h, 150℃ / h, 200℃ / h, or 100-200℃ / h.

[0038] Compared with the prior art, the beneficial effects of this application include:

[0039] This application provides a method for preparing foam ceramic filters using waste chromium corundum with high-volume full-component admixture. First, the waste chromium corundum is ground and graded. Coarse particles are granulated with silica powder, zirconium oxide powder, alumina powder, polyethylene glycol, and polyoxymethylene dimethyl ether, and then sintered in a first sintering process to effectively utilize the coarse particles. Fine particles are mixed with lanthanum oxide and cerium oxide for a second sintering process. This activates the alumina in the fine particles and utilizes the complex oxides formed by lanthanum oxide and cerium oxide with chromium to prevent melting during use. The first and second powders are mixed and sintered in a third sintering process to re-merge the separately treated coarse and fine particles, improving material uniformity and preventing local defects and cracking. Finally, the third powder is mixed with water to obtain a slurry, which is then impregnated with flexible polyurethane foam. Excess slurry is pressed and extruded, followed by a fourth sintering process to obtain a foam ceramic filter with good filtration performance, no impurities introduced, and long service life. Furthermore, due to its good high-temperature resistance, the foam ceramic filter of this application can be manufactured into large-size products (maximum 1.5m). 2 ). Detailed Implementation

[0040] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0041] The waste chromium corundum used in the embodiments of this application is the lining of a waste glass kiln.

[0042] Example 1

[0043] This embodiment provides a method for preparing a foam ceramic filter using waste chromium corundum with a large amount of all components, specifically including the following steps:

[0044] Waste chromium corundum is ground and then sieved through a 200-mesh sieve to obtain coarse particles (oversize) and fine particles (undersize).

[0045] 600g of coarse particles, 100g of silica powder, 50g of zirconium oxide powder, 50g of alumina powder, 50g of polyethylene glycol, and 150g of polyoxymethylene dimethyl ether are mixed and granulated to obtain particles of 5-10mm. Then, the particles are sintered at 1000℃ in air for 2 hours, followed by natural cooling and pulverization. The resulting powder is then sieved to obtain a first powder with a particle size of less than or equal to 200 mesh.

[0046] 950g of fine particles, 20g of lanthanum oxide, and 30g of cerium oxide were mixed and sintered at 1200℃ for 2 hours in air. Then, the mixture was naturally cooled, pulverized, and sieved to obtain a second powder with a particle size of less than or equal to 200 mesh.

[0047] The first powder and the second powder are mixed at a mass ratio of 1:1, and then sintered in air. After that, they are naturally cooled and pulverized in the third stage. The mixture is then sieved to obtain a third powder with a particle size of less than or equal to 200 mesh. The third sintering process includes: sintering at 1200℃ for 2 hours, then rapidly cooling to room temperature within 10 minutes, then heating up to 600℃ for 1 hour and holding for 2 hours; then heating up to 1000℃ for 4 hours and holding for 12 hours; and then heating up to 1600℃ for 1 hour and holding for 1 hour.

[0048] The third powder and water are mixed to obtain a slurry with a solid content of 80wt%. The slurry is impregnated with a soft polyurethane foam with a pore size of 20PPI, and then pressed and dried at room temperature to obtain a blank. The blank is sintered in air at 1400℃ for 2h and cooled at a cooling rate of 100℃ / h to obtain a foam ceramic filter.

[0049] Example 2

[0050] This embodiment provides a method for preparing a foam ceramic filter using waste chromium corundum with a large amount of all components, specifically including the following steps:

[0051] Waste chromium corundum is ground and then sieved through a 200-mesh sieve to obtain coarse particles (oversize) and fine particles (undersize).

[0052] 700g of coarse particles, 95g of silica powder, 45g of zirconium oxide powder, 45g of alumina powder, 15g of polyethylene glycol, and 100g of polyoxymethylene dimethyl ether are mixed and granulated to obtain particles of 5-10mm. Then, the particles are sintered at 800℃ for 1.5h in air atmosphere, followed by natural cooling and first crushing. The particles are then sieved to obtain a first powder with a particle size of less than or equal to 200 mesh.

[0053] 980g of fine particles, 10g of lanthanum oxide, and 10g of cerium oxide were mixed and sintered at 1100℃ for 1 hour in air atmosphere. Then, the mixture was naturally cooled, pulverized, and sieved to obtain a second powder with a particle size of less than or equal to 200 mesh.

[0054] The first powder and the second powder are mixed at a mass ratio of 1:3, and then sintered in air. After that, they are naturally cooled and pulverized in the third stage. The mixture is then sieved to obtain a third powder with a particle size of less than or equal to 200 mesh. The third sintering process includes: sintering at 1200℃ for 1 hour, then rapidly cooling to room temperature within 5 minutes, then heating to 600℃ for 0.5 hours and holding for 1 hour; then heating to 1000℃ for 5 hours and holding for 18 hours; and then heating to 1600℃ for 2 hours and holding for 2 hours.

[0055] The third powder and water are mixed to obtain a slurry with a solid content of 60 wt%. The slurry is impregnated with a soft polyurethane foam with a pore size of 10 PPI, and then pressed and dried at room temperature to obtain a blank. The blank is sintered in air at 1200℃ for 1.5 h and cooled at a cooling rate of 150℃ / h to obtain a foam ceramic filter.

[0056] Example 3

[0057] This embodiment provides a method for preparing a foam ceramic filter using waste chromium corundum with a large amount of all components, specifically including the following steps:

[0058] Waste chromium corundum is ground and then sieved through a 200-mesh sieve to obtain coarse particles (oversize) and fine particles (undersize).

[0059] 800g of coarse particles, 50g of silica powder, 10g of zirconium oxide powder, 10g of alumina powder, 10g of polyethylene glycol, and 120g of polyoxymethylene dimethyl ether are mixed and granulated to obtain particles of 5-10mm. Then, the particles are sintered at 1000℃ in air for 2 hours, followed by natural cooling and pulverization. The resulting powder is then sieved to obtain a first powder with a particle size of less than or equal to 200 mesh.

[0060] 955g of fine particles, 30g of lanthanum oxide, and 15g of cerium oxide were mixed and sintered at 1000℃ for 2 hours in air atmosphere. Then, the mixture was naturally cooled, pulverized, and sieved to obtain a second powder with a particle size of less than or equal to 200 mesh.

[0061] The first powder and the second powder are mixed at a mass ratio of 1:2, and then sintered in air. After that, they are naturally cooled and pulverized in the third stage. The mixture is then sieved to obtain a third powder with a particle size of less than or equal to 200 mesh. The third sintering process includes: sintering at 1200℃ for 2 hours, then rapidly cooling to room temperature within 10 minutes, then heating up to 600℃ for 1 hour and holding for 2 hours; then heating up to 1000℃ for 4 hours and holding for 12 hours; and then heating up to 1600℃ for 1 hour and holding for 1 hour.

[0062] The third powder and water are mixed to obtain a slurry with a solid content of 50wt%. The slurry is impregnated with a soft polyurethane foam with a pore size of 20PPI, and then pressed and dried at room temperature to obtain a blank. The blank is sintered in air at 1300℃ for 2h and cooled at a cooling rate of 200℃ / h to obtain a foam ceramic filter.

[0063] Comparative Example 1

[0064] Unlike Example 1, the waste chromium corundum is not graded; it is ground and used directly to replace coarse and fine particles respectively.

[0065] Comparative Example 2

[0066] Unlike Example 1, the first raw material does not include polyethylene glycol and polyoxymethylene dimethyl ether.

[0067] Comparative Example 3

[0068] Unlike Example 1, the second raw material does not include lanthanum oxide and cerium oxide.

[0069] Comparative Example 4

[0070] Unlike Example 1, the third sintering was carried out directly at 1600°C.

[0071] Comparative Example 5

[0072] Unlike Example 1, the waste chromium corundum is not graded, and after grinding, it is directly mixed with chromium raw materials for the third sintering.

[0073] Comparative Example 6

[0074] Unlike Example 1, the first sintering is not performed; instead, the granulated material is directly mixed with the second powder for the third sintering.

[0075] Comparative Example 7

[0076] Unlike Example 1, a second sintering is not performed. Instead, the first powder is directly mixed with fine particles, lanthanum oxide, and cerium oxide for a third sintering.

[0077] Comparative Example 8

[0078] Unlike Example 1, a third sintering is not performed; instead, the first powder and the second powder are mixed to prepare a slurry.

[0079] The foam ceramic filters obtained in the examples and comparative examples are all designated as 50*50*20mm in size. They were tested using molten aluminum at a temperature of 700-750℃, with each filter capable of filtering 20kg of molten aluminum per test. The following were measured: chromium content detected in the molten aluminum after one filtration; maximum number of uses (regardless of filtration efficiency, only observing for cracking; data are rounded averages from multiple tests); filter porosity; and the percentage increase in tensile strength and elongation of the molten aluminum after one filtration. The test results are as follows:

[0080] Table 1 Test Results

[0081]

[0082]

[0083] As shown in Table 1 above, grading of waste chromium corundum, the use of polyethylene glycol and polyoxymethylene dimethyl ether, lanthanum oxide and cerium oxide, the third sintering method, and tertiary sintering all play important roles in solidifying impurities, especially chromium, in waste chromium corundum. The maximum number of uses, filter porosity, and percentage increase in tensile strength and elongation of molten aluminum in the comparative example all decreased to varying degrees compared to the example, indicating that the method provided in this application has good high-temperature strength and stability, and excellent filtration performance (effectively improving the performance of aluminum after filtering out impurities).

[0084] It should be noted that the ceramic filter prepared by the method provided in this application can also be used for filtering other molten metals, such as molten steel, and can withstand temperatures up to 1800℃.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0086] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing a foam ceramic filter using waste chromium corundum with high dosage of all components, characterized in that, include: Waste chromium corundum is ground and then sieved through a 200-mesh sieve to obtain coarse and fine particles; The first raw material is mixed, granulated, and then sintered for the first time. It is then cooled and pulverized to obtain the first powder. The first raw material, calculated as 100% of its total mass, includes: 60-80% coarse particles, 5-10% silica powder, 1-5% zirconium oxide powder, 1-5% alumina powder, 1-5% polyethylene glycol, and 10-15% polyoxymethylene dimethyl ether. The first sintering temperature is 800-1000℃. The second raw material is mixed, sintered a second time, cooled a second time, and pulverized a second time to obtain the second powder. The second raw material, calculated by its own total mass as 100%, includes: 95-98% fine particles, 1-3% lanthanum oxide, and 1-3% cerium oxide. The temperature of the second sintering is 1000-1200℃. The first powder and the second powder are mixed, subjected to a third sintering, followed by a third cooling and a third pulverization to obtain a third powder. The third sintering includes: sintering at 1200℃ for 1-2 hours, then rapidly cooling to room temperature within 10 minutes, then heating to 600℃ for 0.5-1 hours and holding for 1-2 hours; then heating to 1000℃ for 4-6 hours and holding for 12-24 hours; and then heating to 1600℃ for 1-2 hours and holding for 1-2 hours. The third powder is mixed with water to obtain a slurry, which is then impregnated with a soft polyurethane foam carrier, and then pressed and dried to obtain a blank. The blank is subjected to a fourth sintering and a fourth cooling to obtain a foam ceramic filter; the temperature of the fourth sintering is 1200-1400℃. The mass ratio of the first powder to the second powder is 1:(1-3); The first cooling, the second cooling, and the third cooling are all natural cooling. The particle sizes of the first powder, the second powder, and the third powder are each independently less than or equal to 200 mesh; The solid content of the slurry is 50-80 wt%; The first sintering, the second sintering, and the third sintering are all carried out in an air atmosphere, and the fourth cooling rate is 100-200℃ / h.

2. The method for preparing a foam ceramic filter using waste chromium corundum with high dosage of all components according to claim 1, characterized in that, The flexible polyurethane foam has a pore size of 10-50 PPI.

3. The method for preparing a foam ceramic filter using waste chromium corundum with high dosage of all components according to claim 1, characterized in that, The drying temperature is from room temperature to 100°C.

4. The method for preparing a foam ceramic filter using waste chromium corundum with high dosage of all components according to claim 1, characterized in that, The sintering times for the first, second, and fourth sintering processes are each 1-2 hours.

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