Method for preparing foam ceramic filter by using waste chrome corundum multiple sintering

Abstract

The application provides a method for preparing a foam ceramic filter by multiple sintering of waste chrome corundum, and relates to the field of solid waste utilization. The method comprises the following steps: grinding the waste chrome corundum, and screening to obtain fine particles and coarse particles; mixing the fine particles with cerium oxide and lanthanum oxide to obtain a first mixture, and mixing the coarse particles with zirconium oxide and aluminum oxide to obtain a second mixture; mixing the mixtures with water, hydroxypropyl guar gum and solvent oil to obtain slurries; impregnating the second slurry on a soft polyurethane foam carrier, and then extruding and drying to obtain a first blank; impregnating the first slurry on the first blank, and then drying to obtain a second blank; impregnating the second slurry on the second blank, and then drying to obtain a third blank; sequentially performing first sintering, second sintering and third sintering on the third blank, and then cooling to obtain the foam ceramic filter. The method provided by the application can effectively utilize the waste chrome corundum to prepare the foam ceramic filter with excellent performance.

Description

Technical Field

[0001] This application relates to the field of solid waste utilization, and in particular to a method for preparing foam ceramic filters by multiple sintering of waste chromium corundum. Background Technology

[0002] Waste chromium corundum contains a large amount of alumina, and alumina is the main raw material for foam ceramics. Therefore, recycling waste chromium corundum to prepare foam ceramics is one of the ways to reuse it as a resource and dispose of solid waste.

[0003] In addition to α-alumina, waste chromium corundum also contains Cr2O3. The presence of chromium makes waste chromium corundum unsuitable for direct use in the preparation of foam ceramics. To avoid introducing chromium impurities and ensure filtration efficiency, only a very small amount can be added, which can easily lead to poor filtration performance and short service life. Summary of the Invention

[0004] The purpose of this application is to provide a method for preparing foam ceramic filters by multiple sintering of waste chromium corundum, so as to solve the above-mentioned problems.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] A method for preparing foam ceramic filters using waste chromium corundum through multiple sintering processes includes:

[0007] The waste chromium corundum was ground and sieved to obtain fine particles smaller than 0.15 mm and coarse particles of 0.15-0.3 mm.

[0008] The fine particles are mixed with cerium oxide and lanthanum oxide of the same particle size range to obtain a first mixture, and the coarse particles are mixed with zirconium oxide and alumina of the same particle size range to obtain a second mixture;

[0009] The first mixture and the second mixture are respectively mixed with water, hydroxypropyl guar gum and solvent oil to obtain a first slurry and a second slurry;

[0010] The second slurry is impregnated with flexible polyurethane foam as a carrier, then extruded and dried in the first stage to obtain a first blank; the first blank is then impregnated with the first slurry and dried in the second stage to obtain a second blank; the second blank is then impregnated with the second slurry and dried in the third stage to obtain a third blank.

[0011] The third blank is subjected to a first sintering, a second sintering, and a third sintering in sequence, and then cooled to obtain a foam ceramic filter; the highest temperature of the first sintering is 600-800℃, and the holding time is 6-8h; the highest temperature of the second sintering is 1000-1200℃, and the holding time is 3-5h; the highest temperature of the third sintering is 1300-1350℃, and the holding time is 1-2h.

[0012] Optionally, the maximum temperature of the first sintering can be any value between 600℃, 650℃, 700℃, 750℃, 800℃ or 600-800℃, and the holding time can be any value between 6h, 7h, 8h or 6-8h; the maximum temperature of the second sintering can be any value between 1000℃, 1050℃, 1100℃, 1150℃, 1200℃ or 1000-1200℃, and the holding time can be any value between 3h, 4h, 5h or 3-5h; the maximum temperature of the third sintering can be any value between 1300℃, 1310℃, 1320℃, 1330℃, 1340℃, 1350℃ or 1300-1350℃, and the holding time can be any value between 1h, 1.5h, 2h or 1-2h.

[0013] Preferably, the mass ratio of the fine particles, the cerium oxide, and the lanthanum oxide is 1:(0.05-0.1):(0.05-0.1), and the mass ratio of the coarse particles to the zirconium oxide and the alumina is 1:(0.1-0.5):(1-2).

[0014] Optionally, the mass ratio of the fine particles, the cerium oxide, and the lanthanum oxide can be 1:0.05:0.05, 1:0.08:0.05, 1:0.1:0.05, 1:0.05:0.08, 1:0.08:0.08, 1:0.1:0.08, 1:0.05:0.1, 1:0.08:0.1, 1:0.1:0.1, or 1:(0.05-0.1): The mass ratio of the coarse particles to the zirconium oxide and the alumina can be any value between (0.05-0.1), and can be any value between 1:0.1:1, 1:0.1:1.5, 1:0.1:2, 1:0.3:1, 1:0.3:1.5, 1:0.3:2, 1:0.5:1, 1:0.5:1.5, 1:0.5:2 or 1:(0.1-0.5):(1-2).

[0015] Preferably, the mass ratio of the first mixture, the water, the hydroxypropyl guar gum, and the solvent oil is 1:(5-10):(0.1-0.3):(1-2).

[0016] Optionally, the mass ratio of the first mixture, the water, the hydroxypropyl guar gum, and the solvent oil can be any value between 1:5:0.1:1, 1:8:0.2:1.5, 1:10:0.3:2, or 1:(5-10):(0.1-0.3):(1-2).

[0017] Preferably, the mass ratio of the second mixture, the water, the hydroxypropyl guar gum, and the solvent oil can be any value between 1:(10-20):(0.1-0.3):(1-2).

[0018] Optionally, the mass ratio of the second mixture, the water, the hydroxypropyl guar gum, and the solvent oil can be any value between 1:10:0.1:1, 1:15:0.2:1.5, 1:20:0.3:2, or 1:(10-20):(0.1-0.3):(1-2).

[0019] Preferably, the flexible polyurethane foam has a pore size of 10-30 PPI.

[0020] Optionally, the pore size of the flexible polyurethane foam can be any value between 10 PPI, 20 PPI, 30 PPI, or 10-30 PPI.

[0021] Preferably, the carrier is impregnated with the second slurry for 60-120 minutes, the first slurry is impregnated for 5-10 minutes, and the second blank is impregnated with the second slurry for 30-60 minutes.

[0022] Optionally, the time for the carrier to impregnate the second slurry can be any value between 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min or 60-120 min, the time for impregnating the first slurry can be any value between 5 min, 6 min, 7 min, 8 min, 9 min, 10 min or 5-10 min, and the time for the second blank to impregnate the second slurry can be any value between 30 min, 40 min, 50 min, 60 min or 30-60 min.

[0023] Preferably, the temperatures of the first drying, the second drying, and the third drying are each independently 25-50°C.

[0024] Optionally, the temperatures of the first drying, the second drying, and the third drying can each be independently any value between 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, or 25-50°C.

[0025] Preferably, the first sintering, the second sintering, and the third sintering are all heated to the maximum temperature at a uniform rate of 5-10℃ / min.

[0026] Optionally, the heating rate of the first sintering, the second sintering, and the third sintering can be any value between 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, or 5-10℃ / min.

[0027] Preferably, the first sintering, the second sintering, and the third sintering are all cooled to room temperature in the furnace after completion.

[0028] Preferably, the second sintering is repeated 2-4 times.

[0029] Optionally, the second sintering can be performed 2 times, 3 times, or 4 times.

[0030] Compared with the prior art, the beneficial effects of this application include:

[0031] The method for preparing foam ceramic filters using waste chromium corundum through multiple sintering provided in this application involves grinding and classifying the waste chromium corundum. Chromium in the fine particles is more likely to escape during use, therefore it needs to be mixed with cerium oxide and lanthanum oxide and calcined to form a complex oxide with stronger curing ability. Coarse particles have relatively lower requirements, so zirconium oxide is used for curing treatment, and alumina is added as a pure raw material. To further prevent chromium from escaping into the filtered aluminum liquid during use, the coarse particle slurry is impregnated first, followed by the fine particle slurry, and then the coarse particle slurry is impregnated again, so that the coarse particle slurry layer shields the fine particle layer. However, the interlayer bonding stability is lower after layered impregnation compared to the non-layered process and the two-layer process. Therefore, low-temperature sintering, medium-temperature sintering, and high-temperature sintering are required to improve the interlayer bonding strength and stability, thereby extending the service life. During multiple impregnations, it is necessary to improve the bonding strength between the multiple layers; therefore, hydroxypropyl guar gum is added during slurry preparation. The purpose of adding solvent oil is to improve the uniformity of the slurry, ensuring uniformity during impregnation and the filtration effect and service life during use. Detailed Implementation

[0032] 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.

[0033] It should be noted that the waste chromium corundum used in the embodiments of this application is recycled waste chromium corundum refractory bricks.

[0034] Example 1

[0035] This embodiment provides a method for preparing foam ceramic filters using waste chromium corundum through multiple sintering, specifically including the following steps:

[0036] Waste chromium corundum was ground and sieved to obtain fine particles smaller than 0.15 mm and coarse particles of 0.15-0.3 mm.

[0037] A first mixture is obtained by mixing fine particles with cerium oxide and lanthanum oxide of the same particle size range, and a second mixture is obtained by mixing coarse particles with zirconium oxide and alumina of the same particle size range; the mass ratio of fine particles, cerium oxide and lanthanum oxide is 1:0.08:0.08, and the mass ratio of coarse particles to zirconium oxide and alumina is 1:0.35:1.5.

[0038] The first mixture and the second mixture were mixed with water, hydroxypropyl guar gum, and solvent oil respectively to obtain the first slurry and the second slurry; the mass ratio of the first mixture, water, hydroxypropyl guar gum, and solvent oil was 1:6:0.2:1.5; the mass ratio of the second mixture, water, hydroxypropyl guar gum, and solvent oil was 1:15:0.2:1.5.

[0039] A flexible polyurethane foam with a pore size of 20 PPI was used as a carrier to impregnate a second slurry for 120 min, then extruded and subjected to a first drying to obtain a first preform; the first preform was then impregnated with the first slurry for 10 min and subjected to a second drying to obtain a second preform; the second preform was then impregnated with the second slurry for 60 min and subjected to a third drying to obtain a third preform; the first drying, second drying and third drying were all carried out at room temperature of 25°C;

[0040] The third blank was subjected to three sintering processes in sequence: first, second, and third sintering, followed by cooling to obtain a foam ceramic filter. The highest temperature for the first sintering was 700℃, with a holding time of 8 hours; the highest temperature for the second sintering was 1100℃, with a holding time of 4 hours; and the highest temperature for the third sintering was 1320℃, with a holding time of 1.5 hours. The temperature for each of the first, second, and third sintering processes was increased to the highest temperature at a uniform rate of 5℃ / min. After each sintering process, the blanks were cooled to room temperature in the furnace. The second sintering process was repeated three times.

[0041] Example 2

[0042] This embodiment provides a method for preparing foam ceramic filters using waste chromium corundum through multiple sintering, specifically including the following steps:

[0043] Waste chromium corundum was ground and sieved to obtain fine particles smaller than 0.15 mm and coarse particles of 0.15-0.3 mm.

[0044] A first mixture is obtained by mixing fine particles with cerium oxide and lanthanum oxide of the same particle size range, and a second mixture is obtained by mixing coarse particles with zirconium oxide and alumina of the same particle size range; the mass ratio of fine particles, cerium oxide and lanthanum oxide is 1:0.05:0.1, and the mass ratio of coarse particles to zirconium oxide and alumina is 1:0.1:2.

[0045] The first mixture and the second mixture were mixed with water, hydroxypropyl guar gum, and solvent oil respectively to obtain the first slurry and the second slurry; the mass ratio of the first mixture, water, hydroxypropyl guar gum, and solvent oil was 1:5:0.3:1; the mass ratio of the second mixture, water, hydroxypropyl guar gum, and solvent oil was 1:10:0.3:1.

[0046] A flexible polyurethane foam with a pore size of 10 PPI was used as a carrier to impregnate a second slurry for 60 minutes, then extruded and subjected to a first drying to obtain a first preform; the first preform was then impregnated with the first slurry for 5 minutes and subjected to a second drying to obtain a second preform; the second preform was then impregnated with the second slurry for 30 minutes and subjected to a third drying to obtain a third preform; the temperature of the first drying, the second drying and the third drying were all 50°C;

[0047] The third blank was subjected to three sintering processes in sequence: first, second, and third sintering, followed by cooling to obtain a foam ceramic filter. The maximum temperature for the first sintering was 600℃, with a holding time of 7 hours; the maximum temperature for the second sintering was 1000℃, with a holding time of 5 hours; and the maximum temperature for the third sintering was 1300℃, with a holding time of 2 hours. The temperature for each of the first, second, and third sintering processes was increased to the maximum temperature at a uniform rate of 8℃ / min. After each sintering process, the blanks were cooled to room temperature in the furnace. The second sintering process was repeated twice.

[0048] Example 3

[0049] This embodiment provides a method for preparing foam ceramic filters using waste chromium corundum through multiple sintering, specifically including the following steps:

[0050] Waste chromium corundum was ground and sieved to obtain fine particles smaller than 0.15 mm and coarse particles of 0.15-0.3 mm.

[0051] A first mixture is obtained by mixing fine particles with cerium oxide and lanthanum oxide of the same particle size range, and a second mixture is obtained by mixing coarse particles with zirconium oxide and alumina of the same particle size range; the mass ratio of fine particles, cerium oxide and lanthanum oxide is 1:0.1:0.05, and the mass ratio of coarse particles to zirconium oxide and alumina is 1:0.5:1.

[0052] The first mixture and the second mixture were mixed with water, hydroxypropyl guar gum, and solvent oil respectively to obtain the first slurry and the second slurry; the mass ratio of the first mixture, water, hydroxypropyl guar gum, and solvent oil was 1:10:0.1:2; the mass ratio of the second mixture, water, hydroxypropyl guar gum, and solvent oil was 1:20:0.1:2.

[0053] A flexible polyurethane foam with a pore size of 30 PPI was used as a carrier to impregnate a second slurry for 100 min, then extruded and subjected to a first drying to obtain a first preform; the first preform was then impregnated with the first slurry for 8 min and subjected to a second drying to obtain a second preform; the second preform was then impregnated with the second slurry for 40 min and subjected to a third drying to obtain a third preform; the temperature of the first drying, the second drying and the third drying were all 40℃;

[0054] The third blank was subjected to a first sintering, a second sintering, and a third sintering in sequence, and then cooled to obtain a foam ceramic filter. The maximum temperature for the first sintering was 800℃, and the holding time was 6 hours. The maximum temperature for the second sintering was 1200℃, and the holding time was 3 hours. The maximum temperature for the third sintering was 1350℃, and the holding time was 1 hour. The temperature for the first, second, and third sintering processes was increased to the maximum temperature at a uniform rate of 10℃ / min. After the first, second, and third sintering processes were completed, the blanks were cooled to room temperature in the furnace. The second sintering process was performed once.

[0055] Comparative Example 1

[0056] Unlike Example 1, waste chromium corundum was directly mixed with cerium oxide, lanthanum oxide, zirconium oxide, and aluminum oxide. The mixture was then mixed with water, hydroxypropyl guar gum, and solvent oil in the proportions of Example 1 to prepare the first slurry and the second slurry.

[0057] Comparative Example 2

[0058] Unlike Example 1, cerium oxide and lanthanum oxide are not used in the first mixture, and zirconium oxide and aluminum oxide are not used in the second mixture. Instead, fine and coarse particles are used directly to prepare the slurry.

[0059] Comparative Example 3

[0060] Unlike Example 1, hydroxypropyl guar gum and solvent oil were not used; instead, an equal amount of water was used.

[0061] The prepared filters have 25-30% cracking.

[0062] Comparative Example 4

[0063] Unlike Example 1, the impregnation sequence was adjusted to first slurry, second slurry, and first slurry.

[0064] Comparative Example 5

[0065] Unlike Example 1, only one third sintering is performed, without the first and second sintering.

[0066] The foam ceramic filters obtained in both the examples and comparative examples were prepared to a size of 30*30*20mm and tested with molten aluminum at a temperature of 700-750℃, with each filter filtering 20kg of molten aluminum per test. The following were measured: the detection of chromium in the molten aluminum after one filtration; the maximum number of uses (regardless of filtration efficiency, only observing for cracking); cracked filters prepared in the comparative example were directly removed, and only the uncracked portions were tested; data are averages from multiple tests, rounded to the nearest integer; and the percentage increase in tensile strength and elongation of the molten aluminum after one filtration. The test results are as follows:

[0067] Table 1 Test Results

[0068]

[0069] As shown in Table 1 above, the method provided in this application can effectively improve the filtration effect, inhibit the contamination of chromium elements on molten aluminum during use, and extend the service life.

[0070] 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.

Claims

1. A method for preparing foam ceramic filters using waste chromium corundum through multiple sintering processes, characterized in that, include: The waste chromium corundum was ground and sieved to obtain fine particles smaller than 0.15 mm and coarse particles of 0.15-0.3 mm. The fine particles are mixed with cerium oxide and lanthanum oxide of the same particle size range to obtain a first mixture, and the coarse particles are mixed with zirconium oxide and alumina of the same particle size range to obtain a second mixture; The first mixture and the second mixture are respectively mixed with water, hydroxypropyl guar gum and solvent oil to obtain a first slurry and a second slurry; The second slurry is impregnated with flexible polyurethane foam as a carrier, then extruded and dried in the first stage to obtain a first blank; the first blank is then impregnated with the first slurry and dried in the second stage to obtain a second blank; the second blank is then impregnated with the second slurry and dried in the third stage to obtain a third blank. The third blank is subjected to a first sintering, a second sintering, and a third sintering in sequence, and then cooled to obtain a foam ceramic filter; the highest temperature of the first sintering is 600-800℃, and the holding time is 6-8h; the highest temperature of the second sintering is 1000-1200℃, and the holding time is 3-5h; the highest temperature of the third sintering is 1300-1350℃, and the holding time is 1-2h. The mass ratio of the fine particles, the cerium oxide, and the lanthanum oxide is 1:(0.05-0.1):(0.05-0.1), and the mass ratio of the coarse particles, the zirconium oxide, and the alumina is 1:(0.1-0.5):(1-2).

2. The method for preparing a foam ceramic filter using waste chromium corundum through multiple sintering according to claim 1, characterized in that, The mass ratio of the first mixture, the water, the hydroxypropyl guar gum, and the solvent oil is 1:(5-10):(0.1-0.3):(1-2).

3. The method for preparing a foam ceramic filter using waste chromium corundum through multiple sintering according to claim 1, characterized in that, The mass ratio of the second mixture, the water, the hydroxypropyl guar gum, and the solvent oil is 1:(10-20):(0.1-0.3):(1-2).

4. The method for preparing a foam ceramic filter using waste chromium corundum through multiple sintering according to claim 1, characterized in that, The flexible polyurethane foam has a pore size of 10-30 PPI.

5. The method for preparing a foam ceramic filter using waste chromium corundum through multiple sintering according to claim 1, characterized in that, The carrier is impregnated with the second slurry for 60-120 minutes, the first slurry for 5-10 minutes, and the second blank is impregnated with the second slurry for 30-60 minutes.

6. The method for preparing a foam ceramic filter using waste chromium corundum through multiple sintering according to claim 1, characterized in that, The temperatures for the first drying, the second drying, and the third drying are each independently 25-50℃.

7. The method for preparing a foam ceramic filter using waste chromium corundum through multiple sintering according to claim 1, characterized in that, The first sintering, the second sintering, and the third sintering are all heated to the maximum temperature at a uniform rate of 5-10℃ / min.

8. The method for preparing a foam ceramic filter using waste chromium corundum through multiple sintering according to claim 1, characterized in that, After the first sintering, the second sintering, and the third sintering are completed, the furnace is cooled to room temperature.

9. The method for preparing a foam ceramic filter by multiple sintering of waste chromium corundum according to any one of claims 1-8, characterized in that, The second sintering process is repeated 2-4 times.

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