Method for recycling waste chrome corundum to prepare multi-layer foam ceramic filter

Abstract

The application provides a method for recycling waste chrome corundum to prepare a multilayer foam ceramic filter, 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; calcining to obtain a first powder and a second powder; mixing the first powder, water and polyacrylamide, and performing first stirring to obtain a first slurry; mixing the second powder, ethanol and solvent oil, and performing second stirring to obtain a second slurry; impregnating the first slurry in soft polyurethane foam as a carrier, and then performing extrusion and drying to obtain a first blank; impregnating the second slurry in the first blank again, and drying to obtain a second blank; and performing sintering and cooling on the second blank to obtain a foam ceramic filter. The method provided by the application fully recycles 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 multilayer foam ceramic filters by recycling waste chromium corundum. Background Technology

[0002] The main raw material of foam ceramics is alumina. Waste chromium corundum contains a large amount of alumina. 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 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.

[0004] Therefore, it is necessary to study the above-mentioned issues in order to achieve the effective utilization of waste chromium corundum. Summary of the Invention

[0005] The purpose of this application is to provide a method for preparing multilayer foam ceramic filters by recycling waste chromium corundum, so as to solve the above-mentioned problems.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] A method for preparing multilayer foam ceramic filters by recycling waste chromium corundum includes:

[0008] 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.

[0009] 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;

[0010] The first mixture is calcined at 1200-1400℃ to obtain a first powder, and the second mixture is calcined at 1000-1300℃ to obtain a second powder.

[0011] Optionally, the temperature of the first calcination can be any value between 1200℃, 1300℃, 1400℃ or 1200-1400℃, and the temperature of the second calcination can be any value between 1000℃, 1100℃, 1200℃, 1300℃ or 1000-1300℃.

[0012] The first powder, water, and polyacrylamide are mixed and stirred to obtain a first slurry; the second powder is mixed with ethanol and solvent oil and stirred to obtain a second slurry.

[0013] The main function of polyacrylamide is to improve the uniformity between two impregnations. At the same time, when combined with water and stirred for a short time (just a simple stirring is enough), it forms a relatively rough impregnation surface, which is beneficial for the second impregnation, thereby improving the interlayer stability.

[0014] The first slurry is impregnated with flexible polyurethane foam as a carrier, and then extruded and dried in the first stage to obtain a first blank; then the first blank is impregnated with the second slurry and dried in the second stage to obtain a second blank.

[0015] The second blank is sintered and cooled to obtain a foam ceramic filter.

[0016] Preferably, the mass ratio of the fine particles, the cerium oxide, and the lanthanum oxide is 1:(0.01-0.05):(0.01-0.05), and the mass ratio of the coarse particles to the zirconium oxide and the alumina is 1:(0.1-0.5):(1-3).

[0017] Optionally, the mass ratio of the fine particles, the cerium oxide, and the lanthanum oxide can be 1:0.01:0.01, 1:0.01:0.03, 1:0.01:0.05, 1:0.03:0.01, 1:0.03:0.03, 1:0.03:0.05, 1:0.05:0.01, 1:0.05:0.03, 1:0.05:0.05, or 1:(0.01-0.05) The mass ratio of the coarse particles to the zirconium oxide and the alumina can be any value between (0.01-0.05), and the mass ratio of the coarse particles to the zirconium oxide and the alumina can be any value between 1:0.01:1, 1:0.01:2, 1:0.01:3, 1:0.03:1, 1:0.03:2, 1:0.03:3, 1:0.05:1, 1:0.05:2, 1:0.05:3 or 1:(0.1-0.5):(1-3).

[0018] Preferably, the first calcination and the second calcination are each carried out independently for 1-5 hours.

[0019] Optionally, the times for the first calcination and the second calcination can each be independently 1h, 2h, 3h, 4h, 5h, or any value between 1 and 5h.

[0020] Preferably, the solid content of the first slurry is 40-60%, and the solid content of the second slurry is 20-30%.

[0021] Optionally, the solid content of the first slurry can be any value between 40%, 45%, 50%, 55%, 60%, or 40-60%, and the solid content of the second slurry can be any value between 20%, 25%, 30%, or 20-30%.

[0022] Preferably, the amount of polyacrylamide used is 0.01%-0.05% of the mass of the water.

[0023] Optionally, the amount of polyacrylamide used can be any value between 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or 0.01%-0.05% of the mass of the water.

[0024] Preferably, the volume ratio of ethanol to solvent oil is 1:(1-5).

[0025] Optionally, the volume ratio of ethanol to solvent oil can be any value between 1:1, 1:2, 1:3, 1:4, 1:5 or 1:(1-5).

[0026] Preferably, the first stirring speed is 500-1000 rpm, and the time is 5-10 seconds;

[0027] The second stirring speed is 100-300 rpm, and the time is 1-2 hours.

[0028] Optionally, the speed of the first stirring can be any value between 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, or 500-1000 rpm, and the time can be any value between 5s, 6s, 7s, 8s, 9s, 10s, or 5-10s.

[0029] The second stirring speed can be any value between 100 rpm, 200 rpm, 300 rpm, or 100-300 rpm, and the time can be any value between 1h, 1.5h, 2h, or 1-2h.

[0030] Preferably, the flexible polyurethane foam has a pore size of 10-30 PPI.

[0031] Optionally, the pore size of the flexible polyurethane foam can be any value between 10 PPI, 20 PPI, 30 PPI, or 10-30 PPI.

[0032] Preferably, the soaking time of the first slurry is 1-3 minutes, and the soaking time of the second slurry is 10-30 minutes.

[0033] Optionally, the soaking time of the first slurry can be any value between 1 min, 2 min, 3 min or 1-3 min, and the soaking time of the second slurry can be any value between 10 min, 20 min, 30 min or 10-30 min.

[0034] Preferably, the maximum sintering temperature is 1200-1400℃, and the time is 2-4 hours.

[0035] Optionally, the maximum sintering temperature can be any value between 1200℃, 1300℃, 1400℃ or 1200-1400℃, and the time can be any value between 2h, 3h, 4h or 2-4h.

[0036] Compared with the prior art, the beneficial effects of this application include:

[0037] The method for preparing multilayer foam ceramic filters from recycled waste chromium corundum provided in this application involves grinding and classifying the waste chromium corundum. Fine particles are more prone to escaping during use, therefore they need to be mixed with cerium oxide and lanthanum oxide and calcined to form complex oxides with stronger curing capabilities. Coarse particles have relatively lower requirements, so zirconium oxide is used for curing, and alumina is added as a pure raw material. To further prevent chromium from the fine particles from escaping into the filtered aluminum liquid during use, a first slurry formed from the first powder after calcination of the fine particles is first impregnated, dried, and then impregnated with a second slurry formed from the second powder after calcination of the coarse particles. This allows the coarse particle layer to provide some shielding effect on the fine particle layer. However, the interlayer bonding stability decreases after layered impregnation compared to the non-layered process. Therefore, water is used as a solvent and polyacrylamide as an additive for the first powder, and it is used after simple stirring to form a relatively rough surface on the carrier. The second material uses ethanol and solvent oil as solvents, and after long-term stirring, forms a second slurry with better uniformity and tending towards the first slurry. Based on the aforementioned rough surface, the interlayer bonding strength and stability are improved, thereby increasing the service life. Detailed Implementation

[0038] 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.

[0039] Example 1

[0040] This embodiment provides a method for preparing multilayer foam ceramic filters by recycling waste chromium corundum, specifically including the following steps:

[0041] 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.

[0042] 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.

[0043] The first mixture was calcined at 130°C to obtain the first powder, and the second mixture was calcined at 1200°C to obtain the second powder; the mass ratio of fine particles, cerium oxide and lanthanum oxide was 1:0.03:0.03, and the mass ratio of coarse particles to zirconium oxide and alumina was 1:0.3:2; the first calcination and the second calcination were both 4 hours.

[0044] The first powder, water, and polyacrylamide are mixed and stirred to obtain a first slurry; the second powder is mixed with ethanol and solvent oil and stirred to obtain a second slurry; the solid content of the first slurry is 50%, and the solid content of the second slurry is 25%; the amount of polyacrylamide used is 0.03% of the mass of water; the volume ratio of ethanol to solvent oil is 1:3; the first stirring speed is 800 rpm for 6 seconds; the second stirring speed is 200 rpm for 1.5 hours.

[0045] A first slurry is impregnated with flexible polyurethane foam as a carrier, then extruded and dried to obtain a first blank; the first blank is then impregnated with a second slurry and dried to obtain a second blank; the flexible polyurethane foam has a pore size of 20 PPI; the impregnation time of the first slurry is 2 min, and the impregnation time of the second slurry is 20 min;

[0046] The second blank is sintered and cooled to obtain a foam ceramic filter; the sintering process involves uniform heating, with a maximum temperature of 1300℃ and a time of 3 hours.

[0047] Example 2

[0048] This embodiment provides a method for preparing multilayer foam ceramic filters by recycling waste chromium corundum, specifically including the following steps:

[0049] 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.

[0050] 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.

[0051] The first mixture was calcined at 1200℃ to obtain the first powder, and the second mixture was calcined at 1300℃ to obtain the second powder; the mass ratio of fine particles, cerium oxide and lanthanum oxide was 1:0.01:0.05, and the mass ratio of coarse particles to zirconium oxide and alumina was 1:0.1:3; the first calcination and the second calcination were both 3 hours.

[0052] A first powder, water, and polyacrylamide are mixed and stirred to obtain a first slurry. A second powder is mixed with ethanol and solvent oil and stirred to obtain a second slurry. The solid content of the first slurry is 40%, and the solid content of the second slurry is 30%. The amount of polyacrylamide used is 0.01% of the mass of water. The volume ratio of ethanol to solvent oil is 1:5. The stirring speed for the first stirring is 500 rpm for 10 seconds. The stirring speed for the second stirring is 100 rpm for 2 hours.

[0053] A first slurry is impregnated with flexible polyurethane foam as a carrier, then extruded and dried to obtain a first blank; the first blank is then impregnated with a second slurry and dried to obtain a second blank; the flexible polyurethane foam has a pore size of 10 PPI; the impregnation time of the first slurry is 3 min, and the impregnation time of the second slurry is 10 min;

[0054] The second blank is sintered and cooled to obtain a foam ceramic filter; the sintering process involves uniform heating, with a maximum temperature of 1400℃ and a time of 2 hours.

[0055] Example 3

[0056] This embodiment provides a method for preparing multilayer foam ceramic filters by recycling waste chromium corundum, specifically including the following steps:

[0057] 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.

[0058] 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.

[0059] The first mixture was calcined at 1400℃ to obtain the first powder, and the second mixture was calcined at 1000℃ to obtain the second powder; the mass ratio of fine particles, cerium oxide and lanthanum oxide was 1:0.05:0.01, and the mass ratio of coarse particles to zirconium oxide and alumina was 1:0.5:1; the time for both the first and second calcinations was 1 hour.

[0060] A first powder, water, and polyacrylamide are mixed and stirred to obtain a first slurry. A second powder is mixed with ethanol and solvent oil and stirred to obtain a second slurry. The solid content of the first slurry is 60%, and the solid content of the second slurry is 20%. The amount of polyacrylamide used is 0.05% of the mass of water. The volume ratio of ethanol to solvent oil is 1:1. The stirring speed for the first stirring is 1000 rpm for 5 seconds. The stirring speed for the second stirring is 300 rpm for 1 hour.

[0061] A first slurry is impregnated with flexible polyurethane foam as a carrier, then extruded and dried to obtain a first blank; the first blank is then impregnated with a second slurry and dried to obtain a second blank; the flexible polyurethane foam has a pore size of 30 PPI; the impregnation time of the first slurry is 1 min, and the impregnation time of the second slurry is 30 min;

[0062] The second blank is sintered and cooled to obtain a foam ceramic filter; the sintering process involves uniform heating, with a maximum temperature of 1200℃ and a time of 4 hours.

[0063] Comparative Example 1

[0064] Unlike Example 1, fine and coarse particles are not distinguished and are directly mixed with cerium oxide, lanthanum oxide, zirconium oxide, and aluminum oxide, and the impregnation is only performed once.

[0065] Comparative Example 2

[0066] Unlike Example 1, acrylamide was not used in the first slurry; instead, an equal amount of water was used.

[0067] Comparative Example 3

[0068] Unlike Example 1, the second slurry does not use ethanol and solvent oil, but is replaced with an equal amount of water.

[0069] Comparative Example 4

[0070] Unlike Example 1, the first slurry and the second slurry are mixed and then impregnated once.

[0071] Comparative Example 5

[0072] Unlike Example 1, the speeds and times of the first and second stirring processes are interchanged.

[0073] Comparative Example 6

[0074] Unlike Example 1, cerium oxide, lanthanum oxide, and zirconium oxide were not used; instead, an equal amount of aluminum oxide was used.

[0075] The foam ceramic filters obtained in the examples and comparative examples were all prepared with dimensions of 30*30*20mm. 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: the detection rate of chromium in the molten aluminum after one filtration, the maximum number of uses (regardless of filtration efficiency, only observing for cracking; data are averages from multiple tests, rounded to the nearest whole number), and the percentage increase in tensile strength and elongation of the molten aluminum after one filtration. The test results are as follows:

[0076] Table 1 Test Results

[0077]

[0078]

[0079] 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.

[0080] 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 multilayer foam ceramic filters by recycling waste chromium corundum, 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 is calcined at 1200-1400℃ to obtain a first powder, and the second mixture is calcined at 1000-1300℃ to obtain a second powder. The first powder, water, and polyacrylamide are mixed and stirred to obtain a first slurry; the second powder is mixed with ethanol and solvent oil and stirred to obtain a second slurry. The first slurry is impregnated with flexible polyurethane foam as a carrier, and then extruded and dried in the first stage to obtain a first blank; then the first blank is impregnated with the second slurry and dried in the second stage to obtain a second blank. The second blank is sintered and cooled to obtain a foam ceramic filter; The mass ratio of the fine particles, the cerium oxide, and the lanthanum oxide is 1:(0.01-0.05):(0.01-0.05), and the mass ratio of the coarse particles, the zirconium oxide, and the alumina is 1:(0.1-0.5):(1-3). The first slurry has a solid content of 40-60%, and the second slurry has a solid content of 20-30%. The first stirring speed is 500-1000 rpm, and the time is 5-10 seconds; The second stirring speed is 100-300 rpm, and the time is 1-2 hours.

2. The method for preparing multilayer foam ceramic filters by recycling waste chromium corundum according to claim 1, characterized in that, The first calcination and the second calcination each have an independent time of 1-5 hours.

3. The method for preparing multilayer foam ceramic filters by recycling waste chromium corundum according to claim 1, characterized in that, The amount of polyacrylamide used is 0.01%-0.05% of the mass of the water.

4. The method for preparing multilayer foam ceramic filters by recycling waste chromium corundum according to claim 1, characterized in that, The volume ratio of ethanol to solvent oil is 1:(1-5).

5. The method for preparing multilayer foam ceramic filters by recycling waste chromium corundum according to claim 1, characterized in that, The flexible polyurethane foam has a pore size of 10-30 PPI.

6. The method for preparing multilayer foam ceramic filters by recycling waste chromium corundum according to claim 1, characterized in that, The soaking time for the first slurry is 1-3 minutes, and the soaking time for the second slurry is 10-30 minutes.

7. The method for preparing multilayer foam ceramic filters by recycling waste chromium corundum according to any one of claims 1-6, characterized in that, The maximum sintering temperature is 1200-1400℃, and the time is 2-4 hours.

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