Preparation process of ceramic filter

Abstract

The invention provides a preparation process of a ceramic filter. The preparation process comprises the following steps: S1, weighing the following raw materials in parts by weight: 80-95 parts of silicon carbide particles, 5-15 parts of silicon carbide powder, 1-5 parts of an additive and 10-15 parts of a binding agent; s2, grinding the materials weighed in the step S1 to obtain a mixture A; s3, putting the mixture A obtained in the step S2 into a stirrer, adding a binding agent, and stirring to obtain a granular material B; s4, the granular material B obtained in the S3 is subjected to blank making, and a porous semi-dry blank C is obtained; s5, drying the porous semi-dry green body C obtained in the step S4 to obtain a dry green body D; and S6, sintering the dried green body D obtained in the step S5. The ceramic filter provided by the invention is relatively simple in preparation process and easy to industrialize, and the prepared product is high in porosity, high in strength, erosion-resistant and long in service life. And the main material of the ceramic filter is silicon carbide and a composite material thereof, so that the ceramic filter is pollution-free, does not react with molten aluminum, and is not easy to break in the use process.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic filter manufacturing, and in particular to a preparation process of a ceramic filter. Background Art

[0002] Aluminum smelting and aluminum product production are the foundation of the national economy. During the melting and casting process of aluminum, bubbles, crusts and non-metallic inclusions will greatly destroy the continuity of aluminum metal materials, reduce the effective load-bearing cross-section of the casting, and cause stress concentration, reduce the mechanical properties of the casting, and deteriorate the processing performance. In order to avoid these hazards, the aluminum melt needs to be purified. At present, ceramic filters are often used to remove impurities contained in the aluminum melt by filtering and purification.

[0003] In the prior art, ceramic filters are often prepared by foam impregnation and slurrying. For example, Chinese patent CN107973616A provides a ceramic filter and a preparation method thereof, which uses modified polyurethane foam in the raw material and prepares the ceramic filter through coating, mixing, sintering and other steps; there is also Chinese patent CN108178655A, which provides a method for preparing silicon carbide ceramic filters by adding pore-forming agents. The preparation process requires prefabrication of various types of silicon carbide powders, and then adding the remaining raw material components to the prepared silicon carbide powders, and then obtaining the finished ceramic filter after compression molding and sintering. The ceramic filter preparation process in the above patents is complex and has high requirements for equipment. At the same time, the prepared ceramic filter has low strength and a short service life, which is difficult to meet the needs of modern production. Summary of the invention

[0004] The invention provides a preparation process of a ceramic filter, which is used to solve the problems in the prior art that the preparation process of the ceramic filter is complicated and the performance index of the prepared ceramic filter is poor.

[0005] The present invention provides a preparation process of a ceramic filter, comprising the following steps:

[0006] S1: Weigh the following raw materials by weight: 80-95 parts of silicon carbide particles, 5-15 parts of silicon carbide powder, 1-5 parts of additives, and 10-15 parts of binder;

[0007] S2: grinding and mixing the silicon carbide particles, silicon carbide powder and additives weighed in S1 to obtain a mixture A;

[0008] S3: putting the mixed material A obtained in S2 into a mixer, then adding a binder, and stirring and mixing until uniform to obtain granular material B;

[0009] S4: placing the granular material B obtained in S3 into a filter mold and pressing it by ramming molding to obtain a porous semi-dry body C;

[0010] S5: drying the porous semi-dry body C obtained in S4 in an oven at 100-170° C. to obtain a dry body D;

[0011] S6: placing the dried green body D obtained in S5 in a CVD furnace for sintering. During sintering, the temperature is raised to 1050-1250°C at a rate of 40-120°C / h, kept at this temperature for 1-3h, and then continued to be raised to 1400-1500°C at a rate of 40-120°C / h, and kept at this temperature for another 2-3h. After sintering, the green body is naturally cooled to room temperature to obtain a ceramic filter.

[0012] Optionally, the specific steps of stirring and adding a binder in S3 are:

[0013] (1) Mixture A is put into a mixer, the speed is set to 300-500 r / min, and then 30-40 wt% of a binder is added, and the mixture is stirred for 3-5 min;

[0014] (2) Continue to add 30-40wt% of the binder, increase the speed to 500-700r / min, and continue stirring for 3-5min;

[0015] (3) Add the remaining binder into the mixer and gradually increase the speed to 800 r / min. After reaching 800 r / min, run for 10-15 minutes and end the stirring.

[0016] Optionally, each time the binder is added, it is added dropwise at a uniform speed, and the total duration of each addition does not exceed 30 seconds.

[0017] Optionally, the binder is obtained by mixing silica sol and an auxiliary agent in a mass ratio of 1:(0.5-1).

[0018] Optionally, the auxiliary agent is one or more of sulfonated lignin, polyvinyl alcohol, sodium silicate, dextrin, calcium silicate cement, and carboxymethyl cellulose.

[0019] Optionally, the additive is one or more of aluminum oxide, boron nitride, yttrium oxide, yttrium-stabilized zirconium oxide, and aluminum nitride.

[0020] Optionally, the silicon carbide particles in S1 are large black silicon carbide particles with a purity of ≥98% and a particle size of 2-8 mm.

[0021] Optionally, the silicon carbide powder in S1 has a purity of ≥98% and a particle size of <2 μm.

[0022] Optionally, a ball mill is used for grinding in S2, and the grinding method is dry ball milling.

[0023] Optionally, the average particle size of the mixture A in S2 is 1 mm.

[0024] The preparation process of the ceramic filter provided by the present invention has the beneficial effects that the whole production process is relatively simple and easy to industrialize, and the product has high porosity, high strength, erosion resistance and long service life. In addition, the main material of the ceramic filter is silicon carbide and its composite material, which is non-polluting, does not react with aluminum liquid, and is not easy to break during use. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work also fall within the scope of protection of the present invention.

[0026] The present invention provides a preparation process of a ceramic filter, comprising the following steps:

[0027] S1: Weigh the following raw materials by weight: 80-95 parts of silicon carbide particles, 5-15 parts of silicon carbide powder, 1-5 parts of additives, and 10-15 parts of binder;

[0028] S2: grinding and mixing the silicon carbide particles, silicon carbide powder and additives weighed in S1 to obtain a mixture A;

[0029] S3: putting the mixed material A obtained in S2 into a mixer, then adding a binder, and stirring and mixing until uniform to obtain granular material B;

[0030] S4: placing the granular material B obtained in S3 into a filter mold and pressing it by ramming molding to obtain a porous semi-dry body C;

[0031] S5: drying the porous semi-dry body C obtained in S4 in an oven at 100-170° C. to obtain a dry body D;

[0032] S6: placing the dried green body D obtained in S5 in a CVD furnace for sintering. During sintering, the temperature is raised to 1050-1250°C at a rate of 40-120°C / h, kept at this temperature for 1-3h, and then continued to be raised to 1400-1500°C at a rate of 40-120°C / h, and kept at this temperature for another 2-3h. After sintering, the green body is naturally cooled to room temperature to obtain a ceramic filter.

[0033] The preparation process of the ceramic filter provided by the present invention is based on large silicon carbide particles, in conjunction with silicon carbide powder, additives and binders, and the particles are densely stacked by a molding process, and then sintered at high temperature. The obtained ceramic filter not only has a high porosity, but also has high flexural strength and service life.

[0034] Before sintering, the porous semi-dry body C is first dried to discharge excess water, so as to avoid the subsequent sintering temperature being too high and the body cracking when the water evaporates. During sintering, a multi-stage and multiple heating method is adopted to avoid the body cracking and pulverization caused by the body generating a large amount of gas in a short time due to the rapid heating. During the sintering process, as the temperature gradually rises and the time is extended, the solid particles are bonded to each other, the grains grow, the pores increase and the grain boundaries decrease, and through the transfer of substances, a sintered body with the expected microstructure is finally formed.

[0035] Furthermore, the specific steps of stirring and adding the binder in S3 are:

[0036] (1) Mixture A is put into a mixer, the speed is set to 300-500 r / min, and then 30-40 wt% of a binder is added, and the mixture is stirred for 3-5 min;

[0037] (2) Continue to add 30-40wt% of the binder, increase the speed to 500-700r / min, and continue stirring for 3-5min;

[0038] (3) Add the remaining binder into the mixer and gradually increase the speed to 800 r / min. After reaching 800 r / min, run for 10-15 minutes and end the stirring.

[0039] When adding the binder to the mixture A, the method of adding the binder in batches is also adopted, so that the mixing between the binder and the mixture A is more uniform.

[0040] Furthermore, each time the binder is added, it is added dropwise at a uniform speed, and the total duration of each addition does not exceed 30 seconds.

[0041] Furthermore, the binder is obtained by mixing silica sol and an auxiliary agent in a mass ratio of 1:(0.5-1).

[0042] Furthermore, the auxiliary agent is one or more of sulfonated lignin, polyvinyl alcohol, sodium silicate, dextrin, calcium silicate cement, and carboxymethyl cellulose.

[0043] Furthermore, the additive is one or more of aluminum oxide, boron nitride, yttrium oxide, yttrium-stabilized zirconium oxide, and aluminum nitride.

[0044] Furthermore, the silicon carbide particles in S1 are large black silicon carbide particles with a purity of ≥98% and a particle size of 2-8 mm.

[0045] Furthermore, the purity of the silicon carbide powder in S1 is ≥98% and the particle size is <2 μm.

[0046] Furthermore, a ball mill is used for grinding in S2, and the grinding method is dry ball milling.

[0047] Furthermore, the average particle size of the mixture A in S2 is 1 mm.

[0048] The filter prepared by the preparation process of the ceramic filter provided by the present invention can achieve the performance indicators shown in Table 1:

[0049] Table 1

[0050] <![CDATA[Specific gravity (g / cm 3 )]]> 1.7-2.0 Pore ​​size (μm) 850-1600 Flexural strength at 750℃(MPa) >4.8 Porosity (%) 40-55 Operating temperature(℃) >900 Use time (month) ≥1

[0051] The present invention is further described in detail below in conjunction with specific embodiments.

[0052] Example 1

[0053] A preparation process of a ceramic filter comprises the following steps:

[0054] S1: Weigh the following raw materials by weight: 80 parts of silicon carbide particles, 5 parts of silicon carbide powder, 1 part of additives, and 10 parts of binders;

[0055] The particle size of silicon carbide particles is 2mm and the purity is ≥98%;

[0056] Silicon carbide powder purity ≥98%, particle size <2μm;

[0057] The additives are aluminum oxide, boron nitride, and yttrium oxide, and their mass ratio is 1:1:1;

[0058] The ratio of silica sol to additives in the binder is 1:0.5, and the additives are sulfonated lignin, polyvinyl alcohol, and calcium silicate cement, and their mass ratio is 1:1:1;

[0059] S2: Put the silicon carbide particles, silicon carbide powder and additives weighed in S1 into a ball mill for dry ball milling to obtain a mixture A with an average particle size of 1 mm;

[0060] S3: Put the mixed material A obtained in S2 into a mixer, set the speed of the mixer to 300 r / min, then add 30 wt% of the binder, and stir and mix for 3 minutes; then continue to add 30 wt% of the binder, and increase the speed to 500 r / min, and continue stirring for 3 minutes; finally, add the remaining binder into the mixer, gradually increase the speed to 800 r / min, run for 10 minutes after reaching 800 r / min, and end the stirring to obtain the granular material B;

[0061] S4: placing the granular material B obtained in S3 into a filter mold and pressing it by ramming molding to obtain a porous semi-dry body C;

[0062] S5: drying the porous semi-dry body C obtained in S4 in an oven at 100° C. to obtain a dry body D;

[0063] S6: The dried body D obtained in S5 is placed in a CVD furnace for sintering. During sintering, the temperature is raised to 1050°C at a rate of 40°C / h, kept at this temperature for 1 hour, and then continued to be raised to 1400°C at a rate of 40°C / h, and kept at this temperature for another 2 hours. After sintering, the body is naturally cooled to room temperature to obtain a ceramic filter.

[0064] Example 2

[0065] A preparation process of a ceramic filter comprises the following steps:

[0066] S1: Weigh the following raw materials by weight: 95 parts of silicon carbide particles, 15 parts of silicon carbide powder, 5 parts of additives, and 15 parts of binder;

[0067] The particle size of silicon carbide particles is 8mm and the purity is ≥98%;

[0068] Silicon carbide powder purity ≥98%, particle size <2μm;

[0069] The additives are aluminum oxide, boron nitride, and yttrium oxide, and their mass ratio is 1:1:1;

[0070] The ratio of silica sol to additives in the binder is 1:1, and the additives are sulfonated lignin, polyvinyl alcohol, and calcium silicate cement, and the mass ratio thereof is 1:1:1;

[0071] S2: Put the silicon carbide particles, silicon carbide powder and additives weighed in S1 into a ball mill for dry ball milling to obtain a mixture A with an average particle size of 1 mm;

[0072] S3: Put the mixed material A obtained in S2 into a mixer, set the speed of the mixer to 500 r / min, then add 40 wt% of the binder, and stir and mix for 5 minutes; then continue to add 40 wt% of the binder, and increase the speed to 700 r / min, and continue stirring for 5 minutes; finally, add the remaining binder to the mixer, gradually increase the speed to 800 r / min, run for 15 minutes after reaching 800 r / min, and end the stirring to obtain granular material B;

[0073] S4: placing the granular material B obtained in S3 into a filter mold and pressing it by ramming molding to obtain a porous semi-dry body C;

[0074] S5: drying the porous semi-dry body C obtained in S4 in an oven at 170° C. to obtain a dry body D;

[0075] S6: The dried green body D obtained in S5 is placed in a CVD furnace for sintering. During sintering, the temperature is raised to 1250°C at a rate of 120°C / h, kept at this temperature for 3 hours, and then continued to be raised to 1500°C at a rate of 120°C / h, and kept at this temperature for another 3 hours. After sintering, the green body is naturally cooled to room temperature to obtain a ceramic filter.

[0076] Example 3

[0077] A preparation process of a ceramic filter comprises the following steps:

[0078] S1: Weigh the following raw materials by weight: 90 parts of silicon carbide particles, 10 parts of silicon carbide powder, 3 parts of additives, and 13 parts of binder;

[0079] The particle size of silicon carbide particles is 5mm and the purity is ≥98%;

[0080] Silicon carbide powder purity ≥98%, particle size <2μm;

[0081] The additives are aluminum oxide, boron nitride, and yttrium oxide, and their mass ratio is 1:1:1;

[0082] The ratio of silica sol to additives in the binder is 1:0.75, and the additives are sulfonated lignin, polyvinyl alcohol, and calcium silicate cement, and the mass ratio thereof is 1:1:1;

[0083] S2: Put the silicon carbide particles, silicon carbide powder and additives weighed in S1 into a ball mill for dry ball milling to obtain a mixture A with an average particle size of 1 mm;

[0084] S3: Put the mixed material A obtained in S2 into a mixer, set the speed of the mixer to 400 r / min, then add 35 wt% of the binder, and stir and mix for 4 minutes; then continue to add 35 wt% of the binder, and increase the speed to 600 r / min, and continue stirring for 4 minutes; finally, add the remaining binder to the mixer, gradually increase the speed to 800 r / min, run for 13 minutes after reaching 800 r / min, and end the stirring to obtain granular material B;

[0085] S4: placing the granular material B obtained in S3 into a filter mold and pressing it by ramming molding to obtain a porous semi-dry body C;

[0086] S5: drying the porous semi-dry body C obtained in S4 in an oven at 150° C. to obtain a dry body D;

[0087] S6: The dried green body D obtained in S5 is placed in a CVD furnace for sintering. During sintering, the temperature is raised to 1100°C at a rate of 90°C / h, kept at this temperature for 2 hours, and then continued to be raised to 1450°C at a rate of 90°C / h, and kept at this temperature for another 2.5 hours. After sintering, the green body is naturally cooled to room temperature to obtain a ceramic filter.

[0088] Example 4

[0089] A preparation process of a ceramic filter comprises the following steps:

[0090] S1: Weigh the following raw materials by weight: 80 parts of silicon carbide particles, 5 parts of silicon carbide powder, 1 part of additives, and 10 parts of binders;

[0091] The particle size of silicon carbide particles is 2mm and the purity is ≥98%;

[0092] Silicon carbide powder purity ≥98%, particle size <2μm;

[0093] The additives are alumina, yttrium-stabilized zirconia, and aluminum nitride, with a mass ratio of 1:1:1;

[0094] The ratio of silica sol to auxiliary agent in the binder is 1:0.5, and the ratio of polyvinyl alcohol, dextrin and carboxymethyl cellulose in the auxiliary agent is 1:1:1;

[0095] S2: Put the silicon carbide particles, silicon carbide powder and additives weighed in S1 into a ball mill for dry ball milling to obtain a mixture A with an average particle size of 1 mm;

[0096] S3: Put the mixed material A obtained in S2 into a mixer, set the speed of the mixer to 300 r / min, then add 30 wt% of the binder, and stir and mix for 3 minutes; then continue to add 30 wt% of the binder, and increase the speed to 500 r / min, and continue stirring for 3 minutes; finally, add the remaining binder into the mixer, gradually increase the speed to 800 r / min, run for 10 minutes after reaching 800 r / min, and end the stirring to obtain the granular material B;

[0097] S4: placing the granular material B obtained in S3 into a filter mold and pressing it by ramming molding to obtain a porous semi-dry body C;

[0098] S5: drying the porous semi-dry body C obtained in S4 in an oven at 100° C. to obtain a dry body D;

[0099] S6: The dried body D obtained in S5 is placed in a CVD furnace for sintering. During sintering, the temperature is raised to 1050°C at a rate of 40°C / h, kept at this temperature for 1 hour, and then continued to be raised to 1400°C at a rate of 40°C / h, and kept at this temperature for another 2 hours. After sintering, the body is naturally cooled to room temperature to obtain a ceramic filter.

[0100] Example 5

[0101] A preparation process of a ceramic filter comprises the following steps:

[0102] S1: Weigh the following raw materials by weight: 90 parts of silicon carbide particles, 10 parts of silicon carbide powder, 3 parts of additives, and 13 parts of binder;

[0103] The particle size of silicon carbide particles is 5mm and the purity is ≥98%;

[0104] Silicon carbide powder purity ≥98%, particle size <2μm;

[0105] The additives are alumina, boron nitride, and aluminum nitride in a ratio of 1:1:1;

[0106] The ratio of silica sol to additives in the binder is 1:0.5, and the additives are sulfonated lignin, polyvinyl alcohol, and dextrin, and the mass ratio thereof is 1:1:1;

[0107] S2: Put the silicon carbide particles, silicon carbide powder and additives weighed in S1 into a ball mill for dry ball milling to obtain a mixture A with an average particle size of 1 mm;

[0108] S3: Put the mixed material A obtained in S2 into a mixer, set the speed of the mixer to 400 r / min, then add 35 wt% of the binder, and stir and mix for 4 minutes; then continue to add 35 wt% of the binder, and increase the speed to 600 r / min, and continue stirring for 4 minutes; finally, add the remaining binder to the mixer, gradually increase the speed to 800 r / min, run for 13 minutes after reaching 800 r / min, and end the stirring to obtain granular material B;

[0109] S4: placing the granular material B obtained in S3 into a filter mold and pressing it by ramming molding to obtain a porous semi-dry body C;

[0110] S5: drying the porous semi-dry body C obtained in S4 in an oven at 100-170° C. to obtain a dry body D;

[0111] S6: The dried green body D obtained in S5 is placed in a CVD furnace for sintering. During sintering, the temperature is raised to 1100°C at a rate of 90°C / h, kept at this temperature for 2 hours, and then continued to be raised to 1450°C at a rate of 90°C / h, and kept at this temperature for another 2.5 hours. After sintering, the green body is naturally cooled to room temperature to obtain a ceramic filter.

[0112] Example 6

[0113] A preparation process of a ceramic filter comprises the following steps:

[0114] S1: Weigh the following raw materials by weight: 80 parts of silicon carbide particles, 10 parts of silicon carbide powder, 1 part of additives, and 10 parts of binders;

[0115] The particle size of silicon carbide particles is 5mm and the purity is ≥98%;

[0116] Silicon carbide powder purity ≥98%, particle size <2μm;

[0117] The additive is aluminum oxide;

[0118] The ratio of silica sol to auxiliary agent in the binder is 1:0.5, and the auxiliary agent is sulfonated lignin;

[0119] S2: Put the silicon carbide particles, silicon carbide powder and additives weighed in S1 into a ball mill for dry ball milling to obtain a mixture A with an average particle size of 1 mm;

[0120] S3: Put the mixed material A obtained in S2 into a mixer, set the speed of the mixer to 300 r / min, then add 30 wt% of the binder, and stir and mix for 3 minutes; then continue to add 30 wt% of the binder, and increase the speed to 500 r / min, and continue stirring for 3 minutes; finally, add the remaining binder into the mixer, gradually increase the speed to 800 r / min, run for 10 minutes after reaching 800 r / min, and end the stirring to obtain the granular material B;

[0121] S4: placing the granular material B obtained in S3 into a filter mold and pressing it by ramming molding to obtain a porous semi-dry body C;

[0122] S5: drying the porous semi-dry body C obtained in S4 in an oven at 100-170° C. to obtain a dry body D;

[0123] S6: The dried body D obtained in S5 is placed in a CVD furnace for sintering. During sintering, the temperature is raised to 1050°C at a rate of 40°C / h, kept at this temperature for 1 hour, and then continued to be raised to 1400°C at a rate of 40°C / h, and kept at this temperature for another 2 hours. After sintering, the body is naturally cooled to room temperature to obtain a ceramic filter.

[0124] Example 7

[0125] A preparation process of a ceramic filter comprises the following steps:

[0126] S1: Weigh the following raw materials by weight: 85 parts of silicon carbide particles, 12 parts of silicon carbide powder, 1.5 parts of additives, and 13 parts of binder;

[0127] The particle size of silicon carbide particles is 6mm and the purity is ≥98%;

[0128] Silicon carbide powder purity ≥98%, particle size <2μm;

[0129] The additive is aluminum oxide;

[0130] The ratio of silica sol to additive in the binder is 1:0.5, and polyvinyl alcohol is in the additive;

[0131] S2: Put the silicon carbide particles, silicon carbide powder and additives weighed in S1 into a ball mill for dry ball milling to obtain a mixture A with an average particle size of 1 mm;

[0132] S3: Put the mixed material A obtained in S2 into a mixer, set the speed of the mixer to 350 r / min, then add 35 wt% of the binder, and stir and mix for 4 minutes; then continue to add 40 wt% of the binder, and increase the speed to 600 r / min, and continue stirring for 5 minutes; finally, add the remaining binder into the mixer, gradually increase the speed to 800 r / min, run for 15 minutes after reaching 800 r / min, and end the stirring to obtain the granular material B;

[0133] S4: placing the granular material B obtained in S3 into a filter mold and pressing it by ramming molding to obtain a porous semi-dry body C;

[0134] S5: drying the porous semi-dry body C obtained in S4 in an oven at 160° C. to obtain a dry body D;

[0135] S6: The dried green body D obtained in S5 is placed in a CVD furnace for sintering. During sintering, the temperature is raised to 1150°C at a rate of 90°C / h, kept at this temperature for 1.5 hours, and then continued to be raised to 1400°C at a rate of 100°C / h, and kept at this temperature for another 2 hours. After sintering, the green body is naturally cooled to room temperature to obtain a ceramic filter.

[0136] The performance indicators of the ceramic filters prepared in Examples 1-7 are shown in Table 2:

[0137] Table 2

[0138]

[0139]

[0140] Comparative Example 1

[0141] The difference between Comparative Example 1 and Example 1 is only that no additive is used in the composition.

[0142] Comparative Example 2

[0143] The only difference between Comparative Example 2 and Example 1 is that the binder in the components only includes silica sol, and no auxiliary agent is added.

[0144] Comparative Example 3

[0145] The only difference between Comparative Example 3 and Example 1 is that the mass ratio of silica sol to auxiliary agent in the binder is 1:2.

[0146] Comparative Example 4

[0147] The only difference between Comparative Example 4 and Example 1 is that no additive is used in the components and no auxiliary agent is used in the binder.

[0148] Comparative Example 5

[0149] The only difference between Comparative Example 5 and Example 3 is that the binder is added once in step S3, the stirring speed is 700 r / min, and the stirring time is 15 min.

[0150] Comparative Example 6

[0151] The only difference between Comparative Example 6 and Example 3 is that during sintering in step S6, the dried green body D is placed in a CVD furnace and sintered directly at 1500° C. for 5 hours.

[0152] Comparative Example 7

[0153] The only difference between Comparative Example 7 and Example 2 is that after ball milling in step S2, the average particle size of the mixture A is 5 mm.

[0154] The performance indicators of the ceramic filters prepared in Comparative Examples 1-7 are shown in Table 3:

[0155] Table 3

[0156]

[0157]

[0158] It can be seen from the above examples and comparative examples that the components of the ceramic filter and the parameters in the process of preparing the ceramic filter will have different degrees of influence on the performance indicators of the ceramic filter, which are specifically manifested as follows:

[0159] (1) Comparative Examples 1-4 list the effects of the component content and ratio of the ceramic filter on the performance indicators of the ceramic filter. In Comparative Example 1, no additives were used in the components of the ceramic filter. Compared with Example 1, its pore size increased, and the flexural strength at 750°C (the flexural strengths mentioned below were all tested at 750°C), the use temperature and the use time all decreased. In Comparative Example 2, the binder in the ceramic filter component only contained silica sol, and no auxiliary agent was added. The mass ratio of silica sol to auxiliary agent in the binder of Comparative Example 3 was 1:2. The performance indicators of the ceramic filters prepared by Comparative Examples 2 and 3 decreased to varying degrees in flexural strength, use temperature and use time compared with Example 1. Among them, the decrease in Comparative Example 3 was slightly smaller than that in Comparative Example 2. In Comparative Example 4, no additives were used in the components of the ceramic filter, and no auxiliary agent was used in the binder. The various performance indicators of the obtained ceramic filter were greatly reduced compared with Example 1.

[0160] (2) Comparative Examples 5-7 list the effects of various parameters in the ceramic filter preparation process on the performance indicators of the ceramic filter. In Comparative Example 5, when adding the binder in step S3, all the binder is added at one time. During this process, the binder is unevenly distributed in the mixture A. Compared with Example 3, the flexural strength and operating temperature of the ceramic filter are reduced to varying degrees. In Comparative Example 6, when performing step S6, the dried blank D is directly sintered in a preheated furnace. During this process, the dried blank D is heated too quickly, resulting in it being too brittle. Compared with Example 3, its flexural strength is greatly reduced. In Comparative Example 7, when performing step S2, the average particle size of the ball-milled mixture A is 5 mm, and the bonding between the components is poor. Compared with Example 2, its flexural strength and operating temperature are reduced.

[0161] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features therein may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for preparing a ceramic filter, characterized in that: The following steps are involved: S1: Weigh the following raw materials by weight: 80-95 parts of silicon carbide particles, 5-15 parts of silicon carbide powder, 1-5 parts of additives, and 10-15 parts of binder; S2: grinding and mixing the silicon carbide particles, silicon carbide powder and additives weighed in S1 to obtain a mixture A; S3: putting the mixed material A obtained in S2 into a mixer, then adding a binder, and stirring and mixing to obtain granular material B; S4: placing the granular material B obtained in S3 into a filter mold and pressing it by ramming molding to obtain a porous semi-dry body C; S5: drying the porous semi-dry body C obtained in S4 in an oven at 100-170° C. to obtain a dry body D; S6: placing the dried green body D obtained in S5 in a CVD furnace for sintering. During sintering, the temperature is raised to 1050-1250°C at a rate of 40-120°C / h, kept at this temperature for 1-3h, and then continued to be raised to 1400-1500°C at a rate of 40-120°C / h, and kept at this temperature for another 2-3h. After sintering, the green body is naturally cooled to room temperature to obtain the ceramic filter.

2. The process for preparing the ceramic filter according to claim 1, characterized in that: The specific steps of stirring and adding the binder in S3 are: (1) Mixture A is put into a mixer, the speed is set to 300-500 r / min, and then 30-40 wt% of a binder is added, and the mixture is stirred for 3-5 min; (2) Continue to add 30-40wt% of the binder, increase the speed to 500-700r / min, and continue stirring for 3-5min; (3) Add the remaining binder into the mixer and gradually increase the speed to 800 r / min. After reaching 800 r / min, run for 10-15 minutes and end the stirring.

3. The preparation process of the ceramic filter according to claim 2, characterized in that: Each time the binder is added, it is added dropwise at a uniform speed, and the total duration of each addition does not exceed 30 seconds.

4. The process for preparing the ceramic filter according to claim 1, characterized in that: The binder is obtained by mixing silica sol and an auxiliary agent in a mass ratio of 1: (0.5-1).

5. The process for preparing the ceramic filter according to claim 4, characterized in that: The auxiliary agent is one or more of sulfonated lignin, polyvinyl alcohol, sodium silicate, dextrin, calcium silicate cement, and carboxymethyl cellulose.

6. The process for preparing a ceramic filter according to claim 1, characterized in that: The additive is one or more of aluminum oxide, boron nitride, yttrium oxide, yttrium-stabilized zirconium oxide, and aluminum nitride.

7. The process for preparing a ceramic filter according to claim 1, characterized in that: The silicon carbide particles in S1 are large black silicon carbide particles with a purity of ≥98% and a particle size of 2-8 mm.

8. The process for preparing a ceramic filter according to claim 1, characterized in that: The silicon carbide powder in S1 has a purity of ≥98% and a particle size of <2 μm.

9. The process for preparing a ceramic filter according to claim 1, characterized in that: The grinding in S2 is performed using a ball mill, and the grinding method is dry ball milling.

10. The process for preparing a ceramic filter according to claim 1, characterized in that: The average particle size of the mixture A in S2 is 1 mm.

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