Method for improving firing yield of cordierite DPF honeycomb ceramics

Abstract

The invention discloses a method for improving the firing yield of cordierite DPF honeycomb ceramics, and belongs to the technical field of honeycomb ceramic carrier preparation. The preparation method comprises the following steps: mixing raw materials; kneading mud; performing extrusion molding; drying and shaping; cutting and firing to obtain a cordierite honeycomb ceramic carrier; and performing boundary dimension processing, film covering, hole dotting, mud scraping and drying to obtain a finished product. According to the invention, magnesium hydroxide is used for replacing part or all of talc in a traditional formula of a cordierite porous ceramic structural body, and magnesium hydroxide absorbs a large amount of heat when heated, so that rapid temperature rise of a DPF carrier mud blank caused in an organic matter coke discharge process is slowed down, the temperature gradient of the DPF carrier mud blank in a firing process is reduced, and the sintering temperature of the DPF carrier mud blank is reduced. Therefore, the generation of mud blank cracks is inhibited in the firing process, and the firing yield is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of honeycomb ceramic carrier preparation, and in particular relates to a method for improving the sintering finished product rate of cordierite DPF honeycomb ceramics. Background Art

[0002] With the rapid progress of science and technology and economy, domestic fuel vehicles have been rapidly popularized, and the current ownership is still far greater than that of new energy vehicles. As of the end of June 2024, the national fuel vehicle ownership is 345 million. In addition, at the end of 2023, the national civilian car ownership is 336 million, of which fuel vehicles account for 96%. As the power source of the internal combustion engine, fuel combustion will leave harmful residues, such as carbon soot particles. The National VI emission standard has requirements for PM (particulate mass) and PN (particulate number). If it is not controlled, it will cause serious environmental pollution problems. The currently recognized way to reduce PM and PN is to intercept through a diesel particulate filter (hereinafter also referred to as "DPF"), which can be used as a catalyst carrier for purification and to capture particulate matter in exhaust gas. It can effectively remove particulate matter such as soot discharged from the internal combustion engine.

[0003] Cordierite honeycomb ceramics have the advantages of low thermal expansion coefficient, good thermal stability, good adsorption performance, etc., and are a kind of honeycomb ceramic carrier with excellent performance. However, there are few studies on the physical and chemical reaction mechanism of DPF mud blank firing. At present, most of them adopt methods such as strictly controlling the temperature rise rate of the organic volatilization section in the temperature curve to achieve reasonable control of the radial temperature field distribution of the honeycomb ceramic carrier to avoid cracking of the honeycomb ceramic carrier during the firing process. However, even so, according to statistics, the qualified rate of traditional honeycomb ceramic carrier firing process products is difficult to reach 95%. Therefore, it is necessary to develop a method of cordierite DPF honeycomb ceramics with a high firing rate of mud blanks and a wide adaptability of firing system. Summary of the invention

[0004] The technical problem solved by the invention is to provide a method for improving the firing yield of cordierite DPF honeycomb ceramics. The method has good adaptability to the firing system and can significantly improve the firing yield.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for improving the sintering yield of cordierite DPF honeycomb ceramics comprises the following steps:

[0007] (1) talc, magnesium hydroxide, alumina, silicon dioxide and kaolin are mixed, then a binder and a pore former are added and the mixture is further mixed, and then the mixture is mixed with the liquid material;

[0008] (2) kneading, rough refining and refining the clay in a clay kneading machine to obtain clay material;

[0009] (3) Extruding the clay material in an extruder to obtain a honeycomb ceramic carrier green body;

[0010] (4) The honeycomb ceramic carrier green body is subjected to microwave drying and shaping;

[0011] (5) The dried carrier is cut and fired to obtain a cordierite honeycomb ceramic carrier;

[0012] (6) Dimension processing, lamination, hole punching, mud scraping, drying, and finished product.

[0013] The amount of magnesium hydroxide used in step 1) is 0-15 parts.

[0014] In the step 1), 8.39-41 parts of talc, 28.5 parts of alumina, 20.5-40.07 parts of silicon dioxide, 10 parts of kaolin, 6 parts of binder, and 20 parts of pore-forming agent are used.

[0015] In the step (1), the particle size of talc is 5-35 μm, the particle size of magnesium hydroxide is 5-35 μm, the particle size of aluminum oxide is 5-10 μm, the particle size of silicon dioxide is 5-35 μm, and the particle size of kaolin is 3-8 μm.

[0016] The amount of water added in step (1) is 20-30% of the total weight of the raw materials.

[0017] In the step (2), the sieve used for the rough refining and sieving is 80 mesh, the mud is kneaded for 15 to 20 minutes, aged for 12 to 16 hours, and the sieve used for the refining and sieving is 100 mesh.

[0018] The weight moisture content of the honeycomb ceramic carrier green body after drying in the step (4) is less than 1.0%.

[0019] In the step (5), at room temperature to 200°C, the corresponding heating rate is 20°C / h; at 200°C to 800°C, the corresponding heating rate is 25°C / h to 50°C / h; at 800°C to 1410°C, the corresponding heating rate is 45°C / h; and the temperature is kept at 1410°C for 10 h.

[0020] The DPF product in step (6) has a diameter of 305 mm, a height of 305 mm, a pore density of 200 mesh, and a wall thickness of 11 mil.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] The present invention uses magnesium hydroxide to replace talc in the formula of the cordierite porous ceramic structure or partially replace talc. Magnesium hydroxide absorbs a large amount of heat when heated, thereby slowing down the heating rate of the carrier mud blank, and releases bound water during the thermal decomposition process. The water further absorbs heat and dilutes the oxygen concentration, which helps to inhibit rapid temperature rise, thereby inhibiting the generation of mud blank cracks during the firing process and improving the firing yield rate. Magnesium oxide (MgO) generated after the decomposition of magnesium hydroxide has excellent refractory properties and further slows down the combustion process. DETAILED DESCRIPTION

[0023] The present invention is further illustrated below in conjunction with specific examples. The examples are implemented based on the technical solutions of the present invention. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0024] The raw material requirements used in the following examples are shown in Table 1.

[0025] Table 1 Raw material specifications

[0026]

[0027] Example 1

[0028] A method for improving the sintering yield of cordierite DPF honeycomb ceramics, the specific steps are as follows:

[0029] (1) Talc, magnesium hydroxide, alumina, silicon dioxide and kaolin are mixed, and then a binder and a pore former are added and the mixture is continued to be mixed, and then 22% water, which is the sum of the weight of the inorganic material, the binder and the pore former, is added and the mixture is continued to be mixed. The specific amount of each raw material is shown in Table 2;

[0030] (2) kneading the clay in a clay kneading machine, rough refining (80 mesh screen) for 15 minutes, aging for 12 hours, refining and sieving (100 mesh screen) to obtain clay;

[0031] (3) Extruding the clay material in an extruder to obtain a honeycomb ceramic carrier green body;

[0032] (4) The honeycomb ceramic carrier clay blank is subjected to microwave drying and shaping, and the moisture content of the honeycomb ceramic carrier green body after drying is less than 1.0% (weight percentage);

[0033] (5) The dried carrier was cut and fired to obtain a cordierite honeycomb ceramic carrier. The firing temperature control program was as follows: at room temperature to 200 °C, the corresponding heating rate was 20 °C / h; at 200 to 800 °C, the corresponding heating rate was 25 °C / h; at 800 to 1410 °C, the corresponding heating rate was 45 °C / h; and the temperature was kept at 1410 °C for 10 h.

[0034] (6) Dimension processing, coating, hole punching, scraping, drying, finished product, DPF product diameter 305 mm, height 305 mm, hole density 200 mesh, wall thickness 11 mil.

[0035] The specific product formula and product performance test results are shown in Table 2.

[0036] Table 2 Specific product formula and performance indicators

[0037]

[0038] Wherein, the binder is hydroxypropyl methylcellulose and the pore-forming agent is starch.

[0039] The median pore size was tested by mercury intrusion method (GB / T 21650.1-2008), and the test parameters were set as follows: mercury contact angle of 130°; mercury surface tension of 0.485 N / m; mercury density (20 ℃) ​​of 13.5335 g / mL; pressure data were collected in step mode, and the pressure balance time was 10 s; no pretreatment. The thermal shock performance of honeycomb ceramics GB / T 25994-2010 was used to measure the thermal expansion coefficient. The thermal expansion instrument in GB / T 7320-2018 standard was used to measure the porosity. The floating weight method in GB / T 1966-1996 standard was used to measure the porosity.

[0040] It can be seen from Table 2 that when the amount of magnesium hydroxide replacing talc increases, the firing survival rate of the product increases, which is more improved than the qualified rate of the traditional formula. When the addition amount of magnesium hydroxide is 10% and above to 15%, the qualified rate of the product remains unchanged at 100%.

[0041] Example 2

[0042] The honeycomb ceramic carrier was prepared according to the method in Example 1, except that in step 5), when the temperature was programmed to rise to 200-800 °C, the number of cracks of the product was tested at a heating rate of 50 °C / h. The specific results are shown in Table 3.

[0043] Table 3 Product results of different heating processes

[0044]

[0045] It can be seen from Table 3 that when the heating rate is increased to 50 ℃ / h, the trend of the product qualification rate is the same as that in Table 2. When the amount of magnesium hydroxide replacing talc is more, the quick-burning survival rate of the product is higher, and the qualification rate is improved more than that of the traditional formula. When the addition amount of magnesium hydroxide is 10% and above to 15%, the qualification rate of the product remains unchanged at 100%.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for improving the sintering yield of cordierite DPF honeycomb ceramics, characterized in that: The following steps are involved: (1) talc, magnesium hydroxide, alumina, silicon dioxide and kaolin are mixed, then a binder and a pore former are added and the mixture is further mixed, and then the mixture is mixed with the liquid material; (2) kneading, roughing and refining the clay in a clay kneading machine to obtain clay material; (3) Extruding the clay material in an extruder to obtain a honeycomb ceramic carrier green body; (4) The honeycomb ceramic carrier green body is subjected to microwave drying and shaping; (5) The dried carrier is cut and fired to obtain a cordierite honeycomb ceramic carrier; (6) Dimensional processing, lamination, hole punching, mud scraping, drying, and finished product.

2. The method for improving the sintering yield of cordierite DPF honeycomb ceramics according to claim 1, characterized in that: The amount of magnesium hydroxide used in step 1) is 0-15 parts.

3. The method for improving the sintering yield of cordierite DPF honeycomb ceramics according to claim 1, characterized in that: In the step 1), talc is 8.39-41 parts, alumina is 28.5 parts, silicon dioxide is 20.5-40.07 parts, kaolin is 10 parts, a binder is 6 parts, and a pore-forming agent is 20 parts.

4. The method for improving the sintering yield of cordierite DPF honeycomb ceramics according to claim 1, characterized in that: In the step (1), the particle size of talc is 5-35 μm, the particle size of magnesium hydroxide is 5-35 μm, the particle size of aluminum oxide is 5-10 μm, the particle size of silicon dioxide is 5-35 μm, and the particle size of kaolin is 3-8 μm.

5. The method for improving the sintering yield of cordierite DPF honeycomb ceramics according to claim 1, characterized in that: The amount of water added in step (1) is 20-30% of the total weight of the raw materials.

6. The method for improving the sintering yield of cordierite DPF honeycomb ceramics according to claim 1, characterized in that: In the step (2), the sieve used for the rough refining and sieving is 80 mesh, the mud is kneaded for 15 to 20 minutes, aged for 12 to 16 hours, and the sieve used for the fine refining and sieving is 100 mesh.

7. The method for improving the sintering yield of cordierite DPF honeycomb ceramics according to claim 1, characterized in that: The weight moisture content of the honeycomb ceramic carrier green body after drying in the step (4) is less than 1.0%.

8. The method for improving the sintering yield of cordierite DPF honeycomb ceramics according to claim 1, characterized in that: In the step (5), at room temperature to 200°C, the corresponding heating rate is 20°C / h; at 200°C to 800°C, the corresponding heating rate is 25°C / h to 50°C / h; at 800°C to 1410°C, the corresponding heating rate is 45°C / h; and the temperature is kept at 1410°C for 10 h.

9. The method for improving the sintering yield of cordierite DPF honeycomb ceramics according to claim 1, characterized in that: The DPF product in step (6) has a diameter of 305 mm, a height of 305 mm, a pore density of 200 mesh, and a wall thickness of 11 mil.

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