A silicon carbide ceramic tertiary air damper plate suitable for installation near a kiln head and a preparation method thereof

Abstract

The application belongs to the technical field of tertiary air damper plate, and discloses a silicon carbide ceramic tertiary air damper plate suitable for being installed near a kiln head and a preparation method thereof. The damper plate body is formed by sintering after being formed by silicon carbide ceramic refractory slurry casting. The silicon carbide ceramic refractory slurry comprises the following raw materials in percentage by mass: 70-90% of silicon carbide, 1-5% of binder A, 7-20% of alumina micro powder, and 1-6% of binder B, wherein the sum of the above raw materials is 100%, and 0.2-0.4% of additives and 1-6% of water are additionally added to the total mass of the above raw materials. Binder A is composed of graphite and silica sol, and binder B is composed of calcium acetate, water and pseudo-boehmite fine powder. The silicon carbide ceramic tertiary air damper plate has the advantages of high strength and wear resistance, and can be installed near the kiln head and has a service life of 18-24 months, greatly improving the use effect of the damper plate at the position, realizing more flexible and accurate control of the tertiary air, improving the product stability, and ensuring long-term stable operation of the cement kiln.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tertiary air damper plate, and particularly relates to a silicon carbide ceramic tertiary air damper plate suitable for installation near a kiln head and a preparation method thereof. BACKGROUND

[0002] The tertiary air damper plate is one of key controls of a cement kiln firing system, and is located in a tertiary air pipe; the tertiary air pipe is connected with a cement kiln and a decomposing furnace; the tertiary air can make the coal powder in the decomposing furnace burn; the tertiary air damper plate plays a role in controlling the ventilation volume of the tertiary air per unit time; the ventilation volume directly affects the decomposition efficiency of the decomposing furnace and the ventilation volume of the cement kiln, and further affects the quality and production efficiency of the cement; therefore, the tertiary air damper plate largely determines whether the entire cement kiln firing system can normally operate.

[0003] The installation position of the existing production line tertiary air damper plate is generally near the decomposing furnace; in recent years, technicians find that adjusting the installation position of the tertiary air damper plate to be near the kiln head can more flexibly and accurately control the tertiary air, so as to realize stable cement production and controllable quality. However, the temperature near the kiln head is significantly higher than that near the decomposing furnace, rising from 900-1050 DEG C to 1050-1200 DEG C; the environment temperature is close to or even exceeds the temperature limit that the heat-resistant steel damper plate can withstand; meanwhile, the flow rate of the tertiary air near the kiln head is higher, and the flying sand material is larger; the physical impact on the damper plate is greater, and the wear is more serious; the existing tertiary air damper plate products on the market cannot be installed and used stably for a long time near the kiln head. Therefore, it is urgent to develop a tertiary air damper plate suitable for installation near the kiln head. SUMMARY

[0004] The application aims at solving the problems existing in the prior art, and provides a silicon carbide ceramic tertiary air damper plate suitable for installation near a kiln head and a preparation method thereof; the tertiary air damper plate has the advantages of high strength, high toughness, high wear resistance, heat shock resistance, corrosion resistance and the like, can be installed and used stably for a long time near the kiln head, and realizes more flexible and accurate control of the tertiary air.

[0005] To solve the technical problems proposed in the application, the application provides a silicon carbide ceramic tertiary air damper plate suitable for installation near a kiln head, which comprises a damper plate body; the damper plate body is formed by sintering after being formed by injection molding of silicon carbide ceramic refractory slurry; the silicon carbide ceramic refractory slurry comprises the following raw materials in mass percentage: 70-90% of silicon carbide, 1-5% of binder A, 7-20% of alumina powder and 1-6% of binder B; the sum of the above raw materials is 100%, and 0.2-0.4% of additives and 1-6% of water are additionally added based on the total mass of the above raw materials.

[0006] In the above scheme, the particle size of the silicon carbide is 5-0.1 mm.

[0007] In the above scheme, the binder A comprises the following raw materials in mass percentage: graphite 10-30%, silica sol 70-90%.

[0008] Further, the particle size of the graphite is less than 10 mu m, and the C content is greater than or equal to 98.5%.

[0009] Further, the SiO2 content of the silica sol is greater than or equal to 20%, the pH value is 9-10, and the impurity content is less than or equal to 0.5%.

[0010] In the above scheme, the particle size of the alumina powder is less than 5 mu m, and the purity is greater than 99%.

[0011] In the above scheme, the binder B comprises the following raw materials in mass percentage: calcium acetate 10-20%, water 35-55%, and pseudo-boehmite powder 30-50%.

[0012] Further, the purity of the calcium acetate is greater than or equal to 99%.

[0013] Further, the particle size of the pseudo-boehmite powder is 3-10 mu m, and the purity is greater than or equal to 99%.

[0014] In the above scheme, the additive is a mixture of one or more of metallic silicon, aluminum nitride, and boron carbide with rare earth oxides, and the particle size is less than 5 mu m.

[0015] Further, the rare earth oxide is one of Y2O3, La2O3, and Ti2O3.

[0016] Further, the mass ratio of the sum of the mass of metallic silicon, aluminum nitride, and boron carbide to the mass of the rare earth oxide in the additive is 100:(10-30).

[0017] The application also provides a preparation method of a silicon carbide ceramic tertiary air shutter plate suitable for installation near a kiln head, comprising the following steps:

[0018] 1) Add graphite to silica sol, stir first and then ultrasonic dispersion, repeat several times to obtain a binder A;

[0019] 2) Dissolve calcium acetate in water, then add pseudo-boehmite powder and ultrasonic dispersion to obtain a binder B;

[0020] 3) Add silicon carbide to a mixer, then sequentially add the binder A, a part of alumina powder, the binder B, and the remaining alumina powder to the mixer for mixing, and each time after adding, the mixture needs to be uniformly mixed before adding the next one, and finally, sequentially add the additive and water and mix uniformly to obtain a silicon carbide ceramic refractory slurry;

[0021] 4) adding the silicon carbide ceramic refractory slurry into a mold for slip casting, obtaining a green body after demolding, and sintering the green body in a kiln after drying, to obtain the silicon carbide ceramic tertiary air damper plate.

[0022] In the above scheme, in step 1), the stirring rate is 600-900 rmp, the single stirring time is 10-30 min, the single ultrasonic dispersion time is 10-30 min, and the repetition number is 3-5 times.

[0023] In the above scheme, in step 2), the ultrasonic dispersion time is 10-30 min.

[0024] In the above scheme, in step 3), the mass of the first added alumina micropowder accounts for 3-10% of the total mass of the raw materials, and the mass of the second added alumina micropowder accounts for 4-10% of the total mass of the raw materials.

[0025] In the above scheme, in step 4), the drying temperature is 100-200 DEG C, and the drying time is 24-48 h.

[0026] In the above scheme, in step 4), the sintering temperature is 1380-1600 DEG C, and the sintering time is 2-4 h.

[0027] In the above scheme, the volume density of the silicon carbide ceramic tertiary air damper plate is 2.8-3.1 g / cm 3 , the room temperature bending strength after drying of the green body is 16-20 MPa, the room temperature bending strength after sintering is 22-28 MPa, and the high-temperature wear resistance test 1200 DEG C x 0.5 h wear loss is 2-5 cm 3 .

[0028] In the above scheme, the silicon carbide ceramic tertiary air damper plate is installed in the tertiary air pipe of a cement kiln at a distance of 1-2 m from the kiln head smoke chamber, the service temperature is 1050-1200 DEG C, and the service life is 18-24 months.

[0029] The main technical idea of the application is as follows:

[0030] 1) The present application adds graphite to silica sol, stirs, then ultrasonically treats, and repeats the operation several times to produce binder A, which can cause the graphite to bond with the silicon-oxygen bond of the silica sol, facilitating the bonding and reaction of the two. Binder A not only improves the bonding strength between the carbonized silicon and alumina micropowder after injection molding, so that the green body remains intact during handling, demolding and other operations, reducing the generation of defects; but also, during high-temperature heat treatment, the graphite, metallic silicon, aluminum nitride and boron carbide in the additives react with the silicon-oxygen ions, and reduce the silicon-oxygen ions to elemental silicon, which, under the action of rare earth oxides, produces a gas-liquid-solid phase reaction to promote the nucleation and growth of SiC whiskers with a certain length-diameter ratio, which interweave with each other to improve the wear resistance, toughness, thermal shock resistance and corrosion resistance of the tertiary air damper plate.

[0031] 2) The present application dissolves calcium acetate in water, then adds pseudo-boehmite powder and ultrasonically disperses to produce binder B. The calcium ions produced during the dissolution of calcium acetate will bond with the aluminum-oxygen bond produced after the dispersion and dissolution of pseudo-boehmite, and the acetate ions will uniformly disperse the aggregate formed after the bonding of calcium ions and aluminum-oxygen bond while retaining moisture; binder B reacts within a certain time after injection molding to improve the strength between the combination of carbonized silicon and alumina micropowder formed by binder A, further improving the integrity of the green body; at the same time, binder B is more likely to generate calcium hexaluminate after heat treatment under the action of additives due to the bonding between calcium ions and aluminum-oxygen bond, improving the wear resistance, toughness, thermal shock resistance and corrosion resistance of the tertiary air damper plate, especially its alkali corrosion resistance.

[0032] 3) The selected additives of the present application are used in combination with binder A and binder B to generate SiC whiskers and calcium hexaluminate with an interweaving structure in the tertiary air damper plate at a relatively low temperature, reducing defects caused by expansion or shrinkage during the sintering process, reducing the defects and pores of the tertiary air damper plate, and improving the wear resistance, toughness and corrosion resistance of the tertiary air damper plate.

[0033] 4) The present application adds alumina micropowder twice because the first addition of alumina micropowder can achieve the adhesion of binder A to the surface of carbonized silicon, and the alumina micropowder can protect this coating structure; the second addition of alumina micropowder is to uniformly distribute binder B in the matrix, improve the integrity of the slurry, and make it have uniform bonding strength.

[0034] Compared with the prior art, the present application has the following advantages:

[0035] The silicon carbide ceramic tertiary air damper plate has the advantages of high strength, high toughness, high wear resistance, thermal shock resistance, corrosion resistance and the like, can be installed near the kiln head and used stably for a long time, realizes more flexible and more accurate control of the tertiary air, improves product stability, and guarantees long-term stable operation of the cement kiln. The service life of the silicon carbide ceramic tertiary air damper plate can reach 18-24 months, and the positive effects of energy saving and emission reduction, production safety improvement, product quality stability guarantee and production benefit improvement are achieved. DETAILED DESCRIPTION

[0036] In order to better understand the present application, the content of the present application will be further illustrated below in combination with examples, but the content of the present application is not limited to the following examples only.

[0037] In the following examples, the particle size of the selected silicon carbide is 5-0.1 mm; the particle size of the graphite is less than 10 μm, and the C content is ≥98.5%; the SiO2 content of the silica sol is 20-30%, the pH value is 9-10, and the impurity content is ≤0.5%; the particle size of the alumina micropowder is less than 5 μm, and the purity is greater than 99%; the purity of calcium acetate is ≥99%; the particle size of the pseudo-boehmite powder is 3-10 μm, and the purity is ≥99%; and the water is deionized water.

[0038] In the following examples, the bulk density is measured by the method of GB / T 2997-2015, the cold modulus of rupture after drying of the initial blank and the cold modulus of rupture after sintering are measured by the method of GB / T 3001-201, and the high-temperature wear resistance at 1200℃×0.5h is measured by the method of GB / T 18301-2001.

[0039] Example 1

[0040] A silicon carbide ceramic tertiary air damper plate suitable for installation near the kiln head, wherein the damper plate body is formed by sintering after being formed by grouting of a silicon carbide ceramic refractory slurry, the silicon carbide ceramic refractory slurry comprises the following raw materials in mass percentage: silicon carbide 71%, binder A 5%, alumina micropowder 18%, and binder B 6%, and additionally 0.4% of an additive and 2% of water based on the total mass of the above raw materials.

[0041] The binder A comprises the following raw materials in mass percentage: graphite 25% and silica sol 75%; the binder B comprises the following raw materials in mass percentage: calcium acetate 15%, water 40%, and pseudo-boehmite powder 45%; the additive is a mixture of aluminum nitride, boron carbide and La2O3, and the mass ratio of the sum of the mass of aluminum nitride and boron carbide to the mass of La2O3 is 100:28, and the particle size is less than 5 μm.

[0042] The preparation method of the silicon carbide ceramic tertiary air damper plate of the present embodiment comprises the following steps:

[0043] 1) Add graphite into silica sol, stir at a speed of 850 rmp for 28 min, then ultrasonic dispersion for 27 min, repeat stirring and ultrasonic dispersion for 3-5 times, to obtain binder A;

[0044] 2) Dissolve calcium acetate in water, then add pseudo-boehmite powder, ultrasonic dispersion for 25 min, to obtain binder B;

[0045] 3) Add silicon carbide into a mixer, then add binder A, 9% of total mass of raw materials of alumina powder, binder B, 9% of total mass of raw materials of alumina powder into the mixer in sequence, mix after each addition, then add the next, finally add additives and water in sequence, to obtain silicon carbide ceramic refractory slurry;

[0046] 4) Add silicon carbide ceramic refractory slurry into a mold, to form by injection molding, to obtain green body, dry the green body at 200℃ for 48 h, then sinter in a kiln at 1380℃ for 3.5 h, to obtain silicon carbide ceramic tertiary air damper plate.

[0047] Example 2

[0048] A silicon carbide ceramic tertiary air damper plate suitable for installation near the kiln head, the damper plate body is sintered after being formed by injection molding of silicon carbide ceramic refractory slurry, the silicon carbide ceramic refractory slurry comprises the following raw materials in mass percentage: silicon carbide 80%, binder A 4%, alumina powder 12%, binder B 4%, and 0.3% of additives and 3% of water of total mass of the above raw materials are additionally added;

[0049] The binder A comprises the following raw materials in mass percentage: graphite 20%, silica sol 80%; the binder B comprises the following raw materials in mass percentage: calcium acetate 13%, water 52%, pseudo-boehmite powder 35%; the additives are a mixture of metallic silicon, aluminum nitride and Y2O3, the mass ratio of the sum of the mass of metallic silicon and aluminum nitride to the mass of Y2O3 is 100:15, and the particle size is less than 5 μm.

[0050] The preparation method of the silicon carbide ceramic tertiary air damper plate of the example comprises the following steps:

[0051] 1) Add graphite into silica sol, stir at a speed of 700 rmp for 22 min, then ultrasonic dispersion for 26 min, repeat stirring and ultrasonic dispersion for 3-5 times, to obtain binder A;

[0052] 2) Dissolve calcium acetate in water, then add pseudo-boehmite powder, ultrasonic dispersion for 26 min, to obtain binder B;

[0053] 3) add silicon carbide into the mixer, then add binder A, 6% of alumina powder of the total mass of raw materials, binder B, 6% of alumina powder of the total mass of raw materials into the mixer in turn, mix well after each addition, then add the next one, finally add additives and water in turn and mix well to obtain silicon carbide ceramic refractory slurry;

[0054] 4) add the silicon carbide ceramic refractory slurry into the mold to form by injection molding, get the green body after demolding, dry the green body at 110℃ for 24h, then sinter at 1450℃ for 3h in the kiln to form the silicon carbide ceramic tertiary air damper plate.

[0055] Example 3

[0056] A silicon carbide ceramic tertiary air damper plate suitable for installation near the kiln head, the damper plate body is formed by sintering the silicon carbide ceramic refractory slurry, the silicon carbide ceramic refractory slurry comprises the following raw materials in mass percentage: silicon carbide 89%, binder A 2%, alumina powder 7%, binder B 2%, and 0.2% of the total mass of the above raw materials of additives and 4% of water are added;

[0057] Wherein, binder A comprises the following raw materials in mass percentage: graphite 15%, silica sol 85%; binder B comprises the following raw materials in mass percentage: calcium acetate 18%, water 34%, pseudo-boehmite fine powder 48%; the additive is a mixture of boron carbide and Ti2O3 in a mass ratio of 100:23, with a particle size of less than 5μm.

[0058] The preparation method of the silicon carbide ceramic tertiary air damper plate of the present embodiment comprises the following steps:

[0059] 1) add graphite into silica sol, first stir at a speed of 650rmp for 23min, then ultrasonic dispersion for 19min, repeat stirring and ultrasonic dispersion for 3-5 times to obtain binder A;

[0060] 2) dissolve calcium acetate in water, then add pseudo-boehmite fine powder, ultrasonic dispersion for 15min to obtain binder B;

[0061] 3) add silicon carbide into the mixer, then add binder A, 4% of alumina powder of the total mass of raw materials, binder B, 3% of alumina powder of the total mass of raw materials into the mixer in turn, mix well after each addition, then add the next one, finally add additives and water in turn and mix well to obtain silicon carbide ceramic refractory slurry;

[0062] 4) add the silicon carbide ceramic refractory slurry into the mold to form by injection molding, get the green body after demolding, dry the green body at 150℃ for 36h, then sinter at 1500℃ for 2.5h in the kiln to form the silicon carbide ceramic tertiary air damper plate.

[0063] Comparative Example 1

[0064] Comparative Example 1 differs from Example 1 only in that no rare earth oxide is added to the additive.

[0065] Comparative Example 2

[0066] Comparative Example 2 differs from Example 1 only in that no binder A is added.

[0067] Comparative Example 3

[0068] Comparative Example 3 differs from Example 1 only in that no binder B is added.

[0069] The silicon carbide ceramic tertiary air damper plates obtained in each of the examples and comparative examples were installed in the tertiary air pipe of a cement kiln 1-2 m from the kiln head flue, and were subjected to service life tests, and their performance was evaluated in combination with other performance parameters.

[0070] Table 1

[0071]

[0072] As can be seen from Table 1, the silicon carbide ceramic tertiary air damper plates of the present application have a bulk density of 2.8-3.1 g / cm 3 , a cold modulus of rupture after drying of the green body of 16-20 MPa, a cold modulus of rupture after sintering of 22-28 MPa, and a high-temperature wear resistance of 2-5 cm 3 of wear after 1200°C x 0.5 h. When installed near the kiln head in a service environment temperature of 1050-1200°C, the service life is 18-24 months. The strength and high-temperature wear resistance of the comparative examples are significantly lower than those of the present application, and the service life does not meet expectations.

[0073] In addition, the conventional "metal skeleton + outer lining castable" structure damper plates currently on the market usually begin to have problems such as falling off and cracking when installed near the kiln head, and are used for only 1-2 months at most, and need to be repaired or replaced after being used for half a year. The present application greatly improves the use effect of the damper plates in this position, and greatly saves the repair cost and repair period of the tertiary air damper plates.

[0074] The above examples are merely illustrative and are not intended to limit the embodiments. Other variations and modifications can be made to the above-described embodiments based on the description contained herein, and it is therefore intended that all such variations and modifications be included within the scope of the present application. Obviously, many modifications and variations of the present application are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A silicon carbide ceramic tertiary air damper suitable for installation near the kiln head, comprising a damper body, characterized in that, The gate body is formed by sintering silicon carbide ceramic refractory slurry. The silicon carbide ceramic refractory slurry includes the following raw materials by mass percentage: 70-90% silicon carbide, 1-5% binder A, 7-20% alumina micro powder, and 1-6% binder B, with the sum of the above raw materials being 100%. In addition, 0.2-0.4% of the total mass of the above raw materials are added as additives and 1-6% of water. Among them, binder A is composed of graphite and silica sol, and binder B is composed of calcium acetate, water, and pseudoboehmite fine powder. The additives are one or more of metallic silicon, aluminum nitride, and boron carbide mixed with rare earth oxides.

2. The silicon carbide ceramic tertiary air damper suitable for installation near the kiln head according to claim 1, characterized in that, The binder A comprises the following raw materials by mass percentage: 10-30% graphite and 70-90% silica sol.

3. The silicon carbide ceramic tertiary air damper suitable for installation near the kiln head according to claim 1, characterized in that, The binder B comprises the following raw materials in the following mass percentages: calcium acetate 10-20%, water 35-55%, and pseudoboehmite fine powder 30-50%.

4. The silicon carbide ceramic tertiary air damper suitable for installation near the kiln head according to claim 1, characterized in that, The particle size of the additive is less than 5 μm.

5. The silicon carbide ceramic tertiary air damper suitable for installation near the kiln head according to claim 4, characterized in that, The rare earth oxide is one of Y2O3 and La2O3; the mass ratio of the sum of the masses of metallic silicon, aluminum nitride and boron carbide in the additive to the mass of the rare earth oxide is 100:(10~30).

6. The silicon carbide ceramic tertiary air damper suitable for installation near the kiln head according to claim 1, characterized in that, The silicon carbide has a particle size of 5~0.1mm; the alumina micro powder has a particle size of less than 5μm and a purity of greater than 99%; the graphite has a particle size of less than 10μm and a C content of ≥98.5%; the silica sol has a SiO2 content of ≥20% and a pH value of 9~10; and the pseudoboehmite fine powder has a particle size of 3~10μm and a purity of ≥99%.

7. A method for preparing a silicon carbide ceramic tertiary air damper suitable for installation near the kiln head, as described in any one of claims 1 to 6, characterized in that, Includes the following steps: 1) Add graphite to silica sol, stir first and then ultrasonically disperse, repeat several times to obtain binder A; 2) Dissolve calcium acetate in water, then add boehmite powder and disperse it ultrasonically to obtain binder B; 3) Add silicon carbide to the mixer, and then add binder A, a portion of alumina micro powder, binder B, and the remaining alumina micro powder to the mixer in sequence for mixing. After each addition, the mixture must be mixed evenly before adding the next one. Finally, add the additives and water in sequence and mix evenly to obtain silicon carbide ceramic refractory slurry. 4) Add silicon carbide ceramic refractory slurry into the mold for injection molding. After demolding, a preliminary blank is obtained. After drying, the preliminary blank is sintered in the kiln to obtain a silicon carbide ceramic tertiary air damper.

8. The method for preparing a silicon carbide ceramic tertiary air damper suitable for installation near the kiln head according to claim 7, characterized in that, The mass of alumina micro powder added for the first time accounts for 3-10% of the total mass of the raw materials, and the mass of alumina micro powder added for the second time accounts for 4-10% of the total mass of the raw materials; the drying temperature is 100-200℃, and the drying time is 24-48h; the sintering temperature is 1380-1600℃, and the sintering time is 2-4h.

9. The method for preparing a silicon carbide ceramic tertiary air damper suitable for installation near the kiln head according to claim 7, characterized in that, The bulk density of the silicon carbide ceramic tertiary air damper is 2.8~3.1 g / cm³. 3 The room temperature flexural strength of the initial blank after drying is 16~20MPa, and the room temperature flexural strength after sintering is 22~28MPa. The high temperature abrasion resistance test at 1200℃ for 0.5h shows a wear of 2~5cm. 3 .

10. The method for preparing a silicon carbide ceramic tertiary air damper suitable for installation near the kiln head according to claim 7, characterized in that, The silicon carbide ceramic tertiary air damper is installed in the tertiary air duct of the cement kiln, 1-2m away from the kiln head smoke chamber. The operating temperature is 1050-1200℃, and the service life is 18-24 months.

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