Zirconite electrode brick and preparation method and application thereof

Abstract

The invention belongs to the technical field of refractory materials, and particularly relates to a zircon electrode brick and a preparation method and application thereof. According to the zircon electrode brick, powder and an organic binding agent are subjected to wet grinding to obtain slurry, the slurry is subjected to spray granulation to obtain granulation powder, the granulation powder is subjected to isostatic pressing to obtain a green body, the green body is sintered to obtain the electrode brick, and the powder comprises the following raw materials in percentage by weight: 10-40% of 65-grade zircon powder; 59.3% to 89.6% of 66 grade zirconite powder; and 0.4%-0.7% of titanium dioxide. The high-temperature resistivity and the high-temperature stability are greatly improved, and the service life is long. The invention also provides a preparation method and application in a glass furnace.

Description

Technical Field

[0001] The invention belongs to the technical field of refractory materials, and in particular relates to zircon electrode bricks and a preparation method and application thereof. Background Art

[0002] The energy-saving and consumption-reducing technologies of industrial furnaces such as high-power "fire-electricity" composite melting and all-electric melting of glass melting furnaces have achieved rapid development. Electric melting glass furnaces are mainly heated by electricity. The current in the heating electrode causes the temperature of the electrode bricks to rise, and the flow of the glass liquid to accelerate, resulting in serious erosion around the electrode holes of ordinary dense zircon bricks, increasing the stones in the glass liquid, affecting the quality of the glass, and seriously affecting the service life of the electric melting glass furnace.

[0003] China Utility Model Patent Authorization Announcement No. CN207002556U proposes an electrode layer brick for an electric-melted glass furnace. The method of adding more corrosion-resistant electric-melted high-zirconium bricks as lining at the electrode hole site where corrosion is serious improves the corrosion resistance of the electrode layer brick at the electrode hole site, prolongs the life of the electric-melted glass furnace, and improves the quality of the glass liquid. However, the electrode layer brick is expensive, the workers have to work hard during masonry, and the operation is difficult.

[0004] In the article "Development and Application of High-Resistance Fused-Cast Zirconia Corundum Bricks" in Volume 31, Issue 6 of "Shandong Ceramics", the chemical composition of fused zirconium corundum bricks was rationally designed and controlled to meet the requirements of fused-cast zirconium corundum refractory products for glass melting furnaces. High-resistance and corrosion-resistant fused-cast zirconium corundum bricks were developed, and the high-temperature resistivity of fused zirconium corundum bricks at 1600℃ was increased from about 80Ω·cm to 250Ω·cm. The actual erosion of the kiln was greatly improved, but the high-temperature resistivity was still low.

[0005] In Chinese invention patent application publication numbers CN108727019A, CN116986897A, CN102007089A, and U.S. invention patent publication number US5124287A, zircon bricks improve thermal shock stability and corrosion resistance by adding ZrO2, ZA, MgO, etc. However, the added ZrO2 component is conductive, and this type of thermal shock resistant zircon brick cannot be used in electrode areas.

[0006] Chinese invention patent application publication numbers CN111039682A, CN105060902A, CN102036934A, CN101851107A, CN107117963A and CN102584286A mainly propose technical solutions to improve the creep rate of zircon or zircon composite overflow bricks.

[0007] Chinese invention patent application publication numbers CN106116571A and CN106518107A disclose methods for preparing high-purity dense zircon bricks or layered high-purity zircon refractory materials using quartz powder and zirconium oxide powder.

[0008] Chinese invention patent application publication number CN105272187A proposes a method for preparing zircon ceramics, with zircon as the matrix. The sintering aid in the technical solution is composed of 5% magnesium oxide, 1% yttrium oxide, and 4% titanium dioxide, which account for 5% of the mass of zircon. The high proportion of the additives magnesium oxide and titanium dioxide results in poor volume stability of the ceramic at high temperatures.

[0009] In summary, ordinary zircon bricks have the following problems: low high-temperature resistivity. Due to the heating effect of the current in the electrode on the brick, the temperature of the electrode brick increases and the glass erosion around the electrode hole intensifies, causing abnormal erosion of the electrode brick; ordinary zircon bricks decompose at 1600°C or higher temperatures, resulting in volume expansion and loose structure, which seriously affects the service life of the electrode brick. Summary of the invention

[0010] In order to solve the above technical problems, the present invention provides a zircon electrode brick, which greatly improves high temperature resistivity and high temperature stability and has a long service life. The present invention also provides a preparation method and application of the zircon electrode brick in a glass melting furnace.

[0011] The zircon electrode brick of the present invention is obtained by wet grinding of powder and organic binder to obtain slurry, spray granulation of the slurry to obtain granulated powder, isostatic pressing of the granulated powder to obtain green body, and sintering of the green body to obtain the electrode brick, wherein the powder includes the following raw materials in percentage by weight: 65 grade zircon powder, 10%-40%; Grade 66 zircon powder, 59.3%-89.6%; Titanium dioxide, 0.4%-0.7%; The chemical composition of 65-grade zircon powder is calculated by mass percentage: SiO2<34%, 0.3%<Al2O3<1.0%, 0.1%<Fe2O3<0.2%, ZrO2>65%; preferably, the mass percentage of 0.6%<Al2O3 in 65-grade zircon powder is<1.0%, and the particle size is ≤320 mesh. When Al2O3 in 65-grade zircon powder is lower than 0.6%, it is beneficial to improve the high-temperature resistivity of the product, but the heating permanent line change rate at 1700℃ for 24h is high; when Al2O3 in 65-grade zircon powder is higher than 1.0%, the volume density of the product is low.

[0012] The chemical composition of the 66-grade zircon powder is calculated by mass percentage: SiO2<34%, Al2O3<0.3%, Fe2O3<0.1%, ZrO2>65.7%; preferably, the mass percentage of Al2O3 in the 66-grade zircon powder is less than 0.2%, the mass percentage of Fe2O3 is less than 0.05%, and the particle size is ≤320 mesh. When the mass percentage of Al2O3 in the 66-grade zircon powder is less than 0.3%, it is beneficial to improve the resistivity of the product, especially when the mass percentage of Al2O3 in the 66-grade zircon powder is less than 0.2%, the high-temperature resistivity of the product is the highest, the volume density is high, but the heating permanent line change rate at 1700℃ for 24 hours is only about 30% lower than that of the prior art.

[0013] Preferably, the titanium dioxide is rutile, with a chemical composition of TiO2>98.5% and a particle size of ≤320 mesh. When the amount of titanium dioxide added is less than 0.4%, the volume density is low, which is beneficial to improving the high-temperature resistivity of the product, but the heating permanent line change rate at 1700°C for 24 hours is high and the high-temperature stability is poor; when the amount of titanium dioxide added is greater than 0.7%, for example, adding 1.0% titanium dioxide, it is not beneficial to improving the high-temperature resistivity of the product and the high-temperature stability at 1700°C for 24 hours.

[0014] The wet grinding steps are as follows: firstly wet-grind the 65-grade zircon powder, titanium dioxide, and organic binder, and then add the 66-grade zircon powder and continue wet-grinding to obtain a slurry.

[0015] Preferably, the organic binder is one or both of carboxymethyl cellulose and polyvinyl alcohol, and the added amount is 1.5%-3.0% of the powder mass.

[0016] The method for preparing the zircon electrode brick of the present invention comprises the following steps: (1) The 65-grade zircon powder, titanium dioxide, and organic binder are subjected to the first step of wet grinding for 10-30 minutes until the particle size is 4-8 μm; then the 66-grade zircon powder is added and the second step of wet grinding is carried out for 20-40 minutes until the particle size is 5-9 μm to obtain a batch slurry; The specific steps of step (1) are as follows: adding zirconium oxide balls, water, 65-grade zircon powder, titanium dioxide, and an organic binder into a ball mill for a first step of wet grinding, the grinding time is 10-30 minutes, until the particle size is 4-8 μm; then adding 66-grade zircon powder into the ball mill for a second step of wet grinding, the grinding time is 20-40 minutes, until the particle size is 5-9 μm, to form a batch slurry.

[0017] In step (1), the ratio of the mass of the zirconia ball, the total mass of the powder and the organic binder, and the mass of water is 2:2:1.

[0018] (2) The batch material slurry is spray granulated to form granulated powder, and the granulated powder is isostatically pressed to obtain a green body; (3) Drying and sintering the green body. The green body can be dried naturally or by using equipment. In the case of natural drying, it takes several days, preferably 1-3 days.

[0019] The role of wet grinding is to adjust the particle size of zircon particles so that titanium dioxide, organic binder and zircon particles are evenly distributed. The present invention finds that the wet grinding order of raw materials has an impact on high-temperature resistivity and high-temperature stability of bricks. Grinding 66-grade zircon powder first, or grinding 65-grade and 66-grade zircon powders at the same time, or grinding 65-grade zircon powder and 66-grade zircon powder separately and then mixing them are all unfavorable to high-temperature resistivity. The present invention first wet-grinds 65-grade zircon powder, and then adds 66-grade zircon powder to continue wet grinding, and the high-temperature resistivity of the brick is significantly improved. This is because the impurity components Al2O3, Fe2O3, and TiO2 in 65-grade zircon change in different grinding environments. The impurity components on the grain boundaries of the first-ground 65-grade zircon powder are more stable after sintering, so the resistivity and stability of the electrode brick at high temperature are improved.

[0020] Preferably, the isostatic pressure is 120-180 MPa.

[0021] Preferably, the sintering temperature is 1520-1560° C., the sintering holding time is 36-72 h, and the sintering heating rate is 3-5° C. / h.

[0022] The zircon electrode brick of the present invention is used in a glass melting furnace, and the apparent porosity of the electrode brick is ≤1.0%, and the volume density is ≥4.40g / cm 3 , the heating permanent line change rate at 1700℃ for 24h is ≤6%, and the high temperature resistivity at 1600℃ is ≥1000Ω·cm.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses 65-grade and 66-grade zircon powders, grinds them step by step and then sinters them. The high-temperature resistivity of the obtained products is 4 times higher than that of the high-resistance and corrosion-resistant fused-cast zirconium corundum bricks in the prior art, and 40% higher than that of ordinary zircon bricks. The high high-temperature resistivity can play an insulating role, reduce the heating effect of the current in the electrode on the brick, slow down the glass scouring around the electrode hole, and reduce the heat loss of the electrode brick. 2. The present invention found that when the addition amount of titanium dioxide is in the range of 0.4%-0.7%, the permanent line change rate of the obtained product heated at 1700°C for 24 hours is reduced by about 50% compared with the zircon bricks in the prior art with a titanium dioxide addition amount of 1.0% or 0.3%; zircon electrode bricks have high high-temperature stability, and the volume expansion and loose structure caused by the decomposition of zircon are weakened, which can effectively improve the service life of the electrode bricks.

[0024] 3. The product prepared by the present invention does not require electrode layer brick technology, is easy to operate and has the advantages of low cost; 4. The preparation method of the present invention is simple, easy to operate, scientific and reasonable, and convenient for large-scale industrial production. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be clearly and completely described below in conjunction with embodiments.

[0026] In actual operation, the temperature control allows a fluctuation of 2° C. Unless otherwise specified, all raw materials used in the examples are commercially available.

[0027] Among them, titanium dioxide is rutile type, and the chemical composition of the raw materials is shown in Table 1 below.

[0028] Table 1 Chemical composition of raw materials

[0029] The method for preparing the zircon electrode brick comprises the following steps: (1) Adding zirconium oxide balls, water, 65-grade zircon powder, titanium dioxide, and an organic binder to a ball mill for the first step of wet grinding; then adding the 66-grade zircon powder to the ball mill for the second step of wet grinding to form a batch slurry; wherein the mass ratio of the zirconium oxide balls, the total mass of the powder and the organic binder, and the mass of water is 2:2:1; (2) The batch slurry is subjected to spray granulation to form granulated powder, and the granulated powder is isostatically pressed to obtain a green body with a length of 800 mm, a thickness of 500 mm, and a width of 600 mm; (3) The green body is naturally dried and sintered.

[0030] Examples 1-9 and Comparative Examples 1, 2, 5 and 6 were prepared using the above method.

[0031] The difference between Comparative Example 3 and the above preparation method is that in step (1), zirconium oxide balls, water, grade 65 zircon powder I, grade 66 zircon powder I, titanium dioxide, and an organic binder are added to a ball mill to perform the first step of wet grinding, and then the second step of wet grinding is directly performed without adding grade 66 zircon powder to form a batch slurry.

[0032] The difference between Comparative Example 4 and the above preparation method is that, in step (1), the 66-grade zircon powder I is put into the first step of wet grinding, and the 65-grade zircon powder I is put into the second step of wet grinding.

[0033] The specific raw material dosage and preparation process parameters of Examples 1-9 and Comparative Examples 1-6 are shown in Table 2. Among them, the data corresponding to 65 zircon powder I, 65 zircon powder II, 66 zircon powder I, 66 zircon powder II, titanium dioxide, and organic binder are all percentages of the mass of the powder; the particle size is measured by a laser particle size analyzer, and the particle size here refers to the median diameter, which refers to the particle size corresponding to the cumulative particle size distribution percentage of the sample reaching 50%. Its physical meaning is that particles with a particle size larger than it account for 50%, and particles with a particle size smaller than it also account for 50%, but it does not involve the aspect ratio of the particles.

[0034] Table 2 Raw material dosage and process parameters of Examples 1-9 and Comparative Examples 1-6

[0035] Performance Testing After the obtained electrode bricks were cooled to room temperature in the furnace, samples were cut and tested for bulk density, apparent porosity, compressive strength, high temperature resistivity at 1600℃ and heating permanent line change rate at 1700℃ for 24h. The obtained results are shown in Table 3.

[0036] Among them, the bulk density and porosity are determined using the GB / T2997-2015 test method for bulk density, apparent porosity and true porosity of dense shaped refractory products.

[0037] The chemical composition is determined by GB-T21114-2019 "X-ray fluorescence spectrochemical analysis of refractory materials-cast glass sheet method".

[0038] The high temperature resistivity is measured by the high temperature resistivity test method of fine ceramic thermoelectric materials in JIS R1650-2002. JIS R1612-2010 adopts the DC four-terminal method, with the sample size of Φ3-5mm and the length of 15-20mm.

[0039] The permanent linear change upon heating is determined using the GB-T5988-2007 refractory material permanent linear change test method: the sample size is 50mm×50mm×10mm, the test conditions are 1700℃×24h, the heating rate is 100℃ / h, and the permanent linear change upon heating is expressed as the percentage of volume change after test heating divided by 3.

[0040] Table 3 Physical and chemical index test results of Examples 1-9 and Comparative Examples 1-6

[0041] Compared with Example 6, Comparative Example 1 uses a single type of 65-grade zircon powder I, with an apparent porosity of 5.5% and a bulk density of only 4.02 g / cm 3Although the material's high-temperature resistivity at 1600°C reaches 930Ω·cm, the permanent line change rate of heating at 1700°C for 24 hours is 10.5%, and it cannot be used for a long time at high temperatures.

[0042] Compared with Example 6, Comparative Example 2 uses a single type of 66-grade zircon powder I, and its apparent porosity and volume density are equivalent to those of Example 6. However, the high-temperature resistivity of Example 6 at 1600°C is 40% higher than that of Comparative Example 2, and the heating permanent line change rate at 1700°C for 24 hours is 72% lower than that of Comparative Example 2, which has high resistance and high volume stability.

[0043] Compared with Example 4, in Comparative Example 3, 65-grade zircon powder I and 66-grade zircon powder I are added and ground together. The apparent porosity and volume density of Example 4 are equivalent to those of Comparative Example 3, but the high-temperature resistivity at 1600°C of Example 4 is increased by 94% compared with that of Comparative Example 3, and the heating permanent line change rate at 1700°C for 24 hours is reduced by 77% compared with that of Comparative Example 3. Compared with Comparative Example 3, the high-temperature resistivity at 1600°C and the permanent line change rate at 1700°C for 24 hours of Example 4 are significantly changed, and the Example 4 has high resistance and high volume stability. This indicates that grinding two zircon powder raw materials together will have an adverse effect on the high-temperature resistivity at 1600°C and the high-temperature stability at 1700°C, especially on the high-temperature resistivity.

[0044] Compared with Example 5, in Comparative Example 4, Grade 66 zircon powder I is first ground in the first step of wet grinding, and then Grade 65 zircon powder I is added in the second step of wet grinding for grinding together. The apparent porosity and volume density of Example 5 are equivalent to those of Comparative Example 4, but the 1600°C high temperature resistivity of Example 5 is increased by 49% over that of Comparative Example 4, and the heating permanent line change rate at 1700°C for 24 hours is reduced by 68% over that of Comparative Example 4. Compared with Comparative Example 4, both the 1600°C high temperature resistivity and the permanent line change rate at 1700°C for 24 hours in Example 5 are significantly changed; this indicates that grinding Grade 66 zircon powder first and then adding Grade 65 zircon powder for grinding together will also have an adverse effect on the 1600°C high temperature resistivity and the 1700°C high temperature stability, especially on the 1700°C high temperature stability.

[0045] Compared with Example 1, the titanium dioxide content used in Comparative Example 5 is 0.3%, its apparent porosity reaches 5.0%, and its bulk density is only 4.10 g / cm 3 Although the high temperature resistivity of the material at 1600°C reaches 950Ω·cm, the heating permanent line change rate at 1700°C for 24 hours is 9.7%, which is about 5 times that of Example 1, and the high temperature volume stability is poor.

[0046] Compared with Example 2, the titanium dioxide content used in Comparative Example 6 is 0.8%, and the apparent porosity and volume density of the two are comparable. However, the high temperature resistivity of Comparative Example 6 at 1600°C is about 29% lower than that of Example 2, and the heating permanent line change rate at 1700°C for 24 hours is about 4.5 times that of Example 2.

[0047] Comparative Examples 5 and 6 show that when the content of titanium dioxide in the powder is lower than 0.3%, it will have a significant adverse effect on the high-temperature stability of the product at 1700°C. When the content of titanium dioxide in the powder exceeds 0.7%, it will have an adverse effect on the high-temperature resistivity at 1600°C and the high-temperature stability at 1700°C of the product.

[0048] In summary, the zircon electrode bricks prepared by the preparation method of the present invention have high high-temperature resistivity and high high-temperature volume stability, can reduce the heating effect of the current in the electrode on the bricks, reduce the heat loss and erosion of the electrode bricks, and can effectively improve the service life of the electrode bricks.

Claims

1. A zircon electrode brick, characterized in that: The powder and the organic binder are wet-grinded to obtain a slurry, the slurry is spray-granulated to obtain a granulated powder, the granulated powder is isostatically pressed to obtain a green body, and the green body is sintered to obtain the electrode brick, wherein the powder includes the following raw materials in percentage by weight: 65 grade zircon powder, 10%-40%; Grade 66 zircon powder, 59.3%-89.6%; Titanium dioxide, 0.4%-0.7%; The chemical composition of 65-grade zircon powder is calculated by mass percentage: SiO2<34%, 0.3%<Al2O3<1.0%, 0.1%<Fe2O3<0.2%, ZrO2>65%; The chemical composition of 66-grade zircon powder is calculated by mass percentage: SiO2<34%, Al2O3<0.3%, Fe2O3<0.1%, ZrO2>65.7%; The wet grinding steps are as follows: firstly wet-grind the 65-grade zircon powder, titanium dioxide, and organic binder, and then add the 66-grade zircon powder and continue wet-grinding to obtain a slurry.

2. The zircon electrode brick according to claim 1, characterized in that: The mass percentage of Al2O3 in grade 65 zircon powder is 0.6%<1.0%, and the particle size is ≤320 mesh.

3. The zircon electrode brick according to claim 1, characterized in that: The mass percentage of Al2O3 in grade 66 zircon powder is less than 0.2%, the mass percentage of Fe2O3 is less than 0.05%, and the particle size is ≤320 mesh.

4. The zircon electrode brick according to claim 1, characterized in that: Titanium dioxide is rutile type, the mass percentage of TiO2 is greater than 98.5%, and the particle size is ≤320 mesh.

5. The zircon electrode brick according to claim 1, characterized in that: The organic binder is one or two of carboxymethyl cellulose and polyvinyl alcohol, and the added amount is 1.5%-3.0% of the powder mass.

6. A method for preparing a zircon electrode brick according to any one of claims 1 to 5, characterized in that: The steps include: (1) Wet-grinding grade 65 zircon powder, titanium dioxide, and an organic binder to a particle size of 4-8 μm in the first step; then adding grade 66 zircon powder, and wet-grinding to a particle size of 5-9 μm in the second step to obtain a batch slurry; (2) spray granulating the batch slurry to form granulated powder, and isostatically pressing the granulated powder to obtain a green body; (3) Drying and sintering the green body.

7. The method for preparing zircon electrode brick according to claim 6, characterized in that: The isostatic pressure is 120-180MPa.

8. The method for preparing zircon electrode brick according to claim 6, characterized in that: The sintering temperature is 1520-1560°C, and the sintering holding time is 36-72h.

9. The method for preparing zircon electrode brick according to claim 6, characterized in that: In step (1), the first step wet grinding time is 10-30 min, and the second step wet grinding time is 20-40 min.

10. Use of the zircon electrode brick according to any one of claims 1 to 5 in a glass melting furnace, characterized in that: The apparent porosity of the electrode brick is ≤1.0%, and the volume density is ≥4.40g / cm 3 , the heating permanent line change rate at 1700℃ for 24h is ≤6%, and the high temperature resistivity at 1600℃ is ≥1000Ω·cm.

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