High-purity high-temperature-resistant magnesia-calcium brick and preparation method thereof

Abstract

The invention discloses a high-purity high-temperature-resistant magnesia-calcium brick and a preparation method thereof.The high-purity high-temperature-resistant magnesia-calcium brick is prepared from, by weight, 50%-65% of high-purity magnesia, 15%-25% of high-purity calcium sand and 3%-8% of aluminum oxide; 2%-7% of metal silicon powder; 3%-6% of phenolic resin; 1%-3% of calcium fluoride; 1%-3% of aluminum powder; the invention further discloses a preparation method of the high-purity high-temperature-resistant magnesia-calcium brick. The preparation method comprises the following preparation steps: S1, raw material screening; S2, magnesia pretreatment; S3, calcium sand pretreatment; according to the invention, part of high-purity magnesia forms a porous spherical structure, and part of high-purity calcium sand is promoted to grow in a needle-like crystal form by adopting a crystallization method, so that the calcium sand is interspersed among magnesia particles, the interaction among raw materials is enhanced, and the strength of a green body is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesia-calcia bricks, and particularly to a high-purity high-temperature-resistant magnesia-calcia brick and a preparation method thereof. Background Art

[0002] Magnesia-calcia bricks are a type of refractory material widely used in high-temperature industrial scenarios. It is mainly used for the inner lining of converters and electric furnaces in steel smelting, to withstand the erosion of high-temperature molten steel and slag; as the inner lining in cement rotary kilns, to resist the friction of high-temperature materials and alkaline erosion; in parts such as the tank wall and furnace roof of glass melting furnaces, to withstand the erosion of high-temperature glass liquid, and plays a key role in ensuring the stable operation of high-temperature production links in various industries.

[0003] However, the conventional magnesia-calcia bricks on the market have poor bonding performance. Conventional binders connect raw materials by simple viscosity, and cannot, like phenolic resin, physically adsorb and chemically complex with metal silicon powder and aluminum powder by virtue of active groups, resulting in uneven dispersion of metal silicon powder and difficulty in constructing an effective anti-erosion structure. Their anti-erosion and compressive and flexural strengths are not good. In addition, in terms of anti-environmental erosion, ordinary magnesite and calcite sands have many impurities, are easily hydrolyzed by moisture, generate substances that damage the brick structure, and lack a self-repair mechanism, making it difficult to form a stable protective film in a strong erosion environment.

[0004] Accordingly, this application proposes a high-purity high-temperature-resistant magnesia-calcia brick and a preparation method thereof. Summary of the Invention

[0005] The purpose of the present invention is to solve the deficiencies existing in the prior art, and to propose a high-purity high-temperature-resistant magnesia-calcia brick and a preparation method thereof.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A high-purity high-temperature-resistant magnesia-calcia brick, comprising raw materials in the following weight percentages:

[0008] High-purity magnesite: 50% - 65%, and the magnesia content of the high-purity magnesite is not less than 98%;

[0009] High-purity calcite: 15% - 25%, and the calcium oxide content of the high-purity calcite is not less than 95%; alumina: 3% - 8%, used to improve the high-temperature stability of the brick; metal silicon powder: 2% - 7%, used to enhance the anti-erosion performance of the brick; phenolic resin: 3% - 6%, used to enhance the bonding force between raw materials; calcium fluoride: 1% - 3%, which can promote the sintering process of the brick; aluminum powder: 1% - 3%, used to improve the antioxidant capacity of the brick in a high-temperature environment.

[0010] Preferably, the particle size distribution in the high-purity magnesite is as follows: the proportion of particles with a size greater than 3 mm does not exceed 10%, and the proportion of particles with a size less than 0.075 mm is not less than 30%; the particle size distribution in the high-purity calcia is as follows: the proportion of particles with a size greater than 2 mm does not exceed 15%, and the proportion of particles with a size less than 0.1 mm is not less than 25%.

[0011] Preferably, the alumina can be replaced by cerium oxide or the two can be used in combination; the metallic silicon powder can be replaced by silicon carbide powder or the two can be used in combination.

[0012] Preferably, the phenolic resin is liquid phenolic resin with a solid content of 60% - 70%; the purity of calcium fluoride is not less than 98%; the particle size of the aluminum powder is 180 - 320 mesh.

[0013] The preparation method of the above-mentioned high-purity high-temperature-resistant magnesia-calcia brick includes the following preparation steps:

[0014] S1. Raw material screening: Use a 100 - 200 mesh vibrating screen and image recognition technology to screen the high-purity magnesite and calcia, remove impurities, and ensure that the particle size meets the standard;

[0015] S2. Pretreatment of magnesite: Take a part of the high-purity magnesite after screening and treat it by spray drying technology to form a porous spherical structure;

[0016] S3. Pretreatment of calcia: Take a part of the high-purity calcia after screening, configure it into a suspension, add a specific crystallization inducer, and promote the growth of calcia in the form of needle crystals;

[0017] S4. Mixing: Put the pretreated high-purity magnesite, high-purity calcia and additives into a high-speed mixer for mixing, and at the same time adopt ultrasonic-assisted mixing technology;

[0018] S5. Molding and sintering: Make the mixed material into a mud and inject it into a mold. After precise molding, carry out hot air circulation drying and gradient hot pressing sintering in sequence to obtain the finished product.

[0019] Preferably, in the S2 step, the pressure of spray drying is 0.5 - 1.5 MPa, the flow rate is 5 - 10 L / h, and the drying temperature is 150 - 200 °C.

[0020] Preferably, in the S3 step, the reaction temperature is controlled at 40 - 60 °C, the pH value is 8 - 10, the crystallization inducer added is disodium ethylenediaminetetraacetate, and the addition amount is 0.5% - 1% of the mass of calcia.

[0021] Preferably, in the S4 step, the material of the high-speed mixer is stainless steel 304, the rotation speed is 500 - 800 revolutions per minute, the mixing time is 30 - 60 minutes, and the ultrasonic frequency is 30 - 40 kHz.

[0022] Preferably, in the step S5, the mold has a microstructure, the molding pressure is 15 MPa, the hot air circulation drying temperature is 120 °C, the air blowing rate is 5 m 3 / h, the drying time is 10 hours. During gradient hot pressing and sintering, the brick blank is placed in a gradient heating furnace with specific dimensions, heated at a rate of 5 °C per minute, with a temperature difference of 4 - 6 °C per 10 cm. At 1600 °C, a pressure of 20 MPa is applied and maintained for 3 hours. The furnace chamber dimensions of the gradient heating furnace are 1 - 2 m in length, 0.5 - 1 m in width, and 0.5 - 1 m in height.

[0023] The present invention has the following beneficial effects:

[0024] 1. Through the spray drying technology, part of the high-purity magnesite forms a porous spherical structure, increasing the contact area with other raw materials. The internal pores can store additives, facilitating the uniform dispersion of additives. For part of the high-purity calcia, the chemical induction crystallization method is adopted, adding a specific crystallization inducer, controlling the reaction temperature and pH value, and promoting the growth of calcia in the form of needle-like crystals. The needle-like calcia intersperses between magnesite particles during subsequent mixing and molding, enhancing the interaction between raw materials and improving the strength of the green body.

[0025] 2. Due to its regular shape and large specific surface area, the porous spherical magnesite can more efficiently drive the surrounding raw materials to roll and mix in a high-speed mixer. With the assistance of ultrasonic waves, the mixing efficiency is greatly improved, and the mixing time is shortened by about 25% compared with that of conventional granular raw materials. At the same time, during mixing, the needle-like calcia promotes the flow of materials like a stirring rod due to its slender shape, further ensuring the uniform distribution of each raw material and reducing the defective rate caused by uneven mixing.

[0026] 3. In the sintering stage, the pores of the porous spherical magnesite are conducive to gas discharge, reducing internal defects of the brick body. The needle-like calcia interweaves with each other in the green body, like a steel bar structure, enhancing the structural stability of the brick body. After sintering, a tight and stable structure is formed inside the magnesia-calcia brick. The pores of the porous spherical magnesite effectively block heat conduction, and the enhanced structural stability by the needle-like calcia resists high-temperature deformation. This significantly improves the flexural and compressive strengths of the magnesia-calcia brick, and at the same time greatly enhances the high-temperature resistance performance, enabling it to withstand a higher temperature environment than the magnesia-calcia brick prepared by traditional processes, effectively extending the service life of the product and expanding its application in scenarios with high strength and high temperature requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a flowchart of the steps of a method for preparing a high-purity high-temperature-resistant magnesia-calcia brick proposed by the present invention;

[0028] Figure 2 is a broken line graph of the flexural strength of each embodiment of the present invention within a predetermined period;

[0029] Figure 3It is the broken line graph of the compressive strength of each embodiment of the present invention within a predetermined period;

[0030] Figure 4 It is the single graph of the flexural strength data of a high-purity high-temperature-resistant magnesia-calcia brick of the present invention at 1000 degrees Celsius with a seven-day age;

[0031] Figure 5 It is the graph of the compressive strength test of the rotating block made in the embodiment. Specific embodiments

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0033] Embodiment 1:

[0034] High-purity magnesite: 750 grams, with a magnesium oxide content of 98.5%, 8% of which has a particle size greater than 3 mm, and 35% of which has a particle size less than 0.075 mm;

[0035] High-purity calcia: 100 grams, with a calcium oxide content of 96%, 12% of which has a particle size greater than 2 mm, and 30% of which has a particle size less than 0.1 mm;

[0036] Aluminum oxide: 30 grams. To improve the high-temperature stability, alumina powder with a purity of 99% is used;

[0037] Metallic silicon powder: 30 grams, used to enhance the erosion resistance, with a purity of 98% of the metallic silicon powder;

[0038] Phenolic resin: 50 grams, with a solid content of 65% for the liquid phenolic resin;

[0039] Calcium fluoride: 20 grams, with a purity of 99%, promoting the sintering of the brick body;

[0040] Aluminum powder: 20 grams, with a particle size of 200 mesh to 300 mesh for the aluminum powder, improving the high-temperature oxidation resistance.

[0041] Embodiment 2:

[0042] High-purity magnesite: 500 grams, with a magnesium oxide content of 98.2%, 9% of which has a particle size greater than 3 mm, and 32% of which has a particle size less than 0.075 mm;

[0043] High-purity calcia: 250 grams, with a calcium oxide content of 95.5%, 13% of which has a particle size greater than 2 mm, and 28% of which has a particle size less than 0.1 mm;

[0044] Aluminum oxide: 80 grams, alumina with a purity of 99.5%;

[0045] Silicon metal powder: 70 g, purity 98.5%;

[0046] Phenolic resin: 60 g, solid content 68%;

[0047] Calcium fluoride: 20 g, purity 98.8%;

[0048] Aluminum powder: 20 g, aluminum powder particle size is between 180 mesh and 250 mesh.

[0049] Example 3:

[0050] High-purity magnesia: 600 g, magnesium oxide content 98%, the proportion of particle size greater than 3 mm is 7%, and the proportion of particle size less than 0.075 mm is 33%;

[0051] High-purity calcia: 150 g, calcium oxide content 95.2%, the proportion of particle size greater than 2 mm is 14%, and the proportion of particle size less than 0.1 mm is 26%;

[0052] Aluminum oxide: 50 g, purity 99.2%;

[0053] Silicon metal powder: 40 g, purity 98%;

[0054] Phenolic resin: 100 g, solid content 70%;

[0055] Calcium fluoride: 30 g, purity 99%;

[0056] Aluminum powder: 30 g, aluminum powder particle size is between 220 mesh and 320 mesh.

[0057] Example 4:

[0058] High-purity magnesia: 550 g, magnesium oxide content 98.3%, the proportion of particle size greater than 3 mm is 6%, and the proportion of particle size less than 0.075 mm is 34%;

[0059] High-purity calcia: 200 g, calcium oxide content 95.8%, the proportion of particle size greater than 2 mm is 10%, and the proportion of particle size less than 0.1 mm is 27%;

[0060] Aluminum oxide: 40 g, purity 99.3%;

[0061] Silicon metal powder: 60 g, purity 98.2%;

[0062] Phenolic resin: 80 g, solid content 66%;

[0063] Calcium fluoride: 40 g, purity 98.5%;

[0064] Aluminum powder: 30 g, aluminum powder particle size is between 200 mesh and 280 mesh.

[0065] Operate the raw materials of the above-mentioned embodiments according to the established process preparation steps: First, use a 100-200 mesh vibrating screen and image recognition technology to screen high-purity magnesite and calcite. Then, spray-dry some of the magnesite into porous spheres, and add a crystallization inducer to some of the calcite to make it into needle-shaped crystals. Subsequently, put the pretreated raw materials and additives into a high-speed mixer and mix them with ultrasonic assistance. Finally, make the mud into a mold for molding, and obtain the finished product through hot air circulation drying and gradient hot pressing sintering.

[0066] Example Five:

[0067] Weigh exactly the same raw materials as in Example 1, and use the same method as in the above embodiments, without performing Step S2 and Step S3.

[0068] High-purity magnesite: 750 grams, with a magnesium oxide content of 98.5%, a proportion of particles larger than 3 mm accounting for 8%, and a proportion of particles smaller than 0.075 mm accounting for 35%;

[0069] High-purity calcite: 100 grams, with a calcium oxide content of 96%, a proportion of particles larger than 2 mm accounting for 12%, and a proportion of particles smaller than 0.1 mm accounting for 30%;

[0070] Aluminum oxide: 30 grams. To improve the high-temperature stability, alumina powder with a purity of 99% is used;

[0071] Metallic silicon powder: 30 grams, used to enhance the erosion resistance, with a purity of 98% for the metallic silicon powder;

[0072] Phenolic resin: 50 grams, with a solid content of 65% for the liquid phenolic resin;

[0073] Calcium fluoride: 20 grams, with a purity of 99%, promoting the sintering of the brick body;

[0074] Aluminum powder: 20 grams, with the particle size of the aluminum powder being between 200 mesh and 300 mesh, enhancing the high-temperature oxidation resistance.

[0075] It should be noted that Comparative Example 1 adopts a conventional magnesia-calcia brick formula and preparation process. The proportion of raw materials such as high-purity magnesite and high-purity calcite in the formula deviates from the scope of the present invention. For example, the proportion of high-purity magnesite may be less than 50%. During the preparation process, key innovative steps such as low-temperature plasma activation and multi-dimensional ultrasonic-assisted mixing are lacking, and the equipment parameters are also set according to the traditional process, resulting in its performance indicators such as high-temperature erosion resistance time, thermal shock stability, and the starting temperature of load softening being significantly lower than those of the examples. Comparative Example 2 adopts parameters that deviate extremely from the scope of the present invention. The proportion of each raw material in the formula deviates greatly. For example, the high-purity magnesite may be as high as 70% or as low as 40%. The preparation process parameters also deviate severely, resulting in extremely poor product performance, and the numerical values of various performance indicators in the table are much lower than those of the examples, as shown in Table 1 specifically:

[0076] Table 1: Performance parameters of cement obtained in various embodiments and comparative examples

[0077]

[0078] Further, in terms of high temperature corrosion resistance time, the high temperature corrosion resistance time of Examples 1-5 is 8.2h, 7.7h, 7.4h, 7.6h, and 6.8h, respectively, while Comparative Example 1 is only 4.9h, and Comparative Example 2 is as low as 2.8h. Although the high temperature corrosion resistance time of Example 5 is relatively short in the examples, it is 6.8h, which is still 1.9h higher than Comparative Example 1 and 4h higher than Comparative Example 2. This shows that even if Example 5 does not carry out the pretreatment of spray drying magnesia sand into porous spheres and calcium sand into needle-shaped crystals, its specific raw material ratio, such as 750 grams of high-purity magnesia sand with a magnesium oxide content of 98.5% in coordination with other raw materials, can effectively resist the corrosive medium after the established process treatment, and the corrosion resistance time far exceeds the conventional comparative product, which greatly improves the service life of the product in a high temperature corrosion environment.

[0079] Furthermore, the thermal shock stability of Examples 1-5 is 30.5 times, 27.8 times, 28.6 times, 29.2 times, and 26.9 times, respectively, while that of Comparative Example 1 is 19.6 times, and that of Comparative Example 2 is 14.5 times. The 26.9 times of Example 5 is 7.3 times more than that of Comparative Example 1, and 12.4 times more than that of Comparative Example 2. This is due to the fine screening and activation to ensure the high quality of the raw materials, and the ultrasonic-assisted mixing to make the raw materials evenly dispersed, which enables the brick body to form an extremely stable internal structure. Therefore, in the face of drastic changes in temperature, even if Example 5 does not perform special raw material pretreatment, it can maintain good thermal shock stability performance, and its stability is far superior to that of the comparative example product.

[0080] Furthermore, in terms of the load softening start temperature, Examples 1 to 5 are 1702°C, 1678°C, 1689°C, 1693°C, and 1682°C, respectively, while Comparative Example 1 is 1598°C and Comparative Example 2 is 1545°C. The 1682°C of Example 5 is 84°C higher than that of Comparative Example 1 and 137°C higher than that of Comparative Example 2. This means that Example 5 precisely controls the raw material ratio so that the components work synergistically at high temperatures, and cooperates with processes such as hot air circulation drying and gradient hot pressing sintering to make the crystal structure more stable and orderly, so that when subjected to a certain load, it can start to soften at a higher temperature, showing excellent high temperature stability.

[0081] Specifically, refer to Figure 2, Example 1 relies on 750 grams of high-purity magnesite with a magnesium oxide content of 98.5%, combined with a reasonable particle size distribution, to build a stable basic structure. 30 grams of alumina with a purity of 99% imparts high-temperature stability to the material, enabling the 3-day flexural strength to reach 30.1 MPa, while that of Comparative Example 1 is only 24.5 MPa in 3 days, and Comparative Example 2 is even as low as 22.4 MPa. As time progresses, 30 grams of metallic silicon powder with a purity of 98% strengthens the internal structural bonding force. By 28 days, the flexural strength of Example 1 soars to 38.2 MPa, far exceeding 30.0 MPa of Comparative Example 1 and 29.0 MPa of Comparative Example 2. In Example 2, the amount of high-purity calcia sand is increased to 250 grams, combined with 80 grams of high-purity (99.5%) alumina. The 7-day flexural strength reaches 31.5 MPa, higher than 26.0 MPa of Comparative Example 1 and 25.0 MPa of Comparative Example 2 during the same period. Subsequently, 60 grams of phenolic resin with a solid content of 68% continuously optimizes the internal structure, and the 28-day flexural strength reaches 37.6 MPa, further widening the gap with the comparative examples. Example 3 relies on 100 grams of phenolic resin with a solid content of 70% to provide strong bonding force in the early stage, and the 3-day flexural strength leads the comparative examples. With the synergistic effect of 50 grams of alumina with a purity of 99.2% and other raw materials, the 12-day flexural strength reaches 33.5 MPa, far exceeding the corresponding values of the comparative examples during the same period. In Example 4, the amount of metallic silicon powder is increased to 60 grams (purity 98.2%), and the 18-day flexural strength reaches 35.2 MPa, showing a significant advantage compared with the comparative examples. In Example 5, although the raw material ratio is different from the previous settings, it has its own characteristics. Its 750 grams of high-purity magnesite with a magnesium oxide content of 98.5% provides stable support in the early stage. Due to the lack of special pretreatment of magnesite and calcia sand, to a certain extent, it affects the optimization degree of the internal structure. The 3-day flexural strength is 29.5 MPa, lower than 30.1 MPa of Example 1, but still higher than 24.5 MPa of Comparative Example 1 and 22.4 MPa of Comparative Example 2. As time goes by, by 24 days, 20 grams of calcium fluoride with a purity of 99% promotes the structural compactness, and the flexural strength reaches 34.8 MPa, lower than the originally set 35.3 MPa of Example 5. Compared with the growth trend of Example 1, the speed is slightly slower. This indicates that in the absence of the synergy of special pretreatment, although Example 5 can still maintain a certain increase in flexural strength relying on high-quality raw materials, its structural optimization efficiency is weaker than that of other examples. Compared with the comparative examples, the flexural strength of Example 5 at different time points still has obvious advantages, highlighting the basic role of the raw material formula of the present invention in improving the flexural performance.

[0082] The bricks made from all the above examples and comparative examples are successively placed in a compression testing machine, specifically as Figure 5 shown.

[0083] Refer to Figure 3, 750 grams of high-purity magnesite in Example 1, with a high magnesium oxide content of 98.5%, has a compressive strength of up to 108.7 MPa after 3 days, far exceeding 78.5 MPa of Comparative Example 1 and 73.2 MPa of Comparative Example 2. In high-temperature sintering, 30 grams of alumina with a purity of 99% and 30 grams of metallic silicon powder with a purity of 98% optimize the crystal structure, and the compressive strength soars to 155.6 MPa after 28 days, while Comparative Example 1 and Comparative Example 2 are only 122.5 MPa and 114.8 MPa respectively. 250 grams of high-purity calcia in Example 2 cooperate with 80 grams of alumina with a high purity (99.5%), and the compressive strength reaches 128.3 MPa after 12 days, far exceeding the corresponding values of the comparative examples. 60 grams of phenolic resin with a solid content of 68% improves the bonding of raw materials and further enhances the compressive capacity. 600 grams of high-purity magnesite and 150 grams of high-purity calcia in Example 3 build a stable framework, and 100 grams of phenolic resin with a high solid content (70%) strengthens the internal bonding. The compressive strength reaches 138.6 MPa after 18 days, far beyond the reach of the comparative examples. 50 grams of alumina with a purity of 99.2% and other raw materials continuously enhance the structural stability and promote the increase of compressive strength. 40 grams of alumina with a purity of 99.3% and 60 grams of metallic silicon powder (purity 98.2%) in Example 4 cooperate, and the compressive strength reaches 148.5 MPa after 24 days, significantly higher than that of the comparative examples. 750 grams of high-purity magnesite (magnesium oxide content 98.5%) in Example 5 provides a good compressive basis in the early stage, and 20 grams of aluminum powder (particle size between 200 mesh and 300 mesh) maintains the structural integrity at high temperatures. Due to the lack of special pretreatment of raw materials, there are certain limitations in forming and internal structure optimization. The compressive strength after 3 days is 105.5 MPa, lower than 108.7 MPa of Example 1, but far exceeding that of Comparative Example 1 and Comparative Example 2. By 28 days, the compressive strength reaches 147.8 MPa, lower than the originally set 150.3 MPa. Compared with Example 1, the increase in compressive strength is relatively small. However, compared with the comparative examples, the compressive strength advantage of Example 5 at each time point is still prominent, once again proving the effectiveness of the raw material formula of the present invention in improving the compressive performance. Even if some process links are adjusted, it can still ensure that the product has good compressive performance.

[0084] Specifically, such as Figure 4As shown, a group of bricks made randomly in Example 1, Example 2, and Example 3 respectively were taken. Under the constant temperature condition of 1000 degrees Celsius, the flexural strength of Example 1 decreased from 30.1 MPa at the normal seven-day age to 23 MPa, with a decrease value of 30.1 - 23 = 7.1 MPa, and the decrease amplitude was (30.1 - 23) ÷ 30.1 × 100% ≈ 23.6%. The reason was that the structure constructed by 750 grams of high-purity magnesite with 98.5% magnesium oxide content and 30 grams of alumina with 99% purity was affected by high temperature; for Example 2, it decreased from 31.5 MPa to 26.8 MPa, with a decrease value of 31.5 - 26.8 = 4.7 MPa, and the decrease amplitude was (31.5 - 26.8) ÷ 31.5 × 100% ≈ 14.9%. Because the synergistic effect of 250 grams of high-purity calcium sand and 80 grams of alumina with 99.5% purity maintained the structural stability relatively well at high temperature; for Example 3, it decreased from 30.9 MPa to 23.5 MPa, with a decrease value of 30.9 - 23.5 = 7.4 MPa, and the decrease amplitude was (30.9 - 23.5) ÷ 30.9 × 100% ≈ 23.9%. Relying on the synergy of 100 grams of phenolic resin with 70% solid content and 50 grams of alumina with 99.2% purity and other raw materials, it still retained a certain flexural performance at high temperature. Generally speaking, the flexural strength of each example decreased at high temperature, but due to the unique raw material ratio and process, different degrees of performance advantages were shown, reflecting the adaptability of the raw material ratio of the present invention to different temperature conditions.

[0085] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent replacements or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A high-purity high-temperature resistant magnesia-lime brick, characterized in that: The following raw materials are included in weight percentage: High-purity magnesia sand: 50% to 65%, the magnesium oxide content of the high-purity magnesia sand is not less than 98%; High-purity calcium sand: 15% to 25%, the calcium oxide content of the high-purity calcium sand is not less than 95%; Alumina: 3% to 8%, used to improve the high temperature stability of the brick; Metallic silicon powder: 2% to 7%, used to enhance the anti-corrosion performance of the brick; Phenolic resin: 3% to 6%, used to enhance the bonding strength between raw materials; Calcium fluoride: 1% to 3%, which can promote the sintering process of bricks; Aluminum powder: 1% to 3%, used to improve the oxidation resistance of bricks in high temperature environments.

2. A high-purity high-temperature resistant magnesia-lime brick according to claim 1, characterized in that: The particle size distribution in the high-purity magnesium sand is as follows: the proportion of particles larger than 3 mm does not exceed 10%, and the proportion of particles smaller than 0.075 mm is not less than 30%; the particle size distribution in the high-purity calcium sand is as follows: the proportion of particles larger than 2 mm does not exceed 15%, and the proportion of particles smaller than 0.1 mm is not less than 25%.

3. The high-purity high-temperature resistant magnesia-lime brick according to claim 1, characterized in that: The aluminum oxide may be replaced by cerium oxide or a mixture of the two. The metal silicon powder may be replaced by silicon carbide powder or a mixture of the two.

4. The high-purity high-temperature resistant magnesia-lime brick according to claim 1, characterized in that: The phenolic resin is a liquid phenolic resin with a solid content of 60% to 70%; the purity of the calcium fluoride is not less than 98%; and the particle size of the aluminum powder is 180 meshes to 320 meshes.

5. A method for preparing a high-purity high-temperature resistant magnesia-lime brick according to any one of claims 1 to 4, characterized in that: The method comprises the following preparation steps: S1. Raw material screening: Use 100-200 mesh vibrating screen and image recognition technology to screen high-purity magnesia sand and calcium sand to remove impurities and ensure that the particle size meets the standard; S2, magnesia pretreatment: taking part of the screened high-purity magnesia, and treating it by spray drying technology to form a porous spherical structure; S3. Calcium sand pretreatment: take part of the screened high-purity calcium sand, prepare it into a suspension, add a specific crystallization inducer, and promote the growth of calcium sand in the form of needle-shaped crystals; S4, mixing: putting the pretreated high-purity magnesium sand, high-purity calcium sand and additives into a high-speed mixer for mixing, and using ultrasonic assisted mixing technology; S5, molding and sintering: the mixed materials are made into mud and injected into the mold. After precise molding, hot air circulation drying and gradient hot pressing sintering are carried out in sequence to obtain the finished product.

6. The method for preparing a high-purity high-temperature resistant magnesia-lime brick according to claim 5, characterized in that: In the step S2, the spray drying pressure is 0.5-1.5 MPa, the flow rate is 5-10 L / h, and the drying temperature is 150-200°C.

7. The method for preparing a high-purity high-temperature resistant magnesia-lime brick according to claim 5, characterized in that: In the step S3, the reaction temperature is controlled to be 40-60° C., the pH value is 8-10, and the added crystallization inducing agent is disodium ethylenediaminetetraacetate, and the added amount is 0.5%-1% of the mass of the calcium sand.

8. The method for preparing a high-purity high-temperature resistant magnesia-lime brick according to claim 5, characterized in that: In the step S4, the high-speed mixer is made of stainless steel 304, has a rotation speed of 500-800 rpm, a mixing time of 30-60 minutes, and an ultrasonic frequency of 30-40 kHz.

9. The method for preparing a high-purity high-temperature resistant magnesia-lime brick according to claim 5, characterized in that: In the step S5, the mold has a microstructure, the molding pressure is 15 MPa, the hot air circulation drying temperature is 120° C., and the blowing speed is 5 m / s. 3 / h, drying time is 10 hours. During gradient hot pressing sintering, the bricks are placed in a gradient heating furnace of specific size, heated at 5°C / min, with a temperature difference of 4-6°C per 10cm, and a pressure of 20MPa is applied at 1600°C and kept warm for 3 hours. The size of the gradient heating furnace is 1-2m long, 0.5-1m wide and 0.5-1m high.

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