Rotary kiln refractory and preparation method thereof and rotary kiln refractory brick

Abstract

The application provides a rotary kiln refractory material and a preparation method thereof and a rotary kiln refractory brick, and relates to the technical field of refractory materials.The rotary kiln refractory material provided by the application comprises, in mass parts, 250-350 parts of corundum-mullite aggregate, 70-80 parts of powder additive, 40-60 parts of silicon-aluminum composite sol, 20-40 parts of refractory clay, 8-10 parts of composite steel fiber, 0.5-1.5 parts of adhesive, and 0.1-0.5 parts of plasticizer; wherein the composite steel fiber comprises a steel fiber substrate and an aluminum-magnesium alloy layer plated and solidified on the surface of the substrate. The aluminum-magnesium alloy layer plated on the surface of the steel fiber substrate is converted into a corundum and aluminum-magnesium spinel protective layer in situ at high temperature, the interfacial bonding strength of the composite steel fiber in the refractory material is improved, the erosion of hazardous waste to the refractory brick in the hazardous waste incineration process is blocked to inhibit thermal shock spalling, and the service life of the refractory brick can be effectively improved.

Description

Technical Field

[0001] This invention relates to the field of refractory materials technology, and in particular to a rotary kiln refractory material, its preparation method, and rotary kiln refractory bricks. Background Technology

[0002] Anthracene and carbazole are high-value-added products obtained from the deep processing of coal tar, and have wide applications in modern medicine, high-end dyes and optoelectronic materials. However, the purification processes of anthracene and carbazole, such as distillation, refining and crystallization, generate a large amount of hazardous waste rich in polycyclic aromatic hydrocarbons and heterocyclic compounds. The chemical structure of this type of hazardous waste is relatively stable and difficult to degrade or reuse. Usually, a rotary kiln is used at the end of the production line to treat it at high temperature and harmlessly. The slow rotation of the rotary kiln drives the hazardous waste to rotate in the kiln body, thereby completing the pyrolysis and combustion to treat the hazardous waste harmlessly.

[0003] Currently, high-alumina bricks are commonly used for lining rotary kilns. By adjusting the alumina content in high-alumina bricks, corundum and mullite main crystalline phases can be formed during the molding process, thereby improving the mechanical strength, refractoriness, and thermal shock resistance of the refractory bricks. However, the hazardous waste generated in the anthracene and carbazole production lines produces a large amount of volatile alkali metal salts and highly permeable gases during combustion. These gases permeate along the pores of the refractory bricks and expand inside, causing layered delamination on the surface of the refractory bricks and affecting their service life. Therefore, there is an urgent need to provide a solution to improve these problems. Summary of the Invention

[0004] The purpose of this invention is to provide a rotary kiln refractory material and its preparation method, as well as rotary kiln refractory bricks. By impregnating the surface of the steel fiber matrix with an aluminum-magnesium alloy layer, not only can the oxidation resistance of the steel fiber matrix be improved, but also the aluminum-magnesium alloy layer can be transformed in situ into a corundum and aluminum-magnesium spinel protective layer at high temperatures. This helps to improve the interfacial bonding strength of the composite steel fiber in the refractory material, helps to block the erosion of the refractory bricks by hazardous waste during the incineration of hazardous waste and inhibits thermal shock pulverization, and can effectively improve the service life of the refractory bricks.

[0005] In a first aspect, the present invention provides a rotary kiln refractory material comprising, by weight: 250-350 parts corundum-mullite aggregate, 70-80 parts powder additives, 40-60 parts silica-alumina composite sol, 20-40 parts refractory clay, 8-10 parts composite steel fibers, 0.5-1.5 parts binder, and 0.1-0.5 parts plasticizer; wherein the composite steel fibers comprise a steel fiber matrix and an aluminum-magnesium alloy layer impregnated and cured on the surface of the matrix.

[0006] Optionally, the method for preparing the composite steel fiber includes: degreasing and pickling the steel fiber matrix to obtain an active matrix; immersing the active matrix in a fluxing solution and drying it to obtain a substrate to be plated; immersing the substrate to be plated in molten aluminum-magnesium for 8s-12s and then cooling it to obtain composite fiber; and holding the composite fiber at 400℃-450℃ and then cooling it to obtain composite steel fiber.

[0007] Optionally, the steel fiber matrix is ​​degreased in a degreasing solution; and / or, the degreased steel fiber matrix is ​​pickled in an acid solution; and / or, the fluxing solution contains 80 g / L-120 g / L zinc chloride and 20 g / L-50 g / L potassium fluoride; and / or, the treatment is performed in the fluxing solution for 30 s-60 s; and / or, the treatment is performed in a fluxing solution at 50 ℃-80 ℃.

[0008] Optionally, the composite steel fibers are prepared by immersion coating in an aluminum-magnesium melt at 660℃-680℃; and / or by melting an Al-7Si-0.3Mg alloy to obtain the aluminum-magnesium melt; and / or by cooling at a rate of 5℃ / min-10℃ / min.

[0009] Optionally, the solid content of the silicon-aluminum composite sol is 15wt%-35wt%; and / or, the silicon-aluminum composite sol contains 10wt%-20wt% nano-silica and 5wt%-15wt% nano-alumina; and / or, the length of the composite steel fiber is 15mm-30mm; and / or, the aspect ratio of the composite steel fiber is 40-70.

[0010] Optionally, the powder additive includes one of silicon carbide powder, alumina powder, silica powder, and metal powder; and / or, the average particle size of the powder additive is 1μm-100μm; and / or, the binder includes carboxymethyl cellulose; and / or, the plasticizer includes ethylene glycol; and / or, the refractory clay includes high-alumina clay.

[0011] Optionally, the particle size distribution of the corundum-mullite aggregate is as follows: 50wt%-70wt% aggregate particles with a particle size of 3mm-7mm, 10wt%-25wt% aggregate particles with a particle size of 1mm-3mm, 10wt%-15wt% aggregate particles with a particle size of 0.1mm-1mm, and 5wt%-10wt% aggregate particles with a particle size less than 0.1mm.

[0012] Secondly, the present invention also provides a method for preparing any of the above-mentioned optional rotary kiln refractory materials, comprising: dry mixing corundum-mullite aggregate, refractory clay, powder additives and composite steel fibers to obtain a mixture; mixing silicon-aluminum composite sol with binder and plasticizer to obtain a liquid mixture; and spraying the liquid mixture into the mixture under stirring state to obtain the rotary kiln refractory material.

[0013] Thirdly, the present invention also provides a rotary kiln refractory brick formed by sintering and curing any of the above-mentioned optional rotary kiln refractory materials.

[0014] Optionally, rotary kiln refractory materials are shaped and then sintered at 1300℃-1600℃ for 8-12 hours to obtain rotary kiln refractory bricks.

[0015] The rotary kiln refractory material provided by this invention has at least one of the following beneficial technical effects compared with the prior art: 1. By adding composite steel fibers with an aluminum-magnesium alloy layer impregnated and cured on the surface to refractory materials, the aluminum-magnesium alloy is transformed in situ into a corundum and spinel shell during sintering. This not only improves the oxidation protection of the steel fiber matrix, but also allows it to interweave and sinter with the secondary mullite network formed by the sintering of silicon-aluminum composite sol. This effectively improves the structural stability and density of refractory bricks. Furthermore, when incinerating hazardous waste generated during the production of anthracene and carbazole, it can inhibit the penetration and erosion of flue gas into the refractory bricks, thereby helping to improve the erosion resistance of refractory bricks during use and thus extending their service life. 2. By briefly immersing the steel fiber matrix in molten aluminum-magnesium, the molten magnesium reduces interfacial tension, thereby improving the uniformity of the immersion coating. At the same time, it limits the diffusion reaction of iron and aluminum atoms at the interface, avoiding the formation of excessively thick and continuous brittle intermetallic compounds such as FeAl3 or Fe2Al5, which would lead to a decline in interfacial performance. In addition, the heat treatment at 400℃-450℃ can effectively relax the stress generated during the immersion coating process, which helps to form a Fe-Al-Si transition layer with a strain buffering effect at the interface during the sintering of refractory bricks. This helps to improve the structural stability of the composite steel fiber and the thermal shock spalling resistance of the refractory bricks. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of a composite steel fiber preparation method provided in some embodiments of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art to which this invention pertains.

[0018] This invention provides a rotary kiln refractory material, comprising, by weight: 250-350 parts corundum-mullite aggregate, 70-80 parts powder additives, 40-60 parts silica-alumina composite sol, 20-40 parts refractory clay, 8-10 parts composite steel fibers, 0.5-1.5 parts binder, and 0.1-0.5 parts plasticizer. In practice, during the sintering process of the refractory material, the corundum-mullite aggregate forms a refractory skeleton, while the powder additives and refractory clay fill the refractory skeleton, improving the density of the refractory bricks and reducing porosity.

[0019] Meanwhile, the silica-alumina composite sol, along with the binder and plasticizer, can form a gel network in the refractory material and a mullite network after sintering. The binder and plasticizer are burned off during sintering, avoiding any impact on the refractory brick structure. Furthermore, the trace amounts of binder and plasticizer will not have a significant negative impact on the apparent porosity of the refractory brick. In addition, the composite steel fibers can form a steel skeleton within the refractory brick, thereby improving its mechanical strength and service life.

[0020] Specifically, the composite steel fibers used include a steel fiber matrix and an aluminum-magnesium alloy layer impregnated and cured on the surface of the matrix. In practice, when the refractory material is sintered to form refractory bricks, a dense alumina protective layer forms on the surface of the aluminum-magnesium alloy layer in the composite steel fibers, protecting the internal steel fiber matrix. Furthermore, the aluminum-magnesium alloy layer can also form a magnesium-aluminate spinel phase with the alumina components in the refractory brick, thereby effectively improving the interfacial bonding strength of the composite steel fibers within the refractory brick.

[0021] In some embodiments, see Figure 1 The preparation method of composite steel fibers includes the following steps: S1. The steel fiber matrix is ​​degreased and then acid-washed to obtain the active matrix; S2. The active substrate is immersed in the fluxing solution and then dried to obtain the substrate to be plated; S3. The substrate to be plated is immersed in the aluminum-magnesium melt for 8s-12s and then cooled to obtain composite fibers; S4. Composite fibers are obtained by keeping the composite fibers at 400℃-450℃ and then cooling them.

[0022] In fact, the degreasing and pickling in step S1 can remove grease and oxide impurities on the surface of the steel fiber substrate, which helps to improve the bonding stability between the steel fiber substrate and the surface aluminum-magnesium alloy layer. In addition, after being immersed in the fluxing solution and dried in step S2, a protective layer can be formed on the surface of the active substrate, which can prevent the active substrate from being oxidized and contaminated again, and helps to improve the plating uniformity of the aluminum-magnesium alloy layer. In step S3, short-time immersion plating can inhibit the excessive growth of iron-aluminum intermetallic compounds. Then, after heat preservation and cooling in step S4, the aluminum-magnesium alloy layer and the steel fiber substrate diffuse to form a metallurgical bond.

[0023] Furthermore, the steel fiber matrix used in step S1 includes a stainless steel fiber matrix, such as commercially available conventional products like 304, 310, 330, 430, or 446#. Additionally, the cross-sectional shape of the steel fiber matrix can be circular, and its overall shape can be straight or wavy. This helps to improve the interfacial bonding strength of the composite steel fibers within the refractory brick and reduce its impact on the density of the refractory brick. Specifically, the length of the steel fiber matrix used in step S1 can be 15mm-30mm, and the aspect ratio can be 40-70.

[0024] In some embodiments, the steel fiber matrix may be degreased in a degreasing solution in step S1. In practice, the degreasing solution used can be an organic degreasing agent or an alkaline solution, such as sodium hydroxide solution, sodium carbonate solution, or other degreasing solutions commonly used in the art for cleaning metal surfaces. Furthermore, the steel fiber matrix may be subjected to heating, stirring, ultrasonication, or other methods commonly used in the art in the degreasing solution to improve degreasing efficiency and cleanliness.

[0025] In some embodiments, the degreased steel fiber substrate can be pickled in an acid solution in step S1. In practice, the acid solution used can be one commonly used in the art for etching metal surfaces, such as dilute sulfuric acid, hydrochloric acid, or nitric acid. Furthermore, before pickling, the degreased steel fiber substrate can be rinsed with pure water to remove any alkaline solution adhering to the surface. Additionally, during the etching process, commonly used methods in the art, such as heating, stirring, and ultrasonication, can be employed to improve the etching efficiency.

[0026] In some embodiments, the fluxing solution used in step S2 contains 80 g / L-120 g / L zinc chloride and 20 g / L-50 g / L potassium fluoride dissolved in it. Further, the active substrate can be immersed in the fluxing solution for 30-60 seconds. In practice, during the fluxing process, zinc chloride and potassium fluoride fully wet the surface of the active substrate and form a uniform metal salt protective film after drying, helping to prevent secondary oxidation of the active substrate. Simultaneously, they are rapidly burned off after entering the aluminum-magnesium melt during the immersion process, preventing the introduction of impurities onto the surface of the composite steel fiber.

[0027] Furthermore, the active substrate can be immersed in a flux solution at 50℃-80℃, and commonly used dispersion-enhancing methods in the art, such as stirring and ultrasonication, can be used to improve the dispersibility of the active substrate in the flux solution. In addition, surfactants can be added to the flux solution to reduce the surface tension of the flux solution, thereby facilitating uniform wetting of the active substrate surface by the flux solution.

[0028] In some embodiments, in step S3, the Al-7Si-0.3Mg alloy can be melted and held at 660℃-680℃ to obtain an aluminum-magnesium melt. In fact, magnesium in the aluminum-magnesium melt can reduce the surface tension of the alloy melt, thereby helping to promote rapid wetting of the melt on the surface of the substrate to be plated during the dip-plating process. At the same time, Si can effectively inhibit the growth of iron-aluminum intermetallic compounds during the dip-plating process.

[0029] In some embodiments, in step S4, the composite fibers can be heated to 400℃-450℃ and then cooled at a rate of 5℃ / min-10℃ / min to obtain composite steel fibers. In fact, heating the composite fibers can alleviate the stress generated at the interface during the impregnation process and promote diffusion bonding between the aluminum-magnesium alloy layer and the steel fiber matrix, thus helping to improve the interfacial bonding strength between the steel fiber matrix and the aluminum-magnesium alloy layer in the composite steel fibers.

[0030] In some embodiments, the solid content of the silica-alumina composite sol used can be 15wt%-35wt%. Specifically, the silica-alumina composite sol can disperse 10wt%-20wt% nano-silica and 5wt%-15wt% nano-alumina. In fact, by pre-preparing nano-silica and nano-alumina into a composite sol, it helps to improve the dispersion uniformity of nano-silica and nano-alumina, avoids the agglomeration of nano-silica and nano-alumina during the mixing process, and at the same time, the use of a gel skeleton can effectively improve the density of refractory bricks and thus reduce porosity.

[0031] In some embodiments, the particle size distribution of the corundum-mullite aggregate can be: 50wt%-70wt% aggregate particles with a diameter of 3mm-7mm, 10wt%-25wt% aggregate particles with a diameter of 1mm-3mm, 10wt%-15wt% aggregate particles with a diameter of 0.1mm-1mm, and 5wt%-10wt% aggregate particles with a diameter less than 0.1mm. Further, the mass ratio of corundum aggregate to mullite aggregate in the corundum-mullite aggregate is 1:1 in all different particle size distributions.

[0032] In some embodiments, the powder additive includes one of silicon carbide powder, alumina powder, silica powder, and metal powder. In fact, during the sintering process, silicon carbide powder oxidizes at high temperatures to form a silica protective film, which improves resistance to highly permeable gases such as carbon monoxide and alkaline vapors. Meanwhile, alumina powder can combine with the aluminum-magnesium alloy layer on the surface of the composite steel fiber to form a mullite phase, which helps improve the structural stability of the composite steel fiber and the density of the refractory brick, while reducing the porosity of the refractory brick.

[0033] Further, the powder additive may include silicon carbide powder, alumina powder, silica powder, and metal powder in a mass ratio of (1-3):(0.5-2):(1-3):1. Even further, the metal powder used includes chromium metal powder. Still further, the average particle size of the powder additive can be 1μm-100μm, and the average particle sizes of the silicon carbide powder, alumina powder, silica powder, and metal powder are all independent of each other and can form a gradient size distribution. In addition, the binder used includes carboxymethyl cellulose, the plasticizer used includes ethylene glycol, and the refractory clay used includes high-alumina clay.

[0034] In summary, the present invention also provides a method for preparing rotary kiln refractory material in any of the above embodiments, comprising: dry mixing corundum-mullite aggregate, refractory clay, powder additives and composite steel fibers to obtain a mixture; mixing silicon-aluminum composite sol with binder and plasticizer to obtain a liquid mixture; and spraying the liquid mixture into the mixture under stirring state to obtain rotary kiln refractory material.

[0035] In addition, the present invention also provides rotary kiln refractory bricks formed by sintering and solidifying rotary kiln refractory materials in any of the above embodiments. The rotary kiln refractory materials are pre-shaped during the sintering process and then sintered at 1300℃-1600℃ for 8h-12h to obtain rotary kiln refractory bricks.

[0036] Preparation Example 1: A method for preparing composite steel fibers, comprising the following steps: S1. Immerse a 446# stainless steel fiber matrix with an average length of 20 mm and an aspect ratio of 50 in a 30 g / L sodium hydroxide aqueous solution at 50 °C and ultrasonically clean it for 15 min. After filtration, rinse it three times with deionized water. Then transfer the stainless steel fiber matrix to a 20% (v / v) dilute sulfuric acid solution at 50 °C and ultrasonically clean it for 15 min. After filtration, rinse it with deionized water until the rinsing solution is neutral to obtain the active matrix. S2. Dissolve zinc chloride and potassium fluoride in deionized water at a mass ratio of 5:2 to prepare a fluxing solution with a zinc chloride concentration of 100 g / L and a potassium fluoride concentration of 40 g / L. After keeping the fluxing solution in a 60°C water bath, add the active substrate and sonicate for 45 seconds. Filter the solution and dry it at 80°C for 15 minutes until constant weight to obtain the substrate to be plated. S3. After heating the Al-7Si-0.3Mg alloy to a molten state in a medium-frequency melting furnace, the temperature is held at 670℃ to obtain an aluminum-magnesium melt. The substrate to be coated is added to the aluminum-magnesium melt and stirred for 10 seconds. After filtering, it is cooled to room temperature to obtain composite fibers. S4. After the composite fiber is kept at 420℃ in a vacuum environment for 30 minutes, it is cooled to room temperature at a rate of 10℃ / min to obtain composite steel fiber.

[0037] Preparation Example 2: A method for preparing composite steel fibers, which differs from Preparation Example 1 in that, in step S3, the Al-7Si-0.3Mg-0.5Fe alloy is heated to a molten state in a medium-frequency melting furnace.

[0038] Preparation Example 3: A method for preparing composite steel fibers, which differs from Preparation Example 1 in that step S4 is not performed. The composite fibers obtained in step S3 are composite steel fibers.

[0039] Preparation Example 4: A method for preparing composite steel fibers, which differs from Preparation Example 1 in that, in step S3, the Al-7Si alloy is heated to a molten state in a medium-frequency melting furnace.

[0040] Examples 1-5: A rotary kiln refractory material is provided respectively, and its raw materials and mass fractions are shown in Table 1 below.

[0041] Table 1. Raw materials and mass fractions of rotary kiln refractory materials in Examples 1-5 Corundum-Mullite Aggregate 250 350 280 280 280 Powder Additives 70 80 75 75 75 Silicon-aluminum composite sol 40 60 50 50 50 Refractory clay 20 40 30 30 30 Composite steel fiber 8 10 9 9 9 adhesive 0.5 1.5 1.0 1.0 1.0 plasticizer 0.1 0.5 0.3 0.3 0.3 In Examples 1-5, the corundum-mullite aggregate used was graded as follows: 60wt% of aggregate particles with an average particle size of 5mm, 18wt% of aggregate particles with an average particle size of 2mm, 12wt% of aggregate particles with an average particle size of 0.8mm, and 10wt% of aggregate particles with an average particle size of 0.07mm. In each grade of aggregate particles, the mass ratio of corundum to mullite was 1:1.

[0042] The powder additives used in Examples 1-5 were silicon carbide powder (average particle size 60 μm, purchased from Henan Dongli New Material Co., Ltd., model 220 silicon carbide differential) in a mass ratio of 2:1:2:1, α-alumina powder (average particle size 45 μm, purchased from Zibo Qijia Wear-resistant Ceramics Co., Ltd.), silica powder (average particle size 100 μm), and chromium metal powder (average particle size 30 μm, purchased from Qinghe County Ruijiang Metal Materials Co., Ltd.).

[0043] In Examples 1-5, the binder used was carboxymethyl cellulose, the plasticizer used was ethylene glycol, and the refractory clay used was 100-mesh high-alumina refractory clay purchased from Gongyi Yuying Refractory Materials Co., Ltd. The silica-alumina composite sol used was dispersed with 15wt% nano-silica (average particle size of 100nm) and 10wt% nano-alumina (average particle size of 100nm). In Examples 1-3, the composite steel fibers prepared in Preparation Example 1 were used, and in Examples 4-5, the composite steel fibers prepared in Preparation Examples 2-3 were used respectively.

[0044] The preparation method of rotary kiln refractory material in Examples 1-5 includes: pre-dry mixing multi-graded corundum-mullite aggregate, then adding powder additives, refractory clay and composite steel fibers for dry mixing to obtain a mixture; mixing binder, plasticizer and silica-alumina composite sol to obtain a liquid mixture; and spraying the liquid mixture onto the mixture while stirring to obtain the rotary kiln refractory material.

[0045] Comparative Example 1: A rotary kiln refractory material, which differs from Example 3 in that it uses the composite steel fibers prepared in Preparation Example 4.

[0046] Comparative Example 2: A rotary kiln refractory material, which differs from Example 3 in that it directly uses an untreated 446# stainless steel fiber matrix with an average length of 20 mm and an aspect ratio of 50.

[0047] Comparative Example 3: A rotary kiln refractory material, which differs from Example 3 in that no composite steel fibers are added.

[0048] Comparative Example 4: A rotary kiln refractory material, which differs from Example 3 in that it does not contain silicon-aluminum composite sol, but directly contains 7.5 parts by mass of nano-silica and 5 parts by mass of nano-alumina.

[0049] Performance testing: The rotary kiln refractory materials from Examples 1-5 and Comparative Examples 1-4 were injected into molds and shaped into standard samples. After drying, brick blanks were obtained. The brick blanks were heated to 300°C at a rate of 2°C / min, then to 600°C at a rate of 3°C / min, then to 1000°C at a rate of 5°C / min, and finally to 1500°C at a rate of 2°C / min. The brick blanks were then sintered at this temperature for 8 hours to obtain rotary kiln refractory bricks.

[0050] The apparent porosity (%) of rotary kiln refractory bricks was tested according to the test method for apparent porosity described in GB / T 2997-2015; the room temperature compressive strength (MPa) of rotary kiln refractory bricks was tested according to the compressive strength test method for dense shaped refractory products without padding described in GB / T 5072-2023; and the wear volume (cm³) of rotary kiln refractory bricks was recorded after abrasion testing according to the room temperature abrasion resistance test method described in GB / T 18301-2012. 3 Based on the method described in GB / T 3002-2017, the high-temperature flexural strength (MPa) of the rotary kiln refractory bricks was tested after being kept at 1300℃ for 1 hour. The above test was repeated five times and the average value was calculated. The results are shown in Table 2.

[0051] Based on the static crucible method described in GB / T 8931-2007, rotary kiln refractory bricks were made into crucible shapes, alkali metal slag was placed inside the crucible, and the crucible was held at 1400℃ for 3 minutes. Then, the crucible was cut vertically along the axis, and the maximum erosion penetration depth (mm) was measured. Based on the thermal shock test method described in GB / T 30873-2014, rotary kiln refractory bricks were heated to 1100℃ and held for 20 minutes. Then, they were quickly transferred to 25℃ running water for 3 minutes to cool. The number of cycles required when the broken area of ​​the heated end face of the refractory brick reached 50% was recorded. The above test was repeated five times and the average value was calculated. The results are shown in Table 3.

[0052] Table 2 Apparent porosity, room temperature compressive strength, room temperature wear volume, and high temperature flexural strength of rotary kiln refractory bricks Example 1 15.28 84.04 1.79 10.84 Example 2 15.32 83.22 1.84 10.78 Example 3 15.21 83.68 1.87 11.26 Example 4 15.44 81.36 2.15 10.45 Example 5 15.98 78.53 2.48 9.56 Comparative Example 1 16.32 76.61 2.76 8.82 Comparative Example 2 16.84 73.94 3.12 7.67 Comparative Example 3 17.93 71.26 3.54 6.43 Comparative Example 4 19.17 69.57 4.03 5.24 Table 3 Maximum erosion penetration depth and number of thermal shock cycles for rotary kiln refractory bricks Example 1 1.52 24.8 Example 2 1.58 24.6 Example 3 1.55 25.0 Example 4 1.85 20.8 Example 5 2.38 14.8 Comparative Example 1 2.18 15.6 Comparative Example 2 4.62 9.2 Comparative Example 3 3.25 4.2 Comparative Example 4 3.74 12.8 As can be seen from Tables 2 and 3, the rotary kiln refractory materials provided in Examples 1 to 3 of this invention have a low apparent porosity after being made into refractory bricks. This is because the silica-alumina composite sol can form a gel network in the refractory material during the mixing process to fully encapsulate the solid particles. Furthermore, during sintering, the silica-alumina gel skeleton can be transformed in situ into the mullite phase, which helps to reduce the apparent porosity of the refractory bricks and thus increase their density, thereby improving the structural stability of the refractory bricks at room temperature. In contrast to Example 3, when nano-silica and nano-alumina are directly added to the refractory material of Comparative Example 4 without the composite sol, the nanoparticles are prone to agglomeration during the mixing process, leading to the formation of accumulated pores during sintering. This results in an increased apparent bubble rate and a decrease in structural strength of the refractory bricks.

[0053] Furthermore, in Example 4, the composite steel fiber prepared in Example 2 was used. The aluminum-magnesium alloy layer on its surface is Al-7Si-0.3Mg-0.5Fe. During the high-temperature sintering process, Fe is easily oxidized to form iron oxides. At the same time, it is easy to undergo a eutectic reaction with alumina and silicon oxide in the refractory brick to form a glass phase. Under high-temperature conditions, it is easy to cause interfacial slip, which leads to a decrease in structural strength at high temperatures. In addition, it will also destroy the protective layer that protects the steel fiber matrix, which will cause irreversible oxidation of the internal steel fiber matrix and thus lead to a significant decrease in thermal shock resistance.

[0054] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A rotary kiln refractory material, characterized in that, The composition, by weight, includes: 250-350 parts corundum-mullite aggregate, 70-80 parts powder additives, 40-60 parts silicon-aluminum composite sol, 20-40 parts refractory clay, 8-10 parts composite steel fiber, 0.5-1.5 parts binder, and 0.1-0.5 parts plasticizer; wherein the composite steel fiber comprises a steel fiber matrix and an aluminum-magnesium alloy layer impregnated and cured on the surface of the matrix. The preparation method of the composite steel fiber includes: degreasing and pickling the steel fiber matrix to obtain an active matrix; immersing the active matrix in a fluxing solution and drying it to obtain a substrate to be plated; immersing the substrate to be plated in an aluminum-magnesium melt for 8-12 seconds and then cooling it to obtain composite fiber, wherein the aluminum-magnesium melt is made by melting an Al-7Si-0.3Mg alloy; and holding the composite fiber at 400℃-450℃ and then cooling it to obtain composite steel fiber.

2. The rotary kiln refractory material according to claim 1, characterized in that: The steel fiber matrix is ​​degreased in a degreasing solution and then pickled in an acid solution; the fluxing solution contains 80g / L-120g / L zinc chloride and 20g / L-50g / L potassium fluoride; and the solution is treated in a fluxing solution at 50℃-80℃ for 30s-60s.

3. The rotary kiln refractory material according to claim 1, characterized in that: Composite steel fibers are obtained by immersion coating in molten aluminum-magnesium at 660℃-680℃ and then cooling at a rate of 5℃ / min-10℃ / min.

4. The rotary kiln refractory material according to claim 1, characterized in that: The silicon-aluminum composite sol has a solid content of 15wt%-35wt%, and contains 10wt%-20wt% nano-silica and 5wt%-15wt% nano-alumina dispersed in it; the composite steel fiber has a length of 15mm-30mm and an aspect ratio of 40-70.

5. The rotary kiln refractory material according to claim 1, characterized in that: The powder additive includes one of silicon carbide powder, alumina powder, silica powder, and metal powder; the average particle size of the powder additive is 1μm-100μm; the binder includes carboxymethyl cellulose; the plasticizer includes ethylene glycol; and the refractory clay includes high-alumina clay.

6. The rotary kiln refractory material according to claim 1, characterized in that: The particle size distribution of the corundum-mullite aggregate is as follows: 50wt%-70wt% aggregate particles with a particle size of 3mm-7mm, 10wt%-25wt% aggregate particles with a particle size of 1mm-3mm, 10wt%-15wt% aggregate particles with a particle size of 0.1mm-1mm, and 5wt%-10wt% aggregate particles with a particle size less than 0.1mm.

7. A method for preparing a rotary kiln refractory material as described in any one of claims 1 to 6, characterized in that, include: A mixture is prepared by dry mixing corundum-mullite aggregate, refractory clay, powder additives and composite steel fibers; a mixture is prepared by mixing silica-alumina composite sol with binder and plasticizer; and a rotary kiln refractory material is prepared by spraying the mixture into the stirred mixture.

8. A rotary kiln refractory brick formed by sintering and curing the rotary kiln refractory material as described in any one of claims 1 to 6.

9. The rotary kiln refractory brick according to claim 8, characterized in that, Rotary kiln refractory bricks are obtained by shaping the refractory material and then sintering it at 1300℃-1600℃ for 8-12 hours.

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