A double-chamber lime kiln structure, composite mullite bricks for the kiln body, and their preparation method

Abstract

This application relates to the field of mullite brick technology, specifically disclosing a double-chamber lime kiln structure, a composite mullite brick for the kiln body, and a method for preparing the same. The composite mullite brick for the kiln body of this application is mainly made from the following raw materials: fine mullite powder, aluminum plant waste residue, microsilica powder, binder, pore-forming agent, reinforcing agent, and auxiliary agent. The reinforcing agent is composed of silicon carbide, silicon nitride, and tantalum carbide, and the auxiliary agent is at least two of calcium hexaaluminate, kyanite, and dolomite. The preparation method includes the following steps: mixing and grinding the above raw materials to obtain a mixture; pressing the mixture into brick blanks; drying and calcining the brick blanks to obtain the final product. The mullite brick obtained by this application has high strength and excellent thermal shock resistance.

Description

Technical Field

[0001] This application relates to the field of mullite brick technology, and more specifically, to a double-chamber lime kiln structure, composite mullite bricks for the kiln body, and a method for preparing the same. Background Technology

[0002] As the nation and its residents place increasing emphasis on environmental protection, the traditional lime kiln industry is gradually being phased out due to its severe pollution and high energy consumption. Meanwhile, double-chamber vertical kilns are gaining popularity in China due to their smaller footprint, lower energy consumption, wider range of fuel options, compliance with environmental standards, and higher product quality.

[0003] The double-chamber lime kiln is one of the most advanced lime calcination equipment in the world. It has two parallel kiln chambers connected by a connecting channel in the middle of the lower part of the kiln body. Its calcination process has two main characteristics: parallel flow and heat storage. Parallel flow means that during limestone calcination, the combustion products and limestone flow downwards side by side, which is conducive to calcining high-quality active lime. Heat storage means that the combustion products of kiln A—high-temperature exhaust gas—enter kiln B through the connecting channel at the bottom of the two kiln chambers. In kiln B, the high-temperature exhaust gas flows upwards, preheating the limestone in the preheating zone to a higher temperature and accumulating heat. At the same time, the high-temperature exhaust gas cools down to a very low temperature before being discharged from the kiln chamber. This working principle makes full use of the waste heat of the exhaust gas, ensuring that this type of kiln has a high thermal efficiency.

[0004] Double-chamber lime kilns generally use high-alumina bricks or clay bricks. Currently, high-alumina bricks and clay bricks have poor thermal shock stability and are prone to peeling during use, which affects the service life of the lime kiln.

[0005] Mullite bricks have excellent thermal stability and high load softening temperature, so they are often used to replace high-alumina bricks and clay bricks as materials for lime kilns. However, the strength of mullite bricks is reduced due to changes in the aluminum / silicon ratio during the preparation process, which affects the service life of double-chamber lime kilns. Summary of the Invention

[0006] In order to further improve the strength of mullite bricks and thus extend the service life of double-chamber lime kilns, this application provides a double-chamber lime kiln structure, composite mullite bricks for the kiln body, and a method for preparing the same.

[0007] In the first aspect, this application provides a composite mullite brick for kiln bodies, employing the following technical solution:

[0008] A composite mullite brick for kiln bodies is mainly made of the following raw materials in parts by weight: 40-60 parts of fine mullite powder, 30-40 parts of aluminum plant waste residue, 10-15 parts of microsilica powder, 5-10 parts of binder, 2-3 parts of pore-forming agent, 20-25 parts of reinforcing agent, and 10-15 parts of auxiliary agent. The reinforcing agent is composed of silicon carbide, silicon nitride, and tantalum carbide in a mass ratio of (5-8):(3-4):(1-2). The auxiliary agent is at least two of calcium hexaaluminate, kyanite, and dolomite.

[0009] Preferably, the binder is composed of sodium carboxymethyl starch and pulp waste liquor in a mass ratio of 5:1.

[0010] Preferably, the kyanite is corundum-type kyanite.

[0011] By adopting the above technical solution, this application selects raw materials, mixes them, and adjusts their mass ratios to improve the strength and thermal insulation properties of the resulting mullite bricks. The synergistic effect of the raw materials not only enhances the strength of the mullite bricks but also may produce unexpected technical effects.

[0012] The introduction of aluminum plant waste slag helps to reduce the production cost of mullite bricks and improve their performance. The aluminum plant waste slag and microsilica powder work together. The alumina contained in the aluminum plant waste slag and microsilica powder work together to produce mullite crystalline phase. This phase works together with the added fine mullite powder to increase the proportion of mullite phase in the mullite bricks and thus improve their performance.

[0013] The reinforcing agent is a compound of three components: silicon carbide, silicon nitride, and tantalum carbide. Silicon nitride is a non-oxide with extremely strong covalent bonds, characterized by high temperature resistance, high strength, high hardness, good thermal stability, and good wear resistance. Silicon carbide has a high melting point, high hardness, stable chemical properties, and corrosion resistance. The addition of silicon carbide and silicon nitride facilitates the improvement of the strength of mullite bricks and increases their load softening temperature. Tantalum carbide has a low thermal conductivity, which helps to reduce the thermal conductivity of the resulting mullite bricks and improve their thermal insulation performance, so as to better utilize the mullite bricks in the double-chamber lime kiln and reduce heat loss.

[0014] Kyanite, an auxiliary agent, is abundant and inexpensive. During sintering, as the temperature rises, kyanite decomposes, forming mullite and a silica-rich glassy phase. Alumina begins to transform into a corundum phase. The silica-rich glassy phase reacts with the alumina and corundum phases, undergoing secondary mullitization to generate mullite, further increasing the mullite phase content in the mullite bricks. Using smaller-sized kyanite helps reduce expansion during sintering, further improving the thermal insulation performance of the mullite bricks. Calcium hexaaluminate contains numerous micron-sized pores; its introduction further reduces the thermal conductivity of the mullite bricks, improving their insulation properties. Dolomite contains a significant amount of manganese dioxide, promoting the formation and development of mullite crystals. The manganese ions in manganese dioxide react with silicon dioxide, reducing the quartz phase and disrupting the spatial framework structure created by the quartz phase, thus increasing the density and strength of the resulting mullite bricks.

[0015] The addition of binder facilitates the increase of the adhesion of the blank, making the blank easier to form. The binder is mostly distributed on the surface of mullite particles and at the particle interface. The particles are connected by the binder, thereby improving the overall strength of the resulting mullite brick.

[0016] The introduction of pore-forming agents facilitates their burning off during the sintering process, thereby forming uniformly distributed micro-closed pores in the mullite bricks, which helps to improve the thermal insulation properties of the mullite bricks.

[0017] Preferably, the auxiliary agent is composed of calcium hexaaluminate, kyanite, and dolomite in a mass ratio of (5-9):(1-2):(1-2).

[0018] By adopting the above technical solution, the auxiliary agent is obtained by compounding three components: calcium hexaaluminate, kyanite, and dolomite. The ratio of the three components is adjusted to achieve the optimal ratio, which facilitates the better functioning of the auxiliary agent in mullite bricks. Dolomite has good thermal insulation effect, calcium hexaaluminate facilitates the introduction of micron-sized closed pores into mullite bricks, and the introduction of kyanite facilitates the increase of mullite phase content in mullite bricks. The three components work together to help improve the thermal insulation performance of the prepared mullite bricks, and at the same time, assist in the reactions that may occur during the preparation of mullite bricks, thereby improving the performance of mullite bricks.

[0019] Preferably, the method for preparing silicon nitride includes the following steps: mixing silicon powder, zirconium oxide, glass fiber, nickel salt, polyethylene glycol, water, N-dodecylacrylamide, and ammonium persulfate evenly to obtain preparation solution one; mixing preparation solution one with calcium carbonate and sodium phosphate dodecahydrate, and letting it stand for 30-50 minutes to obtain preparation solution two; mixing preparation solution two with tert-amyl peroxide-2-ethylhexanoate and ferrous chloride, letting it stand, and then drying, sintering, and pulverizing to obtain the final product.

[0020] By adopting the above technical solution, in the preparation process of silicon nitride, nickel salt promotes the transformation of silicon powder into silicon nitride fibers. The fiber structure is interwoven, which facilitates the improvement of the strength of the obtained silicon nitride. Zirconia hinders heat transfer and is distributed between the silicon nitride fibers, which facilitates further reduction of the thermal conductivity of silicon nitride, thereby improving the thermal insulation performance of the obtained mullite brick.

[0021] Preferably, the silicon nitride is modified silicon nitride, and the preparation method of the modified silicon nitride includes the following steps: mixing tetraethyl orthosilicate and water, adjusting the pH to 5-6, hydrolyzing to obtain a mixed solution, mixing the mixed solution and aluminum nitrate solution, allowing it to stand to obtain a mixed gel, immersing the silicon nitride in the mixed gel, removing it and drying it, and then heat-treating the dried silicon nitride with the mixed gel on its surface to obtain the final product.

[0022] By adopting the above technical solution, it was found in the process of preparing mullite bricks that silicon nitride is easily oxidized and easily generates liquid phase substances after oxidation, which leads to a loose structure. Therefore, the strength of the prepared mullite bricks is poor. By coating a layer of mullite on the surface of silicon nitride, on the one hand, it is easy to reduce oxygen diffusion and reduce the oxidation of silicon nitride. On the other hand, mullite has a low thermal conductivity, which is easy to reduce the thermal conductivity of silicon nitride, thereby improving the heat insulation of the prepared mullite bricks and thus improving the sintering properties of the double-chamber lime kiln made from the mullite bricks. The coated mullite crystal phase is needle-shaped or columnar and intersecting to form a network, thereby improving the thermal shock resistance and high-temperature creep resistance of silicon nitride, and thus improving the high-temperature creep resistance of the mullite bricks.

[0023] Preferably, the temperature change stages of the heat treatment are as follows: Stage 1, heating from room temperature to 600-800℃ at a heating rate of 8-10℃ / min; Stage 2, heating from 600-800℃ to 1000-1100℃ at a heating rate of 5-6℃ / min; Stage 3, heating from 1000-1100℃ to 1200-1250℃ at a heating rate of 2-3℃ / min; Stage 4, holding at this temperature for 3-4 hours; Stage 5, cooling from 1200-1250℃ to 1100-1150℃ at a cooling rate of 1-2℃ / min; Stage 6, cooling from 1100-1150℃ to 700-900℃ at a cooling rate of 5-6℃ / min; Stage 7, cooling from 700-900℃ to room temperature at a cooling rate of 8-10℃ / min.

[0024] By adopting the above technical solution and adjusting the heating and cooling rates of the heat treatment, it is helpful to improve the density of the mullite coating on the silicon nitride surface, reduce the occurrence of cracks in the mullite coating, reduce the porosity and high porosity of the mullite coating, thereby improving the oxidation resistance of silicon nitride, reducing the impact of oxygen on the performance of silicon nitride, and thus improving the strength and density of the mullite brick.

[0025] Preferably, the silicon carbide is β-silicon carbide.

[0026] By adopting the above technical solution, the oxidation temperature of β-silicon carbide is relatively high, which reduces the degree of oxidation of silicon carbide during sintering, thereby improving the density and mechanical strength of the resulting mullite bricks.

[0027] Preferably, the aluminum plant waste residue is pretreated aluminum plant waste residue, and the preparation method of the pretreated aluminum plant waste residue includes the following steps: mixing and crushing the aluminum plant waste residue with lithium ceramic stone, sintering, cooling, and grinding to obtain the final product.

[0028] By adopting the above technical solution, after the aluminum plant waste slag is sintered, the alumina content in the waste slag increases, which facilitates better reaction with microsilica powder, further increases the proportion of mullite phase in mullite bricks, and thus improves the strength of mullite bricks. Lithium ceramic stone contains a large amount of silicon dioxide and alumina, which facilitates the further introduction of silicon dioxide and alumina into the aluminum plant waste slag, thereby interacting with other components in mullite bricks and improving the density and mechanical properties of the resulting mullite bricks.

[0029] Preferably, the pore-forming agent is composed of rice husk ash and corn starch in a mass ratio of (5-8):(2-3).

[0030] By adopting the above technical solution, the pore-forming agent is obtained by compounding two components: rice husk ash and corn starch. The ratio of the two components is adjusted to achieve the optimal ratio, so that the pore-forming agent is evenly distributed. After burning, more closed pores are left, which increases the porosity and thus increases the gas-solid interface, which facilitates the reduction of thermal conductivity and helps to improve the thermal insulation performance of mullite bricks.

[0031] Secondly, this application provides a method for preparing composite mullite bricks for kiln bodies, employing the following technical solution:

[0032] A method for preparing composite mullite bricks for kiln bodies includes the following steps:

[0033] (1) Preparation of mixture: The above raw materials are mixed and ground to obtain a mixture;

[0034] (2) Brick blank preparation: The mixture obtained in step (1) is pressed into brick blanks;

[0035] (3) Preparation of mullite bricks: The brick blanks obtained in step (2) are dried and calcined to obtain the bricks.

[0036] Preferably, the pressing in step (2) is performed using a friction press.

[0037] By adopting the above technical solution, the mullite bricks prepared in this application have high strength, good thermal insulation performance, and a simple preparation process.

[0038] Thirdly, this application improves the structure of a double-chamber lime kiln by adopting the following technical solution:

[0039] A double-chamber lime kiln structure is made of composite mullite bricks.

[0040] In summary, this application has the following beneficial effects:

[0041] 1. This application adds mullite fine powder, aluminum plant waste residue, and microsilica powder to the preparation of mullite bricks. The introduction of aluminum plant waste residue facilitates the treatment of solid waste, and the mullite crystal phase generated by aluminum plant waste residue and microsilica powder during sintering, combined with the mullite fine powder, helps to further reduce the content of other impurity phases in mullite bricks, increase the content of mullite phase in mullite bricks, and thus improve the strength and thermal insulation properties of mullite bricks.

[0042] 2. This application adds auxiliary agents and reinforcing agents to the preparation of mullite bricks. The introduction of reinforcing agents helps to improve the low strength caused by the increase of open pores in the mullite phase, which helps to improve the strength of mullite bricks. The introduction of auxiliary agents facilitates the introduction of micron-sized closed pores on the basis of improving the strength of mullite bricks, thereby improving the thermal insulation performance of mullite bricks. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the double-chamber lime kiln structure in Embodiment 1 of this application.

[0044] Explanation of the reference numerals in the attached diagram: 1. Sluice channel; 2. Kiln chamber; 21. First kiln chamber; 22. Second kiln chamber; 23. Intermediate channel; 3. Material distribution bin. Detailed Implementation

[0045] The present application will be further described in detail below with reference to the embodiments.

[0046] The processes, conditions, and experimental methods for implementing this invention, except as specifically mentioned below, are all common knowledge and general knowledge in the field. The scope of protection of this invention is not limited to the following embodiments. All variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of the inventive concept are included in this invention.

[0047] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0048] The double-chamber lime kiln structure of this application is as follows: Figure 1As shown, the device includes a kiln 2 and a material distribution mechanism. The material distribution mechanism includes a material distribution bin 3 and at least two chute channels 1. In this application, there are two chute channels 1. The material distribution bin 3 is connected to the chute channels 1. The kiln 2 includes a first kiln 21 and a second kiln 22. The first kiln 21 is connected to one of the chute channels 1, and the second kiln 22 is connected to the remaining chute channels 1. There is an intermediate channel 23 between the first kiln 21 and the second kiln 22 that allows them to connect. The lower end of the first kiln 21 has an outlet, and the lower end of the second kiln 22 has an outlet.

[0049] The double-chamber lime kiln of this application is made of composite mullite bricks for the kiln body.

[0050] Example

[0051] Example 1

[0052] The composite mullite bricks used in the kiln body of this embodiment include the following raw materials by weight: 40 kg of fine mullite powder, 30 kg of aluminum plant waste slag, 10 kg of microsilica powder, 5 kg of binder, 2 kg of pore-forming agent, 20 kg of reinforcing agent, and 10 kg of auxiliary agent. The mullite fine powder has a particle size distribution of 10% by weight for 80μm, 30% by weight for 180μm, and 60% by weight for 260μm; the aluminum plant waste residue includes the following raw materials by weight percentage: 63% alumina, 3% silicon dioxide, 2% sodium oxide, and a loss on ignition of 32%; the binder is composed of sodium carboxymethyl starch and pulp waste liquor in a mass ratio of 5:1; the pore-forming agent is composed of rice husk ash and corn starch in a mass ratio of 5:2; the reinforcing agent is composed of silicon carbide, silicon nitride, and tantalum carbide in a mass ratio of 5:3:1; the silicon carbide is β-silicon carbide; the auxiliary agent is composed of calcium hexaaluminate and kyanite in a mass ratio of 1:1, wherein the kyanite is corundum-type kyanite; the kyanite particle size is 120μm; the kyanite includes the following raw materials by weight percentage: 60.5% alumina, 39% silicon dioxide, and 0.5% other materials;

[0053] The method for preparing composite mullite bricks for kiln bodies in this embodiment includes the following steps:

[0054] (1) Preparation of mixture: Mullite fine powder, aluminum plant waste residue, microsilica powder, binder, pore-forming agent, reinforcing agent and auxiliary agent are mixed in the above proportions and then rolled to obtain mixture;

[0055] (2) Brick blank preparation: The mixture obtained in step (1) is pressed into brick blanks; the pressing is carried out using a 630T friction press;

[0056] (3) Preparation of mullite bricks: The brick blanks obtained in step (2) are dried and calcined to obtain the bricks. The drying temperature is 120℃ and the drying time is 30h. The calcination temperature is 1500℃, the heating rate is 10℃ / min, and the calcination time is 50h.

[0057] Example 2

[0058] The composite mullite bricks used in the kiln body of this embodiment differ from those in Embodiment 1 in that they include the following raw materials by weight: 60 kg of fine mullite powder, 40 kg of aluminum plant waste slag, 15 kg of microsilica powder, 10 kg of binder, 3 kg of pore-forming agent, 25 kg of reinforcing agent, and 15 kg of auxiliary agent. The pore-forming agent is composed of rice husk ash and corn starch in a mass ratio of 8:3; the reinforcing agent is composed of silicon carbide, silicon nitride, and tantalum carbide in a mass ratio of 8:4:2.

[0059] Example 3

[0060] The composite mullite bricks used in the kiln body of this embodiment differ from those in Embodiment 1 in that they include the following raw materials by weight: 50 kg of fine mullite powder, 35 kg of aluminum plant waste slag, 13 kg of microsilica powder, 8 kg of binder, 3 kg of pore-forming agent, 23 kg of reinforcing agent, and 13 kg of auxiliary agent.

[0061] Example 4

[0062] The kiln body composite mullite bricks used in this embodiment differ from those in Embodiment 3 in that the auxiliary agent is composed of calcium hexaaluminate, kyanite, and dolomite in a mass ratio of 5:1:1.

[0063] Example 5

[0064] The kiln body composite mullite bricks used in this embodiment differ from those in Embodiment 3 in that the auxiliary agent is composed of calcium hexaaluminate, kyanite, and dolomite in a mass ratio of 9:2:2.

[0065] Example 6

[0066] The composite mullite bricks used in the kiln body of this embodiment differ from those in Example 5 in that the preparation method of silicon nitride includes the following steps: silicon powder, zirconium oxide, glass fiber, nickel salt, polyethylene glycol, water, N-dodecylacrylamide, and ammonium persulfate are mixed evenly in a mass ratio of 90:30:5:3:0.01:0.5:0.1:0.01 to obtain preparation liquid one; preparation liquid one is mixed with calcium carbonate and sodium phosphate dodecahydrate in a mass ratio of 40:1:1 and allowed to stand for 45 minutes to obtain preparation liquid two; preparation liquid two is mixed with tert-amyl peroxide-2-ethylhexanoate and ferrous chloride in a mass ratio of 40:1:3 and allowed to stand for 5 days, followed by drying, sintering, and pulverizing to obtain the final product. The drying process involved natural placement for 2 days, followed by drying in an oven at 110℃ for 8 hours to reduce free water content. Sintering was performed under a nitrogen atmosphere, with the temperature raised to 1350℃ at a rate of 13℃ / min and held for 10 hours. The zirconia used was modified zirconia, prepared by mixing silica sol aqueous solution, nano-zirconia, and nano-silicon carbide in a mass ratio of 8:2:1 to obtain a premix. This premix was then spray-dried at 360℃. The silica sol aqueous solution comprised 50% by mass, and the silica sol particles had a particle size of 15 nm.

[0067] Example 7

[0068] The composite mullite bricks used in this embodiment differ from those in Example 6 in that the silicon nitride is modified silicon nitride. The preparation method of the modified silicon nitride includes the following steps: Tetraethyl orthosilicate and ethanol are mixed at a mass ratio of 1:20 to obtain a tetraethyl orthosilicate solution; the tetraethyl orthosilicate solution and water are mixed at a mass ratio of 1:6; the pH is adjusted to 6 using hydrochloric acid; hydrolysis is performed to obtain a mixed solution; after hydrolysis for 20 minutes, the mixed solution and aluminum nitrate solution are mixed at a mass ratio of 1:4; the mixture is allowed to stand until a viscous gel appears, obtaining a mixed gel; silicon nitride is immersed in the mixed gel for 30 minutes, removed, and dried; subsequently, the dried silicon nitride with the mixed gel coating on its surface is heat-treated to obtain the final product. The heat treatment involves raising the temperature from room temperature to 1250°C at a rate of 8°C / min, holding at 1250°C for 4 hours, and then lowering the temperature from 1250°C to room temperature at a rate of 10°C / min. The drying temperature is 100℃ and the drying time is 2 hours.

[0069] Example 8

[0070] The composite mullite bricks used in the kiln body of this embodiment differ from those in Embodiment 7 in that the temperature change stages of the heat treatment are as follows: Stage 1: heating from room temperature to 800℃ at a rate of 8℃ / min; Stage 2: heating from 800℃ to 1000℃ at a rate of 5℃ / min; Stage 3: heating from 1000℃ to 1250℃ at a rate of 3℃ / min; Stage 4: holding at 1250℃ for 4 hours; Stage 5: cooling from 1250℃ to 1150℃ at a rate of 1.5℃ / min; Stage 6: cooling from 1150℃ to 900℃ at a rate of 6℃ / min; Stage 7: cooling from 900℃ to room temperature at a rate of 10℃ / min.

[0071] Example 9

[0072] The composite mullite bricks used in the kiln body of this embodiment differ from those in Embodiment 1 in that the aluminum plant waste slag is pretreated aluminum plant waste slag. The preparation method of the pretreated aluminum plant waste slag includes the following steps: mixing and crushing the aluminum plant waste slag and lithium ceramic stone at a mass ratio of 20:1, followed by sintering, cooling, and grinding to obtain the final product. The particle size of the pretreated aluminum plant waste slag is 300 μm; the sintering temperature is 1200℃, and the sintering time is 2 hours.

[0073] Comparative Example

[0074] Comparative Example 1

[0075] The kiln body of this comparative example uses composite mullite bricks, which differ from Example 1 in that an equal amount of reinforcing agent is used to replace the auxiliary agent.

[0076] Comparative Example 2

[0077] The kiln body of this comparative example uses composite mullite bricks, which differ from Example 1 in that an auxiliary agent is used to replace the reinforcing agent in equal amounts.

[0078] Comparative Example 3

[0079] The composite mullite bricks used in this comparative example differ from those in Example 1 in that they include the following raw materials by weight: 30 kg of fine mullite powder, 25 kg of aluminum plant waste slag, 8 kg of microsilica powder, 3 kg of binder, 2 kg of pore-forming agent, 15 kg of reinforcing agent, and 8 kg of auxiliary agent.

[0080] Comparative Example 4

[0081] The composite mullite bricks used in this comparative example differ from those in Example 1 in that they include the following raw materials by weight: 80 kg of fine mullite powder, 45 kg of aluminum plant waste slag, 18 kg of microsilica powder, 12 kg of binder, 2 kg of pore-forming agent, 26 kg of reinforcing agent, and 17 kg of auxiliary agent.

[0082] Comparative Example 5

[0083] The kiln body of this comparative example uses composite mullite bricks, which differ from those in Example 1 in that the reinforcing agent is silicon carbide.

[0084] Performance testing

[0085] Compressive strength test: The composite mullite bricks for kiln bodies prepared in Examples 1-9 and Comparative Examples 1-5 were tested according to the test method in GB / T5072-2008 "Test Method for Compressive Strength of Refractory Materials at Room Temperature". The test results are shown in Table 1.

[0086] Thermal shock stability test: The composite mullite bricks for kiln bodies prepared in Examples 1-9 and Comparative Examples 1-5 were tested according to the test method in YB / T 376.1-1995 "Test method for thermal shock resistance of refractory products (water quenching method)". The test results are shown in Table 1.

[0087] Thermal insulation performance test: The composite mullite bricks for kiln bodies prepared in Examples 1-9 and Comparative Examples 1-5 were tested according to the test method in YB / T4130-2005 "Test method for thermal conductivity of refractory materials (water flow plate method)". The test results are shown in Table 1.

[0088] Table 1. Performance test results of composite mullite bricks for kiln bodies prepared in Examples 1-9 and Comparative Examples 1-5.

[0089]

[0090] Based on Example 1, Comparative Examples 1-2, and the data in Table 1, it can be seen that the thermal shock stability and compressive strength of the composite mullite bricks for kilns prepared in Example 1 are superior to those prepared in Comparative Examples 1-2. Furthermore, the composite mullite bricks for kilns prepared in Example 1 have a lower thermal conductivity and better insulation performance. The difference between Example 1 and Comparative Examples 1-2 lies in the fact that Example 1 simultaneously added both auxiliary agents and reinforcing agents. This application believes that the simultaneous addition of reinforcing agents and auxiliary agents, with their synergistic effect and interaction with other components in the composite mullite bricks for kilns, helps to improve the thermal shock stability, compressive strength, and insulation performance of the composite mullite bricks for kilns. When an excessive amount of reinforcing agent is added, the compressive strength of the resulting composite mullite bricks for kilns increases, but the thermal conductivity also increases relatively. When an excessive amount of auxiliary agent is added, the thermal conductivity of the resulting composite mullite bricks for kilns decreases, but the compressive strength decreases.

[0091] Based on Example 1, Comparative Examples 3-4, and the data in Table 1, it can be seen that the thermal shock stability, compressive strength, and heat insulation properties of the composite mullite bricks for kiln bodies prepared in Example 1 are better than those prepared in Comparative Examples 3-4. The difference between Example 1 and Comparative Examples 3-4 is that the proportions of the raw materials used to prepare the composite mullite bricks for kiln bodies are different. This application believes that using different proportions of raw materials has a significant impact on the performance of the prepared composite mullite bricks for kiln bodies.

[0092] Based on Example 1 and Comparative Example 5, and the data in Table 1, it can be seen that the performance of the composite mullite brick for kiln body prepared in Example 1 is better than that of the composite mullite brick for kiln body prepared in Comparative Example 5. The difference between Example 1 and Comparative Example 5 is that the reinforcing agent in Example 1 is a compound of three components: silicon carbide, silicon nitride, and tantalum carbide. This application believes that when the reinforcing agent is a compound of three components: silicon carbide, silicon nitride, and tantalum carbide, the three components work together to further improve the performance of the composite mullite brick for kiln body.

[0093] Based on Examples 1-3 and the data in Table 1, it can be seen that the composite mullite bricks for kiln bodies prepared in Examples 1-3 have better thermal shock stability and compressive strength, and lower thermal conductivity. This application believes that the composite mullite bricks for kiln bodies prepared using the raw materials and component ratios of this application have better performance.

[0094] Based on Examples 3-5 and the data in Table 1, it can be seen that the composite mullite bricks for kiln bodies prepared in Examples 4-5 have high thermal shock stability and compressive strength, and low thermal conductivity. The difference between Examples 4-5 and Example 3 is that the auxiliary agent in Examples 4-5 is a compound of three components: calcium hexaaluminate, kyanite, and dolomite. This application believes that the three components of calcium hexaaluminate, kyanite, and dolomite work together and interact with other components in the composite mullite bricks for kiln bodies, which helps to further improve the performance of the composite mullite bricks for kiln bodies.

[0095] Based on Examples 5-6 and the data in Table 1, it can be seen that the composite mullite brick for kiln bodies prepared in Example 6 has better performance. The difference between Example 6 and Example 5 is that the silicon nitride in Example 6 is prepared in-house. This application believes that the introduction of zirconium oxide during the preparation of silicon nitride hinders the spread of heat, thereby reducing the thermal conductivity of the composite mullite brick for kiln bodies. As a result, the composite mullite brick for kiln bodies prepared in this way has better heat preservation properties.

[0096] Based on Examples 6-7 and the data in Table 1, it can be seen that the composite mullite brick for kiln bodies prepared in Example 7 has better performance. The difference between Example 7 and Example 6 is that Example 7 modifies silicon nitride. This application believes that modifying silicon nitride by coating it with a layer of mullite facilitates a further reduction in the thermal conductivity of silicon nitride and reduces oxidation of silicon nitride during sintering, thereby improving the compressive strength and thermal insulation of the prepared composite mullite brick for kiln bodies.

[0097] Based on Examples 7-8 and the data in Table 1, it can be seen that the composite mullite bricks for kiln bodies prepared in Example 8 have better thermal shock stability and compressive strength. The difference between Example 8 and Example 7 is that the heat treatment process was adjusted during the modification of silicon nitride in Example 8, resulting in better performance of the modified silicon nitride. Adding it to the composite mullite bricks for kiln bodies helps to improve the performance of the composite mullite bricks for kiln bodies.

[0098] Combining Examples 1 and 9, and referring to the data in Table 1, it can be seen that the composite mullite bricks for kiln bodies prepared in Example 9 have better thermal shock stability and compressive strength than those prepared in Example 1, and also have a lower thermal conductivity. The difference between Example 9 and Example 1 is that Example 9 pre-treats the aluminum plant waste slag, thereby producing composite mullite bricks for kiln bodies with better performance.

[0099] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A composite mullite brick for kiln bodies, characterized in that, It is mainly made of the following raw materials in parts by weight: 40-60 parts of fine mullite powder, 30-40 parts of aluminum plant waste residue, 10-15 parts of microsilica powder, 5-10 parts of binder, 2-3 parts of pore-forming agent, 20-25 parts of reinforcing agent, and 10-15 parts of auxiliary agent. The reinforcing agent is composed of silicon carbide, silicon nitride, and tantalum carbide in a mass ratio of (5-8):(3-4):(1-2). The auxiliary agent is composed of calcium hexaaluminate, kyanite, and dolomite in a mass ratio of (5-9):(1-2):(1-2). The method for preparing silicon nitride includes the following steps: mixing silicon powder, zirconium oxide, glass fiber, nickel salt, polyethylene glycol, water, N-dodecylacrylamide, and ammonium persulfate evenly to obtain preparation solution one; mixing preparation solution one with calcium carbonate and sodium phosphate dodecahydrate, and letting it stand for 30-50 minutes to obtain preparation solution two; mixing preparation solution two with tert-amyl peroxide-2-ethylhexanoate and ferrous chloride, letting it stand, and then drying, sintering, and pulverizing to obtain the final product; The aluminum plant waste residue is pretreated aluminum plant waste residue. The preparation method of the pretreated aluminum plant waste residue includes the following steps: mixing and crushing the aluminum plant waste residue with lithium ceramic stone, sintering, cooling, and grinding to obtain the final product.

2. The composite mullite brick for kiln bodies according to claim 1, characterized in that, The silicon nitride is modified silicon nitride. The preparation method of the modified silicon nitride includes the following steps: mixing tetraethyl orthosilicate and water, adjusting the pH to 5-6, hydrolyzing to obtain a mixed solution, mixing the mixed solution and aluminum nitrate solution, letting it stand to obtain a mixed gel, immersing silicon nitride in the mixed gel, taking it out and drying it, and then heat-treating the dried silicon nitride with the mixed gel on its surface to obtain the final product.

3. A composite mullite brick for kiln bodies according to claim 2, characterized in that, The temperature change stages of the heat treatment are as follows: Stage 1, heating from room temperature to 600-800℃ at a rate of 8-10℃ / min; Stage 2, heating from 600-800℃ to 1000-1100℃ at a rate of 5-6℃ / min; Stage 3, heating from 1000-1100℃ to 1200-1250℃ at a rate of 2-3℃ / min; Stage 4, holding at this temperature for 3-4 hours; Stage 5, cooling from 1200-1250℃ to 1100-1150℃ at a rate of 1-2℃ / min; Stage 6, cooling from 1100-1150℃ to 700-900℃ at a rate of 5-6℃ / min; Stage 7, cooling from 700-900℃ to room temperature at a rate of 8-10℃ / min.

4. A composite mullite brick for kiln bodies according to claim 1, characterized in that, The silicon carbide is β-silicon carbide.

5. A composite mullite brick for kiln bodies according to claim 1, characterized in that, The pore-forming agent is composed of rice husk ash and corn starch in a mass ratio of (5-8):(2-3).

6. A method for preparing composite mullite bricks for kiln bodies as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) Preparation of mixture: The above raw materials are mixed and ground to obtain a mixture; (2) Brick blank preparation: The mixture obtained in step (1) is pressed into brick blanks; (3) Preparation of mullite bricks: The brick blanks obtained in step (2) are dried and calcined to obtain the bricks.

7. A double-chamber lime kiln structure, characterized in that: The kiln body is made of composite mullite bricks as described in any one of claims 1-5.

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