Low-porosity low-iron low-creep clay brick and preparation method thereof

Abstract

The invention discloses a low-porosity, low-iron and low-creep clay brick and a preparation method thereof, and relates to the technical field of refractory materials, and the low-porosity, low-iron and low-creep clay brick comprises the following components in parts by weight: 30-45 parts of a mullite homogenized material, 12-20 parts of Anhui flint clay, 8-10 parts of sillimanite, 15-25 parts of kaolin, 10-20 parts of andalusite powder, 3-5 parts of raw silicon powder, 2-5 parts of potassium feldspar powder and 0.2-0.5 part of hydroxypropyl methyl cellulose. And 3-6 parts of an aluminum dihydrogen phosphate solution. The high-quality clay brick with low porosity, low iron, low creep deformation and high strength is successfully prepared by optimizing the raw material ratio and a composite binding agent system, and the high-quality clay brick is suitable for high-temperature industrial kilns with harsh performance requirements.

Description

A low-porosity, low-iron, low-creep clay brick and its preparation method Technical Field

[0001] This invention relates to the field of refractory materials technology, and in particular to a low-porosity, low-iron, and low-creep clay brick and its preparation method. Background Technology

[0002] Clay bricks, as traditional aluminosilicate refractory materials, are widely used in thermal equipment such as blast furnaces, hot blast stoves, and coke ovens due to their low cost and good thermal shock stability. However, with the development of modern industrial kilns towards higher furnace temperatures, longer cycles, and lower energy consumption, the performance shortcomings of traditional clay bricks are becoming increasingly prominent. These shortcomings are mainly manifested in the following ways: First, the apparent porosity is high (usually >18%), resulting in poor resistance to slag and alkali erosion, high thermal conductivity, and significant heat loss from the furnace body. Second, the content of impurities such as Fe2O3 in the raw materials is high (usually >1.5%). These impurities form low-melting-point substances at high temperatures, which not only significantly reduce the material's refractoriness and high-temperature strength but also exacerbate creep deformation at high temperatures, affecting the structural stability of the kiln. Third, under long-term high temperatures and loads, traditional clay bricks, due to their high glass phase content and weak mullite crystal network, have insufficient creep resistance, making them prone to structural deformation and shortening the furnace lining life.

[0003] Currently, methods for improving the performance of clay bricks mostly focus on using high-purity raw materials or single additives, but these often fail to simultaneously achieve the three key indicators of low porosity, low iron content, and low creep. For example, simply reducing iron content may lead to insufficient sintering activity; while reducing porosity solely by refining particle size may have limited improvement on high-temperature creep performance. Therefore, developing a clay brick product that can systematically achieve low porosity, low iron content, and low creep through raw material compounding and process optimization is of great significance for improving the service life and reliability of industrial kilns. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a low-porosity, low-iron, and low-creep clay brick and its preparation method. The clay brick has the characteristics of low apparent porosity, low iron content, excellent high-temperature creep resistance, and good volume stability.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a low-porosity, low-iron, and low-creep clay brick, comprising the following components by weight: 30-45 parts mullite homogenizer, 12-20 parts Anhui calcined stone, 8-10 parts sillimanite, 15-25 parts kaolin, 10-20 parts andalusite powder, 3-5 parts raw silica powder, 2-5 parts potassium feldspar powder, 0.2-0.5 parts hydroxypropyl methylcellulose, and 3-6 parts aluminum dihydrogen phosphate solution.

[0006] Furthermore, the mullite homogenized material is composed of a mixture of particles with particle sizes of 5-3 mm and 3-1 mm, with a mixing ratio of 1:5-3:4.

[0007] Furthermore, the sillimanite has a particle size ≤0.2mm, wherein the mass fraction of SiO2 is ≥70% and the mass fraction of Fe2O3 is ≤1.0%.

[0008] Furthermore, the andalusite powder has a particle size ≤0.074mm, wherein the mass fraction of Al2O3 is ≥50% and the mass fraction of Fe2O3 is ≤0.8%.

[0009] Furthermore, the particle size of the raw silicon powder is less than 0.074 mm, and the mass fraction of SiO2 is ≥98%.

[0010] Furthermore, the particle size of the calcined gemstone is 1-0 mm, wherein the mass fraction of Al2O3 is ≥50% and the mass fraction of Fe2O3 is ≤0.5%; the particle size of the kaolin is ≤0.088 mm, wherein the mass fraction of Al2O3 is ≥38% and the mass fraction of Fe2O3 is ≤1.0%; and the particle size of the potassium feldspar powder is ≤0.088 mm.

[0011] This invention also provides a method for preparing low-porosity, low-iron, and low-creep clay bricks, comprising the following steps: weighing each raw material according to the formula ratio; firstly, dry mixing mullite homogenizer with calcined gemstone to obtain mixed aggregate; then dissolving hydroxypropyl methylcellulose in water, and performing a first wet mixing with the resulting solution and the mixed aggregate to coat the aggregate particles; subsequently adding aluminum dihydrogen phosphate solution and water for a second wet mixing; then adding sillimanite, andalusite powder, kaolin, potassium feldspar powder, and raw silica powder for mixing to obtain plastic clay; then pressing the clay into brick blanks; finally drying and firing the brick blanks to obtain the low-porosity, low-iron, and low-creep clay bricks.

[0012] Furthermore, the specific steps include: S2, placing the mullite homogenized material and coke in a mixer and dry mixing for 3 minutes to obtain mixed aggregate; S3, pre-dissolving hydroxypropyl methylcellulose with a particle size of 30-60nm in water to prepare a solution, then adding it to the mixed aggregate obtained in S2, and performing a first wet mixing for 3-5 minutes to ensure that the hydroxypropyl methylcellulose is evenly dispersed and coats the aggregate particles; S4, adding an 80% aluminum dihydrogen phosphate solution and water to the material in S3, and performing a second wet mixing for 3-5 minutes; S5, adding sillimanite and red... S6. Mix and stir the columnar stone powder, kaolin, potassium feldspar powder and raw silica powder for 8-15 minutes to obtain a uniformly mixed clay material with molding plasticity; S7. Press the clay material obtained in S5 into shape under a pressure of 180MPa and hold the pressure for 10 seconds to obtain a brick blank; S8. Dry the brick blank at 110-120℃ for 16 hours, and then raise the temperature to 200℃ and dry for 12 hours; S9. Place the dried brick blank in a tunnel kiln and fire it at 1450-1500℃ for 12-16 hours. After firing, cool it to room temperature with the kiln to obtain the low-porosity, low-iron, and low-creep clay brick.

[0013] Furthermore, in steps S3 and S4, the amount of water added twice is 2%-4% of the total weight of the raw materials.

[0014] Furthermore, in step S5, sillimanite, andalusite powder, binding clay, and raw silica powder are premixed before being added.

[0015] According to the above technical solution, the beneficial effects of the present invention are: 1. In the preparation method of clay bricks, hydroxypropyl methylcellulose (HPMC) solution is added first, followed by aluminum dihydrogen phosphate (ADP) solution. This specific order of addition has a synergistic effect on optimizing the slurry state, improving the microstructure and enhancing the product performance.

[0016] The HPMC molecules added first can rapidly extend and dissolve in the aqueous medium, and preferentially adsorb onto the surface of clay, alumina powder, and other ultrafine powder particles through van der Waals forces and hydrogen bonding. The HPMC polymer chains adsorbed on the particle surface extend into the solution and overlap each other, forming a three-dimensional network structure. This generates a significant steric hindrance effect, which effectively prevents ultrafine particles from approaching and agglomerating due to van der Waals forces. As a result, the mixed system achieves a highly dispersed and uniformly stable pre-protected state immediately after the addition of HPMC.

[0017] When ADP is subsequently added, the surface of the ultrafine particles is covered by a protective layer formed by HPMC polymer chains. This protective layer physically prevents direct contact between the particles through steric hindrance and weakens the Al released from the dissociation of ADP. 3+The direct electrostatic interaction with the particle surface effectively avoids the risk of instantaneous flocculation. ADP can be used as a temporary binder, with its phosphorus-containing anions forming slow and uniform chemical bonds with the hydroxyl groups on the particle surface, gradually forming chemical bond networks such as Al-OP and PO-Si, thus steadily establishing the strength of the green body while avoiding severe flocculation.

[0018] The thorough dispersion of particles achieved through HPMC provides an optimized particle packing framework for the subsequent bonding effect of ADP. ADP bonds and bridges within this uniform framework, promoting a uniform distribution of the bound phase and effectively filling micro-voids, thereby significantly reducing the apparent porosity of the product. This uniform microstructure ensures more consistent moisture removal and shrinkage during drying and sintering, reducing internal stress and microcrack formation. Simultaneously, the aluminum phosphate bound phase formed by ADP reacts with the raw material components at high temperatures to generate a ceramic bound phase with higher refractoriness and strength. This uniform and robust high-temperature bound phase network is crucial for achieving low porosity, high density, and excellent creep resistance in the product.

[0019] 2. In this invention, sillimanite and andalusite irreversibly decompose during high-temperature firing, generating a stable mullite phase accompanied by a significant volume expansion effect. This in-situ expansion can precisely offset the natural shrinkage of the brick body caused by the generation of liquid phase and particle rearrangement during sintering. This not only eliminates the firing shrinkage cracks of conventional materials, but also effectively "tightens" the gaps between particles and seals the interconnected pores through a "micro-expansion extrusion" mechanism, thereby actively reducing the overall apparent porosity of the product and achieving densification of the physical structure.

[0020] 3. This invention uses high-purity, dense mullite homogenized material as a robust framework. Numerous fine needle-like secondary mullite particles, generated from the transformation of sillimanite and andalusite, form a dense, interwoven network within the matrix. Raw silica powder provides active SiO2, which, together with the SiO2 decomposed from the three stones and the Al2O3 provided by the clay, promotes the complete secondary mullite formation reaction. This reduces the content of easily softened silica glass phase in the final product, further strengthening the network. This dual-reinforcement structure of "macro framework-micro network" significantly improves the material's resistance to deformation under high temperature and load, i.e., excellent low creep performance.

[0021] 3. The preferred low-iron raw materials of this invention (mullite homogenization, Anhui coke, and low-iron kaolin) control the introduction of harmful impurities such as Fe2O3 from the source. The complete mullitization of sillimanite and andalusite, along with the participation of raw silica powder, ensures that the final product is dominated by high-purity mullite, greatly reducing the content of the glass phase that easily forms low-melting-point substances at high temperatures. This simultaneously achieves high refractoriness, high load softening point, and excellent resistance to chemical corrosion in the material. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to specific embodiments.

[0024] In the following examples, the raw materials used included: calcined gemstone with an Al2O3 mass fraction ≥ 50% and an Fe2O3 mass fraction ≤ 0.5%; sillimanite with a SiO2 mass fraction ≥ 70% and an Fe2O3 mass fraction ≤ 1.0%; kaolin with an Al2O3 mass fraction ≥ 38% and an Fe2O3 mass fraction ≤ 1.0%; andalusite powder with an Al2O3 mass fraction ≥ 50% and an Fe2O3 mass fraction ≤ 0.8%; and raw silica powder with a SiO2 mass fraction ≥ 98%. The calcined gemstone used was from Anhui province.

[0025] In Example 1, the raw materials added in the example were: 42 parts of mullite homogenizer, 12 parts of Anhui calcined gemstone, 8 parts of sillimanite, 18 parts of kaolin, 12 parts of andalusite powder, 3 parts of potassium feldspar powder, 5 parts of raw silica powder, 0.2 parts of HPMC, and 3 parts of ADP solution.

[0026] The mixture consists of 12 parts of mullite homogenized material with a particle size of 5-3mm and 30 parts of mullite homogenized material with a particle size of 3-1mm, with a mixing ratio of 1:2; the total amount of water added is 4% of the total weight of the raw materials.

[0027] The preparation method of low-porosity, low-iron, and low-creep clay bricks in this embodiment is as follows: S1. Weigh and proportion the raw materials according to the above ratio, and set aside; S2. Weigh and proportion the mullite homogenized material with a particle size of 5-3mm and 3-1mm according to the above ratio, and place it with Anhui coke with a particle size of 1-0mm in a mixing mill and dry mix for 3 minutes to obtain mixed aggregate; S3. Dissolve HPMC with a particle size of 30-60nm in part of the added water to prepare a solution, and add it to the mixed aggregate obtained in S2, and wet mix for 3 minutes to make HPMC evenly dispersed and coat the aggregate particles; S4. Add an 80% ADP solution and the remaining added water to the material in S3, and continue to wet mix for 5 minutes; S5. Add a particle size ≤0 S1) S1. Sievesite with a particle size of 0.2mm, andalusite powder with a particle size of ≤0.074mm, kaolin with a particle size of ≤0.088mm, potassium feldspar powder with a particle size of ≤0.088mm, and raw silica powder with a particle size of ≤0.074mm are pre-mixed and stirred for 8 minutes to obtain a uniformly mixed clay material with molding plasticity; S2. The clay material obtained in S5 is machine-pressed under a pressure of 180MPa and held under pressure for 10 seconds to obtain a brick blank; S3. The brick blank is first dried at 110-120℃ for 16 hours, and then heated to 200℃ and dried for 12 hours; S4. The dried brick blank is placed in a tunnel kiln and fired at 1450℃ for 14 hours. After firing, it is cooled to room temperature with the kiln to obtain the low-porosity, low-iron, and low-creep clay brick.

[0028] In Example 2, the raw materials added in the following weight proportions are: 30 parts of mullite homogenizer, 12 parts of Anhui calcined gemstone, 8 parts of sillimanite, 18 parts of kaolin, 12 parts of andalusite powder, 3 parts of potassium feldspar powder, 5 parts of raw silica powder, 0.3 parts of HPMC, and 5 parts of ADP solution.

[0029] The mixture consists of 5 parts of mullite homogenized material with a particle size of 5-3mm and 25 parts of mullite homogenized material with a particle size of 3-1mm, with a mixing ratio of 1:5; the total amount of water added is 3% of the total weight of the raw materials.

[0030] The preparation method of low-porosity, low-iron, and low-creep clay bricks in this embodiment is as follows: S1. Weigh and proportion the raw materials according to the above ratio and set aside; S2. Weigh and proportion the mullite homogenized material with a particle size of 5-3mm and 3-1mm according to the above ratio, and place it with Anhui coke with a particle size of 1-0mm in a mixer and dry mix for 4 minutes to obtain mixed aggregate; S3. Dissolve HPMC with a particle size of 30-60nm in part of the added water to prepare a solution, and add it to the mixed aggregate obtained in S2, and wet mix for 4 minutes to make HPMC evenly dispersed and coat the aggregate particles; S4. Add an 80% ADP solution and the remaining added water to the material in S3, and continue to wet mix for 5 minutes; S5. Add a particle size ≤0. S5. Sievesite with a particle size of 2mm, andalusite powder with a particle size of ≤0.074mm, kaolin with a particle size of ≤0.088mm, potassium feldspar powder with a particle size of ≤0.088mm, and raw silica powder with a particle size of ≤0.074mm are pre-mixed and stirred for 10 minutes to obtain a uniformly mixed clay material with molding plasticity; S6. The clay material obtained in S5 is machine-pressed under a pressure of 180MPa and held under pressure for 10 seconds to obtain a brick blank; S7. The brick blank is first dried at 110-120℃ for 16 hours, and then heated to 200℃ and dried for 12 hours; S8. The dried brick blank is placed in a tunnel kiln and fired at 1500℃ for 12 hours. After firing, it is cooled to room temperature with the kiln to obtain the low-porosity, low-iron, and low-creep clay brick.

[0031] In Example 3, the raw materials added in the following weight proportions are: 35 parts of mullite homogenizer, 16 parts of Anhui coke, 10 parts of sillimanite, 22 parts of kaolin, 12 parts of andalusite powder, 2 parts of potassium feldspar powder, 3 parts of raw silica powder, 0.5 parts of HPMC, and 6 parts of ADP solution.

[0032] The mixture consists of 15 parts of mullite homogenized material with a particle size of 5-3mm and 20 parts of mullite homogenized material with a particle size of 3-1mm, with a mixing ratio of 3:4; the total amount of water added is 2% of the total weight of the raw materials.

[0033] The preparation method of low-porosity, low-iron, and low-creep clay bricks in this embodiment is as follows: S1. Weigh and proportion the raw materials according to the above ratio and set aside; S2. Weigh and proportion the mullite homogenized material with particle sizes of 5-3mm and 3-1mm according to the above ratio, and place it with Anhui coking stone with a particle size of 1-0mm in a mixer and dry mix for 5 minutes to obtain mixed aggregate; S3. Dissolve HPMC with a particle size of 30-60nm in a portion of the added water to prepare a solution, and add it to the mixed aggregate obtained in S2, and wet mix for 5 minutes to make HPMC evenly dispersed and coat the aggregate particles; S4. Add an 80% ADP solution and the remaining added water to the material in S3, and continue to wet mix for 5 minutes; S5. Add a particle size ≤0 S1) S1. Sievesite with a particle size of 0.2mm, andalusite powder with a particle size of ≤0.074mm, kaolin with a particle size of ≤0.088mm, potassium feldspar powder with a particle size of ≤0.088mm, and raw silica powder with a particle size of ≤0.074mm are pre-mixed and stirred for 15 minutes to obtain a uniformly mixed clay material with molding plasticity; S2. The clay material obtained in S5 is machine-pressed under a pressure of 180MPa and held under pressure for 10 seconds to obtain a brick blank; S3. The brick blank is first dried at 110-120℃ for 16 hours, and then heated to 200℃ and dried for 12 hours; S4. The dried brick blank is placed in a tunnel kiln and fired at 1480℃ for 16 hours. After firing, it is cooled to room temperature with the kiln to obtain the low-porosity, low-iron, and low-creep clay brick.

[0034] The comparative example uses ordinary grade III bauxite clinker (Fe2O3 content of about 1.8%) and conventional bonded clay (Fe2O3 content of about 1.5%), with a small amount of andalusite powder and bauxite powder, without adding potassium feldspar powder and raw silica powder. It is prepared by conventional yellow dextrin combined with water and pressed into shape, according to the conventional clay brick formula and process (fired at 1350-1400℃).

[0035] The performance indicators of the clay bricks prepared in Examples 1-3 and the comparative examples are shown in Table 1 below. The standards used for testing are as follows: apparent porosity and bulk density are based on GB / T 2997; room temperature compressive strength is based on GB / T 5072; load softening onset temperature is based on GB / T 5989; permanent linear change upon heating is based on GB / T 5988; and high-temperature creep resistance is based on GB / T 5073.

[0036] Table 1 Performance indicators of clay bricks prepared in Examples 1-3 and comparative examples As shown in Table 1, compared with the comparative example, the clay bricks prepared in Examples 1-3 of this invention exhibit significantly lower apparent porosity (≤13.2%), significantly reduced Fe2O3 content (≤0.96%), and significantly improved room temperature compressive strength (≥94.2 MPa). In particular, the creep rate at 1450℃ for 50 hours is much lower than that of the comparative example (≤0.42%), and they also demonstrate excellent volume stability (micro-expansion). This invention, through optimized raw material ratios and a composite binder system, successfully prepares high-quality clay bricks with low porosity, low iron content, low creep, and high strength, suitable for high-temperature industrial kilns with stringent performance requirements.

[0037] It should be noted that the above embodiments are only used to illustrate the present invention, but the present invention is not limited to the above embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A low-porosity, low-iron, and low-creep clay brick, characterized in that, The composition by weight is as follows: 30-45 parts mullite homogenate, 12-20 parts charred agate, 8-10 parts sillimanite, 15-25 parts kaolinite, 10-20 parts andalusite powder, 3-5 parts raw silica powder, 2-5 parts potassium feldspar powder, 0.2-0.5 parts hydroxypropyl methylcellulose, and 3-6 parts aluminum dihydrogen phosphate solution.

2. The low-porosity, low-iron, and low-creep clay brick according to claim 1, characterized in that: The mullite homogenized material is composed of a mixture of particles with particle sizes of 5-3 mm and 3-1 mm, with a mixing ratio of 1:5-3:

4.

3. The low-porosity, low-iron, and low-creep clay brick according to claim 1, characterized in that: The sillimanite has a particle size ≤0.2mm, wherein the mass fraction of SiO2 is ≥70% and the mass fraction of Fe2O3 is ≤1.0%.

4. The low-porosity, low-iron, and low-creep clay brick according to claim 1, characterized in that: The andalusite powder has a particle size ≤0.074mm, wherein the mass fraction of Al2O3 is ≥50% and the mass fraction of Fe2O3 is ≤0.8%.

5. A low-porosity, low-iron, and low-creep clay brick according to claim 1, characterized in that: The raw silicon powder has a particle size ≤0.074mm, and the mass fraction of SiO2 is ≥98%.

6. The low-porosity, low-iron, and low-creep clay brick according to claim 1, characterized in that: The particle size of the calcined gemstone is 1-0 mm, wherein the mass fraction of Al2O3 is ≥50% and the mass fraction of Fe2O3 is ≤0.5%; the particle size of the kaolin is ≤0.088 mm, wherein the mass fraction of Al2O3 is ≥38% and the mass fraction of Fe2O3 is ≤1.0%; and the particle size of the potassium feldspar powder is ≤0.088 mm.

7. A method for preparing low-porosity, low-iron, and low-creep clay bricks, used to prepare the low-porosity, low-iron, and low-creep clay bricks as described in any one of claims 1-6, characterized in that, Includes the following steps: Weigh each raw material according to the formula ratio; first, dry mix mullite homogenizer and calcined gemstone to obtain mixed aggregate; then dissolve hydroxypropyl methylcellulose in water, and perform a first wet mixing with the mixed aggregate to coat the aggregate particles; then add aluminum dihydrogen phosphate solution and water for a second wet mixing; next, add sillimanite, andalusite powder, kaolin, potassium feldspar powder and raw silica powder for mixing to obtain plastic clay; then press the clay into brick blanks; finally, dry and fire the brick blanks to obtain the low-porosity, low-iron, and low-creep clay bricks.

8. The method for preparing a low-porosity, low-iron, and low-creep clay brick according to claim 7, characterized in that, Specifically, the following steps are included: S1. Accurately weigh each raw material according to the formula ratio; S2. Place the mullite homogenized material and coke in a mixer and dry mix for 3 minutes to obtain mixed aggregate; S3. Dissolve hydroxypropyl methylcellulose with a particle size of 30-60nm in water beforehand, prepare a solution, and add it to the mixed aggregate obtained in S2. Perform a first wet mix for 3-5 minutes to ensure that the hydroxypropyl methylcellulose is evenly dispersed and coats the aggregate particles; S4. Add an 80% aluminum dihydrogen phosphate solution and water to the material in S3, and perform a second wet mix for 3-5 minutes; S5. Add sillimanite to the material in S4... Andalusite powder, kaolin, potassium feldspar powder, and raw silica powder are mixed and stirred for 8-15 minutes to obtain a uniformly mixed and malleable clay material; S6, the clay material obtained in S5 is machine-pressed under a pressure of 180MPa and held under pressure for 10 seconds to obtain a brick blank; S7, the brick blank is first dried at 110-120℃ for 16 hours, and then heated to 200℃ for 12 hours; S8, the dried brick blank is placed in a tunnel kiln and fired at 1450-1500℃ for 12-16 hours. After firing, it is cooled to room temperature with the kiln to obtain the low-porosity, low-iron, and low-creep clay brick.

9. The method for preparing a low-porosity, low-iron, and low-creep clay brick according to claim 8, characterized in that: In steps S3 and S4, the amount of water added twice is 2%-4% of the total weight of the raw materials.

10. The method for preparing a low-porosity, low-iron, and low-creep clay brick according to claim 8, characterized in that: In step S5, sillimanite, andalusite powder, kaolin, potassium feldspar powder, and raw silica powder are premixed before being added.

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