A lightweight periclase-magnesia spinel refractory material and a preparation method thereof

Abstract

The present application relates to a kind of light periclase-magnesia-alumina spinel refractory and its preparation method.The technical scheme is:10-15wt% modified microporous refractory aggregate I,21-30wt% modified microporous refractory aggregate II and 9-11wt% modified microporous refractory aggregate III are modified microporous refractory aggregate,8-15wt% spinel fine powder and 31-38wt% magnesia fine powder are matrix.First, modified microporous refractory aggregate is placed in a blender, plus 3-8wt% sulfurous acid paper pulp waste liquid of the sum of modified microporous refractory aggregate and matrix, stirring;Then add matrix, stir, under the condition of 150-200MPa, dry, then heat to 1300-1600℃ at a rate of 3-8℃ / min, keep warm for 3-8h, with furnace cooling, to obtain light periclase-magnesia-alumina spinel refractory.The product has nanometer pore-containing multi-scale core-shell structure, low thermal conductivity, high strength, excellent anti-erosion penetration performance and thermal shock stability.

Description

Technical Field

[0001] This invention belongs to the technical field of lightweight magnesia refractory materials. In particular, it relates to a lightweight periclase-magnesia-alumina spinel refractory material and its preparation method. Background Technology

[0002] Industrial kilns are key equipment in high-temperature industries and have made significant contributions to national economic development. However, they are also major energy consumers, facing immense pressure to conserve energy and reduce emissions. Therefore, it is essential to develop lightweight magnesia refractory materials with low thermal conductivity, high strength, and excellent resistance to erosion and penetration as linings for industrial kilns in order to save energy, protect the environment, and achieve sustainable resource utilization.

[0003] Currently, there are reports on lightweight magnesia refractories. For example, the patented technology of "Lightweight periclase-magnesia-alumina spinel refractories and their preparation method" (CN201710632853.0) uses porous periclase-magnesia-alumina spinel ceramic material as aggregate and porous periclase-magnesia-alumina spinel ceramic fine powder, magnesium alumina spinel fine powder and magnesia sand fine powder as matrix to prepare lightweight periclase-magnesia-alumina spinel refractories. Although the thermal conductivity of this product is significantly reduced, the nanopores merge and grow during high-temperature use, resulting in a decrease in the product's resistance to erosion and penetration. Moreover, the spinel distribution cannot be precisely controlled, resulting in lower strength and poor thermal shock stability of the product.

[0004] For example, the patented technology of "Lightweight periclase-magnesia-alumina spinel refractory material for cement rotary kiln and its preparation method" (CN201410059476.2) uses porous periclase-spinel ceramic material as raw material. Although it produces a lightweight magnesium refractory material with low thermal conductivity, the raw material contains a lot of impurities and generates a lot of liquid phase at high temperature, resulting in poor strength and erosion and penetration resistance of the product.

[0005] For example, the patented technology of "a lightweight magnesia-spinel refractory material and its preparation method" (CN201610172527.1) uses the magnesium oxide carbothermic reduction transport oxidation method combined with the reaction sintering method to prepare the lightweight magnesia-spinel refractory material. Although the thermal conductivity of the product is significantly reduced, the product has a dense surface, a loose internal structure and randomly distributed spinel, resulting in low strength, poor thermal shock stability and resistance to erosion and penetration. Summary of the Invention

[0006] The present invention aims to overcome the existing technical defects and provides a method for preparing lightweight periclase-magnesia-alumina spinel refractory materials. The prepared lightweight periclase-magnesia-alumina spinel refractory materials have low thermal conductivity, high strength, excellent thermal shock stability and excellent resistance to erosion and penetration.

[0007] To achieve the above objectives, the technical solution adopted by the present invention comprises the following steps:

[0008] Step 1: Preparation of microporous periclase-magnesia-alumina spinel refractory aggregate

[0009] Step 1.1: Use any one of nano alumina, α-alumina micro powder and aluminum hydroxide micro powder as the aluminum source, or use any two of the mixed powders of nano alumina, α-alumina micro powder and aluminum hydroxide micro powder as the aluminum source, or use a mixed powder of nano alumina, α-alumina micro powder and aluminum hydroxide micro powder as the aluminum source.

[0010] Step 1.2: Place 79-97 wt% of magnesium hydroxide fine powder and 3-21 wt% of the aluminum source in a mixer, add 4.5-5.5 wt% of water (the sum of the magnesium hydroxide fine powder and the aluminum source), and stir for 1-3 hours to obtain a mixture.

[0011] Step 1.3: Press the mixture into shape under 100-200 MPa, dry it at 90-110℃ for 18-36 h, then heat it to 300-400℃ at a rate of 1-3℃ / min and hold it for 0.5-1.5 h, and finally heat it to 1600-1800℃ at a rate of 2-5℃ / min and hold it for 2-5 h. Crush and screen it to obtain microporous periclase-magnesium aluminum spinel refractory aggregates of three particle size grades.

[0012] The three particle size grades of microporous periclase-magnesia-alumina spinel refractory aggregates are: microporous periclase-magnesia-alumina spinel refractory aggregate I with a particle size of less than 5 mm and greater than or equal to 3 mm, microporous periclase-magnesia-alumina spinel refractory aggregate II with a particle size of less than 3 mm and greater than or equal to 1 mm, and microporous periclase-magnesia-alumina spinel refractory aggregate III with a particle size of less than 1 mm and greater than or equal to 0.088 mm; the three particle size grades of microporous periclase-magnesia-alumina spinel refractory aggregates are collectively referred to as microporous periclase-magnesia-alumina spinel refractory aggregates.

[0013] The microporous periclase-magnesium aluminum spinel refractory aggregate has a micro-core-shell structure with porous magnesium oxide containing nanopores as the core and continuous spinel as the shell; the total content of Al2O3 and MgO is >99.55wt%, the apparent porosity is 15-33%, and the bulk density is 2.45-3.18 g / cm³. 3 The average pore size is 254–809 nm, the compressive strength is 60–129 MPa, and the thermal conductivity at 350 °C is 4.7–10.6 W / (m·K).

[0014] Step 2: Preparation of modified microporous refractory aggregate

[0015] Step 2.1: Using 97-99.5 wt% aluminum source and 0.5-3 wt% sodium carboxymethyl cellulose as raw materials, place the raw materials in a mixer and mix for 2-5 hours; then add 0.035-0.15 wt% water-reducing agent, 0.24-1.3 wt% defoamer and 20-50 wt% deionized water to the raw materials, stir evenly, and obtain a thixotropic ceramic slurry.

[0016] The aluminum source mentioned in step 2 is the same as the aluminum source mentioned in step 1.

[0017] Step 2.2: Modify the microporous periclase-magnesia-alumina spinel refractory aggregate I to obtain modified microporous refractory aggregate I.

[0018] The modification refers to placing the microporous periclase-magnesia-alumina spinel refractory aggregate I in a mixer, spraying the thixotropic ceramic slurry into the mixer at a mass ratio of the microporous periclase-magnesia-alumina spinel refractory aggregate I to the thixotropic ceramic slurry of 100:3.2-9.6, stirring while spraying, and then taking out the microporous refractory aggregate I coated with the ceramic slurry and drying it at 90-110℃ for 18-36 hours.

[0019] Step 2.3: The microporous periclase-magnesia-alumina spinel refractory aggregate II and the microporous periclase-magnesia-alumina spinel refractory aggregate III are modified using the same modification method as described in Step 2.2 to obtain the corresponding modified microporous refractory aggregate II and modified microporous refractory aggregate III.

[0020] Step 3: Preparation of lightweight periclase-magnesia-alumina spinel refractory material

[0021] Step 3.1: Use 10-15 wt% of the modified microporous refractory aggregate I, 21-30 wt% of the modified microporous refractory aggregate II and 9-11 wt% of the modified microporous refractory aggregate III as the modified microporous refractory aggregate, and 8-15 wt% of spinel fine powder and 31-38 wt% of magnesia fine powder as the matrix.

[0022] Step 3.2: First, place the modified microporous refractory aggregate in a mixer, add 3-8 wt% of sulfite pulp waste liquor (the sum of the modified microporous refractory aggregate and the matrix), and stir. Then, add the matrix, stir, press into shape under 150-200 MPa, dry at 90-110℃ for 18-36 h, then heat to 1300-1600℃ at a rate of 3-8℃ / min, hold for 3-8 h, and cool with the furnace to obtain lightweight periclase-magnesia-alumina spinel refractory material.

[0023] The lightweight periclase-magnesia-alumina spinel refractory material has a multi-scale core-shell structure with a porous periclase-magnesia-alumina spinel refractory aggregate as the core and a continuous spinel layer as the shell. The porous periclase-magnesia-alumina spinel refractory aggregate has an average particle size of 20-45 μm and an average thickness of 2.0-5.0 μm. The lightweight periclase-magnesia-alumina spinel refractory material has an average thickness of 0.10-0.30 mm for the continuous spinel shell.

[0024] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0025] (1) Based on the new design of phase composition and microstructure, a multi-scale core-shell structure refractory material was created.

[0026] This invention features a completely new design from raw materials to refractory aggregates and then to refractory materials. First, it utilizes the in-situ decomposition of magnesium hydroxide to form a porous MgO core containing nanopores. By introducing an aluminum source with a specific particle size and undergoing an in-situ reaction, a continuous and dense MgAl2O4 shell with a micrometer scale is formed, resulting in a refractory aggregate with a micro-core-shell structure. Compared to existing technologies, the micro-core-shell structure of continuous and dense MgAl2O4 encapsulating porous MgO can be precisely controlled, resulting in aggregate with high purity, stable core-shell structure at high temperatures, low thermal conductivity, and excellent high-temperature service performance. Second, a millimeter-scale MgAl2O4 shell is constructed on the surface of the aggregate with the micro-core-shell structure, forming a serrated interlocking interface structure at the shell / aggregate interface. This, together with the microporous periclase-magnesium aluminum spinel refractory aggregate with the micro-core-shell structure, constitutes a multi-scale core-shell structure, fully leveraging the advantages of nanopores, MgO, and MgAl2O4.

[0027] (2) Multi-scale core-shell structure is beneficial to improving the strength and thermal shock stability of refractory materials.

[0028] First, the aggregate used in this invention has a micro-core-shell structure with a continuous and dense MgAl2O4 shell. The rough surface structure of the aggregate increases the aggregate / matrix contact area, facilitating the formation of a good bonding interface and effectively reducing internal stress during high-temperature use. Furthermore, MgAl2O4 has a low coefficient of thermal expansion, which together improves the strength and thermal shock resistance of the aggregate. Simultaneously, MgAl2O4 acts as a toughening phase, further enhancing the aggregate's strength. The aggregate has high purity, low impurity content, and a low liquid phase content at high temperatures, resulting in structural stability and excellent high-temperature service performance. Second, the multi-scale core-shell structure prepared in this invention forms a serrated interlocking interface structure at the aggregate-shell-matrix interface, ensuring a tight bond between the aggregate-shell and shell-matrix, further improving the strength and thermal shock resistance of the product.

[0029] (3) Multi-scale core-shell structure is beneficial to improving the erosion resistance of refractory materials.

[0030] First, this invention uses microporous periclase refractory aggregate with nanoscale pores, which makes it difficult for molten slag to penetrate. Simultaneously, the high purity of the aggregate results in less liquid phase at high temperatures, leading to less dissolution into the molten slag and improving the erosion resistance of the refractory material. Second, the serrated interlocking interface structure formed at the shell-aggregate interface makes the interface bond tighter, preventing molten slag from penetrating along the shell-aggregate interface and effectively improving the erosion resistance of the refractory material. Furthermore, the MgAl2O4 cross-linked network structure formed at the shell-matrix interface exhibits poor wettability of MgAl2O4 to molten slag, effectively enhancing the erosion resistance of the finished product.

[0031] (4) The preparation process of this invention can precisely control the micro-core-shell structure parameters of the microporous periclase-magnesium aluminum spinel refractory aggregate.

[0032] This invention designs the entire process from raw materials and refractory aggregates to refractory materials. First, the self-made aggregate used in this invention is obtained through the design of raw material ratios and particle sizes, under a certain molding pressure, resulting in a structure with Mg(OH)2 as the skeleton and micro / nano powder filling the spaces between Mg(OH)2 microparticles. By adjusting the firing regime, the in-situ decomposition of Mg(OH)2 is utilized to control the pore size and microparticle size within the multi-microporous MgO microparticles. Simultaneously, by adjusting the proportions of different aluminum sources, the thickness of the continuous and dense MgAl2O4 shell is controlled, forming a cross-linked network structure that bridges the porous MgO microparticles together through neck connections. This produces a multi-microporous periclase-magnesium aluminum spinel refractory aggregate with a micro-core-shell structure, featuring porous magnesia with nanopores as the core and continuous spinel as the shell, thus improving the aggregate's strength and thermal shock stability. Secondly, by modifying the aggregate design, the thickness of the continuous and dense MgAl2O4 shell on the outside of the aggregate is controlled by adjusting the solid content of the ceramic slurry and the mass ratio of refractory aggregate to ceramic slurry. In-situ reaction is used to form a tightly bonded interface between aggregate and shell and shell and matrix. Together with the core-shell structure inside the aggregate, it forms a multi-scale core-shell structure, which improves the erosion and penetration resistance and thermal shock stability of the product.

[0033] The lightweight periclase-magnesia-alumina spinel refractory material prepared by this invention has been tested and found to possess a multi-scale core-shell structure, with a porous periclase-magnesia-alumina spinel refractory aggregate as the core and a continuous spinel shell as the shell. The average particle size of the porous magnesium oxide in the porous periclase-magnesia-alumina spinel refractory aggregate is 20–45 μm, and the average thickness of the continuous spinel shell is 2.0–5.0 μm. The average thickness of the continuous spinel shell in the lightweight periclase-magnesia-alumina spinel refractory material is 0.10–0.30 mm. The apparent porosity is 26–37%, and the bulk density is 2.16–2.60 g / cm³. 3Its compressive strength is 90-150 MPa.

[0034] Therefore, the lightweight periclase-magnesium aluminum spinel refractory material prepared by this invention has a multi-scale core-shell structure with nanopores, low thermal conductivity, high strength, excellent resistance to erosion and penetration, and excellent thermal shock stability. Detailed Implementation

[0035] The present invention will be further described below with reference to specific embodiments, but this is not intended to limit the scope of protection thereof.

[0036] A lightweight periclase-magnesium aluminum spinel refractory material and its preparation method. The steps of the preparation method described in this specific embodiment are as follows:

[0037] Step 1: Preparation of microporous periclase-magnesia-alumina spinel refractory aggregate

[0038] Step 1.1: Use any one of nano alumina, α-alumina micro powder and aluminum hydroxide micro powder as the aluminum source, or use any two of the mixed powders of nano alumina, α-alumina micro powder and aluminum hydroxide micro powder as the aluminum source, or use a mixed powder of nano alumina, α-alumina micro powder and aluminum hydroxide micro powder as the aluminum source.

[0039] Step 1.2: Place 79-97 wt% of magnesium hydroxide fine powder and 3-21 wt% of the aluminum source in a mixer, add 4.5-5.5 wt% of water (the sum of the magnesium hydroxide fine powder and the aluminum source), and stir for 1-3 hours to obtain a mixture.

[0040] Step 1.3: Press the mixture into shape under 100-200 MPa, dry it at 90-110℃ for 18-36 h, then heat it to 300-400℃ at a rate of 1-3℃ / min and hold it for 0.5-1.5 h, and finally heat it to 1600-1800℃ at a rate of 2-5℃ / min and hold it for 2-5 h. Crush and screen it to obtain microporous periclase-magnesium aluminum spinel refractory aggregates of three particle size grades.

[0041] The microporous periclase-magnesium aluminum spinel refractory aggregate has a micro-core-shell structure with porous magnesium oxide containing nanopores as the core and continuous spinel as the shell: the total content of Al2O3 and MgO is >99.55wt%, the apparent porosity is 15-33%, and the bulk density is 2.45-3.18 g / cm³. 3 The average pore size is 254–809 nm, the compressive strength is 60–129 MPa, and the thermal conductivity at 350 °C is 4.7–10.6 W / (m·K).

[0042] Step 2: Preparation of modified microporous refractory aggregate

[0043] Step 2.1: Using 97-99.5 wt% aluminum source and 0.5-3 wt% sodium carboxymethyl cellulose as raw materials, place the raw materials in a mixer and mix for 2-5 hours; then add 0.035-0.15 wt% water-reducing agent, 0.24-1.3 wt% defoamer and 20-50 wt% deionized water to the raw materials, stir evenly, and obtain a thixotropic ceramic slurry.

[0044] The aluminum source mentioned in step 2 is the same as the aluminum source mentioned in step 1.

[0045] Step 2.2: Modify the microporous periclase-magnesia-alumina spinel refractory aggregate I to obtain modified microporous refractory aggregate I;

[0046] The modification refers to placing the microporous periclase-magnesia-alumina spinel refractory aggregate I in a mixer, spraying the thixotropic ceramic slurry into the mixer at a mass ratio of the microporous periclase-magnesia-alumina spinel refractory aggregate I to the thixotropic ceramic slurry of 100:3.2-9.6, stirring while spraying, and then taking out the microporous refractory aggregate I coated with the ceramic slurry and drying it at 90-110℃ for 18-36 hours.

[0047] Step 2.3: The microporous periclase-magnesia-alumina spinel refractory aggregate II and the microporous periclase-magnesia-alumina spinel refractory aggregate III are modified using the same modification method as described in Step 2.2 to obtain the corresponding modified microporous refractory aggregate II and modified microporous refractory aggregate III.

[0048] Step 3: Preparation of lightweight periclase-magnesia-alumina spinel refractory material

[0049] Step 3.1: Use 10-15 wt% of the modified microporous refractory aggregate I, 21-30 wt% of the modified microporous refractory aggregate II and 9-11 wt% of the modified microporous refractory aggregate III as the modified microporous refractory aggregate, and 8-15 wt% of spinel fine powder and 31-38 wt% of magnesia fine powder as the matrix.

[0050] Step 3.2: First, place the modified microporous refractory aggregate in a mixer, add 3-8 wt% of sulfite pulp waste liquor (the sum of the modified microporous refractory aggregate and the matrix), and stir. Then, add the matrix, stir, press into shape under 150-200 MPa, dry at 90-110℃ for 18-36 h, then heat to 1300-1600℃ at a rate of 3-8℃ / min, hold for 3-8 h, and cool with the furnace to obtain lightweight periclase-magnesia-alumina spinel refractory material.

[0051] The lightweight periclase-magnesia-alumina spinel refractory material has a multi-scale core-shell structure with a porous periclase-magnesia-alumina spinel refractory aggregate as the core and a continuous spinel layer as the shell. The porous periclase-magnesia-alumina spinel refractory aggregate has an average particle size of 20-45 μm and an average thickness of 2.0-5.0 μm. The lightweight periclase-magnesia-alumina spinel refractory material has an average thickness of 0.10-0.30 mm.

[0052] In this specific implementation:

[0053] The three particle size grades of microporous periclase-magnesia-alumina spinel refractory aggregates are: microporous periclase-magnesia-alumina spinel refractory aggregate I with a particle size of less than 5 mm and greater than or equal to 3 mm, microporous periclase-magnesia-alumina spinel refractory aggregate II with a particle size of less than 3 mm and greater than or equal to 1 mm, and microporous periclase-magnesia-alumina spinel refractory aggregate III with a particle size of less than 1 mm and greater than or equal to 0.088 mm. These three particle size grades of microporous periclase-magnesia-alumina spinel refractory aggregates are collectively referred to as microporous periclase-magnesia-alumina spinel refractory aggregates.

[0054] The nano-alumina has a particle size of <500nm and an Al2O3 content of >99wt%.

[0055] The particle size of the α-alumina micro powder is <2μm; the Al2O3 content of the α-alumina micro powder is >99wt%.

[0056] The aluminum hydroxide micro powder has a particle size of <2μm and an Al2O3 content of >63wt%.

[0057] The particle size of the magnesium hydroxide fine powder is <42μm; the MgO content of the magnesium hydroxide fine powder is >66wt%.

[0058] The water-reducing agent is sodium lignosulfonate or a polycarboxylate.

[0059] The lignin content in the sodium lignin sulfonate is 45-60 wt%.

[0060] The side chain molecular weight of the polycarboxylate is 700 to 2300.

[0061] The defoamer is dimethyl silicone oil or polyether-modified silicone oil.

[0062] The particle size of the magnesium aluminum spinel fine powder is <0.088 mm; the MgAl2O4 content of the spinel fine powder is >96 wt%.

[0063] The particle size of the fine magnesia powder is <0.088 mm; the MgO content of the fine magnesia powder is >96 wt%.

[0064] The details will not be repeated in the examples.

[0065] Example 1

[0066] A lightweight periclase-magnesium aluminum spinel refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0067] Step 1: Preparation of microporous periclase-magnesia-alumina spinel refractory aggregate

[0068] Step 1.1: Use nano-alumina as the aluminum source.

[0069] Step 1.2: Place 85 wt% of magnesium hydroxide fine powder and 15 wt% of the aluminum source in a mixer, add 4.5 wt% of water (the sum of the magnesium hydroxide fine powder and the aluminum source), and stir for 1 hour to obtain a mixture.

[0070] Step 1.3: The mixture is machine-pressed at 100MPa, dried at 90℃ for 36h, then heated to 300℃ at a rate of 1℃ / min and held for 0.5h, and finally heated to 1600℃ at a rate of 2℃ / min and held for 2h. After crushing and sieving, three particle size grades of microporous periclase-magnesium aluminum spinel refractory aggregate are obtained.

[0071] The microporous periclase-magnesia-alumina spinel refractory aggregate has a micro-core-shell structure with porous magnesium oxide containing nanopores as the core and continuous spinel as the shell: the total content of Al2O3 and MgO is >99.55wt%, the apparent porosity is 33%, and the bulk density is 2.34g / cm³. 3 It has an average pore size of 254 nm, a pressure resistance of 129 MPa, and a thermal conductivity of 10.6 W / (m·K) at 350℃.

[0072] Step 2: Preparation of modified microporous refractory aggregate

[0073] Step 2.1: Using 97wt% aluminum source and 3wt% sodium carboxymethyl cellulose as raw materials, place the raw materials in a mixer and mix for 2 hours; then add 0.035wt% water-reducing agent, 0.8wt% defoamer and 23wt% deionized water to the raw materials, stir evenly, and obtain a thixotropic ceramic slurry.

[0074] The aluminum source mentioned in step 2 is the same as the aluminum source mentioned in step 1.

[0075] Step 2.2: Modify the microporous periclase-magnesia-alumina spinel refractory aggregate I to obtain modified microporous refractory aggregate I;

[0076] The modification refers to placing the microporous periclase-magnesia-alumina spinel refractory aggregate I in a mixer, spraying the thixotropic ceramic slurry into the mixer at a mass ratio of the microporous periclase-magnesia-alumina spinel refractory aggregate I to the thixotropic ceramic slurry of 100:3.2, stirring while spraying, and then taking out the microporous refractory aggregate I coated with the ceramic slurry and drying it at 90°C for 36 hours.

[0077] Step 2.3: The microporous periclase-magnesia-alumina spinel refractory aggregate II and the microporous periclase-magnesia-alumina spinel refractory aggregate III are modified using the same modification method as described in Step 2.2 to obtain the corresponding modified microporous refractory aggregate II and modified microporous refractory aggregate III.

[0078] Step 3: Preparation of lightweight periclase-magnesia-alumina spinel refractory material

[0079] Step 3.1: Use 10 wt% of the modified microporous refractory aggregate I, 30 wt% of the modified microporous refractory aggregate II and 9 wt% of the modified microporous refractory aggregate III as the modified microporous refractory aggregate, and 13 wt% of spinel fine powder and 38 wt% of magnesia fine powder as the matrix.

[0080] Step 3.2: First, place the modified microporous refractory aggregate in a mixer, add 3wt% of sulfite pulp waste liquor (the sum of the modified microporous refractory aggregate and the matrix), and stir. Then, add the matrix, stir, press into shape under 150 MPa, dry at 90°C for 36 h, then heat to 1300°C at a rate of 5°C / min, hold for 5 h, and cool with the furnace to obtain lightweight periclase-magnesium aluminum spinel refractory material.

[0081] The lightweight periclase-magnesia-alumina spinel refractory material prepared in this embodiment was tested and found to have the following characteristics: It possesses a multi-scale core-shell structure with a porous periclase-magnesia-alumina spinel refractory aggregate as the core and a continuous spinel shell as the shell; the average particle size of the porous magnesium oxide in the porous periclase-magnesia-alumina spinel refractory aggregate is 20 μm, and the average thickness of the continuous spinel shell is 4.0 μm; the average thickness of the continuous spinel shell in the lightweight periclase-magnesia-alumina spinel refractory material is 0.10 mm; the apparent porosity is 37%, and the bulk density is 2.16 g / cm³. 3 Its pressure resistance is 90MPa.

[0082] Example 2

[0083] A lightweight periclase-magnesium aluminum spinel refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0084] Step 1: Preparation of microporous periclase-magnesia-alumina spinel refractory aggregate

[0085] Step 1.1: Use α-alumina micro powder as the aluminum source.

[0086] Step 1.2: Place 79 wt% of magnesium hydroxide fine powder and 21 wt% of the aluminum source in a mixer, add 4.8 wt% of water (the sum of the magnesium hydroxide fine powder and the aluminum source), and stir for 2.3 hours to obtain a mixture.

[0087] Step 1.3: The mixture is machine-pressed at 150 MPa, dried at 100℃ for 26 h, then heated to 350℃ at a rate of 3℃ / min and held for 1 h, and finally heated to 1650℃ at a rate of 3℃ / min and held for 3 h. After crushing and sieving, three microporous periclase-magnesia-alumina spinel refractory aggregates of three particle size grades are obtained.

[0088] The microporous periclase-magnesium aluminum spinel refractory aggregate has a micro-core-shell structure with porous magnesium oxide containing nanopores as the core and continuous spinel as the shell: the total content of Al2O3 and MgO is >99.55wt%, the apparent porosity is 30%, and the bulk density is 2.45g / cm³. 3 It has an average pore size of 380 nm, a pressure resistance of 118 MPa, and a thermal conductivity of 4.7 W / (m·K) at 350℃.

[0089] Step 2: Preparation of modified microporous refractory aggregate

[0090] Step 2.1: Using 98wt% aluminum source and 2wt% sodium carboxymethyl cellulose as raw materials, place the raw materials in a mixer and mix for 2.5h; then add 0.1wt% water-reducing agent, 0.24wt% defoamer and 30wt% deionized water to the raw materials, stir evenly, and obtain a thixotropic ceramic slurry.

[0091] The aluminum source mentioned in step 2 is the same as the aluminum source mentioned in step 1.

[0092] Step 2.2: Modify the microporous periclase-magnesia-alumina spinel refractory aggregate I to obtain modified microporous refractory aggregate I.

[0093] The modification refers to placing the microporous periclase-magnesia-alumina spinel refractory aggregate I in a mixer, spraying the thixotropic ceramic slurry into the mixer at a mass ratio of microporous periclase-magnesia-alumina spinel refractory aggregate I to the thixotropic ceramic slurry of 100:6.8, stirring while spraying, and then taking out the microporous refractory aggregate I coated with the ceramic slurry and drying it at 100°C for 26 hours.

[0094] Step 2.3: The microporous periclase-magnesia-alumina spinel refractory aggregate II and the microporous periclase-magnesia-alumina spinel refractory aggregate III are modified using the same modification method as described in Step 2.2 to obtain the corresponding modified microporous refractory aggregate II and modified microporous refractory aggregate III.

[0095] Step 3: Preparation of lightweight periclase-magnesia-alumina spinel refractory material

[0096] Step 3.1: Use 15 wt% of the modified microporous refractory aggregate I, 28 wt% of the modified microporous refractory aggregate II and 11 wt% of the modified microporous refractory aggregate III as the modified microporous refractory aggregate, and 8 wt% of spinel fine powder and 38 wt% of magnesia fine powder as the matrix.

[0097] Step 3.2: First, place the modified microporous refractory aggregate in a mixer, add 8wt% of sulfite pulp waste liquor (the sum of the modified microporous refractory aggregate and the matrix), and stir. Then, add the matrix, stir, press into shape under 180MPa, dry at 100℃ for 26h, then heat to 1600℃ at a rate of 6℃ / min, hold for 3h, and cool with the furnace to obtain lightweight periclase-magnesium aluminum spinel refractory material.

[0098] The lightweight periclase-magnesia-alumina spinel refractory material prepared in this embodiment was tested and found to have the following characteristics: It possesses a multi-scale core-shell structure with a porous periclase-magnesia-alumina spinel refractory aggregate as the core and a continuous spinel shell as the shell; the average particle size of the porous magnesium oxide in the porous periclase-magnesia-alumina spinel refractory aggregate is 28 μm, and the average thickness of the continuous spinel shell is 4.5 μm; the average thickness of the continuous spinel shell in the lightweight periclase-magnesia-alumina spinel refractory material is 0.21 mm; the apparent porosity is 30%, and the bulk density is 2.45 g / cm³. 3 Its pressure resistance is 120MPa.

[0099] Example 3

[0100] A lightweight periclase-magnesium aluminum spinel refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0101] Step 1: Preparation of microporous periclase-magnesia-alumina spinel refractory aggregate

[0102] Step 1.1: Use aluminum hydroxide micro powder as the aluminum source.

[0103] Step 1.2: Place 88 wt% of magnesium hydroxide fine powder and 12 wt% of the aluminum source in a mixer, add 5.5 wt% of water (the sum of the magnesium hydroxide fine powder and the aluminum source), and stir for 1.8 h to obtain a mixture.

[0104] Step 1.3: The mixture is machine-pressed at 200 MPa, dried at 110℃ for 18 hours, then heated to 380℃ at a rate of 3℃ / min and held for 1.5 hours, and finally heated to 1700℃ at a rate of 2℃ / min and held for 4 hours. After crushing and sieving, three microporous periclase-magnesia-alumina spinel refractory aggregates of three particle size grades are obtained.

[0105] The microporous periclase-magnesia-alumina spinel refractory aggregate has a micro-core-shell structure with porous magnesium oxide containing nanopores as the core and continuous spinel as the shell: the total content of Al2O3 and MgO is >99.55wt%, the apparent porosity is 27%, and the bulk density is 2.56g / cm³. 3 It has an average pore size of 420 nm, a pressure resistance of 77 MPa, and a thermal conductivity of 6.9 W / (m·K) at 350℃.

[0106] Step 2: Preparation of modified microporous refractory aggregate

[0107] Step 2.1: Using 99.5 wt% aluminum source II and 0.5 wt% sodium carboxymethyl cellulose as raw materials, place the raw materials in a mixer and mix for 5 hours; then add 0.12 wt% water-reducing agent, 0.9 wt% defoamer and 50 wt% deionized water to the raw materials, stir evenly, and obtain a thixotropic ceramic slurry.

[0108] The aluminum source mentioned in step 2 is the same as the aluminum source mentioned in step 1.

[0109] Step 2.2: Modify the microporous periclase-magnesia-alumina spinel refractory aggregate I to obtain modified microporous refractory aggregate I.

[0110] The modification refers to placing the microporous periclase-magnesia-alumina spinel refractory aggregate I in a mixer, spraying the thixotropic ceramic slurry into the mixer at a mass ratio of microporous periclase-magnesia-alumina spinel refractory aggregate I to the thixotropic ceramic slurry of 100:8.9, stirring while spraying, and then taking out the microporous refractory aggregate I coated with the ceramic slurry and drying it at 110°C for 18 hours.

[0111] Step 2.3: The microporous periclase-magnesia-alumina spinel refractory aggregate II and the microporous periclase-magnesia-alumina spinel refractory aggregate III are modified using the same modification method as described in Step 2.2 to obtain the corresponding modified microporous refractory aggregate II and modified microporous refractory aggregate III.

[0112] Step 3: Preparation of lightweight periclase-magnesia-alumina spinel refractory material

[0113] Step 3.1: Using 15 wt% of the modified microporous refractory aggregate I, 28 wt% of the modified microporous refractory aggregate II and 11 wt% of the modified microporous refractory aggregate III as the modified microporous refractory aggregate, and using 15 wt% spinel fine powder and 31 wt% magnesia fine powder as the matrix.

[0114] Step 3.2: First, place the modified microporous refractory aggregate in a mixer, add 5 wt% of sulfite pulp waste liquor (the sum of the modified microporous refractory aggregate and the matrix), and stir. Then, add the matrix, stir, press into shape under 173 MPa, dry at 110℃ for 18 h, then heat to 1500℃ at a rate of 3℃ / min, hold for 8 h, and cool with the furnace to obtain lightweight periclase-magnesium aluminum spinel refractory material.

[0115] The lightweight periclase-magnesia-alumina spinel refractory material prepared in this embodiment was tested and found to have the following characteristics: It possesses a multi-scale core-shell structure with a porous periclase-magnesia-alumina spinel refractory aggregate as the core and a continuous spinel shell as the shell; the average particle size of the porous magnesium oxide in the porous periclase-magnesia-alumina spinel refractory aggregate is 40 μm, and the average thickness of the continuous spinel shell is 3.8 μm; the average thickness of the continuous spinel shell in the lightweight periclase-magnesia-alumina spinel refractory material is 0.25 mm; the apparent porosity is 26%, and the bulk density is 2.60 g / cm³. 3 Its pressure resistance is 150MPa.

[0116] Example 4

[0117] A lightweight periclase-magnesium aluminum spinel refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0118] Step 1: Preparation of microporous periclase-magnesia-alumina spinel refractory aggregate

[0119] Step 1.1: Use a mixture of nano-alumina and α-alumina micro powder as the aluminum source.

[0120] Step 1.2: Place 97 wt% of magnesium hydroxide fine powder and 3 wt% of the aluminum source into a mixer, add 5.2 wt% of water (the sum of the magnesium hydroxide fine powder and the aluminum source), and stir for 2 hours to obtain a mixture.

[0121] Step 1.3: The mixture is machine-pressed at 150 MPa, dried at 90°C for 32 h, then heated to 400°C at a rate of 3°C / min and held for 1.5 h, and finally heated to 1700°C at a rate of 4°C / min and held for 3 h. After crushing and sieving, three particle size grades of microporous periclase-magnesium aluminum spinel refractory aggregate are obtained.

[0122] The microporous periclase-magnesia-alumina spinel refractory aggregate has a total Al2O3 and MgO content >99.55wt%, an apparent porosity of 25%, and a bulk density of 2.70 g / cm³. 3 It has an average pore size of 400 nm, a pressure resistance of 60 MPa, and a thermal conductivity of 6.3 / (m·K) at 350℃.

[0123] Step 2: Preparation of modified microporous refractory aggregate

[0124] Step 2.1: Using 97wt% aluminum source and 3wt% sodium carboxymethyl cellulose as raw materials, place the raw materials in a mixer and mix for 4 hours; then add 0.085wt% water-reducing agent, 1.3wt% defoamer and 40wt% deionized water to the raw materials, stir evenly, and obtain a thixotropic ceramic slurry.

[0125] The aluminum source mentioned in step 2 is the same as the aluminum source mentioned in step 1.

[0126] Step 2.2: Modify the microporous periclase-magnesia-alumina spinel refractory aggregate I to obtain modified microporous refractory aggregate I.

[0127] The modification refers to placing the microporous periclase-magnesia-alumina spinel refractory aggregate I in a mixer, spraying the thixotropic ceramic slurry into the mixer at a mass ratio of the microporous periclase-magnesia-alumina spinel refractory aggregate I to the thixotropic ceramic slurry of 100:9.6, stirring while spraying, and then taking out the microporous refractory aggregate I coated with the ceramic slurry and drying it at 90°C for 32 hours.

[0128] Step 2.3: The microporous periclase-magnesia-alumina spinel refractory aggregate II and the microporous periclase-magnesia-alumina spinel refractory aggregate III are modified using the same modification method as described in Step 2.2 to obtain the corresponding modified microporous refractory aggregate II and modified microporous refractory aggregate III.

[0129] Step 3: Preparation of lightweight periclase-magnesia-alumina spinel refractory material

[0130] Step 3.1: Using 15 wt% of the modified microporous refractory aggregate I, 21 wt% of the modified microporous refractory aggregate II and 11 wt% of the modified microporous refractory aggregate III as the modified microporous refractory aggregate, and using 15 wt% spinel fine powder and 38 wt% magnesia fine powder as the matrix.

[0131] Step 3.2: First, place the modified microporous refractory aggregate in a mixer, add 7wt% of sulfite pulp waste liquor (the sum of the modified microporous refractory aggregate and the matrix), and stir. Then, add the matrix, stir, press into shape under 156 MPa, dry at 90°C for 32 h, then heat to 1400°C at a rate of 8°C / min, hold for 6 h, and cool with the furnace to obtain lightweight periclase-magnesium aluminum spinel refractory material.

[0132] The lightweight periclase-magnesia-alumina spinel refractory material prepared in this embodiment was tested and found to have the following characteristics: It possesses a multi-scale core-shell structure with a porous periclase-magnesia-alumina spinel refractory aggregate as the core and a continuous spinel shell as the shell; the average particle size of the porous magnesium oxide in the porous periclase-magnesia-alumina spinel refractory aggregate is 33 μm, and the average thickness of the continuous spinel shell is 2.0 μm; the average thickness of the continuous spinel shell in the lightweight periclase-magnesia-alumina spinel refractory material is 0.30 mm; the apparent porosity is 35%, and the bulk density is 2.23 g / cm³. 3 Its pressure resistance is 100MPa.

[0133] Example 5

[0134] A lightweight periclase-magnesium aluminum spinel refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0135] Step 1: Preparation of microporous periclase-magnesia-alumina spinel refractory aggregate

[0136] Step 1.1: Use a mixture of nano-alumina and aluminum hydroxide micro powder as the aluminum source.

[0137] Step 1.2: Place 93wt% of magnesium hydroxide fine powder and 7wt% of aluminum source in a mixer, add 4.9wt% of water (the sum of the magnesium hydroxide fine powder and the aluminum source), and stir for 1.6 hours to obtain a mixture.

[0138] Step 1.3: The mixture is machine-pressed at 170 MPa, dried at 100℃ for 28 h, then heated to 330℃ at a rate of 2.8℃ / min and held for 1.2 h, and finally heated to 1750℃ at a rate of 2.5℃ / min and held for 5 h. After crushing and sieving, three particle size grades of microporous periclase-magnesia-alumina spinel refractory aggregate are obtained.

[0139] The microporous periclase-magnesia-alumina spinel refractory aggregate has a total Al2O3 and MgO content >99.55wt%, an apparent porosity of 20%, and a bulk density of 2.82 g / cm³. 3 It has an average pore size of 521 nm, a compressive strength of 92 MPa, and a thermal conductivity of 7.8 W / (m·K) at 350℃.

[0140] Step 2: Preparation of modified microporous refractory aggregate

[0141] Step 2.1: Using 98 wt% aluminum source and 2 wt% sodium carboxymethyl cellulose as raw materials, place the raw materials in a mixer and mix for 3.3 h; then add 0.15 wt% water-reducing agent, 0.85 wt% defoamer and 20 wt% deionized water to the raw materials, stir evenly, and obtain a thixotropic ceramic slurry.

[0142] The aluminum source mentioned in step 2 is the same as the aluminum source mentioned in step 1.

[0143] Step 2.2: Modify the microporous periclase-magnesia-alumina spinel refractory aggregate I to obtain modified microporous refractory aggregate I.

[0144] The modification refers to placing the microporous periclase-magnesia-alumina spinel refractory aggregate I in a mixer, spraying the thixotropic ceramic slurry into the mixer at a mass ratio of microporous periclase-magnesia-alumina spinel refractory aggregate I to the thixotropic ceramic slurry of 100:4.6, stirring while spraying, and then taking out the microporous refractory aggregate I coated with the ceramic slurry and drying it at 100°C for 28 hours.

[0145] Step 2.3: The microporous periclase-magnesia-alumina spinel refractory aggregate II and the microporous periclase-magnesia-alumina spinel refractory aggregate III are modified using the same modification method as described in Step 2.2 to obtain the corresponding modified microporous refractory aggregate II and modified microporous refractory aggregate III.

[0146] Step 3: Preparation of lightweight periclase-magnesia-alumina spinel refractory material

[0147] Step 3.1: Using 13 wt% of the modified microporous refractory aggregate I, 30 wt% of the modified microporous refractory aggregate II and 11 wt% of the modified microporous refractory aggregate III as the modified microporous refractory aggregate, and using 15 wt% spinel fine powder and 31 wt% magnesia fine powder as the matrix.

[0148] Step 3.2: First, place the modified microporous refractory aggregate in a mixer, add 6wt% of sulfite pulp waste liquor (the sum of the modified microporous refractory aggregate and the matrix), and stir. Then, add the matrix, stir, press into shape under 200MPa, dry at 100℃ for 28h, then heat to 1380℃ at a rate of 4℃ / min, hold for 7h, and cool with the furnace to obtain lightweight periclase-magnesium aluminum spinel refractory material.

[0149] The lightweight periclase-magnesia-alumina spinel refractory material prepared in this embodiment was tested and found to have the following characteristics: It possesses a multi-scale core-shell structure with a porous periclase-magnesia-alumina spinel refractory aggregate as the core and a continuous spinel shell as the shell; the average particle size of the porous magnesium oxide in the porous periclase-magnesia-alumina spinel refractory aggregate is 38 μm, and the average thickness of the continuous spinel shell is 2.8 μm; the average thickness of the continuous spinel shell in the lightweight periclase-magnesia-alumina spinel refractory material is 0.12 mm; the apparent porosity is 33%, and the bulk density is 2.38 g / cm³. 3 Its pressure resistance is 96MPa.

[0150] Example 6

[0151] A lightweight periclase-magnesium aluminum spinel refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0152] Step 1: Preparation of microporous periclase-magnesia-alumina spinel refractory aggregate

[0153] Step 1.1: Use a mixture of α-alumina micro powder and aluminum hydroxide micro powder as the aluminum source.

[0154] Step 1.2: Place 82wt% of magnesium hydroxide fine powder and 18wt% of aluminum source in a mixer, add 5.1wt% of water (the sum of the magnesium hydroxide fine powder and the aluminum source), and stir for 3 hours to obtain a mixture.

[0155] Step 1.3: The mixture is machine-pressed at 100 MPa, dried at 110℃ for 20 h, then heated to 320℃ at a rate of 1.8℃ / min and held for 1 h, and finally heated to 1800℃ at a rate of 4℃ / min and held for 4 h. After crushing and sieving, three microporous periclase-magnesia-alumina spinel refractory aggregates of three particle size grades are obtained.

[0156] The microporous periclase-magnesia-alumina spinel refractory aggregate has a total Al2O3 and MgO content >99.55wt%, an apparent porosity of 18%, and a bulk density of 2.9 g / cm³. 3It has an average pore size of 723 nm, a pressure resistance of 113 MPa, and a thermal conductivity of 9.7 W / (m·K) at 350℃.

[0157] Step 2: Preparation of modified microporous refractory aggregate

[0158] Step 2.1: Using 99 wt% aluminum source and 1 wt% sodium carboxymethyl cellulose as raw materials, place the raw materials in a mixer and mix for 4.5 h; then add 0.112 wt% water-reducing agent, 0.99 wt% defoamer and 46 wt% deionized water to the raw materials, stir evenly, and obtain a thixotropic ceramic slurry.

[0159] The aluminum source mentioned in step 2 is the same as the aluminum source mentioned in step 1.

[0160] Step 2.2: Modify the microporous periclase-magnesia-alumina spinel refractory aggregate I to obtain modified microporous refractory aggregate I.

[0161] The modification refers to placing the microporous periclase-magnesia-alumina spinel refractory aggregate I in a mixer, spraying the thixotropic ceramic slurry into the mixer at a mass ratio of the microporous periclase-magnesia-alumina spinel refractory aggregate I to the thixotropic ceramic slurry of 100:7.7, stirring while spraying, and then taking out the microporous refractory aggregate I coated with the ceramic slurry and drying it at 110°C for 20 hours.

[0162] Step 2.3: The microporous periclase-magnesia-alumina spinel refractory aggregate II and the microporous periclase-magnesia-alumina spinel refractory aggregate III are modified using the same modification method as described in Step 2.2 to obtain the corresponding modified microporous refractory aggregate II and modified microporous refractory aggregate III.

[0163] Step 3: Preparation of lightweight periclase-magnesia-alumina spinel refractory material

[0164] Step 3.1: Using 14 wt% of the modified microporous refractory aggregate I, 28 wt% of the modified microporous refractory aggregate II and 10 wt% of the modified microporous refractory aggregate III as the modified microporous refractory aggregate, and using 13 wt% spinel fine powder and 35 wt% magnesia fine powder as the matrix.

[0165] Step 3.2: First, place the modified microporous refractory aggregate in a mixer, add 5wt% of sulfite pulp waste liquor (the sum of the modified microporous refractory aggregate and the matrix), and stir. Then, add the matrix, stir, press into shape under 195 MPa, dry at 110℃ for 20 h, then heat to 1550℃ at a rate of 7℃ / min, hold for 3 h, and cool with the furnace to obtain lightweight periclase-magnesium aluminum spinel refractory material.

[0166] The lightweight periclase-magnesia-alumina spinel refractory material prepared in this embodiment was tested and found to have the following characteristics: It possesses a multi-scale core-shell structure with a porous periclase-magnesia-alumina spinel refractory aggregate as the core and a continuous spinel shell as the shell; the average particle size of the porous magnesium oxide in the porous periclase-magnesia-alumina spinel refractory aggregate is 45 μm, and the average thickness of the continuous spinel shell is 4.3 μm; the average thickness of the continuous spinel shell in the lightweight periclase-magnesia-alumina spinel refractory material is 0.23 mm; the apparent porosity is 29%, and the bulk density is 2.5 g / cm³. 3 Its pressure resistance is 123 MPa.

[0167] Example 7

[0168] A lightweight periclase-magnesium aluminum spinel refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0169] Step 1: Preparation of microporous periclase-magnesia-alumina spinel refractory aggregate

[0170] Step 1.1: Use a mixture of nano-alumina, α-alumina micro powder and aluminum hydroxide micro powder as the aluminum source.

[0171] Step 1.2: Place 79 wt% of magnesium hydroxide fine powder and 21 wt% of aluminum source into a mixer, add 5.5 wt% of water (the sum of the magnesium hydroxide fine powder and the aluminum source), and stir for 3 hours to obtain a mixture.

[0172] Step 1.3: The mixture is machine-pressed at 200 MPa, dried at 110℃ for 30 h, then heated to 300℃ at a rate of 2℃ / min and held for 1 h, and finally heated to 1800℃ at a rate of 5℃ / min and held for 5 h. After crushing and sieving, three particle size grades of microporous periclase-magnesium aluminum spinel refractory aggregate are obtained.

[0173] The microporous periclase-magnesia-alumina spinel refractory aggregate has a total Al2O3 and MgO content >99.55wt%, an apparent porosity of 15%, and a bulk density of 3.18 g / cm³. 3 It has an average pore size of 809 nm, a pressure resistance of 120 MPa, and a thermal conductivity of 8.9 W / (m·K) at 350℃.

[0174] Step 2: Preparation of modified microporous refractory aggregate

[0175] Step 2.1: Using 99.5 wt% aluminum source and 0.5 wt% sodium carboxymethyl cellulose as raw materials, place the raw materials in a mixer and mix for 3 hours; then add 0.098 wt% water-reducing agent, 1.25 wt% defoamer and 33 wt% deionized water to the raw materials, stir evenly, and obtain a thixotropic ceramic slurry.

[0176] The aluminum source mentioned in step 2 is the same as the aluminum source mentioned in step 1.

[0177] Step 2.2: Modify the microporous periclase-magnesia-alumina spinel refractory aggregate I to obtain modified microporous refractory aggregate I.

[0178] The modification refers to placing the microporous periclase-magnesia-alumina spinel refractory aggregate I in a mixer, spraying the thixotropic ceramic slurry into the mixer at a mass ratio of the microporous periclase-magnesia-alumina spinel refractory aggregate I to the thixotropic ceramic slurry of 100:5.5, stirring while spraying, and then taking out the microporous refractory aggregate I coated with the ceramic slurry and drying it at 110°C for 30 hours.

[0179] Step 2.3: The microporous periclase-magnesia-alumina spinel refractory aggregate II and the microporous periclase-magnesia-alumina spinel refractory aggregate III are modified using the same method as described in Step 2.2 to obtain the corresponding modified microporous refractory aggregate II and modified microporous refractory aggregate III.

[0180] Step 3: Preparation of lightweight periclase-magnesia-alumina spinel refractory material

[0181] Step 3.1: Using 14 wt% of the modified microporous refractory aggregate I, 25 wt% of the modified microporous refractory aggregate II and 11 wt% of the modified microporous refractory aggregate III as the modified microporous refractory aggregate, and 12 wt% of spinel fine powder and 38 wt% of magnesia fine powder as the matrix.

[0182] Step 3.2: First, place the modified microporous refractory aggregate in a mixer, add 7wt% of sulfite pulp waste liquor (the sum of the modified microporous refractory aggregate and the matrix), and stir. Then, add the matrix, stir, press into shape under 190MPa, dry at 110℃ for 30h, then heat to 1480℃ at a rate of 8℃ / min, hold for 5h, and cool with the furnace to obtain lightweight periclase-magnesium aluminum spinel refractory material.

[0183] The lightweight periclase-magnesia-alumina spinel refractory material prepared in this embodiment was tested and found to have the following characteristics: It possesses a multi-scale core-shell structure with a porous periclase-magnesia-alumina spinel refractory aggregate as the core and a continuous spinel shell as the shell; the average particle size of the porous magnesium oxide in the porous periclase-magnesia-alumina spinel refractory aggregate is 42 μm, and the average thickness of the continuous spinel shell is 5.0 μm; the average thickness of the continuous spinel shell in the lightweight periclase-magnesia-alumina spinel refractory material is 0.18 mm; the apparent porosity is 27%, and the bulk density is 2.58 g / cm³. 3 Its pressure resistance is 148MPa.

[0184] By adopting the above technical solution, this specific embodiment has the following positive effects compared with the prior art:

[0185] (1) Based on the new design of phase composition and microstructure, a multi-scale core-shell structure refractory material was created.

[0186] This specific embodiment features a completely new design from raw materials to refractory aggregates and then to refractory materials. First, in-situ decomposition of magnesium hydroxide is used to form a porous MgO core containing nanopores. By introducing an aluminum source with a specific particle size and in-situ reaction, a continuous, dense MgAl2O4 shell with a micrometer scale is formed, resulting in a refractory aggregate with a micro-core-shell structure. Compared to existing technologies, the micro-core-shell structure of continuous, dense MgAl2O4 encapsulating porous MgO can be precisely controlled, resulting in aggregate with high purity, stable core-shell structure at high temperatures, low thermal conductivity, and excellent high-temperature service performance. Second, a millimeter-scale MgAl2O4 shell is constructed on the surface of the aggregate with the micro-core-shell structure, forming a serrated interlocking interface structure at the shell / aggregate interface. This, together with the porous periclase-magnesium aluminum spinel refractory aggregate with the micro-core-shell structure, constitutes a multi-scale core-shell structure, fully utilizing the advantages of nanopores, MgO, and MgAl2O4.

[0187] (2) Multi-scale core-shell structure is beneficial to improving the strength and thermal shock stability of refractory materials.

[0188] First, the aggregate used in this specific embodiment has a micro-core-shell structure with a continuous and dense MgAl2O4 shell. The rough surface structure of the aggregate increases the aggregate / matrix contact area, making it easier to form a good bonding interface. This effectively reduces internal stress in the product during high-temperature use. Furthermore, MgAl2O4 has a low coefficient of thermal expansion, which together improves the strength and thermal shock stability of the aggregate. Simultaneously, MgAl2O4, as a toughening phase, can further enhance the strength of the aggregate. The aggregate has high purity, low impurity content, and a low liquid phase content at high temperatures, resulting in structural stability and excellent high-temperature service performance. Second, the multi-scale core-shell structure prepared in this specific embodiment forms a serrated interlocking interface structure at the aggregate-shell-matrix interface, ensuring a tight bond between the aggregate-shell and shell-matrix, which together improves the strength and thermal shock stability of the product.

[0189] (3) Multi-scale core-shell structure is beneficial to improving the erosion resistance of refractory materials.

[0190] First, this specific embodiment uses microporous periclase refractory aggregate with nanoscale pores, which makes it difficult for molten slag to penetrate. Simultaneously, the aggregate has high purity, resulting in less liquid phase in the aggregate at high temperatures and less dissolution into the molten slag, thus improving the erosion resistance of the refractory material. Second, the serrated interlocking interface structure formed at the shell-aggregate interface makes the interface bond tighter, preventing molten slag from penetrating along the shell-aggregate interface and effectively improving the erosion resistance of the refractory material. Furthermore, the MgAl2O4 cross-linked network structure formed at the shell-matrix interface exhibits poor wettability of MgAl2O4 to molten slag, effectively improving the erosion resistance of the product.

[0191] (4) The preparation process of this specific embodiment can precisely control the micro-core-shell structure parameters of the microporous periclase-magnesium aluminum spinel refractory aggregate.

[0192] This specific embodiment designs the entire process from raw materials and refractory aggregates to refractory materials. First, the self-made aggregate used in this embodiment is designed through raw material proportions and particle size control. Under a certain molding pressure, a structure is obtained with Mg(OH)2 as the skeleton and micro / nano powder filling the spaces between Mg(OH)2 microparticles. By adjusting the firing regime, the in-situ decomposition of Mg(OH)2 is utilized to regulate the pore size and microparticle size within the multi-microporous MgO microparticles. Simultaneously, by adjusting the proportions of different aluminum sources, the thickness of the continuous and dense MgAl2O4 shell is controlled, forming a cross-linked network structure that bridges the porous MgO microparticles together through neck connections. This results in a multi-microporous periclase-magnesium aluminum spinel refractory aggregate with a micro-core-shell structure consisting of porous magnesia with nanopores as the core and continuous spinel as the shell, improving the aggregate's strength and thermal shock stability. Secondly, by modifying the aggregate design, the thickness of the continuous and dense MgAl2O4 shell on the outside of the aggregate is controlled by adjusting the solid content of the ceramic slurry and the mass ratio of refractory aggregate to ceramic slurry. In-situ reaction is used to form a tightly bonded interface between aggregate and shell and shell and matrix. Together with the core-shell structure inside the aggregate, it forms a multi-scale core-shell structure, which improves the erosion and penetration resistance and thermal shock stability of the product.

[0193] The lightweight periclase-magnesia-alumina spinel refractory material prepared in this specific embodiment was tested and found to have the following characteristics: It possesses a multi-scale core-shell structure with a porous periclase-magnesia-alumina spinel refractory aggregate as the core and a continuous spinel shell as the shell; the average particle size of the porous magnesium oxide in the porous periclase-magnesia-alumina spinel refractory aggregate is 20–45 μm, and the average thickness of the continuous spinel shell is 2.0–5.0 μm; the average thickness of the continuous spinel shell in the lightweight periclase-magnesia-alumina spinel refractory material is 0.10–0.30 mm; the apparent porosity is 26–37%, and the bulk density is 2.16–2.60 g / cm³. 3 Its compressive strength is 90-150 MPa.

[0194] Therefore, the lightweight periclase-magnesia-alumina spinel refractory material prepared in this specific embodiment has low thermal conductivity, high strength, excellent resistance to erosion and penetration, and excellent thermal shock stability.

Claims

1. A method for preparing a lightweight periclase-magnesia-alumina spinel refractory material, characterized in that... The preparation method comprises the following steps: Step 1: Preparation of microporous periclase-magnesia-alumina spinel refractory aggregate Step 1.1: Use any one of nano alumina, α-alumina micro powder and aluminum hydroxide micro powder as the aluminum source, or use any two of the mixed powders of nano alumina, α-alumina micro powder and aluminum hydroxide micro powder as the aluminum source, or use a mixture of the three powders of nano alumina, α-alumina micro powder and aluminum hydroxide micro powder as the aluminum source. Step 1.2: Place 79-97 wt% of magnesium hydroxide fine powder and 3-21 wt% of the aluminum source in a mixer, add 4.5-5.5 wt% of water (the sum of the magnesium hydroxide fine powder and the aluminum source), and stir for 1-3 hours to obtain a mixture; Step 1.3: Press the mixture into shape under 100-200 MPa, dry it at 90-110℃ for 18-36 h; then heat it to 300-400℃ at a rate of 1-3℃ / min and hold it for 0.5-1.5 h; then heat it to 1600-1800℃ at a rate of 2-5℃ / min and hold it for 2-5 h, crush it, and sieve it to obtain microporous periclase-magnesium aluminum spinel refractory aggregates of three particle size grades; The three particle size grades of microporous periclase-magnesia-alumina spinel refractory aggregates are: microporous periclase-magnesia-alumina spinel refractory aggregate I with a particle size of less than 5 mm and greater than or equal to 3 mm, microporous periclase-magnesia-alumina spinel refractory aggregate II with a particle size of less than 3 mm and greater than or equal to 1 mm, and microporous periclase-magnesia-alumina spinel refractory aggregate III with a particle size of less than 1 mm and greater than or equal to 0.088 mm; the three particle size grades of microporous periclase-magnesia-alumina spinel refractory aggregates are collectively referred to as microporous periclase-magnesia-alumina spinel refractory aggregates; The microporous periclase-magnesium aluminum spinel refractory aggregate has a micro-core-shell structure with porous magnesium oxide containing nanopores as the core and continuous spinel as the shell: the total content of Al2O3 and MgO is >99.55wt%, the apparent porosity is 15-33%, and the bulk density is 2.45-3.18 g / cm³. 3 The average pore size is 254–809 nm, the compressive strength is 60–129 MPa, and the thermal conductivity at 350℃ is 4.7–10.6 W / (m·K). Step 2: Preparation of modified microporous refractory aggregate Step 2.1: Using 97-99.5 wt% aluminum source and 0.5-3 wt% sodium carboxymethyl cellulose as raw materials, place the raw materials in a mixer and mix for 2-5 hours; then add 0.035-0.15 wt% water-reducing agent, 0.24-1.3 wt% defoamer and 20-50 wt% deionized water to the raw materials, stir evenly, and obtain a thixotropic ceramic slurry; The aluminum source mentioned in step 2 is the same as the aluminum source mentioned in step 1; Step 2.2: Modify the microporous periclase-magnesia-alumina spinel refractory aggregate I to obtain modified microporous refractory aggregate I; The modification refers to placing the porous periclase-magnesia-alumina spinel refractory aggregate I in a mixer, spraying the thixotropic ceramic slurry into the mixer at a mass ratio of the porous periclase-magnesia-alumina spinel refractory aggregate I to the thixotropic ceramic slurry of 100:3.2-9.6, stirring while spraying, and then taking out the porous refractory aggregate I coated with the ceramic slurry and drying it at 90-110℃ for 18-36 hours; Step 2.3: The microporous periclase-magnesia-alumina spinel refractory aggregate II and the microporous periclase-magnesia-alumina spinel refractory aggregate III are modified using the same modification method as described in Step 2.2 to obtain the corresponding modified microporous refractory aggregate II and modified microporous refractory aggregate III. Step 3: Preparation of lightweight periclase-magnesia-alumina spinel refractory material Step 3.1: Using 10-15 wt% of the modified microporous refractory aggregate I, 21-30 wt% of the modified microporous refractory aggregate II and 9-11 wt% of the modified microporous refractory aggregate III as the modified microporous refractory aggregate, and using 8-15 wt% of spinel fine powder and 31-38 wt% of magnesia fine powder as the matrix; Step 3.2: First, place the modified microporous refractory aggregate in a mixer, add 3-8 wt% of sulfite pulp waste liquor (the sum of the modified microporous refractory aggregate and the matrix), and stir. Then, add the matrix, stir, press into shape under 150-200 MPa, dry at 90-110℃ for 18-36 h, then heat to 1300-1600℃ at a rate of 3-8℃ / min, hold for 3-8 h, and cool with the furnace to obtain lightweight periclase-magnesia-alumina spinel refractory material.

2. The method for preparing the lightweight periclase-magnesia-alumina spinel refractory material according to claim 1, characterized in that... The nano-alumina has a particle size of <500nm and an Al2O3 content of >99wt%.

3. The method for preparing the lightweight periclase-magnesia-alumina spinel refractory material according to claim 1, characterized in that... The particle size of the α-alumina micro powder is <2μm; the Al2O3 content of the α-alumina micro powder is >99wt%.

4. The method for preparing the lightweight periclase-magnesia-alumina spinel refractory material according to claim 1, characterized in that... The aluminum hydroxide micro powder has a particle size of <2μm and an Al2O3 content of >63wt%.

5. The method for preparing the lightweight periclase-magnesia-alumina spinel refractory material according to claim 1, characterized in that... The particle size of the magnesium hydroxide fine powder is <42μm; the MgO content of the magnesium hydroxide fine powder is >66wt%.

6. The method for preparing the lightweight periclase-magnesia-alumina spinel refractory material according to claim 1, characterized in that... The water-reducing agent is sodium lignosulfonate or polycarboxylate; the lignin content in the sodium lignosulfonate is 45-60 wt%, and the molecular weight of the side chain in the polycarboxylate is 700-2300.

7. The method for preparing the lightweight periclase-magnesia-alumina spinel refractory material according to claim 1, characterized in that... The defoamer is dimethyl silicone oil or polyether-modified silicone oil.

8. The method for preparing the lightweight periclase-magnesia-alumina spinel refractory material according to claim 1, characterized in that... The spinel powder has a particle size of <0.088 mm and a MgAl2O4 content of >96 wt%.

9. The method for preparing the lightweight periclase-magnesia-alumina spinel refractory material according to claim 1, characterized in that... The particle size of the fine magnesia powder is <0.088 mm; the MgO content of the fine magnesia powder is >96 wt%.

10. A lightweight periclase-magnesia-alumina spinel refractory material, characterized in that... The lightweight periclase-magnesium aluminum spinel refractory material is prepared by the method for preparing lightweight periclase-magnesium aluminum spinel refractory material according to any one of claims 1 to 9. The lightweight periclase-magnesia-alumina spinel refractory material has a multi-scale core-shell structure with a porous periclase-magnesia-alumina spinel refractory aggregate as the core and a continuous spinel layer as the shell. The porous periclase-magnesia-alumina spinel refractory aggregate has an average particle size of 20-45 μm and an average thickness of 2.0-5.0 μm. The lightweight periclase-magnesia-alumina spinel refractory material has an average thickness of 0.10-0.30 mm for the continuous spinel shell.