Highly dense slag-erosion-resistant refractory for smelting furnaces and method for producing the same

Abstract

This invention belongs to the field of refractory materials technology and discloses a high-density refractory material for smelting furnaces resistant to molten slag erosion and its preparation method. The refractory material is based on a system of plate-shaped corundum aggregate, fused white corundum fine aggregate, white corundum fine powder, unmodified active α-Al₂O₃ micropowder, low-calcium binder, and dispersant. It also incorporates citrate-regulated magnesium-aluminum layered precursor modified active alumina micropowder, obtained by in-situ composite of active α-Al₂O₃ micropowder, magnesium salts, aluminum salts, and sodium citrate in an alkaline aqueous phase. During preparation, a reactive matrix slurry is first formed, then wet-mixed with premixed aggregates, followed by molding, curing, drying, and segmented firing. The modified micropowder undergoes controlled in-situ spinelization during firing, which improves matrix density, reduces interconnected pores and interface defects, and enhances the material's resistance to molten slag erosion.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, specifically relating to a high-density refractory material for smelting furnaces resistant to molten slag erosion and its preparation method. Background Technology

[0002] The smelting furnace is a core piece of equipment in the high-temperature smelting process, and its refractory lining directly affects the furnace life, production efficiency, and the quality of the smelted products. Existing high-alumina or corundum refractories typically consist of plate-shaped corundum aggregate, fused white corundum fine aggregate, white corundum fine powder, and activated alumina micro-powder. A matrix slurry is prepared using low-calcium binders such as alumina sol or phosphate, and the refractory body is obtained through molding and high-temperature firing. However, under long-term high-temperature smelting and slag erosion conditions, these materials still suffer from insufficient slag resistance, easy formation of microcracks and interconnecting pores at the aggregate-matrix interface, and difficulty in fully improving material density.

[0003] To address these issues, previous studies have attempted to add MgO powder or pre-synthesized MgA spinel powder to refractory materials to improve slag resistance and firing density. However, these methods have significant shortcomings: firstly, traditional MgO powder is prone to hydration and expansion during wet mixing, leading to cracking of the green body and decreased slurry stability; secondly, pre-synthesized spinel powder has low reactivity and cannot effectively participate in the in-situ reaction at the aggregate-matrix interface during firing, making it difficult to form a continuous spinelized structure to compensate for matrix shrinkage. Furthermore, some studies have employed mechanical mixing of MgO and alumina powder, but the reaction sites are random, the slag-resistant components are not concentrated, and the structure cannot be strengthened specifically in the pore throat and interface regions, thus failing to effectively improve the overall density and high-temperature thermal stability of the material. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a high-density refractory material for smelting furnaces resistant to slag erosion and its preparation method. By introducing citrate to regulate the magnesium-aluminum layered precursor to modify activated alumina micropowder, and synergistically combining it with unmodified activated α-Al2O3 micropowder, white corundum fine powder and corundum aggregate, the material is prepared through reactive matrix slurry preparation, wet mixing and segmented calcination, thereby forming a dense matrix structure and a controlled in-situ spinel structure, thus improving its resistance to slag erosion.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing a highly dense refractory material for a smelting furnace resistant to molten slag erosion includes the following steps: S1. Modified activated alumina micro powder, unmodified activated α-Al2O3 micro powder, white corundum fine powder, binder, dispersant and water are mixed to obtain a reactive matrix slurry. The modified activated alumina micro powder is a citrate-regulated magnesium-aluminum layered precursor modified activated alumina micro powder obtained by in-situ composite of activated α-Al2O3 micro powder, magnesium salt, aluminum salt and sodium citrate in an alkaline aqueous phase. S2. Premix the plate-shaped corundum aggregate and the fused white corundum fine aggregate, then add the reactive matrix slurry in batches and continue wet mixing to obtain a wet mixture; S3. The wet mixture is shaped, cured and dried to obtain a dried green body; S4. The dried blank is sintered in sections to obtain a high-density refractory material for smelting furnaces that is resistant to slag erosion.

[0006] More preferably, the modified activated alumina micro powder is prepared by the following steps: A1. Disperse active α-Al2O3 micro powder in water to obtain an active alumina dispersion; A2. Dissolve magnesium salt, aluminum salt and sodium citrate in water to obtain a magnesium-aluminum mixed solution containing citrate ions; A3. The magnesium-aluminum mixed solution containing citrate is added to the active alumina dispersion to adjust the system to alkalinity and then subjected to in-situ composite treatment. After solid-liquid separation, washing, drying and grinding, the modified active alumina micro powder is obtained.

[0007] More preferably, the magnesium salt is a water-soluble magnesium salt selected from at least one of magnesium nitrate hexahydrate and magnesium chloride hexahydrate; the aluminum salt is a water-soluble aluminum salt selected from at least one of aluminum nitrate nonahydrate and aluminum chloride hexahydrate; and the sodium citrate is trisodium citrate dihydrate.

[0008] More preferably, in step A1, the mass ratio of active α-Al2O3 micro powder to water is 1:(3-5); in step A2, the molar ratio of Mg2+ in magnesium salt to Al3+ in aluminum salt is (2.0-3.0):1, and the amount of sodium citrate added is 1-5% of the total mass of magnesium salt and aluminum salt; in step A3, at least one of ammonia water and sodium hydroxide solution is used to adjust the pH of the system to 8.5-10.0, and in-situ composite treatment is carried out at 50-80℃ for 2-6 hours.

[0009] More preferably, in step S1, the binder is a low-calcium binder, which is selected from one or more of aluminum sol, aluminum dihydrogen phosphate, and silica-alumina sol; the dispersant is selected from one or more of polycarboxylate dispersant, sodium hexametaphosphate, and sodium tripolyphosphate.

[0010] More preferably, in step S4, the segmented firing includes: heating the dried blank to 300-400°C and holding it at that temperature for 1-2 hours, then heating it to 800-1000°C and holding it at that temperature for 1-2 hours, and then heating it to 1450-1600°C and holding it at that temperature for 2-4 hours.

[0011] A high-density refractory material for smelting furnaces resistant to slag erosion is prepared by weight from raw materials comprising the following solid components and effective ingredients: 45-60 parts of plate-shaped corundum aggregate, 10-20 parts of fused white corundum fine aggregate, 5-12 parts of white corundum fine powder, 3-10 parts of unmodified active α-Al2O3 micro powder, 6-15 parts of modified active alumina micro powder, 2.5-8 parts of low-calcium binder (based on effective ingredients), and 0.05-0.3 parts of dispersant; The modified activated alumina micro powder is a citrate-regulated magnesium-aluminum layered precursor modified activated alumina micro powder obtained by in-situ composite of activated α-Al2O3 micro powder, magnesium salt, aluminum salt and sodium citrate in an alkaline aqueous phase; the low-calcium binder is selected from one or more of aluminum sol, aluminum dihydrogen phosphate and silica-alumina sol.

[0012] More preferably, the mass ratio of the modified active alumina micro powder to the unmodified active α-Al2O3 micro powder is (1.0~3.0):1.

[0013] More preferably, the tabular corundum aggregate includes coarse tabular corundum aggregate with a particle size of 3-5 mm and medium tabular corundum aggregate with a particle size of 1-3 mm, the fine electrofused white corundum aggregate has a particle size of 0.1-1 mm, the fine white corundum powder has a particle size of no more than 0.074 mm, and the D50 of the unmodified active α-Al2O3 micro powder is 0.5-3 μm.

[0014] More preferably, the low-calcium binder is composed of aluminum sol and aluminum dihydrogen phosphate, wherein the aluminum sol comprises 2 to 6 parts by weight as effective solid content, and the aluminum dihydrogen phosphate comprises 0.5 to 2 parts by weight as effective content.

[0015] The beneficial effects of this invention are: This invention optimizes the overall performance of refractory materials from raw materials to firing by introducing citrate-regulated magnesium-aluminum layered precursors to modify activated alumina micropowders into refractory materials for smelting furnaces. This modified alumina micropowder is then combined with unmodified activated α-Al₂O₃ micropowder, white corundum fine powder, tabular corundum aggregate, and fused white corundum fine aggregate, along with a low-calcium binder and dispersant to construct a reactive matrix slurry. During the in-situ aqueous composite process, the magnesium-aluminum precursor is uniformly deposited on the surface or between particles of the activated alumina micropowder, providing highly reactive components for subsequent firing. This allows for controlled in-situ spinelization with activated alumina at high temperatures, resulting in moderate micro-expansion that compensates for matrix sintering shrinkage, thereby significantly reducing microcracks and interconnecting pores at the aggregate-matrix interface. The stepwise wet mixing and segmented firing processes further ensure that the modified micropowder is preferentially distributed on the aggregate surface and in easily permeable pore areas, concentrating the in-situ spinelization reaction in critical failure regions and improving the overall material density and skeletal structural stability. The rational proportion of multi-grade aggregates and low-calcium bonding system, along with the synergistic effect of modified micro powder, not only enhances the interfacial bonding strength between the matrix and aggregates, but also effectively inhibits the formation of low-melting-point phases, significantly improving the performance stability of refractory materials under slag erosion, high-temperature thermal shock, and long-term service conditions. Attached Figure Description

[0016] The invention will now be further described with reference to the accompanying drawings.

[0017] Figure 1 This is a schematic diagram of the preparation process of the high-density refractory material for smelting furnaces resistant to slag erosion according to the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Unless otherwise stated, all raw materials used in this invention are commercially available products. The active α-Al₂O₃ micro powder is a commercially available reactive alumina micro powder for refractory materials, with α-Al₂O₃ as its main crystalline phase, an Al₂O₃ content of not less than 99%, and a D50 of 0.5–3 μm. The active α-Al₂O₃ micro powder used in the examples has a D50 of 0.8 μm.

[0020] Example 1: This example provides a high-density refractory material for smelting furnaces resistant to slag erosion and its preparation method. I. Preparation of Modified Activated Alumina Micropowder A1. Weigh 100 parts of active α-Al2O3 micro powder, the D50 of which is 0.8 μm, add it to 300 parts of deionized water, and stir and disperse at room temperature for 30 min to obtain an active alumina dispersion.

[0021] A2. Weigh 8.665 parts of magnesium nitrate hexahydrate and 6.335 parts of aluminum nitrate nonahydrate, so that the molar ratio of Mg2+ in the magnesium salt to Al3+ in the aluminum salt is 2.0:1; then weigh 0.15 parts of trisodium citrate dihydrate, the amount of which added is 1% of the total mass of magnesium nitrate hexahydrate and aluminum nitrate nonahydrate. Add 8.665 parts of magnesium nitrate hexahydrate, 6.335 parts of aluminum nitrate nonahydrate, and 0.15 parts of trisodium citrate dihydrate to 100 parts of deionized water, and stir until completely dissolved to obtain a magnesium-aluminum mixed solution containing citrate ions.

[0022] A3. The magnesium-aluminum mixed solution containing citrate obtained in step A2 is slowly added to the activated alumina dispersion obtained in step A1 over 30 minutes while stirring. The pH of the system is adjusted to 8.5 using ammonia water. In-situ composite treatment is carried out at 50℃ for 2 hours to allow the magnesium-aluminum layered precursor to composite on the surface or between particles of the activated α-Al2O3 micropowder. After the reaction, solid-liquid separation is performed, and the solution is washed with deionized water until the pH of the washing solution is 6.5-7.5. Then, it is dried at 100℃ for 12 hours, ground, and passed through a 200-mesh sieve to obtain activated alumina micropowder modified with citrate-regulated magnesium-aluminum layered precursor.

[0023] II. Preparation of High-Density Refractory Materials for Smelting Furnaces Resistant to Slag Erosion S1. By weight, take 6 parts of the modified activated alumina micro powder obtained in step one, 3 parts of unmodified activated α-Al2O3 micro powder, 5 parts of white corundum fine powder, 0.05 parts of polycarboxylate dispersant, and 3 parts of added water, and simultaneously add a low-calcium binder. The unmodified activated α-Al2O3 micro powder has a D50 of 0.8 μm, and the white corundum fine powder has a particle size not exceeding 0.074 mm. The low-calcium binder is composed of aluminum sol and aluminum dihydrogen phosphate, with 2.5 parts as effective ingredient, of which 2 parts are aluminum sol (effective solid ingredient) and 0.5 parts are aluminum dihydrogen phosphate (effective ingredient). The actual added amounts of aluminum sol and aluminum dihydrogen phosphate are calculated based on their effective ingredients. The 3 parts of added water do not include the moisture contained in the aluminum sol and aluminum dihydrogen phosphate themselves. Add the above components to a mixer and stir at 300 r / min for 20 min to fully disperse the fine powder, modified micro powder, binder and dispersant to obtain a reactive matrix slurry.

[0024] S2. By weight, take 45 parts of tabular corundum aggregate and 10 parts of fused white corundum fine aggregate, wherein the 45 parts of tabular corundum aggregate consists of 25 parts of coarse tabular corundum aggregate with a particle size of 3-5 mm and 20 parts of medium tabular corundum aggregate with a particle size of 1-3 mm, and the particle size of the fused white corundum fine aggregate is 0.1-1 mm. Add the tabular corundum aggregate and the fused white corundum fine aggregate to a planetary mixer and premix for 10 minutes to ensure uniform distribution of aggregates of different particle sizes; then add the reactive matrix slurry obtained in step S1 to the premixed aggregate in 3 portions, wet mixing for 5 minutes after each addition, and continue wet mixing for 10 minutes after all additions are completed to obtain a wet mixture.

[0025] S3. Add the wet mixture obtained in step S2 into the mold and press it into shape under a pressure of 100 MPa. The shaped green body is cured at room temperature for 24 hours, and then placed in an oven at 110℃ for 12 hours to obtain a dried green body.

[0026] S4. The dried blank obtained in step S3 is placed in a high-temperature furnace for segmented firing. During firing, the temperature is increased to 300℃ at a rate of 3℃ / min and held for 1 hour; then increased to 800℃ at a rate of 3℃ / min and held for 1 hour; finally, the temperature is increased to 1450℃ at a rate of 3℃ / min and held for 2 hours. After firing, the blank is cooled to room temperature with the furnace to obtain a high-density refractory material resistant to slag erosion for smelting furnaces.

[0027] Example 2: This example provides a high-density refractory material for smelting furnaces resistant to slag erosion and its preparation method. I. Preparation of Modified Activated Alumina Micropowder In this embodiment, the preparation method of the modified active alumina micro powder is the same as that in Example 1.

[0028] II. Preparation of High-Density Refractory Materials for Smelting Furnaces Resistant to Slag Erosion S1. By weight, take 15 parts of the modified activated alumina micro powder prepared above, 5 parts of unmodified activated α-Al2O3 micro powder, 12 parts of white fused alumina fine powder, 0.3 parts of polycarboxylate dispersant, and 6 parts of added water, and simultaneously add a low-calcium binder. The unmodified activated α-Al2O3 micro powder has a D50 of 0.8 μm, and the white fused alumina fine powder has a particle size not exceeding 0.074 mm. The low-calcium binder is composed of aluminum sol and aluminum dihydrogen phosphate, with 8 parts as effective ingredient, of which 6 parts are aluminum sol and 2 parts are aluminum dihydrogen phosphate. The actual added amounts of aluminum sol and aluminum dihydrogen phosphate are calculated based on their effective ingredients. The 6 parts of added water do not include the moisture contained in the aluminum sol and aluminum dihydrogen phosphate themselves. Add the above components to a mixer and stir at 300 r / min for 25 min to fully disperse the fine powder, modified micro powder, binder and dispersant to obtain a reactive matrix slurry.

[0029] S2. By weight, take 60 parts of tabular corundum aggregate and 20 parts of fused white corundum fine aggregate. The 60 parts of tabular corundum aggregate consist of 35 parts of coarse tabular corundum aggregate with a particle size of 3-5 mm and 25 parts of medium tabular corundum aggregate with a particle size of 1-3 mm. The fused white corundum fine aggregate has a particle size of 0.1-1 mm. Add the tabular corundum aggregate and fused white corundum fine aggregate to a planetary mixer and premix for 10 minutes to ensure uniform distribution of aggregates of different particle sizes. Then, add the reactive matrix slurry obtained in step S1 to the premixed aggregate in three portions, wet mixing for 5 minutes after each addition. After all the slurry has been added, continue wet mixing for 10 minutes to obtain a wet mixture.

[0030] S3. Add the wet mixture obtained in step S2 into the mold and press it into shape under a pressure of 100 MPa. The shaped green body is cured at room temperature for 24 hours, and then placed in an oven at 110℃ for 12 hours to obtain a dried green body.

[0031] S4. The dried blank obtained in step S3 is placed in a high-temperature furnace for segmented firing. During firing, the temperature is increased to 400℃ at a rate of 3℃ / min and held for 2 hours; then increased to 1000℃ at a rate of 3℃ / min and held for 2 hours; finally, the temperature is increased to 1600℃ at a rate of 3℃ / min and held for 4 hours. After firing, the blank is cooled to room temperature with the furnace to obtain a high-density refractory material resistant to slag erosion for smelting furnaces.

[0032] Example 3: This example provides a high-density refractory material for smelting furnaces resistant to slag erosion and its preparation method. I. Preparation of Modified Activated Alumina Micropowder A1. Weigh 100 parts of active α-Al2O3 micro powder, the active α-Al2O3 micro powder having a D50 of 0.8 μm, add it to 400 parts of deionized water, stir and disperse at room temperature for 30 min to obtain an active alumina dispersion.

[0033] A2. Weigh 12.617 parts of magnesium nitrate hexahydrate and 7.383 parts of aluminum nitrate nonahydrate, so that the molar ratio of Mg2+ in the magnesium salt to Al3+ in the aluminum salt is 2.5:1; then weigh 0.6 parts of trisodium citrate dihydrate, the amount of which added is 3% of the total mass of magnesium nitrate hexahydrate and aluminum nitrate nonahydrate. Add 12.617 parts of magnesium nitrate hexahydrate, 7.383 parts of aluminum nitrate nonahydrate, and 0.6 parts of trisodium citrate dihydrate to 120 parts of deionized water, and stir until completely dissolved to obtain a magnesium-aluminum mixed solution containing citrate.

[0034] A3. Slowly add the magnesium-aluminum mixed solution containing citrate obtained in step A2 to the activated alumina dispersion obtained in step A1 while stirring. Adjust the pH of the system to 9.2 with ammonia water, and perform in-situ composite treatment at 65℃ for 4 hours to allow the magnesium-aluminum layered precursor to composite on the surface or between particles of the activated α-Al2O3 micro powder. After the reaction, perform solid-liquid separation and wash with deionized water until the pH of the washing solution is 6.5-7.5. Then dry at 100℃ for 12 hours, grind, and pass through a 200-mesh sieve to obtain activated alumina micro powder modified with citrate-regulated magnesium-aluminum layered precursor.

[0035] II. Preparation of High-Density Refractory Materials for Smelting Furnaces Resistant to Slag Erosion S1. By weight, take 10 parts of the modified activated alumina micro powder obtained in step one, 4 parts of unmodified activated α-Al2O3 micro powder, 8 parts of white fused alumina fine powder, 0.15 parts of polycarboxylate dispersant, and 4.5 parts of added water, and simultaneously add a low-calcium binder. The unmodified activated α-Al2O3 micro powder has a D50 of 0.8 μm, and the white fused alumina fine powder has a particle size not exceeding 0.074 mm. The low-calcium binder is composed of aluminum sol and aluminum dihydrogen phosphate, with 5 parts as effective ingredient, of which 4 parts are aluminum sol and 1 part are aluminum dihydrogen phosphate. The actual added amounts of aluminum sol and aluminum dihydrogen phosphate are calculated based on their effective ingredients. The 4.5 parts of added water do not include the moisture contained in the aluminum sol and aluminum dihydrogen phosphate themselves. Add the above components to a mixer and stir at 300 r / min for 25 min to fully disperse the fine powder, modified micro powder, binder and dispersant to obtain a reactive matrix slurry.

[0036] S2. By weight, take 52 parts of tabular corundum aggregate and 15 parts of fused white corundum fine aggregate. The 52 parts of tabular corundum aggregate consist of 30 parts of coarse tabular corundum aggregate with a particle size of 3-5 mm and 22 parts of medium tabular corundum aggregate with a particle size of 1-3 mm. The fused white corundum fine aggregate has a particle size of 0.1-1 mm. Add the tabular corundum aggregate and fused white corundum fine aggregate to a planetary mixer and premix for 10 minutes to ensure uniform distribution of different aggregate sizes. Then, add the reactive matrix slurry obtained in step S1 to the premixed aggregate in three portions, wet-mixing for 5 minutes after each addition. After all the slurry has been added, continue wet-mixing for 10 minutes to obtain a wet mixture.

[0037] S3. Add the wet mixture obtained in step S2 into the mold and press it into shape under a pressure of 100 MPa. The shaped green body is cured at room temperature for 24 hours, and then placed in an oven at 110℃ for 12 hours to obtain a dried green body.

[0038] S4. The dried blank obtained in step S3 is placed in a high-temperature furnace for segmented firing. During firing, the temperature is increased to 350°C at a rate of 3°C / min and held for 1.5 hours; then increased to 900°C at a rate of 3°C / min and held for 1.5 hours; finally, the temperature is increased to 1550°C at a rate of 3°C / min and held for 3 hours. After firing, the blank is cooled to room temperature with the furnace to obtain a high-density refractory material resistant to slag erosion for smelting furnaces.

[0039] Comparative Example 1: This comparative example does not include citrate to regulate the magnesium-aluminum layered precursor modified activated alumina micro powder. S1. By weight, take 14 parts of unmodified active α-Al2O3 micro powder, 8 parts of white corundum fine powder, 0.15 parts of polycarboxylate dispersant, and 4.5 parts of added water, along with a low-calcium binder. The unmodified active α-Al2O3 micro powder has a D50 of 0.8 μm, and the white corundum fine powder has a particle size not exceeding 0.074 mm. The low-calcium binder consists of aluminum sol and aluminum dihydrogen phosphate, with 5 parts as effective ingredient, of which 4 parts are aluminum sol and 1 part are aluminum dihydrogen phosphate. The actual amounts of aluminum sol and aluminum dihydrogen phosphate added are calculated based on their effective ingredients. The 4.5 parts of added water do not include the water contained in the aluminum sol and aluminum dihydrogen phosphate themselves. Add all the above components to a mixer and stir at 300 r / min for 25 min to fully disperse the fine powder, binder, and dispersant, obtaining a matrix slurry.

[0040] S2. By weight, take 52 parts of tabular corundum aggregate and 15 parts of fused white corundum fine aggregate. The 52 parts of tabular corundum aggregate consist of 30 parts of coarse tabular corundum aggregate with a particle size of 3-5 mm and 22 parts of medium tabular corundum aggregate with a particle size of 1-3 mm. The fused white corundum fine aggregate has a particle size of 0.1-1 mm. Add the tabular corundum aggregate and fused white corundum fine aggregate to a planetary mixer and premix for 10 minutes to ensure uniform distribution of different aggregate sizes. Then, add the matrix slurry obtained in step S1 to the premixed aggregate in three portions, wet-mixing for 5 minutes after each addition. After all the slurry has been added, continue wet-mixing for 10 minutes to obtain a wet mixture.

[0041] S3. Add the wet mixture obtained in step S2 into the mold and press it into shape under a pressure of 100 MPa. The shaped green body is cured at room temperature for 24 hours, and then placed in an oven at 110℃ for 12 hours to obtain a dried green body.

[0042] S4. The dried blank obtained in step S3 is placed in a high-temperature furnace for segmented firing. During firing, the temperature is increased to 350°C at a rate of 3°C / min and held for 1.5 hours; then increased to 900°C at a rate of 3°C / min and held for 1.5 hours; finally, the temperature is increased to 1550°C at a rate of 3°C / min and held for 3 hours. After firing, the blank is cooled to room temperature with the furnace to obtain the refractory material for the smelting furnace of Comparative Example 1.

[0043] Comparative Example 2: This comparative example does not use modified activated alumina micro powder prepared by in-situ aqueous phase composite, but instead uses a mechanical mixture of unmodified activated α-Al2O3 micro powder and high-purity magnesium oxide micro powder. S1. By weight, take 9 parts of unmodified active α-Al2O3 micro powder and 1 part of high-purity magnesium oxide micro powder, and dry mix them for 10 min to obtain mechanically mixed micro powder. The D50 of the unmodified active α-Al2O3 micro powder is 0.8 μm, and the D50 of the high-purity magnesium oxide micro powder is 1.0 μm.

[0044] S2. By weight, take 10 parts of the mechanically mixed micro powder obtained in step S1, 4 parts of unmodified active α-Al2O3 micro powder, 8 parts of white corundum fine powder, 0.15 parts of polycarboxylate dispersant, and 4.5 parts of added water, and simultaneously add a low-calcium binder. The particle size of the white corundum fine powder is no greater than 0.074 mm; the low-calcium binder is composed of aluminum sol and aluminum dihydrogen phosphate, with 5 parts of the low-calcium binder as effective ingredient, of which 4 parts are aluminum sol as effective solid ingredient and 1 part is aluminum dihydrogen phosphate as effective ingredient; the actual added amounts of aluminum sol and aluminum dihydrogen phosphate are calculated based on their effective ingredients, and the 4.5 parts of added water do not include the water contained in the aluminum sol and aluminum dihydrogen phosphate themselves. Add all the above components to a mixer and stir at 300 r / min for 25 min to fully disperse the fine powder, mechanically mixed micro powder, binder, and dispersant, obtaining a matrix slurry.

[0045] S3. By weight, take 52 parts of tabular corundum aggregate and 15 parts of fused white corundum fine aggregate. The 52 parts of tabular corundum aggregate consist of 30 parts of coarse tabular corundum aggregate with a particle size of 3-5 mm and 22 parts of medium tabular corundum aggregate with a particle size of 1-3 mm. The fused white corundum fine aggregate has a particle size of 0.1-1 mm. Add the tabular corundum aggregate and fused white corundum fine aggregate to a planetary mixer and premix for 10 minutes to ensure uniform distribution of different aggregate sizes. Then, add the matrix slurry obtained in step S2 to the premixed aggregate in three portions, wet-mixing for 5 minutes after each addition. After all the slurry has been added, continue wet-mixing for 10 minutes to obtain a wet mixture.

[0046] S4. Add the wet mixture obtained in step S3 into the mold and press it into shape under a pressure of 100 MPa. The shaped green body is cured at room temperature for 24 hours, and then placed in an oven at 110℃ for 12 hours to dry, thus obtaining a dried green body.

[0047] S5. The dried blank obtained in step S4 is placed in a high-temperature furnace for segmented firing. During firing, the temperature is increased to 350°C at a rate of 3°C / min and held for 1.5 hours; then increased to 900°C at a rate of 3°C / min and held for 1.5 hours; finally, the temperature is increased to 1550°C at a rate of 3°C / min and held for 3 hours. After firing, the blank is cooled to room temperature with the furnace to obtain the refractory material for the smelting furnace of Comparative Example 2.

[0048] Comparative Example 3: This comparative example does not use the wet mixing method of "preparing the reactive matrix slurry first and adding the aggregate in batches after premixing". Instead, all solid raw materials are mixed at once, and then the binder and added water are added for wet mixing. I. Preparation of Modified Activated Alumina Micropowder The preparation method of the modified active alumina micro powder is the same as that in Example 3.

[0049] II. Preparation of Refractory Materials for Melting Furnaces S1. By weight, prepare 10 parts modified activated alumina micro powder, 4 parts unmodified activated α-Al2O3 micro powder, 8 parts white fused alumina fine powder, 52 parts tabular fused alumina aggregate, 15 parts fused white fused alumina fine aggregate, 0.15 parts polycarboxylate dispersant, 4.5 parts added water and low-calcium binder. The 52 parts of tabular corundum aggregate consist of 30 parts of coarse tabular corundum aggregate with a particle size of 3-5 mm and 22 parts of medium tabular corundum aggregate with a particle size of 1-3 mm. The fine electrofused white corundum aggregate has a particle size of 0.1-1 mm. The unmodified active α-Al2O3 micro powder has a D50 of 0.8 μm, and the fine white corundum powder has a particle size of no more than 0.074 mm. The low-calcium binder consists of aluminum sol and aluminum dihydrogen phosphate. The low-calcium binder is 5 parts by effective ingredient, of which aluminum sol is 4 parts by effective solid ingredient and aluminum dihydrogen phosphate is 1 part by effective ingredient. The actual addition amounts of aluminum sol and aluminum dihydrogen phosphate are calculated based on the effective ingredients. The 4.5 parts of added water do not include the water contained in the aluminum sol and aluminum dihydrogen phosphate themselves.

[0050] S2. Add 10 parts of modified activated alumina micro powder, 4 parts of unmodified activated α-Al2O3 micro powder, 8 parts of white fused alumina fine powder, 52 parts of tabular fused alumina aggregate, 15 parts of fused white fused alumina fine aggregate and 0.15 parts of polycarboxylate dispersant into a planetary mixer at once. Dry mix for 10 minutes, then add low-calcium binder and 4.5 parts of added water and continue wet mixing for 25 minutes to obtain a wet mixture.

[0051] S3. Add the wet mixture obtained in step S2 into the mold and press it into shape under a pressure of 100 MPa. The shaped green body is cured at room temperature for 24 hours, and then placed in an oven at 110℃ for 12 hours to obtain a dried green body.

[0052] S4. The dried blank obtained in step S3 is placed in a high-temperature furnace for segmented firing. During firing, the temperature is increased to 350°C at a rate of 3°C / min and held for 1.5 hours; then increased to 900°C at a rate of 3°C / min and held for 1.5 hours; finally, the temperature is increased to 1550°C at a rate of 3°C / min and held for 3 hours. After firing, the blank is cooled to room temperature in the furnace to obtain the refractory material for the smelting furnace of Comparative Example 3.

[0053] Comparative Example 4: In this comparative example, the two intermediate heat preservation stages of 350°C and 900°C were omitted. The dried green body was directly heated to 1550°C at the same heating rate and held for 3 hours. The maximum firing temperature and the maximum heat preservation time were the same as in Example 3.

[0054] I. Preparation of Modified Activated Alumina Micropowder In this comparative example, the preparation method of the modified active alumina micro powder is the same as that in Example 3.

[0055] II. Preparation of Refractory Materials for Melting Furnaces S1. By weight, take 10 parts modified activated alumina micro powder, 4 parts unmodified activated α-Al2O3 micro powder, 8 parts white fused alumina fine powder, 0.15 parts polycarboxylate dispersant, and 4.5 parts added water, and simultaneously add a low-calcium binder. The unmodified activated α-Al2O3 micro powder has a D50 of 0.8 μm, and the white fused alumina fine powder has a particle size not exceeding 0.074 mm. The low-calcium binder is composed of aluminum sol and aluminum dihydrogen phosphate, with 5 parts as effective ingredient, of which 4 parts are aluminum sol and 1 part are aluminum dihydrogen phosphate. The actual added amounts of aluminum sol and aluminum dihydrogen phosphate are calculated based on their effective ingredients. The 4.5 parts added water do not include the moisture contained in the aluminum sol and aluminum dihydrogen phosphate themselves. Add the above components to a mixer and stir at 300 r / min for 25 min to fully disperse the fine powder, modified micro powder, binder and dispersant to obtain a reactive matrix slurry.

[0056] S2. By weight, take 52 parts of tabular corundum aggregate and 15 parts of fused white corundum fine aggregate. The 52 parts of tabular corundum aggregate consist of 30 parts of coarse tabular corundum aggregate with a particle size of 3-5 mm and 22 parts of medium tabular corundum aggregate with a particle size of 1-3 mm. The fused white corundum fine aggregate has a particle size of 0.1-1 mm. Add the tabular corundum aggregate and fused white corundum fine aggregate to a planetary mixer and premix for 10 minutes to ensure uniform distribution of different aggregate sizes. Then, add the reactive matrix slurry obtained in step S1 to the premixed aggregate in three portions, wet-mixing for 5 minutes after each addition. After all the slurry has been added, continue wet-mixing for 10 minutes to obtain a wet mixture.

[0057] S3. Add the wet mixture obtained in step S2 into the mold and press it into shape under a pressure of 100 MPa. The shaped green body is cured at room temperature for 24 hours, and then placed in an oven at 110℃ for 12 hours to obtain a dried green body.

[0058] S4. Place the dried blank obtained in step S3 into a high-temperature furnace for firing. During firing, the temperature is directly raised to 1550℃ at a heating rate of 3℃ / min and held for 3 hours. After firing, the blank is cooled to room temperature with the furnace to obtain the refractory material for the smelting furnace of Comparative Example 4.

[0059] Performance testing To verify the technical effects of the present invention, the refractory materials obtained in Examples 1-3 and Comparative Examples 1-4 were used as test samples for testing of bulk density, apparent porosity, room temperature compressive strength, resistance to slag erosion, and thermal shock resistance. Three parallel samples were set up for each group of samples, and the test results are expressed as mean ± standard deviation.

[0060] (1) Bulk density and apparent porosity test: The test was conducted in accordance with GB / T 2997-2015 "Test methods for bulk density, apparent porosity and true porosity of dense shaped refractory products". The fired samples of each group were processed into regular specimens, dried at 110℃ to constant weight, and the bulk density and apparent porosity were determined and calculated using the standard method.

[0061] (2) Room temperature compressive strength test: The test shall be conducted in accordance with GB / T 5072-2023 "Determination of room temperature compressive strength of refractory products". Each group of samples shall be processed into block specimens of uniform size. The maximum load at which the specimen fails shall be determined by a pressure testing machine, and the room temperature compressive strength shall be calculated in accordance with the standard.

[0062] 3) Slag Erosion Resistance Test: The static crucible method was performed according to GB / T 8931-2007 "Test Method for Slag Resistance of Refractory Materials". Each group of samples was processed into crucible-shaped specimens, with a cylindrical cavity of 20 mm diameter and 25 mm depth drilled in the center of each specimen. 20 g of simulated slag from a smelting furnace was added to each cavity. The simulated slag was a CaO-SiO2-Al2O3-MgO system slag, with a mass ratio of 35 parts CaO, 35 parts SiO2, 20 parts Al2O3, and 10 parts MgO. The slag-loaded specimens were placed in a high-temperature furnace, heated to 1550℃ at a rate of 5℃ / min, and held for 3 hours. After cooling, the specimens were cut along the centerline of the cavity, and the maximum erosion depth and maximum penetration depth were measured.

[0063] (4) Thermal shock resistance test: The test was conducted using the air quenching method as specified in GB / T 30873-2014 "Test Method for Thermal Shock Resistance of Refractory Materials". Each group of samples was placed in a high-temperature furnace at 1100℃ for 30 minutes, and then removed and cooled to below 100℃ in room temperature air. This was considered one thermal shock cycle, and five thermal shock cycles were performed consecutively. After the thermal shock cycle, the compressive strength at room temperature after thermal shock was determined according to GB / T5072-2023, and the strength retention rate after thermal shock was calculated as "strength retention rate after thermal shock = compressive strength at room temperature after thermal shock / compressive strength at room temperature before thermal shock × 100%".

[0064] The results are shown in Table 1 below.

[0065] Table 1. Comprehensive performance analysis of each sample in the examples and comparative examples.

[0066] As shown in Table 2, the refractory materials obtained in Examples 1-3 all exhibit high bulk density, low apparent porosity, and good mechanical strength, resistance to slag erosion, and thermal shock resistance. This indicates that the present invention, by introducing citrate to regulate the magnesium-aluminum layered precursor modified activated alumina micropowder, combined with reactive matrix slurry preparation, batch wet mixing after aggregate premixing, and segmented firing processes, can effectively improve the internal pore structure and aggregate-matrix interface bonding state of the material. Among them, Example 2, due to its higher content of modified micropowder, fine powder, and binder, and higher firing temperature, exhibits higher bulk density and room temperature compressive strength. Example 3, using a medium proportion scheme, shows better performance in apparent porosity, maximum erosion depth, maximum penetration depth, and post-thermal shock strength retention rate, indicating that a moderate modified micropowder content and firing regime are more conducive to balancing densification, in-situ spinelization, and thermal shock stability. Compared with Example 3, Comparative Example 1 did not add modified activated alumina micro powder, and its performance decreased the most significantly; Comparative Example 2 used ordinary mechanically mixed micro powder, and the distribution of magnesium source and controllability of reaction were insufficient; Comparative Example 3 did not use stepwise wet mixing, and Comparative Example 4 did not use segmented firing, all of which led to a decrease in densification, slag resistance and thermal shock stability.

[0067] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0068] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing a high-density refractory material for a smelting furnace resistant to slag erosion, characterized in that, Includes the following steps: S1. Modified activated alumina micro powder, unmodified activated α-Al2O3 micro powder, white corundum fine powder, binder, dispersant and water are mixed to obtain a reactive matrix slurry. The modified activated alumina micro powder is a citrate-regulated magnesium-aluminum layered precursor modified activated alumina micro powder obtained by in-situ composite of activated α-Al2O3 micro powder, magnesium salt, aluminum salt and sodium citrate in an alkaline aqueous phase. S2. Premix the plate-shaped corundum aggregate and the fused white corundum fine aggregate, then add the reactive matrix slurry in batches and continue wet mixing to obtain a wet mixture; S3. The wet mixture is shaped, cured and dried to obtain a dried green body; S4. The dried blank is sintered in sections to obtain a high-density refractory material for smelting furnaces that is resistant to slag erosion.

2. The preparation method according to claim 1, characterized in that, The modified activated alumina micro powder is prepared by the following steps: A1. Disperse active α-Al2O3 micro powder in water to obtain an active alumina dispersion; A2. Dissolve magnesium salt, aluminum salt and sodium citrate in water to obtain a magnesium-aluminum mixed solution containing citrate ions; A3. The magnesium-aluminum mixed solution containing citrate is added to the active alumina dispersion to adjust the system to alkalinity and then subjected to in-situ composite treatment. After solid-liquid separation, washing, drying and grinding, the modified active alumina micro powder is obtained.

3. The preparation method according to claim 2, characterized in that, The magnesium salt is a water-soluble magnesium salt, selected from at least one of magnesium nitrate hexahydrate and magnesium chloride hexahydrate; the aluminum salt is a water-soluble aluminum salt, selected from at least one of aluminum nitrate nonahydrate and aluminum chloride hexahydrate; the sodium citrate is trisodium citrate dihydrate.

4. The preparation method according to claim 2, characterized in that, In step A1, the mass ratio of active α-Al2O3 micro powder to water is 1:(3-5); in step A2, the molar ratio of Mg2+ in magnesium salt to Al3+ in aluminum salt is (2.0-3.0):1, and the amount of sodium citrate added is 1-5% of the total mass of magnesium salt and aluminum salt; in step A3, the pH of the system is adjusted to 8.5-10.0 using at least one of ammonia water and sodium hydroxide solution, and in-situ composite treatment is carried out at 50-80℃ for 2-6 hours.

5. The preparation method according to claim 1, characterized in that, In step S1, the binder is a low-calcium binder, which is selected from one or more of aluminum sol, aluminum dihydrogen phosphate, and silica-alumina sol; the dispersant is selected from one or more of polycarboxylate dispersant, sodium hexametaphosphate, and sodium tripolyphosphate.

6. The preparation method according to claim 1, characterized in that, In step S4, the segmented firing process includes: heating the dried blank to 300-400°C and holding it at that temperature for 1-2 hours, then heating it to 800-1000°C and holding it at that temperature for 1-2 hours, and then heating it to 1450-1600°C and holding it at that temperature for 2-4 hours.

7. A highly dense refractory material for smelting furnaces resistant to slag erosion, characterized in that, Based on weight, it is prepared from raw materials including the following solid components and active ingredients: 45-60 parts of tabular corundum aggregate, 10-20 parts of fused white corundum fine aggregate, 5-12 parts of white corundum fine powder, 3-10 parts of unmodified active α-Al2O3 micro powder, 6-15 parts of modified active alumina micro powder, 2.5-8 parts of low-calcium binder based on active ingredients, and 0.05-0.3 parts of dispersant; The modified activated alumina micro powder is a citrate-regulated magnesium-aluminum layered precursor modified activated alumina micro powder obtained by in-situ composite of activated α-Al2O3 micro powder, magnesium salt, aluminum salt and sodium citrate in an alkaline aqueous phase; the low-calcium binder is selected from one or more of aluminum sol, aluminum dihydrogen phosphate and silica-alumina sol.

8. The high-density refractory material for smelting furnaces resistant to slag erosion according to claim 7, characterized in that, The mass ratio of the modified activated alumina micro powder to the unmodified activated α-Al2O3 micro powder is (1.0~3.0):

1.

9. The high-density refractory material for smelting furnaces resistant to slag erosion according to claim 7, characterized in that, The tabular corundum aggregate includes coarse tabular corundum aggregate with a particle size of 3-5 mm and medium tabular corundum aggregate with a particle size of 1-3 mm. The fine electrofused white corundum aggregate has a particle size of 0.1-1 mm. The fine white corundum powder has a particle size of no more than 0.074 mm. The D50 of the unmodified active α-Al2O3 micro powder is 0.5-3 μm.

10. The high-density refractory material for smelting furnaces resistant to slag erosion according to claim 7, characterized in that, The low-calcium binder is composed of aluminum sol and aluminum dihydrogen phosphate. By weight, the aluminum sol is 2 to 6 parts as effective solids and the aluminum dihydrogen phosphate is 0.5 to 2 parts as effective components.

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