Iron-aluminate spinel-mullite solid solution raw material and method for preparing the same

Abstract

The application relates to the technical field of refractory materials, and particularly discloses a hercynite-mullite solid solution raw material and a preparation method thereof. The preparation method of the hercynite-mullite solid solution raw material comprises the following steps: after low-grade high-iron bauxite is crushed and homogenized, the low-grade high-iron bauxite is subjected to a flotation desilication treatment; the ore slurry after the flotation is subjected to a magnetic separation and iron removal treatment, so that the content of Fe2O3 in the ore slurry is controlled to be below 9 wt%; a carbon source is introduced into the ore slurry after the magnetic separation and iron removal, the ore slurry is uniformly mixed, and then the ore slurry is subjected to drying, shaping and sintering in a carbon-embedded atmosphere, and the hercynite-mullite solid solution raw material is obtained. The application realizes high-value and high-quality utilization of the low-grade high-iron bauxite. Through the flotation desilication and magnetic separation and iron removal processes, the contents of SiO2 and Fe2O3 in the raw material are effectively controlled, the low-grade ore which is originally difficult to be directly utilized is converted into qualified refractory material raw material, and the resource utilization efficiency and economic value are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of refractory materials technology, specifically to an iron-aluminum spinel-mullite solid solution raw material and its preparation method. Background Technology

[0002] Ferroaluminum spinel (FeAl2O4) is a refractory material component with excellent properties and a high theoretical density (4.39 g / cm³). -3 It has a high Mohs hardness (7.5), a high refractive index (1.83), a relatively high melting point (1780°C), and a low coefficient of thermal expansion (25~900°C, 8.2~9.0×10⁻⁶). -6 K -1 These characteristics make it an ideal choice for refractory materials in the firing zone of rotary kilns, exhibiting excellent kiln lining properties, resistance to cement clinker erosion, thermal shock resistance, and good sintering-promoting properties.

[0003] However, natural deposits of iron-aluminum spinel are scarce, making its industrial applications primarily reliant on artificial synthesis. Currently, the main methods for synthesizing iron-aluminum spinel include electrofusion, reaction sintering, and molten salt synthesis. Electrofusion typically uses alumina and iron scale (or iron oxide red) as raw materials, synthesized at high temperatures in an electric arc furnace with graphite electrodes. The challenge lies in ensuring the stable presence of FeO and its reaction with Al₂O₃ to form a solid solution. Sintering uses iron-containing materials and alumina as raw materials, involving batching, mixing, molding, and high-temperature sintering. This also requires strict control over the stable presence of FeO during sintering. Molten salt synthesis uses alumina and Fe₂O₃ as raw materials, with carbonaceous materials as reducing agents, reacting in a molten salt medium. These traditional synthesis methods still have limitations in terms of raw material costs, process complexity, and the precision of atmosphere control.

[0004] On the other hand, with industrial development, a large amount of low-grade mineral resources need to be utilized efficiently. The main components of some low-grade bauxite are Al2O3, SiO2, and Fe2O3. The low aluminum content (e.g., Al2O3 50-70 wt%) makes it unsuitable as a high-quality raw material for preparing industrial alumina, while the high Fe2O3 content (e.g., ≥10 wt%) limits its direct application in high-performance refractory materials. Furthermore, excessively high SiO2 content easily forms low-melting-point compounds or glassy phases, further reducing the high-temperature performance of the material. Therefore, how to effectively utilize this type of low-grade high-iron bauxite and transform it into high-value, high-quality high-performance materials is a pressing technical problem that needs to be solved. Based on the above, this invention proposes an iron-aluminum spinel-mullite solid solution raw material and its preparation method. Summary of the Invention

[0005] To address the technical problems in existing technologies, such as low utilization rate of low-grade high-iron bauxite, high silicon and high iron impurity content hindering its use as a raw material for high-performance refractory materials, difficulty in controlling the synthesis atmosphere of iron-aluminum spinel, and unstable solid solution formation, this invention proposes an iron-aluminum spinel-mullite solid solution raw material and its preparation method. This invention pre-treats low-grade high-iron bauxite (flotation desilication, magnetic separation to remove iron) to control its composition, introduces a carbon source into the slurry, and employs a carbon-buried atmosphere for sintering to achieve precise control of the sintering atmosphere, thereby preparing a high-performance iron-aluminum spinel-mullite solid solution raw material.

[0006] In a first aspect, the present invention provides a method for preparing an iron-aluminum spinel-mullite solid solution raw material, employing the following technical solution: A method for preparing an iron-aluminum spinel-mullite solid solution raw material includes the following steps: S1. After crushing and homogenizing the low-grade high-iron bauxite, flotation desilication treatment is carried out to obtain the flotation pulp. S2. The flotation pulp is subjected to magnetic separation to remove iron, so that the Fe2O3 content in the pulp is controlled below 9wt%, and the pulp after magnetic separation and iron removal is obtained. S3. Introduce a carbon source into the slurry after magnetic separation to remove iron, and mix evenly to form a carbon-containing slurry. S4. After drying and molding the carbon-containing slurry, it is fired at 1350-1500℃ in a carbon-buried atmosphere for 0.5-3 hours to obtain iron-aluminum spinel-mullite solid solution raw material.

[0007] Preferably, the low-grade high-iron bauxite in S1 contains 50-70wt% Al2O3, 20-35wt% SiO2, and ≥10wt% Fe2O3.

[0008] Preferably, the low-grade high-iron bauxite in S1 contains 55-65 wt% Al2O3, 22-32 wt% SiO2, and 10-15 wt% Fe2O3.

[0009] Preferably, the flotation process in S1 adopts a separation process of one roughing, one scavenging, and one cleaning. After the concentrate and tailings slurry are dewatered and settled in a thickener, they are transported to the filter press workshop for secondary dewatering by a slurry pump. The secondary dewatering adopts a high-efficiency and energy-saving diaphragm filter press.

[0010] Preferably, after the flotation desilication treatment in S1, the SiO2 content in the slurry is reduced to below 12 wt%.

[0011] Preferably, the magnetic separation in S2 is performed using a high-gradient magnetic separator with a magnetic field strength of 0.3-1 Tesla.

[0012] Preferably, after the magnetic separation and iron removal process in S2, the Fe2O3 content in the slurry is 6-9 wt%.

[0013] Preferably, after the magnetic separation iron removal process in S2, the Fe2O3 content in the slurry is 7-8 wt%.

[0014] Preferably, the carbon source in S3 is selected from one or more of graphite and carbon black.

[0015] Preferably, the amount of carbon source added in S3 accounts for 5-10% of the total mass of the slurry after magnetic separation to remove iron.

[0016] Preferably, the amount of carbon source added in S3 accounts for 6-8% of the total mass of the slurry after magnetic separation to remove iron.

[0017] Preferably, the drying temperature in step S4 is 180-250℃, and the drying time is 35-50h.

[0018] Preferably, the forming method in S4 is extrusion molding.

[0019] Preferably, the firing temperature in S4 is 1400-1480℃ and the firing time is 1-2.5h.

[0020] Secondly, the present invention provides an iron-aluminum spinel-mullite solid solution raw material, which adopts the following technical solution: A kind of iron-aluminum spinel-mullite solid solution raw material is prepared by the above-mentioned preparation method of iron-aluminum spinel-mullite solid solution raw material.

[0021] In summary, the present invention has the following beneficial effects: This invention achieves high-value and high-quality utilization of low-grade high-iron bauxite. By introducing flotation desilication and magnetic separation for iron removal, the SiO2 and Fe2O3 content in the raw materials is effectively controlled, transforming low-grade ore that was originally difficult to use directly into qualified refractory material raw materials, greatly improving resource utilization efficiency and economic value. Experimental results show that the content of harmful impurities in the pretreated raw materials is significantly reduced, creating favorable conditions for the subsequent formation of iron-aluminum spinel-mullite solid solutions.

[0022] This invention effectively solves the challenge of atmosphere control in the synthesis of iron-aluminum spinel. By uniformly introducing a carbon source (such as graphite or carbon black) during the slurry stage and employing a carbon-embedded atmosphere during firing, carbon elements are uniformly dispersed within the bulk material. A reducing atmosphere is controllably generated during high-temperature sintering, promoting the stable existence of FeO and its reaction with Al2O3, thus facilitating the solid solution formation of iron-aluminum spinel and mullite. This precise control of the internal reducing atmosphere avoids the complex external atmosphere control devices required in traditional methods, simplifying the process and resulting in more stable product quality. Experimental data demonstrates that introducing a carbon source and employing a carbon-embedded atmosphere significantly improves the yield and solid solution uniformity of iron-aluminum spinel.

[0023] The iron-aluminum spinel-mullite solid solution raw material prepared by this invention combines the excellent refractory properties of iron-aluminum spinel with the good high-temperature structural stability of mullite, forming a uniform solid solution structure. This results in higher erosion resistance, thermal shock resistance, and better sintering performance, making it a novel raw material for high-performance refractory materials and expanding its application range. Compared with existing technologies, the product of this invention exhibits significant performance advantages in apparent porosity, bulk density, room temperature compressive strength, load softening temperature, and thermal shock resistance, especially demonstrating excellent structural stability and mechanical properties at high temperatures. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the embodiments.

[0025] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0026] Examples 1-3 provide an iron-aluminum spinel-mullite solid solution raw material.

[0027] Example 1 A spinel-mullite solid solution raw material made of iron and aluminum is prepared by the following method: (1) Raw material preparation: Weigh 200 kg of low-grade high-iron bauxite, the composition of which is: Al2O3 58wt%, SiO2 28wt%, Fe2O3 12wt%; (2) Crushing and homogenization: The low-grade high-iron bauxite is coarsely crushed by a jaw crusher, then medium and finely crushed by a cone crusher, and then classified to qualified particle size (passing through a 200-mesh sieve) by a vibrating screen, and then homogenized. (3) Flotation desilication: The homogenized ore is fed into a ball mill for wet grinding to form a slurry (solid content 40%). The slurry is subjected to flotation desilication treatment with one roughing, one scavenging and one cleaning process (the flotation agent is sodium oleate 0.5 kg / ton of ore, the collector is sodium dodecyl sulfate 0.2 kg / ton of ore, the frother is pine oil 0.1 kg / ton of ore, and the pH value is adjusted to 9). After the flotation slurry is dewatered by a thickener, its dry composition is determined to be: Al2O3 61 wt%, SiO2 11 wt%, Fe2O3 12 wt%. (4) Magnetic separation for iron removal: The flotation slurry is fed into a high-gradient magnetic separator with a magnetic field strength of 0.3 Tesla for magnetic separation to remove iron (slurry flow rate 5 m³ / s). 3 / h); after treatment, the slurry was dewatered by pressure filtration, and the Fe2O3 content after drying was determined to be 9wt%; (5) Introducing a carbon source: Mix 100 kg of the dried mud after magnetic separation and iron removal with 6 kg of graphite powder (accounting for 6% of the mud mass) to obtain a carbon-containing slurry. (6) Drying and molding: The carbon-containing slurry is made into a cylinder with a diameter of 20 mm and a height of 20 mm by extrusion molding equipment, and then dried at 180℃ for 50 h; (7) Firing: The dried and shaped cylinder is placed in a high-temperature furnace and fired in a carbon-buried atmosphere (the cylinder is buried in coke particles with a particle size of 3 mm for firing, and the volume ratio of coke to cylinder is 5:1). The cylinder is kept at 1350℃ for 3 hours to obtain iron-aluminum spinel-mullite solid solution raw material.

[0028] Example 2 A spinel-mullite solid solution raw material made of iron and aluminum is prepared by the following method: (1) Raw material preparation: Weigh 200 kg of low-grade high-iron bauxite, the composition of which is: Al2O3 58wt%, SiO2 28wt%, Fe2O3 12wt%; (2) Crushing and homogenization: The low-grade high-iron bauxite is coarsely crushed by a jaw crusher, then medium and finely crushed by a cone crusher, and then classified to qualified particle size (passing through a 200-mesh sieve) by a vibrating screen, and then homogenized. (3) Flotation desilication: The homogenized ore is fed into a ball mill for wet grinding to form a slurry (solid content 40%). The slurry is subjected to flotation desilication treatment with one roughing, one scavenging and one cleaning process (the flotation agent is sodium oleate 0.5 kg / ton of ore, the collector is sodium dodecyl sulfate 0.2 kg / ton of ore, the frother is pine oil 0.1 kg / ton of ore, and the pH value is adjusted to 9.5). After the flotation slurry is dewatered by a thickener, its dry composition is determined to be: Al2O3 61 wt%, SiO2 11 wt%, Fe2O3 12 wt%. (4) Magnetic separation for iron removal: The flotation slurry is fed into a high-gradient magnetic separator with a magnetic field strength of 0.5 Tesla for magnetic separation to remove iron (slurry flow rate 5 m³ / s). 3 / h); after treatment, the slurry was dewatered by pressure filtration, and the Fe2O3 content after drying was determined to be 8wt%; (5) Introducing a carbon source: Mix 100 kg of the dried mud after magnetic separation and iron removal with 8 kg of graphite powder (accounting for 8% of the mud mass) to obtain a carbon-containing slurry. (6) Drying and molding: The carbon-containing slurry is made into a cylinder with a diameter of 20 mm and a height of 20 mm by extrusion molding equipment, and then dried at 200℃ for 40 h; (7) Firing: The dried and shaped cylinder is placed in a high-temperature furnace and fired in a carbon-buried atmosphere (the cylinder is buried in coke particles with a particle size of 4 mm for firing, and the volume ratio of coke to cylinder is 5:1). The cylinder is kept at 1450℃ for 2 hours to obtain iron-aluminum spinel-mullite solid solution raw material.

[0029] Example 3 A spinel-mullite solid solution raw material made of iron and aluminum is prepared by the following method: (1) Raw material preparation: Weigh 200 kg of low-grade high-iron bauxite, the composition of which is: Al2O3 58wt%, SiO2 28wt%, Fe2O3 12wt%; (2) Crushing and homogenization: The low-grade high-iron bauxite is coarsely crushed by a jaw crusher, then medium and finely crushed by a cone crusher, and then classified to qualified particle size (passing through a 200-mesh sieve) by a vibrating screen, and then homogenized. (3) Flotation desilication: The homogenized ore is fed into a ball mill for wet grinding to form a slurry (solid content 40%). The slurry is subjected to flotation desilication treatment by one roughing, one scavenging and one cleaning process (the flotation agent is sodium oleate 0.5 kg / ton of ore, the collector is sodium dodecyl sulfate 0.2 kg / ton of ore, the frother is pine oil 0.1 kg / ton of ore, and the pH value is adjusted to 10). After the flotation slurry is dewatered by a thickener, its dry composition is determined to be: Al2O3 61 wt%, SiO2 11 wt%, Fe2O3 12 wt%. (4) Magnetic separation for iron removal: The flotation slurry is fed into a high-gradient magnetic separator with a magnetic field strength of 1 Tesla for magnetic separation to remove iron (slurry flow rate 5 m³ / s). 3 / h); after treatment, the slurry was dewatered by pressure filtration, and the Fe2O3 content after drying was determined to be 6wt%; (5) Introducing a carbon source: Mix 100 kg of the dried mud after magnetic separation and iron removal with 10 kg of graphite powder (accounting for 10% of the mud mass) to obtain a carbon-containing slurry. (6) Drying and molding: The carbon-containing slurry is made into a cylinder with a diameter of 20 mm and a height of 20 mm by extrusion molding equipment, and then dried at 250℃ for 35 h; (7) Firing: The dried and shaped cylinder is placed in a high-temperature furnace and fired in a carbon-buried atmosphere (the cylinder is buried in coke particles with a particle size of 5 mm for firing, and the volume ratio of coke to cylinder is 5:1). The cylinder is kept at 1500℃ for 0.5h to obtain iron-aluminum spinel-mullite solid solution raw material.

[0030] To verify the comprehensive performance of the iron-aluminum spinel-mullite solid solution raw materials obtained in Examples 1-3 of this invention, Comparative Examples 1-5 were set up, wherein: Comparative Example 1 Comparative Example 1 is the same as Example 1, except that it did not undergo flotation desilication treatment. Details are as follows: A spinel-mullite solid solution raw material made of iron and aluminum is prepared by the following method: (1) Raw material preparation: Weigh 200 kg of low-grade high-iron bauxite, the composition of which is: Al2O3 58wt%, SiO2 28wt%, Fe2O3 12wt%; (2) Crushing and homogenization: The low-grade high-iron bauxite is coarsely crushed by a jaw crusher, then medium and finely crushed by a cone crusher, and then classified to qualified particle size (passing through a 200-mesh sieve) by a vibrating screen, and then homogenized. (3) Magnetic separation for iron removal: The homogenized ore is fed into a ball mill for wet grinding to form a slurry; the slurry is then fed into a high-gradient magnetic separator with a magnetic field strength of 0.3 Tesla for magnetic separation to remove iron (slurry flow rate 5 m³ / s). 3 / h); After treatment, the slurry was dewatered by pressure filtration, and its dried Fe2O3 content was determined to be 9wt% and SiO2 content to be 25wt%; (4) Introducing a carbon source: Mix 100 kg of the dried mud after magnetic separation and iron removal with 6 kg of graphite powder (accounting for 6% of the mud mass) to obtain a carbon-containing slurry. (5) Drying and molding: The carbon-containing slurry is made into a cylinder with a diameter of 20 mm and a height of 20 mm by extrusion molding equipment, and then dried at 180℃ for 50 h; (6) Firing: The dried and shaped cylinder is placed in a high-temperature furnace and fired in a carbon-buried atmosphere (the cylinder is buried in coke particles with a particle size of 3 mm for firing, and the volume ratio of coke to cylinder is 5:1). The cylinder is kept at 1350℃ for 3 hours to obtain iron-aluminum spinel-mullite solid solution raw material.

[0031] Comparative Example 2 Comparative Example 2 is the same as Example 1, except that magnetic separation for iron removal was not performed. Details are as follows: A spinel-mullite solid solution raw material made of iron and aluminum is prepared by the following method: (1) Raw material preparation: Weigh 200 kg of low-grade high-iron bauxite, the composition of which is: Al2O3 58wt%, SiO2 28wt%, Fe2O3 12wt%; (2) Crushing and homogenization: The low-grade high-iron bauxite is coarsely crushed by a jaw crusher, then medium and finely crushed by a cone crusher, and then classified to qualified particle size (passing through a 200-mesh sieve) by a vibrating screen, and then homogenized. (3) Flotation desilication: The homogenized ore is fed into a ball mill for wet grinding to form a slurry (solid content 40%). The slurry is subjected to flotation desilication treatment with one roughing, one scavenging and one cleaning process (the flotation agent is sodium oleate 0.5 kg / ton of ore, the collector is sodium dodecyl sulfate 0.2 kg / ton of ore, the frother is pine oil 0.1 kg / ton of ore, and the pH value is adjusted to 9). After the flotation slurry is dewatered by a thickener, its dry composition is determined to be: Al2O3 61 wt%, SiO2 11 wt%, Fe2O3 12 wt%. (4) Introducing a carbon source: Mix 100 kg of flotation slurry with 6 kg of graphite powder (accounting for 6% of the slurry mass) to obtain a carbon-containing slurry; (5) Drying and molding: The carbon-containing slurry is made into a cylinder with a diameter of 20 mm and a height of 20 mm by extrusion molding equipment, and then dried at 180℃ for 50 h; (6) Firing: The dried and shaped cylinder is placed in a high-temperature furnace and fired in a carbon-buried atmosphere (the cylinder is buried in coke particles with a particle size of 3 mm for firing, and the volume ratio of coke to cylinder is 5:1). The cylinder is kept at 1350℃ for 3 hours to obtain iron-aluminum spinel-mullite solid solution raw material.

[0032] Comparative Example 3 Comparative Example 3 is the same as Example 1, except that no carbon source was introduced. Details are as follows: A spinel-mullite solid solution raw material made of iron and aluminum is prepared by the following method: (1) Raw material preparation: Weigh 200 kg of low-grade high-iron bauxite, the composition of which is: Al2O3 58wt%, SiO2 28wt%, Fe2O3 12wt%; (2) Crushing and homogenization: The low-grade high-iron bauxite is coarsely crushed by a jaw crusher, then medium and finely crushed by a cone crusher, and then classified to qualified particle size (passing through a 200-mesh sieve) by a vibrating screen, and then homogenized. (3) Flotation desilication: The homogenized ore is fed into a ball mill for wet grinding to form a slurry (solid content 40%). The slurry is subjected to flotation desilication treatment with one roughing, one scavenging and one cleaning process (the flotation agent is sodium oleate 0.5 kg / ton of ore, the collector is sodium dodecyl sulfate 0.2 kg / ton of ore, the frother is pine oil 0.1 kg / ton of ore, and the pH value is adjusted to 9). After the flotation slurry is dewatered by a thickener, its dry composition is determined to be: Al2O3 61 wt%, SiO2 11 wt%, Fe2O3 12 wt%. (4) Magnetic separation for iron removal: The flotation slurry is fed into a high-gradient magnetic separator with a magnetic field strength of 0.3 Tesla for magnetic separation to remove iron (slurry flow rate 5 m³ / s). 3 / h); after treatment, the slurry was dewatered by pressure filtration, and the Fe2O3 content after drying was determined to be 9wt%; (5) Drying and molding: The dried slurry material after magnetic separation to remove iron is made into a cylinder with a diameter of 20 mm and a height of 20 mm by extrusion molding equipment, and then dried at 180℃ for 50 h; (6) Firing: The dried and shaped cylinder is placed in a high-temperature furnace and fired in a carbon-buried atmosphere (the cylinder is buried in coke particles with a particle size of 3 mm for firing, and the volume ratio of coke to cylinder is 5:1). The cylinder is kept at 1350℃ for 3 hours to obtain iron-aluminum spinel-mullite solid solution raw material.

[0033] Comparative Example 4 Comparative Example 4 is the same as Example 1, except that no carbon source was introduced and no buried carbon atmosphere was used for firing. Details are as follows: A spinel-mullite solid solution raw material made of iron and aluminum is prepared by the following method: (1) Raw material preparation: Weigh 200 kg of low-grade high-iron bauxite, the composition of which is: Al2O3 58wt%, SiO2 28wt%, Fe2O3 12wt%; (2) Crushing and homogenization: The low-grade high-iron bauxite is coarsely crushed by a jaw crusher, then medium and finely crushed by a cone crusher, and then classified to qualified particle size (passing through a 200-mesh sieve) by a vibrating screen, and then homogenized. (3) Flotation desilication: The homogenized ore is fed into a ball mill for wet grinding to form a slurry (solid content 40%). The slurry is subjected to flotation desilication treatment with one roughing, one scavenging and one cleaning process (the flotation agent is sodium oleate 0.5 kg / ton of ore, the collector is sodium dodecyl sulfate 0.2 kg / ton of ore, the frother is pine oil 0.1 kg / ton of ore, and the pH value is adjusted to 9). After the flotation slurry is dewatered by a thickener, its dry composition is determined to be: Al2O3 61 wt%, SiO2 11 wt%, Fe2O3 12 wt%. (4) Magnetic separation for iron removal: The flotation slurry is fed into a high-gradient magnetic separator with a magnetic field strength of 0.3 Tesla for magnetic separation to remove iron (slurry flow rate 5 m³ / s). 3 / h); after treatment, the slurry was dewatered by pressure filtration, and the Fe2O3 content after drying was determined to be 9wt%; (5) Drying and molding: The dried slurry material after magnetic separation to remove iron is made into a cylinder with a diameter of 20 mm and a height of 20 mm by extrusion molding equipment, and then dried at 180℃ for 50 h; (6) Firing: The dried and shaped cylinder is placed in a high-temperature furnace and fired at 1350°C for 3 hours in an air atmosphere to obtain iron-aluminum spinel-mullite solid solution raw material.

[0034] Comparative Example 5 Comparative Example 5 is the same as Example 1, except that high-grade bauxite is used as the raw material and no carbon source is introduced. Details are as follows: A spinel-mullite solid solution raw material made of iron and aluminum is prepared by the following method: (1) Raw material preparation: Weigh 200 kg of high-grade bauxite, the composition of which is: Al2O3 85wt%, SiO2 5wt%, Fe2O3 1wt%; (2) Crushing and homogenization: High-grade bauxite is coarsely crushed by a jaw crusher, then medium and finely crushed by a cone crusher, and then classified to qualified particle size (passing through a 200-mesh sieve) by a vibrating screen, and then homogenized. (3) Drying and molding: After grinding the high-grade bauxite, it is made into a cylinder with a diameter of 20 mm and a height of 20 mm by extrusion molding equipment, and then dried at 180℃ for 50 h; (4) Firing: The dried and shaped cylinder is placed in a high-temperature furnace and fired at 1350°C for 3 hours in an air atmosphere to obtain iron-aluminum spinel-mullite solid solution raw material.

[0035] The comprehensive properties of the iron-aluminum spinel-mullite solid solution raw materials in Examples 1-3 and Comparative Examples 1-5 of this invention were tested respectively.

[0036] 1. Phase composition (content wt%): Phase analysis was performed using X-ray diffraction, and the relative contents of each phase (FeAl2O4, mullite (3Al2O3·2SiO2), residual Al2O3, residual SiO2, FeO, and Fe3O4) were calculated using the Rietveld refinement method.

[0037] 2. Physical properties: Apparent porosity (%) and bulk density (g / cm³): Tested according to GB / T 2997-2015 "Test methods for bulk density, apparent porosity and true porosity of dense shaped refractory products".

[0038] Room temperature compressive strength (MPa): Tested according to GB / T 5072-2008 "Test method for room temperature compressive strength of refractory materials".

[0039] 3. High-temperature performance: Softening temperature under load (°C, 0.2MPa): Tested according to GB / T 5988-2022 "Test method for permanent linear change of refractory materials under heating", with a pressure of 0.2MPa.

[0040] Flexural strength at 1400℃ (MPa): Tested according to GB / T 3002-2017 "Test Method for High Temperature Flexural Strength of Refractory Materials", with a test temperature of 1400℃.

[0041] Thermal shock resistance (single, water cooling method): The test was conducted according to YB / T 376.3-2004 "Test method for thermal shock resistance of refractory products Part 3: Water quenching crack judgment method". The sample was heated at 1100℃ for 10 minutes and then quickly removed and placed in cold water at 20℃ for 3 minutes. This was repeated until the sample cracked or broke.

[0042] The test results are shown in Table 1: Table 1: Comprehensive performance test data of iron-aluminum spinel-mullite solid solution raw materials in Examples 1-3 and Comparative Examples 1-5 As shown in Table 1, the comprehensive performance of the iron-aluminum spinel-mullite solid solution raw materials prepared in Examples 1-3 of this invention is significantly better than that of Comparative Examples 1-5.

[0043] As shown in Example 1 and Comparative Example 1, the SiO2 content in the raw material of Comparative Example 1 before firing was much higher than that of Example 1 because no flotation desilication treatment was performed. This resulted in a significant reduction in the formation of mullite and iron-aluminum spinel in the product of Comparative Example 1, while the residual SiO2 content was high, and more low-melting-point glass phases were formed. Consequently, the apparent porosity of Comparative Example 1 increased significantly, the bulk density decreased, and the room temperature compressive strength decreased significantly. More importantly, its load softening temperature and 1400℃ hot flexural strength decreased significantly, and its thermal shock resistance also deteriorated. In summary, this demonstrates that flotation desilication treatment plays a crucial role in reducing the SiO2 content in the raw material, promoting the formation of iron-aluminum spinel and mullite, and improving the high-temperature performance and structural stability of the product.

[0044] As shown in Example 1 and Comparative Example 2, the Fe2O3 content in the raw material of Comparative Example 2 was higher than that of Example 1 before firing because no magnetic separation iron removal treatment was performed. Despite the presence of a carbon-buried atmosphere, the excessively high Fe2O3 content resulted in a lower formation of iron-aluminum spinel compared to Example 1, and the residual Al2O3 and Fe3O4 contents were also higher. Excessive iron components easily form low-melting-point compounds or undesirable secondary phases, which act as fluxes to accelerate sintering, but also significantly reduce the load softening temperature and hot flexural strength of the refractory material. The apparent porosity and room-temperature compressive strength of Comparative Example 2 also showed a decline in performance. In summary, magnetic separation iron removal treatment is essential for accurately controlling the Fe2O3 content in the raw material, avoiding the negative impact of excessive iron components on the high-temperature performance of the material, and ensuring the formation of the target iron-aluminum spinel-mullite solid solution structure.

[0045] As shown in Example 1 and Comparative Example 3, Comparative Example 3 was fired in a carbon-buried atmosphere, but no carbon source was introduced into the slurry. Although the external carbon-buried atmosphere could provide a certain reducing environment, the efficiency and uniformity of Fe2O3 reduction to FeO were significantly reduced due to the lack of a uniformly dispersed carbon source inside the block. This resulted in the amount of iron-aluminum spinel and the FeO content in Comparative Example 3 being lower than in Example 1, and more Fe3O4 was formed, indicating insufficient reduction. Its apparent porosity was higher, its bulk density was lower, and its room temperature compressive strength and high temperature performance were significantly lower than those of Example 1. In summary, the uniform introduction of a carbon source into the slurry is crucial for forming an efficient and uniform reducing atmosphere inside the block, thereby fully promoting the formation of FeAl2O4 and improving product performance.

[0046] As shown in Example 1 and Comparative Example 4, Comparative Example 4 did not introduce a carbon source and was calcined in an air atmosphere. Under an oxidizing atmosphere, Fe2O3 in the raw material is difficult to reduce to FeO. Therefore, the product of Comparative Example 4 hardly formed iron-aluminum spinel, but was mainly composed of residual Al2O3, mullite, and Fe2O3. Due to the failure of the key iron-aluminum spinel phase to form effectively, it had the highest apparent porosity, the lowest bulk density, and its room temperature compressive strength and high temperature performance were also much lower than other samples. In summary, this demonstrates that introducing a carbon source and using a carbon-buried atmosphere can significantly improve the overall performance of the prepared iron-aluminum spinel-mullite solid solution raw material.

[0047] As shown in Example 1 and Comparative Example 5, Comparative Example 5 used high-grade bauxite as raw material and was fired in an air atmosphere without introducing a carbon source. Although high-grade bauxite itself has low impurity content and good refractory properties, due to its extremely low Fe2O3 content and firing in an oxidizing atmosphere, almost no iron-aluminum spinel was formed in the product; the main phases were mullite and residual Al2O3. Although it exhibited excellent physical and high-temperature properties in terms of apparent porosity, bulk density, room temperature compressive strength, and load softening temperature, this was mainly due to the inherent advantages of its high-purity raw materials and the formation of a dense mullite-corundum structure. This invention can successfully prepare high-performance refractory materials by utilizing high-iron low-grade bauxite resources that are originally difficult to use directly, through unique pretreatment and atmosphere control methods, achieving high-value and high-quality transformation of low-grade resources, rather than simply preparing general-purpose mullite or corundum products.

[0048] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for preparing an iron-aluminum spinel-mullite solid solution raw material, characterized in that, Includes the following steps: S1. After crushing and homogenizing the low-grade high-iron bauxite, flotation desilication treatment is carried out to obtain the flotation pulp. S2. The flotation pulp is subjected to magnetic separation to remove iron, so that the Fe2O3 content in the pulp is controlled below 9wt%, and the pulp after magnetic separation and iron removal is obtained. S3. Introduce a carbon source into the slurry after magnetic separation to remove iron, and mix evenly to form a carbon-containing slurry. S4. After drying and molding the carbon-containing slurry, it is kept at 1350-1500℃ in a carbon atmosphere for 0.5-3 hours and then fired to obtain iron-aluminum spinel-mullite solid solution raw material.

2. The method for preparing the iron-aluminum spinel-mullite solid solution raw material according to claim 1, characterized in that, The S1 low-grade high-iron bauxite contains 50-70wt% Al2O3, 20-35wt% SiO2, and ≥10wt% Fe2O3.

3. The method for preparing the iron-aluminum spinel-mullite solid solution raw material according to claim 1, characterized in that, The flotation process in S1 adopts a separation process of one roughing, one scavenging, and one cleaning. After the concentrate and tailings slurry are dewatered and settled in a thickener, they are transported to the filter press workshop for secondary dewatering by a slurry pump. The secondary dewatering adopts a high-efficiency and energy-saving diaphragm filter press.

4. The method for preparing the iron-aluminum spinel-mullite solid solution raw material according to claim 1, characterized in that, After the flotation desilication treatment in S1, the SiO2 content in the slurry is reduced to below 12wt%.

5. The method for preparing the iron-aluminum spinel-mullite solid solution raw material according to claim 1, characterized in that, The magnetic separation in S2 is carried out using a high-gradient magnetic separator with a magnetic field strength of 0.3-1 Tesla.

6. The method for preparing the iron-aluminum spinel-mullite solid solution raw material according to claim 1, characterized in that, After the magnetic separation process in S2, the Fe2O3 content in the slurry is 6-9 wt%.

7. The method for preparing the iron-aluminum spinel-mullite solid solution raw material according to claim 1, characterized in that, The carbon source in S3 is selected from one or more of graphite and carbon black.

8. The method for preparing the iron-aluminum spinel-mullite solid solution raw material according to claim 1, characterized in that, The amount of carbon source added in S3 accounts for 5-10% of the total mass of the slurry after magnetic separation to remove iron.

9. The method for preparing the iron-aluminum spinel-mullite solid solution raw material according to claim 1, characterized in that, The drying temperature in S4 is 180-250℃, and the drying time is 35-50h.

10. A kind of iron-aluminum spinel-mullite solid solution raw material, characterized in that, It is prepared by the method of any one of claims 1-9 for the preparation of iron-aluminum spinel-mullite solid solution raw material.

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