Application of a perovskite-spinel mixed concentrate in the preparation of refractory materials

Abstract

The present invention belongs to the field of refractory materials and discloses the use of a perovskite-spinel mixed concentrate in the preparation of refractory materials. The refractory material has perovskite as the main crystal phase and spinel as the secondary crystal phase. The mass fraction of each component of the raw materials is 60-90% perovskite powder, 10-40% spinel powder, and 1-3% of the total mass of the raw materials as a binder. The refractory material has the characteristics of high melting point, low thermal conductivity, and strong corrosion resistance. It has a high refractory temperature and excellent thermal shock stability, and has good corrosion resistance. It can be used as a special refractory material on a large scale. Especially when used in a reducing atmosphere, a low-valent titanium oxide protective layer is formed on the surface of the refractory material, which prevents the high-temperature slag from further corroding the refractory material. Under the synergistic effect of the protective layer and the excellent chemical stability of the spinel phase, the corrosion resistance of the perovskite-spinel composite refractory material is significantly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of refractory materials, and in particular to the application of a perovskite-spinel mixed concentrate in the preparation of refractory materials. Background Art

[0002] After smelting vanadium-titanium magnetite in a blast furnace, a large amount of titanium-containing blast furnace slag is produced. This substance is a typical industrial solid waste, but it also contains valuable valuable metal resources. However, most of the titanium-containing blast furnace slag can only be piled up as waste, occupying a large amount of land while causing environmental pollution and wasting resources. How to treat it in a green and efficient way is an urgent problem. The chemical composition of titanium-containing blast furnace slag mainly includes TiO2, CaO, SiO2, Al2O3, MgO, etc. Many scholars have carried out relevant research on its utilization from the two perspectives of extracting valuable metals and preparing materials, and have achieved certain results. However, the treatment process has never been able to be promoted industrially. Therefore, the application of titanium-containing blast furnace slag faces even more severe challenges.

[0003] Patent CN103343174A discloses a method for utilizing titanium-containing blast furnace slag. The method involves mixing high-temperature titanium-containing blast furnace slag with vanadium-containing steel slag, then injecting an oxidizing gas into the mixed slag for modification. After cooling, the slag undergoes magnetic separation and gravity separation to yield a titanium concentrate primarily composed of perovskite. This method enriches the titanium in the titanium-containing blast furnace slag into perovskite, but the subsequent utilization of the perovskite presents a new challenge. Currently, the application of perovskite is limited to the production of sulfuric acid-process titanium dioxide, and further research is needed to determine its efficient utilization.

[0004] Refractory materials are widely used in various fields of human society, such as steel, glass, petrochemicals, machinery, electricity, and military industry. They are indispensable basic materials to ensure the production operation and technological development of the above industries, and play an irreplaceable and important role in the development of high-temperature industrial production.

[0005] Refractories are classified into basic, acidic, and neutral types. Their raw materials are primarily natural high-melting-point oxides, and their application environments are oxidizing, neutral, or reducing atmospheres. Refractory applications require simultaneous performance requirements, including refractoriness, refractoriness under load, thermal shock resistance, volume stability, slag erosion resistance, and atmospheric resistance. Since most refractories are made from natural raw materials, they cannot meet these requirements, necessitating the use of composite refractories.

[0006] During the steelmaking process (oxidizing atmosphere), in order to improve the thermal shock resistance, volume stability and slag corrosion resistance of refractory materials, CaO-C composite refractory materials are used instead of single CaO, Al2O3-C instead of single Al2O3, and MgO-C instead of MgO.

[0007] Most refractories can meet the requirements of oxidizing or neutral atmospheres, but not those of reducing atmospheres. Blast furnace production operates in a strongly reducing atmosphere, requiring only carbonaceous refractory materials for the lower hearth. Furthermore, to protect other parts of the blast furnace from slag corrosion, titanium-containing materials are added to the charge, generating high-melting-point minerals like TiC. This demonstrates the high demands placed on refractories in reducing atmospheres, limiting the availability of refractory options, and necessitating the urgent need to develop refractory materials suitable for use in reducing atmospheres.

[0008] Perovskite itself has a high melting point (1980°C) and good thermal shock resistance. It can be used in acidic slag systems, alkaline slag systems, or neutral systems. It can be used not only in oxidizing or neutral atmospheres, but also in reducing atmospheres, making it an excellent refractory material. The reason is that in a reducing atmosphere, high-melting-point substances such as TiC are generated, covering the surface of the refractory and protecting it. Perovskite is a neutral refractory material that can be used in both acidic and alkaline slag systems, continuous production, and intermittent production processes. Its performance is far superior to the neutral refractory - corundum (Al2O3). Corundum refractory materials have poor thermal shock resistance and can only be used in blast furnaces (continuous production) and cannot be used in converter processes (intermittent production processes).

[0009] Spinel minerals have the advantages of high melting point, low thermal expansion coefficient, and good high-temperature stability. The melting points of magnesia-alumina spinel and magnesia-chrome spinel are 2135°C and 2350°C, respectively. They are also highly resistant to the corrosive effects of various melts at high temperatures and are only suitable for use in oxidizing or neutral atmospheres. Therefore, introducing spinel as a reinforcing phase into perovskite refractories can significantly enhance thermal shock resistance, volume stability, and corrosion resistance.

[0010] However, spinel-type refractory materials rely on artificial preparation, which is costly and technically difficult, and can only be used in oxidizing or neutral atmospheres. The method for utilizing titanium-containing blast furnace slag disclosed in patent CN103343174A can obtain a mixed concentrate of perovskite and spinel, which provides high-quality raw materials for the preparation of refractory materials and can effectively solve the problem of slag recycling and reuse. Patent CN107324838A provides a high-temperature refractory material and a preparation method thereof, which adds a small amount of perovskite as a mineralizer to promote sintering. Therefore, there is currently no relevant patent for preparing complex phase refractory materials using perovskite as the main component (main crystalline phase). The present invention will directly use the mixed concentrate of perovskite and spinel as raw materials, which can achieve low-cost, short-process production of high-quality perovskite-spinel composite refractory materials that can be used on a large scale. Summary of the Invention

[0011] In view of the problems existing in the prior art, the present invention provides an application of a perovskite-spinel mixed concentrate in the preparation of refractory materials. The refractory materials prepared have the characteristics of high melting point, low thermal conductivity and strong corrosion resistance.

[0012] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0013] The invention discloses an application of a perovskite-spinel mixed concentrate in the preparation of refractory materials.

[0014] The refractory material prepared from the perovskite-spinel mixed concentrate is applied in an oxidizing atmosphere or a neutral atmosphere, and can also be applied in a reducing atmosphere.

[0015] The refractory material prepared from the perovskite-spinel mixed concentrate is applied to an acidic slag system or a neutral slag system, and can also be applied to an alkaline slag system.

[0016] The refractory material prepared from the perovskite-spinel mixed concentrate is applicable to a continuous production process and can also be applied to an intermittent production process.

[0017] The perovskite-spinel mixed concentrate is obtained from titanium-containing slag or prepared by artificial mixing; the titanium-containing slag is one or both of titanium-containing blast furnace slag and electric furnace titanium slag.

[0018] The perovskite-spinel mixed concentrate obtained from titanium-containing slag or prepared by artificial mixing has perovskite as the main crystal phase and spinel as the secondary crystal phase. The mass fraction of perovskite powder is 60% to 90%, and the mass fraction of spinel powder is 10% to 40%. The refractory material preparation process also includes a binder with a mass fraction of 1% to 3%.

[0019] The spinel powder is one of magnesium aluminum spinel and magnesium chromium spinel, or a mixture of the two.

[0020] The binder is one or more of polyvinyl alcohol, dextrin, paraffin and carboxymethyl cellulose.

[0021] The preparation process of the refractory material comprises the following steps:

[0022] Step 1, mixing: weighing a perovskite-spinel mixed concentrate obtained from titanium-containing slag or prepared by artificial mixing, and a binder with a mass fraction of 1-3%, wet ball milling and mixing for 10-20 hours using anhydrous ethanol as a medium, and drying the mixed powder for later use;

[0023] Step 2: Compression molding: The mixed powder is compressed under a pressure of 100-150 MPa to obtain a composite material green body;

[0024] Step 3: Green body sintering: sintering the formed composite green body at 1400-1600° C. for 2-4 hours to obtain a perovskite-spinel composite refractory material.

[0025] In the step 3, the temperature is raised synchronously during sintering, and the heating rate is 2-5° C. / min.

[0026] Beneficial effects of the present invention:

[0027] 1. The refractory material prepared from the perovskite-spinel mixed concentrate has a high refractory temperature, excellent slag corrosion resistance and thermal shock resistance. Whether in an oxidizing atmosphere, a neutral atmosphere, or a reducing atmosphere, it has good corrosion resistance and can be used on a large scale as a special refractory material.

[0028] 2. The refractory material prepared from the perovskite-spinel mixed concentrate is a neutral refractory material with excellent thermal shock resistance and corrosion resistance. It can be used in both continuous and intermittent production processes, and can also be used in acidic, alkaline or neutral slag systems.

[0029] 3. The prepared refractory material has perovskite as the main crystal phase. Perovskite itself is a high-melting-point substance. Spinel particles are introduced as a reinforcing phase. The magnesium-aluminum spinel and magnesium-chromium spinel have stable structures and low thermal expansion coefficients at high temperatures, which improves the high-temperature strength and service life of the material.

[0030] 4. The composite material preparation method of the present invention is simple, low-cost, has a wide range of raw material sources, is non-toxic and harmless to the environment, and is easy to achieve industrial promotion.

[0031] 5. This invention leverages the abundant, stored resources of titanium-containing blast furnace slag and uses perovskite concentrate obtained in previous research as a starting point to develop high-quality refractory materials. The resulting perovskite-spinel composite refractory material recycles industrial waste and provides a novel approach to the utilization of perovskite and even titanium-containing blast furnace slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the XRD pattern of the refractory material obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to examples:

[0034] A perovskite-spinel composite refractory material is prepared from a perovskite-spinel mixed concentrate, wherein the perovskite is the main crystal phase and the spinel is the secondary crystal phase. The mass fractions of the components of the prepared raw materials are: 60-90% perovskite powder, 10-40% spinel powder, and 1-3% of the total mass of the prepared raw materials as a binder.

[0035] The spinel powder is one of magnesium aluminum spinel and magnesium chromium spinel or a mixture of the two. The binder is one of polyvinyl alcohol, dextrin, paraffin wax and carboxymethyl cellulose or more.

[0036] In the following examples, the chemical formula of the magnesium aluminum spinel used is MgAl2O4, and the chemical formula of the magnesium chromium spinel used is MgCr2O4.

[0037] In the following examples, the perovskite-spinel mixed concentrate used has a purity of ≥98%, a particle size of ≤74 μm, an impurity component Fe2O3 content of ≤0.7%, and an SiO2 content of ≤0.6%.

[0038] In the following examples, thermal shock stability is characterized by the number of thermal shock cycles of the sample. The sample is placed in a high-temperature furnace at 1500°C for 20 minutes, taken out and placed in running cold water for cooling, and the sample is observed for cracks. The above process is repeated until the sample cracks.

[0039] In the following examples, erosion resistance was measured using the crucible method. A hole 30-40 mm in diameter and 30-40 mm deep was drilled in the center of the top surface of the resulting perovskite-spinel composite refractory material to form a crucible. A predetermined amount of slag sample was placed in the crucible, heated to 1500°C in a high-temperature furnace for 3 hours, and then the crucible was cut open along its center plane. The maximum depth of penetration and erosion of the slag sample into the refractory material was measured using the side surfaces of the crucible as a reference.

[0040] The perovskite-spinel composite refractory material obtained by the present invention has a refractory temperature of 1300°C to 1900°C, a thermal shock stability cycle of 30 to 40 times, and an erosion depth of 0 to 3 mm and a penetration depth of 1 to 5 mm, respectively. During the research process, it was found that when the perovskite-spinel composite refractory material is used in a reducing atmosphere, a low-valent titanium oxide protective layer is formed on the surface of the refractory material, which hinders further erosion of the refractory material by the high-temperature slag. The synergistic effect of the protective layer and the excellent chemical stability of the spinel phase significantly improves the corrosion resistance of the perovskite-spinel composite refractory material.

[0041] The composite refractory material obtained by the present invention uses perovskite as a matrix. During the sintering process, spinel particles undergo surface diffusion for mass transfer, and the spinel particles are rearranged and evenly and diffusely distributed in the perovskite matrix. Under high temperature, the perovskite and spinel grains are connected to form a new composite phase. The two have a certain bonding strength. When the refractory material comes into contact with the slag, the connection between the perovskite and spinel grains reduces the number of grain boundaries where the perovskite and slag come into contact, thereby weakening the erosion effect of the slag on the refractory material through mass transfer and chemical reactions. At the same time, the presence of spinel particles fills the gaps at the interface of the material, improves its density, reduces the open pores of the refractory material, and reduces the amount of slag entering the material through the pores, thereby slowing down the erosion and penetration rate of the slag on the refractory material. When the temperature changes rapidly, the temperature gradient inside the material will generate thermal stress. Perovskite has a high inherent strength as a skeleton and can withstand thermal stress without being destroyed. Spinel particles have a small thermal expansion coefficient and are introduced into the material as a reinforcing phase. The volume change caused by temperature change is small, and the corresponding temperature stress is small. The interaction between the two makes the perovskite-spinel composite refractory material have good thermal shock resistance.

[0042] Example 1

[0043] A method for preparing a perovskite-spinel composite refractory material comprises the following steps:

[0044] (1) Mixing: According to the raw material ratio of perovskite-spinel composite refractory material, the perovskite-spinel mixed concentrate contains 80% perovskite, 20% magnesia-alumina spinel, and 3% polyvinyl alcohol by weight of the total raw material. The mixture is wet-milled with anhydrous ethanol as the medium for 20 hours, and the mixed powder is dried and set aside;

[0045] (2) Compression molding: The mixed powder is pressed under a pressure of 150 MPa to obtain a composite green body;

[0046] (3) Green body sintering: The formed composite green body is placed in a corundum crucible, placed in a high-temperature furnace and heated to 1400°C at a controlled heating rate of 5°C / min, and sintered for 2 hours. After the insulation is completed, the green body is cooled in the furnace to obtain a perovskite-spinel composite refractory material.

[0047] The following are the application indicators:

[0048] (1) The prepared perovskite-spinel composite refractory material can be used in an intermittent production process or a continuous production process, can be used in acidic slag, alkaline slag or neutral slag, has a thermal shock resistance cycle of 35 times, and an erosion depth and a penetration depth of 2 mm and 3 mm respectively in an oxidizing atmosphere or a neutral atmosphere.

[0049] (2) The prepared perovskite-spinel composite refractory material can be used in an intermittent production process or a continuous production process, can be used for acidic slag, alkaline slag or neutral slag, has a thermal shock resistance cycle of 35 times, and in a reducing atmosphere, has an erosion depth and a penetration depth of 3 mm and 4 mm, respectively.

[0050] The XRD pattern of the perovskite-spinel composite refractory material obtained in Example 1 is as follows: Figure 1 The components and contents are shown in Table 1.

[0051] Table 1 Components and contents of the perovskite-spinel composite refractory material obtained in Example 1

[0052]

[0053] Comparative Example 1

[0054] The difference from step (1) in Example 1 is that 100% by mass of perovskite is used instead of the perovskite-spinel mixed concentrate.

[0055] The prepared perovskite refractory material has a thermal shock resistance of 28 times. Under a reducing atmosphere, the erosion depth and penetration depth are 2 mm and 3 mm respectively.

[0056] Description: Pure perovskite phase refractory materials have stronger slag erosion resistance under reducing atmosphere (high melting point low-valent titanium oxide and TiC are generated on the surface to protect the refractory materials from erosion), and their thermal shock resistance becomes weaker (no spinel phase).

[0057] Comparative Example 2

[0058] The difference from step (1) in Example 1 is that 100% by mass of magnesium-aluminum spinel is used instead of the perovskite-spinel mixed concentrate.

[0059] The prepared spinel refractory material has a thermal shock resistance of 40 times, and the erosion depth and penetration depth under reducing atmosphere are 6 mm and 7 mm respectively.

[0060] Note: Spinel refractory materials cannot be used in reducing atmospheres, as magnesium oxide will be reduced by carbon and the refractory materials will be destroyed.

[0061] Comparative Example 3

[0062] The difference from step (1) in Example 1 is that 40% by mass of perovskite and 60% by mass of magnesia-alumina spinel are used instead of the raw material composition of 80% perovskite and 20% by mass of magnesia-alumina spinel.

[0063] The prepared perovskite-spinel refractory material has a thermal shock resistance of 37 times. In an oxidizing atmosphere, the erosion depth and penetration depth are 3mm and 4mm respectively.

[0064] Note: As the proportion of magnesium aluminum spinel increases, the thermal shock resistance improves, while the perovskite decreases and the slag corrosion resistance deteriorates.

[0065] Comparative Example 4

[0066] The difference from step (1) in Example 1 is that 95% by mass of perovskite and 5% by mass of magnesia-alumina spinel are used instead of the raw material composition of 80% by mass of perovskite and 20% by mass of magnesia-alumina spinel.

[0067] The prepared perovskite-spinel refractory material has a thermal shock resistance of 33 times. In an oxidizing atmosphere, the erosion depth and penetration depth are 1 mm and 2 mm respectively.

[0068] Note: As the perovskite content increases, the slag corrosion resistance improves and the thermal shock resistance decreases.

[0069] Comparative Example 5

[0070] The difference from step (1) in Example 1 is that alumina is used instead of perovskite.

[0071] The prepared corundum-spinel refractory material has a thermal shock resistance cycle of 7 times. Under reducing atmosphere, the erosion depth and penetration depth are 4mm and 5mm respectively.

[0072] Note: Corundum has a large thermal expansion coefficient and poor thermal shock resistance.

[0073] Comparative Example 6

[0074] The difference from step (1) in Example 1 is that fused magnesia is used instead of perovskite.

[0075] The prepared periclase-spinel type refractory material has a thermal shock resistance of 37 times. Under reducing atmosphere, the erosion depth and penetration depth are 8 mm and 10 mm respectively.

[0076] Note: Periclase refractory materials cannot be used in reducing atmospheres. Magnesium oxide is reduced by carbon, resulting in poor slag corrosion resistance and damage to the refractory materials.

[0077] Example 2

[0078] A method for preparing a perovskite-spinel composite refractory material comprises the following steps:

[0079] (1) Mixing: According to the raw material ratio of perovskite-spinel composite refractory material, 70% perovskite, 20% magnesia-alumina spinel, and 10% magnesia-chromium spinel are weighed, and 3% of the total weight of carboxymethyl cellulose is added. The mixture is wet-milled with anhydrous ethanol as the medium for 20 hours, and the mixed powder is dried and set aside;

[0080] (2) Compression molding: The mixed powder is pressed under a pressure of 150 MPa to obtain a composite green body;

[0081] (3) Green body sintering: The formed composite green body is placed in a corundum crucible, placed in a high-temperature furnace and heated to 1400°C at a controlled heating rate of 5°C / min, and sintered for 2 hours. After the insulation is completed, the green body is cooled in the furnace to obtain a perovskite-spinel composite material.

[0082] The prepared perovskite-spinel composite refractory material has a thermal shock resistance cycle of 39 times. In an oxidizing atmosphere, the erosion depth and penetration depth are 4 mm and 5 mm respectively.

[0083] Description: The perovskite phase decreases, the magnesium-chromium spinel increases, the thermal shock resistance is enhanced, and the slag corrosion resistance is weakened. The thermal shock resistance and slag corrosion resistance of magnesium-chromium spinel are stronger than those of magnesium-aluminum spinel.

[0084] Example 3

[0085] A method for preparing a perovskite-spinel composite refractory material comprises the following steps:

[0086] (1) Mixing: According to the raw material ratio of perovskite-spinel composite refractory material, 85% perovskite and 15% magnesia-chromium spinel are weighed, and polyvinyl alcohol (3% of the total weight of the raw materials) is added. Anhydrous ethanol is used as the medium for wet ball milling for 20 hours, and the mixed powder is dried and set aside;

[0087] (2) Compression molding: The mixed powder is pressed under a pressure of 150 MPa to obtain a composite green body;

[0088] (3) Green body sintering: The formed composite green body is placed in a corundum crucible, placed in a high-temperature furnace and heated to 1400°C at a controlled heating rate of 5°C / min, and sintered for 2 hours. After the insulation is completed, the green body is cooled in the furnace to obtain a perovskite-spinel composite refractory material.

[0089] The prepared perovskite-spinel composite refractory material has a thermal shock resistance cycle of 36 times. Under a neutral atmosphere, the erosion depth and penetration depth are 1 mm and 2 mm respectively.

[0090] Note: As the perovskite phase increases, the slag corrosion resistance increases. At the same time, as the magnesia-chromium spinel increases, the thermal shock resistance improves. The thermal shock resistance and slag resistance of magnesia-chromium spinel are better than those of magnesia-aluminum spinel.

Claims

1. Application of a perovskite-spinel mixed concentrate in the preparation of refractory materials, characterized in that: The preparation process of the refractory material comprises the following steps: Step 1, mixing: weighing a perovskite-spinel mixed concentrate obtained from titanium-containing slag or prepared by artificial mixing, adding 1% to 3% of a binder based on the total mass of the perovskite-spinel mixed concentrate, wet ball milling with anhydrous ethanol as a medium for 10 to 20 hours, and drying the mixed powder for later use; Step 2: Compression molding: The mixed powder is pressed under a pressure of 100-150 MPa to obtain a composite material green body; Step 3, green body sintering: sintering the formed composite green body at 1400-1600° C. for 2-4 hours to obtain a perovskite-spinel composite refractory material; The perovskite-spinel mixed concentrate obtained from titanium-containing slag or prepared by artificial mixing has perovskite as the main crystal phase and spinel as the secondary crystal phase. The mass fraction of perovskite powder is 60% to 90%, and the mass fraction of spinel powder is 10% to 40%.

2. The use according to claim 1, characterized in that The refractory material prepared from the perovskite-spinel mixed concentrate is used in an oxidizing atmosphere, a neutral atmosphere or a reducing atmosphere.

3. The use according to claim 1, characterized in that The refractory material prepared from the perovskite-spinel mixed concentrate is applied to an acidic slag system, a neutral slag system or an alkaline slag system.

4. The use according to claim 1, characterized in that The refractory material prepared from the perovskite-spinel mixed concentrate is applied to a continuous production process or an intermittent production process.

5. The use according to claim 2, 3 or 4, characterized in that The titanium-containing slag is one or both of titanium-containing blast furnace slag and electric furnace titanium slag.

6. The use according to claim 1, characterized in that The spinel powder is one of magnesium aluminum spinel and magnesium chromium spinel, or a mixture of the two.

7. The use according to claim 1, characterized in that The binder is one or more of polyvinyl alcohol, dextrin, paraffin and carboxymethyl cellulose.

8. The use according to claim 1, characterized in that In the step 3, the temperature is raised synchronously during sintering, and the heating rate is 2-5°C / min.

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