Alumina spinel-based insulating brick and method for manufacturing the same

Abstract

This invention provides an insulating brick that combines excellent lithium resistance with practically sufficient compressive strength, as well as a simple and efficient method for manufacturing the same. [Solution] A method for producing alumina spinel-based heat-insulating bricks, characterized by using a refractory raw material mainly composed of alumina and containing 10 to 30% by mass of spinel, setting the particle size of the spinel to 100 μm or less, setting the MgO content in the refractory raw material to 2 to 8% by mass, restricting the SiO2 content in the refractory raw material to less than 1.5% by mass, adding a binder to the refractory raw material and kneading it to obtain a molded body of any shape.

Description

[Technical Field]

[0001] The present invention relates to an alumina spinel-based insulating brick that can be used as a lining material for furnaces, and more particularly to an alumina spinel-based insulating brick that can be suitably used as a lining material for a firing furnace for lithium-ion battery cathode materials. [Background technology]

[0002] Alumina-based insulating bricks have excellent heat resistance and thermal shock resistance, and are used as lining materials for various firing furnaces. Furthermore, it is known that the corrosion resistance of alumina-based insulating bricks can be improved by incorporating appropriate components.

[0003] For example, Patent Document 1 (Japanese Patent Publication No. 2004-196637) addresses the objective of "obtaining an amorphous refractory with durability comparable to, for example, alumina-chromium oxide containing chromium oxide, even if it does not substantially contain chromium oxide, for use as a lining for a waste melting furnace," and proposes "an amorphous refractory for a waste melting furnace containing 0.5 to 40% tin oxide by mass."

[0004] In the unshaped refractories for waste melting furnaces described in Patent Document 1 above, it is stated that "the low basicity slag of the waste melting furnace has low viscosity, but at the contact points with the refractory material, the tin oxide contained in the refractory material dissolves into the slag, increasing the viscosity of the slag. Due to the high viscosity of the slag, it adheres to the surface of the refractory material, forming a highly viscous slag film on the surface of the refractory material, which protects the refractory material structure and prevents the penetration of alkaline components into the refractory material structure, thereby improving corrosion resistance."

[0005] Furthermore, Patent Document 2 (Japanese Patent Publication No. 2-184579) addresses the objective of "providing a raw material for refractories that has excellent corrosion resistance and alkali resistance for slag with high basicity, is free from construction constraints such as hydration, and has low thermal conductivity, thus reducing the need for cooling of molten metal, etc." and proposes "a porous spinel-corundum clinker characterized by having a chemical composition of 1-15% MgO and 85-99% Al2O3, with unavoidable impurities derived from other raw materials, a total porosity of 20% or more, and the coexistence and uniform distribution of spinel crystals and corundum crystals."

[0006] The porous spinel-corundum clinker described in Patent Document 2 above is said to "maintain even greater resistance to slag erosion by having a microstructure in which spinel and corundum crystals, which have excellent corrosion resistance to slag erosion, are uniformly distributed on a scale of several micrometers." [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2004-196637 [Patent Document 2] Japanese Patent Application Publication No. 2-184579 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, in recent years, there has been an increasing demand for particularly excellent alkali resistance in the lining materials of firing furnaces. For example, in furnaces used to fire lithium-ion battery cathode materials, pure alumina insulating bricks are used as the lining material, but a problem has arisen where the lithium vapor generated from the lithium-ion battery cathode material reacts with the insulating bricks, causing them to disintegrate.

[0009] More specifically, lithium carbonate and lithium hydroxide are used as raw materials for the cathode material, which volatilize at high temperatures and diffuse into the furnace. The pure alumina insulating brick reacts with the diffused lithium from the surface and is transformed into LiAlO2, but the density of LiAlO2 is 2.6 g / cm³. -3 This is the original 4.0 g cm³ of α-alumina. -3 Because of its lower density, volume expansion occurs. Furthermore, since this reaction occurs from the fine powder portion with a large specific surface area, the alteration and expansion of the fine powder portion that binds the aggregates together leads to the problem of brick embrittlement progressing from the surface.

[0010] In contrast, while the amorphous refractory for waste melting furnaces described in Patent Document 1 and the porous spinel-corundum clinker described in Patent Document 2 have improved resistance to slag erosion, they do not take into account the reaction with lithium vapor and therefore do not have sufficient corrosion resistance in that environment.

[0011] In view of the problems of the conventional technology described above, the object of the present invention is to provide a heat insulating brick that combines excellent lithium resistance and sufficient compressive strength for practical use, and a simple and efficient method for manufacturing the same. [Means for solving the problem]

[0012] To achieve the above objective, the inventors diligently researched the composition of insulating bricks and their manufacturing methods. As a result, they discovered that adding spinel with a particle size of 100 μm or less to a refractory raw material mainly composed of alumina, and restricting the SiO2 content in the refractory raw material to less than 1.5% by mass, is extremely effective, leading to the present invention.

[0013] In other words, the present invention is Using a refractory raw material that mainly consists of alumina and contains 10-30% by mass of spinel, The particle size of the spinel is set to 100 μm or less. The MgO content in the aforementioned refractory raw material is set to 2 to 8% by mass. The SiO2 content in the aforementioned refractory raw material is restricted to less than 1.5% by mass. After adding a binder to the refractory raw material and kneading, a molded body of any shape is obtained. Provided is a method for producing alumina spinel refractory bricks, characterized by the above.

[0014] In the method for producing alumina spinel refractory bricks of the present invention, by adding 10 to 30% by mass of spinel to make the MgO content in the refractory raw material 2% by mass or more, excellent lithium resistance can be exhibited in the obtained alumina spinel refractory bricks. Also, by making the MgO content in the refractory raw material 8% by mass or less, sufficient compressive strength can be imparted to the alumina spinel refractory bricks, and they can be suitably used as the lining material of a firing furnace.

[0015] In addition, the addition of spinel is for uniformly dispersing MgO in the finally obtained alumina spinel refractory bricks and suppressing the reaction between the fine powder part and lithium vapor in the alumina spinel refractory bricks. If the particle size of the spinel exceeds 100 μm, the lithium resistance of the alumina spinel refractory bricks cannot be effectively improved. In addition, by making the particle size of the spinel 100 μm or less, a decrease in the compressive strength of the alumina spinel refractory bricks can be suppressed, and the alumina spinel refractory bricks can be suitably used as the lining material of a firing furnace.

[0016] More specifically, the addition of spinel makes it difficult for the generation of LiAlO2, which causes embrittlement, to occur. The reaction in which lithium species form LiAlO2 from α-alumina or spinel with Li2O is described as follows. Al2O3(s)+Li2O(g)→2LiAlO2(s) (1) MgAl2O4(s)+Li2O(g)→2LiAlO2(s)+MgO(s)(2) (Equation (1) is the reaction from α-alumina, and equation (2) is the reaction from spinel. The standard reaction Gibbs energy ΔG 0 is calculated. For equation (1), it is -322 kJ / mol -1 while for equation (2), it is -287 kJ / mol -1Therefore, for ΔG in Equation (2), 0 is large, and the reaction hardly occurs.

[0017] Also, regarding Equations (1) and (2), when calculating the equilibrium partial pressure P Li2O of Li2O, Equation (1) is 1.10×10 -13 atm, and Equation (2) is 30.0×10 -13 atm, which is much larger. It can be seen that by using spinel, the partial pressure of Li2O at which the reaction starts increases, making the reaction less likely to occur.

[0018] Furthermore, in the method for manufacturing the alumina spinel refractory brick of the present invention, the content of SiO2 in the refractory raw material is regulated to be less than 1.5% by mass. Adding SiO2 less than 1.5% by mass imparts appropriate plasticity to the alumina spinel refractory brick and improves the formability. However, when adding 1.5% by mass or more of SiO2, the lithium resistance of the alumina spinel refractory brick decreases. Here, in the method for manufacturing the alumina spinel refractory brick of the present invention, the addition of SiO2 is not essential, and SiO2 less than 1.5% by mass may be added as necessary.

[0019] Basically, since it becomes easier to react with lithium when containing SiO2, from this perspective, it is not desired to contain it. However, considering the formability, there is a situation where it is desired to add clay. This is because clay imparts appropriate fluidity to the kneaded material (clay soil) before molding, has the effect of suppressing filling unevenness, and also has plasticity to improve the strength of the molded body. For example, for a simple parallel shape, there is no problem even without clay, but when molding complex-shaped products or large-sized products, it is preferable to appropriately add clay.

[0020] Also, in the method for manufacturing the alumina spinel refractory brick of the present invention, it is preferable to add 0% by mass or more and 2% by mass or less of clay to the refractory raw material. By adding 0% by mass or more and 2% by mass or less of clay, the content of SiO2 in the alumina spinel refractory brick can be made more than 0% by mass and less than 1.5% by mass.

[0021] Also, the present invention It mainly consists of alumina, It contains spinel with a particle size of 100 μm or less. It contains 2-8% by mass of MgO, The SiO2 content is regulated to be less than 1.5% by mass. We also offer alumina spinel-based insulating bricks, which feature the following characteristics.

[0022] The alumina spinel-based insulating brick of the present invention is suitably obtained by the method for producing the alumina spinel-based insulating brick of the present invention, and contains 2 to 8% by mass of MgO. The inclusion of 2% by mass or more of MgO provides excellent lithium resistance, while the MgO content of 8% by mass or less ensures sufficient compressive strength.

[0023] Herein, the alumina spinel-based insulating brick of the present invention can be suitably used as a lining material for firing furnaces of lithium-ion battery cathode materials, and it also has excellent corrosion resistance to sodium and potassium, making it suitable for use in environments where corrosion resistance to these alkalis is required.

[0024] Furthermore, in the alumina spinel-based insulating brick of the present invention, the SiO2 content is restricted to less than 1.5% by mass. Adding less than 1.5% by mass of SiO2 imparts appropriate plasticity to the alumina spinel-based insulating brick and improves its moldability, but containing 1.5% by mass or more of SiO2 reduces the lithium resistance of the alumina spinel-based insulating brick. Herein, in the alumina spinel-based insulating brick of the present invention, the inclusion of SiO2 is not essential, and less than 1.5% by mass of SiO2 may be included as needed.

[0025] Furthermore, the alumina spinel-based insulating brick of the present invention is preferably used as a lining material for a firing furnace that generates lithium vapor. The alumina spinel-based insulating brick of the present invention has excellent alkali resistance, and in particular excellent lithium resistance, so even when used as a lining material for a firing furnace that generates lithium vapor, it can suppress expansion and collapse due to reaction with lithium vapor.

[0026] Furthermore, it is preferable that the alumina spinel-based insulating brick of the present invention has a compressive strength of 15 MPa or more. Having a compressive strength of 15 MPa or more makes the alumina spinel-based insulating brick suitable for use as a lining material for various firing furnaces.

[0027] Furthermore, the alumina spinel-based insulating brick of the present invention has a bulk density of 1.45 to 2.15 and a thermal conductivity of 2.0 WK. -1 m -1 The following is preferable: Given its application as an insulating brick, it is required to be lighter and have lower thermal conductivity compared to refractory bricks, with a bulk density of 1.45 to 2.15 and a thermal conductivity of 2.0 WK. -1 m -1 By doing the following, it can be suitably used as an insulating brick. [Effects of the Invention]

[0028] According to the present invention, it is possible to provide a heat-insulating brick that combines excellent lithium resistance and practically sufficient compressive strength, as well as a simple and efficient method for manufacturing the same. [Brief explanation of the drawing]

[0029] [Figure 1] This is a schematic cross-sectional view of a saggar with a test specimen as a lid. [Figure 2] This is a photograph of the exterior of a saggar covered with a test specimen. [Modes for carrying out the invention]

[0030] The following describes in detail representative embodiments of the alumina spinel-based heat-insulating brick and its manufacturing method according to the present invention, but the present invention is not limited to these embodiments.

[0031] 1. Method for manufacturing alumina spinel insulating bricks The present invention relates to a method for producing alumina spinel-based heat-insulating bricks, characterized by adding spinel with a particle size of 100 μm or less to a refractory raw material mainly composed of alumina, and by having an MgO content of 2 to 8% by mass. The main components of the refractory raw material and each added component will be described in detail below.

[0032] (1) Components of fire-resistant raw materials (1-1) Main component (alumina) The main component (refractory aggregate) of the heat-insulating brick of the present invention is alumina, and alumina raw materials with appropriate particle size adjustment can be used. The type of alumina raw material is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known alumina raw materials can be used.

[0033] For the alumina raw material, high-alumina raw materials such as electrofused alumina, sintered alumina, and calcined alumina can be used. In addition, the refractory aggregate may include high-alumina raw materials commonly used as refractory materials, such as electrofused mullite and synthetic mullite, in addition to the alumina raw material.

[0034] As long as alumina is the main raw material, the alumina content in the refractory raw material is not particularly limited, but the alumina content in the refractory raw material is preferably 90% by mass or more, and more preferably 95% by mass or more.

[0035] (1-2) Essential additives The essential additive is spinel, which is added to a concentration of 10-30% by mass of the refractory raw material. As a result, the MgO content in the refractory raw material can be reduced to 2-8% by mass. The addition of spinel improves the lithium resistance of alumina-spinel insulating bricks. Furthermore, spinel is a high-melting-point compound and does not reduce the refractory resistance of alumina-spinel insulating bricks.

[0036] By setting the MgO content in the refractory raw material to 2% by mass or more, the resulting alumina spinel-based insulating brick can exhibit excellent lithium resistance. Furthermore, by setting the MgO content in the refractory raw material to 8% by mass or less, the alumina spinel-based insulating brick can be given sufficient compressive strength and can be suitably used as a lining material for firing furnaces. In the range of 2 to 8% by mass for the MgO content in the refractory raw material, it is preferable to increase the MgO content from the viewpoint of alkali resistance, and to decrease the MgO content from the viewpoint of compressive strength.

[0037] The particle size of spinel added to the refractory raw material must be 100 μm or less. A preferred spinel particle size is 50 μm or less, and a more preferred spinel particle size is 20 μm or less. The problem is that the fine powder portion of alumina spinel insulating bricks expands and falls off due to reaction with lithium vapor. By using fine spinel particles, uniform dispersion can be achieved in the refractory raw material. As a result, lithium penetration is suppressed, and MgO, which directly contributes to improving lithium resistance, can reach the fine powder portion, significantly improving the lithium resistance of the alumina spinel insulating bricks.

[0038] As long as the effects of the present invention are not impaired, the type of spinel to be added to the refractory raw material is not particularly limited, and conventionally known sintered spinel or electrolytic spinel can be used. Furthermore, different types of spinel may be used in combination.

[0039] (1-3) Any additive components (1-3-1)SiO2 SiO2 can be added as an optional additive. Furthermore, when SiO2 is added, clay can be added, for example.

[0040] Here, the SiO2 content in the refractory raw material is regulated to be less than 1.5% by mass. Adding less than 1.5% by mass of SiO2 imparts appropriate plasticity to the alumina spinel insulating brick and improves its moldability, but adding 1.5% by mass or more of SiO2 reduces the lithium resistance of the alumina spinel insulating brick. It is preferable that the SiO2 content in the refractory raw material be 1.0% by mass or less.

[0041] It is preferable to use clay as the SiO2 source, as the addition of clay can improve the moldability of the refractory material. The amount of clay to be added can be adjusted as appropriate while checking the SiO2 content contained in the refractory material, but it is preferable to add 2% by mass or less to the refractory material. By adding 2% by mass or less of clay to the refractory material, it is possible to prevent the SiO2 content of the refractory material from exceeding 1.5% by mass, thereby suppressing a decrease in the reactivity resistance of the alumina spinel insulating brick and improving its moldability by imparting plasticity to the refractory material. On the other hand, if the amount of clay added to the refractory material is 3% by mass or more, the SiO2 content of the refractory material will exceed 1.5% by mass, and the reactivity resistance of the alumina spinel insulating brick will decrease.

[0042] (1-3-2) Binder A binder may be added as appropriate to provide strength to the molded body. This binder may be an organic binder such as starch, dextrin, cellulose, PVA, or phenolic resin, which are commonly used when obtaining molded bodies by press molding. It may be added in powder or aqueous solution form.

[0043] (1-3-3) Others In addition to the main component, alumina, an appropriate amount of water may be added.

[0044] 2. Alumina spinel insulating bricks The alumina spinel-based insulating brick of the present invention is characterized by having alumina as its main component, containing spinel with a particle size of 100 μm or less, containing 2 to 8% by mass of MgO, and having an SiO2 content restricted to less than 1.5% by mass. It can be suitably obtained by the method for producing the alumina spinel-based insulating brick of the present invention. Furthermore, the alumina spinel-based insulating brick of the present invention has the following properties.

[0045] (1) Corrosion resistance The alumina spinel-based insulating brick of the present invention has excellent corrosion resistance to alkali metals such as lithium, sodium, and potassium. As a result, it can be suitably used, for example, as a lining material for firing furnaces of lithium-ion battery cathode materials, where lithium vapor is generated.

[0046] More specifically, the alumina spinel-based insulating brick of the present invention contains an appropriate amount of MgO, and since MgO suppresses the infiltration of lithium and other elements, even if the alumina spinel-based insulating brick of the present invention is kept in a high-temperature environment filled with lithium vapor, for example, the reaction between the lithium vapor and the alumina spinel-based insulating brick is suppressed, and the expansion and collapse of the alumina spinel-based insulating brick can be prevented.

[0047] In addition, while the lithium resistance of alumina spinel-based insulating bricks decreases when they contain 1.5% by mass or more of SiO2, the SiO2 content in the alumina spinel-based insulating bricks of the present invention is restricted to less than 1.5% by mass.

[0048] (2) Heat resistance The alumina-spinel insulating brick of the present invention is manufactured from a refractory raw material to which spinel has been added in order to obtain the effects of MgO. However, spinel is a high-melting-point compound, and the heat resistance of the alumina-spinel insulating brick is not reduced due to the presence of spinel.

[0049] Furthermore, in the alumina spinel-based insulating brick of the present invention, the SiO2 content is restricted to less than 1.5% by mass. Adding less than 1.5% by mass of SiO2 imparts appropriate plasticity to the alumina spinel-based insulating brick and improves its moldability, but containing 1.5% by mass or more of SiO2 reduces the lithium resistance of the alumina spinel-based insulating brick. Herein, in the alumina spinel-based insulating brick of the present invention, the inclusion of SiO2 is not essential, and less than 1.5% by mass of SiO2 may be included as needed.

[0050] (3) Compression strength The alumina spinel-based heat-insulating brick of the present invention ensures sufficient compressive strength by using spinel with a particle size of 100 μm or less as a refractory raw material, setting the upper limit of the spinel addition to 20% by mass, and limiting the MgO content to 8% by mass or less.

[0051] The compressive strength of alumina spinel insulating bricks at room temperature is preferably 15 MPa or higher, and more preferably 18 MPa or higher. Having a compressive strength of 15 MPa or higher makes the alumina spinel insulating bricks suitable for use as lining material in various firing furnaces.

[0052] (4) Bulk density The alumina spinel-based insulating brick of the present invention preferably has a bulk density of 1.45 to 2.15. Its lighter weight compared to refractory bricks makes it suitable for use as an insulating brick. While the bulk density can be adjusted to some extent by the pressing pressure and number of strikes during molding, if the value is too low, the compressive strength decreases. On the other hand, if the value is too high, the compressive strength improves, but the thermal conductivity becomes excessively high.

[0053] (5) Thermal conductivity The alumina spinel-based insulating brick of the present invention has a thermal conductivity of 2.0 WK. -1 m -1 The following is preferable: Its lower thermal conductivity compared to refractory bricks makes it suitable for use as an insulating brick.

[0054] Although typical embodiments of the present invention have been described above, the present invention is not limited to these, and various design modifications are possible, all of which fall within the technical scope of the present invention. [Examples]

[0055] Examples The raw materials were prepared in the proportions shown in Table 1 as Examples 1 to 9. After mixing the raw materials in a high-speed mixer, the binder was added and kneaded, and the mixture was formed into a shape of 230 × 114 × 65 mm using a friction press. During molding, the desired density of the molded body was obtained by adjusting the molding pressure and number of presses. Drying was performed by natural drying for 24 hours, followed by holding at 70°C for 24 hours using a batch-type dryer, and then holding at 140°C for 48 hours. The dried molded bodies were fired at 1650°C in a batch-type gas oven to obtain alumina spinel-based insulating bricks, which are embodiments of the present invention. The values ​​in Table 1 are shown in mass%, and the amount of binder added is shown as the external value relative to the total amount of alumina particles, spinel particles, and clay.

[0056] [Table 1]

[0057] Here, hollow alumina particles, sintered alumina particles, and calcined alumina particles of different particle sizes were used as alumina raw materials. For the spinel raw materials, sintered spinel particles with an Al2O3 content of 70% by mass, sintered spinel particles with an Al2O3 content of 90% by mass, and electrofused spinel particles with an Al2O3 content of 70% by mass were used. A 15% aqueous solution of dextrin was used as the binder.

[0058] Furthermore, the content (mass%) of Al2O3, MgO, and SiO2 in the alumina spinel-based insulating bricks was measured using X-ray fluorescence analysis. A Rigaku ZSX PrimusIII+ was used for the measurement. The obtained values ​​are shown in Table 2. In all examples, the MgO content of the alumina spinel-based insulating bricks was in the range of 2 to 8 mass%, and the SiO2 content was restricted to less than 1.5 mass%.

[0059] [Table 2]

[0060] Table 1 shows Comparative Example 1 to Comparative Example 7 Alumina spinel-based insulating bricks were obtained in the same manner as in the examples, except that the raw materials were adjusted in the proportions shown.

[0061] [evaluation] For each alumina spinel-based insulating brick obtained as examples and comparative examples, corrosion resistance, compressive strength, thermal conductivity, bulk density, and apparent porosity were evaluated. In addition, the formability when molding the refractory raw material was also evaluated.

[0062] (1) Formability The handling properties of the raw horns formed from the refractory raw material after kneading were evaluated. A rating of ◎ indicated no handling problems, while a rating of ○ indicated that the filling of the refractory raw material during molding was slightly insufficient, resulting in grain detachment or minor chipping of the horns when handling the molded body. As shown in Table 2, in all examples, the refractory raw material after kneading exhibited sufficient moldability.

[0063] (2) Corrosion resistance The corrosion resistance of alumina spinel-based insulating bricks was evaluated by a lithium vapor reaction test. As shown in Figure 1, the specimen was convex in shape, with the convex portion measuring 80mm x 80mm x 16mm and the back portion measuring 95mm x 95mm x 14mm. 10g of Li2CO3 was placed in a dense alumina sagger as the corrosive agent, and the specimen was placed on top. The convex portion of the specimen was inserted into the sagger, and the specimen and sagger were sealed with mortar. Figure 2 shows a photograph of the sagger with the specimen on top.

[0064] A sagger covered with the test specimen was held at 1050°C for 24 hours, exposing the protruding parts of the specimen to lithium-containing vapor. The thickness of the four corners of the protrusion was measured before and after the exposure test, and the expansion rate was calculated based on the average value of the increase in thickness. The obtained values ​​are shown in Table 2. Here, a smaller expansion rate indicates better resistance to lithium vapor reactivity (corrosion resistance). An expansion rate of 3% or less was evaluated as ○, and an expansion rate exceeding 3% was evaluated as ×.

[0065] (3) Compression strength Compressive strength was measured on 50mm x 50mm x 50mm specimens using an Amsler-type strength testing apparatus. The results are shown in Table 2. A value of 15MPa or higher was marked with ○, and a value of less than 15MPa was marked with ×.

[0066] (4) Thermal conductivity Measurements were taken at 1000°C using the hot-wire method with two specimens measuring 230mm x 114mm x 65mm. The results are shown in Table 2. 2.0 Wm -1 K -1 In the following cases, ○, 2.0Wm -1 K -1 In the case of "exceeding," we used △.

[0067] (5) Bulk density and apparent porosity The bulk density and apparent porosity of alumina spinel-based insulating bricks were measured (JIS R 2614:1985). The results are shown in Table 2.

[0068] As shown in Table 2, in all examples, the expansion rate of the alumina spinel insulating brick was 3% or less, indicating excellent corrosion resistance to lithium vapor. In contrast, when the alumina spinel insulating brick did not contain MgO (Comparative Example 1), when the SiO2 content was 1.5% by mass or more (Comparative Example 2), when the MgO content was less than 2% by mass (Comparative Examples 3 and 4), and when the particle size of the spinel particles added to the refractory raw material was too large (Comparative Example 6), the alumina spinel insulating brick did not exhibit sufficient corrosion resistance.

[0069] On the other hand, when the MgO content in the alumina spinel-based insulating brick exceeds 8% by mass (Comparative Example 5), good corrosion resistance is observed, but the compressive strength is extremely low. In contrast, in all examples, the compressive strength of the alumina spinel-based insulating brick is 15 MPa or higher.

[0070] Furthermore, in Examples 1 to 8, the bulk density of the alumina spinel insulating bricks was in the range of 1.45 to 2.15, and the thermal conductivity was 2.0 WK. -1 m -1 The following applies. In contrast, the alumina spinel insulating brick obtained in Example 9, which has a high bulk density, has high compressive strength, but its thermal conductivity is 2.2K. -1 m -1 That's how it is.

[0071] From the above results, it can be confirmed that in order to obtain an insulating brick that combines excellent lithium resistance and sufficient compressive strength for practical use, it is extremely important to limit the particle size of spinel to 100 μm or less, to include 2 to 8 mass% of MgO, and to restrict the SiO2 content to less than 1.5 mass% in an alumina spinel insulating brick with alumina as the main component.

Claims

1. Using a refractory raw material that mainly consists of alumina and contains 10 to 30% by mass of spinel, The particle size of the spinel is set to 100 μm or less. Adding more than 0% by mass and 2% by mass or less of clay to the aforementioned refractory raw material, The MgO content in the aforementioned refractory raw material is set to 2 to 8% by mass. SiO in the aforementioned fire-resistant raw material 2 The content is restricted to less than 1.5% by mass. After adding a binder to the aforementioned refractory raw material and kneading it, a molded body of any shape is formed. The bulk density of the alumina spinel-based insulating brick obtained by drying and firing the molded body is set to 1.45 to 2.

15. A method for manufacturing alumina spinel-based thermal insulation bricks characterized by the following.

2. It mainly consists of alumina, It contains spinel with a particle size of 100 μm or less. It contains 2 to 8% by mass of MgO, SiO 2 The content is regulated to be less than 1.5% by mass. The bulk density is 1.45 to 2.

15. Thermal conductivity is 2.0 WK -1 I understand -1 The following: Alumina spinel-based insulating brick characterized by [feature].

3. To be used as a lining material for a firing furnace that generates lithium vapor. The alumina spinel-based insulating brick according to claim 2, characterized by the above.

4. Having a compressive strength of 15 MPa or more, An alumina spinel-based insulating brick according to claim 2 or 3, characterized by the above.

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