Alumina-spinel heat-insulating brick and method for producing same

Abstract

Provided are: a heat-insulating brick having both excellent lithium resistance and a practically sufficient level of compressive strength; and a simple and efficient method for producing the same. A method for producing an alumina-spinel heat-insulating brick according to the present invention is characterized in that a refractory raw material containing alumina as the main component and containing 10-30 mass% of spinel is used, the particle size of the spinel is at most 100 μm, the contained amount of MgO in the refractory raw material is 2-8 mass%, the contained amount of SiO2 in the refractory raw material is restricted to less than 1.5 mass%, and a binder is added to the refractory raw material, followed by kneading, and thereafter, a molded body having an arbitrary shape is obtained.

Description

Alumina Spinel Insulating Brick and Method for Producing the Same

[0001] The present invention relates to an alumina spinel insulating brick that can be used as an inner lining material for furnaces, etc., and particularly relates to an alumina spinel insulating brick that can be suitably used as an inner lining material for a firing furnace of a lithium-ion battery positive electrode material.

[0002] Alumina insulating bricks are excellent in heat resistance, thermal shock resistance, etc., and are used as inner lining materials for various firing furnaces. Also, it is known that corrosion resistance is improved by containing appropriate components in alumina insulating bricks.

[0003] For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-196637), the problem is "to obtain an amorphous refractory having durability comparable to that of, for example, alumina-chromium oxide, even if it does not substantially contain chromium oxide, as an inner lining for a waste melting furnace", and "an amorphous refractory for a waste melting furnace containing 0.5 to 40% of tin oxide by mass ratio" has been proposed.

[0004] In the amorphous refractory for a waste melting furnace described in Patent Document 1 above, "although the low basicity slag of the waste melting furnace has low viscosity, tin oxide contained in the refractory dissolves in the slag at the contact part with the refractory, thereby increasing the viscosity of the slag. And because the viscosity of the slag is high, it adheres to the refractory surface, forming a coating of high-viscosity slag on the refractory surface, protecting the refractory structure and preventing the intrusion of alkaline components into the refractory structure, thereby improving the corrosion resistance."

[0005] Also, in Patent Document 2 (Japanese Patent Application Laid-Open No. 2-184579), the problem is "to provide a raw material for a refractory that is excellent in corrosion resistance and alkali resistance against high basicity slag, has no construction restrictions such as hydration, and has a low thermal conductivity and reduces cooling of molten metal, etc.", and "a porous spinel-cordierite clinker characterized by having a composition in which MgO is 1 to 15%, Al ２ O ３ is 85 to 99%, contains inevitable impurities derived from other raw materials, has a total porosity of 20% or more, and in which spinel crystals and cordierite crystals coexist and are uniformly distributed." has been proposed.

[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."

[0007] JP2004-196637A JP2004-184579A

[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 cathode material raw materials, which volatilize at high temperatures and diffuse into the furnace. The pure alumina insulating brick reacts with the diffused lithium from the surface to form LiAlO ２ It changes to LiAlO ２ The density is 2.6 g / cm³. －３ This is the original α-alumina, 4.0 g / cm³ －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 a problem where the brick becomes brittle 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.

[0012] In order to achieve the above object, the present inventors have conducted intensive research on the composition of heat-insulating bricks and their manufacturing method. As a result, they have found that adding spinel with a particle size of 100 μm or less to a refractory raw material mainly composed of alumina and regulating the content of SiO ２ in the refractory raw material to less than 1.5% by mass is extremely effective, and thus have reached the present invention.

[0013] That is, the present invention provides a method for manufacturing alumina-spinel 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 content of MgO in the refractory raw material to 2 to 8% by mass, regulating the content of SiO ２ in the refractory raw material to less than 1.5% by mass, adding a binder to the refractory raw material and kneading it, and then obtaining a molded body of any shape.

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

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

[0016] More specifically, due to the addition of spinel, LiAlO which causes embrittlement ２The formation of lithium species becomes less likely. ２ As O, α-alumina or spinel can be used to obtain LiAlO ２ The reaction produced is described as follows: Al ２ O ３ (s) + Li ２ O(g) → 2LiAlO ２ (s) (1) MgAl ２ O ４ (s) + Li ２ O(g) → 2LiAlO ２ (s) + MgO(s) (2) Equation (1) is the reaction from α-alumina, and equation (2) is the reaction from spinel. Standard reaction Gibbs free energy ΔG ０ When calculated, equation (1) is -322 kJ mol －１ In contrast, equation (2) is -287 kJ mol －１ Therefore, ΔG in equation (2) ０ The reaction is large and unlikely to occur.

[0017] Also, regarding equations (1) and (2) Li ２ Equilibrium partial pressure P of O Ｌｉ２Ｏ When calculated, equation (1) becomes 1.10 × 10 －１３ For atm, equation (2) is 30.0 × 10 －１３ Li starts to react when spinel is used, which is large atm. ２ It can be seen that the partial pressure of oxygen increases, making the reaction less likely.

[0018] Furthermore, in the method for producing alumina spinel-based heat-insulating bricks of the present invention, SiO in the refractory raw material ２ The content is regulated to be less than 1.5% by mass. ２ Adding 1.5% by mass or more of SiO imparts appropriate plasticity to alumina spinel-based insulating bricks and improves their moldability, but if 1.5% by mass or more of SiO is added, ２ Adding SiO reduces the lithium resistance of the alumina spinel-based insulating brick. Herein, in the method for producing the alumina spinel-based insulating brick of the present invention, ２ The addition of SiO is not mandatory, but less than 1.5% by mass can be added as needed. ２ You just need to add it.

[0019] Basically SiO ２ Because its presence makes it more reactive with lithium, it is undesirable from that perspective, but there are situations where clay is desirable for improved moldability. This is because clay imparts appropriate fluidity to the mixture (clay) before molding, suppresses uneven filling, and also improves the strength of the molded product due to its plasticity. For example, simple, standard shapes can be formed without clay, but it is preferable to add clay as needed when molding complex shapes or large products.

[0020] Furthermore, in the method for producing alumina spinel-based insulating bricks of the present invention, it is preferable to add more than 0% by mass and up to 2% by mass of clay to the refractory raw material. By adding more than 0% by mass and up to 2% by mass of clay, the SiO of the alumina spinel-based insulating brick is ２ The content can be greater than 0% by mass and less than 1.5% by mass.

[0021] Furthermore, the present invention contains alumina as the main component, spinel with a particle size of 100 μm or less, 2 to 8% by mass of MgO, and SiO ２ We also offer alumina spinel-based insulating bricks characterized by having a content of less than 1.5% by mass.

[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 heat insulating brick of the present invention, SiO ２The content is regulated to be less than 1.5% by mass. ２ Adding 1.5% by mass or more of SiO imparts appropriate plasticity to alumina spinel-based insulating bricks and improves their moldability, but if 1.5% by mass or more of SiO is added, ２ The presence of reduces the lithium resistance of the alumina spinel-based insulating brick. Herein, in the alumina spinel-based insulating brick of the present invention, SiO ２ The inclusion of SiO is not mandatory, and less than 1.5% by mass is acceptable if necessary. ２ It is sufficient to include it.

[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 I understand －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. Therefore, a bulk density of 1.45 to 2.15 and a thermal conductivity of 2.0 WK are preferred. －１ I understand －１ By doing the following, it can be suitably used as an insulating brick.

[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.

[0029] This is a schematic cross-sectional view of a saggar covered with a specimen. This is a photograph of the exterior of a saggar covered with a specimen.

[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-Based Thermal Insulation Bricks The method for manufacturing alumina spinel-based thermal insulation bricks of the present invention is characterized by adding spinel with a particle size of 100 μm or less to a refractory raw material mainly composed of alumina, and by setting the MgO content to 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 the refractory raw material (1-1) Main component (alumina) The main component (refractory aggregate) of the heat insulating brick of the present invention is alumina, and alumina raw material 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 additive The essential additive is spinel, which is added in an amount of 10 to 30% by mass of the refractory raw material. As a result, the MgO content in the refractory raw material can be set to 2 to 8% by mass. The addition of spinel can improve the lithium resistance of alumina spinel-based insulating bricks. Furthermore, spinel is a high-melting-point compound and does not reduce the refractory properties of alumina spinel-based 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 the 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, thereby significantly improving the lithium resistance of 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 component (1-3-1) SiO ２ As an optional additive, SiO ２ It can also be added. ２ When adding something, for example, clay can be added.

[0040] Here, SiO in refractory raw materials ２ The content is regulated to be less than 1.5% by mass. Less than 1.5% by mass of SiO ２ Adding 1.5% by mass or more of SiO imparts appropriate plasticity to alumina spinel-based insulating bricks and improves their moldability, but if 1.5% by mass or more of SiO is added, ２Adding SiO reduces the lithium resistance of alumina spinel-based insulating bricks. ２ The content of is preferably 1.0% by mass or less.

[0041] SiO ２ It is preferable to use clay as the source, as the addition of clay can improve the moldability of the refractory material. The amount of clay to add depends on the amount of SiO contained in the refractory material. ２ While it is possible to adjust the amount as appropriate while checking the content, it is preferable to keep the amount added to the refractory raw material to 2% by mass or less. By adding clay to the refractory raw material to 2% by mass or less, the amount of SiO in the refractory raw material is reduced. ２ This prevents the content from exceeding 1.5% by mass, suppressing a decrease in the reactivity resistance of alumina spinel-based insulating bricks, while also imparting plasticity to the refractory raw material and improving moldability. On the other hand, if the amount of clay added to the refractory raw material is 3% by mass or more, the SiO content of the refractory raw material will be reduced. ２ The content of this substance exceeds 1.5% by mass, which reduces the reactivity of the alumina spinel-based insulating brick.

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

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

[0044] 2. Alumina spinel insulating brick The alumina spinel insulating brick of the present invention mainly consists of alumina, contains spinel with a particle size of 100 μm or less, contains 2 to 8% by mass of MgO, and contains SiO ２ It is characterized in that the content of is restricted to less than 1.5% by mass, and can be suitably obtained by the method for producing alumina spinel-based insulating bricks of the present invention. Furthermore, the alumina spinel-based insulating bricks of the present invention have the following properties.

[0045] (1) Corrosion Resistance The alumina spinel-based heat 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 that generate lithium vapor.

[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 the like, 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, 1.5% by mass or more of SiO ２ The presence of SiO reduces the lithium resistance of alumina spinel-based insulating bricks, but in the alumina spinel-based insulating brick of the present invention, ２ The content is regulated to be less than 1.5% by mass.

[0048] (2) Heat Resistance The alumina spinel-based heat 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 compound with a high melting point, and the heat resistance of the alumina spinel-based heat insulating brick is not reduced due to the presence of spinel.

[0049] Furthermore, in the alumina spinel-based heat insulating brick of the present invention, SiO ２ The content is regulated to be less than 1.5% by mass. ２ Adding 1.5% by mass or more of SiO imparts appropriate plasticity to alumina spinel-based insulating bricks and improves their moldability, but if 1.5% by mass or more of SiO is added, ２ The presence of reduces the lithium resistance of the alumina spinel-based insulating brick. Herein, in the alumina spinel-based insulating brick of the present invention, SiO ２ The inclusion of SiO is not mandatory, and less than 1.5% by mass is acceptable if necessary. ２ It is sufficient to include it.

[0050] (3) Compressive strength The alumina spinel-based heat insulating brick of the present invention ensures sufficient compressive strength by setting the particle size of the spinel used as a refractory raw material to 100 μm or less, setting the upper limit of the amount of spinel added to 20% by mass, and setting 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 insulating brick of the present invention preferably has a bulk density of 1.45 to 2.15. It is lighter than refractory bricks and can be suitably used as an insulating brick. The bulk density can be adjusted to some extent arbitrarily by the press pressure and number of blows during molding, but if the value is too small, the compressive strength will decrease. On the other hand, if the value is too large, the compressive strength will improve, but the thermal conductivity will become too high.

[0053] (5) Thermal conductivity The alumina spinel insulating brick of the present invention has a thermal conductivity of 2.0 WK －１ I understand －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.

[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. For drying, the mixture was allowed to air dry for 24 hours, then used a batch-type dryer, holding it at 70°C for 24 hours, followed by holding it at 140°C for 48 hours. The dried molded bodies were fired in a batch-type gas oven at 1650°C to obtain alumina spinel-based insulating bricks, which are examples 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]

[0057] Here, hollow alumina particles, sintered alumina particles, and calcined alumina particles of different particle sizes were used as the alumina raw material. In addition, Al was used as the spinel raw material. ２ O ３ Sintered spinel particles containing 70% by mass, Al ２ O ３ Sintered spinel particles and Al containing 90% by mass ２ O ３ Electrofused spinel particles with a content of 70% by mass were used. A 15% aqueous solution of dextrin was used as the binder.

[0058] Also, Al ２ O ３ , MgO and SiO ２ The content (mass%) of SiO was measured in the alumina spinel-based insulating brick using X-ray fluorescence analysis. A ZSX Primus III+ manufactured by Rigaku Corporation 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 brick was in the range of 2 to 8 mass%, and SiO ２ It can be seen that the content is regulated to be less than 1.5% by mass.

[0059]

[0060] <<Comparative Examples>> Alumina spinel-based insulating bricks were obtained in the same manner as in the examples, except that the raw materials were prepared in the proportions shown in Comparative Examples 1 to 6 in Table 1.

[0061] [Evaluation] For each alumina spinel-based insulating brick obtained as an example and comparative example, 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) Moldability The handling properties of the raw horns after molding the refractory raw material following kneading were evaluated. ◎ was used when there were no problems with handling, and ○ was used when the filling of the refractory raw material during molding was slightly insufficient, resulting in grain detachment or minor chipping of the horns when grasping the molded body. As shown in Table 2, it can be seen that in all examples the refractory raw material after kneading had sufficient moldability.

[0063] (2) The corrosion resistance of the corrosion-resistant alumina spinel insulating brick was evaluated by lithium vapor reaction test. As shown in Figure 1, the specimen was convex in shape, with the convex part measuring 80 mm × 80 mm × 16 mm and the back part measuring 95 mm × 95 mm × 14 mm. Li was used as the corrosive agent in a dense alumina sagger. ２ CO ３ Ten grams of the substance were inserted, and the sagger was covered with the specimen. The protruding part 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 covered with the specimen.

[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) Compressive strength The compressive strength of a 50 mm x 50 mm x 50 mm specimen was measured using an Amsler-type strength testing apparatus. The results are shown in Table 2. ○ was used if the strength was 15 MPa or higher, and × if it was less than 15 MPa.

[0066] (4) Thermal conductivity Two specimens measuring 230 mm × 114 mm × 65 mm were measured using the hot-wire method at 1000°C. The results are shown in Table 2. 2.0 Wm －１ K －１ In the following cases, it is ○, 2.0 Wm －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 insulating bricks were measured (JIS R 2614:1985). The results obtained are shown in Table 2.

[0068] As shown in Table 2, in all examples, the expansion coefficient 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 does not contain MgO (Comparative Example 1), SiO ２ When the content of is 1.5% by mass or more (Comparative Example 2), when the MgO content is less than 2% by mass (Comparative Examples 3 and 4), or when the particle size of the spinel particles added to the refractory raw material is too large (Comparative Example 6), the alumina spinel insulating brick does not have 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, it can be seen that 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 I understand －１ The following is the case. 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 2.2 K. －１ I understand －１ That's how it is.

[0071] Based on the above results, in order to obtain an insulating brick that combines excellent lithium resistance and practically sufficient compressive strength, an alumina spinel insulating brick with alumina as the main component should have a spinel particle size of 100 μm or less, contain 2 to 8 mass% of MgO, and contain SiO ２ It can be confirmed that it is extremely important to regulate the content to less than 1.5% by mass.

Claims

1. A refractory raw material mainly composed of alumina and containing 10 to 30% by mass of spinel is used, the particle size of the spinel is 100 μm or less, the MgO content in the refractory raw material is 2 to 8% by mass, and the SiO in the refractory raw material is ２ A method for producing alumina spinel-based heat-insulating bricks, characterized by restricting the content of 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.

2. A method for producing an alumina spinel-based heat-insulating brick according to claim 1, characterized by adding more than 0% by mass and less than 2% by mass of clay to the refractory raw material.

3. It mainly consists of alumina, contains spinel with a particle size of 100 μm or less, contains 2 to 8% by mass of MgO, and SiO ２ Alumina spinel insulating brick characterized by having a content of less than 1.5% by mass.

4. The alumina spinel insulating brick according to claim 3, characterized in that it is used as a lining material for a firing furnace that generates lithium vapor.

5. The alumina spinel thermal insulation brick according to claim 3, characterized in that it has a compressive strength of 15 MPa or more.

6. The bulk density is 1.45 to 2.15, and the thermal conductivity is 2.0 WK. －１ I understand －１ The alumina spinel-based insulating brick according to claim 3, characterized in that it is as follows:

Images