Low-cement monolithic refractory and method of use thereof

Abstract

The present invention provides a monolithic refractory that can effectively suppress the penetration of alkaline salts in a combustion furnace where an atmosphere containing a large amount of acid, alkaline components, and alkaline salts is formed, and a method for using the monolithic refractory. [Solution] A low-cement monolithic refractory material containing refractory raw materials and alumina cement as main raw materials, with 1-10 mass% BaSO4 as an outer percentage relative to 100 mass% of the main raw materials, characterized in that it is used in a combustion furnace in which an atmosphere containing alkali salts is formed inside the furnace. The BaSO4 content is preferably 3-5 mass%.

Description

[Technical Field]

[0001] The present invention relates to a monolithic refractory used in an atmosphere containing alkali salts, such as a secondary combustion furnace such as a waste melting furnace or an incinerator, and a method for using the same. [Background technology]

[0002] In secondary combustion furnaces, such as waste melting furnaces and incinerators, an atmosphere containing a large amount of acid, alkaline components, and alkaline salts is formed. Furthermore, the temperature inside the furnace reaches approximately 1000°C, creating harsh conditions that favor the formation of low-density sodarite-based minerals. Refractories used under such harsh conditions are prone to spalling and other spalling damage, making it necessary to improve their resistance to alkaline salt penetration.

[0003] In response to this, attempts have been made to improve the corrosion resistance of refractories by adding silicon carbide (SiC) or barium sulfate (BaSO4), but it is known that depending on the amount added and the environment in which it is used, SiC can oxidize and accelerate damage to the refractory.

[0004] Regarding the addition of BaSO4, for example, Patent Document 1 (JP 2006-182576 A) describes a method for providing a castable refractory that is excellent in heat insulation, spalling resistance, and strength characteristics, can suppress the penetration of molten metal such as aluminum, and can be suitably used in the melting and casting of non-ferrous metals such as aluminum, by adding fine alumina powder having a particle size of 10 μm to 100 μm and fine silica powder having a particle size of 1 μm or less to an aggregate made of fused silica containing 95% or more of SiO2 and having a particle size of 20 mm or less. and a powdered raw material made of alumina cement having a particle size of 20 μm or more and 100 μm or less, an infiltration inhibitor made of at least one powder selected from lead oxide, barium oxide, barium sulfate, germanium oxide, and iron oxide, and at least one dispersant selected from condensed sodium phosphate, naphthalene sulfonic acid-based, and polycarboxylic acid-based dispersants, wherein the aggregate is blended in an amount of 60% by weight or more and 85% by weight or less based on the total amount of the aggregate, powdered raw material, and infiltration inhibitor.

[0005] In the castable refractory described in Patent Document 1, it is said that by adding an infiltration inhibitor with low surface tension such as barium sulfate, it is possible to prevent molten aluminum, aluminum alloys, and other non-ferrous metals from penetrating into the refractory, and also to prevent contamination of the molten metal due to erosion, peeling, or chipping of the refractory. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-182576 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the above Patent Document 1, the purpose of using refractories in aluminum melting furnaces and the like is to prevent penetration and erosion by molten aluminum.In contrast, in secondary combustion furnaces such as waste melting furnaces and incinerators, improved alkali salt resistance is required in environments containing large amounts of acid, alkali components, and alkali salts, and it is necessary to consider penetration resistance of a type and mechanism completely different from that of the above Patent Document 1.

[0008] That is, currently, there is no suitable monolithic refractory that can effectively inhibit the penetration of alkaline salts in a combustion furnace where an atmosphere containing a large amount of acid, alkaline components and alkaline salts is formed.

[0009] In view of the problems in the prior art as described above, the object of the present invention is to provide an unshaped refractory that can effectively suppress the penetration of alkaline salts in a combustion furnace in which an atmosphere containing a large amount of acid, alkaline components, and alkaline salts is formed, and a method for using the unshaped refractory. [Means for solving the problem]

[0010] In order to achieve the above-mentioned object, the inventors have conducted extensive research into the composition of monolithic refractories and their methods of use, and as a result have discovered that adding an appropriate amount of BaSO4 to low-cement monolithic refractories is extremely effective, thereby arriving at the present invention.

[0011] That is, the present invention provides: It contains refractory raw materials and alumina cement as its main raw materials, The main raw material contains 1 to 10 mass% of BaSO4 in an outer percentage, It is used in a combustion furnace in which an atmosphere containing an alkali salt is formed. The present invention provides a low-cement monolithic refractory characterized by:

[0012] The greatest feature of the present invention is that an appropriate amount of BaSO4 is added to a low-cement monolithic refractory used in a combustion furnace that requires resistance to alkaline salts. The temperature inside a secondary combustion furnace such as a waste melting furnace or incinerator is raised to about 1000°C, creating a harsh environment in which an atmosphere containing large amounts of acid, alkaline components, and alkaline salts is formed. However, by adding an appropriate amount of BaSO4 to a low-cement monolithic refractory, it is possible to significantly improve the resistance to alkaline salts.

[0013] More specifically, BaSO4, components of the low-cement monolithic refractory, and components contained in the material being treated in the combustion furnace react to produce glass, which can suppress the penetration of alkali salts into the combustion furnace.

[0014] In the low-cement monolithic refractory of the present invention, the content of BaSO4 (outer percentage content relative to the main raw material) is preferably 3 to 5 mass%. By more strictly specifying the content of BaSO4, it is possible to more reliably improve the alkali salt resistance of the low-cement monolithic refractory while suppressing the occurrence of cracks.

[0015] In the low-cement monolithic refractory of the present invention, the main component of the refractory raw material is preferably any one of Al2O3, SiO2, Cr2O3, SiC, ZrO2, and MgO, or a combination thereof. By using these components as the main components of the low-cement monolithic refractory, it is possible to impart heat resistance and mechanical properties suitable for use in combustion furnaces.

[0016] Furthermore, the low-cement monolithic refractory of the present invention is preferably an Al2O3-SiO2 refractory or an Al2O3-SiO2-SiC refractory. By incorporating BaSO4 into the Al2O3-SiO2 refractory or Al2O3-SiO2-SiC refractory, Ba reacts with SiO2 and halogens such as F originating from materials treated in a combustion furnace, thereby efficiently producing glass components.

[0017] Furthermore, the low-cement monolithic refractory of the present invention is preferably a castable refractory. Castable refractories have a high degree of freedom in mix design, and the type and particle size of refractory aggregate and the type and amount of binder can be finely adjusted depending on the equipment used, allowing the properties required for a lining material of a combustion furnace to be selectively imparted. In addition, castable refractories can be easily mechanized in construction work, making it possible to reduce the labor required for furnace construction work and the burden on construction workers.

[0018] The present invention also provides The low-cement monolithic refractory of the present invention is used as a lining material for a combustion furnace in which an atmosphere containing an alkali salt is formed, reacting components contained in the low-cement monolithic refractory with components contained in the material to be treated in the combustion furnace to produce glass; The glass prevents alkali salts from penetrating into the combustion furnace; Also provided is a method for using the low-cement monolithic refractory material.

[0019] In the method of using the low-cement monolithic refractory of the present invention, by using the low-cement monolithic refractory of the present invention as a lining material for a combustion furnace in which an atmosphere containing alkali salts is formed, the effect of improving alkali salt resistance due to the generation of glass can be efficiently utilized.

[0020] Furthermore, in the method for using the low-cement monolithic refractory of the present invention, it is preferable to produce the glass by reacting Ba contained in the low-cement monolithic refractory with SiO contained in the low-cement monolithic refractory and / or halogen such as F originating from the treated material. By reacting Ba contained in the low-cement monolithic refractory with SiO contained in the low-cement monolithic refractory and / or halogen such as F originating from the treated material, it is possible to stably produce glass that contributes to improving alkali salt resistance. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide an amorphous refractory that can effectively suppress the penetration of alkaline salts in a combustion furnace where an atmosphere containing a large amount of acid, alkaline components, and alkaline salts is formed, and a method for using the amorphous refractory. DETAILED DESCRIPTION OF THE INVENTION

[0022] Representative embodiments of the low cement monolithic refractory of the present invention and its method of use will be described in detail below, but the present invention is not limited to these.

[0023] 1. Low-cement monolithic refractories The low-cement monolithic refractory of the present invention contains a refractory raw material and alumina cement as main raw materials, contains 1 to 10 mass% BaSO4 as an outer percentage relative to 100 mass% of the main raw materials, and is characterized by being used in a combustion furnace in which an atmosphere containing an alkali salt is formed inside the furnace. Each component will be described in detail below.

[0024] (1) Main ingredients (1-1) Refractory raw materials The main component of the refractory raw material is preferably any one of Al2O3, SiO2, Cr2O3, SiC, ZrO2, and MgO, or a combination thereof. Here, the type of raw material containing each component is not particularly limited as long as it does not impair the effects of the present invention, and various raw materials conventionally known as raw materials for monolithic refractories can be used. Furthermore, the particle size of the raw material is not particularly limited as long as it does not impair the effects of the present invention, and it is sufficient to perform appropriate particle size adjustment.

[0025] It is more preferable to use mullite (Al2O3-SiO2) and / or cristobalite (SiO2) as the refractory raw material, or to use a mixture of mullite (Al2O3-SiO2) and / or cristobalite (SiO2) with SiC as the refractory raw material. By incorporating BaSO4 into an Al2O3-SiO2 refractory or an Al2O3-SiO2-SiC refractory, Ba reacts with SiO2 and halogens such as F originating from the material being treated in the combustion furnace, thereby efficiently producing glass components.

[0026] (1-2) Alumina cement An appropriate amount of alumina cement (hydraulic cement whose main constituent compound is calcium aluminate) is added to the main raw material. The amount of alumina cement added to the main raw material is not particularly limited as long as it does not impair the effects of the present invention, but is preferably 2 to 7 mass %, more preferably 3 to 6 mass %, and most preferably about 5 mass %.

[0027] While typical castable refractories contain 10% by mass or more of alumina cement as a binder, the low-cement monolithic refractory of the present invention has an upper limit of the alumina cement content in the main raw material of about 7% by mass. As a result, the deterioration of mechanical properties due to the decrease in the melting point of alumina cement in the usage environment (high-temperature environment) is suppressed, and the monolithic refractory is endowed with excellent heat resistance. On the other hand, by including 2% by mass or more of alumina cement in the main raw material, it is possible to impart good mechanical properties such as strength to the monolithic refractory.

[0028] (2) Essential additives The essential added component is barium sulfate (BaSO4), and 1 to 10 mass% of BaSO4 is added in outer percentage to 100 mass% of the main raw material.

[0029] By including 1 mass% or more of BaSO4, it is possible to supply a sufficient amount of Ba component necessary for producing glass. On the other hand, by setting the BaSO4 content to 10 mass% or less, it is possible to suppress the tendency to melt and the occurrence of cracks due to shrinkage. The amount of BaSO4 added is preferably 3 to 5 mass%.

[0030] (3) Optional additives A dispersant may be added to improve the dispersibility of the alumina cement and other additive components in the refractory raw materials and to improve the fluidity of the low-cement monolithic refractory. The amount of dispersant added may be adjusted appropriately depending on the composition of the low-cement monolithic refractory, and may be, for example, 0.01 to 0.5% by weight in outer percent.

[0031] The dispersant is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known dispersants used in monolithic refractories may be used. Examples of the dispersant include appropriate organic acid salts and condensed phosphates. An appropriate amount of water may also be added.

[0032] In addition, the additive component is not particularly limited as long as it does not impair the effects of the present invention, and various additive components conventionally known to be added to monolithic refractories can be used. For example, an SiO component such as microsilica can be added as an optional additive component.

[0033] The low-cement monolithic refractory of the present invention has the above-mentioned composition, and therefore has extremely excellent resistance to alkaline salts, and is used in a combustion furnace in which an atmosphere containing alkaline salts is formed inside the furnace.

[0034] The low-cement monolithic refractory of the present invention can be used in all combustion furnaces in which an atmosphere containing alkaline salts is formed inside the furnace at high temperatures, and can be used as a refractory for secondary combustion furnaces such as waste melting furnaces and incinerators.

[0035] The low-cement monolithic refractory of the present invention is preferably a castable refractory. Castable refractories have a high degree of freedom in mix design, allowing the type and particle size of refractory aggregate and the type and amount of binder to be finely adjusted depending on the equipment used, and the properties required for a lining material of a combustion furnace can be selectively imparted. In addition, castable refractories can be easily mechanized in construction work, making it possible to reduce the labor required for furnace construction work and the burden on construction workers.

[0036] 2. How to use low-cement monolithic refractories The low-cement monolithic refractory of the present invention is used in a combustion furnace in which an atmosphere containing alkaline salts is formed inside the furnace, and by using it as a lining material for the combustion furnace, the alkaline salt resistance of the combustion furnace can be efficiently and effectively improved.

[0037] More specifically, the low-cement monolithic refractory of the present invention is used as a lining material for a combustion furnace in which an atmosphere containing alkaline salts is formed, and the components contained in the low-cement monolithic refractory are reacted with the components contained in the material to be treated in the combustion furnace to produce glass, which can suppress the penetration of alkaline salts into the combustion furnace.

[0038] Furthermore, in the method for using the low-cement monolithic refractory of the present invention, it is preferable to produce glass by reacting Ba contained in the low-cement monolithic refractory with SiO contained in the low-cement monolithic refractory and / or halogen such as F originating from the treated material. By reacting Ba contained in the low-cement monolithic refractory with SiO contained in the low-cement monolithic refractory and / or halogen such as F originating from the treated material, glass that contributes to improving alkali salt resistance can be stably produced.

[0039] In addition, the produced glass reacts with alkalis and alkaline earth elements such as Na originating from the treated material, producing more glass, which makes it possible to more reliably suppress the penetration of alkali salts into the combustion furnace.

[0040] Representative embodiments of the present invention have been described above, but the present invention is not limited to these, and various design modifications are possible, all of which are included in the technical scope of the present invention. [Example]

[0041] Example The raw materials were prepared in the proportions shown in Table 1 as Examples 1 to 5, kneaded in a high-speed mixer, poured into a mold, cured at room temperature for 24 hours, and then dried at 110°C for 24 hours to obtain low-cement monolithic refractories according to the present invention. The values ​​in Table 1 show mass %, and the values ​​for the refractory raw materials and alumina cement are the proportions of each raw material in the main raw materials, while the other values ​​are the proportions of the outer percentage relative to 100% by mass of the main raw materials.

[0042] [Table 1]

[0043] Comparative Example Comparative low-cement monolithic refractories were obtained in the same manner as in the Examples except that the raw materials were adjusted in proportions shown in Table 1 as Comparative Examples 1 to 5.

[0044] The alkali salt resistance of each low-cement monolithic refractory obtained as an example and a comparative example was evaluated. A crucible test was used to evaluate the alkali salt resistance. Specifically, two crucible samples were prepared by drilling a hole of 30 mm diameter and 30 mm depth in the center of a 60 mm × 60 mm × 60 mm low-cement monolithic refractory.

[0045] The crucible sample was dried at 110°C for 24 hours, and then 15g of an erosion agent made of a 1:1:1 mixture of Na2CO3:Na2SO4:KCl was inserted into the hole of the crucible sample. The hole was then covered and heated at 1000°C for 10 hours, after which the condition of the crucible sample was checked.

[0046] The crucible samples were evaluated as follows: ◎ if no cracks were observed, ◯ if almost no cracks were observed, △ if many cracks were observed or if there was a tendency for softening and dissolution, and × if there were many cracks and also some collapsed areas, and the results are shown in Table 1. Note that two crucible samples were evaluated for each low-cement monolithic refractory, so Table 1 shows two evaluation results.

[0047] As shown in Table 1, in all Examples, the low-cement monolithic refractories had excellent alkali salt resistance. In particular, in Example 2, in which the BaSO4 content was 3 mass%, and Example 3, in which the BaSO4 content was 5 mass%, no cracks occurred. In contrast, in the Comparative Examples, cracks and the like were observed in the low-cement monolithic refractories, resulting in erosion of the low-cement monolithic refractories by alkali salts. These results indicate that the addition of less than 1 mass% BaSO4 does not improve the alkali salt resistance of the low-cement monolithic refractories, and that the addition of more than 10 mass% BaSO4 leads to a tendency for melting and the occurrence of cracks due to shrinkage.

[0048] From the above results, it can be seen that the use of low-cement monolithic refractories containing 1 to 10 mass% BaSO4 per 100 mass% of the main raw material is extremely effective in suppressing the penetration of alkaline salts in combustion furnaces, where an atmosphere containing a large amount of acid, alkaline components, and alkaline salts is formed.

Claims

1. A low-cement monolithic refractory is used as a lining material for a combustion furnace in which an atmosphere containing alkaline salts is formed inside the furnace, reacting components contained in the low-cement monolithic refractory with components contained in the material to be treated in the combustion furnace to produce glass; The glass prevents alkali salts from penetrating into the combustion furnace; The low cement monolithic refractory material is an Al 2 O 3 —SiO 2 refractory material or an Al 2 O 3 —SiO 2 —SiC refractory material, The main raw materials are a refractory raw material and alumina cement, and BaSO 4 is contained in an outer percentage of 1 to 10 mass % relative to 100 mass % of the main raw materials. A method for using a low-cement monolithic refractory material characterized by the above.

2. The content of BaSO 4 is 3 to 5 mass %, 2. A method for using the low cement monolithic refractory material according to claim 1,

3. Ba contained in the low cement monolithic refractory and SiO contained in the low cement monolithic refractory ２ and / or F originating from the treated material to produce the glass; 3. A method for using the low cement monolithic refractory material according to claim 1 or 2.

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