JP2018108902A - Light-weight heat insulating unshaped refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-weight heat insulating unshaped refractory stably usable from an initial stage of operation to a final stage, by securing strength after curing/drying and heating, and suppressing shrinkage after heating.SOLUTION: A light-weight heat insulating unshaped refractory is such that: an unshaped refractory powder is composed of light-weight particles having CaO 6AlO(CA6) composition, alumina fine powder having a particle diameter of 1 mm or less, and alumina cement; a ratio of a light-weight aggregate of CA6 composition is 30-70 mass%; a ratio of the alumina fine powder is 10-40 mass%; a ratio of the alumina cement is 20-55 mass%; a coarse particle part larger than a particle diameter 1 mm of the unshaped refractory powder is composed of light-weight particles of CA6 composition; a fine powder part of a particle diameter 1 mm or less of the unshaped refractory powder is composed of light-weight particles of CA6 composition, alumina fine powder and alumina cement; a mass ratio of CaO/AlOin the fine powder part of a particle diameter 1 mm or less of the unshaped refractory powder is larger than 0.13 and less than 0.24.SELECTED DRAWING: None

Description

  The present invention relates to a lightweight heat-insulating amorphous refractory material that can be used as a member or a repair material in places that require heat insulation at high temperatures, such as linings and linings of various kilns.

Lightweight heat-insulating amorphous refractories are used in parts that require both high fire resistance and heat insulation, such as steel pipe heating furnaces, soaking pipes for soaking furnaces, and linings. Conventionally, lightweight heat-insulating amorphous refractories using ceramic fibers have been the mainstream in such areas, but in recent years, materials using lightweight aggregates with a CaO.6Al ₂ O ₃ (CA6) composition have been studied. Yes.

Under such circumstances, as shown in Non-Patent Document 1, the CA6 light weight aggregate is a porous particle of CA6 composition and has a bulk specific gravity of about 0.65 to 0.70 g / cm ³ . It is lightweight and can achieve heat insulation performance comparable to ceramic fibers. Moreover, since CA6 as the main component has a high melting point, high fire resistance can be obtained. Non-Patent Document 1 reports a heat-insulating amorphous refractory made of lightweight aggregate SLA-92 (manufactured by Almatis) having a CA6 composition and cement CA-25R (manufactured by Armatis), which is stable to high temperatures. It has high heat insulation performance.
Non-Patent Document 2 discloses a high-heat-resistant heat-insulating castable using a fine porous aggregate having a CA6 composition, and is particularly excellent in slag resistance and has excellent corrosion resistance.

Furthermore, Patent Document 1, a porous insulation aggregate hexagonal crystal CA6 composition and aggregate, in the adiabatic refractory composition obtained by adding a hydraulic alumina as binder, SiO ₂ in the chemical composition of the oxide in terms Is disclosed, characterized in that is less than 0.5% by weight of the total composition.
Patent Document 2 discloses that a porous heat insulating aggregate mainly composed of CaO.6Al ₂ O ₃ accounts for 65% by mass in a coarse particle region having a particle diameter of 1 mm or more in 100% by mass of the coarse particle region. In a fine particle region with a particle size of less than 75 μm, a total of 65% by mass or more of the alumina raw material and alumina cement account for 100% by mass of the fine particle region, and the chemical composition of the fine particle region is CaO. / Al ₂ O ₃ mass ratio = 0.03 to 0.13 of the refractory powder composition, and an amount of 30 to 50% by mass on the basis of 100% by mass of the refractory powder composition An insulated castable refractory comprising construction water is disclosed.
Furthermore, Patent Document 3 uses a porous insulating aggregate of hexagonal crystals having a CaO.6Al ₂ O ₃ composition as an aggregate, and uses an alumina cement and fine alumina powder in a matrix portion, and has a particle size of 1 mm or less. A heat-insulating refractory composition having a CaO / Al ₂ O ₃ mass ratio of 0.24 to 0.32 is disclosed.

JP 2002-179471 A JP 2009-203090 A JP 2014-37327 A

D. van Garsel, A. Buhr, V. Gnauck, G. routschka, GW Kriechbaum, “Long Term High Temperature Stability of Microporous Calcium Hexaluminate Based Insulating Materials”, Proceedings of Unified International Technical Conference on Refractories (UNITECR), (1999), pp.181-186 Yoshihiro Sakamoto, Kazuya Fujita, Toshiya Kikuchi, “Highly heat-resistant insulation castable using fine porous aggregate” Ceramic Data Book 2002 Industry and Products Vol. 30, pp.153-155

However, lightweight heat-insulated amorphous refractories using lightweight aggregates of CA6 composition as in Non-Patent Documents 1 and 2 need to add a large amount of moisture, and the construction of the lightweight aggregate grains themselves is low. There was a problem that the strength of the body was lowered.
In Patent Document 1, it is said that the strength after curing can be increased by using only hydraulic alumina without using alumina cement as a curing agent. There was a problem that the expression intensity was insufficient because it was difficult to proceed.
Furthermore, in Patent Document 2, by controlling the mass ratio of CaO / Al ₂ O _{3 in} the fine particle part, CA6 is crystallized during high-temperature heating so as to improve the strength. However, in order to reduce the CaO ratio in the fine grain part, it is necessary to keep the addition amount of cement small, and there is a problem that the strength of expression after curing and drying is lowered.
Further, in Patent Document 3, by controlling the CaO / Al ₂ O ₃ mass ratio, CaO · 2Al ₂ O ₃ (CA2) is crystallized during high-temperature heating to reduce the thermal expansion coefficient, thereby improving the heat spalling property. Although there is a problem that the shrinkage after heating increases due to the reaction of CA2 generation, especially when cooling is performed for inspection and repair during operation, there is a problem that a large crack is generated. .

  Accordingly, the object of the present invention is to provide a lightweight, heat-insulating amorphous shape that can be used stably from the beginning to the end of operation by securing the strength after curing / drying and after heating and suppressing the shrinkage after heating to a small extent. To provide refractories.

  In order to solve the above problems, the present inventors have intensively studied a lightweight heat-insulating amorphous refractory that can suppress shrinkage after heating while ensuring the strength after curing and drying, and the strength after curing and drying. It was concluded that it is effective to ensure the amount of cement added to a certain extent and to add alumina powder in order to ensure this. By ensuring the amount of cement, the formation of cement gel is sufficient, and by incorporating alumina particles into the cement gel, the crosslinked structure of calcium hydrate becomes strong.

Furthermore, the present inventors have found that the lightweight heat-insulating amorphous refractory having such a configuration is advantageous in terms of strength development during high-temperature heating. That is, it is thought that a so-called ceramic bond grows between the particles due to the formation of a composite oxide of calcium oxide and aluminum oxide when heated at high temperature, and the strength is developed. It is considered that it is advantageous for the development of strength by securing a sufficient amount of alumina and including strong alumina particles in the bond network. Since the crystallization of the CA2 composition mineral leads to an increase in the residual shrinkage after heating, cracking during the cooling process can be prevented by suppressing the CaO / Al ₂ O ₃ mass ratio.
Based on this discovery, the present invention has been achieved.

That is, according to the present invention, the amorphous refractory powder is composed of CA6 composition lightweight particles, alumina fine powder having a particle size of 1 mm or less, and alumina cement, and the proportion of CA6 composition lightweight aggregate is in the range of 30 to 70 mass%. The ratio of the fine alumina powder is in the range of 10 to 40% by mass, the ratio of the alumina cement is in the range of 20 to 55% by mass, and the coarse particle portion having a particle size of 1 mm or more of the irregular refractory powder. Is composed of light-weight grains of CA6 composition, and the fine powder portion of 1 mm or less in particle size of the irregular refractory powder is composed of light-weight particles of CA6 composition, alumina fine powder and alumina cement, and is 1 mm or less of the amorphous refractory powder. The object of the present invention is to provide a lightweight heat-insulating amorphous refractory characterized in that the CaO / Al ₂ O ₃ mass ratio in the fine powder part is in the range of more than 0.13 and less than 0.24.

  The lightweight heat-insulating amorphous refractory of the present invention is characterized by containing other refractory raw materials in an amount of 15% by mass or less as an outer shell with respect to the amorphous refractory powder.

  Furthermore, the lightweight heat-insulating amorphous refractory of the present invention contains one or more additives selected from the group consisting of curing retarders, curing accelerators, anti-explosion agents, thickeners and dispersants. It is characterized by that.

Moreover, the lightweight heat-insulating amorphous refractory of the present invention is characterized in that the content of SiO ₂ is less than 0.5% by mass.

  According to the present invention, the strength after curing and drying of the lightweight heat-insulating amorphous refractory can be ensured, the shrinkage after heating can be kept small, and stable from the beginning to the end of operation. A lightweight heat insulating amorphous refractory that can be used can be provided.

As the CA6 composition lightweight granule used for the lightweight heat-insulating amorphous refractory of the present invention, the CaO / Al ₂ O ₃ mass ratio is in the range of 0.085 to 0.15, preferably 0.09 to 0.12. Use the one in the range. When the CaO / Al ₂ O ₃ mass ratio of the light-weight granules having a CA6 composition exceeds 0.15 or less than 0.085, the content of the CA6 phase is reduced, which leads to insufficient heat insulation performance. Moreover, in order to ensure heat insulation performance, the bulk specific gravity of the lightweight grain of CA6 composition shall be 1 or less, Preferably it shall be in the range of 0.8-1. When the bulk specific gravity of the light-weight grains having a CA6 composition is less than 0.8, the grain strength is insufficient, and the damage of the grains increases during kneading and construction, which is not preferable.

  The amount of the lightweight aggregate having the CA6 composition is 30 to 70% by mass, preferably 35 to 60% by mass, based on the amorphous refractory powder. When the blending amount of the lightweight aggregate having the CA6 composition exceeds 70% by mass, the strength is insufficient, and when it is less than 30% by mass, the heat insulating property is lowered, which is not preferable. In addition, the coarse-grained part larger than the particle size of 1 mm of the irregular refractory powder is composed of light-weight particles having a total CA6 composition.

Next, the alumina cement used in the lightweight heat-insulating amorphous refractory of the present invention has an Al ₂ O ₃ content of 60 to 86% by mass, preferably 68 to 85% by mass, and a CaO content of 14 to 40% by mass, preferably Is within the range of 15 to 32% by mass. If the Al ₂ O ₃ content of the alumina cement is less than 60% by mass, the shrinkage becomes large and unsuitable, and if it exceeds 86% by mass, the curing strength is insufficiently expressed, which is not preferable. Alumina cement has a specific surface area measured by a Blaine method is 3000 cm ² / g or more, preferably used more than 3500 cm ² / g. Here, it is not preferable to use a material having a specific surface area of less than 3000 cm ² / g because the alumina cement does not diffuse uniformly and the development of strength becomes insufficient. As the specific surface area increases, the particle size of the alumina cement decreases, and the particle size of the alumina cement having a specific surface area of 3000 cm ² / g is about 10 μm.

The compounding quantity of an alumina cement is 20-55 mass% of an amorphous refractory powder, Preferably it exists in the range of 25-50 mass%. If the amount of alumina cement is less than 20% by mass, sufficient strength cannot be obtained, and if it exceeds 55% by mass, the shrinkage after high-temperature heating increases, which is not preferable. Incidentally, the SiO ₂ content of lightweight thermal insulating monolithic refractory in increases, since the shrinkage is increased, the SiO ₂ content of lightweight thermal insulating monolithic refractory in less than 0.5 wt%, preferably 0.2 mass Therefore, it is preferable to use an alumina cement having an SiO ₂ content of less than 1% by mass, preferably less than 0.8% by mass.

Alumina fine powder having a particle size of 1 mm or less used for the lightweight heat-insulating amorphous refractory of the present invention is preferably contained in a light-weight heat-insulating amorphous refractory, because if the SiO ₂ content is high, it leads to shrinkage or a decrease in fire resistance. More preferably, the SiO ₂ content is selected to be less than 0.5% by mass, preferably less than 0.2% by mass, and the one not containing SiO ₂ is used. The raw material species is not particularly limited, and various alumina raw materials that can be normally used as refractory raw materials, that is, white fused alumina, brown fused alumina, sintered alumina, calcined alumina, bauxite, clay clay shale, mullite Etc. can be used.

  The compounding quantity of the alumina fine powder with a particle size of 1 mm or less is in the range of 10 to 40% by mass, preferably 15 to 40% by mass of the amorphous refractory powder. When the blending amount of the alumina fine powder having a particle diameter of 1 mm or less is less than 10% by mass, the shrinkage increases, and when it exceeds 40% by mass, the strength after curing is insufficient, which is not preferable.

  In addition, the ratio of the coarse particle part larger than 1 mm in particle size and the fine particle part smaller than 1 mm in particle size constituting the irregular refractory powder is 20 to 70% by mass, preferably 20%. It is in the range of 30 to 80% by mass, preferably 45 to 80% by mass, and fine powder part having a particle size of 1 mm or less. Here, when the ratio of the coarse part larger than 1 mm is more than 70% by mass, the strength is insufficient, and when it is less than 20% by mass, the heat insulating property is lowered, which is not preferable.

Further, the fine powder portion having a particle size of 1 mm or less constituting the irregular refractory powder is composed of a lightweight aggregate having a CA6 composition, alumina cement, and alumina fine powder having a particle size of 1 mm or less. Here, the fine particle part having a particle size of 1 mm or less is the mass of the CaO component derived from the light aggregate and the alumina cement having the CA6 composition, and the Al ₂ O ₃ component derived from the light aggregate having the CA6 composition, the alumina cement and the fine alumina powder. Ratio, CaO / Al ₂ O ₃ mass ratio is greater than 0.13 and less than 0.24, preferably in the range of 0.14 to 0.20. When the CaO / Al ₂ O ₃ mass ratio of the fine particle part having a particle diameter of 1 mm or less is 0.13 or less, the curing strength is insufficient, and when it is 0.24 or more, shrinkage increases, which is not preferable.

Furthermore, the lightweight heat-insulating amorphous refractory of the present invention can be blended with other refractory raw materials in an amount of 15% by mass or less as an outer shell with respect to the amorphous refractory powder. If the blending amount of the other refractory raw materials exceeds 15% by mass, the heat insulating property is lowered, which is not preferable. Other refractory materials include, for example, alumina coarse particles having a particle diameter of 1 mm, and are selected so that the content of SiO ₂ in the lightweight heat-insulating amorphous refractory is less than 0.5% by mass. If the SiO ₂ content of the lightweight heat-insulating amorphous refractory is 0.5% by mass or more, the shrinkage after heating increases, which is not preferable.

Moreover, what can be mix | blended with a normal amorphous refractory as an additive can be suitably mix | blended with the lightweight heat insulation amorphous refractory of this invention. Such additives include, for example, boron oxide, borax, sodium carbonate salts, carboxylic acids, curing retarders such as saccharides as curing modifiers, curing accelerators such as lithium carbonate and slaked lime, and vinylon as explosion inhibitors. Organic fibers such as pulp, metal powder such as aluminum powder, starch, water-soluble alginates, thickeners such as methylcellulose and carboxymethylcellulose, polycarboxylic acids and their alkali metal salts, alkali metal metaphosphates And dispersants such as naphthalenesulfonic acid formalin condensate salt. When these additives are blended, the blending amount is 5% by mass or less, preferably 2% by mass or less, as an outer shell with respect to the amorphous refractory powder. In addition, siliceous raw materials such as silica flour and clay and silicates form a liquid phase at high temperatures, leading to shrinkage and fire resistance reduction. Therefore, 0.5 mass of lightweight heat-insulating amorphous refractory in terms of SiO ₂ It is preferable that the content is less than% and these are not blended.

  In manufacturing the lightweight heat-insulating amorphous refractory according to the present invention, the raw materials can be sufficiently mixed at the above blending ratio. The mixing method is not particularly limited, and for example, a Nauter mixer, an omni mixer, and other mixers having equivalent mixing ability can be used.

  Next, in the construction of the lightweight heat-insulating amorphous refractory of the present invention, the addition of water is basically performed so as to obtain the required workability. It is set within the range of 30 to 70% by mass, more preferably 40 to 60% by mass with respect to the object. If the amount of added water is less than 30% by mass, the heat insulating performance is deteriorated, and if it exceeds 70% by mass, the expression strength is insufficient.

The construction method of the lightweight heat-insulating amorphous refractory of the present invention is not particularly limited, and various irregular refractory construction methods can be applied with property adjustment. That is, techniques such as casting construction, trowel coating construction, patching construction, dry type and wet spraying construction can be adopted. It is also suitable for use as a precast block that is preliminarily molded into a predetermined shape and installed on site. However, a method of applying a strong load with a rammer or the like as in the case of ramming is not suitable because it leads to damage of the lightweight aggregate. After construction, it can be cured and de-framed as necessary, and dried for actual use.

The product of the present invention was prepared at the blending ratio shown in Tables 1 and 2 below, and the comparative product was prepared at the blending ratio shown in Table 3. The raw materials used and evaluation methods are described below.
Raw materials used:
All CA6 composition lightweight aggregates have a CaO / Al ₂ O ₃ mass ratio of 0.10 and a bulk specific gravity of 0.86;
White fused alumina has an Al ₂ O ₃ content of 99% by mass or more and is free of SiO ₂ ;
The calcined alumina has an Al ₂ O ₃ content of 99% by mass or more and is free of SiO ₂ ;
The brown fused alumina has an Al ₂ O ₃ content of 95% by mass and an SiO ₂ content of 1% by mass;
Bauxite has an Al ₂ O ₃ content of 85% by mass and an SiO ₂ content of 8% by mass;
The clay soil shale has an Al ₂ O ₃ content of 85% by mass and an SiO ₂ content of 8% by mass;
Mullite has an Al ₂ O ₃ content of 61% by mass and an SiO ₂ content of 35% by mass;
The alumina cement 1 has an Al ₂ O ₃ content of 52.5% by mass, a CaO content of 37.4% by mass, a SiO ₂ content of 4.8% by mass, a specific surface area measured by the Blaine method of 4000 cm ² / g, Having a diameter of 7 μm or less;
Alumina cement 2 has an Al ₂ O ₃ content of 69.5 mass%, a CaO content of 29.5 mass%, an SiO ₂ content of 0.3 mass%, a specific surface area measured by the Blaine method of 4000 cm ² / g, Having a diameter of 7 μm or less;
The alumina cement 3 has an Al ₂ O ₃ content of 81.0% by mass, a CaO content of 19.0% by mass, a SiO ₂ content of 0.2% by mass, a specific surface area measured by the Blaine method of 4000 cm ² / g, Having a diameter of 7 μm or less;
Methylcellulose was used as an additive.

  The water content in the table is formulated so that sufficient fluidity can be obtained. Here, the flow value is also measured using the apparatus described in JIS R 2521. After the kneaded material is packed in the flow cone, the flow cone is removed upward and left to stand for 30 seconds. The maximum diameter spread and the direction perpendicular to this were measured with calipers, and the average value was taken as the free flow value. Water was added so that the free flow value was 200 to 250 mm.

Evaluation of heat shrinkage:
The evaluation of the heat shrinkage was performed based on the residual line change rate. The residual line change rate was measured based on JIS R 2554, and the specimen was heated at 1500 ° C. for 3 hours. Evaluation is the absolute value of the negative linear change rate as the shrinkage rate, the shrinkage rate is less than 1.0%, 0.8% or more is “△”, less than 0.8% is “◯”, Those with 1.0% or more were marked “x”.
Strength evaluation:
The strength was evaluated based on JIS R 2553 with the bending strength measured with a Michaelis double-lever bending tester. As the specimen, those dried at 110 ° C. for 24 hours and those dried at 1500 ° C. for 3 hours after drying were used. Evaluation of the specimen after drying at 110 ° C. for 24 hours is “△” when the bending strength is 1.7 MPa or more and less than 2.0 MPa, “◯” when the bending strength is 2.0 MPa or more, and less than 1.7 MPa. It was set as “x”.
Thermal insulation evaluation:
Bulk specific gravity was used as an index of heat insulation performance. The bulk specific gravity was measured by a vacuum method using white kerosene as a medium based on JIS R 2205. A specimen heated at 1500 ° C. for 3 hours was used. A bulk specific gravity of less than 1.3 and not less than 1.2 was designated as “Δ”, a matter having a bulk specific gravity of less than 1.2 was designated as “◯”, and a specimen having a bulk specific gravity of 1.3 or more as “x”.
Comprehensive evaluation:
The final evaluation is that all the shrinkage, strength and thermal insulation evaluations are “Excellent” if one is “Excellent”, “Inferior” if one or more “X”, and “Good” otherwise. It was judged that those with a good evaluation of “excellent” or “good” satisfied the criteria of the present invention.

In the said table | surface, all of this invention products 1-21 were favorable also in shrinkage | contraction, intensity | strength, and heat insulation, and satisfy | filled the reference | standard.
On the other hand, the comparative product 1 was unsuitable because the bulk specific gravity was high and the heat insulating property was insufficient because the blending amount of the lightweight aggregate having the CA6 composition was small;
Comparative product 2 was unsuitable due to the lack of strength due to the large amount of CA6 composition lightweight aggregate;
Comparative product 3 was unsuitable because the amount of alumina cement was small and the strength after drying was insufficient.
Since the amount of the comparative product 4 and the alumina cement was large, the shrinkage was too large and was inappropriate.
Since the comparative product 5 had a large SiO ₂ content, the shrinkage was large and was inappropriate.
The comparative product 6 was also unsuitable because of its large SiO ₂ content and thus large shrinkage.
Since the amount of the alumina fine powder was small, the comparative product 7 had low strength after heating and was unsuitable.
Since the comparative product 8 had a small CaO / Al ₂ O ₃ mass ratio in the fine powder part having a particle diameter of 1 mm or less, the strength after drying was insufficient and was unsuitable.
Since the comparative product 9 had a large CaO / Al ₂ O ₃ mass ratio in the fine powder part having a particle diameter of 1 mm or less, it was unsuitable due to increased shrinkage and insufficient strength after heating.
Since the comparative product 10 is blended with 30% by mass of white fused alumina having a particle size larger than 1 mm as other refractory raw material, the bulk specific gravity becomes too large and the heat insulation is reduced. It was inappropriate.

Claims (4)

The amorphous refractory powder is composed of CaO · 6Al ₂ O ₃ composition lightweight aggregate, alumina fine powder having a particle size of 1 mm or less and alumina cement, and the proportion of CaO · 6Al ₂ O ₃ composition lightweight aggregate is 30 to 70. It is in the range of mass%, the proportion of fine alumina powder is in the range of 10 to 40 mass%, the proportion of alumina cement is in the range of 20 to 55 mass%, and the particle size of the amorphous refractory powder is 1 mm. larger coarse grain portion is made of a lightweight aggregate of CaO · _6Al 2 _{O 3} composition, lightweight aggregates of fines of a particle size less than 1mm monolithic refractory powder CaO · _6Al 2 _{O 3} composition, fine alumina powder A light weight characterized in that the CaO / Al ₂ O ₃ mass ratio in the fine powder portion of 1 mm or less of the amorphous refractory powder is greater than 0.13 and less than 0.24. Refusal And to provide a monolithic refractory.   The lightweight heat-insulating amorphous refractory according to claim 1, wherein the other refractory raw material is contained in an amount of 15% by mass or less as an outer shell with respect to the amorphous refractory powder.   The lightweight heat-insulating amorphous fireproofing of Claim 1 or 2 containing the 1 type (s) or 2 or more types of additive selected from the group which consists of a hardening retarder, a hardening accelerator, an explosion prevention agent, a thickener, and a dispersing agent. object. The lightweight heat-insulating amorphous refractory according to any one of claims 1 to 3, wherein the content of SiO _{2 in} the light-weight heat-insulating amorphous refractory is less than 0.5% by mass.