JP2005067930A - Alumina cement, alumina cement composition, and monolithic refractory using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide alumina cement and an alumina cement composition, both of which, when converted into a monolithic refractory, are hardly influenced by a fire-resistant aggregate or an additive used jointly and can be given high strength. <P>SOLUTION: The alumina cement contains calcium aluminate containing calcium hexaaluminate (CaO-6Al<SB>2</SB>O<SB>3</SB>). The alumina cement composition contains α-Al<SB>2</SB>O<SB>3</SB>and calcium aluminate containing calcium hexaaluminate. A monolithic refractory containing the alumina cement or the alumina cement composition and a fire-resistant aggregate is also provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to an alumina cement, an alumina cement composition, and an amorphous refractory using the same, and more specifically, conventional alumina cement, alumina The present invention relates to an alumina cement, an alumina cement composition, and an amorphous refractory using the same, which are characterized by exhibiting higher strength than a cement composition.

In recent years, the use of amorphous refractories has been increasing in refractories used mainly in the steel field such as blast furnaces and electric furnaces. Among amorphous refractories, castables made of alumina cement and refractory aggregate exhibiting hydraulic properties are often used as binders. In particular, castables such as alumina magnesia, alumina spinel, and alumina zirconia are used for lining the ladle. Reasons for using the castable include that special skills are not required, repair can be performed, and a homogeneous structure can be applied.

The castable used as the ladle lining material is a part exposed to high temperatures, so that it is strong enough to withstand the operating temperature, and it prevents the castable from peeling and dropping due to heat cycle. It will lead to longer life of the tension material.

For this reason, it is desired that alumina cement used as a binder also exhibits high strength, dimensional stability, etc. during castable construction.

In particular, it has been reported that the strength of castable can be increased by adding a specific additive to alumina cement as a binder portion and constructing the castable with a low amount of water.
Japanese Patent Laid-Open No. 2000-264685 Japanese Patent Laid-Open No. 2000-351562

  However, castables using the alumina cement compositions described in these documents require specific additives, and other additives may be added to control workability, There was a problem that it was easily affected by the refractory aggregate and the additive used in combination, such as an increase in strength when the particle size was changed.

In order to solve the above problems, the present inventor has made various studies, and as a result, an alumina cement containing calcium aluminate containing calcium hexaaluminate (CaO.6Al ₂ O ₃ ) as a mineral phase, or calcium hexahexa By using an alumina cement composition containing calcium aluminate containing aluminate and α-Al ₂ O ₃ , the inventors have obtained knowledge that the above problems can be solved and completed the present invention.

That is, the present invention is an alumina cement comprising a calcium aluminate containing calcium hexaaluminate (CaO · _6Al 2 _{O 3)} as a mineral phase, the CaO · _6Al 2 _{O 3} content in the calcium aluminate 5-50% by mass of the alumina cement, the alumina cement composition comprising the alumina cement and α-Al ₂ O ₃ , and the alumina cement or the alumina cement composition and a refractory aggregate Is an amorphous refractory containing

The castable using the alumina cement or the alumina cement composition of the present invention has high strength and is suitable not only for the refractory field such as a ladle lining material but also as a lining material for a chemical plant. It is.

The calcium aluminate used in the present invention contains calcium hexaaluminate (CaO · 6Al ₂ O ₃ ), and the CaO · 6Al ₂ O ₃ content is preferably 5 to 50% by mass.

When the content of CaO.6Al ₂ O ₃ is less than 5% by mass, there is no difference in strength from the conventional product, and the effect of the present invention cannot be obtained. On the other hand, when it exceeds 50% by mass, the calcium aluminate exhibiting hydraulic properties is decreased, so that the curing strength and the strength after drying tend to decrease.

Other mineral phases calcium in aluminate to be used in the present invention, _CaO · _Al 2 _O 3 showing the _{hydraulic, CaO · 2Al 2 O 3,} 12CaO · 7Al 2 O 3 and the like, amorphous Presence does not inhibit the effect of the present invention.

The mineral composition in calcium aluminate can be determined by measuring alumina cement by powder X-ray diffractometry and analyzing / quantifying the diffraction pattern by the lead belt method or the like.

  The calcium aluminate used in the present invention is melted or fired in an electric furnace, a reflection furnace, a rotary kiln, etc. using bauxite, high alumina, refined alumina, etc. as an alumina raw material, limestone, quicklime, etc. as a calcia raw material. The resulting calcium aluminate can be used.

In order to obtain the target mineral composition of the present invention, assuming that CaO is C and Al ₂ O ₃ is A according to the description method of the mineral composition in general cement, the CA ₂ -CA ₆ -α-Al ₂ O ₃ composition is obtained. Examples include a method of synthesizing a product at one time, a method of mixing CA ₆ , CA, CA ₂ , C ₁₂ A ₇ and α-Al ₂ O ₃ to obtain a target mineral composition ratio.

When synthesizing at a time, although it is advantageous in terms of cost, since only a three-component system of CA ₂ -CA ₆ -α-Al ₂ O ₃ can be produced, the mineral composition is limited. When individual minerals are produced, the mineral composition can be optimized, but it is disadvantageous in terms of cost, and the production method has advantages and disadvantages.

Α-Al ₂ O ₃ used in the present invention is obtained by firing or melting an alumina source such as aluminum hydroxide or calcined alumina using a firing device such as a rotary kiln or a melting device such as an electric furnace. It is called alumina, calcined alumina, or easily sintered alumina.

In the present invention, calcium aluminate and α-Al ₂ O ₃ can be blended to make an alumina cement composition, and the blending ratio of calcium aluminate and α-Al ₂ O ₃ is 40 to 40 The amount of α-Al ₂ O ₃ is preferably 60 to 0 parts by mass with respect to 100 parts by mass. When the compounding amount of Al ₂ O ₃ is increased, the fire resistance is increased, but the curing strength and the strength after drying are decreased, and the fluidity may be decreased.

In particular, when a magnesia aggregate is blended to form a castable, if the content of α-Al ₂ O ₃ in the alumina cement composition is large, it reacts with magnesia at a high temperature to generate magnesia spinel, and volume expansion Tend.

The mixing method of the alumina cement or the alumina cement composition is not particularly limited, and so-called mixed pulverization in which each mineral is mixed and then pulverized, or pulverized ones may be mixed.

As the pulverizer for the alumina cement or the alumina cement composition, a pulverizer such as a roller mill, a jet mill, a tube mill, a ball mill, or a vibration mill, which is usually used for fine pulverization of a lump, can be used. It is not limited.

The average particle size of the pulverized alumina cement or alumina cement composition is preferably 30 μm or less, more preferably 10 μm or less. If it is larger than 30 μm, strength development may be reduced.

In the present invention, furthermore, as a curing regulator, citric acid, gluconic acid, tartaric acid, malic acid, and salicylic acid or hydroxycarboxylic acids such as sodium salts and potassium salts thereof or salts thereof, polyacrylic acid or salts thereof, polymethacrylic acid or One or two or more additives selected from the group consisting of the salt and a methacrylic acid-acrylic acid copolymer or a salt thereof can be used in combination. 0.05-5 mass parts is preferable with respect to 100 mass parts of alumina cement or an alumina cement composition, and, as for the usage-amount of an additive, 0.2-3 mass parts is more preferable. If the amount is less than 0.05 parts by mass, the water reducing effect is small and the strength is reduced. If the amount exceeds 5 parts by mass, the curing is delayed, and thus the strength tends to be reduced.

  Also, selected from the group consisting of carbonates such as potassium carbonate, sodium carbonate, potassium bicarbonate and sodium bicarbonate, phosphates such as sodium tripolyphosphate, sodium hexametaphosphate and aluminum phosphate, and sodium borate and boric acid It is possible to use one or two or more inorganic salts in combination. 0.05-5 mass parts is preferable with respect to 100 mass parts of alumina cement or an alumina cement composition, and, as for the usage-amount of inorganic salt, 0.2-3 mass parts is more preferable. If the amount is less than 0.05 parts by mass, the water reducing effect is small and the strength is decreased. If the amount exceeds 5 parts by mass, the curing is delayed, and thus the strength tends to decrease.

As the refractory aggregate used in the present invention, fused alumina, sintered alumina, calcined alumina, alumina such as easily sintered alumina, fused magnesia, sintered magnesia, natural magnesia, magnesia such as calcined magnesia, molten Magnesia spinel such as magnesia spinel and sintered magnesia spinel, and ultra fine powder such as silica fume, colloidal silica, calcined alumina, and easily sintered alumina, other fused silica, calcined mullite, chromium oxide, bauxite, andalusite, sillimanite , Chamotte, quartzite, rholite, clay, zircon, zirconia, dolomite, pearlite, vermiculite, brick scrap, earthenware scrap, silicon nitride, boron nitride, silicon carbide, and silicon nitride iron. In addition, it is possible to use alumina / zirconia clinker or the like obtained by melting alumina and zirconia and having improved heat spalling properties.

In particular, in the amorphous refractory of the present invention, it is desirable to use one or more kinds of refractory aggregates selected from alumina, magnesia and ultrafine powder from the viewpoint of fire resistance, durability and corrosion resistance. .

Alumina according to the present invention is obtained by sintering or melting an Al ₂ O ₃ source such as aluminum hydroxide or calcined alumina into a predetermined size by a sintering device such as a rotary kiln or a melting device such as an electric furnace. It is crushed and sieved, and the mineral composition is aluminum oxide indicated as α-alumina, β-alumina, etc., and it is called sintered alumina, calcined alumina, easily sintered alumina, etc. In general, it is preferable to use α-alumina containing 90% by mass or more of Al ₂ O ₃ .

The magnesia according to the present invention is a molten magnesia or sintered magnesia obtained by melting or firing magnesium hydroxide or magnesium carbonate, light-burned magnesia, calcined magnesia, etc., pulverized to a predetermined size and sieved. Is possible.

The particle size of the refractory aggregate is usually 5 to 3 mm, 3 to 1 mm, 1 mm, 200 mesh, 325 mesh or the like depending on the required physical properties.

In the present invention, it is also possible to use ultrafine powder as the refractory aggregate. Ultra fine powder is a refractory fine powder in which particles with a particle size of 10 μm or less occupy 80% by mass or more, and has an average particle size of 1 μm or less and a specific surface area of 10 m ² / g or more by the BET method. When blended with a refractory, fluidity can be ensured and the strength is increased, which is preferable. Specifically, inorganic fine powders such as silica fume, colloidal silica, easily sintered alumina, amorphous silica, zircon, silicon carbide, silicon nitride, chromium oxide, and titanium oxide can be used. , Colloidal silica, and easily sintered alumina are preferred.

The mixing ratio of the alumina cement or the alumina cement composition and the refractory aggregate in the amorphous refractory of the present invention should be determined as appropriate depending on the construction site, and is not particularly limited. Production of ordinary amorphous refractories In accordance with the method, each material is blended so as to have a predetermined blend, and mixed uniformly using a mixer such as a V-type blender, a cone blender, a nauter mixer, a pan-type mixer, and an omni mixer, or a predetermined blend. It is also possible to directly weigh into a kneader when kneading at a ratio of.

Alumina raw material and calcia raw material were blended at a predetermined ratio, fired in a rotary kiln and then allowed to cool to produce several types of calcium aluminate. The prepared calcium aluminates were mixed in a predetermined amount so as to have the mineral composition shown in Table 1, and pulverized with a ball mill so that the average particle size was 6 μm. To 100 parts by mass of the pulverized product, 0.5 part by mass of sodium citrate, 0.5 part by mass of sodium carbonate, and 0.5 part by mass of polyacrylic acid were added. Add 7 parts of alumina cement, 93 parts of refractory aggregate, 0.5 parts by weight of silica fume, 0.15 parts by weight of vinylon fiber, and add water so that the flow value for 4 minutes is 170 ± 10 mm. And kneading for 4 minutes to obtain an amorphous refractory. The materials were kneaded and cured in a constant temperature room at 20 ° C. The produced amorphous refractory was measured for fluidity, pot life, curing time, curing / drying / baking strength, and evaluated for workability and strength development. The results are shown in Table 2.

<Materials used>
Alumina raw material: Sintered alumina powder, commercial calcia raw material: quick lime, commercial refractory aggregate a: commercial sintered alumina particle size 5-3 mm product 17 parts by mass, 3-1 mm product 25 parts by mass, 1-0 mm product 25 mass Part, 200 mesh inferior article 12 parts by mass, 325 mesh inferior article 4 part by mass 4 parts by mass of finely divided alumina having an average particle size of 2 μm, and commercially available sintered magnesia 6 parts by mass
Sodium citrate: Commercial product Sodium carbonate: Commercial product Polyacrylic acid: Commercial product Silica fume: Commercial product, SiO ₂ 98% or more, carbon 1.3% or less Vinylon fiber: Commercial product, vinylon 100%, length 3 mm
Water: tap water

<Measuring method>
Mineral composition: X-ray diffractometer JDX-3500 manufactured by JEOL Ltd. was used, and the diffraction pattern measured by the powder X-ray diffraction method was analyzed by the lead belt method.
Flowability: The flow value of the kneaded material left for 4 minutes and 30 minutes after kneading was measured according to JIS R2521.
Curing time: 500 g of the produced amorphous refractory was transferred to a poly beaker, and the time taken from pouring water to the peak of hydration exotherm was measured with a platinum resistance temperature detector and a dot recording recorder.
Curing strength: The prepared amorphous refractory was placed on a 4 × 4 × 16 cm mold frame while stamping with a stick, and the surface was flattened with a cement knife, and then the compressive strength after curing for 24 hours was measured. .
Dry strength: A cured specimen for curing strength measurement was dried at 110 ° C. for 24 hours, allowed to cool to room temperature, and the compressive strength was measured.
Firing strength: A cured specimen for measuring dry strength was placed in a siliconite electric furnace, heated to 800 ° C. at a rate of 10 ° C./min, held for 3 hours, allowed to cool to room temperature, and measured for compressive strength.

As is apparent from Table 2, the amorphous refractory compounded with the alumina cement of the present invention was higher in strength than the comparative example.

An alumina cement composition was prepared by mixing 100 parts by mass of the pulverized product obtained in Example 1 with the amount of α-Al ₂ O ₃ shown in Table 3, and 0.5 mass of sodium citrate was added to the alumina cement composition. Part, 0.5 parts by weight of sodium carbonate and 0.5 parts by weight of polyacrylic acid were added. Water was added so that the flow value for 4 minutes was 170 ± 10 mm with respect to 7 parts of the prepared alumina cement composition, 93 parts of refractory aggregate, 0.5 parts by weight of silica fume, 0.15 parts by weight of vinylon fiber, The same procedure as in Example 1 was performed except that the mixture was kneaded for 4 minutes with a mortar mixer to obtain an amorphous refractory. The results are shown in Table 3.

As is apparent from Table 3, the amorphous refractory compounded with the alumina cement composition of the present invention has higher strength than the comparative example.

  It carried out similarly to Example 1 except having used the calcium aluminate as shown in Table 4, and a fireproof aggregate. The results are also shown in Table 4.

<Materials used>
Refractory aggregate b: 17-part mass particle size 5 to 3 mm product of commercially available sintered alumina, 25 mass part 3 to 1 mm product, 25 mass part 1 mm inferior product 8 mass part in 200 mesh inferior product 4 mass part in 325 mesh inferior product, average particle diameter A mixed product of 4 parts by mass of finely divided 2 μm alumina and 10 parts by mass of commercially available sintered magnesia.
Refractory aggregate C: Particle size 8 to 5 mm of commercial sintered alumina 10 parts by mass, 12 parts by mass of 1 mm inferior goods 6 parts by mass of 325 mesh ingots, 12 parts by mass of commercially available fused alumina 5 to 3 mm, 16 parts by mass of 3 to 1 mm Parts, 200 mesh vulgarity 8 parts by mass, commercially available synthetic spinel 1 to 0 mm 20 parts by mass, 200 mesh vulgarity 2 parts by mass.

As is apparent from Table 4, the amorphous refractory blended with the alumina cement composition of the present invention is higher than the comparative example not blended with the alumina cement composition of the present invention even when the types of refractory aggregates are different. Strength was obtained.

Claims (5)

An alumina cement containing calcium aluminate containing calcium hexaaluminate (CaO.6Al ₂ O ₃ ) as a mineral phase. Alumina cement according to claim 1, wherein the CaO · _6Al 2 _{O 3} content is characterized in that 5 to 50 mass%. An alumina cement composition comprising the alumina cement according to claim 1 or 2 and α-Al ₂ O ₃ . An amorphous refractory comprising the alumina cement according to claim 1 or 2 and a refractory aggregate. An amorphous refractory comprising the alumina cement composition according to claim 3 and a refractory aggregate.