JP4459882B2 - Alumina cement composition and amorphous refractory using the same - Google Patents

Description

The present invention relates to an alumina cement composition capable of maintaining fluidity for a long time and exhibiting high strength in construction in a high temperature atmosphere of 30 ° C. or higher as compared with a conventional alumina cement composition.

Conventionally, alumina cement or an alumina cement composition is widely used as a binder for amorphous refractories because of its excellent fire resistance. One of the construction methods for amorphous refractories is so-called casting construction, in which an amorphous refractory mixed with alumina cement, refractory aggregate, and water is poured into the formwork, but the influence of construction temperature during casting. There was a case. In particular, in construction in a high temperature atmosphere at 30 ° C. or higher, there were problems such as filling and casting failure, and the strength of the construction body after drying was reduced.

Therefore, various additives are used in order to ensure sufficient filling and casting time. Non-patent document 1 is cited as a document that describes the basic properties of the mineral composition of alumina cement and the types of additives.
'HIGH ALUMINA CEMENT AND CONCRETES. ', T. D. ROBSON, CONTRACTORS RECORD LIMITED, 1962

However, if you add an amorphous refractory with a curing retarder added for use in the summer and adjust the curing time, for example, when it is applied at a lower temperature than expected, such as around autumn, the curing time will be longer, There was a problem that the strength development was reduced and the schedule after curing was delayed, such as unframed and dried.

In order to solve these problems, it contains an alumina cement composition obtained by blending hydroxycarboxylate and the like with alumina cement, an alumina cement composition obtained by blending inorganic carbonate and the like, and polymethacrylic acid and the like. An alumina cement composition to which various additives are added, such as an alumina cement composition is proposed.
Japanese Patent Publication No. 6-32639 Japanese Patent Publication No. 6-32640 Japanese Patent Publication No.7-61844 Japanese Patent Publication No. 8-259301 Japanese Patent Publication No.8-40757

These additives vary greatly in action depending on the combination and amount of additives used, and the mineral composition of the hydraulic component, and are applied at a particularly high temperature in the steel field, including refractory, ironmaking and steelmaking facilities. If so, it was not enough.

As a result of various studies, the present inventor has obtained knowledge that the above problem can be solved by combining a clinker having a specific mineral composition and a specific additive, and has completed the present invention.

That is, the present invention includes 12CaO · 7 Al ₂ O ₃ 2 to 12% by mass, CaO · Al ₂ O ₃ , CaO · 2 Al ₂ O ₃ , and an alumina cement containing amorphous material, alumina as an additive, An alumina cement composition comprising carboxylic acid and / or a salt thereof, carbonate, and polyacrylic acid and / or a salt thereof, wherein the chemical component of the alumina cement is CaO 22 to 32% by mass, Al ₂ O _{3 The} above-mentioned alumina cement composition, which is 68 to 78% by mass and contains 70 to 50 parts by mass of alumina cement cement and 30 to 50 parts by mass of alumina in a total of 100 parts by mass .

The alumina cement further comprising 1.0 to 2.0% by mass of carboxylic acid and / or salt thereof, 0.2 to 1.0% by mass of carbonate, and 0.5 to 1.5% by mass of polyacrylic acid and / or salt thereof. The alumina cement composition, wherein the carboxylic acid and / or salt thereof is citric acid and / or citrate, the carbonate is sodium carbonate, and the polyacrylate is sodium polyacrylate. Yes, it is an amorphous refractory containing the alumina cement composition and a refractory aggregate.

The amorphous refractory using the alumina cement composition of the present invention has high fluidity and high strength even in construction in a high temperature atmosphere of 30 ° C. or higher. The alumina cement composition of the present invention is suitable not only for the refractory field, but also as a lining material and corrosion resistant material for chemical plants that require high fluidity, corrosion resistance, and wear resistance at high temperatures.

The alumina cement according to the present invention includes CaO · Al ₂ O ₃ (hereinafter referred to as “CA” according to the description method of the mineral composition of the cement), CaO · 2Al ₂ O ₃ (hereinafter referred to as “CA ₂ ”) _, 12CaO · 7Al ₂ O ₃ (hereinafter referred to as “C ₁₂ A ₇ ”) as well as amorphous material, and chemical components of CaO 22 to 32 mass% and Al ₂ O ₃ 68 to 78 mass% Is preferred.

The alumina cement clinker according to the present invention is a high-purity alumina obtained by refining natural raw materials such as red bauxite by a purification method such as a buyer process, an Al ₂ O ₃ source such as bauxite, and a CaO such as limestone and quicklime. The source is blended so as to have a predetermined component ratio, and is obtained by melting or firing in equipment such as an electric furnace, a reflection furnace, a vertical furnace, a flat furnace, a shaft kiln, and a rotary kiln.

As a method of obtaining the target mineral composition of alumina cement, a method of synthesizing CA-CA ₂ -C ₁₂ A ₇ composition at a time, a method of blending CA, CA ₂ and C ₁₂ A ₇ in a predetermined ratio, Examples thereof include a method of synthesizing a CA-CA ₂ composition at a time and blending C ₁₂ A ₇ at a predetermined ratio.

The mixing of the alumina cement may be performed after mixing the clinker and may be pulverized, or each pulverized product may be mixed, and the means for obtaining the target mineral composition ratio is not particularly limited.

The alumina cement according to the present invention includes 2CaO.Al ₂ O ₃ .SiO ₂ (hereinafter referred to as “C ₂ AS”) produced from unavoidable impurities in the raw material in addition to the target CA, CA ₂ and C ₁₂ A _7. ), CaO.TiO ₂ (hereinafter referred to as “CT”), 4CaO.Al ₂ O ₃ .Fe ₂ O ₃ (hereinafter referred to as “C ₄ AF”), and the like. There is no problem as long as the effect is not disturbed. The amount of impurities in the alumina cement is preferably small, and is preferably 2.5% by mass or less. If the amount of impurities is large, the volume change during high-temperature construction of the amorphous refractory using the alumina cement composition of the present invention increases, filling or casting failure may occur, or corrosion resistance to slag may be reduced. is there.

Alumina cement according to the present invention include _{CA, CA 2, C 12 A} 7, and an amorphous. Otherwise, for example, in an irregular refractory compounded with basic aggregates such as magnesia, it will be difficult to secure fluidity and pot life, especially at high temperatures, and filling and casting defects will occur. In some cases, the strength of the body decreases, and so on.

When the alumina cement of the present invention is produced by a firing method, an Al ₂ O ₃ source and a CaO source are mixed or mixed and ground at a predetermined ratio, and fired at a temperature of 1300 ° C. or higher in a rotary kiln. The firing temperature is generally preferably 1400-1600 ° C.

When the alumina cement of the present invention is produced by a melting method, the Al ₂ O ₃ source and the CaO source are mixed or mixed and pulverized at a predetermined ratio, and the melting device such as an electric furnace or a flat furnace is 1500 ° C. or higher, preferably 1600 to After melting at a temperature of 1800 ° C., it is generally cooled by contacting with high-pressure air or the like.

The amorphous content in the alumina cement of the present invention is preferably 18 to 28% by mass. If the amorphous content exceeds 28%, the fluidity at high temperatures may decrease, or the pot life may be shortened. On the other hand, if the amorphous content is less than 18% by mass, there may be a delay in curing and work efficiency may be reduced. The amorphous amount can be quantified using, for example, the Rietveld method by adding quartz to a sample as a standard substance and measuring the X-ray diffraction.

The pulverization of the alumina cement clinker according to the present invention is not particularly limited, and is usually used for fine pulverization of a powder lump, for example, a pulverizer such as a roller mill, a jet mill, a tube mill, a ball mill, a vibration mill or the like is used. Is possible.

Blaine specific surface area of the milled alumina cement is preferably ^{3000~12000cm 2 / g, 4000cm 2 /} g~10000cm 2 / g is more preferable. 3000 cm ^{2 /} is less than g reduces the strength development, whereas exceeding 12000 ^{2 /} g, there is a case where the flowability is decreased.

Alumina as an additive according to the present invention is purified alumina obtained by firing aluminum hydroxide that has been highly purified by a buyer process or the like in a rotary kiln, and contains 95% by mass or more of Al ₂ O _3. It is a pure alumina. In general, it is called high-purity alumina, buyer alumina, easily sintered alumina, or light-burned alumina.

The content of Na ₂ O as an impurity is particularly important for alumina as an additive according to the present invention. When the amount of Na ₂ O is large, the flowability and fire resistance of the amorphous refractory using the alumina cement composition of the present invention may be lowered, or the amount of shrinkage at high temperatures may be increased. The amount of Na ₂ O is preferably 0.5% by mass or less, and more preferably 0.35% by mass or less.

In the present invention, an alumina cement clinker and alumina as an additive are blended and mixed and pulverized by a pulverizer. Alternatively, the alumina as an additive is pulverized to the same particle size as the alumina cement clinker alone, and then the clinker pulverized product. It is also possible to mix with.

The mixing ratio of alumina cement and alumina is preferably 30 to 50 parts by mass of alumina with respect to 70 to 50 parts by mass of alumina cement. When the amount of alumina exceeds 50 parts by mass, fire resistance increases, but curing strength and strength after drying may decrease, and fluidity may also decrease. On the other hand, if it is less than 30 parts by mass, the fire resistance may not be improved.

In the present invention, carboxylic acid and / or its salt, carbonate, and polyacrylic acid and / or its salt are used as additives.

Examples of the carboxylic acid and / or salt thereof according to the present invention include oxycarboxylic acid such as citric acid, tartaric acid, succinic acid, lactic acid and gluconic acid, and / or a salt thereof. Of these, citric acid and / or alkali metal salts thereof are preferred, and among these, use of citric acid and / or sodium citrate is preferred. The particle size of the carboxylic acid or a salt thereof is preferably as fine as possible so that it can be easily dissolved in water when mixed with cement, and is preferably 100 mesh or less, particularly preferably 200 mesh or less. The purity of the carboxylic acid or a salt thereof is not particularly limited, but currently industrially purified carboxylic acid or a salt thereof can be used, and a purity of about 80% by mass or more is preferable. Among them, citric acid and / or its alkali metal salt whose sulfate is 0.05 mass% or less as an impurity, citric acid and / or its alkali metal salt whose pH of 1 mass% aqueous solution at 20 ° C. is in the range of 7 to 10 are used. It is preferable that the pot life is long and the workability is excellent. The content of the carboxylic acid and / or salt thereof of the present invention is preferably 1.0 to 2.0% by mass in the alumina cement composition. If the content of the carboxylic acid and / or salt thereof is less than 1.0% by mass, the water reducing effect tends to be low, or the pot life tends to be short. On the other hand, if the content exceeds 2.0% by mass, curing occurs when the temperature decreases. There is a tendency to delay and decrease the strength development.

Examples of the carbonate according to the present invention include sodium carbonate, potassium carbonate, calcium carbonate, potassium bicarbonate, and sodium bicarbonate. Of these, sodium carbonate is preferably used, and sodium carbonate defined by JISK1201, JISK8624, and JISK8625 can be used. The particle size of the carbonate is preferably as fine as possible so as to be easily dissolved in water when mixed with cement, preferably 100 mesh or less, and more preferably 200 mesh or less. The purity of the alkali metal carbonate is not particularly limited, but it is possible to use an industrially produced alkali metal carbonate, and a purity of about 80% by mass or more is preferable. The content of the alkali metal carbonate of the present invention is preferably 0.2 to 1.0% by mass in the alumina cement composition. When the amount of the alkali metal carbonate is less than 0.2% by mass, the pot life tends to be shortened. On the other hand, when it exceeds 1.0% by mass, the curing is delayed when the temperature is lowered, and the strength development tends to be lowered. There is.

In the present invention, polyacrylic acid and / or a salt thereof is used. As the salt of polyacrylic acid, sodium salt, potassium salt, calcium salt and the like can be used, but use of sodium salt is preferable from the viewpoint of availability. In particular, the use of sodium polyacrylate and / or its salt that is soluble in water having a number average molecular weight of 15,000 or less and whose 40% by weight aqueous solution has a viscosity at 25 ° C. of 1000 mPa · s or less improves fluidity. From the aspect, a viscosity of 100 to 500 mPa · s is more preferable. The viscosity of the aqueous solution of polyacrylic acid and / or a salt thereof can be measured by, for example, a B-type viscometer, but the viscosity tends to increase as the degree of polymerization of polyacrylic acid and / or a salt thereof increases.

In the present invention, when polyacrylic acid and / or a salt thereof is added in the form of an aqueous solution, the dissociation state and pH of ions are not particularly limited, but from the viewpoint of improving fluidity, polyacrylic acid and / or Alternatively, the salt thereof is anionic, and the pH of the 1% by mass slurry at 25 ° C. is preferably neutral to alkaline, and more preferably 7.5 to 11. If it is acidic, the fluidity tends to decrease.

The content of the polyacrylic acid and / or salt thereof of the present invention is preferably 0.5 to 1.5% by mass in the alumina cement composition. When the content of polyacrylic acid and / or its salt is less than 0.5% by mass, the pot life tends to be shortened. On the other hand, when it exceeds 1.5% by mass, curing is delayed when the temperature is lowered, and strength is developed. Tend to decrease.

In the present invention, the method of adding carboxylic acid and / or salt thereof, carbonate, polyacrylic acid and / or salt thereof is not particularly limited, and the respective additives are mixed so as to have a predetermined composition. Mix with pre-ground alumina cement clinker and blender such as V-type blender, corn blender, nauter mixer, pan-type mixer, omni mixer, etc. It can be mixed and pulverized by a pulverizer such as a vibration mill, a tube mill, a ball mill, and a roller mill. Mixed pulverization is preferable because production efficiency is good and inexpensive production is possible.

Examples of the refractory aggregate according to the present invention include alumina such as fused alumina, sintered alumina, calcined alumina, and easily sintered alumina, magnesia such as fused magnesia, sintered magnesia, natural magnesia, and calcined magnesia, and fused magnesia. Magnesia spinel such as spinel and sintered magnesia spinel, and ultrafine powder such as silica fume, colloidal silica, calcined alumina, and easily sintered alumina, other fused silica, calcined mullite, chromium oxide, bauxite, andalusite, sillimanite, Examples thereof include chamotte, quartzite, rholite, clay, zircon, zirconia, dolomite, pearlite, vermiculite, brick waste, ceramic waste, 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.

Among them, in the amorphous refractory according to the present invention, from the viewpoint of fire resistance, durability, and corrosion resistance, it is possible to use one or two or more kinds of refractory aggregates selected from alumina, magnesia and ultrafine powder. preferable.

Examples of magnesia include molten magnesia or sintered magnesia obtained by melting or firing magnesium hydroxide and magnesium carbonate, light-burned magnesia, calcined magnesia, and the like, which are crushed to a predetermined size and sieved.

Furthermore, the ultra fine powder is a refractory fine powder in which particles having a particle size of 10 μm or less occupy 80% by mass or more, an average particle size of 1 μm or less, and a specific surface area by the BET method of 10 m ² / g or more, When blended with an amorphous refractory, fluidity can be secured and high strength is manifested. 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.

In general, refractory aggregates having a size of 5 to 3 mm, 3 to 1 mm, 1 mm, 200 mesh, 325 mesh, and the like are blended according to the purpose of use.

The mixing ratio of the alumina cement composition and the refractory aggregate in the amorphous refractory according to the present invention is appropriately determined according to the construction site and is not particularly limited. In accordance with the usual manufacturing method for irregular refractories, each material is blended to a prescribed blend, using a blender such as a V-type blender, cone blender, nauter mixer, pan-type mixer, and omni mixer. It is possible to carry out uniform mixing in advance or to directly weigh into a kneader.

Furthermore, in the present invention, for the purpose of adjusting the curing, additives such as a retarder, a curing accelerator, a fluidizing agent, etc., which are usually blended in an amorphous refractory, are used in combination as long as fluidity, strength, etc. are not reduced. It is possible.

Examples of the curing accelerator include lithium salts and hydroxides such as Li 2 CO 3, Ca (OH) 2, NaOH, KOH, etc. Among them, the lithium salt has a strong curing promoting action. Examples of the curing retarder include, for example, carboxylic acids, alkali metal carbonates, boric acids, polyacrylic acids, polymethacrylic acids and alkali salts such as hexametaphosphoric acid, tripolyphosphoric acid, pyrophosphoric acid, polycarboxylic acid-based, polyether-based Examples include water reducing agents.

Alumina raw material and calcium raw material were blended at a predetermined ratio and fired at 1400-1800 ° C. in a rotary kiln to produce an alumina cement clinker having the mineral composition and chemical components shown in Table 1. The produced alumina cement clinker and alumina were mixed so that the CaO content of the alumina cement composition was 16% by mass, and pulverized simultaneously with a ball mill to adjust the brane value to 6500 cm ² / g. Next, additive a, additive b, and additive c were mixed in the amounts shown in Table 1 to prepare an alumina cement composition. 97.3 parts by mass of refractory aggregate is mixed with 7.3 parts by mass of this alumina cement composition, and further 0.5 parts by mass of silica flour with respect to 100 parts by mass in total of the alumina cement composition and the refractory aggregate, 0.15 parts by mass of vinylon fiber was added, and water was added so that the flow value immediately after kneading was 180 ± 10 mm, followed by kneading for 4 minutes with a mortar mixer to obtain an amorphous refractory. The materials were kneaded and cured in a constant temperature room at 35 ° C., and the flow value with time and the compressive strength were measured. The results are shown in Table 1.

<Materials used>
Alumina raw material: sintered alumina powder, purity 98.0% by mass
Calcia raw material: Calcium carbonate, purity 96.0% by mass
Alumina: Commercial product, purity 99.0% by mass
Additive a: Sodium citrate, reagent grade 1 additive made by Ishizu Pharmaceutical Co., Ltd. b: Sodium carbonate, reagent grade 1 additive made by Ishizu Pharmaceutical Co., Ltd. c: Sodium polyacrylate, reagent grade 1 fireproof aggregate made by Nippon Pure Chemical Co., Ltd .: A mixture of the following aggregates:
Nippon Light Metal Co., Ltd. WAG5-3mm: 17.0 parts by mass Nippon Light Metal Co., Ltd. WAG3-1mm: 24.5 parts by mass Nippon Light Metal Co., Ltd. WAG1-0mm: 24.5 parts by mass Showa Denko Co., Ltd. Al-170: 2.5 parts by mass MM by Nippon Light Metal Co., Ltd. 22B: 2.5 parts by mass Nippon Light Metal Co., Ltd. NR200F-T: 12.0 parts by mass Almatis T-60 (-45MY): 3.7 parts by mass Ube Chemical Co., Ltd. U99S: 6.0 parts by mass Silica Flower: Product name “971U by Elchem” "
Vinylon fiber: Kuraray brand name “Vinylon”
Water: tap water

<Measuring method>
(1) Flow value: The flow value immediately after kneading of the produced amorphous refractory was measured according to the method described in JISR2521.
(2) Curing compressive strength: Measured according to JIS R 2521. The kneaded material was packed in a 40 × 40 × 160 mm mold and cured in a 35 ° C. constant temperature room for 24 hours, and then the compressive strength of the test piece was measured.
(3) Dry compression strength: Measured according to JIS R 2521. The kneaded material was put into a 40 × 40 × 160 mm mold, cured in a constant temperature room at 35 ° C. for 24 hours, and further dried at 110 ° C. for 24 hours, and the compressive strength of the test piece was measured.

As shown in Table 1, the alumina cement composition of the present invention has good fluidity, long pot life, and high strength.

Experiment No. The same procedure as in Example 1 was conducted except that the mixing ratio of the alumina cement clinker of 1-2 and the alumina was changed to the ratio shown in Table 2. The results are shown in Table 2.

An alumina cement composition composed of 70-50 parts by mass of alumina cement and 30-50 parts by mass of alumina has good fluidity, a long pot life, and high strength.

Experiment No. The same procedure as in Example 1 was conducted, except that 1-2 alumina cement clinker was used and the additive amount was changed as shown in Table 3. The results are shown in Table 3.

As shown in Table 3, the alumina cement composition containing 1.0 to 2.0% by mass of sodium citrate, 0.2 to 1.0% by mass of sodium carbonate, and 0.5 to 1.5% by mass of sodium polyacrylate has good fluidity. Long pot life and high strength.

The same procedure as in Example 3 was performed except that the materials were kneaded and cured in a constant temperature room at 20 ° C. The results are shown in Table 4.

As shown in Table 4, the alumina cement composition containing 1.0 to 2.0 mass% sodium citrate, 0.2 to 1.0 mass% sodium carbonate, and 0.5 to 1.5 mass% sodium polyacrylate has fluidity even at room temperature. Good, long pot life and high strength.

Claims (4)

12CaO · 7 Al ₂ O ₃ 2-12% by mass, CaO · Al ₂ O ₃ , CaO · 2Al ₂ O ₃ , and amorphous cement containing amorphous, and alumina, carboxylic acid and / or salt thereof as an additive 1.0 to 2.0 mass%, 0.2-1.0 mass% of carbonate, as well as polyacrylic acid and / or alumina cement composition characterized by containing the salt 0.5-1.5% by weight. The chemical components of the alumina cement are CaO 22 to 32% by mass, Al ₂ O ₃ 68 to 78% by mass, and 70 to 50 parts by mass of alumina cement and 30 to 50 parts by mass of alumina are included to include 100 parts by mass. The alumina cement composition according to claim 1, wherein The alumina cement composition according to claim 1 or 2, wherein the carboxylic acid and / or salt thereof is citric acid and / or citrate, the carbonate is sodium carbonate, and the polyacrylate is sodium polyacrylate. . An amorphous refractory comprising the alumina cement composition according to any one of claims 1 to 3 and a refractory aggregate.