JPH06321608A - Cement composition and monolithic refractories incorporating the same - Google Patents

Abstract

PURPOSE:To obtain a cement composition and the monolithic refractories incorporating it having an excellent flow property, an adequate hardening time and a property providing high strength, etc., being superior in erosion resistance as the cement composition and as the monolithic refractories incorporating it and having no problem on slaking of a hardened body which has been a defect of a conventional cement composition. CONSTITUTION:The cement composition incorporating Ca-aluminate being a solid- solution product of magnesium spinel and/or magnesia, and the monolithic refractories incorporating the cement composition and the refractory aggregate are composed. The obtained cement composition has remarkably excellent slaking resistance and corrosion resistance to slag, etc., and when it is compounded in the monolithic refractories, a high flow property, an adequate hardening time, and a property providing high strength are obtained. When the cement composition of this patent and the monolithic refractories are used, monolithic basic brick such as MgO-C base or MgO-Cr base which was hard to execute in the conventional product in the points of a slaking property, a durability and strength, is produced and also the durability of a place severe in slag erosion is greatly improved.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a cement composition and an amorphous refractory containing the same, particularly as a cement composition and an amorphous refractory containing the same. Cement composition containing the cement composition, which has the following properties: hardness, moderate curing time, high strength development, and excellent corrosion resistance, and which does not have the problem of digestion of the cured product, which was a drawback of conventional cement compositions. Related to amorphous refractories.

The cement composition of the present invention or an amorphous refractory containing the same is used as a lining material for chemical plants, including refractory fields such as blast furnaces, electric furnaces, cement kilns, lime furnaces and incinerators. It can also be widely used in the field of civil engineering and construction materials, such as fireproof boards and fireproof boards, and especially when used in the field of refractory materials, a great effect can be obtained.

[0003]

2. Description of the Related Art Conventionally, a cement composition or a cement composition containing alumina cement and magnesia and / or zircon, etc. as an amorphous refractory containing the same, and a magnesia spinel basic to alumina cement , An amorphous refractory containing magnesia and / or alumina and the like have been proposed (JP-A-60-112676, JP-A-60-122773, JP-A-60-166273,
And JP-A-60-260476, and JP-A-5-009080.
JP, JP 5-009081 JP, JP 4-198064 JP, JP 4-193773 JP, JP 4-182362 JP, JP 4-243980 JP, JP 4-325450 JP , JP-A-61
-158872 Publication, Ceramic Data Book 1992 p168〜1
75, and Shinagawa White Brick Company Technical Report No. 32 1989 p75-86 etc.).

However, since these cement compositions or amorphous refractories containing the cement compositions are produced by mixing alumina cement with a basic material, the basic material is digested and the digestion is completely prevented. However, there was a problem that the cured body was destroyed.

Here, digestion means that when a basic component such as MgO comes into contact with added water at the time of construction, it becomes a hydroxide such as Mg (OH) ₂ , which expands in volume and hardens. It causes cracks in the body.

In order to prevent the digestion, a basic material to be mixed which has improved digestion resistance has been developed. However, the digestion resistance is not sufficient and it is not yet in practical use. (Asahi Kasei / Nippon Kagaku Co., Ltd. Magnesia Technical Report No.3 p22-29 1990, MgO clinker refractory 1992 p686 with excellent digestion resistance).

Further, it is difficult to improve the digestion resistance of a basic material with a cement composition or an amorphous refractory obtained by mixing the basic material in a powder and / or clinker form. (JP-A-4-357152, JP-A-57-19
No. 1256 bulletin, Shinagawa White Brick Company Technical Report No. 428, 1991, p30-4
3).

Further, it has been proposed to use a mineral composition containing magnesia spinel in calcium aluminate. However, calcium aluminate having CaO.6Al ₂ O ₃ described therein is used as a cement. At this time, there was a problem that it could not be used as a binder for amorphous refractory because it had no hydraulic property, which is the most important function.
(JOURNAL OF MATERIALS SCIENCE LETTERS 11, 1992, p3
15-316).

The present inventor has conducted diligent research, paying attention to the fact that the digestion of a basic material, which is a problem when constructing a basic amorphous refractory, is due to the presence of the post-mixed free basic material. As a result, when producing a cement composition, in the clinker mineral, especially calcium aluminate which is a hydraulic component, in advance, it was found that it is sufficient to solid-dissolve a basic component such as MgO. The invention was completed.

[0010]

That is, the present invention is a cement composition containing a magnesia spinel or a calcium aluminate formed by solid solution of magnesia spinel and magnesia. The cement composition and the refractory aggregate. It is an amorphous refractory containing and.

The present invention will be described in detail below.

The calcium aluminate according to the present invention has a mineral composition of C ₅ A ₃ , CA ₂ , CA, C ₁₂ A, where CaO is C, Al ₂ O ₃ is A, and H ₂ O is H. ₇ , C ₃ A ₅ , C ₃ A, and C ₁₂ A ₇
It contains one or more hydraulic calcium aluminates represented by H and the like, and may also contain non-hydraulic calcium aluminate such as CA ₆ .

The crystalline form of the calcium aluminate of the present invention may be crystalline or amorphous.

Further, the calcium aluminate of the present invention is not particularly limited, but CA from the viewpoint of generating excellent fluidity, appropriate curing time and high strength when it is made into a cement composition. The main component is preferable.

The mineral composition of calcium aluminate contained in the cement composition of the present invention is important, and CaO and A
When the molar ratio of l ₂ O ₃ , that is, C / A exceeds 1, it tends to easily form rapid hardening calcium aluminate such as C ₃ A and C ₁₂ A _{7. 2} or non-hydraulic CA ₆
It is preferred that the mineral composition of the calcium aluminate of the present invention is changed according to the characteristics of the amorphous refractory used.

For example, when blended into a spray-shaped amorphous refractory, rapid hardening is required, so that the calcium aluminate contained in the cement composition of the present invention preferably has a C / A of 1 or more.

[0017] Calcium aluminate of the present invention, as an impurity, calcium aluminate containing _{2CaO · Al 2 O 3 · SiO} 2, 4CaO · Al 2 O 3 · Fe 2 O 3, and CaO · TiO _2, etc. It is also possible to use, but components other than CaO and Al ₂ O ₃ , such as Si
_{O 2, TiO 2, Fe 2} O 3, and K ₂ O, and Na ₂ O such impurities is when used as a castable refractory, cracks, separation decreases may occur due to shrinkage at a high temperature, low melting point Since the formation of the compound lowers the fire resistance and the softening point under load and deteriorates the properties such as corrosion resistance, it is preferable that the content of these impurities is small.

The magnesia spinel in the present invention is
MgO and Al ₂ O ₃ consisting of MgO and Al ₂ O ₃ as a main mineral, the composition ratio of MgO and Al ₂ O ₃ in magnesia spinel, MgO 20 ~ 40 wt%, Al ₂ O ₃ 60-80% by weight. When solid-dissolving magnesia spinel in calcium aluminate, the component ratio of MgO and Al ₂ O ₃ in magnesia spinel is
MgO 25-35 wt% and Al ₂ O ₃ 65-75 wt% are preferred. In the present invention, it is important that magnesia spinel is in solid solution with calcium aluminate. Especially EPM
When the clinker is analyzed by the analysis of A or the like, it is preferable that the magnesia spinel and the calcium aluminate are almost uniformly dispersed in the clinker.

Magnesia in the present invention is MgO, which is preferably dissolved in calcium aluminate in the clinker, and may be partially dissolved in magnesia spinel. Further, in the present invention, when magnesia is analyzed by EPMA or the like to analyze the clinker, it is preferable that the magnesia and the calcium aluminate are almost uniformly dispersed in the clinker. If it is not evenly dispersed, free Mg will be
O tends to be generated and digestion tends to occur easily.

The cement composition of the present invention contains a calcia raw material, an alumina raw material, and a magnesia raw material, so that a magnesia spinel or a magnesium aluminate in which magnesia spinel and magnesia are formed as a solid solution is formed, and an electric furnace, a reverberatory furnace, With open hearth, converter, rotary kiln, etc.,
It can be manufactured by crushing magnesia spinel or a clinker of calcium aluminate, which is a solid solution of magnesia spinel and magnesia, by crushing with a crusher such as a ball mill, a tube mill, a vibration mill, a roller mill, and a tower mill. It is possible.

As described above, in the present invention, any of the methods of melting and / or firing the clinker can be used. However, the blended raw materials such as an electric furnace, a reflex furnace, a high frequency furnace, and a plasma melting furnace can be used. It is preferable to produce the clinker by a melting method capable of completely melting the clinker.

In the case of manufacturing by the melting method, it is preferable to melt at a temperature of 1,500 ° C. or higher in order to completely react the calcia raw material, the alumina raw material and the magnesia raw material.
More preferably melted at a temperature of 00 ° C or higher, 1,800
Most preferably, it melts at a temperature above 0 ° C.

After tapping the melt according to a normal operating method of an electric furnace or the like, it is cooled to a temperature at which it can be handled by a high-speed air stream or a rotary cooler to obtain a target clinker.

Upon melting, the reactivity of CaO, Al ₂ O ₃ and MgO is not good and the specific gravity is easily separated in the furnace.
For example, it is important to maintain a molten state for at least about 5 minutes for a certain period of time to produce a compositionally stable mineral. If the melt holding time is not sufficient, MgO tends not to form a solid solution as magnesia spinel and to exist in the clinker as free MgO.

As the calcia raw material used in the present invention,
Limestone, calcium carbonate, quick lime, calcium hydroxide and the like can be used.

As the alumina raw material, natural alumina raw materials such as shale shale, bauxite, and high-alumina chamotte, waste aluminum ash, alumina sludge, high-alumina slag, wastes such as alumina porcelain, and buyers. Purified alumina such as alumina, fused alumina, and sintered alumina can be used.

Furthermore, various magnesia raw materials can be used.
Those containing MgO can be used. Specifically, magnesium hydroxide extracted from seawater by the seawater method, magnesium carbonate, magnesia clinker obtained by firing them in a kiln, light-burned magnesia, magnesia clinker. Examples include electro-fused magnesia clinker obtained by melting in an electric furnace or the like, natural magnesia mined in China or the like, highly purified purified magnesia, and vapor phase magnesia. Mg of the magnesia raw material used in the present invention
It is preferable that the purity of O is 80% or more because impurities such as SiO ₂ and TiO ₂ are small.

The particle size of the calcia raw material, the alumina raw material, and the magnesia raw material is not particularly limited, but is preferably 30 mm or less and more preferably 5 mm or less from the viewpoint of easy formation of calcium aluminate.

The crystallization rate of the clinker of the present invention can be controlled by adjusting the cooling rate after tapping, and when it is forcibly cooled with high pressure air or the like, the vitrification rate tends to increase. The degree of vitrification can be calculated from the peak area of the diffraction line of a specific mineral composition by the powder X-ray diffraction method.

In the present invention, the vitrification rate is not particularly limited. However, when the clinker has a high vitrification rate, the hydraulic property becomes strong and a high strength cured product can be obtained. Is preferred. The vitrification rate is preferably 30% or more, and more preferably 50% or more from the viewpoint of obtaining high strength.

As for the particle size of the cement composition of the present invention, a finer particle size is preferable because it is excellent in fluidity and strength development.
The specific surface area was measured by the Blaine method specified in 2521.
3,000cm is preferably not less than ² / g, more preferably at least ^{4,000cm 2 / g, 5,000cm 2 /} g or more is most preferred.

The average particle size of the cement composition is 20
μm or less is preferable, and 5 μm or less is more preferable. The smaller the average particle diameter is, the higher fluidity can be exhibited when used by kneading with water, and the cured product can be obtained with a low kneading amount of water, so that a dense structure is obtained and the durability is improved, which is preferable.
In particular, in order to carry out a uniform hydration reaction with water, it is preferable that the number of particles with a large particle size of 90 μm or more is small, and since the hydration reaction proceeds uniformly and it is easy to control the curing property, it exceeds 45 μm. The smaller the particle size, the more preferable.

The composition range of the cement composition of the present invention is such that CaO is 6 to ₃ in 100 parts by weight of CaO, Al ₂ O ₃ and MgO in total.
5 parts by weight, Al ₂ O ₃ 60 to 75 parts by weight, it is preferable that the range of MgO 1 to 30 parts by weight, from the aspect of fluidity, hardenability, and strength development when made into cement, CaO 15 to 25 Parts by weight, A
More preferably, it is 65 to 70 parts by weight of l ₂ O _{3 and 3 to} 20 parts by weight of MgO.

In the present invention, the morphology of the constituent mineral composition is important in addition to the constituent proportions of the respective chemical components. Particularly, when MgO is M, the mineral composition in the cement composition is at least CA.
It is preferable that the main component is MA and the content of free MgO is small.
When free MgO is present, when it is kneaded with water, the cured product expands due to the digestion of MgO, and Mg that elutes when kneaded with water.
Ions tend to deteriorate the fluidity due to the ions.

The form of the mineral composition of the cement composition of the present invention can be specified by the powder X-ray diffraction method, and the contained mineral composition can be specified by the presence or absence of diffraction lines and the diffraction intensity of each mineral composition. , Or it can be quantified.

The presence or absence of solid solution of magnesia spinel or magnesia spinel and magnesia in the clinker is determined by directly measuring the cross-section of the cement particles corresponding to the produced clinker or clinker particles, directly by EPMA, XMA, and ES.
By electron microscope observation such as CA and polarization microscope observation,
It can be confirmed by observing the element arrangement and concentration at the interfaces of MgO, CaO, and Al ₂ O ₃ .

The already ground cement composition is
Utilizing the true specific gravity difference between the minerals of calcium aluminate and magnesia spinel, the pulverized material is subjected to specific gravity separation with a centrifuge, and the X-ray diffraction analysis and chemical component analysis of each separated layer are performed to prepare the clinker beforehand. It is possible to discriminate and determine whether MgO was in solid solution or was added later to calcium aluminate. Specific gravity separation is not possible if magnesia spinel or magnesia spinel and magnesia are in solid solution in the clinker, and if magnesia spinel or magnesia is added later, separation / identification is possible by specific gravity difference. Become.

In the present invention, it is necessary that magnesia spinel or magnesia spinel and magnesia are solid-dissolved in the clinker in advance, and magnesia spinel or magnesia spinel and magnesia are solid-dissolved to form an amorphous refractory. In this case, the digestion resistance and the corrosion resistance are improved.

In the present invention, in order to further improve high fire resistance and corrosion resistance, easily sinterable alumina is mixed and crushed when clinker is crushed, and it is usually used in an alumina cement composition to adjust fluidity and hardenability. It is possible to add a curing modifier such as a dispersant, a curing accelerator and a curing retarder which are used.

As a hardening modifier that can be blended, a condensate of melamines, polycarboxylic acids, and formaldehyde, which has a function of improving properties such as fluidity, pot life, hardening time, and strength development of cement. Surfactants, etc.
Alumina cement hardening modifiers such as sugars, carboxylic acids, phosphoric acids, and boric acids, mixtures of hydroxycarboxylic acids and inorganic carbonates, gluconic acid, citric acid, tartaric acid,
Further, it is possible to use a coagulation modifier composed of a sulfonic acid type anionic surfactant and the like, and a cement admixture composed of citric acid and boric acid. Further, as the curing accelerator, lithium carbonate, calcium hydroxide, magnesium hydroxide or the like can be used.

Further, in the present invention, a mixture of water-soluble polyacrylic acid and / or a salt thereof and an alkali metal carbonate,
Hydroxycarboxylic acid or its salt, and one or more curing agents selected from water-soluble polymethacrylic acid, methacrylic acid-acrylic acid copolymer or salts thereof and alkali metal carbonate, hydroxycarboxylic acid or its salt It is possible to use a regulator or the like.

The cement composition of the present invention or the amorphous refractory material containing the same has good fluidity, appropriate curing time and high strength development, and is also excellent in erosion resistance. The cement composition does not have the problem of digestion of the hardened body, which has been a problem of the conventional cement composition, and can be used in the same manner as the alumina cement to be blended with an ordinary amorphous refractory.

Therefore, alumina aggregates such as sintered alumina, fused alumina, and easily sintered alumina, which are generally blended as an amorphous refractory aggregate, fused magnesia, sintered magnesia, light burned magnesia. , Natural magnesia, magnesia spinel, magnesia aggregates such as magnesite, as well as zircon, zirconia, fused silica, silicon carbide, silicon nitride, silicon iron nitride, boron carbide, loastone, chamotte, etc. Aggregates used for refractories, and further, graphite, silicon carbide, silicon nitride, boride, etc. synthesized by a novel particle surface modification method such as air flow impact method can be used. It is also possible to use ultrafine powder such as silica fume and Aerosil together.

The aggregate to be combined with the cement composition of the present invention should be appropriately set according to the required characteristics of the amorphous refractory. In the case of the iron-related irregular refractory, the alumina aggregate and the magnesia A combination with aggregates and carbonaceous aggregates such as natural graphite, artificial graphite, carbon black, and mitch or pellets thereof is preferable.

In the present invention, the use of an aggregate containing a basic component such as magnesia or magnesia spinel exhibits the characteristics of the cement of the present invention sufficiently from the viewpoint of improving the corrosion resistance when blended with an amorphous refractory. It is preferable because it is possible.

The cement composition of the present invention is mixed with the above-mentioned refractory aggregate and, if necessary, a curing modifier and an explosion-proof material, and then water is added and mixed with a kneader such as a mixer to obtain the purpose. It can be poured into a construction site or a construction mold to be cured, cured, and then dried and used at high temperature.

It is also possible to add additives and explosion-proofing agents to this cement composition or amorphous refractory material depending on the required characteristics.

Furthermore, the method of using the cement composition of the present invention is not particularly limited to the pouring method, but a spraying method, a patching method, a stamping method, and a hand method in which a refractory binder such as ordinary alumina cement is used. It is possible to support various construction methods such as the coloring method.

[0049]

EXAMPLES The present invention will be described in detail below with reference to examples.

Example 1 Quicklime as a calcia raw material, alumina as an alumina raw material, and magnesia as a magnesia raw material were contained as shown in Table 1. After melting at a high temperature of 1,750 to 1,900 ° C. in an electric furnace, the melt was tapped into a ladle. Then, it was left to cool to produce a clinker. Further, the obtained clinker was roughly crushed to 5 mm or less with a jaw crusher and crushed with a batch type ball mill,
A cement composition was obtained. The particle size of this cement composition is JI
It was measured by the Blaine method described in SR 2521. The results are shown in Table 1. According to the method described in JIS R 2521, the obtained cement composition, Toyoura standard sand, and water were kneaded in a thermostatic chamber at 20 ° C. for 3 minutes to obtain mortar, and the cement characteristics were measured. In the comparative example, a conventional alumina cement clinker was used, which was obtained by mixing and crushing magnesia spinel or magnesia spinel and magnesia so that the content of MgO in the cement composition was equal. The results are also shown in Table 1.

<Raw materials used> Quick lime: Quick lime manufactured by Denki Kagaku Kogyo Co., 5-10 mm, CaO98% Alumina: Bayer alumina manufactured by Nippon Light Metal Industry Co., Ltd., product name “NMA 10” Al ₂ O ₃ 99% Magnesia: Ube Chemical Co., Ltd. Made magnesia clinker,
MgO 96% Magnesia Spinel: Shin-Nippon Chemical Co., Ltd. magnesia clinker, trade name "SPL-S" Alumina cement clinker: CaO 34%, Al ₂ O ₃ 65% equivalent

<Physical property measuring method> Particle size: Blaine specific surface area is measured according to the method described in JIS R 2521. Flow value: After mortar after kneading is allowed to stand for a predetermined time,
The spread diameter of what was kneaded for 30 seconds was measured according to the method described in JIS R 2521.Curing time: The mortar after kneading was transferred to an adiabatic container, and the heat generated by hydration was measured with a thermometer, The time taken from the pouring of water to the maximum exothermic temperature was defined as the curing time. Compressive strength: Mortar after kneading is packed in a mold of 40 × 40 × 160 mm, and the compressive strength of the cured product after 24 hours is measured with a pressure type compressive strength measuring machine, and it is the compressive strength after curing for 24 hours. The cured product after the lapse of time was placed in a drier at 110 ° C., dried for 20 hours, allowed to cool to room temperature, and similarly measured to obtain the compressive strength after drying. Digestion resistance: The mortar after kneading is packed in a mold of 40 × 40 × 160 mm, and the hardened product after 24 hours is put in a dryer at 110 ° C, and then placed in a steam curing box containing steam at 150 ° C. twenty four
After leaving for a time, the presence or absence of cracks, the presence or absence of bending, and the expansion rate were evaluated. The generation of cracks and the degree of bending were visually evaluated, and the expansion coefficient was measured by a micrometer with respect to the change in length before and after steam curing.

[0053]

[Table 1]

As is clear from Table 1, the cement composition of the present invention has excellent hydraulic properties, fluidity, strength, and digestion resistance by previously dissolving the basic component in the clinker. Particularly, the digestion resistance is remarkably improved and the strength is high as compared with the comparative example in which the basic aggregate component is post-added to the alumina cement clinker.

Example 2 10 parts by weight of the cement composition produced in Example 1, 50 parts by weight of refractory aggregate A, 15 parts by weight of refractory aggregate B, and 25 parts by weight of refractory aggregate C were mixed, and the mixture was kept in a thermostatic chamber at 20 ° C. In accordance with the method described in JIS R 2553, dry kneading with a mortar mixer for 1 minute and then water 10
Add parts by weight and knead for 3 minutes to obtain an amorphous refractory,
Its physical properties were measured. The results are shown in Table 3.

<Materials used> Fireproof aggregate A: trade name “Sintered Alumina SRW” manufactured by Showa Denko KK,
Weight ratio of 5 to 3 mm product / 3 to 1 mm product / 1 to 0 mm product 2/2 /
Mixture of 1 refractory aggregate B: trade name "Fused Alumina RW92" manufactured by Showa Denko KK,
A mixture of 220Mesh F product / 325Mesh F product in a weight ratio of 2/1 Fireproof aggregate C: product name "Sintered Spinel SPL-" manufactured by Shin Nippon Chemical Co., Ltd.
S ", 1-0mm product / Showa Denko" Electric fused alumina RW92 "200Mes
h F mixture of 3/2 weight ratio

<Measurement method of physical properties> Corrosion resistance: Mortar after kneading is packed in a mold of 40 × 40 × 160 mm, and a cured product after 24 hours is dried in a dryer at 110 ° C., and then at 400 ° C. Dry for 2 hours, fire at 1,000 ° C in a silicon knit electric furnace for an hour, cool to room temperature, immerse the hardened material in high-temperature slag melted in a high-frequency furnace for 10 minutes, and visually check the erosion state and the occurrence of cracks. After the confirmation, the immersion test piece was cut with a diamond cutter, and the erosion state of the slag inside the cured body was analyzed by EPMA. The slag infiltration thickness by this EPMA was defined as the erosion depth. Others were measured according to the mortar measuring method.

[0058]

[Table 2]

As is clear from Table 2, the amorphous refractory containing the cement composition of the present invention has excellent hydraulic properties, fluidity and strength by previously dissolving the basic component in the cement clinker. , And resistant to digestion. In particular, the digestion resistance is significantly improved compared to the comparative example in which the basic aggregate component is post-added to the alumina cement clinker, the length change is small, the high temperature strength is high, and the slag erosion resistance is also significantly improved. is doing.

[0060]

As is apparent from the above examples, the cement composition of the present invention or the amorphous refractory material containing the cement composition is
There is no problem of digestion of basic aggregates such as magnesia and spinel that are blended as aggregates during the production of amorphous refractory, which has been a problem in the past, and it has extremely good digestion resistance and corrosion resistance against slag etc. When blended with a product, high fluidity, an appropriate curing time, and high strength are obtained. When the cement composition or amorphous refractory of the present invention is used, in the conventional one, in terms of digestibility, durability, and strength, it is difficult to construct a base such as MgO-C system or MgO-Cr system. Not only is it possible to make plastic bricks into irregular shapes, but it also has the effect of significantly improving the durability of parts that are heavily eroded by slag. Further, the cement composition of the present invention or an amorphous refractory containing the same, blast furnaces, electric furnaces, cement kilns, lime furnaces, incinerators and other refractory materials field, including lining materials for chemical plants and It can be widely used in the field of civil engineering and construction materials such as fireproof boards. Especially when used in the field of refractories, a great effect can be obtained.

Claims (2)

[Claims] 1. A cement composition comprising magnesia spinel or a calcium aluminate formed by solid solution of magnesia spinel and magnesia. 2. An amorphous refractory containing the cement composition according to claim 1 and a refractory aggregate.