JP2023147603A - Calcium aluminate, alumina cement, and unshaped refractory - Google Patents

Abstract

To provide a calcium aluminate that, when used as cement material, can achieve a delayed curing property and appropriate curing time.SOLUTION: A calcium aluminate has the molar ratio of CaO/Al2O3 of 0.50 or more and 2.00 or less and contains P2O5.SELECTED DRAWING: None

Description

The present invention relates to calcium aluminates, alumina cements, and monolithic refractories.

Alumina cement generally uses limestone or quicklime as _the CaO raw material, purified alumina, bauxite, aluminum ash, etc. as the _Al2O3 raw material, and is made by independently pulverizing calcium aluminate clinker produced by a calcination method or a melting method. Alternatively, it is manufactured by adding alumina and various additives to calcium aluminate clinker, and mixing and pulverizing the mixture. The general method for producing alumina cement and its characteristics are widely known (for example, Non-Patent Documents 1 and 2).

Refractories Vol. 29, pp368-374 (1977) Cement chemistry, 2nd Ed, H. F. W Taylor, pp295-313 (1997)

However, as a result of studies conducted by the present inventor, it has been found that there is room for improvement in the calcium aluminates described in Non-Patent Documents 1 and 2 in terms of delayed curing properties and curing time.

Upon further investigation, the present inventor found that when used as a cement material, by incorporating P ₂ O ₅ components into calcium aluminate whose CaO/Al ₂ O ₃ molar ratio is 0.50 or more and 2.00 or less. The present inventors have discovered that it is possible to realize a calcium aluminate that can provide delayed curing properties and an appropriate curing time, and have completed the present invention.

According to the invention,
A calcium aluminate having a CaO/Al ₂ O ₃ molar ratio of 0.50 or more and 2.00 or less,
_A calcium aluminate is provided that includes _P2O5 .

Further, according to the present invention,
An alumina cement is provided that includes the calcium aluminate described above.

Further, according to the present invention,
A monolithic refractory is provided that includes the above alumina cement and a refractory aggregate.

According to the present invention, there are provided calcium aluminate that can provide delayed curing properties and appropriate curing time when used as a cement material, and alumina cement and monolithic refractory using the same.

The structure of the calcium aluminate of this embodiment will be explained in detail.

The calcium aluminate of this embodiment has a CaO/Al ₂ O ₃ molar ratio of 0.50 to 2.00 and contains P ₂ O ₅ .

The CaO/Al ₂ O ₃ molar ratio of the calcium aluminate is configured to be 0.50 or more and 2.00 or less.
The lower limit of the CaO/Al ₂ O ₃ molar ratio is 0.50 or more, preferably 0.60 or more, and more preferably 0.70 or more. Thereby, it is possible to suppress the curing time from increasing. Moreover, since it can be cured within a predetermined time, workability can be improved.
The upper limit of the CaO/Al ₂ O ₃ molar ratio is 2.00 or less, preferably 1.90 or less, more preferably 1.80 or less. Thereby, shortening of the curing time can be suppressed, and curing retardation can be improved.

The lower limit of the content of P ₂ O ₅ contained in calcium aluminate is, for example, 0.01% by mass or more, preferably 0.02% by mass or more, and more preferably 0.03% by mass or more. Thereby, strength development and cracking resistance can be improved.
The upper limit of the content of P ₂ O ₅ contained in calcium aluminate is, for example, 0.60 mass % or less, preferably 0.55 mass % or less, and more preferably 0.50 mass % or less. Thereby, strength development and cracking resistance can be improved.

Calcium aluminate contains at least P ₂ O ₅ as a chemical component. Thereby, delayed curing properties can be improved. Furthermore, in mortar tests, fluidity and strength development can be improved.
Moreover, the calcium aluminate may further contain SO ₃ and/or ZrO ₂ as chemical components.
P ₂ O ₅ , SO ₃ , and ZrO may be in a solid solution state in the calcium aluminate.
The lower limit of the content of SO ₃ contained in calcium aluminate is, for example, 0.01% by mass or more, preferably 0.02% by mass or more, and more preferably 0.03% by mass or more. Thereby, strength development and cracking resistance can be improved.
The upper limit of the content of SO ₃ contained in calcium aluminate is, for example, 0.90 mass % or less, preferably 0.50 mass % or less, and more preferably 0.25 mass % or less. Thereby, strength development and cracking resistance can be improved.
The lower limit of the content of ZrO ₂ contained in the calcium aluminate is, for example, 0.01% by mass or more, preferably 0.02% by mass or more, and more preferably 0.03% by mass or more. Thereby, strength development can be improved.
The upper limit of the content of ZrO ₂ contained in calcium aluminate is, for example, 0.70 mass % or less, preferably 0.50 mass % or less, and more preferably 0.25 mass % or less. Thereby, strength development can be improved.

Containing P ₂ O ₅ , SO ₃ , and ZrO as chemical components in calcium aluminate means that the content can be measured by fluorescent X-ray measurement.

The types and amounts of chemical components contained in calcium aluminate (CaO, Al ₂ O ₃ , SO _{3 ,} etc.) can be analyzed according to JIS R5204 (fluorescent X-ray analysis method for cement).

Calcium aluminates include CaO・Al ₂ O ₃ (hereinafter may be abbreviated as CA), 2CaO・Al ₂ O ₃・SiO ₂ (hereinafter may be abbreviated as C ₂ AS), CaO・TiO ₂ (hereinafter may be abbreviated as CT), 12CaO・7Al ₂ O ₃ (hereinafter may be abbreviated as C ₁₂ A ₇ ), CaO・2Al ₂ O ₃ (hereinafter abbreviated as CA ₂₎ ), and one or more selected from the group consisting of 3CaO.Al ₂ O ₃ (hereinafter may be abbreviated as C ₃ A), and an amorphous substance. Good too.

When calcium aluminate contains CA, strength development properties can be imparted to alumina cement.
When calcium aluminate contains C ₂ AS and CT, latent hydraulic properties can be imparted to alumina cement.
When calcium aluminate contains C ₁₂ A ₇ , C ₃ A, and amorphous, appropriate rapid hardening can be imparted to alumina cement.
By containing CA ₂ in the calcium aluminate, it is possible to impart appropriate hardening retardation to the alumina cement.

The total content of CA, C ₂ AS, CT, C ₁₂ A ₇ , CA ₂ and C ₃ A in calcium aluminate is as follows: CA, C ₂ AS, CT, C ₁₂ A ₇ , CA ₂ , C ₃ A and For example, it is 10 to 90 mass %, preferably 20 to 80 mass %, and more preferably 30 to 70 mass % out of the total 100 mass % of amorphous.
By adjusting the content of the above mineral composition, desired properties can be imparted to calcium aluminate.
In this specification, "~" indicates that the upper limit value and the lower limit value are included, unless otherwise specified.

The content of CA in the calcium aluminate is, for example, 20 to 80% by mass, preferably 20% to 80% by mass of the total of 100% by mass of CA, C ₂ AS, CT, C ₁₂ A ₇ , CA ₂ , C ₃ A and amorphous. is 30 to 70% by weight, more preferably 40 to 60% by weight.

The content of C ₁₂ A ₇ in calcium aluminate is, for example, 15% by mass or less in 100% by mass of the total of CA, C ₂ AS, CT, C ₁₂ A ₇ , CA ₂ , C ₃ A and amorphous. , preferably 10% by mass or less, more preferably 8% by mass or less.

The content of CA ₂ in the calcium aluminate is, for example, 15% by mass or less, preferably 15% by mass or less, based on the total 100% by mass of CA, C ₂ AS, CT, C ₁₂ A ₇ , CA ₂ , C ₃ A and amorphous. is 10% by mass or less, more preferably 8% by mass or less.

Quantification of CA, C ₂ AS, CT, C ₁₂ A ₇ , CA ₂ , C ₃ A and amorphous in calcium aluminate can be determined by Rietveld analysis based on powder X-ray diffraction patterns.

The lower limit of the Blaine specific surface area of calcium aluminate is, for example, 1,500 cm ² /g or more, preferably 1,800 cm ² /g or more, and more preferably 2,000 cm ² /g or more. Thereby, strength development can be improved.
The upper limit of the Blaine specific surface area of calcium aluminate is, for example, 15,000 cm ² /g or less, preferably 12,000 cm ² /g or less, more preferably 10,000 cm ² /g or less. Thereby, workability during kneading can be improved.

The Blaine specific surface area of calcium aluminate can be measured using a Blaine air permeation device in accordance with JIS R 5201 (physical testing method for cement).

In the volume frequency particle size distribution of calcium aluminate powder measured by laser diffraction scattering method, the particle size at which the cumulative value is 50% is defined as D50.
The lower limit of D50 of calcium aluminate is, for example, 1.0 μm or more, preferably 1.5 μm or more, and more preferably 2.0 μm or more. Thereby, workability during kneading can be improved.
The upper limit of D50 of calcium aluminate is, for example, 30.0 μm or less, preferably 28.0 μm or less, and more preferably 26.0 μm or less. Thereby, strength development can be improved.

When producing calcium aluminate by the melting method, CaO raw material, Al ₂ O ₃ raw material and P ₂ O ₅ raw material are added, if necessary, SO ₃ raw material and/or ZrO ₂ raw material are added, and these are mixed or mixed in a predetermined ratio. It is possible to use a method of pulverizing the material and melting it in a melting furnace such as an electric furnace or a gasification melting furnace at a high temperature of, for example, 1,300°C or higher, preferably 1,500°C or higher, until all unreacted raw materials are removed. can.

In addition, when producing calcium aluminate by the firing method, it is obtained by firing the raw materials mixed in the same manner as above in a rotary kiln. At that time, desired characteristics can be obtained by firing at a high temperature of 1,300°C or higher, preferably 1,500°C or higher.

Examples of CaO raw materials include calcium carbonate (CaCO ₃ ), limestone, quicklime, and the like. Examples of the Al ₂ O ₃ raw material include purified alumina (Al ₂ O ₃ ), bauxite, aluminum residual ash, and the like. Examples of the P ₂ O ₅ raw material include calcium phosphate (Ca ₃ (PO ₄ ) ₂ ). Examples of the SO ₃ raw material include gypsum (mainly containing CaSO ₄ ). Examples of the ZrO ₂ raw material include zirconium oxide (ZrO ₂ ).

Thereafter, if necessary, the particle size of the melt (clinker) obtained by the above method may be appropriately adjusted by performing a crushing/pulverizing treatment or a classification treatment such as sieving.
In addition, for example, a pulverizer such as a roller mill, jet mill, tube mill, ball mill, and vibration mill may be used for the pulverization process.
When the calcium aluminate contains an amorphous material, the amount of amorphous material can be adjusted by controlling the cooling rate of the molten high temperature clinker.
That is, the calcium aluminate of this embodiment may be clinker (in the form of a lump immediately after being melted and fired) or a clinker pulverized product.

The alumina cement of this embodiment contains at least the above calcium aluminate. The alumina cement may further contain α-Al ₂ O ₃ and other known components contained in cement, as long as they do not impede the effects of the invention.

The content of calcium aluminate varies depending on the purpose of use, but is usually, for example, 40 parts by mass or more, preferably 60 parts by mass, and more preferably 80 parts by mass or more in 100 parts by mass of alumina cement.

Known components include, for example, additives such as curing retarders, curing accelerators, and fluidizing agents that are usually added to monolithic refractories for the purpose of improving fluidity.

Examples of the curing accelerator include hydroxides and lithium salts such as Ca(OH) ₂ , Li ₂ CO ₃ , NaOH, and KOH, and among them, lithium salts have a strong curing accelerating effect.
Examples of the curing retarder include carboxylic acids, alkali metal carbonates, boric acids, polyacrylic acids, polymethacrylic acids, and alkali salts such as hexametaphosphoric acid, tripolyphosphoric acid, and pyrophosphoric acid.

The method of blending the additives is not particularly limited, and each additive is blended in a predetermined ratio, and pre-pulverized calcium aluminate clinker is mixed with a V-type blender, corn blender, Nauta mixer, or bread blender. Mix uniformly using a mixer such as a mold mixer or omni mixer, or mix and grind with a crusher such as a vibration mill, tube mill, ball mill, or roller mill after blending with calcium aluminate clinker at a predetermined ratio. It is possible to do so.

Further, the cement composition of this embodiment contains alumina cement (calcium aluminate), water, and sand if necessary. The cement composition may consist of either cement paste, cement mortar or cement concrete.

In this specification, cement paste includes cement and water, cement mortar includes alumina cement, water, and sand (fine aggregate), and cement concrete refers to alumina cement, water, and aggregate (fine aggregate). It can be defined as containing materials such as wood, coarse aggregate).

The monolithic refractory of this embodiment includes the above alumina cement and refractory aggregate.

As the refractory aggregate, refractory aggregates that are normally used for monolithic refractories can be used, and specifically, magnesia such as molten magnesia, sintered magnesia, natural magnesia, and light calcined magnesia, Magnesia spinel such as magnesia spinel and sintered magnesia spinel; alumina such as fused alumina, sintered alumina, light sintered alumina, and easily sintered alumina; Fine powder, others, fused silica, calcined mullite, chromium oxide, bauxite, andalusite, sillimanite, chamotte, silica stone, lowite, clay, zircon, zirconia, dolomite, pearlite, vermiculite, brick waste, pottery waste, silicon nitride, nitride Boron, silicon carbide, silicon iron nitride, etc. can be used.
Among these, carbon aggregates such as magnesia, magnesia spinel, chamotte, alumina, silicon carbide, and ultrafine powder, as well as oil pitch, tar, and scaly graphite are selected from the viewpoint of corrosion resistance, durability, and fire resistance. It is preferable to use one or more of these as the refractory aggregate.

An example of a monolithic refractory may be a low cement castable blended with 99 to 89 parts by mass of refractory aggregate and 1 to 11 parts by mass of alumina cement (range has been changed).

The method for producing monolithic refractories is not particularly limited, and is carried out in accordance with the usual production method for monolithic refractories, by blending each component raw material in a predetermined ratio, using a V-type blender, a cone blender, It is also possible to mix uniformly using a mixer such as a Nauta mixer, a pan-type mixer, or an omni mixer, or to weigh it directly into a kneader when kneading at a predetermined ratio.

Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can be adopted. Further, the present invention is not limited to the above-described embodiments, and the present invention includes modifications, improvements, etc. within a range that can achieve the purpose of the present invention.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the description of these Examples.

<Preparation of calcium aluminate>
Calcium carbonate (CaCO ₃ ) (manufactured by New Lime, heavy calcium carbonate) as a CaO raw material, aluminum oxide (Al ₂ O ₃ ) (A-170, manufactured by Showa Denko) as an Al ₂ O ₃ raw material, and P ₂ O ₅ as a raw material Calcium phosphate (Ca ₃ (PO ₄ ) ₂ , α-TCP manufactured by Taihei Kagaku Sangyo Co., Ltd.) was mixed in various blending ratios, and the raw material mixture was melted at 1,500°C to synthesize calcium aluminate clinker. The calcium aluminate clinker pulverized products of each experimental example shown in Table 1 were prepared by grinding using a ball mill so as to have the Blaine specific surface area shown in Table 1.
However, in clinker 1-5, no P ₂ O ₅ raw material was added.

_In Table 1, _{C2AS : 2CaO.Al2O3.SiO2} , CT: _CaO.TiO2 , _{C12A7 : 12CaO.7Al2O3 , CA2} : _{CaO.2Al2O3 ,} and CA: Represents CaO.Al ₂ O ₃ .

(Analysis method of calcium aluminate clinker)
(1) Chemical components (CaO, Al ₂ O ₃ , P ₂ O ₅ ) Analysis was performed according to JIS R2522.
(2) Mineral composition: Analysis was performed using an X-ray diffraction analyzer "Miniflex" manufactured by Rigaku Corporation. Quantitative analysis was performed by the Rietveld method with the addition of silica as an internal standard, and the amorphous and each mineral was quantified.
(3) D50: Analysis was performed using a particle size distribution analyzer MT3000 manufactured by Microtrac Bell.
(4) Blaine specific surface area: Analysis was performed using a Blaine air permeation device/powderness measuring device manufactured by Tsutsui Rikagaku Kikai Co., Ltd.

<Preparation of mortar>
The above-mentioned calcium aluminate clinker pulverized product was used as alumina cement A, and a kneaded product was prepared using the following kneaded material according to JIS R2521. The following mortar test was conducted using the obtained kneaded material (mortar). The results are shown in Table 2.
(kneaded material)
・Standard sand (Toyoura Silica Sand manufactured by Toyoura Silica Mining Co., Ltd.) 1040g
・Alumina cement A (crushed calcium aluminate clinker product above) 520g
・Tap water 312g

(Mortar evaluation method)
(1) Fluidity: After the kneaded material was left in a thermostatic chamber at 20° C. for a predetermined period of time, it was subjected to falling motion 15 times in accordance with JIS R 5201 (physical testing method for cement) flow test, and the flow value was measured.
(2) Curing time: When the kneaded material was left in a thermostatic chamber at 20° C., the time from water injection until the exothermic temperature reached the maximum was measured with a temperature recorder, and the exothermic time was defined as the exothermic time.
(3) Curing strength: The prepared mixture was poured into a 4 x 4 x 16 cm formwork while stamping with a push rod, the surface was leveled with a cement knife, and the compressive strength after curing for 24 hours. was measured.
(4) Dry strength: The specimen for curing strength measurement was dried at 110° C. for 24 hours, then allowed to cool to room temperature, and the compressive strength was measured.
(5) Crack resistance: The specimen for dry strength measurement (40 x 40 x 160 mm) was repeatedly heated to 1300°C and cooled with water, and the number of repetitions until peeling due to thermal shock was compared.

<Preparation of alumina cement B>
100 parts by mass of α-Al ₂ O ₃ was added to 100 parts by mass of the calcium aluminate produced above, and the mixture was ground to a Blaine specific surface area of 4,800±200 cm ² /g using a ball mill to produce alumina cement B. did.

<Castable combination>
(1) Fireproof aggregate/sintered alumina aggregate 76 parts by mass, silica fume 5 parts by mass, finely powdered alumina 14 parts by mass (2) Alumina cement B 5 parts by mass (3) Additives - Sodium tripolyphosphate 0.05 parts by mass ( (Added at an external rate)
・Boric acid 0.03 parts by mass (added on an external basis)
(4) Added water 6.0 parts by mass (added in proportion)

The mixture blended according to the above <Castable Mixture> was kneaded for 5 minutes in a mixer to produce a kneaded product (unshaped refractory). Using the obtained kneaded material, the following characteristics of the monolithic refractory were evaluated. The results are shown in Table 3.

(Evaluation method for monolithic refractories)
(1) Fluidity: After the kneaded material was left in a thermostatic chamber at 20° C. for a predetermined period of time, it was subjected to falling motion 15 times in accordance with the JIS R2521 flow test, and the flow value was measured.
(2) Curing time: When the kneaded material was left in a thermostatic chamber at 20° C., the time from water injection until the exothermic temperature reached the maximum was measured with a temperature recorder, and the exothermic time was defined as the exothermic time.
(3) Curing strength: The prepared mixture was placed in a 4 x 4 x 16 cm formwork while stamping with a push rod, and the surface was leveled with a cement knife.The compressive strength after curing for 24 hours was determined. It was measured.
(4) Dry strength: The specimen for curing strength measurement was dried at 110° C. for 24 hours, then allowed to cool to room temperature, and the compressive strength was measured.
(5) Crack resistance: The specimen for dry strength measurement (40 x 40 x 160 mm) was repeatedly heated to 1300°C and cooled with water, and the number of repetitions until peeling due to thermal shock was compared.

The calcium aluminate used in the mortar of each Example A and the monolithic refractories of each Experimental Example B can be cured for a longer time than in Comparative Examples A1 and 3 and Comparative Examples B1 and 3, and compared to Comparative Examples A2 and B2. Since the curing time can be shortened compared to that of the conventional method, it was possible to provide delayed curing properties and an appropriate curing time.
The calcium aluminate used in each of these examples can be suitably used as an alumina cement material.

Claims (8)

A calcium aluminate having a CaO/Al ₂ O ₃ molar ratio of 0.50 or more and 2.00 or less,
Calcium aluminate _{containing P2O5} . The calcium aluminate according to claim 1,
A calcium aluminate in which the content of P ₂ O ₅ contained in the calcium aluminate is 0.01% by mass or more and 0.60% by mass or less. Calcium aluminate according to claim 1 or 2,
One selected from the group consisting of CaO.Al ₂ O ₃ , 2CaO.Al ₂ O ₃ .SiO ₂ , CaO.TiO ₂ , 12CaO.7Al ₂ O ₃ , CaO.2Al ₂ O ₃ , and 3CaO.Al ₂ O ₃ or two or more, and calcium aluminate, including amorphous. Calcium aluminate according to any one of claims 1 to 3, comprising:
A calcium aluminate having a Blaine specific surface area of 1,500 cm ² /g or more and 15,000 cm ² /g or less. Calcium aluminate according to any one of claims 1 to 4,
Calcium aluminate having D50 of 1.0 μm or more and 30.0 μm or less, where D50 is the particle diameter at which the cumulative value is 50% in the volume frequency particle size distribution measured by laser diffraction scattering method. Calcium aluminate according to any one of claims 1 to 5, comprising:
Calcium aluminate containing SO ₃ and/or ZrO ₂ . Alumina cement comprising calcium aluminate according to any one of claims 1 to 6. A monolithic refractory comprising the alumina cement according to claim 7 and a refractory aggregate.