KR102363212B1 - Aggregate for refractory materials, manufacturing method thereof, and refractory materials using same - Google Patents

Abstract

Problem: An amorphous refractory material manufactured using a porous heat insulating aggregate having CaO·6Al ₂ O ₃ (CA6) as a crystalline phase WHEREIN: Sufficient strength is ensured and peeling and disintegration are suppressed.
Solution: The water absorption by the boiling method specified in JIS R 2205:1992 when classified into particle sizes of 3 mm or more and less than 6 mm is 50% or more and 100% or less, and the bulk density is 0.40 g/cm 3 By setting it to 0.60 g/cm 3 or less, the breaking strength of CA6 particles is improved, and when a refractory material is manufactured using the CA6 particles, the area of the interface between the CA6 particles in the refractory material and the matrix material is large, the bonding strength is strong, and the refractory material is strength is improved.

Description

Aggregate for refractory materials, manufacturing method thereof, and refractory materials using same

The present invention relates to an aggregate for refractories that can be used in the field of refractory materials such as steel-related furnace materials, a method for manufacturing the same, and a refractory material using the same, and particularly, an aggregate for refractories having thermal insulation properties, workability and long-term stability, and a method for manufacturing the same is about

In the field of steel-related refractories, which is one of the major fields of use of refractory aggregates, the conventional shaft furnace construction method using fixed refractories has recently been mechanized for cost saving and maintenance resource saving. , is being converted to a shaft furnace method using an irregular refractory material. In the shaft furnace method using an irregular refractory material, the necessity of mass construction using a pressure-feeding pump is arisen.

On the other hand, in recent years, it has come to be a situation where it is necessary to work _on CO2 emission reduction from an environmental problem, _and reducing CO2 emission is considered by improving the heat insulation property of the refractory material used for the heating furnace etc. in steel-related.

As a conventional heat insulator used in the steel industry, a method of inserting a ceramic fiber between a refractory material and a support body to improve thermal insulation has been the mainstream, but from November 2015, in the Labor Safety Act, refractory ceramic fiber (RCF) has become " Revisions have been implemented to add to the "Management Class 2 Substances" of "Specified Chemical Substances (Category 2 Substances)", and development of refractory materials with high thermal insulation properties is progressing even without the use of ceramic fibers.

In Patent Document 1, it is proposed to provide a refractory material excellent in heat insulating properties by using CaO·6Al ₂ O ₃ (calcium hexaaluminate, also referred to as CA6 hereafter) for the aggregate for refractories. The proposed aggregate for refractories is porous CA6 grains, which have high thermal insulation properties, are excellent in heat resistance and mechanical strength, and are promising as aggregates for refractories with high thermal insulation properties even without the use of ceramic fibers. The higher the volume of pores per unit weight of the aggregate, the higher the thermal insulation properties. The volume of pores per unit weight can be evaluated by the method for measuring the water absorption by the boiling method specified in JIS R 2205: 1992 "Method for Measuring Apparent Porosity, Water Absorption Rate, and Specific Gravity of Refractory Bricks".

In Patent Document 2, a porous heat insulating aggregate having CaO·6Al ₂ O ₃ as a crystalline phase is blended in a granulation zone, and a refractory powder composition in which an alumina raw material and alumina cement are blended in a fine-grained zone, and an application water. Insulation refractory materials containing the has been proposed, and it is said that it can be used as a heat insulating material covering a skid pipe of a steel piece heating furnace or a crack furnace, or a support pipe supporting the same.

Publication No. PCT/WO00/30999 Japanese Patent Laid-Open No. 2009-203090

As one of the construction methods of irregular refractories, a construction method in which a castable containing aggregate for refractories and alumina cement and water are mixed with a material for irregular refractories is poured into a mold. When the strength after construction is insufficient, peeling or disintegration occurs in the refractory material, and CO ₂ emission increases due to insufficient thermal insulation, and an increase in cost due to repair of the refractory material occurs.

A refractory material using CA6 particles as an aggregate has a structure in which porous CA6 particles are dispersed in a matrix portion composed of an alumina material and alumina cement surrounding it. It is considered that peeling or disintegration of the refractory material occurs when the breaking strength of the CA6 particles is insufficient or when the bonding between the CA6 particles and the matrix is insufficient.

As a result of intensive studies to solve the above problems, the present inventors have found that when a refractory material is manufactured using crushed CA6 particles with a high porosity and a low bulk density, the interface between the CA6 particles in the refractory material and the matrix material The area is large, the bonding force is strong, and the knowledge that the strength of the refractory material is improved was obtained, and the present invention was completed.

In addition, the present inventors have found that, in the production of CA6 particles, by adding an appropriate amount of borax to the raw material, crushed CA6 particles having a low bulk density are easily obtained. obtained the knowledge to improve, leading to the present invention.

That is, in the present invention, when the crystal phase is CA6 and the particle size is classified into 3 mm or more and less than 6 mm, the water absorption by the boiling method specified in JIS R 2205: 1992 is 50% or more and 100% or less, Further, it is an aggregate for refractories having a bulk density of 0.40 g/cm 3 or more and 0.60 g/cm 3 or less, and preferably contains 0.02 mass% or more and 0.4 mass% or less of boron. It relates to an aggregate for irregular refractories.

Moreover, this invention also relates to the refractory body which used the said aggregate for refractories and made alumina cement as a binder.

In addition, the present invention is a method for producing the aggregate for refractory materials obtained by mixing and molding an aggregate raw material comprising a calcia raw material and an alumina raw material with water, and then calcining at 1000 ° C. to 1700 ° C., wherein borax is added to the aggregate raw material It also relates to a method for manufacturing an aggregate for refractories, characterized in that. This manufacturing method is a manufacturing method of the aggregate for refractories, Preferably the addition amount of the borax added to the said aggregate raw material is 0.1 mass % or more and 4.0 mass % or less.

According to the present invention, in an aggregate for refractory materials having a crystalline phase of CA6, when crushed CA6 particles having a high porosity and a low bulk density are used, the area of the interface between the CA6 particles in the refractory material and the matrix material is large and the bonding strength is high. It becomes strong, and the strength improvement of a refractory material becomes possible.

1 shows the results of X-ray diffraction analysis of CA6 particles, which are Examples of the present invention, in comparison with Comparative Examples.

Hereinafter, the present invention will be described in detail.

In the production of CA6 particles, in addition to aggregate raw materials such as calcia raw material and alumina raw material, borax is mixed or mixed and pulverized, and the molar ratio of CaO and Al ₂ O ₃ of calcium aluminate finally synthesized is approximately 1:6. It is preferable to mix|blend so that it may become a ratio, knead|mix with water, and to grind|pulverize what was obtained by baking at the temperature of 1000 degreeC - 1700 degreeC after shaping|molding with a grinder, and to manufacture.

As calcia raw materials, powdered limestone or quicklime, or CaO·Al ₂ O ₃ (CA), CaO·2Al ₂ O ₃ (CA2), 12CaO·7Al ₂ O ₃ (C12A7), 3CaO·Al ₂ O ₃ ( C3A) etc. can be used and you may use these raw materials in combination of multiple types.

As the alumina raw material, alumina (Al ₂ O ₃ ), gibbsite (Al(OH) ₃ ), boehmite (AlO(OH)), etc. can be used, and a combination of a plurality of these raw materials may be used. . However, it is known that the use of gibbsite, which is a hydrate of aluminum, is advantageous in synthesizing porous CA6 particles. By using the alumina raw material containing gibbsite, it is easy to obtain that it is a porous body structure in which flaky primary crystals of CA6 aggregated, and it is preferable.

Moreover, in order to express higher thermal insulation properties, it is effective to synthesize a porous body of CA6 having more pores. For this purpose, it is preferable to add a pore-forming agent to the raw material. For example, by adding a combustible substance to a raw material as a pore-forming agent, the pore-forming agent is burned and vaporized during firing, voids are formed in the synthesized CA6 particles, and CA6 particles with many pores are formed. As a pore-forming agent, it is possible to use starch (corn starch), polyvinyl alcohol, methyl cellulose, an acrylic resin, latex, etc. Among them, the use of starch (corn starch) is preferable because it is possible to form pores having a size of several tens of μm at a relatively low cost.

When using corn starch as a pore-forming agent, it is preferable that the addition amount is 5 mass % or more and 50 mass % or less in total raw materials. When the addition amount is less than 5 mass%, sufficient effect as a pore-forming agent cannot be obtained, and when more than 50 mass%, the volume of pores becomes too large, and sufficient mechanical strength as an aggregate for refractory materials is not obtained, and a factor of cost increase because it can be

In the method for producing an aggregate for a refractory material of the present invention, preferably borax (Na ₂ B ₄ O ₅ (OH) ₄ ·8H ₂ O) is added to the raw material of the aggregate. By adding borax, it acts as a flux during firing and accelerates the diffusion of substances of various raw materials through the formed liquid phase, the residual unreacted raw materials are suppressed, and the bond between the primary crystals of flaky CA6 is strengthened, and CA6 The effect that the intensity|strength as particle|grains becomes high is acquired.

It is preferable that the addition amount of borax added to aggregate raw material is 0.1 mass % or more and 4.0 mass % or less. When the amount added is less than 0.1 mass %, the effect of improving strength cannot be sufficiently obtained, and when it is more than 4.0 mass %, densification occurs due to the progress of sintering, the volume of pores per unit weight of the aggregate is reduced, and sufficient heat insulation is not obtained. because it will not

A method of mixing raw materials such as calcia raw material, alumina raw material, pore-forming agent, borax, etc. is not particularly limited, and each material is blended in a predetermined ratio, and a V-type blender, a cone blender, a Nauter mixer, a pan-type It is possible to uniformly mix by using a mixer, such as a mixer and an omni mixer. Mixing time is not specifically limited, Although there exists an optimal value according to a mixer, 5 minutes or more are preferable, and 15 minutes or more are more preferable. There is no designation of the upper limit of the mixing time.

In the manufacturing method of the aggregate for refractories of this invention, it is preferable to mix raw material containing calcia raw material and an alumina raw material with water, and to inject|throw-in to a kiln after shaping|molding, and to bake at 1000 degreeC - 1700 degreeC. When the firing temperature is lower than 1000°C, the firing becomes insufficient, and unreacted raw materials remain, which causes insufficient strength as a refractory material or poor stability in high temperature use. Further, if the calcination temperature is set to be higher than 1700°C, the equipment becomes large-scale, while the physical properties of the CA6 particles are almost unchanged from that of calcination at 1700°C. As a firing method, it is possible to use facilities, such as an electric furnace, a shuttle kiln, and a rotary kiln.

In the method for producing an aggregate for a refractory material of the present invention, the calcined CA6 calcined product is pulverized to an appropriate particle size with a pulverizer. Although it does not limit as a grinder to be used, Grinders, such as a ball mill, a hammer mill, a vibrating mill, a tower mill, a roller mill, and a jet mill, are preferable.

The present inventors have found that when a calcined CA6 product prepared by adding borax is pulverized to a desired particle size, crushed CA6 particles having a low bulk density are easily obtained, and when a refractory material is manufactured using the CA6 particles , found that the area of the interface between the CA6 particles and the matrix material in the refractory material was large, so that the bonding force was strong, and the strength of the refractory material was improved.

By strengthening the mechanical strength of the CA6 calcined product, wear of the fracture surface at the time of pulverization is suppressed, so it is thought that the production of crushed CA6 particles having a low bulk density after pulverization becomes possible. It is preferable that the quantity of boron contained in the aggregate for irregular refractories of CA6 particle|grains is 0.02 mass % or more and 0.4 mass % or less. When it is less than 0.02 mass %, the effect of improving strength cannot be sufficiently obtained, and when it is more than 0.4 mass %, densification occurs due to the progress of sintering, the volume of pores per unit weight of the aggregate is reduced, and sufficient thermal insulation is not easily obtained. Because.

If only producing CA6 particles with low bulk density, it can be achieved, for example, by increasing the amount of pore-forming agent to increase the volume of pores of CA6 particles, but if there are many pores, the mechanical strength of CA6 particles themselves is inhibited Therefore, the intensity|strength of a refractory material at the time of using it for the aggregate for refractories will be impaired. Therefore, it is necessary to improve the strength of the refractory material to lower the bulk density while suppressing the volume of pores per unit weight of the aggregate within a certain range.

In addition, the present inventors have found that CA6 particles having a desired water absorption (porosity) and bulk density are easily obtained when a CA6 calcined product prepared by adding borax is pulverized, but hardness while maintaining the same water absorption rate in addition to borax The effect of the present invention can be realized by adding an additive that increases

As a criterion for the volume of pores per unit weight of aggregate, it is possible to evaluate the water absorption by the boiling method specified in JIS R 2205:1992. As a result of the present inventor investigating the range of the water absorption rate and bulk density of CA6 particles required to obtain sufficient strength as a refractory material, the boiling method specified in JIS R 2205: 1992 when classifying to a particle size of 3 mm or more and less than 6 mm (煮沸) Law), when the water absorption is 50% or more and 100% or less, and the bulk density is in the range of 0.40 g/cm 3 or more and 0.60 g/cm 3 or less, it is found that the balance between strength and heat insulation as a refractory material is excellent. When the water absorption rate is lower than 50%, the pore volume is small and the thermal insulation property is lowered. When the water absorption rate is larger than 100%, the strength of CA6 particles is lowered and the strength of the refractory material is weakened. Similarly, when the bulk density is smaller than 0.40 g/cm 3 , the strength of the refractory material is weakened, and when the bulk density is larger than 0.60 g/cm 3 , the thermal insulation property is lowered.

The amorphous heat insulation refractory material of the present invention has a water absorption rate of 50% or more and 100% or less by the boiling method defined in JIS R2205:1992 when the crystal phase is CA6, and the particle size is 3 mm or more and less than 6 mm. In addition, a predetermined amount of water is added to a castable containing aggregate for refractories having a bulk density of 0.40 g/cm 3 or more and 0.60 g/cm 3 or less, and alumina cement, and the kneaded is molded by pouring it into a mold.

For example, a castable containing 40 to 70 mass% of CA6 particles of the present invention, 40 to 60 mass% of alumina cement, and 0 to 10 mass% of alumina fine powder having a particle size of less than 45 µm is used. When the compounding quantity of CA6 particle|grains is more than 70 mass %, the intensity|strength as a refractory material runs short, and when less than 40 mass %, sufficient heat insulation property is not acquired. Moreover, when there is more compounding quantity of alumina cement than 60 mass %, sufficient heat insulation property will not be acquired, and when less than 40 mass %, the intensity|strength as a refractory material is insufficient. Alumina fine powder having a particle size of less than 45 μm becomes a matrix component of a heat insulating refractory material by reaction with alumina cement, and the strength is improved compared to the case where alumina fine powder is not blended is not improved.

Although the mixing method of each material in the manufacturing method of the irregular heat insulation refractory body of this invention is not specifically limited, According to the manufacturing method of a normal irregular shape refractory body, each component raw material is mix|blended so that it may become a predetermined ratio, and a ball mill, A method of uniformly mixing using a mixer such as a V-type blender, a cone blender, a Nauter mixer, a pan-type mixer, and an omni mixer is possible.

In the construction of the amorphous insulating refractory material of the present invention, a predetermined amount of water is added to the castable, blended, and kneaded. It is preferable that the compounding quantity of the water to be added is 40-60 mass % in external percentage with respect to the total amount of castable. It is because when less than 40 mass %, sufficient fluidity|liquidity cannot be ensured and it becomes easy to become defective in construction, and when more than 60 mass %, the intensity|strength fall by the fall of the density of a refractory body will arise.

Hereinafter, the present invention will be further described based on Examples.

[Examples 1 to 5, Comparative Examples 1 to 3]

Calcium carbonate or calcium hydroxide as a calcia raw material, aluminum hydroxide as an alumina raw material, corn starch as a pore-forming agent, and borax as an additive were weighed in the formulation shown in Table 1, and then mixed using a Nauter mixer. In addition, the ratio of the calcia raw material and alumina raw material shown in Table ₁ is set so that it may become CaO/ _6Al2O3 .

<Materials used>

Calcium carbonate: Funao Limestone manufactured by Funao Mine

Calcium hydroxide: manufactured by Ito Industries

Aluminum hydroxide: C301N manufactured by Sumitomo Chemical

Cornstarch: Y-3P manufactured by Japanese cornstarch

Borax: Wako Pure Chemical Industry Manufacturing Dehybor

The mixed raw material was shape|molded to about (phi) 20 mm or less with a pan-type granulator, put into an alumina container, and baked at the temperature shown in Table 1 in an electric furnace (atmospheric atmosphere). Then, the CA6 calcined material obtained by standing to cool was grind|pulverized with the roller mill, and the aggregate for irregular refractories which uses CA6 as a crystalline phase was manufactured. The boron content of the aggregate of the obtained CA6 particles was measured by ICP (Inductively Coupled Plasma) emission spectrometry. Moreover, the obtained aggregate of CA6 particle|grains was classified into 3 mm or more and less than 6 mm of particle diameters, and the water absorption rate, bulk density, and aggregate load carrying capacity were measured. A result is shown in Table 1.

<Measuring method of water absorption>

It measured by the measuring method of the water absorption by the boiling method specified in JIS R 2205:1992 "Measuring method of apparent porosity, water absorption, and specific gravity of fire brick". Since the water absorption of the aggregate has a negative correlation with the thermal conductivity of the refractory material manufactured using it, the water absorption rate at which a refractory material with sufficiently low thermal conductivity is obtained is 50% or more ○ (pass), less than 50% × (rejected) ) was set.

<Method for measuring bulk density>

After loading the aggregate of CA6 particles obtained in a glass bottle with an internal volume of 15.8 ㎤ until it overflows from the spout of the glass bottle, tap it several times (falling from a height of 1 cm), and then push the overflowing aggregate from the spout of the glass bottle to even out the glass The value obtained by dividing the weight increment of the bottle by the internal volume was taken as the bulk density.

<Method for measuring aggregate load carrying capacity>

1 grain of CA6 grain of 3 to 6 mm is placed on a horizontal surface plate, the CA6 grain aggregate is pushed in with a load measuring instrument having a plane parallel to the surface plate, and the maximum load until the aggregate is destroyed load-bearing. Here, 10 N or more was made into (circle) (pass), and less than 10 N was made into X (failure) as a criterion for the pass/failure determination of aggregate load carrying capacity.

From Examples 1-5 of Table 1, when boron content exists in the range of 0.02-0.4 mass %, it turns out that aggregate load capacity is high to 10N or more. On the other hand, when CA6 particles were produced without adding borax, the aggregate load carrying capacity was lower than 10 N because the water absorption exceeded 100% and there were many pores. Moreover, when boron content exceeds 0.4 mass % like Comparative Example 2, although the aggregate load capacity is high as 66.3 N, water absorption shows a low value of 50 % or less, It is thought that it becomes disadvantageous as a heat insulation characteristic. Although the aggregate of CA6 particles of Comparative Example 3 contained boron of 0.02 mass% or more and had pores having an absorption rate of 50% or more, the bulk density showed a high value of 0.6 g/cm 3 or more. This is considered to be because the effect of boron addition became insufficient because the calcination temperature was low, and it became difficult to obtain crushed CA6 particles at the time of pulverization of the CA6 calcined product.

The X-ray diffraction analysis evaluation results of the aggregates of CA6 particles of Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1, and the X-ray diffraction spectra of the aggregates of CA6 particles of Examples 1, 3, and 3 are shown. 1 shows. As in Examples 1 to 5 and Comparative Examples 1 and 2, when the calcination temperature is 1450° C., it can be seen that even if calcium carbonate or calcium hydroxide is used as the calcia raw material, almost single-phase CA6 is formed. . On the other hand, from Comparative Example 3, when the sintering temperature is lower than 1000° C., a large amount of unreacted raw material Al ₂ O ₃ or CaO and a reaction intermediate CaO·2Al ₂ O ₃ (CA2) remain, and the sintering temperature is too high. It can be seen that the low

[Examples 6 to 10, Comparative Examples 4 to 6]

The aggregates of CA6 particles obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were classified into particle sizes of 3 mm or more and less than 6 mm (granular), 1 mm or more and less than 3 mm (neutral), and less than 1 mm of particle diameter (fine). , alumina fine powder having an average particle diameter of 2 µm, and alumina cement are weighed in the formulation shown in Table 2, a predetermined amount of water is added, mixed using a universal mixer, and then a 40 mm × 40 mm × 160 mm mold After pouring in, hardening at the temperature of 20 degreeC, and isolation|separation from a mold, it was made to dry at 110 degreeC for 24 hours, and the refractory body which uses CA6 particle|grains as an aggregate was obtained.

<Materials used>

Alumina fine powder: Showa Denko Manufactured AL-170

Alumina Cement: High Alumina Cement Super manufactured by Denka

The bending strength after heat-processing 1400 degreeC for the refractory material obtained by supposing the thread use conditions of a refractory body using an electric furnace was measured. A result is shown in Table 2.

<Measuring method of bending strength>

JIS R 2553: 1992 Measured by the method described in "Strength test method of castable refractories". Here, 1.5 MPa or more was made into ○ (pass), and less than 1.5 MPa was made into X (failed) as a pass/fail judgment criterion of bending strength here.

From Examples 6-10 of Table 2, in the refractory body manufactured using the aggregate of CA6 particle|grains of Examples 1-5, it turns out that bending strength is as high as 1.5 Mpa or more. On the other hand, in the case of the refractory material of Comparative Example 4 using the aggregate of CA6 particles of Comparative Example 1 to which borax was not added, the bending strength was lower than 1.5 MPa. Further, in the case of the refractory material of Comparative Example 5 produced using the aggregate of CA6 particles of Comparative Example 2 in which the boron content exceeds 0.5 mass%, the flexural strength is as high as 2.5 MPa, but as described above, the Comparative Example The water absorption of 2 is a low value of 50 % or less, and it is thought that it becomes disadvantageous as a heat insulation characteristic. In the case of the refractory material of Comparative Example 6 prepared using the CA6 particle aggregate of Comparative Example 3, the bending strength was lower than 1.5 MPa despite the aggregate load carrying capacity of 10 N or more. As in Comparative Example 3, when the CA6 particle aggregate absorption rate was 50% or more and the bulk density was higher than 0.60 g/cm 3 , crushed CA6 particles were not obtained, and when a refractory material was used, the matrix material and CA6 particles It is thought that the area of the interface of is small and the bonding force is weak, and the strength of the refractory material is weakened.

Industrial Applicability

When an appropriate amount of borax is added to the raw material in the production of CA6 particles, the breaking strength of CA6 particles is improved, and when a CA6 calcined product prepared by adding borax is pulverized to a desired particle size, crushing with a low bulk density Phase CA6 particles can be produced, and when a refractory material is manufactured using the CA6 particles, the area of the interface between the CA6 particles in the refractory material and the matrix material is large, so that the bonding force is strong, and the strength of the refractory material is improved. Therefore, this invention is very useful industrially.

Claims (5)

When the crystal phase is CaO·6Al ₂ O ₃ and the particle size is 3 mm or more and less than 6 mm, the water absorption by the boiling method specified in JIS R 2205: 1992 is 50% or more and 100% or less, and Aggregate for refractories, characterized in that the bulk density is 0.40 g/cm 3 or more and 0.60 g/cm 3 or less. The method of claim 1,
An aggregate for refractories containing boron of 0.02 mass% or more and 0.4 mass% or less. The refractory material which used the aggregate for refractory materials of Claim 1 or 2 as an aggregate, and used alumina cement as a binder. In the method for producing the aggregate for refractory materials according to claim 2 obtained by mixing and molding an aggregate raw material containing a calcia raw material and an alumina raw material with water, and then calcining at 1000 ° C. to 1700 ° C., adding borax to the aggregate raw material The manufacturing method of the aggregate for refractory materials of Claim 2 characterized by the above-mentioned. 5. The method of claim 4,
The manufacturing method of the aggregate for refractories whose addition amount of borax added to the said aggregate raw material is 0.1 mass % or more and 4.0 mass % or less.

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