JPH11130529A - High zirconia refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high zirconia refractory having excellent corrosion resistance and foamability, low base-contamination property to molten glass and capable of improving the yield of glass article by crushing a molten and solidified high-zirconia material composed mainly of monoclinic ZrO2 containing matrix glass, mixing the crushed product with a composition similar to the glass matrix and firing the mixture. SOLUTION: The objective refractory having a ZrO2 content of >=85 wt.% and an SiO2 content of <=10 wt.% can be produced by mixing (A) a molten and solidified high-zirconia material composed mainly of monoclinic ZrO2 , containing matrix glass containing Al2 O3 and SiO2 and crushed to particle diameter of <=0.15 mm with (B) a separately prepared composition similar to the matrix glass, having a chemical composition of 50-90 wt.% of SiO2 5-40 wt.% of Al2 O3 , 5-20 wt.% of Na2 O and 0-20 wt.% of ZrO2 and having particle diameter of <=0.15 mm at a B/(A+B) ratio of 2-7 wt.%, forming the mixture by a mold-pressing process or a CIP process and firing the molded article at >=1400 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high zirconia refractory suitable mainly as a refractory for a glass melting tank kiln.

[0002]

2. Description of the Related Art Refractories used in conventional glass melting tank kilns are roughly classified into sintered (bonded) refractories and molten refractories. Sintered (bonded) refractories are produced by molding powder materials that are homogeneously mixed by pressing or the like, and then firing. In this refractory, a gas attached to powder as a raw material and a part of a gas generated during firing remain even after firing, the density of the fired body is low, and the corrosion resistance is low. Low corrosion resistance indicates that when used for melting glass, the probability of occurrence of defects such as bubbles and gravel is high.

On the other hand, a molten refractory is obtained by melting a homogeneously mixed raw material in a melting furnace such as an electric arc furnace, pouring it into a mold, cooling and resolidifying it, and has a dense and developed crystal structure. Among them, refractories containing a relatively large amount of zirconia have excellent corrosion resistance and are used favorably in glass melting furnaces. As a refractory widely used in such a molten refractory, a ZrO ₂ content of 33 to 33 is used.
41% by weight of Al ₂ O ₃ -ZrO ₂ -SiO ₂ refractory material, there is a high zirconia refractory containing ZrO ₂ 80 to 95 wt%. Since the latter has higher corrosion resistance and lower soil contamination than the former, it has recently been widely used as a refractory for high-quality glass melting furnaces.

[0004] Originally, zirconia is 900-1200 ° C.
Since undergoes a phase transition between monoclinic crystal and Akira Masakata at, Y ₂
A sintered body cannot be obtained unless O ₃ or CaO is added to at least partially stabilize zirconia. Even when partially stabilized or stabilized zirconia is used as a refractory for melting glass, the stabilizer is selectively eluted due to alkali or the like in the molten glass or glass volatiles, and the corrosion resistance is extremely low.

[0005] JP-A-7-293851 and JP-A-8-1
No. 04567 discloses a zirconia-based refractory containing molten zirconia as a refractory used in the furnace bottom of a waste melting furnace and a glass melting furnace, and discloses a high zirconia-based molten refractory as molten zirconia. Sintering aids such as clay are used for sintering.

When such a substance as a sintering agent is added, the high-temperature strength and corrosion resistance of the refractory itself decrease. For example, when clay is added to partially stabilized zirconia as a sintering aid, abrasion resistance and uniformity of the structure are reduced (Japanese Patent Publication No.
-18774). Further, when using a high zirconia-based molten refractory, a sintering aid such as clay and the matrix glass react with each other to easily form crystals, and the matrix glass content is relatively reduced, which is accompanied by a phase transition. It becomes difficult to absorb the change in volume, and the thermal cycle resistance decreases.

[0007]

As described above, the sintered refractory has a drawback that it is difficult to use, particularly in a portion in contact with molten glass or glass volatiles, because of its high porosity and low corrosion resistance. On the other hand, high zirconia-based molten refractories contain a large amount of zirconia and are expensive because they melt at about 2500 ° C. and solidify in a mold. Furthermore, casting cavities (voids) are produced by cooling in manufacturing, and a portion containing many of them may be as large as half in volume, resulting in a low product yield. There is a method of pulverizing the part containing many voids and reusing it as a return cullet.However, it is difficult to control the components of the product, and the purity decreases due to iron content mixed during pulverization,
The refractory has not been put to practical use because it loses the advantages of high corrosion resistance and low soil pollution, which are advantages of the refractory.

[0008] It has been desired to develop a refractory which improves the disadvantages of both the combined refractory and the molten refractory as described above and has both advantages. However, such a refractory has not yet been developed. It is an object of the present invention to solve the above problems and to provide a high quality refractory which can be manufactured at low cost. If such a refractory can be manufactured, the yield of the melt should be improved by using it as a furnace material for melting glass or the like. Furthermore, it leads to effective use of zirconia resources.

[0009]

DISCLOSURE OF THE INVENTION The present invention relates to a refractory mainly used in a glass melting tank kiln, which is a high zirconia melt-resolidified material containing a matrix glass containing monoclinic ZrO ₂ as a main component. The present invention provides a high zirconia refractory obtained by sintering a mixture of the pulverized product of the above and a matrix glass-like composition prepared separately.

The high zirconia molten refractory has few pores inside except for the casting cavity. Since there is a high porosity and uneven distribution of pores in a portion having a casting cavity, it is hardly used as a refractory. However, the casting cavity can be easily removed by grinding to some extent. The portion without the casting cavity (the solid phase portion in which pores are removed from the portion having a large number of casting cavity) is only small in size as a refractory, is dense, has a low porosity, and is a product. Compared to the part with no or few casting cavities,
These properties are not inferior at all. Furthermore, the degree of oxidation is rather higher than that of a portion that does not include a casting cavity.

[0011] It is known that molten refractories having a high degree of oxidation have low soil pollution, especially low foaming properties. The refractory of the present invention uses a material having a higher degree of oxidation than a normal molten refractory and is further fired, so that it is expected that the base material contamination is low. Furthermore, since the site including the casting cavity is used, the cost can be reduced and the resources can be effectively used.

The refractory for obtaining the pulverized high zirconia molten refractory used in the present invention can be produced by a usual method for producing a molten refractory, such as the following method. That is,
It can be obtained by pulverizing a portion containing a casting cavity generated during the production of a high zirconia molten refractory as disclosed in JP-B-59-12619 and JP-A-1-100068 by using a pulverizer. Since the casting cavity has a large volume in most cases, it can be almost removed by pulverizing the casting cavity to a particle size of about 5 mm. However, if the size of the crushed material is too large,
This may cause pores in the sintered body, lower the uniformity of the structure, and lower the corrosion resistance.

The pulverized high zirconia melt-resolidified material mainly composed of monoclinic ZrO ₂ containing matrix glass used in the present invention has a structure in which a small amount of matrix glass surrounds a perimeter of a baddelite crystal phase. are those, as long as a main component monoclinic ZrO _2, as a chemical _composition, ZrO 2: 85 to 97 wt%,
SiO _2: 2 to 13 wt%, Al ₂ O _3: may be those well known in the order of less than 1 wt%: less than 3 wt%, Na ₂ O and other.

The monoclinic Zr used in the present invention as described above.
The matrix glass of the pulverized material containing O ₂ as a main component usually contains Al ₂ O ₃ and SiO _2, and often contains Na ₂ O. Further, even when the pulverized product of the molten and re-solidified product is sintered, the chemical composition of the sintered body is almost the same as that of the pulverized product.

The addition of the matrix glass-like composition is as follows:
It plays a role of improving thermal cycle resistance against the heat history during use of the product of the present invention. When only the pulverized high zirconia molten refractory is sintered, zircon is partially generated in the matrix glass phase, and the thermal cycle resistance may be reduced. If a matrix glass-like composition prepared separately is added to this, the amount of the matrix glass phase that plays a role in relaxing the phase transition of zirconia is increased, and the thermal cycle resistance is improved.

In the present invention, the matrix glass-like composition includes, as a main component, a main component forming a matrix glass component contained in a pulverized product containing monoclinic ZrO ₂ as a main component. is intended, for specifically the pulverized material are those usually comprising a matrix glass composed mainly of Al ₂ O ₃ and SiO _2, also Al ₂ O as a matrix glass like compositions used in the present invention
_3, the SiO ₂ as a main component, further in the matrix glass of the usual the pulverized product because they often contain a Na ₂ O, is preferably those containing Na ₂ O.

The amount of the matrix glass-like composition to be added is preferably 2 to 7% by weight based on the total amount of the composition and the pulverized high zirconia melt-resolidified material mainly composed of monoclinic ZrO ₂ . If the amount is less than 2% by weight, the thermal cycle resistance may not be sufficiently improved.
₂ content is high and ZrO ₂ content is low, so that corrosion resistance and high-temperature strength are reduced.

For the same reason, it is desirable that the refractory as a sintered body has a ZrO ₂ content of 85% by weight or more and a SiO ₂ content of 10% by weight or less.

Further, by adjusting the composition of the matrix glass-like composition, the formation of zircon can be suppressed or prevented. Therefore, the chemical composition of the matrix glass-like composition is as follows: SiO ₂ : 50 to 90% by weight, Al ₂ O ₃ : 5
40 wt%, Na ₂ O: 5 to 20 wt%, and ZrO
₂ : 0 to 20% by weight is preferred.

Further, in order to suppress the dissolution of the ZrO ₂ component in the matrix glass-like composition to be added, the Al ₂ O ₃ content of the matrix glass-like composition and the ZrO ₂ content
Preferably, at least one of the _two contents is higher than their proportion in the matrix glass of the high zirconia melt-resolidification product.

Here, the Al ₂ O ₃ component of the matrix glass of the high zirconia molten and re-solidified material is a bulk Al ₂ O _{3 of the} molten and re-solidified material because the Al ₂ O ₃ component does not exist in the baddelite crystal phase. It is calculated from the content and the ZrO ₂ content by the following formula.

Al ₂ O ₃ content (% by weight) of matrix glass = [bulk Al ₂ O ₃ content (% by weight) / (10
0- ZrO ₂ content of bulk (weight%))] × 100.

On the other hand, the ZrO ₂ content of the matrix glass of the high zirconia molten and re-solidified material is determined by an electron beam microanalyzer when the calculated Al ₂ O ₃ content of the matrix glass is about 10 to 20% by weight. When measured, it is usually in the range of 2.0-2.5% by weight.

As a matrix glass-like composition,
B ₂ O ₃ and P ₂ O ₅
May be used as a glass skeleton-modified oxide containing an alkali metal oxide other than Na ₂ O, an alkaline earth metal oxide, or the like.

The matrix glass-like composition is prepared as follows. Silicon dioxide, alumina,
Mix predetermined amounts of sodium carbonate and zirconia,
Using an electric furnace in an oxidizing atmosphere or a method described in JP-A-6-345532, the mixture is melted at a temperature of about 1700 ° C. or more and cooled to room temperature. After the melting, as a means for coarse pulverization, a method in which a high-temperature molten material is directly introduced into water can be adopted.

In the present invention, the particle size of the pulverized high zirconia melt-resolidified product is preferably less than 1.00 mm in consideration of the uniformity of the structure of the sintered body and low porosity. Here, less than 1.00 mm means that the aperture is 1.00 mm.
mm means particles passing through a sieve. Further, in order not to include a non-uniform structure portion (also referred to as worm tracing) peculiar to a high zirconia molten refractory, a particle size of 0.1
It is preferable to use only 5 mm or less, and more preferably only 0.10 mm or less in particle size. This is because the heterogeneous structure containing a large amount of pores and matrix glass has a band shape of about 0.1 mm, but the influence thereof can be eliminated.

The particle size of the matrix glass-like composition is
It is preferable that this is equal to or less than the pulverized high zirconia molten re-solidified material so that it is uniformly distributed around the high zirconia molten refractory during sintering. That is, the preferred particle size of the matrix glass-like composition is 0.15
mm or less.

Further, when an iron pulverizer is used at the time of pulverization, it is preferable to remove the mixed iron by using a magnet after the pulverization or by washing with an acid such as dilute hydrochloric acid. In this way, the soil becomes less polluted.

A pulverized high zirconia melt-resolidified material mixed in a dry or wet process and this matrix glass-like composition are formed by a die pressing method or a CIP method. In particular, molding can be performed without using a binder. However, when many raw materials having a large particle size are used, molding is difficult without using a binder. A binder may be used,
It should not deteriorate the corrosion resistance and foaming properties of the refractory after firing.

The compact is fired at a temperature of 1400 ° C. or higher. By this calcination, the reducing substance in the raw material is oxidized, so that the degree of oxidation further increases. If it is desired to further promote oxidation, the temperature may be maintained at, for example, about 900 ° C. at which oxidation of carbon is completed. The calcination is preferably performed in air or an oxidizing atmosphere under atmospheric pressure or under pressure. The firing temperature is preferably from 1500 to 1700C, particularly preferably from 1550 to 1650C.

Normally, monoclinic zirconia that is not stabilized cannot be sintered due to residual expansion when cooled below the firing temperature, but the sintered product of the present invention can be obtained without cracks. This is presumably because the matrix glass phase surrounding the baddelite phase and the matrix glass-like composition to be added alleviate the residual volume expansion, thereby suppressing the occurrence of cracks.

Since the raw material is a dense and low porosity molten refractory pulverized material, and the matrix glass and the matrix glass-like composition derived from the high zirconia molten and re-solidified material at the time of firing have a low viscosity, Since it flows around the grains, it has a low porosity despite being a sintered refractory. It is also considered that the pores existing to some extent reduce the volume expansion.

During firing, there is almost no grain growth of the badelite, so there is no segregation of zirconia beyond that of the raw material particles. This is because high zirconia molten refractory has many pores and matrix glass, and there is a part where corrosion resistance and base soil pollution are inferior locally.
It is a more homogeneous and highly reliable refractory.

[0034]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples (Examples 1 to 8) and Comparative Examples (Examples 9 to 11), but the present invention is not limited thereto.

An example of the method for producing the product of the present invention will be described below. First, a predetermined amount of desilicated zircon, Bayer alumina, silica sand, and sodium carbonate were weighed and mixed, and then mixed in a 500 kVA single-phase electric arc furnace using a graphite electrode.
At about 50 ° C., it was completely melted. This molten metal is buried in Bayer Alumina with inner dimensions of 160 mm x 200 mm x 3
Hot water was poured into a 50 mm graphite mold and allowed to cool to room temperature. Next, the ingot was cut to obtain a portion including a casting cavity.

This was ground with a jaw crusher and then with an iron pot to obtain a ground product having a particle size of about 1 cm. Next, this was immersed in a 1 mol / L hydrochloric acid aqueous solution to dissolve and remove mixed iron, washed with water, and dried. In addition, by crushing,
About 0.1% by weight of Fe ₂ O ₃ was found to be incorporated. Furthermore, it was pulverized using alumina balls. Then, a pulverized product having a particle size of 0.15 mm or less was obtained using a sieve. Table 1 shows the chemical composition (unit:% by weight). The chemical composition was measured as follows for a fraction of less than 0.15 mm of the pulverized product. The SiO ₂ content and Al ₂ O ₃ content were quantified by a glass bead method using a fluorescent X-ray analyzer,
_The 2O content was determined using an atomic absorption spectrophotometer after decomposition with hydrofluoric acid-sulfuric acid.

[0037]

[Table 1]

On the other hand, the matrix glass-like composition is
A predetermined amount of silicon dioxide, alumina oxide, sodium carbonate, and zirconium oxide (all special grades) were weighed and mixed, and an electric furnace using lanthanum chromite as a heating element was used.
It was prepared by heating at 50 ° C. for 4 hours. This was pulverized with an alumina mortar to obtain a pulverized product having a particle size of 0.15 mm or less. Table 2 shows the chemical composition (unit:% by weight). In addition, the chemical composition is about the fraction of less than 0.15 mm of the pulverized product,
The Al ₂ O ₃ content, Na ₂ O content, and ZrO ₂ content are:
After decomposition with hydrofluoric acid-sulfuric acid, quantification was performed using an ICP emission spectrometer or an atomic absorption spectrometer.

[0039]

[Table 2]

Then, 1000 g of a mixture of the crushed high zirconia re-solidified material and the matrix glass-like composition at a ratio shown in Table 3 was pressed by a die press, and further by a CIP method (1.5 ton / cm ² ). And a raw product was obtained. This is heated at 1600 ° C. for 24 hours in a resistance heating electric furnace.
Fired for hours. All of the sintered bodies were obtained without cracking.

In Example 9, a partially stabilized zirconia sintered product (3 mol% Y ₂ O ₃ added) was used, and in Examples 10 to 11, a high zirconia molten and re-solidified product (sample Z2 in Table 1) and a clay were used. (S
iO ₂ content 77.6% by weight, Al ₂ O ₃ content 17.1
%, Loss on ignition 4.1%) and 9% by weight, respectively.
A mixture treated at 0:10 (Example 10) and 95: 5 (Example 11) in the same manner was used. Examples 1 to 11 above
The following tests were conducted for

For examining the corrosion resistance, a 15 mm × 15 m
A rectangular parallelepiped sample of mx 50 mm was cut out from the fired body and placed in a molten glass for a tube panel filled in a platinum crucible with 1500 pieces.
C. for 48 hours. Then, it was equally divided in the vertical direction, and the erosion amount was measured (Table 3).

Further, in order to examine the foaming property, a 50 mm ×
Cut out a 50 mm x 5 mm plate-shaped sample from the fired body,
An alumina ring having an inner diameter of 30 mm was placed thereon, and the glass was placed therein, heated at 1500 ° C. for 24 hours, and gradually cooled to room temperature. Thereafter, the number of bubbles remaining in the glass was measured using an optical microscope (Table 3).

[0044]

[Table 3]

As can be seen from Table 3, the products of the present invention have excellent corrosion resistance and foamability. From the above, the product of the present invention can be used as a refractory for use in a furnace for melting glass, regardless of contact or non-contact with the molten glass. The refractory of the present invention can be used not only for melting glass but also as a refractory used for melting metals, melting incineration ash, and the like.

[0046]

The fired refractory of high zirconia of the present invention has a uniform structure and composition, has stable quality and reliability, and is excellent in corrosion resistance and foamability. Therefore, it can be used appropriately as a refractory for glass melting tank kilns,
Since glass defects such as bubbles and gravel are unlikely to occur in the molten glass, that is, the soil pollution is low and the yield of glass production is improved, so that the industrial value is great. Further, since the product of the present invention can use a portion containing a casting cavity that cannot be used as a product of a high zirconia-based molten refractory, it can contribute to resource recycling, that is, resource saving.

Claims (7)

[Claims] 1. Monoclinic ZrO containing matrix glass
_2. A high zirconia refractory obtained by sintering a mixture of a pulverized high zirconia melt-resolidified material containing ₂ as a main component and the matrix glass-like composition prepared separately. 2. The refractory according to claim 1, wherein the matrix glass-like composition accounts for 2 to 7% by weight based on the total amount of the high zirconia melt-resolidified product and the pulverized product. 3. The method according to claim 1, wherein the ZrO ₂ content is 85% by weight or more and the SiO ₂ content is 10% by weight or less.
Refractories described in. 4. A matrix glass comprising Al ₂ O ₃ , SiO _2
2 , the chemical composition of the matrix glass-like composition is as follows: SiO ₂ : 50 to 90% by weight, Al ₂ O ₃ : 5 to 4
0 wt%, Na ₂ O: 5 to 20 wt%, and ZrO _2:
The refractory according to claim 1, 2 or 3, wherein the content is 0 to 20% by weight. 5. A matrix glass-like composition of Al ₂ O
5. The refractory according to claim 1, wherein at least one of the ₃ content and the ZrO ₂ content is higher than the proportion of the high zirconia melt-resolidified material in the matrix glass. 6. 6. A sintering mixture comprising a re-solidified high zirconia material having a particle size of less than 0.15 mm and a matrix glass-like composition having a particle size of less than 0.15 mm. The refractory according to 4 or 5. 7. The refractory according to claim 1, wherein the refractory is used in a glass melting tank kiln.