JP2000247647A - Furnace material for vacuum deaerating apparatus for molten glass and vacuum deaerating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the flow rate of molten glass and to decrease the number of air bubbles generated in the molten glass during a vacuum deaerating treatment by forming the furnace portions in direct contact with the molten glass of electroforming refractories subjected to a heat treatment at >=700 deg.C under an oxygen-containing atmosphere. SOLUTION: The electroforming refractories subjected to the heat treatment at >=700 deg.C, more preferably >=1100 deg.C in the oxygen-containing atmosphere are used for the furnace materials of at least the portions in direct contact the molten glass in the flow passages of the vacuum deaerating apparatus. While the atmosphere is sufficient as the oxygen-containing atmosphere, the atmosphere made higher in oxygen partial pressure than the atmospheric pressure is preferably used. The electroforming refractories in direct contact with the molten glass are preferably formed by removing the surfaces thereof by >=5 mm from the surface layers of the casting surfaces of the electroforming refractories prior to the heat treatment. The electroforming refractories are adequately zirconia-base electroforming refractories, alumina-base electroforming refractories, alumina-zirconia-silica-base electroforming refractories, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a furnace material used for a vacuum degassing apparatus for molten glass for removing air bubbles from a continuously supplied molten glass, and to a vacuum degassing apparatus for molten glass using the same.

[0002]

2. Description of the Related Art Conventionally, in order to improve the quality of a formed glass product, a vacuum degassing apparatus for removing bubbles generated in a molten glass before forming the molten glass in a melting tank with a forming apparatus. Is used. FIG. 2 shows such a conventional vacuum degassing apparatus. The vacuum degassing apparatus 100 shown in FIG. 2 is used for a process in which the molten glass G in the melting tank 112 is degassed under reduced pressure and is continuously supplied to the next molding processing tank (not shown). And vacuum suction. The vacuum degassing tank 10 is placed horizontally in the vacuum housing 102.
4 are housed and arranged, and a rising pipe 106 and a descending pipe 108 vertically attached to both ends thereof are housed.

The rising pipe 106 communicates with the vacuum degassing tank 104, and the molten glass G before defoaming is lifted from the melting tank 112 and introduced into the vacuum degassing tank 104. The downcomer 108 is
The molten glass G after the defoaming process is communicated with the vacuum degassing tank 104.
Is lowered from the vacuum degassing tank 104 and led out to the next molding processing tank. Then, in the decompression housing 102,
A heat insulating material 110, such as a heat insulating brick, is provided around the vacuum degassing tank 104, the riser tube 106, and the downcomer tube 108 to cover them with heat. The decompression housing 1
Numeral 02 is made of metal, for example, stainless steel, is vacuum-sucked from the outside by a vacuum pump (not shown) or the like, the inside is depressurized, and a predetermined pressure, for example, 1 / Maintain a reduced pressure of 20 to 1/3 atm.

In the conventional vacuum degassing apparatus 100, the molten glass G at a high temperature, for example, at a temperature of 1200 to 1400 ° C.
Therefore, as disclosed in Japanese Unexamined Patent Application Publication No. 2-221129 filed by the present applicant, the vacuum degassing tank 104, the riser 106 and the downcomer 1
08, etc., the part which is in direct contact with the molten glass G,
Usually, it is formed of a circular pipe made of a noble metal such as platinum or a platinum alloy such as platinum rhodium.

[0005] Here, the portion that is in direct contact with the molten glass G is formed of a circular tube made of a noble metal such as platinum or a platinum alloy because a noble metal such as a platinum alloy has a low high-temperature reactivity with the molten glass and the molten glass G This is because the nonuniformity of the molten glass G due to the reaction with does not occur.

[0006]

The vacuum degassing tank 104 is preferably a circular tube from the viewpoint of mechanical strength, but the thickness cannot be increased because precious metals such as platinum are expensive. . In other words, the diameter of the circular tube cannot be so large in terms of both cost and strength, and the vacuum degassing tank 104
There is also a limit on the flow rate of the molten glass G that can be defoamed by
There was a problem that a vacuum degassing apparatus with a large flow rate could not be constructed. Of course, it is conceivable to lengthen the entire length of the vacuum degassing tank 104 to increase the capacity and increase the flow rate of the molten glass G that can be degassed, but there is a problem that the apparatus becomes longer and expensive.

[0007] The temperature of the melting tank 112 is preferably higher in order to promote the melting of the powdery raw material and to promote the defoaming under reduced pressure by lowering the viscosity of the molten glass G. However, in view of the high-temperature strength of a noble metal such as platinum, the temperature of the molten glass G at the entrance of the conventional vacuum degassing apparatus 100 is set at the above-mentioned predetermined temperature (1200 to 1400).
° C).

On the other hand, the temperature suitable for forming the defoamed molten glass in the forming tank varies depending on the formed product, for example, a plate material or a bottle material.
0-1400 ° C.). Therefore, the flow rate (defoaming amount) of the molten glass G cannot be increased, and the molten glass G
The amount of heat brought by itself is not so large. As a result, there is a problem that the temperature of the molten glass G decreases in the vacuum degassing apparatus 100, and the temperature of the molten glass G at the outlet of the vacuum degassing apparatus 100 becomes lower than the temperature required for molding.

Therefore, in order to overcome the above-mentioned problems, instead of using a noble metal such as an expensive platinum alloy for a portion of the vacuum degassing tank 104, the riser tube 106, or the downcomer tube 108 that directly contacts the molten glass G, It is conceivable to use inexpensive refractories.

However, in general, when the refractory is used in direct contact with the molten glass, fine bubbles are generated in the molten glass from the surface of the refractory. As a mechanism of this bubble generation, carbon dioxide (CO
₂ ) Release of gas such as gas or nitrogen (N ₂ ) gas into the molten glass, oxygen or molten glass in which impurities such as carbon, carbide, nitrogen, and nitride in the refractory are dissolved in the molten glass. Carbon dioxide (CO ₂ ) due to oxidation into components
Generation of gas or nitrogen (N ₂ ) gas is considered. Since such bubbles are not large enough to float in the molten glass and reach the surface thereof, it is difficult to completely remove the bubbles by vacuum degassing.

Usually, an electroformed refractory used for a melting tank or the like is produced by melting a refractory raw material in an arc type electric furnace using a graphite electrode, and then casting, cooling and solidifying the material in a mold. In this production method, it is inevitable that carbon, nitrogen, carbide, nitride and the like are contained as impurities, and it is extremely difficult to produce an electroformed refractory which does not contain these impurities.

[0012] In the case of a usual melting tank for heavy oil combustion or electro-melting, since combustion is performed by excess air or melting in the atmosphere, an atmosphere containing several% or more of oxygen at the time of heating or in the initial stage of operation. , The carbon and nitrogen components of these impurities are oxidized into gases,
Removed from refractories. For this reason, the problem of foaming is mainly limited to the initial stage of melting. For example, Japanese Patent Publication No. 5-9380 discloses, as a prior art,
A technique is described in which the atmosphere in a furnace is maintained in a high-temperature oxidation state, whereby the surface of the refractory exposed to the oxidation atmosphere in the furnace is oxidized to reduce foaming generated in an early stage of operation.

However, in a vacuum degassing apparatus,
Normally, since the defoaming treatment is carried out under an atmosphere of -500 to -600 mmHg under reduced pressure, the oxygen partial pressure is reduced to about 1/3 to 1/5 as compared with an ordinary atmosphere in a dissolving tank. Therefore, when an electroformed refractory such as an alumina-zirconia-silica type, an alumina type, and a zirconia type is used for a surface which is in direct contact with the molten glass, the impurities in the refractory are oxidized at an early stage of operation to remove carbon dioxide, It is difficult to efficiently remove it as a gas such as nitrogen.

The present invention has been made in view of the above-mentioned circumstances, and the manufacturing cost of the apparatus is greatly reduced as compared with the case where a noble metal such as platinum is used, and the flow rate of molten glass can be increased. Furnace material for a vacuum degassing apparatus capable of reducing the number of bubbles generated in molten glass due to impurities in a refractory during a vacuum degassing treatment and obtaining a glass product of excellent quality. Another object is to provide a vacuum degassing apparatus.

[0015]

That is, according to a first aspect of the present invention, there is provided a furnace for use in at least a portion of a flow path of a vacuum degassing apparatus for defoaming molten glass which is in direct contact with the molten glass. Material, in an oxygen-containing atmosphere, at 70
A furnace material for a vacuum degassing apparatus for molten glass, which is an electroformed refractory heat-treated at 0 ° C. or higher. The electroformed refractory as referred to herein is a refractory brick obtained by completely melting a refractory raw material, casting the melt in a mold having a predetermined shape, then gradually cooling and solidifying the molten material. The surface of the heat-treated electroformed refractory, which is in direct contact with the molten glass, is 5 mm from the surface of the cast surface of the electroformed refractory before the heat treatment.
It is preferable that the electroformed refractory is formed by removing at least 1 mm or more, and the electroformed refractory is an alumina-based electroformed refractory, a zirconia-based electroformed refractory, and an alumina-zirconia-silica-based electroformed refractory. It is preferably at least one selected from the group.

Further, as a second aspect, the present invention provides, as a second aspect, a decompression housing to be suctioned under reduced pressure, a decompression degassing tank accommodated in the decompression housing and defoaming the molten glass, and a decompression degassing tank. Introducing means for communicating the molten glass before the defoaming treatment to the vacuum degassing tank, and deriving means for communicating with the vacuum degassing tank and leading the molten glass after the defoaming treatment from the vacuum degassing tank. Wherein the vacuum degassing tank has a flow path constituted by a furnace material for the vacuum degassing device at least in a portion directly in contact with the molten glass. I will provide a. Here, the introduction means and the derivation means are a riser pipe and a downcomer pipe, respectively, and it is preferable that at least the downcomer pipe among the riser pipe and the downcomer pipe is constituted by the furnace material for the vacuum degassing apparatus. .

In a second aspect of the present invention, a decompression housing to be suctioned under reduced pressure, a decompression degassing tank accommodated in the decompression housing and for defoaming molten glass, and a communication with the decompression degassing tank are provided. Introduced means for introducing the molten glass before the defoaming treatment into the vacuum degassing tank, and deriving means for communicating with the vacuum degassing tank and leading the molten glass after the defoaming treatment from the vacuum degassing tank. Wherein the vacuum degassing tank has at least a portion that is in direct contact with the molten glass is made of an electroformed refractory, and has a flow path that is heat-treated at 700 ° C. or more in advance in an oxygen-containing atmosphere. It may be an apparatus for defoaming molten glass under reduced pressure.

Here, the introduction means and the lead-out means are a riser and a downcomer, respectively, and at least the downcomer of the riser and the downcomer is made of an electroformed refractory and has an oxygen-containing atmosphere in advance. It is preferable that the heat treatment is performed at 700 ° C. or higher. Further, the surface of the electroformed refractory, which is in direct contact with the molten glass, is 5 mm from the surface of the casting surface of the electroformed refractory before the heat treatment.
It is preferably an electroformed refractory formed by removing the above, and at least one selected from the group consisting of an alumina-based electroformed refractory, a zirconia-based electroformed refractory, and an alumina-zirconia-silica-based electroformed refractory. Preferably it is a seed.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a furnace material for a vacuum degassing apparatus for molten glass and a vacuum degassing apparatus for molten glass using the same according to the present invention will be described with reference to the accompanying drawings.
This will be described in detail. FIG. 1 is a schematic sectional view of one embodiment of a vacuum degassing apparatus for molten glass according to the second aspect of the present invention.

As shown in FIG. 1, a vacuum degassing apparatus for molten glass 10 according to a second embodiment of the present invention performs a degassing process on a molten glass G in a melting tank 24 under reduced pressure to perform a next forming process (not shown). It is used in a process of continuously supplying a tank, for example, a plate forming processing tank (for example, a float bath) or a forming work tank such as a bottle. The vacuum degassing apparatus 10 includes a generally portal-shaped stainless steel decompression housing 12, a decompression degassing tank 14 which is horizontally housed and disposed in the decompression housing 12, and has a rectangular cross section, and left and right ends of the decompression degassing tank 14. It has an ascending pipe 16 and a descending pipe 18 which are vertically housed and mounted in the respective sections. In addition, the reduced pressure defoaming device 1 of the illustrated example
0, a heat insulating material 20 is filled between the vacuum housing 12 and the vacuum degassing tank 14, the rising pipe 16 and the downcoming pipe 18, and the vacuum degassing tank 14, the rising pipe 16 and the downcoming pipe 1
8 is coated with heat insulation.

In the illustrated example, the upper portion of the riser 16 is housed in the leg 12 a of the decompression housing 12. The lower portion of the riser 16 is provided with the decompression housing 1.
The second projection 12 protrudes from the leg 12 a, is fitted into the open end of the upstream guide duct 26, and is immersed in the molten glass G in the upstream guide duct 26. The upstream guide duct 26 is connected to the melting tank 24. On the other hand, the upper part of the downcomer 18 is housed and arranged in the leg 12 b of the decompression housing 12. The lower portion of the downcomer pipe 18 is provided with the decompression housing 1.
The second projection 12 protrudes from the leg 12b, is fitted into the open end of the downstream guide duct 28, and is immersed in the molten glass G in the downstream guide duct 28. The downstream guide duct 28 is communicated with a next molding processing tank (not shown).

In the illustrated example, the decompression housing 12 is a substantially gate-shaped stainless steel housing having both legs 12a and 12b. The decompression housing 12 accommodates the decompression degassing tank 14, the ascending pipe 16 and the descending pipe 18; It functions as a pressure vessel for maintaining the inside of the vacuum degassing tank 14 under a predetermined pressure reducing condition (described later), and has a suction port 12C at the upper right portion in the drawing for vacuum suctioning the inside to reduce the pressure. The suction port 12C of the decompression housing 12 is connected to a vacuum pump or the like (not shown). Note that the shape and material of the decompression housing 12 are not limited at all, as long as the function is not hindered.

The vacuum degassing tank 14 communicates with the upper end of the riser 16 at the lower left side in FIG. 1 and the downcomer 18 at the lower right side.
The suction ports 14a and 14b for maintaining the inside of the vacuum degassing tank 14 at a predetermined reduced pressure state (set reduced pressure condition) are provided on the upper left and upper right sides of the upper side of the tank. In the vacuum degassing tank 14, the molten glass G introduced from the rising pipe 16 flows toward the right side in the figure and is led out to the downcomer pipe 18. There is provided an upper space 14s for floating air bubbles to break them. Furthermore, in order to stop air bubbles floating in the molten glass G in the vacuum degassing tank 14 to promote foam breaking, and to reduce or prevent the outflow of air bubbles downstream,
Barriers 30a and 30b are provided, a part of which is immersed in the molten glass G and the remainder protrudes into the upper space 14s.

Here, the decompression condition in the decompression degassing tank 14 depends on conditions such as the viscosity (temperature) of the molten glass G.
/ 20 to 1/3 atmosphere. Further, the level difference H between the molten glass G in the melting tank 24 and the molten glass G in the vacuum degassing tank 14 is determined by the molten glass G according to the set pressure reduction conditions.
The level difference is set so as to prevent bumping and overflow of the substrate from the vacuum degassing tank 14. Therefore, when the pressure in the vacuum degassing tank 14 is set to 1/20 to 1/3 atm, the level difference H of the molten glass G between the melting tank 24 and the vacuum degassing tank 14 is about 2.5 to 3.5 m. Becomes

The vacuum degassing tank 14 is a pipe having a predetermined dimension, preferably a rectangular cross section, and a pipe of a predetermined length, preferably a square tubular pipe (square pipe), having a high bulk density. It is composed of dense electroformed refractories. By doing so, the manufacturing cost of the apparatus is significantly reduced as compared with the case where the apparatus is made of a precious metal material such as a platinum alloy, and a large flow of molten glass can be processed. The cross-sectional shape of the flow path of the vacuum degassing tank 14 may be any shape such as a rectangle, a circle, an ellipse, and a polygon, and is not particularly limited. It is preferable because it is possible.

The electroformed refractory is not particularly limited as long as it is a refractory manufactured by electroforming a refractory raw material and then casting it into a predetermined shape, and various known electroformed refractories can be used. Yes, zirconia-based electroformed refractories, alumina-based electroformed refractories, alumina-zirconia-silica (AZS; Al ₂
O ₃ -ZrO ₂ -SiO ₂₎ based electroforming refractories etc. are preferably exemplified.

Incidentally, in the vacuum degassing tank 14, the oxygen partial pressure is 1/3 that of the atmosphere in the melting tank for normal combustion.
It is reduced to about 1/5. Therefore, when a normal electroformed refractory is used on the surface in contact with the molten glass, carbon dioxide, nitrogen, etc. are oxidized in the initial stage of operation by oxidizing impurities causing foaming such as carbon, carbide and nitride in the refractory. It is difficult to efficiently remove it as a gas. Therefore, during the vacuum degassing process, not only during the initial stage of the vacuum degassing process but also thereafter, these impurities are oxidized to oxygen dissolved in the glass and oxides in the glass. There is a problem that a large number of carbon dioxide and nitrogen bubbles are generated intermittently. In this case, the quality of the glass product cannot be sufficiently increased.

Therefore, in the present invention, an electroformed refractory is selected as a furnace material to be used at least in a portion of the flow path of the vacuum degassing apparatus which is in direct contact with the molten glass, and this is heat-treated under predetermined conditions in advance. deep. Accordingly, the present inventors have found that foaming caused by impurities in the refractory is significantly reduced during the vacuum degassing operation, and have led to the present invention. That is, in the present invention, in an oxygen-containing atmosphere, at least 700 ° C., preferably
An electroformed refractory heat-treated at 00 ° C. or higher is used as a furnace material for a vacuum degassing apparatus.

Here, oxygen is used as the oxygen-containing atmosphere.
It is not particularly limited as long as it is contained.
Enclosure is enough. In addition, the partial pressure of oxygen
Alternatively, an enhanced atmosphere may be used. As processing temperature,
Heating at 700 ° C or higher can cause foaming from the furnace material.
It is preferable from the point that the reduction effect is recognized, and is 1100 ° C.
It is particularly preferable to perform a heat treatment. In addition, processing temperature
If the upper limit is appropriately determined according to the electroformed refractory used,
Although not particularly limited, for example, the temperature is 1450 ° C. or less.
You. Above 1450 ° C, alumina-zirconia-silicon
A (AZS; Al_TwoO_Three-ZrO_Two-SiO _Two) Electroforming
This is because high-viscosity glassy material elutes from the refractory.
You.

The heating method is not particularly limited, and heating may be performed by various known methods. Also,
When constructing the vacuum degassing apparatus, an electroformed refractory before heat treatment may be used, and after the apparatus is constructed, the above heat treatment may be performed in advance in an oxygen-containing atmosphere before heating under reduced pressure.

Here, the surface of the electroformed refractory which is in direct contact with the molten glass G is preferably formed by removing at least 5 mm from the surface layer of the casting surface of the electroformed refractory before the above heat treatment. Polishing or cutting is performed to remove 5 mm or more from the surface layer of the cast surface of the electroformed refractory. After removing 5 mm or more from the surface layer of the cast surface, the vicinity of the surface layer of the heat-treated electroformed refractory is compared with the vicinity of the surface layer of the heat-treated electroformed refractory without removing the surface layer of the cast surface. This is because the content of impurities causing foaming is small.

That is, impurities contained in the electroformed refractory,
For example, in the case of carbon, since a refractory raw material containing carbon is melted in an arc type electric furnace using a graphite electrode, furthermore, since a mold is constituted by sand or graphite hardened with an organic resin material, it is manufactured. The vicinity of the surface layer of the electroformed refractory has a higher carbon content than the inside thereof. For example, in the case of a zirconia-based electroformed refractory, the distance from the surface layer of the electroformed refractory is 10 mm or more and 30 mm or more.
The carbon content of impurities contained at a depth of not more than 1 mm is 160 ppm, and the carbon content of impurities contained at a depth of 90 mm or more and 110 mm or less from the surface layer of the electroformed refractory is also 160 ppm. The carbon content as an impurity contained at a depth of 10 mm from the surface layer of the cast refractory is as high as 240 ppm. Since the content of impurities near the surface layer of the electroformed refractory manufactured in this way is higher than that of the inside, in the present invention, the surface layer of the electroformed refractory is removed by polishing or cutting, and the content of impurities is reduced. The inside of the small number of electroformed refractories is made to be the surface of the electroformed refractories that directly contact the molten glass G, and then the electroformed refractories are heated in an oxygen-containing atmosphere. As a result, even if the surface layer on the casting surface is removed, impurities near the surface layer contained in the electroformed refractory can still be oxidized and removed, so that the content of impurities is further reduced.

In the present invention, the surface layer of the casting surface of the electroformed refractory is preferably removed by 5 mm or more, more preferably 10 mm or more, in order to efficiently remove the impurities causing foaming by oxidation. It should be removed. Polishing method and cutting method for removing is not particularly limited, for example, polishing is polished using a known polishing machine such as a plane polishing machine,
Cutting is performed by a known cutting machine. The heat treatment is
Before constructing a vacuum degassing apparatus, a heat treatment may be performed on each of the electroformed refractories from which the surface layer of the casting surface has been removed, and then the electrocast refractories may be assembled to construct a vacuum degassing apparatus. Alternatively, a heat treatment may be performed after a vacuum degassing apparatus is constructed by assembling the electroformed refractory from which the surface layer of the casting surface has been removed.

It is not necessary to constitute the entire vacuum degassing apparatus as the furnace material for the vacuum degassing apparatus with the above-mentioned electroformed refractory.
At least only the portion directly contacting the molten glass may be constituted by the furnace material for the vacuum degassing apparatus. Further, the furnace material for a vacuum degassing apparatus of the present invention may be applied to only a vacuum degassing tank, or may be applied to not only a vacuum degassing tank but also an ascending pipe or a descending pipe. In this case, it is preferable to apply at least to the downcomer. This is because bubbles generated from the surface of the electroformed refractory of the downcomer pipe cannot be removed by defoaming under reduced pressure.

The method of constructing a vacuum degassing tank having a predetermined cross-sectional shape, for example, a rectangular cross-section and a predetermined length using the furnace material for a vacuum degassing apparatus of the present invention is not particularly limited. A rectangular parallelepiped refractory may be staggered three-dimensionally, that is, stacked in a labyrinth structure, and a joint portion between them may be filled with a joint material to form a pipe of a predetermined length, for example, a square tubular pipe, A tube having a short length, for example, a rectangular tube-shaped electroformed refractory may be stacked in a line, and a joint portion therebetween may be filled with a joint material to form a tube of a predetermined length, for example, a square tube. In addition, the length L of the vacuum degassing tank 14 having a predetermined cross-sectional shape used in the present invention is not particularly limited, but the depth, type, viscosity (temperature), In accordance with the flow rate (amount of defoaming treatment) and the flow rate, the molten glass G is removed from the molten glass G in the vacuum degassing tank 14 for a time necessary for the bubbles in the molten glass G to sufficiently float and to be broken and removed. The length may be set to a length capable of staying within the range, that is, a length capable of obtaining a sufficient time for the defoaming treatment.

The riser pipe 16 and the descender pipe 18 are used to maintain the level difference H between the molten glass G in the vacuum degassing tank 14 and the molten glass G in the melting tank 24, respectively. The riser pipe 16 moves the undefoamed molten glass G from the melting tank 24 to the upstream guide duct 26 by reducing the pressure.
And introduced into the vacuum degassing tank 14. Further, the downcomer pipe 18 draws out the defoamed molten glass G from the vacuum degassing tank 14 and lowers it, and sends out the molten glass G to the next forming processing tank (not shown) via the downstream guide duct 28.

Incidentally, also in the present invention, when the defoaming process is started, that is, when the molten glass G is started to flow, each part of the vacuum degassing apparatus 10, that is, the ascending pipe 16, the vacuum degassing tank 14, and the descending pipe. Since the temperature of 18 is lower than the appropriate temperature, heating is necessary for starting operation, and for this purpose, an operation start heating device (not shown) is provided. Further, although not shown, in order to start operation, it is necessary to operate the siphon principle, and not only the upstream guide duct 26 but also the downstream guide duct 28 must have the molten glass G. It is preferable to provide a bypass (not shown) for flowing the molten glass G to the downstream guide duct 28 from above.

Here, the molten glass G to be processed by the vacuum degassing apparatus 10 of the present invention is not particularly limited, and examples thereof include soda lime silica glass and borosilicate glass.

The vacuum degassing apparatus for molten glass according to the present invention is basically constructed as described above, and its operation will be described below.

First, before starting the operation of the vacuum degassing apparatus 10, the flow path 40 is sufficiently heated. This is because the inside of the flow path 40 is heated in advance so that the molten glass G is smoothly suctioned and decompressed into the decompression degassing tank 14 to be decompressed and defoamed. Further, in order to oxidize impurities existing on the surface of the flow channel 40 in advance and suppress bubbles generated from the surface of the refractory, heat treatment is performed at 700 ° C. or more in an oxygen-containing atmosphere. Thereafter, the molten glass G in the melting tank 24 is introduced into the vacuum degassing apparatus 10, that is, the bypass (not shown) is opened, and is introduced from the upstream guide duct 26 into the downstream guide duct 28. The part is immersed in the molten glass G. After completion of the immersion, a vacuum pump (not shown) is operated to evacuate the inside of the vacuum housing 12 from the suction port 12c, and thus evacuate the vacuum degassing tank 14 from the suction ports 14a and 14b. 14 is reduced to 1/20 to 1/3 atmosphere. As a result, the molten glass G smoothly rises in the riser 16 and the downcomer 18 and is introduced into the vacuum degassing tank 14, and the level difference H of the molten glass G between the melting tank 24 and the vacuum degassing tank 14 is reduced. An upper space 14s filled to a predetermined depth in the vacuum degassing tank 14 and evacuated so as to have a predetermined value.
Is formed. After this, the bypass is closed.

Thereafter, the molten glass G rises in the rising pipe 16 from the melting tank 24 via the upstream guide duct 26 and is introduced into the vacuum degassing tank 14. The molten glass G is defoamed under a predetermined decompression condition while flowing in the decompression degassing tank 14. That is, in the vacuum degassing tank 14 under a predetermined reduced pressure condition, the bubbles in the molten glass G float in the molten glass G, are blocked by the barriers 30a and 30b, break, and break in the upper space 14s. And rise to the interface of the molten glass G and break. Thus, bubbles are removed from the molten glass G. The defoamed molten glass G is led out of the vacuum degassing tank 14 to the downcomer pipe 18, descends in the downcomer pipe 18 and is introduced into the downstream guide duct 28. From the molding process tank (not shown).

[0042]

The present invention will be specifically described below with reference to examples and comparative examples. Note that the present invention is not limited to these specific examples.

[Examples 1-4, Comparative Examples 1-2] As a sample, an alumina-zirconia-silica-based refractory (zirconia content of 3), which is one of the refractories constituting the vacuum degassing tank, was used.
3% (trade name: ZB1681 (manufactured by Asahi Glass Co., Ltd.)) was heat-treated in advance in the atmosphere at the treatment temperature shown in Table 1 for 24 hours, and a sample (having a shape of 4 mm × 4 mm × 8 mm) together with soda-lime silica glass was used. 8m
Place in a quartz crucible of mx 8 mm x 10 mm height, 130
The mixture was dissolved at 0 ° C. under a reduced pressure of −600 mmHg for 30 minutes. As for the evaluation of the generation of bubbles from the refractory, the number of bubbles generated in one minute from the surface of the refractory after 30 minutes (4 × 8 mm ² ) was 1 to 2 for “small” and 3 to 5 for “medium”. , And 6 or more were indicated as "many." The evaluation was performed twice for each processing temperature.

Table 1 shows the results.

As is clear from the above results, after heat treatment at 700 ° C. or more, more preferably 1100 ° C. or more,
It can be seen that when the glass is melted under reduced pressure conditions, foaming from the refractory decreases as compared to untreated products and those treated at low temperatures. Therefore, the effect of the present invention is clear.

The vacuum degassing apparatus for molten glass according to the present invention is not limited to the siphon type vacuum degassing apparatus shown in FIG. 1, but is also disclosed in JP-A-5-262530 and JP-A-7-29.
As a matter of course, the present invention may be applied to a horizontal vacuum degassing apparatus disclosed in Japanese Patent No. 1633. The furnace material and the vacuum degassing apparatus for molten glass used in the vacuum degassing apparatus for molten glass according to the present invention have been described with reference to various embodiments, but the present invention is not limited to the above-described embodiments. Of course, various improvements and design changes can be made without departing from the spirit of the present invention.

[0047]

As described in detail above, according to the furnace material for a vacuum degassing apparatus and the vacuum degassing apparatus of the present invention, the molten glass for vacuum degassing of the present invention is replaced with a noble metal such as platinum. The furnace material is used to form a flow path such as a vacuum degassing tank in the vacuum degassing apparatus, so that the manufacturing cost of the apparatus can be greatly reduced and the vacuum degassing can be performed while increasing the flow rate. It is possible to reduce the number of bubbles generated in the molten glass due to impurities in the refractory during the foaming operation, and to obtain a glass product of excellent quality. Further, the electroformed refractory used in the furnace material for the vacuum degassing apparatus has a surface directly in contact with the molten glass before the heat treatment, and the surface is removed by 5 mm or more from the surface of the casting surface. Impurities contained in the surface layer of the electroformed refractory, which causes the generation of bubbles when contacted, are reduced, the number of bubbles in the molten glass can be reduced, and glass products of better quality can be obtained Becomes

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of one embodiment of a vacuum degassing apparatus for molten glass according to the present invention.

FIG. 2 is a schematic sectional view of a conventional vacuum degassing apparatus.

[Explanation of symbols]

 10, 110 Decompression degassing device 12, 102 Decompression housing 12a, 12b Leg 12c Suction port 14, 104 Decompression degassing tank 14a, 14b Suction port 14s Upper space 16, 106 Ascending pipe 18, 108 Descending pipe 20, 110 Insulation material 24, 112 melting tank 26 upstream guide duct 28 downstream guide duct 30a, 30b barrier 40 flow path G molten glass

Claims (9)

[Claims] 1. A furnace material used in at least a portion of a flow path of a vacuum degassing apparatus for defoaming a molten glass, which is in direct contact with the molten glass, at 700 ° C. in an oxygen-containing atmosphere.
A furnace material for a vacuum degassing apparatus for molten glass, which is an electroformed refractory heat-treated as described above. 2. The heat-treated electroformed refractory is formed by removing a surface directly in contact with the molten glass by 5 mm or more from a surface layer of a cast surface of the electroformed refractory before the heat treatment. The furnace material for a vacuum degassing apparatus for molten glass according to claim 1, which is an electroformed refractory obtained. 3. The electroformed refractory according to claim 1, wherein the electroformed refractory is at least one selected from the group consisting of an alumina-based electroformed refractory, a zirconia-based electroformed refractory, and an alumina-zirconia-silica-based electroformed refractory. Or the furnace material for a vacuum degassing apparatus for molten glass according to 2 above. 4. A decompression housing that is suctioned under reduced pressure, a decompression tank that is housed in the decompression housing, and that decompresses and defoams the molten glass; And a deriving unit that communicates with the reduced-pressure defoaming tank, and that guides the molten glass after the defoaming process from the reduced-pressure defoaming tank. A vacuum degassing apparatus for molten glass, characterized in that at least a part directly in contact with the molten glass has a flow path constituted by the furnace material for a vacuum degassing apparatus according to any one of claims 1 to 3. . 5. The vacuum decompression device according to claim 1, wherein said introduction means and said derivation means are a riser and a downcomer, respectively. The vacuum degassing apparatus for molten glass according to claim 4, comprising a furnace material for a foaming apparatus. 6. A decompression housing to be suctioned under reduced pressure, a decompression tank accommodated in the decompression housing for defoaming the molten glass, and a molten glass before being degassed which is communicated with the decompression tank. And a deriving unit that communicates with the reduced-pressure defoaming tank, and that guides the molten glass after the defoaming process from the reduced-pressure defoaming tank. Is a vacuum degassing apparatus for molten glass, characterized in that at least a part in direct contact with the molten glass is made of an electroformed refractory, and has a flow path which has been previously heat-treated at 700 ° C. or more in an oxygen-containing atmosphere. 7. An electroformed refractory formed by removing a surface in direct contact with the molten glass from a surface layer of a casting surface of the electroformed refractory by 5 mm or more before the heat treatment. The furnace material for a vacuum degassing apparatus for molten glass according to claim 6, which is a refractory. 8. The inflow means and the outflow means are an ascending pipe and a descending pipe, respectively. At least the descending pipe of the ascending pipe and the descending pipe is made of an electroformed refractory, and is previously stored in an oxygen-containing atmosphere. The vacuum degassing apparatus for molten glass according to claim 6 or 7, which has been heat-treated at 700 ° C or higher. 9. The electroformed refractory according to claim 6, wherein the electroformed refractory is at least one selected from the group consisting of an alumina-based electroformed refractory, a zirconia-based electroformed refractory, and an alumina-zirconia-silica-based electroformed refractory. The vacuum degassing apparatus for molten glass according to any one of claims 1 to 8.