JPH11240725A - Vacuum deaerator for molten glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the manufacturing cost of an apparatus, to improve the degree of freedom of apparatus design, to construct a vacuum deaerator with a great flow rate and to carry out vacuum deaeration treatment at a high temperature, by making a vacuum deaerating tank, a riser, a downcomer, etc., into a series of a closed line and constructing a flow channel composed of refractory brick. SOLUTION: This vacuum deaerator is equipped with a vacuum deaerating tank 14 installed in a vacuum housing 12, a riser 16 which communicates with the vacuum deaerating tank 14, sucks and raises molten glass and introduces it into the deaerating tank 14, a downcomer 18 for dropping and discharging the molten glass, an upstream side connecting line 22 which communicates with a melting tank 20 or an upstream side open channel having the free surface of molten glass and with the riser 16 and a downstream side connecting line 24 which communicates with a downstream side open channel or a treating tank 26 having the free surface of molten glass and with the downcomer 18. These apparatuses are composed of a series of a closed line. A flow channel directly brought into contact with molten glass in the closed lines is made of refractory brick.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in order to improve the quality of a molded glass product, as shown in FIG. 3, air bubbles generated in the molten glass before the molten glass is melted in a melting furnace by a forming apparatus. Is used. The vacuum degassing apparatus 110 shown in FIG. 3 is used for a process of degassing the molten glass G in the melting tank 120 and continuously supplying the molten glass G to the next processing tank. In this case, the pressure reducing housing 112 is provided in the decompression housing 112 in which the inside is decompressed by vacuum suction.
A decompression degassing tank 114, which is decompressed together, and at both ends thereof,
An ascending pipe 116 and a descending pipe 118 vertically attached downward are arranged, and the lower end of the ascending pipe 116 is immersed in the molten glass G of the upstream pit 122 communicating with the melting tank 120, The lower end of the downcomer 118 is
Similarly, it is immersed in the molten glass G of the downstream pit 124 communicating with the next processing tank (not shown).

The vacuum degassing tank 114 is provided substantially horizontally in a vacuum housing 112 in which the inside is decompressed by vacuum suction by a vacuum pump (not shown). /
Since the pressure has been reduced to 3 to 1/20 atm, the molten glass G in the upstream side pit 122 before the defoaming process is carried out by the rising pipe 116.
And is introduced into the vacuum degassing tank 114,
After the vacuum degassing process is performed in the vacuum degassing tank 114, it is lowered by the downcomer pipe 118 and led out to the downstream pit 124.

The decompression housing 112 is a casing made of metal, for example, stainless steel or heat-resistant steel. The interior of the decompression housing 112 is evacuated by a vacuum pump (not shown) or the like to reduce the pressure therein. The inside of the foam tank 114 is maintained at a predetermined pressure, for example, reduced to 1/20 to 1/3 atmosphere. The vacuum degassing tank 1 in the vacuum housing 112
14, around the riser pipe 116 and the downcomer pipe 118, a heat insulating material 130 such as a refractory brick for thermally insulating these.
Are arranged.

The vacuum degassing apparatus 110 of the prior art is configured to process molten glass G at a high temperature, for example, at a temperature of 1200 to 1400 ° C., so that Japanese Patent Application Laid-Open No. 2-221129 filed by the present applicant is required. As disclosed in Japanese Patent Application Laid-Open Publication No. H10-86, the flow path of the molten glass that directly contacts the molten glass G, such as the vacuum degassing tank 114, the riser pipe 116, and the downcomer pipe 118, is made of platinum or a platinum alloy such as platinum rhodium. It is composed of a circular pipe made of precious metal such as.

Here, the flow path of the molten glass, such as the vacuum degassing tank 114, the riser pipe 116, and the descender pipe 118, is constituted by a circular pipe made of a noble metal such as platinum or a platinum alloy.
Since these noble metals have low reactivity at high temperatures with the molten glass and are very unlikely to react with and elute with the high-temperature molten glass G when they come into contact with the high-temperature molten glass G, the molten glass G
This is because there is no concern that impurities may be mixed into the steel and the strength at high temperatures can be secured to some extent.

In the case where the vacuum degassing tank 114 is formed of a circular pipe made of a noble metal, a noble metal such as platinum is very expensive. Therefore, increasing the wall thickness of the circular pipe immediately increases the cost. The diameter of the circular pipe is limited in terms of both cost and strength, and the diameter of the circular pipe cannot be increased so much.
There is a limit in the flow rate of the molten glass G that can be defoamed in Step 4, and there is a problem in that a reduced-pressure degassing apparatus with a large flow rate cannot be constructed.

Since the molten glass G is obtained by melting and reacting the raw materials of the powder, it is preferable that the temperature of the melting tank 120 be high when melting, and also when defoaming under reduced pressure. Since the viscosity of the molten glass G decreases at high temperatures, it is preferable that the temperature be high. However, while it is necessary to use a noble metal alloy for the vacuum degassing tank 114 or the like from the viewpoint of high-temperature strength, the noble metal is expensive, and the wall thickness of the circular pipe cannot be made too large from the viewpoint of cost. Even if a noble metal such as platinum is used, it is inevitable that the strength decreases as the temperature increases,
The temperature of the molten glass G at the inlet of the vacuum degassing apparatus 110 is:
It was limited to the above-mentioned predetermined temperature (1200-1400 ° C.).

Therefore, if the flow path of the high-temperature molten glass is made of platinum, it must be considered from the design stage that the thin platinum is worn out and eventually has holes, and the production of glass products is temporarily stopped. Therefore, it must be a facility that can repair and renew platinum in a short time. Since the flow path made of platinum (decompression tank, riser pipe, and downcomer pipe) of the known vacuum degassing apparatus is integrated, when repairing and updating the flow path, the pressure reduction condition is released and the pressure reduction tank It was necessary to discharge all the glass inside the riser / downcomer, then lower the entire decompressor to room temperature, and then repair or renew the platinum. At this time, the lower end of the riser / downcomer is appropriate as a position to cut off the edge of the molten glass.Especially, when repairing the riser / downcomer, the pressure should be reduced in order to separate the tube from the high temperature glass reservoir below. It was necessary to suspend the entire defoaming device by at least one meter. However, moving up and down the entire vacuum degassing apparatus 110, which is large, very heavy, and has a sturdy structure that is subjected to high-temperature decompression conditions during operation, has been a very difficult and dangerous operation.

[0010]

As described above, as described above,
The conventional vacuum degassing apparatus 110 includes a vacuum degassing tank 114,
The flow path of the molten glass, such as the riser pipe 116 and the downcomer pipe 118, which directly contacts the molten glass G is made of platinum or a platinum alloy such as platinum rhodium. By the way, such a noble metal such as platinum or a platinum alloy or an alloy thereof is excellent in high-temperature reactivity and high-temperature strength as compared with other metals, but is naturally limited, and has a reduced pressure degassing tank 114.
In order to increase the size of the riser 116, the downcomer 118, etc., it is necessary to increase the thickness of the tank wall or the tube wall. However, this noble metal such as platinum is very expensive, and therefore, the cost of the vacuum degassing apparatus 110 is very high. This cost is dramatically increased because the thickness of the tank wall and tube wall must be increased as the size of the apparatus increases.
When a noble metal alloy is used, there is a limit in increasing the size of the apparatus in terms of cost. Therefore, there is a limit in the flow rate of the molten glass G that can be defoamed in the vacuum degassing tank 114, and there is a problem that a large-volume vacuum degassing apparatus cannot be constructed.

As described above, the conventional vacuum degassing apparatus has a very high defoaming efficiency for molten glass, but has a high cost.
Expensive glass for special applications where fine bubbles for optical or electronic use are not recognized because a large-volume vacuum degassing device cannot be constructed, and glass that can be produced in a relatively small amount. Was used as the main object.

Further, as described above, the temperature of the melting tank is preferably higher when melting the molten glass, and the temperature is preferably higher when performing the degassing treatment under reduced pressure. However, even if a noble metal such as platinum is used, it is inevitable that the strength will decrease as the temperature rises, and increasing the thickness of the vacuum degassing tank directly leads to an increase in cost. The temperature of the molten glass at the inlet of
It was limited to 00-1400 ° C. and could not be raised to any required temperature.

On the other hand, recently, even in the case of mass-produced glass such as inexpensive glass for architectural use and automobiles, it has been required to perform a defoaming treatment by a vacuum degassing apparatus having a high defoaming efficiency. However, as long as precious metal alloys such as platinum constitute a vacuum degassing tank, ascending pipe, downcomer pipe, etc., precious metals such as platinum are too expensive, so glass produced in large quantities can be manufactured using conventional precious metal alloy vacuum degassing. There was a problem that it was impossible at all to perform vacuum degassing treatment with an apparatus in terms of cost.
Therefore, in the conventional vacuum degassing apparatus 110 shown in FIG.
Although it is conceivable to increase the size of the apparatus and increase the flow rate of the defoaming treatment by configuring the furnace material 8 with furnace material, there is a problem that furnace material bubbles are generated in the molten glass from the furnace material surface. .

The vacuum degassing tank 1 of the vacuum degassing apparatus 110
14. If the riser pipe 116 and the downcomer pipe 118 are made of furnace material, there is a joint that joins the furnace materials. Therefore, the joint is deteriorated by the high-temperature molten glass G, and particularly, both lower ends of the riser pipe 116 and the lower pipe 118. The upper and lower pits are 12
2 and 124, the interface between the molten glass G and the air that becomes the free surface of the molten glass G deteriorates. Further, the vacuum degassing apparatus made of a furnace material is a vacuum degassing apparatus mainly made of platinum. The furnace material is made denser than the defoaming device, and the furnace material to be used is also mainly made of electroformed bricks and becomes heavier as a whole. Therefore, as in the conventional vacuum degassing device 110 shown in FIG. It is very difficult to move the vacuum degassing tank 114, the riser pipe 116, the descender pipe 118, and the heat insulating material 130 up and down as one unit, and there is a problem that it is a dangerous operation.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, in which a vacuum degassing tank, an ascending pipe and a descending pipe are made of a refractory electroformed brick which is less expensive than a noble metal alloy such as platinum. By reducing the manufacturing cost of the apparatus, improving the degree of freedom of the apparatus design, enabling the construction of a large-volume vacuum degassing apparatus, and enabling the vacuum degassing processing at a higher temperature, and , Fix the entire vacuum degassing device,
An object of the present invention is to provide a vacuum degassing apparatus for molten glass which can eliminate the operation of vertically moving a vacuum degassing apparatus which is difficult and dangerous.

[0016]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies on the enlargement and large flow rate of a vacuum degassing apparatus for molten glass. In the case of mass production such as glass, the tolerance of the presence of fine bubbles of a certain dimension or less is not as strict as glass for optical or electronic, so for example, in the case of glass for architectural and automotive, Since the presence of fine bubbles with a major axis of 0.3 mm or less is allowed, most of the generated bubbles have a diameter of 0.2 mm or less, and bubbles having a diameter of more than 0.2 mm are generated over time. It has been found that it becomes possible to use a refractory-made electroformed brick which is no longer used as a flow path for molten glass instead of a noble metal alloy.

Further, the vacuum degassing tank, the riser pipe and the downcomer pipe are made of electroformed brick made of refractory which is less expensive than the noble metal alloy, and the molten glass is continuously depressurized and degassed similarly to the case of the noble metal alloy. If it is possible, there is no need to limit the amount of use in terms of cost or limit the size in terms of the accompanying reduction in strength compared to the case of using a precious metal alloy such as platinum. It has been found that the degree of freedom is dramatically improved, a large-volume vacuum degassing apparatus can be constructed, and a vacuum degassing process at a higher temperature becomes possible.

The present inventors have obtained the above findings and have accomplished the present invention. That is, the present invention provides a decompression housing in which the inside is decompressed by vacuum suction, a decompression tank provided in the decompression housing, and a decompression degassing tank for decompressing the molten glass, and communicating with the decompression degassing tank. Provided,
An ascending pipe that sucks and raises the molten glass before vacuum degassing and introduces the vacuum glass into the vacuum degassing tank is provided in communication with the vacuum degassing tank, and the molten glass after vacuum degassing is removed from the vacuum degassing tank. A downcomer pipe that descends and exits, a melting tank having a free surface of molten glass or an upstream connection pipe communicating the upstream open channel with the riser pipe, and a downstream open channel having a free surface of molten glass or A downstream connection pipe that communicates the processing tank with the downcomer pipe, the upstream connection pipe, the riser pipe,
The vacuum degassing tank, the downcomer pipe and the downstream connection pipe are configured as a series of closed pipes, and the flow path that directly contacts the molten glass of the series of closed pipes is made of firebrick. The present invention provides an apparatus for defoaming molten glass under reduced pressure.

Further, the refractory brick constituting the flow path of the molten glass in the series of closed circuits is made of alumina-zirconia-
It is preferably at least one selected from the group consisting of silica-based electroformed refractories, zirconia-based electroformed refractories, and alumina-based electroformed refractories. The decompression housing is a metal casing integrally surrounding the decompression degassing tank, the riser pipe and the downcomer pipe, and a part of each of the upstream and downstream connection pipes. The vacuum degassing tank, the space between the riser pipe and the downcomer pipe and each part of the upstream and downstream connection pipes are filled with a heat insulating material made of refractory brick to have a multilayer cross-sectional structure. Is preferred. Further, the decompression a pressure 1 / 3-1 / 20 atmospheres degassing vessel, it is preferred that the viscosity of flow less molten glass 10 ^4.5 poise at a flow rate not less than 50 mm / sec.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a vacuum degassing apparatus for molten glass of the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.

FIG. 1 is a schematic sectional view of one embodiment of the vacuum degassing apparatus for molten glass of the present invention. As shown in FIG.
The vacuum degassing apparatus 10 for molten glass of the present invention comprises a melting tank 20.
The molten glass G is sucked and raised into the vacuum degassing tank 14 from the inside,
The vacuum degassing process is performed in the depressurized vacuum degassing tank 14, and is used for a process of continuously supplying to the next processing tank 26, for example, a plate-shaped forming processing tank such as a float bath or a forming work tank such as a bottle. Basically, the decompression housing 12, the decompression degassing tank 14, the riser 16 and the downcomer 1
It consists of eight.

The decompression housing 12 functions as a casing (pressure vessel) for ensuring airtightness when depressurizing the decompression and degassing tank 14, and in the present embodiment, is formed in a substantially portal shape. The vacuum degassing tank 14, the rising pipe 16, and the descending pipe 18 are configured so as to surround the entirety. As long as the decompression housing 12 has the airtightness and strength required for the decompression and deaeration tank 14, the material thereof,
The structure is not particularly limited, but is preferably made of metal, particularly stainless steel or heat-resistant steel. The decompression housing 12 is provided with a suction port 12c in the upper right portion for depressurizing the inside by vacuum suction. The inside of the decompression housing 12 is decompressed by vacuum suction by a vacuum pump (not shown), and is disposed substantially at the center thereof. Vacuum degassing tank 1
4 is configured to be maintained at a predetermined pressure, for example, 1/20 to 1/3 atmosphere.

At a substantially central portion of the decompression housing 12, a decompression degassing tank 14 is disposed substantially horizontally. The cross section of the flow path of the vacuum degassing tank 14 may be circular, as in the prior art, but is preferably rectangular for performing vacuum degassing of the molten glass G at a large flow rate. Further, a rectangular shape is preferable from the viewpoint of manufacturing electroformed bricks constituting the vacuum degassing tank 14. The left end of the vacuum degassing tank 14 communicates vertically with the upper end of a rising pipe 16, and the right end of the vacuum degassing vessel 14 communicates with the upper end of a downcomer pipe 18 vertically downward. The ascending pipe 16 and the descending pipe 18 are disposed so as to penetrate through the legs 12a and 12b of the gate-shaped decompression housing 12, respectively.
The lower end of the pipe 8 is connected to the melting tank 20 at a position below the liquid level of the molten glass G in the melting tank 20 and the next processing tank 26 which are configured as open channels, and the next processing line. It communicates with the downstream connection pipe 24 that communicates with the tank 26 to form a series of closed pipes.

Above the vacuum degassing tank 14, the vacuum housing 12 is evacuated by a vacuum pump or the like (not shown) so that the inside of the vacuum degassing chamber 14 has a predetermined pressure (1/2).
Suction holes 14 a and 14 b communicating with the decompression housing 12 are provided in order to maintain the pressure reduced to 0 to 1/3 atm. A space between the decompression housing 12 and the decompression degassing tank 14, the riser pipe 16, and the downcomer pipe 18 is filled with a heat insulating material 30 such as a refractory brick and is covered with heat. It has a multilayer cross-sectional structure such as a heat insulating material 30 made of a brick made of a material and a vacuum degassing tank 14 made of an electroformed brick. The heat insulating material 30 is made of a heat insulating material having air permeability so as not to hinder the vacuum suction of the vacuum degassing tank 14. In the present invention, the lower end of the downcomer pipe 18 and the upstream connection pipe 24 are also used to introduce the molten glass G into the vacuum degassing tank 14 by depressurization when the operation of the vacuum degassing apparatus 10 is started. Since the molten glass G is also required, it is preferable to provide a bypass pipe (not shown) for connecting the upper and downstream connection pipe lines 22 and 24 outside the decompression housing 12.

In the vacuum degassing apparatus 10 of the present invention shown in FIG. 1, a vacuum degassing tank 14, an ascending pipe 16, a descending pipe 18, an upstream connecting pipe 22 and a downstream connecting pipe constituting a series of closed circuits. The path 24, as well as the melting tank 20 and the next processing tank 26, are all formed of electroformed brick. That is,
In the vacuum degassing apparatus 10, the flow path of the molten glass G that is in direct contact with the molten glass G formed as a series of closed circuits from the melting tank 20 having the free surface of the molten glass to the next processing tank 26 is electrically connected. By forming with cast brick, the cost can be greatly reduced compared with the flow path made of platinum or platinum alloy which has been conventionally used. The thickness can be designed to be large, the capacity of the vacuum degassing apparatus 10 can be increased, and the vacuum degassing process can be performed at a higher temperature. In addition, electroformed bricks have higher durability at high temperatures than ordinary refractory bricks, and can minimize foaming and elution of components. In particular, there is almost no elution of components into the molten glass, which is negligible when manufacturing window glasses for architectural or automotive use, bottled glass, and the like.

In the case of mass-produced glass such as architectural and automotive glass, the presence of fine air bubbles having a certain size or less is allowed. For example, in the case of architectural glass,
Since the presence of fine bubbles with a diameter of 0.3 mm or less is acceptable, most bubbles have a diameter of 0.2 mm or less,
Foaming from electroformed bricks whose generation stops when a foam of more than 0.2 mm elapses for a predetermined time is acceptable. According to the results of experiments performed by the present inventors on the vacuum degassing apparatus 10 shown in FIG. 1, the diameter distribution of bubbles generated under the reduced pressure conditions in the above-described vacuum degassing tank 14 has a large number of 0.2 mm or less. However, the amount of bubbles exceeding 0.2 mm is very small, and the soda-lime composition used for architectural and automotive glass is 1
At 285 ° C., after 7 days from the start of the test, the sample was placed at 0.
Generation of bubbles of 2 mm or more is stopped, and
It has been confirmed that bubbles having a size of 2 mm or less continue to be generated. Therefore, the vacuum degassing apparatus 10 using electroformed bricks for all the parts that come into contact with the molten glass G shown in FIG.
It is unsuitable for electronic glass and optical glass, which poses a problem of bubbles up to a bubble diameter of 0.02 mm, but it is not acceptable for architectural glass and automotive glass, which allows bubbles up to a bubble diameter of 0.3 mm. There is no problem even if there are many small bubbles described below, and they can be applied sufficiently.

Accordingly, the shapes of the vacuum degassing tank 14, the riser tube 16 and the downcomer tube 18 are not particularly limited as long as they are at least cylindrical tubes, and their cross-sectional shapes are circular, elliptical, rectangular such as square or rectangular, and other shapes. Polygon. The method of constructing the vacuum degassing tank 14, the riser pipe 16 and the descender pipe 18, the upstream and downstream connection pipes 22 and 24, the melting tank 20, and the next processing tank 26 using the electroformed brick is not particularly limited. For example, for example, small rectangular parallelepiped electroformed bricks may be piled up, and joints between them may be filled with jointing material to form a cylindrical tube of a predetermined length, or a cylindrical tube formed by casting into a cylindrical shape or a square cylindrical shape. May be stacked in a row, and the joints between them may be filled with joint material to form a tubular tube of a predetermined length, or a tube having a rectangular cross section by combining plate-like electroformed bricks A road may be formed, and a joint portion therebetween may be filled with a joint material to form a rectangular tube having a predetermined length.

The electroformed brick is not particularly limited as long as the refractory raw material is electrofused and then cast into a predetermined shape, and various types of conventionally known refractory electroformed bricks can be used. it can. Among them, high corrosion resistance, foaming from the matrix is small in terms, alumina electroforming refractories, zirconia electroforming refractories, alumina - zirconia - silica _{(AZS; Al 2 O 3 -ZrO} 2 -SiO 2) based Preferable examples include electroformed refractories, and specific examples include marsnite (MB, particularly MB-G), ZB-X950, and zirconite (ZB) (all manufactured by Asahi Glass Co., Ltd.).

The electroformed brick used in the present invention has closed pores inside, but the porosity of the cast surface is almost 0. However, if the vacuum degassing tank 14, the riser pipe 16 and the downcomer pipe 18 are increased in size, it is better to use a large electroformed brick, but there is a limit to the size of the electroformed brick itself. It is difficult to manufacture large electroformed bricks. For this reason, in the present invention, it is necessary to finish a plurality of electroformed bricks, and joints are formed between the electroformed bricks. Of course, this joint is filled with a joint material or the like. However, since the denseness is lower than that of electroformed brick, depending on the air or the case (deteriorated state), molten glass G can be circulated. I can't keep it.

Therefore, in the present invention, as described above, the pressure reducing housing 12 made of a heat-resistant steel plate (stainless steel plate or the like) is used to reduce a part of the upstream connection pipe 22 communicating with the melting tank 20 and the rising pipe 16. , Vacuum degassing tank 14, downcomer 1
8, and the downstream connection pipe line 2 communicating with the next processing tank 26
4 is partially covered, and the entire interior of the decompression housing 12 is depressurized. In the present invention, refractory bricks can be configured to be thicker from the beginning, unlike platinum, and therefore, unlike the case of using the expensive and minimal amount of platinum, the frequency of repairing a worn channel is very low. Become. As a result, it is not necessary to incorporate measures for interrupting production from the design stage in order to repair the flow path of the molten glass, and there is no need to raise or lower the entire decompression device. That is, the pressure reducing device and the glass flow paths before and after the pressure reducing device can be fixedly configured, and the lower ends of the riser pipe 16 and the lowering pipe 18 can be freely set like the conventional vacuum degassing apparatus 110 shown in FIG. Since it is not necessary to immerse the molten glass G in the presence of the atmosphere in the molten glass G having a surface, deterioration of the interface between the atmosphere outside the pipe and the molten glass G in the riser pipe 16 and the descending pipe 18, particularly, joints (joint joints) ) Can be prevented from deteriorating. In addition, with such a configuration, the vacuum degassing tank 14 and the riser 1
The vacuum housing 12 including the vacuum chamber 6 and the downcomer pipe 18 can be fixed as a whole, and does not need to be moved up and down as in the conventional vacuum degassing apparatus 110 shown in FIG. The work can be simplified.

The decompression housing 12 has an opening through which the upstream connection pipe 22 and the downstream connection pipe 24 pass. The opening of the decompression housing 12 is connected to the upstream and downstream connection pipes 22 and In order to hermetically join with the outer periphery of 24, it is preferable to adopt a throttle structure as close as possible to connection pipe lines 22 and 24. Therefore, the vicinity of the opening of the decompression housing 12 is preferably made of heat-resistant steel. However, if it is too close to the connection pipelines 22 and 24, the steel material (plate) is heated by the heat flowing through the electroformed brick and the like. Since it will melt, it may be partially water-cooled. The opening of the decompression housing 12 is connected to the upstream and downstream connections 22 and 24.
The air which enters from between the predetermined pressure and the predetermined pressure, for example, 1/20
The pressure loss is kept to a minimum due to the pressure loss of the heat insulating material 30 made of refractory bricks filled up to the vacuum degassing tank 14 maintained at １ ／ 1/3 atm or −400 to −600 mmHg.

In the example shown in FIG. 1, the downstream connection line 24 connected to the lower end of the downcomer 18 communicates directly with the next processing tank 26, but the present invention is not limited to this. It is sufficient that the glass G communicates with a downstream open channel having a free surface, and for example, the glass G may communicate with a stirring tank 30 as shown in FIG. The stirring tank 30 shown in FIG.
Is similarly made of electroformed brick and has a stirrer 34 inside.
And the molten glass G has a free surface. In addition,
In FIG. 2, reference numeral 36 functions as a valve for adjusting the size of an opening through which the molten glass G stirred by the stirrer 34 flows out to the next processing tank, for example, a forming tank, and adjusting the amount of the molten glass G flowing out. Flow control valve (Tweel)
It is.

Although not shown, the upstream connecting line 22 connected to the lower end of the riser 16 is not limited to the one directly connected to the dissolving tank 20 as shown in FIG. It goes without saying that the molten glass G such as a melting tank made of electroformed brick may be communicated with an upstream open channel made of electroformed brick having a free surface.

Next, the operation of the vacuum degassing apparatus for molten glass of the present invention at the time of steady operation will be described. In the vacuum degassing apparatus 10 for molten glass of the present invention shown in FIG. 1, the vacuum degassing tank 14 is evacuated by a vacuum pump (not shown) to reduce the pressure to a predetermined pressure, for example, 1/20 to 1/3 atmosphere. The molten glass G is maintained in the melting tank 20 due to the difference between the atmospheric pressure (atmospheric pressure) of the liquid level in the melting tank 20 or the next processing tank 26 configured as an open channel and the pressure in the decompression housing 12. Alternatively, the liquid is sucked and raised into the vacuum degassing tank 14 through the upstream and downstream connecting pipes 22 and 24 and the rising pipe 16 or the falling pipe 18 disposed below the liquid level of the next processing tank 26, and is configured as a series of closed pipes. The molten glass G in the melting tank 20 and the next processing tank 26
Flows out to the next processing tank 26 in accordance with the difference in the liquid surface height.

At this time, the melting tank 20 or the next processing tank 2
The difference between the liquid level of the molten glass G and the liquid level of the molten glass G sucked and raised into the vacuum degassing tank 14 differs depending on the depressurized pressure in the vacuum degassing tank 14, but is almost the same. ,
The flow rate of the molten glass G in the vacuum degassing tank 14 depends on the viscosity (temperature) of the molten glass G and the liquid level of the molten glass G in the melting tank 20 or the next processing tank 26. It is determined by the difference in height. However, if the flow rate of the molten glass G in the vacuum degassing tank 14 exceeds 50 m / sec, the erosion of the electroformed bricks forming the flow path is accelerated. Therefore, the flow rate of the molten glass G should be 50 m / sec or less. Is preferred.

The molten glass G sucked and raised in the vacuum degassing tank 14 is reduced in pressure to 1/20 to 1/3 atmosphere in the vacuum degassing tank 14, so that bubbles contained in the molten glass G are removed. It rises to the liquid level and breaks bubbles. The reduced-pressure defoaming device 10 removes bubbles contained in the molten glass G in this manner. Of course, the viscosity of the molten glass G decreases as the temperature increases, so that the higher the temperature of the molten glass G, the easier it is to remove bubbles contained in the molten glass G, and the higher the temperature of the molten glass G becomes. As a result, the flow rate of the molten glass G that passes through the vacuum degassing tank 14 and undergoes the defoaming process also increases. Therefore, the viscosity of the molten glass G is 10
It is preferable to be ^4.5 poise or less.

When the operation of the vacuum degassing apparatus 10 is started, the vacuum degassing tank 14, the rising pipe 16 and the downcoming pipe 1
It is preferable to preheat the inner surface (flow path of the molten glass G) of a series of closed conduits composed of the pipe 8 and the upstream and downstream connection conduits 22 and 24 to the same temperature as the molten glass G. If the preheating is insufficient, when the molten glass G is sucked up,
The molten glass G is cooled and solidified, and the subsequent operation may not be possible.

After sufficiently preheating, the molten glass G is poured from the melting tank 20 into the upstream connection pipe 22,
By opening a bypass pipe (not shown), the molten glass G is also poured from the connection pipe 22 to the downstream connection pipe 24, and the upstream and downstream connection pipes 22 and 24 are filled with the molten glass G. Thereafter, by decompressing the inside of the decompression housing 12,
The molten glass G is suctioned and raised from the upstream connection pipe 22 through the riser pipe 16 and from the downstream connection pipe 24 through the downcomer pipe 18 into the vacuum degassing tank 14. The molten glass G rising from the riser pipe 16 and the descending pipe 18 joins in the vacuum degassing tank 14, the pressure in the vacuum degassing tank 14 is reduced to a predetermined pressure, and the liquid of the molten glass G in the vacuum degassing tank 14 is reduced. After the surface has risen to a predetermined height, the bypass conduit (not shown) is closed, and the vacuum degassing apparatus 10 shifts to a steady operation.

Although the vacuum degassing apparatus for molten glass according to the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the scope of the present invention. Of course, you may.

[0040]

As described above in detail, according to the present invention, the vacuum degassing tank, the riser pipe and the downcomer pipe are made of refractory electroformed bricks which are less expensive than noble metal alloys such as platinum. However, similar to the case of precious metal alloys, the molten glass can be continuously degassed under reduced pressure, so that the production cost is lower than when a precious metal alloy such as platinum is used, and the amount used is limited in terms of cost. There is no need to limit the size in view of the decrease in strength due to this, and the degree of freedom in equipment design is dramatically improved. Can also be performed under reduced pressure. Also, by eliminating the need for up-and-down movement of the vacuum degassing apparatus, and by fixing the entire vacuum degassing apparatus, it is possible to eliminate the difficult and dangerous work of vertically moving the vacuum degassing apparatus, and to achieve a safer vacuum degassing apparatus. A foam device can be configured.

[Brief description of the drawings]

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

FIG. 2 shows a schematic sectional view of another embodiment of the vacuum degassing apparatus for molten glass of the present invention.

FIG. 3 is a schematic sectional view of a vacuum degassing apparatus for molten glass of the prior art.

[Explanation of symbols]

 10, 110 Decompression degassing device 12, 112 Decompression housing 12a, 12b Leg 12c Suction port 14, 114 Decompression degassing tank 14a, 14b Suction hole 16, 116 Rise pipe 18, 118 Descending pipe 20, 120 Dissolution tank 22 Upstream side Connection pipe 24 Downstream connection pipe 26 Processing tank 30, 130 Thermal insulation material 32 Stirrer tank 34 Stirrer 36 Flow control valve 122 Upstream pit 124 Downstream pit G Molten glass

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shun Kijima 1-1-1, Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Inside Keihin Plant of Asahi Glass Co., Ltd. (72) Atsushi Tanigaki 1-1-1, Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa Address Asahi Glass Co., Ltd. Keihin Plant

Claims (4)

[Claims] 1. A decompression housing, the interior of which is decompressed by vacuum suction, a decompression degassing tank provided in the decompression housing, and decompression degassing of molten glass, and provided in communication with the decompression degassing tank. A rising pipe for sucking and raising the molten glass before vacuum degassing and introducing the molten glass into the vacuum degassing tank, and provided in communication with the vacuum degassing tank; A downcomer pipe that descends from the tank and leads out; a melting tank having a free surface of the molten glass; or an upstream connection pipe communicating the upstream open channel with the riser pipe; and a downstream opening having a free surface of the molten glass. A downstream connection pipe that communicates the culvert or the treatment tank with the downcomer pipe, the upstream connection pipe, the riser pipe, the vacuum degassing tank, the downcomer pipe, and the downstream connection pipe are connected in series. It is configured as a closed pipe, and the molten gas of these series of closed A vacuum degassing apparatus for molten glass, wherein a flow path directly in contact with the lath is made of refractory brick. 2. A refractory brick constituting a flow path of the molten glass in the series of closed circuits, the refractory brick comprising an alumina-zirconia-silica electroformed refractory, a zirconia electroformed refractory, and an alumina electroformed refractory. The vacuum degassing apparatus for molten glass according to claim 1, which is at least one selected from the group consisting of: 3. The decompression housing according to claim 1, wherein the decompression housing includes:
A metal casing integrally surrounding each part of the riser pipe and the downcomer pipe and the upstream and downstream connection pipes, wherein the decompression housing and the decompression degassing tank, the riser pipe and the descender pipe, and 3. The melt according to claim 1, wherein a space between each of the upstream and downstream connection pipes is filled with a heat insulating material made of a refractory brick to form a multilayer cross-sectional structure. 4. Vacuum degassing equipment for glass. 4. The pressure in the vacuum degassing tank is 1/3 to 1/2.
A 0 atm, vacuum degassing apparatus for molten glass according to any one of claims 1 to 3, characterized in that the viscosity of flow less molten glass 10 ^4.5 poise at a flow rate not less than 50 mm / sec.