TWI394723B - A ductile structure of a molten glass, a vacuum degassing apparatus using the same, a glass manufacturing apparatus using the same, and a vacuum degassing method for molten glass - Google Patents

Description

Catheter structure of molten glass, vacuum degassing apparatus using the same, glass manufacturing apparatus using the same, and vacuum degassing method of molten glass

This invention relates to the construction of a conduit for molten glass. The molten glass conduit structure of the present invention can be used as a conduit for molten glass of a glass manufacturing apparatus, for example, a vacuum degassing vessel, a riser pipe or a downcomer which can be used as a vacuum degassing device. The conduit structure of the molten glass of the present invention is suitable as a riser or a downcomer of a vacuum degassing apparatus.

Further, the present invention relates to a catheter which uses the duct structure as a molten glass, in particular, a vacuum degassing apparatus and a vacuum degassing apparatus which are risers or downcomers of a vacuum degassing apparatus.

Moreover, the present invention relates to a glass manufacturing apparatus using the duct structure as a conduit for molten glass.

In the glass manufacturing apparatus of the vacuum degassing apparatus, the refractory brick may be used as a constituent material of the duct of the molten glass which consists of a hollow tube. In the case of refractory bricks, electroforming bricks are generally used because of heat resistance and corrosion resistance to molten glass.

However, in the case of using electroformed bricks to make a duct for molten glass, since the size of the electroformable brick that can be produced is limited, it is quite difficult to make an integral hollow tube without seams depending on the size of the duct. Therefore, for example, a plurality of electroformed bricks having an opening portion having an opening portion at the center portion are prepared, and this is stacked as a hollow tube. Regarding the formation of an annular electroformed brick, an annular electroformed brick having no seam is sometimes used, but generally, a plurality of electroformed bricks which form a substantially fan shape or a wedge shape are prepared, and these are assembled in the circumferential direction. ring.

Therefore, when an electroformed brick is used to form a conduit for molten glass, a void portion between the electroformed bricks is inevitably present on the inner surface of the hollow tube, that is, in the flow path directly contacting the molten glass. Since the electroformed brick has a dense structure having a low porosity, it is found that the molten glass has less bleeding from the void portion than the fired brick. However, it is quite difficult to completely prevent the molten glass from oozing out of the void portion.

It is also possible to fill the gap between the electroformed bricks constituting the flow path directly contacting the molten glass by the caulking material. However, the general joint filler material has a lower density than the electroformed brick, so the joint filler material directly in contact with the molten glass is more susceptible to erosion than the electroformed brick. Therefore, even if the erosion of the electroformed brick itself is small, there is a problem that the erosion of the void portion between the electroformed bricks is selectively performed. As a result, the bleeding of the molten glass from the void portion can be slowed down compared to the case where the void portion is not filled. However, once the filler material is corroded, the molten glass oozes out from the void portion.

A support wall is provided around the conduit of the molten glass. The support wall presses the duct in the center direction, thereby adhering the gap between the electroformed bricks assembled in a ring shape. Moreover, the support wall has the function of heat insulation or reinforcement of the duct.

The support walls are usually made of refractory bricks. In the case of refractory bricks, fired bricks and the like are usually used in terms of cost surface and heat insulation.

The heat-resistant and heat-insulating properties of the fired bricks are self-evident, but the corrosion resistance of the molten glass is relatively poor compared to the electroformed bricks. Therefore, when the molten glass oozing out from the gap between the electroformed bricks constituting the duct reaches the support wall, the refractory brick (fired brick) constituting the support wall may be significantly eroded by the molten glass. Once the refractory bricks (fired bricks) constituting the support wall are eroded, the life of the vacuum degassing apparatus itself becomes short.

In order to prevent the molten glass from leaking out of the pipeline in the vacuum degassing tank, the riser pipe and the downcomer of the vacuum degassing apparatus, Patent Document 1 discloses a precision grinding of the contact faces of the bricks of the inner surface brick layer. On the other hand, a method of forming a smoothness of 0.5 mm or less and forming a gap between adjacent bricks by 1 mm or less is formed. Further, in Patent Document 1, in order to prevent the molten glass from leaking from the pipe, a method of filling a gap between the inner surface tile layer and the support wall tile layer is also disclosed.

Further, in order to prevent the erosion of the void portion of the refractory brick directly contacting the molten glass and prevent the molten glass from oozing out from the void portion, Patent Document 2 discloses that the cross section of the flow path is formed into a polygonal shape, and the flow rate in the molten glass is higher. The slow corner portion forms a void portion, and the molten glass conduit structure of the cooling pipe is disposed on the outer side portion of the void portion.

The invention described in Patent Document 1 and Patent Document 2 is known to have an effect of suppressing the bleeding of molten glass from the void portion to some extent. However, the inventions described in Patent Document 1 and Patent Document 2 are extremely difficult to completely prevent the molten glass from oozing out from the void portion. In other words, in the case of the invention described in Patent Document 1 and Patent Document 2, it is not possible to completely prevent the fired brick constituting the support wall from being corroded by the molten glass that has leaked from the void portion.

In the case of the invention described in Patent Document 1, the thin plate material filled in the gap between the inner surface brick layer and the supporting wall tile layer is often inferior in density to the electroformed brick. Therefore, the thin plate material is gradually eroded due to the arrival of the molten glass oozing out from the void portion. Therefore, the time for the molten glass oozing out from the void portion to reach the support wall can be made slower than when the thin plate is not used, but once the thin plate is corroded, the molten glass oozing out from the void portion reaches the support wall.

Further, in the invention described in Patent Document 1, the contact surfaces of the bricks of the inner surface brick layer are precisely ground, and the gap between the adjacent bricks is formed to be 1 mm or less, whereby the leakage of the molten glass from the void portion is slowed down, and it is expected The oozing molten glass fills the void portion, but the void portion which is originally a dense structure is gradually eroded by the brick around the void portion, so that the gap may be gradually increased. Therefore, in the long run, the bleeding of the molten glass from the void portion cannot be completely prevented.

On the other hand, in the invention described in Patent Document 2, the void portion is formed at a corner portion where the flow velocity of the molten glass is slow, and the erosion of the void portion is minimized, and the cooling means is provided at the outer portion of the void portion. In order to prevent the molten glass from oozing out from the void portion, even in the corner portion where the flow velocity of the molten glass is slow, the brick around the void portion is gradually eroded by the molten glass. As a result, the gap of the void portion gradually becomes larger, and finally the molten glass may ooze out from the void portion.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2000-7346 (US Pat. No. 6,334,336) Patent Document 2: JP-A-2003-128422

The present invention has been made to solve the problems in the prior art described above, and an object thereof is to provide a duct structure for molten glass for preventing refractory bricks constituting a support wall from being oozing out from a gap portion between electroformed bricks constituting a duct due to molten glass. erosion.

The conduit structure of the molten glass of the present invention is preferably used as a riser or a downcomer of the vacuum degassing apparatus.

Further, an object of the present invention is to provide a vacuum degassing apparatus and a vacuum degassing apparatus which are used as a conduit for molten glass, particularly a riser or a downcomer of a vacuum degassing apparatus, using the duct structure of the molten glass of the present invention.

Further, an object of the present invention is to provide a glass manufacturing apparatus using a conduit for a molten glass of the present invention as a conduit for molten glass.

In order to achieve the above object, the present invention provides a duct structure for molten glass (hereinafter referred to as "conduit structure of the present invention"), which is a duct structure of molten glass, characterized in that the duct structure has a medium made of electroformed brick. a duct formed by an empty pipe and a support wall made of a refractory brick disposed around the duct; and the heat-resistant property is provided between the duct made of the electroformed brick and the support wall structure of the refractory brick, and A barrier layer made of a metal material having good corrosion resistance of molten glass.

In the duct structure of the present invention, it is preferable that the metal material has a total content of Ni and Co of 25% by mass or more, and a total content of Ni, Fe, and Co is 50% by mass or more, and includes Ni, Fe, and Co. At least two selected from the group, and having 15 to 35% by mass of Cr, and a total content of W, Mo, Nb, Ta, and C is 12% by mass or less.

Furthermore, the present invention provides a duct structure for molten glass, which is a duct structure of molten glass, characterized in that the duct structure has a duct composed of a hollow tube made of an electrocast brick, and is disposed around the duct. a support wall made of a refractory brick; and a total content of Ni and Co is 25% by mass or more, and a total content of Ni, Fe, and Co is provided between the duct made of the electroforming brick and the support wall made of the refractory brick. It is an amount of 50% by mass or more, and includes at least two selected from the group consisting of Ni, Fe, and Co, and has 15 to 35 mass% of Cr, and the total content of W, Mo, Nb, Ta, and C is A barrier layer made of a metal material of 12% by mass or less.

In the catheter structure of the present invention, the metal material preferably contains 0.2 to 5% by mass of Al.

In the duct structure of the present invention, the total content of W, Mo, Nb, Ta, C, Zr and Hf of the metal material is preferably 12% by mass or less.

In the catheter structure of the present invention, the thickness of the barrier layer is preferably 2 to 15 mm.

In the duct structure of the present invention, it is preferable that the barrier layer made of the metal material has a structure for absorbing a difference in thermal expansion between the duct made of the electroforming brick and the support wall made of the refractory brick.

In the duct structure of the present invention, it is preferable that a cooling means is disposed outside the barrier layer.

The conduit structure of the present invention is preferably used as the riser pipe or the downcomer in a vacuum degassing apparatus having a riser, a vacuum degassing tank, and a downcomer.

Further, the present invention provides a vacuum degassing apparatus using the catheter construction of the present invention.

Further, the present invention provides a glass manufacturing apparatus using the conduit structure of the present invention as a conduit for molten glass.

Moreover, the present invention provides a vacuum degassing method for molten glass, which is a method for defoaming molten glass under reduced pressure using a vacuum degassing device having a rising tube, a vacuum degassing tank, and a down tube, and is characterized in that: The duct structure of the present invention is at least one of the aforementioned riser pipe and the downcomer pipe.

In the duct structure of the present invention, the molten glass which oozes from the gap between the electroformed bricks constituting the duct is blocked by the barrier layer disposed between the duct made of the electroformed brick and the support wall made of the refractory brick. Therefore, there is no fear that the refractory brick constituting the support wall will be eroded by the molten glass oozing out from the void portion.

Since the barrier layer is made of a metal material which is excellent in heat resistance and corrosion resistance to molten glass, there is no fear that the barrier layer is melted at the time of use, and it is not significantly corroded by the molten glass.

As long as the thickness of the barrier layer is 2 to 15 mm, the mechanical strength of the barrier layer and the corrosion resistance to the molten glass are sufficient. Therefore, when the conduit structure is used, there is no fear that the barrier layer may be damaged. Moreover, by providing a barrier layer between the conduit and the support wall, there is no fear of impeding the function of the support wall, especially the function of the support wall pushing the conduit in the center direction.

The thermal expansion coefficient of the metal material constituting the barrier layer is much larger than that of the electroformed brick constituting the duct and the refractory brick constituting the support wall. Therefore, when the duct structure is used, the difference in thermal expansion between the barrier layer made of a metal material, the duct made of an electrocast brick, and the support wall made of a refractory brick may become a problem. By providing a structure for absorbing the difference in thermal expansion in the barrier layer, the problem caused by the difference in thermal expansion can be prevented.

By arranging the cooling means at the outer side portion of the barrier layer (that is, on the side facing the support wall made of the refractory brick), and cooling the barrier layer by the cooling means, the heat resistance of the barrier layer can be further improved.

Further, when the barrier layer is cooled by the cooling means, it is possible to bleed out from the gap between the electroformed bricks, and the temperature of the molten glass reaching the barrier layer is lowered to be solidified. Thereby, the effect of preventing the bleeding of the molten glass can be further improved.

The vacuum degassing apparatus and the glass manufacturing apparatus of the present invention prevent the refractory bricks constituting the support wall from being corroded by the molten glass which oozes from the gap between the electroformed bricks constituting the duct. Therefore, the life of the device can be greatly extended.

Hereinafter, the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view showing a vacuum degassing apparatus having a duct structure of molten glass of the present invention. The vacuum degassing apparatus 1 shown in Fig. 1 is a step of degassing the molten glass G in the dissolution tank 30 under reduced pressure and then continuously supplying it to the next treatment tank 40.

The vacuum degassing apparatus 1 has a decompression housing 11 that keeps the inside thereof in a reduced pressure state during use. The vacuum degassing tank 12 is accommodated in the decompression housing 11 so that the long axis thereof is oriented in the horizontal direction. A riser pipe 13 oriented in the vertical direction is mounted below one end of the vacuum degassing tank 12, and a downcomer 14 is installed below the other end.

In the vacuum degassing apparatus 1, the vacuum degassing tank 12, the riser 13 and the downcomer 14 are hollow tubes made of electroformed brick having a rectangular cross section. Extension pipes 18 and 19 made of platinum or platinum alloy are provided at the lower ends of the riser pipe 13 and the downcomer pipe 14, respectively. In the decompression housing 11, a support wall 15 made of refractory brick is disposed around the riser 13 and the downcomer 14. A heat insulating material 22 is disposed around the vacuum degassing tank 12.

In the vacuum degassing apparatus 1 shown in Fig. 1, the structure including the riser 13 and the support wall 15, and the structure including the downcomer 14 and the support wall 15 constitute the duct structure of the present invention. Fig. 2 is a partially enlarged view showing a portion including the riser 13 and the support wall 15 of Fig. 1. Fig. 3 is a cross-sectional view showing the second figure taken along line a-a. The riser 13 will be described below, but the downcomer 14 has the same configuration.

In the second and third figures, the riser 13 is a hollow tube having a rectangular cross section, and the hollow portion forming the flow path of the molten glass has a circular cross section. The riser 13 is formed by stacking electroformed bricks 13a. As shown in Fig. 3, by combining two electroformed bricks 13a having a rectangular cross section and having a semicircular notch, a hollow tube structure having a rectangular cross section and a hollow portion having a circular cross section is formed. The riser 13 is formed by stacking such a hollow tube structure. It is preferable that the electroformed brick 13a is subjected to surface finishing by precision grinding in advance so that the brick surface is formed in a state in which there is almost no unevenness. Thereby, the leakage of the molten glass from the gap between the electroformed bricks 13a can be reduced.

A fixing flange 18a provided at an upper end portion of the extension pipe 18 is inserted between the electroforming bricks 13a constituting the lower end of the riser pipe 13 and inserted. Further, the extension pipe 18 is made of platinum or a platinum alloy, and is also a cylindrical body having a circular cross section. Further, the lower end portion of the riser pipe 13 (the lower end opening portion of the pressure reducing casing 11) is sealed by a sealing flange 18b provided near the upper end of the extension pipe 18.

The type of the electroformed brick 13a constituting the riser pipe 13 is not particularly limited, and an electroformed brick used as a constituent material of a furnace or a molten glass duct can be appropriately selected from known bricks. Specifically, there are α-alumina electroforming bricks, α, β-alumina electroforming bricks, β-alumina electroforming bricks, and the like, alumina-based electroforming bricks, zirconia electroforming bricks, and alumina. - Electroformed bricks such as zirconia ceria (AZS) electroformed bricks.

In the specific example of the alumina-based electroforming brick, the α-alumina electroforming brick has an alumina-based electroformed refractory brick (Marsnite) (registered trademark, the same below) A (made by Asahi Glass Co., Ltd.), high aluminum Fused cast refractory (MONOFRAX) A (made by SAINT-GOBAIN TM Co., Ltd.), α, β-alumina electroformed brick, alumina-based electroformed refractory brick G (made by Asahi Glass Co., Ltd.), high-aluminum power Melt cast refractory M (manufactured by SAINT-GOBAIN TM Co., Ltd.), JAGUAR M (made by SOCIETE EUROPEAN DEPRODUITS REFRACTAIRES), and β-alumina electroformed brick, alumina-based electroformed refractory brick U (made by Asahi Glass Co., Ltd.) High alumina electrofusion cast refractory H (manufactured by SAINT-GOBAIN TM Co., Ltd.), JAGUAR H (manufactured by SOCIETE EUROPEAN DE PRODUITS REFRACTAIRES).

A specific example of the zirconia electroformed brick is X-950 (manufactured by Asahi Glass Co., Ltd.).

Specific examples of the AZS electroformed cast brick include Zirconite (AZS electroformed refractory brick) (registered trademark, the same as below) 168l, Zirconite 1691, Zirconite 1711 (made by Asahi Glass Co., Ltd.), high alumina electrofusion cast refractory S4, high Aluminium fused cast refractory S5 (manufactured by SAINT-GOBAIN TM Co., Ltd.), UNICORN 501, UNICORN1 (manufactured by Corhart), FC101, FC4101 (manufactured by WALSH), ZAC1681, ZAC1711 (manufactured by Electro Refractaire) ).

As shown in Fig. 2, the support wall 15 is formed by stacking refractory bricks 15a. As shown in Fig. 3, the refractory brick 15a has a rectangular cross section, and a plurality of refractory bricks are disposed around the riser so as to fill the gap between the riser (electroformed brick 13a) and the pressure reducing casing 11.

In the present specification, the case of refractory bricks generally refers to bricks classified as refractory bricks, except bricks of electroformed bricks, that is, fired bricks.

Since the electroformed brick has excellent heat resistance and corrosion resistance to molten glass, it is suitable as a constituent material of the riser 13 which is in direct contact with the molten glass. However, it is not preferable to form the refractory brick 15a from the electroformed brick from the viewpoint of the cost surface and the heat insulating property.

The support wall 15 must have a function of insulating the riser pipe 13. However, an electroformed brick having a dense structure having a low porosity has a poor thermal insulation capacity than a fired brick having a high porosity. Therefore, if the refractory brick 15a constituting the support wall 15 is made of an electroformed brick having poor heat insulating ability, the support wall 15 becomes very large due to the large amount of heat radiation.

Moreover, the electrocast brick is more expensive than the fired brick, and therefore, if the refractory brick 15a constituting the support wall 15 is an electroformed brick, the manufacturing cost of the vacuum degassing apparatus 1 becomes very high. In addition, the support walls 15 do not need to be all refractory bricks, and may also comprise a part of electroformed bricks.

The refractory brick 15a constituting the support wall 15 is not particularly limited and can be widely selected from fired bricks which can be used as a furnace material or a support wall structure.

Specific examples of the fired brick include clay refractory bricks, zircon refractory bricks, and alumina refractory bricks. Clay refractory bricks include RG, CH, TB (made by Asahi Glass Co., Ltd.) and NEOTEX (manufactured by YOTAI Co., Ltd.). Zircon refractory bricks include, for example, ZR and ZM (made by Asahi Glass Co., Ltd.). Alumina refractory bricks are available in SP-13, 14, and 15 (manufactured by Risei Pellet Co., Ltd.).

In the second and third figures, when the riser 13 is viewed in the radial direction, the electroformed brick 13a constituting the riser 13 is disposed in one layer, and the refractory brick 15a constituting the support wall 15 is provided in two layers. However, this is a positional relationship showing the position at which the electroformed brick 13a is disposed and the position at which the refractory brick 15a is disposed, and does not necessarily mean that a layer of the electroformed brick 13a and the two-layer refractory brick 15a are disposed.

When an ascending pipe of a vacuum degassing apparatus is produced using an electrocast brick, a plurality of electroforming bricks having the same composition or different compositions are used, and these are formed by forming two or more layers along the radial direction of the riser. As for the support wall of the riser, a plurality of refractory bricks having the same composition or different compositions are also used. These are formed by forming two or more layers along the radial direction of the riser, and sometimes three or more layers are formed. And equipped. Also in the case of the duct construction of the present invention, the electroformed brick 13a of Fig. 2 may also use a plurality of electroformed bricks having the same composition or composition, and the electroformed brick 13a may be formed along the radial direction of the riser tube 13. Two or more layers are provided. Further, in the refractory brick 15a of Fig. 2, a plurality of refractory bricks having the same composition or composition may be used, and the refractory bricks 15a may be formed by forming three or more layers along the radial direction of the riser pipe 13. Further, the refractory bricks 15a constituting the support wall 15 may be provided with only one layer along the radial direction of the riser pipe 13.

The duct structure of the present invention is characterized in that a barrier layer 20 is provided between the duct (rising pipe) 13 made of the electroformed brick 13a and the support wall 15 made of the refractory brick 15a.

When the vacuum degassing apparatus 1 is used, the molten glass that has leaked from the gap between the electroformed bricks 13a constituting the riser 13 is blocked by the barrier layer 20. As a result, it is possible to prevent the molten glass that has leaked from the gap between the electroformed bricks 13a from reaching the refractory brick 15a constituting the support wall 15.

In Fig. 2, the barrier layer 20 is formed by stacking an annular body 20a made of a metal material. As shown in Fig. 3, the annular body 20a has a rectangular cross section and has a size capable of accommodating the duct 13. Further, the annular body 20a is formed by welding two sheets of a metal material processed into a substantially gate shape. As shown in Fig. 3, the welded portion 21 of the two thin plates is preferably located at a portion other than the corner portion of the annular body 20a. The corner portion of the annular body 20a is a position where a large stress is applied when the vacuum degassing device 1 is used. If the welded portion is located at the corner of the annular body 20a, the welded portion may be damaged by stress.

The annular body 20a constituting the barrier layer 20 can be produced by using a metal material having excellent heat resistance and excellent corrosion resistance of the molten glass in order to prevent the high-temperature molten glass which is oozing out from the gap between the electroformed bricks 13a.

The metal material used for the annular body 20a is not particularly limited as long as it has heat resistance capable of withstanding a high temperature environment of 600 to 1000 ° C and has good corrosion resistance to molten glass. Therefore, it can also be a platinum alloy such as platinum or platinum-ruthenium. However, platinum or platinum alloys are expensive metal materials, so it is preferable to use the metal materials shown below.

The metal material used for the annular body 20a is preferably a metal material which satisfies the following composition.

. Containing at least two of Ni, Fe or Co.

. The total content of Ni and Co is 25% by mass or more.

. The total content of Ni, Fe, and Co is 50% by mass or more.

. Contains 15 to 35 mass% of Cr.

. The total content of W, Mo, Nb, Ta, and C is 12% by mass or less.

Ni, Fe, and Co are matrix components of the heat resistant alloy, and the metal material used for the annular body 20a includes at least two of these. Therefore, the metal material used for the annular body 20a is any one of the following.

. A metal material containing Ni and Fe.

. A metal material containing Ni and Co.

. A metal material containing Fe and Co.

. A metal material containing Ni, Fe, and Co.

However, the metal material must satisfy the following two conditions at the same time.

. The total content of Ni and Co is 25% by mass or more.

. The total content of Ni, Fe, and Co is 50% by mass or more.

When the total content of Ni and Co is less than 25% by mass, the corrosion resistance of the metal material to the molten glass is inferior. The total content of Ni and Co is preferably 30% by mass or more, and more preferably 40% by mass or more.

If the total content of Ni, Fe, and Co is less than 50% by mass, the matrix component will be insufficient, and thus the mechanical strength of the metal material may be inferior. Further, the superior properties of toughness and ductility are poor, and it is difficult to release the stress caused by the temperature division or the like generated in the barrier layer by plastic deformation of the material. If these stresses are not fully released, the device itself may undergo unexpected deformation.

The total content of Ni, Fe, and Co is preferably 55 mass% or more, and more preferably 60 mass% or more.

Cr is a component that exhibits the high-temperature strength of the metal material, and is also a component that affects the corrosion resistance of the molten glass that has leaked out. Further, when a metal material containing 15 to 35% by mass of Cr is placed in a high temperature environment of 700 ° C to 1000 ° C, a protective film for oxidation is formed on the surface of the metal material. Therefore, the heat resistance of the metal material and the corrosion resistance to the molten glass are improved. When the content of Cr is less than 15% by mass, the above effects cannot be sufficiently exhibited, and therefore the high-temperature strength of the metal material is inferior. Further, since the protective film is not sufficiently formed on the surface of the metal material, the heat resistance of the metal material and the corrosion resistance to the molten glass are inferior. On the other hand, if the content of Cr exceeds 35% by mass, not only the toughness and ductility of the metal material are weakened, but machinability and weldability are deteriorated, and in the case of exposure to high temperatures, many fragile materials are formed in the material. Compound, and there is a possibility of cracking and the like.

The content of Cr is preferably 20 to 35 mass%, more preferably 25 to 35 mass%.

For the same reason as for Cr, the metal material preferably contains 0.2 to 5% by mass of Al. When a metal material containing 0.2 to 5% by mass of Al is placed in a high temperature environment of 900 ° C or higher, specifically 900 ° C to 1200 ° C, a protective film for oxidation is formed on the surface of the metal material.

Therefore, the heat resistance of the metal material and the corrosion resistance to the molten glass are improved. When the content of Al is less than 0.2% by mass, the above effects cannot be sufficiently exhibited. On the other hand, when the content of Al exceeds 5% by mass, there is a possibility that a problem that a uniform material or the like cannot be produced by a general metal plate manufacturing method.

The content of Al is preferably 0.5 to 5% by mass, more preferably 1 to 5% by mass.

W, Mo, Nb, Ta, and C are components which are selectively oxidized when the molten glass is in contact with the metal material, and the total content of these is preferably 12% by mass or less. If the metal material contains a total of more than 12% by mass of these components, the components of the molten glass are selectively oxidized upon contact with the metal material. As a result, intense foaming occurs, and metal materials are quickly consumed.

The metal material is preferably a total content of these components of 10% by mass or less, more preferably 8% by mass or less.

Like the above five components, Zr and Hf are also components which are selectively oxidized when the molten glass is in contact with the metal material. However, the tendency of selective oxidation due to molten glass is weaker than the above five components. Therefore, the metal material is preferably 12% by mass or less based on the total content of W, Mo, Nb, Ta, C, Zr and Hf. The total content of the seven components is preferably 10% by mass or less, more preferably 8% by mass or less.

The metal material which satisfies the above conditions is specifically Haynes Alloy (registered trademark, the same as below) 214 (manufactured by Mitsubishi Material Co., Ltd.), Hastelloy (heat-resistant nickel-base alloy) (registered trademark, the same applies hereinafter) X (manufactured by Mitsubishi Material Co., Ltd.), Inconel (nickel ferrochrome) (registered trademark, the same below) 601 (manufactured by Datong Special Steel Co., Ltd.), and the like. The composition of these metal materials is shown in Table 1.

These metal materials can be appropriately selected depending on the use. When Haynes Alloy 214 containing 4.5% by mass of Al is placed in a high-temperature environment of 1000 ° C. or higher and 1300 ° C or lower, a protective film is formed on the surface of the metal material. Therefore, the temperature of the barrier layer is suitable for use at 1000 ° C or higher. On the other hand, Hastelloy X and Inconel 601 have a high Cr content, and therefore are suitable for use in a temperature of 700 ° C to 1000 ° C in the barrier layer. In addition, Inconel 601 is preferable because it is easy to obtain and can increase the material to be cut.

The barrier layer 20 must be disposed between the riser 13 and the support wall 15 so as not to impede the function of the support wall 15, for example, the function of the support wall 15 pushing the catheter 13 in the center direction (hereinafter sometimes referred to as "catheter push function" "). Specifically, the support wall 15 also has a function of pushing the duct 13 from the outside to prevent the gap from opening. Therefore, the barrier layer 20 is preferably a thin layer. Moreover, the barrier layer 20 is also preferably a thin layer in terms of cost and ease of processing.

As shown in Figs. 2 and 3, when the barrier layer 20 is composed of the annular body 20a made of a metal material, the thickness of the annular body 20a is preferably 2 to 15 mm. When the thickness of the annular body 20a is less than 2 mm, the heat resistance of the annular body 20a, the corrosion resistance to the molten glass, or the mechanical strength will be insufficient. When the vacuum degassing apparatus 1 is used, the annular body 20a is used. It may be damaged. On the other hand, if the thickness of the annular body 20a exceeds 15 mm, the function of the support wall 15 may be hindered, for example, the function of pushing the catheter, which is not preferable in terms of cost and ease of processing. The thickness of the barrier layer is preferably 2 to 8 mm.

The coefficient of thermal expansion of the metal material constituting the annular body 20a is much larger than that of the electroformed brick 13a constituting the riser 13 and the refractory brick 15a constituting the support wall 15. Therefore, when the vacuum degassing apparatus 1 is used, the difference in thermal expansion between the annular body 20a made of a metal material and the electroformed brick 13a and the refractory brick 15a becomes a problem. The annular body 20a constituting the barrier layer 20 preferably has a structure for absorbing this difference in thermal expansion. In Fig. 2, the annular body 20a constituting the barrier layer 20 has a structure (overlapping structure) for absorbing a difference in thermal expansion.

Fig. 4 is an enlarged view showing only the barrier layer 20 of Fig. 2. As shown in Fig. 4, the two annular bodies 20a which are in a stacked relationship with each other have slightly different radial dimensions, and their ends overlap each other (having an overlapping portion 20b). In the present specification, as shown in FIG. 4, a structure in which both end portions of the annular body 20a stacked on each other overlap each other (having the overlapping portion 20b) is referred to as an "overlapping structure". Here, the term "the annular bodies 20a are stacked on each other" means that the two annular bodies 20a are stacked on each other in the up and down direction of FIG. 4, that is, in the longitudinal direction of the riser tube 13. On the other hand, the overlapping of the two end portions of the annular body 20a means that the end portions of the annular body 20a overlap each other in the radial direction of the riser pipe 13.

The overlapping structure shown in Figs. 2 and 4 is a structure for absorbing the difference in thermal expansion between the annular body 20a and the electroformed brick 13a and the refractory brick 15a. In the overlapping structure shown in FIGS. 2 and 4, the upper and lower ends of each annular body 20a are not joined by welding or the like, but a free end is formed. That is, the mutually stacked annular bodies 20a overlap each other only at the ends, and are not joined to each other. Further, the annular body 20a located at the lowermost end is also not joined to the decompression housing 11, but is simply placed at the bottom of the decompression housing 11.

With this configuration, even in the longitudinal direction of the riser pipe 13, a difference in thermal expansion occurs between the annular body 20a and the refractory brick 15a, and the upper and lower ends of the respective annular bodies 20a can be partially increased by the overlap 20b. Large to absorb the difference in thermal expansion. As shown in Fig. 2, the position of the overlapping portion of the annular body 20a is at a position that does not coincide with the position of the gap between the electroformed bricks 13a. This positional relationship is preferably a molten glass which can prevent leakage from the gap between the electroformed bricks 13a.

The difference in thermal expansion between the annular body 20a and the refractory brick 15a also exists in the circumferential direction of the riser pipe 13. However, compared with the longitudinal direction of the riser pipe 13 in which the difference in thermal expansion between the annular body 20a and the refractory brick 15a acts as a total of these, the influence of the difference in thermal expansion between the annular body 20a and the refractory brick 13a is small, and Since the guide 13 is pressed in the center direction by the support wall 15, the influence of the difference in thermal expansion can be alleviated, so that the necessity of countermeasures is low. In addition, the total content of Ni and Co in the metal material constituting the annular body 20a is 25% by mass or more, so that the ductility is good. Therefore, the difference in thermal expansion in the circumferential direction of the riser pipe 13 can be absorbed to some extent by deforming the annular body 20a.

The structure for absorbing the thermal expansion difference in the barrier layer 20 is not limited to the heat expansion difference between the absorbable annular body 20a and the refractory brick 15a, and particularly the thermal expansion difference in the longitudinal direction of the riser pipe 13. The overlapping structure shown in Fig. 2 and Fig. 4 is shown. In another aspect of the structure that absorbs the difference in thermal expansion, the barrier layer 20 may have a tubular body having a rectangular cross section, and a corrugated concavo-convex structure may be provided in the tubular body. Here, the cylindrical body means that the longitudinal direction of the riser pipe 13 is longer than the annular body 20a shown in Fig. 2, and for example, the barrier layer 20 shown in Fig. 2 may be provided with a single tubular body. However, in order not to impede the function of the support wall 15, in particular, the function of the catheter pushing, the corrugated structure is preferably not provided in the entire longitudinal direction of the cylindrical body, but in the portion. Sub-set. Further, since the portion having the corrugated structure is inferior to the mechanical strength of the other portion of the cylindrical body, it is preferable that the portion where the corrugated structure is to be provided does not coincide with the position of the gap between the electroformed bricks 13a.

Moreover, the structure for absorbing the difference in thermal expansion can be provided by forming the barrier layer 20 with the same structure as the duct structure described in Japanese Laid-Open Patent Publication No. 2003-128422. That is, a structure in which a plurality of members made of a metal material are attached as the barrier layer 20 having a rectangular cross section, and if the joint portion between the members made of the metal material is disposed at a corner portion of the rectangular cross section, and the joint portion is slidably engaged, Then, the sliding joint is a structure that absorbs a difference in thermal expansion. In this case, the difference in thermal expansion in the longitudinal direction of the riser pipe 13 can be absorbed, and the difference in thermal expansion in the circumferential direction of the riser pipe 13 can be absorbed.

In the second figure, in the outer portion of the annular body 20a constituting the barrier layer 20, specifically, a cooling pipe 24 is disposed in the refractory brick 15a adjacent to the overlapping portion of the annular body 20a. The cooling pipe 24 is connected to a pump (not shown) provided outside the pressure reducing casing 11. The annular body 20a constituting the barrier layer 20 is cooled by supplying water or air to the cooling pipe 24 from the pump. In order to uniformly cool the annular body 20a, the cooling pipe 24 is preferably provided around the entire circumference of the annular body 20a having a rectangular cross section.

Therefore, in the case where the cooling pipe 24 views the riser pipe 13 from above or below, it is preferable to form a rectangular ring shape or a trapezoidal shape.

By cooling the annular body 20a by using the cooling pipe 24, the temperature of the annular body 20a can be lowered. Thereby, the degree of deterioration of the characteristics due to an increase in the temperature of the annular body 20a can be reduced.

When the annular body 20a is cooled by the cooling pipe 24, the temperature of the molten glass which has ooze out from the gap between the electroformed bricks 15a and reaches the annular body 20a can be lowered and solidified.

Thereby, the effect of preventing the bleeding of the molten glass can be further improved. In order to effectively exert this effect, the cooling pipe 24 is preferably disposed adjacent to the overlapping portion of the annular body 20a.

Although the catheter structure of the present invention has been described above using the drawings, the catheter structure of the present invention is not limited to the configuration shown in the drawings. For example, the duct made of an electrocast brick is not particularly limited as long as it is at least a hollow tube structure, and may be a structure other than a rectangular cross section, for example, a hollow tube having a circular or elliptical cross section, or a cross section. The shape is a polygonal shape other than a rectangle, for example, a hollow tube of a hexagonal shape, an octagonal shape or the like. The cross-sectional shape of the hollow portion forming the flow path of the molten glass may be a shape other than a circular shape, and may be, for example, an elliptical shape, or may be a polygonal shape such as a rectangular shape, a hexagonal shape, or an octagonal shape. When the duct made of an electrocast brick is a hollow tube having a shape other than these, the electroformed brick of a desired shape may be used depending on the cross-sectional shape of the duct and the cross-sectional shape of the hollow portion.

Further, the arrangement of the refractory bricks as the support walls disposed around the ducts may be appropriately selected depending on the cross-sectional shape of the duct.

An amorphous refractory such as a castable refractory, a plastic refractory or a thin plate may be filled between the refractory bricks 15a constituting the support wall 15 or between the refractory bricks 15a and the pressure-reduced outer casing 11.

The cross-sectional shape of the barrier layer made of a metal material can also be appropriately selected depending on the cross-sectional shape of the catheter made of electroformed brick. Further, the structure of the stacked annular body 20a shown in Fig. 2 is not limited, and may be a shape that is longer in the longitudinal direction of the riser tube 13, that is, a cylindrical body. Further, in the second drawing, the height of the annular body 20a in the longitudinal direction of the riser pipe 13 is substantially the same as the height of the electroformed brick 13a, and the annular body 20a is formed as a barrier of the void portion, but is not limited thereto. Here, the height of the annular body 20a may be twice or three times the height of the electroformed brick 13a, and one annular body 20a may form a barrier of two or three void portions.

Further, in the second drawing, two sheets of a metal material processed into a substantially gate shape are welded to the annular body 20a. However, the annular body 20a may be formed without being welded, and may be an annular body having no joint.

In the second drawing, the cooling pipe 24 is disposed at a position adjacent to each overlapping portion of the annular body 20a. However, the position and number of the cooling pipes 24 are not limited thereto. The temperature of the riser pipe 13 is not the same at all points, and the temperature of the lower portion of the riser pipe 13 connected to the extension pipe 18 exposed to the outside is lower than the temperature of the upper portion of the riser pipe 13 close to the vacuum degassing tank 12. Therefore, the molten glass which has leaked from the gap between the electroformed bricks 13a constituting the lower portion of the riser pipe 13 is cooled without using a cooling pipe, and the temperature is known when the annular body 20a is reached or before the annular body 20a is reached. It will also fall and solidify. In this case, the cooling pipe 24 may be provided in an overlapping portion of the annular body 20a located on the upper side of the riser pipe 13. Further, the upper end of the barrier layer 20, that is, the upper end portion of the uppermost annular body 20a, and the lower end portion of the lowermost annular body 20a are not overlapping portions, but each of the decompression defoaming grooves 12 is decompressed. The gap and the gap with the lower cover of the decompression housing 11 may become a flow path of the molten glass that oozes from the gap between the electroformed bricks 13a. Therefore, it is preferable to provide a cooling pipe at the outer side of these parts.

As described above, the duct structure of the present invention will be described with reference to the riser and the downcomer of the vacuum degassing apparatus. However, the duct construction of the present invention is not limited to these, and the duct construction of molten glass can be widely applied to well-known apparatuses. A specific example of the use of the catheter structure of the present invention is, for example, a catheter for molten glass of a glass manufacturing apparatus. More specifically, there are a vacuum degassing tank of a vacuum degassing apparatus, an outflow pipe provided to remove molten glass containing a large amount of impurities from a glass manufacturing apparatus (dissolution tank), and a lens to be formed from molten glass. In the case of an optical component, an outflow pipe for discharging the molten glass to the molding die, a conduit from the dissolution vessel to the molding groove, and the like.

The vacuum degassing method of the molten glass of the present invention is to use at least one of the riser pipe or the downcomer pipe using the conduit structure of the present invention, preferably both of which are vacuum degassing devices, and from the dissolution tank The supplied molten glass is subjected to vacuum degassing by a reduced pressure degassing vessel which is reduced in pressure to a predetermined degree of reduced pressure. The molten glass is preferably continuously supplied and discharged to a vacuum degassing tank.

In order to avoid a temperature difference from the molten glass supplied from the dissolution tank, the vacuum degassing tank is preferably heated to a temperature ranging from 1100 ° C to 1500 ° C, especially from 1250 ° C to 1450 ° C. Further, the flow rate of the molten glass is preferably from 1 to 1,000 tons/day from the viewpoint of productivity.

When the vacuum degassing method is carried out, the decompression outer casing is vacuum-extracted from the outside by a vacuum pump or the like, whereby the inside of the vacuum degassing vessel disposed in the decompression casing is maintained in a predetermined decompressed state. The inside of the vacuum degassing vessel is preferably 38 to 460 mmHg (51 to 613 hPa) under reduced pressure, and more preferably 60 to 253 mmHg (80 to 338 hPa) after decompression in the vacuum degassing vessel.

The glass which is defoamed by the present invention is not limited as long as it is a glass produced by a heat fusion method. Therefore, it may be an alkali glass such as soda lime glass or alkaline borosilicate glass. However, since the bubbles are not easily removed during the clearing step and are used in a display glass substrate or the like, in particular, applications requiring less defects are preferred, and therefore alkali-free glass is preferred. Further, in the case of an alkali-free glass, it is necessary to raise the temperature at the time of defoaming under reduced pressure to a certain temperature, and as long as this is taken into consideration, the effect of the present invention can be more exerted.

The size of each component of the vacuum degassing apparatus can be appropriately selected depending on the vacuum degassing apparatus to be used. In the case of the vacuum degassing tank 12 shown in Fig. 1, the specific dimensions thereof are as follows, for example. Further, the outer diameter and the inner diameter of the cross-sectional rectangle are (long) side dimensions.

Horizontal length: 1~20m outer diameter (section rectangle): 1~7m inner diameter (section rectangle): 0.2~3m

Specific dimensions of the riser 13 and the downcomer 14 are as follows, for example.

Length: 0.2~6m, preferably 0.4~4m outer diameter (section rectangle): 0.5~7m, preferably 0.5~5m inner diameter (cross section): 0.05~0.8m, preferably 0.1~0.6m

Example

Hereinafter, the present invention will be more specifically described based on examples. However, the invention is not limited thereto.

(glass soak test)

In order to select a metal material that can be used as a barrier layer, a glass soaking experiment was performed.

A test piece of 50 × 25 × 3 mm was produced using Haynes Alloy 214, Hastelloy X, and Inconel 601. Further, the same test piece was produced using Inconel 625 and SUS310S which are known as metal materials having good heat resistance. The composition of Haynes Alloy 214, Hastelloy X and Inconel 601 is shown in Table 1. The composition of Inconel 625 and SUS 310 S is shown in Table 2 below.

The prepared test piece was immersed in molten glass in which platinum crucible was placed. As the molten glass, glass A having a softening point of 650 ° C and glass B having a softening point of 658 ° C were used. The temperature of the molten glass at the time of immersion of the test piece was 1200 ° C in the case of glass A and 1000 ° C in the case of glass B.

After 72 hours from the immersion, the test piece was taken out, and the state of the surface of the test piece was visually confirmed, and the state of the cross section was confirmed by an optical microscope. The results are shown in Table 3.

In the table, ◎, ○, and × are as follows, respectively. ◎: By the thin oxide film on the surface of the test piece, the reaction between the molten glass and the metal material can be prevented, and there is almost no change in the surface, and the cross-sectional area of the metal material hardly changes. ○: The thin oxide film on the surface of the test piece is partially destroyed, and a part of the metal material is eroded by the molten glass. ×: The portion of the molten metal soaked in the molten glass is strongly eroded, leaving no prototype.

As is clear from Table 3, Haynes Alloy 214, Hastelloy X, and Inconel 601 have good heat resistance and corrosion resistance to molten glass, and are suitable as a metal material constituting the barrier layer of the catheter structure of the present invention. In particular, Haynes Alloy 214 having an Al content of 4.5% by mass exhibits good heat resistance and corrosion resistance to molten glass even when immersed in molten glass at 1200 ° C, so that the temperature at which the composition is used as a composition becomes 1000 ° C or higher. The metal material of the barrier layer. On the other hand, Inconel 625 having a total content of SUS310S, W, Mo, Nb, Ta, and C having a content of Ni and Co of less than 25% by mass of more than 12% by mass is inferior in corrosion resistance to molten glass, and thus is known not to be used as a constituent. The metal material of the barrier layer. Further, although Inconel 625 is a representative material excellent in both strength and corrosion resistance at high temperatures, the result of the corrosion resistance is not satisfactory. The reason for this is that the easily oxidizable component of Mo or the like which is rich in the material is violently and selectively oxidized by the molten glass.

(Example)

In the present embodiment, the vacuum degassing apparatus 1 shown in Fig. 1 is used to perform vacuum degassing of the molten glass.

In the vacuum degassing apparatus 1, the riser pipe 13, the downcomer 14, and the peripheral portions thereof have the structure shown in Fig. 2 .

The configuration and constituent materials of the respective portions of the vacuum degassing apparatus 1 are as follows.

Decompression housing 11: made of stainless steel

Vacuum degassing tank 12: Manufactured using AZS quality electrocast brick (Zirconite 1711).

Ascending tube 13, descending tube 14: Two electroforming bricks 13a (AZS electroformed brick: Zirconite 1711) are combined to form the shape shown in Fig. 3, and this is stacked. Barrier layer 20: Two sheets (thickness: 3 mm) made of Haynes Alloy 214 which were processed into a substantially gate shape were welded, and an annular body 20a having a rectangular cross section was produced. The annular body 20a is formed into two different outer diameters, and these interactions are stacked to form an overlapping structure shown in Figs. 2 and 4 .

The refractory brick 15a (fired brick (clay refractory brick): TB (made by Asahi Glass Co., Ltd.) is disposed in the gap between the annular body 20a and the decompression housing 11 as shown in Fig. 3, and This will be stacked as shown in Figure 2.

Extension tube 18, 19: made of platinum

The vacuum degassing of the molten glass was carried out under the following conditions.

Vacuum degassing tank 12 temperature: 1300 ° C decompression degassing tank 12 pressure: 150 mmHg molten glass: alkali-free glass flow: 50 tons / day

One year after the defoaming from the reduced pressure, the refractory brick 15a (fired brick) constituting the support wall 15 was not damaged by the molten glass.

(Comparative example)

Except that the barrier layer 20 is not disposed between the riser pipe 13, the downcomer 14 and the support wall 15 made of the fired brick, the vacuum degassing apparatus having the same configuration as that of the embodiment is used. Decompression of the molten glass under reduced pressure. Further, the conditions for carrying out the degassing under reduced pressure are the same as in the examples.

One year after the defoaming from the reduced pressure, the refractory brick 15a (fired brick) constituting the support wall 15 is known to be significantly eroded by the molten glass.

[Industrial use possibility]

The duct structure of the present invention is useful as a duct for molten glass in a glass manufacturing apparatus such as a vacuum degassing apparatus having a rising pipe, a vacuum degassing tank, and a down pipe.

In addition, the contents of the specification, the scope of the application, the drawings and the abstract of the Japanese Patent Application No. 2005-236796, filed on Jan. 17, 2005, are hereby incorporated by reference.

1. . . Vacuum degassing device

11. . . Decompression housing

12. . . Vacuum degassing tank

13. . . Riser

13a. . . Electroformed brick

14. . . Drop tube

15. . . Support wall

15a. . . Refractory brick

18,19. . . Extension tube

18a. . . Fixing flange

18b. . . Sealing flange

20. . . Barrier layer

20a. . . Ring

20b. . . Overlap

twenty one. . . Welding department

twenty two. . . Shaped refractory

twenty four. . . Cooling tube

30. . . Dissolution tank

40. . . Processing tank

Fig. 1 is a cross-sectional view showing a vacuum degassing apparatus having a duct structure of molten glass of the present invention.

Fig. 2 is an enlarged cross-sectional view showing a portion including the riser 13 and the support wall 15 of Fig. 1.

Fig. 3 is a cross-sectional view showing the second figure taken along line a-a.

Fig. 4 is an enlarged view showing only the barrier layer 20 of Fig. 2.

1. . . Vacuum degassing device

11. . . Decompression housing

12. . . Vacuum degassing tank

13. . . Riser

14. . . Drop tube

15. . . Support wall

18. . . Extension tube

19. . . Extension tube

twenty two. . . Shaped refractory

30. . . Dissolution tank

40. . . Processing tank

G. . . Molten glass

Claims (14)

A duct structure of molten glass, characterized in that: the duct structure has: a duct formed of a hollow tube made of electroformed brick, and a support wall made of refractory brick disposed around the duct; in the electroforming brick Between the duct and the support wall made of the refractory brick, a barrier layer made of a metal material having excellent heat resistance and excellent corrosion resistance to molten glass is provided. The duct structure of the molten glass according to the first aspect of the invention, wherein the metal material is at least two selected from the group consisting of Ni, Fe, and Co, and satisfies a total content of 25 masses of Ni and Co. % or more, and the total content of Ni, Fe, and Co is 50% by mass or more, and has 15 to 35% by mass of Cr, and the total content of W, Mo, Nb, Ta, and C is 12% by mass or less. A duct structure of molten glass, characterized in that: the duct structure has: a duct formed of a hollow tube made of electroformed brick, and a support wall made of refractory brick disposed around the duct; in the electroforming brick Between the duct and the support wall made of the refractory brick, a barrier layer made of a metal material is provided, and the metal material includes at least two selected from the group consisting of Ni, Fe, and Co, and satisfies Ni and The total content of Co is 25% by mass or more, and the total content of Ni, Fe, and Co is 50% by mass or more, and has 15 to 35% by mass. Cr, and the total content of W, Mo, Nb, Ta, and C is 12% by mass or less. The duct structure of molten glass according to the second or third aspect of the invention, wherein the metal material further contains 0.2 to 5% by mass of Al. The duct structure of the molten glass according to the second aspect of the invention, wherein the total content of W, Mo, Nb, Ta, C, Zr and Hf of the metal material is 12% by mass or less. The duct structure of molten glass according to any one of the first aspect, wherein the barrier layer has a thickness of 2 to 15 mm. The duct structure of the molten glass according to any one of the first aspect, wherein the temperature of the place where the barrier layer is installed is 1000 to 1300 °C. The duct structure of a molten glass according to any one of the first aspect, wherein the barrier layer is formed by stacking an annular body made of a metal material. The duct structure of a molten glass according to any one of the first aspect, wherein the barrier layer made of the metal material has a duct for absorbing a hollow tube made of the electroformed brick. And a structure in which the thermal expansion of the support wall made of the refractory brick is poor. The duct structure of molten glass according to any one of the first aspect, wherein the cooling means is disposed in an outer portion of the barrier layer. The duct structure of a molten glass according to any one of the first aspect, wherein the vacuum degassing apparatus having a rising pipe, a vacuum degassing tank, and a down pipe is used. It is used as at least one of the aforementioned riser pipe and the aforementioned downcomer. A vacuum degassing device characterized by using a duct structure of molten glass according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11 As a conduit for molten glass. A glass manufacturing apparatus characterized by using a duct structure of molten glass described in any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11 as a melting Glass conduit. A vacuum degassing method for molten glass is a method for defoaming molten glass under reduced pressure using a vacuum degassing device having a rising tube, a vacuum degassing tank and a down tube, and is characterized in that: The duct structure according to any one of the items 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11 is at least one of the riser pipe and the down pipe.