WO2009107801A1

WO2009107801A1 - Vacuum defoaming apparatus for molten glass

Info

Publication number: WO2009107801A1
Application number: PCT/JP2009/053736
Authority: WO
Inventors: 元之広瀬; 達也山下; 勝彦佐野; 裕野尻
Original assignee: 旭硝子株式会社
Priority date: 2008-02-29
Filing date: 2009-02-27
Publication date: 2009-09-03
Also published as: TWI392657B; JPWO2009107801A1; CN101959807B; KR20100085955A; JP5423666B2; TW200948732A; KR101221249B1; CN101959807A

Abstract

Provided is a vacuum defoaming apparatus for molten glass in which the effect of vacuum defoaming is prevented from being reduced by the enlargement of a foam layer due to excessive pressure reduction. The vacuum defoaming apparatus for molten glass provided with a vacuum defoaming tank for raising and braking foam in supplied molten glass, in which the barometric pressure is set to a pressure lower than atmospheric pressure, a riser tube which is connected to the vacuum defoaming tank, for sucking and raising the molten glass before defoaming treatment and introducing the molten glass into the vacuum defoaming tank, and a down comer which is connected to the vacuum defoaming tank, for lowering and guiding the molten glass after the defoaming treatment from the vacuum defoaming tank is characterized by being provided with a hollow-structured atmosphere control unit connected to the vacuum defoaming tank by at least two connecting pipes, the atmosphere control unit being provided with an exhaust port for evacuating the interior of the atmospheric control unit to reduce the pressure and provided with a first gas supply pipe which satisfies the following requirements (1) and (2) in a relationship with at least one of the connecting pipes. (1) A gas stream supplied from the first gas supply pipe crosses a virtual region formed by extending an opening constituted by the atmosphere control unit and the connecting pipe into the atmosphere control unit along the direction of the axis of the connecting pipe. (2) A virtual line extended along the axis of the first gas supply pipe from the tip of the gas supply pipe does not pass through the opening constituted by the atmosphere control unit and the connecting pipe.

Description

Vacuum degassing equipment for molten glass

The present invention relates to a vacuum degassing apparatus for molten glass for removing bubbles from continuously supplied molten glass.

Conventionally, in order to improve the quality of the molded glass product, a clarification process for removing bubbles generated in the molten glass is used before the molten glass in which the raw material is melted in the melting furnace is molded by the molding apparatus. Yes.
In this clarification step, molten glass is introduced into the reduced-pressure atmosphere, and bubbles in the molten glass flow that flows continuously under this reduced-pressure atmosphere are greatly grown to float up the bubbles contained in the molten glass. A vacuum defoaming method is known in which bubbles are removed by breaking bubbles, and then discharged from a reduced-pressure atmosphere.

In such a clarification process, various techniques have been proposed in order to promote the growth of bubbles in the molten glass flow or to break the bubbles.
Patent Document 1 proposes to include various fining accelerators in vitrifiable substances, that is, glass raw materials, in order to improve the performance characteristics of the fining operation. Patent Document 1 lists the property of the gas on the melt material, that is, the property of the gas on the molten glass, as an element that affects the growth of bubbles during clarification under reduced pressure.
Further, Patent Document 2 discloses a foam breaking means for breaking foam generated when molten glass encounters a reduced pressure in a clarification chamber. As the foam breaking means, it is disclosed to use a mechanical rotating body for expanding and rupturing bubbles, or to make a jet flow collide with the foam.

JP 2001-515453 A JP 2003-89529 A

In Patent Document 1, as a method of changing the property of the gas on the molten glass, selection of the partial pressure of air, selection of an atmosphere enriched with a nitrogen type inert gas, and partial pressure of the nitrogen type inert gas are described. Although there is a selection, it does not show at all what kind of property the gas on the molten glass promotes the bubble growth. In addition, during clarification under reduced pressure conditions, volatile gas components from the molten glass and gas components in the bubbles contained in the molten glass are released, so the partial pressure of the selected air and the selected nitrogen type There is a problem that the partial pressure of the active gas is easily reduced. Further, there is a problem that the gas composition of the atmosphere easily changes from the atmosphere enriched with the selected nitrogen type inert gas.

Further, the method described in Patent Document 2 is not always sufficient in terms of breaking the foam generated in the clarification chamber. In other words, the use of a mechanical rotating body or a jet flow can destroy the foam already existing on the molten glass, but the turbulence in the molten glass flow results in the generation of new bubbles. In the clarification chamber, the foam can be locally destroyed, but the newly generated foam cannot be destroyed downstream of the mechanical rotating body or the jet flow. Also, the use of a mechanical rotating body may be a source of contamination of molten glass, and the use of a jet stream may reduce the temperature of the molten glass and reduce the quality of the glass.

Theoretically, the higher the degree of decompression of the atmosphere above the molten glass (the lower the absolute pressure of the atmosphere), the more the effect of decompression defoaming should be improved, and the bubbles in the molten glass flow should decrease. However, in reality, when the degree of decompression of the atmosphere (absolute pressure of the atmosphere) reaches a certain stage, the bubble generation rate exceeds the bubble extinction rate due to bubble breakage, and the foam layer enlarges on the surface of the molten glass, Depressurization defoaming ability will fall. Such a phenomenon is called enlargement of the foam layer due to excessive decompression. As a result, bubbles in the molten glass stream increase on the contrary. Therefore, the range of the degree of pressure reduction (absolute absolute pressure) of the atmosphere that can fully exhibit the effect of vacuum degassing is quite narrow, and the effect of vacuum degassing is affected by external factors such as atmospheric pressure fluctuations. It was.

In order to solve the above-described problems of the prior art, the present invention relates to a vacuum degassing apparatus excellent in the effect of vacuum degassing of molten glass, more specifically, vacuum degassing by enlargement of a foam layer due to excessive vacuuming. An object of the present invention is to provide a vacuum degassing apparatus for molten glass in which the effect of the above is prevented from being lowered.

As a result of intensive studies to achieve the above object, the present inventors have found that gas components generated by bubbles breaking on the surface of the molten glass stay above the molten glass flowing in the vacuum degassing tank. It has been found that the effect of vacuum degassing is reduced. Hereinafter, in this specification, a gas component generated by bubbles breaking on the surface of the molten glass is referred to as “gas component from molten glass”, and the gas component from the molten glass circulates in the vacuum degassing tank. Retaining above the molten glass is referred to as “retaining gas components from the molten glass”.
If the gas component from the molten glass stays, the partial pressure of the gas component from the molten glass increases in the atmosphere above the molten glass (the upper space of the molten glass inside the vacuum degassing tank), so bubbles that float on the surface of the molten glass Is considered to be difficult to break, and the effect of vacuum degassing is reduced.
Further, the present inventors have found that by eliminating the retention of gas components from the molten glass, the bubble breaking speed on the surface of the molten glass is increased, and the enlargement of the foam layer due to excessive decompression can be suppressed.

The present invention has been made on the basis of the above-mentioned findings of the present inventors, and the internal pressure is set to be lower than the atmospheric pressure, and a vacuum degassing tank that floats and breaks bubbles in the supplied molten glass. And a riser pipe that is connected to the vacuum degassing tank and sucks and raises the molten glass before the defoaming process and introduces it into the vacuum degassing tank, and is connected to the vacuum degassing tank and melted after the defoaming process. In a vacuum degassing apparatus for molten glass, comprising a downcomer pipe that descends the glass from the vacuum degassing tank and leads it out,
It has a hollow atmosphere control unit connected to the vacuum deaeration tank by at least two connecting pipes, and the atmosphere control unit is provided with an exhaust port for exhausting and depressurizing the atmosphere control unit. The atmosphere control unit is provided with a first gas supply pipe satisfying the following (1) and (2) in relation to at least one of the connecting pipes, and the vacuum degassing of molten glass is provided: An apparatus (hereinafter referred to as “the vacuum degassing apparatus of the present invention”) is provided.
(1) A virtual region in which an opening formed by the atmosphere control unit and the connection pipe extends into the atmosphere control unit along the tube axis direction of the connection pipe is supplied from the first gas supply pipe Gas flow crosses.
(2) An imaginary line extending from the tip of the first gas supply pipe along the tube axis of the gas supply pipe does not pass through the opening formed by the atmosphere control unit and the connection pipe.

In the vacuum degassing apparatus of the present invention, when the number of the connecting pipes is X, the number of the first gas supply pipes is X-1 or less (however, the number of the first gas supply pipes is 1 or more). It is preferable that

In the vacuum degassing apparatus of the present invention, the gas flow supplied from the first gas supply pipe is preferably a low moisture gas flow having a water vapor concentration of 60 mol% or less.

In the vacuum degassing apparatus of the present invention, it is preferable that a second gas supply pipe for supplying a low moisture gas having a water vapor concentration of 60 mol% or less is further provided in the upper space of the molten glass in the vacuum degassing tank.

In the vacuum degassing apparatus of the present invention, a pressure difference is generated between the atmosphere control unit and the vacuum degassing tank due to the venturi effect generated by supplying the gas flow across the virtual region from the first gas supply pipe, This pressure difference causes a gas flow that circulates between the atmosphere controller and the vacuum degassing tank. This gas flow can eliminate stagnation of gas components from the molten glass. By eliminating the stagnation of gas components from the molten glass, a reduction in the effect of vacuum degassing is prevented.
In addition, by eliminating the retention of gas components from the molten glass, the foam layer is less likely to be enlarged due to excessive decompression. As a result, the degree of vacuum in the vacuum degassing tank can be increased, and the effect of vacuum degassing can be improved.

When a low moisture gas having a water vapor concentration of 60 mol% or less is used as the gas supplied from the first gas supply pipe, in addition to the effect of eliminating the retention of gas components from the molten glass, the molten glass in the vacuum degassing tank The effect of reducing the water vapor concentration is expected in the upper atmosphere. By reducing the water vapor concentration of the atmosphere, it is possible to prevent the bubble layer on the surface of the molten glass in the vacuum degassing tank from being enlarged and to cause bumping, and the effect of vacuum degassing can be further improved.
Moreover, by reducing the water vapor concentration in the atmosphere, it is possible to suppress the volatilization of specific components such as B, Cl, F, and S that are easily volatilized in the molten glass, and the glass by volatilization of these components A change in composition can be suppressed.

Sectional drawing which shows one structural example of the vacuum deaeration apparatus of this invention. The partial enlarged view which showed the vicinity of the virtual area | region 19 of the vacuum degassing apparatus 10. FIG. The elements on larger scale similar to FIG. The elements on larger scale similar to FIG. The elements on larger scale similar to FIG. The elements on larger scale similar to FIG. The elements on larger scale similar to FIG. Sectional drawing which shows another one structural example of the vacuum deaeration apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,10 ': Depressurization degassing apparatus 11: Depressurization defoaming tank 12: Rising pipe 13: Downcomer pipe 14: Atmosphere control part 15, 16: Connection pipe 17: Exhaust port 18: Opening part 19: Virtual area 20: 1st Gas supply pipe 21: Virtual line 24: Second gas supply pipe 100, 120: Gas flow 140: Low moisture gas 200: Melting tank 220: Upstream pit 240: Downstream pit G: Molten glass

The present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view showing an example of the configuration of the vacuum degassing apparatus of the present invention. A vacuum degassing apparatus 10 shown in FIG. 1 includes a vacuum degassing tank 11 having a cylindrical shape. The internal pressure of the vacuum degassing tank 11 is set to be lower than atmospheric pressure, and the bubbles in the supplied molten glass G are floated and broken. An ascending pipe 12 and a descending pipe 13 are connected to the vacuum degassing tank 11. The ascending pipe 12 is a means for introducing the molten glass G that sucks and raises the molten glass G before the defoaming treatment and introduces it into the vacuum degassing tank 11. For this reason, the lower end portion of the rising pipe 12 is immersed in the molten glass G in the upstream pit 220. The molten glass G is supplied from the melting tank 200 to the upstream pit 220. On the other hand, the downcomer 13 is a derivation means for the molten glass G that descends the defoamed molten glass G from the vacuum degassing tank 11 and derives it. For this reason, the lower end of the downcomer 13 is immersed in the molten glass G in the downstream pit 240. The molten glass G in the downstream pit 240 is led to a processing tank (not shown) in a subsequent process.
Hereinafter, in the present specification, the terms “upstream” and “downstream” mean upstream and downstream in the flow direction of the molten glass G flowing through the vacuum degassing apparatus 10.
Although not shown, the vacuum degassing tank 11 is usually housed in a vacuum housing, and the pressure inside the vacuum degassing tank 11 is reduced to a pressure lower than atmospheric pressure by sucking the vacuum housing under reduced pressure. Hold on. On the other hand, when the vacuum degassing tank 11 is not accommodated in the vacuum housing, the upper space of the molten glass G in the vacuum degassing tank 11 is sucked under reduced pressure using a vacuum pump or the like, so that the interior of the vacuum degassing tank 11 is reduced. Is maintained at a reduced pressure below atmospheric pressure.

The vacuum degassing apparatus 10 of the present invention has an atmosphere control unit 14 connected to the vacuum degassing tank 11 by at least two connecting

pipes

15 and 16. The atmosphere control unit 14 has a hollow structure, and is provided with an exhaust port 17 for exhausting and depressurizing the atmosphere control unit 14. The atmosphere control unit 14 forms a path of the gas flow 120 that circulates between the atmosphere control unit 14 and the upper space of the molten glass G in the vacuum degassing tank 11. Therefore, in the vacuum degassing apparatus 10 of the present invention, the atmosphere control unit 14 is exhausted from the exhaust port 17 to reduce the pressure, thereby maintaining the pressure inside the vacuum degassing tank 11 in a reduced pressure state less than atmospheric pressure. When the vacuum degassing apparatus 10 has a vacuum housing, the atmospheric pressure inside the vacuum degassing tank 11 is changed to atmospheric pressure by sucking the vacuum housing under reduced pressure and exhausting the atmosphere control unit 14 from the exhaust port 17 to reduce the pressure. Is maintained at a reduced pressure of less than On the other hand, when the vacuum degassing tank 11 does not have a vacuum housing, the atmospheric pressure inside the vacuum degassing tank 11 is increased by evacuating the atmosphere control unit 14 from the exhaust port 17 using a vacuum pump or the like. Maintain a reduced pressure below atmospheric pressure.

Here, the atmosphere control unit 14 forms a path of the gas flow 120 that circulates between the atmosphere control unit 14 and the upper space of the molten glass G in the vacuum defoaming tank 11. It is necessary to connect to the vacuum degassing tank 11 above the liquid surface of the molten glass G in the vacuum degassing tank 11. For this reason, as shown in FIG. 1, it is a preferable aspect to arrange the atmosphere control unit 14 above the vacuum degassing tank 11. However, if the

connection pipes

15 and 16 are connected to the vacuum degassing tank 11 above the liquid level of the molten glass G in the vacuum degassing tank 11, the atmosphere control unit 14 is connected to the vacuum degassing tank 11 side. You may arrange in the direction.
Moreover, in order to form the path | route of the gas flow 120 which circulates through this atmosphere control part 14 and the upper space of the molten glass G in the vacuum degassing tank 11, at least two

connection pipes

15 and 16 are required. . In the vacuum degassing apparatus 10 shown in FIG. 1, the vacuum degassing tank 11 and the atmosphere control unit 14 are connected by two connecting

pipes

15 and 16, but the vacuum degassing is performed by three or more connecting pipes. The tank 11 and the atmosphere control unit 14 may be connected.
In addition, if the temperature of the gas flow 120 flowing into the vacuum degassing tank 11 is low, the molten glass G in the vacuum degassing tank 11 may be adversely affected, so the atmosphere control unit 14 and the

connection pipes

15 and 16 are It is preferable to have a heating mechanism. However, it is not always necessary to provide a heating mechanism in the atmosphere control unit 14 and all the

connection pipes

15 and 16, and at least the connection pipe (see FIG. 1) on the side where the gas flow 120 flows into the vacuum degassing tank 11. In this case, if the connecting pipe 15) is provided with a heating mechanism, the gas flow 120 having a low temperature flows into the vacuum degassing tank 11 to eliminate the possibility of adversely affecting the molten glass G in the vacuum degassing tank 11. Can do.

The vacuum degassing apparatus 10 of the present invention is provided with a first gas supply pipe 20 that supplies gas into the atmosphere control unit 14. Here, the first gas supply pipe 20 satisfies the following (1) and (2) in relation to at least one connection pipe (in the case of FIG. 1, the connection pipe 16).
(1) A virtual region 19 in which the opening 18 formed by the atmosphere control unit 14 and the connection pipe 16 extends into the atmosphere control unit 14 along the tube axis direction of the connection pipe 16 (in the case of FIG. 1, the atmosphere control unit 14, the gas 100 supplied from the first gas supply pipe 20 crosses the region above the opening 18.
(2) An imaginary line 21 (see FIG. 5) extending from the tip of the first gas supply pipe 20 along the tube axis of the gas supply pipe 20 is an opening 18 formed by the atmosphere control unit 14 and the connection pipe 16. Do not pass through.
Hereinafter, the reason why it is necessary to satisfy (1) and (2) will be described.

When the gas flow 100 is supplied from the first gas supply pipe 20 so as to cross the virtual region 19 above the opening 18, the pressure near the outlet of the first gas supply pipe 20 according to Bernoulli's law (equation (1)). Decreases and a venturi effect occurs.
p / ρ + v ² / 2g + z = const (1)
p: pressure around the outlet of the first gas supply pipe 20 (Pa), ρ: density of the gas flow 100 (kg / m ³ ), g: acceleration of gravity (m / s), v: flow velocity of the gas flow 100 ( m / s), z: height of the outlet of the first gas supply pipe 20 in the atmosphere control unit 14 (height from the bottom of the atmosphere control unit) (m)
As a result, a pressure gradient is generated between the vacuum degassing tank 11 and a pressure difference is generated in which the pressure near the opening 18 is lower than that of the vacuum degassing tank 11. Due to this pressure difference, the pressure in the vicinity of the opening 18 (that is, the pressure on the connecting pipe 16 side) decreases, and the opening 18 passes through the vacuum degassing tank 11 from the opening formed by the atmosphere control unit 14 and the connecting pipe 15. A pressure gradient is generated in the region leading to. As a result, a gas flow that circulates between the atmosphere control unit 14 and the space above the molten glass G in the vacuum degassing tank 11 (hereinafter referred to as “gas flow that circulates between the atmosphere control unit and the vacuum degassing tank”). ) 120 is generated.

Here, the flow velocity v of the gas flow 100 necessary to generate a pressure difference sufficient to generate the gas flow 120 that circulates between the atmosphere controller and the vacuum degassing tank is the density ρ of the gas flow 100, the atmosphere Depending on the height z of the outlet of the first gas supply pipe 20 in the control unit 14 and the area A of the opening 18, the atmosphere control is performed if the flow velocity v of the gas flow 100 satisfies the following equation (2). A pressure difference sufficient to produce a gas stream 120 that circulates between the chamber and the vacuum degassing vessel.
v> A / 0.031 × [5.487 × 10 ⁻⁶ × (1 / 56.3533-1 / ρ) + 19.6 × (0.163−z) +7.5 ² ] ^1/2 (2)
The flow velocity v of the gas flow 100 preferably satisfies the following formula (3), and more preferably satisfies the following formula (4).
v> A / 0.031 × [5.487 × 10 ⁻⁶ × (1 / 56.3533-1 / ρ) + 19.6 × (0.163−z) +8.4 ² ] ^1/2 (3)
v> A / 0.031 × [5.487 × 10 ⁻⁶ × (1 / 56.3533-1 / ρ) + 19.6 × (0.163−z) +9.8 ² ] ^1/2 (4)

As a result of the gas flow 120 that circulates through the atmosphere control unit 14 and the vacuum degassing tank 11, the retention of gas components from the molten glass G is eliminated. That is, the gas component from the molten glass G is carried to the atmosphere control unit 14 by the gas flow 120 without staying. The gas component from the molten glass G carried to the atmosphere control unit 14 is discharged from the exhaust port 17 to the outside. In some cases, a part of the gas component from the molten glass G carried to the atmosphere control unit 14 is carried by the gas flow 120 and returns to the space above the molten glass G in the vacuum degassing tank 11. The presence of a gas flow 120 that circulates through the atmosphere control unit 14 of the molten glass G in the tank 11 and the vacuum degassing tank 11, and the gas component from the molten glass G is diluted by the gas flow 120. For this reason, the risk of stagnation of gas components from the molten glass G is minimized. In addition, when the gas component from the molten glass G is diluted by the gas flow 120, the gas component from the molten glass G adheres to the vacuum degassing apparatus 10 in the process of being cooled or is discharged from the exhaust port 17. After that, adhesion to the system is prevented.
When the gas component from the molten glass G stays, the partial pressure of the gas component from the molten glass G increases in the atmosphere above the molten glass G in the vacuum degassing tank 11, so that bubbles floating on the surface of the molten glass G are generated. It is considered that foaming becomes difficult and the effect of vacuum degassing is reduced.
In the vacuum degassing apparatus 10 of the present invention, the retention of gas components from the molten glass G is eliminated, so that the effect of vacuum degassing does not decrease, and the vacuum degassing effect is excellent.

Further, if the gas component from the molten glass G stays, the foam layer is enlarged due to excessive decompression, and the effect of vacuum degassing is greatly reduced. In the vacuum degassing apparatus 10 of the present invention, the molten glass Since the stagnation of the gas component from G is eliminated, the enlargement of the foam layer due to excessive decompression can be suppressed even when the degree of decompression of the decompression defoaming tank 11 is made higher than before. Therefore, the pressure reduction degree of the vacuum degassing tank 11 can be made higher than before (the absolute pressure of the vacuum degassing tank 11 can be made lower than before), and the effect of the vacuum degassing can be further enhanced. .

As shown in FIG. 1, when a gas flow 120 that circulates through the atmosphere control unit 14 and the vacuum degassing tank 11 is generated, the connecting pipe 16 connects the gas flow 120 to the gas degassing tank 11. The connecting pipe 15 forms a gas flow introduction pipe for introducing the gas flow 120 into the vacuum degassing tank 11. Therefore, like the vacuum degassing apparatus 10 shown in FIG. 1, when the two connecting

pipes

15 and 16 are provided, the first satisfying the above (1) and (2) in relation to either one of the connecting pipes. A gas supply pipe must be provided, and the first gas supply pipe satisfying the above (1) and (2) must not be provided in relation to the other connection pipe. On the other hand, when the vacuum degassing apparatus has three or more connecting pipes, a first gas supply pipe satisfying the above (1) and (2) may be provided in relation to two or more connecting pipes. In relation to at least one connecting pipe, the first gas supply pipe satisfying the above (1) and (2) should not be provided.
That is, in the vacuum degassing apparatus of the present invention, when the number of connection pipes is X, the number of first gas supply pipes is X-1 or less (however, the number of first gas supply pipes is 1 or more). There is a need to.

In order to generate a pressure difference in which the pressure in the vicinity of the opening 18 is lower than that in the vacuum degassing tank 11, the gas flow 100 supplied from the first gas supply pipe 20 needs to cross the virtual region 19. is there. In FIG. 1, the tip of the first gas supply pipe 20 is located in the virtual region 19, and the gas flow 100 is supplied in the upstream direction so as to cross the virtual region 19. FIG. 2 is a partially enlarged view showing the vicinity of the virtual region 19 of the vacuum degassing apparatus 10, and the position of the tip of the first gas supply pipe 20 is different from that in FIG. 1. In FIG. 2, the tip of the first gas supply pipe 20 is located on the downstream side of the virtual region 19 and supplies the gas flow 100 in the upstream direction. A gas flow 100 is supplied in the upstream direction so as to cross the virtual region 19. Such an arrangement may be used as long as the flow rate of the gas flow 100 is sufficiently large and the gas flow 100 can be supplied across the virtual region 19.
Further, in the vacuum degassing apparatus 10 of FIG. 1, the front end of the first gas supply pipe 20 inserted from above the atmosphere control unit 14 is curved in the upstream direction so as to cross the virtual region 19 in the upstream direction. The gas flow 100 is being supplied toward the upstream side, but the first gas supply pipe is inserted in the horizontal direction from the downstream end face of the atmosphere control unit 14, and is directed upstream so as to cross the virtual region 19. A gas stream 100 may be supplied.
On the other hand, FIG. 3 is a partially enlarged view similar to FIG. 2, but the gas flow 100 is supplied in the downstream direction from the first gas supply pipe 20 whose tip is located downstream of the virtual region 19. In this case, since the gas flow 100 does not cross the virtual region 19, the above (1) is not satisfied, and the pressure difference in the vicinity of the opening 18 cannot be caused to be lower than that in the vacuum degassing tank 11. . Even when the arrangement is the same as in FIG. 3, when the tip of the first gas supply pipe 20 is positioned upstream of the virtual region 19 and the gas flow 100 is supplied in the downstream direction, the gas flow 100 is virtually Since the region 19 is traversed, the above (1) is satisfied, and a pressure difference in which the pressure near the opening 18 becomes lower than that in the vacuum degassing tank 11 can be generated.
FIG. 4 is a partially enlarged view similar to FIG. 2, but the direction of the tip of the first gas supply pipe 20 is different from that in FIG. In this case, the gas flow 100 supplied from the first gas supply pipe 20 is supplied toward the bottom of the atmosphere control unit 14 on the front side (downstream side) of the virtual region 19. However, it does not cross the virtual region 19, does not satisfy the above (1), and cannot produce a pressure difference in which the pressure in the vicinity of the opening 18 becomes lower than that in the vacuum degassing tank 11.

In order to generate a pressure difference in which the pressure in the vicinity of the opening 18 is lower than that in the vacuum degassing tank 11, the gas flow 120 supplied from the first gas supply pipe 20 needs to cross the virtual region 19. Yes, the gas flow 100 should not blow into the connecting pipe 16. For this reason, it is necessary to arrange the first gas supply pipe 20 so that the imaginary line 21 extending from the tip of the gas supply pipe 20 along the tube axis of the gas supply pipe 20 does not pass through the opening 18. . FIG. 5 is a partially enlarged view of the vicinity of the virtual region 19 of the vacuum degassing apparatus 10 shown in FIG. In FIG. 5, the virtual line 21 extends in the horizontal direction toward the upstream direction, does not pass through the opening 18, and satisfies the above (2).
FIG. 6 is a partially enlarged view similar to FIG. 5, but the direction of the tip of the first gas supply pipe 20 is different from FIG. 5, and the imaginary line 21 faces obliquely downward and passes through the opening 18. Therefore, the above (2) is not satisfied.
FIG. 7 is a partially enlarged view similar to FIG. 6, where the imaginary line 21 faces obliquely downward, but the height of the first gas supply pipe 20 in the atmosphere control unit 14 is the gas supply pipe of FIG. 6. Therefore, the virtual line 21 does not pass through the opening 18 and satisfies the above (2). Similarly, even when the virtual line 21 faces obliquely downward, the angle at which the virtual line 21 faces obliquely downward is smaller than that of the gas supply pipe 20 of FIG. Satisfy (2).

The vacuum degassing apparatus of the present invention may be provided with the first gas supply pipe so as to satisfy the above (1) and (2), and is not limited to the illustrated embodiment and the embodiment described above. In the illustrated embodiment and the embodiment described above, the supply direction of the gas flow 100 is the upstream direction or the downstream direction. However, the supply direction of the gas flow 100 may be other directions, for example, the front side of the drawing or It may be in the back direction. In this case, the first gas supply pipe 20 is arranged on the back side or the near side of the drawing with respect to the opening 18, and the gas flow 100 is supplied in the front or back direction of the drawing so as to cross the virtual region 19. .

In the illustrated embodiment, the gas flow 100 is supplied in the horizontal direction or obliquely downward, but the gas flow may be supplied in an obliquely upward direction. However, in order to effectively generate a pressure difference in which the pressure in the vicinity of the opening 18 is lower than that in the vacuum degassing tank 11, the supply direction of the gas flow 100 is orthogonal to the tube axis of the connection pipe 16. It is preferable that the direction is the horizontal direction. However, in this case, it is not always necessary to supply the gas flow 100 in a direction perpendicular to the tube axis of the connection pipe 16 in a strict sense, and the gas flow 100 is supplied in a direction substantially orthogonal to the tube axis of the connection pipe 16. do it. Here, the direction substantially orthogonal to the tube axis of the connecting tube 16 is preferably within a range of ± 45 °, and is within a range of ± 25 °, where the direction orthogonal to the tube axis is 0 °. More preferably, the range is ± 15 degrees.

Further, in the illustrated embodiment, the downstream connection pipe 16 is a gas flow outlet pipe and the upstream connection pipe 15 is a gas flow inlet pipe. However, the upstream connection pipe 15 is a gas flow outlet pipe, and the downstream side The connection pipe 16 may be a gas flow introduction pipe. In this case, a first gas supply pipe that satisfies the above (1) and (2) in relation to the connection pipe 15 is provided.
When the number of connection pipes is three or more, the arrangement of the connection pipes forming the gas flow outlet pipes and the connection pipes forming the gas flow introduction pipes can be selected as appropriate. For example, in the vacuum degassing apparatus shown in FIG. 1, when a third connection pipe is provided between the upstream connection pipe 15 and the downstream connection pipe 16, the relationship with the

connection pipes

15 and 16 is satisfied. A first gas supply pipe satisfying the above (1) and (2) may be provided, the

connection pipes

15 and 16 may be gas flow outlet pipes, and the third connection pipe may be a gas flow introduction pipe. Alternatively, a first gas supply pipe satisfying the above (1) and (2) is provided in relation to the third connection pipe, the third connection pipe is used as a gas flow outlet pipe, and the

connection pipes

15 and 16 are gas. It may be a flow introduction pipe.

Further, the direction of the gas flow 120 circulating through the atmosphere control unit 14 and the vacuum degassing tank 11 is not limited to the illustrated mode, and may be the opposite direction to the illustrated mode. For example, when the upstream connection pipe 15 is a gas flow outlet pipe and the downstream connection pipe 16 is a gas flow introduction pipe, the direction of the gas flow circulating through the atmosphere control unit 14 and the vacuum degassing tank 11 is The direction is opposite to the illustrated embodiment.
In the illustrated embodiment, the positional relationship between the two connecting pipes is the upstream side and the downstream side, but the positional relationship between the connecting pipes is not limited to this. For example, the positional relationship between the two connecting pipes may be the front side and the back side of the drawing. In this case, the direction of the gas flow circulating through the atmosphere control unit 14 and the vacuum degassing tank 11 is a direction perpendicular to the direction of the gas flow 120 in the illustrated mode (the direction of the gas flow in the atmosphere control unit 14). And the direction of the gas flow above the molten glass G in the vacuum degassing tank 11 is the front side and back side of the drawing, or the back side and front side of the drawing, respectively. In this case, the direction of the gas flow 120 in the vacuum degassing tank 11 is a direction orthogonal to the moving direction of the molten glass G. When the vacuum degassing tank 11 has a shape that is long in the flow direction of the molten glass G as in the illustrated embodiment, the direction of the gas flow 120 above the molten glass G in the vacuum degassing tank 11 is the same as that of the molten glass G. The same direction as the moving direction or the opposite direction is preferable for eliminating the retention of gas components from the molten glass G, but the vacuum degassing tank has a shape with no significant difference in length in the vertical and horizontal directions (for example, When the planar shape of the vacuum degassing tank is a square, hexagon, octagon, or the like), even if the direction of the gas flow 120 in the vacuum degassing tank 11 is perpendicular to the moving direction of the molten glass G The retention of gas components from the molten glass G can be eliminated.

The component of the gas flow 100 supplied from the first gas supply pipe 20 is not particularly limited when the pressure in the vicinity of the opening 18 causes a pressure difference in which the pressure is lower than that in the vacuum degassing tank 11. However, it is preferable that the components of the gas stream 100 do not adversely affect the molten glass G, the manufactured glass product, and the glass manufacturing equipment, particularly the vacuum degassing apparatus. Therefore, it is preferable that the components of the gas stream 100 do not include corrosive and explosive gases.

When a low moisture gas having a water vapor concentration of 60 mol% or less is used as the gas flow 100 supplied from the first gas supply pipe 20, in addition to the effect of eliminating the retention of gas components from the molten glass G, a vacuum degassing tank 11 is preferable because the effect of reducing the water vapor concentration in the atmosphere above the molten glass G in 11 is expected.
The low moisture gas used as the gas flow 100 is not particularly limited as long as the water vapor concentration is 60 mol% or less. Specific examples of such low moisture gas include air, dry air, inert gas such as N ₂ and Ar, and the like. As the gas flow 100, one of these low moisture gases may be used, or a mixed gas of a plurality of types of low moisture gases may be used.
When a low moisture gas is used as the gas flow 100, the water vapor concentration is preferably 50 mol% or less, more preferably 40 mol% or less, further preferably 30 mol% or less, and further preferably 25 mol% or less. Preferably, it is more preferably 20 mol% or less, further preferably 15 mol% or less, further preferably 10 mol% or less, and particularly preferably 5 mol% or less.

It is preferable that the water vapor concentration in the atmosphere above the molten glass G in the vacuum degassing tank 11 is reduced to 60 mol% or less. By setting the water vapor concentration of the atmosphere to 60 mol% or less, it is possible to prevent the bubble layer on the surface of the molten glass in the vacuum degassing tank from being enlarged and to cause bumping, and the effect of vacuum degassing can be further improved. .
In addition, since the bubble layer on the surface of the molten glass tends to be thinner as the water vapor concentration in the atmosphere is lower, the water vapor concentration in the atmosphere above the molten glass G in the vacuum degassing tank 11 is preferably 50 mol% or less. More preferably, it is 40 mol% or less. And it is preferable for the water vapor concentration to be 30 mol% or less because the foam layer tends to be further thinned.
Moreover, when the water vapor | steam density | concentration of this atmosphere is low, each bubble may shrink | contract or bubble-break depending on glass composition, and since a foam layer becomes still thinner by this, it is preferable. Specifically, when the molten glass is borosilicate glass, when the water vapor concentration is 30 mol% or less, the bubbles tend to contract significantly. The borosilicate glass here has, for example, the following composition.
Composition range: SiO ₂ : 55 to 74, Al ₂ O ₃ : 10 to 20, B ₂ O ₃ : 5 to 12, Al ₂ O ₃ / B ₂ O ₃ : 1.5 to 3, MgO: 0 to 5 , CaO: 0 to 5, SrO: 0 to 12, BaO: 0 to 12, SrO + BaO: 6 to 12 (unit: mass%).
Furthermore, when the water vapor concentration in the atmosphere above the molten glass G in the vacuum degassing tank 11 is low, it is preferable because bubbles having a size that is regarded as a defect hardly remain in a glass product produced through vacuum degassing. . If the water vapor concentration in the atmosphere is further reduced, the probability that a glass product produced through vacuum degassing will be defective is further reduced. Therefore, it is more preferably 25 mol% or less, and more preferably 20 mol% or less. More preferably, it is 15 mol% or less, More preferably, it is 10 mol% or less, More preferably, it is 5 mol% or less.

Moreover, volatilization of the specific components (boron etc.) in the molten glass G can be suppressed by making the water vapor | steam density | concentration of the atmosphere above the molten glass G in the vacuum degassing tank 11 into 60 mol% or less. By suppressing volatilization of components such as boron, it is possible to prevent variation in the composition of boron and the like, and to suppress deterioration in flatness due to composition variation.
In addition, volatilization of other easily volatile components such as Cl, F, and S can be suppressed, so that composition fluctuations of these components can be prevented and deterioration of flatness due to composition fluctuations can be suppressed. can do.
Volatilization of components such as Cl, F, and S is considered to be greatly influenced by moisture in the atmosphere. For example, it is considered that F is volatilized as HF and S is vaporized as H ₂ SO ₄ . Therefore, it is considered that volatilization of the above components and accompanying composition fluctuations of the above components can be suppressed by setting the water vapor concentration in the atmosphere above the molten glass G in the vacuum degassing tank 11 to a certain value or less. It is done.

In addition, the characteristics of glass have very fine specifications depending on the application, and the composition of the glass is determined in great detail so as to meet the specifications. For example, there is naturally a standard for the content of boron, but in the conventional method, since boron is volatilized, it is necessary to use more boron as a raw material. Conventionally, the amount of volatilization of boron varies depending on the conditions, and in some cases, there is a possibility that the standard of the content of boron may be deviated. The vacuum degassing apparatus of the present invention is useful because it can eliminate these problems by suppressing the volatilization of boron.
Also from this point, it can be said that the vacuum degassing apparatus of the present invention can be preferably used particularly when borosilicate glass is vacuum degassed, not to mention ordinary glass.

The low moisture gas used as the gas flow 100 is preferably a gas whose oxygen concentration is lower than the oxygen concentration in the air. The oxygen concentration is more preferably 15% by volume or less, more preferably 10% by volume or less, and more preferably 5% by volume or less. The low moisture gas used as the gas stream 100 is preferably a gas not containing oxygen, such as N ₂ gas, Ar gas, CO ₂ or the like.
Since the vacuum degassing tank 11 is a conduit for molten glass G, it is necessary to use a material excellent in heat resistance and corrosion resistance against molten glass, and platinum or platinum alloys are widely used. By using a gas having an oxygen concentration lower than the oxygen concentration in the air as the low moisture gas used as the gas flow 100, the platinum is oxidized when platinum and a platinum alloy are used as the material of the vacuum degassing tank. This is preferable because it suppresses the life of the vacuum degassing tank and further suppresses the generation of defects derived from platinum in glass products.

Specific examples of the platinum alloy include a platinum-gold alloy and a platinum-rhodium alloy. Other examples of materials having excellent heat resistance and corrosion resistance to molten glass used in a vacuum degassing tank include ceramic non-metallic inorganic materials and dense refractories. Specific examples of dense refractories include, for example, electrocast refractories such as alumina electrocast refractories, zirconia electrocast refractories, alumina-zirconia-silica electrocast refractories, and dense alumina refractories. And dense fired refractories such as dense zirconia-silica refractories and dense alumina-zirconia-silica refractories.
In the vacuum degassing apparatus 10 shown in FIG. 1, similarly to the vacuum degassing tank 11, platinum, a platinum alloy, or a dense refractory material is used as the material of the rising pipe 12 and the down pipe 13 that form a conduit for the molten glass G. Things are used.

The atmosphere control unit 14, the connecting

pipes

15 and 16, and the first gas supply pipe 20 are not particularly limited because they are not conduits for molten glass G. For example, metals such as stainless steel, platinum, and platinum alloys are used. Fire-resistant and corrosion-resistant materials such as materials, ceramics, and alumina can be used.

In the vacuum degassing apparatus 10 of the present invention, the purpose of generating the gas flow 120 that circulates through the atmosphere control unit 14 and the vacuum degassing tank 11 is only required to eliminate the retention of gas components from the molten glass G. Therefore, it is not always necessary to generate the gas flow 120 during the vacuum degassing. Therefore, as long as the retention of gas components from the molten glass G can be eliminated, the gas flow 120 may be periodically generated during the vacuum degassing, for example, at a rate of about 1 to 30 seconds every hour. A gas stream 120 may be generated. In order to generate the gas flow 120 periodically, the gas flow 100 may be supplied periodically from the first gas supply pipe 20.

In the vacuum degassing apparatus 10 of the present invention, in order to reduce the water vapor concentration in the atmosphere above the molten glass G in the vacuum degassing tank 11, the water vapor concentration is 60 mol% or less in the upper space of the molten glass G in the vacuum degassing tank 11. A second gas supply pipe for supplying the low moisture gas 140 may be provided.
FIG. 8 is a sectional view showing another configuration example of the vacuum degassing apparatus of the present invention. In the vacuum degassing apparatus 10 ′ shown in FIG. 8, a second gas supply pipe 24 is inserted from a connection pipe 15 forming a gas flow introduction pipe, and the tip of the second gas supply pipe 24 is a vacuum degassing tank. 11 is located in the upper space of the molten glass G in the interior 11. A specific example of the low moisture gas having a water vapor concentration of 60 mol% or less supplied from the second gas supply pipe 24 is the same as that described for the low moisture gas supplied as the gas flow 100.
The second gas supply pipe is not limited to the embodiment shown in FIG. 8 as long as it can supply a low moisture gas having a water vapor concentration of 60 mol% or less to the upper space of the molten glass G in the vacuum degassing tank 11. For example, the second gas supply pipe may be inserted into the upper space of the molten glass G in the vacuum degassing tank 11 from the connection pipe 16 that forms a gas flow outlet pipe. Further, the second gas supply pipe is inserted into the upper space of the molten glass G in the vacuum degassing tank 11 from a portion other than the

connection pipes

15, 16, for example, from the upstream or downstream end face of the vacuum degassing tank 11. May be. However, as in the embodiment shown in FIG. 8, the supply direction of the low moisture gas 140 is set so as not to obstruct the gas flow 120 (see FIG. 1) so that the gas flow is not disturbed in the vacuum degassing tank 11. Therefore, it is preferable.

Further, the position on the outlet side of the second gas supply pipe 24 is not limited as long as a low moisture gas having a water vapor concentration of 60 mol% or less can be supplied to the upper space of the molten glass G in the vacuum degassing tank 11. It is not limited. For example, in the aspect shown in FIG. 8, the tip of the second gas supply pipe 24 is located in the upper space of the molten glass G in the vacuum degassing tank 11, but the tip of the second gas supply pipe 24 is It may be in the connecting pipe 15 or in the atmosphere control unit 14 above the connecting pipe 15.

The vacuum degassing apparatus of the present invention may have a structure other than the above. For example, in order to form the gas flow 120 near the surface (liquid surface) of the molten glass G, a baffle plate for guiding the gas flow 120 downward may be provided inside the ceiling portion of the vacuum degassing tank 11.

The dimension of each component of the vacuum degassing apparatus 10 of the present invention can be appropriately selected as necessary. The size of the vacuum degassing tank 11 is the same as that of the vacuum degassing apparatus or the vacuum degassing tank 11 used, regardless of whether the vacuum degassing tank 11 is made of platinum, platinum alloy, or dense refractory. It can select suitably according to a shape. In the case of a cylindrical vacuum degassing tank 11 as shown in FIG. 1, an example of the dimensions is as follows.
Horizontal length: 1-20m
Inner diameter: 0.2-3m (circular cross section)
When the vacuum degassing tank 11 is made of platinum or a platinum alloy, the wall thickness is preferably 4 mm or less, more preferably 0.5 to 1.2 mm.
The vacuum degassing tank is not limited to a cylindrical shape having a circular cross section, and may be a substantially cylindrical shape having an elliptical shape or a semicircular cross sectional shape, or a cylindrical shape having a rectangular cross section.

Regardless of whether the riser 12 and the downfall 13 are made of platinum, a platinum alloy, or a dense refractory, they can be appropriately selected according to the vacuum degassing apparatus to be used. For example, in the case of the vacuum degassing apparatus 10 shown in FIG. 1, examples of the dimensions of the ascending pipe 12 and the descending pipe 13 are as follows.
Inner diameter: 0.05 to 0.8 m, more preferably 0.1 to 0.6 m
Length: 0.2-6m, more preferably 0.4-4m
When the ascending pipe 12 and the descending pipe 13 are made of platinum or a platinum alloy, the wall thickness is preferably 0.4 to 5 mm, more preferably 0.8 to 4 mm.

Although the dimension of the atmosphere control part 14 and the

connection pipes

15 and 16 can be suitably set according to the vacuum degassing apparatus to be used, especially a vacuum degassing tank, the example is as follows.
Atmosphere controller <br/> Inner diameter: 0.1 to 3 m, more preferably 0.1 to 2 m
Length: 0.8-22m, more preferably 1-20m
Connecting tube <br/> Inner diameter: 0.05 to 0.5 m, more preferably 0.05 to 0.3 m
Length: 0.1-1m, more preferably 0.1-0.8m
Inner diameter of first gas supply pipe Inner diameter: 3 to 50 mm, more preferably 5 to 20 mm
Although the thickness of the atmosphere control part 14 and the

connection pipes

15 and 16 changes also with structural materials, when it is made from stainless steel, it is preferable that it is as follows, respectively.
Atmosphere controller 0.5-2mm, more preferably 0.5-1.5mm
Connecting pipe 0.5-2mm, more preferably 0.5-1.5mm
Inner diameter of second gas supply pipe Inner diameter: 3 to 50 mm, more preferably 5 to 20 mm

Hereinafter, the present invention will be specifically described based on examples. However, the present invention is not limited to this.
In the embodiment, an air flow analysis in the upper space of the molten glass G in the vacuum degassing tank is performed using Fluent, a venturi effect by supplying a gas flow from the first gas supply pipe to the virtual region, and a venturi The elimination of the retention of gas components from the molten glass due to the gas flow circulating through the atmosphere control part caused by the effect and the upper space of the molten glass in the vacuum degassing tank was evaluated. As the vacuum degassing apparatus, the gas flow 100 from the first gas supply pipe 20 to the virtual region 19 above the opening 18 with the downstream connection pipe 16 is provided as in the vacuum degassing apparatus 10 shown in FIG. Was used as a model to supply the low moisture gas 140 from the second gas supply pipe 24 inserted into the upper space of the molten glass G in the vacuum degassing tank 11 from the connection pipe 15 on the upstream side. Or unlike FIG. 8, the 1st gas supply pipe | tube 20 is installed above the upstream connection pipe 15, the gas flow 100 is supplied, and the molten glass in the pressure reduction degassing tank 11 from the downstream connection pipe 16 is supplied. What supplied the low moisture gas 140 from the 2nd gas supply pipe | tube 24 inserted in the upper space of G was used as a model. The gas flow 100 and the low moisture gas 140 were both modeled as supplying N ₂ .

The dimensions of each part of the vacuum degassing apparatus 10 used as a model are as follows.
Vacuum defoaming tank 11: total length 10m, inner diameter 1m (cross-sectional semicircular shape)
Atmosphere control unit 14: total length 10 m, inner diameter 2 m (cylindrical shape)
Connection pipes 15 and 16: Overall length 0.8 m, inner diameter 0.3 m (cylindrical shape)
Each of the connecting

pipes

15 and 16 has a ceiling portion of the vacuum degassing tank 11, more specifically, a position 0.1 m from the upstream end of the vacuum degassing tank 11, and 0. 0 from the downstream end. It was provided at a position of 1 m.
Exhaust port 17: Provided in the ceiling portion at an inner diameter of 0.05 m (cylindrical shape) and at the center of the atmosphere control unit 14 in the longitudinal direction.
First gas supply pipe 20: Unlike FIG. 8, a circular stainless steel nozzle having an inner diameter of 5 mm was inserted in the horizontal direction from the center of the downstream end of the atmosphere control unit 14. Regardless of whether the first gas supply pipe 20 is installed on the downstream side or the upstream side, the position of the tip of the first gas supply pipe is 5 mm downstream from the opening 18 and the height from the bottom of the atmosphere control unit 14. The position was 10 mm.
Second gas supply pipe 24: A circular stainless steel nozzle having an inner diameter of 15 mm is inserted into the upper space of the molten glass G in the vacuum degassing tank 11 from the ceiling of the atmosphere control section 14 via the connection pipe 15. The position of the tip of the second gas supply pipe was 10 mm below the upper wall surface of the vacuum degassing tank 11.

Analysis was performed for the case where the pressure in the upper space of the molten glass G in the vacuum degassing tank 11 and the atmosphere control unit 14 were constant at a pressure of 350 mmHg and a temperature of 1400 ° C.
For the air flow analysis, a transport model of non-reactive chemical species, a standard k-ε model, and a standard wall function were adopted. The entrance diffusion and diffusion energy were not taken into consideration, and default values were used for other setting parameters. For the fluid physical properties of the airflow analysis, the value of the mixture consisting of N ₂ and volatilized H ₂ O in the Fluent database (below) was used.
Viscosity: 1.72 × 10 ⁻⁵ [kg / m · s]
Thermal conductivity: 0.0454 [W / m · K]
Mass diffusion coefficient: 2.88 × 10 ⁻⁵ [m ² / s]
Density: ρ = pM _w / RT (incompressible ideal gas equation)
Specific heat: c _p = Σ _i Y _i c _{p, i} (mass fraction average formula of specific heat by chemical species) [J / kg · K]
It is considered that a plurality of gases such as SO ₃ , O ₂ , B ₂ O ₃ , H ₂ O and the like are volatilized from the molten glass G in the vacuum degassing tank 11, but in this analysis, only H ₂ O is 2.00 NL for convenience. It was assumed that it volatilized at / min.
Hereinafter, in this specification, the gas volatilized from the molten glass G in the vacuum degassing tank 11 is simply referred to as “volatile gas”.

The movement of the molten glass G in the vacuum degassing tank 11 was not taken into consideration, and N ₂ supplied from the volatilized gas and the second gas supply pipe was defined by the speed boundary condition.
In the airflow analysis, as the concentration of the volatile gas from the molten glass G in the vacuum degassing tank 11, the average concentration of the volatile gas in the atmosphere above the molten glass G (hereinafter referred to as “average concentration of the volatile gas above the molten glass G”). In some cases). The volatilized gas concentration in the vicinity of the liquid surface of the molten glass G (5 mm above the liquid surface of the molten glass) was used as an evaluation index.
Further, the pressure in the vicinity of the opening of the atmosphere control unit 14 and the connection pipe 15 and the pressure in the vicinity of the opening 18 of the atmosphere control unit 14 and the connection pipe 16 (hereinafter, the former is referred to as “upstream side opening part”). Pressure ”and the latter as“ downstream opening pressure ”in some cases.
Further, the amount of gas discharged from the vacuum degassing tank 11 to the atmosphere control unit 14 through the connection pipe 15 and the gas discharged from the vacuum degassing tank 11 to the atmosphere control unit 14 through the connection pipe 16. The gas flow rate (hereinafter, the former is sometimes referred to as “upstream discharge flow rate” and the latter is sometimes referred to as “downstream discharge flow rate”) was evaluated.

(Examples 1, 2, 3, 4, 5 and Comparative Example 1)
In Example 1, the first gas supply pipe 20 is installed in the upper part of the downstream connection pipe 16 and N ₂ is supplied as a gas flow 100 at a volume flow rate of ₂ NL / min. The average of the volatilized gas above the molten glass G Concentration, upstream opening pressure, downstream opening pressure, upstream discharge flow rate and downstream discharge flow rate were evaluated.
In Example 2, the first gas supply pipe 20 is installed on the upper part of the downstream connection pipe 16, and N ₂ is supplied as a gas flow 100 at a volume flow rate of 10 NL / min. Concentration, upstream opening pressure, downstream opening pressure, upstream discharge flow rate and downstream discharge flow rate were evaluated.
In Example 3, the first gas supply pipe 20 is installed in the upper part of the downstream connection pipe 16 and N ₂ is supplied as a gas flow 100 at a volume flow rate of 15 NL / min. Concentration, upstream opening pressure, downstream opening pressure, upstream discharge flow rate and downstream discharge flow rate were evaluated.
In Example 4, the first gas supply pipe 20 is installed in the upper part of the downstream connection pipe 16 and N ₂ is supplied as a gas flow 100 at a volume flow rate of 50 NL / min. The average of the volatilized gas above the molten glass G Concentration, upstream opening pressure, downstream opening pressure, upstream discharge flow rate and downstream discharge flow rate were evaluated.
In Example 5, the first gas supply pipe 20 is installed in the upper part of the upstream connection pipe 15 and N ₂ is supplied as a gas flow 100 at a volume flow rate of 15 NL / min. Concentration, upstream opening pressure, downstream opening pressure, upstream discharge flow rate and downstream discharge flow rate were evaluated.
In Example 6, the first gas supply pipe 20 having an inner diameter of φ20 mm is installed at the upper part of the downstream connection pipe 15 and N ₂ is supplied as a gas flow 100 at a volume flow rate of 50 NL / min. The average concentration of the volatilized gas, the upstream opening pressure, the downstream opening pressure, the upstream discharge flow rate, and the downstream discharge flow rate were evaluated.
In Example 7, the first gas supply pipe 20 having an inner diameter of φ5 mm is installed on the upper side of the connecting pipe 15 on the upstream side of the inner diameter of φ0.2 m, and N ₂ is supplied as a gas flow 100 at a volume flow rate of ₂ NL / min. The average concentration of the volatile gas above the molten glass G, the upstream opening pressure, the downstream opening pressure, the upstream discharge flow rate, and the downstream discharge flow rate were evaluated.
In Comparative Example 1, without supplying the gas flow 100 from the first gas supply pipe 20, the average concentration of the volatilized gas above the molten glass G, the upstream opening pressure, the downstream opening pressure, the upstream discharge flow rate, and The downstream discharge flow rate was evaluated.
The average concentration of the volatile gas above the molten glass G in Examples 1 to 7 is shown as a relative value when the average concentration of the volatile gas in Comparative Example 1 is 100. Moreover, the value of the upstream opening part pressure (Pa) and the downstream opening part pressure (Pa) was shown by the difference with the reference | standard pressure (46,662Pa = 350mmHg) in the vacuum degassing tank 11. FIG. Further, the pressure difference between the upstream opening pressure (Pa) and the downstream opening (opening pressure (Pa) on the side not having the first gas supply pipe 20) minus the first gas supply pipe 20 The opening pressure (Pa) on the side having the same is also shown.
The results are shown in Table 1 below. The results of Examples 1 to 7 are values when the steady state is reached after the supply of the gas flow 100 is started.

(Examples 8 to 13, Comparative Example 2)
In the eighth embodiment, the first gas supply pipe 20 is installed at the upper part of the downstream connection pipe 16 to supply N ₂ as a gas flow 100 at a volume flow rate of 5 NL / min, and the second gas supply pipe 24 is connected to the upstream side. N ₂ is supplied as a low moisture gas 140 at a volume flow rate of 10 NL / min, the average concentration of the volatilized gas above the molten glass G, the upstream opening pressure, the downstream opening pressure, The upstream discharge flow rate and the downstream discharge flow rate were evaluated.
In the ninth embodiment, the first gas supply pipe 20 is installed in the upper part of the downstream connection pipe 16, and N ₂ is supplied as a gas flow 100 at a volume flow rate of 10 NL / min, and the second gas supply pipe 24 is connected to the upstream side. N ₂ is supplied as a low moisture gas 140 at a volume flow rate of 10 NL / min, the average concentration of the volatilized gas above the molten glass G, the upstream opening pressure, the downstream opening pressure, The upstream discharge flow rate and the downstream discharge flow rate were evaluated.
In the tenth embodiment, the first gas supply pipe 20 is installed above the connection pipe 16 on the downstream side, N ₂ is supplied as a gas flow 100 at a volume flow rate of 50 NL / min, and the second gas supply pipe 24 is connected to the upstream side. N ₂ is supplied as a low moisture gas 140 at a volume flow rate of 10 NL / min, the average concentration of the volatilized gas above the molten glass G, the upstream opening pressure, the downstream opening pressure, The upstream discharge flow rate and the downstream discharge flow rate were evaluated.
In the eleventh embodiment, the first gas supply pipe 20 is installed on the upper side of the connection pipe 15 on the upstream side, N ₂ is supplied as the gas flow 100 at a volume flow rate of 10 NL / min, and the second gas supply pipe 24 is connected to the downstream side. N ₂ is supplied as a low moisture gas 140 at a volumetric flow rate of 10 NL / min, the average concentration of the volatilized gas above the molten glass G, the upstream opening pressure, the downstream opening pressure, The upstream discharge flow rate and the downstream discharge flow rate were evaluated.
In the twelfth embodiment, a first gas supply pipe 20 having an inner diameter φ of 20 mm is installed on the upstream side of the connection pipe 15 to supply N ₂ as a gas flow 100 at a volume flow rate of 50 NL / min, and a second gas supply pipe 24 is installed in the upper part of the connecting pipe 16 on the downstream side, N ₂ is supplied as a low moisture gas 140 at a volume flow rate of 15 NL / min, the average concentration of the volatilized gas above the molten glass G, the upstream opening pressure, the downstream side The opening pressure, upstream discharge flow rate, and downstream discharge flow rate were evaluated.
In Example 13, the first gas supply pipe 20 having an inner diameter of φ5 mm is installed at the upper part of the upstream connection pipe 15 having an inner diameter of φ0.2 m, and N ₂ is supplied as a gas flow 100 at a volume flow rate of 15 NL / min. The second gas supply pipe 24 is installed at the upper part of the downstream connection pipe 16 and N ₂ is supplied as a low moisture gas 140 at a volume flow rate of 10 NL / min. The opening pressure, the downstream opening pressure, the upstream discharge flow rate, and the downstream discharge flow rate were evaluated.
In Comparative Example 2, the first gas supply pipe 20 is not installed, the second gas supply pipe 24 is installed at the upper part of the upstream connection pipe 15, and N ₂ is used as the low moisture gas 140 at a volume flow rate of 15 NL / min. The average concentration of the volatile gas above the molten glass G, the upstream opening pressure, the downstream opening pressure, the upstream discharge flow rate, and the downstream discharge flow rate were evaluated.
The average concentration of the volatile gas above the molten glass G in Examples 8 to 13 is shown as a relative value when the average concentration of the volatile gas in Comparative Example 1 is 100. Moreover, the value of the upstream opening part pressure (Pa) and the downstream opening part pressure (Pa) was shown by the difference with the reference | standard pressure (46,662Pa = 350mmHg) in the vacuum degassing tank 11. FIG. The pressure difference between the upstream opening pressure (Pa) and the downstream opening (upstream opening pressure (Pa) −downstream opening pressure (Pa)) is also shown.
The results are shown in Table 2 below. The results of Examples 8 to 13 are values when the steady state is reached after the supply of the gas flow 100 is started.

INDUSTRIAL APPLICABILITY The present invention can be used for the production of various high-quality glass products that do not contain bubbles, and is particularly suitable for vacuum degassing of borosilicate glass.
The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2008-50110 filed on Feb. 29, 2008 are cited here as disclosure of the specification of the present invention. Incorporated.

Claims

The internal pressure is set to less than atmospheric pressure, a vacuum defoaming tank that floats and breaks bubbles in the supplied molten glass, and a vacuum riser that is connected to the vacuum defoaming tank and sucks up the molten glass before defoaming treatment. A riser pipe that is introduced into the vacuum degassing tank and a downcomer pipe connected to the vacuum degassing tank and that descends the molten glass after the defoaming treatment from the vacuum degassing tank. In a vacuum degassing apparatus for glass,
It has a hollow atmosphere control unit connected to the vacuum deaeration tank by at least two connecting pipes, and the atmosphere control unit is provided with an exhaust port for exhausting and depressurizing the atmosphere control unit. The atmosphere control unit is provided with a first gas supply pipe satisfying the following (1) and (2) in relation to at least one of the connecting pipes, and the vacuum degassing of molten glass is provided: apparatus.
(1) A virtual region in which an opening formed by the atmosphere control unit and the connection pipe extends into the atmosphere control unit along the tube axis direction of the connection pipe is supplied from the first gas supply pipe Gas flow crosses.
(2) An imaginary line extending from the tip of the first gas supply pipe along the tube axis of the gas supply pipe does not pass through the opening formed by the atmosphere control unit and the connection pipe.
The number of the first gas supply pipes is X-1 or less (provided that the number of the first gas supply pipes is 1 or more), where X is the number of the connection pipes. 2. A vacuum degassing apparatus for molten glass according to 1.
The molten glass vacuum degassing apparatus according to claim 1 or 2, wherein the gas flow supplied from the first gas supply pipe is a low moisture gas flow having a water vapor concentration of 60 mol% or less.
The second gas supply pipe for supplying a low moisture gas having a water vapor concentration of 60 mol% or less to the upper space of the molten glass in the vacuum degassing tank is further provided. A vacuum degassing apparatus for molten glass as described in 1.
A vacuum degassing method for molten glass using the vacuum degassing apparatus according to claims 1 to 4, wherein the molten glass is supplied with a gas flow from the first gas supply pipe so as to satisfy the following formula: Bubble method.
v> A / 0.031 × [5.487 × 10 −6 × (1 / 56.3533-1 / ρ) + 19.6 × (0.163−z) +7.5 2 ] 1/2
v: Flow velocity (m / s) of the gas flow in the first gas supply pipe
ρ: density of the gas flow in the first gas supply pipe (kg / m 3 )
z: Height (m) of the outlet of the first gas supply pipe in the atmosphere control unit
A: Area of opening (m 2 )