JPH11255519A - Apparatus for defoaming molten glass under reduced pressure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for defoaming a molten glass under a reduced pressure, capable of manifesting a sufficient ability of a melting and defoaming treatment by changing the flow rate of the molten glass by blowing air into a riser of the defoaming apparatus having a depressurizing housing whose the interior is brought into a reduced pressure state, a depressurizing defoaming vessel installed in the housing, and the riser and a down comer of the molten glass communicated to the defoaming vessel. SOLUTION: This depressurizing defoaming apparatus 10 defoaming by sucking and lifting the molten glass G from a dissolving vessel 20 to a depressurizing defoaming vessel 14, carrying out the defoaming treatment in the depressurizing defoaming vessel 14 under a reduced pressure and supplying the treated molten glass to the following step has the depressurizing defoaming vessel 14 in the depressurizing housing, a riser 16 and a down comer 18. The depressurizing housing has a sucking opening 12c, and the interior of the depressurizing defoaming vessel in the interior is vacuum-sucked by a vacuum pump to reduce the pressure to a prescribed pressure. A blowing pipe 32 for blowing air into the molten glass G is arranged at the lower part of the riser 16, so that the flow rate of the molten glass G may be in-creased by a pumping-up effect of an air bubble. The defoaming processing capacity is increased by the blowing of the air without changing the apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

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

[0003] The vacuum degassing tank 114 is horizontally provided in a decompression housing 112 in which the inside is decompressed by vacuum suction by a vacuum pump (not shown). 3 to 1 /
Since the pressure has been reduced to 20 atm, the molten glass G in the upstream side pit 122 before the defoaming treatment is sucked up by the riser pipe 116 and introduced into the decompression degassing tank 114. After the defoaming process is performed, the downcomer 118
And is led out to the downstream pit 124.
In the present invention, the molten glass G is supplied to the rising pipe 116.
The pressure in the molten glass G expands in accordance with the pressure, and the bubbles existing in the molten glass G expand in accordance with the pressure. While the molten glass gradually returns to normal pressure while descending the downcomer 118, the vacuum degassing process is mainly performed in the vacuum degassing tank 114. The decompression housing 112 is a casing made of metal, for example, stainless steel or heat-resistant steel. The interior of the decompression housing 112 is vacuum-evacuated by a vacuum pump (not shown) or the like to reduce the pressure therein. The inside is reduced to a predetermined pressure, for example, 1/3 to 1/20 atm. A heat insulating material 130 such as a fire-resistant brick is provided around the vacuum degassing tank 114, the riser pipe 116, and the downcomer pipe 118 in the vacuum housing 112.

In the conventional vacuum degassing apparatus 110, the molten glass G is sucked and lifted from the melting tank into the vacuum degassing apparatus 110, subjected to a vacuum degassing process, and discharged into a next processing tank, for example, a forming tank. The flow rate (or flow rate) is determined by the difference in liquid level between the upstream pit 122 and the downstream pit 124, and therefore the level difference h between the molten glass bases at the bases of the riser 116 and the downcomer 118, due to the pressure loss therebetween. The condition is determined so as to satisfy the condition of being equal to Δp, that is, the following expression. Δp = ρgh Here, ρ is the density of the molten glass G. At this time, to be precise, it is better to calculate the vacuum degassing tank 114 of the vacuum degassing apparatus 110 separately as an open channel, but assuming that the riser pipe 116, the vacuum degassing tank 114, and the descending pipe 118 are circular pipes, Assuming that the diameter of the circular tube is D and the length is L, the flow velocity u of the molten glass G subjected to the degassing under reduced pressure can be represented by the following equation. Δp = 32 μLu / gD ² (Hagen-Poiseuille equation) where μ is the viscosity of the molten glass G.

[0005] As described above, in the conventional vacuum degassing apparatus 110, the flow rate of the molten glass G subjected to the vacuum degassing process is:
The temperature (viscosity μ) of the molten glass G and the upstream pits 122 and the downstream pits 124 are substantially maintained unless the configuration of the vacuum degassing apparatus 110, the components of the molten glass G, and the manufacturing process are changed.
And the height difference h of the liquid level. Therefore, when changing the flow rate of the molten glass G in the vacuum degassing apparatus 110, the temperature (viscosity μ) of the molten glass G is changed or the liquid level of the upstream pit 122 and the downstream pit 124 is increased. The difference h must be changed.

However, in the conventional vacuum degassing apparatus 110, changing the temperature of the molten glass G is not particularly effective in increasing the flow rate of the molten glass G by increasing the temperature and decreasing the viscosity. It is difficult from the viewpoint of the high-temperature strength of the constituent material of the vacuum degassing apparatus 110, conventionally, a noble metal such as platinum, or an alloy thereof. Therefore, in the conventional vacuum degassing apparatus 110, in order to increase the flow rate of the molten glass G,
It is necessary to increase the height difference h of the liquid level between the upstream pit 122 and the downstream pit 124, but it is also possible to change the height difference h of the liquid level once the vacuum decompression is completed as a facility. The configuration of the foaming device 110 is changed, which is not easy. That is, the conventional vacuum degassing apparatus 110
Due to the configuration of the apparatus, there are many cases where the difference h in the liquid level cannot be changed or it is not desired to change it from other conditions, such as when the level of the entrance is determined by external conditions.

[0007]

As described above, in the conventional vacuum degassing apparatus 110, it is not easy to change the flow rate of the molten glass G. Assuming that the vacuum degassing apparatus 11
At 0, even if the flow rate of the molten glass G was increased and the flow rate was increased, it was found that there was sufficient vacuum degassing treatment capacity, but it still had to be used with low treatment capacity. There was a problem. Therefore, in the conventional vacuum degassing apparatus 110, there is a sufficient vacuum degassing treatment capacity, and it is possible to increase the flow rate of the molten glass G to increase the flow rate of the molten glass G and increase the flow rate of the molten glass G to be degassed under reduced pressure. However, it is not easy to change the flow rate of the molten glass G by changing the difference h between the temperature and the liquid level of the molten glass G, and the capability of the vacuum degassing apparatus 110 cannot be sufficiently exhibited. there were.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to easily increase the flow rate of the molten glass G according to the reduced-pressure defoaming capability without changing the apparatus configuration itself. The flow rate of the molten glass G can be increased,
The vacuum defoaming ability can be maximized,
An object of the present invention is to provide a vacuum degassing apparatus for molten glass capable of improving the degree of freedom in apparatus design.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a decompression housing in which the inside is decompressed by vacuum suction, and a decompression defoaming of the molten glass provided in the decompression housing. A vacuum degassing tank, a rising pipe that is provided in communication with the vacuum degassing tank, suctions the molten glass before vacuum degassing and introduces the molten glass into the vacuum degassing tank, and communicates with the vacuum degassing tank. A downcomer pipe for lowering the molten glass after vacuum degassing from the vacuum degassing tank and leading it out, and air blowing means for blowing air from below the riser pipe. It is an object of the present invention to provide a vacuum degassing apparatus for molten glass, wherein the air is blown into a riser to raise the molten glass in the riser together with the air.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vacuum degassing apparatus for molten glass according to the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

FIG. 1 is a schematic sectional view of a vacuum degassing apparatus for molten glass of the present invention. As shown in FIG. 1, a vacuum degassing apparatus 10 for molten glass of the present invention suctions and raises molten glass G from a melting tank 20 to a vacuum degassing tank 14, and decompresses the vacuum in the depressurized vacuum degassing tank 14. It is used for a process of performing a foaming process and continuously supplying it to the next processing tank 26, for example, a plate-shaped forming tank such as a float bath or a forming work tank such as a bottle. , A vacuum degassing tank 14, an ascending pipe 16 and a descending pipe 18.

The decompression housing 12 functions as a pressure vessel for ensuring airtightness when depressurizing the decompression degassing tank 14. In the present embodiment, the decompression housing 12 is formed substantially in a gate shape and is decompressed and degassed. It is configured to enclose the tank 14 and the upper portions of the riser tube 16 and the downcomer tube 18. The material and structure of the decompression housing 12 are not particularly limited as long as it has the airtightness and strength required for the decompression degassing tank 14, but are made of metal, particularly stainless steel or heat-resistant steel. It is preferable to make it. Decompression housing 1
2 is a suction port 1 for depressurizing the inside by vacuum suction in the upper right part.
2c is provided, and the inside of the decompression housing 12 is depressurized by being evacuated by a vacuum pump (not shown),
The inside of the vacuum degassing tank 14 arranged substantially at the center is reduced to a predetermined pressure, for example, 1/3 to 1/20 atm.

At a substantially central portion of the decompression housing 12, a decompression degassing tank 14 is horizontally disposed. The cross section of the flow path of the vacuum degassing tank 14 may be circular as in the related art.
The present invention is not limited to this. For example, polygons such as ellipses and rectangles and irregular shapes may be used.
In order to perform the vacuum degassing treatment, a rectangular shape is preferable. The left end of the vacuum degassing tank 14 communicates vertically with the upper end of a rising pipe 16, and the right end of the vacuum degassing vessel 14 communicates with the upper end of a downcomer pipe 18 vertically downward. The ascending pipe 16 and the descending pipe 18 are disposed so as to pass through the legs 12a and 12b of the gate-shaped decompression housing 12, respectively. The upstream pit 22 communicating with the tank 20 and the downstream pit 2 communicating with the next processing tank (not shown).
4 is immersed in the molten glass G. Here, the vacuum degassing tank 14, the rising pipe 16 and the descending pipe 18 are preferably made of electroformed refractory bricks in order to perform a vacuum degassing treatment of the molten glass G with a large flow rate. May be made of a noble metal such as platinum, a noble metal alloy, or the like, or all of the flow paths in contact with the molten glass may be made of a noble metal, a noble metal alloy, or the like such as platinum.

Above the vacuum degassing tank 14, the vacuum housing 12 is evacuated by a vacuum pump or the like (not shown) so that the inside of the vacuum degassing tank 14 has a predetermined pressure (1/3).
Suction holes 14 a and 14 b communicating with the decompression housing 12 are provided in order to maintain the pressure reduced to (１ ／ 1/20 atm). The space between the decompression housing 12 and the decompression degassing tank 14, the riser tube 16, and the downcomer tube 18 is filled with a heat insulating material 30, such as a refractory brick, and covered with heat. The heat insulating material 30 is made of a heat insulating material having air permeability so as not to hinder the vacuum suction of the vacuum degassing tank 14.

Downstream of the riser 16 is an upstream pit 22
An air blowing pipe 32, which is an air blowing means of the present invention, for blowing air, for example, preheated air, into the molten glass G therein is disposed. The air supplied from the air blowing pipe 32 becomes bubbles in the molten glass G and rises in the rising pipe 16 together with the molten glass G, and breaks at the liquid level of the molten glass G in the vacuum degassing tank 14. And disappear. At this time, the apparent specific gravity of the molten glass G including a large number of air bubbles in the riser 16 becomes smaller than the specific gravity of the molten glass G in the descender 18, and the pumping effect of the air bubbles increases the riser 16.
From the head toward the downcomer 18, the flow of the molten glass G is accelerated, the flow velocity is increased, and the flow rate of the molten glass G can be increased. Air blow pipe 3
Means for supplying air, for example, preheated air, to 2 is not particularly limited, and a conventionally known air supply means can be applied as it is. Here, the air blowing pipe 32 is preferably made of a noble metal tube such as a platinum tube or an alloy tube thereof. The shape and size of the air blowing pipe 32 are not particularly limited, either.
It is preferable that the vacuum degassing apparatus 10 of the present invention has a shape and dimensions that can generate a foam having a size larger than the size of the foam originally targeted for the defoaming treatment.

Here, in the present invention, the bubbles generated in the molten glass G by the air blown from the air blowing pipe 32 are fine-sized bubbles which are originally limited in the object of the defoaming treatment in the present invention. For example, bubbles having a size much less than 1 mm or less, specifically, bubbles having a diameter of about 0.3 mm or 0.2 mm in architectural glass, for example, several meters in diameter.
It is good to be a foam having a diameter of m to 1 cm, preferably about 5 to 8 mm. This is done so that the precision and efficiency of the defoaming process of micro-sized bubbles that are the target of the defoaming process are not reduced.
This is because the rising force of the bubbles in the molten glass G is increased, the rising of the molten glass G to the liquid surface in the vacuum degassing tank 14 is accelerated, and the foaming at the liquid surface is reliably and promptly performed. Note that the bubbles generated by the air blowing pipe 32 also have an effect of physically combining with the original fine bubbles to be defoamed, and thus also have an effect of improving the defoaming efficiency of the vacuum degassing apparatus 10 of the present invention. Play. Further, it is preferable that air is continuously blown into the molten glass G from the air blowing pipe 32 at a constant pressure to generate air bubbles of a fixed size at predetermined intervals. The amount of air blown into the molten glass G of the riser 16 or the amount of air bubbles present in the molten glass G of the riser 16 is not particularly limited. The lifting force to be applied, and therefore the flow rate of the molten glass G,
That is, it may be appropriately selected according to the defoaming processing amount.

Next, the operation of the vacuum degassing apparatus 10 for molten glass of the present invention will be described. The vacuum degassing tank 14 is evacuated by a vacuum pump (not shown) and maintained at a predetermined pressure, for example, 1/3 to 1/20 atm. Atmospheric pressure (atmospheric pressure) of the liquid surface of the molten glass G in the downstream pit 24
And the decompressed air in the decompression housing 12 through a riser pipe 16 or a downcomer pipe 18.
And a siphon is formed by a series of closed conduits. Then, the molten glass G flows out to the downstream pit 24 according to the difference h in the liquid level of the molten glass G between the upstream pit 22 and the downstream pit 24.

At this time, the height of the liquid surface of the molten glass G in the upstream pit 22 or the downstream pit 24 and the pressure reduction degassing tank 1
The difference between the liquid surface heights of the molten glass G sucked and raised in FIG.
Although it depends on the reduced pressure in the vacuum degassing tank 14, the flow rate of the molten glass G in the vacuum degassing tank 14 is approximately 2.5 m to 3.5 m. And the height h of the liquid surface of the molten glass G between the upstream pit 22 and the downstream pit 24. Since the molten glass G sucked and raised in the vacuum degassing tank 14 is reduced in pressure to 1/3 to 1/20 atm in the vacuum degassing tank 14, bubbles contained in the molten glass G are reduced to a liquid level. Ascends and breaks bubbles. The reduced-pressure defoaming device 10 removes bubbles contained in the molten glass G in this manner.

The rising pipe 16 of such a vacuum degassing apparatus 10
An air blowing pipe 32 for blowing air preheated to substantially the same temperature as the molten glass G is disposed below. When air is blown from the air blowing pipe 32 below the rising pipe 16, the air becomes bubbles 34. Floating in the molten glass G,
It rises in riser 16 together with molten glass G. The apparent specific gravity of the molten glass G including the bubbles 34 is naturally smaller than the specific gravity of the molten glass G, and therefore the specific gravity of the molten glass G in the downcomer 18, and includes the bubbles 34 in the riser 16. Due to this difference in specific gravity, the molten glass G has bubbles 3 at a higher flow rate in the riser tube 16 than in the case where no air is blown, and to a higher position in the vacuum degassing tank 14.
4 and will be sucked up.

Of course, the bubbles 34 that have reached the liquid level in the vacuum degassing tank 14 break down when they rise to the liquid level, leaving only the molten glass G containing fine bubbles to be defoamed. As described above, the position of the liquid surface at this time is higher in the molten glass containing the bubbles 34 and having a smaller apparent specific gravity than in the molten glass not containing the bubbles 34, as shown in FIG. Then, the gradient of the liquid level of the molten glass G in the vacuum degassing tank 14 increases, and the molten glass G flows in the vacuum degassing tank 14 toward the downcomer pipe 18 at a higher flow rate, so that the molten glass to be subjected to the vacuum degassing process. The flow rate of G can be increased.

The diameter of the bubble 34 varies depending on the temperature or pressure, and the suitable bubble diameter varies depending on the composition and viscosity of the molten glass. It is preferable that the bubbles have a diameter of about 1 cm. By increasing or decreasing the amount of the bubbles 34, the flow rate of the molten glass G in the rising pipe 16, that is, the flow rate of the molten glass G flowing in the vacuum degassing tank 14 is reduced. Can be changed. In addition, even if the difference h in the liquid surface height of the molten glass G between the upstream pit 22 and the downstream pit 24 cannot be changed in the vacuum degassing apparatus 10,
Alternatively, even when the liquid level difference h cannot be increased or cannot be obtained due to external conditions of the apparatus configuration, or even when the liquid level difference h is set low, the melting point in the riser pipe 16 as in the present invention is not increased. By blowing air from the air blowing pipe 32 into the glass G, the flow rate of the molten glass G flowing in the vacuum degassing tank 14 can be increased, and a necessary defoaming processing amount can be secured.

Further, when preheated air is used as the air blown into the molten glass G from the air blowing pipe 32, the following effects are obtained. In particular, when the molten glass G is soda glass, O _{2 in} the air easily dissolves into the molten glass G, so that the bubbles 34 become bubbles of air (mainly N ₂ ) excluding O ₂ . Thus, it rises with the molten glass G. Then, dissolved gases such as SO ₂ , CO ₂ , and H ₂ O dissolved in the molten glass G diffuse and flow toward the bubbles 34, and the concentration of the dissolved gas decreases.

In addition, O dissolved in the molten glass G
_2, low O ₂ concentration bubbles in the periphery of the molten glass G (in particular, SO ₂ bubbles caused by sulfate fining agent added in the melting furnace) when there is less of the molten glass G of the O ₂ concentration bubbles To increase the diameter of the foam, rise in the molten glass G, and easily break the foam from the liquid level of the molten glass G in the vacuum degassing tank 14. When the amount of SO ₂ dissolved in the molten glass G is large, the SO ₂ becomes a cause of reboil in a processing tank (not shown).
Using preheated air as the air blown into the molten glass G from the air blowing pipe 32 to reduce the dissolved SO ₂ has an additional effect. Bubbles having a small diameter that cannot be raised in the molten glass G are sent to the downcomer 18.
During the process in which the pressure recovers to the normal pressure while descending, almost all of it is absorbed by the molten glass G and disappears.

As described above, the degassing apparatus for depressurizing molten glass according to the present invention has been described in detail. However, the present invention is not limited to the above-described embodiment, but may be any other liquid that does not depart from the gist of the present invention.
Of course, various improvements and changes may be made.

[0025]

As described above in detail, according to the present invention, the level difference between the molten glass bases at the lower ends of the riser pipe and the lowering pipe, that is, the difference in liquid glass level cannot be increased, or Even if it cannot be changed, an air blowing pipe that blows preheated air to almost the same temperature as the molten glass is arranged below the riser pipe, and air can be blown from the air blow pipe below the riser pipe to make it easier. The flow rate of the molten glass can be increased, and the capacity of the vacuum degassing device can be maximized. Conversely, in the vacuum degassing device with the same degassing capacity, the lower ends of the riser and the downcomer In this case, the difference in the level of the molten glass substrate can be reduced, and the degree of freedom in device design can be increased. When using preheated air as air blown into the molten glass from the air blowing pipe, the molten glass G
Dissolved gases such as SO ₂ , CO ₂ , H ₂ O, etc.
In particular, it is possible to reduce the concentration of SO ₂ and prevent reboil in the next processing tank.

[Brief description of the drawings]

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

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

[Explanation of symbols]

 10,110 Decompression degassing device 12,112 Decompression housing 12a, 12b Leg 12c Suction port 14,114 Decompression degassing tank 14a, 14b Suction hole 16,116 Rise pipe 18,118 Down pipe 20,120 Dissolution tank 22,122 Upstream pit 24,124 Downstream pit 26 Next processing tank 30,130 Insulation material 32 Air blowing pipe 34 Bubble G Molten glass h Difference in liquid level

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

Claims (1)

[Claims] 1. A decompression housing, the interior of which is decompressed by vacuum suction, a decompression degassing tank provided in the decompression housing, and decompression degassing of molten glass, and provided in communication with the decompression degassing tank. A rising pipe for sucking and raising the molten glass before vacuum degassing and introducing the molten glass into the vacuum degassing tank, and provided in communication with the vacuum degassing tank; A downcomer pipe that descends from the tank and leads out, and air blowing means that blows air from below the riser pipe, wherein the air is blown into the riser pipe from the air blower means, and the molten glass and the air are blown together with the air. A vacuum degassing apparatus for molten glass, which is raised in a riser.