JP4821165B2 - Vacuum degassing apparatus for molten glass and method for clarifying molten glass using the vacuum degassing apparatus - Google Patents

Description

  The present invention relates to a vacuum degassing apparatus for molten glass that removes bubbles from continuously supplied molten glass, and a method for refining molten glass using the vacuum degassing apparatus.

Conventionally, in order to improve the quality of molded glass products, a clarification process has been used to remove bubbles generated in the molten glass before the molten glass in which the raw material is melted in the melting furnace is molded by the molding apparatus. .
In this clarification step, sodium sulfate (Na ₂ SO ₄ ) or the like is added as a clarifier in advance to the raw material, and the molten glass obtained by melting the raw material is stored and maintained at a predetermined temperature for a predetermined time, thereby clarifying the clarifier. There is known a method in which bubbles in molten glass are grown and floated and removed. Moreover, the molten glass is introduced into a reduced-pressure atmosphere in which the atmosphere is reduced, and bubbles in the molten glass flow that continuously flows are greatly grown under this reduced-pressure atmosphere so that the bubbles contained in the molten glass are floated and broken. A vacuum degassing method is known which removes and then discharges from a vacuum atmosphere.

  Such a vacuum degassing method is to form a molten glass flow under a reduced pressure atmosphere, grow bubbles contained in the molten glass in a relatively short time, and use the buoyancy of the greatly grown bubbles in the molten glass. The bubbles can be efficiently removed from the surface of the molten glass by floating the bubbles and causing the bubbles to break on the surface of the molten glass. At that time, in order to effectively remove bubbles from the surface of the molten glass flow, the rising speed of the bubbles must be increased so as to float on the surface of the molten glass in a reduced pressure atmosphere. Otherwise, it is discharged in the molten glass flow, and the final product contains bubbles and becomes a large defect.

In order to improve the effect of vacuum degassing, the effect of vacuum degassing can be improved by lowering the pressure of the vacuum atmosphere where vacuum degassing is performed as much as possible to increase the buoyancy rate by increasing the growth of bubbles. It is considered possible.
However, if the pressure in the reduced pressure degassing atmosphere is reduced more than necessary, a large number of new bubbles are generated inside the molten glass, and a number of bubbles floating on the surface of the molten glass float to form a bubble layer without breaking. However, a part of the foam layer may be discharged together with the molten glass, resulting in a molten glass containing bubbles. Further, when the bubble layer grows, the temperature of the liquid surface of the molten glass flow is lowered to make it difficult to break the bubble and further develop the bubble layer. As a result, the interior of the decompressed atmosphere is fully filled with bubbles that do not break. For this reason, the foam layer filled in the room may come into contact with impurities adhering to the ceiling portion of the room, and eventually the impurities may be mixed into the molten glass. Therefore, it is not preferable to reduce the pressure of the reduced pressure atmosphere excessively from the viewpoint of effectively performing the reduced pressure defoaming treatment.

  Effective and reliable removal of bubbles in molten glass requires a process in which bubbles grow large in the molten glass and float to the surface of the molten glass to break the bubbles. Patent Document 1 describes that it is necessary to keep the pressure of the reduced-pressure atmosphere in which the degassing is performed in an appropriate range in order to perform effectively.

  A general configuration of a conventional vacuum degassing apparatus is shown in FIG. The vacuum degassing apparatus 100 shown in FIG. 4 is used for the process of degassing the molten glass G in the melting tank 300 under reduced pressure and continuously supplying it to the next processing tank. The vacuum degassing apparatus 100 has a vacuum housing 101 in which the inside is kept in a vacuum state when in use. In the decompression housing 101, a decompression tank 102 having a cylindrical shape is housed and disposed so that the major axis thereof is oriented in the horizontal direction. In the vicinity of the side edge of the lower surface of the vacuum degassing tank 102, an ascending pipe 103 and a descending pipe 104 oriented in the vertical direction are attached. A part of the ascending pipe 103 and the descending pipe 104 is accommodated in the decompression housing 101.

  The ascending pipe 103 communicates with the vacuum degassing tank 102 and is an introducing means for raising the molten glass G from the melting tank 300 and introducing it into the vacuum degassing tank 102. For this reason, the lower end portion of the ascending pipe 103 is fitted into the opening end of the upstream pit 400 and immersed in the molten glass G in the upstream pit 400. The downcomer 104 communicates with the vacuum degassing tank 102 and is a derivation means for lowering the molten glass G after the vacuum degassing from the vacuum degassing tank 102 and leading it to the next processing tank (not shown). . For this reason, the lower end portion of the downcomer pipe 104 is fitted into the open end of the downstream pit 500 and is immersed in the molten glass G in the downstream pit 500. In the decompression housing 101, a heat insulating material 105 such as a heat insulating brick is provided around the decompression defoaming tank 102, the rising pipe 103 and the descending pipe 104.

  In the vacuum degassing apparatus 100 shown in FIG. 4, the vacuum housing 101 is vacuum-sucked by a vacuum pump (not shown) or the like from the outside, and the inside is held in a vacuum state. Thereby, the inside of the vacuum degassing tank 102 arranged in the vacuum housing 101 is maintained in a predetermined vacuum state, for example, a vacuum state of 1/20 to 1/3 atmospheric pressure (51 to 338 hPa).

JP 2000-302456 A

However, even if the inventor holds the inside of the vacuum degassing tank 102 in a predetermined reduced pressure state, the effect of the vacuum degassing with the molten glass G passing through the vacuum degassing tank 102 is not necessarily limited. I found out that it was not always in an appropriate state.
Since molten glass is a fluid having a very high viscosity, the height of the liquid surface of the molten glass in the vacuum degassing tank is not necessarily uniform. As shown in FIG. 5, there may be a liquid level gradient along the flow direction of the molten glass G due to the drawdown of the molten glass G in the vacuum degassing vessel 102. In the vacuum degassing tank 102 of FIG. 5, the liquid surface height t of the molten glass G is higher on the upstream side and lower on the downstream side with respect to the flow direction of the molten glass. Hereinafter, in the present specification, when the liquid level gradient of the molten glass is referred to, as shown in FIG. 5, the liquid surface height t of the molten glass G is higher on the upstream side and lower on the downstream side. Point to.

  As described above, in the vacuum degassing method, the bubbles contained in the molten glass are grown under reduced pressure, and the bubbles are lifted to break the bubbles on the surface of the molten glass, thereby removing the bubbles. For this reason, the effect of vacuum degassing is affected by the distance that bubbles move to the glass surface, the degree of vacuum inside the molten glass, and the like, in addition to the rising speed of the bubbles. Therefore, the effect is particularly influenced by the liquid surface height t of the molten glass G in the vacuum degassing vessel 102. Therefore, as shown in FIG. 5, when the liquid level gradient of the molten glass G is generated, the effect of the vacuum degassing differs between the upstream side and the downstream side of the vacuum degassing tank 102.

For example, the decompression state of the decompression defoaming tank 102 is set so that the effect of the decompression defoaming is optimal with respect to the liquid surface height t of the molten glass G in the decompression defoaming tank 102 of FIG. 5, since the liquid surface height t ₁ of the molten glass G is higher than t on the upstream side of the vacuum degassing tank 102 in FIG. 5, the effect of vacuum degassing may be insufficient. On the other hand, reduced in pressure downstream of the degassing vessel 102, since the height t ₂ of the liquid surface of the molten glass G is less than t, the effect of vacuum degassing is excessive, new bubbles are generated inside the molten glass G There is a risk. The newly generated bubbles on the downstream side of the vacuum degassing tank 102 cannot be sufficiently removed in the vacuum degassing tank 102. For this reason, the molten glass G containing bubbles is carried to another processing tank through the downcomer pipe 104 and the downstream pit 500.

  The present invention solves the above-described problems of the prior art, and an object thereof is to provide a vacuum degassing apparatus capable of optimizing the vacuum degassing effect in the vacuum degassing tank. The vacuum degassing apparatus can promote the growth of bubbles contained in the molten glass upstream of the vacuum degassing tank, and new bubbles are generated inside the molten glass downstream of the vacuum degassing tank. Can be prevented. Another object of the present invention is to provide a method for clarifying molten glass using the vacuum degassing apparatus.

In order to achieve the above object, the present invention provides a vacuum housing that is sucked in vacuum, a vacuum degassing tank that is provided in the vacuum housing and performs vacuum degassing of molten glass, and communicates with the vacuum degassing tank. An introduction means for introducing molten glass before vacuum degassing into the vacuum degassing tank; and communicating with the vacuum degassing tank; and providing the molten glass after vacuum degassing from the vacuum degassing tank A vacuum degassing apparatus for molten glass, comprising:
The vacuum degassing tank is configured such that the upstream side of the glass flow path is higher than the downstream side, and the vacuum degassing apparatus for molten glass (hereinafter referred to as “the vacuum degassing apparatus of the present invention”). First Embodiment ”).
In 1st Embodiment of the vacuum degassing apparatus of this invention, it is preferable that the said vacuum degassing tank inclines with respect to a horizontal direction so that the upstream of the glass flow path may become higher than a downstream.

The present invention also includes a vacuum housing that is vacuum-sucked, a vacuum degassing tank that is provided in the vacuum housing and performs vacuum degassing of molten glass, and is provided in communication with the vacuum degassing tank. Introducing means for introducing molten glass before foaming into the vacuum degassing tank; Deriving means provided in communication with the vacuum degassing tank; and deriving means for extracting the molten glass after vacuum degassing from the vacuum degassing tank; A vacuum degassing apparatus for molten glass having
It has a mechanism for tilting the glass flow path of the vacuum degassing tank with respect to the horizontal direction by raising the upstream side of the vacuum degassing tank or lowering the downstream side of the vacuum degassing tank. A vacuum degassing apparatus for molten glass (hereinafter referred to as “second embodiment of the vacuum degassing apparatus of the present invention”) is provided.

Moreover, this invention is a method (henceforth "the molten glass clarification method of this invention") which clarifies molten glass using 1st Embodiment or 2nd Embodiment of the vacuum deaeration apparatus of this invention mentioned above. I will provide a.
In the method for refining molten glass of the present invention, it is preferable that the glass flow path of the vacuum degassing tank is inclined 0.1 to 5 degrees with respect to the horizontal direction.
In the method for clarifying molten glass according to the present invention, the height of the liquid surface of the molten glass in the vacuum degassing tank is monitored, and the inclination angle of the glass flow path of the vacuum degassing tank is determined based on the monitoring result. You may adjust.

In the vacuum degassing apparatus of the present invention, since the liquid level gradient of the molten glass does not occur in the vacuum degassing tank, the effect of the vacuum degassing in the vacuum degassing tank is optimized. In particular, the effect of the vacuum degassing becomes excessive on the downstream side of the vacuum degassing tank, and new bubbles are prevented from being generated in the molten glass. As a result, bubbles remaining in the molten glass after the vacuum degassing treatment are reduced, and a high-functional and high-quality glass with few bubbles can be produced.
In the first embodiment of the vacuum degassing apparatus of the present invention, the glass flow path of the vacuum degassing tank has a shape that is inclined so that the upstream side is higher than the downstream side. Without performing a special operation, the effect of vacuum degassing in the vacuum degassing tank can be improved.
In the second embodiment of the vacuum degassing apparatus of the present invention, the inclination angle of the vacuum degassing tank is adjusted to be optimal according to the composition of the molten glass and the temperature or pressure in the vacuum degassing tank. Can do. In addition, using the feedback from the decompression defoaming process, such as the amount of bubbles in the molten glass after decompression defoaming and the liquid surface state of the molten glass in the decompression defoaming tank, the inclination angle of the decompression defoaming tank Can be adjusted to be optimal. Thereby, the vacuum degassing effect in the vacuum degassing tank can be further optimized.

The method for clarifying the molten glass of the present invention is excellent in the effect of clarifying the molten glass because the reduced-pressure defoaming effect in the reduced-pressure defoaming tank is optimized. According to the method for refining the molten glass of the present invention, a high-functional and high-quality glass with few bubbles can be produced.
In the method for clarifying molten glass of the present invention, by monitoring the height of the molten glass in the vacuum degassing tank, and adjusting the inclination angle of the glass flow path of the vacuum degassing tank based on the monitoring result The vacuum defoaming effect in the vacuum degassing tank can be further optimized.

  The present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration example of a first embodiment of a vacuum degassing apparatus according to the present invention. The vacuum degassing apparatus 1 of the present invention has the same configuration as the conventional vacuum degassing apparatus except that the shape of the vacuum degassing tank 12 is different. That is, the vacuum degassing apparatus 1 shown in FIG. 1 has a vacuum housing 11 in which the inside is kept in a vacuum state when in use. In the decompression housing 11, a decompression defoaming tank 12 made of a hollow tube is accommodated and disposed so that its major axis is oriented in the horizontal direction. In the vicinity of the side end of the lower surface of the vacuum degassing tank 12, a rising pipe 13 and a down pipe 14 oriented in the vertical direction are attached. A part of the ascending pipe 13 and the descending pipe 14 is accommodated in the decompression housing 11.

  The ascending pipe 13 communicates with the vacuum degassing tank 12 and is an introduction means that raises the molten glass G before the vacuum degassing from the melting tank 3 and introduces it into the vacuum degassing tank 12. For this reason, the lower end portion of the rising pipe 13 is fitted into the opening end of the upstream pit 4 and is immersed in the molten glass G in the upstream pit 4. The downcomer 14 communicates with the vacuum degassing tank 12 and is a derivation means for lowering the molten glass G after the vacuum degassing from the vacuum degassing tank 12 and leading it to the next processing tank (not shown). . For this reason, the lower end portion of the downcomer pipe 14 is fitted into the opening end of the downstream pit 5 and is immersed in the molten glass G in the downstream pit 5. In the reduced pressure housing 11, a heat insulating material 15 such as a heat insulating brick is provided around the reduced pressure defoaming tank 12, the ascending pipe 13 and the descending pipe 14.

1st Embodiment of the vacuum degassing apparatus of this invention is comprised so that the upstream of the glass flow path of a vacuum degassing tank may become higher than a downstream.
In addition, in this specification, a glass flow path refers to the part which makes the flow path of a molten glass in a pressure reduction degassing tank. In the case of the vacuum degassing apparatus 1 shown in FIG. 1, the lower surface inside part of the vacuum degassing tank 12 made of a hollow tube is the glass flow path 12a. In the vacuum degassing apparatus 1 shown in FIG. 1, the lower surface of the vacuum defoaming tank 12, that is, the glass flow path 12a, is formed by making the shape of the side surface of the vacuum degassing tank 12 expand toward the downstream direction. It inclines with respect to the horizontal direction so that the upstream side is higher than the downstream side.
Hereinafter, in the present specification, when it is referred to as “inclination of the glass flow path of the vacuum degassing tank”, it is inclined with respect to the horizontal direction so that the upstream side of the glass flow path is higher than the downstream side. To express.

In the vacuum degassing tank 12, the inclination angle α of the glass flow path 12a with respect to the horizontal direction is the size of the vacuum degassing tank 12, such as length and diameter, the composition of the molten glass passing through the inside of the vacuum degassing tank 12, and the vacuum degassing tank. 12 can be appropriately selected depending on the use conditions such as temperature and pressure inside. However, the inclination angle α is preferably 0.1 to 5 degrees, and more preferably 0.1 to 0.5 degrees.
If the inclination angle α is in the above range, the liquid level gradient of the molten glass G does not occur in the vacuum degassing tank 12, and the vacuum degassing effect in the vacuum degassing tank 12 is optimal regardless of the part. It becomes. Further, the flow characteristics of the molten glass G in the vacuum degassing apparatus 1 are not adversely affected.

1st Embodiment of the vacuum degassing apparatus of this invention should just be comprised so that the upstream of the glass flow path of a vacuum degassing tank may become higher than a downstream, The vacuum degassing apparatus 1 shown in FIG. Thus, it is not limited to what the lower surface (molten glass flow path 12a) of the vacuum degassing tank 12 inclines with respect to a horizontal direction. For example, the bottom surface of the vacuum degassing tank may have a stepped structure such that the upstream side is higher than the downstream side. Further, in the vacuum degassing apparatus 1 shown in FIG. 1, the molten glass channel 12a is inclined with respect to the horizontal direction over its entire length, but only a part of the molten glass channel 12a is inclined with respect to the horizontal direction. May be. Furthermore, the whole vacuum degassing tank may be inclined with respect to the horizontal direction so that the upstream side is higher than the downstream side.
Moreover, the cross-sectional shape of the vacuum degassing tank 12 may be a polygon such as a rectangle, a hexagon, or an octagon in addition to a circle or an ellipse.
Moreover, the vacuum degassing tank should just function as a flow path of a molten glass, and the shape is not limited to what consists of hollow tubes. For example, the hollow tube may have a concave portion with a semicircular cross-sectional shape from which the upper portion of the hollow tube is removed.

The material constituting the vacuum degassing tank 12 needs to be a material having excellent heat resistance. Specific examples of the constituent material of the vacuum degassing tank 12 include platinum-based materials. The platinum-based material referred to here includes platinum, platinum alloys such as platinum-gold alloys and platinum-rhodium alloys, and reinforced platinum obtained by dispersing metal oxides in platinum or platinum alloys. In reinforced platinum, examples of the metal oxide to be dispersed include Al ₂ O ₃ , 3A group or 4A group metal oxides represented by ZrO ₂ or Y ₂ O ₃ . Other specific examples of the constituent material of the vacuum degassing tank include ceramic-based non-metallic inorganic materials, that is, bricks made of dense refractory, and more specifically, alumina-based electrocast refractories, zirconia Electrocast refractories, electrocast refractories such as alumina-zirconia-silica electrocast refractories, and dense alumina refractories, dense zirconia-silica refractories and dense alumina-zirconia-silica refractories And dense fired refractories. Further, the vacuum degassing tank 12 may be a ceramic non-metallic inorganic material lined with a platinum-based material.

The dimensions of the vacuum degassing tank of the present invention depend on the vacuum degassing apparatus to be used regardless of whether the constituent material of the vacuum degassing tank is a platinum-based material or a ceramic non-metallic inorganic material. It can be selected appropriately. In the case of the vacuum degassing tank 12 shown in FIG. 1, the specific example of the dimension is as follows.
Horizontal length: 1-20m
Inner diameter: 0.2-3m
Difference in height of glass flow path 12a: 10 to 100 mm
When the vacuum degassing tank is composed of a platinum-based material, the wall thickness is preferably 4 mm or less, more preferably 0.5 to 1.2 mm.

In 1st Embodiment of the vacuum degassing apparatus of this invention, components other than a vacuum degassing tank are the same as that of the conventional vacuum degassing apparatus.
The decompression housing 11 is made of metal, for example, stainless steel, and has a shape and dimensions that can accommodate the decompression deaeration tank 12. The ascending tube 13 and the descending tube 14 are hollow tubes forming a flow path of molten glass. Therefore, a material having excellent heat resistance is used as the constituent material of the ascending pipe 13 and the descending pipe 14. Specifically, as the constituent materials of the ascending pipe 13 and the downcomer pipe 14, those exemplified as the constituent materials of the vacuum degassing tank 12 can be used. In addition, when the constituent material of the riser 13 and the downcomer 14 is a platinum-type material, it is a hollow tube with a circular cross section generally. On the other hand, when the constituent material of the ascending pipe 13 and the descending pipe 14 is a ceramic non-metallic inorganic material, it is generally a hollow tube having a rectangular cross-sectional shape. The dimensions of the ascending pipe 13 and the descending pipe 14 can be appropriately selected according to the vacuum degassing apparatus to be used. For example, the dimensions of the ascending pipe 13 and the descending pipe 14 can be configured as follows.
Inner diameter: 0.05 to 0.8 m, more preferably 0.1 to 0.6 m
(If the cross-sectional shape is a rectangular hollow tube, the length of one side)
Length: 0.2-6m, more preferably 0.4-4m
When the riser 13 and the downfall 14 are made of a platinum-based material, the wall thickness is preferably 0.4 to 5 mm, more preferably 0.8 to 4 mm.
As a constituent material of the heat insulating material 15, various known bricks can be used.

Next, a second embodiment of the vacuum degassing apparatus of the present invention will be described. In the second embodiment of the vacuum degassing apparatus of the present invention, the upstream side of the vacuum degassing tank is raised or the downstream side of the vacuum degassing tank is lowered, so that the glass flow path of the vacuum degassing tank is horizontally oriented. It has the mechanism (henceforth this specification "it is called a" glass channel inclination mechanism ").
FIG. 2 is a diagram showing a configuration example of the second embodiment of the vacuum degassing apparatus of the present invention. A vacuum degassing apparatus 1 ′ shown in FIG. 2 has the same configuration as that of a conventional vacuum degassing apparatus except that the glass channel tilting mechanism 20 is provided. In the vacuum degassing apparatus 1 ′ shown in FIG. 2, the glass flow path tilting mechanism 20 is fixed to the lower surface side of the vacuum housing 11, and the screw jacks 21 and 22 that support the vacuum housing 11, and the screw jacks 21 and 22. And a pedestal 23 to which is fixed. In FIG. 2, two screw jacks 21 and 22 are shown, but two screw jacks are also installed at positions corresponding to the back side of the screw jacks 21 and 22 in the figure, and a total of four screw jacks are provided. The decompression housing 11 is supported.

  FIG. 3 is a view showing a state where the glass flow path tilting mechanism 20 is operated in the vacuum degassing apparatus 1 ′. In FIG. 3, the decompression housing 11 is inclined with respect to the horizontal direction by contracting the screw jack 22 fixed to the downstream side of the decompression housing 11 and lowering the downstream side of the decompression housing 11. Thereby, the decompression defoaming tank 12 accommodated in the decompression housing 11 is inclined with respect to the horizontal direction, and the molten glass flow path 12a of the decompression defoaming tank 12 is horizontal so that the upstream side is higher than the downstream side. Inclined with respect to direction.

In the vacuum degassing apparatus 1 ′ shown in FIGS. 2 and 3, the glass channel 12 a of the vacuum degassing tank 12 can be tilted to a desired angle by operating the glass channel tilting mechanism 20. The operation of the glass flow path tilting mechanism 20, that is, the operation of the screw jacks 21 and 22 may be performed manually or mechanically using a motor or the like.
In FIG. 3, when the screw jack 22 is contracted and the downstream side of the decompression housing 11 is lowered, the decompression housing 11 is inclined with respect to the horizontal direction so that the upstream portion is higher than the downstream portion. However, even if the screw jack 21 fixed on the upstream side of the decompression housing 11 is extended to raise the upstream side of the decompression housing 11, the decompression housing is set so that the upstream part is higher than the downstream part. 11 can be inclined with respect to the horizontal direction.

  As shown in FIG. 3, when the decompression housing 11 is inclined, the lower ends of the ascending pipe 13 and the descending pipe 14 approach the wall surfaces of the upstream pit 4 and the downstream pit 5, respectively. Depending on the inclination angle of the decompression housing 11, the ascending pipe 13 and the descending pipe 14 may come into contact with the wall surfaces of the upstream pit 4 and the downstream pit 5, respectively. When the ascending pipe 13 and the descending pipe 14 are made of a platinum-based material, the pipe may be damaged due to contact with the wall surfaces of the upstream pit 4 and the downstream pit 5.

  In the vacuum degassing apparatus 1 ′ shown in FIGS. 2 and 3, when the vacuum housing 11 is inclined, the lower ends of the ascending pipe 13 and the descending pipe 14 come into contact with the wall surfaces of the upstream pit 4 and the downstream pit 5. It has a mechanism to prevent. In the vacuum degassing apparatus 1 ′ shown in FIGS. 2 and 3, the screw jack 21 has a pin receiver 211 for the vacuum housing 11. On the other hand, the screw jack 22 has a roller receiver 221 for the decompression housing 11. By having such a configuration, when the decompression housing 11 is tilted as shown in FIG. 3, the downstream side of the decompression housing 11 that is the roller receiver 221 moves horizontally in the right direction in the drawing. This prevents the lower end portions of the ascending pipe 13 and the descending pipe 14 from coming into contact with the wall surfaces of the upstream pit 4 and the downstream pit 5, respectively.

In the second embodiment of the vacuum degassing apparatus of the present invention, the glass flow path tilting mechanism tilts the vacuum housing by raising the upstream side of the vacuum degassing tank or lowering the downstream side of the vacuum degassing tank. Any mechanism may be used, and the decompression housing 11 that accommodates the decompression defoaming tank 12 is tilted with respect to the horizontal direction like the glass flow path tilting mechanism 20 of the decompression defoaming apparatus 1 ′ shown in FIGS. It is not limited to things. Therefore, for example, the vacuum housing may be tilted with respect to the horizontal direction without tilting the vacuum housing.
Further, the mechanism itself for tilting the decompression housing 11 is not limited to the screw jacks 21 and 22 and the pedestal 23. Other examples include a method using other jack means such as a hydraulic jack, a hydraulic jack or a pneumatic jack, a method using an eccentric cam, and the like. Further, the position for fixing the screw jack is not limited to the lower surface side of the decompression housing as shown in FIGS. For example, a suspended structure in which a screw jack is fixed to the upper surface side of the decompression housing may be used.

  Hereinafter, the clarification method of the molten glass of this invention is demonstrated. The clarification method of the molten glass of the present invention is carried out using the first embodiment or the second embodiment of the vacuum degassing apparatus of the present invention described above. When the first embodiment of the vacuum degassing apparatus of the present invention is used, the glass flow path of the vacuum degassing tank is inclined with respect to the horizontal direction so that the upstream portion is higher than the downstream portion. Therefore, in the vacuum degassing tank, the liquid level gradient due to the drawdown of the molten glass, that is, the liquid surface height t of the molten glass G as shown in FIG. There will be no lowering condition. For this reason, the vacuum degassing effect in the vacuum degassing tank is optimized regardless of the part.

When the second embodiment of the vacuum degassing apparatus of the present invention is used, the glass flow path of the vacuum degassing tank can be inclined at a desired angle, so the composition and flow rate of the molten glass, the vacuum degassing tank inside By adjusting the inclination angle of the glass flow path according to the temperature and the degree of pressure reduction, the pressure reduction defoaming effect in the pressure reduction defoaming tank can always be optimized.
In addition, the amount of bubbles in the molten glass after the vacuum degassing can be confirmed at the outlet portion of the downcomer, and the inclination angle of the glass flow path of the vacuum degassing tank can be adjusted based on the result. For example, when the amount of bubbles in the molten glass increases, a liquid level gradient of the molten glass occurs in the vacuum degassing tank, and new bubbles are generated in the molten glass downstream of the vacuum degassing tank. It may be the cause. At this time, when the glass flow path of the vacuum degassing tank is not inclined, the generation of bubbles in the molten glass can be eliminated by inclining the glass flow path with respect to the horizontal direction. On the other hand, when the glass channel is inclined with respect to the horizontal direction, generation of bubbles in the molten glass can be eliminated by increasing the inclination angle of the glass channel.

  When the second embodiment of the vacuum degassing apparatus of the present invention is used, the liquid level of the molten glass in the vacuum degassing tank is monitored, and the glass in the vacuum degassing tank is based on the monitoring result. The inclination angle of the flow path can also be adjusted. A monitor window for confirming the internal state is provided on the ceiling of the vacuum degassing tank. The height of the liquid surface of the molten glass can be monitored from this monitor window. For example, the height of the liquid level can be monitored by providing a scale indicating the height of the liquid level of the molten glass in the vacuum degassing tank. Monitoring may be performed visually or may be performed using a camera or the like. Moreover, the height of the liquid level can also be monitored by irradiating the liquid level of the molten glass with a laser beam from the monitor window. By comparing the height of the liquid surface of the molten glass obtained from the monitoring with a preset reference height, the presence or absence of the liquid surface gradient of the molten glass and the degree of the liquid surface gradient can be specified. When it is specified that a liquid surface gradient of the molten glass is generated, the liquid surface gradient of the molten glass can be eliminated by inclining the glass flow path of the vacuum degassing tank with respect to the horizontal direction. At this time, the inclination angle of the glass channel can be appropriately selected according to the degree of the liquid level gradient.

  In the vacuum degassing method for molten glass of the present invention, the molten glass supplied from the melting tank is passed through a vacuum degassing tank whose pressure is reduced to a predetermined degree of vacuum, and vacuum degassing is performed. The molten glass is preferably continuously supplied to and discharged from the vacuum degassing tank. In order to prevent a temperature difference from the molten glass supplied from the melting tank, the vacuum degassing tank is heated so that the inside is in a temperature range of 1100 ° C to 1500 ° C, particularly 1250 ° C to 1450 ° C. It is preferable. In addition, it is preferable from the point of productivity that the flow rate of a molten glass is 1-200 tons / day.

  When carrying out the vacuum degassing method, the vacuum housing is vacuum-sucked from the outside by a vacuum pump or the like, thereby maintaining the inside of the vacuum degassing tank disposed in the vacuum housing in a predetermined vacuum state. Here, the inside of the vacuum degassing tank is preferably decompressed to 38 to 460 mmHg (51 to 613 hPa), and more preferably the inside of the vacuum degassing tank is decompressed to 160 to 253 mmHg (213 to 338 hPa). Is preferred.

  In the method for clarifying molten glass of the present invention, the glass flow path of the vacuum degassing tank is preferably inclined 0.1 to 5 degrees with respect to the horizontal direction, and is inclined 0.1 to 0.5 degrees. It is more preferable. If the inclination angle of the glass flow path of the vacuum degassing tank is in the above range, the liquid level gradient of the molten glass does not occur in the vacuum degassing tank, and the vacuum degassing effect in the vacuum degassing tank is Optimized regardless of location. Moreover, the flow characteristics of the molten glass in the vacuum degassing apparatus are not adversely affected.

  The glass clarified by the present invention is not limited in terms of composition as long as it is a glass produced by a heat melting method. Therefore, alkali glass such as lime silica glass or borosilicate glass may be used. However, since it is difficult to remove bubbles during the refining process and is used for applications such as a display glass substrate that require particularly few defects, alkali-free glass is preferred.

Hereinafter, based on an Example, this invention is demonstrated more concretely. However, the present invention is not limited to this.
(Example)
In the examples, the vacuum degassing of the molten glass was performed using the vacuum degassing apparatus 1 ′ shown in FIG. The dimensions and constituent materials of the vacuum degassing apparatus 1 'were as follows.
Vacuum housing 11: Stainless steel vacuum degassing tank 12: Platinum-rhodium alloy (platinum 90% by mass, rhodium 10% by mass) Length: 6m
Inner diameter: 0.6 x 0.4m (installed so that the major axis is parallel to the horizontal direction)
Wall thickness: 1mm
Ascending pipe 13 and descending pipe 14: Made of platinum-rhodium alloy (platinum 90 mass%, rhodium 10 mass%) Length: 3 m
Inner diameter: 0.3m
Wall thickness: 1mm
The screw jacks 21 and 22 were operated to incline the decompression housing 11 as shown in FIG. The inclination angle was 0.4 degrees (the difference in height between the upstream side and the downstream side of the decompression housing 11 was 40 mm).
With the vacuum housing tilted, vacuum degassing of the molten glass was performed under the following conditions.
Temperature inside vacuum degassing tank 12: 1400 ° C
Pressure inside the degassing tank 12: 180 mmHg (240 hPa)
Molten glass: alkali-free glass,
Flow rate: 50 tons / day The amount of bubbles in the molten glass was measured at the outlet of the downcomer 14 (bubble density was measured by the edge light method). As a result, the amount of bubbles generated in the molten glass was less than usual.

(Comparative example)
Using the vacuum degassing apparatus used in the examples, the vacuum degassing of the molten glass was performed under the same conditions as in the examples. However, the decompression housing 11 was not inclined. When the amount of bubbles in the molten glass was measured at the outlet portion of the downcomer 14, an increase in the amount of bubbles was observed more than usual. Except for the presence or absence of the inclination of the decompression housing 11, since it is carried out under exactly the same conditions as in the embodiment, in the comparative example, a liquid surface gradient of the molten glass is generated in the decompression defoaming tank 12, and the liquid surface of the molten glass It is presumed that the effect of the vacuum degassing becomes excessive on the downstream side of the vacuum degassing tank 12 whose height is lowered, and new bubbles are generated inside the molten glass.

FIG. 1 is a diagram showing a configuration example of a first embodiment of a vacuum degassing apparatus according to the present invention. FIG. 2 is a diagram showing a configuration example of the second embodiment of the vacuum degassing apparatus of the present invention. FIG. 3 is a view showing a state where the glass flow path tilting mechanism 20 is operated in the vacuum degassing apparatus of FIG. FIG. 4 is a diagram showing a general configuration of a conventional vacuum degassing apparatus. FIG. 5 shows a state in which a liquid surface gradient of the molten glass has occurred in the vacuum degassing tank of the vacuum degassing apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Depressurization degassing apparatus 11: Decompression housing 12: Depressurization defoaming tank 12a: Glass flow path 13: Rising pipe 14: Downfalling pipe 15: Insulation material 20: Glass flow path inclination mechanism 21, 22: Screw jack 211: Pin receiving 221: Roller receiver 3: Melting tank 4: Upstream pit 5: Downstream pit 100: Vacuum degassing device 101: Depressurized housing 102: Depressurized defoaming tank 102a: Glass flow path 103: Rising pipe 104: Downfall pipe 105: Insulating material 300 : Dissolution tank 400: Upstream pit 500: Downstream pit

Claims (6)

A vacuum housing that is vacuum-sucked, a vacuum degassing tank that is provided in the vacuum housing and performs vacuum degassing of the molten glass, and is provided in communication with the vacuum degassing tank, Decompression of the molten glass having introduction means for introducing into the reduced pressure defoaming tank, and derivation means provided in communication with the reduced pressure defoaming tank and for deriving the molten glass after the reduced pressure defoaming tank from the reduced pressure defoaming tank A defoaming device,
The vacuum degassing tank is configured so that the upstream side of the glass flow path is higher than the downstream side, and the vacuum degassing apparatus for molten glass is characterized.   The vacuum degassing apparatus for molten glass according to claim 1, wherein the vacuum degassing tank is inclined with respect to the horizontal direction so that the upstream side of the glass flow path is higher than the downstream side. A vacuum housing that is vacuum-sucked, a vacuum degassing tank that is provided in the vacuum housing and performs vacuum degassing of the molten glass, and is provided in communication with the vacuum degassing tank, Decompression of the molten glass having introduction means for introducing into the reduced pressure defoaming tank, and derivation means provided in communication with the reduced pressure defoaming tank and for deriving the molten glass after the reduced pressure defoaming tank from the reduced pressure defoaming tank A defoaming device,
It has a mechanism for tilting the glass flow path of the vacuum degassing tank with respect to the horizontal direction by raising the upstream side of the vacuum degassing tank or lowering the downstream side of the vacuum degassing tank. A vacuum degassing apparatus for molten glass.   A method for clarifying molten glass using the vacuum degassing apparatus according to any one of claims 1 to 3.   The method for refining molten glass according to claim 4, wherein the glass flow path of the vacuum degassing tank is inclined 0.1 to 5 degrees with respect to the horizontal direction.   The height of the liquid surface of the molten glass in the vacuum degassing tank is monitored, and the inclination angle of the glass flow path of the vacuum degassing tank is adjusted based on the result of the monitoring. Or the method of clarifying the molten glass of 5.

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