JP3785792B2 - Vacuum degassing equipment for molten glass - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vacuum degassing apparatus for molten glass for removing bubbles from continuously supplied molten glass.
[0002]
[Prior art]
Conventionally, in order to improve the quality of the molded glass product, as shown in FIG. 2, the vacuum degassing is used to remove bubbles generated in the molten glass before the molten glass melted in the melting furnace is molded by the molding apparatus. A foam device is used.
The vacuum degassing apparatus 110 shown in FIG. 2 is used in a process of vacuum degassing the molten glass G in the melting tank 120 and continuously supplying the molten glass G to the next processing tank. In this case, a vacuum degassing tank 114 that is provided in a vacuum housing 112 that is vacuumed by suction to decompress the inside, and a vacuum degassing tank 114 that is decompressed together with the vacuum housing 112, and a lift vertically attached to both ends thereof. The lower end of the rising pipe 116 is immersed in the molten glass G of the upstream pit 122 communicating with the melting tank 120, and the lower end of the lowering pipe 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 decompression defoaming tank 114 is horizontally provided in the decompression housing 112 that is vacuum-sucked by a vacuum pump (not shown) to decompress the inside, and the inside of the decompression defoaming tank 114 is 1/3 to 1 together with the decompression housing 112. Since the pressure is reduced to / 20 atm, the molten glass G before the defoaming process in the upstream pit 122 is sucked up by the riser 116 and introduced into the depressurized defoaming tank 114. After the decompression defoaming process is performed, it is lowered by the downcomer 118 and led to the downstream pit 124. In the present invention, the molten glass G is gradually depressurized while ascending the riser 116, and the bubbles present in the molten glass G are expanded along with this, and the vacuum defoaming tank 114 expands the upper surface from the surface of the molten glass. The defoaming is performed toward the reduced pressure atmosphere, and the molten glass that has been cleaned gradually returns to normal pressure while descending the downcomer 118, but the reduced pressure defoaming treatment is mainly performed in the reduced pressure defoaming tank 114. Done.
The decompression housing 112 is a casing made of metal, for example, stainless steel or heat-resistant steel. The decompression housing 112 is decompressed by vacuum suction from the outside by a vacuum pump (not shown) or the like, and the decompression defoaming tank 114 provided inside. The inside is reduced to a predetermined pressure, for example, 1/3 to 1/20 atm.
A heat insulating material 130 such as a refractory brick is provided around the vacuum degassing tank 114, the rising pipe 116, and the lowering pipe 118 in the vacuum housing 112 to cover them.
[0004]
In the conventional vacuum degassing apparatus 110, the flow rate (or the flow rate of the molten glass G that is suctioned and raised from the melting tank into the vacuum degassing apparatus 110 and subjected to the vacuum degassing process, and flows down to the next processing tank, for example, the molding tank (or The flow rate) is equal to the pressure difference Δp between the difference in liquid level between the upstream pit 122 and the downstream pit 124, and hence the level difference h of the molten glass base at the base of the ascending pipe 116 and the descending pipe 118. The following condition, that is, the following formula is satisfied.
Δp = ρgh
Here, ρ is the density of the molten glass G.
At this time, to be precise, the decompression defoaming tank 114 of the decompression defoaming apparatus 110 may be calculated as a separate opening, but the ascending pipe 116, the decompression defoaming tank 114 and the descending pipe 118 are assumed to be circular pipes, When the diameter of the circular tube is D and the length is L, the flow rate u of the molten glass G to be degassed under reduced pressure can be expressed by the following equation.
Δp = 32 μLu / gD ² (Hagen-Poiseuille equation)
Here, μ is the viscosity of the molten glass G.
[0005]
Thus, in the conventional vacuum degassing apparatus 110, the flow rate of the molten glass G to be subjected to the vacuum degassing treatment is almost as long as the configuration of the vacuum degassing apparatus 110, the components of the molten glass G and the manufacturing process are not changed. It is determined by the temperature h of the molten glass G (viscosity μ) and the difference in the liquid level height h between the upstream pit 122 and the downstream pit 124. Therefore, when the flow rate of the molten glass G in the vacuum degassing apparatus 110 is changed, the temperature (viscosity μ) of the molten glass G is changed or the liquid level between the upstream pit 122 and the downstream pit 124 is increased. The difference h must be changed.
[0006]
However, in the conventional vacuum degassing apparatus 110, changing the temperature of the molten glass G means that the temperature is raised and the viscosity is lowered to increase the flow rate of the molten glass G. It is difficult from the viewpoint of the high temperature strength of the constituent material of the device 110, conventionally a noble metal such as platinum, or an alloy thereof.
For this reason, 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 difference in liquid level height h between the upstream pit 122 and the downstream pit 124. Changing the height difference h of the liquid level also changes the configuration of the vacuum degassing apparatus 110 once completed as equipment, and is not easy. That is, the level h of the liquid level cannot be changed, or it is desired to change from other conditions, such as when the level of the entrance / exit is determined by external conditions due to the configuration of the conventional vacuum degassing apparatus 110. There are many cases that do not exist.
[0007]
[Problems to be solved by the invention]
Thus, in the conventional vacuum degassing apparatus 110, it is not easy to change the flow rate of the molten glass G. Even if the flow rate of the molten glass G is increased by increasing the flow rate of the molten glass G in the vacuum degassing apparatus 110, even if it becomes clear that there is sufficient vacuum degassing processing capability, the processing capability is still low. There was a problem that it had to be done.
Therefore, in the conventional vacuum degassing apparatus 110, there is sufficient vacuum degassing processing capacity, and it is possible to increase the flow rate of the molten glass G to be degassed by increasing the flow rate of the molten glass G. However, it is not easy to change the flow rate of the molten glass G by changing the temperature h of the molten glass G or the difference in liquid level height, and the ability of the vacuum degassing apparatus 110 cannot be fully exhibited. there were.
[0008]
The object of the present invention is to eliminate the above-mentioned problems of the prior art, and easily increase the flow rate of the molten glass G according to the vacuum degassing capability without changing the apparatus configuration itself, and the molten glass that is degassed under reduced pressure. An object of the present invention is to provide a vacuum degassing apparatus for molten glass that can increase the flow rate of G, maximize the vacuum degassing ability, and improve the degree of freedom in apparatus design. .
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention includes a decompression housing that is vacuumed to reduce the inside thereof, a decompression deaeration tank that is provided in the decompression housing and decompresses the molten glass, and this decompression desorption. Provided in communication with the foam tank, the riser pipe that sucks and raises the molten glass before vacuum degassing and introduces it into the vacuum degassing tank, and is provided in communication with the vacuum degassing tank, A downcomer pipe that descends the molten glass from the vacuum degassing tank and leads out, and an air blowing means for blowing air from below the riser pipe,
The present invention provides a vacuum degassing apparatus for molten glass, wherein the air is blown into the riser from the air blowing means, and the molten glass is raised together with the air in the riser.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
A vacuum degassing apparatus for molten glass according to the present invention will be described below in detail based on preferred embodiments shown in the accompanying drawings.
[0011]
FIG. 1 shows a schematic cross-sectional view of a vacuum degassing apparatus for molten glass according to the present invention.
As shown in FIG. 1, the vacuum degassing apparatus 10 for molten glass according to the present invention sucks and raises the molten glass G from the melting tank 20 into the vacuum degassing tank 14, and the vacuum degassing tank 14 is depressurized and depressurized. It is used in a process for performing foam treatment and continuously supplying to the next processing tank, for example, a plate-shaped molding processing tank such as a float bath or a molding work tank such as a bottle. Basically, the decompression housing 12, It consists of a vacuum degassing tank 14, an ascending pipe 16 and a descending pipe 18.
[0012]
The decompression housing 12 functions as a pressure vessel for ensuring airtightness when the decompression deaeration tank 14 is decompressed. In this embodiment, the decompression housing 12 is formed in a substantially portal shape, And it is comprised so that the upper part of the raise pipe 16 and the down pipe 18 may be wrapped. The material and structure of the decompression housing 12 are not particularly limited as long as the decompression housing 12 has airtightness and strength required for the decompression defoaming tank 14, but is made of metal, particularly stainless steel or heat resistant steel. It is preferable to make it.
The decompression housing 12 is provided with a suction port 12c for vacuum suction at the upper right part to decompress the inside, and the inside of the decompression housing 12 is decompressed by a vacuum pump (not shown), and is arranged at the substantially central part thereof. The inside of the reduced pressure degassing tank 14 is configured to be maintained at a predetermined pressure, for example, 1/3 to 1/20 atm.
[0013]
A decompression defoaming tank 14 is disposed horizontally at a substantially central portion of the decompression housing 12. The cross section of the flow path of the vacuum degassing tank 14 may be circular as in the prior art, but the present invention is not limited to this, and may be, for example, a polygonal shape such as an ellipse or a rectangle or an irregular shape. In order to perform the degassing treatment of the molten glass G at a flow rate, a rectangular shape is preferable.
The upper end portion of the rising pipe 16 is connected to the left end portion of the vacuum degassing tank 14 and the upper end portion of the descending pipe 18 is vertically communicated with the right end portion of the vacuum degassing tank 14 downward. The ascending pipe 16 and the descending pipe 18 are disposed so as to penetrate the leg portions 12a and 12b of the decompression housing 12 formed in a gate shape, respectively, and the lower ends of the ascending pipe 16 and the descending pipe 18 are dissolved. It is immersed in the molten glass G of the upstream pit 22 communicating with the tank 20 and the downstream pit 24 communicating with the next processing tank (not shown).
Here, the vacuum degassing tank 14, the rising pipe 16 and the downfalling pipe 18 are preferably made of electrocast refractory bricks in order to perform a vacuum degassing treatment of a large flow rate of molten glass G. May be composed of a noble metal such as platinum, a noble metal alloy, or the like, or all of the flow paths contacting the molten glass may be composed of a noble metal such as platinum or a noble metal alloy.
[0014]
In the upper part of the vacuum degassing tank 14, the vacuum housing 12 is decompressed to a predetermined pressure (1/3 to 1/20 atm) by vacuum suction with a vacuum pump (not shown) or the like. In order to maintain, suction holes 14 a and 14 b communicating with the decompression housing 12 are provided.
The space between the decompression housing 12 and the decompression deaeration tank 14, the rising pipe 16 and the descending pipe 18 is filled with a heat insulating material 30 such as a refractory brick and covered with heat. This heat insulating material 30 is comprised with the heat insulating material which has air permeability so that the vacuum suction of the pressure reduction degassing tank 14 may not be obstructed.
[0015]
Below the ascending pipe 16, 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 in the upstream pit 22 is disposed. The air supplied from the air blowing pipe 32 becomes bubbles in the molten glass G and rises in the riser 16 together with the molten glass G, and breaks the bubbles at the liquid surface 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 containing a large number of air bubbles in the ascending pipe 16 is smaller than the specific gravity of the molten glass G in the descending pipe 18 and descends from the ascending pipe 16 due to the pump-up effect of the air bubbles. A head toward the tube 18 is provided, 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.
The means for supplying air, for example, preheated air, to the air blowing pipe 32 is not particularly limited, and conventionally known air supply means can be applied as it is.
Here, the air blowing pipe 32 is preferably composed 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, but the shape and size are such that the vacuum degassing apparatus 10 of the present invention can generate bubbles having a size larger than the size of the bubbles originally targeted for defoaming treatment. Is preferred.
[0016]
Here, in the present invention, the foam generated in the molten glass G by the air blown from the air blowing pipe 32 is originally a micro-sized foam, for example, 1 mm, which is the limit of defoaming treatment in the present invention. Hereinafter, concretely, it is a foam having a size much larger than that of a glass having a diameter of about 0.3 mm or 0.2 mm, for example, a foam having a diameter of several mm to 1 cm, preferably a diameter of about 5 to 8 mm. Is good. This is to increase the foam rising force in the molten glass G so as not to reduce the accuracy and efficiency of the defoaming process of the micro-sized foam that is the original defoaming process target. This is to speed up the rising of the molten glass G to the liquid level and reliably and quickly break the bubbles on the liquid level. In addition, since the foam produced | generated by the air blowing pipe 32 also has an effect which unites with the fine foam of original defoaming object, it has the effect of improving the defoaming efficiency of the vacuum degassing apparatus 10 of this invention. Play.
Moreover, 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 certain size at predetermined intervals. The amount of air blown into the molten glass G of the riser tube 16 or the amount of air bubbles present in the molten glass G of the riser tube 16 is not particularly limited. What is necessary is just to select suitably according to the ascending force to give, therefore the flow volume of the molten glass G, ie, the defoaming amount.
[0017]
Next, the effect | action of the vacuum degassing apparatus 10 of the molten glass of this invention is demonstrated.
The vacuum degassing tank 14 is vacuumed by a vacuum pump (not shown) and maintained at a predetermined pressure, for example, reduced to 1/3 to 1/20 atm. Due to the difference between the pressure (atmospheric pressure) of the liquid surface of the molten glass G in the downstream pit 24 and the pressure reduced in the decompression housing 12, the suction is raised to the decompression deaeration tank 14 through the ascending pipe 16 or the descending pipe 18. The siphon is constituted by a series of closed pipes. Then, the molten glass G flows out to the downstream pit 24 in accordance with the difference in liquid level height h of the molten glass G between the upstream pit 22 and the downstream pit 24.
[0018]
At this time, the difference between the height of the molten glass G in the upstream pit 22 or the downstream pit 24 and the height of the molten glass G sucked and raised in the vacuum degassing tank 14 is the reduced pressure degassing tank 14. Although it varies depending on the reduced pressure of the inside, it is approximately 2.5 m to 3.5 m, and the flow rate of the molten glass G in the vacuum degassing tank 14 depends on the viscosity (temperature) of the molten glass G and the upstream pit 22. And the difference in the height h of the liquid level of the molten glass G in the downstream pit 24.
The molten glass G sucked and raised in the vacuum degassing tank 14 is decompressed to 1/3 to 1/20 atm in the vacuum degassing tank 14, so that bubbles contained in the molten glass G are on the liquid surface. Ascend and break. The vacuum degassing apparatus 10 is for removing bubbles contained in the molten glass G in this way.
[0019]
An air blowing pipe 32 for blowing air preheated to substantially the same temperature as the molten glass G is disposed below the rising pipe 16 of the vacuum degassing apparatus 10, and air is supplied from the air blowing pipe 32 to the lower side of the rising pipe 16. When blown, this air becomes bubbles 34 and floats in the molten glass G, and rises in the riser 16 together with the molten glass G.
The apparent specific gravity of the molten glass G including the bubbles 34 is naturally lighter than the specific gravity of the molten glass G, and thus the specific gravity of the molten glass G in the downcomer 18, and includes the bubbles 34 in the ascending pipe 16. However, the molten glass G is sucked up together with the bubbles 34 to a higher position in the vacuum degassing tank 14 at a higher flow rate than in the case where no air is blown in due to the difference in specific gravity.
[0020]
Of course, the bubbles 34 that have reached the liquid level in the vacuum degassing tank 14 break up when reaching the liquid level, leaving only the molten glass G containing the fine bubbles that are the original defoaming target. As described above, the position of the surface of the molten glass including the bubbles 34 and the apparent specific gravity is higher than that of the molten glass not including the bubbles 34. Therefore, as shown in FIG. The gradient of the liquid surface of the molten glass G in the bubble tank 14 is increased, and the flow rate of the molten glass G for performing the vacuum degassing process is that it flows in the vacuum degassing tank 14 toward the downcomer 18 at a faster flow rate. Can be increased.
[0021]
The diameter of the bubbles 34 varies depending on the temperature or pressure, and the suitable diameter of the bubbles varies depending on the composition and viscosity of the molten glass. Therefore, although it cannot be generally stated, it is about several mm to 1 cm at the mouth of the air blowing pipe 32. It is preferable to use bubbles of a diameter, and by increasing or decreasing the amount of the bubbles 34, the flow rate of the molten glass G in the ascending pipe 16, that is, the flow rate of the molten glass G flowing in the vacuum degassing tank 14 is changed. Can do. In the vacuum degassing apparatus 10, even if the difference in the height h of the liquid level of the molten glass G between the upstream pit 22 and the downstream pit 24 cannot be changed, or due to the external conditions of the apparatus configuration, this liquid level difference Even if h cannot be increased or cannot be taken, or even if this liquid level difference h is set low, air is blown into the molten glass G in the ascending pipe 16 from the air blowing pipe 32 as in the present invention. Thus, the flow rate of the molten glass G flowing in the vacuum degassing tank 14 can be increased, and a necessary defoaming amount can be ensured.
[0022]
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 produced.
In particular, when the molten glass G is soda glass, since O _{2 in} the air easily dissolves in the molten glass G, the bubbles 34 become air bubbles (mainly N ₂ ) excluding O ₂ . Thus, it rises with the molten glass G.
Then, dissolved gases such as SO ₂ , CO ₂ , H ₂ O and the like dissolved in the molten glass G diffuse and flow toward the bubbles 34, and the concentration of the dissolved gas decreases.
[0023]
Further, when O ₂ dissolved in the molten glass G has bubbles with low O ₂ concentration in the surrounding molten glass G (especially, SO ₂ bubbles caused by a sulfate fining agent added in the melting furnace), The molten glass G flows into bubbles having a low O ₂ concentration to expand the diameter of the bubbles, and the inside of the molten glass G is raised so that bubbles are easily broken from the liquid surface of the molten glass G in the vacuum degassing vessel 14. When there is a large amount of SO ₂ dissolved in the molten glass G, it will cause re-boiling in a processing tank (not shown), so use preheated air as the air blown into the molten glass G from the air blowing pipe 32, Decreasing the dissolved SO ₂ has an additional effect.
Bubbles of such a small diameter that cannot rise in the molten glass G are almost absorbed by the molten glass G and disappear in the process of recovering the pressure to the normal pressure while descending the downcomer 18.
[0024]
As described above, the vacuum degassing apparatus for molten glass according to the present invention has been described in detail. However, the present invention is not limited to the above-described embodiments, and various improvements and modifications may be made without departing from the spirit of the present invention. Of course it is good.
[0025]
【The invention's effect】
As described above in detail, according to the present invention, the difference in level between the molten glass bases at the lower ends of the ascending pipe and the descending pipe, that is, the difference in the height of the molten glass liquid surface cannot be increased or changed. However, an air blowing pipe that blows air preheated to approximately the same temperature as the molten glass is placed below the riser pipe, and the flow rate of the molten glass can be easily reduced by blowing air from the air blowing pipe below the riser pipe. It is possible to increase the capacity of the vacuum degassing apparatus to the maximum, and conversely, in the vacuum degassing apparatus having the same defoaming capacity, the molten glass substrate at the lower end of the rising pipe and the descending pipe Level difference can be reduced, and the degree of freedom in device design can be increased.
Further, as the air blown from the air blow pipe into the molten glass, when using preheated air, dissolved gas SO _2, CO _2, H ₂ O or the like melted into the molten glass G, in particular reducing the concentration of SO ₂ And re-boiling in the next treatment tank can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of an embodiment of a vacuum degassing apparatus for molten glass according to the present invention.
FIG. 2 is a schematic cross-sectional view of a conventional vacuum degassing apparatus for molten glass.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10,110 Depressurization degassing apparatus 12,112 Decompression housing 12a, 12b Leg part 12c Suction port 14,114 Depressurization defoaming tank 14a, 14b Suction hole 16,116 Rising pipe 18,118 Lowering pipe 20,120 Melting tank 22,122 Upstream pits 24,124 Downstream pits 30,130 Insulation 32 Air blowing pipe 34 Bubbles G Molten glass h Difference in liquid level

Claims (1)

A vacuum housing that is vacuumed and depressurized inside, 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. A riser pipe that sucks and raises the previous molten glass and introduces it into the vacuum degassing tank, and is provided in communication with the vacuum degassing tank, and lowers the molten glass after vacuum degassing from the vacuum degassing tank. A downcomer pipe to be led out, and air blowing means for blowing air from below the riser pipe,
A vacuum degassing apparatus for molten glass, wherein the air is blown into the riser from the air blowing means, and the molten glass is raised together with the air in the riser.

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