JPH0280328A - Treatment of molten glass - Google Patents

Abstract

PURPOSE:To reduce a percentage of remaining bubbles in a glass article by improving the ejection of gas from a gas ejecting pipe in the treatment of molten glass by the bubbler method. CONSTITUTION:Periphery of a ceramic bubbler tube 3 extending through decking tiles 1 at the bottom of a glass melting tank upwards into molten glass 2 is surrounded by a double wall water-cooling jacket tube 4 which penetrates the decking tiles 1 and circulates cooling water. An ejecting pipe 3b extending horizontally is provided to the top end of the bubbler tube 3, and an ejecting port 3a is formed by opening a tip end of the ejecting pipe on an external wall of the jacket tube 4. The gas 5 fed to the bubbler tube 3 is ejected in the horizontal direction from the ejecting port 3a, forming thus closed cells 6 arranged in the almost horizontal direction in the glass 2. The glass 2 is stirred when the foams 6 are separated from the ejecting port 3a and floated, and are broken when the foams reach the upper surface of the molten glass and liberate the gas into the atmosphere of a space at the top of the glass melting tank. By this method, generation of uniform quality of a glass body can be prompted and a glass article contg. no foam is obtd. because many foams having minute sizes can be dispersed in the glass 2 without causing bursting of the glass.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for treating molten glass in the glass manufacturing field where the quality of foam, coat 9, etc. of products is a problem.

[Conventional technology]

The glass melting and fining process has a long history.
The classic equipment of a high-temperature melting furnace and its operations have become central to this process technology.

In contrast, we introduced a device with mechanical forcing into this melting and clarification process, and instead of relying solely on conventional classical thermal reactions, thermal convection, etc. Recently, various attempts have been made to improve the efficiency of the process or the quality of the target product, and one of them is to forcibly eject gas from a fumarole into the molten glass in a glass melting tank. One example is a bubbler type, which generates air bubbles and performs bubbling by floating the air bubbles.

To briefly explain the purpose of the current bubbler system when it was developed and the effectiveness of the one currently in use, the original purpose was to blow vertically upward from a large number of bubbler fumaroles installed at the bottom of the melting tank. By jetting gas towards the direction of the glass, and using the interfaces of the many bubbles thus generated, the gas components dissolved in the molten glass are not only released from the free upper surface of the molten glass but also into these bubbles. It is also said that the effect of diffusion into the atmosphere inside the furnace can be improved. However, in industrial practical applications, even if bubbles are generated from multiple bubbler nozzles,
The total surface area of the interface formed by these bubbles in the molten glass is extremely small compared to that of the above-mentioned free upper surface of the glass base, and regarding the diffusion and release of dissolved gas components within the glass base through the bubbler bubble interface, I could hardly expect the effect.

However, the quality of the product can be maintained by increasing the stability of the vortex in this region of the melting tank by combining the vortex caused by the heat convection trap of the glass substrate generated in the melting tank with the artificial vortex created by the bubbler system described above. It has been recognized that the current bubbler system has a vine effect that improves its stability, and the greater effect of the current bubbler system is that it can reduce striae (iodine) caused by local heterogeneity of glass components, which is cited as a quality defect of the product. The above-mentioned artificial vortex generated by the bubbler system in this area creates lively mixing and agitation in the glass base, thereby eliminating striae.

In addition to this, as a mechanical means for eliminating striae, a stirrer system that rotates stirring blades in the substrate has also been widely put into practical use.

[Problem to be solved by the invention]

In conventional technology, both the bubbler system and the stirrer system are effective in terms of the mechanism of mixing and stirring molten glass, but there is no clear mechanism for foaming, which is the most basic quality defect of glass products. Improvements against this background have not yet been made.

Looking at the bubbles contained in molten glass, the larger diameter bubbles float up and disappear before the molding process, but the smaller diameter ones remain and are molded. . In this case, bubbles with a small diameter are r
The smaller the bubble, the greater the osmotic pressure of the gas against the molten glass on the outer periphery (as it melts into the molten glass surrounding the microbubbles, the diameter of the bubble becomes smaller and ultimately disappears, so-called hugging). Ideally, this should be done, but in reality, bubbles will remain in the final product depending on the balance between the gas concentration in the microbubbles and the concentration of gas dissolved in the molten glass surrounding them.

In order to reduce the residual rate of bubbles in the final product from the chemical balance regarding permeation and diffusion of the gas mentioned above, it is necessary to increase the saturation rate of the concentration of gas dissolved in the molten glass in the glass melting and refining process. This is fundamentally important because it keeps the value low.

Considering the above-mentioned approach to improving foam quality in which the dissolved gas components in the molten glass are diffused and eliminated to reduce their concentration, it is possible that the dissolved gas in the liquid is converted into gas through the gas-liquid interface. Diffusion is a physicochemical process, and it is difficult to find mechanical means to promote the efficiency of this diffusion itself.

The problem to be solved here is to find a solution for how to forcibly disperse a large number of air bubbles into molten glass using a mechanical method. However, if one attempts to disperse the large number of bubbles trapped in a liquid with high surface tension, such as in molten glass, by a simple mechanical method, an enormous amount of mechanical energy is required.

That is, in consideration of the fact that it is difficult to form bubbles in molten glass, which is a viscous fluid, by mechanical force, the present invention aims to solve the above problem by improving the jetting of gas from the blow tube into molten glass as described below. It attempts to solve problems.

[Means to solve the problem]

The present invention generates medium-pressure bubbles in the molten glass by forcibly blowing gas into the molten glass from a blow tube inserted into the molten glass in the glass melting tank from the bottom of the tank. In the method for treating molten glass in which 72 pudding/ is carried out by levitation, the gas is ejected from the blowhole almost horizontally, that is, horizontally, or slightly obliquely upward or slightly obliquely downward with respect to the horizontal.

[Effect]

In the present invention, bubbles are formed in a substantially horizontal direction by ejecting the gas used in Buzzlin/in a substantially horizontal direction, that is, horizontally, or slightly diagonally above or slightly diagonally below the horizontal. Since the momentum vector of the ejected gas flow is horizontal or in a near-horizontal direction, even if the amount of gas ejected is increased, the ejected air flow will not melt as compared to the conventional method of ejecting bubbles in the vertical direction. By forming a gas flow path in the glass that communicates directly with the upper surface thereof, it is possible to suppress a phenomenon called so-called blow-through.

That is, even if the jetting flow velocity is increased considerably compared to the conventional vertically upward jetting method, bubbling continues without causing blow-by.

Currently, practical examples of bubbler systems applied to liquid tanks are not limited to glass melting tanks, but are widespread.
In that case, what is required is that the total pressure = static pressure + dynamic pressure of the gas flow at the end of the jet nozzle exceeds the liquid pressure of the liquid tank over the end of the jet nozzle.

In the present invention, it is possible to increase the jet flow velocity, and as a result, the total pressure of the jet flow is mostly composed of quiet pressure in the conventional bubble separation method using buoyancy. On the other hand, it is possible to make the dynamic pressure component the main body of the total pressure.

For this reason, in the present invention, it is possible to continue bubbling by reducing the diameter of this gas jet, and the hydrostatic pressure of the molten glass applied from the outside to the flow path of this small diameter jet causes
This gas jet is broken up to form small diameter bubbles.

Therefore, in the present invention, the upper limit of the amount of the buzzing gas is increased, and the diameter of the generated and floating bubbles is decreased, thereby increasing the bubbler effect.

〔Example〕

A first embodiment of the present invention will be explained with reference to FIGS. 1 to 3.

As shown in FIG. 1, air, He, 02. The supply pipe U of gas such as H2O is a plurality of ceramic nogburer pipes 3 as fumarole pipes installed in the degassing vortex region between the melting zone and the clarification zone of the glass melting tank.
It is connected to the.

As shown in FIG. 2, the ceramic bubbler tube 3 is
It passes through the furnace bottom part 1 of the melting tank and extends upward into the molten glass 2, and is surrounded by a double water-cooled mantle pipe 4 that passes through the furnace bottom part 1 of the melting tank and circulates cooling water. ing. An injection tube 3b extending horizontally is provided at the upper end of the bubbler tube 3, and the tip of the injection tube 3b opens into the outer wall of the double water-cooled mantle tube 4 to form an injection port 3a.

In this embodiment, the gas 5 supplied from the gas supply pipe to the bubbler tube 3 is ejected horizontally from the ejection port 3a to form closed cells 6 arranged in a substantially horizontal direction in the molten glass 2. . As shown in FIG. 3, the bubbles 6 are driven by the upward flow of the molten glass 2 around the bubbles 6 that is induced when the bubbles 6 leave the spout 3a of the nomi-pring tube 3 and float up. The molten glass 2 is stirred. The bubbles 6 rise in the molten glass 2 as shown in FIG.
It reaches its free upper surface and ruptures, releasing the gas therein into the atmosphere in the upper space of the melting tank.

Since the momentum vector of the ejected gas flow (indicated by arrow a in FIG. 2) in the bubble 6 formed in the horizontal direction has a horizontal direction, the amount of ejected gas per hour is increased. However, as long as the diameter of the ejection port at the end of the ejection tube is kept at an appropriately small diameter, the greater the momentum of the ejected gas flow, the more the ejected airflow will flow inside the molten glass 2 even if the bubbles are torn apart in the horizontal direction. It does not blow through towards the upper surface.

Further, the gas jet is divided by the hydrostatic pressure of the molten glass applied to the flow path of the gas jet, and bubbles with a small diameter are formed.

Furthermore, in this embodiment, by increasing the amount of gas ejected from the bubbler, the local upward flow of the molten glass 2 at this portion, which is induced by the volume per hour of the floating bubbles, is strengthened. In addition, in the conventional method, the bubbles were separated from the bubbler tube 3 by balancing the static buoyancy of the bubbles, whereas in this embodiment,
As described above, the inertial force of the jet of gas promotes the separation of bubbles from the bubbler tube 3. That is, the dynamic pressure of the ejected flow determines the strength of the vortex generated within the molten glass 2.

As a result, the stirring, mixing, and homogenization of the glass substrate by the vortex pressure in the molten glass 2 formed by the bubbler, which has been the objective of the conventional bubbler system, can be carried out more actively.

A second embodiment of the present invention will be explained with reference to FIG.

In this embodiment, the structure near the spout of the bubbler tube 3 is changed as follows compared to the first embodiment.

That is, the bubbler tube 3 is made of ceramics, a spout 3a having a horizontal axis is provided at its upper end, and the inner tube 4a of the double water-cooled outer tube 4 is disposed close to the outer periphery of the bubbler tube 3. By arranging the intermediate tube 4c between the outer tube 4b and the inner tube 4a of the outer tube 4, the above-mentioned tube 4a r
4a, and the above pipe 4c*
A double water-cooled jacket tube 4 is formed with a cooling water descending passage between the tubes 4b. Further, the upper end of the ceramic bubbler tube 3 is provided with a spout 3a in the horizontal direction as shown in 5 above, which opens into the inner tube 4a at a position corresponding to the spout 3a and extends outward in the horizontal direction. A truncated conical gas ejection passage 4d is provided which extends outward into a trumpet shape and opens into the outer tube 4c.

In this embodiment, the structure of the ejection port in the first embodiment is changed as described above, and its operation and effect are essentially the same as those in the first embodiment.

In conventional bubbler pipes that eject gas vertically upward, the total amount of gas ejected from all bubbler pipes is 0.
．． 0.04 Nm"/mm, but in the first and second embodiments, the total amount of gas blown out from all the bubbler tubes 3 was increased by about 5 times, that is, V = 0.04 x 5 = 0.04 Nm"/mm. 2 Nm”/fN
A8 L K Increase sales.

Even if the flow rate of the ejected gas flow, and therefore the momentum of the ejected gas flow, was increased in this way, since the ejected direction was horizontal, the floating bubbles were divided into smaller pieces, and there was no problem with the continuation of bubbling. Due to the increase in the flow rate of the ejected gas, the stable continuation of a strong and lively forced vortex flow by the buzz large system was observed in the glass melting tank in the first and second examples compared to the conventional one-bubbler type. .

The gases used in each of the above examples are as follows:
Air, which has been conventionally used for 72-knolling, may be used, but 0□ in air easily dissolves into glass;
Since N2 is a component of bubbles in glass products and is an important target for elimination, N2 is the gas used in the method in which the dissolved gas is diffused into the bubbles and released into the atmosphere inside the top-conditioning furnace. He, N easily melts into glass
It is better to use 20, 02, etc.

〔Effect of the invention〕

As explained above, the present invention allows the gas to be ejected from the fumarole pipe in a substantially horizontal direction, thereby preventing the ejected flow from blowing through to the upper surface of the molten glass even if the amount of the ejected gas and its momentum are increased. On the contrary, it is possible to increase the amount of bubble gas while reducing the diameter of the generated bubbles.

As a result, compared to the conventional method, it is possible to obtain a much higher stirring effect in promoting the homogenization of the glass substrate by stirring and mixing the glass substrate with the conventional buzz large stem.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the entire device used in the first embodiment of the present invention, FIG. 2 is a vertical sectional view of the main parts of the device used in the first embodiment of the present invention, and FIG. The figure is an explanatory diagram showing the movement and floating of bubbles in the first embodiment, and FIG. 4 is a longitudinal cross-sectional view of the main part of the apparatus used in the second embodiment of the present invention. 1... The bottom of the melting tank can be seen here and there, 2... Molten glass. 3... Bubbler tube, 3a... Spout. 4...Double water-cooled mantle, 5...Gas, 6...Bubble. Two agents, patent attorneys Akigai Sakama, are shown in Figure 1 and Figure 2.

Claims (1)

[Claims] By forcefully blowing gas into the molten glass from the bottom of the glass melting tank through a blow tube inserted into the molten glass in the glass melting tank, air bubbles are generated in the molten glass, and the air bubbles float up. A method for treating molten glass that involves bubbling, characterized in that gas is ejected almost horizontally into the molten glass from the blow tube.