JP2003192354A - Glass fusing furnace and method for heating fused glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glass fusing furnace able to alter certainly fused glass to a uniform glass product by protecting the generation of bubbles in high temperature fused glass after a vitrification reaction and a method for heating the fused glass. <P>SOLUTION: The glass fusing furnace has a fusing vessel 22, a throat 23, a working vessel 24 and a feeder 25. An electrode 10 composed of a heat resistant electric conductive film material and a reverse flow protecting means having an electric power supplying means to the electrode in fused glass b are located in at least one or more places among the fusing vessel 22, the throat 23, the working vessel 24 and the feeder 25. The generation of the bubbles is protected by protecting a reverse flow phenomenon of the fused glass from a low temperature area generated with selective electrification to the electrode 10 composed of the heat resistant electric conductive film material lined to one of a side wall, a floor and a ceiling at the glass fusing furnace to a high temperature area. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a glass melting furnace and a method for heating molten glass in the glass melting furnace.

[0002]

2. Description of the Related Art Among the defects of glass products generated in glass manufacturing, bubbles are mixed with the products because they often impair the product quality along with the lumps and often cause deterioration of the function of the product itself in addition to appearance problems. Things have been avoided as much as possible. If classified according to the cause of foam generation in molten glass, bubbles that flow out when unmelted glass during a batch reaction passes through a short path with insufficient clarification, and are involved during physical stirring by a stirrer that is a glass homogenizer. Foam, foam generated from the surface of the refractory due to the reaction of the refractory lining with the glass used in the glass melting furnace or the presence of refractory pores, foam generated by electrolysis in a furnace using electric heating, the temperature of the molten glass Change, composition change of molten glass due to volatilization of glass components, bubbles generated by causing supersaturation of gas dissolved in molten glass due to partial pressure change in molten atmosphere, bubbles generated by redox reaction of metal element, etc. There are many different things.

For this reason, various methods have been tried for defoaming bubbles generated during glass production, based on the above-mentioned causes of bubbles. However, it is clear that it is most desirable that the molten glass is homogenized without generating new bubbles as much as possible after the bubbles in the batch reaction are removed.

As one of the causes of bubbles in the molten glass after the completion of the batch reaction, when a flow occurs in which the molten glass in the high temperature state comes into contact with the molten glass in the lower temperature state, the high temperature melting Bubbles are generated due to an oxidation-reduction reaction occurring at the contact interface between the glass and the low-temperature molten glass or supersaturation of the molten glass-dissolved gas.

No specific measures have been taken to avoid such a phenomenon, that is, the contact itself between the high-temperature molten glass and the low-temperature molten glass, and if the temperature of the molten glass is simply raised, the bubbles rise quickly. Various inventions have been made so far in terms of defoaming by allowing the bubbles generated by the contact phenomenon of the high-temperature low-temperature melt and other phenomena described above to somehow be floated to the surface of the molten glass as quickly as possible from the viewpoint of Came. For example, as shown in FIG. 5, in Japanese Examined Patent Publication No. 55-116631, it is described that an electrode is installed in the throat to promote heat convection in the throat to achieve homogenization. There is a background that activation is effective in promoting defoaming.

In Japanese Patent Publication No. 7-106913, the temperature of the bottom of the throat is measured and the temperature of the riser is raised to promote defoaming. As described above, the electrode installed in the glass melting furnace basically raises the molten glass temperature of bubbles in the molten glass to an appropriate temperature to cause an upward flow in the glass, and at the same time, the temperature rises. It is stated that by reducing the viscosity of the molten glass, the bubbles trapped in the melt facilitate degassing in the furnace atmosphere at the surface of the molten glass,
And has been practiced.

[0007]

However, no matter how the rising flow is given to the molten glass in the furnace to promote defoaming, the number of bubbles that can be defoamed is naturally limited. Moreover, it is difficult to keep the glass flow rate low enough to allow sufficient time for defoaming in situations where high-speed mass production is desired more than expected at the time of designing the glass melting furnace. It often happens that

Further, even if the molten glass is simply kept at a high temperature to reduce the viscosity of the molten glass and promote the defoaming of the bubbles generated in the molten glass, for this reason, the furnace wall of the glass melting furnace is also increased. , Accelerate the deterioration of structural members such as hearth,
When it comes to significantly shortening the life of the glass melting furnace itself, it deviates from the ultimate purpose of satisfying the market demand by introducing an appropriate amount of glass products to the market when needed. There is a risk of missing the glass product opportunity.

Even when the glass melting furnace is designed, if the design is performed on the premise of a high-temperature furnace, as a result of considering that bubbles are mixed again in the glass after clarification, sufficiently stable furnace management is realized. In order to proceed, equipment and heat energy for removing mixed bubbles from the clarified glass are excessively input. And because excessive equipment investment such as inevitably increasing the size of the furnace is required, a large amount of materials to be used is required, and at the same time, a small amount of money is used as a compensation for enlarging the furnace. There are various problems such as difficulty in producing the product type.

Further, inputting an excessive amount of energy more than necessary does not match the global direction of environmental protection, which is to cope with future energy shortage. In the glass manufacturing industry, there is no merit other than defoaming bubbles that have been continuously practiced when melting glass, avoiding excessive energy input as much as possible, It can be said that the time has come to fundamentally change the way of thinking about the clearing of bubbles.

In view of the above situation, the present invention prevents the generation of bubbles in the molten glass in the high temperature state after the vitrification reaction, and thus ensures that the molten glass that has undergone the vitrification reaction is a homogeneous glass product. The purpose is to

[0012]

Means for Solving the Problems The inventors of the present invention have conducted repeated studies to identify the cause of foaming of a phenomenon generally called reboil, which is one of the main causes of the refoaming phenomenon occurring in molten glass after fining. One is that the low temperature glass in the molten state in the glass melting furnace flows backward to the side of the higher temperature glass, causing a drastic change in the solubility of the gas components dissolved in the high temperature glass due to a rapid temperature change, or the contact between the two glasses. It was found that abrupt redox reaction at the interface generates reboil bubbles at the interface between the high temperature glass and the low temperature glass.

The basic idea of the present invention is to take various measures based on the viewpoint of how to prevent the generation of bubbles, not the viewpoint of how to remove the generated bubbles. It means that the invention of the present invention has been reached, and the post-treatment measures after the occurrence of bubbles have been amended as in the inventions made so far, and the flow of molten glass in the furnace before the occurrence of bubbles is dealt with in advance. It was found that the bubble generation itself can be prevented by. Therefore, many conventional inventions have been proposed with the point of how to promote the heat convection of the molten glass from the viewpoint of homogenizing the molten glass in the furnace. Rather, it means that the generation of bubbles itself is prevented by preventing unnecessary heat convection such that the low temperature molten glass and the high temperature molten glass are in direct contact with each other.

The glass melting furnace according to the present invention is provided with a melting tank in which high-temperature molten glass stays for a predetermined time, a throat connected to the melting tank through which molten glass passes, and the molten glass connected to the throat. And a working tank for refining the molten glass that has been cooled to a predetermined temperature for a predetermined time, and a molten glass that has been cooled to a predetermined temperature from the molten glass that is connected to the working tank and has been clarified in a forming section. In a glass melting furnace having a feeder, a low temperature generated in the molten glass of the glass melting furnace having an electrode made of a film-shaped heat-resistant conductive material immersed in the molten glass and a power supply means for energizing the electrode It is characterized in that it is provided with a backflow preventing means for preventing the flow of the molten glass from the region to the high temperature region.

The cross-sectional area perpendicular to the glass flow direction in each of the melting tank, throat and working tank described above is:
The throat is made smaller than either the melting tank or the working tank in order to retain the molten glass for a predetermined time, and the volume must be smaller than that of the melting tank or the working tank. On the other hand,
Regarding the melting tank and the working tank, the size relationship between the cross-sectional area and the volume is not limited. The cross-sectional area and volume of the work tank, feeder, and molding section are smaller than the working section in order to retain the molten glass for a predetermined time in the cross-sectional area and volume with respect to the glass flow direction. There are no restrictions on the spaces between departments.

Working tank, melting tank, throat, working tank,
Both the feeder and the molding part are constructed of heat-resistant material.If the material has erosion resistance to molten glass, it may be inorganic material such as refractory or metallic material such as platinum. Considering structural strength It is possible to use multiple materials properly. And, as a melting means of the glass raw material put into the melting tank, it is possible to perform melting by various methods such as an electric heat source, combustion of fossil fuel, heating by a refined gaseous raw material, and it is possible to use a plurality of melting means in combination. Not to mention possible. In addition, the temperature measurement of the molten glass,
Whatever the means, there is no problem as long as it has a certain accuracy.

Further, the glass melting furnace of the present invention is characterized in that the backflow preventing means is provided in at least one of the melting tank, the throat, the working tank and the feeder.

The above-mentioned backflow prevention means is at least 500.
It is necessary to have a structural material that can withstand a high temperature of ℃ or more, and at the same time be a means that has an erosion resistance to the glass material that melts, and structural strength that can hold the shape to be used at a high temperature is essential. Here, in the glass melting furnace, components such as a melting tank, a throat, a working tank, and a feeder are connected in this order, but the above-mentioned glass melting furnace includes a melting tank, a throat, a working tank, and a feeder. Not all components are required, and even if one of them is missing, it may be functionally acceptable. That is, the glass melting furnace may have a structure without a working tank or a structure with no throat, or a structure without a working tank or feeder. Then, in this case, the glass melting furnace becomes a glass melting furnace in which the components which are not present are removed and adjacent components are connected. Also,
The backflow prevention means in this case can be installed so as to extend over a plurality of locations in the melting tank, throat, working tank, and feeder. Furthermore, there is no need to have only one component such as the melting tank, throat, working tank, feeder, and molding unit depending on the variable factors such as the type of glass material to be melted, application, production amount, glass flow rate, etc. It is also possible to use a glass melting furnace with a structure in which multiple elements are connected in series or in parallel, and it is different from the melting tank, throat, work tank, and feeder in which each component has a special function. Elements can also be used together.

Further, in the glass melting furnace of the present invention, the backflow preventing means is one of electrodes made of a film-shaped heat-resistant conductive material which is lined on any of the furnace side wall, the furnace floor and the furnace ceiling of the glass melting furnace. It is characterized in that electricity is selectively applied to more than one place.

Here, the furnace side wall, the furnace floor, and the furnace ceiling must have the necessary heat resistance, heat insulation, and corrosion resistance, respectively, and the backflow prevention means must be the furnace side wall, the furnace floor, and the furnace floor.
It may be installed over multiple places on the furnace ceiling.
Regarding the lining method of this backflow prevention means, it can be installed on the furnace ceiling, furnace side wall, and furnace floor by a physical method such as a heat-resistant wedge, and even if it is joined and installed with an irregular-shaped refractory, etc. Well, both can be used together. For selective energization, it means energizing only the necessary parts.Therefore, it is possible to energize according to a program that presets how much voltage and how long to apply, or manually select the selective voltage. It is also possible to apply.

In the method for heating molten glass of the present invention, a molten bath in which high temperature molten glass stays for a predetermined time, a throat connected to the molten bath for passing the molten glass, and a predetermined temperature from the molten glass connected to the throat. A working tank for refining the molten glass by supplying the molten glass cooled to the temperature for a predetermined time, and supplying the molten glass cooled to the predetermined temperature from the molten glass that is connected to the working tank and is clarified in the forming part In a method for heating molten glass, which uses a glass melting furnace having a feeder for heating the molten glass in the glass melting furnace, a film disposed in a molten state at a predetermined position of the glass melting furnace in a dipped state. The flow of the molten glass from the low temperature region to the high temperature region generated in the molten glass is prevented by locally heating by energizing the electrode made of a heat-resistant conductive material. Characterized in that it.

Regarding the predetermined position where the selective heating of the glass melting furnace is carried out, it can be used by installing an electrode made of a film-shaped heat-resistant conductive material at a preset position, or during the glass melting. It is possible to improve the heating state of the molten glass by increasing or decreasing the number of predetermined installation positions by constructing the parts where necessity arises. In addition to heating by energizing the electrodes, it is also possible to use other indirect heating means as needed. Further, the retention of the molten glass for a predetermined time depends on the glass production amount, the molten glass temperature, etc., and is not limited.

The method for heating molten glass of the present invention is
The temperature of the molten glass is continuously measured at one or more places in the glass melting furnace, and the phenomenon that the temperature is lower than that of the surrounding molten glass caused by the flow of the molten glass from the low temperature region to the high temperature region is detected. An electrode made of a film-shaped heat-resistant conductive material is arranged at an ascending flow generation site that draws the low-temperature molten glass flow under the molten glass flow, and locally heated by energizing for a predetermined time to suppress the ascending flow of the molten glass. This prevents the molten glass from flowing from the low temperature region to the high temperature region, which occurs in the molten glass.

The molten glass temperature measurement point for specifying the rising flow generation point can be increased or decreased as necessary, and the molten glass is heated by heating an area appropriate for the specified rising flow generation point. It is desirable to prevent the movement of the molten glass between the high temperature region and the low temperature region. At this time, regarding the region to be heated, it is necessary to take care not to overheat the region so that the glass flow is not disturbed more than necessary.

Furthermore, in the method for heating molten glass of the present invention, an electrode made of a film-shaped heat-resistant conductive material is provided in at least one of the melting tank, the throat, the working tank, and the feeder, and the electrode is locally energized for a predetermined time. It is characterized in that the molten glass is prevented from flowing from a low temperature region to a high temperature region generated in the molten glass by heating and suppressing an upward flow of the molten glass.

The method for preventing backflow of molten glass according to the present invention can be used in combination with other methods for preventing backflow. that is,
For example, a method for lowering the temperature of a high-temperature molten glass specific portion that requires a treatment contradictory to heating simultaneously with the present method of heating an appropriate portion to suppress an upward flow, specifically, a heat-resistant water-cooled plate, It is possible to supplement the heating effect of an appropriate place by introducing a heat-resistant water-cooled pipe into a necessary place or by performing air cooling or the like.

The method for heating molten glass of the present invention is
Suppressing the rising flow of molten glass by selectively energizing and heating at one or more locations of an electrode made of a film-shaped heat-resistant conductive material lined on the furnace side wall, furnace floor, or furnace ceiling of the glass melting furnace As a result, the molten glass is prevented from flowing from a low temperature region to a high temperature region which is generated in the molten glass.

Here, since the heating method of the present invention is premised on the implementation by the above-mentioned molten glass furnace, the film-shaped heat-resistant conductive material installed on any of the furnace side wall, the furnace floor and the furnace ceiling. The electrode made of can be increased or decreased in the lining area or the number as required, and the time of energization heating and the applied voltage can be changed at any time.

Glasses of the same composition having different molten glass temperatures have an upper limit on the amount of gas components that can be dissolved depending on the temperature, but the molten glass on the low temperature side has an allowable amount of dissolved gas with respect to the molten glass on the high temperature side. However, since there is a temperature difference between the two molten glasses, contact between the two melts gasifies the gas corresponding to the difference in the allowable amount of dissolved gas at the interface, thereby generating reboil bubbles. Alternatively, an oxygen bubble or the like is generated by a rapid redox reaction occurring at the interface between both glasses having different redox states depending on temperature. Therefore, the larger the temperature difference between the low-temperature side molten glass and the high-temperature side molten glass, the larger the number and volume of reboil bubbles generated by the backflow phenomenon of the molten glass.

What is important for preventing the generation of such reboil bubbles is that the molten glass that has undergone the vitrification reaction has a large temperature difference between the molten glass in the low temperature state and the molten glass in the high temperature state. How do you create a situation where the glass is not in direct contact?

[0031]

The glass melting furnace and the method for heating molten glass according to the present invention include a melting tank in which high-temperature molten glass stays for a predetermined time, a throat connected to the melting tank through which the molten glass passes, and a throat connected to the throat. A working tank for refining the molten glass by holding the molten glass which has been supplied with the molten glass and has been lowered to a predetermined temperature for a predetermined time, and the molten glass which is connected to the working tank and has been refined in a forming part is lowered to a predetermined temperature In a glass melting furnace having a feeder for supplying molten glass, a glass melting furnace having an electrode made of a film-shaped heat-resistant conductive material immersed in the molten glass and a power supply means for energizing the electrode The backflow prevention means for preventing the flow of the molten glass from the low temperature region to the high temperature region generated in the glass is provided. , A work tank, a feeder, and at least one electrode of a film-shaped heat-resistant conductive material, which is lined in the furnace side wall, furnace floor, or furnace ceiling of the glass melting furnace. Since it is configured to selectively energize as described above, melting from a low temperature region to a high temperature region generated in the melting furnace by locally heating a predetermined position of the molten glass using such a glass melting furnace It is possible to reliably prevent the backflow phenomenon of the glass.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION In a glass melting furnace of the present invention, as a solution to this problem, as shown in FIG.
The flow of molten glass from a high temperature region to a low temperature region (α in the figure) by energizing an electrode 10 (hereinafter referred to as electrode 10) made of a film-shaped heat-resistant conductive material, which is constructed on the hearth floor, furnace ceiling, etc. It was found that reboil in the clarified molten glass can be prevented by preventing the locally generated molten glass flow from the low temperature region to the high temperature region against the temperature gradient in the furnace. . And, in this glass melting furnace, in order to prevent an ascending flow that draws the low temperature molten glass flow under the high temperature molten glass flow generated in the glass melting furnace, the temperature rises according to continuous temperature measurement at one or more points in the furnace. It has been found that a heating method is possible in which the generation of an ascending flow is controlled by selectively increasing the current output and heating the electrode 10 at a location where the flow can be suppressed for a predetermined time.

Generally, in a glass melting furnace, the raw materials charged in the vicinity of the raw material charging port react with each other in a high temperature environment in the melting tank. The temperature near the charging port is low, but the temperature rises as the temperature goes to the center of the melting tank. The temperature of the molten glass decreases along the glass flow path in the furnace, passing through a part called the hot spot where the molten glass reaches the maximum temperature in the furnace near the center of the melting tank. Although a gradient is formed, at a location where the cross-sectional area of the plane perpendicular to the flow direction of the molten glass changes abruptly, the flow velocity of the molten glass changes abruptly, forming a flow against the temperature gradient. It is in an easy state.

In particular, with respect to the throat that the molten glass passes through as it flows from the melting tank to the working tank, the above phenomenon is remarkably observed, and the glass flow is likely to be disturbed. As the pattern of turbulence in the molten glass, some patterns appear depending on the furnace operating conditions,
A typical one of them is shown as follows by the explanatory view of FIG.

That is, as shown in FIG. 2 (A), in the glass melting furnace in a normal state, the flow of the molten glass indicated by α melted in the melting vessel of 22 is 22 as a whole even within the throat of 23. It moves from the melting tank toward the 24 working tanks or the melting tank. The velocity distribution of the glass flow at this time is a distribution state represented by a quadratic function such as δ represented by shading in the figure. However, as shown in FIG. 2 (B) over time, in the throat portion 23, due to thermal convection on the side wall of the throat portion 23, the upward forward flow α is accelerated due to the upward flow β in the central portion of the throat, and the lower forward flow α is accelerated. The forward flow is decelerated, and finally a reverse flow γ is generated in the lower part. At this time, the velocity distribution of the glass flow in the throat has a distribution state represented by a cubic function. Once the reverse flow γ is generated, the lower temperature molten glass in the 24 working tanks or the fining tanks flows into the throat, and the reverse flow is further amplified, and finally the lower temperature molten glass in the 24 working tanks or the fining tanks is cooled. 22 for molten glass
Enters into the melting tank and comes into contact with the hot molten glass. In this way, reboil bubbles are generated at the interface between the high temperature molten glass and the low temperature molten glass due to the redox reaction or the abrupt change in the dissolved gas amount. The phenomenon described above can be confirmed not only by flowing colored glass in the furnace, but also by computer simulations that have become frequent in recent years, and small-scale models using viscous fluids. It can be confirmed by experiments.

Although the backflow phenomenon has been described here using the throat as a model, the phenomenon occurring in the feeder is basically the same. However, the bubbles generated by the reboil phenomenon generated in the feeder often have a relatively small volume, and fine reboil bubbles of micron order may be generated, so caution is required.

Next, constituent members constituting each part of the glass melting furnace of the present invention will be described below.

As the film-shaped heat-resistant conductive material used for the electrode in the glass melting furnace of the present invention, platinum and alloys of platinum and other materials are mainly used. Depending on the kind of material melted in the glass melting furnace, molybdenum is used. Other materials may be used. What is important here is the high temperature corrosion resistance as an electrode material when the electrodes are energized, and any material that has sufficiently high high temperature corrosion resistance for a specific glass material can be used as an electrode material. is there. In addition, there are differences in the temperature at which the electrode made of the film-shaped heat-resistant conductive material is used, depending on the part where the glass melting furnace is used. Also, there are several different materials for economic reasons and strength as a structural member. It goes without saying that the use of seeds together can provide a satisfactory function.

The current supplied to the electrodes in the present invention may be a DC power supply, a common frequency AC power supply, or a high frequency AC power supply, and currents from different power supplies for a plurality of use parts in the glass melting furnace. It is also possible to use together. The electrode water-cooling tube used for the electrode back portion of the present invention may be cooled by another medium other than water-cooling, and does not necessarily have to be tubular, and may be a mere buffer material depending on the site and temperature used. Even if you only play a role, there is no problem.

Further, in the electrode made of the film-shaped heat-resistant electrode material of the present invention, basically, the area of the cross section perpendicular to the glass flow direction in the glass melting furnace is smaller than that before and after that. It is easy to control the glass flow in the furnace by using it in a state where it is locally installed centering on, and in some cases such a place is intentionally provided in the glass furnace to melt. It is also possible to control the flow of glass. And, as a typical portion having the above-mentioned structure or a structure similar to the above-mentioned structure in the glass melting furnace, there are a throat, a riser, a feeder, a forebay, etc., but the present invention is applicable to any case Therefore, a plurality of electrodes of the present invention can be used in combination at a plurality of locations.

As the structure of the electrode made of the film-shaped heat-resistant conductive material of the present invention, various shapes from a small area to a large area are conceivable, but representative examples will be described below. Perform.

In melting glass for electronic parts, an electrode made of this film-shaped heat-resistant conductive material is applied to the throat, but the electrode, the thermocouple for measuring the temperature of the molten glass, and the water-cooled tube are as small as 10 cm square. The plate-shaped electrodes arranged in a grid pattern are arranged for each structural unit, and the temperature measurement result by simultaneous measurement at multiple points and the change result of the output based on it are centrally controlled precisely under the computer. If it is found that the temperature measurement result of a certain specific area is lower than that of the surrounding area, the electrode output is increased or decreased to eliminate it, and the local temperature imbalance is eliminated.

Further, the film heat-resistant conductive material used in the glass melting furnace of the present invention has the following large area if it is possible to obtain a sufficient effect without requiring precise control. It is also possible to adopt a structure as an electrode made of a film heat resistant conductive material. That is, in a melting furnace that melts the lighting glass, the length is 2 m, the height is 0.5 m, and the width is 1.
One electrode is installed on the top and side of the throat of m, the terminals are projected on the top and bottom of the side, the terminals are sandwiched by copper clamps, and a copper water cooling pipe is wrapped around the ends of the clamps to cool the clamp tips. Do it. By preventing the backflow phenomenon of low temperature glass from the working tank by heating the molten glass by the platinum electrode, it is possible to prevent the occurrence of reboil bubbles near the throat, which has been a problem until then.
It can be confirmed that the number of bubbles in the product is significantly reduced.

Further, the electrode of the present invention does not necessarily have to have the same thickness even if it is in the form of a film, and the thickness can be changed if necessary in view of structural strength. It is also possible to provide a local depression or, conversely, a protrusion at an unspecified location or a specific location. Further, the electrode does not need to have a square shape in the portion in contact with the molten glass, and may have an elliptical shape, a triangular shape, a comb shape, a strip shape, a shape with a plurality of notches, a trapezoidal shape, or a dome shape. The shape can be freely changed according to the shape in the furnace, such as the shape of the furnace or the shape of a bow.

In the glass melting furnace of the present invention, the thermometer for measuring the temperature inside the furnace, which is used by detecting the flow of the molten glass which flows counter to the temperature gradient, can withstand high temperatures and can perform precise measurement. Any measuring instrument such as thermocouples and optical pyrometers can be used, and it is possible to construct and operate so that quick and accurate measurement can be performed by using multiple measurement methods together.

In addition, in the heating method of the present invention, generally, the furnace can be operated automatically by computer control, but when it is necessary or in an emergency, it can be switched to manual operation so that a reliable response can be taken. .

As a glass melting furnace heating method which is carried out using the glass melting furnace of the present invention, an example corresponding to a manual operation or an example corresponding to a program will be described below.

In a glass tube manufacturing melting furnace to which the glass melting furnace of the present invention is applied, temperature measurement at a plurality of locations near the throat is continuously performed at all times, and the results are observed in large numbers such as the glass melting flow rate and the gas combustion amount. The furnace is operated under the condition that the equipment can be compared with the value. Then, the temperature of the glass cullet mixed in the glass raw material temporarily fluctuated, so that the temperature near the throat fluctuated and an upward flow started to occur in the throat. Since it was captured by, the electrodes made of platinum film-shaped heat-resistant conductive material that can heat the temperature change part to cancel the fluctuation are supplied with 7 kW of power.
It was possible to return the temperature measurement result to the original state by applying it only for a time, and it was possible to prevent the backflow phenomenon that occurs in the throat part.

Further, unlike the heating method which can be carried out as a corrective action against the sudden fluctuation as described above, an intermittent heating method by the following program operation can be adopted.

Melting chamber 10 employing the glass melting furnace of the present case
Glass for optical components of other types is continuously produced by an ultra-small continuous melting furnace with a volume of 1 liter, but such a small melting furnace is apt to be affected by the outside temperature, so normal flow during the day Even if it is formed in the throat part, an upward flow will occur in the flow of the throat part due to the influence of the outside temperature at night. In this case, in consideration of the fluctuation of the external temperature as well as the fluctuation, by composing a program for periodically energizing the electrode made of the platinum film-shaped heat-resistant conductive material of the present invention to prevent the occurrence of an upward flow, Certainly stable production can be realized.

Further, regarding the melting furnace for producing a glass molded body for optical glass molding which employs the glass melting furnace of the present invention, it is necessary to temporarily stop the glass flow rate when the product type is changed. At this time, a temporary backflow from the nozzle of the forming part to the feeder occurs, whereby bubbles with a fine diameter of several microns are recognized in the glass, and there is a problem that the bubbles subsequently become defective. However, it succeeded in suppressing foaming by preventing a part of the glass material from flowing backward through the feeder while the flow of glass was temporarily stopped by the program for the platinum electrode installed in this feeder section, Product yield improved by 10% or more.

Next, examples of the glass melting furnace of the present invention and the heating method by the melting furnace will be described with reference to the drawings.

(Embodiment 1) FIG. 3 is a horizontal schematic view of a glass melting furnace 20 for manufacturing a glass plate which employs a glass melting furnace and a heating method therefor according to an embodiment of the present invention. When the glass raw materials that have been adjusted and mixed in advance are continuously charged into the glass melting furnace 20 through the raw material charging port, the raw materials are deposited on the molten glass as shown in a in the melting tank 22 and the electrode 26 is formed. It is heated by a heat source for melting glass and melts. Molten glass that has reached a sufficiently high temperature after the vitrification reaction is
It flows into the throat of 23. On the throat 23, the platinum electrode 10 of the present invention is lined on the refractory side wall, the ceiling and the hearth. The lining electrode 10 is connected and fixed to 12 voltage converters having a power control function by 13 conductive materials, and the connecting portion between the conductive material 13 and the electrodes 10 is water-cooled to prevent deterioration due to heat. Has been done. Further, the conductive material 13 is installed between the voltage converter 12 and the rectifier 11 so that the DC power supply can be used. In order to suppress heat radiation from the side wall of the throat to the electrode 10, by applying power of about 15 kW, the indicated temperature of a thermometer (not shown) installed in the hearth near the throat in the melting chamber 22 rises by 20 ° C., and power is applied. Thus, it was confirmed that the low temperature molten glass did not flow back from the working tank 24.
Further, the appearance of the plate-shaped glass molded body molded from the working tank through the 25 feeders was inspected. As a result, no bubbles, which were defects caused by reboil, were observed, and the glass melting furnace of the present invention and the heating method thereof were observed. I was able to confirm the effect.

(Embodiment 2) FIG. 4 is a horizontal schematic view of a glass melting furnace 30 for manufacturing a tube glass which employs a glass melting furnace and a heating method therefor according to an embodiment of the present invention. In FIG. 4, the working tank 24, the feeder 25, and the molding unit 27 connected to the working tank 24 are shown. In the feeder 25, the electrode 10 made of platinum in the present invention is lined on the refractory side wall, the ceiling, and the hearth. The inner electrode 10 made of platinum is fixedly connected to 12 voltage converters having a power control function by 13 conductive materials, and the connection between the conductive material 13 and the electrodes 10 is prevented from deterioration due to heat. It is water cooled as much as possible. Further, the conductive material 13 is installed between the voltage converter 12 and the rectifier 11 so that the DC power supply can be used. The molten glass a in the work tank is the electrode 2 in the work tank.
By the heating of 6, it flows into the molding portion of 27 through the feeder 25 while maintaining a sufficiently high temperature. At this time, by applying an electric power of about 9 kW to the electrode 10 in order to prevent the backflow phenomenon of the molten glass from the molding part in the feeder, the temperature indicated by the thermometer installed near the feeder in the work room hearth was 3 ° C.
It was confirmed that the temperature rose and the normal flow of molten glass was secured without backflow from the molding section to the feeder.
Further, when the foam in the tube-draw molded product was examined in detail through the spout 28 from the molding part, even microscopic microscopic bubbles were not observed at all by microscopic inspection, and no reboil bubbles were generated. And the effects of the glass melting furnace of the present invention and the heating method thereof were confirmed.

[0055]

According to the glass melting furnace and the heating method of the present invention, it is possible to reliably prevent the backflow phenomenon of the molten glass from the low temperature region to the high temperature region which occurs in the molten glass as described above. It is possible to prevent the generation of bubbles due to the contact between the high-temperature molten glass and the low-temperature molten glass in, and the molten glass after the vitrification reaction can be surely a homogeneous glass product Is played.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a glass melting furnace of the present invention.

2A and 2B are explanatory views of a backflow phenomenon of molten glass; FIG. 2A is a normal state, and FIG. 2B is a backflow generation state.

FIG. 3 is an explanatory view of an example of a glass melting furnace of the present invention.

FIG. 4 is a partial plan view of another glass melting furnace of the present invention.

FIG. 5 is a throat heating electrode described in JP-B-55-116631.

[Explanation of symbols]

10 electrodes 11 Rectifier 12 Voltage converter 13 Conductive material 22 Melting tank 23 Throat 24 working tanks 25 feeder 27 Molding Department a glass raw material layer b molten glass α Normal flow of molten glass β Upflow of molten glass γ Backflow of molten glass δ Velocity distribution of glass flow

Claims (7)

[Claims] 1. A melting tank in which high-temperature molten glass stays for a predetermined time, a throat connected to the melting tank through which the molten glass passes, and a molten glass which is connected to the throat and supplied with the molten glass to lower a predetermined temperature. A glass melting furnace having a working tank for refining the molten glass by allowing the glass to stay for a predetermined time, and a feeder connected to the working tank and supplying the molten glass lowered to a predetermined temperature from the molten glass that has been fined to a forming part. In, the molten glass from the low temperature region to the high temperature region generated in the molten glass of the glass melting furnace having an electrode made of a film-shaped heat-resistant conductive material immersed in the molten glass and a power supply means for energizing the electrode A glass melting furnace, which is provided with a backflow preventing means for preventing the flow of the glass. 2. The glass melting furnace according to claim 1, wherein the backflow preventing means is provided in at least one of a melting tank, a throat, a working tank, and a feeder. 3. The backflow prevention means selectively energizes one or more locations of an electrode made of a film-shaped heat-resistant conductive material lined on any of a furnace side wall, a furnace floor and a furnace ceiling of a glass melting furnace. It is a structure, The glass melting furnace of Claim 2 characterized by the above-mentioned. 4. A molten tank in which high temperature molten glass stays for a predetermined time, a throat connected to the molten tank through which the molten glass passes, and a molten glass connected to the throat and having a temperature lowered to a predetermined temperature are supplied from the molten glass. Glass melting furnace having a working tank for refining the molten glass by allowing the molten glass to stay for a predetermined time, and a feeder connected to the working tank and supplying the molten glass lowered to a predetermined temperature from the molten glass that has been fined to the forming part In the method for heating molten glass in which the molten glass in the glass melting furnace is heated, an electrode made of a film-shaped heat-resistant conductive material disposed in a molten state in the molten glass at a predetermined position of the glass melting furnace. The molten gas is characterized by preventing the flow of the molten glass from the low temperature region to the high temperature region in the molten glass by energizing the glass and locally heating it. Scan method of heating. 5. The temperature of the molten glass in the high temperature region in the glass melting furnace is continuously measured at one or more points, and the temperature is lower than that of the surrounding molten glass caused by the flow of the molten glass from the low temperature region to the high temperature region. The phenomenon is detected, and an electrode made of a film-shaped heat-resistant conductive material is arranged at an upflow generation site that draws the low-temperature molten glass flow under the high-temperature molten glass flow, and the current is locally energized and heated for a predetermined time. The method for heating molten glass according to claim 4, wherein the molten glass is prevented from flowing from a low temperature region to a high temperature region which occurs in the molten glass by suppressing the upward flow of the molten glass. 6. An electrode made of a film-shaped heat-resistant conductive material is provided in at least one position of a melting tank, a throat, a working tank, and a feeder, and is locally energized and heated to change from a low temperature region generated in molten glass to a high temperature. The molten glass heating method according to claim 4 or 5, wherein the molten glass is prevented from flowing into the region. 7. The molten glass is selectively heated by energizing one or more locations of an electrode made of a film-shaped heat-resistant conductive material lined on a furnace side wall, a furnace floor or a furnace ceiling of a glass melting furnace. 7. The method for heating molten glass according to claim 4, wherein the molten glass is prevented from flowing from the low temperature region to the high temperature region.