Glass melting furnace and method for manufacturing glass article

Abstract

To improve durability of a side block.SOLUTION: The glass melting furnace (1) includes a side block (22). The side block (22) is divided in the vertical direction, and includes a plurality of refractory bricks (23).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a glass melting furnace and a method for manufacturing a glass article. [Background technology]

[0002] BACKGROUND ART Glass melting furnaces have been used to produce various glass articles such as glass sheets. A glass melting furnace includes a melting tank in which glass raw materials are heated and melted to form molten glass.

[0003] Generally, a glass melting furnace uses a combustion burner to heat the inside of a melting tank. Patent Document 1 discloses a glass melting furnace (hereinafter referred to as an "electric melting furnace") that electrically heats molten glass using electrodes inserted into a melting tank through a bottom wall that constitutes the furnace bottom. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 004138 Summary of the Invention [Problem to be solved by the invention]

[0005] The melting tank of a glass melting furnace has a bottom wall and a plurality of side walls erected on the bottom wall. The bottom wall is sometimes called a bottom block, and the side walls are sometimes called side blocks. Glass melting furnaces are required to further improve the durability of the side blocks. [Means for solving the problem]

[0006] A glass melting furnace according to one aspect of the present invention is a glass melting furnace equipped with a side block, the side block being divided in the vertical direction and made up of a plurality of firebricks.

[0007] Furthermore, a method for producing a glass article in one aspect of the present invention is a method for producing a glass article including a melting step of heating and melting glass raw materials in a glass melting furnace to continuously produce molten glass, and the glass melting furnace in one aspect of the present invention is used as the glass melting furnace. [Effects of the Invention]

[0008] According to one aspect of the present invention, the durability of the side block is improved. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an example of a glass melting furnace according to an embodiment of the present invention. FIG. [Figure 2] 1 is a graph showing the relationship between temperature and thermal expansion coefficient for high-zirconia electroformed bricks. [Figure 3] 1 is a flowchart illustrating an example of a method for manufacturing a glass article according to an embodiment of the present invention. [Figure 4] 1 is a cross-sectional view showing a configuration example of a glass melting furnace in one embodiment of the present invention. [Figure 5] FIG. 2 is a cross-sectional view showing an example of a schematic configuration of a main part of a glass melting furnace in another configuration example of an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described below with reference to the drawings. However, the following description is intended to provide a better understanding of the gist of the invention and does not limit the present invention unless otherwise specified. For the sake of convenience, the drawings referred to in the following description show only the main components necessary for explaining the embodiment in a simplified form, and descriptions of well-known technical matters are omitted as appropriate for brevity. The shapes and dimensions of the components in the drawings do not necessarily reflect the actual shapes and dimensions, and have been changed as appropriate for clarity and simplification of the drawings.

[0011] <1. Outline of glass melting furnace> FIG. 1 is a cross-sectional view showing a schematic configuration of an example of a glass melting furnace according to one embodiment of the present invention (hereinafter referred to as "this embodiment").

[0012] As shown in Fig. 1, a glass melting furnace 1 in this embodiment is configured as an electric melting furnace and includes a melting tank 2 capable of storing molten glass G formed by heating and melting glass raw material F. The glass melting furnace 1 also includes an upper structure 3 covering the top of the melting tank 2, and a support structure (not shown) that supports the melting tank 2, the upper structure 3, and the like.

[0013] The melting tank 2 includes a bottom block 21 as a bottom wall constituting the furnace bottom, and side blocks 22 as side walls constituting the furnace wall. The side blocks 22 may be provided upright on the bottom block 21.

[0014] The upper structure 3 includes, for example, a receiving portion 31 arranged on the side block 22 of the melting tank 2, a breast wall 32 arranged on the receiving portion 31, a soffit receiving portion 33 arranged on the breast wall 32, and a ceiling arch 34 having an arch shape with the center portion curved upward. The upper structure 3 may be a structure generally used in glass melting furnaces, and the specific structure of the upper structure 3 is not particularly limited.

[0015] The receiving portion 31 has a first portion located above the side block 22 and a second portion protruding outward beyond the melting tank 2. Supporting the second portion of the receiving portion 31 reduces the load on the side block 22. The receiving portion 31 may be made of, for example, an electrocast refractory material.

[0016] The breast wall 32 is erected on the side blocks 22 via supports 31, and supports the ceiling arch 34 via sill supports 33. The ceiling arch 34 has a bridging structure (arch structure) and is the ceiling of the superstructure 3. Each part of the superstructure 3 is made of refractories (baked refractories, electrocast refractories, etc.) that have excellent heat resistance and corrosion resistance.

[0017] The melting tank 2 and superstructure 3 are supported by a support structure (not shown). This support structure may be a structure generally used in glass melting furnaces, and the specific structure of the support structure is not particularly limited. For example, the support structure may include a support base that supports the melting tank 2 and a support column that supports the superstructure 3. A receiver 31 and a ledge receiver 33 may each be fixed to the support column via metal fittings or the like.

[0018] <2. Summary of the findings of the invention> In a conventional glass melting furnace (hereinafter, for convenience of explanation, referred to as "conventional glass melting furnace C"), the side blocks of the melting tank 2 are made of long refractory bricks (hereinafter, for convenience of explanation, referred to as "integral long bricks") that extend seamlessly in the height direction from the furnace bottom to the receiving portion 31. This is due to the following cost and operational reasons.

[0019] In other words, the larger the size of the refractory brick, the lower the unit price per size. On the other hand, stacking small-sized refractory bricks is difficult if the joint surfaces are not sufficiently flat, and cutting the refractory bricks further increases costs. Furthermore, since the side blocks are subjected to outward pressure from the molten glass in the glass melting furnace, they are supported by pressing down from the side opposite the surface that comes into contact with the molten glass. Therefore, when stacking small-sized refractory bricks, it is necessary to support each refractory brick in a way that presses it down.

[0020] However, in recent years, because the use of combustion burners such as gas burners to heat molten glass G places a high burden on the environment, there has been a trend toward electric melting furnaces that use electrodes to heat molten glass G. In electric melting furnaces, electrodes may penetrate the bottom wall and be inserted into the melting tank, heating the lower part of the molten glass G.

[0021] In a conventional glass melting furnace C, when molten glass G is heated using a combination of a combustion burner and electrodes, the upper structure 3 is heated together with the molten glass G by the combustion burner, so the temperature difference in the vertical direction of the glass melting furnace C is not very large. On the other hand, in an electric melting furnace, most of the liquid surface of the molten glass G is covered with unmelted glass raw material F, so the temperature difference in the vertical direction of the glass melting furnace C becomes relatively large. Furthermore, if the glass material of the molten glass G is a type with a high melting point (for example, the temperature at which the viscosity η becomes logη = 2.5 is 1400°C or higher), the temperature difference in the vertical direction of the glass melting furnace C becomes even larger. Note that in this specification, the "vertical direction" refers to the direction perpendicular to the liquid surface of the molten glass G, and can also be said to be the vertical direction.

[0022] For example, when the molten glass is a high-melting-point, non-alkali glass, electrocast high-zirconia bricks, which have excellent corrosion resistance, are used for the side blocks. However, in a conventional glass melting furnace C, when the molten glass is non-alkali glass and long, one-piece electrocast high-zirconia bricks are used for the side blocks, cracks may occur in the side blocks, leading to breakage.

[0023] As a result of extensive research, the present inventors have come to the following findings: Figure 2 is a graph showing the relationship between temperature (°C) and thermal expansion coefficient (%) for high zirconia electroformed bricks (HZFC).

[0024] As shown in Figure 2, the thermal expansion coefficient of high-zirconia electroformed bricks increases as the temperature rises up to around 1100°C. When the temperature rises above 1100°C, high-zirconia electroformed bricks exhibit a characteristic behavior in which the thermal expansion coefficient decreases sharply from around 1100°C to around 1200°C. This decrease in the thermal expansion coefficient is due to a phase transition of ZrO2.

[0025] Due to the temperature difference in the vertical direction of the glass melting furnace C as described above, the temperature difference in the vertical direction on the inner wall surface of the side block in contact with the molten glass G becomes large. For example, in an electric melting furnace, if the molten glass is alkali-free glass, the temperature of the molten glass G is approximately 1500°C on the vertical side closer to the bottom wall. Furthermore, glass raw material F, which is currently being melted, may be present on the vertical surface (liquid surface) of the molten glass G, and the temperature near the surface of the molten glass G may be approximately 1000°C. In this case, the side block made of high-zirconia electrocast bricks has a portion where the thermal expansion coefficient changes suddenly in the vertical direction. Therefore, in conventional glass melting furnaces C, internal stress can cause cracks or delamination in the side block. As a result, the side block breaks.

[0026] Therefore, in the glass melting furnace 1 of this embodiment, the side block 22 is divided in the vertical direction (see FIG. 1). The side block 22 has a divided structure divided in the vertical direction and is composed of a plurality of refractory bricks 23. As a result, according to this embodiment, even if a temperature difference occurs between the top and bottom of the side block 22 of the melting tank 2 and thermal stress occurs, the possibility of damage to the side block 22 can be reduced.

[0027] The type of molten glass and the type of material of the side blocks are not limited to the above examples. The relationship between temperature and thermal expansion coefficient of the material of the side blocks is called thermal expansion characteristics. Strong internal stress can occur in the side blocks depending on the temperature difference of the molten glass G in the vertical direction and the thermal expansion characteristics of the material of the side blocks.

[0028] <3. Glass Melting Furnace in One Embodiment> The details of the glass melting furnace 1 in this embodiment will be described below with reference to FIG. 1 again. In this embodiment, an example will be described in which the glass melting furnace 1 is an electric melting furnace (sometimes referred to as a fully electric melting furnace) that uses electrodes to heat the melting tank 2, but the present invention is not limited to this. The glass melting furnace 1 may be configured so that heating is primarily performed using electrodes and supplemented by heating using combustion burners. In this case, the proportion of the heat generated by the electrodes to the total heat generated by the electrodes and burners may be 80% or more, or even 90% or more.

[0029] In the glass melting furnace 1 of this embodiment, an electrode 4 is provided at the bottom (furnace bottom) of the melting tank 2, penetrating the bottom block 21 and protruding into the melting tank 2. The tip of the electrode 4 is in contact with the molten glass G in the melting tank 2. The electrode 4 is connected to a power source (not shown) that applies an AC voltage via an electrode cable. The AC voltage applied to the electrode 4 is then applied to the molten glass G through the electrode 4. As a result, electricity flows through the molten glass G, imparting thermal energy to the molten glass G, which heats the molten glass G. The thermal energy imparted to the molten glass G can be adjusted by adjusting the voltage applied to the electrode 4.

[0030] Electrode 4 may be a rod-shaped electrode, or may be a plate-shaped or block-shaped electrode. Electrode 4 may be provided so as to be movable between an advanced position where it advances from the hearth into melting tank 2 and a retracted position where it retreats from within melting tank 2. Electrode 4 may be made of, for example, molybdenum. A known configuration can be adopted as a specific device structure for heating molten glass G using electrode 4, and therefore detailed description thereof will be omitted.

[0031] The glass melting furnace 1 may also include a feeder (not shown in FIG. 1, see FIG. 4 described later) for continuously feeding glass frit F into the melting tank 2, and a glass discharge path (not shown in FIG. 1, see FIG. 4 described later) for discharging the molten glass G. As the feeder, for example, a screw feeder is used. However, the above configuration is merely an example, and the feeding mechanism for the glass frit F is not limited to the above configuration. For example, a batch charger may be used to feed the glass frit F.

[0032] By heating the molten glass G using the electrodes 4, the frit F on the molten glass G is indirectly heated and melted. The glass melting furnace 1 sequentially heats and melts the frit F continuously supplied onto the surface of the molten glass G by the supply device, and sequentially discharges the molten glass G to the outside of the melting tank 2 through the glass discharge path. This allows the continuous production of molten glass G.

[0033] The molten glass G may be, for example, alkali-free glass or lithium aluminosilicate (LAS)-based glass such as Li2O-Al2O3-SiO3-based glass. Glass raw materials F formulated according to the type of molten glass G are charged into the melting tank 2. Here, "alkali-free glass" refers to glass that is substantially free of alkali components (alkali metal oxides), for example, having an alkali component content of less than 0.1% by mass. LAS-based glass refers to glass with an alkali component content of 10% by mass or less. The type of molten glass G is not particularly limited. Alkali-free glass and LAS-based glass have high melting points (temperatures at which the viscosity η reaches logη = 2.5 are 1400°C or higher). Therefore, if the molten glass G is alkali-free glass or LAS-based glass, the temperature difference between the top and bottom of the glass melting furnace C becomes large, and when integral long bricks are used as side blocks, cracks are likely to occur in the side blocks, leading to breakage. Therefore, if the side blocks 22 have a split structure that is split in the vertical direction, the effect of reducing the possibility of breakage becomes more pronounced.

[0034] The glass melting furnace 1 may be a fully electric melting furnace (fully electric melting furnace) that heats and melts glass raw materials F only by electrode heating, or may be an electric melting furnace that uses both electrode heating and burner combustion to produce molten glass G by heating and melting glass raw materials F mainly using electrodes. The glass melting furnace 1 may be equipped with a burner as a heating element. The burner may be disposed, for example, in the superstructure 3. The burner may be used for starting up the glass melting furnace 1 or may be used during continuous operation. Hydrogen or methane may be used as fuel for the burner, in which case environmental impact can be reduced.

[0035] In particular, when the glass melting furnace 1 is a fully electric furnace that uses only electrode heating to heat the molten glass G, there is no combustion heating by a burner above the molten glass G, so the temperature difference between the top and bottom of the glass melting furnace 1 becomes large. This increases the temperature difference between the top and bottom of the side block 22. In a fully electric furnace, the temperature at the top of the melting tank 2 becomes, for example, 1100°C or lower.

[0036] As described above, the side block 22 has a divided structure divided vertically and is composed of a plurality of refractory bricks 23. The refractory bricks 23 may be, for example, electroformed bricks or fired bricks. Compared to fired bricks, electroformed bricks have lower resistivity and higher corrosion resistance against high-temperature molten glass G. Examples of the electroformed bricks include high-zirconia electroformed bricks such as HZFC and AZS (alumina zirconia silica) electroformed bricks. The high-zirconia electroformed bricks have a zirconia content of, for example, 80% by mass or more.

[0037] The side block 22 may include, as the plurality of refractory bricks 23, a first refractory brick 24 arranged in the upper part of the side block 22 and a second refractory brick 25 arranged in the lower part of the side block 22. The first refractory brick 24 and the second refractory brick 25 may be made of the same material type or different materials.

[0038] The glass melting furnace 1 is continuously operated under a condition in which the supply amount of frit F and the outflow amount of molten glass G are controlled so that the surface of the molten glass G does not exceed the height of the side blocks 22, i.e., the upper ends 22a of the side blocks 22. The portion of the side blocks 22 that comes into contact with the liquid surface of the molten glass G, i.e., the position of the interface between the molten glass G and the atmosphere inside the glass melting furnace 1, is referred to as the glass level GL. Furthermore, a collection of frit F located on the surface of the molten glass G is referred to as a batch, and the position of the surface of the batch in the portion of the side blocks 22 that comes into contact with the batch is referred to as the batch level BL.

[0039] When molten glass G is produced by heating and melting mainly using electrodes 4 (including a full electric melting furnace), most of the liquid surface of the molten glass G is covered with batch or bubbles. Also, a portion of the liquid surface of the molten glass G is covered with bubbles, and the bubbles are covered with batch. The area of ​​the portion covered with batch or bubbles in this manner may be 50% or more, or even 70% or more, of the total area of ​​the liquid surface of the molten glass G. On the other hand, the upper limit of this area may be 100% or less, or may be 90% or less.

[0040] Generally, from the viewpoint of production efficiency of molten glass G, the supply amount of glass raw material F and the outflow amount of molten glass G are controlled so that the glass level GL is located above the side block 22. In the glass melting furnace 1, the dividing position of the side block 22 may be located within a range of 10% to 50% or 10% to 30% of the total height of the side block 22 from the upper end 22a of the side block 22 in the vertical direction. This makes it possible to easily operate the glass melting furnace 1 so that the glass level GL is located between the upper end 22a of the side block 22 and the dividing position. It can also be said that the dividing position of the side block 22 is the position of the contact surface where the first refractory brick 24 and the second refractory brick 25 come into contact with each other.

[0041] In the glass melting furnace 1, for example, when producing molten glass G having an alkali content of 10 mass % or less (such as alkali-free glass), electroformed high-zirconia bricks with excellent corrosion resistance are preferably used as the refractory bricks 23. Here, the electroformed high-zirconia bricks have the thermal expansion characteristics described above.

[0042] In the glass melting furnace 1, even when high-zirconia electrocast bricks are used as the refractory bricks 23, the possibility of breakage can be reduced by dividing the side block 22 into the first refractory brick 24 and the second refractory brick 25. This is for the following reason: For example, the temperature of the first refractory brick 24 can be set to about 1000°C, and the temperature of the second refractory brick 25 in contact with the first refractory brick 24 can be set to about 1200°C. This reduces the possibility of large internal stress occurring in the side block 22 even when the thermal expansion coefficients of the first refractory brick 24 and the second refractory brick 25 are different from each other.

[0043] Furthermore, the temperature of the first refractory bricks 24 located at the upper part of the side block 22, i.e., at the glass level GL, is affected by fluctuations in operating conditions. For example, the first refractory bricks 24 may reach a temperature of 1,100°C or higher due to combustion heating by a burner during start-up of the glass melting furnace 1, which will be described later. Alternatively, the temperature distribution of the first refractory bricks 24 in the vertical direction may change over time due to, for example, vertical fluctuations of the batch line BL, the thickness of the batch, or fluctuations in the glass level GL.

[0044] In the glass melting furnace 1, if the first refractory brick 24 is damaged, it is possible to easily replace only the damaged first refractory brick 24. For example, by lowering the glass level GL to the position of the second refractory brick 25 while supporting the upper structure 3 via the receiving portion 31, it is possible to remove and replace the damaged first refractory brick 24 without having to stop the operation of the glass melting furnace 1. This makes it possible to facilitate maintenance of the side blocks 22.

[0045] The first refractory bricks 24, which are subjected to the temperature fluctuations described above, may have better thermal cycle resistance than the second refractory bricks 25. In this case, it is possible to further reduce the possibility of damage to the first refractory bricks 24. The thermal cycle resistance ΔV is measured by the following method.

[0046] First, a cylindrical refractory brick with an outer diameter of 60 mm and a height of 40 mm at room temperature is prepared as a sample. The refractory brick is held at 600°C for 1 hour, and then heated to 1450°C at a heating rate of 180°C / h. Next, the brick is held at 1450°C for 3 hours, and then cooled to 600°C at a cooling rate of 180°C / h. This series of heat treatments constitutes one cycle, and is repeated 30 times. In the final cycle of the 30 cycles, the temperature is lowered to 600°C, and then held at 600°C for 1 hour, after which the refractory brick is allowed to cool until its temperature returns to room temperature.

[0047] The diameter of the heat-treated sample is measured at four locations at 45° intervals, and the average of four measurements is defined as the outer diameter of the heat-treated sample. The height of the heat-treated sample is measured twice at 90° intervals, and the average of two measurements is defined as the height of the heat-treated sample. For example, a second measurement is performed by measuring the sample height using a measuring device (such as a vernier caliper), then rotating the sample (cylinder) 90° around its central axis while keeping the measuring device in place, and measuring the sample height again.

[0048] Then, the volume of the sample after the heat treatment and the volume of the sample before the heat treatment are calculated. The thermal cycle resistance ΔV is calculated using the following formula (1): Heat cycle resistance ΔV = (volume of sample after heat treatment - volume of sample before heat treatment) / volume of sample before heat treatment × 100 (1) It can be calculated as follows.

[0049] The first refractory brick 24 may have a thermal cycle resistance ΔV of, for example, 40% or less, 20% or less, 10% or less, or 5% or less. When the thermal cycle resistance ΔV of the first refractory brick 24 is 40% or less, the possibility of damage to the side block 22 can be reduced. Furthermore, when the thermal cycle resistance ΔV of the first refractory brick 24 is 20% or less, the possibility of damage to the side block 22 can be further reduced. The lower limit of the thermal cycle resistance ΔV may be, for example, 0% or more, or may be greater than 0%.

[0050] As a firebrick having a heat cycle resistance ΔV of 40% or less, for example, a known high-zirconia electroformed brick can be used. In the confirmation test results, when the heat cycle resistance ΔV was approximately 0% or 1%, no cracks were observed in any of the samples after the heat treatment. For the high-zirconia electroformed brick having a heat cycle resistance ΔV of approximately 0%, the heat treatment was changed from 30 cycles to 60 cycles, and the heat cycle resistance ΔV for the 60 cycles of heat treatment was calculated using the formula (1). As a result, the heat cycle resistance ΔV was 1%. In this case, no cracks were observed in the sample after the heat treatment, and the formation of zircon (ZrSiO4), a zirconium silicate mineral, was not confirmed.

[0051] Refractory bricks with excellent thermal cycle resistance ΔV can be relatively expensive. Therefore, the second refractory brick 25 may have a thermal cycle resistance ΔV of 40% or less, or may have a thermal cycle resistance ΔV of more than 40%. For example, the second refractory brick 25 may have a thermal cycle resistance ΔV of 40% or less, or may have a thermal cycle resistance ΔV of 20% or less.

[0052] For example, the second refractory brick 25 may be a known high-zirconia electroformed brick having a thermal cycle resistance ΔV of more than 40%.

[0053] The second refractory bricks 25 may be formed from a material that is less susceptible to cracking during the cooling process after casting and is easier to manufacture than the first refractory bricks 24. In this case, it is possible to reduce the possibility of cracks occurring in the second refractory bricks 25 when the temperature of the glass melting furnace 1 is rising and while the glass melting furnace 1 is operating within a predetermined temperature range. Therefore, it is possible to reduce the risk of the lifespan of the glass melting furnace 1 being shortened due to damage to the second refractory bricks 25.

[0054] As the refractory bricks 23 having a thermal cycle resistance ΔV of 40% or less, for example, electroformed high-zirconia bricks having a barium oxide (BaO) content of more than 0.5% can be used.

[0055] As described above, to suppress the occurrence of cracks, it is desirable that the temperature difference in the vertical direction of one refractory brick 23 be as small as possible. Therefore, the height of the first refractory brick 24 in the vertical direction may be 150 mm to 600 mm, or 200 mm to 500 mm. Furthermore, the width of the first refractory brick 24, which is the length in the thickness direction of the side wall of the melting tank 2 perpendicular to the vertical direction, may be 30 mm to 500 mm, or 100 mm to 400 mm. From the viewpoint of improving the maintainability of the side block 22 (ease of replacing the first refractory brick 24), the length of the first refractory brick 24 in the depth direction (flow direction D, described below) may be 200 mm to 1,000 mm, or 300 mm to 700 mm.

[0056] In the glass melting furnace 1, the first refractory bricks 24 are stacked on top of the second refractory bricks 25. The joint surfaces of the multiple refractory bricks 23 are preferably formed flat by leveling. The refractory bricks 23 thermally expand as the temperature rises. Therefore, there may be gaps between adjacent refractory bricks 23 in the horizontal direction perpendicular to the vertical direction when they are installed at room temperature. The gaps between adjacent refractory bricks 23 are closed by the thermal expansion of the refractory bricks 23 as the temperature of the glass melting furnace 1 rises.

[0057] Furthermore, side block 22 is subjected to outward pressure by molten glass G in melting tank 2. For this reason, a holding member (not shown) may be provided on the outside of side block 22 to press each refractory brick 23 inward, i.e., the side that comes into contact with molten glass G.

[0058] <4. Manufacturing method of glass article> Next, the method for manufacturing a glass article according to this embodiment will be described below with reference to Fig. 3. Fig. 3 is a flowchart showing an example of the method for manufacturing a glass article according to this embodiment.

[0059] The glass article in this embodiment is manufactured by heating and melting glass raw material F in a glass melting furnace 1 to produce molten glass G, and forming the molten glass G into a predetermined shape. The method for manufacturing the glass article in this embodiment includes a start-up step (step S1) of starting up the glass melting furnace 1 by increasing the temperature inside the glass melting furnace 1, a melting step (step S2) of heating and melting the glass raw material F in the glass melting furnace 1 to continuously produce molten glass G, and a forming step (step S3) of forming the molten glass G.

[0060] In the start-up step, the temperature inside the glass melting furnace 1 is raised from room temperature (for example, 20°C±15°C) to a temperature at which the glass raw material F can be melted (melting temperature).

[0061] In the melting step, frit F is supplied into the glass melting furnace 1, which has been heated to a melting temperature after the start-up step. The frit F may be cullet in part or in whole. After the supply of frit F begins, the frit F supplied into the melting tank 2 is melted one after another. As a result, molten glass G is produced one after another and accumulated in the melting tank 2. As a result, the glass level GL of the molten glass G gradually rises in the melting tank 2. Accordingly, the batch line BL of the batch (a collection of frit F) also gradually rises.

[0062] In the melting step, molten glass G is produced by heating and melting glass frit F mainly using electrodes 4. In the melting step, electrical heating is performed using the electrodes 4 so that the temperature inside the glass melting furnace 1 is maintained at an operating temperature equal to or higher than the temperature at which the glass frit F can be melted. While electrically heating the molten glass G stored in the glass melting furnace 1, glass frit F continuously supplied onto the molten glass G is melted to produce new molten glass G, which is then discharged out of the glass melting furnace 1, thereby continuously producing molten glass G.

[0063] In the method for manufacturing a glass article according to this embodiment, the melting step is performed using glass melting furnace 1, thereby reducing the possibility of damage to side block 22 even in the case where a temperature difference occurs between the top and bottom of side block 22 of melting tank 2, causing thermal stress as described above. Furthermore, because side block 22 is divided vertically and composed of multiple firebricks 23, even if side block 22 is damaged, only the damaged portion can be replaced, making side block 22 easy to maintain.

[0064] Furthermore, as described above, when the molten glass G is produced by heating and melting the glass raw material F mainly using electrodes in the melting step, the temperature difference between the top and bottom of the side block 22 becomes large. Even in such a case, the possibility of damage to the side block 22 can be effectively reduced.

[0065] Furthermore, as described above, when molten glass G having an alkali content of 10 mass % or less is produced in the melting step, the molten glass may be highly corrosive to the side blocks 22. Even in such a case, the possibility of damage to the side blocks 22 can be effectively reduced.

[0066] In the method for manufacturing a glass article according to this embodiment, a burner may be used in starting up (start-up step) of glass melting furnace 1. Electrode 4 may be positioned in a retracted position, and then covered from above with a glass plate or cullet placed on bottom block 21 in melting tank 2 to protect electrode 4. After the glass plate or cullet is melted as the temperature in melting tank 2 rises in the melting step, electrode 4 can be inserted into the current-carrying position.

[0067] When burner combustion is used in the start-up step, the melting step may be performed as follows: First, the glass level GL reaches a preset reference position, and the electrical resistivity of the molten glass G becomes lower than the electrical resistivity of the bottom block 21 and the side block 22 as the temperature rises, and then electrical heating by the electrodes 4 may be started.

[0068] When the glass level GL of the molten glass G reaches the reference position and the temperature in the glass melting furnace 1 becomes approximately uniform at the operating temperature, the burner is stopped and electrical heating is started, so that the melting process can be carried out while maintaining the temperature in the glass melting furnace 1.

[0069] After the start of continuous production of molten glass G, the thermal energy imparted to the molten glass G in the melting tank 2 may be generated only by the electrode 4, which reduces the possibility of an increase in the moisture content of the molten glass G in the melting tank 2. As a result, the moisture content of the resulting glass article can be reduced. Furthermore, greenhouse gas emissions can be reduced, and the energy required to melt the glass raw material F can be reduced.

[0070] In a forming step, the molten glass G discharged out of the glass melting furnace 1 is formed in a forming furnace (not shown) provided downstream of the glass melting furnace 1. In this way, a glass article is manufactured using the molten glass G.

[0071] The glass article according to this embodiment is not particularly limited, and this embodiment can be applied to the manufacture of glass articles for various known applications. The glass article may be, for example, a glass plate, a glass tube, or a glass fiber. When the molten glass is alkali-free glass and a glass plate is formed by the overflow method, the float method, the slit method, or the like, the resulting glass plate as a glass article is suitable as a glass substrate for a display. When the molten glass is aluminosilicate glass and a glass plate is formed by the overflow method, the float method, the slit method, or the like, the resulting glass plate as a glass article is suitable as a cover glass for chemical strengthening. Furthermore, when the molten glass is LAS-based glass and a glass article is formed by the float method, the press method, or the roll-out method, a glass article made of crystallized glass having excellent heat resistance and thermal shock resistance is obtained. This glass article is suitable as a top plate for a cooking appliance, a stove window, a fire window, or the like.

[0072] <5. Other configurations> Fig. 4 is a cross-sectional view showing an example of the configuration of the glass melting furnace 1 in this embodiment. In Fig. 4, for clarity of illustration, the structure of the upper structure 3 and the like in the glass melting furnace 1 is shown in a simplified form. Furthermore, the cross section shown in Fig. 4 may or may not be parallel to the cross section shown in Fig. 1. For example, the cross section taken along line II shown in Fig. 4 may correspond to the cross section shown in Fig. 1.

[0073] 4, frit material F is introduced into one longitudinal side of the glass melting furnace 1, and molten glass G is discharged from the other longitudinal side. Specifically, assuming that the flow direction of frit material F is flow direction D, a feeder 6 for supplying frit material F to the melting tank 2 is located upstream of flow direction D, and a glass discharge path 7 for continuously discharging molten glass G from the melting tank 2 is located downstream of flow direction D. The glass discharge path 7 may be in communication with the interior of the melting tank 2 via, for example, an opening 25a formed in a part of a second refractory brick 25 located downstream of flow direction D.

[0074] The feeder 6 may be, for example, a screw feeder, and a plurality of feeders may be provided. The glass frit F is fed from the feeder 6 into the melting tank 2 above the side block 22 located upstream in the flow direction D, for example, through an opening 35a formed in the back wall 35. The feed rate of the glass frit F can be adjusted by controlling the feeder 6. For example, the feed rate of the glass frit F and the discharge rate of the molten glass G can be adjusted so that the glass level GL is in contact with the first refractory brick 24.

[0075] [Another configuration example] FIG. 5 is a cross-sectional view showing an example of a schematic configuration of a main part of a glass melting furnace 1 in another configuration example of this embodiment.

[0076] As described above, the side block 22 may be divided into at least two parts, and in the example shown in Figure 1, the side block 22 is divided into an upper part including the first refractory bricks 24 and a lower part including the second refractory bricks 25.

[0077] As shown in Fig. 5, in the glass melting furnace 1, the first refractory brick 24 may be divided into a plurality of pieces in the vertical direction. This can further reduce the possibility of damage to the side block 22 even in the case where a temperature difference occurs between the top and bottom of the side block 22 of the melting tank 2, causing thermal stress. Furthermore, when the first refractory brick 24, which is the upper refractory brick 23 of the glass melting furnace 1, is damaged, only the upper refractory brick 23, that is, the first refractory brick 24, needs to be replaced. In this case, the first refractory brick 24 to be replaced can be made smaller, making it easier to maintain the side block 22.

[0078] 5, in the glass melting furnace 1, the second refractory brick 25 may be divided into a plurality of pieces in the vertical direction. This makes it easier to replace only the damaged second refractory brick 25 when the second refractory brick 25 is damaged. This makes it easier to maintain the side block 22.

[0079] 〔summary〕 The glass melting furnace according to the first aspect of the present invention includes a side block 22. The side block 22 is divided in the vertical direction and is made up of a plurality of refractory bricks 23.

[0080] The glass melting furnace 1 according to a second aspect of the present invention may be configured such that, in the first aspect, the plurality of refractory bricks 23 are high-zirconia electroformed bricks.

[0081] The glass melting furnace 1 according to a third aspect of the present invention is the same as in the first or second aspect, wherein the plurality of refractory bricks 23 may include a first refractory brick 24 arranged in the upper part of the side block 22 and a second refractory brick 25 arranged in the lower part of the side block 22. The dividing position of the side block 22 may be located within a range of 10% to 50% of the total height of the side block 22 from the upper end 22a of the side block 22 in the vertical direction.

[0082] The glass melting furnace 1 according to aspect 4 of the present invention is any one of aspects 1 to 3, wherein the plurality of refractory bricks 23 include a first refractory brick 24 arranged on the upper part of the side block 22 and a second refractory brick 25 arranged on the lower part of the side block 22, and the first refractory brick 24 may have better heat cycle resistance than the second refractory brick 25.

[0083] The glass melting furnace 1 according to a fifth aspect of the present invention may be configured as in the third or fourth aspect, wherein the second refractory brick 25 is divided into a plurality of pieces in the vertical direction.

[0084] The glass melting furnace 1 according to a sixth aspect of the present invention is any one of the third to fifth aspects, wherein the heat cycle resistance of the first refractory bricks 24 may be 40% or less.

[0085] A method for producing a glass article according to a seventh aspect of the present invention is a method for producing a glass article, comprising a melting step of heating and melting glass raw material F in a glass melting furnace to continuously produce molten glass G, and the glass melting furnace 1 according to any one of the first to sixth aspects of the present invention is used as the glass melting furnace.

[0086] A manufacturing method of a glass article according to an eighth aspect of the present invention is the method of the seventh aspect, wherein the melting step may produce molten glass G by heating and melting mainly using electrodes 4.

[0087] A ninth aspect of the present invention relates to the method for producing a glass article of the seventh or eighth aspect, wherein the melting step may produce molten glass G having an alkali content of 10 mass % or less.

[0088] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in the above description are also included in the technical scope of the present invention. [Explanation of symbols]

[0089] 1. Glass melting furnace 2 Melting tank 4 electrodes 22 Side block (side wall) 22a top end 23 Firebrick 24 First refractory brick 25 Secondary refractory brick

Claims

1. A glass melting furnace equipped with a side block, The side blocks are divided vertically and are made up of a plurality of refractory bricks.

2. 2. The glass melting furnace according to claim 1, wherein the plurality of refractory bricks are high zirconia electroformed bricks.

3. the plurality of refractory bricks include a first refractory brick disposed on an upper portion of the side block and a second refractory brick disposed on a lower portion of the side block; 2. The glass melting furnace according to claim 1, wherein the dividing position of the side block is located within a range of 10% to 50% of the total height of the side block from the upper end of the side block in the vertical direction.

4. the plurality of refractory bricks include a first refractory brick disposed on an upper portion of the side block and a second refractory brick disposed on a lower portion of the side block; 2. The glass melting furnace according to claim 1, wherein the first refractory brick has better thermal cycle resistance than the second refractory brick.

5. 5. The glass melting furnace according to claim 3, wherein the second refractory brick is divided into a plurality of pieces in the vertical direction.

6. 5. The glass melting furnace according to claim 3, wherein the first refractory brick has a thermal cycle resistance ΔV of 40% or less.

7. A method for producing a glass article, comprising a melting step of heating and melting glass raw materials in a glass melting furnace to continuously produce molten glass, A method for manufacturing a glass article, wherein the glass melting furnace according to any one of claims 1 to 4 is used as the glass melting furnace.

8. The method for producing a glass article according to claim 7 , wherein in the melting step, the molten glass is produced by heating and melting mainly using electrodes.

9. The method for producing a glass article according to claim 7 , wherein the melting step produces molten glass having an alkali content of 10 mass % or less.

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