Melting furnace and method for manufacturing glass article

Abstract

To save energy and improve productivity while avoiding a problem of unmelted glass raw material on a melting furnace.SOLUTION: A melting furnace includes: a feeder 5 for feeding a glass raw material Ga on a molten glass Gb from an upstream side in the melting furnace 1; electrodes 6 for heating the molten glass Gb while being immersed in the molten glass Gb; a discharge port 7 for discharging the molten glass Gb from a downstream side end 1b of the melting furnace 1; and a wall structure 9 for suppressing heat radiation to an upstream side space 10a from a downstream side space 10b in an upper space 10 in the melting furnace 1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a melting furnace for producing molten glass and a method for manufacturing glass articles using the same.

Background Art

[0002] As is well known, glass articles typified by glass plates, glass tubes, glass fibers, etc. are manufactured by shaping molten glass produced by heating and melting glass raw materials in a melting furnace into a predetermined shape.

[0003] For example, Patent Document 1 discloses, as main components provided in a melting furnace, a feeder for supplying glass raw materials onto molten glass, an electrode immersed in the molten glass, and a discharge port for discharging the molten glass to a transfer channel.

[0004] Since this type of melting furnace is configured to directly energize the molten glass from the electrode, electrical energy is required to melt the glass raw materials. From the viewpoints of energy saving and productivity, it is desirable that the electrical energy be as little as possible.

[0005] However, when the electrical energy is insufficient, the glass raw materials may not be sufficiently melted, and unmolten glass raw materials may flow out from the discharge port into the transfer channel, causing a problem of mixing into the formed glass articles.

[0006] Therefore, a technique has been put into practical use in which the liquid level of the molten glass is covered with a layer of glass raw materials, that is, a cold top layer, to melt the glass raw materials while preventing heat radiation from the molten glass.

[0007] When this technique is adopted, in order to solve the above-described problem of unmolten glass raw materials, if an attempt is made to maintain a high temperature of the molten glass, the glass raw materials supplied onto the liquid surface of the molten glass will be melted quickly. Therefore, the cold top layer collapses early, the amount of heat radiation from the molten glass increases, and conversely, a problem of a decrease in the temperature of the molten glass occurs.

[0008] In order to address such problems, Patent Document 2 discloses that water is sprayed onto the glass raw materials supplied onto the liquid surface of the molten glass so that the cold top layer does not collapse prematurely even when the temperature of the molten glass is maintained high.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0010]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] However, according to the method of spraying water on the glass raw materials disclosed in Patent Document 2, part of the electric energy is taken away by the cooling by water, so that extra electric energy is required accordingly. Therefore, it becomes difficult to achieve energy saving and productivity improvement.

[0012] As a result of intensive research, the inventors have found that, in addition to the above problems, new problems as described below occur in this type of melting furnace. That is, FIG. 2 of Patent Document 1 shows a configuration in which a glass raw material is supplied from the upstream end of the melting furnace, and molten glass is discharged from the downstream end of the melting furnace. Further, the same figure of the same document shows a configuration in which the liquid level of the molten glass on the upstream side is covered with a cold top layer (a layer of glass raw material), and the liquid level of the molten glass on the downstream side is exposed.

[0013] With such a configuration, the temperature of the upper space on the upstream side in the upper space inside the melting furnace is relatively low, and the temperature of the upper space on the downstream side is relatively high. As a result, heat in the upper space on the downstream side is radiated to the upper space on the upstream side, causing a situation where the temperature of the upper space on the upstream side rises. When the temperature of the upper space on the upstream side rises in this way, the layer of glass raw material existing on the upstream side is likely to collapse. When the layer of glass raw material collapses, the amount of heat radiation from the molten glass increases, resulting in a decrease in the temperature of the molten glass and making it impossible to appropriately heat and melt the glass raw material.

[0014] From the above viewpoints, an object of the present invention is to avoid the problem of unmolten glass raw material in a melting furnace and to achieve energy saving and improvement in productivity.

Means for Solving the Problems

[0015] (1) A first aspect of the present invention devised to solve the above problems is a melting furnace for heating and melting a glass raw material to produce molten glass, comprising a feeder for supplying the glass raw material onto the molten glass from the upstream end of the melting furnace, an electrode for heating the molten glass, and a discharge port for discharging the molten glass from the downstream end or the downstream bottom of the melting furnace, and characterized by comprising a wall structure for suppressing heat radiation from the downstream space to the upstream space in the upper space inside the melting furnace.

[0016] According to such a configuration, the following effects can be obtained. That is, when a feeder for supplying glass raw materials onto the molten glass is arranged at the upstream end of the melting furnace, in the upper space inside the melting furnace, the temperature of the upstream space decreases due to the supplied low-temperature glass raw materials, and the temperature of the downstream space becomes higher than that of the upstream space. And in the above configuration, since it is provided with a wall structure that suppresses heat radiation (heat escape) from the downstream space to the upstream space, an increase in the temperature of the upstream space and a decrease in the temperature of the downstream space can be suppressed. As a result, most of the liquid surface of the molten glass on the upstream side is covered with a layer of glass raw materials, and a state where most of the liquid surface of the molten glass on the downstream side is not covered with a layer of glass raw materials (the liquid surface is covered with a layer of bubbles or is exposed) can be stably maintained. As a result, the collapse of the layer of glass raw materials is prevented, and a problem that the temperature of the molten glass decreases due to the collapse of the layer of glass raw materials and the glass raw materials cannot be appropriately heated and melted is avoided. Moreover, since the collapse of the layer of glass raw materials is prevented due to the wall structure of the melting furnace, it is not necessary to increase the amount of electricity conducted from the electrode to the molten glass, that is, the electrical energy, additionally. As a result, energy saving and productivity improvement can be achieved. Also, since most of the liquid surface of the molten glass on the downstream side is not covered with a layer of glass raw materials, the problem that unmolten glass raw materials flow out from the discharge port and are mixed into the formed glass article does not occur.

[0017] (2) In the configuration of (1) above, the wall structure may include a partition wall that partitions the upper space into an upstream space and a downstream space.

[0018] In this way, heat radiation from the downstream space to the upstream space can be efficiently and surely suppressed by the partition wall.

[0019] (3) In the configuration of (2) above, when the distance from the upstream end to the downstream end of the upper space is L1 and the distance from the upstream end of the upper space to the partition wall is L2, L2 / L1 may be 0.4 to 0.8.

[0020] In this way, since the partition wall is arranged at an appropriate position, it is advantageous in suppressing the temperature rise of the upstream space.

[0021] (4) In the configuration of (2) or (3) above, the wall structure may have a structure in which the height of the ceiling wall of the melting furnace is higher in the upstream space than in the downstream space.

[0022] In this way, the upstream space becomes larger than the downstream space, and the heat radiation area from the upstream space becomes wider. Therefore, the amount of heat radiated to the outside of the furnace is larger in the upstream space than in the downstream space. As a result, the temperature rise in the upstream space and the temperature drop in the downstream space can be suppressed, so that the collapse of the glass raw material layer can be prevented. Therefore, due to the synergistic effect with the provision of the partition wall, the collapse of the glass raw material layer can be more reliably prevented.

[0023] (5) In the configuration of (4) above, when the distance from the liquid surface of the molten glass to the ceiling wall on the upstream side is H1 and the distance from the liquid surface of the molten glass to the ceiling wall on the downstream side is H2, H2 / H1 may be 0.3 to 0.8.

[0024] In this way, the ratio of the height of the ceiling wall on the upstream side to the ceiling wall on the downstream side becomes appropriate, which is advantageous for suppressing the temperature rise in the upstream space.

[0025] (6) In any of the configurations of (1) to (5) above, an all-electric melting method in which the glass raw material is heated and melted only by electrodes may be adopted.

[0026] In this way, the operational effects of each of the configurations of (1) to (5) above can be effectively enjoyed.

[0027] (7) A second aspect of the present invention devised to solve the above problems is a method for manufacturing a glass article, comprising a melting step of heating and melting a glass raw material using a melting furnace according to any of the configurations of (1) to (6) above to generate molten glass, and a forming step of forming the molten glass discharged from the discharge port of the melting furnace into a predetermined shape.

[0028] According to this manufacturing method, substantially the same operational effects as in each of the configurations (1) to (6) above can be obtained.

Advantages of the Invention

[0029] According to the present invention, in a melting furnace, while avoiding the problem of unmolten glass raw materials, energy saving and productivity improvement can be achieved.

Brief Description of the Drawings

[0030]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0031] Hereinafter, a melting furnace and a method for manufacturing a glass article according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0032] (First Embodiment) FIG. 1 is a longitudinal side view of a melting furnace 1 according to the first embodiment, and FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1. In the following description, the X-X direction shown in FIG. 1 will be described as the upstream and downstream direction, and the Y-Y direction shown in FIG. 2 will be described as the width direction.

[0033] As shown in FIG. 1, the melting furnace 1 according to the first embodiment includes a ceiling wall 2, side walls 3, a bottom wall 4, a feeder 5, electrodes 6, and a discharge port 7.

[0034] The side wall 3 is composed of a front wall 3a located on the upstream side shown in the figure, a rear wall 3b located on the downstream side, a right wall 3c located on one side in the width direction shown in FIG. 2, and a left wall 3d located on the other side in the width direction.

[0035] As shown in FIG. 1, in the melting furnace 1, the glass raw material Ga is heated and melted to produce molten glass Gb. The glass raw material Ga may include cullet in addition to natural raw materials and chemical raw materials.

[0036] The feeder 5 supplies the glass raw material Ga onto the molten glass Gb from the upstream end 1a of the melting furnace 1. In the present embodiment, the part 5b on the supply port 5a side of the feeder 5 is supported by the front wall 3a. The feeder 5 is a screw feeder in the illustrated example, but may be other known feeders such as a pusher or a vibrating feeder. The number of feeders 5 may be one, or a plurality may be arranged in the width direction. Further, in the illustrated example, the supply port 5a of the feeder 5 is located at a position where it has entered the melting furnace 1 from the front wall 3a, but it may also be located at a position where it has not entered the melting furnace 1 from the front wall 3a.

[0037] The electrodes 6 are provided on the bottom wall 4. Specifically, the electrodes 6 are rod-shaped, and a plurality of them are provided on the bottom wall 4. These electrodes 6 are immersed in the molten glass Gb and heat the molten glass Gb by passing an electric current to heat and melt the glass raw material Ga. The electrodes 6 are not limited to the form provided on the bottom wall 4, and may be provided on the side wall 3 (for example, the right wall 3c and the left wall 3d), or may be provided on the ceiling wall 2. The shape of the electrodes 6 is not limited to rod shape, and plate-shaped or block-shaped electrodes may be used.

[0038] The discharge port 7 is provided for discharging the molten glass Gb from the downstream end 1b of the melting furnace 1. Specifically, the discharge port 7 is formed at the lower part (the lower end part in the present embodiment) of the rear wall 3b. A transfer channel 8 is connected to the discharge port 7. The molten glass Gb is continuously discharged from the melting furnace 1 to the transfer channel 8 through the discharge port 7. Note that the discharge port 7 may be formed at the downstream bottom of the melting furnace 1 (for example, the downstream region of the bottom wall 4).

[0039] In the melting furnace 1, most of the liquid surface GL of the molten glass Gb on the upstream side is covered with the layer Gc of glass raw materials, and most of the liquid surface GL of the molten glass Gb on the downstream side is not covered with the layer of glass raw materials.

[0040] In this embodiment, heating means such as a burner for heating and melting the glass raw material Ga is not provided. That is, in this embodiment, an all-electric melting method of heating and melting the glass raw material Ga only by the electrodes 6 is adopted. In the start-up process (the process of raising the temperature of the melting furnace 1 from room temperature to a temperature at which the glass raw material Ga can be melted), a burner may be used.

[0041] As a feature of the wall structure of this melting furnace 1, a partition wall 9 is provided. The partition wall 9 partitions the upper space 10 in the melting furnace 1 into an upstream space 10a and a downstream space 10b. The main surface 9c of the partition wall 9 is perpendicular or substantially perpendicular to the upstream and downstream directions. The partition wall 9 is suspended and supported by the ceiling wall 2. The lower end portion 9b of the partition wall 9 is separated above these without contacting the liquid surface GL of the molten glass Gb and the glass raw material Ga. The separation dimension between the lower end portion 9b of the partition wall 9 and the liquid surface GL of the molten glass is, for example, 50 to 300 mm, preferably 50 to 200 mm.

[0042] From the viewpoints of energy saving and productivity improvement, it is preferable that most of the liquid surface GL of the molten glass Gb facing the upstream space 10a is covered with the layer Gc of glass raw materials. For example, it is preferable that 60% or more of the total area of the liquid surface GL of the molten glass Gb facing the upstream space 10a is covered with the layer Gc of glass raw materials, more preferably 70% or more, even more preferably 80% or more, and most preferably 90% or more. On the other hand, the upper limit can be 100% or less. At least a part of the liquid surface GL of the molten glass Gb facing the upstream space 10a may be covered with a layer of bubbles, or a layer Gc of glass raw materials may be deposited on the layer of bubbles. In this paragraph, the total area means the total area of the liquid surface G of the molten glass Gb facing the upstream space 10a.

[0043] From the perspective of reliably suppressing the problem of the unmolten glass raw material Ga flowing out from the discharge port 7, the liquid level GL of the molten glass Gb facing the downstream space 10b is preferably covered by a bubble layer or exposed without being covered by the layer Gc of the glass raw material for the most part. The liquid level GL of the molten glass Gb facing the downstream space 10b is preferably covered by a bubble layer or exposed for 60% or more of the total area, more preferably 70% or more, even more preferably 80% or more, and most preferably 90% or more. On the other hand, the upper limit can be 100% or less. In this paragraph, the total area means the total area of the liquid level G of the molten glass Gb facing the downstream space 10b.

[0044] The partition wall 9 is formed of an AZS electroformed refractory, an alumina electroformed refractory, an alumina zircon refractory, or an electrofused mullite refractory. It is preferable that the partition wall 9 is formed of an alumina zircon refractory or an electrofused mullite refractory having a lower thermal conductivity than the electroformed refractory. Thereby, the effect of suppressing heat dissipation from the downstream space 10b to the upstream space 10a becomes even greater. The thickness of the partition wall 9 is, for example, 100 to 300 mm, preferably 150 to 300 mm.

[0045] When the distance from the upstream end 10x to the downstream end 10y of the upper space 10 is L1 and the distance from the upstream end 10x of the upper space 10 to the partition wall 9 is L2, L2 / L1 is 0.4 to 0.8. Note that the upstream end 10x of the upper space 10 corresponds to the inner surface of the front wall 3a, and the downstream end 10y of the upper space 10 corresponds to the inner surface of the rear wall 3b. Also, the distance to the partition wall 9 means the distance to the center in the thickness direction of the partition wall 9. The lower limit value of L2 / L1 is preferably more than 0.5. The upper limit value of L2 / L1 is preferably 0.7 or less.

[0046] In this embodiment, the partition wall 9 is disposed above the downstream end Gcx of the glass raw material layer Gc. Note that the partition wall 9 may be disposed above the region upstream of the downstream end Gcx of the glass raw material layer Gc. Further, the partition wall 9 may be disposed above the region downstream of the downstream end Gcx of the glass raw material layer Gc, that is, the region where the liquid surface GL of the molten glass Gb is not covered by the glass raw material layer.

[0047] Also, when the distance from the upstream end 10x to the downstream end 10y of the liquid surface GL of the molten glass Gb is defined as L1, and the distance from the upstream end 10x to the downstream end Gcx of the glass raw material layer Gc is defined as L3, L3 / L1 is 0.4 to 0.8. Note that the upstream end 10x of the liquid surface GL of the molten glass Gb and the upstream end 10x of the glass raw material layer Gc both correspond to the inner surface of the front wall 3a, and the downstream end 10y of the liquid surface GL of the molten glass Gb corresponds to the inner surface of the rear wall 3b. The lower limit value of L3 / L1 is preferably more than 0.5. The upper limit value of L3 / L1 is preferably 0.7 or less.

[0048] According to the melting furnace 1 according to the first embodiment described above, the following operational effects can be obtained.

[0049] In the melting furnace 1, when the feeder 5 for supplying the glass raw material Ga onto the molten glass Gb is disposed at the upstream end portion 1a of the melting furnace 1, in the upper space 10 in the melting furnace, the temperature of the upstream space 10a decreases due to the supplied low-temperature glass raw material Ga. Along with this, the temperature of the downstream space 10b becomes higher than the temperature of the upstream space 10a. In addition, since the partition wall 9 is provided in the melting furnace 1, heat radiation from the downstream space 10b to the upstream space 10a is suppressed. Thereby, an increase in the temperature of the upstream space 10a and a decrease in the temperature of the downstream space 10b are suppressed. For this reason, most of the liquid surface of the molten glass Gb on the upstream side is covered with the glass raw material layer Gc, and a state where most of the liquid surface of the molten glass Gb on the downstream side is not covered with the glass raw material layer can be stably maintained. As a result, the collapse of the glass raw material layer Gc is prevented, and a problem in which the temperature of the molten glass Gb decreases due to the collapse of the glass raw material layer Gc and the glass raw material Ga cannot be appropriately heated and melted is avoided.

[0050] Furthermore, due to the wall structure of providing the partition wall 9, the collapse of the layer Gc of the glass raw material is prevented, so that it is not necessary to additionally increase the amount of electricity conducted from the electrode 6 to the molten glass Gb, that is, the electrical energy. As a result, energy conservation and productivity improvement can be achieved. Also, since most of the liquid surface of the downstream molten glass Gb is not covered by the layer of the glass raw material, there is no problem that the unmelted glass raw material Ga flows out from the discharge port 7 into the transfer channel 8 and is mixed into the glass article to be formed.

[0051] Next, a method for manufacturing a glass article according to the first embodiment will be described.

[0052] This manufacturing method includes a melting step, a discharging step, a transferring step, and a forming step.

[0053] The melting step is a step of heating and melting the glass raw material Ga using the above-described melting furnace 1 to generate the molten glass Gb.

[0054] The discharging step is a step of discharging the molten glass Gb into the transfer channel 8 through the discharge port 7 of the melting furnace 1.

[0055] The transferring step is a step of transferring the molten glass Gb generated in the melting furnace 1 to a forming device (not shown) by the transfer channel 8.

[0056] The forming step is a step of forming a glass article (such as a glass plate, a glass tube, or glass fiber) having a predetermined shape from the molten glass Gb by the forming device.

[0057] (Second Embodiment) FIG. 3 is a longitudinal sectional side view showing the melting furnace 1 according to the second embodiment of the present invention, and FIG. 4 is a sectional view taken along line B - B of FIG. 3.

[0058] As shown in FIGS. 3 and 4, the melting furnace 1 according to this second embodiment is different from the melting furnace 1 according to the aforementioned first embodiment in that, as a wall structure, the height of the ceiling wall 2 of the melting furnace 1 is higher on the upstream side than on the downstream side of the partition wall 9. In this case, when the distance from the liquid level GL of the molten glass Gb to the upstream ceiling wall 2a is H1 and the distance from the liquid level GL of the molten glass Gb to the downstream ceiling wall 2b is H2, H2 / H1 is 0.3 to 0.8. Note that the distance to the upstream ceiling wall 2 means the distance to the uppermost part of the inner surface 2aa of the upstream ceiling wall 2a, and the distance to the downstream ceiling wall 2b means the distance to the uppermost part of the inner surface 2ba of the downstream ceiling wall 2b. The lower limit value of H2 / H1 is preferably 0.4 or more. The upper limit value of H2 / H1 is preferably 0.7 or less.

[0059] In this second embodiment, as shown in FIG. 4, the upstream ceiling wall 2 and the downstream ceiling wall 2 have the same shape (an arch shape with the same curvature). Therefore, only the height of the side wall 3 is different between the upstream side and the downstream side.

[0060] Since the other configurations are the same as those of the aforementioned first embodiment, the components common to both embodiments are denoted by the same reference numerals in FIGS. 3 and 4, and the description thereof is omitted.

[0061] According to the melting furnace 1 according to this second embodiment, the following operational effects can be obtained.

[0062] Since the height of the ceiling wall 2 is higher on the upstream side than on the downstream side of the partition wall 9, the upstream space 10a becomes sufficiently larger than the downstream space 10b, and the heat radiation area from the upstream space 10a becomes wider. Specifically, the areas of the front wall 3a, the right wall 3c, and the left wall 3d of the upstream space 10a are wider than the areas of the rear wall 3b, the right wall 3c, and the left wall 3d of the downstream space 10b. Therefore, the amount of heat radiation to the outside of the furnace is greater in the upstream space 10a than in the downstream space 10b. As a result, the temperature rise in the upstream space 10a and the temperature drop in the downstream space 10b are suppressed, and the collapse of the glass raw material layer Gc can be prevented. Therefore, due to the synergistic effect of providing the partition wall 9, the collapse of the glass raw material layer Gc can be more reliably prevented.

[0063] The method for manufacturing a glass article according to the second embodiment includes a melting step, a discharging step, a transferring step, and a forming step, similar to the method for manufacturing a glass article according to the aforementioned first embodiment. The difference from the aforementioned first embodiment lies only in the configuration of the melting furnace 1 used in the melting step, and the other configurations are the same as those in the aforementioned first embodiment.

[0064] FIG. 5 is a longitudinal side view showing a modified example of the melting furnace 1 according to the second embodiment. The difference between the melting furnace 1 according to this modified example and the aforementioned second embodiment is that the partition wall 9 is not provided as the wall structure. Even in the melting furnace 1 according to such a modified example, since the upstream space 10a becomes sufficiently larger than the downstream space 10b, a certain effect of suppressing the temperature rise in the upstream space 10a can be obtained. For the components common to this modified example and the aforementioned second embodiment, the same reference numerals are given in FIG. 5, and the description thereof is omitted.

[0065] As described above, the embodiments of the present invention have been described, but the embodiments of the present invention are not limited to this, and various modifications can be made without departing from the gist of the present invention.

[0066] For example, in the above embodiment, as a wall structure for suppressing heat radiation from the downstream space 10b to the upstream space 10a, a structure in which a single partition wall 9 is provided is adopted. However, for example, a structure in which a plurality of partition walls are provided may also be used. Alternatively, as a wall structure for suppressing heat radiation from the downstream space 10b to the upstream space 10a, a structure in which the height of the ceiling wall 2 is higher in the upstream space 10a than in the downstream space 10b may be used without using the structure of providing the partition wall 9.

Example

[0067] Hereinafter, an example of the melting furnace according to the present invention will be described. Note that the following examples are merely illustrative, and the present invention is not limited to the following examples at all.

[0068] The example is a melting furnace according to the first embodiment shown in FIGS. 1 and 2 described above, in which a partition wall is provided, and the comparative example is the same melting furnace without a partition wall. Both the example and the comparative example are directed only to the structure above the liquid surface of the molten glass in the melting furnace. Therefore, regarding the wall portion of the melting furnace, the side wall portion located above the liquid surface of the molten glass and the ceiling wall are targeted. In the following description, this side wall portion and the ceiling wall are also collectively referred to as the "upper structure".

[0069] Both the example and the comparative example have the following conditions. The dimension in the width direction inside the melting furnace is 2000 mm, the dimension in the upstream and downstream direction is 5000 mm, and the height dimension from the liquid surface of the molten glass to the inner surface of the ceiling wall is 1000 mm. Also, the entire area of the liquid surface of the molten glass on the upstream side is covered with a layer of glass raw material, and the entire area of the liquid surface of the molten glass on the downstream side is exposed.

[0070] The layer of glass raw materials is the thickest at the upstream end, with the thickness at the upstream end being 150 mm. The layer of glass raw materials is assumed to cover the liquid surface of the molten glass up to the central position in the upstream-downstream direction within the melting furnace. The thickness of the layer of glass raw materials at the central position in the upstream-downstream direction is 10 mm. The layer of glass raw materials linearly changes in thickness from the upstream end to the central position in the upstream-downstream direction. The melting temperature of the glass is 1400 °C. The temperature of the liquid surface of the molten glass is also 1400 °C. The liquid surface of the molten glass means the liquid surface covered by the layer of glass raw materials and the exposed liquid surface.

[0071] Table 1 below shows the physical properties, etc. of the glass raw materials and the molten glass. All these values are described in Non-Patent Document 1 (paper). The flow rate of the molten glass is assumed to be 500 kg / hr, and the corresponding reaction heat (5.65×10 5 J / kg×500 kg / hr÷3600 = 7.85×10 4 W) is evenly absorbed from the glass raw materials (the layer of glass raw materials).

[0072]

Table 1

[0073] As other conditions, the emissivity of the refractory forming the upper structure is 0.5, and the thermal conductivity of the partition wall in the examples is 2 W / (m·K). The thickness of the partition wall is 200 mm. The partition wall is provided at the central position in the upstream-downstream direction of the upper space.

[0074] The heat dissipation conditions of the side wall part and the ceiling wall are as follows. That is, the overall heat transfer coefficient considering the heat insulation effect by the refractory forming the side wall part and the ceiling wall is 7 W / m 2 ·K for the side wall part and 8 W / m 2 ·K for the ceiling wall. The temperature outside the furnace is 50 °C.

[0075] Based on the above conditions, numerical simulations of heat conduction analysis of glass raw materials and radiation heat transfer analysis of the upper space were carried out for the upper structures of the examples and comparative examples respectively. Then, the heat dissipation amount from each upper structure of the examples and comparative examples to the outside of the furnace and the average surface temperature of the glass raw materials (glass raw material layer) were calculated. The calculation results are shown in Table 2 below.

[0076]

Table 2

[0077] According to Table 2 above, in the example compared with the comparative example, the heat dissipation amount from the upper structure to the outside of the furnace is reduced by 38 kW. Thus, it can be understood that the electric energy input into the melting furnace, that is, the electric energy for heating and melting the glass raw materials to produce molten glass, is reduced. Also, according to Table 2 above, it can be understood that in the example compared with the comparative example, the surface temperature of the glass raw materials (glass raw material layer) decreases even without using water cooling or air cooling. Therefore, it can also be understood that the example is advantageous in preventing the collapse of the glass raw material layer compared with the comparative example.

Explanation of Signs

[0078] 1 Melting furnace 1a Upstream end of the melting furnace 1b Downstream end of the melting furnace 2 Ceiling wall 2a Upstream ceiling wall 2b Downstream ceiling wall 3 Side wall 5 Feeder 6 Electrode 7 Discharge port 9 Partition wall 10 Upper space 10a Upstream space 10b Downstream space 10x Upstream end of the upper space 10y Downstream end of the upper space Gb Molten glass Gc Cold top layer GL Liquid level of molten glass

Claims

1. A melting furnace for heating and melting glass raw materials to produce molten glass, comprising: a feeder for supplying the glass raw materials onto the molten glass from an upstream end portion of the melting furnace; an electrode for heating the molten glass; a discharge port for discharging the molten glass from a downstream end portion or a downstream bottom portion of the melting furnace, and a wall structure for suppressing heat radiation from a downstream space to an upstream space in an upper space inside the melting furnace.

2. The melting furnace according to claim 1, wherein the wall structure includes a partition wall partitioning the upper space into the upstream space and the downstream space.

3. When the distance from the upstream end to the downstream end of the upper space is L1 and the distance from the upstream end of the upper space to the partition wall is L2, L2 / L1 is 0.4 to 0.

8.

4. The melting furnace according to claim 1 or 2, wherein the wall structure includes a structure in which the height of the ceiling wall of the melting furnace is higher in the upstream space than in the downstream space.

5. When the distance from the liquid surface of the molten glass to the ceiling wall of the upstream space is H1 and the distance from the liquid surface of the molten glass to the ceiling wall of the downstream space is H2, H2 / H1 is 0.3 to 0.

8.

6. The melting furnace according to any one of claims 1 to 3, wherein an all-electric melting method of heating and melting the glass raw materials only by the electrodes is employed.

7. A method for manufacturing a glass article, comprising: a melting step of heating and melting glass raw materials using the melting furnace according to any one of claims 1 to 3 to produce molten glass; and a forming step of forming the molten glass discharged from the discharge port of the melting furnace into a predetermined shape.

Images