Heating furnace and method for manufacturing glass products

Abstract

To extend a life of a heat generator.SOLUTION: A heating furnace (11) includes: a heat generator (21) being energized to generate heat; and an air supply / exhaust system (30) for regulating an internal atmosphere of the heating furnace (11).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a heating furnace and a method for manufacturing glass products.

Background Art

[0002] In the manufacturing process of glass products, a heating furnace is used to melt the glass material or maintain the molten state of the glass material. Heating using an electric heating element can be performed to increase or maintain the temperature inside the heating furnace.

[0003] As the electric heating element, for example, as shown in Patent Document 1, a heating element having a heating portion and a terminal portion, a base material containing 70 wt% or more of MoSi2, and an oxide layer containing crystals formed on the surface of the terminal portion is used.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, a heating element that generates heat by being energized and is installed inside a heating furnace may need to be replaced when a part of the heating element deteriorates or is damaged. Even when using a heating element having an oxide layer like the heating element described in Patent Document 1, it has not been easy to suppress deterioration or damage.

[0006] One aspect of the present invention aims to extend the life of the heating element.

Means for Solving the Problems

[0007] A heating furnace according to one aspect of the present invention includes a heating element that generates heat by being energized and an air supply and exhaust system that adjusts the atmosphere inside the heating furnace.

[0008] According to the above configuration, since the atmosphere in the heating furnace is adjusted by supply and exhaust of gas, the concentration of substances that can adversely affect the heating element in the atmosphere can be reduced. Thereby, the life of the heating element can be extended.

[0009] In the heating furnace according to one aspect of the present invention, the heating element is made of a material containing silicon. According to this configuration, the life of the heating element made of a material containing silicon can be extended.

[0010] In the heating furnace according to one aspect of the present invention, the heating element is made of a material containing molybdenum disilicide or silicon carbide. According to this configuration, the life of the heating element made of a material containing molybdenum disilicide or silicon carbide can be extended.

[0011] The heating furnace according to one aspect of the present invention is a heating furnace for heating a glass material. According to this configuration, the concentration of substances that can adversely affect the heating element in the atmosphere in the heating furnace, which are contained in the glass material, can be reduced.

[0012] In the heating furnace according to one aspect of the present invention, the supply and exhaust system includes a gas supply device and / or an exhaust device that supply and exhaust the atmosphere in the heating furnace, a measuring device that measures the concentration of fluorine and / or boron in the atmosphere in the heating furnace, and a control device that controls the gas supply device and / or the exhaust device based on the measurement result by the measuring device.

[0013] According to the above configuration, the gas supply device and / or the exhaust device can be controlled based on the measurement result of the fluorine and / or boron concentration in the heating furnace, and the atmosphere in the heating furnace can be adjusted. Thereby, the concentration of fluorine and / or boron in the atmosphere in the heating furnace can be reduced, and the life of the heating element can be extended.

[0014] The manufacturing method of a glass product according to one aspect of the present invention includes a step of heating a glass material in a heating furnace equipped with a heating element that generates heat by energization, and a step of supplying and exhausting the atmosphere in the heating furnace.

[0015] According to this method, since the atmosphere in the heating furnace is adjusted by supplying and exhausting air, it is possible to reduce the concentration in the atmosphere of substances contained in the glass material that can have an adverse effect on the heating element. Thereby, the life of the heating element can be extended.

[0016] In the manufacturing method of a glass product according to one aspect of the present invention, the glass raw material contains fluorine or boron. With this configuration, it is possible to reduce the concentration of fluorine or boron in the atmosphere in the heating furnace. Thereby, the life of the heating element can be extended.

[0017] In the manufacturing method of a glass product according to one aspect of the present invention, the heating element is composed of a material containing molybdenum disilicide, and by the step of supplying and exhausting the atmosphere in the heating furnace, in the heating furnace, 70 mg / m 3 The following fluorine concentration conditions and / or 200 mg / m 3 The following boron concentration conditions are satisfied.

[0018] A heating element composed of a material containing molybdenum disilicide may be deteriorated by fluorine or boron. With the above configuration, by supplying and exhausting air in the heating furnace, the fluorine concentration and / or boron concentration in the atmosphere in the furnace can be maintained below the above concentrations, and the life of the heating element can be extended.

[0019] In the manufacturing method of a glass product according to one aspect of the present invention, the heating element is composed of a material containing silicon. With this configuration, the life of the heating element composed of a material containing silicon can be extended.

Effects of the Invention

[0020] According to the present invention, the life of the heating element can be extended.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0022] Hereinafter, one aspect of the present invention will be described with reference to the accompanying drawings.

[0023] 〔Embodiment〕 <Configuration of Melting Furnace 11 (Heating Furnace)> FIG. 1 is a schematic diagram showing the configuration of a melting furnace 11 as an exemplary heating furnace according to the present embodiment. The melting furnace 11 is a heating furnace used to heat and melt a glass material. That is, the melting furnace 11 can be used as a heating furnace for manufacturing glass products. Examples of such glass products include sheet glass, glass fiber, and the like.

[0024] As shown in FIG. 1, the melting furnace 11 includes a melting tank 20, a heating element 21 that generates heat by energization, and an air supply and exhaust system 30 that adjusts the atmosphere in the melting tank 20. The melting tank 20 is a tank that heats a glass material M to molten glass G, and the heating element 21 is provided in the melting tank 20. The air supply and exhaust system 30 is a system that adjusts the atmosphere in the melting tank 20, and includes a gas supply device 31, an exhaust device 32, a measuring device 33, and a control device 34. A plurality of heating elements 21 may be provided in the melting tank 20 as necessary.

[0025] That is, the melting furnace 11 is a facility for implementing a method for manufacturing a glass product, which includes a step of heating a glass raw material in a melting tank 20 provided with a heating element 21 that generates heat by energization, and a step of supplying and exhausting air to and from the atmosphere in the melting tank 20.

[0026] The heating element 21 is, for example, a resistance heating element that generates Joule heat upon energization to generate heat. The heating element 21 is suspended from the ceiling of the melting tank 20 and heats the atmosphere inside the melting tank 20. Examples of the type of the heating element 21 include a molybdenum disilicide heating element, a nickel-chromium based heating element, a silicon carbide heating element, a graphite heating element, and in addition, an iron-chromium-aluminum based heating element, a molybdenum heating element, a tungsten heating element, a platinum heating element, a zirconia heating element, a lanthanum chromite heating element, and the like. The heating element 21 may be composed of a material containing silicon. In particular, the heating element 21 may be composed of a material containing molybdenum disilicide or silicon carbide.

[0027] Normally, a heating furnace heated by an electric heating element does not have an air supply and exhaust system in order to maintain the temperature inside the furnace. The melting furnace 11 according to one aspect of the present invention is provided with an air supply and exhaust system in a heating furnace provided with a heating element, thereby enabling adjustment (reduction) of the concentration of components in the atmosphere inside the furnace that can adversely affect the life of the heating element. Since the atmosphere inside the melting tank 20 is adjusted by air supply and exhaust, the concentration of substances in the atmosphere that can adversely affect the heating element can be reduced.

[0028] Among the various types of heating elements exemplified above, a heating element composed of a material containing silicon forms a dense glassy protective layer around the heating element at the operating temperature and exhibits high oxidation resistance at high temperatures. However, there have been cases where a part of the heating element 21 that heats the atmosphere inside the melting tank 20 deteriorates or is damaged within a service time shorter than the assumed life. The heating element composed of a material containing silicon is specifically a heating element composed of a material containing molybdenum disilicide or silicon carbide.

[0029] As a result of intensive studies, the present inventors have obtained the knowledge that this phenomenon may be caused by fluorine and / or boron volatilized from the glass melt into the atmosphere adversely affecting such a protective layer.

[0030] In the melting furnace 11 of this embodiment, since the atmosphere in the melting tank 20 is adjusted by air supply and exhaust, the concentration of fluorine and / or boron in the atmosphere of the melting furnace 11 can be adjusted. Thereby, the life of the heating element 21 made of a silicon-containing material can be extended.

[0031] The melting tank 20 has an internal space for melting the glass material, and molten glass is generated in the internal space. The wall portion of the melting tank 20 is composed of, for example, a refractory. The inner wall of the melting tank 20 may be lined with platinum or a platinum alloy to prevent corrosion at high temperatures inside. The melting tank 20 is provided with an inlet 22 for charging the glass material M. A belt conveyor 50 or the like as a conveying means is installed at the inlet 22, and the glass material M supplied from the hopper 51 as a raw material supply means is charged into the melting tank 20 by the belt conveyor 50. As the conveying means, a screw charger may be used in addition to the belt conveyor 50. The glass material M may contain, for example, SiO2, Al2O3, B2O3, CaO, MgO, Na2O, K2O, F2 as components. Recycled glass may be used as the glass material M.

[0032] The glass material M charged into the melting tank 20 is generally heated to 1000 °C or higher by radiant heat from the heating element 21 or a gas burner (not shown), and undergoes a vitrification reaction to become a flowable molten glass G. The molten glass G is sent to the forebay 60 connected to the side of the melting tank 20. The molten glass G sent to the forebay 60 then passes through a feeder (not shown) or the like and is sent to the forming process. Then, it is processed into a predetermined product shape by a forming device or the like, and then cooled to become various glass products.

[0033] The gas supply device 31 is a device that supplies gas to the melting tank 20. The gas may include high-temperature air and combustible gas. As the combustible gas, for example, city gas or natural gas can be used. The gas supplied from the gas supply device 31 is supplied into the internal space of the melting tank 20 through the air supply passage 41 and the gas supply port 23 provided on the upper wall or side wall of the melting tank 20. The temperature of the gas supplied from the gas supply device 31 is preferably 1000 °C or higher in order to maintain the temperature inside the melting tank 20.

[0034] The exhaust device 32 can be provided in the exhaust passage 42 for discharging the atmosphere inside the melting tank 20 to the outside. As the exhaust device 32, for example, a well-known fan can be used. As another embodiment of the exhaust device 32, the atmosphere can also be discharged by utilizing the draft effect of a chimney. That is, the gas supply device 31 and / or the exhaust device 32 supply and exhaust the atmosphere inside the melting tank 20.

[0035] The measuring device 33 is a device that measures the fluorine concentration and / or boron concentration in the atmosphere inside the melting tank 20. The fluorine concentration may be measured, for example, by collecting a sample from the exhaust passage 42 and using the lanthanum-alizarin complexone absorption photometry (JIS K0105(2012)). The boron concentration may be measured, for example, by collecting a sample from the exhaust passage 42 and using the ICP emission spectroscopy (JIS K0081(2012)). Alternatively, it may be continuously measured using a fluorine concentration measuring device and / or a boron concentration measuring device that can be provided in the exhaust passage 42.

[0036] The control device 34 is a device that controls the gas supply device 31 and the exhaust device 32. The control device 34 can control the amount of air supplied into the melting tank 20 by controlling the gas supply device 31. Further, the control device 34 can control the amount of exhaust from the melting tank 20 by controlling the exhaust device 32. More specifically, the control device 34 can control the gas supply device 31 and the exhaust device 32 based on the measurement results of the fluorine concentration and / or boron concentration measured by the measuring device 33.

[0037] Note that the air supply and exhaust system 30 shown in FIG. 1 includes a gas supply device 31, an exhaust device 32, a measuring device 33, and a control device 34, but it may include only at least one of the gas supply device 31 and the exhaust device 32.

[0038] In this embodiment, an example is shown in which the heating furnace of the present invention is a glass melting furnace that heats a glass material, but the heating furnace according to the present invention is not limited to a glass melting furnace. For example, it may be a heating furnace that heats and / or melts raw materials other than glass.

[0039] The heating element 21 can be installed not only in the melting tank 20 but also in the forebay 60, the feeder, or other heating furnaces. In this case, these heating furnaces may each be provided with an air supply and exhaust system similar to the air supply and exhaust system 30 described above.

[0040] <Control Example 1> Hereinafter, with reference to FIG. 2, an example of the process (method for adjusting the atmosphere in the melting tank 20) by the control device 34 will be described. FIG. 2 is a flowchart showing the process by an exemplary control device 34. When energization of the heating element 21 is started and heating of the glass material in the melting furnace 11 is started, a series of processes in the flowchart shown in FIG. 2 are executed by the control device 34.

[0041] As shown in FIG. 2, when heating of the glass material is started in the melting furnace 11, the control device 34 controls the gas supply device 31 and the exhaust device 32 to start air supply and exhaust (step S11). In step S11, the control device 34 may control only the gas supply device 31 to start air supply. In this case, the exhaust may be performed naturally through the exhaust flow path 42.

[0042] When the supply and exhaust of gas start in step S11, the control device 34 controls the measuring device 33 to measure the concentration of the target substance based on the measurement schedule (step S12). The target substance is fluorine and / or boron. The target substance to be measured can be set to only fluorine, fluorine and boron, or only boron, depending on components contained in the glass material or the like. Regarding the measurement schedule, the interval between measurements can be arbitrarily set, such as 1 second, 10 seconds, 1 minute, 10 minutes, 1 hour, 24 hours, 10 days, 1 month, etc.

[0043] When the concentration of the target substance is measured by the measuring device 33, the control device 34 determines whether the concentration of the target substance exceeds a threshold value (step S13). In step S13, the threshold value (upper limit value) of the fluorine concentration can be set to, for example, 70 mg / m 3 and the threshold value (upper limit value) of the boron concentration can be set to 200 mg / m 3 .

[0044] When the concentration of the target substance exceeds the threshold value (S13: YES), the control device 34 controls the gas supply device 31 and the exhaust device 32 to increase the supply and exhaust volume (step S14). Thereby, the fluorine concentration and the boron concentration in the atmosphere in the melting tank 20 can be maintained below the above-mentioned threshold values. In step S14, the control device 34 may control only the gas supply device 31 and increase the supply and exhaust volume by increasing the air supply volume. In this case, the exhaust can be performed naturally through the exhaust flow path 42.

[0045] When the heating element 21 is a molybdenum disilicide heating element or a silicon carbide heating element, when the fluorine concentration exceeds 70 mg / m 3 , the fluorine may reduce the viscosity of the protective layer formed around the heating element at the operating temperature. By maintaining the fluorine concentration below 70 mg / m 3 , the influence of fluorine on the protective layer of the heating element can be reduced. Thereby, the life of the heating element can be extended. Since the lower the fluorine concentration, the smaller the influence of fluorine on the protective layer of the heating element, the fluorine concentration is 50 mg / m 3By maintaining the following, the life of the heating element can be further extended.

[0046] When the temperature of the heating element 21 drops, boron can aggregate on the surface of the heating element as boric acid. Boric acid can deteriorate the surface of the heating element 21. When the boron concentration is 200 mg / m 3 By maintaining the following, the possibility of deteriorating the surface of the heating element 21 as described above can be reduced. Thereby, the life of the heating element 21 can be extended. Note that since the lower the boron concentration, the more the aggregation of boron as boric acid can be suppressed, when the boron concentration is 150 mg / m 3 By maintaining the following, the life of the heating element can be extended even more.

[0047] In addition, when measuring both the fluorine concentration and the boron concentration, the control device 34 may execute step S14 when either concentration exceeds the threshold value. In this case, which threshold value the control device 34 uses as a reference for controlling the supply and exhaust air volume can be arbitrarily determined depending on the concentration of each component contained in the glass material. Alternatively, the control device 34 may execute step S14 when both the fluorine concentration and the boron concentration exceed the threshold value.

[0048] Subsequently, the control device 34 determines whether or not the heat treatment of the glass material in the melting tank 20 has been completed (step S15). When the heat treatment has been completed (S15: YES), the control device 34 completes the adjustment process of the atmosphere in the melting tank 20. When the heat treatment has not been completed (S15: NO), the control device 34 returns to the process of S12.

[0049] Also, in step S13, when the target substance concentration does not exceed the threshold value (S13: NO), the control device 34 determines whether or not the supply and exhaust air volume exceeds a reference value (S16). The reference value can be set as a standard value required to replace the atmosphere in the melting tank 20.

[0050] When the supply and exhaust volume exceeds the reference value (S16: YES), the control device 34 controls the gas supply device 31 and the exhaust device 32 to reduce the supply and exhaust volume (step S17). This suppresses excessive supply and exhaust and can improve the energy-saving effect. Thereafter, the control device 34 proceeds to the process of S15.

[0051] When the supply and exhaust volume does not exceed the reference value in step S16 (S16: NO), the control device 34 returns to the process of S12.

[0052] By the control device 34 performing the process as in Control Example 1, the atmosphere in the melting tank 20 can be adjusted so that the fluorine concentration and / or the boron concentration in the melting tank 20 do not exceed the upper limit value. Thereby, the life of the heating element 21 can be extended.

[0053] <Control Example 2> Hereinafter, with reference to FIG. 3, another example of the process (method for adjusting the atmosphere in the melting tank 20) by the control device 34 will be described. FIG. 3 is a flowchart showing the process by an exemplary control device 34. When energization of the heating element 21 is started and heating of the glass material in the melting furnace 11 is started, a series of processes of the flowchart shown in FIG. 3 are executed by the control device 34.

[0054] As shown in FIG. 3, when heating of the glass material is started in the melting furnace 11, the control device 34 controls the measuring device 33 to start monitoring the fluorine concentration and / or the boron concentration (step S21). Note that this monitoring includes monitoring at arbitrarily set intervals such as 10 minutes, 1 hour, 24 hours, 1 day, 1 month, etc., or continuous monitoring.

[0055] The control device 34 determines whether the target object concentration exceeds the upper limit value (step S22). In step S22, the upper limit value of the fluorine concentration can be set to, for example, 70 mg / m 3 and the upper limit value of the boron concentration can be set to 200 mg / m 3

[0056] ​ If the target object concentration exceeds the upper limit value in step S22 (S22: YES), the control device 34 controls the gas supply device 31 and the exhaust device 32 to start air supply and exhaust (step S23). When measuring both the fluorine concentration and the boron concentration, the control device 34 may execute step S23 when either concentration exceeds the threshold value. In this case, which threshold value the control device 34 uses as a reference for controlling the increase in the air supply and exhaust volume can be arbitrarily determined according to the concentration of each component contained in the glass material. Alternatively, the control device 34 may execute step S23 when both the fluorine concentration and the boron concentration exceed the threshold value.

[0057] Next, the control device 34 determines whether the target object concentration exceeds the lower limit value (whether it is less than the lower limit value) (step S24). If the target object concentration is less than the lower limit value (S24: YES), the control device 34 controls the gas supply device 31 and the exhaust device 32 to stop air supply and exhaust.

[0058] Subsequently, the control device 34 determines whether the heat treatment of the glass material in the melting tank 20 has been completed (step S26). If the heat treatment has been completed (S26: YES), the control device 34 completes the adjustment process of the atmosphere in the melting tank 20. If the heat treatment has not been completed (S26: NO), the control device 34 returns to the process of S22.

[0059] In step S22, if the target object concentration does not exceed the upper limit value (S22: NO), the control device 34 proceeds to the process of step S24.

[0060] In step S24, if the target object concentration is not less than the lower limit value (S24: NO), the control device 34 proceeds to the process of step S26.

[0061] By the control device 34 performing the process as in Control Example 2, air supply and exhaust can be performed only when necessary, and the energy saving effect is improved. Thereby, it can contribute to the achievement of the sustainable development goals (SDGs).

[0062] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

Explanation of Reference Numerals

[0063] 11 Melting furnace (heating furnace) 20 Melting tank 21 Heating element 30 Air supply and exhaust system 31 Gas supply device 32 Exhaust device 33 Measuring device 34 Control device

Claims

1. A heating furnace, comprising a heating element that generates heat by energization, and an air supply and exhaust system for adjusting the atmosphere inside the heating furnace, wherein the air supply and exhaust system includes a gas supply device and / or an exhaust device for supplying and exhausting air to and from the atmosphere inside the heating furnace, a measuring device for measuring the concentration of fluorine and / or boron in the atmosphere inside the heating furnace, and a control device for controlling the gas supply device and / or the exhaust device based on the measurement result by the measuring device.

2. The heating furnace according to claim 1, wherein the heating element is made of a material containing silicon.

3. The heating furnace according to claim 2, wherein the heating element is made of a material containing molybdenum disilicide or silicon carbide.

4. The heating furnace according to any one of claims 1 to 3, wherein the heating furnace is for heating a glass material.

5. In a heating furnace equipped with a heating element that generates heat by energization, a step of heating a glass material, a step of supplying and exhausting air to and from the atmosphere inside the heating furnace, a step of measuring the concentration of fluorine and / or boron in the atmosphere inside the heating furnace, and a step of controlling the amount of air supply and exhaust of the atmosphere inside the heating furnace based on the measurement result of the concentration of fluorine and / or boron.

6. The method for manufacturing a glass product according to claim 5, wherein the glass material contains fluorine or boron.

7. The heating element is made of a material containing molybdenum disilicide, and by the step of supplying and exhausting air to and from the atmosphere inside the heating furnace, in the heating furnace, 70 mg / m ３The following fluorine concentration conditions and / or 200 mg / m ３ The method for manufacturing a glass product according to claim 6, which satisfies the following boron concentration conditions.

8. The method for manufacturing a glass product according to claim 5 or 6, wherein the heating element is made of a material containing silicon.

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