Glass melting furnace monitoring method and glass article manufacturing method

Abstract

Provided is a glass melting furnace monitoring method that monitors the melting loss of a refractory (111) that constitutes a glass melting furnace (1) that uses an electrode (14) immersed in molten glass (Gm) to heat and melt a glass raw material (Gr), the glass melting furnace monitoring method comprising: a first temperature sensor (151) disposed in an energized region (16) between the electrode (14); and a second temperature sensor (152) disposed in a non-energized region (17) away from the energized region, the abnormal heating of the refractory (111) being detected using the measured temperature of the first temperature sensor (151) and the measured temperature of the second temperature sensor (152). Thus, in a glass melting furnace, abnormal heating of a refractory that constitutes the glass melting furnace can be detected before the refractory melts.

Description

Technical Field

[0001] The present invention relates to a method for monitoring abnormal heating of refractory materials constituting a glass melting furnace, and a method for manufacturing glass articles using the monitoring method. Background Technology

[0002] Previously, temperature measurements were performed inside the glass melting furnace to ensure operational stability and efficiency. Patent Document 1 discloses a method for obtaining a temperature profile inside the furnace by using a temperature recorder on the surface of the molten glass and temperature measurements obtained from thermocouples inserted inside the furnace.

[0003] In addition, in order to improve the thermal efficiency of the glass melting furnace and suppress the amount of exhaust gas, a method is used to heat the molten glass by passing electricity between electrodes immersed in the molten glass (for example, see Patent Document 2).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-222534

[0007] Patent Document 2: Japanese Patent Application Publication No. 2003-183031 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] The walls and bottom of the glass melting furnace are made of refractory. Generally, the resistivity of refractory is higher than that of molten glass. Therefore, when current is applied between the electrodes, the current flows through the molten glass instead of the refractory.

[0010] However, in recent years, various types of glass have been produced, including alkali-free glass, which has a higher resistivity in its molten state than conventional glass. When heating such molten glass using an electric current between electrodes, the resistivity difference between the molten glass and the refractory is smaller than that of conventional glass, making it easier for the refractory to conduct electricity. Furthermore, with prolonged use, the resistivity of the refractory may decrease due to deterioration of its internal structure. If the resistivity of the refractory is relatively lower than that of the molten glass, the current flowing through the refractory will increase, leading to a rise in its temperature. If the temperature of the refractory rises, its resistivity will decrease, thus creating a vicious cycle of further increases in current and temperature. As a result, abnormal heating and melting of the refractory can occur. Therefore, detecting abnormal heating of the refractory is crucial for improving production safety and stability.

[0011] The objective of this invention is to detect abnormal heating in a glass melting furnace before the refractory constituting the glass melting furnace melts.

[0012] Technical means for solving problems

[0013] The present invention, created to address the aforementioned problems, is a method for monitoring a glass melting furnace. This method monitors the melting loss of the refractory material constituting the glass melting furnace. The glass melting furnace uses electrodes immersed in molten glass to heat the glass raw material to melt it. The monitoring method includes: a first temperature sensor disposed in an energized region between the electrodes; and a second temperature sensor disposed in a non-energized region away from the energized region. Abnormal heating of the refractory material is detected using the measured temperatures of the first and second temperature sensors. Based on this structure, by comparing the temperature of the energized region measured by the first temperature sensor and the temperature of the non-energized region measured by the second temperature sensor, it is possible to identify whether abnormal heating is caused by the energization of the refractory material itself in the energized region.

[0014] In the above structure, preferably, abnormal heating of the refractory is detected when the increase in the temperature difference obtained by subtracting the temperature measured by the second temperature sensor from the temperature measured by the first temperature sensor exceeds a predetermined value. When the refractory does not exhibit abnormal heating, its temperature is determined by the temperature of the molten glass in contact with it. The temperature of the molten glass varies depending on the location within the glass melting furnace; therefore, the temperature of the refractory also varies depending on the location. However, if the operating conditions of the glass melting furnace are changed (e.g., power is supplied), the temperature of the molten glass will change, but the difference in the amount of temperature change caused by the location is relatively small. Therefore, the difference in the amount of temperature change of the refractory caused by the location is also relatively small. Therefore, even if the operating conditions are changed, the temperature difference (comparison temperature difference) obtained by subtracting the temperature measured by the second temperature sensor from the temperature measured by the first temperature sensor remains nearly constant. On the other hand, when the refractory exhibits abnormal heating, its temperature is determined by the temperature of the molten glass in contact with it plus the heat generated inside the refractory. Therefore, regardless of changes in operating conditions, the comparison temperature difference only increases the amount of heat generated inside the refractory. Based on the above, abnormal heating of refractory materials can be detected by monitoring and comparing temperature differences in advance.

[0015] In the above structure, it is preferable that the electrode is disposed on the bottom surface of the glass melting furnace. This structure promotes convection of the molten glass, resulting in glass articles with a uniform composition, and reduces forming defects such as ripples.

[0016] In the above structure, it is preferable that the glass raw material is heated solely by electrical heating using the electrodes. Compared to the case where both a burner and electrodes are used, heating the glass raw material to melt it using only electrodes without a burner requires a significantly increased electrical current to the molten glass, leading to a higher risk of abnormal heating of the refractory. Therefore, when the present invention is applied to heat the glass raw material to melt it using only electrodes without a burner, the effect of detecting abnormal heating of the refractory becomes more significant.

[0017] In the above structure, it is preferable that the first temperature sensor and the second temperature sensor are thermocouples. With this structure, even if the refractory materials constituting the glass melting furnace, the molten glass, or other objects being measured are at high temperatures, the temperature can be measured easily and accurately.

[0018] In the above structure, preferably, the temperature measuring units of the first and second temperature sensors are disposed inside the refractory to measure the temperature of the refractory. The temperature of the refractory in the energized region changes based on the heat transferred from the molten glass and the heat generated by the refractory itself being energized. On the other hand, the temperature of the refractory in the non-energized region changes only due to the heat transferred from the molten glass. Therefore, by monitoring and comparing the temperature difference, the temperature change caused by the heat generated by the refractory itself being energized can be detected.

[0019] In the above structure, preferably, the temperature measuring part of the first temperature sensor is disposed inside the refractory to measure the temperature of the refractory, and the temperature measuring part of the second temperature sensor is disposed at the boundary between the refractory and the molten glass to measure the temperature of the molten glass. The difference between the temperature change of the refractory in the non-energized area and the temperature change of the molten glass is small. Therefore, when the second temperature sensor measures the temperature of the refractory and when it measures the temperature of the molten glass, the change in temperature difference is approximately equal. Furthermore, for the purpose of controlling the operating conditions of the glass melting furnace, temperature sensors for measuring the temperature of the molten glass are usually installed inside the melting furnace. If these temperature sensors are used to measure the temperature of the molten glass in the non-energized area, it is not necessary to reinstall temperature sensors in the non-energized area.

[0020] In the above structure, it is preferable that the temperature measuring parts of both the first and second temperature sensors are covered by a noble metal cap. This structure protects the thermocouples from the high-temperature environment near the molten glass. Furthermore, noble metals have higher thermal conductivity than heat-resistant materials such as oxide ceramics, thus improving the responsiveness of temperature measurement.

[0021] In the above structure, it is preferable to include: a melting step in which the glass raw material is melted using the glass melting furnace employing the glass melting furnace monitoring method; and a forming step in which the molten glass melted in the glass melting furnace is formed. With this structure, glass articles can be manufactured while monitoring the melting loss of the refractory constituting the glass melting furnace.

[0022] Invention Effects

[0023] According to the present invention, in a glass melting furnace, abnormal heating can be detected before the refractory constituting the glass melting furnace melts. Attached Figure Description

[0024] Figure 1 It is a schematic diagram of the manufacturing process of glass items.

[0025] Figure 2 This is a side sectional view of a glass melting furnace.

[0026] Figure 3 yes Figure 2 AA section view in the image.

[0027] Figure 4 This applies when the temperature measuring section of the second temperature sensor is located inside the refractory material. Figure 3 BB section view in the middle.

[0028] Figure 5 This applies when the temperature measuring section of the second temperature sensor is located at the boundary between the refractory and the molten glass. Figure 3 BB section view in the middle.

[0029] Figure 6 It is a graph showing the simulation results of temperature changes in energized and non-energized areas when the input power is increased.

[0030] Figure 7 It is a graph showing the simulation results of changes in temperature difference when the input power is increased.

[0031] Figure 8 It is a graph showing the simulation results of temperature changes in the energized and non-energized regions under the condition of refractory degradation progression.

[0032] Figure 9 It is a graph showing the simulation results of the temperature difference changes under the condition of the refractory metamorphism progress.

[0033] Symbol Explanation

[0034] 1. Melting furnace

[0035] 111 Refractory

[0036] 14 electrodes

[0037] 15 Temperature Sensor

[0038] 151 First Temperature Sensor

[0039] 152 Second Temperature Sensor

[0040] 153 Precious Metal Cap

[0041] 16 Powered Areas

[0042] 17 Non-powered areas

[0043] Gm molten glass

[0044] Gr glass raw materials Detailed Implementation

[0045] An embodiment of the glass melting furnace monitoring method according to the present invention will be described.

[0046] like Figure 1 As shown, the glass article manufacturing apparatus according to this embodiment includes, from the upstream side, a melting furnace 1, a refining tank 2, a homogenizing tank 3, a tank 4, a forming body 5, and supply paths 61-64 connecting these components 1-5. In addition, the manufacturing apparatus includes: a slow cooling furnace (not shown) for slowly cooling the glass strip GR formed by the forming body 5; and a cutting device (not shown) for cutting glass sheets of the desired size from the strip-shaped glass strip GR after slow cooling.

[0047] The melting furnace 1 is a container used for the melting process of glass raw material Gr to obtain molten glass Gm, and is connected to the refining tank 2 via the supply line 61.

[0048] The clarification tank 2 is a container used for a clarification process in which molten glass Gm supplied from the melting furnace 1 is degassed by the action of a clarifying agent or the like, and is connected to the homogenization tank 3 via the supply path 62.

[0049] The homogenization tank 3 is a container used to stir and homogenize the clarified molten glass Gm, and is equipped with a stirrer 31 with stirring blades. The homogenization tank 3 is connected to the tank 4 via a supply line 63.

[0050] Tank 4 is a container used for a conditioning process to adjust the molten glass Gm to a state suitable for forming, including adjusting the viscosity and flow rate of the molten glass Gm. Tank 4 is connected to the forming body 5 via supply path 64.

[0051] Each supply line 61-64 is constructed by connecting multiple supply pipes made of platinum or platinum alloy. The outer periphery of each supply line 61-64 is held in place by refractory material.

[0052] In this embodiment, the forming apparatus for shaping molten glass Gm into a desired shape is composed of a forming body 5. The forming body 5 shapes the molten glass Gm into a strip-shaped glass strip GR using an overflow pull-down method. Specifically, the cross-sectional shape of the forming body 5 (compared to...) Figure 1 The cross-sectional shape of the paper (orthogonal to the paper surface) is roughly wedge-shaped, and an overflow groove (not shown) is formed on the upper part of the molded body 5.

[0053] The forming body 5 causes molten glass Gm to overflow from the overflow channel and flow down along the side walls of both sides of the forming body 5 (the side walls located on the back side of the paper). The forming body 5 causes the flowing molten glass Gm to fuse at the bottom top of the side walls, forming a plate shape.

[0054] The following is for reference Figure 2 The specific structure of the melting furnace 1 will be described.

[0055] like Figure 2 As shown, the melting furnace 1 includes: a melting tank body 11, a screw feeder 12 for supplying glass raw material Gr, a flue 13 for discharging gas from the melting furnace 1 to the outside, an electrode 14 for heating the molten glass Gm by energizing it, and a temperature sensor 15 for monitoring abnormal heating of the refractory 111.

[0056] The melting tank body 11 is heated by electricity to melt the glass raw material Gr to form molten glass Gm. The melting tank body 11 is composed of refractory material 111 (such as zirconia-based electroformed bricks or alumina-based electroformed bricks), which divides the melting space within the furnace. Insulating materials such as insulating bricks (not shown) are arranged around the refractory material 111 to improve the insulation performance of the melting tank body 11. In this embodiment, the melting furnace 1 is a single melting furnace with only one melting space for the glass raw material Gr, but it can also be a multi-melting furnace with multiple melting spaces connected together. Furthermore, the molten glass Gm flows in the X-axis direction.

[0057] In the melting furnace 1, a screw feeder 12 is provided as a raw material supply unit. The screw feeder 12 sequentially supplies glass raw material Gr in such a way that a portion of the molten glass Gm is not covered by the glass raw material Gr. That is, the melting furnace 1 is a so-called semi-hot top type. Alternatively, the melting furnace 1 can also be a so-called cold top type, in which the entire surface of the molten glass Gm is covered by the glass raw material Gr. In addition, the raw material supply unit can also be a pusher, a vibrating feeder, etc.

[0058] In the melting furnace 1, a flue 13 is provided as a gas discharge path for discharging the gas inside the melting furnace 1 to the outside. A fan 131 for conveying gas to the outside is provided in the flue 13. Alternatively, the fan 131 may not be provided.

[0059] In the refractory 111 of the melting furnace 1, multiple electrodes 14 are provided in a state of being immersed in molten glass Gm for electric heating. In this embodiment, no heating unit other than the electrodes 14 located at the bottom of the furnace is provided in the melting furnace 1. The molten glass Gm is heated only by the electric heating of the electrodes 14, thereby indirectly heating and melting the glass raw material Gr supplied to the upper surface of the molten glass Gm. The electrodes 14 are formed, for example, from rod-shaped molybdenum and are supported by electrode supports 141. The electrode supports 141 have internal cooling pipes (not shown). The cooling pipes cool the electrodes 14 and the electrode supports 141 by circulating a liquid cooling material such as water.

[0060] Figure 3 Two electrodes 14, enclosed by a single-dotted line, are paired together. Molten glass Gm is heated by energizing the area between the electrodes 14 (energized region 16). The area away from the energized region (non-energized region 17) is not energized but is heated by convection and radiation from the molten glass Gm.

[0061] The temperature sensor 15 consists of a first temperature sensor 151 and a second temperature sensor 152. The first temperature sensor 151 is disposed in the energized region 16, and the second temperature sensor 152 is disposed in the non-energized region 17. In this embodiment, a thermocouple is used as the temperature sensor 15, but it is not limited to this. A platinum thermometer or a radiation thermometer may also be used.

[0062] like Figure 4 As shown, a temperature sensor mounting hole 18 for mounting a temperature sensor 15 is provided in the refractory 111. In this embodiment, the temperature sensor mounting hole 18 does not penetrate the refractory 111 but is closed. A precious metal cap 153 is installed at the closed end of the temperature sensor mounting hole 18, and the temperature sensor 15 is pressed and fixed to the precious metal cap 153 while being housed within the protective tube 154. This protects the temperature measuring part of the temperature sensor 15 from the influence of high-temperature environments. Furthermore, since the precious metal cap 153 has high thermal conductivity, the temperature of the refractory 111 can be accurately measured. In this embodiment, the precious metal cap 153 is made of platinum, but it is not limited to this. Platinum alloys, iridium, or other high heat-resistant materials can also be used.

[0063] like Figure 5As shown, the temperature sensor mounting hole 18 located in the non-energized area 17 can also penetrate the refractory 111. In this case, the precious metal cap 153 is in direct contact with the molten glass Gm, enabling the measurement of the temperature of the molten glass Gm.

[0064] In the non-energized region 17, the temperature of either the molten glass Gm or the refractory 111 can be measured. Although the temperature of the molten glass Gm differs from that of the refractory 111, both the molten glass Gm and the refractory 111 experience temperature changes associated with changes in operating conditions. Therefore, by comparing the measured temperature with that of the first temperature sensor 151 located in the energized region 16, the purpose of detecting abnormal heating of the refractory 111 according to the present invention can be achieved. Therefore, in the case of an existing second temperature sensor 152 for measuring the temperature of the molten glass Gm or the refractory 111, there is no need to replace the second temperature sensor 152.

[0065] Because the refractory 111 deteriorates due to prolonged exposure to high temperatures, the likelihood of deterioration of the nearby refractory 111 increases as the temperature of the molten glass Gm rises. Furthermore, within the melting furnace 1, there is a tendency for the temperature to rise downstream. Therefore, it is preferable to monitor the downstream energized area 16, where the risk of abnormal heating due to refractory 111 deterioration is high.

[0066] Furthermore, compared to molten glass Gm, glass raw material Gr has a higher resistivity. Therefore, as the proportion of glass raw material Gr mixed in the molten glass Gm increases, it becomes relatively easier to energize the refractory 111, increasing the risk of abnormal heating of the refractory 111. Within the melting furnace 1, as the flow moves upstream, the proportion of glass raw material Gr mixed in the molten glass Gm increases; therefore, it is preferable to monitor the upstream energized region 16.

[0067] The temperature of the unenergized refractory 111 decreases as it moves away from the molten glass Gm. Therefore, the deterioration of the refractory 111 begins at the boundary between the refractory 111 and the molten glass Gm and gradually progresses into the interior of the refractory 111. Thus, the closer the measuring position of the first temperature sensor 151 is to the molten glass Gm, the earlier abnormal heating of the refractory 111 can be detected.

[0068] The first temperature sensor 151 and the second temperature sensor 152 are connected to a control device (not shown). The control device records the measured temperatures of the first temperature sensor 151 and the second temperature sensor 152. When the temperature difference exceeds a specified value, it is determined that abnormal heating has occurred, increasing the risk of melting of the refractory 111. The detection of abnormal heating will be explained below using simulation.

[0069] Two pairs of electrodes 14 are arranged inside the furnace 1 of the simulation object, and a total power input of 98.5 kW is set. The temperature at the midpoint of the pair of electrodes 14, 10 mm from the boundary between the refractory 111 and the molten glass Gm, facing the refractory 111, is used as the temperature measured by the first temperature sensor 151. The temperature at a height of 300 mm from the bottom surface of the furnace 1, located at the boundary between the refractory 111 and the molten glass Gm forming the side of the furnace 1, is used as the temperature measured by the second temperature sensor 152. It should be noted that when reproducing the metamorphic progression of the refractory 111 through simulation, the resistivity of the refractory 111 from the boundary between the refractory 111 and the molten glass Gm to a predetermined depth (metamorphic depth) is set low. A simulation using the finite volume method is performed under the above conditions, and the temperatures measured by the first temperature sensor 151 and the second temperature sensor 152 are obtained.

[0070] Figure 6 This represents the temperature change measured by the first temperature sensor 151 and the second temperature sensor 152 as the power input from electrode 14 into the melting furnace 1 increases. The input power increases by 2.5% each time from 98.5 kW to 10%. On the other hand, the deterioration of the refractory 111 does not progress. If the input power is increased, the temperatures measured by both the first temperature sensor 151 and the second temperature sensor 152 rise by the same amount. Therefore, as... Figure 7 As shown, regardless of changes in the input power, the temperature difference remains roughly constant.

[0071] Figure 8 The temperature change measured by the first temperature sensor 151 and the second temperature sensor 152 indicates the progression of the refractoriness of the refractory 111. The refractoriness depth of the refractory 111 increases by 15 mm at a time from 0 mm to 60 mm. However, the applied power does not increase. If the refractoriness of the refractory 111 is allowed to progress, the temperature measured by the first temperature sensor 151 rises, but the temperature measured by the second temperature sensor 152 remains almost unchanged. Therefore, as... Figure 9 As shown, the temperature difference increases as the refractory 111 deteriorates.

[0072] Even if the temperature measured by the first temperature sensor 151 increases, if the temperature measured by the second temperature sensor 152 also increases in the same way, the temperature difference does not increase. The temperature increase measured by the first temperature sensor 151 is caused by changes in operating conditions such as the input of electricity, so it can be concluded that no abnormal heating has occurred in the refractory 111. On the other hand, if the temperature measured by the first temperature sensor 151 increases, but the temperature measured by the second temperature sensor 152 does not increase, or if the temperature increase measured by the first temperature sensor 151 is greater than the temperature increase measured by the second temperature sensor 152, the temperature difference increases, indicating that abnormal heating has occurred in the refractory 111. Therefore, it is possible to detect whether abnormal heating has occurred in the refractory 111 based on the presence or absence of an increase in the temperature difference.

[0073] Using the method described above, abnormal heating can be detected before the refractory 111 constituting the glass melting furnace 1 melts.

[0074] Furthermore, the present invention is not limited to the structure of the above-described embodiments, nor to the effects described above. Various modifications can be made to the present invention without departing from its spirit.

[0075] In the above embodiment, the glass plate is manufactured using the overflow down-draw method, but it is not limited to this. The flow hole down-draw method or the float glass method can also be used. Furthermore, in the above embodiment, a glass plate has been used as an example of a glass article, but it is not limited to this. Other glass articles such as fiberglass and tubular glass can also be manufactured.

[0076] In the above embodiment, the electrode 14 is arranged only on the bottom surface of the glass melting furnace 1, but it is not limited to this. The electrode 14 may also be arranged on the side surface of the glass melting furnace 1.

[0077] In the above embodiment, the molten glass Gm is heated solely by heating based on the energization between electrodes 14, but heating by a burner can also be combined. In this case, a burner is installed on the refractory 111 above the liquid surface of the molten glass Gm.

[0078] In the above embodiment, single-phase AC power is used for energizing the electrodes 14, but it is not limited to this. Three-phase AC power can also be used. In this case, the three electrodes 14 form a group, and the area between the group of electrodes 14 forms an energized region 16.

[0079] The present invention is suitable for monitoring glass melting furnaces and for manufacturing glass articles using the monitoring method of the glass melting furnace.

Claims

1. A method for monitoring a glass melting furnace, characterized in that, The melting loss of the refractory materials constituting the glass melting furnace is monitored. The glass melting furnace uses electrodes immersed in molten glass to heat the glass raw material to melt it. The glass melting furnace monitoring method includes: A first temperature sensor, disposed in the energized region between the electrodes; and A second temperature sensor is disposed in a non-energized area away from the energized area. The first temperature sensor is disposed in a mounting hole formed in the refractory material. Abnormal heating is detected by using the measured temperatures of the first temperature sensor and the second temperature sensor, as the resistivity of the refractory decreases.

2. The glass melting furnace monitoring method according to claim 1, characterized in that, Subtract the temperature measured by the second temperature sensor from the temperature measured by the first temperature sensor. If the increase in the obtained temperature difference exceeds a specified value, abnormal heating of the refractory is detected.

3. The glass melting furnace monitoring method according to claim 1 or 2, characterized in that, The electrode is disposed on the bottom surface of the glass melting furnace.

4. The glass melting furnace monitoring method according to claim 1 or 2, characterized in that, The glass raw material is heated only by applying electricity using the electrodes.

5. The glass melting furnace monitoring method according to claim 1 or 2, characterized in that, The first temperature sensor and the second temperature sensor are thermocouples.

6. The glass melting furnace monitoring method according to claim 1 or 2, characterized in that, The temperature measuring parts of the first temperature sensor and the second temperature sensor are disposed inside the refractory to measure the temperature of the refractory.

7. The glass melting furnace monitoring method according to claim 1 or 2, characterized in that, The temperature measuring part of the first temperature sensor is disposed inside the refractory material to measure the temperature of the refractory material. The temperature measuring part of the second temperature sensor is disposed at the boundary between the refractory and the molten glass to measure the temperature of the molten glass.

8. The glass melting furnace monitoring method according to claim 1 or 2, characterized in that, The temperature measuring parts of the first temperature sensor and the second temperature sensor are covered by a precious metal cap.

9. A method for manufacturing glass articles, characterized in that, have: The melting process involves melting the glass raw material using the glass melting furnace employing the glass melting furnace monitoring method according to any one of claims 1 to 8; and The forming process involves shaping the molten glass that has been melted in the glass melting furnace.

Images