Method for monitoring glass melting furnace and method for manufacturing glass article

Abstract

To provide a glass melting furnace monitoring method that makes it possible to detect abnormal heat buildup in a refractory material constituting a glass melting furnace before erosion occurs in the refractory material.SOLUTION: This glass melting furnace monitoring method is for monitoring erosion of a refractory material 111 constituting a glass melting furnace for heating and melting a glass material Gr by using electrodes 14 immersed in molten glass Gm. The present invention comprises a first temperature sensor 151 disposed in an energization region between the electrodes 14, and a second temperature sensor 152 disposed in a non-energization region 18 away from the energization region, and involves detecting abnormal heat buildup in the refractory material 111 by using temperatures measured with the first temperature sensor 151 and the second temperature sensor 152.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for monitoring abnormal heat generation of refractories constituting a glass melting furnace, and a method for manufacturing glass articles using the monitoring method.

Background Art

[0002] Conventionally, temperature measurement inside a glass melting furnace has been performed for the purpose of stabilizing and improving operation. In Patent Document 1, a method for obtaining a temperature profile inside the furnace using temperature measurement results by a thermograph on the surface of molten glass or a thermocouple inserted into the furnace is disclosed.

[0003] In addition, for the purpose of improving the thermal efficiency of a glass melting furnace and suppressing the amount of exhaust gas discharged, a method of heating molten glass by passing an electric current between electrodes immersed in the molten glass is used (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The furnace wall and furnace bottom of a glass melting furnace are made of refractories. Generally, since the electrical resistivity of refractories is higher than that of molten glass, when an electric current is passed between electrodes, the current flows through the molten glass rather than the refractories.

[0006] However, in recent years, glasses with various characteristics have been produced, and among them, there are those with a higher electrical resistivity in the molten state, such as non-alkali glass, than conventional glasses. When heating such molten glass using energization between electrodes, the difference in electrical resistivity between the molten glass and the refractory is less than that of conventional glasses, and it is easier for the refractory to be energized. Also, when the refractory is used for a long time, the electrical resistivity of the refractory may decrease due to deterioration such as alteration of the internal structure constituting the refractory. When the electrical resistivity of the refractory decreases relative to that of the molten glass, the current flowing through the refractory increases, and the temperature of the refractory rises. Since the electrical resistivity decreases as the temperature of the refractory rises, it falls into a vicious cycle where the current flowing further increases and the temperature rises. As a result, the refractory may generate abnormal heat and experience melting loss. Therefore, detecting abnormal heat generation in the refractory is important for improving production safety and stability.

[0007] An object of the present invention is to detect abnormal heat generation in a refractory constituting a glass melting furnace before the refractory reaches melting loss in the glass melting furnace.

Means for Solving the Problem

[0008] The present invention devised to solve the above problems is a glass melting furnace monitoring method for monitoring melting loss of a refractory constituting a glass melting furnace that heats and melts glass raw materials using electrodes immersed in molten glass, comprising a first temperature sensor disposed in an energization region between the electrodes and a second temperature sensor disposed in a non-energization region away from the energization region, and detecting abnormal heat generation of the refractory using the measured temperatures of the first temperature sensor and the second temperature sensor. According to such a configuration, the temperature of the energization region measured by the first temperature sensor and the temperature of the non-energization region measured by the second temperature sensor are compared to identify the presence or absence of abnormal heat generation due to energization of the refractory itself in the energization region.

[0009] In the above configuration, it is preferable to detect abnormal heat generation of the refractory when the increase amount of the temperature difference obtained by subtracting the measured temperature of the second temperature sensor from the measured temperature of the first temperature sensor exceeds a predetermined value. When the refractory is not abnormally generating heat, the temperature of the refractory is determined by the temperature of the molten glass with which the refractory is in contact. Since the temperature of the molten glass varies depending on the location in the glass melting furnace, the temperature of the refractory also varies depending on the location. By the way, when the operating conditions (such as input power) of the glass melting furnace are changed, the temperature of the molten glass changes, but the difference in the amount of temperature change of the molten glass depending on the location is relatively small. Therefore, the difference in the amount of temperature change of the refractory depending on the location also becomes relatively small. Thus, even when the operating conditions are changed, the temperature difference (comparative temperature difference) obtained by subtracting the temperature measured by the second temperature sensor from the temperature measured by the first temperature sensor becomes close to being constant. On the other hand, when the refractory is abnormally generating heat, the temperature of the refractory is determined by adding the amount of heat generated inside the refractory to the temperature of the molten glass with which the refractory is in contact. Therefore, regardless of the change in the operating conditions, the comparative temperature difference increases by the amount of heat generated inside the refractory. From the above, by monitoring the comparative temperature difference, abnormal heat generation of the refractory can be detected.

[0010] In the above configuration, it is preferable that the electrode is disposed on the bottom surface of the glass melting furnace. According to such a configuration, the convection of the molten glass can be promoted, a glass article having a uniform composition can be obtained, and molding defects such as veins can be reduced.

[0011] In the above configuration, it is preferable that the glass raw material is heated only by energization heating by the electrode. Compared with the case of using a burner and an electrode in combination, when the glass raw material is heated and melted only by the electrode without using a burner, it is necessary to significantly increase the energization of the molten glass, and the risk of abnormal heat generation of the refractory is high. Therefore, if the present invention is applied to the case where the glass raw material is heated and melted only by the electrode without using a burner, the effect of detecting abnormal heat generation of the refractory becomes more remarkable.

[0012] In the above configuration, it is preferable that the first temperature sensor and the second temperature sensor are thermocouples. According to such a configuration, even if the object to be measured such as the refractory material or the molten glass constituting the glass melting furnace is at a high temperature, the temperature can be easily and accurately measured.

[0013] In the above configuration, it is preferable that the temperature measurement parts of the first temperature sensor and the second temperature sensor are arranged inside the refractory material to measure the temperature of the refractory material. The temperature of the refractory material in the energized area changes due to the heat transmitted from the molten glass and the heat generated by the energization of the refractory material itself. On the other hand, the temperature of the refractory material in the non-energized area changes only due to the heat transmitted from the molten glass. Therefore, by monitoring the comparative temperature difference, the temperature change due to the heat generated by the energization of the refractory material itself can be detected.

[0014] In the above configuration, it is preferable that the temperature measurement part of the first temperature sensor is arranged inside the refractory material to measure the temperature of the refractory material, and the temperature measurement part of the second temperature sensor is arranged at the boundary between the refractory material and the molten glass to measure the temperature of the molten glass. The difference between the temperature change amount of the refractory material in the non-energized area and the temperature change amount of the molten glass is small. For this reason, the change amount of the comparative temperature difference is generally equal when the second temperature sensor measures the temperature of the refractory material and when it measures the temperature of the molten glass. Also, for the purpose of controlling the operating conditions of the glass melting furnace, temperature sensors for measuring the temperature of the molten glass are often installed inside the melting furnace conventionally. If the temperature of the molten glass in the non-energized area is measured using these temperature sensors, there is no need to newly install a temperature sensor in the non-energized area.

[0015] In the above configuration, it is preferable that the first temperature sensor and the second temperature sensor have their temperature measurement parts covered with noble metal caps. According to such a configuration, the thermocouple can be protected from the high-temperature environment near the molten glass. Also, since noble metals have a higher thermal conductivity than heat-resistant materials such as oxide ceramics, the responsiveness of temperature measurement is improved.

[0016] In the above configuration, it is preferable to include a melting step of melting the glass raw material by the glass melting furnace using the glass melting furnace monitoring method according to any one of claims 1 to 8, and a forming step of forming the molten glass melted in the glass melting furnace. According to such a configuration, glass articles can be manufactured while monitoring the wear of the refractory constituting the glass melting furnace.

Advantages of the Invention

[0017] According to the present invention, in a glass melting furnace, abnormal heat generation can be detected before the refractory constituting the glass melting furnace reaches wear.

Brief Description of the Drawings

[0018]

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Embodiments for Carrying Out the Invention

[0019] An embodiment of the glass melting furnace monitoring method according to the present invention will be described.

[0020] 1, the manufacturing apparatus for a glass article according to this embodiment includes, in order from the upstream side, a melting furnace 1, a fining tank 2, a homogenization tank 3, a pot 4, a forming body 5, and supply paths 61 to 64 connecting these respective components 1 to 5. In addition, the manufacturing apparatus includes an annealing furnace (not shown) for annealing the glass ribbon GR formed by the forming body 5, and a cutting device (not shown) for cutting out a glass plate of a desired size from the band-shaped glass ribbon GR after annealing.

[0021] The melting furnace 1 is a vessel for carrying out a melting step in which the charged glass raw material Gr is melted to obtain the molten glass Gm, and is connected to the fining vat 2 by a supply line 61 .

[0022] The fining tank 2 is a container for carrying out a fining step in which the molten glass Gm supplied from the melting furnace 1 is degassed by the action of a fining agent or the like, and is connected to the homogenization tank 3 by a supply line 62 .

[0023] The homogenization vessel 3 is a vessel for stirring the clarified molten glass Gm and performing a homogenization step, and is provided with a stirrer 31 having stirring blades. The homogenization vessel 3 is connected to the pot 4 by a supply line 63.

[0024] The pot 4 is a container for performing a condition adjusting step of adjusting the molten glass Gm to a state suitable for forming, and adjusts the viscosity and flow rate of the molten glass Gm. The pot 4 is connected to the forming body 5 by a supply path 64.

[0025] Each of the supply passages 61 to 64 is formed by connecting a plurality of supply pipes made of platinum or a platinum alloy. The outer circumferential surface of each of the supply passages 61 to 64 is supported by a refractory material.

[0026] In this embodiment, a forming apparatus for shaping molten glass Gm into a desired shape is constituted by a formed body 5. The formed body 5 forms the molten glass Gm into a strip-shaped glass ribbon GR by the overflow down-draw method. Specifically, the formed body 5 has a substantially wedge-shaped cross-sectional shape (the cross-sectional shape orthogonal to the plane of FIG. 1), and an overflow groove (not shown) is formed at the upper part of the formed body 5.

[0027] The formed body 5 causes the molten glass Gm to overflow from the overflow groove and flow down along the side wall surfaces (the side surfaces located on the front and back surfaces of the plane of the paper) on both sides of the formed body 5. The formed body 5 fuses the flowed-down molten glass Gm at the lower apex of the side wall surface and forms it into a plate shape.

[0028] Hereinafter, the specific configuration of the melting furnace 1 will be described with reference to FIG. 2.

[0029] As shown in FIG. 2, the melting furnace 1 includes a melting tank main body 11, a screw feeder 12 for supplying the glass raw material Gr, a flue 13 for discharging the gas in the melting furnace 1 to the outside, an electrode 14 for heating the molten glass Gm by energization, and a temperature sensor 15 for monitoring abnormal heat generation of the refractory 111.

[0030] The melting tank main body 11 melts the glass raw material Gr by electric heating to form molten glass Gm. The melting tank main body 11 is constituted by a refractory 111 (for example, a zirconia-based electrocast brick, an alumina-based electrocast brick, etc.), and partitions and forms a melting space in the furnace. Heat insulating materials such as heat insulating bricks (not shown) are arranged around the refractory 111 to enhance the heat insulation property of the melting tank main body 11. In this embodiment, the melting furnace 1 is a single melter having only one melting space for the glass raw material Gr, but may also be a multi-melter in which a plurality of melting spaces are connected. Also, the molten glass Gm flows in the X-axis direction.

[0031] The melting furnace 1 is provided with a screw feeder 12 as a raw material supply means. The screw feeder 12 sequentially supplies the glass raw material Gr so that a portion of the liquid surface of the molten glass Gm that is not covered by the glass raw material Gr is formed. That is, the melting furnace 1 is of a so-called semi-hot top type. Note that the melting furnace 1 may be of a so-called cold top type in which the entire liquid surface of the molten glass Gm is covered by the glass raw material Gr. Also, the raw material supply means may be a pusher, a vibrating feeder, or the like.

[0032] The melting furnace 1 is provided with a flue 13 as a gas discharge path for discharging the gas in the melting furnace 1 to the outside. A fan 131 for sending the gas to the outside is provided in the flue 13. The fan 131 may not be provided.

[0033] A plurality of electrodes 14 are provided in the refractory 111 of the melting furnace 1 in a state of being immersed in the molten glass Gm for electric heating. In the present embodiment, no heating means other than the electrode 14 provided at the bottom of the furnace is provided in the melting furnace 1. By heating the molten glass Gm only by the electric heating of the electrodes 14, the glass raw material Gr supplied to the upper surface of the molten glass Gm is indirectly heated and melted. The electrode 14 is formed of, for example, rod-shaped molybdenum and is supported by an electrode holder 141. The electrode holder 141 includes a cooling pipe (not shown) inside. The cooling pipe cools the electrode 14 and the electrode holder 141 by circulating a liquid coolant such as water.

[0034] The two electrodes 14 surrounded by the dashed-dotted line in FIG. 3 are paired, and the molten glass Gm is heated by energizing the space between these electrodes 14 (the energization region 16). The region away from the energization region (the non-energization region 17) is not heated by energization, but is heated by the convection and radiation of the molten glass Gm.

[0035] The temperature sensor 15 is composed of a first temperature sensor 151 and a second temperature sensor 152. The first temperature sensor 151 is arranged in the energized region 16, and the second temperature sensor 152 is arranged in the non-energized region 17. In this embodiment, a thermocouple is used as the temperature sensor 15, but it is not limited thereto. A platinum resistance thermometer or a radiation thermometer may also be used.

[0036] As shown in FIG. 4, a temperature sensor mounting hole 18 for mounting the temperature sensor 15 is formed in the refractory 111. In this embodiment, the temperature sensor mounting hole 18 is closed without penetrating the refractory 111. A noble metal cap 153 is attached to the closed end of the temperature sensor mounting hole 18, and the temperature sensor 15 is pressed against and fixed to the noble metal cap 153 while being housed in the protective tube 154. Thereby, the temperature measurement part of the temperature sensor 15 can be protected from the high-temperature environment. In addition, since the noble metal cap 153 has a high thermal conductivity, the temperature of the refractory 111 can be accurately measured. In this embodiment, the noble metal cap 153 is made of platinum, but this is not the only case. Platinum alloy, iridium, or other high heat-resistant materials may be used.

[0037] As shown in FIG. 5, the temperature sensor mounting hole 18 located in the non-energized region 17 may penetrate the refractory 111. In this case, the noble metal cap 153 will directly touch the molten glass Gm, and the temperature of the molten glass Gm can be measured.

[0038] In the non-energized region 17, the temperature of either the molten glass Gm or the refractory 111 may be measured. Although the temperature of the molten glass Gm is different from that of the refractory 111, the temperature change accompanying the change in operating conditions appears in the molten glass Gm and the refractory 111 in the same way. Therefore, by comparing with the measured temperature of the first temperature sensor 151 arranged in the energized region 16, the object of the present invention to detect abnormal heat generation of the refractory 111 can be achieved. Therefore, when an existing second temperature sensor 152 for measuring the temperature of the molten glass Gm or the refractory 111 is installed, there is no need to newly install the second temperature sensor 152.

[0039] Since the refractory 111 deteriorates due to being exposed to a high-temperature environment for a long time, the possibility of the nearby refractory 111 deteriorating increases as the temperature of the molten glass Gm rises. Also, in the melting furnace 1, the temperature tends to rise as it goes downstream. Therefore, it is preferable to monitor the energization region 16 at the most downstream where the risk of the refractory 111 deteriorating and generating abnormal heat is high.

[0040] Moreover, since the electrical resistivity of the glass raw material Gr is higher than that of the molten glass Gm, as the proportion of the glass raw material Gr mixed in the molten glass Gm increases, it becomes relatively easier to energize the refractory 111, and the risk of abnormal heat generation in the refractory 111 increases. In the melting furnace 1, since the proportion of the glass raw material Gr mixed in the molten glass Gm increases as it goes upstream, it is preferable to monitor the energization region 16 at the most upstream.

[0041] The temperature of the non-energized refractory 111 decreases as it moves away from the molten glass Gm. Therefore, the deterioration of the refractory 111 starts from the interface between the refractory 111 and the molten glass Gm and gradually progresses into the refractory 111. For this reason, the closer the measurement position by the first temperature sensor 151 is to the molten glass Gm, the earlier the abnormal heat generation of the refractory 111 can be detected.

[0042] 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, and when the comparison temperature difference exceeds a predetermined value, it determines that abnormal heat generation has occurred and the risk of melting loss of the refractory 111 has increased. Hereinafter, the detection of abnormal heat generation will be described using a simulation.

[0043] Two pairs of electrodes 14 were arranged inside the melting furnace 1 targeted by this simulation, and the power input was set to a total of 98.5 kW. Also, as the temperature measured by the first temperature sensor 151, the temperature at a position 10 mm from the interface between the refractory 111 and the molten glass Gm toward the refractory 111 side, which is in the middle of a pair of electrodes 14, was adopted. As the temperature measured by the second temperature sensor 152, the temperature at a position that is 300 mm from the bottom surface of the melting furnace 1 and is the boundary between the refractory 111 that constitutes the side surface of the melting furnace 1 and the molten glass Gm was adopted. When reproducing the progress of the alteration of the refractory 111 by simulation, the electrical resistivity of the refractory 111 from the interface between the refractory 111 and the molten glass Gm to a predetermined depth (alteration depth) was set low. A simulation using the finite volume method was performed according to the above conditions, and the temperatures measured by the first temperature sensor 151 and the second temperature sensor 152 were obtained.

[0044] Figure 6 shows the changes in the temperatures measured by the first temperature sensor 151 and the second temperature sensor 152 when the power input from the electrode 14 into the melting furnace 1 is increased. The input power is increased by 2.5% each time from 98.5 kW up to 10%. On the other hand, the alteration of the refractory 111 is not advanced. When the input power is increased, the temperatures measured by both the first temperature sensor 151 and the second temperature sensor 152 increase, and the amounts of increase are about the same. For this reason, as shown in Figure 7, regardless of the change in the input power, the comparative temperature difference is almost constant.

[0045] Figure 8 shows the changes in the temperatures measured by the first temperature sensor 151 and the second temperature sensor 152 when the alteration of the refractory 111 has advanced. The alteration depth of the refractory 111 is increased by 15 mm each time from 0 mm up to 60 mm. On the other hand, the input power is not increased. When the alteration of the refractory 111 is advanced, the temperature measured by the first temperature sensor 151 increases, but the temperature measured by the second temperature sensor 152 hardly changes. For this reason, as shown in Figure 9, the comparative temperature difference increases as the alteration of the refractory 111 progresses.

[0046] 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 comparative temperature difference has not increased. Since the increase in the temperature measured by the first temperature sensor 151 is due to fluctuations in operating conditions such as input power, it can be seen that abnormal heat generation has not occurred in the refractory 111. On the other hand, when the temperature measured by the first temperature sensor 151 increases and the temperature measured by the second temperature sensor 152 does not increase, or when the increase in the temperature measured by the first temperature sensor 151 is greater than the increase in the temperature measured by the second temperature sensor 152, the comparative temperature difference has increased, and it can be seen that abnormal heat generation has occurred in the refractory 111. Therefore, it is possible to detect whether abnormal heat generation has occurred in the refractory 111 based on the presence or absence of an increase in the comparative temperature difference.

[0047] According to the method as described above, it is possible to detect abnormal heat generation in the refractory 111 that constitutes the glass melting furnace 1 before it reaches melting loss.

[0048] Note that the present invention is not limited to the configuration of the above-described embodiment, nor is it limited to the above-described effects. The present invention can be variously modified without departing from the gist of the present invention.

[0049] In the above embodiment, a glass plate was created using the overflow down-draw method, but it is not limited to this. The slot down-draw method or the float method may be used. Also, in the above embodiment, a glass plate was described as an example of a glass article, but it is not limited to this. Other glass articles such as glass fiber and tubular glass may be manufactured.

[0050] In the above embodiment, the electrode 14 was arranged only on the bottom surface of the glass melting furnace 1, but it is not limited to this. The electrode 14 may be arranged on the side surface of the glass melting furnace 1.

[0051] In the above embodiment, the molten glass Gm was heated only by energization between the electrodes 14, but heating by a burner may be combined. In this case, the burner is attached to the refractory 111 above the liquid surface of the molten glass Gm.

[0052] In the above embodiment, single-phase AC power supply was used for energization between the electrodes 14, but it is not limited to this. A three-phase AC power supply may be used. In this case, three electrodes 14 form a set, and the space between a set of electrodes 14 becomes the energization region 16.

[0053] The present invention can be suitably used for monitoring a glass melting furnace and for manufacturing glass articles using the method for monitoring the glass melting furnace.

Explanation of Signs

[0054] 1 Melting furnace 111 Refractory 14 Electrodes 15 Temperature sensor 151 First temperature sensor 152 Second temperature sensor 153 Noble metal cap 16 Energization region 17 Non-energization region Gm Molten glass Gr Glass raw material

Claims

1. A method for monitoring the erosion of a refractory material that constitutes a glass melting furnace for heating and melting glass raw materials using electrodes immersed in molten glass, comprising: a first temperature sensor disposed in the energized region between the electrodes; a second temperature sensor disposed in a non-energized region away from the energized region, wherein the first temperature sensor is disposed in a mounting hole opened in the refractory material, characterized in that abnormal heat generation due to a decrease in the electrical resistivity of the refractory material is detected using the measured temperatures of the first temperature sensor and the second temperature sensor.

2. Subtracting the measured temperature of the second temperature sensor from the measured temperature of the first temperature sensor, wherein when the increase amount of the obtained temperature difference exceeds a predetermined value, abnormal heat generation of the refractory material is detected. The method for monitoring a glass melting furnace according to claim 1.

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

4. The method for monitoring a glass melting furnace according to any one of claims 1 to 3, characterized in that the glass raw material is heated only by energization heating by the electrode.

5. The method for monitoring a glass melting furnace according to any one of claims 1 to 4, characterized in that the first temperature sensor and the second temperature sensor are thermocouples.

6. The method for monitoring a glass melting furnace according to any one of claims 1 to 5, characterized in that the temperature measurement parts of the first temperature sensor and the second temperature sensor are disposed inside the refractory material to measure the temperature of the refractory material.

7. The temperature measurement part of the first temperature sensor is disposed inside the refractory material to measure the temperature of the refractory material, and the temperature measurement part of the second temperature sensor is disposed at the boundary between the refractory material and the molten glass to measure the temperature of the molten glass. The method for monitoring a glass melting furnace according to any one of claims 1 to 5.

8. The method for monitoring a glass melting furnace according to claim 6 or 7, characterized in that the first temperature sensor and the second temperature sensor are covered with noble metal caps at the temperature measurement parts.

9. A glass article manufacturing method, comprising: a melting step of melting the glass raw material by the glass melting furnace using the method for monitoring a glass melting furnace according to any one of claims 1 to 8; and a forming step of forming the molten glass melted in the glass melting furnace.

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