Method of manufacturing glass article, heating apparatus for manufacturing glass article, and glass melting furnace

Abstract

To achieve a control of optimizing flow rates of fuel gas and oxygen supplied to an oxygen combustion burner at and after a start-up of the burner.SOLUTION: A method of manufacturing a glass article includes a heating step P2 of heating molten glass 4 with flame 6 formed by a burner 5 supplied with fuel gas and oxygen. The method further includes, before the heating step P2, a start-up step P1 of starting the supplies of the fuel gas and the oxygen to the burner 5 and increasing flow rates of the fuel gas and the oxygen to target flow rates in the heating step P2. In each of the start-up step P1 and the heating step P2, the flow rates of the fuel gas and the oxygen are measured and are controlled on the basis of results of the measurements. A control mode is switched between the start-up step P1 and the heating step P2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a glass article, a heating apparatus for manufacturing a glass article, and a glass melting furnace. [Background technology]

[0002] When manufacturing glass articles such as glass plates, glass tubes, glass fibers, etc., glass raw materials charged into a melting tank of a glass melting furnace are heated and melted to continuously produce molten glass, which is the base material for the glass articles. To heat the glass raw materials and molten glass in the melting tank, a burner disposed in the melting tank may be used (see Patent Document 1).

[0003] Burners create a flame by mixing and burning a fuel gas (natural gas, hydrogen, ammonia, etc.) supplied to the burner with a combustion-supporting gas. Burners include air-fuel burners, which use air as the combustion-supporting gas, and oxygen-fuel burners, which use oxygen. The use of oxygen-fuel burners has the advantages of efficient combustion, making it easy to raise the temperature inside the melting tank, and avoiding the generation of nitrogen oxides (NOx). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-1953 Summary of the Invention [Problem to be solved by the invention]

[0005] When using an oxygen combustion burner, it is necessary to start up the burner to an optimum state for heating the glass raw materials and molten glass. To start up the burner, the supply of fuel gas and oxygen to the burner is started, and the flow rates of the fuel gas and oxygen are increased toward the target flow rates (optimum flow rates for heating the glass raw materials and molten glass).

[0006] When starting up an oxygen combustion burner and while heating glass raw materials and molten glass after start-up, the flow rates of fuel gas and oxygen supplied to the burner are measured, and the flow rates of fuel gas and oxygen are controlled based on the measurement results. However, there has been a problem in that control that can optimize the flow rates both during and after start-up has not been realized.

[0007] The above-mentioned problems do not only occur when an oxygen-fuel combustion burner is provided in the melting tank of a glass melting furnace, but also occur when, for example, an oxygen-fuel combustion burner for heating molten glass is provided in a fining tank for degassing molten glass.

[0008] In view of the above circumstances, the problem to be solved is to realize control that can optimize the flow rates of fuel gas and oxygen supplied to an oxygen combustion burner both at the start-up of the burner and after the start-up of the burner. [Means for solving the problem]

[0009] A first method for manufacturing a glass article to solve the above problem is a method for manufacturing a glass article that includes a heating step in which molten glass is heated by a flame formed by supplying fuel gas and oxygen to a burner, and further includes a start-up step in which, before the heating step, the supply of fuel gas and oxygen to the burner is started and the flow rates of the fuel gas and oxygen are increased toward target flow rates for the heating step, and in each of the start-up step and the heating step, the flow rates of the fuel gas and oxygen are measured and the flow rates of the fuel gas and oxygen are controlled based on the measurement results, and the control mode is switched between the start-up step and the heating step.

[0010] In the first manufacturing method described above, the control mode is switched between the start-up process and the heating process, so that fuel gas and oxygen can be supplied to the burner in a control mode suitable for the start-up process and a control mode suitable for the heating process. As a result, it is possible to control the flow rate to be optimized both when the burner is started up (during the start-up process) and after it is started up (during the heating process).

[0011] The second glass article manufacturing method is a configuration in which, in the above-mentioned first manufacturing method, PID control is performed in each of the start-up process and the heating process, and by switching the control mode, the PID control in the heating process has a larger proportional band and a longer integral time for the fuel gas flow rate than the PID control in the start-up process.

[0012] In the second manufacturing method, the tracking of the actual flow rate (measured flow rate) relative to the target flow rate can be improved in the rise process where the proportional band is relatively small and the integral time is short with respect to the flow rate of the fuel gas. On the other hand, in the heating process where the proportional band is relatively large and the integral time is long, it becomes easier to prevent the actual flow rate from overshooting the target flow rate (the actual flow rate exceeding the target flow rate).

[0013] The third method for manufacturing a glass article is the same as the second method described above, except that the control mode is switched when the flow rate of the fuel gas reaches a control mode switching threshold value in the start-up process.

[0014] In the third manufacturing method, the timing for switching the control mode is determined by a control mode switching threshold. Because the timing for switching is determined by a predetermined threshold, it is possible to prevent the burner startup behavior from changing each time the startup process is performed, and it is possible to stabilize the startup behavior.

[0015] A fourth method for manufacturing a glass article is the same as the third manufacturing method described above, except that the flow rate of fuel gas corresponding to the control mode switching threshold is smaller than the target flow rate of fuel gas in the heating step.

[0016] In the fourth manufacturing method, the control mode switching threshold value that determines the timing for switching the control mode is smaller than the target flow rate of the fuel gas in the heating step, which is more advantageous in preventing the above-mentioned overshoot.

[0017] The fifth method for manufacturing a glass article is the third or fourth manufacturing method described above, except that in the start-up process, the supply of oxygen is started after it is detected that the supply of fuel gas has started.

[0018] In the fifth manufacturing method, the start-up process starts the supply of oxygen after detecting the start of the fuel gas supply. That is, the supply of oxygen to the burner starts after confirming that the fuel gas is being supplied to the burner. This effectively eliminates the risk of an explosion in the melting tank or fining tank of a glass melting furnace due to an improper supply of fuel gas to the burner. More specifically, if fuel gas is not supplied to the burner disposed in the melting tank or fining tank as desired, a situation may arise in which only oxygen, out of the fuel gas and oxygen, continues to be supplied to the burner. In this situation, the melting tank or fining tank becomes filled with oxygen, which may lead to an explosion due to a spark in the tank. However, the fifth manufacturing method effectively eliminates such a risk.

[0019] The sixth glass article manufacturing method is the same as the fifth manufacturing method described above, except that in the start-up process, the flow rate of the fuel gas is gradually increased and the supply of oxygen is started after the flow rate of the fuel gas exceeds an oxygen supply start threshold that is smaller than the control mode switching threshold.

[0020] In the sixth manufacturing method described above, the flow rate of the fuel gas is gradually increased during the start-up process. This is advantageous for slowly mixing the fuel gas and oxygen, making it easier to prevent sudden combustion. Furthermore, in the sixth manufacturing method described above, the supply of oxygen is started during the start-up process after the flow rate of the fuel gas exceeds the oxygen supply start threshold. In other words, the supply of oxygen to the burner is started after it has been more reliably confirmed that fuel gas is being supplied to the burner. This is therefore more advantageous in eliminating the risk of the above-mentioned explosion occurring.

[0021] The seventh glass article manufacturing method is the same as the sixth manufacturing method described above, except that in the start-up process, after starting the supply of oxygen, the flow rate of oxygen is gradually increased, and after the flow rate of fuel gas exceeds an intermediate threshold that is greater than the oxygen supply start threshold and less than the control mode switching threshold, the flow rate of oxygen is controlled so that the flow rate of oxygen becomes a flow rate corresponding to complete combustion of the fuel gas.

[0022] Here, "the flow rate of oxygen corresponds to the complete combustion of the fuel gas" means that the flow rate of oxygen is within the range of -1% to 5% of the flow rate of oxygen required for the complete combustion of the fuel gas, and preferably within the range of 0% to 3%.

[0023] In the seventh manufacturing method, the oxygen flow rate is gradually increased during the start-up process. This is more advantageous for slowly mixing the fuel gas and oxygen, making it easier to prevent sudden combustion. Furthermore, in the seventh manufacturing method, after the fuel gas flow rate exceeds the intermediate threshold during the start-up process, the oxygen flow rate is controlled to a flow rate corresponding to complete combustion of the fuel gas. This prevents incomplete combustion due to an insufficient oxygen flow rate relative to the fuel gas flow rate, or an explosion due to an excessive oxygen flow rate.

[0024] The eighth method for manufacturing a glass article is the same as the seventh method, except that in the start-up process, when the flow rate of the fuel gas is above the oxygen supply start threshold and below the intermediate threshold, the flow rate of oxygen is made greater than the flow rate corresponding to complete combustion of the fuel gas.

[0025] In the start-up process, if oxygen supply to the burner is started after detecting that fuel gas supply to the burner has started, the fuel gas will be supplied before the oxygen. Accordingly, as in the eighth manufacturing method described above, it is preferable to increase the oxygen flow rate at an initial point after oxygen supply has started (the point at which the fuel gas flow rate exceeds the oxygen supply start threshold) above the flow rate corresponding to complete combustion of the fuel gas. This eliminates the oxygen shortage condition relative to the fuel gas supplied earlier, which is advantageous in preventing incomplete combustion.

[0026] The ninth method for manufacturing a glass article is any one of the first to eighth manufacturing methods described above, further comprising a stopping step in which the supply of fuel gas and oxygen to the burner is stopped after the heating step to terminate the formation of the flame, and in the stopping step, the supply of oxygen is stopped after the supply of fuel gas is stopped.

[0027] In the ninth manufacturing method, the supply of oxygen is stopped after the supply of fuel gas is stopped in the stopping step, so that it is possible to prevent unburned fuel gas from remaining.

[0028] The tenth method for manufacturing a glass article is the same as the ninth method, except that in the stopping step, the supply of oxygen is stopped after a predetermined time has elapsed since the supply of fuel gas was stopped.

[0029] In the above tenth manufacturing method, a predetermined time is set between stopping the supply of fuel gas and stopping the supply of oxygen in the stopping process, which is more advantageous in avoiding the remaining unburned fuel gas.

[0030] An eleventh method for manufacturing a glass article is the ninth or tenth method described above, wherein in the stopping step, the flow rate of oxygen is made smaller than the target flow rate of oxygen in the heating step from the time the supply of fuel gas is stopped to the time the supply of oxygen is stopped.

[0031] In the above-mentioned eleventh manufacturing method, the flow rate of oxygen in the stopping process is set to be smaller than the target flow rate of oxygen in the heating process, so that excessive oxygen is prevented from being used to achieve the objective of avoiding the remaining unburned fuel gas.

[0032] A heating device for manufacturing glass articles that solves the above problems comprises a burner, a fuel gas supply device that supplies fuel gas to the burner, an oxygen supply device that supplies oxygen to the burner, and a control device that controls the flow rate of the fuel gas supplied by the fuel gas supply device and the flow rate of the oxygen supplied by the oxygen supply device, and is a heating device for manufacturing glass articles that forms a flame from the fuel gas and oxygen supplied to the burner, and is characterized in that the control device is capable of start-up operation in which the supply of fuel gas and oxygen to the burner is started and the flow rates of the fuel gas and oxygen are increased toward the target flow rates during normal operation, and the control device is configured to be able to switch control modes between start-up operation and normal operation.

[0033] If the burner of the heating device is disposed in the melting tank or fining tank of a glass melting furnace, it is possible to obtain the same functions and effects as those of the first manufacturing method.

[0034] According to the glass melting furnace equipped with the heating device for manufacturing a glass article described above, it is possible to obtain the same functions and effects as those of the first manufacturing method described above. [Effects of the Invention]

[0035] According to the glass article manufacturing method, the heating device for manufacturing a glass article, and the glass melting furnace of the present disclosure, when controlling the flow rates of fuel gas and oxygen supplied to an oxygen combustion burner, it is possible to control the flow rates so as to optimize the flow rates both at the time of start-up of the burner and after start-up of the burner. [Brief explanation of the drawings]

[0036] [Figure 1] 1 is a diagram illustrating a glass melting furnace, a heating device for manufacturing a glass article, and a heating step in a method for manufacturing a glass article. [Figure 2] FIG. 2 is a diagram showing a start-up process and a heating process in the manufacturing method of a glass article. [Figure 3] 1 is a diagram showing a heating step and a stopping step in a manufacturing method of a glass article. DETAILED DESCRIPTION OF THE INVENTION

[0037] Hereinafter, embodiments of a method for manufacturing a glass article, a heating device for manufacturing a glass article, and a glass melting furnace will be described with reference to the accompanying drawings. First, a glass melting furnace used in carrying out the method for manufacturing a glass article will be described.

[0038] 1 shows a glass melting furnace 1. The glass melting furnace 1 includes a melting tank 2 and a heating device 3 (hereinafter simply referred to as heating device 3) for manufacturing glass articles.

[0039] The melting tank 2 is a tank for heating and melting glass raw materials (not shown) that are charged into the melting tank 2 to produce molten glass 4, which is the source of glass articles (e.g., glass sheets, glass tubes, glass fibers, etc.). The heating device 3 is a device for forming a flame 6 from fuel gas and oxygen supplied to a burner 5 to heat the inside of the melting tank 2.

[0040] The melting tank 2 is constructed by arranging a plurality of refractories (bricks) side by side. The melting tank 2 has a side wall 7, and a burner 5 is arranged on the side wall 7.

[0041] The heating device 3 includes the burner 5, a fuel gas supply device 8 that supplies fuel gas to the burner 5, an oxygen supply device 9 that supplies oxygen to the burner 5, and a control device 10 that controls the flow rate of the fuel gas supplied by the fuel gas supply device 8 and the flow rate of oxygen supplied by the oxygen supply device 9.

[0042] The burner 5 is an oxygen combustion burner that receives a supply of fuel gas and oxygen as a combustion-supporting gas, mixes and burns the two to form a flame. As an example, the burner 5 has a double-pipe structure, and is equipped with an inner pipe through which the fuel gas flows and an outer pipe through which oxygen flows.

[0043] The fuel gas may be a hydrocarbon gas such as natural gas, hydrogen gas, or ammonia gas, or a mixture of these gases. In this embodiment, a mixture of hydrogen gas and natural gas (with a flow rate ratio of hydrogen:natural gas=1:1) is used as the fuel gas.

[0044] The fuel gas supply device 8 includes a hydrogen source 11, a hydrogen supply path 12 connecting the hydrogen source 11 and the burner 5, a natural gas source 13, and a natural gas supply path 14 connecting the natural gas source 13 and the burner 5. In Fig. 1, the hydrogen supply path 12 and the natural gas supply path 14 are indicated by very thick lines.

[0045] The hydrogen source 11 and the natural gas source 13 are devices capable of continuously supplying hydrogen and natural gas, respectively. The hydrogen supply path 12 and the natural gas supply path 14 are, for example, each formed of a pipe or a hose. The hydrogen supply path 12 and the natural gas supply path 14 join at a junction 15, and the hydrogen and natural gas are mixed between the junction 15 and the burner 5.

[0046] The oxygen supply device 9 includes a first oxygen source 16, a first oxygen supply path 17 connecting the first oxygen source 16 and the burner 5, a second oxygen source 18, and a second oxygen supply path 19 connecting the second oxygen source 18 and the burner 5. In Fig. 1, the first oxygen supply path 17 and the second oxygen supply path 19 are indicated by very thick lines.

[0047] The first oxygen source 16 and the second oxygen source 18 are devices capable of continuously supplying oxygen. The first oxygen supply path 17 and the second oxygen supply path 19 are, for example, each configured with a pipe or a hose. The first oxygen supply path 17 and the second oxygen supply path 19 join at a joining point 20. The oxygen used here is pure oxygen, and its oxygen concentration is, for example, 90% or more, preferably 95% or more, and more preferably 99% or more.

[0048] The control device 10 includes a hydrogen control mechanism 21 for controlling the flow rate of hydrogen flowing through the hydrogen supply path 12, a natural gas control mechanism 22 for controlling the flow rate of natural gas flowing through the natural gas supply path 14, a first oxygen control mechanism 23 for controlling the flow rate of oxygen flowing through the first oxygen supply path 17, and a second oxygen control mechanism 24 for controlling the flow rate of oxygen flowing through the second oxygen supply path 19.

[0049] In this heating device 3, the flow rate of fuel gas (flow rate ratio of hydrogen:natural gas = 1:1) supplied to burner 5 is controlled by controlling the flow rate of hydrogen using hydrogen control mechanism 21 and the flow rate of natural gas using natural gas control mechanism 22. In addition, the flow rate of oxygen supplied to burner 5 is controlled by controlling the flow rate of oxygen using first oxygen control mechanism 23 and the flow rate of oxygen using second oxygen control mechanism 24.

[0050] The hydrogen control mechanism 21 has a hydrogen flow meter 25, a hydrogen regulator 26, and a hydrogen control valve 27. The natural gas control mechanism 22 has a natural gas flow meter 28, a natural gas regulator 29, and a natural gas control valve 30. The first oxygen control mechanism 23 has a first oxygen flow meter 31, a first oxygen regulator 32, and a first oxygen control valve 33. The second oxygen control mechanism 24 has a second oxygen flow meter 34, a second oxygen regulator 35, and a second oxygen control valve 36.

[0051] Here, the hydrogen control mechanism 21 and the natural gas control mechanism 22 have the same configuration. Therefore, only the configuration of the hydrogen control mechanism 21 will be described in detail below. Furthermore, the first oxygen control mechanism 23 and the second oxygen control mechanism 24 have the same configuration. Therefore, only the configuration of the first oxygen control mechanism 23 will be described in detail below.

[0052] In the hydrogen control mechanism 21, a hydrogen flow meter 25 and a hydrogen control valve 27 are arranged on the hydrogen supply path 12. The hydrogen flow meter 25 measures the actual flow rate of hydrogen circulating through the hydrogen supply path 12 (hereinafter, the measured flow rate will be referred to as the measured flow rate). In this embodiment, a differential pressure flow meter is used as the hydrogen flow meter 25. The hydrogen flow meter 25 sends the value of the measured hydrogen flow rate to the hydrogen regulator 26. The hydrogen regulator 26 compares the measured hydrogen flow rate with a target hydrogen flow rate, and based on the comparison result, adjusts the opening of the hydrogen control valve 27 so that the measured flow rate becomes the target flow rate. In this way, the flow rate of hydrogen circulating through the hydrogen supply path 12 is controlled. The hydrogen regulator 26 also sends the value of the measured hydrogen flow rate to the first oxygen regulator 32 of the first oxygen control mechanism 23.

[0053] The main difference between the configuration of the natural gas control mechanism 22 and the configuration of the hydrogen control mechanism 21 is that the natural gas regulator 29 sends the measured flow rate value of natural gas to the second oxygen regulator 35 of the second oxygen control mechanism 24.

[0054] In the first oxygen control mechanism 23, a first oxygen flow meter 31 and a first oxygen control valve 33 are arranged on the first oxygen supply path 17. The first oxygen flow meter 31 measures the actual flow rate of oxygen flowing through the first oxygen supply path 17 (hereinafter, the measured flow rate will be referred to as the measured flow rate). In this embodiment, a differential pressure flow meter is used as the first oxygen flow meter 31. The first oxygen flow meter 31 sends the value of the measured oxygen flow rate to the first oxygen regulator 32. The first oxygen regulator 32 compares the measured oxygen flow rate with a target oxygen flow rate, and adjusts the opening of the first oxygen control valve 33 based on the comparison result so that the measured flow rate becomes the target flow rate. In this way, the flow rate of oxygen flowing through the first oxygen supply path 17 is controlled.

[0055] The target flow rates of oxygen to be circulated through the first oxygen supply line 17 and the second oxygen supply line 19 are determined from the measured flow rate of hydrogen sent from the hydrogen regulator 26 to the first oxygen regulator 32 and the measured flow rate of natural gas sent from the natural gas regulator 29 to the second oxygen regulator 35, respectively. Specifically, the target flow rate of oxygen to be circulated through the first oxygen supply line 17 is determined by multiplying the measured flow rate of hydrogen by a constant, and the target flow rate of oxygen to be circulated through the second oxygen supply line 19 is determined by multiplying the measured flow rate of natural gas by a constant. The above constants are explained below.

[0056] In determining the target flow rate of oxygen to be circulated through the first oxygen supply path 17, the constant by which the measured flow rate of hydrogen is multiplied is 0.5. That is, [target flow rate of oxygen to be circulated through the first oxygen supply path 17] = [measured flow rate of hydrogen × 0.5]. This is based on the fact that the chemical reaction formula for complete combustion of hydrogen is H2 + 0.5O2 → H2O. On the other hand, in determining the target flow rate of oxygen to be circulated through the second oxygen supply path 19, the constant by which the measured flow rate of natural gas (more specifically, city gas) in this embodiment is multiplied is 2.25. That is, [target flow rate of oxygen to be circulated through the second oxygen supply path 19] = [measured flow rate of natural gas × 2.25]. This is based on the fact that the chemical reaction formula for complete combustion of natural gas in this embodiment is 0.89CH4 + 0.07C2H6 + 0.03C3H8 + 0.01C4H 10 +2.25O2 → 1.17CO2 + 2.17H2O. Hereinafter, the state where the above two equations hold is referred to as the "normal oxygen supply state."

[0057] As will be described in detail later in the description of the glass article manufacturing method, the present heating device 3 can temporarily set the target oxygen flow rate to a flow rate greater than the measured flow rates of hydrogen and natural gas multiplied by the above constants. That is, the target oxygen flow rate to be circulated through the first oxygen supply path 17 can be set to > 0.5 times the measured hydrogen flow rate, or the target oxygen flow rate to be circulated through the second oxygen supply path 19 can be set to > 2.25 times the measured natural gas flow rate. Hereinafter, a state in which the above two inequalities hold is referred to as an "oxygen excess supply state." The present heating device 3 can also temporarily set the target oxygen flow rate to zero, regardless of the measured hydrogen and natural gas flow rates.

[0058] The heating device 3 is capable of operating under the control of the control device 10 in a normal operation for producing a glass article and in a start-up operation for preparing for the normal operation.

[0059] Normal operation is an operating mode when performing the heating step P2 in the glass article manufacturing method described below. On the other hand, start-up operation is an operating mode when performing the start-up step P1 in the glass article manufacturing method. During start-up operation, the supply of fuel gas and oxygen to the burner 5 is started, and the flow rates of the fuel gas and oxygen are increased toward the target flow rates during normal operation (heating step P2). As will be described in detail in the glass article manufacturing method described below, during start-up operation, the heating device 3 is configured to start the supply of oxygen after detecting that the supply of fuel gas has started.

[0060] In the heating device 3, the hydrogen control mechanism 21, natural gas control mechanism 22, first oxygen control mechanism 23, and second oxygen control mechanism 24 control the flow rates of hydrogen, natural gas, and oxygen, respectively, using PID control. Each of the four control mechanisms 21 to 24 is capable of switching the control mode while the heating device 3 is in operation. In other words, by switching the control mode, it is possible to change the settings of the proportional band corresponding to "P" in PID control, the integral time corresponding to "I," and the derivative time corresponding to "D." Note that fuzzy control may be used instead of PID control.

[0061] The following describes a method for manufacturing a glass article using the above-described glass melting furnace 1. This manufacturing method includes, in chronological order, a start-up step P1, a heating step P2, and a shut-down step P3.

[0062] In the heating step P2, as shown in Fig. 1, the inside of the melting tank 2 of the glass melting furnace 1 is heated by a flame 6 formed by a burner 5. This heats the glass raw materials charged into the melting tank 2 and the molten glass 4 produced by melting the raw materials.

[0063] In the start-up process P1 (see FIG. 2) carried out before the heating process P2, the supply of fuel gas and oxygen to the burner 5 is started, and the flow rates of the fuel gas and oxygen are increased toward the target flow rates for the heating process P2. On the other hand, in the stop process P3 (see FIG. 3) carried out after the heating process P2, the supply of fuel gas and oxygen to the burner 5 is stopped to terminate the formation of the flame 6. In this embodiment, before the start-up process P1, the inside of the melting tank 2 of the glass melting furnace 1 is preheated to 1000°C or higher by an air-fired burner that forms a flame from fuel gas and air.

[0064] Hereinafter, a specific aspect of the start-up step P1 and an aspect of the transition from the start-up step P1 to the heating step P2 will be described with reference to FIG.

[0065] 2, the upper graph shows the change over time in the fuel gas flow rate (the total flow rate of hydrogen and natural gas), while the lower graph shows the change over time in the oxygen flow rate (the total flow rate of oxygen flowing through the first oxygen supply path 17 and the second oxygen supply path 19). In each of the upper and lower graphs, the dashed line represents the target flow rate, and the solid line represents the measured flow rate (actual flow rate).

[0066] In the start-up process P1, the target flow rates of the fuel gas and oxygen are gradually increased from zero, and as a result, the measured flow rates of the fuel gas and oxygen also gradually increase from zero. Here, as described above, the target flow rate of oxygen is determined by multiplying the measured flow rates of hydrogen and natural gas that make up the fuel gas by a constant. Therefore, the manner in which the target flow rate and measured flow rate of oxygen increase is determined based on the manner in which the target flow rate and measured flow rate of the fuel gas increase (excluding the period from time zero to time T2, when the measured flow rate of fuel gas ranges from zero to the second threshold value Q2).

[0067] In this embodiment, the target flow rate of the fuel gas increases along a straight line with a constant slope, and the measured flow rate of the fuel gas also increases along a straight line. Three thresholds, a first threshold Q1, a second threshold Q2, and a third threshold Q3, are set in advance for the measured flow rate of the fuel gas in ascending order. The third threshold Q3 is smaller than the target flow rate of the fuel gas in the heating step P2. The times at which the measured flow rate of the fuel gas reaches the first threshold Q1, the second threshold Q2, and the third threshold Q3 are shown in FIG. 2 as time T1, time T2, and time T3, respectively.

[0068] The first threshold Q1 is a threshold (oxygen supply start threshold) that serves as a reference for the timing to start oxygen supply after the start of fuel gas supply, which precedes the start of fuel gas supply in the time series. The second threshold Q2 is a threshold (intermediate threshold) that serves as a reference for the timing to transition the target oxygen flow rate from a flow rate higher than the flow rate corresponding to complete combustion of the fuel gas to a flow rate corresponding to complete combustion. The third threshold Q3 is a threshold (control mode switch threshold) that serves as a reference for the timing to switch the control mode when transitioning from the start-up process P1 to the heating process P2.

[0069] Here, in this embodiment, the target flow rate of the fuel gas is increased along a straight line, but the target flow rate may be increased in other ways as long as the target flow rate increases gradually. For example, the target flow rate of the fuel gas may be increased along a curved line or in a stepwise manner.

[0070] In the start-up process P1, the supply of oxygen is started after it is detected that the supply of fuel gas has started. Specifically, the supply of oxygen is started after the measured flow rate of fuel gas exceeds the first threshold Q1. In other words, from time zero to time T1, when the measured flow rate of fuel gas takes a value between zero and the first threshold Q1, the target flow rate of oxygen is set to zero, and as a result, the measured flow rate of oxygen becomes zero. The first threshold Q1 (Nm 3 / h) is, for example, the target flow rate (Nm 3 / h), and preferably 2% to 7%.

[0071] As described above, oxygen supply begins when the measured flow rate of fuel gas exceeds the first threshold Q1, but the manner in which oxygen is supplied is different between times T1 to T2 when the measured flow rate of fuel gas is between the first threshold Q1 and the second threshold Q2 and after time T2 when the measured flow rate exceeds the second threshold Q2.

[0072] From time T1 to T2, oxygen is supplied under the above-mentioned oxygen excess supply state. That is, the target flow rate of oxygen is set to be greater than the flow rate corresponding to complete combustion of the fuel gas (fuel gas at the measured flow rate). As a result, from time T1 to T2, the measured flow rate of oxygen is greater than the flow rate corresponding to complete combustion of the fuel gas (fuel gas at the measured flow rate). In this embodiment, from time T1 to T2, the target flow rate of oxygen is set to a constant value.

[0073] On the other hand, after time T2, oxygen is supplied under the above-mentioned normal oxygen supply state, rather than the excessive oxygen supply state from time T1 to T2. That is, the target flow rate of oxygen is set to a flow rate corresponding to complete combustion of the fuel gas (fuel gas at the measured flow rate). As a result, after time T2, the measured flow rate of oxygen becomes a flow rate corresponding to complete combustion of the fuel gas (fuel gas at the measured flow rate). Note that the target flow rate of oxygen is set to a flow rate corresponding to complete combustion of the fuel gas (fuel gas at the measured flow rate) not only after time T2 in the start-up process P1, but also in the heating process P2 performed after the start-up process P1.

[0074] Second threshold Q2 (Nm 3 / h) is a value greater than the first threshold Q1 (Q2>Q1), and is, for example, the target flow rate (Nm 3 / h), and preferably 12% to 15%.

[0075] After time T2, when the measured flow rate of the fuel gas reaches the third threshold Q3, the rise-up process P1 ends and the heating process P2 starts. Then, with the transition from the rise-up process P1 to the heating process P2 at time T3, the control mode in the PID control is switched only for the fuel gas flow rate out of the fuel gas flow rate and the oxygen flow rate. Specifically, by switching the control mode, the proportional band is made larger and the integral time is made longer for the fuel gas flow rate in the PID control in the heating process P2 compared to the PID control in the rise-up process P1.

[0076] In the heating step P2, unlike the start-up step P1, the target flow rate of the fuel gas is set to a constant value. As a result, in the heating step P2, the measured flow rate of the fuel gas continues to be close to a constant value. When the heating step P2 is completed, the stop step P3 is executed.

[0077] Third threshold Q3 (Nm 3 / h) is, for example, the target flow rate (Nm 3 / h), and preferably 90% to 100%.

[0078] Hereinafter, a transition from the heating step P2 to the stopping step P3 and a specific aspect of the stopping step P3 will be described with reference to FIG.

[0079] Of the two graphs shown in Figure 3, the upper graph shows the change over time in the fuel gas flow rate (the total flow rate of hydrogen and natural gas), while the lower graph shows the change over time in the oxygen flow rate (the total flow rate of oxygen flowing through the first oxygen supply path 17 and the second oxygen supply path 19). In each of the upper and lower graphs, the dashed line represents the target flow rate, and the solid line represents the measured flow rate (actual flow rate).

[0080] At time T4, when the heating step P2 transitions to the shutdown step P3, the target flow rate of the fuel gas is set to zero, and the measured flow rate of the fuel gas also becomes zero. Thus, the supply of fuel gas is immediately stopped upon transition to the shutdown step P3. On the other hand, oxygen continues to be supplied for a predetermined period of time under the above-described excess oxygen supply state, even after the transition to the shutdown step P3.

[0081] As described above, in the stopping step P3, the supply of oxygen is stopped after the supply of fuel gas is stopped. Specifically, the supply of oxygen is stopped after time T5 has elapsed since the supply of fuel gas was stopped. In other words, the target flow rate of oxygen is set to zero, and the measured flow rate of oxygen becomes zero. From time T4 to T5, the target flow rate of oxygen is set to be sufficiently smaller than the target flow rate of oxygen in the heating step P2. For example, the target flow rate of oxygen (Nm 3 / h) is the target flow rate of oxygen in the heating step P2 (Nm 3 / h), can be set to 10% to 20%, and preferably 12% to 15%. The time required from time T4 to time T5 may be set to, for example, the time required for the fuel gas in the burner 5 or the piping (in the hydrogen supply path 12 and the natural gas supply path 14) to be discharged, and specifically can be set to 5 to 30 seconds. This completes the shutdown step P3.

[0082] Here, the following modifications can also be applied to the above embodiment. That is, a mixed gas having a different flow ratio of hydrogen to natural gas than that of the above embodiment (for example, hydrogen:natural gas=1:2, hydrogen:natural gas=1:3, etc.) may be used as the fuel gas. In this case, it is preferable to keep the amount of heat generated by combustion constant even if the flow ratio of hydrogen to natural gas is changed. Alternatively, only hydrogen or only natural gas may be used as the fuel gas.

[0083] Furthermore, in the above embodiment, the burner 5 is disposed in the melting tank 2 of the glass melting furnace 1, but the burner 5 may also be disposed in the fining furnace (fining tank). [Explanation of symbols]

[0084] 1. Glass melting furnace 3 Heating equipment for manufacturing glass articles 5 Burner 6. Flame 8. Fuel gas supply device 9. Oxygen supply equipment 10 Control device P1 Start-up process P2 Heating process P3 Stop process Q1 First threshold (oxygen supply start threshold) Q2 Second threshold (intermediate threshold) Q3 Third threshold (control mode switching threshold)

Claims

1. A method for manufacturing a glass article, comprising a heating step of heating molten glass with a flame formed by supplying a fuel gas and oxygen to a burner, a start-up step of starting the supply of the fuel gas and the oxygen to the burner before the heating step and increasing the flow rates of the fuel gas and the oxygen toward target flow rates in the heating step, In each of the start-up step and the heating step, the flow rates of the fuel gas and the oxygen are measured, and the flow rates of the fuel gas and the oxygen are controlled based on the measurement results; A method for manufacturing a glass article, comprising switching a control mode between the start-up step and the heating step.

2. PID control is performed in each of the start-up process and the heating process, 2. The method for manufacturing a glass article according to claim 1, wherein by switching the control mode, the proportional band and integral time for the flow rate of the fuel gas are increased and increased in the PID control in the heating process compared to the PID control in the start-up process.

3. The method for manufacturing a glass article according to claim 2, wherein the control mode is switched when the flow rate of the fuel gas reaches a control mode switching threshold value in the start-up step.

4. The method for manufacturing a glass article according to claim 3 , wherein the flow rate of the fuel gas corresponding to the control mode switching threshold is smaller than a target flow rate of the fuel gas in the heating step.

5. 5. The method for manufacturing a glass article according to claim 3, wherein in the start-up step, the supply of oxygen is started after it is detected that the supply of the fuel gas has started.

6. 6. The method for manufacturing a glass article according to claim 5, wherein in the start-up process, the flow rate of the fuel gas is gradually increased, and the supply of oxygen is started after the flow rate of the fuel gas exceeds an oxygen supply start threshold that is smaller than the control mode switching threshold.

7. 7. The method for manufacturing a glass article according to claim 6, wherein in the start-up process, after starting the supply of oxygen, the flow rate of the oxygen is gradually increased, and after the flow rate of the fuel gas exceeds an intermediate threshold that is larger than the oxygen supply start threshold and smaller than the control mode switching threshold, the flow rate of the oxygen is controlled so that the flow rate of the oxygen becomes a flow rate corresponding to complete combustion of the fuel gas.

8. 8. The method for manufacturing a glass article according to claim 7, wherein in the start-up process, when the flow rate of the fuel gas is greater than the oxygen supply start threshold and equal to or less than the intermediate threshold, the flow rate of the oxygen is made greater than a flow rate corresponding to complete combustion of the fuel gas.

9. a stopping step of stopping the supply of the fuel gas and the oxygen to the burner after the heating step to terminate the formation of a flame, 5. The method for manufacturing a glass article according to claim 1, wherein in the stopping step, the supply of the oxygen is stopped after the supply of the fuel gas is stopped.

10. The method for manufacturing a glass article according to claim 9, wherein in the stopping step, the supply of oxygen is stopped after a predetermined time has elapsed since the supply of the fuel gas was stopped.

11. 11. The method for manufacturing a glass article according to claim 10, wherein in the stopping step, the flow rate of the oxygen is made smaller than the target flow rate of the oxygen in the heating step during the period from the stopping of the supply of the fuel gas to the stopping of the supply of the oxygen.

12. a burner, a fuel gas supply device that supplies fuel gas to the burner, an oxygen supply device that supplies oxygen to the burner, and a control device that controls the flow rate of the fuel gas supplied by the fuel gas supply device and the flow rate of the oxygen supplied by the oxygen supply device, A heating apparatus for manufacturing glass articles, which forms a flame from the fuel gas and the oxygen supplied to the burner, the control device is capable of start-up operation in which supply of the fuel gas and the oxygen to the burner is started and the flow rates of the fuel gas and the oxygen are increased toward target flow rates during normal operation, The heating device for manufacturing glass articles, wherein the control device is configured to be able to switch a control mode between the start-up operation and the normal operation.

13. A glass melting furnace equipped with the heating device for producing a glass article according to claim 12.

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