Regenerative burner, industrial furnace, method for manufacturing sintered product, and method for manufacturing heat treated product

Abstract

To provide a regenerative burner which is useful for maintaining combustion of ammonia-containing fuel at high output.SOLUTION: A regenerative burner includes a combustion chamber, a heat exchanging chamber, and a communication path between the combustion chamber and the heat exchanging chamber. The combustion chamber includes: an ignition port in communication with an air supply path and a first fuel path for supplying a first fuel containing one or more selected from ammonia, hydrogen, and carbon hydride; a tip end of at least one fuel nozzle in communication with a second fuel supply path for supplying a second fuel containing ammonia; and a flame injection port. In the presence of a first flame generated at the ignition port and combustion air being supplied into the combustion chamber from the heat exchanging chamber through the communication path, the combustion chamber is configured to burn the second fuel supplied from the tip end of the at least one fuel nozzle into the combustion chamber in the combustion chamber, and eject a second flame from the flame ejection port.SELECTED DRAWING: Figure 1-1

Description

[Technical Field]

[0001] The present invention relates to a regenerative burner. The present invention also relates to an industrial furnace equipped with a regenerative burner. The present invention also relates to a method for producing a fired product. The present invention also relates to a method for producing a heat-treated product using a regenerative burner. [Background technology]

[0002] Regenerative burners have been known as combustion devices used in heating furnaces, combustion furnaces, etc. In addition to burning fuel, regenerative burners also have the function of recovering heat from the combustion exhaust gas using a heat storage medium installed inside. Regenerative burners alternate between combustion and exhaust, allowing the burner itself to recover exhaust heat and achieving highly efficient combustion. For this reason, regenerative burners are widely used in various industrial furnaces as they reduce the fuel consumption of combustion devices and contribute to energy conservation.

[0003] Conventional regenerative burners generally use hydrocarbon fuels such as LNG as fuel. For this reason, the structure of regenerative burners has been optimized for burning hydrocarbon fuels. For example, Japanese Patent Application Laid-Open Publication No. 2019-086202 describes a regenerative burner including a combustion chamber, a heat exchange chamber, and a communication passage between the combustion chamber and the heat exchange chamber, in which the tip of a fuel nozzle and a flame injection port are installed in the combustion chamber, and the fuel introduced from the fuel nozzle into the combustion chamber is combusted in the combustion chamber using combustion air introduced into the combustion chamber through the communication passage, so that a flame can be ejected from the flame injection port, and the fuel nozzle is configured so that the entire amount of fuel combusted by the regenerative burner is introduced into the combustion chamber.

[0004] However, with the recent calls for the realization of a decarbonized society, ammonia, a carbon-neutral fuel that does not emit CO2, is attracting attention. However, ammonia is flame-retardant, its burning speed is about one-sixth that of methane, and it is prone to misfires. For this reason, when using ammonia as a fuel, it is desirable to develop a regenerative burner that is suited to the combustion characteristics of ammonia.

[0005] Japanese Patent Application Laid-Open Publication No. 2016-130619 describes a combustion device for flame retardant fuel that can stabilize flame stabilization even when the flow rate of the fuel mixture is increased so that the supply flow rate of the flame retardant fuel such as ammonia is increased to the same level as the flow rate corresponding to the combustion rate of the hydrocarbon fuel. This combustion device for flame retardant fuel is characterized by comprising a burner that supplies a mixture of flame retardant fuel and an oxidizer into a combustion chamber and burns it, and a swirler that swirls the mixture within the combustion chamber. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-086202 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-130619 Summary of the Invention [Problem to be solved by the invention]

[0007] The regenerative burner described in Patent Document 1 is not optimized for the combustion of ammonia, and there is still room for improvement. The combustion device described in Patent Document 2 is useful for stably burning ammonia, but is not a regenerative burner. In addition, there has been insufficient consideration given to increasing output. For this reason, there is still no regenerative burner suitable for using ammonia as fuel.

[0008] The present invention was created in light of the above circumstances, and one of its objectives is to provide a regenerative burner that is useful for sustaining high-power combustion of ammonia-containing fuel. Another objective of the present invention is to provide an industrial furnace equipped with such a regenerative burner. Yet another objective of the present invention is to provide a method for producing heat-treated products using such a regenerative burner. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above problems. Conventional regenerative burners are configured so that air is supplied to a combustion chamber through a heat exchange chamber, and fuel is also supplied to the combustion chamber to cause a combustion reaction with the air. However, this configuration alone is not sufficient to stably burn an ammonia-containing fuel at high output. The inventors have found that, in order to stably burn an ammonia-containing fuel, it is advantageous to not only supply the ammonia-containing fuel to the combustion chamber, but also to provide a separate ignition port communicating with the fuel and air, and to supply a flame generated at this ignition port to the combustion chamber. The present invention was completed based on this finding, and is exemplified below.

[0010] [Aspect 1] A regenerative burner comprising a combustion chamber, a heat exchange chamber, and a communication passage between the combustion chamber and the heat exchange chamber, the combustion chamber has an ignition port communicating with a first fuel supply passage for supplying a first fuel containing one or more selected from ammonia, hydrogen, and hydrocarbons and an air supply passage, a tip of at least one fuel nozzle communicating with a second fuel supply passage for supplying a second fuel containing ammonia, and a flame injection port; the combustion chamber is configured so that a second fuel supplied from a tip of the at least one fuel nozzle into the combustion chamber is combusted in the combustion chamber in the presence of a first flame generated at the ignition port and combustion air supplied from the heat exchange chamber through the communicating passage into the combustion chamber, and a second flame can be ejected from the flame injection port, The entire amount of the first fuel combusted in the regenerative burner is supplied from a first fuel supply passage to the ignition port, and the entire amount of the second fuel combusted in the regenerative burner is supplied from the second fuel supply passage to the at least one fuel nozzle. Regenerative burner. [Aspect 2] A regenerative burner as described in aspect 1, wherein when the combustion chamber is observed from a horizontal direction perpendicular to a perpendicular line N extending from the opening surface S of the ignition port, if the intersection point of the perpendicular line N and a line segment M extending toward the supply direction of the second fuel from the tip T of at least one fuel nozzle is P, the angle (∠TPS) formed by the line segments TP and PS is 90°≦∠TPS≦110°. [Aspect 3] 3. The regenerative burner according to aspect 1 or 2, wherein the supply direction of the second fuel supplied from the tip of the at least one fuel nozzle is inclined toward the ignition port. [Aspect 4] 4. The regenerative burner according to any one of Aspects 1 to 3, wherein the ejection holes provided at the tip of the at least one fuel nozzle have a structure capable of radially ejecting the second fuel. [Aspect 5] 5. The regenerative burner according to any one of aspects 1 to 4, wherein a tip of the at least one fuel nozzle is provided at a position facing a port on the combustion chamber side of the communication passage. [Aspect 6] A regenerative burner according to any one of Aspects 1 to 5, wherein the ignition port is disposed at a position opposite the flame injection port. [Aspect 7] An industrial furnace comprising a plurality of regenerative burners according to any one of the first to sixth aspects. [Aspect 8] A method for producing a fired product, comprising the step of firing a ceramic molded product using the industrial furnace according to aspect 7. [Aspect 9] A regenerative burner comprising a flame holding chamber, a combustion chamber, a heat exchange chamber, and a communication passage between the combustion chamber and the heat exchange chamber, the flame stabilizing chamber has an ignition port communicating with a first fuel supply passage for supplying a first fuel containing one or more selected from ammonia, hydrogen, and hydrocarbons, and an air supply passage, and a flame outlet communicating with the combustion chamber, the combustion chamber has a flame inlet communicating with a flame outlet of the flame stabilizing chamber, a tip of at least one fuel nozzle communicating with a second fuel supply passage for supplying a second fuel containing ammonia, and a flame injection port; the combustion chamber is configured to combust a second fuel supplied into the combustion chamber from a tip of the at least one fuel nozzle in the presence of a first flame entering the combustion chamber through the flame inlet and combustion air supplied into the combustion chamber from the heat exchange chamber through the communicating passage, and to eject a second flame from the flame injection port, The entire amount of the first fuel combusted in the regenerative burner is supplied from a first fuel supply passage toward the ignition port, and the entire amount of the second fuel combusted in the regenerative burner is supplied from a second fuel supply passage to the at least one fuel nozzle. Regenerative burner. [Aspect 10] When the combustion chamber is observed from a horizontal direction perpendicular to the perpendicular line N extending from the opening plane S at the flame inlet, if the intersection point P between the perpendicular line N and a line segment M extending toward the supply direction of the second fuel from the tip T of at least one fuel nozzle is taken as the intersection point P, the angle (∠TPS) formed by the line segments TP and PS is 90°≦∠TPS≦110°.Regenerative burner described in aspect 9. [Aspect 11] A regenerative burner according to aspect 9 or 10, wherein a supply direction of the second fuel supplied from a tip of the at least one fuel nozzle is inclined toward the flame inlet. [Aspect 12] 12. The regenerative burner according to any one of aspects 9 to 11, wherein the ejection holes provided at the tip of the at least one fuel nozzle have a structure capable of radially ejecting the second fuel. [Aspect 13] 13. The regenerative burner according to any one of aspects 9 to 12, wherein a tip of the at least one fuel nozzle is provided at a position facing a port on the combustion chamber side of the communication passage. [Aspect 14] A regenerative burner according to any one of aspects 9 to 13, which has a space upstream of the ignition port for mixing the first fuel and air to form a premixed gas, and a swirler is installed in the space. [Aspect 15] 15. The regenerative burner according to any one of aspects 9 to 14, wherein the flame inlet is disposed at a position opposite the flame injection port. [Aspect 16] An industrial furnace comprising a plurality of regenerative burners according to any one of aspects 9 to 15. [Aspect 17] A method for producing a heat-treated product, comprising a step of heat-treating a workpiece using the industrial furnace according to aspect 16. [Effects of the Invention]

[0011] The regenerative burner according to one embodiment of the present invention makes it possible to sustain high-power combustion of ammonia-containing fuel. That is, according to one embodiment of the present invention, a highly practical regenerative burner capable of heat-treating workpieces using ammonia-containing fuel is provided. This regenerative burner can reduce CO2 emissions associated with firing, making a major step forward toward a decarbonized society. [Brief explanation of the drawings]

[0012] [Figure 1-1] 1 is a cross-sectional schematic diagram showing a first structural example of a regenerative burner according to the present invention. FIG. [Figure 1-2] 1 is a partially enlarged view of a first structural example of a regenerative burner according to the present invention. [Figure 2-1] FIG. 2 is a cross-sectional schematic diagram showing a second structural example of the regenerative burner according to the present invention. [Figure 2-2]FIG. 2 shows a partially enlarged view of a second structural example of the regenerative burner according to the present invention. [Figure 3] 1 is a side view showing an example of the overall configuration of a continuous heating furnace according to an embodiment of the present invention. [Figure 4] 1 is a configuration example of an industrial furnace equipped with a regenerative burner according to the present invention. [Figure 5] This is an example of the cross-sectional structure of a tunnel kiln-type industrial furnace. DETAILED DESCRIPTION OF THE INVENTION

[0013] <1. Regenerative Burner> Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be understood that the present invention is not limited to the following embodiments, and that appropriate design changes and improvements may be made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

[0014] (1-1. First structure example) 1-1 is a cross-sectional schematic diagram showing a first structural example of a regenerative burner 100 according to the present invention. The regenerative burner 100 according to the first structural example comprises a combustion chamber 110, a heat exchange chamber 120, and a communication passage 130 between the combustion chamber 110 and the heat exchange chamber 120. The inner wall of the combustion chamber 110 can be composed of burner tiles 115.

[0015] The combustion chamber 110 is provided with an ignition port 112c communicating with the first fuel supply passage 112a and the air supply passage 112b, a tip of at least one fuel nozzle 113a, and a flame injection port 114. The combustion chamber 110 is configured so that a second fuel containing ammonia, which is supplied into the combustion chamber 110 from the tip of the at least one fuel nozzle 113a, can be burned in the combustion chamber 110 in the presence of a first flame generated in the ignition port 112c and combustion air supplied into the combustion chamber 110 from the heat exchange chamber 120 through the communication passage 130, and a second flame can be ejected from the flame injection port 114.

[0016] In the illustrated embodiment, first fuel supply path 112a and air supply path 112b are formed by double pipes. Specifically, the double pipes are configured so that a small-diameter tube that constitutes first fuel supply path 112a is coaxially surrounded by a large-diameter tube that constitutes air supply path 112b. Conversely, a double-pipe structure may be configured so that a small-diameter tube that constitutes air supply path 112b is coaxially surrounded by a large-diameter tube that constitutes first fuel supply path 112a. Alternatively, first fuel supply path 112a and air supply path 112b may each be formed by an independent single pipe.

[0017] The first fuel supply passage 112a and the air supply passage 112b are both connected to the ignition nozzle 112c. The first fuel flowing through the first fuel supply passage 112a and the air flowing through the air supply passage 112b preferably meet and mix before reaching the ignition nozzle 112c. Therefore, a space 112e for mixing the first fuel and air to form a premixed gas is preferably provided upstream of the ignition nozzle 112c. An ignition plug 112f is provided in the space 112e, and the first fuel and air can be combusted in the ignition nozzle 112c to generate a first flame. The space 112e may have a tapered shape that narrows toward the downstream side. From the viewpoint of improving combustibility, it is preferable to provide a swirler (not shown) in the space 112e for mixing the first fuel and air to generate a swirling flow in the premixed gas. The walls defining the space 112e are preferably made of a refractory material, such as brick.

[0018] Alternatively, the first fuel flowing through the first fuel supply path 112a and the air flowing through the air supply path 112b may be joined and premixed upstream of the space 112e. For example, if the first fuel supply path 112a and the air supply path 112b are formed as double pipes, the two can be joined upstream of the space 112e by providing one or more holes in the inner pipe. If the first fuel supply path 112a and the air supply path 112b are each formed as independent single pipes, the first fuel supply path 112a and the air supply path 112b can be joined upstream of the space 112e by connecting the first fuel supply path 112a and the air supply path 112b.

[0019] The first fuel may contain one or more fuels selected from ammonia, hydrogen, and hydrocarbons. From the viewpoint of suppressing the amount of CO2 generated during combustion, a high volumetric percentage of ammonia in the first fuel flowing through the first fuel supply passage 112a is desirable. However, in the regenerative burner 100 according to the first structural example, a high volumetric percentage of either or both of hydrogen and hydrocarbons, which are fuels with a higher combustion rate than ammonia, is desirable from the viewpoint of sustaining combustion. Specifically, the total concentration of hydrogen and hydrocarbons in the first fuel is preferably 75% by volume or more, and can be 100% by volume. In one embodiment, the first fuel does not contain ammonia, but contains one or more fuels selected from hydrogen and hydrocarbons. Examples of hydrocarbons include one or more of methane, ethane, propane, and butane. Examples of hydrocarbon blends include city gas 12A and city gas 13A.

[0020] The number of fuel nozzles 113a installed in the regenerative burner 100 according to the first structural example may be one or more, but one is typically used from a cost perspective. The fuel nozzle 113a is connected to a second fuel supply passage 113b for supplying the second fuel, and the second fuel can be supplied into the combustion chamber 110 from the tip of the fuel nozzle 113a. The material constituting the second fuel supply passage 113b is preferably a highly heat-resistant material. Examples include heat-resistant alloys and ceramics, with ceramics being preferred. Furthermore, combustion air can be supplied from the heat exchange chamber 120 into the combustion chamber 110 through the communication passage 130. The cross-sectional area of ​​the communication passage 130 (the cross-sectional area perpendicular to the flow direction of the combustion air flowing through the communication passage 130) is smaller than the cross-sectional area of ​​the heat exchange chamber 120 (the cross-sectional area perpendicular to the flow direction of the combustion air flowing through the communication passage 130), thereby accelerating the combustion air flowing through the communication passage 130. This promotes mixing with the second fuel supplied into the combustion chamber 110 from the tip of the fuel nozzle 113a, making it easier to maintain combustion. The temperature of the combustion air supplied into the combustion chamber 110 is preferably 150°C or higher, and more preferably 300°C or higher, from the viewpoint of reducing unburned ammonia. However, the temperature of the combustion air supplied into the combustion chamber 110 is preferably 600°C or lower, and more preferably 400°C or lower, from the viewpoint of utilizing furnace exhaust heat. Therefore, the temperature of the combustion air supplied into the combustion chamber 110 is preferably, for example, 150 to 600°C, more preferably 300 to 600°C, and even more preferably 300 to 400°C.

[0021] The second fuel supplied into the combustion chamber 110 from the tip of the fuel nozzle 113a contains ammonia. The inclusion of ammonia in the second fuel can reduce the amount of CO2 generated during combustion. From the perspective of reducing the amount of CO2 generated, the ammonia concentration in the second fuel is preferably 75% by volume or more, and can be 100% by volume. Maintaining combustion primarily through the combustion of the first fuel makes it easier to sustain combustion even when the ammonia concentration in the second fuel is high. Supplying the second fuel into the combustion chamber 110 from the fuel nozzle 113a is also effective in increasing the heat output of the regenerative burner 100. The second fuel may be mixed with one or more other fuels. The other fuels are preferably fuels with a higher combustion rate than ammonia. Specific examples include hydrogen and one or more hydrocarbons such as methane, ethane, propane, and butane. Examples of hydrocarbon mixtures include city gas 12A and city gas 13A.

[0022] There are no particular limitations on the type of fuel nozzle 113a, but a nozzle having nozzle holes at its tip that can spray fuel radially is preferred in order to improve mixing with the combustion air introduced from port 131. Furthermore, by spraying the fuel radially toward the primary flame radiated from ignition port 112c, the combustion heat from the primary flame generated at ignition port 112c can be efficiently absorbed, improving combustibility.

[0023] In the presence of the first flame generated at the ignition nozzle 112c and the combustion air supplied from the heat exchange chamber 120 through the communication passage 130 into the combustion chamber 110, the second fuel containing ammonia supplied from the tip of the fuel nozzle 113a into the combustion chamber 110 can be burned in the combustion chamber 110. The presence of the first flame in the combustion chamber 110 contributes to maintaining the second flame, while the combustion of the second fuel in the combustion chamber 110 also contributes to maintaining the first flame. In particular, in the first structural example, the first flame generated at the ignition nozzle 112c provided in the combustion chamber 110 serves as a spark, making it possible to stably burn the second fuel containing ammonia in the combustion chamber 110. Supplying the second fuel into the combustion chamber 110 from the fuel nozzle 113a is also effective in increasing the output of the regenerative burner 100.

[0024] When ignition nozzle 112c is provided in rear wall 116a, the tip of fuel nozzle 113a is preferably provided in upper inner wall 116b of combustion chamber 110, which facilitates supplying fuel toward the primary flame generated in ignition nozzle 112c and is less susceptible to the flow of combustion air from port 131. Furthermore, when ignition nozzle 112c is provided in rear wall 116a, port 131 is preferably provided in lower inner wall 116c of combustion chamber 110. This is because the flow of combustion air from port 131 can be blocked by the flow of flame from ignition nozzle 112c, making it easier for fuel supplied from fuel nozzle 113a to come into contact with the flame. Furthermore, when ignition nozzle 112c is provided in rear wall 116a, port 131 is preferably provided adjacent to rear wall 116a to promote combustion.

[0025] The second fuel supplied into the combustion chamber 110 from the tip of the fuel nozzle 113a is preferably supplied toward the first flame from the viewpoint of promoting combustion. For example, when the combustion chamber 110 is observed from a horizontal direction perpendicular to a perpendicular line N extending from the opening surface S of the ignition port 112c (see FIG. 1-2), if the intersection point P between the perpendicular line N and a line segment M extending from the tip T of the fuel nozzle 113a toward the supply direction of the second fuel is defined as P, the angle (∠TPS) formed by the line segments TP and PS preferably satisfies 90°≦∠TPS≦135°, and more preferably satisfies 90°≦∠TPS≦110°. The supply direction of the second fuel is determined by the orientation of the nozzle. When multiple fuel nozzles 113a are used, it is preferable that at least one fuel nozzle 113a satisfy the angle condition, and it is more preferable that more than half of the fuel nozzles 113a satisfy the angle condition.

[0026] When the fuel nozzle 113a is made of a metal such as a heat-resistant alloy, it is preferable that the fuel nozzle 113a is embedded in the inner wall of the combustion chamber 110 so as not to protrude from the inner wall, in order to prevent oxidation.

[0027] It is preferable that the entire amount of the first fuel combusted in the regenerative burner 100 according to the first structural example is supplied from the first fuel supply passage 112a to the ignition port 112c, and the entire amount of the second fuel combusted in the regenerative burner 100 according to the first structural example is supplied from the second fuel supply passage 113b to at least one fuel nozzle 113a. This configuration can increase the combustion energy generated in the combustion chamber 110, making it easier to sustain combustion in the combustion chamber.

[0028] The flow rate F1 (Nm 3 / hr), and the flow rate F2 (Nm 3(hr) preferably satisfies 1 < F2 / F1, more preferably satisfies 2 ≤ F2 / F1, and even more preferably satisfies 10 ≤ F2 / F1 from the viewpoint of reducing CO2 associated with combustion. Also, from the viewpoint of maintaining combustion, it is preferable to satisfy F2 / F1 ≤ 20, more preferably satisfy F2 / F1 ≤ 10, and even more preferably satisfy F2 / F1 ≤ 5. Therefore, from the viewpoint of balancing CO2 reduction and combustion maintenance, for example, it is preferable to satisfy 1 < F2 / F1 ≤ 20, more preferably satisfy 2 ≤ F2 / F1 ≤ 10, and even more preferably satisfy 2 ≤ F2 / F1 ≤ 5. Note that in this specification, "Nm 3 " refers to the volume in the standard state of 0°C and one atmosphere pressure.

[0029] The heat exchange chamber 120 has an air port 122 and a heat storage body 123 interposed between the communication passage 130 and the air port 122. The heat exchange chamber 120 is configured such that the combustion air introduced into the heat exchange chamber 120 from the air port 122 can be introduced into the combustion chamber 110 through the communication passage 13 after passing through the space filled with the heat storage body 123. Also, the heat exchange chamber 120 is configured such that the exhaust gas introduced into the heat exchange chamber 120 through the communication passage 130 can be discharged from the air port after passing through the space filled with the heat storage body 123. In order to prevent the heat storage body 123 from entering the air port 122, it is preferable to separate the air port 122 and the heat storage body 123 with a breathable separator 125. As the separator 125, for example, a lattice structure or a punching plate made of metal (e.g., SUS) can be used. An entrance / exit 129 for the heat storage body 123 may be provided in the heat exchange chamber 120 so that the heat storage body 123 can be easily exchanged.

[0030] The heat storage body 123 is not particularly limited, and can be provided in the form of a ball, honeycomb, or mesh. The heat storage body 123 can be made of ceramic or metal. Among them, it is preferable to use a ceramic honeycomb as the heat storage body 123, which has excellent heat resistance and small pressure loss, and the material can be optimally selected from SiC-based materials, cordierite, alumina, mullite, aluminum titanate, etc., taking into consideration corrosion resistance and heat resistance.

[0031] The oxygen concentration in the exhaust from a regenerative burner is lower than the oxygen concentration in the air before combustion. Therefore, by using the exhaust with a reduced oxygen concentration as part or all of the combustion air, it is possible to effectively reduce thermal NOx. Therefore, the regenerative burner 100 according to the present invention is preferably configured to allow exhaust from at least one other regenerative burner to be introduced as part or all of the combustion air through the air port 122. From the viewpoint of effectively reducing thermal NOx, the oxygen concentration in the combustion air introduced into the regenerative burner is preferably 19% by volume or less, more preferably 17% by volume or less. An excessively low oxygen concentration in the combustion air introduced into the regenerative burner increases the generation of unburned ammonia and greenhouse gases such as NO. Therefore, the oxygen concentration is preferably 14.5% by volume or more, more preferably 15.5% by volume or more.

[0032] In one embodiment, the air port 122 is connected to a combustion air fan for supplying combustion air, and the inlet of the combustion air fan can be connected to the outlet of an exhaust fan for discharging exhaust from at least one other regenerative burner. The "other regenerative burner" may be the regenerative burner of the present invention or a regenerative burner different from the present invention, but is preferably the regenerative burner of the present invention. In this way, by using the exhaust from the other regenerative burner as part or all of the combustion air, it is possible to simply reduce the oxygen concentration in the combustion air introduced into the regenerative burner.

[0033] (1-2. Second structure example) 2-1 shows a second structural example of a regenerative burner 100 according to the present invention. The regenerative burner 100 according to the second structural example comprises a flame holding chamber 170, a combustion chamber 110, a heat exchange chamber 120, and a communication passage 130 between the combustion chamber 110 and the heat exchange chamber 120. The inner wall of the combustion chamber 110 can be composed of burner tiles 115.

[0034] The flame stabilizing chamber 170 has an ignition port 112c communicating with the first fuel supply passage 112a and the air supply passage 112b, and a flame outlet 171 communicating with the combustion chamber 110. An ignition plug 112f is installed near the ignition port 112c, and a first flame can be generated in the ignition port 112c as a result of combustion of the first fuel and air. The ignition port 112c can be provided in an upstream wall 170a of the flame stabilizing chamber 170, and the flame outlet 171 can be provided in a downstream wall 170b of the flame stabilizing chamber. The inner wall of the flame stabilizing chamber 170 is preferably formed of a refractory material such as brick.

[0035] In the illustrated embodiment, first fuel supply path 112a and air supply path 112b are formed by double pipes. Specifically, the double pipes are configured so that a small-diameter tube that constitutes first fuel supply path 112a is coaxially surrounded by a large-diameter tube that constitutes air supply path 112b. Conversely, a double-pipe structure may be configured so that a small-diameter tube that constitutes air supply path 112b is coaxially surrounded by a large-diameter tube that constitutes first fuel supply path 112a. Alternatively, first fuel supply path 112a and air supply path 112b may each be formed by an independent single pipe.

[0036] The first fuel flowing through the first fuel supply passage 112a and the air flowing through the air supply passage 112b are preferably joined and mixed before reaching the ignition nozzle 112c. Therefore, a space 112e for mixing the first fuel and air to form a premixed gas is preferably provided upstream of the ignition nozzle 112c. The space 112e may have a tapered shape that narrows toward the downstream side. A swirler 112d for generating a swirling flow in the premixed gas is preferably provided in the space 112e for mixing the first fuel and air.

[0037] Alternatively, the first fuel flowing through the first fuel supply path 112a and the air flowing through the air supply path 112b may be joined and premixed upstream of the space 112e. For example, if the first fuel supply path 112a and the air supply path 112b are formed as double pipes, the two can be joined upstream of the space 112e by providing one or more holes in the inner pipe. If the first fuel supply path 112a and the air supply path 112b are each formed as independent single pipes, the first fuel supply path 112a and the air supply path 112b can be joined upstream of the space 112e by connecting the first fuel supply path 112a and the air supply path 112b.

[0038] By providing the flame stabilizing chamber 170 upstream of the combustion chamber 110, it becomes easier to maintain the temperature inside the flame stabilizing chamber 170 at a certain temperature (ignition point) or higher. Maintaining the temperature inside the flame stabilizing chamber 170 at a certain temperature (ignition point) or higher has the effect of improving flame stability inside the flame stabilizing chamber 170. Furthermore, the swirler 112d creates a swirling flow inside the flame stabilizing chamber 170, thereby improving combustibility inside the flame stabilizing chamber 170. As a result, a stable first flame is supplied from the flame stabilizing chamber 170 to the combustion chamber 110, improving the combustion sustainability of the fuel containing ammonia inside the combustion chamber 110.

[0039] The first fuel may contain one or more selected from ammonia, hydrogen, and hydrocarbons. From the viewpoint of suppressing the amount of CO2 generated during combustion, the volumetric ratio of ammonia in the first fuel flowing through the first fuel supply passage 112a is preferably 75% by volume or more, more preferably 90% by volume or more, and can even be 100% by volume. In the regenerative burner 100 according to the second structural example, the presence of the flame stabilization chamber 170 significantly improves the combustibility of the first fuel, making it possible to sustain combustion even when the volumetric ratio of ammonia in the first fuel is high. One or more other fuels may be mixed into the first fuel. The other fuel is preferably a fuel with a higher combustion rate than ammonia. Specifically, hydrogen and / or hydrocarbons may be used. Hydrocarbons include one or more hydrocarbons, such as methane, ethane, propane, and butane. Hydrocarbon blends include city gas 12A and city gas 13A.

[0040] The combustion chamber 110 is provided with a flame inlet 118 communicating with a flame outlet 171 of the flame holding chamber 170, a tip of at least one fuel nozzle 113a communicating with a second fuel supply passage 113b containing ammonia, and a flame injection port 114. The combustion chamber 110 is configured so that, in the presence of a first flame entering the combustion chamber 110 through the flame inlet 118 and combustion air supplied from the heat exchange chamber 120 through the connecting passage 130 into the combustion chamber 110, a second fuel supplied from the tip of the at least one fuel nozzle 113a into the combustion chamber 110 can be combusted within the combustion chamber 110, and a second flame can be ejected from the flame injection port 114.

[0041] The number of fuel nozzles 113a installed in the regenerative burner 100 according to the second structural example may be one or more, but one is typically used for cost reasons. The fuel nozzle 113a is connected to a second fuel supply passage 113b for supplying the second fuel, and the second fuel can be supplied into the combustion chamber 110 from the tip of the fuel nozzle 113a. The material constituting the second fuel supply passage 113b is preferably a highly heat-resistant material. Examples include heat-resistant alloys and ceramics, with ceramics being preferred. Furthermore, combustion air can be supplied from the heat exchange chamber 120 into the combustion chamber 110 through the connecting passage 130. The cross-sectional area of ​​the connecting passage 130 (the cross-sectional area perpendicular to the flow direction of the combustion air flowing through the connecting passage 130) is smaller than the cross-sectional area of ​​the heat exchange chamber 120 (the cross-sectional area perpendicular to the flow direction of the combustion air flowing through the connecting passage 130), thereby accelerating the combustion air flowing through the connecting passage 130. This promotes mixing with the second fuel supplied into the combustion chamber 110 from the tip of the fuel nozzle 113a, making it easier to maintain combustion. The temperature of the combustion air supplied into the combustion chamber 110 is preferably 150°C or higher, and more preferably 300°C or higher, from the viewpoint of reducing unburned ammonia. However, from the viewpoint of utilizing furnace exhaust heat, the temperature of the combustion air supplied into the combustion chamber 110 is easily set to a temperature of 150°C to 400°C. Therefore, the temperature of the combustion air supplied into the combustion chamber 110 is preferably, for example, 150 to 400°C, and more preferably 300 to 400°C.

[0042] The second fuel supplied from the tip of the fuel nozzle 113a into the combustion chamber 110 contains ammonia. The inclusion of ammonia in the second fuel can suppress the amount of CO2 generated during combustion. From the viewpoint of suppressing the amount of CO2 generated during combustion, the volumetric ratio of ammonia in the second fuel is preferably 75% by volume or more, and can be 100% by volume. Supplying the second fuel from the fuel nozzle 113a into the combustion chamber 110 is also effective in increasing the output of the regenerative burner 100. One or more other fuels may be mixed into the second fuel. The other fuel is preferably a fuel with a higher combustion speed than ammonia. Specific examples include hydrogen and one or more hydrocarbons such as methane, ethane, propane, and butane. Examples of hydrocarbon mixture fuels include city gas 12A and city gas 13A.

[0043] Although there are no particular limitations on the type of fuel nozzle 113a, a nozzle having nozzle holes at its tip that can inject fuel radially is preferred for the reason of improving the mixing of the fuel and combustion air. Furthermore, by injecting the fuel radially toward the primary flame that passes through flame inlet 118 and enters combustion chamber 110, the combustion heat from the primary flame that passes through flame inlet 118 and enters combustion chamber 110 can be efficiently absorbed, improving combustibility.

[0044] In the presence of the first flame entering the combustion chamber 110 through the flame inlet 118 and the combustion air supplied from the heat exchange chamber 120 through the connecting passage 130 into the combustion chamber 110, the second fuel containing ammonia supplied from the tip of the fuel nozzle 113a into the combustion chamber 110 can be burned in the combustion chamber 110. The presence of the first flame in the combustion chamber 110 contributes to maintaining the second flame, while the combustion of the second fuel in the combustion chamber 110 also contributes to maintaining the first flame. In particular, in the second structural example, the first flame is protected by the flame holding chamber 170, making it less likely to extinguish. As a result, the first flame acts as a kindling, allowing the second fuel containing ammonia to be stably burned in the combustion chamber 110.

[0045] The tip of fuel nozzle 113a is preferably installed in upper inner wall 116b of combustion chamber 110, where fuel can be easily supplied toward the primary flame in flame inlet 118 and where it is less affected by the flow of combustion air from port 131. Furthermore, when flame inlet 118 is installed in rear wall 116a, port 131 is preferably installed in lower inner wall 116c of combustion chamber 110. This is because the flow of combustion air from port 131 can be blocked by the flow of flame from ignition port 112c, making it easier for fuel supplied from fuel nozzle 113a to come into contact with the flame. Furthermore, when flame inlet 118 is installed in rear wall 116a, it is preferable to install port 131 adjacent to rear wall 116a to promote combustion.

[0046] The second fuel supplied into the combustion chamber 110 from the tip of the fuel nozzle 113a is preferably supplied toward the first flame from the viewpoint of promoting combustion. For example, when the combustion chamber 110 is observed from a horizontal direction perpendicular to a perpendicular line N extending from the opening plane S of the flame inlet 118 (see FIG. 2-2), if the intersection point P between the perpendicular line N and a line segment M extending toward the supply direction of the ammonia-containing fuel from the tip T of the fuel nozzle 113a is defined as P, the angle (∠TPS) formed by the line segments TP and PS preferably satisfies 90°≦∠TPS≦135°, and more preferably satisfies 90°≦∠TPS≦110°. The supply direction of the second fuel is determined by the orientation of the nozzle. When there are multiple fuel nozzles 113a, it is preferable that at least one fuel nozzle 113a satisfies the angle condition, and it is more preferable that more than half of the fuel nozzles 113a satisfies the angle condition.

[0047] In order to prevent oxidation of the fuel nozzle 113a, it is preferable that the fuel nozzle 113a is installed in a state where it is embedded in the inner wall of the combustion chamber 110 so that it does not protrude from the inner wall.

[0048] It is preferable that the total amount of the first fuel burned in the regenerative burner 100 according to the second structural example is supplied from the first fuel supply passage 112a toward the ignition port 112c, and the total amount of the second fuel burned in the regenerative burner 100 is supplied from the second fuel supply passage 113b to at least one fuel nozzle 113a. With this configuration, the combustion energy generated in the combustion chamber 110 can be increased, and the combustion in the combustion chamber 110 becomes easier to sustain.

[0049] The flow rate F1 (Nm 3 / hr) of the first fuel supplied to the ignition port 112c through the first fuel supply passage 112a and the flow rate F2 (Nm 3 / hr) of the second fuel supplied to the fuel nozzle 113a through the second fuel supply passage 113b preferably satisfy 1 < F2 / F1, more preferably satisfy 2 ≤ F2 / F1, and even more preferably satisfy 10 ≤ F2 / F1, from the viewpoint of reducing CO2 associated with combustion. Also, from the viewpoint of maintaining combustion, it is preferable to satisfy F2 / F1 ≤ 20, more preferably satisfy F2 / F1 ≤ 10, and even more preferably satisfy F2 / F1 ≤ 5. Therefore, from the viewpoint of balancing CO2 reduction and combustion maintenance, for example, it is preferable to satisfy 1 < F2 / F1 ≤ 20, more preferably satisfy 2 ≤ F2 / F1 ≤ 10, and even more preferably satisfy 2 ≤ F2 / F1 ≤ 5. Note that "Nm 3 " refers to the volume under standard conditions of 0°C and one atmosphere.

[0050] In the regenerative burner 100 according to the second structural example as well, similar to the regenerative burner 100 according to the first structural example, the heat exchange chamber 120 has an air port 122 and a regenerator 123 interposed between the communication passage 130 and the air port 122. Embodiments of these components are as described for the regenerative burner 100 according to the first structural example, so detailed description is omitted.

[0051] <2. Industrial Furnace> According to one embodiment of the present invention, an industrial furnace is provided that includes one or more regenerative burners according to the above embodiment. The type of industrial furnace is not particularly limited. For example, it can be a continuous furnace such as a tunnel kiln, roller hearth kiln, or pusher kiln, or a single furnace (batch furnace) such as a box kiln, shuttle kiln, cowbell kiln, or elevator kiln. Furthermore, in terms of atmospheric conditions, it can be either an atmospheric firing furnace or a reduction firing furnace. A reduction firing furnace is a firing furnace that performs combustion under conditions where the m value (the ratio of the actual combustion air volume to the theoretical air volume) is less than 1.0.

[0052] 3 is a side schematic view showing an example of the overall configuration of a continuous heating furnace 10 equipped with a regenerative burner according to the embodiment described above. The continuous heating furnace 10 is equipped with an inlet 11, a heating zone 12, a cooling zone 13, and an outlet 14 in that order, and can heat-treat workpieces (not shown) loaded on a cart 15 while transporting them within the furnace from the inlet 11 toward the outlet 14. In the heating zone 12, a plurality of regenerative burners according to the embodiment described above can be installed.

[0053] The heating zone refers to the area in the direction of workpiece travel from the entrance of the continuous heating furnace to the heating equipment installed closest to the exit for heating the furnace. The cooling zone refers to the area in the direction of workpiece travel from just after the heating equipment installed closest to the exit to the exit of the continuous furnace. The concept of "heating" includes "firing." When manufacturing ceramic products, the heating zone 12 can be divided into a preheating zone 12a where debinding takes place and a firing zone 12b where firing takes place.

[0054] 4 illustrates an example configuration of an industrial furnace 400 equipped with multiple regenerative burners 100a, 100b. At least one of the multiple regenerative burners 100a, 100b is a regenerative burner according to an embodiment of the present invention, and preferably all of them are regenerative burners according to an embodiment of the present invention. In the industrial furnace 400, each of the regenerative burners 100a, 100b is configured to be able to introduce exhaust from at least one other regenerative burner (typically one other regenerative burner) as part or all of the combustion air through its own air port 122.

[0055] In the industrial furnace 400 shown in Fig. 4, one regenerative burner 100a is in combustion. Fuel valves 124a1 and 124a2 installed in fuel pipes 168a1 and 168a2 connected to the regenerative burner 100a are open, and fuel is supplied to the regenerative burner 100a through the fuel pipes 168a1 and 168a2. The other regenerative burner 100b is accumulating heat. Fuel valves 124b1 and 124b2 installed in fuel pipes 168b1 and 168b2 connected to the regenerative burner 100b are closed, thereby cutting off the fuel supply.

[0056] By making the fuel pipes 168a1 and 168b1 a double-pipe structure, the fuel and air may be separated and flow within the same pipe. Also, an air pipe (not shown) may be provided separately from the fuel pipes 168a1 and 168b1 to supply air to the regenerative burners 100a and 100b. Even when the fuel pipes 168a1 and 168b1 and the air pipe are provided separately, they may be switched to a double-pipe structure midway through.

[0057] The exhaust gas remaining inside the furnace body 410 after combustion is sucked into the flame injection port 114 of the regenerative burner 100b, which is storing heat, by the suction force of the exhaust fan 144. The exhaust gas then gives heat to the heat storage material as it passes through the heat exchange chamber 120, and is then discharged from the air port 122. The discharged exhaust gas passes through the exhaust pipe 142 and is discharged from the outlet of the exhaust fan 144. A portion of the exhaust gas discharged from the outlet of the exhaust fan 144 passes through the loop piping 150 and flows into the combustion air fan 154. In the illustrated embodiment, the loop piping 150 is connected to the air piping 152 upstream of the combustion air fan 154, so that the exhaust gas discharged from the outlet of the exhaust fan 144 merges with the air flowing through the air piping 152 and can flow into the combustion air fan 154.

[0058] Exhaust gas or a mixture of exhaust gas and air is discharged from the outlet of the combustion air fan 154. Because the oxygen concentration in the exhaust gas is lower than that in air, the oxygen concentration of the gas discharged from the outlet of the combustion air fan 154 is lower than the oxygen concentration in typical air, which is approximately 21% by volume. The proportion of exhaust gas mixed with air can be controlled by adjusting the opening of valve 126 installed in the loop piping 150. The mixture ratio can be set as appropriate, but it is desirable to select it so that the oxygen concentration of the mixed gas satisfies the above-mentioned conditions. The gas discharged from the outlet of the combustion air fan 154 passes through air piping 158 and air port 122 and is supplied as combustion air to the regenerative burner 100a during combustion.

[0059] Every certain time, the regenerative burner switches between the one currently burning and the one currently storing heat. This switching causes regenerative burner 100a, which was previously burning, to begin storing heat, and regenerative burner 100b, which was previously storing heat, to begin burning. This switching is achieved by reversing the open / close states of fuel valves 124a1, 124a2, 124b1, and 124b2, exhaust valves 128a and 128b, and combustion air valves 127a and 127b. Three-way valves may be used for the exhaust valves 128a and 128b and the combustion air valves 127a and 127b to switch the exhaust and combustion air paths. Electrically driven valves such as solenoid valves may be used as the valves. Alternating combustion is achieved by repeating this cycle. Typically, two regenerative burners are paired together and alternate combustion is performed in a cycle of several tens of seconds.

[0060] <3. Manufacturing method of heat-treated products> According to one embodiment of the present invention, a method for manufacturing a heat-treated product is provided, including a step of heat-treating a workpiece using an industrial furnace according to the above embodiment. The workpiece is an article to be heat-treated. Examples of the workpiece include, but are not limited to, electronic components such as ferrite and ceramic capacitors, semiconductor products, ceramic products, pottery, oxide-based refractories, glass products, metal products, and carbon-based refractories such as alumina-graphite and magnesia-graphite. The workpiece also includes kiln tools. The industrial furnace according to the present invention can be used to heat to temperatures above 1000°C, typically above 1200°C, more typically above 1400°C, e.g., 1000-2000°C. The concept of "heating" includes "firing." Applying the present invention to high-temperature furnaces such as firing furnaces improves the energy-saving effects of regenerative burners.

[0061] FIG. 5 illustrates the cross-sectional structure of a tunnel kiln-type industrial furnace 500 equipped with multiple regenerative burners. In the industrial furnace 500, a cart 520 carrying shelves 514 loaded with multiple workpieces 512 moves through the furnace body 510 in the direction of the page. The workpieces 512 are heated while the cart 520 moves through the furnace body 510. Sets of multiple regenerative burners 501, 502, 503, and 504 are installed on the left and right inner walls of the furnace body 510. There is no particular limit to the number of regenerative burners, and they can be set appropriately depending on the size and length of the furnace body 510. However, since alternating combustion is typically performed in pairs of two burners, an even number is preferable. It is also possible to use regenerative burners other than the regenerative burners of the present invention in some locations. Although not shown, a required number of similar sets of regenerative burners are installed in the direction of the page.

[0062] The workpiece 512 is placed between a top plate 516 that forms the uppermost surface of the shelf plate 514 and a bottom plate 518 that forms the lowermost surface of the shelf plate 514. Spaces that are exposed to flames from regenerative burners 501, 502, 503, and 504 are provided above the top plate 516 and below the bottom plate 518. A pair of left and right regenerative burners alternately repeats combustion and exhaust. In Figure 5, one pair of regenerative burners 501 and 504 is burning, and the other pair of regenerative burners 502 and 503 is storing heat. [Example]

[0063] EXAMPLES In the following, examples will be given together with comparative examples to provide a better understanding of the present invention and its advantages, but the present invention is not limited to these examples.

[0064] <Test Nos. 1, 2, and 10 (Comparative Examples)> (Test conditions) A combustion test was carried out under the following conditions using a regenerative burner having the structure shown in FIG. 1-1 (however, without the fuel nozzle 113a for supplying the second fuel containing ammonia into the combustion chamber 110). (1) The orientation of the regenerative burner was the same as in FIG. 1-1, and it was installed so that the flow direction of the combustion air flowing through the communication passage 130 was vertical, and the combustion chamber 110 extended horizontally. (2) First fuel supply passage 112a and air supply passage 112b were formed by double pipes. Specifically, the double pipes were configured so that a small-diameter tube (SUS steel pipe material) constituting first fuel supply passage 112a was coaxially covered by a large-diameter tube (SUS steel pipe material) constituting air supply passage 112b. (3) A mixed gas of ammonia and city gas 13A or one of these gases was supplied from first fuel supply passage 112a to ignition port 112c at the “first ammonia fuel flow rate” and “first city gas 13A fuel flow rate” in Table 1. The total flow rate of both is shown in “first fuel total flow rate F1” in Table 1. (4) Air (at about 25° C.) was supplied from air supply passage 112b toward ignition port 112c at the “first air flow rate” in Table 1. (5) The entire amount of the first fuel to be burned in the regenerative burner was supplied from the first fuel supply passage 112a to the ignition port 112c. (6) The first fuel supply passage 112a and the air supply passage 112b are both connected to the ignition port 112c, and a space 112e is provided upstream of the ignition port 112c for mixing the first fuel and air to form a premixed gas. The wall surface defining the space 112e is formed of bricks. (7) The space 112e had a tapered shape that narrowed toward the downstream side. (8) An ignition plug 112f is installed in the space 112e, and a first flame is generated in the combustion chamber 110 by combustion of the first fuel and air at the ignition port 112c. (9) Combustion air having the "second air temperature" in Table 1 was supplied from the heat exchange chamber 120 through the communication passage 130 into the combustion chamber 110 at the "second air flow rate" in Table 1. The second air temperature was measured using a thermocouple installed near the boundary between the communication passage 130 and the heat storage body 123. The same applies to the following test examples.

[0065] <Test Nos. 3 to 9 (Examples)> Combustion tests were conducted under the following conditions using a regenerative burner with the structure shown in Figure 1-1. (1) The orientation of the regenerative burner was the same as in FIG. 1-1, and it was installed so that the flow direction of the combustion air flowing through the communication passage 130 was vertical, and the combustion chamber 110 extended horizontally. (2) First fuel supply passage 112a and air supply passage 112b were formed by double pipes. Specifically, the double pipes were configured so that a small-diameter tube (SUS steel pipe material) constituting first fuel supply passage 112a was coaxially covered by a large-diameter tube (SUS steel pipe material) constituting air supply passage 112b. (3) A mixed gas of ammonia and city gas 13A or one of these gases was supplied from first fuel supply passage 112a to ignition port 112c at the “first ammonia fuel flow rate” and “first city gas 13A fuel flow rate” in Table 1. The total flow rate of both is shown in “first fuel total flow rate F1” in Table 1. (4) Air (at about 25° C.) was supplied from air supply passage 112b toward ignition port 112c at the “first air flow rate” in Table 1. (5) The entire amount of the first fuel to be burned in the regenerative burner was supplied from the first fuel supply passage 112a to the ignition port 112c. (6) The first fuel supply passage 112a and the air supply passage 112b are both connected to the ignition port 112c, and a space 112e is provided upstream of the ignition port 112c for mixing the first fuel and air to form a premixed gas. The wall surface defining the space 112e is formed of bricks. (7) The space 112e had a tapered shape that narrowed toward the downstream side. (8) An ignition plug 112f is installed in the space 112e, and a first flame is generated in the combustion chamber 110 by combustion of the first fuel and air at the ignition port 112c. (9) One fuel nozzle 113a was provided, and the supply direction of the second fuel from the tip of the fuel nozzle 113a was set so that the angle TPS was 90°. (10) The fuel nozzle 113a has a nozzle diameter that is constant toward the tip, and is configured to discharge fuel in one direction. (11) The tip of the fuel nozzle 113 a is located on the upper inner wall 116 b of the combustion chamber 110 , directly above the port 131 of the communication passage 130 installed on the lower inner wall 116 c of the combustion chamber 110 . (12) Ammonia was supplied from the second fuel supply passage 113b to the fuel nozzle 113a at the "second ammonia fuel flow rate F2" in Table 1. (13) Combustion air having the "second air temperature" in Table 1 was supplied from the heat exchange chamber 120 through the communication passage 130 into the combustion chamber 110 at the "second air flow rate" in Table 1. (14) The entire amount of the second fuel to be burned in the regenerative burner was supplied from the second fuel supply passage 113b (material: alumina) to the fuel nozzle 113a (: alumina).

[0066] <Test Nos. 11 and 12 (Comparative Examples)> A combustion test was carried out under the following conditions using a regenerative burner having the structure shown in FIG. 2-1 (however, without the fuel nozzle 113a for supplying the second fuel containing ammonia into the combustion chamber 110). (1) The orientation of the regenerative burner was the same as in FIG. 2-1, and it was installed so that the flow direction of the combustion air flowing through the communication passage 130 was vertical, and the combustion chamber 110 extended horizontally. (2) First fuel supply passage 112a and air supply passage 112b were formed by double pipes. Specifically, the double pipes were configured so that a small-diameter tube (SUS steel pipe material) constituting first fuel supply passage 112a was coaxially covered by a large-diameter tube (SUS steel pipe material) constituting air supply passage 112b. (3) A mixed gas of ammonia and city gas 13A or one of these gases was supplied from first fuel supply passage 112a to ignition port 112c at the “first ammonia fuel flow rate” and “first city gas 13A fuel flow rate” in Table 1. The total flow rate of both is shown in “first fuel total flow rate F1” in Table 1. (4) Air (at about 25° C.) was supplied from air supply passage 112b toward ignition port 112c at the “first air flow rate” in Table 1. (5) The entire amount of the first fuel to be burned in the regenerative burner was supplied from the first fuel supply passage 112a to the ignition port 112c. (6) The first fuel supply passage 112a and the air supply passage 112b are both connected to the ignition port 112c, and a space 112e is provided upstream of the ignition port 112c for mixing the first fuel and air to form a premixed gas. The wall surface defining the space 112e is formed of bricks. (7) The space 112e did not narrow toward the downstream side, but had a constant diameter. (8) An ignition plug 112f was installed in the space 112e, and a first flame was generated in the flame holding chamber 170 by combustion of the first fuel and air at the ignition port 112c, and the first flame was maintained in the flame holding chamber 170 during the test. The first flame was guided to the combustion chamber 110 through a flame inlet 118 communicating with a flame outlet 171 of the flame holding chamber 170. (9) The space 112e for mixing the first fuel and air is provided with a swirler 112d for generating a swirling flow of the premixed fuel. (10) The flame stabilizing chamber 170 has the ignition port 112c communicating with the first fuel supply passage 112a and the air supply passage 112b, and the flame outlet 171 communicating with the combustion chamber 110. (11) Combustion air having the "second air temperature" in Table 1 was supplied from the heat exchange chamber 120 through the communication passage 130 into the combustion chamber 110 at the "second air flow rate" in Table 1.

[0067] <Test Nos. 13 to 15 (Examples)> Combustion tests were conducted under the following conditions using a regenerative burner with the structure shown in Figure 2-1. (1) The orientation of the regenerative burner was the same as in FIG. 2-1, and it was installed so that the flow direction of the combustion air flowing through the communication passage 130 was vertical, and the combustion chamber 110 extended horizontally. (2) First fuel supply passage 112a and air supply passage 112b were formed by double pipes. Specifically, the double pipes were configured so that a small-diameter tube (SUS steel pipe material) constituting first fuel supply passage 112a was coaxially covered by a large-diameter tube (SUS steel pipe material) constituting air supply passage 112b. (3) A mixed gas of ammonia and city gas 13A or one of these gases was supplied from first fuel supply passage 112a to ignition port 112c at the “first ammonia fuel flow rate” and “first city gas 13A fuel flow rate” in Table 1. The total flow rate of both is shown in “first fuel total flow rate F1” in Table 1. (4) Air (at about 25° C.) was supplied from air supply passage 112b toward ignition port 112c at the “first air flow rate” in Table 1. (5) The entire amount of the first fuel to be burned in the regenerative burner was supplied from the first fuel supply passage 112a to the ignition port 112c. (6) The first fuel supply passage 112a and the air supply passage 112b are both connected to the ignition port 112c, and a space 112e is provided upstream of the ignition port 112c for mixing the first fuel and air to form a premixed gas. The wall surface defining the space 112e is formed of bricks. (7) The space 112e did not narrow toward the downstream side, but had a constant diameter. (8) An ignition plug 112f was installed in the space 112e, and a first flame was generated in the flame holding chamber 170 by combustion of the first fuel and air at the ignition port 112c, and the first flame was maintained in the flame holding chamber 170 during the test. The first flame was guided to the combustion chamber 110 through a flame inlet 118 communicating with a flame outlet 171 of the flame holding chamber 170. (9) The space 112e for mixing the first fuel and air is provided with a swirler 112d for generating a swirling flow of the premixed fuel. (10) The flame stabilizing chamber 170 has the ignition port 112c communicating with the first fuel supply passage 112a and the air supply passage 112b, and the flame outlet 171 communicating with the combustion chamber 110. (11) One fuel nozzle 113a was provided, and the direction in which the second fuel was supplied from the tip of the fuel nozzle 113a was set so that the angle TPS was 90°. (12) The fuel nozzle 113a has a nozzle diameter that is constant toward the discharge port, and is configured to discharge fuel in one direction. (13) The tip of the fuel nozzle 113 a is located on the upper inner wall 116 b of the combustion chamber 110 , directly above the port 131 of the communication passage 130 installed on the lower inner wall 116 c of the combustion chamber 110 . (14) Ammonia was supplied from the second fuel supply passage 113b to the fuel nozzle 113a at the "second ammonia fuel flow rate F2" in Table 1. (15) Combustion air having the "second air temperature" in Table 1 was supplied from the heat exchange chamber 120 through the communication passage 130 into the combustion chamber 110 at the "second air flow rate" in Table 1. (16) The entire amount of the second fuel to be burned in the regenerative burner was supplied from the second fuel supply passage 113b (material: alumina) to the fuel nozzle 113a (material: alumina).

[0068] (evaluation) In the combustion test, the combustion state, burner outlet temperature, ammonia co-firing ratio, and unburned ammonia concentration were evaluated according to the following criteria. The results are shown in Table 1. ·output The output was calculated based on the calorific value of each component of the fuel when it was burned. Burning state OK = Combustion was maintained for more than 5 minutes NG = Combustion could not be maintained for more than 5 minutes and misfire occurred. Burner outlet temperature A thermocouple was placed near the outlet of the flame nozzle 114, and the temperature was measured after it had stabilized. Ammonia co-firing rate Combustion energy ratio of ammonia in fuel supplied to a regenerative burner Unburned ammonia The volume concentration of ammonia in the furnace exhaust gas was measured using a HORIBA exhaust gas analyzer.

[0069] [Table 1]

[0070] <Consideration> Test No. 1 was an example in which ammonia was not used as fuel, but the combustion state was good, and no CO2 reduction effect was obtained. Test No. 2 is an example based on Test No. 1, in which a mixed gas of ammonia and city gas 13A was supplied to the first fuel supply passage 112a, but no fuel was supplied from the fuel nozzle 113a to the combustion chamber, and the combustion state was poor. In Tests 3 to 9, city gas 13A was supplied to the combustion chamber 110 from the first fuel supply passage 112a, and ammonia was supplied from the fuel nozzle 113a through the second fuel supply passage 113b. This resulted in stable combustion even with a high ammonia co-fuel ratio. Tests 8 and 9, in particular, had a high secondary air temperature, which is close to the actual operating conditions of a regenerative burner. When the secondary air temperature is high, it is possible to reduce unburned ammonia even if F2 / F1 is large (in other words, even if F1 is reduced). In an actual regenerative burner, fuel is expected to be constantly supplied from the first fuel supply passage 112a to maintain a constant combustion state during alternating combustion cycles. Even in this case, it is possible to reduce F1, thereby reducing unnecessary fuel consumption. However, in Test No. 10, although the secondary air temperature was high, fuel was not supplied from the fuel nozzle 113a to the combustion chamber 110, as in Test No. 2, and the combustion state was poor. The results of Test Nos. 11 and 12 show that simply providing the flame stabilizing chamber 170 and supplying the ammonia-containing fuel from the first fuel supply passage 112a is not sufficient to increase the output of the regenerative burner. Tests Nos. 13 to 15 were based on the configurations of Tests Nos. 11 and 12, and furthermore, ammonia was supplied to the combustion chamber 110 from the fuel nozzle 113a through the second fuel supply passage 113b, making it possible to sustain the combustion of the ammonia-containing fuel at a high output. [Explanation of symbols]

[0071] 10: Continuous heating furnace 11: Entrance 12: Heating zone 12a: Pre-tropical zone 12b: Firing zone 13: Cooling zone 14:Exit 15: Cart 100: Regenerative burner 100a: Regenerative burner 100b: Regenerative burner 110: Combustion chamber 112a: First fuel supply path 112b: Air supply path 112c: Ignition port 112d: Swara 112e :Space 112f: Spark plug 113a: Fuel nozzle 113b:Second fuel supply path 114:Flame injection port 115: Burner tile 116a: Back wall 116b: Upper inner wall 116c: lower inner wall 118: Flame entrance 120: Heat exchange room 122: Air port 123: Heat storage body 124a1: Fuel valve 124a2: Fuel valve 124b1: Fuel valve 124b2: Fuel valve 125: Separator 126: Valve 127a: Combustion air on-off valve 127b: Combustion air on-off valve 128a: Exhaust valve 128b: Exhaust valve 129: Entrance / exit 130: Communication path 131: Port 142: Exhaust pipe 144: Exhaust fan 150: Loop piping 152: Air piping 154: Combustion air fan 158: Air piping 168a1:Fuel piping 168a2:Fuel piping 168b1:Fuel piping 168b2:Fuel piping 170: Flame holding room 170a: Upstream wall 170b: Downstream wall 171:Flame exit 200: Regenerative burner 400: Industrial furnace 410:Furnace body 500: Industrial furnace 501: Regenerative Burner 502: Regenerative Burner 503: Regenerative Burner 504: Regenerative Burner 510:Furnace body 512: Work 514: Shelf 516: Top plate 518: Bottom plate 520: Cart

Claims

1. A regenerative burner comprising a combustion chamber, a heat exchange chamber, and a communication passage between the combustion chamber and the heat exchange chamber, the combustion chamber has an ignition port communicating with a first fuel supply passage for supplying a first fuel containing one or more selected from ammonia, hydrogen, and hydrocarbons and an air supply passage, a tip of at least one fuel nozzle communicating with a second fuel supply passage for supplying a second fuel containing ammonia, and a flame injection port; the combustion chamber is configured so that a second fuel supplied from a tip of the at least one fuel nozzle into the combustion chamber is combusted in the combustion chamber in the presence of a first flame generated at the ignition port and combustion air supplied from the heat exchange chamber through the communicating passage into the combustion chamber, and a second flame can be ejected from the flame injection port, The entire amount of the first fuel combusted in the regenerative burner is supplied from the first fuel supply passage to the ignition port, and the entire amount of the second fuel combusted in the regenerative burner is supplied from the second fuel supply passage to the at least one fuel nozzle. Regenerative burner.

2. 2. A regenerative burner as described in claim 1, wherein when the combustion chamber is observed from a horizontal direction perpendicular to a perpendicular line N extending from the opening surface S of the ignition port, if the intersection point P between the perpendicular line N and a line segment M extending toward the supply direction of the second fuel from the tip T of at least one fuel nozzle is taken as P, the angle (∠TPS) formed by the line segment TP and the line segment PS is 90°≦∠TPS≦110°.

3. 3. The regenerative burner according to claim 1, wherein the supply direction of the second fuel supplied from the tip of the at least one fuel nozzle is inclined toward the ignition port.

4. 3. The regenerative burner according to claim 1, wherein the nozzle holes provided at the tip of the at least one fuel nozzle have a structure capable of injecting the second fuel radially.

5. 3. The regenerative burner according to claim 1, wherein a tip of the at least one fuel nozzle is provided at a position facing a port on the combustion chamber side of the communication passage.

6. 3. The regenerative burner according to claim 1, wherein the ignition nozzle is disposed at a position opposite to the flame injection nozzle.

7. An industrial furnace comprising a plurality of regenerative burners according to claim 1 or 2.

8. A method for producing a fired product, comprising the step of firing a ceramic molded product using the industrial furnace according to claim 7.

9. A regenerative burner comprising a flame holding chamber, a combustion chamber, a heat exchange chamber, and a communication passage between the combustion chamber and the heat exchange chamber, the flame stabilizing chamber has an ignition port communicating with a first fuel supply passage for supplying a first fuel containing one or more selected from ammonia, hydrogen, and hydrocarbons, and an air supply passage, and a flame outlet communicating with the combustion chamber, the combustion chamber has a flame inlet communicating with a flame outlet of the flame stabilizing chamber, a tip of at least one fuel nozzle communicating with a second fuel supply passage for supplying a second fuel containing ammonia, and a flame injection port; the combustion chamber is configured to combust a second fuel supplied into the combustion chamber from a tip of the at least one fuel nozzle in the presence of a first flame entering the combustion chamber through the flame inlet and combustion air supplied into the combustion chamber from the heat exchange chamber through the communicating passage, and to eject a second flame from the flame injection port, The entire amount of the first fuel combusted in the regenerative burner is supplied from a first fuel supply passage toward the ignition port, and the entire amount of the second fuel combusted in the regenerative burner is supplied from a second fuel supply passage to the at least one fuel nozzle. Regenerative burner.

10. When the combustion chamber is observed from a horizontal direction perpendicular to the perpendicular line N extending from the opening surface S at the flame inlet, if the intersection point P between the perpendicular line N and a line segment M extending toward the supply direction of the second fuel from the tip T of at least one fuel nozzle is taken as P, the angle (∠TPS) formed by the line segment TP and the line segment PS is 90°≦∠TPS≦110°. A regenerative burner as described in claim 9.

11. 11. The regenerative burner according to claim 9 or 10, wherein the supply direction of the second fuel supplied from the tip of the at least one fuel nozzle is inclined toward the flame inlet.

12. 11. The regenerative burner according to claim 9, wherein the nozzle holes provided at the tip of the at least one fuel nozzle have a structure capable of injecting the second fuel radially.

13. 11. The regenerative burner according to claim 9, wherein a tip of the at least one fuel nozzle is provided at a position facing a port on the combustion chamber side of the communication passage.

14. 11. The regenerative burner according to claim 9 or 10, further comprising a space upstream of the ignition port for mixing the first fuel and air to form a premixed gas, and a swirler is installed in the space.

15. 11. The regenerative burner according to claim 9 or 10, wherein the flame inlet is disposed at a position opposite the flame injection port.

16. An industrial furnace comprising a plurality of regenerative burners according to claim 9 or 10.

17. A method for manufacturing a heat-treated product, comprising the step of heat-treating a workpiece using the industrial furnace according to claim 16.

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