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

Abstract

To provide a regenerative burner useful for sustaining combustion of an ammonia-containing fuel with high output.SOLUTION: A flame holding chamber, a combustion chamber, a heat exchanger chamber, and a communication passage between the combustion chamber and the heat exchanger chamber, wherein the flame holding chamber has an ignition port communicating with the first fuel supply passage and the air supply passage, and a flame outlet communicating with the combustion chamber, and the flame outlet communicates with an outlet of a second fuel supply passage capable of flowing a second fuel containing ammonia while bringing the second fuel into thermal contact with an outer peripheral wall of the flame holding chamber, the combustion chamber has a flame inlet communicating with the flame outlet of the flame holding chamber and a flame jet orifice, and is configured to be able to burn the second fuel supplied from the outlet of the second fuel supply passage in the combustion chamber and / or before entering the combustion chamber, in the presence of the first flame entering the combustion chamber through the flame inlet and the combustion air supplied from the heat exchange chamber into the combustion chamber through the communication passage, and eject the second flame from the flame jet orifice.SELECTED DRAWING: Figure 1-1

Description

[Technical Field]

[0001] The present invention relates to a regenerative burner, an industrial furnace equipped with a regenerative burner, and 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 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 supplied to the combustion chamber to cause a combustion reaction with the air. However, it is difficult to stably burn an ammonia-containing fuel with only this configuration. The inventors have found that, in order to stably burn an ammonia-containing fuel at high output, it is advantageous to supply preheated ammonia-containing fuel toward the flame accompanying the combustion of the fuel. The present invention was completed based on this finding, and is exemplified below.

[0010] [Aspect 1] 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 flame outlet is in communication with an outlet of a second fuel supply passage through which the second fuel containing ammonia can flow while being in thermal contact with an outer peripheral wall of the flame stabilizing chamber, The combustion chamber has a flame inlet communicating with the flame outlet of the flame stabilizing chamber, and a flame injection port, and is configured so that, in the presence of a first flame entering the combustion chamber through the flame inlet and combustion air supplied from the heat exchange chamber through the communicating passage into the combustion chamber, a second fuel supplied from an outlet of the second fuel supply passage can be combusted in the combustion chamber and / or before entering the combustion chamber, and a second flame can be ejected from the flame injection port. Regenerative burner. [Aspect 2] 2. The regenerative burner according to claim 1, wherein a catalyst for decomposing ammonia into hydrogen is disposed in the second fuel supply passage. [Aspect 3] 3. The regenerative burner according to aspect 1 or 2, wherein an outer peripheral wall of the flame stabilizing chamber is surrounded by a second fuel supply passage. [Aspect 4] the combustion chamber further includes a tip of at least one fuel nozzle communicating a third fuel containing ammonia to a third fuel supply passage; the combustion chamber is configured to combust a third 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 from the flame inlet and combustion air supplied into the combustion chamber from the heat exchange chamber through the communicating passage, The system is configured such that the entire amount of the first fuel combusted in the regenerative burner is supplied from a first fuel supply passage toward the ignition port, the entire amount of the second fuel combusted in the regenerative burner is supplied from an outlet of a second fuel supply passage, and the entire amount of the third fuel combusted in the regenerative burner is supplied from a third fuel supply passage to the at least one fuel nozzle. The regenerative burner according to any one of the first to third aspects. [Aspect 5] A regenerative burner as described in aspect 4, wherein when the combustion chamber is observed from a horizontal direction perpendicular to a perpendicular line N extending from the opening plane S at the flame inlet, if the intersection point P is the point of intersection between the perpendicular line N and a line segment M extending toward the supply direction of the third fuel from the tip T of at least one fuel nozzle, the angle (∠TPS) formed by the line segments TP and PS is 90°≦∠TPS≦110°. [Aspect 6] Aspect 6. The regenerative burner according to aspect 4 or 5, wherein the supply direction of the third fuel supplied from the tip of the at least one fuel nozzle is inclined toward the flame inlet. [Aspect 7] 7. The regenerative burner according to any one of aspects 4 to 6, wherein the outlet provided at the tip of the at least one fuel nozzle has a structure capable of radially injecting the third fuel. [Aspect 8] A regenerative burner according to any one of aspects 4 to 7, 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 9] A regenerative burner according to any one of aspects 1 to 8, which has a space upstream of the ignition port for mixing a first fuel and air to form a premixed gas, and a swirler is installed in the space. [Aspect 10] 10. The regenerative burner according to any one of aspects 1 to 9, wherein the flame inlet is disposed at a position opposite the flame injection port. [Aspect 11] An industrial furnace comprising a plurality of regenerative burners according to any one of aspects 1 to 10. [Aspect 12] A method for producing a heat-treated product, comprising a step of heat-treating a workpiece using the industrial furnace according to aspect 11. [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 an example of the structure of a regenerative burner according to the present invention. [Figure 1-2] An enlarged view of a portion of Figure 1-1 is shown. [Figure 2] 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 3] 1 is a configuration example of an industrial furnace equipped with a regenerative burner according to the present invention. [Figure 4] 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 is a cross-sectional schematic diagram showing an example of the structure of a regenerative burner 100 according to the present invention. The regenerative burner 100 comprises a flame stabilizing 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.

[0015] The flame stabilizing chamber 170 has an ignition port 111c communicating with the first fuel supply passage 111a and the air supply passage 111b, and a flame outlet 171 communicating with the combustion chamber 110. An ignition plug 111f is installed near the ignition port 111c, and a first flame can be generated in the ignition port 111c as a result of combustion of the first fuel and air. The ignition port 111c 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 170. The inner wall of the flame stabilizing chamber 170 is preferably formed of a refractory material such as brick.

[0016] In the illustrated embodiment, the first fuel supply path 111a and the air supply path 111b are formed by double pipes. Specifically, the double pipes are configured so that a small-diameter tube constituting the first fuel supply path 111a is coaxially surrounded by a large-diameter tube constituting the air supply path 111b. Conversely, a double-pipe structure may be configured so that a small-diameter tube constituting the air supply path 111b is coaxially surrounded by a large-diameter tube constituting the first fuel supply path 111a. Alternatively, the first fuel supply path 111a and the air supply path 111b may each be formed by an independent single pipe. The material constituting the first fuel supply path 111a and the air supply path 111b is preferably a highly heat-resistant material. For example, heat-resistant alloys and ceramics can be used, with ceramics being preferred.

[0017] The first fuel flowing through the first fuel supply passage 111a and the air flowing through the air supply passage 111b are preferably joined and mixed before reaching the ignition port 111c. Therefore, a space 111e for mixing the first fuel and air to form a premixed gas is preferably provided upstream of the ignition port 111c. The space 111e may have a tapered shape that narrows toward the downstream side. A swirler 111d for generating a swirling flow in the premixed gas is preferably provided in the space 111e for mixing the first fuel and air.

[0018] Alternatively, the first fuel flowing through the first fuel supply path 111a and the air flowing through the air supply path 111b may be joined and premixed upstream of the space 111e. For example, if the first fuel supply path 111a and the air supply path 111b are formed as double pipes, the two can be joined by providing one or more holes in the inner pipe upstream of the space 111e. If the first fuel supply path 111a and the air supply path 111b are each formed as independent single pipes, the first fuel supply path 111a and the air supply path 111b can be joined by connecting them upstream of the space 111e.

[0019] 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 111d 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.

[0020] 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 111a is preferably 75% by volume or more, and can be 100% by volume. Other fuels may be mixed into the first fuel. 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.

[0021] Flame outlet 171 is connected to outlet 112b of second fuel supply passage 112a, through which the second fuel can flow while being in thermal contact with outer peripheral wall 170c of flame holding chamber 170. For example, outer peripheral wall 170c of flame holding chamber 170 can be provided between upstream wall 170a of flame holding chamber 170 and downstream wall 170b of flame holding chamber 170, connecting the two. Additional supply of second fuel from outlet 112b of second fuel supply passage 112a, which is connected to flame outlet 171, is effective in increasing the output of regenerative burner 100.

[0022] The outer peripheral wall 170c of the flame stabilizing chamber 170 can become hot due to the presence of the first flame. Therefore, by bringing the second fuel flowing through the second fuel supply passage 112a into thermal contact with the outer peripheral wall 170c of the flame stabilizing chamber 170 in the presence of the first flame, the second fuel can be heated, allowing the high-temperature second fuel to be supplied from the outlet 112b, facilitating ignition. Furthermore, since the flame outlet 171 is connected to the outlet 112b of the flame stabilizing chamber 170, the second fuel supplied from the outlet 112b is further heated by contact with the first flame, further promoting ignition. Furthermore, contact of the high-temperature second fuel with the first flame also has the effect of preventing the first flame from misfiring. The material constituting the outer peripheral wall 170c of the flame stabilizing chamber 170 is preferably a highly heat-resistant material. Examples include heat-resistant alloys and ceramics, with ceramics being preferred. Alternatively, the material forming the outer peripheral wall 170c of the flame stabilizing chamber 170 may be a heat-resistant alloy containing chromium and / or nickel, which is expected to have catalytic activity as an ammonia decomposition catalyst.

[0023] Examples of methods for bringing the second fuel flowing through the second fuel supply passage 112a into thermal contact with the outer peripheral wall 170c of the flame stabilizing chamber 170 include a method of bringing part or all of the outer peripheral wall 170c of the flame stabilizing chamber 170 into direct or indirect physical contact with the second fuel flowing through the second fuel supply passage 112a. A preferred method is to cover part or all of the outer peripheral wall 170c of the flame stabilizing chamber 170 with the second fuel supply passage 112a. A more preferred method is to circumferentially cover part or all of the outer peripheral wall 170c of the flame stabilizing chamber 170 with the second fuel supply passage 112a. The material constituting the second fuel supply passage 112a is preferably a highly heat-resistant material. Examples include heat-resistant alloys and ceramics, with ceramics being preferred.

[0024] When the second fuel flowing through the second fuel supply passage 112a is brought into thermal contact with the outer peripheral wall 170c of the flame stabilizing chamber 170, the outer peripheral wall 170c of the flame stabilizing chamber 170 itself may form part of the wall that defines the second fuel supply passage 112a. In this case, the second fuel comes into direct contact with the outer peripheral wall 170c of the flame stabilizing chamber 170, facilitating heat transfer. Alternatively, the second fuel supply passage 112a may be provided independently of the outer peripheral wall 170c of the flame stabilizing chamber 170. In this case, the second fuel comes into indirect contact with the outer peripheral wall 170c of the flame stabilizing chamber 170 via the wall that defines the second fuel supply passage 112a.

[0025] The second fuel flowing through the second fuel supply passage 112a may be brought into thermal contact with one or both of the upstream wall 170a of the flame holding chamber 170 and the downstream wall 170b of the flame holding chamber 170. This allows further heating of the second fuel. A method for bringing the second fuel flowing through the second fuel supply passage 112a into thermal contact with one or both of the upstream wall 170a of the flame holding chamber 170 and the downstream wall 170b of the flame holding chamber 170 includes, for example, bringing part or all of one or both of the upstream wall 170a of the flame holding chamber 170 and the downstream wall 170b of the flame holding chamber 170 into direct or indirect physical contact with the second fuel flowing through the second fuel supply passage 112a. A preferred method is to cover part or all of one or both of the upstream wall 170a of the flame holding chamber 170 and the downstream wall 170b of the flame holding chamber 170 with the second fuel supply passage 112a.

[0026] When the second fuel flowing through the second fuel supply passage 112a is brought into thermal contact with one or both of the upstream wall 170a of the flame holding chamber 170 and the downstream wall 170b of the flame holding chamber 170, one or both of the upstream wall 170a of the flame holding chamber 170 and the downstream wall 170b of the flame holding chamber 170 may form part of the wall defining the second fuel supply passage 112a. In this case, the second fuel comes into direct contact with one or both of the upstream wall 170a of the flame holding chamber 170 and the downstream wall 170b of the flame holding chamber 170, facilitating heat transfer. Alternatively, the second fuel supply passage 112a may be provided independently of the upstream wall 170a of the flame holding chamber 170 and the downstream wall 170b of the flame holding chamber 170. In this case, the second fuel indirectly contacts one or both of the upstream wall 170a of the flame stabilizing chamber 170 and the downstream wall 170b of the flame stabilizing chamber 170 via the wall that defines the second fuel supply passage 112a.

[0027] It is preferable that outlet 112b of second fuel supply passage 112a is provided on the outer periphery of flame outlet 171 and supplies the second fuel toward flame outlet 171. Outlet 112b may be formed in an annular shape so as to surround the outer periphery of flame outlet 171. At least a portion of the second fuel flowing out from outlet 112b may be carried by the flow of the primary flame and introduced into combustion chamber 110, where it may combust within combustion chamber 110. At least a portion of the second fuel may combust before entering combustion chamber 110. The second fuel supplied from outlet 112b may be introduced into combustion chamber 110 through flame inlet 118, which will be described later, or may be introduced through another route.

[0028] The second fuel supply path 112a may be provided independently of the first fuel supply path 111a. Alternatively, the first fuel supply path 111a and the second fuel supply path 112a may be provided by branching off a common fuel supply path along the way. Examples of branching off a common fuel supply path include a case where the first fuel supply path 111a is branched off to provide the second fuel supply path 112a, and a case where the second fuel supply path 112a is branched off to provide the first fuel supply path 111a.

[0029] The second fuel flowing through the second fuel supply passage 112a contains ammonia. The second fuel flowing through the second fuel supply passage 112a can be in a gaseous state, for example. The second fuel containing ammonia 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 (before passing through a catalyst for decomposing ammonia into hydrogen, as described below, if such a catalyst is disposed in the second fuel supply passage 112a) is preferably 75% by volume or more, and can also be 100% by volume. One or more other fuels may be mixed into the second fuel. As the other fuel, a fuel having a higher combustion rate than ammonia is preferred. Specific examples of the other fuel include hydrogen and one or more hydrocarbons such as methane, ethane, propane, and butane. Examples of hydrocarbon blend fuels include city gas 12A and city gas 13A.

[0030] A catalyst for decomposing ammonia into hydrogen (hereinafter also referred to as an "ammonia decomposition catalyst") is preferably disposed within the second fuel supply passage 112a. By disposing the ammonia decomposition catalyst within the second fuel supply passage 112a, at least a portion of the second fuel passing through the second fuel supply passage 112a can be converted into hydrogen. The combustion rate of hydrogen is significantly higher than that of ammonia. Therefore, by supplying hydrogen from the outlet 112b of the second fuel supply passage 112a, a high effect of maintaining the first flame and the second flame can be obtained.

[0031] The ammonia decomposition catalyst is preferably disposed at a location within the second fuel supply passage 112a for bringing the second fuel into thermal contact with the outer peripheral wall 170c of the flame stabilizing chamber 170 in order to promote the decomposition of ammonia into hydrogen.

[0032] Therefore, the ammonia decomposition catalyst is preferably disposed, for example, at a location where part or all of the outer peripheral wall 170c of the flame stabilizing chamber 170 is brought into direct or indirect physical contact with the second fuel flowing through the second fuel supply passage 112a. Illustratively, the ammonia decomposition catalyst is preferably disposed at a location where part or all of the outer peripheral wall 170c of the flame stabilizing chamber 170 is covered by the second fuel supply passage 112a. When part or all of the outer peripheral wall 170c of the flame stabilizing chamber 170 is circumferentially covered by the second fuel supply passage 112a, the ammonia decomposition catalyst is preferably disposed so as to circumferentially cover part or all of the outer peripheral wall 170c of the flame stabilizing chamber 170.

[0033] The ammonia decomposition catalyst is preferably disposed, for example, at a location where part or all of one or both of the upstream wall 170a of the flame holding chamber 170 and the downstream wall 170b of the flame holding chamber 170 are brought into direct or indirect physical contact with the second fuel flowing in the second fuel supply passage 112a. For example, it is preferably disposed at a location where part or all of one or both of the upstream wall 170a of the flame holding chamber 170 and the downstream wall 170b of the flame holding chamber 170 are covered by the second fuel supply passage 112a.

[0034] As the ammonia decomposition catalyst, any known ammonia decomposition catalyst can be used without any particular limitation. Examples of the ammonia decomposition catalyst include ammonia decomposition catalysts containing one or more elements selected from platinum, palladium, rhodium, iridium, ruthenium, nickel, iron, cobalt, cerium, aluminum, copper, and zinc.

[0035] The combustion chamber 110 is provided with a flame inlet 118 that communicates with a flame outlet 171 of the flame holding chamber 170, and a flame injection port 114. The combustion chamber 110 is configured so that, in the presence of a first flame that enters the combustion chamber 110 through the flame inlet 118 and combustion air that is supplied from the heat exchange chamber 120 through the communication passage 130 into the combustion chamber 110, a second fuel that is supplied from an outlet 112b of the second fuel supply passage 112a can be combusted within the combustion chamber 110 and / or before entering the combustion chamber 110, and a second flame can be ejected from the flame injection port 114.

[0036] Because it is advantageous for sustaining combustion, the flame inlet 118 is preferably installed at a position opposite the flame injection port 114 across the combustion chamber 110 (in the embodiment of FIG. 1-1, on the back wall 116a of the combustion chamber 110).

[0037] 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 of the second fuel supplied into the combustion chamber 110 from the outlet 112b of the second fuel supply passage 112a and / or the third fuel supplied into the combustion chamber 110 from the tip of the fuel nozzle 113a (described later), 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 150°C to 400°C, from the viewpoint of utilizing furnace exhaust heat. Therefore, the temperature of the combustion air supplied into the combustion chamber 110 is preferably 150°C to 400°C, for example, and more preferably 300°C to 400°C.

[0038] The combustion chamber 110 preferably further has a tip of at least one fuel nozzle 113a that communicates with a third fuel supply passage 113b. The number of fuel nozzles 113a installed in the regenerative burner 100 may be one or more, but one is usually used from a cost perspective. The fuel nozzle 113a communicates with a third fuel supply passage 113b for flowing the third fuel, and the third fuel can be supplied into the combustion chamber 110 from the tip of the fuel nozzle 113a. The material forming the third fuel supply passage 113b is preferably a highly heat-resistant material. For example, heat-resistant alloys and ceramics can be used, with ceramics being preferred.

[0039] In this case, the combustion chamber 110 is configured so that a third fuel supplied into the combustion chamber 110 from the tip of at least one fuel nozzle 113a can be combusted in the combustion chamber 110 in the presence of a first flame entering the combustion chamber 110 from the flame inlet 118 and combustion air supplied into the combustion chamber 110 from the heat exchange chamber 120 through the communication passage 130. Supplying the third fuel into the combustion chamber 110 from the fuel nozzle 113a is more effective in sustaining combustion in the combustion chamber 110. It is also effective in increasing the output (heat generation) of the regenerative burner 100.

[0040] The third fuel supplied from the tip of the fuel nozzle 113a into the combustion chamber 110 contains ammonia. The third fuel containing ammonia 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 third fuel supplied from the tip of the fuel nozzle 113a into the combustion chamber 110 is preferably 75% by volume or more, and can also be 100% by volume. One or more other fuels may be mixed into the third fuel. As the other fuel, a fuel having a higher combustion speed than ammonia is preferable. Specific examples include hydrogen and one or more hydrocarbons such as methane, ethane, propane, and butane. Examples of hydrocarbon blend fuels include city gas 12A and city gas 13A.

[0041] Although there are no particular limitations on the type of fuel nozzle 113a, a nozzle having an outlet at its tip that can radially inject the third fuel is preferred in order to improve the mixing of the fuel and combustion air. Furthermore, by injecting the radially injected third fuel toward the first flame that passes through flame inlet 118 and enters combustion chamber 110, the combustion heat from the first flame that passes through flame inlet 118 and enters combustion chamber 110 can be efficiently absorbed, thereby improving combustibility.

[0042] 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 third fuel supplied into the combustion chamber 110 from the tip of the fuel nozzle 113a can be combusted in the combustion chamber 110.

[0043] The presence of the first flame in the combustion chamber 110 contributes to maintaining the second flame, while the combustion of the third fuel in the combustion chamber 110 also contributes to maintaining the first flame. The first flame is protected by the flame stabilization chamber 170, making it less likely to extinguish. Therefore, there is an advantage in that the first flame and the second flame can be easily maintained even if the ammonia concentration in the third fuel supplied into the combustion chamber 110 from the tip of the fuel nozzle 113a is increased.

[0044] The tip of fuel nozzle 113a is preferably installed in upper inner wall 116b of combustion chamber 110, where the third fuel can be easily supplied toward the first flame in flame inlet 118 and the port 131 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 the first flame from flame inlet 118, making it easier for the third fuel supplied from fuel nozzle 113a to come into contact with the first flame. Furthermore, when flame inlet 118 is installed in rear wall 116a, port 131 is preferably installed adjacent to rear wall 116a to promote combustion.

[0045] The third 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. 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 third 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 third 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.

[0046] 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.

[0047] It is preferable that the entire amount of the first fuel combusted in regenerative burner 100 is supplied from first fuel supply passage 111a toward ignition port 111c, the entire amount of the second fuel combusted in regenerative burner 100 is supplied from outlet 112b of second fuel supply passage 112a, and the entire amount of the third fuel combusted in regenerative burner 100 is preferably configured to be supplied from third fuel supply passage 113b to at least one fuel nozzle 113a. With this configuration, it is possible to increase the combustion energy generated in combustion chamber 110, making it easier to sustain combustion in combustion chamber 110.

[0048] 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. The heat exchange chamber 120 is configured so that combustion air introduced into the heat exchange chamber 120 from the air port 122 passes through a space filled with the regenerator 123 and can then be introduced into the combustion chamber 110 through the communication passage 130. The heat exchange chamber 120 is also configured so that exhaust gas introduced into the heat exchange chamber 120 through the communication passage 130 can then be discharged from the air port 122 after passing through the space filled with the regenerator 123. To prevent the regenerator 123 from entering the air port 122, it is preferable to separate the air port 122 and the regenerator 123 with a breathable separator 125. The separator 125 can be, for example, a metal (e.g., stainless steel) grid structure or a punched plate. In order to facilitate replacement of the heat storage medium 123, the heat exchange chamber 120 may be provided with an entrance / exit 129 for the heat storage medium 123.

[0049] 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. In particular, 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, alumina, cordierite, mullite, aluminum titanate, etc., taking into consideration corrosion resistance and heat resistance.

[0050] 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.

[0051] 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.

[0052] <2. Industrial Furnaces> 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.

[0053] 2 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.

[0054] 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.

[0055] 3 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.

[0056] In the industrial furnace 400 shown in FIG. 3, 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. In the illustrated embodiment, the fuel pipe 168a1 branches into a first fuel supply path and a second fuel supply path, which are then supplied to the regenerative burner 100a. 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] <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 the 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.

[0062] FIG. 4 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 partially use regenerative burners other than the regenerative burners of the present invention. Although not shown, a required number of similar sets of regenerative burners are installed in the direction of the page.

[0063] 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 4, one pair of regenerative burners 501 and 504 is burning, and the other pair of regenerative burners 502 and 503 is storing heat. [Explanation of symbols]

[0064] 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 111a: First fuel supply path 111b: Air supply path 111c: Ignition port 111d: Swara 111e :Space 111f: Spark plug 112a:Second fuel supply path 112b:Exit 113a: fuel nozzle 113b:Third fuel supply route 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: Wall 170b: Wall 170c: Outer wall 171:Flame exit 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 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 flame outlet is in communication with an outlet of a second fuel supply passage through which the second fuel containing ammonia can flow while being in thermal contact with an outer peripheral wall of the flame stabilizing chamber, The combustion chamber has a flame inlet communicating with the flame outlet of the flame stabilizing chamber, and a flame injection port, and is configured so that, in the presence of a first flame entering the combustion chamber through the flame inlet and combustion air supplied from the heat exchange chamber through the communicating passage into the combustion chamber, a second fuel supplied from an outlet of the second fuel supply passage can be combusted in the combustion chamber and / or before entering the combustion chamber, and a second flame can be ejected from the flame injection port. Regenerative burner.

2. 2. The regenerative burner according to claim 1, wherein a catalyst for decomposing ammonia into hydrogen is disposed in the second fuel supply passage.

3. 3. The regenerative burner according to claim 1, wherein an outer peripheral wall of the flame stabilizing chamber is surrounded by a second fuel supply passage.

4. the combustion chamber further includes a tip of at least one fuel nozzle communicating a third fuel containing ammonia to a third fuel supply passage; the combustion chamber is configured to combust a third 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 from the flame inlet and combustion air supplied into the combustion chamber from the heat exchange chamber through the communicating passage, The system is configured such that the entire amount of the first fuel combusted in the regenerative burner is supplied from a first fuel supply passage toward the ignition port, the entire amount of the second fuel combusted in the regenerative burner is supplied from an outlet of a second fuel supply passage, and the entire amount of the third fuel combusted in the regenerative burner is supplied from a third fuel supply passage to the at least one fuel nozzle.

3. A regenerative burner according to claim 1 or 2.

5. A regenerative burner as described in claim 4, wherein when the combustion chamber is observed from a horizontal direction perpendicular to a 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 third fuel from the tip T of at least one fuel nozzle is taken as P, the angle (∠TPS) formed by the line segments TP and PS is 90°≦∠TPS≦110°.

6. 5. The regenerative burner according to claim 4, wherein the supply direction of the third fuel supplied from the tip of the at least one fuel nozzle is inclined toward the flame inlet.

7. 5. The regenerative burner according to claim 4, wherein the nozzle provided at the tip of the at least one fuel nozzle has a structure capable of injecting the third fuel radially.

8. 5. The regenerative burner according to claim 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.

9. 3. The regenerative burner according to claim 1, further comprising a space upstream of the ignition port for mixing the first fuel and air to form a premixed gas, and a swirler installed in the space.

10. 3. The regenerative burner according to claim 1, wherein the flame inlet is disposed at a position opposite the flame injection port.

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

12. A method for manufacturing a heat-treated product, comprising the step of heat-treating a workpiece using the industrial furnace according to claim 11.

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