Burners and industrial furnaces

Abstract

To provide a burner and industrial furnace capable of efficiently burning ammonia with a simple configuration. [Solution] The burner 100 has an outer tube 1, an inner tube 2, and a first fuel tube 4. The outer tube 1 guides combustion air along the supply direction 101. The inner tube 2 extends along the supply direction 101 and is surrounded by the outer tube 1. The first fuel tube 4 guides ammonia F1 into the interior of the inner tube 2. The inner tube 2 guides ammonia F1 into the interior of the outer tube 1. The inner tube 2 has a front end portion 21 facing the supply direction 101. The first fuel tube 4 has a preheating portion 45 facing the front end portion 21.

Description

Technical Field

[0001] The present disclosure relates to burners and industrial furnaces.

Background Art

[0002] In a burner that mixes and burns fuel and combustion air, hydrocarbon-based fuel is usually used as the fuel. However, when hydrocarbon-based fuel is burned, greenhouse gases such as carbon dioxide are generated. Therefore, in recent years, for the purpose of reducing greenhouse gases such as carbon dioxide, the use of fuels other than hydrocarbon-based fuels has been considered.

[0003] Ammonia is a fuel other than hydrocarbon-based fuel. However, ammonia is more difficult to burn than hydrocarbon-based fuel. As an example of a combustion device using ammonia as fuel, Japanese Patent Application Laid-Open No. 2023-039681 (Patent Document 1) describes an ammonia fuel combustion device having a reformer that decomposes ammonia fuel into hydrogen gas and nitrogen gas. The reformer has a catalyst and a heating unit that heats the catalyst.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The ammonia fuel combustion device described in Patent Document 1 has a reformer having a catalyst and a heating unit, but a combustion device with a simpler configuration is desired.

[0006] The present disclosure has been made in view of the above problems, and an object thereof is to provide a burner and an industrial furnace that can burn ammonia well with a simple configuration.

Means for Solving the Problems

[0007] The burner according to this disclosure comprises an outer tube, an inner tube, and a first fuel tube. The outer tube guides combustion air along the supply direction. The inner tube extends along the supply direction and is surrounded by the outer tube. The first fuel tube guides ammonia into the interior of the inner tube. The inner tube guides the ammonia into the interior of the outer tube. The inner tube has a front end facing the supply direction. The first fuel tube has a preheating section facing the front end. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a burner and an industrial furnace that can efficiently burn ammonia with a simple configuration. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view showing the configuration of a burner according to the first embodiment. [Figure 2] This is a schematic front view showing the configuration of a burner according to the first embodiment. [Figure 3] This is a schematic diagram showing the configuration of an industrial furnace according to the first embodiment. [Figure 4] This is a schematic diagram illustrating the operation of the burner according to the first embodiment. [Figure 5] This is a schematic cross-sectional view showing the configuration of a burner according to a first modified example of the first embodiment. [Figure 6] This is a schematic cross-sectional view showing the configuration of a burner according to a second modified example of the first embodiment. [Figure 7] This is a schematic front view showing the configuration of a burner according to a second modified example of the first embodiment. [Figure 8] This is a schematic cross-sectional view showing the configuration of a burner according to the second embodiment. [Figure 9] This is a schematic diagram showing the configuration of an industrial furnace according to the second embodiment. [Figure 10] This is a flowchart illustrating the operation of an industrial furnace according to the second embodiment. [Figure 11]This is a schematic cross-sectional view showing the configuration of a burner according to a modified example of the second embodiment. [Figure 12] This is an enlarged schematic cross-sectional view showing the configuration of a burner according to the third embodiment. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described below with reference to the drawings. In the following drawings, the same or corresponding parts will be given the same reference numerals, and their descriptions will not be repeated.

[0011] (First Embodiment) <Burner> First, the configuration of the burner 100 according to the first embodiment will be described. As shown in Figure 1, the burner 100 mainly consists of an outer tube 1, a lid 9, an inner tube 2, a primary combustion tube 3, and a first fuel tube 4.

[0012] The outer tube 1 guides the combustion air along the supply direction 101. The outer tube 1 is provided with an opening 19 and an air inlet 18. The outer tube 1 guides the combustion air from the air inlet 18 to the opening 19. The opening direction of the opening 19 is the same as the supply direction 101. The air inlet 18 opens perpendicular to the supply direction 101.

[0013] The outer tube 1 has an inner circumferential surface 11. The inner circumferential surface 11 is annular. The inner circumferential surface 11 surrounds an axis X. The axis X is a virtual line extending along the feed direction 101. The axis X coincides with the central axis of the inner circumferential surface 11. The axis X passes through the center of the opening 19. The air inlet 18 is open on the inner circumferential surface 11. The outer tube 1 has a flange portion 15. The flange portion 15 is the part used when attaching the burner 100 to the furnace wall 81, which will be described later.

[0014] The lid 9 is attached to the outer tube 1. The lid 9 is attached to the end of the outer tube 1 opposite the opening 19. The shape of the lid 9 is, for example, disc-shaped. The lid 9 extends along a direction perpendicular to the feed direction 101. The axis X may pass through the center of the lid 9.

[0015] The inner tube 2 guides the fuel described below inside the outer tube 1. The inner tube 2 extends along the feed direction 101. The inner tube 2 is surrounded by the outer tube 1. The inner tube 2 surrounds the axis X. The axis X coincides with the central axis of the inner tube 2. The inner tube 2 and the outer tube 1 are arranged concentrically about the axis X.

[0016] The inner tube 2 is made of, for example, stainless steel (SUS). The inner tube 2 has an outer peripheral surface 23. The outer peripheral surface 23 faces the inner peripheral surface 11 of the outer tube 1. The outer peripheral surface 23 faces the air inlet 18. The outer peripheral surface 23 is annular.

[0017] The inner tube 2 has a front end portion 21 and a rear end portion 22. The front end portion 21 is surrounded by the outer tube 1. In other words, the front end portion 21 is located inside the outer tube 1. The front end portion 21 faces the feed direction 101. The rear end portion 22 is closed by, for example, a lid portion 9. The rear end portion 22 faces the direction opposite to the feed direction 101. The axis X passes through the centers of each of the front end portion 21 and the rear end portion 22.

[0018] The inner tube 2 is provided with a jet outlet 29. The jet outlet 29 blows out the fuel. The inside of the inner tube 2 and the inside of the outer tube 1 communicate with each other through the jet outlet 29. The jet outlet 29 is provided, for example, at the front end portion 21. The jet outlet 29 opens, for example, in the feed direction 101.

[0019] The first fuel pipe 4 guides ammonia (hereinafter also referred to as ammonia fuel) inside the inner tube 2. The ammonia may be a gas or a liquid. In the burner 100 according to the first embodiment, the fuel supplied from the inner tube 2 to the outer tube 1 is ammonia. In other words, the inner tube 2 guides ammonia to the inside of the outer tube 1. Note that the burner 100 does not have a catalyst for decomposing ammonia into hydrogen and nitrogen.

[0020] The first fuel pipe 4 is made of, for example, stainless steel. Therefore, even when ammonia fuel is supplied to the inside of the first fuel pipe 4, corrosion of the first fuel pipe 4 can be prevented.

[0021] The interior of the first fuel pipe 4 and the interior of the inner pipe 2 are in communication at a connection port 28. The connection port 28 is provided on the outer circumferential surface 23 of the inner pipe 2. The connection port 28 opens in a direction perpendicular to the supply direction 101. The opening direction of the connection port 28 may be the same as the opening direction of the air inlet 18. The interior of the first fuel pipe 4 and the interior of the outer pipe 1 are in communication via the inner pipe 2.

[0022] In the direction of the extension of axis X, the connection port 28 is provided, for example, between an intermediate position between the cover portion 9 and the front end portion 21 and the cover portion 9. In the direction of the extension of axis X, the connection port 28 is provided, for example, between the central axis C of the air inlet 18 and the cover portion 9.

[0023] The first fuel pipe 4 has a first pipe section 41, a preheating section 45, and a second pipe section 42. The first pipe section 41 is attached to the cover section 9. The interior of the first pipe section 41 is open to the outside of the burner 100, for example, via the cover section 9. Ammonia is supplied to the interior of the first pipe section 41, for example, via the cover section 9. The first pipe section 41 extends along the feed direction 101. The first pipe section 41 is located inside the outer pipe 1. The first pipe section 41 faces the outer circumferential surface 23 of the inner pipe 2.

[0024] The preheating section 45 is connected to the first pipe section 41. The preheating section 45 is located inside the outer pipe 1. The preheating section 45 faces the front end section 21. The preheating section 45 faces, for example, the nozzle 29. The preheating section 45 is located in the feed direction 101 relative to the front end section 21. The preheating section 45 extends along a direction perpendicular to the feed direction 101. The preheating section 45 intersects with axis X.

[0025] The preheating section 45 is, for example, spaced apart from the front end 21 and not connected to it. In other words, the distance E between the preheating section 45 and the front end 21 in the feed direction 101 is, for example, greater than 0 mm. The distance E is 2 times or less the inner diameter (first inner diameter D1) of the inner tube 2. The distance E may be, for example, 1.8 times or less the first inner diameter D1, or 1.5 times or less the first inner diameter D1. The distance E may be, for example, 0.1 times or more the first inner diameter D1, or 0.5 times or more the first inner diameter D1. The preheating section 45 may be in contact with the front end 21. In other words, the distance E may be 0 mm.

[0026] The second pipe section 42 is connected to the preheating section 45. Specifically, the second pipe section 42 is connected to the end of the preheating section 45 opposite to the end to which the first pipe section 41 is connected. From another perspective, the preheating section 45 connects the first pipe section 41 and the second pipe section 42. The second pipe section 42 is located in the direction opposite to the feed direction 101 with respect to the preheating section 45. The second pipe section 42 is in communication with the inner pipe 2 at the connection port 28.

[0027] The second pipe section 42 extends along the feeding direction 101. The second pipe section 42 is located inside the outer pipe 1. The second pipe section 42 faces the outer circumferential surface 23 of the inner pipe 2. The second pipe section 42 is spaced apart from the lid section 9.

[0028] The first pipe section 41, the inner pipe 2, and the second pipe section 42 are aligned along a direction perpendicular to the feeding direction 101. The inner pipe 2 is located between the first pipe section 41 and the second pipe section 42. The second pipe section 42 is located between the inner pipe 2 and the air inlet 18.

[0029] The inner diameter of the first fuel pipe 4 (second inner diameter D2) may be less than or equal to the first inner diameter D1, or it may be approximately the same as the first inner diameter D1. The second inner diameter D2 is determined considering the ammonia flow velocity and pressure loss. The inner diameter of the outer pipe 1 (third inner diameter D3) is, for example, 3 times or more and 8 times or less of the first inner diameter D1. The inner diameter of the opening 19 is set to the third inner diameter D3.

[0030] The primary combustion tube 3 surrounds the front end 21 and the preheating section 45, respectively. The primary combustion tube 3 is spaced apart from, for example, the preheating section 45. The primary combustion tube 3 is located between the inner tube 2 and the outer tube 1. The primary combustion tube 3, the inner tube 2, and the outer tube 1 are arranged concentrically around axis X. The primary combustion tube 3 is located inside the outer tube 1. The primary combustion tube 3 extends along the feed direction 101. The primary combustion tube 3 has a first open end 31 and a second open end 32.

[0031] The first open end 31 is positioned in the feed direction 101 relative to the front end 21. Specifically, in the direction in which the axis X extends, the first open end 31 is positioned between the front end 21 and the opening 19. The first open end 31 faces the feed direction 101.

[0032] The second opening end 32 is opposite the first opening end 31. The second opening end 32 is located in the direction opposite to the feed direction 101 with respect to the front end 21. From another point of view, in the direction in which axis X extends, the front end 21 is located between the first opening end 31 and the second opening end 32. In the direction in which axis X extends, the preheating section 45 is located between the front end 21 and the first opening end 31. Specifically, in the direction in which axis X extends, for example, the preheating section 45 is located between the front end 21 and the point one-third of the distance from the first opening end 31 toward the second opening end 32 toward the front end 21.

[0033] Figure 2 shows the configuration of the burner 100 as viewed in the direction opposite to the feed direction 101. For the sake of clarity, the flange portion 15 and the air inlet 18 are not shown in Figure 2.

[0034] As shown in Figures 1 and 2, the burner 100 has, for example, a plurality of first swirling blades 51 and a plurality of second swirling blades 52. The plurality of first swirling blades 51 and the plurality of second swirling blades 52 are inclined with respect to the feed direction 101, thereby swirling the combustion air and stirring and mixing it with the ammonia fuel, making the difficult-to-burn ammonia fuel more combustible.

[0035] Each of the multiple first swirl vanes 51 extends from the inner tube 2 to the primary combustion tube 3. Each of the multiple first swirl vanes 51 is located between the inner tube 2 and the primary combustion tube 3. Each of the multiple second swirl vanes 52 extends from the primary combustion tube 3 to the outer tube 1. Each of the multiple second swirl vanes 52 is located between the primary combustion tube 3 and the outer tube 1.

[0036] As shown in Figure 1, in the direction of axis X, each of the multiple first orbital blades 51 is located between the first open end 31 and the second open end 32. In the direction of axis X, each of the multiple second orbital blades 52 is located between the first open end 31 and the second open end 32. The multiple second orbital blades 52 are located in the feed direction 101 relative to the multiple first orbital blades 51. Each of the first pipe section 41 and the second pipe section 42 is located between two adjacent first orbital blades 51 from the multiple first orbital blades 51.

[0037] As shown in Figure 2, when viewed in the direction opposite to the feed direction 101 (hereinafter referred to as the front view), the multiple first swirl vanes 51 extend radially around axis X. Specifically, each of the multiple first swirl vanes 51 extends radially outward from the inner tube 2. In the front view, the multiple second swirl vanes 52 extend radially around axis X. Specifically, each of the multiple second swirl vanes 52 extends radially outward from the primary combustion tube 3. The multiple second swirl vanes 52 are located radially outward relative to the multiple first swirl vanes 51. Note that the radially outward direction is perpendicular to the feed direction 101 and is the direction from the inner tube 2 toward the outer tube 1.

[0038] In a front view, the preheating section 45 covers a portion of the front end portion 21. In a front view, the preheating section 45 covers, for example, a portion of the nozzle 29. In other words, in a front view, a portion of the nozzle 29 is exposed, for example, from the preheating section 45.

[0039] As shown in Figure 2, the burner 100 includes a spark plug 6 and a flame detector 7. The spark plug 6 ignites the fuel ejected from the inner tube 2. The flame detector 7 detects the presence or absence of a flame inside the burner 100. Specifically, the flame detector 7 detects, for example, ultraviolet light generated by the flame.

[0040] Although not shown in the diagram, the spark plug 6 and the flame detector 7 are each attached to the cover 9. The spark plug 6 and the flame detector 7 each extend from the cover 9 to the interior of the primary combustion tube 3 along the feed direction 101. In the direction along axis X, the tips of the spark plug 6 and the flame detector 7 are located inside the primary combustion tube 3.

[0041] The inner tube 2 is located between the spark plug 6 and the flame detector 7. In a front view, the preheating section 45 is located between the spark plug 6 and the flame detector 7. In a front view, neither the spark plug 6 nor the flame detector 7 is covered by the preheating section 45. In other words, in a front view, both the rod-shaped spark plug 6 and the flame detector 7 are exposed from the preheating section 45. In addition, a sight hole (not shown) is provided in the cover 9 of the flame detector 7, and a camera for the flame detector 7 is installed outside of it for non-contact monitoring. In that case, the first swirling vane 51 in that part is removed so as not to obstruct the camera's field of view.

[0042] <Industrial Furnace> Next, the configuration of the industrial furnace 200 according to the first embodiment will be described.

[0043] As shown in Figure 3, the industrial furnace 200 mainly consists of the burner 100, furnace wall 81, fastening bolts 86, blower 83, first valve 84, and control unit 82. The industrial furnace 200 is a heat treatment furnace, heating furnace, regenerative thermal oxidizer (RTO), etc.

[0044] The furnace wall 81 forms an internal space 89. A heating object (not shown) is placed in the internal space 89. The burner 100 heats the heating object. The burner 100 is attached to the furnace wall 81. Specifically, the furnace wall 81 and the flange portion 15 of the burner 100 are fastened together, for example, by fastening bolts 86. The portion of the burner 100 located 101 in the feed direction relative to the flange portion 15 is surrounded by the furnace wall 81. The opening 19 of the burner 100 opens toward the internal space 89.

[0045] The blower 83 supplies combustion air to the inside of the outer pipe 1. The blower 83 is connected to the air inlet 18. The first valve 84 opens and closes the supply passage for ammonia F1 to the inside of the first fuel pipe 4.

[0046] The control unit 82 controls the operation of the blower 83. Specifically, the control unit 82 controls the start and stop of the supply of combustion air to the outer pipe 1, as well as the flow rate of the combustion air supplied to the outer pipe 1, by outputting signals to the blower 83.

[0047] The control unit 82 controls the operation of the first valve 84. Specifically, the control unit 82 controls the start and stop of the supply of ammonia F1 to the first fuel pipe 4, as well as the flow rate of ammonia F1 supplied to the first fuel pipe 4, by outputting a signal to the first valve 84.

[0048] The control unit 82 controls the operation of the spark plug 6 (see Figure 2) by outputting a signal to the spark plug 6. The control unit 82 receives a signal from the flame detector 7 (see Figure 2) regarding the presence or absence of a flame inside the burner 100.

[0049] Next, the operation of the burner 100 and industrial furnace 200 according to the first embodiment will be described. As shown in Figure 4, ammonia F1 is supplied into the first fuel pipe 4. Specifically, the control unit 82 (see Figure 3) starts supplying ammonia F1 to the first fuel pipe 4 by controlling the first valve 84 (see Figure 3). The ammonia F1 is supplied into the inner pipe 2 through the first pipe section 41, the preheating section 45, and the second pipe section 42. The ammonia F1 is supplied into the outer pipe 1 from the nozzle 29 of the inner pipe 2.

[0050] Combustion air is supplied to the inside of the outer tube 1 via the air inlet 18. Specifically, the control unit 82 starts supplying combustion air to the outer tube 1 by controlling the blower 83 (see Figure 3). The combustion air flows toward the opening 19 along the supply direction 101. A portion of the combustion air is swirled by a plurality of first swirling blades 51. The remainder of the combustion air is swirled by a plurality of second swirling blades 52.

[0051] The combustion air, swirled by multiple first swirling vanes 51, is mixed with ammonia F1 inside the primary combustion tube 3. The control unit 82 ignites the mixed ammonia F1 by controlling the spark plug 6 (see Figure 2). This generates a flame B inside the primary combustion tube 3. A portion of the ammonia F1 flows along the supply direction 101 without being burned.

[0052] Combustion air, swirled by multiple second swirling vanes 52, is supplied around the flame B. Between the first open end 31 of the primary combustion tube 3 and the opening 19 of the outer tube 1, the combustion air and the unburned ammonia F1 are mixed, causing the ammonia F1 to be combusted secondarily. As a result, the ammonia F1 is combusted in two stages. By combusting the ammonia F1 in two stages, it is possible to suppress the temperature of the flame B from becoming excessively high. As a result, the amount of NOx produced by combustion can be reduced.

[0053] Next, the effects and benefits of the burner 100 and industrial furnace 200 according to the first embodiment will be described.

[0054] According to the burner 100 of the first embodiment, the first fuel pipe 4 guides ammonia F1 into the inner pipe 2. The first fuel pipe 4 has a preheating section 45 facing the front end 21 of the inner pipe 2. Therefore, as shown in Figure 4, the preheating section 45 is located at the base of the flame B. Consequently, the flame B heats the preheating section 45 and the ammonia F1 flowing inside the preheating section 45. As a result, the temperature of the ammonia F1 flowing inside the preheating section 45 rises. This makes the ammonia F1 easier to burn. Specifically, when the ammonia F1 is heated, a portion of the ammonia F1 is decomposed into nitrogen and hydrogen. In other words, the ammonia F1 is reformed. The hydrogen contained in the reformed ammonia F1 makes the ammonia F1 easier to burn. As a result, ammonia F1 can be burned well with a simple configuration.

[0055] The flame B heats both the inner tube 2 and the preheating section 45. As a result, both the inner tube 2 and the first fuel tube 4 expand due to thermal expansion. Consequently, interference between the inner tube 2 and the preheating section 45 may occur due to the difference in the amount of thermal expansion between the inner tube 2 and the first fuel tube 4. In the burner 100 according to the first embodiment, the preheating section 45 is spaced apart from the front end 21. Therefore, even when there is a difference in the amount of thermal expansion between the inner tube 2 and the first fuel tube 4, interference between the inner tube 2 and the preheating section 45 can be prevented.

[0056] The temperature of flame B increases as it moves away from the front end 21 of the inner tube 2, reaching a peak at a certain distance from the front end 21. If the preheating section 45 is located near the point where the temperature of flame B reaches its peak, the preheating section 45 may become excessively heated and melt. According to the burner 100 of the first embodiment, the distance E in the feed direction 101 between the front end 21 and the preheating section 45 is less than or equal to twice the inner diameter (first inner diameter D1) of the inner tube 2. In this way, the distance E between the front end 21 and the preheating section 45 is prevented from becoming excessively long. Therefore, the preheating section 45 can be located at a position where the temperature of flame B is relatively low. This prevents the preheating section 45 from becoming excessively heated.

[0057] The burner 100 according to the first embodiment has a primary combustion tube 3. The primary combustion tube 3 has a first open end 31 located in the feed direction 101 relative to the front end 21. By positioning the preheating section 45 between the front end 21 and the first open end 31, the distance E between the front end 21 and the preheating section 45 is prevented from becoming excessively long. As a result, the preheating section 45 can be positioned at a relatively low temperature of the flame B. This prevents the preheating section 45 from being overheated.

[0058] The industrial furnace 200 according to the first embodiment has the burner 100 described above and a furnace wall 81 to which the burner 100 is attached. Therefore, ammonia F1 can be burned well with a simple configuration.

[0059] (Modification of the first embodiment) The configuration of the burner 100 according to this disclosure is not limited to the above configuration. Specifically, as shown in Figure 5, the nozzle 29 may open to the outer circumferential surface 23 of the inner tube 2. From another point of view, the nozzle 29 may open radially outward. The front end 21 may be closed. The nozzle 29 may open to both the outer circumferential surface 23 and the front end 21.

[0060] When the nozzle 29 opens to the outer surface 23, the ammonia F1 ejected from the inner tube 2 is swirled together with the combustion air by a plurality of first swirling blades 51 and a plurality of second swirling blades 52. Specifically, a portion of the combustion air and a portion of the ammonia F1 are supplied into the primary combustion tube 3 in a swirled state by the plurality of first swirling blades 51. The remaining combustion air and the remaining ammonia F1 are supplied between the first open end 31 of the primary combustion tube 3 and the opening 19 of the outer tube 1 in a swirled state by the plurality of second swirling blades 52. As a result, the ammonia F1 is mixed with the combustion air before being stirred by each of the swirling blades 51 and 52, allowing for better mixing and making the difficult-to-burn ammonia F1 more combustible.

[0061] As shown in Figures 6 and 7, the burner 100 does not have to have a plurality of first swirling blades 51 and a plurality of second swirling blades 52. The primary combustion tube 3 may have a plate-shaped portion 33. The second open end 32 of the primary combustion tube 3 shown in Figure 1 may be closed by the plate-shaped portion 33.

[0062] The plate-shaped portion 33 extends radially outward from the inner tube 2. The plate-shaped portion 33 surrounds the inner tube 2. The plate-shaped portion 33 is in contact with the inner tube 2. As shown in Figure 7, the plate-shaped portion 33 is provided with a plurality of through holes 39. Each of the plurality of through holes 39 extends along the feed direction 101. In a front view, each of the plurality of through holes 39 is exposed from the preheating section 45.

[0063] According to the burner 100 shown in Figures 6 and 7, a portion of the combustion air supplied to the inside of the outer tube 1 is supplied to the inside of the primary combustion tube 3 through a plurality of through holes 39. The remainder of the combustion air flows radially outward through the primary combustion tube 3 toward the opening 19. In this way, the combustion air can be propelled straight and far, increasing the length of the two-stage combustion flame, preventing the ammonia F1 from burning all at once, and making it difficult for the flame temperature to rise, thereby suppressing the generation of NOx.

[0064] (Second Embodiment) Next, the configuration of the burner 100 according to the second embodiment will be described. The burner 100 according to the second embodiment differs from the burner 100 according to the first embodiment mainly in that it has a second fuel pipe 5, and is substantially the same as the burner 100 according to the first embodiment in other respects. The following description will focus on the differences from the burner 100 according to the first embodiment.

[0065] As shown in Figure 8, the burner 100 according to the second embodiment has a second fuel pipe 5. The second fuel pipe 5 is connected to the rear end 22 of the inner pipe 2. The rear end 22 is located outside the outer pipe 1. The inner pipe 2 passes through the lid 9.

[0066] The second fuel pipe 5 guides the ignition fuel F2 into the inner pipe 2. The inside of the second fuel pipe 5 and the inside of the outer pipe 1 are in communication via the inner pipe 2. From another perspective, the inner pipe 2 guides the ignition fuel F2 into the outer pipe 1. In the burner 100 according to the second embodiment, the fuel supplied from the inner pipe 2 to the outer pipe 1 is either ammonia F1, ignition fuel F2, or both ammonia F1 and ignition fuel F2.

[0067] Ignition fuel F2 is, for example, a hydrocarbon fuel. Specifically, ignition fuel F2 is, for example, city gas (13A) mainly composed of methane. The calorific value of ignition fuel F2 is greater than that of, for example, ammonia F1. Ignition fuel F2 may also be hydrogen gas.

[0068] Next, the configuration of the industrial furnace 200 according to the second embodiment will be described. As shown in Figure 9, the industrial furnace 200 according to the second embodiment has a second valve 85. The second valve 85 opens and closes the supply path for ignition fuel F2 into the second fuel pipe 5. The control unit 82 controls the operation of the second valve 85. Specifically, the control unit 82 controls the start and stop of the supply of ignition fuel F2 to the second fuel pipe 5, as well as the flow rate of ignition fuel F2 supplied to the second fuel pipe 5, by outputting a signal to the second valve 85.

[0069] Next, the operation of the industrial furnace 200 according to the second embodiment will be described. As shown in Figure 10, first, the control unit 82 starts supplying ignition fuel F2 to the second fuel pipe 5 by controlling the second valve 85 (step S10). In step S10, the control unit 82 supplies combustion air into the outer pipe 1 by controlling the blower 83. The control unit 82 ignites the ignition fuel F2 by controlling the spark plug 6 (see Figure 2) (step S20). This generates a flame B (see Figure 4).

[0070] Next, the control unit 82 starts supplying ammonia F1 to the first fuel pipe 4 by controlling the first valve 84 (step S30). The flame B heats the preheating section 45 and the ammonia F1 flowing inside the preheating section 45. As a result, the heated ammonia F1 is supplied into the inner pipe 2.

[0071] After step S30, the control unit 82 may continue supplying the ignition fuel F2 or may stop supplying the ignition fuel F2. If the control unit 82 continues supplying the ignition fuel F2, the burner 100 uses both ammonia F1 and ignition fuel F2 as fuel (co-firing). If the control unit 82 stops supplying the ignition fuel F2, the burner 100 uses only ammonia F1 as fuel (exclusive firing).

[0072] The burner 100 according to the second embodiment has a second fuel pipe 5. The second fuel pipe 5 guides the ignition fuel F2 inside the inner pipe 2. Therefore, after ignition using the relatively easy-to-ignite ignition fuel F2, the supply of ammonia F1 can be started. This makes it easier to ignite and start the combustion of the difficult-to-ignite ammonia F1, and also makes it easy to maintain combustion using the heated ammonia F1.

[0073] Normally, when ignition is performed using ammonia F1, unburned ammonia may be discharged from the burner 100. According to the burner 100 of the second embodiment, by starting the supply of ammonia F1 after ignition using a relatively easy-to-ignite ignition fuel F2, heated ammonia F1 can be supplied to the inner pipe 2 immediately after the start of ammonia F1 supply. As a result, reformed ammonia F1 can be supplied to the inner pipe 2 immediately after the start of ammonia F1 supply. Consequently, the discharge of unburned ammonia from the burner 100 can be suppressed.

[0074] The first fuel pipe 4 may guide a preceding gas, such as nitrogen gas, into the inner pipe 2. The industrial furnace 200 may have a switching valve (not shown) that can switch between supplying ammonia F1 to the first fuel pipe 4 and supplying a preceding gas to the first fuel pipe 4. The control unit 82 may supply either ammonia F1, the preceding gas, or both ammonia F1 and the preceding gas to the first fuel pipe 4 by controlling the switching valve. In step S20 described above, the control unit 82 may be supplying the preceding gas to the first fuel pipe 4.

[0075] If the preheating section 45 is heated using flame B while no fluid such as ammonia F1 is supplied to it, and then the supply of ammonia F1 to the preheating section 45 is started, the preheating section 45 will be cooled by the ammonia F1. In this case, the ammonia F1 flowing inside the preheating section 45 may not be sufficiently heated for a while after the start of the ammonia F1 supply. Therefore, in step S20, a lead gas is first supplied to the first fuel pipe 4, and after waiting for the preheating section 45 to heat up, the supply is switched to ammonia F1. By doing so, the decrease in the temperature of the preheating section 45 when switching from the lead gas to ammonia F1 can be suppressed. As a result, the ammonia F1 can be sufficiently heated even immediately after the start of the ammonia F1 supply.

[0076] Furthermore, if the preheating section 45 is heated using flame B without a fluid such as ammonia F1 being supplied to it, the preheating section 45 may become excessively heated. Therefore, in process S20, by first supplying a lead gas to the first fuel pipe 4, the preheating section 45 is cooled using the lead gas, and after waiting for the temperature of the preheating section 45 to drop, the supply of ammonia F1 is switched on, thereby suppressing excessive heating of the ammonia F1. In short, the lead gas is used as a dummy until the temperature of the preheating section 45 stabilizes.

[0077] (Modified version of the second embodiment) As shown in Figure 11, the burner 100 does not necessarily have a primary combustion tube 3, a plurality of first swirling blades 51, and a plurality of second swirling blades 52. The burner 100 may also have a flame holder plate 30.

[0078] The flame holder plate 30 is attached to the inner pipe 2. The flame holder plate 30 surrounds the inner pipe 2. The flame holder plate 30 is positioned in the direction opposite to the feed direction 101 with respect to the front end 21 of the inner pipe 2. Each of the first pipe section 41 and the second pipe section 42 passes through the flame holder plate 30. Although not shown, the flame holder plate 30 is provided with a plurality of through holes 39. The plurality of through holes 39 provided in the flame holder plate 30 correspond to the plurality of through holes 39 shown in Figure 7. When the flame holder plate 30 is heated, the temperature around the nozzle 29 stabilizes, and the combustion state of the flame stabilizes.

[0079] (Third embodiment) Next, the configuration of the burner 100 according to the third embodiment will be described. The burner 100 according to the third embodiment differs from the burner 100 according to the first embodiment mainly in that the preheating section 45 has an uneven surface, and is substantially the same as the burner 100 according to the first embodiment in other respects. The following description will focus on the differences from the burner 100 according to the first embodiment.

[0080] As shown in Figure 12, according to the burner 100 of the third embodiment, the preheating section 45 has a tubular member 46 and a plurality of protrusions 49. The tubular member 46 corresponds to the preheating section 45 of the burner 100 of the first embodiment (see Figure 1).

[0081] Each of the multiple protrusions 49 is provided on the outer circumferential surface (second outer circumferential surface 47) of the pipe member 46. Each of the multiple protrusions 49 extends outward from the second outer circumferential surface 47 of the pipe member 46. The multiple protrusions 49 are, for example, fins.

[0082] The provision of multiple protrusions 49 on the second outer surface 47 increases the surface area of ​​the preheating section 45. This increases the amount of heat the preheating section 45 receives from the flame B. As a result, the ammonia F1 flowing inside the preheating section 45 can be heated more effectively.

[0083] The shape of the multiple protrusions 49 is not particularly limited. The shape of each of the multiple protrusions 49 may be, for example, pin-shaped. Multiple recesses (not shown) may be provided on the second outer peripheral surface 47. The preheating section 45 only needs to have the uneven surface provided on the second outer peripheral surface 47. The outer peripheral surface of the preheating section 45 of the burner 100 according to the second embodiment may have the uneven surface.

[0084] The various aspects of this disclosure are summarized below as an appendix. (Note 1) An outer tube that guides combustion air along the direction of supply, An inner tube extending along the aforementioned feeding direction and surrounded by the outer tube, The inner tube includes a first fuel tube that guides ammonia inside, The inner tube guides the ammonia into the interior of the outer tube. The inner tube has a front end facing the feeding direction, The first fuel pipe is a burner having a preheating section facing the front end. (Note 2) The burner as described in Appendix 1, wherein the distance in the feeding direction between the front end and the preheating section is no more than twice the inner diameter of the inner tube. (Note 3) The preheating section is a burner as described in Appendix 1 or Appendix 2, spaced apart from the front end. (Note 4) The inner tube is further provided with a second fuel tube that guides ignition fuel inside the inner tube, The inner tube is a burner according to any one of the appendices 1 to 3, which guides the ignition fuel into the interior of the outer tube. (Note 5) The system further comprises a primary combustion tube that surrounds the aforementioned front end and is located between the inner tube and the outer tube, The primary combustion tube has an open end located in the feeding direction relative to the front end, In the aforementioned feeding direction, the preheating section is located between the front end and the open end, as described in any one of the appendices 1 to 4, for the burner described in the appendices. (Note 6) The preheating unit is The aforementioned tubular member for guiding the ammonia, A burner according to any one of the appendices 1 to 5, having an uneven surface provided on the outer surface of the pipe member. (Note 7) A burner as described in any one of the items from Appendix 1 to Appendix 6, An industrial furnace comprising a furnace wall on which the aforementioned burner is attached.

[0085] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the embodiments described above, and all modifications within the meaning and scope of the claims are intended to be included. [Explanation of Symbols]

[0086] 1 outer tube 2 Inner tube 3. Primary combustion tube 4 1st fuel pipe 5 2nd fuel pipe 6 Spark plugs 7. Flame detector 9 Lid 11 Inner surface 15 Flange section 18 Air inlet 19 Opening 21 Front end 22 Rear end 23 Outer surface 28 connection ports 29 spout 30 Flame holding plate 31 1st open end 32 2nd open end 33 Plate-like portion 39 Through hole 41. First Section 42. Second Section 45 Preheating section 46 Pipe members 47 Second outer surface 49 Protrusion 51 First rotating blade 52 Second rotating blade 81 Furnace wall 82 Control Unit 83 Blower 84. Valve No. 1 85. Second valve 86 fastening bolts 89 Interior space 100 burners 101 Feed direction 200 industrial furnaces Air for combustion B Flame C center axis D1 First inner diameter D2 2nd inner diameter D3 Third inner diameter E Distance F1 Ammonia F2 ignition fuel X axis

Claims

1. An outer pipe that guides combustion air along the feeding direction, An inner pipe that extends along the feeding direction and is surrounded by the outer pipe, A first fuel pipe that guides ammonia inside the inner pipe, and comprises: The inner pipe guides the ammonia to the inside of the outer pipe, The inner pipe has a front end portion facing the feeding direction, The first fuel pipe has a preheating portion facing the front end portion, a burner.

2. The distance in the feeding direction between the front end portion and the preheating portion is not more than twice the inner diameter of the inner pipe. The burner according to Claim 1.

3. The preheating portion is separated from the front end portion. The burner according to Claim 1 or Claim 2.

4. Further comprises a second fuel pipe that guides ignition fuel inside the inner pipe, The inner pipe guides the ignition fuel to the inside of the outer pipe. The burner according to Claim 1 or Claim 2.

5. Further comprises a primary combustion pipe that surrounds the front end portion and is located between the inner pipe and the outer pipe, The primary combustion pipe has an open end portion located in the feeding direction with respect to the front end portion, In the feeding direction, the preheating portion is located between the front end portion and the open end portion. The burner according to Claim 1 or Claim 2.

6. The preheating portion A pipe member that guides the ammonia, Protrusions and depressions provided on the outer peripheral surface of the pipe member, and has. The burner according to Claim 1 or Claim 2.

7. The burner according to Claim 1 or Claim 2, A furnace wall to which the burner is attached, and comprises. An industrial furnace.

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