burner

Abstract

We provide an adjustable burner that allows for more appropriate EGR depending on the type of fuel used. [Solution] Burner 1 performs combustion by switching between hydrogen gas and hydrocarbon gas. Burner 1 includes an air inlet 36 for introducing air R, and a circulation unit 40 for circulating exhaust gas E2, which is a part of the exhaust gas E from the combustion of hydrogen gas or hydrocarbon gas, back to the air inlet 36. The circulation unit 40 has a flow path through which the exhaust gas E2 flows, and a flow rate regulator 66 attached to the flow path. Compared to hydrocarbon gas, hydrogen gas can maintain combustion even if the circulation amount, which is the flow rate of the circulating exhaust gas E2, is large. When hydrogen gas is combusted, the flow rate regulator does not protrude from the flow path and has a first gap between it and the flow path. When hydrocarbon gas is combusted, the protruding portion 74C of the flow rate regulator 66C protrudes in a rod shape with a second gap smaller than the first gap relative to the flow path.

Description

Technical Field

[0001] The present disclosure relates to a burner that performs exhaust gas recirculation (EGR).

Background Art

[0002] As a combustion device, one described in Japanese Unexamined Patent Application Publication No. 2007-40642 (Patent Document 1) is known. This combustion device includes a burner 2 that can be switched to any one of a stopped state, a low combustion state, and a high combustion state by fuel supply, a can body 3 in which the burner 2 is disposed, a main fan 4 that supplies combustion air to the burner 2, a carbon savings device 6 provided in a flue 5 of the can body 3, a recirculation flow path 9 that connects one end to the downstream side of the carbon savings device 6 and the other end to a combustion air suction port 7 of the main fan 4 or a combustion air path 8 of the burner 2 to recirculate a part of the exhaust gas generated by combustion of the burner 2, a recirculation fan 10 provided in the recirculation flow path 9, and an orifice 11 provided on the upstream side of the recirculation fan 10.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above combustion device, there is no viewpoint of appropriately adjusting the EGR state according to the type of fuel. In the above combustion device, when operating with a different type of fuel, the EGR state may become less appropriate from the viewpoints of suppressing misfire and poor combustion and suppressing the generation amount of nitrogen oxides (NOx). Therefore, the main object of the present disclosure is to provide a burner that can be adjusted to perform more appropriate EGR according to the type of fuel. [Means for solving the problem]

[0005] This specification discloses a burner, which may perform combustion by switching between a first fuel and a second fuel. The burner may be equipped with a combustion air inlet for introducing combustion air. The burner may be equipped with a circulation section for circulating a portion of the exhaust gas from the combustion of the first or second fuel back to the combustion air inlet. The circulation section may have a flow path through which the exhaust gas flows. The circulation section may have a flow rate regulator attached to the flow path. The combustion of the first fuel may be maintained even if the circulation amount, which is the flow rate of the circulating exhaust gas, is greater than that of the second fuel. When the first fuel is combusted, the flow rate regulator may have a first gap between itself and the flow path without protruding from it, or it may protrude in a rod shape with a first gap between itself and the flow path. When the second fuel is combusted, the flow rate regulator may protrude in a rod shape with a second gap smaller than the first gap between itself and the flow path. [Effects of the Invention]

[0006] According to this disclosure, a burner is provided that can be adjusted to perform more appropriate EGR depending on the type of fuel. [Brief explanation of the drawing]

[0007] [Figure 1] This is a central longitudinal cross-sectional view of a burner according to the first embodiment of this disclosure. [Figure 2] This is a partial cross-sectional view of line AA in Figure 1. [Figure 3] Figure 3A is a partial cross-sectional view of the first flow regulator along line AA, Figure 3B is a partial cross-sectional view of the second flow regulator along line AA, and Figure 3C is a partial cross-sectional view of the third flow regulator along line AA. [Figure 4] This is a central longitudinal cross-sectional view of a burner according to the second embodiment of this disclosure. [Figure 5] This is a top view of Figure 4. [Figure 6] Figures 4, 9, and 11 are front views of the burner nozzle. [Figure 7] This is a schematic diagram showing the noise measurement locations. [Figure 8] This graph shows the relationship between the combustion chamber length L2 (mm) and noise level (dB) in study examples 2-1 to 4-6. [Figure 9] This is a central longitudinal cross-sectional view of a burner according to the third embodiment of this disclosure. [Figure 10] This is a partial cross-sectional view of line BB in Figure 9. [Figure 11] This is a central longitudinal cross-sectional view of a burner according to the fourth embodiment of this disclosure. [Figure 12] This is a top view of Figure 11. [Figure 13] This is a central longitudinal cross-sectional view of a four-way valve device used in a burner according to the fifth embodiment. [Modes for carrying out the invention]

[0008] Examples of embodiments and modifications thereof relating to this disclosure will be described below with reference to the drawings as appropriate. However, these embodiments are not limited to the examples and modifications described below.

[0009] [First form] Figure 1 is a central longitudinal cross-sectional view of the burner 1 according to the first embodiment. Figure 2 is a partial cross-sectional view along line AA of Figure 1. Burner 1 is a radiant tube burner installed in the furnace, capable of heating both the atmospheric gas inside the furnace and the object to be heated without direct contact between the atmospheric gas and the combustion. Burner 1 is a single-ended type. However, Burner 1 may be a burner other than a single-ended type. The burner 1 comprises a protruding pipe section 2, a first body 4, a second body 6, and an ignition unit 8.

[0010] The protruding pipe section 2 includes a base 9, an outer pipe 10, an inner pipe 12, a fuel pipe 14, and a burner nozzle 16.

[0011] The base 9 is ring-shaped and plate-shaped. The base 9 is provided on the outside of the furnace of the horizontal furnace wall P. Incidentally, the base 9 may be regarded as a component belonging to a member other than the protruding pipe portion 2, or may be regarded as an independent component. The outer pipe 10 protrudes from the base 9 into the furnace. The outer pipe 10 extends in the vertical direction and protrudes downward. The outer pipe 10 is cylindrical. The lower end, which is the tip of the outer pipe 10, is closed and rounded. The upper end, which is the base end of the outer pipe 10, is open to the outside of the furnace. Incidentally, the base 9 and the outer pipe 10 may be provided in a direction other than the vertical direction, in addition to the horizontal furnace wall P, such that the outer pipe 10 protrudes horizontally from the standing furnace wall. Also, the shape of the outer pipe 10 may be other than cylindrical, such as square tubular.

[0012] The inner pipe 12 is disposed inside the outer pipe 10. The inner pipe 12 extends in the vertical direction. The inner pipe 12 is cylindrical. The virtual central axis of the inner pipe 12 coincides with the virtual central axis of the outer pipe 10. That is, the outer pipe 10 and the inner pipe 12 are coaxially arranged. The lower end of the inner pipe 12 is adjacent to the lower end of the outer pipe 10. The upper end portion of the inner pipe 12 is disposed inside the first body 4. Incidentally, the shape of the inner pipe 12 may be other than cylindrical, such as square tubular. Also, the arrangement of the inner pipe 12 may be other than the above, for example, it may not be coaxial with the outer pipe 10, or the lower end may not be adjacent to the outer pipe 10.

[0013] The fuel pipe 14 is disposed inside the inner pipe 12. The fuel pipe 14 extends in the vertical direction. The fuel pipe 14 is cylindrical. The virtual central axis of the fuel pipe 14 coincides with the virtual central axis of the outer pipe 10 and the virtual central axis of the inner pipe 12. That is, the outer pipe 10, the inner pipe 12, and the fuel pipe 14 are coaxially arranged. The lower end of the fuel pipe 14 is disposed inside the lower part of the inner pipe 12. The upper end of the fuel pipe 14 is located inside the first body 4 and the second body 6. The upper end of the fuel pipe 14 is provided with a fuel inlet (not shown) for receiving fuel from a fuel supply source (not shown). Furthermore, the shape of the fuel pipe 14 may be other than cylindrical, such as a rectangular tube. Also, the arrangement of the fuel pipe 14 may be other than those described above; for example, it does not have to be coaxial with at least one of the outer pipe 10 and the inner pipe 12.

[0014] The fuel here refers to fuel gas, and examples of fuels include hydrogen gas as the first fuel, or hydrocarbon gases as the second fuel. For example, the first and second fuels may be used selectively at the same time, and switched as appropriate when not in combustion. Alternatively, the first and second fuels may be used in mixture form, i.e., co-fired. Hydrocarbon gases include, for example, city gas, petroleum gas, propane gas, and methane gas. In the combustion of hydrogen gas, the flame temperature is higher than that of hydrocarbon gases, resulting in increased NOx emissions. In both the combustion of hydrogen gas and hydrocarbon gases, NOx emissions are suppressed by EGR. In hydrogen gas EGR, due to the good combustibility of hydrogen gas, combustion is maintained even if the flow rate of the circulating exhaust gas E2, i.e., the circulation volume, is high, and combustion is maintained even if the ratio of the circulation volume to the flow rate of air R, an example of combustion air, is high. In hydrocarbon gas EGR, due to the reduced combustibility compared to hydrogen gas, combustion cannot be properly maintained if the flow rate of the circulating exhaust gas E2 is the same as that of hydrogen gas. Furthermore, the second fuel is not limited to hydrocarbon gases; any fuel that can maintain proper combustion when its circulation rate is lower than that of the first fuel is acceptable. Also, the first fuel is not limited to hydrogen gas.

[0015] The burner nozzle 16 has a connecting portion 20, a tapered portion 22, and a combustion cylinder 24. The connecting portion 20 is a cylindrical part that extends vertically. The outer surface of the tip of the fuel pipe 14 is in contact with the inner surface of the connecting portion 20. The burner nozzle 16 is connected to the tip of the fuel pipe 14 at the connecting portion 20. The tapered portion 22 is located below the connecting portion 20. The tapered portion 22 widens downwards. The combustion cylinder 24 is located below the tapered section 22. The combustion cylinder 24 is a cylindrical section that extends vertically. The combustion cylinder 24 is open downwards and has an open space to the outside. The inner diameter of the combustion cylinder 24 is larger than the inner diameter of the connecting section 20. The combustion cylinder 24 is located inside the lower part of the inner tube 12. The burner nozzle 16 is arranged coaxially with the outer tube 10, the inner tube 12, and the fuel tube 14. Furthermore, the shape of the burner nozzle 16 is not limited to those described above. For example, the shape of at least one of the connecting portion 20 and the combustion tube 24 may be a square tube or other shape other than cylindrical. Also, the arrangement of the burner nozzle 16 may be other than those described above. For example, it does not have to be coaxial with at least one of the outer tube 10 and the fuel tube 14.

[0016] The first body 4 is provided on the upper surface of the base 9. The first body 4 includes a base portion 30, an outer wall portion 32, an inner wall portion 34, a connecting portion 35, an air introduction portion 36 as an example of a combustion air introduction portion, an exhaust gas outlet portion 38, and a circulation portion 40.

[0017] The base portion 30 is a plate-shaped member having a hole with a circular cross-section. The hole is located in the center of the base portion 30. The base portion 30 is attached to the upper surface of the base 9. Furthermore, the shape of the holes in the base portion 30 may be a rectangle or other shape besides a circle. Also, the arrangement of the holes in the base portion 30 may be other than in the center.

[0018] The outer wall portion 32 protrudes upward in a cylindrical shape from the base portion 30. Furthermore, the shape of the outer wall portion 32 may be other than cylindrical, such as a rectangular tube.

[0019] The inner wall portion 34 protrudes upward in a cylindrical shape from around the hole in the base portion 30. The inner wall portion 34 is positioned radially inward of the outer wall portion 32. Furthermore, the shape of the inner wall portion 34 may be other than cylindrical, such as a rectangular tube.

[0020] The connecting portion 35 is cylindrical in shape and extends in the left-right direction, extending from the right side of the inner wall portion 34 to the right. The right end of the connecting portion 35 is open on the right side of the outer surface of the outer wall portion 32. Furthermore, the shape of the connecting portion 35 may be other than cylindrical, such as a rectangular tube. Also, the arrangement of the connecting portion 35 may be other than those described above; for example, it may extend forward from the front of the inner wall portion 34.

[0021] The air inlet section 36 includes an air joint 50, an air flange 51, and a mixer section 52. The air joint 50 is a hexagonal cylindrical portion extending in the front-rear direction and protruding rearward from the rear of the outer wall portion 32. The inside of the air joint 50 is connected to the space between the outer wall portion 32 and the inner wall portion 34. An air supply source (not shown) that supplies air R is connected to the air joint 50 via an air flange 51. Air R is air. The air flange 51 is a cylindrical portion extending in the front-rear direction and is connected to the air joint 50. Note that the air joint 50 may have a shape other than a hexagonal cylinder, such as a cylinder, and the shape of the air flange 51 may have a shape other than a cylinder, such as a square tube. Also, the arrangement of at least one of the air joint 50 and the air flange 51 may be other than those described above; for example, it may protrude to the left from the left side of the outer wall portion 32. Air R may be something other than air. The mixer unit 52 is mainly located within the air joint 50 and includes an air nozzle 54 and a mixing pipe 56. The air nozzle 54 is a tapered portion that narrows in diameter from rear to front, and is located inside the air joint 50 and the air flange 51. The mixing pipe 56 is a cylindrical member having an inner diameter smaller than the inner diameter of the central part of the air joint 50. The mixing pipe 56 is located inside the air joint 50, in front of the air nozzle 54. The front end of the mixing pipe 56 has a gap with the rear end of the air nozzle 54 in the radial direction. The mixing pipe 56 may also have a gap in the front-rear direction instead of, or in both the radial and rear directions. The mixer section 52 increases the velocity of the air R introduced from the air flange 51 to the air joint 50. The mixer section 52 also receives the circulated exhaust gas E2. Downstream from the mixer section 52, the exhaust gas-mixed air RE flows. The mixer section 52 may also increase the velocity of the air R by means other than the air nozzle 54 and the mixing pipe 56. Furthermore, the exhaust gas E2 may be mixed with the air R at locations other than the mixer section 52.

[0022] The exhaust gas outlet section 38 includes an exhaust gas joint 57 and an exhaust gas flange 58. The exhaust gas joint 57 is cylindrical in shape and extends in the left-right direction, and is interposed between the connecting portion 35 and the exhaust gas flange 58. The exhaust gas flange 58 is cylindrical in shape and extends in the left-right direction, protruding to the right from the right side of the exhaust gas joint 57. The exhaust gas flange 58 is connected to the inside of the inner wall portion 34 via the exhaust gas joint 57 and the connecting portion 35. An exhaust pipe for exhaust gas E1 (not shown) is connected to the right end, or tip, of the exhaust gas flange 58. The exhaust gas outlet section 38 leads the exhaust gas E1 to the discharge pipe. The exhaust gas E1 is discharged through the discharge pipe. Furthermore, the shape of at least one of the exhaust gas joint 57 and the exhaust gas flange 58 may be other than cylindrical, such as a rectangular tube. Also, the arrangement of the connecting portion 35 may be other than those described above, for example, it may extend in the front-rear direction.

[0023] The circulation section 40 is connected to the exhaust gas joint 57 of the exhaust gas outlet section 38 and the air joint 50 of the air inlet section 36. Alternatively, the circulation section 40 may also be connected to the exhaust gas flange 58 of the exhaust gas outlet section 38 or the air flange 51 of the air inlet section 36. The circulation section 40 includes a first flow path section 60, a direction changing section 62, a second flow path section 64, and a flow rate adjusting body 66.

[0024] The first flow path section 60 extends rearward from the rear of the central part of the exhaust gas joint 57. The first flow path section 60 is connected to the flow path of exhaust gas E. The first flow path section 60 branches off from the exhaust gas joint 57. The direction changing section 62 is a "T"-shaped pipe member that opens on three sides. The front end of the direction changing section 62 is connected to the rear end of the first flow path section 60. The left central part of the direction changing section 62 is connected to the right end of the second flow path section 64. At its rear end, the direction changing section 62 has a mounting section 68 for the flow rate adjustment body 66. The mounting section 68 is a hole opened at the rear end of the direction changing section 62 that opens to the rear. The mounting section 68 has screw threads on its inner surface. The mounting section 68 is part of the direction changing section 62 and is integrated with the direction changing section 62. However, the mounting section 68 is not limited to the above; for example, it may be a hole opened to the right of the direction changing section 62 that opens to the right, or it may be attached by means other than screw threads. Furthermore, the mounting section 68 may be part of the first flow path section 60 or part of the second flow path section 64, or it may be an independent separate member. The second flow path section 64 extends to the left from the left side of the direction change section 62 and connects to the right side of the adjacent section of the air nozzle 54 and mixing pipe 56 in the mixer section 52 of the air introduction section 36. The direction of the second flow path section 64 intersects with the direction of the first flow path section 60. In the first embodiment, the first flow path section 60, the direction changing section 62, and the second flow path section 64 constitute the flow path section of the circulation section 40. Furthermore, at least two of the first flow channel section 60, the direction changing section 62, and the second flow channel section 64 may be integrated into a single unit.

[0025] Figure 3 is a cross-sectional view of the flow regulator 66 along line AA. Three types of flow regulators 66 are provided: flow regulator 66A, shown in Figure 3A as an example of a first flow regulator; flow regulator 66B, shown in Figure 3B as an example of a second flow regulator; and flow regulator 66C, shown in Figure 3C. The flow regulator 66 can be considered as a set of the three types of flow regulators 66A to 66C. Furthermore, the number of types of flow regulators 66 may be two or less, or four or more.

[0026] The flow rate regulator 66A has a head 70 and a threaded portion 72. The head 70 is a flat hexagonal prism and can be used with a wrench to rotate the flow control body 66A around a virtual central axis. The head 70 can be positioned behind the mounting portion 68 and can close the mounting portion 68. The threaded portion 72 extends forward from the front surface of the head 70. The threaded portion 72 is disc-shaped. The outer surface of the threaded portion 72 has a thread groove that fits into the thread groove of the mounting portion 68. The flow regulator 66A does not have any protruding parts. The flow rate regulator 66A can be considered as a cover for the mounting portion 68.

[0027] The flow rate regulator 66B has a head 70, a threaded portion 72, and a protruding portion 74B. The head 70 and threaded portion 72 of the flow rate regulator 66B are the same as those of the head 70 and threaded portion 72 of the flow rate regulator 66A. The projection 74B is rod-shaped and extends forward from the front surface of the threaded portion 72. The projection 74B is cylindrical. The projection 74B extends from the direction changing portion 62 into the first flow path portion 60. The front end, or tip, of the projection 74B is located on the side of the first flow path portion 60 that extends forward in the direction changing portion 62. The size of the projection 74B in the direction intersecting the extension direction, i.e., the diameter φB, is relatively small. The shape of the projection 74B is not limited to a cylindrical shape; it may also be prismatic, conical, or prismatic. Furthermore, the tip of the projection 74B may not reach the first flow path portion 60, but may be located within the forward-extending portion of the direction changing portion 62.

[0028] The flow rate regulator 66C, also shown in Figure 2, has a head 70 and threaded portion 72, as well as a protruding portion 74C, similar to the flow rate regulators 66A and 66B. The protrusion 74C is rod-shaped and, except for its thickness, is the same as that of the protrusion 74B. The diameter φC of the protrusion 74C is larger than the diameter φB of the protrusion 74B, and is approximately 1.4 times that of the protrusion 74B. However, the diameter φC of the protrusion 74C, i.e., its thickness, is not limited to approximately 1.4 times that of the diameter φB of the protrusion 74B; for example, it may be approximately 1.2 times, 1.5 times, or 2 times. Furthermore, the protrusion 74C may differ from the protrusion 74B in elements other than its thickness; for example, its length in the front-to-back direction may be longer than that of the protrusion 74B. Furthermore, the flow rate regulator 66A, which does not have a protruding portion, may be omitted. Also, at least one of the flow rate regulator 66 and the mounting portion 68 may be treated as belonging to other components rather than the circulation portion 40, or as an independent component.

[0029] In the circulation section 40, one of the three types of flow rate regulators 66A to 66C is attached to the mounting section 68. As shown in Figure 3A, when the flow rate regulator 66A is installed, the threaded portion 72 enters the threaded groove of the mounting portion 68 and, together with the head 70, closes the mounting portion 68. The portion extending before and after the direction changing portion 62 and the space inside the first flow path portion 60 are not narrowed because the flow rate regulator 66A has no protruding portion, and are maintained as they are. That is, the flow rate regulator 66A does not protrude into the space inside the direction changing portion 62 and the first flow path portion 60, and has a first gap between it and the direction changing portion 62 that corresponds to that space. As shown in Figure 3B, when the flow rate regulator 66B is installed, the threaded portion 72 enters the threaded groove of the mounting portion 68 and, together with the head 70, closes the mounting portion 68. In addition, the protruding portion 74B protrudes from the portions extending before and after the direction changing portion 62 and from the first flow path portion 60. The space inside the portions extending before and after the direction changing portion 62 and the first flow path portion 60 is narrowed by the protruding portion 74B. The flow rate regulator 66B protrudes from the space inside the direction changing portion 62 and the first flow path portion 60 with a second-first gap that is smaller than the first gap in the case of the flow rate regulator 66A. As shown in Figure 3C, when the flow rate regulator 66C is installed, the threaded portion 72 enters the threaded groove of the mounting portion 68 and, together with the head 70, closes the mounting portion 68. The protruding portion 74C also protrudes from the portion extending before and after the direction change portion 62 and from the first flow path portion 60. In particular, the space between the outer surface of the tip of the protruding portion 74C and the inner surface of the first flow path portion 60 is narrower than the space between the outer surface of the tip of the protruding portion 74B and the inner surface of the first flow path portion 60. The size between the outer surface of the protruding portion 74C and the inner surface of the direction change portion 62 and the first flow path portion is smaller than the size between the outer surface of the protruding portion 74B and the inner surface of the direction change portion 62 and the first flow path portion. The flow rate regulator 66C protrudes from the internal space of the direction change portion 62 and the first flow path portion 60 with a second-2 gap that is smaller than the first gap in the case of the flow rate regulator 66A. Gap 2-1 and Gap 2-2 are examples of the second gap. Gap 2-1 is larger than Gap 2-2. Note that the terms first gap and second gap are relative; for example, Gap 2-1 could be considered the first gap, and Gap 2-2 could be considered a second gap smaller than the first gap.

[0030] The second body 6 is a cap-shaped member, positioned above the first body 4, and covering the upper end of the first body 4. The lower central part of the second body 6 receives the upper end of the fuel pipe 14. Furthermore, the shape of the second body 6 does not have to be cap-shaped. Also, the second body 6 does not have to block the upper end of the first body 4, and the first body 4 itself may have a closed upper end.

[0031] The ignition unit 8 includes a spark plug 80 and a spark rod 82. Plug 80 is mounted on the upper central part of the second body 6. The spark rod 82 is connected to the lower end, or tip, of the plug 80 and extends vertically. The spark rod 82 passes through the fuel pipe 14 and reaches the burner nozzle 16. The lower end, or tip, of the spark rod 82 is located inside the burner nozzle 16. The virtual central axis of the spark rod 82 coincides with the virtual central axis of the fuel pipe 14. However, the virtual central axis of the spark rod 82 does not necessarily have to coincide with the virtual central axis of the fuel pipe 14. The plug 80 is connected to a power line (not shown) and can generate a spark with the burner nozzle 16 via the spark rod 82. The spark emitted from the tip of the spark rod 82 to the burner nozzle 16 can ignite the fuel passing through the fuel pipe 14. Burner 1 is a direct ignition type that can be ignited directly with a spark by the ignition unit 8.

[0032] An example of the operation of such burner 1 is described below. The user connects a fuel supply source to the fuel inlet of fuel pipe 14. Under normal circumstances, the user connects a hydrogen gas supply source to the fuel inlet, and connects a city gas supply source when hydrogen gas is not used as a backup. Combustion of hydrogen gas does not emit carbon monoxide or carbon dioxide compared to the combustion of hydrocarbon gases. Furthermore, if hydrogen gas becomes insufficient, the user can use city gas to avoid interrupting the reactor's operation. When using hydrogen gas, the user attaches the flow regulator 66A shown in Figure 3A to the mounting part 68. On the other hand, when using city gas, the user attaches the flow regulator 66B shown in Figure 3B to the mounting part 68. Furthermore, the user connects the air supply source to the air flange 51. Furthermore, the user connects the exhaust pipe to the tip of the exhaust gas outlet section 38.

[0033] Then, with fuel and air R supplied, the user ignites the fuel using the ignition unit 8. The fuel flows through the fuel pipe 14 and reaches the burner nozzle 16, where it burns in reaction with the exhaust gas mixture air RE, producing a flame F and exhaust gas E. Air R is accelerated by the air inlet 36 and mixed with exhaust gas E2 to become exhaust gas mixed air RE, which is introduced between the outer wall 32 and the inner wall 34 of the first body 4, flows between the inner pipe 12, the fuel pipe 14 and the burner nozzle 16, reaches the tip of the burner nozzle 16, is used for combustion and becomes exhaust gas E.

[0034] The exhaust gas E flows between the outer pipe 10 and the inner pipe 12, reaches the inner wall portion 34 of the first body 4, and goes from the connecting portion 35 to the exhaust gas joint 57. Furthermore, exhaust gas E1, which is part of exhaust gas E, is discharged through the exhaust gas outlet section 38 and the discharge pipe. On the other hand, exhaust gas E2, which is another part of exhaust gas E, is introduced into the circulation section 40 from the exhaust gas joint 57. Exhaust gas E2 is taken into the circulation section 40 in response to the negative pressure created by the flow of air R, which is accelerated in the mixer section 52 within the exhaust gas joint 57.

[0035] The exhaust gas E2 introduced into the circulation section 40 flows through the first flow path section 60 and approaches the direction change section 62. When the fuel is hydrogen gas and a flow regulator 66A is attached to the mounting section 68, the exhaust gas E2 passes between the relatively wide flow regulator 66A and the portion of the first flow path section 60 and the forward portion of the direction change section 62, passes through the direction change section 62, and flows through the second flow path section 64. When the fuel is city gas and a flow regulator 66B or flow regulator 66C is attached to the mounting section 68, the exhaust gas E2 passes between the relatively narrow flow regulator 66B or flow regulator 66C and the portion of the first flow path section 60 and the forward portion of the direction change section 62, passes through the direction change section 62, and flows through the second flow path section 64. When the fuel is city gas, the flow rate of exhaust gas E2 in the circulation section 40 is reduced compared to when the fuel is hydrogen gas, and the circulation rate is suppressed. The flow regulator 66B or flow regulator 66C is selected according to conditions such as the furnace temperature and city gas flow rate during city gas combustion. When the flow regulator 66B is installed, the distance between the first flow path section 60 and the forward portion of the direction change section 62 is wider compared to when the flow regulator 66C is installed, resulting in a relatively larger flow rate of exhaust gas E2. Furthermore, when the fuel is hydrogen gas, the flow rate of exhaust gas E2 may be adjusted by a flow regulator having a protruding portion. Also, a flow regulator 66 suitable for when the fuel is a mixture of hydrogen gas and city gas may be provided and used.

[0036] The exhaust gas E2 flowing through the second flow path 64 reaches the air introduction section 36 and is mixed with the introduced air R. The exhaust gas E2 flows towards the space between the air nozzle 54 and the mixing pipe 56 in the mixer section 52, and is smoothly mixed with air R in the mixer section 52.

[0037] In the first form of burner 1 described above, combustion is performed by switching between hydrogen gas and hydrocarbon gas. Burner 1 includes an air inlet 36 for introducing air R, and a circulation unit 40 for circulating exhaust gas E2, which is a part of the exhaust gas E from the combustion of hydrogen gas or hydrocarbon gas, back to the air inlet 36. The circulation unit 40 has a flow path through which the exhaust gas E2 flows, and a flow rate regulator 66 attached to the flow path. Compared to hydrocarbon gas, hydrogen gas can maintain combustion even if the circulation amount, which is the flow rate of the circulating exhaust gas E2, is large. When hydrogen gas is combusted, the flow rate regulator 66A does not protrude from the flow path and has a first gap between it and the flow path. When hydrocarbon gas is combusted, the protruding parts 74B and 74C of the flow rate regulators 66B and 66C protrude in a rod shape with a second gap smaller than the first gap relative to the flow path. Therefore, a burner 1 is provided that can be adjusted to perform more appropriate EGR depending on the type of fuel.

[0038] Furthermore, the flow regulator 66 includes flow regulators 66A to 66C. Flow regulator 66A does not have a protrusion that extends outward from the flow path, while flow regulators 66B and 66C have rod-shaped protrusions 74B and 74C. When hydrogen gas is combusted, flow regulator 66A is provided. When hydrocarbon gases are combusted, flow regulators 66B and 66C are provided instead of flow regulator 66A. Therefore, adjustments to switch between fuel types can be easily made by replacing the rod-shaped flow regulators 66A to 66C.

[0039] Furthermore, the flow path section includes a first flow path section 60, a second flow path section 64 in a direction intersecting the direction of the first flow path section 60, and a direction changing section 62 connected to the first flow path section 60 and the second flow path section 64. The direction changing section 62 is provided with a mounting section 68 for attaching flow rate regulators 66A to 66C. One of the flow rate regulators 66A to 66C is attached to the mounting section 68. Therefore, the replacement and installation structure for the rod-shaped flow control elements 66A to 66C, which allow for easy switching of fuel types, is made simpler.

[0040] Furthermore, the air inlet section 36 has a mixer section 52 that accelerates the air R. Therefore, the introduction of exhaust gas E2 is made smoother. Also, when combined with the flow rate regulator 66, the burner 1 can be made more compact.

[0041] Furthermore, the above-mentioned first form and its modifications may have the following modifications as appropriate. Multiple burners 1 may be installed in a single furnace. In this case, the configurations of at least two of the burners 1 may differ from each other. The use of burner 1 and the furnace is not particularly limited and can be used, for example, for ceramics or drying.

[0042] [Second form] Figure 4 is a central longitudinal cross-sectional view of the burner 101 according to the second embodiment. Figure 5 is a top view of Figure 4. Figure 6 is a front view of the burner nozzle 116 in the burner 101 of the second embodiment. The second form of burner 101 is the same as the first form of burner 1, except for the burner nozzle, air inlet, exhaust gas outlet, and circulation section. In burner 101, the same components and parts as in burner 1 are given the same reference numerals, and explanations are omitted as appropriate.

[0043] The connecting section 135 of the burner 101 is located on the left side of the first body 4. The air inlet 136 of the burner 101 has an air joint 150, an air flange 151, and a mixer section 52, and extends from the left side of the first body 4 to the left. The exhaust gas outlet 138 of the burner 101 is located above the air inlet 136 and extends to the left from the connecting section 135. The exhaust gas joint 157 has a mounting section 168 at its upper part. The mounting section 168 is part of the exhaust gas joint 157 and is integrated with the exhaust gas joint 157. The mounting section 168 may also be part of the exhaust gas flange 158 or it may be a separate, independent component. The exhaust gas flange 158 of the burner 101 extends to the left and upward from the left end of the exhaust gas joint 157.

[0044] The circulation section 140 of the burner 101 includes a flow path section 160 and a flow rate adjustment body 166. The flow path section 160 extends vertically, from the lower part of the exhaust gas joint 157 to the upper part of the air joint 150 of the air introduction section 136. As in the first embodiment, three types of flow regulators 166 are provided. The lower end, i.e., the tip, of the rod-shaped projection 174 of the flow regulator 166 enters the upper end of the flow path section 160. The base end and the central part of the projection 174 of the flow regulator 166 traverse the exhaust gas joint 157. The flow regulator 166 is attached to a mounting section 168 located at the top of the exhaust gas joint 157. Furthermore, the number of types of flow regulators 166 may be two or less, or four or more.

[0045] In the burner 101, exhaust gas E is divided into exhaust gas E1 and E2 within the exhaust gas joint 157 from the connecting section 135. Exhaust gas E1 is discharged through the exhaust flange 158 and the exhaust pipe. On the other hand, exhaust gas E2 is introduced into the circulation section 140 from the exhaust gas joint 157.

[0046] When the exhaust gas E2 introduced into the circulation section 140 enters the flow path section 160, it flows between the inner surface of the flow path section 160 and the outer surface of the protrusion 174 of the flow rate adjustment body 166. When the fuel is hydrogen gas and a flow regulator 166 without a protrusion is attached to the mounting portion 168, the exhaust gas E2 passes through the relatively wide gap between the flow regulator 166 and the flow path portion 160, i.e., the first gap, and flows within the flow path portion 160. When the fuel is city gas and a flow regulator 166 with a protruding portion is attached to the mounting portion 168 as shown in Figure 4, the exhaust gas E2 passes through the relatively narrow gap between the flow regulator 166 and the flow path portion 160, i.e., the second gap, and flows within the flow path portion 160. When the fuel is city gas, the flow rate of exhaust gas E2 in the circulation portion 140 is reduced compared to when the fuel is hydrogen gas, and the circulation rate is suppressed.

[0047] The exhaust gas E2 flowing through the flow path 160 reaches the air joint 150 of the air inlet 136, where it is mixed with the introduced air R. The exhaust gas E2 flows between the air nozzle 54 and the mixing pipe 56 in the mixer section 52 within the air joint 150, and is smoothly mixed with air R in the mixer section 52.

[0048] Furthermore, the burner nozzle 116 of burner 101 is identical to the burner nozzle 16 of burner 1, except for its length in the vertical direction. The burner nozzle 116 has a connecting portion 20, a tapered portion 22, and a combustion cylinder 124. The vertical length L2 of the combustion cylinder 124 is longer than the vertical length of the combustion cylinder 24. Therefore, the vertical length L1 of the burner nozzle 116 is longer than the vertical length of the burner nozzle 16. If the length L2 of the combustion chamber 124 is greater than or equal to a predetermined lower limit, noise during combustion is suppressed. The vertical length L2 of the combustion chamber 124 can also be considered as the length L2 of the fuel pipe 14 in the extending direction.

[0049] The following describes an example of the relationship between the length L2 of the combustion cylinder 124 and the noise level. Figure 7 is a schematic diagram showing the noise measurement location M. As shown in Figure 7, the noise measurement position M was set at a point L4 = 1000 mm away from the upper end, i.e., the tip, of the flue S, which has a vertical length L3 = 200 mm (millimeters) as a discharge pipe. Then, for burner examples 1-1 to 1-8 of various sizes shown in Table 1, the noise during combustion (dB, A-weighted) at noise measurement position M was measured.

[0050] [Table 1]

[0051] Specifically, in Study Example 1-1, a device was measured with an outer tube size 10, i.e., radiant tube size of 125A, a combustion capacity of 31kW (kilowatts), an inner diameter of the combustion chamber 124, i.e., an inner diameter of 63mm, and a length L2 of the combustion chamber 124 of 36mm. Furthermore, as example 1-2, a system was measured with a radiant tube size of 125A, a combustion capacity of 31kW, an inner diameter of the combustion chamber 124 of 63mm, and a length L2 of the combustion chamber 124 of 23mm. Furthermore, as example 1-3, a system with a radiant tube size of 125A, a combustion capacity of 31kW, and without a burner nozzle 116 was measured. Furthermore, as example 1-4, a system was measured with a radiant tube size of 125A, a combustion capacity of 31kW, an inner diameter of the combustion chamber 124 of 63mm, and a length L2 of the combustion chamber 124 of 86mm.

[0052] Furthermore, as example 1-5, a system was measured with a radiant tube size of 100A, a combustion capacity of 23kW, an inner diameter of 52mm for the combustion chamber 124, and a length L2 of 31mm for the combustion chamber 124. Furthermore, as example 1-6, a device was measured with a radiant tube size of 100A, a combustion capacity of 23kW, an inner diameter of 52mm for the combustion chamber 124, and a length L2 of 81mm for the combustion chamber 124. Furthermore, as example 1-7, a system was measured with a radiant tube size of 80A, a combustion capacity of 15kW, an inner diameter of 41mm for the combustion chamber 124, and a length L2 of 30mm for the combustion chamber 124. Furthermore, as example 1-8, a device was measured with a radiant tube size of 80A, a combustion capacity of 15kW, an inner diameter of 41mm for the combustion chamber 124, and a length L2 of 80mm for the combustion chamber 124.

[0053] Furthermore, in all the measurements of the examples considered, the surface load was 3.7 W / cm². 2 The power consumption was set to watts per square centimeter. The air-fuel ratio was set to 1.2. Furthermore, the fuel was set to city gas. The furnace temperature was set to between 800°C and 1000°C. The background noise level was 71 dBA.

[0054] The noise level in Case Study 1-1 was 99 dB, which was above 85 dB. The noise level in case 1-2 was 98 dB, which was above 85 dB. The noise level in case study 1-3 was 89 dB, which exceeded 85 dB. The noise level in Examples 1-4 was 72 dB. The noise level in case 1-5 was 98 dB, which exceeded 85 dB. The noise level in the case studies 1-6 was 70 dB. The noise level in case 1-7 was 96 dB, which was above 85 dB. The noise level in Example 1-8 was 72 dB. Examples 1-4, 1-6, and 1-8 were those in which the noise level was suppressed to 85 dB or less, and the length L2 of the combustion cylinder 124 was 80 mm or more.

[0055] Furthermore, the noise levels of burners of various sizes, as shown in Table 2 (Examples 2-1 to 2-6), were measured. In the examples 2-1 to 2-6, the radiant tube size was 80A in all cases, the combustion capacity was 15kW, and the inner diameter of the combustion chamber 124 was 41mm.

[0056] [Table 2]

[0057] In Study Example 2-1, the length L2 of the combustion cylinder 124 was 30 mm, and the noise level was 82 dB. The size of Study Example 2-1 is the same as that of Study Example 1-7, but the 96 dB noise level in Study Example 1-7 is due to the flame F entering the burner nozzle 116, which increased the noise level. In all other studies, the flame F did not enter the burner nozzle 116. In Example 2-2, the length L2 of the combustion chamber 124 was 40 mm, and the noise level was 76 dB. In example 2-3, the length L2 of the combustion chamber 124 was 50 mm, and the noise level was 73 dB. In Study Example 2-4, the length L2 of the combustion chamber 124 was 60 mm, and the noise level was 72 dB. In Example 2-5, the length L2 of the combustion chamber 124 was 70 mm, and the noise level was 72 dB. In Study Example 2-6, the length L2 of the combustion chamber 124 was 80 mm, and the noise level was 72 dB. The size of Study Example 2-6 was the same as the size of Study Example 1-8. In the 15kW combustion capacity study examples 2-1 to 2-6, the only examples where noise was suppressed to less than 82dB were study examples 2-2 to 2-6, where the length L2 of the combustion cylinder 124 was 40mm or more.

[0058] Furthermore, the noise levels of burners of various sizes, as shown in Table 3, were measured for examples 3-1 to 3-6. In the examples 3-1 to 3-6, the radiant tube size was 100A in all cases, the combustion capacity was 23kW, and the inner diameter of the combustion chamber 124 was 52mm.

[0059] [Table 3]

[0060] In Study Example 3-1, the length L2 of the combustion chamber 124 was 31 mm, and the noise level was 86 dB. The size of Study Example 3-1 was the same as the size of Study Example 1-5. In Study Example 3-2, the length L2 of the combustion chamber 124 was 41 mm, and the noise level was 82 dB. In Example 3-3, the length L2 of the combustion chamber 124 was 51 mm, and the noise level was 77 dB. In example 3-4, the length L2 of the combustion chamber 124 was 61 mm, and the noise level was 76 dB. In example 3-5, the length L2 of the combustion chamber 124 was 71 mm, and the noise level was 74 dB. In Study Example 3-6, the length L2 of the combustion chamber 124 was 81 mm, and the noise level was 73 dB. The size of Study Example 3-6 was the same as that of Study Example 1-6. In the studies 3-1 to 3-6 with a combustion capacity of 23kW, the only ones where noise was suppressed to 82dB or less were studies 3-2 to 3-6, where the length L2 of the combustion cylinder 124 was 41mm or more.

[0061] Furthermore, the noise levels of burner studies for various sizes, as shown in Table 4 (Examples 4-1 to 4-6), were measured. In the examples 4-1 to 4-6, the radiant tube size was 125A in all cases, the combustion capacity was 31kW, and the inner diameter of the combustion chamber 124 was 63mm.

[0062] [Table 4]

[0063] In Study Example 4-1, the length L2 of the combustion chamber 124 was 36 mm, and the noise level was 84 dB. The size of Study Example 4-1 was the same as the size of Study Example 1-5. In example 4-2, the length L2 of the combustion chamber 124 was 46 mm, and the noise level was 78 dB. In example 4-3, the length L2 of the combustion chamber 124 was 56 mm, and the noise level was 76 dB. In example 4-4, the length L2 of the combustion chamber 124 was 66 mm, and the noise level was 74 dB. In example 4-5, the length L2 of the combustion chamber 124 was 76 mm, and the noise level was 73 dB. In Study Example 4-6, the length L2 of the combustion chamber 124 was 86 mm, and the noise level was 73 dB. The size of Study Example 4-6 was the same as the size of Study Example 1-4. In the 4-1 to 4-6 studies with a combustion capacity of 31 kW, the only ones where noise was suppressed to less than 84 dB were the 4-2 to 4-6 studies, where the length L2 of the combustion cylinder 124 was 46 mm or more.

[0064] Figure 8 is a graph showing the relationship between the length L2 (mm) of the combustion cylinder 124 and the noise level (dB) in Tables 2 to 4, i.e., study examples 2-1 to 4-6. As shown in Figure 8, from the viewpoint of suppressing noise during combustion, preferably the length L2 of the combustion cylinder 124 is 40 mm or more, more preferably the length L2 of the combustion cylinder 124 is 45 mm or more, and even more preferably the length L2 of the combustion cylinder 124 is 50 mm or more. From the viewpoint of noise suppression, there is no upper limit to the length L2 of the combustion cylinder 124, but if the length L2 of the combustion cylinder 124 is too long, the base end portion of the combustion cylinder 124, which is an unnecessary part for combustion, becomes long, so the upper limit of the length L2 of the combustion cylinder 124 is, for example, 150 mm, or 120 mm, 100 mm, 90 mm, or 80 mm. The noise suppression effect achieved by having the length L2 of the combustion cylinder 124 be above a predetermined lower limit can be achieved even when the flow rate of exhaust gas E2 is not adjusted by the flow rate regulator 66, and even when EGR is not performed.

[0065] In the second form of the burner 101 described above, combustion is performed by switching between hydrogen gas and hydrocarbon gas. The burner 101 includes an air inlet 136 for introducing air R, and a circulation unit 140 for circulating exhaust gas E2, which is part of the exhaust gas E from the combustion of hydrogen gas or hydrocarbon gas, back to the air inlet 136. The circulation unit 140 has a flow path 160 through which the exhaust gas E2 flows, and a flow rate regulator 166 attached to the flow path 160. When hydrogen gas is combusted, the flow rate regulator 166 does not protrude from the flow path 160 and has a first gap between itself and the flow path 160. When hydrocarbon gas is combusted, the flow rate regulator 166 protrudes in a rod shape from the flow path 160, having a second gap smaller than the first gap. Therefore, a burner 101 is provided that can be adjusted to perform more appropriate EGR depending on the type of fuel.

[0066] Furthermore, the flow path section 160 extends between the exhaust gas outlet section 138, which discharges the exhaust gas E1, and the air inlet section 136. An attachment section 168 for attaching the flow rate regulator 166 is provided on the exhaust gas joint 157 of the exhaust gas outlet section 138. The flow rate regulator 166 is attached to the attachment section 168. Therefore, the replacement and installation structure for the flow control unit 166, which allows for easy switching of fuel types, is configured more simply.

[0067] Furthermore, the burner 101 includes a fuel pipe 14 through which hydrogen gas or hydrocarbon gas passes, and a burner nozzle 116 connected to the end of the fuel pipe 14. The burner nozzle 116 has an open combustion chamber 124. The length L2 of the combustion chamber 124 in the direction of the fuel pipe 14 is 40 mm or more. Therefore, a burner 101 is provided in which noise during combustion is suppressed.

[0068] Furthermore, the second form described above may have the same modifications as the first form, as appropriate. Furthermore, parts or all of the first form may be combined with parts or all of the second form.

[0069] [Third form] Figure 9 is a central longitudinal cross-sectional view of the burner 201 according to the third embodiment. Figure 10 is a partial cross-sectional view of Figure 9 along line BB. The third form of burner 201 is similar to the first form of burner 1, except for the burner nozzle, exhaust gas outlet, and circulation section. In burner 201, the same components and parts as in burner 1 are given the same reference numerals, and their descriptions are omitted as appropriate.

[0070] The connecting section 235 of the burner 201 is located on the left side of the first body 4. The exhaust gas joint 257 of the exhaust gas outlet section 138 in the burner 201 extends to the left from the connecting section 235. The exhaust flange 258 of burner 201 extends to the left and upward from the left end of the exhaust joint 257.

[0071] The circulation section 240 of the burner 201 includes a first flow path section 260, a direction changing section 262, a second flow path section 264, and a flow rate adjusting body 266.

[0072] The first flow path section 260 extends from the rear of the central part of the exhaust gas joint 257 toward the rear. The first flow path section 260 is connected to the flow path of exhaust gas E. The first flow path section 260 branches off from the exhaust gas joint 257. The direction changing section 262 is an "L"-shaped tubular member that opens on two sides. The front end of the direction changing section 262 is connected to the rear end of the first flow path section 260. The right side of the direction changing section 262 is connected to the left end of the second flow path section 264. At its rear end, the direction changing section 262 has a mounting portion 268 for the flow rate adjuster 266. The mounting portion 268 is cylindrical and extends to the left and right, and is attached to a hole that opens to the left, which is opened on the left side of the direction changing section 262. Note that the mounting portion 268 for the flow rate adjuster 266 is not limited to the above, and may be, for example, a hole that opens to the rear and is integrated with the direction changing section 262, which is opened on the rear side of the direction changing section 262. The second flow path section 264 extends to the right from the right side of the direction changing section 262 and connects to the right side of the adjacent air nozzle 54 and mixing pipe 56 in the mixer section 52 of the air introduction section 36. The direction of the second flow path section 264 intersects with the direction of the first flow path section 260. In the third embodiment, the first flow channel section 260, the direction changing section 262, and the second flow channel section 264 constitute the flow channel section of the circulation section 240.

[0073] The flow rate regulator 266 has a head portion 270, a shaft portion 272, and a bulging portion 274. The flow rate regulator 266 is movable between a first position and a second position to the right of the first position, as shown in Figure 10. The flow rate regulator 266 can be fixed in the first and second positions. In the first position, the flow rate regulator 266 is retracted relative to the second flow path section 264. In the second position, the flow rate regulator 266 is advanced relative to the second flow path section 264. The flow rate regulator 266 is movable forward and backward relative to the second flow path section 264. The flow rate regulator 266 may also be fixed in positions other than the first and second positions. Furthermore, the flow rate regulator 266 may be provided so as to be able to advance relative to the first flow path section 260. The head portion 270 is disc-shaped. The head portion 270 is positioned behind the mounting portion 268. The shaft portion 272 extends to the right from the right side of the head portion 270. The shaft portion 272 passes through the inside of the inner bore of the mounting portion 268 and through the inside of the hole opened in the direction changing portion 262. The shaft portion 272 is in contact with the inner surface of the inner bore of the mounting portion 268. In the first and second positions, the shaft portion 272 is fixed by static friction with the inner surface of the mounting portion 268. The bulge 274 extends to the right from the right end of the shaft portion 272 and bulges outward in the circumferential direction relative to the shaft portion 272. The right end, i.e., the tip, of the bulge 274 is tapered so that the diameter decreases towards the right. In the first position, the bulge 274 extends into the left part of the direction changing portion 262, and in the second position, it is located adjacent to the left end of the second flow channel portion 264 within the direction changing portion 262. In the first position, the tip of the bulge 274 is located to the left of the left end adjacent to the second flow channel portion 264, and in the second position, it is located adjacent to the left end of the second flow channel portion 264. The diameter at the base end of the bulge 274 is slightly smaller than the inner diameter of the second flow channel portion 264. Note that the shape of the bulge 274 is not limited to the above, and for example, it may have no taper. Furthermore, the tip of the bulging portion 274 may reach the second flow channel portion 264 even at the second position. In the third embodiment, the right portion of the shaft portion 272 and the bulging portion 274 constitute rod-shaped projections that protrude into the direction changing portion 262 and the second flow path portion 264 of the flow rate adjustment body 66.

[0074] In the burner 201, exhaust gas E is divided into exhaust gas E1 and E2 at the exhaust gas joint 257 of the exhaust gas outlet section 238 from the connecting section 235. Exhaust gas E1 is discharged through the exhaust flange 258 and the exhaust pipe. On the other hand, exhaust gas E2 is introduced into the circulation section 240 from the exhaust gas joint 257.

[0075] As the exhaust gas E2 introduced into the circulation section 240 passes through the direction change section 262 and enters the second flow path section 264, it flows between the inner surface of the direction change section 262 and the inner surface of the second flow path section 264 and the outer surface of the bulge section 274 of the flow rate adjustment body 266. When the fuel is hydrogen gas and the flow rate adjuster 266 is moved back relative to the second flow path section 264 to the first position by operating the head section 270, the exhaust gas E2 flows through the space between the relatively wide bulge section 274, the inner surface of the direction change section 262 and the inner surface of the second flow path section 264, i.e., the first gap, and flows within the second flow path section 264. When the fuel is city gas, and the flow rate adjuster 266 is moved to the second position relative to the second flow path section 264 by operating the head section 270 as shown in Figure 10, the exhaust gas E2 flows through the second gap between the relatively narrow bulge section 274, the inner surface of the direction change section 262, and the inner surface of the second flow path section 264, i.e., the second gap. When the fuel is city gas, the flow rate of exhaust gas E2 in the circulation section 240 is reduced, and the circulation rate is suppressed, compared to when the fuel is hydrogen gas. Furthermore, the circulation section 240 is not limited to the above-described configuration. For example, the configuration may be set such that the distance between the direction changing section 262 or the second flow path section 264 and the flow changing section 266 increases when the flow rate adjusting body 266 advances, and decreases when the flow rate adjusting body 266 retracts. A specific example of such a configuration is as follows: The inner surface of the direction changing section 262 has a small-diameter section on the flow rate adjusting body 266 side with a relatively small inner diameter, a large-diameter section on the second flow path section 264 side with a relatively large inner diameter, and a stepped surface section at the boundary between the small-diameter section and the large-diameter section. The shaft section 272 passes through the small-diameter section. The bulging section 274 is located in the large-diameter section. The distance between the bulging section 274 and the stepped surface section increases when the bulging section 274 advances toward the second flow path section 264. As the bulging portion 274 retracts relative to the second flow channel portion 264, the gap between the bulging portion 274 and the stepped surface portion becomes smaller.

[0076] The exhaust gas E2 flowing through the second flow path section 264 reaches the air joint 50 of the air introduction section 36, where it is mixed with the introduced air R. The exhaust gas E2 flows between the air nozzle 54 and the mixing pipe 56 in the mixer section 52 within the air joint 50, and is smoothly mixed with air R in the mixer section 52.

[0077] Furthermore, the combustion cylinder 124 of the burner nozzle 116 of the burner 201 is the same as in the second form, and since it is longer than the combustion cylinder 24 of the first form, noise is further suppressed.

[0078] In the third form of the burner 201 described above, combustion is performed by switching between hydrogen gas and hydrocarbon gas. The burner 201 includes an air inlet 36 for introducing air R, and a circulation unit 240 for circulating exhaust gas E2, which is part of the exhaust gas E from the combustion of hydrogen gas or hydrocarbon gas, back to the air inlet 36. The circulation unit 240 has a flow path through which the exhaust gas E2 flows, and a flow rate regulator 266 attached to the flow path. When hydrogen gas is combusted, the flow rate regulator 266 protrudes in a rod shape with a first gap relative to the flow path. When hydrocarbon gas is combusted, the flow rate regulator 266 protrudes in a rod shape with a second gap smaller than the first gap relative to the flow path. Therefore, a burner 201 is provided that can be adjusted to perform more appropriate EGR depending on the type of fuel.

[0079] Furthermore, the flow rate regulating body 266 is equipped with a rod-shaped shaft portion 272 and a bulging portion 274. The shaft portion 272 and the bulging portion 274 are movable back and forth relative to the flow path portion. The first gap and the second gap are switched according to the movement of the shaft portion 272 and the bulging portion 274. Furthermore, when the shaft portion 272 and the bulging portion 274 retract relative to the flow path portion, the system switches to a first gap, and when the shaft portion 272 and the bulging portion 274 advance relative to the flow path portion, the system switches to a second gap. Furthermore, the flow path section includes a first flow path section 260, a second flow path section 264 in a direction intersecting the direction of the first flow path section 260, and a direction changing section 262 connected to the first flow path section 260 and the second flow path section 264. The direction changing section 262 is provided with a mounting section 268 for attaching a flow rate adjuster 266 that can move back and forth relative to the second flow path section 264. Therefore, the movable mounting structure of the flow control unit 266, which allows for easy switching of fuel types, is configured more simply.

[0080] Furthermore, the third form described above may appropriately include at least one of the same modifications as the first form and the same modifications as the second form. Furthermore, at least two of the first form (in whole or in part), the second form (in whole or in part), and the third form (in whole or in part) may be combined as appropriate.

[0081] [Fourth form] Figure 11 is a central longitudinal cross-sectional view of the burner 301 according to the fourth embodiment. Figure 12 is a top view of Figure 11. The fourth form of the burner 301 is similar to the second form of the burner 101, except for the exhaust gas outlet and the circulation section. In the burner 301, the same components and parts as those in the burner 101 are given the same reference numerals, and their descriptions are omitted as appropriate.

[0082] The exhaust gas joint 357 of the exhaust gas outlet 338 in the burner 301 is provided at its upper part with a mounting portion 368 for the flow rate adjuster 366. The mounting portion 368 is the same as the mounting portion 268 of the third embodiment, except for its orientation. The mounting portion 368 is cylindrical and extends in the vertical direction. The exhaust gas flange 358 of the burner 301 extends to the left and upward from the left end of the exhaust gas joint 357.

[0083] The circulation section 340 of the burner 301 includes a flow path section 160 and a flow rate regulator 366. The flow path section 160 extends vertically, from the lower part of the exhaust gas joint 357 to the upper part of the air joint 150 of the air inlet section 136. The flow rate regulator 366 is attached to a mounting portion 368 provided on the upper part of the exhaust gas joint 357, similar to the second embodiment except for its orientation. The flow rate regulator 366 has a head portion 370, a shaft portion 372, and a bulging portion 374.

[0084] The flow rate regulator 366 is movable between a first position and a second position lower than the first position shown in Figure 11. The flow rate regulator 366 can be fixed in the first and second positions. The flow rate regulator 366 may also be fixed in positions other than the first and second positions. The head portion 370 is disc-shaped. The head portion 370 is positioned above the mounting portion 368. The shaft portion 372 extends downward from the lower surface of the head portion 370. The shaft portion 372 passes through the inside of the inner bore of the mounting portion 368 and the inside of the hole opened in the exhaust gas joint 357. The shaft portion 372 is in contact with the inner surface of the inner bore of the mounting portion 368. In the first and second positions, the shaft portion 372 is fixed by static friction with the inner surface of the mounting portion 368. The bulge 374 extends downward from the lower end of the shaft 372 and bulges outward in the circumferential direction relative to the shaft 372. The lower end, or tip, of the bulge 374 is tapered, with the diameter decreasing towards the bottom. At the first position, the lower end of the bulge 374 is located above the flow channel 160, and at the second position, it is located within the flow channel 160. At the first position, the tip of the bulge 374 is located above the upper end of the flow channel 160, and at the second position, it is located below the upper end of the flow channel 160. The diameter at the tip of the bulge 374 is slightly smaller than the inner diameter of the flow channel 160. Note that the shape of the bulge 374 is not limited to the above; for example, it may have no taper. Also, the tip of the bulge 374 does not need to reach the second flow channel 264 even at the second position. In the fourth embodiment, the lower part of the shaft portion 372 and the bulging portion 374 constitute a rod-shaped projection that protrudes from the flow path portion 160 of the flow rate adjustment body 366.

[0085] In the burner 301, exhaust gas E is split into exhaust gas E1 and E2 at the exhaust gas joint 357 of the exhaust gas outlet 338 from the connecting section 135. Exhaust gas E1 is discharged through the exhaust flange 358 and the exhaust pipe. On the other hand, exhaust gas E2 is introduced into the circulation section 340 from the exhaust gas joint 357.

[0086] When the exhaust gas E2 introduced into the circulation section 340 enters the flow path section 160, it flows between the inner surface of the upper end of the flow path section 160 and the outer surface of the bulge section 274 of the flow rate adjustment body 266. When the fuel is hydrogen gas and the flow rate regulator 266 is set to the first position by operating the head unit 370, the exhaust gas E2 flows through the space between the relatively wide bulge 374 and the inner surface of the flow path 160, i.e., the first gap, and flows within the flow path 160. When the fuel is city gas and the flow rate regulator 266 is set to the second position by operating the head unit 370 as shown in Figure 11, the exhaust gas E2 flows through the second gap between the relatively narrow bulge 374 and the inner surface of the upper end of the flow path 160, i.e., the second gap. When the fuel is city gas, the flow rate of exhaust gas E2 in the circulation unit 340 is reduced and the circulation rate is suppressed compared to when the fuel is hydrogen gas.

[0087] The exhaust gas E2 flowing through the flow path 160 reaches the air joint 150 of the air inlet 136, where it is mixed with the introduced air R. The exhaust gas E2 flows between the air nozzle 54 and the mixing pipe 56 in the mixer section 52 within the air joint 150, and is smoothly mixed with air R in the mixer section 52.

[0088] Furthermore, the combustion cylinder 124 of the burner nozzle 116 of the burner 301 is the same as in the second and third forms, and is longer than the combustion cylinder 24 of the first form, thus further suppressing noise.

[0089] In the fourth form of the burner 301 described above, combustion is performed by switching between hydrogen gas and hydrocarbon gas. The burner 301 includes an air inlet 136 for introducing air R, and a circulation unit 340 for circulating exhaust gas E2, which is part of the exhaust gas E from the combustion of hydrogen gas or hydrocarbon gas, back to the air inlet 136. The circulation unit 340 has a flow path 160 through which the exhaust gas E2 flows, and a flow rate regulator 366 attached to the flow path 160. When hydrogen gas is combusted, the flow rate regulator 366 protrudes in a rod shape with a first gap relative to the flow path 160. When hydrocarbon gas is combusted, the flow rate regulator 366 protrudes in a rod shape with a second gap smaller than the first gap relative to the flow path 160. Therefore, a burner 201 is provided that can be adjusted to perform more appropriate EGR depending on the type of fuel.

[0090] Furthermore, the flow rate regulator 366 is equipped with a rod-shaped shaft portion 372 and a bulging portion 374. The shaft portion 372 and the bulging portion 374 are movable forward and backward relative to the flow path portion 160. The first gap and the second gap are switched according to the forward and backward movement of the shaft portion 372 and the bulging portion 374. Furthermore, when the shaft portion 372 and the bulging portion 374 retract relative to the flow channel portion 160, the first gap is activated, and when the shaft portion 372 and the bulging portion 374 advance relative to the flow channel portion 160, the second gap is activated. Furthermore, the flow path section 160 extends between the exhaust gas outlet section 338, which discharges exhaust gas E1, and the air introduction section 136. The exhaust gas joint 357 of the exhaust gas outlet section 338 is provided with an attachment section 368 for attaching a flow rate adjuster 366 that can move back and forth relative to the flow path section 160. Therefore, the movable mounting structure of the flow control unit 366, which allows for easy switching of fuel types, is configured more simply.

[0091] Furthermore, the fourth form described above may appropriately include at least one of the following modifications: the same modifications as the first form, the same modifications as the second form, and the same modifications as the third form. Furthermore, at least two of the following may be combined as appropriate: part or all of the first form, part or all of the second form, part or all of the third form, and part or all of the fourth form.

[0092] [Fifth form] Figure 13 is a central longitudinal cross-sectional view of a four-way valve device 403 used in a burner according to the fifth embodiment. In the fifth form, two burners are used. The two burners are regenerative burners that alternately heat by exchanging the presence or absence of combustion and the intake and exhaust. The two burners may be the same or different. The two burners may also be other types of burners.

[0093] The four-way valve device 403 is an improved version of the one described in the fourth embodiment of Japanese Patent Publication No. 6620192, with the addition of a mixer unit 52, a flow rate regulator 466, and its mounting portion 468. The four-way valve device 403 includes an intake connection section 405, an intake extension section 406, a first intake passage 410, a second intake passage 412, an air flow rate adjustment valve mechanism 413, a first connecting passage 414, a second connecting passage 416, a first exhaust passage 420, a second exhaust passage 422, an exhaust connection section 425, an exhaust extension section 426, a flow path section 427, a first valve 430, a second valve 432, a first cylinder 434 as an example of a first valve moving means, and a second cylinder 436 as an example of a second valve moving means.

[0094] The intake connection section 405 is ring-shaped, connected to an air supply source, and receives air R. The intake extension section 406 is tubular and interposed between the intake connection section 405 and the first intake passage 410. The mixer section 52 is located within the intake extension section 406. The mixer section 52 may also be located in an intake passage other than the intake extension section 406. The first intake passage 410 is adjacent to the intake extension 406. The first intake passage 410 is located to the left of the intake extension 406. The second intake passage 412 is adjacent to the first intake passage 410. The second intake passage 412 is located to the left of the first intake passage 410.

[0095] The first connecting passage 414 is adjacent to the first intake passage 410. The first connecting passage 414 is located below the first intake passage 410. The second connecting passage 416 is adjacent to the second intake passage 412. The second connecting passage 416 is located below the second intake passage 412.

[0096] The first exhaust passage 420 is adjacent to the first intake passage 410. The first exhaust passage 420 is located below the first connecting passage 414. The second exhaust passage 422 is adjacent to the second intake passage 412. The second exhaust passage 422 is located below the second connecting passage 416. The exhaust connection section 425 is located to the left of the second exhaust passage 422, is connected to the second exhaust passage 422, and discharges exhaust gas E1.

[0097] The exhaust extension section 426 is located to the right of the first exhaust passage 420 and receives exhaust gas E, which is the basis for the circulating exhaust gas E2. The exhaust extension section 426 has a mounting section 468 for the flow rate regulator 466. The mounting section 468 is the same as the mounting section 68 of the first embodiment. The mounting section 268 is part of the exhaust extension section 426 and is integrated with the exhaust extension section 426. The flow rate regulator 466 is attached to the mounting section 468 in the same way as the flow rate regulator 66 of the first embodiment. In Figure 13, a flow rate regulator 66B corresponding to the first embodiment is attached.

[0098] The flow path section 427 is tubular and spans between the intake extension section 406 and the exhaust extension section 426, connecting the intake connection section 405 and the exhaust connection section 425. The flow path section 427 may also be connected to an intake passage other than the intake extension section 406, or to an exhaust passage other than the exhaust extension section 426. In the fourth embodiment of Japanese Patent Publication No. 6620192, the flow channel 427 is a diffuser 351. In the fifth embodiment, the exhaust extension section 426 and the flow path section 427 constitute the circulation section 440.

[0099] The first valve 430 is movable between the boundary between the first intake passage 410 and the first connecting passage 414, and between the boundary between the first connecting passage 414 and the first exhaust passage 420. The second valve 432 is movable between the boundary between the second intake passage 412 and the second communication passage 416, and between the boundary between the second communication passage 416 and the second exhaust passage 422. The first cylinder 434 moves the first valve 430 via a linkage mechanism. The second cylinder 436 moves the second valve 432 via a linkage mechanism. Furthermore, at least one of the first cylinder 434 and the second cylinder 436 may be an air cylinder, as in the fourth embodiment of Japanese Patent Publication No. 6620192, and at least one of the first valve 430 and the second valve 432 may be moved without a linkage mechanism.

[0100] The following describes examples of the operation of the two burners and the four-way valve device 403. The first burner is positioned after the four-way valve device 403 and is connected to the four-way valve device 403. The second burner is positioned in front of the four-way valve device 403 and connected to the four-way valve device 403.

[0101] As shown in Figure 13, when the first valve 430 of the four-way valve device 403 is located downward, i.e., at the boundary between the first communication passage 414 and the first exhaust passage 420, and the second valve 432 is located upward, i.e., at the boundary between the second intake passage 412 and the second communication passage 416, the air R becomes exhaust gas mixed air RE in the intake extension section 406, passes through the first intake passage 410 and the first communication passage 414, is supplied to the rear first burner, becomes exhaust gas E in the first burner, and returns to the second exhaust passage 422. A portion of the exhaust gas E is discharged as exhaust gas E1 from the exhaust connection section 425, and the remaining portion is recirculated as exhaust gas E2, entering the intake extension section 406 from the exhaust extension section 426 and the flow path section 427.

[0102] On the other hand, unlike in Figure 13, if the first valve 430 of the four-way valve device 403 is located upward, i.e., at the boundary between the first intake passage 410 and the first connecting passage 414, and the second valve 432 is located downward, i.e., at the boundary between the second connecting passage 416 and the second exhaust passage 422, then the air R becomes exhaust gas mixed air RE in the intake extension section 406, passes through the first intake passage 410, the second intake passage 412, and the second connecting passage 416, is supplied to the front second burner, becomes exhaust gas E in the second burner, and returns to the first exhaust passage 420. A portion of the exhaust gas E is discharged as exhaust gas E1 from the exhaust connection section 425, and the remaining portion is recirculated as exhaust gas E2, entering the intake extension section 406 from the exhaust extension section 426 and the flow path section 427.

[0103] The flow rate of the circulating exhaust gas E2 is regulated by the flow regulator 466. When the fuel is hydrogen gas and a flow regulator 466 without a protrusion is attached to the mounting portion 468, the exhaust gas E2 passes through the relatively wide gap between the flow regulator 466 and the exhaust extension portion 426 and the flow path portion 427, i.e., the first gap, and flows within the flow path portion 427. On the other hand, as shown in Figure 13, when the fuel is city gas and a flow control body 466 having a rod-shaped projection 474 is attached to the mounting portion 468, the exhaust gas E2 passes through the relatively narrow gap between the exhaust extension portion 426 and the flow path portion 427 and the projection 474, i.e., the second gap, and flows within the flow path portion 427. When the fuel is city gas, the flow rate of exhaust gas E2 in the circulation portion 440 is reduced compared to when the fuel is hydrogen gas, and the circulation rate is suppressed.

[0104] In the fifth form of the burner described above, the intake connection section 405 and the intake extension section 406, which serve as the air introduction section, and the circulation section 440 are provided in the four-way valve device 403. Therefore, more appropriate EGR (Exhaust Gas Recirculation) for multiple burners, depending on the type of fuel, can be implemented with a simpler configuration.

[0105] Furthermore, the fifth embodiment described above may appropriately include at least one of the following modifications: the same modifications as the first embodiment, the same modifications as the second embodiment, the same modifications as the third embodiment, and the same modifications as the fourth embodiment. In addition, in the fifth embodiment, the flow rate regulator 466 and mounting portion 468 may be replaced with a retractable flow rate regulator 266 and its mounting portion 268 of the third embodiment, or a retractable flow rate regulator 366 and its mounting portion 368 of the fourth embodiment. Furthermore, at least two of the following may be combined as appropriate: part or all of the first form, part or all of the second form, part or all of the third form, part or all of the fourth form, and part or all of the fifth form. Furthermore, at least one of the first to fifth embodiments described above may be considered a burner system. For example, in the fifth embodiment, the burner system may include two burners and a four-way valve device 403. [Explanation of Symbols]

[0106] 1, 101, 201, 301... Burner 16, 116... Burner nozzle 36, 136, 405... Air inlet (combustion air inlet) 38, 138, 238, 338... Exhaust gas outlet section 40, 140, 240, 340, 440... Circulation section 52. Mixer section 60, 260...First flow channel section (part of the flow channel section) 62, 262... Direction change section (part of the flow path section) 64, 264...Second channel section (part of the channel section) 66, 66A, 66B, 166, 266, 366, 466...Flow rate adjustment body 68, 168, 268, 368, 468... Mounting parts 74B, 74C, 174, 474...Protrusion 160 ··Flow channel section 272, 372... Shaft portion (part of the protruding portion) 274, 374... Bulging portion (part of the protruding portion) 403. Four-way valve device 405...Intake connection section (part of the air introduction section in a four-way valve device) 406. Intake extension section (part of the air introduction section in a four-way valve device) E, E1, E2... Exhaust gas R...Air (combustion air)

Claims

1. A burner in which combustion is performed by switching between a first fuel and a second fuel, A combustion air inlet for introducing combustion air, A circulation unit that circulates a portion of the exhaust gas from the combustion of the first fuel or the second fuel to the combustion air introduction section, It is equipped with, The circulation unit comprises a flow path through which the exhaust gas flows, and a flow rate regulator attached to the flow path. The first fuel maintains combustion even when the circulation volume, which is the flow rate of the circulating exhaust gas, is higher than that of the second fuel. When the first fuel is combusted, the flow rate regulator does not protrude from the flow path and has a first gap between itself and the flow path, or it protrudes in a rod shape while having a first gap with respect to the flow path. When the second fuel is combusted, the flow rate regulator protrudes in a rod shape from the flow path portion, having a second gap smaller than the first gap. The flow rate regulator includes a first flow rate regulator and a second flow rate regulator. The first flow rate regulator does not have a protrusion that protrudes from the flow path, or it has a thin protrusion that protrudes in a rod shape from the flow path. The second flow rate regulator has a thick projection that protrudes in a rod shape from the flow path section, When the first fuel is burned, the first flow rate regulator is provided so as not to be able to move back and forth relative to the flow path. When the second fuel is combusted, the second flow rate regulator is installed in place of the first flow rate regulator so as not to move back and forth relative to the flow path. burner.

2. The aforementioned flow channel section includes a first flow channel section, a second flow channel section in a direction intersecting the direction of the first flow channel section, and a direction changing section connected to the first flow channel section and the second flow channel section. The direction changing section is provided with a mounting section for attaching the flow rate adjustment body. The flow rate regulator is attached to the mounting portion. The burner according to claim 1.

3. The aforementioned flow path extends between the exhaust gas outlet for releasing the exhaust gas and the combustion air introduction section. The exhaust gas outlet section is provided with a mounting section for attaching the flow rate adjustment body. The flow rate regulator is attached to the mounting portion. The burner according to claim 1.

4. The combustion air introduction section has a mixer section that accelerates the combustion air. The burner according to claim 1.

5. A fuel pipe through which the first fuel or the second fuel passes, A burner nozzle connected to the tip of the fuel pipe, It is equipped with, The burner nozzle has an open combustion chamber, The length of the combustion cylinder in the direction of the fuel pipe is 40 mm or more. The burner according to claim 1.

6. The combustion air introduction section and the circulation section are provided in a four-way valve device. The burner according to claim 1.

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