Burner

Abstract

To provide a burner capable of reducing a discharge amount of NOx.SOLUTION: The burner includes a main nozzle, a housing, and an auxiliary nozzle. The main nozzle includes a cylindrical body, a first air flow passage disposed in the cylindrical body so as to include an axis of the cylindrical body, a first fuel flow passage and a second fuel flow passage disposed so as to surround the first air flow passage, a baffle plate provided at a tip end portion of the first air flow passage, a first gas nozzle provided at a tip end portion of the first fuel flow passage, and a second gas nozzle provided at a tip end portion of the second fuel flow passage. The sub-nozzle includes an air port ring attached to an end portion of the housing and a flame stabilizing plate attached to an end portion of the cylindrical body. A space between the air port ring and the flame stabilizing plate communicates with a second air flow path formed between the cylindrical body and the housing, the baffle plate includes a first notch for injecting air from the first air flow path, and the flame stabilizing plate includes a second notch for injecting air from the second air flow path.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to burners. [Background technology]

[0002] Patent Document 1 discloses a burner capable of co-firing fuel gas and hydrogen. This burner has multiple fuel injection holes for injecting fuel gas, multiple hydrogen injection holes for injecting hydrogen, and an air supply unit for supplying combustion air. The fuel injection holes and hydrogen injection holes are arranged alternately around the circumference of the burner axis. The diameter of the hydrogen injection holes is smaller than that of the fuel injection holes. The air supply unit is arranged to surround the outer periphery of the fuel injection holes and hydrogen injection holes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-138017 Summary of the Invention [Problem to be solved by the invention]

[0004] Hydrogen gas is easier to combust than other fuel gases such as liquefied natural gas, and is more likely to produce NOx (nitrogen oxides). There is a demand for reducing NOx emissions in burners that can co-combust hydrogen gas with other fuel gases such as liquefied natural gas.

[0005] An object of the present disclosure is to provide a burner that can reduce NOx emissions. [Means for solving the problem]

[0006] The burner disclosed herein comprises a main nozzle, a cylindrical housing surrounding the outer periphery of the main nozzle, and a cylindrical sub-nozzle surrounding the tip of the main nozzle. The main nozzle comprises a cylindrical body forming the outer periphery of the main nozzle, a first air passage disposed within the cylindrical body so as to include the axis of the cylindrical body, a first fuel passage and a second fuel passage disposed in this order from the axis toward the outer periphery so as to surround the first air passage, a baffle plate provided at the tip of the first air passage, a first gas nozzle provided at the tip of the first fuel passage for injecting a first fuel gas, and a second gas nozzle provided at the tip of the second fuel passage for injecting a second fuel gas. The sub-nozzle comprises an air port ring attached to the end of the housing so as to protrude beyond the tip of the housing, and a flame stabilizer attached to the end of the cylindrical body so as to face the inner circumferential surface of the air port ring. The space between the air port ring and the flame stabilizer is in communication with a second air passage formed between the cylindrical body and the housing. The baffle plate includes a first notch for injecting air from the first air flow path, and the flame holder includes a second notch for injecting air from the second air flow path. [Effects of the Invention]

[0007] The burner of the present disclosure can reduce NOx emissions. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a burner according to an embodiment. [Figure 2] FIG. 2 is a schematic front view showing the burner shown in FIG. [Figure 3] FIG. 3 is a schematic perspective view showing a main nozzle and a flame stabilizing plate of the burner shown in FIG. [Figure 4] FIG. 4 is a graph showing the relationship between the combustion load factor and NOx measured in the test example. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] (1) A burner according to an embodiment of the present disclosure includes a main nozzle, a cylindrical housing surrounding the outer periphery of the main nozzle, and a cylindrical sub-nozzle surrounding the tip of the main nozzle. The main nozzle includes a cylindrical body forming the outer periphery of the main nozzle, a first air flow path disposed within the cylindrical body so as to include the axis of the cylindrical body, a first fuel flow path and a second fuel flow path disposed in this order from the axis toward the outer periphery so as to surround the first air flow path, a baffle plate provided at the tip of the first air flow path, a first gas nozzle provided at the tip of the first fuel flow path for injecting a first fuel gas, and a second gas nozzle provided at the tip of the second fuel flow path for injecting a second fuel gas. The sub-nozzle includes an air port ring attached to the end of the housing so as to protrude beyond the tip of the housing, and a flame stabilizer attached to the end of the cylindrical body so as to face the inner circumferential surface of the air port ring. The space between the air port ring and the flame stabilizer is in communication with a second air flow path formed between the cylindrical body and the housing. The baffle plate includes a first notch for injecting air from the first air flow path, and the flame holder includes a second notch for injecting air from the second air flow path.

[0011] In a burner equipped with a main nozzle and a sub-nozzle, air is injected from the burner in two stages. The first-stage air is injected from the first notch, and the second-stage air is injected from the second notch. A portion of the theoretically required combustion air is injected from the first notch, and the remainder is injected from the second notch. While the first-stage air results in incomplete combustion, the second-stage air can achieve complete combustion. This two-stage combustion reduces the rapid combustion reaction and lowers the flame temperature compared to complete combustion in one go. Lower flame temperatures can reduce NOx emissions. Two-stage combustion is achieved by locating the first and second notches at different positions along the axis of the cylinder. Complete combustion in one go can be achieved, for example, by locating the first and second notches at the same position along the axis of the cylinder.

[0012] The sub-nozzle is positioned to surround the tip of the main nozzle and protrude beyond the tip of the main nozzle. Therefore, a combustion space is formed between the tip surface of the main nozzle and the inner circumferential surface of the sub-nozzle. The first and second notches are provided facing this combustion space. Therefore, the primary air injected from the first notch and the secondary air injected from the second notch are completely mixed in the combustion space, allowing complete combustion to occur in the combustion space.

[0013] The burner has a first fuel flow path and a second fuel flow path in the main nozzle, so it can burn a mixture of hydrogen gas and a fuel gas other than hydrogen gas, such as liquefied natural gas. With the burner, even when two types of combustion gas, including hydrogen gas, are used, NOx emissions can be reduced by two-stage combustion.

[0014] The burner can be used for combustion with either a single fuel gas or a mixture of two fuel gases, for example, the burner can be used for combustion with only hydrogen gas, only a fuel gas other than hydrogen gas such as liquefied natural gas, or a mixture of a fuel gas other than hydrogen gas and hydrogen gas.

[0015] The burner is a pre-mix burner in which the first fuel flow path, the second fuel flow path, the first air flow path, and the second air flow path are independent of one another, and the first fuel gas, the second fuel gas, and the air are sent separately to the combustion space. Pre-mix burners are less likely to cause flashback.

[0016] (2) In the burner of (1) above, the flame stabilizing plate may be a cylinder formed to connect the tip of the cylinder and the tip of the air port ring, and the inner dimensions may increase with increasing distance from the cylinder.

[0017] If the cylinder has an inner dimension that increases with increasing distance from the flame stabilizer, the flame stabilizer can easily restrict the range in which the flame is formed. If the cylinder has an inner dimension that increases with increasing distance from the flame stabilizer, the primary air injected from the first notch and the secondary air injected from the second notch can easily be mixed.

[0018] (3) In the burner of (1) or (2), the first fuel gas and the second fuel gas may be different fuel gases, and the first fuel gas or the second fuel gas may be hydrogen gas.

[0019] Combustion using hydrogen gas does not produce CO2 (carbon dioxide) because the fuel gas does not contain carbon. However, hydrogen gas is more easily combusted and more likely to produce NOx than fuel gases other than hydrogen gas, such as liquefied natural gas. With a burner according to an embodiment of the present disclosure, even when hydrogen gas is used, NOx emissions can be reduced through two-stage combustion. A burner that uses two types of fuel gas, hydrogen gas and a fuel gas other than hydrogen gas, such as liquefied natural gas, can reduce NOx emissions as well as CO2 emissions.

[0020] (4) In any of the burners described in (1) to (3), the first gas nozzle and the second gas nozzle may each have a plurality of injection holes, and the total opening area of ​​the plurality of hydrogen injection holes that inject hydrogen gas may be smaller than the total opening area of ​​the plurality of fuel injection holes that inject fuel gas other than hydrogen gas.

[0021] When the injection speed of each of hydrogen gas and fuel gas other than hydrogen gas is faster than the combustion speed, backfire is less likely to occur. Hydrogen gas has a faster combustion speed than fuel gas other than hydrogen gas. The smaller the total opening area of ​​the multiple hydrogen injection holes, the faster the injection speed of hydrogen gas. For example, when the total opening area of ​​the multiple hydrogen injection holes is smaller than the total opening area of ​​the multiple fuel injection holes, the injection speed of hydrogen gas is likely to be fast. A burner with a high injection speed of hydrogen gas is less likely to cause backfire.

[0022] (5) In the burner of (4) above, the diameter of each of the plurality of hydrogen injection holes may be smaller than the diameter of each of the plurality of fuel injection holes.

[0023] If the diameter of each hydrogen injection hole is smaller than the diameter of each fuel injection hole, the injection speed of hydrogen gas tends to be high. A burner with a high injection speed of hydrogen gas is less likely to cause flashback.

[0024] [Details of the embodiments of the present disclosure] Specific examples of the burner of the present disclosure will be described with reference to the drawings. The same reference numerals in the drawings indicate the same or equivalent parts. In each drawing, for the convenience of explanation, some components may be exaggerated or simplified. The dimensional ratios of each part in the drawings may also differ from the actual ratios. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0025] <Burner> A burner 1 according to an embodiment will be described with reference to Figures 1 to 3. The burner 1 comprises a main nozzle 2, a housing 8, and a sub-nozzle 9. The housing 8 is arranged so as to surround the outer periphery of the main nozzle 2. The sub-nozzle 9 is arranged so as to surround the tip of the main nozzle 2 and protrude beyond the tip of the main nozzle 2. One of the features of the burner 1 is that a combustion space 10 is formed by the tip surface of the main nozzle 2 and the inner circumferential surface of the sub-nozzle 9, and two-stage combustion can occur in this combustion space 10. Another feature of the burner 1 is that the main nozzle 2 is provided with a first fuel flow path 61 and a second fuel flow path 62, making it possible to mix hydrogen gas with a fuel gas other than hydrogen gas, such as liquefied natural gas.

[0026] <Main nozzle> 1, the main nozzle 2 includes a cylindrical body 20, a first air flow path 51, a first fuel flow path 61, a second fuel flow path 62, a baffle plate 3, a first gas nozzle 41, and a second gas nozzle 42. FIG. 1 is a longitudinal cross-sectional view of the burner 1 taken along the axis of the cylindrical body 20.

[0027] [Cylinder] The cylindrical body 20 forms the outer periphery of the main nozzle 2. The first air flow path 51, the first fuel flow path 61, and the second fuel flow path 62 are arranged inside the cylindrical body 20. The first air flow path 51 is arranged so as to include the axis of the cylindrical body 20. The first air flow path 51 extends along the axis of the cylindrical body 20. The first fuel flow path 61 and the second fuel flow path 62 are arranged in this order from the axis of the cylindrical body 20 toward the outer periphery so as to surround the first air flow path 51. The first fuel flow path 61 and the second fuel flow path 62 have an annular shape when viewed from the direction along the axis of the cylindrical body 20, and extend along the axis of the cylindrical body 20.

[0028] In the internal space of the cylindrical body 20, a first wall portion 71 and a second wall portion 72 are arranged.

[0029] The first wall portion 71 has a cylindrical wall portion with open ends. The internal space formed by the first wall portion 71 is the first air flow path 51. The first wall portion 71 has a first end and a second end. A baffle plate 3, which will be described later, is disposed at the first end of the first wall portion 71. The second end of the first wall portion 71 opens to the housing 8, which will be described later. An air supply unit (not shown) is attached to the housing 8, and air is supplied through the air supply unit. Thus, air is supplied from the housing 8 to the first air flow path 51. In this example, the first wall portion 71 has a flange-shaped wall portion that protrudes outward from the second end. This flange-shaped wall portion is connected to the cylindrical body 20. In this example, the flange-shaped wall portion of the first wall portion 71 is connected to the end of the cylindrical body 20.

[0030] The second wall portion 72 has a cylindrical wall portion with open ends. The internal space formed between the first wall portion 71 and the second wall portion 72 is the first fuel flow path 61. The second wall portion 72 has a first end portion and a second end portion. A first gas nozzle 41 (described later) is attached to the inside of the first end portion of the second wall portion 72, and a second gas nozzle 42 (described later) is attached to the outside of the first end portion. In this example, the second wall portion 72 has a flange-shaped wall portion protruding outward from the second end portion. This flange-shaped wall portion is connected to the inner circumferential surface of the cylindrical body 20. Although the second end portion of the second wall portion 72 is open, the flange-shaped wall portion of the first wall portion 71 separates the first fuel flow path 61 from the space within the housing 8. A first supply pipe 73 is attached to the second end portion of the second wall portion 72. The first supply pipe 73 is provided to penetrate the flange-shaped wall portion of the first wall portion 71. The first supply pipe 73 in this example extends in a direction parallel to the axis of the cylindrical body 20, penetrates the housing 8, and is drawn out to the outside. The first fuel flow path 61 is supplied with a first fuel gas from the first supply pipe 73.

[0031] The internal space formed between the second wall portion 72 and the cylindrical body 20 is the second fuel flow path 62. The first fuel flow path 61 and the second fuel flow path 62 are separated by a flange-shaped wall portion of the second wall portion 72. A second supply pipe 74 is attached to the peripheral wall of the cylindrical body 20. In this example, the second supply pipe 74 extends in a direction perpendicular to the axis of the cylindrical body 20, penetrates the housing 8, and is drawn out to the outside. A second fuel gas is supplied to the second fuel flow path 62 from the second supply pipe 74.

[0032] The first air flow path 51, the first fuel flow path 61, and the second fuel flow path 62 are independent of one another. Therefore, the air flowing through the first air flow path 51, the first fuel gas flowing through the first fuel flow path 61, and the second fuel gas flowing through the second fuel flow path 62 are sent separately to the combustion space 10, which will be described later. In the pre-mixing burner 1, in which the air, the first fuel gas, and the second fuel gas are mixed in the combustion space 10, flashback is less likely to occur.

[0033] [Baffle plate] The baffle plate 3 is provided at the tip end of the first air flow path 51. The baffle plate 3 has a first notch 30 for injecting air from the first air flow path 51. The first notch 30 has an outer edge notch 31 provided so as to form a gap 310 between the first notch 30 and the first wall portion 71. The outer edge notch 31 is provided around the entire periphery of the baffle plate 3. Therefore, the outer diameter of the baffle plate 3 is smaller than the inner diameter of the first wall portion 71. Therefore, an annular gap 310 is formed between the baffle plate 3 and the first wall portion 71. The baffle plate 3 is fixed to, for example, a bracket (not shown). The bracket is fixed to the first wall portion 71.

[0034] A plurality of outer edge notches 31 may be provided at intervals along the circumference of the baffle plate. In this case, the outer edge between adjacent outer edge notches 31 of the baffle plate 3 may be fixed to the first wall portion 71. The shape of the gap 310 formed by the plurality of outer edge notches 31 is, for example, an arc shape.

[0035] The first cutout 30 may further include a plurality of holes 32 penetrating the baffle plate 3. In this example, the plurality of holes 32 are provided dispersedly over the entire surface of the baffle plate 3. Dispersed holes 32 mean that the plurality of holes 32 are not unevenly provided on the baffle plate 3, but are uniformly provided over the entire surface of the baffle plate 3. Adjacent holes 32 are provided with a certain amount of space between them. The shape of each of the plurality of holes 32 is, for example, circular, elliptical, or polygonal.

[0036] [First gas nozzle, second gas nozzle] The first gas nozzle 41 is a nozzle for injecting the first fuel gas. The first gas nozzle 41 is provided at the tip of the first fuel flow path 61. The first gas nozzle 41 is provided so as to surround the baffle plate 3. The first gas nozzle 41 has a plurality of injection holes 410. The plurality of injection holes 410 are provided uniformly around the entire circumference of the first gas nozzle 41. Adjacent injection holes 410 are provided with a certain amount of space between them. The number of injection holes 410 and the space between adjacent injection holes 410 can be selected as appropriate.

[0037] The second gas nozzle 42 is a nozzle for injecting the second fuel gas. The second gas nozzle 42 is provided at the tip of the second fuel flow path 62. The second gas nozzle 42 is provided so as to surround the first gas nozzle 41. The second gas nozzle 42 has a plurality of injection holes 420. The plurality of injection holes 420 are provided uniformly around the entire circumference of the second gas nozzle 42. Adjacent injection holes 420 are provided with a certain amount of space between them. The number of injection holes 420 and the space between adjacent injection holes 420 can be selected as appropriate.

[0038] In this example, the first gas nozzle 41 and the second gas nozzle 42 are provided at the same position in the direction along the axis of the cylindrical body 20. The injection holes 410 and the injection holes 420 in this example are provided so that the opening edge of each injection hole 410 and the opening edge of each injection hole 420 are at the same position in the direction along the axis of the cylindrical body 20. The first gas nozzle 41 and the second gas nozzle 42 may be provided at different positions in the direction along the axis of the cylindrical body 20. The injection holes 410 and the injection holes 420 may be provided so that the opening edge of each injection hole 410 and the opening edge of each injection hole 420 are at different positions in the direction along the axis of the cylindrical body 20.

[0039] As will be described later, either the first fuel gas or the second fuel gas may be hydrogen gas. In this example, an example in which the second fuel gas is hydrogen gas will be described. The first fuel gas is a fuel gas other than hydrogen gas, such as liquefied natural gas. In this case, the multiple injection holes 420 provided in the second gas nozzle 42 are hydrogen injection holes, and the multiple injection holes 410 provided in the first gas nozzle 41 are fuel injection holes.

[0040] For example, among the multiple injection holes 410 and the multiple injection holes 420, the total opening area of ​​the multiple injection holes 420 that inject hydrogen gas is smaller than the total opening area of ​​the multiple injection holes 410 that inject fuel gas other than hydrogen gas. If the injection speed of each of hydrogen gas and fuel gas other than hydrogen gas is faster than the combustion speed, backfire is less likely to occur. Hydrogen gas has a faster combustion speed than fuel gas other than hydrogen gas. The smaller the total opening area of ​​the multiple hydrogen injection holes 420, the faster the injection speed of hydrogen gas. If the total opening area of ​​the multiple injection holes 420 is smaller than the total opening area of ​​the multiple injection holes 410, the injection speed of hydrogen gas is likely to be fast. A burner 1 with a fast injection speed of hydrogen gas is less likely to cause backfire.

[0041] Of the multiple injection holes 410 and the multiple injection holes 420, the diameter of each of the multiple injection holes 420 that inject hydrogen gas may be smaller than the diameter of each of the multiple injection holes 410. If the diameter of each injection hole 420 is smaller than the diameter of each injection hole 410, the injection speed of the hydrogen gas tends to be faster. A burner 1 that injects hydrogen gas at a high speed is less likely to flash back.

[0042] As will be described later, the first fuel gas may be hydrogen gas, and the second fuel gas may be a fuel gas other than hydrogen gas, such as liquefied natural gas. In this case, the total opening area of ​​the multiple injection holes 410 may be smaller than the total opening area of ​​the multiple injection holes 420. The diameter of each of the multiple injection holes 410 may be smaller than the diameter of each of the multiple injection holes 420.

[0043] The diameter of each injection hole 410 and the diameter of each injection hole 420 may be selected appropriately depending on the fuel gas to be injected. All of the injection holes 410 may have the same diameter, or injection holes 410 with different diameters may be included among the multiple injection holes 410. All of the injection holes 420 may have the same diameter, or injection holes 420 with different diameters may be included among the multiple injection holes 420.

[0044] In this example, the number of the plurality of injection holes 410 is the same as the number of the plurality of injection holes 420. The number of the plurality of injection holes 410 and the number of the plurality of injection holes 420 may be different.

[0045] Housing As shown in FIG. 1 , the housing 8 is a cylinder that surrounds the outer periphery of the main nozzle 2. A space is formed between the housing 8 and the cylinder 20 of the main nozzle 2. This space is the second air flow path 52. The housing 8 in this example covers the main nozzle 2 all the way to the rear end. In other words, the housing 8 in this example is a cylinder with a bottom. The tip of the main nozzle 2 and a sub-nozzle 9 (described later) are disposed at the open end of the housing 8. The first air flow path 51 and the second air flow path 52 communicate with the internal space of the housing 8. Air is supplied to each of the first air flow path 51 and the second air flow path 52 by an air supply unit (not shown) attached to the housing 8. The supply unit is equipped with a damper. The damper adjusts the amount of air supplied to the first air flow path 51 and the second air flow path 52.

[0046] <Sub-nozzle> As shown in Figures 1 and 2, the sub-nozzle 9 is a cylinder that surrounds the tip of the main nozzle 2. In Figure 2, the sub-nozzle 9 is hatched for ease of understanding. Surrounding the main nozzle 2 means that it surrounds the main nozzle 2 when the burner 1 is viewed from the front, as shown in Figure 2. In this example, the sub-nozzle 9 is arranged so as to overlap the side of the main nozzle 2. The sub-nozzle 9 does not have to overlap the side of the main nozzle 2. The sub-nozzle 9 includes an air port ring 91 and a flame stabilizer 92. For ease of explanation, the second notch 920 (Figure 1) provided in the flame stabilizer 92 is omitted in Figure 2.

[0047] The airport ring 91 is a cylindrical body attached to the end of the housing 8 so as to protrude beyond the tip of the housing 8. A combustion space 10 is formed between the tip surface of the main nozzle 2 and the inner circumferential surface of the sub-nozzle 9. The size of the combustion space 10 can be changed by the protruding length of the airport ring 91. The protruding length of the airport ring 91 is the protruding length of the sub-nozzle 9 from the main nozzle 2. The protruding length of the airport ring 91 is, for example, 20% to 90% of the diameter of the cylindrical body 20. If the protruding length of the airport ring 91 is 20% or more of the diameter of the cylindrical body 20, the air, the first fuel gas, and the second fuel gas are easily mixed in the combustion space 10. If the protruding length of the airport ring 91 is 90% or less of the diameter of the cylindrical body 20, the burner 1 can be easily downsized. The protruding length of the airport ring 91 may be 30% to 50% of the diameter of the cylindrical body 20. As shown in FIG. 1 , the airport ring 91 has a flange portion protruding inward from the tip of the airport ring 91.

[0048] As shown in Figures 1 and 3, the flame stabilizer 92 is attached to the end of the cylindrical body 20 so as to face the inner circumferential surface of the air port ring 91. For ease of understanding, Figure 3 shows the main nozzle 2 and the flame stabilizer 92, but omits the housing 8 and the air port ring 91. The flame stabilizer 92 is a cylindrical body formed to connect the tip of the cylindrical body 20 and the tip of the air port ring 91. In this example, the flame stabilizer 92 connects the outer circumferential surface of the cylindrical body 20 and a flange portion provided on the air port ring 91. As shown in Figure 1, a space 95 is formed between the air port ring 91 and the flame stabilizer 92. This space 95 communicates with the second air flow path 52.

[0049] The flame stabilizer 92 has second notches 920 for injecting air from the second air flow path 52 through the space 95. The second notches 920 are, for example, multiple holes penetrating the flame stabilizer 92. The multiple second notches 920 formed by holes are distributed over the entire surface of the flame stabilizer 92. The multiple second notches 920 being distributed means that the multiple second notches 920 are not unevenly distributed on the flame stabilizer 92 but are uniformly distributed over the entire surface of the flame stabilizer 92. Adjacent second notches 920 are provided with a certain amount of space between them. The shape of each of the multiple second notches 920 formed by holes is, for example, circular, elliptical, or polygonal. The multiple second notches 920 may be arranged so that their size increases from the tip of the cylindrical body 20 toward the tip of the air port ring 91.

[0050] Although not shown, the second notch 920 may include an outer edge notch provided so as to form a gap between the flame stabilizer 92 and the air port ring 91. An annular gap may be formed between the flame stabilizer 92 and the air port ring 91. A plurality of arc-shaped gaps may be formed at intervals along the circumference of the flame stabilizer 92 between the flame stabilizer 92 and the air port ring 91.

[0051] The opening area of ​​the first notch 30 and the opening area of ​​the second notch 920 may be the same or different. When a plurality of first notches 30 and a plurality of second notches 920 are provided, the total opening area of ​​the plurality of first notches 30 and the total opening area of ​​the second notches 920 may be the same or different. The diameter of each of the plurality of first notches 30 and the diameter of each of the plurality of second notches 920 may be the same or different.

[0052] Flame stabilizer 92 has the function of maintaining the formation of flame 100. For example, the inner dimensions of flame stabilizer 92 increase with increasing distance from cylindrical body 20. If flame stabilizer 92 is a cylinder whose inner dimensions increase with increasing distance from cylindrical body 20, flame stabilizer 92 can easily restrict the range in which flame 100 is formed. If flame stabilizer 92 is a cylinder whose inner dimensions increase with increasing distance from cylindrical body 20, primary air injected from first notch 30 and secondary air injected from second notch 920 can easily be mixed. Flame stabilizer 92 in this example has a peripheral shape of a truncated cone.

[0053] The inclination angle of flame stabilizer 92 with respect to the axis of cylindrical body 20 is, for example, 8° or more and 15° or less. The above inclination angle refers to the acute angle of the angle of flame stabilizer 92 with respect to the axis of cylindrical body 20. If the inclination angle of flame stabilizer 92 is 8° or more, flame stabilizer 92 can easily restrict the range in which flame 100 is formed. If the inclination angle of flame stabilizer 92 is 15° or less, the primary air injected from first notch 30 and the secondary air injected from second notch 920 can easily be mixed. The inclination angle of flame stabilizer 92 with respect to the axis of cylindrical body 20 may be 12° or more and 13° or less.

[0054] The first air flow path 51, the second air flow path 52, the first fuel flow path 61, and the second fuel flow path 62 are independent of one another, and the first fuel gas, the second fuel gas, and the air are separately sent to the combustion space 10. In Figure 1, the air flow is indicated by a hollow arrow, the first fuel gas flow by a solid arrow, and the second fuel gas flow by a double arrow. Because the burner 1 is a pre-mixed burner, flashback is unlikely to occur.

[0055] In the burner 1 equipped with the main nozzle 2 and sub-nozzle 9 described above, air is injected from the burner 1 in two stages. The first-stage air is injected from the first notch 30, and the second-stage air is injected from the second notch 920. A portion of the theoretically required combustion air is injected from the first notch 30, and the remainder is injected from the second notch 920. Although the first-stage air results in incomplete combustion, the second-stage air can achieve complete combustion. This two-stage combustion reduces the rapid combustion reaction and lowers the temperature of the flame 100 compared to when complete combustion is achieved in one go. Lowering the temperature of the flame 100 reduces NOx emissions.

[0056] <Fuel gas> The first fuel gas and the second fuel gas can be selected appropriately. The first fuel gas and the second fuel gas may be different fuel gases. Either the first fuel gas or the second fuel gas may be hydrogen gas. For example, if one of the first fuel gas and the second fuel gas is hydrogen gas, the other of the first fuel gas and the second fuel gas is a fuel gas other than hydrogen gas. The fuel gas other than hydrogen gas is, for example, liquefied natural gas or liquefied petroleum gas.

[0057] Combustion of hydrogen gas does not produce CO2 because the fuel gas does not contain carbon. However, compared to liquefied natural gas, hydrogen gas has characteristics such as a faster burning speed, a wider explosion limit, a smaller minimum ignition energy, and a higher theoretical flame temperature. These characteristics make hydrogen gas easier to burn and more likely to produce NOx than other fuel gases.

[0058] As described above, the burner 1 of this embodiment can reduce NOx emissions by using two-stage combustion to lower the temperature of the flame 100 compared to when complete combustion is performed in one go. Therefore, with the burner 1 of this embodiment, even when hydrogen gas is used, NOx emissions can be reduced by using two-stage combustion. The burner 1 that uses two types of fuel gas, hydrogen gas and a fuel gas other than hydrogen gas, such as liquefied natural gas, can reduce NOx emissions as well as CO2 emissions.

[0059] When two types of fuel gas, hydrogen gas and a fuel gas other than hydrogen gas, are used, the mixing ratio of hydrogen gas is, for example, more than 0% and not more than 80%. The mixing ratio of hydrogen gas is the ratio of the volume of hydrogen gas to the total volume of the fuel gas other than hydrogen gas and hydrogen gas. The mixing ratio of hydrogen gas may be more than 0% and not more than 70%, 10% to 70%, or 20% to 70%.

[0060] The first fuel gas may be hydrogen gas, and the second fuel gas may be a fuel gas other than hydrogen gas. The first fuel gas may be a fuel gas other than hydrogen gas, and the second fuel gas may be hydrogen gas. Both the first fuel gas and the second fuel gas may be hydrogen gas. Both the first fuel gas and the second fuel gas may be a fuel gas other than hydrogen gas. Both the first fuel gas and the second fuel gas may be liquefied natural gas.

[0061] In the burner 1 shown in FIG. 1 , combustion using only the second fuel gas may be performed by supplying the second fuel gas to the second fuel flow path 62 without supplying the first fuel gas to the first fuel flow path 61. In this case, the second fuel gas may be hydrogen gas or a fuel gas other than hydrogen gas. Also, in the burner 1 shown in FIG. 1 , combustion using only the first fuel gas may be performed by supplying the first fuel gas to the first fuel flow path 61 without supplying the second fuel gas to the second fuel flow path 62. In this case, the first fuel gas may be hydrogen gas or a fuel gas other than hydrogen gas. When one of the first fuel flow path 61 and the second fuel flow path 62 is used and the other of the first fuel flow path 61 and the second fuel flow path 62 is not used, valves that limit use may be provided in the first supply pipe 73 and the second supply pipe 74.

[0062] [Test example] In the test example, combustion experiments were carried out using a burner 1 shown in Figure 1 with a number of test specimens with different fuel gases, and NOx emissions relative to the combustion load rate were investigated.

[0063] <Test specimen description> The burner structure was the same for all the test specimens. The fuel gases used for each test specimen were as follows:

[0064] In test specimen 1, the fuel gas is liquefied natural gas only. In other words, the hydrogen mixing ratio in test specimen 1 is 0%. In test specimen 1, the first fuel gas is liquefied natural gas, and no second fuel gas is used. In test specimen 1, liquefied natural gas is injected from the first gas nozzle 41, and nothing is injected from the second gas nozzle 42.

[0065] In test specimens 2 to 10, the fuel gas was a mixture of liquefied natural gas and hydrogen gas. The hydrogen mixture ratio was 10% for test specimen 2, 20% for test specimen 3, 30% for test specimen 4, 40% for test specimen 5, 50% for test specimen 6, 60% for test specimen 7, 70% for test specimen 8, 80% for test specimen 9, and 90% for test specimen 10. In test specimens 2 to 10, the first fuel gas was liquefied natural gas, and the second fuel gas was hydrogen gas. In test specimens 2 to 10, liquefied natural gas was injected from the first gas nozzle 41, and hydrogen gas was injected from the second gas nozzle 42.

[0066] In the test specimen 11, the fuel gas is hydrogen gas only. In other words, the hydrogen mixture ratio in the test specimen 11 is 100%. In the test specimen 11, the first fuel gas is not used, and the second fuel gas is hydrogen gas. In the test specimen 11, hydrogen gas is injected from the second gas nozzle 42, and nothing is injected from the first gas nozzle 41.

[0067] In each test specimen, primary air was injected from the first notch 30 of the baffle plate 3 , and secondary air was injected from the second notch 920 of the flame holder plate 92 .

[0068] <Combustion test> For each test specimen, the NOx value was measured while changing the combustion load rate. The combustion load rate is the ratio of actual combustion output to the maximum combustion amount. The NOx value was measured in accordance with JIS B 7953 (2004). The NOx value was converted to O2 = 0%. The results are shown in Figure 4. In the graph in Figure 4, the horizontal axis is the combustion load rate and the vertical axis is the NOx value. In Figure 4, the target NOx value of 197 ppm is shown by a thick solid line.

[0069] As shown in Figure 4, even when using a fuel gas mixture of liquefied natural gas and hydrogen gas, the NOx value meets the target value of 197 ppm as long as the hydrogen mixture ratio is 80% or less. Although NOx is easily generated when hydrogen gas is included, the burner in this example performs two-stage combustion, which is thought to have reduced the NOx value by reducing the sudden combustion reaction and lowering the flame temperature compared to when complete combustion is performed in one go. Although the NOx value increases as the hydrogen mixture ratio increases, if the hydrogen mixture ratio is between 0% and 70%, NOx is well below the target value of 197 ppm.

[0070] For specimens 10 and 11, the NOx values ​​exceeded the target value of 197 ppm depending on the combustion load rate. However, the NOx values ​​were 250 ppm or less for specimen 10 and 300 ppm or less for specimen 11. If the hydrogen mixture ratio is high, complete combustion in one go would not achieve a value of 320 ppm or less. In this example, the burner performs two-stage combustion, so even with a high hydrogen mixture ratio, the NOx values ​​can be reduced compared to complete combustion in one go.

[0071] In specimens 2 to 11, CO2 can be reduced by containing hydrogen gas. [Explanation of symbols]

[0072] 1 Burner 10 Combustion space 100 Flame 2 Main nozzle 20 cylinder 3 baffle plates 30 First notch 31 Outer edge notch 310 Gap 32 holes 41 First gas nozzle 410 Injection hole 42 Second Gas Nozzle 420 Injection hole 51 first air flow path 52 Second air flow path 61 First fuel passage 62 Second fuel flow path 71 First wall 72 Second wall section 73 First supply pipe 74 Second supply pipe 8. Housing 9 Sub-nozzles 91 Airport Ring 92 Flame holding plate 920 Second Notch 95 Space

Claims

1. The main nozzle and a cylindrical housing surrounding the outer periphery of the main nozzle; a cylindrical sub-nozzle surrounding the tip of the main nozzle, The main nozzle is a cylindrical body that forms an outer periphery of the main nozzle; a first air flow path disposed within the barrel to include an axis of the barrel; a first fuel flow path and a second fuel flow path arranged in this order from the axis toward the outer periphery so as to surround the first air flow path; a baffle plate provided at a tip end of the first air flow path; a first gas nozzle provided at a tip end of the first fuel flow path for injecting a first fuel gas; a second gas nozzle provided at a tip end of the second fuel flow path for injecting a second fuel gas, The sub-nozzle is an air port ring attached to an end of the housing so as to protrude beyond the tip of the housing; a flame stabilizer attached to an end of the cylindrical body so as to face an inner circumferential surface of the air port ring; a space between the air port ring and the flame stabilizer plate communicates with a second air flow path formed between the cylindrical body and the housing; the baffle plate includes a first notch for injecting air from the first air flow path; the flame holder includes a second notch for injecting air from the second air flow path; Burner.

2. 2. The burner according to claim 1, wherein the flame stabilizing plate is a cylindrical body formed to connect a tip of the cylindrical body and a tip of the air port ring, and the inner dimensions of the flame stabilizing plate increase with increasing distance from the cylindrical body.

3. the first fuel gas and the second fuel gas are different fuel gases, 3. The burner according to claim 1 or 2, wherein the first fuel gas or the second fuel gas is hydrogen gas.

4. each of the first gas nozzle and the second gas nozzle includes a plurality of injection holes; 4. The burner according to claim 3, wherein a total opening area of ​​a plurality of hydrogen injection holes that inject hydrogen gas among the plurality of injection holes is smaller than a total opening area of ​​a plurality of fuel injection holes that inject a fuel gas other than hydrogen gas.

5. 5. The burner of claim 4, wherein the diameter of each of said plurality of hydrogen injection holes is smaller than the diameter of each of said plurality of fuel injection holes.

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