Burner

Abstract

To provide a burner capable of reducing a discharge amount of NOx.SOLUTION: A tubular body, a first fuel flow passage arranged to include an axis of the tubular body, a plurality of second fuel flow passages arranged side by side on a circumference around the axis, an air flow passage arranged to surround the first fuel flow passage, a first gas nozzle, a plurality of second gas nozzles, and a baffle plate, wherein the first gas nozzle includes a plurality of fuel injection holes for injecting fuel gas other than hydrogen gas from the first fuel flow passage, and each of the second gas nozzles includes a hydrogen injection hole for injecting hydrogen gas from each of the second fuel flow passages, the baffle plate includes a plurality of air ports for injecting air from the air flow path, the first gas nozzle and the second gas nozzles are provided so as to protrude from the baffle plate, the air ports are arranged on a circumference around an axis, and axes of the fuel injection holes are inclined so as to be separated from each other toward a tip of the first gas nozzle.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 of the present disclosure comprises a cylindrical body, a first fuel flow path disposed within the cylindrical body so as to include the axis of the cylindrical body, a plurality of second fuel flow paths arranged side by side on a circle centered on the axis within the cylindrical body, an air flow path disposed within the cylindrical body so as to surround the first fuel flow path, a first gas nozzle provided at the tip of the first fuel flow path, a plurality of second gas nozzles provided at the tip of each of the plurality of second fuel flow paths, and a baffle plate provided at the tip of the air flow path. The first gas nozzle has a plurality of fuel injection holes for injecting a fuel gas other than hydrogen gas from the first fuel flow path. Each of the plurality of second gas nozzles has a hydrogen injection hole for injecting hydrogen gas from each of the plurality of second fuel flow paths. The baffle plate has a plurality of air ports for injecting air from the air flow path. The first gas nozzle and the plurality of second gas nozzles are provided to protrude from the baffle plate. The plurality of air ports are arranged side by side on a circle centered on the axis. The axes of the plurality of fuel injection holes are inclined so as to move away from each other toward the tip of the first gas nozzle. [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 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 comprises a cylindrical body, a first fuel flow path disposed within the cylindrical body so as to include the axis of the cylindrical body, a plurality of second fuel flow paths arranged side by side on a circle centered on the axis within the cylindrical body, an air flow path disposed within the cylindrical body so as to surround the first fuel flow path, a first gas nozzle provided at a tip of the first fuel flow path, a plurality of second gas nozzles provided at a tip of each of the plurality of second fuel flow paths, and a baffle plate provided at a tip of the air flow path. The first gas nozzle has a plurality of fuel injection holes for injecting a fuel gas other than hydrogen gas from the first fuel flow path. Each of the plurality of second gas nozzles has a hydrogen injection hole for injecting hydrogen gas from each of the plurality of second fuel flow paths. The baffle plate has a plurality of air ports for injecting air from the air flow path. The first gas nozzle and the plurality of second gas nozzles are provided so as to protrude from the baffle plate. The plurality of air ports are arranged side by side on a circle centered on the axis. The axes of the plurality of fuel injection holes are inclined so as to move away from each other toward the tip of the first gas nozzle.

[0011] In the burner described in (1) above, the first flame formed by a fuel gas other than hydrogen gas can be a divided flame and a thin-film flame. The first flame is formed by mixing and burning the fuel gas injected from the first gas nozzle and the air injected from each of the multiple air ports. The first gas nozzle has multiple fuel injection holes formed at an angle. Since each of the multiple fuel injection holes is formed at an angle and multiple air ports are formed around the first gas nozzle, the first flame becomes a divided flame divided around the axis of the cylindrical body. The first flame is stretched forward while spreading radially around the axis of the cylindrical body by the air injected from each of the multiple air ports, becoming a bell-shaped thin-film flame.

[0012] In the burner (1) above, the second flame formed by hydrogen gas can also be a divided flame and a thin-film flame. The second flame is formed by mixing and burning hydrogen gas injected from the second gas nozzle with air injected from each of the multiple air ports. Multiple second gas nozzles are arranged in a line around the circumference of the cylindrical body's axis. Each of the multiple second gas nozzles is provided with a hydrogen injection hole. By arranging multiple hydrogen injection holes and multiple air ports in a line around the circumference of the cylindrical body's axis, the second flame becomes a divided flame divided around the cylindrical body's axis. Hydrogen gas has a faster burning speed than fuel gases other than hydrogen gas. Therefore, the second flame is elongated forward along the axis of each of the multiple hydrogen injection holes to become a thin-film flame.

[0013] A divided flame has a larger surface area than a non-divided flame, which increases the contact area between the flame and the combustion gas, cooling the flame and resulting in a lower flame temperature. A thin film flame also has a larger surface area than a non-thin film flame, which increases the contact area between the flame and the combustion gas, cooling the flame and resulting in a lower flame temperature. Lower flame temperatures can reduce NOx emissions.

[0014] The combustion gases from each of the primary and secondary flames are mixed with the air injected from each air port due to the ejector effect. By mixing the combustion gases with the air, the oxygen concentration in the air decreases, combustion slows, and the flame temperature decreases. The lower flame temperature reduces NOx emissions.

[0015] The burner (1) above can form divided flames and thin film flames and can reuse combustion gases, so that it can reduce NOx emissions even though it is a burner that burns hydrogen gas and a fuel gas other than hydrogen gas.

[0016] In the burner (1) above, the fuel gas other than hydrogen gas is injected at an angle from the center of the burner, which makes it difficult for combustion oscillation to occur and enables the stable formation of the first flame. The first gas nozzle and the multiple second gas nozzles are also provided so as to protrude from the baffle plate, which also enables the stable formation of the first flame.

[0017] (2) In the burner of (1) above, at least one of the air ports may be disposed between adjacent second gas nozzles.

[0018] According to the above configuration (2), the first flame and the second flame can be easily made into a divided flame and a thin film flame, respectively.

[0019] (3) In the burner of (1) or (2) above, the inclination angle of the axis of each of the plurality of fuel injection holes with respect to the axis may be 80° or more and 100° or less.

[0020] If the tilt angle is 80° or more, combustion oscillation is unlikely to occur. If the tilt angle is 100° or less, the first flame is likely to be a divided flame and a thin film flame.

[0021] (4) In the burner according to any one of (1) to (3) above, the axis of each of the plurality of hydrogen injection holes may be parallel to the axis of the cylindrical body.

[0022] If the axis of each of the multiple hydrogen injection holes is parallel to the axis of the cylinder, the rapid combustion reaction between hydrogen gas and air can be reduced, thereby lowering the flame temperature.

[0023] (5) In the burner according to any one of (1) to (4) above, the number of the hydrogen injection holes may be less than the number of the fuel injection holes.

[0024] If the number of the plurality of hydrogen injection holes is smaller than the number of the plurality of fuel injection holes, it is easier to stably form the first flame.

[0025] (6) In the burner according to any one of (1) to (4) above, the number of the hydrogen injection holes may be greater than the number of the fuel injection holes.

[0026] When the number of hydrogen injection holes is greater than the number of fuel injection holes, it is easy to shorten the length of the second flame. A shorter flame length makes it easier to downsize the combustion furnace. Furthermore, when the number of hydrogen injection holes is greater than the number of fuel injection holes, the number of split flames created by the second flame increases, reducing the amount of hydrogen in each split second flame and making it easier to reduce total NOx emissions.

[0027] (7) In the burner according to any one of (1) to (6) above, the total opening area of ​​the plurality of hydrogen injection holes may be smaller than the total opening area of ​​the plurality of fuel injection holes.

[0028] 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.

[0029] (8) In the burner described above in (7), 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.

[0030] 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.

[0031] (9) In any of the burners described in (1) to (8) above, the opening edge of each of the plurality of fuel injection holes may be located farther from the baffle plate than the opening edge of the hydrogen injection hole.

[0032] If the fuel injection holes are located closer to the tip of the burner than the hydrogen injection holes, it is easier to form a stable primary flame.

[0033] [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.

[0034] <Burner> A burner 1 according to an embodiment will be described with reference to FIGS. 1 to 3. The burner 1 includes a cylindrical body 2, a baffle plate 3, an air flow path 5, a first fuel flow path 61, multiple second fuel flow paths 62, a first gas nozzle 41, and multiple second gas nozzles 42. The baffle plate 3 is provided at the tip of the air flow path 5. The baffle plate 3 is provided with multiple air ports 30 for injecting air from the air flow path 5. One feature of the burner 1 is that the first gas nozzle 41 is arranged to include the axis of the cylindrical body 2, and multiple second gas nozzles 42 and multiple air ports 30 are provided around the first gas nozzle 41. Another feature of the burner 1 is that the first gas nozzle 41 and each second gas nozzle 42 are provided to protrude from the baffle plate 3. A fuel gas other than hydrogen gas, such as liquefied natural gas, is injected from the first gas nozzle 41. Hydrogen gas is injected from each second gas nozzle 42. This burner 1 can make the first flame 11 formed by a fuel gas other than hydrogen gas and the second flame 12 formed by hydrogen gas into divided flames and thin film flames.

[0035] Fig. 1 is a longitudinal cross-sectional view of the burner 1 cut along the axis of the cylindrical body 2. In Fig. 1, the first flame 11 and the second flame 12 are shown as elongated circles for ease of understanding. Also, in Fig. 1, the second flame 12 is hatched for ease of understanding. In Fig. 2, only the first flame 11 is shown, and the second flame 12 is not shown.

[0036] [Cylinder] The cylindrical body 2 forms the outer periphery of the burner 1. As shown in FIG. 1 , an air flow path 5, a first fuel flow path 61, and multiple second fuel flow paths 62 are arranged within the cylindrical body 2. The first fuel flow path 61 is arranged so as to include the axis of the cylindrical body 2. There is only one first fuel flow path 61. The first fuel flow path 61 extends along the axis of the cylindrical body 2. The multiple second fuel flow paths 62 are arranged side by side on a circumference centered on the axis of the cylindrical body 2. In this example, the multiple second fuel flow paths 62 are arranged side by side at intervals around the entire circumference of the cylindrical body 2. Each second fuel flow path 62 extends along the axis of the cylindrical body 2. The air flow path 5 is arranged so as to surround the first fuel flow path 61. In this example, the air flow path 5 is formed in the space within the cylindrical body 2 other than the first fuel flow path 61 and the second fuel flow path 62.

[0037] The cylindrical body 2 of this example has a front region 21 and a rear region 22. The front region 21 is the portion that is inserted into the combustion furnace 8. The rear region 22 is the portion that is not inserted into the combustion furnace 8. The outer diameter of the rear region 22 is larger than the outer diameter of the front region 21. A step surface is formed on the outer peripheral surface of the cylindrical body 2 due to the difference in outer diameter between the front region 21 and the rear region 22. This step surface is abutted against and fixed to, for example, the combustion furnace 8. The inner diameter of the rear region 22 is larger than the inner diameter of the front region 21. In the cylindrical body 2 of this example, the internal space of the rear region 22 is larger than the internal space of the front region 21. The cylindrical body 2 of this example is a cylindrical body with a bottom.

[0038] In the internal space of the cylindrical body 2, a first cylindrical portion 71 and a plurality of second cylindrical portions 72 are arranged.

[0039] The first cylindrical portion 71 is arranged coaxially with the axis of the cylindrical body 2. There is only one first cylindrical portion 71. The internal space of the first cylindrical portion 71 is the first fuel flow path 61. The first cylindrical portion 71 has a first end and a second end. A first gas nozzle 41, which will be described later, is attached to the first end of the first cylindrical portion 71. The first cylindrical portion 71 extends in a direction parallel to the axis of the cylindrical body 2, penetrates the cylindrical body 2, and is pulled out to the outside. A first gas supply unit, not shown, is attached to the pulled-out second end of the first cylindrical portion 71. A fuel gas other than hydrogen gas is supplied to the first fuel flow path 61 from the first gas supply unit.

[0040] The multiple second cylindrical portions 72 are arranged side by side around the axis of the cylindrical body 2 so as to surround the first cylindrical portion 71. The internal space of each second cylindrical portion 72 is the second fuel flow path 62. Each second cylindrical portion 72 has a first end and a second end. A second gas nozzle 42, which will be described later, is attached to the first end of each second cylindrical portion 72. Each second cylindrical portion 72 extends in a direction parallel to the axis of the cylindrical body 2, penetrates the cylindrical body 2, and is drawn out to the outside. A second gas supply unit, not shown, is attached to the drawn-out second end of each second cylindrical portion 72. Hydrogen gas is supplied to each second fuel flow path 62 from the second gas supply unit.

[0041] The first cylindrical portion 71 and the multiple second cylindrical portions 72 make the air flow path 5, the first fuel flow path 61, and the second fuel flow path 62 independent of one another. Therefore, the air flowing through the air flow path 5, the fuel gas other than hydrogen gas flowing through the first fuel flow path 61, and the hydrogen gas flowing through the second fuel flow path 62 are sent separately to the combustion furnace 8. In a pre-mixing burner 1 in which air, a fuel gas other than hydrogen gas, and hydrogen gas are mixed in the combustion furnace 8, flashback is less likely to occur.

[0042] [First gas nozzle] The first gas nozzle 41 is provided at the tip of the first fuel flow path 61. There is one first gas nozzle 41. The first gas nozzle 41 has a plurality of fuel injection holes 410 for injecting a fuel gas other than hydrogen gas. The fuel gas other than hydrogen gas is, for example, liquefied natural gas or liquefied petroleum gas. The multiple fuel injection holes 410 are provided uniformly around the entire circumference of the tip of the first gas nozzle 41. Adjacent fuel injection holes 410 are provided with a certain amount of space between them. The number of fuel injection holes 410 and the space between adjacent fuel injection holes 410 can be selected as appropriate. The number of fuel injection holes 410 is, for example, 6 to 12.

[0043] The axes of the fuel injection holes 410 are inclined so as to move away from each other toward the tip of the first gas nozzle 41. In other words, the axes of the fuel injection holes 410 are inclined so that the distance from the axis of the cylindrical body 2 increases toward the tip of the first gas nozzle 41. When the axes of the fuel injection holes 410 are inclined, combustion oscillation is less likely to occur. When combustion oscillation is less likely to occur, the first flame 11 can be stably formed. The inclination angle of the axis of each of the fuel injection holes 410 with respect to the axis of the cylindrical body 2 is, for example, 80° or more and 100° or less. The inclination angle refers to the angle of the axis of each of the fuel injection holes 410 with respect to the axis of the cylindrical body 2 that is closest to the tip of the first gas nozzle 41. When the inclination angle is 80° or more, combustion oscillation is less likely to occur. When the inclination angle is 100° or less, the first flame 11 is more likely to be a divided flame and a thin film flame. Divided flames and thin film flames will be described later. The inclination angle of the axis of each of the plurality of fuel injection holes 410 relative to the axis of the cylindrical body 2 may be greater than or equal to 90° and less than or equal to 100°.

[0044] [Second gas nozzle] The second gas nozzle 42 is provided at the tip of each of the multiple second fuel flow paths 62. A plurality of second gas nozzles 42 are provided corresponding to the number of second fuel flow paths 62. Each of the multiple second gas nozzles 42 has a hydrogen injection hole 420 for injecting hydrogen gas. One hydrogen injection hole 420 is provided for each second gas nozzle 42. The number of second gas nozzles 42 is, for example, 5 to 8. The number of hydrogen injection holes 420 is the same as the number of second gas nozzles 42.

[0045] The number of hydrogen injection holes 420 is, for example, smaller than the number of fuel injection holes 410. When the number of hydrogen injection holes 420 is smaller than the number of fuel injection holes 410, it is easier to stably form the first flame 11. The number of hydrogen injection holes 420 may be greater than the number of fuel injection holes 410. When the number of hydrogen injection holes 420 is greater than the number of fuel injection holes 410, it is easier to shorten the length of the second flame 12. When the length of the flame including the second flame 12 is short, it is easier to downsize the combustion furnace 8. Furthermore, when the number of hydrogen injection holes 420 is greater than the number of fuel injection holes 410, the number of split flames divided by the second flame 12 is greater, and the amount of hydrogen in each split second flame 12 is reduced, making it easier to reduce the total amount of NOx emissions. The number of fuel injection holes 410 and the number of hydrogen injection holes 420 may be the same.

[0046] The axis of each of the multiple hydrogen injection holes 420 is, for example, parallel to the axis of the cylindrical body 2. When the axis of each of the multiple hydrogen injection holes 420 is parallel to the axis of the cylindrical body 2, the rapid combustion reaction between hydrogen gas and air can be reduced, thereby lowering the flame temperature. The axis of each of the multiple hydrogen injection holes 420 may be inclined so as to approach the axis of the cylindrical body 2 as it approaches the tip of the second gas nozzle 42.

[0047] The total opening area of ​​the multiple hydrogen injection holes 420 may be smaller than the total opening area of ​​the multiple fuel injection holes 410. 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 420, the faster the injection speed of hydrogen gas. When the total opening area of ​​the multiple hydrogen injection holes 420 is smaller than the total opening area of ​​the multiple fuel injection holes 410, the injection speed of hydrogen gas is more likely to be fast. A burner 1 with a fast injection speed of hydrogen gas is less likely to cause backfire.

[0048] The diameter of each of the multiple hydrogen injection holes 420 may be smaller than the diameter of each of the multiple fuel injection holes 410. If the diameter of each hydrogen injection hole 420 is smaller than the diameter of each fuel injection hole 410, the injection speed of hydrogen gas tends to be faster. A burner 1 with a high injection speed of hydrogen gas is less likely to cause flashback.

[0049] Among the multiple fuel injection holes 410, all of the fuel injection holes 410 may have the same diameter, or fuel injection holes 410 with different diameters may be included. Among the multiple hydrogen injection holes 420, all of the hydrogen injection holes 420 may have the same diameter, or hydrogen injection holes 420 with different diameters may be included.

[0050] The opening edge of each of the multiple fuel injection holes 410 may be located farther from the baffle plate 3 (described later) than the opening edge of the hydrogen injection hole 420. In other words, the opening edge of each of the multiple fuel injection holes 410 and the opening edge of each of the hydrogen injection holes 420 may be located at different positions in the direction along the axis of the cylindrical body 2. If the fuel injection hole 410 is located closer to the tip of the burner 1 than the hydrogen injection hole 420, it is easier to stably form the first flame 11. The opening edge of each of the multiple fuel injection holes 410 and the opening edge of the hydrogen injection hole 420 may be located at the same position in the direction along the axis of the cylindrical body 2.

[0051] [Baffle plate] The baffle plate 3 is provided at the tip of the air flow path 5. The baffle plate 3 is attached, for example, to the inner circumferential surface of the cylindrical body 2, the outer circumferential surface of the first cylindrical portion 71, and the outer circumferential surfaces of each of the multiple second cylindrical portions 72. The baffle plate 3 has multiple air ports 30 for injecting air from the air flow path 5. The multiple air ports 30 are arranged side by side on a circumference centered on the axis of the cylindrical body 2. At least one of the multiple air ports 30 is arranged between adjacent second gas nozzles 42. In this example, each air port 30 is formed by a notch provided on the outer circumferential edge of the baffle plate 3. In this example, the notch formed in the baffle plate 3 is positioned between the outer circumferential surface of the baffle plate 3 and the inner circumferential surface of the cylindrical body 2, so that the multiple air ports 30 are arranged side by side around the axis of the cylindrical body 2. The number of air ports 30 is, for example, the same as the number of fuel injection holes 410. The number of air ports 30 is, for example, 6 to 12. The shape of the air vent 30 is, for example, circular, elliptical, or polygonal.

[0052] The baffle plate 3 may have one or more holes (not shown) formed in the region between the first gas nozzle 41 and the second gas nozzle 42. These holes have a function of preventing vibration. If there are multiple holes, they may be provided dispersedly around the first gas nozzle 41. Dispersed holes mean that the multiple holes are not unevenly provided around the first gas nozzle 41 but are uniformly provided around the first gas nozzle 41. Adjacent holes are provided with a certain amount of space between them. The shape of the holes may be, for example, circular, elliptical, or polygonal.

[0053] The baffle plate 3 is provided slightly inward from the tip of the cylindrical body 2. Therefore, the first gas nozzle 41 and the plurality of second gas nozzles 42 are provided so as to protrude from the baffle plate 3. By providing the first gas nozzle 41 and the plurality of second gas nozzles 42 so as to protrude from the baffle plate 3, the first flame 11 can be stably formed.

[0054] [First Flame, Second Flame] The first flame 11 is formed by mixing and burning fuel gas injected from the multiple fuel injection holes 410 and air injected from each of the multiple air ports 30. Because each of the multiple fuel injection holes 410 is provided at an angle and multiple air ports 30 are provided around the first gas nozzle 41, the first flame 11 becomes a divided flame that is divided around the axis of the cylindrical body 2. The first flame 11 is stretched forward while spreading radially around the axis of the cylindrical body 2 by the air injected from each of the multiple air ports 30, becoming a bell-shaped thin film flame.

[0055] The second flame 12 is formed by mixing and burning hydrogen gas injected from the multiple hydrogen injection holes 420 and air injected from each of the multiple air ports 30. Because the multiple hydrogen injection holes 420 and the multiple air ports 30 are arranged side by side on a circumference centered on the axis of the cylindrical body 2, the second flame 12 becomes a divided flame and a thin film flame that are divided around the axis of the cylindrical body 2.

[0056] Compared to a flame that is not divided, a divided flame has a larger surface area, which increases the contact area between the flame and the combustion gas, cooling the flame and resulting in a lower flame temperature. Compared to a flame that is not divided, a thin film flame also has a larger surface area, which increases the contact area between the flame and the combustion gas, cooling the flame and resulting in a lower flame temperature. Lower flame temperatures can reduce NOx emissions.

[0057] The combustion gas 9 from each of the first flame 11 and the second flame 12 is drawn into the air injected from each of the plurality of air ports 30 due to the ejector effect of the air injected from each of the air ports 30, and is mixed with the air. By mixing the combustion gas 9 with the air, the oxygen concentration in the air decreases, combustion slows, and the flame temperature decreases. The lower flame temperature reduces NOx emissions. For ease of explanation, the combustion gas 9 is indicated by an arrow in FIG. 1.

[0058] The burner 1, which can make each of the first flame 11 and the second flame 12 a divided flame and a thin film flame and can reuse the combustion gas 9, can reduce NOx emissions even though it is a mixed combustion burner that burns hydrogen gas and a fuel gas other than hydrogen gas.

[0059] Combustion using hydrogen gas does not produce CO2 because hydrogen gas does not contain carbon. However, compared to fuel gases other than hydrogen gas, such as liquefied natural gas, hydrogen gas has characteristics such as a fast burning rate, a wide explosion limit, a small minimum ignition energy, and a high theoretical flame temperature. Due to these characteristics, hydrogen gas is more easily combusted and more likely to produce NOx than fuel gases other than hydrogen gas. As described above, the burner 1 of this embodiment can make each of the first flame 11 and the second flame 12 a split flame and a thin-film flame, and can reuse the combustion gas 9, thereby reducing NOx emissions and CO2 emissions.

[0060] [Test example] In the test example, a combustion experiment was carried out using four test specimens with different fuel gases using the burner 1 shown in Figure 1, and NOx emissions relative to the combustion load rate were investigated.

[0061] <Test specimen description> The four test specimens have the same burner structure. The fuels used are different. In test specimens 1 and 2, liquefied natural gas is injected from the first gas nozzle 41, and hydrogen gas is injected from the second gas nozzle 42. In test specimen 1, the ratio of the hydrogen injection amount to the total of the liquefied natural gas injection amount and the hydrogen gas injection amount is 30% by volume. In test specimen 2, the ratio of the hydrogen injection amount to the total of the liquefied natural gas injection amount and the hydrogen gas injection amount is 50% by volume. In test specimen 3, liquefied natural gas is injected from the first gas nozzle 41, and nothing is injected from the second gas nozzle 42. In test specimen 4, hydrogen gas is injected from the second gas nozzle 42, and nothing is injected from the first gas nozzle 41. In all test specimens, air is injected from the air port 30 of the baffle plate 3.

[0062] <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 a value assuming 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 results for test specimen 1 are shown with black circles, the results for test specimen 2 with white circles, the results for test specimen 3 with black squares, and the results for test specimen 4 with white triangles. In Figure 4, the target NOx value of 80 ppm is shown with a thick solid line.

[0063] As shown in Figure 4, Test Specimen 1 and Test Specimen 2, despite the co-combustion of hydrogen gas, achieved NOx values ​​below the target value of 80 ppm. The co-combustion of hydrogen gas in Test Specimen 1 and Test Specimen 2 also reduced CO2 emissions. Test Specimen 3 had the lowest NOx value, but because it used only liquefied natural gas as fuel, it emitted a large amount of CO2. When using liquefied natural gas and hydrogen gas as fuel gas, the first flame 11 and the second flame 12 could be formed by injecting liquefied natural gas from the center of the cylinder 2 and hydrogen gas from near the outer periphery of the cylinder 2, as in the burner 1 shown in Figure 1. When using liquefied natural gas and hydrogen gas as fuel gas, the first flame 11 and the second flame 12 could not be stably formed by injecting hydrogen gas from the center of the cylinder 2 and liquefied natural gas from near the outer periphery of the cylinder 2. [Explanation of symbols]

[0064] 1 Burner 11 First Flame 12 The Second Flame 2 cylinders 21 Anterior area 22 Posterior area 3 baffle plates 30 Air vent 41 First gas nozzle 410 Fuel injection hole 42 Second Gas Nozzle 420 Hydrogen injection hole 5 Air flow path 61 First fuel passage 62 Second fuel flow path 71 First cylinder part 72 Second cylinder part 8 Combustion furnace 9 Combustion Gas

Claims

1. A cylindrical body and a first fuel flow path disposed within the cylinder so as to include an axis of the cylinder; a plurality of second fuel flow paths arranged side by side on a circumference around the axis within the cylindrical body; an air flow path disposed within the cylindrical body so as to surround the first fuel flow path; a first gas nozzle provided at a tip end of the first fuel flow path; a plurality of second gas nozzles provided at the tip ends of the plurality of second fuel flow paths; a baffle plate provided at a tip end of the air flow path, the first gas nozzle includes a plurality of fuel injection holes for injecting a fuel gas other than hydrogen gas from the first fuel flow path, each of the plurality of second gas nozzles includes a hydrogen injection hole for injecting hydrogen gas from each of the plurality of second fuel flow paths; the baffle plate includes a plurality of air ports for injecting air from the air flow path; the first gas nozzle and the plurality of second gas nozzles are provided to protrude from the baffle plate, The plurality of air vents are arranged side by side on a circumference centered on the axis, the axes of the plurality of fuel injection holes are inclined so as to move away from each other toward the tip of the first gas nozzle; Burner.

2. 2. The burner according to claim 1, wherein at least one of said air ports is disposed between adjacent said second gas nozzles.

3. 3. The burner according to claim 1, wherein an inclination angle of the axis of each of the plurality of fuel injection holes with respect to the axis is equal to or greater than 80 degrees and equal to or less than 100 degrees.

4. 3. The burner according to claim 1 or claim 2, wherein the axis of each of the plurality of hydrogen injection holes is parallel to the axis of the cylinder.

5. 3. The burner according to claim 1, wherein the number of said plurality of hydrogen injection holes is smaller than the number of said plurality of fuel injection holes.

6. 3. The burner according to claim 1, wherein the number of said plurality of hydrogen injection holes is greater than the number of said plurality of fuel injection holes.

7. 3. The burner according to claim 1, wherein a total opening area of ​​said plurality of hydrogen injection holes is smaller than a total opening area of ​​said plurality of fuel injection holes.

8. 8. The burner of claim 7, 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.

9. 3. The burner according to claim 1, wherein an opening edge of each of the plurality of fuel injection holes is located farther from the baffle plate than an opening edge of the hydrogen injection hole.

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