A burner for reducing nitrogen oxide emissions, and an air nozzle for this burner.
The burner design with perpendicular shut-off air supply in air nozzles enhances flow momentum to reduce nitrogen oxide emissions at partial loads, addressing the challenge of increased NOx levels in industrial burners.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- アンドリッツ·メタルズ·ジャーマニー·ゲゼルシャフト·ミト·ベシュレンクテル·ハフツング
- Filing Date
- 2024-03-12
- Publication Date
- 2026-06-22
AI Technical Summary
Industrial burners experience increased nitrogen oxide emissions when operated below nominal output, particularly when using hydrogen as a fuel, due to reduced flow momentum affecting chemical reaction kinetics.
A burner design with air nozzles featuring openings for supplying shut-off air perpendicular to combustion air, increasing flow velocity and momentum to reduce NOx emissions without mechanical alteration of the nozzle cross-section.
The design effectively reduces nitrogen oxide formation by enhancing flow momentum and dynamics of the flame, even at reduced burner outputs, thereby minimizing NOx emissions.
Smart Images
Figure 2026520114000001_ABST
Abstract
Description
Technical Field
[0001] An object of the present invention relates to a burner, particularly a flat-frame burner, which has a combustion gas nozzle for supplying a combustion gas, such as natural gas or hydrogen, and a plurality of air nozzles for supplying combustion air, which are arranged substantially in a ring shape around the combustion gas nozzle. It has.
[0002] An object of the present invention also relates to an air nozzle for this burner.
Background Art
[0003] Burners, particularly for industrial use, are often operated with natural gas. In that case, the necessary combustion air is usually supplied via a plurality of air nozzles arranged in a ring shape around the gas outlet. These burners are usually designed for a specific burner output, but they often need to be operated with a lower output.
[0004] When the operating method deviates from the design point, according to experience, the nitrogen oxide emission rate of industrial burners increases. When reducing the combustion output, there is usually a situation of excessive high emission of nitrogen oxides. This can be justified by the fact that as a result of the reduced mass flow rate, the flow momentum at the burner nozzle is reduced, which affects the kinetics of the chemical reactions in the flame.
[0005] Investigations have shown, for example, that the NOx value for an ANDRITZ natural gas burner with a nominal burner output of 300 kW increases by about 450% when this burner is operated with only 25% of the nominal burner output of this burner. In that case, the NOx concentration increases by approximately 70 ppm. This increase is considered insignificant with respect to the acceptable NOx concentration of less than 100 ppm. However, this situation becomes even more dangerous if the burner is powered by hydrogen. The use of hydrogen as a substitute for natural gas induces excessively high combustion temperatures, and consequently, excessively high NOx levels. This is because nitrogen oxide formation is accelerated by higher temperatures. Therefore, for example, the NOx concentration is already around 50 ppm at a nominal burner output of 300 kW, and rises to over 300% at 25% of the nominal burner output. Here, therefore, the NOx concentration is clearly above 150 ppm.
[0006] An object of the present invention is to provide a burner that has lower nitrogen oxide emissions when operated below the nominal burner output compared to more conventional burners.
[0007] The flow momentum of the nozzle is determined by the product of the mass flow rate and the flow outlet velocity. Accordingly, as the mass flow rate decreases, the flow momentum also decreases. When a conventional burner is operated at a lower output, not only the combustion gases but also the combustion air supplied through the air nozzle is reduced. Consequently, the flow momentum in the air nozzle is also reduced, and the NOx level increases. This loss can be compensated for by increasing the flow velocity of the combustion air.
[0008] This loss can be compensated for by increasing the flow velocity of the combustion air. [Overview of the Initiative] [Problems that the invention aims to solve]
[0009] Therefore, the fundamental problem of the present invention is to increase the flow velocity of combustion air during partial-load operation of the burner in order to reduce NOx emissions, without requiring any mechanical action on the nozzle cross-section. [Means for solving the problem]
[0010] This problem is solved by a burner according to claim 1, in particular a flat-flame burner. [Effects of the Invention]
[0011] According to the present invention, each of the burner's air nozzles within the nozzle wall portion on the side of the air nozzle has at least one opening. Through the opening, blocking air can be supplied to the combustion air. Therefore, the shut-off air is basically perpendicular to the combustion air.
[0012] The present invention relates to the concept of loading an air nozzle with shut-off air (pressurized air) to alter the gas flow characteristics before the burner.
[0013] The functional principle of the air nozzle according to the present invention, with an air load for shutoff, is specifically explained in Figure 2.
[0014] Advantageously, the opening within the nozzle wall on the side of the air nozzle is formed in a slit shape and extends at least around the perimeter of the nozzle wall. It is also possible to consider that the opening extends around the entire perimeter of the nozzle wall.
[0015] The air nozzle can have a circular, rectangular, or polygonal cross-section.
[0016] It is advantageous if the air nozzle tapers off just before the opening for supplying shut-off air, when viewed in the direction of combustion air flow. In that case, it is advantageous if the reduction angle at which the air nozzle tapers in front of the opening is between 20° and 50°.
[0017] It is advantageous if the opening in the nozzle wall is arranged within the region of the air nozzle at the position where it has the smallest free cross-section and thus the flow undergoes the greatest acceleration.
[0018] The invention likewise relates to an air nozzle for supplying combustion air for use in a burner, in particular a flat-frame burner. According to the invention, the air nozzle in the nozzle wall on the side of the air nozzle has one opening, through which shut-off air can be supplied to the combustion air, wherein the shut-off air hits the combustion air essentially perpendicularly, wherein the air nozzle tapers in front of the opening for the supply of the shut-off air, seen in the flow direction of the combustion air.
[0019] Hereinafter, embodiments of the invention will be described based on the drawings.
Brief Description of the Drawings
[0020] [Figure 1] This is a schematic cross-sectional view of a burner according to the invention, which is a flat-frame burner here. [Figure 2] This is a detailed view of the air nozzle of the burner of FIG. 1. [Figure 3] This is a view of the flat-frame burner according to the invention of FIG. 1. [Figure 4] This is a view of the functional mode of the air nozzle according to the invention. [Figure 5] This is a view of the functional mode of the air nozzle according to the invention. [Figure 6] This is a view of the geometric parameters of one embodiment of the air nozzle.
Modes for Carrying Out the Invention
[0021] Figure 1 shows a burner 1 according to the present invention in the form of a flat-frame burner. The combustion gas 4, for example, natural gas or hydrogen, is supplied to the combustion gas nozzle 2 via the combustion gas passage 11. The combustion gas nozzle 2 is surrounded by a plurality of air nozzles 3. Combustion air 10 is supplied to the air nozzle 3 via the combustion air supply unit 5 and the combustion air passage 8. Additionally, shut-off air 9 is supplied to the air nozzle 3 via the shut-off air supply unit 6 and the shut-off air passage 7. In this case, the shut-off air 9 is supplied to the combustion air 10 through the opening 12 in the nozzle wall portion 13.
[0022] Figure 2 shows the air nozzle from Figure 1 in detail. In that case, the opening 12 within the nozzle wall 13 is clearly recognizable. In this embodiment, this opening 12 is slit-shaped. The cross-section of the air nozzle 3 is basically square in this example, which can be clearly seen from Figure 3. Here, the slit-shaped opening 12 within the nozzle wall 13 is clearly recognized, and this opening extends parallel to the lateral edge of the nozzle wall 13, which is located on the inside (directed toward the combustion gas nozzle). The burner 1 shown here has 10 air nozzles 3, which are arranged in a ring shape around the combustion gas nozzle. Extensive testing revealed that the air nozzles 3 shown in Figure 2 provide particularly good results when certain geometric preconditions are met.
[0023] These air nozzles function particularly well when the following relationship holds: namely, 0.3 <X / Z<0.5
[0024] In this case, X is the distance from the outlet end 16 of the air nozzle 3 to the opening 12, and Z is the diameter of the air nozzle 3 at the outlet end 16.
[0025] In the example at hand, the air nozzle 3 similarly has a tapered section 15 just before the opening 12 for the shut-off air 9. The nozzle diameter, therefore, decreases toward the opening 12. The reduction angle C of the tapered portion 15 is, here, within the range of 20° or more. In the example at issue here, the air nozzle 3 is tapered only on the side to which the shut-off air 9 is supplied.
[0026] In Figures 4 and 5, the functional principle of the air nozzle 3 according to the present invention is explained. Figure 4 shows the flow behavior of the air nozzle 3 when the burner 1 is operated at its nominal combustion output. For this operating point, the burner 1 is typically designed and its flow behavior for the combustion air 10 is optimal. The supply of shut-off air 9 is not necessary here.
[0027] Figure 5 shows the operating state of the air nozzle 3 inside the burner 1, where the burner is operated at a burner output lower than the nominal burner output. At this time, shut-off air 9 is supplied to the air nozzle 3 through the opening 12. The opening 12 is positioned where the air nozzle 3 has the smallest free cross-section and where the airflow experiences the greatest acceleration.
[0028] In the example at hand, the air nozzle 3 has a circular cross-section, and the opening 12 within the nozzle wall 13 is ring-shaped. The combustion air 10 is pushed inward by the shut-off air 9, which in turn causes the combustion air to curve. The free cross-section for the combustion air 10 is thus reduced, the flow velocity is increased, and consequently, the flow momentum is also increased. Within the region where the combustion air 10 is pushed inward, vortices and negative pressure are generated, and this negative pressure draws in the ambient air 14 within the region of the outlet opening. This is schematically illustrated in Figure 5.
[0029] The shut-off air supply unit 6 can increase the flow momentum of the combustion air 10 in the burner 1, which is operated at a lower output than the nominal burner output, and consequently, the dynamics of the chemical reaction of the flame can be favorably influenced. This induces a reduction in the formation of nitrogen oxides.
[0030] In the embodiments shown in Figures 1 to 3, the shut-off air 9 is supplied from only one side of the nozzle wall 13. As a result, the flow of the combustion air 10 is compressed from one side.
[0031] In the embodiments shown in Figures 4 to 6, the opening 12 within the nozzle wall 13 has a ring-shaped gap. The flow of combustion air 10 is thus compressed from all sides. In all embodiments, the supply of shut-off air 9 effectively reduces the free cross-section of the air nozzle 3 and, accordingly, induces flow acceleration through the air nozzle 3.
[0032] In Figure 6, the air nozzle 3 having a ring-shaped opening 12, as shown in Figures 4 and 5, is illustrated along with its geometric parameters.
[0033] It was found that this air nozzle 3 functions particularly well if the following relationship holds: namely, 0.1 2 / A<0.32
[0034] In this case, B is the distance from the outlet end 16 of the air nozzle 3 to the opening 12, and A is the diameter of the air nozzle 3 at the outlet end 16. While this application relates to the invention described in the claims, it may also encompass the following other embodiments. 1. A burner (1), especially a flat-flame burner, wherein this burner is A combustion gas nozzle (2) for supplying combustion gas (4), for example, natural gas or hydrogen, Basically, multiple air nozzles (3) for supplying combustion air (10) are arranged around the combustion gas nozzle (2) in a ring shape, In the above-mentioned burner having, The air nozzle (3) has at least one opening (12) in each of its lateral nozzle wall portions (13), Through the opening, shut-off air (9) can be supplied to the combustion air (10), Therefore, the shut-off air (9) basically strikes perpendicularly to the combustion air (10). A burner characterized by (1). 2. The burner (1) according to claim 1 above, characterized in that the opening (12) in the nozzle wall portion (13) on the side of the air nozzle (3) is slit-shaped and extends at least around a portion of the nozzle wall portion (13). 3. The burner (1) according to paragraph 2, characterized in that the opening (12) extends around the entire perimeter of the nozzle wall portion (13). 4. The burner (1) according to any one of 1 to 3 above, characterized in that the air nozzle (3) has a circular cross-section. 5. The following relationship holds: that is, 0.3 <X / Z<0.5 In this case, X is the distance from the outlet end (16) of the air nozzle (3) to the opening (12), and Z is the diameter of the air nozzle (3) at the outlet end (16). The burner (1) described in item 4 above, characterized by the above. 6. The burner (1) according to any one of 1 to 3 above, characterized in that the air nozzle (3) has a polygonal shape, particularly a rectangular or square cross-section. 7. The following relationship holds: that is, 0.1<B 2 / A<0.32 In this case, B is the distance from the outlet end (16) of the air nozzle (3) to the opening (12), and A is the diameter of the air nozzle (3) at the outlet end (16). The burner (1) described in 6 above, characterized by the above. 8. The burner (1) according to any one of 1 to 7 above, characterized in that the air nozzle (3) tapers before the opening (12) for supplying shut-off air (9) when viewed in the direction of the flow of combustion air (10). 9. The burner (1) according to item 8 above, characterized in that the reduction angle (C) at which the air nozzle (3) tapers before reaching the opening (12) is between 20° and 50°. 10. The opening (12) within the nozzle wall (13) is within the region of the air nozzle (3), A burner (1) according to any one of 1 to 9 above, characterized in that it has the smallest free cross-section and is arranged accordingly. 11. In an air nozzle (3) for supplying combustion air (10) for use in a burner (1), particularly in a flat-flame burner, The air nozzle has at least one opening (12) within the nozzle wall portion (13) on the side of the air nozzle. Through the opening, shut-off air (9) can be supplied to the combustion air (10), Therefore, the shut-off air (9) basically strikes perpendicularly to the combustion air (10). An air nozzle (3) characterized by the following. 12. The air nozzle (3) according to 11, characterized in that the opening (12) in the lateral nozzle wall portion (13) of the air nozzle (3) is slit-shaped and extends at least around a portion of the nozzle wall portion (13). 13. The air nozzle (3) according to 12 above, characterized in that the opening (12) extends around the entire perimeter of the nozzle wall portion (13). 14. The air nozzle (3) according to any one of the above 11 to 13, characterized in that the air nozzle (3) has a circular cross-section. 15. The following relationship holds: that is, 0.3 <X / Z<0.5 In this case, X is the distance from the outlet end (16) of the air nozzle (3) to the opening (12), and Z is the diameter of the air nozzle (3) at the outlet end (16). The air nozzle (3) described in item 14 above, characterized by the above features. 16. The air nozzle (3) according to any one of the above 11 to 13, characterized in that the air nozzle (3) has a polygonal cross-section. 17. The following relationship holds: that is, 0.1<B 2 / A<0.32 In this case, B is the distance from the outlet end (16) of the air nozzle (3) to the opening (12), and A is the diameter of the air nozzle (3) at the outlet end (16). The air nozzle (3) described in 16 above, characterized by the features described above. 18. The air nozzle (3) according to any one of the above 11 to 17, characterized in that the air nozzle (3) tapers before the opening (12) for supplying shut-off air (9) when viewed in the direction of flow of combustion air (10). 19. The air nozzle (3) according to 18 above, characterized in that the reduction angle (C) at which the air nozzle (3) tapers before reaching the opening (12) is between 20° and 50°. 20. The opening (12) within the nozzle wall (13) is within the region of the air nozzle (3), An air nozzle (3) according to any one of the above 11 to 19, characterized in that it has the smallest free cross-section and is arranged accordingly. [Explanation of Symbols]
[0035] 1 burner 2 Combustion gas nozzle 3. Air nozzle 4. Combustion gases 5. Combustion air supply unit 6. Air supply unit for shutoff 7. Air passage for blocking 8 Combustion air passage 9. Air for blocking 10 Combustion air 11 Combustion gas passage 12 Opening for blocking air 13 Nozzle wall section 14 Ambient air 15. Tapered section 16. Outlet end of air nozzle
Claims
1. A burner (1), in particular a flat-flame burner, wherein this burner is A combustion gas nozzle (2) for supplying combustion gas (4), for example, natural gas or hydrogen, Basically, a plurality of air nozzles (3) for supplying combustion air (10) are arranged around the combustion gas nozzle (2) in a ring shape, In the above-mentioned burner having, The air nozzle (3) has at least one opening (12) in each of its lateral nozzle wall portions (13), Through the opening, shut-off air (9) can be supplied to the combustion air (10), Therefore, the shut-off air (9) basically strikes perpendicularly to the combustion air (10). A burner (1) characterized by the following:
2. The burner (1) according to claim 1, characterized in that the opening (12) in the nozzle wall portion (13) on the side of the air nozzle (3) is slit-shaped and extends at least around a portion of the nozzle wall portion (13).
3. The burner (1) according to claim 2, characterized in that the opening (12) extends around the entire perimeter of the nozzle wall portion (13).
4. The burner (1) according to any one of claims 1 to 3, characterized in that the air nozzle (3) has a circular cross-section.
5. The following relationship holds: that is, 0.3<X / Z<0.5 In this case, X is the distance from the outlet end (16) of the air nozzle (3) to the opening (12), and Z is the diameter of the air nozzle (3) at the outlet end (16). The burner (1) according to feature 4.
6. The burner (1) according to any one of claims 1 to 3, characterized in that the air nozzle (3) has a polygonal shape, particularly a rectangular or square cross-section.
7. The following relationship holds: that is, 0.1<B ２ / A<0.32 In this case, B is the distance from the outlet end (16) of the air nozzle (3) to the opening (12), and A is the diameter of the air nozzle (3) at the outlet end (16). The burner (1) according to feature 6.
8. The burner (1) according to any one of claims 1 to 7, characterized in that the air nozzle (3) tapers before the opening (12) for supplying shut-off air (9) when viewed in the direction of flow of combustion air (10).
9. The burner (1) according to claim 8, characterized in that the reduction angle (C) at which the air nozzle (3) tapers before reaching the opening (12) is between 20° and 50°.
10. The opening (12) within the nozzle wall portion (13) is within the region of the air nozzle (3), A burner (1) according to any one of 1 to 9, characterized in that it has the smallest free cross-section and is arranged accordingly.
11. In a burner (1), particularly in a flat-flame burner, an air nozzle (3) for supplying combustion air (10) is provided. The air nozzle has at least one opening (12) within the nozzle wall portion (13) on the side of the air nozzle. Through the opening, shut-off air (9) can be supplied to the combustion air (10), Therefore, the shut-off air (9) basically strikes perpendicularly to the combustion air (10). An air nozzle (3) characterized by the following:
12. The air nozzle (3) according to claim 11, characterized in that the opening (12) in the nozzle wall portion (13) on the side of the air nozzle (3) is slit-shaped and extends at least around a portion of the nozzle wall portion (13).
13. The air nozzle (3) according to claim 12, characterized in that the opening (12) extends around the entire perimeter of the nozzle wall portion (13).
14. The air nozzle (3) is characterized in that it has a circular cross-section, as described in any one of claims 11 to 13.
15. The following relationship holds: that is, 0.3<X / Z<0.5 In this case, X is the distance from the outlet end (16) of the air nozzle (3) to the opening (12), and Z is the diameter of the air nozzle (3) at the outlet end (16). The air nozzle (3) according to feature 14.
16. The air nozzle (3) is characterized in that it has a polygonal cross-section, as described in any one of claims 11 to 13.
17. The following relationship holds: that is, 0.1<B ２ / A<0.32 In this case, B is the distance from the outlet end (16) of the air nozzle (3) to the opening (12), and A is the diameter of the air nozzle (3) at the outlet end (16). The air nozzle (3) according to feature 16.
18. The air nozzle (3) according to any one of claims 11 to 17 is characterized in that, when viewed in the direction of flow of combustion air (10), it tapers before the opening (12) for supplying shut-off air (9).
19. The air nozzle (3) according to claim 18, characterized in that the reduction angle (C) at which the air nozzle (3) tapers before reaching the opening (12) is between 20° and 50°.
20. The opening (12) within the nozzle wall portion (13) is within the region of the air nozzle (3), The air nozzle (3) according to any one of 11 to 19, characterized in that it has the smallest free cross-section and is arranged accordingly.