Axial staging combustion system suppressing generation of nitrogen oxides in ammonia or hydrogen flame

Abstract

The present invention relates to a gas turbine using carbon-free fuel, such as hydrogen or ammonia and, more specifically, to an axial staging combustion system suppressing the generation of nitrogen oxides in ammonia or hydrogen flames, whereby nitrogen oxides in exhaust gas are reduced after combustion in the gas turbine.

Description

Axial staging combustion system that suppresses nitrogen oxide generation in ammonia or hydrogen flames

[0001] The present invention relates to a gas turbine using a carbon-free fuel such as hydrogen or ammonia, and more specifically, to an axial staging combustion system that suppresses the generation of nitrogen oxides in an ammonia or hydrogen flame and reduces nitrogen oxides in the exhaust gas after combustion of the gas turbine.

[0002]

[0003] As global warming caused by greenhouse gas emissions intensifies, gas turbine engines using hydrocarbon-based fuels are cited as a major cause of environmental problems. To address this, there is a need to convert existing gas turbine engines to carbon-free fuels such as hydrogen or ammonia.

[0004] In particular, ammonia is attracting attention as a next-generation gas turbine fuel because it has lower transportation and storage costs compared to hydrogen, can significantly reduce carbon dioxide emissions through production using renewable energy, and can serve as an effective hydrogen carrier by containing three hydrogen atoms in its molecule.

[0005] However, to apply ammonia to gas turbine systems, issues related to reactivity and exhaust emissions must be resolved in terms of combustion technology. In particular, since ammonia contains nitrogen in its fuel composition, it can generate large amounts of fuel-based nitrogen oxides (Fuel NOx), requiring the development of technologies to reduce them.

[0006]

[0007] The present invention has been devised to solve the aforementioned problems, and the objective of the present invention is to provide an axial staging combustion system that improves thermal efficiency by suppressing nitrogen oxides through fuel-rich combustion in the upstream region of the combustor and increasing the turbine inlet temperature by inducing additional combustion of unburned fuel in the downstream region.

[0008] In particular, the invention provides an axial staging combustion system that further reduces the amount of nitrogen oxides generated by injecting hydrogen / air into the secondary combustion chamber.

[0009]

[0010] A combustion system according to one embodiment of the present invention comprises: a first combustion section formed in which a first combustion region is formed by supplying a first fuel gas and performing first combustion; a second combustion section formed in which a second combustion region is formed, the front end of which is connected to the rear end of the first combustion section and the first combustion gas combusted in the first combustion section is supplied; and a second fuel gas supply section that supplies a second fuel gas to the second combustion region so as to be mixed with the first combustion gas and perform second combustion.

[0011] In addition, the first fuel gas comprises a mixture of ammonia and air, and the second fuel gas is composed of a mixture of hydrogen and air so as to cause spontaneous ignition when mixed with the high-temperature primary combustion gas.

[0012] In addition, the combustion system is further provided with a fuel nozzle section including a first dump section connected to the front end of the first combustion section and having a plurality of first nozzles formed to inject fuel gas into the primary combustion area.

[0013] In addition, the second fuel gas supply unit is connected to the front of the secondary combustion zone and includes a second dump unit having a plurality of second nozzles formed therein, and the number of the second nozzles is formed to be less than the number of the first nozzles.

[0014] In addition, the second dump section is connected to the side of the second combustion section so as to supply a second fuel gas to the second combustion area, and so that the second fuel gas is injected perpendicular to the flow direction of the first combustion gas.

[0015] Additionally, the combustion system further includes a sampling unit for collecting exhaust gas discharged from the second combustion unit; and an analysis unit for analyzing the components of the exhaust gas collected through the sampling unit.

[0016] Additionally, the combustion system further includes a control unit that calculates the supply amount of a second fuel gas or the hydrogen mole fraction at which the nitrogen oxide analyzed through the analysis unit is minimized.

[0017] In addition, the control unit calculates the distance between the front of the first combustion unit and the front of the second combustion unit at which the nitrogen oxide analyzed through the analysis unit is minimized.

[0018] In addition, the diameter of the first nozzle is 6.0 to 7.0 mm, and the diameter of the second nozzle is the same as the first nozzle.

[0019] In addition, the first fuel gas further includes hydrogen.

[0020]

[0021] The axial staging combustion system of the present invention, which suppresses the generation of nitrogen oxides in an ammonia or hydrogen flame according to the above configuration, has the effect of reducing environmental pollution by suppressing the generation of nitrogen oxides that may be included in the exhaust gas of a combustion system using ammonia or hydrogen as fuel.

[0022] In addition, by providing basic information on combustion conditions in the secondary region of an axial multi-stage combustion system, it has the effect of contributing to the activation of an ammonia combustion system.

[0023]

[0024] FIG. 1 is a side view of a combustion system according to an embodiment of the present invention.

[0025] FIG. 2 is a rear view showing the end of the fuel nozzle portion of the present invention.

[0026] FIG. 3 is a side view of the second combustion unit of the present invention.

[0027] FIG. 4 is a plan view of the end of the second nozzle portion of the second combustion portion of the present invention.

[0028] Figure 5 is a graph showing the results of exhaust gas component measurement during single combustion.

[0029] Figure 6 is a graph showing the results of exhaust gas component measurement during multi-stage combustion with additional air injection.

[0030] Figure 7 is a graph showing the results of exhaust gas component measurements during multi-stage combustion with additional injection of a premixed hydrogen / air mixture.

[0031]

[0032] Hereinafter, an embodiment of the present invention as described above will be explained in detail with reference to the drawings.

[0033] FIG. 1 shows a side view of a combustion system (1000) according to one embodiment of the present invention. FIG. 2 shows a rear view showing the end of a fuel nozzle section (100) of the present invention. In addition, FIG. 3 shows a side view of a second combustion section (300) of the present invention, and FIG. 4 shows a plan view of the end of a second dump section of the second combustion section (300) of the present invention.

[0034] As illustrated in FIG. 1, the combustion system (1000) may be configured to include a fuel nozzle section (100), a first combustion section (200), a second combustion section (300), a flame tube (400), a sampling section (500), and a gas analysis section (600). The fuel nozzle section (100) has a first inlet section (110) formed at the front end and a first dump section (120) formed at the rear end. The rear end of the fuel nozzle section (100) may be connected to the first combustion section (200). The fuel nozzle section (100) and the first combustion section (200) may be formed integrally or independently, and are configured to be joined and sealed through room temperature curing (RTV) silicone. Additionally, a second combustion section (300) is provided at the rear end of the first combustion section (200), and a flame tube (400) is provided at the rear end of the second combustion section (300). The second combustion section (300) and the flame tube (400) can each be formed independently and bolted together.

[0035] The fuel nozzle section (100) is configured to receive a first fuel gas (G1) through a first inlet section (110) and supply it to a first combustion section (200) through a first dump section (120). The first inlet section (110) and the first dump section (120) can be connected through a plurality of transfer pipes (150). Accordingly, a plurality of first nozzles (125) can be formed in the first dump section (120), with the rear ends of the plurality of transfer pipes (150) connected thereto.

[0036]

[0037] Referring to FIG. 2, a plurality of first nozzles (125) are formed in the first dump section (120) to be connected to each of the plurality of transfer pipes (150), and may be spaced apart in the radial and circumferential directions. The first dump section (120) has 60 first nozzles (125) with a diameter of 6.5 mm arranged at intervals of 15 mm. If the diameter of the first nozzle (125) exceeds 6.5 mm, there is a possibility that flashback may occur when fuel gas is combusted at a hydrogen fraction of or higher. In addition, if it is less than 6.5 mm, the flow velocity of the fuel gas increases rapidly, so under conditions of high ammonia fraction, the flame may not adhere to the first dump section (120) of the fuel nozzle section (100) and a scattering phenomenon may occur. The first fuel gas (G1) injected into the first combustion unit (200) through the first nozzle (125) is configured to be ignited and combusted through an igniter (121) provided in the first dump unit (120) to generate a flame.

[0038]

[0039] Referring again to FIG. 1, the first combustion section (200) is located at the rear end of the fuel nozzle section (100) and is configured to provide a space for primary combustion by receiving the first fuel gas (G1) injected through the first nozzle (125). Accordingly, a primary combustion zone (201) is formed inside the first combustion section (200), and the front end of the primary combustion zone (201) may be connected to the rear end of the first dump section (120) in which the first nozzles (125) are formed. Meanwhile, the first combustion gas (G1) may be a mixed gas in which ammonia, hydrogen, and air are premixed. Since the reactivity of ammonia fuel is very low, hydrogen, which is a highly reactive fuel, is partially added to increase the reactivity of the first combustion gas (G1).

[0040] The first fuel gas (G1) injected into the primary combustion area (201) of the first combustion unit (200) is ignited and combusted through an igniter (121) provided in the first dump unit (120) to generate a flame, and a primary combustion gas (G11) is generated by combustion. The primary combustion gas (G11) can be supplied to the second combustion unit (200) connected to the rear end of the first combustion unit (100).

[0041] The second combustion unit (300) has a secondary combustion zone (301) formed inside, and the secondary combustion zone (301) is configured to receive primary combustion gas (G11) generated from the first combustion unit (200) and additionally receive a second fuel gas (G2) to perform secondary combustion. The second combustion unit (300) can be positioned 400 mm behind the first combustion unit (200) from the front end. If it is less than 400 mm, the reaction residence time is reduced, and the efficiency of nitrogen oxide reduction in the downstream region may decrease. This is because, for ammonia flames, from a certain fuel-to-air ratio or higher, the degree of reaction between the ammonia reactor and nitrogen oxides in the downstream region increases, causing nitrogen oxides to decrease. In addition, if it exceeds 400 mm, the primary combustion area is excessively expanded, which may increase cost issues in terms of combustion unit shape design.

[0042]

[0043] Referring to FIG. 3, a second inlet (320) is formed at the front end of the second combustion section (300), and a second outlet (320) is formed at the rear end. The second inlet (3200) can be connected to and communicate with the first outlet (210) formed at the rear end of the first combustion unit (200). Accordingly, the primary combustion gas (G11) of the first combustion unit (200) is discharged through the first outlet (210) and supplied to the secondary combustion area (301) through the second inlet (320) of the second combustion unit (300). Meanwhile, the second combustion unit (300) may be equipped with a second fuel gas supply unit (350) for receiving the second fuel gas (G2). The second fuel gas supply unit (350) has a second fuel inlet (351) formed at the front end to receive the second fuel gas (G2), and a second dump unit (352) including a second nozzle (355) formed at the rear end to inject the second fuel gas (G2) into the secondary combustion area (301). The second dump section (352) is configured to be coupled to the front side of the second combustion section (300) so that the second fuel gas (G2) is injected perpendicularly to the primary combustion gas (G11) flowing along the longitudinal direction. When the second fuel gas (G2) is supplied in a direction perpendicular to the flow direction of the primary combustion gas (G11), a jet shear layer is formed between the main flow and the injection area of ​​the second fuel gas (G2), and there is an advantage in that the mixing efficiency can be improved as an additional recirculation area is created.

[0044]

[0045] Referring to FIG. 4, the second dump unit (352) includes a plurality of second nozzles (355), and the second nozzles (355) have a diameter of 6.5 mm, the same as the first nozzle (115) of the first combustion unit (200), and a total of 9 nozzles can be arranged in a grid pattern with a spacing of 9 mm. Accordingly, the second fuel gas (G2) can be injected into the secondary combustion area (301) through the plurality of second nozzles (355).

[0046] The second dump section (352) is a transition piece section that connects the first combustion section (200) and the second combustion section (300), and for the sake of flow optimization, structural advantages, and ease of maintenance, this section may be formed in a rectangular shape. Meanwhile, the reason the number of second nozzles (355) is less than that of the first nozzle (115) is related to the injection momentum ratio supplied from the second nozzle (355), and since the flow rate of the second fuel gas (G2) supplied in that area is generally significantly less than the flow rate of the first combustion gas (G11), the flow velocity may decrease when the number of nozzles is the same. If the flow velocity decreases, the injection momentum of the second nozzle (355) decreases, and mixing may not occur effectively during the process of reacting with the first combustion gas (G11).

[0047] The second fuel gas (G2) may consist of a mixture of hydrogen and air, and the second fuel gas (G2) injected into the secondary combustion zone (301) meets the high-temperature primary combustion gas (G11) and ignites spontaneously to produce exhaust gas (G3) with reduced nitrogen oxides through secondary combustion.

[0048] The exhaust gas (G3) generated in the secondary combustion zone (301) is supplied to a flame pipe (400) connected to the rear end of the second combustion section (300) through the second outlet (320), and a cooling air path and a cooling water path may be formed on the flame pipe (400) to cool the exhaust gas through heat exchange with the exhaust gas.

[0049]

[0050] Meanwhile, as illustrated in FIG. 1, a sampling unit (500) is provided at the front end of the flame tube (400) to collect a portion of the secondary combustion gas (G21). The sampling unit (500) may be a conventional sampling probe. The secondary combustion gas (G21) collected through the sampling unit (500) is transferred to an analysis unit (600) to analyze and measure the components of the gas. The analysis unit (600) may include a first analyzer (610) and a second analyzer (620). The first analyzer (610) receives the secondary combustion gas (G21) from the sampling unit (500) and analyzes and measures the components of nitrogen oxides, hydrogen, ammonia, and oxygen, and the second analyzer (620) receives the secondary combustion gas (G21) from the sampling unit (500) and analyzes and measures the components of nitrous oxide and oxygen. The first analyzer (610) may be, for example, Ecom’s J2KN Pro equipment, and the second analyzer (620) may be Gasmet DX4000.

[0051] Additionally, the secondary combustion gas (G21) delivered to the first analyzer (610) may be configured to supply the first analyzer (610) with nitrogen diluted through a nitrogen diluent (615).

[0052] In the case of the analyzer mentioned above, since there is a maximum measurement concentration for each specific chemical species, it is advisable to conduct the experiment with a lowered measurement concentration by diluting with nitrogen to prevent exceeding that range under specific experimental conditions. Accordingly, the true experimental value can be recalculated through a post-processing step after the experiment is completed.

[0053] It is configured to calculate the amount of second fuel gas that minimizes nitrogen oxides, the mixing ratio of hydrogen and air in the second fuel gas, and the optimal distance from the front of the first combustion section (200) to the second fuel gas supply section (350) through the component analysis of the second combustion gas (G21) as described above. If a chemical species is detected above a certain value, it can be configured to measure the concentration by adding or subtracting it using a nitrogen dilution device.

[0054]

[0055] The following are the experimental results for measuring the exhaust emission characteristics of a premixed ammonia / hydrogen flame using a multi-stage combustor, and the detailed experimental conditions are as follows.

[0056] To determine the primary combustion conditions suitable for multi-stage combustion, an experiment was first conducted under primary combustion conditions without multi-stage combustion. In this experiment, the primary combustion conditions were fixed at an ammonia / hydrogen mole fraction of 80% / 20% and an equivalence ratio of 1.25, and the temperature was set to 450 K under atmospheric pressure conditions.

[0057] Next, in the multi-stage combustion experiment, air was injected into the secondary reaction zone at 20% intervals from 20% to 80% based on the air flow rate of the primary zone, and the temperature was fixed at 450 K.

[0058] In addition, the experiment was conducted by fixing the hydrogen flow rate at 10 kW based on the heat input and adjusting the secondary equivalence ratio from 0.20 to 0.35 in increments of 0.05 for the injection of the premixed hydrogen / air mixture. The temperature of the secondary region was fixed at room temperature to maintain a similar momentum ratio. The combustor used in the experiment features a tunable combustor rig structure, which is used in the industry for combustor development. For exhaust gas analysis, nitrogen oxides, hydrogen, ammonia, and oxygen were measured using Ecom’s J2KN Pro instrument, while nitrous oxide and oxygen were measured using the Gasmet DX4000.

[0059]

[0060] Figure 5 shows a graph representing the results of measuring the components of the exhaust gas during single combustion.

[0061] As described above, in the case of single combustion using only the first combustion unit (200), it was confirmed that a high concentration of nitrogen oxides of approximately 3030 ppmvd was generated under an equivalence ratio of 1.05, and as the equivalence ratio increased, the concentration of nitrogen oxides gradually decreased, and it was confirmed that it decreased to a minimum of 57 ppmvd in the equivalence ratio range of 1.25. In addition, it was found that there was almost no generation of nitrous oxide under this condition. However, in this range, there was a problem in that a small amount of unburned ammonia was generated and a large amount of hydrogen was generated.

[0062]

[0063] Figure 6 shows a graph representing the results of measuring the components of exhaust gas during multi-stage combustion with additional air injection.

[0064] As described, in the multi-stage combustion method, when additional air is injected into the secondary combustion zone (301), the unburned ammonia reacts completely, and the hydrogen also tends to gradually decrease. At this time, the generation of nitrous oxide was hardly observed, similar to the single combustion conditions. However, it was confirmed that a large amount of nitrogen oxides, approximately 1000 to 1600 ppmvd, is generated through the secondary reaction. Through these results, it can be seen that while multi-stage combustion using air can increase combustion efficiency by reducing the amount of unburned ammonia and hydrogen generated, it shows low efficiency in terms of nitrogen oxide generation.

[0065]

[0066] FIG. 7 shows a graph representing the results of measuring the components of exhaust gas during multi-stage combustion with additional injection of a premixed hydrogen / air mixture. When air mixed with hydrogen is additionally injected into the secondary combustion zone (301), the unburned ammonia in the secondary combustion zone is completely reacted, and the hydrogen is reduced from 25,816 ppmvd to 70–140 ppmvd, and nitrous oxide is not significantly generated under these conditions. The most notable result from the above results is the nitrogen oxide concentration, which was confirmed to be approximately 360–400 ppmvd. Since this is about 64% lower than the minimum amount generated during multi-stage combustion using air, it was confirmed through these results that the multi-stage combustion technique using a premixed hydrogen / air mixture is a better alternative than air-based combustion for reducing nitrogen oxide generation.

[0067]

[0068] The technical concept of the present invention should not be interpreted as being limited to the embodiments described above. Not only is the scope of application diverse, but various modifications are possible at the level of a person skilled in the art without departing from the essence of the invention claimed in the claims. Therefore, such improvements and modifications fall within the scope of protection of the present invention insofar as they are obvious to a person skilled in the art.

Claims

1. A first combustion section formed in which a first combustion zone is formed by supplying a first fuel gas and performing primary combustion; A second combustion section having a front end connected to the rear end of the first combustion section and a secondary combustion region formed to which primary combustion gas combusted in the first combustion section is supplied; and A second fuel gas supply unit that supplies a second fuel gas to the secondary combustion zone so that it is mixed with the first combustion gas and subjected to secondary combustion; An axial staging combustion system including 2. In Paragraph 1, The above first fuel gas is, It contains a mixture of ammonia and air, The above second fuel gas is, An axial staging combustion system composed of a mixture of hydrogen and air to spontaneously ignite when mixed with high-temperature primary combustion gas.

3. In Paragraph 1, The above combustion system is, A fuel nozzle section including a first dump section connected to the front end of the first combustion section and having a plurality of first nozzles formed to inject fuel gas into the primary combustion region; An axial staging combustion system further equipped with 4. In Paragraph 3, The above second fuel gas supply unit is, It includes a second dump section connected to the front of the secondary combustion zone and having a plurality of second nozzles formed therein, An axial staging combustion system in which the number of the second nozzles is less than the number of the first nozzles.

5. In Paragraph 4, The above second dump unit is, An axial staging combustion system connected to the side of the second combustion section, wherein a second fuel gas is supplied to the second combustion zone, and the second fuel gas is injected perpendicular to the flow direction of the first combustion gas.

6. In Paragraph 1, The above combustion system is, A sampling unit for collecting exhaust gas discharged from the second combustion unit; and An axial staging combustion system further comprising an analysis unit for analyzing the components of exhaust gas collected through the above-mentioned sampling unit.

7. In Paragraph 6, The above combustion system is, A control unit that calculates the supply amount of a second fuel gas or the hydrogen mole fraction at which the nitrogen oxide analyzed through the above analysis unit is minimized; An axial staging combustion system further comprising 8. In Paragraph 7, The above control unit is, An axial staging combustion system that calculates the distance between the front of the first combustion section and the front of the second combustion section, wherein the nitrogen oxide analyzed through the analysis section is minimized.

9. In Paragraph 4, An axial staging combustion system characterized in that the diameter of the first nozzle is 6.0 to 7.0 mm and the diameter of the second nozzle is the same as the first nozzle.

10. In Paragraph 2, The above first fuel gas is, An axial staging combustion system containing additional hydrogen.

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