Ammonia and hydrogen co-combustion system for reducing combustion instability and exhuast gas emission

Abstract

The present invention relates to a combustion system using a carbon-free fuel such as hydrogen or ammonia, and more specifically, relates to an ammonia and hydrogen co-combustion system which improves the reactivity of ammonia and reduces nitrogen oxides in the exhaust gas after combustion.

Description

Ammonia and hydrogen co-firing system that mitigates combustion instability and exhaust emissions

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

[0002]

[0003] To effectively reduce carbon emissions during power generation, the expansion of renewable energy and the transition to clean energy are essential, and gas (gas turbine) power generation is attracting attention as a power source capable of resolving the intermittency issues of renewable energy. Unlike other power sources, gas turbines enable rapid startup and primarily handle the peak load of electricity demand; their share is growing to the point where they account for more than 30% of total power generation. Furthermore, utilizing surplus renewable energy to produce green hydrogen or ammonia and using these as fuel for gas turbines can not only enhance the utilization of idle power but also significantly contribute to reducing carbon emissions. Thus, gas turbines form a complementary relationship with renewable energy to overcome the instability of power supply caused by the intermittent nature of renewable energy. Additionally, the introduction of hydrogen / ammonia co-firing or full-firing technologies into gas turbines can further accelerate decarbonization in the power generation sector.

[0004] Ammonia is well known as a substance with excellent energy storage capabilities due to its characteristic of easily condensing under relatively low temperature and pressure conditions. Furthermore, because it contains a large amount of hydrogen within its fuel molecules, it is gaining attention as a medium for the economical storage and transportation of hydrogen. In addition, as a carbon-free fuel, ammonia can be used as a direct fuel for power generation, and its utility value is steadily increasing on the path toward the hydrogen economy.

[0005] However, ammonia flames have the disadvantage of very low reactivity and emit nitrogen oxides at levels tens to thousands of times higher than those of natural gas. To utilize ammonia as an eco-friendly, carbon-free fuel, it is necessary to effectively overcome the technical challenges associated with ammonia. Against this backdrop, despite active research on ammonia combustion recently, neither industry nor academia has been able to present a clear solution to these challenges. Therefore, there is a need for the development of carbon-free combustion technology that can dramatically increase the low reactivity of ammonia and maximize the reduction of harmful exhaust substances.

[0006]

[0007] The present invention was devised to solve the above-mentioned problems, and the objective of the present invention is to provide an ammonia and hydrogen co-combustion system, which is a carbon-free combustion technology capable of significantly increasing the low reactivity of ammonia and maximizing the reduction of harmful exhaust substances.

[0008]

[0009] A combustion system according to one embodiment of the present invention comprises: a combustion section formed in which a first fuel gas and a second fuel gas are supplied and combusted; and a fuel nozzle section connected to the upstream end of the combustion section, which supplies the first fuel gas to the combustion section through a plurality of first nozzles and supplies the second fuel gas to the combustion section through a plurality of second nozzles, wherein the fuel nozzle section has the first nozzles and the second nozzles separated from each other to independently control the flow rates of the first and second fuel gases, respectively.

[0010] In addition, the first fuel gas is either a mixture of ammonia and air or a mixture of hydrogen and air, and the second fuel gas is the other of a mixture of ammonia and air or a mixture of hydrogen and air.

[0011] Additionally, a dump section having the first and second nozzles formed therein is provided at the rear end of the fuel nozzle section, and the dump section is divided into an inner area formed at the radial center and an outer area formed on the radial outer perimeter of the inner area, wherein the first nozzle is disposed in the inner area and the second nozzle is disposed in the outer area.

[0012] In addition, a first fuel gas, which is a mixture of ammonia and air, is supplied to the first nozzle, and a second fuel gas, which is a mixture of hydrogen and air, is supplied to the second nozzle.

[0013] In addition, the first fuel gas is supplied to the first nozzle under a rich condition with an equivalent ratio of 1 or more, and the second fuel gas is supplied to the second nozzle under a lean condition with an equivalent ratio of less than 1.

[0014] Additionally, the combustion system further includes a sampling unit for collecting exhaust gas discharged from the combustion unit; and an analysis unit for analyzing the components of the exhaust gas collected through the sampling unit.

[0015] In addition, the combustion system further includes a control unit that controls the flow rate and equivalence ratio of the first and second fuel gases when the nitrogen oxide analyzed through the analysis unit is above a certain value.

[0016] In addition, the control unit detects the components of the exhaust gas in real time or at specific intervals and feeds back the hydrogen mole fraction or supply amount of the additional fuel gas.

[0017] Additionally, the fuel nozzle section comprises: a first housing for receiving the first fuel gas and delivering it to a plurality of first nozzles; a second housing for receiving the second fuel gas and delivering it to a plurality of second nozzles; a plurality of first transfer pipes each connecting a plurality of first outlets formed in the first housing to the plurality of first nozzles; and a plurality of second transfer pipes each connecting a plurality of second outlets formed in the second housing to the plurality of second nozzles.

[0018] Additionally, the first housing is formed in a cylindrical shape, with a first inlet formed at the front end for receiving the first fuel gas and a plurality of first outlets formed at the rear end for discharging the first fuel gas, and the second housing is formed in a ring shape and coupled so that the first housing penetrates through the center, with a second inlet formed on the side for receiving the second fuel gas and a plurality of second outlets formed at the rear end for discharging the second fuel gas.

[0019] In addition, a plurality of the first transfer pipes are spaced apart at the radial center of the first fuel nozzle section, and a plurality of the second transfer pipes are spaced apart at the radial outer circumference to surround the first transfer pipes.

[0020] In addition, the hydrogen flame produced by the second fuel gas injected from the second nozzle is configured to surround the ammonia flame produced by the first fuel gas injected from the first nozzle.

[0021] The ammonia and hydrogen co-firing combustion system of the present invention, configured as described above, has the effect of improving flame stability in an ammonia / hydrogen co-firing environment and preventing environmental pollution by minimizing the emission of nitrogen oxides.

[0022] Furthermore, while the formation of an ammonia / air flame under fuel-rich conditions inevitably leads to the generation of extremely high levels of unburned ammonia and hydrogen, the presence of an adjacent hydrogen flame allows for the re-ignition of ammonia and hydrogen, thereby enabling the securing of high combustion efficiency.

[0023] In addition, it naturally induces the breakdown of flame symmetry in the radial (width) direction of the combustion system, thereby having the effect of reducing combustion vibration.

[0024]

[0025] FIG. 1 is a side view of a combustion system according to an embodiment of the present invention.

[0026] FIG. 2 is a perspective view of a fuel nozzle portion according to an embodiment of the present invention.

[0027] FIG. 3 is a cross-sectional view of the front section showing the combustion gas flow path of the fuel nozzle section according to one embodiment of the present invention.

[0028] FIG. 4 is a rear view showing the dump portion of the fuel nozzle portion of the present invention.

[0029] Figures 5 and 6 are graphs showing the exhaust emission characteristics of an ammonia / hydrogen / air flame.

[0030] Figures 7 and 8 are graphs showing the internal / external ammonia co-firing rate and equivalent ratio according to experimental conditions.

[0031] Figure 9 is a graph showing the measurement results of combustion vibration and major emission concentrations according to experimental conditions.

[0032]

[0033] Hereinafter, an embodiment of the present invention as described above will be explained in detail with reference to the drawings.

[0034] FIG. 1 shows a side view of a combustion system (1000) according to one embodiment of the present invention.

[0035] As illustrated in FIG. 1, the combustion system (1000) may be configured to include a fuel nozzle section (100), a combustion section (200), a flame tube (300), a sampling section (500), and a gas analysis section (not shown). A combustion section (200) is formed at the rear end of the fuel nozzle section (100), and a flame tube (300) is provided at the rear end of the combustion section (200). The fuel nozzle section (100) and the combustion section (200) are formed independently and configured to be joined and sealed through room temperature curing (RTV) silicone. The combustion section (200) and the flame tube (300) are each formed independently and can be bolted together.

[0036] The fuel nozzle section (100) is configured to receive a first fuel gas (G1) and a second fuel gas (G2) and supply them to the combustion section (200), and the performance of the combustion system (1000) can be determined by the diameter of the rear section (120), and since the front section (110) has a manifold-shaped structure installed inside, the diameter of the front section (110) can be formed larger than the diameter of the rear section (120) for ease of processing.

[0037] A choked orifice (121) is provided on the front side of the rear end (120). The choked orifice (121) is formed in the shape of a cylindrical stainless steel block with a width of about 10 mm having three holes drilled in it and serves as an upstream acoustic boundary.

[0038] Additionally, a swirler (122) is provided on the rear end side of the rear end (120). The swirler (122) is composed of multiple vanes having a width of 10 mm and a swirl angle of 40 to 50 degrees. The swirler (122) can be configured to improve flame stability by applying a swirl to the flow of the first and second fuel gases (G1) (G2).

[0039] The combustion section (200) is located at the rear end of the fuel nozzle section (100) and is configured to receive and combust the first and second fuel gases (G1, G2) supplied through the fuel nozzle section (100). A combustion zone (201) is formed inside the combustion section (200), and the front end of the combustion zone (201) can be connected to the rear end of the fuel nozzle section (100).

[0040] The first and second fuel gases (G1, G2) flowing through the combustion section (200) are ignited and combusted through an igniter (175, see FIG. 4) provided at the rear end of the fuel nozzle section (100) to produce an ammonia flame and a hydrogen flame, respectively.

[0041] Thermal energy is generated through the ammonia and hydrogen flames generated in the combustion zone (201), and the combustion gas generated by the flames is supplied to a flame pipe (300) connected to the rear end of the combustion section (200) to exchange heat with cooling air or cooling fluid and then be cooled and discharged as exhaust gas (G3).

[0042] At this time, the fuel nozzle section (100) has the following configuration to independently supply the first fuel gas (G1) and the second fuel gas (G2) to the combustion chamber (200).

[0043]

[0044] FIG. 2 shows a perspective view of a fuel nozzle section (100) according to one embodiment of the present invention, and FIG. 3 shows a cross-sectional view of a shear section (110) showing the combustion gas flow path of the fuel nozzle section (100) according to one embodiment of the present invention.

[0045] Referring to FIGS. 2 and 3, it includes a plurality of first transfer pipes (130) for delivering a first fuel gas (G1) to a combustion chamber (200) and a plurality of second transfer pipes (140) for delivering a second fuel gas (G2) to a combustion chamber (200).

[0046] More specifically, the fuel nozzle section (100) is divided into a front section (110) and a rear section (120). The front section (110) may be formed in a combined form with a first housing (150) for delivering a first fuel gas (G1) to a plurality of first transfer pipes (130) and a second housing (160) for delivering a second fuel gas (G2) to a plurality of second transfer pipes (140). A first space (S10) is formed inside the first housing (150) to allow the first fuel gas (G1) to flow, and a first inlet (111) for receiving the first fuel gas (G1) is formed on the upstream side of the first space (S10), and a plurality of first outlets (115) connected to the first transfer pipes (130) are formed on the rear side. Additionally, a second space (S20) is formed inside the second housing (160) to allow the second fuel gas (G2) to flow, and a second inlet (112) is formed upstream of the second space (S20) to receive the second fuel gas (G2), and a plurality of second outlets (116) connected to the second transfer pipe (140) are formed at the rear end.

[0047] At this time, the first housing (150) is positioned at the radially inner center so that the first fuel gas (G1) flows radially inward and the second fuel gas (G2) flows radially outward, and the second housing (160) is formed in a ring shape and can be coupled so that the first housing (150) passes through the center. Accordingly, a plurality of first transfer pipes (130) each connected to the first outlets (115) of the first housing (150) can also be positioned at the radially center, and a plurality of second transfer pipes (140) each connected to the second outlets (116) of the second housing (160) can be positioned at the radially outer circumference to surround the first transfer pipes (130).

[0048] Injectors may be provided on the first and second transfer pipes to inject the first or second fuel gas into the combustion section.

[0049]

[0050] FIG. 4 shows a rear view of the dump section (170) of the fuel nozzle section (100) of the present invention.

[0051] Referring to FIGS. 1 and 4, a dump section (170) may be formed at the rear end of the fuel nozzle section (100) to inject the first and second fuel gases (G1) and (G2) into the combustion section (200). As described above, the fuel nozzle section (100) has the following configuration to independently supply the first fuel gas (G1) and the second fuel gas (G2) to the combustion chamber (200).

[0052] The dump unit (170) includes a plurality of first nozzles (171) connected to the rear end of the first transfer pipe (130) and a plurality of second nozzles (172) connected to the rear end of the second transfer pipe (140). Meanwhile, the dump unit (170) includes an inner area (A10) connected to the first inlet (111) and an outer area (A20) connected to the second inlet (112) and formed radially outside the inner area (A10) and partitioned from the inner area (A10). Accordingly, the first nozzles (171) can be placed on the inner area (A10), and the second nozzles (172) can be placed on the outer area (A20). Accordingly, the first fuel gas (G1) is configured to be injected independently into the combustion chamber (200) through the inner region (A10), and the second fuel gas (G2) is configured to be injected independently into the combustion chamber (200) through the outer region (A20).

[0053] A plurality of first nozzles (171) and second nozzles (172) may be spaced apart in the radial and circumferential directions as illustrated. Sixty first nozzles (171) and second nozzles (172) with a diameter of 6.5 mm may be arranged in four concentric circles, 16 first nozzles (171) may be placed at the radial center, and 44 second nozzles (172) may be placed at the radial outer side. That is, the first nozzles (171) may be placed in the inner area (A10) and the second nozzles (172) may be placed in the outer area (A20) to form multiple stages in the radial direction.

[0054] Accordingly, it is configured to independently control the flow rate or equivalence ratio of each of the first fuel gas (G1) and the second fuel gas (G2) supplied to the inner region (A10) and the outer region (A20).

[0055] Meanwhile, the first and second fuel gases (G1) and (G2) are injected independently, respectively, and the injection area is divided into an inner area (A10) and an outer area (A20), so that the flame of the first fuel gas (G1) injected through the inner area (A10) moves in a manner where it is enveloped by the flame of the second fuel gas (G2) injected through the outer area (A20).

[0056] In particular, the first fuel gas (G1) forming the inner flame is composed of a mixture of ammonia and air, and the second fuel gas (G2) forming the outer flame is composed of a mixture of hydrogen and air, thereby inducing the inner ammonia flame to be enveloped by the outer hydrogen flame, so as to maximize the stability of the ammonia flame.

[0057] Meanwhile, the first fuel gas (G1) may be an ammonia / air mixture doped with a small amount of hydrogen. For example, it may be a mixed fuel gas composed of 90% ammonia and 10% hydrogen by volume.

[0058] Another reason for supplying the first fuel gas (G1) and the second fuel gas (G2) independently to the combustion chamber to induce a flame is that combustion in a state where ammonia and hydrogen are separated is more advantageous than co-firing in terms of reducing nitrogen oxides.

[0059] Additionally, the first fuel gas (G1) can form an overly rich equivalent ratio condition higher than the stoichiometric ratio equivalent ratio 1, and the second fuel gas (G2) can form a lean equivalent ratio condition lower than the equivalent ratio 1. This is because burning ammonia under a fuel-overly rich condition is advantageous for reducing nitrogen oxide emissions, and burning hydrogen under a fuel-lean condition is advantageous for reducing nitrogen oxide emissions.

[0060] In addition, as illustrated in FIG. 1, a sampling unit (500) is provided at the front end of the flame tube (300) to collect a portion of the exhaust gas (G3). The sampling unit (500) may be a conventional sampling probe. The exhaust gas (G3) collected through the sampling unit (500) is transferred to an analysis unit (not shown) to analyze and measure the components of the gas. The analysis unit includes an analyzer and a nitrogen diluter. The analyzer receives the exhaust gas (G3) from the sampling unit and analyzes and measures the components of nitrogen oxides, hydrogen, ammonia, and oxygen. The analyzer may be, for example, an Ecom J2KN Pro device.

[0061] In addition, the exhaust gas (G3) delivered to the analyzer can be configured to supply nitrogen to the analyzer after diluting it through a nitrogen diluent.

[0062] The system is configured to provide feedback on the supply amount or equivalent ratio of each of the first and second fuel gases (G1, G2) that minimize nitrogen oxides through the component analysis of the exhaust gas (G3) as described above. For example, nitrogen oxides in the exhaust gas (G3) can be measured at a specific time or in real time, and if nitrogen oxides are detected above a certain level, the supply amount of each fuel gas or the equivalent ratio of each fuel gas can be adjusted to reduce nitrogen oxides.

[0063] Cooling air passages and cooling water passages may be formed on the flame tube (300) to cool the exhaust gas through heat exchange with the exhaust gas.

[0064]

[0065] Figure 5 shows a graph illustrating the nitrogen oxide emission characteristics of an ammonia / hydrogen / air flame according to the hydrogen co-firing ratio, and Figure 6 shows a graph illustrating the trend of the generation of major exhaust substances according to the equivalence ratio under fixed hydrogen co-firing ratio conditions.

[0066] As shown in FIG. 5, it can be seen that the nitrogen oxide reduction effect of a flame combusted in 100% hydrogen or 100% ammonia is more favorable than that of co-firing, and as shown in FIG. 6, it can be seen that when co-firing 90% ammonia and 10% hydrogen, combustion under fuel-rich conditions (equivalence ratio 1.4) can significantly reduce the amount of nitrogen oxides generated compared to fuel-lean conditions (equivalence ratio 0.6). Based on these exhaust emission characteristics of the ammonia / hydrogen / air flame, the combustion system of the present invention described above is provided.

[0067] Specifically, to evaluate the applicability of the proposed combustion technique under extreme nitrogen oxide emission conditions, a standard condition of 30 / 70 ammonia / hydrogen co-firing was selected. In the first combustion example, only the fuel flow of hydrogen and ammonia supplied to the inner and outer regions separated radially was adjusted to induce the formation of an ammonia flame in the inner region and a hydrogen flame in the outer region. It can be seen that this aligns with the direction of nitrogen oxide reduction in the calculation results presented in Fig. 5. In addition, the second combustion example was configured to control the air supply (flow) between the inner and outer regions while keeping the flow rates of hydrogen and ammonia supplied to each region constant, thereby forming an equivalence ratio condition that is richer than a specific equivalence ratio in the inner region and, conversely, inducing an equivalence ratio condition that is leaner than the specific equivalence ratio in the outer region. As shown in the results presented in Fig. 6, nitrogen oxides are drastically reduced in the ammonia flame formed in the inner region as the equivalence ratio increases, indicating a significant effect on nitrogen oxide reduction.

[0068] Meanwhile, as it has been confirmed through prior research that in the case of a hydrogen combustion flame in the outer region, nitrogen oxides of 5 ppm or less are generated in the lean region, the second embodiment is configured to further reduce nitrogen oxides in the exhaust gas.

[0069] To verify whether the proposed combustion technique operates normally even under extreme nitrogen oxide emission conditions, the total ammonia co-firing ratio was fixed at 30%, and the operating conditions of the tested conditions are illustrated in FIGS. 7 and 8. As shown in FIGS. 7 and 8, even though ammonia with significantly low reactivity was used directly in a hydrogen-based combustion system, the application of the technology of the present invention did not cause static instability such as lean airflow, and it can be seen that the flame was even stably maintained in a relatively narrow reaction zone.

[0070]

[0071] Figure 9a shows a graph representing the measurement results of pressure perturbation amplitude generated during combustion vibration, and Figure 9b shows a graph representing the measurement results of the concentration of major exhaust substances.

[0072] Referring to Fig. 9a, the X-axis represents the length of the combustor, the Y-axis represents each test condition, and the color of the contour graph represents the dynamic pressure amplitude.

[0073] To more specifically verify the effects of the staging technique according to the present invention, an experiment was conducted by dividing the staging into two sections.

[0074] High-amplitude combustion vibrations mainly occur when the length of the combustion chamber is long.

[0075] The first staging was fuel staging, in which the test was conducted by keeping the flow rate of air supplied to the inner / outer regions constant under UB conditions, while switching only the flow rates of hydrogen and ammonia supplied to the inner / outer regions. It was found that when the first staging technique is applied (UB->F3) based on the reference condition (UB), the amplitude of pressure perturbation is reduced to half the level. Therefore, combustion vibration can be reduced, and the control effect on major exhaust substances has been proven.

[0076] For the second staging, which was an air staging test, the flow rates of hydrogen and ammonia supplied to the inner and outer regions under F3 conditions were kept constant, while a portion of the air supplied to the inner region was diverted to the outer region. In the second staging technique, the effect on combustion vibration intensity was minimal, but the control effect on major exhaust substances was proven.

[0077]

[0078] Referring to Fig. 9b, the X-axis represents concentration, and the Y-axis represents each test condition. (Shared with the Y-axis of Fig. 9a)

[0079] When all proposed staging techniques are applied, it can be seen that nitrogen oxides are reduced by 96% (7764->310 ppm) compared to the baseline condition (UB), unburned ammonia is not generated, and the hydrogen concentration at the downstream end of the combustor drops sharply to the 130 ppm level (130 ppm is lower than the amount of hydrogen slip generated during full hydrogen combustion).

[0080]

[0081] 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 combustion section formed in which a first fuel gas and a second fuel gas are supplied and combusted; and It includes a fuel nozzle unit connected to the front end of the combustion unit, which supplies a first fuel gas to the combustion unit through a plurality of first nozzles and supplies a second fuel gas to the combustion unit through a plurality of second nozzles. The above fuel nozzle section is a combustion system in which the first nozzle and the second nozzle are separated from each other and independently control the flow rates of the first and second fuel gases, respectively.

2. In Paragraph 1, The above first fuel gas is, It is either a mixture of ammonia and air or a mixture of hydrogen and air, and The above second fuel gas is, A combustion system that is either a mixture of ammonia and air or a mixture of hydrogen and air.

3. In Paragraph 2, A dump section having the first and second nozzles formed therein is provided at the rear end of the fuel nozzle section above, and The above dump unit is, An inner region formed at the radial center, and It is divided into an outer region formed on the radial outer perimeter of the inner region mentioned above, and A combustion system in which the first nozzle is disposed in the inner region and the second nozzle is disposed in the outer region.

4. In Paragraph 3, A first fuel gas, which is a mixture of ammonia and air, is supplied to the first nozzle above, and A combustion system in which a second fuel gas, which is a mixture of hydrogen and air, is supplied to the second nozzle.

5. In Paragraph 4, The first fuel gas is supplied to the first nozzle under conditions of excessive richness with an equivalent ratio of 1 or more, and A combustion system in which the second fuel gas is supplied to a second nozzle under lean conditions with an equivalence ratio of less than 1.

6. In Paragraph 1, The above combustion system is, A sampling unit for collecting exhaust gas discharged from the 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 controls the flow rate and equivalence ratio of the first and second fuel gases when the nitrogen oxide analyzed through the analysis unit is above a certain value; A combustion system further including 8. In Paragraph 7, The above control unit is, A combustion system that detects the components of the exhaust gas in real time or at specific intervals and feeds back the hydrogen mole fraction or supply amount of additional fuel gas.

9. In Paragraph 1, The above fuel nozzle part is, A first housing for receiving the above-mentioned first fuel gas and delivering it to a plurality of first nozzles; A second housing for receiving the above-mentioned second fuel gas and delivering it to a plurality of second nozzles; A plurality of first transfer pipes each connecting a plurality of first discharge ports formed in the first housing and the plurality of first nozzles; and A plurality of second transfer pipes each connecting a plurality of second discharge ports formed in the second housing and the plurality of second nozzles; A combustion system including 10. In Paragraph 9, The first housing is cylindrical, and a first inlet is formed at the front end to receive the first fuel gas, and a plurality of first outlets are formed at the rear end to discharge the first fuel gas. The above-mentioned second housing is formed in a ring shape and is coupled so that the first housing penetrates through the center, and a second inlet is formed on the side to receive the second fuel gas, and a plurality of second outlets are formed at the rear end to discharge the second fuel gas, forming a combustion system.

11. In Paragraph 10, A plurality of the above-mentioned first transfer pipes are spaced apart from the radial center of the first fuel nozzle section, and A combustion system in which a plurality of the second transfer pipes are spaced apart around the radially outer circumference to surround the first transfer pipes.

12. In Paragraph 4, A combustion system configured such that a hydrogen flame produced by a second fuel gas injected from the second nozzle surrounds an ammonia flame produced by a first fuel gas injected from the first nozzle.

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