Combustor, combustion system, and combustion method

Abstract

To provide a combustor, a combustion system, and a combustion method, capable of reducing the emission of unburnt fuel.SOLUTION: A combustor AA comprises a first combustion cylinder 10 with one end closed by a bottom 13, a second combustion cylinder 20 having an inner diameter larger than that of the first combustion cylinder 10 and connected to the first combustion cylinder 10, a first nozzle 41 ejecting first fuel from a first ejection port 16 formed in the side wall of the first combustion cylinder 10 in the direction of the bottom 13 along the inner peripheral face of the side wall, and a second nozzle ejecting second fuel from a second ejection port 26 formed in the side wall of the second combustion cylinder 20 in the direction along the inner peripheral face of the side wall. Since the swirling flow of the first fuel is reflected by the bottom 13, the residence time of the first fuel is increased, and a high-temperature reaction region can be formed in the central section of the combustion chamber. As a result, the combustion of the fuel is accelerated, and the emission of unburnt fuel can be reduced.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a combustor, a combustion system, and a combustion method. More specifically, the present invention relates to a combustor, a combustion system, and a combustion method for combusting a flame-retardant fuel such as ammonia.

Background Art

[0002] Against the backdrop of global warming, efforts are underway towards a decarbonized society. Among these, ammonia has attracted attention as a next-generation energy source because it does not emit carbon dioxide during combustion. However, ammonia is a flame-retardant fuel and is difficult to combust stably. Therefore, it has been proposed to use high-calorie city gas or the like as a combustion-supporting fuel.

[0003] In contrast, the inventor of the present application has proposed a combustor that improves the combustibility of fuel without using a high-calorie fuel gas (Patent Document 1). This combustor has a configuration in which a main ejection part is formed at the center of the bottom of the combustion chamber, and a swirling flow generation ejection part is formed on the side wall. The first fuel ejected from the main ejection part forms a main jet flow, and the second fuel ejected from the swirling flow generation ejection part forms a swirling flow. Since active chemical species and thermal energy required for combustion are supplied from the flame of the swirling flow to the main jet flow, the combustibility of the fuel is improved. Therefore, exclusive combustion of ammonia is possible.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the combustor disclosed in Patent Document 1 has a problem of a large amount of unburned ammonia emissions. Specifically, depending on the flow rates of the first fuel and the second fuel, the ammonia concentration in the space around the combustor becomes 1,000 to 2,500 ppm.

[0006] In view of the above circumstances, an object of the present invention is to provide a combustor, a combustion system, and a combustion method capable of reducing the emission amount of unburned fuel.

Means for Solving the Problems

[0007] The combustor of the first aspect includes a cylindrical first combustion cylinder having one end closed at the bottom and the other end open, a cylindrical second combustion cylinder having one end connected to the open end of the first combustion cylinder and having a larger inner diameter than the first combustion cylinder, a first nozzle that ejects a first fuel from a first ejection port formed in a first side wall of the first combustion cylinder in a direction along the inner peripheral surface of the first side wall toward the bottom, and a second nozzle that ejects a second fuel from a second ejection port formed in a second side wall of the second combustion cylinder in a direction along the inner peripheral surface of the second side wall. The combustor of the second aspect is characterized in that, in the first aspect, it further includes a throttle portion connected to the second combustion cylinder and having a flame port with an inner diameter of the open end smaller than the inner diameter of the second combustion cylinder. The combustor of the third aspect is characterized in that, in the first or second aspect, it includes a plurality of the first nozzles that eject the first fuel from each of a plurality of the first ejection ports formed side by side in the circumferential direction and / or in multiple stages in the axial direction of the first combustion cylinder. The combustor of the fourth aspect is characterized in that, in any one of the first to third aspects, it includes a plurality of the second nozzles that eject the second fuel from each of a plurality of the second ejection ports formed side by side in the circumferential direction and / or in multiple stages in the axial direction of the second combustion cylinder. The combustion system of the fifth aspect includes any one of the combustors of the first to fourth aspects, a non-combustible fuel supply source for supplying a non-combustible fuel, an air supply source for supplying air, and the first mixed fuel obtained by mixing the non-combustible fuel and the air is supplied to the first nozzle as the first fuel, and a fuel flow path for supplying the second mixed fuel obtained by mixing the non-combustible fuel and the air to the second nozzle as the second fuel, and the overall equivalence ratio of the first mixed fuel and the second mixed fuel is 1.0 to 1.2, the equivalence ratio of the first mixed fuel is greater than 1.0, and the equivalence ratio of the second mixed fuel is lower than the equivalence ratio of the first mixed fuel. And a flow rate control unit for controlling the flow rates of the non-combustible fuel and the air. The combustion system of the sixth aspect includes any one of the combustors of the first to fourth aspects, a non-combustible fuel supply source for supplying a non-combustible fuel, a combustion-supporting fuel supply source for supplying a combustion-supporting fuel, an air supply source for supplying air, and the first mixed fuel obtained by mixing the non-combustible fuel and the air is supplied to the first nozzle as the first fuel, and a fuel flow path for supplying the second mixed fuel obtained by mixing the combustion-supporting fuel and the air to the second nozzle as the second fuel, and the overall equivalence ratio of the first mixed fuel and the second mixed fuel is 1.0 to 1.2, the equivalence ratio of the first mixed fuel is 1.2 or more, and the equivalence ratio of the second mixed fuel is lower than the equivalence ratio of the first mixed fuel. And a flow rate control unit for controlling the flow rates of the non-combustible fuel, the combustion-supporting fuel, and the air. The combustion system of the seventh aspect is the sixth aspect, wherein the flow rate control unit controls the flow rates of the non-combustible fuel and the combustion-supporting fuel so that the ratio of the combustion-supporting fuel to the total fuel obtained by combining the non-combustible fuel and the combustion-supporting fuel is about 5 to 15% by volume. The combustion method of the eighth aspect is a combustion method using any one of the combustors of the first to fourth aspects, wherein a mixed fuel of a non-combustible fuel and air having an equivalence ratio greater than 1.0 is supplied to the first nozzle as the first fuel, and a mixed fuel of a non-combustible fuel and air having an equivalence ratio less than 1.0 is supplied to the second nozzle as the second fuel. The combustion method according to the ninth aspect is a combustion method using a combustor according to any one of the first to fourth aspects, wherein a mixed fuel of a hardly combustible fuel having an equivalence ratio of 1.3 or more and air is supplied as the first fuel to the first nozzle, and a mixed fuel of a combustion-supporting fuel having an equivalence ratio of 0.7 or less and air is supplied as the second fuel to the second nozzle. The combustion method according to the tenth aspect is characterized in that, in the ninth aspect, the ratio of the combustion-supporting fuel to the total fuel obtained by combining the hardly combustible fuel and the combustion-supporting fuel is about 5 to 15% by volume.

Advantages of the Invention

[0008] According to the first aspect, active chemical species can be supplied by the swirling flows of the first fuel and the second fuel. Further, since the swirling flow of the first fuel is reflected at the bottom, the residence time of the first fuel becomes longer, and a high-temperature reaction region can be generated at the central portion of the combustion chamber. As a result, the combustion of the fuel is promoted, and the discharge amount of unburned fuel can be reduced. According to the second aspect, the swirling radius of the fuel is reduced by the throttle portion, and the active chemical species are concentrated at the swirling center, so that the combustion stability is enhanced. According to the third aspect, by ejecting the first fuel from a plurality of first nozzles, the fuel supply amount to the combustor can be increased, and the combustion heat can be increased. According to the fourth aspect, by ejecting the second fuel from a plurality of second nozzles, the fuel supply amount to the combustor can be increased, and the combustion heat can be increased. According to the fifth aspect, by providing a difference in equivalence ratio between the first mixed fuel and the second mixed fuel, the discharge amount of unburned fuel can be reduced, and the discharge amount of nitrogen oxides can also be reduced. According to the sixth aspect, by using a mixed fuel of a combustion-supporting fuel and air as the second fuel, the discharge amount of unburned fuel can be further reduced, and the discharge amount of nitrogen oxides can be further reduced. According to the seventh aspect, since the ratio of the combustion-supporting fuel to the total fuel is small, the discharge amount of carbon dioxide can be reduced. According to the eighth aspect, by providing a difference in equivalence ratio between the first mixed fuel and the second mixed fuel, the discharge amount of unburned fuel can be reduced, and the discharge amount of nitrogen oxides can also be reduced. According to the ninth aspect, by using a mixed fuel of combustion-supporting fuel and air as the second fuel, the emission amount of unburned fuel can be further reduced, and the emission amount of nitrogen oxides can be further reduced. According to the tenth aspect, since the ratio of the combustion-supporting fuel to the total fuel is small, the emission amount of carbon dioxide can be reduced.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Embodiments for Carrying Out the Invention

[0010] Next, embodiments of the present invention will be described based on the drawings. 〔First Embodiment〕 (Combustor) As shown in FIG. 1, a combustor AA according to a first embodiment of the present invention includes a first combustion cylinder 10, a second combustion cylinder 20, and a throttle portion 30. The combustor AA also has a first nozzle 41 and a second nozzle 42 for supplying fuel therein.

[0011] As shown in FIG. 2, the first combustion cylinder 10 is a bottomed cylindrical member. The first combustion cylinder 10 has a first combustion chamber 11 inside. The cylindrical side wall of the first combustion cylinder 10 is referred to as a first side wall 12. One end (the lower end in FIG. 2) of the first combustion cylinder 10 is closed by a bottom 13, and the other end (the upper end in FIG. 2) is open. Both the first side wall 12 and the bottom 13 are composed of an outer shell 14 formed of a steel material or the like and a heat insulating material 15 covering the entire inside of the outer shell 14.

[0012] The second combustion cylinder 20 is a cylindrical member. The second combustion cylinder 20 has a second combustion chamber 21 inside. The cylindrical side wall of the second combustion cylinder 20 is referred to as a second side wall 22. Similar to the first side wall 12, the second side wall 22 is composed of an outer shell 24 formed of a steel material or the like and a heat insulating material 25 covering the entire inside of the outer shell 24. The outer shell 14 of the first combustion cylinder 10 and the outer shell 24 of the second combustion cylinder 20 may be an integral member. Similarly, the heat insulating material 15 of the first combustion cylinder 10 and the heat insulating material 25 of the second combustion cylinder 20 may be an integral member.

[0013] The first combustion cylinder 10 and the second combustion cylinder 20 are connected in a state where the central axis O coincides. More specifically, one end (the lower end in FIG. 2) of the second combustion cylinder 20 is connected to the open end (the upper end in FIG. 2) of the first combustion cylinder 10. Therefore, the first combustion chamber 11 and the second combustion chamber 21 are continuous spaces. The space combining the first combustion chamber 11 and the second combustion chamber 21 is referred to as the combustion chamber. Also, the inner diameter of the second combustion cylinder 20 is larger than the inner diameter of the first combustion cylinder 10. The inner peripheral surface of the first combustion cylinder 10 and the inner peripheral surface of the second combustion cylinder 20 are connected via an annular second bottom surface 23.

[0014] The throttle part 30 is a substantially plate-shaped member. The throttle part 30 is connected to the open end (the upper end in FIG. 2) of the second combustion cylinder 20. The throttle part 30 has a flame port 31 that penetrates through the front and back. The flame port 31 is an opening with a circular cross-section, and its center is arranged on the central axis O of the first combustion cylinder 10 and the second combustion cylinder 20. The throttle part 30 is composed of an outer shell 34 formed of steel material or the like and a heat insulating material 35 that covers the inner peripheral surface of the outer shell 34. The flame port 31 is formed in the heat insulating material 35.

[0015] The inner diameter of the open end (the opening on the upper surface side in FIG. 2) of the flame port 31 is smaller than the inner diameter of the second combustion cylinder 20. It is preferable that the flame port 31 is in a conical shape with a smaller inner diameter toward the open end, and the inner diameter of the connection end with the second combustion cylinder 20 (the opening on the lower surface side in FIG. 2) is equal to the inner diameter of the second combustion cylinder 20. In this case, the second combustion chamber 21 and the flame port 31 are connected without a step. Alternatively, the flame port 31 may be an opening with an equal inner diameter in the axial direction. In this case, the second combustion chamber 21 and the flame port 31 are connected in a stepped manner.

[0016] The combustor AA is connected to a device such as a boiler or a furnace with the throttle part 30. The thermal energy of the flame released from the flame port 31 is utilized by a device such as a boiler or a furnace.

[0017] Insertion holes for inserting the first nozzle 41 are formed in the first side wall 12 and the second side wall 22. One end of this insertion hole opens to the inner peripheral surface of the first side wall 12. This opening is referred to as the first jet outlet 16. The tip of the first nozzle 41 is disposed at the first jet outlet 16. The first fuel supplied to the first nozzle 41 is jetted from the first jet outlet 16 into the first combustion chamber 11.

[0018] As shown in FIG. 3, in a front view, the first nozzle 41 is disposed obliquely with respect to the central axis O of the combustor AA such that the jetting direction faces the bottom 13. Although not particularly limited, the angle θ of the first nozzle 41 with respect to the central axis O is preferably 30° to 75°. Further, as shown in FIG. 4, in a plan view, the jetting direction of the first nozzle 41 is orthogonal to the radial direction of the combustor AA. Therefore, the first fuel supplied to the first nozzle 41 is jetted along the inner peripheral surface of the first side wall 12 in a direction toward the bottom 13. Thereby, the first fuel forms a swirling flow that advances toward the bottom 13.

[0019] The number of the first nozzles 41 and the first jet outlets 16 may each be one or a plurality. The combustor AA of the present embodiment has two first nozzles 41, 41. Further, two first jet outlets 16, 16 are formed side by side in the circumferential direction in the first combustion cylinder 10. The tips of the first nozzles 41 are disposed at the respective two first jet outlets 16, 16. Therefore, the first fuel is jetted from each of the two first jet outlets 16, 16. When a plurality of first jet outlets 16 are formed in the first combustion cylinder 10, the plurality of first jet outlets 16 are preferably arranged at equal angular intervals in the circumferential direction of the first combustion cylinder 10.

[0020] Note that a plurality of first jet outlets 16 may be formed in multiple stages in the axial direction of the first combustion cylinder 10. In this case, the first combustion cylinder 10 may be lengthened in the axial direction. Further, the inner diameter of the first combustion cylinder 10 may be changed for each stage of the first jet outlet 16. In this case, it is preferable that the inner diameter becomes smaller as it is closer to the bottom 13. Also when the first jet outlets 16 are provided in multiple stages, the tips of the first nozzles 41 are disposed at the respective plurality of first jet outlets 16. Therefore, the first fuel is jetted from each of the plurality of first jet outlets 16.

[0021] As shown in FIG. 2, an insertion hole into which a second nozzle 42 (not shown in FIG. 2) is inserted is formed in the second side wall 22. One end of this insertion hole opens to the inner peripheral surface of the second side wall 22. This opening is referred to as a second ejection port 26. The second ejection port 26 is preferably disposed near the second bottom surface 23. The tip of the second nozzle 42 is disposed at the second ejection port 26. The second fuel supplied to the second nozzle 42 is ejected from the second ejection port 26 into the second combustion chamber 21.

[0022] As shown in FIG. 3, the second nozzle 42 is disposed in a plane orthogonal to the central axis O of the combustor AA. As shown in FIG. 4, the ejection direction of the second nozzle 42 is orthogonal to the radial direction of the combustor AA. Therefore, the second fuel supplied to the second nozzle 42 is ejected in a direction along the inner peripheral surface of the second side wall 22. Thereby, the second fuel forms a swirling flow.

[0023] The number of the second nozzles 42 and the second ejection ports 26 may each be one or a plurality. The combustor AA of the present embodiment has two second nozzles 42, 42. Further, two second ejection ports 26, 26 are formed side by side in the circumferential direction in the second combustion cylinder 20. The tips of the second nozzles 42 are disposed at the respective two second ejection ports 26, 26. Therefore, the second fuel is ejected from each of the two second ejection ports 26, 26. When a plurality of second ejection ports 26 are formed in the second combustion cylinder 20, the plurality of second ejection ports 26 are preferably arranged at equal angular intervals in the circumferential direction of the second combustion cylinder 20.

[0024] Note that a plurality of second ejection ports 26 may be formed in multiple stages in the axial direction of the second combustion cylinder 20. In this case, the second combustion cylinder 20 may be lengthened in the axial direction. Also, the inner diameter of the second combustion cylinder 20 may be changed for each stage of the second ejection port 26. In this case, it is preferable to reduce the inner diameter closer to the second bottom surface 23. Also in the case where the second ejection ports 26 are provided in multiple stages, the tips of the second nozzles 42 are disposed at the respective plurality of second ejection ports 26. Therefore, the second fuel is ejected from each of the plurality of second ejection ports 26.

[0025] Inside the combustor AA (combustion chamber), an igniter (not shown) for igniting the first fuel and the second fuel is arranged. As the igniter, a spark plug, a glow plug, etc. can be used. The arrangement of the igniter is not particularly limited, but for example, it is provided at the bottom 13.

[0026] When the first fuel and the second fuel are supplied to the combustor AA, the first fuel and the second fuel form a swirling flow. This swirling flow can supply active chemical species (OH radicals, H radicals, O radicals, etc.) necessary for combustion. As a result, the combustion stability is enhanced. Also, since the combustion reaction is made uniform in the first combustion chamber 11, the generation of nitrogen oxides can be suppressed. The swirling flow of the first fuel advances toward the bottom 13 in the first combustion chamber 11, then reflects at the bottom 13, and advances toward the second combustion chamber 21. In this way, since the first fuel reciprocates in the first combustion chamber 11, the residence time of the first fuel becomes longer. Thereby, a high-temperature reaction region can be generated at the central part of the combustion chamber. The second fuel swirls around the periphery of this high-temperature reaction region to supply surplus high-temperature air. As a result, the combustion of the fuel is promoted, and the discharge amount of unburned fuel can also be reduced. Further, since the throttle portion 30 narrows the swirling radius of the fuel, exhaust gases with different equivalence ratios concentrate on the swirling center. Thereby, while maintaining the combustion stability, the mixing is promoted and the exhaust gas purification is enhanced.

[0027] Since the combustor AA can stably burn a difficult-to-burn fuel, even if a large amount of the difficult-to-burn fuel is supplied, the combustion can be sustained. Therefore, high-load combustion can be realized. Here, high-load combustion means that the combustion heat per unit volume and per unit time is high.

[0028] The combustor AA of the present embodiment is characterized in that the swirling flow of the first fuel reciprocates in the first combustion chamber 11. From the viewpoint of increasing the streamline distance and residence time of the first fuel, the first jet outlet 16 is preferably arranged closer to the second combustion chamber 21 than the axial center of the first combustion chamber 11. Also, by adjusting the axial length of the first combustion chamber 11, the residence time of the first fuel can be adjusted. Note that the swirling direction of the first fuel and the swirling direction of the second fuel are preferably the same.

[0029] If a configuration is adopted in which the first fuel is ejected from a plurality of first nozzles 41, the fuel supply amount to the combustor AA can be increased, and the combustion heat can be increased. Similarly, if a configuration is adopted in which the second fuel is ejected from a plurality of second nozzles 42, the fuel supply amount to the combustor AA can be increased, and the combustion heat can be increased.

[0030] (Combustion system) Next, the combustion system BB according to the first embodiment of the present invention will be described. As shown in FIG. 5, the combustion system BB has a combustor AA. Further, the combustion system BB has a non-combustible fuel supply source 51. The non-combustible fuel supply source 51 supplies non-combustible fuel. Ammonia, biogas, etc. can be used as the non-combustible fuel. As the non-combustible fuel supply source 51, a gas cylinder for storing non-combustible fuel, a liquefied gas tank, etc. can be used. The combustion system BB has an air supply source 53. The air supply source 53 only needs to be able to supply air and is not particularly limited, but a compressor or the like can be used.

[0031] The combustion system BB has a fuel flow path 54 that connects the non-combustible fuel supply source 51 and the air supply source 53 to the combustor AA. The fuel flow path 54 mixes the non-combustible fuel supplied from the non-combustible fuel supply source 51 and the air supplied from the air supply source 53, and supplies the obtained mixed fuel to the combustor AA. The mixed fuel supplied to the first nozzle 41 of the combustor AA is referred to as the first mixed fuel. Also, the mixed fuel supplied to the second nozzle 42 is referred to as the second mixed fuel. The fuel flow path 54 supplies the first mixed fuel as the first fuel to the first nozzle 41 and supplies the second mixed fuel as the second fuel to the second nozzle 42.

[0032] A flow rate control unit 55 is provided in the fuel flow path 54. The flow rate control unit 55 is composed of a combination of a flow meter and a flow control valve. The flow rate control unit 55 controls the flow rates of the non-combustible fuel and air that are mixed as the first mixed fuel, respectively. By controlling the flow rates of the non-combustible fuel and air, the equivalence ratio and flow rate of the first mixed fuel can be controlled. Similarly, the flow rate control unit 55 controls the flow rates of the non-combustible fuel and air that are mixed as the second mixed fuel, respectively. By controlling the flow rates of the non-combustible fuel and air, the equivalence ratio and flow rate of the second mixed fuel can be controlled.

[0033] Here, the equivalence ratio is the reciprocal of the air-fuel ratio. The air-fuel ratio is an index representing how many times the theoretical amount of air is supplied in a fuel reaction. When the equivalence ratio is greater than 1, it means that the fuel is in an excessive state. When the equivalence ratio is less than 1, it means that the air is in an excessive state.

[0034] For example, the fuel reaction of ammonia is represented by the following formula (1). When air equivalent to 3 mol of oxygen is mixed with 4 mol of ammonia, the air-fuel ratio is 1 and the equivalence ratio is 1. When air equivalent to 6 mol of oxygen is mixed with 4 mol of ammonia, the air-fuel ratio is 2 and the equivalence ratio is 0.5. 4NH3 + 3O2 → 2N2 + 6H2O ···(1)

[0035] (Combustion Method) Next, the combustion method will be described. The first fuel is supplied to the first nozzle 41 of the combustor AA, and the second fuel is supplied to the second nozzle 42. If the fuel is ignited in this state, the fuel burns and a flame is emitted from the flame port 31.

[0036] The combustor AA of the present embodiment has high combustion stability, so combustion can be maintained even when a non-combustible fuel is used. If ammonia is used as the fuel, thermal energy can be obtained without discharging carbon dioxide. Moreover, with the combustor AA of the present embodiment, the discharge amount of unburned fuel can be reduced.

[0037] If the flow rates of the flame-retardant fuel and air are controlled by the flow control unit 55, the equivalence ratio of the first mixed fuel and the equivalence ratio of the second mixed fuel can be adjusted. For example, the equivalence ratio of the first mixed fuel may be set to 1.0, and the equivalence ratio of the second mixed fuel may also be set to 1.0. The flow rate of the first mixed fuel may be the same as, less than, or greater than the flow rate of the second mixed fuel. Even in this case, the flame-retardant fuel can be stably combusted. If ammonia is used as the fuel, exclusive combustion of ammonia can be realized.

[0038] While maintaining the overall equivalence ratio of the first mixed fuel and the second mixed fuel in the range of 1.0 to 1.2, the equivalence ratio of the first mixed fuel may be set to be greater than 1.0, and the equivalence ratio of the second mixed fuel may be set to be lower than the equivalence ratio of the first mixed fuel. That is, while maintaining the overall equivalence ratio in the range of 1.0 to 1.2, a mixed fuel of a flame-retardant fuel and air with an equivalence ratio greater than 1.0 is supplied as the first fuel to the first nozzle 41, and a mixed fuel of a flame-retardant fuel and air with an equivalence ratio lower than the equivalence ratio of the first mixed fuel is supplied as the second fuel to the second nozzle 42. In this way, by providing a difference in the equivalence ratio between the first mixed fuel and the second mixed fuel, the emission amount of unburned fuel can be reduced, and the emission amount of nitrogen oxides can also be reduced.

[0039] From the viewpoint of reducing the emission amount of unburned fuel while maintaining stable combustion, the overall equivalence ratio is preferably in the range of 1.0 to 1.2, and more preferably in the range of 1.0 to 1.1. From the viewpoint of suppressing both unburned fuel and nitrogen oxides, the equivalence ratio of the first mixed fuel is preferably greater than 1.0, more preferably 1.1 or more, and even more preferably 1.2 or more. Also, the equivalence ratio of the second mixed fuel is preferably 1.0 or less, more preferably 0.9 or less, and even more preferably 0.8 or less. Alternatively, the difference in the equivalence ratio between the first mixed fuel and the second mixed fuel is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.4 or more.

[0040] Since the combustor AA has a two-stage combustion chamber in which the first combustion chamber 11 and the second combustion chamber 21 are connected, lean combustion and ultra-lean combustion with a low equivalence ratio of the mixed fuel can be achieved in the second combustion chamber 21. Further, the combustor AA has a throttle portion 30. Since the throttle portion 20 reduces the turning radius of the fuel, the first mixed fuel and the second mixed fuel having different equivalence ratios concentrate on the turning center and their mixing is promoted. Therefore, unburned ammonia can be effectively suppressed.

[0041] 〔Second Embodiment〕 (Combustion System) Next, a combustion system CC according to a second embodiment of the present invention will be described. As shown in FIG. 6, the combustion system CC has a combustor AA. Further, the combustion system CC has an auxiliary fuel supply source 52 in addition to a refractory fuel supply source 51. The auxiliary fuel supply source 52 supplies auxiliary fuel. Methane, petroleum gas, ammonia off-gas (H2 / NH3 / N2 mixture), etc. can be used as the auxiliary fuel. A gas cylinder or the like for storing the auxiliary fuel can be used as the auxiliary fuel supply source 52. Further, the combustion system CC has an air supply source 53.

[0042] The combustion system CC has a fuel flow path 54 that connects the refractory fuel supply source 51, the auxiliary fuel supply source 52, the air supply source 53, and the combustor AA. The fuel flow path 54 mixes the refractory fuel supplied from the refractory fuel supply source 51 and the air supplied from the air supply source 53, and supplies the obtained first mixed fuel as the first fuel to the first nozzle 41. Further, the fuel flow path 54 mixes the auxiliary fuel supplied from the auxiliary fuel supply source 52 and the air supplied from the air supply source 53, and supplies the obtained second mixed fuel as the second fuel to the second nozzle 42.

[0043] A flow rate control unit 55 is provided in the fuel flow path 54. The flow rate control unit 55 controls the flow rates of the flame retardant fuel and air that are mixed as the first mixed fuel, respectively. By controlling the flow rates of the flame retardant fuel and air, the equivalence ratio and flow rate of the first mixed fuel can be controlled. Similarly, the flow rate control unit 55 controls the flow rates of the combustion-supporting fuel and air that are mixed as the second mixed fuel, respectively. By controlling the flow rates of the combustion-supporting fuel and air, the equivalence ratio and flow rate of the second mixed fuel can be controlled.

[0044] (Combustion method) Next, the combustion method will be described. The first mixed fuel is supplied to the first nozzle 41 of the combustor AA, and the second mixed fuel is supplied to the second nozzle 42. If the fuel is ignited in this state, the fuel burns and a flame is emitted from the flame port 31. In this embodiment, it is a co-combustion in which the flame retardant fuel and the combustion-supporting fuel are burned.

[0045] If the flow rates of the flame retardant fuel, the combustion-supporting fuel, and air are controlled by the flow rate control unit 55, the equivalence ratio of the first mixed fuel and the equivalence ratio of the second mixed fuel can be adjusted. Here, while maintaining the overall equivalence ratio in the range of 1.0 to 1.2, it is preferable that the equivalence ratio of the first mixed fuel is 1.2 or more, and the equivalence ratio of the second mixed fuel is lower than the equivalence ratio of the first mixed fuel. That is, while maintaining the overall equivalence ratio in the range of 1.0 to 1.2, a mixed fuel of the flame retardant fuel and air with an equivalence ratio of 1.2 or more is supplied as the first fuel to the first nozzle 41, and a mixed fuel of the combustion-supporting fuel and air with an equivalence ratio lower than the equivalence ratio of the first mixed fuel is supplied as the second fuel to the second nozzle 42. By doing so, the emission amount of unburned fuel can be further reduced, and the emission amount of nitrogen oxides can be further reduced. When ammonia is used as the flame retardant fuel and methane is used as the combustion-supporting fuel, the emission amount of unburned ammonia can be reduced, and the emission amount of nitrogen oxides can be reduced.

[0046] From the viewpoint of reducing the emission of unburned fuel while maintaining stable combustion, the overall equivalence ratio is preferably from 1.0 to 1.2, more preferably from 1.0 to 1.1. From the viewpoint of suppressing unburned fuel and nitrogen oxides, the equivalence ratio of the first mixed fuel is preferably 1.2 or more, more preferably 1.3 or more. Further, the equivalence ratio of the second mixed fuel is preferably 0.8 or less, more preferably 0.7 or less. That is, the combustion in the second combustion chamber 21 is made lean combustion or ultra-lean combustion. Such lean combustion can be realized by adopting a structure for swirling the second fuel. Alternatively, the difference in the equivalence ratios of the first mixed fuel and the second mixed fuel is preferably 0.4 or more, more preferably 0.6 or more. However, from the viewpoint of maintaining stable combustion, the equivalence ratio of the first mixed fuel is preferably 1.5 or less, and the equivalence ratio of the second mixed fuel is preferably 0.5 or more.

[0047] If the flow rates of the flame-retardant fuel and the combustion-supporting fuel are controlled by the flow rate control unit 55, the ratio of the combustion-supporting fuel to the total fuel obtained by combining the flame-retardant fuel and the combustion-supporting fuel can be adjusted. Here, the ratio of the combustion-supporting fuel to the total fuel is preferably 5 to 15% by volume. By reducing the ratio of the combustion-supporting fuel to the total fuel, the amount of carbon dioxide emissions can be reduced.

Example

[0048] (Streamlines of fuel) The flow of fuel inside the combustor was confirmed by computer simulation. Fig. 7 shows the streamlines of the fuel in the combustion chamber. As can be seen from Fig. 7, the first fuel forms a swirling flow that descends toward the bottom on the outer side of the first combustion chamber. This swirling flow is reflected at the bottom and becomes a swirling flow that rises through the center of the first combustion chamber and is supplied to the second combustion chamber. A swirling flow of the second fuel is formed outside the swirling flow of the first fuel that rises through the center of the second combustion chamber.

[0049] In this way, the first fuel forms a swirling flow that reciprocates in the first combustion chamber. From this, it can be confirmed that the residence time of the first fuel is long. Further, since active chemical species are continuously supplied from the swirling flow formed near the outer side of the combustion chamber to the center of the combustion chamber, it can be understood that the combustion of the flame-retardant fuel can be maintained.

[0050] (Stable fuel region) A mixed fuel of ammonia and air was supplied to the combustor having the configuration shown in FIG. 1 and burned. The equivalence ratio of both the first mixed fuel supplied to the first nozzle and the second mixed fuel supplied to the second nozzle is 1.0. While changing the flow rates of the first mixed fuel and the second mixed fuel, it was confirmed whether stable combustion was possible.

[0051] The results are shown in FIG. 8. The hatched region in FIG. 8 is the stable combustion region. As can be seen from FIG. 8, it was confirmed that ammonia-only combustion can be achieved in a wide range of the total flow rate of 10 to 120 L / min. Note that the maximum values of the horizontal axis and the vertical axis in FIG. 8 are 60 L / min, which is due to the performance limit of the fuel supply device. Ammonia-only combustion is also possible in a range of larger flow rates than this.

[0052] (Unburned ammonia concentration, nitrogen oxide concentration) A mixed fuel of ammonia and air was supplied to the combustor having the configuration shown in FIG. 1 and burned. The equivalence ratio of both the first mixed fuel supplied to the first nozzle and the second mixed fuel supplied to the second nozzle is 1.0. The flow rate of the second mixed fuel was set to 30 L / min. While changing the flow rate of the first mixed fuel, the ammonia concentration and the nitrogen oxide concentration in the space around the combustor were measured. The ammonia concentration and the nitrogen oxide concentration were measured with a laser absorption method exhaust gas measuring device (manufactured by Horiba, Ltd., MEXA-1400QL-NX).

[0053] FIG. 9(A) shows the relationship between the flow rate of the first mixed fuel and the unburned ammonia concentration. As can be seen from FIG. 9(A), the unburned ammonia concentration tends to increase as the flow rate of the first mixed fuel increases. However, it was confirmed that the unburned ammonia concentration can be reduced to 120 ppm or less even when the flow rate of the first mixed fuel is 50 L / min (the total flow rate of the first mixed fuel and the second mixed fuel is 80 L / min). This means that the unburned ammonia concentration can be suppressed to about 1 / 100 compared to the combustor disclosed in Patent Document 1.

[0054] Fig. 9(B) shows the relationship between the flow rate of the first mixed fuel and the nitrogen oxide concentration. As can be seen from Fig. 9(B), the nitrogen oxide concentration tends to increase as the flow rate of the first mixed fuel increases (as the total flow rate of the first mixed fuel and the second mixed fuel increases).

[0055] (Simulation of nitrogen oxide concentration) Next, the concentration of nitrogen monoxide (NO) in the combustion chamber was confirmed by computer simulation. Fig. 10(A) shows the NO concentration distribution when the equivalence ratios of the first mixed fuel and the second mixed fuel are both 1.0. The flow rates of the first mixed fuel and the second mixed fuel are both 60 L / min. As can be seen from Fig. 10(A), the NO concentration in the central region of the combustion chamber is 3,000 - 4,000 ppm.

[0056] Fig. 10(B) shows the NO concentration distribution when the equivalence ratio of the first mixed fuel is 1.3 and the equivalence ratio of the second mixed fuel is 0.7. The flow rates of the first mixed fuel and the second mixed fuel are both 60 L / min. As can be seen from Fig. 10(B), the NO concentration in the central region of the combustion chamber is suppressed to 1,000 - 1,500 ppm.

[0057] In both of the above two conditions, the overall equivalence ratio is 1.0 and the total flow rate is 120 L / min. However, by providing a difference between the equivalence ratio of the first mixed fuel and the equivalence ratio of the second mixed fuel, the generation of nitrogen oxides is suppressed. It was confirmed that the emission amount of nitrogen oxides can be reduced by setting the equivalence ratio of the first mixed fuel to be greater than 1.0 and the equivalence ratio of the second mixed fuel to be less than 1.0 as compared with the case where the equivalence ratios of the first mixed fuel and the second mixed fuel are both 1.0.

[0058] (Equivalence ratio actual test) A mixed fuel of ammonia and air was supplied to the combustor configured as shown in Fig. 1 and burned. While keeping the overall equivalence ratio at 1.0, the equivalence ratio of the first mixed fuel was varied in the range of 1.0 to 1.3, and the equivalence ratio of the second mixed fuel was varied in the range of 0.7 to 1.0. The flow rate of the first mixed fuel was 30 L / min, and the flow rate of the second mixed fuel was 30 L / min. At this time, the ammonia concentration and nitrogen oxide concentration in the space around the combustor were measured.

[0059] Fig. 11(A) shows the relationship between the equivalence ratio of the first mixed fuel and the unburned ammonia concentration. Fig. 11(B) shows the relationship between the equivalence ratio of the first mixed fuel and the nitrogen oxide concentration. As can be seen from Fig. 11(A) and Fig. 11(B), as the equivalence ratio of the first mixed fuel increases (as the equivalence ratio of the second mixed fuel decreases), both the unburned ammonia concentration and the nitrogen oxide concentration tend to decrease. In other words, the greater the difference in the equivalence ratios of the first mixed fuel and the second mixed fuel, the more the unburned ammonia concentration and the nitrogen oxide concentration can be reduced. When the equivalence ratio of the first mixed fuel was 1.3 and the equivalence ratio of the second mixed fuel was 0.7, the unburned ammonia concentration was 84 ppm, and the nitrogen oxide concentration (converted to O2 5%) was 945 ppm.

[0060] From the perspective of suppressing both unburned ammonia and nitrogen oxides, it can be said that the equivalence ratio of the first mixed fuel is preferably greater than 1.0, more preferably 1.1 or more, and even more preferably 1.2 or more. Also, the equivalence ratio of the second mixed fuel is preferably less than 1.0, more preferably 0.9 or less, and even more preferably 0.8 or less. Alternatively, the difference in the equivalence ratios of the first mixed fuel and the second mixed fuel is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.4 or more.

[0061] Note that from this test, it was confirmed that at least in the range where the equivalence ratio of the first mixed fuel is 1.0 to 1.3 and the equivalence ratio of the second mixed fuel is 1.0 to 0.7, both unburned ammonia and nitrogen oxides can be suppressed.

[0062] (Methane co-combustion) A combustion test was conducted using a combustor with the configuration shown in Fig. 1. A mixed fuel of ammonia and air was used as the first mixed fuel. A mixed fuel of methane (CH4) and air was used as the second mixed fuel. The total flow rate of the first mixed fuel and the second mixed fuel was set to 60 L / min, and the volume ratio of methane to ammonia was set to 10:90. That is, the proportion of methane in all the fuels was 10% by volume. While varying the air ratio of the second mixed fuel in the range of 1.5 to 2.0, the equivalence ratio of the first mixed fuel was adjusted so that the overall equivalence ratio became 1.0. Also, while varying the air ratio of the second mixed fuel in the range of 1.5 to 2.0, the equivalence ratio of the first mixed fuel was adjusted so that the overall equivalence ratio became 0.95. The nitrogen oxide concentration in the space around the combustor at this time was measured.

[0063] The results are shown in Fig. 12. As can be seen from Fig. 12, it was confirmed that the higher the air ratio of the second mixed fuel (the lower the equivalence ratio), the lower the nitrogen oxide concentration. When the overall equivalence ratio was 1.0, it was confirmed that the nitrogen oxide concentration could be suppressed to 620 to 960 ppm in the range where the air ratio of the second mixed fuel was 1.5 to 2.0 (equivalence ratio was 0.5 to 0.67).

[0064] (Comparison with exclusive ammonia combustion) A mixed fuel of ammonia and air was supplied to the combustor with the configuration shown in Fig. 1 and burned. The equivalence ratio of both the first mixed fuel supplied to the first nozzle and the second mixed fuel supplied to the second nozzle was 1.0. The flow rate of the second mixed fuel was set to 30 L / min. While changing the flow rate of the first mixed fuel, the ammonia concentration and the nitrogen oxide concentration in the space around the combustor were measured.

[0065] Next, a mixed fuel of ammonia and air was used as the first mixed fuel. A mixed fuel of methane (CH4) and air was used as the second mixed fuel. The air ratio of the second mixed fuel was set to 1.5 (equivalence ratio was 0.67), and the flow rate was set to 20 L / min. The equivalence ratio of the first mixed fuel was set to 1.4, and the flow rate was changed in the range of 40 to 80 L / min. The ammonia concentration and the nitrogen oxide concentration in the space around the combustor at this time were measured. Table 1 shows the overall equivalence ratio, the proportion of methane in all the fuels, the ammonia concentration, and the nitrogen oxide concentration.

[0066]

Table 1

[0067] Fig. 13(A) shows the relationship between the flow rate of the first mixed fuel and the concentration of unburned ammonia. Fig. 13(B) shows the relationship between the flow rate of the first mixed fuel and the concentration of nitrogen oxides. As can be seen from Fig. 13(A) and Fig. 13(B), compared with the case of ammonia-only combustion, co-combustion with the addition of methane can reduce both unburned ammonia and nitrogen oxides.

[0068] It was confirmed that the concentration of unburned ammonia can be suppressed to 0.7 to 3 ppm in the range where the flow rate of the first mixed fuel is 40 to 80 L / min.

Explanation of symbols

[0069] AA Combustor 10 First combustion cylinder 11 First combustion chamber 12 First side wall 13 Bottom 16 First jet outlet 20 Second combustion cylinder 21 Second combustion chamber 22 Second side wall 26 Second jet outlet 30 Throttle part 31 Flame outlet 41 First nozzle 42 Second nozzle

Claims

1. A cylindrical first combustion cylinder having one end closed at the bottom and the other end open, A cylindrical second combustion cylinder having one end connected to the open end of the first combustion cylinder and having an inner diameter larger than that of the first combustion cylinder, A first nozzle that injects first fuel from a first injection port formed in a first side wall of the first combustion cylinder in a direction along the inner peripheral surface of the first side wall and toward the bottom, A second nozzle that injects second fuel from a second injection port formed in a second side wall of the second combustion cylinder in a direction along the inner peripheral surface of the second side wall, and comprising A combustor characterized by this.

2. Further comprising a throttle portion connected to the second combustion cylinder and having a flame port with an inner diameter at the open end smaller than the inner diameter of the second combustion cylinder The combustor according to claim 1, characterized by this.

3. Comprising a plurality of the first nozzles that inject the first fuel from each of a plurality of the first injection ports formed side by side in the circumferential direction and / or in multiple stages in the axial direction of the first combustion cylinder The combustor according to claim 1, characterized by this.

4. Comprising a plurality of the second nozzles that inject the second fuel from each of a plurality of the second injection ports formed side by side in the circumferential direction and / or in multiple stages in the axial direction of the second combustion cylinder The combustor according to claim 1, characterized by this.

5. The combustor according to any one of claims 1 to 4, A non-flammable fuel supply source that supplies non-flammable fuel, An air supply source that supplies air, A fuel flow path that supplies a first mixed fuel obtained by mixing the non-flammable fuel and the air as the first fuel to the first nozzle, and supplies a second mixed fuel obtained by mixing the non-flammable fuel and the air as the second fuel to the second nozzle, A flow rate control unit that controls the flow rates of the non-flammable fuel and the air such that the overall equivalence ratio of the first mixed fuel and the second mixed fuel is 1.0 to 1.2, the equivalence ratio of the first mixed fuel exceeds 1.0, and the equivalence ratio of the second mixed fuel is lower than the equivalence ratio of the first mixed fuel, and comprising A combustion system characterized by this.

6. The combustor according to any one of claims 1 to 4, A non-flammable fuel supply source that supplies non-flammable fuel, An auxiliary fuel supply source that supplies auxiliary fuel, An air supply source that supplies air, A fuel flow path that supplies a first mixed fuel obtained by mixing the flame-retardant fuel and the air as the first fuel to the first nozzle, and supplies a second mixed fuel obtained by mixing the auxiliary combustion fuel and the air as the second fuel to the second nozzle, A flow rate control unit that controls the flow rates of the flame-retardant fuel, the auxiliary combustion fuel, and the air such that the overall equivalence ratio of the first mixed fuel and the second mixed fuel is 1.0 to 1.2, the equivalence ratio of the first mixed fuel is 1.2 or more, and the equivalence ratio of the second mixed fuel is lower than the equivalence ratio of the first mixed fuel. A combustion system characterized by this.

7. The flow rate control unit controls the flow rates of the flame-retardant fuel and the auxiliary combustion fuel such that the ratio of the auxiliary combustion fuel to the total fuel obtained by combining the flame-retardant fuel and the auxiliary combustion fuel is 5 to 15% by volume. The combustion system according to claim 6, characterized by this.

8. A combustion method using the combustor according to any one of claims 1 to 4, Supplying a mixed fuel of a flame-retardant fuel and air with an equivalence ratio exceeding 1.0 as the first fuel to the first nozzle, Supplying a mixed fuel of a flame-retardant fuel and air with an equivalence ratio lower than the equivalence ratio of the first mixed fuel as the second fuel to the second nozzle, The overall equivalence ratio of the first mixed fuel and the second mixed fuel is 1.0 to 1.2 A combustion method characterized by this.

9. A combustion method using the combustor according to any one of claims 1 to 4, Supplying a mixed fuel of a flame-retardant fuel and air with an equivalence ratio of 1.2 or more as the first fuel to the first nozzle, Supplying a mixed fuel of an auxiliary combustion fuel and air with an equivalence ratio lower than the equivalence ratio of the first mixed fuel as the second fuel to the second nozzle, The overall equivalence ratio of the first mixed fuel and the second mixed fuel is 1.0 to 1.2 A combustion method characterized by this.

10. The ratio of the auxiliary combustion fuel to the total fuel obtained by combining the flame-retardant fuel and the auxiliary combustion fuel is 5 to 15% by volume. The combustion method according to claim 9, characterized by this.

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