JP2024168313A - Burners and furnaces - Google Patents

Abstract

To achieve both of stable combustion and suppression of NOx emission amount in a burner for burning ammonia.SOLUTION: A burner includes a first nozzle having a main fuel outlet for injecting a fluid mixture of main fuel and primary air, a second nozzle for blowing out secondary air from a secondary air outlet surrounding the main fuel outlet, a flame holding plate which generates a flame holding vortex at the downstream of a peripheral edge of the main fuel outlet, a third nozzle for blowing out a swirl flow of tertiary air from a tertiary air outlet surrounding the secondary air outlet, and a first auxiliary fuel nozzle for injecting first gas fuel containing ammonia from a first auxiliary fuel outlet arranged in the main fuel outlet. During combustion, a circulation flow is generated which includes a forward flow portion in which fluid flows in a direction separating from the main fuel outlet along an inner edge of the flame holding vortex, a backflow portion in which the fluid flows in a direction approaching the main fuel outlet on a burner axis, and a conversion portion from the backflow portion to the forward flow portion. The first auxiliary fuel nozzle injects the first gas fuel to the forward flow portion or the conversion portion of the circulation flow along the flow of the circulation flow.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a burner that burns a gas fuel containing ammonia and a combustion furnace equipped with the burner.

In light of the trend toward reducing carbon dioxide (CO ₂ ) emissions, ammonia (NH ₃ ) has been attracting attention as a fuel that does not emit carbon dioxide when burned. Problems with using ammonia as fuel include its slow burning speed and low flame temperature compared to methane, the main component of city gas, making it difficult to burn and stably, and its high N content that tends to increase NOx emissions. Therefore, as disclosed in Patent Document 1, technology is being developed to suppress NOx emissions in burners that use ammonia as fuel.

The burner in Patent Document 1 includes a fuel supply nozzle that sprays a mixture of solid fuel such as pulverized coal and a carrier gas for the solid fuel, an air nozzle that is arranged outside the fuel supply nozzle and separates and sprays combustion air from the mixture toward the outer periphery, and an ammonia supply nozzle that sprays ammonia gas from downstream of the outlet of the fuel supply nozzle. The ammonia supply nozzle is passed through the air nozzle, and an ammonia outlet is arranged at the air outlet of the air nozzle. The ammonia supply nozzle supplies ammonia gas toward a high-temperature reduction region immediately downstream of the outlet of the fuel supply nozzle, where oxygen has been consumed by the combustion of the fuel and the oxygen concentration has become low. By burning ammonia in the high-temperature reduction region, NOx produced by the combustion is converted into nitrogen by a reduction reaction, thereby suppressing NOx emissions.

JP 2019-203631 A

In the burner of Patent Document 1, a flame-holding vortex is generated between the flow of the mixed fluid and the flow of the combustion air. In addition, a circulating flow is generated in the high-temperature reduction region on the inner circumference of the flame-holding vortex. In ammonia combustion, where it is difficult to stabilize the flame, it is important to protect the flame-holding vortex and the circulating flow in order to maintain the flame. In the burner of Patent Document 1, the flow of ammonia gas emitted from the ammonia supply nozzle passes through the flame-holding vortex and the flow of the mixed fluid toward the high-temperature reduction region. Therefore, if the flow rate of ammonia gas is low, there is a concern that the ammonia gas will be blocked by the flame-holding vortex or the flow of the mixed fluid and will not be able to reach the mixed reduction region. In addition, if the flow rate of ammonia gas is high, there is a concern that the flame-holding vortex and the circulating flow will be disturbed, making it impossible to maintain the flame and causing unstable combustion.

This disclosure has been made in consideration of the above circumstances, and its purpose is to provide a technology that achieves both stable combustion and reduced NOx emissions in a burner that burns ammonia.

In order to solve the above problems, a burner according to one aspect of the present disclosure includes:
A first nozzle having a cylindrical shape centered on a burner axis and having a main fuel outlet for ejecting a mixed fluid of a main fuel and primary air;
a second nozzle having a secondary air outlet surrounding the main fuel outlet and blowing out secondary air from the secondary air outlet;
a flame-holding plate for generating a flame-holding vortex downstream of a periphery of the main fuel outlet;
a third nozzle having a tertiary air outlet surrounding the secondary air outlet and blowing out a swirling flow of tertiary air from the tertiary air outlet;
a first auxiliary fuel nozzle having a first auxiliary fuel outlet arranged in the main fuel outlet and configured to eject a first gas fuel containing ammonia from the first auxiliary fuel outlet;
During combustion, the action of the tertiary air creates a circulating flow that includes a forward flow section in which the fluid flows away from the main fuel outlet along the inner edge of the flame-holding vortex, a reverse flow section in which the fluid flows along the burner axis in a direction toward the main fuel outlet, and a transition section from the reverse flow section to the forward flow section, and the first auxiliary fuel nozzle injects the first gas fuel along the flow of the circulating flow into the forward flow section or the transition section.

In addition, a combustion furnace according to one aspect of the present disclosure includes a combustion chamber and the burner disposed on a wall of the combustion chamber.

This disclosure provides a technology that achieves both stable combustion and reduced NOx emissions in a burner that burns ammonia.

FIG. 1 is a diagram showing a schematic configuration of a boiler equipped with a burner according to an embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view of a burner according to the present disclosure. FIG. 3 is an enlarged cross-sectional view of the outlet of the burner shown in FIG. FIG. 4 is a view of the burner outlet as viewed from the front in the axial direction of the burner. FIG. 5 is a view of the outlet of a burner according to a modified example, seen from the front in the axial direction of the burner.

Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. First, the schematic configuration of a boiler 10 equipped with a burner 5 according to one embodiment of the present disclosure will be described.

<<Overall configuration of boiler 10>>
Fig. 1 is a diagram showing a schematic configuration of a boiler 10 including a burner 5 according to an embodiment of the present disclosure. The boiler 10 shown in Fig. 1 includes a combustion furnace 2 for burning fuel and a boiler body 40 for generating steam by utilizing the combustion heat of the combustion furnace 2. The boiler 10 is a pulverized coal-fired thermal boiler, and uses a powdered or granular fossil fuel (i.e., solid fuel) as a main fuel. However, the boiler to which the burner 5 according to the present disclosure is applied is not limited to a pulverized coal-fired boiler, and may be a mixed combustion boiler using pulverized coal and biomass as a main fuel, a petroleum residue-fired boiler using petroleum residue as a main fuel, or the like.

The combustion furnace 2 has a vertical combustion chamber 20 inside. The combustion furnace 2 according to this embodiment is an inverted vertical furnace, in which a high-temperature reduction zone 21 is formed in the upper part of the combustion chamber 20, a low-temperature oxidation zone 22 is formed in the lower part of the combustion chamber 20, and a constriction section 23 is provided between the high-temperature reduction zone 21 and the low-temperature oxidation zone 22. However, the combustion furnace 2 may also be a vertical furnace in which the high-temperature reduction zone 21 is formed in the lower part of the combustion chamber 20, and the low-temperature oxidation zone 22 is formed in the upper part of the combustion chamber 20.

The portion of the inner wall of the combustion furnace 2 that forms the high-temperature reduction zone 21 is covered with a refractory material 25. At least one burner stage is provided in the furnace wall of the high-temperature reduction zone 21 of the combustion furnace 2 in the vertical direction, and each burner stage is formed by a plurality of burners 5 arranged in the horizontal direction. Each burner 5 blows fuel and air for first-stage combustion into the high-temperature reduction zone 21 to generate a flame. The outlet of the high-temperature reduction zone 21 is connected to the inlet of the low-temperature oxidation zone 22 via a constriction section 23.

The furnace wall of the low-temperature oxidation zone 22 of the combustion furnace 2 is provided with multiple air nozzles 26. Air for second-stage combustion is blown from each air nozzle 26 into the low-temperature oxidation zone 22. The cooling section 24 is located between the constriction section 23 and the multiple air nozzles 26 in the low-temperature oxidation zone 22, and the furnace wall of the cooling section 24 is a water-cooled wall with water pipes of the boiler body 40 running around it. The outlet 11 of the low-temperature oxidation zone 22 is connected to the inlet of the flue 28. The flue 28 is provided with a heat transfer tube 43 of the boiler body 40. The outlet of the flue 28 is connected to the exhaust gas treatment system 30.

In the boiler 10 configured as described above, the air ratio between the fuel supplied to the high-temperature reduction zone 21 and the air for the first stage combustion is maintained at less than 1 (for example, about 0.7). In addition, the high-temperature reduction zone 21, which is covered with refractory material 25, is less susceptible to temperature drops inside the furnace than other parts of the furnace. As a result, the high-temperature reduction zone 21 is in a high-temperature reducing atmosphere with an average air volume of about 1500°C (i.e., an air-deficient atmosphere with an air volume lower than the theoretical air volume), and fuel gasification is promoted in the high-temperature reduction zone 21.

In the high-temperature reduction zone 21, gasified fuel is generated by thermal decomposition of fuel. The gasified fuel flows into the low-temperature oxidation zone 22 through the constriction 23. The air ratio of the low-temperature oxidation zone 22 is maintained at 1 or more (for example, about 1.1) by the air for second-stage combustion supplied to the low-temperature oxidation zone 22 from the air nozzle 26. This creates an oxidizing atmosphere in the low-temperature oxidation zone 22, promoting the combustion of the gasified fuel in the low-temperature oxidation zone 22.

In the low-temperature oxidation zone 22, the combustion of the fuel is completed. The combustion exhaust gas from the low-temperature oxidation zone 22 flows out to the exhaust gas treatment system 30 through the flue 28. The heat of the combustion exhaust gas is recovered by the heat transfer tubes 43 installed in the flue 28 and the furnace wall, and steam is generated in the boiler body 40. The generated steam is used, for example, in a steam turbine of a power generation facility.

<<Configuration of Burner 5>>
Here, the configuration of the burner 5 included in the boiler 10 having the above configuration will be described. The burner 5 is a multi-fuel burner that uses solid fuel as the main fuel and gas fuel containing ammonia as the auxiliary fuel. The solid fuel is a powdered or granular fossil fuel such as pulverized coal. However, the main fuel of the burner 5 is not limited to fossil fuel, and may be biomass or petroleum residue.

Figure 2 is a schematic cross-sectional view of the burner 5 according to the present disclosure, and Figure 3 is an enlarged view of the vicinity of the outlet of the burner 5 in Figure 2. As shown in Figures 2 and 3, the burner 5 has multiple nozzles consisting of a first nozzle 71, a second nozzle 72, and a third nozzle 73 arranged coaxially around a burner axis 70. The extension direction of the burner axis 70 is referred to as the "burner axis direction X".

The first nozzle 71 has a first flow passage 71f extending in the burner axial direction X inside, and a main fuel outlet 71a at the tip, which is the downstream end of the first flow passage 71f. A flame stabilizing plate 77 is provided around the main fuel outlet 71a. The flame stabilizing plate 77 has a truncated cone shape that expands in diameter downstream. A swirl suppression plate 711 is provided in the first flow passage 71f. In addition, a dispersion vane 713 is provided upstream of the swirl suppression plate 711 in the first flow passage 71f.

A heavy oil burner 79 is inserted into the axial center of the first nozzle 71, overlapping with the burner axis 70. The outlet of the heavy oil burner 79 is located approximately in the center of the main fuel outlet 71a. The heavy oil burner 79 is mainly used for ignition.

Solid fuel and primary air are supplied to the first flow passage 71f. The primary air is the air for burning the fuel and also the gas for transporting the solid fuel. The mixed fluid 51 consisting of the solid fuel and the primary air is swirled by the action of the dispersion vanes 713, and the swirling force is weakened by the action of the swirling suppression plate 711, and then ejected from the main fuel outlet 71a in the burner axis direction X.

A second nozzle 72 is provided on the outer periphery of the first nozzle 71. A second flow passage 72f with an annular flow passage cross section is formed between the first nozzle 71 and the second nozzle 72. A secondary air outlet 72a, which is the downstream end of the second flow passage 72f, surrounds the outer periphery of the main fuel outlet 71a. An air cone 72b, which expands in diameter toward the downstream, is provided on the periphery of the secondary air outlet 72a. Secondary air 52 is supplied from the wind box to the second flow passage 72f. The secondary air 52 is blown out from the secondary air outlet 72a toward the outer periphery of the flow of the mixed fluid 51. The flame stabilizing plate 77 and the air cone 72b guide the secondary air 52 blown out from the secondary air outlet 72a so that it is away from the mixed fluid 51 blown out from the first nozzle 71.

A third nozzle 73 is provided on the outer periphery of the second nozzle 72. Between the third nozzle 73 and the second nozzle 72, a third flow passage 73f with a circular flow passage cross section is formed. The tertiary air outlet 73a, which is the downstream end of the third flow passage 73f, surrounds the outer periphery of the secondary air outlet 72a. An air cone 73b, which expands in diameter toward the downstream, is provided on the periphery of the tertiary air outlet 73a. A swirl vane 731 is arranged in the third flow passage 73f. Tertiary air 53 is supplied from the wind box to the third flow passage 73f. The tertiary air 53 is blown out from the tertiary air outlet 73a toward the outer periphery of the secondary air 52 while swirling due to the action of the swirl vane 731. The tertiary air 53 blown out from the third nozzle 73 is guided outward away from the secondary air 52 blown out from the second nozzle 72 by the air cone 72b and the air cone 73b.

The burner 5 is equipped with a first auxiliary fuel nozzle 81 that ejects a first gas fuel 80 and a second auxiliary fuel nozzle 91 that ejects a second gas fuel 90. The first gas fuel 80 and the second gas fuel 90 are combustible gases containing ammonia gas. The first gas fuel 80 and the second gas fuel 90 are not limited to ammonia gas, but may be any combustible gas containing ammonia as a main component, that is, any combustible gas containing 50% or more by volume of ammonia. The first gas fuel 80 and the second gas fuel 90 may have the same composition or different compositions.

Figure 4 is a view of the outlet of the burner 5 seen from the front in the burner axis direction X. As shown in Figures 2, 3 and 4, at least one first auxiliary fuel nozzle 81 is inserted into the first nozzle 71. The first auxiliary fuel nozzle 81 has an auxiliary fuel passage 81f inside and a first auxiliary fuel outlet 81a, which is the downstream end of the auxiliary fuel passage 81f, at its tip. The first auxiliary fuel outlet 81a is located inside the main fuel outlet 71a. In the example shown in Figure 4, multiple first auxiliary fuel outlets 81a are arranged in a ring shape so as to surround the periphery of the heavy oil burner 79. In this case, the opening axis of the multiple first auxiliary fuel outlets 81a is eccentric from the burner axis 70. The opening axis of the first auxiliary fuel outlet 81a is defined as a straight line that passes through approximately the center of the first auxiliary fuel outlet 81a and is parallel to the direction of the first gas fuel 80 ejected from the first auxiliary fuel outlet 81a. Alternatively, as shown in FIG. 5, the first auxiliary fuel nozzle 81 may have an annular first auxiliary fuel outlet 81a that surrounds the heavy oil burner 79. In this manner, the first auxiliary fuel outlet 81a is disposed to avoid the burner axis 70. The first gas fuel 80 is supplied from a gas fuel source to the auxiliary fuel passage 81f of the first auxiliary fuel nozzle 81, and the first gas fuel 80 is ejected from the first auxiliary fuel outlet 81a.

The second auxiliary fuel nozzles 91 are arranged in a line in the circumferential direction on the outer peripheral surface of the first nozzle 71. The second auxiliary fuel nozzle 91 has an auxiliary fuel flow passage 91f inside, and a second auxiliary fuel outlet 91a, which is the downstream end of the auxiliary fuel flow passage 91f, at its tip. The second auxiliary fuel outlets 91a are arranged between the main fuel outlet 71a and the secondary air outlet 72a, and are arranged in a line in the circumferential direction along the outer peripheral edge of the flame holding plate 77. The auxiliary fuel flow passage 91f of the second auxiliary fuel nozzle 91 is supplied with a second gas fuel 90 from a gas fuel source, and the second gas fuel 90 is ejected from the second auxiliary fuel outlet 91a. In addition to the second gas fuel 90, combustion air may be supplied to the auxiliary fuel flow passage 91f of the second auxiliary fuel nozzle 91.

The total flow rate per unit time of ammonia contained in the second gas fuel 90 ejected from the multiple second auxiliary fuel nozzles 91 is greater than the total flow rate per unit time of ammonia contained in the first gas fuel 80 ejected from the first auxiliary fuel nozzle 81. When the burner 5 is equipped with multiple first auxiliary fuel nozzles 81, the total flow rate per unit time of ammonia contained in the second gas fuel 90 ejected from the multiple second auxiliary fuel nozzles 91 is greater than the total flow rate per unit time of ammonia contained in the first gas fuel 80 ejected from the multiple first auxiliary fuel nozzles 81. However, it is also possible to stop fuel ejection from the multiple second auxiliary fuel nozzles 91, that is, to operate the system so that the flow rate of the second gas fuel 90 ejected from the multiple second auxiliary fuel nozzles 91 is zero. In this case, the flow rate of ammonia contained in the first gas fuel 80 ejected from the first auxiliary fuel nozzle 81 may be outside the above constraints.

<Combustion method of burner 5>
Next, a combustion method of the burner 5 having the above-mentioned configuration will be described. As shown in Figures 2 and 3, in the burner 5, the mixed fluid 51 of solid fuel and primary air supplied to the first nozzle 71 swirls due to the action of the dispersion vane 713, and after the swirl force is weakened by the action of the swirl suppression plate 711, it is ejected as a swirling flow from the main fuel outlet 71a. In addition, on the outer periphery side of the main fuel outlet 71a, the secondary air 52 is ejected from the secondary air outlet 72a, and the tertiary air 53 is ejected from the tertiary air outlet 73a. The secondary air 52 is guided by the flame stabilizing plate 77 and the air cone 72b, and is ejected so as to spread toward the outer periphery side around the burner axis 70. Similarly, the tertiary air 53 is guided by the air cone 72b and the air cone 73b, and is ejected so as to spread toward the outer periphery side while swirling.

The solid fuel in the mixed fluid 51 ejected from the main fuel outlet 71a is pyrolyzed and gasified, and this gasified fuel is burned by the primary air. Immediately downstream of the main fuel outlet 71a, a recirculation region 49 is created in which oxygen is consumed by combustion, creating a high-temperature reducing atmosphere. Immediately downstream of the flame-holding plate 77, a flame-holding vortex 55 is created by the action of the flame-holding plate 77. The fluid that forms the flame-holding vortex 55 contains relatively high-temperature burnt gas produced by combustion. The flame-holding vortex 55 has a forward flow section in which the fluid flows away from the main fuel outlet 71a along the flow of the secondary air 52, and a reverse flow section in which the fluid flows toward the main fuel outlet 71a.

In the recirculation region 49 on the inner periphery side of the flame holding vortex 55, a swirling flow of the tertiary air 53 generates a circulation flow 50 that returns the fluid that flows downstream along the inner edge of the flame holding vortex 55 to the main fuel outlet 71a along the burner axis 70. The circulation flow 50 includes a forward flow section in which the fluid flows along the inner edge of the flame holding vortex 55 in a direction away from the main fuel outlet 71a, a reverse flow section in which the fluid flows along the burner axis 70 in a direction approaching the main fuel outlet 71a, a turning section in which the fluid flow changes from the reverse flow section to the forward flow section, and a turning section in which the fluid flow changes from the forward flow section to the reverse flow section. The fluid that forms the circulation flow 50 includes burned gas at a relatively high temperature. The flame holding vortex 55 and the circulation flow 50 constantly exchange heat between the mixture of gasification fuel and primary air and between unburned gas and high-temperature burned gas, promoting combustion and stabilizing the flame. Furthermore, the combustion air and fuel are mixed in stages, in the order of secondary air 52 and tertiary air 53, to cause combustion.

Since the first auxiliary fuel nozzle 81 is positioned at least outside the heavy oil burner 79, a non-reaching area 60 is defined downstream of the main fuel outlet 71a where the first gas fuel 80 ejected from the first auxiliary fuel outlet 81a does not reach. The non-reaching area 60 is shown by hatching in FIG. 2. The non-reaching area 60 is a cylindrical area centered on the burner axis 70, starting from a point on the burner axis 70 immediately downstream of the main fuel outlet 71a and extending in a direction away from the main fuel outlet 71a. The radius of the non-reaching area 60 is the same as or smaller than the radius of the heavy oil burner 79. In the non-reaching area 60, there is a portion of the reverse flow portion of the circulating flow 50 that flows along the burner axis 70.

The first auxiliary fuel nozzle 81 has an adjusted ejection flow rate per unit time and ejection direction so that the ejected first gas fuel 80 reaches the first target position and does not directly reach the non-reachable area 60. The first target position is in the starting area of the forward flow part of the circulation flow 50, or in the transition area where the flow of the circulation flow 50 changes from reverse flow to forward flow. The first gas fuel 80 ejected toward the first target position preferably flows along the flow of the circulation flow 50 to reach the first target position. Here, preferably, the ejection direction of the first auxiliary fuel nozzle 81, that is, the extension direction of the first auxiliary fuel outlet axis, which is the central axis of the outlet of the first auxiliary fuel nozzle 81, is parallel to the burner axis direction X. This makes it possible to avoid interference between the first gas fuel 80 ejected from the first auxiliary fuel nozzle 81 and the flame holding vortex 55, and furthermore, the flow of the mixed fluid of the primary air and the main fuel is not disturbed by the flow of the first gas fuel 80. The first gas fuel 80 that has reached the first target position is taken into the circulation flow 50 at the forward flow section or the changeover section of the circulation flow 50 and combusted. The first gas fuel 80 contains ammonia, but the first gas fuel 80 is burned slowly in the region where the oxygen concentration is diluted by burnt gas, etc., riding on the flow of the circulation flow 50, which is a low flow rate region, thereby suppressing the emission of NOx after combustion. In addition, since the first gas fuel 80 ejected from the first auxiliary fuel outlet 81a does not directly reach the non-reaching region 60, the ejection flow of the first gas fuel 80 does not disturb the flow of the reverse flow section of the circulation flow 50. Therefore, a normal circulation flow 50 is maintained, and the stability of the flame can be maintained.

The second auxiliary fuel nozzle 91 adjusts the ejection flow rate and ejection direction per unit time so that the ejected second gas fuel 90 reaches the second target position. The second target position is in the forward flow portion of the flame holding vortex 55. The ejection flow of the second gas fuel 90 flows along the outer edge of the forward flow portion of the flame holding vortex 55 to reach the second target position, is taken into the flow of the flame holding vortex 55 in the forward flow portion of the flame holding vortex 55, and burns within the flame holding vortex 55. Since the ejection flow of the second gas fuel 90 does not disturb the flow of the flame holding vortex 55, the flame holding vortex 55 is maintained and the flame stability can be maintained. In addition, although the second gas fuel 90 contains ammonia, the second gas fuel 90 is burned within the flame holding vortex 55 where the oxygen concentration is diluted, thereby suppressing the emission of NOx after combustion.

[Summary]
The burner 5 according to the first item of the present disclosure comprises:
A first nozzle 71 having a cylindrical shape centered on a burner axis 70 and having a main fuel outlet 71a for ejecting a mixed fluid 51 of a main fuel and primary air;
a second nozzle 72 having a secondary air outlet 72a surrounding the main fuel outlet 71a and blowing out the secondary air 52 from the secondary air outlet 72a;
A flame-holding plate 77 that generates a flame-holding vortex 55 downstream of the periphery of the main fuel outlet 71 a;
a third nozzle 73 having a tertiary air outlet 73a surrounding the secondary air outlet 72a and blowing out a swirling flow of the tertiary air 53 from the tertiary air outlet 73a;
a first auxiliary fuel nozzle 81 having a first auxiliary fuel outlet 81a arranged within the main fuel outlet 71a and ejecting a first gas fuel 80 containing ammonia from the first auxiliary fuel outlet 81a;
During combustion, the action of the tertiary air 53 creates a circulating flow 50 that includes a forward flow section in which the fluid flows away from the main fuel outlet 71a along the inner edge of the flame holding vortex 55, a reverse flow section in which the fluid flows along the burner axis 70 in a direction toward the main fuel outlet 71a, and a transition section from the reverse flow section to the forward flow section, and the first auxiliary fuel nozzle 81 sprays the first gas fuel 80 along the flow of the circulating flow 50 into the forward flow section or the transition section of the circulating flow 50.

In the burner 5 having the above configuration, the ejection flow of the first gas fuel 80 is taken into the circulation flow 50 at the forward flow section or the changeover section of the circulation flow 50 and is burned in a reducing atmosphere. The first gas fuel 80 contains ammonia, and the ammonia is burned in a reducing atmosphere, thereby suppressing the amount of NOx emissions after combustion. In addition, since the ejection flow of the first gas fuel 80 does not interfere with the flow of the reverse flow section of the circulation flow 50, the normal flow of the circulation flow 50 is not hindered by the ejection flow of the first gas fuel 80. Furthermore, the first auxiliary fuel outlet 81a is disposed within the main fuel outlet 71a, and the ejection flow of the first gas fuel 80 can reach the forward flow section or the changeover section of the circulation flow 50 without interfering with the flame holding vortex 55. Therefore, even if the first gas fuel 80 is ejected, the normal circulation flow 50 and the flame holding vortex 55 are maintained and the flame is held stably, so that stable combustion of the burner 5 can be maintained.

The burner 5 according to the second item is the burner 5 according to the first item, in which the multiple first auxiliary fuel outlets 81a are arranged in a ring shape centered on the burner axis 70, and the opening axes of the multiple first auxiliary fuel outlets 81a are eccentric from the burner axis 70.

In the burner 5 described above, the opening axes of the multiple first auxiliary fuel outlets 81a are eccentric from the burner axis 70, so the flow of the backflow portion of the circulating flow 50 passing above the burner axis 70 is not impeded. Therefore, the flow of the circulating flow 50 is maintained.

The burner 5 according to the third item is the burner 5 according to the first or second item, in which the opening axis of the first auxiliary fuel outlet 81a is parallel to the burner axis 70.

In the burner 5 described above, the first gas fuel 80 is ejected from the first auxiliary fuel outlet 81a parallel to the burner axis 70, so the flow of the first gas fuel 80 does not interfere with the flame-holding vortex 55 formed around the outlet edge of the main fuel outlet 71a. Therefore, the flame-holding vortex 55 is maintained.

The burner 5 according to the fourth item is the burner 5 according to any one of the first to third items, further comprising a second auxiliary fuel nozzle 91 having a second auxiliary fuel outlet 91a arranged on the periphery of the flame stabilizing plate 77 and ejecting a second gas fuel 90 containing ammonia from the second auxiliary fuel outlet 91a;
The second auxiliary fuel nozzle 91 ejects the second gas fuel 90 into the forward flow portion of the flame holding vortex 55 along the flow of the forward flow portion.

In the burner 5 having the above configuration, the ejection flow of the second gas fuel 90 is taken into the flow of the flame holding vortex 55 in the forward flow portion of the flame holding vortex 55 and burns within the flame holding vortex 55. The second gas fuel 90 contains ammonia, but the ammonia burns in a reducing atmosphere, thereby suppressing the amount of NOx emissions after combustion. In addition, since the ejection flow of the second gas fuel 90 does not interfere with the flow in the reverse flow portion of the flame holding vortex 55, the normal vortex of the flame holding vortex 55 is not obstructed by the ejection flow of the second gas fuel 90. Therefore, even if the second gas fuel 90 is ejected, the normal flame holding vortex 55 is maintained and the flame is stably held, so that the stable combustion of the burner 5 can be maintained. Furthermore, in the burner 5, gas fuel is supplied as auxiliary fuel from independent nozzles to the circulation flow 50 and the flame holding vortex 55, respectively, so that the overall supply amount of auxiliary fuel can be increased while maintaining the circulation flow 50 and the flame holding vortex 55 and holding the flame.

The burner 5 according to the fifth aspect is the burner 5 according to the fourth aspect,
The total flow rate per unit time of ammonia contained in the second gas fuel 90 ejected from the second auxiliary fuel nozzle 91 is greater than the total flow rate per unit time of ammonia contained in the first gas fuel 80 ejected from the first auxiliary fuel nozzle 81. Here, the flow rate of ammonia may be a mass flow rate or a volume flow rate.

By having this relationship between the flow rate of ammonia ejected from the first auxiliary fuel nozzle 81 and the flow rate of ammonia ejected from the second auxiliary fuel nozzle 91, it is possible to maintain normal flow of the circulating flow 50 and the flame holding vortex 55 to which ammonia, which is a low heat generating gas, is supplied.

The combustion furnace 2 according to the sixth aspect of the present disclosure comprises a combustion chamber 20 and a burner 5 according to any one of the first to fifth aspects arranged on the wall of the combustion chamber 20.

The burner 5 configured as described above is suitable as a burner 5 to be provided in a combustion furnace 2.

The above discussion of the present disclosure has been presented for purposes of illustration and description, and is not intended to limit the present disclosure to the form disclosed herein. For example, in the foregoing detailed description, various features of the present disclosure are grouped together in a single embodiment for the purpose of streamlining the disclosure, but some of the features may be combined. Additionally, the features included in the present disclosure may be combined into alternative embodiments, configurations, or aspects other than those discussed above.

2: Combustion furnace 5: Burner 20: Combustion chamber 50: Circulation flow 51: Mixed fluid 52: Secondary air 53: Tertiary air 55: Flame holding vortex 70: Burner axis 71: First nozzle 71a: Main fuel outlet 72: Second nozzle 72a: Secondary air outlet 73: Third nozzle 73a: Tertiary air outlet 77: Flame holding plate 80: First gas fuel 81: First auxiliary fuel nozzle 81a: First auxiliary fuel outlet 90: Second gas fuel 91: Second auxiliary fuel nozzle 91a: Second auxiliary fuel outlet

Claims (6)

A first nozzle having a cylindrical shape centered on a burner axis and having a main fuel outlet for ejecting a mixed fluid of a main fuel and primary air;
a second nozzle having a secondary air outlet surrounding the main fuel outlet and blowing out secondary air from the secondary air outlet;
a flame-holding plate for generating a flame-holding vortex downstream of a periphery of the main fuel outlet;
a third nozzle having a tertiary air outlet surrounding the secondary air outlet and blowing out a swirling flow of tertiary air from the tertiary air outlet;
a first auxiliary fuel nozzle having a first auxiliary fuel outlet arranged in the main fuel outlet and configured to eject a first gas fuel containing ammonia from the first auxiliary fuel outlet;
During combustion, the action of the tertiary air generates a circulation flow including a forward flow section in which the fluid flows along the inner edge of the flame-holding vortex in a direction away from the main fuel outlet, a reverse flow section in which the fluid flows on the burner axis in a direction approaching the main fuel outlet, and a switching section from the reverse flow section to the forward flow section, and the first auxiliary fuel nozzle ejects the first gas fuel along the flow of the circulation flow to the forward flow section or the switching section of the circulation flow.
Burner. The first auxiliary fuel outlets are arranged in an annular shape around the burner axis, and the opening axes of the first auxiliary fuel outlets are eccentric from the burner axis.
2. A burner according to claim 1. The opening axis of the first auxiliary fuel outlet is parallel to the burner axis.
A burner according to claim 1 or 2. a second auxiliary fuel nozzle having a second auxiliary fuel outlet arranged on a peripheral edge of the flame stabilizing plate and ejecting a second gas fuel containing ammonia from the second auxiliary fuel outlet;
the second auxiliary fuel nozzle ejects the second gas fuel along a flow of the flame holding vortex to a forward flow portion of the flame holding vortex.
A burner according to claim 1 or 2. a total flow rate per unit time of ammonia contained in the second gas fuel ejected from the second auxiliary fuel nozzle is greater than a total flow rate per unit time of ammonia contained in the first gas fuel ejected from the first auxiliary fuel nozzle.
5. A burner according to claim 4. A combustion chamber;
A burner according to claim 1 or 2, arranged on a wall of the combustion chamber.
Combustion furnace.

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