Furnace

Abstract

A furnace 70 comprises a plurality of fuel ports arranged in a plurality of tiers along the vertical direction. The plurality of tiers include: at least one tier including a plurality of first fuel ports, among the plurality of fuel ports, through which a first fuel F1 that contains nitrogen at a first concentration is supplied to a combustion space S; and at least one tier including a plurality of second fuel ports, among the plurality of fuel ports, through which a second fuel F2 that contains nitrogen at a second concentration higher than the first concentration is supplied to the combustion space S. The plurality of first fuel ports are arranged such that the first fuel F1 is supplied in a tangential direction of a prescribed imaginary circle C1 when viewed in the vertical direction, and the plurality of second fuel ports are arranged such that the second fuel F2 is supplied toward a region inside the imaginary circle C1 when viewed in the vertical direction.

Description

Furnace

[0001] This disclosure relates to a furnace. This application claims the benefit of priority based on Japanese Patent Application No. 2025 - 4666 filed on January 14, 2025, the content of which is incorporated herein by reference.

[0002] The furnace may use tangential combustion (for example, see Patent Document 1). In tangential combustion, a plurality of burners inject fuel in a direction tangent to a predetermined virtual circle in the combustion space. According to such a configuration, a swirling flame is formed in the combustion space.

[0003] Japanese Patent Application Laid - Open No. 2002 - 156103

[0004] When fuel containing nitrogen burns, NOx is generated. For example, in Japan, the emission standards for nitrogen oxides including NOx are set based on the Air Pollution Control Law, and in the development of furnaces, reduction of the amount of NOx is considered. Therefore, even when fuel containing nitrogen is used in the above - mentioned furnace using tangential combustion, it is desirable to reduce the amount of NOx.

[0005] An object of this disclosure is to provide a furnace capable of reducing the amount of NOx when fuel containing nitrogen is used.

[0006] The furnace according to one aspect of this disclosure includes a plurality of fuel ports arranged in a plurality of stages along the vertical direction. The plurality of stages include at least one stage including a plurality of first fuel ports that supply a first fuel containing nitrogen at a first concentration to the combustion space among the plurality of fuel ports, and at least one stage including a plurality of second fuel ports that supply a second fuel containing nitrogen at a second concentration higher than the first concentration to the combustion space among the plurality of fuel ports. The plurality of first fuel ports are arranged to supply the first fuel in a direction tangent to a predetermined virtual circle when viewed in the vertical direction, and the plurality of second fuel ports are arranged to supply the second fuel toward a region inside the virtual circle when viewed in the vertical direction.

[0007] The second fuel may be ammonia.

[0008] At least one stage containing multiple second fuel ports may include one or more stages of multiple stages, excluding the top stage of multiple stages.

[0009] At least one stage containing multiple second fuel ports may include the lowest stage of multiple stages.

[0010] A burner including a second fuel port may be supplied with a second fuel and combustion air at an air-to-air ratio of less than 1.0.

[0011] According to this disclosure, NOx emissions can be reduced when nitrogen-containing fuel is used.

[0012] Figure 1 is a schematic perspective view of a combustion system including a furnace according to the first embodiment. Figure 2 is a schematic diagram showing an example of burner arrangement. Figure 3 is a schematic diagram showing multiple burners viewed in the vertical direction. Figure 4 is a schematic diagram showing multiple burners viewed in the vertical direction of a furnace according to the second embodiment. Figure 5 is a schematic diagram showing multiple burners viewed in the vertical direction of a furnace according to the third embodiment.

[0013] Embodiments of this disclosure will be described in detail below with reference to the attached drawings. The specific dimensions, materials, and numerical values ​​shown in these embodiments are merely illustrative for ease of understanding and do not limit this disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to this disclosure are omitted from the illustrations.

[0014] Figure 1 is a schematic perspective view of a combustion system 100 including a furnace 70 according to a first embodiment. In this embodiment, the furnace 70 is applied to a boiler 80. In other embodiments, the furnace 70 may be applied to equipment other than a boiler 80.

[0015] For example, the combustion system 100 includes a boiler 80 and a control device 90. The combustion system 100 may further include other components.

[0016] The boiler 80 includes the furnace 70.

[0017] The furnace 70 extends vertically. In this embodiment, the furnace 70 includes four side walls 71, 72, 73, and 74. Each of the side walls 71, 72, 73, and 74 extends vertically. In this embodiment, the side walls 71, 72, 73, and 74 form a generally square shape when viewed from above. In other embodiments, the side walls 71, 72, 73, and 74 may form a shape other than a square when viewed from above. The side walls 71, 72, 73, and 74 define a combustion space S. In this disclosure, “combustion space” means the space in which fuel is burned. For example, an outlet may be provided at the bottom of the furnace 70. For example, a hopper may be provided at the outlet.

[0018] The furnace 70 burns fuel. For example, in this embodiment, the furnace 70 uses at least a first fuel and a second fuel (the first fuel and the second fuel will be described in detail later).

[0019] The combustion of fuel generates exhaust gas in the combustion space S. For example, the boiler 80 includes components such as a superheater and a reheater on the rear heat transfer surface 81 located downstream of the combustion space S. For example, the superheater exchanges heat between the exhaust gas and water, thereby generating steam. The boiler 80 is connected to a flue (not shown). The flue guides the exhaust gas from the boiler 80 to a chimney (not shown).

[0020] The furnace 70 employs tangential combustion. Specifically, in this embodiment, the furnace 70 includes a first burner group 10, a second burner group 20, a third burner group 30, and an airport group 40. The first burner group 10, the second burner group 20, the third burner group 30, and the airport group 40 are arranged vertically in this order from bottom to top.

[0021] Each of the burner groups 10, 20, and 30 includes multiple burners B. In Figure 1, for better understanding, burners B are simply represented by black dots. In this embodiment, in each of the burner groups 10, 20, and 30, burners B are located at each of the four corners between the side walls 71, 72, 73, and 74. In this embodiment, in each of the burner groups 10, 20, and 30, the burners B at the four corners are located at approximately the same height.

[0022] The first burner group 10 includes a plurality of burners B arranged in three vertical stages. The second burner group 20 includes a plurality of burners B arranged in five vertical stages. The third burner group 30 includes a plurality of burners B arranged in three vertical stages. Therefore, the furnace 70 includes a total of eleven vertical stages of burners B. For example, the burners B in each stage are arranged along the same horizontal plane so as to surround a predetermined position (e.g., the center) of the combustion space S.

[0023] Figure 2 is a schematic diagram showing an example of the arrangement of burners B. Figure 2 shows an example of the arrangement of multiple burners B of the second burner group 20 arranged in one corner. Note that each burner B of the first burner group 10 and the third burner group 30 may also be configured in the same way as any one of the first burner B1, second burner B2, and third burner B3 shown in Figure 2.

[0024] In this embodiment, each burner B corresponds to one of the following: a first burner B1 that injects a first fuel, a second burner B2 that injects a second fuel, and a third burner B3 that injects a third fuel.

[0025] In this embodiment, the second burner group 20 includes a first burner B1, a second burner B2, and a third burner B3. The arrangement of the burners B in the second burner group 20 is not limited to that shown in Figure 2.

[0026] The first burner B1 is configured to burn the first fuel in the combustion space S. In this embodiment, the first burner B1 includes a first fuel nozzle (first fuel port) N1, a lower air port LP1, and an upper air port UP1. The configuration of the first burner B1 is not limited thereto.

[0027] The first fuel nozzle N1 is configured to supply the first fuel to the combustion space S. The first fuel is a fuel containing nitrogen at a first concentration. For example, in this embodiment, the first fuel is pulverized coal. Hereinafter, this embodiment will be described assuming that the first fuel is pulverized coal.

[0028] In this embodiment, the first fuel nozzle N1 is configured to supply pulverized coal and primary air for delivering the pulverized coal to the combustion space S. The first burner B1 may also be configured to supply secondary air through a gap around the first fuel nozzle N1. For example, the first fuel nozzle N1 may be connected to a crusher (first fuel source) not shown, which supplies pulverized coal.

[0029] The upper air port UP1 and the lower air port LP1 are configured to supply air (secondary air) for burning pulverized coal into the combustion space S.

[0030] For example, in this embodiment, the first burner B1 is configured to supply pulverized coal and air at an air-to-air ratio of less than 1.0. For example, the amount of pulverized coal and air supplied to the first burner B1 may be adjusted by the control device 90. The control device 90 adjusts the amount of pulverized coal and air supplied to the first burner B1 so that the air-to-air ratio is less than 1.0. For example, the control device 90 may adjust the amount of pulverized coal by controlling the amount of coal supplied to the crusher. Alternatively, for example, the control device 90 may adjust the amount of air by controlling an adjustment device such as a damper provided for the first burner B1. For example, the control device 90 may store the settings for the pulverized coal adjustment device and the air adjustment device in advance, or it may control the pulverized coal adjustment device and the air adjustment device according to input from the operator.

[0031] The second burner B2 is configured to burn the second fuel in the combustion space S. In this embodiment, the second burner B2 includes a second fuel nozzle (second fuel port) N2, a lower air port LP2, and an upper air port UP2. The configuration of the second burner B2 is not limited thereto.

[0032] The second fuel nozzle N2 is configured to supply the second fuel and secondary air to the combustion space S. The second fuel is a fuel containing nitrogen at a second concentration. The second concentration is higher than the first concentration. That is, the first concentration is lower than the second concentration. For example, in this embodiment, the second fuel is ammonia. Hereinafter, this embodiment will be described assuming that the second fuel is ammonia.

[0033] The ammonia supplied from the second fuel nozzle N2 may be gaseous ammonia or liquid ammonia. For example, the second fuel nozzle N2 may be connected to a tank (second fuel source) not shown that stores liquid ammonia. For example, if the second fuel nozzle N2 supplies gaseous ammonia, a vaporizer (not shown) may be provided in the line connecting the second fuel nozzle N2 to the tank.

[0034] The lower air port LP2 and the upper air port UP2 are configured to supply air to the combustion space S for burning ammonia.

[0035] For example, in this embodiment, the second burner B2 is configured to supply ammonia and air so that ammonia is burned at an air-to-air ratio of less than 1.0. For example, the amount of ammonia and air supplied to the second burner B2 may be adjusted by the control device 90. The control device 90 adjusts the amount of ammonia and air supplied to the second burner B2 so that the air-to-air ratio is less than 1.0. For example, the control device 90 may adjust the amount of ammonia by controlling an adjustment device such as a valve provided in the line connecting the second burner B2 to the tank. Alternatively, for example, the control device 90 may adjust the amount of air by controlling an adjustment device such as a damper provided for the second burner B2. For example, the control device 90 may store the settings for the ammonia adjustment device and the air adjustment device in advance, or it may control the ammonia adjustment device and the air adjustment device according to input from the operator.

[0036] The third burner B3 is configured to burn the third fuel in the combustion space S. In this embodiment, the third burner B3 includes a third fuel nozzle (third fuel port) N3, a lower air port LP3, and an upper air port UP3. The configuration of the third burner B3 is not limited thereto.

[0037] The third fuel nozzle N3 is configured to supply the third fuel to the combustion space S. For example, the third fuel may be used to increase the temperature of the boiler 80. For example, in this embodiment, the third fuel is diesel fuel. Hereinafter, this embodiment will be described assuming that the third fuel is diesel fuel.

[0038] For example, the diesel fuel supplied from the third fuel nozzle N3 is in a liquid state. For example, the third fuel nozzle N3 may be connected to a tank (not shown) that stores diesel fuel (third fuel source).

[0039] The lower air port LP3 and the upper air port UP3 are configured to supply air to the combustion space S for burning diesel fuel.

[0040] For example, the amount of diesel fuel and the amount of air supplied to the third burner B3 may be adjusted by the control device 90. For example, the control device 90 may adjust the amount of diesel fuel by controlling an adjustment device such as a valve provided in the line connecting the third burner B3 to the tank. Alternatively, for example, the control device 90 may adjust the amount of air by controlling an adjustment device such as a damper provided for the third burner B3.

[0041] For example, at least one of the burners B may be configured to allow vertical adjustment of the direction of fuel and air. For example, tilting the direction of fuel and air downward from the horizontal increases the heat absorption of the furnace 70 and decreases the heat absorption of the rear heat transfer surface 81. In contrast, tilting the direction of fuel and air upward from the horizontal decreases the heat absorption of the furnace 70 and increases the heat absorption of the rear heat transfer surface 81.

[0042] In this embodiment, the horizontal direction of fuel and air in burner B is fixed. In other embodiments, at least one of the burners B may be configured to allow horizontal adjustment of the direction of fuel and air.

[0043] Referring to FIG. 1, in the above embodiment, the second burner group 20 includes the second burner B2, and the first burner group 10 and the third burner group 30 may not include the second burner B2. However, the arrangement of the second burner B2 is not limited thereto. For example, in other embodiments, the first burner group 10 may include the second burner B2. For example, the lowermost burner B of the first burner group 10, that is, the lowermost burner B of the furnace 70, may be the second burner B2. Further, in still other embodiments, both the first burner group 10 and the second burner group 20 may include the second burner B2. In other words, except for the uppermost burner B of the third burner group 30, that is, the uppermost burner B of the furnace 70, the burner B at any stage among the first burner group 10, the second burner group 20, and the third burner group 30 may function as the second burner B2 that supplies ammonia.

[0044] The air port group 40 includes at least one air port 41. The air port 41 supplies air for secondary combustion to the combustion space S. In the present embodiment, the air port group 40 includes a plurality of air ports 41. In other embodiments, the air port group 40 may include only a single air port 41. In the present embodiment, two air ports 41 are provided on each of the side walls 72 and 74. In the present embodiment, the plurality of air ports 41 are arranged in a single row. In other embodiments, the plurality of air ports 41 may be arranged in a plurality of rows along the vertical direction.

[0045] The air port group 40 is arranged downstream of the third burner group 30 in the combustion space S. Specifically, the air port group 40 is arranged above the third burner group 30. The air port group 40 is arranged vertically spaced apart from the third burner group 30. For example, the distance between the air port group 40 and the third burner group 30 in the vertical direction may be longer than the distance between adjacent burners B in the vertical direction.

[0046] The control device 90 controls the combustion system 100. For example, the control device 90 may be implemented by one or more computers. The control device 90 includes components such as a processor 90a, a storage device 90b, and a connector 90c, and these components are connected to each other via a bus. For example, the processor 90a includes a CPU (Central Processing Unit) or the like. For example, the storage device 90b includes a hard disk, a ROM (Read Only Memory) in which programs and the like are stored, and a RAM (Random Access Memory) as a work area or the like. The control device 90 is communicably connected to each component of the combustion system 100 via the connector 90c, either wired or wirelessly. For example, the control device 90 may further include other components such as a display device such as a liquid crystal display or a touch panel, and an input device such as a keyboard, a button, or a touch panel. For example, the operation of the control device 90 may be realized by the processor 90a executing a program stored in the storage device 90b.

[0047] Subsequently, the operation of the furnace 70 will be described.

[0048] In the present embodiment, the first-stage combustion is executed by the first burner group 10, the second burner group 20, and the third burner group 30.

[0049] FIG. 3 is a schematic view showing a plurality of burners B viewed in the vertical direction. FIG. 3 shows the injection directions of pulverized coal F1 and ammonia F2 from the burner B viewed from above.

[0050] The first burner B1 (not shown in FIG. 3) is configured to inject pulverized coal F1 in the direction of the tangent to a predetermined first virtual circle C1 in the combustion space S when viewed from above. For example, the center of the first virtual circle C1 is located at a predetermined position (for example, the center) of the combustion space S when viewed from above. The position of the first virtual circle C1 is not limited to this.

[0051] According to such a configuration, a swirling flow is generated in the combustion space S generally along the first virtual circle C1, and a fireball is formed.

[0052] In the region inside the first virtual circle C1, a fuel-rich zone RZ is formed where the concentration of pulverized coal F1 is relatively high. The fuel-rich zone RZ corresponds to the reduction region.

[0053] Outside the first virtual circle C1, a fuel lean zone LZ is formed where the concentration of pulverized coal F1 is relatively low. The fuel lean zone LZ corresponds to the oxidation region.

[0054] In the combustion of ammonia, the release of NOx can be a problem. To reduce the amount of NOx, it is desirable to burn ammonia in the reducing region.

[0055] Therefore, in this embodiment, the second burner B2 (not shown in Figure 3) is configured to inject ammonia F2 toward the fuel-rich zone RZ, which corresponds to the reduction region, when viewed from above, in the region inside the first virtual circle C1. For example, in this embodiment, the second burner B2 is configured to inject ammonia F2 in the direction of the tangent to a predetermined second virtual circle C2 in the combustion space S. The radius R2 of the second virtual circle C2 is smaller than the radius R1 of the first virtual circle C1. For example, the center of the second virtual circle C2 is located at a predetermined position (e.g., the center) in the combustion space S when viewed from above. The position of the second virtual circle C2 is not limited to this. With such a configuration, ammonia is burned in the reduction region. Therefore, the amount of NOx can be reduced.

[0056] Referring to Figure 1, in this embodiment, the second burner group 20 that injects ammonia is positioned lower than the third burner group 30 that injects pulverized coal. Therefore, unburned ammonia from the second burner group 20 flows upward to the area in front of the third burner group 30 and is burned together with the pulverized coal from the third burner group 30. Thus, the amount of unburned ammonia can be reduced. In another embodiment, if the lowest burner B of the first burner group 10, i.e., the lowest burner B of the furnace 70, is the second burner B2, then the unburned ammonia can be burned by fuel from the other burners B.

[0057] The combustion gases from burner B flow into the area in front of the airport group 40. Airport 41 injects air for second-stage combustion into the combustion space S. The unburned fuels (unburned pulverized coal, unburned ammonia, and unburned diesel fuel) contained in the combustion gases from burner B are completely combusted by the air from airport 41 (second-stage combustion).

[0058] In other embodiments, the furnace 70 may not include the airport group 40. In this case, for example, the first burner B1 of the third burner group 30 may be configured to supply pulverized coal and air at an air ratio of 1.0 or higher.

[0059] As described above, the furnace 70 according to this embodiment includes a plurality of fuel ports N1, N2, N3 arranged in a plurality of stages along the vertical direction. The plurality of stages include at least one stage that includes a plurality of first fuel nozzles (first fuel ports) N1 from the plurality of fuel ports N1, N2, N3, which supply a first fuel containing nitrogen at a first concentration to the combustion space S. The plurality of stages also include at least one stage that includes a plurality of second fuel nozzles (second fuel ports) N2 from the plurality of fuel ports N1, N2, N3, which supply a second fuel containing nitrogen at a second concentration higher than the first concentration to the combustion space S. The plurality of first fuel nozzles N1 are arranged to supply the first fuel F1 in the direction of the tangent to a predetermined first virtual circle C1 when viewed in the vertical direction. The plurality of second fuel nozzles N2 are arranged to supply the second fuel F2 toward the region inside the first virtual circle C1 when viewed in the vertical direction. With this configuration, the combustion of the first fuel generates a swirling flow in the combustion space S, generally along the first virtual circle C1, forming a fireball. The region inside the first virtual circle C1 forms a fuel-rich zone RZ where the concentration of pulverized coal F1 is relatively high. The fuel-rich zone RZ corresponds to a reduction region. Therefore, the second fuel supplied toward the region inside the first virtual circle C1 is burned in the reduction region. Thus, the amount of NOx can be reduced.

[0060] Furthermore, in reactor 70, the second fuel is ammonia. Ammonia is CO ２It is a fuel that does not produce CO2. Therefore, ２ The amount can be reduced.

[0061] Furthermore, in the furnace 70, at least one stage containing a plurality of second fuel nozzles N2 includes one or more stages from the plurality of stages, excluding the uppermost stage. For example, in this embodiment, the second burner group 20 includes the second fuel nozzles N2. With such a configuration, unburned second fuel can be burned by fuel from the uppermost (11th) stage fuel port. Therefore, the amount of unburned second fuel can be reduced.

[0062] Furthermore, in the reactor 70, at least one stage containing multiple second fuel nozzles N2 may include the lowest stage of multiple stages. For example, the lowest burner B of the first burner group 10, i.e., the lowest burner B of the reactor 70, may be the second burner B2. In this case, unburned ammonia can be burned by fuel from the other burners B. Therefore, the amount of unburned second fuel can be reduced.

[0063] Furthermore, in reactor 70, the second burner B2, which includes the second fuel nozzle N2, is supplied with the second fuel and combustion air at an air-to-air ratio of less than 1.0. With this configuration, the amount of NOx can be further reduced.

[0064] Furthermore, the furnace 70 described above may be realized by modifying an existing furnace that performs tangential combustion using pulverized coal and diesel fuel. For example, some of the burners supplying pulverized coal may be modified to supply ammonia as second burners. For example, a second fuel nozzle N2 may be obtained by connecting the ammonia supply line to at least one nozzle supplying pulverized coal. Alternatively, a second fuel port may be obtained by connecting the ammonia supply line to at least one air port. In this case, the orientation of the nozzles and air ports of the corresponding burners is changed so that the ammonia and combustion air are supplied toward a region inside a virtual circle whose tangential direction is used as the injection direction of the pulverized coal. Alternatively, the furnace 70 may be newly manufactured.

[0065] Next, other embodiments will be described.

[0066] Figure 4 is a schematic diagram showing a plurality of burners B in the furnace 70A according to the second embodiment, viewed in the vertical direction.

[0067] Furnace 70A differs from furnace 70 in the position of burner B in the horizontal direction. Other configurations of furnace 70A may be the same as those of furnace 70.

[0068] Specifically, in furnace 70A, burner B is positioned on each of the four side walls 71, 72, 73, and 74, instead of in the corner between side walls 71, 72, 73, and 74.

[0069] Furnace 70A has the same effect as furnace 70. Furthermore, with the above configuration, the distance from burner B to the center of furnace 70A is shorter than that of furnace 70. Therefore, radiation from burner B is increased. Thus, ignition is promoted, and combustion can be stabilized even at low loads.

[0070] Figure 5 is a schematic diagram showing a plurality of burners B of the furnace 70B according to the third embodiment, viewed in the vertical direction.

[0071] Furnace 70B differs from furnace 70 in the horizontal position of the burner B. Also, furnace 70B differs from furnace 70 in the number of burner B. Furnace 70B may be the same as furnace 70 in other configurations.

[0072] Specifically, in furnace 70B, the burners B are positioned on each of the four side walls 71, 72, 73, and 74, instead of in the corners between the side walls 71, 72, 73, and 74. In addition, each of the four side walls 71, 72, 73, and 74 is provided with two rows of burners B spaced apart from each other in the horizontal direction.

[0073] Furnace 70B has the same effect as furnace 70. Furthermore, with the above configuration, the distance from burner B to the center of furnace 70B is shorter than that of furnace 70. Therefore, radiation from burner B is increased. Moreover, with the above configuration, the number of burners B is increased compared to furnace 70. Therefore, ignition is further promoted, and combustion can be further stabilized even at low loads.

[0074] While embodiments have been described above with reference to the attached drawings, this disclosure is not limited to the embodiments described above. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally fall within the technical scope of this disclosure.

[0075] For example, in the above embodiment, ammonia is used as the second fuel. However, the second fuel is not limited to ammonia. For example, by-product gases such as blast furnace gas (BFG), converter gas (LDG), and coke oven gas (COG) contain nitrogen at relatively high concentrations compared to other fuels, so NOx generation can be a problem even when by-product gases are used as fuel. Therefore, in other embodiments, by-product gases may be used as the second fuel. In yet another embodiment, the second fuel may contain both ammonia and by-product gases.

[0076] Furthermore, in the above embodiment, for example, pulverized coal is used as the first fuel. However, the first fuel is not limited to pulverized coal. For example, in another embodiment, biomass may be used as the first fuel. In yet another embodiment, the first fuel may include both pulverized coal and biomass.

[0077] Furthermore, in the above embodiment, for example, diesel fuel is used as the third fuel. However, the third fuel is not limited to diesel fuel. For example, in other embodiments, heavy oil A, heavy oil C, or residual oil may be used as the third fuel. In yet another embodiment, the third fuel may not be used at all.

[0078] Furthermore, in the above embodiment, for example, a first fuel, a second fuel, and a third fuel are used as fuel. In other embodiments, other fuels may be used.

[0079] Furthermore, for example, in the above embodiment, the second fuel is supplied to the combustion space S from the second fuel nozzle N2 of the second burner B2. However, for example, in other embodiments, the furnace does not have to include the second burner B2. In this case, for example, the second fuel may be supplied to the combustion space S from a plurality of air ports in the same stage of at least one of the first burner B1 and the third burner B3, in lieu of or in addition to air. In this case, the plurality of air ports that inject the second fuel function as second fuel ports that supply the second fuel. Furthermore, for example, a plurality of second fuel ports may be additionally formed in at least one of the first burner B1 and the third burner B3 in the same stage. In this case, for example, the plurality of second fuel ports may be formed around the fuel nozzle.

[0080] This disclosure is CO ２ By promoting the use of ammonia, which leads to a reduction in emissions, it can contribute, for example, to Sustainable Development Goal 7, "Ensure access to affordable, reliable, sustainable and modern energy," and Goal 13, "Take urgent action to combat climate change and its impacts."

[0081] 70 Furnace 70A Furnace 70B Furnace B Burner C1 First virtual circle (virtual circle) F1 Pulverized coal (first fuel) F2 Ammonia (second fuel) N1 First fuel nozzle (first fuel port) N2 Second fuel nozzle (second fuel port) S Combustion space

Claims

1. A furnace comprising a plurality of fuel ports arranged in a plurality of stages along the vertical direction, wherein each of the plurality of stages includes at least one stage comprising a plurality of first fuel ports that supply a first fuel containing nitrogen at a first concentration to a combustion space, and at least one stage comprising a plurality of second fuel ports that supply a second fuel containing nitrogen at a second concentration higher than the first concentration to the combustion space, wherein the plurality of first fuel ports are arranged to supply the first fuel in the direction of the tangent to a predetermined virtual circle when viewed in the vertical direction, and the plurality of second fuel ports are arranged to supply the second fuel toward a region inside the virtual circle when viewed in the vertical direction.

2. The furnace according to claim 1, wherein the second fuel is ammonia.

3. The furnace according to claim 1, wherein the at least one stage including the plurality of second fuel ports includes one or more of the plurality of stages, excluding the uppermost stage of the plurality of stages.

4. The furnace according to claim 1, wherein the at least one stage including the plurality of second fuel ports includes the lowest stage of the plurality of stages.

5. The furnace according to claim 1, wherein the burner including the second fuel port is supplied with the second fuel and combustion air at an air ratio of less than 1.0.

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