Combustion device and boiler

Abstract

This combustion device (100) comprises: a burner (4) having an ammonium injection nozzle (41) which faces an injection port (41b) in an inner space of a furnace (2); and an adjustment mechanism (6) which adjusts the opening area of the injection port (41b). The most suitable drawing: Fig. 2.

Description

Combustion equipment and boilers

[0001] This application claims the benefit of priority from Japanese Patent Application No. 2021-025116, filed on February 19, 2021, the contents of which are incorporated herein by reference.

[0002] Among burners installed in furnaces such as boilers, there are burners having ammonia injection nozzles that inject ammonia as fuel. Using ammonia as fuel reduces carbon dioxide emissions. For example, Patent Document 1 discloses a burner that mixes pulverized coal and ammonia as fuel.

[0003] JP 2019-086189 A

[0004] In a burner having an ammonia injection nozzle, NOx is reduced when the ammonia injected from the ammonia injection nozzle reaches the reduction region of the flame (i.e., the region where nitrogen oxides (hereinafter also referred to as NOx), which are the target of reduction, are reduced). However, depending on the operating conditions, the injected ammonia may not be sufficiently supplied to the reduction region of the flame, which may result in an increase in NOx in the exhaust combustion gas. Therefore, a new proposal for reducing NOx is desired.

[0005] An object of the present disclosure is to provide a combustion device and a boiler that are capable of reducing nitrogen oxides (NOx).

[0006] In order to solve the above problems, the combustion device of the present disclosure includes a burner having an ammonia injection nozzle whose injection port faces the internal space of the furnace, and an adjustment mechanism that adjusts the opening area of ​​the injection port.

[0007] A control device may be provided that controls the operation of the adjustment mechanism so that the opening area of ​​the injection port decreases as the flow rate of ammonia in the ammonia injection nozzle decreases.

[0008] The burner may have a pulverized coal injection nozzle with an injection port facing the interior space of the furnace, and may be provided with a control device that controls the operation of the adjustment mechanism based on the flow rate of the pulverized coal in the pulverized coal injection nozzle.

[0009] The furnace may include an air supply unit with an injection port facing the interior space of the furnace, and a control device that controls the operation of the adjustment mechanism based on the air flow rate in the air supply unit.

[0010] A control device may be provided that controls operation of the adjustment mechanism based on the temperature in the interior space of the furnace.

[0011] In order to solve the above problem, the boiler of the present disclosure is equipped with the above combustion device.

[0012] According to the present disclosure, nitrogen oxides (NOx) can be reduced.

[0013] Fig. 1 is a schematic diagram showing a boiler according to this embodiment. Fig. 2 is a schematic diagram showing a combustion device according to this embodiment. Fig. 3 is a flowchart showing an example of a flow of processing performed by a control device according to this embodiment. Fig. 4 is a schematic diagram showing a flame formed by a burner according to this embodiment. Fig. 5 is a schematic diagram showing a state in which the opening area of ​​the injection port of the ammonia injection nozzle according to this embodiment is smaller than that of the example in Fig. 4. Fig. 6 is a schematic diagram showing a combustion device according to a modified example.

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Dimensions, materials, and other specific numerical values ​​shown in the embodiments are merely examples for ease of understanding and, unless otherwise specified, do not limit the present disclosure. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present disclosure are not shown.

[0015] 1 is a schematic diagram showing a boiler 1 according to this embodiment. As shown in FIG. 1, the boiler 1 includes a furnace 2, a flue 3, and a burner 4.

[0016] The furnace 2 is a furnace that burns fuel to generate combustion heat. The following mainly describes an example in which ammonia and pulverized coal are used as fuel in the furnace 2. By using ammonia and pulverized coal as fuel, carbon dioxide emissions are reduced. However, as will be described later, the fuel used in the furnace 2 is not limited to this example.

[0017] The furnace 2 has a cylindrical shape (e.g., a rectangular cylindrical shape) extending vertically. In the furnace 2, high-temperature combustion gas is generated by the combustion of fuel. An outlet 2a is provided at the bottom of the furnace 2 to discharge ash generated by the combustion of the fuel to the outside.

[0018] The flue 3 is a passage that guides the combustion gas generated in the furnace 2 to the outside as exhaust gas. The flue 3 is connected to the upper part of the furnace 2. The flue 3 has a horizontal flue 3a and a rear flue 3b. The horizontal flue 3a extends horizontally from the upper part of the furnace 2. The rear flue 3b extends downward from the end of the horizontal flue 3a.

[0019] The boiler 1 includes a superheater (not shown) that is installed above the furnace 2. In the superheater, heat is exchanged between the combustion heat generated in the furnace 2 and water, thereby generating steam. The boiler 1 may also include various devices (e.g., a reheater, an economizer, or an air preheater) that are not shown in FIG. 1 .

[0020] The burners 4 are provided on the wall at the bottom of the furnace 2. A plurality of burners 4 are provided in the furnace 2 at intervals in the circumferential direction of the furnace 2. Although not shown in FIG. 1 , the plurality of burners 4 are also provided at intervals in the extension direction (vertical direction) of the furnace 2. The burners 4 inject ammonia and pulverized coal as fuel into the furnace 2. The fuel injected from the burners 4 burns, forming a flame F in the furnace 2. The furnace 2 is provided with an ignition device (not shown) that ignites the fuel injected from the burners 4.

[0021] Fig. 2 is a schematic diagram showing a combustion device 100 according to this embodiment. As shown in Fig. 2, the combustion device 100 includes a burner 4, an air supply unit 5, an adjustment mechanism 6, an ammonia tank 7, an ammonia flow meter 8, an exhaust gas analyzer 9, and a control device 10.

[0022] The burner 4 is attached to the wall of the furnace 2 outside the furnace 2. The burner 4 has an ammonia injection nozzle 41 and a pulverized coal injection nozzle 42. The ammonia injection nozzle 41 is a nozzle that injects ammonia. The pulverized coal injection nozzle 42 is a nozzle that injects pulverized coal.

[0023] The ammonia injection nozzle 41 and the pulverized coal injection nozzle 42 have a cylindrical shape. The pulverized coal injection nozzle 42 is arranged coaxially with the ammonia injection nozzle 41 so as to surround the ammonia injection nozzle 41. The ammonia injection nozzle 41 and the pulverized coal injection nozzle 42 form a double cylindrical structure. The central axes of the ammonia injection nozzle 41 and the pulverized coal injection nozzle 42 intersect with the wall of the furnace 2 (specifically, are substantially perpendicular to each other).

[0024] Hereinafter, the radial direction of the burner 4, the axial direction of the burner 4, and the circumferential direction of the burner 4 will also be simply referred to as the radial direction, the axial direction, and the circumferential direction. The furnace 2 side of the burner 4 (the right side in FIG. 2) will be referred to as the leading end side, and the opposite side of the burner 4 from the furnace 2 side (the left side in FIG. 2) will be referred to as the trailing end side.

[0025] The ammonia injection nozzle 41 includes a main body 41a and an injection port 41b. The main body 41a has a cylindrical shape. The central axis of the main body 41a intersects with the wall of the furnace 2 (specifically, is approximately perpendicular to it). The main body 41a has a shape that tapers toward the tip. A supply port (not shown) is provided at the rear of the main body 41a (i.e., the rear end portion). The supply port of the ammonia injection nozzle 41 is connected to the ammonia tank 7. An opening, the injection port 41b, is formed at the tip of the main body 41a. The injection port 41b faces the internal space of the furnace 2. In other words, the injection port 41b faces the internal space of the furnace 2.

[0026] Ammonia is supplied into the main body 41a from the ammonia tank 7 through a supply port (not shown). As shown by arrow A1, the ammonia supplied into the main body 41a flows through the space between the inner periphery of the main body 41a and a valve body 61 of the adjustment mechanism 6 (described later). The ammonia that has passed through the main body 41a is injected from the injection port 41b toward the interior space of the furnace 2. In this way, the ammonia injection nozzle 41 is provided toward the interior space of the furnace 2.

[0027] The pulverized coal injection nozzle 42 includes a main body 42a and an injection port 42b. The main body 42a has a cylindrical shape. The main body 42a is arranged coaxially with the main body 41a of the ammonia injection nozzle 41 so as to surround the main body 41a. The main body 42a has a shape that tapers toward the tip side. A supply port (not shown) is provided at the rear part of the main body 42a (i.e., the rear end portion).

[0028] The supply port of the pulverized coal injection nozzle 42 is connected to a pulverized coal supply source (not shown). An injection port 42b, which is an opening, is formed at the tip of the main body 42a. The axial position of the tip of the main body 42a substantially coincides with the axial position of the tip of the main body 41a of the ammonia injection nozzle 41. The injection port 42b is an annular opening between the tip of the main body 42a and the tip of the main body 41a of the ammonia injection nozzle 41. The injection port 42b faces the internal space of the furnace 2. In other words, the injection port 42b faces the internal space of the furnace 2.

[0029] Pulverized coal is supplied into the main body 42a from a pulverized coal supply source via a supply port (not shown) together with air for transporting the pulverized coal. As shown by arrow A2, the pulverized coal supplied into the main body 42a flows together with the air in the space between the inner periphery of the main body 42a and the outer periphery of the main body 41a of the ammonia injection nozzle 41. The pulverized coal that has passed through the main body 42a is injected from the injection port 42b toward the interior space of the furnace 2. In this way, the pulverized coal injection nozzle 42 is provided toward the interior space of the furnace 2.

[0030] The air supply unit 5 supplies combustion air from the radially outer side to the flame formed by the burner 4 (see flame F in FIG. 1 ). The air supply unit 5 is arranged to cover the area between the tip of the burner 4 and the furnace 2. A flow path 51 through which air flows is formed in the air supply unit 5. The flow path 51 is formed in a cylindrical shape coaxial with the burner 4. The flow path 51 is connected to an air supply source (not shown). An injection port 52 is formed in the end of the flow path 51 on the furnace 2 side.

[0031] As shown by arrow A3, air supplied from an air supply source to the air supply unit 5 passes through a flow path 51 and is sprayed from an injection port 52 toward the interior space of the furnace 2. The injection port 52 faces the interior space of the furnace 2. In other words, the injection port 52 faces toward the interior space of the furnace 2. In this way, the air supply unit 5 is provided facing the interior space of the furnace 2. The air sprayed from the injection port 52 of the air supply unit 5 advances toward the interior space of the furnace 2 while swirling in the circumferential direction.

[0032] The adjustment mechanism 6 adjusts the opening area of ​​the injection port 41b of the ammonia injection nozzle 41. In the example of Fig. 2, the adjustment mechanism 6 has a valve body 61 and a drive device 62. However, as will be described later, the configuration of the adjustment mechanism 6 is not limited to this example.

[0033] The valve element 61 includes a shaft portion 61a and a cone portion 61b. The valve element 61 may be solid or hollow. The shaft portion 61a extends on the central axis of the burner 4. The shaft portion 61a is arranged coaxially with the main body 41a of the ammonia injection nozzle 41 so as to be surrounded by the main body 41a. The shaft portion 61a penetrates the rear portion of the main body 41a of the ammonia injection nozzle 41 and protrudes rearward. The cone portion 61b is attached to the tip of the shaft portion 61a. The cone portion 61b has a shape that tapers toward the tip (in the example of FIG. 2, it is a cone shape). The cone portion 61b is located axially near the tip of the main body 41a of the ammonia injection nozzle 41.

[0034] The drive device 62 moves the valve element 61 in the axial direction. For example, the drive device 62 includes a mechanism that guides the axial movement of the shaft portion 61 a and a device that generates power (for example, a motor, etc.). The drive device 62 can move the valve element 61 in the axial direction by transmitting power to the rear part of the shaft portion 61 a.

[0035] When the axial position of the tip of the cone portion 61b is located rearward of the axial position of the tip of the main body 41a of the ammonia injection nozzle 41 (i.e., on the opposite side from the furnace 2), the injection port 41b of the ammonia injection nozzle 41 becomes a circular opening defined by the inner periphery of the tip of the main body 41a. Therefore, the opening area of ​​the injection port 41b of the ammonia injection nozzle 41 becomes the area of ​​the circular opening defined by the inner periphery of the tip of the main body 41a. In this case, the opening area of ​​the injection port 41b is maximum.

[0036] On the other hand, when the axial position of the tip of the cone portion 61b is closer to the furnace 2 than the axial position of the tip of the main body 41a of the ammonia injection nozzle 41, the injection port 41b of the ammonia injection nozzle 41 becomes an annular opening defined between the inner periphery of the tip of the main body 41a and the outer periphery of the cone portion 61b. Therefore, the opening area of ​​the injection port 41b of the ammonia injection nozzle 41 becomes the area of ​​the annular opening defined between the inner periphery of the tip of the main body 41a and the outer periphery of the cone portion 61b. In this case, the opening area of ​​the injection port 41b is smaller than when the injection port 41b is a circular opening.

[0037] When the axial position of the tip of the cone portion 61b is located closer to the furnace 2 than the axial position of the tip of the main body 41a of the ammonia injection nozzle 41, if the axial position of the valve element 61 changes, the outer diameter of the valve element 61 at the axial position of the tip of the main body 41a changes. This changes the opening area of ​​the annular injection port 41b between the tip of the main body 41a and the cone portion 61b. The closer the axial position of the valve element 61 is to the furnace 2, the larger the outer diameter of the valve element 61 at the axial position of the tip of the main body 41a, and therefore the smaller the opening area of ​​the injection port 41b.

[0038] As described above, the adjustment mechanism 6 can adjust the opening area of ​​the injection port 41b of the ammonia injection nozzle 41 by moving the valve body 61 in the axial direction using the drive device 62. In this embodiment, the adjustment mechanism 6 is provided in the combustion device 100, thereby achieving a reduction in nitrogen oxides (NOx). The action and effect of reducing NOx by the adjustment mechanism 6 will be described later.

[0039] The ammonia flow meter 8 measures the flow rate of ammonia supplied from the ammonia tank 7 to the ammonia injection nozzle 41. The measurement result by the ammonia flow meter 8 is output to the control device 10.

[0040] The exhaust gas analyzer 9 analyzes the components of the exhaust gas, which is the combustion gas discharged from the furnace 2. The analysis results by the exhaust gas analyzer 9 are output to the control device 10.

[0041] The control device 10 includes a central processing unit (CPU), a ROM storing programs and the like, a RAM as a work area, and the like, and controls the entire combustion device 100. In particular, the control device 10 controls the operation of the adjustment mechanism 6. For example, the current axial position of the valve disc 61 is output from the adjustment mechanism 6 to the control device 10. Then, the control device 10 can control the operation of the adjustment mechanism 6 based on the output result from the adjustment mechanism 6 so that the axial position of the valve disc 61 becomes the target position.

[0042] 3 is a flowchart showing an example of the flow of processing performed by the control device 10 according to this embodiment. The processing flow shown in FIG. 3 is executed repeatedly at set time intervals, for example.

[0043] 3 starts, in step S101, the control device 10 acquires the flow rate of ammonia (hereinafter also referred to as the ammonia flow rate) in the ammonia injection nozzle 41. For example, the control device 10 acquires the measurement result of the ammonia flow meter 8 as the flow rate of ammonia in the ammonia injection nozzle 41.

[0044] After step S101, in step S102, the control device 10 sets a target position (specifically, a target axial position) of the valve element 61 based on the ammonia flow rate. Here, the control device 10 sets the target position of the valve element 61 to a position closer to the internal space of the furnace 2 as the ammonia flow rate decreases.

[0045] After step S102, in step S103, the control device 10 acquires the current position (specifically, the current axial position) of the valve element 61. For example, the control device 10 acquires the current position of the valve element 61 from the adjustment mechanism 6.

[0046] After step S103, in step S104, the control device 10 controls the drive device 62 so that the axial position of the valve element 61 becomes the target position, and the processing flow shown in Fig. 3 ends. In step S104, for example, if there is a difference between the current position of the valve element 61 and the target position, the control device 10 moves the valve element 61 so that the difference disappears.

[0047] 3 , the control device 10 controls the operation of the drive device 62 so that the valve body 61 moves in a direction toward the inside of the furnace 2 as the ammonia flow rate decreases. This allows the control device 10 to control the operation of the adjustment mechanism 6 so that the opening area of ​​the injection port 41 b of the ammonia injection nozzle 41 decreases as the ammonia flow rate decreases.

[0048] 4 is a schematic diagram showing a flame F formed by the burner 4 according to this embodiment. In the burner 4, ammonia is injected from the ammonia injection nozzle 41, pulverized coal is injected from the pulverized coal injection nozzle 42, and combustion air is supplied from the air supply unit 5, thereby forming a flame F in front of the burner 4. The flame F formed in this manner has a reduction region in which NOx is reduced. The reduction region is present, for example, radially outward of the region in which the flame F is formed.

[0049] NOx is reduced when the ammonia injected from the ammonia injection nozzle 41 reaches the reduction region of the flame F. Here, when changing the amount of power generation in power generation using the boiler 1, the ammonia co-firing ratio (the proportion of ammonia in the fuel injected from the burner 4) may be changed. In this case, the flow rate of ammonia supplied to the ammonia injection nozzle 41 is changed, thereby changing the flow rate of ammonia at the ammonia injection nozzle 41 (i.e., the ammonia flow rate).

[0050] In the conventional technology, when the flow rate of ammonia in the ammonia injection nozzle 41 (i.e., the ammonia flow rate) decreases, the injection speed of the ammonia injected from the ammonia injection nozzle 41 decreases. As a result, the ammonia injected from the ammonia injection nozzle 41 is not sufficiently supplied to the reduction region of the flame F, which may increase the amount of NOx in the exhaust combustion gas.

[0051] Therefore, in this embodiment, as described above, the operation of the adjustment mechanism 6 is controlled so that the opening area of ​​the injection port 41 b becomes smaller as the ammonia flow rate becomes smaller. Fig. 5 is a schematic diagram showing a state in which the opening area of ​​the injection port 41 b of the ammonia injection nozzle 41 according to this embodiment is smaller than that of the example in Fig. 4.

[0052] In the example of Figure 5, the ammonia flow rate is smaller than in the example of Figure 4. Therefore, the valve body 61 moves in a direction toward the inside of the furnace 2 compared to the example of Figure 4. As a result, the injection port 41b is narrowed by the cone portion 61b, and the opening area of ​​the injection port 41b is reduced. Therefore, a decrease in the injection speed of ammonia due to a decrease in the ammonia flow rate is suppressed. Therefore, the injection speed of ammonia can be maintained at the same level as in the example of Figure 4. Therefore, if ammonia is sufficiently supplied to the reduction region of the flame F in the example of Figure 4, ammonia is also sufficiently supplied to the reduction region of the flame F in the example of Figure 5. In this way, NOx reduction is appropriately achieved.

[0053] As described above, the combustion device 100 according to this embodiment includes the adjustment mechanism 6 that adjusts the opening area of ​​the injection port 41b of the ammonia injection nozzle 41. This suppresses a decrease in the injection speed of ammonia due to changes in operating conditions, thereby reducing NOx. In particular, by controlling the operation of the adjustment mechanism 6 based on the ammonia flow rate, NOx reduction is appropriately achieved.

[0054] Here, from the viewpoint of more effectively reducing NOx, it is preferable to optimize the relationship between the ammonia flow rate and the opening area of ​​the injection port 41b using the measured value of NOx in the exhaust gas discharged from the furnace 2. The measured value of NOx in the exhaust gas discharged from the furnace 2 is obtained, for example, based on the analysis results of the exhaust gas analyzer 9. For example, the measured value of NOx in the exhaust gas when the opening area of ​​the injection port 41b is variously changed for the same ammonia flow rate is accumulated as data. Next, a map defining the relationship between the ammonia flow rate and the opening area of ​​the injection port 41b is created using the accumulated data so that NOx in the exhaust gas is effectively reduced. Then, the control device 10 controls the adjustment mechanism 6 so that the relationship between the ammonia flow rate and the opening area of ​​the injection port 41b becomes the relationship shown in the created map. This more effectively reduces NOx.

[0055] Furthermore, from the viewpoint of more effectively reducing NOx, the control device 10 may control the operation of the adjustment mechanism 6 based on various parameters other than the ammonia flow rate. For example, the control device 10 may control the operation of the adjustment mechanism 6 based on other parameters described below in addition to the ammonia flow rate. Furthermore, for example, the control device 10 may control the operation of the adjustment mechanism 6 based on other parameters described below instead of the ammonia flow rate. Below, examples of various parameters that can be used to control the adjustment mechanism 6 will be described.

[0056] The control device 10 may control the operation of the adjustment mechanism 6 based on the flow rate of pulverized coal in the pulverized coal injection nozzle 42 (hereinafter also referred to as the pulverized coal flow rate). For example, the control device 10 controls the operation of the adjustment mechanism 6 so that the opening area of ​​the injection port 41b becomes smaller as the pulverized coal flow rate increases. The larger the pulverized coal flow rate, the larger the flow rate of air for transporting the pulverized coal. Therefore, the ammonia injected from the ammonia injection nozzle 41 is dragged by the air injected from the pulverized coal injection nozzle 42, making it difficult for the ammonia to spread throughout the entire flame F. Therefore, by reducing the opening area of ​​the injection port 41b, the injection speed of ammonia increases, and ammonia is more likely to be sufficiently supplied to the reduction region of the flame F.

[0057] The control device 10 may control the operation of the adjustment mechanism 6 based on the flow rate of air in the air supply unit 5 (hereinafter also referred to as the supply air flow rate). For example, the control device 10 controls the operation of the adjustment mechanism 6 so that the opening area of ​​the injection port 41b becomes smaller as the supply air flow rate increases. The larger the supply air flow rate, the more the ammonia injected from the ammonia injection nozzle 41 becomes entrained by the air injected from the air supply unit 5, making it more difficult for the ammonia to spread throughout the entire flame F. Therefore, by reducing the opening area of ​​the injection port 41b, the injection speed of the ammonia increases, making it easier for ammonia to be sufficiently supplied to the reduction region of the flame F.

[0058] The control device 10 may control the operation of the adjustment mechanism 6 based on the temperature in the internal space of the furnace 2 (hereinafter also referred to as the furnace temperature). For example, the control device 10 controls the operation of the adjustment mechanism 6 so that the opening area of ​​the injection port 41b decreases as the furnace temperature increases. The higher the furnace temperature, the more the air injected from the pulverized coal injection nozzle 42 and the air supply unit 5 expands, increasing the flow rate of the air. Therefore, the ammonia injected from the ammonia injection nozzle 41 is dragged by the air injected from the pulverized coal injection nozzle 42 and the air supply unit 5, making it difficult for the ammonia to spread throughout the entire flame F. Therefore, by reducing the opening area of ​​the injection port 41b, the injection speed of the ammonia increases, making it easier for ammonia to be sufficiently supplied to the reduction region of the flame F.

[0059] Although the details of the ignition device of the furnace 2 are not mentioned above, an oil burner, for example, is used as the ignition device of the furnace 2. The oil burner ignites by injecting oil into the internal space of the furnace 2. The oil burner is provided on some of the burners 4 (specifically, the lowest burner 4 of the multiple burners 4 arranged in the vertical direction). The oil burner extends on the central axis of the burner 4. The burner 4 described above with reference to FIG. 2 etc. is a burner that does not include an oil burner. However, the adjustment mechanism 6 may be provided on a burner that includes an oil burner. In this case, for example, the oil burner may be provided so as to penetrate the valve body 61 in the axial direction. Alternatively, the oil burner may have the same external shape as the valve body 61, and a mechanism in which the oil burner is provided axially movable in place of the valve body 61 may be used as the adjustment mechanism 6.

[0060] Fig. 6 is a schematic diagram showing a combustion apparatus 100A according to a modified example. As shown in Fig. 6, the combustion apparatus 100A has a different configuration of the valve body of the adjustment mechanism compared to the above-described combustion apparatus 100. The adjustment mechanism 6A of the combustion apparatus 100A has a valve body 161 that is different from the valve body 61 of the above-described adjustment mechanism 6.

[0061] The adjustment mechanism 6A has a drive device 62, similar to the above-described adjustment mechanism 6. The drive device 62 moves the valve body 161 in the axial direction, thereby adjusting the opening area of ​​the injection port 41b of the ammonia injection nozzle 41, similar to the above-described adjustment mechanism 6.

[0062] The valve element 161 of the adjustment mechanism 6A includes a shaft portion 161a and a cone portion 161b. Similar to the shaft portion 61a of the valve element 61 described above, the shaft portion 161a extends on the central axis of the burner 4. The cone portion 161b is attached to the tip of the shaft portion 161a. Similar to the cone portion 61b of the valve element 61 described above, the cone portion 161b has a shape that tapers toward the tip (in the example of FIG. 6, it is a cone shape).

[0063] Here, the outer periphery of the valve element 161 according to the modified example extends along the inner periphery of the main body 41a of the ammonia injection nozzle 41. In other words, the radial gap formed between the inner periphery of the main body 41a and the outer periphery of the valve element 161 is substantially constant regardless of the axial position. Specifically, the shaft portion 161a has a shape that tapers toward the tip. The outer diameter of the tip of the shaft portion 161a is substantially the same as the outer diameter of the rear end of the cone portion 161b. In other words, no step is provided between the shaft portion 161a and the cone portion 161b.

[0064] As described above, the gap between the main body 41a and the valve element 161 is substantially constant regardless of the axial position, which makes it possible to smooth the flow of ammonia within the main body 41a of the ammonia injection nozzle 41. Furthermore, the absence of a step on the outer periphery of the valve element 161 also makes it possible to smooth the flow of ammonia within the main body 41a of the ammonia injection nozzle 41.

[0065] Although the embodiments of the present disclosure have been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to such embodiments. It is clear that a person skilled in the art can conceive of various modifications and alterations within the scope of the claims, and it is understood that such modifications and alterations also fall within the technical scope of the present disclosure.

[0066] In the above example, the adjustment mechanism 6 includes the valve element 61 and the drive device 62, and adjusts the opening area of ​​the injection port 41b of the ammonia injection nozzle 41 by moving the valve element 61 axially using the drive device 62. However, the adjustment mechanism 6 is not limited to the above example as long as it has the function of adjusting the opening area of ​​the injection port 41b of the ammonia injection nozzle 41. For example, if the tip of the main body 41a of the ammonia injection nozzle 41 is itself deformed to change the opening area of ​​the injection port 41b, a mechanism including the tip of the main body 41a and a drive device that drives the tip may correspond to the adjustment mechanism 6. Furthermore, for example, if a member that can move or extend radially inward from the inner periphery of the tip of the main body 41a of the ammonia injection nozzle 41 is provided, a mechanism including the member and a drive device that drives the member may correspond to the adjustment mechanism 6.

[0067] In the above, an example has been described in which the pulverized coal injection nozzle 42 is disposed radially outside the ammonia injection nozzle 41 in the burner 4, and the ammonia injection nozzle 41 and the pulverized coal injection nozzle 42 form a double-cylinder structure. However, the configuration of the burner 4 is not limited to the above example. For example, the pulverized coal injection nozzle 42 may be disposed radially inside the ammonia injection nozzle 41. Furthermore, for example, an air injection nozzle that injects air for combustion may be added to the burner 4. In this case, for example, the burner 4 may have a triple-cylindrical structure, and among the spaces partitioned by the triple-cylindrical structure, the central space may be the ammonia flow path, the space adjacent to the ammonia flow path on the radial outside may be the air flow path, and the space adjacent to the air flow path on the radial outside may be the pulverized coal flow path.

[0068] In the above, an example has been described in which ammonia and pulverized coal are used as fuel in the furnace 2. However, the fuel used in the furnace 2 is not limited to the above example as long as it contains at least ammonia. For example, the fuel used together with ammonia in the furnace 2 may be a fuel other than pulverized coal (for example, natural gas or biomass). Furthermore, for example, the fuel used in the furnace 2 may be ammonia alone.

[0069] The present disclosure contributes to reducing nitrogen oxides (NOx) in combustion equipment used in boilers and the like, and can therefore contribute to, for example, Sustainable Development Goal (SDG) Goal 7 "Ensure access to affordable, reliable, sustainable and modern energy" and Goal 13 "Take urgent action to combat climate change and its impacts."

[0070] 1: Boiler 2: Furnace 4: Burner 5: Air supply unit 6: Adjustment mechanism 6A: Adjustment mechanism 10: Control device 41: Ammonia injection nozzle 41b: Injection port 42: Pulverized coal injection nozzle 42b: Injection port 52: Injection port 100: Combustion device 100A: Combustion device

Claims

1. A combustion device comprising: a burner having an ammonia injection nozzle whose injection port faces the internal space of a furnace; and an adjustment mechanism for adjusting the opening area of ​​the injection port.

2. The combustion device according to claim 1, further comprising a control device that controls the operation of the adjustment mechanism so that the opening area of ​​the injection port becomes smaller as the flow rate of ammonia in the ammonia injection nozzle becomes smaller.

3. A combustion device according to claim 1 or 2, wherein the burner has a pulverized coal injection nozzle whose injection port faces the internal space of the furnace, and the device is equipped with a control device that controls the operation of the adjustment mechanism based on the flow rate of pulverized coal at the pulverized coal injection nozzle.

4. A combustion device according to any one of claims 1 to 3, comprising an air supply unit with an injection port facing the internal space of the furnace, and a control device that controls the operation of the adjustment mechanism based on the air flow rate in the air supply unit.

5. The combustion apparatus according to any one of claims 1 to 4, further comprising a control device that controls the operation of the adjustment mechanism based on the temperature in the internal space of the furnace.

6. A boiler equipped with a combustion device according to any one of claims 1 to 5.