COMBUSTION EQUIPMENT AND STEAM BOILERS

Abstract

A combustion device (100) is provided, comprising: a burner (4) comprising an ammonia injection nozzle (41) having an injection orifice (41b) facing a furnace interior space (2); and an adjustment structure (6) configured to adjust an opening area of ​​the injection orifice (41b).

Description

Description COMBUSTION DEVICES AND STEAM BOILERS Invention Engineering Field This disclosure relates to a combustion device and a steam boiler. This application claims priority benefit of Japanese Patent Application No. 2021-025116 filed on February 19, 2021, and the contents thereof are incorporated herein. Background of the Invention As a burner provided for a steam boiler furnace or the like, a burner comprising an ammonia injection nozzle that injects ammonia as fuel is known. By using ammonia as fuel, the amount of carbon dioxide emissions is reduced. For example, in Patent Literature 1, there is a disclosure of a burner that co-combusts pulverized coal and ammonia as fuel. Patent Literature Citation List Patent Literature 1 : 2019-086189 A Brief Description of the Invention Technical issues Incidentally, in a combustor that includes an ammonia injection nozzle, when the ammonia injected from the ammonia injection nozzle reaches the flame reduction region (i.e., the region where the nitrogen oxides (hereinafter sometimes referred to as NOx) to be reduced are reduced), NOx is reduced. Here, depending on the operating conditions, there is a risk that the injected ammonia may not be sufficiently supplied to the flame reduction region, and NOx in the combustion gas to be exhausted may increase. Therefore, there is a demand for new proposals to reduce NOx. This disclosure is aimed at combustion and boiler capable (NOx). to provide devices to reduce nitrogen oxides Solution to problem To solve the above-mentioned problems, according to the present disclosure, a combustion device is provided, including: a burner including an ammonia injection nozzle having an injection hole facing a chamber in the furnace; and an adjustment structure configured to adjust the opening area of ​​the injection hole. The combustion device may further include a control device configured to control the operation of the adjustment structure so that the opening area of ​​the injection orifice becomes smaller as the ammonia flow rate in the ammonia injection nozzle becomes lower. The burner may include a pulverized coal injection nozzle having an injection orifice facing a chamber in the furnace, and the combustion device may include a control device configured to control the operation of the adjustment structure based on a flow rate of pulverized coal in the pulverized coal injection nozzle. The combustion device may further include: an air supply section having an injection port facing the furnace interior space; and a control device configured to control the operation of the adjustment structure based on the air flow rate in the air supply section. The combustion device may further include a control device configured to control the operation of the adjustment structure based on the temperature within the furnace chamber. To overcome the above-mentioned problems, according to the present disclosure, a steam boiler is provided which includes the above-mentioned combustion device. Disclosure Effects According to this disclosure, it is possible to reduce nitrogen oxides (NOx). Short Description of Image Figure 1 is a schematic view to illustrate a steam boiler according to an embodiment. Figure 2 is a schematic diagram to illustrate a combustion device according to an embodiment. Figure 3 is a flowchart to illustrate an example of the processing flow performed by a control device according to an embodiment. Figure 4 is a schematic view to illustrate the flame formed by a burner according to an embodiment. Figure 5 is a schematic view to illustrate a situation where an opening area of ​​an injection port of an ammonia injection nozzle according to an embodiment is smaller than the example in Figure 4. Figure 6 is a schematic view to illustrate the combustion device according to the modified example. Complete Description of the Invention Now, with reference to the accompanying drawings, embodiments of the present disclosure are described. The dimensions, materials, and other specific numerical values ​​represented in the embodiments are merely examples used to facilitate understanding of the disclosure, and do not limit the disclosure as specifically stated. Elements having substantially the same function and configuration are indicated herein and in the drawings by the same reference symbol to eliminate redundant description. Furthermore, illustrations of elements not directly related to the present disclosure are omitted. Figure 1 is a schematic view to illustrate a steam boiler 1 according to this embodiment. As illustrated in Figure 1, the boiler 1 includes a furnace 2, a flue gas duct 3, and a burner 4. Furnace 2 is a furnace that generates combustion heat by burning fuel. The following describes an example where ammonia and pulverized coal are used as fuel in furnace 2. When ammonia and pulverized coal are used as fuel, the amount of carbon dioxide emissions is reduced. However, as explained later, the fuels used in furnace 2 are not limited to this example. Furnace 2 has a tubular shape (e.g., a rectangular tubular shape) extending vertically. In furnace 2, high-temperature combustion gases are generated when fuel is burned. An outlet hole 2a is formed at the bottom of furnace 2 to discharge the ash content generated by fuel combustion to the outside. The flue gas duct 3 is a path for directing the combustion gases produced in furnace 2 to the outside as flue gas. The flue gas duct 3 is connected to the top of furnace 2. The flue gas duct 3 includes a horizontal flue gas duct 3a and a rear flue gas duct 3b. The horizontal flue gas duct 3a extends in a horizontal direction from the top of furnace 2. The rear flue gas duct 3b extends downward from the end of the horizontal flue gas duct 3a. Boiler 1 includes a superheater (not shown) installed at, for example, the top of furnace 2. In the superheater, heat exchange takes place between the combustion heat generated in furnace 2 and water. As a result, steam is generated. In addition, boiler 1 may also include various types of equipment (e.g., a reheater, an economizer, or an air preheater) not shown in Figure 1. A burner 4 is provided on the wall portion at the bottom of furnace 2. In furnace 2, a plurality of burners 4 are provided at intervals in the circumferential direction of furnace 2. Although not shown in Figure 1, a plurality of burners 4 are provided at intervals also in the transverse direction (up-down direction) of furnace 2. Burner 4 injects ammonia and pulverized coal into furnace 2 as fuel. A flame F is formed in furnace 2 when the fuel injected from burner 4 is burned. In furnace 2, an ignition device (not shown) is provided that ignites the fuel injected from burner 4. Figure 2 is a schematic diagram to illustrate a combustion device 100 according to this embodiment. As illustrated in Figure 2, the combustion device 100 includes a burner 4, an air supply section 5, an adjustment structure 6, an ammonia tank 7, an ammonia flow meter 8, a flue gas analyzer 9, and a control device 10. The burner 4 is installed on the wall portion of the furnace 2 outside the furnace 2. The burner 4 includes an ammonia injection nozzle 41 and a pulverized coal injection nozzle 42. The ammonia injection nozzle 41 is a nozzle for injecting ammonia. The pulverized coal injection nozzle 42 is a nozzle for injecting pulverized coal. The ammonia injection nozzle 41 and the pulverized coal injection nozzle 42 each have a cylindrical shape. The pulverized coal injection nozzle 42 is arranged so as to surround the ammonia injection nozzle 41 coaxially with the ammonia injection nozzle 41. A double cylindrical structure is formed by the ammonia injection nozzle 41 and the pulverized coal injection nozzle 42. The center axes of the ammonia injection nozzle 41 and the pulverized coal injection nozzle 42 intersect with (in particular substantially orthogonal to) a furnace wall portion 2. The radial direction of the burner 4, the axial direction of the burner 4, and the circumferential direction of the burner 4 are hereinafter sometimes simply referred to as the radial direction, the axial direction, and the circumferential direction. The furnace side 2 (right side in FIG. 2) of the burner 4 is referred to as the distal end side, and the side (left side in FIG. 2) of the burner 4 opposite the furnace side 2 is referred to as the rear side. The ammonia injection nozzle 41 includes a main body 41a and an injection port 41b. The main body 41a has a cylindrical shape. A central axis of the main body 41a intersects (particularly substantially orthogonal to) a portion of the furnace wall (2). The main body 41a has a shape that tapers toward the distal end side. At a rear portion (i.e., a portion on the rear end side) of the main body 41a, a supply port (not shown) is formed. The supply port of the ammonia injection nozzle 41 is connected to the ammonia tank 7. An injection port 41b which is an opening is formed at the distal end of the main body 41a. The injection port 41b faces the furnace interior space 2. That is, the injection port 41b is directed toward the furnace interior space 2. Ammonia is supplied from the ammonia tank 7 to the main body 41a through a supply port (not shown). As indicated by arrow A1, the ammonia supplied into the main body 41a flows in the space between the inner peripheral portion of the main body 41a and the valve body 61 of the adjustment structure 6 described later. The ammonia that has passed through the main body 41a is injected from the injection port 41b into the inner space of the furnace 2. In this way, the ammonia injection nozzle 41 is provided so that it is directed into the inner space of the furnace 2. 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 so as to surround the main body 41a coaxially with the main body 41a of the ammonia injection nozzle 41. The main body 42a has a tapered shape toward the distal end side. A supply hole (not shown) is formed at the rear portion (i.e., the portion at the rear end side) of the main body 42a. The supply hole of the pulverized coal injection nozzle 42 is connected to the pulverized coal supply source (not shown). The injection hole 42b which is an opening formed at the distal end of the main body 42a. The axial position of the distal end of the main body 42a basically matches the axial position of the distal end of the main body 41a of the ammonia injection nozzle 41. The injection hole 42b is a circular opening between the distal end of the main body 42a and the distal end of the main body 41a of the ammonia injection nozzle 41. The injection hole 42b faces the inner chamber of the furnace 2. That is, the injection hole 42b is directed toward the inner chamber of the furnace 2. Pulverized coal is supplied from the pulverized coal supply source to the main body 42a through the supply hole (not shown) together with air to carry 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 peripheral part of the main body 42a and the outer peripheral part of the main body 41a from the ammonia injection nozzle 41. The pulverized coal that has passed through the main body 42a is injected from the injection hole 42b into the inner chamber of the furnace 2. In this way, the pulverized coal injection nozzle 42 is directed into the inner chamber of the furnace 2. The air supply section 5 supplies air for combustion from the outer side radially to the flame (see flame F in FIG. 1) formed by the burner 4. The air supply section 5 is arranged so as to cover the area between the distal end portion of the burner 4 and the furnace 2. A flow path 51 that allows air to flow through it is formed in the air supply section 5. The flow path 51 is formed into a cylindrical shape coaxially with the burner 4. The flow path 51 is connected to an air supply source (not shown). An injection hole 52 is formed at the end portion of the flow path 51 on the side of the furnace 2. As shown by arrow A3, the air supplied from the air supply source to the air supply section 5 passes through the flow path 51 and is injected from the injection port 52 into the furnace interior space 2. The injection port 52 faces the furnace interior space 2. That is, the injection port 52 is directed toward the furnace interior space 2. In this way, the air supply section 5 is provided so as to be directed toward the furnace interior space of furnace 2. The air injected from the injection port 52 of the air supply section 5 moves forward toward the furnace interior space 2 while rotating in the circumferential direction. The adjustment structure 6 adjusts the opening area of ​​the injection port 41b of the ammonia injection nozzle 41. In the example in Figure 2, the adjustment structure 6 includes a valve body 61 and an actuating device 62. However, as explained later, the configuration of the adjustment structure 6 is not limited to this example. The valve body 61 includes a shaft portion 61a and a cone portion 61b. The valve body 61 may be solid or hollow. The shaft portion 61a spans the central axis of the burner 4. The shaft portion 61a is arranged so that it is surrounded by the main body 41a coaxially with the main body 41a of the ammonia injection nozzle 41. The shaft portion 61a protrudes rearward through the rear portion of the main body 41a of the ammonia injection nozzle 41. The cone portion 61b is fitted to the distal end of the shaft portion 61a. The cone portion 61b has a shape (conical shape in the example in FIG. 2) that tapers toward the distal end side. The cone portion 61b is located around the distal end of the main body 41a of the ammonia injection nozzle 41 in the axial direction. The actuating device 62 moves the valve body 61 in an axial direction. For example, the actuating device 62 includes a mechanism that guides the movement of the pivot portion 61a in an axial direction and a power-generating device (e.g., a motor). The actuating device 62 can then move the valve body 61 in an axial direction by transmitting power to a rear portion of the pivot portion 61a. When the axial position of the distal end of the cone portion 61b is placed on the back side (i.e., on the side opposite to the furnace side 2) of the axial position of the distal end of the main body 41a of the ammonia injection nozzle 41, the injection hole 41b of the ammonia injection nozzle 41 is a circular opening defined by the inner peripheral portion of the distal end of the main body 41a. Therefore, the opening area of ​​the injection hole 41b of the ammonia injection nozzle 41 is the circular opening area defined by the inner peripheral portion of the distal end of the main body 41a. In this case, the opening area of ​​the injection hole 41b becomes maximum. Meanwhile, when the axial position of the distal end of the conical portion 61b is located on the furnace side 2 of the axial position of the distal end of the main body 41a of the ammonia injection nozzle 41, the injection hole 41b of the ammonia injection nozzle 41 is an annular opening defined between the inner peripheral portion of the distal end of the main body 41a and the outer peripheral portion of the conical portion 61b. Therefore, the opening area of ​​the injection hole 41b of the ammonia injection nozzle 41 is an annular opening area defined between the inner peripheral portion of the distal end of the main body 41a and the outer peripheral portion of the conical portion 61b. In this case, the opening area of ​​the injection hole 41b is smaller compared to the case where the injection hole 41b is an annular opening. In the case where the axial position of the distal end of the cone portion 61b is located on the furnace side 2 of the axial position of the distal end of the main body 41a of the ammonia injection nozzle 41, when the axial position of the valve body 61 is changed, the outer diameter of the valve body 61 at the axial position of the distal end of the main body 41 is changed. As a result, the opening area of ​​the injection hole 41b having a circular shape between the distal end of the main body 41a and the cone portion 61b changes. When the axial position of the valve body 61 becomes closer to the furnace 2, the outer diameter of the valve body 61 at the axial position of the distal end of the main body 41a becomes larger, and accordingly the opening area of ​​the injection hole 41b becomes smaller. As described above, the adjustment structure 6 can adjust the opening area of ​​the injection hole 41b of the ammonia injection nozzle 41 by moving the valve body 61 in the axial direction with the driving device 62. In this embodiment, the reduction of nitrogen oxides (NOx) is achieved by providing the adjustment structure 6 on the combustion device 100. The action and effect of reducing NOx by the adjustment structure 6 will be explained later. 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 provided by the ammonia flow meter 8 is output to the control device 10. The flue gas analyzer 9 analyzes the flue gas components, namely the combustion gas released from the furnace 2. The analysis results provided by the flue gas analyzer 9 are output to the control device 10. The control device 10 includes a central processing unit (CPU), a ROM storage program and the like, a RAM serving as a work area, and the like and controls the entire combustion device 100. Specifically, the control device 10 controls the operation of the adjustment structure 6. For example, the current axial position of the valve body 61 is output from the adjustment structure 6 to the control device 10. Then, the control device 10 can control the operation of the adjustment structure 6 based on the output result provided by the adjustment structure 6 so that the axial position of the valve body 61 is brought to a target position. Figure 3 is a flowchart to illustrate an example of a processing flow performed by a control device 10 according to this embodiment. The processing flow illustrated in Figure 3 is performed repeatedly, for example, at specified time intervals. When the processing flow illustrated in Figure 3 is initiated, at Step S101, the control device 10 obtains the ammonia flow rate (hereinafter sometimes referred to as the ammonia flow rate) at the ammonia injection nozzle 41. For example, the control device 10 obtains the measurement result provided by the ammonia flow meter 8 as the ammonia flow rate at the ammonia injection nozzle 41. In Step S102 following Step S101, the control device 10 sets the target position (specifically, the axial position becomes the target) of the valve body 61 based on the ammonia flow rate. Here, the control device 10 sets a position closer to the inner chamber of the furnace 2 as the target position of the valve body 61 because the ammonia flow rate becomes lower. In Step S103 following Step S102, the control device 10 obtains the current position (specifically, the current axial position) of the valve body 61. For example, the control device 10 obtains the current position of the valve body 61 from the adjustment structure 6. In Step S104 following to Step S103, control device 10 controls actuating device 62 so that the axial position of the valve body 61 is brought to the target position, and the processing flow illustrated in FIG. 3 ends. In Step S104, for example, when there is a difference between the current position and the target position of the valve body 61, control device 10 acts on the valve body 61 so that the difference is eliminated. As described above, in the processing flow illustrated in Figure 3, the control device 10 controls the operation of the actuator 62 so that the valve body 61 is moved toward the inner side of the furnace 2 as the ammonia flow rate becomes lower. With this configuration, the control device 10 can control the operation of the adjustment structure 6 so that the opening area of ​​the injection hole 41b of the ammonia injection nozzle 41 becomes smaller as the ammonia flow rate becomes lower. Figure 4 is a schematic view to illustrate a flame F formed by a burner 4 according to this embodiment. In the burner 4, a flame F is formed in front of the burner 4 when ammonia is injected from an ammonia injection nozzle 41, pulverized coal is injected from a pulverized coal injection nozzle 42, and air for combustion is supplied from an air supply section 5. The flame F thus formed has a reduction region, namely a region where NOx is reduced. The reduction region exists, for example, on the radially outward side of the region where the flame F is formed. When the ammonia injected from the ammonia injection nozzle 41 reaches the flame reduction region F, NOx is reduced. Here, when the amount of power generation in the power plant using steam boiler 1 is changed, the ammonia co-combustion ratio (the ratio of ammonia in the fuel injected from the burner 4) can be changed. In this case, the ammonia flow rate (i.e., the ammonia flow rate) in the ammonia injection nozzle 41 is changed by changing the ammonia flow rate supplied to the ammonia injection nozzle 41. In related technology, when the ammonia flow rate (i.e., ammonia flow rate) in the ammonia injection nozzle 41 is reduced, the injection speed of the ammonia injected from the ammonia injection nozzle 41 is reduced. As a result, the ammonia injected from the ammonia injection nozzle 41 is not sufficiently supplied to the flame reduction region F, and there is a risk that NOx in the combustion gas to be discharged may increase. In view of the above, in this embodiment, as described above, the operation of the adjustment structure 6 is controlled so that the opening area of ​​the injection port 41b becomes smaller as the ammonia flow rate becomes lower. Figure 5 is a schematic view to illustrate a situation where the opening area of ​​the injection port 41b of the ammonia injection nozzle 41 according to this embodiment is smaller compared to the example in Figure 4. In the example in Figure 5, the ammonia flow rate is lower compared to the example in Figure 4. Due to this, the valve body 61 is further moved to the inner side of the furnace 2 compared to the example in Figure 4. With this configuration, the injection hole 41b is narrowed by the conical portion 61b, and the opening area of ​​the injection hole 41b becomes smaller. As a result, the decrease in the ammonia injection speed caused by the decrease in the ammonia flow rate can be suppressed. Therefore, the ammonia injection speed can be maintained at the same level as the example in Figure 4. Therefore, if sufficient ammonia is supplied to the flame reduction region F in the example in Figure 4, sufficient ammonia is supplied to the flame reduction region F also in the example in Figure 5. In this way, NOx reduction can be achieved. As described above, the combustion device 100 according to this embodiment includes an adjustment structure 6 that adjusts the opening area of ​​the injection hole 41b of the ammonia injection nozzle 41. With this configuration, the decrease in the ammonia injection speed caused by the change in operating conditions is suppressed, and therefore NOx is reduced. In particular, when the operation of the adjustment structure 6 is controlled based on the ammonia flow rate, a corresponding reduction in NOx can be achieved. Here, from the viewpoint of further effective NOx reduction, it is preferred that the relationship between the ammonia flow rate and the opening area of ​​the injection port 41b be optimized through the use of NOx measurement values ​​in the flue gas discharged from the furnace 2. The NOx measurement values ​​in the flue gas discharged from the furnace 2 are obtained, for example, based on the analysis results provided by the flue gas analyzer 9. For example, the NOx measurement values ​​in the flue gas given when the opening area of ​​the injection port 41b is varied with respect to the same ammonia flow rate are accumulated as data. Subsequently, a map defining the relationship between the ammonia flow rate and the opening area of ​​the injection port 41b is created through the use of the accumulated data so that NOx in the flue gas is effectively reduced.Then, the control device 10 is directed to control the adjustment structure 6 so that the relationship between the ammonia flow rate and the opening area of ​​the injection hole 41b becomes the relationship indicated by the generated map. Thus, NOx is further reduced effectively. In addition, from the standpoint of further effective NOx reduction, control device 10 may control the operation of the tuning structure 6 based on various parameters in addition to the ammonia flow rate. For example, control device 10 may control the operation of the tuning structure 6 based on other parameters described below in addition to the ammonia flow rate. In addition, for example, control device 10 may control the operation of the tuning structure 6 based on other parameters described below in addition to the ammonia flow rate. Examples of various parameters that may be used to control the tuning structure 6 are described below. The control device 10 can control the operation of the adjustment structure 6 based on the flow rate of pulverized coal (hereinafter sometimes referred to as the flow rate of pulverized coal) in the pulverized coal injection nozzle 42. For example, the control device 10 controls the operation of the adjustment structure 6 so that the opening area of ​​the injection hole 41b becomes smaller as the flow rate of pulverized coal becomes higher. As the flow rate of pulverized coal becomes higher, the flow rate of air for carrying pulverized coal becomes higher. Therefore, the ammonia injected from the ammonia injection nozzle 41 is dragged by the air injected from the pulverized coal injection nozzle 42 and does not easily spread throughout the flame region F. Thus, when the opening area of ​​the injection hole 41b is adjusted smaller, the ammonia injection speed is increased, and ammonia can be easily supplied sufficiently to the flame reduction region F. The control device 10 can control the operation of the adjustment structure 6 based on the air flow rate (hereinafter sometimes referred to as the supplied air flow rate) in the air supply section 5. For example, the control device of Figure 10 controls the operation of the adjustment structure 6 so that the opening area of ​​the injection hole 41b becomes smaller as the supplied air flow rate becomes higher. Because the supplied air flow rate becomes higher, the ammonia injected from the ammonia injection nozzle 41 is dragged by the air injected from the air supply section 5 and does not easily spread throughout the flame region F. Thus, when the opening area of ​​the injection hole 41b is adjusted smaller, the ammonia injection speed is increased, and ammonia can be easily supplied sufficiently to the flame reduction region F. The control device 10 may control the operation of the adjustment structure 6 based on the temperature within the furnace chamber 2 (hereinafter sometimes referred to as the furnace temperature). For example, the control device 10 controls the operation of the adjustment structure 6 so that the opening area of ​​the injection hole 41b becomes smaller as the furnace temperature becomes higher. When the furnace temperature becomes higher, the air injected from the pulverized coal injection nozzle 42 and the air supply section 5 expands, and the air flow rate becomes higher. 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 section 5 and does not easily spread throughout the flame area F. Thus, when the opening area of ​​the injection hole 41b is adjusted smaller, the ammonia injection speed is increased, and ammonia can be easily supplied sufficiently to the flame reduction area F. 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 provides ignition by injecting oil into the furnace chamber 2. An oil burner is provided for at least one of the burners 4 (specifically, the lowest burner 4 of a plurality of burners 4 arranged in an up-down direction). The oil burner extends on the central axis of the burner 4. The burner 4 described above with reference to FIG. 2 and the like is a burner without an oil burner. However, an adjustment structure 6 may be provided for the burner provided by the oil burner. In this case, for example, the oil burner may be provided so as to penetrate the valve body 61 in an axial direction.Alternatively, a mechanism wherein the external shape of the oil burner is arranged to the same shape as the valve body 61 and the oil burner is provided so that it can be moved in the axial direction instead of the valve body 61 can be used as the adjustment structure 6. Figure 6 is a schematic view to illustrate the combustion device 100A according to the modified example. As illustrated in Figure 6, in the combustion device 100A, the valve body configuration of the adjustment structure is different from that of the combustion device 100 described above. The adjustment structure 6A of the combustion device 100A includes a valve body 161 different from the valve body 61 of the adjustment structure 6 described above. The adjustment structure 6A includes a driving device 62 in the same manner as the adjustment structure 6 described above. The adjustment structure 6A is the same as the adjustment structure 6 described above in that the opening area of ​​the injection hole 41b of the ammonia injection nozzle 41 is adjusted when the valve body 161 is moved in the axial direction by the driving device 62. The valve body 161 of the adjustment structure 6A includes a pivot portion 161a and a conical portion 161b. The pivot portion 161a spans the central axis of the burner 4 in the same manner as the pivot portion 61a of the valve body 61 described above. The conical portion 161b is mounted on the distal end of the pivot portion 161a. The conical portion 161b has a shape (conical shape in the example in FIG. 6) that tapers towards the distal end side in the same manner as the conical portion 61b of the valve body 61 described above. Here, the outer peripheral portion of the valve body 161 according to the modified example extends along the inner peripheral portion of the main body 41a of the ammonia injection nozzle 41. That is, the radial clearance formed between the inner peripheral portion of the main body 41a and the outer peripheral portion of the valve body 161 is essentially constant regardless of the axial position. In particular, the shaft portion 161a has a tapered shape toward the distal end side. An outer diameter of the distal end of the shaft portion 161a substantially corresponds to the outer diameter of the rear end of the cone portion 161b. That is, no step is formed between the shaft portion 161a and the cone portion 161b. As described above, if the gap between the main body 41a and valve body 161 are essentially constant regardless of the axial position, the ammonia flow in the main body 41a of the ammonia injection nozzle 41 can be smoothed. In addition, the smoothness of the ammonia flow in the main body 41a of the ammonia injection nozzle 41 is also achieved by the absence of steps in the outer peripheral portion of the valve body 161. Embodiments of the present disclosure have been described above with reference to the accompanying drawings, but, needless to say, the present disclosure is not limited to the above-mentioned embodiments. It is clear that those skilled in the art may arrive at various substitutions and modifications within the scope of the claims, and such examples are construed as naturally encompassing the technical scope of the present disclosure. In the previous description, an example wherein an adjustment structure 6 includes a valve body 61 and a driving device 62 and adjusts the opening area of ​​the injection hole 41b of the ammonia injection nozzle 41 by moving the valve body 61 in the axial direction with the driving device 62 is described. However, the adjustment structure 6 is only required to have the function of adjusting the opening area of ​​the injection hole 41b of the ammonia injection nozzle 41, and the adjustment structure 6 is not limited to the above-mentioned example. For example, when the opening area of ​​the injection hole 41b can be changed by deformation of the distal end portion itself of the main body 41a of the ammonia injection nozzle 41, the mechanism including the distal end portion of the main body 41a and the driving device that moves the distal end portion can correspond to the adjustment structure 6.In addition, for example, when a member that can move or extend radially inward from an inner peripheral portion of a distal end portion of the main body 41a of an ammonia injection nozzle 41 is provided, the mechanism includes a member and a driving device that moves the member can be in accordance with an adjustment structure 6. In the previous description, an example where the pulverized coal injection nozzle 42 is arranged on the radial outer side of the ammonia injection nozzle 41 in the burner 4, and a double-cylinder structure is formed by the ammonia injection nozzle 41 and the pulverized coal injection nozzle 42 is described. However, the configuration of the burner 4 is not limited to the above-mentioned example. For example, the pulverized coal injection nozzle 42 may be arranged on the radial inner side of the ammonia injection nozzle 41. In addition, for example, in the burner 4, an air injection nozzle for injecting air for combustion may be added. In this case, for example, the burner 4 may have a three-cylinder structure.Of the spaces defined by the three-cylinder structure, the space on the center side of the burner 4 can be a flow path for ammonia, the space adjacent to the flow path for ammonia on the outer radial side of the burner 4 can be an air flow path, and the space adjacent to the air flow path on the outer radial side can be a pulverized coal flow path. In the previous description, an example was described where ammonia and pulverized coal were used as fuel in furnace 2. However, the fuel used in furnace 2 is only required to contain at least some ammonia, and the fuel is not limited to the example mentioned above. For example, the fuel used together with ammonia in furnace 2 may be any fuel (e.g., natural gas or biomass) other than pulverized coal. Furthermore, for example, only ammonia may be used as fuel for use in furnace 2. This disclosure contributes to the reduction of nitrogen oxides (NOx) in combustion devices used in boilers or similar, and may therefore contribute to, for example, Goal 7 Ensure access to more affordable, reliable, sustainable and modern energy for all and Goal Take urgent action to combat climate change and its impacts in the Sustainable Development Goals (SDGs). List of Reference Marks 1: boiler, 2: furnace, 4: burner, 5: air supply section, : adjustment structure, 6A: adjustment structure, 10: control device, 41: ammonia injection nozzle, 41b: injection hole, 42: powder coal injection nozzle, 42b: injection hole, 52: injection hole, 100: combustion device, 100A: combustion device

Claims

Claim 1. A combustion device, comprising: a burner comprising an ammonia injection nozzle having an injection orifice facing a chamber in the furnace; and an adjustment structure configured to adjust an opening area of ​​the injection orifice.

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

3. A combustion device according to claim 1 or 2, wherein the burner includes a pulverized coal injection nozzle having an injection orifice facing into a furnace interior space, and wherein the combustion device further comprises a control device configured to control the operation of the adjustment structure based on a flow rate of pulverized coal in the pulverized coal injection nozzle.

4. A combustion device according to any one of claims 1 to 3, further comprising: an air supply section having an injection port facing a chamber in the furnace; and a control device configured to control the operation of the adjustment structure based on an air flow rate in the air supply section.

5. A combustion device according to any one of claims 1 to 4, further comprising a control device configured to control the operation of the adjustment structure based on the temperature in a space within the furnace. 5 6. A steam boiler comprising a combustion device any one of claims 1 to 5.

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