Combustion equipment

Abstract

A combustion device capable of suppressing the generation of nitrogen oxides is provided. [Solution] Ammonia burner 306 is installed by replacing a part of coal burner 304. Auxiliary air is supplied to the pulverized coal injected from coal burner 304 from auxiliary air nozzle 303 adjacent to ammonia burner 306 and equipped with startup fuel burner 307. Auxiliary air nozzle 303 equipped with startup fuel burner 307 is equipped with a damper that can adjust the amount of auxiliary air that can be supplied in the direction of ammonia burner 306. Auxiliary air nozzle 303, sandwiched between coal burner 302 and ammonia burner 306, is divided into upper and lower flow paths 303A and 303B, and the flow rate of each can be controlled by a damper.

Description

[Technical field]

[0001] The present invention relates to a combustion device. [Background technology]

[0002] Conventionally, a boiler in which ammonia is supplied as fuel into a furnace is known. When ammonia is used as fuel, it is necessary to suppress the emission of nitrogen oxides (NOx). For example, in a burner (shown in FIG. 2) disclosed in Patent Document 1, a nozzle that supplies ammonia by rotating from the periphery is installed on a nozzle that inputs ammonia (it is described that the rotation is not necessary), and ammonia is mixed into the swirling pulverized coal flame. More specifically, the following is disclosed. That is, a combustion device 4A that is installed in a furnace and can be burned using ammonia as fuel, includes an inner cylinder nozzle 41 that is arranged in the center as viewed from the fuel injection direction and injects ammonia, and an outer cylinder nozzle 42 that is arranged to surround the inner cylinder nozzle 41 from the radial outside as viewed from the fuel injection direction and injects ammonia around the inner cylinder nozzle 41. Also, a swirler 45 is arranged inside the outer cylinder nozzle 42 and swirls the flow of ammonia injected around the inner cylinder nozzle 41. According to Patent Document 1, ammonia injected from the inner cylinder nozzle 41 forms a reduction region with high ammonia concentration and low oxygen concentration in the center of the flame as viewed from the fuel injection direction. Meanwhile, nitrogen oxides generated by mixing ammonia injected from the outer cylinder nozzle around the inner cylinder nozzle with oxygen and burning are supplied to the reduction region by riding on a circulating flow returning from the outer edge of the flame to the center. As a result, the nitrogen oxides generated at the outer edge of the flame are reduced to nitrogen gas (N2) in the reduction region formed by the ammonia injected from the inner cylinder nozzle. Therefore, according to Patent Document 1, it is possible to suppress an increase in nitrogen oxides in a boiler capable of burning ammonia as fuel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-41748 A Summary of the Invention [Problem to be solved by the invention]

[0004] According to the knowledge of the inventors, in order to suppress the emission of nitrogen oxides, it is preferable that the ammonia-fueled burner uses another fuel to make the combustion environment in the boiler a reducing region and accurately control the air ratio near the ignition point. However, Patent Document 1 does not specifically disclose such a configuration. Furthermore, when ammonia is mixed and burned in the burner shown in Patent Document 1, increasing the ammonia mixed-firing ratio increases the air ratio of the coal nozzle. In the coal nozzle, the amount of conveying air must be kept constant to prevent coal from settling in the nozzle, and increasing the ammonia mixed-firing ratio reduces only the coal feed rate, so the amount of conveying air relative to the coal flow rate increases. This is because, at high ammonia mixed-firing ratios, the air ratio around the ammonia nozzle becomes high, causing a sharp increase in nitrogen oxides derived from ammonia oxidation.

[0005] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a combustion device capable of suppressing the generation of nitrogen oxides. [Means for solving the problem]

[0006] A combustion device according to at least one embodiment of the present invention has a burner for a carbon-containing fuel that burns a carbon-containing fuel in a furnace, and an ammonia burner to which ammonia is supplied through an ammonia supply line is provided adjacent to the burner for the carbon-containing fuel, and ammonia is injected into the furnace by the ammonia burner toward a flame generated by the burner for the carbon-containing fuel, thereby causing combustion. Effect of the Invention

[0007] According to the present invention, a combustion device capable of suppressing the generation of NOx can be provided. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a conceptual diagram of a boiler operation system according to one embodiment. [Diagram 2] FIG. 1 is a conceptual diagram of a burner according to a conventional example. [Figure 3A] FIG. 2 is a cross-sectional view showing the burner arrangement of a boiler before retrofitting according to one embodiment (an example of a coal burner retrofit). [Figure 3B] FIG. 2 is a cross-sectional view showing the burner arrangement of a boiler after retrofitting according to one embodiment (an example of a coal burner retrofit). [Figure 3C] FIG. 2 is a conceptual diagram showing the correspondence relationship between burner arrangements before and after the modification of a boiler according to one embodiment (an example of modification of a coal burner). [Figure 4] FIG. 2 is an illustration of the air flow associated with combustion of an ammonia burner according to one embodiment. [Figure 5A] FIG. 2 is an explanatory diagram showing the relationship between the ammonia burner air ratio and the amount of nitrogen oxides generated in the burner according to the embodiment. [Figure 5B] FIG. 2 is an explanatory diagram showing the relationship between the burner shape, the ammonia burner air ratio, and the amount of nitrogen oxides generated according to one embodiment. [Figure 5C] FIG. 2 is an explanatory diagram showing the relationship between an ammonia co-firing ratio, an ammonia burner air ratio, and an amount of nitrogen oxide generated according to an embodiment. [Figure 6A] FIG. 2 is a cross-sectional view showing the burner arrangement of a boiler before modification according to one embodiment (an example of modification of startup fuel burners). [Figure 6B] FIG. 2 is a cross-sectional view showing the burner arrangement of a boiler after modification according to one embodiment (an example of modification of startup fuel burners). [Figure 6C] FIG. 2 is a conceptual diagram showing the correspondence relationship between burner arrangements before and after modification of a boiler according to one embodiment (an example of modification of a startup fuel burner). [Figure 7A] FIG. 2 is a cross-sectional view showing the burner arrangement of a boiler after modification according to one embodiment (example of modified air nozzles). [Figure 7B] FIG. 2 is a conceptual diagram showing the correspondence relationship between burner arrangements before and after modification of a boiler according to one embodiment (an example of modification of air nozzles). [Figure 8A]FIG. 2 is a cross-sectional view showing the burner arrangement of a boiler after modification according to one embodiment (example of modification of the top air nozzle). [Figure 8B] FIG. 1 is a conceptual diagram showing the corresponding relationship of burner arrangement before and after modification of a boiler according to one embodiment (an example of modification of the air nozzle at the top). [Figure 9] FIG. 2 is a control system diagram of a boiler according to one embodiment. [Figure 10A] FIG. 2 is a flow diagram of a boiler control method according to one embodiment. [Figure 10B] FIG. 2 is a flow diagram of a NOx control process according to one embodiment. [Figure 10C] FIG. 4 is a control logic diagram for calculating a control command value for the amount of combustion air according to the embodiment. [Figure 11A] 1 is an opposed-fire ammonia burner arrangement according to one embodiment; [Figure 11B] 11B is a cross-sectional view taken along the line AA in FIG. 11A. [Figure 11C] 11B is a cross-sectional view taken along the line BB in FIG. 11A. [Figure 11D] FIG. 1 is a side view of an ammonia burner according to an embodiment. [Figure 11E] FIG. 1 is a side view of an oil ammonia burner according to an embodiment. [Figure 12] FIG. 2 is a conceptual diagram showing a reduction-oxidation state in a boiler according to one embodiment. [Figure 13] FIG. 2 is a diagram showing the structure of a spud burner. [Figure 14] FIG. 2 is a diagram showing the structure of a diffuser burner. [Figure 15] FIG. 2 is a diagram showing the structure of a swirler burner. [Figure 16] FIG. 2 is a flow diagram of a boiler retrofit method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0010] FIG. 1 is a conceptual diagram of a boiler operation system 1 according to one embodiment. The boiler operation system 1 includes a boiler 2 incorporated in, for example, a thermal power plant (not shown), a supply system 15 for supplying air and fuel to the boiler 2, and a measurement system 9 for measuring parameters related to the operation of the boiler 2. The fuel supplied from the supply system 15 to the boiler 2 includes ammonia fuel. The ammonia fuel may be either liquid ammonia or ammonia gas. An embodiment in which the ammonia fuel is liquid ammonia will be exemplified below. In one embodiment, the liquid ammonia is supplied to the boiler 2 in a liquid state. The liquid ammonia does not contain gases such as hydrogen gas, but may contain impurities (e.g., urea) to an extent that does not affect combustion in the boiler 2. The liquid ammonia vaporizes into ammonia gas in the boiler 2. The fuel supplied from the supply system 15 to the boiler 2 includes fuel other than ammonia fuel. For example, in the boiler 2, after combustion using other fuel is performed, ammonia is mixed with the other fuel or ammonia is exclusively combusted. The carbon-containing fuel, which is an example of a fuel other than ammonia, is a biomass fuel or a fossil fuel. The fossil fuel is liquefied natural gas, oil such as heavy oil or light oil, or coal such as pulverized coal. In the following, an embodiment in which the carbon-containing fuel is oil and pulverized coal is exemplified.

[0011] The boiler 2 of one embodiment includes a furnace 20 including a furnace wall 19. The furnace wall 19 includes a burner arrangement area 21 in which at least one burner unit 30 is provided, and an additional air supply area 22 in which an additional air supply unit 4 that supplies additional air is provided. The additional air supply area 22 is located downstream of the burner arrangement area 21. The furnace 20 is a cylindrical hollow body in which the fuel injected by the burner unit 30 reacts with the combustion air and is burned, and can have various shapes, for example, a cylindrical shape or a square prism shape. Moreover, the furnace 20 of one embodiment includes a nose 11 that protrudes into the furnace 20. The nose 11 is configured so that gas (e.g., combustion gas and unburned gas) generated in the combustion space 7 of the furnace 20 properly flows to a flow path on the downstream side of the furnace 20. The flow path on the downstream side of the furnace 20 is, for example, a flue 8. At least one burner unit 30 is configured to burn fuel in the combustion space 7 of the furnace 20. In the embodiment illustrated in FIG. 1, the burner units 30 are arranged in three stages along the direction in which gas generated in the combustion space 7 flows (arrow A in FIG. 1). Hereinafter, the burner units 30 in each stage may be referred to as the first burner unit 31, the second burner unit 32, and the third burner unit 33 in order from the downstream side in the gas flow direction, and these three stages of burners may be collectively referred to as the burner unit 30. The burner units 30 may be arranged in two or four stages, for example. The boiler 2 in one embodiment is a swirl combustion boiler, and the burner units 30 provided in each stage are arranged at equal intervals along the circumferential direction of the furnace 20. The number of burner units 30 in each stage is, for example, four, but only one burner unit 30 is illustrated in Fig. 1. Note that the number of burner units 30 in each stage may be three or five or more. The boiler 2 according to another embodiment is an opposed-fire boiler. In this case, at least a pair of burner units 30 are provided in each stage at positions opposed to each other.

[0012] Each burner unit 30 includes at least one burner, which in at least one burner unit 30 is an ammonia burner 306 configured to inject liquid ammonia in liquid form into the interior of the furnace 20. The ammonia burner 306 may be configured to inject only liquid ammonia, or may be configured to inject a carbon-containing fuel and then inject liquid ammonia together with (or instead of) the carbon-containing fuel. In one embodiment, the first burner unit 31 includes an ammonia burner 306. The second burner unit 32 and the third burner unit 33 may or may not include an ammonia burner 306. In other embodiments, the ammonia burner 306 may be included only in the second burner unit 32 or the third burner unit 33. Further, any one of the burner units 30 may include coal burners 302, 304 (pulverized coal burners 302, 304 shown in FIG. 3A) for injecting pulverized coal, which is an example of a carbon-containing fuel, into the furnace 20, a startup fuel burner 307 (see FIG. 3A) for injecting oil, which is an example of a startup fuel, into the furnace 20, or auxiliary air nozzles (air nozzles) 301, 305 (see FIG. 3A) for injecting auxiliary air. Details will be described later.

[0013] In one embodiment, the supply system 15 is configured to supply primary air and fuel to the burner units 30. The fuel (liquid ammonia and carbon-containing fuel in this example) supplied to the burner units 30 may be switched. For example, the burner units 30 of any stage may be supplied with a carbon-containing fuel (e.g., oil) followed by liquid ammonia.

[0014] The measurement system 9 in one embodiment includes a plurality of flow meters for measuring the flow rate of air or fuel supplied from the supply system 15, and a furnace thermometer 6 for measuring a representative temperature in the furnace 20. The representative temperature in the furnace 20 is a temperature that correlates with the gas temperature, which is the temperature of gas in the combustion space 7 of the furnace 20. As an example, the representative temperature in the furnace 20 is the temperature of the inner wall surface of the nose 11 described above (hereinafter referred to as the nose temperature). The nose temperature is measured by the furnace thermometer 6. The representative temperature in the furnace 20 may be, for example, the gas temperature.

[0015] The boiler operation system 1 may be operated by an operator, or may be operated under the control of a control device 5 (see FIG. 9) described later, or may be operated by a combination of these. In the furnace 20 of one embodiment, the supply of ammonia fuel may be started after a fuel other than ammonia fuel (in this example, a carbon-containing fuel) is combusted, and the ammonia fuel may be mixed and combusted with the other fuel.

[0016] The air ratio of combustion generally has a large effect on the generation of nitrogen oxides when fuels containing nitrogen, such as coal and ammonia, are burned. Here, we will explain the case of co-firing ammonia fuel and other fuels, with a comparison example in which one air ratio is calculated for the entire furnace, and an example in which the air ratio is calculated for each of ammonia fuel and carbon-containing fuel as the other fuel. (Comparative Example) The air ratio in the comparative example is the ratio of the amount of air supplied to the furnace 20 to the theoretical amount of air required to combust the ammonia fuel and other fuels supplied to the furnace 20. The amount of air supplied to the furnace 20 does not include additional air. That is, in this example, the air ratio constituting the ammonia co-firing conditions (described in detail later) is also a value obtained by multiplying the total air ratio by the supply ratio of air other than the additional air among all air supplied to the furnace 20. Specifically, the air ratio constituting the ammonia co-firing conditions (hereinafter sometimes referred to as the burner air ratio) is defined by the following formula (1). λ b=λ×(100-AA) / 100 Equation (1) In formula (1), λ b is the burner air ratio, λ is the total air ratio, and AA is the proportion of additional air supplied to the total air supply to boiler 2. In addition, the total air ratio (λ) is defined by equations (2), (3), and (4). λ=Q Air / Q x ...Equation (2) Q x =Q mf ×A mf ...Equation (3) A mf =(100-X) / 100×A car +X / 100×A NH3 ...Equation (4) In formulas (2) to (4), Q Air is the total air supply. Also, Q mf Q is the amount of ammonia fuel and other fuel (carbon-containing fuel in this example) supplied when the combustion performed in the furnace 20 is ammonia co-combustion (co-combustion rate in weight conversion: X%). x is the air flow rate for the air ratio to be 1 during the mixed combustion. mf is the theoretical amount of air for the fuel (in this example, ammonia fuel and carbon-containing fuel) when the above-mentioned mixed combustion is performed, and A car is the theoretical air amount of the carbon-containing fuel, and A NH3 is the theoretical air amount for ammonia fuel. (Example) In the embodiment, an ammonia air ratio, which is a ratio of the amount of air for ammonia combustion supplied to the ammonia fuel to the theoretical air amount of the ammonia fuel supplied to the furnace 20, and an air ratio for other fuel, which is a ratio of the amount of air for combustion supplied to the other fuel to the theoretical air amount of the other fuel, are calculated separately for each fuel. The ammonia air ratio (hereinafter sometimes referred to as the ammonia burner air ratio) is calculated from equations (5) and (6). λ NH3 =Q Air_NH3 / Q x_NH3 ...Equation (5) Q x_NH3 =Q NH3×A NH3 ...Equation (6) Here, λ in Eq. (5) NH3 is the ammonia air ratio, and Q Air_NH3 is the amount of air for ammonia combustion, and Q x_NH3 is the air flow rate for the ammonia fuel air ratio to be 1. Also, Q NH3 is the supply of ammonia fuel, and A NH3 is the theoretical air amount for ammonia fuel. Furthermore, if a carbon-containing fuel is taken as an example of another fuel, the air ratio of the carbon-containing fuel can be calculated using equations (7) and (8). λ car =Q Air_car / Q x_car ...Equation (7) Q x_car =Q car ×A car ...Equation (8) Here, λ in Eq. (7) car is the air ratio of the carbon-containing fuel, and Q Air_car is the amount of air for the combustion of carbon-containing fuel, and Q x_car is the air flow rate for the carbon-containing fuel to have an air ratio of 1. Also, Q in equation (8) car is the supply of carbon-containing fuel, and A car is the theoretical air amount for carbon-containing fuel. As in this embodiment, the ammonia air ratio λ NH3 and the air ratio λ of the carbon-containing fuel car For example, in the boiler 2 in which the ammonia burner 306 and the pulverized coal burner 302 are used (see FIG. 3B), the formulas (5) and (6) are applied to the air ratio of the ammonia burner 306, and the formulas (7) and (8) are applied to the air ratio of the pulverized coal burner 302. In other words, in this case, the parameters of the carbon-containing fuel shown in the formulas (7) and (8) are both parameters of the pulverized coal. Hereinafter, the air ratio refers to that calculated in this embodiment.

[0017] In one embodiment, the coal burner 302 and the ammonia burner 306 are placed separately as shown in Fig. 3A to Fig. 3C which shows an example of a swirl combustion boiler (Fig. 3A shows the boiler before modification, before the ammonia burner 306 is installed). This makes it possible to adjust the air ratio separately, and even if the ammonia co-firing ratio is increased, the ammonia air ratio can be reduced regardless of the operation of the coal burner, suppressing a sudden increase in NOx. The coal burner 302 of this embodiment is configured to burn coal (pulverized coal). In the following description, the coal burner 302 may be referred to as a pulverized coal burner 302.

[0018] In one embodiment, the upper limit of the burner air ratio is 0.8 or less. If the supply of ammonia fuel to the furnace 20 is started under the condition that the burner air ratio is 0.8 or less, the burner air ratio at the start of combustion of the ammonia fuel is also 0.8 or less. This effectively reduces NOx generated in the furnace 20. The upper limit of the burner air ratio may be 0.7 or less. In this case, combustion of ammonia fuel is started under the condition that the air ratio is 0.7 or less, and the generation of excessive NOx is suppressed. In addition, in a boiler 2 having a general size used in a thermal power plant, it is not realistic for the burner air ratio to be less than 0.6. Therefore, the burner air ratio constituting the ammonia co-firing condition, which is the condition that should be satisfied before the supply of ammonia fuel is started, is preferably 0.6 or more and 0.8 or less, and more preferably 0.6 or more and 0.7 or less. In addition, when a plurality of ammonia burners 306 are provided, the ammonia air ratio λ NH3 This is because, since the amount of NOx generated varies greatly depending on the ammonia air ratio as described later, it is possible to precisely calculate the ammonia air ratio for each burner and control the supply amounts of ammonia fuel and ammonia combustion air. Similarly, in order to precisely control the amount of NOx generated by each coal burner 302, the air ratio λ of the carbon-containing fuel is set to λ 2 . car It is preferable to calculate the coal-air ratio.

[0019] The control device 5 (see FIG. 9), which is a component of the boiler 2 in one embodiment, calculates the ammonia-air ratio from the amount of air supplied from the ammonia burner 306 (see FIG. 3B and FIG. 3C) and the amount of air supplied from the auxiliary air nozzles 303 and 305 adjacent to the ammonia burner 306. With regard to the amount of air supplied from the auxiliary air nozzles 303 and 305, only the amount of air contributing to ammonia combustion is calculated as the amount of air for ammonia combustion, and for example, when the auxiliary air nozzle 303 is sandwiched between the ammonia burner 306 and the coal burner 302 as shown in FIG. 3B and FIG. 3C, half of the amount of air is calculated as the air for ammonia burner. If the amount of NOx generated is higher than the reference value, the ammonia burner air ratio is controlled to be reduced, for example, from 0.7 to 0.6. FIG. 5A shows an example of the ammonia burner air ratio and the amount of NOx generated. In this test result, the optimal point of the ammonia burner air ratio is 0.6. If the ammonia burner air ratio is reduced below 0.6, NOx increases. Therefore, if the amount of NOx generated does not decrease even if the ammonia burner air ratio is reduced to 0.6, unburned ammonia reaches the combustion completion region, which is the space in the furnace at approximately the same height as the additional air supply region 22, and is converted to NOx. Therefore, while maintaining the ammonia burner air ratio at 0.6, the ratio of the amount of additional air to the total amount of air input to the boiler 2 is reduced to reduce the amount of unburned ammonia that reaches the combustion completion region, thereby reducing the amount of NOx generated in the combustion completion region.

[0020] 3A to 3C, the ammonia burner 306 is provided by replacing (modifying) a part of the coal burner 304. Auxiliary air is supplied to the pulverized coal injected from the coal burner 304 from an auxiliary air nozzle 303 adjacent to the ammonia burner 306 and having a startup fuel burner 307 installed therein. The auxiliary air nozzle 303 having the startup fuel burner 307 installed therein is provided with a damper that can adjust the amount of auxiliary air that can be supplied in the direction of the ammonia burner 306 (the amount of auxiliary air that can be supplied to the ammonia fuel injected into the furnace 12). In the case where the air nozzle (auxiliary air nozzle) 303 that supplies auxiliary air is sandwiched between the coal burner 302 and the ammonia burner 306, if the amount of air supplied from the nozzle is adjusted to the optimal air amount for the coal burner 302, it will be excessive with respect to the air amount for reducing nitrogen oxides in the ammonia burner 306. Conversely, if the air amount is adjusted to reduce NOx in the ammonia burner, the air amount will be insufficient from the optimal air ratio for the coal burner 302, leading to an increase in unburned carbon in the ash. In this embodiment, auxiliary air nozzle 303 sandwiched between coal burner 302 and ammonia burner 306 is divided into upper and lower flow paths 303A and 303B in accordance with the modification of boiler 2, and the flow rate of each can be controlled by a damper (see Fig. 3C and Fig. 4). This makes it possible to adjust the amount of air for coal burner 302 and ammonia burner 306 individually. In other words, the amount of air supplied to the pulverized coal injected from coal burner 302 and the amount of air supplied to the ammonia fuel injected from ammonia burner 306 can be adjusted individually. The coal burner air ratio is about 0.7 to 0.9. By making it possible to individually adjust the air flow rates from the flow paths 303A and 303B of the auxiliary air nozzle 303, it is possible to suppress the increase in unburned fuel in ash caused by the coal burner and to suppress the increase in NOx caused by the ammonia burner. In addition, by retrofitting the coal burner 304 to the ammonia burner 306, it is also possible to change the existing coal-fired boiler 2 to a boiler 2 that burns ammonia fuel. As shown in FIG. 3, by arranging the ammonia burner 306 adjacent to the coal burner 302, the heat generated by the coal combustion can be utilized for the ammonia combustion, and the ammonia can be burned stably. Furthermore, the amount of NOx contained in the combustion gas discharged from the boiler 2 may be calculated based on the amount of ammonia supplied to the ammonia burner 306 and the amount of combustion air supplied, and the first reference range may be set according to the calculation result. Alternatively, the first reference range may be set based on the measurement result of a measuring device provided in the boiler 2 for measuring the NOx concentration.

[0021] As shown in Figs. 6A to 6C, the boiler 2 according to at least one embodiment of the present invention has a startup fuel burner 307 that burns startup fuel, and the ammonia burner 306 can be provided by replacing (modifying) a part of the startup fuel burner 307. The ammonia burner 306 includes an ammonia nozzle 306A that injects ammonia. The ammonia nozzle 306A also functions as a startup fuel nozzle that injects startup fuel (oil as a specific example). When the boiler 2 is started up, the ammonia nozzle 306A injects startup fuel, and then injects ammonia when the ammonia co-firing conditions are satisfied. In another embodiment, the startup fuel nozzle may be configured as a nozzle separate from the ammonia nozzle 306A and may be provided in the same compartment as the ammonia nozzle 306A. If the startup fuel burner 307 is modified to an ammonia burner 306, the air nozzle 303 on one side adjacent to the coal burners 302, 304 will be lost, and the amount of auxiliary air directed to the coal burner 302 will not be sufficient. For this reason, the air ratio of the coal burners 302, 304 is set to an appropriate value of 0.7 to 0.9 by increasing the amount of air from the auxiliary air nozzles 301, 305 on the opposite side to the ammonia burner 306. In this embodiment, only the air supplied from the ammonia burner 306 is used in the calculation of the ammonia air ratio. By optimizing the air ratio of the coal burners 302 and 304, an increase in unburned fuel in the ash of the coal burners 302 and 304 can be suppressed.

[0022] At least one embodiment of the present invention, as shown in Figures 7A and 7B, has a plurality of auxiliary air nozzles 301, 305 for supplying auxiliary air, and the ammonia burner 306 is provided to replace some of the auxiliary air nozzles 301, 305. In the example of Figure 7B, the ammonia burner 306 is provided to replace the auxiliary air nozzle 305. As in the case of the modification of the startup fuel burner 307, the absence of the auxiliary air nozzle 305 on one side of the coal burner 304 results in a shortage of air for the coal burner 304. Also, if the compartment height of the auxiliary air nozzle 305 is low, it is difficult to install the ammonia burner 306 with a flame holder. The nozzle where the ammonia burner 306 adjacent to the coal burner 304 and the startup fuel burner 307 on the opposite side are installed is used as the auxiliary air nozzle 303, and the amount of air is increased to adjust to a specified amount. In this case, the auxiliary air nozzle 303 is on one side in the coal burner 304 shown in Fig. 7B, but since the upper coal burner 302 has auxiliary air nozzles 301 and 303 on the top and bottom, the air flow path of the startup oil burner is divided into upper and lower flow paths 303A and 303B, and the flow rate of each can be controlled with a damper so that the air amount can be increased only in the lower flow path 303B, and the air ratio of each of the coal burners 304 can be optimized, thereby suppressing the increase of unburned fuel in the ash. In the boiler 2 before the retrofit, if the wind box height where the auxiliary air nozzle 305 is installed is lower than the height of the coal burner 302 and the startup fuel burner 307, an ammonia burner 306 without a flame stabilizer and with a low wind box height is installed. For example, a premixing type spud nozzle as shown in Fig. 13 is used.

[0023] In the boiler 2 according to at least one embodiment of the present invention, as shown in Figures 8A and 8B, the ammonia burner 306 is provided by replacing (modifying) the auxiliary air nozzle 301 located at the top of the burner arrangement area 21. The ammonia burner 306 is provided adjacent to the coal burner 302. As in the previous example where the ammonia burner 306 is installed in the auxiliary air nozzle 305, the absence of the auxiliary air nozzle 301 on one side of the coal burner 302 causes a shortage of air for the coal burner 302. Also, if the compartment height of the auxiliary air nozzle 301 is low, it is difficult to install the ammonia burner 306 with a flame stabilizer. The air flow path of the startup fuel burner 307 is divided into upper and lower flow paths 303A and 303B, making it possible to control the flow paths 303A and 303B individually, and if the wind box height is low, a partial premixing nozzle (see Figure 13), which is an ammonia nozzle with a low wind box height and no flame stabilizer, is installed. In this case, ammonia can be used not only as a fuel but also as a denitrification agent.

[0024] The burners used in the above embodiment are diffusion combustion burners or partial premixed combustion burners (also called spud burners). Diffusion combustion burners can use swirler or diffuser types as flame holders. Figure 13 shows an example of the structure of a partial premixed spud burner, Figure 14 shows an example of the structure of a diffuser burner, and Figure 15 shows an example of the structure of a swirler burner. An example of a spud burner is shown in Figure 13. The spud burner is composed of a nozzle 132 that supplies ammonia into the inside of a wind box 131, and an outer cylinder 133. Combustion air is supplied from the wind box 131, and a damper for adjusting the flow rate is installed upstream of the wind box 131. Ammonia is injected into the outer cylinder 133, and is premixed with the combustion air that flows in through the gap between the nozzle 132 and the outer cylinder 133 before being injected into the furnace. Ammonia spontaneously ignites when it is mixed with an amount of air suitable for ignition by the high-temperature gas in the furnace. Since ammonia and air are partially premixed, the ignition point is formed at the point where the overall nozzle blowing flow rate matches the combustion speed of the premixed ammonia and air. Figure 14 shows an example of the structure of a diffuser burner. An ammonia nozzle 142 and a disk-shaped flame holder 143 (called a diffuser) are installed at the tip of the ammonia nozzle 142 inside a wind box 141. Ammonia is injected from multiple holes 142A installed in the ammonia nozzle 142 (two holes 142A are shown in the figure). Combustion air is supplied from the wind box 141, and a damper is installed upstream to adjust the flow rate. As the combustion air flows around the flame holder 143 at an accelerated speed, a vortex is formed on the outer periphery of the disk-shaped flame holder 143. Ammonia is caught in this vortex and mixed with the air to ignite, so the ignition point is formed on the flame holder 143. FIG. 15 shows an example of the structure of a swirler burner. An ammonia nozzle 152 and a flame holder 153 (called a swirler) having swirl vanes are installed inside a wind box 151 at the tip of the ammonia nozzle 152. Ammonia is injected from a number of holes 152A installed in the ammonia nozzle 152 (two holes 152A are shown in the figure). Combustion air is supplied from the wind box 151, and a damper for adjusting the flow rate is installed upstream. When the combustion air passes through the flame holder 153, it becomes a swirling flow by the swirl vanes and flows around the outer periphery of the ammonia nozzle 152. The swirling flow generates a circulating flow inside the swirling flow, so the ammonia and the circulating flow mix and ignite. As a result, the ignition point of the ammonia flame is formed near the downstream side of the flame holder 153.

[0025] FIG. 16 is a flow chart showing the boiler retrofitting method of the present invention. As described above with reference to FIG. 3C, FIG. 6C, FIG. 7B, and FIG. 8B, the boiler 2 before retrofitting includes a pulverized coal burner 302 and a plurality of injection units for injecting pulverized coal, a startup fuel which may be oil, or auxiliary air. Each injection unit is a coal burner 304, a startup fuel burner 307, or an auxiliary air nozzle 301, 303. S11 shown in FIG. 16 shows a process of replacing this injection unit with an ammonia burner 306. By carrying out S11, for example, an existing boiler 2 capable of coal-fired combustion can be retrofitted to a boiler 2 for burning ammonia fuel.

[0026] A boiler control method according to one embodiment (see FIG. 10B ) is a boiler control method for controlling the supply amounts of ammonia fuel, pulverized coal, and combustion air in a boiler 2 including a furnace 20 including a furnace wall 19, an ammonia burner 306 provided in the furnace wall 19 and burning ammonia fuel, and pulverized coal burners 302, 304 provided in a position on the furnace wall 19 different from the ammonia burner 306 and burning pulverized coal, the boiler control method controlling the supply amounts of the ammonia fuel, the pulverized coal, and combustion air in a boiler 2 including a furnace 20 including a furnace wall 19, an ammonia burner 306 provided in the furnace wall 19 and burning ammonia fuel, the ammonia burner 306 being provided in a position different from the ammonia burner 306 and burning pulverized coal, the boiler control method controlling the supply amounts of the ammonia fuel, the pulverized coal, and combustion air in a boiler 2 including a furnace wall 20 including a furnace wall 19 including a furnace wall 20 including a furnace wall 19 including ammonia burner 306 provided in the furnace wall 19 The method includes a first calculation step (S10-1) of calculating an ammonia air ratio which is a ratio of the amount of air for ammonia combustion supplied to the ammonia fuel, a second calculation step (S10-2) of calculating a pulverized coal air ratio which is a ratio of the amount of air for pulverized coal combustion supplied to the pulverized coal to a theoretical amount of air required for combusting the pulverized coal, and a control step (S10-3) of controlling the supply amount so that the ammonia air ratio satisfies a first standard range and the pulverized coal air ratio satisfies a second standard range. The upper limit value of the first standard range of the ammonia air ratio is preferably set to be smaller than the upper limit value of the second standard range of the pulverized coal air ratio. The optimal value of the air ratio for minimizing NOx emissions is about 0.6 for ammonia fuel, which is smaller than that for pulverized coal (usually about 0.7 to 0.8). Setting the upper limit value of the standard range with reference to the optimal value makes it easier to minimize NOx emissions.

[0027] 9 shows a specific configuration of a boiler operation system 1 according to an embodiment. The boiler operation system 1 includes a control device 5 for controlling the operation of the boiler 2, in addition to the boiler 2, the supply system 15, and the measurement system 9 described above. In one embodiment, the control device 5 includes a processor 91, a ROM 92, a RAM 93, and a memory 94. The processor 91 is configured to read out the boiler operation program stored in the ROM 92, load it into the RAM 93, and execute instructions included in the boiler operation program. The processor 91 is a CPU, a GPU, an MPU, a DSP, various other arithmetic devices, or a combination of these. The processor 91 may be realized by an integrated circuit such as a PLD, an ASIC, an FPGA, and an MCU. The memory 94 stores various data associated with the execution of the boiler operation program. One example of the memory 94 is a flash memory. The processor 91 is electrically connected to the supply system 15 and the measurement system 9. The processor 91 in one embodiment is configured to generate an other fuel combustion command for burning a fuel other than ammonia fuel in the furnace 20, an ammonia supply start command for starting the supply of ammonia fuel to the supply system 15, and an ammonia combustion start command for starting the combustion of ammonia in the furnace 20. In one embodiment, these control commands are sent to the supply system 15. In one embodiment, the processor 91 generates an ammonia supply start command when it is determined based on the measurement result of the measurement system 9 that the ammonia co-combustion condition for starting ammonia co-combustion is satisfied. In addition, in one embodiment, the processor 91 initiates an ammonia mono-combustion command when it is determined that the ammonia co-combustion condition for starting ammonia mono-combustion is satisfied. The ammonia mono-combustion condition is, for example, that the representative temperature in the furnace 20 has reached a specified temperature, that a specified time has elapsed since ammonia co-combustion was started, that a specified set value has been reached after a specified input operation was performed by the operator, or a combination of these.

[0028] The supply system 15 includes a primary air supply system 110 for supplying primary air, an additional air supply system 120 for supplying additional air, an ammonia supply system 100 for supplying liquid ammonia, an oil supply system 80 for supplying oil, and a pulverized coal supply system 70 for supplying pulverized coal. Each of the oil supply system 80 and the pulverized coal supply system 70 is an example of a system for supplying a carbon-containing fuel. Primary air, liquid ammonia, pulverized coal, and oil are supplied to the burner unit 30, and additional air is supplied to an additional air supply section 4 provided in the furnace wall 19. The supply system 15 is configured to be controlled by a control device 5.

[0029] An air supply line 112 of the primary air supply system 110 is connected to all of the burner units 30. The air supply line 112 is provided with a flow rate adjustment valve 116 for adjusting the flow rate of the primary air, and a switching valve 118 for switching the communication state of the air supply line 112. An air supply line 122 of the additional air supply system 120 is connected to the additional air supply unit 4. The air supply line 122 is provided with a flow rate adjustment valve 126 for adjusting the flow rate of the additional air, and a switching valve 128 for switching the communication state of the air supply line 122. The flow rate adjustment valves 116 , 126 and the switching valves 118 , 128 are configured to operate in response to control commands sent from the control device 5 .

[0030] The ammonia supply system 100 includes the above-mentioned ammonia burner 306, an ammonia tank 101 in which liquid ammonia is stored, an ammonia supply line 102 connecting the ammonia tank 101 and the ammonia burner 306, a pump 103 provided in the ammonia supply line 102, a pressure regulating valve 105 for adjusting the pressure of the ammonia supply line 102, a switching valve 107 provided in the ammonia supply line 102 and for switching the communication state between the ammonia tank 101 and the ammonia burner 306, and a flow rate control valve 108 for adjusting the flow rate of liquid ammonia flowing through the ammonia supply line 102. The pressure regulating valve 105, the switching valve 107, and the flow rate regulating valve 108 are configured to operate in response to a control command from the processor 91. This allows the ammonia supply system 100 to change between a supply stop state in which no ammonia burner 306 supplies liquid ammonia, and a supply state in which liquid ammonia is supplied to all of the ammonia burners 306. As described later, when the ammonia supply system 100 is in a supply stop state, oil is supplied from the oil supply system 80 to the ammonia burners 306 of the second burner unit 32 and the third burner unit 33.

[0031] An oil supply system 80 of one embodiment includes an oil supply device 81, an oil supply line 82 connecting the oil supply device 81 and an ammonia burner 306, an oil flow rate regulating valve 86 for regulating the flow rate of oil flowing through the oil supply line 82, and a switching valve 88 for switching the communication state of the oil supply line 82. The oil supply line 82 of this example is connected to the ammonia burners 306 of the second burner unit 32 and the third burner unit 33. In one embodiment, the oil supply device 81, the oil flow rate regulating valve 86, and the switching valve 88 are configured to operate in response to a control command from the control device 5. This allows the oil supply system 80 to change between a supply state in which oil is supplied to the ammonia burner 306 connected to the oil supply line 82, and a supply stop state in which the supply of oil is stopped. In another embodiment, the oil supply line 82 may be connected to the start-up fuel burner 37 for injecting the oil. The oil supply line 82 may also be configured to receive atomized steam. In this case, the oil and atomized steam are supplied to the burner unit 30.

[0032] A pulverized coal supply system 70 of one embodiment includes a pulverized coal supply device 71 for supplying pulverized coal using a carrier gas, a pulverized coal supply line 72 connecting the pulverized coal supply device 71 and the burner unit 30, a pulverized coal flow rate control valve 76 for adjusting the flow rate of the pulverized coal flowing through the pulverized coal supply line 72, and a switching valve 78 for switching the communication state of the pulverized coal supply line 72. The pulverized coal supply line 72 of this example is connected to the first burner unit 31, the second burner unit 32, and the third burner unit 33. The pulverized coal supply device 71, the pulverized coal flow rate adjustment valve 76, and the switching valve 78 are configured to operate in response to a control command from the control device 5. This allows the pulverized coal supply system 70 to change between a supply stop state in which the supply of pulverized coal is stopped, and a supply state in which pulverized coal is supplied to the burner unit 30. When the pulverized coal supply system 70 is in the supply state, pulverized coal is supplied to the pulverized coal burners 302, 304 described above.

[0033] The measurement system 9 includes an air flow meter 114 for measuring the flow rate of primary air supplied by the primary air supply system 110, an air flow meter 124 for measuring the flow rate of additional air supplied by the additional air supply system 120, an ammonia flow meter 109 for measuring the flow of ammonia fuel supplied by the ammonia supply system 100, an oil flow meter 84 for measuring the flow rate of oil supplied by the oil supply system 80, a pulverized coal flow meter 74 for measuring the flow rate of pulverized coal supplied by the pulverized coal supply system 70, and the furnace thermometer 6 described above. These flow meters are configured to send their measurements to a processor 91 .

[0034] The boiler operation system 1 operates in accordance with a control command sent from the processor 91, for example, as shown in the flowchart of FIG. 10A. First, a command to burn other fuels is sent from the processor 91 to the supply system 15 (S51). As a result, the primary air supply system 110 and the additional air supply system 120 each supply air. At this time, the ammonia supply system 100 is in a supply stop state, and the oil supply system 80 and the pulverized coal supply system 70 are both in a supply state. Therefore, oil and pulverized coal are supplied to the burner unit 30. At this time, the ammonia burner 306 of the first burner unit 31 is stopped, and the ammonia burners 306 of the second burner unit 32 and the third burner unit 33 inject oil. Inside the furnace 12, oil and pulverized coal are burned. After that, in response to the ammonia co-firing condition being satisfied (S53: YES), an ammonia supply start command is sent from the processor 91 to the supply system 15 (S55). The oil supply system 80 changes to a supply stop state, and the ammonia supply system 100 changes to a supply state. As a result, the first burner unit 31 injects liquid ammonia, and the fuel injected from the second burner unit 32 and the third burner unit 33 is switched from oil to liquid ammonia. The pulverized coal supply system 70 maintains the supply state. As a result, ammonia and pulverized coal are co-firing in the boiler 2. After that, in response to the ammonia combustion condition being satisfied (S57: YES), the control device 5 sends an ammonia combustion command to the supply system 15 (S59). The pulverized coal supply system 70 changes to a supply stop state, and the burners that had been functioning as coal burners are stopped. In addition, the ammonia supply system 100 increases the amount of liquid ammonia supplied. As a result, ammonia combustion is performed in the boiler 2. In another embodiment, the supply system 15 that has received the other fuel combustion command from the processor 91 may first supply oil to the burner unit 30, and then supply oil and pulverized coal to the burner unit 30. After the ammonia supply start command is sent to the supply system 15, ammonia fuel and oil may be mixed and burned, or ammonia fuel, pulverized coal, and oil may be mixed and burned.

[0035] 10B is a flowchart showing a NOx control process according to one embodiment. The NOx control process is a control method for suppressing the amount of NOx generated when ammonia fuel and another fuel (pulverized coal in this example) are mixed and burned. In the NOx control process, the processor 91 first reads the boiler load and the ammonia co-firing ratio (as a more specific example, the co-firing ratio of ammonia and pulverized coal) (S61). The reading is performed when the processor 91 receives a demand. The processor 91 executes a first calculation to calculate an ammonia air ratio, which is a ratio of the amount of air for ammonia combustion supplied to the ammonia fuel to the amount of air required for combusting the ammonia fuel (S10-1). The method of calculating the ammonia air ratio is as described above. Next, the processor 91 executes a second calculation to calculate a pulverized coal air ratio, which is the ratio of the amount of pulverized coal combustion air supplied to the pulverized coal to the theoretical amount of air required to combust the pulverized coal (S10-2). car The calculation method for is as described above. Next, the processor 91 controls the respective supply amounts of ammonia fuel, pulverized coal, and combustion air so that the ammonia air ratio calculated in S10-1 satisfies the first reference range and the pulverized coal air ratio calculated in S10-2 satisfies the second reference range (S10-3). More specifically, as an example, the processor 91 controls the liquid ammonia flow rate control valve 108, the pulverized coal flow rate control valve 76, and the primary air flow rate control valve 116, respectively. The processor 91 determines whether or not ammonia co-combustion has ended (S63). While ammonia co-combustion is being performed (S63: NO), the processor 91 repeats S10-1, S10-2, and S10-3 in order. When it is determined that ammonia co-combustion has ended (S63: YES), the processor 91 ends the NOx control process.

[0036] FIG. 10C shows the control logic for the amount of air for coal and ammonia. The control device 5 multiplies the measurement value of the pulverized coal flow meter 74 of the coal burner 302 (pulverized coal burner 302) by the coal burner air ratio (indicated value) and the theoretical coal air amount, thereby determining the amount of combustion air for the coal burner 302 (Q Air_car ) is calculated. The difference between the calculated combustion air amount of the coal burner 302 and the combustion air amount (measured value) of the coal burner 302 is calculated by the control device 5 to obtain a combustion air amount control command value for the coal burner 302. Similarly, the combustion air amount (Q Air_NH3 ) is calculated. The difference between the calculated amount of combustion air for the ammonia burner 306 and the amount of combustion air for the ammonia burner 306 (measured value) is calculated, and the control device 5 determines an ammonia burner combustion air amount command value.

[0037] The arrangement of ammonia burners in the case of opposed combustion burners is shown in Figures 11A to 11E. In opposed combustion, pulverized coal is supplied from one coal pulverizer to burners installed horizontally on each wall, so when ammonia co-firing is performed, all of the horizontally arranged burners are replaced with ammonia combustion burners. Figure 11A shows an example in which six stages of burners are arranged, three on each of the front and rear walls. One stage of burners is made up of multiple burners installed horizontally. Figure 11A(a) shows a schematic diagram of the burner arrangement of boiler 2 capable of firing only coal before the retrofit. One of the six burner stages is used as a spare burner and is shut down during normal operation. In (a), reference numeral 1104 indicates the shut down burner. At startup, coal burner stages 1101, 1102, and 1105 are coal burners equipped with oil burners to heat the inside of the furnace with oil. (b) and (c) of Figure 11A show examples of modifications (examples of burner arrangement) to convert the boiler 2 in (a) into a boiler 2 that uses ammonia fuel. (b) shows a case where the coal burners 1103, 1106 and the idle burner 1104 are modified into an ammonia burner 1108. In this case, the coal burners 1103, 1106 are modified into ammonia-only burners 1107, 1109. (c) shows an example where burners 1101, 1102, 1105 equipped with coal burners and oil burners are modified into burners 1120, 1121, 1123 that can be used for both ammonia and oil. In this case, the idle burner 1104 is operated as the coal burner 1104. Figures 11B and 11D show an example of burner arrangement and a side view of the ammonia burner in the AA section of Figure 11A (b). Figures 11C and 11E show an example of burner arrangement and a side view of the oil + ammonia burner in the BB section of Figure 11A (c). In the opposed combustion burner, ammonia (or oil only at start-up) is injected from the center, and primary, secondary, and tertiary air flow paths are provided around it as air for ammonia combustion. When calculating the ammonia air ratio for each opposed combustion burner, only the air supplied to the ammonia burner as the air for ammonia combustion (the above-mentioned primary to tertiary air) is considered. In opposed combustion, there are no auxiliary air nozzles like in swirl combustion. Figure 12 shows a schematic diagram of the state inside the furnace when ammonia is co-firing. Upstream of the combustion completion zone, which is the space inside the furnace where additional air is supplied, a reducing and denitrifying atmosphere with insufficient air (air ratio of 1 or less) is formed by pulverized coal combustion, so by injecting an ammonia burner here with an air ratio of 1 or less, ammonia can be injected into the high-temperature (usually 1400°C or higher) reducing atmosphere formed by the coal burner, and the thermal decomposition and reduction of ammonia can occur even with counter combustion. In Figure 12, the ammonia burner is injected into the high-temperature reducing atmosphere formed by coal with an ammonia burner air ratio of 0.8 or less, so the reducing atmosphere of the coal is not damaged and the ammonia is mixed with the high-temperature coal flame to cause pyrolysis and reduction. By individually controlling the air ratio of each independent burner, it is possible to control the amount of NOx generated while avoiding mutual interference.

[0038] (Example) 5A to 5C, the results of identifying the relationship between the ammonia burner air ratio and the amount of NOx emissions when coal and ammonia are mixed and burned by a combustion test will be described. Figures 5A and 5B are graphs showing the relationship between the burner air ratio and the amount of NOx emissions when the ammonia mixed-firing ratio is a predetermined value (Figure 5B shows the relationship for each burner type). This combustion test was carried out in a horizontal cylindrical combustion furnace, and the co-firing ratio of ammonia and pulverized coal was 25% in terms of heat value. The coal burner and ammonia burner were installed separately vertically, with the coal burner at the top and the ammonia burner at the bottom, and auxiliary air nozzles were installed above and below each burner. Three types of ammonia burners were used: a spud burner, which is a premixed type burner, and a diffuser type and swirler type, which are diffusion type burners with different flame holder structures. In this test, the oxygen concentration at the furnace outlet was set to approximately 4%, and in order to correct the difference in the oxygen concentration at the furnace outlet, NOx was converted to a 6% concentration according to the following (Equation 9) for comparison. NOx (6% conversion value) = NOx actual measurement value × (21% - 6%) ÷ (21% - actual measurement oxygen concentration at furnace outlet) (Equation 9)

[0039] First, we will consider the relationship between the air ratio of the ammonia burner and NOx emissions when the ammonia burner is of the spud type and the co-firing ratio is 33%. Figure 5C is a graph showing the relationship between the burner air ratio and NOx emissions when the ammonia co-firing ratio is changed. As shown in Figure 5C, NOx is lowest when the ammonia burner air ratio is 0.6, and NOx increases when the air ratio is higher or lower than this. When the ammonia burner air ratio is 0.8, the NOx value is about 1.5 times that of 0.6. In general, the NOx value in the case of coal firing is about 150 to 200 ppm, so if the ammonia burner air ratio is 0.8 or less, there is no significant difference from coal firing. Also, the increase in NOx is greater when the ammonia burner air ratio is higher. Although NOx increases when the ammonia burner air ratio is zero, that is, when only ammonia is injected from the ammonia burner, it was possible to co-firing with coal. If the ammonia burner air ratio is reduced below 0.6, NOx starts to increase, so if NOx does not decrease even when it is reduced to 0.6, there is a possibility that unburned ammonia has reached the oxidation zone (combustion completion zone) downstream of the additional air injection section and is being converted to NOx. Therefore, it is necessary to reduce the NOx generated in the combustion completion zone by reducing the additional air injection rate and increasing the coal burner air ratio while keeping the ammonia burner air ratio at 0.6, thereby reducing the amount of unburned ammonia that reaches the downstream of the additional air injection section. When the ammonia co-firing ratio is reduced to 25%, 22%, and 11% in a spud-type burner, the lowest point of NOx generation depending on the air ratio of the ammonia burner has not been confirmed, but the air ratio at which NOx is minimal tends to become even lower. In addition, the NOx value tends to increase when the ammonia co-firing ratio is reduced to 25% or less. This is thought to be due to an increase in auxiliary air from the adjacent coal burner, which mixes with the ammonia burner side, effectively increasing the air ratio of the ammonia burner. In such cases, the NOx value can be controlled by further reducing the air ratio of the ammonia burner from 0.6. As described above, even when the ammonia co-firing ratio was changed from 11% to 33%, the amount of NOx generated could be suppressed by appropriately controlling the air ratio of the ammonia burner, which shows that even if the primary air ratio of the coal burner (the ratio of the theoretical air ratio of coal to the amount of primary air) increases with an increase in the co-firing ratio, the NOx value can be controlled below a certain value by individually controlling the air ratios of the coal burner and ammonia burner.

[0040] Next, as shown in Figure 5B, when a diffusion-type burner has a diffuser or swirler type flame stabilizer, the diffuser type tends to generate less NOx than the swirler type. The diffuser type has a disk-shaped diffuser installed at the tip of the burner, and the air flows around this to stabilize the flame, so the ignition point is very close to the burner. On the other hand, the swirler type uses a swirler to generate a swirling flow centered on the burner, and the ignition point is formed downstream of the burner tip because the flame is stabilized by the circulating flow. The reducing atmosphere formed by the ammonia burner is between the ignition point and the additional air injection point, so it is thought that the closer the ignition point is to the tip of the burner, the longer the distance of the reducing atmosphere and the longer the residence time of the reducing atmosphere, which in turn advances the reduction of NOx. Although the air ratio of the ammonia burner that minimizes NOx has not been determined for the diffusion type burner, it tends to be lower than the spud type, and it can be said that it is possible to control the ammonia burner air ratio that reduces NOx the most for each burner type.

[0041] The above describes the embodiments of the present invention, but the present invention is not limited to the above-described embodiments, and also includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0042] In this specification, expressions expressing relative or absolute configuration, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," do not only strictly represent such a configuration, but also represent a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions indicating that things are in an equal state, such as "identical," "equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to shapes such as a rectangular shape or a cylindrical shape in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect is obtained. In addition, in this specification, the expressions "comprise," "include," or "have" a certain element are not exclusive expressions that exclude the presence of other elements. [Explanation of symbols]

[0043] 2: Boiler 4: Additional air supply 5: Control device 8: Rear flue 9: Measurement system 11: Nose 12: Furnace 15: Supply system 19: Furnace wall 20: Furnace 21: Burner placement area 22: Additional air supply area 30: Burner unit 31: First burner unit 32: Second burner unit 33: 3rd burner unit 37: Start-up fuel burner 50: Ammonia burner 70: Pulverized coal supply system 71:Pulverized coal supply device 72: Pulverized coal supply line 74:Coal flow meter 76: Pulverized coal flow control valve 78: Switching valve 80: Oil supply system 81:Oil supply device 82: Oil supply line 84: Oil flow meter 86: Oil flow control valve 88: Switching valve 91: Processor 92:ROM 93: RAM 94: Memory 100: Ammonia supply system 101: Ammonia tank 102: Ammonia supply line 103: Pump 105: Pressure regulating valve 107: Switching valve 108: Flow control valve 109: Ammonia flow meter 110: Primary air supply system 114: Primary air flow meter 116: Primary air flow control valve 118: Switching valve 120: Additional air supply system 124: Additional air flow meter 126: Additional air flow control valve 128: Switching valve 131: Wind box 132: Ammonia supply nozzle 133: Outer cylinder 141: Wind box 142: Ammonia supply nozzle 143: Flame holder (diffuser) 151: Wind box 152: Ammonia nozzle 153: Flame holder (swirler) 301: Auxiliary air nozzle 302: Pulverized coal burner 303: Auxiliary air nozzle 303: Air nozzle 304: Pulverized coal burner 305: Auxiliary air nozzle 306: Ammonia burner 306A: Ammonia nozzle 1101 : Coal burner with oil burner for start-up 1102 : Coal burner with oil burner for start-up 1103 : Coal burner 1104 : Coal burner 1105 : Coal burner with oil burner for start-up 1106 : Coal burner 1107: Ammonia burner 1108: Ammonia burner 1109: Ammonia burner 1120: Start-up oil burner / ammonia dual-use burner 1121: Start-up oil burner / ammonia dual-use burner 1123: Start-up oil burner / ammonia dual-use burner

Claims

1. A combustion apparatus having a burner for a carbon-containing fuel that burns a carbon-containing fuel in a furnace, characterized in that an ammonia burner to which ammonia is supplied through an ammonia supply line is provided adjacent to the burner for the carbon-containing fuel, and the ammonia burner injects ammonia into the furnace toward a flame generated by the burner for the carbon-containing fuel, thereby burning the ammonia.

2. A combustion apparatus having a burner for carbon-containing fuel, which mixes a carbon-containing fuel with combustion air and burns it in a furnace, characterized in that an ammonia burner to which ammonia is supplied through an ammonia supply line is provided adjacent to the burner for the carbon-containing fuel, and the ammonia burner injects ammonia into the furnace toward a flame generated by the burner for the carbon-containing fuel, thereby burning the ammonia.

3. A combustion apparatus having a burner for carbon-containing fuel that injects a carbon-containing fuel into a furnace and burns it in the furnace, characterized in that an ammonia burner to which ammonia is supplied through an ammonia supply line is provided adjacent to the burner for the carbon-containing fuel, and ammonia is injected from the ammonia burner into the furnace in which the carbon-containing fuel is being combusted, thereby burning the ammonia.

4. A combustion apparatus in which ammonia supplied through an ammonia supply line is mixed with combustion air by an ammonia burner and burned in a furnace, the combustion apparatus being characterized in that a carbon-containing fuel burner to which a carbon-containing fuel is supplied through a carbon-containing fuel supply line is provided adjacent to the ammonia burner, ammonia is injected into the furnace from the ammonia burner, and a carbon-containing fuel is injected into the furnace from the carbon-containing fuel burner, thereby performing mixed combustion of ammonia and the carbon-containing fuel in the furnace.

5. 5. The combustion apparatus according to claim 4, wherein the ammonia burner includes an ammonia nozzle, and ammonia injected from the ammonia nozzle is premixed with combustion air and injected from the ammonia burner into the furnace.

6. The combustion device according to claim 4 or 5, further comprising an ammonia flow rate regulating valve for regulating the amount of ammonia supplied to the ammonia burner through the ammonia supply line, an air flow rate regulating valve for regulating the amount of combustion air supplied to the ammonia burner through an air supply line, a carbon-containing fuel flow rate regulating valve for regulating the amount of carbon-containing fuel supplied to the carbon-containing fuel burner through the carbon-containing fuel supply line, and a control device for controlling the ammonia flow rate regulating valve, the air flow rate regulating valve, and the carbon-containing fuel flow rate regulating valve.

7. The combustion device according to any one of claims 1 to 3, further comprising an ammonia flow rate regulating valve that regulates the amount of ammonia supplied to the ammonia burner through the ammonia supply line, a carbon-containing fuel flow rate regulating valve that regulates the amount of carbon-containing fuel supplied to the carbon-containing fuel burner through a carbon-containing fuel supply line, and a control device that controls the ammonia flow rate regulating valve and the carbon-containing fuel flow rate regulating valve.

8. The combustion device according to claim 6 or 7, wherein the control device generates an ammonia supply start command when it is determined that an ammonia co-combustion condition for starting ammonia co-combustion is satisfied.

9. The combustion device according to any one of claims 6 to 8, wherein the control device generates an ammonia combustion start command when it is determined that an ammonia combustion condition for starting ammonia combustion is satisfied.

10. The ammonia combustion conditions are: The combustion device according to claim 9, characterized in that the representative temperature in the furnace reaches a specified temperature, a specified time has elapsed since ammonia co-firing was started, a specified set value has been reached after a specified input operation is performed by an operator, or a combination of these.

11. 11. The combustion device according to claim 1, wherein the ammonia injected by the ammonia burner is liquid ammonia, which is vaporized into ammonia gas in the furnace and burned.

12. The combustion apparatus according to any one of claims 1 to 11, wherein the carbon-containing fuel is a biomass fuel or a fossil fuel.

13. Combustion device according to any one of claims 1 to 11, wherein the carbon-containing fuel is liquefied natural gas.

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