WO2023037867A1 - Boiler, boiler control method, and boiler modification method - Google Patents

Abstract

In the present invention burners in a boiler are arranged separately as ammonia burners and fine powdered coal burners. Specifically, a boiler according to a number of embodiments of the present invention includes: a furnace that includes a furnace wall; an ammonia burner that is provided on the furnace wall, and that burns an ammonia fuel; and a fine powdered coal burner that is provided at a different position on the furnace wall than the ammonia burner, and that burns fine powdered coal.

Description

BOILER, BOILER CONTROL METHOD, AND BOILER MODIFICATION METHOD

The present invention relates to a boiler that burns ammonia and pulverized coal, a boiler control method, and a boiler modification method.
This application is based on Japanese Patent Application No. 2021-146609 filed with the Japan Patent Office on September 9, 2021 and Japanese Patent Application No. 2021-200928 filed with the Japan Patent Office on December 10, 2021. Priority is claimed and its contents are hereby incorporated by reference.

　Conventionally, boilers in which ammonia is supplied as fuel to the furnace are known. When ammonia is used as fuel, it is necessary to suppress the emission of nitrogen oxides (NOx). For example, in the burner disclosed in Patent Document 1 (shown in FIG. 2), a nozzle for supplying ammonia is swirled around the nozzle for supplying ammonia (it is stated that the nozzle does not have to be swirled), and the nozzle is swirled. Ammonia is mixed in the pulverized coal flame. Further details are disclosed in the following disclosures. That is, a combustion device 4A that is installed in a furnace and capable of burning ammonia as a fuel includes an inner cylinder nozzle 41 that is arranged in the center when viewed from the direction of fuel injection and that injects ammonia, and the direction of fuel injection. and an outer cylinder nozzle 42 that surrounds the inner cylinder nozzle 41 from the outside in the radial direction when viewed from above and injects ammonia around the inner cylinder nozzle 41 . Further, a swirler 45 is provided inside the outer cylinder nozzle 42 to swirl the flow of ammonia injected around the inner cylinder nozzle 41 . According to Patent Document 1, the ammonia injected from the inner cylinder nozzle 41 forms a reduction region in which the concentration of ammonia is high and the concentration of oxygen is low in the central portion of the flame when viewed from the fuel injection direction. On the other hand, the nitrogen oxides produced by mixing and burning ammonia injected from the outer cylinder nozzle around the inner cylinder nozzle ride on the circulating flow that recirculates from the outer edge of the flame toward the center. supplied to the reduction region. As a result, nitrogen oxides produced at the outer edge of the flame are reduced to nitrogen gas (N2) in the reduction zone 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 using fuel.

Japanese Unexamined Patent Application Publication No. 2020-41748

According to the knowledge of the inventors, in order to suppress the amount of nitrogen oxide emissions, the ammonia fuel burner uses another fuel to make the combustion environment in the boiler a reducing region, and the air ratio near the ignition point is preferably controlled precisely. However, Patent Document 1 does not specifically disclose such a configuration.
Further, when co-firing ammonia with the burner disclosed in Patent Document 1, increasing the co-firing rate of ammonia increases the air ratio of the coal nozzle. In order to prevent the coal from settling in the nozzle, the amount of conveying air must be kept constant. Increasing the ammonia co-firing rate only reduces the amount of coal fed, so the amount of conveying air increases relative to the coal flow rate. do. As a result, when the co-firing rate of ammonia is high, the air ratio around the ammonia nozzle becomes high, resulting in a rapid increase in nitrogen oxides derived from ammonia oxidation.

Therefore, an object of the present invention is to provide a boiler, a boiler control method, and a boiler modification method that can burn ammonia fuel under conditions that can suppress the generation of nitrogen oxides.

The burner arrangement of the boiler according to at least one embodiment of the present invention is to separate ammonia and pulverized coal burners.
That is, a boiler according to at least one embodiment of the present invention includes a furnace including a furnace wall, an ammonia burner provided on the furnace wall for burning ammonia fuel, and a position different from the ammonia burner on the furnace wall. and a pulverized coal burner for burning pulverized coal.

The boiler includes a control device that controls the supply amounts of the ammonia fuel, the pulverized coal, and the combustion air, and the control device controls the theoretical amount of air required for burning the ammonia fuel. A first calculation unit that calculates an ammonia-air ratio, which is the ratio of the ammonia combustion air amount supplied to the fuel, and a theoretical amount of air required to burn the pulverized coal, which is supplied to the pulverized coal a second calculation unit that calculates a pulverized coal-air ratio that is a ratio of air amounts for pulverized coal combustion; and a control unit for controlling the supply amount.

The first calculation unit calculates the ammonia air ratio for each of the plurality of ammonia burners,
The control unit is characterized in that the supply amount is controlled such that each of the ammonia air ratios satisfies the first reference range.

An air nozzle provided adjacent to the ammonia burner on the furnace wall,
The first calculation unit calculates the ammonia air ratio using the amount of air for ammonia combustion that includes the amount of air supplied to the ammonia fuel in the amount of air injected from the air nozzle. do.

The upper limit of the first reference range is lower than the upper limit of the second reference range.

The first reference range is characterized by being 0.8 or less.

The first reference range is characterized by being 0.7 or less.

The first reference range is characterized by being set based on the value of nitrogen oxides in the combustion gas discharged from the furnace.

The boiler has an auxiliary air nozzle adjacent to the ammonia burner and supplying auxiliary air, and the auxiliary air nozzle is provided with a damper capable of adjusting the amount of auxiliary air that can be supplied in the direction of the ammonia burner. Characterized by

The ammonia burner is
an ammonia nozzle for injecting the ammonia fuel;
and a starting fuel nozzle for injecting starting fuel.

The ammonia burner is characterized by being provided adjacent to the pulverized coal burner.

The ammonia burner is characterized by being provided adjacent to the pulverized coal burner.

The furnace wall includes a burner arrangement area in which the ammonia burner and the pulverized coal burner are provided, and an additional air supply area in which an additional air supply section for supplying additional air is provided downstream of the burner arrangement area, The ammonia burner is characterized by being positioned on the uppermost stage of the burner arrangement area.

The ammonia burner is characterized by being a diffusion burner or a partially premixed burner.

The diffusion burner or the partially premixed burner is characterized by being a partially premixed spud type burner, a diffusion type swirler type with a different flame stabilizer structure, or a diffuser type burner.

A boiler control method according to at least one embodiment of the present invention includes a furnace including a furnace wall, an ammonia burner provided on the furnace wall for burning ammonia fuel, and a position different from the ammonia burner on the furnace wall. and a pulverized coal burner for burning pulverized coal, a boiler control method for controlling the supply amounts of the ammonia fuel, the pulverized coal, and combustion air, the boiler control method necessary for burning the ammonia fuel a first calculation step of calculating an ammonia air ratio, which is the ratio of the ammonia combustion air amount supplied to the ammonia fuel to the theoretical air amount, and calculating the theoretical air amount required to burn the pulverized coal. On the other hand, a second calculation step of calculating a pulverized coal-air ratio that is a ratio of the pulverized coal combustion air amount supplied to the pulverized coal; and a control step of controlling the supply amount so that the charcoal-air ratio satisfies a second reference range.

A boiler modification method according to at least one embodiment of the present invention comprises a furnace including a furnace wall, a pulverized coal burner provided on the furnace wall for burning pulverized coal, and a position different from the pulverized coal burner on the furnace wall. and a control device, wherein at least one of the plurality of injection units is equipped with ammonia fuel. The control device includes a replacement step of replacing the ammonia burner to be burned, and controls the supply amounts of the ammonia fuel, the pulverized coal, and the combustion air, and the theoretical amount of air required to burn the ammonia fuel a first calculation unit that calculates an ammonia air ratio, which is a ratio of the amount of air for combustion of ammonia supplied to the ammonia fuel; a second calculation unit that calculates a pulverized coal-air ratio that is a ratio of the pulverized coal combustion air amount supplied to the and a control unit for controlling the supply amount so as to satisfy a reference range.

According to the present invention, it is possible to provide a boiler, a boiler control method, and a boiler modification method that can burn ammonia fuel under conditions that can suppress the generation of NOx.

1 is a conceptual diagram of a boiler operating system according to one embodiment; FIG. It is a conceptual diagram of a burner showing a conventional example. FIG. 4 is a cross-sectional view showing the burner arrangement of the boiler before modification according to one embodiment (example of modification of coal burners). FIG. 4 is a cross-sectional view showing the burner arrangement of the boiler after modification according to one embodiment (example of modification of the coal burner). FIG. 2 is a conceptual diagram showing the correspondence relationship of burner arrangement before and after modification of a boiler according to one embodiment (an example of modification of a coal burner). FIG. 4 is an explanatory diagram of air flow related to combustion of an ammonia burner according to one embodiment; FIG. 4 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 one embodiment. FIG. 4 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. FIG. 4 is an explanatory diagram showing the relationship among the ammonia co-firing rate, the ammonia burner air ratio, and the amount of nitrogen oxides generated according to one embodiment. FIG. 4 is a cross-sectional view showing the burner arrangement of the boiler before modification according to one embodiment (an example of modification of the start-up fuel burner). FIG. 4 is a cross-sectional view showing the burner arrangement of the boiler after modification according to one embodiment (an example of modification of the start-up fuel burner). FIG. 4 is a conceptual diagram showing a corresponding relationship of burner arrangement before and after modification of a boiler according to one embodiment (example of modification of start-up fuel burners). FIG. 4 is a cross-sectional view showing the burner arrangement of the boiler after remodeling according to one embodiment (an example of remodeling air nozzles). FIG. 4 is a conceptual diagram showing the correspondence relationship of burner arrangement before and after modification of the boiler according to one embodiment (example of modification of air nozzles). FIG. 4 is a cross-sectional view showing the burner arrangement of the boiler after modification according to one embodiment (an example of modification of the uppermost air nozzle). FIG. 4 is a conceptual diagram showing the corresponding relationship of burner arrangement before and after modification of the boiler according to one embodiment (an example of modification of the air nozzle at the uppermost stage). It is a control system diagram of a boiler according to one embodiment. 1 is a flow diagram of a method for controlling a boiler according to one embodiment; FIG. FIG. 4 is a flow diagram of NOx control processing according to one embodiment; FIG. 4 is a control logic diagram for calculating a combustion air amount control command value according to one embodiment; 1 is an ammonia burner arrangement of opposed combustion burners according to one embodiment. FIG. 11B is a cross-sectional view taken along line AA in FIG. 11A. FIG. 11B is a cross-sectional view taken along line BB in FIG. 11A. It is a side view of an ammonia burner concerning one embodiment. It is a side view of an oil ammonia burner concerning one embodiment. FIG. 4 is a conceptual diagram showing a reduction-oxidation state in a boiler according to one embodiment; It is a figure which shows the structure of a spud burner. It is a figure which shows the structure of a diffuser burner. It is a figure which shows the structure of a swirler burner. It is a flow chart of a boiler remodeling method.

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

FIG. 1 is a conceptual diagram of a boiler operating system 1 according to one embodiment.
The boiler operation system 1 includes, for example, a boiler 2 incorporated in 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. and
The fuel supplied to the boiler 2 from the supply system 15 contains ammonia fuel. The ammonia fuel can be either liquid ammonia or ammonia gas. The following illustrates embodiments in which the ammonia fuel is liquid ammonia. In one embodiment, the boiler 2 is supplied with liquid ammonia in liquid form. Liquid ammonia does not contain gas such as hydrogen gas, but may contain impurities (for example, urea) that do not affect combustion in the boiler 2 . Liquid ammonia is vaporized into ammonia gas within the boiler 2 .
Further, the fuel supplied from the supply system 15 to the boiler 2 includes fuel other than ammonia fuel. For example, after combustion using another fuel is performed in the boiler 2, mixed combustion of ammonia and another fuel or single combustion of ammonia is performed.
Carbon-containing fuels, which are examples of fuels other than ammonia, include biomass fuels and fossil fuels. Fossil fuels are liquefied natural gas, oils such as heavy or light oil, or coal such as pulverized coal. The following exemplifies embodiments in which the carbon-containing fuel is oil and pulverized coal.

The boiler 2 of one embodiment includes a furnace 20 that includes a furnace wall 19 . The furnace wall 19 includes a burner placement 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 section 4 for supplying 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 burns, and may take various forms such as a cylindrical shape and a square prism shape.
The furnace 20 of one embodiment also includes a nose 11 that projects into the furnace 20 . The nose 11 is configured so that gases (eg, combustion gases and unburned gases) produced in the combustion space 7 of the furnace 20 properly flow into the flow path downstream of the furnace 20 . An exemplary flow path downstream of the furnace 20 is the flue 8 .
The at least one burner unit 30 is arranged such that fuel burns 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 the 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 a first burner unit 31, a second burner unit 32, and a third burner unit 33 in order from the downstream side in the gas flow direction, and these three stage burners are collectively referred to. may be referred to as a burner unit 30. Note that the burner units 30 may be arranged in two stages or four stages.
The boiler 2 of one embodiment is a swirling combustion type boiler, and the burner units 30 provided in each stage are arranged at regular intervals along the circumferential direction of the furnace 20 . Although the number of burner units 30 in each stage is four as an example, only one burner unit 30 in each stage is illustrated in FIG. The number of burner units 30 in each stage may be three or five or more.
A boiler 2 according to another embodiment is a facing combustion type boiler. In this case, at least one pair of burner units 30 in each stage are provided at positions facing each other.

Each burner unit 30 includes at least one burner. In at least one burner unit 30 , the burner is an ammonia burner 306 configured to inject liquid ammonia into the furnace 20 while it is in a liquid state. Ammonia burner 306 may be configured to inject only liquid ammonia. Alternatively, the ammonia burner 306 may be configured to inject liquid ammonia with (or instead of) the carbon-containing fuel after injecting the carbon-containing fuel.
In one embodiment, 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 the ammonia burner 306 . In other embodiments, ammonia burner 306 may be included only in second burner unit 32 or third burner unit 33 .
Additionally, either burner unit 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 starting fuel burner 307 (see FIG. 3A) for injecting oil, which is an example of a starting fuel, into the furnace 20, an auxiliary air nozzle (air nozzle) 301 for injecting auxiliary air, 305 (see FIG. 3A). Details will be described later.

In one embodiment, the supply system 15 is configured to supply the burner unit 30 with primary air and fuel. The fuel supplied to the burner unit 30 (liquid ammonia and carbon-containing fuel in this example) may be switched. For example, the burner unit 30 of either stage may be supplied with liquid ammonia after the carbon-containing fuel (eg, oil) is supplied.

The measurement system 9 of one embodiment includes a plurality of flowmeters for measuring the flow rate of air or fuel supplied from the supply system 15, and a furnace thermometer 6 for measuring the representative temperature inside the furnace 20. . The representative temperature in the furnace 20 is the temperature that correlates with the gas temperature, which is the temperature of the 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 (hereinafter referred to as nose temperature). Nose temperature is measured by a furnace thermometer 6 . The representative temperature inside the furnace 20 may be, for example, the gas temperature.

The boiler operating system 1 may be operated by an operator, controlled by a controller 5 (see FIG. 9), which will be described later, or by a combination thereof.
In the furnace 20 of one embodiment, even if the supply of the ammonia fuel is started after the fuel other than the ammonia fuel (the carbon-containing fuel in this example) is burned, and the ammonia fuel and the other fuel are co-combusted. good.

In general, the air ratio at the time of combustion has a great effect on the generation of nitrogen oxides when fuel containing nitrogen such as coal and ammonia is burned. Here, in the case of co-firing ammonia fuel and other fuel, as a comparative example, when one air ratio is calculated for the entire furnace, as an example, the air ratio is calculated for ammonia fuel and carbon-containing fuel as another fuel. The case of calculation will be explained below.
(Comparative example)
The air ratio of the comparative example is the ratio of the amount of air supplied to the furnace 20 to the theoretical amount of air required to burn the ammonia fuel and other fuels supplied to the furnace 20 . The amount of air supplied to the furnace 20 described above does not include additional air. In other words, in this example, the air ratio constituting the ammonia co-firing condition (details will be described later) is also a value obtained by multiplying the total air ratio by the supply ratio of the air other than the additional air in the total air supplied to the furnace 20 . Specifically, the air ratio (hereinafter sometimes referred to as the burner section air ratio) that constitutes the ammonia co-firing condition is defined by the following equation (1).
λ _b = λ x (100-AA)/100 Equation (1)
In equation (1), _λb is the burner section air ratio, λ is the total air ratio, and AA is the ratio of additional air supplied to the total amount of air supplied to the boiler 2 .
Also, the total air ratio (λ) is defined by equations (2), (3), and (4).
λ=Q _Air /Q _x Expression (2)
Q _x = Q _mf × A _mf Expression (3)
A _mf = (100−X)/100×A _car +X/100×A _NH3 Formula (4)
In equations (2)-(4), Q _Air is the total air supply. Further, Q _mf is the supply amount of ammonia fuel and other fuel (carbon-containing fuel in this example) when the combustion in the furnace 20 is ammonia co-firing (co-firing ratio in terms of weight: X%). be. _Qx is the air flow rate for the air ratio to be 1 during co-firing. A _mf is the theoretical air amount of the fuel (ammonia fuel and carbon-containing fuel in this example) when the above co-firing is performed, A _car is the theoretical air amount of the carbon-containing fuel, and A _NH3 is the amount of ammonia fuel. This is the theoretical air volume.
(Example)
In the embodiment, the ammonia air ratio, which is the ratio of the ammonia combustion air amount supplied to the ammonia fuel to the theoretical air amount of the ammonia fuel supplied to the furnace 20, and the theoretical air amount of the other fuel , other fuel air ratios, which are ratios of combustion air amounts supplied to other fuels, are calculated separately for each fuel.
The ammonia-air ratio (hereinafter also referred to as the ammonia burner-air ratio) is obtained from equations (5) and (6).
λ _NH3 = Q _{Air_NH3} /Q _{x_NH3} Equation (5)
Q _{x_NH3} = Q _NH3 x A _NH3 Formula (6)
Here, λ _NH3 in equation (5) is the ammonia air ratio, Q _{Air_NH3} is the ammonia combustion air amount, and Q _{x_NH3} is the air flow rate for the ammonia fuel air ratio to be 1. Also, Q _NH3 in the equation (6) is the supply amount of ammonia fuel, and A _NH3 is the theoretical air amount of the ammonia fuel.
Taking carbon-containing fuel as another fuel, the air ratio of carbon-containing fuel can be obtained from equations (7) and (8).
_λcar = _{Qair_car} / _{Qx_car} Equation (7)
Q _{x_car} = Q _car x A _car Equation (8)
Here, λ _car in equation (7) is the air ratio of the carbon-containing fuel, Q _{Air_car} is the amount of air for combustion of the carbon-containing fuel, and Q _{x_car} is the air ratio of the carbon-containing fuel to be 1. is the air flow rate. Also, Q _car in equation (8) is the supply amount of the carbon-containing fuel, and A _car is the theoretical air amount of the carbon-containing fuel.
As in the present embodiment, by calculating the ammonia air ratio λ _NH3 and the carbon-containing fuel air ratio λ _car , they can be individually adjusted. 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 for the air ratio of the ammonia burner 306, and the formula (7) and (8) apply. In other words, in this case, the parameters of the carbon-containing fuel expressed by equations (7) and (8) are both parameters of pulverized coal.
Henceforth, air ratios refer to those calculated in this example.

In one embodiment, coal burner 302 and ammonia burner 306 are separated as shown in FIGS. ). As a result, the air ratio can be adjusted individually, and even if the co-firing ratio of ammonia is increased, the air ratio of ammonia can be reduced regardless of the operation of the coal burner, suppressing a sharp increase in NOx.
In addition, the coal burner 302 of this embodiment is configured to burn coal (pulverized coal). In the following description, coal burner 302 may be referred to as pulverized coal burner 302 .

In one embodiment, the upper limit of the burner section 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 section air ratio may be 0.7 or less. In this case, combustion of the ammonia fuel is started under the condition that the air ratio is 0.7 or less, and excessive generation of 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 section air ratio to be less than 0.6. Therefore, the burner part air ratio constituting the ammonia co-firing condition, which is a condition to be satisfied before starting the supply of ammonia fuel, is preferably 0.6 or more and 0.8 or less, more preferably 0.6 or more and 0.7 or less.
When a plurality of ammonia burners 306 are provided, it is preferable to calculate the ammonia air ratio λ _NH3 for each ammonia burner 306 unit. As will be described later, the amount of NOx generated varies greatly depending on the ammonia air ratio, so the ammonia air ratio is strictly calculated for each burner so that the supply amounts of ammonia fuel and ammonia combustion air can be controlled.
It is preferable to calculate the carbon-containing fuel air ratio λ _car (coal-air ratio) for each coal burner 302 so that the coal burner 302 can similarly control the amount of NOx generated with high accuracy.

Controller 5 (see FIG. 9), which is a component of boiler 2 in one embodiment, adjusts the ammonia air ratio to the amount of air supplied from ammonia burner 306 (see FIGS. 3B and 3C) and the amount of air adjacent to ammonia burner 306. It is calculated from the amount of air supplied from the auxiliary air nozzles 303 and 305. Regarding the amount of air supplied from the auxiliary air nozzles 303 and 305, only the amount of air contributing to combustion of ammonia is calculated as the amount of air for combustion of ammonia. If it is sandwiched adjacent to 306 and coal burner 302, half the amount of air is calculated as ammonia burner air.
When the NOx generation amount is higher than the reference value, control is performed to lower the ammonia burner air ratio from 0.7 to 0.6, for example. FIG. 5A shows an example of the ammonia burner air ratio and the amount of NOx generated. In this test result, the optimal point for the ammonia burner air ratio is 0.6. If the ammonia burner air ratio is lowered below 0.6, the amount of NOx increases. Unburned ammonia reaches the completion zone 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 introduced into the boiler 2 is reduced to reduce the amount of unburned ammonia that reaches the combustion completion zone. This reduces NOx generated in the combustion completion zone.

Ammonia burner 306 replaces (modifies) a portion of coal burner 304 as shown in FIGS. 3A-3C. Pulverized coal injected from the coal burner 304 is supplied with auxiliary air from an auxiliary air nozzle 303 adjacent to the ammonia burner 306 and having a starting fuel burner 307 installed therein. The auxiliary air nozzle 303 in which the starting fuel burner 307 is installed is 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 ammonia fuel injected into the furnace 12). Prepare.
When an air nozzle (auxiliary air nozzle) 303 that supplies auxiliary air is sandwiched between the coal burner 302 and the ammonia burner 306, adjusting the amount of air supplied from the nozzle to the optimum air amount for the coal burner 302 results in The amount of air to reduce nitrogen oxides in burner 306 is in excess. Conversely, if the air amount is adjusted to reduce the NOx of the ammonia burner, the air amount becomes insufficient from the optimum air ratio of the coal burner 302, leading to an increase in unburned ash.
In this regard, in the present embodiment, the auxiliary air nozzle 303 sandwiched between the coal burner 302 and the ammonia burner 306 is divided vertically into flow paths 303A and 303B along with modification of the boiler 2, and the respective flow rates can be controlled by dampers. (See FIGS. 3C and 4). Thereby, the air amounts for the coal burner 302 and the ammonia burner 306 can be individually adjusted. In other words, the amount of air supplied to the pulverized coal injected from the coal burner 302 and the amount of air supplied to the ammonia fuel injected from the ammonia burner 306 can be individually adjusted. 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 of unburned components in the ash by the coal burner and to suppress the increase of NOx by the ammonia burner. Further, by modifying the coal burner 304 to an ammonia burner 306, the existing boiler 2 exclusively for burning coal can be changed to a boiler 2 that burns ammonia fuel.
By arranging the ammonia burner 306 adjacent to the coal burner 302 as shown in FIG. 3, the heat of coal combustion can be utilized for ammonia combustion, and ammonia can be stably burned.
Further, based on the amount of ammonia supplied to the ammonia burner 306 and the amount of combustion air supplied, the amount of NOx generated in the combustion gas discharged from the boiler 2 is calculated, and depending on the calculation result, A first reference range may be set. Alternatively, the first reference range may be set based on the measurement results of a measuring device that measures the NOx concentration provided in the boiler 2 .

The boiler 2 according to at least one embodiment of the present invention has a starting fuel burner 307 that burns starting fuel as shown in FIGS. 6A to 6C, and the ammonia burner 306 is one of the starting fuel burners 307. It can be provided by replacing (modifying) the part. The ammonia burner 306 includes an ammonia nozzle 306A that injects ammonia. The ammonia nozzle 306A also functions as a start-up fuel nozzle that injects start-up fuel (oil as a specific example). When starting the boiler 2, the ammonia nozzle 306A injects starting fuel, and then injects ammonia when the ammonia co-firing condition is satisfied. Note that, in other embodiments, the starting fuel nozzle may be configured as a nozzle separate from the ammonia nozzle 306A and provided in the same compartment as the ammonia nozzle 306A.
If the starting fuel burner 307 is modified to the ammonia burner 306, the air nozzle 303 on one side adjacent to the coal burners 302 and 304 is eliminated, and a sufficient amount of auxiliary air for the coal burner 302 cannot be secured.
Therefore, by increasing the amount of air from the auxiliary air nozzles 301 and 305 on the opposite side to the ammonia burner 306, the air ratio of the coal burners 302 and 304 is set to an appropriate value of 0.7 to 0.9. . In this embodiment, only the air supplied from the ammonia burner 306 is used for calculating the ammonia air ratio.
By optimizing the air ratio of the coal burners 302 and 304, it is possible to suppress an increase in the unburned content in the ash in the coal burners 302 and 304.

A boiler 2 according to at least one embodiment of the present invention has a plurality of auxiliary air nozzles 301 and 305 for supplying auxiliary air as shown in FIGS. A part of 305 is replaced and provided. In the example of FIG. 7B, an ammonia burner 306 is provided to replace the auxiliary air nozzle 305 .
As with the modification of the starter fuel burner 307, the loss of the auxiliary air nozzle 305 on one side of the coal burner 304 causes the coal burner 304 to run out of air. 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 stabilizer.
A nozzle in which an ammonia burner 306 adjacent to the coal burner 304 and a starting fuel burner 307 on the opposite side are installed is used as an auxiliary air nozzle 303, and the amount of air is increased to adjust to a predetermined air amount. At this time, the coal burner 304 shown in FIG. 7B has the auxiliary air nozzle 303 on one side, but the coal burner 302 on the upper side has the auxiliary air nozzles 301 and 303 on the upper and lower sides. It is divided into flow paths 303A and 303B vertically, and each flow rate can be controlled by a damper so that the air amount can be increased only in the lower flow path 303B, and the air ratio of the coal burner 304 can be optimized. It is possible to suppress an increase in medium unburned fuel.
In the boiler 2 before modification, if the height of the windbox where the auxiliary air nozzle 305 is installed is lower than the height of the coal burner 302 and the starting fuel burner 307, the height of the windbox without the flame stabilizer A low ammonia burner 306 is installed. For example, a premixed spud nozzle or the like shown in FIG. 13 is used.

In the boiler 2 according to at least one embodiment of the present invention, as shown in FIGS. 8A and 8B, the auxiliary air nozzle 301 located at the uppermost stage of the burner arrangement area 21 is replaced (remodeled) to replace the ammonia burner. 306 is provided. Ammonia burner 306 is provided adjacent to coal burner 302 .
As in the previous example in which the ammonia burner 306 is installed in the auxiliary air nozzle 305, the amount of air in the coal burner 302 becomes insufficient due to the absence of the auxiliary air nozzle 301 on one side of the coal burner 302. Moreover, when the compartment height of the auxiliary air nozzle 301 is low, it is difficult to attach the ammonia burner 306 with a flame stabilizer. The air flow path of the starting fuel burner 307 is divided vertically into flow paths 303A and 303B so that the flow paths 303A and 303B can be individually controlled. Install a partial premix nozzle (see Figure 13) which is an ammonia nozzle with a low windbox height.
In this case, ammonia can be used not only as a fuel but also as a denitration agent.

A diffusion combustion burner or a partially premixed combustion burner (also called a spud burner) is used as the burner used in the above embodiment. In a diffusion combustion burner, a swirler type or a diffuser type can be used as a flame stabilizer. FIG. 13 shows an example of a structural drawing of a partially premixed spud burner, FIG. 14 shows an example of a structural drawing of a diffuser burner, and FIG. 15 shows an example of a structural drawing of a swirler burner.
FIG. 13 shows an example of a spud burner. The spud burner is composed of a nozzle 132 for supplying ammonia to the inside of the wind box 131 and an outer cylinder 133 . Combustion air is supplied from a wind box 131 , and a damper for flow rate adjustment is installed upstream of the wind box 131 . Ammonia is injected into the outer cylinder 133 and injected into the furnace while being premixed with the combustion air that flows in from the gap between the nozzle 132 and the outer cylinder 133 . Ammonia spontaneously ignites when it is mixed with an ignitable amount of air by the hot gases in the furnace. Since ammonia and air are partially premixed, the ignition point is formed at the point where the blowing flow rate of the entire nozzle coincides with the combustion rate of the premixed ammonia and air.
FIG. 14 shows an example of a structural drawing of a diffuser burner. An ammonia nozzle 142 and a disk-shaped flame stabilizer 143 (called a diffuser) are installed at the tip of the ammonia nozzle 142 inside the wind box 141 . Ammonia is injected from a plurality of holes 142A provided in an ammonia nozzle 142 (two holes 142A are shown in the figure). Combustion air is supplied from a wind box 141, and a damper for adjusting the flow rate is installed on the upstream side. Since the combustion air flows around the flame stabilizer 143 at an accelerated rate, a vortex is formed on the outer circumference of the disk-shaped flame stabilizer 143 . An ignition point is formed on the flame stabilizer 143 because ammonia is caught in this vortex and mixed with air to ignite.
FIG. 15 shows an example of a structural drawing of a swirler burner. An ammonia nozzle 152 and a flame stabilizer 153 (referred to as a swirler) having swirl vanes are installed inside the wind box 151 at the tip of the ammonia nozzle 152 . Ammonia is injected from a plurality of holes 152A provided in the ammonia nozzle 152 (two holes 152A are shown in the figure). Combustion air is supplied from a wind box 151, and a damper for adjusting the flow rate is installed on the upstream side. When the combustion air passes through the flame stabilizer 153 , it turns into a swirling flow by the swirl vanes and flows around the ammonia nozzle 152 . A circulating flow is generated inside the swirling flow, and the ammonia and the circulating flow are mixed and ignited. Therefore, the ignition point of the ammonia flame is formed near the downstream side of the flame stabilizer 153 .

FIG. 16 is a flow chart showing the boiler modification method of the present invention. As already described with reference to FIGS. 3C, 6C, 7B, and 8B, the boiler 2 before modification includes a pulverized coal burner 302 and a pulverized coal burner 302, a starting fuel, which may be pulverized coal, such as oil, or auxiliary air. and a plurality of injection parts for injecting. Each jet is a coal burner 304, a starting fuel burner 307, or an auxiliary air nozzle 301,303. Then, S11 shown in FIG. 16 shows the step of replacing this injection part with the ammonia burner 306. FIG. By executing S11, for example, an existing boiler 2 capable of burning only coal can be modified into a boiler 2 for burning ammonia fuel.

A boiler control method according to one embodiment (see FIG. 10B) includes a furnace 20 including a furnace wall 19, an ammonia burner 306 provided on the furnace wall 19 for burning ammonia fuel, and the ammonia burner on the furnace wall 19. In a boiler 2 including pulverized coal burners 302 and 304 that are provided at positions different from 306 and burn pulverized coal, a boiler control method for controlling the supply amounts of the ammonia fuel, the pulverized coal, and combustion air. A first calculation step (S10-1) of calculating an ammonia air ratio, which is a ratio of the amount of ammonia combustion air supplied to the ammonia fuel to the theoretical amount of air required to burn the ammonia fuel. and a second calculation step (S10- 2) and a control step (S10-3) of controlling the supply amount so that the ammonia air ratio satisfies the first reference range and the pulverized coal air ratio satisfies the second reference range.
The upper limit of the first reference range for the ammonia-air ratio is preferably set smaller than the upper limit of the second reference range for the pulverized coal-air ratio. The optimum 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). By referring to the optimum value and setting the upper limit of the reference range, it becomes easier to minimize the NOx emissions.

FIG. 9 shows a specific configuration of the boiler operating system 1 according to one embodiment. The boiler operation system 1 includes a controller 5 for controlling the operation of the boiler 2 in addition to the boiler 2 , supply system 15 and measurement system 9 already described.
The controller 5 of one embodiment includes a processor 91 , ROM 92 , RAM 93 and memory 94 .
The processor 91 is configured to read the boiler operating program stored in the ROM 92, load it into the RAM 93, and execute the instructions contained in the boiler operating program. The processor 91 is a CPU, GPU, MPU, DSP, various arithmetic devices other than these, or a combination thereof. Processor 91 may be implemented by an integrated circuit such as PLD, ASIC, FPGA, and MCU. The memory 94 stores various data as the boiler operation program is executed. The memory 94 is flash memory as an example. Processor 91 is electrically connected to supply system 15 and measurement system 9 .
The processor 91 of one embodiment includes a different fuel combustion command for burning a fuel other than ammonia fuel in the furnace 20, an ammonia supply start command for causing the supply system 15 to start supplying the ammonia fuel, and an ammonia is configured to generate an ammonia mono-firing start command for starting mono-firing of the ammonia in the furnace 20. In one embodiment, these control commands are sent to delivery system 15 .
The processor 91 of one embodiment generates an ammonia supply start command when determining based on the measurement result of the measurement system 9 that the ammonia co-firing conditions for starting the ammonia co-firing are satisfied. In addition, when the processor 91 of one embodiment determines that the ammonia mono-firing condition for starting ammonia mono-firing is satisfied, the processor 91 initiates an ammonia mono-firing command. The ammonia single-firing conditions are, for example, that the representative temperature in the furnace 20 has reached a specified temperature, that a specified time has elapsed since the start of ammonia co-combustion, and that a specified set value has been set after a specified input operation has been performed by the operator. or a combination of these.

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, and an oil supply system. and a pulverized coal supply system 70 for supplying pulverized coal. Oil supply system 80 and pulverized coal supply system 70 are each an example of a system for supplying carbon-containing fuel.
Primary air, liquid ammonia, pulverized coal and oil are supplied to the burner unit 30 and additional air is supplied to the additional air supply 4 provided in the furnace wall 19 . The supply system 15 is arranged to be controlled by the controller 5 .

An air supply line 112 of the primary air supply system 110 is connected to all burner units 30 . The air supply line 112 is provided with a flow control 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 4 . The air supply line 122 is provided with a flow control 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 control valves 116 , 126 and switching valves 118 , 128 are configured to operate according to control commands sent from the control device 5 .

The ammonia supply system 100 includes the above-described 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, and a pump provided in the ammonia supply line 102. 103, a pressure regulating valve 105 for regulating the pressure of the ammonia supply line 102, a switching valve 107 provided in the ammonia supply line 102 for switching the state of communication between the ammonia tank 101 and the ammonia burner 306, and ammonia supply. and a flow control valve 108 for regulating the flow rate of liquid ammonia flowing through the line 102 .
The pressure control valve 105 , switching valve 107 and flow control valve 108 are configured to operate according to control instructions from the processor 91 . Thereby, the ammonia supply system 100 can change between a supply stop state in which none of the ammonia burners 306 supply liquid ammonia and a supply state in which all the ammonia burners 306 are supplied with liquid ammonia. As will be 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 .

The 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 the ammonia burner 306, and an oil flow control valve 86 for adjusting the flow rate of the 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 burner 306 of each of the second burner unit 32 and the third burner unit 33 .
In one embodiment, the oil supply device 81 , the oil flow control valve 86 and the switching valve 88 are configured to operate according to control commands from the control device 5 . Thereby, the oil supply system 80 can 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 oil supply is stopped.
Note that in another embodiment, the oil supply line 82 may be connected to the starting fuel burner 37 for injecting oil. Also, the oil supply line 82 may be configured to receive atomized vapor. In this case oil and atomized steam are supplied to the burner unit 30 .

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, and pulverized coal supply. A pulverized coal flow control valve 76 for adjusting the flow rate of pulverized coal flowing through the line 72 and a switching valve 78 for switching the communication state of the pulverized coal supply line 72 are provided. 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 according to control commands from the control device 5 . Thereby, the pulverized coal supply system 70 can change between a supply stop state in which the pulverized coal supply is stopped and a supply state in which the 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 and 304 described above.

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, and an air flow rate meter 114 for measuring the flow rate of additional air supplied by the additional air supply system 120. meter 124, an ammonia flow meter 109 for measuring the diversion 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, and a pulverized coal supply system. It includes a pulverized coal flow meter 74 for measuring the flow rate of pulverized coal supplied by 70 and the furnace thermometer 6 already mentioned.
These flow meters are configured to send measurement results to processor 91 .

The boiler operating system 1 operates according to control commands sent from the processor 91, for example, as shown in the flowchart of FIG. 10A.
First, the processor 91 sends another fuel combustion command to the supply system 15 (S51). Thereby, 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 both the oil supply system 80 and the pulverized coal supply system 70 are in a supply state. Therefore, the burner unit 30 is supplied with oil and pulverized coal. 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.
Thereafter, when the ammonia co-firing condition is satisfied (S53: YES), the processor 91 sends an ammonia supply start command to the supply system 15 (S55). The oil supply system 80 changes to the supply stop state, and the ammonia supply system 100 changes to the 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, the boiler 2 co-fires ammonia and pulverized coal.
After that, when the ammonia mono-firing condition is satisfied (S57: YES), the control device 5 sends an ammonia mono-firing command to the supply system 15 (S59). The pulverized coal supply system 70 changes to the supply stop state, and the burners functioning as coal burners are stopped. Also, the ammonia supply system 100 increases the amount of liquid ammonia supplied. As a result, in the boiler 2, mono-firing of ammonia is performed.
Note that, in another embodiment, the supply system 15 that receives 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 . Further, after the ammonia supply start command is sent to the supply system 15, co-firing of ammonia fuel and oil may be performed, or co-firing of ammonia fuel, pulverized coal, and oil may be performed.

FIG. 10B is a flowchart showing NOx control processing according to one embodiment. The NOx control process is a control method for suppressing the NOx generation amount when co-firing ammonia fuel and another fuel (pulverized coal in this example).
In the NOx control process, the processor 91 first reads the boiler load and the ammonia co-firing rate (a more specific example of the co-firing rate of ammonia and pulverized coal) (S61). Reading is executed when the processor 91 receives a demand.
The processor 91 performs a first calculation to calculate the ammonia air ratio, which is the ratio of the amount of air for combustion of ammonia supplied to the ammonia fuel to the amount of air required to burn the ammonia fuel (S10-1). . The method for calculating the ammonia air ratio is as described above.
The processor 91 then performs a second calculation to calculate the 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 burn the pulverized coal. (S10-2). The method of calculating the pulverized coal air ratio (λ _car ), which is an example of the air ratio of the carbon-containing fuel, is as described above.
Next, the processor 91 controls ammonia fuel, The supply amounts of pulverized coal and combustion air are controlled (S10-3). More specifically, as an example, processor 91 controls liquid ammonia flow control valve 108, pulverized coal flow control valve 76, and primary air flow control valve 116, respectively.
The processor 91 determines whether or not the ammonia co-firing has ended (S63). While ammonia co-firing is being performed (S63: NO), the processor 91 repeats S10-1, S10-2, and S10-3 in order. If it is determined that the ammonia co-firing has ended (S63: YES), the processor 91 ends the NOx control process.

FIG. 10C shows the coal and ammonia air content control logic. The control device 5 multiplies the measured 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 controlling the combustion of the coal burner 302. Calculate the amount of air (Q _{Air — car} ). 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 obtained, and the control device 5 obtains the combustion air amount control command value of the coal burner 302 . Similarly, the combustion air amount (Q _{Air — NH3} ) of the ammonia burner 306 is calculated by multiplying the measured value of the ammonia flow meter 109 by the ammonia burner air ratio and the ammonia theoretical air amount. The difference between the calculated combustion air amount of the ammonia burner 306 and the combustion air amount (measured value) of the ammonia burner 306 is taken, and the control device 5 obtains the ammonia burner combustion air amount command value.

The arrangement of the ammonia burners in the case of opposed combustion burners is shown in FIGS. 11A-11E. In facing combustion, pulverized coal is supplied from a single coal grinder to burners installed horizontally on each wall, so when co-firing with ammonia, all horizontally arranged burners are replaced with ammonia combustion burners. It will be. FIG. 11A shows an example in which burners are arranged in six stages, each in three stages, on the front and rear walls. A single-stage burner consists of a plurality of horizontally installed burners.
FIG. 11A (a) schematically shows the burner arrangement of the boiler 2 capable of firing only coal before modification. One stage of the six-stage burners is used as a spare burner and is inactive during normal operation. In (a), reference numeral 1104 indicates a rest burner. Coal burner stages 1101, 1102, 1105 are coal burners with oil burners in order to heat the furnace with oil at start-up.
(b) and (c) of FIG. 11A show a modified example (burner arrangement example) for changing the boiler 2 of (a) to a boiler 2 using ammonia fuel. (b) shows a case where the coal burners 1103 and 1106 and the idle burner 1104 are remodeled into an ammonia burner 1108. FIG. In this case, the coal burners 1103 and 1106 are modified into ammonia-only burners 1107 and 1109 . (c) shows an example in which burners 1101, 1102 and 1105 equipped with a coal burner and an oil burner are modified into burners 1120, 1121 and 1123 for both ammonia and oil. At this time, the idle burner 1104 operates as a coal burner 1104 .
FIGS. 11B and 11D respectively show a burner arrangement example and a side view of the ammonia burner in the AA cross section of (b) of FIG. 11A. FIGS. 11C and 11E respectively show an example of burner arrangement and a side view of the oil+ammonia burner in the BB cross section of (c) of FIG. 11A. In the opposed combustion burner, ammonia (or oil only at startup) is injected from the center, and primary, secondary, and tertiary air passages are provided around it as ammonia combustion air.
In calculating the ammonia-air ratio for each opposing combustion burner, only the air supplied to the ammonia burner as ammonia combustion air (primary to tertiary air described above) is considered. In opposed combustion there is no auxiliary air nozzle as in swirl combustion.
FIG. 12 schematically shows the state inside the furnace in the case of co-firing with ammonia. In the upstream of the combustion completion zone, which is the space in the furnace that supplies additional air (additional air), a reducing and denitrifying atmosphere with insufficient air (air ratio is 1 or less) is formed by pulverized coal combustion. By injecting the air ratio at 1 or less, ammonia can be injected into the reducing atmosphere at a high temperature (usually 1400 ° C. or higher) formed by the coal burner, and thermal decomposition and reduction of ammonia can occur. But I can.
In FIG. 12, the ammonia burner is introduced into the high-temperature reducing atmosphere formed by coal at an ammonia burner air ratio of 0.8 or less, so that the reducing atmosphere of the coal is not damaged, and thermal decomposition occurs by mixing with the high-temperature coal flame. Reduction can occur. By controlling the air ratio of each independent burner individually, mutual interference can be avoided and the amount of NOx generated can be controlled.

(Example)
With reference to FIGS. 5A to 5C, the result of specifying the relationship between the ammonia burner air ratio and the amount of NOx emissions when co-firing coal and ammonia by a combustion test will be described. 5A and 5B are graphs showing the relationship between the burner air ratio and the NOx emission amount when the ammonia co-firing ratio is a predetermined value (FIG. 5B shows the relationship for each burner type).
This combustion test was carried out in a horizontal cylindrical combustion furnace, and the co-firing rate of ammonia and pulverized coal was 25% in terms of calorific value. The coal burner and the ammonia burner were installed separately in the vertical direction, with the coal burner at the top, the ammonia burner at the bottom, and auxiliary air nozzles above and below each burner. Three types of ammonia burners were used: a spud burner, which is a premixed burner, and a diffuser type burner and a swirler type, which are diffusion type burners with different structures of flame stabilizers.
In this test, the oxygen concentration at the furnace outlet was set to about 4%, and NOx was compared by converting to 6% concentration according to the following (Equation 9) in order to correct the difference in the oxygen concentration at the furnace outlet.
NOx (6% conversion value) = NOx measured value × (21% - 6%) ÷ (21% - measured furnace outlet oxygen concentration) (Formula 9)

First, the relationship between the air ratio of the ammonia burner and the amount of NOx emissions when the ammonia burner is a spud type and the co-firing rate is 33% will be examined. FIG. 5C is a graph showing the relationship between the burner air ratio and the amount of NOx emissions when the ammonia co-firing ratio is changed. As shown in FIG. 5C, NOx drops most when the ammonia burner air ratio is 0.6, and NOx increases at both higher and lower air ratios. At an ammonia burner air ratio of 0.8, the NOx value is about 1.5 times the NOx value at 0.6. Generally, 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 big difference from coal firing. Also, the higher the ammonia burner air ratio, the greater the increase in NOx. Even if the ammonia burner air ratio is zero, that is, if only ammonia is injected from the ammonia burner, NOx will increase, but co-firing with coal was possible. If the ammonia burner air ratio is lowered below 0.6, NOx will start to increase. may have reached and converted to NOx. Therefore, while maintaining the ammonia burner air ratio at 0.6, by reducing the additional air injection rate to increase the coal burner air ratio and reduce the amount of unburned ammonia that reaches the downstream of the additional air injection unit, It is necessary to reduce NOx generated in the complete combustion zone.
When the ammonia co-firing rate was reduced to 25%, 22%, and 11% with the spud type burner, the lowest point of NOx generation due to the air ratio of the ammonia burner could not be confirmed, but the tendency is that the air ratio that minimizes NOx further increases. tends to be lower. Also, the NOx value tends to increase when the ammonia co-firing rate is lowered to 25% or less. It is considered that this is because the auxiliary air of the adjacent coal burner is increased, so that a part of the air is mixed in the ammonia burner side, and the air ratio of the ammonia burner is substantially increased. In such a case, the NOx value can be controlled by further lowering the air ratio of the ammonia burner from 0.6.
In this way, even when the ammonia co-firing rate was changed from 11% to 33%, the NOx value was able to suppress the amount of NOx generation by appropriately controlling the air ratio of the ammonia burner. Even if the ratio (ratio between the theoretical air ratio of coal and 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 controlling the air ratios of the coal burner and the ammonia burner individually. It is shown that.

Next, as shown in FIG. 5B, when the flame stabilizer is a diffuser type and a swirler type in a diffusion type burner, the amount of NOx generated tends to be lower in the diffuser type than in the swirler type. In the diffuser type, a disc-shaped diffuser is installed at the tip of the burner, and air flows around it to stabilize the flame, so the ignition point is close to the burner. On the other hand, in the swirler type, a swirl flow centered on the burner is generated by the swirler, and the circulating flow stabilizes the flame, so that the ignition point is formed downstream from the tip of the burner.
Since the reducing atmosphere formed by the ammonia burner is between the ignition point and the additional air input point, 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, and the more NOx is reduced. That's what I think.
The air ratio for the ammonia burner that minimizes NOx even for the diffusion type burner has not been determined, but it tends to be lower than that of the spud type burner. It can be said that it can be controlled.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and includes modifications of the above-described embodiments and modes in which these modes are combined as appropriate.

As used herein, expressions such as "in a certain direction", "along a certain direction", "parallel", "perpendicular", "center", "concentric" or "coaxial", etc. express relative or absolute arrangements. represents not only such arrangement strictly, but also the state of being relatively displaced with a tolerance or an angle or distance to the extent that the same function can be obtained.
For example, expressions such as "identical", "equal", and "homogeneous", which express that things are in the same state, not only express the state of being strictly equal, but also have tolerances or differences to the extent that the same function can be obtained. It shall also represent the existing state.
Further, in this specification, expressions representing shapes such as a quadrilateral shape and a cylindrical shape not only represent shapes such as a quadrilateral shape and a cylindrical shape in a geometrically strict sense, but also within the range in which the same effect can be obtained. , a shape including an uneven portion, a chamfered portion, and the like.
Moreover, in this specification, the expressions “comprising”, “including”, or “having” one component are not exclusive expressions excluding the presence of other components.

<Others>
The contents described in the several embodiments described above can be understood, for example, as follows.

1) A boiler (2) according to at least one embodiment of the present disclosure,
a furnace (2) comprising a furnace wall (19);
an ammonia burner (50) provided on the furnace wall (19) for burning ammonia fuel;
Pulverized coal burners (302, 304) for burning pulverized coal, provided at positions different from the ammonia burner (50) on the furnace wall (19);
including.

2) In some embodiments, the boiler (2) of 1) above, wherein
A control device (5) for controlling the amount of supply of the ammonia fuel, the pulverized coal, and the combustion air,
The control device (5) is
a first calculation unit that calculates an ammonia air ratio, which is a ratio of the amount of ammonia combustion air supplied to the ammonia fuel to the theoretical amount of air required to burn the ammonia fuel;
a second calculation unit that calculates a pulverized coal air ratio, which is a ratio of the amount of pulverized coal combustion air supplied to the pulverized coal to the theoretical amount of air required to burn the pulverized coal;
a control unit that controls the supply amount such that the ammonia air ratio satisfies a first reference range and the pulverized coal air ratio satisfies a second reference range;
have

3) In some embodiments, the boiler (2) of 2) above, wherein
The first calculation unit calculates the ammonia air ratio for each of the plurality of ammonia burners (50),
The control unit controls the supply amount so that each ammonia-air ratio satisfies the first reference range.

4) In some embodiments, the boiler (2) of 2) or 3) above,
An air nozzle (303) provided adjacent to the ammonia burner (50) on the furnace wall (19),
The first calculation unit calculates the ammonia air ratio using the ammonia combustion air amount including the air amount supplied to the ammonia fuel in the air amount injected from the air nozzle (303).

5) In some embodiments, the boiler (2) of any one of 2) to 4) above,
The upper limit of the first reference range is lower than the upper limit of the second reference range.

6) In some embodiments, the boiler (2) of any one of 2) to 5) above,
The first reference range is 0.8 or less.

7) In some embodiments, the boiler (2) of any one of 2) to 5) above,
The first reference range is 0.7 or less.

8) In some embodiments, the boiler (2) of any one of 2) to 7) above,
The first reference range is set based on the value of nitrogen oxides in the combustion gas discharged from the furnace (2).

9) In some embodiments, the boiler (2) of any one of 1) to 8) above,
Adjacent to the ammonia burner (50), an auxiliary air nozzle (303) for supplying auxiliary air,
Said auxiliary air nozzle (303) is provided with a damper which can regulate the amount of auxiliary air which can be supplied in the direction of said ammonia burner (50).

10) In some embodiments, the boiler (2) of any one of 1) to 9) above, wherein
The ammonia burner (50) is
an ammonia nozzle (142, 152) for injecting the ammonia fuel;
and a starting fuel nozzle (ammonia nozzle 306A) for injecting starting fuel.

11) In some embodiments, the boiler (2) of any one of 1) to 10) above, wherein
The ammonia burner (50) is provided adjacent to the pulverized coal burner (302, 304).

12) In some embodiments, the boiler (2) of 8) above, wherein
The furnace wall (19) comprises:
a burner arrangement area where the ammonia burner (50) and the pulverized coal burner (302, 304) are provided;
an additional air supply area provided with an additional air supply section that supplies additional air downstream of the burner arrangement area,
The ammonia burner (50) is positioned at the top of the burner arrangement area.

13) In some embodiments, the boiler (2) of any one of 1) to 12) above, wherein
Said ammonia burner (50) is a diffusion burner or a partially premixed burner.

14) In some embodiments, the boiler (2) of 13) above,
The diffusion burner or the partially premixed burner is a partially premixed spud type burner, a diffusion type swirler type burner having a different flame stabilizer structure, or a diffuser type burner.

15) A boiler control method according to at least one embodiment of the present disclosure,
a furnace (2) comprising a furnace wall (19);
an ammonia burner (50) provided on the furnace wall (19) for burning ammonia fuel;
Pulverized coal burners (302, 304) for burning pulverized coal, provided at positions different from the ammonia burner (50) on the furnace wall (19);
A boiler control method for controlling the supply amount of the ammonia fuel, the pulverized coal and the combustion air in a boiler comprising
a first calculation step (S10-1) of calculating an ammonia air ratio, which is the ratio of the amount of ammonia combustion air supplied to the ammonia fuel to the theoretical amount of air required to burn the ammonia fuel;
A second calculation step (S10-2) of calculating a pulverized coal air ratio, which is a ratio of the amount of pulverized coal combustion air supplied to the pulverized coal to the theoretical amount of air required to burn the pulverized coal. and,
a control step (S10-3) of controlling the supply amount such that the ammonia air ratio satisfies a first reference range and the pulverized coal air ratio satisfies a second reference range;
have

16) A boiler modification method according to at least one embodiment of the present disclosure,
a furnace (2) comprising a furnace wall (19);
Pulverized coal burners (302, 304) provided on the furnace wall (19) for burning pulverized coal;
a plurality of injection parts provided at positions different from the pulverized coal burners (302, 304) on the furnace wall (19) for injecting pulverized coal, starting fuel, or auxiliary air;
a controller (5);
A boiler modification method for a boiler comprising
A replacement step of replacing at least one of the plurality of injection units with an ammonia burner (50) that burns ammonia fuel;
The control device (5) for controlling the supply amounts of the ammonia fuel, the pulverized coal, and the combustion air,
a first calculation unit that calculates an ammonia air ratio, which is a ratio of the amount of ammonia combustion air supplied to the ammonia fuel to the theoretical amount of air required to burn the ammonia fuel;
a second calculation unit that calculates a pulverized coal air ratio, which is a ratio of the amount of pulverized coal combustion air supplied to the pulverized coal to the theoretical amount of air required to burn the pulverized coal;
and a control unit for controlling the supply amount such that the ammonia air ratio satisfies a first reference range and the pulverized coal air ratio satisfies a second reference range.

2: Boiler 4: Additional air supply unit 5: Control device 8: Rear flue 9: Measurement system 11: Nose 12: Furnace 15: Supply system 19: Furnace wall 20: Furnace 21: Burner arrangement area 22: Additional air supply area 30 : Burner unit 31 : First burner unit 32 : Second burner unit 33 : Third burner unit 37 : Starting 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 adjustment valve 107: Switching valve 108: Flow adjustment 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 : Outside Cylinder 141: wind box 142: ammonia supply nozzle 143: flame stabilizer (diffuser)
151: wind box 152: ammonia nozzle 153: flame stabilizer (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 starting oil burner 1102: For starting Coal burner with oil burner 1103: Coal burner 1104: Coal burner 1105: Coal burner with starting oil burner 1106: Coal burner 1107: Ammonia burner 1108: Ammonia burner 1109: Ammonia burner 1120: Starting oil burner/ammonia burner 1121: Start oil burner/ammonia dual use burner 1123: Start oil burner/ammonia dual use burner

Claims (16)

1. a furnace including a furnace wall;
   an ammonia burner provided on the furnace wall for burning ammonia fuel;
   a pulverized coal burner provided at a position different from the ammonia burner on the furnace wall for burning pulverized coal;
   including boiler.
2. A control device for controlling the supply amount of the ammonia fuel, the pulverized coal, and the combustion air,
   The controller is
   a first calculation unit that calculates an ammonia air ratio, which is a ratio of the amount of ammonia combustion air supplied to the ammonia fuel to the theoretical amount of air required to burn the ammonia fuel;
   a second calculation unit that calculates a pulverized coal air ratio, which is a ratio of the amount of pulverized coal combustion air supplied to the pulverized coal to the theoretical amount of air required to burn the pulverized coal;
   a control unit that controls the supply amount such that the ammonia air ratio satisfies a first reference range and the pulverized coal air ratio satisfies a second reference range;
   2. The boiler of claim 1, comprising:
3. The first calculation unit calculates the ammonia air ratio for each of the plurality of ammonia burners,
   3. The boiler according to claim 2, wherein the controller controls the supply amount so that each of the ammonia air ratios satisfies the first reference range.
4. An air nozzle provided adjacent to the ammonia burner on the furnace wall,
   The first calculation unit calculates the ammonia air ratio using the amount of air for ammonia combustion that includes the amount of air supplied to the ammonia fuel in the amount of air injected from the air nozzle. The boiler according to claim 2 or 3.
5. The boiler according to claim 2 or 3, wherein the upper limit of the first reference range is lower than the upper limit of the second reference range.
6. The boiler according to claim 2 or 3, wherein the first reference range is 0.8 or less.
7. The boiler according to claim 2 or 3, wherein the first reference range is 0.7 or less.
8. The boiler according to claim 2 or 3, wherein the first reference range is set based on the value of nitrogen oxides in the combustion gas discharged from the furnace.
9. Adjacent to the ammonia burner, comprising an auxiliary air nozzle for supplying auxiliary air,
   The auxiliary air nozzle comprises a damper that can adjust the amount of auxiliary air that can be supplied in the direction of the ammonia burner.
   The boiler according to any one of claims 1 to 3, characterized in that:
10. The ammonia burner is
    an ammonia nozzle for injecting the ammonia fuel;
    4. The boiler according to any one of claims 1 to 3, further comprising a starting fuel nozzle for injecting starting fuel.
11. The boiler according to any one of claims 1 to 3, wherein the ammonia burner is provided adjacent to the pulverized coal burner.
12. The furnace wall is
    a burner arrangement area in which the ammonia burner and the pulverized coal burner are provided;
    an additional air supply area provided with an additional air supply section that supplies additional air downstream of the burner arrangement area,
    The boiler according to claim 8, wherein the ammonia burner is positioned at the uppermost stage of the burner arrangement area.
13. The boiler according to any one of claims 1 to 3, wherein the ammonia burner is a diffusion burner or a partially premixed burner.
14. The diffusion type burner or the partially premixed burner is a partially premixed spud type burner, a diffusion type swirler type burner having a different flame stabilizer structure, or a diffuser type burner. 14. A boiler according to Item 13.
15. a furnace including a furnace wall;
    an ammonia burner provided on the furnace wall for burning ammonia fuel;
    a pulverized coal burner provided at a position different from the ammonia burner on the furnace wall for burning pulverized coal;
    A boiler control method for controlling the supply amount of the ammonia fuel, the pulverized coal and the combustion air in a boiler comprising
    a first calculation step of calculating an ammonia air ratio, which is the ratio of the amount of ammonia combustion air supplied to the ammonia fuel to the theoretical amount of air required to burn the ammonia fuel;
    a second calculating step of calculating a pulverized coal air ratio, which is a ratio of the amount of pulverized coal combustion air supplied to the pulverized coal to the theoretical amount of air required to burn the pulverized coal;
    a control step of controlling the supply amount such that the ammonia air ratio satisfies a first reference range and the pulverized coal air ratio satisfies a second reference range;
    A boiler control method comprising:
16. a furnace including a furnace wall;
    a pulverized coal burner provided on the furnace wall for burning pulverized coal;
    a plurality of injection units provided at positions different from the pulverized coal burner on the furnace wall and injecting pulverized coal, starting fuel, or auxiliary air;
    a controller;
    A boiler modification method for a boiler comprising
    A replacement step of replacing at least one of the plurality of injection units with an ammonia burner that burns ammonia fuel;
    The control device for controlling the supply amounts of the ammonia fuel, the pulverized coal, and the combustion air,
    a first calculation unit that calculates an ammonia air ratio, which is a ratio of the amount of ammonia combustion air supplied to the ammonia fuel to the theoretical amount of air required to burn the ammonia fuel;
    a second calculation unit that calculates a pulverized coal air ratio, which is a ratio of the amount of pulverized coal combustion air supplied to the pulverized coal to the theoretical amount of air required to burn the pulverized coal;
    and a control unit for controlling the supply amount such that the ammonia-air ratio satisfies a first reference range and the pulverized coal-air ratio satisfies a second reference range.

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