KR20240041970A - Boilers, boiler control methods, and boiler modification methods - Google Patents

Abstract

The burners in the boiler are arranged separately for ammonia and pulverized coal burners. Specifically, the boiler according to some embodiments of the present invention includes a furnace including a furnace wall, an ammonia burner provided on the furnace wall and burning ammonia fuel, and an ammonia burner located in a different position from the ammonia burner on the furnace wall. It is provided and includes a pulverized coal burner for burning pulverized coal.

Description

Boilers, boiler control methods, and boiler modification methods

The present invention relates to a boiler burning ammonia and pulverized coal, a boiler control method, and a boiler modification method.

This application claims priority 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. claim, and its contents are cited here.

Conventionally, boilers in which ammonia is supplied as fuel into a furnace are known. When ammonia is used as a fuel, it is necessary to suppress nitrogen oxide (NOx) emissions. For example, in the burner disclosed in Patent Document 1 (shown in FIG. 2), a nozzle for supplying ammonia is installed by rotating it from the surroundings to the nozzle for supplying ammonia (it is stated that rotation is not necessary), and a rotating pulverized coal flame is installed. Ammonia is mixed in. More specifically, there is the following disclosure. That is, it is a combustion device 4A installed in a furnace and capable of burning ammonia as fuel, including an inner cylinder nozzle 41 disposed at the center when viewed from the fuel injection direction and spraying ammonia, and an inner cylinder nozzle 41 viewed from the fuel injection direction. It is arranged to surround (41) from the outside in the radial direction and is provided with an outer cylinder nozzle (42) that sprays ammonia around the inner cylinder nozzle (41). Additionally, a swirler 45 is disposed inside the outer cylinder nozzle 42 and rotates the flow of ammonia sprayed around the inner cylinder nozzle 41. According to Patent Document 1, ammonia injected from the inner cylinder nozzle 41 forms a reduction area in which the ammonia concentration is high and the oxygen concentration is low in the center of the flame when viewed from the fuel injection direction. On the other hand, nitrogen oxides generated when ammonia injected from the outer cylinder nozzle around the inner cylinder nozzle mixes with oxygen and combusts are supplied to the reduction zone through a circulating flow that circulates from the outer edge of the flame toward the center. As a result, nitrogen oxides generated at the outer edge of the flame are reduced in the reduction zone formed by ammonia sprayed from the inner cylinder nozzle and become nitrogen gas (N2). Therefore, according to Patent Document 1, in a boiler capable of burning ammonia as fuel, it is possible to suppress the increase in nitrogen oxides.

Japanese Patent Publication No. 2020-41748

According to the inventors' knowledge, in order to suppress the emission of nitrogen oxides, it is desirable for the ammonia fuel burner to use a different fuel to set the combustion environment in the boiler to a reduction region and to accurately control the air ratio near the ignition point. However, Patent Document 1 does not specifically disclose such a configuration.

Additionally, when co-firing ammonia with the burner disclosed in Patent Document 1, if the co-firing rate of ammonia is increased, the air ratio of the coal nozzle increases. In coal nozzles, the amount of conveying air needs to be kept constant in order to prevent coal from settling within the nozzle, and increasing the ammonia co-firing rate only reduces the amount of coal fed, so the amount of conveying air relative to the coal flow rate increases. As a result, when the ammonia mixing rate is high, the air ratio around the ammonia nozzle increases, causing 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 capable of burning 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 such that the ammonia and pulverized coal burners are arranged separately.

That is, the 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 and burning ammonia fuel, and an ammonia burner located on the furnace wall at a different position from the ammonia burner. It is provided and includes a pulverized coal burner for burning pulverized coal.

The boiler is provided with a control device that controls the supply amounts of the ammonia fuel, the pulverized coal, and combustion air, and the control device is configured to control the ammonia supplied to the ammonia fuel with respect to the theoretical amount of air required to burn the ammonia fuel. A first calculation unit for calculating the ammonia air ratio, which is the ratio of the amount of air for combustion, and a second calculation unit for calculating the pulverized coal air ratio, which is the ratio of the amount of air for combustion of pulverized coal supplied to the pulverized coal with respect to the theoretical air amount required for combustion of the pulverized coal; It is characterized by having a control unit that controls 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 first calculation unit calculates the ammonia-air ratio for each of the plurality of ammonia burners,

The control unit is characterized in that it controls the supply amount so that each ammonia-air ratio satisfies the first standard range.

An air nozzle is provided on the furnace wall adjacent to the ammonia burner,

The first calculation unit is characterized in that the ammonia air ratio is calculated using the amount of ammonia combustion air that includes the amount of air supplied to the ammonia fuel among the amount of air injected from the air nozzle.

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 as being 0.8 or less.

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

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

The boiler is adjacent to the ammonia burner and has an auxiliary air nozzle that supplies auxiliary air, and the auxiliary air nozzle has a damper that can adjust the amount of auxiliary air that can be supplied in the direction of the ammonia burner. It is characterized by

The ammonia burner,

An ammonia nozzle for spraying the ammonia fuel,

Starting fuel nozzle that injects starting fuel

It is characterized by including.

The ammonia burner is characterized in that it is provided adjacent to the pulverized coal burner.

The ammonia burner is characterized in that it is 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 part for supplying additional air is provided downstream of the burner arrangement area, and the ammonia burner is , It is characterized in that it is located at the top of the burner placement area.

The ammonia burner is characterized as a diffusion type burner or a partial premixing type burner.

The diffusion type burner or the partial premixing type burner is characterized in that it is a spad type of a partial premixing type, a swirler type with a different structure of the flame saver in a diffusion type, or a diffuser type.

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 and burning ammonia fuel, and an ammonia burner located on the furnace wall at a different position from the ammonia burner. A boiler control method for controlling supply amounts of the ammonia fuel, the pulverized coal, and combustion air in a boiler provided and including a pulverized coal burner for burning pulverized coal, wherein the theoretical air amount required to burn the ammonia fuel is: A first calculation step of calculating the ammonia air ratio, which is the ratio of the amount of air for combustion of ammonia supplied to the ammonia fuel, and calculating the pulverized coal air ratio, which is the ratio of the amount of air for combustion of pulverized coal supplied to the pulverized coal with respect to the theoretical air amount required to burn the pulverized coal. A boiler control method comprising a second calculation step and a control step for 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.

A boiler modification method according to at least one embodiment of the present invention includes a furnace including a furnace wall, a pulverized coal burner provided on the furnace wall and burning pulverized coal, and the pulverized coal burner is provided at a different position in the furnace wall. A boiler modification method comprising a plurality of injection units that inject pulverized coal, starting fuel, or auxiliary air, and a control device, wherein at least one of the plurality of injection units is replaced with an ammonia burner that burns ammonia fuel. The control device, which has a substitution step and controls the supply amounts of the ammonia fuel, the pulverized coal, and the combustion air, determines the amount of ammonia combustion air supplied to the ammonia fuel with respect to the theoretical air amount required to burn the ammonia fuel. A first calculation unit for calculating the specific ammonia air ratio, a second calculation unit for calculating the pulverized coal air ratio which is the ratio of the amount of air for combustion of pulverized coal supplied to the pulverized coal with respect to the theoretical air amount required for combustion of the pulverized coal, and the ammonia air ratio It is a boiler modification method having a control unit that controls the supply amount to meet the first standard range and the pulverized coal-air ratio to meet the second standard range.

According to the present invention, a boiler capable of burning ammonia fuel under conditions that can suppress the generation of NOx, a boiler control method, and a boiler modification method can be provided.

1 is a conceptual diagram of a boiler operation system according to one embodiment.
Figure 2 is a conceptual diagram of a burner showing a conventional example.
Fig. 3A is a cross-sectional view showing the burner arrangement of a boiler before modification according to one embodiment (example of modification of a coal burner).
FIG. 3B is a cross-sectional view showing the burner arrangement of a boiler after modification according to one embodiment (example of modification of a coal burner).
Fig. 3C is a conceptual diagram showing the correspondence between burner arrangements before and after modification of a boiler according to one embodiment (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. 5A 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. 5B 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. 5C is an explanatory diagram showing the relationship between the ammonia co-firing ratio, the ammonia burner air ratio, and the amount of nitrogen oxides generated according to one embodiment.
FIG. 6A is a cross-sectional view showing the burner arrangement of the boiler before modification according to one embodiment (example of modification of starting fuel burner).
FIG. 6B is a cross-sectional view showing the burner arrangement of the boiler after modification according to one embodiment (example of modification of starting fuel burner).
Fig. 6C is a conceptual diagram showing the correspondence between burner arrangements before and after modification of the boiler according to one embodiment (example of modification of starting fuel burner).
Fig. 7A is a cross-sectional view showing the burner arrangement of the boiler after modification according to one embodiment (example of modification of air nozzle).
Fig. 7B is a conceptual diagram showing the correspondence between burner arrangements before and after modification of the boiler according to one embodiment (example of modification of air nozzle).
Fig. 8A is a cross-sectional view showing the burner arrangement of the boiler after modification according to one embodiment (example of modification of the air nozzle at the uppermost stage).
Fig. 8B is a conceptual diagram showing the correspondence between burner arrangements before and after modification of the boiler according to one embodiment (example of modification of the uppermost air nozzle).
9 is a control system diagram of a boiler according to one embodiment.
10A is a flowchart of a boiler control method according to one embodiment.
10B is a flowchart of NOx control processing according to one embodiment.
FIG. 10C is a control logic diagram for calculating a control command value for the amount of combustion air according to one embodiment.
11A is an ammonia burner arrangement of an opposing combustion burner according to one embodiment.
FIG. 11B is a cross-sectional view taken along the arrow line AA in FIG. 11A.
FIG. 11C is a cross-sectional view taken along the arrow line BB in FIG. 11A.
Figure 11D is a side view of an ammonia burner according to one embodiment.
Figure 11E is a side view of an oil ammonia burner according to one embodiment.
FIG. 12 is a conceptual diagram showing a reduction-oxidation state in a boiler according to one embodiment.
Figure 13 is a diagram showing the structure of a spad burner.
Figure 14 is a diagram showing the structure of a diffuser burner.
Figure 15 is a diagram showing the structure of a swirler burner.
Figure 16 is a flow chart of the boiler modification method.

Hereinafter, several 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 embodiments or shown in the drawings are not intended to limit the scope of the present invention and are merely illustrative examples.

Fig. 1 is a conceptual diagram of a boiler operation system 1 according to one embodiment.

The boiler operation system 1 includes, for example, a boiler 2 built into a thermal power plant (not shown), a supply system 15 for supplying air and fuel to the boiler 2, and the boiler 2. A measurement system 9 for measuring parameters related to operation is provided.

The fuel supplied to the boiler 2 from the supply system 15 includes ammonia fuel. The ammonia fuel may be either liquid ammonia or ammonia gas. Below, an embodiment in which the ammonia fuel is liquid ammonia is illustrated. In one embodiment, liquid ammonia is supplied to the boiler 2 in a liquid form. Liquid ammonia does not contain gas such as hydrogen gas, but may contain impurities (for example, urea) to a degree that does not affect combustion in the boiler 2. Liquid ammonia vaporizes into ammonia gas within the boiler (2).

Additionally, the fuel supplied to the boiler 2 from the supply system 15 includes fuels other than ammonia fuel. For example, after combustion using another fuel is performed within the boiler 2, co-combustion of ammonia and another fuel or 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, oil such as heavy oil or diesel, or coal such as pulverized coal. Below, an embodiment in which the carbon-containing fuel is oil and pulverized coal is exemplified.

The boiler 2 in one embodiment includes a furnace 20 including a furnace wall 19. The furnace wall 19 has 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 part 4 for supplying additional air (additional air) is provided. ) includes. The additional air supply area 22 is located downstream of the burner arrangement area 21.

The furnace 20 is a cylindrical hollow body for combustion by reacting the fuel injected by the burner unit 30 with combustion air, and may take various shapes, such as a cylindrical shape or a square pillar shape.

Additionally, the furnace 20 of one embodiment includes a nose 11 that protrudes toward the inside of the furnace 20. The nose 11 is configured to allow gases (for example, combustion gas and unburned gas) generated in the combustion space 7 of the furnace 20 to properly flow into the flow path on the downstream side of the furnace 20. The flow path on the downstream side of the furnace 20 is a flue 8 as an example.

At least one burner unit 30 is configured to combust fuel in the combustion space 7 of the furnace 20 . In the embodiment illustrated in FIG. 1, the burner unit 30 is 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 at each stage are 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 of the gas flow direction. In some cases, these three stages of burners are collectively referred to as burner unit 30. Additionally, the burner unit 30 may be arranged in two or four stages.

The boiler 2 of one embodiment is a rotating combustion boiler, and a plurality of burner units 30 provided at each stage are arranged at equal intervals along the circumferential direction of the furnace 20. As an example, the number of burner units 30 in each stage is four, but FIG. 1 shows only one burner unit 30 in each stage. Additionally, the number of burner units 30 in each stage may be three or five or more.

Boiler 2 according to another embodiment is an opposed combustion type boiler. In this case, at least one burner unit 30 in each stage is provided at a position 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 in a liquid state into the inside of the furnace 20. The ammonia burner 306 may be configured to spray only liquid ammonia. Alternatively, the ammonia burner 306 may be configured to inject liquid ammonia along 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 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.

In addition, any burner unit 30 may include coal burners 302 and 304 (pulverized coal burners 302 and 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 starting fuel, into the furnace 20, and an auxiliary air nozzle (air nozzle) 301 for injecting auxiliary air. 305) (see FIG. 3A) may be included. Details will be described later.

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

The measurement system 9 of 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 the representative temperature within the furnace 20. do. The representative temperature within the furnace 20 is a temperature that is correlated 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 within 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. Additionally, the representative temperature within the furnace 20 may be, for example, gas temperature.

The boiler operation system 1 may be operated by operation by an operator, may be operated by control by 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 is started after fuels other than ammonia fuel (carbon-containing fuel in this example) are burned, and co-combustion of ammonia fuel and other fuels may be performed.

The air ratio at the time of combustion generally has a large influence on the generation of nitrogen oxides when fuel containing nitrogen, such as coal or ammonia, is burned. Here, for the case of co-firing ammonia fuel and other fuels, for the case of calculating one air ratio in the entire furnace as a comparative example, and for the case of calculating the air ratio for each of the ammonia fuel and the carbon-containing fuel as another fuel as an example. This is explained below.

(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 burn the ammonia fuel and other fuels supplied to the furnace 20. The amount of air supplied to the above-described furnace 20 does not include additional air (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 additional air among the total air supplied to the furnace 20. Specifically, the air ratio constituting the ammonia co-firing conditions (hereinafter sometimes referred to as the burner unit air ratio) is defined by the following equation (1).

λ _b =λ×(100-AA)/100… Equation (1)

In equation (1), λ _b is the burner unit air ratio, λ is the total air ratio, and AA is the supply ratio of additional air among the total air supply to the boiler 2.

Additionally, 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 equations (2) to (4), Q _Air is the total air supply amount. In addition, Q _mf is the supply amount of ammonia fuel and a fuel other than ammonia fuel (carbon-containing fuel in this example) when the combustion performed within the furnace 20 is ammonia co-combustion (co-combustion rate in weight conversion: X%). Q _x is the air flow rate for the air ratio to become 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 theoretical air amount of the ammonia fuel.

(Example)

In the embodiment, the ammonia air ratio, which is the ratio of the amount of ammonia combustion air supplied to the ammonia fuel with respect to the theoretical air amount of the ammonia fuel supplied to the furnace 20, and the amount of combustion air supplied to the other fuels with respect to the theoretical air amount of the other fuels. The air ratio for different fuels is calculated separately for each fuel.

The ammonia air ratio (hereinafter sometimes 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 ×A _NH3 … Equation (6)

Here, λ _NH3 in equation (5) is the ammonia-air ratio, Q _{Air_NH3} is the air amount for ammonia combustion, and Q _{x_NH3} is the air flow rate for the ammonia fuel air ratio to be 1. Additionally, Q _NH3 in equation (6) is the supply amount of ammonia fuel, and A _NH3 is the theoretical air amount of ammonia fuel.

In addition, taking carbon-containing fuel as an example as another fuel, the air ratio of carbon-containing fuel is required from 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 _car in equation (7) is the air ratio of the carbon-containing fuel, Q _{Air_car} is the air amount for combustion of the carbon-containing fuel, and Q _{x_car} is the air flow rate for the air ratio of the carbon-containing fuel to be 1. Additionally, Q _car in equation (8) is the supply amount of carbon-containing fuel, and A _car is the theoretical air amount of carbon-containing fuel.

As in this embodiment, the ammonia air ratio λ _NH3 and the carbon-containing fuel air ratio λ _car can be individually adjusted by calculating each. For example, in the boiler 2 in which the ammonia burner 306 and the pulverized coal burner 302 are used (see FIG. 3b), equations (5) and (6) are applied to the air ratio of the ammonia burner 306, , Equations (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 expressed in equations (7) and (8) all become parameters of pulverized coal.

Hereafter, the air ratio refers to the one calculated in this example.

In one embodiment, the coal burner 302 and the ammonia burner 306 are arranged separately as shown in FIGS. 3A to 3C, which are examples of a swirl combustion boiler (FIG. 3A shows the coal burner 302 before the ammonia burner 306 is installed. Shows boiler before modification). As a result, the air ratio can be adjusted individually, 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, and the rapid increase in NOx can be suppressed.

Additionally, 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 the pulverized coal burner 302.

In one embodiment, the upper limit of the burner portion air ratio is 0.8 or less. When 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 also becomes 0.8 or less. As a result, NOx generated in the furnace 20 is effectively reduced.

The upper limit of the burner unit 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 production of excessive NOx is suppressed.

Additionally, in the boiler 2 having a general size used in thermal power plants, it is not realistic for the burner portion air ratio to be less than 0.6. Therefore, the burner air ratio constituting the ammonia co-firing condition, which is a condition that must be met before starting the supply of ammonia fuel, 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, it is desirable to calculate the ammonia-air ratio λ _NH3 for each ammonia burner 306. As described later, since the amount of NOx generation changes significantly depending on the ammonia-air ratio, this is to strictly calculate the ammonia-air ratio for each burner and control the supply amount of ammonia fuel and ammonia combustion air.

Likewise, in order to control the NOx generation amount of the coal burner 302 with high precision, it is desirable to calculate the air ratio λ _car (coal-air ratio) of the carbon-containing fuel for each coal burner 302.

The control device 5 (see FIG. 9), which is a component of the boiler 2 in one embodiment, controls the ammonia air ratio, the amount of air supplied from the ammonia burner 306 (see FIGS. 3B and 3C), and the ammonia burner 306. ) is calculated from the amount of air supplied from the auxiliary air nozzles (303, 305) adjacent to the The amount of air supplied from the auxiliary air nozzles 303 and 305 is calculated as the amount of air for ammonia combustion, and only the amount of air contributing to ammonia combustion is calculated. For example, as shown in FIGS. 3B and 3C, the auxiliary air nozzle 303 is used to produce ammonia. When fitted adjacent to the burner 306 and the coal burner 302, half of the air volume is calculated as air for the ammonia burner.

When the NOx generation amount is higher than the standard value, control is performed to lower the ammonia burner air ratio from, for example, 0.7 to 0.6. Figure 5a shows an example of ammonia burner air ratio and NOx generation amount. In this test result, the optimal point of the ammonia burner air ratio is 0.6. If the ammonia burner air ratio is lowered than 0.6, NOx increases, so if the NOx generation amount does not decrease even if lowered to 0.6, unburned ammonia reaches the combustion completion zone, which is a space within the furnace at approximately the same height as the additional air supply area 22, Convert to NOx. Therefore, while maintaining the ammonia burner air ratio at 0.6, the ratio of the amount of additional air (additional air) to the total amount of air input into the boiler 2 is reduced, thereby reducing the amount of unburned ammonia that reaches the combustion completion zone, thereby reducing combustion. We aim to reduce NOx generated at the completion station.

The ammonia burner 306 is provided by partially replacing (remodeling) the coal burner 304, as shown in FIGS. 3A to 3C. The 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 equipped with a starting fuel burner 307. The auxiliary air nozzle 303 on which the starting fuel burner 307 is installed has 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 for ammonia combustion injected into the furnace 12). Equipped with a damper that can adjust the amount.

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, the amount of air supplied from the same nozzle is the optimal air amount for the coal burner 302. If adjusted to , the amount of air required to reduce nitrogen oxides in the ammonia burner 306 becomes excessive. Conversely, if the air quantity is adjusted to reduce NOx in the ammonia burner, the air quantity becomes insufficient from the optimal air ratio of the coal burner 302, leading to an increase in unburned fuel in the coal burner.

In this regard, in this embodiment, the auxiliary air nozzle 303 sandwiched between the coal burner 302 and the ammonia burner 306 is divided into upward and downward flow paths 303A and 303B as the boiler 2 is remodeled. And, each flow rate can be controlled with a damper (see FIGS. 3C and 4). Thereby, the amount of air for the coal burner 302 and the ammonia burner 306 can be adjusted individually. 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 around 0.7 to 0.9.

By allowing the air flow rate from the passages 303A and 303B of the auxiliary air nozzle 303 to be individually adjusted, it becomes possible to suppress the increase in unburned fuel in the coal burner and NOx increase due to the ammonia burner. Additionally, by converting the coal burner 304 into an ammonia burner 306, the existing coal-fired boiler 2 can be changed into a boiler 2 that burns ammonia fuel.

In addition, by arranging the ammonia burner 306 adjacent to the coal burner 302 as shown in FIG. 3, heat from coal combustion can be utilized for ammonia combustion and ammonia can be stably burned.

In addition, based on the supply amount of ammonia supplied to the ammonia burner 306 and the supply amount of combustion air, the amount of NOx generated in the combustion gas discharged from the boiler 2 is calculated, and a first standard is set according to the calculation result. You can set a range. 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 for burning starting fuel, as shown in FIGS. 6A to 6C, and the ammonia burner 306 is used for starting. It can be prepared by replacing (remodeling) part of the fuel burner 307. The ammonia burner 306 includes an ammonia nozzle 306A that sprays ammonia. The ammonia nozzle 306A also functions as a starting fuel nozzle that injects starting fuel (oil as a specific example). When starting the boiler 2, the ammonia nozzle 306A injects starting fuel and then injects ammonia according to the ammonia co-firing conditions being met. Additionally, in another embodiment, the starting fuel nozzle may be configured as a nozzle different from the ammonia nozzle 306A, and may be provided in the same compartment as the ammonia nozzle 306A.

When the starting fuel burner 307 is converted to an ammonia burner 306, the air nozzle 303 on one side adjacent to the coal burners 302 and 304 is eliminated, ensuring a sufficient amount of auxiliary air for the coal burner 302. You won't be able to do it.

For this reason, 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 to calculate the ammonia-air ratio.

By optimizing the air ratio of the coal burners 302 and 304, it is possible to suppress the increase in unburned fuel content in the coal burners 302 and 304.

The 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. 7A and 7B, and the ammonia burner 306 has, Some of the auxiliary air nozzles 301 and 305 are replaced. In the example of FIG. 7B, an ammonia burner 306 is provided by replacing the auxiliary air nozzle 305.

As in the case of modification of the starting fuel burner 307, the auxiliary air nozzle 305 on one side of the coal burner 304 is missing, resulting in a shortage of air in the coal burner 304. In addition, when the compartment height of the auxiliary air nozzle 305 is low, it is difficult to install the ammonia burner 306 equipped with a flame holder.

The nozzle in which the ammonia burner 306 adjacent to the coal burner 304 and the starting fuel burner 307 on the opposite side are installed is used as the auxiliary air nozzle 303 and this air volume is increased to adjust the air volume to a predetermined amount. do. At this time, in the coal burner 304 shown in FIG. 7B, the auxiliary air nozzle 303 is on one side, but since the upper coal burner 302 has auxiliary air nozzles 301 and 303 above and below, the oil burner for starting The air flow path is divided into upper and lower flow paths (303A, 303B), each flow rate can be controlled with a damper so that only the lower flow path (303B) can increase the air volume, and the air ratio of the coal burner 304 is adjusted to By being able to optimize, it is possible to suppress the increase in unconnected portions of congregations.

In the boiler 2 before modification, when the upwind height at which the auxiliary air nozzle 305 is installed is lower than the height of the coal burner 302 or the starting fuel burner 307, the upwind height without the flame breaker is Install low ammonia burner (306). For example, the premixed spad nozzle of 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 top of the burner arrangement area 21 is replaced (modified). ), an ammonia burner 306 is provided. The ammonia burner 306 is provided adjacent to the coal burner 302.

As in the previous example in which the ammonia burner 306 is installed in the auxiliary air nozzle 305, the auxiliary air nozzle 301 on one side of the coal burner 302 is missing, resulting in a shortage of air in the coal burner 302. In addition, when the compartment height of the auxiliary air nozzle 301 is low, it is difficult to install the ammonia burner 306 equipped with a flame holder. The air flow path of the starting fuel burner 307 is divided into upper and lower channels into flow paths 303A and 303B, and the flow paths 303A and 303B are individually controllable, and when the upwind height is low, upwind height is controlled without a flame suppressor. Install a partial premix nozzle (see Figure 13), which is a low ammonia nozzle.

In this case, it becomes possible to use ammonia not only as a fuel but also as a denitrifying agent.

The burner used in the above embodiment is a diffusion combustion type burner or a partial premixed combustion type burner (also referred to as a spad burner). In a diffusion combustion burner, a swirler type or diffuser type can be used as a flame insulator. FIG. 13 shows an example of a structural diagram of a partial premixed spad burner, FIG. 14 shows an example of a structural diagram of a diffuser burner, and FIG. 15 shows an example of a structural diagram of a swirler burner.

Figure 13 shows an example of a spad burner. The spad burner is composed of a nozzle 132 and an external cylinder 133 that supply ammonia to the inside of the windshield 131. Combustion air is supplied from the upwind 131, and a damper for flow rate adjustment is installed on the upstream side of the upwind 131. Ammonia is injected inside the outer cylinder 133, and is injected into the furnace while premixed with combustion air introduced from the gap between the nozzle 132 and the outer cylinder 133. Ammonia is naturally ignited when the high temperature gas in the furnace is mixed with an amount of air suitable for ignition. Since ammonia and air are partially premixed, the ignition point is formed at the point where the ejection flow rate of the entire nozzle matches the combustion rate of the premixed ammonia and air.

Figure 14 shows an example of a structural diagram of a diffuser burner. Inside the windshield 141, an ammonia nozzle 142 and a disk-shaped flame heater 143 (referred to as a diffuser) are installed at the tip of the ammonia nozzle 142. Ammonia is sprayed from a plurality of holes 142A provided in the ammonia nozzle 142 (two holes 142A are shown in the drawing). Combustion air is supplied from the windward side 141, and a damper to adjust the flow rate is installed on the upstream side. Since the combustion air flows at an accelerated rate around the flame heater 143, a vortex is formed on the outer periphery of the disk flame heater 143. Since ammonia is mixed into this vortex and ignites by mixing with air, an ignition point is formed on the flame insulator 143.

Figure 15 shows an example of a structural diagram of a swirler burner. Inside the windshield 151, an ammonia nozzle 152 and a flame heater 153 (referred to as a swirler) having a rotating blade are installed at the tip of the ammonia nozzle 152. Ammonia is sprayed from a plurality of holes 152A provided in the ammonia nozzle 152 (two holes 152A are shown in the drawing). Combustion air is supplied from the windward side 151, and a damper to adjust the flow rate is installed on the upstream side. When the combustion air passes through the flame suppressor 153, it becomes a swirling flow due to the rotating blade and flows around the outer periphery of the ammonia nozzle 152. Because the circulating flow is generated inside the swirling flow, the ammonia and the circulating flow are mixed and ignited. For this reason, the ignition point of the ammonia flame is formed near the downstream side of the flame insulator 153.

Figure 16 is a flow chart showing the boiler modification method of the present invention. As described above using FIGS. 3C, 6C, 7B, and 8B, the boiler 2 before modification injects pulverized coal burner 302, pulverized coal, starting fuel that may be oil, for example, or auxiliary air. It is provided with a plurality of injection units. Each injection unit is a coal burner 304, a starting fuel burner 307, or an auxiliary air nozzle 301, 303. And S11 shown in FIG. 16 shows the process of replacing this injection part with the ammonia burner 306. By executing S11, for example, an existing boiler 2 capable of burning coal can be converted 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 and burning ammonia fuel, In the boiler 2, which is provided in a different position from the ammonia burner 306 on the furnace wall 19 and includes pulverized coal burners 302 and 304 for burning pulverized coal, the ammonia fuel, the pulverized coal and the combustion A boiler control method for controlling the supply amount of air, the first calculation step (S10-1) of calculating the ammonia air ratio, which is the ratio of the amount of ammonia combustion air supplied to the ammonia fuel to the theoretical air amount required to burn the ammonia fuel. And, a second calculation step (S10-2) of calculating the pulverized coal air ratio, which is the ratio of the amount of air for combustion of pulverized coal supplied to the pulverized coal, with respect to the theoretical air amount required to burn the pulverized coal, and the ammonia air ratio is in the first reference range There is also a control step (S10-3) for controlling the supply amount so that the pulverized coal air ratio satisfies the second standard range.

It is preferable that the upper limit of the first reference range for the ammonia-air ratio is set smaller than the upper limit of the second reference range for the pulverized coal-air ratio. The optimal value of the air ratio for minimizing NOx emissions is about 0.6 for ammonia fuel, and is smaller than that for pulverized coal (usually about 0.7 to 0.8). By setting the upper limit of the reference range with reference to the optimal value, it becomes easy to minimize NOx emissions.

Fig. 9 shows a specific configuration of the boiler operation system 1 according to one 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.

Control device 5 in one embodiment includes a processor 91, ROM 92, RAM 93, and memory 94.

The processor 91 is configured to read 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, GPU, MPU, DSP, various computing devices other than these, or a combination thereof. The processor 91 may be realized by integrated circuits such as PLD, ASIC, FPGA, and MCU. The memory 94 stores various data as the boiler operation program is executed. The memory 94 is, for example, flash memory. The processor 91 is electrically connected to the supply system 15 and the measurement system 9.

The processor 91 of one embodiment includes a fuel combustion command for burning other fuels 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 , and is configured to generate an ammonia combustion start command for starting the combustion of ammonia within the furnace 20. In one embodiment, these control commands are sent to the supply system 15.

The processor 91 of one embodiment generates an ammonia supply start command when it is determined based on the measurement result of the measurement system 9 that the ammonia co-firing condition for starting ammonia co-firing is met. Additionally, when the processor 91 of one embodiment determines that the ammonia combustion condition for starting ammonia combustion is satisfied, it starts an ammonia combustion command. Ammonia combustion conditions include, for example, that the representative temperature in the furnace 20 reaches the specified temperature, that a specified time has elapsed since ammonia co-firing is started, and that a specified set value is reached after a specified input operation from the operator. reached, 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, It is provided with an oil supply system 80 for supplying oil, and a pulverized coal supply system 70 for supplying pulverized coal. The oil supply system 80 and the pulverized coal supply system 70 are examples of systems for supplying carbon-containing fuel, respectively.

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 section 4 provided on the furnace wall 19. The supply system 15 is configured to be controlled by a control device 5.

The 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 rate adjustment valve 116 for adjusting the flow rate of primary air and a switching valve 118 for switching the communication state of the air supply line 112.

The 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 additional air, and a switching valve 128 for switching the communication state of the air supply line 122.

The flow rate adjustment valves 116 and 126 and the switching valves 118 and 128 are configured to operate in accordance with control commands sent from the control device 5.

The ammonia supply system 100 includes the ammonia burner 306 described above, 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 103 provided in the ammonia supply line 102, a pressure adjustment valve 105 for adjusting the pressure of the ammonia supply line 102, and an ammonia tank 101 provided in the ammonia supply line 102. and a switching valve 107 for switching the communication state of the ammonia burner 306, and a flow rate adjustment valve 108 for adjusting the flow rate of liquid ammonia flowing through the ammonia supply line 102.

The pressure adjustment valve 105, the switching valve 107, and the flow rate adjustment valve 108 are configured to operate in accordance with 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 supplies liquid ammonia and a supply state in which liquid ammonia is supplied to all ammonia burners 306 . As described later, when the ammonia supply system 100 is in a supply stop state, oil is supplied to the ammonia burners 306 of the second burner unit 32 and the third burner unit 33 from the oil supply system 80. supplied.

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 the oil flowing through the oil supply line 82. It is provided with an oil flow rate adjustment valve 86 for adjusting the flow rate, and a switching valve 88 for switching the communication state of the oil supply line 82. The oil supply line 82 in this example is connected to each ammonia burner 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 adjustment valve 86, and the switching valve 88 are configured to operate in accordance with a control command from the control device 5. As a result, 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 supply of oil is stopped.

Additionally, in another embodiment, the oil supply line 82 may be connected to a starting fuel burner 37 for injecting oil. Additionally, the oil supply line 82 may be configured to allow atomization vapor to flow into it. In this case, oil and atomized vapor are supplied to the burner unit 30.

The 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, It is provided with a pulverized coal flow rate adjustment valve 76 for adjusting the flow rate of 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 in 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 accordance with a control command from the control device 5. As a result, the pulverized coal supply system 70 can change between a supply stop state in which the supply of pulverized coal 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 the flow rate of additional air supplied by the additional air supply system 120. An air flow meter 124 for measuring, an ammonia flow meter 109 for measuring the utilization of ammonia fuel supplied by the ammonia supply system 100, and an ammonia flow meter 109 for measuring the flow rate of oil supplied by the oil supply system 80. It includes an oil flow meter 84, 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 measurement results to the processor 91.

The boiler operation system 1 operates by control commands sent from the processor 91, for example, as shown in the flowchart shown in FIG. 10A.

First, a command for burning other fuel 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 state, and both the oil supply system 80 and the pulverized coal supply system 70 are in a supply state. Accordingly, 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 spray oil. Inside the furnace 12, oil and pulverized coal are burned.

Afterwards, as the ammonia co-firing condition is 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 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 converted from oil to liquid ammonia. The pulverized coal supply system 70 maintains the supply state. As a result, co-firing of ammonia and pulverized coal is performed in the boiler 2.

Then, depending on 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 burner functioning as a coal burner stops. Additionally, the ammonia supply system 100 increases the supply amount of liquid ammonia. As a result, combustion of ammonia occurs in the boiler 2.

Additionally, in another embodiment, the supply system 15, which has received the other fuel combustion command from the processor 91, first supplies oil to the burner unit 30 and then supplies oil and pulverized coal to the burner unit 30. You may supply it. Additionally, after an 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. NOx control treatment is a control method that suppresses the amount of NOx generated 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-combustion ratio (as a more specific example, the co-combustion ratio of ammonia and pulverized coal) (S61). Reading is performed 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 ammonia combustion 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.

Next, the processor 91 performs a second calculation to calculate the pulverized coal air ratio, which is the ratio of the amount of air for combustion of pulverized coal supplied to the pulverized coal to the theoretical amount of air required to combust the pulverized coal (S10-2). The method for calculating the pulverized coal air ratio (λ _car ), which is an example of the air ratio of carbon-containing fuel, is as described above.

Subsequently, the processor 91 configures the ammonia fuel, pulverized coal, and combustion air so that the ammonia air ratio calculated in S10-1 satisfies the first standard range and the pulverized coal air ratio calculated in S10-2 satisfies the second standard range. Control each supply amount (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 ammonia co-firing has ended (S63). While ammonia co-firing is being executed (S63: “No”), the processor 91 repeats S10-1, S10-2, and S10-3 in order. When it is determined that ammonia co-firing is finished (S63: "Yes"), the processor 91 ends the NOx control process.

Figure 10c shows the control logic of the amount of air for coal and ammonia. 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 (indicating value) and the coal theoretical air amount, Calculate the amount of air for combustion (Q _{Air_car} ). The difference between the calculated combustion air quantity of the coal burner 302 and the combustion air quantity (measured value) of the coal burner 302 is taken, and the control device 5 obtains the combustion air quantity control command value of the coal burner 302. . Similarly, the combustion air quantity (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 theoretical ammonia air quantity. The difference between the calculated combustion air quantity of the ammonia burner 306 and the combustion air quantity (measured value) of the ammonia burner 306 is taken, and the ammonia burner combustion air quantity command value is obtained in the control device 5.

The arrangement of the ammonia burner in the case of an opposed combustion burner is shown in Figures 11A to 11E. In opposed combustion, pulverized coal is supplied from one coal crusher to burners installed on each wall in the horizontal direction, so when performing ammonia co-firing, all horizontally arranged burners are replaced with ammonia combustion burners. Figure 11a shows an example in which six stages of burners are arranged in three stages each on the front and rear walls. The first stage burner consists of a plurality of burners installed horizontally.

Figure 11a (a) schematically shows the burner arrangement of the boiler 2 capable of burning coal before modification. The first stage of the six-stage burner is idle during normal operation to be used as a spare burner. In (a), symbol 1104 indicates a rest burner. In order to heat the inside of the furnace with oil during startup, the coal burner stages 1101, 1102, and 1105 are coal burners equipped with oil burners.

11A (b) and (c) show an example of modification (burner arrangement example) for converting the boiler 2 of (a) into a boiler 2 using ammonia fuel. (b) shows a case where the coal burners 1103 and 1106 and the paper burner 1104 are converted into an ammonia burner 1108. In this case, the coal burners (1103, 1106) are converted into ammonia burners (1107, 1109). (c) shows an example of converting burners 1101, 1102, and 1105 equipped with a coal burner and an oil burner into burners 1120, 1121, and 1123 for both ammonia and oil. At this time, the paper burner 1104 is operated as a coal burner 1104.

Figures 11b and 11d show a burner arrangement example and a side view of an ammonia burner on the A-A cross section of Figure 11a (b), respectively. FIGS. 11C and 11E show a burner arrangement example and a side view of an oil + ammonia burner on the B-B cross section in (c) of FIG. 11A, respectively. In the opposing combustion burner, ammonia (or oil only during startup) is injected from the center, and primary, secondary, and tertiary air passages as ammonia combustion air are provided around it.

In calculating the ammonia air ratio in the counter combustion burner unit, only the air supplied to the ammonia burner as 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 schematically shows the state within the furnace in the case of ammonia co-firing. Upstream of the combustion completion area, which is the space within the furnace that supplies additional air (additional air), a reducing denitrification atmosphere with insufficient air (air ratio of 1 or less) is formed due to combustion of pulverized coal, so an ammonia burner is used to reduce the air ratio to 1 or less. By adding ammonia, ammonia can be introduced into a reducing atmosphere at a high temperature (usually above 1400°C) created by a coal burner, and thermal decomposition and reduction of ammonia can be generated through counter combustion.

In Figure 12, the ammonia burner is put into the high-temperature reducing atmosphere formed by coal at an ammonia burner air ratio of 0.8 or less, so the reducing atmosphere of the coal is not damaged, and it can be mixed with the high-temperature coal flame to cause thermal decomposition and reduction. By individually controlling the air ratio of each independent burner, the amount of NOx generated can be controlled to avoid interference with each other.

(Example)

5A to 5C, the relationship between the ammonia burner air ratio and NOx emissions when co-firing coal and ammonia is explained by combustion tests. FIGS. 5A and 5B are graphs showing the relationship between the burner unit air ratio and NOx emissions when the ammonia co-firing ratio is a predetermined value (in FIG. 5B, the relationship for each burner type is shown).

In this combustion test, it was conducted in a horizontal cylindrical combustion furnace, and the co-combustion rate of ammonia and pulverized coal was 25% in terms of calorific value. The coal burner and the ammonia burner were installed in separate vertical arrangements, with the coal burner at the top and the ammonia burner at the bottom, and auxiliary air nozzles at the top and bottom of each burner. For the ammonia burner, three burners were used: a spad burner, which is a premixing type burner, and a diffuser type and swirler type, which are diffusion type burners with different structures.

In addition, the furnace outlet oxygen concentration in this test was set to about 4%, and NOx was compared by converting the NOx concentration to 6% according to the following (Equation 9) to correct for the difference in furnace outlet oxygen concentration.

NOx (6% converted value) = NOx actual measured value × (21% - 6%) ÷ (21% - actual measured furnace outlet oxygen concentration) … (Equation 9)

First, the relationship between the air ratio and NOx emissions of the ammonia burner when the ammonia burner is a spade type and the co-fueling ratio is 33% is examined. FIG. 5C is a graph showing the relationship between the burner unit air ratio and NOx emissions when the ammonia co-firing ratio is changed. As shown in Figure 5c, NOx decreases the most when the ammonia burner air ratio is 0.6, and NOx increases even if the air ratio is higher or lower than this. If the ammonia burner air ratio is 0.8, it is about 1.5 times the NOx value of 0.6. Generally, the NOx value in the case of coal combustion 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 combustion. Additionally, the higher the ammonia burner air ratio, the greater the increase in NOx. The ammonia burner air ratio was zero, that is, even if only ammonia was injected from the ammonia burner, NOx increased, but co-burning with coal was possible. If the ammonia burner air ratio is lowered than 0.6, NOx increases, so if NOx does not decrease even if lowered to 0.6, unburned ammonia reaches the oxidation zone (combustion completion zone) downstream of the additional air inlet and is converted to NOx. There is a possibility. Therefore, while maintaining the ammonia burner air ratio at 0.6, the additional air input rate is reduced to increase the coal burner air ratio, and by reducing the amount of unburned ammonia reaching the downstream of the additional air input section, the amount of unburned ammonia generated at the combustion completion zone is reduced. There is a need to reduce NOx.

When the ammonia co-firing ratio is reduced to 25%, 22%, and 11% with a spad type burner, the lowest point of NOx generation due to the air ratio of the ammonia burner has not been confirmed, but the air ratio at which NOx is minimum tends to be lower. There is a tendency. Additionally, the NOx value tends to increase when the ammonia co-firing ratio is lowered to 25% or less. This is believed to be because the auxiliary air of the adjacent coal burner is increasing, and some of it is mixed into the ammonia burner, thereby substantially increasing the air ratio of the ammonia burner. In this case, the NOx value can be controlled by lowering the air ratio of the ammonia burner from 0.6.

In this way, even when the ammonia co-firing ratio is changed from 11% to 33%, the NOx value can be suppressed by appropriately controlling the air ratio of the ammonia burner, and the primary air ratio of the coal burner (the theoretical air ratio of coal) can be suppressed. This shows that even if the ratio of primary air volume increases due to an increase in the mixed combustion ratio, the NOx value can be controlled below a certain value by individually controlling the air ratio of the coal burner and ammonia burner.

Next, as shown in FIG. 5B, in the case of a diffusion type burner with a diffuser type and a swirler type flame holder, the diffuser type tends to have a lower NOx generation amount than the swirler type. In the diffuser type, a disk-shaped diffuser is installed at the tip of the burner, and air flows into it to insulate the flame, so the ignition point is immediately near the burner. On the other hand, in the swirler type, a swirler generates a swirling flow centered on the burner and the flame is maintained by the circulating flow, so an ignition point is formed on the downstream side of the burner tip.

Since the reducing atmosphere formed in an ammonia burner is between the ignition point and the additional air input point, it is thought that the closer the ignition point is to the tip of the burner, the longer the distance of the reducing atmosphere is, the longer the residence time of the reducing atmosphere is, and the more NOx reduction progresses. do.

Even for diffusion type burners, the air ratio of the ammonia burner that minimizes NOx is not calculated, but it tends to be lower than that of the spad type, so it can be said that it can be controlled with the ammonia burner air ratio that reduces NOx the most for each burner type. You can.

Although embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and also includes forms in which modifications are made to the above-described embodiments and forms in which these forms are appropriately combined.

In this specification, expressions expressing relative or absolute arrangement such as “in a certain direction,” “along a certain direction,” “parallel,” “orthogonal,” “center,” “concentric,” or “coaxial,” strictly mean Not only does it indicate such an arrangement, but it also indicates a state of relative displacement with a tolerance or an angle or distance that allows the same function to be obtained.

For example, expressions that indicate that things are in an equal state, such as “same,” “equivalent,” and “homogeneous,” not only indicate a strictly equal state, but there is also a difference in tolerance or the degree to which the same function is obtained. It should also indicate the existing state.

In addition, in this specification, expressions representing shapes such as a square shape or a cylindrical shape not only represent shapes such as a square shape or a cylindrical shape in a geometrically strict sense, but also represent irregularities or chamfers to the extent that the same effect is obtained. The shape including the base, etc. shall also be shown.

In addition, in this specification, the expressions “to include,” “include,” or “to have” one component are not exclusive expressions that exclude the presence of other components.

<Other>

The content described in the several embodiments described above can be understood as follows, for example.

1) The boiler 2 according to at least one embodiment of the present disclosure,

A furnace (2) including a furnace wall (19),

An ammonia burner (50) provided on the furnace wall (19) and burning ammonia fuel,

Pulverized coal burners (302, 304) are provided in a different position from the ammonia burner (50) on the furnace wall (19) and burn pulverized coal.

Includes.

2) In some embodiments, it is the boiler 2 described in 1) above,

Provided with a control device (5) for controlling the supply amounts of the ammonia fuel, the pulverized coal, and the combustion air,

The control device 5 is,

A first calculation unit for calculating an ammonia air ratio, which is the ratio of the amount of ammonia combustion air supplied to the ammonia fuel to the theoretical air amount required to burn the ammonia fuel;

A second calculation unit for calculating the pulverized coal air ratio, which is the ratio of the amount of air for combustion of pulverized coal supplied to the pulverized coal, with respect to the theoretical air amount required to combust the pulverized coal,

A control unit that controls the supply amount so that the ammonia air ratio satisfies the first standard range and the pulverized coal air ratio satisfies the second standard range.

has

3) In some embodiments, it is the boiler 2 described in 2) above,

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 standard range.

4) In some embodiments, it is the boiler 2 described in 2) or 3) above,

An air nozzle 303 is provided on the furnace wall 19 to be adjacent to the ammonia burner 50,

The first calculation unit calculates the ammonia-air ratio using the amount of ammonia combustion air that includes the amount of air supplied to the ammonia fuel among the amount of air injected from the air nozzle 303.

5) In some embodiments, it is the boiler 2 according to any 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, it is the boiler 2 according to any of 2) to 5) above,

The first reference range is 0.8 or less.

7) In some embodiments, it is the boiler 2 according to any of 2) to 5) above,

The first reference range is 0.7 or less.

8) In some embodiments, it is the boiler 2 according to any 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, it is the boiler 2 according to any of 1) to 8) above,

An auxiliary air nozzle (303) is adjacent to the ammonia burner (50) and supplies auxiliary air,

The auxiliary air nozzle 303 is provided with a damper that can adjust the amount of auxiliary air that can be supplied in the direction of the ammonia burner 50.

10) In some embodiments, it is the boiler 2 according to any of 1) to 9) above,

The ammonia burner 50,

Ammonia nozzles (142, 152) for spraying the ammonia fuel,

Starting fuel nozzle that injects starting fuel (ammonia nozzle (306A))

Includes.

11) In some embodiments, the boiler 2 according to any of 1) to 10) above,

The ammonia burner 50 is provided adjacent to the pulverized coal burners 302 and 304.

12) In some embodiments, it is the boiler 2 described in 8) above,

The furnace wall (19) is,

A burner arrangement area where the ammonia burner 50 and the pulverized coal burners 302 and 304 are provided,

It includes an additional air supply area provided with an additional air supply unit that supplies additional air downstream from the burner arrangement area,

The ammonia burner 50 is located at the top of the burner placement area.

13) In some embodiments, the boiler 2 according to any of 1) to 12) above,

The ammonia burner 50 is a diffusion type burner or a partial premixing type burner.

14) In some embodiments, it is the boiler 2 described in 13) above,

The diffusion type burner or the partial premixing type burner is a partial premixing type burner, a spad type, a diffusion type with a different flame sintering type, or a diffuser type burner.

15) A boiler control method according to at least one embodiment of the present disclosure,

A furnace (2) including a furnace wall (19),

An ammonia burner (50) provided on the furnace wall (19) and burning ammonia fuel,

Pulverized coal burners (302, 304) are provided in a different position from the ammonia burner (50) on the furnace wall (19) and burn pulverized coal.

A boiler control method for controlling the supply amounts of the ammonia fuel, the pulverized coal, and the combustion air in a boiler including,

A first calculation step (S10-1) of calculating the ammonia air ratio, which is the ratio of the amount of ammonia combustion air supplied to the ammonia fuel with respect to the theoretical air amount required to burn the ammonia fuel,

A second calculation step (S10-2) of calculating the pulverized coal air ratio, which is the ratio of the amount of air for combustion of pulverized coal supplied to the pulverized coal, with respect to the theoretical air amount required to combust the pulverized coal;

A control step (S10-3) for controlling the supply amount so that the ammonia air ratio satisfies the first standard range and the pulverized coal air ratio satisfies the second standard range.

has

16) A boiler modification method according to at least one embodiment of the present disclosure,

A furnace (2) including a furnace wall (19),

Pulverized coal burners (302, 304) provided on the furnace wall (19) and burning pulverized coal,

A plurality of injection units provided at a different position from the pulverized coal burners (302, 304) on the furnace wall (19) and spraying pulverized coal, starting fuel, or auxiliary air,

Control unit(5)

This is a boiler modification method for a boiler equipped with,

Provided with a substitution step for 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 for calculating an ammonia air ratio, which is the ratio of the amount of ammonia combustion air supplied to the ammonia fuel to the theoretical air amount required to burn the ammonia fuel;

A second calculation unit for calculating the pulverized coal air ratio, which is the ratio of the amount of air for combustion of pulverized coal supplied to the pulverized coal, with respect to the theoretical air amount required to combust the pulverized coal,

A control unit that controls the supply amount so that the ammonia air ratio satisfies the first standard range and the pulverized coal air ratio satisfies the second standard range.

has

2: Boiler
4: Additional air supply
5: Control unit
8: Rear flue
9: Measurement system
11: Nose
12: Brazier
15: Supply system
19: Furnace wall
20: Brazier
21: Burner placement area
22: Additional air supply area
30: Burner unit
31: first burner unit
32: second burner unit
33: third burner unit
37: Fuel burner for starting
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 adjustment valve
78: diverter valve
80: Oil supply system
81: Oil supply device
82: Oil supply line
84: Oil flow meter
86: Oil flow adjustment valve
88: diverter 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: Diverter 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 Sang
132: Ammonia supply nozzle
133: outer cylinder
141: Wind Sang
142: Ammonia supply nozzle
143: Heat insulator (diffuser)
151: Wind Sang
152: Ammonia nozzle
153: Heater (Swiller)
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 having an oil burner for starting
1102: Coal burner having an oil burner for starting
1103: Coal burner
1104: Coal burner
1105: Coal burner having an oil burner for starting
1106: Coal burner
1107: Ammonia burner
1108: Ammonia burner
1109: Ammonia burner
1120: Starting oil burner/ammonia dual burner
1121: Starting oil burner/ammonia dual burner
1123: Starting oil burner/ammonia dual burner

Claims (16)

A furnace including a furnace wall,
An ammonia burner provided on the furnace wall and burning ammonia fuel,
A pulverized coal burner provided in a different position from the ammonia burner on the furnace wall and burning pulverized coal.
Boiler containing. According to paragraph 1,
Provided with a control device for controlling the supply amounts of the ammonia fuel, the pulverized coal, and the combustion air,
The control device is,
A first calculation unit for 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 unit for calculating the pulverized coal air ratio, which is the ratio of the amount of air for combustion of pulverized coal supplied to the pulverized coal, with respect to the theoretical air amount required to combust the pulverized coal,
A control unit that controls the supply amount so that the ammonia air ratio satisfies the first standard range and the pulverized coal air ratio satisfies the second standard range.
A boiler characterized by having a. According to paragraph 2,
The first calculation unit calculates the ammonia-air ratio for each of the plurality of ammonia burners,
The control unit is a boiler characterized in that it controls the supply amount so that each ammonia air ratio satisfies the first standard range. According to paragraph 2 or 3,
An air nozzle is provided on the furnace wall adjacent to the ammonia burner,
The first calculation unit is a boiler characterized in that the ammonia air ratio is calculated using the amount of ammonia combustion air that includes the amount of air supplied to the ammonia fuel among the amount of air injected from the air nozzle. According to paragraph 2 or 3,
A boiler, characterized in that the upper limit of the first reference range is lower than the upper limit of the second reference range. According to paragraph 2 or 3,
A boiler, characterized in that the first reference range is 0.8 or less. According to paragraph 2 or 3,
A boiler, characterized in that the first reference range is 0.7 or less. According to paragraph 2 or 3,
A boiler, characterized in that the first reference range is set based on the value of nitrogen oxides in combustion gas discharged from the furnace. According to any one of claims 1 to 3,
An auxiliary air nozzle is adjacent to the ammonia burner and supplies auxiliary air,
The auxiliary air nozzle is provided with a damper that can adjust the amount of auxiliary air that can be supplied in the direction of the ammonia burner.
A boiler characterized by: According to any one of claims 1 to 3,
The ammonia burner,
An ammonia nozzle for spraying the ammonia fuel,
Starting fuel nozzle that injects starting fuel
A boiler comprising: According to any one of claims 1 to 3,
A boiler, characterized in that the ammonia burner is provided adjacent to the pulverized coal burner. According to clause 8,
The furnace wall is,
A burner arrangement area where the ammonia burner and the pulverized coal burner are provided,
It includes an additional air supply area provided with an additional air supply unit that supplies additional air downstream from the burner arrangement area,
The ammonia burner is located at the top of the burner placement area.
A boiler characterized by: According to any one of claims 1 to 3,
A boiler, characterized in that the ammonia burner is a diffusion type burner or a partial premixing type burner. According to clause 13,
The boiler is characterized in that the diffusion type burner or the partial premixing type burner is a spad type of the partial premixing type, a swirler type with a different structure of the flame stabilization type as a diffusion type, or a diffuser type burner. A furnace including a furnace wall,
An ammonia burner provided on the furnace wall and burning ammonia fuel,
A pulverized coal burner provided in a different position from the ammonia burner on the furnace wall and burning pulverized coal.
A boiler control method for controlling the supply amounts of the ammonia fuel, the pulverized coal, and the combustion air in a boiler including,
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 air amount required to burn the ammonia fuel;
A second calculation step of calculating the pulverized coal air ratio, which is the ratio of the amount of air for combustion of pulverized coal supplied to the pulverized coal, with respect to the theoretical air amount required to combust the pulverized coal;
A control step for 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.
A boiler control method characterized by having a. A furnace including a furnace wall,
A pulverized coal burner provided on the furnace wall and burning pulverized coal,
In the furnace wall, the pulverized coal burners are provided at different positions and include a plurality of injection units that inject pulverized coal, starting fuel, or auxiliary air,
controller
This is a boiler modification method for a boiler equipped with,
Provided with a substitution step for 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 for calculating an ammonia air ratio, which is the ratio of the amount of ammonia combustion air supplied to the ammonia fuel to the theoretical air amount required to burn the ammonia fuel;
A second calculation unit for calculating the pulverized coal air ratio, which is the ratio of the amount of air for combustion of pulverized coal supplied to the pulverized coal, with respect to the theoretical air amount required to combust the pulverized coal,
A control unit that controls the supply amount so that the ammonia air ratio satisfies the first standard range and the pulverized coal air ratio satisfies the second standard range.
Boiler modification method with.

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