TW202328593A - 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 combusts ammonia and pulverized coal, a boiler control method, and a boiler reconstruction method. This case 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. quoted here.

Conventionally, there are known boilers that supply ammonia as fuel into the furnace. When ammonia is used as fuel, it is necessary to suppress the emission of nitrogen oxides (NOx). For example, in the burner (shown in FIG. 2 ) disclosed in Patent Document 1, the nozzle for injecting ammonia is provided with a nozzle that revolves around and supplies ammonia (it may not be revolved in the description), so that ammonia is mixed with the swirling pulverized coal. Flame. In addition, it is disclosed as follows. That is, the combustion device 4A installed in a furnace and capable of combusting ammonia as a fuel includes: an inner tube nozzle 41 arranged at the center as viewed from the fuel injection direction and injecting ammonia; and an outer tube nozzle 42 from which As viewed in the injection direction of the fuel, it is arranged to surround the inner cylinder nozzle 41 from the outside in the radial direction, and ammonia is injected around the inner cylinder nozzle 41 . Furthermore, a swirl 45 is provided, which is disposed inside the outer cylinder nozzle 42 and swirls 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 reducing region with a high ammonia concentration and a low oxygen concentration in the center of the flame when viewed from the fuel injection direction. On the other hand, the nitrogen oxides generated by the combustion of ammonia mixed with oxygen injected from the nozzle of the outer cylinder to the periphery of the nozzle of the inner cylinder flow back from the outer edge of the flame toward the center and are supplied to the reducing area along the circulation flow. As a result, the nitrogen oxides generated at the outer edge of the flame are reduced to nitrogen (N2) in the reduction region formed by the ammonia injected from the nozzle of the inner tube. Therefore, according to Patent Document 1, an increase in nitrogen oxides can be suppressed in a boiler capable of burning ammonia as a fuel. [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2020-41748

[Problem to be solved by the invention]

From the point of view of the inventors, in order to suppress the emission of nitrogen oxides, the ammonia fuel burner uses other fuels to make the combustion environment in the boiler a reducing area, and it is better to correctly control the air ratio near the ignition point. . However, Patent Document 1 does not specifically disclose such a configuration. Furthermore, when ammonia is co-combusted with the burner shown in Patent Document 1, if the co-combustion (co-combustion) rate of ammonia is increased, the air ratio of the coal nozzle increases. In the coal nozzle, in order to prevent the coal in the nozzle from settling, it is necessary to maintain a certain amount of conveying air. If the ammonia co-firing rate is increased, the amount of carbon supplied will decrease, so the amount of conveying air relative to the coal flow will increase. Therefore, when the ammonia mixing rate is high, the air ratio around the ammonia nozzle becomes high, and a rapid increase of nitrogen oxides due to ammonia oxidation occurs.

Therefore, an object of the present invention is to provide a boiler, a boiler control method, and a boiler retrofit method capable of burning ammonia fuel under conditions that suppress the generation of nitrogen oxides. [Technical means to solve the problem]

The burner arrangement of the boiler according to at least one embodiment of the present invention is such that 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 installed on the furnace wall to burn ammonia fuel, and a burner different from the ammonia burner installed on the furnace wall. The position and the pulverized coal burner that makes the pulverized coal burn.

The boiler is provided with a control device for controlling the supply of the ammonia fuel, the pulverized coal, and the air for combustion. The ammonia-to-air ratio is the ratio of the theoretical amount of air necessary for the combustion of the above-mentioned ammonia fuel; the second calculation unit calculates the amount of air used for combustion of the pulverized coal supplied to the pulverized coal to the amount necessary for the combustion of the pulverized coal. The ratio of the theoretical air amount is the pulverized coal air ratio; and the control unit controls 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 first calculation unit calculates the ammonia-air ratio for each of the plurality of ammonia burners, The control unit controls the supply amount so that each of the ammonia-air ratios satisfies the first reference range.

The furnace wall is equipped with an air nozzle adjacent to the ammonia burner, The first calculating unit calculates the ammonia air ratio using the ammonia combustion air amount including the air amount supplied to the ammonia fuel among the air amount 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 aforementioned first reference range is 0.8 or less.

The aforementioned first reference range is 0.7 or less.

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

The boiler has an auxiliary air nozzle adjacent to the ammonia burner for supplying 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.

The aforementioned ammonia burner, comprising: Ammonia nozzles injecting the aforementioned ammonia fuel, A fuel nozzle for priming that injects fuel for priming.

The ammonia burner is provided adjacent to the pulverized coal burner.

The ammonia burner is provided adjacent to the pulverized coal burner.

The aforementioned furnace wall includes: a burner arrangement area, which is provided with the aforementioned ammonia burner and the aforementioned pulverized coal burner; and an additional air supply area, which is provided with an additional air supply area downstream of the aforementioned burner arrangement area. The additional air supply unit for air, the ammonia burner, is located at the uppermost stage of the burner arrangement area.

The aforementioned ammonia burner is a diffusion burner or a partial premix burner.

The aforementioned diffusion burner or the aforementioned partial premixing burner is any of a partial premixing joint type, a diffusion type and a swirler type or a diffuser type in which the structure of the flame retainer is different.

A boiler control method according to at least one embodiment of the present invention is to control the supply of ammonia fuel, pulverized coal, and combustion air in a boiler, the boiler comprising: a furnace having a furnace wall; A combustion ammonia burner, a pulverized coal burner installed at a position different from the ammonia burner on the furnace wall and burning the pulverized coal, is characterized in that it has: a first calculation step, which calculates the The ratio of the amount of air used for ammonia combustion supplied by the ammonia fuel to the theoretical air amount necessary for the combustion of the aforementioned ammonia fuel is the ammonia-to-air ratio; the second calculation step is to calculate the amount of air used for the combustion of pulverized coal supplied to the aforementioned pulverized coal For the ratio of the theoretical air amount necessary for the combustion of the aforementioned pulverized coal, that is, the pulverized coal air ratio; and a control step, which controls the aforementioned supply amount so that the aforementioned ammonia air ratio satisfies the first reference range and the aforementioned pulverized coal air ratio satisfies Second base range.

According to at least one embodiment of the present invention, the boiler reconstruction method includes: a furnace including a furnace wall, a pulverized coal burner installed on the furnace wall to burn pulverized coal, A plurality of injection units for injecting pulverized coal or start-up fuel or auxiliary air at different positions of the burner, and a control device, the boiler reconstruction method includes replacing at least one of the aforementioned plurality of injection units with an ammonia injection unit for burning ammonia fuel. In the step of replacing the burner, the aforementioned control device for controlling the supply amount of the aforementioned ammonia fuel, the aforementioned pulverized coal, and the air for combustion includes: a first calculation unit that calculates the ratio of the amount of air for ammonia combustion supplied to the aforementioned ammonia fuel to the The ammonia-to-air ratio is the ratio of the theoretical amount of air necessary to combust the above-mentioned ammonia fuel; the second calculation unit calculates the amount of air used for combustion of the pulverized coal supplied to the pulverized coal according to the theory necessary to combust the pulverized coal. The air amount ratio is a pulverized coal air ratio; and a control unit that controls the supply amount so that the ammonia air ratio satisfies a first reference range and the pulverized coal air ratio satisfies a second reference range. [Effect of Invention]

According to the present invention, it is possible to provide a boiler, a boiler control method, and a boiler retrofit method capable of burning ammonia fuel under the condition that the generation of NOx can be suppressed.

Hereinafter, several embodiments of the present invention will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples.

Fig. 1 is a conceptual diagram of a boiler operating system 1 according to an embodiment. The boiler operation system 1 includes, for example, a boiler 2 incorporated in a thermal power plant not shown in the figure, a supply system 15 for supplying air and fuel to the boiler 2 , and a measurement system 9 for measuring parameters related to the operation of the boiler 2 . The fuel supplied to the boiler 2 from the supply system 15 contains ammonia fuel. The ammonia fuel may be either liquid ammonia or ammonia gas. Hereinafter, an embodiment in which the ammonia fuel is liquid ammonia will be described. In one embodiment, liquid ammonia is supplied to the boiler 2 in a liquid state. Although liquid ammonia does not contain gas such as hydrogen, it may contain impurities (for example, urea) to such an extent that it does not affect the combustion of the boiler 2 . The liquid ammonia is gasified into ammonia gas in the boiler 2 . In addition, the fuel supplied from the supply system 15 to the boiler 2 includes fuel other than ammonia fuel. For example, in the boiler 2, mixed combustion of ammonia and other fuels (co-combustion) or exclusive combustion of ammonia (dedicated combustion) is performed after combustion using other fuels is performed. An example of fuel other than ammonia, that is, carbon-containing fuel, is biomass fuel, fossil fuel, or the like. Fossil fuels are oils such as liquefied natural gas, heavy oil or light oil, or coal such as pulverized coal. Hereinafter, an embodiment in which the carbonaceous fuel is oil and pulverized coal will be exemplified.

A boiler 2 according to one embodiment includes a furnace 20 including a furnace wall 19 . The furnace wall 19 includes a burner arrangement area 21 where at least one burner unit 30 is provided, and an additional air supply area 22 where an additional air supply unit 4 for supplying additional air (extra air) is provided. The additional air supply area 22 is located further downstream than the burner arrangement area 21 . The furnace 20 is a tubular hollow body for burning the fuel injected by the burner unit 30 by reacting with the combustion air, and may have various forms such as a cylindrical shape or a square column shape, for example. Moreover, the stove 20 of one embodiment includes the nose part 11 which protrudes toward the inside of the stove 20. As shown in FIG. The nose portion 11 is for making the gas (for example, combustion gas and unburned gas) generated in the combustion space 7 of the furnace 20 flow through the flow path on the downstream side of the furnace 20 appropriately. The flow path on the downstream side of the furnace 20 is the flue 8 as an example. At least one burner unit 30 burns fuel in the combustion space 7 of the furnace 20 . In the embodiment shown in FIG. 1 , the burner unit 30 is arranged in three stages along the flow direction of the gas generated in the combustion space 7 (arrow A in FIG. 1 ). Hereinafter, the burner units 30 of each stage may be referred to as the first burner unit 31, the second burner unit 32, and the third burner unit 33 in order from the downstream side of the gas flow direction. In some cases, these three-stage burners may be collectively referred to as the burner unit 30 . Also, the burner unit 30 may be divided into two stages, four stages, or the like and arranged. The boiler 2 of one embodiment is a rotary combustion boiler, and the burner units 30 provided in each stage are arranged in plural at equal intervals along the circumferential direction of the furnace 20 . The number of burner units 30 in each stage is four as an example, but only one burner unit 30 in each stage is shown in FIG. 1 . In addition, the number of burner units 30 in each stage may be three or five or more. The boiler 2 of another embodiment is a counter-fired boiler. In this case, at least one pair of burner units 30 in each stage is provided at positions facing each other.

Each burner unit 30 includes at least one burner. Furthermore, in at least one burner unit 30 , the burner is an ammonia burner 306 that injects liquid ammonia into the interior of the furnace 20 in a liquid state. The ammonia burner 306 may inject only liquid ammonia. Alternatively, the ammonia burner 306 may inject liquid ammonia together with (or instead of) the carbon-containing fuel after injecting the carbon-containing fuel. In one embodiment, the first burner unit 31 includes an ammonia burner 306 . The second burner unit 32 and the third burner unit 33 may or may not contain the ammonia burner 306 . In other embodiments, the ammonia burner 306 may include only the second burner unit 32 or the third burner unit 33 . In addition, any burner unit 30 includes coal burners 302, 304 for injecting pulverized coal as an example of carbonaceous fuel into the furnace 20 (the pulverized coal burners 302, 304 shown in FIG. 3A) It is also possible to include a starting fuel burner 307 (refer to FIG. 3A ) for injecting oil as an example of starting fuel into the furnace 20, and also include an auxiliary air nozzle (air nozzle) 301 for injecting auxiliary air. , 305 (refer to FIG. 3A ) are also available. Details will be described later.

In one embodiment, the supply system 15 supplies primary air and fuel to the burner unit 30 . The fuel supplied to the burner unit 30 (in this example, liquid ammonia and fuel containing carbon) can be switched. For example, liquid ammonia may be supplied to the burner unit 30 of any stage after supplying carbon-containing fuel (for example, oil).

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 in the furnace 20. The representative temperature in the furnace 20 is the temperature of the gas in the combustion space 7 of the furnace 20, that is, the temperature related to the gas temperature. 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 the nose temperature). The temperature of the nose is measured by the stove thermometer 6 . In addition, the representative temperature in the furnace 20 may be, for example, a gas temperature.

The boiler operation system 1 may be operated by an operator's operation, controlled by a control device 5 (see FIG. 9 ) described later, or a combination thereof. In the furnace 20 of one embodiment, the supply of the ammonia fuel is started after the combustion of other fuels (carbon-containing fuels in this example) other than the ammonia fuel, and mixed combustion of the ammonia fuel and other fuels may also be performed.

When burning nitrogen-containing fuels such as coal and ammonia, the air ratio at the time of combustion generally has a large influence on the generation of nitrogen oxides. Here, the mixed combustion of ammonia fuel and other fuels will be explained as follows: the case where the entire furnace is calculated as a single air ratio as a comparative example, and the respective air ratios of ammonia fuel and carbon-containing fuel as other fuels are calculated as an example. Case. (Comparative example) The air ratio of the comparative example is the ratio of the air supply amount to the furnace 20 to the theoretical air amount necessary to combust the ammonia fuel supplied to the furnace 20 with other fuels. The above air supply amount to the furnace 20 does not include additional air (extra air). That is to say, in this example, the air ratio constituting the ammonia co-firing condition (details will be described later) is the value obtained by multiplying the supply ratio of air other than additional air among all the air supplied to the furnace 20 by the total air ratio . Specifically, the air ratio constituting the ammonia co-combustion condition (hereinafter sometimes referred to as the burner unit air ratio) is defined by the following formula (1). In the formula (1), λ _b is the burner portion air ratio, λ is the total air ratio, and AA is the supply ratio of additional air to the total air supply amount to the boiler 2 . Also, the total air ratio (λ) is defined by Expression (2), Expression (3), and Expression (4). In formula (2) ~ formula (4), Q _Air is the total air supply. Also, 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 mixed combustion of ammonia (co-combustion ratio in terms of weight: X%). Q _x is the air flow rate for making the air ratio 1 during the mixed combustion. A _mf is the theoretical air volume of the fuel (ammonia fuel and carbon-containing fuel in this example) when the above-mentioned mixed combustion is in progress, A _car is the theoretical air volume of the carbon-containing fuel, A _NH3 is the theoretical air volume of the ammonia fuel. (Example) In the example, it is calculated according to the fuel: the ratio of the amount of air used for ammonia combustion supplied to the ammonia fuel to the theoretical air volume of the ammonia fuel supplied to the furnace 20, that is, the ammonia-to-air ratio, and the combustion air supplied to other fuels. The ratio of the amount of air used to the theoretical air amount of other fuels is also the air ratio of other fuels. The ammonia-air ratio (hereinafter also referred to as the ammonia burner air ratio) is obtained from equations (5) and (6). Here, λ _NH3 in the formula (5) is the ammonia-air ratio, Q _{Air_NH3} is the amount of air for ammonia combustion, and Q _{x_NH3} is the air flow rate for making the air ratio of ammonia fuel to 1. Also, Q _NH3 in the formula (6) is the supply amount of ammonia fuel, and A _NH3 is the theoretical air amount of ammonia fuel. In addition, when carbon-containing fuel is used as another fuel as an example, the air ratio of carbon-containing fuel is obtained by Equation (7) and 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 used for combustion of the carbon-containing fuel, and Q _{x_car} is the air flow rate for making the carbon-containing fuel air ratio 1. In addition, Q _car in the formula (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, the ammonia-air ratio λ _NH3 and the air ratio λ _car of carbon-containing fuels are individually calculated, thereby enabling individual adjustments. For example, in a boiler 2 (see FIG. 3B ) using an ammonia burner 306 and a pulverized coal burner 302, formulas (5) and (6) are applied to the air ratio of the ammonia burner 306, and for pulverized coal combustion The air ratio of device 302 is applicable to formulas (7), (8). In other words, in this case, the parameters of the carbon-containing fuel shown in formula (7) and formula (8) all become parameters of pulverized coal. Hereinafter, the air ratio refers to the one calculated in this embodiment.

In one embodiment, the coal burner 302 and the ammonia burner 306 are arranged separately as shown in Fig. 3A to Fig. 3C as an example of a convoluted combustion boiler (Fig. ). In this way, the air ratio can be individually adjusted, and even if the co-combustion rate of ammonia is increased, the air ratio of ammonia can be reduced regardless of the operation of the coal burner, and the rapid increase of NOx can be suppressed. Also, the coal burner 302 of this embodiment is configured to burn coal (coal powder). In the following description, the coal burner 302 may refer to the pulverized coal burner 302 .

In one embodiment, the upper limit of the burner portion air ratio is 0.8 or less. If the supply of ammonia fuel to the furnace 20 is started under the condition that the air ratio of the burner portion is 0.8 or less, the air ratio of the burner portion at the start of combustion of the ammonia fuel is also 0.8 or less. Thereby, the NOx generated in the furnace 20 is effectively reduced. The upper limit of the burner portion air ratio may be 0.7 or less. In this case, the 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. Also, in a boiler 2 of a general scale used in a thermal power plant, it is not practical to have an air ratio in the burner portion of less than 0.6. Therefore, the burner portion air ratio constituting the ammonia co-combustion 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, and more preferably 0.6 or more and 0.7 or less. Also, when plural ammonia burners 306 are installed, it is preferable to calculate the ammonia-air ratio λ _NH3 for each ammonia burner 306 unit. As will be described later, since the ammonia-air ratio greatly changes the NOx generation amount, it is necessary to strictly calculate the ammonia-air ratio in units of burners, thereby controlling the supply of ammonia fuel and ammonia combustion air. Similarly, the coal burner 302 calculates the air ratio λ _car (coal-air ratio) of the carbon-containing fuel in units of each coal burner 302 to control the amount of NOx generation with high precision.

The control device 5 (refer to FIG. 9 ), which is a constituent element of the boiler 2 of one embodiment, is based on the amount of air supplied from the ammonia burner 306 (refer to FIG. 3B , FIG. 3C ), and the amount of air supplied from the ammonia burner 306 adjacent to the ammonia burner 306. Calculate the ammonia-to-air ratio based on the amount of air supplied by the auxiliary air nozzles 303, 305. The amount of air supplied from the auxiliary air nozzles 303, 305 is calculated as the amount of air used for ammonia combustion only by using the amount of air that contributes to the combustion of ammonia. For example, as shown in FIGS. 3B and 3C, the auxiliary air nozzle 303 is adjacent to the When the ammonia burner 306 and the coal burner 302 are sandwiched, half of the air volume is calculated as air for the ammonia burner. When the NOx generation amount is higher than the reference value, control is performed to lower the ammonia burner air ratio from, for example, 0.7 to 0.6. An example of the air ratio of the ammonia burner and the amount of NOx generated shown in FIG. 5A is shown. In this test result, the optimum point of the ammonia burner air ratio is 0.6. If the air ratio of the ammonia burner is lowered to lower than 0.6, NOx will increase. Therefore, even if the air ratio of the ammonia burner is lowered to 0.6, the amount of NOx generated cannot be reduced. This is the furnace where the unburned ammonia reaches approximately the same height as the additional air supply area 22 The inner space is the area where the combustion is completed, and it is converted into NOx. Therefore, the air ratio of the ammonia burner is kept at 0.6, the ratio of the amount of additional air (extra air) to the total amount of air injected into the boiler 2 is reduced, and the amount of unburned ammonia reaching the combustion-completed area is reduced, thereby reducing the amount of air in the combustion zone. NOx generated in the end area.

The ammonia burner 306 is installed instead of (modified) a part of the coal burner 304 as shown in FIGS. 3A to 3C . The pulverized coal injected from the coal burner 304 is adjacent to the ammonia burner 306 , and auxiliary air is supplied from the auxiliary air nozzle 303 provided with the starting fuel burner 307 . The auxiliary air nozzle 303 provided with the start-up fuel burner 307 is equipped with a damper, which can adjust the amount of auxiliary air that can be supplied to the direction of the ammonia burner 306 (the auxiliary air that can be supplied to the ammonia fuel injected in the stove 12). amount of air). In the case where the air nozzle (auxiliary air nozzle) 303 for supplying auxiliary air is sandwiched between the coal burner 302 and the ammonia burner 306, if the amount of air supplied from the nozzle is adjusted to be most suitable for the coal burner 302 The amount of air would be too much for the amount of air used to reduce the nitrogen oxides of the ammonia burner 306. Conversely, if the air volume is adjusted to reduce the NOx of the ammonia burner, the air volume for the optimum air ratio of the coal burner 302 will be insufficient, resulting in an increase in unburned components in the ash. At this point, in this embodiment, the auxiliary air nozzle 303 surrounded by the coal burner 302 and the ammonia burner 306 is divided into flow paths 303A and 303B up and down along with the transformation of the boiler 2, and can be used The respective flow rates are controlled by dampers (see FIG. 3C and FIG. 4 ). Thereby, the amount of air directed toward 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 air ratio of the coal burner is about 0.7~0.9. The air flow rates from the flow paths 303A and 303B of the auxiliary air nozzle 303 can be adjusted individually, thereby suppressing the increase of unburned components in the ash of the coal burner and suppressing the increase of NOx in the ammonia burner. Furthermore, the coal burner 304 is transformed into an ammonia burner 306, whereby the existing boiler 2 dedicated for burning coal can be changed into a boiler 2 burning ammonia fuel. Also, as shown in FIG. 3 , the ammonia burner 306 is arranged adjacent to the coal burner 302 , so that the heat of coal combustion can be used for ammonia combustion, and the ammonia can be stably combusted. Also, the NOx generation amount contained in the combustion gas discharged from the boiler 2 is calculated based on the ammonia supply amount supplied to the ammonia burner 306 and the combustion air supply amount, and the first reference range may be set according to the calculation result. Alternatively, the first reference range may be set based on the measurement results of the NOx concentration measurement device installed in the boiler 2 .

The boiler 2 of at least one embodiment of the present invention, as shown in FIGS. 6A to 6C , has a start-up fuel burner 307 for burning start-up fuel, and the ammonia burner 306 can burn start-up fuel. A part of the device 307 is replaced (modified) to be installed. The ammonia burner 306 includes an ammonia nozzle 306A for injecting ammonia. The ammonia nozzle 306A also functions as a start-up fuel nozzle that injects start-up fuel (specifically, oil as an example). When the boiler 2 is started, the ammonia nozzle 306A injects start-up fuel, and thereafter, ammonia is injected in response to satisfying the ammonia co-firing condition. In another embodiment, the start-up fuel nozzle is configured differently from the ammonia nozzle 306A, and may be installed in the same section as the ammonia nozzle 306A. In the case of changing the start-up fuel burner 307 to the ammonia burner 306, the air nozzle 303 on one side adjacent to the coal burner 302, 304 will disappear, and the auxiliary power to the coal burner 302 cannot be sufficiently ensured. air volume. Therefore, for the auxiliary air nozzles 301, 305 on the side opposite to the ammonia burner 306, the air volumes from these sides are respectively increased, whereby the air ratio of the coal burners 302, 304 becomes an appropriate value of 0.7~0.9 . In this embodiment, only the air supplied from the ammonia burner 306 is used for the calculation of the ammonia-air ratio. By optimizing the air ratio of the coal burners 302, 304, the increase of unburned components in the ash of the coal burners 302, 304 can be suppressed.

The boiler 2 according to at least one embodiment of the present invention, as shown in Fig. 7A and Fig. 7B, has a plurality of auxiliary air nozzles 301, 305 for supplying auxiliary air, and the ammonia burner 306 is the auxiliary air nozzle 301, 305 Part of is replaced to set. In the example of FIG. 7B , an ammonia burner 306 is provided instead of the auxiliary air nozzle 305 . Similar to the modification of the start-up fuel burner 307, the auxiliary air nozzle 305 on one side of the coal burner 304 disappears, and thus the air volume of the coal burner 304 becomes insufficient. In addition, when the section height of the auxiliary air nozzle 305 is low, it is difficult to install the ammonia burner 306 having an inflammator. The nozzle provided with the start-up fuel burner 307 on the side opposite to the ammonia burner 306 adjacent to the coal burner 304 is used as the auxiliary air nozzle 303 to increase the amount of air to adjust to a predetermined air volume. quantity. At this time, as shown in Figure 7B, in the coal burner 304, the auxiliary air nozzle 303 will become one side, but the coal burner 302 on the upper side has auxiliary air nozzles 301, 303 up and down, so that the starting The air flow path of the oil burner is divided into flow paths 303A and 303B up and down, and the air volume can be increased only in the lower flow path 303B, and the respective flow rates can be controlled at the damper, so that the air ratios of the coal burner 304 can be optimized respectively. Optimization, whereby the increase of unburned components in the ash can be suppressed. In the boiler 2 before modification, if the height of the air box where the auxiliary air nozzle 305 is installed is lower than the height of the coal burner 302 or the start-up fuel burner 307, the air box is installed without a flame protector. Lower height ammonia burner 306. For example, the pre-mixing type joint nozzle of Fig. 13 is used.

In the boiler 2 of at least one embodiment of the present invention, as shown in FIGS. 8A and 8B , the auxiliary air nozzle 301 arranged at the uppermost stage of the burner arrangement area 21 is replaced (modified) to provide ammonia injection. device 306. The ammonia burner 306 is provided adjacent to the coal burner 302 . Similar to 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 will disappear, and thus the air volume of the coal burner 302 will be insufficient. Also, when the section height of the auxiliary air nozzle 301 is low, it is difficult to install the ammonia burner 306 having an inflammator. The air flow path of the start-up fuel burner 307 is divided into flow paths 303A and 303B up and down, and the flow paths 303A and 303B can be individually controlled, and if the height of the air box is low, the wind box is installed without an inflame protector. Ammonia nozzles with low tank heights are also partial premix nozzles (see Figure 13). In this case, ammonia is utilized not only as a fuel but also as a denitration agent.

The burner used in the foregoing embodiments is a diffusion burner or a partial premixed burner (also called a joint burner). In the diffusion combustion burner, a swirler type or a diffuser type can be used as a flame retainer. FIG. 13 shows an example of a structural diagram of a partial premixing joint 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 swirl burner. An example of a joint burner is shown in FIG. 13 . The joint 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 the air box 131 , and a damper for adjusting the flow rate is provided on the upstream side of the air box 131 . Ammonia is sprayed into the outer cylinder 133, mixed with combustion air flowing in from the gap between the nozzle 132 and the outer cylinder 133, and injected into the furnace. Ammonia spontaneously ignites when mixed into an air volume suitable for ignition by the high temperature gases in the furnace. Ammonia and air are partly premixed, so the ignition point is formed at the point where the blowing flow velocity of the entire nozzle and the combustion velocity of the premixed ammonia and air match. An example of a structural diagram of a diffuser burner is shown in FIG. 14 . Inside the bellows 141 , an ammonia nozzle 142 is provided, and a disk-shaped flame retainer 143 (also referred to as a diffuser) is provided at the front end 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 figure). Combustion air is supplied from the air box 141, and a damper for adjusting the flow rate is provided on the upstream side. The combustion air flows at an accelerated rate around the flame retainer 143, so a vortex is formed on the outer periphery of the flame retainer 143 of the disc. This vortex will entrain ammonia to mix with air and ignite, so the ignition point is formed on the flame protector 143 . FIG. 15 shows an example of a structural diagram of a swirl burner. Inside the wind box 151 , an ammonia nozzle 152 is provided and a flame retainer 153 (also referred to as a swirler) having spiral blades is provided at the front end 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 figure). Combustion air is supplied from the air box 151, and a damper for adjusting the flow rate is provided on the upstream side. When the combustion air passes through the flame protector 153 , it flows around the ammonia nozzle 152 as a swirling flow by swirling the blades. By virtue of the swirling flow, the circulating flow takes place inside the swirling flow so that the ammonia and the circulating flow will mix and ignite. Therefore, the ignition point of the ammonia flame is formed near the downstream side of the flame protector 153 .

Fig. 16 is a flow chart showing the boiler reconstruction method of the present invention. As explained using Fig. 3C, Fig. 6C, Fig. 7B, and Fig. 8B, the boiler 2 before transformation is provided with: a pulverized coal burner 302; Use fuel, or auxiliary air. Each injection unit is a coal burner 304 , a starting fuel burner 307 , or auxiliary air nozzles 301 and 303 . Then, S11 shown in FIG. 16 shows the process of replacing the injector with the ammonia burner 306 . By executing S11, for example, the existing boiler 2 for burning coal can be transformed into a boiler 2 for burning ammonia fuel.

One embodiment of the boiler control method (see FIG. 10B ) is to control the supply of ammonia fuel, pulverized coal and combustion air in the boiler 2. The boiler 2 includes: a furnace 20 containing a furnace wall 19; 19 and the ammonia burner 306 that burns the aforementioned ammonia fuel, and the pulverized coal burners 302 and 304 that are arranged at a position different from the aforementioned ammonia burner 306 on the aforementioned furnace wall 19 and burn the aforementioned pulverized coal, the control method , having: a first calculation step (S10-1), which calculates the ratio of the amount of air used for ammonia combustion supplied to the aforementioned ammonia fuel to the theoretical air amount necessary for burning the aforementioned ammonia fuel, that is, the ammonia-to-air ratio; Calculation step (S10-2), which calculates the ratio of the amount of air used for pulverized coal combustion supplied to the aforementioned pulverized coal to the theoretical air amount necessary for the combustion of the aforementioned pulverized coal, that is, the pulverized coal air ratio; and the control step (S10 -3) The supply amount is controlled so that the ammonia-air ratio satisfies a first reference range and the pulverized coal-air ratio satisfies a second reference range. The upper limit of the first reference range of the ammonia-to-air ratio is preferably set smaller than the upper limit of the second reference range of the pulverized coal-to-air ratio. The optimum value of the air ratio for minimizing NOx emissions is about 0.6 in the case of ammonia fuel, which is smaller than that in the case of pulverized coal (usually about 0.7~0.8). Referring to this optimum value, the upper limit value of the reference range is set, whereby the NOx emission amount can be easily minimized.

Fig. 9 is a specific structure of a boiler operating system 1 according to an embodiment. The boiler operation system 1 includes a control device 5 for controlling the operation of the boiler 2 in addition to the above-mentioned boiler 2 , supply system 15 , and measurement system 9 . The control device 5 of one embodiment includes a processor 91 , a ROM 92 , a RAM 93 , and a memory 94 . Processor 91 reads the boiler operation program stored in ROM92 and loads it into RAM93, and executes the command contained in the boiler operation program. The processor 91 is CPU, GPU, MPU, DSP, various calculation devices other than these, or a combination of these. The processor 91 may also be realized by integrated circuits such as PLD, ASIC, FPGA, and MCU. The memory 94 stores various data related to the execution of the boiler operation program. The memory 94 is, for example, a cache memory. The processor 91 is electrically connected to the supply system 15 and the measurement system 9 . The processor 91 of one embodiment is to generate the following instructions: make other fuels other than the ammonia fuel burn in the stove 20, the other fuel combustion instructions, the ammonia supply start instruction to make the supply system 15 start the supply of the ammonia fuel, and the ammonia fuel to start the ammonia supply. The special-purpose combustion of the ammonia that starts in the stove 20 starts the instruction of special-purpose combustion. In one embodiment, the 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 that the ammonia co-firing condition for starting the ammonia co-firing is satisfied based on the measurement result of the measurement system 9 . Furthermore, the processor 91 of one embodiment starts the ammonia dedicated combustion command when it is judged that the ammonia dedicated combustion condition for starting the ammonia dedicated combustion is satisfied. The ammonia-only combustion conditions include, for example, when the representative temperature in the furnace 20 reaches a predetermined temperature, when a predetermined time elapses from the start of ammonia co-firing, when the operator performs a predetermined input operation and reaches a predetermined set value, or the like. combinations etc.

The supply system 15 includes: a primary air supply system 110 for supplying primary air, an additional air supply system 120 for supplying additional air, an ammonia supply system 100 for supplying liquid ammonia, an oil supply system 80 for supplying oil, and an air supply system 120 for supplying coal. Pulverized coal supply system 70 for powder. The oil supply system 80 and the pulverized coal supply system 70 are each an example of a system for supplying carbonaceous fuel. Primary air, liquid ammonia, coal powder, and oil are supplied to the burner unit 30 , and additional air is supplied to the additional air supply unit 4 provided on the furnace wall 19 . The above-mentioned supply system 15 is controlled by the control device 5 .

The air supply lines 112 of the primary air supply system 110 are all connected to the burner unit 30 . The air supply line 112 is provided with a flow rate adjustment valve 116 for adjusting the flow rate of the primary air, and a switching valve 118 for switching the communication state of the air supply line 112 . 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 regulating valves 116 , 126 and switching valves 118 , 128 operate in response to control commands sent from the control device 5 .

The ammonia supply system 100 includes: the above-mentioned ammonia burner 306, an ammonia tank 101 storing liquid ammonia, an ammonia supply line 102 connecting the ammonia tank 101 and the ammonia burner 306, and a pump provided on the ammonia supply line 102. 103. The pressure regulating valve 105 for adjusting the pressure of the ammonia supply pipeline 102, the switching valve 107 that is arranged on the ammonia supply pipeline 102 and switches the communication state between the ammonia tank 101 and the ammonia burner 306, and adjusts the flow in the ammonia supply pipeline 102. A flow regulating valve 108 for the flow of liquid ammonia. The pressure regulating valve 105 , the switching valve 107 , and the flow regulating valve 108 operate in response to control instructions from the processor 91 . Accordingly, the ammonia supply system 100 can be changed between a supply stop state in which no liquid ammonia is supplied to any of the ammonia burners 306 and a supply state in which liquid ammonia is supplied to all the ammonia burners 306 . 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 .

An oil supply system 80 of one embodiment includes: an oil supply device 81, an oil supply line 82 connecting the oil supply device 81 to the ammonia burner 306, and an oil supply line 82 for adjusting the flow rate of oil flowing in the oil supply line 82. Flow adjustment valve 86 and switching valve 88 for switching the communication state of 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 regulating valve 86 , and the switching valve 88 operate in response to control commands from the control device 5 . Accordingly, the oil supply system 80 can be changed between a supply state in which oil is supplied to the ammonia burner 306 connected to the oil supply line 82 and a supply stop state in which the supply of oil is stopped. In another embodiment, the oil supply line 82 may be connected to the start-up fuel burner 37 for injecting oil. In addition, the oil supply line 82 may flow in the atomized steam. In this case, oil and atomized steam 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 for connecting the pulverized coal supply device 71 to the burner unit 30, A pulverized coal flow regulating valve 76 for adjusting the flow rate of pulverized coal flowing in the pulverized coal supply line 72 , and a switching valve 78 for switching the connection state of the pulverized coal supply line 72 . The pulverized coal supply line 72 of this example is connected to the first burner unit 31 , the second burner unit 32 , and the third burner unit 33 . The pulverized coal supply device 71 , the pulverized coal flow regulating valve 76 , and the switching valve 78 operate in response to control commands from the control device 5 . Accordingly, the pulverized coal supply system 70 can be changed between the supply stop state in which the pulverized coal supply is stopped and the supply state in which the pulverized coal is supplied to the burner unit 30 . The pulverized coal supply system 70 supplies pulverized coal to the above-mentioned pulverized coal burners 302 and 304 in the supply state.

The measurement system 9 includes: an air flowmeter 114 for measuring the flow rate of the primary air supplied by the primary air supply system 110, an air flowmeter for measuring the flow rate of the additional air supplied by the additional air supply system 120 124. The ammonia flow meter 109 used to measure the flow of ammonia fuel supplied by the ammonia supply system 100, the oil flow meter 84 used to measure the flow of oil supplied by the oil supply system 80, used to measure the A pulverized coal flow meter 74 for the flow of pulverized coal supplied by the pulverized coal supply system 70, and the above-mentioned furnace thermometer 6. The flow meters send the measurement results to the processor 91 .

Boiler operation system 1 is operated, for example, as a flowchart shown in FIG. 10A by a control command sent from processor 91 . First, another fuel combustion command is transmitted from the processor 91 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 the supply stop state, and the oil supply system 80 and the pulverized coal supply system 70 are also in the supply state. Then, 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 burner 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, since the ammonia co-firing condition is satisfied (S53: YES), the processor 91 transmits 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. Thereby, 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 a supply state. As a result, mixed combustion of ammonia and pulverized coal proceeds in the boiler 2 . Afterwards, since the ammonia burning condition is satisfied (S57: YES), the control device 5 transmits an ammonia burning command to the supply system 15 (S59). The pulverized coal supply system 70 changes to the supply stop state, and the burner operating as a coal burner stops. And, the ammonia supply system 100 increases the supply amount of liquid ammonia. As a result, exclusive combustion of ammonia takes place in the boiler 2 . Also, in other embodiments, the supply system 15 that receives other fuel combustion instructions from the processor 91 first supplies oil to the burner unit 30 before supplying oil and pulverized coal to the burner unit 30. . Also, after the ammonia supply start command is sent to the supply system 15, mixed combustion of ammonia fuel and oil may be performed, or mixed combustion of ammonia fuel, pulverized coal, and oil may be performed.

Fig. 10B is a flowchart showing NOx control processing in one embodiment. The NOx control process is a control method for suppressing the amount of NOx generated when ammonia fuel is combusted with other fuels (in this example, pulverized coal). In the NOx control process, first, the processor 91 reads the boiler load and the co-firing ratio of ammonia (more specifically, the co-firing ratio of ammonia and pulverized coal) (S61). Reading is performed by the processor 91 upon receiving a request command. The processor 91 executes a first calculation ( S10 - 1 ) of calculating the ratio of the amount of air for ammonia combustion supplied to the ammonia fuel to the amount of air necessary for combustion of the ammonia fuel, that is, the ammonia-to-air ratio. The calculation method of the ammonia-air ratio is the same as above. Next, the processor 91 executes a second calculation (S10-2) which calculates the ratio of the amount of air for pulverized coal combustion supplied to the pulverized coal to the theoretical air volume necessary to combust the pulverized coal, that is, the pulverized coal air ratio. The calculation method of the pulverized coal-air ratio (λ _car ), which is an example of the air ratio of carbon-containing fuel, is the same as above. Next, the processor 91 controls the respective supply amounts of ammonia fuel, pulverized coal, and combustion air (S10-3), so that the ammonia-to-air ratio calculated in S10-1 satisfies the first reference range, and makes the ratio calculated in S10-2 satisfy the first reference range. The pulverized coal air ratio meets the second reference range. As a more detailed example, the processor 91 individually controls the flow rate adjustment valve 108 for liquid ammonia, the flow rate control valve 76 for pulverized coal, and the flow rate control valve 116 for primary air. The processor 91 judges whether the co-firing of ammonia is finished (S63). During the execution of ammonia co-firing (S63: NO), the processor 91 repeatedly executes S10-1, S10-2, and S10-3 in sequence. When it is judged that the mixed combustion of ammonia is completed (S63: YES), the processor 91 ends the NOx control process.

Figure 10C shows the control logic for coal and ammonia air volume. The control device 5 multiplies the measured value of the pulverized coal flow meter 74 of the coal burner 302 (powdered coal burner 302) by the air ratio (indicating value) of the coal burner and the theoretical air volume of the coal to calculate the coal flow rate. Combustion air quantity (Q _{Air_car} ) of the burner 302 . The difference between the calculated combustion air volume of the coal burner 302 and the combustion air volume (measured value) of the coal burner 302 is taken out, and the combustion air volume control command value of the coal burner 302 is obtained by the control device 5 . Similarly, the ammonia burner air ratio and the ammonia theoretical air volume are multiplied by the measured value of the ammonia flowmeter 109 to calculate the combustion air volume (Q _{Air — NH3} ) of the ammonia burner 306 . The difference between the calculated combustion air amount of the ammonia burner 306 and the ammonia burner 306 combustion air amount (measured value) is obtained, and the control device 5 obtains the ammonia burner combustion air amount command value.

The arrangement of the ammonia burner in the case of the opposing combustion burner is shown in FIGS. 11A to 11E . Opposite combustion is to supply pulverized coal from a coal pulverizer to the burners installed in the horizontal direction on each wall, so in the case of ammonia co-firing, all the horizontally arranged burners are replaced with ammonia combustion device. FIG. 11A shows an example in which three burners in total are arranged on the front and rear walls, a total of six burners. The one-stage burner is composed of a plurality of burners arranged in the horizontal direction. (a) of FIG. 11A schematically shows the burner arrangement of the boiler 2 capable of coal-only combustion before transformation. One of the six-stage burners is used as a backup burner, so it is disabled during normal operation. Symbol 1104 at (a) indicates deactivation of the burner. Oil is used to heat the furnace during startup, so the coal burner sections 1101, 1102, and 1105 are coal burners equipped with oil burners. (b) and (c) of FIG. 11A show a modified example (burner arrangement example) for making the boiler 2 of (a) into a boiler 2 using ammonia fuel. (b) shows the case where the coal burners 1103 and 1106 and the deactivated burner 1104 are converted into an ammonia burner 1108 . In this case, the coal burners 1103 and 1106 are converted into ammonia-only combustion burners 1107 and 1109 . (c) shows an example in which burners 1101, 1102, and 1105 provided with coal burners and oil burners are converted into burners 1120, 1121, and 1123 for both ammonia and oil. The deactivated burner 1104 is operating as a coal burner 1104 at this time. Fig. 11B and Fig. 11D are the burner arrangement example and the side view of the ammonia burner respectively showing the A-A section of Fig. 11A (b). Fig. 11C and Fig. 11E are the burner arrangement example and the oil+ammonia burner side view respectively showing the B-B section of Fig. 11A (c). In the counter-combustion burner, ammonia (or oil used at start-up) is injected from the center, and flow paths for primary, secondary, and tertiary air for ammonia combustion are provided around it. When calculating the ammonia-to-air ratio of the unit of the opposing combustion burner, only the air supplied to the ammonia burner as air for ammonia combustion (the aforementioned primary to tertiary air) is considered. In the opposite combustion, there is no auxiliary air nozzle like the spiral combustion. FIG. 12 schematically shows the state in the furnace in the case of co-firing ammonia. In the upstream of the furnace space where the additional air (extra air) is supplied, that is, the area where the combustion is completed, there will be a denitration and reduction environment with insufficient air (air ratio below 1) due to the combustion of pulverized coal. Therefore, the ammonia burner The air ratio is lower than 1, so that the high temperature (usually above 1400°C) formed by the coal burner can be used to inject ammonia into the reducing environment, resulting in the thermal decomposition and reduction of ammonia, which can also be used in the opposite combustion. In Figure 12, the ammonia burner is used for the high-temperature reducing environment formed by coal. The ammonia burner is put into the air ratio below 0.8, so it will not damage the reducing environment of coal, and it can be mixed with high-temperature coal flames. Thermal decomposition and reduction occur. By individually controlling the air ratio of each independent burner, the amount of NOx generation can be controlled without mutual interference.

(Example) Referring to FIG. 5A to FIG. 5C , the result of specifying the relationship between the air ratio of the ammonia burner and the NOx emission amount through a combustion test when coal and ammonia are co-combusted will be described. 5A and 5B are graphs showing the relationship between the air ratio of the burner unit and the NOx emission amount when the mixed combustion ratio of ammonia is a predetermined value (in FIG. 5B, the relationship of each burner type is shown). This combustion test is carried out with a horizontal cylindrical combustion furnace, and the co-firing ratio of ammonia and pulverized coal is 25% in terms of heat conversion. The coal burner and the ammonia burner are installed separately in the vertical direction, the coal burner is installed on the upper part, the ammonia burner is installed on the lower part, and auxiliary air nozzles are installed above and below each burner. The ammonia burner uses three types of burners: a joint burner which is a premix type burner, a diffuser type burner, and a diffuser type and a swirl type burner in which the structure of the flame retainer is different. In addition, in this test, the oxygen concentration at the furnace outlet was set at approximately 4%, and NOx was converted to a concentration of 6% according to the following (Formula 9) for comparison in order to correct the difference in the oxygen concentration at the furnace outlet. NOx (6% conversion value) = NOx measured value × (21%-6%) ÷ (21%-actually measured furnace outlet oxygen concentration)・・・・・・(Formula 9)

First, the relationship between the air ratio of the ammonia burner and the NOx emission amount in the case where the ammonia burner is a joint type and the mixed combustion ratio is 33% is examined. Fig. 5C is a graph showing the relationship between the air ratio of the burner portion and the emission amount of NOx when the mixed combustion ratio of ammonia is changed. As shown in Figure 5C, the ammonia burner air ratio at 0.6 results in the lowest NOx, and the air ratio goes higher or lower than this to increase the NOx. When the air ratio of the ammonia burner is 0.8, the NOx value will be about 1.5 times that of 0.6. Generally, in the case of coal combustion, the NOx value is around 150 to 200ppm, so as long as the air ratio of the ammonia burner is below 0.8, there is not much difference from coal combustion. Also, the higher the ammonia burner air ratio, the greater the increase in NOx. Even if the air ratio of the ammonia burner is zero, that is, only ammonia is injected from the ammonia burner, although NOx will increase, it can be mixed with coal for combustion. If the air ratio of the ammonia burner is lowered to lower than 0.6, NOx will increase instead. Therefore, even if the air ratio of the ammonia burner is lowered to 0.6, the NOx cannot be reduced. It may be that the unburned ammonia reaches the oxidation area downstream of the extra air input part (combustion completion area ), and converted into NOx. Therefore, it is necessary to keep the air ratio of the ammonia burner at 0.6, reduce the extra air input rate and increase the air ratio of the coal burner to reduce the amount of unburned ammonia reaching the downstream of the extra air input part, thereby reducing the combustion rate. NOx generated in the end area. When the joint burner reduces the mixed combustion ratio of ammonia to 25%, 22%, and 11%, the lowest point of NOx generation due to the air ratio of the ammonia burner cannot be confirmed, but it tends to make NOx become The minimum air ratio tends to be lower and lower. Also, the NOx value tends to increase when the ammonia co-firing ratio is reduced to 25% or less. This may be because a part of the auxiliary air of the adjacent coal burner is mixed with the side of the ammonia burner and the air ratio of the ammonia burner is substantially increased. In this case, the air ratio of the ammonia burner can be lowered to lower than 0.6, thereby controlling the NOx value. As shown above, even if the mixed combustion ratio of ammonia is changed from 11% to 33%, the NOx value can be suppressed by properly controlling the air ratio of the ammonia burner, even if the coal burner The primary air ratio (the ratio of the theoretical air ratio of coal to the primary air volume) increases due to the increase of the mixed combustion rate, and the air ratio of the coal burner and ammonia burner can also be individually controlled to control the NOx value at a certain level value below.

Next, as shown in Fig. 5B, in the diffuser type burner, when the flame arrester is a diffuser type and a swirler type, the NOx generation tends to be lower in the diffuser type than in the swirl type. . The diffuser type is to install a disc-shaped diffuser at the front end of the burner, so that the air can circle around to keep the flame, and the ignition point will be very close to the burner. On the other hand, in the swirler type, a swirling flow around the burner is generated by a swirling flow, and the flame is maintained by the circulating flow, thereby forming an ignition point on the downstream side of the front end of the burner. The reducing environment formed by the ammonia burner is between the ignition point and the extra air injection point, so the closer the ignition point is to the front of the burner, the longer the distance of the reducing environment and the longer the residence time of the reducing environment. Promote NOx reduction. The air ratio of the ammonia burner that minimizes NOx cannot be obtained even for the diffusion burner, but it tends to be lower than that of the joint type, so it can be said that it can be controlled in each burner form Ammonia burner air ratio to minimize NOx.

As mentioned above, although the embodiment of this invention was described, this invention is not limited to the said embodiment, The form which added the deformation|transformation to the said embodiment, and the form which combined these forms suitably is included.

In this manual, relative or absolute configuration expressions such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" are not Strictly means only such an arrangement, but also includes a tolerance, or a state of relative displacement with an angle or a distance to the extent that the same function can be obtained. For example, expressions that express the equal state of things such as "same", "equivalent" and "homogeneous" do not strictly express only the equal state, but also include tolerances, or there are differences in the degree to which the same function can be obtained. poor state. In addition, in this specification, expressions such as a square shape or a cylindrical shape do not only represent shapes such as a square shape or a cylindrical shape in a geometrically strict sense, but are within the range where the same effect can be obtained. , including shapes such as unevenness or chamfering. In addition, in this specification, expressions such as "having", "containing", or "having" one of the constituent elements are not exclusive expressions excluding the existence of other constituent elements.

＜Other＞ The contents described in the above-mentioned several embodiments can be grasped as follows, for example.

1) The boiler (2) of at least one embodiment of the present invention, comprising: a stove (2) with a stove wall (19), An ammonia burner (50) installed on the furnace wall (19) to burn ammonia fuel, The pulverized coal burners (302, 304) which are arranged on the furnace wall (19) at different positions from the ammonia burner (50) and burn pulverized coal.

2) In several embodiments, it is the boiler (2) described in 1) above, A control device (5) is provided for controlling the supply amount of the aforementioned ammonia fuel, the aforementioned pulverized coal, and combustion air, The control device (5) has: A first calculation unit that calculates the ratio of the amount of air for ammonia combustion supplied to the ammonia fuel to the theoretical air amount necessary for the combustion of the ammonia fuel, that is, the ammonia-to-air ratio; a second calculation unit that calculates the ratio of the amount of air for pulverized coal combustion supplied to the pulverized coal to the theoretical amount of air necessary to combust the pulverized coal, that is, the pulverized-coal air ratio; and A control unit controls the supply amount so that the ammonia-air ratio satisfies a first reference range and the pulverized coal-air ratio satisfies a second reference range.

3) In several embodiments, it is the boiler (2) described in the above 2), 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 of the ammonia-air ratios satisfies the first reference range.

4) In several embodiments, it is the boiler (2) described in 2) or 3) above, The aforementioned furnace wall (19) is equipped with an air nozzle (303) adjacent to the aforementioned ammonia burner (50), The first calculating unit calculates the ammonia air ratio using the ammonia combustion air amount including the air amount supplied to the ammonia fuel among the air injected from the air nozzle (303).

5) In several embodiments, it is the boiler (2) described in any one of the above-mentioned 2) to 4), The upper limit of the first reference range is lower than the upper limit of the second reference range.

6) In several embodiments, it is the boiler (2) described in any one of the above-mentioned 2) to 5), The aforementioned first reference range is 0.8 or less.

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

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

9) In several embodiments, it is the boiler (2) described in any one of the above 1) to 8), equipped with an auxiliary air nozzle (303) adjacent to the aforementioned ammonia burner (50) to supply auxiliary air, The auxiliary air nozzle (303) has a damper capable of adjusting the amount of auxiliary air, and the auxiliary air can be supplied in the direction of the ammonia burner (50).

10) In several embodiments, it is the boiler (2) described in any one of the above 1) to 9), The aforementioned ammonia burner (50) contains: Ammonia nozzles (142, 152) injecting the aforementioned ammonia fuel, A fuel nozzle for priming (ammonia nozzle 306A) that injects fuel for priming.

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

12) In several embodiments, it is the boiler (2) described in the above 8), The aforementioned stove wall (19) contains: A burner configuration area, which is provided with the aforementioned ammonia burner (50) and the aforementioned pulverized coal burner (302, 304); and an additional air supply area, which is provided with an additional air supply part that supplies additional air further downstream than the aforementioned burner arrangement area, The aforementioned ammonia burner (50) is located at the uppermost section of the aforementioned burner arrangement area.

13) In several embodiments, it is the boiler (2) described in any one of the above 1) to 12), The aforementioned ammonia burner (50) is a diffusion burner or a partial premix burner.

14) In several embodiments, it is the boiler (2) described in the above 13), The aforementioned diffusion burner or the aforementioned partial premixing burner is any of the partial premixing joint type, diffusion type, and swirler type or diffuser type burner with different structures of flame retainers.

15) The boiler control method of at least one embodiment of the present invention, the boiler includes: a stove (2) with a stove wall (19), An ammonia burner (50) installed on the furnace wall (19) to burn ammonia fuel, The pulverized coal burners (302, 304) which are arranged on the furnace wall (19) at a position different from the ammonia burner (50) to burn pulverized coal, Controlling the supply of the aforementioned ammonia fuel, the aforementioned pulverized coal, and the air for combustion in the aforementioned boiler, the boiler control method has: The first calculation step (S10-1), which calculates the ratio of the amount of air used for ammonia combustion supplied to the ammonia fuel to the theoretical air amount necessary for the combustion of the ammonia fuel, that is, the ammonia-to-air ratio; A second calculation step (S10-2) of calculating the ratio of the amount of air for pulverized coal combustion supplied to the aforementioned pulverized coal to the theoretical amount of air necessary for burning the aforementioned pulverized coal, that is, the pulverized-air ratio; and A control step (S10-3) of controlling the supply amount so that the ammonia-air ratio satisfies a first reference range and the pulverized coal-air ratio satisfies a second reference range.

16) The boiler reconstruction method of at least one embodiment of the present invention, the boiler contains: a stove (2) with a stove wall (19), The pulverized coal burner (302,304) that is arranged on the aforementioned furnace wall (19) and makes the pulverized coal combust, A plurality of injection parts for injecting pulverized coal or starting fuel or auxiliary air, which are arranged at positions different from the pulverized coal burners (302, 304) of the aforementioned furnace wall (19), control device (5), The boiler modification method, having a replacement step of replacing at least one of the plurality of injection parts with an ammonia burner (50) that burns ammonia fuel, The aforementioned control device (5) for controlling the supply of the aforementioned ammonia fuel, the aforementioned pulverized coal, and the combustion air has: A first calculation unit that calculates the ratio of the amount of air for ammonia combustion supplied to the ammonia fuel to the theoretical air amount necessary for the combustion of the ammonia fuel, that is, the ammonia-to-air ratio; a second calculation unit that calculates the ratio of the amount of air for pulverized coal combustion supplied to the pulverized coal to the theoretical amount of air necessary to combust the pulverized coal, that is, the pulverized-coal air ratio; and A control unit controls the supply amount so 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: Measuring system 11: Nose 12: Stove 15: Supply system 19: Stove wall 20: Stove 21: Burner configuration area 22: Additional air supply area 30: Burner unit 31: 1st burner unit 32: 2nd burner unit 33: The 3rd burner unit 37: Fuel burner for starting 50: Ammonia burner 70: Pulverized coal supply system 71: Pulverized coal supply device 72: Pulverized coal supply pipeline 74: Coal flow meter 76: Pulverized coal flow adjustment valve 78: switch valve 80: Oil supply system 81: Oil supply device 82: Oil supply pipeline 84: Oil flow meter 86: Oil flow adjustment valve 88:Switching valve 91: Processor 92: ROM 93: RAM 94: Memory 100: Ammonia supply system 101: Ammonia tank 102: Ammonia supply pipeline 103: pump 105: Pressure regulating valve 107: switching valve 108: Flow adjustment valve 109: Ammonia flow meter 110:1 secondary air supply system 114:1 secondary air flow meter 116:1 secondary air flow regulating valve 118: switching valve 120: Additional air supply system 124: Additional air flow meter 126: Additional air flow regulating valve 128: switching valve 131: Bellows 132: Ammonia supply nozzle 133: Outer cylinder 141: Bellows 142: Ammonia supply nozzle 143: Flame protector (diffuser) 151: Bellows 152:Ammonia nozzle 153: Flame protector (cyclone) 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 start-up oil burner 1102: Coal burner with start-up oil burner 1103: Coal Burner 1104: Coal Burner 1105: Coal burner with start-up oil burner 1106: Coal Burner 1107: Ammonia burner 1108: Ammonia burner 1109: Ammonia burner 1120: Start-up oil burner/ammonia dual-purpose burner 1121: Start oil burner/ammonia dual-purpose burner 1123: Start oil burner/ammonia dual-purpose burner

[ Fig. 1 ] A conceptual diagram of a boiler operating system according to an embodiment. [ Fig. 2 ] A conceptual diagram showing a burner of a previous example. [ Fig. 3A ] A cross-sectional view showing burner arrangement of a boiler before modification according to an embodiment (modified example of coal burner). [ Fig. 3B ] A cross-sectional view showing burner arrangement of a modified boiler according to an embodiment (modified example of a coal burner). [FIG. 3C] A conceptual diagram showing a correspondence relationship between burner arrangements before and after modification of a boiler according to an embodiment (a modified example of a coal burner). [ Fig. 4 ] An explanatory diagram of air flow related to combustion in an ammonia burner according to an embodiment. [ Fig. 5A ] 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 ] An explanatory diagram showing the relationship among the shape of the burner, the air ratio of the ammonia burner, and the amount of nitrogen oxides generated in one embodiment. [ Fig. 5C ] An explanatory diagram showing the relationship between the ammonia co-firing ratio, the ammonia burner air ratio, and the amount of nitrogen oxides generated in one embodiment. [ Fig. 6A ] A cross-sectional view showing burner arrangement of a boiler before modification according to an embodiment (modified example of a fuel burner for start-up). [ Fig. 6B ] A cross-sectional view showing burner arrangement of a modified boiler according to an embodiment (a modified example of a fuel burner for start-up). [FIG. 6C] A conceptual diagram showing a correspondence relationship between burner arrangements before and after modification of a boiler according to an embodiment (retrofit example of a start-up fuel burner). [ Fig. 7A ] A cross-sectional view showing burner arrangement of a modified boiler according to one embodiment (a modified example of an air nozzle). [ Fig. 7B ] A conceptual diagram showing a correspondence relationship between burner arrangements before and after modification of a boiler according to an embodiment (a modified example of an air nozzle). [ Fig. 8A ] A cross-sectional view showing burner arrangement of a modified boiler according to an embodiment (modified example of the uppermost air nozzle). [FIG. 8B] A conceptual diagram showing the correspondence relationship of the burner arrangement before and after modification of the boiler of one embodiment (modification example of the uppermost air nozzle). [ Fig. 9 ] A control system diagram of a boiler according to an embodiment. [FIG. 10A] A flowchart of a boiler control method according to an embodiment. [FIG. 10B] A flowchart of NOx control processing in one embodiment. [FIG. 10C] A control logic diagram for calculating the control command value of the amount of combustion air in one embodiment. [ Fig. 11A ] Arrangement of an ammonia burner of an opposed combustion burner according to an embodiment. [FIG. 11B] A sectional view taken along line A-A of FIG. 11A in the arrow direction. [FIG. 11C] A sectional view taken along line B-B of FIG. 11A in the arrow direction. [ Fig. 11D ] A side view of an ammonia burner according to an embodiment. [ Fig. 11E ] A side view of an ammonia burner according to an embodiment. [ Fig. 12 ] A conceptual diagram showing an oxidation-reduction state in a boiler according to an embodiment. [ Fig. 13 ] A diagram showing the structure of a joint burner. [ Fig. 14 ] A diagram showing the structure of a diffuser burner. [ Fig. 15 ] A diagram showing the structure of a swirl burner. [ Fig. 16 ] A flow chart of a boiler retrofitting method.

301: Auxiliary air nozzle

302: Pulverized coal burner

303: Auxiliary air nozzle

303A: flow path

303B: flow path

304: Pulverized coal burner

305: Auxiliary air nozzle

306: Ammonia burner

Claims (16)

A boiler comprising: a furnace with a furnace wall, Ammonia burners installed on the wall of the aforementioned furnace to burn ammonia fuel, A pulverized coal burner which is installed at a position different from the ammonia burner on the furnace wall and burns pulverized coal. The boiler as described in Claim 1, wherein, A control device is provided to control the supply amount of the aforementioned ammonia fuel, the aforementioned pulverized coal, and the air for combustion, The control unit, with: A first calculation unit that calculates the ratio of the amount of air for ammonia combustion supplied to the ammonia fuel to the theoretical air amount necessary for the combustion of the ammonia fuel, that is, the ammonia-to-air ratio; a second calculation unit that calculates the ratio of the amount of air for pulverized coal combustion supplied to the pulverized coal to the theoretical amount of air necessary to combust the pulverized coal, that is, the pulverized-coal air ratio; and A control unit controls the supply amount so that the ammonia-air ratio satisfies a first reference range and the pulverized coal-air ratio satisfies a second reference range. The boiler as described in claim 2, wherein, The first calculation unit calculates the ammonia-air ratio for each of the plurality of ammonia burners, The control unit controls the supply amount so that each of the ammonia-air ratios satisfies the first reference range. The boiler as described in claim 2 or 3, wherein, The furnace wall is equipped with an air nozzle adjacent to the ammonia burner, The first calculating unit calculates the ammonia air ratio using the ammonia combustion air amount including the air amount supplied to the ammonia fuel among the air amount injected from the air nozzle. 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. The boiler according to claim 2 or 3, wherein the first reference range is 0.8 or less. The boiler according to claim 2 or 3, wherein the first reference range is 0.7 or less. 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. The boiler as described in any one of claims 1 to 3, wherein, having an auxiliary air nozzle adjacent to the aforementioned ammonia burner for supplying auxiliary air, The said auxiliary air nozzle is provided with the damper which can adjust the quantity of auxiliary air which can be supplied to the direction of the said ammonia burner. The boiler as described in any one of claims 1 to 3, wherein, The aforementioned ammonia burner, comprising: Ammonia nozzles injecting the aforementioned ammonia fuel, A fuel nozzle for priming that injects fuel for priming. The boiler according to any one of claims 1 to 3, wherein the ammonia burner is provided adjacent to the pulverized coal burner. The boiler as described in Claim 8, wherein, The aforementioned furnace wall contains: A burner configuration area, which is provided with the aforementioned ammonia burner and the aforementioned pulverized coal burner; and an additional air supply area, which is provided with an additional air supply part that supplies additional air further downstream than the aforementioned burner arrangement area, The aforementioned ammonia burner is located at the uppermost section of the aforementioned burner arrangement area. The boiler according to any one of claims 1 to 3, wherein the ammonia burner is a diffusion burner or a partial premix burner. The boiler according to claim 13, wherein the diffusion burner or the partial premixing burner is a partial premixing joint type, diffusion type and swirler type with different structures of flame retainers Or diffuser type of any kind of burner. A method of controlling a boiler comprising: a furnace with a furnace wall, Ammonia burners installed on the wall of the aforementioned furnace to burn ammonia fuel, a pulverized coal burner installed at a position different from the ammonia burner on the wall of the aforementioned furnace to burn pulverized coal, Controlling the supply of the aforementioned ammonia fuel, the aforementioned pulverized coal, and the air for combustion in the aforementioned boiler, the boiler control method has: A first calculation step, which calculates the ratio of the amount of air for ammonia combustion supplied to the ammonia fuel to the theoretical air amount necessary for the combustion of the ammonia fuel, that is, the ammonia-to-air ratio; A second calculation step of calculating the ratio of the amount of air for pulverized coal combustion supplied to the aforementioned pulverized coal to the theoretical amount of air necessary for combusting the aforementioned pulverized coal, that is, the pulverized coal air ratio; and A control step of controlling the supply amount so that the ammonia-air ratio satisfies a first reference range and the pulverized coal-air ratio satisfies a second reference range. A boiler reconstruction method, the boiler has: a furnace with a furnace wall, A pulverized coal burner installed on the wall of the aforementioned furnace to burn pulverized coal, A plurality of injection parts for injecting pulverized coal or starting fuel or auxiliary air, which are installed at different positions on the furnace wall from the pulverized coal burner, control device, The boiler modification method, having a replacement step of replacing at least one of the plurality of injection parts with an ammonia burner that burns ammonia fuel, The aforementioned control device for controlling the supply of the aforementioned ammonia fuel, the aforementioned pulverized coal, and the air for combustion has: A first calculation unit that calculates the ratio of the amount of air for ammonia combustion supplied to the ammonia fuel to the theoretical air amount necessary for the combustion of the ammonia fuel, that is, the ammonia-to-air ratio; a second calculation unit that calculates the ratio of the amount of air for pulverized coal combustion supplied to the pulverized coal to the theoretical amount of air necessary to combust the pulverized coal, that is, the pulverized-coal air ratio; and A control unit controls the supply amount so 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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