Ammonia-fueled boiler system

Abstract

To provide an ammonia fuel boiler system capable of suppressing emission of NOx.SOLUTION: An ammonia fuel boiler system includes: a furnace having a burner arrangement region and an addition air input region located downstream of the burner arrangement region; an ammonia burner provided in the burner arrangement region to burn first fuel containing ammonia fuel; and a controller configured to specify target burner air supply amount to the burner arrangement region that enables NOx emission amount to become a prescribed value or lower on the basis of a characteristic value correlated with residual ammonia amount in burning of fuel and to control burner air supply amount to the burner arrangement region so as to attain the specified target burner air supply amount.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an ammonia-fueled boiler system. [Background technology]

[0002] Conventionally, ammonia-fueled boilers in which ammonia is supplied as fuel into a furnace have been known. For example, in an ammonia-fueled boiler disclosed in Patent Document 1, both pulverized coal and ammonia are supplied to burners provided in the furnace body. As a result, ammonia and pulverized coal are mixed and burned in the combustion chamber of the furnace body. This document also discloses that NOx emissions are reduced by devising an arrangement pattern of the burners. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-112280 Summary of the Invention [Problem to be solved by the invention]

[0004] In an ammonia combustion boiler system, whether or not the configuration disclosed in Patent Document 1 is adopted, it is preferable to have other measures to suppress NOx emissions.

[0005] An object of the present disclosure is to provide an ammonia-fueled boiler system that can suppress NOx emissions. [Means for solving the problem]

[0006] In accordance with at least one embodiment of the present disclosure, an ammonia-fueled boiler system includes: a furnace having a burner arrangement area and an additional air injection area located downstream of the burner arrangement area; an ammonia burner provided in the burner arrangement area for burning a first fuel containing ammonia fuel; a controller configured to specify a target burner air supply amount to the burner arrangement area based on a characteristic value correlated with the amount of residual ammonia in the combustion of the first fuel, such that NOx emissions are equal to or less than a specified value, and to control the burner air supply amount to the burner arrangement area so as to realize the specified target burner air supply amount; Equipped with. [Effects of the Invention]

[0007] According to the present disclosure, an ammonia-fueled boiler system capable of suppressing NOx emissions can be provided. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a conceptual diagram of an ammonia-fueled boiler system according to one embodiment. [Figure 2] FIG. 1 is a conceptual diagram illustrating a boiler according to an embodiment. [Figure 3] 1 is a graph conceptually showing the results of an experiment verifying the relationship between the concentration of residual ammonia and NOx emissions in a boiler according to one embodiment. [Figure 4A] This is a graph conceptually showing the results of an experiment in which the relationship between the burner air ratio and the residual ammonia concentration was verified by changing the co-firing ratio (burner temperature 1600°C). [Figure 4B] This is a graph conceptually showing the results of an experiment in which the relationship between the burner air ratio and the residual ammonia concentration was verified by changing the co-firing ratio (burner temperature 1400°C). [Figure 4C] This is a graph conceptually showing the results of an experiment in which the relationship between the burner air ratio and the residual ammonia concentration was verified by changing the co-firing ratio (burner temperature 1300°C). [Figure 5] 4 is a flowchart showing the burner air supply amount according to the first embodiment. [Figure 6] 10 is a flowchart showing the burner air supply amount according to the second embodiment. [Figure 7] FIG. 2 is a conceptual diagram illustrating the electrical configuration of a controller according to an embodiment. [Figure 8] 10 is a flowchart showing a control process for a burner air supply amount according to a third embodiment. [Figure 9A] FIG. 2 is a conceptual diagram of an additional air port according to one embodiment, viewed from the furnace side. [Figure 9B] 9B is a cross-sectional view taken along the line AA in FIG. 9A. DETAILED DESCRIPTION OF THE INVENTION

[0009] Preferred embodiments of the present disclosure will be described below with reference to the drawings. The present invention is not limited to these embodiments, and when there are multiple embodiments, the present invention also includes configurations that combine the embodiments. In the following description, "upper" and "upper" refer to the upper side in the vertical direction, and "lower" and "lower" refer to the lower side in the vertical direction, and the vertical direction is not precise and may include errors. Furthermore, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure. For example, expressions expressing relative or absolute arrangement such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" not only express such an arrangement exactly, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions such as "identical," "equal," and "homogeneous" that indicate that something is in an equal state not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, 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 the strict geometric sense, but also represent shapes including uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained. On the other hand, the expressions "comprise," "include," or "have" one element are not exclusive expressions that exclude the presence of other elements. Note that the same components will be denoted by the same reference numerals and the description thereof will be omitted.

[0010] <Outline of Ammonia Fuel Boiler System 1> FIG. 1 is a schematic diagram illustrating an ammonia-fueled boiler system 1 according to an embodiment of the present disclosure. The ammonia-fueled boiler system 1 of this embodiment is incorporated into a thermal power plant. A boiler 10 constituting the ammonia-fueled boiler system 1 is capable of burning a first fuel containing ammonia fuel and a second fuel other than ammonia fuel, and exchanging heat generated by the combustion with feedwater or steam to generate superheated steam. The ammonia fuel may be either liquid ammonia or ammonia gas. The liquid ammonia may be a pure liquid ammonia or a liquid mixture in which a small proportion of water is mixed with liquid ammonia. The second fuel may be any fuel other than ammonia fuel, and may be a solid fuel, liquid fuel, or gaseous fuel. The following describes an embodiment in which the second fuel includes coal. The coal used as fuel is pulverized coal. The boiler 10 may be either a single-fuel coal combustion, a mixed-fuel combustion of coal and ammonia fuel, or a single-fuel ammonia combustion.

[0011] In this embodiment, as shown in Fig. 1, a boiler 10 has a furnace 11, a combustion device 12, and a combustion gas passage 13. The furnace 11 has a hollow rectangular cylindrical shape and is installed vertically. A furnace wall 101 constituting the furnace 11 is composed of a plurality of heat transfer tubes and fins connecting these, and exchanges heat generated by the combustion of at least one of pulverized coal fuel and ammonia gas with water or steam circulating inside the heat transfer tubes, thereby suppressing a temperature rise in the furnace wall 101.

[0012] The combustion device 12 is provided on the lower side of the furnace wall 101 that constitutes the furnace 11. In this embodiment, the combustion device 12 has multiple burners (e.g., 21, 22, 23, 24, and 25) attached to the furnace wall 101. The boiler 10 according to one embodiment is a swirl-fired boiler, and the burners provided in each stage are arranged at equal intervals along the circumferential direction of the furnace 11. For example, the burners 21, 22, 23, 24, and 25 are arranged in multiple stages (e.g., five stages in FIG. 1 ) along the vertical direction, with each set being equally spaced along the circumferential direction of the furnace 11. However, the shape of the furnace, the number of burners in each stage, and their arrangement are not limited to this embodiment. The boiler 10 according to another embodiment is an opposed-fired boiler. In this case, at least one pair of burners is provided in each stage, facing each other.

[0013] An ammonia fuel supply unit 60 for supplying ammonia fuel to the boiler 10 is connected to the burners 21, 22, and 23 via an ammonia supply pipe 69. As an example, the ammonia supply pipe 69 is connected to a tank that stores ammonia. In the following description, the burners 21, 22, and 23 may be referred to as first burners 81.

[0014] In an embodiment employing a liquid ammonia injection method in which the first burner 81 injects liquid ammonia, the ammonia supply pipe 69 supplies high-pressure liquid ammonia to the first burner 81. In this case, the ammonia supply pipe 69 may be provided with a heat insulating material to prevent evaporation of the liquid ammonia. In an embodiment employing an ammonia gas injection method in which the first burner 81 injects ammonia gas, the ammonia supply pipe 69 may be provided with at least one ammonia vaporizer for vaporizing the liquid ammonia. The ammonia vaporizer may be configured to vaporize the liquid ammonia by using steam generated in the boiler 10, combustion gas in the boiler 10, or seawater outside the boiler system as a direct or indirect heat source. The first burner 81 may be configured to inject another fuel in addition to the ammonia fuel. In other words, the first burner 81 is understood to be a burner configured to burn a first fuel including ammonia fuel.

[0015] The burners 24, 25 are connected to a plurality of pulverizers (mills) 34, 35 via pulverized coal supply pipes 29, 33 (in the following description, the burners 24, 25 may be collectively referred to as second burners 82, the pulverizers 34, 35 may be collectively referred to as pulverizers 3, and the pulverized coal supply pipes 29, 33 may be collectively referred to as pulverized coal supply pipes 38). The second burners 82 are understood to be burners configured to burn a second fuel other than ammonia fuel (pulverized coal in this example). The pulverizer 3 is configured, for example, such that a pulverizing table (not shown) is supported within a housing so as to be rotatable, and a plurality of pulverizing rollers (not shown) are supported above the pulverizing table so as to be rotatable in conjunction with the rotation of the pulverizing table. When coal is fed between the multiple crushing rollers and the crushing table, it is crushed and transported by carrier gas (primary air, oxidizing gas, combustion air, carrier air) to a classifier (not shown) in the housing of the crusher 3, and the pulverized coal fuel classified into particles within a predetermined particle size range can be supplied to the burners 24, 25 (second burner 82) from the pulverized coal supply pipes 29, 33 (38). The carrier gas also plays a role in drying the pulverized coal fuel.

[0016] The above-mentioned conveying gas is delivered to the pulverizer 3 from a primary air fan (PAF) 31, which takes in outside air, via an air pipe 30. The air pipe 30 includes a hot air induction pipe 30A through which hot air heated by an air heater 42 flows from the primary air fan 31; a cold air induction pipe 30B through which cold air at near room temperature flows from the primary air fan 31 without passing through the air heater 42; and a conveying gas flow path 30C through which the hot air and cold air merge and flow. The hot air induction pipe 30A and the cold air induction pipe 30B are provided with a hot air damper 30D and a cold air damper 30E, respectively. The opening degrees of these dampers are adjusted according to the supply conditions of pulverized coal fuel, thereby adjusting the flow rate and temperature of the conveying gas flowing through the conveying gas flow path 30C.

[0017] Furnace 11 is also provided with a wind box 36 at the mounting positions of burners 21, 22, 23, 24, and 25, and one end of an air duct (airway) 37 is connected to this wind box 36. The other end of air duct 37 is provided with a forced draft fan (FDF) 32. Air duct 37 is also provided with a wind box damper 28 for adjusting the amount of air supplied to wind box 36. The opening degree of wind box damper 28 is controlled by a controller 90 (see FIG. 2), which will be described later.

[0018] Above the installation position of the burners 21 in the furnace 11 (above the wind box 36), multiple additional air ports (AA ports) 17 are provided for supplying additional air (AA) for combustion to the combustion completion zone 16 (see FIG. 2) in the furnace 11. The ends of additional air ducts (AA ducts) 27 branching off from the air duct 37 are connected to the additional air ports 17, and a portion of the air supplied from the forced draft fan 32 can be supplied to the additional air ports 17 via the additional air ducts 27 as additional air for combustion. In this embodiment, the additional air ports 17 are provided with additional air adjustment dampers 26. The opening degree of the additional air adjustment dampers 26 is controlled by a controller 90 (see FIG. 2), which will be described later.

[0019] 1, the combustion gas passage 13 is connected to the vertical upper part of the furnace 11. The combustion gas passage 13 is provided with superheaters 102, 103, 104, reheaters 105, 106, and an economizer 107 as heat exchangers for recovering heat from the combustion gas, and heat is exchanged between the combustion gas generated in the furnace 11 and the feedwater or steam flowing inside each heat exchanger. The furnace 11 of one embodiment includes a nose 11A that protrudes into the furnace 11. The nose 11A is configured so that gases (e.g., combustion gases and unburned gases) generated in the main combustion zone 15 (see FIG. 2) and the combustion completion zone 16 (see FIG. 2) in the furnace 11 properly flow into the flue 14 located downstream of the furnace 11. The nose 11A of one embodiment is provided with a gas thermometer 6 for measuring the nose temperature, which is the temperature of the inner wall surface of the nose 11A. The nose temperature may be treated as the temperature of the combustion gas in the furnace 11.

[0020] As shown in FIG. 1 , the combustion gas passage 13 is connected downstream to a flue 14 through which the combustion gas that has undergone heat exchange is discharged. An air heater 42 is provided in the flue 14 for heating the air flowing through the air duct 37 and the air pipe 30. In the air heater 42, heat exchange occurs between the outside air flowing through the air duct 37 and the combustion gas flowing through the flue 14, thereby raising the temperature of the combustion air supplied to the burners 21, 22, 23, 24, and 25. Furthermore, in the air heater 42, heat exchange occurs between the outside air flowing toward the hot air induction pipe 30A and the combustion gas flowing through the flue 14, thereby converting the outside air into hot air. Therefore, it can be understood that the air heater 42 is configured to heat the outside air using the exhaust heat of the boiler 10.

[0021] Furthermore, a denitration device 43 is provided in the flue 14 at a position upstream of the air heater 42. The denitration device 43 supplies a reducing agent, such as ammonia or urea water, that has the ability to reduce nitrogen oxides into the flue 14, and removes and reduces the nitrogen oxides in the combustion gas by promoting the reaction between the nitrogen oxides in the combustion gas to which the reducing agent has been supplied and the reducing agent through the catalytic action of a denitration catalyst provided in the denitration device 43. A gas duct 41 connected to the flue 14 is provided with a dust collector 44, such as an electrostatic precipitator, an induced draft fan (IDF) 45, a desulfurization device 46, and the like, at a position downstream of the air heater 42, and a chimney 50 is provided at the downstream end.

[0022] Meanwhile, when the multiple pulverizers 34, 35 (3) are driven, the generated pulverized coal fuel is supplied to the burners 24, 25 (second burner 82) together with carrier gases (primary air, oxidizing gas, combustion air, and carrier air) through the pulverized coal supply pipes 29, 33 (38). Furthermore, the exhaust gas discharged from the flue 14 exchanges heat with the air heater 42, and heated combustion air (primary air, secondary air, and oxidizing gas) is supplied to the burners 21, 22, 23, 24, and 25 from the air duct 37 through the wind box 36. The burners 24, 25 (second burner 82) inject a pulverized coal fuel mixture, which is a mixture of the pulverized coal fuel and the carrier gas, into the furnace 11, and also inject combustion air into the furnace 11. At this time, the pulverized coal fuel mixture is ignited, forming a flame. A flame is generated in the lower part of the furnace 11, and high-temperature combustion gas rises inside the furnace 11 and is discharged into the combustion gas passage 13. Simultaneously with the start of injection of the pulverized coal fuel mixture (or after the pulverized coal fuel mixture is ignited), the burners 21, 22, and 23 (first burner 81) inject a first fuel containing ammonia fuel into the furnace 11, causing combustion of the first fuel and resulting in mixed combustion of pulverized coal and ammonia. In this embodiment, air is used as the oxidizing gas. An oxidizing gas having a higher or lower oxygen content than air may be used by optimizing the fuel flow rate.

[0023] 1, the combustion gas undergoes heat exchange in a second superheater 103, a third superheater 104, a first superheater 102 (hereinafter sometimes simply referred to as superheaters), a second reheater 106, a first reheater 105 (hereinafter sometimes simply referred to as reheaters), and an economizer 107, which are arranged in a combustion gas passage 13, and then nitrogen oxides are reduced and removed in a denitration device 43, particulate matter is removed in a dust collector 44, and sulfur oxides are removed in a desulfurization device 46, before being discharged into the atmosphere from a chimney 50. Note that the heat exchangers do not necessarily have to be arranged in the order described above with respect to the combustion gas flow.

[0024] Furthermore, Figure 1 does not accurately show the positions of each heat exchanger (superheaters 102, 103, 104, reheaters 105, 106, and economizer 107) in the combustion gas passage 13, and the arrangement order of each heat exchanger relative to the combustion gas flow is not limited to that shown in Figure 1.

[0025] The second fuel injected by the second burner 82 may be a solid fuel such as biomass fuel, PC (Petroleum Coke) fuel generated during oil refining, or petroleum residue. The fuel is not limited to solid fuels; petroleum fuels such as heavy oil, light oil, and heavy oil, and liquid fuels such as industrial wastewater can also be used. Furthermore, gaseous fuels (natural gas, by-product gas, etc.) can also be used. Furthermore, the present invention can be applied to a multi-fuel boiler that uses a combination of these fuels.

[0026] <Example of detailed structure of boiler 10> FIG. 2 is a schematic diagram showing details of a boiler 10 according to an embodiment of the present disclosure. The furnace 11 of the boiler 10 has a burner arrangement area 4 and an additional air injection area 5 located downstream of the burner arrangement area 4. A first burner 81 and a second burner 82 are provided in the burner arrangement area 4, and an additional air injection area 5 is provided with an additional air port 17. Furthermore, the burner arrangement area 4 is provided with an air nozzle 8 configured to inject combustion air supplied from an air duct 37. The combustion air injected from the air nozzle 8 according to this embodiment is secondary air. Note that an air nozzle 8 different from the air nozzle 8 shown in FIG. 2, or at least one of the air nozzles 8 shown in FIG. 2, may be incorporated into the first burner 81 or the second burner 82. For example, the air nozzle 8 may be arranged to surround a first nozzle (described below) of the first burner 81, or may be arranged to surround a second nozzle (described below) of the second burner 82. In this case, the combustion air injected by the air nozzle 8 may be primary air or secondary air.

[0027] The arrangement pattern of the first burners 81, second burners 82, and air nozzles 8 in the burner arrangement area 4 is exemplified below. In the burner arrangement area 4, an air nozzle 8, a second burner 82, an air nozzle 8, a first burner 81, an air nozzle 8, a second burner 82, and an air nozzle 8 are provided in this order from the top in the vertical direction. Each of the air nozzles 8 is connected to an air supply pipe 19 provided with an air damper 18. Each of the air supply pipes 19 is configured to communicate between the air duct 37 and the air nozzle 8. The amount of combustion air supplied to each air nozzle 8 is adjusted by changing the opening degree of the air damper 18 corresponding to each air nozzle 8. In this embodiment, the air dampers 18 are connected to a controller 90, for example, via an angle-adjusting IP converter (not shown). The opening degree of each air damper 18 is adjusted in response to a command sent from the controller 90. In the embodiment illustrated in FIG. 2, a plurality of air nozzles 8 are arranged in the vertical direction between the first burner 81 and the second burner .

[0028] The first burner 81 according to the present embodiment includes a first nozzle for injecting a first fuel containing ammonia fuel, and an ammonia supply path 181 for supplying the ammonia fuel to the first nozzle. The ammonia supply path 181 is connected to the above-described ammonia supply pipe 69. Although not shown in detail, the ammonia supply pipe 69 is provided with an adjustment unit for adjusting the amount of ammonia fuel supplied to the first burner 81. The adjustment unit according to the present embodiment is a flow rate adjustment valve for adjusting the flow rate of liquid ammonia. The adjustment unit according to other embodiments may be an ammonia pump for feeding liquid ammonia, and the amount of ammonia fuel supplied may be adjusted by changing the drive rate of the ammonia pump. In any of the embodiments, the adjustment unit is a component of the ammonia fuel supply unit 60, and the controller 90 controls the adjustment unit.

[0029] Each of the plurality of second burners 82 includes a second nozzle for injecting coal and a coal supply path 182 for supplying coal (pulverized coal) using carrier air. The coal supply path 182 is connected to the above-mentioned pulverized coal supply pipe 38. That is, the coal supply path 182 is configured to supply pulverized coal fuel to the second nozzle using carrier air. The supply amount of pulverized coal fuel is adjusted by changing the drive amount of the pulverizer 3. The drive amount of the pulverizer 3 is controlled by the controller 90.

[0030] In the above configuration, the burner section air ratio (λ), which is the ratio of the amount of combustion air supplied to the burner arrangement area 4 to the theoretical amount of air required for combustion of the first fuel and the second fuel, is defined as follows: λ=(Q a1 +Q a2 +Q a2f ) / Q th (A) (Q a1 : Flow rate of combustion air for the first fuel (ammonia fuel), Q a2 : Secondary air flow rate of the second fuel (pulverized coal fuel in this example), Q a2f : flow rate of air for transporting the second fuel, Qth: theoretical air volume for the first and second fuels) In the following description, the amount of combustion air supplied to the burner arrangement area 4 may be referred to as the burner air supply amount (or burner air volume). The controller 90 as a component of the boiler 10 controls so that the burner section air ratio defined by the formula (A) becomes not less than the lower limit value. This is because if the burner section air ratio falls below the lower limit value, there is a risk of misfire or the like occurring in the furnace 11. The theoretical air volume (Q th ) in the formula (A) may be specified based on the pulverized coal flow meter 39 provided in the pulverized coal supply pipe 38 and the ammonia flow meter 68 provided in the ammonia supply pipe 69. Also, the burner air supply amount (Q a1 +Q a2 +Q a2f ) in the formula (A) may be specified based on air flow meters (not shown) provided in each of the air duct 37, the additional air duct 27, and the air pipe 30, and the opening degrees of the respective air dampers 18.

[0031] The control of the burner section air ratio described above includes at least one of control of the opening degree of the windbox damper 28, control of the opening degree of each air damper 18, control of the opening degree of the additional air adjustment damper 26, control of the driving amount of the pulverizer 3, or control of the adjustment section. Note that when coal is not adopted as the fuel of the boiler 10 and another fuel is adopted, instead of the control of the driving amount of the pulverizer 3, the driving amount of the device that supplies the other fuel may be controlled.

[0032] <Relationship between NOx emission amount and burner section air ratio> The inventors have found that the NOx emission amount from the boiler 10 can be controlled by adjusting the burner air supply amount (Q a1 +Q a2 +Q a2f ) defined by the above formula (A). Hereinafter, the details will be described using FIGS. 3, 4A to 4C.

[0033] 3 is a graph conceptually showing the results of an experiment verifying the relationship between the concentration of residual ammonia in the boiler 10 and the amount of NOx emissions. The residual ammonia is ammonia that remains in the burner arrangement region 4 as a result of combustion of the first fuel containing ammonia fuel. The residual ammonia includes ammonia gas that remains without being burned in the main combustion region 15 of the furnace 11, and is not necessarily limited to ammonia that comes into contact with the burner arrangement region 4 that constitutes the furnace 11. According to the graph in the figure, when the burner temperature, which is the temperature in the main combustion region 15, is between 1300°C and 1400°C, NOx emissions tend to increase when the residual ammonia concentration exceeds a specified concentration of approximately 100 ppm. According to the inventors' findings, this is because residual ammonia has the property of converting to NOx in the additional air injection region 5. Therefore, it is necessary to prevent the amount of residual ammonia from becoming excessive. On the other hand, whether the burner temperature is between 1300°C and 1400°C or 1600°C, if the residual ammonia concentration is too low, NOx emissions tend to increase sharply. According to the inventors' findings, this is because ammonia as a reducing agent is insufficient in the furnace 11. Based on the above considerations, the amount of residual ammonia needs to be optimized to suppress NOx emissions. The inventors further investigated what parameters are preferable for adjusting the amount of residual ammonia.

[0034] 4A to 4C are graphs conceptually showing the results of experiments conducted to verify the relationship between the burner air ratio and the residual ammonia concentration by changing the co-firing ratio of ammonia fuel and coal. Fig. 4A shows the results of experiments conducted under conditions where the burner temperature was 1600°C, and Fig. 4B and Fig. 4C show the results of experiments conducted under conditions where the burner temperatures were 1400°C and 1300°C, respectively. As can be seen from the figure, the amount of residual ammonia (residual ammonia concentration) decreases as the burner air ratio increases (however, according to the knowledge of the inventors, a burner air ratio of 0.9 or less is preferable from the viewpoint of avoiding a sudden increase in NOx emissions). From the above results, it can be seen that the amount of residual ammonia can be controlled by adjusting the burner air ratio. Also, as shown in formula (A), the burner air ratio is determined by the theoretical air amount (Q th ), and this theoretical air amount is determined by the supply amounts of the first fuel and the second fuel. However, since the fuel supply amount is determined by the load (i.e., demand) of the ammonia-fueled boiler system 1, it can be difficult to change. Therefore, the remaining parameter that contributes to the burner air ratio, the burner air amount (Q in formula (A)), a1 , Q a2 , and Q a2f It can be seen that it is preferable to control the burner air ratio through adjustment of the amount of residual ammonia. Through the above investigations, the inventors have found that it is preferable to adjust the amount of residual ammonia, which needs to be an optimum value for suppressing NOx emissions, through control of the amount of burner air supplied.

[0035] In the following description, the control process for the burner air supply amount for reducing NOx emissions will be described in the order of first, second, and third embodiments.

[0036] <Burner Air Supply Amount Control Process According to the First Embodiment> In the first embodiment, the burner air supply rate is controlled based on a characteristic value (hereinafter also referred to as the residual ammonia characteristic value) that correlates with the amount of residual ammonia. The residual ammonia characteristic value may be an output value of an ammonia measuring instrument 9 that measures the ammonia concentration in the burner arrangement region 4. The measured ammonia concentration and the amount of residual ammonia are correlated. In addition, to improve responsiveness, it is preferable to employ a laser-type gas measuring instrument as the ammonia measuring instrument 9. This measuring instrument is configured to measure the ammonia concentration based on the absorption spectrum of laser light that has passed through the gas in the main combustion region 15. As another example, the residual ammonia characteristic value may be an estimated value estimated from the burner air ratio. As described above with reference to FIGS. 4A to 4C, the burner air ratio and the residual ammonia concentration are correlated to a certain extent. Therefore, if the relationship between the two parameters is stored in the memory 91B described below in the form of a function or a data table, the amount of residual ammonia can be estimated. Alternatively, the amount of residual ammonia can be estimated even if the relationship between the two parameters is learned by a learning model.

[0037] A controller 90, which is a component of the boiler 10, is configured to specify a target burner air supply rate (hereinafter sometimes referred to as a target burner air supply rate) based on the residual ammonia characteristic value, such that the NOx emissions will be equal to or less than a specified value. Furthermore, the controller 90 is configured to control the burner air supply rate so as to realize the specified target burner air supply rate. According to the above configuration, for example, when the residual ammonia amount is relatively large, the burner air supply rate is increased. This increases the burner section air ratio, making it possible to keep the NOx emissions equal to or less than the specified value. Conversely, when the residual ammonia amount is too small, resulting in a shortage of ammonia as a reducing agent and potentially excessive NOx emissions, the burner air supply rate is reduced and the residual ammonia amount increases. As a result, an ammonia-fueled boiler system 1 capable of suppressing NOx emissions is realized.

[0038] A controller 90 according to some embodiments controls the burner air supply rate by controlling the ratio (AA ratio) between the burner air supply rate and the additional air supply rate supplied to the additional air injection region 5. As a more specific example, the controller 90 is configured to control the ratio between the burner air supply rate and the additional air supply rate based on a residual ammonia characteristic value so that NOx emissions are below a specified value. Therefore, the additional air supply rate decreases or increases in accordance with an increase or decrease in the burner air supply rate. According to the above configuration, when the residual ammonia is relatively low, the additional air supply rate (AA ratio) increases, sufficient air is supplied to the combustion completion region 16 in the furnace 11, and the generation of unburned fuel can be suppressed. Therefore, the generation of unburned fuel (unburned carbon in this example) can be suppressed while suppressing NOx emissions.

[0039] The controller 90 according to some embodiments may determine the target burner air supply rate based on the temperature of the gas (unburned gas and combustion gas) flowing toward the additional air injection area 5 in the furnace 11 and the residual ammonia characteristic value. The gas temperature is, for example, the burner temperature or nose temperature. As described above with reference to FIGS. 4A to 4C, the burner temperature has a specific relationship with the residual ammonia concentration. Furthermore, according to the inventors' findings, the nose temperature has a specific relationship with the burner temperature. The relationship between the residual ammonia amount and the burner temperature (or nose temperature) may be stored in advance in the memory 91B (described later) in the form of a function or a data table, or the relationship between the two parameters may be learned in advance in a learning model. According to the above configuration, the target burner air supply rate for optimizing the residual ammonia amount can be determined more accurately based on the residual ammonia characteristic value and the gas temperature. This makes it possible to more reliably suppress NOx emissions.

[0040] In some embodiments, when determining the target burner air supply rate, the controller 90 may further refer to the mixed-combustion ratio of a first fuel containing ammonia fuel and a second fuel containing coal (hereinafter simply referred to as the mixed-combustion ratio). That is, the controller 90 may determine the target burner air supply rate based on the temperature of the gas flowing toward the additional air injection area 5, the mixed-combustion ratio, and the residual ammonia characteristic value. As can be seen from the graphs shown in FIGS. 4A to 4C, the amount of residual ammonia correlates not only with the burner temperature but also with the mixed-combustion ratio. This correlation may be stored in advance in memory 91B (described later) in the form of a function or data table, or may be learned in advance using a learning model. According to the above configuration, the target burner air supply rate can be determined more accurately based on the gas temperature, mixed-combustion ratio, and the residual ammonia characteristic value. This makes it possible to more reliably suppress NOx emissions.

[0041] Furthermore, the controller 90 according to some embodiments is configured to control the burner arrangement region 4 so that the amount of unburned carbon generated in the furnace 11 is equal to or less than a predetermined amount. That is, the controller 90 is configured to control the burner air supply amount so that the NOx emissions are equal to or less than a predetermined value and the amount of unburned carbon is equal to or less than the predetermined amount. According to the knowledge of the inventors, the amount of unburned carbon generated in the furnace 11 varies depending on the burner air supply amount. With the above configuration, the generation of both NOx and unburned carbon can be suppressed by controlling the burner air supply amount. Note that the amount of unburned carbon (UBC) according to one embodiment can be calculated based on the temperature in the furnace 11, the amount of pulverized coal supplied, and the combustion air (primary air and secondary air) supplied to the second burner 82.

[0042] The controller 90 according to some embodiments includes a processor and a memory. The memory includes a ROM, a RAM, and a flash memory. The processor is configured to read a boiler operation program stored in the ROM, load it into the RAM, and execute instructions included in the boiler operation program. The boiler operation program includes a burner air volume control program for executing the burner air volume control process described below. The processor is a CPU, a GPU, an MPU, a DSP, various other computing devices, or a combination of these. The processor may be implemented by an integrated circuit such as a PLD, an ASIC, an FPGA, or an MCU. The flash memory included in the memory stores various data as the boiler operation program is executed. A specific configuration example of the controller 90 will be described later with reference to FIG. 7.

[0043] The burner air amount control process according to the first embodiment will be described with reference to FIG. 5. In the following description, steps may be abbreviated as "S." First, the controller 90 determines whether the NOx emission amount is equal to or less than a specified value (S5). As one example, the controller 90 determines whether the NOx emission amount is equal to or less than a specified value based on the output result of a NOx measuring instrument (not shown) that may be provided at the inlet of the desulfurization device 46, for example. As another example, the controller 90 may estimate the NOx emission amount based on values ​​such as the burner air ratio, the temperature inside the furnace, the burner air supply amount, and the supply amounts of the first fuel and the second fuel, and determine whether the estimated NOx emission amount is equal to or less than a specified value.

[0044] If it is determined that the NOx emissions exceed the specified value (S5: No), a target burner air supply rate for reducing the NOx emissions is identified. Prior to a detailed description of the specific flow, a simulation process is repeated at least once (S11-S19), in which the burner air supply rate is virtually changed and the NOx emissions resulting from the change are calculated. The simulation process is repeated to find an appropriate target burner air supply rate. Then, processing is executed to achieve the target burner air supply rate found by the search (S51, S53).

[0045] The details of S11 to S19 will be explained. The controller 90 virtually imparts a deviation to the current burner air supply rate (S11). Then, as virtual results resulting from this, the combustion temperature, which is the gas temperature in the main combustion region 15 of the furnace 11, and the UBC amount are acquired (S13). As a specific example, the controller 90 calculates the combustion temperature based on the burner air supply rate to which the deviation has been added, the combustion heat amount of the first fuel including ammonia fuel, the fuel heat amount of the second fuel including coal, and a relational equation for heat balance in the furnace 11. Furthermore, the controller 90 determines the UBC amount by calculation based on the burner air supply rate to which the deviation has been added, the calculated combustion temperature, and the supply rate of pulverized coal. In calculating the UBC amount, a specified equation for predicting the UBC amount may be used.

[0046] The controller 90 acquires the residual ammonia characteristic value (S15). As one example, the controller 90 acquires the output result of the ammonia measuring instrument 9 and acquires the residual ammonia concentration in the furnace 11. As another example, the controller 90 may determine the amount of residual ammonia by calculation based on the acquisition result of S13.

[0047] The controller 90 calculates and obtains the NOx emission amount based on the processing results of S11, S13, and S15 (S17). For example, the controller 90 calculates and obtains the NOx emission amount based on the virtual burner air supply amount obtained in S11, the combustion temperature obtained in S13, and the residual ammonia characteristic value obtained in S15. Note that in S17, the mixed combustion ratio in the boiler 10 and the residence time of the first fuel and the second fuel in the furnace may be referenced. In this case, a more accurate NOx emission amount can be obtained. Specifically, the residence time in the furnace is the time from when the first fuel and the second fuel are introduced into the furnace 11 until they reach the nose 11A. The residence time in the furnace can be calculated based on the flow rate of the combustion air supplied to the burner arrangement area 4, the flow rates of the first fuel and the second fuel, the cross-sectional area (constant value) of the furnace 11, and the height (constant value) of the furnace 11.

[0048] The controller 90 determines whether the NOx emission amount acquired in S17 is equal to or less than a specified value and whether the UBC amount acquired in S13 is equal to or less than a specified carbon amount (S19). If these conditions (hereinafter also referred to as termination conditions) are not met (S19: NO), the deviation of the burner air supply rate virtually assigned in S11 is deemed to be inappropriate. The controller 90 returns the process to S11 and repeats S11 to S19. The deviation newly assigned to the burner air supply rate (S11) may be determined by applying a gradient method. When an appropriate burner air supply rate deviation is assigned by repeating the process (S11), the termination condition is satisfied (S19: YES). The burner air supply rate deviation that satisfies the termination condition is treated as an appropriate solution obtained by the search, and the controller 90 transitions the process to S51.

[0049] Details of S51 and S53 will be explained. The controller 90 specifies the target burner air supply rate (S51). As a specific example, the controller 90 specifies the target burner air supply rate based on the deviation of the burner air supply rate that satisfied the termination condition (S11) and the current burner air supply rate. The controller 90 controls various dampers so that the target burner air supply rate specified in S51 is realized. As a more specific example, the opening control of the wind box damper 28, the opening control of each air damper 18, and the opening control of the additional air adjustment damper 26 are controlled, and the target burner air supply rate is supplied to the burner arrangement area 4.

[0050] After executing S53, the controller 90 returns the process to S5. If the NOx emissions are equal to or less than the specified value (S5: YES), the controller 90 ends the burner air amount control process. In another embodiment, a virtual deviation may be applied to the supply amount of additional air in addition to the burner air supply amount in S11. That is, the total amount of supplied air may be maintained constant, and a virtual deviation may be applied to the distribution (AA rate) between the burner air supply amount and the additional air supply amount. In this case, in S53, the opening degrees of various dampers are controlled so that the specified AA rate is achieved. Furthermore, it is not necessary to acquire the UBC amount in S13, and the termination condition in S19 does not have to include the UBC amount being equal to or less than the specified carbon amount.

[0051] <Example of burner air amount control process according to the second embodiment> Fig. 6 is a flowchart showing a burner air amount control process according to a second embodiment. In the flowchart of this figure, the same step numbers are assigned to steps that are the same as those in the flowchart shown in Fig. 5. In the second embodiment, as in the first embodiment, the burner air supply amount is controlled based on the residual ammonia characteristic value. In the burner air amount control process according to the second embodiment, S21 to S27 are executed instead of S11 to S19 (see Fig. 5), which are simulation processes. In S21 to S27, the adjustment amount of the burner air supply amount according to the residual ammonia amount is specified. Details thereof will be explained below.

[0052] When the controller 90 determines that the NOx emission amount exceeds the specified value (S5: NO), it acquires a predetermined value, which is a threshold value for determining whether the amount of residual ammonia is large or small (S21). This predetermined value is acquired based on the type of coal contained in the second fuel, the furnace temperature, and the residence time of the first fuel and the second fuel in the furnace, for example, by referring to a function formula or a data table. The details of S21 will be described later.

[0053] 6, the controller 90 determines whether the amount of residual ammonia is equal to or less than the predetermined value acquired in S21 (S23). The amount of residual ammonia may be acquired based on, for example, the output result of the ammonia measuring instrument 9, or may be acquired based on the burner section air ratio, etc.

[0054] If it is determined that the residual ammonia amount is equal to or less than the predetermined value (S23: YES), it is assumed that the determination in S5 that the NOx emissions amount exceeds the specified value is due in part to an insufficient residual ammonia amount. In other words, it is assumed that the NOx emissions exceed the specified value because the actual residual ammonia concentration in the boiler 10 is lower than the residual ammonia concentration exemplified at point P or point Q in FIG. 3. In this case, the controller 90 determines the amount of decrease in the burner air supply rate to make the residual ammonia amount exceed the predetermined value (S25). The controller 90 determines the target burner air supply rate based on the determination result in S25 and the current burner air supply rate (S51), and executes S53 similar to that in the first embodiment. As a result, the target burner air supply rate increases, and the residual ammonia amount decreases. After executing S53, the controller 90 returns the process to S5.

[0055] If it is determined that the residual ammonia amount exceeds the predetermined value (S23: NO), it is assumed that the determination in S5 that the NOx emission amount exceeds the predetermined value is due in part to an excessive residual ammonia amount. In other words, it is assumed that the NOx emission amount exceeds the predetermined value because the actual residual ammonia concentration in the boiler 10 is higher than the residual ammonia concentration illustrated at point Q in FIG. 3 . In this case, the controller 90 determines an increase in the burner air supply rate so that the residual ammonia amount is equal to or less than the predetermined value (S27). The controller 90 determines a target burner air supply rate based on the determination result in S27 and the current burner air supply rate (S51), and executes S53 similar to the first embodiment. As a result, the target burner air supply rate increases, and the residual ammonia amount decreases. With the above configuration, the burner air supply rate is controlled according to the residual ammonia amount inside the furnace 11, thereby more reliably suppressing NOx emissions.

[0056] Details of S21 will be explained. The burner air amount control process is continuously executed while the boiler 10 is operating. While the boiler 10 is operating, combustion conditions such as the type of coal, the furnace temperature, and the residence time of the first fuel and the second fuel in the furnace are changed. In this case, the amount of residual ammonia that minimizes NOx emissions may also change (see FIG. 3), so in S21 the controller 90 changes the setting of a predetermined value that serves as a criterion for determining whether the amount of residual ammonia is large or small. As a more specific example, when the coal type is changed during operation of the boiler 10, data indicating the change in coal type is input to the controller 90, and the predetermined value is acquired based on the data. In this case, the data indicating the change in coal type corresponds to an instruction to change the predetermined value. Alternatively, if the in-furnace temperature is changed as a result of a demand to change the boiler load being input to the controller 90, the predetermined value may be set and changed in accordance with the change. In this case, the demand to change the boiler load corresponds to an instruction to change the predetermined value. Also, when the in-furnace residence temperatures of the first fuel and the second fuel are changed, the predetermined value may be set and changed in accordance with the change. According to the above configuration, the amount of residual ammonia can be controlled in accordance with the combustion conditions of the ammonia-fueled boiler system 1, thereby more reliably suppressing NOx emissions.

[0057] <Example of burner air amount control process according to the third embodiment> 7 and 8, a burner air amount control process according to the third embodiment will be illustrated. In the third embodiment, a learning model 95 is used to identify the target burner air supply amount.

[0058] 7 is a conceptual diagram showing the configuration of a controller 90 according to one embodiment of the present disclosure. The controller 90 includes a control device 91 and an arithmetic device 92. In one embodiment, the arithmetic device 92 executes arithmetic processing using a learning model 95, and the control device 91 executes the remaining control processing for operating the boiler 10.

[0059] The control device 91 includes a processor 91A (hereinafter also referred to as the control processor 91A) and a memory 91B that stores a boiler operation program. The control processor 91A executes control processing for operating the boiler 10 based on the boiler operation program. The arithmetic device 92 includes a processor 92A (hereinafter also referred to as the calculation processor 92A), which may be, for example, a GPU, a CPU, or an FPGA, and a memory 92B that stores a learning model 95. The calculation processor 92A is configured to input specified data to the learning model 95 in response to a command from the control processor 91A and output output data of the learning model 95 to the control device 91. In this case, the control processor 91A sends input data of the learning model 95 to the calculation processor 92A, and the output data of the learning model 95 is sent from the calculation processor 92A to the control processor 91A.

[0060] The learning model 95 is configured to output, when characteristic values ​​indicating the combustion conditions in the furnace 11 are input, NOx emissions that are below a specified value and other process values. The characteristic values ​​indicating the combustion conditions that serve as input data for the learning model 95 include a numerical value indicating the type of coal contained in the second fuel, the burner air supply rate, the AA rate, and the supply rates of the first fuel and the second fuel. The process values ​​that serve as output data for the learning model 95 include the UBC amount, the temperature of the heat transfer surface, and the steam temperature. The training data that associates these input data with the output data is obtained, for example, based on various measurement results during the operation of the ammonia-fueled boiler system 1 by an operator. In some embodiments, the weighting coefficients of the neural network that constitutes the learning model 95 may be adjusted in response to the input of the training data.

[0061] Figure 8 is a flowchart showing the burner air amount control process according to the third embodiment. In this figure, the same steps as those in the burner air amount control process of Figure 5 are given the same step numbers. In the burner air amount control process according to the third embodiment, steps S31 to S39 are executed instead of steps S11 to S19 (see Figure 5).

[0062] When the controller 90 determines that the NOx emissions exceed the specified value (S5: NO), it acquires an evaluation function and an evaluation reference value (S31). Both the evaluation function and the evaluation reference value are used to determine whether the output data of the learning model 95 is appropriate. The evaluation function is configured to assign weights to various parameters included in the output data from the learning model 95 and score the output data. In this embodiment, multiple types of evaluation functions are stored in the memory 91B of the control device 91, and each evaluation function has a different scoring logic (i.e., a different weighting pattern for various parameters). Each evaluation function reflects a weighting pattern based on the properties that should be prioritized depending on the operating conditions of the ammonia-fueled boiler system 1, such as environmental friendliness, economy, stability, or balance. In this embodiment, the operator selects an evaluation function from these according to the desired property. Meanwhile, the evaluation reference value includes a specified carbon amount for determining whether the UBC amount is appropriate and an evaluation threshold for determining whether the score output from the evaluation function is appropriate. The evaluation reference value may be determined by the controller 90 based on a process value acquired by a measuring instrument, such as the temperature inside the furnace.

[0063] The controller 90 virtually assigns deviations to the characteristic values ​​indicating the current combustion conditions of the ammonia-fueled boiler system 1 (S33). The controller 90 inputs the characteristic values ​​to which deviations have been assigned in S33 into the learning model 95, and acquires various parameters (NOx emissions and process values) output from the learning model 95 (S35). At this time, the NOx emissions included in the various parameters are below a specified value. This is because the learning model 95 has been machine-trained to achieve this. Next, the controller 90 inputs the various parameters acquired in S35 into the evaluation function acquired in S31 (S37).

[0064] The controller 90 determines whether the output data of the learning model 95 obtained in S35 and the score obtained from the evaluation function in S37 satisfy a specified condition (S39). The specified condition is that the UBC amount obtained in S35 is equal to or less than a specified carbon amount, and the score obtained from the evaluation function in S37 is equal to or greater than the evaluation reference value obtained in S31. If the specified condition is not satisfied (S39: NO), the controller 90 returns the process to S33. If the specified condition is satisfied (S39: YES), the deviation virtually assigned in S33 is deemed appropriate, and an appropriate deviation for the burner air supply rate is determined. The controller 90 determines a target burner air supply rate based on the deviation and the current burner air supply rate (S51). The controller 90 then proceeds to S53. According to the above configuration, an appropriate target burner air supply rate can be determined by using the learning model 95.

[0065] <Other> 9A and 9B are conceptual diagrams showing an additional air port 17 according to some embodiments. The additional air port 17 includes a primary additional air nozzle 205 and a secondary additional air nozzle 214 surrounding the primary additional air nozzle 205. A primary flow straightener 204 formed of a porous plate is provided inside the primary additional air nozzle 205. The primary additional air passes through the primary flow straightener 204, resulting in a straightened flow and being supplied to the combustion completion zone 16 of the furnace 11. The amount of primary additional air supplied is adjusted by changing the opening of a primary damper 203 located upstream of the primary flow straightener 204 using the controller 90. A secondary damper 212 is provided at the secondary additional air nozzle 214, and a secondary flow straightener 213 formed of a porous plate is provided downstream of the secondary damper 212. A guide vane 215 is provided at the outlet of the secondary additional air nozzle 214. The guide vane 215 extends into the furnace 11 and also extends horizontally outward so as to be spaced apart from the primary additional air nozzle 205. The secondary additional air passing through the secondary damper 212, the opening of which is adjusted by the controller 90, is rectified via the secondary rectifier 213 and then spread horizontally by the guide vane 215 before being supplied to the combustion completion zone 16. For example, in the burner air amount control process shown in FIG. 5, the openings of the primary damper 203 and the secondary damper 212 may be controlled in conjunction with the execution of S53. The primary damper 203 and the secondary damper 212 are specific examples of the additional air adjusting damper 26 shown in FIG. 1.

[0066] In the additional air port 17 having the above configuration, straight-flowing primary additional air is supplied from the primary additional air nozzle 205, and horizontally spreading secondary additional air is supplied from the secondary additional air nozzle 214. In an embodiment in which the boiler 10 is an opposed-fired boiler, the controller 90 adjusts the supply amounts of straight-flowing primary additional air and horizontally spreading secondary additional air by changing the opening degrees of the primary damper 203 and the secondary damper 212. This allows the additional air port 17 to uniformly supply additional air to the combustion completion zone 16, thereby suppressing NOx emissions.

[0067] Although not shown in detail, in an embodiment in which the boiler 10 is a swirl combustion boiler, a tilt mechanism (angle adjustment mechanism) may be provided to change the angle of the additional air blown out from the additional air port 17, for example, up or down. The tilt mechanism is driven and controlled by the controller 90. The time required for the gas flowing from the main combustion region 15 to the combustion completion region 16 to mix with the additional air from the additional air port 17 is appropriately adjusted by driving the tilt mechanism with the controller 90. This prevents the gas and the additional air from mixing too quickly, and prevents the local generation of high-temperature gas in the furnace 11. This prevents the generation of an overly rich flame, thereby reducing NOx emissions.

[0068] <Summary> Some embodiments of the present disclosure can be understood as follows, for example.

[0069] 1) At least one embodiment of the ammonia-fueled boiler system (1) of the present disclosure includes: a furnace (11) having a burner arrangement area (4) and an additional air injection area (5) located downstream of the burner arrangement area; an ammonia burner (first burner 81) provided in the burner arrangement area for burning a first fuel containing ammonia fuel; a controller (90) configured to specify a target burner air supply amount to the burner arrangement area based on a characteristic value correlated with the amount of residual ammonia in the combustion of the first fuel, such that NOx emissions are equal to or less than a specified value, and to control the burner air supply amount to the burner arrangement area so as to realize the specified target burner air supply amount; Equipped with.

[0070] According to the inventors' findings, ammonia remaining in the burner installation area may convert to Nox in the additional air injection area. Therefore, it is necessary to prevent the amount of residual ammonia from becoming excessive. On the other hand, if the amount of residual ammonia is too low, there will be a shortage of ammonia as a reducing agent in the furnace, resulting in excessive Nox. Therefore, the amount of residual ammonia must be an optimal value to suppress the amount of Nox generated. According to the configuration of 1) above, the controller determines a target burner air supply amount based on the amount of residual ammonia so that the NOx emissions will be below a specified value. The controller then controls the burner air supply amount to achieve the specified target burner air supply amount. As a result, for example, when the amount of residual ammonia is relatively high, the burner air supply amount is increased. Since the burner air ratio is increased, NOx emissions can be reduced to a set value or less. Conversely, when there is too little residual ammonia, there will be a shortage of ammonia as a reducing agent, which could result in excessive NOx emissions, the burner supply air amount is reduced. Since the burner air ratio is reduced, NOx emissions can be reduced to a specified value or less. As a result, an ammonia-fueled boiler system capable of suppressing Nox emissions is realized.

[0071] 2) In some embodiments, the ammonia-fueled boiler system described in 1) above, The controller is configured to control the ratio between the burner air supply amount and the additional air supply amount supplied to the additional air injection area based on the characteristic value so that the NOx emission amount is equal to or less than the specified value.

[0072] According to the above configuration 2), when the amount of residual ammonia is relatively small, the amount of additional air supplied is increased, thereby making it possible to suppress the generation of unburned fuel while suppressing NOx emissions.

[0073] 3) In some embodiments, the ammonia-fueled boiler system according to 1) or 2) above, The controller When the amount of residual ammonia is equal to or less than a predetermined value, the burner air supply amount is controlled to be reduced; When the amount of residual ammonia exceeds the predetermined value, the burner air supply amount is controlled to increase.

[0074] According to the above configuration 3), the burner air supply amount is controlled in accordance with the amount of ammonia remaining in the furnace, so that NOx emissions can be more reliably suppressed.

[0075] 4) In some embodiments, the ammonia-fueled boiler system described in 3) above, The controller is configured to change the setting of the predetermined value in response to a change instruction.

[0076] According to the above configuration 4), the amount of residual ammonia can be controlled in accordance with the operating conditions of the ammonia boiler system, so that the amount of Nox emissions can be more reliably suppressed.

[0077] 5) In some embodiments, the ammonia-fueled boiler system according to any one of 1) to 4) above, The controller is configured to determine the target burner air supply amount based on the temperature of gas heading toward the additional air injection area in the furnace and the characteristic value correlated with the amount of residual ammonia.

[0078] According to the findings of the inventors, the amount of residual ammonia correlates not only with the burner air supply rate but also with the temperature of the gas heading toward the additional air injection area. According to the configuration of 5) above, the target burner air supply rate for optimizing the amount of residual ammonia can be more accurately determined based on the characteristic value correlated with the amount of residual ammonia and the gas temperature. Therefore, NOx emissions can be more reliably suppressed.

[0079] 6) In some embodiments, the ammonia-fueled boiler system according to any one of 1) to 5) above, a coal burner (second burner 82) provided in the burner arrangement area for burning a second fuel including coal; The controller is configured to control the amount of burner air supplied to the burner arrangement area so that the NOx emissions are below the specified value and the amount of unburned carbon generated in the furnace is below a specified carbon amount.

[0080] According to the findings of the inventors, the amount of unburned carbon produced varies depending on the amount of air supplied to the burner. According to the configuration of 6) above, the generation of both NOx and unburned carbon can be suppressed by controlling the amount of air supplied to the burner.

[0081] 7) At least one embodiment of the ammonia-fueled boiler system (1) of the present disclosure includes: a furnace (11) having a burner arrangement area (4) and an additional air injection area (5) located downstream of the burner arrangement area; an ammonia burner (first burner 81) provided in the burner arrangement area for burning fuel containing ammonia; a controller (90) configured to specify a target burner air supply amount using a learning model (95) for outputting a NOx emission amount and other process values ​​that are equal to or less than a specified value when a characteristic value indicating a combustion condition in the furnace is input, and to control the burner air supply amount to the burner arrangement area so as to realize the specified target burner air supply amount; An ammonia-fueled boiler system comprising:

[0082] According to the above configuration 7), the learning model can be used to identify an appropriate target burner air supply amount. [Explanation of symbols]

[0083] 1: Ammonia fuel boiler system 4: Burner placement area 5: Additional air injection area 10: Boiler 11: Furnace 81: First burner (ammonia burner) 82: Second burner (coal burner) 90: Controller 95: Learning model

Claims

1. a furnace having a burner arrangement area and an additional air injection area located downstream of the burner arrangement area; an ammonia burner provided in the burner arrangement area for burning a first fuel containing ammonia fuel; a controller configured to specify a target burner air supply amount to the burner arrangement area based on a characteristic value correlated with the amount of residual ammonia in the combustion of the first fuel, such that NOx emissions are equal to or less than a specified value, and to control the burner air supply amount to the burner arrangement area so as to realize the specified target burner air supply amount; An ammonia-fueled boiler system comprising:

2. The controller is configured to control the ratio between the burner air supply amount and the additional air supply amount supplied to the additional air injection area based on the characteristic value so that the NOx emission amount is equal to or less than the specified value.

10. The ammonia-fueled boiler system of claim 1.

3. The controller When the amount of residual ammonia is equal to or less than a predetermined value, the burner air supply amount is controlled to be reduced; When the amount of residual ammonia exceeds the predetermined value, the burner air supply amount is controlled to be increased.

3. The ammonia-fueled boiler system according to claim 1 or 2.

4. The controller is configured to change the setting of the predetermined value in response to a change instruction.

4. The ammonia-fueled boiler system of claim 3.

5. The controller is configured to determine the target burner air supply amount based on the temperature of gas heading toward the additional air injection area in the furnace and the characteristic value correlated with the amount of residual ammonia.

5. An ammonia-fueled boiler system according to any one of claims 1 to 4.

6. a coal burner provided in the burner arrangement area for burning a second fuel including coal; The controller is configured to control the amount of burner air supplied to the burner arrangement area so that the NOx emission amount is equal to or less than the specified value and so that the amount of unburned carbon generated in the furnace is equal to or less than a specified carbon amount.

6. An ammonia-fueled boiler system according to any one of claims 1 to 5.

7. a furnace having a burner arrangement area and an additional air injection area located downstream of the burner arrangement area; an ammonia burner provided in the burner arrangement area for burning a first fuel containing ammonia fuel; a controller configured to, when a characteristic value indicating a combustion condition in the furnace is input, specify a target burner air supply amount using a learning model for outputting a NOx emission amount and other process values ​​that are equal to or less than a specified value, and to control the burner air supply amount to the burner arrangement area so as to realize the specified target burner air supply amount; Equipped with An ammonia-fueled boiler system, wherein the characteristic values ​​input to the learning model include the supply amount of the first fuel.

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