TW202246701A - Boiler operation method and control device for boiler - Google Patents

Abstract

This boiler operation method comprises: a step for combusting another fuel apart from an ammonia fuel in a furnace; a step for determining whether determination conditions are satisfied, said determination conditions being that an air ratio, which is a ratio of an air supply amount to the furnace relative to a theoretical air amount required for combusting the other fuel supplied to the furnace, is no greater than an upper limit value, and that a representative temperature within the furnace is no less than a lower limit value; and a step for beginning supply of the ammonia fuel to the furnace if the determination conditions are at least satisfied. Moreover, the upper limit value of the air ratio that constitutes one of the determination conditions is 0.8 or less.

Description

Boiler operating method and boiler control device

The present invention relates to a boiler operating method and a boiler control device. This case claims priority based on Japanese Patent Application No. 2021-059232 filed with the Japan Patent Office on March 31, 2021, the contents of which are incorporated herein.

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 boiler disclosed in Patent Document 1, the discharge of NOx is not suppressed by supplying ammonia fuel to the upper burner among the multiple burners. [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2020-112280

[Problem to be solved by the invention]

According to the knowledge of the inventors, in order to suppress the emission of NOx, it is preferable to adjust the combustion environment in the boiler using another fuel before starting the supply of ammonia fuel. However, Patent Document 1 does not specifically disclose such a configuration.

The present invention relates to a method for operating a boiler and a control device for the boiler, which start the supply of ammonia fuel under the condition that the generation of NOx can be suppressed. [Technical means to solve the problem]

A boiler operating method according to at least one embodiment of the present invention includes: the step of burning a fuel other than ammonia fuel in a furnace; Judging that the ratio of the amount of air supplied to the furnace to the theoretical amount of air necessary to combust the other fuel supplied to the furnace, that is, the air ratio, is below the upper limit, and the representative temperature inside the furnace is above the lower limit The step of judging whether the condition is satisfied; and Initiating the step of supplying the aforementioned ammonia fuel to the aforementioned furnace when the aforementioned judging condition is at least satisfied, The upper limit of the air ratio constituting the determination condition is 0.8 or less.

A boiler control device according to at least one embodiment of the present invention, It has a furnace and a supply system configured to supply ammonia fuel and other fuels to the furnace, and the control device for the boiler includes: a combustion command generation unit that generates another fuel combustion command for burning the aforementioned other fuel in the furnace; A judging unit for judging that the ratio of the amount of air supplied to the furnace to the theoretical amount of air necessary to combust the other fuel supplied to the furnace, that is, the air ratio, is below an upper limit, and the representative in the furnace Whether the judgment condition that the temperature is above the lower limit value is satisfied; and an ammonia supply command generation unit that determines at least the satisfaction of the determination condition by the determination unit, and generates an ammonia supply start command for causing the supply system to start supplying the ammonia fuel to the furnace, The upper limit of the air ratio constituting the determination condition is 0.8 or less. [Effect of Invention]

According to the present invention, it is possible to provide a method for operating a boiler and a control device for a boiler, which start the supply of 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 or exclusive combustion of ammonia 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 and at least one burner unit 30 provided on the furnace wall 19 . 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. In addition, in at least one burner unit 30 , the burner is an ammonia burner 50 that injects liquid ammonia into the furnace 20 in a liquid state. The ammonia burner 50 may inject only liquid ammonia. Alternatively, the ammonia burner 50 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 50 . The second burner unit 32 and the third burner unit 33 may or may not contain the ammonia burner 50 . In other embodiments, the ammonia burner 50 may include only the second burner unit 32 or the third burner unit 33 . In addition, any burner unit 30 may include a fuel burner 35 (see FIG. 4 ) for injecting carbon-containing fuel into the furnace 20 . 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 supply system 15 of one embodiment supplies secondary air (extra air) through the supply unit 4 provided on the furnace wall 19 on the downstream side of the burner unit 30 .

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. 5 ) 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.

In one embodiment, the conditions for starting supply of the ammonia fuel are usage judgment conditions. The judgment conditions are satisfied when the air ratio is not more than the upper limit and the representative temperature in the furnace 20 is not less than the lower limit. The air ratio constituting the judgment condition is the ratio of the air supply amount to the furnace 20 to the theoretical air amount necessary to combust other fuel supplied to the furnace 20 . In one embodiment, the aforementioned air supply to the furnace 20 does not include secondary air (additional air). That is, in this example, the air ratio constituting the judgment condition is the value obtained by multiplying the total air ratio by the supply ratio of air other than secondary air among all the air supplied to the furnace 20 . Specifically, the air ratio constituting the judgment condition (hereinafter sometimes referred to as the burner unit air ratio) is defined by the following equation (1). λ _b =λ×(100-AA)/100 ・・・Equation (1) In Equation (1), λ _b is the burner part air ratio, λ is the total air ratio, and AA is the total air supply to boiler 2 The supply ratio of secondary air in the volume. Also, the total air ratio (λ) is defined by Expression (2), Expression (3), and Expression (4). λ=Q _Air ／Q _x・・・Formula (2) Q _x =Q _mf ×A _mf・・・Formula (3) A _mf =(100-X)／100×A _car +X／100×A _NH3・・・Equation (4) In Equation (2) to Equation (4), Q _Air is the total air supply amount. 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 ammonia mixed combustion (mixed 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, and A _NH3 is the theoretical air volume of the ammonia fuel. Formulas (1) to (3) are formulas that are also applicable to the mixed combustion of ammonia fuel and carbon-containing fuel. In addition, in order to obtain the air ratio constituting the determination condition (that is, the air ratio of the burner portion before the start of ammonia fuel supply), each of X and A _NH3 is set to 0, and Q _mf is set to only carbon-containing fuel. Supply amount, and apply formula (1) ~ formula (3). Hereinafter, λ _b defined by the formula (1) may be referred to as the burner unit air ratio not only before the start of ammonia fuel supply but also during ammonia mixed combustion or ammonia exclusive combustion.

In one embodiment, the upper limit of the burner portion air ratio constituting the determination condition 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 constituting the determination condition 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 determination condition is preferably 0.6 to 0.8, more preferably 0.6 to 0.7.

In one embodiment, the representative temperature in the furnace 20 constituting the judgment condition is the aforementioned nose temperature. The lower limit of nasal temperature is above 1120°C. According to the knowledge of the inventors, if the nose temperature is 1120°C or higher, the gas temperature is 1400°C or higher, and the thermal decomposition of ammonia can be sufficiently performed with a relatively short residence time in the furnace. Then, the supply of ammonia fuel is started when the nose temperature is 1120° C. or higher, whereby the generation of NOx can be suppressed. In addition, the residence time in the furnace is the time until the fuel reaches the nose 11 after being injected into the furnace 20 . The residence time in the furnace can be calculated based on, for example, the air flow rate of primary air and secondary air, the supply flow rate of carbonaceous fuel, the cross-sectional area of the furnace 20 (fixed value), and the height of the furnace 20 (fixed value). Therefore, the residence time in the furnace can be obtained based on the measurement results of the plurality of flowmeters included in the measurement system 9 .

The determination condition in one embodiment may also include the condition that the residence time in the furnace of other fuel (carbon-containing fuel in this example) is 0.5 seconds or more. According to the findings of the inventors, it is known that the ammonia fuel charged into the furnace 20 can be sufficiently thermally decomposed if the residence time of ammonia in the furnace is 0.5 seconds or more. The supply of ammonia fuel is started when the residence time of other fuels in the furnace is 0.5 seconds or more, so the residence time of ammonia in the furnace can also be 0.5 seconds or more, which can reduce the amount of NOx produced. The longer the residence time in the furnace, the more favorable the combustion environment for thermal decomposition of ammonia fuel can be formed. However, in the boiler 2 with general specifications used in thermal power plants, the residence time of fuel (including other fuels and ammonia fuel) in the furnace is as long as 2.0 seconds to 3.0 seconds, for example. Therefore, the residence time in the furnace constituting the judgment condition may be 0.5 seconds or more and 3.0 seconds or less, or may be 0.5 seconds or more and 2.0 seconds or less.

Fig. 2 is a flow chart showing a method of operating the boiler 2 according to one embodiment. Hereinafter, "step" may be abbreviated as "S".

In the operation method of the boiler 2 of one embodiment, first, combustion of fuel other than ammonia fuel is started in the furnace 20 (S11). In one embodiment, when the load on the boiler 2 increases (for example, when the boiler 2 is started), the supply system 15 supplies fuel other than ammonia fuel (carbon-containing fuel in this example) to the burner unit 30 . Also, the load on the boiler 2 is, for example, the heat of steam generated by the boiler 2 .

Next, it is judged whether or not the above-mentioned judgment condition is satisfied (S13). In S13 of one embodiment, it is judged that the air ratio of the burner part is 0.8 or less, and the nose part temperature which is a representative temperature in the furnace 20 is 1120 degrees C or more. Whether the judgment condition is satisfied is judged based on the measurement result of the measurement system 9 . In one embodiment, when the load on the boiler 2 increases, combustion using another fuel is performed in the furnace 20 until the determination condition is satisfied (S13: NO). Thereby, the temperature inside the furnace 20 rises. According to the knowledge of the inventors, when the heat load of the boiler 2 increases, the temperature of the gas in the furnace 20 is relatively low, and if ammonia fuel is supplied to the furnace 20 at this time, excessive NOx is generated. When the load on the boiler 2 increases, the supply of ammonia fuel is not started until the determination condition is satisfied, so that the generation of NOx can be suppressed. In addition, when the load of the boiler 2 increases, the concept includes the time when the heat load of the boiler (2) decreases and then increases. In another embodiment, in S13, instead of determining whether the burner portion air ratio is 0.8 or less, it may be determined whether the burner portion air ratio is 0.7 or less. In addition, the determination condition in S13 may include the condition that the residence time of other fuels in the furnace is 0.5 seconds or more. In this case, the residence time in the furnace of other fuel is acquired based on the measurement result of the measurement system 9 . Also, whether or not a condition different from the judgment condition is satisfied may be judged together in S13.

When it is judged that at least the judgment condition is satisfied (S13: YES), the supply of ammonia fuel is started (S15). In one embodiment, the supply system 15 supplies the ammonia fuel to the burner unit 30 together with the carbon-containing fuel, and the mixed combustion of the ammonia fuel and the carbon-containing fuel is performed in the furnace 20 . At this time, the mixed combustion rate of ammonia in terms of heat is, for example, 20% or more. According to the knowledge of the inventors, when the mixed combustion rate of ammonia and other fuels in terms of heat is 20% or more, the amount of NOx generated in the furnace 20 tends to increase. Therefore, it is significant to reduce the amount of NOx generated when the ammonia co-combustion with a co-combustion rate of 20% or more is performed. In one embodiment, the air ratio of the burner portion during mixed combustion of ammonia is 0.6 or more and 0.7 or less. According to the knowledge of the inventors, the amount of NOx emission can be suppressed by performing ammonia co-combustion under the condition that the air ratio of the burner portion is 0.6 to 0.7.

Fig. 3 is a cross-sectional view showing the structure of an ammonia burner 50 according to an embodiment. As mentioned above, the ammonia fuel supplied to the boiler 2 is liquid ammonia as an example. The ammonia burner 50 is equipped with: an ammonia supply path 52, which is supplied with liquid ammonia from the supply system 15 (refer to FIG. 1 ); and an ammonia injection nozzle 54, which injects the liquid ammonia supplied from the ammonia supply path 52 into Spray to the inside of the furnace 20. The ammonia burner 50 is a single-fluid nozzle for injecting liquid ammonia in a liquid state without using an auxiliary fluid. More specifically, the ammonia burner 50 is a swirl injection nozzle (swirl atomizer) that makes the injected liquid ammonia into a liquid film in a diffused shape. Alternatively, the ammonia burner 50 may be a fan nozzle that makes the injected liquid ammonia into a sheet-like liquid film, or a general injection type sprayer that injects liquid ammonia in a simple liquid jet flow state may be used. Regardless of the embodiment, the liquid ammonia sprayed into the furnace 20 is easily atomized, and the liquid ammonia is easily vaporized in the combustion space 7 .

The ammonia burner 50 of one embodiment further includes a mechanism 60 having a flame-preserving effect for maintaining the combustion flame generated in the furnace 20 . In the case of using flame-retardant liquid ammonia as a fuel, there is a possibility of flameout in the furnace 20 . In order to avoid flameout, liquid ammonia needs to be vaporized in the furnace 20 for further thermal decomposition. At this point, the combustion flame is maintained by means of the mechanism 60 having the above-mentioned flame-preserving effect, whereby the liquid ammonia can obtain heat for gasification and thermal decomposition, so the flameout in the furnace 20 can be suppressed.

In one embodiment, the mechanism 60 having an anti-inflammatory effect is a cyclone type. As a more specific example, the mechanism 60 having an anti-inflammatory effect includes an inner cylinder 62 in which the ammonia injection nozzle 54 is arranged, an outer cylinder 64 arranged to surround the inner cylinder 62 , and a swirler 65 . The outer cylinder 64 of one embodiment includes a first outer cylinder 64A surrounding the inner cylinder 62 and a second outer cylinder 64B surrounding the first outer cylinder 64A. Between the first outer cylinder 64A and the inner cylinder 62, an air supply path 63A communicating with the inside of the furnace 20 is formed. Similarly, an air supply path 63B communicating with the inside of the furnace 20 is also formed between the first outer cylinder 64A and the second outer cylinder 64B. The air flowing through the air supply paths 63A and 63B is primary air supplied from the supply system 15 (see FIG. 1 ). The swirler 65 is provided in the air supply path 63A, and imparts a swirl force to the air flowing in the air supply path 63A. The air supplied to the furnace 20 from the air supply path 63A is given a swirl force (arrow B) by the swirler 65 . Thereby, the mixing of the liquid ammonia injected from the ammonia injection nozzle 54 and the air is promoted. Then, the diffusion of liquid ammonia is promoted inside the furnace 20, and the thermal decomposition of the liquid ammonia in the furnace 20 is facilitated. In addition, in other embodiments, the mechanism 60 having an anti-inflammatory effect may be a diffuser type instead of a cyclone type. In addition, the ammonia burner 50 does not have to include the mechanism 60 having an anti-inflammatory effect.

Fig. 4 is an explanatory diagram of a specific structure of a burner unit 30 according to an embodiment. The burner unit 30 shown in FIG. 4 is switched to ammonia-only combustion after the mixed combustion rate of ammonia becomes about 50% in terms of heat. The burner unit 30 is an existing burner unit as an example. Therefore, some components of the burner unit 30 may not be used. Alternatively, this constituent element may be used only in ammonia mixed combustion, and may not be used in ammonia-only combustion. The burner unit 30 of each stage has five injection patterns 40 . Each injection pattern 40 supplies fuel or air to the furnace 20 . As an example, each injection mode 40 is any one of the aforementioned ammonia burner 50 , the fuel burner 35 for injecting carbon-containing fuel, or the air nozzle 42 for injecting primary air. The first burner unit 31 , the second burner unit 32 , and the third burner unit 33 of the burner unit 30 all have the same structure. Specifically, the two outermost injection patterns 40 are air nozzles 42 , and the injection pattern 40 in the center is an ammonia burner 50 . Furthermore, the injection pattern 40 between the ammonia burner 50 and the upper air nozzle 42 is the fuel burner 35, and the remaining one injection pattern 40 is not used. In the example of FIG. 4, the fuel burners 35 of the burner unit 30 are all coal burners that inject pulverized coal as a carbon-containing fuel. In one embodiment, the fuel injected from the ammonia burner 50 of the first burner unit 31 is only liquid ammonia, and the fuel injected from the ammonia burner 50 of the second burner unit 32 and the third burner unit 33 The fuel is oil and liquid ammonia.

The burner unit 30 operates, for example, as follows. First, combustion using carbonaceous fuel is performed. Specifically, the air nozzle 42 injects primary air, and the fuel burner 35 injects pulverized coal. At this time, the ammonia burner 50 of the first burner unit 31 does not operate, and each of the ammonia burners 50 of the second burner unit 32 and the third burner unit 33 injects oil. Thereafter, liquid ammonia is injected from the ammonia burner 50 of the first burner unit 31 , and the fuel injected from the remaining two ammonia burners 50 is switched from oil to liquid ammonia. Thereby, mixed combustion of ammonia is performed in the furnace 20 . Thereafter, the injection of pulverized coal is stopped at the three fuel burners 35 of the burner unit 30 , and the fuel injected to the furnace 20 becomes only liquid ammonia from the three ammonia burners 50 . Thereby, the combustion in the furnace 20 is switched from the mixed combustion of ammonia to the exclusive combustion of ammonia.

Fig. 5 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 dedicated combustion of ammonia begins in the stove 20 with a dedicated combustion start command for ammonia. 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 judged that the above judgment condition is satisfied based on the measurement result of the measurement system 9 . Furthermore, the processor 91 of one embodiment starts the ammonia-only combustion command when it determines that the ammonia-only combustion condition for starting the ammonia-only 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 after starting ammonia mixed combustion, when a predetermined parameter reaches a set value after a predetermined input operation is performed by an operator, or etc. combinations etc.

The supply system 15 includes: a primary air supply system 110 for supplying primary air, a secondary air supply system 120 for supplying secondary air, an ammonia supply system 100 for supplying liquid ammonia, an oil supply system 80 for supplying oil, and A pulverized coal supply system 70 for supplying pulverized coal. 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 secondary air is supplied to the 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 secondary air supply system 120 is connected to the supply part 4 . The air supply line 122 is provided with a flow rate adjustment valve 126 for adjusting the flow rate of the secondary 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 50, an ammonia tank 101 storing liquid ammonia, an ammonia supply line 102 connecting the ammonia tank 101 and the ammonia burner 50, 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 50, 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 ammonia burner 50 and a supply state in which liquid ammonia is supplied to all the ammonia burners 50 . 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 50 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 50, 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 50 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 50 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 fuel burner 35 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 each fuel burner 35 of 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 fuel burner 35 (see FIG. 4 ) which operates as a coal burner in a supply state.

The measurement system 9 includes: an air flow meter 114 used to measure the flow rate of the primary air supplied by the primary air supply system 110 , an air flow meter 114 used to measure the flow rate of the secondary air supplied by the secondary air supply system 120 The flow meter 124, the ammonia flow meter 109 used to measure the flow of the ammonia fuel supplied by the ammonia supply system 100, the oil flow meter 84 used to measure the flow of the oil supplied by the oil supply system 80, used to measure The pulverized coal flow meter 74 for the flow rate of the 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 . Thereby, the processor 91 of one embodiment can judge whether the judgment condition is satisfied.

The boiler operation system 1 operates as follows, for example, by a control command sent from the processor 91 . First, the processor 91 transmits other fuel combustion commands to the supply system 15 . Thereby, the primary air supply system 110 and the secondary 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 50 of the first burner unit 31 is stopped, and the ammonia burner 50 of the second burner unit 32 and the third burner unit 33 inject oil. Thereafter, since the determination condition is satisfied, the processor 91 transmits an ammonia supply start command to the supply system 15 . 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-only combustion conditions are satisfied, the control device 5 transmits an ammonia-only combustion command to the supply system 15 . The pulverized coal supply system 70 changes to a supply stop state, and the fuel burner 35 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. 6 is a flowchart showing boiler operation control processing according to one embodiment. The boiler operation control process is started, for example, when an operator of the boiler operation system 1 inputs a start instruction.

In the boiler operation control process, first, the processor 91 generates another fuel combustion command (S51). In one embodiment, the processor 91 executes S51 when the load on the boiler 2 increases (for example, when the boiler 2 is started). The generated other fuel combustion command is transmitted to the supply system 15, whereby the combustion of carbon-containing fuel, which is an example of fuel other than ammonia fuel, is started. As a specific example, the supply system 15 and the burner unit 30 operate as described above, starting the combustion of oil and carbonaceous fuel. The processor 91 that executes S51 is an example of another fuel combustion instruction unit that generates an other fuel combustion instruction for burning another fuel (carbon-containing fuel in this example) in the furnace 20 .

Next, the processor 91 judges whether the judgment condition is satisfied based on the measurement result of the measurement system 9 (S53). The processor 91 that executes S53 is an example of a judging unit that judges whether or not a judging condition is satisfied. The judgment conditions in one embodiment include the following conditions (A) to (C), and when all of (A) to (C) are satisfied, the processor 91 judges that the judgment conditions are satisfied. (A) The ratio of the amount of air supplied to the furnace 20 to the theoretical amount of air necessary to combust another fuel (carbon-containing fuel in this example), that is, the air ratio is 0.8 or less. (B) The nose temperature, which is a representative temperature in the furnace 20, is 1120° C. or higher. (C) The residence time of other fuels in the furnace 20 is 0.5 seconds or more. Whether or not the condition (A) is satisfied is judged based on formulas (1) to (3) and the measurement results of the measurement system 9 . Whether or not the condition (B) is satisfied is judged based on the measurement result of the furnace thermometer 6 . Whether or not the condition (C) is satisfied is judged based on the measurement results of the measurement system 9 . The processor 91 is on standby until the determination condition is satisfied (S53: NO). In one embodiment, when the load on the boiler 2 increases, another fuel is burned in the furnace 20 until the determination condition is satisfied. Moreover, in another embodiment, the upper limit of the air ratio stipulated in the condition (A) may be 0.7.

When judging that the judging condition is satisfied (S53: YES), the processor 91 generates an ammonia supply start command (S55). The generated ammonia supply start command is transmitted to the supply system 15 . At this point, the supply system 15 and the burner unit 30 operate as previously described. The processor 91 that executes S55 is an example of an ammonia supply command generation unit that generates an ammonia supply start command for causing the supply system 15 to start supplying ammonia fuel to the furnace 20 . In one embodiment, the ammonia co-combustion rate (calorie conversion) of the boiler 2 is 20% or more and 50% or less. And, at this time, the burner part air ratio in the furnace 20 is 0.7 or less.

Next, the processor 91 judges whether or not the ammonia-only combustion conditions for performing ammonia-only combustion in the boiler 2 are satisfied (S57). The ammonia-only combustion condition in one embodiment is, for example, a certain period of time elapsed from the start of S53. The processor 91 is on standby until the ammonia-only combustion conditions are satisfied (S57: NO). During this period, mixed combustion of ammonia and other fuels is carried out in the boiler 2 .

When judging that the ammonia-only combustion conditions are satisfied (S57: YES), the processor 91 generates an ammonia-only combustion command. The generated ammonia-specific combustion commands are transmitted to the supply system 15 . The supply system 15 and burner unit 30 operate as previously described for the dedicated combustion of ammonia. In one embodiment, the air ratio of the burner portion during ammonia-only combustion is 0.9 or less. Thereby, during ammonia-only combustion, the respective emission amounts of carbon dioxide and NOx can be suppressed.

(Summarize) Hereinafter, the outline|summary is described about the operation method of the boiler 2 and the control apparatus 5 for boilers which concerns on some embodiments.

(1) A method for operating a boiler (2) according to at least one embodiment of the present invention, comprising: The step of burning fuel other than ammonia fuel in the furnace (20) (S11, S51); It is determined that the ratio of the air supply amount to the furnace (20) to the theoretical air amount necessary to burn the other fuel supplied to the furnace (20), that is, the air ratio (burner part air ratio) is an upper limit value Below, and the step of judging whether the representative temperature in the aforementioned stove (20) is more than the lower limit value is met (S13, S53); and Initiating the step (S15, S55) of supplying the aforementioned ammonia fuel to the aforementioned furnace (20) when the aforementioned judging condition is at least satisfied, The upper limit of the air ratio constituting the determination condition is 0.8 or less.

According to the findings of the inventors, if ammonia is burned in the furnace (20) under the condition that the air ratio (burner portion air ratio) constituting the judgment condition is 0.8 or less, it can effectively reduce the air temperature in the furnace (20). NOx produced. Furthermore, it was found that thermal decomposition of ammonia in the furnace (20) is necessary to suppress the generation of NOx, and this thermal decomposition is accelerated if the gas temperature in the furnace (20) is above a certain temperature. Also, the representative temperature within the furnace (20) is related to the gas temperature within the furnace (20). According to the configuration of (1) above, it is possible to realize the operation method of the boiler (2) which starts the supply of ammonia fuel under the condition that the generation of NOx is suppressed.

(2) In several embodiments, among the structures of the above-mentioned (1), When the heat load of the boiler (2) rises, the aforementioned other fuels are combusted until the aforementioned judgment conditions are satisfied (S13: NO, S53: NO). After the aforementioned judgment conditions are met, the aforementioned furnace (20 ) to supply the aforementioned ammonia fuel.

According to the findings of the inventors, when the thermal load of the boiler (2) increases, the gas temperature in the furnace (20) is relatively low, and if ammonia fuel is supplied to the furnace (20) at this time, excessive NOx will be generated . In this regard, according to the structure of (2) above, when the load of the boiler (2) increases, the supply of ammonia fuel is not started until the satisfaction determination condition is satisfied, so that the NOx emission amount can be suppressed.

(3) In several embodiments, in the structure of the above (1) or (2), The upper limit of the air ratio constituting the determination condition is 0.7 or less.

According to the knowledge of the inventors, if the air ratio of the burner part is 0.7 or less, the ratio of oxygen in the furnace (20) will decrease, and the amount of NOx generated when ammonia fuel is supplied to the furnace (20) will decrease. . Furthermore, it was found that if the air ratio of the burner part is 0.7 or less, the reduction reaction of ammonia and NOx is promoted in the furnace (20), and the NOx emission amount is reduced. Then, according to the configuration of (3) above, the NOx emission amount can be suppressed.

(4) In several embodiments, in any one of the above-mentioned (1) to (3), The aforementioned lower limit value of the nose temperature of the aforementioned furnace (20) as the aforementioned representative temperature constituting the aforementioned determination condition is 1120° C. or higher.

According to the findings of the inventors, it was found that when the gas temperature in the furnace (20) is 1400° C. or higher, thermal decomposition of ammonia can be sufficiently performed with a relatively short residence time in the furnace. In addition, it was found that when the nose temperature is 1120°C or higher, the gas temperature becomes 1400°C or higher. According to the structure of (4) above, since the supply of the ammonia fuel is started when the nose temperature is 1120° C. or higher, the amount of NOx emission can be suppressed.

(5) In several embodiments, in any one of the above-mentioned (1) to (4), The aforementioned judgment condition is that the residence time in the furnace until the other fuel reaches the nose (11) of the aforementioned furnace (20) after being charged into the aforementioned furnace (20) is 0.5 seconds or more.

According to the knowledge of the inventors, it is known that if the residence time of ammonia in the furnace is 0.5 seconds or more, the ammonia fuel put into the furnace (20) will be thermally decomposed by more than 80%. According to the structure of (5) above, the supply of ammonia fuel is started when the residence time of other fuels in the furnace is 0.5 seconds or more, so the residence time in the furnace at the start of ammonia combustion may be 0.5 seconds or more. Thereby, the NOx emission amount can be suppressed.

(6) In several embodiments, in any one of the above-mentioned (1) to (5), In the aforementioned furnace (20), the mixed combustion rate of the supplied ammonia fuel and the aforementioned other fuels is 20% or more in terms of heat.

According to the knowledge of the inventors, when the mixed combustion rate of ammonia and other fuels is 20% or more, the amount of NOx generated in the furnace (20) tends to increase. Therefore, under the condition that the mixed combustion ratio is 20% or more, it is significant to reduce the amount of NOx generated. According to the configuration of (6) above, the determination condition is satisfied before the start of combustion with a mixed combustion rate of 20% or more. Therefore, even when the mixed combustion rate is 20% or more, the amount of NOx generated can be reduced.

(7) In several embodiments, in any one of the above-mentioned (1) to (6), In the step of starting the supply of the ammonia fuel (S15, S55), the mixed combustion rate of ammonia is 50% or less in terms of heat, and the ammonia fuel is started so that the air ratio in the furnace (20) becomes 0.7 or less. supply, A step ( S59 ) of performing dedicated combustion of the ammonia fuel so that the air ratio in the furnace ( 20 ) becomes 0.9 or less after the supply of the ammonia fuel is started.

According to the knowledge of the inventors, when ammonia co-combustion is carried out under the conditions that the co-combustion ratio in terms of heat is 50% or less and the air ratio of the burner part is 0.7 or less, the amount of NOx emissions decreases. Furthermore, according to the findings of the inventors, the ammonia-only combustion under the condition that the air ratio of the burner portion becomes 0.9 or less can further reduce the NOx emission amount. According to the structure of (7) above, it is possible to sequentially perform ammonia mixed combustion and ammonia exclusive combustion while reducing NOx emission. Furthermore, by performing ammonia-only combustion, the emission of carbon dioxide can be suppressed. In addition, by reducing the air ratio of the burner portion during ammonia co-combustion to 0.7 or less, it is possible to give priority to suppressing the increase in NOx emission over suppressing the increase in the generation of unburned ammonia. Therefore, the amount of NOx emission can be effectively suppressed also during ammonia co-combustion.

(8) A control device (5) for a boiler according to at least one embodiment of the present invention, A furnace (20) and a supply system configured to supply ammonia fuel and other fuels to the furnace (20) are provided, and the control device for the boiler (2) includes: a combustion command generation unit (91) that generates another fuel combustion command for burning the aforementioned other fuel in the furnace (20); A judging unit (91) for judging that the ratio of the air supply amount to the furnace (20) to the theoretical air amount necessary to burn the other fuel supplied to the furnace (20), that is, the air ratio is an upper limit value, and the representative temperature in the aforementioned stove (20) is whether the judging condition is satisfied above the lower limit; and An ammonia supply command generation unit (91), which determines that the determination condition is at least satisfied by the determination unit (S53: YES), and generates ammonia supply for causing the supply system to start supplying the ammonia fuel to the furnace (20). start command, The upper limit of the air ratio constituting the determination condition is 0.8 or less.

According to the structure of (8) above, it is possible to realize the control device (5) for the boiler which starts the supply of ammonia fuel under the condition that the generation of NOx can be suppressed by the same reason as in (1) above.

(Example 1) Referring to FIG. 7 , the result of specifying the relationship between the burner portion air ratio and the NOx emission amount by a combustion test will be described. Fig. 7 is a graph showing the relationship between the burner portion air ratio and the NOx discharge amount. In this combustion test, a tube-type downer furnace (DTF) and a single burner test furnace extending in the vertical direction were used. The combustion test carried out by DTF is the special combustion of ammonia, the mixed combustion of ammonia and coal powder, and the special combustion of coal powder. The mixed combustion rate of ammonia mixed combustion is 25% or 50% in terms of heat. Moreover, the combustion test carried out with a single burner test furnace is dedicated to the combustion of pulverized coal.

First, the relationship between the air ratio in the burner section and the NOx emission amount during ammonia-only combustion will be examined. As shown in Fig. 7, the NOx emission amount of the ammonia-only combustion with the air ratio in the burner part being 1.0 is more than 6 times the NOx emission amount of the pulverized coal-only combustion of the DTF or single burner test furnace. On the other hand, it was found that the NOx emission amount of ammonia-only combustion in which the air ratio of the burner part is 0.9 or less is lower than that of pulverized coal-only combustion. In particular, it was found that the NOx emission amount of ammonia-only combustion with an air ratio of 0.8 in the burner portion was the lowest in this combustion test. In addition, the NOx emission amount of ammonia-only combustion in which the air ratio of the burner section is less than 0.8 is predicted to be less than the emission amount when the air ratio of the burner section is 0.8. This is because the lower the air ratio of the burner part, the less oxygen is used for combustion in the combustion space 7. As a result, compared with the oxidation reaction of nitrogen, the thermal decomposition of ammonia gas is promoted, and the NOx is also promoted. Reduction reaction (It is thought that the same tendency will also occur when ammonia mixed combustion or ammonia exclusive combustion is carried out). From the above review, it can be seen that in order to reduce the NOx emission of ammonia-only combustion, the upper limit of the air ratio of the burner part is preferably 0.9 or less, more preferably 0.8 or less, and more preferably 0.7 or less. Also, when a boiler 2 of a general scale is in operation for thermal power generation, it is not practical to have an air ratio of the burner portion less than 0.6 (this is also the case when ammonia mixed combustion or pulverized coal dedicated combustion is carried out). Therefore, the lower limit of the burner portion air ratio is 0.6 or more.

Next, the relationship between the air ratio of the burner part and the NOx emission amount in ammonia co-combustion is examined. As shown in Fig. 7, it is known that the ammonia mixed combustion (mixed combustion ratio: 25% and 50%) in the burner part with an air ratio of 0.8 has a higher NOx emission than that of pulverized coal combustion, but compared with The air ratio of the burner part is 1.0 for ammonia-only combustion, which is significantly reduced. In addition, it was found that the amount of NOx emitted during ammonia co-combustion with an air ratio of 0.7 or less in the burner section (co-combustion rate: 50%) is higher than that of pulverized coal-only combustion with an air ratio in the burner section of 0.8 The quantity is relatively low. The NOx emission amount of ammonia co-combustion (co-combustion rate: 25%) when the air ratio of the burner part is 0.7 was not measured. However, the NOx emission when the ammonia mixed combustion rate is 25% is predicted to be lower than that when the ammonia co-firing rate is 50%. This is because the supply amount of ammonia fuel, which is a NOx generation factor, to the furnace 20 decreases as the ammonia mixed combustion rate decreases. Accordingly, it was found that the upper limit of the air ratio in the burner portion during ammonia co-combustion is preferably 0.8 or less, more preferably 0.7 or less, in order to reduce NOx emissions. In addition, the lower limit of the air ratio of the burner portion when ammonia mixed combustion is performed is 0.6 or more as described above.

(Example 2) Next, with reference to Fig. 8 and Fig. 9, the relationship between the typical temperature in the furnace 20, the residence time of ammonia in the furnace, and the amount of NOx emission will be described. Fig. 8 is a graph showing the relationship between the gas temperature and the necessary residence time of ammonia. The gas temperature is an example of the representative temperature in the furnace 20 . The necessary residence time is the residence time of the ammonia fuel necessary for thermal decomposition of 80% of the ammonia fuel supplied to the furnace 20 in the combustion space 7 . The thermal decomposition of ammonia is represented by the following (chemical formula A). 2NH ₃ →N ₂ +3H ₂・・・(Chemical formula A) The more the proportion of thermally decomposed ammonia increases, the less the proportion of ammonia converted into NOx decreases, so the NOx emission will decrease. In the graph shown in Fig. 8, the necessary residence time is 0.741 seconds at a gas temperature of 1400°C, 0.569 seconds at a gas temperature of 1500°C, and 0.452 seconds at a gas temperature of 1600°C. It can be seen from FIG. 8 that as long as the gas temperature is above 1400° C., 80% of the ammonia fuel can be thermally decomposed in the furnace 20 even if the necessary residence time is less than 1 second. On the other hand, when the gas temperature is 1300°C, the necessary residence time is expected to be 2 seconds or more, and particularly when the gas temperature is 1200°C, the necessary residence time is about 10 seconds. It was found that even if the boiler 2 is operated under such conditions, it is difficult to thermally decompose 80% of the ammonia fuel. It can be seen from the above that in order to thermally decompose 80% of the ammonia fuel supplied to the furnace 20 in the combustion space 7, the gas temperature is preferably 1400°C or higher. In addition, the required residence time shown in FIG. 8 is a numerical value obtained by calculation. The boiler 2 with a general scale used in a thermal power plant actually has a gas temperature much higher than 1200°C even if the load on the boiler is extremely small.

Fig. 9 is a graph showing the relationship between the nose temperature and the gas temperature of the burner. It was found that the nose temperature was 1113°C when the gas temperature was 1400°C. Therefore, it was found that as long as the nose temperature is 1120°C or higher, the gas temperature is 1400°C or higher, and the NOx emission is reduced.

(Example 3) Referring to FIG. 10 , the relationship between the ammonia mixed combustion rate and the NOx emission amount will be described. Fig. 10 is a graph showing the relationship between the ammonia mixed combustion rate and the NOx emission amount. The graph shown in FIG. 10 shows the NOx emission amounts when the ammonia co-combustion rate is 0%, 25%, 50%, and 100% under the same combustion conditions of the boiler 2 . In addition, the ammonia co-combustion rate shown in the graph of FIG. 10 is a rate converted into heat, and the ammonia co-combustion rate of 100% is synonymous with the exclusive combustion of ammonia. It can be seen from Fig. 10 that when the mixed combustion rate of ammonia exceeds 20%, the NOx emission increases. Therefore, it is found that the reduction of NOx emission is significant in ammonia co-combustion where the co-combustion rate exceeds 20%. Furthermore, it was found that when the mixed combustion rate of ammonia is 50%, the NOx emission amount significantly increases. Therefore, it is found that reducing the NOx emission amount is significant in ammonia co-combustion in which the co-combustion rate of ammonia is 20% or more and 50% or less.

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.

2: Boiler 5: Control device 11: Nose 15: Supply system 20: Stove 91: Processor

[ Fig. 1 ] A conceptual diagram of a boiler operating system according to an embodiment. [ Fig. 2 ] A flow chart showing a method of operating a boiler according to an embodiment. [ Fig. 3 ] A cross-sectional view showing the structure of an ammonia burner according to an embodiment. [ Fig. 4 ] An explanatory diagram of a specific structure of a burner unit according to an embodiment. [ Fig. 5 ] A concrete structure of a boiler operation system according to an embodiment. [ Fig. 6 ] A flowchart showing boiler operation control processing according to one embodiment. [ Fig. 7 ] A graph showing the relationship between the burner portion air ratio and the NOx emission amount according to one embodiment. [ Fig. 8 ] A graph showing the relationship between the gas temperature and the necessary residence time of ammonia in one embodiment. [ Fig. 9 ] A graph showing the relationship between the nose temperature and the gas temperature of the burner part according to one embodiment. [ Fig. 10 ] A graph showing the relationship between the ammonia co-combustion rate in terms of heat and the NOx emission amount according to one embodiment.

Claims (8)

A method for operating a boiler, comprising: the step of burning a fuel other than ammonia fuel in a furnace; Judging that the ratio of the amount of air supplied to the furnace to the theoretical amount of air necessary to combust the other fuel supplied to the furnace, that is, the air ratio, is below the upper limit, and the representative temperature inside the furnace is above the lower limit The step of judging whether the condition is satisfied; and Initiating the step of supplying the aforementioned ammonia fuel to the aforementioned furnace when the aforementioned judging condition is at least satisfied, The upper limit of the air ratio constituting the determination condition is 0.8 or less. The operation method of the boiler as described in Claim 1, wherein, When the heat load of the boiler increases, the other fuel is burned until the determination condition is satisfied, and the ammonia fuel is started to be supplied to the furnace after the determination condition is satisfied. The operation method of the boiler as described in Claim 1 or 2, wherein, The upper limit of the air ratio constituting the determination condition is 0.7 or less. The operation method of the boiler as described in Claim 1 or 2, wherein, The aforementioned lower limit value of the nose temperature of the aforementioned stove as the aforementioned representative temperature constituting the aforementioned judgment condition is 1120° C. or higher. The operation method of the boiler as described in Claim 1 or 2, wherein, The above-mentioned determination condition is that the residence time in the furnace after the other fuel is injected into the furnace until it reaches the nose of the furnace is 0.5 seconds or more. The method for operating a boiler according to claim 1 or 2, wherein in the furnace, the mixed combustion rate of the supplied ammonia fuel and the other fuel is 20% or more in terms of heat. The operation method of the boiler as described in Claim 1 or 2, wherein, In the step of starting the supply of the ammonia fuel, the mixed combustion rate of ammonia is 50% or less in terms of heat, and the supply of the ammonia fuel is started so that the air ratio in the furnace becomes 0.7 or less, It includes the step of performing exclusive combustion of the ammonia fuel so that the air ratio in the furnace becomes 0.9 or less after the supply of the ammonia fuel is started. A control device for a boiler, It has a furnace and a supply system configured to supply ammonia fuel and other fuels to the furnace, and the control device for the boiler includes: a combustion command generation unit that generates another fuel combustion command for burning the aforementioned other fuel in the furnace; A judging unit for judging that the ratio of the amount of air supplied to the furnace to the theoretical amount of air necessary to combust the other fuel supplied to the furnace, that is, the air ratio, is below an upper limit, and the representative in the furnace Whether the judgment condition that the temperature is above the lower limit value is satisfied; and an ammonia supply command generation unit that determines at least the satisfaction of the determination condition by the determination unit, and generates an ammonia supply start command for causing the supply system to start supplying the ammonia fuel to the furnace, The upper limit of the air ratio constituting the determination condition is 0.8 or less.

Images