Boiler system and method of operating the boiler system

Abstract

To provide a boiler system capable of effectively suppressing discharge of ammonia to the atmosphere by using a simple configuration, and an operating method for the boiler system.SOLUTION: A boiler system includes: a boiler that burns fuel containing ammonia; a desulfurizer configured to apply desulfurization treatment to exhaust gas from the boiler; and a controller. The controller is configured to control an operation of the desulfurizer in accordance with presence / absence of occurrence of accidental fire of ammonia flames in the boiler. For example, the accidental fire of the ammonia flames is determined on the basis of a detection result from a flame detector.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a boiler system and a method for operating a boiler system.

Background Art

[0002] A boiler in which ammonia is supplied as fuel into a furnace is known. For example, in the boiler disclosed in Patent Document 1, ammonia co-firing in which ammonia burns in a furnace together with coal is performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The amount of ammonia used as fuel is very large compared to, for example, the amount of ammonia used as a catalyst for denitrification of combustion gas. Therefore, when ammonia misfire occurs in the furnace, a large amount of unburned ammonia is generated. It is preferable to effectively suppress the release of this large amount of ammonia into the atmosphere with a simple configuration, but the above patent documents do not disclose a specific configuration.

[0005] An object of the present disclosure is to provide a boiler system and a method for operating a boiler system that can effectively suppress the release of ammonia into the atmosphere with a simple configuration.

Means for Solving the Problems

[0006] A boiler system according to at least one embodiment of the present disclosure includes a boiler including an ammonia burner, a desulfurization device configured to perform desulfurization treatment on the exhaust gas from the boiler, a controller, and Equipped with, The aforementioned controller, If no misfire is detected in the ammonia burner and a boiler trip is detected, a stop command is generated to stop the desulfurization process. If a misfire in the ammonia burner is detected and a boiler trip is detected, the desulfurization apparatus is configured to continue operating so that ammonia contained in the exhaust gas is recovered.

[0007] The operating method of a boiler system according to at least one embodiment of this disclosure is: If no misfire is detected in the ammonia burner in the boiler, and a boiler trip is detected, a stop command is generated to stop the desulfurization device, which is configured to desulfurize the exhaust gas from the boiler. If a misfire in the ammonia burner is detected and a boiler trip is detected, the operation of the desulfurization apparatus is continued so that ammonia contained in the exhaust gas is recovered. [Effects of the Invention]

[0008] This disclosure provides a boiler system and a method for operating the boiler system that can effectively suppress the release of ammonia into the atmosphere with a simple configuration. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of a boiler system according to one embodiment. [Figure 2] This is a conceptual diagram of a desulfurization apparatus according to one embodiment. [Figure 3] This is a conceptual diagram illustrating a boiler according to one embodiment. [Figure 4] This is a conceptual diagram illustrating an extraction unit and an ammonia resupply line according to one embodiment. [Figure 5] This is a flowchart illustrating the operation method of a boiler system according to one embodiment. [Modes for carrying out the invention]

[0010] An embodiment of the present invention will be described below with reference to the drawings. Note that the present invention is not limited by this embodiment, and if there are multiple embodiments, they may be constructed by combining each embodiment. In the following description, "up" or "above" refers to the upper side in the vertical direction, and "down" or "below" refers to the lower side in the vertical direction; the vertical direction is not precise and includes errors. Furthermore, the dimensions, materials, shapes, and relative arrangements of the components described or shown in the drawings as embodiments are not intended to limit the scope of this disclosure, but are merely illustrative examples. For example, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" should not only strictly describe such arrangements, but also describe states of relative displacement with tolerances or angles or distances that allow for the same function to be achieved. For example, expressions such as "identical," "equal," and "homogeneous" that describe things being in an equal state not only describe a state of being strictly equal, but also describe a state in which there is a tolerance or a difference that is sufficient to achieve the same function. For example, expressions describing shapes such as squares or cylinders shall not only represent geometrically precise shapes such as squares or cylinders, but also shapes that include protrusions, chamfers, etc., to the extent that the same effect can be achieved. On the other hand, expressions such as "possessing," "including," or "having" one component are not exclusive expressions that exclude the existence of other components. Note that similar configurations may be denoted by the same reference numerals and their explanations may be omitted.

[0011] <1. Overall configuration of boiler system 1> Figure 1 is a schematic diagram showing a boiler system 1 in this embodiment, which includes a boiler that primarily uses ammonia fuel and other fuels besides ammonia fuel.

[0012] The boiler 10 included in the boiler system 1 of this embodiment is a boiler capable of burning other fuels and ammonia fuel by a burner, and generating superheated steam by exchanging heat between the heat generated by this combustion and feed water or steam. As the other fuel, solid fuels such as biomass fuel and coal are used. Coal as the solid fuel is, for example, pulverized fine coal fuel. Further, the ammonia fuel is liquid ammonia or ammonia gas. Hereinafter, an embodiment in which the ammonia fuel is liquid ammonia will be exemplified.

[0013] The boiler 10 has a furnace 11, combustion devices 20 and 50, and a combustion gas passage 12. The furnace 11 has a hollow shape of a square cylinder and is installed along the vertical direction. The furnace wall 101 constituting the inner wall surface of the furnace 11 is composed of a plurality of heat transfer tubes and fins connecting the heat transfer tubes to each other, and recovers the heat generated by the combustion of the pulverized coal fuel by exchanging heat with water or steam flowing inside the heat transfer tubes, and suppresses the temperature rise of the furnace wall 101.

[0014] The combustion devices 20 and 50 are installed in the lower region of the furnace 11. In this embodiment, the combustion device 20 is configured to inject pulverized coal fuel into the furnace 11. Further, the combustion device 50 is configured to atomize liquid ammonia with an atomizing fluid (spray medium) and inject it into the furnace 11. The atomizing fluid of this embodiment is atomizing steam.

[0015] The combustion device 20 has a plurality of burners 21 attached to the furnace wall 101, and the combustion device 50 has a plurality of ammonia burners 51. At the tip of each burner 21, an injection nozzle (not shown) configured to inject pulverized coal fuel into the furnace 11 is provided. Further, at the tip of each ammonia burner 51, a two-fluid injection nozzle (not shown) configured to atomize liquid ammonia with an atomizing fluid and inject it into the furnace 11 is provided. The burner 21 and the ammonia burner 51 are arranged at equal intervals along the circumferential direction of the furnace 11 (for example, four burners installed at each corner of the square furnace 11 are regarded as one set), and are arranged in a plurality of stages along the vertical direction. In the example of FIG. 1, two stages of one set of burners 21 and four stages of one set of ammonia burners 51 are arranged. In FIG. 1, for the sake of illustration, only two of the burners in one set are shown, and the reference numerals 21 and 51 are attached to each set. The shape of the furnace, the number of stages of the burners, the number of burners in one stage, the arrangement of the burners, etc. are not limited to this embodiment. In addition, the combustion method in the furnace 11 may be either a swirling combustion method or a counter combustion method. Depending on the combustion method adopted, the shape of the furnace 11 and the arrangement of the plurality of burners 21 and the plurality of ammonia burners 51 may be appropriately changed.

[0016] Each burner 21 of the combustion device 20 is connected to a plurality of mills (pulverizers) 31A, 31B (hereinafter, may be collectively referred to as "mill 31") via a plurality of pulverized coal fuel supply pipes 22A, 22B (hereinafter, may be collectively referred to as "pulverized coal fuel supply pipe 22"). The mill 31 is, for example, a vertical roller mill in which a pulverizing table (not shown) is supported rotatably inside, and a plurality of pulverizing rollers (not shown) are supported rotatably in conjunction with the rotation of the pulverizing table above the pulverizing table. The solid fuel pulverized by the cooperation of the pulverizing roller and the pulverizing table is conveyed to a classifier (not shown) provided in the mill 31 by the primary air (transport gas, oxidizing gas) supplied to the mill 31. In the classifier, it is classified into pulverized coal fuel with a particle size suitable for combustion in the burner 21 and coarse pulverized coal fuel with a particle size larger than the above-mentioned particle size. The pulverized coal fuel passes through the classifier and is supplied to the burner 21 through the pulverized coal fuel supply pipe 22 together with the primary air. The coarse pulverized coal fuel that does not pass through the classifier falls onto the pulverizing table inside the mill 31 due to its own weight and is pulverized again. In addition, a safety shut-off valve 25 for shutting off the supply of pulverized coal fuel when a boiler trip occurs is provided in each of the pulverized coal fuel supply pipes 22. The method for detecting a boiler trip will be described later.

[0017] The ammonia burner 51 of the combustion device 50 is connected to the fuel supply unit 90. The fuel supply unit 90 in this embodiment includes a supply line 92 connected to the combustion device 50. In this example, liquid ammonia is supplied to the combustion device 50 via the supply line 92 while maintaining a liquid phase state. Although detailed illustrations are omitted, the supply line 92 may include an ammonia supply line for supplying liquid ammonia and an atomizing fluid supply line for supplying an atomizing fluid, such as steam, to the combustion device 50. The supply line 92 is also provided with at least one safety shut-off valve 95 configured to operate in the event of a boiler trip.

[0018] An air register 23 is provided on the outside of the furnace 11 at the mounting positions of the burner 21 and the ammonia burner 51, and one end of an air duct 24 is connected to this air register 23. A forced draft fan (FDF) 32 is connected to the other end of the air duct 24. The air supplied from the forced draft fan 32 is heated by an air preheater 42 installed in the air duct 24 (details will be described later), and is supplied to the burner 21 as secondary air (combustion air, oxidizing gas) via the air register 23 and introduced into the furnace 11.

[0019] The combustion gas passage 12 is connected to the upper vertical part of the furnace 11. The combustion gas passage 12 is equipped with superheaters 102A, 102B, 102C (hereinafter sometimes collectively referred to as "superheater 102"), reheaters 103A, 103B (hereinafter sometimes collectively referred to as "reheater 103"), and an economizer 104 as heat exchangers for recovering heat from the combustion gas. Heat exchange takes place between the combustion gas generated in the furnace 11 and the feedwater or steam circulating inside each heat exchanger. Note that the arrangement and shape of each heat exchanger are not limited to the configuration shown in Figure 1.

[0020] Downstream of the combustion gas passage 12 is a flue 13 through which the combustion gas, whose heat has been recovered by the heat exchanger, is discharged. An air preheater (air heater) 42 is installed between the flue 13 and the air duct 24, and heat exchange takes place between the air flowing through the air duct 24 and the combustion gas flowing through the flue 13. By heating the primary air supplied to the mill 31 and the secondary air supplied to the burner 21, heat is further recovered from the combustion gas after heat exchange with water or steam.

[0021] Furthermore, a denitrification device 43 may be provided in the flue 13 at a position upstream of the air preheater 42. The denitrification device 43 supplies a reducing agent, such as ammonia or urea solution, which has the effect of reducing nitrogen oxides, to the combustion gas flowing through the flue 13. The reaction between the nitrogen oxides (NOx) in the combustion gas to which the reducing agent has been supplied and the reducing agent is promoted by the catalytic action of a denitrification catalyst installed in the denitrification device 43, thereby removing and reducing nitrogen oxides in the combustion gas. A gas duct 41 is connected downstream of the air preheater 42 in the flue 13. The gas duct 41 is equipped with dust collection devices 44, such as an electrostatic precipitator, to remove ash and other particles from the combustion gas, and environmental devices such as a desulfurization device 46 to remove sulfur oxides, as well as an induced draft fan (IDF) 45 to guide the exhaust gas to these environmental devices. The downstream end of the gas duct 41 is connected to the chimney 47, and the combustion gas treated by the environmental devices is discharged outside the system as exhaust gas.

[0022] In the boiler 10, when multiple mills 31 are driven, the crushed and classified pulverized coal fuel is supplied to the burner 21 via the pulverized coal fuel supply pipe 22 along with primary air. Liquid ammonia and atomizing fluid are also supplied to the ammonia burner 51 from the fuel supply unit 90. Furthermore, secondary air heated by the air preheater 42 is supplied to the burner 21 and the ammonia burner 51 via the air duct 24 and the air register 23. Burner 21 injects a pulverized coal fuel mixture, which is a mixture of pulverized coal fuel and primary air, into the furnace 11, along with secondary air. The pulverized coal fuel mixture injected into the furnace 11 ignites and reacts with the secondary air to form a flame. Ammonia burner 51 injects secondary air into the furnace 11 along with liquid ammonia atomized by an atomizing fluid. The liquid ammonia injected into the furnace 11 vaporizes into fuel gas and burns by reacting with the secondary air. The high-temperature combustion gas generated by the combustion of pulverized coal fuel and fuel gas rises inside the furnace 11 and flows into the combustion gas passage 12. Furthermore, the timing of the injection of liquid ammonia into the furnace 11 may be after the temperature inside the furnace 11 has risen to a certain temperature due to the combustion of pulverized coal fuel. For example, after the boiler 10 is started up and pulverized coal fuel is exclusively burned, liquid ammonia may be injected into the furnace 11, and ammonia co-firing may occur with the fuel gas from the vaporized liquid ammonia and the pulverized coal fuel. After that, the injection of pulverized coal fuel may be stopped and ammonia exclusive burning may be performed. Furthermore, in this embodiment, air is used as the oxidizing gas (primary air, secondary air), but it may also be a gas with a higher or lower oxygen content than air, and stable combustion can be achieved in the furnace 11 by adjusting the ratio of oxygen to the supplied fuel amount to an appropriate range.

[0023] The combustion gas flowing into the combustion gas passage 12 undergoes heat exchange with water and steam in the superheater 102, reheater 103, and economizer 104 located inside the combustion gas passage 12, before being discharged into the flue 13. There, nitrogen oxides are removed in the denitrification device 43, and after heat exchange with primary and secondary air in the air preheater 42, it is further discharged into the gas duct 41. Ash and other contaminants are removed in the dust collector 44, and sulfur oxides are removed in the desulfurization device 46 before being discharged out of the system through the chimney 47. Note that the arrangement of each heat exchanger in the combustion gas passage 12 and each device from the flue 13 to the gas duct 41 does not necessarily have to be in the order described above with respect to the combustion gas flow.

[0024] In this embodiment, if a boiler trip occurs, the safety shut-off valves 25 and 95 activate, and the fuel supply to the boiler 10 is immediately stopped. At this time, devices such as the denitrification unit 43 also stop immediately. However, if a misfire of the ammonia burner 51 occurs along with the boiler trip, the desulfurization unit 46 continues to operate and recovers unburned ammonia contained in the combustion gas, which is the exhaust gas from the boiler 10 (details will be described later).

[0025] The boiler described herein is not limited to the embodiments described above. As the solid fuel used in the boiler, coal, biomass fuel, petroleum coke (PC), petroleum residue, etc., may be used instead of or in conjunction with pulverized coal fuel. Furthermore, the fuel used in boilers combined with ammonia fuel is not limited to solid fuels; liquid fuels such as heavy oil, light oil, heavy crude oil, and industrial wastewater can also be used. In addition, gaseous fuels such as natural gas, various petroleum gases, and by-product gases generated in steelmaking processes can also be used. Furthermore, this can also be applied to co-firing boilers that use a combination of these various fuels.

[0026] Furthermore, in the boiler of this disclosure, the ammonia fuel injected into the furnace may be ammonia gas instead of liquid ammonia. For example, in an embodiment in which ammonia gas is injected into the furnace, an atomizing fluid supply line may not be provided. The injection nozzle of the ammonia burner may be configured to inject ammonia gas. Furthermore, the ammonia supply line may be provided with at least one ammonia vaporizer for vaporizing the supplied liquid ammonia. The ammonia vaporizer may be configured to vaporize liquid ammonia using steam generated in the boiler, combustion gases in the boiler, or seawater outside the boiler system as a direct or indirect heat source.

[0027] <2. Detailed configuration of the desulfurization unit 46> Referring to Figure 2, a detailed configuration of a desulfurization apparatus 46 according to one embodiment of the present disclosure is illustrated. Figure 2 is a conceptual diagram illustrating the desulfurization apparatus 46 according to one embodiment.

[0028] The boiler system 1 includes a desulfurization apparatus 46 configured to desulfurize the exhaust gas from the boiler 10. In this embodiment, the desulfurization apparatus 46 employs a wet method for desulfurization using an absorbent liquid. As an example, the absorbent liquid is an alkaline aqueous solution using an alkaline reagent such as calcium hydroxide, sodium hydroxide (caustic soda), magnesium hydroxide, or ammonia. Below, an embodiment in which the absorbent liquid is calcium hydroxide will be given as an example.

[0029] The desulfurization apparatus 46 includes a desulfurization tower 461 having an inlet 462 and an outlet 463, and in which a reservoir for absorbent liquid is formed; a first spraying device 61 configured to spray the absorbent liquid inside the desulfurization tower 461; and a limestone supply device 55 configured to supply limestone to the reservoir inside the desulfurization tower 461. The exhaust gas from the boiler 10 flows into the desulfurization tower 461 via the inlet 462 and mixes with the absorbent liquid sprayed by the first spraying device 61. The exhaust gas is subjected to desulfurization treatment by dissolving sulfur oxides contained in the exhaust gas in the absorbent liquid. The exhaust gas is then discharged from the desulfurization apparatus 46 via the outlet 463 and released into the atmosphere through the chimney 47 (see Figure 1).

[0030] The configuration of the first spraying device 61 is as follows, as an example. The first spraying device 61 includes an absorbent liquid circulation line 611 for circulating the absorbent liquid that forms a liquid reservoir in the desulfurization tower 461, a pump 612 provided in the absorbent liquid circulation line 611, and a spraying unit 615 to which the desulfurization treatment is supplied by the drive of the pump 612. The pump 612 is electrically connected to the controller 110. In the first spraying device 61 having the above structure, when the pump 612 is driven based on a command from the controller 110, the absorbent liquid that forms the liquid reservoir is supplied to the spraying unit 615 via the absorbent liquid circulation line 611. As a result, the spraying unit 615 sprays the absorbent liquid into the interior of the desulfurization tower 461.

[0031] The configuration of the limestone supply device 55 is as follows, as an example. The limestone supply device 55 has a limestone storage section 551, which may be, for example, a limestone slurry tank; a limestone supply line 552 connected to the limestone storage section 551 and the desulfurization tower 461; and a limestone supply unit 554 provided on the limestone supply line 552. The limestone supply unit 554 is, for example, a pump electrically connected to the controller 110. In the limestone supply device 55 having the above structure, when the limestone supply unit 554 is driven based on a command output from the controller 110, limestone stored in the limestone storage section 551 is supplied to the liquid reservoir of the desulfurization tower 461.

[0032] The desulfurization apparatus 46 described above performs desulfurization treatment on the exhaust gas by spraying an absorbent liquid onto the exhaust gas during the normal operation of the boiler 10. If a boiler trip occurs without a misfire in the ammonia burner 51 of this embodiment (the specific detection method will be described later), the desulfurization apparatus 46 stops operation based on a command from the controller 110. Specifically, if a misfire in the ammonia burner 51 is not detected and a boiler trip is detected, the controller 110 generates a stop command to stop the desulfurization treatment. In this example, the stop command is sent to the pump 612 and the limestone supply unit 554 of the desulfurization apparatus 46, thereby stopping the operation of the desulfurization apparatus 46.

[0033] The desulfurization unit 46 in this embodiment also has the function of recovering ammonia contained in the exhaust gas. Specifically, if a boiler trip occurs along with a misfire of the ammonia burner 51 (the specific detection method will be described later), the controller 110 determines that it will not generate the above-mentioned stop command. As a result, the desulfurization unit 46 continues to operate. The spraying of the absorbent liquid in the desulfurization unit 46 continues, but the unburned ammonia contained in the exhaust gas is recovered by the absorbent liquid, and the ammonia recovery treatment of the exhaust gas is performed. In other words, the absorbent liquid at this time also functions as wash water for recovering ammonia. By determining that it will not generate a stop command, the controller 110 continues to operate the desulfurization unit 46 so that the ammonia contained in the exhaust gas is recovered by this absorbent liquid. Hereafter, the absorbent liquid may be referred to as "wash water".

[0034] With the above configuration, if a boiler trip occurs without a misfire in the ammonia burner 51, it is unlikely that a large amount of unburned ammonia will be contained in the exhaust gas from the boiler 10, and there is little need for the desulfurization unit 46 to continue operating. In this case, the desulfurization unit 46 will stop operating, thus suppressing unnecessary operation of the desulfurization unit 46. On the other hand, if both a misfire in the ammonia burner 51 and a boiler trip occur, the exhaust gas tends to contain a large amount of unburned ammonia. In this case, the controller 110 continues to operate the desulfurization unit 46 so that the ammonia contained in the exhaust gas is recovered. Since the desulfurization unit 46 has both the function of performing desulfurization treatment on the exhaust gas and the function of recovering ammonia contained in the exhaust gas, the configuration of the boiler system 1 is simplified. Thus, a boiler system 1 is realized that can effectively suppress the release of ammonia into the atmosphere using the desulfurization unit 46.

[0035] In other embodiments, the desulfurization apparatus 46 may employ a dry method in which activated carbon or coal ash is used as an adsorbent for desulfurization. Alternatively, a semi-dry method (spray-dry method) may be employed in which limestone slurry is sprayed to convert sulfur oxides into powders such as calcium sulfite for desulfurization. Even in such embodiments, if a misfire of the ammonia burner 51 and a boiler trip are detected, the desulfurization apparatus 46 can be operated without stopping, and unburned ammonia contained in the exhaust gas can be recovered.

[0036] A desulfurization apparatus 46 according to one embodiment of the present disclosure includes a spraying device 60 configured to spray cleaning water for recovering ammonia into the exhaust gas flow path. The spraying device 60 is an apparatus that includes the first spraying device 61 described above. With the above configuration, the sprayed cleaning water and the exhaust gas mix well, so that ammonia contained in the exhaust gas can be recovered efficiently. Therefore, the release of ammonia into the atmosphere can be further suppressed.

[0037] The spraying device 60 of this embodiment includes a second spraying device 62 in addition to the first spraying device 61. The second spraying device 62 is a dedicated device for spraying cleaning water, for example, in the event of a misfire of the ammonia burner 51 and a boiler trip. In other words, the second spraying device 62 does not operate during the normal operation of the boiler 10. The second spraying device 62 includes a wash water circulation line 621, a pump 622, and a spraying unit 625. The pump 622 is electrically connected to the controller 110. The second spraying device 62 has the same configuration as the first spraying device 61 described above. That is, the wash water circulation line 621 corresponds to the absorbent liquid circulation line 611 (wash water circulation line 611) of the first spraying device 61. Similarly, the pump 622 corresponds to the pump 612, and the spraying unit 625 corresponds to the spraying unit 615. To avoid repetition in the explanation, the individual components and operations of the second spraying device 62 are omitted.

[0038] According to the above configuration, if a misfire in the ammonia burner 51 is detected and a boiler trip is detected, the second spraying device 62 will perform a cleaning water spraying operation in addition to the first spraying device 61. Therefore, more unburned ammonia contained in the exhaust gas can be recovered. The second spraying device 62 may be placed in a location other than that shown in Figure 2. For example, it may be placed at the inlet 462 of the desulfurization device 46. Also, the washing water sprayed by the second spraying device 62 may be water (industrial water). This is because even water can absorb a certain amount of ammonia if the supply volume is large enough.

[0039] A spraying device 60 according to one embodiment of the present disclosure further includes a pH adjustment device 70 configured to start an operation to reduce the pH of the washing water after the desulfurization device 46 has been in operation (i.e., after the ammonia burner 51 has misfired and the boiler has tripped). The pH adjustment device 70 of this embodiment includes the limestone supply device 55 described above and a pH measuring device 71 electrically connected to the controller 110. After the desulfurization device 46 has been in operation, the controller 110 controls the limestone supply unit 554 so that the pH of the liquid reservoir, determined based on the measurement results of the pH measuring device 71, becomes less than 7. Preferably, the pH of the liquid reservoir is adjusted to be 3 or higher and less than 6. For example, if the pH of the liquid reservoir is higher than 7, an additive such as a pH adjusting agent is added from an inlet (not shown) to lower the pH.

[0040] The wash water mixed with the exhaust gas is more acidic, as this allows unburned ammonia to dissolve more easily in the wash water. This is thought to be because, in the chemical formula (1) below, which shows the dissolution of ammonia gas contained in the exhaust gas into the wash water, the equilibrium shifts to the left as the pH decreases. NH4 + +OH - →NH3↑+H2O (1) According to the above configuration, if a misfire in the ammonia burner 51 is detected and a boiler trip is detected, the pH of the sprayed cleaning water is reduced, allowing for more efficient recovery of unburned ammonia contained in the exhaust gas.

[0041] Furthermore, a boiler system 1 according to one embodiment of the present disclosure includes an ammonia measuring instrument 80 configured to measure the ammonia concentration of exhaust gas at at least one of the inlet 462 side or outlet 463 side of the desulfurization unit 46. In this embodiment, the ammonia measuring instrument 80 electrically connected to the controller 110 includes a first ammonia measuring instrument 81 for measuring the ammonia concentration of exhaust gas flowing into the desulfurization unit 46 and a second ammonia measuring instrument 82 for measuring the ammonia concentration of exhaust gas flowing out of the desulfurization unit 46. The controller 110 is configured to generate an ammonia recovery stop command for the desulfurization unit 46 to stop operation, provided that the measurement results of the ammonia measuring instrument 80 satisfy the specified return conditions after the desulfurization unit 46 has been operating for a while. The ammonia recovery stop command is the same as the stop command described above.

[0042] The defining condition in this embodiment is that the difference between the ammonia concentration at the inlet side, determined based on the detection result of the first ammonia meter 81, and the ammonia concentration at the outlet side, determined based on the detection result of the second ammonia meter 82, is below a specified concentration. In other embodiments, the ammonia meter 80 may consist of only either the first ammonia meter 81 or the second ammonia meter 82. For example, in an embodiment where only the second ammonia meter 82 is provided, the recovery condition is satisfied if the measurement result of the second ammonia meter 82 falls below the specified concentration.

[0043] According to the above configuration, if the ammonia concentration based on the measurement results of the ammonia measuring instrument 80 meets the specified recovery conditions, the desulfurization unit 46 will stop its operation, which had been ongoing. Since unnecessary operation of the desulfurization unit 46 is suppressed, efficient operation of the desulfurization unit 46 is achieved.

[0044] An ammonia measuring instrument 80 according to one embodiment of the present disclosure is a laser-type gas measuring instrument configured to measure ammonia concentration based on the absorption spectrum of laser light transmitted through exhaust gas. As a more specific example, the first ammonia measuring instrument 81 has a light-emitting unit 81A for irradiating light toward the exhaust gas flow path on the inlet 462 side, and a light-receiving unit 81B for receiving light from the light-emitting unit 81A. Similarly, the second ammonia measuring instrument 82 has a light-emitting unit 82A for irradiating light toward the exhaust gas on the outlet 463 side, and a light-receiving unit 82B for receiving light from the light-emitting unit 82A. Ammonia gas has a unique light absorption spectrum that absorbs light. Furthermore, the absorbance correlates with the ammonia gas concentration. Therefore, by spectrally analyzing the output signals from the light-receiving units 81B and 82B, it is possible to measure the ammonia concentration at both the inlet 462 and the outlet 463. Additionally, the light absorption spectrum of ammonia gas differs from that of sulfur compounds, nitrogen compounds, and carbon compounds contained in the exhaust gas. Therefore, by performing gas measurement using a laser method, the ammonia gas concentration can be accurately measured without being affected by other gases.

[0045] With the above configuration, the ammonia measuring instrument 80 being a laser-type gas measuring instrument allows for more accurate measurement of the ammonia concentration. Therefore, it is possible to suppress false detections that the ammonia concentration has decreased sufficiently even when the concentration of unburned ammonia in the exhaust gas has not actually decreased sufficiently. Thus, it is possible to more reliably suppress the release of ammonia into the atmosphere after the desulfurization unit 46 is shut down.

[0046] <3. Details of detection of misfire and boiler trip in ammonia burner 51> Referring to Figure 3, details of the method for detecting a misfire in the ammonia burner 51 and the method for detecting a boiler trip are illustrated. Figure 3 is a conceptual diagram of a boiler 10 according to one embodiment of the present disclosure.

[0047] <3-1. Detection of misfire in ammonia burner 51> A boiler system 1 according to one embodiment of the present disclosure further comprises a flame detector 121 configured to detect whether or not the ammonia burner 51 has misfired. The flame detector 121 is located inside a compartment (not shown) provided in the furnace 11. Inside another compartment vertically adjacent to the compartment in which the flame detector 121 is located, the ammonia burner 51 may be located, or an air nozzle (not shown) for supplying secondary air, which is mainly used for the combustion of ammonia gas, may be located.

[0048] The controller 110, which is electrically connected to the flame detector 121, is configured to determine whether or not the ammonia burner 51 has misfired based on the detection result of the flame detector 121. With this configuration, the controller 110 can accurately determine whether or not the ammonia burner 51 has misfired based on the detection result of the flame detector 121. Therefore, misjudgments regarding the presence or absence of a misfire in the ammonia burner 51 are suppressed.

[0049] <3-2. Boiler Trip Detection> The boiler system 1 of this embodiment further includes an interlock 122 configured to cause a boiler trip when at least one of a plurality of stop conditions is met. The interlock 122 is electrically connected to, for example, an emergency stop switch input by an operator. That is, the stop conditions that cause a boiler trip include the activation of the emergency stop switch. In other embodiments, the controller 110 may be connected to at least one of a temperature measuring instrument for measuring the temperature inside the furnace 11 (e.g., the temperature of the nose wall) or a pressure measuring instrument for measuring the pressure inside the furnace 11. If the measurement results of these instruments do not meet the specified conditions, the interlock 122 is activated and the safety shut-off valves 25, 95 are activated. The controller 110 of this embodiment is configured to determine whether or not a boiler trip has occurred based on the output signal from the interlock 122. With the above configuration, the controller 110 can more accurately determine whether or not a boiler trip has occurred based on the output signal from the interlock 122.

[0050] <4. Reuse of ammonia recovered by the desulfurization unit 46> Referring to Figure 4, an example of a method for reusing ammonia recovered by the desulfurization unit 46 is illustrated. Figure 4 is a conceptual diagram illustrating an extraction unit 35 and an ammonia resupply line 36 according to one embodiment of the present disclosure.

[0051] A boiler system 1 according to one embodiment of the present disclosure further comprises an extraction unit 35 configured to extract ammonia from wash water, and an ammonia resupply line 36 configured to supply the ammonia extracted by the extraction unit 35 to a boiler 10. In this embodiment, the extraction unit 35 is connected to the desulfurization tower 461 of the desulfurization apparatus 46 via the wash water line 49. For example, when the ammonia recovery operation of the desulfurization apparatus 46 is completed and the boiler 10 resumes normal operation, the pump 59 provided in the wash water line 49 is driven, sending wash water from the liquid reservoir of the desulfurization tower 461 to the extraction unit 35. The extraction unit 35, which may be a stripper for example, performs an ammonia stripping treatment on the wash water, separating it into ammonia gas and wash water from which the ammonia gas has been recovered. The treated wash water flows through the wash water line 49 and returns to the desulfurization tower 461. The ammonia gas flows through the ammonia resupply line 36 and is supplied to the boiler 10. In an embodiment in which the ammonia burner 51 of the combustion apparatus 50 injects ammonia gas instead of liquid ammonia, the ammonia resupply line 36 may be connected to the supply line 92 described above.

[0052] According to the above configuration, the boiler system 1 can be operated efficiently because unburned ammonia gas contained in the exhaust gas is reused as ammonia fuel.

[0053] <5. Operating procedure for boiler system 1> Referring to Figure 5, an example of the operation method of the boiler system 1 according to one embodiment of the present disclosure will be given. Figure 5 is a flowchart of the operation method of the boiler system 1 according to one embodiment. In the following description, "step" may be abbreviated as "S". At the start of this flowchart, the boiler 10 is in normal operation, and the first spraying device 61 of the desulfurization device 46 is operating.

[0054] First, the controller 110 determines whether or not a boiler trip has occurred (S11). For example, based on the output signal of the interlock 122, the controller 110 determines whether or not a boiler trip has occurred. If it is determined that no boiler trip has occurred (S11: NO), the controller 110 goes into standby mode and the boiler 10 continues to operate. If a misfire occurs in the ammonia burner 51 while the controller 110 is in standby mode, the ammonia injected from the ammonia burner 51 is burned by the flames generated in the furnace 11 due to the combustion of other fuels. Therefore, even if the boiler 10 continues to operate, the generation of a large amount of unburned ammonia in the furnace 11 is suppressed.

[0055] If it is determined that a boiler trip has occurred (S11: YES), the controller 110 determines whether a misfire has occurred in the ammonia burner 51 (S13). For example, whether or not a misfire has occurred in the ammonia burner 51 is determined based on the detection result of the flame detector 121. If it is determined that no misfire has occurred in the ammonia burner 51 (S13: NO), the controller 110 activates the safety shut-off valves 25 and 95 to stop the fuel supply to the boiler 10 and generates a stop command (S15). The generated stop command is sent to the desulfurization unit 46, the desulfurization unit 46 stops operating, and this flowchart ends. When a boiler trip occurs without a misfire in the ammonia burner 51, it is unlikely that a large amount of unburned ammonia will be generated in the furnace 11. Therefore, even if the desulfurization unit 46 stops operating, it is unlikely that a large amount of ammonia will be released into the atmosphere. After this flowchart is completed, the boiler 10 will resume operation once the operator performs the prescribed procedures on the boiler system 1.

[0056] On the other hand, if it is determined that a misfire has occurred in the ammonia burner 51 (S13: YES), the controller 110 determines not to generate a stop command and proceeds to S17. As a result, the desulfurization unit 46 continues to operate, and ammonia recovery treatment can be performed instead of desulfurization treatment. The controller 110 starts operating the second sprayer 62 (S17). In the desulfurization unit 46, the second sprayer 62 starts operating in addition to the first sprayer 61 which was operating before the boiler trip occurred, so more washing water is sprayed. When executing S17, the controller 110 may also operate the pH measuring device 71 to reduce the pH of the washing water.

[0057] The controller 110 determines whether the measurement result from the ammonia measuring instrument 80 satisfies the specified recovery conditions (S19). Until the measurement result satisfies the specified recovery conditions (S19: NO), the controller 110 remains on standby, and the desulfurization unit 46 performs the ammonia recovery operation. If it is determined that the recovery conditions have been satisfied (S19: YES), the controller 110 generates an ammonia recovery stop command and sends it to the desulfurization unit 46 (S21). As a result, the desulfurization unit 46 stops operating, the ammonia recovery process ends, and this flowchart also ends.

[0058] <6. Summary> The contents described in some of the embodiments above can be understood, for example, as follows:

[0059] 1) A boiler system (1) according to at least one embodiment of the present disclosure is A boiler (10) including an ammonia burner (51), A desulfurization apparatus (46) configured to perform desulfurization treatment on the exhaust gas from the boiler, Controller (110) and Equipped with, The aforementioned controller, If no misfire is detected in the ammonia burner and a boiler trip is detected, a stop command is generated to stop the desulfurization process. If a misfire in the ammonia burner is detected and a boiler trip is detected, the desulfurization apparatus is configured to continue operating so that ammonia contained in the exhaust gas is recovered.

[0060] According to the configuration described in 1) above, if a boiler trip occurs without a misfire in the ammonia burner, it is unlikely that a large amount of unburned ammonia will be present in the exhaust gas from the boiler, and there is little need for the desulfurization unit to continue operating. In this case, the desulfurization unit will stop operating, thus suppressing unnecessary operation of the desulfurization unit. On the other hand, if both a misfire in the ammonia burner and a boiler trip occur, the exhaust gas tends to contain a large amount of unburned ammonia. In this case, the controller continues to operate the desulfurization unit so that the ammonia contained in the exhaust gas is recovered. Since the desulfurization unit has both the function of performing desulfurization treatment on the exhaust gas and the function of recovering ammonia contained in the exhaust gas, the boiler system configuration becomes simpler. Thus, a boiler system that can effectively suppress the release of ammonia into the atmosphere with a simple configuration is realized.

[0061] 2) In some embodiments, the boiler system described in 1) above, The desulfurization apparatus includes a spraying device (60) configured to spray cleaning water for recovering the ammonia in the flow path of the exhaust gas.

[0062] According to the configuration described in 2) above, the sprayed washing water and exhaust gas mix well, allowing for efficient recovery of ammonia contained in the exhaust gas. Therefore, the release of ammonia into the atmosphere can be further suppressed.

[0063] 3) In some embodiments, the boiler system described in 2) above, The aforementioned spraying device is A first spraying device (61) is configured to continue the spraying operation of the washing water, which was being performed before the boiler trip was detected, even after the desulfurization device continues to operate. The system includes a second spraying device (62) configured to start the spraying operation of the washing water, which was stopped before the boiler trip was detected, after the desulfurization device has continued to operate.

[0064] According to the configuration described in 3) above, if a misfire in the ammonia burner is detected and a boiler trip is detected, the second spraying device will perform a cleaning water spraying operation in addition to the first spraying device. Therefore, more unburned ammonia contained in the exhaust gas can be recovered.

[0065] 4) In some embodiments, the boiler system is as described in 2) or 3) above, The desulfurization apparatus further includes a pH adjustment device (70) configured to start an operation to reduce the pH of the washing water after the desulfurization apparatus has been in operation.

[0066] According to the configuration described in 4) above, when a misfire in the ammonia burner is detected and a boiler trip is detected, the pH of the sprayed cleaning water is reduced, allowing for more efficient recovery of unburned ammonia contained in the exhaust gas.

[0067] 5) In some embodiments, a boiler system according to any one of 1) to 4) above, The system further includes a flame detector (121) configured to detect whether or not the ammonia burner has misfired, The controller is configured to determine whether or not the ammonia burner has misfired based on the detection result of the flame detector.

[0068] According to the configuration described in 5) above, the controller can accurately determine whether or not the ammonia burner has misfired based on the detection results of the flame detector.

[0069] 6) In some embodiments, a boiler system according to any one of 1) to 5) above, The system further comprises an interlock (122) configured to cause the boiler trip when at least one of a plurality of stop conditions is met, The controller is configured to determine whether or not the boiler tripped based on the output signal from the interlock.

[0070] According to the configuration described in 6) above, the controller can more accurately determine whether or not a boiler trip has occurred based on the interlock output signal.

[0071] 7) In some embodiments, a boiler system according to any one of 1) to 6) above, The desulfurization apparatus further comprises an ammonia measuring instrument (80) configured to measure the ammonia concentration of the exhaust gas at at least one of the inlet or outlet sides, The controller is configured to generate an ammonia recovery stop command to stop the operation of the desulfurization apparatus, provided that the measurement result of the ammonia measuring instrument satisfies the specified recovery conditions after the desulfurization apparatus has been in operation for a period of time.

[0072] According to the configuration described in 7) above, if the ammonia concentration based on the measurement results of the ammonia measuring instrument meets the specified recovery conditions, the desulfurization unit will stop its operation, which had been continuing. Therefore, unnecessary operation of the desulfurization unit is suppressed, and efficient operation of the desulfurization unit is achieved.

[0073] 8) In some embodiments, the boiler system described in 7) above, The ammonia measuring instrument is a laser-type gas measuring instrument configured to measure the ammonia concentration based on the absorption spectrum of laser light transmitted through the exhaust gas.

[0074] According to the configuration described in 8) above, the ammonia measuring instrument is a laser-type gas measuring instrument, which allows for more accurate measurement of ammonia concentration. Therefore, the release of ammonia into the atmosphere after the desulfurization equipment is shut down can be more reliably suppressed.

[0075] 9) In some embodiments, a boiler system according to any of 1) to 8) above, The desulfurization apparatus includes a spraying device (60) configured to spray cleaning water for recovering the ammonia in the flow path of the exhaust gas, An extraction unit (35) configured to extract the ammonia from the washing water, An ammonia resupply line (36) configured to supply the ammonia extracted by the extraction unit to the boiler, To further prepare.

[0076] According to the configuration described in 9) above, the boiler system can be operated efficiently because unburned ammonia contained in the exhaust gas is reused as ammonia fuel.

[0077] 10) A method for operating a boiler system (1) according to at least one embodiment of the present disclosure is: If no misfire is detected in the ammonia burner contained in the boiler, and a boiler trip is detected, a stop command is generated to stop the desulfurization device configured to desulfurize the exhaust gas from the boiler (S15). If a misfire in the ammonia burner is detected and a boiler trip is detected, the operation of the desulfurization apparatus is continued so that ammonia contained in the exhaust gas is recovered (S13:YES).

[0078] According to the configuration described in 10) above, for the same reasons as described in 1) above, a boiler system operation method is realized that can effectively suppress the release of ammonia into the atmosphere with a simple configuration. [Explanation of Symbols]

[0079] 1: Boiler System 10: Boiler 21: Burner 35:Extraction part 36: Ammonia resupply line 46: Desulfurization equipment 51: Ammonia burner 60: Spraying equipment 61: 1st spraying device 62:Second spraying device 70:pH adjustment device 80: Ammonia measuring instrument 110: Controller 121: Frame Detector 122: Interlock 462: Entrance 463 :Exit

Claims

1. A boiler that burns fuel containing ammonia, A desulfurization apparatus configured to perform desulfurization treatment on the exhaust gas from the boiler, Controller and Equipped with, The controller controls the operation of the desulfurization apparatus to continue if a misfire of the ammonia flame in the boiler occurs. Boiler system.

2. A boiler that burns fuel containing ammonia, A desulfurization apparatus configured to perform desulfurization treatment on the exhaust gas from the boiler, Controller and Equipped with, The controller is a boiler system that controls the operation of the desulfurization unit to continue in the event of a misfire of the ammonia flame in the boiler and a boiler trip.

3. A boiler that burns fuel containing ammonia, A desulfurization apparatus configured to perform desulfurization treatment on the exhaust gas from the boiler, an ammonia measuring instrument configured to measure the ammonia concentration of the exhaust gas at at least one of the inlet or outlet sides of the desulfurization apparatus, Controller and Equipped with, When a misfire of the ammonia flame in the boiler occurs and the boiler trips, the controller will stop the operation of the desulfurization unit if the measurement result of the ammonia measuring instrument satisfies the specified recovery conditions, provided that the desulfurization unit continues to operate. Boiler system.

4. A method for operating a boiler system comprising a boiler that burns a fuel containing ammonia, and a desulfurization apparatus configured to desulfurize the exhaust gas from the boiler, If a misfire of the ammonia flame occurs in the boiler, the desulfurization apparatus is controlled to continue operating. Operating procedures for a boiler system.

5. A method for operating a boiler system comprising: a boiler for burning fuel containing ammonia; a desulfurization apparatus configured to desulfurize the exhaust gas from the boiler; and an ammonia measuring instrument configured to measure the ammonia concentration of the exhaust gas at at least one of the inlet or outlet sides of the desulfurization apparatus, If a misfire of the ammonia flame occurs in the boiler and the boiler trips, and the desulfurization unit continues to operate, the operation of the desulfurization unit will be stopped on the condition that the measurement results of the ammonia measuring instrument satisfy the specified recovery conditions. Operating procedures for a boiler system.

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