Boiler system and operating method for 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 of operating a boiler system. [Background technology]

[0002] Boilers in which ammonia is supplied as fuel to a furnace are known. For example, the boiler disclosed in Patent Document 1 performs ammonia co-combustion in which ammonia is combusted together with coal in the furnace. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-112280 A Summary of the Invention [Problem to be solved by the invention]

[0004] The amount of ammonia used as fuel is much larger than the amount of ammonia used as a catalyst for denitration of combustion gas, for example. Therefore, when ammonia misfires in a 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 document does not disclose a specific configuration.

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

[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 a desulfurization treatment on the exhaust gas from the boiler; Controller and Equipped with The controller: If a misfire of the ammonia burner is not detected and a boiler trip is detected, a stop command is generated to stop the desulfurization treatment; When a misfire in the ammonia burner and a trip of the boiler are detected, the operation of the desulfurization device is continued so that the ammonia contained in the exhaust gas is recovered.

[0007] According to at least one embodiment of the present disclosure, a method for operating a boiler system includes: When a misfire of an ammonia burner included in the boiler is not detected and a boiler trip is detected, a stop command is generated to stop a desulfurization device configured to perform a desulfurization treatment on exhaust gas from the boiler; When a misfire in the ammonia burner and a trip of the boiler are detected, the operation of the desulfurization device is continued so that the ammonia contained in the exhaust gas is recovered. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a boiler system that can effectively suppress the release of ammonia into the atmosphere with a simple configuration, and a method for operating a boiler system. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of a boiler system according to one embodiment. [Diagram 2] FIG. 1 is a conceptual configuration diagram of a desulfurization device according to an embodiment. [Diagram 3] FIG. 1 is a conceptual explanatory diagram of a boiler according to an embodiment. [Figure 4] FIG. 2 is a conceptual illustration of an extraction section and an ammonia resupply line according to one embodiment. [Diagram 5] 1 is a flowchart of a method for operating a boiler system according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to this embodiment, and when there are multiple embodiments, the present invention also includes a configuration in which each embodiment is combined. In the following description, up and above refer to the upper side in the vertical direction, and down and below refer to the lower side in the vertical direction, and the vertical direction is not precise and includes an error. Furthermore, the dimensions, materials, shapes, relative arrangements, and the like of the components described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure. For example, expressions expressing relative or absolute configuration, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such a configuration, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions indicating that things are in an equal state, such as "identical," "equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to rectangular shapes, cylindrical shapes, etc. in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect is obtained. On the other hand, the expressions "comprise", "include", or "have" a certain element are not exclusive expressions excluding the presence of other elements. In addition, the same components are denoted by the same reference numerals and the description thereof may be omitted.

[0011] <1. Overall configuration of boiler system 1> FIG. 1 is a schematic configuration diagram showing a boiler system 1 according to the present embodiment, which includes a boiler using ammonia fuel and a fuel other than ammonia fuel as main fuels.

[0012] The boiler 10 included in the boiler system 1 of this embodiment is a boiler that can burn other fuel and ammonia fuel with a burner and generate superheated steam by exchanging heat generated by this combustion with feed water or steam. As the other fuel, a solid fuel such as biomass fuel or coal is used. The coal as the solid fuel is, for example, pulverized coal fuel. The ammonia fuel is liquid ammonia or ammonia gas. In the following, an embodiment in which the ammonia fuel is liquid ammonia is illustrated.

[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 rectangular cylinder shape and is installed vertically. 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, and recovers heat generated by the combustion of pulverized coal fuel by heat exchange with water and steam flowing inside the heat transfer tube, while suppressing 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 inside of the furnace 11. In addition, the combustion device 50 is configured to atomize liquid ammonia with an atomizing fluid (atomizing medium) and inject the atomized ammonia into the inside of the furnace 11. The atomizing fluid in 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. An injection nozzle (not shown) configured to inject pulverized coal fuel into the furnace 11 is provided at the tip of each burner 21. In addition, a two-fluid injection nozzle (not shown) configured to atomize liquid ammonia with an atomizing fluid and inject the ammonia into the furnace 11 is provided at the tip of each ammonia burner 51. The burners 21 and ammonia burners 51 are arranged at equal intervals along the circumferential direction of the furnace 11 (for example, four burners installed at each corner of the rectangular furnace 11), and are arranged in multiple tiers along the vertical direction. In the example of FIG. 1, one set of burners 21 is arranged in two tiers, and one set of ammonia burners 51 is arranged in four tiers. Note that, for convenience of illustration, FIG. 1 shows only two burners out of one set, and each set is given the reference numerals 21 and 51. The shape of the furnace, the number of burner tiers, the number of burners in one tier, the arrangement of the burners, and the like are not limited to this embodiment. The combustion method in the furnace 11 may be either a swirl combustion method or an opposed combustion method. Depending on the combustion method to be 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] The burners 21 of the combustion device 20 are connected to a plurality of mills (pulverizers) 31A, 31B (hereinafter, sometimes collectively referred to as "mills 31") via a plurality of pulverized coal fuel supply pipes 22A, 22B (hereinafter, sometimes collectively referred to as "pulverized coal fuel supply pipes 22"). The mill 31 is, for example, a vertical roller mill in which a pulverizing table (not shown) is supported inside so as to be rotatable and a plurality of pulverizing rollers (not shown) are supported above the pulverizing table so as to be rotatable in conjunction with the rotation of the pulverizing table. The solid fuel pulverized by the cooperation of the pulverizing rollers and the pulverizing table is transported to a classifier (not shown) provided in the mill 31 by primary air (carrier gas, oxidizing gas) supplied to the mill 31. In the classifier, the pulverized coal fuel is classified into pulverized coal fuel having a particle size smaller than that suitable for combustion in the burner 21 and coarse pulverized coal fuel having a particle size larger than the particle size. The pulverized coal fuel passes through the classifier and is supplied to the burner 21 together with primary air via the pulverized coal fuel supply pipe 22. The coarse pulverized coal fuel that does not pass through the classifier falls onto a grinding table by its own weight inside the mill 31 and is re-ground. Each of the pulverized coal fuel supply pipes 22 is provided with a safety shutoff valve 25 for cutting off the supply of pulverized coal fuel in the event of a boiler trip. A method for detecting a boiler trip will be described later.

[0017] The ammonia burner 51 of the combustion device 50 is connected to a fuel supply unit 90. The fuel supply unit 90 of 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 not shown in detail, the supply line 92 may include an ammonia supply line for supplying liquid ammonia, and an atomized fluid supply line for supplying an atomized fluid, which may be, for example, steam, to the combustion device 50. The supply line 92 is also provided with at least one safety shutoff valve 95 configured to operate when a boiler trip occurs.

[0018] An air register 23 is provided on the outside of the furnace 11 at the mounting position of the burner 21 and the ammonia burner 51, and one end of an air duct (air duct) 24 is connected to the air register 23. A forced draft fan (FDF: Forced Draft Fan) 32 is connected to the other end of the air duct 24. 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 via the air register 23 as secondary air (combustion air, oxidizing gas), and is introduced into the furnace 11.

[0019] The combustion gas passage 12 is connected to the vertical upper part of the furnace 11. The combustion gas passage 12 is provided with superheaters 102A, 102B, and 102C (hereinafter, sometimes collectively referred to as "superheaters 102"), reheaters 103A and 103B (hereinafter, sometimes collectively referred to as "reheaters 103"), and a coal economizer 104 as heat exchangers for recovering heat from the combustion gas, and heat is exchanged between the combustion gas generated in the furnace 11 and feed water or steam flowing inside each heat exchanger. The arrangement and shape of each heat exchanger are not limited to the form shown in FIG. 1.

[0020] A flue 13 is connected to the downstream side of the combustion gas passage 12, and discharges the combustion gas whose heat has been recovered by the heat exchanger. An air preheater (air heater) 42 is provided between the flue 13 and the air duct 24, and heat is exchanged between the air flowing through the air duct 24 and the combustion gas flowing through the flue 13, thereby heating the primary air supplied to the mill 31 and the secondary air supplied to the burner 21, thereby recovering further heat from the combustion gas after heat exchange with water and steam.

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

[0022] In the boiler 10, when the multiple mills 31 are driven, pulverized and classified pulverized coal fuel is supplied together with primary air to the burner 21 via the pulverized coal fuel supply pipe 22. In addition, liquid ammonia and atomized fluid are supplied from the fuel supply unit 90 to the ammonia burner 51. Furthermore, secondary air heated by the air preheater 42 is supplied from the air duct 24 to the burner 21 and the ammonia burner 51 via the air register 23. The burner 21 injects a pulverized coal fuel mixture, which is a mixture of pulverized coal fuel and primary air, into the furnace 11, and also injects secondary air into the furnace 11. The pulverized coal fuel mixture injected into the furnace 11 is ignited and reacts with the secondary air to form a flame. The ammonia burner 51 injects secondary air into the furnace 11 together with liquid ammonia atomized by the atomizing fluid. The liquid ammonia injected into the furnace 11 is vaporized into fuel gas, which reacts with the secondary air and burns. High-temperature combustion gas generated by the combustion of pulverized coal fuel and fuel gas rises in the furnace 11 and flows into the combustion gas passage 12. The timing at which liquid ammonia is injected into the furnace 11 may be after the temperature inside the furnace 11 has risen to a certain temperature by the combustion of the pulverized coal fuel. For example, after the mono-combustion of the pulverized coal fuel is performed at the start of the boiler 10, liquid ammonia may be injected into the furnace 11, and ammonia-mixed combustion of the fuel gas vaporized from the liquid ammonia and the pulverized coal fuel may be performed. After that, the injection of the pulverized coal fuel may be stopped, and mono-combustion of ammonia may be performed. In addition, in this embodiment, air is used as the oxidizing gas (primary air, secondary air), but the oxidizing gas may have a higher or lower oxygen content than air, and stable combustion in the furnace 11 can be achieved by adjusting the ratio of the amount of oxygen to the amount of fuel supplied within an appropriate range.

[0023] The combustion gas flowing into the combustion gas passage 12 exchanges heat with water and steam in a superheater 102, a reheater 103, and a coal economizer 104 arranged inside the combustion gas passage 12, and is then discharged into the flue 13, where nitrogen oxides are removed in a denitration device 43, and the combustion gas exchanges heat with primary air and secondary air in an air preheater 42, and is then discharged into a gas duct 41, where ash and the like are removed in a dust collector 44, and sulfur oxides are removed in a desulfurization device 46, and the combustion gas is then discharged to the outside of the system from a chimney 47. Note that the arrangement of the heat exchangers in the combustion gas passage 12 and the devices from the flue 13 to the gas duct 41 with respect to the combustion gas flow does not necessarily have to be in the order described above.

[0024] In this embodiment, when a boiler trip occurs, the safety shutoff valves 25, 95 are actuated, and the supply of fuel to the boiler 10 is immediately stopped. At this time, devices such as the denitration device 43 are also immediately stopped. However, when a misfire of the ammonia burner 51 occurs at the same time as the boiler trip, the desulfurization device 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 of the present disclosure is not limited to the above-mentioned embodiment. The solid fuel used in the boiler may be coal, biomass fuel, petroleum coke (PC) fuel, petroleum residue, etc., instead of or in addition to pulverized coal fuel. The fuel for the boiler to be combined with ammonia fuel is not limited to solid fuels, and may also be petroleum fuels such as heavy oil, light oil, and heavy oil, or liquid fuels such as industrial wastewater. In addition, gaseous fuels such as natural gas, various petroleum gases, and by-product gases generated in the steelmaking process may also be used. Furthermore, the present invention can be applied to a multi-fuel boiler that uses a combination of these various fuels.

[0026] Furthermore, in the boiler of the present disclosure, the ammonia fuel injected into the interior of the furnace may be ammonia gas instead of liquid ammonia. For example, in an embodiment in which ammonia gas is injected into the furnace, the atomizing fluid supply line may not be provided. And, 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 the liquid ammonia by utilizing steam generated in the boiler, combustion gas in the boiler, or seawater outside the boiler system as a direct or indirect heat source.

[0027] <2. Detailed configuration of desulfurization device 46> A detailed configuration of a desulfurization device 46 according to an embodiment of the present disclosure is illustrated with reference to Fig. 2. Fig. 2 is a conceptual explanatory diagram of the desulfurization device 46 according to an embodiment.

[0028] The boiler system 1 includes a desulfurization device 46 configured to perform desulfurization treatment on exhaust gas from the boiler 10. In the desulfurization device 46 of this embodiment, a wet method is adopted in which desulfurization treatment is performed using an absorption liquid. As an example, the absorption liquid is an alkaline aqueous solution using an alkaline reagent such as calcium hydroxide, sodium hydroxide (caustic soda), magnesium hydroxide, or ammonia. In the following, an embodiment in which the absorption liquid is calcium hydroxide is illustrated.

[0029] The desulfurization device 46 includes a desulfurization tower 461 having an inlet 462 and an outlet 463 and in which a pool of absorbing liquid is formed, a first spraying device 61 configured to spray the absorbing liquid into the inside of the desulfurization tower 461, and a limestone supplying device 55 configured to supply limestone to the pool in the inside of the desulfurization tower 461. Exhaust gas from the boiler 10 flows into the inside of the desulfurization tower 461 via the inlet 462 and mixes with the absorbing liquid sprayed by the first spraying device 61. The sulfur oxides contained in the exhaust gas are dissolved in the absorbing liquid, and the exhaust gas is subjected to a desulfurization process. Thereafter, the exhaust gas is discharged from the desulfurization device 46 via the outlet 463 and released into the atmosphere from a chimney 47 (see FIG. 1).

[0030] The first spraying device 61 is configured as follows, for example. The first spraying device 61 includes an absorbent circulation line 611 for circulating the absorbent forming the liquid pool in the desulfurization tower 461, a pump 612 provided in the absorbent circulation line 611, and a spraying unit 615 to which desulfurization treatment is supplied by driving 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 forming the liquid pool is supplied to the spraying unit 615 via the absorbent circulation line 611. As a result, the spraying unit 615 sprays the absorbent inside the desulfurization tower 461.

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

[0032] The desulfurization device 46 as described above performs desulfurization treatment on the exhaust gas by spraying an absorbing liquid onto the exhaust gas during normal operation of the boiler 10. When a boiler trip occurs without a misfire of the ammonia burner 51 of this embodiment (a specific detection method will be described later), the desulfurization device 46 stops operation based on a command from the controller 110. In detail, when a misfire of 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. The stop command of this example is sent to the pump 612 and the limestone supply unit 554 of the desulfurization device 46, and the desulfurization device 46 stops operation.

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

[0034] According to the above configuration, when a boiler trip occurs without misfire of 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 to continue operating the desulfurization device 46. At this time, the desulfurization device 46 stops operating, so that unnecessary operation of the desulfurization device 46 is suppressed. On the other hand, when both a misfire of the ammonia burner 51 and a boiler trip occur, a large amount of unburned ammonia tends to be contained in the exhaust gas. At this time, the controller 110 continues operating the desulfurization device 46 so that the ammonia contained in the exhaust gas is recovered. Since the desulfurization device 46 has both a function of performing a desulfurization process on the exhaust gas and a function of recovering the ammonia contained in the exhaust gas, the configuration of the boiler system 1 is simplified. As described above, the boiler system 1 is realized that can effectively suppress the release of ammonia into the atmosphere using the desulfurization device 46.

[0035] In addition, the desulfurization device 46 according to another embodiment may employ a dry method in which activated carbon, coal ash, or the like is used as an adsorbent to perform desulfurization. Alternatively, a semi-dry method (spray-dry method) in which limestone slurry is sprayed to convert sulfur oxides into powder such as calcium sulfite to perform desulfurization may be employed. Even in such an embodiment, if the desulfurization device 46 continues to operate without stopping when a misfire in the ammonia burner 51 and a boiler trip are detected, unburned ammonia contained in the exhaust gas can be recovered.

[0036] The desulfurization device 46 according to one embodiment of the present disclosure includes a spraying device 60 configured to spray wash water for recovering ammonia into the exhaust gas flow path. The spraying device 60 is a device including the above-mentioned first spraying device 61. According to the above-mentioned configuration, the sprayed wash water and the exhaust gas are well mixed, so that the ammonia contained in the exhaust gas can be efficiently recovered. 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 a first spraying device 61. The second spraying device 62 is, for example, a dedicated device for spraying cleaning water when a misfire occurs in the ammonia burner 51 and the boiler trips. In other words, the second spraying device 62 does not operate during normal operation of the boiler 10. The second spraying device 62 includes a cleaning 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 a configuration similar to that of the first spraying device 61 described above. That is, the cleaning water circulation line 621 corresponds to the absorbing liquid circulation line 611 (cleaning 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 duplication of explanation, explanations of the components and operations of the second spraying device 62 will be omitted.

[0038] According to the above configuration, when misfire of the ammonia burner 51 is detected and also when a boiler trip is detected, the second sprinkler 62 executes the operation of sprinkling cleaning water in addition to the first sprinkler 61. Therefore, it is possible to recover more unburned ammonia contained in the exhaust gas. The second spraying device 62 may be disposed at a position other than that shown in Fig. 2. For example, it may be disposed at the inlet 462 of the desulfurization device 46. The cleaning water sprayed by the second spraying device 62 may be water (industrial water). This is because water can absorb a certain amount of ammonia if a large amount is supplied.

[0039] The spraying device 60 according to an embodiment of the present disclosure further includes a pH adjustment device 70 configured to start an operation of reducing the pH of the wash water after the desulfurization device 46 continues to operate (i.e., after the ammonia burner 51 misfires and the boiler trips). The pH adjustment device 70 of this embodiment includes the above-mentioned limestone supply device 55 and a pH measurement device 71 electrically connected to the controller 110. After the desulfurization device 46 continues to operate, the controller 110 controls the limestone supply unit 554 so that the pH of the liquid pool determined based on the measurement result of the pH measurement device 71 becomes less than 7. The pH of the liquid pool is preferably adjusted to 3 or more and less than 6. For example, if the pH of the liquid pool exceeds 7, an additive such as a pH adjuster is introduced through an introduction port (not shown) to reduce the pH.

[0040] The more acidic the wash water that is mixed with the exhaust gas, the easier it is for unburned ammonia to dissolve in the wash water. This is thought to be because, in the following chemical formula (1), which shows that ammonia gas contained in exhaust gas dissolves in wash water, the equilibrium shifts to the left as the pH decreases. NH4 + +OH - →NH3↑+H2O (1) According to the above configuration, when misfire of the ammonia burner 51 and a boiler trip are detected, the pH of the cleaning water to be sprayed is reduced, so that unburned ammonia contained in the exhaust gas can be recovered more efficiently.

[0041] Moreover, the boiler system 1 according to an embodiment of the present disclosure includes an ammonia meter 80 configured to measure the ammonia concentration of the exhaust gas at least on the inlet 462 side or the outlet 463 side of the desulfurization device 46. In this embodiment, the ammonia meter 80 electrically connected to the controller 110 includes a first ammonia meter 81 for measuring the ammonia concentration of the exhaust gas flowing into the desulfurization device 46 and a second ammonia meter 82 for measuring the ammonia concentration of the exhaust gas flowing out from the desulfurization device 46. The controller 110 is configured to generate an ammonia recovery stop command for the desulfurization device 46 to stop operation on the condition that the measurement result of the ammonia meter 80 satisfies a specified return condition after the operation of the desulfurization device 46 continues. The ammonia recovery stop command is a command similar to the stop command described above.

[0042] The specified condition in this embodiment is that the difference between the ammonia concentration on the inlet side calculated based on the detection result of the first ammonia measuring instrument 81 and the ammonia concentration on the outlet side calculated based on the detection result of the second ammonia measuring instrument 82 falls below the specified concentration. In other embodiments, the ammonia measuring instrument 80 may include only either the first ammonia measuring instrument 81 or the second ammonia measuring instrument 82. For example, in an embodiment in which only the second ammonia measuring instrument 82 is provided, the return condition is satisfied if the measurement result of the second ammonia measuring instrument 82 falls below the specified concentration.

[0043] According to the above configuration, when the ammonia concentration based on the measurement result of the ammonia measuring instrument 80 satisfies the specified restoration condition, the desulfurization device 46 stops the continued operation. Since unnecessary operation of the desulfurization device 46 is suppressed, efficient operation of the desulfurization device 46 is realized.

[0044] The ammonia measuring instrument 80 according to an embodiment of the present disclosure is a laser-type gas measuring instrument configured to measure an ammonia concentration based on an 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 the 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 the light from the light-emitting unit 82A. Ammonia gas has a unique light absorption spectrum that absorbs light. In addition, the absorbance correlates with the concentration of ammonia gas. Therefore, by performing spectrum analysis on the output signals output from the light receiving units 81B and 82B, it is possible to measure the ammonia concentration at each of the inlet 462 and the outlet 463. In addition, the light absorption spectrum of ammonia gas is different from the light absorption spectra of the sulfur compound gas, the nitrogen compound gas, and the carbon compound gas contained in the exhaust gas. Therefore, by performing gas measurement using a laser method, the concentration of ammonia gas can be accurately measured without being affected by other gases.

[0045] According to the above configuration, since the ammonia measuring instrument 80 is a laser type gas measuring instrument, the ammonia concentration can be measured more accurately. Therefore, it is possible to suppress erroneous detection that the ammonia concentration has sufficiently decreased when the concentration of unburned ammonia contained in the exhaust gas is not actually sufficiently decreased. Therefore, it is possible to more reliably suppress the release of ammonia into the atmosphere after the operation of the desulfurization device 46 is stopped.

[0046] <3. Details of detection of ammonia burner 51 misfire and boiler trip> A method for detecting misfire in the ammonia burner 51 and a method for detecting a boiler trip will be illustrated in detail with reference to Fig. 3. Fig. 3 is a conceptual explanatory diagram of a boiler 10 according to an embodiment of the present disclosure.

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

[0048] The controller 110 electrically connected to the flame detector 121 is configured to determine the presence or absence of misfire in the ammonia burner 51 based on the detection result of the flame detector 121. According to the above configuration, the controller 110 can accurately determine the presence or absence of misfire in the ammonia burner 51 based on the detection result of the flame detector 121. Therefore, erroneous determination of the presence or absence of misfire in the ammonia burner 51 is suppressed.

[0049] <3-2. Boiler trip detection> The boiler system 1 of the present embodiment further includes an interlock 122 configured to cause a boiler trip when at least one of a plurality of stop conditions is satisfied. 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 operation of the emergency stop switch. In another embodiment, the controller 110 may be connected to at least one of a temperature measuring instrument for measuring the temperature (for example, the temperature of the nose wall) in the furnace 11 and a pressure measuring instrument for measuring the pressure in the furnace 11. If the measurement results of these measuring instruments do not satisfy the specified conditions, the interlock 122 is activated and the safety shutoff valves 25, 95 are activated. The controller 110 of the present embodiment is configured to determine the presence or absence of a boiler trip based on the output signal from the interlock 122. According to the above configuration, the controller 110 can more accurately determine the presence or absence of a boiler trip based on the output signal from the interlock 122.

[0050] <4. Reuse of ammonia recovered by the desulfurization unit 46> A method for reusing ammonia recovered by the desulfurization device 46 will be illustrated with reference to Fig. 4. Fig. 4 is a conceptual explanatory diagram of the extraction section 35 and the ammonia resupply line 36 according to one embodiment of the present disclosure.

[0051] The boiler system 1 according to one embodiment of the present disclosure further includes an extraction section 35 configured to extract ammonia from the cleaning water, and an ammonia resupply line 36 configured to supply the ammonia extracted by the extraction section 35 to the boiler 10. The extraction section 35 of this embodiment is connected to the desulfurization tower 461 of the desulfurization device 46 via the wash water line 49. For example, when the ammonia recovery operation of the desulfurization device 46 is completed and the boiler 10 resumes normal operation, the pump 59 provided on the wash water line 49 is driven to send the wash water from the liquid pool of the desulfurization tower 461 to the extraction section 35. The extraction section 35, which may be a stripper, separates the wash water into ammonia gas and the wash water from which the ammonia gas has been recovered by subjecting the wash water to an ammonia stripping treatment. 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 re-supply line 36 and is supplied to the boiler 10. In an embodiment in which the ammonia burner 51 of the combustion device 50 injects ammonia gas instead of liquid ammonia, the ammonia re-supply line 36 may be connected to the above-mentioned supply line 92.

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

[0053] <5. Operating method of boiler system 1> Referring to Fig. 5, an operation method of the boiler system 1 according to an embodiment of the present disclosure is illustrated. Fig. 5 is a flowchart of the operation method of the boiler system 1 according to an 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, the controller 110 determines whether or not a boiler trip has occurred based on an output signal from the interlock 122. If it is determined that a boiler trip has not occurred (S11: NO), the controller 110 waits and the boiler 10 continues to operate. If an accident occurs in the ammonia burner 51 while the controller 110 is waiting, the ammonia injected from the ammonia burner 51 is burned by a flame generated in the furnace 11 in association with 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] When it is determined that a boiler trip has occurred (S11: YES), the controller 110 determines whether or not a misfire has occurred in the ammonia burner 51 (S13). For example, the presence or absence of a misfire in the ammonia burner 51 is determined based on, for example, the detection result of the flame detector 121. When it is determined that a misfire in the ammonia burner 51 has not occurred (S13: NO), the controller 110 operates the safety shutoff valves 25, 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 device 46, which stops operation, 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 device 46 stops operation, it is unlikely that a large amount of ammonia will be released into the atmosphere. After the process of this flowchart is completed, the operator takes the prescribed action on the boiler system 1, and the boiler 10 resumes operation.

[0056] On the other hand, when it is determined that misfire of the ammonia burner 51 has occurred (S13: YES), the controller 110 determines not to generate a stop command and shifts the process to S17. As a result, the desulfurization device 46 continues to operate, and the ammonia recovery process can be executed instead of the desulfurization process. The controller 110 starts the operation of the second spraying device 62 (S17). In the desulfurization device 46, in addition to the first spraying device 61 that has been operating since before the boiler trip, the second spraying device 62 starts operating, so that more cleaning water is sprayed. Note that, when executing S17, the controller 110 may operate the pH measuring device 71 to reduce the pH of the cleaning water.

[0057] The controller 110 judges whether or not the measurement result of the ammonia measuring device 80 satisfies a specified return condition (S19). Until the measurement result satisfies the specified return condition (S19: NO), the controller 110 waits, and the desulfurization device 46 executes the ammonia recovery operation. If it is judged that the return condition is satisfied (S19: YES), the controller 110 generates an ammonia recovery stop command and sends it to the desulfurization device 46 (S21). As a result, the desulfurization device 46 stops operating, the ammonia recovery process ends, and this flowchart also ends.

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

[0059] 1) The boiler system (1) according to at least one embodiment of the present disclosure includes: a boiler (10) including an ammonia burner (51); a desulfurization device (46) configured to subject exhaust gas from the boiler to a desulfurization treatment; Controller (110) Equipped with The controller: If a misfire of the ammonia burner is not detected and a boiler trip is detected, a stop command is generated to stop the desulfurization treatment; When a misfire in the ammonia burner and a trip of the boiler are detected, the operation of the desulfurization device is continued so that the ammonia contained in the exhaust gas is recovered.

[0060] According to the configuration of 1) above, if a boiler trip occurs without misfire of the ammonia burner, it is unlikely that a large amount of unburned ammonia will be contained in the exhaust gas from the boiler, and there is little need to continue operating the desulfurization device. In this case, the desulfurization device stops operating, and unnecessary operation of the desulfurization device is suppressed. On the other hand, if both a misfire of the ammonia burner and a boiler trip occur, a large amount of unburned ammonia tends to be contained in the exhaust gas. In this case, the controller continues operating the desulfurization device so that the ammonia contained in the exhaust gas is recovered. Since the desulfurization device has both a function of performing desulfurization treatment on the exhaust gas and a function of recovering the ammonia contained in the exhaust gas, the configuration of the boiler system is simplified. As described above, 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 according to 1) above, The desulfurization device includes a sparging device (60) configured to sparge wash water in a flow path of the exhaust gas for recovering the ammonia.

[0062] According to the above configuration 2), the sprayed cleaning water and the exhaust gas are thoroughly mixed together, so that the ammonia contained in the exhaust gas can be efficiently collected, thereby further suppressing the release of ammonia into the atmosphere.

[0063] 3) In some embodiments, the boiler system according to 2) above, The spraying device is a first spraying device (61) configured to continue the spraying operation of the cleaning water that has been performed before the boiler trip is detected even after the operation of the desulfurization device continues; and a second spraying device (62) configured to start the operation of spraying the wash water, which had been stopped before the boiler trip was detected, after the operation of the desulfurization device continues.

[0064] According to the above configuration 3), when a misfire of the ammonia burner is detected and a boiler trip is detected, the second sprinkler performs the operation of sprinkling cleaning water in addition to the first sprinkler, so that more unburned ammonia contained in the exhaust gas can be recovered.

[0065] 4) In some embodiments, the boiler system according to 2) or 3) above, The desulfurization apparatus further includes a pH adjustment device (70) configured to initiate an operation to reduce the pH of the wash water after continued operation of the desulfurization apparatus.

[0066] According to the above configuration 4), when misfire of the ammonia burner is detected and a boiler trip is detected, the pH of the sprayed cleaning water is reduced, so that unburned ammonia contained in the exhaust gas can be recovered more efficiently.

[0067] 5) In some embodiments, the boiler system according to any one of 1) to 4) above, 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 above configuration 5), the controller can accurately determine whether or not a flame has occurred in the ammonia burner based on the detection result of the flame detector.

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

[0070] According to the above configuration 6), the controller can more accurately determine whether or not the boiler has tripped, based on the output signal of the interlock.

[0071] 7) In some embodiments, the boiler system according to any one of 1) to 6) above, an ammonia meter (80) configured to measure an ammonia concentration of the exhaust gas at least on one of an inlet side or an outlet side of the desulfurization device; The controller is configured to generate an ammonia recovery stop command for the desulfurization device to stop operation on condition that, after continuing operation of the desulfurization device, the measurement result of the ammonia measuring instrument satisfies a specified recovery condition.

[0072] According to the above configuration 7), when the ammonia concentration based on the measurement results of the ammonia meter satisfies the specified recovery condition, the desulfurization device stops its continued operation. This prevents unnecessary operation of the desulfurization device, thereby realizing efficient operation of the desulfurization device.

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

[0074] According to the above configuration 8), since the ammonia meter is a laser type gas meter, the ammonia concentration can be measured more accurately. Therefore, it is possible to more reliably prevent ammonia from being released into the atmosphere after the operation of the desulfurization device is stopped.

[0075] 9) In some embodiments, the boiler system according to any one of 1) to 8) above, The desulfurization device includes a sparging device (60) configured to sparge wash water for recovering the ammonia in a flow path of the exhaust gas, an extraction section (35) configured to extract the ammonia from the wash water; an ammonia resupply line (36) configured to supply the ammonia extracted by the extraction section to the boiler; It further comprises:

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

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

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

[0079] 1: Boiler system 10: Boiler 21: Burna 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 device configured to perform a desulfurization treatment on the exhaust gas from the boiler; Controller and Equipped with The controller controls the operation of the desulfurization device depending on whether or not an ammonia flame misfire occurs in the boiler. Boiler system.

2. A boiler that burns fuel containing ammonia; A desulfurization device configured to perform a desulfurization treatment on the exhaust gas from the boiler; Controller and Equipped with The boiler system further comprises a controller for controlling operation of the desulfurization device according to whether or not an ammonia flame misfire has occurred in the boiler and whether or not the boiler has tripped.

3. A boiler that burns fuel containing ammonia; A desulfurization device configured to perform a desulfurization treatment on the exhaust gas from the boiler; an ammonia meter configured to measure an ammonia concentration of the exhaust gas at at least one of an inlet side or an outlet side of the desulfurization device; Controller and Equipped with The controller stops operation of the desulfurization device when a trip of the boiler occurs and a measurement result of the ammonia measuring device satisfies a specified recovery condition. Boiler system.

4. A method for operating a boiler system including a boiler that burns a fuel containing ammonia and a desulfurization device configured to perform a desulfurization treatment on exhaust gas from the boiler, comprising: The operation of the desulfurization device is controlled depending on whether or not an ammonia flame misfire occurs in the boiler. How to operate a boiler system.

5. A method for operating a boiler system including: a boiler that burns fuel containing ammonia; a desulfurization device configured to perform a desulfurization treatment on exhaust gas from the boiler; and an ammonia meter configured to measure an ammonia concentration of the exhaust gas at least on one of an inlet side and an outlet side of the desulfurization device, When the boiler trips, the operation of the desulfurization device is stopped on condition that the measurement result of the ammonia meter satisfies a specified recovery condition. How to operate a boiler system.

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