Boiler system, power generation plant, and method of operating boiler system

Abstract

To downsize a boiler system.SOLUTION: A boiler system comprises: a boiler 10 for burning ammonia fuel to generate steam; a fuel supply system 20 for supplying the boiler 10 with ammonia fuel; and a vacuum unit 30 for evacuating the ammonia fuel in the fuel supply system 20 to guide the ammonia fuel remaining in the fuel supply system 20 into a furnace 12 of the boiler 10. The boiler system further comprises: a purge gas supply unit 40 for supplying the fuel supply system 20 with purge gas; and a storage unit 50 for storing the ammonia fuel and the purge gas discharged from the fuel supply system 20 by the purge gas supply unit 40.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a boiler system, a power plant, and a method of operating a boiler system. [Background technology]

[0002] BACKGROUND ART A boiler system is known that generates steam by burning ammonia supplied into a furnace as fuel (for example, Patent Document 1). Patent Document 1 describes a boiler system including a boiler that uses ammonia fuel and a fuel other than ammonia fuel as its main fuels. This system includes an ammonia fuel supply pipe for supplying ammonia fuel stored in an ammonia tank to the boiler. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-178840 Summary of the Invention [Problem to be solved by the invention]

[0004] After the system is shut down, ammonia fuel remaining in the fuel supply system, such as the fuel supply pipe, may corrode the pipes, etc. To prevent this, the ammonia fuel remaining in the fuel supply system after the system is shut down may be discharged from the fuel supply system. One possible method for discharging ammonia fuel remaining in the fuel supply system is to supply a purge gas or the like into the fuel supply system, push out the ammonia fuel in the fuel supply system, and then guide the ammonia fuel to a predetermined facility (for example, a purge gas storage tank). However, with this method, the purge gas is also guided to the predetermined facility along with the ammonia fuel. Therefore, the capacity of the predetermined facility needs to be determined taking into account the purge gas, and therefore the capacity of the predetermined facility needs to be increased. This means that the predetermined facility may become larger, which may in turn increase the size of the entire system.

[0005] The present disclosure has been made in consideration of the above circumstances, and aims to provide a boiler system and power generation plant that can be made smaller, as well as a method for operating a boiler system. [Means for solving the problem]

[0006] In order to solve the above problems, the boiler system, power plant, and boiler system operating method of the present disclosure employ the following measures. A boiler system according to one aspect of the present disclosure includes a boiler that generates steam by burning ammonia fuel, a fuel supply system that supplies ammonia fuel to the boiler, and a vacuum unit that draws a vacuum on the ammonia fuel in the fuel supply system, thereby guiding the ammonia fuel remaining in the fuel supply system to a predetermined facility.

[0007] Furthermore, a method for operating a boiler system according to one aspect of the present disclosure includes the boiler system including a boiler that generates steam by burning ammonia fuel, a fuel supply system that supplies ammonia fuel to the boiler, and a vacuum unit that evacuates the ammonia fuel in the fuel supply system, and includes a step of guiding the ammonia fuel remaining in the fuel supply system to a predetermined facility by evacuating the ammonia fuel in the fuel supply system with the vacuum unit. [Effects of the Invention]

[0008] According to the present disclosure, the boiler system can be made smaller. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram showing a boiler system according to a first embodiment of the present disclosure. [Figure 2] 1 is a schematic configuration diagram showing a boiler system according to a first embodiment of the present disclosure. [Figure 3] 3 is a flowchart showing an example of processing performed by the boiler system according to the first embodiment of the present disclosure. [Figure 4] 1 is a schematic configuration diagram showing a boiler system according to a first embodiment of the present disclosure. [Figure 5] 3 is a flowchart showing an example of processing performed by the boiler system according to the first embodiment of the present disclosure. [Figure 6] FIG. 4 is a schematic configuration diagram showing a boiler system according to a second embodiment of the present disclosure. [Figure 7] FIG. 10 is a schematic configuration diagram showing a boiler system according to a third embodiment of the present disclosure. [Figure 8] FIG. 10 is a schematic configuration diagram showing a boiler system according to a modified example of the third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of a boiler system, a power plant, and a method of operating a boiler system according to the present disclosure will be described with reference to the drawings.

[0011] [First embodiment] The power plant 1 of this embodiment includes a boiler system 2 that generates steam, a steam turbine (not shown) that is driven by the steam generated by the boiler system 2, and a power generation section (not shown) that generates electricity using the driving force of the steam turbine.

[0012] 1 is a schematic configuration diagram showing a boiler system 2 of this embodiment. The boiler system 2 includes a boiler (predetermined facility) 10 that generates steam, an ammonia supply system (fuel supply system) 20 that supplies ammonia fuel to the boiler 10, a solid fuel supply system (not shown) that supplies solid fuel to the boiler 10, a vacuum unit 30 that introduces ammonia fuel in the ammonia fuel supply system to the boiler 10, a purge gas supply unit 40 that supplies purge gas to the ammonia supply system 20, and a purge gas storage unit (storage unit) 50 that can store the purge gas.

[0013] The boiler 10 of this embodiment is a boiler that can generate steam by burning pulverized fuel made by pulverizing solid fuel and ammonia using a burner 11 and exchanging the heat generated by this combustion with feedwater or steam. As the solid fuel, biomass fuel, coal, etc. are used. The ammonia fuel may be liquid or gas.

[0014] The boiler 10 generates steam by exchanging heat between the combustion gas generated in the furnace 12 and feedwater in a heat exchanger. The boiler 10 has a furnace 12 and a plurality of burners 11. The burners 11 are arranged at equal intervals along the circumferential direction of the furnace 12 as one set, and are arranged in a plurality of stages along the vertical direction. Note that, for convenience of illustration, only one burner 11 is shown in each drawing. The shape of the furnace 12, the number of stages of the burners 11, the number of burners 11 per stage, the arrangement of the burners 11, etc. are not limited to this embodiment.

[0015] A burner 11 connected to a solid fuel supply system is supplied with solid fuel that has been dried and pulverized in a mill (not shown), and forms a flame in a furnace 12 by burning the supplied solid fuel.

[0016] Ammonia fuel is supplied to the burner 11 connected to the ammonia supply system 20, and a flame is formed in the furnace 12 by burning the supplied ammonia fuel.

[0017] The ammonia supply system 20 includes an ammonia tank 21 that stores ammonia fuel, and an ammonia supply facility 22 that supplies the ammonia fuel stored in the ammonia tank 21 to the boiler 10. The ammonia supply system 20 also includes a first ammonia supply pipe 23 that connects the ammonia tank 21 and the ammonia supply facility 22, and a second ammonia supply pipe 24 that connects the ammonia supply facility 22 and the boiler 10 (more specifically, the burner 11).

[0018] The first ammonia supply pipe 23 guides the ammonia fuel stored in the ammonia tank 21 to the ammonia supply equipment 22. A pump 23a is provided in the first ammonia supply pipe 23. The ammonia fuel flows through the first ammonia supply pipe 23 by the driving force of the pump 23a.

[0019] The second ammonia supply pipe 24 guides the ammonia fuel discharged from the ammonia supply facility 22 to the boiler 10 (more specifically, the burner 11). The second ammonia supply pipe 24 is provided with a first on-off valve 24a, a second on-off valve 24b, and a flow rate control valve 24c, in this order from the upstream side. The first on-off valve 24a and the second on-off valve 24b can be switched between an open state and a closed state. Furthermore, the flow rate control valve 24c can adjust the flow rate of the ammonia fuel flowing through the second ammonia supply pipe 24 toward the boiler 10 by adjusting the opening degree.

[0020] The vacuum section 30 draws a vacuum on the ammonia fuel in the ammonia supply system 20, thereby leading the ammonia fuel remaining in the ammonia supply system 20 to the furnace 12 of the boiler 10. The ammonia fuel led to the furnace 12 is combusted in the furnace 12. The vacuum section 30 includes a first ammonia discharge pipe 31 branching off from the second ammonia supply pipe 24, a vacuum facility 32 to which the downstream end of the first ammonia discharge pipe 31 is connected, and a second ammonia discharge pipe 33 connecting the vacuum facility 32 to the boiler 10 (more specifically, the furnace 12).

[0021] The first ammonia discharge pipe 31 connects the second ammonia supply pipe 24 and the vacuum facility 32. The upstream end of the first ammonia discharge pipe 31 is connected to a midpoint of the second ammonia supply pipe 24. Specifically, the upstream end of the first ammonia discharge pipe 31 is connected to a portion of the second ammonia supply pipe 24 that is downstream of the first on-off valve 24a and upstream of the second on-off valve 24b. The upstream end of the first ammonia discharge pipe 31 is connected to a portion of the second ammonia supply pipe 24 that is downstream of a connection position of a first purge gas pipe 42, which will be described later.

[0022] The first ammonia discharge pipe 31 guides the ammonia fuel remaining in the second ammonia supply pipe 24 to the vacuum facility 32. A third on-off valve 31a is provided in the first ammonia discharge pipe 31. The third on-off valve 31a can be switched between an open state and a closed state to switch between a state in which ammonia fuel flows through the first ammonia discharge pipe 31 and a state in which it does not flow through the first ammonia discharge pipe 31.

[0023] The vacuum equipment 32 creates a vacuum inside the first ammonia discharge pipe 31, thereby guiding the ammonia fuel remaining in the ammonia supply system 20 to the boiler 10. Specifically, the vacuum equipment 32 creates a pressure inside the first ammonia discharge pipe 31 that is lower than atmospheric pressure.

[0024] An example of the vacuum equipment 32 is a liquid ring vacuum pump. When a liquid ring vacuum pump is used as the vacuum equipment 32, an alkaline solution (e.g., a sodium hydroxide solution, an ammonia solution, etc.) may be used as the liquid used for the liquid seal. By doing so, the ammonia fuel sucked from the second ammonia supply pipe 24 can be made less likely to dissolve in the liquid used for the liquid seal.

[0025] Another example of the vacuum equipment 32 is an ejector. When an ejector is used as the vacuum equipment 32, air or steam may be used as the driving fluid. When air is used as the driving fluid, the air is introduced into the furnace 12 of the boiler 10 together with the ammonia fuel, which may result in the generation of nitrogen oxides (NOx) in the furnace 12. On the other hand, when steam is used as the driving fluid, the generation of NOx in the furnace 12 can be suppressed. When the generation of NOx in the furnace 12 is tolerable, air may be used as the driving fluid. By using air as the driving fluid, the structure of the vacuum equipment 32 and the piping system for supplying the driving fluid can be simplified.

[0026] The second ammonia discharge pipe 33 guides the ammonia fuel discharged from the vacuum facility 32 into the furnace 12 of the boiler 10. The downstream end of the second ammonia discharge pipe 33 is connected to the furnace 12 of the boiler 10. 1, the downstream end of the second ammonia discharge pipe 33 may be connected to an intermediate position of the second ammonia supply pipe 24. Specifically, the downstream end of the second ammonia discharge pipe 33 may be connected to a portion of the second ammonia supply pipe 24 downstream of the flow rate control valve 24c. With this configuration, the ammonia fuel remaining in the ammonia supply system 20 can be guided to the burner 11 of the boiler 10 and combusted by the burner 11.

[0027] A fourth on-off valve 33a is provided in the second ammonia discharge pipe 33. The fourth on-off valve 33a can switch between an open state and a closed state, thereby switching between a state in which ammonia fuel flows through the second ammonia discharge pipe 33 and a state in which ammonia fuel does not flow through the second ammonia discharge pipe 33.

[0028] The purge gas supply unit 40 supplies a purge gas (for example, nitrogen) to the ammonia supply system 20, thereby guiding the ammonia fuel remaining in the ammonia supply system 20 to the boiler . The purge gas supply unit 40 includes a purge gas supply device 41 that supplies purge gas, and a first purge gas pipe 42 through which the purge gas discharged from the purge gas supply device 41 flows. The purge gas supply device 41 supplies a purge gas into the first purge gas pipe .

[0029] The first purge gas pipe 42 guides the purge gas discharged from the purge gas supply device 41 to the ammonia supply system 20. The downstream end of the first purge gas pipe 42 is connected to the second ammonia supply pipe 24. In detail, the downstream end of the first purge gas pipe 42 is connected to a part of the second ammonia supply pipe 24 that is downstream of the first on-off valve 24a and upstream of the branch position of the first ammonia discharge pipe 31. A fifth on-off valve 42a is provided in the first purge gas pipe 42. The fifth on-off valve 42a can be switched between an open state and a closed state, thereby switching between a state in which purge gas flows through the first purge gas pipe 42 and a state in which purge gas does not flow through the first purge gas pipe 42.

[0030] The purge gas storage section 50 according to this embodiment stores the ammonia fuel pushed out by the purge gas when the boiler 10 is unable to perform combustion processing of the ammonia fuel, such as during an emergency shutdown of the boiler 10. The purge gas reservoir 50 includes a purge gas storage tank 52 that stores the purge gas, and a second purge gas pipe 51 through which the purge gas introduced into the purge gas storage tank 52 flows.

[0031] The second purge gas pipe 51 guides the ammonia fuel and purge gas discharged from the ammonia supply system 20 to the purge gas storage tank 52. The upstream end of the second purge gas pipe 51 is connected to the first ammonia discharge pipe 31. In detail, the upstream end of the second purge gas pipe 51 is connected to the first ammonia discharge pipe 31 on the upstream side of the third on-off valve 31 a. A sixth on-off valve 51a is provided in the second purge gas pipe 51. The sixth on-off valve 51a can be switched between an open state and a closed state to switch between a state in which purge gas flows through the second purge gas pipe 51 and a state in which purge gas does not flow through the second purge gas pipe 51.

[0032] The boiler system 2 also includes a control unit (not shown) that controls the opening and closing of each on-off valve, the opening degree of the flow rate adjustment valve 24c, and the starting and stopping of the pump 23a. The controller includes, for example, a CPU (Central Processing Unit: Processor), a main memory, a secondary storage, etc. Furthermore, the controller may include a communication unit for transmitting and receiving information to and from other devices. The main storage device is composed of writable memory such as cache memory and RAM (Random Access Memory), and is used as a working area for reading the execution program of the CPU and writing the processing data by the execution program. A secondary storage device is a non-transitory computer-readable storage medium, such as a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, or a semiconductor memory. For example, a series of processes for realizing various functions is stored in a secondary storage device in the form of a program, and the CPU reads this program into the main storage device and executes information processing and arithmetic operations to realize various functions. Note that the program may be pre-installed in the secondary storage device, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Examples of computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0033] [Normal operation] Next, the flow of ammonia fuel during normal operation of the boiler system 2 will be described with reference to FIG. During normal operation, as shown in Fig. 1, the first on-off valve 24a and the second on-off valve 24b are in an open state. Furthermore, the third on-off valve 31a, the fourth on-off valve 33a, the fifth on-off valve 42a, and the sixth on-off valve 51a are in a closed state. As a result, the ammonia fuel stored in the ammonia tank 21 is led to the burner 11 of the boiler 10 via the first ammonia supply pipe 23 and the second ammonia supply pipe 24. The ammonia fuel led to the burner 11 is combusted in the burner 11. The burner 11 forms a flame in the furnace 12 by combusting the ammonia fuel.

[0034] [Residual ammonia fuel discharge operation] Next, a processing procedure and a flow of ammonia fuel in an operation for discharging ammonia fuel remaining in the ammonia supply system 20 after the supply of ammonia fuel to the boiler 10 is stopped will be described with reference to Figures 2 to 5. When the supply of ammonia fuel to the boiler 10 is stopped, ammonia fuel remains in the ammonia supply system 20.

[0035] Batch Processing First, a case where ammonia fuel is discharged in a batch process will be described. 3, when stopping the supply of ammonia fuel to the boiler 10, first, the second on-off valve 24b is closed in step S1. Next, in order to limit the range in which the ammonia fuel is discharged, the first on-off valve 24a is closed.

[0036] Next, in step S2, the vacuum equipment 32 is operated. Specifically, the third on-off valve 31a and the fourth on-off valve 33a are opened, and the vacuum equipment 32 is operated. As a result, as shown in FIG. 2, the ammonia fuel remaining in the ammonia supply system 20 (specifically, the second ammonia supply piping 24) is sucked by the vacuum equipment 32 and introduced into the furnace 12 of the boiler 10 via the first ammonia discharge piping 31 and the second ammonia discharge piping 33. The ammonia fuel introduced into the furnace 12 is combusted by the flame of another burner 11 (for example, a burner 11 that combusts solid fuel). The vacuum equipment 32 is operated until it becomes impossible to evacuate the ammonia fuel. When it becomes impossible to evacuate the ammonia fuel, the process proceeds to step S3.

[0037] In step S3, the vacuum facility 32 is temporarily stopped. Specifically, the third on-off valve 31a and the fourth on-off valve 33a are closed, and the vacuum facility 32 is stopped. Once the vacuum facility 32 is stopped, the process proceeds to step S4.

[0038] In step S4, purge gas is introduced into the ammonia supply system 20. Specifically, the purge gas supply device 41 is operated and the fifth on-off valve 42a is opened to introduce the purge gas into the ammonia supply system 20. For example, in step S2, the vacuum equipment 32 may evacuate the ammonia supply system 20 until the pressure in the ammonia supply system 20 reaches 0.1 bar, and then in step S4, the pressure in the ammonia supply system 20 may be increased to 5.0 bar. By pressurizing in this manner, the ammonia supply system 20 becomes 98% purge gas and 2% ammonia fuel.

[0039] In step S5, the vacuum equipment 32 is restarted. Specifically, the fifth on-off valve 42a is closed, and the third on-off valve 31a and the fourth on-off valve 33a are opened. The vacuum equipment 32 is also started. By restarting the vacuum equipment 32, the fluid (purge gas and ammonia fuel) in the ammonia supply system 20 is introduced into the furnace 12 of the boiler 10. If evacuation is no longer possible, the process proceeds to step S6.

[0040] In step S6, the vacuum facility 32 is again stopped. Specifically, the third on-off valve 31a and the fourth on-off valve 33a are closed, and the vacuum facility 32 is stopped. Once the vacuum facility 32 is again stopped, the process proceeds to step S7.

[0041] In step S7, the ammonia concentration in the ammonia supply system 20 is detected, and it is determined whether the concentration is equal to or lower than a predetermined concentration. If it is determined that the ammonia concentration is not equal to or lower than the predetermined concentration, the process returns to step S4. If it is determined that the ammonia concentration is equal to or lower than the predetermined concentration, the process ends.

[0042] [Continuous processing] The method for discharging the ammonia fuel is not limited to the batch process described above, and for example, the ammonia fuel may be discharged by a continuous process. The case where ammonia fuel is discharged in a continuous process will be described below. 5, when stopping the supply of ammonia fuel to the boiler 10, first, in step S11, the second on-off valve 24b is closed. Next, in order to limit the range in which the ammonia fuel is discharged, the first on-off valve 24a is closed.

[0043] Next, in step S12, the vacuum equipment 32 is operated. Specifically, the third on-off valve 31a and the fourth on-off valve 33a are opened, and the vacuum equipment 32 is operated. As a result, as shown in FIG. 2, the ammonia fuel remaining in the ammonia supply system 20 (specifically, the second ammonia supply piping 24) is sucked by the vacuum equipment 32 and introduced into the furnace 12 of the boiler 10 via the first ammonia discharge piping 31 and the second ammonia discharge piping 33. The ammonia fuel introduced into the furnace 12 is combusted by the flame of another burner 11 (for example, a burner 11 that combusts solid fuel). The vacuum equipment 32 is operated until it becomes impossible to evacuate the ammonia fuel. When it becomes impossible to evacuate the ammonia fuel, the process proceeds to step S13.

[0044] In step 13, while the vacuum equipment 32 is operating, purge gas is introduced into the ammonia supply system 20. Specifically, the fifth on-off valve 42a is opened, and purge gas is continuously introduced into the ammonia supply system 20 at a flow rate that can be processed by the vacuum equipment 32. The flow rate of the purge gas may be adjusted by, for example, replacing the fifth on-off valve 42a with a flow rate adjustment valve and adjusting the aperture of the flow rate adjustment valve. Alternatively, the flow rate of the purge gas may be adjusted by providing an orifice in the first purge gas pipe 42. By introducing the purge gas into the ammonia supply system 20 in step 13, the ammonia fuel remaining in the ammonia supply system 20 is introduced into the furnace 12 of the boiler 10 together with the purge gas supplied from the purge gas supply device 41, as shown in FIG. 4 .

[0045] Next, in step S14, the ammonia concentration in the ammonia supply system 20 is detected, and it is determined whether the concentration is equal to or lower than a predetermined concentration. If it is determined that the ammonia concentration is not equal to or lower than the predetermined concentration, the process proceeds to step S15, where the introduction of purge gas continues. Then, the process proceeds to S14 again. If it is determined in step S14 that the ammonia concentration is equal to or lower than the predetermined concentration, the process ends.

[0046] The determination of whether to terminate the process may be based on factors other than the ammonia concentration. For example, the determination of whether to terminate the process may be based on the supply amount of purge gas. The determination of whether to terminate the process may also be based on the supply time of purge gas.

[0047] According to this embodiment, the following advantageous effects are achieved. Ammonia fuel cannot be released directly into the atmosphere due to its toxicity and odor. Therefore, in the boiler 10 that uses ammonia fuel, it may be difficult to treat the ammonia fuel discharged from the ammonia supply system 20 using purge gas or the like. As described above, since ammonia fuel cannot be released into the atmosphere, it is conceivable to temporarily store the ammonia fuel discharged from the ammonia supply system 20 using purge gas or the like in a purge gas storage tank together with the purge gas. However, in this method, the purge gas requires a volume several times the volume of the piping, which may increase the volume of the purge gas storage tank. Another option is to absorb the discharged ammonia fuel into water and store it as ammonia water, but this method could increase the cost of treating the ammonia water.

[0048] In this embodiment, the ammonia fuel remaining in the ammonia supply system 20 is evacuated by the vacuum equipment 32, and the ammonia fuel remaining in the ammonia supply system 20 is introduced to the boiler 10. This allows the ammonia fuel to be combusted in the boiler 10. Therefore, the ammonia fuel remaining in the ammonia supply system 20 can be easily and appropriately treated. Therefore, costs can be reduced compared to a method of treating ammonia water in which ammonia fuel is adsorbed onto water.

[0049] Furthermore, in this embodiment, when the ammonia fuel is being evacuated by the vacuum facility 32, the ammonia fuel remaining in the ammonia supply system 20 is mainly introduced to the boiler 10. That is, a large amount of purge gas or the like is not introduced to the boiler 10. This reduces the impact on the operation of the boiler 10. Therefore, the boiler 10 can be used as a facility for treating ammonia fuel. Furthermore, since the boiler 10, which is an existing device installed in the system, can be used as the equipment for treating ammonia fuel, the entire boiler system 2 can be made smaller than when a new treatment facility is installed, and costs can also be reduced.

[0050] [Second embodiment] Next, a second embodiment of the present disclosure will be described with reference to FIG. The boiler system 2B according to this embodiment differs from the first embodiment in that the ammonia fuel evacuated by the vacuum equipment 32 is introduced into the purge gas storage tank 52, not into the boiler 10. Only the configurations different from the first embodiment will be described below, and the same configurations as those in the first embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted.

[0051] In this embodiment, the downstream end of the second ammonia discharge pipe 33B is connected to the second purge gas pipe 51. In detail, the downstream end of the second ammonia discharge pipe 33B is connected to the second purge gas pipe 51 at a position downstream of the sixth on-off valve 51a.

[0052] The vacuum section 30B according to this embodiment introduces the ammonia fuel evacuated from the ammonia supply system 20 by the vacuum equipment 32 into the purge gas storage tank 52 via the second ammonia discharge pipe 33B and the second purge gas pipe 51.

[0053] According to this embodiment, the following advantageous effects are achieved. In this embodiment, the ammonia fuel is guided to the purge gas storage tank 52 by evacuating the ammonia supply system 20 using the vacuum equipment 32, and then the purge gas is supplied into the ammonia supply system 20, thereby guiding the ammonia fuel remaining in the ammonia supply system 20 to the purge gas storage tank 52. As a result, the ammonia fuel can be discharged by the purge gas in a state in which the amount of ammonia fuel remaining in the ammonia supply system 20 is reduced. Therefore, the ammonia fuel remaining in the ammonia supply system 20 can be guided to the purge gas storage tank 52 with a small amount of purge gas, and the amount of purge gas guided to the purge gas storage tank 52 is reduced. Therefore, the purge gas storage tank 52 can be made smaller. Consequently, the entire boiler system 2 can be made smaller.

[0054] Furthermore, for example, if the vacuum equipment 32 can evacuate the purge gas to 1 / 10 of atmospheric pressure, the capacity of the purge gas storage tank 52 can also be reduced to 1 / 10. Therefore, the purge gas storage tank 52 can be made smaller. Furthermore, if the purge gas can be evacuated to 1 / 10 of atmospheric pressure and the amount of purge gas can be reduced to approximately twice the volume of the piping of the ammonia supply system 20 or less, the volume ratio of purge gas to ammonia fuel in the purge gas storage tank 52 will be 20:80. In this case, even if air is used as the purge gas, the ammonia concentration will fall outside the flammable concentration range. Therefore, air can be used as the purge gas. Therefore, the cost required for supplying the purge gas can be reduced compared to when an inert gas such as nitrogen is used as the purge gas.

[0055] It is desirable to use a liquid ring vacuum pump for the vacuum equipment 32 of this embodiment. This is because if an ejector is used as the vacuum equipment 32, the working fluid (air, steam, etc.) of the ejector will also be introduced into the purge gas storage tank 52, which may prevent the purge gas storage tank 52 from being sufficiently compact.

[0056] [Third embodiment] Next, a third embodiment of the present disclosure will be described with reference to FIG. The boiler system 2C according to this embodiment differs from the second embodiment in that a vacuum pump 61 connected to a condenser 60 provided in the boiler system 2C is used as the vacuum equipment. Only the configurations different from the second embodiment will be described below, and the same reference numerals will be used to designate the same configurations as the second embodiment, and detailed description thereof will be omitted.

[0057] The boiler system 2C according to this embodiment includes a condenser 60 that condenses steam that is supplied from the boiler 10 to a turbine (not shown) and discharged after driving the turbine (not shown), a plurality of vacuum pumps 61 that are installed to maintain a vacuum state inside the condenser 60 by discharging non-condensable gases inside the condenser 60 to the outside of the system, and solenoid valves 62 that are provided upstream and downstream of the vacuum pump 61. The plurality of vacuum pumps 61 are arranged in parallel.

[0058] In this embodiment, the downstream end of the first ammonia discharge pipe 31C is connected to the inlet pipe of the vacuum pump 61. In addition, the upstream end of the second ammonia discharge pipe 33C is connected to the outlet pipe of the vacuum pump 61.

[0059] The vacuum section 30C according to this embodiment introduces ammonia fuel vacuumed from the ammonia supply system 20 by one of a plurality of vacuum pumps 61 into the purge gas storage tank 52 via the second ammonia discharge pipe 33C and the second purge gas pipe 51. At this time, the solenoid valves 62 provided on the upstream side and downstream side of the vacuum pump 61 are both closed.

[0060] According to this embodiment, the following advantageous effects are achieved. In this embodiment, the ammonia fuel in the ammonia supply system 20 is vacuumed using the existing vacuum pump 61 provided in the boiler system 2. This makes it possible to reduce the number of devices required compared to when a new device for vacuuming the ammonia fuel in the ammonia supply system 20 is separately provided. Therefore, the entire boiler system 2 can be made smaller.

[0061] The present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure. For example, in the third embodiment, when ammonia is used as a chemical for water quality control of the feedwater to the boiler 10, and it is acceptable for ammonia to be mixed into the condensate inside the condenser 60, the ammonia fuel in the ammonia supply system 20 may be led to the condenser 60 as in a boiler system 2D shown in Fig. 8. In this case, the downstream end of the first ammonia discharge pipe 31D is connected to the condenser 60. By connecting the downstream end of the first ammonia discharge pipe 31D to the condenser 60 in this way, the system configuration can be simplified compared to, for example, a case where the downstream end of the first ammonia discharge pipe 31D is connected to another pipe.

[0062] The boiler system, the power plant, and the method of operating the boiler system described in the above-described embodiments can be understood, for example, as follows. A boiler system according to a first aspect of the present disclosure includes a boiler (10) that generates steam by burning ammonia fuel, a fuel supply system (20) that supplies ammonia fuel to the boiler (10), and a vacuum unit (30) that draws a vacuum on the ammonia fuel in the fuel supply system (20) to guide the ammonia fuel remaining in the fuel supply system (20) to a predetermined facility (10, 50).

[0063] The above-described configuration includes a vacuum unit that vacuums the ammonia fuel in the fuel supply system to guide the ammonia fuel remaining in the fuel supply system to a predetermined facility. This allows the ammonia fuel in the fuel supply system to be guided to the predetermined facility by the vacuum unit. Therefore, the ammonia fuel can be appropriately treated in the predetermined facility.

[0064] Another possible method for guiding the ammonia fuel in the fuel supply system to the predetermined equipment is to supply a purge gas or the like into the ammonia fuel system, and use the purge gas to push out the ammonia fuel in the fuel supply system, thereby guiding the ammonia fuel to the predetermined equipment (for example, a purge gas storage tank). However, with this method, the purge gas is also guided to the predetermined equipment along with the ammonia fuel. Therefore, the capacity of the predetermined equipment needs to be determined taking into account the purge gas, and therefore the capacity of the predetermined equipment needs to be increased. This could result in an increase in the size of the predetermined equipment. Furthermore, there is a possibility that the cost would increase.

[0065] On the other hand, in the above configuration, the ammonia fuel in the fuel supply system is introduced to the predetermined equipment by vacuuming. As a result, when the ammonia fuel is being vacuumed in the vacuum section, the ammonia fuel remaining in the fuel supply system is mainly introduced to the predetermined equipment. Therefore, compared to a case where the ammonia fuel is introduced to the predetermined equipment by supplying a purge gas or the like into the fuel supply system, for example, the predetermined equipment can be made smaller. Ultimately, the entire boiler system can be made smaller.

[0066] Note that after the ammonia fuel in the fuel supply system is guided to the designated facility by the vacuum section, purge gas may be supplied into the fuel supply system, thereby ensuring that the ammonia fuel remaining in the fuel supply system is guided to the designated facility. Even in this case, the ammonia fuel remaining in the fuel supply system can be guided to the designated facility with a small amount of purge gas, thereby reducing the amount of purge gas guided to the designated facility. Therefore, the designated facility can be made smaller. Ultimately, the entire boiler system can be made smaller.

[0067] Furthermore, in the above configuration, when the ammonia fuel is being evacuated by the vacuum section, mainly the ammonia fuel remaining in the fuel supply system is led to the predetermined equipment. In other words, a large amount of purge gas or the like is not led to the predetermined equipment. As a result, even a device (e.g., a boiler) that is not suitable for receiving a large amount of purge gas or the like can be adopted as the predetermined equipment. This improves the degree of freedom in selecting the predetermined equipment. Therefore, for example, when an existing device (e.g., a boiler) installed in a boiler system is selected as the predetermined equipment to which the ammonia fuel is led, the entire boiler system can be made smaller than when new predetermined equipment is installed. Furthermore, costs can be reduced.

[0068] A boiler system according to a second aspect of the present disclosure is the boiler system of the first aspect, wherein the predetermined equipment (10) includes the boiler (10).

[0069] In the above configuration, the predetermined facility includes a boiler. In the above configuration, when the ammonia fuel is being evacuated by the vacuum unit, mainly the ammonia fuel remaining in the fuel supply system is led to the predetermined equipment. In other words, a large amount of purge gas, etc. is not led to the predetermined equipment. As a result, even a device (e.g., a boiler, etc.) that is not suitable for being supplied with a large amount of purge gas, etc., can be adopted as the predetermined equipment. Therefore, the degree of freedom in selecting the predetermined equipment can be improved. Therefore, a boiler, which is an existing device installed in the system, can be applied as the predetermined equipment. By applying a boiler as the predetermined equipment, the entire boiler system can be made smaller than when new predetermined equipment is installed.

[0070] A boiler system according to a third aspect of the present disclosure is the boiler system of the first aspect, further comprising: a purge gas supply unit (40) that supplies a purge gas to the fuel supply system (20); and a storage unit (50) that stores the ammonia fuel and the purge gas discharged from the fuel supply system (20) by the purge gas supply unit (40), and the predetermined facility (50) has the storage unit (50).

[0071] The above-described configuration includes a vacuum section and a purge gas supply section. This allows the ammonia fuel in the fuel supply system to be guided to the storage section by the vacuum section, and then the purge gas can be supplied into the fuel supply system. Therefore, compared to a case where the ammonia fuel in the fuel supply system is guided to the storage section only by the vacuum section, the ammonia fuel remaining in the fuel supply system can be reliably guided to the storage section. Furthermore, compared to the case where the ammonia fuel remaining in the fuel supply system is guided to the storage section by purge gas from the beginning, the ammonia fuel remaining in the fuel supply system can be guided to the storage section with less purge gas. Therefore, the amount of purge gas guided to the storage section is reduced. Therefore, the storage section can be made smaller. Ultimately, the entire boiler system can be made smaller.

[0072] A boiler system according to a fourth aspect of the present disclosure is the boiler system of any one of the first to third aspects, wherein the vacuum section (30) has a liquid ring vacuum pump.

[0073] In the above configuration, the ammonia fuel remaining in the fuel supply system can be guided to a predetermined facility by the liquid ring vacuum pump.

[0074] A boiler system according to a fifth aspect of the present disclosure is the boiler system of any one of the first to third aspects, wherein the vacuum section (30) has an ejector.

[0075] In the above configuration, the ammonia fuel remaining in the fuel supply system can be guided to a predetermined facility by the ejector.

[0076] A boiler system according to a sixth aspect of the present disclosure is the boiler system of any of the first to third aspects, further comprising: a condenser (60) that condenses steam generated in the boiler (10); and a vacuum pump (61) that discharges gas from the condenser, and the vacuum section (30) has the vacuum pump (61).

[0077] In the above configuration, the vacuum unit has a vacuum pump that discharges gas from the condenser. That is, the ammonia fuel in the ammonia fuel system is vacuumed using the existing vacuum pump of the boiler system. This allows the number of parts to be reduced compared to when a new device is provided to vacuum the ammonia fuel in the ammonia fuel system. Therefore, the entire boiler system can be made smaller.

[0078] A power plant according to a first aspect of the present disclosure includes the boiler system (2) according to any one of the first to sixth aspects, and a generator that generates electricity by utilizing steam generated in the boiler (10).

[0079] In a first aspect of the present disclosure, a method for operating a boiler system includes a boiler (2) including a boiler (10) that generates steam by burning ammonia fuel, a fuel supply system (20) that supplies ammonia fuel to the boiler (10), and a vacuum unit (30) that evacuates the ammonia fuel in the fuel supply system (20), and includes a step of guiding the ammonia fuel remaining in the fuel supply system (20) to predetermined equipment (10, 50) by evacuating the ammonia fuel in the fuel supply system (20) with the vacuum unit (30). [Explanation of symbols]

[0080] 1: Power plant 2: Boiler system 10: Boiler (specified equipment) 11: Burner 12: Furnace 20: Ammonia supply system (fuel supply system) 21: Ammonia tank 22: Ammonia supply facility 23: First ammonia supply pipe 23a: Pump 24: Second ammonia supply pipe 24a: First shut-off valve 24b: Second shut-off valve 24c: Flow control valve 30: Vacuum section 31: First ammonia discharge pipe 31a: Third shut-off valve 32: Vacuum equipment 33: Second ammonia discharge pipe 33a: Fourth opening / closing valve 40: Purge gas supply unit 41: Purge gas supply device 42: First purge gas pipe 42a: 5th opening / closing valve 50: Purge gas storage section (storage section) 51: Second purge gas piping 51a: 6th opening / closing valve 52: Purge gas storage tank (prescribed facility) 60: Condenser 61: Vacuum pump 62: Solenoid valve

Claims

1. a boiler that generates steam by burning ammonia fuel; a fuel supply system for supplying ammonia fuel to the boiler; a vacuum unit that draws a vacuum on the ammonia fuel in the fuel supply system, thereby leading the ammonia fuel remaining in the fuel supply system to a predetermined facility.

2. The boiler system according to claim 1 , wherein the predetermined equipment includes the boiler.

3. a purge gas supply unit that supplies a purge gas to the fuel supply system; a storage unit that stores the ammonia fuel and the purge gas discharged from the fuel supply system by the purge gas supply unit, The boiler system according to claim 1 , wherein the predetermined facility includes the storage section.

4. The boiler system according to claim 1 , wherein the vacuum section comprises a liquid ring vacuum pump.

5. The boiler system according to claim 1 , wherein the vacuum section comprises an ejector.

6. a condenser for condensing steam generated in the boiler; a vacuum pump that discharges gas from the condenser, The boiler system according to claim 1 , wherein the vacuum section includes the vacuum pump.

7. The boiler system according to claim 1; a generator that generates electricity by using the steam generated in the boiler.

8. 1. A method of operating a boiler system, comprising: The boiler system includes: a boiler that generates steam by burning ammonia fuel; a fuel supply system that supplies ammonia fuel to the boiler; and a vacuum unit that evacuates the ammonia fuel in the fuel supply system; A method for operating a boiler system, comprising the step of guiding the ammonia fuel remaining in the fuel supply system to a predetermined facility by evacuating the ammonia fuel in the fuel supply system with the vacuum section.

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