Boiler system

Abstract

This invention provides a boiler system that can effectively utilize the heat contained in ammonia decomposition gas. Furthermore, it provides a boiler system that can maintain the temperature of the ammonia decomposition gas at the boiler inlet within a predetermined temperature range. [Solution] The boiler system comprises an ammonia decomposition device that decomposes ammonia to produce ammonia decomposition gas containing hydrogen and nitrogen, a boiler that burns the ammonia decomposition gas as fuel, an ammonia decomposition gas supply line that supplies the ammonia decomposition gas from the ammonia decomposition device to the boiler, a feedwater line that supplies feedwater to the boiler, and a heat exchanger that heats the feedwater by exchanging heat between the ammonia decomposition gas and the feedwater.

Description

Technical Field

[0001] The present invention relates to a boiler system.

Background Art

[0002] In recent years, from the perspective of reducing carbon dioxide emissions, the use of ammonia fuel that does not emit carbon dioxide during combustion has been spreading. Boilers and the like that use ammonia decomposition gas obtained by decomposing ammonia fuel into nitrogen and hydrogen as fuel have also been developed, and boiler systems including an ammonia decomposition device and a boiler are also known (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] High temperature is required for the decomposition of ammonia, and the temperature of the ammonia decomposition gas at the outlet of the ammonia decomposition device generally reaches a high temperature of 400°C or higher. Supplying such a high-temperature ammonia decomposition gas to a boiler is not preferable in terms of ensuring the safety of fuel pipes and heat loss due to heat dissipation. Therefore, it is necessary to remove heat from the ammonia decomposition gas to a predetermined temperature. Furthermore, from the perspective of energy conservation and the like, it is also required to effectively utilize the retained heat of the ammonia decomposition gas. In addition, it is necessary to maintain the temperature of the ammonia decomposition gas supplied to the boiler within a predetermined range to perform stable combustion.

[0005] Therefore, in a boiler that uses ammonia decomposition gas as fuel, it is required to effectively utilize the retained heat of the ammonia decomposition gas and maintain the temperature of the ammonia decomposition gas at the inlet of the boiler within a predetermined temperature range.

[0006] The present invention aims to provide a boiler system that can effectively utilize the heat contained in ammonia decomposition gas, and further aims to provide a boiler system that can maintain the temperature of the ammonia decomposition gas at the boiler inlet within a predetermined temperature range. [Means for solving the problem]

[0007] The present invention solves the above problem by the following means.

[0008] The present invention relates to a boiler system comprising: an ammonia decomposition device that decomposes ammonia to produce ammonia decomposition gas containing hydrogen and nitrogen; a boiler that burns the ammonia decomposition gas as fuel; an ammonia decomposition gas supply line that supplies the ammonia decomposition gas from the ammonia decomposition device to the boiler; a feedwater line that supplies feedwater to the boiler; and a heat exchanger that heats the feedwater by exchanging heat between the ammonia decomposition gas and the feedwater.

[0009] Furthermore, the boiler system preferably comprises a control unit for controlling the boiler system, a gas temperature detection unit for detecting the temperature of the ammonia decomposition gas flowing into the boiler, and a water flow rate adjustment unit for adjusting the amount of feedwater flowing into the heat exchanger. The control unit controls the amount of feedwater flowing in using the water flow rate adjustment unit, based on the detection result of the gas temperature detection unit, so that the ammonia decomposition gas is within a predetermined temperature range.

[0010] Furthermore, the boiler system includes a feedwater tank for storing the feedwater supplied to the boiler, and a circulation line for circulating the feedwater between the feedwater tank and the heat exchanger, and it is preferable that the water flow rate adjustment unit is provided in the circulation line.

[0011] Furthermore, the boiler system preferably includes a makeup water line for supplying makeup water to the feedwater tank, a water temperature detection unit for detecting the water temperature of the feedwater tank or the water temperature of the circulation line, a water level detection unit for detecting the water level of the feedwater tank, and a makeup water volume adjustment unit provided in the makeup water line for adjusting the amount of makeup water supplied to the feedwater tank, wherein the control unit adjusts the amount of makeup water based on the detection results of the water level detection unit and the detection results of the water temperature detection unit.

[0012] Furthermore, the control unit includes an abnormality determination unit that determines an abnormality in the boiler system based on the detection result of the water temperature detection unit and the detection result of the water level detection unit. Preferably, the abnormality determination unit determines an abnormality if at least one of the detection result of the water temperature detection unit and the detection result of the water level detection unit deviates from a preset tolerance range.

[0013] Furthermore, the boiler system includes an air supply line that supplies combustion air to the boiler, an air supply amount adjustment unit that adjusts the amount of combustion air supplied, a second heat exchanger that exchanges heat between the combustion air and the ammonia decomposition gas and heats the combustion air, and an ammonia decomposition gas flow rate adjustment unit that adjusts the flow rate of the ammonia decomposition gas flowing into the second heat exchanger. Preferably, the control unit adjusts the amount of ammonia decomposition gas flowing into the second heat exchanger by the ammonia decomposition gas flow rate adjustment unit so that the ammonia decomposition gas is within a predetermined temperature range, based on the detection result of the gas temperature detection unit.

[0014] Furthermore, the boiler system includes a cooling water line that supplies cooling water to cool the ammonia decomposition gas, a cooling water flow rate adjustment unit that adjusts the flow rate of the cooling water in the cooling water line, and a third heat exchanger that exchanges heat between the ammonia decomposition gas and the cooling water and heats the cooling water. Preferably, the control unit adjusts the amount of cooling water supplied by the cooling water flow rate adjustment unit based on the detection result of the gas temperature detection unit so that the ammonia decomposition gas is within a predetermined temperature range.

[0015] Furthermore, the boiler system comprises an air supply line for supplying combustion air to the boiler, an air supply amount adjustment unit for adjusting the amount of combustion air supplied, a second heat exchanger for exchanging heat between the combustion air and the ammonia decomposition gas and heating the combustion air, an ammonia decomposition gas flow rate adjustment unit for adjusting the flow rate of the ammonia decomposition gas flowing into the second heat exchanger, a cooling water line for supplying cooling water to cool the ammonia decomposition gas, a cooling water adjustment unit for adjusting the flow rate of the cooling water in the cooling water line, and a third heat exchanger for exchanging heat between the ammonia decomposition gas and the cooling water and heating the cooling water. Preferably, the control unit adjusts the amount of ammonia decomposition gas flowing into the second heat exchanger by the ammonia decomposition gas flow rate adjustment unit, or adjusts the flow rate of the cooling water by controlling the cooling water adjustment unit, based on the detection result of the gas temperature detection unit, so that the ammonia decomposition gas is within a predetermined temperature range, or performs at least one of these actions. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a boiler that can effectively utilize the heat contained in ammonia decomposition gas, and furthermore, a boiler that can maintain the temperature of the ammonia decomposition gas at the boiler inlet within a predetermined temperature range. [Brief explanation of the drawing]

[0017] [Figure 1] This is a diagram illustrating the configuration of the boiler system according to the first embodiment. [Figure 2] This is a flowchart illustrating the temperature control of ammonia decomposition gas in the boiler system of the first embodiment. [Figure 3] This figure illustrates an example of the temperature change of ammonia decomposition gas in the boiler system of the first embodiment, and the first target temperature, second target temperature, third target temperature, first control temperature range, second control temperature range, and third control temperature range of the ammonia decomposition gas. [Figure 4] This is a flowchart illustrating the control of the circulating water supply volume between the first heat exchanger and the water supply tank. [Figure 5]It is a flowchart for explaining the level control of the water supply tank. [Figure 6] It is a flowchart for explaining the air supply heat exchange control regarding the second heat exchanger. [Figure 7] It is a flowchart for explaining the cooling water volume control regarding the third heat exchanger. [Figure 8] It is a diagram for explaining the configuration of the boiler system of the second embodiment.

Modes for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings and the like. Note that each of the drawings shown below, including FIG. 1, is a schematically shown diagram, and the sizes and shapes of each part are exaggerated as appropriate for easy understanding. In the following embodiments, an example of applying the boiler system of the present invention to a steam boiler that burns ammonia decomposition gas as fuel gas to generate steam will be described.

[0019] (First Embodiment) FIG. 1 is a diagram for explaining the configuration of the boiler system of the first embodiment. The boiler system 1 of the present embodiment is applied to a boiler 60 that burns ammonia decomposition gas F1 and supplies steam to a load device (not shown). The boiler system 1 of the present embodiment includes a boiler 60, an ammonia decomposition device 11, a water supply tank 22, a pump 23 as a water volume adjustment unit, a blower 31, a gas temperature detection unit 13, a first heat exchanger 51, a second heat exchanger 52, a third heat exchanger 53, an ammonia decomposition gas supply line L100, a water supply line L210, a makeup water line L220, a circulation line L230, an air supply line L300, a cooling water line L400, etc. Note that the "line" in this specification is a general term for a flow path, a route, a pipeline, etc.

[0020] Boiler 60, equipped with a boiler, burner, water tubes, etc. (not shown), generates steam by the heat produced when ammonia decomposition gas F1 is burned as fuel. Boiler 60 is equipped with a steam supply line and an exhaust gas line (not shown). The steam supply line is connected to the boiler (not shown) on the upstream side and to load equipment (not shown) on the downstream side, supplying steam to the load equipment. The exhaust gas line discharges the exhaust gas produced by combustion to the outside of boiler 60. The upstream side of the exhaust gas line is connected to the upper part of the boiler's circumferential surface, and the downstream side of the exhaust gas line is open to the atmosphere.

[0021] The ammonia decomposition gas supply line L100 supplies the fuel, ammonia decomposition gas F1, from the ammonia decomposition unit 11 to the boiler 60. The upstream end of the ammonia decomposition gas supply line L100 is connected to the ammonia decomposition unit 11, and the downstream end of the ammonia decomposition gas supply line L100 is connected to the boiler 60. The ammonia decomposition apparatus 11 is a device that decomposes ammonia supplied from an ammonia source (not shown) into ammonia decomposition gas F1 containing hydrogen and nitrogen. The ammonia decomposition gas F1 contains hydrogen, nitrogen, and undecomposed ammonia.

[0022] The ammonia decomposition gas supply line L100 is equipped with, from upstream, a first heat exchanger 51, a second shut-off valve (not shown), a second flow rate control valve 15, a third heat exchanger 53, a buffer tank 12, a gas temperature detection unit 13, etc. In the ammonia decomposition gas supply line L100, a branch line L110A for supplying ammonia decomposition gas F1 to the second heat exchanger 52 is connected downstream of the first heat exchanger 51 and upstream of the second shut-off valve (not shown) and the second flow rate control valve 15. In the ammonia decomposition gas supply line L100, a branch line L110B for returning the ammonia decomposition gas F1 that has exited the second heat exchanger 52 back to the ammonia decomposition gas supply line L100 is connected downstream of the second shut-off valve (not shown) and the second flow rate control valve 15 and upstream of the third heat exchanger 53. The branch line L110A is equipped with, in order from the upstream side, a first shut-off valve (not shown) and a first flow control valve 14. Details of the first heat exchanger 51, the second heat exchanger 52, and the third heat exchanger 53 will be described later.

[0023] The buffer tank 12 is a tank for temporarily storing ammonia decomposition gas F1. By installing the buffer tank 12 in the ammonia decomposition gas supply line L100, fluctuations in the flow rate of ammonia decomposition gas F1 can be suppressed. The gas temperature detection unit 13 detects the temperature of the ammonia decomposition gas F1 flowing into the boiler 60. The gas temperature detection unit 13 is electrically connected to the control unit 70, and the control unit 70 can obtain the temperature of the ammonia decomposition gas F1 flowing into the boiler 60 from the gas temperature detection unit 13.

[0024] The branch line L110A branches off from the ammonia decomposition gas supply line L100 and supplies ammonia decomposition gas F1 to the second heat exchanger 52. The connection point between the branch line L110A and the ammonia decomposition gas supply line L100 is upstream of the second shut-off valve and the second flow control valve 15 (not shown). The branch line L110B returns the ammonia decomposition gas F1 that has exited the second heat exchanger 52 to the ammonia decomposition gas supply line L100. The connection point between the branch line L110B and the ammonia decomposition gas supply line L100 is downstream of the second shut-off valve and the second flow control valve 15 (not shown).

[0025] The first shut-off valve (not shown) is a valve that opens and closes the flow path of the branch line L110A and is located upstream of the first flow control valve 14. The first flow control valve 14 is installed in the branch line L110A and is a valve that adjusts the flow rate of the ammonia decomposition gas F1 flowing through the branch line L110A. The first flow control valve 14 is electrically connected to the control unit 70, and the opening degree of the valve is controlled based on a signal transmitted from the control unit 70. Note that the positions of the first shut-off valve (not shown) and the first flow control valve 14 in the branch line L110A may be reversed, and the first shut-off valve may be located downstream of the first flow control valve 14.

[0026] The second shut-off valve (not shown) is a valve that opens and closes the flow path of the ammonia decomposition gas supply line L100, and is located downstream of the connection point between the branch line L110A and the ammonia decomposition gas supply line L100, and upstream of the second flow control valve 15. The second flow control valve 15 is installed in the ammonia decomposition gas supply line L100 and is a valve that adjusts the flow rate of the ammonia decomposition gas F1. The second flow control valve 15 is electrically connected to the control unit 70, and the opening degree of the valve is controlled based on signals transmitted from the control unit 70. Note that the positions of the second shut-off valve (not shown) and the second flow control valve 15 in the ammonia decomposition gas supply line L100 may be reversed, and the second shut-off valve may be located downstream of the second flow control valve 15.

[0027] When the first shut-off valve (not shown) of the branch line L110A is closed, and the second shut-off valve (not shown) and the second flow control valve 15 of the ammonia decomposition gas supply line L100 are open, the ammonia decomposition gas F1 does not flow into the branch line L110A, but instead flows through the ammonia decomposition gas supply line L100 to the buffer tank 12. When the first shut-off valve and first flow rate control valve 14 (not shown) of branch line L110A are open, and the second shut-off valve and second flow rate control valve 15 (not shown) of ammonia decomposition gas supply line L100 are open, a predetermined amount of ammonia decomposition gas F1 flows from branch line L110A to the second heat exchanger 52 at a predetermined flow rate, according to the opening degree of the first flow rate control valve 14, and returns from branch line L110B to the ammonia decomposition gas supply line L100 after passing through the second heat exchanger 52. The control unit 70 can control the ratio of the flow rate of ammonia decomposition gas F1 flowing from branch line L110A to the second heat exchanger 52 to the flow rate of ammonia decomposition gas F1 that does not pass through the second heat exchanger 52 by adjusting the opening degrees of the first flow rate control valve 14 and the second flow rate control valve 15.

[0028] The feedwater line L210 supplies feedwater W1 to the boiler 60. In this embodiment, the feedwater line L210 has a feedwater tank 22 on its upstream side and is connected to the boiler 60 on its downstream side. The feedwater line L210 is also equipped with a pump 21 as a flow rate adjustment unit to adjust the amount of feedwater W1 supplied to the boiler 60. Note that, in addition to the pump 21, a flow rate adjustment valve or the like that can adjust the flow rate of the feedwater W1 may also be provided.

[0029] The feedwater tank 22 is located upstream of the feedwater line L210 and stores the feedwater W1 supplied to the boiler 60. The feedwater tank 22 is connected to the makeup water line L220 and the feedwater line L210, and stores the makeup water W2 supplied by the makeup water line L220 as feedwater W1. The feedwater tank 22 is also connected to the circulation line L230, which circulates a portion of the stored feedwater W1 as circulating water between the feedwater tank 22 and the first heat exchanger 51. Furthermore, the feedwater tank 22 in this embodiment includes a water temperature detection unit 24 for detecting the water temperature of the feedwater tank 22 and a water level detection unit 25 for detecting the water level of the feedwater tank 22.

[0030] The water temperature detection unit 24 detects the water temperature of the water supply tank 22. The water temperature detection unit 24 is electrically connected to the control unit 70, and the control unit 70 can obtain the water temperature of the water supply tank 22 from the water temperature detection unit 24. The water level detection unit 25 detects the water level in the water supply tank 22. The water level detection unit 25 is electrically connected to the control unit 70, and the control unit 70 can obtain the water level of the water supply tank 22 from the water level detection unit 25.

[0031] The makeup water line L220 supplies makeup water W2 to the water tank 22. The upstream side of the makeup water line L220 is connected to a water source (not shown), and the downstream side of the makeup water line L220 is connected to the water tank 22. The makeup water line L220 is equipped with a makeup water volume control valve 26. The replenishment water volume control valve 26 is a replenishment water volume control unit that adjusts the amount of replenishment water supplied to the water supply tank 22, and for example, a motor valve is used. The replenishment water volume control valve 26 is electrically connected to the control unit 70 and is controlled based on signals transmitted from the control unit 70. Alternatively, a pump or the like may be provided instead of the replenishment water volume control valve 26 as the replenishment water volume control unit.

[0032] The circulation line L230 circulates feedwater (circulating water) W3 between the feedwater tank 22 and the first heat exchanger 51. The feedwater (circulating water) W3 flowing through this circulation line L230 is part of the feedwater W1 stored in the feedwater tank 22. The circulation line L230, together with the feedwater tank 22 and the feedwater line L210, is part of the feedwater system that supplies feedwater W1 to the boiler 60. This circulation line L230 is equipped with a pump 23. Pump 23 is a water flow rate adjustment unit that adjusts the amount of feedwater (circulating water) W3 flowing into the first heat exchanger 51. In this embodiment, an example is shown in which pump 23 is used as the water flow rate adjustment unit, but it is not limited to this, and a flow control valve or the like that which can adjust the flow rate of feedwater (circulating water) W3 may be used.

[0033] The air supply line L300 supplies combustion air A1 to the boiler 60. In this embodiment, the upstream side of the air supply line L300 is connected to the blower 31, and the downstream side of the air supply line L300 is connected to the boiler 60. The air supply line L300 includes, from the upstream side, the blower 31, the second heat exchanger 52, the air temperature detection unit 33, and the like. The blower 31 supplies combustion air A1 to the boiler 60. The blower 31 comprises a fan and a motor that rotates the fan. The blower 31 can adjust the rotational speed of the motor by controlling the frequency of the inverter 32, thereby controlling the amount of combustion air A1 supplied. In other words, the inverter 32 is an air supply volume adjustment unit that adjusts the amount of combustion air A1 supplied to the boiler 60. The inverter 32 is electrically connected to the control unit 70 and is controlled based on signals transmitted from the control unit 70.

[0034] A damper (not shown) may be provided in the air supply line L300. The damper can adjust the amount of combustion air A1 supplied to the boiler 60 by adjusting its opening. Specifically, the damper is rotatably provided so as to be able to move between a closed state, which blocks the flow path of the air supply line L300, and an open state, which rotates from this closed state by a predetermined angle (for example, 90 degrees) to open the flow path of the air supply line L300. The damper is electrically connected to the control unit 70 and is controlled based on signals transmitted from the control unit 70. Such a damper may be provided as an air supply volume adjustment unit instead of the inverter 32. Alternatively, both the inverter 32 and the damper may be provided as an air supply volume adjustment unit.

[0035] The air temperature detection unit 33 detects the temperature of the combustion air A1 flowing into the boiler 60. The air temperature detection unit 33 is electrically connected to the control unit 70, and the control unit 70 can obtain the temperature of the combustion air A1 from the air temperature detection unit 33.

[0036] The cooling water line L400 supplies cooling water W4 to cool the ammonia decomposition gas F1. The upstream end of the cooling water line L400 is connected to a cooling water supply source (not shown) and passes through a third heat exchanger 53. The downstream end of the cooling water line L400 is connected to a drainage line (not shown) and the cooling water W4 is discharged outside the boiler system 1. The cooling water flow rate control valve 41 is a cooling water flow rate control unit that adjusts the flow rate of the cooling water W4 in the cooling water line L400, and is located upstream of the third heat exchanger 53. The cooling water flow rate control valve 41 is electrically connected to the control unit 70 and is controlled based on signals transmitted from the control unit 70.

[0037] The first heat exchanger 51 exchanges heat between the ammonia decomposition gas F1 and the feedwater (circulating water) W3 to cool the ammonia decomposition gas F1 and heat the feedwater (circulating water) W3. The first heat exchanger 51 is connected to an ammonia decomposition gas supply line L100 and a circulation line L230. The second heat exchanger 52 exchanges heat between the ammonia decomposition gas F1 and the combustion air A1 to cool the ammonia decomposition gas F1 and heat the combustion air A1. The second heat exchanger 52 is connected to branch lines L110A and L110B and an air supply line L300. The third heat exchanger 53 exchanges heat between the ammonia decomposition gas F1 and the cooling water W4, thereby cooling the ammonia decomposition gas F1. The third heat exchanger 53 is connected to the ammonia decomposition gas supply line L100 and the cooling water line L400.

[0038] The control unit 70 controls the operation of each part of the boiler system 1. The control unit 70 in this embodiment includes an abnormality detection unit 71, an abnormality notification unit 72, a storage unit (not shown), and the like. The control unit 70 is composed of an arithmetic processor such as a PLC (Programmable Logic Controller), a DSP (Digital Signal Processor), or an FPGA (Field Programmable Gate Array). The various functions of the control unit 70 are realized, for example, by executing predetermined software (programs) stored in the memory unit. The various functions of the control unit 70 may be realized through the cooperation of hardware and software, or they may be realized by hardware (electronic circuits) alone.

[0039] The control unit 70 controls the temperature of the ammonia decomposition gas F1 supplied to the boiler 60 so that it is within a predetermined temperature range, based on the detection results of the gas temperature detection unit 13. Specifically, the control unit 70 controls the pump 23, which is a water flow rate adjustment unit, to adjust the amount of water (circulating water) W3 supplied to the first heat exchanger 51. In addition, the control unit 70 also adjusts the flow rate of the ammonia decomposition gas F1 to the second heat exchanger 52 by opening and closing the first shut-off valve and the second shut-off valve (not shown) and adjusting the opening of the first flow rate adjustment valve 14 and the second flow rate adjustment valve 15, or adjusts the amount of cooling water W4 supplied by the cooling water flow rate adjustment valve 41, or at least one of these. Furthermore, the control unit 70 adjusts the amount of replenishment water using the replenishment water volume adjustment valve 26 based on the detection results of the water level detection unit 25 and the water temperature detection unit 24, thereby controlling the water temperature and water level of the water supply tank 22 to within a predetermined range.

[0040] The abnormality determination unit 71 determines an abnormality in the boiler system 1 based on the detection results of the water temperature detection unit 24 and the water level detection unit 25. Specifically, the abnormality determination unit 71 determines an abnormality in the boiler system 1 if at least one of the following occurs: the detection result of the water temperature detection unit 24 falls outside the preset allowable range for water temperature, or the detection result of the water level detection unit 25 falls outside the preset allowable range for water level. In this embodiment, the abnormality determination unit 71 determines an abnormality in the boiler system 1 if both the detection result of the water temperature detection unit 24 and the detection result of the water level detection unit 25 fall outside the allowable range. Furthermore, the abnormality detection unit 71 also determines abnormalities in the operation of the boiler system 1, such as abnormalities in the temperature of the ammonia decomposition gas F1.

[0041] The abnormality notification unit 72 notifies of an abnormality based on the determination result of the abnormality determination unit 71. Specifically, it notifies the operator of the boiler system 1 of the abnormality by outputting a display indicating the abnormality to a display unit (not shown) or by sounding an alarm sound to indicate the abnormality. The abnormality notification unit 72 may also notify a boiler system monitoring device or a maintenance terminal device located remotely, for example.

[0042] (Temperature control of ammonia decomposition gas F1 in boiler system 1) The temperature control of the ammonia decomposition gas F1 in the boiler system 1 of this embodiment will be described below with reference to Figure 2 and other figures. Figure 2 is a flow chart showing the temperature control of ammonia decomposition gas F1 in the boiler system 1 of the first embodiment. Figure 3 is a diagram illustrating an example of the temperature change of ammonia decomposition gas F1 in the boiler system 1 of the first embodiment, and the first target temperature, second target temperature, third target temperature, first control temperature range, second control temperature range, and third control temperature range of the ammonia decomposition gas. Figure 4 is a flowchart illustrating the control of the circulating water supply volume between the first heat exchanger 51 and the water supply tank 22. Figure 5 is a flow chart illustrating the level control of the water supply tank 22. Figure 6 is a flowchart illustrating the supply air heat exchange control for the second heat exchanger 52. Figure 7 is a flowchart illustrating the cooling water flow rate control for the third heat exchanger 53.

[0043] In this embodiment, when the ammonia decomposition unit 11 starts up and generates ammonia decomposition gas F1 and begins supplying it to the boiler 60, the boiler system 1 circulates a portion of the feedwater W1 stored in the feedwater tank 22 between the first heat exchanger 51 and the feedwater tank 22 via a circulation line L230 or the like, recovering the heat contained in the ammonia decomposition gas F1 into the feedwater (circulating water) W3, and performing circulating feedwater volume control S100 to heat the feedwater (circulating water) W3. At this time, the amount of water stored in the feedwater tank 22 is controlled by tank level control S200. Furthermore, when the boiler system 1 needs to further remove heat from the ammonia decomposition gas F1 that has exchanged heat with the feedwater (circulating water) W3 by the first heat exchanger 51, it performs heat exchange with the combustion air A1 by the second heat exchanger 52 in addition to the heat exchange with the feedwater (circulating water) W3 by the first heat exchanger 51 using air supply heat exchange control S400. Furthermore, in addition to these, the cooling water control S600 performs heat exchange with the cooling water W4 in the third heat exchanger 53. Through this control, the boiler system 1 controls the temperature of the ammonia decomposition gas F1 to be within a predetermined temperature range (in this embodiment, for example, 30 to 50°C). Details of the control will be described later.

[0044] As shown in Figure 3, the first target temperature T1, the second target temperature T2, and the third target temperature T3 are the target temperatures for temperature control of the ammonia decomposition gas F1. These target temperatures are set in ascending order as the first target temperature T1, the second target temperature T2, and the third target temperature T3. All of these temperatures are within a predetermined temperature range that is preferable for the ammonia decomposition gas F1 supplied to the boiler 60. In this embodiment, as an example, the operating temperature range for the fuel gas equipment specifications of the boiler 60 is set to 0 to 60°C, the preferred predetermined temperature range for the ammonia decomposition gas F1 supplied to the boiler 60 is set to 30 to 50°C, and the more preferred target control temperature range is set to 30 to 45°C. Also in this embodiment, as an example, the first target temperature T1 is set to 30°C, the second target temperature T2 to 38°C, and the third target temperature T3 to 45°C.

[0045] The first target temperature T1 is the target temperature when heat exchange is performed by the first heat exchanger 51, the second target temperature T2 is the target temperature when heat exchange is performed by the second heat exchanger 52 in addition to the first heat exchanger 51, and the third target temperature T3 is the target temperature when heat exchange is performed by the third heat exchanger 53 in addition to the first heat exchanger 51 and the second heat exchanger 52.

[0046] The first control temperature range is the temperature range of the ammonia decomposition gas F1 that undergoes heat exchange by the second heat exchanger 52. The upper limit TU1 of the first control temperature range is the temperature at which heat exchange by the second heat exchanger 52 begins, and the lower limit TD1 of the first control temperature range is the temperature at which heat exchange by the second heat exchanger 52 ends. The second control temperature range is the temperature range of the ammonia decomposition gas F1 that undergoes heat exchange by the third heat exchanger 53. The upper limit TU2 of the second control temperature range is the temperature at which heat exchange by the third heat exchanger 53 begins, and the lower limit TD2 of the second control temperature range is the temperature at which heat exchange by the third heat exchanger 53 stops. The third control temperature upper limit TU3 is the temperature at which the safe shutdown control of boiler system 1 is initiated.

[0047] As shown in Figure 3, the following settings are used in descending order of temperature: the lower limit of the first control temperature range TD1, the upper limit of the first control temperature range TU1, the lower limit of the second control temperature range TD2, the upper limit of the second control temperature range TU2, and the upper limit of the third control temperature range TU3. In this embodiment, as an example, the first control temperature range is set to 35-40°C (lower limit TD1 of the first control temperature range is 35°C, and upper limit TU1 is 40°C), the second control temperature range is set to 42-47°C (lower limit TD2 of the second control temperature range is 42°C, and upper limit TU2 is 47°C), and the third control temperature upper limit TU3 is set to 50°C.

[0048] The control unit 70 of the boiler system 1 controls the temperature of the ammonia decomposition gas F1 according to the flow shown in Figure 2. The flow shown in Figure 2 assumes that the control unit 70 repeats a series of processes according to this flow at each calculation timing (for example, once per second). First, the control unit 70 of the boiler system 1 performs heat exchange between the ammonia decomposition gas F1 and the feedwater (circulating water) W3 flowing through the circulation line L230 using the first heat exchanger 51. At this time, in S100, the amount of circulating feedwater is controlled so that the temperature of the ammonia decomposition gas F1 reaches a first target temperature T1 (30°C in this embodiment).

[0049] The circulating water supply control in S100 will be explained with reference to Figure 4. In S101, the control unit 70 acquires the detection result from the gas temperature detection unit 13 (the temperature of the ammonia decomposition gas F1 flowing into the boiler 60). Next, in S102, the control unit 70 determines whether the detection result of the gas temperature detection unit 13 (temperature of the ammonia decomposition gas F1 flowing into the boiler 60) exceeds the first target temperature T1. If the detection result of the gas temperature detection unit 13 exceeds the first target temperature T1, the process proceeds to S103. If the detection result of the gas temperature detection unit 13 is less than or equal to the first target temperature T1, the process proceeds to S104.

[0050] In S103, the control unit 70 increases the amount of water flowing through the circulation line L230 (recirculating water) W3. Specifically, it controls the pump 23, which is a water flow rate adjustment unit, to increase the amount of water flowing to the first heat exchanger 51, and then terminates the circulation water flow rate control.

[0051] In S104, the control unit 70 determines whether the detection result of the gas temperature detection unit 13 (temperature of the ammonia decomposition gas F1 flowing into the boiler 60) is less than the first target temperature T1. If the detection result of the gas temperature detection unit 13 is less than the first target temperature T1, the process proceeds to S105. If the detection result of the gas temperature detection unit 13 is greater than or equal to the first target temperature T1 (i.e., when combined with the determination result in S102, the temperature of the ammonia decomposition gas F1 is the first target temperature T1), the circulating feedwater rate control is terminated.

[0052] In S105, the control unit 70 controls the amount of feedwater (circulating water) W3 supplied to the first heat exchanger 51. Specifically, the control unit 70 controls the pump 23, which is a water flow rate adjustment unit, to reduce the amount of water supplied to the first heat exchanger 51. As a result, the temperature of the ammonia decomposition gas F1 rises. The control unit 70 then controls the amount of feedwater (circulating water) W3 supplied to the first heat exchanger 51 in this way, and terminates the circulating water flow rate control.

[0053] Next, in S200, the control unit 70 performs tank level control to control the water temperature and water level of the water supply tank 22. The tank level control (level control of the water supply tank 22) will be explained with reference to Figure 5. First, in S201, the control unit 70 acquires the detection result of the water temperature detection unit 24 (water temperature of the water supply tank 22). Next, in S202, the control unit 70 acquires the detection result of the water level detection unit 25 (water level of the water supply tank 22). Next, in S203, the control unit 70 determines whether the detection result of the water temperature detection unit 24 (water temperature of the water supply tank 22) exceeds the upper limit of the controlled water temperature. The upper limit of the controlled water temperature is the upper limit of the allowable range of water temperature that has been set in advance for the water supply (circulating water) W3 used for heat exchange in the first heat exchanger 51. If the detection result of the water temperature detection unit 24 exceeds the upper limit of the controlled water temperature, the process proceeds to S204; if the detection result of the water temperature detection unit 24 is at or below the upper limit of the controlled water temperature, the process proceeds to S207.

[0054] In S204, the control unit 70 determines whether the detection result of the water level detection unit 25 (water level in the water supply tank 22) is below the management upper limit water level. The management upper limit water level is the upper limit of the preset allowable range of water levels that can be used for water temperature adjustment, with respect to the water level in the water supply tank 22, which has been set in advance. If the detection result of the water level detection unit 25 is below the management upper limit water level, the process proceeds to S205. If the detection result of the water level detection unit 25 exceeds the management upper limit water level, the process proceeds to S206.

[0055] In S205, the control unit 70 controls the amount of replenishment water to increase the amount of replenishment water. Specifically, the control unit 70 controls the replenishment water volume control valve 26 to increase the amount of replenishment water W2. As a result, the water temperature in the water supply tank 22 decreases and the water level rises. After controlling the amount of replenishment water in S205, the control unit 70 terminates the tank level control.

[0056] In S206, the control unit 70 controls the amount of replenishment water. Specifically, the control unit 70 controls the replenishment water volume control valve 26 to reduce the amount of replenishment water W2. This lowers the water level in the water supply tank 22 and restores it to within the preset allowable range for the water level in the water supply tank 22. Furthermore, at this time, the detection result of the water temperature detection unit 24 exceeds the upper limit of the controlled water temperature, and the detection result of the water level detection unit 25 exceeds the upper limit of the controlled water level. Therefore, the abnormality determination unit 71 determines that there is an abnormality in the boiler system 1, as the water temperature and water level of the feedwater tank 22 have deviated from the permissible range. The abnormality notification unit 72 acquires the judgment result from the abnormality determination unit 71 and notifies of any abnormalities in the water temperature and water level of the water supply tank 22. For example, the abnormality notification unit 72 may display the abnormality in the water temperature and water level of the water supply tank 22 on a display unit (not shown) or sound an alarm indicating the abnormality in the water temperature and water level. After performing control such as reducing the amount of replenishment water in S206, the control unit 70 terminates the tank level control.

[0057] In S207, the control unit 70 determines whether the detection result of the water temperature detection unit 24 (water temperature of the water supply tank 22) is below the control limit water temperature. The control limit water temperature is the lower limit of the preset allowable range of water temperature for the water supply (circulating water) W3 used for heat exchange in the first heat exchanger 51. If the detection result of the water temperature detection unit 24 is below the lower limit water temperature, the process proceeds to S208. If the detection result of the water temperature detection unit 24 is at or above the lower limit water temperature (i.e., when combined with the judgment result in S203, the water temperature of the water supply tank 22 is within the preset allowable range of water temperature), the control unit 70 proceeds to S211.

[0058] In S208, the control unit 70 determines whether the detection result of the water level detection unit 25 (water level in the water supply tank 22) is above the control limit water level. The control limit water level is the lower limit of the preset allowable range of water levels that can be used for water temperature adjustment, with respect to the water level in the water supply tank 22. If the detection result of the water level detection unit 25 is above the control limit water level, proceed to S209. If the detection result of the water level detection unit 25 is below the control limit water level, proceed to S210.

[0059] In S209, the control unit 70 controls the replenishment water volume control valve 26 to reduce the amount of replenishment water. As a result, the water temperature in the water tank 22 rises, and the water temperature in the water tank 22 recovers to within the acceptable range. After performing the control to reduce the amount of replenishment water in S209, the control unit 70 terminates the tank level control.

[0060] In S210, the control unit 70 controls the supply water volume adjustment valve 26 to increase the supply water volume. As a result, the amount of supply water W1 stored in the supply water tank 22 increases, and the supply water tank 22 recovers to an acceptable water level. Furthermore, in S210, the water temperature in the feedwater tank 22 is lower than the lower limit water temperature, and the water level is lower than the lower limit water level. Therefore, the abnormality determination unit 71 determines that there is an abnormality in the boiler system 1, as the water temperature and water level in the feedwater tank 22 are outside the acceptable range. The abnormality notification unit 72 acquires the judgment result from the abnormality determination unit 71 and notifies of any abnormalities in the water temperature and water level of the water supply tank 22. For example, the abnormality notification unit 72 may display the abnormality in the water temperature and water level of the water supply tank 22 on a display unit (not shown) or sound an alarm indicating the abnormality in the water temperature and water level. After performing control such as increasing the amount of replenishment water in S210, the control unit 70 terminates the tank level control.

[0061] In addition, in S210, the control unit 70 controls the amount of replenishment water, which may cause the water temperature in the water supply tank 22 to drop further. However, if the water temperature in the water supply tank 22 is lower than the lower limit temperature, the effect of removing heat from the ammonia decomposition gas F1 will not decrease. Therefore, the abnormality determination unit 71 may only determine if there is an abnormality in the water level of the water supply tank 22, and the abnormality notification unit 72 may notify of the abnormality in the water level.

[0062] In S211, the control unit 70 determines whether the detection result of the water level detection unit 25 (water level in the water supply tank 22) is below the upper limit of the management level. If the detection result of the water level detection unit 25 is below the upper limit of the management level, the process proceeds to S212. If the detection result of the water level detection unit 25 exceeds the upper limit of the management level, the process proceeds to S213. In S212, the control unit 70 determines whether the detection result of the water level detection unit 25 (water level in the water supply tank 22) is above the control limit water level. If the detection result of the water level detection unit 25 is above the control limit water level, the water temperature and water level of the water supply tank 22 are within the control range, and the control unit 70 terminates tank level control. If the detection result of the water level detection unit 25 is below the control limit water level, the process proceeds to S214.

[0063] In S213, the control unit 70 controls the replenishment water volume control valve 26 to reduce the amount of replenishment water. As a result, the water level in the water tank 22 decreases, and the water level in the water tank 22 recovers to within the acceptable range. After performing the control to reduce the amount of replenishment water in S213, the control unit 70 terminates the tank level control. In S214, the control unit 70 controls the replenishment water volume control valve 26 to increase the replenishment water volume. As a result, the water level in the water supply tank 22 increases, and the water supply tank 22 recovers to a water level within the allowable range. After performing the control to increase the replenishment water volume in S213, the control unit 70 terminates the tank level control. In addition to the above example, if the detection result of the water temperature detection unit 24 in S207 is above the control limit water temperature (i.e., when combined with the judgment result in S203, the water temperature of the water supply tank 22 is within the preset allowable range of water temperature), the control unit 70 may terminate the tank level control.

[0064] Next, in steps S301 to S305, the control unit 70 determines whether the detection result of the gas temperature detection unit 13 (temperature of the ammonia decomposition gas F1 flowing into the boiler 60) is within the first control temperature range. First, in S301, the control unit 70 determines whether the detection result of the gas temperature detection unit 13 exceeds the upper limit TU1 of the first control temperature range. If the detection result of the gas temperature detection unit 13 exceeds the upper limit TU1 of the first control temperature range, proceed to S302, set the supply air heat exchange control flag to 1, and proceed to S305. If the detection result of the gas temperature detection unit 13 is less than or equal to the upper limit TU1 of the first control temperature range, proceed to S303.

[0065] In S303, the control unit 70 determines whether the detection result of the gas temperature detection unit 13 is less than the lower limit TD1 of the first control temperature. If the detection result of the gas temperature detection unit 13 is less than the lower limit TD1 of the first control temperature, proceed to S304, set the supply air heat exchange control flag to 0, and proceed to S305. If the detection result of the gas temperature detection unit 13 is greater than or equal to the lower limit TD1 of the first control temperature, proceed to S305. In S305, the control unit 70 determines whether the air supply heat exchange control flag is 1 or not. If the air supply heat exchange control flag is 1, the process proceeds to S400; otherwise, it returns to the circulating water supply control in S100. Even when proceeding to S400, heat exchange in the first heat exchanger 51 continues.

[0066] Next, in S400, the control unit 70 performs air supply heat exchange control. Air supply heat exchange control will be explained with reference to Figure 6. In S401, the control unit 70 opens a first shut-off valve (not shown) of the branch line L110A and controls the opening degree of the first flow control valve 14 to start supplying an amount of ammonia decomposition gas F1 to the second heat exchanger 52 in proportion to the opening degree of the first flow control valve 14. Next, the process proceeds to S402, where the control unit 70 obtains the detection result from the gas temperature detection unit 13 (the temperature of the ammonia decomposition gas F1 flowing into the boiler) and proceeds to S403. In S403, the control unit 70 determines whether the detection result of the gas temperature detection unit 13 (temperature of the ammonia decomposition gas F1 flowing into the boiler) exceeds the second target temperature T2. If the detection result of the gas temperature detection unit 13 exceeds the second target temperature T2, the process proceeds to S404; otherwise, the process proceeds to S405.

[0067] In S404, the control unit 70 adjusts the opening of the first flow control valve 14 to increase the flow rate of ammonia decomposition gas F1 flowing into the second heat exchanger 52. This increases the amount of ammonia decomposition gas F1 that is removed by the second heat exchanger 52, thereby enhancing the effect of removing heat from the ammonia decomposition gas F1. After controlling the flow rate of ammonia decomposition gas F1 in S404, the control unit 70 terminates the supply air heat exchange control.

[0068] In S405, the control unit 70 determines whether the detection result of the gas temperature detection unit 13 (temperature of the ammonia decomposition gas F1 flowing into the boiler) is less than the second target temperature T2. If the detection result of the gas temperature detection unit 13 is less than the second target temperature T2, the process proceeds to S406. If the detection result of the gas temperature detection unit 13 is less than or equal to the second target temperature T2 (i.e., when combined with the determination result in S403, the temperature of the ammonia decomposition gas F1 flowing into the boiler is the second target temperature T2), the control unit 70 terminates the air supply heat exchange control.

[0069] In S406, the control unit 70 adjusts the opening of the first flow control valve 14 to reduce the flow rate of ammonia decomposition gas F1 flowing into the second heat exchanger 52. This reduces the amount of ammonia decomposition gas F1 that is removed by the second heat exchanger 52, weakening the effect of removing heat from the ammonia decomposition gas F1. After performing the control to reduce the flow rate of ammonia decomposition gas F1 in S406, the control unit 70 terminates the supply air heat exchange control.

[0070] Next, in S501 to S505, the control unit 70 determines whether the detection result of the gas temperature detection unit 13 (temperature of the ammonia decomposition gas F1 flowing into the boiler 60) is within the second control temperature range. In S501, the control unit 70 determines whether the detection result of the gas temperature detection unit 13 exceeds the upper limit TU2 of the second control temperature range. If the detection result of the gas temperature detection unit 13 exceeds the upper limit TU2 of the second control temperature range, the process proceeds to S502, the cooling water control flag is set to 1, and the process proceeds to S505. If the detection result of the gas temperature detection unit 13 is less than or equal to the upper limit TU2 of the second control temperature range, the process proceeds to S503.

[0071] In S503, the control unit 70 determines whether the detection result of the gas temperature detection unit 13 is less than the lower limit TD2 of the second control temperature range. If the detection result of the gas temperature detection unit 13 is less than the lower limit TD2 of the second control temperature range, the process proceeds to S504, the cooling water control flag is set to 0, and the process proceeds to S505. If the detection result of the gas temperature detection unit 13 is greater than or equal to the lower limit TD2 of the second control temperature range, that is, if the detection result of the gas temperature detection unit 13 is within the temperature range of the second control temperature range, the process proceeds to S505.

[0072] In S505, the control unit 70 determines whether the cooling water control flag is 1 or not. If the cooling water flag is 1, the process proceeds to S600 and the cooling water volume control is performed. If the cooling water control flag is not 1, the process returns to S100 for circulating water volume control. In this case, even when proceeding to S600, the heat exchange in the first heat exchanger 51 and the heat exchange in the second heat exchanger 52 are continued.

[0073] The cooling water control of the S600 will be explained with reference to Figure 7. In S601, the control unit 70 opens the cooling water volume control valve 41, which is the cooling water volume adjustment unit, to supply cooling water W4 to the cooling water line L400. This initiates heat exchange between the ammonia decomposition gas F1 and the cooling water W4 in the third heat exchanger 53. Next, the process proceeds to S602, where the control unit 70 acquires the detection result from the gas temperature detection unit 13 (the temperature of the ammonia decomposition gas F1 flowing into the boiler).

[0074] Next, the process proceeds to S603, where the control unit 70 determines whether the detection result of the gas temperature detection unit 13 (temperature of the ammonia decomposition gas F1 flowing into the boiler) exceeds the third target temperature T3. If the detection result of the gas temperature detection unit 13 exceeds the third target temperature T3, the process proceeds to S604; otherwise, the process proceeds to S605.

[0075] In S604, the control unit 70 adjusts the opening of the cooling water flow control valve 41 to increase the amount of cooling water W4 flowing into the third heat exchanger 53. This enhances the heat removal effect of the ammonia decomposition gas F1 in the third heat exchanger 53. After performing this control, the control unit 70 terminates the cooling water flow control.

[0076] Furthermore, in S605, the control unit 70 determines whether the detection result of the gas temperature detection unit 13 (the temperature of the ammonia decomposition gas F1 flowing into the boiler) is less than the third target temperature T3. If the detection result of the gas temperature detection unit 13 is less than the third target temperature, the process proceeds to S606. If the detection result of the gas temperature detection unit 13 is greater than or equal to the third target temperature T3 (i.e., when combined with the determination result in S603, the temperature of the ammonia decomposition gas F1 is the third target temperature T3), the control unit 70 terminates the cooling water flow rate control.

[0077] In S606, the control unit 70 adjusts the opening of the cooling water flow control valve 41 to reduce the amount of cooling water W4 flowing into the third heat exchanger 53. This reduces the heat removal effect of the ammonia decomposition gas F1 in the third heat exchanger 53. After performing this control, the control unit 70 terminates the cooling water flow control.

[0078] Next, the process proceeds to S700, where the abnormality determination unit 71 determines whether the detection result of the gas temperature detection unit 13 (temperature of the ammonia decomposition gas F1 flowing into the boiler 60) is below the third control temperature upper limit TU3. If the detection result of the gas temperature detection unit 13 is below the third control temperature upper limit TU3, the process returns to the circulating feedwater volume control in S100. If the detection result of the gas temperature detection unit 13 is above the third control temperature upper limit TU3, the process proceeds to S800. At this time, the abnormality determination unit 71 also determines that there is an abnormality in the temperature of the ammonia decomposition gas F1. In S800, the control unit 70 performs safe shutdown control of the boiler 60 based on the determination of the abnormality determination unit 71. The abnormality notification unit 72 also notifies of the abnormality based on the determination of the abnormality determination unit 71.

[0079] As described above, the boiler system 1 effectively utilizes the heat contained in the ammonia decomposition gas F1 by exchanging heat with feedwater (circulating water) W3, combustion air A1, and cooling water W4 through the first heat exchanger 51 to the third heat exchanger 53, thereby heating the feedwater W1 and combustion air A1 stored in the feedwater tank 22. Furthermore, it can maintain the temperature of the ammonia decomposition gas F1 at the inlet of the boiler 60 within a predetermined temperature range.

[0080] As described above, this embodiment can achieve the following effects. (1) The boiler system 1 comprises an ammonia decomposition device 11 that decomposes ammonia to produce ammonia decomposition gas F1 containing hydrogen and nitrogen, a boiler 60 that burns the ammonia decomposition gas F1 as fuel, an ammonia decomposition gas supply line L100 that supplies the ammonia decomposition gas F1 from the ammonia decomposition device 11 to the boiler 60, a feedwater line L210 that supplies feedwater W1 to the boiler 60, and a first heat exchanger 51 which is a heat exchanger that heats the feedwater W1 stored in the feedwater tank 22 by exchanging heat between the ammonia decomposition gas F1 and the feedwater (circulating water) W3.

[0081] Therefore, the heat contained in the ammonia decomposition gas F1 can be recovered into the feedwater (circulating water) W3 via the first heat exchanger 51, and the temperature of the ammonia decomposition gas F1 can be lowered to a predetermined temperature range. This makes it possible to maintain the temperature of the ammonia decomposition gas F1 at the inlet of the boiler 60 within a predetermined temperature range. In addition, the heat exchange can heat the feedwater W1 stored in the feedwater tank 22, so the heat contained in the ammonia decomposition gas F1 can be effectively utilized.

[0082] (2) The boiler system 1 described in (1) above comprises a control unit 70 for controlling the boiler system 1, a gas temperature detection unit 13 for detecting the temperature of the ammonia decomposition gas F1 flowing into the boiler 60, and a pump 23 which is a water flow rate adjustment unit for adjusting the amount of feedwater (circulating water) W3 flowing into the first heat exchanger 51. Based on the detection result of the gas temperature detection unit 13, the control unit 70 controls the amount of feedwater (circulating water) W3 flowing in by the pump 23, which is a water flow rate adjustment unit, so that the ammonia decomposition gas F1 is within a predetermined temperature range. Therefore, the boiler system 1 can effectively cool the temperature of the ammonia decomposition gas F1 to a predetermined temperature range by adjusting the amount of heat recovered in the feedwater (circulating water) W3. Furthermore, by suppressing temperature changes in the ammonia decomposition gas F1, the boiler system 1 can stabilize the combustion of the boiler 60.

[0083] (3) The boiler system 1 described in (2) above includes a feedwater tank 22 for storing feedwater W1 supplied to the boiler 60, and a circulation line L230 for circulating feedwater (circulating water) W3 between the feedwater tank 22 and the first heat exchanger 51. A pump 23, which is a water flow rate adjustment unit, is provided in the circulation line L230. Therefore, since the feedwater (circulating water) W3 used for heat exchange with the ammonia decomposition gas F1 circulates between the feedwater tank 22 and the first heat exchanger 51, the range of adjustment for the amount of feedwater (circulating water) W3 flowing into the first heat exchanger 51 is expanded, and heat can be stored in the feedwater W1 stored in the feedwater tank 22, allowing the feedwater W1 to be used more efficiently for heat removal from the ammonia decomposition gas F1. In addition, the heat from the ammonia decomposition gas F1 can effectively heat the feedwater W1 stored in the feedwater tank 22.

[0084] (4) The boiler system 1 described in (3) above includes a makeup water line L220 that supplies makeup water W2 to a feedwater tank 22, a water temperature detection unit 24 that detects the water temperature of the feedwater tank 22 or the water temperature of the circulation line L230, a water level detection unit 25 that detects the water level of the feedwater tank 22, and a makeup water volume adjustment valve 26 which is a makeup water volume adjustment unit provided in the makeup water line L220 and adjusts the amount of makeup water supplied to the feedwater tank 22. The control unit 70 adjusts the amount of makeup water using the makeup water volume adjustment valve 26, which is a makeup water volume adjustment unit, based on the detection results of the water level detection unit 25 and the detection results of the water temperature detection unit 24.

[0085] Therefore, the amount of replenishment water supplied to the feedwater tank 22 is adjusted based on the water level in the feedwater tank 22 and the water temperature in the feedwater tank 22 or the water temperature in the circulation line L230. This allows the temperature of the feedwater (circulating water) W3 used for heat exchange to be kept below a predetermined temperature, enabling the boiler system 1 to effectively utilize the heat recovered from the ammonia decomposition gas F1 and maintain the cooling effect on the ammonia decomposition gas F1.

[0086] (5) The boiler system 1 described in (4) above includes an abnormality determination unit 71 in which the control unit 70 determines an abnormality in the boiler system 1 based on the detection result of the water temperature detection unit 24 and the detection result of the water level detection unit 25. The abnormality determination unit 71 determines an abnormality if at least one of the detection result of the water temperature detection unit 24 and the detection result of the water level detection unit 25 deviates from a preset tolerance range. Therefore, the boiler system 1 can be operated safely, and the temperature of the ammonia decomposition gas F1 can be maintained within a predetermined range.

[0087] (6) The boiler system 1 described in (2) to (5) above includes an air supply line L300 that supplies combustion air A1 to the boiler 60, an inverter 32 which is an air supply amount adjustment unit that adjusts the amount of combustion air A1 supplied, a second heat exchanger 52 that heats the combustion air A1 by exchanging heat between the combustion air A1 and ammonia decomposition gas F1, and a first flow rate adjustment valve 14 which is an ammonia decomposition gas flow rate adjustment unit that adjusts the flow rate of ammonia decomposition gas F1 flowing into the second heat exchanger 52. Based on the detection result of the gas temperature detection unit 13, the control unit 70 adjusts the flow rate of ammonia decomposition gas F1 to the second heat exchanger 52 by adjusting the first flow rate adjustment valve 14 so that the ammonia decomposition gas F1 is within a predetermined temperature range.

[0088] Therefore, by exchanging heat between the ammonia decomposition gas F1, which could not be removed by heat exchange with the feedwater (circulating water) W3, and the combustion air A1 in the second heat exchanger 52, the ammonia decomposition gas F1 can be cooled, maintaining its temperature within a predetermined temperature range, and the combustion air A1 can be heated, allowing for effective utilization of thermal energy.

[0089] (7) The boiler system 1 described in (2) to (6) above includes a cooling water line L400 that supplies cooling water W4 to cool the ammonia decomposition gas F1, a cooling water flow rate adjustment valve 41 which is a cooling water flow rate adjustment unit that adjusts the flow rate of the cooling water W4 in the cooling water line L400, and a third heat exchanger 53 which exchanges heat between the ammonia decomposition gas F1 and the cooling water W4 and heats the cooling water W4. Based on the detection result of the gas temperature detection unit 13, the control unit 70 adjusts the amount of cooling water W4 supplied by the cooling water flow rate adjustment valve 41 which is a cooling water flow rate adjustment unit so that the ammonia decomposition gas F1 is within a predetermined temperature range.

[0090] Therefore, the heat retained in the ammonia decomposition gas F1 that could not be removed by heat exchange with the feedwater (circulating water) W3 can be cooled by heat exchange with the cooling water W4 using the third heat exchanger 53, and the temperature of the ammonia decomposition gas F1 can be maintained within a predetermined temperature range.

[0091] (8) The boiler system 1 described in (2) to (7) above comprises an air supply line L300 for supplying combustion air A1 to a boiler 60, an inverter 32 which is an air supply amount adjustment unit for adjusting the amount of combustion air A1 supplied, a second heat exchanger 52 which heats the combustion air A1 by exchanging heat between the combustion air A1 and ammonia decomposition gas F1, a first flow rate adjustment valve 14 which is an ammonia decomposition gas flow rate adjustment unit for adjusting the flow rate of ammonia decomposition gas F1 flowing into the second heat exchanger, a cooling water line L400 for supplying cooling water W4 to cool the ammonia decomposition gas F1, a cooling water flow rate adjustment valve 41 which is a cooling water adjustment unit for adjusting the flow rate of cooling water W4 in the cooling water line L400, and a third heat exchanger 53 which heats the cooling water W4 by exchanging heat between the ammonia decomposition gas F1 and the cooling water W4. Based on the detection result of the gas temperature detection unit 13, the control unit 70 adjusts the flow rate of the ammonia decomposition gas F1 flowing into the second heat exchanger 52 using the first flow rate adjustment valve 14, which is the ammonia decomposition gas flow rate adjustment unit, or adjusts the flow rate of the cooling water W4 using the cooling water flow rate adjustment valve 41, which is the cooling water adjustment unit, so that the ammonia decomposition gas F1 is within a predetermined temperature range, or performs at least one of these actions.

[0092] Therefore, based on the temperature of the ammonia decomposition gas F1 flowing into the boiler 60, the system determines when to start heat exchange in the second heat exchanger 52 and the third heat exchanger 53, and adjusts the flow rate of the ammonia decomposition gas F1 flowing into the second heat exchanger 52 and the flow rate of the cooling water W4 flowing into the third heat exchanger 53. This allows for more effective removal of the heat contained in the ammonia decomposition gas F1 and maintains the temperature of the ammonia decomposition gas within a predetermined temperature range.

[0093] (Second Embodiment) Figure 8 is a diagram illustrating the boiler system 2 of the second embodiment. The boiler system 2 of the second embodiment is similar in form to the boiler system 1 of the first embodiment described above, except that it does not have a feedwater tank 22, a water temperature detection unit 24, a water level detection unit 25, a circulation line L230, and a makeup water line L220. Therefore, parts that perform the same functions as those of the first embodiment described above are given the same reference numerals or the same reference numerals at the end, and redundant explanations are omitted as appropriate. The boiler system 2 of this embodiment does not include a feedwater tank 22, a water temperature detection unit 24, a water level detection unit 25, a circulation line L230, or a makeup water line L220, but it does include a feedwater line L240.

[0094] The feedwater line L240 is connected to a feedwater source (not shown) on its upstream side and to the boiler 60 on its downstream side. The feedwater line L240 also passes through a first heat exchanger 51, and a pump 21 is located downstream of the first heat exchanger 51. This pump 21 is a feedwater flow rate adjustment unit that adjusts the flow rate of feedwater W1 to the boiler 60, and also functions as a water flow rate adjustment unit that adjusts the flow rate of feedwater W1 into the first heat exchanger 51. In Figure 8, an example is shown in which the pump 21 is located downstream of the first heat exchanger 51, but it is not limited to this and may be located upstream.

[0095] Therefore, in the boiler system 2 of this embodiment, the circulating feedwater volume control S100 shown in Figure 2 of the first embodiment is not performed. Furthermore, in the boiler system 2 of this embodiment, the feedwater W1 is not stored in the feedwater tank 22, but is heat-exchanged with the ammonia decomposition gas F1 in the first heat exchanger 51 and supplied to the boiler 60. In a boiler system like the boiler system 2 of this embodiment, the flow rate of the ammonia decomposition gas F1 (fuel flow rate) and the flow rate of the feedwater W1 to the boiler 60 (steam flow rate produced by fuel combustion and heat exchange) are basically proportional. Therefore, the temperature of the ammonia decomposition gas F1 after heat exchange with the feedwater W1 is maintained at approximately a constant level. Therefore, in the boiler system 2 of this embodiment, similar to the boiler system 1 of the first embodiment, the heat contained in the ammonia decomposition gas F1 can be effectively utilized, and the temperature of the ammonia decomposition gas F1 at the inlet of the boiler 60 can be maintained within a predetermined temperature range.

[0096] As described above, this embodiment can achieve the following effects. (9) The boiler system 2 comprises an ammonia decomposition device 11 that decomposes ammonia to produce ammonia decomposition gas F1 containing hydrogen and nitrogen, a boiler 60 that burns the ammonia decomposition gas F1 as fuel, an ammonia decomposition gas supply line L100 that supplies the ammonia decomposition gas F1 from the ammonia decomposition device 11 to the boiler 60, a feedwater line L210 that supplies feedwater W1 to the boiler 60, and a first heat exchanger 51 which is a heat exchanger that heats the feedwater W1 by exchanging heat between the ammonia decomposition gas F1 and the feedwater W1.

[0097] Therefore, the heat contained in the ammonia decomposition gas F1 can be removed by the feedwater W1 via the first heat exchanger 51, and the temperature of the ammonia decomposition gas F1 can be lowered to a predetermined temperature range. This makes it possible to maintain the temperature of the ammonia decomposition gas at the inlet of the boiler 60 within a predetermined temperature range. In addition, since the feedwater W1 can be heated by heat exchange, the heat contained in the ammonia decomposition gas F1 can be effectively utilized.

[0098] (Transformed form) The present invention is not limited to the embodiments described above, and various modifications and changes are possible, all of which fall within the scope of the present invention.

[0099] In the first embodiment, the water temperature detection unit 24 was described as detecting the water temperature of the water supply tank 22, but it is not limited to this, and may be provided in the circulation line L230 to detect the temperature of the water supply (circulating water) W3 flowing through the circulation line L230.

[0100] In each embodiment, the cooling water line L400 is shown to be equipped with a cooling water flow rate control valve 41, thereby adjusting the flow rate. However, the embodiment is not limited to this, and a configuration may be provided upstream of the third heat exchanger 53 with only a shut-off valve (not shown), and by opening the shut-off valve, a fixed amount of cooling water W4 may be supplied to the cooling water line L400.

[0101] In each embodiment, the gas temperature detection unit 13 for detecting the temperature of the ammonia decomposition gas F1 is shown to be located downstream of the ammonia decomposition gas supply line L100 and near the inlet of the boiler 60. However, the embodiment is not limited to this, and gas temperature detection units for detecting the temperature of the ammonia decomposition gas F1 after it has left each heat exchanger may be provided and each may be electrically connected to the control unit 70. The control unit 70 may also adjust, as appropriate, the amount of feedwater (circulating water) W3 or feedwater W1 supplied to the first heat exchanger 51, the amount of combustion air A1 supplied to the second heat exchanger 52, and the amount of cooling water W4 supplied to the third heat exchanger 53, based on the detection results of each gas temperature detection unit (temperature of the ammonia decomposition gas F1 after it leaves each heat exchanger).

[0102] In each embodiment, the air supply line L300 is branched upstream of the second heat exchanger 52, and the branched line is connected back to the air supply line L300 through the second heat exchanger 52. A flow control valve (not shown) or the like is provided in the branched line, and the control unit 70 controls the flow control valve or the like to adjust the amount of combustion air A1 supplied to the second heat exchanger 52. In this case, the ammonia decomposition gas supply line L100 may be configured without the first flow control valve 14 in the branch line L110A.

[0103] In each embodiment, in order to protect the equipment on the air supply side, the control unit 70 may perform control to keep the temperature of the combustion air A1 below a predetermined temperature range based on the temperature of the combustion air A1 detected by the air temperature detection unit 33. If the temperature of the combustion air A1 detected by the air temperature detection unit 33 exceeds a specified temperature, the control unit 70 adjusts the opening of the first flow rate control valve 14 to reduce the flow rate of ammonia decomposition gas F1 flowing into the second heat exchanger 52, thereby reducing the temperature rise of the combustion air A1. By implementing this type of control, boiler systems 1 and 2 can protect the air supply equipment, such as boiler 60, and continue operating safely. In this case, as described above, the air supply line L300 may be branched upstream of the second heat exchanger 52, and the branched line may be reconnected to the air supply line L300 through the second heat exchanger 52. A flow control valve (not shown) or the like may be provided in the branched line, and the control unit 70 may control the flow control valve or the like to adjust the amount of combustion air A1 supplied to the second heat exchanger 52.

[0104] In the first embodiment, an example was shown in which, when the detection result of the water temperature detection unit 24 is higher than the upper limit water temperature and the detection result of the water level detection unit 25 is higher than the upper limit water level, the abnormality determination unit 71 notifies of an abnormality in the boiler system 1 in S206. Also in the first embodiment, an example was shown in which, when the detection result of the water temperature detection unit 24 is lower than the lower limit water temperature and the detection result of the water level detection unit 25 is lower than the lower limit water level, the abnormality determination unit 71 notifies of an abnormality in the boiler system 1 in S210. However, the system is not limited to these examples, and the abnormality determination unit 71 may determine an abnormality in the feedwater tank 22 when at least one of the water temperature or water level deviates from a preset allowable range. While it is preferable for the water temperature in the water supply tank 22 to meet the management temperature range, from the standpoint of cooling the ammonia decomposition gas F1 through heat exchange with the water supply tank 22, it is not a problem if the water temperature in the water supply tank 22 is lower than the management lower limit water temperature. Therefore, the abnormality detection unit 71 may only detect abnormalities in the water level of the water supply tank 22, and the abnormality notification unit 72 may only notify of abnormalities in the water level. This configuration allows for safer operation of the boiler system 1.

[0105] In each embodiment, if the temperature of the ammonia decomposition gas F1 is not cooled to a predetermined range by heat exchange in the first heat exchanger 51, the control unit 70 starts heat exchange in the second heat exchanger 52, and then starts heat exchange in the third heat exchanger 53. However, the control unit 70 may, if the temperature of the ammonia decomposition gas F1 is not cooled to a predetermined range by heat exchange in the first heat exchanger 51, first start heat exchange in the third heat exchanger 53, and then start heat exchange in the second heat exchanger 52, or it may start heat exchange in the second heat exchanger 52 and the third heat exchanger 53 simultaneously.

[0106] In each embodiment, the control unit 70 is shown to include an abnormality notification unit 72, but it is not limited to this, and may also include an abnormality operation control unit that stops the boiler operation based on the determination result of the abnormality determination unit 71. Furthermore, in each embodiment, the abnormality notification unit 72 and the abnormality operation control unit may both be included.

[0107] In each embodiment, the positions of the first heat exchanger 51, the second heat exchanger 52, and the third heat exchanger 53 are not limited to those shown in Figures 1 and 8, but may be changed as appropriate. For example, the second heat exchanger 52 may be provided in the ammonia decomposition gas supply line L100, or the second heat exchanger 52 and the third heat exchanger 53 may be located upstream of the first heat exchanger 51 in the ammonia decomposition gas supply line L100.

[0108] In each embodiment, the control unit 70 opens a first shut-off valve (not shown) provided in the branch line L110A and adjusts the opening of the first flow rate adjustment valve 14 when starting heat exchange between the ammonia decomposition gas F1 and the combustion air A1 in the second heat exchanger 52, thereby allowing a portion of the ammonia decomposition gas F1 flowing through the ammonia decomposition gas supply line L100 to flow into the second heat exchanger 52. However, the control unit 70 is not limited to this, and may perform the following control as long as it can adjust the ratio between the flow rate of the ammonia decomposition gas F1 flowing into the second heat exchanger 52 and the flow rate of the ammonia decomposition gas F1 flowing downstream without flowing into the second heat exchanger 52. The control unit 70 may open a first shut-off valve (not shown) and reduce the opening of the second flow rate control valve 15 to allow a predetermined amount of ammonia decomposition gas F1 to flow into the second heat exchanger 52. In this case, the first flow rate control valve 14 does not need to be provided in the branch line L110A. Alternatively, the control unit 70 may control the opening degree of the second flow control valve 15 instead of the opening degree of the first flow control valve 14. Furthermore, the control unit 70 may be configured to control the opening degree of both the first flow control valve 14 and the second flow control valve 15.

[0109] In the first embodiment, in S206 of the tank level control in S200, the control unit 70 is shown to perform control to reduce the amount of replenishment water. However, the control unit 70 is not limited to this and may also perform control to reduce the amount of supply water (circulating water) W3 flowing through the circulation line L230. In this case, the amount of feedwater (circulating water) W3 flowing into the first heat exchanger 51 decreases, which may reduce the heat removal effect of the ammonia decomposition gas F1. However, the boiler system 1 of the first embodiment is equipped with a second heat exchanger 52 and a third heat exchanger 53, and these heat exchangers sufficiently remove heat from the ammonia decomposition gas F1, allowing it to be kept within a predetermined temperature range.

[0110] While each embodiment and its variations can be used in combination as appropriate, a detailed explanation is omitted. Furthermore, the present invention is not limited to the embodiments described above.

[0111] Furthermore, since the present invention promotes the use of ammonia as a fuel that does not emit carbon dioxide, it can contribute, for example, to United Nations Sustainable Development Goal (SDG) 7, "Ensure access to affordable, reliable, sustainable and modern energy." [Explanation of Symbols]

[0112] 1,2 Boiler System 11. Ammonia decomposition device 12 Buffer Tank 13 Gas temperature detection unit 22 Water tank 23 Pump (water flow rate adjustment unit) 24 Water temperature detection unit 25 Water level detection unit 26. Water supply volume adjustment valve (water supply volume adjustment section) 31 Blower 32. Inverter (Air Intake Volume Adjustment Unit) 41 Cooling water volume control valve (cooling water volume control section) 51. First heat exchanger (heat exchanger) 52 Second heat exchanger 53 Third heat exchanger 60 boilers 70 Control Unit 71 Abnormality determination section 72 Anomaly Reporting Department L100 Ammonia Decomposition Gas Supply Line L210, L240 Water supply line L220 Water supply line L230 Circulation Line L300 Air Supply Line L400 Coolant Line

Claims

1. An ammonia decomposition apparatus that decomposes ammonia to produce ammonia decomposition gas containing hydrogen and nitrogen, A boiler that burns the aforementioned ammonia decomposition gas as fuel, an ammonia decomposition gas supply line that supplies the ammonia decomposition gas from the ammonia decomposition apparatus to the boiler, A feedwater line that supplies feedwater to the boiler, A heat exchanger that heats the feedwater by exchanging heat between the ammonia decomposition gas and the feedwater, A boiler system equipped with [a specific feature / feature].

2. A control unit that controls the boiler system, A gas temperature detection unit for detecting the temperature of the ammonia decomposition gas flowing into the boiler, A water flow rate adjustment unit adjusts the amount of water flowing into the heat exchanger, Equipped with, The control unit, Based on the detection result of the gas temperature detection unit, the water flow rate adjustment unit controls the inflow rate of the water supply so that the ammonia decomposition gas is within a predetermined temperature range. The boiler system according to claim 1.

3. A feedwater tank for storing the feedwater supplied to the boiler, A circulation line for circulating the water supply between the water supply tank and the heat exchanger, Equipped with, The water volume adjustment unit is provided in the circulation line, The boiler system according to claim 2.

4. A supply water line for supplying supply water to the aforementioned water tank, A water temperature detection unit for detecting the water temperature of the water supply tank or the water temperature of the circulation line, A water level detection unit for detecting the water level in the water supply tank, A supply water volume adjustment unit is provided in the supply water line and adjusts the amount of supply water supplied to the water tank, Equipped with, The control unit, Based on the detection results of the water level detection unit and the detection results of the water temperature detection unit, the amount of replenishment water is adjusted by the replenishment water amount adjustment unit. The boiler system according to claim 3.

5. The control unit includes an abnormality determination unit that determines an abnormality in the boiler system based on the detection result of the water temperature detection unit and the detection result of the water level detection unit. The abnormality determination unit determines an abnormality if at least one of the detection results of the water temperature detection unit and the detection results of the water level detection unit deviates from a preset tolerance range. The boiler system according to claim 4.

6. An air supply line that supplies combustion air to the boiler, An air supply volume adjustment unit for adjusting the amount of combustion air supplied, A second heat exchanger that exchanges heat between the combustion air and the ammonia decomposition gas and heats the combustion air, an ammonia decomposition gas flow rate adjustment unit that adjusts the flow rate of the ammonia decomposition gas flowing into the second heat exchanger, Equipped with, The control unit, Based on the detection result of the gas temperature detection unit, the ammonia decomposition gas flow rate adjustment unit adjusts the amount of ammonia decomposition gas flowing into the second heat exchanger so that the ammonia decomposition gas is within a predetermined temperature range. The boiler system according to claim 2.

7. A cooling water line that supplies cooling water to cool the ammonia decomposition gas, A cooling water flow rate adjustment unit for adjusting the flow rate of the cooling water in the aforementioned cooling water line, A third heat exchanger that exchanges heat between the ammonia decomposition gas and the cooling water and heats the cooling water, Equipped with, The control unit, Based on the detection result of the gas temperature detection unit, the amount of cooling water supplied by the cooling water volume adjustment unit is adjusted so that the ammonia decomposition gas is within a predetermined temperature range. The boiler system according to claim 2.

8. An air supply line that supplies combustion air to the boiler, An air supply volume adjustment unit for adjusting the amount of combustion air supplied, A second heat exchanger that exchanges heat between the combustion air and the ammonia decomposition gas and heats the combustion air, an ammonia decomposition gas flow rate adjustment unit that adjusts the flow rate of the ammonia decomposition gas flowing into the second heat exchanger, A cooling water line that supplies cooling water to cool the ammonia decomposition gas, A cooling water adjustment unit that adjusts the flow rate of the cooling water in the aforementioned cooling water line, A third heat exchanger that exchanges heat between the ammonia decomposition gas and the cooling water and heats the cooling water, Equipped with, The control unit, based on the detection result of the gas temperature detection unit, adjusts the ammonia decomposition gas so that it falls within a predetermined temperature range. The ammonia decomposition gas flow rate adjustment unit adjusts the amount of ammonia decomposition gas flowing into the second heat exchanger, or The flow rate of the cooling water is adjusted by the cooling water adjustment unit. Do at least one of these: The boiler system according to claim 2.

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