Hydrogen combustion boiler

Abstract

To provide a hydrogen combustion boiler that reduces a heat loss due to purging inside a furnace and has high responsiveness to load demands.SOLUTION: A hydrogen combustion boiler comprises: a boiler body; a blower; a burner having a main burner and a pilot burner; a hydrogen supply line that supplies a hydrogen-based fuel gas containing at least 50% hydrogen to the main burner; a first shut-off valve that opens and closes the flow path of the hydrogen-based fuel gas; an inert gas supply line connected to the hydrogen supply line; a second shut-off valve that opens and closes the flow path of an inert gas; a fuel supply line for the pilot burner; a third shut-off valve that opens and closes the flow path of a fuel for the pilot burner; an air supply line that supplies air to the burner; and a control unit. The control unit has a combustion control unit that controls combustion of the main burner and the pilot burner, and after opening the third shut-off valve to start combustion of the pilot burner, the combustion control unit closes the first shut-off valve and opens the second shut-off valve, thereby performing inert gas purging control on the hydrogen supply line.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a hydrogen-fired boiler that uses, as fuel, a hydrogen-based fuel gas containing at least 50% hydrogen. [Background technology]

[0002] Hydrogen-fired boilers that use hydrogen gas as fuel have been known in the past and have attracted attention because they do not generate carbon dioxide when burning fuel (see, for example, Patent Document 1). Hydrogen gas has a faster combustion speed than hydrocarbon gases and a wider combustion range when mixed with air, so it is necessary to prevent backfire, which occurs when the flame generated in the burner flows back into the hydrogen supply line that supplies hydrogen gas to the burner. In particular, if hydrogen gas remains in the hydrogen supply line when the burner combustion stops, this remaining hydrogen gas may mix with air and cause backfire when the burner restarts combustion.

[0003] Therefore, in order to improve safety in hydrogen-fired boilers, a commonly adopted method is to purge the furnace and the hydrogen supply line with inert gas when combustion is stopped, and then, when combustion is restarted, purge the furnace and the hydrogen supply line with inert gas again before restarting combustion in the burner. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-065579 Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, in a boiler that uses hydrogen gas as fuel, purging of the furnace is required both when combustion is stopped and when it is restarted, which causes problems such as heat loss and a delay in response to load demands, because the furnace is purged both when combustion is stopped and when it is restarted. Therefore, there was a demand for a hydrogen-fired boiler that could reduce heat loss and respond quickly to load demands.

[0006] An object of the present invention is to provide a hydrogen-fired boiler that reduces heat loss due to purging inside the furnace and has high responsiveness to load demands. [Means for solving the problem]

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

[0008] The hydrogen-fired boiler of the present invention comprises a boiler body, a blower, a burner including a main burner that burns a hydrogen-based fuel gas containing at least 50% hydrogen and a pilot burner that ignites the main burner, a hydrogen supply line that supplies the hydrogen-based fuel gas to the main burner, a first shutoff valve that is provided in the hydrogen supply line and that opens and closes the flow path of the hydrogen-based fuel gas, an inert gas supply line that is connected to the hydrogen supply line near the first shutoff valve and downstream of the first shutoff valve and that supplies an inert gas to the hydrogen supply line, a second shutoff valve that is provided in the inert gas supply line and that opens and closes the flow path of the inert gas, and the pilot burner. The system comprises a pilot burner fuel supply line that supplies pilot burner fuel to a burner, a third shut-off valve provided in the pilot burner fuel supply line that opens and closes the flow path of the pilot burner fuel, an air supply line that supplies air from the blower to the burner, and a control unit, wherein the control unit comprises a combustion control unit that controls combustion of the main burner and combustion of the pilot burner, and after opening the third shut-off valve to start combustion of the pilot burner, the combustion control unit closes the first shut-off valve and opens the second shut-off valve, and performs inert gas purge control to supply the inert gas to the hydrogen supply line.

[0009] Furthermore, it is preferable that the air supply line comprises a main air supply line that supplies air to the main burner, a pilot air supply line that supplies air to the pilot burner, and an air amount adjustment unit that adjusts the amount of air supplied to the main burner, and that the pilot air supply line is connected to the upstream side of the air amount adjustment unit in the air supply line.

[0010] Furthermore, it is preferable that the hydrogen-fired boiler be equipped with a main flame detection unit that detects the flame of the main burner and sends the result to the combustion control unit, and a pilot flame detection unit that detects the flame of the pilot burner and sends the result to the combustion control unit.

[0011] Furthermore, it is preferable that the combustion control unit closes the second shutoff valve to complete the inert gas purge when the main flame detection unit cannot detect a flame during the inert gas purge control.

[0012] Furthermore, it is preferable that the control unit includes an air amount memory unit that stores a first air amount corresponding to the air amount used to purge the furnace interior and a second air amount that is smaller than the first air amount and is required for combustion by the pilot burner, and that when combustion of the hydrogen-based fuel gas in the main burner is stopped, the combustion control unit purges the furnace interior with the first air amount, and after purging of the furnace interior is completed, the air amount adjustment unit stops the supply of air to the main burner air supply line and continues the supply of air to the pilot air supply line with the second air amount.

[0013] Furthermore, when stopping the combustion of the hydrogen-based fuel gas in the main burner, it is preferable that the combustion control unit opens the second shut-off valve to start an inert gas purge, and then closes the first shut-off valve to stop the supply of the hydrogen-based fuel gas.

[0014] Furthermore, when starting combustion in the main burner after combustion of the hydrogen-based fuel gas in the main burner has stopped, purging of the hydrogen supply line with inert gas has been completed, and combustion in the pilot burner is continuing, it is preferable that the combustion control unit opens the second shut-off valve for a predetermined time to purge the hydrogen supply line with inert gas, and then opens the first shut-off valve to start combustion in the main burner.

[0015] Furthermore, when starting combustion in the main burner after combustion of the hydrogen-based fuel gas in the main burner has stopped and the inert gas is being purged into the hydrogen supply line, it is preferable that the combustion control unit opens the first shut-off valve and starts combustion in the main burner after purging of the inert gas into the hydrogen supply line is completed. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a hydrogen-fired boiler that reduces heat loss due to purging inside the furnace and has high responsiveness to load demands. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram illustrating the configuration of a hydrogen combustion boiler 1 according to an embodiment. [Figure 2] 2 is a diagram showing a time chart illustrating the operating state and the operation of each part in the hydrogen combustion boiler 1 of the embodiment. FIG. [Figure 3] FIG. 1 is a time chart illustrating the operating state and the operation of each part in a conventional hydrogen combustion boiler. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the figures shown below, including FIG. 1, are schematic diagrams, and the size and shape of each part are appropriately exaggerated to make them easier to understand.

[0019] (Embodiment) FIG. 1 is a diagram illustrating the configuration of a hydrogen combustion boiler 1 according to this embodiment. The hydrogen combustion boiler 1 of this embodiment is a boiler that uses hydrogen gas G1, which is a hydrogen-based fuel gas, as fuel, and is, for example, a once-through boiler. 1, the hydrogen-fired boiler 1 includes a boiler body 10, a burner 20, a blower 41, and a control unit 80. The hydrogen-fired boiler 1 also includes a hydrogen supply line L100, an inert gas supply line L200, a pilot burner fuel supply line L300, and an air supply line L400. In this specification, the term "line" is a general term for a flow path, a passage, a conduit, etc. In this specification and claims, the term "hydrogen-based fuel gas" refers not only to hydrogen gas consisting of only hydrogen, but also to a mixed gas consisting of hydrogen and other gases containing at least 50% hydrogen. Therefore, in this embodiment, an example in which hydrogen gas G1 is used as the hydrogen-based fuel gas will be described, but the hydrogen-based fuel gas is not limited to this, and a mixed gas containing at least 50% hydrogen may also be used.

[0020] The boiler body 10 is configured to include a lower header, a plurality of water tubes, an upper header (none of which are shown), and a combustion chamber B, and generates steam by heating water supplied to the boiler body 10. In the following description, the inside of the combustion chamber B will be referred to as the inside of the furnace as appropriate. The burner 20 is disposed on top of the can body 10. The burner 20 includes a main burner 21, a pilot burner 22, a window box 23, and a main flame detector and a pilot flame detector (not shown). The main burner 21 burns hydrogen gas G1 in the combustion chamber B of the can body 10. For ease of understanding, the flame stabilizing units of each burner are omitted from FIG. 1.

[0021] The main burner 21 is a burner that burns hydrogen gas G1 as fuel. The pilot burner 22 is provided inside or near the main burner 21 and ignites the main burner 21. In this embodiment, the pilot burner 22 and the main burner 21 have the same fuel ejection axis, and a configuration in which the pilot burner 22 is arranged inside the main burner 21 will be described as an example. During operation, this hydrogen-fired boiler 1 starts combustion in the pilot burner 22 before stopping combustion in the main burner 21, continues combustion in the pilot burner 22 even while combustion in the main burner 21 is stopped, and stops combustion in the pilot burner 22 after ignition of the main burner 21. Therefore, in the hydrogen-fired boiler 1, combustion is not interrupted even when combustion in the main burner 21 is stopped or ignited, and at least one of the main burner 21 and the pilot burner 22 continues combustion.

[0022] In the hydrogen-fired boiler 1 of this embodiment, the main burner 21 burns hydrogen gas G1 supplied from a hydrogen supply line L100 as fuel, and the pilot burner 22 burns pilot burner fuel G3 supplied from a pilot burner fuel supply line L300. The pilot burner fuel G3 is a gaseous fuel such as city gas 13A. Therefore, the main burner 21 and the pilot burner 22 use different fuels for combustion. The window box 23 is connected to a main air supply line L410, which will be described later, and supplies combustion air A1 required for combustion by the main burner 21.

[0023] The main flame detection unit detects the flame of the main burner 21 and transmits the result to a combustion control unit 81 of the control unit 80, which will be described later. The pilot flame detection unit detects the flame of the pilot burner 22 and transmits the result to the combustion control unit 81 of the control unit 80. These flame detection units can use optical sensors such as ultraviolet flame detectors that can detect flames.

[0024] The hydrogen supply line L100 supplies hydrogen gas G1 as fuel to the main burner 21. The downstream side of the hydrogen supply line L100 is connected to the main burner 21, and the upstream side is connected to a supply source (not shown) that supplies the hydrogen gas G1. The hydrogen supply line L100 is provided with a flame arrestor 51, first shutoff valves V11 and V12 that open and close the flow path of hydrogen gas G1, a hydrogen flow rate adjustment valve V13, a hydrogen main valve V14, and a first atmosphere open section 110.

[0025] The flame arrestor 51 is disposed on the hydrogen supply line L100 downstream of the connection position with the inert gas supply line L200, which will be described later. The flame arrestor 51 prevents backfire that occurs in the hydrogen supply line L100 from progressing upstream. The first shut-off valves V11, V12 are disposed on the hydrogen supply line L100 upstream of the flame arrestor 51. The first shut-off valves V11, V12 are configured as solenoid valves and open and close the flow path of the hydrogen supply line L100. In this embodiment, the first shut-off valve V12 is disposed upstream of the first shut-off valve V11 and in the vicinity of the first shut-off valve V11.

[0026] The hydrogen flow rate adjustment valve V13 is disposed on the hydrogen supply line L100, upstream of the first shutoff valve V12. The hydrogen flow rate adjustment valve V13 adjusts the flow rate of the hydrogen gas G1 flowing through the hydrogen supply line L100. The hydrogen flow rate adjustment valve V13 is, for example, configured by a gas governor. The hydrogen main valve V14 is disposed upstream of the hydrogen flow rate adjustment valve V13. In this embodiment, the hydrogen main valve V14 is configured as a manual valve, and opens and closes the flow path of the hydrogen supply line L100.

[0027] The first atmosphere release section 110 is arranged upstream of the hydrogen main valve V14. The first atmosphere release section 110 includes an atmosphere release line L150 and a first atmosphere release valve V15 arranged in this atmosphere release line L150. The first atmosphere release section 110 opens the first atmosphere release valve V15 to purge the hydrogen supply line L100 upstream of the hydrogen main valve V14 with an inert gas and replace it with hydrogen.

[0028] The inert gas supply line L200 is a line that supplies the inert gas G2 into the combustion chamber B of the can body 10 via the hydrogen supply line L100. The upstream side of the inert gas supply line L200 is connected to the supply source 200 of the inert gas G2, and the downstream side is connected to the hydrogen supply line L100 between the first shutoff valve V11 and the flame arrestor 51. In this embodiment, the downstream side of the inert gas supply line L200 is connected to the hydrogen supply line L100 near the downstream side of the first shutoff valve V11. As the inert gas G2, a gas having a specific gravity lighter than that of oxygen, such as nitrogen, helium, neon, etc. In this embodiment, an example in which nitrogen is used as the inert gas G2 will be described.

[0029] The inert gas supply line L200 is provided with second shutoff valves V21 and V22, an orifice 52, and a flow rate sensor (not shown). The second shutoff valves V21, V22 are configured by electromagnetic valves and open and close the flow path of the inert gas supply line L200. The second shutoff valves V21, V22 are electrically connected to the control unit 80 and are controlled based on signals transmitted from the control unit 80. In this embodiment, the second shutoff valve V22 is disposed upstream of the second shutoff valve V21 and in the vicinity of the second shutoff valve V21. The orifice 52 is disposed downstream of the second shutoff valve V21 in the inert gas supply line L200. The orifice 52 throttles the inert gas G2 flowing through the inert gas supply line L200, thereby reducing the pressure of the inert gas G2 flowing downstream.

[0030] The inert gas supply line L200 supplies the inert gas G2 at a pressure higher than the pressure of the hydrogen gas G1 supplied to the hydrogen supply line L100 downstream of the first shutoff valve V11. That is, the pressure of the inert gas G2 upstream of the orifice 52 in the inert gas supply line L200 is set to be higher than the pressure of the hydrogen gas G1 supplied to the hydrogen supply line L100 downstream of the first shutoff valve V11 when the main burner 21 is in the maximum combustion state.

[0031] Furthermore, the pressure of the inert gas G2 downstream of the orifice 52 in the inert gas supply line L200 is set to be lower than the pressure of the hydrogen gas G1 supplied downstream of the first shutoff valve V11 in the hydrogen supply line L100 in a minimum combustion state of the main burner 21. As a result, the pressure of the inert gas G2 downstream of the orifice 52 becomes lower than the sum of the pressure of the hydrogen gas G1 downstream of the first shutoff valve V11 in the hydrogen supply line L100 and the reverse pressure of the first shutoff valve V11.

[0032] The pilot burner fuel supply line L300 is a line that supplies pilot burner fuel G3 to the pilot burner 22. In this embodiment, an example will be described in which city gas 13A, which is a gaseous fuel, is used as the pilot burner fuel G3. Note that LNG, LPG, etc. can also be used as the pilot burner fuel. The upstream side of the pilot burner fuel supply line L300 is connected to a fuel source (not shown), and the downstream side is connected to the pilot burner 22. The pilot burner fuel supply line L300 is also provided with an orifice 53, third shutoff valves V31 and V32, and a fuel flow rate adjustment valve V33. Although not shown, the pilot burner fuel supply line L300 is also provided with a needle valve or a ball valve downstream of the orifice 53.

[0033] The orifice 53 is disposed downstream of the third shutoff valve V31 on the pilot burner fuel supply line L300. The orifice 53 throttles the pilot burner fuel G3 flowing through the pilot burner fuel supply line L300, thereby reducing the pressure of the pilot burner fuel G3 flowing downstream. The third shutoff valves V31, V32 are configured by solenoid valves and open and close the flow path of the pilot burner fuel supply line L300. The third shutoff valves V31, V32 are electrically connected to the control unit 80 and are controlled based on signals sent from the control unit 80. In this embodiment, the third shutoff valve V32 is disposed upstream of the third shutoff valve V31. The fuel flow rate adjustment valve V33 adjusts the flow rate of the pilot burner fuel G3 flowing through the pilot burner fuel supply line L300. The fuel flow rate adjustment valve V33 is configured by, for example, a gas governor. In this embodiment, the fuel flow rate adjustment valve V33 is provided between the third shutoff valve V31 and the third shutoff valve V32.

[0034] The air supply line L400 supplies air A0 to the burner 20. This air A0 corresponds to combustion air used for combustion by the main burner 21 and pilot burner 22 of the burner 20, air used for purging the inside of the furnace, etc. The upstream side of the air supply line L400 is connected to the blower 41. Furthermore, the air supply line L400 branches into a main air supply line L410 and a pilot air supply line L420 on the downstream side. The main air supply line L410 has a damper 43, and is connected at its downstream side to the window box 23 of the burner 20. The main air supply line L410 supplies the main burner 21 with air A1 for combustion.

[0035] The pilot air supply line L420 branches off from the air supply line L400 upstream of a damper 43 provided in the main air supply line L410. The downstream side of the pilot air supply line L420 is connected to the pilot burner fuel supply line L300 downstream of an orifice 53. The pilot air supply line L420 supplies combustion air A2 to the pilot burner 22. Therefore, pilot burner fuel G3 and the combustion air A2 for the pilot burner 22 are supplied to the pilot burner 22 in a premixed state from the pilot burner fuel supply line L300.

[0036] The blower 41 supplies air A0 to the burner 20. The blower 41 includes a fan (not shown) and a motor (not shown) that rotates the fan. The blower 41 can adjust the rotation speed of the motor by controlling the frequency of the inverter 42, thereby controlling the supply amount of air A0 flowing through the air supply line L400. The inverter 42 is electrically connected to the control unit 80 and is controlled based on a signal transmitted from the control unit 80 .

[0037] The damper 43 adjusts the amount of air A1 supplied from the main air supply line L410 to the main burner 21 by adjusting the opening degree of the damper. Specifically, the damper 43 is provided rotatable between a closed state in which the flow path of the main air supply line L410 is blocked, and an open state in which the damper 43 rotates a predetermined angle (e.g., 90 degrees) from the closed state and opens the flow path of the first air supply line 410. The damper 43 is electrically connected to the control unit 80 and is controlled based on a signal transmitted from the control unit 80.

[0038] In this embodiment, when blower 41 is activated, the frequency of blower 41 can be changed to four frequencies: a combustion frequency for blowing the amount of air corresponding to the combustion of main burner 21, a purge frequency for blowing the amount of air required to purge the furnace (inside combustion chamber B), an ignition frequency for blowing the amount of air required to ignite main burner 21, and a pilot frequency for blowing the amount of air required for combustion of pilot burner 22. The motor of blower 41 rotates at a rotation speed corresponding to each frequency, and the amount of air A0 blown into air supply line L400 changes.

[0039] In addition, in this embodiment, the opening of the damper 43 can be changed to four levels: a purge opening (fully open), which is an opening corresponding to the amount of air required to purge the furnace (inside combustion chamber B); a combustion opening, which is an opening corresponding to the amount of air required for combustion of the main burner 21; an ignition opening, which is an opening corresponding to the amount of air required to ignite the main burner 21; and a pilot opening (fully closed), which is an opening that stops the supply of air A1 to the main burner 21 in order to continue combustion of the pilot burner 22. In the hydrogen combustion boiler 1 of this embodiment, the air amount adjustment unit that adjusts the amount of air A1 supplied to the main burner 21 is an inverter 42 and a damper 43, and the amount of air A1 supplied to the main burner 21 is controlled by a combination of the frequency of the blower 41 and the opening degree of the damper 43.

[0040] The control unit 80 includes a combustion control unit 81 and a storage unit 82 . The control unit 80 is configured with 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 80 are realized, for example, by executing predetermined software (programs) stored in the storage unit 82. The various functions of the control unit 80 may be realized by a combination of hardware and software, or may be realized only by hardware (electronic circuits).

[0041] The combustion control unit 81 controls the combustion of the main burner 21 and the combustion of the pilot burner 22. Specifically, the combustion control unit 81 opens and closes the first shutoff valves V11, V12 to control the start and stop of the supply of hydrogen gas G1 to the main burner 21, thereby controlling the start and stop of combustion of the main burner 21. The combustion control unit 81 also opens and closes the third shutoff valves V31, V32 to control the start and stop of the supply of pilot burner fuel G3 (city gas 13A in this embodiment) to the pilot burner 22, thereby controlling the start and stop of combustion of the pilot burner 22. In addition, the combustion control unit 81 performs inert gas purge control, which controls the start and completion of inert gas purging into the hydrogen supply line L100, by opening and closing the second shut-off valves V21 and V22 to control the start and stop of the supply of inert gas G2 (nitrogen in this embodiment). Furthermore, the combustion control unit 81 starts and stops the blower 41, and when the blower 41 is started, it changes the frequency of the inverter 42 to control the rotation speed of the motor of the blower 41 and control the amount of air blown.

[0042] The memory unit 82 stores various setting information. The memory unit 82 also serves as an air amount memory unit, and stores a first air amount corresponding to the amount of air when purging the inside of the furnace (inside combustion chamber B) while continuing combustion of the pilot burner 22, and a second air amount that is smaller than the first air amount and is the amount of air required for combustion of the pilot burner 22. The first air amount corresponds to the total amount of in-furnace purge air required for purging the inside of the furnace and the amount of air used for combustion of the pilot burner 22. The second air amount corresponds to the amount of air used for combustion of the pilot burner 22, and does not include the amount of air used for combustion of the main burner 21. Furthermore, the memory unit 82, as an air amount memory unit, further stores a third air amount, which is the amount of air required for combustion by the pilot burner 22 and ignition of the main burner 21, and a fourth air amount, which is the amount of air required for combustion by the main burner 21. The fourth air amount is the amount of air for combustion by the main burner 21, and does not include the amount of air for combustion by the pilot burner 22. The control unit 80 is not limited to the above example, and may be configured to include an air volume storage unit in addition to the storage unit 82.

[0043] In the hydrogen combustion boiler 1 of this embodiment, when combustion of the main burner 21 is stopped, an inert gas purge (piping purge) is performed in which the hydrogen gas G1 remaining downstream of the first shut-off valve V11 of the hydrogen supply line L100 that supplies the hydrogen gas G1, i.e., downstream of the connection point with the inert gas supply line L200, is purged with inert gas G2, and the hydrogen gas G1 remaining in the furnace (inside the combustion chamber B) is purged with air (inside the furnace purge). Furthermore, in the hydrogen combustion boiler 1 of this embodiment, when the main burner 21 starts combustion, an inert gas purge (pipe purge) is performed to purge with the inert gas G2, but the inside of the furnace is not purged. The control of combustion in each burner and the inert gas purge control in the hydrogen combustion boiler 1 of this embodiment will be specifically described below.

[0044] (Regarding the operation of the combustion control unit and each shutoff valve, etc.) Figure 2 is a time chart illustrating the operating state and operation of each part of the hydrogen-fired boiler 1 of this embodiment. Figure 2 shows the request signal to the hydrogen-fired boiler 1, the operating state of the hydrogen-fired boiler 1, the combustion states of the main burner 21 and pilot burner 22, the states of pipe purging and furnace purging, the frequency of the blower 41, the opening degree of the damper 43, and the open / close states of the first shutoff valves V11 and V12, the second shutoff valves V21 and V22, and the third shutoff valves V31 and V32.

[0045] When the main burner 21 is to be combusted, the combustion control unit 81 opens the first shutoff valves V11 and V12 of the hydrogen supply line L100 and supplies hydrogen gas G1 to the main burner 21. The combustion control unit 81 also reads the amount of air required for combustion of the main burner 21 (fourth air amount) from the memory unit 82, which is an air amount memory unit, selects the frequency of the blower 41 and the opening of the damper 43 according to that amount of air, and controls the inverter 42 and the damper 43. As a result, the blower 41 rotates the motor at a rotation speed corresponding to the combustion frequency, the opening of the damper 43 becomes the combustion opening required for combustion of the main burner 21, the amount of air A1 required for combustion of the main burner 21 is supplied to the main burner 21, and the main burner 21 burns hydrogen gas G1 as fuel.

[0046] At this time, the second shutoff valves V21 and V22 provided on the inert gas supply line L200 are closed by the combustion control unit 81. The combustion control unit 81 also closes the third shutoff valves V31 and V32 provided on the pilot burner fuel supply line L300.

[0047] Next, when the control unit 80 receives a signal to stop combustion of the main burner 21, the combustion control unit 81 issues instructions to each unit to start combustion of the pilot burner 22 and to perform furnace purging and inert gas purging (piping purging). The combustion control unit 81 reads the first air amount from the storage unit 82, which is an air amount storage unit, and based on this, instructs the inverter 42 to set the frequency of the blower 41 to a purge frequency for supplying the first air amount according to the furnace purging. As a result, the blower 41 supplies air of the first air amount to the air supply line L400. Furthermore, the combustion control unit 81 instructs the damper 43 to change the opening to a purge opening according to the purging of the inside of the furnace. As a result, the opening of the damper 43 becomes the purge opening (fully open).

[0048] Furthermore, the combustion control unit 81 opens the third shutoff valves V31, V32 of the pilot burner fuel supply line L300, starts the supply of pilot burner fuel G3 (city gas 13A in this embodiment) to the pilot burner 22, and ignites it with an ignition device (not shown) to start combustion in the pilot burner 22. At this time, an amount of air A1 required for combustion in the pilot burner 22 is supplied from the air supply line L400 via the pilot air supply line L420, and the pilot burner fuel G3 and combustion air A2 are mixed in advance in the pilot burner fuel supply line L300 and supplied to the pilot burner 22.

[0049] Next, when the pilot flame detection unit detects the flame of the pilot burner 22, it transmits a detection signal to the combustion control unit 81. Upon receiving the detection signal, the combustion control unit 81 starts inert gas purge control. As inert gas purge control, the combustion control unit 81 opens the second shutoff valves V21 and V22 provided on the inert gas supply line L200 and closes the first shutoff valves V11 and V12 on the hydrogen supply line L100 after the pilot burner 22 starts combustion. In this embodiment, the combustion control unit 81 first opens the second shutoff valves V21 and V22 provided on the inert gas supply line L200 after the pilot burner 22 starts combustion. This causes inert gas G2 to be supplied to the downstream side of the connection point of the hydrogen supply line L100 with the inert gas supply line L200 and to the main burner 21, and inert gas purge (piping purge) is initiated. This inert gas purge is performed for a predetermined time by the combustion control unit 81 while supplying inert gas G2 at a predetermined flow rate.

[0050] Next, after starting the inert gas purge, the combustion control unit 81 closes the first shutoff valves V11 and V12 of the hydrogen supply line L100. This stops the supply of hydrogen gas G1 to the main burner 21. Since the inert gas purge continues, the hydrogen gas G1 remaining in the piping of the hydrogen supply line L100 downstream of the connection point between the hydrogen supply line L100 and the inert gas supply line L200 is purged. As described above, the combustion control unit 81 of this embodiment opens the second shutoff valves V21 and V22 to start the supply of inert gas G2, and then closes the first shutoff valves V11 and V12 to stop the supply of hydrogen gas G1. This prevents the hydrogen-fired boiler 1 from backfiring in the hydrogen supply line L100 connected to the main burner 21.

[0051] Next, after the first shut-off valves V11 and V12 are closed, when combustion of the main burner 21 stops, the main flame detection unit that detects the flame of the main burner 21 stops sending the detection signal of the flame of the main burner 21 to the combustion control unit 81. When the combustion control unit 81 ceases to receive signals from the main flame detection unit, after a predetermined time, it closes the second shut-off valves V21 and V22 provided in the inert gas supply line L200, stops the supply of inert gas G2, and completes the inert gas purge. Even after the second shutoff valves V21 and V22 are closed, the combustion control unit 81 continues blowing air at the purge frequency using the blower 41, and purge air is supplied from the main burner 21 into the furnace, purging the furnace (combustion chamber B) for a predetermined time and ventilating the furnace. During this time, the pilot burner 22 continues combustion. As a result, hydrogen gas G1 and other gases remaining in the furnace are exhausted to the outside of combustion chamber B and combusted by the pilot burner 22.

[0052] When ventilation of the furnace interior is completed by purging the interior with air, the combustion control unit 81 instructs the damper 43 to change its opening to the pilot opening (fully closed). At this time, the combustion control unit 81 also instructs the inverter 42 to change the pilot frequency to one that blows the second air volume, which is the amount of air required for combustion in the pilot burner 22. As a result, the blower 41 sends combustion air A2 required for combustion in the pilot burner 22 to the air supply line L400. Because the damper 43 is closed, the combustion air A2 is sent from the pilot air supply line L420 to the pilot burner fuel supply line L300, where it is mixed with pilot burner fuel G3 and supplied to the pilot burner 22. As a result, combustion in the pilot burner 22 continues even when the hydrogen-combustion boiler 1 is shut down.

[0053] As described above, the hydrogen-fired boiler 1 of this embodiment continues combustion by the pilot burner 22 while performing furnace purging and inert gas purging (piping purging) when combustion by the main burner 21 is stopped, and even during the subsequent operation shutdown state (standby state). This maintains a flame in the furnace, preventing fuel gas such as hydrogen gas G1 from accumulating in the furnace and burning all at once (explosive combustion) at the time of ignition. Furthermore, after purging the interior of the furnace, the hydrogen-combustion boiler 1 of this embodiment supplies to the pilot burner 22 a second amount of air A2 that is smaller than the first amount of air for purging the interior of the furnace and is the amount of air required for combustion by the pilot burner 22, thereby suppressing heat radiation within the furnace and reducing heat loss, and further reducing the power consumption of the blower 41. This also allows the pilot burner 22 to burn stably.

[0054] If the damper 43 were closed while the frequency of the blower 41 remained at the purge frequency without changing it to the pilot frequency, the amount of air to the pilot air supply line L420 would increase significantly, preventing stable combustion in the pilot burner 22. Therefore, in this embodiment, the combustion control unit 81 lowers the frequency of the blower 41 to a pilot frequency appropriate for the second air amount, thereby supplying a constant amount of air A2 required for combustion in the pilot burner 22 from the air supply line L400 via the pilot air supply line L420 to the pilot burner 22 and maintaining stable combustion in the pilot burner 22.

[0055] Next, when the control unit 80 receives a command to start combustion in the hydrogen-fired boiler 1, the combustion control unit 81 opens the second shutoff valves V21 and V22, and inert gas G2 is supplied to the inert gas supply line L200, starting inert gas purging. The inert gas G2 flows downstream of the connection point of the hydrogen supply line L110 with the inert gas supply line L200 and is released from the main burner 21 into the combustion chamber B. This performs an inert gas purging (piping purging) of the piping of the hydrogen supply line L110 downstream of the first shutoff valves V11 and V12. This prevents backfire in the hydrogen supply line L100 due to air or the like that has entered the hydrogen supply line L100 when combustion of the main burner 21 resumes while combustion is stopped in the main burner 21 and the pilot burner 22.

[0056] Next, after performing an inert gas purge (pipe purge) of the hydrogen supply line L100 for a predetermined time, the combustion control unit 81 instructs the inverter 42 to change the frequency to an ignition frequency for igniting the main burner 21. The combustion control unit 81 also instructs the damper 43 to change the ignition opening degree corresponding to the ignition of the main burner 21. At this time, the combustion control unit 81 closes the second shutoff valves V21 and V22 to stop the supply of the inert gas G2 and completes the inert gas purge, and opens the first shutoff valves V11 and V12 to start the supply of the hydrogen gas G1 to the main burner 21 through the hydrogen supply line L100. The order in which the second shutoff valves V21 and V22 are closed and the first shutoff valves V11 and V12 are opened is not limited to the above, and they may be performed simultaneously, or the first shutoff valves V11 and V12 may be opened first and then the second shutoff valves V21 and V22 may be closed.

[0057] As a result, the blower 41 sends air A0 to the air supply line L400 at an air volume (third air volume) corresponding to the combustion of the pilot burner 22 and the ignition of the main burner 21. Of the air A0 sent to the air supply line L400, air A1 at an air volume corresponding to the ignition of the main burner 21 is supplied from the main air supply line L410 to the main burner 21 by the damper 43. Then, the main burner 21 is ignited by the pilot burner 22, and combustion of the main burner 21 begins. The main flame detection unit detects the flame of the main burner 21 and transmits a detection signal to the combustion control unit 81.

[0058] Furthermore, of the air A0, air A2 for combustion in the pilot burner 22 is supplied from the pilot air supply line L420 to the pilot burner fuel supply line L300, and is mixed in advance with fuel for the pilot burner before being supplied to the pilot burner 22, thereby maintaining combustion in the pilot burner 22.

[0059] Next, when the combustion control unit 81 receives a detection signal detecting the flame of the main burner 21 from a main flame detection unit (not shown), it instructs the inverter 42 to change the combustion frequency to one that corresponds to the combustion of the main burner 21. As a result, the blower 41 sends combustion air A0 to the air supply line L400 in an amount (fourth air amount) that is suitable for combustion of the main burner 21. At this time, the combustion control unit 81 also closes the third shutoff valves V31, V32 of the pilot burner fuel supply line L300 to stop the supply of the pilot burner fuel G3 to the pilot burner 22. This causes the pilot burner 22 to stop combustion.

[0060] Next, when the flame of the pilot burner 22 goes out, the pilot flame detection unit (not shown) stops transmitting the detection signal detecting the flame of the pilot burner 22. When reception of the detection signal from the pilot flame detection unit stops, the combustion control unit 81 instructs the damper 43 to change the combustion opening to a degree that corresponds to the combustion of the main burner 21. As a result, the opening of the damper 43 becomes the combustion opening, and an amount of air A1 suitable for combustion (fourth air amount) is supplied from the main air supply line L410 to the main burner 21. As a result, the main burner 21 can perform sufficient combustion.

[0061] If the flame of the main burner 21 goes out and the flame detection signal from the main flame detector ceases (i.e., the main burner 21 has finished combustion) during inert gas purging (pipe purging) after the first shutoff valves V11 and V12 are closed (after the main burner combustion has stopped), the combustion control unit 81 may then close the second shutoff valves V21 and V22 to stop the supply of inert gas G2 and complete the inert gas purging (pipe purging) in less time than specified. This allows the hydrogen-fired boiler 1 to shorten the time required for inert gas purging and reduce the amount of inert gas G2 used for inert gas purging. Furthermore, even if inert gas purging is performed for a predetermined time, if the main flame detection unit detects the flame of the main burner 21 and the combustion control unit 81 receives a detection signal, the combustion control unit 81 may continue inert gas purging until the flame detection signal from the main flame detection unit ceases, that is, until the flame of the main burner 21 disappears and combustion ends.

[0062] Furthermore, if the control unit 80 receives a signal to start combustion of the main burner 21 while the first shutoff valves V11 and V12 are closed, combustion of the main burner 21 has ended, and inert gas is being purged into the hydrogen supply line L100, the combustion control unit 81 may open the first shutoff valves V11 and V12, change the frequency of the inverter 42 to the ignition frequency, change the opening of the damper 43 to the ignition opening corresponding to ignition, ignite the main burner 21, and start combustion of the main burner 21, without purging the hydrogen supply line L100 with inert gas, which is performed before combustion of the main burner 21 starts. This allows the hydrogen-fired boiler 1 to omit the inert gas purging (piping purging) that is performed before combustion of the main burner 21 starts, thereby shortening the response time until combustion resumes.

[0063] Figure 3 is a time chart illustrating the operating state and operation of each part of a conventional hydrogen-fired boiler. Similar to Figure 2, Figure 3 shows the request signal to the hydrogen-fired boiler, the operating state of the hydrogen-fired boiler, the combustion state of the main burner and pilot burner, the state of inert gas purging (piping purging) and furnace purging, the frequency of the blower, the opening of the damper, and the open / close states of the first, second, and third shutoff valves. This conventional hydrogen combustion boiler has the same configuration as the hydrogen combustion boiler 1 of this embodiment, but differs from the hydrogen combustion boiler 1 of this embodiment in the control of purging when the main burner stops and starts combustion.

[0064] In a conventional hydrogen-fired boiler, as shown in Figure 3, after the main burner stops burning, hydrogen gas remaining in the hydrogen supply line and furnace is discharged, and post-purging (purging the piping with inert gas and purging the furnace with air) is performed to enhance safety, and the boiler enters a standby state after post-purging is completed. At this time, the pilot burner in the conventional hydrogen-fired boiler stops burning. Furthermore, in a conventional hydrogen-fired boiler, when the main burner starts burning, pre-purging (purging the piping with inert gas and purging the furnace with air) is performed to prevent flashback and enhance safety, and then the pilot burner starts burning, and the main burner is ignited by the pilot burner to start combustion. Then, after the main burner starts burning, the pilot burner stops burning.

[0065] Therefore, in conventional hydrogen-fired boilers, when restarting combustion after the main burner has stopped, two purging operations (post-purge and pre-purge) are performed while the pilot burner and main burner are stopped, which causes a drop in the temperature inside the furnace and a large heat loss.In addition, conventional hydrogen-fired boilers must purge twice, once when combustion stops and once when combustion starts, resulting in a delayed response to fluctuations in load demand.

[0066] In contrast, in the hydrogen-fired boiler 1 of this embodiment, combustion by the pilot burner 22 continues in the standby state after combustion by the main burner 21 has stopped. Furthermore, in the hydrogen-fired boiler 1 of this embodiment, only the hydrogen supply line L100 is purged with an inert gas (piping purging) at the start of combustion, and the inside of the furnace is not purged with air. Therefore, the hydrogen-fired boiler 1 of this embodiment can avoid the heat loss that accompanies purging the inside of the furnace with air at the start of combustion. Furthermore, the hydrogen combustion boiler 1 of this embodiment can quickly respond to combustion in the main burner, and can speed up response to load requests, thereby improving followability.

[0067] Furthermore, in the hydrogen-fired boiler 1 of this embodiment, if the control unit 80 receives a signal to start combustion of the main burner 21 during inert gas purging (piping purging) after combustion of the main burner 21 has stopped, the combustion control unit 81 will control the main burner 21 to start combustion without performing the inert gas purging (piping purging) that is performed before combustion starts. This makes it possible to improve responsiveness to fluctuations in load demand.

[0068] Furthermore, in the hydrogen-fired boiler 1 of this embodiment, if the detection signal detecting the flame of the main burner 21 ceases to be received from the main flame detection unit during inert gas purging after combustion of the main burner 21 has stopped, the combustion control unit 81 stops the inert gas purging with the inert gas G2 after a predetermined time has elapsed. This makes it possible to shorten the purging time using the inert gas G2 and also reduce the amount of inert gas G2 used. Furthermore, in the hydrogen-fired boiler 1 of this embodiment, even if inert gas purging has been performed for a specified time, if the combustion control unit 81 receives a signal from the main flame detection unit detecting a flame in the main burner 21, the combustion control unit 81 continues inert gas purging until a predetermined time has elapsed since the signal detecting the flame ceases to be received. This ensures that combustion in the main burner 21 is stopped.

[0069] According to the present embodiment described above, the following effects can be achieved. (1) The hydrogen combustion boiler 1 includes a boiler body 10, a blower 41, a burner 20 including a main burner 21 that burns hydrogen gas G1, which is a hydrogen-based fuel gas containing at least 50% hydrogen, and a pilot burner 22 that ignites the main burner 21, a hydrogen supply line L100 that supplies the hydrogen gas G1 to the main burner 21, first shutoff valves V11 and V12 that are provided on the hydrogen supply line L100 and that open and close the flow path of the hydrogen gas G1, and a second shutoff valve V11 that is connected to the hydrogen supply line L100 near the first shutoff valve V11 and downstream of the first shutoff valve V11. the pilot burner 22; an inert gas supply line L200 that supplies an inert gas G2 to the pilot burner 22; second shutoff valves V21, V22 that are provided in the inert gas supply line L200 and that open and close the flow path of the inert gas G2; a pilot burner fuel supply line L300 that supplies a pilot burner fuel G3 to the pilot burner 22; third shutoff valves V31, V32 that are provided in the pilot burner fuel supply line L300 and that open and close the flow path of the pilot burner fuel G3; an air supply line L400 that supplies air A0 from a blower 41 to the burner 20; and a control unit 80. The control unit 80 is equipped with a combustion control unit 81 that controls the combustion of the main burner 21 and the combustion of the pilot burner 22. After opening the third shut-off valves V31 and V32 to start the combustion of the pilot burner 22, the combustion control unit 81 closes the first shut-off valves V11 and V12 and opens the second shut-off valves V21 and V22, thereby performing inert gas purge control to supply inert gas G2 to the hydrogen supply line L100. As a result, the pilot burner 22 continues combustion even after the main burner 21 has stopped burning due to the supply of hydrogen gas G1 to the main burner 21, including while the hydrogen supply line L100 is being purged (pipe purged) with inert gas G2. This allows the hydrogen-fired boiler 1 to maintain a flame in the furnace, preventing fuel gas such as hydrogen gas G1 from accumulating in the furnace and combusting all at once (explosive combustion) upon ignition. Therefore, the hydrogen-fired boiler 1 does not require purging (pre-purging) of the furnace when the main burner 21 restarts combustion, thereby suppressing heat loss due to heat radiation. Furthermore, because the pilot burner 22 continues combustion even while the main burner 21 is stopped, the hydrogen-fired boiler 1 can immediately resume combustion when the main burner 21 restarts combustion, thereby speeding up response to load demands and improving followability.

[0070] (2) In the hydrogen combustion boiler 1 described in (1) above, the air supply line L400 includes a main air supply line L410 that supplies air to the main burner 21, a pilot air supply line L420 that supplies air to the pilot burner 22, and a damper 43 as an air volume adjustment unit that adjusts the amount of air supplied to the main burner 21, and the pilot air supply line L420 is connected to the air supply line L400 upstream of the damper 43 that is the air volume adjustment unit. As a result, when the hydrogen-fired boiler 1 stops combustion of the main burner 21, it can supply combustion air A2 to the pilot burner 22 via the pilot air supply line L420 while changing the opening of the damper 43, which is an air adjustment unit, to stop the blowing of air from the main burner 21 into the combustion chamber B, thereby reducing heat radiation. This allows the hydrogen-fired boiler 1 to further suppress heat loss. In addition, because the pilot air supply line L420 is connected upstream of the damper 43, the hydrogen-fired boiler 1 can stably supply combustion air A2 to the pilot burner 22 without being affected by changes in the opening of the damper.

[0071] (3) The hydrogen combustion boiler 1 described in (1) or (2) above is equipped with a main flame detection unit that detects the flame of the main burner 21 and transmits the result to the combustion control unit 81, and a pilot flame detection unit that detects the flame of the pilot burner 22 and transmits the result to the combustion control unit 81. As a result, the hydrogen-fired boiler 1 is equipped with detectors that individually detect the flames of the main burner 21 and the pilot burner 22, so the combustion state of each burner can be detected individually and more reliably. This allows the combustion control unit 81 to more reliably control inert gas purging, etc.

[0072] (4) In the hydrogen combustion boiler 1 described in (3) above, when the combustion control unit 81 cannot detect a flame in the main flame detection unit during inert gas purge control, it closes the second shut-off valves V21 and V22 to complete the inert gas purge. As a result, the combustion control unit 81 stops the inert gas purge after the flame of the main burner 21 has gone out and combustion has ended. Therefore, the hydrogen-combustion boiler 1 can more reliably purge the pipe of the hydrogen supply line L100.

[0073] (5) In the hydrogen-combustion boiler 1 described in (2) above, the control unit 80 includes a memory unit 82, which is an air amount memory unit that stores a first air amount corresponding to the amount of purge air in the furnace used to purge the furnace, and a second air amount that is smaller than the first air amount and is required for combustion by the pilot burner 22. When stopping the combustion of hydrogen gas G1 in the main burner 21, the combustion control unit 81 purges the furnace using the first air amount, and after purging the furnace is complete, stops the supply of air to the main air supply line L410 using the damper 43, which is an air amount adjustment unit, and continues the supply of air to the pilot air supply line L420 using the second air amount. Therefore, the hydrogen-fired boiler 1 can reduce the amount of air blown after purging the furnace, and supply only the air A2 for combustion by the pilot burner 22 to the burner 20. This reduces heat loss and the power consumption of the blower 41. This also allows the pilot burner 22 to burn stably.

[0074] (6) In the hydrogen combustion boiler 1 described in (1) to (5) above, when the combustion of hydrogen gas G1 in the main burner 21 is stopped, the combustion control unit 81 opens the second shut-off valves V21 and V22 to start inert gas purging, and then closes the first shut-off valves V11 and V12 to stop the supply of hydrogen gas G1. Therefore, the hydrogen combustion boiler 1 starts the supply of the inert gas G2 first and then stops the supply of the hydrogen gas G1, thereby allowing the hydrogen gas G1 remaining in the hydrogen supply line L100 to be sufficiently discharged, preventing backfire from the main burner 21 into the hydrogen supply line L100.

[0075] (7) In the hydrogen combustion boiler 1 described in (1) to (6) above, when combustion of hydrogen gas G1 in the main burner 21 is stopped, inert gas purging to the hydrogen supply line L100 is completed, and combustion in the pilot burner 22 is continuing, when combustion of the main burner 21 is to be started, the combustion control unit 81 opens the second shut-off valves V21 and V22 for a predetermined time to purge the hydrogen supply line L100 with inert gas, and then opens the first shut-off valves V11 and V12 to start combustion in the main burner 21. This allows the hydrogen-fired boiler 1 to prevent backfire in the hydrogen supply line L100 when combustion of the main burner 21 resumes due to air or the like that has entered the hydrogen supply line L100 when combustion of the main burner 21 is stopped and the pilot burner 22 is still burning.

[0076] (8) In the hydrogen combustion boiler 1 described in (1) to (7) above, when combustion of hydrogen gas G1 in the main burner 21 is stopped and inert gas is being purged into the hydrogen supply line L100, when combustion of the main burner 21 is to be started, the combustion control unit 81 opens the first shut-off valves V11 and V12 after the inert gas purging into the hydrogen supply line L100 is completed, and combustion of the main burner 21 is started. In conventional hydrogen-fired boilers, in addition to purging the hydrogen supply line L100 with an inert gas, the inside of the furnace is also purged (pre-purged) before combustion begins in the main burner 21. However, in the hydrogen-fired boiler 1 of this embodiment, combustion in the main burner 21 can begin without purging the inside of the furnace, which allows for a faster response to load demands and improved tracking performance.

[0077] (Variations) The present invention is not limited to the above-described embodiment, and various modifications and variations are possible, and these are also within the scope of the present invention.

[0078] In the present embodiment, an example has been shown in which, when combustion of the main burner 21 is stopped, the combustion control unit 81 opens the third shutoff valves V31, V32 to start combustion of the pilot burner 22, and then, as inert gas purge control, opens the second shutoff valves V21, V22 to start supplying the inert gas G2 to the hydrogen supply line L100, and then closes the first shutoff valves V11, V12. However, the present invention is not limited to this, and the closing of the first shutoff valves V11, V12 and the opening of the second shutoff valves V21, V22 may be performed simultaneously, or the second shutoff valves V21, V22 may be opened after the first shutoff valves V11, V12 are closed.

[0079] In this embodiment, an example is shown in which a main flame detection unit and a pilot flame detection unit (not shown) are provided, but a configuration in which one flame detection unit detects the flame of the main burner 21 and the flame of the pilot burner 22 may also be used.

[0080] In this embodiment, the pilot burner 22 is an example of a premixed type pilot burner in which the pilot burner fuel G3 and the combustion air A2 are supplied in a premixed state, but this is not limited to this, and the pilot burner 22 may also be a premixed type pilot burner in which the combustion air is mixed with the fuel in a flame holding section (not shown) at the lower end of the pilot burner 22.

[0081] The present invention is not limited to the above-described embodiments and variations, and may be combined as desired.

[0082] The present invention promotes the use of hydrogen, which does not emit carbon dioxide, as a fuel, and can therefore contribute, for example, to Goal 7 of the United Nations-led Sustainable Development Goals (SDGs), which is to "ensure access to affordable, reliable, sustainable and modern energy." [Explanation of symbols]

[0083] 1 Hydrogen-fired boiler 10 can body 20 Burner 21 Main Burner 22 Pilot Burner 24 Main flame detector 25 Pilot flame detector 41 Blower 43 Damper 80 Control Unit 81 Combustion control unit 82 Memory unit (air volume memory unit) B Combustion chamber (inside the furnace) L100 Hydrogen Supply Line L200 Inert gas supply line L300 Pilot burner fuel supply line L400 Air Supply Line L410 Main Air Supply Line L420 Pilot air supply line V11, V12 First shutoff valve V21, V22 Second shutoff valve V31, V32 Third shutoff valve

Claims

1. A can body and A blower and a burner including a main burner that burns a hydrogen-based fuel gas containing at least 50% hydrogen and a pilot burner that ignites the main burner; a hydrogen supply line for supplying the hydrogen-based fuel gas to the main burner; a first shutoff valve provided in the hydrogen supply line for opening and closing a flow path of the hydrogen-based fuel gas; an inert gas supply line connected to the hydrogen supply line near the first shutoff valve and downstream of the first shutoff valve, for supplying an inert gas to the hydrogen supply line; a second shutoff valve provided in the inert gas supply line for opening and closing a flow path of the inert gas; a pilot burner fuel supply line for supplying pilot burner fuel to the pilot burner; a third shutoff valve provided in the pilot burner fuel supply line for opening and closing a flow path of the pilot burner fuel; an air supply line that supplies air from the blower to the burner; A control unit; Equipped with the control unit includes a combustion control unit that controls combustion of the main burner and combustion of the pilot burner, The combustion control unit After the third shutoff valve is opened to start combustion in the pilot burner, a hydrogen combustion boiler, wherein the first shutoff valve is closed and the second shutoff valve is opened, and an inert gas purge control is performed to supply the inert gas to the hydrogen supply line.

2. The air supply line a main air supply line for supplying air to the main burner; a pilot air supply line for supplying air to the pilot burner; an air amount adjusting unit that adjusts the amount of air supplied to the main burner; Equipped with the pilot air supply line is connected to the air supply line upstream of the air amount adjusting unit; 2. The hydrogen-fired boiler according to claim 1.

3. a main flame detection unit that detects the flame of the main burner and transmits the detected flame to the combustion control unit; a pilot flame detection unit that detects a flame of the pilot burner and transmits the detected flame to the combustion control unit; Equipped with 2. The hydrogen-fired boiler according to claim 1.

4. When the main flame detection unit cannot detect a flame during the inert gas purge control, the combustion control unit: closing the second shutoff valve to complete the inert gas purge; 4. The hydrogen-fired boiler according to claim 3.

5. the control unit includes an air amount storage unit that stores a first air amount corresponding to an air amount for purging the inside of the furnace and a second air amount that is an air amount required for combustion by the pilot burner and is smaller than the first air amount, When the combustion of the hydrogen-based fuel gas in the main burner is stopped, The combustion control unit purging the furnace with the first amount of air; After the purging of the furnace is completed, the air amount adjusting unit stops supplying air to the main air supply line, and continues supplying air to the pilot air supply line at the second air amount.

3. The hydrogen-fired boiler according to claim 2.

6. When the combustion of the hydrogen-based fuel gas in the main burner is stopped, the combustion control unit opens the second shutoff valve to start an inert gas purge, and then closes the first shutoff valve to stop the supply of the hydrogen-based fuel gas.

2. The hydrogen-fired boiler according to claim 1.

7. When starting combustion in the main burner in a state in which combustion of the hydrogen-based fuel gas in the main burner has stopped, inert gas purging to the hydrogen supply line has been completed, and combustion in the pilot burner is continuing, the combustion control unit opens the second shutoff valve for a predetermined time to purge the hydrogen supply line with an inert gas, and then opens the first shutoff valve to start combustion in the main burner.

2. The hydrogen-fired boiler according to claim 1.

8. When the combustion of the hydrogen-based fuel gas in the main burner is stopped and the inert gas purge control to the hydrogen supply line is being performed, the combustion of the main burner is started. the combustion control unit opens the first shutoff valve after completing the inert gas purging into the hydrogen supply line, and starts combustion in the main burner.

2. The hydrogen-fired boiler according to claim 1.

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