Boiler

Abstract

To provide a boiler which can treats the residual ammonia generated by a stop of a boiler combustion without requiring a special ammonia treatment device.SOLUTION: A boiler includes: a burner 20 that burns a first fuel F1 with faster combustion speed than ammonia and an ammonia fuel F2; a first fuel supply line 100; an ammonia supply line 200; a purge gas supply line 300 that supplies a purge gas G1 to the ammonia supply line 200; a can body 10 that collects heat from the combustion gas; and a control part 40 that controls the combustion of the burner 20. The control part 40 includes a combustion stop control part 42 which, when stopping the combustion of the burner 20, starts supply of the predefined amount of purge gas G1 from the purge gas supply line 300 to the burner 20 via the ammonia supply line 200, stops the supply of the ammonia fuel F2, continues the combustion of the first fuel F1 for a predefined period of time T1, and stops the supply of the first fuel F1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a boiler. [Background technology]

[0002] Decarbonization (carbon neutrality) has become a global trend to protect the future from global warming. Ammonia is a carbon-free fuel that does not produce carbon dioxide when burned because it is composed of hydrogen and nitrogen and does not contain carbon. By replacing part of the hydrocarbon fuels such as natural gas and petroleum fuels with ammonia fuel, carbon dioxide emissions can be reduced, and it is attracting attention as one of the next-generation energies. On the other hand, because ammonia is harmful to the human body, in boilers that burn ammonia fuel, purging is performed with, for example, an inert gas in order to remove the ammonia fuel from the piping when combustion is stopped. The ammonia purged with the inert gas cannot be released directly into the atmosphere, and therefore must be treated with an ammonia detoxification device, etc. Patent Document 1 discloses that the ammonia remaining in the combustion device is introduced into an ammonia recovery tank together with the inert gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-6230 A Summary of the Invention [Problem to be solved by the invention]

[0004] The method of recovering ammonia in an ammonia recovery tank or an absorption device has problems such as the need for large equipment and facilities, as well as the need to treat the ammonia absorbent.

[0005] An object of the present invention is to provide a boiler capable of treating residual ammonia generated when combustion in the boiler is stopped, without requiring a special ammonia treatment device. [Means for solving the problem]

[0006] The present invention relates to a boiler comprising: a burner for burning a first fuel having a faster combustion speed than ammonia and an ammonia fuel; a first fuel supply line for supplying the first fuel to the burner; an ammonia supply line for supplying the ammonia fuel to the burner; a purge gas supply line for supplying a purge gas to the ammonia supply line; a boiler body for recovering heat from a combustion gas generated by burning a fuel in the burner; and a control unit for controlling combustion of the burner, wherein the control unit comprises a combustion stop control unit for starting a supply of a predetermined amount of purge gas from the purge gas supply line to the burner via the ammonia supply line, stopping the supply of the ammonia fuel, continuing the combustion of the first fuel for a predetermined time T1, and stopping the supply of the first fuel when the combustion of the burner is to be stopped.

[0007] Moreover, it is preferable that the ammonia supply line includes an ammonia fuel cutoff valve that cuts off the supply of the ammonia fuel, the purge gas supply line includes a purge gas cutoff valve that cuts off the supply of the purge gas, and when stopping combustion of the burner that is burning the ammonia fuel, the combustion stop control unit opens the purge gas cutoff valve together with closing of the ammonia fuel cutoff valve or a predetermined time T2 before the closure of the ammonia fuel cutoff valve.

[0008] It is also preferable that the burner is connected to an air supply line that supplies air to the burner, and the control unit is provided with a post-purge control unit that increases the amount of air supplied from the air supply line for a predetermined time T3 after the supply of the first fuel from the first fuel supply line is stopped.

[0009] The purge gas is preferably a hydrocarbon gas.

[0010] The purge gas is preferably air. Effect of the Invention

[0011] According to the present invention, it is possible to provide a boiler capable of treating ammonia without requiring a special ammonia treatment device. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram showing a schematic configuration of an ammonia-mixed combustion boiler according to a first embodiment of the present invention. FIG. [Diagram 2] FIG. 4 is a diagram showing a schematic configuration of an ammonia-mixed combustion boiler according to a second embodiment of the present invention. [Diagram 3] FIG. 10 is a diagram illustrating a schematic configuration of an ammonia-mixed combustion boiler according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] (First embodiment) Hereinafter, an ammonia-mixed combustion boiler 1 as a boiler according to a first embodiment of the present invention will be described with reference to the drawings. The ammonia-mixed combustion boiler 1 of the first embodiment is a steam boiler that burns fuel, heats water, and generates steam, and supplies the steam to a load device (not shown).

[0014] FIG. 1 is a diagram illustrating a schematic configuration of an ammonia-mixed combustion boiler 1 according to the first embodiment. 1, the ammonia-mixed combustion boiler 1 includes a boiler body 10, a burner 20, a blower 30, and a control unit 40. The ammonia-mixed combustion boiler 1 also includes a first fuel supply line 100, an ammonia supply line 200, a purge gas supply line 300, and an air supply line 400. In this specification, the term "line" is a general term for a flow path, a passage, a duct, and the like.

[0015] The boiler body 10 recovers heat from the combustion gas generated by burning fuel in the burner 20. The boiler body 10 includes a lower header, a plurality of water tubes, an upper header (none of which are shown), a combustion chamber B, etc., and heats water supplied to the boiler body 10 to generate steam. The burner 20 combusts a first fuel F1, which has a faster combustion speed than ammonia, and an ammonia fuel F2 in the combustion chamber B of the can body 10. The burner 20 is disposed in the upper part of the can body 10. In this embodiment, the first fuel having a faster combustion speed than ammonia may be a liquid fuel or a gaseous fuel. As the liquid fuel, an oil fuel, an alcohol fuel, or the like may be used. As the gaseous fuel, hydrogen may be used in addition to a hydrocarbon gas such as LNG or LPG.

[0016] The blower 30 supplies air A1 to the burner 20. The blower 30 includes a fan and a motor that rotates the fan, and the number of rotations of the motor can be adjusted by controlling the frequency with an inverter (not shown). The blower 30 is electrically connected to the control unit 40, and is controlled by a signal transmitted from the control unit 40, which will be described later. The control unit 40 controls the combustion of the burner 20 of the ammonia-mixed combustion boiler 1. The control unit 40 will be described in detail later.

[0017] The first fuel supply line 100 supplies a first fuel F1 from a first fuel supply source (not shown) to the burner 20. The upstream side of the first fuel supply line 100 is connected to the first fuel supply source, and the downstream side of the first fuel supply line 100 is connected to the burner 20. The first fuel supply line 100 includes, from the upstream side, a main valve 101, a first fuel flow rate sensor 102, a first shutoff valve 103, a flow rate adjustment valve 104, and a second shutoff valve 105.

[0018] The main valve 101 is configured as a manual valve, and opens and closes the flow path of the first fuel supply line 100. The first fuel flow rate sensor 102 detects the flow rate of the first fuel F1 flowing through the first fuel supply line 100. The first fuel flow rate sensor 102 is electrically connected to the control unit 40, and the detection result of the first fuel flow rate sensor 102 can be acquired by the control unit 40. The first shutoff valve 103 and the second shutoff valve 105 are configured by electromagnetic valves, and open and close the flow path of the first fuel supply line 100 to supply or stop the supply of the first fuel F1. The first shutoff valve 103 and the second shutoff valve 105 are electrically connected to the control unit 40, and are controlled by a signal transmitted from the control unit 40. The flow rate control valve 104 is an adjustment valve that adjusts the flow rate of the first fuel F1 supplied to the burner 20 by adjusting the opening degree of the valve based on the detection result of the first fuel flow rate sensor 102. The flow rate control valve 104 is electrically connected to the control unit 40 and is controlled by a signal transmitted from the control unit 40.

[0019] The ammonia supply line 200 supplies ammonia fuel F2 from an ammonia supply source (not shown) to the burner 20. The upstream side of the ammonia supply line 200 is connected to the ammonia supply source, and the downstream side of the ammonia supply line 200 is connected to the burner 20. The ammonia supply line 200 includes, from the upstream side, a main valve 201, an ammonia fuel flow rate sensor 202, a first shutoff valve 203 serving as an ammonia fuel shutoff valve, a flow rate adjustment valve 204, and a second shutoff valve 205 serving as an ammonia fuel shutoff valve.

[0020] The main valve 201 is configured by a manual valve, and opens and closes the flow path of the ammonia supply line 200. The ammonia fuel flow rate sensor 202 detects the flow rate of the ammonia fuel F2 flowing through the ammonia supply line 200. The ammonia fuel flow rate sensor 202 is electrically connected to the control unit 40, and the detection result of the ammonia fuel flow rate sensor 202 can be acquired by the control unit 40. The first shutoff valve 203 and the second shutoff valve 205 are configured by electromagnetic valves, and open and close the flow path of the ammonia supply line 200 to supply or stop the supply of the ammonia fuel F2. The first shutoff valve 203 and the second shutoff valve 205 are electrically connected to the control unit 40 and are controlled by a signal transmitted from the control unit 40. The flow rate control valve 204 is an adjustment valve that adjusts the flow rate of the ammonia fuel F2 supplied to the burner 20 by adjusting the opening degree of the valve based on the detection result of the ammonia fuel flow rate sensor 202. The flow rate control valve 204 is electrically connected to the control unit 40 and is controlled by a signal transmitted from the control unit 40.

[0021] The purge gas supply line 300 supplies the purge gas G1 from a purge gas supply source (not shown) to the ammonia supply line 200. The upstream side of the purge gas supply line 300 is connected to the purge gas supply source, and the downstream side of the purge gas supply line 300 is connected to the vicinity of the downstream side of the second shutoff valve 205 of the ammonia supply line 200. The purge gas supply line 300 includes, from the upstream side, a main valve 301, a purge gas flow sensor 302, a first shutoff valve 303 as a purge gas shutoff valve, a flow rate adjustment valve 304, and a second shutoff valve 305 as a purge gas shutoff valve.

[0022] The main valve 301 is configured by a manual valve, and opens and closes the flow path of the purge gas supply line 300 . The purge gas flow sensor 302 detects the flow rate of the purge gas G1 flowing through the purge gas supply line 300. The purge gas flow sensor 302 is electrically connected to the control unit 40, and the detection result of the purge gas flow sensor 302 can be acquired by the control unit 40. The first shutoff valve 303 and the second shutoff valve 305 are configured by electromagnetic valves, and open and close the flow path of the purge gas supply line 300 to supply or stop the purge gas G1. The first shutoff valve 303 and the second shutoff valve 305 are electrically connected to the control unit 40 and are controlled by a signal transmitted from the control unit 40. The flow rate control valve 304 is an adjustment valve that adjusts the flow rate of the purge gas G1 supplied to the burner 20 through the ammonia supply line 200 by adjusting the opening degree of the valve based on the detection result of the purge gas flow rate sensor 302. The flow rate control valve 304 is electrically connected to the control unit 40 and is controlled by a signal transmitted from the control unit 40.

[0023] The air supply line 400 supplies air to the burner 20. The upstream side of the air supply line 400 is connected to the blower 30, and the downstream side of the air supply line 400 is connected to the burner 20.

[0024] As shown in FIG. 1, the control unit 40 includes a combustion control unit 41, a combustion stop control unit 42, a post-purge control unit 43, and a storage unit 44. The control unit 40 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 40 are realized, for example, by executing predetermined software (programs) stored in the storage unit 44. The various functions of the control unit 40 may be realized by a combination of hardware and software, or may be realized only by hardware (electronic circuits). The storage unit 44 stores various setting information. For example, the storage unit 44 may store a predetermined time T0, a predetermined time T1, a predetermined time T2, a predetermined time T3, etc., which will be described later.

[0025] The combustion control unit 41 (control unit 40) controls the combustion of the burner 20. In this embodiment, the combustion control unit 41 (control unit 40) performs control to supply the first fuel F1 after starting the supply of air A1, and to start the supply of the ammonia fuel F2 after a predetermined time T0 has elapsed since the start of combustion of the first fuel F1. Specifically, the combustion control unit 41 (control unit 40) starts the blower 30 to supply air A1 at a predetermined flow rate to the burner 20. The main valve 101, the main valve 201, and the main valve 301 are each open. The combustion control unit 41 (control unit 40) opens the first shutoff valve 103 and the second shutoff valve 105, and adjusts the flow rate control valve 104 so as to achieve a predetermined flow rate based on the detection result of the first fuel flow rate sensor 102. As a result, the first fuel F1 is supplied at a predetermined flow rate to the burner 20, and the first fuel F1 is combusted in the burner 20. After a predetermined time T0 has elapsed since the first fuel F1 started to burn in the burner 20, the combustion control unit 41 (control unit 40) opens the first shutoff valve 203 and the second shutoff valve 205, and adjusts the flow rate control valve 204 so as to achieve a predetermined flow rate based on the detection result of the ammonia fuel flow rate sensor 202. As a result, a predetermined flow rate of ammonia fuel F2 is supplied to the burner 20, and mixed combustion of the first fuel F1 and the ammonia fuel F2 is started in the burner 20. Here, the predetermined time T0 refers to a time sufficient for the combustion of the first fuel F1 to become stable.

[0026] When stopping the combustion of the burner 20, the combustion stop control unit 42 starts supplying a predetermined amount of purge gas G1 from the purge gas supply line 300 to the burner 20 via the ammonia supply line 200, stops the supply of ammonia fuel F2, continues the combustion of the first fuel F1 for a predetermined time T1, and stops the supply of the first fuel F1. Specifically, when the mixed combustion of the first fuel F1 and the ammonia fuel F2 in the burner 20 is stopped, the combustion stop control unit 42 opens the first shutoff valve 303 and the second shutoff valve 305, and adjusts the flow rate control valve 304 so as to achieve a predetermined flow rate based on the detection result of the purge gas flow rate sensor 302. As a result, a predetermined flow rate of purge gas G1 is supplied to the burner 20 through the ammonia supply line 200. Thereafter, the combustion stop control unit 42 closes the first shutoff valve 203 and the second shutoff valve 205 to stop the supply of the ammonia fuel F2. When a predetermined flow rate of purge gas G1 is supplied to the burner 20 through the ammonia supply line 200, the combustion stop control unit 42 does not stop the supply of the first fuel F1 to the burner 20, and continues the combustion of the first fuel F1 in the burner 20 for a predetermined time T1. After continuing the combustion of the first fuel F1 in the burner 20 for a predetermined time T1, the combustion stop control unit 42 closes the first shutoff valve 103 and the second shutoff valve 105 to stop the combustion of the first fuel F1 in the burner 20.

[0027] As a result, when the combustion of the burner 20 is stopped, the combustion of the first fuel F1 continues while the purge gas G1 is flowing to the burner 20, so that the ammonia fuel F2 contained in the purge gas G1 can be removed by combustion. Further, the flow rate of the purge gas G1 supplied to the burner 20 is adjusted by the flow rate control valve 304 so that the ratio (flow rate of purge gas G1 / flow rate of ammonia fuel F2) between the speed of the purge gas G1 ejected from the burner 20 and the speed of the ammonia fuel F2 ejected from the burner 20 (for example, the speed of the ammonia fuel F2 in a low combustion state) is within a predetermined range based on the detection result of the purge gas flow rate sensor 302. Alternatively, the flow rate of the purge gas G1 supplied to the burner 20 is adjusted by the flow rate control valve 304 so that the ratio (flow rate of purge gas G1 / flow rate of ammonia fuel F2) between the flow rate of the purge gas G1 ejected from the burner 20 and the flow rate of the ammonia fuel F2 ejected from the burner 20 (for example, the flow rate of the ammonia fuel F2 in a low combustion state) is within a predetermined range. This makes it possible to suppress flame failure and incomplete combustion of the residual ammonia when switching from the ammonia fuel F2 to the purge gas G1. Furthermore, the amount of purge gas supplied can be detected by the purge gas flow rate sensor 302, and when the required amount of purge gas has been supplied, combustion can be stopped to prevent an unnecessary increase in steam pressure. In industrial furnaces, the furnace wall temperature is maintained at a high temperature by heat insulation materials, etc., even after the burner combustion is stopped, but in a steam boiler, when the burner combustion is stopped, the surface temperature of the water tube filled with water and steam drops rapidly toward the saturated steam temperature. For this reason, in the ammonia co-firing boiler 1, when the purge gas G1 supplied to the burner 20 via the ammonia supply line 200 flows into the boiler body 10 in a flameless state, the unburned ammonia is likely to be discharged directly outside the boiler. However, by supplying the ammonia fuel F2 contained in the purge gas G1 via the ammonia supply line 200 to the burner 20 in a state where the first fuel F1 is being burned, the ammonia fuel F2 can be burned and removed, and the discharge of the unburned ammonia outside the boiler can be suppressed.

[0028] The predetermined time T1 is preferably longer than a time sufficient for starting to supply a predetermined amount of purge gas G1 to the burner 20 via the ammonia supply line 200. In addition, the amount of purge gas G1 is preferably sufficient to replace the ammonia fuel F2 remaining in the ammonia supply line 200 downstream of the second shutoff valve 205. As a result, the ammonia fuel F2 remaining in the ammonia supply line 200 downstream of the second shutoff valve 205 is pushed out by the purge gas G1 or mixed with the purge gas G1 and supplied to the burner 20, where it is burned and removed. This makes it possible to more effectively suppress the discharge of unburned ammonia out of the boiler.

[0029] When stopping the combustion of the burner 20 that is burning the ammonia fuel F2, the combustion stop control unit 42 preferably opens the first shutoff valve 303 and the second shutoff valve 305 as the purge gas shutoff valve together with closing the first shutoff valve 203 and the second shutoff valve 205 as the ammonia fuel shutoff valve, or a predetermined time T2 before closing the first shutoff valve 203 and the second shutoff valve 205 as the ammonia fuel shutoff valve. Note that the predetermined time T2 is preferably set to a time taking into consideration an operation delay of the purge gas shutoff valve or a governor (not shown) as a pressure regulator, for example, from 1 second to 3 seconds, and more preferably from 1 second to 2 seconds. As a result, when the combustion of the ammonia fuel F2 is stopped in the burner 20, the gas flow in the ammonia supply line 200 is taken over from the flow of the ammonia fuel F2 to the flow of the mixed gas of the ammonia fuel F2 and the purge gas G1, so that interruption of the gas flow and fluctuation in the flow rate (flow velocity) of the gas flow can be suppressed and the flame can be maintained. In addition, since the flow of the ammonia fuel F2 is not stopped, the generation of unburned ammonia due to flame failure or extinguishing in the burner 20 can be suppressed.

[0030] By setting the predetermined time T2 to a time equivalent to the operation delay of the first shutoff valve 303 and the second shutoff valve 305 as purge gas shutoff valves, or the governor as a pressure regulator, the first shutoff valve 303 and the second shutoff valve 305 of the purge gas supply line 300 start to be opened before the predetermined time T2 at which the first shutoff valve 203 and the second shutoff valve 205 of the ammonia supply line 200 are closed. This makes it possible to shorten the time difference between the stop of the supply of ammonia fuel and the start of the supply of purge gas, thereby further suppressing the flow rate (flow velocity) fluctuation and maintaining a stable flame. In addition, by providing governors as pressure regulators in the ammonia supply line 200 and the purge gas supply line 300, and setting the primary pressures of the governors of both lines to be higher than the set secondary pressures of the governors of each line, it is possible to prevent backflow of the ammonia fuel F2 and the purge gas G1.

[0031] After stopping the supply of the first fuel F1 from the first fuel supply line 100, the post-purge control unit 43 increases the amount of air supplied from the air supply line 400 for a predetermined time T3. Specifically, when the combustion of the burner 20 is stopped by the combustion stop control unit 42, the supply of a predetermined amount of purge gas G1 is started from the purge gas supply line 300 to the burner 20 via the ammonia supply line 200, the supply of the ammonia fuel F2 is stopped, and the combustion of the first fuel F1 is continued for a predetermined time T1, after which the first shutoff valve 103 and the second shutoff valve 105 are closed to stop the supply of the first fuel F1. Next, the post-purge control unit 43 performs control to increase the frequency of the inverter of the blower 30 for a predetermined time T3, and increases the amount of air supplied from the air supply line 400.

[0032] As a result, the first shutoff valve 103 and the second shutoff valve 105 are closed to stop the supply of the first fuel F1, and the boiler body 10 of the ammonia co-firing boiler 1 is post-purged with air A1, thereby improving safety when the boiler is stopped. In addition, the ammonia fuel F2 remaining in the ammonia supply line 200 is pushed out by the purge gas G1, and the ammonia fuel F2 is burned and removed by the burner 20 in which the combustion of the first fuel F1 continues. Then, the boiler body 10 of the ammonia-mixed combustion boiler 1 is post-purged with the air A1, thereby further improving safety when the boiler is stopped.

[0033] It is preferable that the predetermined time T3 is longer than the time required for a predetermined amount of air A1 to be supplied, which is sufficient to push out the combustion gas remaining in the can body 10 from the can body 10. This allows the boiler body 10 of the ammonia-mixed combustion boiler 1 to be post-purged with air over a sufficient period of time, thereby further improving safety when the boiler is stopped.

[0034] In this embodiment, the purge gas G1 is preferably a hydrocarbon gas. Since the hydrocarbon gas is supplied to the ammonia supply line 200, the remaining ammonia fuel F2 and the hydrocarbon gas are supplied in a premixed state to the burner 20. Combustion of the hydrocarbon gas promotes combustion of the ammonia fuel F2, and the ammonia fuel F2 can be more reliably treated without discharging unburned ammonia.

[0035] In this embodiment, the purge gas G1 is preferably air. The purge gas supply source connected to the upstream side of the ammonia supply line 200 is preferably a supply source that supplies pressurized air, such as a compressor. Since air pressurized by a compressor or the like is supplied to the ammonia supply line 200, the remaining ammonia fuel F2 and the air are supplied to the burner 20 in a premixed state. This makes it possible to more reliably combust the ammonia fuel F2 and to process the ammonia fuel F2 without discharging unburned ammonia.

[0036] According to the ammonia-mixed combustion boiler 1 of the present embodiment described above, the following effects are achieved.

[0037] (1) The ammonia-mixed combustion boiler 1 of this embodiment includes a burner 20 that burns a first fuel F1 and an ammonia fuel F2, the first fuel F1 having a faster combustion speed than ammonia, a first fuel supply line 100 that supplies the first fuel F1 to the burner 20, an ammonia supply line 200 that supplies an ammonia fuel F2 to the burner 20, a purge gas supply line 300 that supplies a purge gas G1 to the ammonia supply line 200, a boiler body 10 that recovers heat from the combustion gas generated by burning the fuel in the burner 20, and a control unit 40 that controls the combustion of the burner 20. When the combustion of the burner 20 is stopped, the control unit 40 includes a combustion stop control unit 42 that starts supplying a predetermined amount of purge gas G1 from the purge gas supply line 300 to the burner 20 via the ammonia supply line 200, stops supplying the ammonia fuel F2, continues the combustion of the first fuel F1 for a predetermined time T1, and stops supplying the first fuel F1. As a result, when the combustion of the burner 20 is stopped, the combustion of the first fuel F1 continues while the purge gas G1 is flowing to the burner 20, so that the ammonia fuel F2 contained in the purge gas G1 can be removed by combustion. In industrial furnaces, the furnace wall temperature is maintained at a high temperature by heat insulation materials, etc., even after the burner combustion is stopped, but in a steam boiler, when the burner combustion is stopped, the surface temperature of the water tube filled with water and steam drops rapidly toward the saturated steam temperature. Therefore, in the ammonia co-firing boiler 1, when the purge gas G1 supplied to the burner 20 through the ammonia supply line 200 flows into the boiler body 10 in a flameless state, the unburned ammonia is likely to be discharged directly outside the boiler. However, by supplying the ammonia fuel F2 contained in the purge gas G1 through the ammonia supply line 200 to the burner 20 in a state where the first fuel F1 is being burned, the ammonia fuel F2 can be burned and removed, and the discharge of the unburned ammonia outside the boiler can be suppressed. Therefore, the ammonia-mixed combustion boiler 1 as a boiler does not require a special ammonia treatment device, and can treat the residual ammonia that is generated when the boiler stops burning.

[0038] (2) In the ammonia co-firing boiler 1 described in (1), the ammonia supply line 200 is provided with a first shutoff valve 203 and a second shutoff valve 205 as ammonia fuel shutoff valves that shut off the supply of ammonia fuel F2, the purge gas supply line 300 is provided with a first shutoff valve 303 and a second shutoff valve 305 as purge gas shutoff valves that shut off the supply of purge gas G1, and the combustion stop control unit 42 opens the first shutoff valve 303 and the second shutoff valve 305 as purge gas shutoff valves together with closing the first shutoff valve 203 and the second shutoff valve 205 as ammonia fuel shutoff valves or a predetermined time T2 before the closure of the first shutoff valve 203 and the second shutoff valve 205 as ammonia fuel shutoff valves when stopping combustion of the burner 20 that is burning the ammonia fuel F2. As a result, when the combustion of the ammonia fuel F2 is stopped in the burner 20, the gas flow in the ammonia supply line 200 is taken over from the flow of the ammonia fuel F2 to the flow of the mixed gas of the ammonia fuel F2 and the purge gas G1, so that interruption of the gas flow and fluctuation in the flow rate (flow velocity) of the gas flow can be suppressed and the flame can be maintained. In addition, since the flow of the ammonia fuel F2 is not stopped, the generation of unburned ammonia due to flame failure or extinguishing in the burner 20 can be suppressed.

[0039] (3) The ammonia co-fuel boiler 1 described in (1) or (2) is connected to the burner 20 and includes an air supply line 400 that supplies air to the burner 20. The control unit 40 includes a post-purge control unit 43 that increases the amount of air supplied from the air supply line 400 for a predetermined time T3 after the supply of the first fuel F1 from the first fuel supply line 100 is stopped. As a result, the ammonia fuel F2 remaining in the ammonia supply line 200 is pushed out by the purge gas G1, and the ammonia fuel F2 is burned and removed by the burner 20 in which the combustion of the first fuel F1 continues. Then, the first shutoff valve 103 and the second shutoff valve 105 are closed to stop the supply of the first fuel F1, and the boiler body 10 of the ammonia co-firing boiler 1 is post-purged with air, thereby improving safety when the boiler is stopped.

[0040] (4) In the ammonia-mixed combustion boiler 1 described in (1) to (3), the purge gas G1 is a hydrocarbon gas. Since the hydrocarbon gas is supplied to the ammonia supply line 200, the remaining ammonia fuel F2 and the hydrocarbon gas are premixed and supplied to the burner 20. This makes it possible to more reliably combust the ammonia fuel F2 and to process the ammonia fuel F2 without discharging unburned ammonia.

[0041] (5) In the ammonia-mixed combustion boiler 1 described in (1) to (4), the purge gas G1 is air. Since air compressed by a compressor or the like is supplied to the ammonia supply line 200, the remaining ammonia fuel F2 and the air are premixed and supplied to the burner 20. This ensures that the ammonia fuel F2 is combusted, and the ammonia fuel F2 can be treated without discharging unburned ammonia.

[0042] Second embodiment Next, an ammonia-mixed combustion boiler 1 according to a second embodiment of the present invention will be described with reference to the drawings. Fig. 2 is a diagram showing a schematic configuration of the ammonia-mixed combustion boiler 1 according to the second embodiment of the present invention.

[0043] 2, the ammonia-mixed combustion boiler 1 includes a boiler body 10, a burner 20, a blower 30, and a control unit 40. The ammonia-mixed combustion boiler 1 also includes a first fuel supply line 100, an ammonia supply line 200, a purge gas supply line 300, and an air supply line 400. In this embodiment, except for the purge gas supply line 300, the configuration is the same as in the first embodiment, so the same reference numerals are used and the description will be omitted.

[0044] The purge gas supply line 300 branches off from the air supply line 400 and is connected to the vicinity of the downstream side of the second shutoff valve 205 of the ammonia supply line 200. The pressure of the purge gas G1 needs to be higher than the pressure of the ammonia fuel F2 flowing through the ammonia supply line 200. Therefore, it is preferable that the purge gas supply line 300 branches off from the air supply line 400 upstream of an air flow rate regulator (damper or the like) (not shown) disposed in the air supply line 400. In this embodiment, the air A1 supplied from the blower 30 connected to the upstream side of the air supply line 400 is supplied to the purge gas supply line 300 branched from the air supply line 400. In other words, the purge gas G1 supplied from the purge gas supply line 300 to the ammonia supply line 200 is the air A1. As a result, air A1 is supplied to the ammonia supply line 200, and the remaining ammonia fuel F2 and air A1 are supplied to the burner 20 in a premixed state, so that the ammonia fuel F2 can be burned more reliably and the ammonia fuel F2 can be treated without discharging unburned ammonia. In addition, the cost required for the purge gas is low. Since the cost is low, frequent purging can be easily handled.

[0045] According to the ammonia-mixed combustion boiler 1 of the present embodiment described above, the following effects are achieved.

[0046] (6) In the ammonia-mixed combustion boiler 1 described in (1) to (5), the purge gas G1 is air A1. As a result, air A1 is supplied to the ammonia supply line 200, and the remaining ammonia fuel F2 and air A1 are supplied to the burner 20 in a premixed state, so that the ammonia fuel F2 can be burned more reliably and the ammonia fuel F2 can be treated without discharging unburned ammonia. In addition, the cost required for the purge gas is low. Since the cost is low, frequent purging can be easily handled.

[0047] Third embodiment Next, an ammonia-mixed combustion boiler 1 according to a third embodiment of the present invention will be described with reference to the drawings. Fig. 3 is a diagram showing a schematic configuration of the ammonia-mixed combustion boiler 1 according to the third embodiment of the present invention.

[0048] 3, the ammonia-mixed combustion boiler 1 includes a boiler body 10, a burner 20, a blower 30, and a control unit 40. The ammonia-mixed combustion boiler 1 also includes a first fuel supply line 100, an ammonia supply line 200, a purge gas supply line 300, and an air supply line 400. In this embodiment, except for the purge gas supply line 300, the configuration is the same as in the first embodiment, so the same reference numerals are used and the description will be omitted.

[0049] The purge gas supply line 300 branches off from the first fuel supply line 100 and is connected to the ammonia supply line 200 near the downstream side of the second shutoff valve 205 . In this embodiment, the first fuel F1 is supplied to the purge gas supply line 300 branched from the first fuel supply line 100 from a first fuel supply source connected to the upstream side of the first fuel supply line 100. In other words, the purge gas G1 supplied from the purge gas supply line 300 to the ammonia supply line 200 is the first fuel F1. In this embodiment, the first fuel F1 is preferably a hydrocarbon gas such as LNG or LPG. Since the first fuel F1 is supplied to the ammonia supply line 200, the remaining ammonia fuel F2 and the first fuel F1 are supplied in a premixed state to the burner 20. This makes it possible to more reliably combust the ammonia fuel F2 and treat the ammonia fuel F2 without discharging unburned ammonia. In addition, it is not necessary to install a special facility for supplying the purge gas G1, and the facility configuration can be simplified.

[0050] According to the ammonia-mixed combustion boiler 1 of the present embodiment described above, the following effects are achieved.

[0051] (7) In the ammonia-mixed combustion boiler 1 described in (1) to (6), the purge gas G1 is the first fuel F1. Since the first fuel F1 is supplied to the ammonia supply line 200, the remaining ammonia fuel F2 and the first fuel F1 are supplied in a premixed state to the burner 20. This makes it possible to more reliably combust the ammonia fuel F2 and treat the ammonia fuel F2 without discharging unburned ammonia. In addition, it is not necessary to install a special facility for supplying the purge gas G1, and the facility configuration can be simplified.

[0052] Although the preferred embodiment of the ammonia-mixed combustion boiler 1 according to the present invention has been described above, the present invention is not limited to the above-described embodiment and can be modified as appropriate.

[0053] In the first embodiment, the purge gas G1 may be a hydrocarbon gas, an inert gas, etc. The ammonia fuel is a gas fuel containing ammonia as a main component, and may be an ammonia decomposition gas containing ammonia. For example, when city gas 13A is used as the purge gas G1 as the hydrocarbon gas, the theoretical air amount of the city gas 13A is about three times that of ammonia, so the flow rate of the city gas 13A as the purge gas G1 is preferably set to 0.2 to 0.4 times that of the ammonia fuel F2. This makes it easier to continue combustion when the city gas 13A as the purge gas G1 is ejected from the burner 20 without adjusting the flow rate of the air A1 supplied to the burner 20, and also makes it possible to suppress the generation of unburned substances such as carbon monoxide due to the combustion of the city gas 13A as the purge gas G1. For example, when nitrogen gas is used as an inert gas for the purge gas G1, the ammonia fuel F2 burns at the start of purging, and the ratio of nitrogen gas gradually increases, so that the flow rate of the nitrogen gas as the purge gas G1 is preferably set to 0.2 to 1 times that of the ammonia fuel F2. This allows the amount of air required for burning the ammonia fuel F2 to be supplied to the burner 20 without adjusting the flow rate of the air A1 supplied to the burner 20, and the generation of unburned ammonia can be suppressed. In addition, when the combustion of the burner 20 is stopped, the ammonia supply line 200 is filled with nitrogen gas as an inert gas, so that the safety of the ammonia co-firing boiler 1 when it is stopped can be further improved.

[0054] In the burner 20, the predetermined time T0 is a time sufficient for the combustion of the first fuel F1 to be stabilized as a condition for starting the mixed combustion of the first fuel F1 and the ammonia fuel F2, but is not limited thereto. The predetermined time T0 may be a condition for starting the mixed combustion of the first fuel F1 and the ammonia fuel F2 when a predetermined flow rate of the first fuel F1 is supplied, when the combustion rate of the first fuel F1 reaches a predetermined combustion rate, or when the exhaust gas temperature of the first fuel F1 discharged from the can body 10 reaches a predetermined exhaust gas temperature. Even in such a case, the discharge of unburned ammonia to the outside of the can body 10 can be suppressed by burning the first fuel F1 and the ammonia fuel F2 together.

[0055] When stopping the mixed combustion of the first fuel F1 and the ammonia fuel F2 in the burner 20, the combustion stop control unit 42 opens the first shutoff valve 303 and the second shutoff valve 305 and supplies a predetermined flow rate of purge gas G1 to the burner 20 via the ammonia supply line 200, and then closes the first shutoff valve 203 and the second shutoff valve 205 to stop the supply of the ammonia fuel F2, but is not limited to this. When the mixed combustion of the first fuel F1 and the ammonia fuel F2 in the burner 20 is stopped, in order to suppress abrupt fluctuations in the combustion amount of the burner 20 and enable continuous combustion, the supply of the purge gas G1 can be started after the supply of the ammonia fuel F2 is stopped, or the supply of the ammonia fuel F2 can be stopped and the supply of the purge gas G1 can be started simultaneously, depending on the dynamic characteristics of the combustion equipment. Furthermore, when stopping the mixed combustion of the first fuel F1 and the ammonia fuel F2 in the burner 20, the combustion stop control unit 42 may close the first shutoff valve 203 and the second shutoff valve 205 to stop the supply of the ammonia fuel F2, and then open the first shutoff valve 303 and the second shutoff valve 305 to supply a predetermined flow rate of the purge gas G1 to the burner 20 via the ammonia supply line 200. Furthermore, the combustion stop control unit 42 may close the first shutoff valve 203 and the second shutoff valve 205 and open the first shutoff valve 303 and the second shutoff valve 305.

[0056] The upstream side of the purge gas supply line 300 is connected to a purge gas supply source, and the downstream side of the purge gas supply line 300 is connected to the vicinity of the downstream side of the second shutoff valve 205 of the ammonia supply line 200, but is not limited thereto. The downstream side of the purge gas supply line 300 may be connected to the upstream side of the second shutoff valve 205 of the ammonia supply line 200. When the supply of ammonia is stopped, the first shutoff valve 203 of the ammonia supply line 200 is closed, the first shutoff valve 303 and the second shutoff valve 305 of the purge gas supply line are opened, and a predetermined flow rate of purge gas G1 is supplied to the burner 20 via the ammonia supply line 200, and then the first shutoff valve 303 and the second shutoff valve 305 are closed and the second shutoff valve 205 of the ammonia supply line 200 may be closed. This allows purging downstream of the second shutoff valve 205 of the ammonia supply line, and prevents ammonia from accumulating.

[0057] The combustion stop control unit 42 opens the first shutoff valve 303 and the second shutoff valve 305, and adjusts the flow control valve 304 to achieve a predetermined flow rate based on the detection result of the purge gas flow sensor 302, but is not limited to this. A fixed pressure loss unit such as an orifice may be provided instead of the flow control valve 304 to adjust the purge gas flow rate.

[0058] Although a steam boiler is exemplified, the present invention is not limited to steam boilers and may be a hot water boiler or a heat transfer medium boiler. In addition, the present invention treats the residual ammonia generated when combustion is stopped, and is particularly effective in boilers in which combustion is started and stopped more frequently during normal use than in power generation boilers, such as small once-through boilers and small-scale once-through boilers. [Explanation of symbols]

[0059] 1. Ammonia co-firing boiler 10 can body 20 Burner 40 Control section 42 Combustion stop control unit 43 Post purge control unit 100 First fuel supply line 200 Ammonia supply line 203 First shutoff valve (ammonia fuel shutoff valve) 205 Second shutoff valve (ammonia fuel shutoff valve) 300 Purge gas supply line 303 First shutoff valve (purge gas shutoff valve) 305 Second shutoff valve (purge gas shutoff valve) 400 Air Supply Line A1 Air F1 1st fuel F2 Ammonia Fuel G1 Purge Gas T1 Predetermined time T2 Predetermined time T3 Predetermined time

Claims

1. a burner for burning a first fuel having a burning speed faster than that of ammonia and an ammonia fuel; a first fuel supply line for supplying the first fuel to the burner; an ammonia supply line for supplying the ammonia fuel to the burner; a purge gas supply line for supplying a purge gas to the ammonia supply line; a boiler body for recovering heat from combustion gas generated by burning fuel in the burner; A control unit for controlling the combustion of the burner, the control unit is configured to, when stopping combustion of the burner, start supplying a predetermined amount of purge gas from the purge gas supply line through the ammonia supply line to the burner, stop the supply of the ammonia fuel, continue combustion of the first fuel for a predetermined time T1, and stop the supply of the first fuel.

2. The ammonia supply line an ammonia fuel cutoff valve that cuts off the supply of the ammonia fuel; The purge gas supply line is a purge gas shutoff valve that shuts off the supply of the purge gas; 2. The boiler according to claim 1, wherein, when stopping combustion of the burner that is burning the ammonia fuel, the combustion stop control unit opens the purge gas cutoff valve together with closing of the ammonia fuel cutoff valve or a predetermined time T2 before closing of the ammonia fuel cutoff valve.

3. an air supply line connected to the burner for supplying air to the burner; 3. The boiler according to claim 1, wherein the control unit includes a post-purge control unit that increases an amount of air supplied from the air supply line for a predetermined time T3 after the supply of the first fuel from the first fuel supply line is stopped.

4. The boiler according to claim 1 or 2, wherein the purge gas is a hydrocarbon gas.

5. The boiler of claim 3 , wherein the purge gas is air.

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