Combustion device, and ammonia evaluation method

Abstract

To provide a combustion device co-combusting ammonia and first fuel (such as hydrogen and a hydrocarbon) with a higher combustion rate than ammonia, capable of preventing ammonia from leaking outside of the device, and a method of evaluating ammonia.SOLUTION: The combustion device comprises a burner burning ammonia fuel and first fuel, a first fuel supply line, an ammonia fuel supply line, a NOx detection unit detecting the concentration of NOx in the combustion gas, and a controller. The controller comprises a combustion controller controlling the burner so that the combustion is carried out in either of combustion modes, i.e., a first fuel combustion mode and a mixed combustion mode, a reference NOx storage unit storing a reference NOx level set based on the NOx concentration in the combustion gas by the first fuel combustion mode, and a NOx evaluation unit evaluating the presence of ammonia based on the NOx concentration detected by the NOx detection unit during combustion in the first fuel combustion mode and on the reference NOx level.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a combustion device and an ammonia evaluation method. [Background technology]

[0002] Conventionally, hydrocarbon fuels such as natural gas and petroleum fuels have been used as burner fuels in combustion devices such as boilers. Various combustion devices have been developed that aim to reduce carbon dioxide emissions by replacing part of this hydrocarbon fuel with ammonia, which does not generate carbon dioxide (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6332578 Summary of the Invention [Problem to be solved by the invention]

[0004] In a combustion apparatus that mixes and burns ammonia with a first fuel (such as a hydrogen-based fuel gas or a hydrocarbon) that has a faster combustion speed than ammonia, leakage of ammonia outside the apparatus is undesirable from the standpoint of danger to the human body, etc. Therefore, in such a combustion device, when combustion is stopped, measures are taken such as purging the piping through which the ammonia is supplied with an inert gas or the like after the supply of ammonia is stopped, and burning the ammonia remaining in the piping with a burner, etc. However, ammonia has a high adsorptivity, and even if a predetermined volume of inert gas is flowed, ammonia may be adsorbed and remain inside the piping or on the surfaces of valves, etc.

[0005] Furthermore, in such a combustion device, if a valve that starts or cuts off the supply of ammonia breaks down during the combustion of the first fuel, ammonia will leak into the burner. If the ammonia leak goes unnoticed and combustion is stopped, the ammonia will leak out of the device, which is undesirable.

[0006] In view of the above, an object of the present invention is to provide a combustion apparatus that suppresses leakage of ammonia to the outside of the combustion apparatus that mixes and burns ammonia with a first fuel (hydrogen-based fuel gas, hydrocarbon, or the like) that has a faster combustion speed than ammonia, and an ammonia evaluation method. [Means for solving the problem]

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

[0008] The present invention relates to a combustion device comprising: a burner to which ammonia fuel and a first fuel having a faster combustion speed than the ammonia fuel are supplied and combusted; a first fuel supply line to supply the first fuel to the burner; an ammonia fuel supply line to supply the ammonia fuel to the burner; a NOx detection unit to detect a NOx concentration in exhaust gas generated by combustion of at least one of the first fuel and the ammonia fuel sprayed from the burner; and a control unit, wherein the control unit is a combustion control unit that controls the burner to perform combustion in either a first fuel combustion mode in which the first fuel is burned or a multi-combustion mode in which the first fuel and the ammonia fuel are multi-combusted; a reference NOx storage unit that stores a reference NOx level that is set based on the NOx concentration of exhaust gas in the first fuel combustion mode; and a NOx evaluation unit that evaluates the presence of ammonia based on the NOx concentration detected by the NOx detection unit during combustion in the first fuel combustion mode and the reference NOx level.

[0009] Furthermore, it is preferable that the combustion device includes a purge gas supply line that supplies a purge gas to the ammonia fuel supply line, the control unit further includes a purge control unit that controls the supply of the purge gas from the purge gas supply line to the ammonia fuel supply line, and at least one of when the burner starts combustion and when the burner stops combustion, the combustion control unit causes the burner to combust in the first fuel combustion mode, and the purge control unit supplies the purge gas to the ammonia fuel supply line based on the evaluation result of the NOx evaluation unit.

[0010] Furthermore, in the combustion device, it is preferable that, at least in the case of starting combustion of the burner or stopping combustion of the burner, the combustion control unit causes the burner to combust in the first fuel combustion mode, and the purge control unit starts and stops supplying the purge gas to the ammonia fuel supply line a plurality of times.

[0011] Preferably, the control unit includes an ammonia leakage determination unit that determines leakage of ammonia based on the evaluation result of the NOx evaluation unit while the burner is burning in the first fuel combustion mode.

[0012] The control unit preferably includes an abnormality response operation control unit that controls an abnormality response operation based on the determination of the ammonia leak determination unit.

[0013] The present invention relates to an ammonia evaluation method for a combustion device including a burner to which ammonia fuel and a first fuel having a faster combustion speed than the ammonia fuel are supplied and combusted, a first fuel supply line to supply the first fuel to the burner, an ammonia fuel supply line to supply the ammonia fuel to the burner, a NOx detection unit to detect a NOx concentration in combustion gas generated by combustion of at least one of the first fuel and the ammonia fuel ejected from the burner, and a control unit including a combustion control unit that controls the burner to perform combustion in either a first fuel combustion mode to combust the first fuel or a mixed-combustion mode to mixed-combust the first fuel and the ammonia fuel, the method including: a first step of detecting a NOx concentration in the combustion gas by the NOx detection unit during combustion in the first fuel combustion mode; a second step of creating and storing NOx information by associating the NOx concentration detected in the first step with time information regarding the time when the NOx concentration was detected; and a third step of evaluating the presence of ammonia based on the multiple NOx information stored in the second step. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a combustion apparatus that suppresses leakage of ammonia to the outside of the combustion apparatus that mixes and burns ammonia with a first fuel (hydrogen-based fuel gas, hydrocarbon, or the like) that has a faster combustion speed than ammonia, and an ammonia evaluation method. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a diagram schematically illustrating the configuration of a combustion device according to a first embodiment and an ammonia-mixed combustion boiler including the combustion device. [Figure 2] FIG. 2 is a diagram showing an example of the relationship between the ammonia co-firing ratio and the NOx concentration in exhaust gas. [Figure 3] 1 shows an example of the relationship between the reference NOx level and a change in NOx concentration in exhaust gas during post-purging using purge gas when combustion in a burner is stopped in the combustion device of the first embodiment. [Figure 4]FIG. 10 is a diagram schematically illustrating the configuration of a combustion device according to a second embodiment and an ammonia-mixed combustion boiler including the combustion device. [Figure 5] 10 shows an example of the relationship between the reference NOx level and a change in NOx concentration in exhaust gas during post-purging using purge gas when combustion in a burner is stopped in a combustion device of a second embodiment. [Figure 6] FIG. 10 is a diagram schematically illustrating the configuration of a combustion device according to a third embodiment and an ammonia-mixed combustion boiler including the combustion device. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings, etc. Note that the drawings shown below, including Fig. 1, are schematic diagrams, and the size and shape of each part are appropriately exaggerated to facilitate understanding. A combustion device according to an embodiment of the present invention will be described below with reference to the drawings. The combustion device of this embodiment is applied to an ammonia-mixed combustion boiler. This ammonia-mixed combustion boiler is a boiler that can simultaneously combust ammonia and a first fuel that has a faster combustion rate than ammonia, and may be a boiler that can simultaneously combust ammonia and the first fuel, as well as combust ammonia alone (ammonia mono-combustion). The ammonia-mixed combustion boiler is a steam boiler that combusts ammonia and the first fuel to heat water and generate steam, and supplies the steam to a load device (not shown).

[0017] (First embodiment) FIG. 1 is a diagram schematically illustrating the configuration of an ammonia-mixed combustion boiler 1 equipped with a combustion device 10 according to the first embodiment. The combustion device 10 of this embodiment is a combustion device that burns a first fuel F1 and an ammonia fuel F2 as fuels in a burner 24, and is used in an ammonia co-firing boiler 1. The combustion device 10 includes a burner 24, a control unit 40, a first fuel supply line 100, an ammonia fuel supply line 200, a combustion air supply line 300, a purge gas supply line 700, etc. The ammonia co-firing boiler 1 includes the combustion device 10, a boiler body 20, a water supply line 500, a steam supply line 600, an exhaust gas line 400, etc. In this specification, the term "line" is a general term for a flow path, a passage, a duct, etc.

[0018] The boiler body 20 is configured to include a lower header 21, a plurality of water tubes 22, an upper header 23, and a combustion space B. The boiler body 20 recovers heat from the combustion gas generated by the combustion of fuel in the combustion space B, and heats water W1 supplied to the boiler body 20 to generate steam S1.

[0019] The burner 24 combusts in the combustion space B a first fuel F1 and an ammonia fuel F2, which have a faster combustion speed than ammonia. The burner 24 is disposed on the upper part of the boiler body 20. The burner 24 includes a burner body 25 and a wind box 26. The burner body 25 is connected to a first fuel supply line 100 and an ammonia fuel supply line 200. The wind box 26 is connected to a combustion air supply line 300.

[0020] In this embodiment, first, the first fuel F1 and the combustion air A1 are supplied to the burner 24, and combustion is initiated. Next, the ammonia fuel F2 is supplied to the combustion section of the first fuel F1. At this time, a predetermined amount of the combustion air A1 corresponding to the total amount of the first fuel F1 and the ammonia fuel F2 is supplied to the burner 24. The first fuel F1, which has a faster combustion rate than ammonia, may be a liquid fuel or a gaseous fuel. Examples of the liquid fuel that can be used include oil fuel, alcohol fuel, and the like. Examples of the gaseous fuel that can be used include hydrogen-based fuel gases including hydrogen gas and mixed gases containing hydrogen, liquefied natural gas (hereinafter referred to as LNG), liquefied petroleum gas (LPG), and city gas (13A). In this embodiment, an example using LNG will be described.

[0021] The first fuel supply line 100 supplies a first fuel F1 from a first fuel supply source (not shown) to the burner 24. 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 24. The first fuel supply line 100 is equipped with, 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.

[0022] 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 signals transmitted from the control unit 40. The flow rate control valve 104 is a control valve that adjusts the opening degree of the valve to thereby adjust the flow rate of the first fuel F1 supplied to the burner 24. The flow rate control valve 104 is electrically connected to the control unit 40, and the control unit 40 sends a signal to the flow rate control valve 104 to control the opening degree in accordance with the required combustion amount.

[0023] The ammonia fuel supply line 200 supplies ammonia fuel F2 from an ammonia supply source (not shown) to the burner 24. The upstream side of the ammonia fuel supply line 200 is connected to the ammonia supply source, and the downstream side of the ammonia fuel supply line 200 is connected to the burner 24. The ammonia fuel supply line 200 is provided with, from the upstream side, a main valve 201, an ammonia fuel flow rate sensor 202, a first shutoff valve 203, a flow rate adjustment valve 204, and a second shutoff valve 205.

[0024] The main valve 201 is configured as a manual valve, and opens and closes the flow path of the ammonia fuel supply line 200. The ammonia fuel flow rate sensor 202 detects the flow rate of the ammonia fuel F2 flowing through the ammonia fuel 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.

[0025] 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 fuel 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 signals transmitted from the control unit 40. The flow rate control valve 204 is a control valve that adjusts the opening degree of the valve to thereby adjust the flow rate of the ammonia fuel F2 supplied to the burner 24. The flow rate control valve 204 is electrically connected to the control unit 40, and the control unit 40 transmits a signal to the flow rate control valve 204 to control the opening degree in accordance with the required combustion amount.

[0026] The combustion air supply line 300 supplies combustion air A1 to the burner 24. In this embodiment, the combustion air A1 is supplied to the wind box 26 of the burner 24. The upstream side of the combustion air supply line 300 is connected to a blower 301, and the downstream side of the combustion air supply line 300 is connected to the wind box 26. From the upstream side, the combustion air supply line 300 is equipped with the blower 301, a combustion air flow rate sensor 303, and a damper 304 as a combustion air adjustment unit.

[0027] The blower 301 supplies combustion air A1 to the burner 24. The blower 301 includes a fan and a motor that rotates the fan, and the number of rotations and rotation speed of the motor can be adjusted by controlling the frequency with the inverter 302. Therefore, by controlling the frequency of the inverter 302, the amount of combustion air A1 supplied to the burner 24 can be adjusted. The inverter 302 is electrically connected to the control unit 40 and is controlled by a signal sent from the control unit 40.

[0028] The combustion air flow rate sensor 303 detects the flow rate of the combustion air A1 flowing through the combustion air supply line 300. The combustion air flow rate sensor 303 is electrically connected to the control unit 40, and the detection result of the combustion air flow rate sensor 303 can be acquired by the control unit 40.

[0029] The damper 304 adjusts the amount of combustion air A1 supplied to the burner 24 by adjusting the opening degree of the damper. Specifically, the damper 304 is arranged to be rotatable between a closed state in which the flow path of the combustion air supply line 300 is blocked, and an open state in which the damper 304 rotates from the closed state by a predetermined angle (e.g., 90 degrees) to open the flow path of the combustion air supply line 300. The damper 304 is electrically connected to the control unit 40 and is controlled by a signal transmitted from the control unit 40.

[0030] The purge gas supply line 700 supplies a purge gas G1 from a purge gas supply source (not shown) to the ammonia fuel supply line 200. The upstream side of the purge gas supply line 700 is connected to the purge gas supply source, and the downstream side of the purge gas supply line 700 is connected to a portion of the ammonia fuel supply line 200 downstream of the second shutoff valve 205 and in the vicinity of the second shutoff valve 205. The purge gas supply line 700 includes, from the upstream side, a main valve 701, a first shutoff valve 703, a second shutoff valve 705, and the like.

[0031] The main valve 701 is configured as a manual valve, and opens and closes the flow path of the purge gas supply line 700 . The first shutoff valve 703 and the second shutoff valve 705 are configured by electromagnetic valves, and open and close the flow path of the purge gas supply line 700 to supply or stop the purge gas G1. The first shutoff valve 703 and the second shutoff valve 705 are electrically connected to the control unit 40, and are controlled by signals transmitted from the control unit 40. The purge gas supply line 700 further includes a flow rate sensor and an orifice (not shown). The flow rate sensor is a detection unit that detects the flow rate of the purge gas G1. The flow rate sensor is electrically connected to the control unit 40, and the control unit 40 can acquire the detection result of the flow rate sensor. The orifice adjusts the flow rate of the purge gas G1.

[0032] Combustion gas generated by combustion of at least one of the first fuel F1 and the ammonia fuel F2 is heat exchanged in the can body 20 and flows through an exhaust gas line 400 as exhaust gas E1, and is discharged to the outside. The upstream side of the exhaust gas line 400 is connected to the upper part of the circumferential surface of the can body 20, and the downstream side of the exhaust gas line 400 is open to the atmosphere. A NOx sensor 401 is provided in the exhaust gas line 400.

[0033] The NOx sensor 401 is a NOx detection unit that detects the NOx concentration in the exhaust gas E1. The NOx sensor 401 is electrically connected to the control unit 40, and the detection result of the NOx sensor 401 can be acquired by the control unit 40.

[0034] The water supply line 500 supplies water W1 from a water supply source (not shown) to the boiler body 20. The upstream side of the water supply line 500 is connected to the water supply source, and the downstream side of the water supply line 500 is connected to the lower header 21. The water supply line 500 is equipped with a main valve 501. The main valve 501 is configured as a manual valve and opens and closes the flow path of the water supply line 500.

[0035] The steam supply line 600 supplies steam S1 from the boiler body 20 to a load device (not shown). The upstream side of the steam supply line 600 is connected to the upper header 23 of the boiler body 20, and the downstream side of the steam supply line 600 is connected to the load device. The steam supply line 600 is equipped with a main steam valve 601. The main steam valve 601 is configured as a manual valve and opens and closes the flow path of the steam supply line 600.

[0036] The control unit 40 controls various operations such as combustion of the combustion device 10. As shown in FIG. 1, the control unit 40 includes a storage unit 41, a combustion control unit 43, a NOx evaluation unit 44, and a purge control unit 45. The control unit 40 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 40 are realized by executing predetermined software (programs) stored in the storage unit 41, for example. 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).

[0037] The storage unit 41 stores various setting information. The storage unit 41 also includes a reference NOx level storage unit . The reference NOx level storage unit 42 stores a reference NOx level that is set based on the NOx concentration in the exhaust gas E1 (combustion gas) when the first fuel F1 is being burned (for example, in the first fuel combustion mode). The reference NOx level is set based on the NOx concentration in the exhaust gas E1 (combustion gas) when only the first fuel F1 is used as fuel and combusted in the burner 24. In the present embodiment, as an example, with regard to the NOx concentration in the exhaust gas E1 when only the first fuel F1 is used as fuel and combusted in the burner 24, a NOx concentration that takes into account an allowable NOx concentration derived from ammonia residue that does not cause harm to humans, etc. is stored in advance as the reference NOx level. The present invention is not limited to the above example, and the control unit 40 may include a reference NOx level storage unit 42 in addition to the storage unit 41.

[0038] The reference NOx level is not limited to the above example, and may be stored as the NOx value generated by the combustion of the first fuel F1 under combustion conditions such as a predetermined combustion amount and air ratio, or as a fluctuation range of the NOx value generated by the combustion of the first fuel F1 under predetermined combustion conditions, plus NOx generation resulting from an allowable amount of residual ammonia that does not cause harm to humans, etc. Alternatively, the reference NOx level may be stored as a graph or an approximation formula showing fluctuations depending on the air ratio of the NOx value generated by the combustion of the first fuel F1 at a predetermined combustion amount, plus a predetermined margin.

[0039] Furthermore, when the combustion of the first fuel F1 and the ammonia fuel F2 is switched from mixed combustion to combustion of only the first fuel F1, the NOx concentration in the exhaust gas E1 gradually decreases depending on the duration of combustion of the first fuel F1 (excluding fluctuations immediately after the start of combustion). The reference NOx level may be set taking into consideration the decrease in the NOx concentration in the exhaust gas that accompanies the duration of combustion of the first fuel F1.

[0040] Furthermore, a plurality of reference NOx concentrations may be set, such as a reference NOx concentration (for example, a first reference NOx concentration) when the combustion of the first fuel F1 continues stably, a reference NOx concentration (for example, a second reference NOx concentration) during combustion for a predetermined period after switching from mixed combustion of the first fuel F1 and ammonia fuel F2 to the first fuel F1, and a reference NOx concentration (for example, a third reference NOx concentration) when the purge gas G1 and the first fuel F1 are supplied to and combusted in the burner 24. Furthermore, the reference NOx concentration may include a predetermined margin.

[0041] The combustion control unit 43 controls combustion in the burner 24. The combustion control unit 43 of the present embodiment controls the burner 24 to perform combustion in either a first-fuel combustion mode in which the first fuel F1 is burned, or a mixed-combustion mode in which the first fuel F1 and ammonia fuel F2 are mixed and burned. When the burner 24 is combusted in the first fuel combustion mode, the combustion control unit 43 opens the first shut-off valve 103 and the second shut-off valve 105 of the first fuel supply line 100 and closes the first shut-off valve 103 and the second shut-off valve 205 of the ammonia fuel supply line 200. The combustion control unit 43 also adjusts the valve opening of the flow rate control valve 104 in accordance with the required combustion amount. Furthermore, the combustion control unit 43 starts the blower 301 and adjusts at least one of the inverter 302 and the damper 304 to supply combustion air A1 at a predetermined flow rate in accordance with the first fuel combustion mode to the burner 24. This starts combustion of the first fuel F1.

[0042] When the burner 24 is to be combusted in the mixed-combustion mode, the combustion control unit 43 opens the first shutoff valve 103 and the second shutoff valve 105 of the first fuel supply line 100, and opens the first shutoff valve 103 and the second shutoff valve 205 of the ammonia fuel supply line 200. The combustion control unit 43 also starts the blower 301 and adjusts at least one of the inverter 302 and the damper 304 to supply combustion air A1 to the burner 24 at a predetermined flow rate according to the mixed-combustion mode. The combustion control unit 43 then adjusts the valve openings of the flow rate control valves 104 and 204 according to the required combustion amount. This starts mixed-combustion of the first fuel F1 and the ammonia fuel F2.

[0043] In addition, in both the first fuel combustion mode and the mixed combustion mode, the combustion control unit 43 starts the blower 301 and adjusts at least one of the inverter 302 and the damper 304 to supply combustion air A1 to the burner 24 at a predetermined flow rate according to each combustion mode.

[0044] The NOx evaluation unit 44 evaluates the presence of ammonia based on the NOx concentration detected by the NOx sensor 401 during combustion in the first fuel combustion mode and the reference NOx level stored in the reference NOx level storage unit 42. The reference NOx level is, for example, a NOx concentration obtained by taking into account the NOx concentration of the exhaust gas E1 when only the first fuel F1 is burned in the burner 24 as fuel, with a margin of a NOx concentration resulting from an allowable amount of residual ammonia that does not cause harm to humans, etc. If the NOx concentration detected by the NOx sensor 401 is below the reference NOx level, the NOx evaluation unit 44 evaluates that a significant amount of ammonia is not present in the first fuel F1 supplied to the burner 24. If the NOx concentration detected by the NOx sensor 401 is equal to or greater than the reference NOx level, the NOx evaluation unit 44 evaluates that a significant amount of ammonia is present in the first fuel F1 supplied to the burner 24. If it is evaluated that a significant amount of ammonia is present in the first fuel F1 supplied to the burner 24, it can detect the risk of leakage of the ammonia fuel F2 due to, for example, failure to close the shutoff valve of the ammonia fuel supply line 200.

[0045] The purge control unit 45 controls the supply of purge gas G1 from the purge gas supply line 700 to the ammonia fuel supply line 200. Specifically, in at least one of the cases when the burner 24 starts combustion and when the burner 24 stops combustion, the combustion control unit 43 causes the burner 24 to combust in the first fuel combustion mode. At this time, the purge control unit 45 supplies purge gas G1 to the ammonia fuel supply line 200 based on the evaluation result of the NOx evaluation unit 44.

[0046] Fig. 2 is a diagram showing an example of the relationship between the ammonia co-firing ratio and the NOx concentration in the exhaust gas E1. In Fig. 2, the vertical axis represents the NOx concentration normalized by the NOx concentration when only the first fuel F1 is burned (i.e., the value when the NOx concentration when only the first fuel F1 is burned is set to 1), and the horizontal axis represents the ammonia co-firing ratio (volume fraction). As shown in Figure 2, when the ammonia co-firing ratio (volume fraction) is changed from 0 vol% to a small amount, the NOx concentration in exhaust gas E1 increases rapidly. For example, when the ammonia co-firing ratio (volume fraction) is changed to 13 vol%, the NOx concentration is 10 times higher than when the ammonia co-firing ratio is 0 vol%. The NOx concentration continues to increase as the ammonia co-firing ratio increases, but the change is gradual. In other words, it is inferred that the rate of change in NOx concentration is large when the ammonia co-firing ratio is small. Therefore, a change in the NOx concentration in the exhaust gas E1 can be used as an indicator of whether or not ammonia is present in the fuel combusted by the burner 24.

[0047] Fig. 3 shows an example of the relationship between the reference NOx level and the change in NOx concentration in the exhaust gas E1 during post-purging by the purge gas G1 when combustion in the burner 24 is stopped in the combustion device 10 of the first embodiment. In Fig. 3, the first shutoff valve 103 and the second shutoff valve 205 of the first fuel supply line 100 are shown as first fuel supply line shutoff valves, the first shutoff valve 203 and the second shutoff valve 205 of the ammonia fuel supply line 200 are shown as ammonia supply line shutoff valves, and the first shutoff valve 703 and the second shutoff valve 705 of the purge gas supply line 700 are shown as purge gas supply line shutoff valves. The operation of each unit will be described below with reference to FIG. During combustion operation, the combustion device 10 of this embodiment performs combustion in the multi-fuel combustion mode, as described above.

[0048] When stopping the combustion of the burner 24, the combustion control unit 43 switches the combustion in the burner 24 from the multi-fuel combustion mode to the first fuel combustion mode. The combustion control unit 43 closes the first shutoff valve 203 and the second shutoff valve 205 of the ammonia fuel supply line 200, and the purge control unit 45 opens the first shutoff valve 703 and the second shutoff valve 705 of the purge gas supply line 700 to start supplying the purge gas G1 to the ammonia fuel supply line 200. At this time, the combustion control unit 43 keeps the first shutoff valve 103 and the second shutoff valve 105 of the first fuel supply line 100 open. In addition, without being limited to the above example, the opening of the first shutoff valve 703 and the second shutoff valve 705 of the purge gas supply line 700 by the purge control unit 45 may be performed after the first shutoff valve 203 and the second shutoff valve 205 of the ammonia fuel supply line 200 are closed.

[0049] When the supply of the purge gas G1 starts, the ammonia fuel F2 remaining in the ammonia fuel supply line 200 is discharged by the purge gas G1. Therefore, it is presumed that the ammonia concentration in the ammonia fuel supply line 200 is also equivalent to that during combustion in the multi-combustion mode, and the NOx concentration detected by the NOx sensor 401 is approximately equivalent to the NOx concentration during combustion in the multi-combustion mode. The NOx evaluation unit 44 evaluates the presence of ammonia based on the NOx concentration detected by the NOx sensor 401 and the reference NOx level read out from the reference NOx level storage unit 42. If the NOx concentration detected by the NOx sensor 401 is equal to or higher than the reference NOx level, the NOx evaluation unit 44 evaluates that a significant amount of ammonia is present in at least one of the first fuel F1 and the purge gas G1 supplied to the burner 24. The purge control unit 45 acquires the evaluation result of the NOx evaluation unit 44 and continues supplying the purge gas G1 to the ammonia fuel supply line 200.

[0050] When the supply of purge gas G1 starts, the ammonia in ammonia fuel supply line 200 is discharged and the ammonia concentration gradually decreases. Accordingly, the NOx concentration detected by NOx sensor 401 also begins to decrease. The NOx evaluation unit 44 evaluates the presence of ammonia based on the NOx concentration detected by the NOx sensor 401 and the reference NOx level read out from the reference NOx level storage unit 42, and if the evaluation result indicates the presence of ammonia, the purge control unit 45 continues to supply the purge gas G1 to the ammonia fuel supply line 200.

[0051] When the NOx concentration detected by the NOx sensor 401 falls below the reference NOx level read from the reference NOx level storage unit 42, the NOx evaluation unit 44 evaluates that a significant amount of ammonia is not present in the first fuel F1 and the purge gas G1 in the combustion of the burner 24. The purge control unit 45 acquires the evaluation result and, based on the result, stops the supply of the purge gas G1 to the ammonia fuel supply line 200. Specifically, the purge control unit 45 closes the first shutoff valve 703 and the second shutoff valve 705 of the purge gas supply line 700. Next, the combustion control unit 43 closes the first shutoff valve 103 and the second shutoff valve 105 of the first fuel supply line 100, and stops the combustion of the burner 24.

[0052] As described above, in the combustion device 10 of this embodiment, when combustion is stopped, the purge control unit 45 performs piping purging of the ammonia fuel supply line 200 with the purge gas G1 while continuing combustion with the first fuel F1. At this time, the purge control unit 45 continues piping purging of the ammonia fuel supply line 200 until the NOx concentration in the exhaust gas E1 falls below the reference NOx level. Therefore, the ammonia fuel F2 that tends to remain in the piping of the ammonia fuel supply line 200 by being adsorbed to the piping, for example, can be sufficiently discharged to the burner 24 and combusted. Therefore, the combustion device 10 can prevent ammonia from leaking out of the combustion device 10 and the ammonia co-firing boiler 1.

[0053] According to the present embodiment described above, the following effects can be achieved. (1) The combustion device 10 includes a burner 24 to which ammonia fuel F2 and a first fuel F1 having a faster combustion rate than the ammonia fuel F2 are supplied and combusted, a first fuel supply line 100 to supply the first fuel F1 to the burner 24, an ammonia fuel supply line 200 to supply the ammonia fuel F2 to the burner 24, a NOx sensor 401 that is a NOx detection unit that detects the NOx concentration in exhaust gas E1 that is a combustion gas generated by combustion of at least one of the first fuel F1 or the ammonia fuel F2, and a control unit 40, and the control unit 40 The burner 24 is provided with a combustion control unit 43 that controls combustion in either a first fuel combustion mode in which a first fuel F1 is burned, or a mixed combustion mode in which the first fuel F1 is mixed with an ammonia fuel F2, a reference NOx level storage unit that stores a reference NOx level that is set based on the NOx concentration in exhaust gas E1, which is combustion gas in the first fuel combustion mode, and a NOx evaluation unit that evaluates the presence of ammonia based on the NOx concentration detected by the NOx detection unit during combustion in the first fuel combustion mode and the reference NOx level.

[0054] Therefore, the combustion device 10 can detect ammonia leakage using a general NOx sensor, using the NOx concentration in the exhaust gas E1 during combustion of the first fuel F1 as an index. Furthermore, when an ammonia leakage is detected, the combustion device 10 can control the operation of the combustion device 10 accordingly.

[0055] (2) The combustion device 10 also includes a purge gas supply line 700 that supplies a purge gas G1 to the ammonia fuel supply line 200, and the control unit 40 further includes a purge control unit 45 that controls the supply of the purge gas G1 from the purge gas supply line 700 to the ammonia fuel supply line 200, and when at least one of the burner 24 starts combustion and the burner 24 stops combustion, the combustion control unit 43 causes the burner 24 to combust in the first fuel combustion mode, and the purge control unit 45 supplies the purge gas G1 to the ammonia fuel supply line 200 based on the evaluation result of the NOx evaluation unit 44.

[0056] Therefore, the combustion device 10 includes a purge gas supply line 700 and a purge control unit 45. During combustion in the first fuel combustion mode, the purge control unit 45 supplies purge gas G1 to the ammonia fuel supply line 200 based on the evaluation result of the NOx evaluation unit 44. Therefore, the supply of purge gas G1 can be stopped by detecting that the ammonia concentration has become equal to or lower than a predetermined value using the NOx concentration as an index. This makes it possible to appropriately adjust the amount of purge gas G1 used and the time required for purging, thereby reducing the cost and time required for purging. Furthermore, since the supply of purge gas G1 can be continued until the ammonia concentration becomes equal to or lower than a predetermined value using the NOx concentration in the exhaust gas E1 as an index, the ammonia remaining in the ammonia fuel supply line 200 can be more reliably discharged and burned by the burner 24.

[0057] (Second embodiment) FIG. 4 is a diagram schematically illustrating the configuration of a combustion device according to the second embodiment and an ammonia-mixed combustion boiler including the combustion device. The combustion device 10 of the second embodiment differs from the first embodiment in that a third shutoff valve 206 is provided in the ammonia fuel supply line 200, and a purge control unit 45 that controls the supply of the purge gas G1 intermittently supplies the purge gas G1 multiple times. Therefore, parts that perform the same functions as those in the first embodiment described above are denoted by the same reference numerals or with the same reference numerals at the end, and duplicated explanations will be omitted as appropriate.

[0058] The third shutoff valve 206 is provided in the ammonia fuel supply line 200 downstream of the connection point with the purge gas supply line 700. The third shutoff valve 206 is configured by a solenoid valve, opens and closes the flow path of the ammonia fuel supply line 200, and starts or stops the supply of a mixed gas of purge gas G1 and ammonia fuel F2 supplied from the purge gas supply line 700 (described later) to the burner 24. The third shutoff valve 206 is electrically connected to the control unit 40, and is controlled by a signal transmitted from the control unit 40.

[0059] Fig. 5 shows an example of the relationship between the reference NOx level and the change in NOx concentration in the exhaust gas E1 during post-purging by the purge gas G1 when combustion in the burner 24 is stopped in the combustion device 10 of the second embodiment. In Fig. 5, similar to Fig. 3, the first shutoff valve 103 and the second shutoff valve 105 of the first fuel supply line 100 are shown as first fuel supply line shutoff valves, the first shutoff valve 203 and the second shutoff valve 205 of the ammonia fuel supply line 200 are shown as ammonia fuel supply line shutoff valves, and the first shutoff valve 703 and the second shutoff valve 705 of the purge gas supply line 700 are shown as purge gas supply line shutoff valves.

[0060] The operation of each part of the combustion device 10 of this embodiment will be described with reference to FIG. The combustion device 10 of this embodiment performs combustion in a mixed combustion mode during combustion operation. When stopping combustion in the burner 24, the combustion control unit 43 switches combustion in the burner 24 from the mixed combustion mode to the first fuel combustion mode. The combustion control unit 43 closes the first shutoff valve 203 and the second shutoff valve 205 of the ammonia fuel supply line 200, and keeps the first shutoff valve 103 and the second shutoff valve 105 of the first fuel supply line 100 open. In addition, the purge control unit 45 keeps the third shutoff valve 206 of the ammonia fuel supply line 200 open.

[0061] Next, the purge control unit 45 closes the third shutoff valve 206 of the ammonia fuel supply line 200, and then opens the first shutoff valve 703 and the second shutoff valve 705 of the purge gas supply line 700 to start supplying the purge gas G1 to the ammonia fuel supply line 200. When the purge gas G1 is supplied to the ammonia fuel supply line 200 with the third shutoff valve 206 closed, the pressure in the piping of the ammonia fuel supply line 200 increases, and the ammonia remaining in the piping between the second shutoff valve 205 and the third shutoff valve 206 is diluted, resulting in a decrease in its concentration.

[0062] The purge control unit 45 closes the first shutoff valve 703 and the second shutoff valve 705 of the purge gas supply line 700 after supplying the purge gas G1 for a predetermined time. Next, the purge control unit 45 opens the third shutoff valve 206 of the ammonia fuel supply line 200, and the pressure in the piping between the second shutoff valve 205 and the third shutoff valve 206 of the ammonia fuel supply line 200 is released, so that the purge gas G1 containing ammonia can be efficiently discharged to the burner 24.

[0063] The ammonia contained in the purge gas G1 is burned together with the first fuel F1 in the burner 24, thereby increasing the NOx concentration in the exhaust gas E1. The NOx sensor 401 detects the NOx concentration in the exhaust gas E1 and outputs the result to the control unit 40. The NOx evaluation unit 44 evaluates the presence of ammonia based on the NOx concentration detected by the NOx sensor 401 and the reference NOx level read from the reference NOx level storage unit 42. If the NOx concentration detected by the NOx sensor 401 is equal to or higher than the reference NOx level, the NOx evaluation unit 44 evaluates that ammonia is present in the purge gas supplied to the burner 24.

[0064] When the purge control unit 45 obtains an evaluation that ammonia is present from the NOx evaluation unit 44, the purge control unit 45 again supplies the purge gas G1 to the ammonia fuel supply line 200. That is, the purge control unit 45 closes the third shutoff valve 206 of the ammonia fuel supply line 200, opens the first shutoff valve 703 and the second shutoff valve 705 of the purge gas supply line 700, and supplies the purge gas G1 to the ammonia fuel supply line 200 for a predetermined time. Next, the purge control unit 45 opens the third shutoff valve 206 to release the purge gas G1, and discharges the purge gas G1 that has accumulated in the ammonia fuel supply line 200 and contains ammonia to the burner 24.

[0065] The NOx sensor 401 detects the NOx concentration in the exhaust gas E1 and outputs the result to the control unit 40. The NOx evaluation unit 44 evaluates ammonia based on the NOx concentration in the exhaust gas E1 after the third shutoff valve 206 of the ammonia fuel supply line 200 is opened, which is obtained from the NOx sensor 401, and the reference NOx level read out from the reference NOx level storage unit 42. If the evaluation result of the NOx evaluation unit 44 indicates the presence of ammonia, the purge control unit 45 again performs a series of operations related to purging the pipes with the purge gas G1.

[0066] The detection of the NOx concentration by the NOx sensor 401 may be performed a predetermined time after the third shut-off valve 206 is opened, or, for example, the average value of the detection results of the NOx concentration for a certain period after the third shut-off valve 206 is opened may be used, or the maximum value of the NOx concentration for a certain period after the third shut-off valve 206 is opened may be used.

[0067] Due to the intermittent purging by the purge control unit 45 as described above, the ammonia concentration contained in the purge gas G1 in the ammonia fuel supply line 200 decreases stepwise as shown in Fig. 5. As shown in Fig. 5, after the second piping purge, the amount of ammonia fuel F2 remaining in the piping of the ammonia fuel supply line 200 is small, and the NOx concentration during the piping purge is lower than the NOx concentration during the first piping purge.

[0068] If the NOx concentration acquired from the NOx sensor 401 falls below the reference NOx level, the NOx evaluation unit 44 evaluates that ammonia is not present. The purge control unit 45, which has acquired the evaluation result of the NOx evaluation unit 44, ends the piping purging with the purge gas G1 to the ammonia fuel supply line 200, and closes the third shutoff valve 206. At this time, the first shutoff valve 703 and the second shutoff valve 705 of the purge gas supply line 700 are in a closed state. The combustion control unit 43 closes the first shutoff valve 103 and the second shutoff valve 105 of the first fuel supply line 100 to stop the supply of the first fuel F1 and stop the combustion of the burner .

[0069] As described above, in the present embodiment, the purge control unit 45 intermittently performs piping purging of the ammonia fuel supply line 200 with the purge gas G1 multiple times until the ammonia concentration in the purge gas falls below a predetermined value, thereby making it possible to efficiently treat the ammonia remaining in the ammonia fuel supply line 200.

[0070] According to the present embodiment described above, in addition to the above effects (1) and (2), the following effects can be achieved. (3) In the combustion device 10, when the burner 24 starts to burn or when the burner 24 stops to burn, the combustion control unit 43 causes the burner 24 to burn in the first fuel combustion mode, and the purge control unit 45 supplies and stops the purge gas G1 to the ammonia fuel supply line 200 multiple times. As a result, when combustion is stopped or started, the ammonia fuel supply line 200 is purged with the purge gas G1 multiple times during combustion in the first fuel combustion mode, so that ammonia that is likely to remain in the piping, such as by being adsorbed on the inner wall of the piping of the ammonia fuel supply line 200, can be discharged into the combustion space B and combusted by the burner 24.

[0071] (Third embodiment) The combustion device 10 of the third embodiment is similar to the first embodiment described above, except that the control unit 40 further includes an ammonia leak determination unit 46 and an abnormality response operation control unit 47. Therefore, parts that perform the same functions as those in the first embodiment described above are denoted by the same reference numerals or with the same reference numerals at the end, and duplicate explanations will be omitted as appropriate. FIG. 6 is a diagram schematically illustrating the configuration of a combustion device 10 according to the third embodiment and an ammonia-mixed combustion boiler 1 including the combustion device 10. 6, in the combustion device 10 of this embodiment, the control unit 40 includes an ammonia leak determination unit 46 and an abnormality response operation control unit 47 in addition to a storage unit 41, a combustion control unit 43, a NOx evaluation unit 44, and a purge control unit 45. This combustion device 10 is applied to an ammonia-mixed combustion boiler 1.

[0072] The ammonia leakage determination unit 46 determines whether or not there is an ammonia leak based on the evaluation result of the NOx evaluation unit 44 while the burner 24 is burning in the first fuel combustion mode. The abnormality response operation control unit 47 controls the abnormality response operation based on the determination of the ammonia leak determination unit 46.

[0073] If the first shutoff valve 203 and the second shutoff valve 205 of the ammonia fuel supply line 200 fail to close for some reason (valve abnormality (breakdown, garbage trapped), abnormality in the control signal), leakage of the ammonia fuel F2 into the ammonia fuel supply line 200 occurs. The combustion device 10 of this embodiment is provided with an ammonia leakage determination unit 46 and stores an ammonia leakage reference level in the reference NOx level storage unit 42, thereby detecting such leakage of the ammonia fuel F2, and is provided with an abnormality response operation control unit 47, thereby controlling the operation to respond to the leakage of ammonia.

[0074] In this embodiment, the combustion control unit 43 closes the first shutoff valve 203 and the second shutoff valve 205 of the ammonia fuel supply line 200 to stop the supply of ammonia fuel F2, and while the burner 24 is burning in the first fuel combustion mode, the ammonia leakage determination unit 46 determines whether or not there is an ammonia leak, based on the detection result of the NOx sensor 401 and the ammonia leakage reference level stored in the reference NOx level storage unit 42. Also, similar to the first embodiment described above, the first fuel F1 is combusted during piping purging with the purge gas G1, and the ammonia leakage determination unit 46 determines whether or not there is an ammonia leak, based on the detection result of the NOx sensor 401 and the ammonia leakage determination reference level stored in the reference NOx level storage unit 42.

[0075] The ammonia leakage reference level stored in the reference NOx level storage unit 42 is a NOx concentration that exceeds the NOx concentration defined by the reference NOx level. Furthermore, if such a NOx concentration continues for a predetermined time or more (for example, several minutes or more), the ammonia leakage determination unit 46 determines that there is ammonia leakage. The ammonia leakage determination unit 46 determines that an ammonia leak has occurred when the detection result of the NOx sensor 401 indicates an NOx concentration that exceeds the ammonia leakage reference level and such an NOx concentration continues for a predetermined time.

[0076] When the ammonia leak determination unit 46 determines that there is an ammonia leak, the abnormality response operation control unit 47 performs an operation based on the determination result, such as issuing an alarm, displaying an abnormality on a display unit (not shown), or stopping the operation of the ammonia co-firing boiler 1.

[0077] Therefore, the combustion device 10 can detect leakage of ammonia from the first shutoff valve 203 and the second shutoff valve 205 of the ammonia fuel supply line 200 by the ammonia leakage determination unit 46, and when leakage of ammonia is detected, the abnormality response operation control unit 47 can take action to respond to the leakage of ammonia, so that leakage of ammonia to the outside of the system can be suppressed and the safety of the combustion device 10 and the ammonia co-firing boiler 1 can be improved.

[0078] According to the present embodiment described above, in addition to the above effects (1) to (3), the following effects can be achieved. (4) The combustion device 10 includes an ammonia leakage determination unit 46 in which the control unit 40 determines whether or not ammonia is leaking based on the evaluation result of the NOx evaluation unit 44 while the burner 24 is burning in the first fuel combustion mode. Therefore, the combustion device 10 can detect leakage of the ammonia fuel F2 from the first shutoff valve 203 and the second shutoff valve 205 of the ammonia fuel supply line 200 by the ammonia leakage determination unit, and can prevent leakage of ammonia from the combustion device 10 and the ammonia co-firing boiler 1 to the outside, thereby improving safety.

[0079] (5) Furthermore, the combustion device 10 includes an abnormality response operation control unit 47 in which the control unit 40 controls the abnormality response operation based on the determination of the ammonia leak determination unit 46 . Therefore, when an abnormality such as an ammonia leak is detected, a corresponding action can be taken quickly, preventing leakage of ammonia to the outside of the combustion device 10 and the ammonia-mixed combustion boiler 1 and improving safety. This also leads to prediction of abnormalities in important parts of the combustion device 10 and the ammonia-mixed combustion boiler 1, such as the first shutoff valve 203 and the second shutoff valve 205 of the ammonia fuel supply line 200 and the combustion control unit 43, and making it possible to prevent serious ammonia leakage before it occurs.

[0080] (Fourth embodiment) The combustion device of the fourth embodiment has the same configuration as the combustion device 10 of the first embodiment, and is applied to an ammonia-mixed combustion boiler 1. The fourth embodiment is an ammonia evaluation method in which the NOx evaluation unit 44 evaluates the presence of ammonia in the combustion device without requiring a reference NOx level in the evaluation of ammonia. Therefore, parts that perform the same functions as those in the first embodiment described above are given the same reference numerals or the same reference numerals with the same suffixes, and redundant explanations will be omitted as appropriate.

[0081] In this embodiment, the method for evaluating ammonia in the NOx evaluation unit 44 of the combustion device includes the following steps. First, the control unit 40 performs a first step of detecting the NOx concentration in the combustion gas (exhaust gas E1) using the NOx sensor 401 while the burner 24 is burning in the first fuel combustion mode. Next, the control unit 40 performs a second step of creating NOx information that associates the NOx concentration detected by the NOx sensor 401 in the first step with time information about the time when the NOx concentration was detected, and storing the NOx information in a NOx information storage unit (not shown). This NOx information storage unit may be provided in the storage unit 41 or the control unit 40, or may be provided outside the combustion device and be capable of communicating with the control unit 40 and the NOx sensor 401.

[0082] The control unit 40 sets the first step and the second step as one set and repeats the set a number of times, whereby the NOx information storage unit stores a number of pieces of NOx information. The NOx information is, for example, information regarding the change in NOx concentration over time for a predetermined time from the start of combustion of the first fuel F1 in the first fuel combustion mode. This predetermined time is preferably longer than the time it takes for the first fuel supply line 100 to be filled with the first fuel F1 and the response time of the NOx sensor 401. The NOx information may also be the average and variance of the NOx concentration for each fixed time period.

[0083] Next, the NOx evaluation unit 44 acquires the plurality of pieces of NOx information stored in the second step, and performs a third step of evaluating the presence of ammonia based on the plurality of pieces of NOx information. The first and second steps may be performed by an AI or the like that is provided outside the combustion device 10 and that can communicate with the control unit 40, rather than by the control unit 40. The third step may also be performed by an AI or the like that is outside the combustion device 10. By providing these first and second steps, data on time-series fluctuations in NOx concentration in the first fuel combustion mode can be learned by an AI or other device external to the combustion device, and the presence of ammonia can be evaluated based on multiple pieces of NOx information without setting a reference NOx level. Furthermore, even if the amount of NOx generated by combustion in the combustion device changes due to aging or other reasons, the presence of ammonia can be evaluated with high accuracy by continuing to learn using AI.

[0084] According to the present embodiment described above, the following effects can be achieved. (6) The ammonia evaluation method includes a burner 24 to which an ammonia fuel F2 and a first fuel F1 having a faster combustion speed than the ammonia fuel F2 are supplied and combusted, a first fuel supply line 100 to supply the first fuel F1 to the burner 24, an ammonia fuel supply line 200 to supply the ammonia fuel F2 to the burner 24, an NOx sensor that is an NOx detection unit that detects the NOx concentration of exhaust gas E1 that is a combustion gas generated by combustion of at least one of the first fuel F2 and the ammonia fuel ejected from the burner, and a first fuel F1 that is supplied to the burner 24 and combusted by the burner 24. The combustion device includes a control unit (40) having a combustion control unit (43) that controls combustion to be performed in either a first combustion mode or a mixed combustion mode in which a first fuel (F1) and an ammonia fuel (F2) are mixed and burned. The combustion device includes: a first step of detecting the NOx concentration in the exhaust gas (E1) by a NOx sensor during combustion in the first fuel combustion mode; a second step of creating and saving NOx information that associates the NOx concentration detected in the first step with time information regarding the time when the NOx concentration was detected; and a third step of evaluating the presence of ammonia based on the multiple pieces of NOx information saved in the second step.

[0085] Therefore, by having an AI or the like external to the combustion device perform the first and second steps, the AI ​​or the like external to the combustion device 10 can learn the NOx data for the first fuel combustion mode, enabling a more accurate evaluation of the presence of ammonia. Therefore, ammonia leakage can be detected with higher accuracy based on the NOx concentration.

[0086] (Variations) The present invention is not limited to the above-described embodiments, and various modifications and variations are possible, and these are also within the scope of the present invention. In each embodiment, the combustion control unit 43 may be provided with an ammonia fuel mono-combustion mode in which only ammonia fuel is burned, and may control combustion in the burner 24 in any of the first fuel combustion mode, the multi-fuel combustion mode, and the ammonia mono-combustion mode.

[0087] In each embodiment, an example has been shown in which LNG is used as the first fuel F1, but the present invention is not limited to this, and a hydrogen-based fuel gas such as hydrogen gas may be used as the first fuel F1.

[0088] In each of the present embodiments, the combustion device is applied to an ammonia co-firing boiler 1, but the present invention is not limited to this and may be used in other devices that co-firing the first fuel F1 and the ammonia fuel F2. For example, the combustion device of each of the embodiments may be an industrial furnace (heat treatment furnace, sintering furnace, calcination furnace, etc.).

[0089] In the second embodiment, the third shutoff valve 206 of the ammonia fuel supply line 200 may not be provided. In such a case, the connection point between the purge gas supply line L700 and the ammonia fuel supply line 200 is located upstream of the second shutoff valve 205, so that the second shutoff valve 205 can function as the third shutoff valve 206. Therefore, the configurations of the combustion device 10 and the ammonia co-firing boiler 1 can be simplified. On the other hand, by providing the third shutoff valve 206 as in the combustion device 10 of the second embodiment, there is no need to frequently open and close the second shutoff valve 205, whose main purpose is to shut off the ammonia fuel F2, so that failure of the second shutoff valve 205 can be suppressed.

[0090] Furthermore, in the second embodiment, a slow-open type valve may be used as the third shutoff valve 206. By adopting such a configuration, it is possible to suppress a sudden inflow of the purge gas G1 during piping purging, and it is possible to stabilize the combustion of the first fuel F1 during the inflow of the purge gas G1.

[0091] In each embodiment, the ammonia fuel F2 and the first fuel F1 may be mixed in advance and supplied to the burner 24, and the mixed gas may be ejected from the burner 24 and combusted.

[0092] In each embodiment, the first fuel supply line 100 is provided with the first shutoff valve 103 and the second shutoff valve 105, but the present invention is not limited to this, and the number of shutoff valves may be one. The same applies to the ammonia fuel supply line 200 and the purge gas supply line 700.

[0093] In each embodiment, the purging of the ammonia fuel supply line 200 with the purge gas G1 is performed when the burner 24 stops combustion, but the present invention is not limited to this and may be performed when the burner 24 starts combustion.

[0094] The present invention is not limited to the above-described embodiments, but may be combined with other embodiments as desired.

[0095] Furthermore, since the present invention promotes the use of ammonia as a fuel, which does not emit carbon dioxide, it can contribute to, for example, 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]

[0096] 1. Ammonia co-firing boiler 10 Combustion equipment 20 can body 24 Burner 40 Control Unit 42 Reference NOx level memory section 43 Combustion control unit 44 NOx Evaluation Section 45 Purge control section 100 First fuel supply line 200 Ammonia fuel supply line 300 Combustion air supply line 400 Exhaust gas line 500 water supply line 600 Steam Supply Line 700 Purge gas supply line F1 1st fuel F2 ammonia fuel G1 Purge Gas A1 Combustion air B. Combustion space

Claims

1. a burner to which ammonia fuel and a first fuel having a combustion speed faster than that of the ammonia fuel are supplied and combusted; a first fuel supply line that supplies the first fuel to the burner; an ammonia fuel supply line for supplying the ammonia fuel to the burner; a NOx detection unit that detects a NOx concentration in combustion gas generated by combustion of at least one of the first fuel and the ammonia fuel ejected from the burner; A control unit; Equipped with The control unit a combustion control unit that controls the burner to perform combustion in either a first fuel combustion mode in which the first fuel is burned or a mixed combustion mode in which the first fuel and the ammonia fuel are mixed and burned; a reference NOx storage unit that stores a reference NOx level that is set based on the NOx concentration of the combustion gas in the first fuel combustion mode; a NOx evaluation unit that evaluates the presence of ammonia based on the NOx concentration detected by the NOx detection unit during combustion in the first fuel combustion mode and the reference NOx level; A combustion device comprising:

2. a purge gas supply line that supplies a purge gas to the ammonia fuel supply line; the control unit further includes a purge control unit that controls the supply of the purge gas from the purge gas supply line to the ammonia fuel supply line, At least one of when the burner starts combustion and when the burner stops combustion, The combustion control unit causes the burner to combust in the first fuel combustion mode, and The purge control unit supplies the purge gas to the ammonia fuel supply line based on the evaluation result of the NOx evaluation unit. The combustion device of claim 1 .

3. At least one of when the burner starts combustion and when the burner stops combustion, The combustion control unit causes the burner to combust in the first fuel combustion mode, and the purge control unit starts and stops supplying the purge gas to the ammonia fuel supply line a plurality of times; The combustion device according to claim 2.

4. the control unit includes an ammonia leakage determination unit that determines leakage of ammonia based on the evaluation result of the NOx evaluation unit while the burner is combusting in the first fuel combustion mode. The combustion device of claim 1 .

5. The control unit includes an abnormality response operation control unit that controls an abnormality response operation based on the determination of the ammonia leak determination unit. The combustion device according to claim 4.

6. a burner to which ammonia fuel and a first fuel having a combustion speed faster than that of the ammonia fuel are supplied and combusted; a first fuel supply line that supplies the first fuel to the burner; an ammonia fuel supply line for supplying the ammonia fuel to the burner; a NOx detection unit that detects a NOx concentration in combustion gas generated by combustion of at least one of the first fuel and the ammonia fuel ejected from the burner; a control unit including a combustion control unit that controls the burner to perform combustion in either a first fuel combustion mode in which the first fuel is burned or a mixed combustion mode in which the first fuel and the ammonia fuel are mixed and burned; In a combustion device comprising: a first step of detecting a NOx concentration in the combustion gas by the NOx detection unit during combustion in the first fuel combustion mode; a second step of creating and storing NOx information by associating the NOx concentration detected in the first step with time information regarding the time when the NOx concentration was detected; a third step of evaluating the presence of ammonia based on the plurality of NOx information stored in the second step; An ammonia evaluation method comprising:

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