Ammonia combustion device, and ammonia combustion method

Abstract

To carry out stable ignition using ammonia.SOLUTION: An ammonia combustion device comprises a main burner 30 to be supplied with ammonia-containing fuel gas from a main flow path 22 to burn the fuel gas, a reforming unit 20 generating reformed ammonia gas of a reforming ratio of 40% or higher resulting from decomposing a part of the ammonia into hydrogen and nitrogen, and a pilot unit to be supplied with the reformed ammonia gas from the reforming unit 20, to perform ignition for combustion in the main burner 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed in the present application relates to an ammonia combustion device and an ammonia combustion method. [Background technology]

[0002] In recent years, there has been much anticipation for the direct combustion of ammonia, which does not emit CO2 during combustion. However, ammonia has a slow combustion speed (about 1 / 5 that of city gas 13A) and a low adiabatic flame temperature (about -220°C compared to city gas 13A), making its combustion characteristics significantly different from those of hydrocarbon fuels such as city gas. Furthermore, its low ignition properties mean that the flame is easily blown away, making it difficult to achieve stable ignition performance and stable combustion conditions.

[0003] Various proposals have been made to utilize such ammonia as fuel, and Japanese Patent No. 7076930 discloses the use of reformed ammonia fuel in which part of the ammonia is reformed into hydrogen and nitrogen. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7076930 Summary of the Invention [Problem to be solved by the invention]

[0005] However, Patent Document 1 uses reformed ammonia fuel for all combustion processes, and does not describe or suggest combustion at the time of ignition.

[0006] In consideration of the above, the present disclosure aims to provide an ammonia combustion device and an ammonia combustion method that can perform stable ignition using ammonia. [Means for solving the problem]

[0007] The ammonia combustion device of the first aspect includes: a main burner that receives fuel gas containing ammonia from a main flow path and combusts the fuel gas; a reforming unit that generates reformed ammonia gas with a reforming rate of 40% or more by decomposing a portion of the ammonia into hydrogen and nitrogen; and a pilot unit that receives the reformed ammonia gas from the reforming unit and ignites the reformed ammonia gas for combustion in the main burner.

[0008] According to the ammonia combustion device of the first aspect, ignition for combustion in the main burner is performed using reformed ammonia gas with a reforming rate of 40% or more, so that the ammonia-containing gas can be ignited stably.

[0009] In the ammonia combustion device of a second aspect, the reformed ammonia gas has a reforming rate of less than 50%.

[0010] According to the second aspect of the ammonia combustion device, by using a reformed ammonia gas with a reforming rate of less than 50%, NO X This can reduce emissions.

[0011] The ammonia combustion apparatus of the third aspect includes a control unit that controls the main valve to start supplying the fuel gas from the main flow path to the main burner when the temperature inside the combustion furnace in which the combustion flame of the main burner is maintained is 750°C or higher.

[0012] According to the ammonia combustion apparatus of the third aspect, combustion in the main burner can be carried out stably after ignition.

[0013] In the ammonia combustion apparatus of the fourth aspect, after starting to supply the fuel gas to the main burner, the control unit controls the reforming rate in the reforming unit so that the reformed ammonia gas reformed in the reforming unit and having a reforming rate of less than 40% is supplied to the main flow path as the fuel gas.

[0014] According to the ammonia combustion apparatus of the fourth aspect, the reforming rate of the reformed ammonia gas supplied to the main burner after ignition can be made lower than that at the time of ignition, so that the size of the reforming section can be made smaller.

[0015] In the ammonia combustion apparatus of the fifth aspect, after the supply of the fuel gas from the main flow path to the main burner starts, the control unit controls a valve so that the ammonia gas that does not pass through the reforming unit is supplied to the main flow path as the fuel gas.

[0016] According to the ammonia combustion device of the fifth aspect, the reformer can be left unused during steady combustion other than at the time of ignition.

[0017] The ammonia combustion method of the sixth aspect reforms part of ammonia into hydrogen and nitrogen to generate reformed ammonia gas with a reforming rate of 40% or more, and uses the reformed ammonia gas to ignite combustion in a main burner.

[0018] According to the ammonia combustion method of the sixth aspect, ignition for combustion in the main burner is performed using reformed ammonia gas with a reforming rate of 40% or more, so that the ammonia-containing gas can be ignited stably.

[0019] In the ammonia combustion method of a seventh aspect, the reformed ammonia gas has a reforming rate of less than 50%.

[0020] According to the seventh aspect of the ammonia combustion method, by using a reformed ammonia gas with a reforming rate of less than 50%, NO X This can reduce emissions.

[0021] In the ammonia combustion method of the eighth aspect, when the temperature inside the combustion furnace where the combustion flame of the main burner is maintained is 750° C. or higher, the supply of main combustion fuel gas to the main burner is started.

[0022] According to the eighth aspect of the ammonia combustion method, combustion in the main burner can be carried out stably after ignition.

[0023] In the ammonia combustion method of the ninth aspect, after the supply of the fuel gas for main combustion to the main burner is started, reformed ammonia gas having a reforming rate of less than 40% is supplied to the main burner.

[0024] According to the ammonia combustion method of the ninth aspect, the reforming rate of the reformed ammonia gas supplied to the main burner after ignition can be made lower than that at the time of ignition, so that the load of reforming can be reduced.

[0025] In the ammonia combustion method of the tenth aspect, after starting the supply of fuel gas for main combustion to the main burner, unreformed ammonia gas is supplied to the main burner as the fuel gas for main combustion.

[0026] According to the ammonia combustion method of the tenth aspect, reforming can be made unnecessary during steady combustion other than at the time of ignition. [Effects of the Invention]

[0027] According to the present disclosure, stable ignition can be achieved using ammonia. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a schematic configuration diagram of an ammonia combustion device according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing a part of a main burner of the first embodiment. [Figure 3] FIG. 2 is a block diagram showing a control system of the ammonia combustion apparatus of the first embodiment. [Figure 4] 4 is a flowchart of a main combustion switching process. [Figure 5] FIG. 1 is a schematic configuration diagram of an ammonia combustion device according to a second embodiment. [Figure 6] FIG. 10 is a view showing a part of a main burner of a second embodiment. [Figure 7] FIG. 10 is a schematic configuration diagram of an ammonia combustion apparatus according to a third embodiment. [Figure 8]10 is a flowchart of a second main combustion switching process. [Figure 9] FIG. 10 is a schematic configuration diagram of an ammonia combustion apparatus according to a third embodiment. [Figure 10] 1 is a graph showing the relationship between the reforming rate and the amount of unburned ammonia gas and NOx emissions. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0030] [First embodiment] 1 shows a schematic configuration of an ammonia combustion apparatus 10A according to a first embodiment. The ammonia combustion apparatus 10A includes a reforming section 20 and a main burner 30. A main gas passage 22, a pilot gas passage 24, and an air passage 26 are connected to the main burner 30.

[0031] 2, a central passage 32 is formed in the center, a pilot passage 34 is formed on the outer periphery of the central passage 32, and an outer passage 36 is formed on the outer periphery of the pilot passage 34. The main gas passage 22 is connected to the central passage 32, the pilot gas passage 24 branched from the main gas passage 22 is connected to the pilot passage 34, and the air passage 26 is connected to the outer passage 36. The main gas passage 22 is connected to the reforming section 20, and the air passage 26 is connected to the air supply section 16.

[0032] The main burner 30 does not necessarily have to be of the coaxial type as shown in FIG. 2, and other configurations can also be used.

[0033] A main gas regulating valve 22V is provided in the main gas flow path 22, an air regulating valve 26V is provided in the air flow path 26, and a pilot gas regulating valve 24V is provided in the pilot gas flow path 24. The main gas regulating valve 22V, the air regulating valve 26V, and the pilot gas regulating valve 24V are connected to a control unit 40, which will be described later, and the opening / closing and flow rate of these valves are controlled by the control unit 40.

[0034] The main burner 30 is installed facing the internal combustion space R of the combustion furnace 39. The combustion furnace 39 is provided with an internal furnace temperature sensor 38 that measures the temperature of the internal combustion space R. The temperature acquired by the internal furnace temperature sensor 38 is defined as the internal furnace temperature T3. The internal furnace temperature sensor 38 is connected to a control unit 40 (described later) and outputs the internal furnace temperature T3 to the control unit 40. The combustion furnace 39 is also provided with a flue 39A that discharges combustion exhaust gas.

[0035] A fuel supply pipe 21 is connected to the reforming section 20, and ammonia gas (fuel gas) is supplied to the reforming section 20 from the fuel supply section 18 via the fuel supply pipe 21. The reforming section 20 contains a catalyst that decomposes the ammonia gas into hydrogen and nitrogen. The reforming section 20 is also provided with a heater (not shown) and is heated by the heater. In the reforming section 20, a portion of the supplied ammonia is decomposed into hydrogen and nitrogen, and a mixed gas of ammonia gas, hydrogen, and nitrogen (reformed ammonia gas) is sent to the main gas flow path 22. The reforming section 20 is provided with a reforming temperature sensor 28 that measures the temperature inside the reforming section 20. The temperature acquired by the reforming temperature sensor 28 is defined as a reforming temperature T2. The reforming temperature sensor 28 is connected to a control section 40 (described later) and outputs the reforming temperature T2 to the control section 40.

[0036] The fuel supply unit 18 is connected to a control unit 40, which adjusts the flow rate of the ammonia gas that is delivered.

[0037] The ammonia combustion apparatus 10A includes a control unit 40. As shown in Fig. 3, the control unit 40 is connected to the air supply unit 16, the fuel supply unit 18, the main gas regulating valve 22V, the air regulating valve 26V, the pilot gas regulating valve 24V, the furnace temperature sensor 38, and the reforming temperature sensor 28. The control unit 40 includes a CPU (Central Processing Unit) 41, a ROM (Read Only Memory) 42, a RAM (Random Access Memory) 43, an input / output interface (I / O) 44, and a storage unit 45.

[0038] The CPU 41, ROM 42, RAM 43, and I / O 44 are connected to each other via a bus 46. The I / O 44 is connected to various functional units including a storage unit 45. These functional units can communicate with the CPU 41 via the I / O 44.

[0039] The storage unit 45 may be, for example, a hard disk drive (HDD), a solid state drive (SSD), or a flash memory. The storage unit 45 stores a control program for controlling each part of the ammonia combustion device 10A and various data (for example, a main switching temperature T1 and an ignition reforming rate M1). The control program and various data may be stored in the ROM 42.

[0040] In this embodiment, a main combustion switching process program is stored as part of the control program. In addition, data used in this process, such as the main switching temperature T1, the ignition reforming rate M1, and the main combustion reforming rate M2, are stored.

[0041] Here, the main switching temperature T1, the ignition reforming rate M1, and the main combustion reforming rate M2 will be explained. The main burner 30 is ignited by reformed ammonia gas that has been partially reformed in the reforming section 20. The reformed ammonia gas is supplied to the main burner 30 from the pilot passage 34. After ignition, the reformed ammonia gas is supplied to the main burner 30 from the main gas passage 22 via the central passage 32, and combustion in the main burner 30 is carried out.

[0042] The reforming rate of ammonia gas in the reforming section 20 when the reformed ammonia gas supplied from the pilot passage 34 to the main burner 30 is ignited is defined as the ignition reforming rate M1. The ignition reforming rate M1 is set to be 40% or more. In addition, the ignition reforming rate M1 is preferably less than 50%. After a predetermined condition is satisfied after ignition, the reformed ammonia gas is supplied from the main gas passage 22 to the main burner 30 via the central passage 32 and combusted in the main burner 30, and the reforming rate of the ammonia gas in the reforming section 20 is defined as the main combustion reforming rate M2. The change control of the reforming rate is performed by adjusting the flow rate of ammonia gas supplied from the fuel supply section 18, and by adjusting the temperature of the reforming section 20 by a heater (not shown) based on the reforming temperature T2, etc.

[0043] The main switching temperature T1 is the predetermined temperature condition inside the furnace after ignition, and is set to a temperature at which the reformed ammonia gas can continue to burn stably. The main switching temperature T1 is preferably 750°C or higher.

[0044] Next, the effects of this embodiment will be described.

[0045] Before ignition, the main gas regulating valve 22V is closed, and the openings of the air regulating valve 26V and the pilot gas regulating valve 24V are adjusted to provide the flow rate at the time of ignition. When a command to start combustion is input, ammonia gas is supplied from the fuel supply unit 18 to the reforming unit 20 via the fuel supply pipe 21 at the flow rate at the time of ignition. The supplied ammonia gas is partially reformed in the reforming unit 20, and the reformed ammonia gas at an ignition reforming rate M1 is supplied to the main burner 30 via the main gas flow path 22, the pilot gas flow path 24, and the pilot flow path 34. In addition, air is supplied from the air flow path 26 to the main burner 30 via the outer flow path 36. Ignition is then performed by an ignition device (not shown).

[0046] According to this embodiment, ignition is performed with reformed ammonia gas having a reforming rate of 40% or more, so that the ammonia-containing gas can be ignited stably. In addition, by igniting with reformed ammonia gas having a reforming rate of less than 50%, NO X This can reduce emissions.

[0047] In the control unit 40, after the completion of the furnace pre-purge (scavenging) operation, when a command to start combustion is input and the ignition operation is performed, the main combustion switching processing program is executed. As shown in FIG. 4, the main combustion switching processing program acquires the furnace temperature T3 from the furnace temperature sensor 38 in step S10, and determines in step S12 whether the furnace temperature T3 is equal to or higher than the main switching temperature T1. If the determination is affirmative, the program adjusts the aperture of the air adjustment valve 26V to change the air flow rate in step S14, opens the main gas adjustment valve 22V to deliver the reformed ammonia gas at the desired main combustion flow rate in step S16, and closes the pilot gas adjustment valve 24V in step S18. Note that if there is no problem with the combustion of the reformed ammonia gas supplied from the pilot flow path 34 between steps 10 and 12 (until T3 reaches T1), the aperture of the air adjustment valve 26V may be adjusted at the start (corresponding to step 14). In step S20, the reforming rate is changed so that the reforming rate of the ammonia gas in the reforming unit 20 is changed from the ignition reforming rate M1 to the main combustion reforming rate M2. The change in the reforming rate is performed by adjusting the flow rate of the ammonia gas supplied from the fuel supply unit 18 and also by adjusting the temperature of the reforming unit 20 by a heater (not shown).

[0048] As a result, steady main combustion is performed in the main burner 30. According to this embodiment, ignition and pilot combustion are performed by the reformed ammonia gas when the furnace temperature is at room temperature, and after the furnace temperature T3 reaches or exceeds the main switching temperature T1, the reformed ammonia gas is burned at a desired flow rate for main combustion, so that combustion of the reformed ammonia gas can be performed stably. Note that in step S18, combustion may continue together with combustion of the main gas without closing the pilot gas adjustment valve 24V.

[0049] Furthermore, after the start of supply of the reformed ammonia gas from the main gas passage 22 to the main burner 30, the reformed ammonia gas with a reforming rate of less than 40%, which is lower than the rate at the time of ignition, is supplied as fuel gas to the main gas passage 22. Therefore, the burden on the reforming section 20 to reform the reformed ammonia gas for main combustion is reduced, and the size of the reforming section 20 can be made relatively small.

[0050] [Second embodiment] Next, a second embodiment will be described. In this embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0051] Fig. 5 shows a schematic configuration of an ammonia combustion apparatus 10B of the second embodiment. The ammonia combustion apparatus 10B of the second embodiment differs from the first embodiment in that a pilot burner 50 is provided downstream of a pilot gas regulating valve 24V, and that a coaxial main burner 30-2 has a central passage 32 formed in the center and an outer passage 36 formed on the outer periphery of the central passage, as shown in Fig. 6.

[0052] The pilot burner 50 is a burner for igniting the main burner 30. The pilot burner 50 is connected to a confluence 42. A pilot air passage 27 branched from the air passage 26 and a pilot gas passage 24 are connected to the confluence 42. Air for ignition is supplied to the confluence 42 from the pilot air passage 27, and reformed ammonia gas is supplied from the pilot gas passage 24. The air and the reformed ammonia gas are mixed in the confluence 42 and supplied to the pilot burner 50. The pilot burner 50 is ignited by an ignition device (not shown).

[0053] In this embodiment, the pilot burner 50 is used to enable more stable ignition.

[0054] In addition, in this embodiment, ignition is performed with reformed ammonia gas having a reforming rate of 40% or more, so that the ammonia-containing gas can be ignited stably. In addition, by igniting with reformed ammonia gas having a reforming rate of less than 50%, NO X This can reduce emissions.

[0055] Furthermore, in this embodiment as well, the control unit 40 executes the main combustion switching processing program, and after the furnace temperature T3 becomes equal to or higher than the main switching temperature T1, the reformed ammonia gas is combusted at the desired flow rate for main combustion, thereby enabling stable combustion of the reformed ammonia gas.

[0056] [Third embodiment] Next, a third embodiment will be described. In this embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0057] 7 shows a schematic configuration of an ammonia combustion apparatus 10C of the third embodiment. In the ammonia combustion apparatus 10C of this embodiment, a main gas passage 22 is connected to a fuel supply pipe 21 upstream of the reforming section 20. In addition, a pilot gas passage 24 is connected to the reforming section 20. Therefore, ammonia gas is supplied from the fuel supply section 18 to the central passage 32 of the main burner 30.

[0058] In this embodiment, ignition is also performed with reformed ammonia gas having a reforming rate of 40% or more supplied from the pilot gas passage 24, so that the ammonia-containing gas can be ignited stably. In addition, by performing ignition with reformed ammonia gas having a reforming rate of less than 50%, NO X This can reduce emissions.

[0059] When a command to start combustion is input after the completion of the furnace pre-purge (scavenging) operation, the control unit 40 performs the ignition operation and executes the second main combustion switching processing program. As shown in Fig. 8, the second main combustion switching processing program does not include step S20 of the main combustion switching processing program.

[0060] According to this embodiment, after the furnace temperature T3 becomes equal to or higher than the main switching temperature T1, the reformed ammonia gas is combusted at a desired flow rate for main combustion, so that the ammonia gas can be combusted stably. Note that in step S18, the pilot gas adjustment valve 24V may not be closed and combustion may be continued together with the main gas combustion.

[0061] Furthermore, when the supply of reformed ammonia gas from the pilot gas passage 24 is cut off at the time of switching to the main combustion, ammonia gas is supplied as fuel gas from the main gas passage 22 to the main burner 30 without passing through the reforming section 20, so that reforming of ammonia gas becomes unnecessary during steady combustion of the main burner after ignition.

[0062] [Fourth embodiment] Next, a fourth embodiment will be described. In this embodiment, the same parts as those in the first to third embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0063] 9 shows a schematic configuration of an ammonia combustion apparatus 10D of the fourth embodiment. In the ammonia combustion apparatus 10D of this embodiment, as in the third embodiment, the main gas passage 22 is connected to the fuel supply pipe 21 upstream of the reforming section 20. In addition, the pilot gas passage 24 is connected to the reforming section 20. Therefore, ammonia gas is supplied from the fuel supply section 18 to the central passage 32 of the main burner 30.

[0064] Furthermore, in this embodiment, as in the second embodiment, a pilot burner 50 is provided downstream of the pilot gas regulating valve 24V, and a central flow passage 32 is formed in the center of the main burner 30-2, as shown in Figure 5.

[0065] The pilot burner 50 is connected to the confluence 42. The confluence 42 is connected to a pilot air passage 27 branched from the air passage 26 and a pilot gas passage 24. Air for ignition is supplied to the confluence 42 from the pilot air passage 27, and reformed ammonia gas is supplied from the pilot gas passage 24. The air and the reformed ammonia gas are mixed in the confluence 42 and supplied to the pilot burner 50. The pilot burner 50 is ignited by an ignition device (not shown).

[0066] In this embodiment, the pilot burner 50 is used to enable more stable ignition.

[0067] In this embodiment, when a command to start combustion is input to the control unit 40 after the completion of the furnace pre-purge (scavenging) operation, the ignition operation is performed and the second main combustion switching processing program is executed. After the furnace temperature T3 reaches or exceeds the main switching temperature T1, ammonia gas can be burned at a desired flow rate for main combustion, thereby enabling stable combustion of ammonia gas. Note that in step S18, the pilot gas adjustment valve 24V may not be closed and combustion may continue together with the combustion of the main gas.

[0068] Furthermore, when the supply of reformed ammonia gas from the pilot gas passage 24 is cut off at the time of switching to the main combustion, ammonia gas is supplied as fuel gas from the main gas passage 22 to the main burner 30 without passing through the reforming section 20, so that reforming of ammonia gas becomes unnecessary during steady combustion of the main burner after ignition.

[0069] <Test example> Figure 10 shows the relationship between the ammonia gas reforming rate and unburned ammonia gas, and the relationship between the ammonia gas reforming rate and NO2 when reformed ammonia gas with different ammonia gas reforming rates is ignited and burned in a combustion furnace at room temperature. X1 is a graph showing the relationship between NOx emission concentration (assuming that the NOx emission concentration at a reforming rate of 40% is 1.0) and the amount of ammonia gas emitted from the flue as unburned gas when the reforming rate is less than 40%, but it was confirmed that at reforming rates of 40% or more, the emission of unburned ammonia gas is almost eliminated.

[0070] Also, up to a reforming rate of 40%, NO X The emission concentration of NO is less than 1.0, but at a reforming rate of 50% to 60%, X It was confirmed that the NO emission concentration increased to about 2.6. When the reforming rate exceeded 60%, the amount of ammonia gas itself decreased, so NO X It is thought that the emission concentration of

[0071] Thus, combustion tests in a combustion furnace have shown that reformed ammonia gas with a reforming rate of 40% or more can be combusted well, and NO emissions are low when reformed ammonia gas with a reforming rate of less than 50% is combusted. X It was confirmed that emissions could be reduced. [Explanation of symbols]

[0072] 10A Ammonia Combustion Device 10B Ammonia combustion device 10C Ammonia Combustion Device 10D Ammonia Combustion Apparatus 20 Modification section 22 Main gas flow path 30 Main Burner 34 Pilot flow path (pilot section) 40 Control Unit 50 Pilot burner (pilot section)

Claims

1. a main burner to which a fuel gas containing ammonia is supplied from the main flow path and which burns the fuel gas; a reforming unit that generates reformed ammonia gas with a reforming rate of 40% or more by decomposing a portion of ammonia into hydrogen and nitrogen; a pilot section to which the reformed ammonia gas is supplied from the reforming section and which ignites combustion in the main burner; An ammonia combustion device comprising:

2. 2. The ammonia combustion device according to claim 1, wherein the reformed ammonia gas has a reforming rate of less than 50%.

3. 2. The ammonia combustion apparatus according to claim 1, further comprising: a control unit that controls a main valve to start supplying the fuel gas from the main flow path to the main burner when a temperature inside the combustion furnace in which a combustion flame of the main burner is maintained is 750°C or higher.

4. 4. The ammonia combustion apparatus according to claim 3, wherein the control unit controls a reforming rate in the reforming unit so that, after starting to supply the fuel gas from the main flow path to the main burner, reformed ammonia gas reformed in the reforming unit at a reforming rate of less than 40% is supplied to the main flow path as the fuel gas.

5. 4. The ammonia combustion apparatus according to claim 3, wherein the control unit controls a valve so that, after starting supply of the fuel gas to the main burner, ammonia gas that does not pass through the reforming unit is supplied to the main flow path as the fuel gas.

6. Part of the ammonia is reformed into hydrogen and nitrogen to produce reformed ammonia gas with a reforming rate of 40% or more, The reformed ammonia gas is used to ignite combustion in a main burner. Ammonia combustion method.

7. 7. The method for burning ammonia according to claim 6, wherein the reformed ammonia gas has a reforming rate of less than 50%.

8. 7. The method for burning ammonia according to claim 6, wherein the supply of fuel gas for main combustion to the main burner is started when the temperature inside the combustion furnace in which the combustion flame of the main burner is maintained is 750°C or higher.

9. 9. The ammonia combustion method according to claim 8, wherein after the supply of the main combustion fuel gas to the main burner is started, a reformed ammonia gas having a reforming rate of less than 40% is supplied to the main burner.

10. 9. The ammonia combustion method according to claim 8, wherein after starting the supply of fuel gas for main combustion to the main burner, unreformed ammonia gas is supplied to the main burner as the fuel gas for main combustion.

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