JP7507699B2 - Industrial Furnace - Google Patents

Description

The present invention relates to an industrial furnace equipped with a combustion burner that mixes ammonia or other low-combustible fuel with combustion air and burns it. In particular, the present invention is characterized in that, when the flame that is burning the ammonia or other low-combustible fuel in the combustion burner goes out, the low-combustible fuel can be reliably prevented from being exhausted from inside the industrial furnace to the outside using simple equipment.

In combustion burners, which mix fuel with combustion air and burn it, highly combustible hydrocarbon fuels are generally used as the fuel.

However, when hydrocarbon fuel is mixed with combustion air and burned in a combustion burner in this way, there is a problem in that a large amount of greenhouse gases such as carbon dioxide is generated.

In recent years, there has been a demand to reduce greenhouse gases such as carbon dioxide, and the use of fuels other than hydrocarbon fuels has been considered.

It has also been known for some time that ammonia, a low-combustibility fuel, can be used as fuel in combustion burners.

However, ammonia has poorer combustibility than hydrocarbon fuels and is prone to misfires during combustion, which can lead to problems such as ammonia being discharged from the inside of an industrial furnace to the outside and having a negative impact on the environment. In addition, when the combustion conditions are strengthened to fully burn ammonia, there is a problem in that NOx is easily generated during combustion.

In the past, when burning ammonia, a low-combustibility fuel with poor combustibility, a diffuser was placed downstream of the burner tip that ejects ammonia into the fuel, and the ammonia was mixed with naturally aspirated combustion air by bypassing the diffuser, and the ammonia and combustion air thus mixed were made to swirl and remain above the diffuser for combustion, as shown in Patent Document 1, which has been proposed to increase the combustibility of the ammonia.

However, when the combustion air is naturally aspirated as in Patent Document 1, it is difficult to use it in a large combustion burner that burns a large amount of ammonia. Also, when the ammonia and the combustion air are made to swirl and remain on the upper side of the diffuser as described above, and the ammonia is burned all at once, the flame temperature during combustion becomes high, resulting in the generation of large amounts of NOx.

Patent Document 2 also proposes premixing ammonia, a low-combustibility fuel, with combustion air to make it homogenous, and then burning the premixed gas while swirling it with a swirler to strongly stir it, thereby increasing the combustibility of the ammonia.

However, when a premixed gas of ammonia and combustion air is swirled and strongly stirred by a swirler and burned as in Patent Document 2, there is a problem that the ammonia is burned all at once, raising the flame temperature and generating a lot of NOx, just as in Patent Document 1.

In addition, in both of the above-mentioned patent documents 1 and 2, if the flame of the combustion burner burning low-combustible fuel such as ammonia goes out, the unburned low-combustible fuel such as ammonia is exhausted from inside the industrial furnace to the outside, and in particular when the low-combustible fuel is ammonia, it is toxic and emits an irritating odor even at only 1 ppm, causing a problem of adverse effects on the environment.

Japanese Utility Model Publication No. 50-8257 JP 2016-130619 A

The present invention aims to solve the above-mentioned problems in industrial furnaces equipped with combustion burners that mix low-combustibility fuels such as ammonia with combustion air and burn them.

In other words, the objective of the present invention is to reliably prevent low-combustible fuel such as ammonia from being exhausted from inside the industrial furnace to the outside, even if the flame burning the low-combustible fuel such as ammonia goes out, in an industrial furnace in which low-combustible fuel such as ammonia is mixed with combustion air and burned by a combustion burner, using simple equipment.

In order to solve the above-mentioned problems, the industrial furnace according to the present invention is provided with an industrial furnace in which low combustible fuel supplied through a low combustible fuel supply pipe is mixed with combustion air supplied through an air supply pipe and burned in the furnace by a combustion burner, the industrial furnace is provided with a flame detection device which detects the state of the flame in the combustion burner, a control device which outputs the state of the flame detected by the flame detection device, and a processing burner which burns the high combustible fuel supplied through a high combustible fuel pipe in the furnace, and when an extinguishment of the flame in the combustion burner is detected by the flame detection device and output to the control device, the control device stops the supply of low combustible fuel to the combustion burner through the low combustible fuel supply pipe, while supplying high combustible fuel to the processing burner through the high combustible fuel pipe, and supplies combustion air through an air supply pipe different from the air supply pipe , thereby burning the low combustible fuel in the furnace together with the high combustible fuel and preventing the low combustible fuel in the furnace from being exhausted to the outside.

In this way, a flame detection device that detects the state of the flame in the combustion burner, a control device that outputs the state of the flame detected by the flame detection device, and a processing burner that burns the high-combustible fuel supplied through the high-combustible fuel pipe in the furnace are provided, and the flame misfire in the combustion burner is detected by the flame detection device and output to the control device, which stops the supply of low-combustible fuel to the combustion burner through the low-combustible fuel supply pipe and supplies high-combustible fuel to the processing burner through the high-combustible fuel pipe to combust the low-combustible fuel in the furnace together with the high-combustible fuel. This prevents the low-combustible fuel remaining in the furnace without being burned from being exhausted to the outside of the industrial furnace even if the flame in the combustion burner misfires.

Furthermore, in the industrial furnace of the present invention, when the high combustible fuel is supplied to the processing burner through the high combustible fuel pipe as described above and the low combustible fuel in the furnace is combusted together with the high combustible fuel, combustion air is supplied to the processing burner through an air supply pipe, so that the high combustible fuel is reliably combusted by the combustion air and the low combustible fuel in the furnace is reliably combusted together with the high combustible fuel.

In addition, in the low combustible fuel combustion burner according to the present invention, ammonia NH ₃ can be used as the low combustible fuel. Even if ammonia NH ₃ is used as the low combustible fuel in this way and the flame in the combustion burner goes off and ammonia NH ₃ remains in the furnace without being burned, this ammonia NH ₃ is burned together with the highly combustible fuel in the furnace, and ammonia NH ₃ is not exhausted from the furnace to the outside, causing adverse effects on the environment.

As the highly combustible fuel, hydrogen _H2 or a hydrocarbon fuel can be used, but it is particularly preferable to use hydrogen _H2 . Since hydrogen _H2 does not generate carbon dioxide when burned, when hydrogen _H2 is used as the highly combustible fuel, it is possible to prevent the generation of greenhouse gases such as carbon dioxide when it is burned together with a low-combustible fuel, as in the case of using a hydrocarbon fuel. When hydrogen _H2 is used as the highly combustible fuel, it is preferable to store hydrogen _H2 in a hydrogen cylinder and supply hydrogen _H2 from the hydrogen cylinder to the treatment burner through a highly combustible fuel pipe so that it can be easily installed and used as needed.

In the industrial furnace of the present invention, the low-combustible fuel supplied through the low-combustible fuel supply pipe is mixed with the combustion air supplied through the air supply pipe and burned in the furnace by the combustion burner, as described above. A flame detection device that detects the state of the flame in the combustion burner, a control device that outputs the state of the flame detected by the flame detection device, and a processing burner that burns the high-combustible fuel supplied through the high-combustible fuel pipe in the furnace are provided. The flame detection device detects the misfire of the flame in the combustion burner and outputs it to the control device. This control device stops the supply of low-combustible fuel to the combustion burner through the low-combustible fuel supply pipe and supplies high-combustible fuel to the processing burner through the high-combustible fuel pipe, so that the low-combustible fuel in the furnace is burned together with the high-combustible fuel. Therefore, even if the flame in the combustion burner misfires, the low-combustible fuel that remains unburned in the furnace is burned together with the high-combustible fuel, and it becomes possible to prevent the low-combustible fuel from being exhausted from the industrial furnace to the outside with simple equipment.

FIG. 1 is a schematic cross-sectional view illustrating a state in which low-combustibility fuel supplied through a low-combustibility fuel supply pipe is mixed with combustion air supplied through an air supply pipe and combusted in the furnace by a combustion burner in an industrial furnace according to one embodiment of the present invention. This is a schematic cross-sectional diagram showing a state in which, in an industrial furnace according to the same embodiment, when a flame detection device detects that a flame in a combustion burner has gone out, the control device stops the supply of low combustible fuel to the combustion burner through the low combustible fuel supply pipe and supplies high combustible fuel to a processing burner through the high combustible fuel pipe, thereby burning the low combustible fuel together with the high combustible fuel in the furnace.

The following describes in detail an industrial furnace according to an embodiment of the present invention with reference to the accompanying drawings. Note that the industrial furnace according to the present invention is not limited to the embodiment shown below, and can be modified as appropriate within the scope of the invention.

In the industrial furnace of this embodiment, as shown in Figs. 1 and 2, ammonia _NH3 as a low combustible fuel is supplied to a combustion burner 11 provided in a furnace 10 through a low combustible fuel supply pipe 12, and combustion air Air is supplied from a blower 13 through an air supply pipe 14, so that the ammonia _NH3 is mixed with the combustion air Air and combusted in the furnace 10 by the combustion burner 11. The combustion exhaust gas after the combustion of ammonia _NH3 is led from the furnace 10 through a flue 31 to a chimney 30 and exhausted to the outside.

In addition, in this embodiment, a flame detection device 21 is provided to detect the state of the flame in the combustion burner 11, and the state of the flame detected by this flame detection device 21 is output to the control device 20.

In this embodiment, hydrogen _H2 is used as the highly combustible fuel, and hydrogen _H2 is supplied from a hydrogen cylinder 15 containing hydrogen _H2 through a highly combustible fuel pipe 16 to a processing burner 17, which burns the hydrogen H2 in the furnace 10. In this embodiment, hydrogen _H2 is supplied from the hydrogen cylinder 15 to the processing burner 17, but it is also possible to supply hydrogen _H2 to the processing burner 17 from _a hydrogen supply device (not shown) that can continuously supply hydrogen _H2 .

In this embodiment, in order to ensure that hydrogen H ₂ is combusted in the furnace 10 by the treatment burner 17, when hydrogen H ₂ is combusted, combustion air Air is supplied to the treatment burner 17 through the air supply pipe 18. When hydrogen H ₂ is combusted in the furnace 10 by the treatment burner 17, if the temperature in the furnace 10 is equal to or higher than the self-combustion temperature of hydrogen H ₂ or ammonia NH ₃ and the amount of oxygen required to combust hydrogen H ₂ is present in the furnace 10, it is not necessary to supply combustion air Air to the treatment burner 17 as described above. However , in this way, when hydrogen H ₂ is combusted in the furnace 10 by the treatment burner 17, even if the temperature in the furnace 10 is equal to or lower than the self-combustion temperature of hydrogen H ₂ or ammonia NH ₃ or if the amount of oxygen required to combust hydrogen H ₂ is not present in the furnace 10, hydrogen H ₂ is reliably combusted together with ammonia NH ₃ in the treatment burner 17 by the combustion air Air.

Here, in this embodiment, when ammonia NH ₃ , which is a low combustible fuel, is burned in the combustion burner 11, as shown in Fig. 1, the control device 20 opens the on-off valve 12a provided in the low combustible fuel supply pipe 12 to supply ammonia NH ₃ to the combustion burner 11, and starts the blower 13 to supply combustion air Air through the air supply pipe 14, while closing the on-off valve 16a provided in the high combustible fuel pipe 16 that supplies hydrogen H ₂ , which is a high combustible fuel, from the hydrogen cylinder 15 to the treatment burner 17, and the on-off valve 18a provided in the air supply pipe 18 to prevent hydrogen H ₂ from being supplied to the treatment burner 17. In the figure, the open states of the on-off valves 12a, 16a, and 18a are shown in white, and the closed states are shown in black.

The ammonia (NH _{3 )} supplied through the low combustible fuel supply pipe 12 as described above is mixed with the combustion air (Air) supplied through the air supply pipe 14, and combusted in the furnace 10 by the combustion burner 11.

The state of the flame in which ammonia NH ₃ is burned in the furnace 10 by the combustion burner 11 is detected by the flame detection device 21, and the result is output to the control device 20.

Here, when the flame of ammonia NH ₃ being burned in the furnace 10 by the combustion burner 11 goes out and ammonia NH ₃ is no longer burned, as shown in Fig. 2, the flame detector 21 detects the flame extinction in the combustion burner 11 and outputs the result to the control device 20. Then, this control device 20 closes the opening and closing valve 12a in the low combustible fuel supply pipe 12 to prevent ammonia NH ₃ from being supplied to the combustion burner 11, while opening the opening and closing valve 16a in the high combustible fuel pipe 16 to supply hydrogen H ₂ , which is a highly combustible fuel, from the hydrogen cylinder 15 to the treatment burner 17, and opens the opening and closing valve 18a in the air supply pipe 18 to supply combustion air Air to the treatment burner 17, so that the ammonia NH ₃ remaining in the furnace 10 without being burned is burned together with the highly combustible fuel hydrogen H ₂ .

In this way, the ammonia _NH3 remaining in the furnace 10 without being combusted by the combustion burner 11 is combusted together with the highly combustible fuel hydrogen _H2 , and the ammonia _NH3 is prevented from being led from the inside of the furnace 10 through the flue 31 to the chimney 30 and exhausted to the outside, so that adverse effects on the environment can be easily suppressed.

In addition, in this embodiment, hydrogen _H2 is used as the highly combustible fuel supplied to the processing burner 17 through the highly combustible fuel pipe 16. This prevents the generation of greenhouse gases such as carbon dioxide when the highly combustible fuel is combusted together with ammonia _NH3 , which is a low combustible fuel, as occurs when a hydrocarbon fuel is used as the highly combustible fuel.

Furthermore, in this embodiment, hydrogen _H2 as a highly combustible fuel is stored in a hydrogen cylinder 15, and hydrogen _H2 is supplied from this hydrogen cylinder 15 to the treatment burner 17 through a highly combustible fuel pipe 16. Therefore, the equipment for supplying hydrogen _H2 to the treatment burner 17 can be installed easily and at low cost.

Reference Signs List 10: Furnace 11: Combustion burner 12: Low flammability fuel supply pipe 12a: Opening and closing valve 13: Blower 14: Air supply pipe 15: Hydrogen cylinder 16: High flammability fuel pipe 16a: Opening and closing valve 17: Treatment burner 18: Air supply pipe 18a: Opening and closing valve 20: Control device 21: Flame detection device 30: Chimney 31: Flue Air: Combustion air _H2 : Hydrogen (highly flammable fuel)
_NH3 : Ammonia (low combustibility fuel)

Claims (4)

1. An industrial furnace in which low combustible fuel supplied through a low combustible fuel supply pipe is mixed with combustion air supplied through an air supply pipe and burned inside the furnace by a combustion burner, the industrial furnace comprising: a flame detection device for detecting a flame state in the combustion burner; a control device which outputs the flame state detected by the flame detection device; and a processing burner for burning the high combustible fuel supplied through a high combustible fuel pipe in the furnace, wherein when an extinction of a flame in the combustion burner is detected by the flame detection device and output to the control device, the control device stops the supply of low combustible fuel to the combustion burner through the low combustible fuel supply pipe, while supplying high combustible fuel to the processing burner through the high combustible fuel pipe and supplying combustion air through an air supply pipe different from the air supply pipe , thereby burning the low combustible fuel in the furnace together with the high combustible fuel and preventing the low combustible fuel in the furnace from being exhausted to the outside. The industrial furnace according to claim 1, characterized in that the low-combustibility fuel is ammonia. The industrial furnace according to claim 1 or 2, characterized in that the highly combustible fuel is hydrogen. The industrial furnace according to claim 3, characterized in that the highly combustible fuel hydrogen is stored in a hydrogen cylinder and supplied from the hydrogen cylinder to the treatment burner through a highly combustible fuel pipe.

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