JP2014043387A - Combustion system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion system which can improve the combustion efficiency of a combustion device.SOLUTION: A combustion system includes a combustion device 1 using ammonia gas as a fuel, a pyrolysis device 3 heating ammonia gas to decompose it into nitrogen gas and hydrogen gas, and a hydrogen gas heat exchanger 4 that exchanges heat between hydrogen gas decomposed and generated by the pyrolysis device 3, and ammonia gas to be decomposed by the pyrolysis device 3. The combustion device 1 includes supply means 12 that supplies hydrogen gas for which heat exchange is performed by the hydrogen gas heat exchanger 4.

Description

  The present invention relates to a combustion system including a combustion device using ammonia gas as fuel.

  In recent years, an ammonia engine has attracted attention as an engine using a renewable fuel from the viewpoint of environmental conservation such as prevention of global warming. However, since the ammonia engine uses flame retardant ammonia gas as a fuel, it is necessary to devise measures for making the ammonia gas easily burnable. For this reason, the conventional ammonia engine arranges a plurality of spark plugs in the combustion chamber and generates ignition fire nuclei at a plurality of locations so that ammonia gas is easily burned (for example, Patent Document 1). reference).

JP 2010-159705 A

However, in this type of ammonia engine, the efficiency of ammonia gas supplied into the combustion chamber is still low, and ammonia odor is generated from the exhaust pipe due to incomplete combustion. is there.
This invention is made | formed in view of this situation, and it aims at providing the combustion system which can improve the combustion efficiency of a combustion apparatus.

In order to achieve the above object, a combustion system of the present invention is a combustion system including a combustion apparatus using ammonia gas as a fuel, and a thermal decomposition apparatus that heats the ammonia gas and decomposes it into nitrogen gas and hydrogen gas; A hydrogen gas heat exchanger that exchanges heat between the hydrogen gas decomposed and generated by the thermal decomposition apparatus and the ammonia gas decomposed by the thermal decomposition apparatus, and the combustion apparatus includes the hydrogen gas therein It has a supply means which supplies the hydrogen gas heat-exchanged with the gas heat exchanger.
According to the combustion system of the present invention, the ammonia gas is decomposed into nitrogen gas and hydrogen gas by the thermal decomposition apparatus, and this combustible hydrogen gas is supplied to the combustion apparatus. Can be made. Moreover, in the hydrogen gas heat exchanger, the ammonia gas can be heated by the heat of the decomposed hydrogen gas, so that the hydrogen gas can be efficiently decomposed and generated from the ammonia gas. Thereby, the combustion efficiency of a combustion apparatus can further be improved. In addition, since hydrogen gas is supplied to the combustion device at a lower temperature than when it is decomposed, it is possible to suppress the supply means of the combustion device from being heated and damaged by the hydrogen gas.

The combustion system preferably includes an exhaust gas heat exchanger that exchanges heat between exhaust gas exhausted from the combustion device and ammonia gas decomposed by the thermal decomposition device.
In this case, in the exhaust gas heat exchanger, the ammonia gas can be preheated by the heat of the exhaust gas exhausted from the combustion device, so that the hydrogen gas can be decomposed and generated more efficiently from the ammonia gas.

The hydrogen gas heat exchanger preferably exchanges heat of the ammonia gas heat-exchanged by the exhaust gas heat exchanger.
In this case, ammonia gas is heated with a relatively low temperature exhaust gas in the exhaust gas heat exchanger and then heated with a relatively high temperature hydrogen gas in the hydrogen gas heat exchanger, so the ammonia gas is efficiently heated. I can do it.

The hydrogen gas heat exchanger has a cylindrical member that covers the outside of the thermal decomposition apparatus, and the hydrogen gas and ammonia supplied into the thermal decomposition apparatus by introducing the hydrogen gas into the cylindrical member. It is preferable to exchange heat with the gas.
In this case, since the hydrogen gas heat exchanger can be integrally provided outside the thermal decomposition apparatus, the entire system can be made compact.

The combustion system is provided with a plurality of the pyrolysis devices, and the cylinder member is provided with a plurality so as to cover the outside of each of the pyrolysis devices, and the plurality of the pyrolysis devices are connected in series. A first introduction path for sequentially introducing ammonia gas into the thermal decomposition apparatus, and hydrogen gas discharged from the thermal decomposition apparatus disposed on the most downstream side of the first introduction path are sequentially introduced into the cylinder members. It is preferable to provide the 2nd introduction path for this.
In this case, hydrogen gas can be efficiently decomposed and generated from ammonia gas by sequentially introducing ammonia gas into a plurality of thermal decomposition apparatuses. Further, since heat is sequentially exchanged between the hydrogen gas generated by decomposition and the ammonia gas introduced into each thermal decomposition apparatus, the ammonia gas can be efficiently heated and the hydrogen gas can be efficiently converted. Can be cooled to.

In the combustion system, it is preferable that the order of introducing hydrogen gas through the second introduction path is reverse to the order of introduction of ammonia gas through the first introduction path.
In this case, since the ammonia gas and the hydrogen gas that are heat-exchanged with each other in each cylinder member can be in an appropriate temperature relationship, the heat exchange between the ammonia gas and the hydrogen gas can be performed efficiently.

  According to the combustion system of the present invention, the combustion efficiency of the combustion apparatus can be improved.

It is a mimetic diagram showing composition of an ammonia engine system concerning a 1st embodiment of the present invention. It is sectional drawing which shows the thermal decomposition apparatus of the said ammonia engine system. It is sectional drawing which shows the hydrogen gas heat exchanger of the said ammonia engine system. It is a schematic diagram which shows the structure of the thermal decomposition and heat exchange of the ammonia engine system which concerns on the 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing a configuration of an ammonia engine system (combustion system) according to a first embodiment of the present invention. In FIG. 1, an ammonia engine system of this embodiment includes an ammonia engine (combustion device) 1 using 100% ammonia gas as a fuel, a tank 2 for storing ammonia gas, and a thermal decomposition device 3 for decomposing ammonia gas. A cracked product gas heat exchanger (hydrogen gas heat exchanger) 4 for exchanging heat between the cracked product gas containing hydrogen gas and nitrogen gas generated by cracking and ammonia gas, and an exhaust gas and ammonia gas of the ammonia engine 1 And an exhaust gas heat exchanger 5 for exchanging heat with each other.

  The ammonia engine 1 includes a cylinder 11 having a combustion chamber 11a therein, supply means 12 for supplying cracked product gas into the combustion chamber 11a, and hydrogen gas in the cracked product gas supplied into the combustion chamber 11a. The ignition apparatus 13 and the discharge means 14 which discharge | emit the exhaust gas after combustion from the inside of the combustion chamber 11a are provided.

  The cylinder 11 includes a cylindrical cylinder liner 11b, a cylinder head 11c that covers an upper opening of the cylinder liner 11b, and a piston 11d that is provided in the cylinder liner 11b so as to reciprocate. A space surrounded by the cylinder liner 11b, the cylinder head 11c, and the piston 11d is a combustion chamber 11a. The cylinder head 11c is formed with a supply hole 11c1 for supplying the decomposition product gas into the combustion chamber 11a and a discharge hole 11c2 for discharging the exhaust gas to the outside.

The ignition device 13 is made of, for example, an ignition plug, and is fixed so as to penetrate in the thickness direction at the center of the cylinder head 11c. An igniter 13 a that ignites hydrogen gas in the decomposition product gas is provided at the lower end of the ignition device 13.
The supply means 12 includes a supply valve 12a for opening and closing the supply hole 11c1 of the cylinder head 11c, and heat is exchanged in the cracked gas heat exchanger 4 by opening the supply valve 12a by a drive means (not shown). The decomposition product gas is supplied from the supply hole 11c1 into the combustion chamber 11a.
The discharge means 14 includes a discharge valve 14a that opens and closes the discharge hole 11c2 of the cylinder head 11c, and exhausts exhaust gas after combustion in the combustion chamber 11a by opening the discharge valve 14a by a drive means (not shown). The gas is discharged from the hole 11c2.

FIG. 2 is a cross-sectional view showing the thermal decomposition apparatus 3. In FIG. 2, the thermal decomposition apparatus 3 heats ammonia gas (NH ₃ ) and performs an endothermic decomposition reaction into nitrogen gas (N ₂ ) and hydrogen gas (H ₂ ) as shown in the following formula (1). Is.
2NH ₃ → N ₂ + 3H ₂ (1)
The pyrolysis apparatus 3 includes a case 31 whose inside is sealed, an outer metal tube 32 fixed to the case 31, an inner metal tube 33 fixed to the outer metal tube 32, and an inner metal tube 33. A heater 34 and a temperature detection sensor 35 are provided.

  The outer metal tube 32 is disposed inside the case 31. Both end portions in the axial direction of the outer metal tube 32 pass through both side walls 31a and 31b of the case 31 and are fixed to the side walls 31a and 31b. Lid members 36 and 37 for closing these openings are attached to both ends of the outer metal tube 32 in the axial direction, and the inside of the outer metal tube 32 is sealed.

The inner metal tube 33 is disposed along the axial direction inside the outer metal tube 32. Both end portions in the axial direction of the inner metal tube 33 are fixed to the lid members 36 and 37 through the lid members 36 and 37, respectively. A sealed heat insulating space S is formed between the outer metal tube 32 and the inner metal tube 33.
An inlet port 33a is formed at one end (left end in FIG. 2) in the axial direction of the inner metal tube 33 so that ammonia gas heat-exchanged by the cracked product gas heat exchanger 4 is introduced from the inlet port 33a. (See FIG. 1). A discharge pipe 38 extending radially outward is connected to the other axial end of the inner metal pipe 33 (the right end in FIG. 2), and is decomposed and generated from the ammonia gas introduced into the inner metal pipe 33. The cracked product gas is discharged from the discharge pipe 38.

The heater 34 is made of a heating wire such as a nichrome wire that generates heat when energized, and is arranged in a spiral shape along the inner peripheral surface of the inner metal tube 33. The heater 34 heats the ammonia gas introduced into the inner metal tube 33 to a predetermined temperature (700 to 900 ° C.). In addition to the heating wire, the heater 34 may use other heat sources such as heat rays, plasma heat, hot air, infrared rays, and electromagnetic waves.
The temperature detection sensor 35 is made of, for example, a thermocouple wire, and is arranged along the axial direction inside the inner metal tube 33. By measuring the temperature of the ammonia gas in the inner metal pipe 33 by the temperature detection sensor 35, the energization to the heater 34 is controlled.

  In FIG. 1, the exhaust gas heat exchanger 5 includes a case 51 having an introduction port 51a and an exhaust port 51b, and a metal exhaust gas introduction pipe 52 disposed through the case 51. Low temperature (0 ° C. or lower) ammonia gas is introduced from the tank 2 into the inlet 51 a of the case 51. An opening / closing valve 6 is provided in a connection path connecting the tank 2 and the introduction port 51a. A discharge port 51b of the case 51 is configured to discharge ammonia gas after heat exchange.

  One end (the lower end in FIG. 1) of the exhaust gas introduction pipe 52 communicates with the exhaust hole 11c2 of the ammonia engine 1, and high-temperature (about 400 ° C.) exhaust gas exhausted from the exhaust hole 11c2 is introduced into the exhaust gas. It is introduced into the pipe 52 and exhausted to the outside. At that time, when the exhaust gas passes through the exhaust gas introduction pipe 52 disposed in the case 51 of the exhaust gas heat exchanger 5, the high-temperature exhaust gas and the low-temperature ammonia gas introduced into the case 51 Heat exchange between the two. That is, the high temperature exhaust gas is cooled by the low temperature ammonia gas, and the low temperature ammonia gas is preheated to a predetermined temperature (about 20 ° C.) by the high temperature exhaust gas.

  FIG. 3 is a cross-sectional view showing the cracked product gas heat exchanger 4. In FIG. 3, the decomposition product gas heat exchanger 4 of the present embodiment includes a metal outer cylindrical member 41 formed in a substantially cylindrical shape, and a metal outer cylinder member 41 disposed coaxially within the outer cylindrical member 41. An inner cylindrical member 42. The outer cylinder member 41 is formed by integrally forming a main body 41a and an introduction portion 41b and a discharge portion 41c that are larger in diameter than the outer diameter of the main body 41a at both axial ends of the main body 41a. .

An introduction port 41b1 is formed in the introduction part 41b, and the introduction port 41b1 communicates with the discharge pipe 38 of the thermal decomposition apparatus 3 (see FIG. 1). Thereby, the decomposition product gas discharged from the thermal decomposition apparatus 3 is introduced into the outer cylindrical member 41 of the decomposition product gas heat exchanger 4.
A discharge port 41c1 is formed in the discharge part 41c, and the discharge port 41c1 communicates with the supply hole 11c1 of the ammonia engine 1 (see FIG. 1). An adjustment valve 9 is provided in the middle of the communication path. Thereby, the decomposition product gas introduced into the outer cylinder member 41 is supplied to the ammonia engine 1 after heat exchange. At that time, the supply amount of the cracked product gas to the ammonia engine 1 is adjusted by adjusting the opening and closing of the regulating valve 9.

  Both ends in the axial direction of the inner cylinder member 42 are fixed to the introduction part 41b and the discharge part 41c of the outer cylinder member 41, respectively. An inlet 42a for introducing ammonia gas is formed at one axial end of the inner cylindrical member 42 (upper end in FIG. 3), and ammonia is introduced at the other axial end of the inner cylindrical member 42 (lower end in FIG. 3). A discharge port 42b for discharging gas is formed. A heater 44 and a temperature detection sensor 45 are disposed inside the inner cylindrical member 42.

The heater 44 is made of a heating wire such as a nichrome wire that generates heat when energized, and is arranged in a spiral shape along the inner peripheral surface of the inner cylindrical member 42. The heater 44 heats the ammonia gas introduced into the inner cylinder member 42. In addition to the heating wire, the heater 44 may use other heat sources such as heat rays, plasma heat, hot air, infrared rays, and electromagnetic waves.
The temperature detection sensor 45 is made of, for example, a thermocouple wire, and is disposed along the axial direction inside the inner cylindrical member 42. By measuring the temperature of the ammonia gas in the inner cylinder member 42 by the temperature detection sensor 45, energization to the heater 44 is controlled.

As shown in FIG. 1, the inlet 42 a of the inner cylinder member 42 communicates with the outlet 51 b of the exhaust gas heat exchanger 5, and the ammonia gas heat-exchanged by the exhaust gas heat exchanger 5 is decomposed product gas. It is introduced into the inner cylindrical member 42 of the heat exchanger 4 and heated by the heater 44. Thereby, heat exchange is performed between the ammonia gas introduced into the inner cylinder member 42 and the decomposition product gas introduced into the outer cylinder member 41. That is, the decomposition product gas is cooled to about 50 ° C. by a low temperature (about 20 ° C.) ammonia gas, and the low temperature ammonia gas is about 400 ° C. by the high temperature (700 to 900 ° C.) decomposition product gas and the heater 44. Heated.
The discharge port 42b of the inner cylinder member 42 communicates with the inlet 33a of the thermal decomposition apparatus 3, and the ammonia gas introduced into the inner cylinder member 42 is introduced into the thermal decomposition apparatus 3 after heat exchange.

  As described above, according to the ammonia engine system of the present embodiment, the thermal decomposition apparatus 3 decomposes ammonia gas into nitrogen gas and hydrogen gas, and supplies the ammonia engine 1 with the decomposition product gas containing hydrogen gas that is easy to burn. Therefore, the ammonia engine 1 can be burned efficiently, and the ammonia odor can be suppressed. Moreover, the low-temperature ammonia gas in the tank 2 is introduced into the exhaust gas heat exchanger 5 and heated by the high-temperature exhaust gas, and then introduced into the cracked product gas heat exchanger 4 and further introduced by the high-temperature cracked product gas. Since it is heated, the sufficiently heated ammonia gas can be introduced into the thermal decomposition apparatus 3. As a result, hydrogen gas can be efficiently decomposed and produced from ammonia gas, so that the combustion efficiency of the ammonia engine can be further improved.

In addition, since the high-temperature decomposition product gas decomposed and generated by the thermal decomposition apparatus 3 is introduced into the decomposition product gas heat exchanger 4 and cooled by low-temperature ammonia gas, the decomposition product gas is cooled at a lower temperature than that during decomposition generation. In this state, the ammonia engine 1 can be supplied. Thereby, it can suppress that the supply valve 12a, piping, etc. of the supply means 12 of the ammonia engine 1 are heated and damaged by the decomposition product gas.
In addition, the ammonia gas is heated by the exhaust gas heat exchanger 5 with a relatively low temperature exhaust gas and then preheated by the decomposition product gas heat exchanger 4 with a relatively high temperature decomposition product gas. It can be heated efficiently.

  FIG. 4 is a schematic diagram showing a configuration of thermal decomposition and heat exchange of the ammonia engine system according to the second embodiment of the present invention. In FIG. 4, the ammonia engine system of the present embodiment includes a plurality (six in this embodiment) of thermal decomposition apparatuses 3, a plurality (six in this embodiment) of cracked product gas heat exchangers 4, and a single unit. The exhaust gas heat exchanger 5 is provided. In addition, the number of the thermal decomposition apparatuses 3 and the number of the cracked product gas heat exchangers 4 can be set to an arbitrary number of two or more according to the amount of fuel. Further, the ammonia engine system of the present embodiment includes the ammonia engine 1 and the tank 2 as in the first embodiment, but these are not shown in FIG.

  The thermal decomposition apparatus 3 includes a heater 34 and a temperature detection sensor 35 disposed inside an inner metal tube 33. Both end portions in the axial direction of the inner metal tube 33 are fixed to an outer cylindrical member 41 described later. An inlet 33a for introducing ammonia gas is formed at one axial end of the inner metal tube 33, and an exhaust port for discharging decomposition product gas decomposed from the ammonia gas at the other axial end of the inner metal tube 33. 33b is formed. As will be described later, ammonia gas that has not been decomposed in the inner metal tube 33 is also discharged from the discharge port 33b.

  The cracked product gas heat exchanger 4 has an outer cylinder member 41 that covers the outer side of the inner metal tube 33 of the pyrolyzer 3. An inlet 41b1 for introducing decomposition product gas is formed at one axial end of the outer cylindrical member 41, and a discharge port 41c1 for discharging heat exchanged decomposition product gas is formed at the other axial end of the inner metal tube 33. Is formed. As a result, heat exchange is performed between the ammonia gas introduced into the inner metal tube 33 of the thermal decomposition apparatus 3 and the decomposition product gas introduced into the outer cylindrical member 41. That is, the decomposition product gas is cooled by the low temperature ammonia gas, and the low temperature ammonia gas is heated by the high temperature decomposition product gas.

The ammonia engine system of this embodiment further includes a first introduction path 7 that connects a plurality of thermal decomposition apparatuses 3 in series, and a second introduction path 8 that connects a plurality of cracked gas heat exchangers 4 in series. ing.
The first introduction path 7 sequentially introduces ammonia gas into each thermal decomposition apparatus 3, and a plurality of (this book) connecting one inlet 33a and the other outlet 33b of the adjacent thermal decomposition apparatuses 3 are connected. In the embodiment, there are five introduction path portions 7a to 7e. The inlet 33a of the thermal decomposition apparatus 3 arranged in the most upstream (the rightmost side in FIG. 4) communicates with the outlet 51b of the exhaust gas heat exchanger 5. As a result, the ammonia gas heat-exchanged in the exhaust gas heat exchanger 5 is introduced into the most upstream thermal decomposition apparatus 3 through the introduction path portion 7 a and decomposed by being heated by the heater 34.

  At that time, the ammonia gas may be discharged from the thermal decomposition apparatus 3 without being decomposed without being sufficiently heated to the predetermined temperature. In such a case, the ammonia gas discharged from the most upstream thermal decomposition apparatus 3 is disposed on the downstream side from the right side to the left side in FIG. 4 via the introduction path portions 7b to 7e. 3 is gradually heated by being introduced sequentially. Thereby, the quantity of the ammonia gas discharged | emitted without being decomposed | disassembled from the discharge port 33b of the thermal decomposition apparatus 3 arrange | positioned in the most downstream (leftmost side of FIG. 4) can be reduced.

  The second introduction path 8 sequentially introduces the cracked gas into each outer cylindrical member 41 (cracked gas heat exchanger 4), and the inlet path 8a composed of a plurality of (six in this embodiment) pipes. ~ 8f. The introduction path portion 8a connects the discharge port 33b of the thermal decomposition apparatus 3 disposed on the most downstream side (the leftmost side in FIG. 4) and the introduction port 41b1 of the outer cylindrical member 41 that covers the outside of the thermal decomposition apparatus 3. ing. The introduction path portions 8b to 8f connect one introduction port 41b1 and the other discharge port 41c1 of the adjacent outer cylindrical members 41 to each other.

  Thereby, the decomposition product gas discharged from the thermal decomposition apparatus 3 arranged on the most downstream side is sequentially transferred to the outer cylindrical members 41 from the left side to the right side in FIG. 4 through the introduction path portions 8a to 8f. be introduced. That is, the order of introduction of the decomposition product gas through the second introduction path 8 is reverse to the order of introduction of the ammonia gas through the first introduction path 7. The rightmost side of FIG. 4, that is, the discharge port 41 c 1 of the outer cylindrical member 41 into which the decomposition product gas is finally introduced communicates with the supply hole 11 c 1 of the ammonia engine 1.

With the above configuration, the decomposition product gas discharged from the thermal decomposition apparatus 3 disposed on the most downstream side is sequentially introduced into each outer cylindrical member 41, and is heat-exchanged with the ammonia gas and gradually cooled. Thereafter, the ammonia engine 1 is supplied.
Further, the temperature of the decomposition product gas in the outer cylindrical member 41 increases from the right side to the left side in FIG. 4, that is, as the temperature of the ammonia gas sequentially introduced into each thermal decomposition apparatus 3 gradually increases. Can be gradually higher. Therefore, the ammonia gas and the decomposition product gas that are heat-exchanged with each other in each outer tubular member 41 can be in an appropriate temperature relationship. Note that other configurations of the present embodiment are the same as those of the first embodiment, and thus the description thereof is omitted.

As described above, according to the ammonia engine system of the present embodiment, the cracked product gas heat exchanger 4 is composed of the outer cylindrical member 41 that covers the outside of the heat cracker 3, so Can be integrally provided on the outside. Thereby, the whole system can be made compact.
In addition, by sequentially introducing ammonia gas into the plurality of thermal decomposition apparatuses 3, hydrogen gas can be efficiently decomposed and generated from the ammonia gas. Further, since heat is sequentially exchanged between the cracked gas containing the cracked hydrogen gas and the ammonia gas introduced into each thermal cracking device 3, the ammonia gas can be efficiently heated. The decomposition product gas can be efficiently cooled.

  In addition, since the order of introduction of the decomposition product gas through the second introduction path 8 is reversed to the order of introduction of the ammonia gas through the first introduction path 7, the decomposition and generation of ammonia gas exchanged with each other in the outer cylindrical member 41. The gas can be in an appropriate temperature relationship. Thereby, in each outer cylinder member 41, heat exchange with ammonia gas and decomposition product gas can be performed efficiently.

The above-described embodiments are all illustrative and not restrictive. The scope of right of the present invention is defined by the claims, and all modifications within the scope equivalent to the configurations described therein are included in the technical scope of the present invention.
For example, the hydrogen gas heat exchanger 4 in the above-described embodiment is configured to exchange heat between the decomposition gas containing hydrogen gas and nitrogen gas generated by decomposition from ammonia gas. That's fine. Further, the ammonia gas is heat-exchanged in the order of the exhaust gas heat exchanger 5 and the hydrogen gas heat exchanger 4, but the order may be reversed.

  Furthermore, in the above-described embodiment, an ammonia engine is used as the combustion device, but a gas burner using ammonia gas as a fuel may be applied. In this case, the exhaust gas heat exchanger 5 may use the atmospheric gas heated by the combustion flame of the gas burner as the exhaust gas.

1 Ammonia engine (combustion device)
3 Thermal decomposition equipment 4 Decomposition product gas heat exchanger (hydrogen gas heat exchanger)
5 Exhaust gas heat exchanger 7 First introduction path 8 Second introduction path 12 Supply means 41 Outer cylinder member (cylinder member)

Claims (6)

A combustion system including a combustion device using ammonia gas as fuel,
A thermal decomposition apparatus for heating ammonia gas to decompose it into nitrogen gas and hydrogen gas;
A hydrogen gas heat exchanger that exchanges heat between the hydrogen gas decomposed and generated by the thermal decomposition apparatus and the ammonia gas decomposed by the thermal decomposition apparatus,
The combustion system includes supply means for supplying hydrogen gas heat-exchanged by the hydrogen gas heat exchanger therein.   The combustion system according to claim 1, further comprising an exhaust gas heat exchanger that exchanges heat between exhaust gas exhausted from the combustion device and ammonia gas decomposed by the thermal decomposition device.   The combustion system according to claim 2, wherein the hydrogen gas heat exchanger performs heat exchange on the ammonia gas heat-exchanged by the exhaust gas heat exchanger.   The hydrogen gas heat exchanger has a cylindrical member that covers the outside of the thermal decomposition apparatus, and the hydrogen gas and ammonia supplied into the thermal decomposition apparatus by introducing the hydrogen gas into the cylindrical member. The combustion system according to any one of claims 1 to 3, wherein heat is exchanged with a gas. A plurality of the pyrolysis devices are provided,
A plurality of the cylindrical members are provided so as to cover the outer sides of the respective pyrolysis devices,
A plurality of the thermal decomposition apparatuses connected in series, and a first introduction path for sequentially introducing ammonia gas to each of the thermal decomposition apparatuses;
The combustion according to claim 4, further comprising: a second introduction path for sequentially introducing hydrogen gas discharged from the thermal decomposition apparatus disposed on the most downstream side of the first introduction path into the cylinder members. system.   6. The combustion system according to claim 5, wherein the order in which hydrogen gas is introduced through the second introduction path is reverse to the order in which ammonia gas is introduced through the first introduction path.

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