Ammonia decomposition reactor

Abstract

This ammonia decomposition reactor is provided with: a shell having a shell body, a medium inlet nozzle, and a medium outlet nozzle; a plurality of reaction tubes that extend in an axial direction so as to traverse the internal space of the shell body and in which a target gas can flow; a support plate that is fixed to the inner surface of the shell body and to which the inlets and / or the outlets of the plurality of reaction tubes is fixed; an inflow part having an inflow body connected to the inlets of the plurality of reaction tubes; and an outflow part having an outflow body connected to the outlets of the plurality of reaction tubes. A nitride layer is formed on a contact surface with which the target gas can come into contact while flowing.

Description

Ammonia decomposition reactor

[0001] This disclosure relates to an ammonia decomposition reactor. This application claims priority to Japanese Patent Application No. 2025-023989 filed in Japan on February 18, 2025, the content of which is incorporated herein by reference.

[0002] An ammonia decomposition system converts ammonia into hydrogen and nitrogen gas. Ammonia is a low-cost chemical raw material. It has a high energy density, is easy to compress and liquefy, is convenient for storage and transportation, and has the advantage that no CO is generated even when burned. Therefore, the idea of using ammonia as a hydrogen transport carrier has received wide attention. Furthermore, the high mass density and volumetric hydrogen storage density of ammonia are promising as a hydrogen transport carrier. In addition, the nitrogen gas generated by catalytic decomposition of ammonia is an excellent protective gas and can be widely applied in the semiconductor industry and metallurgical industry. ２ Moreover, the high mass density and volumetric hydrogen storage density of ammonia are promising as a hydrogen transport carrier. In addition, the nitrogen gas generated by catalytic decomposition of ammonia is an excellent protective gas and can be widely applied in the semiconductor industry and metallurgical industry.

[0003] For the decomposition of ammonia, catalytic reactions using heat are widely utilized. In this case, a reactor with a structure such as the heat exchanger described in Patent Document 1 may be employed.

[0004] Japanese Utility Model Publication No. 58-107495

[0005] By the way, when ammonia is decomposed, the reactor becomes very high temperature. Therefore, the reactor used for ammonia decomposition needs to have a structure that can withstand the decrease in allowable stress caused by exposure to a high-temperature environment and thermal deformation accompanying temperature changes. Furthermore, since the region through which ammonia passes in the reactor becomes a nitriding environment, it is necessary to create the reactor from a material having both nitriding resistance and high-temperature strength. Therefore, there are very large restrictions on the material constituting the reactor. In contrast, it is desired to relax the material restrictions.

[0006] This disclosure provides an ammonia decomposition reactor capable of relaxing material restrictions.

[0007] The ammonia decomposition reactor according to this disclosure comprises a shell having a cylindrical shell body extending around an axis, a medium inlet nozzle for supplying a heating medium into the shell body, and a medium outlet nozzle positioned away from the medium inlet nozzle in the axial direction of the axis for discharging the heating medium from the shell body to the outside; a plurality of reaction tubes extending in the axial direction so as to traverse the space inside the shell body and through which a target gas containing ammonia can flow; a support plate fixed to the shell body to which at least one of the inlets and outlets of the plurality of reaction tubes is fixed; an inlet section having an inlet body fixed to the shell body and connected to the inlets of the plurality of reaction tubes, and an ammonia inlet section for supplying the target gas into the inlet body; and an outlet section having an outlet body fixed to the shell body and connected to the outlets of the plurality of reaction tubes, and an ammonia outlet section for discharging the target gas from the inside of the outlet body to the outside, wherein a nitride layer is formed on the contact surface through which the target gas can flow and come into contact.

[0008] The ammonia decomposition reactor of this disclosure allows for the relaxation of material constraints.

[0009] This is a schematic diagram showing an ammonia decomposition reactor according to the first embodiment. This is an enlarged view of a key part detailing the contact surface and nitride layer in the region through which the target gas flows in the ammonia decomposition reactor according to the first embodiment. This is an enlarged view of a key part detailing the curved surface connecting the support plate and the inner surface of the shell body in the ammonia decomposition reactor according to the first embodiment. This is a modified example of the first embodiment, an enlarged view of a key part detailing the contact surface and nitride layer in which the target gas flows and comes into contact in the ammonia decomposition reactor. This is a modified example of the first embodiment, an enlarged view of a key part detailing the curved surface connecting the support plate and the inner surface of the shell body in the ammonia decomposition reactor. This is a schematic diagram showing an ammonia decomposition reactor according to the second embodiment. This is a schematic diagram showing an ammonia decomposition reactor according to the third embodiment. This is a schematic diagram showing an ammonia decomposition reactor according to the fourth embodiment. This is a schematic diagram showing an ammonia decomposition reactor according to the fifth embodiment. This is an enlarged view of a key part detailing the connection between the support plate and the reaction tube in the ammonia decomposition reactor according to the sixth embodiment. This is a schematic diagram showing an ammonia decomposition reactor according to the seventh embodiment. This is a schematic diagram showing an ammonia decomposition reactor according to the eighth embodiment. This is a schematic diagram showing an ammonia decomposition reactor according to the ninth embodiment.

[0010] Hereinafter, embodiments for implementing the ammonia decomposition reactor and the method for starting the ammonia decomposition reactor according to this disclosure will be described with reference to the attached drawings. However, this disclosure is not limited to these embodiments.

[0011] <First Embodiment> (Ammonia Decomposition Reactor) The ammonia decomposition reactor 1 generates hydrogen and nitrogen by thermally decomposing target gas A, which contains ammonia as a raw material. Target gas A is the gas to be decomposed in the ammonia decomposition reactor 1 and is a gas with a high ammonia content. In addition to ammonia, target gas A may also contain hydrogen, nitrogen, and impurities (water, oil, etc.). The hydrogen and nitrogen produced in the ammonia decomposition reactor 1 are stored externally and used for various purposes. As shown in Figure 1, the ammonia decomposition reactor 1 comprises a shell 2, a plurality of reaction tubes 3, a support plate 4, an inlet 5, and an outlet 6.

[0012] The shell 2 has a hollow structure. The shell 2 is designed to allow a high-temperature heating medium S to flow through its interior. The heating medium S is a fluid that is hotter than the target gas A supplied to the ammonia decomposition reactor 1. In this embodiment, the heating medium S is, for example, superheated steam at a temperature of 500 degrees Celsius or higher. The shell 2 is made of a metal material with high high-temperature strength, such as stainless steel. In this embodiment, the shell 2 has a shell body 21, a medium inlet nozzle 22, and a medium outlet nozzle 23.

[0013] The shell body 21 is designed to allow a high-temperature heating medium S to flow through its interior. The shell body 21 is formed in a cylindrical shape extending around an axis. The shell body 21 is positioned so that its axis coincides with the horizontal direction and is formed in a cylindrical shape with both ends open. It is preferable to make the inner diameter of the shell 2 as large as possible in order to suppress uneven flow of the heating medium S inside it. A medium inlet nozzle 22 and a medium outlet nozzle 23 are integrally connected to the shell body 21.

[0014] The medium inlet nozzle 22 is an opening that sends the heating medium S into the shell body 21. The medium outlet nozzle 23 is an opening that sends the heating medium S from inside the shell body 21 to the outside. The medium outlet nozzle 23 is positioned away from the medium inlet nozzle 22 in the axial direction Da along the axis. The medium inlet nozzle 22 and the medium outlet nozzle 23 are positioned above the shell body 21, which is positioned vertically in a direction Dv that intersects the axis, relative to the shell body 21 when it is positioned horizontally. The medium inlet nozzle 22 and the medium outlet nozzle 23 are formed in a cylindrical shape that extends upward from the top of the shell body 21 in the vertical direction Dv. The lower ends of the medium inlet nozzle 22 and the medium outlet nozzle 23 are open on the inner circumferential surface of the shell body 21 so as to communicate with the inside of the shell body 21.

[0015] Furthermore, the shell body 21 of this embodiment has an inlet cylindrical portion 211, an outlet cylindrical portion 212, and an expandable portion 213. The inlet cylindrical portion 211 is connected to a medium inlet nozzle 22. The inlet cylindrical portion 211 is formed in a cylindrical shape extending around an axis. The outlet cylindrical portion 212 is connected to a medium outlet nozzle 23. The outlet cylindrical portion 212 is formed in a cylindrical shape extending around an axis. The outlet cylindrical portion 212 is positioned away from the inlet cylindrical portion 211 on the second side Da2 in the axial direction Da.

[0016] The expandable section 213 connects the inlet cylinder 211 and the outlet cylinder 212. The expandable section 213 is expandable and contractible so that the inlet cylinder 211 and the outlet cylinder 212 can move in the axial direction Da. The expandable section 213 has a structure that functions like an expansion joint, for example. The expandable section 213 in this embodiment has a bellows structure like a bellows tube.

[0017] In this embodiment, the side on which the medium inlet nozzle 22 is located relative to the medium outlet nozzle 23 is the first side Da1 in the axial direction Da. Conversely, the side on which the medium outlet nozzle 23 is located relative to the medium inlet nozzle 22 is the second side Da2 in the axial direction Da.

[0018] Each reaction tube 3 extends axially Da across the internal space of the shell body 21. Each reaction tube 3 is a straight tube that extends straight axially Da. The target gas A can flow through the inside of each reaction tube 3. Multiple reaction tubes 3 are arranged such that the heating medium S flowing inside the shell body 21 from the medium inlet nozzle 22 to the medium outlet nozzle 23 passes between the multiple reaction tubes 3 and comes into contact with the outer surface of the reaction tubes 3, thereby heating the high-temperature target gas A flowing inside. Multiple reaction tubes 3 are spaced apart in the vertical direction Dv and in the width direction perpendicular to the axial direction Da and the vertical direction Dv (the direction intersecting the axis in this embodiment). Multiple reaction tubes 3 are arranged in a so-called staggered pattern such that adjacent reaction tubes 3 in the width direction have different installation heights in the vertical direction Dv. For example, the multiple reaction tubes 3 are arranged such that, when viewed from the axial direction Da, the centerlines of the three closest reaction tubes 3 form a triangle (an equilateral or isosceles triangle). Each reaction tube 3 is made of a metallic material with high high-temperature strength and nitriding resistance, such as a nickel-based alloy. Each reaction tube 3 may be made of a different material from the shell 2, or it may be made of the same material as the shell 2.

[0019] The support plate 4 is fixed to the shell body 21. The support plate 4 is positioned to extend inward toward the interior of the shell body 21. The support plate 4 supports a plurality of reaction tubes 3. At least one of the inlets and outlets of the plurality of reaction tubes 3 is fixed to the support plate 4. The support plate 4 is made of a metal material with high high-temperature strength and nitridation resistance, such as a nickel-based alloy. The support plate 4 may be made of a different material from the shell 2, or it may be made of the same material as the shell 2. The support plate 4 in this embodiment has a first support plate 41 and a second support plate 42.

[0020] The first support plate 41 and the second support plate 42 are formed in a flat plate shape having a surface perpendicular to the axial direction Da. The first support plate 41 supports the ends of the multiple reaction tubes 3, which are the inlets. The second support plate 42 supports the ends of the multiple reaction tubes 3, which are the outlets. Therefore, the first support plate 41 and the second support plate 42 are spaced apart in the axial direction Da. The first support plate 41 and the second support plate 42 also have through holes through which the multiple reaction tubes 3 can be inserted. Therefore, the multiple reaction tubes 3 are fixed to the first support plate 41 and the second support plate 42 with the multiple reaction tubes 3 inserted through the through holes. Specifically, the multiple reaction tubes 3 are fixed to the first support plate 41 and the second support plate 42 by strength welding (yield welding) with the reaction tubes 3 as expanded tubes with surface contact. Furthermore, when viewed from the width direction, the first support plate 41 is spaced apart from the medium inlet nozzle 22 on the first side Da1 in the axial direction Da. When viewed from the width direction, the second support plate 42 is positioned at a distance of Da2 on the second side in the axial direction Da relative to the medium outlet nozzle 23.

[0021] Furthermore, the first support plate 41 is positioned at the boundary between the inlet body 51 and the shell body 21 in the axial direction Da. The first support plate 41 is connected to the inlet cylinder 211 and the inlet body 51. The first support plate 41 is not connected to the telescopic section 213. The first support plate 41 separates the internal space of the inlet body 51 from the internal space of the shell body 21. The second support plate 42 is positioned at the boundary between the outlet body 61 and the shell body 21 in the axial direction Da. The second support plate 42 is connected to the outlet cylinder 212 and the outlet body 61. The second support plate 42 is not connected to the telescopic section 213. The second support plate 42 separates the internal space of the outlet body 61 from the internal space of the shell body 21.

[0022] The inlet section 5 forms an internal space through which the target gas A supplied to the multiple reaction tubes 3 flows. The inlet section 5 is made of a metal material with high high-temperature strength and nitridation resistance, such as a nickel-based alloy. The inlet section 5 may be made of a different material from the shell 2, or it may be made of the same material as the shell 2. The inlet section 5 in this embodiment has an inlet body 51 and an ammonia inlet section 52.

[0023] The inlet body 51 is fixed to the shell body 21. The inlet body 51 is connected to the end (first end) of the first side Da1 of the shell body 21 in the axial direction Da, so as to be integral with the shell body 21. The inlet body 51 is formed in a bottomed cylindrical shape with a central axis so as to be coaxial with the shell body 21. The inlet body 51 forms a space where the target gas A temporarily accumulates between the surface of the first support plate 41 facing the first side Da1 in the axial direction Da.

[0024] The ammonia inlet 52 supplies high-temperature target gas A into the inlet body 51. The ammonia inlet 52 is fixed to the inlet body 51. The ammonia inlet 52 is integrally connected to the inlet body 51 so as to extend from the inlet body 51 to the first side Da1 in the axial direction Da. Therefore, the ammonia inlet 52 is positioned on the opposite side of the first support plate 41 in the axial direction Da relative to the inlet body 51. The ammonia inlet 52 is formed in a piping shape with a central axis so as to be coaxial with the shell body 21. The ammonia inlet 52 is connected to piping that is connected to the supply source of target gas A located outside.

[0025] The outlet section 6 forms an internal space through which the target gas A discharged from the multiple reaction tubes 3 flows in. The outlet section 6 is made of a metal material with high high-temperature strength and nitridation resistance, such as a nickel-based alloy. The outlet section 6 may be made of a different material from the shell 2, or it may be made of the same material as the shell 2. The outlet section 6 in this embodiment has an outlet body 61 and an ammonia outlet section 62.

[0026] The outlet body 61 is fixed to the shell body 21. The outlet body 61 is integrally connected to the shell body 21 at the end of the second side Da2 of the shell body 21 in the axial direction Da (second end). In other words, the outlet body 61 is connected to the end of the shell body 21 on the opposite side of the axial direction Da from the inlet body 51G. The outlet body 61 is formed in a bottomed cylindrical shape with a central axis so as to be coaxial with the shell body 21. The outlet body 61 forms a space where the target gas A temporarily accumulates between the surface of the second support plate 42 facing the second side Da2 in the axial direction Da.

[0027] The ammonia outlet section 62 discharges the target gas A from inside the outlet body 61 to the outside. The ammonia outlet section 62 is fixed to the outlet body 61. The ammonia outlet section 62 is integrally connected to the outlet body 61 so as to extend from the outlet body 61 to the first side Da1 in the axial direction Da. Therefore, the ammonia outlet section 62 is positioned on the opposite side of the second support plate 42 in the axial direction Da relative to the outlet body 61. The ammonia outlet section 62 is formed in a piping shape with a central axis so as to be coaxial with the shell body 21. The ammonia outlet section 62 is connected to piping that is connected to the destination of the target gas A located outside.

[0028] Furthermore, as shown in Figure 2, in the ammonia decomposition reactor 1, a nitrided layer 8 is formed on the contact surfaces 7 that the target gas A can flow through and come into contact with. The contact surfaces 7 are all surfaces located in the region that the target gas A can come into contact with during the operation of the ammonia decomposition reactor 1. Specifically, the contact surfaces 7 in this embodiment are the inner surface of the reaction tube 3, the inner surface of the inlet 5, the inner surface of the outlet 6, the surface of the first support plate 41 facing the first side Da1 in the axial direction Da, and the surface of the second support plate 42 facing the second side Da2 in the axial direction Da. Therefore, the nitrided layer 8 covers all contact surfaces 7 that the target gas A may come into contact with when it flows through. It is preferable that the nitrided layer 8 is free from cracks. Also, if the contact surfaces 7 are made of, for example, a nickel-based alloy or stainless steel, the nitrided layer 8 is formed as a metallic nitride layer. The nitrided layer 8 is formed to be very thin compared to the plate thickness of the member having the contact surfaces 7. The nitrided layer 8 is formed to a thickness of, for example, several tens of micrometers to several hundred micrometers.

[0029] Such a nitrided layer 8 is formed, for example, during the manufacture of the ammonia decomposition reactor 1. However, the nitrided layer 8 is not limited to being formed during manufacture, as long as it is formed before steady-state operation of the ammonia decomposition reactor 1. Specifically, the nitrided layer 8 may be formed during startup before steady-state operation of the ammonia decomposition reactor 1. For example, as a method of starting the ammonia decomposition reactor 1, the target gas A or another gas containing nitrogen may be passed through the ammonia decomposition reactor 1 once before steady-state operation, and the nitrided layer 8 may be formed on the contact surface 7 that the target gas A or the other gas passes through and comes into contact with. In other words, by passing the target gas A or the other gas through the ammonia decomposition reactor 1, which does not yet have a nitrided layer 8 formed, the target gas A or the other gas comes into contact with the contact surface 7 that does not yet have a nitrided layer 8 formed. In this way, the ammonia decomposition reactor 1 may be started in such a way that the nitrided layer 8 is formed on the contact surface 7 before steady-state operation. Furthermore, when performing steady-state operation after startup, the target gas A is first supplied to the ammonia decomposition reactor 1. After that, the heating medium S is supplied to the ammonia decomposition reactor 1 after a certain period of time has elapsed since the supply of the target gas A.

[0030] Furthermore, as shown in Figure 3, the support plate 4 is connected to the inner surface of the shell body 21 by a curved surface 43. Specifically, the first support plate 41 and the second support plate 42 are connected via the curved surface 43 so as to be smoothly connected to the inner surface of the shell body 21, rather than perpendicularly. In addition, the curved surface 43 is formed as a recess from at least a portion of the inner surface of the support plate 4 and the shell body 21. In this embodiment, the curved surface 43 is formed as a recess in the axial direction Da from the surfaces of the first support plate 41 and the second support plate 42 facing the axial direction Da. The first support plate 41 and the second support plate 42 are welded and fixed to the shell body 21 at a position offset in the axial direction Da with respect to the curved surface 43.

[0031] (Effects) In the ammonia decomposition reactor 1 of this first embodiment, a nitrided layer 8 is already formed on the contact surface 7 that comes into contact with the target gas A when it flows through it. Therefore, even when a high-temperature target gas A is supplied to the ammonia decomposition reactor 1 at room temperature, such as at the start of operation, the nitrided layer 8 can suppress the rapid temperature rise of the contact surface 7 that comes into contact with the target gas A. Thus, the high-temperature strength required of the member having the contact surface 7 can be suppressed. Furthermore, because the nitrided layer 8 is already formed, it is possible to suppress the formation of a new nitrided layer 8 on the contact surface 7 during operation. Therefore, it is possible to suppress the localized propagation of the nitrided layer 8 by partially forming a nitrided layer 8 on the contact surface 7 or by cracking a newly formed nitrided layer 8. In other words, the nitriding resistance required of the member having the contact surface 7 can be suppressed. As a result, the material constraints of the member having the contact surface 7 in the ammonia decomposition reactor 1 can be relaxed.

[0032] Furthermore, the inlet body 51, first support plate 41, reaction tube 3, second support plate 42, and outlet body 61 are exposed to the high-temperature target gas A, while the shell body 21, which fixes the inlet body 51, first support plate 41, second support plate 42, and outlet body 61, is exposed to a heating medium S that is hotter than the target gas A. As a result, a difference in thermal expansion occurs between the inlet body 51, first support plate 41, second support plate 42, and outlet body 61 and the shell body 21. In particular, the difference in thermal expansion between the reaction tube 3, which is long in the axial direction Da, and the shell body 21 becomes large. In this state, the stress generated in the first support plate 41 and second support plate 42, which are connected to both the reaction tube 3 and the shell body 21, becomes large. In particular, since a nitrided layer 8 is also formed on the first support plate 41 and second support plate 42, which fix the end of the reaction tube 3, there is a concern that cracking of the nitrided layer 8 may occur due to local stress. However, in this embodiment, the shell body 21 has an expandable portion 213 that can expand and contract in the axial direction Da between the inlet cylindrical portion 211 to which the first support plate 41 is connected and the outlet cylindrical portion 212 to which the second support plate 42 is connected. Therefore, the difference in thermal expansion between the reaction tube 3 and the shell body 21 can be absorbed by the expandable portion 213. Consequently, stress generated in the first support plate 41 and the second support plate 42 can be suppressed, and cracking of the nitrided layer 8 can be prevented. This makes it possible to alleviate the material constraints of the first support plate 41 and the second support plate 42.

[0033] Furthermore, the first support plate 41 and the second support plate 42 are connected to the inner surface of the shell body 21 by a curved surface 43. Therefore, compared to the case where the first support plate 41 and the second support plate 42 are connected to the inner surface of the shell body 21 at a right angle, the stress generated between the first support plate 41 and the second support plate 42 and the inner surface and corners of the shell body 21 can be reduced. One surface of the first support plate 41 and the second support plate 42 in the axial direction Da is exposed to the target gas A, and the opposite surface is exposed to the heating medium S. Therefore, a temperature difference is generated between the surfaces on both sides of the first support plate 41 and the second support plate 42 in the axial direction Da. As a result, large stresses are generated in the first support plate 41 and the second support plate 42. However, by reducing the stress generated between the first support plate 41 and the second support plate 42 and the inner surface and corners of the shell body 21, cracking of the nitrided layer 8 near the connection portion between the support plate 4 and the inner surface of the shell body 21 can be suppressed even if the stress on the first support plate 41 and the second support plate 42 increases. This makes it possible to alleviate material constraints on the shell 2, the first support plate 41, and the second support plate 42.

[0034] Furthermore, the curved surface 43 is formed as a recess in the axial direction Da from the first support plate 41 and the second support plate 42. Therefore, it is possible to suppress the bending of the first support plate 41 and the second support plate 42 due to heat. Consequently, deformation of the first support plate 41 and the second support plate 42 can be suppressed, and cracking of the nitrided layer 8 on the surface of the first support plate 41 and the second support plate 42 can be suppressed. This makes it possible to alleviate material constraints on the first support plate 41 and the second support plate 42.

[0035] Furthermore, curved surfaces 43 with depressions are formed on both sides of the first support plate 41 and the second support plate 42 in the axial direction Da. Therefore, both thermal expansion and contraction of the first support plate 41 and the second support plate 42 can be suppressed. Consequently, the deformation of the first support plate 41 and the second support plate 42 can be stably suppressed, and cracking of the nitrided layer 8 on the surface of the first support plate 41 and the second support plate 42 can be suppressed. This allows for a relaxation of material constraints on the first support plate 41 and the second support plate 42.

[0036] Furthermore, the nitrided layer 8 is not limited to being formed with a uniform thickness. On the contact surface 7, the nitrided layer 8 closer to the ammonia inlet 52 may be formed thicker than the nitrided layer 8 closer to the ammonia outlet 62. Specifically, as shown in Figure 4, as a modification, the nitrided layer 8A on the inner surface of the reaction tube 3 may be formed thicker in the axial direction Da closer to the inlet body 51 than closer to the outlet body 61. Also, the nitrided layer 8A may be formed thicker at the inlet 5 than at the outlet 6.

[0037] This structure allows for the protection of areas with high concentrations of the target gas A near the ammonia inlet 52 with a thicker nitride layer 8A. Therefore, a nitride layer 8A of the necessary thickness to protect the contact surface 7 can be formed throughout the entire ammonia decomposition reactor 1. Consequently, the entire contact surface 7 of the ammonia decomposition reactor 1 can be stably protected.

[0038] Furthermore, the curved surface 43 is not limited to a structure formed by being recessed in the axial direction Da from the first support plate 41 or the second support plate 42. The curved surface 43 may also be formed by being recessed from the inner surface of the shell body 21. As shown in Figure 5, as a modification, the curved surface 43A may be formed by being recessed from the inner surface of the shell body 21 that faces the radial direction, which is perpendicular to the axial direction Da.

[0039] Even with this structure, it is possible to suppress the bending of the first support plate 41 and the second support plate 42 due to heat. This suppresses deformation of the first support plate 41 and the second support plate 42, and prevents cracking of the nitrided layer 8 on the surface of the first support plate 41 and the second support plate 42.

[0040] <Second Embodiment> Next, the ammonia decomposition reactor 1A of the second embodiment according to the present disclosure will be described. In the second embodiment described below, components common to the first embodiment are denoted by the same reference numerals in the figures and their descriptions are omitted. The ammonia decomposition reactor 1A of the second embodiment differs from the first embodiment in the structure around the shell body 21A.

[0041] As shown in FIG. 6, the ammonia decomposition reactor 1A of the second embodiment further includes a temperature suppression unit. In the ammonia decomposition reactor 1A, the shell body 21A does not have an expansion / contraction part 213.

[0042] The temperature suppression unit 9 suppresses the temperature rise of at least one of the shell body 21A, the inflow body 51, and the outflow body 61H. The temperature suppression unit 9 is capable of suppressing the temperature rise of the shell body 21A exposed to the heating medium S. Specifically, the temperature suppression unit 9 suppresses the temperature rise of the inner surface of the shell body 21A in a state heated by heated steam. Further, the temperature suppression unit 9 suppresses the temperature rise of the inflow body 51 and the outflow body 61 exposed to the high-temperature target gas A. That is, the temperature suppression unit 9 suppresses the temperature rise of the inner surfaces of the inflow body 51 and the outflow body 61 in a state heated by the target gas A.

[0043] The temperature suppression unit 9 of the present embodiment has a heat insulating member 91 disposed on at least one inner surface of the shell body 21A, the inflow body 51, and the outflow body 61. The heat insulating member 91 is disposed on the inner surfaces of the shell body 21A, the inflow body 51, and the outflow body 61, making it difficult for heat to be transmitted to each inner surface. Specifically, the heat insulating member 91 of the present embodiment has a first heat insulating member 911 disposed on the inner surface of the shell body 21A, a second heat insulating member 912 disposed on the inner surface of the inflow part 5, and a third heat insulating member 913 disposed on the inner surface of the outflow part 6.

[0044] The first heat insulating member 911 covers the inner surface of the shell body 21A from the inside. That is, the first heat insulating member 911 covers the inner surface of the shell body 21A that contacts the heating medium S. The first heat insulating member 911 is formed of a material having a lower thermal conductivity than the material of the shell body 21A.

[0045] The second insulating member 912 covers the inner surfaces of the inlet body 51 and the ammonia inlet 52 from the inside. In other words, the second insulating member 912 covers the inner surfaces of the inlet body 51 and the ammonia inlet 52 that come into contact with the target gas A. Therefore, the second insulating member 912 is positioned to cover the nitrided layer 8 in the inlet body 51 and the ammonia inlet 52. The second insulating member 912 is made of a material with lower thermal conductivity than the material of the inlet body 51 and the ammonia inlet 52. The second insulating member 912 may be made of the same material as the first insulating member 911, or it may be made of a different material.

[0046] The third insulating member 913 covers the inner surfaces of the outlet body 61 and the ammonia outlet 62 from the inside. In other words, the third insulating member 913 covers the inner surfaces of the outlet body 61 and the ammonia outlet 62 that come into contact with the target gas A. Therefore, the third insulating member 913 is positioned to cover the nitrided layer 8 in the outlet body 61 and the ammonia outlet 62. The third insulating member 913 is made of a material with lower thermal conductivity than the material of the outlet body 61 and the ammonia outlet 62. The third insulating member 913 may be made of the same material as the first insulating member 911 and the second insulating member 912, or it may be made of a different material.

[0047] (Function and Effect) In the ammonia decomposition reactor 1A of the second embodiment as described above, the temperature rise of the shell main body 21A, the inflow main body 51, and the outflow main body 61 is suppressed by the temperature suppression unit 9. Particularly in this embodiment, the inner surfaces of the shell main body 21A, the inflow main body 51G, and the outflow main body 61 are protected by the heat insulating member 91. Specifically, the inner surface of the shell main body 21A is protected by the first heat insulating member 911 so as not to directly contact the heating medium S. The inner surface of the inflow main body 51 is protected by the second heat insulating member 912 so as not to directly contact the target gas A. The inner surface of the outflow main body 61 is protected by the third heat insulating member 913 so as not to directly contact the target gas A. As a result, the temperature of the high-temperature fluid is transmitted to the inner surfaces of the shell main body 21A, the inflow main body 51, and the outflow main body 61 through the heat insulating member 91 without the high-temperature fluid directly contacting them. Therefore, the temperature rise of the shell main body 21A, the inflow main body 51, and the outflow main body 61 can be suppressed. As a result, the shell main body 21A, the inflow main body 51, and the outflow main body 61 can be relieved from being in a high-temperature environment and the deformation can be suppressed. Therefore, the difference in thermal expansion between the shell main body 21A, the inflow main body 51, and the outflow main body 61 and the reaction tube 3 can be suppressed. Therefore, the stress generated on the first support plate 41 and the second support plate 42 can be suppressed, and the cracking of the nitride layer 8 can be suppressed. Thereby, the material constraints of the shell 2, the inflow portion 5, the outflow portion 6, the first support plate 41, and the second support plate 42 can be relaxed.

[0048] Note that the heat insulating member 91 is not limited to a structure in which it is disposed on all of the shell main body 21A, the inflow main body 51, and the outflow main body 61. For example, only a part of the first heat insulating member 911, the second heat insulating member 912, and the third heat insulating member 913 may be disposed.

[0049] <Third Embodiment> Next, the ammonia decomposition reactor 1B of the third embodiment according to the present disclosure will be described. In the third embodiment described below, the components common to the first embodiment and the second embodiment are denoted by the same reference numerals in the drawings and the description thereof is omitted. The ammonia decomposition reactor 1B of the third embodiment is different from the second embodiment in the structure of the temperature suppression unit 9B.

[0050] As shown in Figure 7, in the ammonia decomposition reactor 1B of the third embodiment, the temperature control unit 9B has a cooling unit 92. The cooling unit 92 is positioned on the outer surface of at least one of the shell body 21A, the inlet body 51, and the outlet body 61, and cools the shell body 21A, the inlet body 51, and the outlet body 61 from the outside. Specifically, the cooling unit 92 of this embodiment is capable of cooling the outer surface of the shell body 21A. The cooling unit 92 has a cooling casing 921.

[0051] The cooling casing 921 covers the shell body 21A from the outside. The cooling casing 921 is supplied with a cooling medium W that is at a lower temperature than the heating medium S and the target gas A. The cooling medium W is, for example, cooling water. The cooling medium W is supplied into the cooling space from a position close to the medium outlet nozzle 23 in the axial direction Da. The cooling medium W that has passed through the cooling space is discharged to the outside of the cooling casing 921. The cooling medium W is discharged to the outside of the cooling space from a position close to the medium inlet nozzle 22 in the axial direction Da. The cooling casing 921 is formed in a cylindrical shape with a central axis that coincides with the shell body 21A. In other words, the cooling casing 921 surrounds the shell body 21A from the outside, like a double pipe.

[0052] (Effects) In this third embodiment of the ammonia decomposition reactor 1B, the outer surface of the shell body 21A is cooled by the cooling unit 92. In particular, in this embodiment, the outer surface of the shell body 21A is directly cooled by the cooling medium W supplied to the cooling casing 921. As a result, the temperature rise of the shell body 21A can be suppressed. Therefore, the shell body 21A can be made to avoid being in a high-temperature environment, and the deformation of the shell body 21A can be suppressed. Consequently, the difference in thermal expansion between the reaction tube 3 and the shell body 21A can be suppressed. This suppresses the stress generated in the first support plate 41 and the second support plate 42, and suppresses cracking of the nitrided layer 8. This makes it possible to alleviate the material constraints of the shell 2A, the first support plate 41, and the second support plate 42.

[0053] Furthermore, the cooling casing 921 is not limited to a structure that covers the shell body 21A. The cooling casing 921 may also cover the inlet body 51 and the outlet body 61H. In this case, the cooling casing 921 may cover the shell body 21A, the inlet body 51, and the outlet body 61 with a single component, or it may cover the shell body 21A, the inlet body 51, and the outlet body 61 separately with different components.

[0054] <Fourth Embodiment> Next, the ammonia decomposition reactor 1C of the fourth embodiment according to the present disclosure will be described. In the fourth embodiment described below, components common to the first to third embodiments are denoted by the same reference numerals in the figures and their descriptions are omitted. The ammonia decomposition reactor 1C of the fourth embodiment differs from the second and third embodiments in the structure of the temperature suppression unit 9C.

[0055] As shown in Figure 8, in the ammonia decomposition reactor 1C of the fourth embodiment, the temperature control unit 9C has a cooling unit 92C. The cooling unit 92C of this embodiment has a cooling tube 925.

[0056] The cooling tube 925 covers the shell body 21A from the outside. The cooling tube 925 is formed in a tubular shape through which the cooling medium W can flow. The cooling tube 925 is arranged to wrap around the outer surface of the shell body 21A in a spiral shape. The cooling medium W is supplied to the inside of the cooling tube 925. The cooling medium W is supplied to the inside of the cooling tube 925 from a position close to the medium outlet nozzle 23 in the axial direction Da. The cooling medium W that has passed through the inside of the cooling tube 925 is discharged to the outside of the cooling tube 925. The cooling medium W is discharged to the outside of the cooling tube 925 from a position close to the medium inlet nozzle 22 in the axial direction Da.

[0057] (Effects) The ammonia decomposition reactor 1C of this fourth embodiment can obtain the same effects as the third embodiment. Specifically, the outer surface of the shell body 21A is cooled by the cooling tube 925. As a result, the temperature rise of the shell body 21A can be suppressed. As a result, the shell body 21A can be made to lessen the high-temperature environment and its deformation can be suppressed. Therefore, the difference in thermal expansion between the reaction tube 3 and the shell body 21A can be suppressed. This suppresses the stress generated in the first support plate 41 and the second support plate 42 and suppresses cracking of the nitrided layer 8. This makes it possible to alleviate the material constraints of the shell 2A, the first support plate 41 and the second support plate 42.

[0058] Furthermore, since the cooling tube 925 is wrapped around the outer surface of the shell body 21A, the temperature rise of the shell body 21A can be suppressed with a simpler structure. In addition, since the cooling tube 925 can be wrapped around the shell body 21A afterward, it can also be used to modify existing ammonia decomposition reactors 1C.

[0059] Furthermore, the cooling tube 925 is not limited to a structure that covers the shell body 21A. The cooling tube 925 may also cover the inlet body 51 and the outlet body 61. In this case, the cooling tube 925 may cover the shell body 21A, the inlet body 51, and the outlet body 61 with a single component, or it may cover the shell body 21A, the inlet body 51, and the outlet body 61 separately with different components.

[0060] <Fifth Embodiment> Next, the ammonia decomposition reactor 1D of the fifth embodiment according to the present disclosure will be described. In the fifth embodiment described below, components common to the first to fourth embodiments described above are denoted by the same reference numerals in the figures and their descriptions are omitted. As shown in Figure 9, the ammonia decomposition reactor 1D of the fifth embodiment further comprises a space partition plate 11 that divides the space inside the shell body 21A.

[0061] The space partition plate 11 divides the space inside the shell body 21A into a heating space Sh and an insulating space Si. The heating space Sh is the space where the heating medium S is present. The insulating space Si is the space where air is present facing the support plate 4. The insulating space Si is not connected to the heating space Sh, the inside of the inlet body 51, or the inside of the outlet body 61, and is a completely independent space. In other words, the heating medium S and the target gas A cannot enter the insulating space Si. The space partition plate 11 is arranged inside the shell body 21A at an axial distance Da from the support plate 4. In this embodiment, the space partition plate 11 has a first space partition plate 111 and a second space partition plate 112.

[0062] The first space partition plate 111 forms an insulating space Si between itself and the first support plate 41. The first space partition plate 111 is fixed to the inner surface of the shell body 21A. The first space partition plate 111 is formed in a flat plate shape with a surface perpendicular to the axial direction Da. The first space partition plate 111 supports the middle of multiple reaction tubes 3. When viewed from the width direction, the first space partition plate 111 is positioned between the medium inlet nozzle 22 and the first support plate 41 in the axial direction Da.

[0063] The second space partition plate 112 forms an insulating space Si between itself and the second support plate 42. The second space partition plate 112 is fixed to the inner surface of the shell body 21A. The second space partition plate 112 is formed in a flat plate shape with a surface perpendicular to the axial direction Da. The second space partition plate 112 supports the middle of multiple reaction tubes 3. When viewed from the width direction, the second space partition plate 112 is positioned between the medium outlet nozzle 23 and the second support plate 42 in the axial direction Da.

[0064] (Effects) In this fifth embodiment of the ammonia decomposition reactor 1D, the first support plate 41 is positioned relative to the heating space Sh via an insulating space Si by the first space partition plate 111. Also, the second support plate 42 is positioned relative to the heating space Sh via an insulating space Si by the second space partition plate 112. Therefore, the first support plate 41 and the second support plate 42 do not come into direct contact with the heating medium S. Consequently, it is possible to prevent the first support plate 41 and the second support plate 42 from coming into contact with both the target gas A and the heating medium S. Therefore, it is possible to suppress the temperature difference between the surfaces on both sides of the first support plate 41 and the second support plate 42 in the axial direction Da. As a result, it is possible to suppress the generation of large stresses in the first support plate 41 and the second support plate 42. Consequently, it is possible to suppress cracking of the nitrided layer 8 on the surfaces of the first support plate 41 and the second support plate 42, and cracking of the nitrided layer 8 near the connection portion between the support plate 4 and the inner surface of the shell body 21A. This makes it possible to alleviate material constraints on the shell 2, the first support plate 41, and the second support plate 42.

[0065] <Sixth Embodiment> Next, the ammonia decomposition reactor 1E of the sixth embodiment according to the present disclosure will be described. In the sixth embodiment described below, components common to the first to fifth embodiments described above are denoted by the same reference numerals in the figures and their descriptions are omitted. The fixing structure of the reaction tube in the sixth embodiment differs from that of the other embodiments.

[0066] As shown in Figure 10, in the ammonia decomposition reactor 1E of the sixth embodiment, the reaction tube 3 is connected to the support plate 4E by butt welding (internal welding). Specifically, the first support plate 41 and the second support plate 42, which are the support plates 4E of this embodiment, have a plate body 46 and a plurality of protrusions 47. In this embodiment, the first support plate 41 is given as an example in Figure 10 and will be described. In the second support plate 42, the direction of protrusion of the protrusions 47 is opposite to that of the first support plate 41 in the axial direction Da.

[0067] The plate body 46 is formed in a flat shape. The plate body 46 is fixed to the inner surface of the shell body 21A. The plate body 46 has through holes that communicate with the inside of multiple reaction tubes 3. The through holes formed in the plate body 46 are the same size as the inner diameter of the reaction tubes 3 and smaller than the outer diameter of the reaction tubes 3. In other words, reaction tubes cannot be inserted into the through holes formed in the plate body 46.

[0068] Multiple protrusions 47 project cylindrically from the plate body 46 in the axial direction Da. Multiple protrusions 47 project toward the interior of the shell body 21A. Multiple protrusions 47 are formed integrally with the plate body 46 as a single component without welding or other means. Multiple protrusions 47 are arranged in the same number as the number of reaction tubes 3 on a single plate body 46. Each protrusion 47 is formed in a cylindrical shape with the same outer diameter as each reaction tube 3. Each protrusion 47 is formed to the same size as the inner diameter of each reaction tube 3 and the through hole in the plate body 46. The tip of each protrusion 47 is fixed to the tip of the reaction tube 3 by butt welding.

[0069] (Effects) In this sixth embodiment of the ammonia decomposition reactor 1E, the welded portion between the reaction tube 3 and the support plates 4E, which are the first support plate 41 and the second support plate 42, is not located on the surface of the plate body 46 on which the nitrided layer 8 is formed. Therefore, the connection portion between the reaction tube 3 and the support plates 4E can be prevented from being exposed to the nitriding environment in which the target gas A is present. As a result, cracking of the nitrided layer 8 in the first support plate 41 and the second support plate 42 can be suppressed. This makes it possible to alleviate material constraints on the first support plate 41 and the second support plate 42.

[0070] <Seventh Embodiment> Next, the ammonia decomposition reactor 1F of the seventh embodiment according to the present disclosure will be described. In the seventh embodiment described below, components common to the first to sixth embodiments are denoted by the same reference numerals in the figures and their descriptions are omitted. The internal structure of the ammonia decomposition reactor 1F of the seventh embodiment differs from that of the other embodiments.

[0071] As shown in Figure 11, the ammonia decomposition reactor 1F of the seventh embodiment comprises a shell 2F, a plurality of reaction tubes 3F, a support plate 4F, an inlet 5F, and an outlet 6F.

[0072] The shell 2F differs from other embodiments in the structure of the shell body 21F. The shell body 21F is formed in a cylindrical shape extending around an axis. The shell body 21F is formed in a closed-bottom cylindrical shape with only one end open. The shell body 21F has an open end on the first side Da1 in the axial direction Da, and a closed end on the second side Da2 in the axial direction Da. A medium inlet nozzle 22 positioned near the end of the first side Da1 in the axial direction Da and a medium outlet nozzle 23 positioned near the end of the second side Da2 in the axial direction Da are integrally connected to the shell body 21F.

[0073] Multiple reaction tubes 3F extend axially Da across the internal space of the shell body 21F. Each reaction tube 3F is formed in a U-shape within the shell body 21F, bending on one side of the axial direction Da (in this embodiment, the second side Da2 of the axial direction Da). Therefore, the ends of the multiple reaction tubes 3F are all located close to the end of the first side Da1 of the axial direction Da of the shell body 21F. Consequently, within each reaction tube 3F, the target gas A flows from the first side Da1 to the second side Da2 of the axial direction Da, changes direction at the end of the second side Da2 of the axial direction Da, and flows from the second side Da2 to the first side Da1 of the axial direction Da.

[0074] The support plate 4F is fixed to the inner surface of the shell body 21F. In this embodiment, only one support plate 4F is provided. Both the inlets and outlets of the multiple reaction tubes 3F are fixed to the support plate 4F. The support plate 4F is formed in a flat plate shape with a surface perpendicular to the axial direction Da. Furthermore, when viewed from the width direction, the support plate 4F is positioned away from the media inlet nozzle 22 on the first side Da1 in the axial direction Da. The support plate 4F is also positioned at the boundary between the inlet body 51F and outlet body 61F and the shell body 21F in the axial direction Da. The support plate 4F demarcates the internal space of the inlet body 51F and outlet body 61F from the internal space of the shell body 21F.

[0075] The inlet section 5F and outlet section 6F are arranged differently relative to the shell 2F. Specifically, the inlet body 51F and outlet body 61F are fixed to one end of the shell body 21F in the axial direction Da. The inlet body 51F and outlet body 61F are positioned at a location where they overlap in the axial direction Da and are aligned in the vertical direction Dv.

[0076] More specifically, the inlet body 51F is connected to the upper half of the first end (first end) of the shell body 21F in the axial direction Da, so as to be integrated with the shell body 21F. The ammonia inlet 52F is connected to the inlet body 51F so as to extend upward from the inlet body 51F in the vertical direction Dv.

[0077] The outlet body 61F is fixed to the shell body 21F. The outlet body 61F is connected to the lower half of the end (first end) of the first side Da1 of the shell body 21F in the axial direction Da, so as to be integrated with the shell body 21F. Therefore, the inlet body 51F and the outlet body 61F are arranged adjacent to each other in the vertical direction Dv such that their positions in the axial direction Da overlap. The inlet body 51F and the outlet body 61F are fixed to the shell body 21F in a state where they are completely separated so that the internal spaces of each other are independent. The ammonia outlet section 62F is connected integrally with the outlet body 61F so as to extend downward from the outlet body 61F in the vertical direction Dv.

[0078] Furthermore, the inlet body 51F and the outlet body 61F are not limited to a structure in which they are arranged side by side in the vertical direction Dv. For example, the inlet body 51F and the outlet body 61F may be arranged side by side in the width direction.

[0079] (Effects) In this seventh embodiment of the ammonia decomposition reactor 1F, both ends of the reaction tube 3F are fixed by a single support plate 4F. In other words, even if the reaction tube 3F undergoes thermal deformation due to the heat of the target gas A or heating medium S, the effect on the support plate 4F that fixes the reaction tube 3F can be suppressed. As a result, the effect of the thermal deformation of the reaction tube 3F on the shell body 21F that fixes the support plate 4F can also be suppressed. Therefore, stress generated in the support plate 4F and the shell body 21F can be suppressed, and cracking of the nitrided layer 8 can be prevented. This makes it possible to relax the material constraints of the shell 2F and the support plate 4F.

[0080] <Eighth Embodiment> Next, the ammonia decomposition reactor 1G of the eighth embodiment according to the present disclosure will be described. In the eighth embodiment described below, components common to the first to seventh embodiments are denoted by the same reference numerals in the figures and their descriptions are omitted. The internal structure of the ammonia decomposition reactor 1G of the eighth embodiment differs from that of the other embodiments.

[0081] As shown in Figure 12, the ammonia decomposition reactor 1G of the eighth embodiment comprises a shell 2F, a plurality of reaction tubes 3G, a support plate 4G, an inlet 5G, and an outlet 6G.

[0082] Multiple reaction tubes 3G extend axially Da across the internal space of the shell body 21F. Each reaction tube 3G has a double-tube structure in which the target gas A flowing through it folds back at one end in the axial direction Da. The inlet and outlet of each reaction tube 3G are spaced apart in the axial direction Da. In other words, each reaction tube 3G has a structure similar to a cooling tube in a bayonet-type heat exchanger using a double tube. Specifically, each reaction tube 3G has an outer tube 31 and an inner tube 32.

[0083] The outer tube 31 extends axially Da across the internal space of the shell body 21F. The outer tube 31 extends straight axially Da. The outer tube 31 is formed in a closed-bottom cylindrical shape with only one end open. The outer tube 31 has an open end on the first side Da1 in the axial direction Da, and a closed end on the second side Da2. The target gas A can flow through the inside of the outer tube 31. Therefore, a nitride layer 8 is formed on the inner circumferential surface of the outer tube 31. The outer tube 31 is positioned to be in direct contact with the heating medium S flowing inside the shell body 21F.

[0084] The inner tube 32 is formed to have a smaller diameter than the outer tube 31. The inner tube 32 is inserted inside the outer tube 31. The inner tube 32 is inserted inside the outer tube 31 with its outer circumferential surface separated from the inner circumferential surface of the outer tube 31. The inner tube 32 extends axially Da across the space inside the outer tube 31. The inner tube 32 extends straight axially Da. The inner tube 32 is formed in a cylindrical shape with both ends open. The second end of the inner tube 32 in the axial direction Da2 is located inside the outer tube 31. The second end of the inner tube 32 in the axial direction Da2 is located slightly away from the inner surface of the first end of the outer tube 31 in the axial direction Da1 on the first side Da1 of the outer tube 31. The first end of the inner tube 32 in the axial direction Da1 is located outside the outer tube 31. The first end of the inner tube 32 in the axial direction Da is positioned at a distance from the first end of the outer tube 31 in the axial direction Da relative to the first end of the outer tube 31 in the axial direction Da. The target gas A is allowed to flow inside the inner tube 32. The inner tube 32 is prevented from directly contacting the heating medium S flowing inside the shell body 21F. The outer surface of the inner tube 32 is exposed to the target gas A flowing inside the outer tube 31. Therefore, nitride layers 8 and 8A are formed on the inner and outer surfaces of the inner tube 32.

[0085] The support plate 4G of this embodiment has a first support plate 41G and a second support plate 42G. The first support plate 41G and the second support plate 42G are formed in a flat plate shape having a surface perpendicular to the axial direction Da. The first support plate 41G supports the end of the first side Da1 in the axial direction Da of the outer tube 31, which is the inlet of the plurality of reaction tubes 3G. The second support plate 42G supports the end of the second side Da2 in the axial direction Da of the inner tube 32, which is the outlet of the plurality of reaction tubes 3G. Therefore, the first support plate 41G and the second support plate 42G are arranged apart in the axial direction Da. When viewed from the width direction, the first support plate 41G is arranged apart from the media inlet nozzle 22 on the first side Da1 in the axial direction Da. When viewed from the width direction, the second support plate 42G is arranged apart from the first support plate 41G on the first side Da1 in the axial direction Da.

[0086] The inlet section 5G and the outlet section 6G are arranged differently with respect to the shell 2F. Specifically, the inlet body 51G and the outlet body 61G are arranged on one side of the shell body 21F in the axial direction Da, and are aligned in the axial direction Da.

[0087] More specifically, the interior of the inlet body 51G is in communication with the outer tube 31. In other words, the interior of the inlet body 51G faces the inlet of the reaction tube 3G. The inlet body 51G is connected to the end of the first side Da1 of the shell body 21F in the axial direction Da, so as to be integrated with the shell body 21F. The inlet body 51G is positioned between the first support plate 41G and the second support plate 42G in the axial direction Da. The ammonia inlet section 52G is connected integrally with the inlet body 51G so as to extend upward from the inlet body 51G in the vertical direction Dv.

[0088] The interior of the outlet body 61G is in communication with the internal tube 32. In other words, the interior of the outlet body 61G faces the outlet of the reaction tube 3G. The outlet body 61G is fixed to the inlet body 51G. The outlet body 61G is connected to the end of the first side Da1 of the inlet body 51G in the axial direction Da, so as to be integrated with the inlet body 51G. Therefore, the inlet body 51G and the outlet body 61G are arranged adjacent to each other in the axial direction Da, with the second support plate 42G in between. The inlet body 51G and the outlet body 61G are fixed to each other in a state where their internal spaces are completely separated so as to be independent of each other.

[0089] (Effects) In this eighth embodiment of the ammonia decomposition reactor 1G, the reaction tube 3G has a double-tube structure. That is, even if the reaction tube 3G undergoes thermal deformation due to the heat of the target gas A or heating medium S, the double-tube structure in which the outer tube 31 and inner tube 32 are separated from each other can suppress the effect on the first support plate 41G and the second support plate 42G that fix the reaction tube 3G. As a result, the effect of the thermal deformation of the reaction tube 3G on the shell body 21F that fixes the first support plate 41G and the second support plate 42G can also be suppressed. Therefore, the stress generated in the first support plate 41G and the second support plate 42G and the shell body 21F can be suppressed, and cracking of the nitrided layer 8 can be suppressed. This makes it possible to relax the material constraints of the shell 2F, the first support plate 41G, and the second support plate 42G.

[0090] <Ninth Embodiment> Next, the ammonia decomposition reactor 1H of the ninth embodiment according to the present disclosure will be described. In the ninth embodiment described below, components common to the first to eighth embodiments are denoted by the same reference numerals in the figures and their descriptions are omitted. The ammonia decomposition reactor 1H of the seventh embodiment differs from the other embodiments in that at least one of the inlet body 51 and the outlet body 61H is movable.

[0091] As shown in Figure 13, the ammonia decomposition reactor 1H of the ninth embodiment comprises a shell 2H, a plurality of reaction tubes 3, a support plate 4H, an inlet 5, and an outlet 6H.

[0092] The shell 2H differs from other embodiments in the structure of the shell body 21H. The shell body 21H is formed in a cylindrical shape extending around an axis. The shell body 21H is formed in a closed-bottom cylindrical shape with one end being widely open. The shell body 21H has an open end on the first side Da1 in the axial direction Da, and a closed end on the second side Da2 in the axial direction Da. The end of the second side Da2 in the axial direction Da of the shell body 21H has a through hole through which the ammonia outlet portion 62H, which will be described later, can be inserted. The shell body 21H is integrally connected to a medium inlet nozzle 22 positioned near the end of the first side Da1 in the axial direction Da, and a medium outlet nozzle 23 positioned near the end of the second side Da2 in the axial direction Da.

[0093] The support plate 4H of this embodiment includes a first support plate 41 and a second support plate 42H. The second support plate 42H is formed in a flat plate shape with a surface perpendicular to the axial direction Da. The second support plate 42H supports the outlets of a plurality of reaction tubes 3. Therefore, the first support plate 41 and the second support plate 42H are arranged apart in the axial direction Da. When viewed from the width direction, the second support plate 42H is arranged apart from the first support plate 41 on the first side Da1 in the axial direction Da. The second support plate 42H is movable in the axial direction Da together with the outflow body 61H.

[0094] The outlet section 6H is connected to the shell body 21H so as to be movable in the axial direction Da. In this embodiment, the outlet section 6H has an outlet body 61H and an ammonia outlet section 62H.

[0095] The outflow body 61H is located inside the shell body 21H. The outflow body 61H is not fixed to the shell body 21H. Therefore, the outflow body 61H is located inside the shell body 21H in a movable state. The outflow body 61H is located away from the inflow body 51 on the second side Da2 in the axial direction Da. The outflow body 61H is formed in a bottomed cylindrical shape with a central axis so that it is located coaxially with the shell body 21H. The second support plate 42H is fixed to the end of the first side Da1 in the axial direction Da of the outflow body 61H.

[0096] The ammonia outlet section 62H is fixed to the outlet body 61H. The ammonia outlet section 62H is integrally connected to the outlet body 61H so as to extend from the outlet body to the first side Da1 in the axial direction Da. Therefore, the ammonia outlet section 62H is positioned on the opposite side of the second support plate 42H in the axial direction Da relative to the outlet body 61H. The ammonia outlet section 62H is expandable and contractible along the axial direction. The ammonia outlet section 62H is a pipe having a bellows structure, such as a bellows tube. The ammonia outlet section 62H is positioned inserted through a through hole in the shell body 21H so as to penetrate the end of the second side Da2 in the axial direction Da of the shell body 21H.

[0097] (Effects) In this ninth embodiment of the ammonia decomposition reactor 1H, the outlet body 61H moves axially Da inside the shell body 21H. In other words, the outlet body 61H is movable relative to the inlet body 51 fixed to the shell body 21H in the axial Da direction. Therefore, even if the reaction tube 3 undergoes thermal deformation due to the heat of the target gas A or heating medium S, the outlet body 61H moves, absorbing the deformation of the reaction tube 3. Consequently, the effect of thermal deformation of the reaction tube 3 on the first support plate 41 and the second support plate 42H that fix the reaction tube 3 can be suppressed. As a result, the effect of thermal deformation of the reaction tube 3 on the shell body 21H that fixes the first support plate 41 and the second support plate 42H can also be suppressed. Therefore, stress generated in the first support plate 41, the second support plate 42H and the shell body 21H can be suppressed, and cracking of the nitrided layer 8 can be suppressed. This allows for the relaxation of material constraints on the shell 2H, the first support plate 41, and the second support plate 42H.

[0098] Furthermore, it is not limited to the outflow body 61H being movable in the axial direction Da relative to the shell body 21H. At least one of the inflow body 51 and the outflow body 61H needs to be connected to the shell body 21H so as to be movable in the axial direction Da. Therefore, only the inflow body 51 may be movable in the axial direction Da relative to the shell body 21H, or both the inflow body 51 and the outflow body 61H may be movable in the axial direction Da relative to the shell body 21H.

[0099] (Other Embodiments) Although embodiments of the present disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and may include design changes and the like that do not depart from the gist of the present disclosure.

[0100] For example, the ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, and 1H are not limited to structures having only the configurations described in the embodiments above. Specifically, multiple plate materials for supporting multiple reaction tubes 3, 3F, and 3G may be arranged inside the shell bodies 21, 21A, 21F, and 21H. Furthermore, the first embodiment does not necessarily have an expandable section 213 or curved surfaces 43 and 43A.

[0101] Furthermore, each embodiment may be implemented in any combination. For example, the first embodiment may include the heat insulating member 91 of the second embodiment, and the temperature suppression parts 9, 9B, and 9C of the third and fourth embodiments. Furthermore, the connection of the reaction tubes 3, 3F, and 3G in each embodiment may be performed by butt welding as in the fifth embodiment.

[0102] <Note> The ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, and 1H described in each embodiment can be understood, for example, as follows.

[0103] (1) The ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H according to the first embodiment consist of a cylindrical shell body 21, 21A, 21F, 21H extending around an axis, a medium inlet nozzle 22 for supplying a heating medium S into the interior of the shell body 21, 21A, 21F, 21H, and the shell body 21, 21H, which are arranged apart from the medium inlet nozzle 22 in the axial direction Da along the axis. Shells 2, 2A, 2F, 2H having a medium outlet nozzle 23 for sending the heating medium S inside A, 21F, 21H to the outside; a plurality of reaction tubes 3, 3F, 3G extending in the axial direction Da so as to traverse the space inside the shell bodies 21, 21A, 21F, 21H, and through which a target gas A containing ammonia can flow; and a plurality of the reaction tubes 3, 3F, 3G fixed to the shell bodies 21, 21A, 21F, 21H. Support plates 4, 4E, 4F, 4G, 4H to which at least one of the inlet and outlet of G is fixed; inlet bodies 51, 51F, 51G fixed to the shell bodies 21, 21A, 21F, 21H and connected to the inlets of a plurality of reaction tubes 3, 3F, 3G; inlet sections 5, 5F, 5G having ammonia inlet sections 52, 52F, 52G that send the target gas A into the interior of the inlet bodies 51, 51F, 51G; and the shell body 21, The device comprises outlet sections 6, 6F, 6G, 6H, each having an outlet body 61, 61F, 61G, 61H fixed to 21A, 21F, 21H and connected to the outlets of the plurality of reaction tubes 3, 3F, 3G, and an ammonia outlet section 62, 62F, 62G, 62H that sends the target gas A from inside the outlet bodies 61, 61F, 61G, 61H to the outside, and nitride layers 8, 8A are formed on the contact surfaces 7 through which the target gas A flows and comes into contact.

[0104] With this configuration, even when a high-temperature target gas A is supplied to ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, and 1H in a room-temperature state, such as at the start of operation, the nitrided layers 8, 8A can suppress the rapid temperature rise of the contact surface 7 in contact with the target gas A. Therefore, the high-temperature strength required of the component having the contact surface 7 can be suppressed. Furthermore, because the nitrided layers 8, 8A are already formed, it is possible to suppress the formation of new nitrided layers 8, 8A on the contact surface 7 during operation. Therefore, it is possible to suppress the localized propagation of nitrided layers 8, 8A by preventing partial formation of nitrided layers 8, 8A on the contact surface 7 or cracking of newly formed nitrided layers 8, 8A. In other words, the nitriding resistance required of the component having the contact surface 7 can be suppressed. As a result, the material constraints of the component having the contact surface 7 in ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, and 1H can be relaxed.

[0105] (2) The ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H according to the second embodiment are the ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H according to (1), wherein the support plates 4, 4E, 4F, 4G, 4H are connected to the inner surfaces of the shell bodies 21, 21A, 21F, 21H by curved surfaces 43, 43A.

[0106] With this configuration, the stress generated between the support plates 4, 4E, 4F, 4G, 4H and the inner surfaces and corners of the shell bodies 21, 21A, 21F, 21H can be alleviated compared to the case where the support plates 4, 4E, 4F, 4G, 4H are connected to the inner surfaces of the shell bodies 21, 21A, 21F, 21H at right angles. One surface of the support plates 4, 4E, 4F, 4G, 4H is exposed to the target gas A in the axial direction Da, and the opposite surface is exposed to the heating medium S. Therefore, a temperature difference is generated between the two surfaces of the support plates 4, 4E, 4F, 4G, 4H in the axial direction Da. As a result, large stresses are generated in the support plates 4, 4E, 4F, 4G, 4H. However, by mitigating the stress generated on the inner surfaces and corners of the support plates 4, 4E, 4F, 4G, 4H and the shell bodies 21, 21A, 21F, 21H, even if the stress on the support plates 4, 4E, 4F, 4G, 4H increases, cracking of the nitrided layers 8, 8A near the connection points between the support plates 4, 4E, 4F, 4G, 4H and the inner surfaces of the shell bodies 21, 21A, 21F, 21H can be suppressed. This allows for a relaxation of material constraints on the shells 2, 2A, 2F, 2H and the support plates 4, 4E, 4F, 4G, 4H.

[0107] (3) The ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H according to the third embodiment are the ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H of (2), wherein the curved surfaces 43, 43A are formed by being recessed from at least a part of the inner surface of the support plates 4, 4E, 4F, 4G, 4H and the shell bodies 21, 21A, 21F, 21H.

[0108] With this configuration, the bending of the support plates 4, 4E, 4F, 4G, and 4H due to heat can be suppressed. Therefore, deformation of the support plates 4, 4E, 4F, 4G, and 4H can be suppressed, and cracking of the nitrided layers 8 and 8A on the surfaces of the support plates 4, 4E, 4F, 4G, and 4H can be suppressed. This allows for a relaxation of the material constraints of the support plates 4, 4E, 4F, 4G, and 4H.

[0109] (4) The ammonia decomposition reactor 1 according to the fourth embodiment is any one of the ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H of (1) to (3), wherein the inlet bodies 51, 51F, 51G are formed in a bottomed cylindrical shape and connected to the ends of the shell bodies 21, 21A in the axial direction Da, the outlet body 61 is formed in a bottomed cylindrical shape and connected to the end of the shell body 21 on the opposite side of the inlet body 51 in the axial direction Da, and the support plates 4, 4E are arranged at the boundary between the inlet body 51 and the shell body 21 in the axial direction Da, and the space inside the inlet body 51 and the The shell body 21 has a first support plate 41 that partitions the internal space of the shell body 21, and a second support plate 42 that is positioned at the boundary between the outflow body 61 and the shell body 21 in the axial direction Da, and partitions the internal space of the outflow body 61 and the internal space of the shell body 21. The shell bodies 21, 21A, 21F, and 21H have an inlet cylinder portion 211 to which the medium inlet nozzle 22 and the first support plate 41G are connected, an outlet cylinder portion 212 to which the medium outlet nozzle 23 and the second support plate 42 are connected, and an expandable / contractable portion 213 that can expand and contract to move the inlet cylinder portion 211 and the outlet cylinder portion 212 in the axial direction Da.

[0110] With this configuration, the difference in thermal expansion between the reaction tube 3 and the shell body 21H can be absorbed by the expansion / contraction portion 213. Therefore, stress generated in the first support plate 41 and the second support plate 42 can be suppressed, and cracking of the nitrided layers 8 and 8A can be prevented. This makes it possible to alleviate the material constraints of the first support plate 41 and the second support plate 42.

[0111] (5) The ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H according to the fifth embodiment are any one of the ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H described in (1) to (4), wherein the nitrided layer 8A at the contact surface 7 is thicker at the position closer to the ammonia inlet 52, 52F, 52G than at the position closer to the ammonia outlet 62, 62F, 62G, 62H.

[0112] With this configuration, regions with high concentrations of target gas A near the ammonia inlet sections 52, 52F, and 52G can be protected by a thicker nitride layer 8A. Therefore, a nitride layer 8A of the necessary thickness to protect the contact surface 7 can be formed over the entire ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, and 1H. Thus, the entire contact surface 7 of the ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, and 1H can be stably protected.

[0113] (6) The ammonia decomposition reactor 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H according to the sixth embodiment is any one of the ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H described in (1) to (5), and has temperature suppression units 9, 9B, 9C that suppress the temperature rise of at least one of the shell bodies 21, 21A, 21F, 21H, the inlet bodies 51, 51F, 51G, and the outlet bodies 61, 61F, 61G, 61H.

[0114] With this configuration, the high-temperature environment of the shell bodies 21, 21A, 21F, 21H, inlet bodies 51, 51F, 51G, and outlet bodies 61, 61F, 61G, 61H can be mitigated, and deformation can be suppressed. Therefore, the difference in thermal expansion between the shell bodies 21, 21A, 21F, 21H, inlet bodies 51, 51F, 51G, and outlet bodies 61, 61F, 61G, 61H and the reaction tubes 3, 3F, 3G can be suppressed. As a result, the stress generated in the support plates 4, 4E, 4F, 4G, 4H can be suppressed, and cracking of the nitrided layers 8, 8A can be suppressed. This allows for the relaxation of material constraints on the shells 2, 2A, 2F, 2H, inlet sections 5, 5F, 5G, outlet sections 6, 6F, 6G, 6H, and support plates 4, 4E, 4F, 4G, 4H.

[0115] (7) The ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H according to the seventh embodiment are the ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H of (6), wherein the temperature suppression units 9, 9B, 9C have a heat insulating member 91 disposed on the inner surface of at least one of the shell bodies 21, 21A, 21F, 21H, the inlet bodies 51, 51F, 51G, and the outlet bodies 61, 61F, 61G, 61H.

[0116] With this configuration, the temperature of the high-temperature fluid is transmitted to at least one inner surface of the shell bodies 21, 21A, 21F, 21H, inlet bodies 51, 51F, 51G, and outlet bodies 61, 61F, 61G, 61H via the heat insulating member 91, without the high-temperature fluid directly contacting it. As a result, the temperature rise of at least one of the shell bodies 21, 21A, 21F, 21H, inlet bodies 51, 51F, 51G, and outlet bodies 61, 61F, 61G, 61H can be suppressed. Consequently, the exposure of at least one of the shell bodies 21, 21A, 21F, 21H, inlet bodies 51, 51F, 51G, and outlet bodies 61, 61F, 61G, 61H to a high-temperature environment can be mitigated, and deformation can be suppressed. Therefore, the difference in thermal expansion between at least one of the shell bodies 21, 21A, 21F, 21H, inlet bodies 51, 51F, 51G, and outlet bodies 61, 61F, 61G, 61H and the reaction tubes 3, 3F, 3G can be suppressed. As a result, stress generated in the support plates 4, 4E, 4F, 4G, 4H can be suppressed, and cracking of the nitrided layers 8, 8A can be prevented. This allows for a relaxation of material constraints on the shells 2, 2A, 2F, 2H, inlet sections 5, 5F, 5G, outlet sections 6, 6F, 6G, 6H, and support plates 4, 4E, 4F, 4G, 4H.

[0117] (8) The ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H according to the eighth embodiment are the ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H of (6) or (7), wherein the temperature suppression units 9, 9B, 9C have cooling units 92, 92C that cool the outer surface of the shell bodies 21, 21A, 21F, 21H.

[0118] With this configuration, the cooling units 92 and 92C can suppress the temperature rise of the shell bodies 21, 21A, 21F, and 21H. As a result, the high-temperature environment of the shell bodies 21, 21A, 21F, and 21H can be mitigated, and deformation of the shell bodies 21, 21A, 21F, and 21H can be suppressed. Therefore, the difference in thermal expansion between the reaction tubes 3, 3F, and 3G and the shell bodies 21, 21A, 21F, and 21H can be suppressed. This reduces the stress generated in the support plates 4, 4E, 4F, 4G, and 4H, and suppresses cracking of the nitrided layers 8 and 8A. This allows for the relaxation of material constraints on the shells 2, 2A, 2F, and 2H and the support plates 4, 4E, 4F, 4G, and 4H.

[0119] (9) An ammonia decomposition reactor 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H according to the ninth embodiment is any one of the ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H described in (1) to (8), further comprising a space partition plate 11 which is arranged inside the shell body 21, 21A, 21F, 21H, away from the support plates 4, 4E, 4F, 4G, 4H in the axial direction Da, and divides the space inside the shell body 21, 21A, 21F, 21H into a heating space Sh in which the heating medium S is present and an insulating space Si in which air is present facing the support plates 4, 4E, 4F, 4G, 4H.

[0120] With this configuration, the support plates 4, 4E, 4F, 4G, and 4H are positioned relative to the heating space Sh via an insulating space Si by the space partition plate 11. Therefore, the support plates 4, 4E, 4F, 4G, and 4H do not directly contact the heating medium S. Consequently, it is possible to prevent the support plates 4, 4E, 4F, 4G, and 4H from contacting both the target gas A and the heating medium S. Therefore, it is possible to suppress the temperature difference between the surfaces on both sides of the support plates 4, 4E, 4F, 4G, and 4H in the axial direction Da. As a result, it is possible to suppress the generation of large stresses in the support plates 4, 4E, 4F, 4G, and 4H. Consequently, it is possible to suppress cracking of the nitrided layers 8, and 8A on the surfaces of the support plates 4, 4E, 4F, 4G, and 4H, as well as cracking of the nitrided layers 8, and 8A near the connection points between the support plates 4, 4E, 4F, 4G, and 4H and the inner surfaces of the shell bodies 21, 21A, 21F, and 21H. This allows for the relaxation of material constraints on the shells 2, 2A, 2F, 2H and the support plates 4, 4E, 4F, 4G, 4H.

[0121] (10) The ammonia decomposition reactor 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H according to the tenth embodiment is any one of the ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H described in (1) to (9), wherein the support plates 4, 4E, 4F, 4G, 4H have a plate body 46 formed in the shape of a flat plate and a plurality of protrusions 47 that protrude cylindrically from the plate body 46 in the axial direction Da, and the reaction tubes 3, 3F, 3G have at least one of the ends of the inlet and outlet connected to the ends of the protrusions 47.

[0122] With this configuration, the welded portions between the reaction tubes 3, 3F, 3G and the support plates 4, 4E, 4F, 4G, 4H are not located on the surface of the plate body 46 where the nitrided layers 8, 8A are formed. Therefore, the connection portions are not exposed to the nitriding environment in which the target gas A is present. As a result, cracking of the nitrided layers 8, 8A on the support plates 4, 4E, 4F, 4G, 4H can be suppressed. This allows for a relaxation of material constraints on the support plates 4, 4E, 4F, 4G, 4H.

[0123] (11) The ammonia decomposition reactor 1F according to the eleventh embodiment is any one of the ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H of (1) to (3), wherein the reaction tube 3F is formed in a U-shape so as to bend on one side in the axial direction Da within the shell body 21F, the plurality of reaction tubes 3F are supported at both ends by a single support plate 4F, and the inlet body 51F and the outlet body 61F are fixed to one end of the shell body 21F in the axial direction Da at positions where they overlap in the axial direction Da and are aligned in a direction intersecting the axis.

[0124] With this configuration, both ends of the reaction tube 3F are fixed by a single support plate 4F. This means that even if the reaction tube 3F undergoes thermal deformation due to the heat of the target gas A or heating medium S, the impact on the support plate 4F that fixes the reaction tube 3F can be suppressed. As a result, the effect of the thermal deformation of the reaction tube 3F on the shell body 21F that fixes the support plate 4F can also be suppressed. Therefore, stress generated in the support plate 4F and the shell body 21F can be suppressed, and cracking of the nitrided layers 8 and 8A can be prevented. This allows for a relaxation of material constraints on the shell 2F and the support plate 4F.

[0125] (12) The ammonia decomposition reactor 1G according to the twelfth embodiment is any one of the ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H of (1) to (3), wherein the reaction tube 3G has a double-tube structure having an outer tube 31 and an inner tube 32 inserted into the outer tube 31 such that its outer peripheral surface is separated from the inner peripheral surface of the outer tube 31, and the inlet body 51G whose interior is in communication with the outer tube 31 and the outlet body 61G whose interior is in communication with the inner tube 32 are arranged side by side in the axial direction Da with respect to the shell bodies 21, 21A.

[0126] In this configuration, the reaction tube 3G has a double-tube structure. This means that even if the reaction tube 3G undergoes thermal deformation due to the heat of the target gas A or heating medium S, the double-tube structure, in which the outer tube 31 and inner tube 32 are separated from each other, can suppress the effect on the support plate 4G that fixes the reaction tube 3G. As a result, the effect of the thermal deformation of the reaction tube 3G on the shell bodies 21, 21A that fix the support plate 4G can also be suppressed. Therefore, the stress generated in the support plate 4G and the shell bodies 21, 21A can be suppressed, and cracking of the nitrided layers 8, 8A can be prevented. This allows for a relaxation of material constraints on the shells 2, 2A and the support plate 4G.

[0127] (13) The ammonia decomposition reactor 1H according to the 13th embodiment is any one of the ammonia decomposition reactors 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H of (1) to (3), wherein at least one of the inlet body 51 and the outlet body 61H is connected to the shell bodies 21, 21A so as to be movable in the axial direction Da.

[0128] With this configuration, one of the inlet body 51 and the outlet body 61H is movable relative to the other in the axial direction Da. Therefore, even if the reaction tube 3 undergoes thermal deformation due to the heat of the target gas A or heating medium S, one of the inlet body 51 or the outlet body 61H moves, absorbing the deformation of the reaction tube 3. Consequently, the effect of thermal deformation of the reaction tube 3G on the support plate 4H that fixes the reaction tube 3 can be suppressed. As a result, the effect of thermal deformation of the reaction tube 3 on the shell body 21H that fixes the support plate 4H can also be suppressed. Therefore, stress generated in the support plate 4H and the shell body 21H can be suppressed, and cracking of the nitrided layers 8 and 8A can be suppressed. This allows for a relaxation of material constraints on the shell 2H and the support plate 4H.

[0129] The ammonia decomposition reactor of this disclosure allows for the relaxation of material constraints.

[0130] 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H Ammonia decomposition reactor 2, 2A, 2F, 2H Shell 21, 21A, 21F, 21H Shell body 211 Inlet tube 212 Outlet tube 213 Telescopic section 22 Medium inlet nozzle 23 Medium outlet nozzle 3, 3F, 3G Reaction tube 31 Outer tube 32 Inner tube 4, 4E, 4F, 4G, 4H Support plate 41, 41G First support plate 42, 42G, 42H Second support plate 43, 43A Curved surface 46 Plate body 47 Protruding section 5, 5F, 5G Inlet section 51, 51F, 51G Inlet body 52, 52F, 52G Ammonia inlet section 6, 6F, 6G, 6H Outlet section 61, 61F, 61G, 61H Outlet body 62, 62F, 62G, 62H Ammonia outlet 7 Contact surface 8, 8A Nitrided layer S Heating medium A Target gas 9, 9B, 9C Temperature suppression section 91 Insulation member 911 First insulation member 912 Second insulation member 913 Third insulation member 92, 92C Cooling section 921 Cooling casing 925 Cooling tube W Cooling medium 11 Space partition plate 111 First space partition plate 112 Second space partition plate Si Insulation space Sh Heating space Da Axial direction Da1 First side Da2 Second side Dv Vertical direction

Claims

1. An ammonia decomposition reactor comprising: a shell formed in the shape of a cylinder extending around an axis, a medium inlet nozzle for supplying a heating medium into the shell body, and a medium outlet nozzle positioned away from the medium inlet nozzle in the axial direction of the axis, for supplying the heating medium from inside the shell body to the outside; a plurality of reaction tubes extending in the axial direction so as to traverse the space inside the shell body, through which a target gas containing ammonia can flow; a support plate fixed to the shell body, to which at least one of the inlets and outlets of the plurality of reaction tubes is fixed; an inlet section fixed to the shell body and having an inlet body connected to the inlets of the plurality of reaction tubes, and an ammonia inlet section for supplying the target gas into the inlet body; and an outlet section fixed to the shell body and having an outlet body connected to the outlets of the plurality of reaction tubes, and an ammonia outlet section for supplying the target gas from inside the outlet body to the outside, wherein a nitride layer is formed on the contact surface through which the target gas can flow and come into contact.

2. The ammonia decomposition reactor according to claim 1, wherein the support plate is connected to the inner surface of the shell body at a curved surface.

3. The ammonia decomposition reactor according to claim 2, wherein the curved surface is formed by recessing from at least a portion of the inner surface of the support plate and the shell body.

4. The ammonia decomposition reactor according to claim 1, wherein the inlet body is formed in the shape of a bottomed cylinder and connected to the end of the shell body in the axial direction, the outlet body is formed in the shape of a bottomed cylinder and connected to the end of the shell body on the opposite side of the axial direction from the inlet body, the support plate comprises a first support plate positioned at the boundary between the inlet body and the shell body in the axial direction and dividing the internal space of the inlet body from the internal space of the shell body, and a second support plate positioned at the boundary between the outlet body and the shell body in the axial direction and dividing the internal space of the outlet body from the internal space of the shell body, and the shell body comprises an inlet cylindrical portion to which the medium inlet nozzle and the first support plate are connected, an outlet cylindrical portion to which the medium outlet nozzle and the second support plate are connected, and an expandable portion that is expandable and contractible so as to move the inlet cylindrical portion and the outlet cylindrical portion in the axial direction.

5. The ammonia decomposition reactor according to claim 1 or 2, wherein the nitrided layer closer to the ammonia inlet is formed thicker on the contact surface than the nitrided layer closer to the ammonia outlet.

6. The ammonia decomposition reactor according to claim 1 or 2, further comprising a temperature suppression unit that suppresses the temperature rise of at least one of the shell body, the inlet body, and the outlet body.

7. The ammonia decomposition reactor according to claim 6, wherein the temperature suppression unit has an insulating member disposed on the inner surface of at least one of the shell body, the inlet body, and the outlet body.

8. The ammonia decomposition reactor according to claim 6, wherein the temperature suppression unit has a cooling unit that cools the outer surface of the shell body.

9. The ammonia decomposition reactor according to claim 1 or 2, further comprising a space partition plate positioned axially away from the support plate inside the shell body, which divides the space inside the shell body into a heating space where the heating medium is present and an insulating space where air is present facing the support plate.

10. The ammonia decomposition reactor according to claim 1 or 2, wherein the support plate has a plate body formed in the shape of a flat plate and a plurality of protrusions that protrude cylindrically from the plate body in the axial direction, and the reaction tube has at least one of its inlet and outlet ends connected to the ends of the protrusions.

11. The ammonia decomposition reactor according to claim 1 or 2, wherein the reaction tube is formed in a U-shape so as to bend on one side in the axial direction within the shell body, the plurality of reaction tubes are supported at both ends by a single support plate, and the inlet body and the outlet body are fixed to one end of the shell body in the axial direction at positions where they overlap in the axial direction and are aligned in a direction intersecting the axis.

12. The ammonia decomposition reactor according to claim 1 or 2, wherein the reaction tube has a double-tube structure comprising an outer tube and an inner tube inserted into the outer tube such that its outer surface is separated from the inner surface of the outer tube, and the inlet body, whose interior is in communication with the outer tube, and the outlet body, whose interior is in communication with the inner tube, are arranged side by side in the axial direction on one side in the axial direction with respect to the shell body.

13. The ammonia decomposition reactor according to claim 1 or 2, wherein at least one of the inlet body and the outlet body is connected to the shell body so as to be movable in the axial direction.

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