Method for producing hydrogen gas, and apparatus for producing hydrogen gas

Abstract

The present invention provides a hydrogen gas production method and a hydrogen gas production apparatus that reduce the production cost of hydrogen gas and enable the production of hydrogen gas more cheaply and efficiently than conventional methods. [Solution] A hydrogen gas production method comprising: a decomposition step A, in which ammonia is introduced into a decomposition column 12 of an ammonia decomposition unit 10 to obtain decomposition gas; and a purification step B, in which residual ammonia and nitrogen gas are separated from the decomposition gas in a purification unit 20A to obtain purified hydrogen gas. The present invention further includes an ammonia heating step C, in which the off-gas containing residual ammonia and nitrogen gas separated from the decomposition gas in the purification step B is mixed with air and burned in the combustor 31 of the ammonia heating section 30, thereby heating the ammonia before it is introduced into the decomposition tower 12 using the heat of combustion of the burned off-gas.

Description

Technical Field

[0001] The present invention relates to a hydrogen gas production method and a hydrogen gas production apparatus.

Background Art

[0002] Techniques for using hydrogen gas as fuel for fuel cell vehicles and the like have been developed. However, it is difficult to transport a large amount of hydrogen gas. For example, in order to transport a large amount of hydrogen gas, it is necessary to liquefy the hydrogen gas at an ultra-low temperature, and in order to transport a large amount of hydrogen gas at room temperature, it is necessary to compress the hydrogen gas under high pressure.

[0003] Therefore, techniques have been developed to react hydrogen gas with nitrogen gas to produce ammonia, then transport the produced ammonia in large quantities, and then decompose it into hydrogen gas at the use point for utilization. In this technical field, techniques have been proposed to decompose ammonia at the use point of the transport destination to obtain a mixed gas of hydrogen gas and nitrogen gas, and to separate hydrogen gas and nitrogen gas from the mixed gas for utilization of hydrogen gas (Patent Documents 1 and 2).

[0004] As described in Patent Documents 1 and 2, ammonia decomposes when heated and brought into contact with an ammonia decomposition catalyst (hereinafter, also simply referred to as "catalyst"), generating a mixed gas of hydrogen gas and nitrogen gas. The mixed gas obtained by decomposing ammonia contains unreacted ammonia gas. On the other hand, for hydrogen gas used as fuel for fuel cell vehicles, high-purity hydrogen gas is required. Therefore, in order to use the mixed gas obtained by decomposing ammonia as fuel for fuel cell vehicles, it is necessary to remove nitrogen gas and residual unreacted ammonia gas contained in the mixed gas obtained by decomposing ammonia to a low concentration. For example, in order to use hydrogen gas as fuel for fuel cell vehicles, it is necessary to reduce the concentration of ammonia contained in the hydrogen gas to 0.1 ppm or less and the concentration of nitrogen gas to 300 ppm or less.

[0005] Patent documents 1 and 2 disclose a technology for removing ammonia from a mixed gas obtained by decomposing ammonia using thermal swing adsorption (TSA) with zeolite, and further removing nitrogen gas using pressure swing adsorption (PSA). A device that adsorbs and removes specific components from a mixed gas using thermal swing adsorption (TSA) is sometimes called a TSA device. TSA stands for Thermal Swing Adsorption. A device that adsorbs and removes specific components from a mixed gas using pressure swing adsorption (PSA) is sometimes called a PSA device. PSA stands for Pressure Swing Adsorption. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 6850449 [Patent Document 2] Patent No. 6763817 [Overview of the project] [Problems that the invention aims to solve]

[0007] According to the technologies described in Patent Documents 1 and 2, undecomposed ammonia and nitrogen gas can be removed from a mixed gas obtained by decomposing ammonia. A PSA (Potentially Absorbed Ammonia) apparatus purifies hydrogen gas by adsorbing impurities such as nitrogen gas onto an adsorbent packed in an adsorption tower equipped with the PSA apparatus under high pressure. Various processes are known for operating such a PSA apparatus, including a depressurization process and a regeneration process, as shown below. The depressurization process is a process in which the pressure inside the adsorption tower is reduced after purification, the adsorbed impurities are desorbed from the adsorbent, and exhausted together with the mixed gas remaining in the adsorption tower. The regeneration process is a process in which a portion of the purified hydrogen gas is introduced into the adsorption tower in the opposite direction to the purification process, and the mixed gas containing the desorbed impurities and hydrogen gas is discharged.

[0008] A TSA (Total Suspension Assembly) system is a thermal regeneration type ammonia removal system that uses zeolite or similar materials. It requires a regeneration process to desorb ammonia, an impurity adsorbed onto the zeolite, and exhaust it into the system. Hereafter, the exhaust gas discharged from the PSA system and the regeneration process of the TSA system is sometimes referred to as "off-gas."

[0009] Off-gases emitted during the regeneration process of PSA (Pressure Surveillance) systems contain hydrogen gas. Similarly, off-gases emitted during the regeneration process of TSA (Transmission Surveillance) systems contain ammonia. Therefore, since off-gases emitted from PSA and TSA systems contain hydrogen gas and ammonia, conventionally, these off-gases were burned and released into the atmosphere for safety reasons.

[0010] Incidentally, the decomposition of ammonia is an endothermic reaction, and in order to decompose ammonia at the point of use, the ammonia decomposition catalyst needs to be heated to about 900°C. Furthermore, ammonia is generally transported to the point of use in the form of liquefied ammonia. Therefore, in order to decompose ammonia with a catalyst, the liquefied ammonia needs to be vaporized at the point of use, which requires heating to account for the heat of vaporization. For this reason, conventional hydrogen gas production methods, such as those described in Patent Documents 1 and 2, require a large amount of heat supply at the point of use to vaporize the liquefied ammonia and then heat the vaporized ammonia to the desired temperature. Consequently, conventional hydrogen gas production methods consume a large amount of electricity, increasing production costs and making it difficult to produce inexpensive hydrogen.

[0011] Therefore, the present invention aims to provide a hydrogen gas production method and a hydrogen gas production apparatus that can reduce the production cost of hydrogen gas and produce hydrogen gas more cheaply and efficiently than conventional methods. [Means for solving the problem]

[0012] To achieve the above objective, the present invention provides the following means. [1] Decomposition step A involves introducing ammonia into a decomposition tower and decomposing the ammonia to obtain a decomposition gas containing nitrogen gas and hydrogen gas, A method for producing hydrogen gas, comprising a purification step B for separating residual ammonia and nitrogen gas from the decomposition gas to obtain purified hydrogen gas, A method for producing hydrogen gas, further comprising an ammonia heating step C, in which the off-gas containing the residual ammonia and nitrogen gas separated from the decomposition gas in the purification step B is mixed with air and burned in a combustor, and the ammonia before being introduced into the decomposition tower is heated by the heat of combustion of the burned off-gas. [2] The purification step B is: The process includes a purification step b1 in which the residual ammonia and nitrogen gas in the decomposition gas are separated by a PSA apparatus using a pressure fluctuation adsorption method to obtain the hydrogen gas, The hydrogen gas production method according to [1], characterized in that, in the ammonia heating step C, the off-gas discharged from the PSA device is burned in the combustor. [3] The purification step B is: Ammonia removal step b2a: The residual ammonia in the decomposition gas is removed by a TSA apparatus that separates it by a temperature swing adsorption method. A pressurization step b2b is performed to pressurize the decomposition gas from which the residual ammonia has been removed, The process includes a purification step b2c in which the nitrogen gas in the pressurized decomposition gas is separated by a PSA apparatus using a pressure fluctuation adsorption method to obtain the hydrogen gas, The off-gas discharged from the PSA device is used as the regeneration gas for the TSA device. The hydrogen gas production method according to [1], characterized in that, in the ammonia heating step C, the off-gas generated during the regeneration of the TSA apparatus is burned in the combustor. [4] The hydrogen gas production method according to any one of [1] to [3], characterized in that the combustor is a catalytic combustor that burns the off-gas and air with a catalyst. [5] The combustor comprises a housing and a cylindrical partition wall located inside the housing, The interior of the housing is divided into a first section located inside the partition wall and a second section located between the partition wall and the housing. The catalyst is filled into the first compartment, and the off-gas and air are burned in the first compartment. The hydrogen gas production method according to [4], characterized in that ammonia before being introduced into the decomposition tower is circulated in the second compartment and the ammonia is heated. [6] An ammonia decomposition unit that decomposes ammonia to produce a decomposition gas containing nitrogen gas and hydrogen gas, A purification unit that removes residual ammonia and nitrogen gas from the generated decomposition gas, A hydrogen gas production apparatus comprising: an ammonia heating unit that mixes the off-gas containing the residual ammonia and nitrogen gas removed in the purification unit with air and burns it in a combustor, thereby heating the ammonia before it is introduced into the ammonia decomposition unit using the heat of combustion of the burned off-gas. [7] The hydrogen gas production apparatus according to [6], characterized in that the purification unit has a PSA device that separates the residual ammonia and nitrogen gas in the decomposition gas by pressure fluctuation adsorption. [8] The hydrogen gas production apparatus according to [6], characterized in that the purification unit includes a TSA device for separating the residual ammonia in the decomposition gas by a temperature swing adsorption method, and a PSA device for separating the nitrogen gas in the decomposition gas by a pressure fluctuation adsorption method. [9] The hydrogen gas production apparatus according to any one of [6] to [8], characterized in that the ammonia heating section has a catalytic combustor that burns the off-gas and air with a catalyst.

[10] The catalytic combustor comprises a housing and a cylindrical partition wall located inside the housing, The interior of the housing is divided into a first section located inside the partition wall and a second section located between the partition wall and the housing. The catalyst is filled in the first compartment, and the off-gas and air are combusted in the first compartment. The hydrogen gas production apparatus according to [9], characterized in that ammonia before being introduced into the ammonia decomposition unit is circulated in the second compartment to heat the ammonia.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a hydrogen gas production method and a hydrogen gas production apparatus capable of reducing the production cost of hydrogen gas and producing hydrogen gas at a lower cost and with higher efficiency than in the prior art. In particular, in the present invention, the off-gas generated in the purification of the decomposition gas obtained by decomposing ammonia is combusted, and the combustion heat generated by the combustion is used to heat the ammonia before being introduced into the decomposition tower. Thereby, for example, when the ammonia before being introduced into the decomposition tower is liquefied ammonia, the liquefied ammonia is appropriately vaporized by the above-described heating, and the vaporized ammonia gas is further heated. Naturally, even when the ammonia before being introduced into the decomposition tower is ammonia gas, the ammonia gas is appropriately heated. Conventionally, the vaporization and heating of ammonia before being introduced into the decomposition tower have been performed by heating means such as an electric heater. According to the present invention, the power consumption required for the production of hydrogen gas can be significantly reduced as compared with the conventional method. By vaporizing and heating the ammonia before being introduced into the decomposition tower, the decomposition efficiency of ammonia in the decomposition tower can be improved well, and the generation amount per unit amount of ammonia of the purified hydrogen gas can also be increased. Further, for example, by using the off-gas discharged from the PSA apparatus as the regeneration gas of the TSA apparatus, the generation amount per unit amount of ammonia of the purified hydrogen gas can be further increased.

Brief Description of the Drawings

[0014] [Figure 1] It is a system diagram showing a schematic configuration of a hydrogen gas production apparatus according to a first embodiment of the present invention. [Figure 2] It is a cross-sectional view showing a schematic configuration of a combustor used in the hydrogen gas production apparatus shown in FIG. 1. [Figure 3]It is a system diagram showing a schematic configuration of a hydrogen gas production apparatus according to a second embodiment of the present invention. [Figure 4] It is a system diagram showing a schematic configuration of a hydrogen gas production apparatus according to a third embodiment of the present invention. [Figure 5] It is a system diagram showing a schematic configuration of a conventional hydrogen gas production apparatus.

MODE FOR CARRYING OUT THE INVENTION

[0015] [[ID=,13]] The following definitions of terms apply throughout this specification and the claims. "Decomposition gas" means a mixed gas containing hydrogen gas obtained by decomposing ammonia. In addition to hydrogen gas, the decomposition gas contains impurities (such as nitrogen gas, methane gas, moisture, etc.). Further, in addition to hydrogen gas and the above-mentioned impurities, the decomposition gas also contains unreacted ammonia (hereinafter also referred to as "unreacted ammonia"). "Residual ammonia" means unreacted ammonia in the decomposition gas. Residual ammonia in the decomposition gas is treated as an impurity of the decomposition gas.

[0016] "Purification process" means a process of separating residual ammonia and nitrogen gas from the decomposition gas and recovering purified hydrogen gas. <, "Adsorption process" is one of the processes included in the purification process, and means a process of adsorbing at least one kind of impurity contained in the decomposition gas in an adsorption tower and recovering hydrogen gas with a higher purity than the decomposition gas introduced into the adsorption tower. [[ID=2,6]]Among the adsorption processes, a process of adsorbing residual ammonia and nitrogen gas contained in the decomposition gas in the adsorption tower under high pressure and recovering purified hydrogen gas may be referred to as an "adsorption purification process". The adsorption purification process can be carried out using a PSA apparatus that separates impurities in the decomposition gas by the pressure swing adsorption method. Among the adsorption processes, the step of removing residual ammonia from the decomposition gas by adsorbing it in a thermal regenerative adsorption tower is sometimes referred to as the "ammonia removal process." The ammonia removal process can be carried out using a TSA (Transfer Saturation Adsorption) apparatus that separates impurities from the decomposition gas by the temperature swing adsorption method. Among the adsorption processes, the process performed after the ammonia removal process, in which nitrogen gas contained in the decomposition gas is adsorbed in an adsorption tower under high pressure and purified hydrogen gas is recovered, is sometimes referred to as the "adsorption purification process." The nitrogen adsorption purification process can be carried out using a PSA (Pressure Sweep Adsorption) apparatus that separates impurities in the decomposition gas by pressure fluctuation adsorption.

[0017] The "depressurization process" refers to the process of reducing the pressure inside the adsorption tower after the adsorption process and discharging any remaining decomposition gases from within the tower. The "regeneration process" refers to the process of removing the decomposition gases remaining in the adsorption tower. Within the regeneration process, the process of removing the decomposition gases remaining in the adsorption tower using a vacuum pump is referred to as the "exhaust process," and the process of introducing a portion of the hydrogen gas purified in the adsorption process into the adsorption tower while simultaneously performing the vacuum pump discharge to remove impurities is referred to as the "exhaust regeneration process." In the ammonia removal process, the process of introducing regenerated gas into the adsorption tower while heating it to remove impurities is referred to as the "aeration regeneration process." "Regenerated gas" refers to the gas introduced during the regeneration process to remove impurities remaining in the adsorption tower. Generally, the regenerated gas used is hydrogen gas of higher purity than the decomposition gas introduced into the adsorption tower being regenerated. For example, in the exhaust gas regeneration process, as mentioned above, a portion of the hydrogen gas purified in the adsorption process is used as the regenerated gas. "Off-gas" refers to the gas discharged from an adsorption tower during the depressurization or regeneration process.

[0018] <First Embodiment> The hydrogen gas production apparatus and hydrogen gas production method according to the first embodiment to which the present invention is applied will be described in detail below with reference to the drawings. Note that, for the sake of clarity, the drawings used in the following description may show enlarged versions of key features, and the dimensional ratios of each component may not be the same as those in reality.

[0019] <Hydrogen gas production equipment> Figure 1 is a schematic diagram showing the general configuration of the hydrogen gas production apparatus 1A of the first embodiment. As shown in Figure 1, the hydrogen gas production apparatus 1A includes an ammonia supply source 2, an air supply source 3, an ammonia decomposition unit 10, a purification unit 20A, an ammonia heating unit 30, and lines L1 to L8.

[0020] Ammonia supply source 2 is a supply source for ammonia, which is used as raw material to obtain decomposition gas containing nitrogen gas and hydrogen gas in the ammonia decomposition unit 10. The ammonia heating section 30 is a heating section for heating ammonia before it is introduced into the ammonia decomposition section 10. As will be described in more detail later, the ammonia heating section 30 has a combustor 31 that mixes the off-gas, which includes residual ammonia and nitrogen gas separated from the decomposition gas, with air and burns it. The air supply source 3 is a supply source for supplying air to the ammonia heating unit 30.

[0021] The ammonia decomposition unit 10 is for decomposing ammonia to produce decomposition gas containing nitrogen gas and hydrogen gas. The ammonia decomposition unit 10 decomposes the introduced ammonia into nitrogen gas and hydrogen gas by introducing ammonia into a decomposition tower 12 located in the reaction chamber 11 of the ammonia decomposition unit 10. The purification section 20A is a purification section that separates residual ammonia and nitrogen gas from the decomposition gas produced in the ammonia decomposition section 10 to obtain purified hydrogen gas.

[0022] The components of the hydrogen gas production apparatus 1A are described below. The ammonia supply source 2 supplies ammonia to the ammonia heating unit 30 via line L1. One end of line L1 is connected to the ammonia supply source 2, and the other end is connected to the ammonia heating unit 30. Ammonia is supplied to the ammonia supply source 2 by known methods such as cylinders, tanks, trucks, and pipelines.

[0023] The ammonia heating section 30 is used to heat the ammonia before it is introduced into the ammonia decomposition section 10 by burning the off-gas containing residual ammonia and nitrogen gas separated from the decomposition gas in the purification process described later in the combustor 31, and using the heat of combustion. The combustor 31 is a device that burns off-gas, which is separated from the decomposition gas in the purification process and discharged from the adsorption tower in the depressurization or regeneration process, mixed with air supplied from the air supply source 3. The off-gas discharged from the adsorption tower in the depressurization or regeneration process is supplied to the combustor 31 via line L7. In the ammonia heating section 30, for example, if the ammonia supplied from the ammonia supply source 2 is liquefied ammonia, it is preferable to heat the liquefied ammonia to vaporize it into gaseous ammonia. Although not particularly limited, if the ammonia supplied to the ammonia heating section 30 is already gaseous, or if liquefied ammonia has been vaporized, it is preferable to further heat the gaseous ammonia to 100°C, more preferably to 200°C, even more preferably to 300°C, and particularly preferably to 400°C. Of course, the ammonia may also be heated to 400°C or higher in the ammonia heating section 30.

[0024] Line L7 is connected at one end to the ammonia heating section 30 and at the other end to the TSA device 21, which is part of the purification section 20A. Off-gas discharged from, for example, one of the two adsorption towers 21a and 21b provided in the TSA device 21, which is in the regeneration process, is supplied to the ammonia heating section 30 via line L7. Line L8 is connected at one end to the air supply source 3 and at the other end to line L7. The air supply source 3 introduces air into line L7 via line L8, and by mixing oxygen gas with the off-gas, the off-gas becomes a practical fuel for the combustor 31 in the ammonia heating section 30.

[0025] The ammonia heating unit 30 supplies heated ammonia to the ammonia decomposition unit 10 via line L2. One end of line L2 is connected to the ammonia heating unit 30, and the other end is connected to the ammonia decomposition unit 10.

[0026] The ammonia decomposition unit 10 decomposes the heated ammonia supplied from the ammonia heating unit 30 to produce a decomposition gas containing nitrogen gas and hydrogen gas. The ammonia decomposition unit 10 decomposes ammonia into nitrogen gas and hydrogen gas by the ammonia decomposition reaction shown in the following formula (1). This decomposition reaction is carried out, for example, in a decomposition tower 12 provided in the reaction chamber 11 of the ammonia decomposition unit 10. 2NH3 → N2 + 3H2 ... (1)

[0027] The ammonia decomposition unit 10 is not particularly limited and may be a known reactor. For example, one example of the ammonia decomposition unit 10 carries out the ammonia decomposition reaction shown in equation (1) above by supplying heat such as combustion heat. Therefore, the ammonia decomposition unit 10 stably supplies heat to the reaction chamber 11. The reaction chamber 11 is filled with an ammonia decomposition catalyst. The ammonia decomposition catalyst promotes the ammonia decomposition reaction. Known catalysts such as nickel and ruthenium can be used as ammonia decomposition catalysts.

[0028] Line L3 is connected at one end to the ammonia decomposition unit 10 and at the other end to the TSA device 21, which is part of the purification unit 20A. A cooler 16 is provided in the middle of line L3. The cooler 16 is for cooling the decomposition gas supplied from the ammonia decomposition unit 10 to the TSA device 21 in the middle of line L3. There are no particular restrictions on the cooler 16; for example, shell-and-tube type, multi-tube type, plate type, etc., can be used.

[0029] The TSA apparatus 21 removes unreacted ammonia contained in the decomposition gas obtained by the ammonia decomposition reaction. The TSA apparatus 21 has a known separation and purification mechanism, such as an ammonia adsorbent. The TSA apparatus 21 shown in Figure 1 has two adsorption towers 21a and 21b as a separation and purification mechanism for adsorbing and removing unreacted ammonia. In the TSA apparatus 21, an ammonia removal process is performed as an adsorption process, in which residual ammonia contained in the decomposition gas is adsorbed in thermally regenerated adsorption towers 21a and 21b to remove residual ammonia from the decomposition gas.

[0030] The number of adsorption towers in the TSA apparatus 21 is not limited to a configuration having two adsorption towers, as in this embodiment. However, having two adsorption towers is more preferable in that it does not complicate the apparatus.

[0031] The adsorption tower of the TSA apparatus 21 is filled with an adsorbent. The adsorbent is preferably one that can adsorb unreacted ammonia contained in the decomposition gas. Specifically, zeolite, activated carbon, activated alumina, etc., can be used as adsorbents, and these may be used individually or in combination of two or more. Among these, zeolite is preferred as the adsorbent.

[0032] Line L4 is connected at one end to the TSA unit 21 and at the other end to the PSA unit 22, which is part of the purification section 20A. A pump 5a is provided in line L4. Pump 5a is used to improve the gas separation performance of the PSA unit 22 by increasing the pressure of the decomposition gas introduced into the PSA unit 22.

[0033] The PSA unit 22 is a device that purifies hydrogen gas contained in the decomposition gas supplied via line L4. The PSA unit 22 has at least two or more adsorption towers. The PSA unit 22 shown in Figure 1 has three adsorption towers 22a, 22b, and 22c. The decomposition gas contains impurities such as nitrogen gas and methane gas in addition to hydrogen gas. The PSA unit 22 removes these impurities from the decomposition gas to purify the hydrogen gas. Specifically, the PSA unit 22 performs an adsorption purification process, in which impurities such as nitrogen gas contained in the decomposition gas from which residual ammonia has been removed in the TSA unit 21 are adsorbed under high pressure in an adsorption tower, and the purified hydrogen gas is recovered.

[0034] The number of adsorption towers in the PSA device 22 is not limited to the configuration having three adsorption towers as in this embodiment. In other words, the number of adsorption towers is not limited to three. From the viewpoint of hydrogen gas purification efficiency and suppression of pressure fluctuations of the raw material gas, the number of adsorption towers is preferably 2 to 8, and more preferably 2 to 4 in terms of not complicating the device.

[0035] The adsorption tower of the PSA device 22 is filled with an adsorbent. The adsorbent is preferably one that can selectively adsorb impurity gases other than hydrogen (nitrogen gas, methane gas, water vapor, ammonia, etc.) contained in the decomposition gas obtained by decomposing ammonia. Specifically, activated carbon, activated alumina, zeolite, etc., can be used as adsorbents, and these may be used individually or in combination of two or more. Among these, zeolite is preferred as the adsorbent.

[0036] As the zeolite, type A zeolite or type X zeolite is preferred, and it is more preferable that it has been ion-exchanged with lithium or calcium. It is preferable that the adsorbent contains type A zeolite or type X zeolite that has been ion-exchanged with lithium or calcium, because this removes methane gas, nitrogen gas, etc.

[0037] Line L5 is connected at one end to the PSA device 22 and is a line for extracting purified hydrogen gas from the adsorption tower (e.g., adsorption tower 22a) in the adsorption process of the PSA device 22. The other end of line L5 is connected to a hydrogen gas recovery unit for recovering the purified hydrogen gas, for example, although it is not shown in the figure.

[0038] Line L6 is connected to the PSA device 22 at one end and to the TSA device 21 at the other end. Line L6 is a regeneration gas line that utilizes the off-gas discharged from the adsorption tower (e.g., adsorption tower 22c) in the regeneration or depressurization process of the PSA device 22 as the regeneration gas for the TSA device 21. The regeneration process of the PSA device 22 includes an exhaust process and an exhaust regeneration process. The off-gas discharged in the regeneration process and depressurization process (hereinafter also simply referred to as "regeneration process, etc.") of the PSA device 22 contains hydrogen gas, which is the regeneration gas, and impurities such as nitrogen gas removed from the decomposition gas in the adsorption process. A pump 5b is provided in line L6. Pump 5b is used to supply the off-gas from the PSA device 22 to the TSA device 21 and the combustor 31.

[0039] As described above, the hydrogen gas production apparatus 1A of this embodiment utilizes the off-gas discharged in the regeneration process of the PSA apparatus 22 as the regeneration gas for the TSA apparatus 21. Furthermore, the off-gas discharged in the regeneration process of the TSA apparatus 21 is used as a practical fuel for the combustor 31 in the ammonia heating section 30. The hydrogen gas production apparatus 1A of this embodiment can heat the ammonia before it is introduced into the ammonia decomposition section 10 by utilizing the heat of combustion generated by the combustion of the combustor 31 in the ammonia heating section 30. As a result, for example, if the ammonia before it is introduced into the ammonia decomposition section 10 is liquefied ammonia, the liquefied ammonia will be appropriately vaporized by the heating described above, and the vaporized ammonia gas will be further heated. Naturally, even if the ammonia before it is introduced into the ammonia decomposition section 10 is ammonia gas, the ammonia gas will be appropriately heated. Conventionally, the vaporization and heating of ammonia before it is introduced into the decomposition tower has been carried out by heating means such as electric heaters, but the hydrogen gas production apparatus 1A of this embodiment can significantly reduce the power consumption required for hydrogen gas production compared to conventional methods. Furthermore, by vaporizing and heating the ammonia before introducing it into the decomposition tower, the efficiency of ammonia decomposition in the tower can be significantly improved, and the amount of purified hydrogen gas generated per unit amount of ammonia can be increased. Moreover, for example, by using the off-gas discharged from the PSA unit as the regeneration gas for the TSA unit, the amount of purified hydrogen gas generated per unit amount of ammonia can be further increased. In this specification, "heating ammonia" includes heating and vaporizing liquefied ammonia when the ammonia to be heated is liquefied ammonia, unless otherwise specified.

[0040] The off-gas discharged during the regeneration process of the PSA unit 22 contains hydrogen gas, which is the regenerated gas, and impurities such as nitrogen gas removed from the decomposition gas in the adsorption process. The off-gas discharged during the regeneration process of the TSA unit contains ammonia. Therefore, the off-gas discharged from the PSA and TSA units contains hydrogen gas and ammonia, and conventionally, such off-gas needs to be treated in an appropriate manner for safety reasons. For example, conventionally, off-gas containing hydrogen gas and ammonia was burned and discharged into the atmosphere for safety reasons. On the other hand, in the hydrogen gas production apparatus 1A of this embodiment, the off-gas discharged during the regeneration process of the PSA unit 22 is used as the regenerated gas for the TSA unit 21. Therefore, the flow paths of the off-gas from the TSA unit 21 and the PSA unit 22 can be consolidated into a single system, making the regeneration processes of the TSA unit 21 and the PSA unit 22 more efficient, and also simplifying the treatment of the combustion gas after the off-gas is burned in the combustor 31.

[0041] <Combustion device> Next, an example of a combustor 31 used in the ammonia heating section 30 will be described with reference to Figure 2. Figure 2 is a cross-sectional view showing the schematic configuration of a combustor used in the hydrogen gas production apparatus shown in Figure 1. However, the combustor 31 used in the ammonia heating section 30 is not limited to the combustor 31 shown in Figure 2. The combustor 31 used in the ammonia heating section 30 can be any device that can mix off-gases discharged in the regeneration process of the purification section 20A, such as the TSA device 21 and PSA device 22, with air and burn them, and utilize the heat of combustion for vaporization and heating of ammonia.

[0042] The combustor 31 shown in Figure 2 is a catalytic combustor 40 that burns off-gas and air using a catalyst 45a. In the following explanation, the terms "upper" and "lower" are used for convenience of explanation and do not limit the direction in which each component is installed.

[0043] The catalytic combustor 40 shown in Figure 2 has a housing 43 and a cylindrical partition wall 44 located inside the housing 43. The inside of the housing 43 that constitutes the catalytic combustor 40 is divided into a first partition 41 located inside the partition wall 44 and a second partition 42 located between the partition wall 44 and the housing 43. In the catalytic combustor 40 configured in this way, the first partition 41 is the compartment for burning off-gas and air, and the second partition 42 is the compartment for heating ammonia.

[0044] The catalytic combustor 40 shown in Figure 2 has a cylindrical compartment wall 44 located inside the housing 43, which is a cylindrical, bottomed, and capped structure extending vertically. Therefore, the first compartment 41 surrounded by the compartment wall 44 is composed of a cylindrical compartment with a bottomed and capped structure extending vertically. Alumina particles 46 are packed into the bottom of the first compartment 41. The alumina particles 46 packed into the bottom are there to protect the catalyst 45a from flowing out and being crushed.

[0045] Within the first compartment 41, a catalyst 45a is packed above the packed alumina, and a catalyst layer 45 is provided within the first compartment 41 in the vertical direction. There are no particular restrictions on the type of catalyst packed into the first compartment 41, and it may be a conventionally known oxidation catalyst. Examples of catalysts to be packed into the first compartment 41 include precious metal catalysts such as platinum (Pt) and palladium (Pd).

[0046] Two insertion holes are provided on the upper surface of the first compartment 41. An off-gas introduction pipe 47 is inserted into one of the insertion holes, and a combustion exhaust gas discharge pipe 50 is inserted into the other insertion hole. The combustion exhaust gas discharge pipe 50 is a discharge pipe for discharging combustion exhaust gas generated by the combustion of off-gas and air within the first compartment 41 to the outside. The tip of the combustion exhaust gas discharge pipe 50 is located near the upper surface of the first compartment 41 and discharges the combustion exhaust gas near the upper surface of the first compartment 41 to the outside.

[0047] The off-gas introduction pipe 47 consists of a long pipe extending in the vertical direction. The off-gas introduction pipe 47, inserted through an insertion hole on the upper surface of the first compartment 41, is arranged to penetrate the catalyst layer 45 within the first compartment 41. In the example shown in Figure 2, the off-gas introduction pipe 47 is arranged in the vertical direction until its tip reaches the alumina particles 46 filled on the bottom side of the first compartment 41. The other end of the off-gas introduction pipe 47 is connected to a line L7 extending from the TSA device 21, which constitutes part of the purification section 20A (see Figure 1). As previously explained, the line L7 extending from the TSA device 21 merges with a line L8 connected to the air supply source 3 along the way. The line L7 connected to the off-gas introduction pipe 47 contains a mixture of off-gas discharged from the TSA device 21 (see Figure 1) and air supplied from the air supply source 3.

[0048] The mixed gas of off-gas and air (hereinafter also simply referred to as "mixed gas") introduced into the off-gas introduction pipe 47 is released into the first compartment 41 at the tip of the off-gas introduction pipe 47, that is, near the bottom of the first compartment 41. The mixed gas released into the first compartment 41 flows upward from the bottom of the first compartment 41, moving through the first compartment 41 and coming into contact with the catalyst 45a that constitutes the catalyst layer 45. When the temperature of the catalyst layer 45 (catalyst 45a) reaches a temperature at which catalytic combustion is possible, the mixed gas is burned by catalytic combustion. The combustion exhaust gas produced by the combustion is discharged to the outside via the combustion exhaust gas discharge pipe 50 provided on the upper side of the first compartment 41.

[0049] The second compartment 42 is located between the compartment wall 44 and the housing 43 and is configured to surround the first compartment 41, which is provided with a catalyst layer 45. The housing 43, which forms the outer circumferential surface of the second compartment 42, is provided with two insertion holes. An ammonia introduction pipe 48 is inserted into one of the insertion holes, and an ammonia outlet pipe 49 is inserted into the other insertion hole. The ammonia introduction pipe 48 is connected to line L1, which is connected to the ammonia supply source 2, and introduces ammonia supplied from the ammonia supply source 2 via line L1 into the second compartment 42. The ammonia outlet pipe 49 is connected to line L2, which is connected to the ammonia decomposition unit 10 (see Figure 1). The ammonia outlet pipe 49 discharges the ammonia heated in the second compartment 42 from within the second compartment 42 and supplies the heated ammonia to line L2, which is connected to the ammonia decomposition unit 10 (see Figure 1).

[0050] When off-gas and air are burned in the first compartment 41, the heat of combustion is transferred to the second compartment 42 via the compartment wall 44, and the ammonia circulating in the second compartment 42 is heated. The ammonia introduced into the second compartment 42 may be a gas or a liquid. The ammonia heated in the second compartment 42 is supplied to the ammonia decomposition unit 10 (see Figure 1) via the ammonia outlet pipe 49 and line L2.

[0051] Since the second compartment 42 is configured to surround the first compartment 41, it is not easily constrained by the internal volume of the second compartment 42, and can easily accommodate, for example, an increase in the capacity of the second compartment 42. For example, by increasing the capacity of the second compartment 42, the effect of pressure rise due to the vaporization of liquid ammonia can be reduced. For this reason, the catalytic combustor 40 shown in Figure 2 is a combustor 31 that is particularly suitable for both gaseous ammonia and liquid ammonia.

[0052] The catalytic combustor 40 shown in Figure 2 is one embodiment of a combustor having a double-tube structure comprising an outer tube and an inner tube. In such a catalytic combustor 40, only the upper sides of both the partition wall 44 constituting the inner tube and the housing 43 constituting the outer tube may be fixed to the device housing the housing 43. By configuring it in this way, it becomes possible to more effectively absorb the thermal expansion of the partition wall 44 constituting the inner tube and the housing 43 constituting the outer tube due to the heat of combustion.

[0053] <Hydrogen gas production method> Next, a hydrogen gas production method according to the first embodiment to which the present invention is applied will be described in detail. The hydrogen gas production method according to the first embodiment is carried out using the hydrogen gas production apparatus 1A of the first embodiment shown in Figure 1, which has been described above. The hydrogen gas production method according to the first embodiment is a hydrogen gas production method that includes a decomposition step A, a purification step B, and an ammonia heating step C.

[0054] Decomposition step A is a process in which ammonia is introduced into a decomposition tower and decomposed to obtain decomposition gas containing nitrogen gas and hydrogen gas. Decomposition step A is carried out in the ammonia decomposition section 10 of the hydrogen gas production apparatus 1A shown in Figure 1.

[0055] Purification step B is a process in which residual ammonia and nitrogen gas are separated from the decomposition gas obtained in decomposition step A to obtain purified hydrogen gas. Purification step B is carried out in the purification section 20A of the hydrogen gas production apparatus 1A shown in Figure 1.

[0056] In the hydrogen gas production method of the first embodiment, the purification step B preferably includes an ammonia removal step b2a, a pressurization step b2b, and a purification step b2c. Ammonia removal step b2a is a process in which residual ammonia in the decomposition gas is removed by a TSA (Temperature Swing Adsorption) apparatus that separates it using a temperature swing adsorption method. The pressurization step b2b is a process of pressurizing the decomposition gas from which residual ammonia has been removed by the ammonia removal step b2a. The purification step b2c is a process in which nitrogen gas from the decomposition gas pressurized in the pressurization step b2b is separated using a PSA (Pressure Sweep Adsorption) device that separates nitrogen gas by pressure fluctuation adsorption to obtain hydrogen gas. The hydrogen gas obtained in the purification step b2c is recovered as purified hydrogen gas. In the purification process B configured as described above, it is preferable to use the off-gas discharged from the PSA unit as the regeneration gas for the TSA unit.

[0057] Ammonia heating step C is a process in which the off-gas, which contains residual ammonia and nitrogen gas separated from the decomposition gas in purification step B, is mixed with air and burned in a combustor, and the heat of combustion from the burned off-gas is used to heat the ammonia before it is introduced into the decomposition tower. Ammonia heating step C is performed in the ammonia heating section 30 of the hydrogen gas production apparatus 1A shown in Figure 1. In the hydrogen gas production method of the first embodiment, as described above, when the off-gas discharged from the PSA device is used as the regeneration gas for the TSA device, it is preferable to burn the off-gas generated during the regeneration of the TSA device in a combustor.

[0058] There are no particular restrictions on the combustor used in the ammonia heating process C; any combustor that can burn off-gas mixed with air and utilize the heat of combustion for vaporization and heating of ammonia is acceptable. For example, a catalytic combustor 40 that burns off-gas and air using a catalyst 45a, such as the combustor 31 shown in Figure 2, can be cited as a preferred example. That is, a catalytic combustor 40 having a housing 43 and a cylindrical partition wall 44 located inside the housing 43, such as the combustor 31 shown in Figure 2, can be cited as a preferred example. In a catalytic combustor 40 configured in this way, the inside of the housing 43 is divided into a first compartment 41 located inside the partition wall 44 and a second compartment 42 located between the partition wall 44 and the housing 43. The catalyst 45a is filled into the first compartment 41, and off-gas and air are burned in the first compartment 41. Then, ammonia before being introduced into the decomposition tower is circulated into the second compartment 42 and heated.

[0059] <Second Embodiment> Next, a hydrogen gas production apparatus and hydrogen gas production method according to a second embodiment to which the present invention is applied will be described in detail with reference to Figure 3. In the following embodiments, parts that are the same as or equivalent to those described in the prior embodiments will be denoted by the same reference numerals, and their descriptions may be omitted. In embodiments where only a part of the components is described, the components described in the prior embodiments can be applied to the other parts of the components. In the following embodiments, parts of each embodiment can be partially combined, even if not explicitly stated, as long as it does not cause any particular problems with the combination.

[0060] <Hydrogen gas production equipment> Figure 3 is a schematic diagram showing the general configuration of the hydrogen gas production apparatus 1B of the second embodiment. As shown in Figure 3, the hydrogen gas production apparatus 1B includes an ammonia supply source 2, an air supply source 3, an ammonia decomposition unit 10, a purification unit 20B, an ammonia heating unit 30, and lines L11 to L17. The configuration of the purification unit 20B in the hydrogen gas production apparatus 1B of the second embodiment differs from that of the hydrogen gas production apparatus 1A of the first embodiment (see Figure 1, hereafter the same) described above. The ammonia supply source 2, air supply source 3, ammonia decomposition unit 10, and ammonia heating unit 30 in the hydrogen gas production apparatus 1B of the second embodiment are configured in the same way as the components in the hydrogen gas production apparatus 1A of the first embodiment. Lines L11 to L17 connect the components of the hydrogen gas production apparatus 1B of the second embodiment and supply appropriate gas to each component via lines L11 to L17.

[0061] The purification section 20B is a purification section for obtaining purified hydrogen gas by separating residual ammonia and nitrogen gas from the decomposition gas produced in the ammonia decomposition section 10. In the hydrogen gas production apparatus 1B of the second embodiment, this purification section 20B is composed of a PSA apparatus 23 that adsorbs residual ammonia and nitrogen gas contained in the decomposition gas in an adsorption tower under high pressure and recovers the purified hydrogen gas. The PSA unit 23 is a device that purifies hydrogen gas contained in the decomposition gas supplied via line L13. The PSA unit 23 has at least two or more adsorption towers. The PSA unit 23 shown in Figure 3 has three adsorption towers 23a, 23b, and 23c.

[0062] The adsorption tower of the PSA device 23 is filled with an adsorbent. The adsorbent is preferably one that can selectively adsorb impurity gases other than hydrogen (nitrogen gas, methane gas, water vapor, ammonia, etc.) contained in the decomposition gas obtained by decomposing ammonia. Specifically, activated carbon, activated alumina, zeolite, etc., can be used as adsorbents, and these may be used individually or in combination of two or more. Among these, zeolite is preferred as the adsorbent.

[0063] As the zeolite, type A zeolite or type X zeolite is preferred, and it is more preferable that it has been ion-exchanged with lithium or calcium. It is preferable that the adsorbent contains type A zeolite or type X zeolite that has been ion-exchanged with lithium or calcium, because this removes methane gas, nitrogen gas, etc.

[0064] Line L14 is connected at one end to the PSA device 23 and is a line for extracting purified hydrogen gas from the adsorption tower (e.g., adsorption tower 23a) in the adsorption process of the PSA device 23. The other end of line L5 is connected to a hydrogen gas recovery unit for recovering the purified hydrogen gas, for example, although it is not shown in the figure.

[0065] Line L15 is connected at one end to the PSA device 23 and at the other end to the ammonia heating unit 30. Line L15 is a gas line for utilizing the off-gas discharged from the adsorption tower (e.g., adsorption tower 23c) in the regeneration or depressurization process of the PSA device 23 as a practical fuel for the combustor 31 in the ammonia heating unit 30. The hydrogen gas production apparatus 1B of the second embodiment configured in this way can obtain the same effects and advantages as the hydrogen gas production apparatus 1A of the first embodiment described above.

[0066] <Hydrogen gas production method> Next, the hydrogen gas production method of the second embodiment will be described in detail. The hydrogen gas production method of the second embodiment is carried out using the hydrogen gas production apparatus 1B of the second embodiment shown in Figure 3, which has been described above. The hydrogen gas production method of the second embodiment is a hydrogen gas production method that includes a decomposition step A, a purification step B, and an ammonia heating step C.

[0067] Decomposition step A is a process in which ammonia is introduced into a decomposition tower and decomposed to obtain a decomposition gas containing nitrogen gas and hydrogen gas. Decomposition step A is carried out in the ammonia decomposition section 10 of the hydrogen gas production apparatus 1B shown in Figure 3.

[0068] Purification step B is a process in which residual ammonia and nitrogen gas are separated from the decomposition gas obtained in decomposition step A to obtain purified hydrogen gas. Purification step B is carried out in the purification section 20B of the hydrogen gas production apparatus 1B shown in Figure 3.

[0069] In the hydrogen gas production method of the second embodiment, the purification step B preferably includes a purification step b1 in which residual ammonia and nitrogen gas in the decomposition gas are separated by a PSA apparatus that separates them by pressure fluctuation adsorption to obtain hydrogen gas.

[0070] Ammonia heating step C is a process in which the off-gas, which contains residual ammonia and nitrogen gas separated from the decomposition gas in purification step B, is mixed with air and burned in a combustor, and the heat of combustion from the burned off-gas is used to heat the ammonia before it is introduced into the decomposition tower. Ammonia heating step C is performed in the ammonia heating section 30 of the hydrogen gas production apparatus 1B shown in Figure 3. In the hydrogen gas production method of the second embodiment, as described above, it is preferable to burn the off-gas discharged from the PSA device in a combustor.

[0071] <Third Embodiment> Next, a hydrogen gas production apparatus and hydrogen gas production method according to a third embodiment to which the present invention is applied will be described in detail with reference to Figure 4.

[0072] <Hydrogen gas production equipment> Figure 4 is a schematic diagram showing the general configuration of the hydrogen gas production apparatus 1C of the third embodiment. As shown in Figure 4, the hydrogen gas production apparatus 1C includes an ammonia supply source 2, an air supply source 3, an ammonia decomposition unit 10, a purification unit 20A, an ammonia heating unit 30, and lines L1, L4~L9, L22, and L23. The configuration of lines L22 and L23 in the hydrogen gas production apparatus 1C of the third embodiment differs from that of the hydrogen gas production apparatus 1A of the first embodiment (see Figure 1) described above. In the hydrogen gas production apparatus 1C of the third embodiment, the ammonia supply source 2, air supply source 3, ammonia decomposition unit 10, purification unit 20A, and ammonia heating unit 30 are configured in the same way as the components in the hydrogen gas production apparatus 1A of the first embodiment. Lines L1, L2~L9 are also configured in the same way as lines L1, L2~L9 in the hydrogen gas production apparatus 1A of the first embodiment.

[0073] Line L22, like line L2 of the hydrogen gas production apparatus 1A in the first embodiment, has one end connected to the ammonia heating section 30 and the other end connected to the ammonia decomposition section 10. Line L23 is connected at one end to the ammonia decomposition unit 10 and at the other end to the TSA device 21, which is part of the purification unit 20A.

[0074] In the hydrogen gas production apparatus 1C of the third embodiment, lines L22 and L23 are connected to a heat exchanger 15 midway along each line, and heat is exchanged between the ammonia flowing through line L22 and the decomposition gas flowing through line L23 by this heat exchanger 15. The decomposition gas flowing through line L23 is a very high-temperature gas due to the ammonia decomposition reaction in the ammonia decomposition unit 10, and for example, the decomposition gas immediately after being discharged from the ammonia decomposition unit 10 may be a high-temperature gas of 700 to 1000°C. On the other hand, the ammonia flowing through line L22 is heated to a certain temperature in the ammonia heating unit 30. Here, if the temperature of the decomposition gas discharged from the ammonia decomposition unit 10 is higher than the temperature of the ammonia flowing through line L22, the ammonia flowing through line L22 can be further heated by the heat exchanger 15 described above. For example, although not particularly limited, such a heat exchanger 15 can further heat the ammonia to about 600°C. A cooler 16 is provided downstream of the heat exchanger 15 in line L23. Therefore, by performing heat exchange between the ammonia flowing through line L22 and the decomposition gas flowing through line L23, it is possible to reduce the load on the cooler 16.

[0075] <Hydrogen gas production method> The hydrogen gas production method of the third embodiment can be carried out in the same manner as the hydrogen gas production method of the first embodiment, except that heat exchange takes place between the ammonia flowing through line L22 and the decomposition gas flowing through line L23, as described above. [Examples]

[0076] The present invention will be specifically described below with reference to examples. [Example 1] Hydrogen gas was produced using a hydrogen gas production apparatus 1A configured as shown in Figure 1. The ammonia supplied from ammonia source 2 was liquid ammonia. In the ammonia decomposition section 10, a nickel catalyst was used as the ammonia decomposition catalyst. The TSA device 21 used was one that was filled with zeolite as an adsorbent. For the PSA device 22, one filled with zeolite as an adsorbent was used. As the combustor 31 of the ammonia heating section 30, a catalytic combustor 40 as shown in Figure 2 was used. In the first compartment 41 for burning off-gas and air, alumina particles 46 were packed at the bottom, and a catalyst layer 45 was provided by packing platinum (Pt) as a catalyst 45a above them.

[0077] In Example 1, ammonia was first supplied from the ammonia supply source 2 to the catalytic combustor 40 (see Figure 2) of the ammonia heating unit 30 via line L1. The ammonia flowing through line L1 was at a pressure of 50 kPaG and a temperature of 25°C.

[0078] Next, the ammonia supplied to the ammonia heating unit 30 was heated in the catalytic combustor 40 (see Figure 2). The heated ammonia was supplied to the ammonia decomposition unit 10 via line L2. The ammonia flowing through line L2 was at a pressure of 45 kPaG and a temperature of 400°C.

[0079] Next, the ammonia supplied to the ammonia decomposition unit 10 was decomposed to produce a decomposition gas containing nitrogen gas and hydrogen gas. The heated decomposition gas was supplied to the TSA device 21 via line L3. The decomposition gas discharged from the ammonia decomposition unit 10 was at a high temperature of 900°C immediately after discharge, so it was cooled by a cooler 16 installed in the middle of line L3. After cooling by the cooler 16, the decomposition gas had a pressure of 25 kPaG and a temperature of 40°C.

[0080] Next, the TSA unit 21 removed unreacted ammonia from the decomposition gas. The decomposition gas, from which the ammonia had been removed, was supplied to the PSA unit 22 via line L4. The decomposition gas flowing through line L4 had a pressure of 20 kPaG and a temperature of 25°C. A pump 5a was also provided in line L4, and the decomposition gas after passing through pump 5a had a pressure of 300 kPaG and a temperature of 40°C.

[0081] Next, the PSA unit 22 purified the hydrogen gas by removing impurities from the decomposition gas supplied through line L4. The purified hydrogen gas was recovered through line L5. The hydrogen gas flowing through line L5 was at a pressure of 295 kPaG and a temperature of 25°C.

[0082] Off-gas discharged from the adsorption tower (e.g., adsorption tower 22c) in the regeneration or depressurization process of the PSA unit 22 was supplied as regeneration gas to the TSA unit 21 via line L6. The off-gas flowing through line L6 had a pressure of 10 kPaG and a temperature of 40°C. Off-gas discharged from the adsorption tower (e.g., adsorption tower 21b) in the regeneration process of the TSA apparatus 21 was supplied to the ammonia heating section 30 via line L7. The off-gas flowing through line L7 had a pressure of 5 kPaG and a temperature of 25-200°C. In Example 1, purified hydrogen gas was produced using the method described above.

[0083] [Example 2] Hydrogen gas was produced using a hydrogen gas production apparatus 1B configured as shown in Figure 3. The hydrogen gas production apparatus 1B used in Example 2 was configured similarly to the hydrogen gas production apparatus 1A shown in Figure 1, except that the TSA apparatus 21 (see Figure 1) was not used, and instead a PSA apparatus 23 filled with activated alumina and zeolite as adsorbents was used.

[0084] The gas pressure and temperature flowing through each line in the hydrogen gas production apparatus 1B used in Example 2 are as follows: The ammonia flowing through line L11 was at a pressure of 50 kPaG and a temperature of 25°C. The ammonia flowing through line L12 was at a pressure of 45 kPaG and a temperature of 400°C. After cooling line L13 with cooler 16, the decomposition gas had a pressure of 30 kPaG and a temperature of 40°C. The hydrogen gas flowing through line L14 was at a pressure of 295 kPaG and a temperature of 25°C. The off-gas flowing through line L15 had a pressure of 5 kPaG and a temperature of 25°C.

[0085] [Example 3] Hydrogen gas was produced using a hydrogen gas production apparatus 1C configured as shown in Figure 4. The hydrogen gas production apparatus 1C used in Example 3 was configured similarly to the hydrogen gas production apparatus 1A shown in Figure 1, except that lines L22 and L23 were connected to a heat exchanger 15 midway along each line. In the hydrogen gas production apparatus 1C used in Example 3, heat exchange was performed between the ammonia flowing through line L22 and the decomposition gas flowing through line L23 using the aforementioned heat exchanger 15.

[0086] The gas pressure and temperature flowing through each line in the hydrogen gas production apparatus 1C used in Example 3 are as follows: The ammonia flowing through line L21 was at a pressure of 50 kPaG and a temperature of 25°C. The ammonia flowing through line L22 before being introduced into heat exchanger 15 had a pressure of 45 kPaG and a temperature of 400°C, while the ammonia after being introduced into heat exchanger 15 had a pressure of 45 kPaG and a temperature of 600°C. The decomposition gas flowing through line L23 after cooling by the cooler 16 had a pressure of 25 kPaG and a temperature of 40°C. The decomposition gas from which ammonia had been removed flowing through line L24 had a pressure of 20 kPaG and a temperature of 25°C. The decomposition gas after passing through pump 5a in line L4 had a pressure of 300 kPaG and a temperature of 40°C. The hydrogen gas flowing through line L25 was at a pressure of 295 kPaG and a temperature of 25°C. The off-gas flowing through line L26 had a pressure of 10 kPaG and a temperature of 40°C. The off-gas flowing through line L27 had a pressure of 5 kPaG and a temperature of 25-200°C.

[0087] [Comparative Example 1] Hydrogen gas was produced using a hydrogen gas production apparatus 100 configured as shown in Figure 5. The hydrogen gas production apparatus 100 used in Comparative Example 1 was configured in the same way as the hydrogen gas production apparatus 1A shown in Figure 1, except that it did not have the ammonia heating section 30 of the hydrogen gas production apparatus 1A shown in Figure 1.

[0088] In the hydrogen gas production apparatus 100 shown in Figure 5, reference numeral 102 indicates an ammonia supply source, reference numeral 110 indicates an ammonia decomposition unit, reference numeral 120 indicates a purification unit, reference numerals 105a and 105b indicate pumps, and reference numeral 116 indicates a cooler. The ammonia decomposition unit 110 decomposes the introduced ammonia into nitrogen gas and hydrogen gas by introducing ammonia into a decomposition tower 12 located in the reaction chamber 11 of the ammonia decomposition unit 10. The purification unit 120 consists of a TSA unit 121 and a PSA unit 22. The TSA unit 121 has two adsorption towers 121a and 121b. The PSA unit 22 has three adsorption towers 122a, 122b, and 122c.

[0089] The gas pressure and temperature flowing through each line L101 to L106 in the hydrogen gas production apparatus 100 used in Comparative Example 1 are as follows. The ammonia flowing through line L101 was at a pressure of 50 kPaG and a temperature of 25°C. The decomposition gas flowing through line L102 after cooling by cooler 116 had a pressure of 25 kPaG and a temperature of 40°C. The decomposition gas from which ammonia had been removed flowing through line L103 had a pressure of 20 kPaG and a temperature of 25°C. Furthermore, the decomposition gas after passing through pump 105a in line L103 had a pressure of 300 kPaG and a temperature of 40°C. The hydrogen gas flowing through line L104 was at a pressure of 295 kPaG and a temperature of 25°C. The off-gas flowing through line L105 had a pressure of 10 kPaG and a temperature of 40°C. The off-gas flowing through line L106 had a pressure of 10 kPaG and a temperature of 25-200°C.

[0090] [result] In the manufacturing methods of Examples 1 and 2, the ammonia is heated by the ammonia heating unit before being introduced into the ammonia decomposition unit, which increases the temperature of the ammonia gas entering the decomposition column. As a result, the power consumption of the heater heating the decomposition column of the ammonia decomposition unit was reduced by 40% compared to the manufacturing method of Comparative Example 1. In the manufacturing method of Example 3, the ammonia heated by the ammonia heating unit is further heated by heat exchange with the decomposition gas discharged from the decomposition column, which reduces the power consumption of the heater by approximately 60% compared to the manufacturing method of Comparative Example 1.

[0091] In the manufacturing methods of Examples 1 and 3, by utilizing the off-gas discharged from the PSA device as the regeneration gas for the TSA device, the amount of purified hydrogen gas generated per unit amount of ammonia could be increased by approximately 10% compared to the manufacturing method of Comparative Example 1. [Explanation of Symbols]

[0092] 1A, 1B, 1C, 100…Hydrogen gas production equipment, 2…Ammonia supply source, 3…Air supply source, 5a, 5b…Pumps, 10…Ammonia decomposition section, 11…Reaction chamber, 12…Decomposition tower, 15…Heat exchanger, 16…Cooler, 20A, 20B…Purification section, 21…TSA unit, 21a, 21b…Adsorption tower (Adsorption tower for TSA unit), 22, 23…PSA unit, 22a, 22b, 22c, 23a, 23b, 23c ...Adsorption tower (adsorption tower of PSA device), 30...Ammonia heating section, 31...Combustor, 40...Catalytic combustor, 41...First compartment, 42...Second compartment, 43...Housing, 44...Compartment wall, 45...Catalyst layer, 45a...Catalyst, 46...Alumina particles, 47...Off-gas inlet pipe, 48...Ammonia inlet pipe, 49...Ammonia outlet pipe, 50...Combustion exhaust gas discharge pipe, L1~L9, L11~L17, L21~L29...Lines.

Claims

1. Decomposition step A involves introducing ammonia into a decomposition tower and decomposing the ammonia to obtain a decomposition gas containing nitrogen gas and hydrogen gas, A method for producing hydrogen gas, comprising a purification step B for separating residual ammonia and nitrogen gas from the decomposition gas to obtain purified hydrogen gas, A method for producing hydrogen gas, further comprising an ammonia heating step C, in which the off-gas containing the residual ammonia and nitrogen gas separated from the decomposition gas in the purification step B is mixed with air and burned in a combustor, and the ammonia before being introduced into the decomposition tower is heated by the heat of combustion of the burned off-gas.

2. The aforementioned purification step B is The process includes a purification step b1 in which the residual ammonia and nitrogen gas in the decomposition gas are separated by a PSA apparatus using a pressure fluctuation adsorption method to obtain the hydrogen gas, The hydrogen gas production method according to claim 1, characterized in that, in the ammonia heating step C, the off-gas discharged from the PSA device is burned in the combustor.

3. The aforementioned purification step B is Ammonia removal step b2a, in which the residual ammonia in the decomposition gas is removed by a TSA apparatus that separates it by a temperature swing adsorption method, A pressurization step b2b is performed to pressurize the decomposition gas from which the residual ammonia has been removed, The process includes a purification step b2c in which the nitrogen gas in the pressurized decomposition gas is separated by a PSA apparatus using a pressure fluctuation adsorption method to obtain the hydrogen gas, The off-gas discharged from the PSA device is used as the regeneration gas for the TSA device. The hydrogen gas production method according to claim 1, characterized in that, in the ammonia heating step C, the off-gas generated during the regeneration of the TSA apparatus is burned in the combustor.

4. The hydrogen gas production method according to any one of claims 1 to 3, characterized in that the combustor is a catalytic combustor that burns the off-gas and air with a catalyst.

5. The combustor comprises a housing and a cylindrical partition wall located inside the housing. The interior of the housing is divided into a first section located inside the partition wall and a second section located between the partition wall and the housing. The catalyst is filled into the first compartment, and the off-gas and air are burned in the first compartment. The hydrogen gas production method according to claim 4, characterized in that ammonia before being introduced into the decomposition tower is circulated within the second compartment and the ammonia is heated.

6. An ammonia decomposition unit that decomposes ammonia to produce a decomposition gas containing nitrogen gas and hydrogen gas, A purification unit that removes residual ammonia and nitrogen gas from the generated decomposition gas, A hydrogen gas production apparatus comprising: an ammonia heating unit which mixes the off-gas containing the residual ammonia and nitrogen gas removed in the purification unit with air and burns it in a combustor, thereby heating the ammonia before it is introduced into the ammonia decomposition unit using the heat of combustion of the burned off-gas.

7. The hydrogen gas production apparatus according to claim 6, characterized in that the purification unit has a PSA device for separating the residual ammonia and nitrogen gas in the decomposition gas by pressure fluctuation adsorption.

8. The hydrogen gas production apparatus according to claim 6, characterized in that the purification unit includes a TSA apparatus for separating the residual ammonia in the decomposition gas by a temperature swing adsorption method, and a PSA apparatus for separating the nitrogen gas in the decomposition gas by a pressure fluctuation adsorption method.

9. The hydrogen gas production apparatus according to any one of claims 6 to 8, characterized in that the ammonia heating section has a catalytic combustor that burns the off-gas and air with a catalyst.

10. The catalytic combustor comprises a housing and a cylindrical partition wall located inside the housing. The interior of the housing is divided into a first section located inside the partition wall and a second section located between the partition wall and the housing. The catalyst is filled into the first compartment, and the off-gas and air are burned in the first compartment. The hydrogen gas production apparatus according to claim 9, characterized in that ammonia before being introduced into the ammonia decomposition section is circulated within the second compartment and the ammonia is heated.

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