Hydrogen purification system and method for purifying hydrogen

Abstract

According to exemplary embodiments of the present invention, provided are a hydrogen purification system and a method for purifying hydrogen, the hydrogen purification system comprising: a first reactor configured to produce a metal nitride and a hydrogen-rich gas by reacting a mixed gas containing hydrogen and nitrogen with a metal absorbent; and a second reactor configured to receive the metal nitride from the first reactor and regenerate same into the metal absorbent, wherein the pressure of the first reactor is 1-5 bar.

Description

Hydrogen purification system and method for purifying hydrogen

[0001] The present invention relates to a hydrogen purification system.

[0002] In addition, the present invention relates to a method for purifying hydrogen.

[0003] Hydrogen can reduce dependence on fossil fuels and serve as a sustainable energy source. High-purity hydrogen is used in various high-value-added industries, such as fuel cells, chemical manufacturing, and metal processing. Furthermore, hydrogen is highly valuable as a clean energy source because it does not emit carbon dioxide when burned and has a high energy density.

[0004] Typically, hydrogen can be produced by decomposing reactants containing hydrogen. Examples of hydrogen-containing reactants include methane (CH4), water vapor (H2O), and ammonia (NH3). However, the reaction products produced after the reaction contain not only hydrogen but also other byproducts (e.g., carbon, nitrogen, etc.). Therefore, to obtain high-purity hydrogen, the development of a technology to purify hydrogen from the reaction products is necessary.

[0005] Previously, technologies for purifying hydrogen by controlling the pressure of the reactor, such as Pressure Swing Adsorption (PSA), have been proposed. However, PSA requires the reactor to be maintained at a high pressure and is performed at near room temperature. Therefore, if the hydrogen production reaction is performed at high temperatures, the reaction product must be cooled, and the reactor pressure must be increased using means such as a compressor. Consequently, excessive energy loss occurs during the hydrogen purification process.

[0006] Therefore, it is necessary to develop hydrogen purification technology that can minimize energy loss during the hydrogen production process.

[0007] (Patent Document 1) Republic of Korea Patent Publication No. 10-2024-0023427.

[0008] The technical idea of ​​the present invention aims to solve a problem by providing a hydrogen purification system and a method for purifying hydrogen that can minimize energy loss during the hydrogen production process.

[0009] The objectives of the present invention are not limited to the above-described content. Those skilled in the art will have no difficulty understanding the additional objectives of the present invention from the overall description of the present invention.

[0010] According to exemplary embodiments of the present invention, a hydrogen purification system is provided. The hydrogen purification system comprises a first reactor configured to react a mixed gas containing hydrogen and nitrogen with a metal absorbent to produce a metal nitride and a hydrogen-rich gas, and a second reactor configured to receive the metal nitride from the first reactor and regenerate it with the metal absorbent, wherein the pressure of the first reactor is 1 to 5 bar.

[0011] The above mixed gas may be derived from ammonia.

[0012] The reaction of the above mixed gas and the above metal absorbent can be performed at 700 to 800°C.

[0013] The nitrogen absorption capacity of the above metal absorbent may be 1 to 7 wt% / hr.

[0014] The above metal absorbent may include a metal having an oxidation number of 0.

[0015] The above metal absorbent may be any one of manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), calcium (Ca), molybdenum (Mo), and alloys thereof.

[0016] The above metal absorbent may contain, in weight %, at least one of zinc (Zn), magnesium (Mg), and strontium (Sr) in an amount of 10 wt% or less (including 0%).

[0017] The regeneration of the above metal absorbent can be performed at a temperature of 800°C or higher.

[0018] The regeneration of the above metal absorbent can be performed in a reducing gas atmosphere at a temperature range of 600 to 1000°C.

[0019] The second reactor may be configured to perform regeneration of the metal absorbent at a temperature lower than the temperature of the first reactor.

[0020] The above reducing gas may be tail gas derived from the iron making process.

[0021] The above reducing gas may be any one of hydrogen (H2), methane (CH4), nitrogen (N2), and a mixed gas thereof.

[0022] When the reaction of the metal absorbent is completed, the first reactor may be configured to be switched to the second reactor.

[0023] According to other exemplary embodiments of the present invention, a method for purifying hydrogen is provided. The method for purifying hydrogen includes the steps of providing a mixed gas containing hydrogen and nitrogen to a first reactor containing a metal absorbent, reacting the mixed gas with the metal absorbent at a pressure of 1 to 5 bar to provide a metal nitride and a hydrogen-rich gas, and regenerating the metal nitride with the metal absorbent.

[0024] The reaction of the above mixed gas and the above metal absorbent can be performed at 700 to 800°C.

[0025] The step of regenerating the above metal nitride can be performed at a temperature of 800°C or higher.

[0026] The step of regenerating the above metal nitride can be performed in a reducing gas atmosphere at a temperature range of 600 to 1000°C.

[0027] According to exemplary embodiments of the present invention, a hydrogen purification system and a method for purifying hydrogen can be provided that can minimize energy loss in a hydrogen production process.

[0028] The various advantageous and beneficial effects of the present invention are not limited to the above-described contents, and will be more easily understood in the course of explaining specific embodiments of the present invention.

[0029] Figure 1 is a drawing for explaining a hydrogen purification system according to exemplary embodiments.

[0030] Figure 2 is a flowchart illustrating a method for purifying hydrogen according to exemplary embodiments.

[0031] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, it should be noted that the terms and words used in this specification and claims should not be construed as limited to their conventional or dictionary meanings. Based on the principle that the inventor can appropriately define the concepts of terms to best explain his or her invention, they should be interpreted in a way that aligns with the technical spirit of the present invention.

[0032] Hereinafter, when describing with reference to drawings, identical or corresponding components are given the same drawing reference numerals and redundant descriptions thereof are omitted.

[0033] In the embodiments below, terms such as first, second, etc. are not used in a limiting sense, but are used for the purpose of distinguishing one component from another.

[0034] In the following embodiments, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0035] In the embodiments below, terms such as “include” or “have” mean that a feature or component described in the specification is present, and do not preclude the possibility that one or more other features or components may be added.

[0036] For convenience of explanation, the sizes of components in the drawings may be exaggerated or reduced. For example, the sizes and thicknesses of each component shown in the drawings are arbitrarily indicated for convenience of explanation, and thus the present invention is not necessarily limited to what is shown.

[0037] If a particular embodiment is capable of being implemented differently, a particular process sequence may be performed in a different order than described. For example, two processes described in succession may be performed substantially simultaneously, or in a reverse order from the described order.

[0038] In addition, when describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description is omitted.

[0039] Below, the present invention will be described in detail through each embodiment or example of the present invention. It should be noted that each embodiment or example described in this specification is not limited to a single embodiment or example, but may be combined with other embodiments or examples. Therefore, the citation of a claim in the patent claims is only an example of an embodiment, and the technical concept of the present invention should not be interpreted solely as a combination of the cited claim, and combinations with various claims also fall within the scope of the technical concept of the present invention.

[0040] Hereinafter, the present invention will be described in detail through examples. However, it should be noted that the examples described below are intended only to illustrate and concretize the present invention and are not intended to limit the scope of the invention. This is because the scope of the invention is determined by the matters set forth in the patent claims and matters reasonably inferred therefrom.

[0041]

[0042] [Hydrogen Purification System]

[0043] FIG. 1 is a drawing for explaining a hydrogen purification system (1000) according to exemplary embodiments.

[0044] Referring to FIG. 1, the hydrogen purification system (1000) includes a first reactor (100) and a second reactor (200).

[0045] The first reactor (100) can be configured to react a mixed gas containing hydrogen and nitrogen with a metal absorbent to provide a metal nitride and a hydrogen-rich gas.

[0046] More specifically, the first reactor (100) can accommodate a mixed gas and a metal absorbent. In the first reactor (100), the metal absorbent can selectively absorb nitrogen in the mixed gas, thereby increasing the hydrogen content of the mixed gas. Consequently, the first reactor (100) can provide a hydrogen-rich gas with an increased hydrogen content.

[0047] The first reactor (100) may include a pipeline that can be fluidly connected to an external device to receive a mixed gas. The first reactor (100) may be fluidly connected to a hydrogen storage tank to deliver hydrogen-rich gas to the external hydrogen storage tank. As a non-limiting example, the first reactor (100) may be configured to have an openable top to manage the metal absorbent.

[0048] According to exemplary embodiments, the pressure of the first reactor (100) may be 1 to 5 bar. As a more specific example, the pressure of the first reactor (100) may be 1 to 3 bar. The pressure of the first reactor (100) may be 1 to 2 bar. In this way, the pressure of the first reactor (100) is controlled in a pressure range closer to atmospheric pressure than in the conventional PSA method. Therefore, additional energy may not be required to raise the pressure of the first reactor (100) to a high pressure. Furthermore, the energy required to maintain the pressure of the first reactor (100) at a high pressure can be saved, thereby increasing the energy efficiency of the hydrogen purification process.

[0049] As a non-limiting example, the pressure of the first reactor (100) may be controlled by any one of a back pressure regulator, a pressure regulator, and a combination thereof. In this way, the first reactor (100) is controlled at an atmospheric pressure level, and thus does not require a pressure application device that consumes excessive energy, such as a compressor.

[0050] According to exemplary embodiments, the mixed gas may be derived from ammonia. More specifically, the mixed gas may be formed by an ammonia reforming reaction according to the following reaction scheme 1.

[0051] [Reaction Formula 1]

[0052] 2NH3→ N2+ 3H2… ΔH = 92 kJ / mol

[0053] As a non-limiting example, the mixed gas may contain, by volume, 60 to 75% hydrogen and 25 to 40% nitrogen. Additionally, the mixed gas may further contain ammonia.

[0054] The metal absorbent may be any one of manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), calcium (Ca), molybdenum (Mo), and alloys thereof. As a non-limiting example, the metal absorbent may be provided in the form of a pure metal or an alloy that does not contain an oxide.

[0055] A metal absorbent can selectively absorb nitrogen in a mixed gas by reacting with the nitrogen contained in the mixed gas to form a metal nitride. In the present invention, the term "metal nitride" includes not only a compound formed by a chemical bond between a metal and nitrogen, but also a form in which nitrogen is dissolved within the crystal structure of the metal. According to exemplary embodiments, the metal absorbent may include a metal having an oxidation state of 0. Such metals have a higher reactivity toward nitrogen than toward hydrogen. In particular, the metal absorbent can react with nitrogen at relatively low pressures. That is, under low pressure (particularly, atmospheric pressure), the metal absorbent can selectively chemically react with nitrogen in the mixed gas, thereby increasing the hydrogen purity (content) of the mixed gas. In this way, the metal absorbent according to exemplary embodiments can chemically absorb nitrogen at low pressures. Therefore, it can absorb nitrogen with a higher selectivity than an adsorption method that simply physically fixes gas to a surface, and can firmly capture nitrogen. Furthermore, it can contribute to improving the energy efficiency of the hydrogen purification system (1000).

[0056] As a non-limiting example, the metal absorbent may contain, in weight percent, one or more of zinc (Zn), magnesium (Mg), and strontium (Sr) in an amount of 10 wt% or less (including 0 wt%). This may improve the corrosion resistance and mechanical properties of the metal absorbent.

[0057] As a non-limiting example, the metal absorbent may be provided in the form of a powder, pellet, honeycomb, or a combination thereof. However, the form in which the metal absorbent is provided is not limited to these, and the metal absorbent may be provided in various forms as long as a sufficient contact area with the mixed gas can be secured.

[0058] According to exemplary embodiments, the nitrogen absorption capacity of the metal absorbent may be 1 to 7 wt% / hr. That is, the metal absorbent may absorb nitrogen corresponding to 1 to 7 wt% of the weight of the metal absorbent per hour.

[0059] According to exemplary embodiments, the reaction between the mixed gas and the metal absorbent may be performed at 700 to 800°C. As a more specific example, the reaction between the mixed gas and the metal absorbent may be performed at 750 to 800°C.

[0060] Since typical hydrogen production reactions occur at high temperatures, the mixed gas can contain high-temperature thermal energy. Therefore, by reacting the mixed gas with the metal absorbent at high temperatures, the energy loss occurring throughout the entire hydrogen production process can be minimized. However, if the reaction temperature between the mixed gas and the metal absorbent is excessively high, the physical and chemical properties of the metal absorbent, such as changes in the crystal grains of the metal absorbent, can change. Furthermore, nitrogen can be desorbed from the metal absorbent, reducing hydrogen purification efficiency. Therefore, by limiting the reaction temperature between the mixed gas and the metal absorbent to a specific temperature range, deformation of the metal absorbent can be prevented and hydrogen purification efficiency can be improved.

[0061] Hydrogen-rich gas contains less nitrogen than the mixed gas. Hydrogen-rich gas may contain 0 to 20 vol% nitrogen by volume.

[0062] The second reactor (200) is configured to receive the metal nitride from the first reactor (100) and regenerate it into the metal absorbent. In this way, the hydrogen purification system (1000) can increase hydrogen purification efficiency because the metal absorbent can be reused.

[0063] The second reactor (200) can accommodate a metal nitride. The internal temperature of the second reactor (200) can be controlled for the regeneration of the metal absorbent. The atmosphere gas of the second reactor (200) can be controlled for the regeneration of the metal absorbent. For this purpose, as a non-limiting example, the second reactor (200) can be equipped with a heating means such as a burner or a heater. The second reactor (200) can include a pipeline for supplying an atmosphere gas for the regeneration of the metal nitride. The second reactor (200) can be configured so that the upper part can be opened and closed for the management of the metal nitride or the metal absorbent after regeneration.

[0064] The second reactor (200) can receive metal nitride from the first reactor (100) in various ways. According to exemplary embodiments, the metal nitride received in the first reactor (100) can be transferred to the second reactor (200). In this case, the metal absorbent can be periodically regenerated, and if necessary, the metal absorbent can be continuously supplied to the first reactor (100), thereby enabling continuous hydrogen purification.

[0065] According to other exemplary embodiments, when the reaction of the metal absorbent is completed, the first reactor (100) may be configured to be switched to the second reactor (200). That is, by controlling the internal conditions of the reactor, the absorption of hydrogen and the regeneration of the metal absorbent can be performed in a single reactor. To this end, the first reactor (100) may be switched to the second reactor (200) by controlling a heating means such as a burner or heater, and an on-off valve of a pipeline connected to the reactor. This allows the transport of metal nitride for the regeneration of the metal absorbent to be omitted. In addition, the overall configuration of the hydrogen purification system (1000) may be simplified, making management easier, and damage and contamination of the metal nitride or metal absorbent that may occur during transport may be minimized.

[0066] When the reaction of the metal absorbent is completed, metal nitride is mainly distributed inside the first reactor (100). According to exemplary embodiments, whether the reaction of the metal absorbent is completed can be determined based on the ratio of metal nitride among the total metal accommodated in the first reactor (100). As one example, the content of metal nitride can be determined by sampling the metals accommodated in the first reactor (100). As another example, the content can be determined by observing the external characteristics (gloss, etc.) of the metal absorbent accommodated inside the first reactor (100).

[0067] Additionally, when the reaction of the metal absorbent is completed, the nitrogen content of the hydrogen-rich gas provided from the first reactor (100) may increase. According to exemplary embodiments, whether the reaction of the metal absorbent is completed may be determined based on the nitrogen content of the hydrogen-rich gas provided from the first reactor (100). That is, when the nitrogen content of the hydrogen-rich gas is outside the allowable error range, the reaction of the metal absorbent may be determined to be completed.

[0068] According to exemplary embodiments, the regeneration of the metal absorbent may be performed at a temperature of 800°C or higher. More specifically, the regeneration of the metal absorbent may be performed at a temperature range of 800°C to 1000°C. The regeneration of the metal absorbent may be performed at a temperature range of 800°C to 900°C. The regeneration of the metal absorbent may be performed at a temperature higher than the reaction temperature of the mixed gas and the metal absorbent. This allows nitrogen dissolved in the crystal structure of the metal to be released to the outside and regenerated into the metal absorbent. Furthermore, as the chemical bond between the metal and nitrogen is broken down at high temperatures, nitrogen is released in gaseous form, allowing the metal absorbent to be regenerated.

[0069] According to other exemplary embodiments, the regeneration of the metal absorbent may be performed in a reducing gas atmosphere at a temperature ranging from 600 to 1000°C. As a more specific example, the regeneration of the metal absorbent may be performed in a reducing gas atmosphere at a temperature ranging from 600 to 900°C. As a more specific example, the regeneration of the metal absorbent may be performed in a reducing gas atmosphere at a temperature ranging from 600 to 800°C. The regeneration of the metal absorbent may be performed at a temperature lower than the reaction temperature of the mixed gas and the metal absorbent. The reducing gas acts as a type of reducing agent and can weaken the bond between the metal and nitrogen. This makes it easier to regenerate the metal absorbent. Additionally, even at relatively low temperatures, nitrogen in the metal nitride is released to the outside and can be regenerated into the metal absorbent.

[0070] According to exemplary embodiments, the reducing gas may be tail gas derived from the steelmaking process. Tail gas generated from the steelmaking process is a byproduct of steel production and contains reducing gases. Furthermore, tail gas may primarily be generated during the molten iron production process in a blast furnace. Since the molten iron production process is performed in a high-temperature environment, tail gas derived from the steelmaking process may contain high-temperature thermal energy. Therefore, utilizing tail gas from the steelmaking process can efficiently supply the reducing gas and thermal energy required for the regeneration of the metal absorbent. This allows for the provision of a hydrogen purification system linked to the steelmaking process.

[0071] The reducing gas may be any one of hydrogen (H2), methane (CH4), nitrogen (N2), or a mixture thereof.

[0072]

[0073] [Method of Purifying Hydrogen]

[0074] Figure 2 is a flowchart illustrating a method for purifying hydrogen according to exemplary embodiments.

[0075] Referring to FIG. 2, a method for purifying hydrogen includes a mixed gas supply step (P1), a nitrogen absorption step (P2), and a metal absorbent regeneration step (P3). The mixed gas may be derived from ammonia. That is, it may be a reformed gas produced by an ammonia decomposition reaction.

[0076] The mixed gas providing step (P1) can be performed by providing a mixed gas containing hydrogen and nitrogen to a first reactor containing a metal absorbent.

[0077] The mixed gas may contain hydrogen and nitrogen. The mixed gas may further contain ammonia.

[0078] The metal absorbent may be any one of manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), calcium (Ca), molybdenum (Mo), and alloys thereof. Further, as a non-limiting example, the metal absorbent may include, in weight %, 10 wt% or less (including 0%) of at least one of zinc (Zn), magnesium (Mg), and strontium (Sr).

[0079] As a non-limiting example, the metal absorbent may be accommodated in the first reactor in any of the following forms: powder, pellet, honeycomb, or a combination thereof. However, the form in which the metal absorbent is provided is not limited to these, and the metal absorbent may be provided in various forms as long as a sufficient contact area with the mixed gas can be secured.

[0080] The nitrogen absorption step (P2) can be performed by reacting the metal absorbent with the mixed gas at a pressure of 1 to 5 bar to provide a metal nitride and a hydrogen-rich gas. In this way, nitrogen in the mixed gas can be selectively absorbed at a relatively low pressure close to atmospheric pressure. Furthermore, nitrogen can be robustly absorbed with a higher selectivity than by adsorbing nitrogen onto the metal surface.

[0081] According to exemplary embodiments, the reaction between the mixed gas and the metal absorbent can be performed at a temperature of 700 to 800°C. More specifically, the reaction between the mixed gas and the metal absorbent can be performed at a temperature of 750 to 800°C. This minimizes energy loss occurring throughout the entire hydrogen production process.

[0082] The step (P3) of regenerating the metal nitride may be performed at a temperature of 800°C or higher. As a more specific example, the regeneration of the metal absorbent may be performed at a temperature range of 800 to 1000°C. As a more specific example, the regeneration of the metal absorbent may be performed at a temperature range of 800 to 900°C. The regeneration of the metal absorbent may be performed at a temperature higher than the reaction temperature of the mixed gas and the metal absorbent.

[0083] The step of regenerating the metal nitride may be performed in a reducing gas atmosphere at a temperature ranging from 600 to 1000°C. As a more specific example, the regeneration of the metal absorbent may be performed in a reducing gas atmosphere at a temperature ranging from 600 to 900°C. As a more specific example, the regeneration of the metal absorbent may be performed in a reducing gas atmosphere at a temperature ranging from 600 to 800°C. The regeneration of the metal absorbent may be performed at a temperature lower than the reaction temperature of the mixed gas and the metal absorbent.

[0084] The reducing gas may be tail gas derived from the ironmaking process. The reducing gas may be any one of hydrogen (H2), methane (CH4), nitrogen (N2), or a mixture thereof.

[0085] [Example Exam]

[0086] (Example 1)

[0087] To verify the efficiency of the hydrogen purification system, experiments were conducted under atmospheric pressure. The mixed gas was assumed to be a 3:1 hydrogen (H2) to nitrogen (N2) mixture obtained through the decomposition of ammonia (NH3). Iron (Fe) was used as the metal absorbent, and it was assumed that approximately 1 wt% of N was adsorbed per hour relative to the weight of Fe.

[0088] Afterwards, the hydrogen purification efficiency was confirmed by varying the weight of Fe (weight of the metal absorbent) and the flow rate of the mixed gas. The test results are shown in Table 1 below.

[0089] Classification Test Example 1 Test Example 2 Test Example 3 Test Example 4 Test Example 5 Fe weight (g) 3000 3000 3000 1000 1500 N2 remove (L / h) 24 24 24 8 12 Mixed gas supply flow rate (mL / min) 2000 3000 4000 1000 1000 Hydrogen content of hydrogen-rich gas (vol%) 93.75 86.5 48 3.3 38 6.5 49 3.75

[0090] Referring to Table 1, it can be confirmed that the hydrogen content of the hydrogen-rich gas is higher than the hydrogen content of the mixed gas (approximately 75%). In other words, it was confirmed that nitrogen in the mixed gas can be selectively absorbed using the metal absorbent according to the exemplary embodiments.

[0091] (Example 2)

[0092] Experiments were conducted to verify the regeneration efficiency of the metal absorbent. Test Example 6 assumed a case where the temperature was higher than that during the nitrogen absorption reaction of the metal absorbent. Test Example 7 assumed a case where hydrogen gas was used as the reducing gas. Test Example 8 assumed a case where a reducing gas with a hydrogen:nitrogen ratio of 7:3 was used. In addition, detailed conditions of the metal absorbent regeneration experiment were set as shown in Table 2 below. For Test Examples 7 and 8, it was assumed that the desorbed nitrogen did not react with the reducing gas.

[0093] Classification Test Example 6 Test Example 7 Test Example 8 Gas-inGas-outGas-inGas-outGas-inGas-outTemperature (℃) 800℃ or more600~1000℃600~1000℃Nitrogen flow rate (mL / min) 0200207090Nitrogen mass flow rate (g / hr) 01.501.55.256.75Hydrogen flow rate (mL / min)--1001003030Hydrogen mass flow rate (g / hr)--0.540.540.160.16Hydrogen fraction (vol%)--10083.343025

[0094] Referring to Table 2, it was confirmed that the nitrogen content in the exhaust gas increased. That is, according to exemplary embodiments of the present invention, it was confirmed that nitrogen can be desorbed from the metal nitride and regenerated into a metal absorbent.

[0095] Although the present invention has been described with reference to the above embodiments, it will be understood by those skilled in the art that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

[0096] (Explanation of symbols)

[0097] 1000: Hydrogen Purification System

[0098] 100: Reactor 1

[0099] 200: Second Reactor

Claims

1. A first reactor configured to react a mixed gas containing hydrogen and nitrogen with a metal absorbent to produce a metal nitride and a hydrogen-rich gas; A second reactor configured to receive the metal nitride from the first reactor and regenerate it with the metal absorbent; A hydrogen purification system in which the pressure of the first reactor is 1 to 5 bar.

2. In paragraph 1, The above mixed gas is a hydrogen purification system derived from ammonia.

3. In paragraph 1, A hydrogen purification system in which the reaction of the above mixed gas and the above metal absorbent is performed at 700 to 800°C.

4. In paragraph 1, A hydrogen purification system in which the nitrogen absorption capacity of the above metal absorbent is 1 to 7 wt% / hr.

5. In paragraph 1, The above metal absorbent is a hydrogen purification system including a metal having an oxidation number of 0.

6. In paragraph 5, A hydrogen purification system wherein the above metal absorbent is any one of manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), calcium (Ca), molybdenum (Mo), and alloys thereof.

7. In paragraph 6, A hydrogen purification system, wherein the metal absorbent comprises, in weight %, at least one of zinc (Zn), magnesium (Mg), and strontium (Sr), in an amount of 10 wt% or less (including 0%).

8. In paragraph 1, A hydrogen purification system in which the regeneration of the above metal absorbent is performed at a temperature of 800°C or higher.

9. In paragraph 1, A hydrogen purification system in which the regeneration of the above metal absorbent is performed in a reducing gas atmosphere at a temperature range of 600 to 1000°C.

10. In paragraph 9, A hydrogen purification system wherein the second reactor is configured to perform regeneration of the metal absorbent at a temperature lower than the temperature of the first reactor.

11. In paragraph 9, The above reducing gas is a hydrogen purification system that is tail gas derived from the iron and steel making process.

12. In paragraph 9, A hydrogen purification system in which the above reducing gas is any one of hydrogen (H2), methane (CH4), nitrogen (N2) and a mixed gas thereof.

13. In paragraph 1, A hydrogen purification system configured such that when the reaction of the metal absorbent is completed, the first reactor is switched to the second reactor.

14. A step of providing a mixed gas containing hydrogen and nitrogen to a metal absorbent; A step of reacting the metal absorbent and the mixed gas at a pressure of 1 to 5 bar to provide a metal nitride and a hydrogen-rich gas; and A method for purifying hydrogen, comprising the step of regenerating the metal nitride with the metal absorbent.

15. In paragraph 14, The above mixed gas is a method for purifying hydrogen derived from ammonia.

16. In paragraph 14, A method for purifying hydrogen, wherein the reaction of the above mixed gas and the above metal absorbent is performed at 700 to 800°C.

17. In paragraph 14, A method for purifying hydrogen, wherein the step of regenerating the above metal nitride is performed at a temperature of 800°C or higher.

18. In paragraph 14, The step of regenerating the above metal nitride is a method for purifying hydrogen, which is performed in a reducing gas atmosphere at a temperature range of 600 to 1000°C.

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