Ammonia decomposition system and method using same

Abstract

According to exemplary embodiments of the present invention, there may be provided an ammonia decomposition system with enhanced energy efficiency and a method using same by recycling thermal energy generated during an ammonia decomposition process.

Description

Ammonia decomposition system and method using the same

[0001] The present invention relates to an ammonia decomposition system and a method using the same.

[0002] More specifically, the present invention relates to an ammonia decomposition system and a method for producing electricity using hydrogen generated by decomposing ammonia.

[0003] Hydrogen is an essential substance in our daily lives and can be said to have been widely used as early as 100 years ago. Major applications of hydrogen include serving as a basic raw material for the production of ammonia, which is a raw material for nitrogen fertilizers; as a basic raw material for methanol, which is used as a solvent or disinfectant; and as a raw material for hydro-cracking to lighten the decomposition of heavy petroleum components. Recently, it has also been used as a raw material for fuel cells. Therefore, if hydrogen can be produced in an environmentally friendly and economical manner, its utilization in various fields, including those mentioned above, will be possible. Furthermore, the widespread use of hydrogen is expected to ultimately contribute to the reduction of environmental pollutants such as carbon dioxide emissions.

[0004] Considering stability and energy costs, it is desirable to store and transport in a liquid state. In this regard, since ammonia liquefies at -33°C compared to hydrogen at -253°C, transporting hydrogen in the form of ammonia may be more efficient. Additionally, ammonia exists as a stable compound at atmospheric pressure and, unlike hydrogen, has a low risk of explosion, making it a subject of great interest as a hydrogen carrier. Ammonia can provide hydrogen according to the following reaction equation 1.

[0005] [Reaction Equation 1]

[0006] 2NH3→ N2+ 3H2;ΔH=+46 kJ / mol

[0007] As shown in reaction equation 1 above, a certain amount of energy is consumed to obtain hydrogen from ammonia, so there is a need for research on technology to increase energy efficiency in the hydrogen production process.

[0008] (Patent Document 1) Republic of Korea Published Patent Application No. 10-2023-0083367

[0009] The problem that the technical concept of the present invention aims to solve is to provide an ammonia decomposition system with excellent energy efficiency and a method using the same.

[0010] The problems of the present invention are not limited to those described above. A person skilled in the art to which the present invention pertains will have no difficulty understanding additional problems of the present invention from the overall details of the specification.

[0011] According to exemplary embodiments for solving the problems of the present invention, an ammonia decomposition system is provided. The ammonia decomposition system may include: an ammonia decomposition device comprising a first reactor configured to decompose gaseous ammonia at 400 to 700°C and provide a reaction gas, and a burner configured to heat the first reactor by burning a fuel gas; a first heat exchanger configured to provide a first heat medium and a cooled reaction gas through heat exchange between a first refrigerant and the reaction gas; a second heat exchanger configured to provide a second refrigerant and the gaseous ammonia through heat exchange between the first heat medium and liquid ammonia; a hydrogen purification device configured to purify the cooled reaction gas to provide hydrogen gas and a process tail gas; and a fuel cell utilizing the hydrogen gas as fuel.

[0012] Based on the flow of the reaction gas, a third heat exchanger is further included upstream of the first heat exchanger, and the third heat exchanger may be configured to preheat the gaseous ammonia by heat-exchanging the reaction gas and the gaseous ammonia.

[0013] It may further include a cooling device configured to cool the above fuel cell.

[0014] The above cooling device may be configured to provide the first refrigerant and to receive the second refrigerant.

[0015] The temperature of the above hydrogen gas may be 60°C or lower.

[0016] It further includes a fourth heat exchanger configured to heat the hydrogen gas to 500 to 750°C by heat-exchanging the hydrogen gas and the combustion exhaust gas generated from the burner, and the fuel cell may be a solid oxide type fuel cell.

[0017] The above process tail gas can be supplied to the burner.

[0018] The fuel cell is configured to provide electricity, steam, and unused hydrogen gas, and may be configured to provide the unused hydrogen gas to the burner.

[0019] The hydrogen content of the above unused hydrogen gas may be 0 to 40% of the hydrogen content in the above hydrogen gas.

[0020] The first refrigerant may include one or more of cooling water and glycol-based refrigerants.

[0021] According to other exemplary embodiments of the present invention, a method using an ammonia decomposition system is provided. The method may include the steps of: decomposing gaseous ammonia at 400 to 700°C to provide a reaction gas comprising hydrogen, nitrogen, and undecomposed ammonia; cooling the reaction gas using a first refrigerant to provide a first heat medium and the cooled reaction gas; heat-exchanging the first heat medium with liquid ammonia to provide the gaseous ammonia; purifying the cooled reaction gas to provide hydrogen gas and process tail gas; and providing the hydrogen gas to a fuel cell to produce power.

[0022] According to exemplary embodiments of the present invention, an ammonia decomposition system with improved energy efficiency and a method using the same can be provided by recycling thermal energy generated during the ammonia decomposition process.

[0023] The various and beneficial advantages and effects of the present invention are not limited to those described above and will be more easily understood in the process of explaining specific embodiments of the present invention.

[0024] FIG. 1 is a drawing for illustrating an ammonia decomposition system according to exemplary embodiments.

[0025] FIG. 2 is a drawing for illustrating an ammonia decomposition apparatus according to exemplary embodiments.

[0026] FIG. 3 is a drawing for illustrating an ammonia decomposition system according to other exemplary embodiments.

[0027] FIG. 4 is a drawing for illustrating an ammonia decomposition system according to other exemplary embodiments.

[0028] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings. Instead, based on the principle that the inventor can appropriately define the concepts of terms to best describe his invention, they should be interpreted in a meaning and concept consistent with the technical spirit of the present invention.

[0029] In the following descriptions with reference to the drawings, identical or corresponding components are assigned the same reference numerals, and redundant descriptions thereof will be omitted.

[0030] In the following embodiments, the terms first, second, etc. are used not in a limiting sense, but for the purpose of distinguishing one component from another component.

[0031] In the following embodiments, the singular expression includes the plural expression unless the context clearly indicates otherwise.

[0032] In the following embodiments, terms such as "include" or "have" mean that the features or components described in the specification are present, and do not preclude the possibility that one or more other features or components may be added.

[0033] In the drawings, the size of components may be exaggerated or reduced for convenience of explanation. For example, the size and thickness of each component shown in the drawings are depicted arbitrarily for convenience of explanation, so the present invention is not necessarily limited to what is illustrated.

[0034] Where an embodiment can be implemented differently, a specific process sequence may be performed differently from the order described. For example, two processes described consecutively may be performed substantially simultaneously or proceed in the reverse order of the description.

[0035] In addition, in describing the present invention, if it is determined that a detailed description of related known components or functions may obscure the essence of the invention, such detailed description is omitted.

[0036] The present invention will be described in detail below through each embodiment. It should be noted that each embodiment described in this specification is not limited to a single embodiment but may also be combined with other embodiments. Accordingly, the citation of claims in the patent claims is merely an example of an embodiment, and the technical concept of the present invention should not be interpreted as being limited only to a combination with the cited claims; rather, combinations with various claims are also included within the scope of the technical concept of the present invention.

[0037] The present invention will be described in detail below through examples. However, it should be noted that the following examples are intended merely to illustrate and embody the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the patent claims and matters reasonably inferred therefrom.

[0038] [Ammonia Decomposition System]

[0039] (Example 1)

[0040] FIG. 1 is a drawing for illustrating an ammonia decomposition system (10) according to exemplary embodiments.

[0041] FIG. 2 is a drawing for explaining an ammonia decomposition device (100) according to exemplary embodiments.

[0042] Referring to FIGS. 1 and 2, the ammonia decomposition system (10) may include an ammonia decomposition device (100), a first heat exchanger (200), a second heat exchanger (300), a hydrogen purification device (400), a fuel cell (500), and a cooling device (600).

[0043] The ammonia decomposition device (100) may include a first reactor (110) configured to decompose gaseous ammonia at 400 to 700°C and provide reaction gas, and a burner (120) configured to heat the first reactor (110).

[0044] If the temperature inside the first reactor (110) is less than 400°C, the decomposition efficiency of gaseous ammonia may decrease. If the temperature inside the first reactor (110) exceeds 700°C, energy costs may increase excessively, and the hydrogen production efficiency may decrease.

[0045] The first reactor (110) is not particularly limited as long as it can create a high-temperature atmosphere to carry out the ammonia decomposition reaction and provide a reaction gas to the outside. As a non-limiting example, the first reactor may be any one of a fluidized bed reactor, a batch reactor, a rotary reactor, and a combination thereof.

[0046] According to exemplary embodiments, the first reactor (110) may contain an ammonia decomposition catalyst. As a result, gaseous ammonia supplied to the first reactor (110) can be effectively decomposed. The type of ammonia decomposition catalyst is not particularly limited. As a non-limiting example, the ammonia decomposition catalyst may include any one of a precious metal, a transition metal, or an alloy thereof as an active metal. More specifically, the ammonia decomposition catalyst may include any one of Ru, Ni, Fe, Co, and an alloy thereof as an active metal. The ammonia decomposition catalyst may be provided in the form of a supported catalyst in which the active metal is supported on a ceramic, but the present invention is not limited thereto.

[0047] According to exemplary embodiments, the ammonia decomposition rate of the first reactor (110) may be 81 to 100%.

[0048] Gaseous ammonia may be provided from the second heat exchanger (300). To this end, the first reactor (110) may be fluidly connected to the second heat exchanger (300). In the present invention, being fluidly connected means that two devices or facilities are connected using a fluid transfer means, such as a pipeline, so that at least one fluid can move to both sides or one side.

[0049] Gaseous ammonia is a gas mainly containing ammonia and is used as a raw material for producing hydrogen in the first reactor (110). Gaseous ammonia may consist of ammonia, except for unavoidable impurities that may be mixed during the ammonia storage and transport process. Unavoidable impurities may refer to metal particles originating from pipelines, storage facilities, etc., or atmospheric air contained in trace amounts (less than 1 part by weight based on 100 parts by weight of ammonia).

[0050] The reaction gas is a gas produced through the decomposition of ammonia and may contain hydrogen, nitrogen, and unreacted ammonia. As a result, the reaction gas discharged from the first reactor (110) may have high thermal energy corresponding to the internal temperature of the first reactor (110). As a non-limiting example, the temperature of the reaction gas discharged from the first reactor (110) may be 400 to 700°C. The temperature of the reaction gas discharged from the first reactor (110) may be substantially the same as the temperature of the first reactor (110).

[0051] The burner (120) can be configured to heat the first reactor (110) by burning fuel gas. Combustion exhaust gas of 500 to 900°C can be generated by the combustion reaction of the fuel gas. In this way, the heat energy required for the ammonia decomposition reaction can be provided through the burner (120).

[0052] A first reactor (110) can be placed through the burner (120).

[0053] The burner (120) may include a burner body (121) through which a first reactor (110) is disposed and in which a combustion reaction between combustion air and fuel gas occurs inside, and an outlet (122) through which combustion exhaust gas is discharged.

[0054] The burner body (121) may include an inlet (I) that supplies fuel gas and combustion air into an internal space. At the outlet of the inlet (I) where the fuel gas and combustion air are discharged, a flame (F) and high-temperature combustion exhaust gas may be formed due to the combustion reaction between the fuel gas and the air. As a result, the inside of the burner body (121) is created into a high-temperature atmosphere, and the thermal energy required for ammonia decomposition can be provided by indirectly heating the first reactor (110). The inlet (I) may each include independent flow paths for the flowing gas and combustion air, but the present invention is not necessarily limited thereto.

[0055] The exhaust port (122) can provide a flow path for supplying high-temperature combustion exhaust gas from the burner body (121) to subsequent equipment. To this end, the exhaust port (122) can be fluidically connected to subsequent equipment.

[0056] Fuel gas may be used without limitation as long as it is a gas capable of providing a certain amount of thermal energy upon combustion. As a non-limiting example, the fuel gas may include any one of ammonia, hydrogen, natural gas, and mixtures thereof. However, in the case of natural gas, greenhouse gases such as carbon dioxide may be generated upon combustion. Therefore, more preferably in terms of carbon dioxide reduction, the fuel gas may include any one of ammonia, hydrogen, and mixtures thereof.

[0057] Combustion air may be atmospheric air containing about 20 to 22 vol% oxygen. However, the present invention is not limited thereto, and additional excess air may be added for a sufficient combustion reaction.

[0058] The first heat exchanger (200) may be configured to provide a first heat medium and a cooled reaction gas through heat exchange between the first refrigerant and the reaction gas. The reaction gas discharged from the ammonia decomposition device (100) may contain high-temperature thermal energy. According to exemplary embodiments, energy efficiency can be improved by recovering the thermal energy contained in the high-temperature reaction gas and recycling it within the ammonia decomposition system (10). Additionally, the reaction gas can be sufficiently cooled to facilitate handling in a subsequent hydrogen purification process.

[0059] The structure of the first heat exchanger (200) is not particularly limited as long as it can recover the thermal energy of the reaction gas. As an example, the first heat exchanger (200) may be provided with a first refrigerant flow path and a reaction gas flow path independently. The first refrigerant flow path and the reaction gas flow path may be arranged adjacently. As a result, the first heat medium may be generated at the downstream end of the first refrigerant flow path by heat exchange between the first refrigerant and the reaction gas.

[0060] The temperature of the reaction gas discharged from the first heat exchanger (200) is not particularly limited as long as it is lower than the initial temperature of the reaction gas discharged from the first heat exchanger (200). As a non-limiting example, the temperature of the reaction gas cooled in the first heat exchanger (200) may be 15 to 60°C.

[0061] According to exemplary embodiments, the first refrigerant may include one or more of water and glycol-based refrigerants. Since water has a relatively high specific heat, a large amount of thermal energy can be recovered from the same temperature change. Glycol-based refrigerants have a relatively low freezing point, so constant fluidity can be ensured even in harsh cooling environments, and at the same time, because they have a relatively high boiling point, they do not easily vaporize, making them easy to manage within the process. Glycol-based refrigerants may include one or more of ethylene glycol, propylene glycol, and mixtures thereof, but the present invention is not necessarily limited thereto.

[0062] The first heat medium refers to a first refrigerant heated by recovering thermal energy from a reaction gas, and its composition may be substantially the same except that the phase of the first refrigerant and some of the medium are different. As a non-limiting example, the temperature of the first heat medium may be 200 to 650°C. More specifically, the temperature of the first heat medium may be 200 to 250°C.

[0063] The second heat exchanger (300) may be configured to provide a second refrigerant and gaseous ammonia through heat exchange between the first heat medium and liquid ammonia. According to exemplary embodiments, the energy generated in the ammonia decomposition reaction can be used to vaporize the liquid ammonia, thereby improving the energy efficiency of the ammonia decomposition system (10).

[0064] The second heat exchanger (300) is not particularly limited as long as it can vaporize liquid ammonia using the thermal energy of the first heat medium. As one example, the second heat exchanger (300) may be provided with a first heat medium path and an ammonia path independently. The first heat medium path and the ammonia path may be arranged adjacent to each other. As a result, the first heat medium can heat the liquid ammonia to generate gaseous ammonia at the downstream end of the ammonia path.

[0065] The second refrigerant is a first heat medium that has recovered its cooling capacity through the vaporization of liquid ammonia, and its composition may be substantially the same as that of the first heat medium, except that the phase of some medium is different. As a non-limiting example, the temperature of the second refrigerant may be 0 to 70°C. More specifically, the temperature of the second refrigerant may be 0 to 70°C.

[0066] The hydrogen purification device (400) may be configured to purify the reaction gas cooled in the first heat exchanger (200) to provide hydrogen gas and process tail gas.

[0067] The hydrogen purification device (400) is not particularly limited as long as it can separate hydrogen from the reaction gas to provide high-purity hydrogen. As a non-limiting example, the hydrogen purification device (400) may include one or more of a PSA device, a TSA device, a VSA device, a VPSA device, a membrane separator, and a combination thereof.

[0068] The process tail gas may contain nitrogen and undissolved ammonia. Additionally, the process tail gas may contain undissolved hydrogen. According to exemplary embodiments, the process tail gas may be supplied to a burner (120). Since the process tail gas contains gaseous components having a predetermined calorific value, it can be used as fuel gas for the burner (120). In this way, the hydrogen purification byproduct can be recycled, thereby increasing the resource efficiency of the ammonia decomposition system (10).

[0069] The fuel cell (500) is provided in the form of a fuel cell system comprising a fuel cell stack in which a plurality of unit cells, each having a fuel electrode, an electrolyte, and an air electrode stacked sequentially, are stacked, and a control system (BOP) for supporting the operation of the fuel cell stack. The control system refers to facilities that support the stable operation of the fuel cell (500), such as a cooling pipeline. At this time, hydrogen gas may be supplied to the fuel electrode, and working air may be supplied to the air electrode. Working air may refer to ambient air.

[0070] The fuel cell (500) can use hydrogen gas as fuel. As a result, it can generate electricity and water. As a result, the fuel cell (500) can provide electricity, water, and unused hydrogen gas that is not used as fuel to subsequent processes or facilities.

[0071] The generated power can be supplied and used in various applications where the ammonia decomposition system (10) is applied. As one example, the fuel cell (500) can be installed on a ship to supply power. As another example, the fuel cell (500) can be deployed in a large-scale industrial facility to supply power.

[0072] According to exemplary embodiments, the fuel cell (500) may be configured to provide unused hydrogen gas to the burner (120). Depending on the operating conditions of the fuel cell (500), the water produced by the fuel cell reaction may be provided in a liquid or gaseous state. As one example, if the water is provided in a liquid state, the unused hydrogen gas in a gaseous state can be easily separated and provided to the burner (120) without a separate separation device. As another example, if the water is provided in a gaseous state, the water can be absorbed using a moisture recovery device such as a hollow fiber membrane humidifier and the unused hydrogen gas can be provided to the burner (120). As yet another example, the water (steam) in a gaseous state and the unused hydrogen gas can be provided to the burner (120) without separation. In this case, the steam can function as a heat medium to promote the combustion reaction.

[0073] The hydrogen content of the unused hydrogen gas may be 0 to 40% of the hydrogen content in the hydrogen gas. More specifically, the hydrogen content of the unused hydrogen gas may be 10 to 40% of the hydrogen content in the hydrogen gas. As one example, the hydrogen content of the unused hydrogen gas may be controlled by the operating conditions (fuel utilization rate, voltage, etc.) of the fuel cell (500). As another example, the content of the unused hydrogen gas may be determined according to the specifications of the hydrogen purifier (400).

[0074] According to exemplary embodiments, the temperature of the hydrogen gas may be 60°C or lower. In this case, the hydrogen gas may be appropriately heated before being supplied to the fuel cell (500). Alternatively, the fuel cell (500) may be a polymer electrolyte fuel cell (PEMFC). A PEMFC operates at a relatively low temperature (70°C or lower). Thus, the hydrogen gas provided after hydrogen purification can be used as fuel for the fuel cell (500) by utilizing its own thermal energy or by applying only a small amount of thermal energy. This allows for an improvement in the energy efficiency of the ammonia decomposition system (10).

[0075] According to exemplary embodiments, the ammonia decomposition system (10) may further include a cooling device (600). The cooling device (600) may be configured to cool the fuel cell (500). This may contribute to maintaining the performance of the fuel cell (500) constant by cooling the reaction heat generated in the fuel cell (500). To this end, the cooling device (600) may be configured to supply a refrigerant to a cooling pipeline within the fuel cell (500). To this end, the cooling device (600) and the fuel cell (500) may be fluidly connected to each other.

[0076] According to exemplary embodiments, the cooling device (600) may be configured to provide a first refrigerant and receive a second refrigerant. The second refrigerant is a heat medium that has recovered its cooling amount in the second heat exchanger (300) and may be provided as the first refrigerant through the cooling device (600). In this way, the resource efficiency of the ammonia decomposition system (10) can be improved by circulating the refrigerant starting from the cooling device (600). In this case, the cooling device (600) may include a fuel cell cooling unit (610) that cools the fuel cell (500) and a refrigerant circulation unit (620) that receives the second refrigerant and provides the first refrigerant. As one example, the fuel cell cooling unit (610) and the refrigerant circulation unit (620) may be arranged adjacent to each other so that the heat medium used for cooling the fuel cell (500) can be cooled using the second refrigerant stored in the refrigerant circulation unit (620). As another example, the fuel cell cooling unit (610) and the refrigerant circulation unit (620) are configured as independent facilities, and the fuel cell cooling unit (610) can cool the heat medium used to cool the fuel cell (500) using an independent cooling device such as a cooling fan.

[0077] (Example 2)

[0078] FIG. 3 is a drawing for illustrating an ammonia decomposition system (20) according to other exemplary embodiments.

[0079] Referring to FIG. 3, the ammonia decomposition system (20) may further include a third heat exchanger (700).

[0080] A third heat exchanger (700) may be positioned upstream of the first heat exchanger (200) based on the flow of the reaction gas. In the present invention, "based on the flow of a fluid" means based on the direction in which the fluid moves within the system. In this example, the reaction gas may flow through the third heat exchanger (700) to the first heat exchanger (200).

[0081] The third heat exchanger (700) can be configured to preheat the gaseous ammonia by exchanging heat between the reaction gas and the gaseous ammonia. This can further improve the ammonia decomposition efficiency in the first reactor (110).

[0082] The structure of the third heat exchanger (700) is not particularly limited as long as it can achieve heat exchange between the reaction gas and the gaseous ammonia. As a non-limiting example, the third heat exchanger (700) may include a reaction gas path and a gaseous ammonia path arranged adjacent to each other.

[0083] According to exemplary embodiments, the temperature of the gaseous ammonia discharged from the third heat exchanger (700) may be 400 to 600°C. In this case, as a non-limiting example, the temperature of the reaction gas discharged from the third heat exchanger (700) may be 250 to 550°C.

[0084] In addition, the configuration that overlaps with the ammonia decomposition system (10) according to Example 1 can be applied in the same way to the ammonia decomposition system (20), so a detailed description is omitted.

[0085] (Example 3)

[0086] FIG. 4 is a drawing for illustrating an ammonia decomposition system (30) according to other exemplary embodiments.

[0087] Referring to FIG. 6, the ammonia decomposition system (30) may further include a fourth heat exchanger (800).

[0088] The fourth heat exchanger (800) may be configured to heat the hydrogen gas generated in the hydrogen purification device (400) to 500 to 750°C by heat-exchanging the hydrogen gas generated from the burner with the combustion exhaust gas generated from the burner. More specifically, the fourth heat exchanger may be configured to heat the hydrogen gas to 650 to 750°C. When the fuel cell (501) is operated under high temperature conditions, the efficiency of the fuel cell (500) can be improved by heating the hydrogen gas using the high-temperature combustion exhaust gas in this way.

[0089] According to exemplary embodiments, the fuel cell (501) may be a solid oxide fuel cell. Since the solid oxide fuel cell operates at high temperatures and uses a solid oxide as an electrolyte, it has excellent durability and lifespan and relatively excellent power generation efficiency. Thus, according to exemplary embodiments, the hydrogen gas can be heated using the heat generated in the ammonia decomposition system (10), allowing for efficient integration with the solid oxide fuel cell, which has excellent durability, lifespan, and power generation efficiency.

[0090] In addition, configurations that overlap with the ammonia decomposition system (10, 20) according to Example 1 and Example 2 can be applied in the same way to the ammonia decomposition system (30), so a detailed description is omitted.

[0091] [Method using an ammonia decomposition system]

[0092] A method using an ammonia decomposition system may include the steps of: decomposing gaseous ammonia at 400 to 700°C to provide a reaction gas containing hydrogen, nitrogen, and undecomposed ammonia; cooling the reaction gas using a first refrigerant to provide a first heat medium and the cooled reaction gas; heat-exchanging the first heat medium with liquid ammonia to provide the gaseous ammonia; purifying the cooled reaction gas to provide hydrogen gas and process tail gas; and providing the hydrogen gas to a fuel cell to produce electricity.

[0093] The step of providing the reaction gas can be performed in the ammonia decomposition device (100) described above. For the step of providing the reaction gas, refer to the description of the ammonia decomposition device (100).

[0094] The step of providing the cooled reaction gas can be performed in the first heat exchanger (200) described above. For the step of providing the cooled reaction gas, refer to the description of the first heat exchanger (200).

[0095] The step of providing gaseous ammonia can be performed in the second heat exchanger (300) described above. For the step of providing gaseous ammonia, refer to the description of the second heat exchanger (300).

[0096] The step of providing hydrogen gas and process tail gas can be performed in the hydrogen purification device (400) described above. For the step of providing hydrogen gas and process tail gas, refer to the description of the hydrogen purification device (400).

[0097] The step of producing power can be performed in the fuel cell (500) described above. For the step of producing power, refer to the description of the fuel cell (500).

[0098] According to exemplary embodiments, gaseous ammonia can be preheated using a first heat medium. In this case, the preheating of gaseous ammonia can be performed in the second heat exchanger (300) described above.

[0099] Furthermore, the configuration described in the ammonia decomposition system (10, 20, 30) can be applied without limitation to the method using the ammonia decomposition system, so a detailed description is omitted.

[0100] Although the invention has been described with reference to the above embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as described in the following claims.

[0101] (Explanation of symbols)

[0102] 10,20,30: Ammonia decomposition system

[0103] 100: Ammonia decomposition device

[0104] 110: First reactor

[0105] 120: Burner

[0106] 200: First heat exchanger

[0107] 300: Second heat exchanger

[0108] 400: Hydrogen purification unit

[0109] 500, 501: Fuel cell

[0110] 600: Cooling unit

[0111] 700: 3rd heat exchanger

[0112] 800: 4th heat exchanger

Claims

1. An ammonia decomposition device comprising a first reactor configured to decompose gaseous ammonia at 1,400 to 700°C and provide reaction gas, and a burner configured to heat the first reactor by burning fuel gas; A first heat exchanger configured to provide a first heat medium and a cooled reaction gas through heat exchange between a first refrigerant and the reaction gas; A second heat exchanger configured to provide a second refrigerant and gaseous ammonia through heat exchange between the first heat medium and liquid ammonia; A hydrogen purification device configured to purify the above-mentioned cooled reaction gas to provide hydrogen gas and process tail gas; and Ammonia decomposition system comprising a fuel cell that uses the above hydrogen gas as fuel 2. In Paragraph 1, Based on the flow of the reaction gas, it further includes a third heat exchanger positioned upstream of the first heat exchanger, and The above third heat exchanger is an ammonia decomposition system configured to preheat the gaseous ammonia by heat-exchanging the reaction gas and the gaseous ammonia.

3. In Paragraph 1, An ammonia decomposition system further comprising a cooling device configured to cool the above fuel cell.

4. In Paragraph 3, The above cooling device is, An ammonia decomposition system configured to provide the first refrigerant and accommodate the second refrigerant.

5. In Paragraph 1, An ammonia decomposition system in which the temperature of the hydrogen gas is 60°C or lower.

6. In Paragraph 1, It further includes a fourth heat exchanger configured to heat the hydrogen gas to 500~750℃ by heat-exchanging the hydrogen gas and the combustion exhaust gas generated from the burner, and The above fuel cell is an ammonia decomposition system that is a solid oxide type fuel cell.

7. In Paragraph 1, The above process tail gas is an ammonia decomposition system supplied to the above burner.

8. In Paragraph 1, The above fuel cell is, It is configured to provide electricity, steam, and unused hydrogen gas, and An ammonia decomposition system configured to supply the above unused hydrogen gas to the burner.

9. In Paragraph 8, An ammonia decomposition system in which the hydrogen content of the above-mentioned unused hydrogen gas is 0 to 40% of the hydrogen content in the above-mentioned hydrogen gas.

10. In Paragraph 1, The above-mentioned first refrigerant is an ammonia decomposition system comprising one or more of cooling water and glycol-based refrigerants.

11. A step of decomposing gaseous ammonia at 400~700℃ to provide a reaction gas containing hydrogen, nitrogen, and undecomposed ammonia; A step of cooling the reaction gas using a first refrigerant to provide a first heat medium and the cooled reaction gas; A step of providing gaseous ammonia by heat-exchanging the first heat medium with liquid ammonia; A step of purifying the cooled reaction gas to provide hydrogen gas and process tail gas: and A method comprising the step of providing the above hydrogen gas to a fuel cell to produce power.

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