Hydrogen production system

Abstract

The present invention relates to a hydrogen production system, wherein the arrangement of catalysts in first and second catalyst regions is optimized according to the measurement value of NOx on the outer wall of a reaction tube and the average measurement value of NOx at an exhaust gas outlet, thereby securing sufficient ammonia decomposition efficiency despite the utilization of various catalysts.

Description

Hydrogen production system

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

[0002] In modern chemical processes, the design of high-efficiency thermochemical decomposition reactors is necessary for the efficient treatment of ammonia decomposition reactions. Unlike general gas decomposition reactions, ammonia decomposition is a strongly endothermic reaction at high temperatures, which presents a problem that makes it difficult to apply existing designs or operating methods.

[0003] In particular, while the use of catalysts can improve ammonia decomposition efficiency, changes in the composition and arrangement of the catalyst can affect the efficiency. However, since catalysts are placed inside the reactor, there are many variables to consider during the design process, making it difficult to optimize their placement. Therefore, it is necessary to develop a technology that can optimize catalyst placement and improve ammonia decomposition efficiency.

[0004] The problem that the technical concept of the present invention aims to solve is to provide a hydrogen production system that can be operated efficiently by optimizing the arrangement of catalysts.

[0005] 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.

[0006] According to exemplary embodiments for solving the problem of the present invention, a hydrogen production system is provided. The hydrogen production system comprises: a combustion furnace including a burner configured to use ammonia fuel and an exhaust gas outlet; and a reaction tube disposed in the internal space of the combustion furnace and including a flow path through which ammonia gas can flow, wherein the reaction tube comprises a first catalyst region in which the NOx measurement value at the outer wall of the reaction tube is higher than the average NOx measurement value at the exhaust gas outlet and a second catalyst region in which the NOx measurement value at the outer wall of the reaction tube is lower than the average NOx measurement value at the exhaust gas outlet, and the first catalyst disposed in the first catalyst region may be a catalyst having a higher catalytic activity than the second catalyst disposed in the second catalyst region.

[0007] The average ammonia content of the first catalyst region is 25 to 100% in mass%, and the average ammonia content of the second catalyst region may be 0 to 25% in mass%.

[0008] The above reaction tube can satisfy the following relationship 1.

[0009] [Relationship 1]

[0010]

[0011] In the above equation 1, [Ru] is the ratio of Ru catalyst at a position spaced L away from the ammonia gas inlet, L is the distance spaced from the ammonia gas inlet of the reaction tube, and Lo is the total length of the reaction tube.

[0012] The average temperature of the first catalyst region is 400 to 550°C, and the average temperature of the second catalyst region may be 600 to 750°C.

[0013] The second catalyst region may be positioned adjacent to the exhaust gas outlet.

[0014] Based on the flow direction of the ammonia gas, the first catalyst region and the second catalyst region can be arranged sequentially.

[0015] A Ru-based catalyst may be disposed in the first catalyst region, and a Ni-based catalyst may be disposed in the second catalyst region.

[0016] It may further include an SCR reactor that is fluidically connected to the exhaust gas outlet and configured to remove NOx discharged through the exhaust gas outlet.

[0017] The above ammonia fuel may be a process tail gas derived from a hydrogen purification process.

[0018] It may further include a first heat exchanger configured to heat exchange the exhaust gas discharged from the exhaust gas outlet and the ammonia fuel.

[0019] It may further include a second heat exchanger configured to heat exchange the flue gas discharged from the flue gas outlet and the ammonia gas.

[0020] According to exemplary embodiments of the present invention, by optimizing the arrangement of catalysts, a hydrogen production system can be provided that can secure sufficient ammonia decomposition efficiency even when utilizing various catalysts.

[0021] 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.

[0022] FIG. 1 is a drawing for illustrating a hydrogen production system according to exemplary embodiments.

[0023] FIG. 2 is a drawing for illustrating catalyst arrangements according to exemplary embodiments.

[0024] FIG. 3 is a drawing for illustrating a hydrogen production system according to exemplary embodiments.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] In the following embodiments, the singular expression includes the plural expression unless the context clearly indicates otherwise.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] (Example 1)

[0036] FIG. 1 is a drawing for illustrating a hydrogen production system (10) according to exemplary embodiments.

[0037] FIG. 2 is a drawing for illustrating catalyst arrangements according to exemplary embodiments.

[0038] Referring to FIG. 1, the hydrogen production system (10) may include a combustion furnace (100) and a reaction tube (200).

[0039] The hydrogen production system (10) may be a single ammonia reforming reactor comprising a combustion furnace (100) and a reaction tube (200). However, the present invention is not limited thereto, and the hydrogen production system (10) may refer to a series of hydrogen production processes including an ammonia reforming reactor. In this case, the hydrogen production system (10) may include a plurality of ammonia reforming reactors connected in series and / or parallel.

[0040] The combustion furnace (100) includes a burner (110) and an exhaust gas outlet (120). The combustion furnace (100) is a type of hot box for providing thermal energy required for an ammonia decomposition reaction to a reaction tube (200). The combustion furnace (100) can heat and maintain the reaction tube (200) at a target temperature. The combustion furnace (100) may include an internal space (S) in which the reaction tube (200) is accommodated and a flame (F) generated from the burner (110) is provided.

[0041] In a vertical coordinate system consisting of X, Y, and Z directions that are substantially perpendicular to each other, the combustion furnace (100) may extend in the Z direction. The combustion furnace (100) may extend in the Z direction to have a first length. The length direction of the combustion furnace (100) may be substantially parallel to the Z direction. The length direction of the combustion furnace (100) may be substantially perpendicular to the X direction and the Y direction. Unless otherwise defined in the present invention, the Z direction may be referred to as the first direction. The X direction may be referred to as the second direction. The Y direction may be referred to as the third direction.

[0042] A burner (110) may be positioned at the top of the combustion furnace (100). More specifically, the burner (110) may be positioned above the midpoint of the combustion furnace (100). The midpoint of the combustion furnace (100) may refer to the half-length point of the first length. The burner (110) may be positioned adjacent to the upper side of the combustion furnace (100) to provide a flame to the internal space (S). An ammonia gas inlet of the reaction tube (200) is positioned at the upper side of the combustion furnace (100). As a result, a strong endothermic reaction may occur at the upper side of the combustion furnace (100) due to the high ammonia content. Consequently, the temperature of the reaction tube (200) may be lowered, which may reduce the efficiency of the ammonia decomposition reaction. However, according to exemplary embodiments, the burner (110) may be positioned at the top of the combustion furnace (100) to directly heat the upper side of the reaction tube (200). Therefore, the efficiency of the ammonia decomposition reaction can be improved by compensating for heat loss caused by the strong endothermic reaction.

[0043] The burner (110) may be configured to use ammonia fuel. In the present invention, using ammonia fuel is not necessarily limited to using fuel composed solely of ammonia, and may include cases where ammonia is mixed with other fuel components. To this end, the burner (110) may include an air nozzle for injecting combustion air and an ammonia fuel nozzle for injecting ammonia fuel. Ammonia gas or liquid ammonia may be supplied to the burner (110). Additionally, to increase the heat output of the flame, additional fuel nozzles may be included. By using ammonia as fuel in this way, hydrogen can be generated during the combustion process, and the generation of carbon dioxide can be minimized by replacing fossil fuels.

[0044] According to exemplary embodiments, the ammonia fuel may be a process tail gas derived from a hydrogen purification process. To obtain high-purity hydrogen gas, a hydrogen purification process may be performed to separate hydrogen from the reaction gas produced in the ammonia decomposition process. According to exemplary embodiments, the reaction gas may be discharged from a reaction tube (200). The reaction gas may contain nitrogen, hydrogen, and undissolved ammonia. Through the hydrogen purification process, the reaction gas may be separated into high-purity hydrogen gas and process tail gas. Since this process tail gas contains nitrogen and undissolved ammonia, it may be used as fuel for a burner (110). Thus, according to exemplary embodiments, a hydrogen production system (10) with improved resource efficiency may be provided.

[0045] Exhaust gas may be formed by a combustion reaction in the burner (110). Exhaust gas is a byproduct formed by the combustion reaction. Since the burner (110) uses ammonia as fuel for the combustion reaction, NOx such as NO, NO2, or N2O may be formed. This exhaust gas may be discharged to the outside of the combustion furnace (100) through the exhaust gas outlet (120).

[0046] The exhaust gas outlet (120) may be positioned at the bottom of the combustion furnace (100). More specifically, the exhaust gas outlet (120) may be positioned below the midpoint of the combustion furnace (100). The exhaust gas outlet (120) may be positioned adjacent to the lower side of the combustion furnace (100) to discharge exhaust gas from the internal space (S) to the outside. The exhaust gas may flow from the top to the bottom of the combustion furnace (100) and be discharged to the outside of the combustion furnace (100) through the exhaust gas outlet (120). The exhaust gas outlet (120) may be positioned on the lower outer wall of the combustion furnace (100) to communicate with the internal space (S). As a non-limiting example, the exhaust gas outlet (120) may include a damper or a circulator.

[0047] The reaction tube (200) is disposed in the internal space (S) of the combustion furnace and may include a flow path (P) through which ammonia gas can flow. The flow path (P) may be separated from the internal space (S) of the combustion furnace (100) by the outer wall (W) of the reaction tube (200). The reaction tube (200) may extend in the Z direction to have a second length. The longitudinal direction of the reaction tube (200) may be substantially parallel to the Z direction. The longitudinal direction of the reaction tube (200) may be substantially parallel to the longitudinal direction of the combustion furnace (100).

[0048] The reaction tube (200) may include a catalyst disposed on the flow path (P). The catalyst can improve hydrogen production efficiency by catalyzing the ammonia decomposition reaction. As a non-limiting example, the catalyst may be provided in the form of active metal powder pellets. The catalyst may be provided in the form of a supported catalyst in which an active metal is supported on a ceramic support such as alumina. It is not particularly limited as long as it is provided in the flow path (P) of the reaction tube (200) and can come into contact with ammonia gas, and the present invention is not limited to the above-described forms of catalyst provision.

[0049] According to exemplary embodiments, the reaction tube (200) contains catalysts of various compositions. However, since the active temperature and other properties differ depending on the composition of the active catalyst, it is necessary to optimize the arrangement according to the composition of the active catalyst.

[0050] According to exemplary embodiments, a catalyst can be arranged based on the degree of NOx generation. As described above, NOx is a byproduct of the ammonia combustion reaction. During ammonia combustion, the reaction for NOx formation may follow Reaction Scheme 1 below, but is not necessarily limited thereto.

[0051] [Reaction Equation 1]

[0052] 4NH3 + 5O2 → 4NO + 6H2O

[0053] Such NOx formation reactions can occur when oxygen is supplied in excess of ammonia in a high-temperature atmosphere. At this time, the internal space (S) of the combustion chamber (100) is maintained in a high-temperature atmosphere by the flame (F) generated from the burner (110). As a result, unburned ammonia discharged from the burner (110) can be oxidized in the high-temperature oxidizing atmosphere of the combustion chamber (100) to form NOx. Additionally, as the flame supply from the burner (110) continues, the temperature of the outer wall (W) of the reaction tube (200) can also continuously rise. From the above, oxidation of unburned ammonia may occur on the outer wall (W) of the reaction tube (200), and additionally, an oxidation reaction according to any one of the following reaction equations may occur, further increasing the concentration of NOx.

[0054] [Reaction Equation 2]

[0055] N2 + O2 → 2NO

[0056] [Reaction Equation 3]

[0057] 2NO + O2 → 2NO2

[0058] According to exemplary embodiments, if the NOx measurement value at the outer wall (W) of the reaction tube (200) is higher than the average NOx measurement value at the flue gas outlet (120), a first catalyst with relatively high catalytic activity can be placed to induce a high-intensity ammonia decomposition reaction. A high NOx measurement value at the outer wall (W) of the reaction tube (200) means that the temperature of the outer wall (W) is high or the oxygen concentration in the surrounding area is high. Therefore, by inducing a strong endothermic reaction through the first catalyst with high catalytic activity, the outer wall (W) of the reaction tube (200) can be locally cooled to minimize the NOx formation reaction and efficiently produce hydrogen. Meanwhile, if the NOx measurement value is low, a second catalyst with relatively low activity can be used to minimize excessive temperature imbalance between the internal space (S) of the combustion furnace (100) and the reaction tube (200). As a result, equipment stability can be increased.

[0059] In the design phase of a hydrogen production system, it may be somewhat difficult to determine the catalyst placement based simply on the temperature distribution of the flow path (P) of the reaction tube (200). This is because, in order to predict or simulate the internal (R) temperature distribution of the reaction tube (200), various variables must be considered, such as the heat quantity of the flame generated from the burner (110), the temperature profile of the internal space (S) of the combustion furnace, and the structure, material, and temperature profile of the outer wall (W) of the reaction tube (200). Furthermore, even when the hydrogen production system (10) is actually operated, it may be somewhat difficult to directly measure the temperature of the flow path (P) of the reaction tube (200). However, according to exemplary embodiments, as shown in FIG. 2, the catalyst placement can be determined based on the NOx distribution inside the combustion furnace (100). This NOx concentration can be easily predicted based on the temperature distribution of the internal space (S) of the combustion furnace, the oxygen concentration distribution, or the temperature distribution of the outer wall (W) of the reaction tube (200). In addition, when operating the actual hydrogen production system (10), the NOx concentration at a specific point can be easily measured using a gas analyzer such as an infrared absorption analyzer. Therefore, by placing the catalyst based on the NOx measurement value at the outer wall (W) of the reaction tube (200), the placement of the catalyst can be determined efficiently and easily.

[0060] The reaction tube (200) may include a first catalyst region (R1) in which the NOx measurement value at the outer wall (W) is higher than the average NOx measurement value at the exhaust gas outlet (120), and a second catalyst region (R2) in which the NOx measurement value at the outer wall (W) of the reaction tube (200) is lower than the average NOx measurement value at the exhaust gas outlet (120). In the present invention, the NOx measurement value and the average measurement value refer to the result obtained by measuring the volume% of NOx, simulating, or combining these methods. The reaction tube (200) may include a plurality of the first catalyst region (R1) and the second catalyst region (R2).

[0061] The arrangement of the first catalyst region (R1) and the second catalyst region (R2) is not particularly limited as long as the above-described conditions regarding the NOx concentration measured at the exhaust gas outlet (120) are satisfied. According to exemplary embodiments, the first catalyst region (R1) and the second catalyst region (R2) may be arranged sequentially with respect to the ammonia gas flow direction. The first catalyst region (R1) and the second catalyst region (R2) may be arranged alternately in multiple numbers. The first catalyst region (R1) may be located upstream of the second catalyst region (R2) in the ammonia gas flow direction. The first catalyst region (R1) may be located downstream of the second catalyst region (R2) in the ammonia gas flow direction. According to exemplary embodiments, the first catalyst region (R1) may be arranged adjacent to the exhaust gas outlet (120) and the second catalyst region (R2) may be arranged adjacent to the burner (110).

[0062] The temperature of the outer wall (W) of the reaction tube (200) in the first catalyst region (R1) may be lower than the temperature of the outer wall (W) of the reaction tube (200) in the second catalyst region (R2).

[0063] According to exemplary embodiments, the average temperature of the first catalyst region (R1) may be 400 to 550°C. The average temperature of the second catalyst region (R2) may be 600 to 750°C. The temperature of each catalyst region (R1, R2) refers to the temperature of the reaction tube (200) flow path (P) in the part where each region (R1, R2) is located.

[0064] According to exemplary embodiments, the average ammonia content of the first catalyst region (R1) may be 25 to 100% in mass%, and the average ammonia content of the second catalyst region (R2) may be 0 to 25% in mass%. In this case, the first catalyst region (R1) may be located upstream of the second catalyst region (R2) in the direction of the ammonia gas flow. More specifically, the first catalyst region (R1) may be positioned adjacent to the ammonia gas inlet of the reaction tube (200). The second catalyst region (R2) may be positioned adjacent to the reaction gas outlet of the reaction tube (200). In this way, the ammonia decomposition efficiency can be further increased by additionally considering the average ammonia content in each catalyst region.

[0065] According to exemplary embodiments, a Ru-based catalyst may be placed in the first catalyst region (R1), and a Ni-based catalyst may be placed in the second catalyst region (R2). A Ru-based catalyst is a catalyst that uses Ru as the active metal and has relatively excellent catalytic activity. A Ni-based catalyst is a catalyst that uses Ni as the active metal and has relatively low catalytic activity. However, placing a Ni-based catalyst in the first catalyst region (R1) or a Ru-based catalyst in the second catalyst region (R2) is not entirely excluded.

[0066] According to exemplary embodiments, the reaction tube (200) can satisfy the following relationship 1.

[0067] [Relationship 1]

[0068]

[0069] In the above relationship 1, [Ru] is the ratio of Ru catalyst at a position spaced apart by a distance L from the ammonia gas inlet, L is the distance from the ammonia gas inlet of the reaction tube, and Lo is the total length of the reaction tube. Lo may be a second length. In this way, the arrangement of catalysts within the reaction tube (200) can be optimized by adjusting the ratio of Ru catalyst according to the distance from the ammonia gas inlet. At this time, the ratio of Ru catalyst refers to the weight ratio of Ru-based catalysts among all catalysts located at that point.

[0070] (Example 2)

[0071] FIG. 3 is a drawing for illustrating a hydrogen production system (20) according to exemplary embodiments.

[0072] Referring to FIG. 3, the hydrogen production system (20) may further include one or more of an SCR reactor (300), a first heat exchanger (400), and a second heat exchanger (500). In FIG. 3, for convenience of illustration, a hydrogen production system (20) including all of the SCR reactor (300), the first heat exchanger (400), and the second heat exchanger (500) is depicted, but the present invention is not necessarily limited thereto.

[0073] The SCR reactor (300) is fluidically connected to the exhaust gas outlet (120) and may be configured to remove NOx discharged from the exhaust gas outlet (120). To this end, the SCR reactor may include a catalyst for the reduction of NOx.

[0074] As a non-limiting example, the catalyst of the SCR reactor (300) may use one or more of V, Ti, W, Mo, Ru, Pd, Pt, and alloys thereof as the active metal. The SCR reactor (300) may be provided in the form of a supported catalyst in which the active metal is supported on a support such as ceramic.

[0075] The SCR reactor (300) can inject a reducing agent into a flue gas flow containing NOx. The reducing agent is not particularly limited as long as it can reduce NOx, but as a non-limiting example, it may be one or more of ammonia gas, urea, and a mixture thereof.

[0076] The temperature of the SCR reactor (300) can be 200 to 500°C as a non-limiting example.

[0077] The first heat exchanger (400) may be configured to exchange heat between the exhaust gas discharged from the exhaust gas outlet (120) and the ammonia fuel. To this end, the first heat exchanger (400) may include an exhaust gas path and an ammonia fuel path arranged adjacent to each other. Since the exhaust gas contains high-temperature heat, it can indirectly heat the ammonia fuel. As a result, the ammonia fuel can be preheated, thereby increasing the combustion efficiency of the burner (110).

[0078] The second heat exchanger (500) may be configured to exchange heat between the exhaust gas discharged from the exhaust gas outlet (120) and the ammonia gas. To this end, the second heat exchanger (500) may include an exhaust gas path and an ammonia gas path arranged adjacent to each other. Since the exhaust gas contains high-temperature heat, it can indirectly heat the ammonia gas. As a result, the ammonia gas can be preheated, thereby increasing the ammonia decomposition efficiency of the reaction tube (200).

[0079] When including a first heat exchanger (400) and a second heat exchanger (500) that are independent of each other, the arrangement order of the first heat exchanger (400) and the second heat exchanger (500) is not particularly limited. As one example, the first heat exchanger (400) may be positioned upstream of the second heat exchanger (500) based on the flow of exhaust gas. As another example, the second heat exchanger (500) may be positioned upstream of the first heat exchanger (400) based on the flow of exhaust gas.

[0080] 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.

Claims

1. A combustion furnace comprising a burner configured to use ammonia fuel and an exhaust gas outlet; and It includes a reaction tube disposed in the internal space of the combustion furnace and comprising a flow path through which ammonia gas can flow, and The above reaction tube is, It includes a first catalyst region in which the NOx measurement value at the outer wall of the reaction tube is higher than the average NOx measurement value at the flue gas outlet, and a second catalyst region in which the NOx measurement value at the outer wall of the reaction tube is lower than the average NOx measurement value at the flue gas outlet. A hydrogen production system in which the first catalyst disposed in the first catalyst region has a higher catalytic activity than the second catalyst disposed in the second catalyst region.

2. In Paragraph 1, The average ammonia content of the first catalyst region is 25 to 100% by mass, and A hydrogen production system in which the average ammonia content of the second catalyst region is 0 to 25% in mass%.

3. In Paragraph 1, The above reaction tube is a hydrogen production system satisfying the following relationship 1. [Relationship 1] (In the above Equation 1, [Ru] is the ratio of Ru catalyst at a position spaced L away from the ammonia gas inlet, L is the distance from the ammonia gas inlet of the reaction tube, and Lo is the total length of the reaction tube.) 4. In Paragraph 1, The average temperature of the first catalyst region is 400 to 550°C, and A hydrogen production system in which the average temperature of the second catalyst region is 600 to 750°C.

5. In Paragraph 1, The above second catalyst region is a hydrogen production system positioned adjacent to the above flue gas outlet.

6. In Paragraph 1, A hydrogen production system in which the first catalyst region and the second catalyst region are sequentially arranged based on the flow direction of the ammonia gas.

7. In Paragraph 1, A Ru-based catalyst is disposed in the first catalyst region above, and A hydrogen production system in which a Ni-based catalyst is disposed in the second catalyst region.

8. In Paragraph 1, A hydrogen production system further comprising an SCR reactor fluidically connected to the above-mentioned flue gas outlet and configured to remove NOx discharged through the above-mentioned flue gas outlet.

9. In Paragraph 1, The above ammonia fuel is a hydrogen production system that is a process tail gas derived from a hydrogen purification process.

10. In Paragraph 1, A hydrogen production system further comprising a first heat exchanger configured to heat exchange the flue gas discharged from the flue gas outlet and the ammonia fuel.

11. In Paragraph 1, A hydrogen production system further comprising a second heat exchanger configured to heat exchange the flue gas discharged from the flue gas outlet and the ammonia gas.

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