Ammonia synthesis reactor and method for manufacturing ammonia using same

Abstract

The present invention provides an ammonia synthesis reactor and a method for manufacturing ammonia using the ammonia synthesis reactor, the ammonia synthesis reactor comprising: a sealed cylindrical main body; an inlet which is connected to the cylindrical main body, and through which a first fluid stream containing hydrogen gas and nitrogen gas is introduced; a shell disposed at the center of the cylindrical main body; a tube bundle which is accommodated in the shell, and through which the first fluid stream flows; at least one catalyst bed which is disposed between the inner wall of the cylindrical main body and the shell, and in which a second fluid stream containing ammonia is generated while the first fluid stream passes therethrough; a central pipe which is disposed between the outer wall of the shell and the catalyst bed, and which guides the flow direction of the second fluid stream; and an outlet which is connected to the cylindrical main body, and through which the second fluid stream is discharged.

Description

A reactor for ammonia synthesis and a method for producing ammonia using the same

[0001] The present invention relates to a reactor for ammonia synthesis and a method for producing ammonia using the same.

[0002] This invention is derived from research conducted as part of the Ministry of Trade, Industry and Energy's International Joint Energy Research Project. [Project No.: RS-2023-00303645, Research Project Title: Development of Green Ammonia-Based Green Hydrogen Storage Technology and Optimal Transport Model]

[0003] Ammonia is a fundamental chemical essential for various industrial sectors, including fertilizers, chemical raw materials, and pharmaceuticals. In particular, its importance has been increasing recently as its potential as a hydrogen carrier and clean fuel has been highlighted.

[0004] Most commercially used ammonia production methods currently are based on the Haber-Bosch process. The Haber-Bosch process produces ammonia (NH3) by reacting nitrogen (N2) and hydrogen (H2) using iron-based catalysts under high temperature (400–500°C) and high pressure (150–300 bar) conditions. Conventional Haber-Bosch processes utilize natural gas steam reforming for the preparation of reactants and preheating. This process generates a large amount of carbon dioxide, leading to an increase in carbon emissions for the entire ammonia production process.

[0005] Korean registered patent No. 1737235 discloses a technology for burning combustion air and main fuel using one or more types of powder fuel (pulverized coal, petro coke, etc.) or gas (LNG, etc.), but since this also introduces fossil fuel-based fuel into the burner, there is a problem of carbon dioxide emission.

[0006] Furthermore, the ammonia synthesis reaction is a highly exothermic reaction; if proper temperature control is not maintained, catalyst degradation occurs, leading to a decrease in conversion rate. Therefore, effectively controlling the reaction temperature is critical in ammonia synthesis reactors, and to achieve this, the design of the internal heat exchange system is a key factor.

[0007] European Patent No. 3497059 discloses a converter for ammonia synthesis in which catalyst layers are arranged in series. However, as the heat exchanger is fixedly positioned on the upper part of the catalyst bed, there are limitations on space utilization and problems with the device becoming large. In addition, the heat exchangers between multiple beds have separated gas streams, and due to the structure of intermediate cooling of the partially converted synthesis gas inside the heat exchanger, there are problems requiring multiple inlet means and complex conduits.

[0008] Therefore, there is a need to develop a reactor for ammonia synthesis and a method for producing ammonia that can reduce the size of the device and improve energy efficiency while reducing carbon dioxide emissions.

[0009] The present invention was developed based on the background described above, and aims to provide a compact reactor for ammonia synthesis by simplifying the design and arrangement of the heat exchanger.

[0010] In addition, it aims to efficiently cool the heat generated by the ammonia synthesis reaction without injecting a separate low-temperature gas or refrigerant into the reactor.

[0011] In addition, the invention aims to provide a method for producing ammonia that does not emit carbon dioxide through the combustion of hydrogen or a mixture of hydrogen and ammonia gases.

[0012] One aspect of the present invention relates to a reactor for ammonia synthesis comprising: a sealed cylindrical body; an inlet connected to the cylindrical body through which a first fluid stream including hydrogen gas and nitrogen gas is introduced; a shell disposed in the center of the cylindrical body; a bundle of tubes contained within the shell through which the first fluid stream flows; at least one catalyst bed disposed between the inner wall of the cylindrical body and the shell, through which the first fluid stream passes to generate a second fluid stream including ammonia; a central tube disposed between the outer wall of the shell and the catalyst bed, which guides the flow direction of the second fluid stream; and an outlet connected to the cylindrical body through which the second fluid stream is discharged, wherein the second fluid stream generated in the catalyst bed is introduced into the shell through the central tube and then discharged through the outlet.

[0013] According to one embodiment of the present invention, a reactor for ammonia synthesis may be provided, comprising a plurality of baffles that divide the interior of the shell into a plurality of sections along the length of the shell, wherein the baffles cause the second fluid stream to flow in a zigzag shape within the shell, thereby improving the heat exchange efficiency with the first fluid stream passing through the tube bundle.

[0014] According to one embodiment of the present invention, a reactor for synthesizing ammonia may be provided, wherein the catalyst bed has a cylindrical shape that coaxially surrounds the shell, and the catalyst bed has a plurality of through holes formed therein and filled with catalyst, and the first fluid stream flows towards the shell in a radial flow or an axial-radial flow inside the catalyst bed while synthesizing ammonia.

[0015] According to one embodiment of the present invention, a reactor for ammonia synthesis may be provided, wherein a first through hole communicating with the catalyst bed and a second through hole communicating with the shell are formed in the central tube, and the second fluid stream flows into the central tube through the first through hole and then flows into the shell through the second through hole.

[0016] According to one embodiment of the present invention, a reactor for ammonia synthesis may be provided, wherein the tube bundle is formed to communicate the upper and lower portions of the shell so that the first fluid stream moves from the lower portion to the upper portion.

[0017] According to one embodiment of the present invention, a reactor for ammonia synthesis may be provided, wherein heat exchange is performed between a first fluid stream flowing within the tube bundle and a second fluid stream flowing within the shell.

[0018] According to one embodiment of the present invention, a reactor for ammonia synthesis may be provided, comprising a partition installed vertically inside the shell, wherein the interior of the shell is divided into two semi-cylindrical regions by the partition, and a second fluid stream passing through the catalyst bed is independently introduced into the region divided by the partition.

[0019] According to one embodiment of the present invention, an ammonia synthesis reactor may be provided, wherein the inlet is formed at the bottom of the cylindrical body and the outlet is formed at the top of the cylindrical body, the second through hole of the central tube is formed at the bottom of the central tube, and the second fluid stream passing through the catalyst bed flows downward along the central tube and then flows into the shell through the second through hole and flows upward along the baffle and the partition wall.

[0020] According to one embodiment of the present invention, an ammonia synthesis reactor may be provided, wherein the inlet and the outlet are formed at the bottom of the cylindrical body, the second through hole of the central tube is formed at the top of the central tube, and the second fluid stream passing through the catalyst bed flows upward along the central tube and then flows into the shell through the second through hole and flows downward along the baffle and the partition wall.

[0021] Another aspect of the present invention relates to a method for producing ammonia using the ammonia synthesis reactor, comprising the steps of: preheating a hydrogen gas stream and a nitrogen gas stream using a preheater; supplying the preheated hydrogen gas stream and the nitrogen gas stream to a gas mixer to produce a mixed gas stream containing hydrogen gas and nitrogen gas; supplying the mixed gas stream to the ammonia synthesis reactor to synthesize ammonia and producing a crude synthesis gas stream containing the ammonia and unreacted hydrogen gas and nitrogen gas; condensing at least a portion of the crude synthesis gas stream using a condenser; and separating liquid ammonia from the crude synthesis gas stream using a gas-liquid separator and supplying the separated crude synthesis gas stream to the preheater and the gas mixer for recirculation.

[0022] According to one embodiment of the present invention, a method for producing ammonia may be provided, wherein a mixture of hydrogen and air or a mixture of hydrogen, ammonia, and air is injected into the preheater as a combustion gas, and the combustion heat generated by burning the combustion gas is used to preheat a hydrogen gas stream and a nitrogen gas stream.

[0023] According to one embodiment of the present invention, a method for producing ammonia may be provided, wherein the ammonia injected as the combustion gas is gaseous ammonia recovered from a crude synthesis gas stream separated in the gas-liquid separator.

[0024] According to one embodiment of the present invention, a method for producing ammonia may be provided, wherein the gas mixer mixes a hydrogen gas stream and a nitrogen gas stream preheated in the preheater with a crude synthesis gas stream separated in a gas-liquid separator to produce a mixed gas stream containing hydrogen gas and nitrogen gas in a predetermined molar ratio.

[0025] According to one embodiment of the present invention, a method for producing ammonia may be provided in which the molar ratio of hydrogen gas to nitrogen gas in the mixed gas stream is 3 to 4.

[0026] According to one embodiment of the present invention, a method for producing ammonia may be provided, further comprising the step of supplying steam generated by burning the combustion gas to the gas mixer to indirectly heat the mixed gas stream inside the gas mixer.

[0027] According to one embodiment of the present invention, a method for producing ammonia may be provided, further comprising the step of supplying steam generated by burning the combustion gas to a steam turbine to produce electricity.

[0028] According to one embodiment of the present invention, a method for producing ammonia may be provided in which the internal temperature of the reactor for ammonia synthesis is maintained at 400°C to 500°C.

[0029] According to one embodiment of the present invention, a method for producing ammonia may be provided in which the pressure of the reactor for ammonia synthesis is maintained at 10 bar to 100 bar.

[0030] According to one embodiment of the present invention, a method for producing ammonia may be provided, further comprising the step of condensing at least a portion of the crude synthesis gas stream into liquid ammonia using steam condensate generated by indirectly heating the mixed gas stream inside the gas mixer in the condenser.

[0031] According to one embodiment of the present invention, a method for producing ammonia may be provided, further comprising the step of indirectly heating the mixed gas stream by supplying steam generated by condensing at least a portion of the crude synthesis gas stream to the gas mixer.

[0032] According to one embodiment of the present invention, a method for producing ammonia may be provided, further comprising the step of producing electricity by supplying steam generated by condensing at least a portion of the crude synthesis gas stream to a steam turbine.

[0033] According to the present invention, by simplifying the design and arrangement of the heat exchanger, a compact reactor for ammonia synthesis can be provided.

[0034] In addition, the heat generated by the ammonia synthesis reaction can be efficiently cooled without injecting a separate low-temperature gas or refrigerant into the reactor.

[0035] In addition, a method for producing ammonia that does not emit carbon dioxide can be provided through the combustion of hydrogen or a mixture of hydrogen and ammonia gas.

[0036] FIG. 1 is a front view of a reactor for ammonia synthesis according to one embodiment of the present invention.

[0037] FIG. 2 is a schematic diagram showing the flow of fluid flowing inside a shell and a tube bundle in a reactor for ammonia synthesis according to one embodiment of the present invention.

[0038] FIG. 3 is a schematic diagram showing the flow of fluid flowing inside one or more catalyst beds in a reactor for ammonia synthesis according to one embodiment of the present invention.

[0039] FIG. 4 is a front view of a reactor for ammonia synthesis according to another embodiment of the present invention.

[0040] FIG. 5 is a schematic diagram showing the flow of fluid flowing inside a shell and a tube bundle in a reactor for ammonia synthesis according to another embodiment of the present invention.

[0041] Figure 6 is a diagram showing the overall process of the ammonia manufacturing method according to the present invention.

[0042] The embodiments of the present invention are illustrative for the purpose of explaining the technical concept of the present invention. The scope of rights according to the present invention is not limited to the embodiments presented below or the specific descriptions thereof. The technical concept of the present invention includes various modifications, equivalents, alternatives, and embodiments selectively combined from all or part of each embodiment of the present invention. Furthermore, the scope of rights of the technical concept of the present invention is not limited to the various embodiments presented below or the specific descriptions thereof.

[0043] Terms used in this specification, including technical or scientific terms, may have the meaning generally understood by those skilled in the art to which this specification pertains, unless otherwise defined.

[0044] Expressions used herein such as “comprising,” “may compose,” “possessing,” “possessing,” “having,” and “possessing” imply the existence of the subject feature (e.g., function, operation, or component, etc.) and do not exclude the existence of other additional features. In other words, such expressions should be understood as open-ended terms implying the possibility of including other embodiments.

[0045] Singular expressions used in this specification may include the meaning of the plural form unless otherwise indicated by the context, and this applies likewise to singular expressions described in the claims.

[0046] Expressions such as "first," "second," or "first," "second" as used in this specification are used to distinguish one object from another when referring to a plurality of objects of the same kind, unless otherwise indicated in the context, and do not limit the order or importance of the objects.

[0047] A reactor (10) for ammonia synthesis according to the present invention comprises a sealed cylindrical body (100), an inlet (101) connected to the cylindrical body (100) into which a first fluid stream (F1) containing hydrogen gas and nitrogen gas is introduced, a shell (110) disposed in the center of the cylindrical body, a tube bundle (120) contained within the shell (110) through which the first fluid stream (F1) flows, at least one catalyst bed (130) disposed between the inner wall of the cylindrical body (100) and the shell (110) and through which a second fluid stream (F2) containing ammonia is generated as the first fluid stream (F1) passes, a central tube (111) disposed between the outer wall of the shell (110) and the catalyst bed (130) and guiding the flow direction of the second fluid stream (F2), and a second fluid connected to the cylindrical body (100). It includes an outlet (102) through which the stream (F2) flows out.

[0048] The cylindrical body (100) serves to stably support and protect internal components under high pressure and high temperature reaction conditions. For example, it can be made of a material with excellent pressure resistance, heat resistance, and corrosion resistance, such as chrome-molybdenum alloy steel or stainless steel, so that deformation or breakage does not occur even under high pressure and high temperature conditions.

[0049] The inlet (101) is connected to the cylindrical body (100) and provides a passage through which a first fluid stream (F1) containing hydrogen gas and nitrogen gas flows into the reactor (10) for ammonia synthesis. The inlet (101) is connected to one end of the tube bundle (120) so that the first fluid stream (F1) can flow into the tube bundle (120).

[0050] The central tube (111) is positioned between the outer wall of the shell (110) and the catalyst bed (130) and guides the flow direction of the second fluid stream (F2). The central tube (111) includes a first through hole (112) communicating with the catalyst bed (130) and a second through hole (113) communicating with the shell (110), through which the second fluid stream can flow sequentially. Specifically, the second fluid stream (F2) that has passed through the catalyst bed (130) can flow into the interior of the central tube (111) through the first through hole (112) of the central tube, then flow upward or downward along the inner wall of the central tube (111), and then flow into the interior of the shell (110) through the second through hole (113) of the central tube.

[0051] The shell (110) is positioned in the center of the cylindrical body (100) to accommodate the tube bundle (120) and guide the flow of fluid. Specifically, the shell (110) is a cylindrical structure positioned coaxially with the cylindrical body (100) and forms a fluid flow space while stably supporting the tube bundle (120) inside. The shell (110) independently provides paths for the first fluid stream (F1) and the second fluid stream (F2), thereby enabling effective heat exchange without the high-temperature reaction product and the low-temperature reactant mixing with each other.

[0052] A tube bundle (120) is housed inside a shell (110) and forms a flow path for a first fluid stream (F1) containing hydrogen gas and nitrogen gas. The tube bundle (120) may have a structure in which a plurality of vertical tubes are arranged in a circular pattern. For example, when viewed from a plane, the vertical tubes may be arranged in a concentric shape. The tube bundle (120) is formed to communicate the upper and lower parts of the shell (110) so that the first fluid stream (F1) moves from the lower part to the upper part. For example, the tubes may be arranged in a circular pattern while maintaining a constant spacing from each other, thereby forming a flow path in which the first fluid stream (F1) can be uniformly distributed and rise from the lower part to the upper part. This circular bundle structure effectively utilizes the internal space of the shell (110) while maximizing the contact area with the second fluid stream (F2) flowing along the shell (110) side, allowing for efficient heat exchange between the first fluid stream (F1) and the second fluid stream (F2). The combination of the shell (110) and the tube bundle (120) forms the structure of a shell-tube heat exchanger, enabling efficient heat exchange between two fluid streams of different temperatures. The first fluid stream (F1) discharged through the outlet at the top of the tube bundle (120) flows into the upper part of the catalytic reaction zone where the catalyst bed (130) is placed.

[0053] A catalyst bed (130) is positioned between the inner wall of a cylindrical body (100) and a shell (110), and forms a main reaction zone where an ammonia synthesis reaction takes place as a first fluid stream (F1) passes through. The catalyst bed (130) may have a cylindrical shape that coaxially surrounds the shell (110). A catalyst is filled inside the catalyst bed (130), and as the catalyst, an iron-based catalyst, a ruthenium-based catalyst, a cobalt-molydenium-based catalyst, etc., may be used. A plurality of through holes (134) are formed in the outer wall of the catalyst bed (130). This allows a first fluid stream (F1), containing hydrogen gas and nitrogen gas, to flow into the catalyst bed (130) from a tube bundle (120). Ammonia is synthesized as the first fluid stream (F1) flows toward the shell (110) in a radial flow or an axial-radial flow inside the catalyst bed (130). Here, radial flow refers to a fluid stream flowing in a direction perpendicular to the central axis of the reactor, and axial-radial flow refers to a flow in which the fluid stream simultaneously has an axial component along the length of the reactor and a radial component perpendicular to the central axis of the reactor. Such radial flow or axial-radial flow allows the fluid stream to pass evenly through the catalyst bed, thereby minimizing pressure drop within the catalyst bed and increasing the efficiency of the catalyst through uniform gas and temperature distribution, enabling the synthesis of ammonia with a stable yield. In particular, radial flow can significantly reduce pressure drop compared to axial flow. Pressure drop refers to the pressure difference that occurs between the inlet and outlet when the fluid stream passes through the catalyst bed (130), and is caused by the resistance experienced by the fluid stream as it passes through the catalyst bed (130).When the pressure drop is reduced, the uniformity of the flow within the catalyst bed (130) is improved, thereby enhancing reaction efficiency. Additionally, the uniformity of the temperature distribution prevents the formation of hot spots, thereby improving reaction stability and reducing the energy consumption of the gas compressor used to supply the fluid stream to the reactor (10) for ammonia synthesis. Both radial flow and axial-radial flow may exist within the catalyst bed (130), but preferably, radial flow may be effective in reducing the pressure drop.

[0054] A catalyst bed (130) according to one embodiment of the present invention may include a first catalyst bed (131), a second catalyst bed (132), and a third catalyst bed (133). Between the inner wall of the cylindrical body (100) and the shell (110), a catalyst bed sheet may be installed to partition a catalyst reaction zone along the longitudinal direction of the shell (110) and to maintain a uniform temperature gradient within the reactor. The catalyst beds (131, 132, 133) may be disposed in each catalyst reaction zone. A through hole (135) is formed in the catalyst bed sheet so that each catalyst reaction zone communicates with one another, through which a first fluid stream (F1) can be introduced in parallel into each catalyst reaction zone. That is, the first fluid stream (F1) can be introduced simultaneously and independently into each catalyst reaction zone. In other words, the first fluid stream (F1) introduced from the tube bundle (120) is introduced into a catalytic reaction zone where the first catalyst bed (131) is placed, and then a portion of it may be introduced into a catalytic reaction zone where the second catalyst bed (132) is placed through a through hole (135) formed in the catalyst bed sheet supporting the first catalyst bed (131). Afterward, a portion of the first fluid stream (F1) introduced into the catalytic reaction zone where the second catalyst bed (132) is placed may be introduced into a catalytic reaction zone where the third catalyst bed (133) is placed through a through hole (135) in the catalyst bed sheet supporting the second catalyst bed (132). In this way, the first fluid stream (F1) passes through each catalyst bed (131, 132, 133) and causes a catalytic reaction. The first fluid stream (F1) is synthesized into ammonia as it flows toward the shell (110) in a radial flow or axial-radial flow from the catalyst beds (131, 132, 133) within each catalytic reaction zone.A second fluid stream (F2) containing synthesized ammonia may be introduced into the interior of the central tube (111) through a first through-hole (112) of the central tube communicating with the catalyst bed (130), and then into the shell (110) through a second through-hole (113) of the central tube communicating with the shell (110). In this specification, the description is based on an embodiment having three catalyst beds, but is not limited thereto. A catalyst bed according to one embodiment may include one or more catalyst beds.

[0055] The outlet (102) is connected to the cylindrical body (100) and provides a passage through which a second fluid stream (F2) containing ammonia is discharged to the outside of the ammonia synthesis reactor (10). The outlet (102) is connected to one end of the shell (110) so that the second fluid stream (F2), having completed heat exchange inside the shell (110), can be smoothly discharged to the outside.

[0056] The interior of the shell (110) is divided into two independent semi-cylindrical regions by a vertically installed partition (150). The partition (150) is installed in the center of the shell (110) to allow a second fluid stream (F2) to flow independently from both sides of the interior of the shell (110). The structure of this partition (150) prevents fluid mixing and asymmetric flow that may occur in the center of the shell (110). The partition (150) is formed to extend along the longitudinal direction of the shell (110) and suppresses the occurrence of a dead zone, which is an area where fluid stagnates or hardly flows, by ensuring that the second fluid stream (F2) is uniformly distributed and flows in each region. In addition, the partition (150) has the effect of minimizing pressure drop by reducing the generation of vortices. Through this, the heat flow of the second fluid stream (F2) is improved and the overall heat exchange efficiency is enhanced.

[0057] A plurality of baffles (140) may be included inside the shell (110). The baffles (140) are structures that divide the interior of the shell (110) into multiple zones along the length of the shell (110) and serve to guide the flow direction of the second fluid stream (F2) flowing inside the shell. The baffles (140) are formed by extending inward by a predetermined length from the inner wall and partition wall (150) of the shell (110) and are installed on both sides relative to the central partition wall (150). Each baffle (140) is installed alternately at regular intervals along the length of the shell (110) to form a flow path through which the second fluid stream (F2) can pass. Due to this structure, the second fluid stream (F2) forms a zigzag flow when moving from one baffle to the next. In this specification, embodiments are described based on an example in which baffles (140) are alternately installed at regular intervals along the longitudinal direction of the shell (110), but are not limited thereto. A baffle (140) according to one embodiment may have a semicircular plate shape corresponding to the internal shape of the cylindrical shell (110) on both sides relative to the central partition (150), and may be implemented in various forms. For example, a circular through hole may be formed in the baffle (140) at a position adjacent to the central axis of the shell (110) and the partition (150), and a through hole may be placed in the next baffle (140) located downstream at a position spaced apart from the partition (150) and adjacent to the inner wall of the shell (110) so that the second fluid stream (F2) flows in a zigzag shape. As another example, another wall may be formed in the baffle (140) that extends in a direction parallel to the partition wall (150), and circular through holes may be arranged in the upstream baffle (140) and the downstream baffle (140) with this wall in between, so that the second fluid stream (F2) does not flow directly from the through hole formed in the upstream baffle (140) to the through hole formed in the downstream baffle (140), but flows by bypassing this wall and flows spirally.The configuration of these various baffles (140) lengthens the flow path of the second fluid stream (F2), thereby increasing the residence time of the fluid and allowing heat exchange with the first fluid stream (F1) to be more effective. In particular, in the case of a spiral flow, the heat exchange efficiency can be further improved as the fluid moves while rotating inside the shell (110).

[0058] The present invention will be described below with reference to the drawings.

[0059] FIG. 1 is a front view of a reactor (10) for ammonia synthesis according to one embodiment of the present invention. According to one embodiment of the present invention, a first fluid stream (F1) containing hydrogen gas and nitrogen gas can be supplied through an inlet (101) formed at the bottom of a cylindrical body (100). The first fluid stream (F1) passes through a tube bundle (120) contained within a shell (110) and reaches the top of the cylindrical body (100). The first fluid stream (F1) that reaches the top of the cylindrical body (100) is distributed in parallel to each catalytic reaction zone in which a first catalyst bed (131), a second catalyst bed (132), and a third catalyst bed (133) are arranged through a through hole (135) of a catalyst bed sheet. A first fluid stream (F1) passing through the through hole (134) of each catalyst bed is synthesized into ammonia while flowing toward the shell (110) via a radial flow or axial-radial flow inside the catalyst bed (130). At this time, since the ammonia synthesis reaction is an exothermic reaction, the temperature of the second fluid stream (F2), which contains the synthesized ammonia and unreacted gas, rises above the temperature of the first fluid stream (F1). The high-temperature second fluid stream (F2) is introduced into the interior of the central tube (111) through the first through hole (112) of the central tube communicating with the catalyst bed (130). In one embodiment of the present invention, a second through hole (113) communicating with the shell (110) is formed in the lower part of the central tube (111). Accordingly, the second fluid stream (F2) that has passed through each catalyst bed (130) flows downward along the inner wall of the central tube (111) and then enters the interior of the shell (110) through the lower second through hole (113). At this time, the second fluid stream (F2) is introduced independently from both sides due to the partition wall (150) that divides the interior of the shell (110) into two semi-cylindrical regions.The high-temperature second fluid stream (F2) introduced into the shell (110) flows upward in a zigzag pattern through the baffle (140) and is cooled through co-current indirect heat exchange with the low-temperature first fluid stream (F1) flowing upward within the tube bundle (120). Co-current heat exchange is a method in which two fluid streams exchange heat while flowing in the same direction. Since the temperature difference between the two fluid streams is greatest in the lower region where the inlet (101) is located, the heat exchange efficiency is maximum, and as it moves toward the upper region where the outlet (102) is located, the temperature difference between the two fluid streams gradually decreases, thereby reducing the heat exchange efficiency. According to this co-current indirect heat exchange, since less heat exchange occurs in the upper region, the reactant gas can be supplied to the catalyst bed at a relatively constant temperature, and the temperature gradient inside the reactor can be maintained gently, thereby improving temperature uniformity. The second fluid stream (F2), cooled through parallel indirect heat exchange, is discharged through an outlet (102) formed at the top of the cylindrical body (100).

[0060] FIG. 2 is a schematic diagram showing the flow of fluid flowing inside a shell and a tube bundle in a reactor for ammonia synthesis according to one embodiment of the present invention.

[0061] Referring to FIG. 2, a first fluid stream (F1) containing hydrogen gas and nitrogen gas is introduced through an inlet (101) formed at the bottom of a cylindrical body (100) and then flows vertically upward from the bottom to the top of a tube bundle (120). A second fluid stream (F2) containing ammonia synthesized in a catalyst bed (130) is introduced into the interior of a central tube (111) through a first through-hole (112) of a central tube communicating with the catalyst bed (130), flows downward along the inner wall of the central tube (111), and then enters the interior of a shell (110) through a second through-hole (113) at the bottom. At this time, the second fluid stream (F2) is introduced independently from both sides due to a partition wall (150) that divides the interior of the shell (110) into two semi-cylindrical regions. A second fluid stream (F2) of high temperature introduced into the interior of the shell (110) is guided in a zigzag shape by the baffle (140) and flows, thereby performing indirect heat exchange in parallel with a first fluid stream (F1) of relatively low temperature passing through the interior of the tube bundle (120). During this heat exchange process, the second fluid stream (F2) of high temperature is cooled, and at the same time, the first fluid stream (F1) passing through the tube bundle (120) is heated. The zigzag flow formed by the baffle (140) increases the residence time of the second fluid stream (F2) and improves the contact area with the tube bundle (120). This improves the heat exchange efficiency between the first fluid stream (F1) and the second fluid stream (F2), and consequently contributes to improving the energy efficiency of the entire process.

[0062] FIG. 3 is a schematic diagram showing the flow of fluid flowing inside one or more catalyst beds in a reactor for ammonia synthesis according to one embodiment of the present invention.

[0063] Referring to FIG. 3, the first fluid stream (F1) is synthesized into ammonia as it passes through the catalyst bed (130) in a radial flow or an axial-radial flow. Here, radial flow means that the fluid stream flows in a direction perpendicular to the central axis of the reactor, as illustrated by the arrow in FIG. 3, and axial-radial flow (not shown) means that the fluid stream proceeds in the axial direction, which is the length direction of the reactor, within the catalyst bed (130), while simultaneously flowing radially toward the shell (110) perpendicular to the central axis of the reactor. The second fluid stream (F2) containing the synthesized ammonia is introduced into the interior of the central tube (111) through the first through hole (112) of the central tube communicating with the catalyst bed (130), and then into the interior of the shell (110) through the second through hole (113) of the central tube communicating with the shell (110).

[0064] FIG. 4 is a front view of a reactor for ammonia synthesis according to another embodiment of the present invention. FIG. 5 is a schematic diagram showing the flow of fluid flowing inside a shell and a tube bundle in a reactor for ammonia synthesis according to another embodiment of the present invention.

[0065] Referring to FIGS. 4 and 5, the inlet (101) and outlet (102) of the ammonia synthesis reactor (10) according to another embodiment of the present invention are both formed at the bottom of the cylindrical body (100). A first fluid stream (F1) supplied through the bottom inlet (101) passes through a tube bundle (120) contained within a shell (110) and reaches the top of the cylindrical body (100). The first fluid stream (F1) that reaches the top of the cylindrical body (100) is distributed in parallel to each catalytic reaction zone in which a first catalyst bed (131), a second catalyst bed (132), and a third catalyst bed (133) are arranged through a through hole (135) of the catalyst bed sheet. A first fluid stream (F1) passing through the through hole (134) of each catalyst bed is synthesized into ammonia while flowing toward the shell (110) via a radial flow or axial-radial flow inside the catalyst bed (130). A second fluid stream (F2) of high temperature is introduced into the interior of the central tube (111) through the first through hole (112) of the central tube communicating with the catalyst bed (130). In another embodiment of the present invention, a second through hole (113) communicating with the shell (110) is formed at the top of the central tube (111). Accordingly, the second fluid stream (F2) passing through each catalyst bed (130) flows upward along the inner wall of the central tube (111) and then enters the interior of the shell (110) through the second through hole (113) at the top. At this time, the second fluid stream (F2) is introduced independently from both sides due to the partition (150) that divides the inside of the shell (110) into two semi-cylindrical regions. The high-temperature second fluid stream (F2) introduced into the shell (110) flows downward in a zigzag pattern through the baffle (140) and is cooled through counter-current indirect heat exchange with the low-temperature first fluid stream (F1) flowing upward within the tube bundle (120).The counter-flow heat exchange method is a method in which two fluid streams exchange heat while flowing in opposite directions. Since the temperature difference between the fluid streams in the lower and upper regions is constant, it has the advantage of having a higher overall heat exchange efficiency compared to the parallel-flow heat exchange method. Additionally, due to the high heat exchange efficiency of the counter-flow indirect heat exchange method, the second fluid stream (F2) is cooled to a lower temperature, which can reduce the load on the condenser (40) during the subsequent condensation stage, thereby improving the energy efficiency and facility operating costs of the subsequent process. Furthermore, since there is little degradation in heat exchange performance even when the size of the ammonia synthesis reactor (10) increases, it is advantageous for designing large reactors. The second fluid stream (F2) cooled through the counter-flow indirect heat exchange is discharged through the outlet (102) formed at the bottom of the cylindrical body (100).

[0066] Figure 6 is a diagram showing the overall process of the ammonia manufacturing method according to the present invention.

[0067] Referring to FIG. 6, the method for producing ammonia according to the present invention comprises the following steps.

[0068] First, the method includes the step of supplying a hydrogen gas stream and a nitrogen gas stream to a preheater (20) to preheat them. Combustion gas is injected into the preheater (20), and this combustion gas may be a mixture of hydrogen and air or a mixture of hydrogen, ammonia, and air. In the preheater (20), the hydrogen gas stream and the nitrogen gas stream are preheated using the combustion heat generated by burning the combustion gas. At this time, the ammonia injected as combustion gas may be gaseous ammonia and unreacted hydrogen recovered from the crude synthesis gas stream separated in the gas-liquid separator (50) described later. Additionally, the steam generated by burning the combustion gas may be supplied to a gas mixer (30) and used to indirectly heat the mixed gas stream inside the gas mixer (30). By using a mixture of hydrogen and air or a mixture of hydrogen, ammonia, and air as the combustion gas, the preheater (20) according to the present invention enables carbon-free heating that does not emit any carbon dioxide, unlike conventional preheating methods using fossil fuels. In addition, the economic efficiency of the process can be improved by recycling the gaseous ammonia recovered from the gas-liquid separator (50) into combustion gas.

[0069] Next, the process includes the step of supplying a hydrogen gas stream and a nitrogen gas stream preheated in a preheater (20) to a gas mixer (30) to produce a mixed gas stream containing hydrogen gas and nitrogen gas. In the gas mixer (30), the preheated hydrogen gas stream and the nitrogen gas stream are mixed with the crude synthesis gas stream separated in the gas-liquid separator (50) described later to produce a mixed gas stream having a predetermined molar ratio. At this time, the molar ratio of hydrogen gas to nitrogen gas in the mixed gas stream is maintained at 3 to 4, taking into account the stoichiometric ratio of the ammonia synthesis reaction. Generally, since the ammonia synthesis reaction follows the reaction equation N2 + 3H2 → 2NH3, the theoretical molar ratio of hydrogen gas to nitrogen gas is 3; however, in the actual process, it is desirable to supply an excess of hydrogen to shift the reaction equilibrium and improve the conversion rate. In one embodiment of the present invention, the process may further include the step of indirectly heating the mixed gas stream by supplying steam generated by burning the combustion gas in the preheater (20) to the gas mixer (30). Additionally, the process may further include a step of supplying steam generated by burning combustion gas in a preheater (20) to a steam turbine (60) to produce electricity. As a result, the energy efficiency of the entire process can be improved by effectively utilizing the thermal energy generated during the combustion process.

[0070] Next, the method includes the step of supplying the mixed gas stream to an ammonia synthesis reactor (10) to synthesize ammonia and producing a crude synthesis gas stream containing the ammonia, unreacted hydrogen gas, and nitrogen gas. The interior of the ammonia synthesis reactor (10) is maintained at a temperature of 400°C to 500°C and a pressure of 10 bar to 100 bar. These temperature and pressure conditions are optimized by considering the reaction rate of the ammonia synthesis reaction and the heat exchange efficiency inside the reactor. If the internal temperature and pressure are below the lower limit, the reaction rate and yield of ammonia synthesis are significantly lowered, and if they exceed the upper limit, the heat exchange efficiency decreases along with an increase in the internal exothermic temperature, which may deactivate the catalyst, and the reaction efficiency may decrease due to a large internal temperature deviation. In the ammonia synthesis reactor (10), ammonia is synthesized from the mixed gas stream to produce a crude synthesis gas stream containing ammonia, unreacted hydrogen gas, and nitrogen gas. In the ammonia manufacturing method according to the present invention, by using the aforementioned ammonia synthesis reactor (10), the temperature and flow distribution can be made uniform through radial flow or axial-radial flow in the catalyst bed, and the reaction heat can be effectively removed through a shell-tube type heat exchanger structure while being utilized for preheating the reactants. In addition, since self-heat exchange is possible within the reactor without a separate external heat exchanger, there is an advantage of being able to achieve an overall compact design.

[0071] Next, the method includes the step of condensing at least a portion of the crude synthetic gas stream into liquid ammonia using a condenser (40). In the condenser (40), a portion of the crude synthetic gas stream is condensed using steam condensate generated by indirectly heating the mixed gas stream inside the gas mixer (30). The steam generated by condensing at least a portion of the crude synthetic gas stream can be supplied to the gas mixer (30) to be used for indirectly heating the mixed gas stream, or supplied to a steam turbine (60) to be used for generating electricity.

[0072] Next, the method includes the step of separating liquid ammonia from the crude synthesis gas stream using a gas-liquid separator (50) and recirculating the separated crude synthesis gas stream by supplying it to a preheater (20) or a gas mixer (30). The crude synthesis gas stream separated in the gas-liquid separator (50) is supplied to the gas mixer (30) and recirculated. Additionally, the gaseous ammonia recovered from the crude synthesis gas stream separated in the gas-liquid separator (50) can be injected into the preheater (20) as a combustion gas. This recirculation process has the effect of improving the overall process yield through the reuse of unreacted gas.

[0073] The ammonia manufacturing method according to the present invention has the following characteristic effects. First, by burning hydrogen or a mixture of hydrogen and ammonia gas in a preheater (20), a method for manufacturing ammonia that does not emit carbon dioxide can be provided. Second, within the shell (110) of the ammonia synthesis reactor (10), a high-temperature second fluid stream (F2) and a low-temperature first fluid stream (F1) perform indirect heat exchange in a parallel or counter-flow manner, thereby maximizing energy efficiency and providing a compact ammonia synthesis reactor (10). Third, by utilizing the steam generated in the preheater (20) or condenser (40) for heating the gas mixer (30) or for generating electricity in the steam turbine (60), and by supplying the crude synthesis gas stream separated in the gas-liquid separator (50) to the preheater (20) or gas mixer (30) for recirculation, energy efficiency and the economic feasibility of the process can be improved.

[0074] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention can be implemented in other specific forms without changing its technical concept or essential features.

[0075] Therefore, the embodiments described above should be understood as exemplary in all respects and not limiting. The scope of the invention is defined by the claims rather than by the detailed description above, and all modifications or modified forms derived from the meaning and scope of the claims and equivalents thereof should be interpreted as being included within the scope of the invention.

Claims

1. A sealed cylindrical body; An inlet connected to the above-mentioned cylindrical body, into which a first fluid stream including hydrogen gas and nitrogen gas is introduced; A shell positioned in the center of the above-mentioned cylindrical body; A tube bundle accommodated within the shell, through which the first fluid stream flows; At least one catalyst bed disposed between the inner wall of the cylindrical body and the shell, wherein a second fluid stream containing ammonia is generated as the first fluid stream passes through; A central tube disposed between the outer wall of the shell and the catalyst bed, guiding the flow direction of the second fluid stream; and A reactor for ammonia synthesis connected to the above-mentioned cylindrical body and comprising an outlet through which the second fluid stream flows out, The second fluid stream generated in the catalyst bed flows into the shell via the central tube and then flows out through the outlet. Ammonia synthesis reactor.

2. In Paragraph 1, It includes a plurality of baffles that divide the interior of the shell into multiple sections along the length of the shell, and The baffle improves the heat exchange efficiency with the first fluid stream passing through the tube bundle by causing the second fluid stream to flow in a zigzag pattern within the shell. Ammonia synthesis reactor.

3. In Paragraph 1 or 2, The catalyst bed has a cylindrical shape that coaxially surrounds the shell, and A plurality of through holes are formed in the catalyst bed and filled with catalyst, and Ammonia is synthesized as the first fluid stream flows toward the shell in a radial flow or axial-radial flow inside the catalyst bed. Ammonia synthesis reactor.

4. In Paragraph 1 or 2, In the central tube above, a first through hole communicating with the catalyst bed and a second through hole communicating with the shell are formed, and The second fluid stream flows into the central tube through the first through hole and then flows into the shell through the second through hole. Ammonia synthesis reactor.

5. In Paragraph 1 or 2, The above tube bundle is formed to connect the upper and lower parts of the shell so that the first fluid stream moves from the lower part to the upper part. Ammonia synthesis reactor.

6. In Paragraph 1 or 2, Heat exchange is performed between a first fluid stream flowing within the tube bundle and a second fluid stream flowing within the shell. Ammonia synthesis reactor.

7. In Paragraph 1 or 2, It includes a bulkhead installed vertically inside the shell, and The interior of the shell is divided into two semi-cylindrical regions by the partition wall, and The second fluid stream passing through the catalyst bed flows independently into the area partitioned by the bulkhead, Ammonia synthesis reactor.

8. In Paragraph 7, The inlet is formed at the bottom of the cylindrical body, and the outlet is formed at the top of the cylindrical body. The second through hole of the central tube is formed in the lower part of the central tube, and The second fluid stream passing through the catalyst bed flows downward along the central tube, then enters the shell through the second through hole and flows upward along the baffle and the bulkhead. Ammonia synthesis reactor.

9. In Paragraph 7, The above inlet and the above outlet are formed at the bottom of the cylindrical body, and The second through hole of the central tube is formed in the upper part of the central tube, and The second fluid stream passing through the catalyst bed flows upward along the central tube, then enters the shell through the second through hole and flows downward along the baffle and the bulkhead. Ammonia synthesis reactor.

10. A method for producing ammonia using the ammonia synthesis reactor described in paragraph 1, wherein A step of preheating the hydrogen gas stream and the nitrogen gas stream using a preheater; A step of supplying the above preheated hydrogen gas stream and nitrogen gas stream to a gas mixer to produce a mixed gas stream containing hydrogen gas and nitrogen gas; A step of supplying the mixed gas stream to the ammonia synthesis reactor to synthesize ammonia, and producing a crude synthesis gas stream containing the ammonia, unreacted hydrogen gas, and nitrogen gas; A step of condensing at least a portion of the crude synthesis gas stream using a condenser; and The method comprises the step of separating liquid ammonia from the crude synthesis gas stream using a gas-liquid separator, and supplying the separated crude synthesis gas stream to the preheater and the gas mixer for recirculation. Ammonia manufacturing method.

11. In Paragraph 10, A mixture of hydrogen and air or a mixture of hydrogen, ammonia, and air is injected into the preheater as a combustion gas, and the combustion heat generated by burning the combustion gas is used to preheat the hydrogen gas stream and the nitrogen gas stream. Ammonia manufacturing method.

12. In Paragraph 11, The ammonia injected as the combustion gas is gaseous ammonia recovered from the crude synthesis gas stream separated in the gas-liquid separator, Ammonia manufacturing method.

13. In Paragraph 10 or 11, The above gas mixer mixes the hydrogen gas stream and nitrogen gas stream preheated in the above preheater with the crude synthesis gas stream separated in the gas-liquid separator to produce a mixed gas stream containing hydrogen gas and nitrogen gas in a predetermined molar ratio. Ammonia manufacturing method.

14. In Paragraph 13, The molar ratio of hydrogen gas to nitrogen gas in the above mixed gas stream is 3 to 4, Ammonia manufacturing method.

15. In Paragraph 11, A method further comprising the step of supplying steam generated by burning the combustion gas to the gas mixer to indirectly heat the mixed gas stream inside the gas mixer. Ammonia manufacturing method.

16. In Paragraph 11, A method further comprising the step of producing electricity by supplying steam generated by burning the above combustion gas to a steam turbine. Ammonia manufacturing method.

17. In Paragraph 10 or 11, The internal temperature of the above-mentioned ammonia synthesis reactor is maintained at 400℃ to 500℃, Ammonia manufacturing method.

18. In Paragraph 10 or 11, The pressure of the above-mentioned ammonia synthesis reactor is maintained at 10 bar to 100 bar, Ammonia manufacturing method.

19. In Paragraph 10 or 11, The method further comprises the step of condensing at least a portion of the crude synthesis gas stream into liquid ammonia using steam condensate generated by indirectly heating the mixed gas stream inside the gas mixer in the condenser. Ammonia manufacturing method.

20. In Paragraph 19, The method further comprises the step of indirectly heating the mixed gas stream by supplying steam generated by condensing at least a portion of the above crude synthesis gas stream to the gas mixer. Ammonia manufacturing method.

21. In Paragraph 19, The method further comprises the step of producing electricity by supplying steam generated by condensing at least a portion of the above crude synthetic gas stream to a steam turbine. Ammonia manufacturing method.

Images