Reactor and method for producing ammonia decomposition mixture using the same

Abstract

The present invention provides a radial flow reactor in which temperature unevenness is difficult to occur even if an endothermic reaction is performed, pressure loss is small, and maintenance work is easy, and a method for producing an ammonia decomposition mixture using the same. The reactor of the present invention is a so-called radial flow reactor having a cylindrical reaction vessel arranged vertically, and a reaction region in which a chemical reaction is performed inside the reaction vessel, and in the reaction region, a catalyst member having a heater portion that generates heat by electric conduction and a catalyst arranged so as to be capable of being heated by the heater portion is arranged in a concentric circle shape in a cross section of the reaction vessel perpendicular to the axial direction.

Description

Reactor and method for producing ammonia decomposition mixture using the reactor Technical Field

[0001] This invention relates to reactors suitable for ammonia decomposition reactions, etc. Background Technology

[0002] The ammonia decomposition reaction is one in which the number of gas molecules increases as the reaction proceeds. At low reaction pressures, the reaction proceeds in equilibrium. On the other hand, the lower the pressure, the higher the volumetric flow rate, which in turn requires a larger reactor volume. Furthermore, considering the pressures required for subsequent separation and purification processes, it cannot be said that low pressure is always sufficient.

[0003] For example, the methanol synthesis reaction is one in which the number of molecules decreases as the reaction proceeds, and high reaction pressure is advantageous for equilibrium. This reaction uses a radial flow reactor, which results in lower pressure loss compared to a conventional cylindrical reactor. By appropriately configuring cooling pipes, the temperature distribution within the reactor is optimized, thereby improving the conversion rate.

[0004] Patent document 1 describes a reactor consisting of a shell-and-tube heat exchanger made up of a shell and cooling tubes. More specifically, the reactor comprises: a shell consisting of an upright cylinder, an upper tube sheet with an outwardly convex curved surface that closes the upper part of the upright cylinder, and a lower tube sheet with an outwardly convex curved surface that closes the lower part of the upright cylinder; a cylindrical ventilatory wall provided facing most of the inner circumference of the upright cylinder, and connected to the upright cylinder by means of its upper and lower ends; at least one external circumferential opening provided to connect the cylindrical ventilatory wall, the external circumferential space between the upright cylinder, and the outside of the shell; a central tube disposed at the center of the upright cylinder, with its upper end closed, and multiple holes provided in a range substantially corresponding to the ventilatory cylindrical wall to form ventilation, the lower end penetrating the lower tube sheet and the lower cover described later, and opening to the outside of the shell by means of the lower end opening; and multiple cooling pipes connected to the upper and lower tube sheets respectively at their upper and lower ends, and connected to the outside of the shell and open thereto, wherein the catalyst is filled in the shell at least corresponding to the ventilatory portion of the ventilatory inner wall.

[0005] Patent Document 2 describes a reactor comprising a filling region, i.e., a continuous filling layer containing granular filler, within an upright cylindrical reaction vessel; and an outer flow path and an inner flow path, respectively disposed on the outer and inner sides of the filling region in a cross-section perpendicular to the axial direction of the reaction vessel, allowing fluid to flow axially, configured such that fluid can flow between the filling region and the outer flow path, and also between the filling region and the inner flow path. The reactor includes at least one of an outer partition structure and an inner partition structure. The outer partition structure includes a partition plate that axially divides the filling region with a gap between itself and the inner edge of the filling region, allowing the granular filler to pass through, and a shut-off portion that blocks the axial flow of fluid in the outer flow path. The inner partition structure includes a partition plate that axially divides the filling region with a gap between itself and the outer edge of the filling region, allowing the granular filler to pass through, and a shut-off portion that blocks the axial flow of fluid in the inner flow path. Such a reactor, as described in Non-Patent Document 1, has been practically implemented as the MRF-Z (registered trademark) reactor.

[0006] On the other hand, Patent Document 3 describes a catalytic reaction system using a catalyst that promotes a chemical reaction of a fluid being processed. This catalytic reaction system includes a chamber for the fluid being processed to flow through, a catalyst component disposed within the chamber in a manner that allows it to contact the fluid being processed, and a control device for supplying electricity to the catalyst component. The catalyst component has multiple catalyst elements arranged in a multi-stage manner along the flow direction of the fluid being processed. Each catalyst element has a heater section that heats up when energized, and a carrier on the surface of the heater section that supports a catalyst substance. The control device independently controls the temperature of each catalyst element.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 4-180827

[0010] Patent document 2 Japanese Patent Application Publication No. 2011-206648

[0011] Patent document 3 Japanese Patent Application Publication No. 2015-98408

[0012] Non-patent literature

[0013] Non-patent literature 1

[0014] https: / / www.toyo-eng.com / jp / ja / products / petrochmical / metha nol / Summary of the Invention

[0015] The problem that the invention aims to solve

[0016] Even in the ammonia decomposition reaction, a radial flow reactor as described in Patent Documents 1-2 is used. It is believed that compared to the catalyst-packed layers in conventional cylindrical reactors, the pressure loss is lower, and the reaction within the reactor can be optimized by controlling the heating amount. Furthermore, unlike the methanol synthesis reaction, the flow is directed from the inside out. It is also believed that as the flow proceeds within the reactor, the flow rate decreases, the dynamic pressure decreases, and thus the decomposition reaction proceeds favorably at equilibrium.

[0017] However, when using the reactors in Patent Documents 1 and 2 for ammonia decomposition, since the ammonia decomposition reaction is endothermic, the ammonia needs to be heated by an external furnace or heat exchanger before being supplied. Even so, uneven temperature distribution due to fluid flow within the reactor leads to reduced efficiency. Furthermore, even if the fluid flow within the reactor can be controlled, a temperature difference will occur between the upstream and downstream sides. Therefore, when attempting to control the overall reaction temperature within the reactor, overheating can occur due to variations in location, thus accelerating catalyst degradation. While the reactor in Patent Document 3 can control different temperatures on the upstream and downstream sides, a large pressure loss in the catalyst bed is foreseeable. Moreover, since the wiring and temperature sensors required for each catalyst bed are located on the side of the reactor, maintenance operations such as replacement become difficult, especially for large-scale applications.

[0018] Therefore, the object of the present invention is to provide a radial flow reactor that is difficult to produce temperature unevenness, has low pressure loss, and is easy to maintain, even when an endothermic reaction is carried out, and a method for manufacturing an ammonia decomposition mixture using the reactor.

[0019] Methods for solving problems

[0020] This invention is a reactor having an upright cylindrical reaction vessel and a reaction zone inside the reaction vessel where a chemical reaction takes place.

[0021] In the aforementioned reaction zone, in a cross-section perpendicular to the axial direction of the aforementioned reaction vessel, catalyst components are arranged in a concentric circle. Each catalyst component includes a heater section that generates heat when energized, and a catalyst configured to be heated by the heater section.

[0022] The above-mentioned reaction vessel has:

[0023] An outer flow path is formed in a cross-section perpendicular to the axial direction of the reaction vessel, located outside the reaction region and communicating with the outside of the reaction vessel.

[0024] A central side flow path is formed in a cross-section perpendicular to the axial direction of the reaction vessel, on the side closer to the center than the reaction region, and is connected to the outside of the reaction vessel.

[0025] An outer flow path wall, which divides the reaction zone from the outer flow path and allows fluid flow; and

[0026] The central side flow path wall divides the reaction zone and the central side flow path, and allows fluid to flow through.

[0027] Furthermore, the present invention provides a method for manufacturing an ammonia decomposition mixture, which uses the aforementioned reactor to manufacture an ammonia decomposition mixture based on the decomposition reaction of ammonia gas, comprising:

[0028] The process of introducing the aforementioned ammonia gas from the aforementioned central side flow path;

[0029] The process of heating the catalyst by energizing the heater section described above;

[0030] The process of performing the above-mentioned ammonia decomposition reaction in the above-mentioned reaction zone to generate an ammonia decomposition mixture; and

[0031] The process of discharging the above-mentioned ammonia decomposition mixture from the above-mentioned outer flow path.

[0032] The effects of the invention

[0033] According to the present invention, a radial flow reactor is provided that is difficult to produce temperature unevenness, has low pressure loss, and is easy to maintain, even when an endothermic reaction is carried out, as well as a method for manufacturing an ammonia decomposition mixture using the reactor. Attached Figure Description

[0034] Figure 1 is a schematic longitudinal sectional view showing an example of the configuration of the reactor of the present invention.

[0035] Figure 2 is a schematic cross-sectional view showing an example of the configuration of the reactor of the present invention.

[0036] Figure 3 is a schematic diagram showing the surface structure of the outer or central flow path wall. In Figure 3(a), a hole is formed on the surface, and in Figure 3(b), a slit is formed on the surface.

[0037] Figure 4 is a schematic perspective view showing an example of the composition of the catalyst support line.

[0038] Figure 5 is a schematic top view showing an example of the configuration of a catalyst component using a catalyst carrying line. Detailed Implementation

[0039] Figure 1 (longitudinal sectional view) and Figure 2 (cross-sectional view) show examples of the configuration of the reactor of the present invention. The reactor 1 of the present invention is a so-called radial flow reactor, having an upright reaction vessel 2 that is at least cylindrical in the central part, and a reaction zone 10 in which the chemical reaction takes place inside the reaction vessel 2. Inside the reaction vessel 2, in a cross-section perpendicular to the axial direction of the cylindrical reaction vessel 2, an outer flow path 20 is formed on the outer side of the reaction zone 10, and a central flow path 30 is formed on the central side of the reaction zone 10.

[0040] An outer flow path wall 22 is provided at the boundary between the reaction zone 10 and the outer flow path 20. That is, the outer flow path wall 22 divides the reaction zone 10 and the outer flow path 20. In a cross-section perpendicular to the axial direction of the reaction vessel 2, the area outside the outer flow path wall 22 becomes the outer flow path 20. For example, as shown in FIG3, holes 23 or slits 24 are formed on the outer flow path wall 22, penetrating the front and back surfaces of the outer flow path wall 22, allowing fluid to flow from the reaction zone 10 to the outer flow path 20, or from the outer flow path 20 to the reaction zone 10.

[0041] The outer flow path wall 22 is, for example, cylindrical and arranged concentrically in a cross-section perpendicular to the axial direction of the reaction vessel 2. For example, as shown in FIG1, the lower part of the outer flow path wall 22 is connected to the lower part of the reaction vessel 2, and the upper part of the outer flow path wall 22 is connected to the outer edge of the disc-shaped upper plate 12. The outer flow path 20, divided by the outer flow path wall 22, is formed on the outer edge inside the cylindrical reaction vessel 2, and is therefore sometimes referred to as a "shell" or "outer basket". Furthermore, as shown in FIG1, the outer flow path 20 formed on the outside of the outer flow path wall 22 is connected to the outside of the reaction vessel 2 via a connecting passage 21 formed on the upper part of the reaction vessel 2.

[0042] A central side flow path wall 32 is disposed at the boundary between the reaction region 10 and the central side flow path 30. That is, the central side flow path wall 32 divides the reaction region 10 and the central side flow path 30. In a cross-section perpendicular to the axial direction of the reaction vessel 2, the central side (inner side) of the central side flow path wall 32 becomes the central side flow path 30. For example, as shown in FIG3, a hole 33 or a slit 34 is formed in the central side flow path wall 32, which penetrates the front and back surfaces of the central side flow path wall 32 and allows fluid to flow. Fluid can flow from the reaction region 10 to the central side flow path 30, or from the central side flow path 30 to the reaction region 10.

[0043] The central side flow path wall 32 is, for example, tubular and arranged along the central axis of the reaction vessel 2. As shown in FIG1, for example, the upper part of the central side flow path wall 32 is closed, and the lower part of the central side flow path wall 32 penetrates the reaction vessel 2. The central side flow path 30, divided by the central side flow path wall 32, is formed in a tubular shape in the central part of the cylindrical reaction vessel 2, and is therefore referred to as a "central tube". Moreover, as shown in FIG1, for example, the central side flow path 30 formed on the central side (inner side) of the central side flow path wall 32 is connected to the outside of the reaction vessel 2 through the lower end of the tubular central side flow path wall 32 that penetrates the lower part of the reaction vessel 2, i.e., the central side flow path connecting passage 31.

[0044] If the reactor 1 is as described above, the fluid (reactant) introduced into the reaction vessel 2 flows radially in a cross-section perpendicular to the axial direction of the reaction vessel 2, thereby enabling at least a portion of the reactant to react in the reaction zone 10. More specifically, the fluid (reactant) supplied to the reaction vessel 2 from the central side flow path via the connecting passage 31 flows in the central side flow path 30 and is introduced into the reaction zone 10 through the central side flow path wall 32. Then, at least a portion of the fluid (reactant) reacts in the reaction zone 10, after which the fluid (reaction mixture) flows through the outer flow path wall 22 in the outer flow path 20 and is discharged to the outside from the outer flow path via the connecting passage 21. Alternatively, the fluid (reactant) supplied to the reaction vessel 2 from the outer flow path via the connecting passage 21 flows in the outer flow path 20 and is introduced into the reaction zone 10 through the outer flow path wall 22. Then, at least a portion of the fluid (reaction material) reacts in the reaction zone 10, after which the fluid (reaction mixture) flows through the central side flow path wall 32, flows in the central side flow path 30, and is discharged to the outside from the central side flow path via the connecting passage 31.

[0045] The reaction zone 10 typically contains a catalyst to react the reactants. In typical radial flow reactors, granular catalyst is often packed into the reaction zone 10. However, in endothermic reactions, for example, the temperature decreases as the reaction proceeds, necessitating the maintenance of the temperature in the reaction zone 10. Current methods include heating the reaction zone 10 before introducing the reactants via a furnace or heat exchanger, or heating the reaction zone 10 by inserting a tubular pipe and allowing a heat transfer medium to flow within the pipe. However, these methods often result in uneven temperature distribution within the reaction zone 10, leading to reduced efficiency. Furthermore, since the reaction occurs as a fluid flowing radially within a cross-section perpendicular to the axial direction of the reaction vessel 2, the concentration of the reactants varies depending on the radial position of the reaction zone 10, resulting in variations in the optimal temperature. Additionally, heat transfer media such as steam or combustion exhaust gases are typically used as heating sources, but these are primarily generated through the combustion of fossil fuels, thus emitting carbon dioxide. While methods using electricity to generate heat transfer media exist, this indirect heating method is inefficient.

[0046] Therefore, in the reaction zone 10 of the reactor 1 of the present invention, a catalyst component 11 is arranged concentrically in a cross-section perpendicular to the axial direction of the reaction vessel 2. This catalyst component 11 can be heated by a heater section that generates heat through electricity. Accordingly, the catalyst can be directly heated by energizing the heater section, resulting in faster reaction start and stop, less temperature unevenness, lower pressure loss compared to conventional catalyst-packed reactors, and optimal temperature distribution for the reaction. Since the catalyst component 11 is arranged concentrically in a cross-section perpendicular to the axial direction of the reaction vessel 2, it is preferably formed in a cylindrical shape. The cylindrical catalyst component 11 can be disposed directly at the bottom of the reaction zone 1 or disposed on a base plate 13 provided at the bottom. Furthermore, the heating source uses electricity from renewable energy sources, thereby suppressing carbon dioxide production.

[0047] As the catalyst component 11, any component having a heater section that heats up when energized and a catalyst configured to be heated by the heater section is acceptable. However, for example, as shown in FIG4, it can be formed from a catalyst support wire 40, which has a linear heating wire 41 serving as the heater section and a catalyst layer 42 containing the catalyst disposed on the surface of the heating wire 41. The linear heating wire 41 can be composed of a single wire or multiple wires bundled together. The catalyst layer 42 can, for example, have a carrier and a catalyst supported on the carrier.

[0048] The material constituting the heater section (e.g., heating wire 41) is preferably a material that has the electrical property of being able to self-heat to a specified temperature by energizing it. For example, it can be at least one metal selected from the group consisting of copper, magnesium, calcium, nickel, cobalt, vanadium, niobium, chromium, titanium, aluminum, silicon, molybdenum, tungsten and iron, or an alloy thereof.

[0049] As a support, it is sufficient to select an appropriate material from those capable of supporting the catalyst, such as silicon dioxide (SiO2), aluminum oxide (Al2O3), titanium dioxide (TiO2), magnesium oxide (MgO), calcium oxide (CaO), cesium oxide (Cs2O), and praseodymium oxide (Pr6O). 11 Composite materials containing lanthanum oxide (La₂O₃), activated carbon, etc., can also be used. In particular, alumina is preferred, and γ-alumina is even more preferred in terms of manufacturing.

[0050] The catalyst supported on the support can be any catalyst that promotes the reaction occurring in reaction region 10. Examples include iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), and gold (Au). Composite materials containing these can also be used. In particular, ruthenium or nickel is preferred.

[0051] A cylindrical catalyst component 11 using catalyst support wires 40, as shown in FIG5, can be formed by winding the catalyst support wires 40 into a spiral or mesh shape (multiple spirals) to form a ring shape, stacking them in multiple stages, and connecting the ends 40a of each catalyst support wire 40. A cylindrical catalyst component 11 can also be formed by winding the catalyst support wires 40 into a spiral or mesh shape, and by winding the entire component into a spiral or mesh shape.

[0052] Furthermore, as shown in Figures 1 and 2, in the reaction zone 10, multiple catalyst components 11 (11a, 11b, 11c) are arranged concentrically in a cross-section perpendicular to the axial direction of the reaction vessel 2. Moreover, the electrical current supplied to each of these multiple catalyst components 11 (11a, 11b, 11c) can be independently controlled, thereby allowing each catalyst to be controlled at an optimal temperature based on its radial position within the reaction zone 10. The number of catalyst components 11 disposed in the reaction zone 10 is preferably 1 to 6, more preferably 2 to 4. Furthermore, the wires (not shown) used to supply power to the catalyst components 11 and the temperature sensors (not shown) used to detect the temperature of the catalyst components 11 are centrally located at the bottom or top of the reactor 1, thereby facilitating the inspection and replacement of the catalyst components, wires, and temperature sensors.

[0053] Examples of reactions that occur in the reactor 1 of the present invention include the decomposition of ammonia, the steam reforming of hydrocarbons, the decomposition of methanol, the dehydrogenation of organic hydrides, endothermic decomposition reactions in the gas phase, and, in particular, reactions for the production of hydrogen. The decomposition of ammonia is especially preferred. Since these reactions are endothermic, heating with minimal temperature unevenness and temperature control are very important; therefore, the reactor 1 of the present invention is preferred.

[0054] Here, an embodiment of the ammonia decomposition reaction (production of the ammonia decomposition mixture) using reactor 1 of the present invention will be described. The ammonia decomposition reaction is carried out in the presence of a ruthenium or nickel catalyst according to the following reaction formula.

[0055] 2NH3→N2+3H2

[0056] This reaction is endothermic, therefore, minimal temperature unevenness and precise temperature control are crucial for efficient reaction. Furthermore, the number of gas molecules increases as the reaction proceeds.

[0057] From the above perspective, when using the reactor 1 of the present invention to carry out the decomposition reaction of ammonia, it is preferable to introduce ammonia from the central side flow path 30 and discharge the ammonia decomposition mixture to the outer flow path 20. Accordingly, since the reactants move from the central side of the reaction zone 10 to the outer side, it is considered that the flow rate decreases as the reaction proceeds, thereby reducing the dynamic pressure, which is advantageous in terms of reaction equilibrium.

[0058] More specifically, firstly, ammonia gas, used as a reaction feedstock, is introduced into the central side flow path 30 via a connecting passage 31. The ammonia gas introduced into the central side flow path 30 flows within it and is introduced into the reaction zone 10 through the central side flow path wall 32. The catalyst in the catalyst component 11 located in the reaction zone 10 is heated by energizing the heater section of the catalyst component 11. Accordingly, the ammonia gas introduced into the reaction zone 10 undergoes a decomposition reaction, generating an ammonia decomposition mixture. The ammonia decomposition mixture generated in the reaction zone 10 is discharged from the reaction zone 10 through the outer flow path wall 22 into the outer flow path 20, flows within the outer flow path 20, and is discharged to the outside via the outer flow path connecting passage 21.

[0059] The temperature of the heater section of the catalyst component 11 can be set according to the concentration of ammonia, the type of catalyst, etc., but is preferably 350 to 700°C, and more preferably 400 to 650°C. The pressure of the reaction zone 10 can be set according to the concentration of ammonia, the type of catalyst, etc., but is preferably 0 to 0.9 MPaG.

[0060] Symbol explanation:

[0061] 1 Reactor; 2 Reaction vessel; 10 Reaction zone; 11 Catalyst component; 12 Upper plate; 13 Bottom plate; 20 Outer flow path; 21 Connecting path for outer flow path; 22 Outer flow path wall; 23 Hole; 24 Slit; 30 Central side flow path; 31 Connecting path for central side flow path; 32 Central side flow path wall; 33 Hole; 34 Slit; 40 Catalyst carrying line; 40a End; 41 Heating wire; 42 Catalyst layer.

Claims

1. A reactor, characterized in that, The reaction vessel comprises an upright cylindrical reaction container and a reaction zone inside the reaction container where a chemical reaction takes place. In the reaction zone, catalyst components are arranged concentrically in a cross-section perpendicular to the axial direction of the reaction vessel. Each catalyst component has a heater section that generates heat by electricity and a catalyst configured to be heated by the heater section. The reaction vessel has: an outer flow path formed in a cross-section perpendicular to the axial direction of the reaction vessel, located outside the reaction zone and communicating with the outside of the reaction vessel; and a central flow path. The flow path is formed in a cross-section perpendicular to the axial direction of the reaction vessel, on the side closer to the center than the reaction region, and communicates with the outside of the reaction vessel; an outer flow path wall divides the reaction region and the outer flow path, and allows fluid flow; and a central flow path wall divides the reaction region and the central flow path, and allows fluid flow; the catalyst component is formed by a catalyst carrying line, the catalyst carrying line having a linear heating wire as the heater part, and a catalyst layer containing the catalyst disposed on the surface of the heating wire.

2. The reactor according to claim 1, characterized in that, The catalyst support wire is spiral or mesh-like.

3. The reactor according to claim 1, characterized in that, The catalyst layer has a support and a catalyst supported on the support.

4. The reactor according to claim 3, characterized in that, The carrier is γ-alumina.

5. The reactor according to claim 1, characterized in that, The catalyst is ruthenium or nickel.

6. The reactor according to claim 1, characterized in that, In the reaction region, in a cross-section perpendicular to the axial direction of the reaction vessel, a plurality of catalyst components are arranged in a concentric circle.

7. The reactor according to claim 6, characterized in that, The amount of electricity supplied to each of the catalyst components can be controlled independently.

8. The reactor according to claim 1, characterized in that, The outer flow path wall has holes or slits that allow the fluid to flow through.

9. The reactor according to claim 1, characterized in that, The central side flow path wall has holes or slits that allow the fluid to flow through.

10. The reactor according to any one of claims 1 to 9, characterized in that, It is a reactor used for the decomposition reaction of ammonia.

11. A method for producing an ammonia decomposition mixture, comprising using the reactor of claim 10 to produce an ammonia decomposition mixture based on the decomposition reaction of ammonia gas, the method being characterized by comprising: a step of introducing the ammonia gas from the central side flow path into the reaction zone; a step of energizing the heater section to heat the catalyst; a step of carrying out the decomposition reaction of the ammonia gas in the reaction zone to generate the ammonia decomposition mixture; and a step of discharging the ammonia decomposition mixture from the reaction zone to the outer flow path.

12. The method for manufacturing the ammonia decomposition mixture according to claim 11, characterized in that, The temperature of the heater section is 350–700°C.

13. The method for manufacturing the ammonia decomposition mixture according to claim 11, characterized in that, The pressure in the reaction zone is 0–0.9 MPaG.

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