Reactor and method for producing ammonia decomposition mixture using the same

Abstract

To provide a radial-flow type reactor which hardly causes temperature unevenness even in endothermic reaction, of which pressure loss is small, and which is easily maintained, and to provide a production method of an ammonia decomposition mixture using the same.SOLUTION: A reactor relating to the invention is a so-called radial-flow type reactor that includes a cylindrical reaction vessel installed upright and a reaction zone for conducting chemical reaction in the reaction vessel. In the reaction zone, catalyst members including a heater unit to generate heat with power supply and a catalyst arranged so as to be heated by the heater unit are concentrically arranged in the cross-section perpendicular to the axial direction of the reaction vessel.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reactor suitable for ammonia decomposition reactions and the like. [Background technology]

[0002] The ammonia decomposition reaction is a reaction in which the number of gas molecules increases as the reaction progresses, and the lower the reaction pressure, the more the reaction proceeds in equilibrium. On the other hand, the lower the pressure, the greater the volumetric flow rate and the larger the required reactor volume. Also, considering the pressure required for the subsequent separation and purification processes, it cannot be said that a low pressure is always better.

[0003] For example, the methanol synthesis reaction is a reaction in which the number of molecules decreases as the reaction progresses, and a higher reaction pressure is advantageous for the equilibrium reaction. For this reaction, a radial flow reactor is used, which has lower pressure loss than a conventional cylindrical reactor, and by appropriately arranging the cooling pipes, the temperature distribution within the reactor can be optimized, thereby improving the conversion rate.

[0004] Patent Document 1 describes a reactor consisting of a shell-and-tube heat exchanger composed of a shell and cooling tubes. More specifically, this reactor has a shell consisting of an upright cylinder, an upper tube plate with an outwardly convex curved surface closing the upper part of the upright cylinder, and a lower tube plate with an outwardly convex curved surface closing the lower part of the upright cylinder; a cylindrical permeable wall provided facing the inner circumference of most of the upright cylinder and connected to the upright cylinder at its upper and lower ends; at least one provided outer peripheral opening connecting the outer peripheral space between the permeable wall and the upright cylinder with the outside of the shell; a central tube disposed at the center of the upright cylinder, the upper end of which is closed, the permeable cylindrical wall having a number of holes in an area substantially corresponding to the permeable cylindrical wall to make it permeable, and the lower end of which penetrates the lower tube plate and a lower header cover described below and opens to the outside of the shell; and a number of cooling tubes whose upper and lower ends are connected to the upper and lower tube plates, respectively, and open to the outside of the shell. A catalyst is filled in the shell at least in a manner corresponding to the permeable portions of the permeable inner wall.

[0005] Patent Document 2 describes a reactor configured within an upright cylindrical reactor vessel, including a packed region containing a continuous packed bed of granular packing, and an outer flow path and an inner flow path, respectively located on the outer and inner sides of the packed region in a cross section perpendicular to the axial direction of the reactor vessel, through which a fluid can flow in the axial direction. The reactor is configured to allow fluid flow between the packed region and the outer flow path, and between the packed region and the inner flow path. This reactor includes at least one of the following partition structures: an outer partition structure including a partition plate that axially divides the packed region by forming a gap between the inner edge of the packed region and a partition plate that allows the granular packing to pass through, and a blocking section that blocks axial fluid flow in the outer flow path; and an inner partition structure including a partition plate that axially divides the packed region by forming a gap between the outer edge of the packed region and a partition plate that allows the granular packing to pass through, and a blocking section that blocks axial fluid flow in the inner flow path. Such a reactor has been put to practical use as the MRF-Z® reactor, as described in Non-Patent Document 1.

[0006] Meanwhile, Patent Document 3 describes a catalytic reaction system that uses a catalyst to promote a chemical reaction of a fluid to be treated. This catalytic reaction system includes a chamber through which the fluid to be treated flows, a catalyst member disposed in the chamber so as to be in contact with the fluid to be treated, and a control device that supplies power to the catalyst member, the catalyst member having a plurality of catalyst bodies disposed in multiple stages along the flow direction of the fluid to be treated, each catalyst body having a heater section that generates heat when energized and a carrier that supports a catalytic substance disposed on the surface of the heater section, and the control device controls the temperature of each catalyst body independently of one another. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 4-180827 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-206648 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-98408 [Non-patent literature]

[0008] [Non-Patent Document 1] https: / / www.toyo-eng.com / jp / ja / products / petrochemical / methanol / Summary of the Invention [Problem to be solved by the invention]

[0009] In the ammonia decomposition reaction, too, it is believed that the use of a radial flow reactor such as those described in Patent Documents 1 and 2 can reduce pressure loss compared to a conventional cylindrical reactor or other catalyst-packed bed reactor, and by controlling the heat input, it is possible to optimize the reaction in the reactor. Furthermore, contrary to the methanol synthesis reaction, by circulating the flow from the inside to the outside, the flow rate decreases as the flow through the reactor, and the dynamic pressure decreases, which is thought to favor the equilibrium of the decomposition reaction.

[0010] However, when performing an ammonia decomposition reaction using the reactors of Patent Documents 1 and 2, because the ammonia decomposition reaction is an endothermic reaction, it was necessary to heat the ammonia using an external heating furnace or heat exchanger before supplying it. Even so, temperature unevenness could occur depending on the fluid flow within the reactor, resulting in reduced efficiency. Furthermore, even if the fluid flow within the reactor could be controlled, temperature differences would occur between the upstream and downstream sides. Therefore, attempting to control the reaction temperature throughout the reactor would result in excessive heating in some locations, accelerating catalyst degradation. While the reactor of Patent Document 3 could control different temperatures upstream and downstream within the reactor, it suffered from significant pressure loss in the catalyst layer. Furthermore, the electrical wires and temperature sensors required for each catalyst layer would be located on the side of the reactor, making maintenance work such as replacing these components difficult, making it particularly difficult to scale up.

[0011] Therefore, an object of the present invention is to provide a radial flow reactor that is less likely to cause temperature unevenness even when an endothermic reaction is carried out, has small pressure loss, and is easy to maintain, and a method for producing an ammonia decomposition mixture using the same. [Means for solving the problem]

[0012] The present invention comprises a cylindrical reaction vessel disposed upright; a reaction region in which a chemical reaction occurs inside the reaction vessel; and In the reaction region, a catalyst member having a heater unit that generates heat when energized and a catalyst that is arranged so as to be heatable by the heater unit is concentrically arranged in a cross section perpendicular to the axial direction of the reaction vessel, The reaction vessel comprises: an outer flow path formed outside the reaction zone in a cross section perpendicular to the axial direction of the reaction vessel and communicating with the outside of the reaction vessel; a central flow path formed on the central side of the reaction vessel relative to the reaction region in a cross section perpendicular to the axial direction of the reaction vessel, the central flow path communicating with the outside of the reaction vessel; an outer channel wall that separates the reaction region from the outer channel and allows a fluid to flow through; a central channel wall that separates the reaction region from the central channel and allows a fluid to flow therethrough; With death, The catalyst member is a catalyst-supporting wire having a wire-shaped heating wire as the heater portion and a catalyst layer containing the catalyst disposed on the surface of the heating wire; It is formed by It is a reactor.

[0013] The present invention also provides a method for producing an ammonia decomposition mixture by a decomposition reaction of ammonia using the reactor, comprising: introducing the ammonia through the central channel; a step of energizing the heater unit to heat the catalyst; conducting the ammonia decomposition reaction in the reaction zone to produce an ammonia decomposition mixture; discharging the ammonia decomposition mixture from the outer flow path; have A method for producing an ammonia decomposition mixture. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a radial flow reactor that is less likely to cause temperature unevenness even when an endothermic reaction is carried out, has small pressure loss, and is easy to maintain, and a method for producing an ammonia decomposition mixture using the same. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic vertical cross-sectional view showing an example of the configuration of a reactor according to the present invention. FIG. [Figure 2] 1 is a schematic cross-sectional view showing an example of the configuration of a reactor according to the present invention. FIG. [Figure 3] 1A and 1B are schematic diagrams showing the surface structure of an outer channel wall or a central channel wall, in which (a) holes are formed in the surface, and (b) slits are formed in the surface. [Figure 4] FIG. 2 is a schematic perspective view showing an example of the configuration of a catalyst-carrying wire. [Figure 5] FIG. 2 is a schematic plan view showing an example of the configuration of a catalyst member using a catalyst-carrying wire. DETAILED DESCRIPTION OF THE INVENTION

[0016] An example of the configuration of a reactor according to the present invention is shown in Fig. 1 (longitudinal cross-sectional view) and Fig. 2 (transverse cross-sectional view). The reactor 1 according to the present invention is a so-called radial flow reactor, and includes a reaction vessel 2 arranged upright, at least the central portion of which is cylindrical, and a reaction zone 10 in which a 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 outside the reaction zone 10, and a central flow path 30 is formed closer to the center than the reaction zone 10.

[0017] An outer channel wall 22 is disposed at the boundary between the reaction region 10 and the outer channel 20. That is, the outer channel wall 22 separates the reaction region 10 from the outer channel 20, and the region outside the outer channel wall 22 in a cross section perpendicular to the axial direction of the reaction vessel 2 forms the outer channel 20. As shown in FIG. 3 , for example, the outer channel wall 22 is formed with holes 23 or slits 24 that penetrate the front and back surfaces of the outer channel wall 22 and allow fluid to flow therethrough, allowing fluid to flow from the reaction region 10 to the outer channel 20 or from the outer channel 20 to the reaction region 10.

[0018] The outer flow path wall 22 has, for example, a cylindrical shape and is arranged concentrically in a cross section perpendicular to the axial direction of the reaction vessel 2. For example, as shown in FIG. 1 , 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 disk-shaped upper plate 12. The outer flow path 20 defined by the outer flow path wall 22 is formed on the outer edge of the cylindrical reaction vessel 2, and is therefore sometimes called an "outer shell" or an "outer basket." The outer flow path 20 formed outside the outer flow path wall 22 is connected to the outside of the reaction vessel 2 through an outer flow path communicating passage 21 formed in the upper part of the reaction vessel 2, as shown in FIG. 1 , for example.

[0019] A central-side channel wall 32 is disposed at the boundary between the reaction region 10 and the central-side channel 30. That is, the central-side channel wall 32 separates the reaction region 10 from the central-side channel 30, and the region on the central side (inner side) of the central-side channel wall 32 in a cross section perpendicular to the axial direction of the reaction vessel 2 becomes the central-side channel 30. As shown in FIG. 3 , for example, the central-side channel wall 32 has holes 33 or slits 34 formed therein that penetrate the front and back surfaces of the central-side channel wall 32 and allow fluid to flow therethrough, allowing fluid to flow from the reaction region 10 to the central-side channel 30 or from the central-side channel 30 to the reaction region 10.

[0020] The center-side channel wall 32 is, for example, pipe-shaped and is disposed along the central axis of the reaction vessel 2. For example, as shown in FIG. 1 , the upper part of the center-side channel wall 32 is closed, and the lower part of the center-side channel wall 32 penetrates the reaction vessel 2. The center-side channel 30 separated by the center-side channel wall 32 is formed in a pipe shape in the center of the cylindrical reaction vessel 2, and is therefore sometimes called a "center pipe." The center-side channel 30 formed on the center side (inside) of the center-side channel wall 32 communicates with the outside of the reaction vessel 2 through a center-side channel communicating passage 31, which is the lower end of the pipe-shaped center-side channel wall 32 that penetrates the bottom of the reaction vessel 2, as shown in FIG. 1 .

[0021] In the reactor 1 as described above, the fluid (reaction raw material) introduced into the reaction vessel 2 flows in the radial direction in a cross section perpendicular to the axial direction of the reaction vessel 2, thereby allowing at least a portion of the reaction raw material to react in the reaction region 10. More specifically, the fluid (reaction raw material) supplied into the reaction vessel 2 from the center-side flow path communicating passage 31 flows through the center-side flow path 30, passes through the center-side flow path wall 32, and is introduced into the reaction region 10. Then, after at least a portion of the fluid (reaction raw material) reacts in the reaction region 10, the fluid (reaction mixture) passes through the outer flow path wall 22 and flows through the outer flow path 20, and is discharged to the outside through the outer flow path communicating passage 21. Alternatively, the fluid (reaction raw material) supplied into the reaction vessel 2 from the outer flow path communicating passage 21 flows through the outer flow path 20, passes through the outer flow path wall 22, and is introduced into the reaction region 10. After at least a portion of the fluid (reaction raw material) reacts in the reaction region 10, the fluid (reaction mixture) passes through the central side flow path wall 32, flows through the central side flow path 30, and is discharged to the outside through the central side flow path connecting passage 31.

[0022] The reaction zone 10 typically contains a catalyst for reacting the reactant materials. In typical radial flow reactors, the reaction zone 10 is often filled with a granular catalyst. However, for example, when performing an endothermic reaction, the temperature of the reaction zone 10 decreases as the reaction progresses, making it necessary to maintain the temperature. Conventional methods include heating the reactant materials using a furnace or heat exchanger before introducing them, or passing a heat transfer medium through tubular piping in the reaction zone 10. However, these methods tend to result in temperature variations within the reaction zone 10, resulting in reduced efficiency. Furthermore, because the reaction proceeds while the fluid flows radially in a cross section perpendicular to the axial direction of the reaction vessel 2, the concentration of the reactant materials varies depending on the radial position in the reaction zone 10, and the optimal temperature may differ. Furthermore, heat transfer media such as steam or combustion exhaust gas are typically used as a heat source, but these are mainly generated by the combustion of fossil fuels and therefore emit carbon dioxide. While heat transfer media can also be generated using electricity, this method is indirect heating and therefore less efficient.

[0023] Therefore, in the reaction region 10 of the reactor 1 of the present invention, catalyst members 11, which can heat the catalyst using a heater that generates heat when electricity is applied, are arranged concentrically in a cross section perpendicular to the axial direction of the reaction vessel 2. This allows the catalyst to be directly heated by applying electricity to the heater, resulting in quick reaction start and stop, less temperature unevenness, less pressure loss compared to conventional catalyst-packed bed reactors, and an optimal temperature distribution for the reaction. Since the catalyst members 11 are arranged concentrically in a cross section perpendicular to the axial direction of the reaction vessel 2, they are preferably cylindrical. The cylindrical catalyst members 11 can be placed directly on the bottom of the reaction region 1 or on a bottom plate 13 installed at the bottom. Furthermore, carbon dioxide generation can be suppressed by using electricity derived from renewable energy as the heating source.

[0024] The catalyst member 11 may be any member that has a heater portion that generates heat when current is applied and a catalyst that is arranged so as to be heatable by the heater portion, but for example, as shown in FIG. 4, it can be formed from a catalyst-supported wire 40 that has a wire-shaped heating wire 41 as the heater portion and a catalyst layer 42 containing a catalyst arranged on the surface of the heating wire 41. The wire-shaped heating wire 41 may be made of a single wire or a bundle of multiple wires. The catalyst layer 42 can have, for example, a carrier and a catalyst supported on the carrier.

[0025] The material constituting the heater portion (e.g., heating wire 41) is preferably a material having electrical properties that enable it to self-heat to a predetermined temperature when electricity is passed through it, and is, for example, selected from at least one metal or alloy thereof selected from the group consisting of copper, magnesium, calcium, nickel, cobalt, vanadium, niobium, chromium, titanium, aluminum, silicon, molybdenum, tungsten, and iron.

[0026] The carrier may be appropriately selected from materials capable of supporting the catalyst, such as silicon oxide (SiO2, silica), aluminum oxide (Al2O3, alumina), titanium oxide (TiO2, titania), magnesium oxide (MgO), calcium oxide (CaO), cesium oxide (Cs2O), praseodymium oxide (Pr6O 11 Examples of the material include lanthanum oxide (La2O3), activated carbon, and composite materials containing these can also be used. Among these, alumina is preferred, and γ-alumina is more preferred from the viewpoint of manufacturing.

[0027] The catalyst to be supported on the carrier may be appropriately selected from catalysts that promote the progress of the reaction carried out in the 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), and composite materials containing these metals may also be used. Among these, ruthenium or nickel is preferred.

[0028] 5, a cylindrical catalyst member 11 using a catalyst support wire 40 can be formed by winding the catalyst support wire 40 in a spiral or mesh shape (multiple spiral shapes) to form a doughnut shape as a whole, stacking them in multiple stages, and connecting the ends 40a of the catalyst support wires 40. The cylindrical catalyst member 11 may also be formed by winding the catalyst support wire 40 in a spiral or mesh shape and winding it up as a whole in a spiral or mesh shape.

[0029] 1 and 2, the reaction region 10 may have a plurality of catalyst members 11 (11a, 11b, 11c) concentrically arranged in a cross section perpendicular to the axial direction of the reaction vessel 2. By independently controlling the amount of electricity supplied to the plurality of catalyst members 11 (11a, 11b, 11c), it becomes possible to control the temperature of each catalyst to an optimum value depending on the radial position of the reaction region 10. The number of catalyst members 11 arranged in the reaction region 10 is preferably 1 to 6, and more preferably 2 to 4. Furthermore, by concentrating the electric wires (not shown) for supplying electricity to the catalyst members 11 and the temperature sensors (not shown) for detecting the temperatures of the catalyst members 11 at the bottom or top of the reactor 1, inspection and replacement of the catalyst members, electric wires, and temperature sensors can be facilitated.

[0030] Reactions that can be performed in the reactor 1 of the present invention include, for example, gas phase endothermic decomposition reactions, particularly reactions for producing hydrogen, such as the decomposition reaction of ammonia, the steam reforming reaction of hydrocarbons, the decomposition reaction of methanol, and the dehydrogenation reaction of organic hydrides. Among these, the reactor 1 is suitable for the decomposition reaction of ammonia. These reactions are endothermic reactions, and therefore, heating and temperature control with minimal temperature unevenness are very important, making the reactor 1 of the present invention suitable for use.

[0031] Here, an embodiment of the ammonia decomposition reaction (production of an ammonia decomposition mixture) using the reactor 1 of the present invention will be described. The ammonia decomposition reaction proceeds according to the following reaction formula in the presence of a ruthenium or nickel catalyst. 2NH3 → N2 + 3H2 Since this reaction is endothermic, it is extremely important to heat and control the temperature evenly to ensure efficient reaction. In addition, the number of gas molecules increases as the reaction progresses.

[0032] From this perspective, when performing an ammonia decomposition reaction using the reactor 1 of the present invention, it is preferable to introduce ammonia from the central flow path 30 and discharge the ammonia decomposition mixture into the outer flow path 20. By doing so, the reaction raw materials move from the center to the outside of the reaction region 10, and as the reaction proceeds, the flow rate decreases and the dynamic pressure decreases, which is thought to be advantageous for the reaction equilibrium.

[0033] More specifically, first, ammonia, a reaction raw material, is introduced from the central-side passageway communicating passage 31 into the central-side passageway 30. The ammonia introduced into the central-side passageway 30 flows within the central-side passageway 30, passes from the central-side passageway 30 through the central-side passageway wall 32, and is introduced into the reaction region 10. The catalyst of the catalyst member 11 installed in the reaction region 10 is heated by energizing the heater portion of the catalyst member 11. This causes a decomposition reaction of the ammonia introduced into the reaction region 10, producing an ammonia decomposition mixture. The ammonia decomposition mixture produced in the reaction region 10 passes from the reaction region 10 through the outer passageway wall 22, is discharged into the outer passageway 20, flows through the outer passageway 20, and is discharged to the outside through the outer passageway communicating passageway 21.

[0034] The temperature of the heater portion of the catalyst member 11 may be set depending on the ammonia concentration, the type of catalyst, etc., but is preferably 350 to 700° C., and more preferably 400 to 650° C. The pressure in the reaction region 10 may be set depending on the ammonia concentration, the type of catalyst, etc., but is preferably 0 to 0.9 MPaG. [Explanation of symbols]

[0035] 1. Reactor 2. Reaction vessel 10 Reaction Area 11 Catalyst components 12 Upper plate 13 Bottom plate 20 Outer channel 21 Communication path for outside flow path 22 Outer channel wall 23 holes 24 Slit 30 Center side channel 31 Communication path for center side flow path 32 Center side channel wall 33 holes 34 Slit 40 Catalyst-supported wire 40a End 41 Heating wire 42 Catalyst layer

Claims

1. a cylindrical reaction vessel disposed upright; a reaction region in which a chemical reaction occurs inside the reaction vessel; and In the reaction region, a catalyst member having a heater unit that generates heat when energized and a catalyst arranged so as to be heatable by the heater unit is concentrically arranged in a cross section perpendicular to the axial direction of the reaction vessel, The reaction vessel comprises: an outer flow path formed outside the reaction zone in a cross section perpendicular to the axial direction of the reaction vessel and communicating with the outside of the reaction vessel; a central flow path formed on the central side of the reaction vessel relative to the reaction region in a cross section perpendicular to the axial direction of the reaction vessel, the central flow path communicating with the outside of the reaction vessel; an outer channel wall that separates the reaction region from the outer channel and allows a fluid to flow through; a central channel wall that separates the reaction region from the central channel and allows a fluid to flow therethrough; and The catalyst member is a catalyst-supporting wire having a wire-shaped heating wire as the heater portion and a catalyst layer containing the catalyst disposed on the surface of the heating wire; It is formed by Reactor.

2. The catalyst-carrying wire is wound in a spiral or mesh shape.

10. The reactor of claim 1.

3. The catalyst layer includes a carrier and a catalyst supported on the carrier.

3. The reactor according to claim 1 or 2.

4. The support is gamma alumina The reactor of claim 3.

5. The catalyst is ruthenium or nickel The reactor according to any one of claims 1 to 4.

6. In the reaction zone, a plurality of the catalyst members are concentrically arranged in a cross section perpendicular to the axial direction of the reaction vessel. The reactor according to any one of claims 1 to 5.

7. The amount of current applied to the catalyst members can be controlled independently. The reactor of claim 6.

8. The outer flow path wall is formed with holes or slits through which the fluid can flow. The reactor according to any one of claims 1 to 7.

9. The central flow path wall has holes or slits through which the fluid can flow. The reactor according to any one of claims 1 to 8.

10. A reactor for the decomposition reaction of ammonia The reactor according to any one of claims 1 to 9.

11. A method for producing an ammonia decomposition mixture by ammonia decomposition reaction using the reactor according to claim 10, introducing the ammonia into the reaction zone through the central channel; a step of energizing the heater unit to heat the catalyst; conducting the ammonia decomposition reaction in the reaction zone to produce an ammonia decomposition mixture; discharging the ammonia decomposition mixture from the reaction zone into the outer flow channel; have Method for producing an ammonia decomposition mixture.

12. The temperature of the heater is 350 to 700°C. A method for producing the ammonia decomposition mixture of claim 11.

13. The pressure in the reaction zone is 0 to 0.9 MPaG. A method for producing an ammonia decomposition mixture according to claim 11 or 12.

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