methane reactor
By placing methanation catalyst between tubes, the reactor achieves uniform gas flow and extended catalyst life, addressing density unevenness issues and maintaining high methane conversion rates.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TOYOTA JIDOSHA KK
- Filing Date
- 2024-11-08
- Publication Date
- 2026-05-20
AI Technical Summary
Density unevenness in the catalyst state within reaction tubes leads to varying gas flow and methane conversion rates, resulting in decreased efficiency and shortened catalyst lifespan in methanation reactors.
The methanation reactor design places methanation catalyst between tubes instead of filling it into each tube, allowing uniform gas flow and maintaining a high methane conversion rate even with density unevenness.
This design ensures homogeneous gas flow and extended catalyst life, maintaining high methane conversion rates and preventing thermal degradation, while allowing for a smaller reactor configuration.
Smart Images
Figure 2026083836000001_ABST
Abstract
Description
Technical Field
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[0001] The present disclosure relates to a methanation reactor.
Background Art
[0002] Patent Document 1 discloses a methanation reactor in which a Ni-based catalyst is filled in the shell side of a vertical shell-and-tube heat exchanger, and a raw material gas mainly composed of H2, CO, CO2, and H2O flows into the catalyst filling part to cause a methanation reaction.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] When density unevenness occurs in the catalyst state in each reaction tube, a difference occurs in the gas flow in each reaction tube, and the methane conversion rate may decrease.
[0005] The present disclosure has been made in view of such problems, and an object thereof is to provide a methanation reactor that can equalize the gas flow and maintain a high methane conversion rate even when density unevenness occurs in the catalyst.
Means for Solving the Problems
[0006] One aspect for achieving the above object is a methanation reactor including a plurality of tubes in a shell, a heat medium disposed in the tubes, and a methanation catalyst disposed between the tubes, wherein methane is generated when a raw material gas passes through the methanation catalyst disposed between the tubes;
[0007] In the methanation reactor according to this disclosure, the methanation catalyst is not filled into each tube, but rather placed between the tubes (for example, in a continuously connected state). The raw material gas then passes through the methanation catalyst to cause a methanation reaction and generate a product gas (methane). Therefore, compared to the case where the methanation catalyst is filled into the tubes, even if density unevenness occurs within the catalyst, the gas flow can be made uniform, and the catalyst life can be extended without reducing the methane conversion rate. [Effects of the Invention]
[0008] According to this disclosure, it is possible to provide a methanation reactor that can homogenize the gas flow and maintain a high methane conversion rate even when density unevenness occurs within the catalyst. [Brief explanation of the drawing]
[0009] [Figure 1] This figure illustrates an example of a methanation reactor according to this embodiment. [Figure 2] This is a diagram illustrating an example of a conventional methanation reactor. [Figure 3] This figure illustrates the shape of the tubes in the methanation reactor according to this embodiment. [Figure 4] This figure illustrates another example of a methanation reactor according to this embodiment. [Figure 5] This figure illustrates yet another example of a methanation reactor according to this embodiment. [Modes for carrying out the invention]
[0010] Specific embodiments applying this disclosure will be described in detail below with reference to the drawings. However, this disclosure is not limited to the following embodiments. Also, for clarity, the following description and drawings have been simplified as appropriate. Figures 1, 4, and 5 are diagrams illustrating various examples of a methanation reactor according to this embodiment, respectively. Figure 2 is a diagram illustrating an example of a conventional methanation reactor. Furthermore, Figure 3 is a diagram illustrating the shape of the tubes in the methanation reactor according to this embodiment.
[0011] A methanation reactor, which synthesizes a product gas (methane CH4) from raw material gases (e.g., carbon dioxide CO2 and hydrogen H2) by a methanation reaction, has multiple tubes 6 (reaction tubes) inside a shell 7, as shown in Figure 2. The methanation reaction is an exothermic reaction that generates a large amount of heat, represented by the chemical equation "(raw material gas) CO2 + 4H2 = (product gas) CH4 + 2H2O + 165kJ". Therefore, the methanation reaction has a reaction temperature peak, and if the catalyst environment temperature in the reaction system is too low, the catalyst may be deactivated, and if the temperature is too high, the methanation reaction may slow down or the catalyst may degrade due to thermal degradation. For this reason, it is known that the methanation reaction requires heat control using a heat transfer medium or the like to maintain the temperature of the methanation catalyst at an appropriate temperature. It is also known that the reaction rate of the methanation reaction is affected by the amount of raw material gas.
[0012] Figure 2(a-1) is a schematic cross-sectional view of a conventional methanation reactor cut parallel to the axial direction (the direction of gas flow in the shell), and Figure 2(a-2) is a schematic cross-sectional view of the same methanation reactor cut perpendicular to the axial direction. In the methanation reactor shown in Figure 2, a methanation catalyst 2 is filled into multiple reaction tubes 6 arranged inside a shell 7, which is a roughly cylindrical container, and a heat transfer medium 1 (thermal fluid) such as oil flows around it.
[0013] In the case of a large shell-and-tube type methanation reactor with multiple reaction tubes 6, as shown in Figure 2, the ease of flow of the raw material gas 3 may vary partially due to changes in the state of the methanation catalyst 2 packed in each reaction tube 6. Examples of changes in the state of the methanation catalyst include bridging of granular catalyst, pulverization (powdering), volume contraction (thermal contraction) due to heat effects during use, and migration. When such changes occur, as shown in Figures 2(b) and 2(c), the gas pressure drop in each reaction tube 6 differs, and the raw material gas 3 (CO2 and hydrogen H2) concentrates in the reaction tube section where the gas flows easily (lower pressure drop). As a result, there may be significant unevenness in the methanation reaction 5 between the tubes 6, and the amount of methanation reaction in each reaction tube 6 may differ. In the tube 6 where the raw material gas 3 flows easily and the methanation reaction 5 is concentrated, more raw material gas than expected is processed, which accelerates thermal contraction (volume reduction) and degradation of the methanation catalyst 2 due to the reaction heat, further widening the difference in gas flow resistance (pressure drop difference). On the other hand, in tubes 6 where the raw material gas 3 does not flow easily, the temperature may not reach a range sufficient to maintain the methane reaction 5, causing the methane reaction to slow down or become inactive, and the raw material gas 3 is discharged as unreacted gas.
[0014] In Figure 2(a-1), of the six tubes 6 shown, the methanation catalyst 2 is in a catalytic state where the raw material gas 3 does not flow easily in the 3rd, 5th, and 6th tubes from the left side of the page. As a result, no product gas (methane) 4 is generated in these tubes 6. Furthermore, in Figure 2(b), of the six tubes 6 shown, the first and fifth tubes from the left side of the page are in a state where the methanation reaction 5 is less likely to occur due to a change in the catalytic state of the methanation catalyst 2. In Figure 2(c), thick arrows indicate that the methanation reaction is activated, while thin arrows indicate that the methanation reaction is poor.
[0015] Thus, in the methanation reactor shown in Figure 2, if there is a large difference in the gas flow in each reaction tube 6, it can lead to a decrease in the overall methane conversion rate (the percentage converted to methane) and a shortened catalyst lifespan, potentially reducing economic efficiency.
[0016] On the other hand, the methanation reactor according to this disclosure (hereinafter also referred to as "this reactor"), as shown in Figure 1, comprises a shell 7 which is a roughly cylindrical container, a plurality of tubes 6, a heat transfer medium 1 placed inside each tube 6, and a methanation catalyst 2 placed between each tube 6. When the raw material gas 3 passes through the methanation catalyst 2 placed between each tube 6, a methanation reaction 5 occurs and a product gas (methane) 4 is generated. Figure 1(a-1) is a schematic cross-sectional view of the reactor when it is cut parallel to the axial direction (the gas flow direction of the shell 7), and Figure 1(a-2) is a schematic cross-sectional view of the reactor when it is cut perpendicular to the axial direction.
[0017] Thus, in this reactor, instead of confining the methanation catalyst 2 in individual tubes 6, the methanation catalyst 2 is arranged between each tube 6 within the shell 7, as shown in Figure 1(a-2). In other words, the methanation catalyst 2 can be packed into the shell so as to fill the space between the shell 7 (more specifically the inner shell) and each tube 6 (heat transfer tube) through which the heat transfer medium flows. In this reactor, the methanation catalyst 2 can be arranged in a continuously connected state within the shell 7, and even if density unevenness (difference in back pressure) occurs within the methanation catalyst 2, the raw material gas 3 can pass through the nearby methanation catalyst, thus homogenizing the gas flow and enabling a uniform methanation reaction. As a result, in this reactor, the raw material gas can flow freely without stagnation and the methanation reaction can continue, thus achieving a longer and more uniform catalyst life without reducing the overall methane conversion rate. Thus, this reactor can maintain a higher methane conversion rate compared to conventional methanation reactors, and the equipment configuration can be made smaller if the performance is the same as conventional reactors. Furthermore, this reactor may be used as a large-scale methane reactor and a large-volume methane producer without reducing its scale.
[0018] This reactor is a shell-and-tube type heat exchanger. Inside each of the multiple arranged tubes 6, a heat medium 1 such as oil is flowing. Also, a methanation catalyst 2 is arranged between each tube 6, and a raw material gas 3 (reaction gas) has a structure that flows between each tube. Note that the heat medium 1 can be flowed inside the multiple tubes 6 and between the outer shell and the inner shell as shown in FIG. 1(a-2) etc., enabling easy temperature control of the catalyst and easily preventing the methanation reaction from being inactivated or the catalyst from suffering thermal degradation.
[0019] The shape, material, arrangement, configuration, etc. of each member and material constituting this reactor can be appropriately set within the range where the effects of the present disclosure can be obtained from those conventionally known, and are not particularly limited. For this reason, in this specification, descriptions other than the important parts of this reactor are omitted. The heat medium 1 can appropriately use a fluid such as oil used in the field of heat exchangers, and is not particularly limited. Conventionally known methanation catalysts 2 can be used, and can contain a metal having methanation catalyst performance. As the methanation catalyst, for example, it can contain a stabilized zirconia carrier in which a stabilizing element is solid-dissolved and has at least one of a tetragonal crystal structure and a cubic crystal structure, and Ni supported on the stabilized zirconia carrier, but is not limited thereto. Also, the stabilizing element can be, for example, at least one transition element selected from the group consisting of Mn, Fe, and Co, but is not limited thereto. Conventionally known raw material gases 3 can be used. For example, as described above, it can contain gaseous carbon dioxide gas and hydrogen gas, and further may contain carbon monoxide etc. Also, the product gas 4 can contain, for example, methane gas and water vapor. This reactor can also be equipped with, for example, metering valves for raw material gas, heat medium, etc., temperature adjustment parts, analyzers for gas concentration, etc., sensors such as temperature sensors, flow sensors, concentration sensors, and a control part for controlling these. These can appropriately use those conventionally known and are not particularly limited.
[0020] In this reactor, the shape of the tube 6 can be appropriately set to prevent variations in the amount of heat exchanged between the methanation catalyst 2 and the heat transfer medium 1. For example, the round tube shown in Figure 3(c) can be made into a polygon, such as a triangle or quadrilateral, by hydroforming or the like, in the central part of the tube 6, more specifically, the part that contacts the methanation catalyst 2, perpendicular to the axial direction, as shown in Figures 3(a) and 3(b). It is preferable that the cross-sectional shapes of both ends of the tube 6 in the axial direction be round to facilitate flange connection. Here, as shown in Figures 3(a) and (b), the polygons such as triangles and quadrilaterals may have at least some of their sides curved inward or outward, for example, and their corners may be rounded, and can be appropriately set within the range in which the effects of this disclosure can be obtained. In other words, the polygon that is the cross-sectional shape of the tube may be a roughly polygonal shape such as a roughly triangular or roughly quadrilateral, and these shapes may also be included. Thus, this reactor may be a methanation reactor with a shell-and-tube structure using tubes with irregular cross-sectional shapes.
[0021] Figures 4(a) and (b) show an example of this reactor using a tube 6 with a square cross-section. In this reactor, a heat transfer medium 1 such as oil flows inside the tube with a square cross-section and between the outer shell and the inner shell. The cross-sectional shape of the inner shell may be circular, as shown in Figures 1(a-2), 5(a), and 5(b), similar to the outer shell, but it may also be an uneven shape, as shown in Figure 4(b). In this reactor as well, as shown in these figures, a catalyst space equal to or greater than that of the tube filled with the methanation catalyst 2 in the conventional methanation reactor shown in Figure 4(c) can be secured. Furthermore, it can be seen that the heat transfer distance to each catalyst particle can be secured in this reactor, and that heat exchange performance equal to or better than that of the conventional structure can be secured.
[0022] Figures 5(a) and 5(b) show an example of this reactor using a tube 6 with a triangular cross-sectional shape. In this reactor, a heat transfer medium 1 such as oil flows inside the triangular cross-sectional tube and between the outer shell and the inner shell. In this reactor as well, as shown in these figures, a catalyst space equal to or greater than that of the inner diameter of the tube filled with the methanation catalyst 2 in the conventional methanation reactor shown in Figure 5(c) can be secured. Furthermore, in this reactor, the heat transfer distance to each catalyst particle can be secured, and it can be seen that heat exchange performance equal to or better than that of the conventional structure can be secured. In addition, in this reactor, it is possible to greatly improve the ratio of catalyst area to heat transfer medium path area, so the reactor size can be easily reduced when the equipment has the same performance as the conventional structure. The difference between the reactor in Figure 5(a) and the reactor in Figure 5(b) is that the orientation (phase) of the triangular cross-sectional tubes is alternately changed (the arrangement and number of tubes are the same). Both reactors can accommodate a larger amount of catalyst than conventional structures, and the heat transfer distance to the catalyst particles can be shortened compared to conventional structures, further improving heat exchange performance.
[0023] Thus, in this reactor, even if density variations occur within the catalyst, the gas flow becomes uniform, allowing a high methane conversion rate to be maintained. Furthermore, in this reactor, the total amount of catalyst and the heat exchange capacity, in other words, the heat transfer distance to each catalyst particle, can be freely designed, making it easy to lower the upper limit of the catalytic reaction temperature. This suppresses thermal degradation of the catalyst and extends its lifespan.
[0024] This disclosure is not limited to the embodiments described above, and may be modified as appropriate without departing from its spirit. This reactor can be effectively used, for example, in fields such as energy conversion devices such as fuel cells and internal combustion engines, and chemical plants. [Explanation of Symbols]
[0025] 1. Heat transfer medium (oil) 2. Methanation catalyst 3. Raw material gas 4. Produced gas (methane) 5. Methanation reaction 6 tubes 7 Shell
Claims
1. The shell comprises a plurality of tubes, a heat transfer medium placed inside the tubes, and a methane catalyst placed between each tube. A methanation reactor in which methane is produced by passing a raw material gas through the methanation catalyst placed between each tube.
2. The methanation reactor according to claim 1, wherein the methanation catalysts, which are arranged between each tube, are arranged in a continuously connected manner within the shell.
3. The methane reactor according to claim 1 or 2, wherein the heat transfer medium flows through the plurality of tubes and between the outer shell and the inner shell.
4. The methanation reactor according to claim 1 or 2, wherein the cross-sectional shape perpendicular to the axial direction of the portion of the tube that contacts the methanation catalyst is triangular or quadrilateral.