Methane generating system

Abstract

To provide a methane generating system equipped with a reactor in which heat medium circulates around a plurality of heat transfer tubes, generation of temperature variation by each heat transfer tube is suppressed.SOLUTION: A methane generating system comprises: a reactor 100 having a plurality of heat transfer tubes 104 in which catalyst used for methane generation reaction is provided, and a cylindrical shell 101 housing the plurality of heat transfer tubes 104; and a temperature adjustment device 200 which is connected such that heat medium can pass through an outer peripheral part 101a of the reactor 100, and supplies heat medium to the reactor 100 to adjust the temperature of catalyst. A heat medium flow channel 111 through which heat medium circulates around the heat transfer tubes 104 is formed inside the shell 101. On a shell cross section, a central region 101b where the heat transfer tubes 104 and the heat medium flow channel 111 cannot be arranged is provided for the central part of the shell 101. The heat transfer tubes 104 and the heat medium flow channel 111 are arranged between the outer peripheral part 101a of the shell 101 and the central region 101b.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a methanation system. [Background technology]

[0002] In the methane production reaction, which involves reacting carbon dioxide and hydrogen, temperature control is important for increasing methane production efficiency. Specifically, when producing methane using a catalyst, the catalyst temperature rises due to the catalytic reaction, reducing methane production efficiency. Therefore, it is necessary to keep the catalyst temperature within a specified range to prevent a decrease in methane production efficiency.

[0003] Patent Document 1 discloses a methane generator in which multiple heat transfer tubes filled with a catalyst are arranged in parallel and housed in a shell. This methane generator has a structure in which the inside of the shell has a heat transfer tube space filled with a catalyst through which gas flows, and a space outside the heat transfer tube through which a heat transfer medium flows. The shell has an inlet and outlet for the heat transfer medium on the outer periphery, and the heat transfer medium is circulated around the heat transfer tube to adjust the temperature inside the heat transfer tube. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7145978 Summary of the Invention [Problem to be solved by the invention]

[0005] However, because the heat transfer tubes are located at different distances from the outer periphery of the shell and at different distances from the heat transfer medium inlet and outlet, the flow rate of the heat transfer medium flowing around each heat transfer tube tends to vary from one heat transfer tube to another, which results in variations in the cooling capacity of each heat transfer tube, making it difficult to maintain the entire system at an appropriate temperature for the methane production reaction.

[0006] Furthermore, in order to increase the amount of methane produced in a methane generator, it is necessary to increase the number of heat transfer tubes and the size of the shell. Increasing the size of the shell increases the distance from the outer periphery to the center of the shell, which tends to increase the variation in the flow rate of the heat transfer medium flowing around the heat transfer tubes near the outer periphery and the center of the shell. In other words, increasing the number of heat transfer tubes and enlarging the shell tends to result in more pronounced variations in the cooling capacity of each heat transfer tube.

[0007] The present invention has been made in consideration of such problems, and aims to suppress temperature variations between heat transfer tubes in a methane generation system equipped with a reactor in which a heat medium flows around multiple heat transfer tubes. [Means for solving the problem]

[0008] One aspect of the present invention is A methane generation system for generating methane by a methane generation reaction using carbon dioxide and hydrogen as raw material gases, a reactor having a plurality of heat transfer tubes inside which a catalyst used in the methane production reaction is provided, and a cylindrical shell accommodating the plurality of heat transfer tubes; a temperature adjusting device connected to the outer periphery of the shell so that a heat medium can pass therethrough, and which supplies a heat medium to the reactor to adjust the temperature of the catalyst; Equipped with a heat medium flow path through which the heat medium flows is formed around the heat transfer tube inside the shell, a central region in which the heat transfer tube and the heat medium flow path cannot be disposed is provided in a central portion of the shell in a shell cross section perpendicular to an axial direction of the shell, The methane generation system is characterized in that the heat transfer tubes and the heat medium flow paths are arranged between the outer periphery of the shell and the central region. [Effects of the Invention]

[0009] By providing a central region in the center of the shell where no heat transfer tubes or heat medium flow paths are located, the distance between the outer periphery and the center of the shell can be shortened. This reduces variations in the flow rate of cooling oil between the outer periphery and the center of the heat medium shell. As a result, temperature variations among the multiple heat transfer tubes can be suppressed, allowing each of the multiple heat transfer tubes to be adjusted to a temperature suitable for the methane production reaction, allowing the methane production reaction to proceed efficiently. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a configuration diagram showing a methane gas generation system. [Figure 2] FIG. 2 is a front view of the reactor of the first embodiment. [Figure 3] FIG. 2 is a cross-sectional view of the reactor of the first embodiment. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 2. [Figure 5] FIG. 5 is an enlarged cross-sectional view of a part of FIG. [Figure 6] FIG. 10 is a front view of a reactor according to a second embodiment. [Figure 7] FIG. 4 is a cross-sectional view of a reactor according to a second embodiment. [Figure 8] FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 6. [Figure 9] FIG. 9 is an enlarged cross-sectional view of a part of FIG. 8. [Figure 10] FIG. 10 is a cross-sectional view showing a modified example of the reactor. DETAILED DESCRIPTION OF THE INVENTION

[0011] (First embodiment) 1. Overview of the methane generation system The methane generation system 10 of this embodiment will be described below with reference to Figures 1 to 5. As shown in Figure 1, the methane generation system 10 includes a reactor 100 and a temperature adjustment device 200.

[0012] The reactor 100 is a methane generation device that uses carbon dioxide and hydrogen as raw material gases to generate methane through a catalytic reaction. Here, a brief description of the reactor 100 will be given, and the configuration of the reactor 100 will be described in detail later.

[0013] Carbon dioxide is supplied to the reactor 100 from a carbon dioxide supply device (not shown), and hydrogen is supplied from a hydrogen supply device (not shown). In the reactor 100, methane is produced by a methane production reaction using carbon dioxide and hydrogen as raw material gases. The reactor 100 is provided with a catalyst that promotes the methane production reaction, and methane is produced, for example, by the methane production reaction shown below.

[0014] CO2+4H2→CH4+2H2O The gas produced by this methane production reaction contains methane and water (water vapor).

[0015] The catalyst installed in the reactor 100 exhibits high catalytic activity within a predetermined temperature range. Therefore, it is necessary to maintain the catalyst temperature in the reactor 100 within a predetermined temperature range. Specifically, at the start of the methane production reaction, the catalyst needs to be heated to raise its temperature to its activation temperature. After the start of the methane production reaction, the catalyst becomes hot due to heat generated by the catalytic reaction, so it needs to be cooled.

[0016] The temperature adjustment device 200 supplies a heat medium to the reactor 100 from the outside and adjusts the temperature of the reactor 100. The temperature adjustment device 200 is connected to the outer periphery 101a of the shell 101 that constitutes the reactor 100 so that the heat medium can pass through. The temperature adjustment of the heat medium by the temperature adjustment device 200 includes heating and cooling of the heat medium. Therefore, the temperature adjustment device 200 includes a heating device that heats the heat medium and a cooling device that cools the cooling oil, and can adjust the heat medium to a desired temperature. Any fluid can be used as the heat medium, and cooling oil is used in this embodiment.

[0017] The temperature adjustment device 200 includes a supply device that supplies temperature-adjusted cooling oil to the reactor 100. As the supply device, for example, a pump that pressure-feeds the cooling oil can be used.

[0018] 2. Configuration of Reactor 100 Next, the configuration of the reactor 100 will be described with reference to Figs. 2 to 4. The reactor 100 is configured as a multi-tube heat exchanger (shell-and-tube heat exchanger) in which a large number of heat transfer tubes 104 are housed in a shell 101. In Figs. 2 and 3, the up-down direction is the axial direction of the shell 101 and the heat transfer tubes 104. Fig. 4 shows a cross section perpendicular to the axial direction of the shell 101, and the direction perpendicular to the plane of the paper is the axial direction of the shell 101 and the heat transfer tubes 104. In this specification, the cross section perpendicular to the axial direction of the shell 101 is also simply referred to as a shell cross section.

[0019] As shown in FIGS. 2 and 3, the reactor 100 includes a shell 101. The shell 101 is configured as a cylindrical container. The shell 101 of this embodiment has a cylindrical shape with a circular shell cross section. A pair of plates 102 and 103 are provided on both end sides of the reactor 100. By covering both ends of the shell 101 with the pair of plates 102 and 103, an enclosed space is formed inside the shell 101.

[0020] A plurality of heat transfer tubes 104 are housed inside the shell 101. The heat transfer tubes 104 are cylindrical tubes through which gas can pass. In FIG. 3, the direction from top to bottom in the drawing is the gas flow direction when gas flows inside the heat transfer tubes 104. The gas flow direction is parallel to the axial direction of the shell 101. In FIG. 3, the upper side in the drawing is the upstream side of the gas flow, and the lower side in the drawing is the downstream side of the gas flow.

[0021] The heat transfer tube 104 is a catalytic tube, and a catalyst (not shown) is filled inside the heat transfer tube 104. The catalyst is a catalyst for promoting the methane production reaction, and for example, a titanium-based catalyst or a nickel-based catalyst can be used.

[0022] The heat transfer tubes 104 are arranged in parallel. A predetermined interval is provided between adjacent heat transfer tubes 104. In this embodiment, the heat transfer tubes 104 each have the same shape. The axial direction of the heat transfer tubes 104 is parallel to the axial direction of the shell 101.

[0023] Both ends of the heat transfer tubes 104 are fixed to a pair of plates 102, 103. A plurality of through holes are formed in the plates 102, 103 corresponding to the plurality of heat transfer tubes 104. The upstream ends of the heat transfer tubes 104 in the gas flow direction are inserted into the through holes of the first plate 102 and fixed thereto. The downstream ends of the heat transfer tubes 104 in the gas flow direction are inserted into the through holes of the second plate 103 and fixed thereto. The arrangement of the heat transfer tubes 104 in a cross section perpendicular to the axial direction of the shell 101 is determined by the arrangement of the through holes formed in the plates 102, 103.

[0024] A pair of headers 105, 106 are provided on both ends of the shell 101. The first header 105 on the gas inlet side is fixed to the first plate 102, and the second header 106 on the gas outlet side is fixed to the second plate 103. The headers 105, 106 are fastened to the plates 102, 103, for example, by bolts (not shown). The upstream end of the heat transfer tube 104 in the gas flow direction communicates with the first header 105, and the downstream end of the heat transfer tube 104 in the gas flow direction communicates with the second header 106.

[0025] The first header 105 is provided with a gas inlet 107 through which the raw material gas flows in. The second header 106 is provided with a gas outlet 108 through which the produced gas flows out. The raw material gas that flows into the first header 105 from the gas inlet 107 is distributed and supplied to each of the multiple heat transfer tubes 104. The produced gas produced inside the heat transfer tubes 104 flows out of the heat transfer tubes 104, collects in the second header 106, and flows out from the gas outlet 108 to the outside.

[0026] 2 and 3, a peripheral inlet 109 for allowing cooling oil to flow into the interior and a peripheral outlet 110 for allowing cooling oil to flow out from the interior are provided in the outer peripheral portion 101a of the shell 101. The peripheral inlet 109 and the peripheral outlet 110 are through-holes provided in the outer peripheral portion 101a of the shell 101.

[0027] The peripheral inlet 109 and the peripheral outlet 110 are connecting parts of the reactor 100 to the temperature adjustment device 200. The peripheral inlet 109 is an inlet-side connecting part, and the peripheral outlet 110 is an outlet-side connecting part.

[0028] In this embodiment, there are four peripheral inlets 109 and four peripheral outlets 110. When viewed from the axial direction of the shell 101, the four peripheral inlets 109 and the four peripheral outlets 110 are provided at 90° intervals.

[0029] 3 and 4, inside the shell 101, the space around the heat transfer tubes 104 is configured as a heat medium flow path 111 through which cooling oil flows. The internal space of the shell 101 includes the heat transfer tubes 104 and the heat medium flow path 111.

[0030] Cooling oil supplied from the temperature adjustment device 200 flows into the heat medium flow path 111 through the peripheral inlet 109. The inflowing cooling oil passes through the heat medium flow path 111 and then flows out through the peripheral outlet 110. The cooling oil flowing through the heat medium flow path 111 passes around the heat transfer tube 104 and exchanges heat with the catalyst and gas inside through the wall surface of the heat transfer tube 104. The temperature of the catalyst and gas inside the heat transfer tube 104 is adjusted by the cooling oil supplied from the temperature adjustment device 200.

[0031] 3, the direction from bottom to top in the drawing is the flow direction of the cooling oil in the heat medium flow path 111, with the bottom in the drawing being the upstream side of the cooling oil flow and the top in the drawing being the downstream side of the cooling oil flow. The cooling oil flow direction is parallel to the axial direction of the shell 101. The gas flowing inside the heat transfer tube 104 and the cooling oil flowing in the heat medium flow path 111 flow in opposite directions in a counterflow manner.

[0032] 3. Description of hollow portion 101b 3 and 4, a hollow portion 101b is provided in the center of the interior of the shell 101 as viewed from the axial direction. The hollow portion 101b is formed to extend along the axial direction of the shell 101, and is provided from one end side to the other end side in the axial direction of the shell 101. The hollow portion 101b is a central region provided in the center of the cross section of the shell, and is an arrangement-prohibited region where the heat transfer tubes 104 and the heat medium flow paths 111 cannot be arranged.

[0033] In this embodiment, the hollow portion 101b has a cylindrical shape with a circular cross section. The hollow portion 101b has a hollow structure with an internal space extending parallel to the axial direction of the shell 101. Nothing is provided in the internal space of the hollow portion 101b.

[0034] The shell 101 has a double-pipe structure including an outer circumferential portion 101a and a hollow portion 101b. In a cross section of the shell, the outer circumferential portion 101a and the hollow portion 101b are concentric circles of different sizes. In a cross section of the shell, the space between the outer circumferential portion 101a and the hollow portion 101b is an annular shape surrounded by two concentric circles. The heat transfer tubes 104 are arranged in the space between the outer circumferential portion 101a and the hollow portion 101b. In the space between the outer circumferential portion 101a and the hollow portion 101b, the area around the heat transfer tubes 104 is configured as a heat medium flow path 111 through which cooling oil flows. In other words, the space between the outer circumferential portion 101a and the hollow portion 101b is an arrangement area in which the heat transfer tubes 104 and the heat medium flow path 111 can be arranged.

[0035] Both ends of hollow portion 101b are fixed to first plate 102 and second plate 103. Through holes corresponding to hollow portion 101b are formed in first plate 102 and second plate 103. Both ends of hollow portion 101b are fixed in a state where they are inserted into the through holes of first plate 102 and second plate 103.

[0036] As shown in Fig. 3, a lid 101c is provided at the upstream end of the hollow portion 101b in the gas flow. The lid 101c is a blocking part that blocks one end from the other end of the internal space of the hollow portion 101b. Therefore, the first header 105 on the upstream side of the gas flow and the second header 106 on the downstream side of the gas flow are not in communication with each other through the hollow portion 101b, and the source gas in the first header 105 does not flow into the second header 106 through the hollow portion 101b. In this embodiment, the lid 101c closes the upstream end of the hollow portion 101b in the gas flow, and the source gas in the first header 105 cannot flow into the hollow portion 101b.

[0037] In this embodiment, the lid 101c is provided only on one end side of the hollow portion 101b, and the lid 101c does not seal the internal space of the hollow portion 101b. The downstream end of the gas flow of the hollow portion 101b is open, and the interior of the hollow portion 101b communicates with the second header 106. Therefore, the produced gas in the second header 106 can flow into the interior of the hollow portion 101b.

[0038] As shown in Figures 4 and 5, in the cross section of the shell, the heat transfer tubes 104 are arranged in a circumferential direction in the space between the outer circumferential portion 101a and the hollow portion 101b. In the cross section of the shell, the heat transfer tubes 104 are arranged in at least one row in a circumferential direction around the hollow portion 101b. The heat transfer tubes 104 arranged in a circumferential direction are arranged in a ring shape in multiple rows along multiple circles. The multiple circles in which the heat transfer tubes 104 are arranged have different radii and form concentric circles. In the example shown in Figure 4, the heat transfer tubes 104 are arranged in three rows along three concentric circles.

[0039] The heat transfer tubes 104 are arranged in multiple rows and are arranged in layers in each row. The cell cross section can be divided into multiple layered regions in which the heat transfer tubes 104 are arranged in a row in the circumferential direction. In the example shown in Figure 4, the shell cross section is divided into three layered regions. One layered region in the shell cross section includes multiple heat transfer tubes 104 arranged in a row in the circumferential direction. Each layered region has a certain width and includes the heat transfer tubes 104 on the circumference connecting the heat transfer tubes 104 arranged in a row in the circumferential direction. In Figure 4, the boundaries of the layered regions in the shell cross section are indicated by dashed double-dashed lines.

[0040] For example, the multiple layered regions are designated as a first layered region, a second layered region, and a third layered region from the outer periphery 101a toward the hollow portion 101b of the shell cross section. The heat transfer tube 104 in the first layered region is designated as the first heat transfer tube 104a, the heat transfer tube 104 in the second layered region is designated as the second heat transfer tube 104b, and the heat transfer tube 104 in the third layered region is designated as the third heat transfer tube 104c. The first heat transfer tube 104a, the second heat transfer tube 104b, and the third heat transfer tube 104c are arranged in this order from the outer periphery toward the center of the shell cross section. The first heat transfer tube 104a is arranged closest to the outer periphery 101a. The third heat transfer tube 104c is arranged closest to the hollow portion 101b and farthest from the outer periphery 101a.

[0041] 4, 24 first heat transfer tubes 104a, 18 second heat transfer tubes 104b, and 12 third heat transfer tubes 104c are provided. In other words, a total of 54 heat transfer tubes 104 are provided inside the shell 101 of this embodiment.

[0042] The size of the hollow portion 101b in the cross section of the shell can be set arbitrarily. The hollow portion 101b in this embodiment is provided in a space in the center of the cross section of the shell, where multiple heat transfer tubes 104 can be arranged in a ring shape.

[0043] In the cross section of the shell, the circular region inside the third heat transfer tube 104c arranged on the innermost side is large enough to accommodate a plurality of (for example, about five) heat transfer tubes 104 arranged in an annular shape. In other words, the region in which the hollow portion 101b is arranged is large enough to accommodate at least one row of heat transfer tubes 104 arranged in an annular shape in the center of the cross section of the shell. In the example shown in Fig. 4, the region in which the hollow portion 101b is arranged is large enough to accommodate one row of heat transfer tubes 104, but it may also be large enough to accommodate multiple rows of heat transfer tubes 104.

[0044] The heat transfer tubes 104 belonging to each layered region are arranged evenly in the circumferential direction. In the first layered region, the first heat transfer tubes 104a are arranged at equal intervals. In the second layered region, the second heat transfer tubes 104b are arranged at equal intervals. In the third layered region, the third heat transfer tubes 104c are arranged at equal intervals.

[0045] As shown in FIG. 5, the heat transfer tubes 104 are arranged as evenly spaced as possible in the radial direction of the shell cross section. That is, the first heat transfer tube 104a, the second heat transfer tube 104b, and the third heat transfer tube 104c are arranged as evenly spaced as possible on a line extending radially from the center of the shell cross section. On a line extending radially from the center of the shell cross section, the distance between the outer peripheral portion 101a and the first heat transfer tube 104a is L1, the distance between the first heat transfer tube 104a and the second heat transfer tube 104b is L2, the distance between the second heat transfer tube 104b and the third heat transfer tube 104c is L3, and the distance between the third heat transfer tube 104c and the hollow portion 101b is L4. While L1, L2, L3, and L4 can be set arbitrarily, it is desirable to make them as even as possible. In this embodiment, for example, L1 is used as a reference, and the lengths of L2, L3, and L4 are set within a range of 0.5 to 2 times L1.

[0046] In the cross section of the shell, there are portions where the distance between adjacent heat transfer tubes 104 is narrower, portions where the distance between the heat transfer tubes 104 and the outer circumferential portion 101a is narrower, and portions where the distance between the heat transfer tubes 104 and the hollow portion 101b is narrower. Therefore, in the cross section of the shell, the heat medium flow path 111 includes a region surrounded by multiple heat transfer tubes 104, a region surrounded by multiple heat transfer tubes 104 and the outer circumferential portion 101a, and a region surrounded by multiple heat transfer tubes 104 and the hollow portion 101b. In this embodiment, the heat transfer tubes 104 are arranged as evenly spaced as possible so that the variation in cross-sectional area of ​​each region included in the heat medium flow path 111 is small.

[0047] According to the present embodiment described above, it is possible to suppress variations in the flow rate of cooling oil in the heat medium flow path 111. As a result, it is possible to suppress variations in temperature among the plurality of heat transfer tubes 104, and therefore it is possible to adjust each of the plurality of heat transfer tubes 104 to a temperature suitable for the methane production reaction, thereby allowing the methane production reaction to proceed efficiently. The reason why variations in the flow rate of cooling oil in the heat medium flow path 111 can be suppressed will be explained below.

[0048] At the upstream part of the cooling oil flow immediately after the cooling oil flows into the heat medium flow path 111, the flow rate of the cooling oil tends to be high on the outer periphery side of the shell 101 close to the outer periphery inlet 109, and tends to be low on the central side of the shell 101 far from the outer periphery inlet 109. This tends to result in large variations in the flow rate of the cooling oil between the outer periphery side and the inner periphery side of the shell cross section.

[0049] Even in the downstream portion of the cooling oil flow just before the cooling oil flows out of the heat medium flow path 111, the flow rate of the cooling oil tends to be high on the outer periphery side of the shell 101 close to the outer periphery outlet 110, and tends to be low on the central side of the shell 101 away from the outer periphery outlet 110. This tends to result in large variations in the flow rate of the cooling oil between the outer periphery side and the inner periphery side of the shell cross section.

[0050] In this embodiment, the distance from the outer periphery to the center of the shell 101 can be shortened by a simple configuration in which a hollow portion 101b is provided in the center of the shell cross section. This reduces the variation in the flow rate of cooling oil between the outer periphery and the center of the shell 101 in the upstream portion of the cooling oil flow in the heat medium flow path 111. Similarly, it reduces the variation in the flow rate of cooling oil between the outer periphery and the center of the shell 101 in the downstream portion of the cooling oil flow in the heat medium flow path 111.

[0051] Furthermore, in the circular region at the center of the cross section of the shell, the cross-sectional area of ​​each region of the heat medium flow path 111 surrounded by the plurality of heat transfer tubes 104 tends to vary greatly. In contrast, in this embodiment, a hollow portion 101b is arranged in the center of the shell cross section, and the hollow portion 101b is provided in the center of the shell cross section, where the heat transfer tubes 104 and heat medium flow paths 111 cannot be arranged, and the heat transfer tubes 104 are arranged between the outer periphery 101a of the shell cross section and the hollow portion 101b. The space between the outer periphery 101a of the shell cross section and the hollow portion 101b is annular, making it easy to arrange the heat transfer tubes 104 evenly. This effectively reduces variations in the cross-sectional area of ​​the heat medium flow paths 111.

[0052] Furthermore, if the number of heat transfer tubes 104 is increased and the shell 101 is made larger in order to increase the amount of methane produced, the distance from the outer periphery to the center of the shell 101 becomes longer, which tends to increase the variation in the flow rate of the cooling oil. In contrast, according to this embodiment, by providing a hollow portion 101b in the center of the shell cross section, it is possible to effectively reduce the variation in the flow rate of the cooling oil, and it is possible to easily accommodate an increase in the number of heat transfer tubes 104 and an increase in the size of the shell 101.

[0053] Furthermore, when the number of heat transfer tubes 104 is increased to increase the number of layers of the heat transfer tubes 104 arranged in an annular shape, it is possible to reduce the proportion of the hollow portion 101b in the interior of the shell 101. Therefore, when the number of heat transfer tubes 104 is increased, the benefit of reducing variations in the flow rate of the cooling oil by providing the hollow portion 101b outweighs the reduction in the arrangement space for the heat transfer tubes 104 and the heat medium flow path 111 by providing the hollow portion 101b.

[0054] In this embodiment, the hollow portion 101b provided in the center of the shell cross section has a hollow structure. This allows the hollow portion 101b to be lighter than when the central region has a solid structure, and prevents the weight from increasing due to the provision of the hollow portion 101b. In particular, when the shell 101 is enlarged, the effect of reducing the weight of the hollow portion 101b becomes significant.

[0055] In this embodiment, the hollow portion 101b is provided with a lid portion 101c that separates one end from the other end, so that the first header 105 and the second header 106 are not in communication with each other through the hollow portion 101b, and the raw material gas in the first header 105 does not flow unreacted into the second header 106 through the hollow portion 101b.

[0056] In this embodiment, the lid 101c is provided on one end of the hollow portion 101b, and the other end is open, so the inside of the hollow portion 101b is not an airtight space. Therefore, even if heat generated in the heat transfer tube 104 during methane production is transferred to the hollow portion 101b via the cooling oil, gas expansion inside the hollow portion 101b can be suppressed, and problems caused by gas expansion can be suppressed.

[0057] In this embodiment, the upstream end of the hollow portion 101b in the gas flow direction is closed by the lid portion 101c, so that the source gas containing carbon dioxide and hydrogen does not stagnate inside the hollow portion 101b.

[0058] In this embodiment, the distance L1 between the outer circumferential portion 101a and the first heat transfer tube 104a, the distance L2 between the first heat transfer tube 104a and the second heat transfer tube 104b, the distance L3 between the second heat transfer tube 104b and the third heat transfer tube 104c, and the distance L4 between the third heat transfer tube 104c and the hollow portion 101b are set so that, when L1 is used as the reference, the lengths of L2, L3, and L4 are within a range of 0.5 to 2 times L1. This makes it possible to reduce variations in the cross-sectional area of ​​the region of the heat medium flow path 111 surrounded by the heat transfer tubes 104, the region surrounded by the heat transfer tubes 104 and the outer circumferential portion 101a, and the region surrounded by the heat transfer tubes 104 and the hollow portion 101b.

[0059] (Second embodiment) Next, a second embodiment of the present invention will be described with reference to Figures 6 to 9. The same parts as those in the first embodiment are given the same reference numerals and their description will be omitted, and only the different parts will be described.

[0060] 1. Description of the inlet-side reservoir 112 and the outlet-side reservoir 113 6 and 7, the shell 101 of the second embodiment is provided with an inlet-side reservoir 112 and an outlet-side reservoir 113. The inlet-side reservoir 112 is provided upstream of the cooling oil flow, and the outlet-side reservoir 113 is provided downstream of the cooling oil flow.

[0061] The reservoirs 112 and 113 are provided to cover the outer periphery of the shell 101. The reservoirs 112 and 113 and the shell 101 have a double-pipe structure. The reservoirs 112 and 113 are configured as chambers having a predetermined volume, and are capable of storing the cooling oil that passes through the outer peripheral inlet 109 and the outer peripheral outlet 110.

[0062] The inlet-side reservoir 112 is provided with a reservoir inlet 114, and cooling oil flows into the inlet-side reservoir 112 from the outside through the reservoir inlet 114. The outlet-side reservoir 113 is provided with a reservoir outlet 115, and cooling oil flows out of the outlet-side reservoir 113 to the outside through the reservoir outlet 115.

[0063] The reservoirs 112 and 113 are provided corresponding to the peripheral inlet 109 and the peripheral outlet 110, which are the connection parts of the shell 101 with the temperature adjustment device 200. The inlet-side reservoir 112 is provided at a position corresponding to the peripheral inlet 109, and the outlet-side reservoir 113 is provided at a position corresponding to the peripheral outlet 110.

[0064] The inlet-side reservoir 112 communicates with the heat medium flow path 111 via the peripheral inlet 109, and the cooling oil in the inlet-side reservoir 112 flows into the heat medium flow path 111 via the peripheral inlet 109. The outlet-side reservoir 113 communicates with the heat medium flow path 111 via the peripheral outlet 110, and the cooling oil in the heat medium flow path 111 flows out into the outlet-side reservoir 113 via the peripheral outlet 110.

[0065] 7, in the inlet-side reservoir 112, the reservoir inlet 114 and the peripheral inlet 109 are formed at different positions in the axial direction of the shell 101. In particular, the peripheral inlet 109 is located closer to the second plate 103 than the reservoir inlet 114, i.e., upstream of the cooling oil flow in the axial direction of the shell 101. This prevents the cooling oil that has flowed from the reservoir inlet 114 into the inlet-side reservoir 112 from flowing linearly toward the peripheral inlet 109, thereby suppressing variations in the flow rate of the heat medium flowing through the multiple peripheral inlets 109.

[0066] In the outlet-side reservoir 113, the reservoir outlet 115 and the peripheral outlet 110 are formed at different positions in the axial direction of the shell 101. In particular, the peripheral outlet 110 is located closer to the first plate 102 than the reservoir outlet 115, i.e., downstream of the cooling oil flow in the axial direction of the shell 101. This prevents the cooling oil that has flowed from the peripheral outlet 110 into the outlet-side reservoir 113 from flowing linearly toward the reservoir outlet 115, thereby suppressing variations in the flow rate of the heat medium flowing through the multiple peripheral outlets 110.

[0067] 2. Positional relationship between the outer peripheral inlet 109 and the first heat transfer tube 104a 8 and 9, the peripheral inlet 109 of the second embodiment is provided facing the outermost heat transfer tube 104 (first heat transfer tube 104a) in the radial direction of the shell cross section. The peripheral inlet 109 is located on a straight line connecting the center of the shell cross section and the first heat transfer tube 104a. The through hole constituting the peripheral inlet 109 is formed so that the axial direction intersects with the first heat transfer tube 104a. The hole diameter of the peripheral inlet 109 is smaller than the outer diameter of the first heat transfer tube 104a.

[0068] The outer circumferential inlets 109 are provided opposite all of the first heat transfer tubes 104a. That is, the number of outer circumferential inlets 109 is the same as the number of first heat transfer tubes 104a. In the example shown in Fig. 8, 23 outer circumferential inlets 109 are provided corresponding to the 23 first heat transfer tubes 104a.

[0069] The outer circumferential outlet 110 of the second embodiment has the same configuration as the outer circumferential inlet 109 shown in Figures 8 and 9. That is, the outer circumferential outlet 110 is provided opposite the first heat transfer tube 104a provided on the outermost periphery, the hole diameter of the outer circumferential outlet 110 is smaller than the outer diameter of the first heat transfer tube 104a, and the outer circumferential outlet 110 is provided opposite all of the first heat transfer tubes 104a.

[0070] According to the second embodiment, the cooling oil that passes through the outer circumferential inlet 109 provided opposite the first heat transfer tube 104a and flows into the heat medium flow path 111 collides with the outer circumferential surface of the first heat transfer tube 104a as it flows toward the center of the shell cross section, thereby reducing its flow rate. This makes it possible to suppress variations in the flow rate and flow rate of the cooling oil around the outer circumferential inlet 109 in the heat medium flow path 111, and thereby suppress variations in the temperature of the heat transfer tube 104.

[0071] Furthermore, the cooling oil that passes through the outer circumferential outlet 110 provided opposite the first heat transfer tube 104a and flows out of the heat medium flow path 111 bypasses the first heat transfer tube 104a before reaching the outer circumferential outlet 110, and therefore cannot flow directly into the outer circumferential outlet 110, resulting in a decrease in flow velocity. This makes it possible to further suppress variations in the flow velocity and flow rate of the cooling oil around the outer circumferential outlet 110 in the heat medium flow path 111, and thus makes it possible to further suppress variations in the temperature of the heat transfer tube 104.

[0072] Furthermore, in the second embodiment, the hole diameter of the outer peripheral inlet 109 is smaller than the outer diameter of the first heat transfer tube 104a. As a result, most of the cooling oil flowing in from the outer peripheral inlet 109 collides with the first heat transfer tube 104a, thereby enhancing the effect of reducing the flow rate of the cooling oil. Similarly, in the second embodiment, the hole diameter of the outer peripheral outlet 110 is smaller than the outer diameter of the first heat transfer tube 104a. As a result, most of the cooling oil flowing out from the outer peripheral outlet 110 bypasses the first heat transfer tube 104a before reaching the outer peripheral outlet 110, thereby effectively reducing the flow rate of the cooling oil.

[0073] Furthermore, in the second embodiment, the same number of outer circumferential inlets 109 as the number of first heat transfer tubes 104a are provided. Therefore, the cooling oil can be dispersed over the entire outer periphery of the shell cross section and can flow as uniformly as possible into the heat medium flow path 111. This also makes it possible to suppress variations in the flow speed and amount of cooling oil around the outer circumferential inlets 109 in the heat medium flow path 111, and to suppress variations in the temperature of the heat transfer tubes 104.

[0074] Similarly, in the second embodiment, the same number of outer circumferential outlets 110 as the first heat transfer tubes 104a are provided. Therefore, the cooling oil can be dispersed over the entire outer periphery of the cross section of the shell and discharged as uniformly as possible from the heat medium flow path 111. This also makes it possible to suppress variations in the flow speed and flow rate of the cooling oil around the outer circumferential outlets 110 in the heat medium flow path 111, and to suppress variations in the temperature of the heat transfer tubes 104.

[0075] Moreover, in the second embodiment, an inlet-side reservoir 112 is provided to store the cooling oil before it flows into the heat medium flow path 111. This allows the cooling oil to be uniformly supplied from the inlet-side reservoir 112 to the multiple outer circumferential inlets 109, thereby suppressing variations in the flow speed and flow rate of the cooling oil for each outer circumferential inlet 109. Similarly, in the second embodiment, an outlet-side reservoir 113 is provided to store the cooling oil after it flows from the heat medium flow path 111. This allows the cooling oil to be uniformly discharged from the multiple outer circumferential outlets 110 to the outlet-side reservoir 113, thereby suppressing variations in the flow speed and flow rate of the cooling oil for each outer circumferential outlet 110.

[0076] Furthermore, the configuration of the second embodiment can suppress temperature variations in the heat transfer tubes 104 in the axial direction of the shell 101. Immediately after flowing into the heat medium flow path 111, the cooling oil flows toward the center of the shell cross section, so the cooling oil flows toward the center of the shell cross section while flowing downstream. Therefore, in the axial direction of the shell 101, the flow rate of the cooling oil at the center of the shell cross section tends to be low near the peripheral inlet 109 and the peripheral outlet 110 of the heat medium flow path 111. On the other hand, in the axial direction of the shell 101, the flow rate of the cooling oil at the center of the shell cross section tends to be high near the middle between the peripheral inlet 109 and the peripheral outlet 110 of the heat medium flow path 111. As a result, temperature variations are likely to occur in the heat transfer tubes 104 in the axial direction of the shell 101.

[0077] In contrast to this, in the second embodiment, by providing the outer peripheral inlet 109 opposite to the first heat transfer tube 104a, variations in the flow velocity and flow rate of the cooling oil are suppressed around the outer peripheral inlet 109. As a result, the cooling oil that has flowed into the heat medium flow path 111 can flow toward the downstream side of the cooling oil flow at a uniform flow rate over the entire cross section of the shell, and temperature variations in the heat transfer tubes 104 over the entire shell 101 can be suppressed.

[0078] Furthermore, in the second embodiment, by providing the outer peripheral outlet 110 opposite the first heat transfer tube 104a, variations in the flow speed and flow rate of the cooling oil are suppressed around the outer peripheral outlet 110. This also allows the cooling oil that has flowed into the heat medium flow path 111 to flow toward the downstream side of the cooling oil flow at a uniform flow rate over the entire cross section of the shell, thereby suppressing temperature variations in the heat transfer tubes 104 over the entire shell 101.

[0079] (Other embodiments) The present invention is not limited to the above-described embodiments, and can be applied to various embodiments within the scope of the present invention.

[0080] For example, in each of the above embodiments, an example has been described in which a hollow portion 101b is provided as a central region inside the shell 101. However, the central region does not necessarily have to have a hollow structure. The central region may be any region where the heat transfer tubes 104 and the heat medium flow paths 111 cannot be arranged, and may have, for example, a solid structure with a solid interior.

[0081] In addition, in the above-described embodiments, examples have been described in which the heat transfer tubes 104 are arranged in multiple rows between the outer circumferential portion 101a and the hollow portion 101b in the cross section of the shell. However, other configurations may also be used. For example, as shown in Fig. 10, a configuration may be used in which only one row of heat transfer tubes 104 is arranged circumferentially between the outer circumferential portion 101a and the hollow portion 101b. In this way, when only one row of heat transfer tubes 104 is arranged between the outer circumferential portion 101a and the hollow portion 101b, the distance between the outer circumferential side and the center of the shell 101 can be made as close as possible, and variations in the flow rate of cooling oil between the outer circumferential side and the center of the shell 101 in the heat medium flow path 111 can be effectively reduced.

[0082] In addition, in each of the above embodiments, the cover 101c is provided at the upstream end of the hollow portion 101b in the gas flow direction as a blocking portion that blocks one end from the other end of the hollow portion 101b, but the blocking portion may be provided at a different location. The blocking portion may be capable of blocking one end from the other end of the hollow portion 101b, and for example, a cover may be provided as the blocking portion at the downstream end of the hollow portion 101b in the gas flow direction.

[0083] In addition, in the above second embodiment, an example was described in which two storage sections 112, 113 corresponding to the peripheral inlet 109 and the peripheral outlet 110, respectively, are provided, but it is sufficient that at least an inlet side storage section 112 corresponding to the peripheral inlet 109 is provided.

[0084] Furthermore, in the above second embodiment, an example was described in which the peripheral inlet 109 and the peripheral outlet 110 are arranged to face the first heat transfer tube 104a, but it is sufficient that at least the peripheral inlet 109 is arranged to face the first heat transfer tube 104a.

[0085] Furthermore, in the second embodiment, an example has been described in which the reservoirs 112, 113 are provided at positions corresponding to the peripheral inlet 109 and the peripheral outlet 110, but the reservoirs 112, 113 may also be omitted. When the inlet-side reservoir 112 is omitted, cooling oil is supplied directly from the temperature adjustment device 200 to the multiple peripheral inlets 109. When the outlet-side reservoir 113 is omitted, cooling oil is supplied directly from the multiple peripheral inlets 109 to the temperature adjustment device 200. [Explanation of symbols]

[0086] 100 reactor 101 Shell 101a Outer periphery 101b Hollow part (center area) 101c Lid (blocking part) 101e Inlet side central reservoir 101f Exit side central storage area 104 Heat transfer tube 109 Heat medium inlet 110 Heat medium outlet 111 Heat transfer medium flow path 112 Inlet reservoir 113 Outlet side storage section 200 Temperature control device

Claims

1. A methane generation system for generating methane by a methane generation reaction using carbon dioxide and hydrogen as raw material gases, a reactor having a plurality of heat transfer tubes inside which a catalyst used in the methane production reaction is provided, and a cylindrical shell accommodating the plurality of heat transfer tubes; a temperature adjusting device connected to an outer periphery of the shell so that a heat medium can pass therethrough, and which supplies the heat medium to the reactor to adjust the temperature of the catalyst; Equipped with a heat medium flow path through which the heat medium flows is formed around the heat transfer tube inside the shell, a central region in which the heat transfer tube and the heat medium flow path cannot be disposed is provided in a central portion of a shell cross section perpendicular to the axial direction of the shell, The methane generation system, wherein the heat transfer tubes and the heat medium flow paths are arranged between the outer periphery of the shell and the central region.

2. The methane generation system according to claim 1 , wherein the central region is a hollow portion having an internal space extending parallel to the axial direction of the shell.

3. The methane generation system according to claim 2 , wherein the hollow portion is provided with a blocking portion that blocks one end side from the other end side of the internal space.

4. The blocking portion does not seal the internal space of the hollow portion, The methane generation system according to claim 3 , wherein the hollow portion is configured to allow the raw material gas or the methane to flow into the hollow portion.

5. The methane generation system according to claim 1 , wherein the heat transfer tubes are arranged in at least one row in the shell cross section in a circumferential direction around the central region.

6. The methane generation system according to claim 1 , wherein the heat transfer tubes are arranged at equal intervals in the circumferential direction in the shell cross section.

7. a peripheral inlet through which the heat medium flows from the temperature adjustment device into the heat medium flow path is provided on the outer periphery of the shell, The methane generation system according to claim 1 , wherein the peripheral inlet is provided opposite the heat transfer tubes arranged side by side in the circumferential direction on the outermost side of the shell cross section.

8. The methane generation system according to claim 7 , wherein the hole diameter of the outer peripheral inlet is smaller than the outer diameter of the heat transfer tube in the shell cross section.

9. The methane generation system of claim 7, wherein an inlet-side reservoir capable of storing the heat transfer medium passing through the peripheral inlet is provided at a position corresponding to the peripheral inlet on the outer periphery of the shell.

10. an outer circumferential outlet through which the heat medium flows from the heat medium flow path to the temperature adjustment device is provided on an outer circumferential portion of the shell; The methane generation system according to claim 1 , wherein the outer peripheral outlet is provided opposite the heat transfer tubes arranged side by side in the circumferential direction on the outermost side of the shell cross section.

11. The methane generation system according to claim 10 , wherein the hole diameter of the outer peripheral outlet is smaller than the outer diameter of the heat transfer tube in the shell cross section.

12. The methane generation system of claim 10, wherein an outlet-side storage section capable of storing the heat transfer medium passing through the peripheral outlet is provided at a position corresponding to the peripheral outlet on the outer periphery of the shell.

13. The hollow portion is provided with an inlet-side central storage portion capable of storing the heat medium in an internal space, The methane generation system according to claim 2 , wherein the heat medium can flow into the heat medium flow path from the inlet-side central reservoir.

14. The hollow portion is provided with an outlet-side central reservoir portion capable of storing the heat medium in an internal space, The methane generation system according to claim 2 , wherein the heat medium can flow from the heat medium flow path to the outlet-side central reservoir.

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