Methanation reaction method and methanation reaction system

Abstract

This invention provides a methanation reaction method in which the lifespan of the catalyst can be extended by diluting it with ceramic balls, and the ceramic balls can be recovered and reused after use. [Solution] A raw material gas containing carbon dioxide and / or carbon monoxide and hydrogen is introduced into a catalyst-packed bed 3 in which ceramic balls 7 and catalyst 4 are filled in at least a portion to generate a methane-containing gas. Then, the used ceramic balls 7 and catalyst 4 removed from at least a portion 3a of the catalyst-packed bed 3 are separated using magnetic separation, and a catalyst different from the separated ceramic balls 7 and catalyst 4 is packed into at least a portion 3a of the catalyst-packed bed 3 to reuse the ceramic balls 7.

Description

TECHNICAL FIELD

[0001] The present invention relates to a methanation reaction method and a methanation reaction system for generating a methane-containing gas by bringing a raw material gas containing carbon dioxide and / or carbon monoxide and hydrogen into contact with a catalyst. BACKGROUND ART

[0002] Methanation of CO2, which generates methane by bringing carbon dioxide and hydrogen into contact with a catalyst, was reported by Sabatier in the early 20th century. The reaction formula for CO2 methanation is as follows. CO2+4H2→CH4+2H2O(ΔH=-165kJ / mol(298K)) (1)

[0003] In recent years, CO2 methanation has attracted attention. This is because CO2 methanation enables reduction of CO2, a greenhouse gas, allows hydrogen produced from surplus power of renewable energy such as solar power generation and wind power generation to be stored in the form of fuel gas, and the produced methane can be used as city gas.

[0004] As a reactor for performing CO2 methanation, Patent Document 1 discloses a methanation reactor in which a tubular catalyst packed bed is filled with a catalyst, a raw material gas containing carbon dioxide and hydrogen is caused to flow through the catalyst packed bed, and the raw material gas is brought into contact with the catalyst to synthesize methane. As the catalyst, for example, a catalyst in which metal particles such as nickel are supported on a carrier such as zirconia is used. The catalyst serves to lower the activation energy of the reaction and allow the synthesis of methane to proceed smoothly.

[0005] The CO2 methanation represented by Reaction Formula 1 is an exothermic reaction. As CO2 methanation proceeds, a rapid temperature rise occurs on the upstream side in the longitudinal direction of the catalyst packed bed or in the gas flow direction, and there is a problem that thermal degradation of the catalyst proceeds particularly in a region with a high temperature.

[0006] Furthermore, Sabatier has also reported the methanation of CO, represented by the following reaction equation (2). The methanation of CO is also an exothermic reaction, and, similar to the methanation of CO2, a rapid temperature rise occurs in the longitudinal direction of the catalyst packed bed or upstream in the direction of gas flow, leading to the problem of thermal degradation of the catalyst in the high-temperature region. CO+3H2→CH4+H2O(ΔH=-206kJ / mol(298k)) (2)

[0007] To prevent thermal degradation of the catalyst in high-temperature regions, Patent Document 2 discloses an invention that extends the lifespan of the catalyst by diluting the catalyst with ceramic balls, that is, by filling the catalyst packing bed with a mixture of the catalyst and ceramic balls or by alternately stacking the catalyst and ceramic balls. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 6984098 [Patent Document 2] Japanese Patent Publication No. 2003-321400 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, the invention described in Patent Document 2 has the problem that it is difficult to separate the catalyst and ceramic balls after use, and both are discarded.

[0010] This invention has been made in view of the above problems, and aims to provide a methanation reaction method and a methanation reaction system that can extend the lifespan of the catalyst by diluting it with ceramic balls, and can recover and reuse the ceramic balls after use. [Means for solving the problem]

[0011] To solve the above problems, one aspect of the present invention is a methanation reaction method which involves introducing a raw material gas containing carbon dioxide and / or carbon monoxide and hydrogen into a catalyst-packed bed in which ceramic balls and a catalyst are packed in at least a portion to generate a methane-containing gas, then separating the used ceramic balls and catalyst removed from at least a portion of the catalyst-packed bed using magnetic separation, and packing at least a portion of the catalyst-packed bed with a catalyst different from the separated ceramic balls and catalyst, thereby reusing the ceramic balls.

[0012] Another aspect of the present invention is a methanation reaction system comprising: a methanation reactor that generates a methane-containing gas by introducing a raw material gas containing carbon dioxide and / or carbon monoxide and hydrogen into a catalyst-packed bed in which ceramic balls and a catalyst are filled in at least a portion; and a magnetic separator that separates the used ceramic balls and the catalyst removed from the catalyst-packed bed using magnetic separation, wherein a catalyst different from the separated ceramic balls and catalyst is packed into at least a portion of the catalyst-packed bed, and the ceramic balls are reused. [Effects of the Invention]

[0013] According to the present invention, the lifespan of the catalyst can be extended by diluting it with ceramic balls, and the ceramic balls can be recovered and reused after use. [Brief explanation of the drawing]

[0014] [Figure 1] This figure shows an example of a methanation reaction system according to an embodiment of the present invention. [Figure 2] Figure 2(a) shows a longitudinal cross-sectional view of the catalyst packed bed, Figure 2(b) is a graph showing the relationship between the catalyst packed bed height and temperature / methane concentration when the catalyst is not diluted with ceramic balls, and Figure 2(c) is a graph showing the relationship between the catalyst packed bed height and temperature / methane concentration when the catalyst is diluted with ceramic balls. [Modes for carrying out the invention]

[0015] Hereinafter, the methanation reaction method and methanation reaction system according to embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the methanation reaction method and methanation reaction system of the present invention can be embodied in various forms and are not limited to the embodiments described herein. These embodiments are provided with the intention that those skilled in the art will be able to fully understand the invention by making full disclosures in the specification. (Methanation reaction system)

[0016] Figure 1 shows a schematic diagram of a methanation reaction system according to an embodiment of the present invention. The methanation reaction system comprises a methanation reactor 1 (hereinafter simply referred to as reactor 1) and a magnetic separator 8.

[0017] Figure 1 shows a longitudinal cross-sectional view of an example of reactor 1. Reactor 1 is supplied with a raw material gas containing carbon dioxide and hydrogen adjusted to a molar ratio of 1:4. Reactor 1 comprises a vessel 2 and a plurality of tubular catalyst packed beds 3 arranged parallel to each other within the vessel 2. The raw material gas is supplied from the inlet port 2a to the buffer region at the top of the vessel 2, and then flows from top to bottom through the plurality of catalyst packed beds 3. In the catalyst packed beds 3, the raw material gas comes into contact with the catalyst 4, and methanation of CO2, represented by reaction equation (1), proceeds. CO2+4H2→CH4+2H2O(ΔH=-165kJ / mol(298k)) (1)

[0018] The catalyst packed bed 3 is divided into multiple parts 3a to 3b by partitioning members 5 in the longitudinal direction or in the direction of gas flow. The partitioning members 5 are not particularly limited as long as they can permeate gas and partition the catalyst packed bed 3, for example, wire mesh, grating, perforated metal, ceramic, etc.

[0019] Part 3a is filled with the catalyst 4 and the ceramic balls 7. Part 3b is filled with the catalyst 4. The catalyst 4 has the role of lowering the activation energy of the reaction and accelerating the reaction rate of CO2 methanation. The catalyst 4 is obtained by supporting metal particles such as Ni, Co, Fe, Cu, Ru, and Rh on an oxide carrier such as zirconia, magnesia, alumina, silica, zeolite, and calcium phosphate. The shape of the catalyst 4 is not particularly limited, and may be powdery, pellet-shaped, or columnar. The structure of the catalyst 4 is also not particularly limited, and may be a porous structure or a honeycomb structure. Note that part 3b may also be filled with the catalyst 4 and the ceramic balls 7, or the catalyst packed bed 3 may not be divided into a plurality of parts.

[0020] The ceramic balls 7 have magnetism. The ceramic balls 7 do not have the role of accelerating the reaction rate of CO2 methanation. The ceramic ball 7 includes, for example, a magnetic body and a refractory material covering the periphery of the magnetic body. The magnetic body is, for example, a metal such as Fe, Ni, or Co, or a magnet such as neodymium. The refractory material is alumina, silica, alumina-silica, zirconia, magnesia, or the like. Note that the ceramic balls may be produced by forming clay balls, drying and firing the formed clay balls, and applying a magnetic force to the ceramic balls to impart magnetism to the ceramic balls.

[0021] By the methanation of CO2 in the catalyst packed bed 3, a gas containing methane (CH4) and water vapor (H2O) is generated. The generated gas unavoidably contains CO2, H2, CO and the like. The generated gas passes through the buffer region in the lower part of the container 2, and then is discharged from the discharge port 2b of the container 2.

[0022] The generated gas discharged from the reactor 1 is condensed by a condenser (not shown) connected to the discharge port 2b, and separated into a gas containing methane and water. The gas containing methane from which water has been separated is supplied to a demand destination after impurities such as CO2 and CO are removed by, for example, a decarbonation device or the like.

[0023] CO2 methanation is an exothermic reaction. The catalyst packed bed 3 is operated in a temperature range of, for example, 300°C to 500°C. If the catalyst packed bed 3 is below 300°C, harmful nickel carbonyls will be formed in the catalyst 4. To prevent the catalyst packed bed 3 from falling below 300°C, heated raw material gas may be supplied to the reactor 1 at the beginning of operation, or the catalyst packed bed 3 may be heated by a heater (not shown).

[0024] On the other hand, if the catalyst packed bed 3 is at a high temperature of 500°C or higher, thermal degradation of the catalyst 4 will progress. To prevent the catalyst packed bed 3 from reaching a high temperature of 500°C or higher, the catalyst packed bed 3 is cooled by a refrigerant supplied into the container 2 from the refrigerant inlet port 6a. The refrigerant can be vapor, oil, etc. After heat exchange with the catalyst packed bed 3, the refrigerant is discharged from the refrigerant outlet port 6b. Alternatively, a portion of the generated gas cooled by a condenser connected to the discharge port 2b may be circulated to the inlet port 2a of the reactor 1, and the catalyst packed bed 3 may be cooled by diluting the raw material gas with the generated gas.

[0025] The magnetic separator 8 separates the ceramic balls 7 and the catalyst 4 using the magnetic force of the magnet 11. The magnetic separator 8 is not particularly limited and can be a drum type, belt conveyor type, suspension type, etc. Figure 1 shows a drum type magnetic separator as an example of the magnetic separator 8. The magnetic separator 8 comprises a case 12 having an input port 12a, a drum 13 rotatably mounted in the case 12, and a branching plate 14 for separating the ceramic balls 7 and the catalyst 4. The magnet 11 is housed in the drum 13 in a non-rotatable manner.

[0026] When ceramic balls 7 and catalyst 4 are introduced onto the rotating drum 13 from the input port 12a, the ceramic balls 7, which have a stronger magnetism than catalyst 4, are attracted to the drum 13 by the magnetic force of magnet 11, carried along by the rotation of the drum 13, and fall to the left side of the branching plate 14 in areas where the magnetic force of magnet 11 does not reach. Meanwhile, catalyst 4 is carried along by the rotation of the drum 13 and falls from the surface of the drum 13 to the right side of the branching plate 14. This separates the ceramic balls 7 and catalyst 4. The separated ceramic balls 7 and catalyst 4 are discharged from their respective outlets.

[0027] Figure 2(a) shows a longitudinal cross-sectional view of the catalyst packed bed 3. As described above, the catalyst packed bed 3 is divided into multiple parts 3a and 3b by partitioning members 5. Part 3a is packed with ceramic balls 7 and catalyst 4. Part 3a may be packed with a mixture of ceramic balls 7 and catalyst 4, or with ceramic balls 7 and catalyst 4 stacked alternately. Part 3b is packed with catalyst 4.

[0028] The catalyst packed bed 3 is supplied with a raw material gas containing carbon dioxide (CO2) and hydrogen (H2). Methanation of CO2 in the catalyst packed bed 3 generates a gas containing methane (CH4) and water vapor (H2O). The resulting gas inevitably contains CO2, H2, CO, etc. (Effect of catalyst dilution)

[0029] Figure 2(b) shows the relationship between catalyst packing height, temperature, and methane concentration when catalyst 4 is not diluted with ceramic balls 7. When catalyst 4 is not diluted with ceramic balls 7, a rapid temperature increase occurs upstream of the catalyst packing bed 3 in the longitudinal direction or in the direction of gas flow, followed by a rapid temperature decrease downstream, and then the temperature becomes almost constant. In the high-temperature region 21 upstream of the catalyst packing bed 3, thermal degradation of catalyst 4 progresses. This is because sintering of the supported metal such as nickel progresses in the high-temperature region, reducing the specific surface area of ​​the supported metal and decreasing the activity of catalyst 4.

[0030] Figure 2(c) shows the relationship between catalyst packing height, temperature, and methane concentration when catalyst 4 is diluted with ceramic balls 7. By diluting catalyst 4 with ceramic balls 7, the temperature of catalyst packing 3 rises gradually from upstream to downstream, and then gradually decreases. This suppresses a rapid temperature rise in the longitudinal direction or upstream in the gas flow direction of catalyst packing 3, thereby extending the lifespan of catalyst 4. (Methanation method)

[0031] Diluting catalyst 4 with ceramic balls 7 can extend the lifespan of catalyst 4, but when reactor 1 is operated for a predetermined time, the catalyst 4 still deteriorates. After the predetermined time of operation, when catalyst 4 has deteriorated, the ceramic balls 7 and catalyst 4 are removed from part 3a. At the same time, catalyst 4 is removed from part 3b. Then, as shown in Figure 1, the used ceramic balls 7 and catalyst 4 removed from part 3a are separated using magnetic separation.

[0032] Subsequently, a catalyst other than the separated ceramic balls 7 and catalyst 4 (for example, a new catalyst, a catalyst 4 extracted from part 3a and reconditioned, or a catalyst 4 extracted from part 3b) is filled into part 3a, and the ceramic balls 7 are reused. The catalyst 4 extracted from part 3b is less degraded than the catalyst 4 extracted from part 3a, so the catalyst 4 extracted from part 3b can also be reused.

[0033] Furthermore, the present invention is not limited to being embodied in the above embodiments, and can be embodied in other embodiments without changing the gist of the invention.

[0034] In the above embodiment, an example of performing CO2 methanation in a reactor was described, but CO methanation may also be performed in the reactor, or CO and CO2 methanation may be performed in the reactor.

[0035] In the above embodiment, the ceramic balls are made magnetic, and the ceramic balls are attracted and separated by the magnets of the magnetic separator. However, the catalyst may be made magnetic, and the catalyst may be attracted and separated by the magnets of the magnetic separator.

[0036] In the above embodiment, an example was described in which a plurality of tubular catalyst packed beds were arranged in the reactor. However, the configuration of the reactor is not limited to this, and for example, a catalyst packed bed that extends over almost the entire cross-section of the reactor may be provided. [Explanation of Symbols]

[0037] 1…Methanation reactor 3…Catalyst packed bed 4…Catalyst 7…Ceramic balls 8...Magnetic separator

Claims

1. A raw material gas containing carbon dioxide and / or carbon monoxide and hydrogen is introduced into a catalyst-packed bed in which ceramic balls and a catalyst are filled to at least part of the bed to produce a methane-containing gas. Subsequently, the used ceramic balls and catalyst, removed from at least a portion of the catalyst packed bed, are separated using magnetic separation. A methanation reaction method in which a catalyst different from the separated ceramic balls and catalyst is packed into at least a portion of the catalyst-packed bed, and the ceramic balls are reused.

2. The methanation reaction method according to claim 1, characterized in that the ceramic ball is magnetic.

3. The methanation reaction method according to claim 1 or 2, characterized in that the ceramic ball comprises a magnetic material and a refractory material covering the periphery of the magnetic material.

4. A methanation reactor that generates a methane-containing gas by introducing a raw material gas containing carbon dioxide and / or carbon monoxide and hydrogen into a catalyst-packed bed in which ceramic balls and a catalyst are filled in at least part of the bed, The system includes a magnetic separator that separates the used ceramic balls and catalyst removed from the catalyst packed bed using magnetic separation, A methanation reaction system in which a catalyst different from the separated ceramic balls and catalyst is packed into at least a portion of the catalyst packing bed, and the ceramic balls are reused.

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