METHANIZATION DEVICE, METHANIZATION PROCESS, DEVICE FOR THE DIRECT DECOMOTION OF HYDROGEN AND PROCESS FOR THE DIRECT DECOMOTION OF HYDROGEN

Abstract

A methanization device is provided for removing a saturated hydrocarbon from a feed gas containing methane and a saturated hydrocarbon by methanation, wherein a saturated hydrocarbon with at least two carbon atoms reacts with hydrogen and the saturated hydrocarbon is converted into methane. The methanization device comprises: at least two catalyst layers, each consisting of a catalyst for methanation, wherein the catalyst layers are arranged at intervals in the direction of flow of a mixed gas containing a feed gas and a hydrogen-containing gas; a hydrogen supply line for supplying a hydrogen-containing gas to the upstream side of the catalyst layer on the side furthest upstream in the direction of flow of the mixed gas;a feed line for supplying the feed gas to each space between two catalyst layers that are adjacent to each other in the direction of flow of the mixed gas, and to the upstream side of the catalyst layer on the side furthest upstream in the direction of flow of the mixed gas; and a cooler arranged between two adjacent catalyst layers in the direction of flow of the mixed gas, which cools the mixed gas exiting the catalyst layer on the upstream side of the two adjacent catalyst layers.

Description

Technical field

[0001] The present disclosure relates to a methanization device, a methanization process, a device for the direct decomposition of hydrocarbons and a process for the direct decomposition of hydrocarbons. The present application claims priority based on JP 2023-220345, filed with the Japanese Patent Office on December 27, 2023, the contents of which are hereby incorporated by reference. State of the art

[0002] Currently, the production of various energy sources is largely dependent on fossil fuels such as oil, coal, and natural gas, and from the perspective of global environmental protection, an increase in carbon dioxide emissions from the combustion of fossil fuels is considered problematic. The Paris Agreement, adopted in 2015, calls for a reduction in carbon dioxide emissions to combat climate change. Reducing carbon dioxide emissions from the combustion of fossil fuels is a crucial issue in thermal power plants and similar facilities. While a process for separating and recovering emitted carbon dioxide has been investigated from an energy perspective, a technique for generating energy without carbon dioxide emissions by using an alternative fuel to fossil fuels has also been explored.

[0003] Therefore, hydrogen, a clean fuel that releases no carbon dioxide when burned, has attracted attention as an alternative to fossil fuels. Hydrogen can be produced, for example, by steam reforming the methane contained in natural gas. However, this production process generates carbon monoxide as a byproduct, which is eventually oxidized and released as carbon dioxide. Water electrolysis, photocatalytic processes, and similar methods have been investigated as ways to produce hydrogen from water without using fossil fuels. However, these processes are very energy-intensive and economically problematic.

[0004] A process for producing hydrogen and carbon through the direct decomposition of hydrocarbons has now been developed. The direct decomposition of hydrocarbons is characterized by the fact that hydrogen can be produced as a fuel without carbon dioxide emissions. While the carbon produced as a byproduct is solid and therefore easily immobilized, carbon itself can be effectively used in a wide range of applications, such as electrode material, tire material, and building material. A process for the direct decomposition of a hydrocarbon into hydrogen and carbon was developed in which a supported catalyst is brought into contact with a hydrocarbon gas. However, a problem arose: carbon, which is a product of the direct decomposition reaction of the hydrocarbon, adheres to the catalyst, causing the catalytic activity to decrease within a short time.

[0005] Against this background, the applicant of the present disclosure has developed a process for the direct decomposition of a hydrocarbon into carbon and hydrogen using a catalyst, which is a supportless catalyst consisting of an aggregate of a plurality of iron particles, as described in patent document 1. The applicant believes that, according to this process, the activity of the catalyst is maintained by the development of a new active site, even when carbon, which is a product of the direct decomposition reaction of a hydrocarbon, adheres to the catalyst, and that therefore the activity of this reaction can be maintained over a long period of time.

[0006] For example, natural gas is used as a feedstock for the direct decomposition reaction of a hydrocarbon. Besides methane, natural gas also contains saturated hydrocarbons with two or more carbon atoms, such as ethane, propane, and butane (hereinafter referred to as "saturated hydrocarbon C2+"). Saturated hydrocarbon C2+ is more reactive than methane, and therefore, at temperatures that trigger the direct decomposition reaction of methane, side reactions such as thermal decomposition and polymerization reactions of saturated hydrocarbon C2+ can lead to, for example, pipeline blockages. When a feedstock gas containing saturated hydrocarbon C2+ is used as a raw material for the direct decomposition reaction of a hydrocarbon, it is necessary to remove the saturated hydrocarbon C2+ from the feedstock gas to suppress such a risk.

[0007] When ethane, propane, and butane are used as examples of saturated hydrocarbons C2+, the saturated hydrocarbons C2+ react with hydrogen to form methane, as shown in the following reaction formulas (1) to (3), and thus the saturated hydrocarbons C2+ can be removed from the starting gas. In general, the synthesis of methane from hydrogen and carbon dioxide is often referred to as methanation, but in the present disclosure, as shown in the following reaction formulas (1) to (3), a reaction in which a saturated hydrocarbon C2+ is converted to methane by reacting the saturated hydrocarbon C2+ with hydrogen is defined as "methanation". C2H6 + H2 → 2CH4 ··· (1) C3H8 + 2H2 → 3CH4 ··· (2) C4H 10 + 3H2 → 4CH4 ··· (3) List of prior art documents

[0008] Patent document 1: JP 7089235 B Brief description of the invention: Technical problem

[0009] Depending on the temperature conditions of the methanation process, the methane contained in the feed gas or in a portion of the converted methane can decompose directly into hydrogen and carbon. In this case, the methanation catalyst degrades due to carbon adhesion, leading to a reduction in methanation activity and thus potentially impairing the performance in removing the saturated hydrocarbon C2+ from the feed gas.

[0010] Taking into account the above circumstances, it is an object of at least one embodiment of the present disclosure to provide a methanization device, a methanization process, a device for the direct decomposition of hydrocarbons and a process for the direct decomposition of hydrocarbons which are capable of suppressing the deterioration of a catalyst for methanization. Solution to the problem

[0011] To accomplish the above-mentioned task, a methanization device according to the present disclosure is a methanization device for removing a saturated hydrocarbon C2+ with two or more carbon atoms from a starting gas containing methane and the saturated hydrocarbon C2+ by methanation, wherein the saturated hydrocarbon C2+ is converted into methane by reaction with hydrogen, wherein the methanization device includes: at least two catalyst layers constructed from a catalyst for methanation, wherein the at least two catalyst layers are arranged at intervals in the flow direction of a mixed gas containing the starting gas and a hydrogen-containing gas;a hydrogen supply line configured to supply the hydrogen-containing gas to the upstream side of the most upstream catalyst layer in the direction of flow of the mixed gas; an outlet gas supply line configured to supply the outlet gas both to the upstream side of the most upstream catalyst layer in the direction of flow of the mixed gas and to a space between two adjacent catalyst layers in the direction of flow of the mixed gas; and a cooler arranged between two adjacent catalyst layers in the direction of flow of the mixed gas, which cools the mixed gas exiting an upstream catalyst layer in the direction of flow between the two adjacent catalyst layers.

[0012] A methanization process according to the present disclosure is a methanization process for removing a saturated hydrocarbon C2+ with two or more carbon atoms from a starting gas containing methane and the saturated hydrocarbon C2+ by methanation, wherein the saturated hydrocarbon C2+ is converted to methane by reaction with hydrogen, the methanization process comprising: causing a hydrogen-containing gas to flow into a most upstream catalyst layer of at least two catalyst layers constructed from a catalyst for methanation, the at least two catalyst layers being arranged at intervals in the flow direction of a mixed gas containing the starting gas and the hydrogen-containing gas; causing a portion of the starting gas to flow into the most upstream catalyst layer in the flow direction of the mixed gas;Introducing a residue of the initial gas between two adjacent catalyst layers in the direction of flow of the mixed gas; cooling the mixed gas exiting an upstream catalyst layer of the two adjacent catalyst layers; and causing the cooled mixed gas and the initial gas introduced between the two adjacent catalyst layers in the direction of flow of the mixed gas to flow into a downstream catalyst layer of the two adjacent catalyst layers. Advantageous effects of the invention

[0013] According to the methanation device and methanation process of the present disclosure, the temperature of the mixed gas flowing through each catalyst layer increases due to the methanation in each catalyst layer. By dividing and supplying the initial gas to each catalyst layer, the methanation in each catalyst layer can be carried out gently. Furthermore, by cooling the mixed gas exiting each catalyst layer, the temperature of the mixed gas flowing into the adjacent catalyst layer in the direction of flow can be reduced. Thus, even if the temperature of the mixed gas increases due to methanation in each catalyst layer, this increase can be suppressed to such an extent that direct decomposition of methane does not occur, and consequently, the adhesion of carbon to the catalyst for methanation can also be suppressed.As a result, deterioration of the catalyst for methanation can be suppressed. Brief description of the drawings Fig. Figure 1 is a schematic configuration diagram of a device for the direct decomposition of hydrocarbons including a methanization device according to an embodiment of the present disclosure. Fig. Figure 2 is a schematic configuration diagram of a methanization device from a simulation 1. Fig. Figure 3 is a schematic configuration diagram of a methanization device from Simulation 2. Fig. Figure 4 is a schematic configuration diagram of a methanization device from Simulation 3. Description of embodiments

[0014] A methanization device and a methanization process according to embodiments of the present disclosure are described below with reference to the drawings. The embodiments described below each illustrate an aspect of the present disclosure, do not limit this disclosure, and can be modified as desired within the scope of the technical concept of the present disclosure. <Konfiguration einer Methanisierungsvorrichtung und einer Vorrichtung zur direkten Zersetzung von Kohlenwasserstoff gemäß einer Ausführungsform der vorliegenden Offenbarung>

[0015] In the following, a methanization device according to one embodiment of the present disclosure is described as a component of a device for the direct decomposition of hydrocarbons. However, the present disclosure is not limited to this embodiment and can be a component of any device or be used as a standalone device. As in Fig. Figure 1 shows a device 1 for the direct decomposition of hydrocarbons according to an embodiment of the present disclosure, comprising a methanization device 2 and a reactor 22. The methanization device 2 and the reactor 22 are connected to each other via a process gas supply line 5. The direct decomposition device 1 can include a gas chromatograph 16 with which a portion of the gas flowing through the process gas supply line 5 (process gas described later) can be sampled and the composition of the gas measured.

[0016] The methanization device 2 encloses a housing 10, which contains a catalyst layer 11, composed of a catalyst for methanation, and a cooler 13. The catalyst layer 11 comprises two catalyst layers, namely a first catalyst layer 11a and a second catalyst layer 11b, arranged at intervals between the two ends of the housing 10. As described later, the gas flows within the housing 10 from one end section of the housing 10 to the other end section, and a catalyst layer located upstream in the direction of gas flow is referred to as the first catalyst layer 11a, and a catalyst layer located downstream is referred to as the second catalyst layer 11b.Any suitable catalyst for methanation can be used; examples include a supported catalyst where nickel, iron, cobalt, or a noble metal element is mounted on aluminum oxide. The shape of the catalyst is not particularly restricted; any suitable form can be used, such as tablets, rings, extruded pellets, or granules.

[0017] In the housing 10, a space 12 is formed between the first catalyst layer 11a and the second catalyst layer 11b, and the cooler 13 is arranged in the space 12. The configuration of the cooler 13 is not particularly restricted, but the cooler 13 can, for example, be configured such that the gas described above is cooled by heat exchange with any coolant.

[0018] In the configuration of Fig.In the housing 10, two catalyst layers (i.e., the first catalyst layer 11a and the second catalyst layer 11b) and an intermediate cooler 13 (i.e., in space 12) are provided. However, three or more catalyst layers can also be provided, i.e., at least two catalyst layers, and in the configuration in which three or more catalyst layers are provided, the cooler 13 is located in each of the spaces 12 between two adjacent catalyst layers in the flow direction of the gas described above.

[0019] The methanization device 2 further includes a hydrogen supply line 3, configured to introduce hydrogen-containing gas into the housing 10, and an outlet gas supply line 4, configured to introduce outlet gas into the housing 10. The hydrogen supply line 3 is connected to the housing 10 on the upstream side of the first catalyst layer 11a in the direction of gas flow within the housing 10. The hydrogen supply line 3 may be equipped with a flow control valve 14, configured to regulate the amount of hydrogen-containing gas supplied to the housing 10. The hydrogen-containing gas flowing through the hydrogen supply line 3 may be pure hydrogen or a mixture of hydrogen and a component (such as a noble gas, nitrogen, or methane) that does not contribute to methanation.The starting gas is a gas containing methane and saturated hydrocarbons C2+ with two or more carbon atoms (such as ethane, propane, or butane). Examples of starting gases include natural gas, compressed natural gas (CNG), town gas, liquefied petroleum gas (LPG), and naphtha. Therefore, the gas flowing through housing 10, as described above, is a mixed gas containing the hydrogen-containing gas supplied to housing 10 via hydrogen supply line 3 and the starting gas supplied to housing 10 via the starting gas supply line 4.

[0020] The initial gas supply line 4 branches into two branch lines 4a and 4b. One branch line 4a is connected to the housing 10 on the upstream side of the first catalyst layer 11a in the direction of flow of the mixed gas described above in the housing 10, while the other branch line 4b is connected to the housing 10 between the first catalyst layer 11a and the second catalyst layer 11b. Branch line 4a can either be connected to the housing 10 without merging with the hydrogen supply line 3, or it can be connected as shown in Fig.As shown in Figure 1, the branch line 4b converges with the hydrogen supply line 3. The branch line 4b can be connected to the housing 10 to provide a connection to the chamber 12, and the outlet gas flowing into the chamber 12 through branch line 4b can enter the cooler 13 on the upstream side, the cooler 13 on the downstream side, or flow into a region where the cooler 13 is located. Branch lines 4a and 4b can be equipped with flow control valves 15a and 15b, respectively, configured to regulate the amount of outlet gas supplied to the housing 10 via branch lines 4a and 4b, respectively.The hydrogen supply line 3 can include a branch line such as the outlet gas supply line 4, and each of the branch lines of the hydrogen supply line 3 can be connected to the housing 10 on the upstream side of the first catalyst layer 11a and between the first catalyst layer 11a and the second catalyst layer 11b.

[0021] Reactor 22 contains a catalyst 20 for the direct decomposition reaction of a hydrocarbon. Reactor 22 is equipped with a heater 21 (for example, a jacket through which steam flows) which serves to increase the temperature inside reactor 22, in particular the temperature of the catalyst 20. A product gas flow line 6 is connected to reactor 22 on the side opposite the catalyst 20, from the point where the process gas supply line 5 is connected to reactor 22.

[0022] The catalyst 20 is not particularly restricted; for example, it can be a carrierless catalyst consisting of an aggregate of numerous iron particles. In reactor 22, each particle of catalyst 20 can be in a steady state or in a fluidized bed state, in which the particles are suspended in the feed gas and float due to the upward injection of the process gas described later. During the reaction of the hydrocarbon with catalyst 20, carbon and hydrogen are produced, with the carbon adhering to the particles of catalyst 20. In the case of the formation of a fluidized bed by catalyst 20, the particles of catalyst 20 rub against each other, so that the carbon adhering to the particles of catalyst 20 is physically removed from the particles.If a fixed-bed reactor is used as reactor 22, for example a carbon remover can be provided outside reactor 22 to remove the carbon adhering to catalyst 20 from the catalyst 20.

[0023] The direct decomposition device 1 may further include a hydrogen return line 7, which connects the product gas flow line 6 to the hydrogen supply line 3. The hydrogen return line 7 may be equipped with a valve 8, which may be either an on / off valve or a flow control valve. <Funktionsweise der Methanisierungsvorrichtung gemäß Ausführungsform der vorliegenden Offenbarung>

[0024] The following describes the operation of the methanization device according to an embodiment of the present disclosure (a methanization process). The hydrogen-containing gas flows into the housing 10 via the hydrogen supply line 3 on the upstream side of the first catalyst layer 11a. A portion of the initial gas, which flows through the initial gas supply line 4, enters the housing 10 via the branch line 4a on the upstream side of the first catalyst layer 11a.

[0025] The hydrogen-containing gas and the initial gas, which flow into the housing 10 on the upstream side of the first catalyst layer 11a, enter the first catalyst layer 11a. In the first catalyst layer 11a, the saturated hydrocarbon C2+ in the initial gas reacts with hydrogen in the hydrogen-containing gas to form methane through the action of the catalyst for methanation, and a mixed gas containing methane, unreacted saturated hydrocarbon C2+ and unreacted hydrogen flows out of the first catalyst layer 11a and into space 12.Although the temperature of the mixed gas increases due to the heat of reaction of methanation, as described above, the methanation in the first catalyst layer 11a proceeds more mildly (the amount of methanation decreases) in the operation described above than in the case where the entire quantity of the output gas flowing through the output gas supply line 4 is directed into the housing 10 on the upstream side of the first catalyst layer 11a, and thus the temperature increase of the mixed gas exiting the first catalyst layer 11a can be suppressed.

[0026] In the methanization device 2 with the in Fig.In the configuration shown in Figure 1, the catalyst layer 11 is divided into two parts to feed the feed gas into two parts. However, if the number of subdivisions of the catalyst layer 11 (i.e., the number of subdivisions of the feed gas) is increased, the flow rate of the feed gas passing through the first catalyst layer 11a decreases, and thus the methanation in the first catalyst layer 11a becomes gentler, further suppressing the temperature rise of the mixed gas exiting the first catalyst layer 11a.If the temperature rise of the mixed gas exiting the first catalyst layer 11a can be suppressed to such an extent that no direct decomposition of methane takes place, the direct decomposition reaction of methane in the first catalyst layer 11a can be suppressed, and the adhesion of carbon to the catalyst forming the first catalyst layer 11a for methanation can be suppressed, thereby suppressing the deterioration of the catalyst for methanation.

[0027] The mixed gas flowing into chamber 12 is cooled by heat exchange with a coolant flowing in cooler 13. The cooled mixed gas and the initial gas flow through branch line 4b into the second catalyst layer 11b. In the second catalyst layer 11b, the saturated hydrocarbon C2+ reacts with hydrogen to form methane according to the same principle as in the first catalyst layer 11a. Since the mixed gas, cooled by cooler 13, flows into the second catalyst layer 11b, the temperature of the mixed gas can be suppressed to a temperature at which no direct decomposition of methane occurs, even if the temperature of the mixed gas in the second catalyst layer 11b rises due to such methanation.This can suppress the direct decomposition reaction of methane in the second catalyst layer 11b, and prevent carbon from adhering to the catalyst for methanation forming the second catalyst layer 11b, and therefore suppress the deterioration of the catalyst for methanation.

[0028] In such a methanation process, the temperature of the mixed gas flowing through the first catalyst layer 11a and the second catalyst layer 11b does indeed rise due to the methanation in these layers. However, by supplying the initial gas separately to the first and second catalyst layers 11b, the methanation process can be carried out gently. Furthermore, by cooling the mixed gas exiting the first catalyst layer 11a, the temperature of the mixed gas flowing into the adjacent second catalyst layer 11b in the direction of flow can be reduced.Accordingly, even if the temperature of the mixed gas increases due to methanation in the first catalyst layer 11a and the second catalyst layer 11b, this increase can be suppressed to such an extent that no direct decomposition of methane occurs, and thus the adhesion of carbon to the catalyst for methanation can be suppressed. Consequently, deterioration of the catalyst for methanation can be prevented.

[0029] In such a methanation process, the feed gas is split and fed via branch lines 4a and 4b. Therefore, the flow rate of the mixed gas flowing through the second catalyst layer 11b is greater than the flow rate of the mixed gas flowing through the first catalyst layer 11a. Consequently, the amount of catalyst forming the second catalyst layer 11b is preferably greater than the amount of catalyst forming the first catalyst layer 11a. Accordingly, the amount of catalyst in each of the first catalyst layers 11a and the second catalyst layer 11b can be adjusted to a suitable quantity according to the amount of mixed gas flowing through each of the first catalyst layers 11a and the second catalyst layer 11b, and thus the methanation can be carried out in each of the first catalyst layer 11a and the second catalyst layer 11b under suitable conditions.If the catalyst layer 11 is composed of three or more catalyst layers, the amount of catalyst formed by each catalyst layer is preferably increased if the catalyst layer is arranged further downstream in the direction of flow of the mixed gas.

[0030] In such a methanation process, the concentrations of hydrogen and saturated hydrocarbons (C2+) in each catalyst layer are lower than in a gas containing only hydrogen. This is achieved when the hydrogen-containing gas contains a component that does not contribute to methanation. Consequently, the temperature rise of the mixed gas due to the heat generated during methanation in each catalyst layer is suppressed, allowing for gentle methanation in each layer. This suppression of the temperature rise in each catalyst layer is sufficient to prevent direct methane decomposition, thus preventing carbon adhesion to the catalyst and catalyst degradation.

[0031] In such a methanization process, the feed rate of the hydrogen-containing gas is preferably adjusted so that the concentration ratio of hydrogen to the saturated hydrocarbon C2+ in the mixed gas is 1 or more. To convert ethane, which has the fewest carbon atoms among the saturated hydrocarbons C2+, into methane, one molecule of hydrogen is required for every molecule of ethane. By setting such conditions, the saturated hydrocarbons C2+ in the starting gas can be stoichiometrically converted into methane.

[0032] In the configuration with the gas chromatograph 16 and the flow control valve 14, a decrease in the methanation activity in the methanation device 2 can be detected from the measurement result of the gas chromatograph 16. When a decrease in methanation activity is detected, the feed rate of hydrogen-containing gas through the flow control valve 14 can be increased. As the feed rate of hydrogen-containing gas increases, the hydrogen concentration in the mixed gas rises. In this case, carbon, a polymerization reaction product, or similar substances adhering to the catalyst for methanation readily react with hydrogen. Therefore, the adhering carbon, polymerization reaction product, or similar substances can be converted into a gas such as methane to remove the adhering substances from the catalyst.This means that it is possible to suppress the deterioration of the catalyst for methanation due to a product formed by side reactions such as thermal decomposition and polymerization reactions of the saturated hydrocarbon C2+, or it is possible to regenerate the deteriorated catalyst.

[0033] If the feed gas contains sulfur, the catalyst for methanation can be impaired by the sulfur content. Therefore, it is preferable to remove the sulfur content from the feed gas before it flows into the housing 10 by providing a desulfurization device in the feed gas supply line 4.

[0034] Functioning of the device for the direct decomposition of hydrocarbons according to an embodiment of the present disclosure

[0035] The following describes the operation of the device for the direct decomposition of hydrocarbons according to an embodiment of the present disclosure (a method for the direct decomposition of hydrocarbons). The mixed gas exiting the second catalyst layer 11b flows out of the housing 10, passes through the process gas supply line 5 as process gas, and enters the reactor 22. The process gas flowing into the reactor 22 passes through the catalyst 20 and comes into contact with it. The hydrocarbon in the process gas is thereby directly decomposed into hydrogen and carbon. If, for example, methane is used as the hydrocarbon in the direct decomposition reaction, a reaction takes place in the reactor 22 as described by the following reaction formula (4). CH4 → 2H2 + C ··· (4)

[0036] The carbon produced by the direct decomposition process adheres to the catalyst 20, and the hydrogen produced, along with an unreacted hydrocarbon, flows out of reactor 22 as product gas and through the product gas flow line 6. The carbon can be recovered by removing the catalyst 20 from reactor 22 after stopping the supply of process gas to reactor 22, and optionally by removing the carbon adhering to the catalyst 20 with a carbon remover. The hydrogen is recovered by regenerating a reaction gas flowing through the product gas flow line 6. Hydrogen can be purified by providing a hydrogen refiner in the product gas flow line 6.In this case, with a low conversion rate of the hydrocarbon, the hydrogen concentration in the process gas is low, but the concentration of hydrogen as the end product can be increased using the hydrogen refining process.

[0037] When saturated hydrocarbons C2+, such as ethane or propane, are present alongside methane in a process gas, ethane or propane, for example, are also directly decomposed into hydrogen and carbon, as shown in the following reaction formulas (5) and (6). However, at a temperature that causes a direct decomposition reaction of methane (preferably 600 °C to 900 °C), side reactions such as the thermal decomposition of saturated hydrocarbons C2+ and a polymerization reaction (tar formation) can also occur, which is associated with the thermal decomposition. Such side reactions can, for example, lead to blockages in pipelines. C2H6 → 2C + 3H2 ··· (5) C3H8 → 3C + 4H2 ··· (6)

[0038] In the direct decomposition process of hydrocarbons according to one embodiment of the present disclosure, the process gas from which at least some of the saturated hydrocarbon C2+ has been removed by converting the initial gas to methane is used as the starting gas for the direct decomposition reaction in the methanization device 2. That is, the concentration of the saturated hydrocarbon C2+ in the process gas used as the starting gas for the direct decomposition reaction is lower than that of the original starting gas supplied to the methanization device 2.In contrast to the case in which the initial feed gas supplied to the methanization device 2 is used as the feed gas for the direct decomposition reaction, in the direct decomposition of hydrocarbon method according to an embodiment of the present disclosure it is possible to suppress a side reaction such as a polymerization reaction (tar formation) that accompanies the thermal decomposition of the saturated hydrocarbon C2+ and thus, for example, to reduce the risk of pipeline blockage.

[0039] If the hydrogen return line 7 is provided, at least a portion of the product gas is fed into the hydrogen supply line 3, and thus the hydrogen-containing gas flowing through the hydrogen supply line 3 flows together with the product gas into the housing 10 on the upstream side of the first catalyst layer 11a. This means that at least a portion of the product gas can be used as at least a portion of the hydrogen-containing gas. Since the amount of hydrogen that needs to be directly supplied to the direct decomposition device 1 can be reduced, the operating costs of the direct decomposition device 1 can therefore be lowered.

[0040] If valve 8, an on / off valve, is provided in the hydrogen return line 7, closing valve 8 allows the entire quantity of product gas to be transferred to a storage unit or hydrogen consumption device (not shown) without the product gas being used even partially as hydrogen-containing gas. If valve 8 is a flow control valve, the quantity of product gas used as at least a portion of the hydrogen-containing gas can be adjusted. <Simulation zur Überprüfung der Wirkung des Methanisierungsverfahrens der vorliegenden Offenbarung>

[0041] The following describes a simulation that was carried out to verify the effect of the methanation process of the present disclosure. According to the inventors' investigation in the present disclosure, the preferred temperature range for the methanation described above is 250 °C to 360 °C, whereas the preferred temperature range for the direct decomposition reaction of methane, as described above, is 600 °C to 900 °C. Therefore, it is assumed that the effect of the methanation process of the present disclosure will be adequately achieved if the temperature of the mixed gas exiting each catalyst layer can be controlled to 360 °C or less. (Simulation 1)

[0042] As in Fig.As shown in Figure 2, a simulation was performed using a methanation device configured to provide five catalyst layers I to V in a housing. A feed gas was divided and supplied to the individual catalyst layers as shown in Figures (1) to (5), and a hydrogen gas was supplied to the upstream side of the most upstream catalyst layer I. The composition of the feed gas was 89 vol% methane, 6 vol% ethane, 4 vol% propane, and 1 vol% butane. The adiabatic temperature rise is approximately 180 °C when saturated hydrocarbons C2+ (ethane, propane, or butane) in such a feed gas are converted to methane by methanation in all catalyst layers I to V.In Simulation 1, the ratio of hydrogen concentration to saturated hydrocarbon concentration (C2+) was set to 1.5, and the conditions for the entry of each gas into each catalyst layer were calculated such that the adiabatic temperature rise in each of the catalyst layers (I to V) is 60 °C. The mixed gas, whose temperature has been increased by the heat generated during methanation, is cooled by heat exchange with the coolant in the cooler between the adjacent catalyst layers, thus reducing the temperature by 60 °C. The results are shown in Table 1 below. [Table 1-I] catalyst layer into which each gas flows Flow rate of the mixed gas [Nm³] 3 / Hours.] Hydrogen flow rate [Nm³] 3 / Hours.] Hydrocarbon flow rate [Nm³] 3 / Hours.] methane Saturated hydrocarbon C2+ In total I 393 283 108 12 110 II 543 259 134 16 150 III 753 227 187 23 210 IV 1043 181 258 32 290 V 1439 95 351 43 394 totality 1439 283 1028 128 1156 [Table 1-II] Saturated hydrocarbon content C2+ [Vol.-%] Temperature increase [°C] 3,0 60 3,0 60 3,0 60 3,1 60 3,0 60 8,9 180

[0043] According to Table 1, the temperature of the mixed gas exiting each catalyst layer can be adjusted to 110 Nm by adjusting the supply quantities of the initial gases (1) to (5). 3 / Std. in (1), 150 Nm 3 / Std. in (2), 210 Nm 3 / Std. in (3), 290 Nm 3 / Std. in (4) and 394 Nm 3 / Std. in (5) to 360 °C or less. (Simulation 2)

[0044] As in Fig. As shown in Figure 3, a simulation was performed with a methanation device configured such that two catalyst layers, catalyst layer I and II, were provided in a housing. A feed gas was split as shown in (1) and (2) and fed to the individual catalyst layers, and a hydrogen gas was fed to the upstream side of the most upstream catalyst layer I. In Simulation 2, methane is assumed to be produced at a flow rate of 1121 Nm³ / s. 3 / hr. hydrogen gas is supplied to the upstream side of catalyst layer I, assuming that the hydrogen-containing gas contains a component that does not contribute to methanation. The adiabatic temperature rise in Simulation 2 is approximately 100 °C when the saturated hydrocarbon C2+ in the feed gas, with the same composition as in Simulation 1, is converted to methane through methanation in both catalyst layers I and II. In Simulation 2, analogous to Simulation 1, the ratio of the hydrogen concentration to the saturated hydrocarbon concentration C2+ was set to 1.5, and the conditions for the entry of each gas into each catalyst layer were calculated such that the adiabatic temperature rise in each of catalyst layers I and II was 60 °C.The mixed gas of feed gas and hydrogen gas is cooled by heat exchange with the coolant in the cooler between catalyst layers I and II to reduce the temperature by 60 °C. The results are shown in Table 2 below. The hydrogen feed rate given in Table 2 is a flow rate excluding the methane flow rate. [Table 2-I] catalyst layer into which each gas flows Flow rate of the mixed gas [Nm³] 3 / Hours.] Hydrogen flow rate [Nm³] 3 / Hours.] Hydrocarbon flow rate [Nm³] 3 / Hours.] methane Saturated hydrocarbon C2+ In total I 2070 283 413 51 463 II 2560 259 616 77 693 totality 2560 283 1156 128 1156 [Table 2-II] Saturated hydrocarbon content C2+ [Vol.-%] Temperature increase [°C] 3,0 60 2,9 60 5,0 100

[0045] According to Table 2, the temperature of the mixed gas exiting each catalyst layer can be adjusted to 463 Nm by adjusting the supply quantities of the initial gases (1) and (2). 3 / Std. in (1) and 693 Nm 3 / Std. in (2) to 360 °C or less. (Simulation 3)

[0046] As in Fig.As shown in Figure 4, a simulation was performed with a methanation device configured such that three catalyst layers (catalyst layers I to III) were provided in a housing. A feed gas was split and supplied to the individual catalyst layers as shown in (1) to (3), and hydrogen gas was supplied to the upstream side of the most upstream catalyst layer I. Analogous to Simulation 2, in Simulation 3 it is assumed that methane is supplied at a flow rate of 720 Nm³ / s. 3 / hr is supplied to the hydrogen gas, which is fed to the upstream side of catalyst layer I, assuming that the hydrogen-containing gas contains a component that does not contribute to methanation. The adiabatic temperature rise in Simulation 2 is approximately 120 °C when the saturated hydrocarbon C2+ in the feed gas, with the same composition as in Simulation 1, is converted to methane by methanation in all catalyst layers I to III. In Simulation 3, the ratio of the hydrogen concentration to the saturated hydrocarbon concentration C2+ was set to 1.5, and the conditions for the entry of each gas into each catalyst layer were calculated such that the adiabatic temperature rise in each of the catalyst layers I to III was 60 °C or less.The mixed gas of feed gas and hydrogen gas is cooled by heat exchange with the coolant in the cooler between the adjacent catalyst layers to reduce the temperature by 60 °C. The results are shown in Table 3 below. The hydrogen feed rate given in Table 3 is a flow rate value excluding the methane quantity. [Table 3-I] catalyst layer into which each gas flows Flow rate of the mixed gas [Nm 3 / Hours.] Hydrogen flow rate [Nm 3 / Hours.] methane Hydrocarbon flow rate [Nm³] 3 [Hr.] Saturated hydrocarbon C2+ In total I 1259 283 226 28 254 II 1648 255 347 43 391 III 2159 212 453 56 509 totality 2159 283 1028 128 1156 [Table 3-II] Saturated hydrocarbon content C2+ [Vol.-%] Temperature increase [°C] 2,2 45 2,6 52 2,6 52 5,9 120

[0047] According to Table 3, the temperature of the mixed gas exiting each catalyst layer can be adjusted to 254 Nm by adjusting the supply quantities of the initial gases (1) to (3). 3 / Std. in (1), 391 Nm 3 / Std. in (2) and 509 Nm 3 / Std. in (3) to 360 °C or less.

[0048] Simulations 1 to 3 show that the catalyst layer built up from the catalyst for methanation is divided into a multitude of layers, the feed gas is split and fed to each catalyst layer, and the mixed gas exiting each catalyst layer is cooled in the cooler. Even if the temperature of the mixed gas rises due to methanation in each catalyst layer, the temperature can be suppressed to such an extent that direct decomposition of methane does not occur.

[0049] The content described in each of the embodiments described above is to be understood, for example, as follows.

[0050] [1] A methanization device according to one aspect is a methanization device (2) for removing a saturated hydrocarbon C2+ having two or more carbon atoms from a feedstock gas containing methane and the saturated hydrocarbon C2+ by methanation, wherein the saturated hydrocarbon C2+ is converted to methane by reaction with hydrogen, the methanization device comprising: at least two catalyst layers (11a, 11b) composed of a catalyst for methanation, the at least two catalyst layers (11a, 11b) being arranged at intervals in the direction of flow of a mixed gas containing the feedstock gas and a hydrogen-containing gas; a hydrogen supply line (3) configured to supply the hydrogen-containing gas to the upstream side of a most upstream catalyst layer (11a) in the direction of flow of the mixed gas;an outlet gas supply line (4) configured to supply the outlet gas both to the upstream side of the most upstream catalyst layer (11a) in the direction of flow of the mixed gas and to a space between two adjacent catalyst layers (11a, 11b) in the direction of flow of the mixed gas; and a cooler (13) arranged between two adjacent catalyst layers (11a, 11b) in the direction of flow of the mixed gas, which cools the mixed gas exiting from an upstream catalyst layer (11a) of the two adjacent catalyst layers (11a, 11b) in the direction of flow of the mixed gas.

[0051] According to the methanation device of the present disclosure, the temperature of the mixed gas flowing through each catalyst layer increases due to the methanation process in each catalyst layer. By dividing and supplying the initial gas to each catalyst layer, the methanation process in each catalyst layer can be carried out gently. Furthermore, by cooling the mixed gas exiting each catalyst layer, the temperature of the mixed gas flowing into the adjacent catalyst layer can be reduced. Therefore, even if the temperature of the mixed gas increases due to methanation in each catalyst layer, this increase can be suppressed to such an extent that direct decomposition of methane does not occur, and thus the adhesion of carbon to the catalyst for methanation is also prevented.As a result, deterioration of the catalyst for methanation can be suppressed.

[0052] [2] A methanization device according to another aspect is the methanization device according to [1], wherein the amount of catalyst forming each of the at least two catalyst layers (11a, 11b) is greater when the catalyst layer (11b) is located further downstream in the direction of flow of the mixed gas.

[0053] In the configuration described above [1], the distribution and supply of the feed gas to each catalyst layer increases the amount of mixed gas flowing through the catalyst layer on the downstream side. Therefore, according to the above configuration, the amount of catalyst in each catalyst layer can be adjusted to a suitable quantity corresponding to the amount of mixed gas flowing through that particular catalyst layer, and thus methanation can be carried out in each catalyst layer under suitable conditions.

[0054] [3] A methanization apparatus according to another aspect is the methanization apparatus according to [1] or [2], wherein the catalyst is a supported catalyst in which nickel, iron, cobalt or a precious metal element is supported on aluminium oxide.

[0055] According to such a configuration, methanation can be carried out appropriately in each catalyst layer.

[0056] [4] A device for the direct decomposition of hydrocarbons according to one aspect includes: the methanization device according to one of [1] to [3]; a reactor (22) containing a catalyst (20) for the direct decomposition reaction of a hydrocarbon; and a process gas supply line (5) configured to supply process gas exiting the methanization device (2) to the reactor (22).

[0057] According to the apparatus for the direct decomposition of hydrocarbons of the present disclosure, the content of saturated hydrocarbons C2+ in the process gas is reduced compared to the starting gas, thereby suppressing the risk caused by side reactions such as thermal decomposition and polymerization reaction of saturated hydrocarbons C2+.

[0058] [5] A device for the direct decomposition of hydrocarbons according to another aspect is the device for the direct decomposition of hydrocarbons according to [4], including: a product gas flow line (6) through which a product gas containing hydrogen, which is produced by direct decomposition of hydrocarbons in the reactor (22), flows after exiting the reactor; and a hydrogen return line (7) which connects the product gas flow line (6) to the hydrogen supply line (3).

[0059] In such a configuration, at least some of the hydrogen in the product gas is used as at least some of the hydrogen to be supplied to the methanization device, thereby reducing the amount of hydrogen to be supplied to the direct decomposition device, which in turn leads to a reduction in the operating costs of the hydrocarbon direct decomposition device.

[0060] [6] A methanization process according to one aspect is a methanization process for removing a saturated hydrocarbon C2+ having two or more carbon atoms from a feedstock gas containing methane and the saturated hydrocarbon C2+ by methanation, wherein the saturated hydrocarbon C2+ is converted to methane by reaction with hydrogen, wherein the methanization process includes: causing a hydrogen-containing gas to flow into a most upstream catalyst layer (11a) of at least two catalyst layers (11a, 11b) constructed from a catalyst for methanation, wherein the at least two catalyst layers (11a, 11b) are arranged at intervals in the direction of flow of a mixed gas containing the feedstock gas and a hydrogen-containing gas;Causing a portion of the initial gas to flow into the most upstream catalyst layer (11a) in the direction of flow of the mixed gas; introducing a remainder of the initial gas between two adjacent catalyst layers (11a, 11b) in the direction of flow of the mixed gas; cooling the mixed gas exiting an upstream catalyst layer (11a) of the two adjacent catalyst layers (11a, 11b); and causing the cooled mixed gas and the initial gas introduced between the two adjacent catalyst layers (11a, 11b) in the direction of flow of the mixed gas to flow into a downstream catalyst layer (11b) of the two adjacent catalyst layers (11a, 11b).

[0061] According to the methanation process of the present disclosure, the temperature of the mixed gas flowing through each catalyst layer increases due to the methanation in each catalyst layer. By dividing and supplying the initial gas to each catalyst layer, the methanation in each catalyst layer can be carried out gently. Furthermore, by cooling the mixed gas exiting each catalyst layer, the temperature of the mixed gas flowing into the adjacent catalyst layer in the direction of flow can be reduced. Thus, even if the temperature of the mixed gas increases due to methanation in each catalyst layer, this increase can be suppressed to such an extent that direct decomposition of methane does not occur, and consequently, the adhesion of carbon to the catalyst for methanation can also be suppressed. As a result, deterioration of the catalyst for methanation can be prevented.

[0062] [7] Another methanization process is the methanization process according to [6], in which the amount of hydrogen-containing gas supplied is adjusted so that the concentration ratio of hydrogen to the saturated hydrocarbon C2+ in the mixed gas is 1 or more.

[0063] To convert ethane, which has the fewest carbon atoms among the saturated hydrocarbons (C2+), into methane, one molecule of hydrogen is required for every molecule of ethane. Therefore, according to this process, the saturated hydrocarbons (C2+) in the starting gas can be stoichiometrically converted into methane.

[0064] [8] Another aspect of methanization is the methanization process according to [6] or [7]. The hydrogen-containing gas contains hydrogen and a component that does not contribute to methanization.

[0065] In this process, the concentrations of hydrogen and saturated hydrocarbons (C2+) in each catalyst layer are lower than with hydrogen alone. This suppresses the temperature rise of the mixed gas due to the heat generated during methanation in each catalyst layer, allowing for gentle methanation in each layer. As a result, the temperature rise of the mixed gas in each catalyst layer is suppressed to such an extent that direct decomposition of methane does not occur. Consequently, carbon adhesion to the catalyst and catalyst degradation are also prevented.

[0066] [9] Another aspect of methanization is the methanization process according to [6] to [8], which includes: detecting a decrease in methanization activity; and increasing the amount of hydrogen-containing gas supplied when a decrease in activity is detected.

[0067] According to such a method, it is possible to suppress the deterioration of the catalyst for methanation due to a product formed by side reactions such as thermal decomposition and polymerization reactions of the saturated hydrocarbon C2+, or it is possible to regenerate the deteriorated catalyst.

[0068]

[10] Another methanization process is the methanization process according to one of [6] to [9], where the starting gas is natural gas, compressed natural gas, town gas, liquefied petroleum gas or naphtha.

[0069] According to such a process, a generally available hydrocarbon gas can be used as the starting gas without the need for separate processing of the starting gas.

[0070]

[11] A method for the direct decomposition of hydrocarbons according to one aspect includes: Conversion of the saturated hydrocarbon C2+ in the feed gas to methane by the methanation process according to [6] to

[10] ; and direct decomposition of methane in a process gas, i.e. a gas after the conversion of the saturated hydrocarbon C2+ to methane, into hydrogen and carbon by contacting the process gas with a catalyst (20) for the direct decomposition reaction of a hydrocarbon.

[0071] According to the direct decomposition process of hydrocarbons disclosed herein, the content of saturated hydrocarbons C2+ in the process gas is reduced compared to the starting gas, thereby suppressing the risk caused by side reactions such as thermal decomposition and polymerization of saturated hydrocarbons C2+.

[0072]

[12] A process for the direct decomposition of hydrocarbons according to another aspect is the process for the direct decomposition of hydrocarbons according to

[11] , wherein at least a part of a product gas containing hydrogen, which is produced by direct decomposition of methane in the process gas into hydrogen and carbon, is used as at least a part of the hydrogen-containing gas which is supplied to the catalyst layer (11a) located furthest upstream in the direction of flow of the mixed gas of the catalyst layers (11a, 11b) arranged at intervals.

[0073] In this process, at least some of the hydrogen in the product gas is used as at least some of the hydrogen to be used in the methanization process, thereby reducing the amount of hydrogen required in the methanization process and thus lowering the operating costs of the device for the direct decomposition of hydrocarbons. List of reference symbols 1 Direct decomposition device 2 Methanization device 3 Hydrogen supply line 4. Outlet gas supply line 5 Process gas supply line 6 Product gas flow line 7 Hydrogen return line 11a First catalyst layer (catalyst layer) 11b Second catalyst layer (catalyst layer) 13 coolers 20 catalyst 22 Reactor QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2023-220345

[0001] JP 7089235 B

[0008]

Claims

Methanization device for removing a saturated hydrocarbon with two or more carbon atoms from a feed gas containing methane and the saturated hydrocarbon by methanation, wherein the saturated hydrocarbon is converted to methane by reaction with hydrogen, the methanization device comprising: at least two catalyst layers constructed from a catalyst for methanation, wherein the at least two catalyst layers are arranged at intervals in the flow direction of a mixed gas containing the feed gas and a hydrogen-containing gas; a hydrogen supply line configured to supply the hydrogen-containing gas to the upstream side of a most upstream catalyst layer in the flow direction of the mixed gas;an outlet gas supply line configured to supply the outlet gas both to the upstream side of the most upstream catalyst layer in the direction of flow of the mixed gas and to a space between two adjacent catalyst layers in the direction of flow of the mixed gas; and a cooler arranged in the direction of flow of the mixed gas between two adjacent catalyst layers, cooling the mixed gas exiting from an upstream catalyst layer of the two adjacent catalyst layers in the direction of flow of the mixed gas. Methanization device according to claim 1, wherein the amount of catalyst forming each of the at least two catalyst layers is greater when the catalyst layer is arranged further downstream in the direction of flow of the mixed gas. Methanization apparatus according to claim 1 or 2, wherein the catalyst is a supported catalyst in which nickel, iron, cobalt or a precious metal element is supported on aluminium oxide. Apparatus for the direct decomposition of hydrocarbons, comprising: the methanization apparatus according to claim 1 or 2; a reactor containing a catalyst for the direct decomposition reaction of a hydrocarbon; and a process gas supply line configured to supply a process gas, i.e., a gas exiting the methanization apparatus, to the reactor. Apparatus for the direct decomposition of hydrocarbons according to claim 4, comprising: a product gas flow line through which a product gas containing hydrogen, which is generated by direct decomposition of hydrocarbons in the reactor, flows after exiting the reactor; and a hydrogen return line connecting the product gas flow line to the hydrogen supply line. Methanization process for removing a saturated hydrocarbon with two or more carbon atoms from a feedstock gas containing methane and the saturated hydrocarbon by methanation, wherein the saturated hydrocarbon is converted to methane by reaction with hydrogen, the methanization process comprising: causing a hydrogen-containing gas to flow into a most upstream catalyst layer of at least two catalyst layers constructed from a catalyst for methanation, the at least two catalyst layers being arranged at intervals in the direction of flow of a mixed gas containing the feedstock gas and the hydrogen-containing gas; causing a portion of the feedstock gas to flow into the most upstream catalyst layer in the direction of flow of the mixed gas;Introducing a residue of the initial gas between two adjacent catalyst layers in the direction of flow of the mixed gas; cooling the mixed gas exiting an upstream catalyst layer of the two adjacent catalyst layers; and causing the cooled mixed gas and the initial gas introduced between the two adjacent catalyst layers in the direction of flow of the mixed gas to flow into a downstream catalyst layer of the two adjacent catalyst layers. Methanization process according to claim 6, wherein the feed rate of the hydrogen-containing gas is adjusted such that the concentration ratio of hydrogen to saturated hydrocarbon in the mixed gas is 1 or more. Methanization process according to claim 6 or 7, wherein the hydrogen-containing gas contains hydrogen and a component that does not contribute to methanization. Methanization process according to claim 6 or 7, comprising: detecting a decrease in methanization activity; and increasing the feed rate of the hydrogen-containing gas when a decrease in activity is detected. Methanization process according to claim 6 or 7, wherein the starting gas is natural gas, compressed natural gas, town gas, liquefied petroleum gas or naphtha. A method for the direct decomposition of hydrocarbons, comprising: converting the saturated hydrocarbon in the feed gas to methane by the methanation process according to claim 6 or 7; and directly decomposing methane in a process gas, i.e. a gas after the conversion of the saturated hydrocarbon to methane, into hydrogen and carbon by contacting the process gas with a catalyst for the direct decomposition reaction of a hydrocarbon. A process for the direct decomposition of hydrocarbons according to claim 11, wherein at least a part of a product gas containing hydrogen, which is produced by direct decomposition of methane in the process gas into hydrogen and carbon, is used as at least a part of the hydrogen-containing gas which is supplied to the catalyst layer furthest upstream in the direction of flow of the mixed gas of the at least two catalyst layers arranged at intervals.

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