Methanation apparatus, methanation method, direct decomposition apparatus of hydrocarbon, and direct decomposition method of carbon hydride

Abstract

To provide a methanation apparatus capable of suppressing deterioration of a catalyst for methanation, a methanation method, a direct decomposition apparatus of hydrocarbons, and a direct decomposition method of hydrocarbons.SOLUTION: A methanation apparatus for removing saturated hydrocarbons from a raw material gas by methanation where saturated hydrocarbons having two or more carbon atoms and hydrogen react to convert the saturated hydrocarbons into methane includes at least two catalyst layers 11a, 11b arranged with gaps in between and being catalyst layers for methanation, a hydrogen supply line 3 to provide a hydrogen-containing gas upstream of the most upstream catalyst layer in a circulation direction of a mixed gas, and a raw material gas supply line 4 to supply the raw material gas between an upstream side than the most upstream side catalyst layer and adjacent two catalyst layers, and a cooler 13 that is situated between two adjacent catalyst layers and cools the mixed gas flowing out from the upstream catalyst layer in a circulation direction of the mixed gas among the two adjacent catalyst layers.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a methanation apparatus, a methanation method, a hydrocarbon direct decomposition apparatus, and a hydrocarbon direct decomposition method.

Background Art

[0002] Currently, the production of various types of energy greatly depends on fossil fuels such as petroleum, coal, and natural gas. However, from the perspective of global environmental conservation, an increase in the emission amount of carbon dioxide emitted by the combustion of fossil fuels is regarded as a problem. In the Paris Agreement agreed upon in 2015, in order to address the climate change issue, a reduction in the emission amount of carbon dioxide is required. In thermal power plants and the like, reducing the emission amount of carbon dioxide due to the combustion of fossil fuels has become an important issue. While a process for separating and recovering the emitted carbon dioxide is being intensively studied, technologies for producing energy without emitting carbon dioxide using alternative fuels to fossil fuels are also being studied.

[0003] Therefore, hydrogen, which is a clean fuel that does not emit carbon dioxide by combustion, has been attracting attention as an alternative fuel to fossil fuels. Hydrogen can be produced, for example, by steam reforming of methane contained in natural gas. However, in this production method, carbon monoxide is generated as a by-product, and the carbon monoxide is ultimately oxidized and emitted as carbon dioxide. On the other hand, as methods for producing hydrogen from water without using fossil fuels, water electrolysis methods, photocatalytic methods, and the like have been studied, but these methods require a large amount of energy and have economic problems.

[0004] On the other hand, methods for directly decomposing hydrocarbons to produce hydrogen and carbon have been developed. The characteristics of the direct decomposition of hydrocarbons are that hydrogen fuel can be obtained without discharging carbon dioxide, and the by-produced carbon is solid and can be easily immobilized, and the carbon itself can be effectively utilized in a wide range of applications such as electrode materials, tire materials, and building materials. So far, a method has been developed to directly decompose hydrocarbons into hydrogen and carbon by bringing a supported catalyst into contact with a hydrocarbon gas. However, the problem has been that the catalytic activity decreases in a short time due to the attachment of carbon, which is a product of the direct decomposition reaction of hydrocarbons, to the catalyst.

[0005] On the other hand, as described in Patent Document 1, the applicant of the present disclosure has developed a method for directly decomposing hydrocarbons into carbon and hydrogen using a catalyst that is an unsupported catalyst of an aggregate of a plurality of iron particles. According to this method, even if carbon, which is a product of the direct decomposition reaction of hydrocarbons, adheres to the catalyst, the activity is maintained by expressing new active sites, so it is considered that the activity of this reaction can be maintained for a long time.

[0006] When using, for example, natural gas as the raw material gas for the direct decomposition reaction of hydrocarbons, natural gas contains saturated hydrocarbons having two or more carbon atoms such as ethane, propane, and butane in addition to methane (hereinafter referred to as "saturated hydrocarbon C2+"). Since saturated hydrocarbon C2+ is more reactive than methane, side reactions such as thermal decomposition and polymerization reactions of saturated hydrocarbon C2+ may cause, for example, blockage of pipes at the temperature for causing the direct decomposition reaction of methane. When a raw material gas containing saturated hydrocarbon C2+ is used as the raw material for the direct decomposition reaction of hydrocarbons, it is necessary to remove saturated hydrocarbon C2+ from the raw material gas in order to suppress such risks.

[0007] Taking ethane, propane, and butane as examples of saturated hydrocarbons C2+, as shown in the following reaction formulas (1) to (3), each saturated hydrocarbon C2+ reacts with hydrogen to convert each saturated hydrocarbon C2+ into methane, thereby enabling removal from the raw material gas. Generally, synthesizing methane from hydrogen and carbon dioxide is often referred to as methanation. However, in this disclosure, as shown in reaction formulas (1) to (3), the reaction in which saturated hydrocarbon C2+ reacts with hydrogen to convert saturated hydrocarbon C2+ into methane will be defined as "methanation". C2H6 + H2 → 2CH4 ···(1) C3H8 + 2H2 → 3CH4 ···(2) C4H 10 + 3H2 → 4CH4 ···(3)

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, depending on the temperature conditions of methanation, a part of the methane contained in the raw material gas or the converted methane may be directly decomposed into hydrogen and carbon. Then, carbon adheres to the methanation catalyst, causing the methanation catalyst to deteriorate and the activity of methanation to decrease. As a result, the performance of removing saturated hydrocarbon C2+ from the raw material gas may decrease.

[0010] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a methanation apparatus, a methanation method, a hydrocarbon direct decomposition apparatus, and a hydrocarbon direct decomposition method that can suppress the deterioration of the catalyst for methanation.

Means for Solving the Problems

[0011] To achieve the above object, the methanation apparatus according to the present disclosure is a methanation apparatus that removes a saturated hydrocarbon C2+ from a raw material gas containing methane and the saturated hydrocarbon C2+ by methanation in which a saturated hydrocarbon C2+ having two or more carbon atoms reacts with hydrogen to convert the saturated hydrocarbon C2+ into methane. The methanation apparatus includes at least two catalyst layers composed of the catalyst for methanation, at least two catalyst layers provided at intervals in the flow direction of a mixed gas containing the raw material gas and a hydrogen-containing gas, a hydrogen supply line for supplying the hydrogen-containing gas upstream of the catalyst layer on the most upstream side in the flow direction of the mixed gas, a raw material gas supply line for supplying the raw material gas to each of the upstream side of the catalyst layer on the most upstream side in the flow direction of the mixed gas and between two adjacent catalyst layers in the flow direction of the mixed gas, and a cooler provided between two adjacent catalyst layers in the flow direction of the mixed gas for cooling the mixed gas flowing out from the catalyst layer on the upstream side in the flow direction of the mixed gas among the two adjacent catalyst layers.

[0012] In addition, the methanation method according to the present disclosure is a methanation method for removing saturated hydrocarbon C2+ from a raw material gas containing methane and the saturated hydrocarbon C2+ by methanation in which a saturated hydrocarbon C2+ having two or more carbon atoms reacts with hydrogen to convert the saturated hydrocarbon C2+ into methane. The method includes at least two catalyst layers composed of the catalyst for methanation. Among the at least two catalyst layers provided at intervals in the flow direction of a mixed gas containing the raw material gas and a hydrogen-containing gas, a step of flowing the hydrogen-containing gas through the catalyst layer on the most upstream side, a step of flowing a part of the raw material gas through the catalyst layer on the most upstream side in the flow direction of the mixed gas, a step of supplying the remainder of the raw material gas between two adjacent catalyst layers in the flow direction of the mixed gas, a step of cooling the mixed gas flowing out from the catalyst layer on the upstream side among the two adjacent catalyst layers, and a step of flowing the cooled mixed gas and the raw material gas supplied between two adjacent catalyst layers in the flow direction of the mixed gas through the catalyst layer on the downstream side among the two adjacent catalyst layers.

Advantages of the Invention

[0013] According to the methanation apparatus and the methanation method of the present disclosure, the temperature of the mixed gas flowing through each catalyst layer increases due to methanation in each catalyst layer. However, by dividing and supplying the raw material gas to each catalyst layer, methanation in each catalyst layer can be moderated. Further, by cooling the mixed gas flowing out from each catalyst layer, the temperature of the mixed gas flowing into the adjacent catalyst layer in the flow direction of the mixed gas can be decreased. Thereby, even if the temperature of the mixed gas increases due to methanation in each catalyst layer, it can be suppressed to such an extent that direct decomposition of methane does not occur. Therefore, attachment of carbon to the catalyst for methanation can be suppressed, and as a result, deterioration of the catalyst for methanation can be suppressed.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0015] Hereinafter, a methanation apparatus and a methanation method according to an embodiment of the present disclosure will be described with reference to the drawings. The embodiments described below show one aspect of the present disclosure, do not limit this disclosure, and can be arbitrarily changed within the scope of the technical idea of this disclosure.

[0016] <Configuration of a Methanation Apparatus and a Hydrocarbon Direct Decomposition Apparatus According to an Embodiment of the Present Disclosure> In the following embodiments, a methanation apparatus according to an embodiment of the present disclosure will be described as one component of a hydrocarbon direct decomposition apparatus, but it is not limited to this form, and it may be one component of any apparatus or a form used as a single apparatus. As shown in FIG. 1, a hydrocarbon direct decomposition apparatus 1 according to an embodiment of the present disclosure includes a methanation apparatus 2 and a reactor 22. The methanation apparatus 2 and the reactor 22 are communicated by a treated gas supply line 5. The direct decomposition apparatus 1 may include a gas chromatography 16 for sampling a part of the gas (treated gas described later) flowing through the treated gas supply line 5 and measuring the composition of the gas.

[0017] The methanation device 2 includes a housing 10. Inside the housing 10, a catalyst layer 11 composed of a methanation catalyst and a cooler 13 are provided. The catalyst layer 11 includes two catalyst layers provided at an interval between both ends of the housing 10, that is, a first catalyst layer 11a and a second catalyst layer 11b. As will be described later, in the housing 10, gas flows in a direction from one end of the housing 10 toward the other end. In the gas flow direction, the upstream catalyst layer is the first catalyst layer 11a, and the downstream catalyst layer is the second catalyst layer 11b. As the methanation catalyst, any methanation catalyst can be used, and examples thereof include supported catalysts in which nickel, iron, cobalt, or a noble metal element is supported on alumina. The catalyst shape is not particularly limited, and catalysts of any shape such as a tablet shape, a ring shape, an extruded shape, and a granular pellet shape can be used.

[0018] A space 12 is formed between the first catalyst layer 11a and the second catalyst layer 11b inside the housing 10, and a cooler 13 is provided in the space 12. The configuration of the cooler 13 is not particularly limited, but the cooler 13 may have, for example, a configuration in which the above-described gas and an arbitrary refrigerant exchange heat to cool the gas.

[0019] In the configuration of FIG. 1, two catalyst layers (that is, a first catalyst layer 11a and a second catalyst layer 11b) and one cooler 13 provided between them (that is, inside the space 12) are provided in the housing 10. However, a form in which three or more catalyst layers, that is, at least two catalyst layers are provided may also be used. In a configuration in which three or more catalyst layers are provided, a cooler 13 is provided in each of the spaces 12 between two adjacent catalyst layers in the above-described gas flow direction.

[0020] The methanation apparatus 2 further includes a hydrogen supply line 3 for supplying a hydrogen-containing gas into the housing 10 and a raw material gas supply line 4 for supplying a raw material gas into the housing 10. The hydrogen supply line 3 is connected to the housing 10 upstream of the first catalyst layer 11a in the above-described gas flow direction within the housing 10. A flow rate control valve 14 for adjusting the supply amount of the hydrogen-containing gas into the housing 10 may be provided in the hydrogen supply line 3. The hydrogen-containing gas flowing through the hydrogen supply line 3 may be pure hydrogen gas or a mixed gas of components that do not contribute to methanation (noble gas, nitrogen, methane, etc.) and hydrogen. The raw material gas is a gas containing methane and a saturated hydrocarbon C2+ having two or more carbon atoms (ethane, propane, butane, etc.). For example, natural gas, compressed natural gas (CNG), town gas, liquefied petroleum gas, naphtha, etc. can be used as the raw material gas. Therefore, the above-described gas flowing through the housing 10 is a mixed gas including the hydrogen-containing gas supplied into the housing 10 via the hydrogen supply line 3 and the raw material gas supplied into the housing 10 via the raw material gas supply line 4.

[0021] The raw material gas supply line 4 branches into branch lines 4a and 4b. One branch line 4a is connected to the housing 10 upstream of the first catalyst layer 11a in the flow direction of the above-mentioned mixed gas in the housing 10, and the other branch line 4b is connected to the housing 10 between the first catalyst layer 11a and the second catalyst layer 11b. The branch line 4a may be connected to the housing 10 without merging with the hydrogen supply line 3, or may merge with the hydrogen supply line 3 as shown in FIG. 1. The branch line 4b only needs to be connected to the housing 10 so as to communicate with the space 12. The raw material gas flowing into the space 12 through the branch line 4b may flow upstream of the cooler 13, or may flow downstream of the cooler 13, or may flow into the region where the cooler 13 is provided. Flow control valves 15a and 15b for adjusting the supply amount of the raw material gas supplied into the housing 10 through the branch lines 4a and 4b may be provided in the branch lines 4a and 4b respectively. The hydrogen supply line 3 may be provided with branch lines like the raw material gas supply line 4, and each of the branch lines of the hydrogen supply line 3 may be connected to the housing 10 upstream of the first catalyst layer 11a and between the first catalyst layer 11a and the second catalyst layer 11b respectively.

[0022] A catalyst 20 for the direct decomposition reaction of hydrocarbons is accommodated in the reactor 22. The reactor 22 is provided with a heating device 21 (for example, a jacket through which steam flows) for heating the interior of the reactor 22, particularly the catalyst 20. A product gas flow line 6 is connected to the reactor 22 on the side opposite to the position where the treated gas supply line 5 is connected to the reactor 22 with respect to the catalyst 20.

[0023] The catalyst 20 is not particularly limited, and for example, it may be a non-supported catalyst that is an aggregate of a plurality of iron particles. In the reactor 22, each particle of the catalyst 20 may be in a stationary state, or may be in a fluidized bed state in which the particles are suspended in the raw material gas by ejecting the processed gas described later upward. When hydrocarbons react with the catalyst 20, carbon and hydrogen are generated, and the carbon adheres to the particles of the catalyst 20. When the catalyst 20 forms a fluidized bed, the carbon adhering to the particles of the catalyst 20 is physically removed from the particles by the particles of the catalyst 20 rubbing against each other. When, for example, a fixed bed reactor is used as the reactor 22, a carbon removal device may be provided outside the reactor 22 in order to remove the carbon adhering to the catalyst 20 from the catalyst 20.

[0024] The direct decomposition device 1 may further include a hydrogen recycle line 7 that communicates the product gas flow line 6 and the hydrogen supply line 3. A valve 8 that may be either an on-off valve or a flow rate control valve may be provided in the hydrogen recycle line 7.

[0025] <Operation of the methanation device according to an embodiment of the present disclosure> Next, the operation (methanation method) of the methanation device according to an embodiment of the present disclosure will be described. A hydrogen-containing gas flows into the housing 10 upstream of the first catalyst layer 11a through the hydrogen supply line 3. A part of the raw material gas flowing through the raw material gas supply line 4 flows into the housing 10 upstream of the first catalyst layer 11a through the branch line 4a.

[0026] The hydrogen-containing gas and the raw material gas that flow into the housing 10 upstream of the first catalyst layer 11a flow into the first catalyst layer 11a. In the first catalyst layer 11a, by the action of the catalyst for methanation, the saturated hydrocarbon C2+ in the raw material gas reacts with the hydrogen in the hydrogen-containing gas to produce methane, and a mixed gas containing methane, unreacted saturated hydrocarbon C2+, and unreacted hydrogen flows out of the first catalyst layer 11a and into the space 12. Although the temperature of the mixed gas rises due to the heat of reaction by such methanation, compared with the case where the total amount of the raw material gas flowing through the raw material gas supply line 4 is supplied into the housing 10 upstream of the first catalyst layer 11a, in the above-described operation, the methanation in the first catalyst layer 11a becomes gentle (the reaction amount of methanation decreases), so that the temperature rise of the mixed gas flowing out of the first catalyst layer 11a can be suppressed.

[0027] In the methanation apparatus 2 having the configuration shown in FIG. 1, the catalyst layer 11 is divided into two and the raw material gas is divided into two and supplied. However, if the number of divisions of the catalyst layer 11 (that is, the number of divisions of the raw material gas) is increased, the flow rate of the raw material gas flowing through the first catalyst layer 11a becomes small, so that the methanation in the first catalyst layer 11a becomes gentler, and the temperature rise of the mixed gas flowing out of the first catalyst layer 11a can be more suppressed. If the temperature rise of the mixed gas flowing out of the first catalyst layer 11a can be suppressed to such an extent that direct decomposition of methane does not occur, the occurrence of the direct decomposition reaction of methane in the first catalyst layer 11a can be suppressed, and the adhesion of carbon to the catalyst for methanation constituting the first catalyst layer 11a can be suppressed, so that the deterioration of the catalyst for methanation can be suppressed.

[0028] The mixed gas flowing into the space 12 is cooled by exchanging heat with the refrigerant flowing through the cooler 13. The thus-cooled mixed gas and the source gas flowing in through the branch line 4b flow into the second catalyst layer 11b. Also in the second catalyst layer 11b, in the same principle as in the first catalyst layer 11a, saturated hydrocarbons C2+ and hydrogen react to produce methane. Since the mixed gas cooled by the cooler 13 flows into the second catalyst layer 11b, even if the temperature of the mixed gas in the second catalyst layer 11b rises due to such methanation, the temperature of the mixed gas can be suppressed to a temperature at which direct decomposition of methane does not occur. As a result, the occurrence of the direct decomposition reaction of methane can be suppressed also in the second catalyst layer 11b, and the adhesion of carbon to the catalyst for methanation constituting the second catalyst layer 11b can be suppressed, so that the deterioration of the catalyst for methanation can be suppressed.

[0029] According to such a methanation method, due to methanation in each of the first catalyst layer 11a and the second catalyst layer 11b, the temperature of the mixed gas flowing through each of the first catalyst layer 11a and the second catalyst layer 11b rises. However, by dividing and supplying the source gas to each of the first catalyst layer 11a and the second catalyst layer 11b, methanation in each of the first catalyst layer 11a and the second catalyst layer 11b can be moderated. Further, by cooling the mixed gas flowing out from the first catalyst layer 11a, the temperature of the mixed gas flowing into the adjacent second catalyst layer 11b in the flow direction of the mixed gas can be lowered. Thereby, even if the temperature of the mixed gas rises due to methanation in each of the first catalyst layer 11a and the second catalyst layer 11b, it can be suppressed to such an extent that direct decomposition of methane does not occur. Thus, the adhesion of carbon to the catalyst for methanation can be suppressed, and as a result, the deterioration of the catalyst for methanation can be suppressed.

[0030] In such a methanation method, since the raw material gas is split and supplied through the branch lines 4a and 4b, the flow rate of the mixed gas flowing through the second catalyst layer 11b is larger than the flow rate of the mixed gas flowing through the first catalyst layer 11a. Therefore, it is preferable to increase the amount of the catalyst constituting the second catalyst layer 11b as compared with the amount of the catalyst constituting the first catalyst layer 11a. Thereby, since the amount of the catalyst for each of the first catalyst layer 11a and the second catalyst layer 11b can be adjusted to an appropriate amount according to the amount of the mixed gas flowing through each of the first catalyst layer 11a and the second catalyst layer 11b, methanation in each of the first catalyst layer 11a and the second catalyst layer 11b can be carried out under appropriate conditions. In addition, when the catalyst layer 11 is composed of three or more catalyst layers, the amount of the catalyst constituting each catalyst layer may be increased as the catalyst layer on the downstream side in the flow direction of the mixed gas is increased.

[0031] In such a methanation method, when the hydrogen-containing gas contains components that do not contribute to methanation, the concentrations of hydrogen and saturated hydrocarbon C2+ in each catalyst layer are lower than those when the hydrogen-containing gas contains only hydrogen. Therefore, the temperature rise of the mixed gas due to the heat generated during methanation in each catalyst layer is suppressed, so that methanation in each catalyst layer can be made gentle. As a result, the temperature rise of the mixed gas in each catalyst layer can be suppressed to such an extent that direct decomposition of methane does not occur, so that carbon deposition on the methanation catalyst can be suppressed and deterioration of the methanation catalyst can be suppressed.

[0032] In such a methanation method, it is preferable to adjust the supply amount of the hydrogen-containing gas so that the concentration ratio of hydrogen to saturated hydrocarbon C2+ in the mixed gas becomes 1 or more. In order to convert ethane, which has the smallest number of carbon atoms among saturated hydrocarbons C2+, into methane, one molecule of hydrogen is required for one molecule of ethane. Therefore, by adjusting to such conditions, the saturated hydrocarbon C2+ in the raw material gas can be converted into methane stoichiometrically.

[0033] In a configuration provided with a gas chromatography 16 and a flow rate control valve 14, it is possible to detect a decrease in the activity of the methanation in the methanation apparatus 2 from the measurement results of the gas chromatography 16. When a decrease in the activity of the methanation is detected, the supply amount of the hydrogen-containing gas can be increased by the flow rate control valve 14. When the supply amount of the hydrogen-containing gas is increased, the concentration of hydrogen in the mixed gas increases. Then, since it becomes easier for hydrogen to react with carbon, polymerization reactants, etc. attached to the catalyst for methanation, the attached carbon, polymerization reactants, etc. can be converted into gases such as methane, and the deposits can be removed from the catalyst. That is, it is possible to suppress the deterioration of the methanation catalyst by products generated by side reactions such as thermal decomposition and polymerization reactions of saturated hydrocarbons C2+ or to regenerate the deteriorated catalyst.

[0034] If the raw material gas contains a sulfur component, the catalyst for methanation may be deteriorated by the sulfur component. Therefore, it is preferable to provide a desulfurization device in the raw material gas supply line 4 to remove the sulfur component from the raw material gas before the raw material gas flows into the housing 10.

[0035] <Operation of the hydrocarbon direct decomposition apparatus according to an embodiment of the present disclosure> Next, the operation (hydrocarbon direct decomposition method) of the hydrocarbon direct decomposition apparatus according to an embodiment of the present disclosure will be described. The mixed gas flowing out from the second catalyst layer 11b flows out of the housing 10, flows through the treated gas supply line 5 as treated gas, and flows into the reactor 22. The treated gas flowing into the reactor 22 passes through the catalyst 20 while contacting the catalyst 20. At this time, the hydrocarbons in the treated gas are directly decomposed into hydrogen and carbon. Taking methane as an example of the hydrocarbon in this direct decomposition reaction, the reaction represented by the following reaction formula (4) occurs in the reactor 22. CH4→2H2+C ···(4)

[0036] The carbon generated by the direct decomposition method adheres to the catalyst 20, and the generated hydrogen flows out of the reactor 22 as product gas together with the unreacted hydrocarbon and flows through the product gas flow line 6. The recovery of carbon can be carried out by recovering the catalyst 20 from the reactor 22 after stopping the supply of the treated gas to the reactor 22 and removing the carbon adhering to the catalyst 20 by a carbon removal device if necessary. The recovery of hydrogen is carried out by recovering the reaction gas flowing through the product gas flow line 6. By providing a hydrogen purification device in the product gas flow line 6, hydrogen can be purified. In this case, when the conversion rate of the hydrocarbon is low, the hydrogen concentration in the treated gas becomes low, but the hydrogen purification device can increase the concentration of hydrogen as the final product.

[0037] In addition to methane as the hydrocarbon, if saturated hydrocarbons C2+ such as ethane and propane are contained in the treated gas, for example, ethane and propane are also directly decomposed into hydrogen and carbon as shown in the following reaction formulas (5) and (6). However, at the temperature for causing the direct decomposition reaction of methane (preferably 600°C to 900°C), side reactions such as thermal decomposition of saturated hydrocarbons C2+ and accompanying polymerization reactions (tar formation) may also occur, and such side reactions may cause, for example, blockage of pipes. C2H6→2C+3H2···(5) C3H8→3C+4H2···(6)

[0038] However, in the method for directly decomposing hydrocarbons according to an embodiment of the present disclosure, in the methanation apparatus 2, at least a part of the saturated hydrocarbon C2+ in the raw material gas is converted into methane, and the treated gas removed thereby is used as the raw material gas for the direct decomposition reaction. That is, the concentration of saturated hydrocarbon C2+ in the treated gas used as the raw material gas for the direct decomposition reaction is lower than that in the initial raw material gas supplied to the methanation apparatus 2. Therefore, compared with the case where the initial raw material gas supplied to the methanation apparatus 2 is used as the raw material gas for the direct decomposition reaction, in the method for directly decomposing hydrocarbons according to an embodiment of the present disclosure, side reactions such as polymerization reactions (tar formation) accompanying the thermal decomposition of saturated hydrocarbon C2+ can be suppressed, so that the risk of pipe blockage and the like can be reduced.

[0039] When the hydrogen recycle line 7 is provided, at least a part of the product gas is supplied to the hydrogen supply line 3, so that the hydrogen-containing gas flowing through the hydrogen supply line 3 flows into the housing 10 upstream of the first catalyst layer 11a together with the product gas. That is, at least a part of the product gas can be used as at least a part of the hydrogen-containing gas. Thereby, the amount of hydrogen supplied to the direct decomposition apparatus 1 can be reduced, so that the operation cost of the direct decomposition apparatus 1 can be reduced.

[0040] When the valve 8, which is an on-off valve, is provided in the hydrogen recycle line 7, by closing the valve 8, the entire amount of the product gas can be transferred to a storage unit (not shown) or a hydrogen-consuming facility without using the product gas as at least a part of the hydrogen-containing gas. When the valve 8 is a flow rate regulating valve, the amount of the product gas used as at least a part of the hydrogen-containing gas can be adjusted.

[0041] <Simulation for verifying the effects of the methanation method of the present disclosure> Next, a simulation conducted to verify the effects of the methanation method of the present disclosure will be described. According to the study by the inventors of the present disclosure, while the suitable temperature range for the above methanation is 250°C to 360°C, the suitable temperature range for the direct decomposition reaction of methane is 600°C to 900°C as described above. Therefore, in the methanation method of the present disclosure, if the temperature of the mixed gas flowing out from each catalyst layer can be controlled to 360°C or lower, it is considered that the above effects can be appropriately achieved.

[0042] (Simulation 1) As shown in FIG. 2, a simulation was performed in a methanation apparatus in which five catalyst layers of catalyst layers I to V are provided in a housing, the raw material gas is divided into each catalyst layer and supplied as (1) to (5), and hydrogen gas is supplied upstream of the most upstream catalyst layer I. The composition of the raw material gas was 89 vol% methane, 6 vol% ethane, 4 vol% propane, and 1 vol% butane. The adiabatic temperature rise when saturated hydrocarbons C2+ (ethane, propane, butane) in such a raw material gas are converted to methane by methanation throughout catalyst layers I to V is about 180°C. In Simulation 1, on the basis that the ratio of the concentration of hydrogen to the concentration of saturated hydrocarbon C2+ is 1.5, the conditions of each gas flowing into each catalyst layer were calculated such that the adiabatic temperature rise in each of catalyst layers I to V is 60°C. At that time, it is assumed that the mixed gas whose temperature has risen due to the heat generation during the above methanation is cooled by heat exchange with a refrigerant in a cooler between adjacent catalyst layers, and the temperature drops by 60°C. The results are shown in Table 1 below.

[0043] [Table 1]

[0044] According to Table 1, the supply amounts of the raw material gases (1) to (5) are (1) 110 Nm 3 / hr, (2) 150 Nm 3 / hr, (3) 210 Nm 3 / hr, (4) 290 Nm 3 / hr, (5) 394 Nm 3 By setting it to / hr, the temperature of the mixed gas flowing out from each catalyst layer can be controlled to 360°C or lower.

[0045] (Simulation 2) As shown in Figure 3, a simulation was conducted on a methanation apparatus configured such that two catalyst layers, catalyst layer I and catalyst layer II, are provided in a housing, raw material gas is divided and supplied to each catalyst layer as in (1) and (2), and hydrogen gas is supplied upstream of the most upstream catalyst layer I. In Simulation 2, assuming that the hydrogen-containing gas contains components that do not contribute to methanation, 1121 Nm 3 / hr of methane is supplied to the hydrogen gas supplied upstream of catalyst layer I. When the saturated hydrocarbon C2+ in the raw material gas with the same composition as in Simulation 1 is converted to methane by methanation throughout catalyst layers I and II, the adiabatic temperature rise is approximately 100°C in Simulation 2. Also in Simulation 2, similar to Simulation 1, with the ratio of the concentration of hydrogen to the concentration of saturated hydrocarbon C2+ set to 1.5, the conditions of each gas flowing into each catalyst layer were calculated such that the adiabatic temperature rise in each of catalyst layers I and II is 60°C. At that time, it is assumed that the mixed gas of the raw material gas and the hydrogen gas is cooled by heat exchange with a refrigerant in a cooler between catalyst layers I and II, and the temperature drops by 60°C. The results are shown in Table 2 below. The supplied amount of hydrogen in Table 2 is the flow rate excluding the supplied amount of methane.

[0046] [Table 2]

[0047] According to Table 2, by setting the supplied amounts of the raw material gases (1) and (2) to (1) 463 Nm 3 / hr, (2) 693 Nm 3 / hr, the temperature of the mixed gas flowing out from each catalyst layer can be controlled to 360°C or lower.

[0048] (Simulation 3) As shown in Fig. 4, simulations were carried out for a methanation apparatus configured such that three catalyst layers, i.e., catalyst layers I to III, are provided in a housing, raw material gas is divided and supplied to each catalyst layer as shown in (1) to (3), and hydrogen gas is supplied upstream of the catalyst layer I on the most upstream side. In Simulation 3, as in Simulation 2, assuming that the component not contributing to methanation is contained in the hydrogen-containing gas, 720 Nm 3 / hr of methane is supplied to the hydrogen gas supplied upstream of the catalyst layer I. When the saturated hydrocarbon C2+ in the raw material gas having the same composition as in Simulation 1 is converted to methane by methanation throughout the catalyst layers I to III, the adiabatic temperature rise in Simulation 2 is about 120°C. In Simulation 3, with the ratio of the concentration of hydrogen to the concentration of saturated hydrocarbon C2+ being 1.5, the conditions of each gas flowing into each catalyst layer were calculated such that the adiabatic temperature rise in each of the catalyst layers I to III is 60°C or less. At that time, it is assumed that the mixed gas of the raw material gas and the hydrogen gas is cooled by heat exchange with a refrigerant in a cooler between adjacent catalyst layers, and the temperature drops by 60°C. The results are shown in Table 3 below. The hydrogen supply amount in Table 3 is the flow rate excluding the methane supply amount.

[0049]

Table 3

[0050] According to Table 3, by setting the supply amounts of the raw material gases (1) to (3) to (1) 254 Nm 3 / hr, (2) 391 Nm 3 / hr, and (3) 509 Nm 3 / hr, the temperature of the mixed gas flowing out of each catalyst layer can be controlled to 360°C or lower.

[0051] From Simulations 1 to 3, the catalyst layer composed of the catalyst for methanation is divided into a plurality of layers, the raw material gas is divided and supplied to each catalyst layer, and the mixed gas flowing out from each catalyst layer is cooled by a cooler, so that even if the temperature of the mixed gas rises due to methanation in each catalyst layer, the direct decomposition of methane can be suppressed to such an extent that it does not occur.

[0052] The content described in each of the above embodiments is understood as follows, for example.

[0053] [1] The methanation apparatus according to one aspect is a methanation apparatus (2) for removing the saturated hydrocarbon C2+ from a raw material gas containing methane and the saturated hydrocarbon C2+ by methanation in which the saturated hydrocarbon C2+ having two or more carbon atoms reacts with hydrogen to convert the saturated hydrocarbon C2+ into methane, at least two catalyst layers (11a, 11b) composed of the catalyst for methanation, the at least two catalyst layers (11a, 11b) being provided at intervals in the flow direction of the mixed gas containing the raw material gas and the hydrogen-containing gas, a hydrogen supply line (3) for supplying the hydrogen-containing gas upstream of the catalyst layer (11a) on the most upstream side in the flow direction of the mixed gas, a raw material gas supply line (4) for supplying the raw material gas to each of the upstream side of the catalyst layer (11a) on the most upstream side in the flow direction of the mixed gas and between two adjacent catalyst layers (11a, 11b) in the flow direction of the mixed gas, a cooler (13) provided between two adjacent catalyst layers (11a, 11b) in the flow direction of the mixed gas, for cooling the mixed gas flowing out from the catalyst layer (11a) on the upstream side in the flow direction of the two adjacent catalyst layers (11a, 11b), and comprising.

[0054] According to the methanation apparatus of the present disclosure, the temperature of the mixed gas flowing through each catalyst layer rises due to methanation in each catalyst layer. However, by dividing and supplying the raw material gas to each catalyst layer, methanation in each catalyst layer can be moderated. Furthermore, by cooling the mixed gas flowing out from each catalyst layer, the temperature of the mixed gas flowing into the adjacent catalyst layer in the flow direction of the mixed gas can be lowered. As a result, even if the temperature of the mixed gas rises due to methanation in each catalyst layer, it can be suppressed to such an extent that direct decomposition of methane does not occur. Therefore, it is possible to suppress carbon from adhering to the catalyst for methanation, and as a result, deterioration of the catalyst for methanation can be suppressed.

[0055] [2] The methanation apparatus according to another aspect is the methanation apparatus of [1], wherein The amount of the catalyst constituting each of the at least two catalyst layers (11a, 11b) is larger in the downstream catalyst layer (11b) in the flow direction of the mixed gas.

[0056] According to the configuration of [1] above, by dividing and supplying the raw material gas to each catalyst layer, the amount of the mixed gas flowing through the downstream catalyst layer becomes larger. Therefore, according to the above configuration, the amount of the catalyst in each catalyst layer can be made an appropriate amount according to the amount of the mixed gas flowing through each catalyst layer, so that methanation in each catalyst layer can be carried out under appropriate conditions.

[0057] [3] The methanation apparatus according to still another aspect is the methanation apparatus according to [1] or [2], wherein The catalyst is a supported catalyst in which nickel, iron, cobalt, or an alkali metal element is supported on alumina.

[0058] According to such a configuration, methanation can be appropriately carried out in each catalyst layer.

[0059] [4] The hydrocarbon direct decomposition apparatus according to one aspect is [1] to [3] Any one of the methanation apparatuses, and A reactor (22) containing a catalyst (20) for the direct decomposition reaction of hydrocarbons, A treated gas supply line (5) for supplying a treated gas, which is the gas flowing out from the methanation apparatus (2), to the reactor (22), is provided.

[0060] According to the hydrocarbon direct decomposition apparatus of the present disclosure, since the content of saturated hydrocarbon C2+ in the treated gas is lower than that in the raw material gas, the risk caused by side reactions such as thermal decomposition and polymerization reaction of saturated hydrocarbon C2+ can be suppressed.

[0061] [5] A hydrocarbon direct decomposition apparatus according to another aspect is the hydrocarbon direct decomposition apparatus of [4], A product gas flow line (6) through which a product gas containing hydrogen generated by direct decomposition of hydrocarbons in the reactor (22) flows after flowing out of the reactor, A hydrogen recycle line (7) that communicates the product gas flow line (6) and the hydrogen supply line (3), is provided.

[0062] According to such a configuration, since at least a part of the hydrogen in the product gas is used as at least a part of the hydrogen supplied to the methanation apparatus, the amount of hydrogen supplied to the direct decomposition apparatus can be reduced, and as a result, the operating cost of the hydrocarbon direct decomposition apparatus can be reduced.

[0063] [6] A methanation method according to one aspect is A methanation method for removing saturated hydrocarbon C2+ from a raw material gas containing methane and the saturated hydrocarbon C2+ by methanation in which a saturated hydrocarbon C2+ having two or more carbon atoms reacts with hydrogen to convert the saturated hydrocarbon C2+ into methane, At least two catalyst layers (11a, 11b) composed of the catalyst for the methanation, and a step of flowing the hydrogen-containing gas through the catalyst layer (11a) on the most upstream side among the at least two catalyst layers (11a, 11b) provided at intervals in the flow direction of the mixed gas containing the raw material gas and the hydrogen-containing gas. A step of flowing a part of the raw material gas through the catalyst layer (11a) on the most upstream side in the flow direction of the mixed gas. A step of supplying the remainder of the raw material gas between two adjacent catalyst layers (11a, 11b) in the flow direction of the mixed gas. A step of cooling the mixed gas flowing out from the catalyst layer (11a) on the upstream side among the two adjacent catalyst layers (11a, 11b). A step of flowing the cooled mixed gas and the raw material gas supplied between two adjacent catalyst layers (11a, 11b) in the flow direction of the mixed gas through the catalyst layer (11b) on the downstream side among the two adjacent catalyst layers (11a, 11b). Including.

[0064] According to the methanation method of the present disclosure, due to the methanation in each catalyst layer, the temperature of the mixed gas flowing through each catalyst layer rises. However, by dividing and supplying the raw material gas to each catalyst layer, the methanation in each catalyst layer can be moderated. Furthermore, by cooling the mixed gas flowing out from each catalyst layer, the temperature of the mixed gas flowing into the adjacent catalyst layer in the flow direction of the mixed gas can be lowered. As a result, even if the temperature of the mixed gas rises due to methanation in each catalyst layer, it can be suppressed to such an extent that direct decomposition of methane does not occur. Therefore, it is possible to suppress the adhesion of carbon to the catalyst for methanation, and as a result, it is possible to suppress the deterioration of the catalyst for methanation.

[0065] [7] The methanation method according to another aspect is the methanation method of [6], Adjust the supply amount of the hydrogen-containing gas so that the concentration ratio of hydrogen to the saturated hydrocarbon C2+ in the mixed gas is 1 or more.

[0066] In order to convert ethane, which has the fewest carbon atoms among saturated hydrocarbons C2+ , into methane, one molecule of hydrogen is required per molecule of ethane. Therefore, according to such a method, stoichiometrically, saturated hydrocarbons C2+ in the raw material gas can be converted into methane.

[0067] [8] The methanation method according to still another aspect is the methanation method of [6] or [7], wherein the hydrogen-containing gas contains a component that does not contribute to the methanation and hydrogen.

[0068] According to such a method, since the concentrations of hydrogen and saturated hydrocarbons C2+ in each catalyst layer are lower than those in the case where only hydrogen is supplied, the temperature rise of the mixed gas due to the heat generated during methanation in each catalyst layer is suppressed. Therefore, methanation in each catalyst layer can be moderated. As a result, the temperature rise of the mixed gas in each catalyst layer can be suppressed to such an extent that direct decomposition of methane does not occur. Therefore, it is possible to suppress the adhesion of carbon to the methanation catalyst and suppress the deterioration of the methanation catalyst.

[0069] [9] The methanation method according to still another aspect is the methanation method of any one of [6] to [8], including a step of detecting a decrease in the activity of the methanation, and a step of increasing the supply amount of the hydrogen-containing gas when the decrease in the activity is detected.

[0070] According to such a method, it is possible to suppress the deterioration of the methanation catalyst due to products generated by side reactions such as thermal decomposition and polymerization reactions of saturated hydrocarbons C2+ , or to regenerate the deteriorated catalyst.

[0071]

[10] The methanation method according to still another aspect is the methanation method of any one of [6] to [9], ​The raw material gas is natural gas, compressed natural gas, town gas, liquefied petroleum gas, or naphtha.

[0072] According to such a method, generally available hydrocarbon gas can be used as the raw material gas without separately preparing the raw material gas.

[0073]

[11] A method for directly decomposing hydrocarbons according to one embodiment is [6] -

[10] By any of the methanation methods, converting the saturated hydrocarbon C2+ in the raw material gas into methane, Contacting the treated gas, which is the gas after converting the saturated hydrocarbon C2+ into methane, with a catalyst (20) for the direct decomposition reaction of hydrocarbons to directly decompose methane in the treated gas into hydrogen and carbon and including.

[0074] According to the method for directly decomposing hydrocarbons of the present disclosure, since the content of saturated hydrocarbon C2+ in the treated gas is lower than that in the raw material gas, the risk caused by side reactions such as thermal decomposition and polymerization reaction of saturated hydrocarbon C2+ can be suppressed.

[0075]

[12] Another method for directly decomposing hydrocarbons according to an embodiment is the method for directly decomposing hydrocarbons of

[11] , At least a part of the product gas containing hydrogen generated by directly decomposing methane in the treated gas into hydrogen and carbon is used as at least a part of the hydrogen-containing gas supplied to the catalyst layer (11a) on the most upstream side among at least two catalyst layers (11a, 11b) provided at intervals in the flow direction of the mixed gas.

[0076] According to such a method, since at least a part of the hydrogen in the product gas is used as at least a part of the hydrogen used in the methanation method, the amount of hydrogen used in the methanation method can be reduced, and as a result, the operating cost of the hydrocarbon direct decomposition apparatus can be reduced.

Explanation of symbols

[0077] 1 Direct decomposition device 2 Methanation device 3 Hydrogen supply line 4 Raw material gas supply line 5 Treated gas supply line 6 Product gas circulation line 7 Hydrogen recycle line 11a First catalyst layer (catalyst layer) 11b Second catalyst layer (catalyst layer) 13 Cooler 20 Catalyst 22 Reactor

Claims

1. A methanation apparatus for removing a saturated hydrocarbon from a raw material gas containing methane and the saturated hydrocarbon by methanation in which a saturated hydrocarbon having two or more carbon atoms reacts with hydrogen to convert the saturated hydrocarbon into methane, at least two catalyst layers composed of the catalyst for methanation, the at least two catalyst layers being provided at intervals in the flow direction of a mixed gas containing the raw material gas and a hydrogen-containing gas, a hydrogen supply line for supplying the hydrogen-containing gas upstream of the catalyst layer on the most upstream side in the flow direction of the mixed gas, a raw material gas supply line for supplying the raw material gas to each of the upstream side of the catalyst layer on the most upstream side in the flow direction of the mixed gas and between two adjacent catalyst layers in the flow direction of the mixed gas, a cooler provided between two adjacent catalyst layers in the flow direction of the mixed gas, for cooling the mixed gas flowing out from the catalyst layer on the upstream side in the flow direction of the two adjacent catalyst layers A methanation apparatus comprising the same.

2. The methanation apparatus according to claim 1, wherein the amount of the catalyst constituting each of the at least two catalyst layers increases toward the catalyst layer on the downstream side in the flow direction of the mixed gas.

3. The methanation apparatus according to claim 1 or 2, wherein the catalyst is a supported catalyst in which nickel, iron, cobalt, or a noble metal element is supported on alumina.

4. The methanation apparatus according to claim 1 or 2, a reactor containing a catalyst for the direct decomposition reaction of hydrocarbons, and a treated gas supply line for supplying the treated gas, which is the gas flowing out from the methanation apparatus, to the reactor A hydrocarbon direct decomposition apparatus comprising the same.

5. A product gas flow line through which a product gas containing hydrogen generated by direct decomposition of a hydrocarbon in the reactor flows after flowing out of the reactor, and a hydrogen recycle line connecting the product gas flow line and the hydrogen supply line The hydrocarbon direct decomposition apparatus according to claim 4, comprising the same.

6. A methanation method for removing a saturated hydrocarbon from a raw material gas containing methane and the saturated hydrocarbon by methanation in which a saturated hydrocarbon having two or more carbon atoms reacts with hydrogen to convert the saturated hydrocarbon into methane, At least two catalyst layers composed of the catalyst for the methanation, and a step of flowing the hydrogen-containing gas through the catalyst layer on the most upstream side among the at least two catalyst layers provided at intervals in the flow direction of the mixed gas containing the raw material gas and the hydrogen-containing gas; A step of flowing a part of the raw material gas through the catalyst layer on the most upstream side in the flow direction of the mixed gas; A step of supplying the remainder of the raw material gas between two adjacent catalyst layers in the flow direction of the mixed gas; A step of cooling the mixed gas flowing out from the catalyst layer on the upstream side among the two adjacent catalyst layers; A step of flowing the cooled mixed gas and the raw material gas supplied between two adjacent catalyst layers in the flow direction of the mixed gas through the catalyst layer on the downstream side among the two adjacent catalyst layers A methanation method including the above steps.

7. The methanation method according to claim 6, wherein the supply amount of the hydrogen-containing gas is adjusted so that the concentration ratio of hydrogen to the saturated hydrocarbon in the mixed gas is 1 or more.

8. The methanation method according to claim 6 or 7, wherein the hydrogen-containing gas contains a component that does not contribute to the methanation and hydrogen.

9. A step of detecting a decrease in the activity of the methanation; A step of increasing the supply amount of the hydrogen-containing gas when the decrease in the activity is detected The methanation method according to claim 6 or 7, including the above steps.

10. The methanation method according to claim 6 or 7, wherein the raw material gas is natural gas, compressed natural gas, city gas, liquefied petroleum gas, or naphtha.

11. A step of converting the saturated hydrocarbon in the raw material gas into methane by the methanation method according to claim 6 or 7; A step of directly decomposing methane in the treated gas into hydrogen and carbon by bringing the treated gas, which is the gas after converting the saturated hydrocarbon into methane, into contact with a catalyst for the direct decomposition reaction of hydrocarbons A method for directly decomposing hydrocarbons including the above steps.

12. The method for directly decomposing hydrocarbons according to claim 11, wherein at least a part of the product gas containing hydrogen generated by directly decomposing methane in the treated gas into hydrogen and carbon is used as at least a part of the hydrogen-containing gas supplied to the catalyst layer on the most upstream side among the at least two catalyst layers provided at intervals in the flow direction of the mixed gas.

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