Methanation reactor and method for producing methane using same

Abstract

The present invention relates to a methanation reactor and a method for producing methane using same. The methanation reactor comprises: an ammonia decomposition unit in which a decomposition reaction of supplied ammonia into nitrogen and hydrogen occurs; a methanation unit to which a mixed gas including at least one of carbon dioxide and carbon monoxide and hydrogen are supplied and in which a methane formation reaction occurs; and a hydrogen separation membrane disposed between the ammonia decomposition unit and the methanation unit and connected to one side of the ammonia decomposition unit and one side of the methanation unit. The reactor can provide the effects of improving energy efficiency and producing high-quality methane through mutual hydrogen-heat exchange.

Description

Methanation reactor and method for producing methane using the same

[0001] The present invention relates to a methanation reactor and a method for producing methane using the same, and more specifically, to a carbon dioxide reduction technology utilizing ironmaking byproduct gas.

[0002] Carbon dioxide is a major greenhouse gas and is identified as one of the causes of global warming and climate change. To address this, efforts to reduce carbon dioxide emissions are ongoing, and among these, the development of technologies to chemically convert emitted carbon dioxide into high-value compounds for recycling is actively underway. In particular, the technology to convert carbon dioxide into methane is important in terms of energy storage and recycling.

[0003] Methanation is a reaction in which carbon dioxide and hydrogen react to produce methane and water, offering the advantage of not only converting carbon dioxide into useful compounds but also utilizing methane as a fuel and energy storage medium.

[0004] However, the methanation reaction generates a significant amount of heat, leading to the formation of hot spots where temperatures rise excessively. This induces catalyst deactivation, resulting in reduced technological productivity. Furthermore, the hydrogen production process required for methanation is energy-intensive, involving high energy consumption and potentially leading to carbon emissions.

[0005] Meanwhile, ammonia is a compound capable of stably storing and transporting hydrogen, making it a more efficient and safer alternative to conventional hydrogen storage methods. However, the decomposition reaction of ammonia is also an energy-intensive process, and obtaining high-purity hydrogen presents the problem of requiring an additional process to separate nitrogen, an inert substance.

[0006] Therefore, there is a need to develop technologies that can generate methane in an economical and eco-friendly manner.

[0007] The present invention aims to provide a steelmaking byproduct gas methanation system capable of efficiently producing methane by selectively supplying hydrogen from ammonia to generate methane with high yield and self-supplying the heat required for the ammonia decomposition reaction.

[0008] In addition, the present invention aims to provide a method for producing methane having high yield and high energy efficiency characteristics by using the above-described methanation system.

[0009] The problems of the present invention are not limited to those described above. A person skilled in the art to which the present invention pertains will have no difficulty understanding additional problems of the present invention from the overall contents of this specification.

[0010] In order to solve the technical problem of the present invention described above, according to an exemplary embodiment of the present invention, a methanation reactor (1000) with further improved energy efficiency is provided. The methanation reactor (1000) comprises an ammonia decomposition unit (100) in which a decomposition reaction of supplied ammonia into nitrogen and hydrogen takes place, a methanation unit in which a mixed gas comprising at least one of carbon dioxide and carbon monoxide and hydrogen are supplied and a methane generation reaction takes place, and a hydrogen separation membrane disposed between the ammonia decomposition unit (100) and the methanation unit and connected to one side of the ammonia decomposition unit (100) and one side of the methanation unit, wherein the hydrogen separation membrane may mutually exchange hydrogen and heat so that hydrogen generated from the ammonia decomposition unit (100) selectively moves to the methanation unit and heat generated from the methanation unit moves to the ammonia decomposition unit (100).

[0011] The above ammonia decomposition unit may include a first inlet to which ammonia is supplied, a first outlet to which a gas containing nitrogen decomposed from ammonia is discharged, and an ammonia decomposition catalyst layer.

[0012] The above methanation unit may include a second inlet to which a mixed gas comprising at least one of carbon monoxide and carbon dioxide is supplied, a second outlet to which a gas containing methane is discharged after the methanation reaction, and a methanation reforming catalyst layer.

[0013] The above hydrogen separation membrane may comprise at least one selected from palladium, palladium alloy, ceramic oxide, and metal-ceramic composite.

[0014] The content of carbon dioxide and carbon monoxide in the above mixed gas may be 60 vol% or more based on the total volume.

[0015] The above ammonia decomposition unit may further include a pressure regulator that forms the pressure conditions necessary for the decomposition reaction.

[0016] The flow rate ratio of the supplied ammonia and mixed gas may be 1.5:1 to 3:1.

[0017] The above ammonia decomposition catalyst layer may include one or more transition metals selected from ruthenium (Ru), nickel (Ni), and cobalt (Co).

[0018] The above methanogenic reforming catalyst layer may include one or more transition metals selected from nickel (Ni), ruthenium (Ru), and iron (Fe).

[0019] The above methanation unit may further include a dehydration unit that separates and removes water vapor from a gas containing methane.

[0020] The above mixed gas may be at least one selected from converter gas (Linz Donawitz Gas, LDG) and Finex off gas (FOG).

[0021] According to another exemplary embodiment of the present invention, a method for producing methane using a methanation reactor is provided, comprising the steps of: decomposing ammonia in an ammonia decomposition unit to produce nitrogen and hydrogen; selectively transferring the hydrogen produced by the decomposition of ammonia to a methanation unit through a hydrogen separation membrane; a mixed gas comprising at least one of carbon dioxide and carbon monoxide and the transferred hydrogen to undergo a methane production reaction in the methanation unit; and transferring heat generated in the methanation unit to an ammonia decomposition unit through a hydrogen separation membrane.

[0022] In one embodiment of the present invention, the methanation reactor (1000) can supply heat required for the ammonia decomposition reaction and provide hydrogen required for the methanation reaction through a process in which the ammonia decomposition reaction and the methanation reaction are linked, so the production process is efficient.

[0023] In addition, in one embodiment of the present invention, the methanation reactor (1000) can continuously maintain high methane productivity by suppressing the formation of a hot spot caused during methane production and can produce high-purity methane by selectively supplying hydrogen.

[0024] In addition, in one embodiment of the present invention, the method for producing methane using the methanation reactor (1000) can significantly increase energy efficiency through mutual hydrogen-heat exchange between the ammonia decomposition unit and the methanation unit, and can provide high-purity methane.

[0025] FIG. 1 schematically illustrates the configuration of a methanation reactor (1000) according to one embodiment of the present invention.

[0026] FIG. 2 illustrates the feed flow rate, specific gas components, and content in relation to the reaction performed in a methanation reactor (1000) according to Example 1 of the present invention.

[0027] Figure 3 illustrates the feed flow rate, specific gas components, and content in relation to the reaction performed in a methanation reactor according to Comparative Example 1 of the present invention.

[0028] Preferred embodiments of the present invention will be described below with reference to the attached drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0029] In addition, embodiments of the present invention are provided to more fully explain the present invention to those with average knowledge in the relevant technical field.

[0030] In drawings, the shapes and sizes of elements may be exaggerated for clearer explanation.

[0031] In describing the embodiments of the present invention, if it is determined that a detailed description of known technology related to the present invention may unnecessarily obscure the essence of the present invention, such detailed description will be omitted. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, such definitions should be based on the content throughout this specification. The terms used in the detailed description are merely for describing the embodiments of the present invention and should not be limited in any way. Unless explicitly stated otherwise, expressions in the singular form include the meaning of the plural form.

[0032] In this description, expressions such as “include” or “equipped” are intended to refer to certain characteristics, numbers, steps, actions, elements, parts or combinations thereof, and should not be interpreted to exclude the existence or possibility of one or more other characteristics, numbers, steps, actions, elements, parts or combinations thereof other than those described.

[0033] Unless otherwise specifically defined in the specification of the present invention, % units mean weight %.

[0034] In this specification, terms such as 'top', 'upper', 'upper surface', 'lower', 'lower surface', 'lower surface', and 'side surface' are based on the drawings and may actually vary depending on the direction in which the elements or components are arranged.

[0035] Additionally, throughout the specification, when it is said that one part is 'connected' to another part, this includes not only cases where they are 'directly connected,' but also cases where they are 'indirectly connected' with other elements in between.

[0036] The present invention will be described in detail below through each embodiment or example of the invention. It should be noted that each embodiment or example described in this specification is not limited to a single embodiment or example, but may also be combined with other embodiments or examples. Accordingly, the citation of claims in the patent claims is merely an example of an embodiment, and the technical concept of the present invention should not be interpreted as being limited only to a combination with the cited claims; rather, combinations with various claims are also included within the scope of the technical concept of the present invention.

[0037] The present invention relates to a methanation reactor (1000) that improves energy efficiency by linking an ammonia decomposition reaction and a methanation reaction, and has a high methane conversion yield.

[0038] Specifically, a methanation reactor (1000) according to one embodiment of the present invention may include an ammonia decomposition unit (100) in which a decomposition reaction of supplied ammonia into nitrogen and hydrogen takes place, a methanation unit (200) in which a mixed gas comprising at least one of carbon dioxide and carbon monoxide and hydrogen are supplied and a methane generation reaction takes place, and a hydrogen separation membrane (300) disposed between the ammonia decomposition unit and the methanation unit and connected to one side of the ammonia decomposition unit and one side of the methanation unit.

[0039] The above hydrogen separation membrane (300) mutually exchanges hydrogen and heat so that hydrogen generated from the ammonia decomposition unit selectively moves to the methanation unit and heat generated from the methanation unit moves to the ammonia decomposition unit, thereby supplying the hydrogen required for the methanation reaction from the ammonia decomposition unit (100) and sufficiently supplying the heat required for the ammonia decomposition reaction from the methanation unit (200). In other words, it can provide the advantage of producing methane with a high yield even without an additional energy supply device.

[0040] Ammonia has a high hydrogen storage capacity (17.6 wt%, 108 g / L). Ammonia molecules decompose into hydrogen and nitrogen at high temperatures as shown in Reaction Scheme 1 below, which is an advantage as it can produce hydrogen without emitting carbon dioxide. However, the biggest problem is that the ammonia decomposition reaction is an endothermic reaction that proceeds at high temperatures and pressures, requiring a large amount of energy. The temperature of the ammonia decomposition reaction is 200 ℃ or 250 ℃ or higher, and can mainly be 300 to 600 ℃.

[0041] [Reaction Equation 1]

[0042] NH3→ 0.5N2+ 1.5H2 (ΔH = 46.4 kJ / mol)

[0043] In one example, the ammonia decomposition unit (100) may include a first inlet (not shown) into which ammonia is supplied, a first outlet (not shown) into which a gas containing nitrogen decomposed from ammonia is discharged, and a decomposition catalyst layer.

[0044] The decomposition catalyst layer for promoting ammonia decomposition may include one or more selected from ruthenium (Ru), platinum (Pt), nickel (Ni), iron (Fe), cobalt (Co), molybdenum (Mo), tungsten (W), and vanadium (V). Specifically, if it includes one or more transition metals selected from ruthenium (Ru), nickel (Ni), and cobalt (Co), it may be more advantageous for selectively supplying hydrogen.

[0045] In one non-limiting embodiment, a co-catalyst may be added to improve the activity of the ammonia decomposition catalyst. The type of co-catalyst is known and can be used without limitation as long as it is intended to increase the activity of the metal catalyst and improve its stability.

[0046] As shown in reaction equation 1 above, after the decomposition of ammonia, the generated nitrogen is discharged outside the ammonia decomposition unit through the first outlet, and at least a portion of the generated hydrogen is transferred to the methanation unit (200) through the hydrogen separation membrane (300). Specifically, 60 Vol% or more, 70 Vol% or more, 80 Vol% or more, 90 Vol% or more, or 100 Vol% of the generated hydrogen can be selectively permeated through the hydrogen separation membrane.

[0047] Specifically, when the ammonia supply flow rate is 2 N㎥ / h, the hydrogen flow rate may be 3 N㎥ / h, and preferably, the hydrogen flow rate passing through the hydrogen separation membrane may be 2 N㎥ / h or more, 2.5 N㎥ / h or more, or 2.7 N㎥ / h or more.

[0048] Additionally, the ammonia decomposition unit (100) may further include a pressure regulating unit that forms pressure conditions necessary for the decomposition reaction. Specifically, the pressure regulating unit is positioned at the introduction of a first inlet to which ammonia is supplied, and can increase the pressure to a preset pressure before supplying ammonia. For example, when increasing the pressure to 1.5 to 9 bar, 2 to 8 bar, or 2.5 to 5 bar, the membrane permeation rate of hydrogen, which is the product, can be increased without reducing the ammonia decomposition rate.

[0049] The methanation unit (200) is a part where the methanation reaction takes place and may include a second inlet (not shown) to which a mixed gas containing at least one of carbon monoxide and carbon dioxide is supplied, a second outlet (not shown) to which a gas containing methane is discharged after the methanation reaction, and a reforming catalyst layer.

[0050] The mixed gas containing at least one of the carbon monoxide and carbon dioxide may be a mixed gas having a carbon dioxide and carbon monoxide content of 40% or more, 50% or more, 60% or more, or 70% or more. Specifically, it may be a steelmaking byproduct gas, and for example, it may be blast furnace gas (BFG), converter gas (Linz Donawitz Gas, LDG), coke oven gas (COG), or Finex off gas (FOG).

[0051] More specifically, it may be one or more selected from converter gas and FINEX off-gas. The converter gas or FINEX off-gas is rich in carbon dioxide and carbon monoxide, so it can efficiently supply carbon monoxide and / or carbon dioxide.

[0052] Table 1 below shows the composition of steelmaking byproduct gases. In the case of converter gas and FINEX off-gas, carbon monoxide and carbon dioxide are contained in an amount of 70 Vol% or more, and the partial pressure of carbon dioxide and carbon monoxide is high, which may be advantageous for the methanation reaction.

[0053] Composition (Volume %) Coke Oven Gas (COG) Converter Gas (LDG) Blast Furnace Gas (BFG) FINEX Off-Gas (FOG) N2 7.7 18 49.6 10.6 H25 5.5 23.7 11 CO2 2.1 12 21.1 46.6 CO6 46 825.2 30.3 CH4 25.3 00 1.1 Other 3.0 0.4 0.4

[0054] The methanation unit (200) can produce methane by reacting at least one of carbon monoxide and carbon dioxide with hydrogen in the presence of a catalyst.

[0055] Methane can be produced through low-temperature reactions conducted at 70°C or below via biological reactions by microorganisms, or through thermochemical reactions conducted at 200°C or above via fixed-bed or fluidized-bed catalysts. Since low-temperature reactions have low reaction rates and yields, production via thermochemical reactions using catalysts is predominant. The reaction equation for the thermochemical methanation reaction using a catalyst is as follows.

[0056] [Reaction Equation 2]

[0057] CO2+ 4H2→ CH4+ 2H2O (ΔH = -164 kJ / mol, 298 K)

[0058] [Reaction Equation 3]

[0059] CO + 3H2→ CH4+ H2O (ΔH = -206 kJ / mol, 298 K)

[0060] Since all of the above reactions occur rapidly and are exothermic, if they are carried out continuously, the reduction in catalyst lifespan due to heat generation may become a problem, and because methane is produced along with water, the conversion rate of reactants and the yield of methane may decrease.

[0061] A methanation reactor (1000) according to one embodiment of the present invention can provide the effect of suppressing the generation of hot spots in the methanation unit (200) caused by reaction heat by allowing continuous heat exchange from the methanation unit (200) where the reaction is performed through a hydrogen separation membrane. That is, by controlling the heat generated by the reaction and simultaneously providing the reaction heat through the hydrogen separation membrane as energy for the endothermic reaction of the ammonia decomposition unit (100), the conversion rate of methane can be increased.

[0062] At this time, it is preferable that the flow rate of the mixed gas containing at least one of carbon monoxide and carbon dioxide supplied to the ammonia decomposition unit and the ammonia supplied to the methanation unit be supplied in a ratio of 1.1:1 to 4:1. Specifically, when supplied in a ratio of 1.5:1 to 3:1, high-quality methane can be synthesized through the methanation reactor (1000) according to the present invention. When supplied in a ratio of 1.8:1 to 2.5:1, methane with a purity of 80% or more can be synthesized, so the efficiency of the device can be greatly improved.

[0063] The modified catalyst layer of the above-mentioned methanation unit (200) may include a transition metal-based catalyst. Specifically, for example, it may include one or more selected from iron (Fe), nickel (Ni), cobalt (Co), and ruthenium (Ru). More specifically, if it includes one or more transition metals selected from nickel (Ni), ruthenium (Ru), and iron (Fe), it may be better to promote the methanation reaction through high hydrogenation.

[0064] In one example, the transition metal-based catalyst may be supported on one or more supports selected from alumina (Al2O3), silica (SiO2), titania (TiO2), ceria (CeO2), and magnesia (MgO).

[0065] The above-mentioned modified catalyst layer may exist in the form of fixed particles within the methanation unit (200), or in the form of a fluidized bed due to fluid flow.

[0066] In one example, the modified catalyst layer may include a co-catalyst to improve catalyst performance. For example, potassium (K) and sodium (Na) may be used as alkali metals, cerium (Ce) and lanthanum (La) as rare earth metals, and molybdenum (Mo) and tungsten (W) as transition metals.

[0067] As shown in reaction schemes 2 and 3 above, H2O is additionally produced as a product of the methanation reaction in addition to methane. In order to obtain pure methane, the methanation unit (200) may further include a dehydration unit capable of separating and / or removing H2O. Accordingly, the problem of a decrease in the conversion rate of the reaction due to reaction equilibrium can be prevented.

[0068] As an example, the dehydration unit can separate and remove H2O in the form of condensate by cooling it in the form of water vapor, or separate and remove it by adsorbing water vapor including a dehumidifying adsorbent.

[0069] The hydrogen separation membrane (300) may be a metal-based membrane, a ceramic-based membrane, or a composite membrane of metal and ceramic. Specifically, it may include at least one selected from palladium (Pd), palladium alloy, ceramic oxide, and metal-ceramic composite.

[0070] The above palladium alloy may include, in addition to palladium, one or more metals selected from tungsten (W), molybdenum (Mo), copper (Cu), silver (Ag), gold (Au), platinum (Pt), nickel (Ni), titanium (Ti), chromium (Cr), lanthanum (La), cerium (Ce), and niobium (Nb).

[0071] Ceramic-based membranes are YSZ, BaZrO₃, BaCeO₃, SrCeO₃, La (₁) It may include SrCoO₃ series.

[0072] Specifically, the metal-ceramic composite membrane may be a silica-based porous membrane having pores capable of permeating only hydrogen on a porous support such as alumina. Alternatively, after forming the above silica-based porous membrane, a metal membrane permeable to hydrogen, such as Pd, may be formed by plating such as electroless plating.

[0073] In addition, the present invention may provide a method for producing methane using a methanation reactor according to the technical concept described above. Specifically, the method may include the steps of: decomposing ammonia in an ammonia decomposition unit to produce nitrogen and hydrogen; selectively transferring the hydrogen produced by the decomposition of ammonia to a methanation unit through a hydrogen separation membrane; a mixed gas comprising at least one of carbon dioxide and carbon monoxide and the transferred hydrogen to undergo a methanation reaction in the methanation unit; and transferring the heat generated in the methanation unit to the ammonia decomposition unit through a hydrogen separation membrane.

[0074] The mixed gas containing at least one of the carbon dioxide and carbon monoxide mentioned above is a byproduct gas of steelmaking, specifically converter gas, FINEX off-gas, or a mixed gas thereof. In this case, when ammonia and the mixed gas are supplied in a ratio of 1.1:1 to 4:1, specifically 1.5:1 to 3:1, high-quality methane can be synthesized. More specifically, when supplied in a ratio of 1.8:1 to 2.5:1, methane with a purity of 80% or higher can be synthesized, thereby providing an energy-efficient method for producing methane.

[0075] The present invention will be described in detail below through examples. However, it should be noted that the examples described below are intended merely to illustrate and embody the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the patent claims and matters reasonably inferred therefrom.

[0076] Examples

[0077] Example 1

[0078] Ammonia was supplied at a flow rate of 2 N㎥ / h to the ammonia decomposition unit (100), and ironmaking byproduct gas (Finex Off Gas, FOG) was supplied at a flow rate of 1 N㎥ / h to the methanation unit (200), and a methanation reaction was performed through a methanation reactor (1000) according to one embodiment of the present invention. As a result of the ammonia decomposition reaction, the flow rate of the gas containing nitrogen and hydrogen was 4 N㎥ / h, and the hydrogen that passed through the palladium-based hydrogen separation membrane out of the hydrogen at a flow rate of 3.0 N㎥ / h was 2.7 N㎥ / h, and high-purity hydrogen was supplied to the methanation unit to carry out the methanation reaction. The specific gas components according to the above reaction are shown in FIG. 2.

[0079] As a result of a methanation reaction performed using the methanation reactor according to the present invention, high-quality methane with a purity of 87% was obtained based on the product gas from which moisture was removed.

[0080] Comparative Example 1

[0081] A methanation reaction was carried out in a methanation apparatus comprising a heat exchange reactor configuration in which only heat exchange can occur between the ammonia decomposition unit and the methanation unit without a hydrogen separation membrane disposed between the ammonia decomposition unit and the methanation unit. The specific gaseous components resulting from the above reaction are shown in FIG. 3.

[0082] When a mixed gas containing hydrogen and nitrogen produced through an ammonia decomposition reaction is supplied to a methanation unit, the formation of a hot spot in the methanation unit can be suppressed through heat exchange, but as a result, methane with a purity of 43% is produced based on the product gas from which moisture has been removed, and compared with a comparative example, it can be confirmed that the methanation reactor according to the present invention can significantly increase the methane conversion rate through the selective supply of hydrogen.

[0083] The present invention has been described in more detail above through drawings and embodiments. However, the configurations described in the drawings or embodiments described in this specification are merely one embodiment of the present invention and do not represent all technical concepts of the present invention; therefore, it should be understood that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0084] [Explanation of the symbol]

[0085] 1000: Methanation reactor

[0086] 100: Ammonia decomposition unit

[0087] 200: Methanization Unit

[0088] 300: Hydrogen separation membrane

[0089] 10: Methanation reactor not containing a hydrogen separation membrane

Claims

1. An ammonia decomposition unit in which ammonia is supplied and a decomposition reaction from ammonia into nitrogen and hydrogen takes place; A methanation unit in which a mixed gas comprising at least one of carbon dioxide and carbon monoxide and hydrogen are supplied, and a methane production reaction takes place; and It includes a hydrogen separation membrane disposed between the ammonia decomposition unit and the methanation unit and connected to one side of the ammonia decomposition unit and one side of the methanation unit, and The above hydrogen separation membrane is a methanation reactor in which hydrogen generated from an ammonia decomposition unit selectively moves to a methanation unit and heat generated from the methanation unit moves to an ammonia decomposition unit through mutual hydrogen-heat exchange.

2. In Paragraph 1, The above ammonia decomposition unit is a methanation reactor comprising a first inlet to which ammonia is supplied, a first outlet to which a gas containing nitrogen decomposed from ammonia is discharged, and an ammonia decomposition catalyst layer.

3. In Paragraph 1, The above methanation unit is a methanation reactor comprising a second inlet to which a mixed gas containing at least one of carbon monoxide and carbon dioxide is supplied, a second outlet to which a gas containing methane is discharged after a methanation reaction, and a methanation reforming catalyst layer.

4. In Paragraph 1, The above hydrogen separation membrane is a methanation reactor comprising at least one selected from palladium, palladium alloy, ceramic oxide, and metal-ceramic composite.

5. In Paragraph 1, A methanation reactor in which the content of carbon dioxide and carbon monoxide in the above-mentioned mixed gas is 60 vol% or more based on the total volume.

6. In Paragraph 1, The above ammonia decomposition unit is a methanation reactor further comprising a pressure regulator that forms pressure conditions necessary for the decomposition reaction.

7. In Paragraph 1, A methanation reactor in which the flow rate ratio of the supplied ammonia and mixed gas is 1.5:1 to 3:

1.

8. In Paragraph 2, A methanation reactor comprising one or more transition metals selected from ruthenium (Ru), nickel (Ni), and cobalt (Co), wherein the ammonia decomposition catalyst layer comprises 9. In Paragraph 3, A methanation reactor comprising one or more transition metals selected from nickel (Ni), ruthenium (Ru), and iron (Fe), wherein the methanation reforming catalyst layer comprises 10. In Paragraph 1, The above methanation unit is a methanation reactor further comprising a dehydration unit that separates and removes water vapor from a gas containing methane.

11. In Paragraph 1, A methanation reactor in which the above mixed gas is at least one selected from converter gas (Linz Donawitz Gas, LDG) and Finex off gas (FOG).

12. A step in which ammonia is decomposed in an ammonia decomposition unit to produce nitrogen and hydrogen; A step in which hydrogen generated by the decomposition of the above ammonia is selectively transferred to a methanation unit through a hydrogen separation membrane; A step in which a methane production reaction occurs in a methanation unit using a mixed gas comprising at least one of carbon dioxide and carbon monoxide and the transferred hydrogen; and A method for producing methane using a methanation reactor, comprising the step of transferring heat generated in the methanation unit to an ammonia decomposition unit through a hydrogen separation membrane.

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