Methanol production method and methanol production device

Abstract

A methanol production method comprising: a step (A) in which a hydrocarbon-containing gas is reformed to obtain a reformed gas; a step (B) in which a hydrogen-containing gas is mixed with the hydrocarbon-containing gas and / or the reformed gas; a step (C) for obtaining methanol and an unreacted gas by reacting a portion of the reformed gas in the presence of a catalyst; a step (D) in which the remainder of the reformed gas is subjected to a shift reaction to obtain a shift reaction gas; and a step (E) for separating carbon dioxide from the shift reaction gas to obtain a carbon dioxide-rich gas and a carbon dioxide separation unit exhaust gas, at least a portion of which is used as a fuel for the step (A) and / or the boiler.

Description

Technical Field

[0001] The present invention relates to a method for producing methanol and a methanol production apparatus. Background Art

[0002] In an existing industrial method for producing methanol from natural gas, synthesis gas obtained by steam reforming of natural gas (main component: methane) as a raw material is synthesized into methanol. The steam reforming reaction is an endothermic reaction. In order to maintain a temperature suitable for the reaction (about 1000°C), a large amount of fuel needs to be burned to supply energy, and a large amount of carbon dioxide is discharged. As a method for reducing the amount of discharged carbon dioxide, for example, a method of recovering carbon dioxide from combustion exhaust gas (post-combustion carbon dioxide recovery) can be cited. Post-combustion carbon dioxide recovery is a well-established technology, and there are examples of its application to commercial plants. However, since the carbon dioxide concentration in the combustion exhaust gas of the gas after steam reforming (reformed gas) is as low as 10 mol% or less, the equipment or energy required for carbon dioxide recovery is relatively large.

[0003] Therefore, as a carbon dioxide reduction method, in recent years, a method has been proposed in which carbon dioxide is separated and recovered from reformed gas or unreacted gas after methanol synthesis, which has a relatively high carbon dioxide concentration, and then the low-carbon emission gas (main component: hydrogen) is used as a combustion fuel. This is the mainstream carbon dioxide reduction method in methanol production from natural gas.

[0004] Such a method generally has a hydrogen recovery device (PSA), a carbon dioxide recovery device, and a water gas shift reactor for increasing the hydrogen and carbon dioxide concentrations as components, and various device selections, configuration sequences, and gas compositions have been reported.

[0005] For example, Patent Document 1 discloses that, for the purpose of reducing carbon dioxide emissions, at least a part of a synthesis gas stream is supplied to a water gas shift reactor upstream of a pipeline for supplying the synthesis gas stream to a methanol reaction apparatus, or a gas mainly composed of hydrogen obtained therefrom is supplied to a combustion heating apparatus or the like.

[0006] In addition, Patent Document 2 discloses a method in which a purge gas from a synthesis apparatus is supplied to a shift reactor and then supplied to a hydrogen separation apparatus in order to increase methanol production and reduce energy consumption by reducing the purge gas generated from the methanol synthesis apparatus. The recovered hydrogen is recycled, and the off-gas is discharged out of the system.

[0007] In Patent Document 3, for the purpose of improving the stoichiometric value of the feed supplied to the methanol reactor, it is disclosed that a part of the reformed gas stream is passed through a shift reactor, and then the obtained gas is passed through a hydrogen separation device to merge hydrogen with the reformed gas stream, thereby adjusting the M value of the reformed gas stream, and thus a significant reduction in the consumption of natural gas used in the production of synthesis gas can be achieved, etc.

[0008] Patent Document 4 discloses a method for producing hydrogen and methanol simultaneously by passing reformed gas through a shift reactor.

[0009] Prior art documents

[0010] Patent documents

[0011] Patent Document 1: Publication No. EP3674261

[0012] Patent Document 2: Publication No. US2017 / 0197894

[0013] Patent Document 3: Publication No. EP3844135

[0014] Patent Document 4: US Patent No. 10160704 Summary of the invention

[0015] Technical problem to be solved by the invention

[0016] However, in Patent Document 1, perhaps because the focus is on carbon dioxide reduction, it cannot be said that the gas stream supplied to the methanol synthesis reactor is sufficiently adjusted to a gas composition suitable for methanol synthesis.

[0017] In Patent Document 2, although it is disclosed that the purge gas generated from the methanol synthesis device is recycled by hydrogen through a shift reaction, it cannot be said to be a gas composition suitable for methanol synthesis, and it is not sufficient in terms of reducing the carbon dioxide emissions of the entire system.

[0018] In Patent Document 3, although it describes improving the stoichiometric value of the feed supplied to the methanol reactor, etc., it is not sufficient in terms of reducing the carbon dioxide emissions of the entire system.

[0019] In Patent Document 4, although it is disclosed that reformed gas is passed through a shift reactor to produce hydrogen and methanol simultaneously, it cannot be said that it is sufficiently adjusted to a gas composition suitable for methanol synthesis. In addition, it is not sufficient in terms of reducing the carbon dioxide emissions of the entire system.

[0020] The present invention is made in view of the above circumstances, and the object of the present invention is to provide a method for producing methanol with a low carbon dioxide emission per unit production of methanol and excellent carbon yield in a method for producing methanol using natural gas as a raw material.

[0021] Technical solution for solving technical problems

[0022] The inventors of the present invention conducted in-depth research to solve the above technical problems, and as a result, it was found that a manufacturing method including specified processes in a specified order can provide a manufacturing method of methanol with a low carbon dioxide emission per unit production of methanol and excellent carbon yield, thus completing the present invention. That is, the present invention is as described below.

[0023] [1] A method for manufacturing methanol, comprising:

[0024] A step (A) of reforming a hydrocarbon-containing gas to obtain a reformed gas;

[0025] A step (B) of mixing a hydrogen-containing gas with the hydrocarbon-containing gas and / or the reformed gas;

[0026] A step (C) of reacting a part of the reformed gas in the presence of a catalyst to obtain methanol and unreacted gas;

[0027] A step (D) of subjecting the remaining part of the reformed gas to a shift reaction to obtain a shift reaction gas; and

[0028] A step (E) of separating carbon dioxide from the shift reaction gas to obtain a carbon dioxide-rich gas and a carbon dioxide separation unit off-gas,

[0029] At least a part of the carbon dioxide separation unit off-gas is used as fuel for the step (A) and / or a boiler.

[0030] [2] The method for manufacturing methanol according to [1], further comprising: a step (F) of removing sulfur from the hydrocarbon-containing gas.

[0031] [3] The method for manufacturing methanol according to [1] or [2], further comprising: a step (G) of obtaining refined methanol from the methanol.

[0032] [4] The method for manufacturing methanol according to any one of [1] to [3], wherein the molar flow rate of the reformed gas used in the step (C) is 50 to 95 mol% relative to the molar flow rate of the reformed gas obtained in the step (A).

[0033] [5] The method for manufacturing methanol according to any one of [1] to [4], wherein the water vapor generated in the step (C) is used for the step (G) and / or the step (E).

[0034] [6] The method for manufacturing methanol according to any one of [1] to [5], wherein the water vapor recovered in the step (A) is used for the step (G) and / or the step (E).

[0035] [7] The methanol production method according to any one of [1] to [6], wherein the heat recovered in the step (A) is used as a heat source for at least any one of the step (G) and the step (E).

[0036] [8] The methanol production method according to any one of [1] to [7], wherein the step (D) is carried out in the presence of a catalyst.

[0037] [9] The methanol production method according to any one of [1] to [8], wherein the carbon monoxide concentration in the shift reaction gas is 0.01 to 1.0 mol%.

[0038]

[10] The methanol production method according to any one of [1] to [9], wherein when the molar flow rate of carbon dioxide contained in the shift reaction gas is set to 100 mol%, the molar flow rate of carbon dioxide contained in the carbon dioxide-rich gas is 80 to 100 mol%.

[0039]

[11] The methanol production method according to any one of [1] to

[10] , wherein at least a part of the unreacted gas is supplied to the shift reaction unit and / or the boiler.

[0040]

[12] The methanol production method according to any one of [1] to

[11] , further comprising: a step (H) of separating methane from the gas discharged from the carbon dioxide separation unit to obtain a methane-rich gas and a gas discharged from the methane separation unit,

[0041] The gas discharged from the methane separation unit is supplied as fuel to the step (A) and / or the boiler.

[0042]

[13] The methanol production method according to any one of [1] to

[12] , wherein the gas discharged from the carbon dioxide separation unit and / or the gas discharged from the methane separation unit is mixed with the hydrocarbon-containing gas and / or the reformed gas.

[0043]

[14] The methanol production method according to any one of [1] to

[13] , wherein when the molar flow rate of methane contained in the gas discharged from the carbon dioxide separation unit is set to 100 mol%, the molar flow rate of methane contained in the methane-rich gas is 50 to 99 mol%.

[0044]

[15] A methanol production apparatus, comprising:

[0045] A reforming unit,

[0046] A methanol synthesis unit,

[0047] A shift reaction unit, and

[0048] Carbon dioxide separation unit

[0049] The carbon dioxide separation unit exhaust gas obtained through the carbon dioxide separation unit is used as fuel for the reforming unit and / or the boiler.

[0050]

[16] The methanol production device according to

[15] , further comprising a desulfurization unit.

[0051]

[17] The methanol production device according to

[15] or

[16] , further comprising: a methane separation unit for separating methane from the carbon dioxide separation unit exhaust gas.

[0052] Effects of the invention

[0053] According to the present invention, it is possible to provide a method for producing methanol with a low carbon dioxide emission per unit production of methanol and excellent carbon yield. Brief description of the drawings

[0054] Figure 1 It is a schematic diagram showing an example of the production device used in the methanol production method of the present invention.

[0055] Figure 2 It is a schematic diagram showing another example of the production device used in the methanol production method of the present invention.

[0056] Figure 3 It is a schematic diagram showing yet another example of the production device used in the methanol production method of the present invention.

[0057] Figure 4 It is a schematic diagram showing still another example of the production device used in the methanol production method of the present invention.

[0058] Figure 5 It is a schematic diagram showing an example of the production device used in the methanol production method equivalent to the comparative example.

[0059] Figure 6 It is a schematic diagram showing another example of the production device used in the methanol production method equivalent to the comparative example.

[0060] Figure 7 It is a schematic diagram showing yet another example of the production device used in the methanol production method equivalent to the comparative example.

[0061] Figure 8 It is a schematic diagram showing still another example of the production device used in the methanol production method equivalent to the comparative example.

[0062] Figure 9 It is a schematic diagram showing another example of the production device used in the methanol production method equivalent to the comparative example. Detailed Embodiment

[0063] Hereinafter, while referring to the drawings as needed, the method for implementing the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. However, the present invention is not limited to the following present embodiment. The present invention can be variously modified within the scope not departing from its gist. In addition, in the drawings, the same reference numerals are assigned to the same elements, and repeated descriptions are omitted. Further, the positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. In addition, the dimensional ratios of the drawings are not limited to the ratios shown. In addition, in the present embodiment, unless otherwise specified, the molar flow rate refers to the molar flow rate per unit time (kmol / h).

[0064] [Methanol Production Method]

[0065] The methanol production method of the present embodiment is the following methanol production method, which includes:

[0066] Step (A) of reforming a hydrocarbon-containing gas to obtain a reformed gas;

[0067] Step (B) of mixing a hydrogen-containing gas with the above hydrocarbon-containing gas and / or the above reformed gas;

[0068] Step (C) of reacting a part of the above reformed gas in the presence of a catalyst to obtain methanol and unreacted gas;

[0069] Step (D) of subjecting the remaining part of the above reformed gas to a shift reaction to obtain a shift reaction gas; and

[0070] Step (E) of separating carbon dioxide from the above shift reaction gas to obtain a carbon dioxide-rich gas and a carbon dioxide separation unit off-gas,

[0071] At least a part of the above carbon dioxide separation unit off-gas is used as fuel for the above step (A) and / or the boiler.

[0072] Hereinafter, the methanol production method of the present embodiment will be described using the Figures 1 to 4 methanol production apparatus. However, the methanol production method of the present embodiment is not limited to the embodiment using the Figures 1 to 4 production apparatus.

[0073] [Step (A)]

[0074] Step (A) in the methanol production method of the present embodiment is as Figures 1 to 4As shown, it is a process of reforming a hydrocarbon-containing gas 1 through a reforming unit 30 to obtain a reformed gas 5. Specifically, it is a process of reacting the hydrocarbon-containing gas with steam at a specified temperature to generate a reformed gas mainly composed of hydrogen (H2), carbon monoxide (CO), and carbon dioxide (CO2) for methanol synthesis.

[0075] As the reforming method, there is no particular limitation, and examples include steam reforming (SMR), autothermal reforming (ATR), two-stage reforming (SMR + ATR), and partial oxidation method. In addition, when the hydrocarbon-containing gas is natural gas or naphtha, a pre-reforming process may also be included in which a pre-reforming reactor is provided upstream of the reforming unit to reform natural gas or naphtha at about 500 °C to produce a methane-rich gas (not particularly limited, for example, the CH4 content ratio is about 30 to 50 mol%). In addition, from the viewpoint of obtaining a gas composition suitable for methanol synthesis, steam reforming is preferably used. When steam reforming is used in step (A), step (A) is a process of reforming a reforming mixed gas formed by mixing a hydrocarbon-containing gas and steam to obtain a reformed gas.

[0076] The reforming temperature in step (A) can be a temperature known in the art and is not particularly limited. For example, it can be set to 750 °C to 1000 °C. In addition, in step (A), a catalyst can be used. As such a catalyst, a catalyst known in the art can be used and is not particularly limited. Examples include nickel-based catalysts.

[0077] As the hydrocarbon-containing gas, there is no particular limitation, and examples include purified gas and fossil fuel gas. As the purified gas, there is no particular limitation, and examples include methane, ethane, propane, butane, and their mixed gases. As the fossil fuel gas, examples include natural gas (NG) mainly composed of methane, liquefied petroleum gas (LPG), and naphtha. When the hydrocarbon-containing gas is a fossil fuel gas, since the gas component contains sulfur, it is preferable to use the gas that has undergone the subsequent desulfurization process as the hydrocarbon-containing gas.

[0078] The heat recovered in step (A) can be used as a heat source for at least any one of step (G) and step (E).

[0079] [Step (B)]

[0080] Step (B) in the methanol production method of the present embodiment is a step of mixing the hydrocarbon-containing gas 1 and / or the reformed gas 5 with the hydrogen-containing gas 2. Figures 1 to 4 It shows a method of mixing the hydrogen-containing gas 2 and the hydrocarbon-containing gas 1 upstream of the reforming unit 30. Thereby, a gas composition suitable for methanol synthesis can be prepared. In addition, when the methanol production method of the present embodiment includes a desulfurization process, it can be used for sulfur removal in the desulfurization unit 20.

[0081] As the hydrogen-containing gas, there is no particular limitation. For example, the gas discharged from the carbon dioxide separation unit 12 can be used, or the gas discharged from the methane separation unit 16 shown in Figure 4 can be used, or hydrogen produced outside the system can be used.

[0082] When hydrogen produced outside the system is used in step (B), there is no particular limitation. For example, from the viewpoint of reducing carbon dioxide emissions, hydrogen obtained using renewable energy is preferably used. More specifically, examples include: by-product hydrogen from petroleum refining equipment, by-product hydrogen from chemical processes, blue hydrogen such as by-product hydrogen combined with CCS, hydrogen with adjusted gas composition by PSA, etc., hydrogen from water electrolysis or brine electrolysis, hydrogen obtained by other electrolysis techniques, and hydrogen obtained by steam reforming.

[0083] [Step (C)]

[0084] In the methanol production method of the present embodiment, step (C) is as shown in Figures 1 to 4 wherein a part 7a of the reformed gas is supplied to the methanol synthesis unit 40 and reacted in the presence of a catalyst to obtain methanol 8 and unreacted gas 9. In addition, the unreacted gas 9 can be merged with the gas in pipeline 14 as shown in Figure 2 or can be merged with the gas in pipeline 7b as shown in Figure 3 and Figure 4 .

[0085] In addition, although not shown in Figures 1 to 4 , in step (C), by cooling the reaction mixture obtained by the reaction and then performing gas-liquid separation, methanol can be obtained as a liquid phase and unreacted gas can be obtained as a gas phase. As the method of gas-liquid separation, existing well-known methods can be used, and there is no particular limitation. For example, a high-pressure separator can be used.

[0086] In addition, the unreacted gas refers to the gas that has not been used in the methanol synthesis reaction. The unreacted gas depends on the conditions of the methanol synthesis reaction, but as its composition, it is a mixed gas that can contain hydrogen, carbon monoxide, carbon dioxide, methane, nitrogen, etc. At least a part of the unreacted gas is preferably supplied to the shift reaction unit and / or the boiler. Thereby, the carbon dioxide emission can be further reduced.

[0087] A part of the reformed gas means not 100 mol% of the reformed gas. As a part of the reformed gas, the molar flow rate of the reformed gas used in step (C) is preferably 50 to 95 mol%, more preferably 60 to 90 mol%, relative to the molar flow rate of the reformed gas obtained in step (A) above. When the molar flow rate of the reformed gas used in step (C) is 95 mol% or less, there is a tendency for a more excellent reduction in carbon dioxide emissions, and when it is 50 mol% or more, there is a tendency for a more excellent methanol production amount.

[0088] The gas temperature at the inlet of the methanol synthesis unit 40 is appropriately set according to the type or amount of the catalyst, the shape of the reactor, the reaction pressure, etc., and is preferably 170 to 260 °C, more preferably 170 to 220 °C, and further preferably 170 to 200 °C. If the inlet gas temperature is 170 °C or higher, there is a tendency for the reactivity to increase, and if it is 260 °C or lower, there is a tendency for the equipment cost to be reduced.

[0089] The gas pressure at the inlet of the methanol synthesis unit 40 is preferably 4.9 to 14.7 MPaG, more preferably 5.0 to 11.0 MPaG, and further preferably 5.0 to 10.0 MPaG. If the inlet gas pressure is 4.9 MPaG or higher, there is a tendency for the reactivity to increase, and if it is 14.7 MPaG or lower, there is a tendency for the manufacturing efficiency to increase.

[0090] The relationship (M value) of the molar percentages of CO, CO2, and H2 in the reformed gas 7a supplied to the methanol synthesis unit 40 calculated by the following formula is preferably 1.3 to 5.0, more preferably 1.3 to 3.0, further preferably 1.3 to 2.0, and particularly preferably 1.3 to 1.5. If the M value is 1.3 or higher, there is a tendency for by-products to decrease, and if it is 5.0 or lower, there is a tendency for excellent carbon yield.

[0091] M value = (H2 mol%) / (2 × CO mol% + 3 × CO2 mol%)

[0092] Here, the carbon yield refers to the ratio of the molar flow rate of methanol produced in the methanol synthesis unit to the total molar flow rate of carbon monoxide and carbon dioxide contained in the reformed gas supplied to the methanol synthesis unit.

[0093] From the viewpoints of maintaining reactivity, suppressing by-products, and protecting the catalyst, the reaction temperature of the methanol synthesis unit 40 is preferably 200 to 300 °C, more preferably 200 to 280 °C, and further preferably 200 to 270 °C.

[0094] The type of the methanol synthesis unit 40 is not particularly limited. For example, a unit having a mechanism capable of controlling the reaction temperature is preferred. Specifically, for example, a heat exchange type reactor and a quench type adiabatic reactor can be cited. As the heat exchange type reactor, there is no particular limitation, and for example, a multitubular heat exchange type reactor and a radial flow type reactor can be cited.

[0095] In the case of using a multitubular heat exchange type reactor, the reaction temperature is controlled by indirect heat exchange with pressurized boiling water to obtain saturated steam (water vapor). The boiling water circulates between the steam drum and the shell side of the reactor, and the water vapor is recovered from the steam drum. The water vapor obtained in this synthesis system is preferably used as a heat source for the purification process of the methanol solution downstream in the synthesis process. In addition, the pressurized boiling water is preferably at 220°C to 260°C.

[0096] In the case of adopting an adiabatic reactor, it has one or more catalyst layers inside. When there are two or more layers, the reaction temperature is controlled by branching a part of the synthesis reactor feed gas as a quench gas through a cooling gas as an intermediate layer and supplying it. An evaporator is provided at the reactor outlet gas as a heat recovery device to recover water vapor, and it can also be used as a heat source for the purification process of the downstream methanol solution in the same way.

[0097] The catalyst used in the synthesis is preferably a methanol synthesis catalyst containing copper atoms and zinc atoms as essential components. Such a catalyst is reduced from the oxide state by a reducing gas, such as hydrogen, carbon monoxide, or a mixed gas thereof, whereby the copper is activated and has catalytic activity. In addition to copper atoms and zinc atoms, the catalyst may also contain aluminum atoms and / or chromium atoms as main third components. The catalyst containing copper and zinc as essential components can be prepared by a known method. This catalyst can be prepared, for example, by the methods described in Japanese Patent Publication No. 51-44715, Japanese Patent No. 2695663, Japanese Patent Publication No. 6-35401, Japanese Unexamined Patent Publication No. 10-272361, and Japanese Unexamined Patent Publication No. 2001-205089.

[0098] A preferred catalyst is a methanol synthesis catalyst containing copper atoms and zinc atoms in an atomic ratio (copper / zinc) of 2.0 to 3.0 and containing aluminum atoms. As such a catalyst, there is no particular limitation, and for example, a catalyst prepared by the method described in Japanese Unexamined Patent Publication No. 8-299796 and a catalyst described in International Publication No. 2011 / 048976 can be cited.

[0099] As specific examples of the preferred catalyst, the following can be cited: the examples and comparative examples of International Publication No. 2011 / 048976, such as the catalysts used in Example 2 and Example 3. Additionally, a more preferred atomic ratio (copper / zinc) of copper atoms and zinc atoms in the catalyst is in the range of 2.1 to 3.0. In addition, a methanol synthesis catalyst containing 3 to 20% by mass of alumina is further preferred. The catalyst is not particularly limited as described above and can be prepared, for example, by the method described in International Publication No. 2011 / 048976. More specifically, for example, it includes: a step of mixing an aqueous solution containing copper, an aqueous solution containing zinc, and an aqueous alkali solution to form a precipitate containing copper and zinc; a step of mixing the obtained precipitate with an alumina hydrate having a pseudo-boehmite structure to obtain a mixture; and a step of molding the obtained mixture so that the density becomes 2.0 to 3.0 g / mL. Here, as the molding method, tableting, extrusion molding, and rolling granulation can be cited, for example. However, the catalyst used in this embodiment is not limited to the above catalysts and the catalysts prepared by the above preparation methods, and other catalysts having equivalent methanol synthesis activity can also be used.

[0100] [Process (D)]

[0101] Process (D) in the methanol production method of this embodiment is as Figures 1 to 4 shown, and it is a process (D) of supplying the remaining part 7b of the reformed gas to the shift reaction unit 50 to carry out a shift reaction to obtain a shift reaction gas 10. It can also be as Figure 3 and Figure 4 shown, and supply the unreacted gas 9 together with the remaining part 7b of the reformed gas to the shift reaction unit 50. The shift reaction is a reaction in which carbon monoxide in the reformed gas reacts with steam to mainly produce a shift reaction gas containing water and carbon dioxide.

[0102] The shift reaction gas is the gas obtained through process (D) and contains water and carbon dioxide generated by the reaction of carbon monoxide and hydrogen.

[0103] The shift reaction is preferably carried out in the presence of a catalyst. As the catalyst, existing well-known catalysts can be used and there is no particular limitation. For example, transition metal oxides or platinum can be cited. As the transition metal oxide, there is no particular limitation, and for example, iron oxide (Fe3O4) can be cited.

[0104] The remainder of the reformed gas in step (D) refers to the reformed gas with a molar flow rate obtained by removing the reformed gas used in step (C) from the reformed gas obtained in step (A). The molar flow rate of the reformed gas used in step (D) is preferably 5 to 50 mol% with respect to the molar flow rate of the reformed gas obtained in step (A) described above, and more preferably 10 to 40 mol%. When the molar flow rate of the reformed gas used in step (D) is 5 mol% or more, there is a tendency for a more excellent reduction in carbon dioxide emissions, and when it is 50 mol% or less, there is a tendency for a more excellent methanol production amount.

[0105] The reaction temperature of the water gas shift reaction is preferably 400°C to 700°C, and the reaction pressure is preferably 0.5 to 2.0 MPaG.

[0106] In the water gas shift reaction, steam supplied from outside the system can also be mixed in the water gas shift reaction unit.

[0107] The concentration of carbon monoxide in the water gas shift reaction gas (10) is preferably 0.01 to 1.0 mol%, and more preferably 0.01 to 0.1 mol%. Thereby, the amount of carbon dioxide discharged to the outside of the system due to the combustion of carbon monoxide can be reduced, and there is a tendency to further reduce the carbon dioxide emissions per unit production amount of methanol.

[0108] [Step (E)]

[0109] Step (E) in the methanol production method of the present embodiment is as Figures 1 to 4 shown, which is a step of supplying the water gas shift reaction gas 10 to the carbon dioxide separation unit 60 to separate carbon dioxide and obtain the carbon dioxide-rich gas 11 and the carbon dioxide separation unit off-gas 12.

[0110] As the carbon dioxide separation method, existing well-known methods can be used and there is no particular limitation. Examples include: physical absorption method, physical adsorption method, chemical absorption method, chemical adsorption method, membrane separation method, cryogenic separation method, and electroadsorption method.

[0111] In addition, the carbon dioxide-rich gas separated and recovered in step (E) is not discharged into the atmosphere. Thereby, the carbon dioxide emissions can be reduced. As a treatment method for such a separated and recovered carbon dioxide-rich gas, there is no particular limitation. Examples include burying it underground by the CCS method, selling it as dry ice or industrial carbon dioxide gas, and using it as a raw material for chemical products.

[0112] In addition, the carbon dioxide separation unit off-gas obtained in step (E) mainly contains hydrogen. Therefore, it can be mixed with the hydrocarbon-containing gas 1 and / or the reformed gas 5 as a hydrogen-containing gas, or can be used as a heat source for step (A) through the pipeline 14, or can be used as a heat source for a boiler through the pipeline 13.

[0113] In step (E), when the molar flow rate of carbon dioxide contained in the reformed reaction gas 10 is set to 100 mol%, the molar flow rate of carbon dioxide contained in the carbon dioxide-rich gas is preferably 80 to 100 mol%, more preferably 90 to 100 mol%, and still more preferably 95 to 99.9 mol%. Thereby, there is a tendency that the reduction of carbon dioxide emissions is more excellent.

[0114] In step (E), when water vapor is sometimes required for absorbing or adsorbing and separating carbon dioxide, the water vapor recovered in the above step (A) or the water vapor generated in step (C) can also be used.

[0115] In addition, the heat recovered in step (A) can also be used in step (E), or it can be used in the form of supplying renewable energy from the outside.

[0116] [Step (F)]

[0117] The methanol production method of the present embodiment preferably further includes step (F). Step (F) is as Figures 2 to 4 shown, which is a step of supplying the hydrocarbon-containing gas 1 to the desulfurization unit 20 to obtain the desulfurized gas 4 from which sulfur components have been removed. When the hydrocarbon-containing gas is a fossil fuel gas, this step (F) is particularly required because it contains sulfur components. That is, since sulfur compounds become catalyst poisons for the catalysts used in steps (A) and (C), when the hydrocarbon-containing gas contains sulfur components, it is preferably removed in advance in step (F). As the desulfurization method, existing well-known methods can be used, and there is no particular limitation. Examples include dry methods using adsorbents or catalysts, and wet methods using absorption liquids such as amine systems. In the case of using the dry method, it cannot be generalized depending on the type of sulfur compound to be removed and the type of catalyst used, but the operating temperature can be set to 0 to 400°C.

[0118] [Step (G)]

[0119] The methanol production method of the present embodiment preferably further includes step (G). The details of step (G) are not shown in Figures 1 to 4 and it is a step of obtaining refined methanol from methanol 8.

[0120] As a method for obtaining refined methanol in step (G), existing well-known methods can be used, and there is no particular limitation. For example, a distillation column having a reboiler and a condenser can be used. In this case, by distilling methanol, high-purity methanol can be obtained from the bottom or the middle section of the column.

[0121] In step (G), the water vapor recovered in step (A) or the water vapor generated in step (C) can also be used. By using water vapor, for example, in the case of distillation using a distillation column, the fluid discharged from the top of the column can be absorbed or adsorbed. As a result, the carbon dioxide emission can be further reduced.

[0122] In step (G), the heat recovered in step (A) can also be used. Such heat is not particularly limited. For example, in the case of distillation using a distillation column, it can be used as the heat required for a reboiler. As a result, the carbon dioxide emission can be further reduced. In addition, it can also be used as heat in the form of renewable energy supplied from the outside.

[0123] [Step (H)]

[0124] The methanol production method of the present embodiment preferably further includes step (H). The details of step (H) are as Figure 4 shown, which is a step of supplying the carbon dioxide separation unit off-gas 12 to the methane separation unit 70, separating methane from the carbon dioxide separation unit off-gas 12, and obtaining a methane-rich gas 15 and a methane separation unit off-gas 16.

[0125] As the method for separating methane in step (H), a conventionally known method can be adopted and is not particularly limited. For example, physical adsorption method and membrane separation method can be mentioned.

[0126] Regarding the methane separation efficiency, when the molar flow rate of methane contained in the carbon dioxide separation unit off-gas is set to 100 mol%, the molar flow rate of methane contained in the above methane-rich gas is preferably 50 to 99 mol%, more preferably 70 to 99 mol%, and further preferably 90 to 99 mol%. As a result, the amount of carbon dioxide discharged to the outside of the system due to the combustion of methane can be reduced, and there is a tendency to further reduce the carbon dioxide emission per unit production of methanol.

[0127] The methane separation unit off-gas can also be used as the heat source for step (A) and / or the boiler.

[0128] In addition, since the methane separation unit off-gas 16 mainly contains hydrogen, it can also be used as a hydrogen-containing gas, mixed with the hydrocarbon-containing gas 1 and / or the reformed gas 5, and can be used as the heat source for step (A) through pipeline 14, and can also be used as the heat source for the boiler through pipeline 13.

[0129] In addition, as shown in Figure 4 , the methane-rich gas 15 can also be supplied to the reforming unit 30 through pipeline 2.

[0130] [Other steps]

[0131] In addition to the above steps, the methanol production method of this embodiment may also include other steps as needed.

[0132] As other steps, there is no particular limitation. For example, it may also have a methane recovery step of mixing the rich methane gas obtained in step (H) with a hydrocarbon-containing gas.

[0133] [Methanol production device]

[0134] The methanol production device of this embodiment is a device for implementing the above methanol production method, and examples thereof may include Figures 1 to 4 the device shown in the schematic diagram.

[0135] The methanol production device of this embodiment is a methanol production device as follows. As Figure 1 shown, it includes a reforming unit 30, a methanol synthesis unit 40, a shift reaction unit 50, and a carbon dioxide separation unit 60. The carbon dioxide separation unit discharge gas 12 obtained through the above carbon dioxide separation unit 60 is used as fuel for the above reforming unit 30 and / or the boiler.

[0136] The reforming unit 30 includes a reforming reactor and may also include other equipment as needed. The reforming reactor reacts a hydrocarbon-containing gas with steam at a specified temperature to generate a reformed gas mainly composed of hydrogen (H2), carbon monoxide (CO), and carbon dioxide (CO2) for methanol synthesis.

[0137] The methanol synthesis unit 40 includes a methanol synthesis reactor that reacts the reformed gas in the presence of a catalyst to produce methanol and unreacted gas, and may also include other equipment as needed.

[0138] The shift reaction unit 50 includes a shift reactor and may also include other equipment as needed. The shift reactor performs a shift reaction on the reformed gas to generate a shift reaction gas.

[0139] The carbon dioxide separation unit 60 includes a carbon dioxide separator that separates carbon dioxide from the shift reaction gas to generate a carbon dioxide-rich gas and a carbon dioxide separation unit discharge gas, and may also include other equipment as needed.

[0140] In addition, the methanol production device of this embodiment preferably further includes a desulfurization unit 20 as Figure 2 shown.

[0141] The desulfurization unit 20 includes a desulfurizer that removes sulfur components from the hydrocarbon-containing gas and may also include other equipment as needed.

[0142] The methanol production device of this embodiment is as Figure 3 and Figure 4As shown, the pipeline 9 for preferably circulating unreacted gas is connected to the shift reaction unit 50. Thereby, the carbon dioxide emission can be further reduced.

[0143] The methanol production apparatus of the present embodiment is as Figure 4 shown, and preferably further includes a methane separation unit 70 that separates methane from the gas discharged from the carbon dioxide separation unit. Thereby, the carbon dioxide emission can be further reduced.

[0144] The methane separation unit 70 includes a methane separator that separates methane from the gas discharged from the carbon dioxide separation unit to generate a methane-rich gas and a gas discharged from the methane separation unit, and may also include other equipment as needed.

[0145] Examples

[0146] Hereinafter, the methanol production method and production apparatus of the present invention will be described in detail by way of examples and comparative examples, but the present invention is not limited by any of these.

[0147] The catalyst used in methanol synthesis can be any one of a catalyst prepared by the method described in Example 1 of Japanese Patent Publication No. 51-44715 (methanol synthesis catalyst A), a catalyst prepared by the method described in Example 1 of Japanese Unexamined Patent Publication No. 8-299796 (methanol synthesis catalyst B), a catalyst prepared by the method described in Example 3 of International Publication No. 2011 / 048976 (methanol synthesis catalyst C), or a catalyst prepared by the method described in Comparative Example 4 of Japanese Unexamined Patent Publication No. 8-299796 (methanol synthesis catalyst D). In addition, the amount of the catalyst used in each of the following examples and comparative examples is all set to the same amount.

[0148] [Example 1]

[0149] In Example 1, the production apparatus shown in Figure 2 was used. Each condition is shown in Table 1. That is, shale gas (CH4: 94.3 mol%, C2H6: 2.7 mol%, C3H8: 0.6 mol%, C4H 10 : 0.2 mol%, C5H 12: 0.2 mol%, CO2: 0.5 mol%, N2: 1.5 mol%), after performing steam reforming reaction, the synthesis gas thus generated is used for the synthesis of methanol. As the catalyst in the methanol synthesis reactor in the methanol synthesis unit, methanol synthesis catalyst C is used. In addition, regarding the temperature and pressure of each pipeline, they are set to be the values shown in Table 1. A multitubular heat exchange type reactor is used as the methanol synthesis reactor. The set conditions are: the pressure of the fluid in contact with the catalyst in the reactor is 10.0 MPaG, the shell pressure is set to 4.0 MPaG, and the temperature is between 200 and 234 °C. In addition, the reaction pressure in the reformer is 1.9 MPaG and the temperature is 860 °C. In addition, regarding the molar flow rate distribution of pipeline 7a and pipeline 7b, it is set to a distribution ratio that can sufficiently provide the heat required for temperature rise in the reforming unit.

[0150] In addition, although Figure 2 is not shown, the methanol 8 obtained from the methanol synthesis unit 40 is cooled to below the dew point of methanol, i.e., 45 °C, which promotes the condensation of methanol.

[0151] In addition, the material balance for Example 1 is shown in Table 1. The vertical column of Table 1 is Figure 2 the pipeline numbers shown, and the horizontal column is the temperature (°C), pressure (MPaG), and molar flow rate (kmol / h) of the substances flowing through each pipeline.

[0152] [Table 1]

[0153]

[0154] The methanol production amount (tons / day), carbon dioxide emission amount (tons / day), and carbon dioxide emission amount per unit methanol (tons-CO2 / ton-MeOH) obtained in Example 1 are shown in Table 9.

[0155] In addition, the methanol production amount (tons / day) in Example 1 in Table 9 is calculated by multiplying the molar flow rate (kmol / h) of methanol in pipeline 8 in Table 1 by the molar mass of methanol (g / mol) and 24 (h).

[0156] In addition, the carbon dioxide emission amount (tons / day) in Example 1 in Table 9 is calculated by multiplying the sum of the molar flow rates (kmol / h) of carbon atoms in pipelines 9, 13, and 14 in Table 1 by the molar mass of carbon dioxide (g / mol) and 24 (h).

[0157] [Example 2]

[0158] In Example 2, the manufacturing apparatus shown in Figure 3 is used. The pipelines are as shown in Figure 3Except for the changes shown, methanol synthesis was carried out under the same conditions as in Example 1. The material balance is shown in Table 2.

[0159] [Table 2]

[0160]

[0161] The methanol production amount (tons / day), carbon dioxide emission amount (tons / day), and carbon dioxide emission amount per unit of methanol (tons-CO2 / tons-MeOH) obtained in Example 2 are shown in Table 9.

[0162] Among them, the methanol production amount (tons / day) in Example 2 in Table 9 was calculated by multiplying the molar flow rate (kmol / h) of methanol in pipeline 8 in Table 2 by the molar mass of methanol (g / mol) and 24 (h).

[0163] In addition, the carbon dioxide emission amount (tons / day) in Example 2 in Table 9 was calculated by multiplying the sum of the molar flow rates (kmol / h) of carbon atoms in pipelines 13 and 14 in Table 2 by the molar mass of carbon dioxide (g / mol) and 24 (h).

[0164] [Example 3]

[0165] In Example 3, the manufacturing device shown in Figure 4 was used. The pipelines were changed as shown in Figure 4 and the material balance was changed as shown in Table 3. Except for this, methanol synthesis was carried out under the same conditions as in Example 1. The material balance is shown in Table 3.

[0166] [Table 3]

[0167]

[0168] The methanol production amount (tons / day), carbon dioxide emission amount (tons / day), and carbon dioxide emission amount per unit of methanol (tons-CO2 / tons-MeOH) obtained in Example 3 are shown in Table 9.

[0169] Furthermore, the methanol production amount (tons / day) in Example 3 in Table 9 was calculated by multiplying the molar flow rate (kmol / h) of methanol in pipeline 8 in Table 3 by the molar mass of methanol (g / mol) and 24 (h).

[0170] In addition, the carbon dioxide emission amount (tons / day) in Example 3 in Table 9 was calculated by multiplying the sum of the molar flow rates (kmol / h) of carbon atoms in pipelines 13 and 14 in Table 3 by the molar mass of carbon dioxide (g / mol) and 24 (h).

[0171] [Comparative Example 1]

[0172] In Comparative Example 1, the manufacturing apparatus shown in Figure 5 was used. Except that the manufacturing apparatus shown in Figure 5 does not have a shift reaction unit and a carbon dioxide separation unit, and the pipeline was changed as shown in Figure 5 , methanol synthesis was carried out under the same conditions as in Example 1. The material balance is shown in Table 4.

[0173] [Table 4]

[0174]

[0175] The methanol production amount (tons / day), carbon dioxide emission amount (tons / day), and carbon dioxide emission amount per unit of methanol (tons-CO2 / tons-MeOH) obtained in Comparative Example 1 are shown in Table 9.

[0176] Among them, the methanol production amount (tons / day) in Comparative Example 1 in Table 9 was calculated by multiplying the molar flow rate (kmol / h) of methanol in pipeline 8 in Table 4 by the molar mass of methanol (g / mol) and 24 (h).

[0177] In addition, the carbon dioxide emission amount (tons / day) in Comparative Example 1 in Table 9 was calculated by multiplying the total of the molar flow rates (kmol / h) of carbon atoms in pipelines 9, 13, and 14 in Table 4 by the molar mass of carbon dioxide (g / mol) and 24 (h).

[0178] [Comparative Example 2]

[0179] In Comparative Example 2, the manufacturing apparatus shown in Figure 6 was used. Figure 6 Except that the manufacturing apparatus shown in Figure 6 does not have a shift reaction unit and the pipeline was changed as shown in

[0180] , methanol synthesis was carried out under the same conditions as in Example 1. The material balance is shown in Table 5.

[0181]

[0182] The methanol production amount (tons / day), carbon dioxide emission amount (tons / day), and carbon dioxide emission amount per unit of methanol (tons-CO2 / tons-MeOH) obtained in Comparative Example 2 are shown in Table 9.

[0183] Among them, the methanol production amount (tons / day) in Comparative Example 2 in Table 9 was calculated by multiplying the molar flow rate (kmol / h) of methanol in pipeline 8 in Table 5 by the molar mass of methanol (g / mol) and 24 (h).

[0184] In addition, the carbon dioxide emissions (tons / day) in Comparative Example 2 in Table 9 were calculated by multiplying the total molar flow rate (kmol / h) of carbon atoms in pipelines 9, 13, and 14 in Table 5 by the molar mass of carbon dioxide (g / mol) and 24 (h).

[0185] [Comparative Example 3]

[0186] In Comparative Example 3, the manufacturing apparatus shown in Figure 7 was used. Except that the manufacturing apparatus shown in Figure 7 did not have a carbon dioxide separation unit and the pipelines were changed as shown in Figure 7 , methanol synthesis was carried out under the same conditions as in Example 1. The material balance is shown in Table 6.

[0187] [Table 6]

[0188]

[0189] The methanol production amount (tons / day), carbon dioxide emissions (tons / day), and carbon dioxide emissions per unit of methanol (tons-CO2 / ton-MeOH) obtained in Comparative Example 3 are shown in Table 9.

[0190] In addition, the methanol production amount (tons / day) in Comparative Example 3 in Table 9 was calculated by multiplying the molar flow rate (kmol / h) of methanol in pipeline 8 in Table 6 by the molar mass of methanol (g / mol) and 24 (h).

[0191] In addition, the carbon dioxide emissions (tons / day) in Comparative Example 3 in Table 9 were calculated by multiplying the total molar flow rate (kmol / h) of carbon atoms in pipelines 9, 13, and 14 in Table 6 by the molar mass of carbon dioxide (g / mol) and 24 (h).

[0192] [Comparative Example 4]

[0193] In Comparative Example 4, the manufacturing apparatus shown in Figure 8 was used. Except that the carbon dioxide separation unit in the manufacturing apparatus shown in Figure 8 was arranged upstream of the shift reaction unit and the pipelines were changed as shown in Figure 8 , methanol synthesis was carried out under the same conditions as in Example 1. The material balance is shown in Table 7.

[0194] [Table 7]

[0195]

[0196] The methanol production amount (tons / day), carbon dioxide emissions (tons / day), and carbon dioxide emissions per unit of methanol (tons-CO2 / ton-MeOH) obtained in Comparative Example 4 are shown in Table 9.

[0197] Among them, the methanol production amount (tons per day) in Comparative Example 4 in Table 9 is calculated by multiplying the molar flow rate (kmol / h) of methanol in pipeline 8 in Table 7 by the molar mass of methanol (g / mol) and 24 (h).

[0198] In addition, the carbon dioxide emission amount (tons per day) in Comparative Example 4 in Table 9 is calculated by multiplying the total of the molar flow rates (kmol / h) of carbon atoms in pipelines 9, 13, and 14 in Table 7 by the molar mass of carbon dioxide (g / mol) and 24 (h).

[0199] [Comparative Example 5]

[0200] In Comparative Example 5, the manufacturing apparatus shown in Figure 9 was used. Except that in the manufacturing apparatus shown in Figure 9 the shift reaction unit is arranged downstream of pipeline 5 and upstream of pipeline 6, and the pipeline is changed as shown in Figure 9 , methanol synthesis was carried out under the same conditions as in Example 1. The material balance is shown in Table 8.

[0201] In addition, in Comparative Example 5, since the heat balance with the reforming unit is maintained, for example, compared with Example 1, the molar flow rate of the carbon raw material flowing into the methanol synthesis unit is larger, and even if the carbon yield is less than 96%, the methanol production amount equivalent to that in Example 1 is formally obtained.

[0202] [Table 8]

[0203]

[0204] The methanol production amount (tons per day), carbon dioxide emission amount (tons per day), and carbon dioxide emission amount per unit methanol (tons-CO2 / ton-MeOH) obtained in Comparative Example 5 are shown in Table 9.

[0205] Among them, the methanol production amount (tons per day) in Comparative Example 5 in Table 9 is calculated by multiplying the molar flow rate (kmol / h) of methanol in pipeline 8 in Table 8 by the molar mass of methanol (g / mol) and 24 (h).

[0206] In addition, the carbon dioxide emission amount (tons per day) in Comparative Example 5 in Table 9 is calculated by multiplying the total of the molar flow rates (kmol / h) of carbon atoms in pipelines 9, 13, and 14 in Table 8 by the molar mass of carbon dioxide (g / mol) and 24 (h).

[0207] The results obtained in Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Table 9 below. Herein, if the carbon yield is 95.0 mol% or more and the carbon dioxide emission / methanol production is 0.400 or less, it corresponds to an Example, and otherwise it corresponds to a Comparative Example.

[0208] [Table 9]

[0209]

[0210] Herein, the definitions of the respective terms in Table 9 are as follows.

[0211] <Methanol synthesis pressure>

[0212] Indicates the gas pressure at the inlet of the methanol synthesis reactor.

[0213] <Recycle ratio>

[0214] The recycle ratio is the ratio of the molar flow rate of the recycle gas to the molar flow rate of the reformed gas supplied in the methanol synthesis unit. Herein, the recycle gas refers to the gas obtained by separating methanol and water from the outlet gas of the methanol synthesis reactor in the methanol synthesis unit, and is the gas that is mixed with the reformed gas supplied to the unit from the outside and supplied to the methanol synthesis reactor in the unit.

[0215] <Shell pressure>

[0216] Refers to the pressure on the inner side of the shell side and the outer side of the tubes in a multitubular heat exchange type reactor.

[0217] <M value at the inlet of the methanol synthesis unit>

[0218] Refers to the M value at the inlet of the methanol synthesis unit.

[0219] <H2 / CO at the inlet of the methanol synthesis unit>

[0220] Refers to the ratio of the number of moles of carbon monoxide to the number of moles of hydrogen at the inlet of the methanol synthesis unit.

[0221] <Amount of catalyst>

[0222] Refers to the mass ratio of the amount of catalyst in each Example or Comparative Example when the amount of catalyst used in the production apparatus of Example 1 is set to 100%.

[0223] <Carbon yield>

[0224] Refers to the ratio of the molar flow rate of methanol contained in the outlet gas of the methanol synthesis unit to the total amount of the molar flow rates of carbon monoxide and carbon dioxide contained in the reformed gas supplied to the methanol synthesis unit.

[0225] Industrial applicability

[0226] The present invention has industrial applicability in the method and apparatus for manufacturing methanol.

[0227] Explanation of symbols:

[0228] 20... desulfurization unit, 30... reforming unit, 40... methanol synthesis unit, 50... shift reaction unit, 60... carbon dioxide separation unit, 70... methane separation unit, 1, 2, 3, 4, 5, 6, 7a, 7b, 8, 9, 10, 11, 12, 13, 14, 15, 16... pipelines.

Claims

1. A method for manufacturing methanol, wherein, comprising: Process (A) for reforming a hydrocarbon-containing gas to obtain a reformed gas; Process (B) for mixing a hydrogen-containing gas with the hydrocarbon-containing gas and / or the reformed gas; Process (C) for reacting a part of the reformed gas in the presence of a catalyst to obtain methanol and unreacted gas; Process (D) for subjecting the remaining part of the reformed gas to a shift reaction to obtain a shift reaction gas; and Process (E) for separating carbon dioxide from the shift reaction gas to obtain a carbon dioxide-rich gas and a carbon dioxide separation unit off-gas, At least a part of the carbon dioxide separation unit off-gas is used as fuel for the process (A) and / or the boiler.

2. The method for manufacturing methanol according to claim 1, wherein, Further includes: Process (F) for removing sulfur from the hydrocarbon-containing gas.

3. The method for manufacturing methanol according to claim 1, wherein, Further includes: Process (G) for obtaining refined methanol from the methanol.

4. The method for manufacturing methanol according to claim 1, wherein, The molar flow rate of the reformed gas used in the process (C) is 50 to 95 mol% relative to the molar flow rate of the reformed gas obtained in the process (A).

5. The method for manufacturing methanol according to claim 3, wherein, The water vapor generated in the process (C) is used for the process (G) and / or the process (E).

6. The method for manufacturing methanol according to claim 3, wherein, The water vapor recovered in the process (A) is used for the process (G) and / or the process (E).

7. The method for manufacturing methanol according to claim 3, wherein, The heat recovered in the process (A) is used as a heat source for at least any one of the process (G) and the process (E).

8. The method for manufacturing methanol according to claim 1, wherein, The process (D) is carried out in the presence of a catalyst.

9. The method for manufacturing methanol according to claim 1, wherein, The carbon monoxide concentration in the shift reaction gas is 0.01 to 1.0 mol%.

10. The method for manufacturing methanol according to claim 1, wherein, When the molar flow rate of carbon dioxide contained in the shift reaction gas is set to 100 mol%, the molar flow rate of carbon dioxide contained in the carbon dioxide-rich gas is 80 to 100 mol%.

11. The method for manufacturing methanol according to claim 1, wherein, At least a part of the unreacted gas is supplied to a shift reaction unit and / or the boiler.

12. The method for manufacturing methanol according to claim 1, wherein, Further includes: Process (H) for separating methane from the carbon dioxide separation unit off-gas to obtain a methane-rich gas and a methane separation unit off-gas, The methane separation unit off-gas is supplied as fuel for the process (A) and / or the boiler.

13. The method for manufacturing methanol according to claim 12, wherein, The carbon dioxide separation unit off-gas and / or the methane separation unit off-gas is mixed with the hydrocarbon-containing gas and / or the reformed gas.

14. The method for manufacturing methanol according to claim 12, wherein, When the molar flow rate of methane contained in the carbon dioxide separation unit off-gas is set to 100 mol%, the molar flow rate of methane contained in the methane-rich gas is 50 to 99 mol%.

15. A methanol production device, wherein, Comprises: A reforming unit, A methanol synthesis unit, A shift reaction unit, and A carbon dioxide separation unit, The carbon dioxide separation unit off-gas obtained through the carbon dioxide separation unit is used as fuel for the reforming unit and / or the boiler.

16. The methanol production device according to claim 15, wherein, Further comprises a desulfurization unit.

17. The methanol production device according to claim 15, wherein, Further comprises: A methane separation unit for separating methane from the carbon dioxide separation unit off-gas.

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