Method for producing liquid fuel and system for synthesizing liquid fuel

Abstract

The main purpose of the present invention is to reduce the temperature difference between the gas temperature at the inlet and the gas temperature at the outlet of a reactor in a conversion reaction for converting a raw material gas containing carbon oxide and hydrogen gas into a liquid fuel. A method for producing a liquid fuel according to an embodiment of the present invention comprises: a step in which a starting material gas containing at least a carbon oxide and hydrogen gas is introduced into a reactor in which a catalyst is housed; and a step for generating a liquid fuel from the raw material gas by a conversion reaction in the presence of the catalyst, the raw material gas further containing an inert gas, and the ratio of the carbon monoxide concentration to the carbon dioxide concentration in the carbon oxide being 0.9 or less.

Description

Technical Field

[0001] The invention relates to a method for producing liquid fuel and a liquid fuel synthesis system. Background Art

[0002] In recent years, in order to achieve a carbon-neutral society, it has been proposed to treat carbon oxides such as carbon monoxide and carbon dioxide as carbon resources and convert them into liquid fuels that are useful as industrial basic raw materials. For example, Patent Document 1 discloses a liquid fuel synthesis system that uses a membrane reactor (Japanese: メンブレンアクタ) containing a catalyst and a water vapor separation membrane to perform a conversion reaction of a raw gas containing carbon dioxide (CO2) and hydrogen (H2) into methanol.

[0003] Prior art literature Patent Literature Patent Document 1: Japanese Patent Application Publication No. 2018-8940 Summary of the invention

[0004] Problems to be solved by the invention In the above-mentioned reforming reaction of reforming a raw gas containing carbon oxides and hydrogen into a liquid fuel, there is a desire to reduce the temperature difference between the gas temperature at the inlet and the gas temperature at the outlet of the reactor.

[0005] The main object of the present invention is to reduce the temperature difference between the gas temperature at the inlet and the gas temperature at the outlet of a reactor in a reforming reaction of reforming a raw gas containing carbon oxides and hydrogen into a liquid fuel.

[0006] Technical solutions to solve problems [1] According to one embodiment of the present invention, a method for producing a liquid fuel comprises: a step of allowing a raw gas containing at least carbon oxides and hydrogen to flow into a reactor containing a catalyst; and a step of generating a liquid fuel from the raw gas through a conversion reaction in the presence of the catalyst, wherein the raw gas also contains an inert gas, and the ratio of the carbon monoxide concentration in the carbon oxides to the carbon dioxide concentration is less than 0.9.

[0007] [2] In the production method described in [1] above, the concentration of the inert gas in the raw material gas may be greater than or equal to 1 volume % and less than or equal to 55 volume %.

[0008] [3] In the manufacturing method described in [1] or [2] above, the ratio of the inert gas concentration in the raw material gas to the carbon dioxide concentration may be greater than or equal to 0.05 and less than or equal to 1.5.

[0009] [4] In the production method described in any one of [1] to [3] above, the carbon oxide concentration in the raw material gas may be greater than or equal to 5% by volume and less than or equal to 50% by volume.

[0010] [5] In the production method described in any one of [1] to [4] above, the concentration of the hydrogen gas in the raw material gas may be greater than or equal to 20% by volume and less than or equal to 85% by volume.

[0011] [6] In the production method described in any one of [1] to [5] above, the temperature of the raw material gas when flowing into the reactor may be 40° C. or higher and 350° C. or lower.

[0012] [7] The production method described in any one of [1] to [6] above may also include a step of preparing the raw material gas using a gas containing an inert gas recovered from the atmosphere or biogas and carbon dioxide.

[0013] [8] In the production method described in any one of [1] to [7] above, the reactor may include a water vapor separation membrane that allows water vapor to pass through.

[0014] [9] In the production method described in any one of [1] to [7] above, the reactor may include a liquid fuel separation membrane that allows at least the liquid fuel to permeate.

[0015]

[10] According to another embodiment of the present invention, a method for producing a liquid fuel comprises: a step of flowing a raw gas containing at least carbon oxides and hydrogen into a reactor containing a catalyst; and a step of generating a liquid fuel from the raw gas through a reforming reaction in the presence of the catalyst, wherein the raw gas further contains an inert gas, and the liquid fuel contains methanol, and based on the thermodynamic equilibrium calculation results of the reforming reaction under the conditions of 200°C and 4 MPa (G) when the ratio of the carbon monoxide concentration (CO) in the carbon oxides to the carbon dioxide concentration (CO2) and the ratio of the inert gas concentration (Inert) to the carbon dioxide concentration (CO2) in the raw gas are changed, the slope a of an approximate straight line produced by linear approximation (Y=aX+b) for points plotted with (Inert+CO) / CO2 in the raw gas as the X-axis and (ratio of the calorific value after suppression)×(ratio of the increase in combustion energy obtained) as the Y-axis is less than 1.4, and ... each CO / CO2 ratio is less than 1.4, and the slope a of an approximate straight line produced by linear approximation (Y=aX+b) for points plotted with each CO / CO2 ratio is less than 1.4, and the slope a of an approximate straight line produced by linear approximation (Y=aX+b) for points plotted with each CO / CO2 ratio is less than 1.4, and the slope a of an approximate straight line produced by linear appro In the case of the above-mentioned raw gas, the above-mentioned plotting is performed on a total of 18 data when the Inert / CO2 ratio is changed in the range of 0 to 1.6 at a scale of 0.1 and when the Inert / CO2 ratio is 0.05. The ratio of the above-mentioned suppressed calorific value and the ratio of the above-mentioned increased combustion energy are values ​​calculated by the following formulas: Ratio of suppressed calorific value = (calorific value calculated under the reference condition - calorific value calculated when using each raw gas) / calorific value calculated under the reference condition; Ratio of the obtained increased combustion energy = (combustion energy of generated methanol calculated when using each raw gas - combustion energy of generated methanol calculated under the reference condition) / combustion energy of generated methanol calculated under the reference condition (here, the above-mentioned reference condition is the case of using a raw gas containing only carbon dioxide and hydrogen at a ratio of CO2 / H2=1 / 3, and the above-mentioned combustion energy of generated methanol is a value calculated by "Formula: Combustion energy of generated methanol = amount of methanol generated × high calorific value of methanol").

[0016]

[11] In the manufacturing method described in

[10] above, the product of the ratio of the suppressed calorific value and the ratio of the obtained combustion energy increase may be greater than -3.

[0017]

[12] A liquid fuel synthesis system according to an embodiment of the present invention comprises: a reactor which accommodates a catalyst, wherein the catalyst promotes a conversion reaction from a raw gas containing at least carbon oxides and hydrogen to a liquid fuel; and a raw gas supply unit which supplies a gas containing carbon oxides, hydrogen and an inert gas and in which the ratio of the carbon monoxide concentration in the carbon oxides to the carbon dioxide concentration is less than 0.9 as the raw gas to the reactor.

[0018]

[13] In the liquid fuel synthesis system described in

[12] above, the concentration of the inert gas in the raw gas may be greater than 1 volume % and less than 55 volume %.

[0019]

[14] In the liquid fuel synthesis system described in

[12] or

[13] above, the ratio of the inert gas concentration in the raw gas to the carbon dioxide concentration may be greater than 0.05 and less than 1.5.

[0020]

[15] In the liquid fuel synthesis system described in any one of

[12] to

[14] above, the liquid fuel synthesis system may also include a gas recovery unit, which recovers inert gas and carbon dioxide from the atmosphere or biogas, and the gas containing inert gas and carbon dioxide supplied from the gas recovery unit is supplied to the reactor as a component of the raw gas.

[0021]

[16] In the liquid fuel synthesis system described in any one of

[12] to

[15] above, the reactor may include a water vapor separation membrane that allows water vapor to pass through.

[0022]

[17] In the liquid fuel synthesis system described in any one of

[12] to

[15] above, the reactor may include a liquid fuel separation membrane that allows at least the liquid fuel to pass through.

[0023] Effects of the Invention In the method for producing liquid fuel according to the embodiment of the present invention, a gas containing carbon oxides, hydrogen and an inert gas is used as a raw gas, thereby reducing the temperature difference between the gas temperature at the inlet and the gas temperature at the outlet of the reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram for explaining a method for producing a liquid fuel according to one embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram illustrating a structure of an example of a reactor that can be used in the method for producing a liquid fuel according to an embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram illustrating a structure of an example of a reactor that can be used in the method for producing a liquid fuel according to an embodiment of the present invention.

[0027] Figure 4 This is a schematic diagram illustrating a structure of an example of a reactor that can be used in the method for producing a liquid fuel according to an embodiment of the present invention.

[0028] Figure 5 This is a schematic diagram illustrating a structure of an example of a reactor that can be used in the method for producing a liquid fuel according to an embodiment of the present invention.

[0029] Figure 6 Schematic diagram for explaining a liquid fuel synthesis system used in a method for producing a liquid fuel according to an embodiment of the present invention.

[0030] Figure 7 (a) and (b) are graphs created based on the results of thermodynamic equilibrium calculations for liquid fuel production when the ratio of N 2 is changed with respect to raw gas having various CO / CO 2 ratios. DETAILED DESCRIPTION

[0031] Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited to these embodiments. In addition, in order to make the description clearer, the accompanying drawings schematically show the width, thickness, shape, etc. of each part compared with the embodiments, but this is only an example and does not limit the interpretation of the present invention.

[0032] A. Methods for producing liquid fuel A method for producing a liquid fuel according to an embodiment of the present invention includes: A step of flowing a raw material gas containing at least carbon oxides and hydrogen into a reactor containing a catalyst (step I); and A step of producing a liquid fuel from the raw gas by a reforming reaction in the presence of the catalyst (step II).

[0033] Typically, the raw material gas further contains an inert gas. The ratio of the carbon monoxide concentration in the carbon oxides to the carbon dioxide concentration is, for example, 0.9 or less.

[0034] The method for producing a liquid fuel according to the embodiment of the present invention typically further includes a step of causing a product gas containing the liquid fuel to flow out from the reactor (step III).

[0035] In this specification, liquid fuel refers to a fuel that is in a liquid state at room temperature and pressure, or a fuel that can be liquefied under room temperature and pressure. Examples of fuels that are in a liquid state at room temperature and pressure include methanol, ethanol, n H 2（m－2n） (m is an integer less than 90, n is an integer less than 30), and mixtures thereof. Examples of the fuel that can be liquefied under normal temperature and pressure include propane, butane, and mixtures thereof.

[0036] As an example of the above-mentioned conversion reaction, the reaction formula of the reaction that may occur when synthesizing methanol by catalytic hydrogenation of a raw material gas containing carbon monoxide, carbon dioxide and hydrogen in the presence of a catalyst is as follows. In the reaction of formula (2), methanol is generated as a product and water is generated as a by-product. It should be noted that regarding the calorific value, the calorific value when the reaction proceeds to the right side is recorded in each formula, and a negative sign indicates heat generation, and a positive sign indicates endothermicity.

[0037] CO+2H2 CH3OH: -90.8 kJ / mol (1) CO2+3H2 CH3OH+H2O: -49.2kJ / mol (2) CO+H2O CO2+H2: -41.2kJ / mol (3) Figure 1 Schematic diagram for explaining a method for producing a liquid fuel according to one embodiment of the present invention. Figure 1 The method for producing a liquid fuel according to the embodiment shown is performed using a liquid fuel synthesis system 1, which includes a reactor 100 that accommodates a catalyst, and a raw gas supply unit 200 that supplies a raw gas to the reactor 100. The liquid fuel synthesis system 1 also includes a purge gas supply unit 300 that supplies a purge gas to the reactor 100. The raw gas supply unit 200 includes a first gas storage unit 210 and a pressurizing unit 220. The purge gas supply unit 300 includes a second gas storage unit 310 and a heating unit 320. Figure 1 A method for producing a liquid fuel according to an embodiment of the present invention will be described.

[0038] A-1. Process (I) In step (I), a raw material gas containing carbon oxides, hydrogen, and an inert gas is flowed into a reactor containing a catalyst.

[0039] The reactor typically includes a gas inlet for allowing a raw material gas to flow in, a gas outlet for allowing a product gas containing a product to flow out, and a space connecting these, and a catalyst is accommodated in the space.

[0040] The shape of the reactor is not particularly limited, and may be, for example, monolithic, flat, tubular, cylindrical, cylindrical, polygonal, etc. The monolithic shape refers to a shape having a plurality of cells penetrating in the longitudinal direction, and is a concept including a honeycomb shape.

[0041] exist Figure 1In the illustrated embodiment, the reactor 100 is a so-called membrane reactor, and includes a water vapor separation membrane 110, a catalyst 120, a non-permeable side space 100A, and a permeable side space 100B. In the illustrated example, the water vapor separation membrane 110 is supported by a porous support 130. The reactor 100 also includes a first inlet s1 and a first outlet d1 communicated via the non-permeable side space 100A, and a second inlet s2 and a second outlet d2 communicated via the permeable side space 100B. In the reactor 100, the non-permeable side space 100A is a space for accommodating a catalyst. The reactor 100 preferably has heat resistance and pressure resistance suitable for the desired synthesis conditions of the liquid fuel.

[0042] The water vapor separation membrane 110 allows water vapor, which is a byproduct of the conversion reaction from the raw material gas to the liquid fuel, to pass therethrough, thereby shifting the reaction equilibrium of the above formula (2) to the product side by utilizing the equilibrium shift effect.

[0043] The molecular diameter of water (0.26 nm) is close to the molecular diameter of hydrogen (0.296 nm). Therefore, it is not only water vapor as a byproduct of the conversion reaction that may permeate the water vapor separation membrane 110, but also part of the hydrogen contained in the raw gas may permeate the water vapor separation membrane 110. In addition, as described later, when helium is used as the inert gas, part of the helium contained in the raw gas may permeate the water vapor separation membrane 110.

[0044] The water vapor separation membrane 110 preferably has a relative humidity of 100 nmol / (s·Pa·m 2 ) or more. The water vapor permeability coefficient can be obtained by a known method (see Ind. Eng. Chem. Res., 40, 163-175 (2001)).

[0045] The water vapor separation membrane 110 preferably has a separation factor of 100 or more. The larger the separation factor, the easier it is for water vapor to pass through, and the harder it is for components other than water vapor (hydrogen, carbon oxides, inert gases, and liquid fuels, etc.) to pass through. The separation factor can be obtained by a known method (see Fig. 1 of "Separation and Purification Technology 239 (2020) 116533").

[0046] As the water vapor separation membrane 110, an inorganic membrane can be used. The inorganic membrane has heat resistance, pressure resistance, and water vapor resistance, so it is preferred. As the inorganic membrane, zeolite membrane, silica membrane, alumina membrane, and composite membranes thereof can be cited. For example, an LTA type zeolite membrane having a molar ratio (Si / Al) of silicon element (Si) to aluminum element (Al) of 1.0 or more and 3.0 or less is preferred because it has excellent water vapor permeability.

[0047] The zeolite membrane used as the water vapor separation membrane 110 can be obtained by the production method described in, for example, Japanese Patent Application Publication No. 2004-66188. The silica membrane used as the water vapor separation membrane 110 can be obtained by the production method described in, for example, International Publication No. 2008 / 050812.

[0048] The porous support 130 is made of a porous material. As the porous material, ceramic materials, metal materials, resin materials, and composite members thereof can be used, and ceramic materials are particularly preferred. As the aggregate of the ceramic material, alumina (Al2O3), titanium dioxide (TiO2), mullite (Al2O3·SiO2), ceramic granules, cordierite (Mg2Al4Si5O 18 ), and composite materials containing two or more of them, etc., if the availability, clay stability and corrosion resistance are taken into consideration, alumina is preferred. As an inorganic binder for the ceramic material, at least one of titanium dioxide, mullite, sinterable alumina, silicon dioxide, glass powder, clay mineral, and sinterable cordierite can be used. The ceramic material may not contain an inorganic binder.

[0049] The average pore size of the porous support can be set to be greater than 5 μm and less than 25 μm. The average pore size of the porous support can be measured by mercury intrusion. The porosity of the porous support can be set to be greater than 25% and less than 50%. The average particle size of the porous material constituting the porous support can be set to be greater than 1 μm and less than 100 μm. In this embodiment, the average particle size refers to the arithmetic mean of the maximum diameters of 30 particles (randomly selected) measured by cross-sectional microstructure observation using a SEM (Scanning Electron Microscope).

[0050] The catalyst 120 promotes the conversion reaction from the raw gas to the liquid fuel. The catalyst is arranged in the non-permeable side space 100A. The catalyst is preferably filled in the non-permeable side space 100A, but can also be arranged on the surface of the water vapor separation membrane 110 in a layered or island shape. In the case where the catalyst is in a particle shape as shown in the example, the particle size (diameter) of the catalyst particles can be set to, for example, 0.5 mm or more and 10 mm or less. The catalyst particles can be composed of only the catalyst, or can be a structure in which the catalyst is supported on the carrier particles. The carrier particles are preferably porous particles.

[0051] As the catalyst, any catalyst suitable for the conversion reaction to the desired liquid fuel can be used. Specifically, metal catalysts (copper, palladium, etc.), oxide catalysts (zinc oxide, zirconium oxide, gallium oxide, etc.), and composite catalysts thereof (copper-zinc oxide, copper-zinc oxide-alumina, copper-zinc oxide-chromium oxide-alumina, copper-cobalt-titanium dioxide, and catalysts obtained by modifying these with palladium, etc.) can be used.

[0052] The reactor is not limited to the above-mentioned examples. Figure 2 As illustrated, the reactor 101 may be a flow reactor including a gas inlet s3, a gas outlet d3, a space 101A connecting the gas inlet s3, and a catalyst (catalyst particles) 120 disposed (filled) in the space 101A. In the reactor 101, a raw gas containing carbon oxides, hydrogen, and an inert gas flows in from the gas inlet s3, and a product gas (product gas a) containing liquid fuel, by-products, and unreacted raw gas (residual raw gas) flows out from the gas outlet d3.

[0053] As described above, the raw gas contains carbon oxides, hydrogen, and an inert gas. As the carbon oxide, at least carbon dioxide is used, and carbon monoxide can be further used within the range in which the effect of the present invention can be obtained. The raw gas preferably contains carbon dioxide at a higher ratio than carbon monoxide. When the ratio of the carbon monoxide concentration in the carbon oxides in the raw gas to the carbon dioxide concentration (CO volume % / CO2 volume %, hereinafter sometimes referred to as "CO / CO2 ratio") is large, there is a case where the temperature unevenness suppression effect in the reactor when the inert gas is mixed is weak, and the effect of the present invention cannot be fully obtained. Specifically, in the reaction of formula (1) and the reaction of formula (2), the calorific value of the reaction of formula (1) is large. In addition, the reaction of formula (1) has a large equilibrium conversion rate compared with the reaction of formula (2), and the calorific value is further increased. Therefore, when the above-mentioned CO / CO2 ratio is large, the temperature unevenness suppression effect in the reactor when the inert gas is mixed becomes weak. The above-mentioned CO / CO2 ratio is typically less than 0.9. Here, when the inlet temperature of the reactor decreases, the equilibrium conversion rate increases, and therefore, the temperature change caused by heat generation increases. Therefore, from the viewpoint of equilibrium conversion rate and temperature unevenness, when operating at an inlet temperature of less than 250°C, the CO / CO2 ratio is preferably less than 0.5, and when operating at an inlet temperature of less than 230°C, the CO / CO2 ratio is preferably less than 0.2. It should be noted that the reaction of formula (3) occurs after the catalyst passes through, so the lower limit of the CO / CO2 ratio is not particularly limited. From the viewpoint of easy control, the CO / CO2 ratio is preferably set to be greater than 0.02. It should be noted that the above CO / CO2 ratio is the CO / CO2 ratio in the raw gas at the reactor inlet (specifically, the first inlet s1). In the case of recycling the remaining raw gas, it is the CO / CO2 ratio in the raw gas prepared using the remaining raw gas. In addition, other records related to the content ratio, ratio, etc. of each gas contained in the raw gas are also records about the raw gas at the reactor inlet.

[0054] The carbon oxide concentration in the raw gas (the total concentration in the case of including carbon monoxide and carbon dioxide) is, for example, 5% by volume or more and 50% by volume or less, preferably 10% by volume or more and 40% by volume or less. In one embodiment, the carbon dioxide concentration in the raw gas is, for example, 5% by volume or more and 50% by volume or less, preferably 9% by volume or more and 35% by volume or less. In one embodiment, the carbon monoxide concentration in the raw gas is, for example, 23% by volume or less, preferably 20% by volume or less. The hydrogen concentration in the raw gas is, for example, 20% by volume or more and 85% by volume or less, preferably 30% by volume or more and 80% by volume or less.

[0055] As the inert gas, nitrogen, helium, argon, etc. can be cited, and only one or more than two can be used in combination. The inert gas concentration in the raw gas is, for example, 1% by volume or more, preferably 2% by volume or more, more preferably 3% by volume or more, and further preferably 5% by volume or more, for example, 55% by volume or less, preferably 30% by volume or less, and more preferably 10% by volume or less. If the inert gas concentration is less than 1% by volume, there is a situation where the temperature unevenness in the reactor cannot be fully suppressed, and the effect of the present invention cannot be fully obtained. If the inert gas concentration exceeds 55% by volume, there is a situation where the concentration of the reaction component becomes dilute, and the target liquid fuel cannot be fully obtained. In one embodiment, the ratio of the inert gas concentration in the raw gas to the carbon dioxide concentration (inert gas volume % / CO2 volume %, hereinafter, sometimes referred to as "Inert / CO2 ratio") is, for example, 0.05 or more, preferably 0.15 or more. By setting the Inert / CO2 ratio to 0.15 or more, from the perspective of controlling the detector and the mixing valve, the control of the Inert / CO2 ratio becomes simple, so it is preferred. The Inert / CO2 ratio in the raw gas is, for example, less than 1.5, preferably less than 1.1. If the Inert / CO2 ratio is small, the temperature unevenness in the reactor cannot be fully suppressed, and the effect of the present invention cannot be fully obtained. If the Inert / CO2 ratio is large, the concentration of the reaction component becomes dilute, and the amount of liquid fuel generated becomes insufficient. In addition, if the Inert / CO2 ratio is less than 1.1, the proportion of the excess raw gas discharged outside the system by purification when recycling can be appropriately suppressed, which is advantageous from the viewpoint of reducing raw material losses.

[0056] Similar to the Inert / CO2 ratio, from the perspective of taking into account the temperature unevenness suppression effect in the reactor and the amount of liquid fuel generated, the total ratio of the inert gas concentration and the carbon monoxide concentration in the raw gas to the carbon dioxide concentration ((inert gas volume % + CO volume %) / CO2 volume %) is, for example, 0.05 or more, for example, 2.4 or less. From the perspective of ease of control, the above ratio is preferably 0.07 or more, and from the perspective of reducing raw material losses, it is preferably 2.2 or less. In addition, from the perspective of balancing conversion rate and temperature unevenness, for example, when operating at an inlet temperature of less than 250°C, the above ratio is preferably 2.2 or less.

[0057] The total concentration of carbon oxides, hydrogen and inert gas in the raw material gas is, for example, 80% by volume to 100% by volume, preferably 96% by volume to 100% by volume. The raw material gas may consist essentially of only carbon oxides, hydrogen and inert gas.

[0058] Figure 7(a) is a graph produced using Excel based on the results of thermodynamic equilibrium calculations, which is a thermodynamic equilibrium calculation of the reactions of equations (1) to (3) when the ratio of N2 is changed with respect to raw material gases having various CO / CO2 ratios. Figure 7 (b) is to Figure 7 The graph (a) is obtained by enlarging the range of Y=-0.3 to 0.1. In the graph, the X-axis represents (N2+CO) / CO2 in the raw gas, and the Y-axis represents (ratio of calorific value after suppression)×(ratio of the increase in combustion energy obtained).

[0059] When making the above graph, the raw gas containing only CO2 and H2 at a ratio of CO2 / H2=1 / 3 (CO2 volume%+H2 volume%=100 volume%, CO / CO2 ratio=0, (N2+CO) / CO2 ratio=0) is used as the reference condition, and "(calorific value calculated under the reference condition - calorific value calculated when using each raw gas) / calorific value calculated under the reference condition" is defined as the "ratio of calorific value after suppression", and "(combustion energy of methanol generated calculated when using each raw gas - combustion energy of methanol generated calculated under the reference condition) / combustion energy of methanol generated calculated under the reference condition" is defined as the "ratio of the increase in combustion energy obtained". Here, "combustion energy of methanol generated" is calculated by "amount of methanol generated×high heating value (HHV) of methanol".

[0060] In the graph, a total of 18 data (i.e., data when the N2 / CO2 ratio was changed in the range of 0 to 1.6 in 0.1 steps and when the N2 / CO2 ratio was 0.05) are plotted for the cases where raw gas having various CO / CO2 ratios was used.

[0061] In the graph, the X-axis is an index that takes into account both the ratio of N2 associated with the suppression of heat generation and the ratio of CO associated with the amount of liquid fuel generated. In the graph produced by the above-mentioned production method based on the results of thermodynamic equilibrium calculations performed under the following conditions, the value a of the slope when an approximate straight line is produced by linear approximation (Y=aX+b) for the 18 points plotted for the raw gas at each CO / CO2 ratio is preferably less than 1.4. The lower limit of the value a is not particularly limited, but can be, for example, greater than -0.2. If the value a exceeds 1.4, it is difficult to balance the effect of suppressing temperature unevenness in the reactor and the amount of liquid fuel generated. In addition, from the viewpoint of making it easier to balance the effect of suppressing temperature unevenness in the reactor and the amount of liquid fuel generated, the value a is preferably less than 0.7.

[0062] The temperature unevenness in the reactor may be caused by the heat generated in the synthesis reaction of the liquid fuel. Therefore, by diluting the raw gas with an inert gas to inhibit the synthesis reaction of the liquid fuel (as a result, by inhibiting the calorific value), it can help to inhibit the temperature unevenness in the reactor. On the other hand, if the synthesis reaction of the liquid fuel is inhibited, the amount of liquid fuel generated may decrease. Therefore, the Y axis of the graph can be used as an indicator of the balance between the inhibitory effect of temperature unevenness and the amount of liquid fuel generated. Specifically, the inhibitory effect of temperature unevenness and the amount of liquid fuel generated are in a compromise relationship. If one side is a positive large value, the other side becomes a negative large value, and the product tends to be away from 0. Therefore, if the value of the Y axis is close to 0, it can be regarded as a balance between the two. In the graph produced by the above-mentioned production method based on the results of the thermodynamic equilibrium calculation performed under the following conditions, the value of the Y axis is preferably above -3, more preferably above -1.5, and the upper limit is not particularly limited, but for example, it can be below 0.1. If the value of the Y axis is less than -3, there is a situation where the balance between the inhibitory effect of temperature unevenness in the reactor and the amount of liquid fuel generated becomes insufficient.

[0063] As described above, when the raw gas of the composition in which the slope value a of the approximate straight line in the above-mentioned chart is preferably 1.4 or less, preferably 0.7 or less is used, the slope value a is preferably 1.4 or less or 0.7 or less, and the raw gas of the composition in which the value of the Y axis is -3 or more is used to manufacture the liquid fuel, the balance between the suppression effect of temperature unevenness and the amount of liquid fuel generated can be well maintained. For example, according to the above-mentioned chart, when the CO / CO2 ratio in the raw gas is 0.9 or less, the value of the Y axis is in the range of -3 or more, and the manufacture of the liquid fuel that has achieved the balance between the suppression effect of temperature unevenness and the amount of liquid fuel generated can be carried out. In addition, it can be seen that by adding N2 to the raw gas, the balance can be improved. In addition, it can be seen that when the CO / CO2 ratio is 0.9 or less, the value of the slope a of the approximate straight line is 1.4 or less, and the balance between the suppression effect of temperature unevenness and the amount of liquid fuel generated can be well maintained. It should be noted that the reaction conditions of the method for manufacturing liquid fuel according to an embodiment of the present invention are not limited to the following reaction conditions used in the thermodynamic equilibrium calculation.

[0064] The thermodynamic equilibrium calculations were performed under the following conditions using a database of thermodynamic data built into the chemical equilibrium calculation software "MALT". However, the thermodynamic data used is not limited thereto, and for example, the database of the NIST Chemistry web book published by the National Institute of Standards and Technology (NIST) of the United States may be used.

[0065] Reaction temperature: 200℃ Reaction pressure: 4MPa (G) Raw gas composition: H2 / CO2=3 : In the range of N2 / CO2 = 0 to 1.6, the scale is 0.1 and 0.05 : CO / CO2=0.02, 0.1, 0.3, 0.5, 0.6, 0.9, 1.0 The raw gas is prepared by mixing the components to form the desired composition. In one embodiment, the raw gas is prepared using carbon dioxide concentrated gas recovered from the atmosphere by direct air recovery technology (DAC). The carbon dioxide concentrated gas obtained by DAC contains inert gas (representatively nitrogen) recovered from the atmosphere and carbon dioxide. Specifically, the carbon dioxide concentrated gas obtained by DAC may contain a small amount of nitrogen (for example, 0.05% by volume and 60% by volume) from the atmosphere in addition to high concentrations of carbon dioxide (for example, 30% by volume or more and 99.9% by volume or less). In addition, the concentration of carbon monoxide is low. Therefore, when the raw gas is prepared using the carbon dioxide concentrated gas obtained by DAC, there is no need to prepare inert gas separately and mix it, or the amount of inert gas prepared separately can be reduced. In another embodiment, the raw gas is prepared using carbon dioxide concentrated gas recovered from biogas. Biogas is a gas produced by fermentation (methane fermentation) using biomass such as kitchen waste, paper waste, and livestock feces as raw materials. The main components of biogas are methane and carbon dioxide, and can further contain nitrogen and the like. By using a separation membrane, carbon dioxide can be recovered from biogas to obtain carbon dioxide concentrated gas. In addition to carbon dioxide, the carbon dioxide concentrated gas recovered from biogas may also contain inert gas (typically nitrogen), and the concentration of carbon monoxide is low. Therefore, when using carbon dioxide concentrated gas recovered from biogas to prepare raw gas, there is no need to prepare inert gas separately and mix it, or the amount of inert gas prepared separately can be reduced. In one embodiment, the liquid fuel synthesis system 1 can also be configured as: it also has a gas recovery unit that recovers inert gas (typically nitrogen) and carbon dioxide from the atmosphere through DAC, or a gas recovery unit that recovers inert gas (typically nitrogen) and carbon dioxide from biogas using a separation membrane, and supplies carbon dioxide concentrated gas (gas containing inert gas and carbon dioxide recovered from the atmosphere or biogas) from the gas recovery unit to the raw gas supply unit. The carbon dioxide concentrated gas can be directly supplied to the raw gas supply unit from the gas recovery unit, or it can be supplied to the raw gas supply unit as a component of the purge gas after passing through the reactor. The gas recovery unit includes, for example, a carbon dioxide adsorbing material (e.g., an amine compound) that adsorbs carbon dioxide by contact with a gas containing carbon dioxide and releases the carbon dioxide by heating, reducing pressure, etc., and the carbon dioxide adsorbing material can be used to recover a gas containing an inert gas and high-concentration carbon dioxide from the atmosphere. In addition, for example, the gas recovery unit includes a separation membrane such as a carbon dioxide permeable membrane, and can recover a carbon dioxide-enriched gas containing an inert gas and high-concentration carbon dioxide from a gas containing carbon dioxide such as biogas.

[0066] The feed gas flows into the reactor at the desired temperature and pressure. Figure 1 In the embodiment shown, the gas containing carbon oxides, hydrogen and inert gas stored in the first gas storage unit 210 is mixed with the remaining raw gas, and after being pressurized and heated in the booster unit 220, it flows into the non-permeable side space 100A of the reactor 100 through the pipeline L1 as raw gas. The booster unit 220 is composed of a compressor, a supercharger, etc. It should be noted that in the example shown in the figure, the raw gas prepared in advance to a desired composition is supplied to the reactor from the first gas storage unit 210, but the raw gas can flow into the reactor with a desired composition, and is not limited to the embodiment shown in the figure. For example, carbon oxides, hydrogen and inert gas can also be made to flow into the reactor separately from their respective supply sources.

[0067] The temperature of the raw material gas when flowing into the reactor (in other words, the temperature of the raw material gas at the gas inlet of the reactor) is, for example, 40°C to 350°C, preferably 180°C to 330°C.

[0068] The pressure of the raw material gas when flowing into the reactor (in other words, the pressure at the gas inlet of the reactor) is, for example, 1.0 MPa(G) to 6.0 MPa(G), preferably 2.0 MPa(G) to 6.0 MPa(G).

[0069] The flow rate of the raw material gas flowing into the reactor is, for example, 1000 / h to 50000 / h, preferably 2000 / h to 20000 / h, and more preferably 3000 / h to 12000 / h in terms of space velocity GHSV.

[0070] A-2. Step (II) In step (II), liquid fuel is generated from raw gas by a conversion reaction in the presence of a catalyst. For example, as shown in reaction formulas (1) to (2), methanol is generated by catalytic hydrogenation of carbon oxides and hydrogen in the presence of a catalyst. The generated liquid fuel and byproduct (representatively water) are both in a gaseous state at the time of synthesis, and remain in a gaseous state at least until they flow out of the reactor.

[0071] according to Figure 1In the embodiment shown, the raw gas flows into the non-permeable side space 100A through the first inlet s1, and the conversion reaction from the raw gas to the liquid fuel is promoted by the catalyst 120 to synthesize the liquid fuel. In addition, water vapor as a by-product and hydrogen in the raw gas (and inert gas depending on the type) pass through the water vapor separation membrane 110 and flow into the permeable side space 100B. The purge gas for purging them flows from the second inlet s2 to the permeable side space 100B through the pipeline L3. Specifically, the purge gas stored in the second gas storage unit 310 is heated to a desired temperature (for example, 150° C. or more and 350° C. or less) in the heating unit 320, and then flows into the permeable side space 100B of the reactor 100 through the pipeline L3. As the purge gas, any appropriate gas such as nitrogen, carbon oxides, hydrogen, and a mixed gas thereof can be used.

[0072] The reactions of reaction formulas (1) to (3) are all equilibrium reactions. In order to improve both the conversion rate and the reaction rate, it is preferred to react them at high temperature and high pressure. The reaction temperature (in other words, the temperature of the space containing the catalyst in the reactor) is, for example, 180°C or more, preferably 200°C or more and 350°C or less, and more preferably 200°C or more and 300°C or less. The reaction pressure (in other words, the pressure of the space containing the catalyst in the reactor) is, for example, 1 MPa (G) or more, preferably 2.0 MPa (G) or more and 6.0 MPa (G) or less, and more preferably 2.5 MPa (G) or more and 4.0 MPa (G) or less.

[0073] In the reactions of formula (1) and (2), the generation of methanol is an exothermic reaction. Therefore, a temperature difference (temperature unevenness) may occur inside the reactor due to the generated heat and gas flow. If such a temperature difference occurs, the equilibrium conversion rate decreases in the part with high temperature, so there is a situation where the reaction yield decreases. In contrast, according to the manufacturing method of an embodiment of the present invention, by diluting the raw material gas with an inert gas, it is possible to suppress excessive temperature rise inside the reactor and reduce the temperature difference between the gas temperature at the inlet and the gas temperature at the outlet of the reactor. As a result, the uniformity of the reactor temperature can be improved and the decrease in conversion rate can be suppressed.

[0074] A-3. Step (III) In step (III), a product gas containing liquid fuel is discharged from the reactor. The product gas typically contains liquid fuel and residual raw material gas. Therefore, it is preferred to separate and recover the liquid fuel from the product gas.

[0075] The temperature of the product gas when flowing out of the reactor (in other words, the temperature of the product gas at the gas outlet of the reactor) is, for example, 200° C. to 350° C., preferably 200° C. to 300° C.

[0076] The difference between the gas temperature at the gas inlet and the gas temperature at the gas outlet (gas temperature at the gas outlet - gas temperature at the gas inlet) is, for example, 10° C. to 100° C., preferably 20° C. to 50° C. Here, the gas temperature at the gas inlet refers to the gas temperature immediately after entering the 20% of the total length of the reactor from the gas inlet, and the gas temperature at the outlet gas outlet refers to the gas temperature immediately after the gas outlet.

[0077] exist Figure 1 In the illustrated embodiment, the product gas flows out from the reactor 100 (more specifically, the non-permeate side space 100A) to the line L2 through the first outlet d1. In addition, the water vapor and hydrogen gas etc. that have passed through the water vapor separation membrane 110 and flowed into the permeate side space 100B flow out from the reactor 100 (more specifically, the permeate side space 100B) to the line L4 as a gas containing water vapor together with the purge gas through the second outlet d2.

[0078] The product gas flowing out of the reactor 100 flows into the drain elbow 400 arranged downstream of the reactor 100. The drain elbow 400 liquefies the liquid fuel in the gas state and separates the remaining raw gas from the liquid fuel. Thus, the liquid fuel is recovered. On the other hand, the remaining raw gas after separation returns to the upstream through the pipeline L5 and mixes with the gas flowing out of the first gas storage unit, thereby obtaining the raw gas. From the perspective of adjusting the composition of the raw gas, the residual raw gas can be purified as needed. The recycling rate of the residual raw gas in the raw gas (the volume % of the residual raw gas in the raw gas) can be, for example, 15% or more and 85% or less. The obtained raw gas is pressurized and heated in the booster 220 and flows into the reactor 100 through the pipeline L1. As described above, in the embodiment of the present invention, since the concentration ratio of each gas in the raw gas is appropriately controlled, even when the remaining raw gas is recycled, the liquid fuel can be continuously produced while taking into account the temperature unevenness suppression effect in the reactor and the amount of liquid fuel generated.

[0079] Similarly, the gas containing water vapor flowing out of the reactor 100 is liquefied by the condensable byproduct (typically water vapor) by using the drain elbow 500, and is separated and recovered from the remaining gas. If necessary, hydrogen gas or the like can be recovered from the separated gas and reused as part of the raw material gas.

[0080] B. Modification The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the structure shown in the above-described embodiment may be replaced with a structure that is substantially the same as the structure shown in the above-described embodiment, a structure that has the same function and effect, or a structure that can achieve the same purpose.

[0081] B-1. Modification 1 The reactor can be a combination of multiple reactors. Figure 3 As shown, the reactor may be configured as follows: a reactor 100 as a membrane reactor is disposed upstream of the reactor 100. Figure 2 The structure of the flow-type reactor 101 shown in the figure. The reactor 100 has a water vapor separation membrane 110, a catalyst 120, a non-permeable side space 100A, and a permeable side space 100B. The water vapor separation membrane 110 is typically supported by a porous support (not shown). According to the reactor with such a structure, the product gas a containing liquid fuel, water vapor, and excess raw gas flowing out of the reactor 101 flows into the permeable side space 100A of the reactor 100, and the conversion reaction from the excess raw gas to liquid fuel is promoted. The product gas b containing the liquid fuel generated in the reactors 101 and 100 flows out from the non-permeable side space 100A. The water vapor and the purge gas that have passed through the water vapor separation membrane 110 flow out from the permeable side space 100B as a gas containing water vapor.

[0082] There is no limit to the number of reactors 100 disposed downstream of the flow-type reactor 101. Figure 4 As shown, two or more reactors 100 can be connected in series and / or in parallel. It should be noted that in the figure, only the flow of the product gas is shown downstream of the reactor 101.

[0083] B-2. Modification 2 Regarding the reactor of the above-mentioned embodiment, as a separation membrane for separating water vapor and liquid fuel, a structure is used in which a water vapor separation membrane that allows water vapor to pass through is used to separate water vapor from the permeation side space to the non-permeation side space, but a structure may also be used in which a liquid fuel separation membrane that allows liquid fuel to pass through is used to separate liquid fuel from the permeation side space to the non-permeation side space. For example, Figure 5The reactor 102 shown has a liquid fuel separation membrane 150, a catalyst 120, a non-permeable side space 102A, and a permeable side space 102B. The liquid fuel separation membrane 150 can be supported by a porous support body (not shown). According to such a structure, the liquid fuel permeates from the non-permeable side space 102A to the permeable side space 102B, so that the reaction equilibrium of the above formulas (1) and (2) can be shifted to the product side. As a separation membrane that selectively allows liquid fuel to pass through, a separation membrane described in Japanese Patent Gazette No. 2020-23488 can be used. It should be noted that in the present invention, as a separation membrane that separates water vapor and liquid fuel, it has a higher selective permeability to one side than to the other side, and as long as the effect of the present invention can be obtained, the two may not be completely separated. For example, the liquid fuel separation membrane allows liquid fuel to pass through with a higher selectivity than water vapor, and does not completely separate the two.

[0084] B-3. ​​Modification 3 As described above, the raw gas can be prepared using carbon dioxide concentrated gas recovered from the atmosphere by DAC or carbon dioxide concentrated gas recovered from biogas by separation membrane (for example, a gas containing inert gas and carbon dioxide recovered from the atmosphere or biogas). Therefore, the liquid fuel synthesis system used in the method for producing liquid fuel according to an embodiment of the present invention may also be configured as follows: it also includes a gas recovery unit that recovers inert gas and carbon dioxide from the atmosphere by DAC or recovers inert gas and carbon dioxide from biogas by separation membrane, and the carbon dioxide concentrated gas supplied from the gas recovery unit is supplied to the reactor as a constituent component of the raw gas. For example, it may also be as follows Figure 6 The liquid fuel synthesis system 2 shown in FIG. 1 is configured as follows: the purge gas supply unit 300 includes a gas recovery unit 340 and a hydrogen generation unit 360, and the purge gas prepared by mixing the carbon dioxide concentrated gas supplied from the gas recovery unit 340 and the hydrogen supplied from the hydrogen generation unit 360 is supplied to the reactor 100 as a constituent component of the raw gas. In the modification 3, the carbon dioxide contained in the raw gas may be entirely derived from the carbon dioxide concentrated gas recovered by the gas recovery unit 340, or only partially derived from the carbon dioxide concentrated gas.

[0085] The gas recovery unit 340 typically includes a carbon dioxide adsorbing material (e.g., an amine compound) that adsorbs carbon dioxide by contact with a gas containing carbon dioxide and releases carbon dioxide by heating, reducing pressure, etc., and the carbon dioxide adsorbing material can be used to recover carbon dioxide concentrated gas containing inert gas and high concentration of carbon dioxide from the atmosphere. Alternatively, the gas recovery unit 340 includes a separation membrane such as a carbon dioxide permeable membrane, and can recover carbon dioxide concentrated gas containing inert gas and high concentration of carbon dioxide from a gas containing carbon dioxide such as biogas. The hydrogen generation unit 360 is, for example, a hydrogen production device using water electrolysis technology.

[0086] Industrial Applicability The method for producing a liquid fuel according to the embodiment of the present invention can be applied to producing a liquid fuel such as methanol.

[0087] Explanation of symbols 100: Reactor 100A: Non-permeable side space 100B: Through side space 110: Water vapor separation membrane 120: Catalyst 200: Raw gas supply unit 300: Purge gas supply unit.

Claims

1. A method for producing a liquid fuel, comprising: A step of flowing a raw material gas containing at least carbon oxides and hydrogen into a reactor containing a catalyst; as well as a step of generating liquid fuel from the raw gas through a reforming reaction in the presence of the catalyst, The raw material gas also contains an inert gas, The ratio of the carbon monoxide concentration in the carbon oxides to the carbon dioxide concentration is 0.9 or less.

2. The manufacturing method according to claim 1, wherein: The inert gas concentration in the raw material gas is greater than or equal to 1 volume % and less than or equal to 55 volume %.

3. The manufacturing method according to claim 1, wherein: A ratio of the inert gas concentration in the raw material gas to the carbon dioxide concentration is greater than or equal to 0.05 and less than or equal to 1.

5.

4. The manufacturing method according to claim 1, wherein: The carbon oxide concentration in the raw material gas is greater than or equal to 5% by volume and less than or equal to 50% by volume.

5. The manufacturing method according to claim 1, wherein: The hydrogen gas concentration in the raw material gas is greater than or equal to 20 volume % and less than or equal to 85 volume %.

6. The manufacturing method according to claim 1, wherein: The temperature of the raw material gas when flowing into the reactor is 40° C. or higher and 350° C. or lower.

7. The manufacturing method according to claim 1, wherein: The production method includes a step of preparing the raw material gas using a gas containing an inert gas recovered from the atmosphere or biogas and carbon dioxide.

8. The manufacturing method according to any one of claims 1 to 7, wherein: The reactor has a water vapor separation membrane that allows water vapor to permeate.

9. The manufacturing method according to any one of claims 1 to 7, wherein: The reactor has a liquid fuel separation membrane that allows at least the liquid fuel to permeate.

10. A method for producing a liquid fuel, comprising: A step of flowing a raw material gas containing at least carbon oxides and hydrogen into a reactor containing a catalyst; as well as a step of generating liquid fuel from the raw gas through a reforming reaction in the presence of the catalyst, The raw material gas also contains an inert gas, The liquid fuel comprises methanol, The slope a of the approximate straight line produced by linear approximation (Y=aX+b) for the points plotted with (Inert+CO) / CO2 in the raw gas as the X-axis and (the ratio of the calorific value after suppression)×(the ratio of the increase in combustion energy obtained) as the Y-axis is 1.4 or less based on the thermodynamic equilibrium calculation result, which is the thermodynamic equilibrium calculation result for the conversion reaction under the conditions of 200°C and 4MPa(G) when the ratio of the carbon monoxide concentration CO in the carbon oxides to the carbon dioxide concentration CO2 and the ratio of the inert gas concentration Inert to the carbon dioxide concentration CO2 in the raw gas are changed, Regarding the case where the raw gas of each CO / CO2 ratio is used, the plot is performed for a total of 18 data when the Inert / CO2 ratio is changed in the range of 0 to 1.6 in 0.1 steps and when the Inert / CO2 ratio is 0.

05. The ratio of the suppressed calorific value and the ratio of the obtained combustion energy increase are values ​​calculated by the following formulae: The ratio of the calorific value after being suppressed = (the calorific value calculated under the reference conditions - the calorific value calculated when each raw material gas is used) / the calorific value calculated under the reference conditions; The ratio of the increase in combustion energy obtained = (combustion energy of methanol generated when using each raw gas - combustion energy of methanol generated under the reference condition) / combustion energy of methanol generated under the reference condition, Here, the benchmark condition is the case where a raw gas containing only carbon dioxide and hydrogen at a ratio of CO2 / H2=1 / 3 is used, and the combustion energy of the generated methanol is a value calculated by the following formula, that is, the combustion energy of the generated methanol = the amount of methanol generated × the high calorific value of methanol.

11. The manufacturing method according to claim 10, wherein: The product of the ratio of the suppressed calorific value and the ratio of the obtained combustion energy increase is greater than or equal to -3.

12. A liquid fuel synthesis system comprising: A reactor containing a catalyst for promoting a conversion reaction of a raw gas containing at least carbon oxides and hydrogen into a liquid fuel; and A raw material gas supply unit supplies a gas containing carbon oxides, hydrogen and an inert gas, wherein the ratio of the carbon monoxide concentration in the carbon oxides to the carbon dioxide concentration is 0.9 or less, as the raw material gas to the reactor.

13. The liquid fuel synthesis system according to claim 12, wherein: The inert gas concentration in the raw material gas is greater than or equal to 1 volume % and less than or equal to 55 volume %.

14. The liquid fuel synthesis system according to claim 12, wherein: A ratio of the inert gas concentration in the raw material gas to the carbon dioxide concentration is greater than or equal to 0.05 and less than or equal to 1.

5.

15. The liquid fuel synthesis system according to claim 12, wherein: The liquid fuel synthesis system further includes a gas recovery unit that recovers inert gas and carbon dioxide from the atmosphere or biogas. The gas containing the inert gas and carbon dioxide supplied from the gas recovery unit is supplied to the reactor as a constituent component of the raw material gas.

16. The liquid fuel synthesis system according to any one of claims 12 to 15, wherein: The reactor has a water vapor separation membrane that allows water vapor to permeate.

17. The liquid fuel synthesis system according to any one of claims 12 to 15, wherein: The reactor has a liquid fuel separation membrane that allows at least the liquid fuel to permeate.

Images