Synthetic gas production method and synthetic gas production system

Abstract

To provide a synthesis gas production method and a synthesis gas production system, which can effectively utilize carbon dioxide at low cost and improve productivity while reducing a burden on environment.SOLUTION: There is provided a synthesis gas production method from biomass feedstock, comprising: a synthesis gas production step of producing synthesis gas containing hydrogen, carbon monoxide, and carbon dioxide from the supplied biomass raw material, water, and carbon dioxide; wherein the carbon dioxide supplied to the synthesis gas production step contains carbon dioxide in the synthesis gas.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a synthesis gas production method and a synthesis gas production system. [Background technology]

[0002] Efforts aimed at mitigating or reducing the impact of climate change have been ongoing for some time, and research and development into reducing carbon dioxide emissions is being carried out to achieve this. In recent years, synthetic fuels made from hydrogen generated from electricity generated by renewable energy sources and carbon sources such as biomass and carbon dioxide emitted from factories have been attracting attention as an alternative to fossil fuels.

[0003] The general procedure for producing liquid fuels such as methanol and gasoline using biomass as a feedstock is as follows: A liquid fuel is produced from biomass feedstock through the following steps: a gasification process in which biomass feedstock that has undergone a specified pretreatment is gasified together with water and oxygen in a gasifier to produce a synthesis gas containing hydrogen and carbon monoxide; a cleaning process in which the synthesis gas produced is cleaned and tar is removed; an H2 / CO ratio adjustment process in which the H2 / CO ratio of the synthesis gas that has undergone the cleaning process is adjusted to a target ratio appropriate for the liquid fuel to be produced; a desulfurization process in which sulfur components are removed from the synthesis gas that has undergone the H2 / CO ratio adjustment process; and a fuel production process in which liquid fuel is produced from the synthesis gas that has undergone the desulfurization process.

[0004] The H2 / CO ratio of the synthesis gas produced through the gasification process often does not reach the target ratio, resulting in a hydrogen deficiency. For this reason, by supplying steam during the gasification process, it is possible to increase the H2 / CO ratio to closer to 2.0, which is the preferred ratio for the Fischer-Tropsch synthesis reaction (hereinafter also referred to as the FT synthesis reaction).

[0005] Carbon dioxide contained in the synthesis gas is discharged as part of the off-gas before being supplied to the FT synthesis reaction. However, discharging carbon dioxide into the environment places a heavy burden on the environment.

[0006] Patent Document 1 discloses an invention in which, in a fuel production system for producing synthetic fuel from biomass feedstock as described above, hydrogen is produced using electricity generated by renewable energy and the produced hydrogen is mixed with synthesis gas produced by a gasifier, thereby adjusting the H2 / CO ratio to a target ratio without the need for a shift reactor. According to the fuel production system in Patent Document 1, hydrogen is produced by an electrolysis device using electricity generated using renewable energy, thereby making it possible to suppress carbon dioxide generation throughout the entire fuel production system. Patent Document 2 proposes a method for producing various hydrocarbon oils from natural gas, which includes a step of recycling the off-gas as fuel for heating a gasification furnace. According to the production method of Patent Document 1, the off-gas can be recycled. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2021-147504 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-214528 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the fuel production system of Patent Document 1 requires an increased supply of hydrogen, which increases the cost of producing hydrogen. Furthermore, in the manufacturing method of Patent Document 2, the off-gas is burned as fuel for heating the gasification furnace, but carbon dioxide is not burned, and therefore, there is a problem in that carbon dioxide cannot be used effectively. Furthermore, in reducing carbon dioxide emissions, simply recycling off-gas as fuel requires discharging the carbon dioxide produced by combustion, which places a heavy burden on the environment. In order to solve the above-mentioned problems, the present application aims to provide a synthesis gas production method and a synthesis gas production system that can effectively utilize carbon dioxide at low cost and improve productivity while reducing the burden on the environment, thereby contributing to mitigating or reducing the impact of climate change. [Means for solving the problem]

[0009] [1] A method for producing synthesis gas from biomass feedstock, comprising: a synthesis gas production step of producing synthesis gas containing hydrogen, carbon monoxide, and carbon dioxide from the supplied biomass raw material, water, and carbon dioxide; The synthesis gas production method, wherein the carbon dioxide supplied to the synthesis gas production step comprises carbon dioxide contained in the synthesis gas.

[0010] The synthesis gas production method of the present invention does not require an increase in the amount of hydrogen supplied, is low cost, and can effectively utilize carbon dioxide as a raw material for synthesis gas production. Furthermore, because carbon dioxide is consumed as a raw material, carbon dioxide emissions can be reduced, thereby reducing the burden on the environment. Furthermore, renewable energy can be used to provide the necessary electricity, improving productivity while reducing the burden on the environment.

[0011] [2] The synthesis gas production method according to [1], further comprising a carbon dioxide supplying step of supplying carbon dioxide in the synthesis gas to the synthesis gas production step.

[0012] The synthesis gas production method of the present invention does not require an increase in the amount of hydrogen supplied, making it low cost, and by supplying the carbon dioxide in the synthesis gas as a raw material for synthesis gas production, the carbon dioxide can be effectively utilized.

[0013] [3] The method for producing a synthesis gas according to [1] or [2], further comprising a gas purification step of separating the synthesis gas into an off-gas containing carbon dioxide and hydrocarbons and a purified synthesis gas containing hydrogen and carbon monoxide.

[0014] The synthesis gas production method of the present invention can improve energy efficiency and reduce environmental impact by recycling off-gas containing carbon dioxide and hydrocarbons. Furthermore, by supplying purified synthesis gas containing hydrogen and carbon monoxide to the FT synthesis reaction, the productivity of liquid fuels can be improved.

[0015] [4] The synthesis gas production method according to [3], further comprising a gas separation step of separating the off-gas into a gasification assisting gas containing carbon dioxide and a heat source gas containing hydrocarbons.

[0016] The synthesis gas production method of the present invention can increase the amount of carbon dioxide supplied by supplying a gasification assisting gas containing carbon dioxide to the synthesis gas production process. In addition, the heat source gas containing hydrocarbons can be recycled as fuel for heating the gasification furnace used in the synthesis gas production process, thereby further improving energy efficiency and further reducing the burden on the environment.

[0017] [5] The synthesis gas production method according to [4], further comprising a heat source gas supplying step of supplying the heat source gas as a heat source in a synthesis gas production step.

[0018] The synthesis gas production method of the present invention can further improve energy efficiency and reduce the burden on the environment by recycling the hydrocarbon-containing heat source gas as fuel for heating the gasification furnace used in the synthesis gas production process.

[0019] [6] The synthesis gas production method according to any one of [1] to [5], further comprising a steam supplying step of supplying steam as water in the synthesis gas production step so that a mass ratio expressed as [mass of steam] / [mass of biomass] is 1.3 or more.

[0020] In the synthesis gas production method of the present invention, the rate of hydrogen generation can be increased by adjusting the amount of steam supplied, and the molar ratio (number of moles of hydrogen) / (number of moles of carbon monoxide) during synthesis gas production can be adjusted to 2.0 or higher. Furthermore, by supplying carbon dioxide to the synthesis gas, the reverse shift reaction (a reaction that produces carbon monoxide and water from hydrogen and carbon dioxide) can be promoted, consuming carbon dioxide and hydrogen to produce carbon monoxide. This makes it possible to produce synthesis gas with a molar ratio (number of moles of hydrogen) / (number of moles of carbon monoxide) close to 2.0, which is optimal for the FT synthesis reaction, thereby further improving productivity.

[0021] [7] The synthesis gas production method according to any one of [1] to [6], further comprising a carbon dioxide supplying step of supplying carbon dioxide to the synthesis gas production step so that the molar ratio of [number of moles of hydrogen] / [number of moles of carbon monoxide] in the synthesis gas to be obtained is 1.95 to 2.05.

[0022] The synthesis gas production method of the present invention adjusts the amount of carbon dioxide supplied so that the molar ratio (number of moles of hydrogen) / (number of moles of carbon monoxide) during synthesis gas production is 1.95 to 2.05, thereby consuming carbon dioxide and producing carbon monoxide through the reverse shift reaction. This makes it possible to produce synthesis gas with a molar ratio (number of moles of hydrogen) / (number of moles of carbon monoxide) close to 2.0, which is optimal for the FT synthesis reaction, thereby further improving productivity. Furthermore, because carbon dioxide is consumed as a raw material, carbon dioxide emissions can be reduced, thereby mitigating the burden on the environment.

[0023] [8] A fuel production system for producing fuel from biomass feedstock, comprising: a gasification device that produces synthesis gas containing hydrogen, carbon monoxide, carbon dioxide, and hydrocarbons from the supplied biomass feedstock, water, and carbon dioxide; a carbon dioxide supplying device that supplies carbon dioxide in the synthesis gas to the gasification device.

[0024] The synthesis gas production system of the present invention can be operated at low cost without the need to increase the amount of hydrogen supplied, and by supplying carbon dioxide to the synthesis gas production process, the amount of carbon dioxide supplied can be increased, thereby further improving energy efficiency and further reducing the burden on the environment.

[0025] [9] The synthesis gas production system according to [8], further comprising a gas purification device that separates the synthesis gas into an off-gas containing carbon dioxide and hydrocarbons and a purified synthesis gas containing hydrogen and carbon monoxide.

[0026] The synthesis gas production system of the present invention can improve energy efficiency and reduce environmental impact by recycling off-gas containing carbon dioxide and hydrocarbons. Furthermore, by supplying purified synthesis gas containing hydrogen and carbon monoxide to the FT synthesis reaction, it can improve liquid fuel productivity.

[0027]

[10] The synthesis gas production system according to [9], further comprising a gas separation device that separates the off-gas into a gasification assisting gas containing carbon dioxide and a heat source gas containing hydrocarbons.

[0028] The synthesis gas production system of the present invention can increase the amount of carbon dioxide supplied by supplying a gasification assisting gas containing carbon dioxide to the synthesis gas production process. In addition, the heat source gas containing hydrocarbons can be recycled as fuel for heating the gasification furnace used in the synthesis gas production process, thereby further improving energy efficiency and reducing the burden on the environment.

[0029]

[11] The synthesis gas production system according to

[10] , further comprising a heat source gas supply device for supplying the heat source gas as a heat source in a synthesis gas production process.

[0030] The synthesis gas production system of the present invention can further improve energy efficiency and reduce the burden on the environment by recycling the heat source gas containing hydrocarbons as fuel for heating the gasification furnace used in the synthesis gas production process.

[0031]

[12] The synthesis gas production system according to any one of [8] to

[11] , further comprising a steam supply device that supplies steam as water to the gasification device so that the mass ratio expressed as [mass of steam] / [mass of biomass] is 1.3 or more.

[0032] The synthesis gas production system of the present invention can increase the hydrogen generation rate by adjusting the amount of steam supplied, and can adjust the molar ratio (number of moles of hydrogen) / (number of moles of carbon monoxide) during synthesis gas production to 2.0 or higher. Furthermore, by supplying carbon dioxide to the system, the reverse shift reaction can be promoted, consuming carbon dioxide and hydrogen to produce carbon monoxide. This makes it possible to produce synthesis gas with a molar ratio (number of moles of hydrogen) / (number of moles of carbon monoxide) close to 2.0, which is optimal for the FT synthesis reaction, thereby further improving productivity.

[0033]

[13] The synthesis gas production system according to any one of [8] to

[12] , further comprising a carbon dioxide supplying device that supplies carbon dioxide to the gasification device so that the molar ratio of the synthesis gas obtained, expressed as [number of moles of hydrogen] / [number of moles of carbon monoxide], is 1.95 to 2.05.

[0034] The synthesis gas production system of the present invention adjusts the carbon dioxide supply rate so that the molar ratio (number of moles of hydrogen) / (number of moles of carbon monoxide) during synthesis gas production is 1.95 to 2.05, thereby consuming carbon dioxide and producing carbon monoxide through the reverse shift reaction. This makes it possible to produce synthesis gas with a molar ratio (number of moles of hydrogen) / (number of moles of carbon monoxide) close to 2.0, which is optimal for the FT synthesis reaction, thereby further improving productivity. Furthermore, because carbon dioxide is consumed as a raw material, carbon dioxide emissions can be reduced, thereby mitigating the burden on the environment. [Effects of the Invention]

[0035] The present invention provides a synthesis gas production method and system that can effectively utilize carbon dioxide at low cost and improve productivity while reducing the burden on the environment, thereby contributing to mitigating or reducing the impact of climate change. [Brief explanation of the drawings]

[0036] [Figure 1] 1 is a flowchart showing the configuration of a synthesis gas production method according to one embodiment of the present invention. [Figure 2] 1 is a flowchart showing a configuration of a fuel production method according to one embodiment of the present invention. [Figure 3] 10 is a flowchart showing the configuration of a fuel production method according to another embodiment of the present invention. [Figure 4] 1 is a schematic diagram showing the configuration of a synthesis gas production system according to one embodiment of the present invention. [Figure 5] 1 is a schematic diagram showing the configuration of a fuel production system according to an embodiment of the present invention. [Figure 6] FIG. 10 is a schematic diagram showing the configuration of a fuel production system according to another embodiment of the present invention. [Figure 7] 1 is a flowchart showing a specific procedure of a fuel production method of the present invention. [Figure 8] 1 is a graph showing amounts of components in a synthesis gas in an example. DETAILED DESCRIPTION OF THE INVENTION

[0037] The present invention will be outlined below. The synthesis gas produced by the reforming reaction of biomass feedstock flows into the bottom of a bubble column reactor installed in the FT unit. The bubble column reactor is filled with a slurry consisting of liquid hydrocarbons, the product of the FT synthesis reaction, and catalyst particles. As the synthesis gas rises within the slurry, hydrocarbons are produced by the FT synthesis reaction with carbon monoxide and hydrogen.

[0038] The liquid hydrocarbons synthesized are introduced into a separator as a slurry together with catalyst particles, where they are separated into solid components such as catalyst particles and a liquid component containing liquid hydrocarbons (Fischer-Tropsch oil). The separated solid components are returned to the bubble column reactor. The liquid components are fed to a fractionator, where they are heated and fractionated based on differences in boiling points, and then hydrotreated, or hydrotreated and then fractionated to produce naphtha, SAF (Sustainable Aviation Fuel), diesel, and liquid fuels consisting of heavy fractions.

[0039] Typically, the optimal synthesis gas for FT synthesis has an H2 / CO ratio close to 2.0. Therefore, the present invention does not require a shift reactor to adjust the ratio to the optimal level, and produces synthesis gas with an H2 / CO ratio close to 2.0 while effectively utilizing carbon dioxide.

[0040] Hereinafter, an embodiment of the method for removing heavy hydrocarbons according to the present invention will be specifically described, although the present invention is not limited to the following embodiment.

[0041] <<Synthetic gas production method>> Hereinafter, a synthesis gas production method according to one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing the configuration of the synthesis gas production method according to this embodiment. In the biomass raw material supply step S2, biomass raw materials such as rice husks, bagasse, and wood are subjected to a predetermined pretreatment, and the pretreated biomass raw materials are supplied via a raw material supply line to a gasification furnace of a gasification apparatus that performs the synthesis gas production step S3. Here, the pretreatment of the biomass raw materials includes, for example, a drying step for drying the raw materials and a crushing step for crushing the raw materials. The method for supplying the biomass raw material to the gasification furnace is not particularly limited, and any known supply method can be used.

[0042] In the hydrogen supply step S12, hydrogen is supplied to the synthesis gas production step. Before supplying hydrogen to the synthesis gas production step, a purification step for increasing the purity of hydrogen and a pressurization step for pressurizing hydrogen may be performed. The method for supplying hydrogen to the gasification furnace is not particularly limited, and any known supply method can be used. If a sufficient amount of hydrogen is produced in the synthesis gas production step S3 described below, the hydrogen supply step S12 does not need to be performed. For example, by increasing the amount of water vapor supplied, described below, the reaction represented by formula (1-1) described below can proceed more easily. As a result, even when hydrogen is not supplied from an external source, it is possible to produce a sufficient amount of hydrogen to react with carbon dioxide and cause the reverse shift reaction to proceed, and to produce synthesis gas with an H2 / CO ratio of close to 2.0, which is optimal for the FT reaction. When hydrogen is supplied from an external source, the mass ratio of hydrogen supplied, expressed as [mass of hydrogen] / [mass of biomass], is 0.01 to 0.05, preferably 0.01 to 0.04, and more preferably 0.01 to 0.03. When the mass ratio is within the above range, it becomes easier to adjust the ratio of hydrogen to carbon monoxide during synthesis gas production to a higher value, and hydrogen is more likely to react with carbon dioxide in the reverse shift reaction. This allows for reduced carbon dioxide emissions even when no steam is supplied or when only a small amount of steam is supplied, making it possible to produce synthesis gas while reducing the burden on the environment. Furthermore, by recycling the carbon source and reducing the amount of biomass supplied, the generation of by-products such as tar can be reduced.

[0043] In the steam supply step S14, in the synthesis gas production process, steam is supplied so that the mass ratio expressed as [mass of steam] / [mass of biomass] is 1.3 or more. By supplying steam, the biomass and steam react with each other, and the reaction expressed by formula (1-1) described below proceeds. The method for supplying water vapor is not particularly limited, and any known method can be used. There are no particular limitations on the method for adjusting the steam so that the mass ratio expressed as [mass of steam] / [mass of biomass] is 1.3 or more, and adjustment may be made using a steam supply amount adjustment device such as a valve that adjusts the amount of steam supplied into the gasification furnace based on the mass of biomass supplied into the gasification furnace. The mass ratio expressed as [mass of steam] / [mass of biomass] is preferably 1.3 to 2.0, more preferably 1.4 to 1.8, and even more preferably 1.5 to 1.75. When the mass ratio is within the above range, it becomes easier to adjust the proportion of hydrogen contained in the synthesis gas to a higher level, and hydrogen is more likely to react with carbon dioxide in the reverse shift reaction. Therefore, even when no or only a small amount of steam is supplied, carbon dioxide emissions can be reduced, and synthesis gas can be produced while reducing the burden on the environment. Furthermore, by recycling the carbon source and reducing the amount of biomass supplied, the generation of by-products such as tar can be reduced.

[0044] In the carbon dioxide supply step S41, the carbon dioxide contained in the synthesis gas is supplied to the synthesis gas production step. Before supplying the carbon dioxide to the synthesis gas production step, a gas separation step for increasing the purity of the carbon dioxide and a pressurization step for pressurizing the carbon dioxide may be performed. The method for supplying carbon dioxide in the off-gas to the gasification furnace is not particularly limited, and any known gas supply method can be used.

[0045] In the synthesis gas production step S3, the biomass raw material, hydrogen, water, and carbon dioxide are reacted to produce synthesis gas containing hydrogen, carbon monoxide, carbon dioxide, and hydrocarbons. The reaction conditions for producing the synthesis gas are not particularly limited, and known reaction conditions can be used. The synthesis gas may be produced by carrying out the reaction under a nitrogen gas stream. When water and carbon dioxide are introduced into a gasification furnace that has already been charged with biomass raw materials, a total of eight types of gasification reactions and their reverse reactions, such as those shown in the following formulas (1-1) to (1-8), occur in the gasification furnace, producing synthesis gas containing hydrogen, carbon monoxide, carbon dioxide, and hydrocarbons. Here, the water molecules in the following formulas may be derived from the biomass raw materials or may be introduced as water vapor.

[0046] [ka]

[0047] [ka]

[0048] The mass ratio expressed as [mass of carbon dioxide] / [mass of biomass] is preferably 0.01 to 0.05, more preferably 0.01 to 0.04, and even more preferably 0.01 to 0.03. When the mass ratio is within the above range, the reaction of carbon dioxide with hydrogen proceeds more easily, and carbon dioxide is also more easily consumed as a raw material for synthesis gas, which helps to reduce the burden on the environment. In addition, surplus hydrogen can be recovered and reused in the synthesis gas production process, which helps to further improve energy efficiency.

[0049] In the synthesis gas production process S3, in the first step, biomass feedstock, hydrogen, and water are reacted to produce a synthesis gas precursor with an H2 / CO ratio greater than 2.0. In the second step, carbon dioxide is supplied from an external source to promote the reverse shift reaction, producing a synthesis gas with a molar ratio (number of moles of hydrogen) / (number of moles of carbon monoxide) close to 2.0, which is optimal for the FT synthesis reaction. In the synthesis gas production process S3, these multi-step reactions may be performed sequentially or as a one-pot reaction. The H2 / CO ratio of the synthesis gas precursor is preferably greater than 2.0, more preferably 2.2 or greater, and may even be 2.5 or greater. When the H2 / CO ratio of the synthesis gas precursor is equal to or greater than the lower limit, sufficient hydrogen is present for the reverse shift reaction, and the reverse shift reaction is facilitated by supplying carbon dioxide to the precursor. This facilitates the production of a synthesis gas with a molar ratio (number of moles of hydrogen) / (number of moles of carbon monoxide) close to 2.0. Furthermore, carbon dioxide can be more easily consumed as a raw material for synthesis gas, which reduces carbon dioxide emissions and the burden on the environment.

[0050] After the synthesis gas production step S3 and before the Fischer-Tropsch synthesis step S6, a gas purification step S4 and a gas pressurization step S5 may be performed. In the gas purification step S4, hydrogen is mixed, if necessary, with the synthesis gas produced by the gasification reactions and their reverse reactions shown in the above formulas (1-1) to (1-8) to adjust the H2 / CO ratio of the synthesis gas to a predetermined target ratio. The synthesis gas is then purified by removing undesirable substances contained in the synthesis gas in order to supply it to the next gas pressure increasing step S5. For example, the H2 / CO ratio of the purified synthesis gas is preferably 1.95 to 2.05, more preferably 1.98 to 2.02, and even more preferably 2.0. By keeping the H2 / CO ratio of the purified synthesis gas within the above range, it is possible to obtain a synthesis gas with a molar ratio (number of moles of hydrogen) / (number of moles of carbon monoxide) close to 2.0, which is optimal for the FT synthesis reaction. The synthesis gas is purified and separated into a purified synthesis gas having an H / CO ratio of close to 2.0 and an off-gas containing carbon dioxide. The obtained off-gas containing carbon dioxide may be supplied to the synthesis gas production step S4 as is, or may be supplied after further separation in a gas separation step S9 described below. The method for purifying the synthesis gas is not particularly limited, and any known purification method can be used.

[0051] In a gas separation step S9 (not shown), the off-gas is separated into a gasification assisting gas containing carbon dioxide and a heat source gas containing hydrocarbons. The method for separating the gas is not particularly limited, and known separation methods can be used. For example, by passing the off-gas through a column that separates the off-gas based on molecular size, a gasification assisting gas containing carbon dioxide can be obtained as a first fraction, and then a heat source gas containing hydrocarbons can be obtained as a second fraction. Alternatively, the hydrocarbons in the off-gas can be adsorbed into the column to obtain a gasification assisting gas as a first fraction, and then the column can be placed under reduced pressure to recover the hydrocarbons adsorbed in the column, thereby obtaining a heat source gas containing hydrocarbons as a second fraction. Examples of column packing materials include alumina, activated alumina, celite, and porous polymers. Alternatively, the off-gas can be separated by distillation, or the off-gas can be cooled to condense and separate the heat source gas containing hydrocarbons. In the gas separation step S9, the FT off-gas produced in the Fischer-Tropsch synthesis step S6 may be separated into a gasification assisting gas containing carbon dioxide and a heat source gas containing hydrocarbons, similar to the above-mentioned off-gas.

[0052] In a heat source gas supplying step (not shown), the heat source gas is supplied as a heat source in a synthesis gas production step. The method for burning the heat source gas is not particularly limited, and any known method can be used. Carbon dioxide produced by burning the heat source gas may be used as the carbon dioxide supplied in the carbon dioxide supply step S41.

[0053] In a synthesis gas production method according to another embodiment of the present invention, the carbon dioxide supplied in the carbon dioxide supply step S41 may be derived from a source other than synthesis gas, and may be, for example, air or carbon dioxide contained in FT off-gas. The other steps can be the same as those described with reference to FIG.

[0054] <<Liquid fuel manufacturing method>> FIG. 2 is a flowchart showing the configuration of the liquid fuel production method according to this embodiment. The steps from the biomass raw material supply step S2 to the heat source gas supply step can be the same as those described with reference to FIG.

[0055] In the gas pressurization step S5, the pressure of the synthesis gas to be supplied to the Fischer-Tropsch synthesis step is adjusted to a predetermined pressure (e.g., 3 MPa) according to the reaction conditions of the Fischer-Tropsch reaction, and then this synthesis gas is supplied to the subsequent Fischer-Tropsch synthesis step. The method for pressurizing the synthesis gas is not particularly limited, and any known pressure adjustment method can be used.

[0056] In the Fischer-Tropsch synthesis step S6, the synthesis gas is subjected to a Fischer-Tropsch synthesis reaction, and then FT off-gas containing carbon dioxide is separated to produce Fischer-Tropsch oil. The reaction conditions in the Fischer-Tropsch synthesis step S6 are not particularly limited, and known reaction conditions can be used. In the Fischer-Tropsch synthesis step S6, Fischer-Tropsch oil, which is a raw material for methanol, gasoline, etc., and FT off-gas containing carbon dioxide and hydrocarbons are obtained from the synthesis gas. Examples of hydrocarbons contained in the FT off-gas include hydrocarbons having 1 to 5 carbon atoms.

[0057] After the Fischer-Tropsch synthesis step S6 and before the fractionation step S8, there may be a hydrocracking step S7 in which the Fischer-Tropsch oil is hydrocracked. In the hydrocracking step S7, the heavy fraction (approximately C 21 or more) is hydrocracking using hydrogen to change the carbon number to C 20 This hydrocracking reaction uses catalysts and heat to break the C-C bonds in hydrocarbons with a large carbon number to produce hydrocarbons with a smaller carbon number and lower molecular weight, resulting in liquid fuels consisting of naphtha, SAF, diesel, and heavier fractions. The reaction conditions for the hydrocracking are not particularly limited, and known reaction conditions can be used. In addition, when the total mass of hydrocarbons produced after the FT synthesis reaction is 10 t or less, if the hydrocracking step S7 is performed after the Fischer-Tropsch synthesis step and before the fractionation step S8, the amount of hydrocarbons fractionated in the fractionation step S8 will be reduced, resulting in excellent energy efficiency.

[0058] In the fractionation step S8, the Fischer-Tropsch oil is hydrocracked, and then the liquid fuel and the FT off-gas are fractionated. Specifically, the liquid fuel is fractionated into naphtha fraction (boiling point less than approximately 200°C), SAF fraction (boiling point approximately 200 to 300°C), diesel fraction (boiling point approximately 200 to 350°C), and heavy fraction (boiling point above approximately 350°C). The gas obtained during fractional distillation is recovered as FT off-gas. Carbon dioxide contained in the off-gas may be used as carbon dioxide to be supplied in the carbon dioxide supply step S41. The method of fractional distillation is not particularly limited, and any known fractional distillation method can be used.

[0059] FIG. 3 is a flowchart showing the configuration of the fuel production method according to this embodiment. The steps from the biomass feedstock supply step S2 to the Fischer-Tropsch synthesis step S6 can be the same as those described with reference to FIG.

[0060] In a fractionation step S8, the Fischer-Tropsch oil and the FT off-gas are fractionated after the Fischer-Tropsch synthesis step and before the Fischer-Tropsch oil is subjected to hydrorefining or hydrocracking. The method of fractional distillation is not particularly limited, and any known fractional distillation method can be used.

[0061] After the Fischer-Tropsch synthesis step, the fractionation step S8 may be followed by a hydrotreating step S17 of hydrotreating the Fischer-Tropsch oil and a hydrocracking step S7 of hydrocracking the Fischer-Tropsch oil. In the hydrorefining step S17, the unsaturated bonds of the unsaturated hydrocarbons contained in the liquid fuel after fractionation are hydrogenated to convert them into saturated hydrocarbons, which are then refined. In the hydrocracking step S7, the heavy fraction (approximately C ) obtained after fractional distillation of the Fischer-Tropsch oil is 21 The above is hydrocracking using hydrogen. When the mass of the synthesis gas exceeds 10 tons, performing the hydrotreating step S17 and hydrocracking step S7 after the Fischer-Tropsch synthesis step and after the fractionation step S8 reduces the amount of fractionation in the fractionation step S8, resulting in excellent energy efficiency. Unlike the hydrocracking step S7, the hydrotreating step S17 does not cleave the C—C bonds of hydrocarbons, and therefore hardly produces by-products with significantly different carbon numbers and boiling points. The reaction conditions for the hydrocracking are not particularly limited, and known reaction conditions can be used. The reaction conditions for hydrotreating are not particularly limited, and known reaction conditions can be used. Carbon dioxide produced in hydrocracking and hydrotreating may be used as the carbon dioxide supplied in the carbon dioxide supply step S41.

[0062] <<Synthetic gas production system>> FIG. 4 is a schematic diagram showing the configuration of a synthesis gas production system according to this embodiment. The synthesis gas production system according to this embodiment is a system for carrying out the synthesis gas production method of Fig. 1. Therefore, the explanation of the fuel production system according to this embodiment is not particularly limited as long as it can carry out the contents explained in the synthesis gas production method of Fig. 1, and conventional devices can be used.

[0063] In the gasification device 3, the biomass material, hydrogen, water, and carbon dioxide are reacted to produce a synthesis gas containing hydrogen, carbon monoxide, carbon dioxide, and hydrocarbons. A hydrogen production device or hydrogen supply device 10 supplies hydrogen to the gasifier. In the gas separation device 9, the off-gas is separated into a gasification assisting gas containing carbon dioxide and a heat source gas containing hydrocarbons. A carbon dioxide supplying device (not shown) supplies the gasification assisting gas as a raw material to the gasification device 3. The carbon dioxide supplying device is not particularly limited, but may be a pipe connecting the gas separation device 9 and the gasification device 3, or may be composed of a carbon dioxide tank for storing carbon dioxide between the gas separation device 9 and the gasification device 3 and a pipe connecting the carbon dioxide tank and the gasification device 3. A heat source gas supply device (not shown) supplies the heat source gas as a heat source for heating a gasification furnace used to produce synthesis gas in the gasification device 3. The steam supplying device 14 supplies steam to the gasification device 3.

[0064] <<Fuel production system>> FIG. 5 is a schematic diagram showing the configuration of a fuel production system according to this embodiment. The fuel production system according to this embodiment is a system for carrying out the fuel production method of Fig. 2. Therefore, the explanation of the fuel production system according to this embodiment is not particularly limited as long as it can carry out the contents explained in the fuel production method of Fig. 2, and conventional devices can be used. Furthermore, the biomass material supply device 2 to the gas refinery device 4 can be the same as those described with reference to FIG.

[0065] In a Fischer-Tropsch unit (FT unit) 6, the synthesis gas is subjected to a Fischer-Tropsch synthesis reaction, and then FT off-gas containing carbon dioxide is separated to produce Fischer-Tropsch oil. In the hydrocracker 7, the heavy fraction (approximately C 21The above-mentioned materials are hydrocracking using hydrogen to obtain liquid fuels consisting of naphtha, SAF, diesel, and heavy fractions. When the total mass of hydrocarbons produced after the FT synthesis reaction is 10 tons or less, providing a hydrocracker 7 downstream of the Fischer-Tropsch unit 6 and upstream of the fractionator (S) 8 reduces the amount of hydrocarbons fractionated in the fractionator (S) 8, resulting in excellent energy efficiency. In the fractionation unit (S) 8, the Fischer-Tropsch oil is hydrocracked, and then the liquid fuel and the FT off-gas are fractionated.

[0066] FIG. 6 is a schematic diagram showing the configuration of a fuel production system according to this embodiment. The fuel production system according to this embodiment is a system for carrying out the fuel production method of Fig. 3. Therefore, the explanation of the fuel production system according to this embodiment is not particularly limited as long as it can carry out the contents explained in the fuel production method of Fig. 3, and conventional devices can be used. Furthermore, the biomass raw material supply device 2 to the Fischer-Tropsch unit 6 can be the same as those described with reference to FIG.

[0067] In a fractionator (L) 8, downstream of the Fischer-Tropsch unit and upstream of a hydrocracker that hydrocracks the Fischer-Tropsch oil, liquid fuel and the FT off-gas are fractionated.

[0068] In the hydrotreating unit 17, the unsaturated bonds of the unsaturated hydrocarbons contained in the liquid fuel after fractionation are hydrogenated to convert them into saturated hydrocarbons, which are then refined. In the hydrocracker 7, the heavy fraction (approximately C ) obtained after fractional distillation of the Fischer-Tropsch oil is 21 The above is hydrocracking using hydrogen. When the mass of the synthesis gas exceeds 10 tons, providing a hydrotreating unit 17 and a hydrocracking unit 7 downstream of the Fischer-Tropsch unit 6 and downstream of the fractionation unit (L) 8 reduces the amount of gas fractionated in the fractionation unit (L) 8, resulting in excellent energy efficiency.

[0069] FIG. 7 is a flowchart showing the specific steps of the fuel production method of the present invention. First, the initial synthesis gas is produced, and it is determined whether the amount of CO2 recovered from the off-gas is equal to or greater than a threshold. If the determination is YES, the amount of steam supplied to the next gasification reaction is increased, and operation is performed to increase the amount of hydrogen produced. The recovered CO2 is supplied to this, and the reverse shift reaction is carried out to consume hydrogen and carbon dioxide and produce carbon monoxide, thereby producing synthesis gas with an H2 / CO ratio close to 2.0, which is optimal for the FT synthesis reaction. The obtained synthesis gas is supplied to the FT synthesis reaction, and finally liquid fuel is synthesized. If the determination is NO, the obtained synthesis gas is supplied directly to the FT synthesis reaction without supplying CO2 from an external source. [Example]

[0070] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0071] <Example 1> The amount of water vapor supplied was adjusted so that the molar ratio expressed as [number of moles of hydrogen] / [number of moles of carbon monoxide] was 2.0 or higher, and the mass ratio expressed as [mass of water vapor] / [mass of biomass feedstock] (hereinafter also referred to as S / B ratio) was the value shown in Tables 1 and 2. The content of each component in the synthesis gas precursor was measured at each elapsed time and S / B ratio. The results are shown in Tables 1 and 2. The amounts of components in the synthesis gas are shown in Figure 8.

[0072] [Table 1]

[0073] [Table 2]

[0074] As shown in Figure 8, it was found that by adjusting the amount of water vapor supplied, a synthesis gas precursor with a high hydrogen content, where the molar ratio expressed as [moles of hydrogen] / [moles of carbon monoxide] exceeds 2.0, can be obtained. It is presumed that the reverse shift reaction occurs when carbon dioxide is supplied to the obtained synthesis gas precursor, and therefore it is possible to adjust a synthesis gas with a molar ratio expressed as [moles of hydrogen] / [moles of carbon monoxide] of 2.0 or more to a value close to 2.0.

[0075] The present invention is not limited to the above-described embodiments, and includes modifications and improvements within the scope of achieving the object of the present invention. [Explanation of symbols]

[0076] 1, 11 Fuel production system 2. Biomass raw material supply device 3 Gasifier 4 Gas purification equipment 5. Gas pressure generator 6. Fischer-Tropsch Unit (FT Unit) 7 Hydrocracker 8 Fractionation device 9 Gas Separator 10 Hydrogen production equipment or hydrogen supply equipment 13 Control device 14 Steam supply device 17 Hydrotreating Unit 30. Synthetic gas production system

Claims

1. A method for producing synthesis gas from biomass feedstock, comprising: a synthesis gas production step of producing synthesis gas containing hydrogen, carbon monoxide, and carbon dioxide from the supplied biomass raw material, water, and carbon dioxide; The synthesis gas production method, wherein the carbon dioxide supplied to the synthesis gas production step comprises carbon dioxide contained in the synthesis gas.

2. 2. The synthesis gas production method according to claim 1, further comprising a carbon dioxide supplying step of supplying carbon dioxide in the synthesis gas to the synthesis gas production step.

3. 2. The synthesis gas production method according to claim 1, further comprising a gas purification step of separating the synthesis gas into an off-gas containing carbon dioxide and hydrocarbons and a purified synthesis gas containing hydrogen and carbon monoxide.

4. 4. The synthesis gas production method according to claim 3, further comprising a gas separation step of separating the off-gas into a gasification-assisting gas containing carbon dioxide and a heat source gas containing hydrocarbons.

5. 5. The synthesis gas production method according to claim 4, further comprising a heat source gas supplying step of supplying the heat source gas as a heat source in a synthesis gas production step.

6. 2. The synthesis gas production method according to claim 1, further comprising a steam supplying step of supplying steam as water in the synthesis gas production step so that a mass ratio expressed as [mass of steam] / [mass of biomass] is 1.3 or more.

7. 2. The synthesis gas production method according to claim 1, further comprising a carbon dioxide supplying step of supplying carbon dioxide so that the molar ratio of [number of moles of hydrogen] / [number of moles of carbon monoxide] in the synthesis gas to be obtained is 1.95 to 2.

05.

8. A fuel production system for producing fuel from biomass feedstock, comprising: a gasification device that produces synthesis gas containing hydrogen, carbon monoxide, carbon dioxide, and hydrocarbons from the supplied biomass feedstock, water, and carbon dioxide; a carbon dioxide supplying device that supplies carbon dioxide in the synthesis gas to the gasification device.

9. 9. The synthesis gas production system according to claim 8, further comprising a gas purification device that separates the synthesis gas into an off-gas containing carbon dioxide and hydrocarbons and a purified synthesis gas containing hydrogen and carbon monoxide.

10. 10. The synthesis gas production system according to claim 9, further comprising a gas separation device that separates the off-gas into a gasification-assisting gas containing carbon dioxide and a heat source gas containing hydrocarbons.

11. The synthesis gas production system according to claim 10 , further comprising a heat source gas supply device for supplying the heat source gas as a heat source in a synthesis gas production process.

12. 9. The synthesis gas production system according to claim 8, further comprising a steam supply device that supplies steam as water to the gasification device so that a mass ratio expressed as [mass of steam] / [mass of biomass] is 1.3 or more.

13. 9. The synthesis gas production system according to claim 8, further comprising a carbon dioxide supplying device that supplies carbon dioxide to the gasification device so that the molar ratio of [number of moles of hydrogen] / [number of moles of carbon monoxide] in the synthesis gas obtained is 1.95 to 2.05.

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