Methanol production method

Abstract

Industrially and efficiently produce methanol from waste [Solution] Producing methanol from waste The process includes a gas obtaining step (S1) for obtaining a gas containing carbon oxides and hydrogen from waste, and a conversion step (S6) for contacting at least a portion of the gas with a catalyst and converting it into methanol in the gas phase. In the conversion step (S6), the converted methanol and high-boiling components including water are condensed and removed from the reaction system, thereby progressing the reaction.

Description

[Technical Field]

[0001] The present invention relates to a method for producing methanol from waste materials. [Background technology]

[0002] Burnable waste is usually disposed of by landfilling or incineration. Landfilling, as well as incineration, emits carbon dioxide and heat. Therefore, improvements are needed from the perspective of global environmental issues such as global warming.

[0003] In consideration of global environmental issues and with the aim of making effective use of waste, methods have been developed for converting waste into hydrogen, a high-energy substance, or methanol or dimethyl ether, one of the most basic organic substances. For example, Patent Document 1 discloses a waste treatment system that includes a step of synthesizing methanol from hydrogen and carbon dioxide obtained by gasifying waste. Meanwhile, Patent Document 2 discloses a method for producing methanol by condensing the product from carbon dioxide and hydrogen, a carbon oxide such as carbon dioxide. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2012-017893 publication [Patent Document 2] Japanese Patent Application Publication No. 2005-298413 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the system disclosed in Patent Document 1, the synthesis of methanol from carbon dioxide is not necessarily carried out efficiently due to equilibrium constraints. On the other hand, in the methanol production disclosed in Patent Document 2, hydrogen used as a raw material is currently often produced industrially by steam reforming of natural gas and is generally derived from fossil fuels. Therefore, the production method disclosed in Patent Document 2 is not necessarily sufficient for industrially and efficiently producing methanol using raw materials that are environmentally friendly.

[0006] One aspect of the present invention aims to industrially and efficiently produce methanol from waste. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, one aspect of the present invention provides a method for producing methanol, comprising: a gas obtaining step of obtaining a gas containing carbon oxides and hydrogen from a waste material; and a conversion step of bringing at least a portion of the gas into contact with a catalyst and converting it into methanol in the gas phase. The conversion step is characterized in that the converted methanol and high-boiling components containing water are condensed and discharged outside the reaction system, thereby progressing the reaction. [Effects of the Invention]

[0008] According to one aspect of the present invention, methanol can be produced industrially and efficiently from waste. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a flowchart showing an example of a method for producing methanol according to a first embodiment of the present invention. [Figure 2] FIG. 1 is a system diagram schematically illustrating the configuration of a methanol production apparatus according to a first embodiment of the present invention. [Figure 3] FIG. 2 is a cross-sectional view of an exemplary first reactor taken along a plane perpendicular to the bottom surface. [Figure 4] 1 is a flowchart showing an example of a method for producing methanol according to a second embodiment of the present invention. [Figure 5] FIG. 1 is a system diagram schematically illustrating the configuration of a methanol production apparatus according to a second embodiment of the present invention. [Figure 6] 1 is a flowchart showing an example of a method for producing methanol according to a third embodiment of the present invention. [Figure 7] FIG. 1 is a system diagram schematically illustrating the configuration of a methanol production apparatus according to a third embodiment of the present invention. [Figure 8] FIG. 1 is a system diagram schematically illustrating the configuration of a methanol production apparatus according to a comparative example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Embodiment 1] A method for producing methanol according to one embodiment of the present invention will be described in detail below with reference to the accompanying drawings, along with a production apparatus used therein. Note that the drawings used below are for explaining the present invention and may differ in size from the actual dimensions.

[0011] Fig. 1 is a flowchart showing an example of a methanol production method according to this embodiment. As shown in Fig. 1, the methanol production method of the present invention includes a gas obtaining step S1 in which waste is decomposed to obtain (gasify) a gas containing carbon oxides and hydrogen (H2) (referred to as waste-derived gas G1), and a conversion step S6 in which the gas is used as a raw material gas to synthesize methanol from at least a portion of the carbon oxides and hydrogen contained in the raw material gas. Here, carbon oxide includes at least one of carbon monoxide (CO) and carbon dioxide (CO2), and when both are included, the ratio of the two is not particularly limited.

[0012] The flowchart shown in FIG. 1 includes the gas obtaining step S1 and the conversion step S6, as well as a gas cleaning step S2, a gas adjusting step S3, and a purification step S7. Each step will be described in detail below. In this embodiment, the flowchart shown in FIG. 1 and a methanol production apparatus (hereinafter simply referred to as the "production apparatus") that realizes the production flow shown in the flowchart will be described as an example. However, the gas cleaning step S2, the gas adjusting step S3, and the purification step S7 are steps that can be incorporated into the production flow as needed. The steps shown in the drawings in this specification are merely typical examples and do not limit the scope of the present invention in any way.

[0013] (Configuration of methanol production equipment) First, an example of the configuration of a manufacturing apparatus 100 according to an embodiment of the present invention will be described. Fig. 2 is a system diagram that schematically shows the configuration of the manufacturing apparatus 100 according to the first embodiment.

[0014] As shown in Fig. 2, the production apparatus 100 of this embodiment is generally configured to include a gas acquisition apparatus 1, a gas cleaning apparatus 3, a gas composition adjustment apparatus 4, a first reactor 2, a purification apparatus 5, and paths L1 to L12. The production apparatus 100 of this embodiment is an apparatus for producing methanol from waste. The methanol production method of the present invention is a method in which a gas containing carbon oxides and hydrogen obtained by decomposing waste is supplied to the first reactor 2 as a raw material gas, and a reaction for converting the gas into methanol is carried out.

[0015] In this embodiment, the waste may be any organic material from which a gas containing hydrogen and carbon oxides can be obtained in the gas obtaining step S1. Examples of the waste include food waste, paper waste, textile waste, plastic waste, sewage sludge, human waste, livestock waste, waste oil, rubber tires, black liquor, blackstrap molasses, and mixtures thereof.

[0016] The gas capture apparatus 1 is an apparatus for carrying out a gas capture step S1 in which waste (target material) is decomposed to capture a gas containing carbon oxides and hydrogen (referred to as waste-derived gas G1). The gas capture apparatus 1 reacts waste supplied from a waste supply path L1 within the apparatus. As the gas capture apparatus 1, known apparatuses such as a fixed-bed furnace, a fluidized-bed furnace, a bubbling-type fluidized-bed furnace, a circulating fluidized-bed furnace, and a circulating moving-bed furnace can be used.

[0017] A waste-derived gas G1 supply path L2 is provided between the gas acquisition device 1 and the gas scrubbing device 3. As a result, the waste-derived gas G1 is supplied to the gas scrubbing device 3.

[0018] The gas scrubbing apparatus 3 is an apparatus that performs a gas scrubbing step S2 in which impurities are removed from the waste-derived gas G1 to scrub the gas. The gas scrubbing step S2 can be performed by a known method, and the gas scrubbing apparatus 3 can be a known apparatus such as a wet scrubber or an electric dust collector.

[0019] A cleaned gas supply path L3 is provided between the gas cleaning device 3 and the gas component adjusting device 4. As a result, a cleaned gas G2, which is a gas that has been cleaned by the gas cleaning device 3, is supplied to the gas component adjusting device 4.

[0020] The gas component adjusting device 4 is a device that performs the gas adjustment step S3 of adjusting the components of the raw material gas to be supplied to the first reactor 2. The gas component adjusting device 4 is provided with a hydrogen supply path L4, through which hydrogen can be supplied. The gas component adjusting device 4 is also provided with a carbon dioxide discharge path L5, through which carbon dioxide can be discharged. The gas adjustment performed in the gas component adjusting device 4 will be described in detail in the description of the gas component adjusting step below.

[0021] A raw material gas supply line L6 is provided between the gas composition adjuster 4 and the first reactor 2. As a result, an adjusted gas G3, which is a gas adjusted in the gas composition adjuster 4, is supplied as a raw material gas to the first reactor 2. The gas supplied as the raw material gas to the first reactor 2 may be a waste-derived gas G1 or a cleaned gas G2, depending on the configuration of the production apparatus.

[0022] The first reactor 2 is a reactor in which a gas containing carbon oxides and hydrogen, which is supplied as a raw material gas, is reacted in the presence of a catalyst to convert it into methanol, thereby carrying out a conversion step S6. Figure 3 is a cross-sectional view of an exemplary first reactor 2 cut along a plane perpendicular to the bottom surface.

[0023] As shown in FIG. 3 , the first reactor 2 includes a reaction vessel 201, a catalyst layer 202, a permeable wall 203, and a condensation surface 205 separated from the permeable wall 203 by a space 204. The reaction vessel 201 is a pressure-resistant metal vessel made of, for example, stainless steel. The catalyst layer 202 is a region where the raw material gas comes into contact with the catalyst 220 and the reaction proceeds. The catalyst layer 202 is filled with a catalyst 220 suitable for the reaction. The permeable wall 203 is made of a porous material that allows gas to pass through. The permeable wall 203 is made of a material that allows the reaction gas 232 generated by the reaction in the catalyst layer 202 to pass through but does not allow the catalyst 220 to pass through. The space 204 is a space formed between the permeable wall 203 and the condensation surface 205. The condensation surface 205 cools the reaction gas 232 that has passed through the permeable wall 203 to a temperature below its dew point and condenses high-boiling components, including methanol and water. The term "high boiling point component" refers to a component with a high boiling point, and in this specification, refers to a component with a high boiling point contained in the reaction gas generated in the methanol conversion reaction. That is, in this specification, the term "high boiling point component" refers to a component that condenses at a temperature equal to or lower than the dew point of the reaction gas generated in the methanol conversion reaction, and includes methanol and water.

[0024] The first reactor 2 may be provided with a first heat medium region 252 through which a first heat medium 251 flows to maintain the condensation surface 205 at a temperature equal to or lower than the dew point of the reaction gas 232. In addition, the first reactor 2 may be provided with a second heat medium region 222 through which a second heat medium 221 flows to recover heat generated by the reaction in the catalyst layer 202.

[0025] A condensate recovery line L7 is provided between the first reactor 2 and the purification device 5. As a result, the condensate containing methanol and water condensed in the first reactor 2 is discharged outside the reaction system and supplied to the purification device 5.

[0026] The purification device 5 is a device that performs the purification step S7, in which the condensate is produced and water and impurities are separated to purify methanol. The condensate obtained from the first reactor 2 is obtained as a liquid mixture containing the product methanol and water. The method for extracting methanol from the mixture in the purification device 5 is not particularly limited, but methanol may be obtained by removing water and impurities through dehydration and purification treatment using a known method, for example. Examples of dehydration and purification treatment methods include distillation and membrane separation.

[0027] An unreacted gas resupply line L10 may be provided between the first reactor 2 and the gas composition adjusting device 4. This allows unreacted carbon oxides and / or hydrogen to be recovered as unreacted gas in the conversion step S6 in the first reactor 2 and returned to the gas composition adjusting device 4 for reuse. The first reactor 2 may also be provided with an exhaust gas discharge line L9. This allows the unreacted gas to be discharged as exhaust gas. Note that the unreacted gas may be recovered as needed and then combusted before being released as exhaust gas to be used as thermal energy for the conversion step S6 to methanol.

[0028] (Method of producing methanol) The method for producing methanol according to the first embodiment is carried out, for example, according to the flowchart shown in Fig. 1. Note that the flowchart shown in Fig. 1 is an example, and the present invention is not limited to this. Each step in the method for producing methanol according to the first embodiment will be described in detail.

[0029] (Gas acquisition process S1) The gas obtaining step S1 is a step of obtaining a gas containing carbon oxides and hydrogen from waste. When waste containing unsaturated hydrocarbon components, such as plastic waste, is used as the waste, it is assumed that the reactions represented by the following formulas (1) to (4) occur in the gas obtaining device 1 due to the reaction between the hydrocarbon and water vapor or oxygen.

[0030] CnH2n+nH2O→nCO+2nH2(1) CnH2n+2nH2O→nCO2+3nH2(2) CnH2n+0.5nO2→nCO+nH2(3) CnH2n+nO2→nCO2+nH2(4) In the above formulas (1) and (3), carbon monoxide is produced along with hydrogen, but the methanol production method of the present invention may also include a step in which carbon monoxide and water are used as raw materials to obtain carbon dioxide and hydrogen through the reaction of formula (5) below. Furthermore, the method may also include a step in which carbon monoxide and oxygen are used as raw materials to obtain thermal energy and carbon dioxide required for the gasification reaction (gas production reaction) through the reaction of formula (6) below.

[0031] CO+H2O→CO2+H2(5) CO+0.5O2→CO2(6) In the reactions of the above formulas (1) to (6), 1 to 3 moles of hydrogen are obtained per mole of carbon atoms.

[0032] On the other hand, when waste containing naturally occurring organic matter is used as the waste, it is thought that, for example, a reaction represented by the following formula (7) and / or a reaction represented by the following formula (8) occurs within the gas acquisition device 1.

[0033] (C6H12 O6)n → 6nCO + 6nH2(7) (C6H 12 O6)n + 6nH2O → 6nCO2 + 12nH2(8) In the above formula (7), carbon monoxide is produced together with hydrogen, but carbon dioxide and hydrogen may be obtained by using the carbon monoxide and water as raw materials and subjecting them to the reaction of the above formula (5). In the above formulas (7) to (8), 1 to 2 moles of hydrogen are obtained per mole of carbon atom.

[0034] In the reaction for obtaining carbon monoxide and hydrogen from organic substances as described above, the reaction may need to be carried out at a higher temperature than in the reaction for obtaining carbon dioxide and hydrogen. Also in view of the energy cost involved in raising the temperature, it is expected that the method for obtaining carbon dioxide and hydrogen may be more advantageous.

[0035] (Gas cleaning process S2) The gas cleaning step S2 is a step of cleaning the waste-derived gas G1 by removing impurities from the gas. The waste-derived gas G1 may contain impurities such as soot and fly ash, which may poison the catalyst. In addition, the waste-derived gas G1 may contain other impurities such as reaction-inhibiting components such as sulfur and nitrogen. In such cases, it is preferable to clean the waste-derived gas G1 in the gas cleaning step S2 before supplying it to the first reactor 2 in the subsequent stage. The gas cleaning step S2 is usually performed depending on the solid components and reaction-inhibiting components contained in the waste-derived gas G1, and is performed by a conventionally known cleaning method.

[0036] By cleaning the gas in the gas cleaning step S2, the deterioration rate of the catalyst used in the conversion step S6 can be reduced, and the catalyst life can be extended.

[0037] (Gas adjustment process S3) The gas adjustment step S3 is a step for adjusting the components of the gas to be supplied to the conversion step S6 described below. The amount of hydrogen required for methanol production is 2 moles per mole of carbon monoxide (CO) and 3 moles per mole of carbon dioxide (CO2). Therefore, the volume fractions of hydrogen, carbon monoxide, and carbon dioxide in the raw material gas supplied to the first reactor 2 in the subsequent stage are ideally adjusted so that the index SN shown in the following formula (9) becomes 2. In the following formula (9), yH2, yCO2, and yCO are the volume fractions of hydrogen, carbon dioxide, and carbon monoxide, respectively, in the raw material gas supplied to the first reactor 2.

[0038] SN=(yH2-yCO2) / (yCO+yCO2) (9) On the other hand, even when high-energy waste such as polyolefin is used as waste, it may be necessary to secure thermal energy through the oxidation reaction of carbon monoxide shown in the above formula (6) in order to carry out gasification without inputting thermal energy from an external source. Therefore, as the proportion of carbon dioxide increases, the index SN shown in the above formula (9) becomes approximately 1.

[0039] In the methanol production method of the present invention, when the waste-derived gas G1 obtained in the gas obtaining step S1 contains hydrogen, carbon dioxide, and carbon monoxide, these three components can be supplied to the first reactor 2. However, when the value of the indicator SN is low, it is preferable to add a gas adjustment step in which the SN value is adjusted in advance before the waste-derived gas G1 is supplied as a raw material gas to the first reactor 2. The value of the indicator SN is preferably adjusted to be between 1 and 10, and more preferably between 1.5 and 3.

[0040] One example of a method for adjusting the value of the index SN in the gas adjustment step S3 is a method for removing at least a portion of carbon dioxide from the waste-derived gas G1 obtained in the gas acquisition step S1. The carbon dioxide removed here may be used for another purpose. Specifically, for example, by treating the waste-derived gas G1 with a chemical adsorption method using an amine solution, carbon dioxide, an acidic gas, can be removed and a gas containing hydrogen and carbon monoxide can be obtained. In addition to the chemical adsorption method, carbon dioxide, which has the highest boiling point of the three components, can be separated by cryogenic separation to obtain a gas containing hydrogen and carbon monoxide. Carbon dioxide may also be separated by a membrane separation method using a separation membrane that selectively blocks carbon dioxide, or more preferably, a separation membrane that selectively allows carbon dioxide to pass through.

[0041] Another example of a method for adjusting the value of the index SN in the gas adjustment step S3 is a method of adding (supplementing) hydrogen (hydrogen gas) to the waste-derived gas G1 obtained in the gas acquisition step S1. Methods for obtaining this hydrogen include known techniques such as reforming of fossil fuels, decomposition reactions, thermal decomposition or dehydrogenation reactions of hydrocarbons, electrolysis of water or brine, water decomposition using a photocatalyst, and ammonia decomposition.

[0042] Examples of the thermal cracking reaction of hydrocarbons include a method for producing lower olefins by thermal cracking of naphtha, a method for obtaining hydrogen by thermal cracking of methane, etc. Examples of the dehydrogenation reaction of hydrocarbons include a method for producing ethylene by dehydrogenating ethane, a method for producing propylene by dehydrogenating propane, a method for producing toluene by dehydrogenating methylcyclohexane, and a method for producing cyclohexanone by dehydrogenating cyclohexanol, etc.

[0043] Another method for adjusting the value of the index SN in the gas adjustment process S3 is to modify or decompose at least a portion of the carbon oxide contained in the waste-derived gas G1 obtained in the gas acquisition process S1, thereby changing the ratio of carbon monoxide to carbon dioxide contained in the waste-derived gas G1.

[0044] The gas adjustment step S3 may be performed by carrying out at least one of the following processes: (i) adding hydrogen to the gas; (ii) removing at least a portion of the carbon dioxide from the gas; and (iii) decomposing or reforming at least a portion of the carbon oxides in the gas.

[0045] By adjusting the gas components in the gas adjustment step S3, the raw material composition can be adjusted to a composition suitable for the methanol conversion reaction (synthesis reaction) in the subsequent conversion step S6, thereby improving the conversion rate to methanol in the conversion step S6.

[0046] (Conversion step S6) The conversion step S6 is a step in which at least a portion of the gas obtained from the waste is brought into contact with a catalyst and converted into methanol in the gas phase. In the conversion step S6, the converted methanol and high-boiling components, including water, are condensed and removed from the reaction system, thereby promoting the reaction. This allows carbon oxides and hydrogen to be converted to an equilibrium conversion rate or higher. Here, the equilibrium conversion rate refers to at least one of the equilibrium conversion rates of carbon oxides in the feed gas on a carbon basis and a hydrogen basis, calculated from the equilibrium composition according to the reaction temperature and pressure.

[0047] Here, the catalyst 220 used in the conversion step S6 will be described. When methanol is obtained by the reaction of carbon dioxide and hydrogen, water is produced as a by-product, as represented by the following formula (10). On the other hand, when methanol is obtained by the reaction of carbon monoxide and hydrogen, water is not produced as a by-product, as represented by the following formula (11).

[0048] CO2 + 3H2 → CH3OH + H2O (49.4 kJ / mol (exothermic reaction)) (10) CO + 2H → CHOH (90.4 kJ / mol (exothermic reaction)) (11) The water produced as a by-product in the reaction of formula (10) may reduce the reaction activity of the catalyst and decrease the productivity of methanol. Therefore, in the methanol production method of the present invention, it is preferable to use a catalyst that is less susceptible to the influence of water.

[0049] For this reason, in this embodiment, it is preferable to use, as the catalyst 220, a catalyst whose activity is unlikely to decrease due to water, such as a copper-based catalyst. For example, a catalyst containing copper, zinc, aluminum, and silicon as essential components and optionally containing zirconium, palladium, and gallium is used as the catalyst 220. Generally, catalysts used to obtain methanol by reacting carbon dioxide and hydrogen tend to also be able to obtain methanol when carbon monoxide and hydrogen are used as raw materials. For this reason, catalysts containing components such as copper are suitable for use in the methanol production method of this embodiment because they are active in both the reaction between carbon dioxide and hydrogen and the reaction between carbon monoxide and hydrogen, and are also durable against the by-product water.

[0050] When a copper-containing catalyst is used as catalyst 220, its particle size is not particularly limited, but may be, for example, 1 mm to 20 mm, 2 mm to 20 mm, 3 mm to 20 mm, 3 mm to 15 mm, or 3 mm to 10 mm. Having the particle size of catalyst 220 within the above range not only makes catalyst 220 easy to handle, but is also advantageous in terms of the strength of catalyst 220 and is also suitable when catalyst 220 is loaded into a fixed bed to form catalyst layer 202. The method for producing catalyst 220 with the above particle size is not particularly limited, and known methods can be used. A tableting method is preferably used.

[0051] The reaction temperature in the catalyst layer 202 may be, for example, about 180° C. to 260° C., and preferably 220° C. to 240° C. The reaction pressure may be, for example, about 0.2 MPaG to 10 MPaG, and preferably 1 MPaG to 5 MPaG.

[0052] By using the first reactor 2, 60% or more, preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more of at least one of carbon oxides and hydrogen in the feed gas supplied to the first reactor 2 is converted to methanol. When the carbon oxides include both carbon monoxide and carbon dioxide, the conversion rate here is calculated based on at least one of carbon monoxide, carbon dioxide, and hydrogen. This makes it possible to produce methanol in excess of the equilibrium composition, and allows for a reduction in the scale of the facility per unit amount of methanol produced.

[0053] The conversion step in the first reactor 2 may be carried out in the presence of a so-called inert gas that does not contribute to the conversion reaction or to a decrease in the activity of the catalyst.

[0054] In this embodiment, the waste-derived gas G1 obtained in the gas acquisition step S1 can be used as a raw material gas in the conversion step S6. In the conversion step S6, some or all of the carbon monoxide, carbon dioxide, and hydrogen in the raw material gas are used. On the other hand, carbon dioxide or hydrogen obtained outside the production equipment may be added to the waste-derived gas G1 obtained in the gas acquisition step S1 to provide the raw material gas used in the conversion step S6. The method for obtaining the carbon dioxide or hydrogen that can be added here is not particularly limited, and for example, carbon dioxide obtained when burning fossil fuels to generate electricity may be added. The gas adjustment step S3 may be performed after the gas acquisition step S1, before the raw material gas is supplied to the first reactor 2 in which the conversion step S6 is performed, or may be performed simultaneously with the supply of the raw material gas. Furthermore, the gas adjustment step S3 may be performed in one step or in multiple steps.

[0055] According to one aspect of the present invention, methanol can be produced from waste materials more efficiently in a small-scale facility, thereby enabling effective utilization of waste materials and contributing to reducing carbon dioxide emissions derived from fossil fuels that are associated with conventional methanol production.

[0056] [Embodiment 2] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0057] Fig. 4 is a flowchart showing an example of a methanol production method according to Embodiment 2. As shown in Fig. 4, the methanol production method according to Embodiment 2 differs from Embodiment 1 in that a preliminary conversion step S4 is included between the gas preparation step S3 and the conversion step S6. The flowchart shown in Fig. 4 is an example, and is not intended to be limiting. For example, the gas preparation step S3 may be moved or added between the preliminary conversion step S4 and the conversion step S6.

[0058] 5 is a system diagram showing a schematic configuration of a methanol production apparatus (production apparatus 100A) according to Embodiment 2. The production apparatus 100A is generally configured to include a gas acquisition apparatus 1, a gas cleaning apparatus 3, a gas composition adjustment apparatus 4, a first reactor 2, a purification apparatus 5, a second reactor 6, and paths L1 to L13. The production apparatus 100A is similar to the production apparatus 100 of Embodiment 1, except that it further includes the second reactor 6 and a path L13 for supplying a raw gas for preliminary conversion.

[0059] A preliminary conversion raw material gas supply line L13 is provided between the gas composition adjuster 4 and the second reactor 6. As a result, an adjusted gas G3, which is a gas adjusted by the gas composition adjuster 4, is supplied to the second reactor 6 as a preliminary conversion raw material gas.

[0060] The second reactor 6 is a reactor for carrying out a pre-conversion step S4 in which a gas containing carbon oxides and hydrogen, supplied as a pre-conversion feed gas, is allowed to reach the equilibrium composition of the methanol conversion reaction. The second reactor 6 may be, for example, a general fixed-bed catalytic reactor packed with a solid catalyst, or may be a reactor having the same structure as the first reactor 2. As described above, the first reactor 2 can proceed with the reaction beyond the equilibrium of the methanol conversion reaction. However, the reaction may be allowed to proceed to the equilibrium composition in the second reactor 6, which is located upstream of the first reactor 2, and the resulting pre-conversion gas G4 may then be supplied to the first reactor 2 as the feed gas through the feed gas supply line L6.

[0061] The method for producing methanol according to the second embodiment is carried out, for example, according to the flowchart shown in Fig. 4. Explanation of the same steps as those in the first embodiment will be omitted, and the preliminary conversion step S4 will be explained below.

[0062] (Pre-conversion step S4) The preliminary conversion step S4 is a step in which a gas containing carbon oxides and hydrogen is converted to methanol until it reaches the equilibrium composition for the methanol conversion reaction. In the second reactor 6, the carbon oxides and hydrogen in the preliminary conversion feed gas are preferably converted to methanol until a predetermined conversion rate or higher is reached. This predetermined conversion rate is, for example, 80% of the equilibrium conversion rate of carbon oxides in the preliminary conversion feed gas, calculated from the equilibrium composition according to the reaction temperature and pressure. It is also more desirable to separate high-boiling components, including methanol and water, from the gas obtained in the second reactor 6 and adjust the composition before supplying the gas to the first reactor. Here, the equilibrium conversion rate refers to the conversion rate calculated from the equilibrium composition according to the reaction temperature and pressure. When a typical solid catalyst reactor is used as the second reactor 6, it is not necessary to condense the product water and methanol by cooling. In this case, it is also possible to recover the reaction heat generated during the methanol conversion reaction from the carbon oxides and hydrogen at a higher temperature. Furthermore, when a mixed gas containing carbon monoxide and carbon dioxide is used as the feed gas for preliminary conversion, the methanol conversion reaction from carbon monoxide represented by formula (11) proceeds preferentially due to the equilibrium between the two reactions represented by formulas (10) and (11). Therefore, it is possible to recover a larger amount of reaction heat in the preliminary conversion step S4. In the preliminary conversion step S4, a preferred embodiment is to use a general solid catalyst reactor as the second reactor 6 from the viewpoint of effective use of thermal energy.

[0063] The reaction temperature in the catalyst layer of the second reactor 6 may be, for example, about 180° C. to 260° C., and preferably 220° C. to 240° C. The reaction pressure may be, for example, about 0.2 MPaG to 10 MPaG, and preferably 1 MPaG to 5 MPaG.

[0064] By allowing the reaction to proceed to an equilibrium composition in the preliminary conversion step S4, the conversion of carbon oxides and hydrogen beyond equilibrium can proceed more quickly in the conversion step S6. In other words, by performing the preliminary conversion step S4, the efficiency of the conversion reaction in the conversion step S6 can be improved.

[0065] [Embodiment 3] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0066] Fig. 6 is a flowchart showing an example of a methanol production method according to Embodiment 3. As shown in Fig. 6, the methanol production method according to Embodiment 3 differs from Embodiment 2 in that a condensation step S5 is included between the preliminary conversion step S4 and the conversion step S6. The flowchart shown in Fig. 6 is an example, and is not intended to be limiting. For example, the gas adjustment step S3 may be moved or added between the preliminary conversion step S4 and the condensation step S5 and / or between the condensation step S5 and the conversion step S6.

[0067] 7 is a system diagram schematically illustrating the configuration of a methanol production apparatus (production apparatus 100B) according to Embodiment 3. The production apparatus 100B is generally configured to include a gas acquisition apparatus 1, a gas cleaning apparatus 3, a gas composition adjustment apparatus 4, a first reactor 2, a purification apparatus 5, a second reactor 6, a condensation apparatus 7, and paths L1 to L15. The production apparatus 100B is similar to the production apparatus 100A of Embodiment 2, except that it further includes the condensation apparatus 7, a post-conversion gas supply path L14, and a condensate recovery path L15.

[0068] A pre-conversion gas supply line L14 is provided between the second reactor 6 and the condenser 7. This allows the pre-conversion gas G4, which is the reaction gas pre-converted by the second reactor 6, to be supplied to the condenser 7.

[0069] The condenser 7 is a device that condenses high boiling components contained in the post-pre-conversion gas G4. A known condenser can be used as the condenser 7. A condensate recovery path L15 is provided between the condenser 7 and the purification device 5. As a result, the condensate condensed in the condenser 7 is supplied to the purification device 5 and purified.

[0070] A raw material gas supply line L6 is provided between the condenser 7 and the first reactor 2. This allows the post-condensation step gas G5 that has been condensed by the condenser 7 to be supplied to the first reactor 2 as a raw material gas.

[0071] The method for producing methanol according to the third embodiment is carried out, for example, according to the flowchart shown in Fig. 6. Explanations of the same steps as those in the first and second embodiments will be omitted, and the condensation step S5 will be explained below.

[0072] (Condensation process S5) The condensation step S5 is a step of condensing high boiling components contained in the pre-conversion gas G4. These high boiling components include water and methanol. The condensation step S5 condenses the high boiling components contained in the pre-conversion gas G4 and removes them from the reaction system. This allows the conversion of carbon oxides and hydrogen beyond equilibrium in the conversion step S6 to be achieved with the condensation of fewer high boiling components. This allows the first reactor 2 to be made smaller.

[0073] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Example]

[0074] Below, examples of the methanol production method according to the above-described embodiment that are within the scope of the present invention (Example 1, Example 2, and Example 3) and an example of the methanol production method that is outside the scope of the present invention (Comparative Example) will be described.

[0075] Example 1 In Example 1, a specific example of the method for producing methanol according to the above-mentioned Embodiment 1 will be described. That is, a method for producing methanol carried out using the above-mentioned production apparatus 100 shown in FIG. 2 will be described according to the flowchart of FIG. 1. Note that members having the same functions as those described in the above-mentioned embodiment will be denoted by the same reference numerals, and their description will not be repeated. The same applies to other Examples.

[0076] In the manufacturing apparatus 100, waste material as the target is supplied to the gas acquisition device 1 via a path L1 to obtain a waste-derived gas G1 (gas acquisition step S1). The composition of the waste-derived gas G1 obtained in the gas acquisition step S1 is 45 vol% H2, 30 vol% CO2, 20 vol% CO2, and 5 vol% N2.

[0077] The resulting waste-derived gas G1 is supplied to the gas scrubbing device 3 via a line L2, and a scrubbed gas G2 is obtained (gas scrubbing step S2).

[0078] The obtained cleaned gas G2 is supplied to the gas composition adjuster 4 via a path L3. In addition, the unreacted gas circulated from the downstream first reactor 2 is supplied to the gas composition adjuster 4 via a path L10. By adding H2 via a path L4, the index SN of the adjusted gas G3 discharged from the gas composition adjuster 4 is adjusted to 2 (gas adjustment step S3).

[0079] The adjusted gas G3, whose index SN has been adjusted, is supplied to the first reactor 2 via a path L6 and converted into methanol and water (conversion step S6). In the conversion step S6, the produced methanol and water are condensed and discharged outside the reaction system, thereby allowing the reaction to proceed.

[0080] Unreacted gas is discharged from the first reactor 2 via a path L8. 50% of the discharged unreacted gas is returned to the gas composition regulator 4 via a path L10 for reuse, and the remaining 50% is discharged as exhaust gas via a path L9.

[0081] The condensate condensed in the first reactor 2 is supplied to the purification device 5 via a path L7. Water and impurities removed from the supplied condensate are discharged via a path L11, and purified methanol is obtained via a path L12 (purification step S7).

[0082] According to this embodiment, a waste-derived gas G1 is obtained from waste, and methanol can be synthesized using the gas as a raw material gas. Furthermore, according to this embodiment, 88.3% of the carbon dioxide contained in the waste-derived gas G1 obtained by the gas obtaining apparatus 1 is obtained as methanol, based on the carbon atoms.

[0083] Example 2 In Example 2, a specific example of the method for producing methanol according to the above-mentioned Embodiment 2 will be described. That is, the method for producing methanol carried out using the above-mentioned production apparatus 100A shown in Figure 5 will be described in accordance with the flowchart of Figure 4.

[0084] In the manufacturing apparatus 100A, waste material as the target is supplied to the gas acquisition apparatus 1 via a path L1 to obtain a waste-derived gas G1 (gas acquisition step S1). The composition of the waste-derived gas G1 obtained in the gas acquisition step S1 is 45 vol% H2, 30 vol% CO2, 20 vol% CO2, and 5 vol% N2.

[0085] The resulting waste-derived gas G1 is supplied to the gas scrubbing device 3 via a line L2, and a scrubbed gas G2 is obtained (gas scrubbing step S2).

[0086] The obtained cleaned gas G2 is supplied to the gas composition adjuster 4 via a path L3. In addition, the unreacted gas circulated from the downstream first reactor 2 is supplied to the gas composition adjuster 4 via a path L10. By adding H2 via a path L4, the index SN of the adjusted gas G3 discharged from the gas composition adjuster 4 is adjusted to 2 (gas adjustment step S3).

[0087] The adjusted gas G3, whose index SN has been adjusted, is supplied to the second reactor 6 via a line L13 and converted into methanol and water (pre-conversion step S4). In the pre-conversion step S4, the reaction is allowed to proceed until an equilibrium conversion rate is reached, which is calculated from the equilibrium composition according to the reaction temperature and pressure.

[0088] The pre-conversion gas G4 obtained through the pre-conversion step S4 is supplied to the first reactor 2 via a line L6 and converted into methanol and water (conversion step S6). In the conversion step S6, the produced methanol and water are condensed and discharged outside the reaction system, thereby allowing the reaction to proceed.

[0089] Unreacted gas is discharged from the first reactor 2 via a path L8. 50% of the discharged unreacted gas is returned to the gas composition regulator 4 via a path L10 for reuse, and the remaining 50% is discharged as exhaust gas via a path L9.

[0090] The condensate condensed in the first reactor 2 is supplied to the purification device 5 via a path L7. Water and impurities removed from the supplied condensate are discharged via a path L11, and purified methanol is obtained via a path L12 (purification step S7).

[0091] According to this embodiment, a waste-derived gas G1 is obtained from waste, and methanol can be synthesized using the gas as a raw material gas. Furthermore, according to this embodiment, 88.3% of the carbon dioxide contained in the waste-derived gas G1 obtained by the gas obtaining apparatus 1 is obtained as methanol, based on the carbon atoms.

[0092] Example 3 In Example 3, a specific example of the method for producing methanol according to the above-mentioned Embodiment 3 will be described. That is, the method for producing methanol carried out using the above-mentioned production apparatus 100B shown in Figure 7 will be described in accordance with the flowchart of Figure 6.

[0093] In the manufacturing apparatus 100B, waste material as the target is supplied to the gas acquisition apparatus 1 via a path L1 to obtain a waste-derived gas G1 (gas acquisition step S1). The composition of the waste-derived gas G1 obtained in the gas acquisition step S1 is 45 vol% H2, 30 vol% CO2, 20 vol% CO2, and 5 vol% N2.

[0094] The resulting waste-derived gas G1 is supplied to the gas scrubbing device 3 via a line L2, and a scrubbed gas G2 is obtained (gas scrubbing step S2).

[0095] The obtained cleaned gas G2 is supplied to the gas composition adjuster 4 via a path L3. In addition, the unreacted gas circulated from the downstream first reactor 2 is supplied to the gas composition adjuster 4 via a path L10. By adding H2 via a path L4, the index SN of the adjusted gas G3 discharged from the gas composition adjuster 4 is adjusted to 2 (gas adjustment step S3).

[0096] The adjusted gas G3, whose index SN has been adjusted, is supplied to the second reactor 6 via a line L13 and converted into methanol and water (pre-conversion step S4). In the pre-conversion step S4, the reaction is allowed to proceed until an equilibrium conversion rate is reached, which is calculated from the equilibrium composition according to the reaction temperature and pressure.

[0097] The pre-conversion gas G4 obtained through the pre-conversion step S4 is supplied to the condenser 7 via a line L14, where methanol and water are condensed (condensation step S5).

[0098] The gas G5 obtained through the condensation step S5 is supplied to the first reactor 2 via a path L6 and converted into methanol and water (conversion step S6). In the conversion step S6, the produced methanol and water are condensed and discharged outside the reaction system, thereby allowing the reaction to proceed.

[0099] Unreacted gas is discharged from the first reactor 2 via a path L8. 50% of the discharged unreacted gas is returned to the gas composition regulator 4 via a path L10 for reuse, and the remaining 50% is discharged as exhaust gas via a path L9.

[0100] The condensate condensed in the first reactor 2 is supplied to the purification device 5 via a path L7. The condensate condensed in the condenser 7 is supplied to the purification device 5 via a path L15. Water and impurities removed from the supplied condensate are discharged via a path L11, and purified methanol is obtained via a path L12 (purification step S7).

[0101] According to this embodiment, a waste-derived gas G1 is obtained from waste, and methanol can be synthesized using the gas as a raw material gas. Furthermore, according to this embodiment, 91.5% of the carbon oxides contained in the waste-derived gas G1 obtained in the gas obtaining apparatus 1 are obtained as methanol, based on the carbon atoms. Furthermore, the proportion of the condensate condensed in the first reactor 2 to the total condensate supplied to the purification apparatus 5 is reduced to 80.6%. The remaining condensate is condensed in the condenser 7.

[0102] (Comparative Example) In this comparative example, a specific example of a methanol production method outside the scope of the present invention will be described. Figure 8 is a system diagram that schematically shows the configuration of a production apparatus 500 according to the comparative example. In the comparative example, a methanol production method carried out using the production apparatus 500 shown in Figure 8 will be described.

[0103] The production apparatus 500 differs from the production apparatus 100 of Example 1 in that it includes a reactor 50 outside the scope of the present invention and a separation apparatus 51 instead of the first reactor 2, which is within the scope of the present invention. More specifically, the reactor 50 is a reactor for carrying out a methanol conversion reaction, but is not an internal condensation type reactor that condenses the converted methanol and high-boiling components, including water, and discharges them outside the reaction system. The rest of the configuration is the same as that of the production apparatus 100 of Example 1.

[0104] In the manufacturing apparatus 500, waste material, which is the target material, is supplied to the gas acquisition apparatus 1 via a path L1 to obtain a waste-derived gas G1. The composition of the waste-derived gas G1 obtained in the gas acquisition step S1 is H2: 45 vol%, CO: 30 vol%, CO2: 20 vol%, and N2: 5 vol%.

[0105] The resulting waste-derived gas G1 is supplied to the gas scrubbing device 3 via a line L2, and a scrubbed gas G2 is obtained.

[0106] The resulting cleaned gas G2 is supplied to the gas composition adjuster 4 via a path L3. In addition, unreacted gas circulated from the downstream separator 51 is supplied to the gas composition adjuster 4 via a path L10. By adding H2 via a path L4, the index SN of the adjusted gas G3 discharged from the gas composition adjuster 4 is adjusted to 2.

[0107] The adjusted gas G3 with the adjusted index SN is supplied to the reactor 50 via the line L6 and converted into methanol and water.

[0108] The produced methanol and water, together with unreacted gas, are supplied as a gas mixture G6 to a separator 51. In the separator 51, the gas mixture G6 is separated into an unreacted gas G7 and a condensed liquid G8 by a gas-liquid separation operation.

[0109] The unreacted gas is discharged from the separation device 51 via a path L8. 50% of the discharged unreacted gas is returned to the gas composition adjustment device 4 via a path L10 for reuse, and the remaining 50% is discharged as exhaust gas via a path L9.

[0110] The condensate G8 obtained from the separator 51 is fed to the purifier 5 via line L7. Water and impurities removed from the fed condensate are discharged via line L11, and purified methanol is obtained via line L12.

[0111] According to this comparative example, a waste-derived gas G1 is obtained from waste, and the gas is used as a raw material gas to synthesize methanol. Furthermore, according to this comparative example, 56.0% of the carbon dioxide contained in the waste-derived gas G1 obtained by the gas obtaining apparatus 1 is obtained as methanol, based on the carbon atoms.

[0112] (Summary of Examples) From the above results, the proportion of carbon oxides contained in the waste-derived gas G1 obtained by the gas acquisition apparatus 1 that is obtained as methanol based on the carbon atoms of the carbon oxides is 56.0% in the comparative example, which is outside the scope of the present invention, while it is 88.3% in Examples 1 and 2, which are within the scope of the present invention. This demonstrates that the present invention significantly improves the proportion of carbon oxides contained in the waste-derived gas G1 obtained by the gas acquisition apparatus 1 that is obtained as methanol based on the carbon atoms of the carbon oxides. This means that the present invention improves the methanol yield based on the carbon atoms of the carbon oxides contained in the waste-derived gas G1 supplied as a feed gas. In other words, it has been demonstrated that the present invention can efficiently produce methanol using a waste-derived gas obtained from waste as a feed gas.

[0113] Furthermore, in Example 3, the proportion of carbon oxides contained in the waste-derived gas G1 obtained by the gas acquisition apparatus 1 that are obtained as methanol based on carbon atoms is 91.5%. This demonstrates that the proportion of carbon oxides contained in the waste-derived gas G1 that are obtained by the gas acquisition apparatus 1 that are obtained as methanol based on carbon atoms can be further improved by adding the preliminary conversion step and the condensation step.

[0114] Furthermore, in Example 3, the ratio of the condensate condensed in the first reactor 2 to the total condensate amount was reduced to 80.6%. This demonstrates that the addition of the preliminary conversion step and the condensation step reduces the ratio of the condensate condensed in the first reactor 2 to the total condensate amount. [Explanation of symbols]

[0115] S1: Gas acquisition process S2: Gas cleaning process S3: Gas adjustment process S4: Pre-conversion process S5: Condensation process S6... Conversion process S7...Refining process 1. Gas acquisition device 2. First reactor 3. Gas cleaning equipment 4. Gas composition adjustment device 5... Purification equipment 6. Second reactor 7. Condenser

Claims

1. a gas obtaining step of obtaining a gas containing carbon oxides and hydrogen from the waste; a conversion step of contacting at least a portion of the gas with a catalyst and converting it to methanol in the vapor phase; The method for producing methanol, wherein the conversion step is performed by condensing converted methanol and high-boiling components containing water and removing them from the reaction system, thereby progressing the reaction.

2. The method further comprises a preliminary conversion step between the gas obtaining step and the conversion step, in which carbon oxides and hydrogen in the gas are converted to a predetermined equilibrium conversion rate or higher; 2. The method for producing methanol according to claim 1, wherein the predetermined equilibrium conversion is 80% of the equilibrium conversion of carbon oxides in the gas based on carbon.

3. 3. The method for producing methanol according to claim 2, further comprising a condensation step between the preliminary conversion step and the conversion step, in which a reaction gas generated in the preliminary conversion reaction in the preliminary conversion step is condensed and high-boiling components in the reaction gas are removed from the reaction system.

4. 4. The method for producing methanol according to claim 1, wherein in the conversion step, a conversion rate of at least one of carbon oxides and hydrogen in the gas supplied to the conversion step to methanol is 60% or more.

5. 5. The method for producing methanol according to claim 1, further comprising, between the gas obtaining step and the conversion step, a gas adjusting step for adjusting components of a gas to be supplied to the conversion step.

6. 4. The method for producing methanol according to claim 2, further comprising, between the gas obtaining step and the preliminary conversion step, a gas adjusting step for adjusting components of a gas to be supplied to the preliminary conversion step.

7. The gas adjusting step includes: removing at least a portion of the carbon dioxide from the gas; or 7. The method for producing methanol according to claim 5, further comprising adding hydrogen gas to the gas.

8. 8. The method for producing methanol according to claim 5, wherein the gas conditioning step is carried out by removing at least a portion of the carbon dioxide from the gas using a separation membrane that selectively allows carbon dioxide to permeate or that selectively blocks carbon dioxide permeation.

9. 7. The method for producing methanol according to claim 5, wherein the gas conditioning step is carried out by decomposing or reforming at least a portion of carbon oxides in the gas.

10. 7. The method for producing methanol according to claim 5, wherein the gas adjustment step is performed by adding hydrogen to the gas.

11. 11. The method for producing methanol according to claim 1, wherein the gas supplied to the conversion step has an index SN value calculated by the following formula (I) of 1 or more and 10 or less: SN=(yH ２ -yCO ２ ) / (yCO+yCO ２ )・・・(I) In formula (I), yH ２ , yCO ２ and yCO are the volume fractions of hydrogen, carbon dioxide and carbon monoxide, respectively, in the gas subjected to the conversion step.

12. The gas adjusting step includes the following steps: (i) adding hydrogen to the gas; (ii) removing at least a portion of the carbon dioxide from the gas. (iii) decomposing or reforming at least a portion of the carbon oxides in the gas; 7. The method for producing methanol according to claim 5 or 6, wherein the method is carried out by carrying out at least one of the following steps:

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