Method for separating and recovering carbon dioxide

Abstract

This method for separating and recovering carbon dioxide is a method for separating and recovering carbon dioxide comprising: a step (a) for separating carbon dioxide from a carbon dioxide-containing gas and obtaining a precipitate, by bringing the gas into contact with a solution of an amine compound A that has the ability to react with and solidify carbon dioxide; a step (b) for storing the precipitate; and a step (c) for separating carbon dioxide from the stored precipitate using clean energy and obtaining the amine compound A. There are present, during a one day interval, a time zone in which step (c) is performed and a time zone in which step (c) is not performed.

Description

Carbon dioxide separation and capture method

[0001] The present invention relates to a method for separating and recovering carbon dioxide.

[0002] Various methods have been studied for directly recovering carbon dioxide from the atmosphere. For example, Patent Document 1 discloses a method for recovering CO2 from combustion exhaust gas under atmospheric pressure, which is characterized by contacting an aqueous solution containing a specific diamine compound with the combustion exhaust gas. ２ A method for removing

[0003] Japanese Patent Application Publication No. 8-257353

[0004] In existing carbon dioxide separation and capture methods using an amine solution, after carbon dioxide is absorbed into the amine solution, energy is required to capture the carbon dioxide from the aqueous amine solution. Carbon dioxide capture is usually carried out on a regular basis, but if the energy required for carbon dioxide capture is provided by an energy production method that emits carbon dioxide (for example, thermal power generation), the amount of carbon dioxide separated and captured increases because carbon dioxide is generated during energy production, which is undesirable.

[0005] The present invention is a method for separating and recovering carbon dioxide, and an object of the present invention is to provide a method that can sufficiently reduce the amount of carbon dioxide newly generated when carrying out the method.

[0006] One aspect of the present invention relates to a method for separating and recovering carbon dioxide, the method comprising: (a) a step of separating carbon dioxide from a gas containing carbon dioxide, the step comprising contacting the gas with a solution of an amine compound A that has the property of reacting with carbon dioxide to solidify, thereby obtaining a precipitate; (b) a step of storing the precipitate; and (c) a step of using clean energy to remove carbon dioxide from the stored precipitate and obtain amine compound A.

[0007] According to the present invention, the amine compound solidifies and forms a precipitate by absorbing carbon dioxide, and thus the precipitate of the amine compound that has absorbed carbon dioxide can be stored. Then, by releasing carbon dioxide from the stored precipitate when clean energy is available, carbon dioxide can be separated and recovered from a gas containing carbon dioxide without increasing the amount of carbon dioxide separated and recovered. In contrast, in existing carbon dioxide separation and recovery methods using an amine solution, the amine compound remains dissolved in the solution after carbon dioxide has been recovered. Therefore, if the amine compound is to be stored after absorbing carbon dioxide, it must be stored in the form of an amine solution, which requires a huge tank for storing the amine solution, resulting in increased equipment costs and being impractical.

[0008] In addition, the method may perform step (c) during an upward demand response of energy. Since energy costs are generally low during an upward demand response, it is preferable to perform step (c) during an upward demand response.

[0009] The method may further include a step of underground storing the carbon dioxide captured through step (c). By carrying out this step, the captured carbon dioxide can be trapped underground.

[0010] That is, the present invention includes the following [1] to [3]. [1] A method for separating and capturing carbon dioxide, comprising: (a) a step of separating carbon dioxide from a gas containing carbon dioxide, the step comprising: obtaining a precipitate by contacting the gas with a solution of amine compound A that has the property of reacting with carbon dioxide to solidify; (b) a step of storing the precipitate; and (c) a step of removing carbon dioxide from the stored precipitate using clean energy and obtaining the amine compound A. [2] The method for separating and capturing carbon dioxide according to [1], in which the step (c) is carried out during an energy demand response. [3] The method for separating and capturing carbon dioxide according to [1] or [2], further comprising a step of underground storing the carbon dioxide captured via the step (c).

[0011] According to the present disclosure, it is possible to provide a method for separating and capturing carbon dioxide, which can sufficiently reduce the amount of carbon dioxide newly generated when carrying out the method.

[0012] FIG. 1 is a schematic diagram showing one embodiment of a carbon dioxide separation and capture system according to the present invention.

[0013] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. In the following description, the same or equivalent parts will be denoted by the same reference numerals, and duplicate explanations will be omitted. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings.

[0014] [Carbon Dioxide Separation and Capture System] FIG. 1 is a schematic diagram showing a carbon dioxide separation and capture system according to this embodiment. The carbon dioxide separation and capture system 100 (hereinafter also referred to as "system 100") shown in this figure includes a cooling device 10, a carbon dioxide absorption device 20 (hereinafter also referred to as "absorption device 20"), a solid-liquid separation device 30, a storage container 40, and an amine regeneration device 50 (hereinafter also referred to as "regeneration device 50"). In the system 100, carbon dioxide is separated from the gas by utilizing gas-liquid contact between the gas and a solution containing a specific amine compound in the absorption device 20, and the amine compound is solidified to produce a precipitate. The precipitate is separated in the solid-liquid separation device 30 and then stored in the storage container 40. The stored precipitate is then processed in the regeneration device 50, where carbon dioxide is desorbed from the precipitate and the precipitate is regenerated into a liquid amine compound.

[0015] The cooling device 10 is a device that cools the gas transferred through the flow path L1. The gas transferred through L1 contains at least carbon dioxide. The gas may be a gas mixed with gases other than carbon dioxide, such as exhaust gas from a factory or exhaust gas from an automobile. The gas may be cooled, for example, by contacting the gas with water. Alternatively, the system 100 may not include the cooling device 10, and may instead cool the gas by contacting a solution of a specific amine compound with the gas in the absorption device 20.

[0016] The gas that has passed through the cooling device 10 is also transferred to the absorption device 20 through flow path L2. The absorption device 20 is a device that separates carbon dioxide from the gas and obtains a precipitate by utilizing gas-liquid contact between the gas and a solution containing an amine compound A, which will be described later. The solution containing an amine compound A is supplied through flow path L10. The solution containing an amine compound A may contain an amine compound A, which is supplied through flow paths L5 and L9, which will be described later.

[0017] The amine compound A in this embodiment is a compound represented by the following formula (1).

[0018] In formula (1), m is 0 or 1; R １ and R ２ are each independently an alkyl group, an alkoxy group, a carboxy group, an alkyloxycarbonyl group, a formyl group, an alkylcarbonyl group, an alkylthio group, a sulfo group, an alkyloxysulfonyl group, a nitro group, a hydroxyl group, a thiol group, a cyano group, or a halogen atom. The alkyl group may have a substituent. １ and p ２ are each independently 1 or 2. When m is 0, q １ is an integer from 0 to 11, provided that p １ +q １ is 12 or less, and when m is 1, q １ is an integer from 0 to 10, provided that p １ +q １ is less than or equal to 11. １ is an integer from 0 to 10, and q １ is an integer of 2 or more, two or more R １ may be the same or different, and q ２ is an integer of 2 or more, two or more R ２ may be the same or different, and q １ is an integer of 2 or more, and two or more R １ When R is an alkyl group which may have a substituent, two or more R １ may be bonded to each other to form a ring, and q ２ is an integer of 2 or more, and two or more R ２When R is an alkyl group which may have a substituent, two or more R ２ may be bonded to each other to form a ring, provided that m is 0 and p １ is 2, and p １ The case where the two amino groups marked with are positioned meta to each other is excluded.

[0019] The compound represented by the above formula (1) is preferably a compound represented by the following general formula (11A), (12A) or (11B).

[0020] In the formula, R １１ , R １２ , R １３ and R ２１ are each independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a carboxy group, an alkyloxycarbonyl group having 2 to 11 carbon atoms, a formyl group, an alkylcarbonyl group having 2 to 11 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, a sulfo group, an alkyloxysulfonyl group having 1 to 10 carbon atoms, a nitro group, a hydroxyl group, a thiol group, a cyano group, or a halogen atom. The alkyl group may have an amino group as a substituent. １１ and q １２ are each independently an integer of 0 to 6. １１ is an integer of 2 or more, two or more R １１ may be the same or different, and q １２ is an integer of 2 or more, two or more R １２ may be the same or different. １１ is an integer of 2 or more, and two or more R １１ is an alkyl group which may have an amino group as a substituent, two or more R １１ may be bonded to each other to form a ring, and q １２ is an integer of 2 or more, and two or more R １２ is an alkyl group which may have an amino group as a substituent, two or more R １２ may be bonded to each other to form a ring. １３ and q ２１ are each independently an integer of 0 to 4, and q１３ is an integer of 2 or more, two or more R １３ may be the same or different, and q ２１ is an integer of 2 or more, two or more R ２１ may be the same or different, and q １３ is an integer of 2 or more, and two or more R １３ is an alkyl group which may have an amino group as a substituent, two or more R １３ may be bonded to each other to form a ring, and q ２１ is an integer of 2 or more, and two or more R ２１ is an alkyl group which may have an amino group as a substituent, two or more R ２１ may be bonded to each other to form a ring, except for the case in which, in general formula (12A), two amino groups directly bonded to carbon atoms constituting the cyclohexane ring skeleton are positioned at meta positions relative to each other.

[0021] The compound (11A), compound (12A) or compound (11B) is preferably a compound represented by the following general formula (111A), (121A), (122A) or (111B).

[0022] In the formula, R １１１ , R １２１ , R １２２ , R １３１ and R ２１１ are each independently an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an alkyloxycarbonyl group having 2 to 6 carbon atoms, a formyl group, an alkylcarbonyl group having 2 to 6 carbon atoms, an alkylthio group having 1 to 5 carbon atoms, a hydroxyl group, a thiol group, a cyano group, or a halogen atom. The alkyl group may have an amino group as a substituent. １１１ , q １２１ and q １２２ are each independently an integer of 0 to 4. １１１ is an integer of 2 or more, two or more R １１１ may be the same or different, and q １２１ is an integer of 2 or more, two or more R １２１may be the same or different, and q １２２ is an integer of 2 or more, two or more R １２２ may be the same or different. １１１ is an integer of 2 or more, and two or more R １１１ is an alkyl group which may have an amino group as a substituent, two or more R １１１ may be bonded to each other to form a ring, and q １２１ is an integer of 2 or more, and two or more R １２１ is an alkyl group which may have an amino group as a substituent, two or more R １２１ may be bonded to each other to form a ring, and q １２２ is an integer of 2 or more, and two or more R １２２ is an alkyl group which may have an amino group as a substituent, two or more R １２２ may be bonded to each other to form a ring. １３１ and q ２１１ are each independently an integer of 0 to 2, and q １３１ If is 2, then two R １３１ may be the same or different, and q ２１１ If is 2, then two R ２１１ may be the same or different, and q １３１ is 2 and two R １３１ is an alkyl group which may have an amino group as a substituent, two R １３１ may be bonded to each other to form a ring, and q ２１１ is 2 and two R ２１１ is an alkyl group which may have an amino group as a substituent, two R ２１１ may be bonded to each other to form a ring.

[0023] In this embodiment, the property of amine compound A to react with carbon dioxide and solidify is utilized. Therefore, it is preferable to bring a solution of amine compound A into contact with a gas under conditions that facilitate precipitation of a reaction product (precipitate; carbamic acid derivative) of amine compound A and carbon dioxide. Specific measures that can be considered to facilitate precipitation of a reaction product of amine compound A and carbon dioxide include the following: (1) Lowering the reaction temperature during the reaction of amine compound A with carbon dioxide; (2) Increasing the concentration of amine compound A in the solution; (3) Using a diamine (having two amino groups) as amine compound A; and (4) Increasing the contact area between the solution and air.

[0024] From the viewpoint of the above (1), the temperature inside the absorption device 20 is, for example, 0 to 90°C or 5 to 60°C, and preferably 5 to 40°C. From the viewpoint of the above (2), the concentration of the amine compound A in the solution is, for example, 0.05 to 10 M, preferably 0.08 to 3 M, and more preferably 0.1 to 1 M. The concentration unit "M" represents "mol / L." When the amine compound A is a liquid in the environment inside the absorption device 20, the amine compound A may be diluted with a solvent or may be used without being diluted with a solvent.

[0025] The solution of amine compound A contains, for example, water as a solvent. The solvent is not limited to water and may be an organic solvent. Examples of organic solvents include sulfoxides such as dimethyl sulfoxide (DMSO); amides such as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc); lactams (cyclic amides) such as N-methyl-2-pyrrolidone; alcohols such as methanol, ethanol, and 2-propanol (IPA); hydrocarbons (aromatic hydrocarbons) such as toluene, o-xylene, m-xylene, and p-xylene; ethers (compounds having an ether bond) such as tetrahydrofuran (THF), 1,4-dioxane, tetrahydropyran, dibutyl ether, and 1,2-dimethoxyethane; nitriles (compounds having a cyano group) such as propionitrile and acetonitrile; and esters (carboxylic acid esters) such as ethyl acetate and butyl acetate. The solvent is preferably polar. Furthermore, the solvent preferably has a high boiling point and a low vapor pressure at room temperature. By using such a solvent, evaporation of the solvent can be suppressed. From this viewpoint, the boiling point of the solvent is preferably 100°C or higher, and may be, for example, 190°C or higher. The boiling point of the solvent is, for example, 200°C or lower because of its relatively easy availability. One solvent may be used alone, or two or more solvents may be used in combination. As the solvent, an aqueous mixed solvent containing water and one or two or more organic solvents may be used, or a non-aqueous mixed solvent containing two or more organic solvents may be used. In addition, the amine compound may be used without diluting it with a solvent.

[0026] After passing through the absorption device 20, the solution containing the precipitate is transferred to the solid-liquid separator 30 through a flow path L3, and the gas from which carbon dioxide has been separated is transferred through a flow path L4. The solid-liquid separator 30 is used to separate the precipitate from the solution.

[0027] The solid-liquid separator 30 is configured, for example, by a combination of a liquid cyclone and a filter. The solution containing the precipitate is sent to the liquid cyclone and separated into the precipitate and the solution. The solution is transferred to a filter, and the precipitate remaining in the solution is filtered out by the filter. The precipitate adhering to the filter may be recovered by backwashing the filter. Note that while a combination of a liquid cyclone and a filter is exemplified here, the solid-liquid separator may also be configured using only a filter without using a liquid cyclone. The precipitate may also be separated from the solution by natural settling, or by a separator. This separator has a partition plate and a mesh placed in the liquid phase, and the liquid level can be controlled to pass through the mesh and filter out the precipitate through the mesh.

[0028] The solution separated in the solid-liquid separator 30 is transferred through a flow path L5. When the solution contains an amine compound A, the amine compound A may be transferred to, for example, the absorber 20 and reused for separating and recovering carbon dioxide from the gas. The flow path L5 may be connected to a flow path L10 or a flow path L9, or may be directly connected to the absorber 20.

[0029] The precipitate (slurry containing the precipitate) obtained in the solid-liquid separation device 30 is transferred to a storage container 40 through a flow path L6. The storage container 40 is used for temporarily storing the precipitate. By storing the precipitate, carbon dioxide can be desorbed from the precipitate at any time to obtain amine compound A. Therefore, clean energy can be used to desorb carbon dioxide from the precipitate to obtain amine compound A. In existing carbon dioxide separation and capture methods using an amine solution, the amine compound remains dissolved in the solution after carbon dioxide capture. Therefore, if the amine compound is stored after absorbing carbon dioxide, it must be stored in the amine solution state, which requires a large tank for storing the amine solution, resulting in increased equipment costs. However, by using amine compound A, which solidifies upon absorbing carbon dioxide, the storage tank can be made smaller than when the amine compound is stored in the amine solution state. This allows carbon dioxide to be separated and captured from a carbon dioxide-containing gas without increasing the amount of carbon dioxide newly generated and separated and captured, while suppressing increases in equipment costs. Furthermore, by temporarily storing the precipitate, carbon dioxide can be desorbed from the precipitate during an energy demand response, which can reduce energy costs.

[0030] The precipitate stored in the storage container 40 is transferred to the regeneration device 50 through a flow path L7 at the timing when carbon dioxide is desorbed. The regeneration device 50 uses clean energy to desorb carbon dioxide from the precipitate and obtain the amine compound A.

[0031] Clean energy refers to energy produced by power generation methods that produce as little carbon dioxide as possible during power generation, such as solar power generation, wind power generation, hydroelectric power generation, geothermal power generation, biomass power generation, and nuclear power generation. In other words, clean energy may be energy produced by at least one power generation method selected from the group consisting of solar power generation, wind power generation, hydroelectric power generation, geothermal power generation, biomass power generation, and nuclear power generation. Clean energy is also called carbon-neutral energy.

[0032] In the regeneration device 50, the energy used to desorb carbon dioxide from the precipitate preferably consists essentially of clean energy, from the viewpoint of not increasing the amount of newly generated carbon dioxide separated and recovered, but part of the energy may be provided by energy other than clean energy. The proportion of clean energy in the energy used to desorb carbon dioxide from the precipitate may be, for example, 70% or more, 80% or more, or 90% or more, from the viewpoint of not increasing the amount of newly generated carbon dioxide separated and recovered.

[0033] The carbon dioxide is desorbed from the deposit by, for example, heating the deposit, that is, the regeneration device 50 may be a heating device.

[0034] The carbon dioxide desorbed from the precipitate is transported through the flow path L8 and stored, for example, underground. This allows the captured carbon dioxide to be trapped underground. The captured carbon dioxide may also be stored in a storage container such as a cylinder.

[0035] By heating the precipitate, carbon dioxide is desorbed from the precipitate and amine compound A is produced. The amine compound A obtained by desorbing carbon dioxide from the precipitate is transferred through flow path L9. The amine compound A may be transferred to, for example, absorption device 20 and reused for separating and recovering carbon dioxide from gas. This allows a series of processes, including the separation and recovery of carbon dioxide, the production of amine compound A from the precipitate, and the reuse of amine compound A, to be integrated.

[0036] [Method for separating and capturing carbon dioxide] A method for separating and capturing carbon dioxide from a gas using the system 100 will be described. For the method for separating and capturing carbon dioxide, the description of the carbon dioxide separation and capture system described above can be referenced as appropriate. The method for separating and capturing carbon dioxide according to this embodiment includes at least the following steps: (a) a step of separating carbon dioxide from a gas containing carbon dioxide, in which a precipitate is obtained by contacting the gas with a solution of amine compound A that has the property of solidifying upon reaction with carbon dioxide; (b) a step of storing the precipitate; and (c) a step of removing carbon dioxide from the stored precipitate using clean energy and obtaining amine compound A.

[0037] <Step (a)> As described above, step (a) is a step of obtaining a precipitate by bringing a solution of amine compound A, which has the property of solidifying upon reaction with carbon dioxide, into contact with a gas. The amine compound A is as described above.

[0038] The method for contacting the solution of amine compound A with the gas is not particularly limited, and a method that increases the contact area between the solution and air is preferred. For example, gas-liquid contact may be performed using a scrubber. The method for separating and recovering carbon dioxide may further include a step of removing gases other than carbon dioxide using an adsorbent or the like before or after step (a).

[0039] <Step (b)> As described above, step (b) is a step of storing the precipitate. The precipitate may be stored in an environment in which the precipitate is not denatured, and for example, the precipitate may be stored in an environment at room temperature and normal pressure. The method for separating and capturing carbon dioxide may further include a step of performing solid-liquid separation between steps (a) and (b).

[0040] A slurry containing the precipitate is separated from the solution by a step of solid-liquid separation of the solution and the precipitate. The slurry is a suspension containing water and the precipitate, and the content of the precipitate relative to the total mass of the slurry is, for example, 10 to 50 mass% or 20 to 40 mass%. When the content of the precipitate is 10 mass% or more, the energy required to heat the slurry in the step of regenerating amine compound A from the precipitate tends to be reduced. When the content of the precipitate is 50 mass% or less, the energy required for solid-liquid separation tends to be reduced.

[0041] <Step (c)> As described above, the step (c) is a step of removing carbon dioxide from the precipitate stored in the step (b) by utilizing clean energy and obtaining amine compound A. The clean energy is as described above.

[0042] Carbon dioxide can be desorbed from the precipitate by, for example, heating the precipitate. The heating temperature is, for example, 50 to 150°C, preferably 60 to 140°C, and more preferably 60 to 120°C. A heating temperature of 60°C or higher tends to enable sufficient regeneration of amine compound A, while a heating temperature of 150°C or lower tends to suppress decomposition of the generated amine compound A. As a method for desorbing carbon dioxide from the precipitate other than heating, for example, a method in which the precipitate is placed in an environment with a low carbon dioxide partial pressure and carbon dioxide is desorbed from the precipitate can be mentioned.

[0043] Step (c) may be carried out during a time period when the supply of clean energy is high in one day. This makes it easier to separate and recover carbon dioxide from a gas containing carbon dioxide without further increasing the amount of carbon dioxide separated and recovered. For example, when the clean energy is energy generated by solar power generation, step (c) is carried out using energy generated by solar power generation during the day, and step (c) is not carried out at night, so that carbon dioxide can be separated and recovered from a gas containing carbon dioxide without increasing the amount of carbon dioxide separated and recovered.

[0044] Step (c) may be carried out during a time period of the day when energy demand is low. For example, if the clean energy is energy generated by nuclear power generation, step (c) is not carried out during the daytime because energy demand is high, and the implementation of thermal power generation, etc. can be suppressed, thereby suppressing an increase in the amount of carbon dioxide separated and captured. On the other hand, carrying out step (c) at night is preferable because surplus energy can be effectively utilized. Note that, normally, energy demand is low at night, so surplus energy is generated and used in storage batteries, etc., but using this in storage batteries, etc. is not preferable because of the large energy loss. Furthermore, energy costs are generally low during times when energy demand is low, so this is also preferable in this respect.

[0045] Step (c) may be performed during an upward energy demand response. Demand response refers to changing an energy demand pattern by controlling energy resources, and an upward demand response refers to a time when the energy demand pattern is shifting in the direction of increasing the demand amount. During an upward demand response, energy costs are generally low, so it is preferable to perform step (c) during an upward demand response.

[0046] The carbon dioxide separation and capture method may further include a step of storing the carbon dioxide captured through step (c) underground. By carrying out this step, the captured carbon dioxide can be trapped underground. The carbon dioxide captured through step (c) may be stored in a storage container such as a cylinder. By carrying out this step, the captured carbon dioxide can be transported.

[0047] The method for separating and recovering carbon dioxide may further include a step of reusing the amine compound A produced in the step (c) in the step (a). By carrying out this step, a series of processes including the separation and recovery of carbon dioxide, the production of amine compound A from the precipitate, and the reuse of amine compound A can be carried out in an integrated manner.

[0048] L1, L2, L3, L4, L5, L6, L7, L8, L9, L10...flow path, 10...cooling device, 20...carbon dioxide absorption device, 30...solid-liquid separation device, 40...storage vessel, 50...amine regeneration device, 100...carbon dioxide separation and recovery system.

Claims

1. A method for separating and recovering carbon dioxide, comprising: (a) a step of separating carbon dioxide from a gas containing carbon dioxide, the step comprising contacting the gas with a solution of amine compound A that has the property of reacting with carbon dioxide to solidify, to obtain a precipitate; (b) a step of storing the precipitate; and (c) a step of removing carbon dioxide from the stored precipitate using clean energy and obtaining amine compound A, wherein there are time periods in a day when step (c) is performed and time periods when step (c) is not performed.

2. A method for separating and capturing carbon dioxide as described in claim 1, wherein the amount of clean energy supplied during the time period in which step (c) is carried out is greater than the amount of clean energy supplied during the time period in which step (c) is not carried out.

3. A method for separating and capturing carbon dioxide as described in claim 1, wherein the energy demand during the time period in which step (c) is carried out is less than the energy demand during the time period in which step (c) is not carried out.

4. A method for separating and recovering carbon dioxide as described in claim 1, wherein the time period during which step (c) is carried out is during an energy increase demand response period.

5. A method for separating and capturing carbon dioxide described in any one of claims 1 to 4, further comprising a step of storing the carbon dioxide captured via step (c) underground.

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