Method for separating and recovering carbon dioxide

Abstract

To provide a method for separating and recovering carbon dioxide, the method enabling sufficient reduction of carbon dioxide which is newly generated when the method is implemented.SOLUTION: A method for separating and recovering carbon dioxide is provided, comprising: (a) a step which is a step of separation of carbon dioxide from gas including carbon dioxide, and in which a precipitate is obtained by bringing an amine compound having the property of being solidified when reacting with carbon dioxide, into contact with the gas; (b) a step of storing the precipitate; and (c) a step of utilizing clean energy thereby removing carbon dioxide and obtaining an amine compound A, from the stored precipitate. In the method for separating and recovering carbon dioxide, there exist in one day: a time zone of implementing the (c) step; and a time zone of not implementing the (c) step.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

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

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-257353 Summary of the Invention [Problem to be solved by the invention]

[0004] In the existing carbon dioxide separation and capture method using an amine solution, after carbon dioxide is absorbed into the amine solution, energy is required to capture carbon dioxide from the aqueous amine solution. Usually, carbon dioxide capture is performed 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 by the energy production, which is not preferable.

[0005] The present invention is a method for separating and capturing carbon dioxide, and an object of the present invention is to provide a method capable of sufficiently reducing the amount of newly generated carbon dioxide when the method is carried out. [Means for solving the problem]

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

[0007] According to the present invention, the amine compound absorbs carbon dioxide, and the amine compound solidifies to form a precipitate, so that 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 the existing carbon dioxide separation and recovery method using an amine solution, the amine compound after carbon dioxide recovery exists in a state dissolved in the solution. Therefore, if the amine compound is stored after absorbing carbon dioxide, it needs to be stored in the state of an amine solution, and a huge tank is required to store the amine solution, which leads to an increase in equipment costs and is not practical.

[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 storing the carbon dioxide captured through step (c) underground. 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, comprising contacting the gas with a solution of an amine compound A having a property of reacting with carbon dioxide to solidify, to obtain a precipitate; (b) storing the precipitate; (c) removing carbon dioxide from the stored precipitate by utilizing clean energy and obtaining the amine compound A; A method for separating and capturing carbon dioxide, comprising: [2] A method for separating and capturing carbon dioxide described in [1], in which step (c) is carried out during an increase in energy demand response. [3] The method for separating and capturing carbon dioxide described in [1] or [2], further comprising a step of storing the carbon dioxide captured via step (c) underground. Effect of the Invention

[0011] According to the present disclosure, it is possible to provide a method for separating and capturing carbon dioxide, which is capable of sufficiently reducing the amount of newly generated carbon dioxide when the method is carried out. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing one embodiment of a carbon dioxide separation and capture system according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 corresponding parts are denoted by the same reference numerals, and duplicated descriptions will be omitted. In addition, unless otherwise specified, the positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings.

[0014] [Carbon dioxide 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 in the absorption device 20 and a solution containing a specific amine compound, and the amine compound is solidified to generate a precipitate. After the precipitate is separated in the solid-liquid separation device 30, it is stored in the storage container 40. The stored precipitate is treated in the regeneration device 50, 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, for example, exhaust gas from a factory or exhaust gas from an automobile. The gas may be cooled, for example, by contacting the gas with water. Moreover, the system 100 may not include the cooling device 10, and may 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 the 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 described below. The solution containing an amine compound A is supplied through a flow path L10. The solution containing an amine compound A may contain an amine compound A supplied through flow paths L5 and L9 described below.

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

[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. p1 and p2 are each independently 1 or 2. When m is 0, q1 is an integer of 0 to 11, provided that p1+q1 is 12 or less, and when m is 1, q1 is an integer of 0 to 10, provided that p1+q1 is 11 or less. q1 is an integer of 0 to 10, and when q1 is an integer of 2 or more, two or more R 1 may be the same or different, and when q2 is an integer of 2 or more, two or more R 2 may be the same or different, q1 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, q2 is an integer of 2 or more, and two or more R 2 When 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, except when m is 0, p1 is 2, and the two amino groups to which p1 is attached are positioned at the meta position relative to each other.

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

[0020] In the formula, R 11 , R 12 , R 13 and R 21are 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 If is an integer of 2 or more, then 2 or more R 11 may be the same or different, and q 12 If is an integer of 2 or more, then 2 or more R 12 may be the same or different. 11 is an integer of 2 or more, and there are two or more R 11 When R 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, q 12 is an integer of 2 or more, and there are two or more R 12 When R 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 q 13 If is an integer of 2 or more, then 2 or more R 13 may be the same or different, and q 21 If is an integer of 2 or more, then 2 or more R 21 may be the same or different, and q 13 is an integer of 2 or more, and there are two or more R 13 When R 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, q 21 is an integer of 2 or more, and there are two or more R 21 When R is an alkyl group which may have an amino group as a substituent, two or more R21 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 a 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). [ka]

[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 If is an integer of 2 or more, then 2 or more R 111 may be the same or different, and q 121 If is an integer of 2 or more, then 2 or more R 121 may be the same or different, and q 122 If is an integer of 2 or more, then 2 or more R 122 may be the same or different. 111 is an integer of 2 or more, and there are two or more R 111 When R 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, q 121 is an integer of 2 or more, and there are two or more R 121When R 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, q 122 is an integer of 2 or more, and there are two or more R 122 When R 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 there are two R 131 When R 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, q 211 is 2 and there are two R 211 When R 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 become solid is utilized. Therefore, it is preferable to contact the solution of amine compound A with gas under conditions where the reaction product (precipitate, carbamic acid derivative) of amine compound A and carbon dioxide is likely to precipitate. Specifically, the following measures can be considered. (1) Decreasing the reaction temperature during the reaction between amine compound A and carbon dioxide. (2) Increasing the concentration of amine compound A in the solution. (3) A diamine (having two amino groups) is used as the amine compound A. (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, it may be used without diluting it with a solvent.

[0025] The solution of the 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 (carboxylates) such as ethyl acetate and butyl acetate. The solvent is preferably polar. In addition, the solvent is preferably one that has a high boiling point and a low vapor pressure at room temperature. By using such a solvent, the 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 it is relatively easy to obtain. The solvent may be used alone or in combination of two or more. 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. The amine compound may also be used without diluting it with a solvent.

[0026] After passing through the absorber 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 for separating 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, where it is separated into the precipitate and the solution. The solution is transferred to the filter, and the precipitate remaining in the solution is filtered out by the filter. The precipitate adhering to the filter may be collected by backwashing the filter. Although the combination of a liquid cyclone and a filter is exemplified here, the solid-liquid separator may be configured only with a filter without using a liquid cyclone. The precipitate may be separated from the solution by natural sedimentation, or the precipitate may be separated from the solution by a separator. This separator has a partition plate and a mesh provided in the liquid phase, and the liquid level can be controlled to pass through the mesh and the precipitate can be filtered out by 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 the flow path L10 or the flow path L9, or may be directly connected to the absorber 20.

[0029] The precipitate (slurry containing the precipitate) obtained by the solid-liquid separation device 30 is transferred to the storage container 40 through the flow path L6. The storage container 40 is for temporarily storing the precipitate. By storing the precipitate, carbon dioxide can be desorbed from the precipitate at any time to obtain the amine compound A. Therefore, clean energy can be used to desorb carbon dioxide from the precipitate to obtain the amine compound A. In the existing carbon dioxide separation and recovery method using an amine solution, the amine compound after carbon dioxide recovery exists in a state dissolved in the solution. Therefore, if the amine compound is stored after absorbing carbon dioxide, it needs to be stored in the state of an amine solution, and a huge tank is required to store the amine solution, which increases the equipment cost. However, by using the amine compound A that is solidified by absorbing carbon dioxide, the storage tank can be made smaller than when it is stored in the state of an amine solution. This makes it possible to separate and recover carbon dioxide from a gas containing carbon dioxide without increasing the amount of carbon dioxide separated and recovered, while suppressing an increase in equipment costs. In addition, by temporarily storing the precipitate, carbon dioxide can be desorbed from the precipitate during an increase in energy demand response, making it possible to reduce energy costs.

[0030] The precipitate stored in the storage container 40 is transferred to the regenerator 50 through a flow path L7 at the timing of desorbing carbon dioxide. The regenerator 50 is for desorbing carbon dioxide from the precipitate by using clean energy and obtaining an amine compound A.

[0031] Clean energy refers to energy generated by a power generation method that generates 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 generated 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 when desorbing carbon dioxide from the precipitate is preferably substantially clean energy, but a part of the energy may be supplied by energy other than clean energy. The proportion of clean energy in the energy used when desorbing carbon dioxide from the precipitate may be, for example, 70% or more, 80% or more, or 90% or more.

[0033] The desorption of carbon dioxide from the precipitate is carried out, for example, by heating the precipitate, i.e., 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, for example, stored 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] The amine compound A obtained by desorbing carbon dioxide from the precipitate is transferred through a flow path L9. The amine compound A may be transferred to, for example, an absorption device 20 and reused for separating and recovering carbon dioxide from a gas. This makes it possible to integrate a series of processes including separation and recovery of carbon dioxide, production of amine compound A from the precipitate, and reuse of amine compound A.

[0036] [Method of separating and capturing carbon dioxide] A method for separating and recovering carbon dioxide from a gas using the system 100 will be described. The method for separating and recovering 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, 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) storing the precipitate. (c) A process of removing carbon dioxide from the stored precipitate using clean energy and obtaining amine compound A.

[0037] <(a) Process> As described above, the step (a) is a step of obtaining a precipitate by contacting a gas with a solution of an amine compound A having a property of reacting with carbon dioxide to be solidified. The amine compound A is as described above.

[0038] The method of contacting the solution of amine compound A with 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 the step (a).

[0039] <(b) Process> 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, for example, in an environment at room temperature and normal pressure. The method for separating and recovering 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 process 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 for heating the slurry in the process of regenerating the amine compound A from the precipitate tends to be small. When the content of the precipitate is 50 mass% or less, the energy required for solid-liquid separation tends to be small.

[0041] <(c) Process> 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 the amine compound A. The clean energy is as described above.

[0042] Carbon dioxide can be released 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. When the heating temperature is 60° C. or higher, amine compound A tends to be sufficiently regenerated, and when the heating temperature is 150° C. or lower, decomposition of the generated amine compound A tends to be suppressed. As a method for releasing carbon dioxide from the precipitate by a method other than heating, for example, a method in which the precipitate is placed in an environment with a low partial pressure of carbon dioxide and carbon dioxide is released 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 a 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 times of day when energy demand is low. For example, when the clean energy is energy generated by nuclear power generation, energy demand is high during the day, so step (c) is not carried out and thermal power generation, etc. can be suppressed, thereby suppressing an increase in the amount of carbon dioxide separated and captured. On the other hand, energy demand is low at night, so surplus energy is generated, which would normally be used in storage batteries, etc., but this is not preferable because of the large energy loss. On the other hand, carrying out step (c) at night is preferable because it allows the surplus energy to be used effectively. Furthermore, energy costs are generally low during times of low energy demand, so this is also preferable in this respect.

[0045] Step (c) may be performed during an upward demand response of energy. Demand response means changing an energy demand pattern by controlling an energy resource, and an upward demand response means a time when the energy demand pattern is shifting in a direction to increase 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 the amine compound A from the precipitate, and the reuse of the amine compound A can be carried out in an integrated manner. [Explanation of symbols]

[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 capturing carbon dioxide, comprising the steps of: (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 having a property of reacting with carbon dioxide to solidify, to obtain a precipitate; (b) storing the precipitate; (c) removing carbon dioxide from the stored precipitate by utilizing clean energy and obtaining amine compound A; Equipped with A method for separating and capturing carbon dioxide, wherein there are time periods during a day when the step (c) is carried out and time periods when the step (c) is not carried out.

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

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

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

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

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