Separation structure and separation method

Abstract

To provide a carbon dioxide recovery device that can recover carbon dioxide with low energy, and to provide a carbon dioxide recovery method device.SOLUTION: A separation structure 10 is used for separating a hydrophilic solvent from composite liquid containing the hydrophilic solvent and a hydrophobic solvent which are separated from each other. The separation structure 10 includes: a porous substrate 20 including through-holes TH; and a porous surface layer 21 disposed at inner surfaces of the through-holes TH.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a separation structure and a separation method.

Background Art

[0002] Technologies (DAC: Direct Air Capture) for directly removing carbon dioxide from gases containing carbon dioxide (CO2) (for example, air), which is considered to be one of the factors contributing to global warming, have been developed.

[0003] For example, Patent Document 1 mentions DAC using an aqueous amine solution as an absorbent for carbon dioxide. When carbon dioxide is dissolved in the aqueous amine solution, neutral amine and carbon dioxide react to form carbamate ions and protonated amine, thereby absorbing carbon dioxide. On the other hand, when carbamate ions and protonated amine are heated, neutral amine and carbon dioxide are generated, thereby recovering carbon dioxide.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in DAC using an aqueous amine solution as an absorbent for carbon dioxide, since the water content in the aqueous amine solution is as high as about 70 wt%, a large amount of energy is required to heat the absorbent that has absorbed carbon dioxide.

[0006] Therefore, if the water content in the aqueous amine solution can be reduced, the energy required for heating the absorbent can be reduced. For example, when carbon dioxide is dissolved in an absorbent containing ether, amine, and water, a composite liquid in which a hydrophilic solvent containing carbon dioxide, amine, and water and a hydrophobic solvent containing ether are liquid-liquid phase separated is obtained. Therefore, it is effective to separate the hydrophilic solvent from this composite liquid.

[0007] An object of the present invention is to provide a separation structure and a separation method capable of efficiently separating a hydrophilic solvent from a composite liquid in which a hydrophilic solvent and a hydrophobic solvent are liquid-liquid phase separated.

Means for Solving the Problems

[0008] The separation structure according to the present invention is used for separating a hydrophilic solvent from a composite liquid containing a hydrophilic solvent and a hydrophobic solvent separated from each other. The separation structure includes a porous substrate having through holes and a porous surface layer disposed on the inner surface of the through holes.

Effects of the Invention

[0009] According to the present invention, it is possible to provide a carbon dioxide recovery device and a carbon dioxide recovery method device capable of recovering carbon dioxide with low energy.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0011] (Configuration of the separation structure 10) FIG. 1 is a perspective view of the separation structure 10. FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1. FIG. 3 is a cross-sectional view taken along line B-B of FIG. 2.

[0012] The separation structure 10 is used to separate a hydrophilic solvent from a composite liquid containing a hydrophilic solvent and a hydrophobic solvent that are separated from each other. The separation method using the separation structure 10 will be described later.

[0013] The separation structure 10 includes a base material 20, a surface layer 21, a trapping substance 22, a first seal portion 23, and a second seal portion 24.

[0014] 1. Base material 20 The base material 20 is a monolithic porous body. In the present embodiment, the "monolithic shape" means a shape having a plurality of through holes formed in the longitudinal direction, and is a concept including a honeycomb shape. However, the outer shape of the base material 20 is not limited to the monolithic shape, and may be a flat plate shape, a tube shape, a cylindrical shape, a columnar shape, or a prismatic shape.

[0015] The length of the base material 20 is not particularly limited, but can be, for example, 150 mm to 2000 mm. The diameter of the base material 20 is not particularly limited, but can be, for example, 30 mm to 220 mm.

[0016] The base material 20 has a first end face S1, a second end face S2, and a side face S3. The first end face S1 is provided opposite to the second end face S2. The side face S3 is continuous with the outer edges of the first end face S1 and the second end face S2. The base material 20 has a plurality of through holes TH that are continuous with the first end face S1 and the second end face S2. The plurality of through holes TH extend along the longitudinal direction of the base material 20.

[0017] The base material 20 is a porous body. As the porous material constituting the base material 20, a ceramic material, a metal material, a resin material, etc. can be used, and a ceramic material is particularly suitable.

[0018] The ceramic material contains an aggregate. As the aggregate, alumina (Al2O3), titania (TiO2), mullite (Al2O3·SiO2), celite, and cordierite (Mg2Al4Si5O 18 ) etc. can be used, and alumina is particularly suitable in consideration of easy availability.

[0019] The ceramic material may contain an inorganic binder. The inorganic binder is a binder for binding aggregate particles and is an inorganic component that sinters and solidifies at a temperature at which the aggregate particles do not sinter. As the inorganic binder, titania, magnesia, calcia, mullite, easily sinterable alumina, silica, glass frit, clay mineral, easily sinterable cordierite, etc. can be used. The easily sinterable alumina can be used when the aggregate particles are alumina and has an average particle size of 1 / 10 or less of the average particle size of the aggregate particles. The easily sinterable cordierite is a cordierite that can be used when the aggregate particles are cordierite and has an average particle size of 1 / 10 or less of the average particle size of the aggregate particles.

[0020] The porosity of the base material 20 is not particularly limited, but can be 25% or more and 50% or less. The porosity of the base material 20 can be measured by calculation by binarizing an image obtained by FE-SEM observation.

[0021] The average pore diameter of the base material 20 is not particularly limited, but can be 5 μm or more and 25 μm or less. The average pore diameter of the base material 20 is not particularly limited, but can be 10 μm or more and 20 μm or less. The average pore diameter of the base material 20 can be measured by a mercury porosimeter. The thickness of the base material 20 (so-called partition wall thickness) between the two cells CL is not particularly limited, but can be 0.5 mm or more and 2.0 mm or less.

[0022] The base material 20 can be formed by firing (for example, 900 ° C to 1600 ° C, 1 hour to 100 hours) a porous material formed body formed by extrusion molding, press molding, or casting molding.

[0023] 2. Surface layer 21 The surface layer 21 is formed on the inner surface of each through hole TH formed in the base material 20. Therefore, the surface layer 21 is formed in a cylindrical shape.

[0024] The space inside the surface layer 21 is a cell CL through which the composite liquid flows. The number and position of the cells CL can be changed as appropriate. Also, the cross-sectional shape of the cell CL is not limited to circular, and may be a polygon with three sides or more, such as a triangle.

[0025] The surface layer 21 is a porous body. The surface layer 21 is composed of a hydrophilic ceramic material. Examples of the aggregate of the ceramic material constituting the surface layer 21 include those that can be used for the above-described base material 20. The ceramic material constituting the surface layer 21 may contain an inorganic binder. Examples of the inorganic binder include those that can be used for the above-described base material 20.

[0026] The surface layer 21 preferably contains Si. Thereby, since the hydrophilicity of the surface layer 21 can be enhanced, the permeation performance of the hydrophilic solvent contained in the composite liquid can be improved.

[0027] The porosity of the surface layer 21 is not particularly limited, but can be 20% or more and 50% or less, and preferably 25% or more and 40% or less. The porosity of the surface layer 21 can be measured by calculation by binarizing an image obtained by FE-SEM observation.

[0028] The thickness of the surface layer 21 is not particularly limited, but can be 3 μm or more and 50 μm or less, and preferably 5 μm or more and 20 μm or less. The average pore diameter of the surface layer 21 is smaller than the average pore diameter of the base material 20. The value of the average pore diameter of the surface layer 21 is not particularly limited, but can be 0.01 μm or more and 5 μm or less, and preferably 0.05 μm or more and 1 μm or less. The average pore diameter of the surface layer 21 can be measured by the air flow method described in ASTM F316.

[0029] The surface layer 21 can be formed by applying a slurry in which a ceramic material, a sintering aid (for example, silica or magnesia), an organic binder, a pH adjuster, and a surfactant are mixed to the inner surface of the through-hole TH of the base material 20 by a flow-down method, a filtration method, or a dip method, and then firing (for example, at 900°C to 1600°C for 1 hour to 100 hours).

[0030] 3. Trap substance 22 The trap substance 22 is disposed on the inner surface of the surface layer 21. The trap substance 22 adheres to the inner surface of the surface layer 21. The trap substance 22 may be a powder or a mass formed by aggregating powders.

[0031] The trap substance 22 has the property of adsorbing the hydrophobic solvent contained in the composite liquid. Specifically, the trap substance 22 has a lipophilic group having an affinity for the ether contained in the hydrophobic solvent. As the trap substance 22, for example, a silane coupling material is suitable. For example, when a fluorine-based silane coupling material is used, the hydrophilic side binds to the surface layer 21 and the hydrophobic side is exposed to the cell CL, so that the inner surface of the cell CL can be partially hydrophobized.

[0032] The trap substance 22 can be formed by applying a slurry containing a silane coupling material to the inner surface of the surface layer 21 by a flow-down method, a filtration method, or a dip method and then drying it.

[0033] 4. First and second seal portions 22, 23 The first seal portion 23 covers substantially the entire surface of the first end face S1 and a part of the side face S3. The first seal portion 23 suppresses the infiltration of the composite liquid into the first end face S1 of the base material 20. As the material constituting the first seal portion 23, glass, metal, or the like can be used, and glass is preferable in consideration of the compatibility with the thermal expansion coefficient of the base material 20.

[0034] The second seal portion 24 covers substantially the entire surface of the second end face S2 and a part of the side face S3. The second seal portion 24 suppresses the infiltration of the composite liquid into the second end face S2 of the base material 20. As the material constituting the second seal portion 24, glass, metal, or the like can be used, and glass is preferable in consideration of the compatibility with the thermal expansion coefficient of the base material 20.

[0035] (Separation method) The separation method according to this embodiment is a method for separating a hydrophilic solvent from a composite liquid containing a hydrophilic solvent and a hydrophobic solvent separated from each other. In the separation method according to this embodiment, the separation structure 10 is used.

[0036] FIG. 4 is a flowchart for explaining the separation method according to this embodiment.

[0037] The separation method according to this embodiment includes an absorbent preparation step, a carbon dioxide adsorption step, a rough separation step, a separation step, a phase change step, and a heating step.

[0038] 1. Absorbent preparation step An absorbent is prepared by mixing ether, amine, and water. In the absorbent, ether, amine, and water form a homogeneous phase in which they are uniformly mixed.

[0039] Ether has hydrophobicity. As the ether, DEGDEE (diethylene glycol diethyl ether), DEGEME (diethylene glycol ethyl methyl ether), DEGDME (diethylene glycol dimethyl ether), etc. can be used.

[0040] The solubility parameter value of the ether (solubility parameter value, hereinafter abbreviated as "SP value") can be 8.0 or more and 9.0 or less, but is not limited thereto.

[0041] The SP value of the ether is calculated using the Fedors method described in "Polymer Engineering and Science, Feburuary, 1974, Vol. 14, No. 2 P. 147~154". The unit of the SP value is (cal / cm 3 ) 1 / 2 is.

[0042] As the amine, EAE (2-(ethylamino)ethanol), DAP (1,3-diaminopropane), MAE (2(methylamino)ethanol), AEE (2-(2-aminoethoxy)ethanol), PAE (2-(propylamino)ethanol), 2-(3-aminopropoxy)ethanol, 2-(2-methylaminoethoxy)ethanol, 5-amino-1-pentanol, 6-amino-1-hexanol, etc. can be used.

[0043] The SP value of the amine is 11.5 or more and 13.2 or less. When the SP value of the amine exceeds 13.2, in the carbon dioxide adsorption step described later, the hydrophilic solvent and the hydrophobic solvent will not be liquid-liquid phase-separated. Therefore, MEA (2-aminoethanol) with an SP value of 14.3 cannot be used as the amine. When the SP value of the amine is less than 11.5, in this step, ether, amine, and water will not be mixed.

[0044] The SP value of the amine is preferably 11.5 or more and less than 12.0. Thereby, in the subsequent carbon dioxide adsorption step, the hydrophilic solvent and the hydrophobic solvent can be liquid-liquid phase-separated with higher accuracy.

[0045] The SP value of the amine is calculated using the Fedors method, similar to the SP value of ether.

[0046] Preferably, the ratio of the SP value of the amine to the SP value of ether is 1.28 or more and 1.65 or less, and the SP value of the amine is 11.5 or more and 13.2 or less. Thereby, in the subsequent carbon dioxide adsorption step, the hydrophilic solvent and the hydrophobic solvent can be liquid-liquid phase-separated with higher accuracy.

[0047] As combinations where the ratio of the SP value of the amine to the SP value of the ether is 1.28 or more and 1.65 or less, and the SP value of the amine is 11.5 or more and 13.2 or less, there are DEGDEE-EAE, DEGEME-EAE, DEGEME-DAP, DEGEME-MAE, DEGDME-EAE, DEGDME-DAP, DEGDME-MAE, DEGDME-AEE, DEGEME-PAE, DEGDME-PAE, but are not limited thereto.

[0048] The content rate of the ether in the absorption liquid can be 10 wt% or more and 70 wt% or less. The content rate of the amine in the absorption liquid can be 5 wt% or more and 30 wt% or less. The content rate of water in the absorption liquid can be 5 wt% or more and 20 wt% or less.

[0049] 2. Carbon dioxide adsorption step Next, carbon dioxide is dissolved in the absorption liquid. Thereby, a composite liquid containing a hydrophilic solvent and a hydrophobic solvent separated from each other is generated.

[0050] The hydrophilic solvent is generated by the binding of carbon dioxide to the amine contained in the absorption liquid. The hydrophilic solvent contains carbamate ions (RR’NCOO - ) and protonated amine (RR’NH2 + ). The hydrophilic solvent is an aqueous phase with strong interaction with water. When the hydrophilic solvent is generated, carbon dioxide is absorbed by the absorption liquid.

[0051] The hydrophobic solvent is generated by liquid-liquid phase separation of the ether from the aqueous phase as the hydrophilic solvent, which is an aqueous phase, is generated in the absorption liquid. The hydrophobic solvent mainly contains ether. The hydrophobic solvent is an organic phase. Since the hydrophobic solvent is typically lighter than the hydrophilic solvent, it floats on the hydrophilic solvent.

[0052] 3. Rough separation step Next, a part of the hydrophobic solvent is removed from the composite liquid.

[0053] The method for removing the hydrophobic solvent is not particularly limited. For example, the hydrophobic solvent, which is the supernatant liquid, can be removed by an extraction method.

[0054] This step is performed to improve the separation efficiency in the subsequent separation step. In this step, it is sufficient to remove a part of the hydrophobic solvent, and it is not necessary to remove all of the hydrophobic solvent.

[0055] 4. Separation step Next, the hydrophilic solvent is separated from the composite liquid using the above-described separation structure 10. Specifically, when the composite liquid is supplied to one end of each cell CL of the separation structure 10, the hydrophilic solvent contained in the composite liquid sequentially permeates through the surface layer 21 and the base material 20, while the hydrophobic solvent does not permeate through the surface layer 21.

[0056] The hydrophilic solvent that has sequentially permeated through the surface layer 21 and the base material 20 flows out from the side surface S3 of the base material 20. The hydrophobic solvent that does not permeate through the surface layer 21 is discharged from the other end of each cell CL.

[0057] Most of the hydrophobic solvent is discharged from each cell CL, but the hydrophobic solvent approaching the surface layer 21 is adsorbed by the trapping substance 22. As a result, it is possible to suppress the surface of the surface layer 21 from being widely covered by the hydrophobic solvent, and thus it is possible to suppress the separation coefficient of the hydrophilic solvent from decreasing.

[0058] In this step, since the hydrophilic solvent naturally infiltrates into the hydrophilic surface layer 21, it is not necessary to pressurize the composite liquid supplied to each cell CL.

[0059] 5. Phase change step If the surface of the surface layer 21 is covered by the hydrophobic solvent during the above-described separation step being continuously performed for a long time, the separation coefficient of the hydrophilic solvent will decrease.

[0060] Therefore, in this embodiment, the supply of the composite liquid is temporarily stopped, and carbon dioxide is circulated through each cell CL. As a result, carbon dioxide binds to the amine mixed in the hydrophobic solvent to form an aqueous phase. The generated aqueous phase detaches from the hydrophobic solvent and sequentially permeates through the surface layer 21 and the base material 20. As a result, since the hydrophobic solvent covering the surface layer 21 is removed, the separation factor of the hydrophilic solvent can be restored.

[0061] When the separation factor of the hydrophilic solvent has sufficiently recovered after this step, the above-described separation step is resumed. When the separation factor of the hydrophilic solvent does not sufficiently recover even after this step, the process proceeds to the next heating step.

[0062] 6. Heating Step When the separation factor of the hydrophilic solvent does not recover even after the above-described phase change step, the separation structure 10 is heated. As a result, the hydrophobic solvent (mainly ether) covering the surface of the surface layer 21 can be volatilized and removed, so that the separation factor of the hydrophilic solvent can be restored.

[0063] (Modification Example of the Embodiment) Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the invention.

[0064] [Modification Example 1] In the above embodiment, it is assumed that the entire inner surface of the surface layer 21 is exposed, but at least a part of the inner surface of the surface layer 21 may be covered with a hydrophilic polymer layer. As a result, it is possible to suppress the adhesion of the hydrophobic solvent to the polymer layer, and thus it is possible to suppress a decrease in the separation factor of the hydrophilic solvent.

[0065] [Modification Example 2] In the above embodiment, the separation structure 10 is assumed to have the trap substance 22 disposed on the inner surface of the surface layer 21, but it may not have the trap substance 22.

[0066] [Modification Example 3] In the above embodiment, the rough separation step is carried out before the separation step, but the rough separation step may not be carried out.

[0067] [Modification Example 4] In the above embodiment, the phase change step is carried out after the separation step, but the phase change step may not be carried out. That is, it may directly shift from the separation step to the heating step.

Explanation of Reference Numerals

[0068] 10 Separation structure 20 Substrate 21 Surface layer 22 Trapping substance 23 First seal portion 24 Second seal portion CL Cell TH Through-hole

Claims

A separation structure for separating a hydrophilic solvent from a composite liquid containing a hydrophilic solvent and a hydrophobic solvent, which is produced by dissolving carbon dioxide in an absorbent liquid containing an ether, an amine, and water and is separated from each other, comprising: a porous substrate having through holes; a porous surface layer disposed on the inner surface of the through holes; and comprising: The hydrophilic solvent contains carbamate ions and protonated amine; The hydrophobic solvent contains the ether; Separation structure.

2. Further comprising a trap substance disposed on the inner surface of the surface layer for adsorbing the hydrophobic solvent; The separation structure according to claim 1.

3. The ratio of the SP value of the amine to the SP value of the ether is 1.28 or more and 1.65 or less; The SP value of the amine is 11.5 or more and 13.2 or less; The separation structure according to claim 1 or 2.

4. A step of producing a composite liquid containing a hydrophilic solvent and a hydrophobic solvent separated from each other by dissolving carbon dioxide in an absorbent liquid containing an ether, an amine, and water; and A step of separating the hydrophilic solvent from the composite liquid containing the hydrophilic solvent and the hydrophobic solvent separated from each other using a separation structure, The hydrophilic solvent contains carbamate ions and protonated amine; The hydrophobic solvent contains the ether; The separation structure has a porous substrate having a plurality of through holes and a porous surface layer disposed on the inner surface of the plurality of through holes; Separation method.

5. The separation structure further has a trap substance disposed on the inner surface of the surface layer for adsorbing the hydrophobic solvent; The separation method according to claim 4.

6. The ratio of the SP value of the amine to the SP value of the ether is 1.28 or more and 1.65 or less; The SP value of the amine is 11.5 or more and 13.2 or less; The separation method according to claim 4 or 5.

7. Further comprising a step of supplying carbon dioxide to the surface layer after the step of separating the hydrophilic solvent from the composite liquid; The separation method according to any one of claims 4 to 6.

8. Further comprising a step of removing a part of the hydrophobic solvent from the composite liquid before the step of separating the hydrophilic solvent from the composite liquid; The separation method according to any one of claims 4 to 7.

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