Carbon dioxide capture system with pH control function

Abstract

The present invention provides a carbon dioxide capture system with pH control functionality, allowing electrolyte recirculation.

Description

Technical Field

[0001] This invention relates to a carbon dioxide capture system with pH control function, which enables electrolyte recirculation. Background Technology

[0002] Recently, research on electrochemical water electrolysis has been actively underway to adapt to the development of renewable energy and address climate change. Furthermore, technologies for capturing, storing, and converting carbon dioxide (CO2), a greenhouse gas, have also become important.

[0003] Representative carbon dioxide capture technologies include amine-based methods, methods using solid absorbents, and methods using membrane contactors.

[0004] Amine-based carbon dioxide capture methods require significant energy to regenerate the amine compounds and their high corrosiveness impacts equipment durability.

[0005] Due to the deterioration of absorbent performance, the method of capturing carbon dioxide using solid absorbents requires regular replacement of the absorbent, and the absorption rate of carbon dioxide is relatively slow.

[0006] The method of capturing carbon dioxide using membrane contactors utilizes the difference in solubility based on the gas type. Specifically, this method contacts a gas mixture containing carbon dioxide with an aqueous solution to dissolve and separate the carbon dioxide contained in the gas mixture into the aqueous solution. The method of capturing carbon dioxide using membrane contactors has the advantage of high collection efficiency because the reaction between the aqueous solution and carbon dioxide is rapid, and it offers relatively low cost and low energy requirements. Typically, when water is used in an aqueous solution, the carbon dioxide removal efficiency is shown to be around 85%. Similarly, when propylene carbonate is added to water, a typical carbon dioxide removal efficiency is shown to be around 91%. However, regardless of current technological levels, new technologies are needed to provide even higher removal rates in order to get closer to or achieve carbon neutrality. Summary of the Invention

[0007] In one aspect, the present invention provides a system with very high carbon dioxide capture efficiency.

[0008] In another respect, the present invention provides a system capable of continuously capturing carbon dioxide.

[0009] In another aspect, the present invention provides a system capable of selectively collecting carbon dioxide contained in a gas mixture.

[0010] In another aspect, the present invention provides a system that is easy to scale up.

[0011] The invention is not limited to the aspects described above. Other aspects and embodiments of the invention will become clearer from the following description.

[0012] According to one embodiment of the present invention, a carbon dioxide capture system may include: an electrolyte storage unit for storing a first electrolyte containing an aqueous alkaline carbonate solution; an intake unit for preparing a concentrate by dissolving carbon dioxide contained in a gas mixture into the first electrolyte supplied from the electrolyte storage unit; a degassing unit for degassing and discharging carbon dioxide from the concentrate supplied from the intake unit; a distribution unit for receiving and distributing discharge liquid discharged from the degassing unit; a first reaction unit for preparing carbonate and an aqueous alkaline aqueous solution by receiving a portion of the discharge liquid from the distribution unit and reacting the portion with a hydroxide; and a second reaction unit for preparing a second electrolyte and supplying the second electrolyte to the electrolyte storage unit, the preparation being accomplished by receiving the remaining portion of the discharge liquid from the distribution unit and the aqueous aqueous solution from the first reaction unit and reacting the remaining portion of the discharge liquid with the aqueous aqueous solution.

[0013] Alkaline carbonate aqueous solutions may include one or more selected from sodium carbonate (Na2CO3) aqueous solutions, potassium carbonate (K2CO3) aqueous solutions, and combinations thereof.

[0014] The concentration of alkaline carbonate aqueous solution can be from 0.0001M to 0.5M.

[0015] The pH value of the first electrolyte can be between 9 and 12.5.

[0016] The inhalation unit may include an intake separation membrane installed therein to divide the space of the inhalation unit into an electrolyte flow space and a gas mixture flow space. Carbon dioxide contained in the gas mixture and flowing in the gas mixture flow space can pass through the intake separation membrane and dissolve in a first electrolyte flowing in the electrolyte flow space.

[0017] The gas mixture may include one or more selected from steelmaking by-product gases, waste gases, and combinations thereof.

[0018] The pressure in the gas mixture flow space can be from 0.1 bar to 10 bar.

[0019] The pressure in the gas mixture flow space is lower than the pressure in the electrolyte flow space. The pressure difference between the gas mixture flow space and the electrolyte flow space can be less than 3 bar.

[0020] The ratio of the flow rate of the gas mixture to the flow rate of the first electrolyte supplied to the intake unit (flow rate of the gas mixture / flow rate of the first electrolyte) can be in the range of 0.1 to 15.

[0021] The pH of the concentrate may be between 6 and 9.

[0022] The degassing unit may include a degassing separation membrane installed therein to divide the space of the degassing unit into a concentrate flow space and a carbon dioxide flow space. Carbon dioxide contained in the concentrate flowing in the concentrate flow space can pass through the degassing separation membrane and be discharged into the carbon dioxide flow space.

[0023] The effluent may include one or more selected from aqueous solutions of sodium bicarbonate (NaHCO3), aqueous solutions of potassium bicarbonate (KHCO3), and combinations thereof.

[0024] The pH value of the effluent can be between 7 and 9.

[0025] Hydroxides may include hydroxides of one or more metal ions selected from calcium (Ca), magnesium (Mg), strontium (Sr), copper (Cu), lithium (Li), barium (Ba), iron (Fe), and combinations thereof.

[0026] The molar ratio of the partially discharged liquid and hydroxide that react with each other in the first reaction unit can be in the range of 1:0.5 to 1:2.

[0027] Carbonates may include carbonates of one or more metal ions selected from calcium (Ca), magnesium (Mg), strontium (Sr), copper (Cu), lithium (Li), barium (Ba), iron (Fe), and combinations thereof.

[0028] The first reaction unit may also include a filtration unit for separating and recovering carbonates.

[0029] Alkaline aqueous solutions may include one or more selected from sodium hydroxide (NaOH) aqueous solution, potassium hydroxide (KOH) aqueous solution, and combinations thereof.

[0030] The pH value of an alkaline aqueous solution can be between 12 and 14.

[0031] The molar ratio of the remaining effluent from the reaction in the second reaction unit to the alkaline aqueous solution can be in the range of 1:0.5 to 1:1.2.

[0032] The pH value of the second electrolyte discharged from the second reaction unit can be between 9 and 12.5.

[0033] According to the present invention, a system with very high carbon dioxide capture efficiency can be obtained.

[0034] According to the present invention, a system capable of continuously capturing carbon dioxide can be obtained.

[0035] According to the present invention, a system capable of selectively capturing carbon dioxide from a gas mixture can be obtained.

[0036] According to the present invention, a system that is easily expandable can be obtained.

[0037] The advantages and effects of this invention are not limited to those described above. In other words, this invention should be understood to include all advantages and effects that can be derived and / or inferred from the following description and illustrative examples. Attached Figure Description

[0038] Figure 1 A carbon dioxide capture system according to an example embodiment of the present invention is shown;

[0039] Figure 2 An inhalation unit according to an example embodiment of the present invention is shown;

[0040] Figure 3 A degassing unit according to an example embodiment of the present invention is shown;

[0041] Figure 4 A graph showing the measurement results of the carbon dioxide concentration emitted by the carbon dioxide capture system according to the exemplary embodiment of the present invention detailed in Example 1 is shown.

[0042] Figure 5 The X-ray diffraction pattern of the precipitate obtained according to the exemplary embodiment of the invention detailed in Example 2 is shown. Detailed Implementation

[0043] As described above, aspects, embodiments, objects, other objects, features, and advantages of the invention will be readily understood from the following description of certain embodiments depicted in the accompanying drawings. However, the invention is not limited to the exemplary embodiments described herein and may be implemented in other forms. Therefore, the aspects and exemplary embodiments described and detailed herein are provided merely to provide additional illustration and clarification of the disclosure, so as to more fully convey the spirit of the invention to those skilled in the art.

[0044] In describing each drawing, similar reference numerals are used for similar parts. In the drawings, the dimensions of the structures are enlarged from actual dimensions to make the invention clear. Terms such as first, second, etc., may be used to describe various parts, but the parts should not be limited by these terms. These terms are used only for the purpose of distinguishing one part from another. For example, a first part may be named a second part, and similarly, a second part may be named a first part, without departing from the scope of the invention. Unless the context clearly specifies otherwise, singular expressions include plural expressions.

[0045] In this specification, terms such as “comprising,” “including,” “containing,” or “having” (and similar terms) are used to specify the presence of features, numbers, steps, actions, parts, components, or combinations thereof described in the specification, and should not be construed as excluding the possibility of the presence or addition of one or more other features, numbers, steps, actions, parts, components, or combinations thereof (i.e., “open” language). These terms also include the terms “consisting of” and “substantially composed of”, which are intended to limit the specifically stated features, quantities, steps, actions, parts, components, or combinations thereof and their equivalents. Furthermore, when a portion of a layer, membrane, region, plate, etc., is referred to as being “on” another portion, this includes not only being “directly” on or at least overlapping with a region of the other portion, but also having the other portion in between. Conversely, when a portion of a layer, membrane, region, plate, etc., is referred to as being “below” another portion, this includes not only being “directly below” the other portion or at least overlapping with a region of the other portion, but also having the other portion in between.

[0046] Unless otherwise specified, all figures, values, and / or expressions used in this specification to represent the amounts of components, reaction conditions, polymer compositions, and formulations should be understood as approximate values, as these values ​​inherently reflect the various uncertainties arising from the measurements used to obtain them. Therefore, in all cases, they should be interpreted as being defined by the term "about". Furthermore, when numerical ranges are disclosed in this specification, unless otherwise stated, these ranges are continuous and include all values ​​from the specified minimum to the maximum value. Additionally, if a range refers to integers, unless otherwise stated, it includes all integers from the specified minimum to the maximum value.

[0047] Figure 1 A carbon dioxide capture system according to an exemplary embodiment of the present invention is shown. (Refer to...) Figure 1The carbon dioxide capture system may include: an electrolyte storage unit 10 configured to store a first electrolyte A containing an alkaline carbonate aqueous solution; an intake unit 20 configured to prepare a concentrate B by dissolving carbon dioxide contained in a gas mixture into the first electrolyte A supplied from the electrolyte storage unit 10; a degassing unit 30 configured to degas and release carbon dioxide from the concentrate B supplied from the intake unit 20; a distribution unit 40 configured to receive and distribute effluent C discharged from the degassing unit 30; a first reaction unit 50 configured to prepare carbonate and an alkaline aqueous solution D by receiving a portion of effluent C1 from the distribution unit 40 and reacting the portion of effluent C1 with a hydroxide; and a second reaction unit 60 configured to prepare a second electrolyte E and supply the second electrolyte E to the electrolyte storage unit 10, the preparation being accomplished by receiving a remaining portion of effluent C2 from the distribution unit 40 and an alkaline aqueous solution D from the first reaction unit 50 and reacting the remaining portion of effluent C2 with the alkaline aqueous solution D.

[0048] In an implementation scheme, the electrolyte storage unit 10 may include a storage tank capable of storing the first electrolyte A.

[0049] In the implementation scheme, the first electrolyte A may include an alkaline aqueous solution of carbonate.

[0050] In embodiments, the alkaline carbonate aqueous solution may include one or more selected from sodium carbonate (Na₂CO₃) aqueous solution, potassium carbonate (K₂CO₃) aqueous solution, and combinations thereof. In embodiments, the alkaline carbonate aqueous solution preferably includes a potassium carbonate aqueous solution. In the following description of some non-limiting illustrative embodiments of the invention, the first electrolyte A will be described as containing a potassium carbonate aqueous solution, but the scope of the first electrolyte A is not limited thereto.

[0051] In the implementation scheme, the concentration of the alkaline carbonate aqueous solution can be from about 0.0001M to 0.5M. By using a low-concentration alkaline carbonate aqueous solution as the first electrolyte A, the solubility and selectivity of carbon dioxide contained in the gas mixture can be increased.

[0052] In one embodiment, the first electrolyte A may have a pH of approximately 9 to 12.5. In embodiments where the pH of the first electrolyte A is within this range, the carbon dioxide absorption rate of the first electrolyte A can be maximized.

[0053] Figure 2 An inhalation unit 20 according to an exemplary embodiment of the present invention is shown. (Refer to...) Figure 2The inhalation unit 20 may include an inhalation separation membrane 21 installed therein. The inhalation separation membrane 21 can divide the internal space of the inhalation unit 20 into an electrolyte flow space 22 and a gas mixture flow space 23.

[0054] In one embodiment, a first electrolyte A may be provided to the electrolyte flow space 22. In another embodiment, a gas mixture containing carbon dioxide may be supplied from the outside to the gas mixture flow space 23. In yet another embodiment, the first electrolyte A and the gas mixture may flow in opposite directions in a counter-flow arrangement. For example, as... Figure 2 As shown, when the first electrolyte A is supplied to the upper part of the suction unit 20 and discharged to the lower part of the suction unit 20, the gas mixture can be supplied to the lower part of the suction unit 20 and discharged to the upper part of the suction unit 20. This example configuration can be used to increase the contact time between the first electrolyte A and the gas mixture.

[0055] In one embodiment, the intake separation membrane 21 may comprise hollow fiber made of a polyolefin material (e.g., polypropylene). Suitably, the surface of the intake separation membrane 21 includes micropores, allowing the gas mixture to pass through. However, in such an embodiment, the micropores do not allow the first electrolyte A to diffuse through the intake separation membrane 21.

[0056] The area of ​​the suction separation membrane 21 is not particularly limited; for example, it can be 1m². 2 up to 500m 2 Within the range. In some embodiments, the area refers to the total area of ​​the intake separation membrane 21. In some other embodiments, the area may also refer to the reaction area where the first electrolyte A and the gas mixture come into contact with the intake separation membrane 21.

[0057] In implementations, a gas mixture may refer to a gas mixture containing carbon dioxide, nitrogen, oxygen, and hydrogen. In some implementations, a gas mixture may include one or more of steelmaking by-product gases, waste gases, and combinations thereof; however, it should be understood that the gas mixture is not limited thereto. For example, any gas, such as fossil fuel combustion gases or biomass combustion gases, as long as the gas contains the aforementioned components, may be included in the gas mixture.

[0058] In these embodiments, carbon dioxide contained in the gas mixture has high solubility in the first electrolyte A under high pressure. In these embodiments, residual gases such as nitrogen and oxygen have low solubility in the first electrolyte A. In these embodiments, at the interface between the gas mixture and the intake separation membrane 21, carbon dioxide passes through the intake separation membrane 21 and is dissolved and separated in the first electrolyte A, while the residual gases are discharged as residual gases.

[0059] In the implementation scheme, carbon dioxide can be dissolved in the first electrolyte A via the following reaction formula 1. In reaction formula 1, it is assumed that the first electrolyte A is an aqueous solution of potassium carbonate.

[0060] [Reaction Formula 1]

[0061] H₂O + CO₂ → H₂O + +HCO3 -

[0062] K + +CO3 2- +H + →KHCO3

[0063] K + +HCO3 - →KHCO3

[0064] Overall reaction (Net): K2CO3 + H2O + CO2 → 2KHCO3

[0065] Most of the carbon dioxide contained in the gas mixture in the intake unit 20 is soluble in the first electrolyte A. In some specific embodiments, the carbon dioxide content in the residual gas discharged from the intake unit 20 may be in the range of less than about 0.1% by weight.

[0066] The carbon dioxide absorption rate of the first electrolyte A can be adjusted in various ways.

[0067] For example, in one embodiment, the pressure in the gas mixture flow space 23 may be lower than the pressure in the electrolyte flow space 22. In this embodiment, the pressure in the gas mixture flow space 23 may be in the range of about 0.1 bar to 10 bar. In this embodiment, the pressure difference between the gas mixture flow space 23 and the electrolyte flow space 22 may be in the range of less than about 3 bar. When the pressure difference exceeds 3 bar, the suction separation membrane 21 may be damaged.

[0068] In some additional embodiments, the ratio of the flow rate of the gas mixture to the flow rate of the first electrolyte A supplied to the inhalation unit 20 (flow rate of the gas mixture / flow rate of the first electrolyte) can be in the range of about 0.1 to 15. For example, when the carbon dioxide content in the gas mixture is less than 25% by volume, the ratio of the flow rate of the gas mixture to the flow rate of the first electrolyte A (flow rate of the gas mixture / flow rate of the first electrolyte) can be in the range of 1 to 10. When the carbon dioxide content in the gas mixture is greater than 25% by volume and less than or equal to 50% by volume, the ratio of the flow rate of the gas mixture to the flow rate of the first electrolyte A (flow rate of the gas mixture / flow rate of the first electrolyte) can be in the range of 1 to 15. When the carbon dioxide content in the gas mixture is greater than 50% by volume and less than or equal to 75% by volume, the ratio of the flow rate of the gas mixture to the flow rate of the first electrolyte A (flow rate of the gas mixture / flow rate of the first electrolyte) can be in the range of 0.1 to 9. When the carbon dioxide content in the gas mixture is greater than 75% by volume and less than or equal to 100% by volume, the ratio of the flow rate of the gas mixture to the flow rate of the first electrolyte A (flow rate of the gas mixture / flow rate of the first electrolyte) can be in the range of 0.1 to 7. When the flow rate ratio falls within this range, the carbon dioxide absorption rate of the first electrolyte A can be increased.

[0069] In the intake unit 20, carbon dioxide in the first electrolyte A can be dissolved to prepare a concentrated solution B, which is then supplied to the downstream degassing unit 30. The pH value of the concentrated solution B can be between 6 and 9.

[0070] Figure 3 A degassing unit 30 according to an exemplary embodiment of the present invention is shown. In this embodiment, the degassing unit 30 may include a degassing separation membrane 31 installed therein. In this embodiment, the degassing separation membrane 31 can divide the internal space of the degassing unit 30 into a concentrate flow space 32 and a carbon dioxide flow space 33.

[0071] In one embodiment, the degassing membrane 31 may comprise hollow fibers made of a polyolefin material (e.g., polypropylene). In another embodiment, the surface of the degassing membrane 31 includes micropores, so that concentrate B may not pass through the degassing membrane 31, but carbon dioxide emitted from concentrate B is allowed to pass through it.

[0072] In this embodiment, the degassing unit 30 degasses the carbon dioxide dissolved in the concentrate B and supplies the carbon dioxide to the carbon dioxide flow space 33. More specifically, in this embodiment, the concentrate B is supplied to the concentrate flow space 32, and the gas in the carbon dioxide flow space 33 is discharged to the outside, thus degassing the carbon dioxide dissolved in the concentrate B. To achieve this, the pressure within the degassing unit 30 needs to be adjusted. Therefore, the concentrate B can be separated into carbon dioxide degassing effluent C and carbon dioxide.

[0073] In the implementation scheme, the pressure inside the degassing unit 30 can be normal pressure or vacuum, but is not limited to these, as long as the pressure is high enough to degas the carbon dioxide in the concentrate B.

[0074] In the implementation scheme, the carbon dioxide discharged from the degassing unit 30 may have a purity of more than 80% by volume, for example, more than 90% by volume, more than 95% by volume, or more than 99.9% by volume.

[0075] In an embodiment, the effluent C may include one or more of sodium bicarbonate (NaHCO3) aqueous solution, potassium bicarbonate (KHCO3), and combinations thereof, produced by reacting the first electrolyte A with carbon dioxide. That is, the effluent C may be the first electrolyte in which the remaining amount of carbon dioxide (i.e., undegassed carbon dioxide) is dissolved. As described herein, the carbon dioxide dissolved in the effluent C may be solidified and collected in the first reaction unit 50.

[0076] In the implementation scheme, the pH value of the effluent C can be approximately 7 to 9.

[0077] In this embodiment, the dispensing unit 40 can be used to distribute the effluent C to the first reaction unit 50 and the second reaction unit 60. The ratio of effluent C dispensed from the dispensing unit 40 is not particularly limited. In this embodiment, the ratio can be appropriately adjusted according to the molar ratio of the required raw materials in the first reaction unit 50 and the second reaction unit 60.

[0078] In one embodiment, the first reaction unit 50 may receive a portion of the effluent C1 from the distribution unit 40 and precipitate and recover the carbon dioxide dissolved in that portion of the effluent C1. In some specific embodiments, the portion of effluent C1 may react with hydroxide to precipitate and recover carbon dioxide in the form of carbonate.

[0079] In embodiments, the hydroxide may include hydroxides of one or more metal ions selected, such as calcium (Ca), magnesium (Mg), strontium (Sr), copper (Cu), lithium (Li), barium (Ba), iron (Fe), and combinations thereof. In embodiments, the hydroxide may preferably include calcium hydroxide. Hereinafter, for illustrative purposes, the hydroxide will be described as containing calcium hydroxide (Ca(OH)2), but the scope of the hydroxide is not limited thereto.

[0080] As shown in reaction equation 2 below, a portion of the effluent C1 can react with the hydroxide to produce carbonate and an alkaline aqueous solution D. In reaction equation 2 below, for illustrative purposes, it is assumed that the effluent is potassium bicarbonate (KHCO3) and the hydroxide is calcium hydroxide.

[0081] [Reaction 2]

[0082] KHCO3 + Ca(OH)2 → KOH + H2O + CaCO3

[0083] In the embodiments, the carbonate may include carbonates of one or more metal ions, such as calcium (Ca), magnesium (Mg), strontium (Sr), copper (Cu), lithium (Li), barium (Ba), iron (Fe), and combinations thereof.

[0084] In the implementation scheme, the first reaction unit 50 may further include a filtration unit (not shown) for separating and recovering carbonates.

[0085] In the embodiments, the alkaline aqueous solution D may include one or more of sodium hydroxide (NaOH) aqueous solution, potassium hydroxide (KOH) aqueous solution, and combinations thereof.

[0086] In the implementation scheme, the operating temperature of the first reaction unit 50 is not particularly limited, and it can be operated at room temperature (20°C ± 5°C) or below 80°C using a temperature control device.

[0087] In this embodiment, the molar ratio of the partially discharged liquid C1 and the hydroxide that react with each other in the first reaction unit 50 can be in the range of about 1:0.5 to 1:2. When the molar ratio falls within this range, the reaction between the two components can occur sufficiently.

[0088] In the implementation scheme, the alkaline aqueous solution D may have a pH of about 12 to 14.

[0089] In an embodiment, in the carbon dioxide capture system according to the invention, the pH of the effluent C is too low to be used as an electrolyte, while the alkaline aqueous solution D has a high pH. Therefore, the remaining portion C2 of the effluent reacts with the alkaline aqueous solution D in the second reaction unit 60, converting the resulting solution into a second electrolyte E with a suitable pH. The invention has an established system capable of continuously capturing carbon dioxide by providing the second electrolyte E to the electrolyte storage unit 10.

[0090] In the embodiment, in the second reaction unit 60, the remaining portion C2 of the effluent and the alkaline aqueous solution D can react as shown in Reaction Formula 3 below to produce the second electrolyte E. In Reaction Formula 3 below, for illustrative purposes, it is assumed that the remaining portion C2 of the effluent is potassium bicarbonate and the alkaline aqueous solution D is potassium hydroxide. However, as described herein, the range of the remaining portion C2 of the effluent and the alkaline aqueous solution D is not limited thereto.

[0091] [Reaction 3]

[0092] KHCO3 + KOH → K2CO3 + H2O

[0093] According to reaction formula 3, the second electrolyte E may include the same alkaline carbonate aqueous solution as the first electrolyte A.

[0094] There is no particular limitation on the operating temperature of the second reaction unit 60, and in some embodiments, it can be operated at room temperature (20℃±5℃) or below 80℃ using a temperature control device.

[0095] In the embodiment, the molar ratio of the remaining portion C2 of the effluent that reacts with each other in the second reaction unit 60 to the alkaline aqueous solution D can be in the range of about 1:0.5 to 1:1.2 or about 1:0.9 to 1:1.1. When the molar ratio falls within this range, the pH of the second electrolyte E can be adjusted to be the same as or similar to the pH of the first electrolyte A.

[0096] In the implementation scheme, the second electrolyte E may have a pH of about 9 to 12.5 or about 11 to 12.

[0097] According to the present invention, an alkaline carbonate aqueous solution is used as the first electrolyte A. By using an intake unit and a degassing unit including a membrane, carbon dioxide contained in the gas mixture can be captured efficiently.

[0098] Meanwhile, the present invention can maximize the carbon dioxide capture rate by collecting the remaining carbon dioxide that has not been degassed by the degassing unit again through the first reaction unit 50.

[0099] Furthermore, the present invention allows the system to recover the second electrolyte through the second reaction unit 60 and then recycle the second electrolyte, thereby enabling continuous operation.

[0100] Other embodiments and forms of the invention will be described in more detail through the following examples. The following examples are provided merely to aid in understanding the invention, and the scope of the invention is not limited thereto. Example 1, Comparative Example 1, and Comparative Example 2

[0101] Constructed based on Figure 2 and Figure 3 The unit comprises an inhalation unit and a degassing unit. A membrane containing hollow fibers made of polypropylene is used as both the inhalation separation membrane and the degassing separation membrane.

[0102] The first electrolyte according to Example 1 contains 0.1 M K₂CO₃ and has a pH of approximately 11.61. The first electrolyte according to Comparative Example 1 is water and has a pH of approximately 7. The first electrolyte according to Comparative Example 2 contains 2 M K₂CO₃ and has a pH of approximately 8.6.

[0103] The gas mixture supplied to the inhalation unit consists of carbon dioxide and nitrogen at a flow rate of 1:3. Specifically, carbon dioxide is supplied to the inhalation unit at a flow rate of 3.75 L / min, and nitrogen is supplied at a flow rate of 11.25 L / min. The pressure in the inhalation unit is adjusted to approximately 6 bar.

[0104] Approximately 50 L of a first electrolyte is supplied to the intake unit at a flow rate of approximately 5 L / min, dissolving carbon dioxide in the first electrolyte to obtain a concentrate and residual gas discharged from the intake unit. The concentrate is then supplied to a degassing unit to degas the carbon dioxide, and the carbon dioxide and effluent discharged from the degassing unit are collected.

[0105] The contents of carbon dioxide and nitrogen in the residual gas emitted by the intake unit were measured, and the composition of carbon dioxide emitted by the degassing unit was also measured. Based on the results, the carbon dioxide absorption rate was calculated, as shown in Table 1.

[0106] [Table 1]

[0107]

[0108] Referring to Table 1, it was found that Example 1, which used a first electrolyte with a pH of 9 to 12.5, had a high absorption rate of carbon dioxide contained in the gas mixture, and was able to recover high-purity carbon dioxide from the degassing unit compared with Comparative Examples 1 and 2.

[0109] Figure 4A graph showing the carbon dioxide concentration emitted by the carbon dioxide capture system according to Example 1 is presented. Specifically, after a process of dissolving carbon dioxide in a first electrolyte in the intake unit, the carbon dioxide concentration in the residual gas discharged from the intake unit was measured. An initial dissolution rate of 99.99% was found to have lasted for approximately 80 minutes.

[0110] Example 2

[0111] The effluent obtained in Example 1 reacted with calcium hydroxide in a 1:1 molar ratio. Specifically, calcium hydroxide powder was added to the effluent and allowed to react at room temperature (20°C ± 5°C) for approximately 5 minutes. This reaction is identical to reaction formula 2 above, as shown below.

[0112] [Reaction 2]

[0113] KHCO3 + Ca(OH)2 → KOH + H2O + CaCO3

[0114] After the reaction, the pH of the alkaline aqueous solution was approximately 13.28. The precipitate was recovered and subjected to X-ray diffraction analysis. The results are as follows: Figure 5 As shown. (Refer to...) Figure 5 The precipitate was found to be calcium carbonate (CaCO3).

[0115] According to the present invention, residual carbon dioxide in the effluent can also be captured in the form of carbonate.

[0116] Examples 3 to 7, Comparative Example 3 and Comparative Example 4

[0117] The second electrolyte was prepared by reacting the effluent obtained in Example 1 with the alkaline aqueous solution obtained in Example 2 at the molar ratios shown in Table 2. The effluent contained potassium bicarbonate (KHCO3). The alkaline aqueous solution contained potassium hydroxide (KOH). The second electrolyte contained potassium carbonate (K2CO3).

[0118] Measure the pH value of each second electrolyte.

[0119] [Table 2]

[0120] Classification <![CDATA[Molar ratio of KHCO3:KOH]]> pH of the second electrolyte Comparative Example 3 1:2 12.81 Comparative Example 4 1:1.5 12.61 Example 3 1:1.2 12.32 Example 4 1:1.1 12.00 Example 5 1:1 11.63 Example 6 1:0.9 11.07 Example 7 1:0.5 10.09

[0121] Referring to Table 2, when the molar ratio of the remaining effluent from the reaction in the second reaction unit to the alkaline aqueous solution is in the range of 1:0.5 to 1:1.2, the pH of the second electrolyte is controlled at a level similar to that of the first electrolyte (from 9 to 12.5) so that the second electrolyte can be recycled into the electrolyte of the carbon dioxide capture system. When the pH of the second electrolyte is high, salts precipitate on the intake separation membrane and / or degassing separation membrane. As a result, the contact area of ​​the materials decreases. Therefore, the dissolution rate may decrease, and the separation membrane may be damaged.

[0122] Since the experimental examples and embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to the above-described experimental examples and embodiments. Various modifications and improvements made by those skilled in the art using the basic concepts of the present invention are also included within the scope of the present invention.

Claims

1. A carbon dioxide capture system, comprising: An electrolyte storage unit is configured to store, retain, or contain a first electrolyte solution containing an aqueous solution of alkaline carbonates; An inhalation unit is in fluid communication with the electrolyte storage unit and a gas source, the inhalation unit being configured to (i) receive the first electrolyte from the electrolyte storage unit, (ii) receive a gas mixture containing carbon dioxide from the gas source, and (iii) prepare a concentrate by dissolving carbon dioxide in the gas mixture into the first electrolyte; A degassing unit, which is in fluid communication with the inhalation unit and the emission device, is configured to (i) degas carbon dioxide from the concentrate supplied by the inhalation unit to provide a degassed concentrate, and (ii) emit carbon dioxide. A distribution unit, which is in fluid communication with the degassing unit and with at least one distribution line, is configured to (i) receive the degassing concentrate from the degassing unit and distribute the degassing concentrate through the at least one distribution line; A first reaction unit, which is in fluid communication with the distribution unit, is configured to react at least a portion of the degassed concentrate from the distribution unit with hydroxide under certain conditions to prepare carbonate and an alkaline aqueous solution. and A second reaction unit, which is in fluid communication with (a) an electrolyte storage unit, (b) a distribution unit and (c) a first reaction unit, and is configured to (i) react the remaining portion of the degassed concentrate from the distribution unit with a certain amount of alkaline aqueous solution from the first reaction unit to prepare a second electrolyte, and (ii) supply the second electrolyte to the electrolyte storage unit.

2. The system according to claim 1, wherein the alkaline carbonate aqueous solution comprises one or more of sodium carbonate (Na2CO3) aqueous solution, potassium carbonate (K2CO3) aqueous solution, and combinations thereof.

3. The system according to claim 1, wherein the concentration of the alkaline carbonate aqueous solution is from 0.0001M to 0.5M.

4. The system according to claim 1, wherein the pH value of the first electrolyte is 9 to 12.

5.

5. The system of claim 1, wherein the inhalation unit includes an inhalation separation membrane that divides the internal space of the inhalation unit into an electrolyte flow space and a gas mixture flow space, and in, The inhalation separation membrane is permeable to carbon dioxide contained in the gas mixture flowing in the gas mixture flow space, and allows carbon dioxide to dissolve in the first electrolyte in the electrolyte flow space.

6. The system of claim 1, wherein the gas mixture comprises one or more selected from steelmaking by-product gases, waste gases, and combinations thereof.

7. The system of claim 5, wherein the pressure of the gas mixture flow space is 0.1 bar to 10 bar.

8. The system of claim 5, wherein the pressure in the gas mixture flow space is lower than the pressure in the electrolyte flow space. in, The pressure difference between the gas mixture flow space and the electrolyte flow space is in the range of less than 3 bar.

9. The system of claim 1, wherein the ratio of the flow rate of the gas mixture to the flow rate of the first electrolyte supplied to the inhalation unit is in the range of 0.1 to 15.

10. The system of claim 1, wherein the pH of the concentrate is 6 to 9.

11. The system according to claim 1, wherein the degassing unit includes a degassing separation membrane that divides the internal space of the degassing unit into a concentrate flow space and a carbon dioxide flow space, and in, The degassing separation membrane is permeable to carbon dioxide contained in the concentrate flowing in the concentrate flow space, and allows carbon dioxide to be discharged into the carbon dioxide flow space through the degassing separation membrane.

12. The system according to claim 1, wherein the degassing concentrate comprises one or more of an aqueous solution of sodium bicarbonate (NaHCO3), an aqueous solution of potassium bicarbonate (KHCO3), and combinations thereof.

13. The system of claim 1, wherein the pH of the degassing concentrate is 7 to 9.

14. The system of claim 1, wherein the hydroxide comprises hydroxides of one or more metal ions selected from calcium (Ca), magnesium (Mg), strontium (Sr), copper (Cu), lithium (Li), barium (Ba), iron (Fe), and combinations thereof.

15. The system according to claim 1, wherein the molar ratio of the partially degassed concentrate and the hydroxide that react with each other in the first reaction unit is in the range of 1:0.5 to 1:

2.

16. The system of claim 1, wherein the carbonate comprises carbonates of one or more metal ions selected from calcium (Ca), magnesium (Mg), strontium (Sr), copper (Cu), lithium (Li), barium (Ba), iron (Fe), and combinations thereof, and The first reaction unit also includes a filtration unit configured to separate and recover carbonates.

17. The system of claim 1, wherein the alkaline aqueous solution comprises one or more of an aqueous solution of sodium hydroxide (NaOH), an aqueous solution of potassium hydroxide (KOH), and combinations thereof.

18. The system of claim 1, wherein the pH value of the alkaline aqueous solution is 12 to 14.

19. The system according to claim 1, wherein the molar ratio of the remaining portion of the degassed concentrate reacting with each other in the second reaction unit to the alkaline aqueous solution is in the range of 1:0.5 to 1:1.

2.

20. The system of claim 1, wherein the pH of the second electrolyte discharged from the second reaction unit is from 9 to 12.5.

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