CARBON DIOXIDE SEPARATION SYSTEM WITH pH CONTROL FUNCTION

Abstract

The disclosure relates to a carbon dioxide separation system with a pH control function that enables the recycling of an electrolyte solution.

Description

TECHNICAL AREA

[0001] The present disclosure relates to a carbon dioxide separation system with a pH control function that enables the recycling of an electrolyte solution. BACKGROUND

[0002] Recently, research in the field of electrochemical water electrolysis has been actively promoted in line with the development of renewable energies to address climate change. Furthermore, technologies for capturing, storing, and converting carbon dioxide (CO2) to reduce greenhouse gases have gained importance.

[0003] Representative methods for carbon dioxide removal include methods based on amine compounds, methods using solid absorbents, and methods using membrane contactors.

[0004] The carbon dioxide capture process based on amine compounds requires a lot of energy to regenerate the amine compounds and impairs the durability of the equipment due to its highly corrosive properties.

[0005] The process, which uses solid absorbents to capture carbon dioxide, requires regular replacement due to the decreasing efficiency of the absorbents and has a slow absorption rate of carbon dioxide.

[0006] In processes that utilize membrane contactors for carbon dioxide removal, the differences in solubility depending on the type of gas are exploited. Specifically, in this process, a carbon dioxide-containing gas mixture is brought into contact with an aqueous solution to dissolve the carbon dioxide contained in the gas mixture and separate it into the aqueous solution. The process using membrane contactors for carbon dioxide removal offers the advantage of high removal efficiency, as the reaction between the aqueous solution and the carbon dioxide occurs rapidly, and provides relatively low costs and energy consumption. When the aqueous solution contains water, the carbon dioxide removal efficiency is typically around 85%. When propylene carbonate is added to the water, the carbon dioxide removal efficiency is typically around 91%.Regardless of the current state of the art, new technologies with higher separation efficiencies are needed to approach or achieve carbon neutrality. SUMMARY OF THE REVELATION

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

[0008] In another aspect, the present disclosure provides a system capable of continuously separating carbon dioxide.

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

[0010] In yet another aspect, the present revelation provides a system that can easily be scaled up.

[0011] The various aspects of this disclosure are not limited to those mentioned above. Other aspects and embodiments of this disclosure will become clearer from the following description and can be realized by means and combinations thereof, as set forth in the claims.

[0012] According to one embodiment of the present disclosure, the carbon dioxide separation system may comprise: an electrolyte storage unit for storing a first electrolyte solution containing an aqueous alkaline carbonate solution; an inlet unit for producing a concentrated liquid by dissolving carbon dioxide contained in a gas mixture in the first electrolyte solution supplied by the electrolyte storage unit; a degassing unit for degassing carbon dioxide from the concentrated liquid supplied by the inlet unit and for releasing the carbon dioxide; a distribution unit for receiving a discharge liquid released by the degassing unit and for distributing the discharge liquid;a first reaction unit for producing a carbonate and an aqueous alkaline solution by taking up a portion of the drain liquid from the distribution unit and reacting that portion with hydroxide; and a second reaction unit for producing a second electrolyte solution and supplying the second electrolyte solution to the electrolyte storage unit, wherein the production is carried out by taking up the remaining portion of the drain liquid from the distribution unit and an aqueous alkaline solution from the first reaction unit and reacting the remaining portion of the drain liquid with the aqueous alkaline solution.

[0013] The aqueous alkaline carbonate solution may comprise one or more solutions selected from the group consisting of an aqueous sodium carbonate solution (Na2CO3), an aqueous potassium carbonate solution (K2CO3), and combinations thereof.

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

[0015] The first electrolyte solution can have a pH value of 9 to 12.5.

[0016] The inlet unit can include an inlet divider membrane installed within it to separate its space into an electrolyte flow chamber and a gas mixture flow chamber. The carbon dioxide contained in the gas mixture and flowing in the gas mixture flow chamber can pass through the inlet divider membrane and dissolve in the first electrolyte solution flowing in the electrolyte flow chamber.

[0017] The gas mixture may include one or more gases selected from the group consisting of by-product gas from steel production, exhaust gas and combinations thereof.

[0018] The gas mixture flow chamber can have a pressure of 0.1 bar to 10 bar.

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

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

[0021] The concentrated liquid can have a pH value of 6 to 9.

[0022] The degassing unit can contain an installed degassing separation membrane, which divides its space into a flow chamber for concentrated liquid and a carbon dioxide flow chamber. The carbon dioxide contained in the concentrated liquid flowing into the concentrated liquid flow chamber can pass through the degassing separation membrane and be discharged into the carbon dioxide flow chamber.

[0023] The draining fluid may comprise one or more liquids selected from the group consisting of an aqueous sodium bicarbonate (NaHCO3) solution, an aqueous potassium bicarbonate (KHCO3) solution and combinations thereof.

[0024] The draining fluid can have a pH value of 7 to 9.

[0025] The hydroxide may comprise a hydroxide of one or more metal ions selected from the group consisting of calcium (Ca), magnesium (Mg), strontium (Sr), copper (Cu), lithium (Li), barium (Ba), iron (Fe) and combinations thereof.

[0026] The molar ratio of the portion of the draining liquid and the hydroxide reacted with each other in the first reaction unit can be in the range of 1:0.5 to 1:2.

[0027] The carbonate may comprise a carbonate of one or more metal ions selected from the group consisting of 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 filter unit that separates and recovers the carbonate.

[0029] The aqueous alkaline solution may comprise one or more solutions selected from the group consisting of an aqueous sodium hydroxide (NaOH) solution, an aqueous potassium hydroxide (KOH) solution and combinations thereof.

[0030] The aqueous alkaline solution can have a pH value of 12 to 14.

[0031] A molar ratio between the remaining part of the draining liquid and the aqueous alkaline solution that react with each other in the second reaction unit can be in a range of 1:0.5 to 1:1.2.

[0032] The second electrolyte solution, which is drained from the second reaction unit, can have a pH value of 9 to 12.5.

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

[0034] According to the present disclosure, a system can be obtained that is capable of continuously separating carbon dioxide.

[0035] According to the present disclosure, a system can be obtained which is capable of selectively separating carbon dioxide from a gas mixture.

[0036] According to the present disclosure, a system can be obtained that can be easily scaled up.

[0037] The benefits and effects of this disclosure are not limited to those mentioned above. That is to say, this disclosure should be understood to encompass all benefits and effects that can be derived and / or inferred from the following description and illustrative examples. BRIEF DESCRIPTION OF THE FIGURES Fig. Figure 1 shows a carbon dioxide capture system according to an embodiment of the present disclosure; Fig. Figure 2 shows an inlet unit according to an exemplary embodiment of the present disclosure; Fig. Figure 3 shows a degassing unit according to an exemplary embodiment of the present disclosure; Fig. Figure 4 shows a diagram of the results of the measurement of the concentration of carbon dioxide emitted from the carbon dioxide capture system according to an exemplary embodiment of the present disclosure as described in Example 1; and Fig. Figure 5 shows a diagram of the X-ray diffraction analysis of a precipitate obtained according to the exemplary embodiment of the present disclosure as described in Example 2. DETAILED DESCRIPTION OF PERFORMANCE FORMS

[0038] As mentioned above, aspects, embodiments, objects, other objects, features, and advantages of the present disclosure are easily understood through the following description of certain embodiments as illustrated in the accompanying drawings. However, the present disclosure is not limited to the embodiments described herein and can also be implemented in other forms. The detailed aspects and embodiments presented here serve only to further illustrate and clarify the disclosed content, in order to better convey the meaning of the present disclosure to the person skilled in the art.

[0039] In the description of each drawing, similar reference symbols are used for similar components. In the accompanying drawings, the dimensions of the structures have been enlarged from their actual size for the sake of clarity of this disclosure. Terms such as "first," "second," etc., may be used to describe different components, but the components should not be limited by these terms. The terms are used only to distinguish the individual components from one another. For example, a first component may be referred to as a second component, and likewise, the second component may be referred to as a first component, without this deviating from the scope of this disclosure. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0040] In this specification, terms such as "comprise," "include," "contain," or "exhibit" (and similar terms) are used to specify the presence of features, numbers, steps, actions, components, parts, or combinations thereof, as described in the specification, and should not be interpreted as excluding the possibility of the presence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof (i.e., "open" language). These terms also include the terms "consisting of" and "essentially consisting of," which are intended to be limited to the specifically named features, numbers, steps, actions, components, parts, or combinations thereof and their equivalents. When referring to a part of a layer, membrane, area, plate, etc.,When a part is said to be "on" another part, this includes not only that it is "directly above" the other part or at least partially overlapping it, but also cases where another part is located in between. Conversely, when a part of a layer, membrane, area, plate, etc., is described as being "under" another part, this includes not only that it is "immediately beneath" the other part or at least partially overlapping it, but also cases where another part is located in between.

[0041] Unless otherwise specified, all numbers, values, and / or expressions used to represent the components, reaction conditions, polymer compositions, and amounts of formulations in this specification are to be understood as approximate values, since these values ​​inherently reflect the various inaccuracies resulting from the measurements used to determine them. Accordingly, they are to be indicated in all cases with the term "approximately." Where numerical ranges are specified in this specification, these ranges are continuous and include all values ​​from the minimum value to the specified maximum value, unless otherwise specified. Where the range refers to integers, it includes all integers from the minimum value to the specified maximum value, unless otherwise specified.

[0042] Fig.Figure 1 shows a carbon dioxide capture system according to an embodiment of the present disclosure. Referring to Fig.1. The carbon dioxide capture system may comprise: an electrolyte storage unit 10 for storing a first electrolyte solution A containing an aqueous alkaline carbonate solution; an inlet unit 20 for producing a concentrated liquid B by dissolving carbon dioxide contained in a gas mixture in the first electrolyte solution A supplied by the electrolyte storage unit 10; a degassing unit 30 for degassing carbon dioxide from the concentrated liquid B supplied by the inlet unit 20 and for releasing the carbon dioxide; a distribution unit 40 for receiving a discharge liquid C released by the degassing unit 30 and for distributing the discharge liquid C.a first reaction unit 50 for producing a carbonate and an aqueous alkaline solution D by taking up part C1 of the drain liquid from the distribution unit 40 and reacting part C1 of the drain liquid with hydroxide, and a second reaction unit 60 for producing a second electrolyte solution E and supplying the second electrolyte solution E to the electrolyte storage unit 10, wherein the production is carried out by taking up the remaining part C2 of the drain liquid from the distribution unit 40 and an aqueous alkaline solution D from the first reaction unit 50 and reacting the remaining part C2 of the drain liquid with the aqueous alkaline solution D.

[0043] In embodiments, the electrolyte storage unit 10 can include a storage tank that can store the first electrolyte solution A.

[0044] In embodiments, the first electrolyte solution A can comprise the aqueous alkaline carbonate solution.

[0045] The aqueous alkaline carbonate solution may, in embodiments, comprise one or more solutions selected from an aqueous sodium carbonate (Na₂CO₃) solution, an aqueous potassium carbonate (K₂CO₃) solution, and combinations thereof. In embodiments, the aqueous alkaline carbonate solution may preferably comprise an aqueous potassium carbonate solution. In the following description of some non-limiting, illustrative embodiments of the present disclosure, the first electrolyte solution A is described as containing an aqueous potassium carbonate solution, but the scope of the first electrolyte solution A is not limited thereto.

[0046] In embodiments, the aqueous alkaline carbonate solution can have a concentration of approximately 0.0001 M to 0.5 M. The solubility and selectivity of the carbon dioxide contained in the gas mixture can be increased by using a low concentration of an aqueous alkaline carbonate solution as the first electrolyte solution A.

[0047] In embodiments, the first electrolyte solution A can have a pH value of approximately 9 to 12.5. In embodiments where the first electrolyte solution A has a pH value within this range, the carbon dioxide absorption rate of the first electrolyte solution A can be maximized.

[0048] Fig. Figure 2 shows an inlet unit 20 according to an embodiment of the present disclosure. Referring to Fig.2. The inlet unit 20 can include an inlet separating membrane 21 installed therein. The inlet separating membrane 21 can divide an interior space of the inlet unit 20 into an electrolyte flow space 22 and a gas mixture flow space 23.

[0049] In embodiments, the first electrolyte solution A can be introduced into the electrolyte flow chamber 22. In embodiments, a carbon dioxide-containing gas mixture can be supplied to the gas mixture flow chamber 23 from the outside. In embodiments, the first electrolyte solution A and the gas mixture can flow in opposite directions in a countercurrent arrangement. For example, if, as in Fig.As shown in Figure 2, the first electrolyte solution A is supplied to the upper part of the inlet unit 20 and discharged into the lower part of the inlet unit 20. Similarly, the gas mixture can be supplied to the lower part of the inlet unit 20 and discharged into the upper part of the inlet unit 20. This example configuration can be used to increase the contact time between the first electrolyte solution A and the gas mixture.

[0050] In embodiments, the inlet separating membrane 21 can comprise a hollow fiber made of a polyolefin material, such as polypropylene. A surface of the inlet separating membrane 21 suitably has fine pores so that the gas mixture can pass through the inlet separating membrane 21. In such embodiments, however, the fine pores do not allow diffusion of the first electrolyte solution A through the inlet separating membrane 21.

[0051] The area of ​​the inlet separating membrane 21 is not particularly limited and can, for example, be between 1 m² 2 and 500 m 2 In some embodiments, the area refers to the total area of ​​the inlet separating membrane 21. In some other embodiments, the area may also refer to a reaction area in which the first electrolyte solution A and the gas mixture come into contact through the inlet separating membrane 21.

[0052] In some embodiments, the gas mixture may refer to a mixture comprising carbon dioxide, nitrogen, oxygen, and hydrogen. In some embodiments, the gas mixture may include one or more gases from steelmaking by-products, exhaust gases, and combinations thereof; however, it is clear that the gas mixture is not limited to these. For example, any gas, such as combustion gas from fossil fuels or biomass, may be included in the gas mixture, as long as the gas contains the components mentioned above.

[0053] In certain embodiments, the carbon dioxide contained in the gas mixture has a high solubility in the first electrolyte solution A at high pressure. In such embodiments, the other gases, such as nitrogen and oxygen, have a low solubility in the first electrolyte solution A. In these embodiments, the carbon dioxide passes through the inlet separating membrane 21 at the interface between the gas mixture and the inlet separating membrane 21 and is dissolved and separated in the first electrolyte solution A, while the other gases are discharged as residual gases.

[0054] In embodiments, the carbon dioxide can be dissolved in the first electrolyte solution A by the reaction formula 1 below. In reaction formula 1, it is assumed that the first electrolyte solution A is an aqueous potassium carbonate solution. [Reaction formula 1] H2O + CO2 → H + + HCO3 - K + + CO3 2- + H +→ KHCO3 K + + HCO3 - → KHCO3 Net: K2CO3 + H2O + CO2 → 2KHCO3

[0055] Most of the carbon dioxide contained in the gas mixture in the inlet unit 20 may be dissolved in the first electrolyte solution A. In some specific embodiments, the carbon dioxide content in the residual gases derived from the inlet unit 20 may be in the range of approximately 0.1 wt.% or less.

[0056] The carbon dioxide absorption rate of the first electrolyte solution A can be adjusted in various ways.

[0057] In a particular embodiment, the pressure in the gas mixture flow chamber 23 can, for example, be lower than the pressure in the electrolyte flow chamber 22. In embodiments, the pressure of the gas mixture flow chamber 23 can be in a range of approximately 0.1 bar to 10 bar. In embodiments, the pressure difference between the gas mixture flow chamber 23 and the electrolyte flow chamber 22 can be in a range of approximately 3 bar or less. If the pressure difference is greater than 3 bar, the inlet separating membrane 21 may be damaged.

[0058] In some further embodiments, the ratio between the flow rate of the gas mixture and the flow rate of the first electrolyte solution A supplied to the inlet unit 20 (flow rate of the gas mixture / flow rate of the first electrolyte solution) can be in a range of approximately 0.1 to 15. For example, if the carbon dioxide content of the gas mixture is in the range of 25 volume% or less, the ratio of the flow rate of the gas mixture to the flow rate of the first electrolyte solution A (flow rate of the gas mixture / flow rate of the first electrolyte solution) can be in the range of 1 to 10. If the carbon dioxide content in the gas mixture is more than 25 volume% and 50 volume% or less, the ratio of the flow rate of the gas mixture to the flow rate of the first electrolyte solution A (flow rate of the gas mixture / flow rate of the first electrolyte solution) can be in the range of 1 to 15.If the carbon dioxide content in the gas mixture is more than 50% by volume and 75% by volume or less, the ratio of the gas mixture flow rate to the flow rate of the first electrolyte solution A (gas mixture flow rate / first electrolyte solution flow rate) can range from 0.1 to 9. If the carbon dioxide content in the gas mixture is more than 75% by volume and 100% by volume or less, the ratio of the gas mixture flow rate to the flow rate of the first electrolyte solution A (gas mixture flow rate / first electrolyte solution flow rate) can range from 0.1 to 7. If the flow rate ratio falls within this range, the carbon dioxide absorption rate of the first electrolyte solution A can be increased.

[0059] In the inlet unit 20, carbon dioxide can be dissolved in the first electrolyte solution A to produce a concentrated liquid B, and the concentrated liquid B is directed to the degassing device 30 at the rear end. The concentrated liquid B can have a pH value of 6 to 9.

[0060] Fig. Figure 3 shows a degassing unit 30 according to an embodiment of the present disclosure. In embodiments, the degassing unit 30 can include a degassing separation membrane 31 installed therein. In embodiments, the degassing separation membrane 31 can divide an interior space of the degassing unit 30 into a flow space for concentrated liquid 32 and a carbon dioxide degassing space 33.

[0061] In embodiments, the degassing membrane 31 can comprise a hollow fiber made of a polyolefin material, such as polypropylene. In embodiments, the surface of the degassing membrane 31 has micropores so that the concentrated liquid B cannot pass through the degassing membrane 31, but the carbon dioxide escaping from the concentrated liquid B can pass through the degassing membrane 31.

[0062] In some embodiments, the degassing unit 30 can degas the carbon dioxide dissolved in the concentrated liquid B and supply the carbon dioxide to the carbon dioxide degassing chamber 33. More precisely, the concentrated liquid B is directed into the flow chamber for concentrated liquid 32, and the gases in the carbon dioxide degassing chamber 33 are discharged to the outside, allowing the carbon dioxide dissolved in the concentrated liquid B to be degassed. To achieve this, the pressure in the degassing unit 30 is adjusted. This allows the concentrated liquid B to be separated into the carbon dioxide-degassed discharge liquid C and carbon dioxide.

[0063] In embodiments, the pressure in the degassing unit 30 can be normal pressure or vacuum, but is not limited to this, as long as it is a pressure at which the carbon dioxide can be degassed in the concentrated liquid B.

[0064] In embodiments, the carbon dioxide discharged from the degassing unit 30 can have a purity of about 80 volume % or more, for example about 90 volume % or more, about 95 volume % or more or about 99.9 volume % or more.

[0065] In embodiments, the draining liquid C can comprise one or more solutions of an aqueous sodium bicarbonate (NaHCO3) solution, prepared by a reaction of the first electrolyte solution A and carbon dioxide, potassium bicarbonate (KHCO3), and combinations thereof. That is, the draining liquid C can be a first electrolyte solution in which the remaining amount of carbon dioxide (i.e., that which has not been degassed) is dissolved. The carbon dioxide dissolved in the draining liquid C can solidify and be collected in the first reaction unit 50, as described here.

[0066] In embodiments, the draining fluid C can have a pH value of approximately 7 to 9.

[0067] In embodiments, the distribution unit 40 can be used to distribute the drain liquid C to the first reaction unit 50 and the second reaction unit 60. The ratio of the drain liquid C distributed by the distribution unit 40 is not particularly limited. In embodiments, the ratio can be appropriately adjusted depending on the molar ratio of the raw materials required in the first reaction unit 50 and the second reaction unit 60.

[0068] In some embodiments, the first reaction unit 50 can take up a portion C1 of the drain liquid from the distribution unit 40 and precipitate and recover the carbon dioxide dissolved in that portion C1 of the drain liquid. In some specific embodiments, the portion C1 of the drain liquid can react with hydroxide to precipitate and recover the carbon dioxide in the form of carbonate.

[0069] In embodiments, the hydroxide may comprise a hydroxide 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. In embodiments, the hydroxide may preferably comprise calcium hydroxide. Hereinafter, for the purpose of reference in the description of this disclosure, the hydroxide is described as containing calcium hydroxide (Ca(OH)₂), but the scope of the hydroxide is not limited thereto.

[0070] The portion of the draining liquid C1 can be reacted with the hydroxide, as shown in reaction formula 2 below, and a carbonate and an aqueous alkaline solution D can be prepared. In reaction formula 2 below, for illustrative purposes, the draining liquid is assumed to be potassium bicarbonate (KHCO3) and the hydroxide is calcium hydroxide. [Reaction formula 2] KHCO3 + Ca(OH)2 → KOH + H2O + CaCO3

[0071] In embodiments, the carbonate may comprise a carbonate 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.

[0072] In embodiments, the first reaction unit 50 may further include a filter unit (not shown) that separates and recovers the carbonate.

[0073] In embodiments, the aqueous alkaline solution D may comprise one or more solutions of an aqueous sodium hydroxide (NaOH) solution, an aqueous potassium hydroxide (KOH) solution and combinations thereof.

[0074] The operating temperature of the first reaction unit 50 is not particularly limited and can be operated at room temperature (20°C ± 5°C) or at a temperature of 80°C or less using a temperature control device.

[0075] In embodiments, the molar ratio of component C1 of the draining liquid and the hydroxide reacting with each other in the first reaction unit 50 can be in a range of approximately 1:0.5 to 1:2. If the molar ratio lies within this range, the reaction of the two components can proceed sufficiently.

[0076] In embodiments, the aqueous alkaline solution D can have a pH value of approximately 12 to 14.

[0077] In embodiments of the carbon dioxide separation system according to the present disclosure, the pH of the drain liquid C is too low to be used as an electrolyte, and the aqueous alkaline solution D has a high pH. Therefore, the remaining portion C2 of the drain liquid reacts with the aqueous alkaline solution D in the second reaction unit 60 to transform the resulting solution into a second electrolyte solution E with a suitable pH. The present disclosure describes a system capable of continuously separating carbon dioxide by supplying the second electrolyte solution E to the electrolyte storage unit 10.

[0078] In embodiments, in the second reaction unit 60, the remaining portion C2 of the draining liquid and the aqueous alkaline solution D can be reacted as shown in the following reaction formula 3 to produce a second electrolyte solution E. For illustrative purposes, the following reaction formula 3 assumes that the remaining portion C2 of the draining liquid is potassium bicarbonate and the aqueous alkaline solution D is potassium hydroxide. However, as described herein, the extent of the remaining portion of the draining liquid C2 and the aqueous alkaline solution D is not limited to this. [Reaction formula 3] KHCO3 + KOH → K2CO3 + H2O

[0079] According to reaction formula 3, the second electrolyte solution E can comprise the same aqueous alkaline carbonate solution as the first electrolyte solution A.

[0080] The operating temperature of the second reaction unit 60 is not particularly limited and in some embodiments can be operated at room temperature (20°C ± 5°C) or at a temperature of 80°C or less using a temperature control device.

[0081] In embodiments, the molar ratio of the remaining portion C2 of the draining liquid and the aqueous alkaline solution D, which react with each other in the second reaction unit 60, can be in a range of approximately 1:0.5 to 1:1.2 or approximately 1:0.9 to 1:1.1. If the molar ratio falls within this range, the pH of the second electrolyte solution E can be adjusted to the same or a similar pH as the pH of the first electrolyte solution A.

[0082] In embodiments, the second electrolyte solution E can have a pH value of about 9 to 12.5 or about 11 to 12.

[0083] According to the present disclosure, an aqueous alkaline carbonate solution is used as the first electrolyte solution A. The carbon dioxide contained in the gas mixture can be separated with high efficiency using the inlet unit or the degassing unit, which comprises a membrane.

[0084] At the same time, the present disclosure 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.

[0085] Furthermore, the present disclosure enables the continuous operation of the system by recovering the second electrolyte solution through the second reaction unit 60 and subsequently returning it to the cycle.

[0086] Further embodiments and forms of the present disclosure are described in more detail with reference to the following examples. The following examples serve only to improve understanding of the present disclosure and are not to be understood as limiting the scope of the present disclosure. Example 1, Comparative Example 1 and Comparative Example 2

[0087] An inlet unit and a degassing unit were installed according to the specifications. Fig. 2 and Fig. 3. The inlet and degassing separation membranes used were those containing a hollow polypropylene fiber.

[0088] The first electrolyte solution according to Example 1 contained 0.1 M K₂CO₃ and had a pH of approximately 11.61. The first electrolyte solution according to Comparative Example 1 was water and had a pH of approximately 7. The first electrolyte solution according to Comparative Example 2 contained 2 M K₂CO₃ and had a pH of approximately 8.6.

[0089] A gas mixture containing carbon dioxide and nitrogen in a 1:3 ratio was supplied to the inlet unit. Specifically, carbon dioxide was supplied to the inlet unit at a flow rate of 3.75 l / min and nitrogen at a flow rate of 11.25 l / min. The pressure in the inlet unit was set to approximately 6 bar.

[0090] Approximately 50 liters of the first electrolyte solution were fed into the inlet unit at a flow rate of about 5 liters / minute, and carbon dioxide dissolved in the first electrolyte solution, resulting in a concentrated liquid and residual gases discharged from the inlet unit. The concentrated liquid was fed to the degassing unit to degas the carbon dioxide, and the carbon dioxide discharged from the degassing unit and the discharged liquid were collected.

[0091] The carbon dioxide and nitrogen content of the residual gases discharged from the inlet unit was measured, and the composition of the carbon dioxide discharged from the degassing unit was measured. Based on these results, the carbon dioxide absorption rate was calculated and is shown in Table 1. [Table 1] Assignment First electrolyte solution pH value of the first electrolyte solution pH value of the drain fluid Carbon dioxide absorption rate [%] Comparative example 1 Water 7 4,65 94,42 Comparative example 2 2 M KHCO3 8,6 8,23 83,94 Example 1 0.1 M K2CO3 11,61 8,12 99,9

[0092] Table 1 shows that Example 1, in which the first electrolyte solution with a pH of 9 to 12.5 was used, had a high absorption rate of the carbon dioxide contained in the gas mixture and was able to recover high-purity carbon dioxide from the degassing unit compared to Comparison Example 1 and Comparison Example 2.

[0093] Fig.Figure 4 shows a diagram of the concentration of carbon dioxide emitted from the carbon dioxide capture system according to Example 1. In particular, after carrying out a procedure for dissolving carbon dioxide in the initial electrolyte solution in the inlet unit, the concentration of carbon dioxide in the residual gases discharged from the inlet unit was measured. It was found that the initial dissolution rate of the carbon dioxide was 99.99% and lasted for approximately 80 minutes. Example 2

[0094] The drain liquid obtained in Example 1 was reacted with calcium hydroxide in a 1:1 molar ratio. Specifically, calcium hydroxide powder was added to the drain liquid and allowed to react for approximately 5 minutes at room temperature (20°C ± 5°C). The reaction corresponds to the reaction formula 2 described above and shown below. [Reaction formula 2] KHCO3 + Ca(OH)2 → KOH + H2O + CaCO3

[0095] After the reaction, the aqueous alkaline solution had a pH of approximately 13.28, and the precipitate was collected and subjected to X-ray diffraction analysis. The results are presented in Fig. 5 shown. With reference to Fig. 5. It was determined that the precipitation was calcium carbonate (CaCO3).

[0096] According to the present disclosure, carbon dioxide remaining in the draining fluid could also be separated in the form of carbonate. Examples 3 to 7, comparative example 3 and comparative example 4

[0097] A second electrolyte solution was prepared by reacting the drain liquid obtained in Example 1 with the aqueous alkaline solution obtained in Example 2 in the molar ratio given in Table 2 below. The drain liquid contained potassium bicarbonate (KHCO3). The aqueous alkaline solution contained potassium hydroxide (KOH). The second electrolyte solution contained potassium bicarbonate (KHCO3).

[0098] The pH value of every second electrolyte solution was measured. [Table 2] Assignment KHCO3 : KOHmol ratio pH value of the second electrolyte solution 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

[0099] Referring to Table 2, if the molar ratio of the remaining portion of the drain liquid and the aqueous alkaline solution reacted in the second reaction unit was in the range of 1:0.5 to 1:1.2, the pH of the second electrolyte solution was adjusted to a level similar to that of the first electrolyte solution (9 to 12.5) so that the second electrolyte solution could be recycled to an electrolyte solution in the carbon dioxide capture system. At a high pH of the second electrolyte solution, salt precipitated on the inlet separation membrane and / or the degassing separation membrane. This reduced the contact area of ​​the materials. Consequently, the dissolution rate could decrease, and the separator could be damaged.

[0100] Since the experimental examples and examples of this disclosure have been described in detail above, the scope of this disclosure is not limited to the experimental examples and examples described above. Various modifications and improvements made by those skilled in the art using the basic concept of this disclosure as defined in the following claims also fall within the scope of this disclosure.

Claims

Carbon dioxide capture system comprising: an electrolyte storage unit configured to store, retain, or contain a first electrolyte solution containing an aqueous alkaline carbonate solution; an inlet unit in liquid connection with the electrolyte storage unit and a gas supply, the inlet unit being configured to (i) receive the first electrolyte solution from the electrolyte storage unit, (ii) receive a carbon dioxide-containing gas mixture from the gas supply, and (iii) produce a concentrated liquid by dissolving the carbon dioxide from the gas mixture in the first electrolyte solution;a degassing unit in liquid connection with the inlet unit and a drain, wherein the degassing unit is configured to (i) degasse carbon dioxide from the concentrated liquid supplied by the inlet unit, thus providing a degassed concentrated liquid, and (ii) discharge the carbon dioxide; a distribution unit in liquid connection with the degassing unit and with at least one distribution line, wherein the distribution unit is configured to (i) receive the degassed concentrated liquid from the degassing unit and distribute the degassed concentrated liquid via the at least one distribution line;a first reaction unit in liquid connection with the distribution unit and configured to react at least a portion of the degassed concentrated liquid from the distribution unit with a hydroxide under conditions to produce a carbonate and an aqueous alkaline solution; and a second reaction unit in liquid connection with (a) the electrolyte storage unit, (b) the distribution unit, and (c) the first reaction unit, configured to (i) react the remaining portion of the degassed concentrated liquid from the distribution unit with an amount of the aqueous alkaline solution from the first reaction unit to produce a second electrolyte solution, and (ii) supply the second electrolyte solution to the electrolyte storage unit. System according to claim 1, wherein the aqueous alkaline carbonate solution comprises one or more solutions selected from the group consisting of an aqueous sodium carbonate solution (Na2CO3), an aqueous potassium carbonate solution (K2CO3) and combinations thereof. System according to claim 1, wherein the aqueous alkaline carbonate solution has a concentration of 0.0001 M to 0.5 M. System according to claim 1, wherein the first electrolyte solution has a pH value of 9 to 12.

5. System according to claim 1, wherein the inlet unit comprises an inlet separating membrane which divides its interior into an electrolyte flow space and a gas mixture flow space, and wherein the inlet separating membrane is permeable to the carbon dioxide contained in the gas mixture which flows in the gas mixture flow space and allows the carbon dioxide to diffuse into the first electrolyte solution in the electrolyte flow space. System according to claim 1, wherein the gas mixture comprises one or more gases selected from by-product gas of steel production, exhaust gas and combinations thereof. System according to claim 1, wherein the gas mixture flow chamber has a pressure of 0.1 bar to 10 bar. System according to claim 1, wherein the pressure in the gas mixture flow chamber is lower than the pressure in the electrolyte flow chamber, wherein the pressure difference between the gas mixture flow chamber and the electrolyte flow chamber is in a range of 3 bar or less. System according to claim 1, wherein the ratio between the flow rate of the gas mixture and the flow rate of the first electrolyte solution supplied to the inlet unit is in a range of 0.1 to 15. System according to claim 1, wherein the concentrated liquid has a pH value of 6 to 9. System according to claim 1, wherein the degassing unit comprises a degassing separation membrane which divides its interior into a flow space for concentrated liquid and a carbon dioxide flow space, and wherein the degassing separation membrane is permeable to the carbon dioxide contained in the concentrated liquid which flows in the flow space for concentrated liquid and allows the carbon dioxide to pass through the degassing separation membrane to be released into the carbon dioxide flow space. System according to claim 1, wherein the draining fluid comprises one or more fluids selected from an aqueous sodium bicarbonate (NaHCO3) solution, an aqueous potassium bicarbonate (KHCO3) solution and combinations thereof. System according to claim 1, wherein the draining liquid has a pH value of 7 to 9. System according to claim 1, wherein the hydroxide comprises a hydroxide of one or more metal ions of calcium (Ca), magnesium (Mg), strontium (Sr), copper (Cu), lithium (Li), barium (Ba), iron (Fe) and combinations thereof. System according to claim 1, wherein the molar ratio of the portion of the draining liquid and the hydroxide reacted with each other in the first reaction unit is in the range of 1:0.5 to 1:

2. System according to claim 1, wherein the carbonate comprises a carbonate of one or more metal ions from calcium (Ca), magnesium (Mg), strontium (Sr), copper (Cu), lithium (Li), barium (Ba), iron (Fe) and combinations thereof, and the first reaction unit further comprises a filter unit configured to separate and recover the carbonate. System according to claim 1, wherein the aqueous alkaline solution comprises one or more solutions of an aqueous sodium hydroxide (NaOH) solution, an aqueous potassium hydroxide (KOH) solution and combinations thereof. System according to claim 1, wherein the aqueous alkaline solution has a pH value of 12 to 14. System according to claim 1, wherein a molar ratio between the remaining part of the draining liquid and the aqueous alkaline solution which are reacted together in the second reaction unit is in a range of 1:0.5 to 1:1.

2. System according to claim 1, wherein the second electrolyte solution drained from the second reaction unit has a pH value of 9 to 12.5.

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