KR20180133688A - Method for separating carbon dioxide and system for separating carbon dioxide - Google Patents

Abstract

The present invention relates to a system and a method for selectively separating carbon dioxide from industrial waste gas or the like based on an electrochemical system. By using the system and the method for separating carbon dioxide, concentrated carbon dioxide with high purity can be efficiently separated from a gas mixture with minimum energy.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for separating carbon dioxide and a carbon dioxide separation system,

The present invention relates to a method and system capable of selectively separating carbon dioxide from industrial waste gases and the like.

Carbon dioxide (CO ₂ ) is known as a typical greenhouse gas that causes global warming. Recently, it has been reported that it causes acidification of seawater and rainwater, thereby adversely affecting ecosystem. It is also known that when the concentration of atmospheric carbon dioxide exceeds the standard value (0.038% v / v), it causes respiratory diseases and suffocation. Therefore, it is a common obligation for countries around the world to recognize the problems that occur when the concentration of atmospheric carbon dioxide exceeds the standard value and to reduce the emission of carbon dioxide. Starting with the Vienna Convention in 1985, the CO 2 emissions were limited by the Montreal Protocol (1987), the Climate Change Convention (1992), the Kyoto Protocol (1997), and the Paris Agreement (2015) .

Carbon dioxide is a major source of gas in the combustion process of fossil fuel-based fuels such as coal and oil. The use of fossil fuels and the positive correlation between GDP and population growth and industrial development have accelerated the generation of carbon dioxide, which is still increasing. Currently, 80 million tons of carbon dioxide is generated annually.

Generally, about 8 to 15% of carbon dioxide is contained in fossil fuel-based exhaust gas. Accordingly, CCUS (Carbon Capture Utilization and Storage) technology, which combines Carbon Capture and Storage (CCS), which captures and stores carbon dioxide, and Carbon Capture and Utilization (CCU), which captures and recycles carbon dioxide, is attracting attention.

CCUS technology encompasses all technologies for selectively separating, transporting, storing and exploiting carbon dioxide in exhaust gases. In the currently commercialized CCUS process, the collection stage accounts for 50% to 70% of the total cost, so an efficient and low-cost collection method is required to reduce the processing cost.

Currently, there are three methods for separating and collecting carbon dioxide. These three methods are pre-combustion, post-combustion, and oxy-fuel combustion. Combustion after combustion is a method for separating carbon dioxide from the mixture gas generated after fuel combustion. The pre-combustion trap is a method for separating carbon dioxide from a mixture of carbon dioxide and hydrogen in the fuel through oxygen, and oxygen combustion is a method for separating carbon dioxide It is a method of separating carbon dioxide with water through oxygen. Each capture method converts the carbon dioxide in the fuel into a gas form and then separates it by absorption, adsorption, and membrane. Different separation methods are applied according to the demand type of the fuel. Among the separation methods, the absorption method is the most effective method and selectively captures carbon dioxide in the exhaust gas through chemical bonding with carbon dioxide using an amine-based material as an absorbent. However, carbon dioxide ionized by chemical bonding has a disadvantage in that it is difficult to reverse to a gas form which is easy to recycle, and an additional step is required to recycle the used absorbent.

The present invention is intended to provide a method and system capable of selectively separating carbon dioxide from industrial waste gases and the like.

According to an embodiment of the present invention, there is provided a plasma display panel comprising: a first electrode; A second electrode; A cation exchange membrane positioned between the first electrode and the second electrode; And a pair of first and second compartments separated by the cation exchange membrane, the first compartment being located on the first electrode side and the second compartment being located on the second electrode side. A carbon dioxide ion or a salt thereof is generated by trapping carbon dioxide in a mixed gas containing carbon dioxide in a second compartment where a voltage is applied so that the first electrode becomes an anode and the second electrode becomes a cathode, Stage 1; And a second step of recycling the carbonic acid ions or salts thereof to carbon dioxide in a second compartment where hydrogen ions are generated by applying a voltage such that the first electrode is a cathode and the second electrode is an anode. Method is provided.

According to another embodiment of the present invention, there is provided a carbon dioxide separation system in a gas mixture containing carbon dioxide, comprising: a first electrode; A second electrode; A cation exchange membrane positioned between the first and second electrodes; A pair of first and second compartments separated by the cation exchange membrane, the compartment being located in a first compartment and a second compartment located on the first electrode side; And a power supply device for applying a voltage such that the first electrode becomes an anode and the second electrode becomes a cathode, and then applies a voltage such that the first electrode becomes a cathode and the second electrode becomes an anode, System is provided.

The carbon dioxide separation method and the carbon dioxide separation system according to an embodiment of the present invention can selectively remove carbon dioxide from industrial waste gas and the like with low energy. As a result, carbon dioxide, a representative greenhouse gas, can be economically and efficiently removed. In addition, the method and system are expected to provide carbon dioxide that is useful for applications requiring ultra-high purity carbon dioxide, such as chemical reaction processes, by providing high purity, concentrated carbon dioxide.

FIG. 1 is a schematic view showing a first step (10) and a second step (20) using an electrolytic apparatus including a pair of first and second compartments separated by a cation exchange membrane.
FIG. 2 shows a first step 10, a second step 20 and a second step 20 after the second step using an electrolytic apparatus comprising a pair of first and second compartments separated by a cation exchange membrane. Fig. 8 is a schematic view showing a step 10 '.
3 schematically shows a first stage 10 and a second stage 20 using an electrolytic apparatus including two pairs of first and second compartments including one bipolar membrane .
4 is a diagram schematically showing an electrolytic apparatus including five bipolar membranes including four bipolar membranes.
FIG. 5 is a graph showing changes in the concentration of inorganic carbon in the second compartment with time when a voltage of 2.5 V and 3 V is applied to the first and second electrodes in Example 1. FIG.

Hereinafter, a carbon dioxide separation method, a carbon dioxide separation system, and the like according to a specific embodiment of the present invention will be described.

According to an embodiment of the present invention, there is provided a plasma display panel comprising: a first electrode; A second electrode; A cation exchange membrane positioned between the first electrode and the second electrode; And a pair of first and second compartments separated by the cation exchange membrane, the first compartment being located on the first electrode side and the second compartment being located on the second electrode side. A carbon dioxide ion or a salt thereof is generated by trapping carbon dioxide in a mixed gas containing carbon dioxide in a second compartment where a voltage is applied so that the first electrode becomes an anode and the second electrode becomes a cathode, Stage 1; And a second step of recycling the carbonic acid ions or salts thereof to carbon dioxide in a second compartment where hydrogen ions are generated by applying a voltage such that the first electrode is a cathode and the second electrode is an anode. Method is provided.

The method of separating carbon dioxide according to one embodiment can selectively remove carbon dioxide from industrial waste gas or the like with low energy based on the electrochemical system. Accordingly, the carbon dioxide separation method can provide an economical CCUS technology in place of the collecting process which occupies 50 to 70% of the total cost of the conventional CCUS (Carbon Capture Utilization and Storage) technology, It is possible to efficiently remove carbon dioxide, which is a representative greenhouse gas.

The method of separating carbon dioxide according to one embodiment can provide concentrated carbon dioxide of high purity. Therefore, it is expected that the method of separating carbon dioxide according to one embodiment can provide carbon dioxide which is useful in a field requiring ultra-high purity carbon dioxide, for example, a chemical reaction process in which carbon dioxide is used as a precursor.

In addition, the method of separating carbon dioxide according to one embodiment of the present invention uses an amine-based trapping agent, which is a typical trapping agent for carbon dioxide, or a hydroxide ion generated by electrolysis of water instead of ammonia, and thus regenerates to recover the carbon dioxide- There is an advantage that a separate process is not necessary.

Hereinafter, a method for separating carbon dioxide according to one embodiment will be described in detail with reference to FIG.

Referring to FIG. 1, the method for separating carbon dioxide includes a first electrode (1st EL); A second electrode (2nd EL); A cation exchange membrane (CEM) positioned between the first electrode and the second electrode; And a pair of first and second compartments separated by the cation exchange membrane, wherein the first compartment (1st CP) located on the first electrode side and the second compartment ; ≪ / RTI > 2nd CP). The device may be referred to herein as an electrolysis device.

In the first step, when a voltage is applied such that the first electrode is an anode and the second electrode is a cathode, an oxidation reaction occurs in the first compartment located on the first electrode side relative to the cation exchange membrane, And a reduction reaction may occur in the second section located on the second electrode side. That is, in this specification, 'anode' means 'oxidizing electrode' and 'cathode' means 'reducing electrode'.

In the first step, if a voltage is applied so that the first electrode becomes an anode and the second electrode becomes a cathode, hydrogen ions may be generated in the first compartment and hydroxide ions may be generated in the second compartment (see 10 in FIG. 1) .

For example, if the first electrode is provided in the first compartment, hydrogen ions may be generated due to the oxidation reaction as shown in Equation 1 or 2 below.

[Formula 1]

2H ₂ O → 4H ⁺ + O ₂ + 4e ^-

[Formula 2]

H ₂ ^- & gt ^; 2H ⁺ + 2e ^-

If the second electrode is provided in the second compartment, hydroxide ions may be generated due to a reduction reaction as shown in the following formula (3).

[Formula 3]

2H ₂ O + 2e ^- ? 2OH ^- + H ₂

As another example, if the electrolytic device includes a bipolar membrane as described below (see FIGS. 3 and 4), at least one of the first and second sections may be in contact with the bipolar membrane. When a voltage is applied to the first and second electrodes, water is separated into hydrogen ions and hydroxide ions by the bipolar membrane. If the voltage is applied to the first and second electrodes so that the first electrode is an anode and the second electrode is a cathode, the first and second compartments, which are in contact with the bipolar membrane, Hydroxide ions are supplied to the second compartment where hydrogen ions are supplied and which are in contact with the bipolar membrane.

On the other hand, if a voltage is applied such that the first electrode is a cathode and the second electrode is an anode in the second step, the same reaction as the second compartment in the first compartment occurs in the first compartment, The same reaction as the first compartment of the first stage occurs.

For example, if a first electrode is provided in the first compartment and a second electrode is provided in the second compartment, a reduction reaction occurs in the first compartment of the second stage to generate hydroxide ions, In the two compartments, an oxidation reaction occurs as shown in the formula 1 or 2 to generate hydrogen ions (see 20 in FIG. 1).

In another example, as described above, the electrolytic device includes a bipolar membrane (see FIGS. 3 and 4), and in accordance with the second step, the first and second electrodes are made to be the cathode and the anode, respectively, When a voltage is applied to the electrode, hydroxide ions are supplied to the first compartment in contact with the bipolar membrane and hydrogen ions are supplied to the second compartment in contact with the bipolar membrane (see 20 in FIG. 3).

Accordingly, the kind of ions generated in the first and second compartments can be determined depending on which of the first and second electrodes is a positive or negative electrode.

The first and second compartments may be filled with a solvent in which electrolytes are dissolved for stable operation of the electrolytic apparatus, high collection efficiency and re-conversion efficiency of carbon dioxide. The solvent may be water, and the electrolyte may be various salts that dissolve in water and dissociate into cations and anions. By way of non-limiting example, the electrolyte may be a hydrochloride, sulfate, nitrate, carbonate, hydroxide, oxide, or a mixture thereof. More specifically, the electrolyte is selected from the group consisting of sodium chloride, potassium chloride, lithium chloride, rubidium chloride, calcium chloride, magnesium chloride, sodium sulfate, potassium sulfate, lithium sulfate, rubidium sulfate, calcium sulfate, magnesium sulfate, sodium nitrate, Potassium carbonate, calcium carbonate, magnesium carbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, calcium hydroxide, magnesium hydroxide, sodium oxide, potassium oxide, lithium oxide, calcium carbonate, magnesium carbonate, sodium carbonate, potassium carbonate, lithium carbonate, rubidium carbonate, Rubidium oxide, calcium oxide, magnesium oxide, aluminum oxide, or a mixture thereof.

In the method of separating carbon dioxide, a voltage is applied to the first and second electrodes so that hydrogen ions are generated in any one of the first and second compartments and hydroxide ions are generated in the other of the first and second compartments . The applied voltage is determined by the type and concentration of the electrolyte contained in the first and second compartments, the kind of oxidation reaction occurring in any one of the first and second compartments, or the reduction reaction occurring in the other compartment of the first and second compartments Type and the like.

More specifically, the first electrode and the second electrode are provided with a voltage of not less than 0.42 V, not less than 0.83 V, not less than 1.03 V or not less than 2.06 V, not more than 10 V, not more than 7 V, not more than 5 V, The following voltage can be applied. Within this range, carbon dioxide in the mixed gas can be efficiently separated with a small energy.

According to the method for separating carbon dioxide in the embodiment, the mixed gas may be directly supplied to any one of the first and second compartments to collect carbon dioxide in the mixed gas in any of the compartments. As described later, in the first step, the mixed gas is directly fed to the second compartment to collect carbon dioxide in the mixed gas. In the second step, the mixed gas is directly fed to the first compartment to collect the carbon dioxide in the mixed gas, When the first step is repeated, the carbon dioxide in the mixed gas can be collected by directly supplying the mixed gas to the second compartment. Accordingly, the carbon dioxide separation method is advantageous in that it is not necessary to provide a separate collecting device such as a scrubber in order to collect carbon dioxide in the mixed gas.

The mixed gas may be applied to the first and second electrodes before applying a voltage to the first and second electrodes, or after applying a voltage to the first and second electrodes, It can be supplied to any one compartment.

For example, the mixed gas may be supplied after sufficiently generating hydroxide ions in any one of the first and second compartments by applying a voltage to the first and second electrodes. Specifically, when the voltage is applied to the first and second electrodes, hydroxide ions are sufficiently generated, the pH of any one of the first and second compartments is about 10 to 14, about 11 to 14, about 12 To about 14, about 13 to about 14, about 10 to about 13, about 11 to about 13, about 12 to about 13, about 10 to about 12, about 11 to about 12 or about 10 to about 11. By supplying the mixed gas to any one of the compartments having such a pH, it is possible to improve the collection efficiency of carbon dioxide in the mixed gas.

The mixed gas may be supplied continuously or periodically to any one of the first and second sections. In one example, the mixed gas may be supplied periodically when the pH of any one of the first and second compartments reaches the above-described range.

The method for separating carbon dioxide can separate pure carbon dioxide from various mixed gases containing carbon dioxide. Examples of such a mixed gas include a mixed gas requiring separation of carbon dioxide, an industrial waste gas discharged from a natural gas power plant, a cement refinery, etc., and an exhaust gas discharged from a combustion process of a fuel.

The ratio of carbon dioxide in the mixed gas is not particularly limited, but may be 2 vol% or more, 5 vol% or more, 10 vol% or more, 15 vol% or more, 20 vol% or more, 30 vol% or more, 40 vol% % ≪ / RTI > In this range, more pure and concentrated carbon dioxide can be obtained. On the other hand, the upper limit of the carbon dioxide ratio in the mixed gas is not particularly limited, and may be 100 vol% or less, 90 vol% or less, 80 vol% or less, 70 vol% or 60 vol% or less.

In the first step, the second partition is a region where hydroxide ions are generated when a voltage is applied to the first and second electrodes. Accordingly, in the first step, carbon dioxide in the mixed gas supplied to the second compartment according to the following formula (4) can be selectively collected by hydroxide ions present in the second compartment.

[Formula 4]

CO ₂ + OH ^- > HCO ₃ ^-

In the method for separating carbon dioxide according to this embodiment, the carbon dioxide in the mixed gas can be collected at atmospheric pressure. The atmospheric pressure means the natural pressure which is not pressurized or decompressed. Specifically, the carbon dioxide in the mixed gas can be collected in a pressure range of about 0.100 to 0.102 MPa.

Also, in the method for producing carbon dioxide according to one embodiment, the carbon dioxide in the mixed gas may be collected at a temperature of about 15 to 80 ° C or about 15 to 60 ° C. Accordingly, the mixed gas such as the industrial waste gas or the exhaust gas can be directly supplied to the first or second compartment without cooling, and the carbon dioxide can be collected from the mixed gas.

The pH of any one of the first and second compartments in which carbon dioxide is trapped in the mixed gas may be at least about 4, at least about 5, at least about 6, at least about 7, at least about 8, at least about 9, at least about 10, 11, or about 12 or more, and can be about 14 or less, about 13 or less, or about 12 or less. Among these, in order to selectively capture carbon dioxide, the pH of any one of the first and second compartments in which carbon dioxide is captured in the mixed gas is about 10 to 14, about 11 to 14, about 12 to 14, about 13 to 14, About 10 to about 13, about 11 to about 13, about 12 to about 13, about 10 to about 12, about 11 to about 12, or about 10 to about 11.

On the other hand, the mixed gas carbon dioxide is selectively captured by the hydroxyl ion bicarbonate ion (HCO ₃ ^-) The bicarbonate ion (HCO ₃ ^-) to generate the higher the pH is changed to carbonate ions (CO ₃ ^2-) . Therefore, the carbon dioxide in the mixed gas supplied to any one of the first and second compartments can be collected by the hydroxide ions to produce carbonate ions and / or carbonate ions. In the present specification, the term " carbonate ion " is used to collectively refer to a carbonate ion, a carbonate ion, or a mixture of a carbonate ion and a carbonate ion.

Further, when carbon dioxide capture is continuously performed in any one of the first and second compartments, the concentration of the carbonic acid ions in any one of the compartments is increased, and some carbonate ions combine with the dissociated cations in the electrolyte to form salts Can be precipitated. Therefore, when a mixed gas is supplied to any one of the first and second compartments in which a voltage is applied to the first and second electrodes and hydroxide ions are generated, the carbon dioxide in the mixed gas is collected to form carbonic acid ions, A salt thereof, or a salt of a carbonate ion may be produced.

In order to improve the collection efficiency of carbon dioxide, any one of the above-described electrolytes in which the hydroxide ions in the first and second compartments are generated may include a carbonate, a hydroxide, or a mixture thereof. That is, in the first stage, the second compartment may contain a carbonate, a hydroxide, or a mixture thereof as an electrolyte, and the first compartment in the second stage may include a carbonate, a hydroxide, or a mixture thereof as an electrolyte. Therefore, in the first step, carbonate, hydroxide or a mixture thereof is supplied to the second compartment, and carbonate, hydroxide or a mixture thereof is supplied to the first compartment in the second step.

Specific examples of the carbonate, hydroxide and mixtures thereof include sodium carbonate, potassium carbonate, lithium carbonate, rubidium carbonate, calcium carbonate, magnesium carbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, magnesium hydroxide, magnesium hydroxide, .

The carbonates supplied as electrolytes to any one of the first and second compartments in which hydroxide ions are generated are dissociated into cations and carbonate ions (CO ₃ ^2- ), and the carbonate ions are dissolved in carbon dioxide Can be collected to generate hydrogen carbonate ions.

[Formula 5]

CO ₂ + CO ₃ ^2- + H ₂ O ^- > 2HCO ₃ ^-

Also, the hydroxide supplied as an electrolyte to one of the compartments in which hydroxide ions are generated in the first and second compartments is also dissociated into cations and hydroxide ions, and the hydroxide ion collects carbon dioxide in the mixed gas, Hydrogen ions can be generated.

The carbon dioxide in the initial mixed gas can be stably trapped by the carbonate, the hydroxide, or the mixture thereof supplied as the electrolyte to one of the compartments in which the hydroxide ion is generated in the first and second compartments. The carbon dioxide in the mixed gas can be continuously collected by the hydroxide ions generated by applying the voltage to the first and second electrodes.

The hydroxide ions dissociated from the carbonate ions dissociated from the carbonate supplied to the electrolyte and the hydroxide supplied to the electrolyte or generated by applying the voltage to the first and second electrodes have an advantage of selectively capturing the carbon dioxide in the mixed gas, There is an advantage in that the carbon dioxide can be regenerated without supplying any additional energy in the second step of re-conversion to carbon dioxide.

The concentration of the carbonate, hydroxide, or mixture thereof supplied to the electrolyte can be appropriately adjusted in consideration of the collection efficiency and economical efficiency of the carbon dioxide. Specifically, the electrolyte may be supplied at a concentration below the saturation concentration of the electrolyte, and more specifically, the electrolyte may be supplied at 1% to 50%, 1% to 30%, or 22% to 28% have. As an example, the saturation concentration of sodium carbonate at 15 ° C is 1.55 M. Therefore, when sodium carbonate is used as the electrolyte, the concentration of sodium carbonate in the first and second compartments in which hydroxide ions are generated ranges from 0.0155 to 0.775 M, 0.0155 to 0.465 M, or 0.341 to 0.434 M based on 15 ° C, Can be supplied. Within this range, it is possible to collect carbon dioxide economically and efficiently.

In the first step, when carbon dioxide is collected to sufficiently generate carbonate ions or salts thereof, a voltage may be applied such that the first electrode becomes the cathode and the second electrode becomes the anode.

When carbon dioxide is captured and the carbonate ion or its salt is sufficiently generated, the pH of the first or second compartment, the concentration of carbonic acid ions in the electrolyte of the first or second compartment, or the electrical conductivity of the first or second compartment And so on.

For example, when a voltage is applied to the first and second electrodes in the first step, hydroxide ions are generated in the second compartment, so that the second compartment has a high pH or, in the first step, The second compartment may exhibit a high pH by feeding a carbonate, hydroxide or mixtures thereof. However, since the hydroxide ion and carbonate ion are used to collect carbon dioxide as shown in Equation 4 and Equation 5, the pH of the second compartment in the first step is gradually lowered as carbon dioxide is collected. As a result of experiments conducted by the present inventors, it has been found that as the carbon dioxide is collected in the first step, the pH of the second compartment gradually decreases to reach a constant value of about 7 to 9, about 7 to 8.5 or about 7.5 to 8.5 Respectively. It can be seen that the reaction of the second compartment reaches equilibrium since the pH of the second compartment of the first stage is maintained at a constant value. Accordingly, when the pH of the second compartment of the first stage is maintained at a constant value between about 7 and 9, the voltage may be applied such that the first electrode becomes the cathode and the second electrode becomes the anode.

As another example, hydrogen ions are continuously generated in the first compartment while the carbon dioxide is collected in the second compartment of the first stage, so that the pH of the first compartment is gradually lowered. Accordingly, when the pH of the first compartment of the first step is 0 to 3, 1 to 3, 2 to 3, 0 to 2, 1 to 2 or 0 to 1, the first electrode becomes the cathode, A voltage can be applied so as to be an anode.

As another example, if the concentration of the carbonic acid ions in the second compartment is directly or indirectly measured to generate sufficient carbonic acid ions, for example, if the concentration is higher than the saturated concentration, the first electrode becomes the cathode and the second electrode A voltage can be applied so as to be an anode.

As another example, as the carbon dioxide is captured in the second compartment of the first stage, the concentration of carbonic acid ions increases to increase the electrical conductivity of the second compartment. Thus, the electrical conductivity of the second compartment of the first stage is measured so that the increase in the electrical conductivity is from 0 mS / cm to 50 mS / cm, from 10 mS / cm to 50 mS / cm, from 20 mS / cm to 50 mS / cm, The voltage can be applied so that the first electrode becomes the cathode and the second electrode becomes the anode when the mobility is from 30 mS / cm to 50 mS / cm or from 40 mS / cm to 50 mS / cm.

The method of applying the voltage to the first and second electrodes so that the first electrode functioning as the anode in the first step becomes the cathode and the second electrode functioning as the cathode become the anode is not particularly limited, and the first and second By setting which one of the first and second electrodes functions as an anode or a cathode in a power supply connected to the electrode and applying a voltage to the first and second electrodes. Normally, it is very easy to set which of the two electrodes in the power supply apparatus is to function as the anode. Therefore, when a signal indicating that carbonate ions or salts thereof are sufficiently generated through the sensors installed in the first and second compartments is received, the first and second steps can be performed by setting the anode and the cathode to be mutually changed. Signals that the carbonate ion or its salt is sufficiently generated means that the pH of the first or second compartment, the concentration of the carbonate ion or the electric conductivity has reached a certain value, as described above.

When a voltage is applied to the first and second electrodes so that the first electrode functioning as an anode functions as a cathode and the second electrode functioning as a cathode functions as an anode in the first step, The salt is converted back to carbon dioxide.

Specifically, when a voltage is applied to the first and second electrodes so that the first electrode is a cathode and the second electrode is an anode, the first compartment becomes a region where hydroxide ions are generated and the second compartment generates hydrogen ions Area. Therefore, the carbonate ion or its salt present in the second compartment can be converted to carbon dioxide according to the following equations (6) and (7), according to the principle of maintaining pH equilibrium. Specifically, the carbonate ion dissolved in the electrolytic solution or the carbonate ion dissociated from the carbonate is converted into a bicarbonate ion as shown in the following Formula 6, and the hydrogen carbonate ion can be converted into carbon dioxide as shown in Formula 7 below.

[Formula 6]

CO ₃ ^2- + H ^{+ -} & gt ^; HCO ₃ ^-

[Equation 7]

HCO ₃ ^- + H ^{+ -} & gt ^; CO ₂ + H ₂ O

In particular, in the method of separating carbon dioxide according to one embodiment, since carbon dioxide or hydroxide ions are used as a trapping agent, it is possible to convert the captured carbon dioxide into carbon dioxide without adding any additives or supplying energy.

The second step may convert the carbonate ion or its salt to carbon dioxide under atmospheric pressure. Specifically, the carbonate ion or its salt may be recycled to carbon dioxide at a pressure range of about 0.100 to 0.102 MPa.

Further, in the second step, the carbonate ion or its salt may be recycled to carbon dioxide at a temperature of about 15 to 80 ° C or about 15 to 60 ° C. Accordingly, even if the mixed gas such as industrial waste gas or exhaust gas is used immediately without cooling, carbon dioxide can be separated from the mixed gas with excellent efficiency.

The pH of the second compartment in which the carbonate ion or salt thereof is converted back to carbon dioxide in the second step may be about 7 or less, about 6 or less, about 5 or less, about 4 or less, about 3 or less or about 2 or less, 0 or more, about 1 or more, or about 2 or more. Among these, the pH of the second compartment in the second stage is preferably from about 0 to about 6, from about 0 to about 5, from about 0 to about 4, from about 0 to about 3, from about 0 to about 2, from about 0 to about 1 About 1 to about 6, about 1 to about 5, about 1 to about 4, about 1 to about 3, about 2 to about 6, about 2 to about 5, about 2 to about 4, or about 2 to about 3.

On the other hand, when hydrogen ions are generated through the oxidation reaction of hydrogen gas, a lower voltage is required compared with the case where hydrogen ions are generated through oxidation reaction of water. In the second compartment of the first stage, hydrogen gas is generated according to Equation 3. In the second compartment of the second stage, the hydrogen gas is oxidized to generate hydrogen ions, thereby further saving energy.

Specifically, in the second step, when the carbonic acid ion or its salt is converted into carbon dioxide by the hydrogen ion generated through the oxidation reaction of the hydrogen gas as shown in Formula 2, the first and second electrodes are implanted with 0.83 V to 2 V Can be applied. By applying a voltage in this range, the energy for separating carbon dioxide can be greatly reduced. The theoretical voltage for generating hydrogen ions and oxygen gas by oxidizing water is 2.06 V. Therefore, by controlling the voltage range as described above, the hydrogen gas produced in the second compartment of the first stage is consumed and the generation of oxygen gas in the second compartment of the second stage is suppressed, thereby improving the purity of carbon dioxide .

On the other hand, as the ratio of carbon dioxide in the mixed gas increases, the efficiency of collecting carbon dioxide increases and the purity and yield of carbon dioxide obtained by recycling the carbonate ion or its salt can be improved. Accordingly, the method for separating carbon dioxide according to one embodiment can pre-process the mixed gas before the first step.

For example, a gas other than carbon dioxide may be removed from the mixed gas by bringing the mixed gas into contact with the solvent before supplying the mixed gas to the first or second compartment.

When using the industrial waste gases, such as described above in the mixed gas mixed gas of carbon dioxide in addition to gases such as _{SO x, HF, HCl, NH} 3, Cl 2, SiF 4, O 2, N 2, CO, NO x, SH 2 . ≪ / RTI >

CO ₂ does not dissolve well in water having a pH of 3.5 to 5.5, but SO _x , HF, HCl, NH ₃ , Cl ₂ , SiF ₄ and the like can be dissolved smoothly. Therefore, pH is about 3.5 to 7, 3.5 to 6, from about 3.5 to 5.5, about 3.5 to 5, or is contacted with from about 3.5 to 4, the water for the water in the pH range than the CO ₂ from the gas mixture to the gas mixture A gas having a high solubility such as SO _x , HF, HCl, NH ₃ , Cl ₂ , SiF ₄ and the like can be removed in advance.

Specifically, the mixed gas is passed through a container or a tube containing water in the pH range, or water in the pH range is injected into the flow of the mixed gas to remove other gases than CO _{2 in} the mixed gas in advance .

For example, the step of pretreating the mixed gas may be performed using a scrubber. Specifically, a pretreated mixed gas can be obtained by filling the scrubber with water having the above-mentioned pH range and then dispersing the mixed gas at a high pressure through a multicomponent sparger or the like into the scrubber. In addition, a mixed gas may be supplied to the inlet of the scrubber, and water of the pH range may be injected into the flow of the mixed gas to obtain a mixed gas pretreated from the outlet of the scrubber.

In addition, the gas other than CO _{2 that} has not been removed in the pretreatment step can be removed naturally because it is not dissolved in the electrolytic solution of the high pH of one of the compartments in which the hydroxide ions are generated in the first and second compartments. Specifically, gases such as O ₂ , N ₂ , CO, NO _x , and SH _{2 in} the mixed gas are not dissolved in the electrolytic solution having a high pH, and even if a mixed gas containing such gas is supplied to the first or second compartment, It is possible to collect CO ₂ selectively.

On the other hand, the inventors of the present invention have found that when the mixed gas includes CO ₂ and SO ₂ , SO ₂ improves the CO ₂ capturing efficiency and recycling efficiency. Therefore, if the mixed gas includes CO ₂ and SO ₂ , carbon dioxide can be separated from the mixed gas more efficiently even if the pretreatment process is omitted. In addition, sulfuric acid ions (SO ₄ ^2- ) can be obtained from SO ₂ with the separation of carbon dioxide.

Specifically, when the mixed gas is supplied to the second compartment of the first stage as described above, the carbon dioxide in the mixed gas is trapped by the hydroxide ion as shown in the formula (4). The sulfur dioxide in the mixed gas can be collected by the hydroxide ion as shown in the following equation (8).

[Equation 8]

SO ₂ + OH ^- & gt ^; SO ₃ ^2- + H ⁺

At this time, since the mixed gas is not pretreated, the mixed gas may contain NO _x . However, as described above, NO _x is not dissolved in the electrolytic solution of high pH. Therefore, NO _x can be removed because it does not melt into the electrolyte when supplying the mixed gas to the second compartment of the first stage.

As the sulfur dioxide is continuously trapped by the hydroxide ion as shown in the formula 8, the concentration of sulfite ions (sulfite, SO ₃ ^2- ) in the second compartment of the first step is increased as in the carbonate ion, The sulfurous acid ion may bind to a cation derived from an electrolyte or the like and precipitate as a salt. Therefore, when the mixed gas is supplied to the second compartment of the first stage, carbon dioxide in the mixed gas is collected to generate a carbonate ion, a carbonate ion and a salt thereof, or a salt of a carbonate ion, And a sulfite ion, a sulfite ion and its salt, or a sulfite ion salt may be produced.

As described above, a voltage is applied to the first and second electrodes so that the first electrode functioning as the anode in the first step becomes the cathode and the second electrode functioning as the cathode becomes the anode, Ion or a salt thereof to carbon dioxide, and a sulfate ion or a salt thereof from a sulfite ion or a salt thereof. The first and second steps may be performed as described above, unless otherwise described.

The sulfite ion dissociated from the sulfite ion or its salt present in the second compartment of the second step may generate hydrogen ions by reacting with water as shown in the following formula (9).

[Equation 9]

SO ₃ ^2- + H ₂ O → SO ₄ ^2- + 2H ⁺ + 2e ^-

Since the carbonate ion or its salt in the second section of the second step is converted back to carbon dioxide by the hydrogen ion, the reaction of generating the sulfate ion from the sulfite ion generating the hydrogen ion can promote the re-conversion of the carbon dioxide have. In addition, the sulfate ion generated from the sulfite ion can increase the total ion amount in the second section to improve the electric conductivity.

On the other hand, since the pair of first and second compartments are separated by the cation exchange membrane, the hydrogen ions generated in the second compartment of the second stage can be moved to the first compartment through the cation exchange membrane by the electrical attraction. However, even in such a case, the sulfide ion or its salt in the second section additionally generates hydrogen ions as shown in the above formula (9), so that the carbon dioxide conversion efficiency may not be lowered.

On the other hand, in the second section of the second stage, hydrogen ions and oxygen gas are generated due to the oxidation reaction of water as in the above-mentioned formula (1). As a result, not only carbon dioxide but also oxygen gas is released from the second compartment of the second stage, so that the purity of carbon dioxide obtained from the second compartment of the second stage can be lowered. However, in the second step, the sulfite ion dissociated from the sulfite ion or its salt present in the second compartment may consume oxygen gas generated in the second compartment by reacting with oxygen to generate sulfate ions . Accordingly, the purity of carbon dioxide emitted from the second compartment of the second stage can be improved.

[Equation 10]

² SO ₃ ^{2 -} + O ^{2 -} > ₂ SO ₄ ^{2 -}

On the other hand, in order to re-convert carbon dioxide from carbonic acid ions or salts thereof in the second compartment in the second step, hydrogen ions are required. These hydrogen ions are not electrolyzed in water according to the above formula 1 but sulfite ions according to the above formula If it is supplied through the oxidation reaction of the salt, oxygen gas is prevented from being generated in the second compartment of the second stage, and carbon dioxide of high purity can be provided.

Specifically, a voltage of 1.03 V to 2 V may be applied to the first and second electrodes to minimize oxygen gas generated in the second compartment of the second stage. Since the theoretical voltage for generating hydrogen ions and oxygen gas by oxidizing water is 2.06 V, the generation of oxygen gas can be suppressed by adjusting the voltage range as described above.

Meanwhile, in the method for separating carbon dioxide according to one embodiment, the first step may be repeated after the second step. Accordingly, high purity and high concentration of carbon dioxide can be continuously separated from the mixed gas.

Referring to FIG. 2, in the first compartment (1st CP) of the second stage, hydroxide ions are generated similarly to the second compartment (2nd CP) of the first stage (see 10 and 20 in FIG. 2). Therefore, the second step can capture carbon dioxide in the mixed gas containing carbon dioxide in the first compartment to produce carbonic acid ions or salts thereof (see 20 in FIG. 2). Since the method of collecting carbon dioxide in the second compartment of the first stage has been described in detail above, a detailed description of the method of collecting carbon dioxide in the first compartment of the second stage will be omitted. As an example, in the first step, carbonate, hydroxide, or a mixture thereof is supplied to the second compartment as an electrolyte in order to improve the collection efficiency of carbon dioxide. In the second compartment, a carbonate, a hydroxide, The mixture can be fed. Also, in the first compartment of the second stage, sulfur dioxide can be collected together with carbon dioxide, as in the case of collecting sulfur dioxide together with carbon dioxide in the second compartment of the first stage.

As described above, if carbon dioxide in the mixed gas is captured in the first compartment (1st CP) of the second stage to generate carbonic acid ions or salts thereof, hydrogen ions are generated in the first compartment when the first step is repeated The carbonate ion or its salt may be recycled to carbon dioxide (see 10 ' in Fig. 2). This makes it possible to utilize both the first and second compartments of a pair, so that more carbon dioxide can be separated from more mixed gas.

The above-described first and second steps may be performed using the electrolytic apparatus described above. Hereinafter, the electrolytic apparatus used in the carbon dioxide separation method according to one embodiment will be described in detail.

1, the electrolytic apparatus includes a first electrode (1st EL); A second electrode (2nd EL); A cation exchange membrane (CEM) positioned between the first electrode and the second electrode; And a pair of first and second compartments separated by the cation exchange membrane, wherein the first compartment (1st CP) located on the first electrode side and the second compartment ; 2nd CP).

As described above, in the second compartment of the first stage, the carbon dioxide in the mixed gas is captured by the hydroxide ion, and in the second compartment of the second stage, the carbonate ion or its salt can be converted back to carbon dioxide by hydrogen ions . If the pair of first and second compartments are separated by the anion exchange membrane, the hydroxide ions may pass through the anion exchange membrane to the other compartment by electrical attraction, and the collection efficiency of the carbon dioxide may be lowered. On the other hand, if the pair of first and second compartments are separated by the cation exchange membrane, the hydrogen ions may pass through the cation exchange membrane by electrical attraction to the other compartments, thereby reducing the re-conversion efficiency of the carbon dioxide. In the case of the anion exchange membrane, only the ionic hydroxide ion passes through the anion exchange membrane. However, in the case of the cation exchange membrane, in addition to the hydrogen ion, there are dissociated cations from the electrolyte. Considering this point, it can be seen that the degree of reduction of the capture efficiency of the carbon dioxide by the movement of the hydroxide ion by the anion exchange membrane is larger than the degree that the hydrogen ion migrates by the cation exchange membrane to reduce the conversion efficiency of the carbon dioxide. Further, referring to FIG. 1, 20, there are many paths through which hydrogen ions are supplied compared with hydroxide ions. For example, hydrogen ions can be obtained from hydrogen gas generated during the capture of carbon dioxide. When sulfur dioxide is captured together with carbon dioxide, sulfate ions are generated from sulfite ions and hydrogen ions are further generated. Therefore, in the method of separating carbon dioxide according to the above embodiment, both the trapping efficiency and the re-conversion efficiency of carbon dioxide are maintained at a good level by adopting the cation exchange membrane.

The method of separating carbon dioxide according to one embodiment may further include regenerating the electrolyte after the second step. After the electrolyte is regenerated, the first step can be repeated.

The step of regenerating the electrolyte may be performed by mixing the electrolytic solution of the first and second compartments and supplying the uniformly mixed electrolytic solution to the first and second compartments.

More specifically, in the step of regenerating the electrolyte, a voltage is applied to the first and second electrodes to adjust the pH of one of the compartments to 3 to 5, the pH of the other compartment to 11 to 12, And the electrolyte of the second compartment may be mixed to produce an electrolyte solution having a pH of 8 to 10. The electrolytic solution having the pH of 8 to 10 thus produced can be supplied again to the first and second compartments.

The electrolytic apparatus may include at least two pairs of first and second compartments using a bipolar membrane. When a voltage is applied to the first and second electrodes, water is separated into hydrogen ions and hydroxide ions by the bipolar membrane, and the hydrogen ions and the hydroxide ions can move by the electrical attraction. In the electrolytic apparatus, the bipolar membrane may be replaced with a water passage of which the side wall is composed of a bipolar membrane. When water is supplied to the water transfer passages and a voltage is applied to the first and second electrodes, water is separated into hydrogen ions and hydroxide ions in the bipolar membrane in which water is sidewall. Hydrogen ions are supplied to the compartment located on the anode side with respect to the cation exchange membrane located between the first and second compartments of the pair of first and second compartments by electrical attraction, Hydroxide ions can be supplied by the attraction force.

Referring to FIG. 3, the electrolytic apparatus includes a first electrode (1st EL); A second electrode (2nd EL); A bipolar membrane (BM) positioned between the first and second electrodes; Two cation exchange membranes (CEM) positioned between the first electrode (1st EL) and the bipolar membrane (BM) and between the bipolar membrane (BM) and the second electrode (2nd EL); Two first compartments (1st CP) and two second compartments (1st EL) located on the first electrode (1st EL) side and two second compartments (1st CP) separated by the respective cation exchange membranes (CEM) (2 < nd > CP). Referring to FIG. 4, the electrolytic apparatus includes a first electrode (1st EL); A second electrode (2nd EL); Two or more bipolar membranes (BM) positioned between the first and second electrodes; Three or more cation exchange membranes (CEM) positioned between the first electrode (1st EL) and the bipolar membrane (BM), between the bipolar membrane and the bipolar membrane, and between the bipolar membrane (BM) and the second electrode (2nd EL); Three or more pairs of first and second compartments separated by the respective cation exchange membranes (CEM), wherein at least three first compartments (1st CP) located on the first electrode (1st EL) side and a second compartment EL) side of the second partition (2nd CP).

When such an electrolytic apparatus is used, a mixed gas may be supplied to each of the two or more second compartments in the first step. Further, in the second step, the mixed gas may be supplied to each of the two or more first compartments. The carbonic acid ions or salts thereof generated in the compartment may be re-converted to carbon dioxide in the compartment while changing roles of the first and second electrodes as the cathode and the anode.

The electrolytic device may be constructed as is known in the art. Hereinafter, the components constituting the electrolytic apparatus will be described in detail.

As the cation exchange membrane, various types of cation exchange membranes, which are applied to an electrolytic apparatus or a fuel cell, can be used. Specifically, as the cation exchange membrane, for example, Nafion of Dupont Co., Ltd. or CMX of Tokuyama Corporation of Japan may be used.

The first and second electrodes may be disposed at appropriate positions to apply an electrical attraction to the ion species contained in the first and second sections. The shapes of the first and second electrodes are not particularly limited, and may be variously modified as known in the art to which the present invention pertains.

As the first and second electrodes, various types of electrodes applied to an electrolytic device, a fuel cell, or the like may be used. For example, as the first and second electrodes, various types of conductors may be used, or an electrode including an electrode substrate and a catalyst coated on the electrode substrate may be used. As the conductor, a conductor such as titanium (Ti), stainless steel, nickel (Ni), nickel / chromium (Ni / Cr) alloy, platinum (Pt), gold (Au), palladium (Pd), iridium Rh), ruthenium (Ru), or an oxide thereof. In the electrode including the catalyst coated on the electrode substrate, a carbon cloth or the like can be used as the electrode substrate. Examples of the catalyst include platinum (Pt), ruthenium (Ru), osmium (Os) (Pd), iridium (Ir), carbon (C), other transition metals, and mixtures thereof.

The first and second electrodes may be connected to a power supply. The power supply device may apply a voltage in the above-described range to the first and second electrodes and may change the roles of the first and second electrodes as the anode and the cathode. Can be used.

The electrolytic apparatus may be connected to one or more reservoirs so as to continuously supply a mixed gas, an electrolytic solution or the like to the electrolytic apparatus and collect carbon dioxide or the like obtained from the electrolytic apparatus.

In addition, the electrolytic apparatus may include a fluid flow rate regulator capable of regulating the flow rate of fluid or the like; A sensor for monitoring the condition of the first and second compartments; And an electrical signal relating to the electrolytic apparatus and a recording apparatus capable of recording the change in the solution state of each of the compartments.

In addition to the above-described configuration, the electrolytic apparatus may further include a structure commonly employed in an electrolytic apparatus known in the art, or may be employed as one part of a large-scale facility in connection with other apparatus parts.

According to another embodiment of the present invention, there is provided a carbon dioxide separation system in a mixed gas including carbon dioxide, comprising: a first electrode; A second electrode; A cation exchange membrane positioned between the first and second electrodes; A pair of first and second compartments separated by the cation exchange membrane, the compartment being located in a first compartment and a second compartment located on the first electrode side; And a power supply device for applying a voltage such that the first electrode becomes an anode and the second electrode becomes a cathode, and then applies a voltage such that the first electrode becomes a cathode and the second electrode becomes an anode, System is provided.

The carbon dioxide separation system is a system capable of performing the above-described separation method of carbon dioxide, which has been described above in detail, and a detailed description thereof will be omitted.

The method of separating carbon dioxide according to an embodiment of the present invention is expected to be applicable to various technical fields for separating, using, or treating carbon dioxide because it enables purely separating carbon dioxide from a mixed gas discharged in a combustion process. Particularly, it is expected that the method of separating carbon dioxide is useful for cost reduction of CCUS technology, and can provide carbon dioxide which is useful for fields requiring ultra-high purity carbon dioxide, for example, in a chemical reaction process.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG. However, this is provided as an example of the invention, and the scope of the invention is not limited thereto in any sense.

Example : Separation of Carbon Dioxide

Carbon dioxide was separated from the mixed gas using an electrolytic apparatus as shown in FIG. Specifically, about 0.4 M aqueous sodium carbonate solution was supplied to the first and second compartments as an electrolytic solution at 15 캜. A voltage of 4 V is applied to the first and second electrodes so that the first electrode becomes the anode and the second electrode becomes the cathode, and a mixed gas containing 10 vol% of carbon dioxide in the second section is supplied at a rate of 80 cc / min (See 10 in Fig. 2).

The initial pH of the second compartment at room temperature was measured to be about 11.75. It was confirmed that as the carbon dioxide was continuously collected, the pH was gradually lowered to about 7.9 and maintained.

When the pH reaches a constant value in the second compartment, it can be expected that the reaction in the second compartment reaches equilibrium. Thus, when the pH of the second compartment reaches a certain value, a voltage of 2.5 V or 3 V is applied to the first and second electrodes so that the first electrode becomes the cathode and the second electrode becomes the anode Reference).

As the second electrode functions as an anode, hydrogen ions are generated in the second compartment. When a voltage of 2.5 V is applied to the first and second electrodes, the pH is decreased from 8 to 6.7, and a voltage of 3 V is applied , It was confirmed that the pH was lowered from 8 to 1.8. As a result, the carbonate ion or its salt generated in the second compartment was again converted to carbon dioxide and released.

FIG. 5 shows a change in concentration of inorganic carbon in the second compartment with time after applying a voltage such that the first electrode becomes a cathode and the second electrode becomes an anode. Referring to FIG. 5, when a voltage of 3 V is applied to the first and second electrodes, it is confirmed that a greater amount of carbon dioxide is emitted faster than when a voltage of 2.5 V is applied. However, it is confirmed that when about 3 hours have elapsed whether the voltage of 3 V is applied to the first and second electrodes or the voltage of 2.5 V is applied, all the carbon dioxide trapped in the second compartment is released.

When a voltage of 2.5 V was applied to the first and second electrodes and a voltage of 3 V was applied to the first and second electrodes, carbon dioxide having a purity of about 90 vol% was emitted in the second compartment.

On the other hand, as the second electrode functions as an anode and the first electrode functions as a cathode, hydroxyl ions are generated in the first compartment, and carbon dioxide is captured when a mixed gas is supplied to the first compartment. Thereafter, when the pH of the first compartment is gradually lowered and reaches a predetermined value, a voltage of 4 V is applied to the first and second electrodes so that the first electrode becomes the anode and the second electrode becomes the cathode, Carbon dioxide was collected from the second compartment while converting the produced carbonate ion or its salt to carbon dioxide (see 10 'in FIG. 2). It was confirmed that carbon dioxide could be continuously separated from the mixed gas by repeating this process.

: 양극(anode)

: 음극(cathode)
1st EL: 제 1 전극(first electrode)
2nd EL: 제 2 전극(second electrode)
1st CP: 제 1 구획(first compartment)
2nd CP: 제 2 구획(second compartment)
CEM: 양이온 교환막(cation exchange membrane)
BM: 바이폴라막(bipolar membrane)
Mix: 혼합가스
10: 제 1 단계의 모습
20: 제 2 단계의 모습
10': 제 2 단계 후 제 1 단계의 모습

: Anode

: Cathode
1st EL: First electrode:
2nd EL: second electrode (second electrode)
1st CP: First compartment
2nd CP: second compartment
CEM: cation exchange membrane
BM: bipolar membrane
Mix: Mixed gas
10: The first stage
20: The appearance of the second stage
10 ': After the second stage, the first stage

Claims (20)

A first electrode; A second electrode; A cation exchange membrane positioned between the first electrode and the second electrode; And a pair of first and second compartments separated by the cation exchange membrane, the first compartment being located on the first electrode side and the second compartment being located on the second electrode side. to,
A first step of generating a carbonic acid ion or a salt thereof by capturing carbon dioxide in a mixed gas containing carbon dioxide in a second compartment where a first electrode is an anode and a second electrode is a cathode to generate a hydroxide ion, ; And
And a second step of recycling the carbonic acid ions or salts thereof to carbon dioxide in a second compartment where hydrogen ions are generated by applying a voltage such that the first electrode is a cathode and the second electrode is an anode. .
The method of separating carbon dioxide according to claim 1, wherein a voltage of 0.42 V to 10 V is applied to the first and second electrodes.
The method of claim 1, wherein the mixed gas comprises at least 2 vol% of carbon dioxide.
The method of claim 1, wherein the second compartment in the first step comprises a carbonate, hydroxide or a mixture thereof as an electrolyte.
The method according to claim 1, wherein, in the first step, when the pH of the second compartment is maintained at a constant value between 7 and 9, a voltage is applied so that the first electrode becomes the cathode and the second electrode becomes the anode. Way.
The method according to claim 1, wherein, in the first step, when the pH of the first compartment is 0 to 3, the voltage is applied so that the first electrode becomes the cathode and the second electrode becomes the anode.
The method of separating carbon dioxide according to claim 1, wherein in the first step, when the concentration of carbonic acid ions in the second compartment is equal to or higher than the saturation concentration, a voltage is applied so that the first electrode becomes the cathode and the second electrode becomes the anode.
The method according to claim 1, wherein, when the amount of increase in the electrical conductivity in the second section of the first step is 10 mS / cm to 50 mS / cm, a voltage is applied so that the first electrode becomes the cathode and the second electrode becomes the anode , A method for separating carbon dioxide.
The method of claim 1, wherein a voltage of 0.83 V to 2 V is applied to the first and second electrodes.
The method of separating carbon dioxide according to claim 1, wherein the mixed gas is contacted with water having a pH of 3.5 to 7 and then injected into the second compartment.
The separation method of carbon dioxide according to claim 1, wherein the second compartment in the first step collects carbon dioxide in the mixed gas to produce carbonic acid ions or salts thereof, and collects sulfur dioxide to produce sulfite ions or salts thereof .
12. The method of separating carbon dioxide according to claim 11, wherein in the second section of the second step, the carbonic acid ion or its salt is converted into carbon dioxide and the sulfate ion or a salt thereof is produced from the sulfite ion or a salt thereof.
13. The method of claim 12, wherein a voltage of 1.03 V to 2 V is applied to the first and second electrodes.
The method of claim 1, wherein the first step is repeated after the second step.
The method for separating carbon dioxide according to claim 1, wherein the second step comprises capturing carbon dioxide in a mixed gas containing carbon dioxide in the first compartment to produce a carbonic acid ion or a salt thereof.
The method of claim 1, wherein the second compartment in the first stage comprises a carbonate, hydroxide or a mixture thereof as an electrolyte, and the first compartment in the second stage comprises a carbonate, hydroxide, A method for separating carbon dioxide.
16. The method of claim 15, wherein the carbonic acid ion or salt thereof is recycled to carbon dioxide in the first compartment of the first stage, which is repeated after the second step.
2. The device of claim 1, wherein the device comprises: a first electrode; A second electrode; A bipolar membrane positioned between the first electrode and the second electrode; Two cation exchange membranes between the first electrode and the bipolar membrane and between the bipolar membrane and the second electrode; Two pairs of first and second compartments separated by the respective cation exchange membranes and including two first compartments located on the first electrode side and two second compartments located on the second electrode side, A method for separating carbon dioxide.
2. The device of claim 1, wherein the device comprises: a first electrode; A second electrode; Two or more bipolar membranes positioned between the first electrode and the second electrode; Three or more cation exchange membranes between the first electrode and the bipolar membrane, between the bipolar membrane and the bipolar membrane, and between the bipolar membrane and the second electrode; Three or more pairs of first and second compartments separated by the respective cation-exchange membranes, wherein the first and second compartments include at least three first compartments located on the first electrode side and three or more second compartments located on the second electrode side A method of separating carbon dioxide using a device.
A carbon dioxide separation system in a mixed gas comprising carbon dioxide,
A first electrode; A second electrode; A cation exchange membrane positioned between the first and second electrodes; A pair of first and second compartments separated by the cation exchange membrane, the compartment being located in a first compartment and a second compartment located on the first electrode side; And a power supply device for applying a voltage such that the first electrode becomes an anode and the second electrode becomes a cathode, and then applies a voltage such that the first electrode becomes a cathode and the second electrode becomes an anode, system.

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