Carbon dioxide capture and biogas upgrading system utilizing electrodeionization device connected with microbubble generator

Abstract

The present invention relates to a carbon dioxide capture and biogas upgrading system using an electrodeionization device connected to a microbubble generator, the system according to the present invention being provided with an electrodeionization device (400) having a pair of electrodes (410, 410), the present invention relates to a system for purifying biogas comprising a stack of electrodes (420, 420) and a bipolar membrane (BP) (430), an alkaline resin wafer (BRW) (440), a cation exchange membrane (CEM) (450), an acidic resin wafer (ARW) (460) and a bipolar membrane (BP) (470) arranged in sequence between the electrodes, the system consisting of a process comprising the steps of: 1) saturating carbon dioxide in biogas in a 1% NaCl aqueous solution; (2) carrying out microbubbling on carbon dioxide bubbles saturated in the NaCl aqueous solution until the size is 10-50 microns, and dispersing; and (3) enabling the mixture of the biogas and the NaCl aqueous solution to sequentially pass through an alkaline chamber and an acid chamber of an electrodeionization device based on a cation exchange membrane (CEM).

Description

Technical Field

[0001] The present invention relates to a carbon dioxide capture and biogas upgrading system using an electrodeionization device connected to a microbubble generator, and more particularly, to a system for capturing carbon dioxide in biogas and upgrading biogas using a cationic diaphragm-based electrodeionization process and a microbubble generating device. Background Art

[0002] In recent years, due to the mandatory reduction of carbon dioxide, which is the main cause of the increase in greenhouse gases, etc., attention to the use of biogas (a mixture of methane, carbon dioxide, and other gases generated when organic wastes such as food waste, sewage sludge, and animal manure decompose) has been increasing.

[0003] Biogas generated in the anaerobic digester of a biogas production facility using food waste and food wastewater as mixed raw materials contains 55 - 60% methane gas and 35 - 40% carbon dioxide. In this biogas, 32% is used for external supply, 17% is used for power generation, and the rest is consumed as a self-heat source around the production facility or burned through a flare stack. Therefore, biogas is not effectively used at present.

[0004] In addition, in recent years, attention to research on carbon capture and utilization (CCU) that realizes high value-added of carbon dioxide and recycles it has been increasing. The carbon capture and utilization (CCU) goes beyond the carbon capture and storage (CCS) technology that simply captures and sequesters carbon dioxide.

[0005] Therefore, a great deal of research and development is being carried out on the upgrading of biogas by separating or capturing carbon dioxide in biogas to increase the content of methane.

[0006] To separate carbon dioxide from biogas, mainly a wet separation process using water and an adsorption process using a catalyst are used. However, due to the large amount of water and catalyst used in these processes, high costs are required, and the purity of the captured carbon dioxide is about 90%, showing a low purity that is not suitable for reuse.

[0007] Electrodeionization (EDI) is an applied technology that combines two technologies, electrodialysis and ion exchange. It has been used since the late 1950s, and this technology aims to minimize the concentration polarization phenomenon existing in the electrodialysis process.

[0008] In an electrodeionization cell, a cation-exchange membrane (CEM) and an anion-exchange membrane (AEM) are alternately arranged between an anode and a cathode to form a dilution zone and a concentration zone.

[0009] The ion exchanger filled in the dilution zone of the electrodeionization cell acts as a conductor due to the presence of functional groups that play a cross-linking role between the ion diaphragms, thus offsetting the concentration polarization of electrodialysis (ED).

[0010] Regarding resin wafer-electrodeionization (RW-EDI) that uses porous ion exchange resin of the electrodeionization process in the form of a wafer, due to the high surface area of the resin wafer, gas-liquid exchange is well achieved, thereby improving the electrical efficiency and separation efficiency.

[0011] The present invention is based on the following: By connecting the electrodeionization process based on a cation-exchange membrane (CEM) and a microbubble device, only carbon dioxide in biogas can be captured, thereby upgrading biogas.

[0012] [Prior art documents]

[0013] (Patent document)

[0014] Korean Patent Publication No. 10-1522317 (May 15, 2015)

[0015] Korean Patent Publication No. 10-2024-0114573 (July 24, 2024)

[0016] Korean Patent Publication No. 10-1541994 (July 29, 2015) Summary of the invention

[0017] (I) Technical problems to be solved

[0018] The object of the present invention is to provide an electrodeionization technology connected to a microbubble generator, which can capture carbon dioxide in biogas with high purity while upgrading biogas, and the biogas is produced from a mixed raw material of food waste and food wastewater by an anaerobic digestion facility.

[0019] The object of the present invention is to provide an electrodeionization technology connected to a microbubble generator, which can capture carbon dioxide in biogas and reuse it, thereby reducing the costs and energy consumption related to the production and maintenance of biogas production facilities.

[0020] The object of the present invention is to provide an electro-deionization technology connected to a microbubble generator, which can capture carbon dioxide in biogas with high purity and recycle it, thereby contributing to carbon neutrality by reducing carbon dioxide.

[0021] (II) Technical Solution

[0022] To achieve the above object, more specifically, the present invention provides the following technical solutions.

[0023] In the system for capturing carbon dioxide from biogas and upgrading biogas of the present invention, the system consists of a process including the following steps: 1) saturating carbon dioxide in biogas in 1% NaCl aqueous solution; 2) microbubbleizing carbon dioxide bubbles saturated in NaCl aqueous solution to a size of 10 - 50 μm and dispersing them; 3) sequentially passing the mixture of biogas - NaCl aqueous solution through the alkaline chamber and the acidic chamber of an electro-deionization device based on a cation exchange membrane (CEM).

[0024] When the mixture of biogas - NaCl aqueous solution passes through the alkaline chamber of the electro-deionization device, the pH becomes alkaline, and carbon dioxide in biogas is converted into bicarbonate, while methane in biogas remains gaseous.

[0025] After the methane in the biogas is separated in gaseous form, when the NaCl aqueous solution rich in bicarbonate passes through the acidic chamber of the electro-deionization device, the pH becomes acidic, and the bicarbonate in the NaCl aqueous solution is converted into gaseous carbon dioxide.

[0026] The electro-deionization device has a pair of electrodes and a stack body in which a bipolar membrane (BP), an alkaline resin wafer (BRW), a cation exchange membrane (CEM), an acidic resin wafer (ARW), and a bipolar membrane (BP) are arranged in sequence between the electrodes.

[0027] The alkaline chamber and the acidic chamber of the electro-deionization device are separated by a cation exchange membrane (CEM), and the fluid flow channels in the alkaline chamber are formed in the alkaline resin wafer (BRW), and the fluid flow channels in the acidic chamber are formed in the acidic resin wafer (ARW).

[0028] The flow ratio (carbon dioxide mL / NaCl aqueous solution mL) in the step of saturating carbon dioxide in biogas in 1% NaCl aqueous solution is set to 0.6.

[0029] The voltage inside the stack body of the electro-deionization device is set to 2V.

[0030] (III) Beneficial Effects

[0031] The carbon dioxide capture and biogas upgrading system using an electro-deionization device connected to a microbubble generator according to the present invention can capture 40% of the carbon dioxide in biogas and reuse it, thereby having the effect of reducing the costs and energy consumption related to the production and maintenance of biogas production facilities.

[0032] In addition, the captured high-purity carbon dioxide can be used for the growth of thermophilic hydrogen-methanogenic bacteria in biogas production facilities, and when the captured high-purity carbon dioxide is liquefied, there is an effect of obtaining ultra-high-purity carbon dioxide that can be used in semiconductor manufacturing.

[0033] In addition, the carbon dioxide capture and reuse technology of the system according to the present invention has the effect of contributing to the global carbon neutrality policy and greenhouse gas emission reduction policy. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a flowchart of the overall configuration and process of the RW-EDI CO2 capture system according to an embodiment of the present invention.

[0035] Figure 2 is a flowchart of the configuration and fluid inside the RW-EDI stack of the RW-EDI CO2 capture system according to an embodiment of the present invention.

[0036] Figure 3 is a flowchart of the ionic fluid inside the RW-EDI stack of the RW-EDI CO2 capture system according to an embodiment of the present invention.

[0037] Figure 4 is a flowchart of the alkaline flow and biogas fluid inside the RW-EDI stack of the RW-EDI CO2 capture system according to an embodiment of the present invention.

[0038] Figure 5 is a flowchart of the acidic flow and carbon dioxide fluid inside the RW-EDI stack of the RW-EDI CO2 capture system according to an embodiment of the present invention.

[0039] Figure 6 is a diagram showing the redistribution of carbonate according to pH.

[0040] [DESCRIPTION OF REFERENCE NUMERALS]

[0041] 100: Biogas

[0042] 200: 1% NaCl aqueous solution

[0043] 300: Microbubble generator

[0044] 400: Electro-deionization device (RW-EDI stack)

[0045] 410: Cathode

[0046] 420: Anode

[0047] 430: Bipolar membrane (BP)

[0048] 440: Basic Resin Wafer (BRW)

[0049] 441: Basic Compartment

[0050] 450: Cation Exchange Membrane (CEM)

[0051] 460: Acidic Resin Wafer (ARW)

[0052] 461: Acidic Compartment

[0053] 470: Bipolar membrane (BP)

[0054] 500: Gas-liquid separator 1

[0055] 501: Separated methane gas

[0056] 600: Gas-liquid separator 2

[0057] 601: Released carbon dioxide

[0058] F1: Mixture of NaCl aqueous solution rich in carbonate and methane gas

[0059] F2: Carbonate-concentrated process liquid

[0060] F3: Acidified liquid containing gaseous carbon dioxide

[0061] F4: Decarbonated 1% NaCl aqueous solution Detailed implementation manners

[0062] Hereinafter, with reference to the accompanying drawings, specific implementation manners of the present invention will be described. In addition, when explaining the present invention, when the relevant well-known functions are obvious to those skilled in the art and it is judged that they may unnecessarily obscure the gist of the present invention, their detailed descriptions are omitted.

[0063] Regarding the terms used in the description, the "RW-EDI CO2 capture system" is an abbreviation of "a carbon dioxide capture and biogas upgrading system that utilizes an electro-deionization device connected to a microbubble generator". The % concentration of the NaCl aqueous solution represents weight %, and the % concentration of each component of the biogas represents the volume % of each component.

[0064] Figure 1 It is a flowchart of the overall configuration and process of the RW-EDI CO2 capture system according to an embodiment of the present invention. Figure 2 It is a flowchart of the configuration inside the RW-EDI stack of the RW-EDI CO2 capture system and the fluid. Figure 3 It is a flowchart of the ionic fluid inside the RW-EDI stack of the RW-EDI CO2 capture system. Figure 4 It is a flowchart of the alkaline flow and biogas fluid inside the RW-EDI stack of the RW-EDI CO2 capture system according to an embodiment of the present invention. Figure 5 It is a flowchart of the acidic flow and carbon dioxide fluid inside the RW-EDI stack of the RW-EDI CO2 capture system according to an embodiment of the present invention.

[0065] The RW-EDI CO2 capture system according to an embodiment of the present invention consists of the following process: By treating the biogas 100 produced by an anaerobic digestion facility from a mixed raw material of food waste and food wastewater with an electro-deionization device 400 connected to a microbubble generator 300, only the carbon dioxide in the biogas is captured, thereby upgrading the biogas (increasing the purity of methane in the biogas).

[0066] The biogas 100 treated according to an embodiment of the present invention consists of 57 - 61% methane, 38 - 42% carbon dioxide, and 1% other components.

[0067] The electro-deionization device 400 according to an embodiment of the present invention has a pair of electrodes (410, 420) and a stack in which bipolar membranes (BP) 430, alkaline resin wafers (BRW) 440, cation exchange membranes (CEM) 450, acidic resin wafers (ARW) 460, and bipolar membranes (BP) 470 are arranged in sequence between the electrodes.

[0068] In summary, the electro-deionization device 400 according to an embodiment of the present invention consists of a pair of cells, and the pair of cells includes an alkaline resin wafer (BRW) 440 and an acidic resin wafer (ARW) 460 separated by a cation exchange membrane (CEM) 450. The alkaline resin wafer (BRW) 440 and the acidic resin wafer (ARW) 460 are respectively separated from the electrodes (410, 420) by bipolar membranes (BP) (410, 470).

[0069] According to one embodiment of the present invention, an alkaline resin wafer (BRW) 440 and an acidic resin wafer (ARW) 460 are respectively assembled with a 4 mm PE gasket covered with EVA foam having a total thickness of 7.4 mm, and formed into a size of length × width × thickness = 175 × 120 × 7.3 mm.

[0070] The alkaline resin wafer (BRW) 440 and the PE EVA foam gasket form an alkaline chamber 441 of the electro-deionization device 400, and the acidic resin wafer (ARW) 460 and the PE EVA foam gasket form an acidic chamber 461. The alkaline chamber 441 and the acidic chamber 461 are separated by a cation exchange membrane (CEM) 450.

[0071] The fluid flow channels in the alkaline chamber 441 are formed in the alkaline resin wafer (BRW) 440, and the fluid flow channels in the acidic chamber 461 are formed in the acidic resin wafer (ARW) 460.

[0072] The designed pH change range in the electro-deionization device 400 according to one embodiment of the present invention is as follows: the pH in the acidic chamber is 3 to 4, and the pH in the alkaline chamber is 9 to 11.

[0073] In a chemical solution containing water (such as sodium chloride solution, sulfuric acid solution, hydrochloric acid solution, etc.), the concentrations of carbon dioxide and bicarbonate / carbonate highly depend on the pH.

[0074] At a pH above 9, all carbon dioxide is converted into carbonate and bicarbonate, and at a pH below 4, there is no bicarbonate / carbonate (Pismenskaya et al., 2020). Therefore, by controlling the electrochemical pH change, carbon dioxide can be captured under alkaline conditions and released under acidic conditions.

[0075] The following chemical formulas show the change process of carbon dioxide according to the pH of the aqueous solution. Figure 6 is a diagram showing the redistribution of carbonate according to the pH.

[0076] H2O H + +OH -

[0077] CO2 (gas (g)) + H2O CO2 (aqueous solution (aq)) + H2O H2CO3 H + +HCO3 -

[0078] CO2 (aqueous solution) + OH - HCO3 -

[0079] HCO3 - +H + H2O + CO2 (gas)

[0080] The RW-EDI CO2 capture system according to an embodiment of the present invention is configured such that carbon dioxide contained in biogas 100 is saturated in a 1% NaCl aqueous solution at the front end of an electro-deionization device and then passed through a microbubble generator 300.

[0081] The 1% NaCl aqueous solution is a process liquid designed to have an optimal concentration for capturing and releasing carbon dioxide from biogas containing 40 ± 2% carbon dioxide.

[0082] The Na + ion concentration in the 1% NaCl aqueous solution is 0.1741 mol / L, which is a concentration containing a sufficient amount of Na + ions as counterions for HCO3 - 、CO3 2- and OH - and the ion concentration of the 1% NaCl aqueous solution has a sufficiently high conductivity, with a conductivity of 18.6 mS / m.

[0083] A high-concentration NaCl aqueous solution can be reused in the system through the circulation of the process liquid, which is beneficial for reducing the operating cost of the system. However, when the salt concentration increases, the solubility of carbon dioxide decreases, resulting in the problem of more frequent membrane regeneration being required.

[0084] In addition, the maximum solubility of carbon dioxide in water at 20 °C is 88 mL of carbon dioxide / 100 mL of water, and the carbon dioxide / water ratio is 0.88. However, the solubility of carbon dioxide in a 1% NaCl aqueous solution is lower than that in water. Considering that the supply temperature of the 1% NaCl aqueous solution according to an embodiment of the present invention is 22 - 25 °C, in the RW-EDI CO2 capture system according to an embodiment of the present invention, in order to obtain the maximum solubility of carbon dioxide in the 1% NaCl aqueous solution, the carbon dioxide / 1% NaCl aqueous solution flow rate ratio is controlled below 0.8.

[0085] The microbubble generator 300 is a device that functions to split gas bubbles into fine bubbles by a rotating screw when liquid and gas are mixed and injected simultaneously in the feed section. In the RW-EDICO2 capture system according to an embodiment of the present invention, carbon dioxide saturated in a 1% NaCl aqueous solution is dispersed into air bubbles with a size of 10 - 50 μm to increase the reaction area, thereby improving the capture rate, capture amount, and capture purity of carbon dioxide in the subsequent electro-deionization device 400.

[0086] The microbubble generator 300 according to an embodiment of the present invention can be designed into a simple structure such as a stack of electro-deionization devices 400, thereby increasing the size and quantity, and can be designed to fit various spaces, thus improving the space utilization rate.

[0087] The gas-liquid mixture passing through the microbubble generator 300 passes through the alkaline chamber 441 of the electro-deionization device 400, the pH becomes alkaline, carbon dioxide is converted into bicarbonate, and methane remains in the gaseous state.

[0088] Then, the mixture F1 of the 1% NaCl aqueous solution rich in carbonate and methane gas leaves the electro-deionization device 400 and moves to the gas-liquid separator 1500, where it is separated into gas and liquid.

[0089] The separated methane gas is collected in a Tedlar sampling bag and then analyzed by GC-TCD. The carbonate-concentrated process liquid F2 moves to the acidic chamber 461 of the electro-deionization device 400, the pH becomes acidic, and bicarbonate is converted into gaseous carbon dioxide.

[0090] The acidified liquid F3 containing gaseous carbon dioxide leaves the electro-deionization device 400 and moves to the gas-liquid separator 2600 to release carbon dioxide. The released carbon dioxide is collected in a Tedlar gas sampling bag and analyzed by GC-TCD.

[0091] For further operation, the decarbonized 1% NaCl aqueous solution F4 is recycled, and the concentrations of carbon dioxide, carbonate, and bicarbonate in the 1% NaCl aqueous solution are measured using a TOC-VCPH and taken as the total inorganic carbon.

[0092] [Experimental Example 1]

[0093] Experiment on the carbon dioxide capture efficiency according to the flow rate ratio of carbon dioxide / 1% NaCl aqueous solution and whether the microbubble generator is applied

[0094] In the RW-EDI CO2 capture system according to an embodiment of the present invention operating as described above, the concentration of carbon dioxide in the supplied biogas 100 is relatively high (about 40%). Therefore, in order to increase the solubility of carbon dioxide in the 1% NaCl aqueous solution, it is very important to increase the contact area between the carbon dioxide gas and the 1% NaCl aqueous solution. However, due to the solubility of carbon dioxide in the 1% NaCl aqueous solution, the saturation amount of carbon dioxide in the 1% NaCl aqueous solution is limited. Therefore, as described above, the flow rate ratio of carbon dioxide / 1% NaCl aqueous solution must be controlled below 0.8. In order to find the optimal flow rate ratio conditions, experiments were conducted at three flow rate ratios of 0.4, 0.6, and 0.8.

[0095] In addition, the microbubble generator 300 is provided to provide better gas distribution and high contact between the process liquid and the resin wafer. For the setting effect of the microbubble generator 300, experiments were conducted in combination with the above-mentioned flow rate ratio.

[0096] For this experiment, the biogas 100 was supplied to the system at a pressure of 1 - 1.1 bar (bar). The microbubble generator 300 used an off-the-shelf product sold in South Korea. The cation exchange membrane (CEM) 450 of the electro-deionization device 4D00 used NEOSEPTA of Japan's ASTOM Corporation. The internal voltage of the stack of the electro-deionization device 400 was set to 2 ± 0.1 V (electrode voltage 10 ± 0.4 V), and the operation time of the system was set to 4 cycles (120 minutes).

[0097] The following Table 1 shows the experimental results of the carbon dioxide capture efficiency according to the flow rate ratio of carbon dioxide / 1% NaCl aqueous solution and the application of the microbubble generator.

[0098] [Table 1]

[0099]

[0100] According to the experimental results, when the flow rate ratio of carbon dioxide / 1% NaCl aqueous solution is 0.8, the microbubble generator 300 increases the capture efficiency by an average of 13.3%. When the flow rate ratio of carbon dioxide / 1% NaCl aqueous solution is 0.6, the microbubble generator 300 increases the capture efficiency by an average of 13.4%. When the flow rate ratio of carbon dioxide / 1% NaCl aqueous solution is 0.4, the microbubble generator 300 increases the capture efficiency by an average of 7.1%. When the flow rate ratio of carbon dioxide / 1% NaCl aqueous solution is 0.6, the maximum increase in capture efficiency is shown.

[0101] [Experimental Example 2]

[0102] Experiment on the purity of carbon dioxide released according to the internal voltage of the stack of the electro-deionization device

[0103] In the bipolar membrane (BP) of the electro-deionization device 400 according to an embodiment of the present invention, H2O H + + OH - The voltage required for the reaction is 1.2V.

[0104] Meanwhile, in order to effectively capture and release carbon dioxide contained in the biogas 100, the pH in the alkaline chamber 441 of the electro-deionization device 400 according to an embodiment of the present invention must be changed to above 9, and the pH in the acidic chamber 461 must be changed to below 4. When the minimum voltage inside the stack of the electro-deionization device 400 is 1.5V, this change in pH was confirmed.

[0105] That is, when the voltage inside the stack is lower than 1.5V, the pH changes, but the pH in the alkaline chamber 441 is 8.7 ± 0.2 and does not increase to above 9, while the pH in the acidic chamber 461 is 5 ± 0.4 and does not decrease to below 4.

[0106] Therefore, an experiment on the purity of the released carbon dioxide according to the voltage inside the stack of the electro-deionization device 400 was conducted to find the appropriate voltage inside the stack.

[0107] For this experiment, the flow ratio of carbon dioxide / 1% NaCl aqueous solution in the system was set to 0.6 (the flow rate of biogas was 45 milliliters (cc) / minute, and the flow rate of 1% NaCl aqueous solution was 30 mL / minute). The voltage inside the stack was set to 1.5V, 2V, 2.5V, and 3V respectively, and the remaining experimental conditions were set to the same conditions as in Experimental Example 1 above.

[0108] To maintain the voltage inside the stack at 1.5V, an electrode voltage of 8.7 ± 0.2V was used. To maintain the voltage inside the stack at 2V, an electrode voltage of 10 ± 0.4V was used. To maintain the voltage inside the stack at 2.5V, an electrode voltage of 12 ± 0.2V was used. To maintain the voltage inside the stack at 3V, an electrode voltage of 15 ± 0.3V was used. The applied current was maintained in the range of 1.75 ± 0.3A.

[0109] The following Table 2 shows the experimental results of the purity of the released carbon dioxide according to the voltage inside the stack of the electro-deionization device.

[0110] [Table 2]

[0111]

[0112] According to the results of this experiment, it was confirmed that when the voltage inside the stack was set to 2V, the purity of the released carbon dioxide was 97.43%, showing the highest purity. When the voltage inside the stack was 2.5V and 3V, due to the increased gas permeability of the membrane, the gases inside the stack crossed each other and caused contamination, resulting in a decrease in the purity of the released carbon dioxide.

[0113] In addition, it was confirmed that the optimal operating time of the system was 4 cycles (120 minutes). After 4 cycles (120 minutes), the resistance of the membrane increased, and a higher applied voltage was required to maintain 2V inside the stack. Therefore, a process of washing and reactivating the cation exchange membrane (CEM) 450 and the resin wafers (440, 460) was needed.

[0114] The reactivation of the cation exchange membrane (CEM) 450 and the resin wafers (440, 460) was completed through the following process.

[0115] 1) Stop the supply of biogas, 1% NaCl aqueous solution, and electricity, and replace the 1% NaCl aqueous solution with distilled water.

[0116] 2) Wash the system with distilled water for 2 minutes without applying current.

[0117] 3) Wash the inside of the stack with distilled water, apply a voltage of 4 - 5V and a current of 3A for 10 minutes. After the above washing is completed, stop the supply of electricity and rinse the inside of the stack with distilled water for 10 minutes (repeat 3 times).

[0118] In addition, it was confirmed that the reaction rate of the cation exchange membrane (CEM) 450 used in the electro - deionization process would decrease after being used 5 times, and it was confirmed that when it was washed with the rinsing solution and reused every 4 times, it returned to its original state. Therefore, semi - permanent use could be achieved. In addition, it was confirmed that the rinsing solution could be reused at least 15 times and at most 20 times.

[0119] Above, although the technical idea of the present invention has been described in conjunction with the accompanying drawings, this only exemplarily illustrates the preferred embodiments of the present invention and does not limit the present invention. In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the technical idea of the present invention.

[0120] Industrial Applicability

[0121] The carbon dioxide capture and biogas upgrading system using an electro-deionization device connected to a microbubble generator according to the present invention can capture 40% of the carbon dioxide in biogas and reuse it, thereby reducing the costs and energy consumption associated with the production and maintenance of biogas production facilities. The captured high-purity carbon dioxide can be used for the growth of thermophilic hydrogenotrophic methanogens in biogas production facilities, and when the captured high-purity carbon dioxide is liquefied, it can be used in the manufacture of semiconductors, so it has very useful industrial applicability.

Claims

1. A carbon dioxide capture and biogas upgrading system using an electro-deionization device connected to a microbubble generator, which captures carbon dioxide from biogas and upgrades the biogas. The system consists of a process including the following steps: 1) Saturate carbon dioxide in biogas in a 1% NaCl aqueous solution; 2) Microbubble carbon dioxide bubbles saturated in the NaCl aqueous solution to a size of 10 - 50 μm and disperse them; 3) Pass the biogas - NaCl aqueous solution mixture successively through the alkaline chamber and the acidic chamber of an electro-deionization device based on a cation exchange membrane (CEM).

2. The carbon dioxide capture and biogas upgrading system using an electro-deionization device connected to a microbubble generator according to claim 1, wherein, When the biogas - NaCl aqueous solution mixture passes through the alkaline chamber of the electro-deionization device, the pH becomes alkaline, carbon dioxide in the biogas is converted into bicarbonate, and methane in the biogas remains in a gaseous state.

3. The carbon dioxide capture and biogas upgrading system using an electro-deionization device connected to a microbubble generator according to claim 2, wherein, After the methane in the biogas is separated in a gaseous state, when the NaCl aqueous solution rich in bicarbonate passes through the acidic chamber of the electro-deionization device, the pH becomes acidic, and the bicarbonate in the NaCl aqueous solution is converted into gaseous carbon dioxide.

4. The carbon dioxide capture and biogas upgrading system using an electro-deionization device connected to a microbubble generator according to claim 1, wherein, The electro-deionization device has a pair of electrodes (410, 420), and a stack body in which bipolar membranes (BP) (430), alkaline resin wafers (BRW) (440), cation exchange membranes (CEM) (450), acidic resin wafers (ARW) (460), and bipolar membranes (BP) (470) are arranged in sequence between the electrodes.

5. The carbon dioxide capture and biogas upgrading system using an electro-deionization device connected to a microbubble generator according to claim 4, wherein, The alkaline chamber and the acidic chamber of the electro-deionization device are separated by a cation exchange membrane (CEM) (450). The fluid flow channel in the alkaline chamber is formed in the alkaline resin wafer (BRW) (440), and the fluid flow channel in the acidic chamber is formed in the acidic resin wafer (ARW) (460).

6. The carbon dioxide capture and biogas upgrading system using an electro-deionization device connected to a microbubble generator according to claim 1, wherein, The flow ratio in the step of saturating carbon dioxide in biogas in a 1% NaCl aqueous solution, that is, carbon dioxide mL / NaCl aqueous solution mL, is 0.

6.

7. The carbon dioxide capture and biogas upgrading system using an electro-deionization device connected to a microbubble generator according to claim 4, wherein, The voltage inside the stack body of the electro-deionization device is 2V.

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