Carbon dioxide capture and biogas upgrading system using an electrodeionization device connected to a micro-bubble generator

Abstract

The present application relates to a kind of carbon dioxide capture and biogas upgrading system using the electric deionization device connected with microbubble generator, according to the system of the present application, with electric deionization device (400), the electric deionization device (400) has a pair of electrode (410,420) and the stack of bipolar membrane (BP) (430), basic resin wafer (BRW) (440), cation exchange membrane (CEM) (450), acidic resin wafer (ARW) (460) and bipolar membrane (BP) (470) are sequentially arranged between the electrode, the system is composed of the process including the following steps: 1) carbon dioxide in biogas is saturated in 1% NaCl aqueous solution;2) carbon dioxide bubble saturated in NaCl aqueous solution is microbubble to 10-50 μm size and is dispersed;3) the mixture of biogas-NaCl aqueous solution is sequentially passed through the basic chamber and acidic chamber of electric deionization device based on cation exchange membrane (CEM).

Description

TECHNICAL FIELD

[0001] The present application relates to a carbon dioxide capture and biogas upgrading system using an electrodeionization device connected to a microbubble generator, and more specifically, to a system for capturing carbon dioxide in biogas using an electrodeionization process based on a cationic membrane and a microbubble generating device and upgrading the biogas. BACKGROUND

[0002] In recent years, as a result of the mandatory reduction of carbon dioxide, which is the main cause of the increase in greenhouse gases, and the like, there has been increasing interest in the use of biogas, which is a mixture of methane, carbon dioxide, and other gases produced when organic waste such as food waste, sewage sludge, and animal manure is decomposed.

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

[0004] In addition, in recent years, there has been increasing interest in research on Carbon Capture & Utilization (CCU), which goes beyond the Carbon Capture & Storage (CCS) technology that simply captures and stores carbon dioxide, to achieve high value-added utilization of carbon dioxide.

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

[0006] In order to separate carbon dioxide from biogas, a wet separation process using water and an adsorption process using a catalyst are mainly used, but 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%, which shows a low purity that is not suitable for reuse.

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

[0008] In the 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 functions as a conductor due to the presence of a functional group that functions as a crosslinking agent between ion membranes, thereby canceling the concentration polarization of electrodialysis (ED).

[0010] As for Resin Wafer-Electrodeionization (RW-EDI) using a resin wafer in which a porous ion exchange resin of an electrodeionization process is made in the form of a wafer, gas-liquid exchange is well achieved due to the high surface area of the resin wafer, thereby improving the electrical efficiency and separation efficiency.

[0011] The present application is completed based on the fact that by connecting an electrodeionization process based on a cation-exchange membrane (CEM) and a microbubble device, only carbon dioxide in biogas can be captured, and thus biogas can be upgraded.

[0012] [Related Art]

[0013] (Patent Document)

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

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

[0016] Korean Patent No. 10-1541994 (July 29, 2015) SUMMARY

[0017] (I) Technical Problem to be Solved

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

[0019] The present application aims to provide an electrodeionization technology connected to a microbubble generator, which can capture carbon dioxide in biogas and reuse it, thereby reducing the cost and energy consumption amount related to production and maintenance of a biogas production facility.

[0020] The purpose of this invention is to provide an electrodeionization technology connected to a microbubble generator, which can capture carbon dioxide from biogas with high purity and reuse it, thereby contributing to carbon neutrality by reducing carbon dioxide.

[0021] (II) Technical Solution

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

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

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

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

[0026] The electrodeionization device comprises a pair of electrodes and a stack of bipolar membranes (BP), basic resin wafers (BRW), cation exchange membranes (CEM), acid resin wafers (ARW), and bipolar membranes (BP) arranged sequentially between the electrodes.

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

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

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

[0030] (III) Beneficial Effects

[0031] The carbon dioxide capture and biogas upgrading system according to the present invention, which utilizes an electrodeionization device connected to a microbubble generator, can capture and reuse up to 40% of the carbon dioxide in biogas, thereby reducing the costs and energy consumption associated with the production and maintenance of biogas production facilities.

[0032] Furthermore, the captured high-purity carbon dioxide can be used for the growth of high-temperature methane bacteria in biogas production facilities, and when the captured high-purity carbon dioxide is liquefied, it can be used to obtain ultra-high-purity carbon dioxide that can be used in semiconductor manufacturing.

[0033] Furthermore, the carbon dioxide capture and reuse technology of the system of the present invention has the effect of contributing to the ongoing global carbon neutrality policies and greenhouse gas emission reduction policies. Attached Figure Description

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

[0035] Figure 2 This is a flowchart illustrating the structure and fluid flow within the RW-EDI stack of an RW-EDI CO2 capture system according to one embodiment of the present invention.

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

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

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

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

[0040] [Explanation of reference numerals in the attached figures]

[0041] 100: Biogas

[0042] 200:1% NaCl aqueous solution

[0043] 300: Microbubble generator

[0044] 400: Electrodeionization 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: A mixture of carbonate-rich NaCl aqueous solution and methane gas.

[0059] F2: Carbonate Concentration Process Liquid

[0060] F3: An acidified liquid containing gaseous carbon dioxide.

[0061] F4: 1% NaCl aqueous solution after decarbonization Detailed Implementation

[0062] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, in describing the present invention, detailed descriptions of relevant well-known functions that are obvious to those skilled in the art and are deemed unnecessary to obscure the main points of the invention will be omitted.

[0063] Regarding the terminology used in this description, "RW-EDI CO2 capture system" is short for "carbon dioxide capture and biogas upgrading system using an electro-deionization device connected to a microbubble generator," and the % concentration of NaCl aqueous solution is expressed as weight % and the % concentration of each component of biogas is expressed as volume %.

[0064] Figure 1 This is a flowchart illustrating the overall structure and process of an RW-EDI CO2 capture system according to one embodiment of the present invention. Figure 2 This is a flowchart illustrating the internal structure and fluid flow of the RW-EDI stack in the RW-EDI CO2 capture system. Figure 3 This is a flowchart of the ion fluid inside the RW-EDI stack of the RW-EDI CO2 capture system. Figure 4 This is a flowchart illustrating the alkaline flow and biogas fluid within the RW-EDI stack of an RW-EDI CO2 capture system according to one embodiment of the present invention. Figure 5 This is a flowchart of the acidic flow and carbon dioxide fluid inside the RW-EDI stack of an RW-EDI CO2 capture system according to one embodiment of the present invention.

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

[0066] According to one embodiment of the invention, the biogas 100 is composed of 57-61% methane, 38-42% carbon dioxide and 1% other components.

[0067] According to one embodiment of the present invention, the electrodeionization device 400 comprises a pair of electrodes (410, 420) and a stack in which 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 are arranged sequentially between the electrodes.

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

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

[0070] The alkaline resin wafer (BRW) 440 and the PE EVA foam pad form the alkaline chamber 441 of the electro-deionization device 400, and the acidic resin wafer (ARW) 460 and the PE EVA foam pad form the 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 on the alkaline resin wafer (BRW) 440, and the fluid flow channels in the acidic chamber 461 are formed on the acidic resin wafer (ARW) 460.

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

[0073] In water-containing chemical solutions (sodium chloride solution, sulfuric acid solution, hydrochloric acid solution, etc.), the concentrations of carbon dioxide and bicarbonate / carbonate are highly dependent on pH.

[0074] At pH values ​​above 9, all carbon dioxide is converted into carbonates and bicarbonates, while at pH values ​​below 4, no bicarbonate / carbonate is present (Pismenskaya et al., 2020). Therefore, by controlling electrochemical pH changes, carbon dioxide can be captured under alkaline conditions and released under acidic conditions.

[0075] The following chemical formulas illustrate the changes in carbon dioxide according to the pH of the aqueous solution. Figure 6 This is a diagram showing the redistribution of carbonates according to 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] According to one embodiment of the present invention, the RW-EDI CO2 capture system is configured such that carbon dioxide contained in biogas 100 is saturated in a 1% NaCl aqueous solution at the front end of the electro-deionization device and then passed through a microbubble generator 300.

[0081] A 1% NaCl aqueous solution is a process liquid designed to capture and release carbon dioxide from biogas containing 40±2% carbon dioxide at the optimal concentration.

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

[0083] High-concentration NaCl aqueous solutions can be reused in the system through the recycling of process solutions, which helps to reduce the operating costs of the system. However, as the salt concentration increases, the solubility of carbon dioxide decreases, thus requiring more frequent membrane regeneration.

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

[0085] The microbubble generator 300 is a device that, when liquid and gas are mixed and injected simultaneously in the feeding section, splits gas bubbles into fine bubbles by rotating a screw. In the RW-EDICO2 capture system according to one 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 downstream electro-deionization device 400.

[0086] According to one embodiment of the present invention, the microbubble generator 300 can be designed as a simple structure such as a stack of electro-deionization devices 400, thereby increasing the size and quantity, and can be designed to suit various spaces, thereby improving space utilization.

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

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

[0089] The separated methane gas was collected in a Tedra sampling bag and then analyzed by GC-TCD. The carbonate concentrate process liquid F2 was moved to the acid chamber 461 of the electro-deionization device 400, where the pH became acidic and the bicarbonate was converted into gaseous carbon dioxide.

[0090] Acidified liquid F3 containing gaseous carbon dioxide leaves the electro-deionization unit 400 and moves to the gas-liquid separator 2600, where it releases carbon dioxide. The released carbon dioxide is collected in a Tedra gas sampling bag and analyzed by GC-TCD.

[0091] For further processing, the decarbonized 1% NaCl aqueous solution F4 was recycled. The concentrations of carbon dioxide, carbonate, and bicarbonate in the 1% NaCl aqueous solution were measured using TOC-VCPH and used as the total inorganic carbon.

[0092] [Experimental Example 1]

[0093] Experiments based on the carbon dioxide / 1% NaCl aqueous solution flow ratio and the carbon dioxide capture efficiency with or without the application of a microbubble generator.

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

[0095] In addition, the microbubble generator 300 was set up to provide better gas distribution and high contact between the process liquid and the resin wafer. The effect of setting up the microbubble generator 300 was tested in conjunction with the above-mentioned flow ratio.

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

[0097] Table 1 below shows the experimental results based on the flow rate ratio of carbon dioxide / 1% NaCl aqueous solution and the efficiency of carbon dioxide capture with or without the application of a microbubble generator.

[0098] [Table 1]

[0099]

[0100] According to the results of this experiment, when the flow rate ratio of carbon dioxide to 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 to 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 to 1% NaCl aqueous solution is 0.4, the microbubble generator 300 increases the capture efficiency by an average of 7.1%; and when the flow rate ratio of carbon dioxide to 1% NaCl aqueous solution is 0.6, the greatest increase in capture efficiency is observed.

[0101] [Experimental Example 2]

[0102] An experiment based on the purity of the released carbon dioxide determined by the internal voltage of the stack of the electro-deionization device.

[0103] H2O in a bipolar membrane (BP) of an electro-deionization device 400 according to one embodiment of the present invention H + +OH - The reaction requires a voltage of 1.2V.

[0104] At the same time, in order to effectively capture and release the carbon dioxide contained in the biogas 100, the pH in the alkaline chamber 441 of the electro-deionization device 400 according to one 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. This pH change was confirmed when the minimum voltage inside the stack of the electro-deionization device 400 was 1.5V.

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

[0106] Therefore, experiments were conducted to determine the purity of the released carbon dioxide based on the internal voltage of the stack of the electro-deionization device 400, in order to find a suitable voltage inside the stack.

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

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

[0109] Table 2 below shows the experimental results of the purity of the released carbon dioxide based on the internal voltage of the stack of the electro-deionization device.

[0110] [Table 2]

[0111]

[0112] Based on 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, the purity of the released carbon dioxide decreased because the permeability of the membrane to the gas increased, and the gases inside the stack crossed each other and caused contamination.

[0113] Furthermore, the optimal operating time of the system was confirmed to be 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 required.

[0114] The reactivation of the cation exchange membrane (CEM) 450 and resin wafers (440, 460) is accomplished 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 an electric current.

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

[0118] Furthermore, it was confirmed that the reaction rate of the cation exchange membrane (CEM) 450 used in the electro-deionization process decreases after 5 uses, and that it can be restored to its original state by washing with a rinsing solution every 4 uses, thus achieving semi-permanent use. In addition, it was confirmed that the rinsing solution can be reused a minimum of 15 times and a maximum of 20 times.

[0119] While the technical concept of the present invention has been described above in conjunction with the accompanying drawings, this is merely an illustrative description of preferred embodiments of the invention and does not limit the scope of the invention. Furthermore, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the technical concept of the present invention.

[0120] Industrial applicability

[0121] The carbon dioxide capture and biogas upgrading system according to the present invention, utilizing an electrodeionization device connected to a microbubble generator, can capture and reuse up to 40% of the carbon dioxide in biogas, thereby reducing the costs and energy consumption associated with the production and maintenance of biogas production facilities. Furthermore, the captured high-purity carbon dioxide can be used for the growth of thermophilic methane bacteria in biogas production facilities, and when the captured high-purity carbon dioxide is liquefied, it can be used for semiconductor manufacturing, thus possessing very useful industrial applicability.

Claims

1. A carbon dioxide capture and biogas upgrading system utilizing an electro-deionization device connected to a microbubble generator, said system capturing carbon dioxide from biogas and upgrading the biogas. The system comprises a process including the following steps: 1) Saturate the carbon dioxide in biogas with a 1% NaCl aqueous solution to obtain a mixture of biogas and NaCl aqueous solution; 2) Microbubbling the carbon dioxide bubbles in the mixture saturated with biogas-NaCl aqueous solution obtained in step 1) to a size of 10-50 μm and dispersing them; 3) Pass the biogas-NaCl aqueous solution mixture obtained in step 2) sequentially through the alkaline chamber and 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 as described in claim 1, wherein, When the biogas-NaCl aqueous solution mixture obtained in step 2) passes through the alkaline chamber of the electro-deionization device, the pH becomes alkaline, the carbon dioxide in the biogas is converted into bicarbonate, and the methane in the biogas remains in a gaseous state.

3. The carbon dioxide capture and biogas upgrading system utilizing 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 it passes through the acidic chamber of the electro-deionization device in an aqueous NaCl solution rich in bicarbonate, 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 according to claim 1, utilizing an electro-deionization device connected to a microbubble generator, wherein, The electrodeionization device comprises a pair of electrodes (410, 420) and a stack of bipolar membrane (BP) (430), basic resin wafer (BRW) (440), cation exchange membrane (CEM) (450), acid resin wafer (ARW) (460) and bipolar membrane (BP) (470) arranged sequentially between the electrodes.

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

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

6.

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

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