A carbon dioxide capture method based on flow electrode capacitive deionization

Abstract

This invention discloses a carbon dioxide capture method based on flow electrode capacitive deionization, comprising: constructing a three-chamber flow electrode capacitive deionization device, including an anode chamber, a cathode chamber, and an intermediate chamber, wherein the intermediate chamber is isolated from the anode and cathode chambers by an ion exchange membrane; connecting the intermediate chamber to a gas-liquid contact system, wherein the gas-liquid contact system is a closed system including an absorbent and a gas component; introducing a carbon dioxide-containing gas into the gas-liquid contact system; applying a positive voltage between the anode and cathode of the flow electrode capacitive deionization device, causing ions generated by the dissolution and ionization of carbon dioxide in the gas-liquid contact system to be captured in the flow electrode; and applying a reverse voltage to release the captured carbon dioxide. This invention achieves a breakthrough in carbon dioxide capture technology through the innovative coupling of flow electrode capacitive deionization and a gas-liquid mass transfer system.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide capture technology, and particularly relates to a carbon dioxide capture method based on flow electrode capacitance deionization. Background Technology

[0002] Currently, the mainstream carbon dioxide capture technologies mainly fall into three categories: amine absorption, chemisorption, and cryogenic separation. Amine absorption captures carbon dioxide through a chemical reaction between an alcoholic amine solution and the carbon dioxide. This technology is mature and can achieve a capture efficiency of over 80%, but it has significant drawbacks: the solution regeneration process consumes a large amount of heat energy (typically higher than 120 kJ / mol CO2), resulting in high operating costs; simultaneously, amine compounds are prone to volatilization and leakage, causing equipment corrosion and secondary environmental pollution. Chemisorption uses solid adsorbents (such as molecular sieves and metal-organic frameworks) to capture carbon dioxide. While this avoids the risk of liquid leakage, its regeneration energy consumption is still as high as 100-200 kJ / mol CO2, and the adsorbent is prone to pulverization and failure due to repeated heating and cooling operations. Cryogenic separation relies on deep cryogenic liquefaction technology to separate carbon dioxide in an ultra-low temperature environment. This process is extremely energy-intensive and requires huge equipment investment, making it only suitable for high-concentration carbon dioxide sources. The aforementioned technologies all face two common challenges: 1. Regeneration energy consumption bottleneck: Whether it's solution regeneration (amine method) or adsorbent activation (adsorption method), both require a continuous external input of high-grade heat energy, causing the capture cost to account for more than 70% of the overall carbon capture and storage (CCUS) cost; 2. Chemical reagent dependence: Amine solutions need to be replenished with fresh reagents regularly to maintain activity, and solid adsorbents also have short lifespans, leading to ongoing operational complexity and environmental risks. It is worth noting that the emerging capacitive deionization (CDI) technology has shown low energy consumption advantages in the field of ion separation, but its fixed electrode structure has limitations in ion adsorption capacity and saturation. Flow electrode capacitive deionization (FCDI), by introducing a recyclable flow electrode, significantly improves ion storage capacity and continuous operation capability, and has been successfully applied in the field of seawater desalination. However, existing technologies have never applied FCDI to carbon dioxide capture: on the one hand, the mass transfer process of carbon dioxide dissolving from the gas phase to the liquid phase and ionizing into ions has efficiency limitations; on the other hand, the ions generated by ionization (H+)... + HCO3 - CO3 2- The migration mechanism during the capacitive capture stage is still unclear. This has resulted in the technological potential of FCDI in the field of carbon capture remaining untapped for a long time. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a carbon dioxide capture method based on flow electrode capacitive deionization. Through the innovative coupling of flow electrode capacitive deionization with a gas-liquid mass transfer system, a breakthrough in carbon dioxide capture technology has been achieved.

[0004] To achieve the above objectives, the present invention provides a carbon dioxide capture method based on flow electrode capacitance deionization, comprising:

[0005] A three-chamber flow electrode capacitive deionization device is constructed, comprising an anode chamber, a cathode chamber, and an intermediate chamber, wherein the intermediate chamber is isolated from the anode chamber and the cathode chamber by an ion exchange membrane;

[0006] The intermediate chamber is connected to a gas-liquid contact system, which is a closed system comprising an absorbent liquid and a gas component.

[0007] A gas containing carbon dioxide is introduced into the gas-liquid contact system;

[0008] A positive voltage is applied between the anode and cathode of the flow electrode capacitor deionization device, so that the ions generated by the dissolution and ionization of carbon dioxide in the gas-liquid contact system are captured into the flow electrode.

[0009] Applying a reverse voltage causes the captured carbon dioxide to be released.

[0010] Optionally, the three-chamber flow electrode capacitive deionization device includes:

[0011] The cation exchange membrane and the anion exchange membrane are respectively disposed between the intermediate chamber and the anode chamber and the cathode chamber;

[0012] A graphite current collector is disposed in the anode chamber and the cathode chamber, and the surface of the graphite current collector is provided with a serpentine flow channel;

[0013] The gas-liquid contact system is connected to the water inlet pipe and water outlet pipe of the intermediate chamber through a pipeline, and a water distribution device is provided at the end of the water inlet pipe.

[0014] Optionally, the fabrication process of the flow electrode includes:

[0015] Mix activated carbon with deionized water;

[0016] Stir at 300 r / min for 1 hour to form a homogeneous slurry with an activated carbon mass loading of 2.5 wt%.

[0017] Optionally, the applied forward voltage ranges from 0.1V to 1.2V; the applied reverse voltage is 1.2V.

[0018] Optionally, the operation process of the gas-liquid contact system includes:

[0019] Maintain a stirring rate of 530 r / min in a closed system;

[0020] The flow rate of the absorption liquid was controlled at 10 mL / min using a peristaltic pump.

[0021] Optionally, the absorbent is a nanofluid, and its preparation process includes:

[0022] Nanoparticles are added to a deionized water-based solution;

[0023] Stir at 200 rpm for 30 minutes;

[0024] Dispersion is achieved by ultrasonic treatment for 1 hour.

[0025] Optionally, the carbon dioxide capture process includes two stages:

[0026] First stage: Carbon dioxide dissolves in the absorbent and ionizes to generate hydrogen ions, bicarbonate ions, and carbonate ions;

[0027] Second stage: The ions migrate to the flow electrode for storage under the action of an electric field.

[0028] Optionally, the method employs an isolated closed-loop operation mode, including:

[0029] The circulation of the absorbent liquid in the intermediate chamber is controlled by a peristaltic pump;

[0030] The electrode solutions in the anode and cathode chambers are continuously stirred to maintain homogeneity.

[0031] Technical effects of this invention: This invention achieves a breakthrough in carbon dioxide capture technology through the innovative coupling of flow electrode capacitive deionization (FCDI) with a gas-liquid mass transfer system. Its technical effects are mainly reflected in the following four dimensions:

[0032] 1. Revolutionary reduction in energy consumption:

[0033] Energy consumption for regeneration is reduced by more than 95%: Traditional amine absorption methods consume as much as 120-200 kJ / mol CO2 for regeneration, while this invention uses electric field-driven ion migration to replace the thermal regeneration process, achieving a capture energy consumption of 5.72 kJ / mol CO2 at an operating voltage of 0.4V. This revolutionary breakthrough stems from the physical mechanism of capacitive adsorption, completely avoiding the dependence of traditional technologies on high-grade thermal energy.

[0034] High-efficiency recovery with reverse voltage: Applying a reverse voltage of 1.2V can release the captured carbon dioxide within 20 minutes. The recovery process does not require external energy input and only uses the energy of electrode discharge to complete the desorption cycle.

[0035] 2. Fundamental improvement in environmental friendliness:

[0036] Zero chemical additives: The flow electrode only requires activated carbon-water mixture slurry (2.5wt%), and the absorbent in the intermediate chamber uses pure water or nanofluid, completely eliminating equipment corrosion and environmental pollution caused by the volatilization and leakage of amine solvents.

[0037] Non-toxic nanofluid enhancement: Alumina / copper oxide nanoparticle-enhanced absorbent liquid improves ion conduction efficiency while avoiding secondary pollution, solving the problem of pulverization and failure of traditional adsorbents.

[0038] 3. Leapfrog optimization of operational performance:

[0039] Capture efficiency doubled: Under optimized stirring conditions, the system capture efficiency reached 31.77%, which is 143% higher than the basic efficiency without electric field, and significantly higher than the efficiency limit of low temperature separation method under low concentration gas source.

[0040] Breakthrough in continuous operation capability: The flowing electrode is continuously regenerated through an external storage tank, and with the isolated closed-loop (ICC) operation mode, it supports thousands of hours of continuous and stable operation in large-scale industrial scenarios, solving the saturation deactivation bottleneck of the fixed electrode capacitance method.

[0041] 4. System compatibility and scalability:

[0042] Modular architecture adapts to multiple scenarios: The three-chamber reactor and the gas-liquid contact system are connected by standardized interfaces, which can flexibly match the needs of flue gas treatment of different scales and avoid the complex pipeline modification of traditional amine process.

[0043] Synergistic enhancement of gas-liquid mass transfer and capacitive capture: Through a two-stage mechanism design (dissolution and ionization → electro-adsorption), gas-liquid mass transfer is identified as the rate-limiting step for the first time, providing a precise optimization path for subsequent technology upgrades.

[0044] Mechanism of effect: directional migration of ions under the action of electric field replaces thermal energy-driven chemical bond breaking (the root cause of energy consumption reduction); the unlimited ion storage space of the flowing electrode breaks the saturation limit of the fixed electrode (the basis for continuous operation); the spatiotemporal decoupling design of gas-liquid mass transfer and capacitive capture (the core of efficiency improvement). Attached Figure Description

[0045] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0046] Figure 1 This is a schematic diagram of the structure of the three-chamber flow electrode capacitor deionization device according to an embodiment of the present invention;

[0047] Figure 2 This is a schematic diagram of the gas pressure change and the conductivity change of the intermediate chamber solution during the charging and discharging process according to an embodiment of the present invention, wherein (a) is the gas pressure change during the charging and discharging process, and (b) is the conductivity change of the intermediate chamber solution during the charging and discharging process.

[0048] Figure 3This is a schematic diagram of the two stages of CO2 capture by FCDI according to an embodiment of the present invention;

[0049] Figure 4 The diagram shows the CO2 capture performance of FCDI under different voltages in this embodiment of the invention, including capture quantity, capture rate, capture efficiency, and energy consumption, where (a) represents the capture quantity and (b) represents the capture rate.

[0050] Figure 5 This is a schematic diagram of the changes in gas pressure and current during the CO2 capture process of FCDI under different voltages in an embodiment of the present invention, where (a) is the relative gas pressure and (b) is the current;

[0051] Figure 6 The diagram shows the CO2 capture performance of FCDI under different stirring rates in this embodiment of the invention, including capture amount, capture rate, capture efficiency, and energy consumption, where (a) represents the capture amount and (b) represents the capture rate.

[0052] Figure 7 The diagram shows the CO2 capture performance of FCDI under different nanofluid absorption liquids in embodiments of the present invention, where (a) represents the pressure change, (b) represents the capture amount, and (c) represents the capture rate. Detailed Implementation

[0053] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0054] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0055] like Figure 1 As shown, this embodiment provides a carbon dioxide capture method based on flow electrode capacitance deionization, including:

[0056] A three-chamber flow electrode capacitive deionization device is constructed, comprising an anode chamber, a cathode chamber, and an intermediate chamber, wherein the intermediate chamber is isolated from the anode chamber and the cathode chamber by an ion exchange membrane;

[0057] The intermediate chamber is connected to a gas-liquid contact system, which is a closed system comprising an absorbent liquid and a gas component.

[0058] A gas containing carbon dioxide is introduced into the gas-liquid contact system;

[0059] A positive voltage is applied between the anode and cathode of the flow electrode capacitor deionization device, so that the ions generated by the dissolution and ionization of carbon dioxide in the gas-liquid contact system are captured into the flow electrode.

[0060] Applying a reverse voltage causes the captured carbon dioxide to be released.

[0061] Furthermore, the three-chamber flow electrode capacitor deionization device includes:

[0062] The cation exchange membrane and the anion exchange membrane are respectively disposed between the intermediate chamber and the anode chamber and the cathode chamber;

[0063] A graphite current collector is disposed in the anode chamber and the cathode chamber, and the surface of the graphite current collector is provided with a serpentine flow channel;

[0064] The gas-liquid contact system is connected to the water inlet pipe and water outlet pipe of the intermediate chamber through a pipeline, and a water distribution device is provided at the end of the water inlet pipe.

[0065] Furthermore, the fabrication process of the flow electrode includes:

[0066] Mix activated carbon with deionized water;

[0067] Stir at 300 r / min for 1 hour to form a homogeneous slurry with an activated carbon mass loading of 2.5 wt%.

[0068] Furthermore, the range of the applied positive voltage is 0.1V to 1.2V; the applied reverse voltage is 1.2V.

[0069] Furthermore, the operation process of the gas-liquid contact system includes:

[0070] Maintain a stirring rate of 530 r / min in a closed system;

[0071] The flow rate of the absorption liquid was controlled at 10 mL / min using a peristaltic pump.

[0072] Furthermore, the absorbent is a nanofluid, and its preparation process includes:

[0073] Nanoparticles are added to a deionized water-based solution;

[0074] Stir at 200 rpm for 30 minutes;

[0075] Dispersion is achieved by ultrasonic treatment for 1 hour.

[0076] Furthermore, the carbon dioxide capture process comprises two stages:

[0077] First stage: Carbon dioxide dissolves in the absorbent and ionizes to generate hydrogen ions, bicarbonate ions, and carbonate ions;

[0078] Second stage: The ions migrate to the flow electrode for storage under the action of an electric field.

[0079] Furthermore, the method employs an isolated closed-loop operation mode, including:

[0080] The circulation of the absorbent liquid in the intermediate chamber is controlled by a peristaltic pump;

[0081] The electrode solutions in the anode and cathode chambers are continuously stirred to maintain homogeneity.

[0082] Specifically, the implementation process of this embodiment includes:

[0083] Reactor Structure: The FCDI used in this embodiment is a three-chamber cell consisting of a polyethylene separator and an intermediate spacer (5cm × 6cm × 0.5mm) made of 100-mesh nylon fabric; two ion exchange membranes; and two graphite current collectors with etched serpentine flow channels (2.4mm wide, 2mm deep). The effective contact area between the ion exchange membranes and the flow electrode is 16.3cm². 2 These components are held together using plexiglass end plates, such as... Figure 1 As shown. The electrode slurry is connected to an external storage tank via a polyethylene pipe. The intermediate chamber is also connected to the external gas-liquid contact system via a polyethylene pipe. The gas-liquid contact system is a closed system of approximately 350 mL sealed with a rubber ring, comprising 120 mL of absorbent and 200 mL of gas components. The system is connected to a differential pressure gauge (DP360, Sanliang, China), a gas bag (500 mL, E-switch, China), an FCDI inlet pipe, and an FCDI outlet pipe via four extended pipes. The end of the pipe connecting the gas-liquid contact system to the FCDI inlet pipe extends below the water level, and the end of the pipe connecting the gas-liquid contact system to the FCDI outlet pipe is connected to a conical water distribution device made of nylon cloth.

[0084] Electrode solution preparation: Add 37.5g of commercial activated carbon to 1462.5mL of deionized water and stir at 300r / min for 1h using a digital precision electric stirrer (or stir for 12h using a magnetic stirrer) to fully homogenize the two to prepare an activated carbon flow electrode with a mass loading of 2.5wt% and a carbon content of 1500g.

[0085] Air tightness verification: After assembling the apparatus for each experiment, an air tightness verification experiment is conducted before the experiment begins. The specific procedure is as follows: Before each experiment, use a syringe (500mL) to fill the sealed system with about 250mL of nitrogen gas, let it stand for 5 minutes, and observe the change in gas pressure inside the system to verify the air tightness of the system. If the change in gas pressure is not significant, it can be concluded that the air tightness of the system is good.

[0086] Reactor Operation: The FCDI operates in an isolated closed-loop (ICC) mode to capture CO2 from a standard gas mixture. Unless otherwise specified, the anolyte and cathode electrode solutions are continuously stirred throughout the experiment to maintain homogeneity. The flow rates of the intermediate absorbent and the flowing electrode are controlled at approximately 10 mL / min by a precision digital peristaltic pump. Before the experiment, keep valves 3 and 7 closed, open valves 1, 2, 5, 6, 8, and 9, and disconnect valve 4. Start the FCDI's inlet and outlet pumps to allow the absorbent in the gas-liquid contact system to enter the FCDI's intermediate chamber. After the first drop of absorbent reaches valve 9 via valve 2, immediately close valves 1, 2, 4, 5, 6, 8, and 9 and the pumps to fill the FCDI intermediate chamber and system piping with absorbent. Disconnect the two-way valve 9, connect the hose corresponding to valve 9 to a vacuum pump, and open valve 2 to evacuate the system. Once the vacuum pump reading stabilizes and stops decreasing, quickly close valve 2, connect valve 9, and turn off the vacuum pump. Open valve 4 to connect a 500mL gas bag pre-filled with a mixed gas (N2:CO2 = 85:15) to the system. Then open valves 1, 2, 5, 6, 7, 8, and 9 to fill the system with the standard mixed gas, and compress the gas bag to achieve an initial relative pressure of 1.7 ± 0.1 kPa. Immediately afterward, turn on the peristaltic pump, power supply, barometer, and conductivity meter to begin testing. During the charging phase, a constant voltage was applied between the two electrodes for 240 minutes, and the current, voltage, conductivity, and headspace pressure of the gas-liquid contact system were continuously monitored throughout the experiment. After charging, unless otherwise specified, a reverse voltage of 1.2V was applied for discharge for 20 minutes.

[0087] Nanofluids were prepared using a two-step method. A certain mass of nanoparticles was weighed according to experimental requirements and slowly added to a deionized water-based solution. The solution was then stirred at 200 rpm for 30 min using a magnetic stirrer, followed by ultrasonication for 1 h to obtain the nanofluid absorbent liquid.

[0088] By introducing gas into a closed system and recording the pressure change over time, the dissolved capacity can be calculated from the pressure change. Since N2 does not participate in the reaction in the absorption experiment, the amount of N2 can be considered constant during the reaction process and will not cause pressure changes. The pressure change is caused by the change in the amount of CO2 in the system. Therefore, the change in CO2 content in the system can be approximately calculated using the ideal gas equation.

[0089] From PV = nRT, we can obtain:

[0090]

[0091] P is the pressure (Pa), and V is the gas volume (m³). 3), T is the temperature (K) (273+ degrees Celsius), n is the amount of substance of the gas (mol), R is the molar gas constant (also called the universal gas constant) (J / (mol·K)), generally R is taken as 8.314 J / (mol·K). Δn: change in the amount of substance of CO2 gas (mol), i.e. CO2 capture amount (mol), ΔP: change in system pressure (Pa).

[0092] CO2 capture efficiency EF removal (%)

[0093]

[0094] n0: Initial amount of CO2 (mol), P0: Initial system pressure (kPa)

[0095] CO2 capture rate R removal :

[0096]

[0097] t: time (h).

[0098] CO2 recovery efficiency:

[0099]

[0100] P2: System pressure after recovery (kPa); P1: System pressure after the removal (capture) process (kPa).

[0101] CO2 capture energy consumption (kWh / mol):

[0102]

[0103] Experimental methods:

[0104] (1) Feasibility Verification: A forward voltage of 1.2V was first applied between the positive and negative electrodes of the capacitor device, followed by a reverse voltage of 1.2V after 4 hours to verify that FCDI could capture CO2. During the process, changes in gas pressure and solution conductivity within the device were monitored. If the gas pressure decreased with the application of the forward voltage and increased with the application of the reverse voltage, it indicated the success of the electro-adsorption and release process of CO2 gas within the system. Conductivity data reflects the dissolution and ionization of CO2 in water.

[0105] (2) Experiment on the effect of voltage on CO2 capture efficiency

[0106] To investigate the effect of different charging voltages on the CO2 capture efficiency of FCDI, the charging voltages were adjusted to 0V, 0.1V, 0.4V, 0.8V, and 1.2V, the reaction temperature was 25℃, and the stirring rate in the gas-liquid contact system was 530 r / min. All experiments were repeated three times to eliminate errors.

[0107] (3) Experiment on the effect of stirring rate on CO2 capture effect

[0108] To investigate the effect of different stirring rates on the CO2 capture efficiency of FCDI, the stirring rates in the gas-liquid contact system were adjusted to 0 r / min, 130 r / min, 350 r / min, 530 r / min, and 700 r / min, respectively, with the charging voltage set to 0.4 V and the reaction temperature set to 25 °C.

[0109] (4) Speed ​​Limiting Step Recognition Test

[0110] The rate limiting conditions in the two stages of capacitive capture process were analyzed by observing the deionization status of the system after aeration saturation.

[0111] Feasibility verification experiment of FCDI for CO2 capture

[0112] The concept of capacitive CO2 capture has been proposed in existing technologies, but there are no reports on FCDI (Fuel-Coefficient Capacitor Injection) CO2 capture. To verify the feasibility of FCDI CO2 capture, a system was built, and a forward voltage was applied to the system for 4 hours, followed by a reverse voltage after 4 hours. The changes in gas pressure within the system, i.e., the changes in CO2 partial pressure, were observed. Figure 2 (a)

[0113] After applying a constant positive voltage of 1.2V, the relative pressure within the system gradually decreased and stabilized over 0-4 hours, decreasing from 1.71 kPa (0h) to -3.19 kPa (4h). When a reverse voltage of 1.2V was applied at the 4th hour, the headspace pressure gradually increased to -1.25 kPa (16h). The partial pressure of CO2 in the headspace gas responded accordingly to the voltage; the pressure decrease was due to the capacitive capture of CO2 by the system solution, while the pressure increase was due to the release of CO2 promoted by the applied reverse voltage. A similar trend of decreasing and increasing CO2 pressure with the application of both positive and reverse voltages was observed in the study by Kokoszka et al., revealing the "Supercapacitive Swing Adsorption" effect of CO2. Furthermore, the conductivity values ​​monitored in the system solution in this embodiment also reflect the capacitive capture process of CO2 within the system.

[0114] from Figure 2As shown in (b), after applying a positive voltage, the solution conductivity of the system rapidly increased from 1.93 μS / cm to 11.28 μS / cm within 0–0.45 h. This indicates that CO2 was dissolved in the original pure water system and successfully ionized into the corresponding ions (H+). + HCO3 - CO3 2- Within 0.45–4 hours, the conductivity decreased. This indicates that ions dissociated from CO2 were captured by the capacitor into the electrode solution and thus left the intermediate chamber solution. However, after applying a reverse voltage, the conductivity increased significantly, indicating that the ions stored in the electrode were released back into the intermediate chamber solution.

[0115] like Figure 3 As shown, FCDI CO2 capture is divided into two stages. The first stage: Gas CO2 in the gas-liquid contact system dissolves into the solution within the system, and the absorbed CO2 gas is converted into ions (H+) in the aqueous absorbent. + HCO3 - CO3 2- Second stage: dissociated ions H + HCO3 - CO3 2- Under the influence of an electric field, CO2 is adsorbed and stored in the flow electrode. Through these two stages, gaseous CO2 is successfully captured and stored in the electrode. The release and recovery of CO2 is the reverse process. When a reverse voltage is applied to the FCDI, HCO3... - CO3 2- Released from the electrode into the intermediate chamber, with H + The CO2 is then absorbed and released as gaseous CO2 in the intermediate chamber, causing the pressure to rise further and completing the CO2 recovery. During charging, the solution conductivity decreased for most of the time, indicating that in the simultaneous two-stage process, the rate of CO2 dissolution and dissociation into ions in the first stage was lower than in the second stage, potentially limiting the overall capture rate. Furthermore, there was a hysteresis in the response of pressure and conductivity after applying a reverse voltage. Both pressure and conductivity initially decreased for a short period before increasing, a hysteresis phenomenon reported in previous studies. This may be due to the different response rates of the two stages to voltage application.

[0116] The applied power intensity is an important factor affecting the performance of FCDI. In order to explore the influence of different voltage intensities on CO2 capture by FCDI, the charging voltage was adjusted to 0V, 0.1V, 0.4V, 0.8V and 1.2V in the same FCDI system, and the CO2 capture amount, removal rate, removal efficiency and energy consumption under different voltage conditions were compared.

[0117] Figure 4 The CO2 capture performance of FCDI under different voltages is shown in (a) capture amount and capture rate, and (b) capture efficiency and energy consumption. It can be seen that increasing the voltage intensity can improve the CO2 capture performance of FCDI. Without applied voltage (0V), the system has a certain CO2 capture capacity, with a CO2 capture amount, removal rate, and capture efficiency of 0.163±0.007mmol, 0.041±0.002mmol / h, and 13.05±0.58%, respectively. This may be due to the absorption of CO2 by the gas-liquid contact mass transfer within the system itself. When voltage is applied, even a 0.1V voltage application significantly improves the system's capture performance, with CO2 capture amount, removal rate, and capture efficiency of 0.318±0.019mmol, 0.080±0.005mmol / h, and 25.50±1.51%, respectively. When the voltage was further increased to 0.4V, the CO2 capture amount, removal rate, and capture efficiency further improved to 0.397±0.019mmol, 0.099±0.005mmol / h, and 31.77±1.50%, respectively, an increase of approximately 143.45% compared to 0V. These results demonstrate that applying voltage enables capacitive capture of CO2, and increasing the applied voltage intensity improves the performance of capacitive capture. Voltage is a crucial parameter affecting the deionization performance of FCDIs. Chang et al. previously found that increasing the voltage enhances the deionization performance of FCDIs. In the study by Kokoszka et al., cyclic GCD tests were performed using DC currents of 2mA and 10mA, similarly demonstrating that the effect of capacitive CO2 capture increases with increasing voltage. However, further increasing the voltage from 0.4V to 0.8V and 1.2V did not further improve the CO2 capture performance of the FCDI, with capture efficiencies reaching 31.40±1.52% and 31.68±0.59%, respectively. This is likely because when the applied voltage reaches 0.4V or higher, the low gas-liquid mass transfer efficiency in the first stage results in little impact on overall performance from increasing the voltage intensity, thus limiting the improvement of overall performance.

[0118] according to Figure 5 The changes in gas pressure (a) and current (b) during CO2 capture by FCDI under different voltages are shown. Further analysis of the energy consumption of FCDI at different voltages reveals that the energy consumption per unit of CO2 captured by FCDI increases with increasing voltage. When the voltage increases from 0.1V to 0.4V, 0.8V, and 1.2V, the energy consumption increases from 1.10±0.43kJ / mol to 5.72±0.55kJ / mol, 14.34±3.27kJ / mol, and 67.64±9.67kJ / mol, respectively.

[0119] according to Figure 6CO2 capture performance of FCDI at different stirring rates: (a) Capture amount and capture rate; (b) Capture efficiency and energy consumption. Increasing the stirring rate can improve the CO2 capture performance of FCDI. Without stirring (stirring rate of 0), the system has a low CO2 capture capacity, with CO2 capture amount, removal rate, and capture efficiency of 0.194±0.010 mmol, 0.049±0.003 mmol / h, and 15.55±0.80%, respectively. When the stirring rate is increased to 130 r / min, the CO2 capture amount, removal rate, and capture efficiency increase to 0.362±0.042 mmol, 0.090±0.011 mmol / h, and 28.99±3.38%, respectively. When the stirring rate was further increased to 350 r / min and 530 r / min, the CO2 capture amount, removal rate, and capture efficiency increased to 0.382±0.026 mmol, 0.095±0.006 mmol / h, and 30.60±2.04%, and 0.397±0.019 mmol, 0.099±0.005 mmol / h, and 31.77±1.50%, respectively. The capture efficiency at 530 r / min was approximately 104.31% higher than that at 0 r / min. Increased stirring rate leads to enhanced mass transfer within the liquid and increased activity of liquid micro-elements at the gas-liquid interface, promoting gas-liquid mass transfer and thus improving the overall capacitive capture effect. However, when the stirring rate was further increased to 700 r / min, the CO2 capture performance of FCDI decreased slightly compared to 530 r / min. The CO2 capture rate decreased to 0.389 ± 0.014 mmol, and the capture efficiency decreased to 31.19 ± 1.12%. This may be because the mass transfer improvement brought about by increasing the stirring rate has reached its limit, and further increasing the stirring rate can no longer further promote gas-liquid mass transfer. CO2 dissolution in water is a typical rate-limiting step.

[0120] Further analysis of the energy consumption of FCDI at different stirring rates reveals that the energy consumption per unit of CO2 captured by FCDI generally decreases with increasing stirring rate. The lowest energy consumption per unit of removal was achieved at a stirring rate of 530 r / min, which is 5.72 ± 0.55 kJ / mol.

[0121] Capacitive CO2 capture mainly consists of two stages. Stage 1: CO2 dissolves in the absorbent and is converted into HCO3. - CO3 2- Phase Two: Capacitive Capture of HCO3 - CO3 2- Plasma.

[0122] Calculations showed that the total CO2 content in the system was 1.23508 mmol. Therefore, an equal molar amount of sodium bicarbonate was introduced to observe the effect of the second-stage capacitive capture. Simultaneously, the rate-limiting conditions of the two stages in the capacitive capture process were analyzed by saturating the system with aeration and observing the deionization status after saturation.

[0123] Based on conductivity data, it can be found that, without the limitation of the first stage (CO2 absorption by the absorbent), FCDI can remove HCO3 from the system within half an hour. - The presence of ions indicates that the second-stage ion capture is not the rate-limiting step in the system. The impaired gas-liquid mass transfer in the first stage is the main factor contributing to the low capture rate.

[0124] Based on conductivity data, the maximum conductivity within the system after aeration saturation equilibrium is approximately 18 μS / cm. The decrease in conductivity reflects a decrease in ion concentration within the system. The first stage, gas entering the liquid and ionizing, is the process of ion generation; the second stage, ion capture by the capacitor, is the process of ion consumption. After applying an electric field, the gas-liquid mass transfer in the first stage and the capacitive ion capture in the second stage occur simultaneously. However, the conductivity shows a decreasing trend, decreasing by about two-thirds within the first two hours, indicating that the rate of ion capture in the second stage is faster than the rate of ion generation in the first stage, and that most of the CO2 capture is completed within the first two hours.

[0125] Nanofluids enhance the capacitive trapping performance of FCDI:

[0126] In this embodiment, the first stage of capacitive CO2 capture, i.e., the gas mass transfer into the liquid stage, is the rate-limiting stage. Therefore, preliminary experiments were conducted to enhance the mass transfer rate in the first stage, thereby improving the overall capture rate. Nanofluids can effectively enhance gas-liquid mass transfer efficiency. Therefore, Al2O3 and CNTs were selected to prepare nanofluids, and their performance in enhancing capacitive capture was investigated.

[0127] like Figure 7 The diagram shows the CO2 capture performance of FCDI with different nanofluid absorbents, where (a) represents the pressure change, (b) represents the capture amount, and (c) represents the capture rate. Under the same initial pressure (CO2 amount), FCDI using nanofluid as the absorbent exhibits significantly superior CO2 capture performance compared to FCDI using pure water as the absorbent. Within 4 hours, the FCDI using CNT nanofluid absorbent showed the largest pressure decrease. Figure 7 (a) thus results in the highest CO2 capture. For example... Figure 7(b) Within 4 hours, the CO2 capture capacity of FCDI containing CNT nanofluid reached 0.47 ± 0.04 mmol, and that of FCDI containing Al2O3 nanofluid reached 0.44 ± 0.01 mmol, representing increases of 12% and 18% respectively compared to FCDI using water as the absorbent. This demonstrates that nanofluids enhance the capacitive CO2 capture performance of FCDI. Figure 7 (c) Within 4 hours, the CO2 capture rates of FCDI using CNT nanofluids and Al2O3 nanofluids as absorbents were both higher than those of the blank FCDI using water as absorbent. Nanoparticles can effectively enhance the efficiency of gas-liquid mass transfer. Liang et al. found that TiO2 nanofluids were more effective than mixed MEA / MDEA solutions in improving CO2 capture performance, with an adsorption rate increase of up to 25%. Chandrasekar et al. used Al2O3 nanofluids to increase the CO2 adsorption rate in the system by more than 10%. CNTs are also common nanoparticles used to enhance gas-liquid mass transfer. Nabipour et al. used Fe3O4 and functionalized carbon nanotubes to enhance CO2 absorption, and functionalized carbon nanotubes showed superior enhancement performance, 7.3% higher than Fe3O4.

[0128] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A carbon dioxide capture method based on flow electrode capacitive deionization, characterized in that, include: A three-chamber flow electrode capacitive deionization device is constructed, comprising an anode chamber, a cathode chamber, and an intermediate chamber, wherein the intermediate chamber is isolated from the anode chamber and the cathode chamber by an ion exchange membrane; The intermediate chamber is connected to a gas-liquid contact system, which is a closed system comprising an absorbent liquid and a gas component. A gas containing carbon dioxide is introduced into the gas-liquid contact system; A positive voltage is applied between the anode and cathode of the flow electrode capacitor deionization device, so that the ions generated by the dissolution and ionization of carbon dioxide in the gas-liquid contact system are captured into the flow electrode. Applying a reverse voltage causes the captured carbon dioxide to be released; The three-chamber flow electrode capacitive deionization device includes: The cation exchange membrane and the anion exchange membrane are respectively disposed between the intermediate chamber and the anode chamber and the cathode chamber; A graphite current collector is disposed in the anode chamber and the cathode chamber, and the surface of the graphite current collector is provided with a serpentine flow channel; The gas-liquid contact system is connected to the water inlet pipe and water outlet pipe of the intermediate chamber through a pipeline, and a water distribution device is provided at the end of the water inlet pipe; The operation process of a gas-liquid contact system includes: Maintain a stirring rate of 530 r / min in a closed system; The flow rate of the absorption liquid was controlled at 10 mL / min using a peristaltic pump; The method employs an isolated closed-loop operation mode, including: The circulation of the absorbent liquid in the intermediate chamber is controlled by a peristaltic pump; The electrode solutions in the anode and cathode chambers are continuously stirred to maintain homogeneity.

2. The carbon dioxide capture method based on flow electrode capacitance deionization as described in claim 1, characterized in that, The fabrication process of the flow electrode includes: Mix activated carbon with deionized water; Stir at 300 r / min for 1 hour to form a homogeneous slurry with an activated carbon mass load of 2.5 wt%.

3. The carbon dioxide capture method based on flow electrode capacitance deionization as described in claim 1, characterized in that, The range of the applied positive voltage is 0.1V to 1.2V; A reverse voltage of 1.2V is applied.

4. The carbon dioxide capture method based on flow electrode capacitance deionization as described in claim 1, characterized in that, The absorbent is a nanofluid, and its preparation process includes: Nanoparticles are added to a deionized water-based solution; Stir at 200 rpm for 30 minutes; Dispersion is achieved by ultrasonic treatment for 1 hour.

5. The carbon dioxide capture method based on flow electrode capacitance deionization as described in claim 1, characterized in that, The carbon dioxide capture process consists of two stages: First stage: Carbon dioxide dissolves in the absorbent and ionizes to generate hydrogen ions, bicarbonate ions, and carbonate ions; Second stage: The ions migrate to the flow electrode for storage under the action of an electric field.

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