A multi-stage electrochemical carbon capture device and method of capture

Abstract

The application provides a multistage electrochemical carbon capture device and a capture method. The device comprises an absorption device, a preliminary desorption device and a deep desorption device, which are connected in series. The absorption device is a first electrolytic cell for absorbing and capturing carbon dioxide. The preliminary desorption device is a second electrolytic cell for preliminarily desorbing electrolyte in the first electrolytic cell. The deep desorption device is a third electrolytic cell for deeply desorbing electrolyte in the second electrolytic cell to release carbon dioxide. The electrolyte discharge outlets of the first, second and third electrolytic cells are connected in series by pipes. The multistage electrochemical carbon capture device can realize step-by-step desorption of carbon dioxide, reduce overall energy consumption, improve the desorption efficiency and capture purity of carbon dioxide, reduce electrode polarization and prolong the service life of the electrode.

Description

Technical Field

[0001] This application belongs to the technical field of carbon capture devices, specifically relating to a multi-stage electrochemical carbon capture device and capture method. Background Technology

[0002] Global warming is closely related to carbon dioxide emissions. Current chemical adsorption methods often use amine solutions to absorb carbon dioxide, but these methods suffer from high energy consumption and severe damage from dissolution and degradation. Electrochemical carbon dioxide capture technology, driven by voltage, theoretically consumes less energy, is more environmentally friendly, and offers greater flexibility for subsequent technology promotion and application.

[0003] However, the currently widely used single-stage electrochemical systems still suffer from problems such as requiring high voltage or long operating times for a single desorption cycle, resulting in insufficient energy density and low desorption efficiency. In addition, single-stage capture is difficult to achieve high-purity carbon dioxide enrichment, has a concentration gradient bottleneck, and continuous high current density causes electrode polarization, leading to rapid failure of electrode materials. Summary of the Invention

[0004] This application provides a multi-stage electrochemical carbon capture device and method, aiming to solve the problems of high energy consumption, low desorption efficiency, low carbon dioxide enrichment purity, short electrode lifespan, and poor system stability of existing electrochemical carbon capture devices.

[0005] The first aspect of this application provides a multi-stage electrochemical carbon capture device, including an absorption device, a preliminary desorption device, and a deep desorption device, wherein the absorption device, the preliminary desorption device, and the deep desorption device are connected in series in sequence.

[0006] The absorption device is a first electrolytic cell used to absorb and capture carbon dioxide; The preliminary desorption device is a second electrolytic cell, used for the preliminary desorption of the electrolyte in the first electrolytic cell; The deep desorption device is a third electrolytic cell, used to deeply desorb the electrolyte in the second electrolytic cell and release carbon dioxide; The electrolyte outlets of the first electrolytic cell, the second electrolytic cell, and the third electrolytic cell are connected in series via pipes.

[0007] The multi-stage electrochemical carbon capture device described in this application optimizes energy consumption and efficiency through multi-stage desorption. By decomposing the high-energy-consuming desorption process into two steps—"preliminary" and "deep" desorption—it avoids the energy barrier of single-stage high-voltage desorption and significantly reduces the total system energy consumption.

[0008] According to some embodiments of the multi-stage electrochemical carbon capture device described in this application, the anode of the first electrolytic cell is a carbon fiber cloth coated with MnO2 / CNT, the cathode of the first electrolytic cell is a nickel mesh loaded with Cu / ZIF-8 catalyst, and the electrolyte used in the first electrolytic cell is a 0.5-1.5 mol / L potassium hydroxide solution.

[0009] According to some embodiments of the multi-stage electrochemical carbon capture device described in this application, the anode of the second electrolytic cell is a carbon fiber cloth coated with MnO2 / CNT, the cathode of the second electrolytic cell is a nickel mesh, and the electrolyte used in the second electrolytic cell is the electrolyte that has absorbed carbon dioxide and flows out of the first electrolytic cell.

[0010] According to some embodiments of the multi-stage electrochemical carbon capture device described in this application, the anode of the third electrolytic cell is a carbon fiber cloth coated with MnO2 / CNT, the cathode of the third electrolytic cell is a nickel mesh loaded with a nitrogen-doped carbon catalyst, and the electrolyte used in the third electrolytic cell is the electrolyte after preliminary desorption flowing out of the second electrolytic cell.

[0011] According to some embodiments of the multi-stage electrochemical carbon capture device described in this application, it also includes a molecular sieve adsorption column, a stripping tower, a regeneration tank, and a working liquid tank. The carbon dioxide generated by desorption in the third electrolytic cell is purified by a molecular sieve adsorption column. The desorption liquid generated by the third electrolytic cell is treated by a stripping tower to remove residual carbon dioxide, flows into a regeneration tank to adjust the pH, and is then transported to a working liquid tank for reuse.

[0012] The second aspect of this application provides a method for capturing carbon dioxide, implemented using the multi-stage electrochemical carbon capture device described in the first aspect of this application.

[0013] According to some embodiments of the carbon dioxide capture method described in this application, the method includes the following steps: passing flue gas containing carbon dioxide into a first electrolytic cell, where the electrolyte in the first electrolytic cell reacts with the carbon dioxide to achieve carbon dioxide enrichment; the electrolyte enriched with carbon dioxide flows into a second electrolytic cell for preliminary desorption, and the electrolyte after preliminary desorption flows into a third electrolytic cell for deep desorption to release carbon dioxide.

[0014] According to some embodiments of the carbon dioxide capture method described in this application, the voltage for the first electrolytic cell to absorb and capture carbon dioxide is 0.8-1.2V, and the hydraulic residence time of the electrolyte in the first electrolytic cell is 15-25min.

[0015] According to some embodiments of the carbon dioxide capture method described in this application, the voltage for initial desorption in the second electrolytic cell is 1.8-2.2V, and the hydraulic residence time of the electrolyte in the second electrolytic cell is 8-12min.

[0016] According to some embodiments of the carbon dioxide capture method described in this application, the voltage for deep desorption in the third electrolytic cell is 2.8-3.5V, and the hydraulic residence time of the electrolyte in the third electrolytic cell is 5-10 minutes.

[0017] According to some embodiments of the carbon dioxide capture method described in this application, the method further includes the steps of: conveying the desorption liquid generated by the third electrolyzer to a stripping tower to remove residual carbon dioxide, then conveying it to a regeneration tank, adjusting the pH of the desorption liquid to 10-11, and then conveying it to a working liquid tank for reuse.

[0018] According to some embodiments of the carbon dioxide capture method described in this application, the method further includes the step of: conveying the carbon dioxide generated by desorption in the third electrolytic cell to a molecular sieve adsorption column for purification.

[0019] According to some embodiments of the carbon dioxide capture method described in this application, the flow rate of flue gas entering the first electrolytic cell is 3-8 L / min.

[0020] According to some embodiments of the carbon dioxide capture method described in this application, the volume content of carbon dioxide in the flue gas is 10%-20%.

[0021] The beneficial effects of this application include: the multi-stage electrochemical carbon capture device described in this application achieves stepwise desorption of carbon dioxide through the series connection of multi-stage electrolyzers, reducing overall energy consumption (20-30% lower than that of a single-stage system); it improves the desorption efficiency and capture purity of carbon dioxide (up to 99.5% or more), reduces electrode polarization, and extends the service life of the electrodes.

[0022] The multi-stage electrochemical carbon capture device described in this application is highly flexible, easy to integrate with existing carbon capture processes, and the electrolyte can be recycled, reducing operating costs. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the multi-stage electrochemical carbon capture device described in this application. Detailed Implementation

[0024] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0025] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0026] This application provides a multi-stage electrochemical carbon capture device, including an absorption device, a preliminary desorption device, and a deep desorption device, wherein the absorption device, the preliminary desorption device, and the deep desorption device are connected in series. The absorption device is a first electrolytic cell used to absorb and capture carbon dioxide; The preliminary desorption device is a second electrolytic cell, used for the preliminary desorption of the electrolyte in the first electrolytic cell; The deep desorption device is a third electrolytic cell, used to deeply desorb the electrolyte in the second electrolytic cell and release carbon dioxide; The electrolyte outlets of the first electrolytic cell, the second electrolytic cell, and the third electrolytic cell are connected in series via pipes.

[0027] The multi-stage electrochemical carbon capture device described in this application optimizes energy consumption and efficiency through multi-stage desorption. By decomposing the high-energy-consuming desorption process into two steps—"preliminary" and "deep" desorption—it avoids the energy barrier of single-stage high-voltage desorption and significantly reduces the total system energy consumption.

[0028] In some embodiments of this application, the anode of the first electrolytic cell is a carbon fiber cloth coated with MnO2 / CNT, the cathode of the first electrolytic cell is a nickel mesh supported on a Cu / ZIF-8 catalyst, and the electrolyte used in the first electrolytic cell is a 0.5-1.5 mol / L potassium hydroxide solution. Under applied voltage, an electrochemical reduction reaction occurs at the cathode. The Cu / ZIF-8 catalyst utilizes its large specific surface area to enrich CO2 molecules, and through the catalytic effect of Cu, greatly promotes the reaction of CO2 with OH- in the electrolyte. - The reaction (CO2 + OH) - →HCO3 - This allows for the efficient absorption and chemical fixation of carbon dioxide. At the anode, the oxygen evolution reaction (OER) occurs, providing a continuous and stable current.

[0029] In some embodiments of this application, the anode of the second electrolytic cell is a carbon fiber cloth coated with MnO2 / CNT, the cathode of the second electrolytic cell is a nickel mesh, and the electrolyte used in the second electrolytic cell is the electrolyte that has absorbed carbon dioxide flowing out of the first electrolytic cell. Under a relatively high voltage, the anode MnO2 / CNT catalyzes the oxidation of water to produce a large amount of H2O. + (2H2O→4H) + +O2+4e - These H + It will protonate the bicarbonate (HCO3) from the first electrolyzer. - +H + →CO2↑+H2O), forcing approximately 50%-70% of the carbon dioxide to be "initially desorbed" as a gas. The cathode primarily undergoes the hydrogen evolution reaction (HER), forming a current loop.

[0030] In some embodiments of this application, the anode of the third electrolytic cell is a carbon fiber cloth coated with MnO2 / CNT, the cathode of the third electrolytic cell is a nickel mesh loaded with a nitrogen-doped carbon catalyst, and the electrolyte used in the third electrolytic cell is the electrolyte from the second electrolytic cell after preliminary desorption. At a relatively higher voltage, the anode continues to generate a high concentration of H2. + This process "forces" protonation of the remaining, more tightly bound carbonate / bicarbonate residues in the solution, achieving "deep desorption" and releasing the vast majority of the remaining CO2. Because nitrogen-doped carbon cathodes exhibit excellent hydrogen evolution reaction (HER) catalytic activity and stability at high potentials, the deep desorption process can be carried out efficiently and energy-savingly.

[0031] In some embodiments of this application, a molecular sieve adsorption column, a stripping tower, a regeneration tank, and a working fluid tank are also included. The carbon dioxide produced by desorption in the third electrolytic cell is purified by a molecular sieve adsorption column to remove water vapor carried in the CO2 gas and trace amounts of oxygen produced by the anode side reaction. The purified carbon dioxide has a purity of over 99.5%.

[0032] The desorbed liquid produced by the third electrolytic cell is treated by a stripping tower to remove residual carbon dioxide, flows into a regeneration tank to adjust the pH, and is then transferred to the working liquid tank for reuse. The pH of the liquid flowing into the regeneration tank is adjusted to 10.0-11.0, preferably 10.5. Under these alkaline conditions, the electrolyte regains its high reactivity to CO2, ensuring that after being pumped back to the first electrolytic cell, it can immediately restart the efficient capture process, achieving closed-loop operation of the system.

[0033] The working liquid tank is connected to the first electrolytic cell via a pipeline, supplying electrolyte into the first electrolytic cell. The working liquid tank ensures a continuous and stable supply of electrolyte to the first electrolytic cell, thereby guaranteeing the continuity and stability of the entire process. Furthermore, within the working liquid tank, the solution is thoroughly mixed and homogenized, ensuring its stable properties and optimizing the electrolyte supply to the first electrolytic cell.

[0034] This application also provides a method for capturing carbon dioxide, implemented using the multi-stage electrochemical carbon capture device described in the first aspect of this application.

[0035] In some embodiments of this application, the process includes the following steps: Flue gas containing carbon dioxide is introduced into a first electrolytic cell; the electrolyte in the first electrolytic cell reacts with the carbon dioxide to enrich it; the electrolyte enriched with carbon dioxide flows into a second electrolytic cell for preliminary desorption; the electrolyte after preliminary desorption flows into a third electrolytic cell for deep desorption, releasing carbon dioxide. In the first electrolytic cell, the electrolyte undergoes an electrochemical absorption reaction with CO2 in the flue gas to generate carbonates, achieving CO2 enrichment; in the second electrolytic cell, the carbonates partially decompose, releasing approximately 50-70% of the CO2, reducing the load on the third electrolytic cell; in the third electrolytic cell, the remaining carbonates completely decompose, releasing high-purity CO2, achieving complete desorption.

[0036] The significance of multi-stage voltage settings lies in optimizing energy consumption and desorption efficiency step by step, avoiding the high energy consumption and electrode damage of single-stage systems. In some embodiments of this application, the voltage for the first electrolytic cell to absorb and capture carbon dioxide is 0.8-1.2V, such as 0.8V, 1.0V, 1.12V, 1.2V, etc., and the hydraulic residence time of the electrolyte in the first electrolytic cell is 15-25min, such as 15min, 18min, 20min, 22min, 25min, etc. Within this voltage range, efficient absorption can be ensured while reducing energy consumption and avoiding electrode polarization.

[0037] In some embodiments of this application, the voltage for initial desorption in the second electrolytic cell is 1.8-2.2V, such as 1.8V, 1.9V, 2.0V, 2.1V, 2.2V, etc., and the hydraulic residence time of the electrolyte in the second electrolytic cell is 8-12min, such as 8min, 9min, 10min, 12min, etc. Within this voltage range, partial desorption can be triggered, reducing the load of subsequent deep desorption and improving overall efficiency.

[0038] In some embodiments of this application, the voltage for deep desorption in the third electrolytic cell is 2.8-3.5V, such as 2.8V, 3.0V, 3.2V, 3.3V, 3.5V, etc., and the hydraulic residence time of the electrolyte in the third electrolytic cell is 5-10min, such as 5min, 6min, 8min, 10min, etc. Within this voltage range, the remaining carbon dioxide can be forced to be completely released, ensuring high-purity desorption.

[0039] The electrodes of each stage of the carbon capture device described in this application are customized according to the chemical reactions they undertake (absorption, primary desorption, and deep desorption). In particular, the use of stable MnO2 / CNT anodes and ZIF-8-based cathodes with high specific surface area effectively reduces electrode polarization and deactivation, and improves the long-term stability of the system.

[0040] In some embodiments of this application, the method further includes the steps of: conveying the desorption liquid generated by the third electrolytic cell to a stripping tower to remove residual carbon dioxide, then conveying it to a regeneration tank, adjusting the pH of the desorption liquid to 10-11, and then conveying it to a working liquid tank for reuse.

[0041] In some embodiments of this application, the step of: conveying the carbon dioxide generated by desorption in the third electrolytic cell to a molecular sieve adsorption column for purification.

[0042] In some embodiments of this application, the flow rate of flue gas entering the first electrolytic cell is 3-8 L / min; for example, 3 L / min, 4 L / min, 5 L / min, 6 L / min, 8 L / min, etc.

[0043] In some embodiments of this application, the carbon dioxide content in the flue gas is 10%-20%.

[0044] The technical solution of this application will be further explained and illustrated below with reference to the embodiments.

[0045] Example 1 A multi-stage electrochemical carbon capture device includes an absorption device, a preliminary desorption device, and a deep desorption device, which are connected in series. In this embodiment, the absorption device is a first electrolytic cell used to absorb and capture carbon dioxide; the preliminary desorption device is a second electrolytic cell used to perform preliminary desorption of the electrolyte in the first electrolytic cell; and the deep desorption device is a third electrolytic cell used to perform deep desorption of the electrolyte in the second electrolytic cell, releasing carbon dioxide. The electrolyte outlets of the first, second, and third electrolytic cells are connected in series via pipelines.

[0046] To maximize the enrichment of carbon dioxide in the flue gas within the first electrolytic cell, the anode of the first electrolytic cell is a carbon fiber cloth coated with MnO2 / CNT, the cathode of the first electrolytic cell is a nickel mesh loaded with Cu / ZIF-8 catalyst, and the electrolyte used in the first electrolytic cell is a 1 mol / L potassium hydroxide solution. To achieve partial desorption of the enriched carbon dioxide electrolyte, the anode of the second electrolytic cell is a carbon fiber cloth coated with MnO2 / CNT, the cathode of the second electrolytic cell is a nickel mesh, and the electrolyte used in the second electrolytic cell is the electrolyte from the first electrolytic cell after absorbing carbon dioxide. To completely release carbon dioxide from the electrolyte, the anode of the third electrolytic cell is a carbon fiber cloth coated with MnO2 / CNT, the cathode of the third electrolytic cell is a nickel mesh loaded with nitrogen-doped carbon catalyst, and the electrolyte used in the third electrolytic cell is the electrolyte from the second electrolytic cell after preliminary desorption.

[0047] To facilitate purification and reuse in subsequent processes, this embodiment also includes a molecular sieve adsorption column, a stripping tower, a regeneration tank, and a working liquid tank; the carbon dioxide desorbed from the third electrolytic cell is purified by the molecular sieve adsorption column; water vapor carried in the CO2 gas and trace amounts of oxygen generated by the anode side reaction are removed to obtain carbon dioxide with a purity of over 99.5%. The desorbed liquid generated by the third electrolytic cell is treated by a stripping tower to remove residual carbon dioxide, flows into a regeneration tank to adjust the pH, and is then transported to a working liquid tank for reuse, thus realizing the closed-loop operation of the system.

[0048] Example 2 A method for capturing carbon dioxide, implemented using the multi-stage electrochemical carbon capture device described in Example 1 of this application; The specific operating steps include: Flue gas with a carbon dioxide volume content of 15% is introduced into the first electrolytic cell (the flue gas flow rate is controlled at 5 L / min). The operating voltage of the first electrolytic cell is set to 1.0 V, and the hydraulic residence time of the electrolyte in the first electrolytic cell is controlled at 20 min. The electrolyte that has absorbed carbon dioxide in the first electrolytic cell is transferred to the second electrolytic cell. The operating voltage of the second electrolytic cell is set to 2.0 V, and the hydraulic residence time of the electrolyte in the second electrolytic cell is controlled at 10 min, so that the electrolyte that has absorbed carbon dioxide undergoes preliminary desorption. The initially desorbed electrolyte is transferred to the third electrolytic cell. The operating voltage of the third electrolytic cell is set to 3.0 V, and the hydraulic residence time of the electrolyte in the third electrolytic cell is controlled at 5 min, so as to achieve deep desorption of carbon dioxide. The carbon dioxide desorbed from the third electrolytic cell is transported to a molecular sieve adsorption column for purification. The desorbed liquid from the third electrolytic cell is then transported to a stripping tower to remove residual carbon dioxide, and then to a regeneration tank. The pH of the desorbed liquid is adjusted to 10.5, and then it is transported to a working liquid tank, and finally from the working liquid tank to the first electrolytic cell for reuse.

[0049] Comparative Example 1 The only difference between the carbon dioxide capture method described in Comparative Example 1 and Example 2 is that the operating voltages of the second and third electrolyzers during the carbon dioxide capture process described in Comparative Example 1 are different from those in Example 2.

[0050] The specific operating steps include: Flue gas with a carbon dioxide volume content of 15% is introduced into the first electrolytic cell (the flue gas flow rate is controlled at 5 L / min). The operating voltage of the first electrolytic cell is set to 1.0 V, and the hydraulic residence time of the electrolyte in the first electrolytic cell is controlled at 20 min. The electrolyte that has absorbed carbon dioxide in the first electrolytic cell is then transferred to the second electrolytic cell. The operating voltage of the second electrolytic cell is set to 1.0 V, and the hydraulic residence time of the electrolyte in the second electrolytic cell is controlled at 10 min, allowing the electrolyte that has absorbed carbon dioxide to undergo initial desorption. The initially desorbed electrolyte is then transferred to the third electrolytic cell. The operating voltage of the third electrolytic cell is set to 2.0 V, and the hydraulic residence time of the electrolyte in the third electrolytic cell is controlled at 5 min, achieving deep desorption of carbon dioxide. The carbon dioxide desorbed from the third electrolytic cell is transported to a molecular sieve adsorption column for purification. The desorbed liquid from the third electrolytic cell is then transported to a stripping tower to remove residual carbon dioxide, and then to a regeneration tank. The pH of the desorbed liquid is adjusted to 10.5, and then it is transported to a working liquid tank, and finally from the working liquid tank to the first electrolytic cell for reuse.

[0051] Comparative Example 2 The only difference between the carbon dioxide capture method described in Comparative Example 2 and Example 2 is that the operating voltage of the second electrolyzer during the carbon dioxide capture process in Comparative Example 2 is different from that in Example 2.

[0052] The specific operating steps include: Flue gas with a carbon dioxide volume content of 15% is introduced into the first electrolytic cell (the flue gas flow rate is controlled at 5 L / min). The operating voltage of the first electrolytic cell is set to 1.0 V, and the hydraulic residence time of the electrolyte in the first electrolytic cell is controlled at 20 min. The electrolyte that has absorbed carbon dioxide in the first electrolytic cell is transferred to the second electrolytic cell. The operating voltage of the second electrolytic cell is set to 3.0 V, and the hydraulic residence time of the electrolyte in the second electrolytic cell is controlled at 10 min, so that the electrolyte that has absorbed carbon dioxide undergoes preliminary desorption. The initially desorbed electrolyte is transferred to the third electrolytic cell. The operating voltage of the third electrolytic cell is set to 3.0 V, and the hydraulic residence time of the electrolyte in the third electrolytic cell is controlled at 5 min, so as to achieve deep desorption of carbon dioxide. The carbon dioxide desorbed from the third electrolytic cell is transported to a molecular sieve adsorption column for purification. The desorbed liquid from the third electrolytic cell is then transported to a stripping tower to remove residual carbon dioxide, and then to a regeneration tank. The pH of the desorbed liquid is adjusted to 10.5, and then it is transported to a working liquid tank, and finally from the working liquid tank to the first electrolytic cell for reuse.

[0053] Comparative Example 3 The only difference between the carbon dioxide capture method described in Comparative Example 3 and Example 2 is that only one electrolytic cell is used for desorption during the carbon dioxide capture process described in Comparative Example 3 (the preliminary desorption operation of the second electrolytic cell is omitted).

[0054] The specific operating steps include: Flue gas with a carbon dioxide volume content of 15% is introduced into the first electrolytic cell (flue gas flow rate controlled at 5 L / min). The operating voltage of the first electrolytic cell is set to 1.0 V, and the hydraulic residence time of the electrolyte in the first electrolytic cell is controlled at 20 min. The electrolyte that has absorbed carbon dioxide in the first electrolytic cell is transferred to the third electrolytic cell. The operating voltage of the third electrolytic cell is set to 3.5 V, and the hydraulic residence time of the electrolyte in the third electrolytic cell is controlled at 5 min, achieving deep desorption of carbon dioxide. The carbon dioxide desorbed in the third electrolytic cell is transferred to a molecular sieve adsorption column for purification. The desorbed liquid from the third electrolytic cell is transferred to a stripping tower to remove residual carbon dioxide, then transferred to a regeneration tank. The pH of the desorbed liquid is adjusted to 10.5, then transferred to a working liquid tank, and finally transferred back to the first electrolytic cell for reuse.

[0055] The effects of the carbon dioxide capture methods described in Example 1 and Comparative Examples 1-3 of this application were studied, and the results are shown in Table 1.

[0056] Table 1

[0057] As can be seen from Table 1, the method for capturing carbon dioxide in flue gas described in this application has the advantages of high capture rate, high purity of carbon dioxide, low energy consumption, and long mechanical life.

[0058] In Comparative Example 1, the operating voltages of the second and third electrolytic cells were set too low, resulting in incomplete carbon dioxide desorption and substandard purity. In Comparative Example 2, the operating voltage of the second electrolytic cell was set too high, leading to excessive carbon dioxide desorption, excessive energy consumption, and damage to the electrodes due to the high voltage. Comparative Example 3 omitted the preliminary desorption operation, resulting in low overall system efficiency, excessive energy consumption, and low comprehensive efficiency.

[0059] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A multi-stage electrochemical carbon capture device, characterized in that, It includes an absorption device, a preliminary desorption device, and a deep desorption device, wherein the absorption device, the preliminary desorption device, and the deep desorption device are connected in series. The absorption device is a first electrolytic cell used to absorb and capture carbon dioxide; The preliminary desorption device is a second electrolytic cell, used for the preliminary desorption of the electrolyte in the first electrolytic cell; The deep desorption device is a third electrolytic cell, used to deeply desorb the electrolyte in the second electrolytic cell and release carbon dioxide; The electrolyte outlets of the first electrolytic cell, the second electrolytic cell, and the third electrolytic cell are connected in series via pipes.

2. The multi-stage electrochemical carbon capture device according to claim 1, characterized in that, The anode of the first electrolytic cell is a carbon fiber cloth coated with MnO2 / CNT, the cathode of the first electrolytic cell is a nickel mesh loaded with Cu / ZIF-8 catalyst, and the electrolyte used in the first electrolytic cell is a 0.5-1.5 mol / L potassium hydroxide solution.

3. The multi-stage electrochemical carbon capture device according to claim 1, characterized in that, The anode of the second electrolytic cell is a carbon fiber cloth coated with MnO2 / CNT, the cathode of the second electrolytic cell is a nickel mesh, and the electrolyte used in the second electrolytic cell is the electrolyte that has absorbed carbon dioxide and flows out of the first electrolytic cell.

4. The multi-stage electrochemical carbon capture device according to claim 1, characterized in that, The anode of the third electrolytic cell is a carbon fiber cloth coated with MnO2 / CNT, the cathode of the third electrolytic cell is a nickel mesh loaded with a nitrogen-doped carbon catalyst, and the electrolyte used in the third electrolytic cell is the electrolyte that has undergone preliminary desorption from the second electrolytic cell.

5. The multi-stage electrochemical carbon capture device according to claim 1, characterized in that, It also includes molecular sieve adsorption columns, stripping towers, regeneration tanks, and working fluid tanks; The carbon dioxide generated by desorption in the third electrolytic cell is purified by a molecular sieve adsorption column. The desorption liquid generated by the third electrolytic cell is treated by a stripping tower to remove residual carbon dioxide, flows into a regeneration tank to adjust the pH, and is then transported to a working liquid tank for reuse.

6. A method for capturing carbon dioxide, characterized in that, The multi-stage electrochemical carbon capture device according to any one of claims 1-5 is used.

7. The method for capturing carbon dioxide according to claim 6, characterized in that, Includes the following steps: Flue gas containing carbon dioxide is passed into the first electrolytic cell, where the electrolyte reacts with the carbon dioxide to enrich it. The electrolyte enriched with carbon dioxide flows into the second electrolytic cell for preliminary desorption, and the electrolyte after preliminary desorption flows into the third electrolytic cell for deep desorption to release the carbon dioxide.

8. The method for capturing carbon dioxide according to claim 7, characterized in that, The voltage for absorbing and capturing carbon dioxide in the first electrolytic cell is 0.8-1.2V, and the hydraulic residence time of the electrolyte in the first electrolytic cell is 15-25min. And / or, the voltage for initial desorption in the second electrolytic cell is 1.8-2.2V, and the hydraulic residence time of the electrolyte in the second electrolytic cell is 8-12min; And / or, the voltage for deep desorption in the third electrolytic cell is 2.8-3.5V, and the hydraulic residence time of the electrolyte in the third electrolytic cell is 5-10min.

9. The method for capturing carbon dioxide according to claim 7, characterized in that, The process also includes the following steps: the desorbent produced by the third electrolytic cell is transported to the stripping tower to remove residual carbon dioxide, then to the regeneration tank, the pH of the desorbent is adjusted to 10-11, and then to the working tank for reuse. And / or, it also includes the step of: conveying the carbon dioxide generated by desorption in the third electrolytic cell to a molecular sieve adsorption column for purification.

10. The method for capturing carbon dioxide according to claim 7, characterized in that, The flow rate of flue gas entering the first electrolytic cell is 3-8 L / min; And / or, the volumetric carbon dioxide content in the flue gas is 10%-20%.

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