Carbon dioxide capture method

Abstract

The application provides a carbon dioxide capturing method. The carbon dioxide capturing method comprises the following steps: spraying an alkaline solution through a spraying structure, so that the alkaline solution flowing out of the spraying structure chemically reacts with carbon dioxide gas in a gas to absorb the carbon dioxide gas; buffering the solution after the chemical reaction with the carbon dioxide gas through a buffering structure, and making the solution buffered in the buffering structure flow out through the spraying structure; detecting the concentration of hydroxyl ions and / or the concentration of carbonate ions in the solution in the buffering structure in real time, and supplementing the alkaline solution or water in the buffering structure according to the concentration of hydroxyl ions and the concentration of carbonate ions; if the concentration of hydroxyl ions is less than or equal to m and the concentration of carbonate ions is n, stopping the operation of a circulating pump to make the solution buffered in the buffering structure enter an electrolysis device to be electrolyzed. The application effectively solves the problem that the capturing efficiency of carbon dioxide gas and the overall energy consumption of the carbon dioxide capturing system in the prior art are difficult to control.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide capture technology, and more specifically, to a method for capturing carbon dioxide. Background Technology

[0002] Currently, the mainstream CO2 capture methods both domestically and internationally include liquid amine adsorption and solid membrane adsorption. However, these methods can only capture high concentrations of CO2 and cannot capture CO2 over a wide concentration range, such as low concentrations of CO2 in the air.

[0003] In the prior art, in order to solve the above problems, a method is adopted to capture carbon sources with a wide concentration range, such as air and flue gas, using inorganic alkalis such as potassium hydroxide as liquid absorbents. The captured inorganic alkali solution is converted into a carbonate aqueous solution and can be regenerated by electrolysis.

[0004] However, during electrolysis, both excessively high and low carbonate concentrations can lead to increased electrolytic cell voltage, increasing system energy consumption. For the remaining inorganic alkali, if the concentration is too high, all hydroxide ions in the inorganic alkali must be consumed before carbonate electrolysis can proceed, resulting in significant energy consumption. Conversely, if the concentration is too low, the carbon dioxide capture efficiency cannot be effectively guaranteed during the capture process. Therefore, existing carbon dioxide capture systems struggle to control both capture efficiency and overall energy consumption. Summary of the Invention

[0005] The main objective of this invention is to provide a carbon dioxide capture method to solve the problem that the capture efficiency and overall energy consumption of carbon dioxide gas in existing carbon dioxide gas capture systems are difficult to control.

[0006] To achieve the above objectives, the present invention provides a carbon dioxide capture method, comprising: spraying an alkaline solution through a spray structure to allow the alkaline solution flowing out of the spray structure to chemically react with carbon dioxide gas in the gas, thereby absorbing the carbon dioxide gas; buffering the solution after the chemical reaction with the carbon dioxide gas through a buffer structure, and the solution buffered in the buffer structure flowing out through the spray structure; wherein, the hydroxide and / or carbonate concentrations in the solution within the buffer structure are monitored in real time, and alkaline solution or water is added to the buffer structure according to the hydroxide and carbonate concentrations; during the real-time monitoring of the hydroxide and / or carbonate concentrations in the solution within the buffer structure, if the detected hydroxide concentration is less than or equal to m and the carbonate concentration is n, the circulation pump is controlled to stop operating, so that the solution buffered in the buffer structure enters an electrolysis device for electrolysis.

[0007] Furthermore, the method for the solution buffered in the buffer structure to flow out through the spray structure includes: starting a circulation pump to pump the solution buffered in the buffer structure through a pipeline into the spray structure.

[0008] Furthermore, the method of replenishing the buffer structure with alkaline solution or water according to the hydroxide and / or carbonate concentrations includes: if the detected hydroxide concentration is less than m and the carbonate concentration is less than n, replenishing the buffer structure with alkaline solution; if the detected hydroxide concentration is less than or equal to m and the carbonate concentration is greater than n, replenishing the buffer structure with water.

[0009] Furthermore, the method for real-time detection of hydroxide ion concentration in the solution within the buffer structure includes: sending the solution into a potentiometric titrator, adding a standard acid with a calibrated H+ concentration to the solution, continuously stirring during the titration process and recording the first differential curve of the added standard acid volume and the solution potential until the first differential curve of the solution potential reaches the first peak, and calculating the hydroxide ion concentration of the solution using the standard acid volume consumed at this time.

[0010] Furthermore, the method for real-time detection of carbonate concentration in the solution within the buffer structure includes: adding a standard acid with a calibrated H+ concentration to the solution, continuously stirring and recording the first-order differential curve of the added standard acid volume and the solution potential during the titration process, until the first-order differential curve of the solution potential reaches the first peak, and recording the volume of standard acid consumed at this time as V1; continuing to add the standard acid with a calibrated H+ concentration to the solution, continuing to stir and recording the first-order differential curve of the added standard acid volume and the solution potential during the titration process, until the first-order differential curve of the solution potential reaches the second peak, and recording the volume of standard acid consumed at this time as V2; and calculating the carbonate concentration of the solution using the difference between V2 and V1.

[0011] Furthermore, m is greater than or equal to 0.1 mol / L and less than or equal to 5 mol / L; and / or n is greater than or equal to 1 mol / L and less than or equal to 6 mol / L.

[0012] Furthermore, m is greater than or equal to 0.3 mol / L and less than or equal to 2 mol / L; and / or n is greater than or equal to 2 mol / L and less than or equal to 5.5 mol / L.

[0013] Furthermore, during the process of the solution buffered in the buffer structure entering the electrolysis device for electrolysis, the carbon dioxide capture method also includes: adjusting the amount of electricity applied to the electrolysis device to control the production ratio and / or output of carbon dioxide gas and hydrogen gas per unit time in the electrolysis device.

[0014] Furthermore, the method for adjusting the amount of electricity applied to the electrolysis equipment includes: obtaining a preset amount of electricity Q applied to the electrolysis equipment when the production ratio of carbon dioxide gas and hydrogen gas is 1; and increasing nQ on the basis of the preset amount of electricity Q to adjust the production ratio of carbon dioxide gas and hydrogen gas; wherein, n=1,2,3,…,N (N≤n).

[0015] Furthermore, in the process of adjusting the production ratio of carbon dioxide gas and hydrogen gas, the carbon dioxide capture method also includes: real-time detection of the electrolyte content in the electrolysis equipment; if the electrolyte content is less than a preset value, adding electrolyte to the electrolysis equipment; wherein the electrolyte is an alkali metal sulfate, alkali metal nitrate, or alkali metal phosphate.

[0016] Furthermore, the method for caching the solution after chemical reaction with carbon dioxide gas through a caching structure includes: setting at least two caching structures to switch between operation, each caching structure selectively caching the solution after chemical reaction with carbon dioxide gas; wherein, if the carbonate concentration in one caching structure reaches a preset concentration value, this caching structure is deactivated and the other caching structures are activated.

[0017] The present invention utilizes an alkaline solution sprayed through a spray structure to allow the alkaline solution flowing out of the spray structure to chemically react with carbon dioxide gas, thereby absorbing the carbon dioxide. During this process, a buffer structure stores the solution after the chemical reaction with the carbon dioxide gas. The buffered solution then flows out again through the spray structure, achieving solution recycling. During the carbon dioxide capture process, the hydroxide and / or carbonate concentrations in the solution within the buffer structure are monitored in real time. Based on these concentrations, alkaline solution or water is added to the buffer structure. This precise control of the final hydroxide and carbonate concentrations in the solution, achieved through alkaline replenishment or water addition, precisely meets the requirements of subsequent electrolysis processes, reduces overall system energy consumption, and solves the problem of difficulty in controlling the capture efficiency and overall energy consumption of carbon dioxide capture systems in existing technologies, thus improving the capture efficiency of the carbon dioxide capture system. In the process of real-time detection of hydroxide and / or carbonate concentrations in the solution within the buffer structure, if the hydroxide concentration is less than or equal to m and the carbonate concentration is n, the circulation pump is controlled to stop running so that the solution buffered in the buffer structure can enter the electrolysis device for electrolysis. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 A flowchart illustrating an embodiment of the carbon dioxide capture method according to the present invention is shown;

[0020] Figure 2 It shows Figure 1 The carbon dioxide capture method in the article is a method for treating different concentrations of hydroxide and carbonate ions in the solution within the buffer structure. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0023] In this invention, unless otherwise stated, directional terms such as "up" and "down" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction; similarly, for ease of understanding and description, "left" and "right" are generally used in relation to the left and right shown in the accompanying drawings; "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention.

[0024] To address the difficulty in controlling the capture efficiency and overall energy consumption of carbon dioxide in existing carbon dioxide capture systems, this application provides a carbon dioxide capture method.

[0025] Example 1

[0026] like Figure 1 and Figure 2 As shown, carbon dioxide capture methods include:

[0027] An alkaline solution is sprayed through a spray structure, so that the alkaline solution flowing out of the spray structure reacts chemically with carbon dioxide gas in the gas to absorb carbon dioxide gas.

[0028] The solution after chemical reaction with carbon dioxide gas is buffered by a buffer structure, and the solution buffered in the buffer structure flows out through a spray structure.

[0029] Among them, the concentration of hydroxide ions and / or carbonate ions in the solution within the buffer structure is detected in real time, so as to replenish the buffer structure with alkaline solution or water according to the concentration of hydroxide ions and carbonate ions.

[0030] During the real-time monitoring of hydroxide and / or carbonate concentrations in the solution within the buffer structure, if the detected hydroxide concentration is less than or equal to m and the carbonate concentration is n, the circulation pump is stopped so that the solution buffered within the buffer structure can enter the electrolysis equipment for electrolysis.

[0031] The technical solution of this embodiment uses a spray structure to spray an alkaline solution, causing the alkaline solution flowing out of the spray structure to chemically react with carbon dioxide gas, thereby absorbing the carbon dioxide gas. During this process, a buffer structure is used to buffer the solution after the chemical reaction with the carbon dioxide gas. The buffered solution then flows out again through the spray structure, achieving solution recycling. During the carbon dioxide gas capture process, the hydroxide and / or carbonate concentrations in the solution within the buffer structure are monitored in real time. Based on these concentrations, alkaline solution or water is added to the buffer structure. By supplementing with alkaline solution or adding water, the final concentrations of hydroxide and carbonate in the solution are precisely controlled, thus meeting the requirements of subsequent electrolysis processes, reducing the overall system energy consumption, and solving the problem of difficulty in controlling the carbon dioxide capture efficiency and overall energy consumption in existing carbon dioxide capture systems, thereby improving the capture efficiency of the carbon dioxide capture system. In the process of real-time detection of hydroxide and / or carbonate concentrations in the solution within the buffer structure, if the hydroxide concentration is less than or equal to m and the carbonate concentration is n, the circulation pump is controlled to stop running so that the solution buffered in the buffer structure can enter the electrolysis device for electrolysis.

[0032] In this embodiment, the method for the solution buffered within the buffer structure to flow out through the spray structure includes:

[0033] Start the circulation pump to pump the solution buffered in the buffer structure to the spray structure via pipeline.

[0034] Specifically, during the carbon dioxide capture system's process of capturing carbon dioxide gas, a circulating pump pumps the solution stored in the buffer structure to the spray structure via pipelines for reuse, achieving solution recycling and avoiding resource waste. Simultaneously, the circulating pump ensures that the spray structure can spray an alkaline solution to react with CO2, thereby improving the spray reliability of the spray structure and the overall operational reliability of the carbon dioxide capture system.

[0035] In this embodiment, the method for replenishing the buffer structure with alkaline solution or water according to the hydroxide and / or carbonate concentrations includes:

[0036] If the concentration of hydroxide ions is less than m and the concentration of carbonate ions is less than n, add alkaline solution to the buffer structure.

[0037] If the detected hydroxide concentration is less than or equal to m and the carbonate concentration is greater than n, water is added to the buffer structure.

[0038] Specifically, an initial alkaline solution is placed in the buffer structure at the bottom of the carbon dioxide capture system, and a circulation pump is started to capture carbon dioxide gas. The concentrations of hydroxide and carbonate ions in the buffer structure are monitored in real time. When the hydroxide concentration in the buffer structure is ≥ m and the carbonate concentration is < n, or the hydroxide concentration is > m and the carbonate concentration is ≥ n, the circulation pump continues to run without any related measures. When the hydroxide concentration in the buffer structure is < m and the carbonate concentration is < n, the alkaline solution replenishment device is started to replenish the buffer structure with alkaline solution, and the concentrations of hydroxide and carbonate ions in the buffer structure are monitored again. When the hydroxide concentration in the buffer structure is ≤ m and the carbonate concentration is > n, the water replenishment system is started to replenish the buffer structure with water, and the concentrations of hydroxide and carbonate ions in the buffer structure are monitored again.

[0039] Optionally, methods for real-time detection of hydroxide ion concentration in the solution within the buffer structure include:

[0040] The solution is fed into a potentiometric titrator, and a standard acid with a calibrated H+ concentration is added to the solution. During the titration process, the solution is continuously stirred and the first differential curve of the added standard acid volume and the solution potential is recorded until the first differential curve of the solution potential reaches the first peak. The hydroxide concentration of the solution is calculated using the volume of standard acid consumed at this point.

[0041] In this embodiment, a standardized HCl solution with an actual concentration of 0.2404 mol / L was slowly added to the solution as the titrant. Titration continued until the pH reached below 2. The volume of standard acid added and the change in solution pH were recorded, and the recorded volume of standard acid added and pH were plotted as a pH-V curve. Based on the recorded curve, the first-order numerical differential curve of ΔpH / ΔV-V was calculated and plotted. The maximum value of the first-order numerical differential was taken as the equivalence point. The titration equivalence point volume was obtained through the first-order numerical differential. The corresponding equivalence point is EP1 shown in the standard acid volume pH-V change graph. The OH- concentration of the solution was calculated by combining the equivalence point volume with the concentration. The titration lasted approximately 10 minutes from start to finish.

[0042] In other embodiments not shown in the accompanying drawings, the alkalinity of the solution in the neutral leaching process is determined. A calibrated HCl solution with a standardized H+ concentration of 0.1107 mol / L is slowly added to the solution as the titrant, titrating until the pH is approximately 3. The volume of standard acid consumed and the change in solution pH are recorded, and the recorded titration volume and pH are plotted as a pH-V graph. Based on the recorded curve, the first-order numerical differential curve of ΔpH / ΔV-V is calculated and plotted. The volume of standard acid corresponding to the maximum value of the first-order numerical differential is taken as the equivalence point. The titration equivalence point volume is obtained through the first-order numerical differential, and the corresponding pH at the equivalence point is 5.02. The OH- concentration of the solution is calculated from the equivalence point volume and concentration. The titration takes approximately 10 minutes from start to finish.

[0043] In other embodiments not shown in the accompanying drawings, the alkalinity of the solution after acidification is determined using a standardized HCl solution with an actual concentration of 0.1107 mol / L as the titrant. The solution is slowly titrated until the pH reaches approximately 3.8. The volume of standard acid consumed and the change in solution pH are recorded, and the recorded titration volume and pH are plotted as a pH-V graph. Based on the recorded curve, the first-order numerical differential curve of ΔpH / ΔV-V is calculated and plotted. The volume of standard acid corresponding to the maximum value of the first-order numerical differential is the equivalence point. The titration equivalence point volume is obtained through the first-order numerical differential, and the corresponding pH at the equivalence point is 4.42. The OH- concentration of the solution is calculated from the equivalence point volume and concentration. The titration takes approximately 10 minutes from start to finish.

[0044] In other embodiments not shown in the accompanying drawings, the standard acid used in the calibration experiment (i.e., the H+ concentration of the prepared hydrochloric acid aqueous solution is calibrated using a known method) is employed, in accordance with the national standard GB / T601-2003. This method employs two calibrations: first, the concentration of the standard alkali is calibrated; then, a calibrated alkali standard solution of known concentration is used to calibrate the standard acid. One embodiment of the alkali standard is as follows: A primary-grade potassium hydrogen phthalate standard is dried to constant weight at 105–110°C; 110 g of sodium hydroxide is dissolved in 100 ml of carbon dioxide-free water; the solution is placed in a sealed polyethylene container and allowed to stand until clear; 10.8 ml of the clear upper layer is taken and diluted with water to 1000 ml to prepare a sodium hydroxide titrant. Weigh 0.1377 g of potassium hydrogen phthalate standard material that has been dried to constant weight as described above, add water to 50-60 ml, stir until completely dissolved, and titrate using an automatic potentiometric titrator according to the endpoint determination principle of the above examples. The titration equivalence point volume is obtained by the first numerical derivative of the graph, and the equivalence point pH is 8.81. The concentration of the sodium hydroxide titrant is calculated based on this. The titration lasts approximately 5 minutes from start to finish. Use the titrant with the standard-calibrated concentration to standardize the hydrochloric acid titrant. Dilute 27 ml of hydrochloric acid with water to 1000 ml to prepare the hydrochloric acid titrant. Add 3.0000 ml of this hydrochloric acid titrant to a beaker, add water to 50-60 ml, stir for 90 seconds, and titrate using an automatic potentiometric titrator according to the endpoint determination principle of Examples 1-3. The titration equivalence point volume is obtained by the first numerical derivative of the graph, and the equivalence point pH is 7.45. The concentration of H+ in the standard hydrochloric acid was calculated based on the concentration of the sodium hydroxide titrant and the volume of hydrochloric acid added. The titration took approximately 5 minutes from start to finish.

[0045] In this embodiment, the method for real-time detection of carbonate concentration in the solution within the buffer structure includes:

[0046] A standard acid with a calibrated H+ concentration is added dropwise to the solution. During the titration, the mixture is continuously stirred, and the first-order differential curve of the added standard acid volume and the solution potential is recorded until the first-order differential curve of the solution potential reaches the first peak. The volume of standard acid consumed at this point is recorded as V1. The standard acid with a calibrated H+ concentration is then added dropwise to the solution. During the titration, the mixture is continuously stirred, and the first-order differential curve of the added standard acid volume and the solution potential is recorded until the first-order differential curve of the solution potential reaches the second peak. The volume of standard acid consumed at this point is recorded as V2. The carbonate concentration of the solution is calculated using the difference between V2 and V1.

[0047] Optionally, m is greater than or equal to 0.1 mol / L and less than or equal to 5 mol / L; and / or n is greater than or equal to 1 mol / L and less than or equal to 6 mol / L. This allows for more flexible selection of the values ​​of m and n to meet different usage requirements and operating conditions.

[0048] Optionally, m is greater than or equal to 0.3 mol / L and less than or equal to 2 mol / L; and / or n is greater than or equal to 2 mol / L and less than or equal to 5.5 mol / L. This allows for more flexible selection of the values ​​of m and n to meet different usage requirements and operating conditions.

[0049] In this embodiment, m is 0.1 mol / L and n is 6 mol / L. An alkaline solution is sprayed through a spray structure to allow the alkaline solution flowing from the spray structure to chemically react with carbon dioxide gas. During the replenishment of carbon dioxide gas, the hydroxide and carbonate concentrations in the solution within the buffer structure are monitored in real time. When the hydroxide concentration in the buffer structure is ≥0.1 mol / L and the carbonate concentration is <6 mol / L, or when the hydroxide concentration is >0.1 mol / L and the carbonate concentration is ≥6 mol / L, the circulation pump continues to run without any related measures. When the hydroxide concentration in the buffer structure is <0.1 mol / L and the carbonate concentration is <6 mol / L, the alkaline solution replenishment device is activated to replenish the buffer structure, and the hydroxide and carbonate concentrations within the buffer structure continue to be monitored. When the hydroxide concentration in the buffer structure is ≤0.1 mol / L and the carbonate concentration is >6 mol / L, the water replenishment system is activated to replenish the buffer structure, and the hydroxide and carbonate concentrations within the buffer structure continue to be monitored. If the detected hydroxide concentration is less than or equal to 0.1 mol / L and the carbonate concentration is 6 mol / L, the circulation pump is stopped so that the solution buffered in the buffer structure can enter the electrolysis equipment for electrolysis.

[0050] It should be noted that the values ​​of m and n are not limited to these and can be adjusted according to working conditions and usage requirements.

[0051] It should be noted that the unit kWh / kgCO2 represents the electrical energy (kWh) consumed by the electrolysis equipment to produce 1 kg of CO2 during the electrolysis process.

[0052] In this embodiment, during the process of the solution buffered within the buffer structure entering the electrolysis device for electrolysis, the carbon dioxide capture method further includes:

[0053] Adjust the amount of electricity applied to the electrolysis equipment to control the ratio and / or output of carbon dioxide gas and hydrogen gas per unit time in the electrolysis equipment.

[0054] Specifically, during the electrolytic regeneration of alkali, absorbed carbon dioxide gas is released, while high-value-added hydrogen gas is produced. Carbon dioxide gas can be hydrogenated to synthesize various chemicals, providing a good foundation for the comprehensive utilization of carbon dioxide gas. However, different chemicals require different ratios of carbon dioxide and hydrogen gas. Therefore, it is essential to control the output ratio of carbon dioxide and hydrogen gas during the electrolytic regeneration of inorganic alkali. Adding electrolyte components to the electrolysis equipment enhances conductivity, thereby reducing electrolysis energy consumption. After the carbonate is electrolyzed, water can be electrolyzed to further produce hydrogen gas. Therefore, by changing the applied electricity, the output ratio of carbon dioxide and hydrogen gas per unit time of the electrolysis equipment can be controlled, greatly improving the applicability of the system.

[0055] In this embodiment, the method for adjusting the amount of electricity applied to the electrolysis equipment includes:

[0056] A preset amount of electricity Q is applied to the electrolysis equipment when the production ratio of carbon dioxide gas and hydrogen gas is 1. The production ratio of carbon dioxide gas and hydrogen gas is adjusted by adding nQ to the preset amount of electricity Q; where n=1,2,3,…,N (N≤n).

[0057] Specifically, taking the processing of a solution containing 1 mol of carbonate ions per unit time as an example, the electrolyte added to the electrolysis equipment is potassium sulfate, and the concentration of potassium sulfate at the anode is set to 0.5 mol / L. The applied power is controlled so that the power obtained by 1 mol of carbonate solution is 53.6 A·h, and the production ratio of carbon dioxide gas and hydrogen gas is 1:1. Based on this, for every additional 53.6 A·h of applied power, the production of carbon dioxide gas becomes 0, while the production of hydrogen gas increases by 1 mol, meaning the production ratio of CO2 and H2 per unit time becomes 1:2, thus achieving adjustable output ratios of carbon dioxide gas and hydrogen gas. In this embodiment, the applied power is controlled so that the power obtained by 1 mol of carbonate solution is 54.0 A·h, the power consumption of the electrolysis equipment is measured to be 3.30 kWh / kgCO2, and the production ratio of carbon dioxide gas and hydrogen gas is 1:1.01.

[0058] In this embodiment, the carbon dioxide capture method further includes the following steps during the adjustment of the carbon dioxide and hydrogen production ratio:

[0059] The electrolyte content in the electrolysis equipment is monitored in real time. If the electrolyte content is less than the preset value, electrolyte is added to the electrolysis equipment. The electrolyte is an alkali metal sulfate, alkali metal nitrate, or alkali metal phosphate.

[0060] Optionally, the preset value is 0. Specifically, during the adjustment of the carbon dioxide and hydrogen production ratio, if the electrolyte content is less than the preset value, electrolyte is added to the anode of the electrolysis equipment. By changing the applied electricity, the production ratio of carbon dioxide and hydrogen per unit time of the electrolysis equipment is controlled. This significantly reduces the overall energy consumption of the system while ensuring the carbon dioxide capture efficiency, so that the carbon dioxide capture system can control the carbon dioxide capture efficiency and overall energy consumption.

[0061] Alternatively, the alkali metal sulfate may be potassium sulfate or sodium sulfate.

[0062] Optionally, the alkali metal nitrate is potassium nitrate or sodium nitrate.

[0063] Optionally, the alkali metal phosphate is potassium phosphate or sodium phosphate.

[0064] Optionally, the alkaline solution is an alkali metal hydroxide.

[0065] Optionally, a method for buffering a solution after a chemical reaction with carbon dioxide gas using a buffer structure includes:

[0066] At least two buffer structures are configured to switch between each other. Each buffer structure can selectively buffer the solution after the chemical reaction with the carbon dioxide gas. If the carbonate concentration in one buffer structure reaches a preset concentration value, this buffer structure is deactivated and the other buffer structures are activated.

[0067] In this embodiment, there are two buffer structures. When the carbonate concentration in the first buffer structure reaches a preset concentration value, the second buffer structure is activated to capture CO2 through the alkaline solution in the second buffer structure and drain the carbonate solution in the first buffer structure. Then, fresh alkaline solution is replenished. After the carbonate concentration in the second buffer structure reaches the preset concentration value, the first buffer structure is activated again, and so on, alternating between the two.

[0068] Alternatively, the alkali metal hydroxide may be potassium oxyoxide or sodium hydroxide.

[0069] In this embodiment, the carbon dioxide capture method is applicable to a gas absorption system used to absorb carbon dioxide gas. The gas absorption system includes a housing and a gas absorption assembly, having an inlet and an outlet, with the inlet and outlet positioned opposite each other. The gas absorption assembly is disposed within the housing and downstream of the gas pretreatment device. The gas absorption assembly includes an interconnected liquid supply device and a spray structure for providing an alkaline solution; the alkaline solution flowing from the spray structure chemically reacts with the carbon dioxide gas in the gas to absorb the carbon dioxide gas.

[0070] Optionally, the gas absorption system can be a cross-flow absorption system or a counter-flow absorption system. In a cross-flow absorption system, the air or flue gas inlet direction is aligned with the exhaust direction. In a counter-flow absorption system, the air or flue gas inlet direction is at an angle to the exhaust direction.

[0071] Optionally, the spray structure is a nozzle.

[0072] Optionally, the gas absorption assembly includes packing material and a water collector. The packing material is located below the spray structure. The water collector is positioned opposite the packing material. This design provides ample contact surface between CO2 and the alkaline solution through the packing material, allowing for sufficient reaction between CO2 in the air or flue gas and the alkaline solution, further enhancing the CO2 capture and absorption efficiency of the gas absorption assembly. The water collector is used to recover the absorbent within the gas absorption assembly, reducing the amount of fine water droplets carried in the gas discharged from the assembly. Furthermore, this design allows for more flexible placement of the water collector to meet different usage requirements and operating conditions, while also improving the processing flexibility for operators.

[0073] Specifically, the alkaline solution falls from the spray structure into the packing material in droplet form, flows as a liquid film within the packing material, and then falls again as droplets into the buffer structure. The pretreated gas comes into full contact with the alkaline solution in the water spray zone of the gas absorption component and within the packing material, causing a chemical reaction between the CO2 in the air or flue gas and the alkaline solution, thereby capturing the CO2. The captured CO2 exists in the form of carbonate and bicarbonate ions within the buffer structure, and the reacted solution is transported to the subsequent process system for further treatment via a circulating pump. Simultaneously, the buffer structure is equipped with a first liquid supply device to replenish the water and hydroxide ions consumed in the solution.

[0074] Optionally, the packing material is a thin-film type water-spreading packing material.

[0075] Optionally, the water collector is a PVC water collector, and the water collector is supported by a bracket.

[0076] In this embodiment, the gas absorption assembly further includes a buffer structure. The buffer structure is located below the packing material and is used to buffer the solution after the chemical reaction with carbon dioxide gas. By storing the solution after the chemical reaction with carbon dioxide gas through the buffer structure, it is convenient for post-processing of the solution and also enables the recycling of the solution to avoid resource waste.

[0077] In this embodiment, the buffer structure and the liquid supply device are the same structure. In the initial stage of operation of the gas absorption system, an alkaline solution is placed in the buffer structure. The alkaline solution is sprayed onto the packing material through the spray structure to react with CO2 in the air or flue gas. After the reaction is completed, the solution is buffered in the buffer structure so that it can re-enter the spray structure to continue spraying, thereby realizing the recycling of the alkaline solution until the carbonate concentration in the alkaline solution reaches a preset value. At this time, the capture and absorption of CO2 is stopped, and the solution in the buffer structure is replaced with an alkaline solution.

[0078] It should be noted that the relationship between the buffer structure and the liquid supply device is not limited to this and can be adjusted according to operating conditions and usage requirements. Optionally, the buffer structure and the liquid supply device are connected to provide an alkaline solution to the spray structure through the liquid supply device. The solution after reacting with CO2 is buffered in the buffer structure so that it can re-enter the spray structure for continued spraying.

[0079] Optionally, there may be one buffer structure; or there may be multiple buffer structures, which can be selectively used. In this way, during the operation of the gas absorption system, the usage status (used or not used) of the buffer structure can be adjusted according to the carbonate concentration within the buffer structure, so as to replenish the spray structure with fresh alkaline solution, thereby achieving rapid and efficient CO2 capture by the gas absorption system.

[0080] Optionally, multiple buffer structures are included, and the gas absorption assembly also includes a main pipeline, multiple branch pipelines, and multiple control valves. The first end of the main pipeline is connected to the spray structure. Multiple branch pipelines are configured one-to-one with multiple buffer structures, with each branch pipeline's two ends connected to its corresponding buffer structure and the second end of the main pipeline, respectively. Multiple control valves are configured one-to-one with multiple branch pipelines, each controlling the on / off state of its corresponding branch pipeline. At any given time, at least one control valve is in the open state. This allows control of the on / off state of the corresponding branch pipeline via control valves, thereby controlling the usage state of the buffer structure connected to that branch pipeline. This makes it easier and simpler for operators to control the usage state of the buffer structure, reducing control difficulty. Simultaneously, the above configuration allows multiple buffer structures to be connected in parallel, ensuring that at any given time, at least one buffer structure is in use to provide alkaline solution to the spray structure.

[0081] In this embodiment, the gas absorption assembly also includes a circulation pump. The circulation pump is located on the main pipeline or a branch pipeline to pump the solution entering the buffer structure to the spray structure. This circulation pump ensures that the spray structure can spray an alkaline solution to react with CO2, thereby improving the spray reliability of the spray structure and the overall operational reliability of the gas absorption system.

[0082] Example 2

[0083] The carbon dioxide capture method in Example 2 differs from that in Example 1 in that the values ​​of m and n are different, as is the amount of electricity applied to control the electrolysis equipment.

[0084] In this embodiment, m is 0.3 mol / L, n is 5.5 mol / L, and the amount of electricity applied to the electrolysis device is controlled so that the amount of electricity obtained by 1 mol of carbonate solution is 55.1 A·h. The power consumption of the electrolysis device is measured to be 3.36 kWh / kgCO2, and the production ratio of carbon dioxide gas and hydrogen gas is 1:1.03.

[0085] Example 3

[0086] The carbon dioxide capture method in Example 3 differs from that in Example 1 in that the values ​​of m and n are different, as is the amount of electricity applied to control the electrolysis equipment.

[0087] In this embodiment, m is 5 mol / L, n is 1 mol / L, and the power consumption of the electrolysis equipment is measured to be 11.46 kWh / kgCO2. The amount of electricity applied to the electrolysis equipment is controlled so that the amount of electricity obtained by 1 mol carbonate solution is 187.6 A·h, and the production ratio of carbon dioxide gas and hydrogen gas is 1:3.5.

[0088] Example 4

[0089] The carbon dioxide capture method in Example 4 differs from that in Example 1 in that the values ​​of m and n are different, as is the amount of electricity applied to control the electrolysis equipment.

[0090] In this embodiment, m is 0.1 mol / L, n is 5.3 mol / L, and the amount of electricity applied to the electrolysis device is controlled so that the amount of electricity obtained by 1 mol of carbonate solution is 54.1 A·h. The power consumption of the electrolysis device is measured to be 3.29 kWh / kgCO2, and the production ratio of carbon dioxide gas and hydrogen gas is 1:1.

[0091] Example 5

[0092] The carbon dioxide capture method in Example 5 differs from that in Example 1 in that the values ​​of m and n are different, as is the amount of electricity applied to control the electrolysis equipment.

[0093] In this embodiment, m is 2.5 mol / L, n is 0.5 mol / L, and the amount of electricity applied to the electrolysis device is controlled so that the amount of electricity obtained by 1 mol carbonate solution is 187.6 A·h. The power consumption of the electrolysis device is measured to be 11.83 kWh / kgCO2, and the production ratio of carbon dioxide gas and hydrogen gas is 1:3.5.

[0094] Example 6

[0095] The carbon dioxide capture method in Example 6 differs from that in Example 1 in that the amount of electricity applied to the electrolysis equipment is different.

[0096] In this embodiment, the amount of electricity applied to the electrolysis equipment is controlled so that the amount of electricity obtained from a solution containing 1 mol of carbonate is 107.2 A·h, the power consumption of the electrolysis equipment is measured to be 6.63 kWh / kgCO2, and the production ratio of carbon dioxide gas and hydrogen gas is 1:2.01.

[0097] Table 1 shows a detailed comparison of the power consumption of the electrolysis equipment and the production ratio of carbon dioxide and hydrogen in all the above embodiments.

[0098] Table 1 compares the power consumption of the electrolysis equipment and the production ratio of carbon dioxide and hydrogen in each embodiment.

[0099] <![CDATA[Power consumption (kWh / kgCO2) of electrolysis equipment]]> The production ratio of carbon dioxide gas and hydrogen gas (vol%) Example 1 3.30 1:1.01 Example 2 3.36 1:1.03 Example 3 11.46 1:3.5 Example 4 3.29 1:1 Example 5 11.83 1:3.5 Example 6 6.63 1:2.01

[0100] Based on the above comparison, the following conclusions can be drawn:

[0101] 1. Comparing Examples 3 and 5, it can be seen that the carbon dioxide capture method described in this application can accurately control the hydroxide and / or carbonate concentrations in the solution within the buffer structure. When the solution within the buffer structure is fed into the electrolysis equipment for electrolysis, the range of hydroxide and carbonate concentrations in the solution includes, but is not limited to, the preferred range of this application. Limiting them to the preferred range of this application is beneficial to reducing the energy consumption of the electrolysis equipment, thereby reducing the process cost of the carbon dioxide capture system. This effectively solves the problem that the capture efficiency and overall energy consumption of carbon dioxide gas in the prior art are difficult to control.

[0102] 2. Comparing Examples 1 to 6, it can be seen that the carbon dioxide capture method described in this application achieves an adjustable ratio of carbon dioxide gas and hydrogen gas produced during the electrolysis process. The ratio of carbon dioxide gas and hydrogen gas produced in the system can be flexibly adjusted according to the actual needs of the downstream carbon dioxide gas utilization device, which greatly improves the applicability of the system.

[0103] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0104] An alkaline solution is sprayed through a spray structure, causing a chemical reaction between the alkaline solution flowing out of the spray structure and the carbon dioxide gas, thereby absorbing the carbon dioxide. During this process, a buffer structure stores the solution after the chemical reaction with the carbon dioxide gas. The buffered solution then flows out again through the spray structure, achieving solution recycling. During the carbon dioxide capture process, the hydroxide and / or carbonate concentrations in the solution within the buffer structure are monitored in real time. Based on these concentrations, alkaline solution or water is added to the buffer structure. This precise control of the final hydroxide and carbonate concentrations in the solution, achieved through alkaline replenishment or water addition, meets the requirements of subsequent electrolysis processes, reduces the overall system energy consumption, and solves the problem of difficulty in controlling the carbon dioxide capture efficiency and overall energy consumption in existing carbon dioxide capture systems, thus improving the capture efficiency of the carbon dioxide capture system. In the process of real-time detection of hydroxide and / or carbonate concentrations in the solution within the buffer structure, if the hydroxide concentration is less than or equal to m and the carbonate concentration is n, the circulation pump is controlled to stop running so that the solution buffered in the buffer structure can enter the electrolysis device for electrolysis.

[0105] Obviously, the embodiments described above are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0106] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0107] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0108] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for capturing carbon dioxide, characterized in that, include: An alkaline solution is sprayed through a spray structure, causing the alkaline solution flowing out of the spray structure to chemically react with carbon dioxide gas in the gas, thereby absorbing the carbon dioxide gas. The solution after chemical reaction with the carbon dioxide gas is buffered by the buffer structure, and the solution buffered in the buffer structure flows out through the spray structure. The system monitors the hydroxide and carbonate concentrations in the solution within the buffer structure in real time, and replenishes the buffer structure with alkaline solution or water based on the hydroxide and carbonate concentrations. During the real-time detection of hydroxide and carbonate concentrations in the solution within the buffer structure, if the hydroxide concentration is less than or equal to m and the carbonate concentration is n, the circulation pump is controlled to stop running so that the solution buffered in the buffer structure can enter the electrolysis device for electrolysis. The method for real-time detection of carbonate concentration in the solution within the buffer structure includes: The solution is fed into a potentiometric titrator. A standard acid with a calibrated H+ concentration is added to the solution. During the titration process, the solution is continuously stirred, and the first differential curve of the added standard acid volume and the solution potential is recorded until the first differential curve of the solution potential reaches the first peak. The volume of the standard acid consumed at this point is recorded as V1. The standard acid with a calibrated H+ concentration is added to the solution again. During the titration process, the solution is continuously stirred, and the first differential curve of the added standard acid volume and the solution potential is recorded until the first differential curve of the solution potential reaches the second peak. The volume of the standard acid consumed at this point is recorded as V2. The carbonate concentration of the solution is calculated using the difference between V2 and V1. m is greater than or equal to 0.1 mol / L and less than or equal to 5 mol / L; and / or n is greater than or equal to 1 mol / L and less than or equal to 6 mol / L.

2. The carbon dioxide capture method according to claim 1, characterized in that, The method for the solution buffered within the buffer structure to flow out through the spray structure includes: Start the circulation pump to pump the solution buffered in the buffer structure to the spray structure via pipeline.

3. The carbon dioxide capture method according to claim 1, characterized in that, The method of replenishing the buffer structure with alkaline solution or water according to the hydroxide ion concentration and / or the carbonate ion concentration includes: If the hydroxide concentration is detected to be less than m and the carbonate concentration is detected to be less than n, an alkaline solution is added to the buffer structure. If the hydroxide concentration is less than or equal to m and the carbonate concentration is greater than n, water is added to the buffer structure.

4. The carbon dioxide capture method according to claim 1, characterized in that, The method for real-time detection of hydroxide ion concentration in the solution within the buffer structure includes: The solution is fed into a potentiometric titrator, and a standard acid with a calibrated H+ concentration is added to the solution. During the titration process, the solution is continuously stirred and the first differential curve of the added standard acid volume and the solution potential is recorded until the first differential curve of the solution potential reaches the first peak. The hydroxide concentration of the solution is calculated using the volume of the standard acid consumed at this time.

5. The carbon dioxide capture method according to claim 1, characterized in that, m is greater than or equal to 0.3 mol / L and less than or equal to 2 mol / L; and / or n is greater than or equal to 2 mol / L and less than or equal to 5.5 mol / L.

6. The carbon dioxide capture method according to claim 1, characterized in that, During the process of the solution buffered within the buffer structure entering the electrolysis device for electrolysis, the carbon dioxide capture method further includes: Adjust the amount of electricity applied to the electrolysis equipment to control the ratio and / or output of carbon dioxide gas and hydrogen gas per unit time in the electrolysis equipment.

7. The carbon dioxide capture method according to claim 6, characterized in that, The method for adjusting the amount of electricity applied to the electrolysis equipment includes: A preset amount of electricity Q is applied to the electrolysis equipment when the production ratio of carbon dioxide gas and hydrogen gas is 1. The production ratio of carbon dioxide gas and hydrogen gas is adjusted by adding nQ to the preset amount of electricity Q. Wherein, n=1,2,3,…,N, and N≤n.

8. The carbon dioxide capture method according to claim 6, characterized in that, In adjusting the production ratio of carbon dioxide and hydrogen, the carbon dioxide capture method further includes: The electrolyte content in the electrolysis equipment is monitored in real time. If the electrolyte content is less than a preset value, electrolyte is added to the electrolysis equipment. The electrolyte is an alkali metal sulfate, an alkali metal nitrate, or an alkali metal phosphate.

9. The carbon dioxide capture method according to claim 1, characterized in that, The method for buffering the solution after the chemical reaction with the carbon dioxide gas using the buffer structure includes: At least two buffer structures are configured to switch between each other. Each buffer structure can selectively buffer the solution after the chemical reaction with the carbon dioxide gas. If the carbonate concentration in one buffer structure reaches a preset concentration value, this buffer structure is deactivated and the other buffer structures are activated.

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