A system and method for in-situ capture and purification of carbon dioxide

Abstract

This invention belongs to the field of CO2 purification and utilization technology, and discloses a system and method for in-situ carbon dioxide capture and purification. The system includes a reactor body, a top percolation screen, a bottom percolation screen, and a heating jacket. The reactor body is equipped with a gas flow channel, a liquid flow channel, and a pure CO2 collection channel. During system operation, water is first circulated to rehydrate and activate the solid phase change scavenger. Then, CO2-containing gas is introduced, uniformly dispersed through the bottom percolation screen, and comes into contact with the solid phase change scavenger to achieve selective CO2 adsorption. After adsorption saturation, the solid phase change scavenger is heated in-situ by the heating jacket to cause a phase transition and release high-purity CO2. This invention integrates CO2 capture, desorption, purification, and recovery into the same reactor, resulting in a simple structure, low energy consumption, and high product purity.

Description

Technical Field

[0001] This invention belongs to the field of CO2 purification and utilization technology, specifically relating to a carbon dioxide in-situ capture and purification system and method. Background Technology

[0002] With the massive consumption of fossil fuels, CO2 emissions have become a major factor contributing to global climate change. Industries such as thermal power plants, cement plants, steel mills, and chemical plants emit large amounts of CO2-containing flue gas. Meanwhile, high-purity CO2 has wide-ranging applications in food processing, chemical synthesis, oil extraction, electronics manufacturing, and healthcare. Therefore, developing efficient and low-energy-consumption CO2 capture and purification technologies is of great significance.

[0003] Currently, common CO2 capture technologies mainly include chemical absorption, physical adsorption, membrane separation, and cryogenic condensation. Chemical absorption uses amine solutions as absorbents, offering high capture efficiency and mature industrial applications, but suffers from severe equipment corrosion, high regeneration energy consumption, secondary pollution caused by solvent degradation and volatilization, and the need for additional purification of desorption products. Physical adsorption uses porous materials such as activated carbon and molecular sieves, resulting in relatively simple equipment structures and low corrosivity, but exhibits poor adsorption selectivity, a significant decrease in adsorption capacity under low CO2 partial pressures, high regeneration energy consumption, and low product concentration due to CO2 released during desorption mixing with purge gas, requiring multi-stage purification. Membrane separation offers compact equipment and continuous operation, but membrane materials have limited separation performance, insufficient stability in sulfur- and dust-containing flue gas, and high equipment costs. Cryogenic condensation is only suitable for high-concentration CO2 separation; for low-concentration flue gas, multi-stage compression and deep cooling are required, resulting in extremely high energy consumption and poor economic efficiency. The above methods generally suffer from the bottleneck that capture and purification cannot be completed in the same process. The resulting CO2 enriched products contain various impurities such as nitrogen, water vapor, and sulfur oxides, and require multiple post-processing stages to obtain high-purity CO2. The process is lengthy and requires large equipment investment.

[0004] In recent years, the technology of capturing CO2 using the "memory effect" of layered double hydroxides (LDH) has attracted attention. LDH is calcined at medium and low temperatures to form layered double oxides (LDO). Under rehydration conditions, LDO can revert to the layered structure of LDH, fixing CO2 in the form of carbonate ions between the layers. This material system exhibits good selectivity for CO2. However, currently, this technology is mostly at the stage of laboratory material performance testing, lacking an industrial production system that matches its characteristics. Existing related patents (such as CN202411145695.7) adopt a split multi-unit structure, where the calcination reactor and the capture reaction tank are independent of each other. The captured material needs to be transported between different units, resulting in complex equipment, high energy consumption, and CO2 purity easily affected by the transportation process.

[0005] Therefore, developing an integrated production system that can integrate CO2 rehydration activation, in-situ adsorption and capture, heating desorption and high-purity collection in the same reactor is of great practical significance. This system simplifies equipment structure, reduces operating energy consumption, shortens process flow, and improves the purity of product CO2. Summary of the Invention

[0006] The purpose of this invention is to provide a carbon dioxide in-situ capture and purification system and method, which solves the problems of complex structure, high energy consumption, long process flow and insufficient CO2 purity of existing CO2 capture and purification equipment.

[0007] This invention is achieved through the following technical solution: This invention discloses an in-situ carbon dioxide capture and purification system, comprising: Reactor body; The reactor body is filled with a solid phase change trapping agent for selective adsorption and desorption of CO2. A top percolation screen, located at the top of the reactor body, is used to prevent the loss of solid phase change trap particles and prolong the residence time of gas in the reactor. A bottom percolation screen is installed at the bottom of the reactor body to uniformly disperse the CO2-containing gas entering the reactor body. The solid phase change trap is located between the top and bottom permeation screens; the pore size of the bottom permeation screen is larger than that of the top permeation screen. A heating jacket, wrapped around the outside of the reactor body, is used for in-situ heating and desorption of the solid phase change trap. The reactor body is equipped with a gas flow channel, a liquid flow channel and a pure CO2 collection channel, and each channel is equipped with a control valve.

[0008] Furthermore, the gas flow channel includes a gas inlet located at the bottom of the reactor body and a gas outlet located at the top of the reactor body, and a gas closure switch is provided at the gas inlet and the gas outlet respectively; The liquid flow channel includes a water inlet located at the top of the reactor body and a water outlet located at the bottom of the reactor body, and a water flow closure switch is provided at the water inlet and the water outlet respectively; The pure CO2 collection channel is connected to the bypass of the gas outlet and is equipped with a pure CO2 collection closing switch.

[0009] Furthermore, the gas closing switch, water flow closing switch, and pure CO2 collection closing switch are all one-way valves.

[0010] Furthermore, the solid phase change trapping agent is LDO, which can recover to LDH in a rehydrated environment by relying on the memory effect, and fix CO2 in the interlayer in the form of carbonate during the recovery process; the LDH undergoes a phase transformation to form LDO and releases CO2 under heating and calcination.

[0011] Furthermore, the reactor body is a vertically arranged cylindrical structure.

[0012] Furthermore, both the top and bottom percolation screens are made of stainless steel.

[0013] Furthermore, the pore size of the bottom permeate screen is 3~5μm, and the pore size of the top permeate screen is 0.1~0.5μm.

[0014] Furthermore, the CO2-containing gas is industrial flue gas or air.

[0015] This invention also discloses a method for in-situ capture and purification of carbon dioxide, comprising the following steps: S1: Open the control valve of the liquid flow channel to introduce water into the reactor body, so that the solid phase change capture agent is activated in the rehydrated environment, and then close the control valve of the liquid flow channel. S2: Open the control valve of the gas flow channel to introduce CO2-containing gas into the reactor body. After the gas is evenly dispersed through the bottom filter screen, it comes into contact with the activated solid phase change trap. The solid phase change trap selectively adsorbs and fixes CO2 by relying on the memory effect, thereby achieving in-situ CO2 capture. S3: When the solid phase change scavenger is saturated with adsorption, close the control valves of the gas flow channel and the liquid flow channel, and open the control valves of the heating jacket and the pure CO2 collection channel. Heat and calcine the saturated solid phase change scavenger in situ to cause it to undergo a phase transition and release high-purity CO2, which is then collected through the pure CO2 collection channel. S4: Close the control valves of the heating jacket and the pure CO2 collection channel, return to step S1, and enter the next cycle until the preset number of cycles is reached, at which point the cycle stops.

[0016] Furthermore, in S2, the volume fraction of CO2 in the CO2-containing gas is 0.04% to 25%.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses an in-situ carbon dioxide capture and purification system, comprising a reactor body with a top percolation screen at the top and a bottom percolation screen at the bottom; a heating jacket surrounds the reactor body; the reactor body has gas flow channels, liquid flow channels, and a pure CO2 collection channel, each channel equipped with a control valve; the bottom percolation screen has a larger pore size than the top percolation screen. A solid phase change trapping agent is filled inside the reactor body for selective adsorption and desorption of CO2. Within the same reactor body, the rehydration and activation of the solid phase change scavenger, in-situ CO2 capture, heating desorption, and high-purity CO2 collection are completed sequentially. This eliminates the need for material transport between different units in traditional split systems, simplifies the equipment structure, and reduces equipment investment and operating energy consumption. At the same time, the large-pore permeate screen at the bottom ensures that the CO2-containing gas entering the reactor body is evenly dispersed and fully contacts the solid phase change scavenger filled between the two permeate screens. The small-pore permeate screen at the top prevents the loss of scavenger particles and prolongs the residence time of the gas in the reactor. The two work together to increase the gas-solid contact efficiency and reaction time, thereby improving the CO2 capture efficiency and enabling capture, desorption, purification, and high-purity CO2 collection to be completed sequentially within the same reactor.

[0018] Furthermore, the specific locations of the gas flow channel, liquid flow channel, and pure CO2 collection channel were defined. The gas inlet and outlet are located at the bottom and top of the reactor body, respectively, while the water inlet and outlet are located at the top and bottom, respectively. The pure CO2 collection channel is located on the gas outlet pipe. This bottom-inlet, top-outlet layout allows CO2-containing gas to naturally pass through the trap bed during its ascent, opposite to the direction of gravity, which is beneficial for gas distribution and flow uniformity. The water flows from the top to the bottom, utilizing gravity to achieve natural infiltration and discharge, forming counter-current or cross-flow contact with the gas, which is beneficial for uniform wetting during rehydration activation and rapid drainage after the reaction. The pure CO2 collection channel is located on the gas outlet pipe to facilitate the direct collection of high-purity CO2 escaping from the top during the desorption stage. Each channel is equipped with a dedicated shut-off switch for independent control, thereby ensuring the flexibility of system switching at each stage and the reliability of operation.

[0019] Furthermore, specific numerical ranges were defined for the bottom percolator mesh pore size of 3–5 μm and the top percolator mesh pore size of 0.1–0.5 μm. This precise numerical definition of pore size difference gives the dual percolators a clear functional division: the 3–5 μm pore size at the bottom is sufficient to allow gas and liquid to pass through smoothly and achieve uniform dispersion, while effectively blocking most of the trap particles (particle size is usually greater than 5 μm) from entering the bottom pipe; the small pore size at the top of 0.1–0.5 μm can efficiently block fine trap particles from being carried out of the reactor by the airflow or water flow, while the small pore structure reduces the gas velocity and prolongs the residence time when the gas passes through, forming a gas flow pattern of "rapid dispersion at the bottom, full reaction in the middle, and slow passage at the top" in combination with the large pore size at the bottom. Compared with undifferentiated filters or single filter schemes, this significantly improves the trap utilization rate and CO2 capture efficiency.

[0020] Furthermore, the solid phase change trapping agent was specified as LDO, which can recover to LDH in a rehydrated environment through the memory effect and fix CO2 in the interlayer as carbonate ions. LDH undergoes a phase transition under heating and calcination to form LDO and release CO2. This choice of trapping agent is the core material basis for the system's capture and purification capabilities: LDO exhibits high selectivity for CO2 during rehydration activation and CO2 capture, while only CO3 is fixed in the interlayer. 2- It does not adsorb gaseous impurities such as N2 and O2 that are present in large quantities in flue gas. Therefore, the gas released during heating and desorption is high-purity CO2, without the need for additional gas separation or purification processes. At the same time, the phase change process is completely reversible, and the solid phase change scavenger can be recycled multiple times in the same reactor, reducing the consumption cost and replenishment frequency of the solid phase change scavenger.

[0021] Furthermore, the CO2-containing gas was limited to industrial flue gas or air. The volume fraction of CO2 in industrial flue gas is typically 10%–25%, while the volume fraction of CO2 in air is only about 0.04%, a difference of hundreds of times. The system's ability to operate effectively across such a wide concentration range demonstrates, on the one hand, the extremely high affinity and selectivity of the solid phase change trap for CO2, and on the other hand, that the gas distribution and extended residence time design of the dual-permeation filter effectively adapts to the treatment needs of gases with different concentrations and flow rates. This allows the same equipment to be used for treating high-concentration flue gas from stationary emission sources, as well as for direct air capture in open environments, demonstrating excellent application flexibility and promising prospects for widespread adoption.

[0022] This invention also discloses a method for in-situ capture and purification of carbon dioxide. In step S1, water is passed through to rehydrate and activate the solid phase change precipitator; in step S2, gas is passed through for in-situ CO2 capture; in step S3, after adsorption saturation, the gas and water channels are closed, and the heating jacket and pure CO2 collection channel are opened for in-situ heating and calcination to release high-purity CO2; in step S4, the heating jacket and pure CO2 collection channel are closed, and the process returns to step S1 to begin the next cycle. The rehydration step in step S1 activates the LDO into an LDH structure with capture activity, providing a chemical basis for subsequent capture; in step S2, the bottom permeation filter ensures uniform gas dispersion, and the precipitator achieves selective adsorption through the memory effect; in step S3, the gas and water channels are closed, and then the heating jacket and pure CO2 collection channel are opened, forming a sealed desorption environment to ensure that the released CO2 is not diluted or contaminated, directly obtaining high-purity CO2; in step S4, the heating and collection channels are closed, and the process returns to step S1, forming a completely closed material cycle. No additional precipitator or intermediate treatment is required, achieving continuous and automated cyclic operation, reducing manual intervention and operating costs. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a carbon dioxide in-situ capture and purification production system according to the present invention; Figure 2 This is a top view schematic diagram of an in-situ carbon dioxide capture and purification production system according to the present invention; Among them, 1. Gas closing switch; 2. Water flow closing switch; 3. Top infiltration screen; 4. Heating jacket; 5. Solid phase change trap; 6. Bottom infiltration screen; 7. Pure CO2 collection closing switch.

[0024] Figure 3 The graph shows the variation of CO2 cyclic capture performance of solid phase change traps under flue gas conditions with a CO2 volume fraction of 10%. Figure 4 The X-ray diffraction (XRD) patterns of the circulating products under flue gas conditions with a CO2 volume fraction of 10% are shown. Figure 5 The graph shows the variation of CO2 cyclic capture performance of solid phase change traps under flue gas conditions with a CO2 volume fraction of 25%. Figure 6 The XRD patterns of the recycle products under flue gas conditions with a CO2 volume fraction of 25% are shown. Figure 7 This is a graph showing the variation in CO2 cyclic capture performance of a solid phase change trap under air conditions. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0026] The components described and illustrated in the accompanying drawings and embodiments of this invention can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely to illustrate one selected embodiment of the invention. All other embodiments obtained by those skilled in the art based on the accompanying drawings and embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0027] To facilitate understanding of this invention, the relevant terms for solid phase change traps will first be explained: LDH is an abbreviation for Layered Double Hydroxide, also known as hydrotalcite supergroup minerals. It has a layered structure with water and exchangeable anions between the layers. LDO is an abbreviation for Layered Double Oxide, a bimetallic oxide formed by the calcination of LDH at medium and low temperatures. LDO exhibits structural memory, meaning it can revert to the layered structure of LDH under rehydration conditions, fixing CO2 as carbonate ions between the layers during this process. The principle is that calcination removes interlayer water and anions from LDO, resulting in a metastable layered structure. When re-in contact with water, water molecules enter the interlayer, driving the layers to regain their ordered arrangement, while simultaneously converting dissolved CO2 into CO3. 2- Fixed between layers.

[0028] like Figure 1 and Figure 2 As shown, the present invention discloses an in-situ carbon dioxide capture and purification system, including a reactor body, a gas flow channel, a liquid flow channel and a pure CO2 collection channel.

[0029] The reactor body adopts a vertical cylindrical structure and is made of stainless steel. Inside the reactor body, there are top percolation screens 3 and bottom percolation screens 6, with a solid phase change trap 5 filling the space between them. The solid phase change trap 5 is LDO, which can recover to LDH in a rehydrated environment through memory effect, and during the recovery process, it fixes CO2 in the interlayer as carbonate ions.

[0030] The top percolator 3 is used to prevent the solid phase change scavenger 5 particles from escaping, while allowing gas and circulating water to pass through. The bottom percolator 6 is used to uniformly disperse the gas flow entering the reactor body and prevent the solid phase change scavenger 5 from entering the bottom pipeline. The pore size of the bottom percolator 6 is 3~5μm, and the pore size of the top percolator 3 is 0.1~0.5μm. The larger pore size of the bottom percolator 6 compared to the top percolator 3 allows the gas to be fully dispersed when entering from the bottom. After passing through the scavenger layer, the flow velocity decreases and the residence time is prolonged when passing through the small-pore top filter, thereby increasing the contact opportunity between CO2 and the scavenger.

[0031] The reactor body is covered with a heating jacket 4, which is used to calcine the solid phase change trapping agent 5 in the chamber. This causes the LDH that has captured carbon dioxide to undergo a phase transformation under calcination, forming LDO and releasing purified CO2, thus achieving CO2 desorption.

[0032] like Figure 1 As shown, the gas flow channel includes a gas inlet located at the bottom of the reactor body and a gas outlet located at the top of the reactor body. Gas inlet and outlet are respectively equipped with gas shut-off switches 1. CO2-containing gas enters from the bottom, is uniformly dispersed by the bottom permeate filter 6, and then comes into full contact with the solid phase change trapping agent 5, achieving selective CO2 adsorption.

[0033] like Figure 1 As shown, the liquid flow channel includes a water inlet located at the top of the reactor body and a water outlet located at the bottom of the reactor body, and a water flow closure switch 2 is provided at the water inlet and the water outlet respectively.

[0034] like Figure 2 As shown, the pure CO2 collection channel is connected to the bypass of the gas outlet and is equipped with a pure CO2 collection closing switch 7, which is located at the top of the reactor body.

[0035] During system operation, the water flow closed switch 2 is first opened to introduce water into the reactor body to form a rehydrated environment, and then the water flow closed switch 2 is closed; next, the gas closed switch 1 is opened to introduce CO2-containing gas into the reactor body. After the gas is evenly dispersed through the bottom permeate filter 6, it comes into contact with the solid phase change trap 5. The selective adsorption and capture of CO2 is achieved through the rehydration and regeneration of the solid phase change trap 5.

[0036] Once the solid phase change trap 5 reaches saturation, the gas shut-off switch 1 is closed, and the pure CO2 collection shut-off switch 7 is opened. The reactor body is then heated and calcined in situ through the heating jacket 4, causing the solid phase change trap 5 to undergo a phase transition, thereby releasing high-purity CO2 and completing the collection.

[0037] Then, turn off the heating jacket 4 and the pure CO2 collection closed switch 7, and turn on the water flow closed switch 2 or the gas closed switch 1 again according to the above steps. The system will enter the next cycle until the preset number of cycles is reached and the cycle stops.

[0038] Specifically, the method for determining whether the adsorption of solid phase change trap 5 has reached saturation includes one of the following: Outlet concentration monitoring: The CO2 concentration in the reactor outlet gas is monitored by a gas concentration detector (such as an infrared CO2 analyzer). When the outlet concentration reaches 90% to 95% of the inlet concentration, the adsorbent is considered to have penetrated (close to saturation). Time control: Based on the adsorbent saturation time determined experimentally, a timed switching method is adopted; Temperature monitoring: The adsorption process is exothermic, and the adsorption progress is determined by monitoring changes in bed temperature.

[0039] The preset number of cycles in this invention can be pre-set by the operator according to the operating conditions, or determined based on the degradation of the capture agent's performance or system shutdown conditions. Specifically, in actual production, the preset number of cycles depends on the following factors: Capacitor performance degradation: As the number of cycles increases, the capture capacity of LDO / LDH will gradually decrease. When it decreases to a level that is not economically feasible, the capture agent needs to be replaced and the cycle terminated. Operator's judgment: The operator can preset the number of cycles based on the working conditions; System downtime conditions: such as equipment maintenance, repair, etc.

[0040] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0041] Example 1 This embodiment discloses an in-situ carbon dioxide capture and purification system suitable for low-concentration CO2 flue gas, specifically for the cyclic capture and purification of flue gas with a CO2 volume fraction of 10%. The in-situ carbon dioxide capture and purification system mainly includes a reactor body, a gas flow channel, a liquid flow channel, a solid phase change trapping agent 5, a top percolation screen 3, a bottom percolation screen 6, and a pure CO2 collection channel.

[0042] In practice, the solid phase change trap 5 is first placed between the top percolator 3 and the bottom percolator 6 to form a reaction layer, and water is introduced into the system through the water inlet to create a rehydrated environment. Subsequently, CO2 flue gas with a volume fraction of 10% is continuously introduced into the system through the gas inlet. After the flue gas comes into full contact with the solid phase change trap 5 inside the system, an in-situ mineralization reaction occurs.

[0043] During the reaction, the solid phase change trap 5 gradually recovers to the LDH layered structure by utilizing its memory effect, while converting CO2 in the flue gas into CO3. 2- The form is fixed in the interlayer, realizing in-situ capture and purification of CO2. After the reaction is completed, the system is thermally regenerated by heating jacket 4, so that LDH is converted back into LDO, and pure CO2 gas is released and collected through the pure CO2 collection port.

[0044] After completing one capture-regeneration cycle, the water is refilled and 10% CO2 flue gas is introduced. The above steps are repeated to achieve continuous cyclic capture.

[0045] To evaluate the cyclic capture performance of the system, CO2 capture amount (mg / g) was used as the evaluation index. The CO2 capture amount was tested using an HCS-800 high-frequency infrared carbon-sulfur analyzer: approximately 0.05 g of each cyclic capture product was weighed into a crucible, and 0.4 g of iron and 1.5 g of tungsten were added as flux. The crucible was then placed in the high-frequency infrared carbon-sulfur analyzer and burned at 2000–2200℃ in an oxygen atmosphere. The carbon content was then detected using the high-frequency infrared carbon-sulfur analyzer. The CO2 capture amount in the sample was thus obtained.

[0046] like Figure 3 The figure shows the changes in the system's cyclic capture performance under flue gas conditions with a CO2 volume fraction of 10%. Experimental results show that, under flue gas conditions with a CO2 volume fraction of 10%, the average capture amounts of the rehydrated products after 4 h and 6 h of reaction are 99.36 mg / g and 99.85 mg / g, respectively. With increasing cycle number, the CO2 capture amounts of the rehydrated products after 4 h and 6 h of reaction remain stable, indicating that the system has good cyclic capture stability.

[0047] To verify whether the recycled products can recover the LDH structure during the CO2 cyclic capture process, the phase structure of the recycled products was determined using a D8-Advance X-ray diffractometer: the test used a Cu target, a Kα ray source, a scanning speed of 2° / min, and a scanning angle of 5~80°.

[0048] Under flue gas conditions with a CO2 volume fraction of 10%, X-ray diffraction (XRD) analysis of the products after the 1st, 4th, and 7th cycles revealed the following: Figure 4The XRD pattern of the recycled products is shown. The recycled products, reacted for 4 h under flue gas conditions with a CO2 volume fraction of 10%, exhibit typical diffraction peaks characteristic of hydrotalcite structure. The crystallinity does not change significantly with increasing cycle number, and the average crystallinity of the three-cycle products is 90.95%. As the cycle continues, the characteristic peaks of LDH remain at a high intensity, indicating that the layered structure of the material has good stability under flue gas conditions with a CO2 volume fraction of 10%, and can maintain a strong structural memory effect.

[0049] Example 2 Unlike Example 1, this example specifically involves the cyclic capture and purification of flue gas with a CO2 volume fraction of 25%.

[0050] In practice, solid phase change scavenger 5 (LDO) is filled into the system reactor, and water is introduced into the system through the water inlet to create a rehydration reaction environment. Subsequently, CO2 flue gas with a volume fraction of 25% is continuously introduced into the system through the gas inlet. The CO2 enters the rehydration system and reacts with the LDO.

[0051] During the rehydration process, LDO gradually recovers and forms the LDH layered structure, while converting CO2 into CO3. 2- The system is fixed in a fixed form to achieve in-situ capture of high-concentration CO2 flue gas. After the reaction, the system is thermally regenerated by heating jacket 4, causing LDH to be converted back into LDO, while releasing pure CO2 gas, which is collected through the pure CO2 collection port.

[0052] After completing one capture-regeneration cycle, the water is refilled and 25% CO2 flue gas is introduced. The above steps are repeated to achieve continuous cyclic capture.

[0053] like Figure 5 The figure shows the changes in the system's cyclic capture performance under flue gas conditions with a CO2 volume fraction of 25%. Experimental results show that after 10 cycles of calcination desorption-rehydration adsorption, the average capture amounts of the rehydrated products after 4 h and 6 h of reaction under flue gas conditions with a CO2 volume fraction of 25% were 100.89 mg / g and 100.61 mg / g, respectively. Furthermore, with increasing cycle number, the CO2 capture amount of the rehydrated products after 4 h and 6 h of reaction under flue gas conditions with a CO2 volume fraction of 25% remained stable, indicating that the system can maintain good capture capacity after multiple cycles.

[0054] Under flue gas conditions with a CO2 volume fraction of 25%, X-ray diffraction analysis of the products after the 1st, 4th, and 7th cycles revealed the following: Figure 6The XRD pattern of the recycled products is shown. The recycled products, reacted for 4 h under flue gas conditions with a CO2 volume fraction of 25%, exhibit typical diffraction peaks characteristic of hydrotalcite structure. The crystallinity does not change significantly with increasing cycle number, and the average crystallinity of the products from three cycles is 91.68%. These results indicate that the solid phase change trap LDO can effectively recover the LDH layered structure during rehydration. As the cycle continues, the LDH characteristic peaks maintain a high intensity, indicating that the layered structure of the material has good stability under flue gas conditions with a CO2 volume fraction of 25%, and can maintain a strong structural memory effect.

[0055] Example 3 Unlike Example 1, this example focuses on the cyclic capture and purification of CO2 in the air.

[0056] In practice, solid phase change scavenger 5 (LDO) is filled into the system reactor, and water is introduced into the system through the water inlet to create a rehydration reaction environment. Subsequently, air is continuously introduced into the system through the gas inlet, and CO2 enters the rehydration system and reacts with the LDO.

[0057] During the rehydration process, LDO gradually recovers and forms the LDH layered structure, while converting CO2 into CO3. 2- The system is fixed in a fixed form to achieve in-situ capture of CO2 from the air. After the reaction, the system is thermally regenerated by heating jacket 4, causing LDH to be converted back into LDO, while releasing pure CO2 gas, which is collected through the pure CO2 collection port.

[0058] After completing one capture-regeneration cycle, water is refilled and air is introduced again. The above steps are repeated to achieve continuous cyclic capture.

[0059] Figure 7 The figure shows the variation of CO2 cyclic capture performance of solid phase change scavenger 5 under air conditions. Experimental results indicate that after five cycles of calcination-desorption-rehydration adsorption, the CO2 capture amount of the product after 1 h of rehydration is lower than that after 2 h and 4 h of rehydration. Specifically, the capture capacity is slightly lower after 1 h of rehydration, but the overall performance remains stable; after 2 h of rehydration, the material exhibits a higher CO2 capture capacity, reaching a maximum of approximately 100 mg / g in the fourth cycle; after 4 h of rehydration, the capture amount in each cycle remains between 80 and 90 mg / g, indicating good system cyclic stability. Different rehydration times did not lead to a significant decrease in the material's capture performance, and the residual CO2 content after cycling remained consistently within the range of 18–20 mg / g, indicating that the scavenger maintains good structural stability during cycling and can stably achieve CO2 cyclic capture and regeneration.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A carbon dioxide in-situ capture and purification system, characterized in that, include: Reactor body; The reactor body is filled with a solid phase change trap (5) for selective adsorption and desorption of CO2; A top percolation screen (3) is set at the top of the reactor body to block the loss of solid phase change trap (5) particles and prolong the residence time of gas in the reactor; Bottom permeation screen (6) is set at the bottom of the reactor body to uniformly disperse the CO2-containing gas entering the reactor body; The solid phase change trap (5) is located between the top permeate screen (3) and the bottom permeate screen (6); the pore size of the bottom permeate screen (6) is larger than that of the top permeate screen (3); A heating jacket (4) is wrapped around the outside of the reactor body and is used to perform in-situ heating and desorption of the solid phase change trap (5); The reactor body is equipped with a gas flow channel, a liquid flow channel and a pure CO2 collection channel, and each channel is equipped with a control valve.

2. The carbon dioxide in-situ capture and purification system according to claim 1, characterized in that, The gas flow channel includes a gas inlet located at the bottom of the reactor body and a gas outlet located at the top of the reactor body, and a gas closure switch (1) is provided at the gas inlet and the gas outlet respectively. The liquid flow channel includes a water inlet located at the top of the reactor body and a water outlet located at the bottom of the reactor body, and a water flow closing switch (2) is provided at the water inlet and the water outlet respectively. The pure CO2 collection channel is connected to the bypass of the gas outlet and is equipped with a pure CO2 collection closing switch (7).

3. The carbon dioxide in-situ capture and purification system according to claim 2, characterized in that, The gas closing switch (1), water flow closing switch (2) and pure CO2 collection closing switch (7) are all one-way valves.

4. The carbon dioxide in-situ capture and purification system according to claim 1, characterized in that, The solid phase change trap (5) is LDO.

5. The carbon dioxide in-situ capture and purification system according to claim 1, characterized in that, The reactor body is a vertically arranged cylindrical structure.

6. The carbon dioxide in-situ capture and purification system according to claim 1, characterized in that, Both the top permeation screen (3) and the bottom permeation screen (6) are made of stainless steel.

7. The carbon dioxide in-situ capture and purification system according to claim 1, characterized in that, The bottom permeation screen (6) has a pore size of 3~5μm, and the top permeation screen (3) has a pore size of 0.1~0.5μm.

8. The carbon dioxide in-situ capture and purification system according to claim 1, characterized in that, The CO2-containing gas is industrial flue gas or air.

9. A method for in-situ capture and purification of carbon dioxide, characterized in that, The carbon dioxide in-situ capture and purification system according to any one of claims 1 to 8 includes the following steps: S1: Open the control valve of the liquid flow channel to introduce water into the reactor body, so that the solid phase change capture agent (5) is activated in the rehydrated environment, and then close the control valve of the liquid flow channel; S2: Open the control valve of the gas flow channel and introduce CO2 gas into the reactor body. After the gas is evenly dispersed through the bottom filter screen (6), it comes into contact with the activated solid phase change trap (5). The solid phase change trap (5) selectively adsorbs and fixes CO2 by relying on the memory effect, so as to achieve CO2 in-situ capture. S3: When the solid phase change trap (5) is saturated with adsorption, close the control valve of the gas flow channel and the control valve of the liquid flow channel, open the control valve of the heating jacket (4) and the pure CO2 collection channel, and heat and calcine the saturated solid phase change trap (5) in situ to cause it to undergo phase transformation and release high-purity CO2, which is then collected through the pure CO2 collection channel. S4: Close the control valves of the heating jacket (4) and the pure CO2 collection channel, return to step S1, and enter the next cycle until the preset number of cycles is reached, and the cycle stops.

10. The method for in-situ capture and purification of carbon dioxide according to claim 9, characterized in that, In S2, the volume fraction of CO2 in the CO2-containing gas is 0.04%~25%.

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