Low-concentration CO2 purification process resistant to impurities and interference

Abstract

This invention relates to the field of gas separation technology and discloses a pressure swing adsorption (PSA) purification process for low-concentration CO2 resistant to impurity interference, comprising the following steps: S1: Adsorption step: The raw gas containing impurities and CO2 is passed into a main adsorption tower containing a composite adsorbent under adsorption pressure, so that CO2 is selectively adsorbed to obtain purified tail gas; S2: Regeneration step: The main adsorption tower is regenerated, including: S2.1: Pressure equalization and depressurization: The gas in the main adsorption tower is released to recover pressure energy; S2.2: Vacuuming: Vacuum desorption is performed on the main adsorption tower to obtain CO2 product gas; This invention uses a composite adsorbent with a gradient structure, whose hydrophobic outer shell effectively blocks moisture erosion, and the inner layer preferentially chemically fixes SO2. x NO x It removes acidic impurities, thereby protecting the core amine sites from highly selective CO2 adsorption and significantly improving its resistance to poisoning and long-term stability under complex flue gas conditions.

Description

Technical Field

[0001] This invention relates to the field of gas separation technology, and in particular to a low-concentration CO2 pressure swing adsorption purification process resistant to impurity interference. Background Technology

[0002] In many industrial sectors such as steel, cement, and chemicals, the flue gas emitted during production typically contains 5% to 30% low-concentration carbon dioxide (CO2). Capturing and purifying this low-concentration CO2 is one of the important technical approaches to achieving carbon resource recycling and mitigating the greenhouse effect. Currently, for the separation and purification of such gas sources, pressure swing adsorption (PSA) technology is widely studied and applied due to its relatively low energy consumption and flexible operation. This technology mainly utilizes the differences in the adsorption capacity of solid adsorbents for different gas components. Through periodic pressure changes, it achieves selective adsorption and desorption of CO2, thereby obtaining product gas with high purity.

[0003] However, existing conventional adsorption processes still have certain shortcomings when treating low-concentration CO2 flue gas with complex compositions: Since flue gas is often accompanied by a large amount of water vapor, sulfur oxides, nitrogen oxides and various organic impurities, traditional adsorbents are easily interfered with by these impurities, resulting in competitive adsorption or chemical poisoning, which leads to a rapid decline in CO2 adsorption capacity and selectivity, and it is difficult to maintain product purity and recovery rate in the long term. In addition, during long-term adsorption and regeneration cycles, adsorbent particles are prone to gradual densification and caking due to repeated airflow impact, pressure changes and temperature and humidity fluctuations. Caking will significantly increase the bed pressure drop, hinder uniform gas distribution, and seriously reduce separation efficiency and energy economy. Summary of the Invention

[0004] The technical problem to be solved by this invention is that in the prior art, traditional adsorbents are easily affected by complex impurities, resulting in performance degradation, and the adsorbent bed is prone to caking during long-term operation, leading to decreased separation efficiency and increased energy consumption. To address this, we propose a low-concentration CO2 pressure swing adsorption purification process that is resistant to impurity interference.

[0005] To achieve the above objectives, this application adopts the following technical solution: a low-concentration CO2 pressure swing adsorption purification process resistant to impurity interference, comprising the following steps:

[0006] S1: Adsorption step: The raw gas containing impurities and CO2 is passed into the main adsorption tower containing composite adsorbent under adsorption pressure, so that CO2 is selectively adsorbed to obtain purified tail gas.

[0007] S2: Regeneration Step: Regeneration of the main adsorption tower, including the following steps:

[0008] S2.1: Pressure equalization and depressurization: The gas inside the main adsorption tower is released to recover pressure energy;

[0009] S2.2: Vacuuming: Vacuum desorption is performed on the main adsorption tower to obtain CO2 product gas;

[0010] S2.3: Mild hot purging: Heated purging gas is introduced into the main adsorption tower, and the adsorbent bed is heated from the inside of the main adsorption tower. After purging, purging tail gas is obtained.

[0011] S3: Gas treatment step: Return the purge tail gas to the raw material gas and repeat the adsorption treatment in step S1.

[0012] The main adsorption tower includes a shell with a pair of porous limiting plates inside. The space between the two porous limiting plates is used to fill the composite adsorbent. A vibration loosening assembly is provided on the porous limiting plates. The vibration loosening assembly includes rubber bearings embedded in the middle of the porous limiting plates. An outer shaft is provided between the two rubber bearings. An inner shaft is rotatably provided inside the outer shaft. A universal joint is installed at the upper end of the inner shaft. A main shaft corresponding to the universal joint is rotatably installed at the upper end of the shell. A second drive source for driving the main shaft to rotate is installed at the top of the shell. The upper end of the universal joint is connected to the main shaft by a movable key. A crossbar extending into the composite adsorbent is provided on the side wall of the outer shaft. A hollow convex ring is provided at the end of the outer shaft. A circular plate is rotatably provided in the convex ring. Grooves are symmetrically provided on opposite sides of the circular plate. A counterweight slider is provided in one of the grooves. The circular plate is driven to rotate by the inner shaft.

[0013] Preferably, the composite adsorbent is prepared by the following steps:

[0014] a) Provide a porous carrier;

[0015] b) Loading oxide components for capturing acidic impurity metals onto a porous support;

[0016] c) On a porous support loaded with metal oxide components, an amine compound is loaded as a CO2 selective adsorption component, followed by hydrophobic surface modification.

[0017] Preferably, in step S2.1, the leaked gas is directed to the raw material gas inlet manifold.

[0018] Preferably, the feed gas passes through a pretreatment tower before entering the main adsorption tower for dehydration and removal of some organic impurities.

[0019] Preferably, the housing is provided with a discharge mechanism for discharging the composite adsorbent. The discharge mechanism includes an adsorbent discharge cylinder that is vertically and movably sleeved on the outside of the housing and corresponds to the porous limiting plate below. The adsorbent discharge cylinder is hollow, with an annular opening on the side of its upper end facing the housing and a through hole at the bottom. The circumferential sidewall of the housing is provided with a through groove corresponding to the porous limiting plate below. A traction plate is installed on the inner ring of the adsorbent discharge cylinder, located below the annular opening and extending into the housing through the through groove. The end of the traction plate away from the adsorbent discharge cylinder is connected to the porous limiting plate below. A first drive source for driving the adsorbent discharge cylinder to rise and fall is installed on the side of the housing. The outer shaft is connected to the inner wall of the rubber bearing on the porous limiting plate below by a movable key.

[0020] Preferably, the lower end sidewall of the outer shaft is provided with an arc-shaped outer blade plate. The outer blade plate has a hollow structure and an opening at the bottom. An inner blade plate is vertically and movably connected to the inside of the opening. An elastic structure is provided between the top of the inner blade plate and the inner wall of the outer blade plate.

[0021] Preferably, a one-way bearing is installed on the inner wall of the outer shaft, and the inner shaft is connected to the inner wall of the one-way bearing by a key along the axial direction;

[0022] The outer shaft is equipped with a vibration intensity adjustment mechanism, which includes a connecting column installed at the bottom of the perforated limiting plate below. A traction shell is installed at the bottom of the connecting column. The bottom of the inner shaft is rotatably connected to the traction shell through a rubber bearing. The inner shaft passes through the circular plate and is connected to the circular plate by a movable key. The side wall of the inner shaft is provided with a sloping groove corresponding to the convex ring. The inner wall of the sloping groove is inclined. The counterweight slider is movably connected to the inner side of the groove along the radial direction of the circular plate. The side wall of the counterweight slider is provided with a traction arm extending to the inner side of the sloping groove. The inner wall of the sloping groove is provided with an inclined guide rail. The end of the traction arm is movably connected to the guide rail.

[0023] Preferably, the sidewall of the circular plate is movably provided with ball bearings, and the circular plate rotates and engages with the inner wall of the convex ring through the ball bearings.

[0024] Preferably, a heat-conducting shell is provided on the inner periphery of the shell between two porous limiting plates, a heat exchange coil is provided inside the heat-conducting shell, and a heat-conducting arm is provided on the inner wall of the heat-conducting shell extending to the gap between adjacent crossbars.

[0025] Preferably, the bottom of the traction shell is conical.

[0026] The technical effects and advantages of this invention are as follows:

[0027] In this invention, a composite adsorbent with a gradient structure is used, whose hydrophobic outer shell effectively blocks water erosion, while the inner layer preferentially chemically immobilizes SO₂. x NO xThe adsorbent removes acidic impurities, thus protecting the core amine sites for highly selective CO2 adsorption. This significantly improves the adsorption resistance and long-term stability under complex flue gas conditions. Simultaneously, a regeneration strategy combining internal heating and reverse thermal purging is employed. Uniform internal heating avoids localized overheating damage to the composite adsorbent, while reverse thermal purging efficiently desorbs residual strongly adsorbed impurities. This synergistic approach achieves deep and gentle regeneration of the composite adsorbent, fundamentally solving the problems of incomplete regeneration or rapid thermal aging associated with traditional methods. Through this synergistic design, long-term stability of CO2 product purity and recovery rate is achieved under low-concentration, high-impurity feed gas conditions, while significantly reducing regeneration energy consumption.

[0028] In this invention, the vibration loosening component installed in the main adsorption tower can automatically and moderately loosen the composite adsorbent bed after each process cycle, effectively preventing caking, maintaining low pressure drop and efficient mass transfer of the bed, and can also start a high-intensity vibration mode when replacing the composite adsorbent to fluidize the adsorbent, and achieve rapid unloading in conjunction with the discharge mechanism, thereby greatly improving maintenance efficiency and greatly improving the operating environment. Attached Figure Description

[0029] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts:

[0030] Figure 1 This is a schematic diagram of the process flow of the present invention;

[0031] Figure 2 This is a schematic diagram illustrating the specific process of the regeneration steps in this invention;

[0032] Figure 3 This is a schematic diagram of the main adsorption tower of the present invention;

[0033] Figure 4 This is a schematic diagram of the internal structure of the main adsorption tower of the present invention;

[0034] Figure 5 This is a schematic diagram of the cross-sectional structure of the adsorbent cylinder of the present invention;

[0035] Figure 6 This is a schematic diagram of the overall mating structure of the second driving source, the porous limiting plate, and the outer shaft of the present invention;

[0036] Figure 7 For the present invention Figure 6 A structural diagram from the bottom perspective;

[0037] Figure 8 This is a schematic diagram of the multi-hole limiting plate and the outer shaft of the present invention in a disassembled state;

[0038] Figure 9 This is a schematic diagram of the structure of the outer blade and inner blade in the disassembled state of the present invention;

[0039] Figure 10 This is a schematic cross-sectional view of the convex ring of the present invention;

[0040] Figure 11 This is a schematic diagram of the heat exchange coil and heat-conducting shell of the present invention in their disassembled state.

[0041] Legend: 1. Shell; 2. Raw material gas inlet valve; 3. Tail gas outlet valve; 4. Hot purge gas inlet valve; 5. Pressure equalizing valve; 6. Multifunctional outlet valve; 7. Heat exchange coil; 8. Adsorbent cylinder; 9. First drive source; 10. Perforated limiting plate; 11. Through groove; 12. Traction plate; 13. Outer shaft; 14. Outer blade; 15. Annular opening; 16. Second drive source; 17. Main shaft; 18. Universal joint; 19. Traction shell; 20. Inner shaft; 21. Convex ring; 22. Connecting column; 23. Crossbar; 24. Inner blade; 25. Heat-conducting shell; 26. Elastic structure; 27. Heat-conducting arm; 28. Circular plate; 29. ​​Groove; 30. Counterweight slider; 31. Inclined groove; 32. Traction arm. Detailed Implementation

[0042] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0043] Reference Figures 1-11 As shown, this invention provides a technical solution: a low-concentration CO2 pressure swing adsorption purification process resistant to impurity interference, mainly targeting low-concentration (5%-30%) CO2 containing complex impurities (H2O, SO2, etc.). x NO x It treats CO2 flue gas (such as hydrocarbons), and the core consists of a pretreatment tower and a main adsorption tower connected in series. Through precise timing control, it achieves intermittent cyclic continuous operation.

[0044] As the first-stage purification unit, the pretreatment tower is filled with high-capacity hydrophobic zeolite or modified alumina adsorbents. Its main function is to deeply remove water vapor, dust and some large molecular organic matter from the raw gas.

[0045] The main adsorption tower is a vertical pressure vessel, specifically a vertical shell 1. Inside the shell 1, a pair of parallel porous limiting plates 10 are installed, with composite adsorbent filled between the two porous limiting plates 10. A heat exchange coil 7 is arranged around the composite adsorbent on the inner side of the shell 1. To protect the heat exchange coil 7, it is preferably arranged within an annular heat-conducting shell 25. Furthermore, to facilitate heat exchange with the inner composite adsorbent, heat-conducting arms 27 extending towards the center can be provided on the inner wall of the heat-conducting shell 25, thereby reducing the temperature gradient. The heat exchange coil 7 can be flexibly connected to either a cooling water circulation system or a low-temperature hot water circulation system via a three-way switching valve outside the tower. This allows for cooling during the adsorption stage and gentle internal heating during the regeneration stage. The shell 1 is equipped with multiple dedicated valve interfaces: a raw material gas inlet valve 2 and a multi-functional outlet valve 6 at the bottom, and an exhaust gas outlet valve 3 and a hot purge gas inlet valve 4 at the top. In addition, a pressure equalization valve 5 is provided on the side of the shell 1. The downstream pipeline of the multi-functional outlet valve 6 is equipped with a diversion control valve group, preferably a two-position three-way valve, which can selectively guide the airflow to the product gas buffer tank or return it to the exhaust gas return branch at the front end of the raw material gas main. The pipeline of the pressure equalization valve 5 is connected to a dedicated pressure equalization branch on the inlet side of the raw material gas blower, thereby safely recovering pressure energy and avoiding contamination of the product gas.

[0046] The composite adsorbent used in this process is prepared through the following steps to obtain a gradient functional structure: First, spherical γ-alumina supports with a particle size of 2-4 mm are selected, soaked and washed in dilute nitric acid solution until neutral, and then dried and activated at 120℃; then, the activated supports are immersed in 0.5 mol / L magnesium nitrate solution, dried, and calcined at 450℃ for 4 hours to firmly load magnesium oxide (MgO) nanoparticles onto the supports, forming active sites for capturing acidic impurities; next, the above supports are immersed in 40 wt% polyethyleneimine (PEI) aqueous solution using a vacuum-assisted impregnation method to ensure that the solution fully enters the pores, and then dried at 80℃ under vacuum for 12 hours to stabilize and immobilize PEI, forming core sites for chemical adsorption of CO2; to further improve stability, the obtained adsorbent is hydrophobically treated in an atmosphere containing silane coupling agent to form a hydrophobic film on its outermost surface.

[0047] The complete process cycle is as follows: the initial state is set so that both the pretreatment tower and the main adsorption tower are in a standby state at normal temperature and pressure, and the internal heat exchange coil 7 of the main adsorption tower is connected to the cooling water system.

[0048] Phase 1: Main Tower Adsorption Period. The inlet and outlet valves of the pretreatment tower are opened, and simultaneously, the raw gas inlet valve 2 and tail gas outlet valve 3 of the main adsorption tower are opened sequentially. The low-concentration raw gas, pressurized to approximately 0.15 MPa by a blower, first enters the pretreatment tower from the bottom. Most of the water vapor, dust, and some large organic molecules are captured by the adsorbent. The pretreated purified gas flows out from the top of the pretreatment tower and then enters the main adsorption tower from the bottom through the opened raw gas inlet valve 2. The purified gas passes through the composite adsorbent bed packed in the main adsorption tower from bottom to top. During this process, CO2 molecules in the gas are strongly chemically adsorbed by amine sites; while residual trace acidic impurities (such as SO2) are adsorbed... x NO x The nitrogen and oxygen components on the carrier are preferentially adsorbed or captured by the reaction. The weakly adsorbed components such as nitrogen and oxygen that are not adsorbed are discharged from the tail gas outlet valve 3 at the top of the shell 1 as tail gas. The entire adsorption stage is an exothermic process. Therefore, cooling water is continuously introduced into the heat exchange coil 7 to maintain the bed temperature in the optimal adsorption temperature range of 50-60℃ to ensure high adsorption capacity and rate. An online gas analyzer can be installed on the outlet pipeline at the top of the shell 1 to detect CO2. When the CO2 concentration rises to the preset value, it indicates that the composite adsorbent bed is about to penetrate and the adsorption step is over. The control system immediately closes the raw material gas inlet valve 2 and the tail gas outlet valve 3 of the main adsorption tower to stop the gas intake. The system then enters the regeneration period.

[0049] The second stage is the regeneration period. The first step of the regeneration period is pressure equalization and reduction. Keep all other valves in the main adsorption tower closed and open the pressure equalization valve 5 to connect the inside of the shell 1 with the dedicated pressure equalization branch on the inlet side of the raw material gas blower. At this time, the pressure inside the shell 1 (about 0.15MPa) is higher than the pressure of this branch. The high-pressure gas flows to this branch through the pressure equalization valve 5 until the two pressures are balanced. This process effectively recovers the pressure energy of the gas and reduces the pressure of the main adsorption tower to medium pressure. The pressure drop causes a small amount of weakly adsorbed gases such as N2 and O2 that have been physically adsorbed to be desorbed and returned to the front end of the system with the airflow. After completion, the pressure equalization valve 5 is closed.

[0050] Next, reverse vacuuming is performed. The multi-functional outlet valve 6 at the bottom of the main adsorption tower is opened, and the pipeline is switched to the product gas buffer tank via the subsequent diversion control valve group. Then, the pressure inside the main adsorption tower is rapidly reduced to negative pressure by the vacuum pump. According to the adsorption equilibrium principle, the partial pressure of CO2 in the gas phase drops sharply, disrupting the original adsorption equilibrium and driving a large number of chemically adsorbed CO2 molecules to desorb. The desorbed high-concentration CO2 gas flows downward from the adsorbent bed, is extracted through the multi-functional outlet valve 6 and the diversion pipeline, and is sent to the product gas buffer tank. This is the main step in obtaining the product gas.

[0051] The process then proceeds to a gentle hot purging step. First, the three-way valve connecting the heat exchange coil 7 in the main adsorption tower is switched to the hot water circulation system, injecting 90°C hot water into the heat exchange coil 7 to provide uniform and gentle heating from the inside of the adsorbent bed. Next, the hot purging gas inlet valve 4 is opened, allowing a stream of pure nitrogen gas, precisely temperature-controlled to 100°C by an electric heater, to be injected from the top of the tower at a low, constant flow rate. Simultaneously, the multi-functional outlet valve 6 remains open, but the subsequent diversion control valve group is switched to the tail gas return branch connected to the front end of the return feed gas main. In this way, 100°C hot nitrogen gas enters through the hot purging gas inlet valve 4 and penetrates from top to bottom in a reverse direction. The composite adsorbent bed is internally heated synchronously. The synergistic effect of this internal heating and countercurrent hot gas purging provides sufficient but not excessive heat energy to desorb strongly adsorbed residual moisture, hydrocarbons and other impurities, as well as a small amount of deeply adsorbed CO2. The hot purge tail gas containing these desorbed components is discharged from the multi-functional outlet valve 6 and guided back to the front end of the feed gas main of the entire system through the tail gas return branch. After mixing with the feed gas, it re-enters the pretreatment tower for treatment. In this way, the trace amount of CO2 entrained in the tail gas can be recovered, and the desorbed impurities are captured again by the pretreatment tower, realizing the material closed loop of the system and avoiding CO2 loss and secondary pollution.

[0052] During the tens of minutes of gentle hot purging of the main adsorption tower, the system has a sufficient time window to regenerate the nearly saturated pretreatment tower. The specific operation is as follows: cut off the raw gas to the pretreatment tower, close its inlet and outlet valves, and then use a stream of medium-temperature hot nitrogen to perform a simple purging regeneration of the pretreatment tower. The desorbed water vapor and other impurities are directly discharged into the air. Since the impurities adsorbed by the pretreatment tower are relatively simple, its regeneration process can be completed in a short time, thus ensuring that the pretreatment tower is also regenerated before the main adsorption tower regeneration is completed, and both can enter the adsorption preparation state for the next cycle simultaneously.

[0053] Finally, cooling and preparation are carried out. After the hot purging step of the main adsorption tower is completed, the hot purging gas inlet valve 4 is closed first. Then, the medium in the heat exchange coil 7 is switched from hot water back to cooling water to cool the bed. Next, the multi-functional outlet valve 6 is closed. Finally, the raw material gas inlet valve 2 is slightly opened to introduce a small amount of gas purified by the pretreatment tower and the main adsorption tower is slowly pressurized to atmospheric pressure. At this point, the internal temperature of the main adsorption tower has dropped to near the adsorption temperature, the pressure has returned to atmospheric pressure, the activity of the composite adsorbent has been basically restored, and the entire system returns to its initial state, waiting to start the next complete cycle that includes adsorption and regeneration.

[0054] This process effectively solves the core problems of adsorbent degradation and incomplete regeneration in the purification of low-concentration, high-impurity CO2 flue gas by combining a regeneration strategy of specialized adsorbent, internal gentle heating and reverse thermal purging, and closed-loop recovery of purging tail gas, thus achieving stable and efficient resource utilization.

[0055] To facilitate the handling of the caking problem of the composite adsorbent between the two porous limiting plates 10 after each process cycle, a vibration loosening component is provided on the porous limiting plates 10. As one embodiment, the vibration loosening component includes rubber bearings embedded in the middle of the two porous limiting plates 10. An outer shaft 13 is provided in each of the two rubber bearings. Multiple one-way bearings are evenly installed on the inner side of the outer shaft 13. A vertical inner shaft 20 is provided on the inner wall of each one-way bearing. A universal joint 18 is installed at the upper end of the inner shaft 20. A main shaft 17 corresponding to the universal joint 18 is rotatably installed at the upper end of the housing 1. The upper end of the universal joint 18 is movably inserted into the bottom of the main shaft 17. To prevent relative rotation between the two, the upper end of the universal joint 18 and the lower end of the main shaft 17 are connected... The inner side is configured with a key connection. The top of the housing 1 is equipped with a second drive source 16 for driving the main shaft 17 to rotate. The second drive source 16 can be a geared motor or the main shaft 17 can be rotated by a motor driving a gear set. The side wall of the outer shaft 13 is provided with multiple crossbars 23 extending into the composite adsorbent. The gap between the crossbars 23 corresponds to the heat-conducting arm 27 to avoid motion interference when the crossbars 23 rotate. The upper and lower ends of the outer shaft 13 are connected with convex rings 21 with a diameter larger than that of the outer shaft 13. The convex rings 21 are hollow. A circular plate 28 is rotatably arranged in the convex ring 21. The opposite sides of the circular plate 28 are symmetrically provided with grooves 29. One of the grooves 29 is provided with a counterweight slider 30. The circular plate 28 is driven to rotate by the inner shaft 20.

[0056] To facilitate rapid discharge of the composite adsorbent during subsequent replacements, a discharge mechanism is provided on the housing 1. In one embodiment, the discharge mechanism includes an annular adsorbent discharge cylinder 8 vertically and movably sleeved on the outside of the housing 1, corresponding to the porous limiting plate 10 below. The adsorbent discharge cylinder 8 is hollow, with an annular opening 15 on its upper end facing the housing 1 and a through hole at its bottom. A through groove 11 corresponding to the porous limiting plate 10 is provided on the circumferential sidewall of the housing 1. Initially, the lower inner ring of the adsorbent discharge cylinder 8 can block the through groove 11. A traction plate 12 is installed below the annular opening 15 and extends into the inner side of the housing 1 through the through groove 11. One end of the traction plate 12 extending into the inner side of the housing 1 is fixedly connected to the lower porous limiting plate 10. A first drive source 9 for driving the adsorbent discharge cylinder 8 to rise and fall is installed on the side of the housing 1. There are at least two first drive sources 9, which are arranged opposite to each other and are preferably hydraulic cylinders. The upper end of the outer shaft 13 is fixedly connected to the inner wall of the rubber bearing on the upper porous limiting plate 10 and is connected to the inner wall of the rubber bearing on the lower porous limiting plate 10 by a movable key, so as to ensure that the lower porous limiting plate 10 can undergo relative axial displacement with the outer shaft 13.

[0057] To improve discharge efficiency, an arc-shaped outer blade plate 14 is provided on the lower side wall of the outer shaft 13. The outer blade plate 14 rotates and rises with the outer shaft 13, which can guide the composite adsorbent to the periphery of the porous limiting plate 10, thereby facilitating discharge. In order to accommodate the descent of the porous limiting plate 10 below, the outer blade plate 14 is set as a hollow structure with an opening at the bottom. An inner blade plate 24 is vertically and movably connected to the inside of the opening. An elastic structure 26 is provided between the top of the inner blade plate 24 and the inner wall of the outer blade plate 14. The elastic structure 26 is preferably a spring, which ensures that the inner blade plate 24 can be pushed down. After the porous limiting plate 10 below descends, the inner blade plate 24 can descend to the upper surface of the porous limiting plate 10 below.

[0058] To reduce caking and accelerate discharge when replacing the composite adsorbent, a vibration intensity adjustment mechanism is provided on the outer shaft 13. This mechanism includes a connecting column 22 mounted at the bottom of the porous limiting plate 10 below. A traction shell 19 is mounted at the bottom of the connecting column 22. The bottom of the traction shell 19 is tapered to reduce wind resistance. The bottom of the inner shaft 20 is rotatably connected to the traction shell 19 via a rubber bearing. The inner shaft 20 is axially connected to the inner wall of a one-way bearing via a movable key. The inner shaft 20 also passes through a circular plate 28, and is also connected to the circular plate 28 via a movable key. The side wall of the inner shaft 20 is provided with a protruding ring 2. The inclined groove 31 corresponding to 1 has an inclined inner wall. The counterweight slider 30 is radially connected to the inner side of the groove 29 along the circular plate 28. The side wall of the counterweight slider 30 is provided with a traction arm 32 extending to the inner side of the inclined groove 31. The inner wall of the inclined groove 31 is provided with an inclined guide rail. The end of the traction arm 32 is movably connected to the guide rail. The configuration is such that when the inner shaft 20 descends, the traction arm 32 can push the counterweight slider 30 to move away from the axis of the inner shaft 20. In order to reduce the friction of the circular plate 28, a ball is movably provided on the side wall of the circular plate 28. The circular plate 28 rotates with the inner wall of the convex ring 21 through the ball.

[0059] It should be noted that the upper part is a split structure, which is assembled by at least two bolts. During filling, the composite adsorbent can be filled by removing the upper end cap of the shell 1 and part of the porous limiting plate 10 above.

[0060] The detailed working principles of the vibration loosening components, discharge mechanism, and vibration intensity adjustment mechanism in the main adsorption tower are as follows:

[0061] At the end of each process cycle, the second drive source 16 drives the main shaft 17 to rotate, which in turn drives the inner shaft 20 to rotate via the universal joint 18. At this time, the one-way bearing between the outer shaft 13 and the inner shaft 20 is in a free state. Combined with the constraint of the composite adsorbent on the crossbar 23 and the outer leaf plate 14, the inner shaft 20 will not drive the outer shaft 13 to rotate. The rotation of the inner shaft 20 will drive the circular plate 28 to rotate. Since the circular plate 28 has symmetrically arranged grooves 29 on opposite sides, and one of the grooves 29 contains a counterweight slider 30, the uneven mass distribution of the circular plate 28 will cause centrifugal force imbalance during rotation, resulting in vibration. This vibration is further exacerbated by the rubber bearing between the outer shaft 13 and the porous limiting plate 10, and the bottom of the inner shaft 20. The rubber bearing between the outer shaft 13, the crossbar 23, and the inner shaft 20 can achieve overall micro-vibration of the outer shaft 13, the crossbar 23, and the inner shaft 20. The crossbar 23 extends inside the composite adsorbent, thus it can vibrate and loosen the composite adsorbent, reducing caking. Moreover, the rubber bearing not only ensures the vibration of the outer shaft 13, the crossbar 23, and the inner shaft 20, but also has a vibration isolation function, preventing vibration from causing vibration of structures such as the porous limiting plate 10. The universal joint 18 at the upper end of the inner shaft 20 and the movable key connecting the upper end of the universal joint 18 to the main shaft 17 can adapt to the vibration of the lower outer shaft 13, the crossbar 23, and the inner shaft 20. Vibration can effectively prevent caking, maintain low pressure drop in the bed, and achieve efficient mass transfer. After completion, the second drive source 16 is turned off, and subsequent process cycles are performed.

[0062] Finally, when the composite adsorbent between the two porous limiting plates 10 needs to be completely replaced, the first drive source 9 drives the adsorbent cylinder 8 to descend. The adsorbent cylinder 8 drives the lower porous limiting plate 10 to descend via the traction plate 12. The inner ring of the adsorbent cylinder 8 releases the blockage of the through groove 11, and at the same time, the annular opening 15 gradually matches the through groove 11. Due to the descent of the lower porous limiting plate 10, the composite adsorbent also descends. When the lower porous limiting plate 10 descends, it also drives the connecting column 22 and the traction housing 19 to descend synchronously. Since the upper end of the universal joint 18 can extend and retract with the main shaft 17... The inner shaft 20 is driven to descend by the traction housing 19, thus causing relative displacement between the inner shaft 20 and the circular plate 28. With the cooperation of the inclined groove 31 and the traction arm 32, the counterweight slider 30 moves away from the axis of the inner shaft 20, increasing the eccentricity. Therefore, at the same rotational speed, the vibration intensity can increase. The second drive source 16 continues to drive the inner shaft 20 to rotate through the main shaft 17 and the universal joint 18, thereby continuing to generate vibration in the composite adsorbent. Furthermore, due to the increased distance between the two porous limiting plates 10, the loose composite adsorbent can slowly be discharged from the through groove 11 into the adsorbent discharge cylinder 8. Finally... The adsorbent falls through the through-hole at the bottom of the adsorbent discharge cylinder 8 and can be collected by a special collection device. When the composite adsorbent is almost discharged, the second drive source 16 stops. Due to the descent of the lower porous limiting plate 10 and the reduction of the composite adsorbent, the inner leaf plate 24 gradually moves down, and the bottom of the inner leaf plate 24 corresponds to the top of the lower porous limiting plate 10. Finally, the second drive source 16 is controlled to reverse. At this time, when the inner shaft 20 rotates, it will drive the outer shaft 13 to rotate synchronously through the one-way bearing. Then, the outer shaft 13, inner shaft 20, crossbar 23 and outer leaf plate 14 rotate synchronously and slowly as a whole. The guide plate 14 allows the remaining composite adsorbent to be discharged, while the crossbar 23 can also agitate the composite adsorbent, increasing the discharge speed. Moreover, the gap between the heat-conducting arm 27 and the crossbar 23 corresponds, so the crossbar 23 will not interfere with the movement of the heat-conducting arm 27 when it rotates. When filling with new composite adsorbent, remove the upper end cap and other structures of the shell 1, remove part of the upper porous limiting plate 10, and control the lower porous limiting plate 10 to rise and reset. Finally, fill through the opening of the upper porous limiting plate 10, and then reinstall the removed part of the upper porous limiting plate 10.

[0063] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A low-concentration CO2 pressure swing adsorption purification process resistant to impurity interference, characterized in that, Includes the following steps: S1: Adsorption step: The raw gas containing impurities and CO2 is passed into the main adsorption tower containing composite adsorbent under adsorption pressure, so that CO2 is selectively adsorbed to obtain purified tail gas. S2: Regeneration Step: Regeneration of the main adsorption tower, including the following steps: S2.1: Pressure equalization and depressurization: The gas inside the main adsorption tower is released to recover pressure energy; S2.2: Vacuuming: Vacuum desorption is performed on the main adsorption tower to obtain CO2 product gas; S2.3: Mild hot purging: Heated purging gas is introduced into the main adsorption tower, and the adsorbent bed is heated from the inside of the main adsorption tower. After purging, purging tail gas is obtained. S3: Gas treatment step: Return the purge tail gas to the raw material gas and repeat the adsorption treatment in step S1. The main adsorption tower includes a shell, with a pair of porous limiting plates inside the shell. A composite adsorbent is filled between the two porous limiting plates. A vibration loosening assembly is provided on the porous limiting plates. The vibration loosening assembly includes rubber bearings embedded in the middle of the porous limiting plates. An outer shaft is provided between the two rubber bearings. An inner shaft is rotatably provided inside the outer shaft. A universal joint is installed at the upper end of the inner shaft. A main shaft corresponding to the universal joint is rotatably installed at the upper end of the shell. A second drive source for driving the main shaft is installed at the top of the shell. The upper end of the universal joint is connected to the main shaft by a movable key. A crossbar extending into the composite adsorbent is provided on the side wall of the outer shaft. A hollow convex ring is connected to the end of the outer shaft. A circular plate is rotatably provided in the convex ring. Grooves are symmetrically provided on opposite sides of the circular plate. A counterweight slider is provided in one of the grooves. The circular plate is driven to rotate by the inner shaft. The housing is provided with a discharge mechanism for discharging the composite adsorbent. The discharge mechanism includes an adsorbent cylinder that is vertically and movably sleeved on the outside of the housing and corresponds to the porous limiting plate below. The adsorbent cylinder is hollow, with an annular opening on the side of its upper end facing the housing and a through hole at the bottom. The circumferential sidewall of the housing is provided with a through groove corresponding to the porous limiting plate below. A traction plate is installed on the inner ring of the adsorbent cylinder, located below the annular opening and extending into the housing through the through groove. The end of the traction plate away from the adsorbent cylinder is connected to the porous limiting plate below. A first drive source for driving the adsorbent cylinder to rise and fall is installed on the side of the housing. The outer shaft is connected to the inner wall of the rubber bearing on the porous limiting plate below by a movable key. The inner wall of the outer shaft is fitted with a one-way bearing, and the inner shaft is connected to the inner wall of the one-way bearing by a key along the axial direction. The outer shaft is equipped with a vibration intensity adjustment mechanism, which includes a connecting column installed at the bottom of the perforated limiting plate below. A traction shell is installed at the bottom of the connecting column. The bottom of the inner shaft is rotatably connected to the traction shell through a rubber bearing. The inner shaft passes through the circular plate and is connected to the circular plate by a movable key. The side wall of the inner shaft is provided with a sloping groove corresponding to the convex ring. The inner wall of the sloping groove is inclined. The counterweight slider is movably connected to the inner side of the groove along the radial direction of the circular plate. The side wall of the counterweight slider is provided with a traction arm extending to the inner side of the sloping groove. The inner wall of the sloping groove is provided with an inclined guide rail. The end of the traction arm is movably connected to the guide rail.

2. The low-concentration CO2 pressure swing adsorption purification process resistant to impurity interference according to claim 1, characterized in that: The composite adsorbent is prepared by the following steps: a) Provide a porous carrier; b) Loading oxide components for capturing acidic impurity metals onto a porous support; c) On a porous support loaded with metal oxide components, an amine compound is loaded as a CO2 selective adsorption component, followed by hydrophobic surface modification.

3. The low-concentration CO2 pressure swing adsorption purification process resistant to impurity interference according to claim 1, characterized in that: In step S2.1, the leaked gas is directed to the raw material gas inlet manifold.

4. The low-concentration CO2 pressure swing adsorption purification process resistant to impurity interference according to claim 1, characterized in that: Before being introduced into the main adsorption tower, the raw gas first passes through a pretreatment tower for dehydration and removal of some organic impurities.

5. The low-concentration CO2 pressure swing adsorption purification process resistant to impurity interference according to claim 1, characterized in that: The lower end sidewall of the outer shaft is provided with an arc-shaped outer blade plate. The outer blade plate has a hollow structure and an opening at the bottom. An inner blade plate is vertically and movably connected to the inside of the opening. An elastic structure is provided between the top of the inner blade plate and the inner wall of the outer blade plate.

6. The low-concentration CO2 pressure swing adsorption purification process resistant to impurity interference according to claim 1, characterized in that: The circular plate has movably arranged ball bearings on its sidewall, and the circular plate rotates and engages with the inner wall of the convex ring through the ball bearings.

7. The low-concentration CO2 pressure swing adsorption purification process resistant to impurity interference according to claim 1, characterized in that: The inner periphery of the housing is provided with a heat-conducting shell located between two porous limiting plates. The heat-conducting shell is provided with a heat exchange coil inside, and the inner wall of the heat-conducting shell is provided with a heat-conducting arm extending to the gap between adjacent crossbars.

8. The low-concentration CO2 pressure swing adsorption purification process resistant to impurity interference according to claim 1, characterized in that: The bottom of the traction shell is conical.

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