Direct air carbon capture system

Abstract

The invention relates to the technical field of air carbon capture, in particular to a direct air carbon capture system which comprises an adsorption unit and an absorption unit, the adsorption unit comprises at least three adsorption towers which are arranged in parallel, each adsorption tower comprises an adsorption time sequence, a heating regeneration time sequence and a cooling time sequence which are performed in sequence, and at the same moment, the adsorption time sequence and the heating regeneration time sequence are in parallel connection. At least one adsorption tower performs an adsorption time sequence, one adsorption tower performs a heating regeneration time sequence, one adsorption tower performs a cooling time sequence, and the absorption unit comprises an absorption tower and a regeneration tower and is used for further separating mixed gas treated by the adsorption unit. According to the invention, carbon dioxide is directly captured from air, through sequential control of the adsorption tower, the air introduction process does not need to be stopped at intervals, uninterrupted air carbon capture is realized, and through absorption and regeneration of the absorption tower and the regeneration tower of the absorption unit, carrier gas and carbon dioxide are separated, and a high-concentration CO2 product is output.

Description

Technical Field

[0001] The present invention relates to the technical field of air carbon capture, and in particular to a direct air carbon capture system. Background Art

[0002] Direct air capture (DAC) is a carbon capture technology that captures, utilizes and stores carbon dioxide. Compared with other carbon capture technologies, DAC has no geographical restrictions and can place the capture point and storage point in one place, reducing transportation costs. It can also solve the emission problems of many CO2 distribution sources such as transportation and construction industries, and avoid the performance of adsorbents being affected by high concentrations of pollutants in flue gas (such as NO x 、SO x Therefore, DAC is considered to be a very promising carbon capture technology.

[0003] At present, the mainstream solutions for air capture are solid adsorption and liquid absorption. In the solid adsorption process, carbon capture is mainly completed by the adsorption tank through the adsorption, heating regeneration and cooling stages in sequence. After the air is introduced to complete the adsorption stage, the air must be stopped, and the air must be introduced again after the heating regeneration and cooling stages are completed for the next round of carbon capture. This causes CO2 adsorption to be not a continuous process, and the intermittent interruption of air introduction seriously affects the efficiency of air carbon capture. At the same time, because the carrier gas needs to be introduced to guide CO2 during the carbon capture process, the final output CO2 product concentration is low. Summary of the invention

[0004] The present invention provides a direct air carbon capture system to solve the above-mentioned defects of the existing air capture solid adsorption method, realize the efficient carbon capture process, and output high-concentration CO2 products.

[0005] The present invention provides a direct air carbon capture system, comprising an adsorption unit and an absorption unit.

[0006] The adsorption unit includes at least three adsorption towers arranged in parallel, the adsorption tower is connected to an external air source through a first pipeline, the adsorption tower is filled with an adsorbent for adsorbing carbon dioxide, the adsorption tower is high-point diffused through a second pipeline, the adsorption tower is connected to a carrier gas source through a third pipeline, and the adsorption tower is connected to the absorption unit through a fourth pipeline.

[0007] Each of the adsorption towers includes an adsorption sequence, a heating regeneration sequence and a cooling sequence that are performed in sequence. In the adsorption sequence, the first pipeline, the adsorption tower and the second pipeline are connected in sequence to pass air into the adsorption tower and adsorb carbon dioxide in the air; in the heating regeneration sequence, the third pipeline, the adsorption tower and the fourth pipeline are connected in sequence to heat and regenerate the adsorbent of the adsorption tower through a carrier gas and output the carrier gas and carbon dioxide; in the cooling sequence, the adsorbent of the adsorption tower is cooled by passing the carrier gas through the third pipeline.

[0008] At the same time, at least one of the at least three adsorption towers performs the adsorption sequence, at least one of the adsorption towers performs the heating regeneration sequence, and at least one of the adsorption towers performs the cooling sequence.

[0009] The absorption unit includes an absorption tower and a regeneration tower. The absorption tower is connected to the fourth pipeline to receive the carrier gas and carbon dioxide output by the adsorption tower in the heating regeneration sequence. The absorption tower is connected to a lean amine liquid source to absorb carbon dioxide through the lean amine liquid. The absorption tower is connected to the regeneration tower, and the regeneration tower is used to receive the amine liquid from the absorption tower and separate the carbon dioxide.

[0010] According to a direct air carbon capture system provided by the present invention, the first pipeline is connected to an air compressor, which is used to compress external air and input it into the adsorption tower through the first pipeline; and / or, a carrier gas compressor is arranged in the fourth pipeline, which is used to compress the carrier gas and carbon dioxide outputted from the adsorption tower, and input them into the absorption tower through the fourth pipeline.

[0011] According to a direct air carbon capture system provided by the present invention, the second pipeline is further connected to the first pipeline via a fifth pipeline, and a circulating compressor is provided in the fifth pipeline.

[0012] According to a direct air carbon capture system provided by the present invention, the absorption tower is provided with a carrier gas separation outlet, the adsorption tower is provided with a cold carrier gas interface and a hot carrier gas interface, the third pipeline includes a cold carrier gas pipeline and a hot carrier gas pipeline, the cold carrier gas pipeline connects the carrier gas separation outlet of the absorption tower and the cold carrier gas interface of the adsorption tower, and is used for introducing cold carrier gas into the adsorption tower when the adsorption tower is in the cooling sequence; the hot carrier gas pipeline is connected to the hot carrier gas interfaces of all the adsorption towers, and is used for inputting the hot carrier gas output by the adsorption tower in the cooling sequence into the adsorption tower in the heating regeneration sequence.

[0013] According to a direct air carbon capture system provided by the present invention, a regeneration cooler is provided on the fourth pipeline, and a first gas-liquid separator and a pressure regulating valve are provided on the cold carrier gas pipeline.

[0014] According to a direct air carbon capture system provided by the present invention, a regeneration heater is provided on the hot carrier gas pipeline, and the hot carrier gas pipeline is also connected to a carrier gas supplementary pipeline, and the carrier gas supplementary pipeline is connected to the inlet side of the regeneration heater.

[0015] According to a direct air carbon capture system provided by the present invention, a rich amine liquid inlet and a separation gas outlet are arranged on the top of the regeneration tower, the absorption tower is connected to the rich amine liquid inlet through a rich amine liquid pipeline, the separation gas outlet is connected to a second gas-liquid separator, and the gas outlet of the second gas-liquid separator is used to output carbon dioxide.

[0016] A lean amine liquid outlet is provided at the bottom of the regeneration tower, and the lean amine liquid outlet is connected to the absorption tower via a lean amine liquid pipeline to serve as a lean amine liquid source for the absorption tower. A lean liquid pump and a lean liquid cooler are provided in the lean amine liquid pipeline.

[0017] According to a direct air carbon capture system provided by the present invention, a semi-lean amine liquid outlet is provided in the middle of the regeneration tower, and the semi-lean amine liquid outlet is connected to the middle of the absorption tower through a semi-lean amine liquid pipeline to output the semi-lean amine liquid to the absorption tower, and a semi-lean amine liquid cooler and a semi-lean amine liquid pump are provided in the semi-lean amine liquid pipeline.

[0018] According to a direct air carbon capture system provided by the present invention, the adsorption unit comprises a plurality of adsorption sub-units arranged in parallel, and the plurality of adsorption sub-units are stacked and used in coordination.

[0019] Each of the adsorption subunits includes a plurality of adsorption towers. At the same time, among the plurality of adsorption towers of each of the adsorption subunits, one of the adsorption towers performs the heating regeneration sequence, another of the adsorption towers performs the cooling sequence, and the remaining adsorption towers all perform the adsorption sequence, and all the adsorption towers performing the adsorption sequence have a time difference in starting and ending the adsorption sequence respectively.

[0020] According to a direct air carbon capture system provided by the present invention, a programmable valve is provided on the inlet and outlet pipelines of each of the adsorption towers, so as to change the number of the adsorption towers performing the adsorption sequence at the same time by opening and closing the programmable valve. When the programmable valve on the inlet and outlet pipelines of the adsorption tower is opened, the adsorption tower performs the adsorption sequence, and when the programmable valve on the inlet and outlet pipelines of the adsorption tower is closed, the adsorption tower stops working.

[0021] In the direct air carbon capture system provided by the present invention, each adsorption tower of the adsorption unit sequentially performs adsorption timing, heating regeneration timing and cooling timing. By adjusting the program-controlled valves of the adsorption tower inlet and outlet pipelines, a certain time difference exists in the working timing of each adsorption tower. At the same time, at least one adsorption tower in the adsorption unit performs adsorption timing, at least one adsorption tower performs heating regeneration timing, and at least one adsorption tower performs cooling timing. In this way, in the direct air carbon capture process, the air introduction process does not need to be stopped at intervals, and uninterrupted air carbon capture is achieved. After carbon dioxide is adsorbed by the adsorption unit, it is regenerated and guided by the carrier gas, and the carrier gas and carbon dioxide enter the absorption unit. Through the absorption and regeneration of the absorption tower and the regeneration tower, the carrier gas and carbon dioxide are separated, and a high-concentration CO2 product is output. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 It is a schematic structural diagram of the direct air carbon capture system provided by the present invention.

[0024] Figure 2 It is a schematic diagram of the operation of the adsorption unit provided by the present invention in the time period 0→T.

[0025] Figure 3 It is a schematic diagram of the operation of the adsorption unit provided by the present invention in a time period of T→2T.

[0026] Figure 4 It is a schematic diagram of the operation of the adsorption unit provided by the present invention in a time period of 2T→3T.

[0027] Figure 5 It is a schematic diagram of a program-controlled valve in a direct air carbon capture system provided by the present invention being in an open state.

[0028] Figure 6 It is a schematic diagram of a program-controlled valve in a direct air carbon capture system provided by the present invention being in a closed state.

[0029] Figure 7 It is a structural schematic diagram of the adsorption unit provided by the present invention adopting a cyclic adsorption method.

[0030] Figure 8 It is a schematic diagram of the structure of the absorption unit provided by the present invention with a semi-lean amine liquid pipeline.

[0031] Fig. 9It is a schematic diagram of the operation of the adsorption unit using eight adsorption towers provided by the present invention in the time period of 0 to 4 hours.

[0032] Fig.10 It is a schematic diagram of the operation of the adsorption unit using eight adsorption towers provided by the present invention during a period of 4 to 8 hours.

[0033] Fig.11 It is a schematic diagram of the operation of the adsorption unit using eight adsorption towers provided by the present invention during a period of 8 to 12 hours.

[0034] Fig.12 It is a schematic diagram of the operation of the adsorption unit using eight adsorption towers provided by the present invention during a period of 12 to 16 hours.

[0035] Fig.13 It is a schematic diagram of the operation of the adsorption unit using eight adsorption towers provided by the present invention during a period of 16 to 20 hours.

[0036] Fig.14 It is a schematic diagram of the operation of the adsorption unit using eight adsorption towers provided by the present invention during a period of 20 to 24 hours.

[0037] Fig.15 It is a schematic diagram of the operation of the adsorption unit using eight adsorption towers provided by the present invention during a 24-28h period.

[0038] Fig.16 It is a schematic diagram of the operation of the adsorption unit using eight adsorption towers provided by the present invention during a period of 28 to 32 hours.

[0039] Figure numerals: 1. adsorption tower; 2. absorption tower; 3. regeneration tower; 4. air compressor; 5. carrier gas compressor; 6. circulation compressor; 7. regeneration cooler; 8. first gas-liquid separator; 9. pressure regulating valve; 10. regeneration heater; 11. second gas-liquid separator; 12. lean liquid pump; 13. lean liquid cooler; 14. lean-rich liquid heat exchanger; 15. semi-lean amine liquid cooler; 16. semi-lean amine liquid pump. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limitations on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0042] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0043] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0044] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0045] Combine the following Figures 1 to 16 The specific structure and working implementation process of the direct air carbon capture system of the present invention are described.

[0046] One embodiment of the present invention provides a direct air carbon capture system, see Figure 1 As shown, it includes an adsorption unit and an absorption unit. Among them, the adsorption unit includes at least three adsorption towers 1 arranged in parallel, the adsorption tower 1 is connected to an external air source through a first pipeline, the adsorption tower 1 is filled with an adsorbent for adsorbing carbon dioxide, the adsorption tower 1 is high-point released through a second pipeline, the adsorption tower 1 is connected to a carrier gas source through a third pipeline, and the adsorption tower 1 is connected to the absorption unit through a fourth pipeline. The absorption unit includes an absorption tower 2 and a regeneration tower 3, the absorption tower 2 is connected to the fourth pipeline to receive the carrier gas and carbon dioxide output by the adsorption tower 1 in the heating regeneration sequence, the absorption tower 2 is connected to a lean amine liquid source to absorb carbon dioxide through the lean amine liquid, the absorption tower 2 is connected to the regeneration tower 3, and the regeneration tower 3 is used to receive the amine liquid of the absorption tower 2 and separate the carbon dioxide.

[0047] In the direct air carbon capture system of the present embodiment, each adsorption tower 1 of the adsorption unit includes an adsorption sequence, a heating regeneration sequence and a cooling sequence that are performed in sequence. In the adsorption sequence, the first pipeline, the adsorption tower 1 and the second pipeline are sequentially connected to pass air into the adsorption tower 1 and adsorb carbon dioxide in the air; in the heating regeneration sequence, the third pipeline, the adsorption tower 1 and the fourth pipeline are sequentially connected to heat and regenerate the adsorbent of the adsorption tower 1 through a carrier gas and output the carrier gas and carbon dioxide; in the cooling sequence, the adsorbent of the adsorption tower 1 is cooled by passing a carrier gas through the third pipeline. At the same time, at least one of the at least three adsorption towers 1 performs an adsorption sequence, at least one of the adsorption towers 1 performs a heating regeneration sequence, and at least one of the adsorption towers 1 performs a cooling sequence.

[0048] It can be understood that each adsorption tower 1 of the adsorption unit performs adsorption sequence, heating regeneration sequence and cooling sequence in turn. By adjusting the program-controlled valve of the inlet and outlet pipelines of the adsorption tower 1, there is a certain time difference in the working sequence of each adsorption tower 1. At the same time, at least one adsorption tower 1 in the adsorption unit performs adsorption sequence, at least one adsorption tower 1 performs heating regeneration sequence, and at least one adsorption tower 1 performs cooling sequence. In this way, in the direct air carbon capture process, the air introduction process does not need to be stopped at intervals, and uninterrupted air carbon capture is achieved. After carbon dioxide is adsorbed by the adsorption unit, it is regenerated and guided by the carrier gas. The carrier gas and carbon dioxide enter the absorption unit, and the carrier gas and carbon dioxide are separated through absorption and regeneration by the absorption tower 2 and the regeneration tower 3, and a high-concentration CO2 product is output.

[0049] The following combination Figures 2 to 4To explain the working process of the adsorption unit of this embodiment, it is necessary to understand that, for the working process of the adsorption unit, during the adsorption sequence of the adsorption tower 1, air enters the adsorption tower 1 from the first pipeline for carbon capture, and the CO2 in the air is adsorbed and released through the second pipeline via a high point; after a certain adsorption time, the adsorption tower 1 in the adsorption state needs to enter a heating and regeneration sequence, and hot carrier gas is introduced from the third pipeline to the adsorption tower 1 in the adsorption state, and the adsorption tower 1 after heating and regeneration removes CO2, and the carrier gas and the removed CO2 are transported to the absorption unit from the fourth pipeline at the outlet of the adsorption tower 1; although the adsorption tower 1 after the heating and regeneration sequence has removed CO2, it does not have adsorption capacity due to the high temperature of the adsorbent. In the cooling sequence, the carrier gas input from the third pipeline is used as cooling gas to cool the adsorption tower 1 after heating and regeneration, and it can be put into adsorption again after cooling to room temperature. See. Figures 2 to 4 As shown, Figure 2 , Figure 3 , Figure 4 The three stages of the complete process of air carbon capture by the three adsorption towers 1 of this embodiment are respectively illustrated. Figure 5 and Figure 6 The schematic opening and closing states of the program-controlled valves fully illustrate the three stages of air carbon capture, and the above three stages are repeated continuously to achieve the complete process of air carbon capture. Each adsorption tower 1 adopts sequential control (sequential control / timing control) logic, and the timing table is shown in the following table.

[0050] exist Figure 2 In the time period 0→T, the first adsorption tower 1 performs the adsorption sequence, the second adsorption tower 1 performs the heating regeneration sequence, and the third adsorption tower 1 performs the cooling sequence. Air is introduced into the first adsorption tower 1 through the first pipeline to adsorb carbon dioxide in the air, and then released at a high point through the second pipeline; at the same time, hot carrier gas is introduced into the second adsorption tower 1 through the third pipeline (at this time, the second adsorption tower 1 is in the state after adsorption), the adsorbent is regenerated and carrier gas and carbon dioxide are output, and the carrier gas and carbon dioxide enter the absorption unit through the fourth pipeline; at the same time, cold carrier gas is introduced into the third adsorption tower 1 through the third pipeline (at this time, the adsorbent of the third adsorption tower 1 is in a high temperature state), and the adsorption tower after heating and regeneration is cooled down to room temperature together with the loaded adsorbent, and can be put into the adsorption sequence again.

[0051] exist Figure 3 In the time period T→2T, the first adsorption tower 1 performs a heating regeneration sequence, the second adsorption tower 1 performs a cooling sequence, and the third adsorption tower 1 performs an adsorption sequence. Figure 2After the stage shown, the states of each programmable valve are adjusted, air is introduced into the third adsorption tower 1 through the first pipeline to adsorb carbon dioxide in the air, and then it is released at a high point through the second pipeline; at the same time, hot carrier gas is introduced into the first adsorption tower 1 through the third pipeline (at this time, the first adsorption tower 1 is in an adsorbed state), the adsorbent is regenerated, and the carrier gas and carbon dioxide are output, and the carrier gas and carbon dioxide enter the absorption unit through the fourth pipeline; at the same time, cold carrier gas is introduced into the second adsorption tower 1 through the third pipeline (at this time, the adsorbent of the second adsorption tower 1 is in a high-temperature state), and the adsorption tower after heating and regeneration together with the loaded adsorbent is cooled to room temperature and can be put into the adsorption sequence again.

[0052] exist Figure 4 In the time period 2T→3T, the first adsorption tower 1 performs a cooling sequence, the second adsorption tower 1 performs an adsorption sequence, and the third adsorption tower 1 performs a heating regeneration sequence. Figure 3 After the stage shown, the states of the various programmable valves are adjusted again, and air is introduced into the second adsorption tower 1 through the first pipeline to adsorb carbon dioxide in the air, and then released at a high point through the second pipeline; at the same time, hot carrier gas is introduced into the third adsorption tower 1 through the third pipeline (at this time the third adsorption tower 1 is in an adsorbed state), the adsorbent is regenerated, and carrier gas and carbon dioxide are output, and the carrier gas and carbon dioxide enter the absorption unit through the fourth pipeline; at the same time, cold carrier gas is introduced into the first adsorption tower 1 through the third pipeline (at this time the adsorbent of the first adsorption tower 1 is in a high temperature state), and the adsorption tower after heating and regeneration together with the loaded adsorbent is cooled to room temperature and can be put into the adsorption sequence again.

[0053] go through Figure 4 After the stage shown, adjust the status of each program-controlled valve again and enter Figure 2 The above three stages are then continuously cycled to achieve uninterrupted air carbon capture and efficient carbon capture. The single-stage time interval T can be any value, usually 8h, 16h or 24h or other longer time can be selected according to the number of adsorption towers and the adsorbent loading amount.

[0054] See again Figure 1As shown, in this embodiment, a carrier gas needs to be introduced to guide CO2 during the carbon capture process, resulting in the adsorption tower 1 after the heating regeneration sequence outputting a mixture of carrier gas and CO2, wherein the CO2 product concentration is relatively low. In this embodiment, the carrier gas and CO2 mixture output by the adsorption tower 1 after the heating regeneration sequence is further absorbed and separated after entering the absorption unit. In the absorption tower 2 of the absorption unit, the carrier gas and CO2 mixture are separated by a lean amine liquid source connected to the absorption tower 2, and the separated amine liquid mixed with CO2 is introduced into the regeneration tower 3. The regeneration tower 3 separates CO2 from the amine liquid to obtain a high-concentration CO2 product.

[0055] In some embodiments of the direct air carbon capture system of the present invention, the first pipeline is connected to an air compressor 4, which is used to compress external air and input it into the adsorption tower 1 through the first pipeline; and / or, a carrier gas compressor 5 is arranged in the fourth pipeline, which is used to compress the carrier gas and carbon dioxide output by the adsorption tower 1, and input them into the absorption tower 2 through the fourth pipeline.

[0056] It is understandable that the existing mainstream air capture solutions, whether solid adsorption or liquid absorption, are all atmospheric adsorption / absorption processes with poor adsorption / absorption effects, resulting in a large number of adsorption / absorption equipment and a large area, which is not conducive to the cost reduction and efficiency improvement required for future large-scale commercial promotion (matching million-ton green alcohol / SAF). In this embodiment, an air compressor 4 is arranged in the air inlet pipeline of the adsorption unit, and the air containing 0.03~0.04% CO2 is pressurized to 0.6~0.8MPa by the air compressor, and enters the adsorption tower 1 from bottom to top to realize high-pressure adsorption of the adsorption unit. A carrier gas compressor 5 is arranged in the carrier gas inlet pipeline of the absorption unit. The CO2-containing carrier gas exiting the adsorption tower 1 is cooled to 40°C and then enters the carrier gas compressor 5 of the absorption unit. The carrier gas is pressurized to 4.0~6.0MPa by the carrier gas compressor 5 and enters the absorption tower 2 from bottom to top. The lean amine liquid sprayed from the top of the absorption tower 2 is fully in contact with the carrier gas in the absorption tower, and the CO2 in the carrier gas is absorbed and enters the lean amine liquid, while the carrier gas is not absorbed and flows out from the top of the absorption tower 2.

[0057] The direct air carbon capture system of this embodiment adopts a high-pressure adsorption / absorption process. When the air processing capacity is the same, the adsorption / absorption equipment and pipeline size are smaller, and the space is saved. At the same time, as the adsorption / absorption pressure increases, the CO2 partial pressure in the air / carrier gas increases synchronously, which is more conducive to improving the adsorption / absorption effect (for the same adsorbent / absorbent, the dynamic adsorption / absorption amount increases), and the adsorbent / absorbent loading amount can be reduced, which helps to reduce construction costs.

[0058] In the existing embodiment of the present invention, the air is a one-way pass type. Since the CO2 concentration in the air is extremely low (0.03-0.04%), the one-way capture rate of CO2 in the air is low. Therefore, for the same CO2 capture amount, the air processing amount is large, resulting in a large flow rate and high energy consumption of the air compressor 4. In other embodiments of the present invention, see Figure 7 As shown, the second pipeline is also connected to the first pipeline through the fifth pipeline, and a circulating compressor 6 is provided in the fifth pipeline. The adsorption unit of this embodiment adopts a circulating adsorption method. By adding a circulating compressor 6, most of the air at the outlet of the adsorption tower 1 is recompressed back to the inlet of the adsorption tower 1, and adsorbed again to increase the single-pass capture rate of CO2 in the air. The other processes and operating parameters of the adsorption unit remain unchanged. In this embodiment, the air compressor 4 has a significant energy-saving effect because the flow rate is greatly reduced; at the same time, the power consumption of the circulating compressor 6 is only used to overcome the resistance drop of air (fresh air + circulating gas) passing through the adsorption tower 1, so the total energy consumption of the air compressor 4 and the circulating compressor 6 can be greatly reduced.

[0059] In some embodiments of the direct air carbon capture system of the present invention, the absorption tower 2 is provided with a carrier gas separation outlet, the adsorption tower 1 is provided with a cold carrier gas interface and a hot carrier gas interface, the third pipeline includes a cold carrier gas pipeline and a hot carrier gas pipeline, the cold carrier gas pipeline connects the carrier gas separation outlet of the absorption tower 2 and the cold carrier gas interface of the adsorption tower 1, and is used to introduce cold carrier gas into the adsorption tower 1 when the adsorption tower 1 is in a cooling sequence; the hot carrier gas pipeline is connected to the hot carrier gas interfaces of all the adsorption towers 1, and is used to input the hot carrier gas output by the adsorption tower 1 in the cooling sequence into the adsorption tower 1 in the heating regeneration sequence.

[0060] In this embodiment, the carrier gas separated by the absorption unit is used as the carrier gas source of the adsorption unit, so as to realize the recycling of the carrier gas. Figure 1 As shown, a regeneration cooler 7 is arranged on the fourth pipeline, a first gas-liquid separator 8 and a pressure regulating valve 9 are arranged on the cold carrier gas pipeline, and a regeneration heater 10 is arranged on the hot carrier gas pipeline.

[0061] It can be understood that the CO2-containing carrier gas from the adsorption unit is pressurized to 4.0~6.0MPa by the carrier gas compressor 5, enters the absorption tower 2 from bottom to top, and the lean amine liquid sprayed from the top of the tower is fully in contact with the carrier gas in the absorption tower. The CO2 in the carrier gas is absorbed and enters the lean amine liquid, while the carrier gas is not absorbed, flows out from the top of the absorption tower 2, enters the first gas-liquid separator 8, is throttled to below 0.6~0.8MPa (basically the same as the pressure after air pressurization) by the pressure reducing valve 9, and enters the cold carrier gas pipeline of the adsorption unit again as cooling gas. The carrier gas in the cold carrier gas pipeline is introduced into the adsorption tower 1 from bottom to top when the adsorption tower 1 is in the cooling sequence, and the adsorption tower 1 and the loaded molecular sieve that have finished the heating regeneration sequence (the temperature is 220~250℃ at this time) are cooled. Then the carrier gas flows out from the hot carrier gas interface on the top of the adsorption tower 1 and enters the hot carrier gas pipeline. In the hot carrier gas pipeline, it enters the regeneration heater 10 (electric heater or heat exchanger with heat transfer oil as heat medium), and after being heated to 250℃, the adsorption tower 1 that has finished the adsorption sequence is heated and regenerated from top to bottom. After being heated by the hot carrier gas, CO2 is desorbed from the adsorbent and carried out of the adsorption tower 1 by the carrier gas (by controlling the carrier gas flow rate, the CO2 concentration in the carrier gas is 3~10%), so that the adsorption tower 1 completes the heating regeneration process. The CO2-containing carrier gas leaving the adsorption tower 1 is cooled to 40℃ by the regeneration cooler 7, and enters the absorption tower 2 of the absorption unit through the fourth pipeline carrier gas compressor 5, completing the recycling of the carrier gas.

[0062] This embodiment uses heated carrier gas to desorb the adsorbed CO2 and carry it out of the adsorption tower with the carrier gas flow, thereby completing the regeneration of the adsorption saturated adsorption tower. The adsorption unit related equipment and pipelines do not need to be designed to resist negative pressure, and are relatively small in size; at the same time, there is no requirement for the waterproofness of the adsorbent, which can reduce the manufacturing difficulty and procurement cost. Moreover, since the adsorption unit of this embodiment uses carrier gas for thermal regeneration, the CO2 concentration in the carrier gas after desorption can be maintained at a relatively high concentration by adjusting parameters such as the carrier gas inlet flow rate, inlet temperature and operating pressure, thereby reducing the size of the downstream absorption unit equipment and pipelines, and reducing the energy consumption of the regeneration tower 3. Furthermore, in some specific examples, the hot carrier gas pipeline is also connected to a carrier gas replenishment pipeline, which is connected to the inlet side of the regeneration heater 10, and the circulating carrier gas can be appropriately replenished through the carrier gas replenishment pipeline.

[0063] In some embodiments of the direct air carbon capture system of the present invention, a rich amine liquid inlet and a separated gas outlet are provided at the top of the regeneration tower 3, the absorber 2 is connected to the rich amine liquid inlet through a rich amine liquid pipeline, and the separated gas outlet is connected to the second gas-liquid separator 11, and the gas outlet of the second gas-liquid separator 11 is used to output carbon dioxide. A lean amine liquid outlet is provided at the bottom of the regeneration tower 3, and the lean amine liquid outlet is connected to the absorber 2 through a lean amine liquid pipeline as a lean amine liquid source for the absorber 2, and a lean liquid pump 12 and a lean liquid cooler 13 are provided in the lean amine liquid pipeline, and the lean amine liquid pipeline and the rich amine liquid pipeline are heat exchanged through a lean-rich liquid heat exchanger 14.

[0064] It can be understood that in this embodiment, amine liquid is used as the absorbent of the absorption unit. Specifically, the amine liquid is recycled through the absorption tower 2 and the regeneration tower 3. A lean amine liquid outlet is set at the bottom of the regeneration tower 3. The lean amine liquid after stripping and regeneration in the regeneration tower 3 enters the lean amine liquid pipeline, and enters the top of the absorption tower 2 after heat recovery by the lean-rich liquid heat exchanger 14, pressurization by the lean liquid pump 12, and cooling by the lean liquid cooler 13. The CO2-containing carrier gas after cooling from the adsorption unit is pressurized by the carrier gas compressor 5 and enters the absorption tower 2, and the CO2 therein is absorbed by the lean amine liquid flowing down from the top of the absorption tower 2. The lean amine liquid absorbs CO2 to form rich amine liquid, which flows out from the bottom of the absorption tower 2 and enters the rich amine liquid pipeline. After heat exchange with the lean amine liquid flowing out from the bottom of the regeneration tower 3 in the lean-rich liquid heat exchanger 14, the temperature is increased and it enters the regeneration tower 3 for stripping and regeneration until the CO2 content of the lean amine liquid meets the process indicators, and then enters the lean amine liquid pipeline to form an amine liquid circulation. High-purity CO2 flows out from the separated gas outlet at the top of the regeneration tower 3, is recovered by the condenser through the amine liquid recovery device, and is sent to the CO2 storage or downstream application device after the foam is removed by the second gas-liquid separator 11.

[0065] When the DAC scale is large (hundreds of thousands of tons or even millions of tons), in order to reduce the amount of carrier gas used in the adsorption unit, it is necessary to increase the CO2 content in the carrier gas after regeneration of the adsorption tower 1. For the absorption of carrier gas with high CO2 content, if the Figure 1 In some examples of the direct air carbon capture system of the present invention, see Figure 8 As shown, a semi-lean amine liquid outlet is provided in the middle of the regeneration tower 3, and the semi-lean amine liquid outlet is connected to the middle of the absorption tower 2 through a semi-lean amine liquid pipeline to output the semi-lean amine liquid to the absorption tower 2. A semi-lean amine liquid cooler 15 and a semi-lean amine liquid pump 16 are provided in the semi-lean amine liquid pipeline. By adding a semi-lean liquid pipeline from the regeneration tower 3 to the absorption tower 2, a carrier gas absorption process suitable for a higher CO2 content can be established.

[0066] The regeneration gas (high CO2 content carrier gas) after cooling down from the adsorption unit is pressurized by the carrier gas compressor 5 and enters the bottom of the absorption tower 2, where it is countercurrently contacted with the lean amine liquid and semi-lean liquid fed at the top and middle. The carrier gas from which CO2 is removed flows out from the top of the absorption tower and returns to the adsorption unit as the regeneration gas (carrier gas) of the adsorption tower 1. The rich amine liquid flows out from the bottom of the absorption tower 2, is throttled and decompressed, and is heat exchanged with the lean amine liquid (amine liquid from which CO2 is removed by steam stripping regeneration) flowing out from the bottom of the regeneration tower 3 in the lean-rich liquid heat exchanger. It is then heated and enters the regeneration tower, where it is stripped and regenerated in the regeneration tower 3. Semi-lean liquid and lean amine liquid flow out from the middle and bottom of the tower respectively, and are refluxed to the absorption tower 2 after being cooled and pressurized.

[0067] Based on the direct air carbon capture system in the above-mentioned embodiments or examples, the adsorption tower 1 is filled with an adsorbent. In some embodiments of the present invention, the adsorbent is preferably a molecular sieve, and its regeneration temperature is 200-250°C. Activated carbon or alumina can also be selected, and its regeneration temperature is 80-100°C and 150-200°C.

[0068] In some examples of the present invention, the carrier gas used in the adsorption unit is nitrogen, natural gas, hydrogen and other gases that do not have oxidizing properties. At this time, the amine liquid (absorbent) of the absorption unit can use ordinary monoethanolamine, diethanolamine, diisopropanolamine or N-methyldiethanolamine, which can avoid the oxidative degradation of the amine liquid in an oxygen environment. Of course, based on the matching scheme of the carrier gas and the amine liquid, there can also be some alternatives. For example, the amine liquid still uses ordinary MEA / MDEA amine liquid. According to the application scenario and the surrounding available resources, while ensuring safety, the carrier gas can consider natural gas, hydrogen, etc. In addition, air can be used as the carrier gas, and the corresponding amine liquid can select an antioxidant composite amine, or an antioxidant can be added to the ordinary amine liquid.

[0069] In the three-tower process illustrated in the above embodiments or examples, since the CO2 concentration in the air is very low, the time actually in the adsorption timing stage is relatively long (8h or 24h), and the time in the heating regeneration timing stage and the cooling timing stage is relatively short (4h / 4h). The heating regeneration stage can be controlled by adjusting the carrier gas flow rate and the regeneration heater temperature to ensure that the CO2 concentration in the carrier gas is relatively stable throughout the whole stage, so as to facilitate the stable operation of the subsequent absorption unit.

[0070] For large-scale DAC matching large-scale green methanol / SAF preparation, a DAC process flow with multiple adsorption units can be adopted. In some embodiments of the direct air carbon capture system of the present invention, the adsorption unit includes multiple adsorption subunits arranged in parallel, and multiple adsorption subunits are superimposed and used in combination. Each adsorption subunit includes multiple adsorption towers 1. At the same time, among the multiple adsorption towers 1 of each adsorption subunit, one of the adsorption towers 1 performs a heating regeneration sequence, another of the adsorption towers 1 performs a cooling sequence, and the remaining adsorption towers 1 all perform an adsorption sequence, and all the adsorption towers 1 performing the adsorption sequence have a time difference in the start and end of the adsorption sequence.

[0071] It can be understood that the flow chart of the adsorption subunit is multiple towers (taking eight towers as an example) as follows Figures 9 to 16 As shown. In this embodiment, a complete operation cycle is 32 hours, including 24 hours of adsorption phase, 4 hours of heating and regeneration phase, and 4 hours of cooling phase. At any time, there are six adsorption towers 1 in the adsorption timing phase, one adsorption tower 1 in the heating and regeneration timing phase, and one adsorption tower 1 in the cooling timing phase. Among the six adsorption towers in the adsorption state, the i-th tower is 4 hours faster than the i+1-th tower.

[0072] Each adsorption tower adopts sequential control (sequential control / timing control) logic, and the timing table is shown in the following table.

[0073] As shown in the above table, for the eight-tower process, the recommended complete cycle, adsorption time, heating regeneration time and cooling time are 32h, 24h, 4h, and 4h, respectively. The heating regeneration time and cooling time are both reference time. The complete cycle time is the product of the number of towers and the heating regeneration time / cooling time. The adsorption time is the complete cycle minus the heating regeneration time and cooling time. There is a time difference between the adsorption towers in the adsorption sequence. The time difference between two adjacent adsorption towers is the reference time. For example, the heating regeneration time and cooling time are both , the number of towers is , the complete cycle is defined as The adsorption time is set to , there are two adjacent absorption towers with adsorption sequence It can be understood that, through this arrangement of the present embodiment, it can be satisfied that within the same time period, the efficiency of the adsorption tower 1 performing the adsorption sequence and the adsorption tower 1 performing the heating regeneration sequence and the cooling sequence are consistent, and there is no need to separately control the carrier gas volume or each sequence stage.

[0074] Of course, the complete cycle, adsorption time, heating regeneration time and cooling time can be based on the reference time, multiplied by any multiple such as 1.5, 2, etc., to obtain other corresponding complete cycles, adsorption time, heating regeneration time and cooling time, which can be specifically set according to actual site needs. The number of adsorption towers 1 is not limited to the eight towers in the above embodiment, and the number of towers of the remaining number can also be used. Specifically, the schematic flow chart of four to seven towers shown in the table below can be referred to. Considering the factors such as the complex program of the adsorption system control program, the failure rate of the equipment valve, etc., the number of adsorption towers 1 generally does not exceed ten.

[0075] Based on the multi-tower scheme embodiment of the above-mentioned direct air carbon capture system, when the adsorption subunit adopts a multi-tower scheme, in some specific examples, a programmable valve is provided on the inlet and outlet pipelines of each adsorption tower 1 to change the number of adsorption towers 1 performing adsorption sequence at the same time by opening and closing the programmable valve. When the programmable valve on the inlet and outlet pipelines of the adsorption tower 1 is opened, the adsorption tower 1 performs the adsorption sequence. When the programmable valve on the inlet and outlet pipelines of the adsorption tower 1 is closed, the adsorption tower 1 stops working.

[0076] In this example, when the process requires or an equipment / valve failure occurs, the control system can close the inlet and outlet programmable valves of the relevant adsorption tower 1 to switch the number of adsorption towers between 3 and n. Taking the eight-tower process as an example, when the process requires or an adsorption tower 1 (such as the first adsorption tower) fails, refer to Fig. 9 As shown, all six program-controlled valves (three above the top of the tower and three below the bottom of the tower) at the inlet and outlet of the faulty adsorption tower are closed through the control program, that is, the seven-tower process is switched, and the operation cycle and the adsorption stage time are adjusted according to the seven-tower process in the control program. When it is necessary to close the program-controlled valves at the inlet and outlet of another adsorption tower 1 (such as the second adsorption tower), the six-tower process is switched, and the three-tower process can be eventually switched to the three-tower process. Conversely, the three-tower process can also be switched to the eight-tower process in sequence. In this embodiment, the program-controlled valves on the inlet and outlet pipelines of each adsorption tower 1 are controlled by the control program to open and close, so as to realize the conversion between eight towers and three towers, which can facilitate the non-stop maintenance and repair of the direct air carbon capture system.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A direct air carbon capture system, characterized in that: It includes an adsorption unit and an absorption unit; The adsorption unit comprises at least three adsorption towers (1) arranged in parallel, the adsorption tower (1) is connected to an external air source via a first pipeline, the adsorption tower (1) is filled with an adsorbent for adsorbing carbon dioxide, the adsorption tower (1) is high-point diffused via a second pipeline, the adsorption tower (1) is connected to a carrier gas source via a third pipeline, and the adsorption tower (1) is connected to the absorption unit via a fourth pipeline; Each of the adsorption towers (1) comprises an adsorption sequence, a heating regeneration sequence and a cooling sequence which are performed in sequence. In the adsorption sequence, the first pipeline, the adsorption tower (1) and the second pipeline are connected in sequence to introduce air into the adsorption tower (1) and adsorb carbon dioxide in the air; In the heating regeneration sequence, the third pipeline, the adsorption tower (1) and the fourth pipeline are connected in sequence, so as to heat and regenerate the adsorbent in the adsorption tower (1) through the carrier gas and output the carrier gas and carbon dioxide; in the cooling sequence, the adsorbent in the adsorption tower (1) is cooled by the carrier gas through the third pipeline; At the same time, among the at least three adsorption towers (1), at least one of the adsorption towers (1) performs the adsorption sequence, at least one of the adsorption towers (1) performs the heating regeneration sequence, and at least one of the adsorption towers (1) performs the cooling sequence; The absorption unit comprises an absorption tower (2) and a regeneration tower (3); the absorption tower (2) is connected to the fourth pipeline to receive the carrier gas and carbon dioxide output by the adsorption tower (1) in the heating regeneration sequence; the absorption tower (2) is connected to a lean amine liquid source to absorb carbon dioxide through the lean amine liquid; the absorption tower (2) is connected to the regeneration tower (3); the regeneration tower (3) is used to receive the amine liquid from the absorption tower (2) and separate the carbon dioxide.

2. The direct air carbon capture system according to claim 1, characterized in that The first pipeline is connected to an air compressor (4), and the air compressor (4) is used to compress external air and input the air into the adsorption tower (1) through the first pipeline; and / or, A carrier gas compressor (5) is provided in the fourth pipeline, and the carrier gas compressor (5) is used to compress the carrier gas and carbon dioxide output from the adsorption tower (1), and input the compressed carrier gas and carbon dioxide into the absorption tower (2) through the fourth pipeline.

3. The direct air carbon capture system according to claim 2, characterized in that: The second pipeline is also connected to the first pipeline via a fifth pipeline, and a circulating compressor (6) is provided in the fifth pipeline.

4. The direct air carbon capture system according to claim 1, characterized in that The absorption tower (2) is provided with a carrier gas separation outlet, the adsorption tower (1) is provided with a cold carrier gas interface and a hot carrier gas interface, the third pipeline comprises a cold carrier gas pipeline and a hot carrier gas pipeline, the cold carrier gas pipeline connects the carrier gas separation outlet of the absorption tower (2) and the cold carrier gas interface of the adsorption tower (1), and is used to introduce cold carrier gas into the adsorption tower (1) when the adsorption tower (1) is in the cooling sequence; the hot carrier gas pipeline is connected to the hot carrier gas interfaces of all the adsorption towers (1), and is used to input the hot carrier gas outputted by the adsorption tower (1) in the cooling sequence into the adsorption tower (1) in the heating regeneration sequence.

5. The direct air carbon capture system according to claim 4, characterized in that: The fourth pipeline is provided with a regeneration cooler (7), and the cold carrier gas pipeline is provided with a first gas-liquid separator (8) and a pressure regulating valve (9).

6. The direct air carbon capture system according to claim 5, characterized in that A regeneration heater (10) is arranged on the hot carrier gas pipeline, and the hot carrier gas pipeline is also connected to a carrier gas replenishment pipeline, and the carrier gas replenishment pipeline is connected to the inlet side of the regeneration heater (10).

7. The direct air carbon capture system according to claim 1, characterized in that The top of the regeneration tower (3) is provided with a rich amine liquid inlet and a separated gas outlet, the absorption tower (2) is connected to the rich amine liquid inlet via a rich amine liquid pipeline, the separated gas outlet is connected to a second gas-liquid separator (11), and the gas outlet of the second gas-liquid separator (11) is used to output carbon dioxide; A lean amine liquid outlet is provided at the bottom of the regeneration tower (3), and the lean amine liquid outlet is connected to the absorption tower (2) via a lean amine liquid pipeline to serve as a lean amine liquid source for the absorption tower (2). A lean liquid pump (12) and a lean liquid cooler (13) are provided in the lean amine liquid pipeline.

8. The direct air carbon capture system according to claim 7, characterized in that A semi-lean amine liquid outlet is provided in the middle of the regeneration tower (3), and the semi-lean amine liquid outlet is connected to the middle of the absorption tower (2) through a semi-lean amine liquid pipeline to output the semi-lean amine liquid to the absorption tower (2), and a semi-lean amine liquid cooler (15) and a semi-lean amine liquid pump (16) are provided in the semi-lean amine liquid pipeline.

9. The direct air carbon capture system according to any one of claims 1 to 8, characterized in that: The adsorption unit includes a plurality of adsorption subunits arranged in parallel, and the plurality of adsorption subunits are stacked and used in coordination; Each of the adsorption subunits comprises a plurality of the adsorption towers (1). At the same time, among the plurality of the adsorption towers (1) of each of the adsorption subunits, one of the adsorption towers (1) performs the heating regeneration sequence, another of the adsorption towers (1) performs the cooling sequence, and the remaining adsorption towers (1) all perform the adsorption sequence, and all the adsorption towers (1) performing the adsorption sequence have a time difference in the start and end of the adsorption sequence.

10. The direct air carbon capture system according to claim 9, characterized in that A program-controlled valve is provided on the inlet and outlet pipelines of each of the adsorption towers (1), so that the number of the adsorption towers (1) performing the adsorption sequence at the same time can be changed by opening and closing the program-controlled valve. When the program-controlled valve on the inlet and outlet pipelines of the adsorption tower (1) is opened, the adsorption tower (1) performs the adsorption sequence. When the program-controlled valve on the inlet and outlet pipelines of the adsorption tower (1) is closed, the adsorption tower (1) stops working.

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