Carbon dioxide capture system capable of controlling escape of organic amine and carbon dioxide capture method

Abstract

The invention provides a carbon dioxide capture system and a carbon dioxide capture method capable of controlling escape of organic amine. The carbon dioxide trapping system comprises an absorption tower, water washing equipment, concentration and purification equipment and a desorption tower, and an organic amine absorbent can be introduced into the absorption tower; a rich-phase absorbent outlet of the absorption tower is connected with a rich-phase absorbent inlet of the desorption tower through a heat exchanger, and a regenerated absorbent outlet of the desorption tower is connected with a lean-phase absorbent inlet of the absorption tower through a heat exchanger; the washing equipment is arranged inside and / or outside the absorption tower, a washing liquid outlet of the washing equipment is connected with a washing liquid inlet of the concentration and purification equipment, and a clear liquid outlet of the concentration and purification equipment is connected with a clear liquid inlet of the washing equipment. The carbon dioxide trapping system not only helps to reduce the solvent loss caused by organic amine escape, but also can further reduce the operation cost of the system and improve the overall efficiency of the carbon trapping technology.

Description

Technical Field

[0001] The present invention relates to a carbon dioxide capture system and a carbon dioxide capture method capable of controlling the escape of organic amines, and in particular to a carbon dioxide capture system and a carbon dioxide capture method based on an amine-based absorbent, capable of controlling the escape of organic amines and promoting the recycling of organic amines, and belongs to the technical field of carbon dioxide capture. Background Art

[0002] Carbon dioxide (CO 2 ) accounts for more than 70%-80% of the world's total greenhouse gas emissions. The greenhouse effect caused by the continued growth of its emissions has brought about consequences such as global warming, which has attracted widespread attention from all over the world. Considering the current installed capacity of power generation and energy security needs, the thermal power industry will become a key area for the application of carbon dioxide capture, utilization and storage (CCUS) technology. It is estimated that by 2060, 1 billion tons / year of CO 2 In addition, after improving production efficiency and reaching production peak, industries such as steel, cement, and chemicals still need to rely on CCUS technology to further reduce CO emissions. 2 .

[0003] In many CO 2 Among the capture technologies, organic amine chemical absorption has excellent CO 2 The separation capacity, low vapor pressure, low cost and good recyclability make it widely used in post-combustion capture of coal-fired / gas-fired power plants. However, there are still some problems in the actual operation of this technology, such as the absorbent and its degradation products (NH 3 The organic amines and their degradation products in the flue gas after carbon capture are likely to be discharged into the atmosphere with the flue gas after carbon capture, which will not only cause environmental pollution, but also lead to solvent loss and cost increase, thus restricting the large-scale application of this technology. Therefore, achieving deep emission reduction of organic amines and their degradation products in the flue gas after carbon capture is the prerequisite for the further promotion and development of organic amine chemical absorption technology.

[0004] In recent years, researchers have conducted a number of research attempts to solve the problem of pollutant emissions generated by organic amines in the carbon capture process. At present, common flue gas treatment devices after decarbonization mainly include water washing equipment and demisters. However, water washing equipment is not very effective in treating saturated gases such as organic amines, NH 3 The effect is not ideal, and the demister has limited efficiency in removing small-size aerosol particles. Although other methods such as wet electrostatic precipitator, acid cleaning, colloidal gas foam, and interstage cooling have been developed, some of them are still in the laboratory research stage or only have simulation results, and have not yet made a breakthrough in practical application.

[0005] Regarding the emission of organic amines, current research mainly focuses on how to control the emission of these pollutants, but the recovery of organic amines is rarely involved. In fact, taking the water washing process as an example, the amine concentration in the water washing liquid is very low (<4%) and cannot be directly reused in the carbon capture system; therefore, simply controlling the emission of organic amines is not enough to meet the recovery and concentration requirements under the circulation of absorbents in the actual operation of the carbon capture system. Therefore, how to design and implement a system that can effectively control the escape of amine-based absorbents and simultaneously achieve their recycling has become the key to reducing absorbent loss and secondary pollutant emissions during the large-scale application of amine-based absorption methods. Solving this problem is of great significance for improving carbon capture efficiency, reducing operating costs, and reducing environmental pollution.

[0006] Reference 1 discloses a waste gas collection device, which includes a dispersion tank, a spray dispersion pipe, a waste gas delivery pipe, a water inlet pipe, a sewage pipe, a circulation pump, a heat exchanger, a water supply pipe, a buffer condensation tank, and a vacuum pump. The device aims to address the problems of insufficient waste gas treatment and low efficiency generated during the production process of hollow fiber ultrafiltration membranes; however, the patent does not involve the escape of organic amines in the carbon dioxide capture system.

[0007] Reference 2 discloses a method for treating reverse osmosis concentrate, which includes water inlet, pretreatment unit, MABR biological treatment unit, phosphorus removal unit, sedimentation tank, and effluent, and is aimed at the problems of high salt content and difficulty in degrading pollutants in reverse osmosis concentrate from urban sewage treatment plants; however, this patent and the escape control and recycling of amine-based carbon capture absorbents are not related.

[0008] It can be seen that although patented technologies for waste gas collection and sewage treatment already exist, they do not touch upon the issues in the field of carbon capture. Therefore, how to effectively recover the escaped organic amines has become a technical problem that needs to be solved urgently.

[0009] References:

[0010] Reference 1: CN211963649U

[0011] Reference 2: CN114560598A Summary of the invention

[0012] Problem that the invention aims to solve

[0013] In the process of capturing carbon dioxide using organic amine solution, due to the volatilization of the absorbent and its degradation products, its escape behavior is affected by the flue gas temperature, the type of absorbent and the CO 2 The impact of multiple factors such as load. The emission of organic amines into the atmosphere without effective control will not only cause serious environmental pollution, but also pose a threat to human health.

[0014] In view of the above technical problems existing in the prior art, the present invention first provides a carbon dioxide capture system. The carbon dioxide capture system of the present invention can control the escape of organic amines, promote the recycling of organic amines, and reduce the solvent loss caused by the escape of organic amines.

[0015] Furthermore, the present invention also provides a method for capturing carbon dioxide, which is simple and easy to implement, and the raw materials are easy to obtain, and is suitable for mass production.

[0016] Solution to the Problem of the Present Invention

[0017] [1] A carbon dioxide capture system comprising an absorption tower, a water washing device, a concentration and purification device, and a desorption tower, wherein:

[0018] The absorption tower can be fed with an organic amine absorbent;

[0019] The rich-phase absorbent outlet of the absorption tower is connected to the rich-phase absorbent inlet of the desorption tower through a heat exchanger, and the regeneration absorbent outlet of the desorption tower is connected to the lean-phase absorbent inlet of the absorption tower through a heat exchanger;

[0020] The water washing device is arranged inside and / or outside the absorption tower, the washing liquid outlet of the water washing device is connected to the washing liquid inlet of the concentration and purification device, and the clear liquid outlet of the concentration and purification device is connected to the clear liquid inlet of the water washing device.

[0021] [2] The carbon dioxide capture system according to [1] above, wherein the water washing equipment includes more than one level of water washing equipment; each level of the water washing equipment includes a spray layer, a water washing filler layer and a liquid collection layer, wherein:

[0022] The spray layer is provided with a clear liquid inlet for spraying the decarbonized flue gas with the clear water and / or the clear liquid;

[0023] The water-washed filler layer is used to make the decarbonized flue gas contact with the clean water and / or the clean liquid;

[0024] The liquid collecting layer is provided with the washing liquid outlet for collecting the washing liquid flowing out of the water-washing filler layer.

[0025] [3] The carbon dioxide capture system according to [2] above, wherein the water washing equipment comprises a primary water washing equipment, an intermediate water washing equipment and a final water washing equipment connected in sequence, and the number of the intermediate water washing equipment is greater than or equal to 0; wherein,

[0026] The final clear liquid inlet of the final water washing device is connected to the clear liquid outlet of the concentration and purification device;

[0027] The final-stage washing liquid outlet of the final-stage washing device is connected to the intermediate-stage clear liquid inlet of the intermediate-stage washing device;

[0028] The intermediate washing liquid outlet of the intermediate washing device is connected to the primary clear liquid inlet of the primary washing device;

[0029] The primary washing liquid outlet of the primary water washing device is connected to the washing liquid inlet of the concentration and purification device.

[0030] [4] A carbon dioxide capture system according to any one of [1] to [3] above, wherein the concentration and purification equipment comprises an ultrafiltration unit and a membrane treatment unit connected in sequence; wherein:

[0031] The washing liquid inlet of the ultrafiltration unit is connected to the washing liquid outlet of the water washing device;

[0032] The clear liquid outlet of the membrane treatment unit is connected to the clear liquid inlet of the water washing device;

[0033] The concentrated solution outlet of the membrane treatment unit is connected to the lean phase absorbent inlet of the absorption tower;

[0034] Preferably, the ultrafiltration unit comprises an ultrafiltration membrane, and the pore size of the ultrafiltration membrane is 10-100 nm.

[0035] [5] The carbon dioxide capture system according to [4] above, wherein the membrane treatment unit includes more than one level of membrane treatment units;

[0036] Preferably, each stage of the membrane treatment unit comprises a nanofiltration membrane or a reverse osmosis membrane, the pore size of the nanofiltration membrane is 1 to 10 nm; the pore size of the reverse osmosis membrane is 0.1 to 1 nm.

[0037] [6] The carbon dioxide capture system according to [4] or [5] above, wherein the membrane treatment unit comprises a primary membrane treatment unit, an intermediate membrane treatment unit and a final membrane treatment unit, and the number of the intermediate membrane treatment units is greater than or equal to 0; wherein,

[0038] The filtrate inlet of the primary membrane treatment unit is connected to the filtrate outlet of the ultrafiltration unit and the intermediate concentrated solution outlet of the intermediate membrane treatment unit respectively; the primary concentrated solution outlet of the primary membrane treatment unit is connected to the lean phase absorbent inlet of the absorption tower;

[0039] The intermediate clear liquid inlet of the intermediate membrane treatment unit is connected to the primary clear liquid outlet of the primary membrane treatment unit and the final concentrated liquid outlet of the final membrane treatment unit respectively;

[0040] The final clear liquid inlet of the final membrane treatment unit is connected to the intermediate clear liquid outlet of the intermediate membrane treatment unit, and the final clear liquid outlet of the final membrane treatment unit is connected to the clear liquid inlet of the water washing device.

[0041] [7] A method for capturing carbon dioxide using the carbon dioxide capture system described in any one of [1] to [6] above, comprising the following steps:

[0042] The flue gas is transported to an absorption tower, and an absorbent is introduced into the absorption tower; in the absorption tower, the absorbent absorbs carbon dioxide in the flue gas to generate a rich-phase absorbent and decarbonized flue gas;

[0043] The rich phase absorbent is transported to a desorption tower via a heat exchanger for desorption treatment;

[0044] The decarbonized flue gas is transported to a water washing device, mixed with clean water and subjected to water washing treatment to obtain a washing liquid;

[0045] The washing liquid is transported to a concentration and purification device for concentration and purification to obtain a clear liquid and a concentrated liquid;

[0046] Optionally, the clear liquid is transported to a water washing device, so that the clear liquid is mixed with the decarbonized flue gas and then subjected to a water washing treatment;

[0047] Optionally, the concentrated solution is transported to the absorption tower to absorb carbon dioxide in the flue gas and generate a rich-phase absorbent and decarbonized flue gas.

[0048] [8] The carbon dioxide capture method according to [7] above, wherein the water washing equipment comprises a primary water washing equipment, an intermediate water washing equipment and a final water washing equipment connected in sequence, and the number of the intermediate water washing equipment is greater than or equal to 0; the water washing treatment comprises the following steps:

[0049] The decarbonized flue gas is transported to a final water washing device for final water washing treatment to obtain a final washing liquid;

[0050] The final-stage washing liquid is transported to the intermediate-stage water washing equipment through the final-stage washing liquid outlet, and the decarbonized flue gas is subjected to intermediate-stage water washing treatment to obtain the intermediate-stage washing liquid;

[0051] The intermediate-level washing liquid is transported to the primary water washing equipment through the intermediate-level washing liquid outlet, and the decarbonized flue gas is subjected to primary water washing treatment to obtain the primary washing liquid;

[0052] The primary washing liquid is transported to a concentration and purification device for concentration and purification.

[0053] [9] The carbon dioxide capture method according to [7] or [8] above, wherein the concentration and purification equipment comprises an ultrafiltration unit and a membrane treatment unit connected in sequence; wherein:

[0054] The washing liquid is transported to an ultrafiltration unit for ultrafiltration treatment to obtain a filtrate;

[0055] The filtrate is transported to the membrane treatment unit for membrane treatment to obtain a concentrated solution and a clear solution.

[0056]

[10] The carbon dioxide capture method according to [9] above, wherein the membrane treatment unit comprises a primary membrane treatment unit, an intermediate membrane treatment unit and a final membrane treatment unit, and the number of the intermediate membrane treatment units is greater than or equal to 0; the membrane treatment comprises the following steps:

[0057] The filtrate is transported to a primary membrane treatment unit for primary membrane treatment to obtain a primary concentrated solution and a primary clear solution; the primary concentrated solution is transported to an absorption tower to be mixed with the absorbent; the primary clear solution is transported to an intermediate membrane treatment unit for intermediate membrane treatment to obtain an intermediate concentrated solution and an intermediate clear solution;

[0058] The intermediate concentrated liquid is transported to the primary membrane treatment unit to be mixed with the filtrate; the intermediate clear liquid is transported to the final membrane treatment unit for final membrane treatment to obtain a final concentrated liquid and a final clear liquid; the final concentrated liquid is transported to the intermediate membrane treatment unit to be mixed with the intermediate clear liquid, and the final clear liquid is transported to a water washing device for water washing treatment.

[0059] Effects of the Invention

[0060] The carbon dioxide capture system of the present invention not only helps to reduce the solvent loss caused by the escape of organic amines, but also can further reduce the system operation cost and improve the overall efficiency of carbon capture technology.

[0061] The carbon dioxide capture method of the present invention is simple and easy to implement, the raw materials are easy to obtain, and it is suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 A flow chart showing a carbon dioxide capture system according to Embodiment 1 of the present invention.

[0063] Figure 2 A flow chart of a carbon dioxide capture system according to Embodiment 2 of the present invention is shown.

[0064] Figure 3 A flow chart showing a carbon dioxide capture system according to Example 3 of the present invention.

[0065] Description of Reference Numerals

[0066] 1: Absorption tower; 2: Water washing equipment; 3: Concentration and purification equipment; 4: Desorption tower; 5: Heat exchanger;

[0067] 11: absorption tower packing layer; 12: absorption tower demister;

[0068] 21: primary water washing equipment; 22: secondary water washing equipment; 23: tertiary water washing equipment;

[0069] 201: spray layer; 202: water-washed packing layer; 203: liquid collection layer;

[0070] 31: ultrafiltration unit; 32: membrane treatment unit;

[0071] 321: primary membrane treatment unit; 322: secondary membrane treatment unit; 323: tertiary membrane treatment unit;

[0072] 41: condenser; 42: reboiler; 43: packing layer of desorption tower; 44: demister of desorption tower;

[0073] 61, 62: Circulation pump. DETAILED DESCRIPTION

[0074] Various exemplary embodiments, features and aspects of the present invention will be described in detail below. The word "exemplary" used here means "used as an example, embodiment or illustrative". Any embodiment described here as "exemplary" is not necessarily interpreted as being superior or better than other embodiments.

[0075] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In other examples, methods, means, equipment and steps well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0076] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0077] In this specification, the word "may" means both performing a certain process and not performing a certain process.

[0078] In this specification, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc., mean that the specific elements (e.g., features, structures, properties and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0079] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints numerical values ​​A and B.

[0080] In this specification, the unit names used are all international standard unit names, and unless otherwise stated, the "%" used indicates weight or mass percentage.

[0081] It is to be understood that the "connection" referred to in this specification may include a direct connection between devices, or an indirect connection through a pipeline, a conveyor (eg, a pump), or the like.

[0082] <First aspect>

[0083] like Figure 1 As shown, the first aspect of the present invention provides a carbon dioxide capture system, which includes an absorption tower 1, a water washing device 2, a concentration and purification device 3 and a desorption tower 4, wherein:

[0084] The absorption tower 1 can be fed with an organic amine absorbent;

[0085] The rich-phase absorbent outlet of the absorption tower 1 is connected to the rich-phase absorbent inlet of the desorption tower 4 through the heat exchanger 5, and the regeneration absorbent outlet of the desorption tower 4 is connected to the lean-phase absorbent inlet of the absorption tower 1 through the heat exchanger 5;

[0086] The water washing device 2 is arranged inside or outside the absorption tower 1, the washing liquid outlet of the water washing device 2 is connected to the washing liquid inlet of the concentration and purification device 3, and the clear liquid outlet of the concentration and purification device 3 is connected to the clear liquid inlet of the water washing device 2.

[0087] The carbon dioxide capture system of the present invention not only helps to reduce the solvent loss caused by the escape of organic amines, but also can further reduce the system operation cost and improve the overall efficiency of carbon capture technology.

[0088] Absorption tower

[0089] The absorption tower 1 is a device for removing carbon dioxide from flue gas, and the absorption tower 1 may be provided with an absorption tower packing layer 11. An organic amine absorbent may be introduced into the absorption tower 1 of the present invention. The organic amine absorbent of the present invention may achieve carbon capture of carbon dioxide in flue gas in the absorption tower 1 and produce a mixed absorption liquid containing carbon dioxide.

[0090] The absorption tower 1 may include a flue gas inlet, a flue gas outlet after decarbonization, a lean phase absorbent inlet and a rich phase absorbent outlet. The flue gas inlet is generally located at the bottom of the absorption tower 1 for flue gas to flow in. The flue gas outlet after decarbonization is located at the top of the absorption tower 1 for flue gas to flow out. The lean phase absorbent inlet is located near the flue gas outlet for the inflow of one or more combinations of organic amine absorbent, regeneration absorbent and concentrated solution. The rich phase absorbent outlet is located near the flue gas inlet for discharging the rich phase absorbent that has absorbed carbon dioxide. The rich phase absorbent outlet of the absorption tower 1 can be connected to the rich phase absorbent inlet of the desorption tower 4 through a circulating pump 61 and a heat exchanger 5.

[0091] In the absorption tower 1, one or more of the organic amine absorbent, regenerative absorbent and concentrated solution flows from the top to the bottom, and the flue gas flows from the bottom to the top. Thus, the flue gas flowing into the absorption tower 1 is fully countercurrently contacted with one or more of the organic amine absorbent, regenerative absorbent and concentrated solution, and the carbon dioxide in the flue gas is absorbed by one or more of the organic amine absorbent, regenerative absorbent and concentrated solution to become a rich phase absorbent, which flows out from the rich phase absorbent outlet.

[0092] In some specific embodiments, the top of the absorption tower 1 is provided with an absorption tower demister 12, which is generally composed of a filler and a wire mesh filling layer. The absorption tower demister 12 is used to separate the absorbent liquid carried in the flue gas after carbon capture to reduce the absorbent escape loss.

[0093] In some specific embodiments, the organic amine absorbent includes organic amine. The present invention can improve the absorption capacity and rate of carbon dioxide by using organic amine. The organic amine includes a primary amine or a salt thereof, a secondary amine or a salt thereof, a tertiary amine or a salt thereof, or a quaternary amine or a salt thereof. Preferably, the organic amine includes ethanolamine (MEA), diethanolamine (DEA), triethylamine (TEA), N,N-diethylethanolamine (DEEA), dipropylenetriamine (DPTA), methyldiethanolamine (MDEA), dimethylethanolamine (DMEA), tetramethyldipropylenetriamine (TMBPA), hydroxyethylethylenediamine (AEEA), pentamethyldiethylenetriamine (PMDTA), triethylenetetramine (TETA), dimethylaminopropylamine (DMAPA), N-methylpyrrolidone (NMP), isobutanolamine (AMP), diethylenetriamine (DETA), diisopropanolamine (DIPA), piperazine (PZ) in one or a combination of two or more.

[0094] In some specific embodiments, the organic amine absorbent may also be a phase separation absorbent. Specifically, the phase separation absorbent may include an organic amine, a phase separation agent and water (H 2 O). Taking the total mass of the composite organic amine phase-change absorbent as 100%, the content of the organic amine is 20-50%, the content of the phase separation agent is 30-70%, and the content of water is 20-50%.

[0095] Specifically, the phase separation process of carbon dioxide after absorption can be achieved by using a phase change phase separation agent. In the present invention, a non-protonic polar solvent is used as a phase separation agent. Specifically, the phase separation agent includes one or a combination of two or more of polyethylene glycol dimethyl ether (NHD), dimethyl sulfoxide (DMSO), cyclopentane sulfone (TMS), N,N-dimethylformamide (DMF), acetone (propanol), and 1,3-dimethyl-2-imidazolidinone (IL).

[0096] Furthermore, the organic amine absorbent of the present invention may also contain inorganic ammonia, for example, some ammonia water or the like.

[0097] Desorption tower

[0098] The desorber 4 of the present invention is used to desorb the rich phase absorbent to obtain the regenerated absorbent, and the desorber 1 may be provided with a desorber packing layer 43. The desorber 4 of the present invention includes a rich phase absorbent inlet and a regenerated absorbent outlet. The regenerated absorbent outlet of the desorber 4 of the present invention may be connected to the lean phase absorbent inlet of the absorber 1 through a circulating pump 62 and a heat exchanger 5.

[0099] The present invention realizes desorption of carbon dioxide by allowing the rich phase absorbent to exchange heat with the heat exchange medium in the heat exchange flow path in the heat exchanger 5, and further allows the regenerated absorbent to exchange heat with the heat exchange medium in the heat exchange flow path, thereby saving energy consumption on the heat exchange flow path and increasing the carbon dioxide absorption capacity of the regenerated absorbent refluxed to the absorption tower 1. In addition, the heat exchange medium in the heat exchanger 5 can be one of a gas phase medium and a liquid medium, wherein the gas phase medium can be water vapor, carbon dioxide, etc., and the liquid phase medium can be water, heat transfer oil, etc.

[0100] In some specific embodiments, a desorption tower demister 44 is provided at the top of the desorption tower 4. The desorption tower demister 44 is generally composed of a filler and a wire mesh filling layer. The desorption tower demister 44 of the present invention is used to separate the absorbent droplets carried in the regeneration gas generated after desorption.

[0101] In some specific embodiments, a condenser 41 is provided at the top of the desorption tower 4. The condenser 41 is used to condense the gas phase components generated after desorption to obtain a condensed gas phase composition and a condensed liquid phase composition. The condensed gas phase composition can be discharged from the desorption tower 4, and the condensed liquid phase composition can be reused in the desorption tower 4.

[0102] Furthermore, a reboiler 42 is disposed at the bottom of the desorption tower 4, and the reboiler 42 can be used to heat the absorbent with external steam and achieve thermal regeneration of the absorbent.

[0103] Washing equipment

[0104] In the present invention, the water washing device 2 can be arranged inside and / or outside the absorption tower 1. When the water washing device 2 is arranged inside the absorption tower 1, the water washing device 2 includes a clear liquid inlet and a washing liquid outlet. Since the water washing device 2 is arranged inside the absorption tower 1, there is no need to set a flue gas inlet after decarbonization. Generally speaking, the water washing device 2 can be arranged at the top of the absorption tower 1, and the flue gas after decarbonization will directly go up to the water washing device 2.

[0105] When the water washing device 2 is arranged outside the absorption tower 1, the water washing device 2 comprises a decarbonized flue gas inlet, a clear liquid inlet and a washing liquid outlet. The decarbonized flue gas outlet of the absorption tower 1 of the present invention is connected to the decarbonized flue gas inlet of the water washing device 2.

[0106] In addition, it should be noted that when the water washing equipment 2 of the present invention includes more than two stages of water washing equipment 2, a part of the water washing equipment 2 can be arranged inside the absorption tower 1, and a part of the water washing equipment 2 can be arranged outside the absorption tower 1. Considering the size of the absorption tower 1, the first-stage water washing equipment 21 can be arranged inside the absorption tower 1.

[0107] The decarbonized flue gas is washed with water by the water washing device 2, so that the organic amine therein is dissolved in water to form a washing liquid. The clear liquid inlet of the water washing device 2 of the present invention can be directly fed with tap water, or can be the clear liquid treated by the concentrated purification device 3.

[0108] In some specific embodiments, the water washing equipment 2 includes more than one level of water washing equipment 2; each level of the water washing equipment 2 is provided with a spray layer 201, a water washing packing layer 202 and a liquid collecting layer 203; wherein the spray layer 201 is provided with a clear liquid inlet for spraying the decarbonized flue gas with the clear water and / or the clear liquid; the water washing packing layer 202 is used to make the decarbonized flue gas contact with the clear water and / or the clear liquid; the liquid collecting layer 203 is provided with the washing liquid outlet for collecting the washing liquid flowing out of the water washing packing layer 202. Afterwards, the washing liquid outlet of the water washing equipment 2 is connected to the washing liquid inlet of the concentration and purification equipment 3, that is, the washing liquid is transported to the concentration and purification equipment 3.

[0109] In some specific embodiments, the water washing equipment includes a primary water washing equipment, an intermediate water washing equipment and a final water washing equipment which are connected in sequence, and the number of the intermediate water washing equipment is greater than or equal to 0; wherein, the final clear liquid inlet of the final water washing equipment is connected to the clear liquid outlet of the concentration and purification equipment; the final washing liquid outlet of the final water washing equipment is connected to the intermediate clear liquid inlet of the intermediate water washing equipment; the intermediate washing liquid outlet of the intermediate water washing equipment is connected to the first clear liquid inlet of the primary water washing equipment; and the first washing liquid outlet of the first water washing equipment is connected to the washing liquid inlet of the concentration and purification equipment.

[0110] When the number of intermediate washing equipment is 0, then Figure 2 As shown, the water washing equipment includes a primary water washing equipment 21 and a secondary water washing equipment 22; wherein, the secondary clear liquid inlet of the secondary water washing equipment 22 is connected to the clear liquid outlet of the concentration and purification equipment 3; the secondary washing liquid outlet of the secondary water washing equipment 22 is connected to the primary clear liquid inlet of the primary water washing equipment 21; the primary washing liquid outlet of the primary water washing equipment 21 is connected to the washing liquid inlet of the concentration and purification equipment 3.

[0111] When the number of intermediate washing equipment is 1, such as Figure 3As shown, the water washing equipment 2 includes a primary water washing equipment 21, a secondary water washing equipment 22 and a tertiary water washing equipment 23, wherein the secondary water washing equipment 22 is an intermediate water washing equipment; wherein, the tertiary clear liquid inlet of the tertiary water washing equipment 23 is connected to the clear liquid outlet of the concentration and purification equipment 3; the tertiary washing liquid outlet of the tertiary water washing equipment 23 is connected to the secondary clear liquid inlet of the secondary water washing equipment 22; the secondary washing liquid outlet of the secondary water washing equipment 22 is connected to the primary clear liquid inlet of the primary water washing equipment 21; the primary washing liquid outlet of the primary water washing equipment 21 is connected to the washing liquid inlet of the concentration and purification equipment 3.

[0112] It should be noted that when there are two or more intermediate-stage water washing equipments in the present invention, the connection relationship between the intermediate-stage water washing equipments is the same as or similar to the connection relationship between the intermediate-stage water washing equipments and the primary water washing equipment or the final water washing equipment.

[0113] For example, when the number of intermediate stages is 2, the water washing equipment includes a primary water washing equipment, a secondary water washing equipment, a tertiary water washing equipment and a quaternary water washing equipment, wherein the secondary water washing equipment and the tertiary water washing equipment are intermediate-stage water washing equipment; the fourth-stage clear liquid inlet of the fourth-stage water washing equipment is connected to the clear liquid outlet of the concentration and purification equipment; the fourth-stage washing liquid outlet of the fourth-stage water washing equipment is connected to the third-stage clear liquid inlet of the third-stage water washing equipment; the third-stage washing liquid outlet of the third-stage water washing equipment is connected to the second-stage clear liquid inlet of the secondary water washing equipment; the second-stage washing liquid outlet of the second-stage water washing equipment is connected to the first-stage clear liquid inlet of the primary water washing equipment; the first-stage washing liquid outlet of the primary water washing equipment is connected to the washing liquid inlet of the concentration and purification equipment, that is, the washing liquid is transported to the concentration and purification equipment.

[0114] Concentration and purification equipment

[0115] The washing liquid outlet of the water washing device 2 is connected to the washing liquid inlet of the concentration and purification device 3, and the clear liquid outlet of the concentration and purification device 3 is connected to the clear liquid inlet of the water washing device 2 to form a cycle. Figure 1 As shown, the concentration and purification equipment 3 includes an ultrafiltration unit 31 and a membrane treatment unit 32 connected in sequence; wherein the washing liquid inlet of the ultrafiltration unit 31 is connected to the washing liquid outlet of the water washing equipment 2; the clear liquid outlet of the membrane treatment unit 32 is connected to the clear liquid inlet of the water washing equipment 2; and the concentrated liquid outlet of the membrane treatment unit 32 is connected to the lean phase absorbent inlet of the absorption tower 1.

[0116] Preferably, the membrane treatment unit 32 is also provided with a clear liquid outlet. When the clear liquid is excessive, the clear liquid outlet can be opened to properly release part of the clear liquid.

[0117] The ultrafiltration unit 31 has a washing liquid inlet and a filtrate outlet. The washing liquid outlet of the water washing device 2 is connected to the washing liquid inlet of the ultrafiltration unit 31, and the washing liquid is filtered by the ultrafiltration unit 31 to obtain a filtrate. The filtrate outlet of the ultrafiltration unit 31 is connected to the filtrate inlet of the membrane treatment unit 32, so that the filtrate enters the membrane treatment unit 32.

[0118] In the present invention, the ultrafiltration unit 31 includes an ultrafiltration (UF) membrane, the pore size of which is 10 to 100 nm; the ultrafiltration membrane uses pressure difference to perform membrane separation, and can intercept most substances between 2 and 100 nm, such as rust, sediment, suspended matter, colloids, macromolecular organic matter, etc. in water, and allow small molecules and soluble solids to pass through. The membrane can be made of hollow fiber, polysulfone, ceramic membrane, etc.

[0119] In some specific embodiments, the membrane treatment unit 31 includes more than one level of membrane treatment unit 32; preferably, each level of the membrane treatment unit 32 includes a nanofiltration membrane or a reverse osmosis membrane, the pore size of the nanofiltration membrane is 1 to 10 nm; the pore size of the reverse osmosis membrane is 0.1 to 1 nm.

[0120] In the present invention, the pore size of the nanofiltration membrane is 1 to 10 nm; the nanofiltration membrane can intercept substances with a molecular weight of 1 to 2 nm and a molecular weight of 200 to 800, and the ability to intercept dissolved salts is 20 to 98%, allowing solvent molecules, low molecular weight solutes or low-valent ions to pass through, and the removal rate of soluble monovalent ions is lower than that of high-valent ions. The material of the membrane, such as polyamide, needs to be electrified and pressurized, and the operating pressure is 0.35 to 3 MPa.

[0121] The pore size of the reverse osmosis membrane is 0.1-1 nm. The reverse osmosis membrane can intercept all dissolved salts and all organic matter with a molecular weight greater than 100, and basically only allows water molecules to pass through. The material of the membrane is polyacrylamide, and its operating pressure can be 10.5 MPa, and the flux is 6-10 L / (m 2 h).

[0122] In some specific embodiments, the membrane treatment unit 32 includes a primary membrane treatment unit, an intermediate membrane treatment unit and a final membrane treatment unit, and the number of the intermediate membrane treatment units is greater than or equal to 0; wherein,

[0123] The filtrate inlet of the primary membrane treatment unit is respectively connected to the filtrate outlet of the ultrafiltration unit and the intermediate-stage concentrated liquid outlet of the intermediate-stage membrane treatment unit, and the primary concentrated liquid outlet of the primary membrane treatment unit is connected to the lean phase absorbent inlet of the absorption tower; the intermediate-stage clear liquid inlet of the intermediate-stage membrane treatment unit is respectively connected to the primary clear liquid outlet of the primary membrane treatment unit and the final-stage concentrated liquid outlet of the final-stage membrane treatment unit; the final-stage clear liquid inlet of the final-stage membrane treatment unit is connected to the intermediate-stage clear liquid outlet of the intermediate-stage membrane treatment unit, and the final-stage clear liquid outlet of the final-stage membrane treatment unit is connected to the clear liquid inlet of the water washing equipment.

[0124] When the number of intermediate membrane treatment units is 0, then Figure 2 As shown, the membrane treatment unit 32 includes a primary membrane treatment unit 321 and a secondary membrane treatment unit 322; wherein, the filtrate inlet of the primary membrane treatment unit 321 is respectively connected to the filtrate outlet of the ultrafiltration unit 31 and the secondary concentrated liquid outlet of the secondary membrane treatment unit 322, the primary clear liquid outlet of the primary membrane treatment unit 321 is connected to the secondary clear liquid inlet of the secondary membrane treatment unit 322, the primary concentrated liquid outlet of the primary membrane treatment unit 321 is connected to the lean phase absorbent inlet of the absorption tower 1, and the secondary clear liquid outlet of the secondary membrane treatment unit 322 is connected to the clear liquid inlet of the water washing equipment 2.

[0125] When the number of intermediate membrane treatment units is 1, then Figure 3 As shown, the membrane treatment unit 32 includes a primary membrane treatment unit 321, a secondary membrane treatment unit 322 and a tertiary membrane treatment unit 323; the filtrate inlet of the primary membrane treatment unit 321 is respectively connected to the filtrate outlet of the ultrafiltration unit 31 and the secondary concentrated liquid outlet of the secondary membrane treatment unit 322, and the primary concentrated liquid outlet of the primary membrane treatment unit 321 is connected to the lean phase absorbent inlet of the absorption tower 1; the secondary clear liquid inlet of the secondary membrane treatment unit 322 is respectively connected to the primary clear liquid outlet of the primary membrane treatment unit 321 and the tertiary concentrated liquid outlet of the tertiary membrane treatment unit 323; the tertiary clear liquid inlet of the tertiary membrane treatment unit 323 is connected to the secondary clear liquid outlet of the secondary membrane treatment unit 322; the tertiary clear liquid outlet of the tertiary membrane treatment unit 323 is connected to the clear liquid inlet of the water washing equipment 2.

[0126] It should be noted that when there are two or more intermediate membrane treatment units in the present invention, the connection relationship between the intermediate membrane treatment units is the same as or similar to the connection relationship between the intermediate membrane treatment unit and the primary membrane treatment unit or the final membrane treatment unit.

[0127] For example, when the number of intermediate membrane treatment units is 2, the membrane treatment units include a primary membrane treatment unit, a secondary membrane treatment unit, a tertiary membrane treatment unit and a quaternary membrane treatment unit; the filtrate inlet of the primary membrane treatment unit is respectively connected to the filtrate outlet of the ultrafiltration unit and the secondary concentrated liquid outlet of the secondary membrane treatment unit, and the primary concentrated liquid outlet of the primary membrane treatment unit is connected to the lean phase absorbent inlet of the absorption tower; the secondary clear liquid inlet of the secondary membrane treatment unit is respectively connected to the primary clear liquid outlet of the primary membrane treatment unit and the tertiary concentrated liquid outlet of the tertiary membrane treatment unit; the tertiary clear liquid inlet of the tertiary membrane treatment unit is respectively connected to the secondary clear liquid outlet of the secondary membrane treatment unit and the quaternary concentrated liquid outlet of the quaternary membrane treatment unit; the quaternary clear liquid inlet of the quaternary membrane treatment unit is connected to the tertiary clear liquid outlet of the tertiary membrane treatment unit; the quaternary clear liquid outlet of the quaternary membrane treatment unit is connected to the clear liquid inlet of the water washing equipment.

[0128] In addition, it should be noted that if the concentration of the concentrated solution (such as the primary concentrated solution) transported to the absorption tower 1 is too low, a distillation device or a rectification device can be used to treat the concentrated solution to make the concentration of the concentrated solution more appropriate. In addition, the concentrated solution can also be transported to the reboiler 42 of the desorption tower 4 to treat the concentrated solution, so as to make the concentration of the concentrated solution more appropriate.

[0129] The present invention can effectively control the escape of organic amines, promote their recycling, and reduce the loss of solvents caused by the escape by using the technology of coupling the water washing device 2 with the concentration and purification device 3 (ultrafiltration unit 31, membrane treatment unit 32).

[0130] <Second Aspect>

[0131] The second aspect of the present invention provides a method for capturing carbon dioxide using the carbon dioxide capture system according to the first aspect of the present invention, comprising the following steps:

[0132] The flue gas is transported to an absorption tower, and an absorbent is introduced into the absorption tower; in the absorption tower, the absorbent absorbs carbon dioxide in the flue gas to generate a rich-phase absorbent and decarbonized flue gas;

[0133] The rich phase absorbent is transported to a desorption tower via a heat exchanger for desorption treatment;

[0134] The decarbonized flue gas is transported to a water washing device, mixed with clean water and subjected to water washing treatment to obtain a washing liquid;

[0135] The washing liquid is transported to a concentration and purification device for concentration and purification to obtain the clear liquid and the concentrated liquid;

[0136] Optionally, the clear liquid is transported to a water washing device, so that the clear liquid is mixed with the decarbonized flue gas and then subjected to a water washing treatment;

[0137] Optionally, the concentrated solution is transported to the absorption tower to absorb carbon dioxide in the flue gas and generate a rich-phase absorbent and decarbonized flue gas.

[0138] In some specific embodiments, the water washing equipment includes a primary water washing equipment, an intermediate water washing equipment and a final water washing equipment connected in sequence, and the number of the intermediate water washing equipment is greater than or equal to 0; then the water washing treatment includes the following steps:

[0139] The decarbonized flue gas is transported to a final water washing device for final water washing treatment to obtain a final washing liquid;

[0140] The final-stage washing liquid is transported to the intermediate-stage water washing equipment through the final-stage washing liquid outlet, and the decarbonized flue gas is subjected to intermediate-stage water washing treatment to obtain the intermediate-stage washing liquid;

[0141] The intermediate-level washing liquid is transported to the primary water washing equipment through the intermediate-level washing liquid outlet, and the decarbonized flue gas is subjected to primary water washing treatment to obtain the primary washing liquid;

[0142] The primary washing liquid is transported to a concentration and purification device for concentration and purification.

[0143] In some specific embodiments, the concentration and purification equipment comprises an ultrafiltration unit and a membrane treatment unit connected in sequence; wherein,

[0144] The washing liquid is transported to an ultrafiltration unit for ultrafiltration treatment to obtain a filtrate;

[0145] The filtrate is transported to the membrane treatment unit for membrane treatment to obtain a concentrated solution and a clear solution.

[0146] In some specific embodiments, the membrane treatment unit includes a primary membrane treatment unit, an intermediate membrane treatment unit and a final membrane treatment unit, and the number of the intermediate membrane treatment units is greater than or equal to 0; then the membrane treatment includes the following steps:

[0147] The filtrate is transported to a primary membrane treatment unit for primary membrane treatment to obtain a primary concentrated solution and a primary clear solution; the primary concentrated solution is transported to an absorption tower to be mixed with the absorbent; the primary clear solution is transported to an intermediate membrane treatment unit for intermediate membrane treatment to obtain an intermediate concentrated solution and an intermediate clear solution;

[0148] The intermediate concentrated solution is transported to the primary membrane treatment unit to be mixed with the filtrate; the intermediate clear solution is transported to the final membrane treatment unit for final membrane treatment to obtain a final concentrated solution and a final clear solution;

[0149] The final concentrated liquid is transported to the intermediate membrane treatment unit to be mixed with the intermediate clear liquid, and the final clear liquid is transported to a water washing device for water washing treatment.

[0150] The carbon dioxide capture method of the present invention is simple and easy to implement, the raw materials are easy to obtain, and it is suitable for mass production.

[0151] Example

[0152] The embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific conditions are specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0153] Example 1

[0154] like Figure 1 As shown in the figure, a coal-fired power plant burns CO 2 Capture device, designed flue gas volume is 1500Nm 3 / h, the carbon dioxide concentration is about 10%. The organic amine absorbent used in the carbon capture process is: 30% by mass of MEA, and the rest is water.

[0155] The MEA concentration in the flue gas after decarbonization at the top of the absorption tower is 122 mg / Nm 3 After washing with water in the built-in water washing equipment in the absorption tower, the MEA concentration in the flue gas after decarbonization dropped to 45mg / Nm 3 The MEA concentration in the washing liquid increases from 1.2% to 3.9% and enters the concentration purification equipment.

[0156] After the large particles of impurities are filtered out by the ultrafiltration unit of the concentration and purification equipment, the obtained filtrate enters the membrane treatment unit composed of nanofiltration membrane for membrane treatment. The MEA concentration in the obtained clear liquid is 1.2%, and it enters the water washing equipment; the MEA concentration in the obtained concentrated liquid is 11%, and it enters the absorption tower.

[0157] Example 2

[0158] A coal-fired boiler flue gas carbon capture system, processing flue gas volume of 3600Nm 3 / h, flue gas inlet temperature 40℃, carbon dioxide concentration 12%, absorbent flow rate 600L / h, absorbent temperature set to 40℃. Flue gas enters the absorbent tower after being pretreated by the alkaline scrubber. The composite amine absorbent used in the carbon capture process is a combination of AMP, MEA and water; the mass fraction of AMP is 22%, the mass fraction of MEA is 12%, and the rest is water.

[0159] The AMP concentration in the flue gas after decarbonization at the top of the absorption tower is 165 mg / Nm 3 , MEA concentration is 57mg / Nm 3 After secondary water washing, the AMP concentration in the flue gas dropped to 23 mg / Nm 3 , MEA concentration dropped to 8 mg / Nm 3 After primary water washing, the AMP concentration in the flue gas is 6 mg / Nm 3 , MEA concentration is 2mg / Nm 3 .

[0160] The total concentration of AMP and MEA (i.e., amine concentration) in the secondary washing liquid increases from 0.9% at the inlet to 2.3% at the outlet, and the amine concentration of the primary washing liquid increases from 2.3% at the inlet to 5.5% at the outlet; after the primary washing liquid enters the ultrafiltration unit to remove impurities, the obtained filtrate enters the primary membrane treatment unit composed of a reverse osmosis membrane for membrane treatment, the obtained primary concentrated solution (amine concentration 15.4%) is returned to the absorption tower, the primary clear solution (amine concentration 1.4%) enters the secondary membrane treatment unit composed of a reverse osmosis membrane for membrane treatment, the obtained secondary concentrated solution (amine concentration 5.5%) is returned to the primary membrane treatment unit for membrane treatment, and the obtained secondary clear solution (amine concentration 0.9%) is returned to the secondary washing equipment.

[0161] Example 3

[0162] A coal-fired boiler flue gas carbon capture system, processing flue gas volume of 3600Nm 3 / h, flue gas inlet temperature 40℃, carbon dioxide concentration 10%, absorbent flow rate 600L / h, absorbent temperature set to 30℃. Flue gas enters the absorbent tower after being pretreated by the alkali scrubber. The two-phase absorbent used in the carbon capture process is a combination of AEEA, DEEA and water; the mass fraction of AEEA is 25%, the mass fraction of DEEA is 50%, and the rest is water.

[0163] The total concentration of DEEA and AEEA (i.e. amine concentration) in the flue gas after decarbonization at the top of the absorption tower is 810 mg / Nm 3 After three-stage water washing, the amine concentration dropped to 152 mg / Nm 3 After secondary water washing, the amine concentration dropped to 64 mg / Nm 3 After primary water washing, the amine concentration dropped to 10 mg / Nm 3 .

[0164] The total concentration of DEEA and AEEA (i.e., amine concentration) in the tertiary washing liquid increases from 0.2% at the inlet to 1.2%, the amine concentration in the secondary washing liquid increases from 1.2% at the inlet to 3.4% at the outlet, and the amine concentration in the primary washing liquid increases from 3.4% at the inlet to 8.7% at the outlet; after the primary washing liquid enters the ultrafiltration unit to remove impurities, the obtained filtrate enters the primary membrane treatment unit composed of nanofiltration membrane, the obtained primary concentrated solution (amine concentration 22.4%) is returned to the absorption tower, the primary clear solution (amine concentration 4.1%) enters the secondary membrane treatment unit composed of reverse osmosis membrane for membrane treatment, the obtained secondary concentrated solution (amine concentration 8.7%) is returned to the primary membrane treatment unit for membrane treatment, the obtained secondary clear solution (amine concentration 1.3%) enters the tertiary membrane treatment unit composed of reverse osmosis membrane for membrane treatment, the obtained tertiary concentrated solution (amine concentration 4.1%) is returned to the secondary membrane treatment unit for membrane treatment, and the obtained tertiary clear solution (amine concentration 0.2%) is returned to the tertiary washing equipment.

[0165] It should be noted that, although the technical solution of the present invention is introduced with specific examples, those skilled in the art will appreciate that the present invention should not be limited thereto.

[0166] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A carbon dioxide capture system, characterized in that: It includes absorption tower, water washing equipment, concentration and purification equipment and desorption tower, among which: The absorption tower can be fed with an organic amine absorbent; The rich-phase absorbent outlet of the absorption tower is connected to the rich-phase absorbent inlet of the desorption tower through a heat exchanger, and the regeneration absorbent outlet of the desorption tower is connected to the lean-phase absorbent inlet of the absorption tower through a heat exchanger; The water washing device is arranged inside and / or outside the absorption tower, the washing liquid outlet of the water washing device is connected to the washing liquid inlet of the concentration and purification device, and the clear liquid outlet of the concentration and purification device is connected to the clear liquid inlet of the water washing device.

2. The carbon dioxide capture system according to claim 1, characterized in that The water washing equipment includes more than one level of water washing equipment; each level of the water washing equipment includes a spray layer, a water washing filler layer and a liquid collection layer, wherein: The spray layer is provided with a clear liquid inlet for spraying the decarbonized flue gas with clean water and / or the clear liquid; The water-washed filler layer is used to make the decarbonized flue gas contact with the clean water and / or the clean liquid; The liquid collecting layer is provided with the washing liquid outlet for collecting the washing liquid flowing out of the water-washing filler layer.

3. The carbon dioxide capture system according to claim 2, characterized in that The water washing equipment includes a primary water washing equipment, an intermediate water washing equipment and a final water washing equipment which are connected in sequence, and the number of the intermediate water washing equipment is greater than or equal to 0; wherein, The final clear liquid inlet of the final water washing device is connected to the clear liquid outlet of the concentration and purification device; The final-stage washing liquid outlet of the final-stage washing device is connected to the intermediate-stage clear liquid inlet of the intermediate-stage washing device; The intermediate washing liquid outlet of the intermediate washing device is connected to the primary clear liquid inlet of the primary washing device; The primary washing liquid outlet of the primary water washing device is connected to the washing liquid inlet of the concentration and purification device.

4. The carbon dioxide capture system according to any one of claims 1 to 3, characterized in that: The concentration and purification equipment comprises an ultrafiltration unit and a membrane treatment unit connected in sequence; wherein, The washing liquid inlet of the ultrafiltration unit is connected to the washing liquid outlet of the water washing device; The clear liquid outlet of the membrane treatment unit is connected to the clear liquid inlet of the water washing device; The concentrated solution outlet of the membrane treatment unit is connected to the lean phase absorbent inlet of the absorption tower; Preferably, the ultrafiltration unit comprises an ultrafiltration membrane, and the pore size of the ultrafiltration membrane is 10-100 nm.

5. The carbon dioxide capture system according to claim 4, characterized in that The membrane treatment unit includes more than one level of membrane treatment units; Preferably, each stage of the membrane treatment unit comprises a nanofiltration membrane or a reverse osmosis membrane, the pore size of the nanofiltration membrane is 1 to 10 nm; the pore size of the reverse osmosis membrane is 0.1 to 1 nm.

6. The carbon dioxide capture system according to claim 4 or 5, characterized in that The membrane treatment unit includes a primary membrane treatment unit, an intermediate membrane treatment unit and a final membrane treatment unit, and the number of the intermediate membrane treatment units is greater than or equal to 0; wherein, The filtrate inlet of the primary membrane treatment unit is connected to the filtrate outlet of the ultrafiltration unit and the intermediate concentrated solution outlet of the intermediate membrane treatment unit respectively; the primary concentrated solution outlet of the primary membrane treatment unit is connected to the lean phase absorbent inlet of the absorption tower; The intermediate clear liquid inlet of the intermediate membrane treatment unit is connected to the primary clear liquid outlet of the primary membrane treatment unit and the final concentrated liquid outlet of the final membrane treatment unit respectively; The final clear liquid inlet of the final membrane treatment unit is connected to the intermediate clear liquid outlet of the intermediate membrane treatment unit, and the final clear liquid outlet of the final membrane treatment unit is connected to the clear liquid inlet of the water washing device.

7. A method for capturing carbon dioxide using the carbon dioxide capture system according to any one of claims 1 to 6, characterized in that: The following steps are involved: The flue gas is transported to an absorption tower, and an absorbent is introduced into the absorption tower; in the absorption tower, the absorbent absorbs carbon dioxide in the flue gas to generate a rich-phase absorbent and decarbonized flue gas; The rich phase absorbent is transported to a desorption tower via a heat exchanger for desorption treatment; The decarbonized flue gas is transported to a water washing device, mixed with clean water and subjected to water washing treatment to obtain a washing liquid; The washing liquid is transported to a concentration and purification device for concentration and purification to obtain a clear liquid and a concentrated liquid; Optionally, the clear liquid is transported to a water washing device, so that the clear liquid is mixed with the decarbonized flue gas and then subjected to a water washing treatment; Optionally, the concentrated solution is transported to the absorption tower to absorb carbon dioxide in the flue gas and generate a rich-phase absorbent and decarbonized flue gas.

8. The method for capturing carbon dioxide according to claim 7, characterized in that: The water washing equipment includes a primary water washing equipment, an intermediate water washing equipment and a final water washing equipment connected in sequence, and the number of the intermediate water washing equipment is greater than or equal to 0; the water washing process includes the following steps: The decarbonized flue gas is transported to a final water washing device for final water washing treatment to obtain a final washing liquid; The final-stage washing liquid is transported to the intermediate-stage water washing equipment through the final-stage washing liquid outlet, and the decarbonized flue gas is subjected to intermediate-stage water washing treatment to obtain the intermediate-stage washing liquid; The intermediate-level washing liquid is transported to the primary water washing equipment through the intermediate-level washing liquid outlet, and the decarbonized flue gas is subjected to primary water washing treatment to obtain the primary washing liquid; The primary washing liquid is transported to a concentration and purification device for concentration and purification.

9. The method for capturing carbon dioxide according to claim 7 or 8, characterized in that: The concentration and purification equipment comprises an ultrafiltration unit and a membrane treatment unit connected in sequence; wherein, The washing liquid is transported to an ultrafiltration unit for ultrafiltration treatment to obtain a filtrate; The filtrate is transported to the membrane treatment unit for membrane treatment to obtain a concentrated solution and a clear solution.

10. The method for capturing carbon dioxide according to claim 9, characterized in that: The membrane treatment unit includes a primary membrane treatment unit, an intermediate membrane treatment unit and a final membrane treatment unit, and the number of the intermediate membrane treatment units is greater than or equal to 0; the membrane treatment includes the following steps: The filtrate is transported to a primary membrane treatment unit for primary membrane treatment to obtain a primary concentrated solution and a primary clear solution; the primary concentrated solution is transported to an absorption tower to be mixed with the absorbent; the primary clear solution is transported to an intermediate membrane treatment unit for intermediate membrane treatment to obtain an intermediate concentrated solution and an intermediate clear solution; The intermediate concentrated liquid is transported to the primary membrane treatment unit to be mixed with the filtrate; the intermediate clear liquid is transported to the final membrane treatment unit for final membrane treatment to obtain a final concentrated liquid and a final clear liquid; the final concentrated liquid is transported to the intermediate membrane treatment unit to be mixed with the intermediate clear liquid, and the final clear liquid is transported to a water washing device for water washing treatment.

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