Method for capturing carbon dioxide in low-temperature flue gas and coupling nitrogen purification

Abstract

The invention discloses a method for capturing carbon dioxide in low-temperature flue gas and coupling with nitrogen purification, which comprises the following steps: pressurizing the low-temperature flue gas and then carrying out first constant-pressure variable-pressure adsorption treatment to obtain decarburized gas and carbon dioxide concentrated gas; and carrying out second constant-pressure variable-pressure adsorption treatment on the decarburized gas to obtain high-purity nitrogen. The method provided by the invention can simultaneously recover carbon dioxide and nitrogen from the low-temperature flue gas, and the obtained carbon dioxide and nitrogen have high purity, so that the method is especially suitable for the treatment working condition that the content of carbon dioxide in the flue gas is low and the content of nitrogen in the flue gas is high. In addition, the captured carbon dioxide is used as an activation medium to be used in the activation process of the activated carbon carbon dioxide adsorbent, and resource utilization is achieved. The method has the advantages of high efficiency, energy conservation, low cost, environmental protection and the like, has remarkable economic benefits, and has relatively high industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of gas separation and resource utilization technology. Specifically, this invention relates to a method for capturing carbon dioxide and purifying nitrogen in low-temperature flue gas. Background Technology

[0002] Due to global dependence on fossil fuels, emissions from industry and daily life are increasing, leading to the greenhouse effect, which has become one of the world's major environmental problems. Among the various greenhouse gases contributing to climate change, carbon dioxide (CO2) has the greatest impact on global warming, with its emissions continuously rising and significantly affecting climate change. Therefore, developing effective flue gas carbon dioxide capture technologies to control carbon dioxide emissions and achieve carbon reduction targets has become one of the important technological approaches to addressing global warming.

[0003] Burning coal, natural gas, and oil for power generation and heating is the world’s largest single energy-related source of carbon emissions. Coal-fired power generation accounts for the largest proportion of carbon dioxide emissions, about 40% of the total, and has the greatest potential to contribute to global carbon dioxide emission reduction.

[0004] Currently, the main technologies for capturing carbon dioxide in flue gas from coal-fired power plants include chemical absorption, physical absorption, membrane separation, and adsorption. Chemical absorption typically uses alkanolamine solvents, which, while highly efficient at absorbing carbon dioxide, suffer from problems such as high energy consumption due to absorbent degradation and regeneration, and environmental pollution caused by absorbent leakage or volatilization. Physical absorption relies on the solubility differences of gases under high pressure, but requires high operating pressure and consumes a lot of energy. Membrane separation separates carbon dioxide through selective permeation of the membrane, but the separation performance and lifespan of the membrane limit its large-scale application, and the high investment and operating costs of membrane separation equipment further hinder its large-scale industrial application. Adsorption utilizes solid adsorbents for selective adsorption of carbon dioxide, offering advantages such as relatively low energy consumption and simple operation, and is therefore widely used.

[0005] In practical industrial flue gas treatment, flue gas typically exhibits characteristics such as low temperature (40-150℃) and relatively stable pressure. It contains not only carbon dioxide but also a large amount of nitrogen and other trace impurities, resulting in a complex composition that is difficult to separate. This makes carbon dioxide recovery and nitrogen resource utilization challenging, and the capture rate is relatively low. Therefore, developing efficient, energy-saving, and stable carbon dioxide capture and nitrogen purification technologies tailored to this complex gas composition and specific operating conditions has become an urgent problem to be solved. Summary of the Invention

[0006] The present invention aims to at least partially solve one of the technical problems in the related art.

[0007] Therefore, this invention proposes a method for capturing carbon dioxide and purifying nitrogen in low-temperature flue gas. Based on constant-pressure two-stage pressure swing adsorption (PSA) technology, this invention separates and recovers carbon dioxide and nitrogen from low-temperature flue gas, achieving efficient capture of carbon dioxide and purification of high-purity nitrogen. The captured carbon dioxide is then used as an activation medium in the activation process of activated carbon adsorbents, providing a new approach for industrial flue gas treatment and gas resource utilization.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: This invention provides a method for capturing carbon dioxide and purifying nitrogen in low-temperature flue gas, comprising the following steps: The low-temperature flue gas is pressurized and then subjected to a first constant pressure swing adsorption treatment to obtain decarbonized gas and carbon dioxide concentrated gas. The decarbonized gas is subjected to a second constant-pressure pressure swing adsorption treatment to obtain high-purity nitrogen gas.

[0009] In some embodiments, the temperature of the low-temperature flue gas is 40~150°C; And / or, the mass concentration of CO2 in the low-temperature flue gas is ≥15%, and the mass concentration of N2 is ≥70%.

[0010] In some embodiments, the mass concentration of carbon dioxide in the decarbonized gas is ≤2%.

[0011] In some embodiments, the first constant pressure swing adsorption process is as follows: the pressurized low-temperature flue gas is first subjected to carbon dioxide adsorption using a porous carbon adsorbent under constant pressure, and then the pressure is reduced to desorb and regenerate the porous carbon adsorbed with carbon dioxide, releasing concentrated carbon dioxide gas. Optionally, the porous carbon adsorbent has a micropore ratio of ≥95% and a specific surface area of ​​≥1200 m². 2 / g; wherein the pore size of the micropores is <2nm; Optionally, the constant pressure adsorption during carbon dioxide adsorption is 0.2~1.0 MPa, and the adsorption time is 90~120 s.

[0012] Furthermore, the vacuum degree during the desorption and regeneration of the porous carbon is -60kPa to 0.1MPa, and the regeneration time is ≤30s; And / or, the carbon dioxide concentration in the concentrated carbon dioxide gas released by the desorption and regeneration of the porous carbon is ≥60%, and the concentrated carbon dioxide gas is reused as an activation medium to prepare porous carbon carbon dioxide adsorbent.

[0013] In some embodiments, the second constant pressure swing adsorption process is as follows: the decarbonized gas is first subjected to nitrogen adsorption using a molecular sieve under constant pressure, and then the pressure is reduced to desorb and regenerate the molecular sieve containing nitrogen, thereby releasing nitrogen. Optionally, the molecular sieve is a 5A molecular sieve or a 13X molecular sieve, and the pore size of the molecular sieve is 0.4~0.8 nm; Optionally, the constant pressure adsorption during nitrogen adsorption is 0.2~1.0 MPa, and the adsorption time is 60~90 s.

[0014] Furthermore, the vacuum degree during the desorption and regeneration of the molecular sieve is -60kPa to 0.1MPa, and the regeneration time is 30 to 45s.

[0015] In some embodiments, the purity of the high-purity nitrogen gas is ≥99.9%.

[0016] The advantages and beneficial effects of the embodiments of the present invention are as follows: This invention achieves high carbon dioxide capture rates and ultrapure nitrogen extraction from low-temperature flue gas through a two-stage constant-pressure pressure swing adsorption process, combined with the size sieving and selective adsorption characteristics of molecular sieves. Furthermore, the captured carbon dioxide can be used in the activation process of activated carbon adsorbents, realizing resource utilization. This method is simple, easy to operate, and features low equipment cost, low energy consumption, and high recovery efficiency, providing a new approach to industrial flue gas treatment and gas resource utilization, and possesses significant industrial application value. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0018] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0019] In this invention, when a value is described as a range, it should be understood that such disclosure includes disclosure of all possible subranges within that range, as well as specific numerical values ​​falling within that range, regardless of whether specific numerical values ​​or specific subranges are explicitly specified.

[0020] In this invention, the terms “comprising” and “including” and their various variations mean that other elements or wholes may be included but are not specifically described.

[0021] In this invention, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0022] This invention provides a method for capturing carbon dioxide and purifying nitrogen in low-temperature flue gas, comprising the following steps: The low-temperature flue gas is pressurized and then subjected to a first constant pressure swing adsorption treatment to obtain decarbonized gas and carbon dioxide concentrated gas. The decarbonized gas is subjected to a second constant-pressure pressure swing adsorption treatment to obtain high-purity nitrogen gas.

[0023] In some embodiments, the temperature of the low-temperature flue gas is 40~150°C; And / or, the mass concentration of CO2 in the low-temperature flue gas is ≥15%, and the mass concentration of N2 is ≥70%.

[0024] The flue gas in this embodiment of the invention is low-temperature flue gas. When treating it, there is no need for pretreatment operations such as cooling and dehumidification, which simplifies the treatment process and reduces the treatment cost.

[0025] In some embodiments, the mass concentration of carbon dioxide in the decarbonized gas is ≤2%.

[0026] In some embodiments, the first constant pressure swing adsorption process is as follows: the pressurized low-temperature flue gas is first subjected to carbon dioxide adsorption using a porous carbon adsorbent under constant pressure, and then the pressure is reduced to desorb and regenerate the porous carbon adsorbed with carbon dioxide, releasing concentrated carbon dioxide gas. Optionally, the porous carbon adsorbent has a micropore ratio of ≥95% and a specific surface area of ​​≥1200 m². 2 / g; wherein the pore size of the micropores is <2nm; Optionally, the constant pressure adsorption during carbon dioxide adsorption is 0.2~1.0 MPa, and the adsorption time is 90~120 s. The inventors have found through research that if the adsorption pressure is too high, the adsorption capacity of the adsorbent for carbon dioxide will decrease, and it may even cause blockage of the adsorbent pores, affecting the adsorption efficiency; however, if the adsorption pressure is too low, the adsorbent will not fully adsorb carbon dioxide, resulting in an excessively high residual concentration of carbon dioxide in the decarbonized gas, failing to achieve the expected decarbonization effect; furthermore, by controlling the adsorption time within the range of 90~120 s, the embodiments of this invention can ensure the sufficient absorption of CO2 by the porous carbon adsorbent.

[0027] Furthermore, the vacuum degree during desorption and regeneration of the porous carbon is -60 kPa to 0.1 MPa, and the regeneration time is ≤30 s. The inventors have found through research that if the desorption and regeneration pressure is too high, it will lead to incomplete desorption, resulting in poor adsorbent regeneration and affecting the adsorption efficiency of the next round. However, if the desorption and regeneration pressure is too low, it will lead to excessive regeneration energy consumption and may also damage the adsorbent structure and shorten its service life. Therefore, it is advantageous to control the vacuum degree during the desorption and regeneration of the porous carbon in the range of -60 kPa to 0.1 MPa in this embodiment of the invention. And / or, the carbon dioxide concentration in the concentrated carbon dioxide gas released by the desorption and regeneration of the porous carbon is ≥60%, and the concentrated carbon dioxide gas is reused as an activation medium to prepare porous carbon carbon dioxide adsorbent.

[0028] It should be noted that the porous carbon produced using the carbon dioxide concentrate gas regenerated by the above desorption must meet the following performance requirements: micropores (pore size <2nm) ≥95%, specific surface area ≥1200m². 2 / g, and then the activated carbon can be reused in the adsorption of carbon dioxide in low-temperature flue gas. If there is a surplus, the surplus porous carbon can be sold.

[0029] In this embodiment of the invention, the concentrated carbon dioxide gas obtained from desorption and regeneration is used as an activation medium in the activation process of porous carbon preparation to activate the porous carbon. The prepared porous carbon can be further used to adsorb carbon dioxide in low-temperature flue gas (the surplus porous carbon can be commercially sold). In this way, the cycle is repeated to realize the recycling of resources, avoid resource waste, and greatly reduce production costs.

[0030] Furthermore, when using the carbon dioxide concentrate as an activation medium to prepare porous carbon adsorbent, the activation temperature is 800~1100℃, the activation time is 1~10h, and the flow rate of the carbon dioxide concentrate is 5~15t CO2 / t activated raw material (i.e., 5~15 tons of carbon dioxide concentrate are introduced into each ton of activated raw material). Furthermore, the aforementioned activated raw materials include one or a mixture of two of the following: biomass raw materials and coal-based raw materials.

[0031] In some embodiments, the pressure of the decarbonized gas is ≥0.15 MPa. The outlet tail gas obtained after the first constant pressure swing adsorption treatment—the decarbonized gas—still maintains a high pressure. Therefore, when it is directly subjected to the second constant pressure swing adsorption treatment, the residual pressure can be used to achieve the second constant pressure swing adsorption directly, without the need for any intermediate compressor or vacuum pump to achieve the pressurization effect, or only a small amount of pressurization is required. This not only simplifies the process equipment but also reduces energy consumption, resulting in high economic benefits.

[0032] In some embodiments, the second constant pressure swing adsorption process is as follows: the decarbonized gas is first subjected to nitrogen adsorption using a molecular sieve under constant pressure, and then the pressure is reduced to desorb and regenerate the molecular sieve containing nitrogen, thereby releasing nitrogen. Optionally, the molecular sieve is a 5A molecular sieve or a 13X molecular sieve, and the pore size of the molecular sieve is 0.4~0.8 nm; Optionally, the constant pressure adsorption during nitrogen adsorption is 0.2~1.0 MPa, and the adsorption time is 60~90 s.

[0033] Furthermore, the vacuum degree during the desorption and regeneration of the molecular sieve is -60kPa to 0.1MPa, and the regeneration time is 30 to 45s.

[0034] In some embodiments, the purity of the high-purity nitrogen gas is ≥99.9%.

[0035] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. Unless otherwise stated, all raw materials used in the embodiments are conventional commercially available products, or can be prepared by known methods; and the experimental methods not specified in the embodiments are conventional methods and conditions well known in the art.

[0036] Example 1 This embodiment provides a method for carbon dioxide capture coupled with nitrogen purification in low-temperature flue gas, including the following steps: First, low-temperature flue gas at 120℃ (with a CO2 mass concentration of 20%, an N2 mass concentration of 64%, and impurities of 16%) was pressurized to 0.7 MPa. Porous carbon was used to adsorb carbon dioxide from the low-temperature flue gas. After 100 seconds of adsorption, decarbonized gas (with a CO2 mass concentration ≤1.8%) was obtained. Then, the porous carbon containing adsorbed carbon dioxide was desorbed and regenerated. The vacuum degree during desorption and regeneration was controlled at -60 kPa, and the regeneration time was 30 seconds, yielding a concentrated carbon dioxide gas with a capture rate of 92.2% and a carbon dioxide mass concentration of 65%. Then, nitrogen in the decarbonized gas is adsorbed and separated using 5A molecular sieve at a constant pressure of 0.7 MPa. After an adsorption time of 70 s, the 5A molecular sieve with adsorbed nitrogen is desorbed and regenerated. The vacuum degree of the 5A molecular sieve desorption and regeneration is controlled at -60 kPa and the regeneration time is 35 s to obtain high-purity nitrogen with a purity of 99.95%, CO2 residue <0.1%, and nitrogen recovery rate of 95%.

[0037] Example 2 This embodiment provides a method for carbon dioxide capture coupled with nitrogen purification in low-temperature flue gas, including the following steps: First, low-temperature flue gas at 80℃ (with a CO2 mass concentration of 15%, an N2 mass concentration of 80%, and impurities of 5%) is pressurized to 0.5 MPa. Porous carbon is used to adsorb carbon dioxide from the low-temperature flue gas. After adsorption for 120 seconds, decarbonized gas (with a CO2 mass concentration ≤1.5%) is obtained. Then, the porous carbon containing adsorbed carbon dioxide is desorbed and regenerated. The vacuum degree during desorption and regeneration is controlled at -50 kPa, and the regeneration time is 25 seconds, yielding concentrated carbon dioxide gas. This concentrated carbon dioxide gas has a capture rate of 90.5% and a carbon dioxide mass concentration of 62%. Then, nitrogen in the decarbonized gas was adsorbed and separated using 13X molecular sieve under a constant pressure of 0.5 MPa for 70 s. After adsorption, the 13X molecular sieve with adsorbed nitrogen was desorbed and regenerated. The vacuum degree of the 13X molecular sieve desorption and regeneration was controlled at -55 kPa and the regeneration time was 40 s to obtain high-purity nitrogen with a purity of 99.98%, CO2 residue <0.1%, and nitrogen recovery rate of 96%.

[0038] Example 3 This embodiment provides a method for carbon dioxide capture coupled with nitrogen purification in low-temperature flue gas, including the following steps: First, low-temperature flue gas at 100℃ (with a CO2 mass concentration of 18%, an N2 mass concentration of 77%, and impurities of 5%) was pressurized to 0.8 MPa. Porous carbon was used to adsorb carbon dioxide from the low-temperature flue gas. After 90 seconds of adsorption, decarbonized gas (with a CO2 mass concentration ≤1.9%) was obtained. Then, the porous carbon containing adsorbed carbon dioxide was desorbed and regenerated. The vacuum degree during desorption and regeneration was controlled at -55 kPa, and the regeneration time was 28 seconds, yielding a concentrated carbon dioxide gas. This concentrated carbon dioxide gas had a capture rate of 91.8% and a carbon dioxide mass concentration of 63%. Then, nitrogen in the decarbonized gas was adsorbed and separated using 5A molecular sieve at a constant pressure of 0.8 MPa for 70 s. After adsorption, the 5A molecular sieve with adsorbed nitrogen was desorbed and regenerated. The vacuum degree of the 5A molecular sieve desorption and regeneration was controlled at -58 kPa and the regeneration time was 38 s to obtain high-purity nitrogen with a purity of 99.96%, CO2 residue <0.1%, and nitrogen recovery rate of 94%.

[0039] Example 4 This embodiment provides a method for carbon dioxide capture coupled with nitrogen purification in low-temperature flue gas, including the following steps: First, low-temperature flue gas at 60℃ (with a CO2 mass concentration of 16%, an N2 mass concentration of 79%, and impurities of 5%) was pressurized to 0.6 MPa. Porous carbon was used to adsorb carbon dioxide from the low-temperature flue gas. After adsorption for 110 seconds, decarbonized gas (with a CO2 mass concentration ≤1.7%) was obtained. Then, the porous carbon containing adsorbed carbon dioxide was desorbed and regenerated. The vacuum degree during desorption and regeneration was controlled at -58 kPa, and the regeneration time was 27 seconds, yielding concentrated carbon dioxide gas. This concentrated carbon dioxide gas had a capture rate of 91.0% and a carbon dioxide mass concentration of 64%. Then, nitrogen in the decarbonized gas was adsorbed and separated using 13X molecular sieve under a constant pressure of 0.6 MPa. After an adsorption time of 75 s, the 13X molecular sieve with adsorbed nitrogen was desorbed and regenerated. The vacuum degree of the 13X molecular sieve desorption and regeneration was controlled at -57 kPa and the regeneration time was 37 s to obtain high-purity nitrogen with a purity of 99.97%, CO2 residue <0.1%, and nitrogen recovery rate of 95.5%.

[0040] Example 5 This embodiment provides a method for carbon dioxide capture coupled with nitrogen purification in low-temperature flue gas, including the following steps: First, low-temperature flue gas at 150℃ (with a CO2 mass concentration of 17%, an N2 mass concentration of 78%, and impurities of 5%) was pressurized to 0.9 MPa. Porous carbon was used to adsorb carbon dioxide from the low-temperature flue gas. After adsorption for 105 seconds, decarbonized gas (with a CO2 mass concentration ≤1.6%) was obtained. Then, the porous carbon containing adsorbed carbon dioxide was desorbed and regenerated. The vacuum degree during desorption and regeneration was controlled at -52 kPa, and the regeneration time was 29 seconds, yielding concentrated carbon dioxide gas. This concentrated carbon dioxide gas had a capture rate of 93.0% and a carbon dioxide mass concentration of 66%. Then, nitrogen in the decarbonized gas was adsorbed and separated using 5A molecular sieve at a constant pressure of 0.9 MPa for 70 s. After adsorption, the 5A molecular sieve with adsorbed nitrogen was desorbed and regenerated. The vacuum degree of the 5A molecular sieve desorption and regeneration was controlled at -59 kPa and the regeneration time was 36 s to obtain high-purity nitrogen with a purity of 99.99%, CO2 residue <0.1%, and nitrogen recovery rate of 97%.

[0041] Comparative Example 1 This comparative example provides a method for carbon dioxide capture coupled with nitrogen purification in low-temperature flue gas, including the following steps: First, low-temperature flue gas at 120℃ (with a CO2 mass concentration of 20%, an N2 mass concentration of 75%, and impurities of 5%) was pressurized to 0.1 MPa. Porous carbon was used to adsorb carbon dioxide from the low-temperature flue gas. After 100 seconds of adsorption, decarbonized gas (with a CO2 mass concentration of 3.5%) was obtained. Then, the porous carbon containing adsorbed carbon dioxide was desorbed and regenerated. The vacuum degree during desorption and regeneration was controlled at -60 kPa, and the regeneration time was 30 seconds, yielding concentrated carbon dioxide gas. This concentrated carbon dioxide gas had a capture rate of 78.0% and a carbon dioxide mass concentration of 55%. Then, nitrogen in the decarbonized gas was adsorbed and separated using 5A molecular sieve at a constant pressure of 0.1 MPa. After an adsorption time of 70 s, the 5A molecular sieve with adsorbed nitrogen was desorbed and regenerated. The vacuum degree of the 5A molecular sieve desorption and regeneration was controlled at -60 kPa and the regeneration time was 35 s to obtain high-purity nitrogen with a purity of 98.5%, CO2 residue of 0.5%, and a nitrogen recovery rate of 85%.

[0042] Comparative Example 2 This comparative example provides a method for carbon dioxide capture coupled with nitrogen purification in low-temperature flue gas, including the following steps: First, low-temperature flue gas at 120℃ (with a CO2 mass concentration of 20%, an N2 mass concentration of 75%, and impurities of 5%) was pressurized to 1.2 MPa. Porous carbon was used to adsorb the carbon dioxide from the low-temperature flue gas. After 100 seconds of adsorption, the CO2 mass concentration in the resulting decarbonized gas was 2.5%. Then, the porous carbon containing adsorbed carbon dioxide was desorbed and regenerated. The vacuum degree during desorption and regeneration was controlled at -30 kPa, and the regeneration time was 30 seconds, yielding a concentrated carbon dioxide gas with a capture rate of 82.0% and a carbon dioxide mass concentration of 58%. Then, nitrogen in the decarbonized gas was adsorbed and separated using 5A molecular sieve at a constant pressure of 1.2 MPa. After an adsorption time of 70 s, the 5A molecular sieve with adsorbed nitrogen was desorbed and regenerated. The vacuum degree of the 5A molecular sieve desorption and regeneration was controlled at -30 kPa and the regeneration time was 35 s to obtain high-purity nitrogen with a purity of 99.0%, CO2 residue of 0.3%, and a nitrogen recovery rate of 88%.

[0043] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0044] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for carbon dioxide capture coupled with nitrogen purification from low temperature flue gas, characterized in that, The method comprises the following steps: The low-temperature flue gas is pressurized and then subjected to first constant-pressure pressure swing adsorption treatment to obtain decarburization gas and carbon dioxide concentrated gas; The decarburization gas is subjected to second constant-pressure pressure swing adsorption treatment to obtain high-purity nitrogen gas.

2. The method of claim 1, wherein, The temperature of the low-temperature flue gas is 40-150 ℃. And / or, the mass concentration of CO2 in the low-temperature flue gas is ≥15%, and the mass concentration of N2 is ≥70%.

3. The method of claim 1, wherein, The mass concentration of carbon dioxide in the decarburization gas is ≤2%.

4. The method of claim 1, wherein, The first constant-pressure pressure swing adsorption treatment process is as follows: the pressurized low-temperature flue gas is first subjected to carbon dioxide adsorption on a porous carbon adsorbent under constant pressure, and then the porous carbon adsorbed with carbon dioxide is subjected to desorption regeneration under reduced pressure to release carbon dioxide concentrated gas. Optionally, the micropore ratio of the porous carbon adsorbent is > 95%, the specific surface area is > 1200 m 2 / g; wherein the micropore has a pore size < 2 nm; Optionally, the constant-pressure adsorption pressure during carbon dioxide adsorption is 0.2-1.0 MPa, and the adsorption time is 90-120 s.

5. The method of claim 4, wherein the method is characterized by, The vacuum degree during desorption regeneration of the porous carbon is -60 kPa to 0.1 MPa, and the regeneration time is ≤30 s. And / or, the mass concentration of carbon dioxide in the carbon dioxide concentrated gas released by desorption regeneration of the porous carbon is ≥60%, and the carbon dioxide concentrated gas is used as an activation medium for preparing a porous carbon carbon dioxide adsorbent.

6. The method of claim 1, wherein, The second constant-pressure pressure swing adsorption treatment process is as follows: the decarburization gas is first subjected to nitrogen adsorption on a molecular sieve under constant pressure, and then the molecular sieve adsorbed with nitrogen is subjected to desorption regeneration under reduced pressure to release nitrogen. Optionally, the molecular sieve is a 5A molecular sieve or a 13X molecular sieve, and the pore size of the molecular sieve is 0.4-0.8 nm. Optionally, the constant-pressure adsorption pressure during nitrogen adsorption is 0.2-1.0 MPa, and the adsorption time is 60-90 s.

7. The method of claim 6, wherein the method is characterized by, The vacuum degree during desorption regeneration of the molecular sieve is -60 kPa to 0.1 MPa, and the regeneration time is 30-45 s.

8. The method of claim 1, wherein, The purity of the high-purity nitrogen gas is ≥99.9%.