A carbon dioxide capture device and method

Abstract

The present disclosure relates to a device and method for capturing carbon dioxide, the device comprising a first-stage compressor comprising an air inlet and an air outlet in communication with a raw gas source; a first-stage membrane separation unit comprising an air inlet in communication with the first-stage compressor outlet, a first-stage retentate air outlet and a first-stage permeate air outlet; a second-stage compressor comprising an air inlet in communication with the first-stage membrane separation unit retentate outlet, and a second-stage compressor air outlet; a second-stage membrane separation unit comprising an air inlet in communication with the second-stage compressor outlet, a second-stage permeate air outlet and a second-stage retentate air outlet; a power generation device comprising an air inlet in communication with the second-stage retentate air outlet; and a pressure swing adsorption unit comprising an air inlet in communication with the first-stage permeate air outlet and the second-stage permeate air outlet, and a carbon dioxide product gas outlet. The device and method of the present disclosure can substantially reduce the cost of CO2 capture while ensuring that CO2 gas with a purity exceeding a preset threshold is obtained.

Description

Technical Field

[0001] The present disclosure relates to the technical field of carbon capture, and particularly to a carbon dioxide capture device and method. Background Art

[0002] Carbon dioxide (CO2) capture (transportation), utilization, and storage (the industry generally refers to it as CCUS) is a recognized carbon neutrality backup technology at home and abroad. Among them, carbon capture is the most important and costliest link, directly related to the success or failure of the entire CCUS industrial chain. From the perspective of combustion principles, regardless of what kind of hydrocarbon fuel is applied in what kind of occasion, basically air is introduced for combustion. Therefore, most of the flue gas after combustion is nitrogen (N2), with a proportion greater than 80%, and the proportion of carbon dioxide (CO2) is between 4% and 15%. It is a low-pressure and low-concentration carbon source, which is a technical difficulty in carbon capture in the industry.

[0003] Common carbon dioxide (CO2) capture methods or technologies in the industry include cryogenic distillation, chemical solvent absorption, physical solvent absorption, membrane separation, pressure swing adsorption, etc. Among them, ① cryogenic distillation is suitable for capturing high-concentration (CO2 content > 80%) carbon sources at medium and low pressures, ② physical solvent absorption is suitable for capturing medium and high-concentration (CO2 content > 30%) carbon sources at high pressures, and ③ chemical solvent absorption is the mainstream technology with the highest application maturity, especially suitable for capturing low-concentration (CO2 content < 20%) carbon sources at high pressures (pressure > 2.0 MPa), ④ pressure swing adsorption is suitable for capturing medium-concentration (CO2 content > 20%) carbon sources at medium pressures; ⑤ membrane separation is suitable for medium and low-concentration (CO2 content < 20%) at medium pressures. Therefore, for the limitation of low concentration, the available carbon capture technologies are chemical solvent absorption and membrane separation.

[0004] Membrane separation is to utilize the difference in the permeation rate of CO2 and other gas components in the membrane due to differences in molecular size, condensability, and reactivity under a certain pressure (difference) condition to achieve separation. It is a "coarse grain" carbon capture process with significant advantages such as low energy consumption, no solvent volatilization, small floor area, and insignificant magnification effect. When applied to low-concentration carbon source capture occasions, since multiple stages of membranes need to be set up to achieve product purity, and a booster pump needs to be configured in front of each stage of the membrane, which increases the cost input and energy consumption, and the economy is not optimistic when applied alone.

[0005] Currently, when the flue gas carbon capture methods and technologies are applied alone, there are problems of high operating energy consumption and cost, poor economy, and it is difficult to popularize and promote. Summary of the Invention

[0006] The following is an overview of the subject matter described in detail in this article. This overview is not intended to limit the scope of protection of the claims.

[0007] This disclosure provides a carbon dioxide capture device, the device comprising:

[0008] A primary compressor, including an inlet and an outlet connected to the raw material gas source;

[0009] A membrane separation unit includes an air inlet connected to the outlet of a primary compressor, a permeate gas outlet, and a permeate gas outlet.

[0010] The secondary compressor includes an inlet connected to the permeate outlet of the primary membrane separation unit and an outlet of the secondary compressor.

[0011] The two-stage membrane separation unit includes an air inlet connected to the outlet of the secondary compressor, a two-stage permeate gas outlet, and a two-stage residual permeate gas outlet.

[0012] The power generation unit includes an air inlet connected to the outlet of the second-stage residual gas; and,

[0013] The pressure swing adsorption unit includes an inlet connected to a first-stage permeate gas outlet and a second-stage permeate gas outlet, and a carbon dioxide product gas outlet.

[0014] In one exemplary embodiment provided in this disclosure, the pressure swing adsorption unit includes a first adsorption tower and a second adsorption tower. The first adsorption tower and the second adsorption tower are configured such that when the first adsorption tower adsorbs carbon dioxide, the carbon dioxide in the second adsorption tower is desorbed and output as product gas, and when the second adsorption tower adsorbs carbon dioxide, the carbon dioxide in the first adsorption tower is desorbed and output as product gas.

[0015] In one exemplary embodiment provided in this disclosure, the first adsorption tower and the second adsorption tower are referred to as a set of adsorption towers, and the pressure swing adsorption unit includes two or more sets of adsorption towers.

[0016] In one exemplary embodiment provided in this disclosure, the first adsorption tower and the second adsorption tower are provided with packing material, and the packing material in the first adsorption tower and the second adsorption tower are each independently selected from any one or more of activated carbon and silica gel.

[0017] In one exemplary embodiment provided in this disclosure, the activated carbon has a particle size of 1.8 mm to 5 mm; optionally, the silica gel has a particle size of 2 mm to 5 mm.

[0018] In one exemplary embodiment provided in this disclosure, the first adsorption tower is filled with activated carbon and silica gel from bottom to top, and the volume ratio of the activated carbon to the silica gel is (3 to 4):(6 to 7).

[0019] In one exemplary embodiment provided in this disclosure, the second adsorption tower is filled with activated carbon and silica gel from bottom to top, and the volume ratio of the activated carbon to the silica gel is (3 to 4):(6 to 7).

[0020] In one exemplary embodiment provided in this disclosure, the first adsorption tower is filled with alumina, activated carbon and silica gel in sequence from bottom to top, wherein the alumina is present in a very small amount and the volume ratio of alumina to activated carbon can be (0.001 to 0.5):(3 to 4); the second adsorption tower is filled with alumina, activated carbon and silica gel in sequence from bottom to top, wherein the alumina is present in a very small amount and the volume ratio of alumina to activated carbon is (0.001 to 0.5):(3 to 4).

[0021] In one exemplary embodiment provided in this disclosure, the silicone is a microporous silicone.

[0022] In another aspect, this disclosure provides a carbon dioxide replenishment method using the above-described apparatus, the method comprising:

[0023] The raw material gas is compressed by the first-stage compressor and then transported to the first-stage membrane separation unit for CO2 enrichment to obtain a first-stage permeate gas rich in CO2 components and a first-stage residual gas leaning in CO2 components.

[0024] The first-stage permeate gas is compressed by the second-stage compressor, and the compressed first-stage permeate gas is sent to the second-stage membrane separation unit for CO2 enrichment, resulting in a first-stage permeate gas rich in CO2 components and a second-stage permeate gas poor in CO2 components.

[0025] The second-stage permeate gas and the first-stage permeate gas enter the pressure swing adsorption unit, and CO2 product gas with a purity exceeding a set threshold is obtained through the pressure swing adsorption unit.

[0026] The residual gas from the second stage enters the power generation unit to recover pressure energy before being discharged.

[0027] In one exemplary embodiment provided in this disclosure, the threshold is 95 vol.% or higher.

[0028] In one exemplary embodiment provided in this disclosure, the raw gas is purified flue gas after cooling and removal of impurities, and the CO2 content in the raw gas is 6 vol.% to 15 vol.%, and the nitrogen content in the raw gas is 80 vol.% to 93 vol.%.

[0029] In one exemplary embodiment provided in this disclosure, the first-stage permeate gas and the second-stage permeate gas enter the pressure swing adsorption unit to continuously output CO2 product gas, including the following steps:

[0030] 1) The first-stage permeate gas and the second-stage permeate gas enter the first adsorption tower to adsorb CO2, and the adsorption of CO2 in the first adsorption tower is completed;

[0031] 2) The first-stage permeate gas and the second-stage permeate gas enter the second adsorption tower to adsorb CO2, and the adsorption of CO2 in the second adsorption tower is completed; at the same time, the first adsorption tower desorbs CO2 under reduced pressure and outputs it as product gas.

[0032] 3) The two-stage permeate gas and the first-stage permeate gas enter the first adsorption tower to adsorb CO2, and the adsorption of CO2 in the first adsorption tower is completed; at the same time, the second adsorption tower desorbs CO2 under reduced pressure and outputs it as product gas.

[0033] Repeating steps 2) and 3) ensures a continuous output of product gas.

[0034] Compared with the prior art, the technical solutions provided in this disclosure have at least some or all of the following advantages:

[0035] The technical solution provided in this disclosure combines a first-stage membrane separation unit, a second-stage membrane separation unit, a pressure swing adsorption unit, and a power generation device, which can significantly reduce the cost of carbon dioxide capture (250 yuan / ton to 350 yuan / ton) while ensuring that CO2 product gas with a purity exceeding a preset threshold is obtained.

[0036] Other features and advantages of this disclosure will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the disclosure. Other advantages of this disclosure may be realized and obtained by means of the methods described in the specification. Attached Figure Description

[0037] The accompanying drawings are used to provide an understanding of the technical solutions of this disclosure and form part of the specification. They are used together with the embodiments of this disclosure to explain the technical solutions of this disclosure and do not constitute a limitation on the technical solutions of this disclosure.

[0038] Figure 1 A schematic diagram illustrating the process flow of a carbon dioxide capture apparatus according to an embodiment of the present disclosure is shown.

[0039] Figure reference numerals: 1. Feed gas; 2. First-stage compressor; 3. First-stage membrane separation unit; 31. First-stage permeate gas; 32. First-stage residual permeate gas; 4. Second-stage compressor; 5. Second-stage membrane separation unit; 51. Second-stage permeate gas; 52. Second-stage residual permeate gas; 6. Pressure swing adsorption unit; 7. Power generation unit. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this disclosure clearer, the embodiments of this disclosure are described in detail below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be arbitrarily combined with each other.

[0041] This disclosure provides a carbon dioxide capture device, the device comprising:

[0042] A primary compressor, including an inlet and an outlet connected to the raw material gas source;

[0043] A membrane separation unit includes an air inlet connected to the outlet of a primary compressor, a permeate gas outlet, and a permeate gas outlet.

[0044] The secondary compressor includes an inlet connected to the permeate outlet of the primary membrane separation unit and an outlet of the secondary compressor.

[0045] The two-stage membrane separation unit includes an air inlet connected to the outlet of the second-stage compressor, a second-stage permeate gas outlet, and a second-stage residual permeate gas outlet.

[0046] The power generation unit includes an air inlet connected to the outlet of the second stage residual gas;

[0047] The pressure swing adsorption unit includes an inlet connected to a first-stage permeate gas outlet and a second-stage permeate gas outlet, and a carbon dioxide product gas outlet.

[0048] In some exemplary embodiments, a first-stage membrane separation unit and a second-stage membrane separation unit utilize the principle that different gas components have different permeation properties in membrane materials and membrane modules to perform gas separation.

[0049] In some exemplary embodiments, the power generation device is a turbine power generation device, which can recover most of the pressure energy of the secondary percolating gas and reduce the overall energy consumption of the device.

[0050] In some exemplary embodiments, the pressure swing adsorption unit includes a first adsorption tower and a second adsorption tower, wherein the first adsorption tower and the second adsorption tower are configured such that when the first adsorption tower adsorbs carbon dioxide, the carbon dioxide in the second adsorption tower is desorbed and output as product gas, and when the second adsorption tower adsorbs carbon dioxide, the carbon dioxide in the first adsorption tower is desorbed and output as product gas.

[0051] In some exemplary embodiments, the first adsorption tower and the second adsorption tower are referred to as a set of adsorption towers, and the pressure swing adsorption unit includes two or more sets of adsorption towers.

[0052] In some exemplary embodiments, the first adsorption tower and the second adsorption tower are provided with packing material, and the packing material in the first adsorption tower and the second adsorption tower is independently selected from any one or more of activated carbon and silica gel.

[0053] In some exemplary embodiments, the activated carbon has a particle size of 1.8 mm to 5 mm; optionally, the silica gel has a particle size of 2 mm to 5 mm.

[0054] In some exemplary embodiments, the first adsorption tower is filled with activated carbon and silica gel from bottom to top, and the volume ratio of the activated carbon to the silica gel is (3 to 4):(6 to 7).

[0055] In some exemplary embodiments, the first adsorption tower is filled with activated carbon and silica gel from bottom to top, and the volume ratio of the activated carbon to the silica gel is (3 to 4):(6 to 7).

[0056] In some exemplary embodiments, the first adsorption tower is filled with alumina, activated carbon and silica gel in sequence from bottom to top, wherein the alumina is present in a very small amount and the ratio of alumina to activated carbon can be (0.001 to 0.01):(3 to 4); the second adsorption tower is filled with alumina, activated carbon and silica gel in sequence from bottom to top, wherein the alumina is present in a very small amount and the ratio of alumina to activated carbon can be (0.001 to 0.01):(3 to 4).

[0057] In some exemplary embodiments, the silicone is a microporous silicone.

[0058] In another aspect, this disclosure provides a carbon dioxide replenishment method using the above-described apparatus, the method comprising:

[0059] The raw material gas is compressed by the first-stage compressor and then transported to the first-stage membrane separation unit for CO2 enrichment to obtain a first-stage permeate gas rich in CO2 components and a first-stage residual gas leaning in CO2 components.

[0060] The first-stage permeate gas is compressed by the second-stage compressor, and the compressed first-stage permeate gas is sent to the second-stage membrane separation unit for CO2 enrichment, resulting in a first-stage permeate gas rich in CO2 components and a second-stage permeate gas poor in CO2 components.

[0061] The second-stage permeate gas and the first-stage permeate gas enter the pressure swing adsorption unit, and CO2 product gas with a purity exceeding a set threshold is obtained through the pressure swing adsorption unit.

[0062] The residual gas from the second stage enters the power generation unit to recover pressure energy before being discharged.

[0063] In one exemplary embodiment provided in this disclosure, the threshold is 95 vol.% or higher.

[0064] In one exemplary embodiment provided in this disclosure, the gas after CO2 adsorption by the adsorption tower is discharged, wherein the CO2 content is less than 0.8 vol.%, and is referred to as decarbonized purified gas.

[0065] In one exemplary embodiment provided in this disclosure, the raw gas is purified flue gas after cooling and removal of impurities, and the CO2 content in the raw gas is 6 vol.% to 15 vol.%, and the nitrogen content in the raw gas is 80 vol.% to 93 vol.%.

[0066] In one exemplary embodiment provided in this disclosure, the first-stage permeate gas and the second-stage permeate gas enter the pressure swing adsorption unit to continuously output CO2 product gas, including the following steps:

[0067] 1) The first-stage permeate gas and the second-stage permeate gas enter the first adsorption tower to adsorb CO2, and the adsorption of CO2 in the first adsorption tower is completed;

[0068] 2) The first-stage permeate gas and the second-stage permeate gas enter the second adsorption tower to adsorb CO2, and the adsorption of CO2 in the second adsorption tower is completed; at the same time, the first adsorption tower desorbs CO2 under reduced pressure and outputs it as product gas.

[0069] 3) The two-stage permeate gas and the first-stage permeate gas enter the first adsorption tower to adsorb CO2, and the adsorption of CO2 in the first adsorption tower is completed; at the same time, the second adsorption tower desorbs CO2 under reduced pressure and outputs it as product gas.

[0070] Repeating steps 2) and 3) ensures a continuous output of product gas.

[0071] In some exemplary embodiments, the second-stage permeate gas is delivered to a power generation device for generating electricity and recovering pressure energy.

[0072] In some exemplary embodiments, the pressure swing adsorption unit employs a single-stage decarbonization process. The mixed gas enters the adsorption tower from the bottom for adsorption, where components such as CO2, sulfides, and water are adsorbed. At the bottom of the adsorption tower, a vacuum method is used to enrich the CO2 product gas with a purity greater than 95%.

[0073] In some exemplary embodiments, CO2 product gas can be continuously output by setting up larger adsorption towers and more packing material, using only two or more adsorption towers for alternating adsorption and desorption. Setting up more adsorption towers can better utilize pressure and reduce the amount of adsorbent to be loaded at one time, thereby reducing the initial investment cost.

[0074] In some exemplary embodiments, the pressure swing adsorption unit employs a single-stage decarbonization process. The mixed gas enters the adsorption tower from the bottom for adsorption, where components such as CO2, sulfides, and water are adsorbed. At the bottom of the adsorption tower, a vacuum method is used to enrich the CO2 product gas with a purity greater than 95%.

[0075] Example 1:

[0076] The flue gas feedstock is pretreated (heat exchange and cooling, impurity removal). Its gas composition and operating conditions (absolute pressure) are as follows: Feedstock gas processing capacity: 5 × 10⁻⁶ 4 Nm 3 / h, raw material gas pressure: 0.15MPa, raw material gas temperature: 30℃, product CO2 purity: ≥95%, raw material gas composition: CO2 content 6 vol.% to 12%, N2 content 85 vol.% to 91 vol.% and the balance is NO2 content.

[0077] See Figure 1 After being compressed in the primary compressor (1.8 MPa, 40℃), the compressed gas first enters a membrane separation unit (CO2 / N2 separation coefficient of 20). Utilizing the permeation properties of different components in the membrane material and membrane module, it is separated into a first-stage permeate gas relatively rich in CO2 (CO2 content 42.7%, N2 content 47.6%, flow rate 10842 m³ / h). 3 / h), and a section of residual gas with relatively low CO2 content (CO2 content 3.51%, N2 content 95.35%, flow rate 39158m³ / h). 3 / h). Subsequently, a section of permeate gas goes directly to the subsequent pressure swing adsorption unit. The first section of permeate gas, after passing through a two-stage compressor (1.7 MPa, 40℃), is input into the second-stage membrane (CO2 / N2 separation coefficient of 20), producing a second section of permeate gas after permeation separation (CO2 content 15.70%, N2 content 79.5%, flow rate 6837 m³ / h). 3 / h) and second-stage permeate gas (CO2 content 0.92%, N2 content 98.7%, flow rate 32320m³ / h) 3 / h). The second-stage permeate gas passes through a turbine connected to a power generation unit (reducing the pressure from 1.6MPa to atmospheric pressure), recovering most of the pressure energy (recovery rate 80%, recoverable energy consumption approximately 5000KW / h, reducing the overall energy consumption of the unit). The second-stage permeate gas mixes with the first-stage permeate gas output from the first-stage membrane to form a mixed gas (CO2 content 32.4%, N2 content 59.9%, flow rate 17680m³ / h). 3 / h) It goes to the pressure swing adsorption unit for the next concentration process.

[0078] The pressure swing adsorption (PSA) unit employs a single-stage carbon removal process. PSA is a dynamic process, and the time-series flow is described in detail below. The PSA unit consists of eight adsorption towers, which are sequentially filled from bottom to top with alumina, activated carbon, and fine-porous silica gel. The volume ratio of alumina, activated carbon, and silica gel is 0.1:2.0:7.5. ≥98.5% CO2 product gas is obtained from the bottom of the adsorption tower.

[0079] Pressure swing adsorption (PSA) can be performed using eight adsorption towers according to Example 2 of Chinese Patent 201811067331.1.

[0080] Example 1 ultimately yielded a continuous CO2 product gas with a purity exceeding 98.5%, a CO2 recovery rate exceeding 80%, and a process recovery operating cost of 250 to 300 yuan / ton, significantly lower than the cost of existing flue gas CO2 capture methods (400 yuan / ton). Furthermore, if the pressure swing adsorption unit is placed between the first-stage and second-stage membrane separation units, under the same conditions, the cost of the flue gas CO2 capture method in the comparative example is approximately 400 to 450 yuan / ton.

[0081] The carbon dioxide capture device and method disclosed herein overcome the shortcomings of high operating energy consumption and cost of conventional solvent absorption methods for capturing / separating carbon sources from flue gas. It integrates the advantages of membrane and pressure swing adsorption gas separation technologies, combining the two to reduce the operating energy consumption and cost of the carbon capture process.

Claims

1. A carbon dioxide capture device, characterized in that, The trapping device includes: A primary compressor, including an inlet and an outlet connected to the raw material gas source; A membrane separation unit includes an air inlet connected to the outlet of a primary compressor, a permeate gas outlet, and a permeate gas outlet. The secondary compressor includes an inlet connected to the permeate outlet of the primary membrane separation unit and an outlet of the secondary compressor. The two-stage membrane separation unit includes an air inlet connected to the outlet of the secondary compressor, a two-stage permeate gas outlet, and a two-stage residual permeate gas outlet. The power generation unit includes an air inlet connected to the outlet of the second-stage residual gas; and, The pressure swing adsorption unit includes an inlet connected to a first-stage permeate gas outlet and a second-stage permeate gas outlet, and a carbon dioxide product gas outlet. The raw material gas is purified flue gas after cooling and removing impurities, and the CO2 content in the raw material gas is 6 vol.% to 15 vol.%.

2. The collection device according to claim 1, characterized in that, The pressure swing adsorption unit includes a first adsorption tower and a second adsorption tower. The first adsorption tower and the second adsorption tower are configured such that when the first adsorption tower adsorbs carbon dioxide, the carbon dioxide in the second adsorption tower is desorbed and output as product gas, and when the second adsorption tower adsorbs carbon dioxide, the carbon dioxide in the first adsorption tower is desorbed and output as product gas.

3. The collection device according to claim 2, characterized in that, The first adsorption tower and the second adsorption tower are referred to as a set of adsorption towers, and the pressure swing adsorption unit includes two or more sets of adsorption towers.

4. The collection device according to claim 2 or 3, characterized in that, The first adsorption tower and the second adsorption tower are equipped with packing materials, and the packing materials in the first adsorption tower and the second adsorption tower are each independently selected from any one or more of activated carbon and silica gel.

5. The collection device according to claim 4, characterized in that, The activated carbon has a particle size of 1.8 mm to 5 mm; the silica gel has a particle size of 2 mm to 5 mm.

6. The collection device according to claim 4, characterized in that, The first adsorption tower is filled with activated carbon and silica gel from bottom to top, and the volume ratio of the activated carbon to the silica gel is 3 to 4: 6 to 7. The second adsorption tower is filled with activated carbon and silica gel from bottom to top, with the volume ratio of activated carbon to silica gel being 3 to 4:6 to 7.

7. A method for capturing carbon dioxide, characterized in that, The method, using the collection device according to any one of claims 2 to 6, comprises: The raw material gas is compressed by the first-stage compressor and then transported to the first-stage membrane separation unit for CO2 enrichment to obtain a first-stage permeate gas rich in CO2 components and a first-stage residual gas leaning in CO2 components. The first-stage permeate gas is compressed by the second-stage compressor, and the compressed first-stage permeate gas is sent to the second-stage membrane separation unit for CO2 enrichment, resulting in a first-stage permeate gas rich in CO2 components and a second-stage permeate gas poor in CO2 components. The second-stage permeate gas and the first-stage permeate gas enter the pressure swing adsorption unit, and CO2 product gas with a purity exceeding a set threshold is obtained through the pressure swing adsorption unit. The residual gas from the second stage enters the power generation unit to recover pressure energy before being discharged. The threshold is 95 vol.% or higher; The raw material gas is purified flue gas after cooling and removing impurities, and the CO2 content in the raw material gas is 6 vol.% to 15 vol.%.

8. The method according to claim 7, characterized in that, The nitrogen content in the raw gas is 80 vol.% to 93 vol.%.

9. The method according to claim 7 or 8, characterized in that, The primary compressor compresses the raw material gas to 30°C to 55°C and 1.5MPa to 2.0MPa. The secondary compressor compresses the first-stage permeate gas to 40°C and 1.7 MPa; The CO2 / N2 separation coefficient of the membrane separation unit is 20; The CO2 / N2 separation coefficient of the two-stage membrane separation unit is 20.

10. The method according to claim 7 or 8, characterized in that, The first-stage permeate gas and the second-stage permeate gas enter the pressure swing adsorption unit, continuously outputting CO2 product gas, including the following steps: 1) The first-stage permeate gas and the second-stage permeate gas enter the first adsorption tower to adsorb CO2, and the adsorption of CO2 in the first adsorption tower is completed; 2) The first-stage permeate gas and the second-stage permeate gas enter the second adsorption tower to adsorb CO2, and the CO2 adsorption in the second adsorption tower is completed; at the same time, the first adsorption tower desorbs CO2 under reduced pressure and outputs it as product gas. 3) The two-stage permeate gas and the first-stage permeate gas enter the first adsorption tower to adsorb CO2, and the adsorption of CO2 in the first adsorption tower is completed; at the same time, the second adsorption tower desorbs CO2 under reduced pressure and outputs it as product gas. Repeating steps 2) and 3) ensures a continuous output of product gas.

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