Method for capturing CO2 by utilizing modified gasification device

Abstract

The invention provides a method for capturing CO2 by using a modified gasification device, and relates to the technical field of CO2 capturing, and the method comprises the following steps: (a) introducing synthesis gas into a raw material gas desulfurization tower for desulfurization treatment, and then feeding into a CO conversion part for conversion reaction, so that CO is converted into CO2 and H2, and converted gas is obtained; (b) introducing the shift gas into a shift gas desulfurization tower to remove H2S, then feeding the shift gas into a CO2 removal tower to be in countercurrent contact with a lean solvent at the bottom of a solvent regeneration tower in the tower, removing CO2 from the tower top, then feeding the shift gas into a PSA unit, and feeding the solvent at the bottom of the tower into a solvent stripping tower; and (c) compressing CO2 gas at the top of the solvent regeneration tower through a compressor, feeding the compressed CO2 gas into a dehydration unit for dehydration, returning the compressed CO2 gas to the compressor for pressurization, and outputting the pressurized CO2 as a product. According to the invention, CO2 emission of the whole plant can be reduced, liquid CO2 production can be carried out, and the technical effect of effectively capturing CO2 by using the existing gasification device is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of CO2 capture, and in particular to a method for capturing CO2 by utilizing a modified gasification device. Background Art

[0002] As the world actively responds to climate change and strives to achieve its goals, carbon capture, utilization, and storage (CCUS) technology is gaining attention as a key carbon reduction strategy. CCUS technology aims to capture carbon dioxide (CO2) emitted from industrial processes and, through specific methods, utilize or store it deep underground, effectively reducing its concentration in the atmosphere.

[0003] Refineries equipped with gasification units, facing high natural gas prices and a no-carbon tax policy, are using liquid asphalt gasification to process asphalt residue to produce high-value syngas. While some hydrogen is recovered in the PSA unit for use in hydrogenation units, the vast majority is used upstream as fuel gas. However, compared to natural gas, syngas produces approximately three times the CO2 emissions of purchased natural gas for the same calorific value. With the gradual implementation of carbon tax policies, environmental and economic pressures on refineries are increasing.

[0004] On the one hand, CO2 capture systems are primarily categorized into pre-combustion capture, post-combustion capture, oxyfuel combustion, chemical looping combustion, and direct air capture, depending on how they are integrated with the energy system. On the other hand, CO2 capture methods, such as absorption, adsorption, membrane separation, and cryogenic fractionation, are primarily categorized based on the specific technical means and separation principles used in the process.

[0005] In summary, there is an urgent need for a method to capture CO2 using existing equipment to reduce emissions.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for capturing CO2 by modifying a gasification device, using an existing gasification device to capture CO2. By modifying the gasification device and adding a CO2 capture system, not only can the CO2 emissions of the entire plant be reduced, but also liquid CO2 production can be achieved.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0009] A method for capturing CO2 by modifying a gasification device comprises the following steps:

[0010] (a) The synthesis gas is passed into a raw gas desulfurization tower for desulfurization treatment, and then sent to a CO shift unit for a shift reaction, converting CO into CO2 and H2 to obtain shift gas;

[0011] (b) the shift gas is passed into a shift gas desulfurization tower to remove H2S, and then sent to a CO2 removal tower to countercurrently contact with the lean solvent at the bottom of the solvent regeneration tower in the tower, and the CO2 is removed from the top of the tower before entering the PSA unit, and the solvent at the bottom of the tower enters the solvent stripping tower;

[0012] (c) The CO2 gas at the top of the solvent regeneration tower is compressed by a compressor, sent to a dehydration unit to remove water, and then returned to the compressor for pressurization. The pressurized CO2 is then exported as a product.

[0013] Furthermore, the rich solvent from the bottom of the raw gas desulfurization tower enters the solvent stripping tower after heat exchange, the acid gas from the top of the tower is sent to the sulfur device, and the lean solvent from the bottom of the tower is sent to the CO2 removal tower.

[0014] Furthermore, the rich solvent at the bottom of the CO2 removal tower enters the solvent regeneration tower after throttling and heat exchange, and the lean solvent at the bottom of the tower is sent to the CO2 removal tower.

[0015] Furthermore, in step (a), the absorbent used in the raw gas desulfurization tower includes at least one of N-methyldiethanolamine, diethanolamine and ethanolamine;

[0016] Preferably, the synthesis gas is passed through a raw gas desulfurization tower to remove H2S to below 300 ppm.

[0017] Furthermore, in step (b), the shift gas desulfurization tower removes H2S by solid adsorption;

[0018] Preferably, the shift gas is passed through a shift gas desulfurization tower to remove H2S to below 0.1ppm to 5ppm.

[0019] Furthermore, the absorbent used in the CO2 removal tower includes at least one of N-methyldiethanolamine, diethanolamine and ethanolamine.

[0020] Furthermore, the temperature of the primary shift reaction in the shift reaction is 200°C-260°C;

[0021] Preferably, the temperature of the secondary shift reaction in the shift reaction is 200°C-260°C;

[0022] Preferably, the temperature of the tertiary shift reaction in the shift reaction is 200°C-240°C.

[0023] Furthermore, in step (c), an air cooler is provided between stages of the compressor.

[0024] Furthermore, in step (c), the method of removing water includes removing water through molecular sieves and drying;

[0025] The molecular sieve includes 3A / 4A molecular sieve.

[0026] Furthermore, the drying adopts a double-tower process;

[0027] The operating method of the double-tower process includes:

[0028] While one tower is performing adsorption operation, the other tower is performing regeneration and cooling operation.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects:

[0030] The method for capturing CO2 by utilizing the modified gasification device provided by the present invention utilizes the existing gasification device to capture CO2. By modifying the gasification device and adding a CO2 capture system, not only can the CO2 emissions of the entire plant be reduced, but also liquid CO2 production can be carried out. In short, the method of the present invention can achieve a higher CO2 recovery rate, higher CO2 purity and lower H2S content while effectively reducing CO2 emissions through the coordinated cooperation of various steps, and can meet the raw material requirements of various downstream application devices, thereby achieving the technical effect of effectively capturing CO2 by utilizing the existing gasification device. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 A schematic flow chart of a method for capturing CO2 using a modified gasification device provided in one embodiment of the present invention.

[0033] Icons: 1-Feed gas desulfurization tower; 2-Solvent stripping tower; 3-First-stage shift reactor; 4-Second-stage shift reactor; 5-Third-stage shift reactor; 6-Shift gas desulfurization tower; 7-CO2 removal tower; 8-Solvent regeneration tower; 9-CO2 compressor; 10-CO2 molecular sieve dehydration tower; 11-PSA unit; 12-Feed gas inlet and outlet heat exchanger; 13-Solvent stripping tower top air cooler; 14-Solvent stripping tower top water cooler; 15-Solvent stripping tower top reflux tank; 16-Solvent stripping tower top reflux pump; 17-Solvent stripping tower bottom reboiler; 18-Solvent stripping tower bottom pump; 19-Solvent stripping tower feed heat exchanger; 20-Shift gas feed / third-stage shift gas heat exchanger; 21-Shift gas gas-liquid separation tank; 22 - bottom pump of conversion gas gas-liquid separation tank; 23- first-stage conversion reactor inlet and outlet heat exchanger; 24- first-stage conversion gas spray tower; 25- second-stage conversion gas spray tower; 26- third-stage conversion gas / deoxygenated water heat exchanger; 27- third-stage conversion gas air cooler; 28- third-stage conversion gas separator tank; 29- third-stage conversion gas separator tank bottom pump; 30- deoxygenated water booster pump; 31- CO2 removal tower bottom pump; 32- solvent regeneration tower inlet and outlet heat exchanger; 33- solvent regeneration tower bottom pump; 34- solvent regeneration tower bottom reboiler; 35- solvent regeneration tower top air cooler; 36- solvent regeneration tower top water cooler; 37- solvent regeneration tower top reflux tank; 38- solvent regeneration tower top reflux pump; 39- CO2 product air cooler; 40- lean solvent cooler. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] The present invention provides a method for capturing CO2 by modifying a gasification device, comprising the following steps:

[0036] (a) The synthesis gas is passed into a raw gas desulfurization tower for desulfurization treatment, and then sent to a CO shift unit for a shift reaction, converting CO into CO2 and H2 to obtain shift gas;

[0037] (b) The resulting shift gas is passed into a shift gas desulfurization tower to remove H2S, and then sent to a CO2 removal tower to countercurrently contact with the lean solvent at the bottom of the solvent regeneration tower. After CO2 is removed from the top of the tower, it enters the PSA unit, and the solvent at the bottom of the tower enters the solvent stripping tower;

[0038] (c) The CO2 gas at the top of the solvent regeneration tower is compressed by a compressor and sent to a dehydration unit to remove water. The gas is then returned to the compressor for pressurization, and the pressurized CO2 is then exported as a product.

[0039] Through the coordinated cooperation of various steps, the method of the present invention can achieve a higher CO2 recovery rate, higher CO2 purity and lower H2S content while effectively reducing CO2 emissions. It can meet the raw material requirements of various downstream application devices and achieve the technical effect of effectively capturing CO2 using existing gasification equipment.

[0040] In a preferred embodiment, the rich solvent from the bottom of the raw gas desulfurization tower can enter the solvent stripping tower after heat exchange, the acid gas from the top of the tower can be sent to the sulfur device, and the lean solvent from the bottom of the tower can be sent to the CO2 removal tower.

[0041] In a preferred embodiment, the rich solvent at the bottom of the CO2 removal tower can enter the solvent regeneration tower after throttling and heat exchange, and the lean solvent at the bottom of the tower can be sent to the CO2 removal tower.

[0042] A typical method for capturing CO2 by modifying a gasification unit is shown in the schematic diagram. Figure 1 The process consists of units for raw gas desulfurization, solvent regeneration, CO shift, shift gas desulfurization, CO2 removal, CO2 dehydration, and CO2 compression, including the following steps:

[0043] Raw gas desulfurization: The synthesis gas from the gasification unit enters the raw gas desulfurization tower 1 for desulfurization treatment, and the desulfurized gas is then sent to the CO conversion part;

[0044] It should be noted that the synthesis gas of the gasification unit is mainly H2 (hydrogen) and CO (carbon monoxide), containing a certain amount of CO2 (carbon dioxide) and H2S (hydrogen sulfide). The specific composition is 30%-40% hydrogen, 40%-50% carbon monoxide, 1%-5% carbon dioxide and 0.5%-2% hydrogen sulfide.

[0045] Solvent stripping: The rich solvent from the bottom of the raw gas desulfurization tower enters the solvent stripping tower 2 after heat exchange, the acid gas at the top of the tower is sent to the sulfur device, and the lean solvent at the bottom of the tower is sent to the CO2 removal tower 7;

[0046] CO shift: After desulfurization, the gas is heat exchanged, washed, and separated, and then mixed with high-pressure steam to undergo a low-temperature shift reaction to convert CO into CO2 and H2 to obtain shift gas;

[0047] The obtained shift gas is sent to the shift gas desulfurization part after cooling and liquid separation;

[0048] Shift gas desulfurization: The shift gas is passed into the shift gas desulfurization tower 6 to remove a small amount of H2S in the shift gas to obtain desulfurized shift gas;

[0049] CO2 removal: The desulfurized shift gas is passed into the CO2 removal tower 7 and countercurrently contacts with the lean solvent from the bottom of the solvent regeneration tower 8. After CO2 is removed from the top of the tower, it enters the PSA unit 11, and the solvent at the bottom of the tower enters the solvent stripping tower 2;

[0050] Solvent regeneration: The rich solvent at the bottom of the CO2 removal tower is sent to the solvent regeneration tower 8 after throttling and heat exchange, and the lean solvent at the bottom of the tower is sent to the CO2 removal tower 7;

[0051] CO2 compression: The CO2 gas from the top of the solvent regeneration tower 8 is compressed by the CO2 compressor 9 and sent to the dehydration unit to remove a small amount of water. The dehydrated CO2 is then returned to the CO2 compressor for pressurization to reach the output pressure of the CO2;

[0052] CO2 dehydration: The pressurized CO2 enters the dehydration unit and is dried by molecular sieves.

[0053] In a preferred embodiment, for raw gas desulfurization and CO2 removal, considering the large scale of the device, a mature and reliable organic amine absorption method can be used, and the absorbent can be selected from N-methyldiethanolamine (MDEA), diethanolamine (DEA), ethanolamine (MEA) and other compound solvents; for conversion gas desulfurization, a solid adsorption method can be used.

[0054] In a preferred embodiment, in order to meet the CO shift feedstock requirements, H2S in the synthesis gas can be removed to below 300 ppm; in order to meet the sulfur content requirements of the subsequent CO2 product, H2S in the shift gas can be removed to below 0.1 ppm to 5 ppm.

[0055] In a preferred embodiment, a three-stage low-temperature shift reaction can be set to convert CO into CO2 and H2. Specifically, the synthesis gas is first mixed with high-pressure steam, and then heat-exchanged with the shift reaction gas from the first-stage shift reaction to reach the temperature requirement of the first-stage shift reaction (200°C-260°C). The outlet temperature of the first-stage shift reactor 3 is raised to 400°C-450°C, and heat-exchanged with the feed of the first-stage shift reaction. Then, the gas enters the bottom of the first-stage shift gas spray tower 24, and the gas from the shift reaction gas separator tank and the gas after the shift reaction is sprayed into the top of the tower. The hot condensate is supplemented with a portion of high-pressure steam from the system in the middle of the tower; after the temperature of the first-stage conversion gas is cooled to 200℃-260℃, it enters the second-stage conversion reactor 4, and the gas at the outlet of the second-stage conversion reactor 4 is heated to 300℃-350℃, and is cooled through the second-stage conversion gas spray tower 25. After the second-stage conversion reaction gas is cooled to 200℃-240℃, it enters the third-stage conversion reactor 5, and the reaction product at the outlet of the third-stage conversion reactor 5 is heat exchanged and cooled to room temperature, and then gas-liquid separation is carried out in the conversion gas liquid separator.

[0056] In a preferred embodiment, the CO2 gas can be compressed according to the gas source pressure step, and an air cooler can be set between the compressor stages to help remove excess compression heat in the compression process in a timely manner and save compression energy consumption.

[0057] In a preferred embodiment, the CO2 dehydration method can select a suitable technology according to the water dew point requirement, for example, a 3A / 4A molecular sieve adsorption dehydration process can be selected, and a double-tower process can be adopted.

[0058] In the present invention, the operating method of the double-tower process includes:

[0059] While one tower is performing adsorption operation, the other tower is performing regeneration and cooling operation.

[0060] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples were prepared according to existing methods or directly purchased from the market.

[0061] Example 1

[0062] A method for capturing CO2 by modifying a gasification device, wherein the process comprises units of raw gas desulfurization, solvent regeneration, CO shift, shift gas desulfurization, CO2 removal, CO2 dehydration, and CO2 compression, including the following steps:

[0063] Raw gas desulfurization: The synthesis gas from the gasification unit enters the raw gas desulfurization tower 1 for desulfurization treatment, and the desulfurized gas is then sent to the CO conversion part;

[0064] Wherein, the absorbent used in the raw gas desulfurization tower includes at least one of N-methyldiethanolamine, diethanolamine and ethanolamine;

[0065] Solvent stripping: The rich solvent from the bottom of the raw gas desulfurization tower enters the solvent stripping tower 2 after heat exchange, the acid gas at the top of the tower is sent to the sulfur device, and the lean solvent at the bottom of the tower is sent to the CO2 removal tower 7;

[0066] CO shift: After desulfurization, the gas is heat exchanged, washed, and separated, and then mixed with high-pressure steam to undergo a low-temperature shift reaction to convert CO into CO2 and H2 to obtain shift gas;

[0067] Among them, the temperature of the first-stage shift reaction of the low-temperature shift reaction is 200°C-260°C, the temperature of the second-stage shift reaction is 200°C-260°C, and the temperature of the third-stage shift reaction is 200°C-240°C;

[0068] The obtained shift gas is sent to the shift gas desulfurization part after cooling and liquid separation;

[0069] Shift gas desulfurization: The shift gas is passed into the shift gas desulfurization tower 6 to remove a small amount of H2S in the shift gas to obtain desulfurized shift gas;

[0070] Among them, the shift gas desulfurization tower removes H2S by solid adsorption;

[0071] CO2 removal: The desulfurized shift gas is passed into the CO2 removal tower 7 and countercurrently contacts with the lean solvent from the bottom of the solvent regeneration tower 8. After CO2 is removed from the top of the tower, it enters the PSA unit 11, and the solvent at the bottom of the tower enters the solvent stripping tower 2;

[0072] Wherein, the absorbent used in the CO2 removal tower includes at least one of N-methyldiethanolamine, diethanolamine and ethanolamine;

[0073] Solvent regeneration: The rich solvent at the bottom of the CO2 removal tower is sent to the solvent regeneration tower 8 after throttling and heat exchange, and the lean solvent at the bottom of the tower is sent to the CO2 removal tower 7;

[0074] CO2 compression: The CO2 gas from the top of the solvent regeneration tower 8 is compressed by the CO2 compressor 9 and sent to the dehydration unit to remove a small amount of water. The dehydrated CO2 is then returned to the CO2 compressor for pressurization to reach the output pressure of the CO2;

[0075] CO2 dehydration: The CO2 gas at the top of the solvent regeneration tower is pressurized and then enters the dehydration unit for drying through a molecular sieve. After dehydration, the CO2 returns to the compressor for pressurization and external transmission.

[0076] Among them, the molecular sieve adopts 3A / 4A molecular sieve.

[0077] Example 2

[0078] The only difference between this embodiment and embodiment 1 is that the CO2 gas is compressed in stages according to the gas source pressure, and air coolers are provided between the compressor stages to promptly remove excess compression heat during the compression process, thereby saving compression energy consumption.

[0079] The rest are the same as in Example 1.

[0080] Example 3

[0081] The only difference between this embodiment and embodiment 1 is that a double-tower process is used to dehydrate and dry CO2, and the operation method includes:

[0082] When one tower is performing adsorption operation, the other tower is performing regeneration and cooling operation;

[0083] The rest are the same as in Example 1.

[0084] Comparative Example 1

[0085] The only difference between this comparative example and Example 1 is that the synthesis gas is not subjected to desulfurization treatment, but is directly fed into the CO shift part for shift reaction;

[0086] The rest are the same as in Example 1.

[0087] Compared with Example 1, the drawback of this comparative example is that the undesulfurized synthesis gas will cause poisoning and deactivation of the shift catalyst, resulting in performance degradation, thereby leading to a series of adverse consequences such as substandard CO conversion rate and equipment corrosion.

[0088] Comparative Example 2

[0089] The only difference between this comparative example and Example 1 is that the shift gas is not subjected to H2S removal but is directly fed into the CO2 removal tower;

[0090] The rest are the same as in Example 1.

[0091] Compared with Example 1, the defect of this comparative example is that both H2S and CO2 in the conversion gas will be removed in the CO2 removal tower, which increases the processing load and energy consumption of the CO2 removal tower and the solvent regeneration tower, and also cannot obtain pure CO2 product.

[0092] Comparative Example 3

[0093] The only difference between this comparative example and Example 1 is that the CO2 gas is not compressed by a compressor but is directly fed into the dehydration unit;

[0094] The rest are the same as in Example 1.

[0095] Compared with Example 1, the defect of this comparative example is that the CO2 gas is not compressed by a compressor and has a low pressure, which will result in the dehydration effect failing to meet the CO2 product index requirements.

[0096] Test example

[0097] The method for capturing CO2 using a modified gasification device in Example 1 was tested;

[0098] Table 1 shows the composition of synthesis gas (i.e. raw gas), with a flow rate of 380,000 Nm 3 / h;

[0099] Table 2 shows the equipment operating conditions;

[0100] Table 3 shows the obtained logistics information.

[0101] Table 1

[0102] Components <![CDATA[H2]]> CO <![CDATA[CO2]]> <![CDATA[H2S]]> other V％ 41 52.5 4 1.5 1

[0103] Table 2

[0104] Temperature, °C Pressure, MPa other Raw gas inlet device 50 5.6 380,000 standard cubic meters / hour Raw gas desulfurization tower 60-70 5.55 Solvent stripping tower 102 0.1 Primary shift reactor 210-400 5.3 Secondary shift reactor 210-315 5.2 Three-stage shift reactor 210-242 5.15 Shift gas desulfurization tower 40 4.85 <![CDATA[CO2 Removal Tower]]> 60-70 4.8 Solvent regeneration tower 96 0.05 <![CDATA[CO2 compressor]]> 40 / 110 0.02 / 15.0

[0105] Table 3

[0106] Raw gas Shift gas <![CDATA[CO2 product]]> Hydrogen-rich synthesis gas Flow rate, t / h 290 510 309.4 68.6 Pressure, MPag 5.6 4.85 15 4.75 Temperature, °C 50 40 45 60 <![CDATA[H2,V%]]> 41 55.6 0.06 92.8 <![CDATA[CO2,V%]]> 4 42.1 99.3 3.6

[0107] It can be seen that the three-stage conversion rate of the CO2 capture process of the present invention is 95%, the solvent adopts 40%-50% composite MDEA solution, the purity of the CO2 product is 99%, and the recovery rate is 90%.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for capturing CO2 by modifying a gasification device, characterized in that: The following steps are involved: (a) The synthesis gas is passed into a raw gas desulfurization tower for desulfurization treatment, and then sent to a CO shift unit for a shift reaction, converting CO into CO2 and H2 to obtain shift gas; (b) the shift gas is passed into a shift gas desulfurization tower to remove H2S, and then sent to a CO2 removal tower to countercurrently contact with the lean solvent at the bottom of the solvent regeneration tower in the tower, and the CO2 is removed from the top of the tower before entering the PSA unit, and the solvent at the bottom of the tower enters the solvent stripping tower; (c) The CO2 gas at the top of the solvent regeneration tower is compressed by a compressor, sent to a dehydration unit to remove water, and then returned to the compressor for pressurization. The pressurized CO2 is then exported as a product.

2. The CO2 capture method according to claim 1, characterized in that: The rich solvent from the bottom of the raw gas desulfurization tower enters the solvent stripping tower after heat exchange, the acid gas from the top of the tower is sent to the sulfur device, and the lean solvent at the bottom of the tower is sent to the CO2 removal tower.

3. The CO2 capture method according to claim 1, characterized in that: The rich solvent at the bottom of the CO2 removal tower enters the solvent regeneration tower after throttling and heat exchange, and the lean solvent at the bottom of the tower is sent to the CO2 removal tower.

4. The method for capturing CO2 according to any one of claims 1 to 3, characterized in that: In step (a), the absorbent used in the raw gas desulfurization tower includes at least one of N-methyldiethanolamine, diethanolamine and ethanolamine; Preferably, the synthesis gas is passed through a raw gas desulfurization tower to remove H2S to below 300 ppm.

5. The CO2 capture method according to claim 4, characterized in that: In step (b), the shift gas desulfurization tower removes H2S by solid adsorption; Preferably, the shift gas is passed through a shift gas desulfurization tower to remove H2S to below 0.1ppm to 5ppm.

6. The method for capturing CO2 according to claim 1, characterized in that: The absorbent used in the CO2 removal tower includes at least one of N-methyldiethanolamine, diethanolamine and ethanolamine.

7. The method for capturing CO2 according to claim 1, characterized in that: The temperature of the primary shift reaction in the shift reaction is 200°C-260°C; Preferably, the temperature of the secondary shift reaction in the shift reaction is 200°C-260°C; Preferably, the temperature of the tertiary shift reaction in the shift reaction is 200°C-240°C.

8. The method for capturing CO2 according to claim 1, characterized in that: In step (c), an air cooler is provided between the stages of the compressor.

9. The method for capturing CO2 according to claim 1, characterized in that: In step (c), the method of removing water includes removing water through molecular sieves and drying; The molecular sieve includes 3A / 4A molecular sieve.

10. The method for capturing CO2 according to claim 9, characterized in that: The drying adopts a double-tower process; The operating method of the double-tower process includes: While one tower is performing adsorption operation, the other tower is performing regeneration and cooling operation.

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