Method and process for improving residual cold utilization efficiency and net carbon reduction amount of flue gas carbon capture and dry ice making system

Abstract

The invention discloses a method and a process for improving residual cold utilization efficiency and net carbon reduction of a flue gas carbon capture and dry ice making system, and the process comprises the following steps: a carbon-containing pregnant solution preparation step: CO2-containing raw flue gas is cooled, desulfurized and dedusted through a pretreatment tower, and enters an absorption tower to contact and react with a decarburized barren solution to obtain decarburized flue gas and the carbon-containing pregnant solution; and the decarburized flue gas is emptied through a chimney. According to the invention, waste cold gradient utilization is adopted, the cold energy of the refined tail gas is firstly recovered to cool low-pressure CO2, and then the low-pressure CO2 is mixed with the discharged low-temperature CO2 gas, so that gradient utilization of energy is realized, cold and heat of the refined tail gas can be more completely recovered, the energy utilization efficiency is improved, and the energy waste is reduced; the device has the advantages of effectively improving the residual cold utilization efficiency and net carbon reduction of the flue gas carbon capture and dry ice making system and being good in energy conservation and emission reduction effect.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon capture and utilization, and in particular to a method and process for improving the residual cooling utilization efficiency and net carbon reduction of a flue gas carbon capture and dry ice making system. Background Art

[0002] Carbon capture, utilization and storage (CCUS) technology is an effective means of direct CO2 emission reduction. The "China Carbon Dioxide Capture, Utilization and Storage (CCUS) Annual Report (2021)" believes that CCUS technology is the only technical option for low-carbon utilization of fossil energy in my country. Organic amine absorption technology is currently the most widely studied and mature CO2 capture technology, and CO2 dry ice production technology is a very mature CO2 utilization technology. There are industrial application cases where these two technologies are combined to meet the carbon reduction needs of enterprises; at this stage, the high energy consumption and high operating costs of carbon capture and dry ice production systems limit their large-scale industrial application, and high energy consumption also leads to high carbon emissions within the boundaries of the system.

[0003] Waste heat recovery and utilization technology is an important means of energy conservation and emission reduction. By recovering waste heat from industrial processes, energy utilization efficiency can be improved and energy waste can be reduced. There are also some problems in the actual application of waste heat utilization in carbon capture and dry ice making systems. For example, the efficiency of the heat exchanger is not high and the waste heat cannot be completely recovered. In addition, although the existing dry ice production technology can produce a large amount of dry ice, it requires a lot of electricity and consumes a lot of energy. In addition, due to the conversion rate problem in the production process, a large amount of low-temperature carbon dioxide gas will be generated, which increases carbon emissions and wastes waste cold. Therefore, how to improve the utilization efficiency of waste cold and the net carbon reduction of carbon capture and dry ice making systems has become a problem that needs to be solved urgently. Summary of the invention

[0004] In order to solve the problems raised in the above-mentioned background technology, the purpose of the present invention is to provide a method and process for improving the utilization efficiency of residual cooling and the net carbon reduction of flue gas carbon capture and dry ice making systems, which has the advantages of effectively improving the utilization efficiency of residual cooling and the net carbon reduction of flue gas carbon capture and dry ice making systems and having good energy-saving and emission reduction effects.

[0005] To achieve the above object, the present invention provides the following technical solution: a method and process for improving the residual cooling efficiency and net carbon reduction of flue gas carbon capture and dry ice making system, comprising the following steps: The steps of making carbon-rich liquid: the raw flue gas containing CO2 is cooled, desulfurized and dusted through the pretreatment tower, and then enters the absorption tower to contact and react with the decarbonized lean liquid to obtain decarbonized flue gas and carbon-rich liquid. The decarbonized flue gas is discharged through the chimney; The steps of producing low-pressure CO2 gas are as follows: the carbon-rich liquid enters the regeneration tower for regeneration to obtain a decarbonized lean liquid and a carbon-rich gas with a CO2 concentration greater than 40%. The decarbonized lean liquid enters the absorption tower for recycling. The carbon-rich gas, after cooling and gas-liquid separation, enters the amine recovery tower to remove the organic amine gas, and obtains a low-pressure CO2 gas with a content greater than 90% and a pressure less than 10kPa. High-pressure CO2 gas production steps: low-pressure CO2 gas is processed in turn by refined tail gas residual cooling recovery device, CO2 buffer tank, precooler, and CO2 compression equipment to obtain high-pressure CO2 gas with a pressure of 2.2MPa~2.5MPa; Liquid CO2 production steps: High-pressure CO2 gas is processed by CO2 impurity removal and purification equipment and CO2 liquefaction and refining equipment in turn to obtain liquid CO2 with a concentration greater than 99.9%, which is stored in a CO2 storage tank; Dry ice production steps: Liquid CO2 is transported to the dry ice machine to produce dry ice products; Steps for utilizing the discharged low-temperature CO2 gas: The operation of the CO2 storage tank and the dry ice machine generates low-temperature CO2 gas that needs to be discharged, namely the CO2 storage tank exhaust gas and the dry ice machine exhaust gas. The two low-temperature CO2 gases are mixed through a pipeline and enter the CO2 buffer tank, where they are directly mixed with the low-pressure CO2 gas, and the CO2 gas is cooled by 5℃~15℃; Steps for utilizing low-temperature refined tail gas: The low-temperature refined tail gas generated during the operation of the CO2 liquefaction and refining equipment is transported to the refined tail gas residual cooling recovery device through a pipeline, and the low-pressure CO2 gas is cooled by 1°C~5°C through indirect heat exchange and then discharged.

[0006] As a preferred embodiment of the present invention, the step of utilizing the exhaust low-temperature CO2 gas is as follows: the exhaust gas from the dry ice machine is CO2 gas with a temperature of -70℃~-60℃, a pressure of less than 3kPa, and a concentration of more than 99.9%; the exhaust gas from the CO2 storage tank is CO2 gas with a temperature of -60℃~-40℃, a pressure of less than 3kPa, and a concentration of more than 99.9%. The two CO2 gases are mixed through a pipeline to obtain a low-temperature CO2 mixed gas with a temperature of -65℃~-50℃, a pressure of less than 3kPa, and a concentration of more than 99.9%.

[0007] As a preferred embodiment of the present invention, the low-temperature refined tail gas utilization step is: the low-temperature CO2 mixed gas is transported to the CO2 buffer tank via a pipeline, enters from the top of the CO2 buffer tank, and is directly mixed with the low-pressure CO2 gas from the refined tail gas after-cooling recovery device. The temperature of the low-pressure CO2 gas at the outlet of the CO2 buffer tank is 5°C to 15°C lower than the temperature of the low-pressure CO2 gas at the inlet of the CO2 buffer tank.

[0008] As a preferred embodiment of the present invention, the step of utilizing the externally exhausted low-temperature CO2 gas is as follows: when the low-temperature CO2 mixed gas enters the CO2 buffer tank from the top, two inlets are set, and one inlet is used as a backup.

[0009] As a preferred method of the present invention, the low temperature refined tail gas utilization step is: the low temperature refined tail gas discharged from the CO2 liquefaction and refining equipment is composed of N2, O2, CO2, SO2, NO X , VOCs, with a temperature of -50℃~-25℃ and a pressure of less than 5kPa. It is transported to the refined tail gas residual cooling recovery device through a pipeline, and indirectly exchanges heat with the low-pressure CO2 gas from the amine recovery tower to reduce the temperature of the low-pressure CO2 gas by 1℃~5℃. The low-temperature refined tail gas after residual cooling is directly discharged through the exhaust pipe.

[0010] As a preferred embodiment of the present invention, the low-temperature refined tail gas utilization step is as follows: the refined tail gas after-cooling recovery device is arranged at the front end of the CO2 buffer tank.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention adopts the cascade utilization of waste cooling. By first recovering the cold of refined tail gas to cool the low-pressure CO2, and then mixing it with the discharged low-temperature CO2 gas, the cascade utilization of energy is realized. The cold and heat of refined tail gas can be recovered more completely, the energy utilization efficiency is improved, and the energy waste is reduced. The device has the advantages of effectively improving the utilization efficiency of waste cooling of flue gas carbon capture and dry ice making system, as well as the net carbon reduction and good energy saving and emission reduction effects.

[0012] 2. The present invention improves the utilization efficiency of waste cooling. Since the waste cooling of indirect heat exchange is not fully utilized, the waste cooling of low-temperature CO2 is fully recovered by directly mixing the discharged low-temperature CO2 gas with the low-pressure CO2 gas, thereby further improving the waste cooling recovery efficiency.

[0013] 3. The present invention improves the CO2 utilization rate and net carbon reduction of the system, recovers the exhausted CO2 gas, and directly mixes it with the low-pressure CO2 gas, and enters the compression, purification and refining process. Less carbon dioxide gas is generated during the production process, and the net carbon reduction is higher.

[0014] 4. The present invention solves the problem of freezing of low-temperature CO2 gas mixed with low-pressure CO2 gas. The low-temperature CO2 gas enters from the top of the CO2 buffer, and a spare inlet is provided, thereby effectively solving the problem of freezing of condensed water generated by the cooled low-pressure CO2 gas.

[0015] 5. The present invention reduces the number of heat exchangers for waste cooling and the externally discharged CO2, and the waste cooling recovery technology of the present invention can reduce energy waste and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Process flow chart for improving the efficiency of waste cooling and net carbon reduction in flue gas carbon capture and dry ice making systems.

[0017] In the figure: 1. CO2-containing raw flue gas; 2. Pretreatment tower; 3. Absorption tower; 4. Decarbonized flue gas; 5. Carbon-rich liquid; 6. Decarbonized lean liquid; 7. Regeneration tower; 8. Carbon-rich gas; 9. Amine recovery tower; 10. Refined tail gas residual cooling recovery device; 11. CO2 buffer tank; 12. Precooler; 13. CO2 compression equipment; 14. CO2 impurity removal and purification equipment; 15. CO2 liquefaction and refining equipment; 16. CO2 storage tank; 17. Dry ice machine; 18. CO2 storage tank exhaust gas; 19. Dry ice machine exhaust gas; 20. Refined tail gas; 21. Refined tail gas venting. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] like Figure 1 As shown, a method and process for improving the residual cooling efficiency and net carbon reduction of flue gas carbon capture and dry ice making system comprises the following steps: The steps of making the carbon-rich liquid 5 are as follows: the CO2-containing raw flue gas 1 is cooled, desulfurized and dusted by passing through the pretreatment tower 2, and then enters the absorption tower 3 to contact and react with the decarbonized lean liquid 6 to obtain the decarbonized flue gas 4 and the carbon-rich liquid 5, and the decarbonized flue gas 4 is discharged through the chimney; The steps of producing low-pressure CO2 gas are as follows: the carbon-rich liquid 5 enters the regeneration tower 7 for regeneration to obtain the decarbonized lean liquid 6 and the carbon-rich gas 8 with a CO2 concentration greater than 40%. The decarbonized lean liquid 6 enters the absorption tower 3 for recycling. The carbon-rich gas 8 is cooled and separated from the gas and liquid, and then enters the amine recovery tower 9 to remove the organic amine gas, thereby obtaining a low-pressure CO2 gas with a content greater than 90% and a pressure less than 10 kPa. High-pressure CO2 gas production steps: low-pressure CO2 gas is processed in turn by the refined tail gas residual cooling recovery device 10, the CO2 buffer tank 11, the precooler 12, and the CO2 compression equipment 13 to obtain high-pressure CO2 gas with a pressure of 2.2MPa~2.5MPa; Liquid CO2 production steps: high-pressure CO2 gas is processed by CO2 impurity removal and purification equipment 14 and CO2 liquefaction and refining equipment 15 in sequence to obtain liquid CO2 with a concentration greater than 99.9%, which is stored in a CO2 storage tank 16; Dry ice production steps: liquid CO2 is transported to the dry ice machine 17 to produce dry ice products; Utilization steps of exhausting low-temperature CO2 gas: The operation process of CO2 storage tank 16 and dry ice machine 17 generates low-temperature CO2 gas that needs to be exhausted, namely, CO2 storage tank exhaust gas 18 and dry ice machine exhaust gas 19. The two low-temperature CO2 gases are mixed through a pipeline and enter the CO2 buffer tank 11, where they are directly mixed with the low-pressure CO2 gas, and the CO2 gas is cooled by 5°C to 15°C. Low-temperature refined tail gas utilization steps: The low-temperature refined tail gas 20 generated during the operation of the CO2 liquefaction and refining equipment 15 is transported to the refined tail gas residual cooling recovery device 10 through a pipeline, and the low-pressure CO2 gas is cooled by 1°C~5°C through indirect heat exchange and then discharged.

[0020] refer to Figure 1 , the steps of utilizing the discharged low-temperature CO2 gas are as follows: the dry ice machine exhaust gas 19 is CO2 gas with a temperature of -70℃~-60℃, a pressure of less than 3kPa, and a concentration of more than 99.9%. The CO2 storage tank exhaust gas 18 is CO2 gas with a temperature of -60℃~-40℃, a pressure of less than 3kPa, and a concentration of more than 99.9%. The two CO2 gases are mixed through a pipeline to obtain a low-temperature CO2 mixed gas with a temperature of -65℃~-50℃, a pressure of less than 3kPa, and a concentration of more than 99.9%.

[0021] As a technical optimization scheme of the present invention, the utilization efficiency of waste cooling is effectively improved. Since the waste cooling due to indirect heat exchange is not fully utilized, the waste cooling of low-temperature CO2 is fully recovered by directly mixing the discharged low-temperature CO2 gas with the low-pressure CO2 gas, thereby further improving the waste cooling recovery efficiency.

[0022] refer to Figure 1 , low-temperature refined tail gas utilization steps: low-temperature CO2 mixed gas is transported to the CO2 buffer tank 11 through a pipeline, enters from the top of the CO2 buffer tank 11, and is directly mixed with the low-pressure CO2 gas from the refined tail gas after-cooling recovery device 10. The temperature of the low-pressure CO2 gas at the outlet of the CO2 buffer tank 11 is 5°C~15°C lower than the temperature of the low-pressure CO2 gas at the inlet of the CO2 buffer tank 11.

[0023] As a technical optimization solution of the present invention, it effectively improves the system CO2 utilization rate and net carbon reduction, recovers the exhausted CO2 gas and directly mixes it with the low-pressure CO2 gas, and enters the compression, purification and refining process. Less carbon dioxide gas is generated during the production process, and the net carbon reduction is higher.

[0024] refer to Figure 1 , the steps of utilizing the discharged low-temperature CO2 gas: when the low-temperature CO2 mixed gas enters from the top of the CO2 buffer tank 11, two inlets are set, and one inlet is used as a backup.

[0025] As a technical optimization solution of the present invention, the problem of freezing of low-temperature CO2 gas mixed with low-pressure CO2 gas is effectively solved. The low-temperature CO2 gas enters from the top of the CO2 buffer, and a spare inlet is set, thereby effectively solving the problem of condensed water generated by the low-pressure CO2 gas after cooling and freezing when it is cooled.

[0026] refer to Figure 1 , low temperature refined tail gas utilization steps: low temperature refined tail gas 20 discharged from CO2 liquefaction and refining equipment 15 is composed of N2, O2, CO2, SO2, NO X , VOCs, with a temperature of -50℃~-25℃ and a pressure of less than 5kPa, and is transported to the refined tail gas residual cooling recovery device 10 through a pipeline, and indirectly exchanges heat with the low-pressure CO2 gas from the amine recovery tower 9 to reduce the temperature of the low-pressure CO2 gas by 1℃~5℃. The low-temperature refined tail gas 20 after residual cooling is directly discharged through the exhaust pipe.

[0027] As a technical optimization solution of the present invention, it effectively reduces the number of heat exchangers for waste cooling and the external CO2 emission, and the waste cooling recovery technology of the present invention can reduce energy waste and is thus environmentally friendly.

[0028] refer to Figure 1 , low temperature refined tail gas utilization steps: the refined tail gas aftercooling recovery device 10 is arranged at the front end of the CO2 buffer tank 11.

[0029] As a technical optimization solution of the present invention, it effectively reduces energy waste.

[0030] The working principle and use process of the present invention: When used, it mainly includes the following steps: Step 1: The raw flue gas 1 containing CO2 is cooled, desulfurized and dusted through the pretreatment tower 2, the flue gas temperature is reduced to 45°C, and the SO2 content is reduced to 5mg / Nm 3 , the particle content is reduced to 1mg / Nm 3, and then enters from the bottom of the absorption tower 3, contacts and reacts with the decarbonized lean liquid 6 in countercurrent to obtain decarbonized flue gas 4 and carbon-rich liquid 5. The decarbonized flue gas 4 is discharged through the chimney. Step 2: The carbon-rich liquid 5 enters the regeneration tower 7 for heating and regeneration to obtain decarbonized lean liquid 6 and carbon-rich gas 8 with a CO2 concentration of 48%. The decarbonized lean liquid 6 enters the absorption tower 3 for recycling. After cooling and gas-liquid separation, the carbon-rich gas 8 enters the amine recovery tower 9 to remove the organic amine gas to obtain a low-pressure CO2 gas with a content of 95%, a pressure of 800Pa, and a temperature of 40°C. Step 3: Low-pressure CO2 gas The body is processed by the refined tail gas residual cooling recovery device 10, the CO2 buffer tank 11, the precooler 12, and the CO2 compression equipment 13 in sequence to obtain a high-pressure CO2 gas with a temperature of 40°C, a pressure of 2.5MPa, and a content of 99.5%. Step 4: The high-pressure CO2 gas is processed by the CO2 impurity removal and purification equipment 14 and the CO2 liquefaction and refining equipment 15 in sequence to obtain a liquid CO2 with a temperature of -25°C and a concentration of 99.99%, which is stored in the CO2 storage tank 16; the liquid CO2 is transported to the dry ice machine 17 to produce dry ice products. Step 5: Dry The exhaust gas 19 of the ice machine is CO2 gas with a temperature of -65°C, a pressure of about 500Pa, and a concentration of 99.9%. The exhaust gas 18 of the CO2 storage tank is CO2 gas with a temperature of -45°C, a pressure of about 700Pa, and a concentration of 99.9%. The two CO2 gases are mixed through a pipeline to obtain a low-temperature CO2 mixed gas with a temperature of -60°C, a pressure of about 650Pa, and a concentration of 99.9%. The low-temperature CO2 mixed gas is transported to the CO2 buffer tank 11 through a pipeline, enters from the top of the CO2 buffer tank 11, and mixes with the residual cooling return gas from the refined tail gas. The low-pressure CO2 gas from the receiver 10 is directly mixed, and the temperature of the low-pressure CO2 gas at the outlet of the CO2 buffer tank 11 is 12°C lower than that of the low-pressure CO2 gas at the inlet of the CO2 buffer tank 11. Step six: The low-temperature refined tail gas 20 discharged from the CO2 liquefaction and refining equipment 15 has a temperature of -45°C and a pressure of about 350Pa, and is transported to the refined tail gas residual cooling recovery device 10 through a pipeline, and indirectly exchanges heat with the low-pressure CO2 gas from the amine recovery tower 9 to reduce the temperature of the low-pressure CO2 gas by 2°C. The low-temperature refined tail gas 20 after residual cooling is directly discharged through the exhaust pipe.

[0031] The above are the specific steps of this embodiment. Through these steps, the residual cooling efficiency and net carbon reduction of the flue gas carbon capture and dry ice making system can be effectively improved, thereby achieving the purpose of energy saving and emission reduction.

[0032] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0033] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method and process for improving the residual cooling efficiency and net carbon reduction of flue gas carbon capture and dry ice making systems, characterized in that: The following steps are involved: The steps of preparing the carbon-rich liquid are as follows: the CO2-containing raw flue gas (1) is cooled, desulfurized and dusted by passing through a pretreatment tower (2), and then enters an absorption tower (3) to contact and react with the decarbonized lean liquid (6) to obtain decarbonized flue gas (4) and carbon-rich liquid (5), and the decarbonized flue gas (4) is discharged through a chimney; The steps of producing low-pressure CO2 gas are as follows: the carbon-rich liquid (5) enters the regeneration tower (7) for regeneration to obtain a decarbonized lean liquid (6) and a carbon-rich gas (8) with a CO2 concentration greater than 40%. The decarbonized lean liquid (6) enters the absorption tower (3) for recycling. The carbon-rich gas (8) enters the amine recovery tower (9) for removal of organic amine gas after cooling and gas-liquid separation to obtain a low-pressure CO2 gas with a CO2 content greater than 90% and a pressure less than 10 kPa. The steps of producing high-pressure CO2 gas are as follows: the low-pressure CO2 gas is processed in sequence by a refined tail gas residual cooling recovery device (10), a CO2 buffer tank (11), a precooler (12), and a CO2 compression device (13) to obtain a high-pressure CO2 gas with a pressure of 2.2 MPa to 2.5 MPa; Liquid CO2 production steps: The high-pressure CO2 gas is processed in sequence by a CO2 impurity removal and purification device (14) and a CO2 liquefaction and refining device (15) to obtain liquid CO2 with a concentration greater than 99.9%, which is then stored in a CO2 storage tank (16); Dry ice production steps: liquid CO2 is transported to a dry ice machine (17) to produce dry ice products; Steps for utilizing the discharged low-temperature CO2 gas: During the operation of the CO2 storage tank (16) and the dry ice machine (17), low-temperature CO2 gas to be discharged is generated, namely, the CO2 storage tank exhaust gas (18) and the dry ice machine exhaust gas (19). The two low-temperature CO2 gases are mixed through a pipeline and enter the CO2 buffer tank (11), where they are directly mixed with the low-pressure CO2 gas, and the CO2 gas is cooled by 5°C to 15°C. Low-temperature refined tail gas utilization steps: The low-temperature refined tail gas (20) generated during the operation of the CO2 liquefaction and refining equipment (15) is transported to the refined tail gas residual cooling recovery device (10) through a pipeline, and the low-pressure CO2 gas is cooled by 1°C to 5°C through indirect heat exchange and then discharged.

2. A method and process for improving the residual cooling efficiency and net carbon reduction of flue gas carbon capture and dry ice making system according to claim 1, characterized in that: The step of utilizing the exhaust low-temperature CO2 gas is as follows: the exhaust gas (19) from the dry ice machine is CO2 gas with a temperature of -70°C to -60°C, a pressure of less than 3kPa, and a concentration of more than 99.9%, and the exhaust gas (18) from the CO2 storage tank is CO2 gas with a temperature of -60°C to -40°C, a pressure of less than 3kPa, and a concentration of more than 99.9%. The two CO2 gases are mixed through a pipeline to obtain a low-temperature CO2 mixed gas with a temperature of -65°C to -50°C, a pressure of less than 3kPa, and a concentration of more than 99.9%.

3. A method and process for improving the residual cooling efficiency and net carbon reduction of flue gas carbon capture and dry ice making system according to claim 1, characterized in that: The low-temperature refined tail gas utilization step is as follows: the low-temperature CO2 mixed gas is transported to the CO2 buffer tank (11) through a pipeline, enters from the top of the CO2 buffer tank (11), and is directly mixed with the low-pressure CO2 gas from the refined tail gas after-cooling recovery device (10). The temperature of the low-pressure CO2 gas at the outlet of the CO2 buffer tank (11) is 5°C to 15°C lower than the temperature of the low-pressure CO2 gas at the inlet of the CO2 buffer tank (11).

4. A method and process for improving the residual cooling efficiency and net carbon reduction of flue gas carbon capture and dry ice making system according to claim 1, characterized in that: The step of utilizing the discharged low-temperature CO2 gas is as follows: when the low-temperature CO2 mixed gas enters from the top of the CO2 buffer tank (11), two inlets are provided, and one inlet is used as a backup.

5. A method and process for improving the residual cooling efficiency and net carbon reduction of flue gas carbon capture and dry ice making system according to claim 1, characterized in that: The low temperature refined tail gas utilization step: the low temperature refined tail gas (20) discharged from the CO2 liquefaction and refining equipment (15) is composed of N2, O2, CO2, SO2, NO X , VOCs, with a temperature of -50℃~-25℃ and a pressure of less than 5kPa, and is transported to the refined tail gas residual cooling recovery device (10) through a pipeline, and indirectly exchanges heat with the low-pressure CO2 gas from the amine recovery tower (9), thereby reducing the temperature of the low-pressure CO2 gas by 1℃~5℃. The low-temperature refined tail gas (20) after the residual cooling is utilized is directly discharged through the exhaust pipe.

6. A method and process for improving the residual cooling efficiency and net carbon reduction of flue gas carbon capture and dry ice making system according to claim 1, characterized in that: The low-temperature refined tail gas utilization step: the refined tail gas aftercooling recovery device (10) is arranged at the front end of the CO2 buffer tank (11).

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