Flue gas carbon dioxide trapping system

Abstract

The invention relates to the technical field of flue gas treatment, and discloses a flue gas carbon dioxide trapping system which comprises a compressor for pressurizing flue gas, a first gas-liquid separator for removing water drops, a spraying liquefier and a second gas-liquid separator for performing contact heat exchange with the water-drop-removed flue gas, the spraying liquefier is internally provided with a spraying layer for spraying supercooled liquid carbon dioxide, the spraying liquefier is provided with an air inlet, an ice discharge port, an exhaust port and a liquid discharge port, the liquid carbon dioxide discharged from the liquid discharge port is shunted to a circulation branch and a product branch, and the liquid carbon dioxide in the circulation branch is cooled to a supercooled state and then flows back to the spraying layer; the flue gas and the supercooled liquid carbon dioxide are in direct contact for countercurrent flow heat exchange, so that the carbon dioxide in the flue gas is condensed and liquefied, most of the liquid carbon dioxide is recycled as a cooling medium, and meanwhile, residual moisture in the flue gas is desublimated into ice by utilizing low temperature and floats away from the liquid surface by virtue of density difference, so that adsorption-free deep dehydration is realized.

Description

Technical Field

[0001] This invention relates to the field of flue gas treatment technology, and in particular to a flue gas carbon dioxide capture system. Background Technology

[0002] Carbon capture and extraction (CCIE) is the process of separating and purifying carbon dioxide (CO2) from flue gas. The separated carbon dioxide is then permanently stored or utilized. CCIE is one of the main measures to reduce carbon dioxide emissions into the environment and mitigate global greenhouse gas emissions.

[0003] Existing methods for handling flue gas containing medium to high concentrations of carbon dioxide typically involve first pressurizing the gas with a compressor, then performing simple gas-liquid separation, and finally cooling it to the condensation temperature of carbon dioxide. Since the condensation temperatures of other gases (nitrogen (N2), oxygen (O2), etc.) are much lower than those of carbon dioxide, they do not condense at the condensation temperature of carbon dioxide, thus separating the carbon dioxide from the flue gas. However, the temperature of the cryogenic liquefaction process during cooling is usually below 0°C. If the dew point temperature of the residual moisture in the flue gas is above 0°C, the moisture will freeze directly into a solid state (sublimation) upon contact with the heat exchanger wall, thereby clogging the heat exchanger channels. This conventional process requires a final dehydration using an adsorption dryer after simple gas-liquid separation and before cryogenic cooling. After the flue gas passes through the moisture-absorbing material filled in the dryer, most of the gaseous moisture is absorbed, and the pressure dew point after drying is lower than the process temperature of the subsequent refrigeration cooling stage. This ensures that the small amount of residual moisture in the flue gas during cryogenic liquefaction will not freeze on the heat exchanger wall due to the pressure dew point being lower than the process temperature of the cooling stage, thus ensuring continuous operation. However, using adsorption drying to remove moisture from gases has several drawbacks. First, during the desiccant regeneration and desorption process, there is a process of cold blowing with product gas (dry, low-temperature carbon dioxide), resulting in some product gas loss. Second, the resistance of the adsorbent packing and the heating required during the regeneration and desorption process both lead to energy consumption losses. Summary of the Invention

[0004] The purpose of this invention is to provide a flue gas carbon dioxide capture system that uses direct countercurrent heat exchange between flue gas and subcooled liquid carbon dioxide. This allows the carbon dioxide in the flue gas to condense and liquefy, and most of the liquid carbon dioxide to be recycled as a cooling medium. At the same time, the low temperature causes the residual water in the flue gas to condense into ice and float off the liquid surface due to the density difference, thereby achieving deep dehydration without adsorption.

[0005] To achieve the above objectives, the present invention provides a flue gas carbon dioxide capture system, comprising: A compressor is used to pressurize flue gas; The first gas-liquid separator is used to remove large water droplets from the pressurized flue gas. A spray liquefaction unit is used for contact heat exchange with flue gas after water droplets have been removed. The upper part of the spray liquefaction unit is provided with a spray layer, and the bottom of the spray liquefaction unit is a liquid storage area. The spray layer sprays supercooled liquid carbon dioxide. The ratio of the mass flow rate of the liquid carbon dioxide sprayed into the spray liquefaction unit to the mass flow rate of the flue gas entering the spray liquefaction unit is greater than 5. The spray liquefaction unit is provided with an air inlet above its liquid surface for inputting flue gas, an ice discharge port at its liquid surface for discharging sublimated ice, an exhaust port at its top for discharging uncondensed gas, and a liquid outlet at its bottom for discharging liquid carbon dioxide. The liquid carbon dioxide discharged from the liquid outlet is diverted to a circulation branch and a product branch. The liquid carbon dioxide in the circulation branch is cooled to a supercooled state and then flows back to the spray layer. The liquid carbon dioxide in the product branch is output as a product.

[0006] As a preferred embodiment of the present invention, the compressor is used to pressurize the flue gas to 2.5MPa to 3.0MPa; the temperature of the supercooled liquid carbon dioxide sprayed by the spray layer is -35℃ to -25℃; and the temperature inside the spray liquefaction unit is -25℃ to -20℃.

[0007] In a preferred embodiment of the present invention, the circulation branch is connected to the input end of the cooler, the output end of the cooler is connected to the spray layer, the product branch is connected to the second gas-liquid separator for gas-liquid separation, and a first regulating valve is provided on the product branch.

[0008] As a preferred embodiment of the present invention, it further includes a purification device, which includes a distillation column, a top condenser connected to the top of the distillation column, and a reboiler connected to the bottom of the distillation column; the liquid outlet and the gas outlet of the second gas-liquid separator are both connected to the distillation column; and the exhaust port is connected to the top condenser.

[0009] As a preferred embodiment of the present invention, the flue gas output from the first gas-liquid separator after removing water droplets is diverted to a first flue gas branch and a second flue gas branch. A second regulating valve is provided on the first flue gas branch. After the flue gas from the second flue gas branch provides the heat required for distillation to the reboiler, it merges with the flue gas from the first flue gas branch and enters the air inlet. The mass flow rate of the flue gas from the first flue gas branch is greater than the mass flow rate of the flue gas from the second flue gas branch.

[0010] In a preferred embodiment of the present invention, the ice discharge port is connected to the ice tank, and the gas outlet of the ice tank is connected to the second gas-liquid separator.

[0011] As a preferred embodiment of the present invention, the high-purity liquid carbon dioxide distilled from the distillation column is cooled by a distillation cooler and then sent to a storage tank.

[0012] As a preferred embodiment of the present invention, the ratio of the mass of liquid carbon dioxide sprayed into the spray liquefaction unit to the mass of flue gas entering the spray liquefaction unit is 8 to 20.

[0013] As a preferred embodiment of the present invention, a vertical labyrinth channel is provided in the liquid storage area. The input end of the vertical labyrinth channel is located on the side near the air inlet, and the output end of the vertical labyrinth channel is located on the side near the liquid outlet. The vertical labyrinth channel includes a horizontal partition and a vertical baffle, and a plurality of the vertical baffles are arranged alternately on the bottom surface of the horizontal partition and the bottom surface of the spray liquefaction device.

[0014] As a preferred embodiment of the present invention, the spray layer includes a subcooled spray layer and multiple rapid cooling spray layers arranged from top to bottom, and a filler layer is provided between the subcooled spray layer and the rapid cooling spray layer.

[0015] Compared with the prior art, the flue gas carbon dioxide capture system of this invention has the following advantages: This invention employs countercurrent heat exchange by directly contacting flue gas with subcooled liquid carbon dioxide sprayed from top to bottom. The flue gas is rapidly cooled, and the carbon dioxide with a higher condensation temperature becomes liquid, separating from other gaseous components (nitrogen, oxygen, etc.) with lower condensation temperatures. The uncondensed gaseous components are discharged from the exhaust port at the top of the spray liquefaction unit. The carbon dioxide in the flue gas condenses into liquid carbon dioxide and falls back to the liquid storage area at the bottom of the spray liquefaction unit. The liquid carbon dioxide in the flue gas is separated through low-temperature liquefaction. Most of the separated liquid carbon dioxide is cooled and recycled back to the spray layer as a cooling medium, while the remaining liquid carbon dioxide is output as a product. Moreover, the small amount of water remaining in the flue gas entering the spray liquefaction unit liquefies before the carbon dioxide in the flue gas, directly sublimating into ice (solid). Since the density of ice is less than that of liquid carbon dioxide, it floats above the liquid carbon dioxide at the bottom of the spray liquefaction unit. The ice can be dehydrated from the ice discharge port with the small amount of discharged liquid carbon dioxide, eliminating the need for deep dehydration of the flue gas using adsorption drying. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below.

[0017] Figure 1 This is a schematic diagram of a flue gas carbon dioxide capture system provided by the present invention; Figure 2 This is a schematic diagram of the structure of the spray liquefaction device provided by the present invention; In the diagram, the components are: compressor 1; first gas-liquid separator 2; first flue gas branch 21; second flue gas branch 22; second regulating valve 23; spray liquefaction unit 3; spray layer 31; subcooled spray layer 311; rapid cooling spray layer 312; packing layer 313; air inlet 32; ice discharge port 33; exhaust port 34; liquid discharge port 35; circulation branch 351; product branch 352; first regulating valve 353; liquid discharge pump 354; vertical labyrinth channel 36; horizontal partition 361; vertical baffle 362; cooler 4; second gas-liquid separator 5; distillation column 61; column top condenser 62; reboiler 63; distillation cooler 64; storage tank 65; second refrigeration system 66; distillation gas-liquid separator 67; ice tank 7; and first refrigeration system 8. Detailed Implementation

[0018] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0019] In the description of this invention, it should be understood that the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0020] like Figures 1 to 2 As shown, a preferred embodiment of the present invention provides a flue gas carbon dioxide capture system, comprising: Compressor 1 is used to pressurize the flue gas; The first gas-liquid separator 2 is used to remove large water droplets from the pressurized flue gas. A spray liquefaction unit 3 is used for contact heat exchange with the flue gas after water droplets have been removed. The upper part of the spray liquefaction unit 3 is provided with a spray layer 31, and the bottom of the spray liquefaction unit 3 is a liquid storage area. The spray layer 31 sprays supercooled liquid carbon dioxide. The ratio of the mass flow rate of the liquid carbon dioxide sprayed into the spray liquefaction unit 3 to the mass flow rate of the flue gas entering the spray liquefaction unit 3 is greater than 5. The spray liquefaction unit 3 is provided with an air inlet 32 ​​located above its liquid surface for inputting flue gas. The system includes an ice discharge port 33 located at the liquid surface for discharging sublimated ice, an exhaust port 34 located at the top for discharging uncondensed gas, and a liquid discharge port 35 located at the bottom for discharging liquid carbon dioxide. The liquid carbon dioxide discharged from the liquid discharge port 35 is diverted to a circulation branch 351 and a product branch 352. The liquid carbon dioxide in the circulation branch 351 is cooled to a supercooled state and then flows back to the spray layer 31. The liquid carbon dioxide in the product branch 352 is output as a product.

[0021] This invention employs countercurrent heat exchange by direct contact between flue gas and subcooled liquid carbon dioxide sprayed from top to bottom. The flue gas is rapidly cooled, and the carbon dioxide with a higher condensation temperature becomes liquid, separating from other gaseous components (nitrogen, oxygen, etc.) with lower condensation temperatures. The uncondensed gaseous components are discharged from the exhaust port 34 at the top of the spray liquefaction unit 3. The carbon dioxide in the flue gas condenses into liquid carbon dioxide and falls back to the liquid storage area at the bottom of the spray liquefaction unit 3. The liquid carbon dioxide in the flue gas is separated through low-temperature liquefaction. The separated liquid carbon dioxide contains a large portion of the liquid carbon dioxide. After cooling, the liquid carbon dioxide is recirculated to the spray layer 31 as a cooling medium, while the remaining liquid carbon dioxide is output as a product. Moreover, the small amount of water remaining in the flue gas entering the spray liquefaction unit 3 liquefies before the carbon dioxide in the flue gas and directly condenses into ice (solid). Since the density of ice is less than that of liquid carbon dioxide, it floats above the liquid carbon dioxide at the bottom of the spray liquefaction unit 3. The ice can be discharged from the ice discharge port 33 along with a small amount of discharged liquid carbon dioxide, thus achieving dehydration. There is no need to use adsorption drying to deeply dehydrate the flue gas, which fundamentally avoids the energy consumption and product loss caused by adsorption drying.

[0022] For example, the compressor 1 is used to pressurize the flue gas to 2.5MPa to 3.0MPa; the temperature of the subcooled liquid carbon dioxide sprayed by the spray layer 31 is -35℃ to -25℃; the temperature of the internal space of the spray liquefaction unit 3 is -25℃ to -20℃. The flue gas enters from the bottom of the spray liquefaction unit 3 and flows towards the top. The flue gas exchanges heat with the liquid carbon dioxide sprayed from top to bottom by the spray layer 31 in a countercurrent manner. The flue gas is rapidly cooled, and the carbon dioxide reaches the saturation temperature (-25℃ to -20℃) at 1.7MPa to 2.0MPa, and the gaseous carbon dioxide condenses into a liquid state. Through direct contact heat exchange between the low-temperature subcooled liquid carbon dioxide and the flue gas, when the two reach a gas-liquid balance... In equilibrium, carbon dioxide in the flue gas condenses into a liquid state. The originally low-temperature supercooled liquid carbon dioxide absorbs heat and heats up to a near-saturated state. When the sprayed liquid carbon dioxide (-35℃ to -25℃) comes into contact with the flue gas and absorbs heat, its temperature rises to near the saturation temperature (-25℃ to -20℃) at that pressure. At this point, the liquid carbon dioxide has released sensible heat and cold energy to the maximum extent, but has not yet vaporized in large quantities. The cold energy has been released, but the liquid remains liquid. Since the supercooling needs to be achieved by external refrigeration energy consumption, the power consumption of the refrigeration system increases significantly for every 1℃ decrease. This ensures the heat transfer temperature difference and avoids the waste of cold energy, achieving the best balance between maximizing the efficiency of cold energy utilization and the stability of system operation.

[0023] For example, the circulation branch 351 is connected to the input end of the cooler 4, the output end of the cooler 4 is connected to the spray layer 31, the product branch 352 is connected to the second gas-liquid separator 5 for gas-liquid separation, the product branch 352 is provided with a first regulating valve 353, the power for the liquid carbon dioxide discharged from the discharge port 35 of the spray liquefier 3 is provided by the discharge pump 354, the ratio of the liquid carbon dioxide discharged from the discharge port 35 to the circulation branch 351 and the product branch 352 is adjusted by the first regulating valve 353, when the liquid carbon dioxide discharged from the product branch 352 is output as the primary product of liquid carbon dioxide, a small amount of non-condensable gas and a small amount of vaporized carbon dioxide are removed by the second gas-liquid separator 5, and the liquid carbon dioxide can be output as the primary product.

[0024] When the liquid carbon dioxide discharged from product branch 352 is output as a high-purity liquid carbon dioxide product, the flue gas carbon dioxide capture system also includes a purification device. The purification device includes a distillation column 61, a top condenser 62 connected to the top of the distillation column 61, and a reboiler 63 connected to the bottom of the distillation column 61. The reboiler 63 provides heat to vaporize and rise the light components, and the top condenser 62 provides cooling to condense and reflux the rising carbon dioxide gas. The purification is carried out by vaporization-recooling liquefaction. The high-purity liquid carbon dioxide obtained by multiple cycles is discharged from the bottom of the distillation column 61. This part is a general technology and will not be described in detail. The liquid outlet and gas outlet of the second gas-liquid separator 5 are both connected to the distillation column 61. The gaseous material separated by the second gas-liquid separator 5 is sent to the distillation column 61 for carbon dioxide recovery, and the liquid material separated by the second gas-liquid separator 5 is used for carbon dioxide purification. The exhaust port 34 is connected to the top condenser 62. The uncondensed gas discharged from the exhaust port 34 at the top of the spray liquefaction unit 3 is sent to the distillation condenser for cooling and recovery of gaseous carbon dioxide. Furthermore, the output end of the top condenser 62 is connected to a distillation gas-liquid separator 67 to achieve gas-liquid separation, provide pure liquid carbon dioxide reflux liquid and discharge the final waste gas, thereby ensuring the stable and efficient operation of the distillation column 61. Specifically, the cooling capacity of both the cooler 4 and the top condenser 62 is provided by the first refrigeration system 8, which is a shared supporting facility.

[0025] Furthermore, the flue gas output from the first gas-liquid separator 2, after water droplets have been removed, is diverted to the first flue gas branch 21 and the second flue gas branch 22. The first flue gas branch 21 is equipped with a second regulating valve 23. After the flue gas from the second flue gas branch 22 provides the heat required for distillation to the reboiler 63, it merges with the flue gas from the first flue gas branch 21 and enters the air inlet 32. The second regulating valve 23 is located on the front side of the junction of the second flue gas branch 22 and the first flue gas branch 21. By dynamically regulating the flue gas volume of the second flue gas branch 22 through the second regulating valve 23, some of the waste heat in the flue gas can be recovered for use in the distillation process, realizing energy integration and optimization within the system. The mass flow rate of the flue gas in the first flue gas branch 21 is greater than that in the second flue gas branch 22 to ensure sufficient heat transfer temperature difference and achieve efficient heat transfer in the carbon dioxide liquefaction process.

[0026] For example, the ice discharge port 33 is connected to the ice tank 7, and the gas outlet of the ice tank 7 is connected to the second gas-liquid separator 5. After the ice melts into water in the ice tank 7, it is finally discharged to the wastewater recovery system. The liquid carbon dioxide flowing into the ice tank 7 is vaporized in the ice tank 7, and the vaporized carbon dioxide is then recycled into the distillation column 61 through the second gas-liquid separator 5.

[0027] For example, the distillation column 61 distills high-purity liquid carbon dioxide (in a saturated state), which is then cooled by the distillation cooler 64 and sent to the storage tank 65. After being cooled by the distillation cooler 64, the high-purity liquid carbon dioxide changes from a saturated state to a slightly subcooled state and is then sent to the storage tank 65 for temporary storage, so that the pressure in the storage tank 65 remains stable and pressure fluctuations and product losses caused by flash evaporation of liquid carbon dioxide are avoided. The cooling capacity is provided by the second refrigeration system 66.

[0028] For example, the ratio of the flow rate of liquid carbon dioxide sprayed into the spray liquefaction unit 3 to the mass of flue gas entering the spray liquefaction unit 3 is 8~20, that is, a spraying condition with a liquid / gas ratio of 8~20. Specifically, the mass ratio of liquid carbon dioxide output from the circulation branch 351 to the liquid carbon dioxide output from the product branch 352 is 8~20. Based on the circulation ratio, the liquid carbon dioxide output from the product branch 352 is 1, originating from newly condensed carbon dioxide in the flue gas. Since the circulation ratio is 8~20, the amount recirculated (from circulation branch 351) is... The output of liquid carbon dioxide (CO2) is 8 to 20 times that of the output of product branch 352. This ensures sufficient contact between flue gas and liquid carbon dioxide, effectively reduces energy consumption, avoids excessive height of spray liquefaction unit 3, and balances spray heat transfer effect and refrigeration system energy consumption. Although the high mass flow ratio of the two results in good contact heat exchange effect and allows for a slightly higher condensation operating temperature, the power consumption of the drain pump 354 increases rapidly. Conversely, a low mass flow ratio requires a lower condensation operating temperature and a taller spray liquefaction unit 3 to extend the gas-liquid contact time.

[0029] Specifically, such as Figure 2 As shown, a vertical labyrinth channel 36 is provided in the liquid storage area. The input end of the vertical labyrinth channel 36 is located on the side near the air inlet 32, and the output end of the vertical labyrinth channel 36 is located on the side near the drain outlet 35. The vertical labyrinth channel 36 includes a horizontal baffle 361 and a vertical baffle 362. Several vertical baffles 362 are arranged alternately on the bottom surface of the horizontal baffle 361 and the bottom surface of the spray liquefaction device 3. Liquid carbon dioxide has to go through several descending and ascending processes in the vertical labyrinth channel 36 before reaching the drain outlet 35 at the bottom of the spray liquefaction device 3. The liquid carbon dioxide falling from above is prone to carrying a large number of air bubbles. The vertical labyrinth channel 36 can remove the air bubbles carried in the liquid carbon dioxide, ensuring pumping safety and product purity.

[0030] For example, such as Figure 2 As shown, the spray layer 31 includes a subcooled spray layer 311 and multiple rapid-cooling spray layers 312 arranged from top to bottom. A packing layer 313 is provided between the subcooled spray layer 311 and the rapid-cooling spray layer 312. The upper subcooled spray layer 311 uses packing to enhance heat exchange, while the lower multiple rapid-cooling spray layer 312 uses empty tower spraying to ensure good heat exchange effect. In other embodiments, the number of packing layers 313 can be increased to eliminate empty tower spraying, or the height of the spray liquefier 3 can be increased without packing layers 313.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A flue gas carbon dioxide capture system, characterized in that, include: A compressor is used to pressurize flue gas; The first gas-liquid separator is used to remove large water droplets from the pressurized flue gas. A spray liquefaction unit is used for contact heat exchange with flue gas after water droplets have been removed. The upper part of the spray liquefaction unit is provided with a spray layer, and the bottom of the spray liquefaction unit is a liquid storage area. The spray layer sprays supercooled liquid carbon dioxide. The ratio of the mass flow rate of the liquid carbon dioxide sprayed into the spray liquefaction unit to the mass flow rate of the flue gas entering the spray liquefaction unit is greater than 5. The spray liquefaction unit is provided with an air inlet above its liquid surface for inputting flue gas, an ice discharge port at its liquid surface for discharging sublimated ice, an exhaust port at its top for discharging uncondensed gas, and a liquid outlet at its bottom for discharging liquid carbon dioxide. The liquid carbon dioxide discharged from the liquid outlet is diverted to a circulation branch and a product branch. The liquid carbon dioxide in the circulation branch is cooled to a supercooled state and then flows back to the spray layer. The liquid carbon dioxide in the product branch is output as a product.

2. The flue gas carbon dioxide capture system as described in claim 1, characterized in that, The compressor is used to pressurize the flue gas to 2.5MPa to 3.0MPa; the temperature of the supercooled liquid carbon dioxide sprayed by the spray layer is -35℃ to -25℃; the temperature inside the spray liquefaction unit is -25℃ to -20℃.

3. The flue gas carbon dioxide capture system as described in claim 1, characterized in that, The circulation branch is connected to the input end of the cooler, the output end of the cooler is connected to the spray layer, the product branch is connected to the second gas-liquid separator for gas-liquid separation, and the product branch is provided with a first regulating valve.

4. The flue gas carbon dioxide capture system as described in claim 3, characterized in that, It also includes a purification device, which includes a distillation column, a top condenser connected to the top of the distillation column, and a reboiler connected to the bottom of the distillation column; the liquid outlet and the gas outlet of the second gas-liquid separator are both connected to the distillation column; and the exhaust port is connected to the top condenser.

5. The flue gas carbon dioxide capture system as described in claim 4, characterized in that, The flue gas output from the first gas-liquid separator, after water droplets have been removed, is diverted to a first flue gas branch and a second flue gas branch. A second regulating valve is provided on the first flue gas branch. After the flue gas from the second flue gas branch provides the heat required for distillation to the reboiler, it merges with the flue gas from the first flue gas branch and enters the air inlet. The mass flow rate of the flue gas from the first flue gas branch is greater than that of the flue gas from the second flue gas branch.

6. The flue gas carbon dioxide capture system as described in claim 4, characterized in that, The ice discharge port is connected to the ice tank, and the gas outlet of the ice tank is connected to the second gas-liquid separator.

7. The flue gas carbon dioxide capture system as described in claim 4, characterized in that, The distillation column distills high-purity liquid carbon dioxide, which is then cooled by a distillation cooler and sent to a storage tank.

8. The flue gas carbon dioxide capture system as described in claim 1, characterized in that, The ratio of the mass of liquid carbon dioxide sprayed into the spray liquefaction unit to the mass of flue gas entering the spray liquefaction unit is 8 to 20.

9. The flue gas carbon dioxide capture system as described in claim 1, characterized in that, The liquid storage area is provided with a vertical labyrinth channel. The input end of the vertical labyrinth channel is located on the side near the air inlet, and the output end of the vertical labyrinth channel is located on the side near the liquid outlet. The vertical labyrinth channel includes a horizontal partition and a vertical baffle. Several vertical baffles are arranged alternately on the bottom surface of the horizontal partition and the bottom surface of the spray liquefaction device.

10. The flue gas carbon dioxide capture system as described in claim 1, characterized in that, The spray layer includes a subcooled spray layer and multiple rapid cooling spray layers arranged from top to bottom, with a filler layer between the subcooled spray layer and the rapid cooling spray layer.

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