Trapping system and process for treating carbon dioxide in flue gas

Abstract

The invention relates to the technical field of carbon capture, in particular to a capture system and process for treating carbon dioxide in flue gas. The trapping system comprises a trapping unit which is provided with gas-liquid mass transfer equipment, a regeneration tower and a solution circularly flowing between the gas-liquid mass transfer equipment and the regeneration tower and is used for absorbing and desorbing carbon dioxide; the liquefaction unit is communicated with the regeneration tower and is used for compressing, drying and liquefying the carbon dioxide discharged from the regeneration tower; wherein the solution has two states: carbon dioxide is absorbed in the gas-liquid mass transfer equipment to form a rich solution, and the carbon dioxide is desorbed in the regeneration tower to form a barren solution; the trapping unit is provided with a process module for treating a solution, and the gas-liquid mass transfer equipment is communicated with the regeneration tower through the process module. In the invention, through the process module, the heat exchange efficiency of the trapping system is greatly optimized, the energy consumption required by rich liquid regeneration is reduced, and the size of equipment in the trapping system is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon capture, and in particular to a capture system and process for treating carbon dioxide in flue gas. Background Art

[0002] The global emission of carbon dioxide into the atmosphere due to the combustion of fossil raw materials reaches about 20 billion tons each year, exacerbating the greenhouse effect. Among them, electricity production accounts for the highest proportion of carbon dioxide emissions, accounting for 39%. Therefore, eliminating carbon dioxide from flue gas emitted by power plants is an effective way to control global warming. The chemical absorption method using alcohol amine solution as absorbent is the most widely used carbon dioxide capture (PCC) technology in existing power plants. In the process of treating power plant flue gas, the alcohol amine solutions used are mostly monoethanolamine (MEA), N-methyldiethanolamine (MDEA), N-methyldiethanolamine (MDEA) + piperazine (PZ), etc.

[0003] At present, the main challenge of using the alcohol amine method to capture carbon dioxide is how to reduce the excessive energy required for absorbent regeneration. Taking monoethanolamine (MEA) as an example, when using the alcohol amine method for capture, due to the low concentration of carbon dioxide in the flue gas generated by the power plant, the partial pressure of carbon dioxide in the flue gas is also low, which leads to the need for the flue gas treatment system to increase the circulation volume of monoethanolamine solution, and to compensate for the lack of decarbonization efficiency by increasing the volume of monoethanolamine solution, which leads to the over-sized equipment in the system and excessive energy consumption. Moreover, if the absorbent circulates too much in the system, it will greatly increase the corrosion effect on the system equipment and greatly shorten the life of the system. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the related art. To this end, the present invention proposes a capture system and process for treating carbon dioxide in flue gas, so as to improve the efficiency of carbon dioxide capture by the absorbent to reduce the circulation volume, thereby reducing the equipment size of the capture system, and optimizing the heat exchange process of the absorbent to reduce the energy consumption of the capture system.

[0005] In a first aspect, the present invention provides a capture system for treating carbon dioxide in flue gas, the capture system comprising: a capture unit, provided with a gas-liquid mass transfer device, a regeneration tower, and a solution circulating between the gas-liquid mass transfer device and the regeneration tower, for absorbing and desorbing carbon dioxide; a liquefaction unit, connected to the regeneration tower, for compressing, drying and liquefying the carbon dioxide discharged from the regeneration tower; The solution has two states: absorbing carbon dioxide in the gas-liquid mass transfer device to form a rich liquid, and desorbing carbon dioxide in the regeneration tower to form a lean liquid; The capture unit is provided with a process module for treating the solution, and the gas-liquid mass transfer device is connected with the regeneration tower through the process module.

[0006] According to a capture system for treating carbon dioxide in flue gas provided by the present invention, the process module includes: a rich liquid buffer tank, which is arranged on the loop for transporting rich liquid from the gas-liquid mass transfer equipment to the regeneration tower, and is used to screen out semi-lean liquid that has insufficiently absorbed carbon dioxide from the rich liquid and return it to the gas-liquid mass transfer equipment.

[0007] According to a capture system for treating carbon dioxide in flue gas provided by the present invention, the process module comprises: a heat exchange circuit arranged between the rich liquid buffer tank and the regeneration tower; The heat exchange circuit has two parallel branches, one of which is provided with a lean-rich liquid heat exchanger, and the other is provided with a carbon dioxide-rich liquid heat exchanger and a solution heat exchanger, which are used to perform flow diversion and multi-stage heat exchange treatment on the rich liquid, and can efficiently heat the rich liquid discharged from the gas-liquid mass transfer device and entering the regeneration tower.

[0008] According to a capture system for treating carbon dioxide in flue gas provided by the present invention, the process module includes: a filtering component, which is arranged on the loop for transporting lean liquid from the regeneration tower to the gas-liquid mass transfer device, and is used to filter the lean liquid.

[0009] According to a capture system for treating carbon dioxide in flue gas provided by the present invention, the filter assembly comprises a particle filter, an activated carbon filter and a membrane filter connected in series in sequence.

[0010] According to a capture system for processing carbon dioxide in flue gas provided by the present invention, the capture unit is also provided with an absorption tower, and the absorption tower is connected in parallel with the gas-liquid mass transfer device for use in rotation with the gas-liquid mass transfer device during maintenance.

[0011] According to the present invention, a capture system for processing carbon dioxide in flue gas also includes a water scrubber, and the gas outlet at the upper end of the water scrubber is connected to the gas inlet of the gas-liquid mass transfer equipment; the flue gas first enters the water scrubber, and after dust removal and cooling treatment, it enters the gas-liquid mass transfer equipment for decarbonization treatment.

[0012] A capture system for treating carbon dioxide in flue gas provided by the present invention further comprises a liquid separator tower, one end of which is connected to the gas outlet of the gas-liquid mass transfer device, and the bottom end of which is connected to the rich liquid buffer tank; The decarbonized flue gas enters the liquid separator tower for cooling, and the solution carried by the flue gas is condensed and liquefied and transported to the rich liquid buffer tank.

[0013] In a second aspect, the present invention provides a process for treating carbon dioxide in flue gas, which is implemented by the above-mentioned capture system for treating carbon dioxide in flue gas, and comprises the following steps: S1, pre-treating the flue gas, removing dust from the flue gas, and cooling the flue gas to below 40°C; S2, capturing carbon dioxide in the pre-treated flue gas, and then discharging the decarbonized flue gas; S3. The carbon dioxide is liquefied and then stored.

[0014] According to a process for treating carbon dioxide in flue gas provided by the present invention, the capturing of carbon dioxide in the flue gas after pretreatment comprises: The pretreated flue gas is transported to the gas-liquid mass transfer equipment, so that the flue gas enters the bottom of the gas-liquid mass transfer equipment under a slightly positive pressure, and a solution for absorbing and desorbing carbon dioxide is added from the top of the gas-liquid mass transfer equipment, so that the solution and the flue gas are in reverse contact to absorb the carbon dioxide in the flue gas to form a rich liquid, and then the rich liquid is transported to the regeneration tower, so that the rich liquid releases carbon dioxide in the regeneration tower.

[0015] The above one or more technical solutions in the present invention have at least one of the following technical effects: The process module greatly optimizes the heat exchange efficiency of the capture system, reduces the energy consumption required for rich liquid regeneration, and improves the absorption efficiency of carbon dioxide by the solution through the gas-liquid mass transfer equipment, greatly reducing the capture system's demand for solution circulation, thereby reducing the size of each device in the capture system.

[0016] In addition to the technical problems solved by the present invention, the technical features of the technical solutions constituted, and the advantages brought about by the technical features of these technical solutions described above, other technical features of the present invention and the advantages brought about by these technical features will be further explained in conjunction with the accompanying drawings or will be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A schematic diagram of the structure of a capture unit in a capture system provided in an embodiment of the present invention.

[0019] Figure 2 A schematic diagram of the structure of a liquefaction unit in a capture system provided in an embodiment of the present invention.

[0020] Reference numerals: 100, capture unit; 110, gas-liquid mass transfer equipment; 120, regeneration tower; 121, reboiler; 130, process module; 131, rich liquid buffer tank; 140, heat exchange circuit; 141, lean and rich liquid heat exchanger; 142, carbon dioxide and rich liquid heat exchanger; 143, solution heat exchanger; 150, filter assembly; 151, particle filter; 152, activated carbon filter; 153, membrane filter; 160, absorption tower; 170, water washing tower; 171, fan; 180, liquid separator tower; 101, carbon dioxide liquid separator; 102, carbon dioxide cooler; 103, lean liquid cooler; 200, liquefaction unit; 210, compression module; 211 , first-stage compressor; 212, first-stage cooler; 213, first-stage liquid separator; 214, second-stage compressor; 215, second-stage cooler; 216, second-stage liquid separator; 217, third-stage compressor; 218, third-stage cooler; 219, third-stage liquid separator; 220, drying module; 221, first drying tower; 222, second drying tower; 223, electric heater; 224, cooler; 225, regeneration gas liquid separator; 230, liquefaction module; 231, first liquefier; 232, second liquefier; 233, front liquid separator; 234, rear liquid separator; 235, carbon dioxide storage tank; 201, carbon dioxide buffer tank; 202, Freon refrigeration unit. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all 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.

[0022] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limitations on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0023] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0024] In the embodiments of the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0025] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0026] Among the existing CO2 capture and storage technologies, the amine decarbonization method is the most realistic method. After absorbing CO2 with amine solution as absorbent, the temperature of desorbing the amine solution to release CO2 is usually around 120°C. The desorption energy consumption usually accounts for more than 80% of the total energy consumption required for the operation of the capture system.

[0027] At present, the main challenge of using the alcohol amine method to capture carbon dioxide is how to reduce the excessive energy required for absorbent regeneration. Taking monoethanolamine (MEA) as an example, when using the alcohol amine method for capture, due to the low concentration of carbon dioxide in the flue gas generated by the power plant, the partial pressure of carbon dioxide in the flue gas is also low, which leads to the need for the flue gas treatment system to increase the circulation volume of monoethanolamine solution, and to compensate for the lack of decarbonization efficiency by increasing the volume of monoethanolamine solution, which leads to the over-sized equipment in the system and excessive energy consumption. Moreover, if the absorbent circulates too much in the system, it will greatly increase the corrosion effect on the system equipment and greatly shorten the life of the system.

[0028] In order to solve the above problems, in an embodiment of the present invention, a capture system for treating carbon dioxide in flue gas is introduced.

[0029] like Figure 1 and Figure 2 As shown, the capture system includes a capture unit 100 and a liquefaction unit 200. The capture unit 100 is provided with a gas-liquid mass transfer device 110, a regeneration tower 120, and a solution circulating between the gas-liquid mass transfer device 110 and the regeneration tower 120 for absorbing and desorbing carbon dioxide.

[0030] The liquefaction unit 200 is in communication with the regeneration tower 120 , and is used to compress, dry and liquefy the carbon dioxide discharged from the regeneration tower 120 .

[0031] The solution used to capture carbon dioxide in flue gas in the present invention adopts a new composite absorbent. With a variety of organic amines as the base solvent, defoamers, corrosion inhibitors, antioxidants, etc. are added according to the mixed gas environment. Moreover, it is compositely processed under specific conditions according to a certain ratio and addition sequence. Compared with the process using monoethanolamine (MEA) as the absorbent at the same molar concentration, the composite absorbent in the present invention has improved absorption capacity and greatly reduced regeneration energy consumption, which well solves the problems of equipment corrosion and amine degradation.

[0032] Furthermore, the solution has two states: a rich liquid is formed by absorbing carbon dioxide in the gas-liquid mass transfer device 110 , and a lean liquid is formed by desorbing carbon dioxide in the regeneration tower 120 .

[0033] The capture unit 100 is provided with a process module 130 for treating the solution. The gas-liquid mass transfer device 110 is connected to the regeneration tower 120 through the process module 130 .

[0034] In particular, the gas-liquid mass transfer device 110 uses a rotating packed bed (RPB). The rotating packed bed improves gas-liquid contact and reaction through the centrifugal force brought by the high-speed rotation of the rotor, accelerates the renewal of the gas-liquid interface, and obtains an extremely thin liquid film for gas-liquid mass transfer through the high-speed rotation of the packing, greatly improving the mass transfer efficiency.

[0035] Due to the enhanced mass transfer process, the size of the rotating packed bed is significantly smaller than that of the conventional absorption tower 160. Studies have shown that the rotating packed bed has lower energy consumption when performing a carbon dioxide capture process for flue gas emitted by a power plant under the same capture efficiency. By using a rotating packed bed as the gas-liquid mass transfer device 110, the equipment size of the capture system can be greatly reduced, the mass transfer efficiency can be improved, and the investment and operating costs of the capture system can be greatly reduced.

[0036] Furthermore, the capture unit 100 further includes a fan 171, a water scrubber 170, and a washing water circulation unit. The flue gas is compressed by the fan 171 and sent to the water scrubber 170, and the washed flue gas is sent to the rotating packed bed (RPB). The rich liquid after absorbing carbon dioxide enters the regeneration tower 120, where the rich liquid is desorbed, releasing carbon dioxide to become lean liquid, and refluxes to the rotating packed bed (RPB).

[0037] like Figure 1 As shown, a washing water circulation unit is provided below the water washing tower 170. The washing water circulation unit includes a buffer tank, a water washing pump, and a water washing cooler 224 connected in sequence. The liquid outlet at the bottom of the water washing tower 170 is connected to the buffer tank. The water washing cooler 224 is connected to the liquid inlet on the side of the water washing tower 170. The washing water is pressurized by the water washing pump and sent to the water washing cooler 224 for cooling and then returned to the water washing tower 170 for recycling.

[0038] In this embodiment, the capture system greatly optimizes the heat exchange efficiency of the capture system through the process module 130, reduces the energy consumption required for rich liquid regeneration, and improves the absorption efficiency of the solution for carbon dioxide through the gas-liquid mass transfer equipment 110, greatly reducing the capture system's demand for solution circulation volume, thereby reducing the size of each device in the capture system.

[0039] Based on the above embodiment, in another embodiment of the present invention, a capture system for treating carbon dioxide in flue gas is introduced.

[0040] The process module 130 includes a rich liquid buffer tank 131 . The rich liquid buffer tank 131 is disposed on a loop for conveying rich liquid from the gas-liquid mass transfer device 110 to the regeneration tower 120 , and is used to screen out semi-lean liquid that has insufficiently absorbed carbon dioxide from the rich liquid and return it to the gas-liquid mass transfer device 110 .

[0041] Furthermore, the process module 130 includes: a heat exchange circuit 140 disposed between the rich liquid buffer tank 131 and the regeneration tower 120 .

[0042] The heat exchange loop 140 has two parallel branches. A lean-rich liquid heat exchanger 141 is provided in one branch. A carbon dioxide-rich liquid heat exchanger 142 and a solution heat exchanger 143 are provided in the other branch for diverting and multi-stage heat exchange treatment of the rich liquid. The capture unit 100 can efficiently heat the rich liquid discharged from the gas-liquid mass transfer device 110 and entering the regeneration tower 120 through the heat exchange loop 140.

[0043] Specifically, when the rich liquid is transported from the rich liquid buffer tank 131 to the regeneration tower 120, a portion of the rich liquid flows through the lean-rich liquid heat exchanger 141 and then directly flows into the regeneration tower 120; the remaining rich liquid flows through the carbon dioxide and rich liquid heat exchanger 142 and the solution heat exchanger 143 in sequence, and then flows into the regeneration tower 120. The two portions of rich liquid converge in front of the rich liquid inlet at the upper end of the regeneration tower 120.

[0044] Based on the above embodiment, in another embodiment of the present invention, a capture system for treating carbon dioxide in flue gas is introduced.

[0045] The process module 130 includes: A filter assembly 150. The filter assembly 150 is disposed on a loop for transporting lean liquid from the regeneration tower 120 to the gas-liquid mass transfer device 110, and is used to filter the lean liquid.

[0046] Furthermore, the filter assembly 150 includes a particle filter 151 , an activated carbon filter 152 , and a membrane filter 153 which are sequentially connected in series.

[0047] When the lean liquid flows back to the gas-liquid mass transfer device 110, part of it passes through the filter assembly 150, and the other part passes through the lean liquid cooler 103. The filter assembly 150 includes a particle filter 151, an activated carbon filter 152, and a membrane filter 153. The lean liquid cooler 103 is arranged in parallel with the filter assembly 150.

[0048] After filtering through the sequentially connected particle filter 151, activated carbon filter 152 and membrane filter 153, part of the lean liquid may flow into the absorption tower 160 or the gas-liquid mass transfer device 110. Alternatively, after passing through the lean liquid cooler 103, part of the lean liquid may flow into the absorption tower 160 or the gas-liquid mass transfer device 110.

[0049] A semi-lean liquid pump is also arranged in series in the pipeline for conveying the lean liquid between the rotating packed bed and the rich liquid buffer tank 131 .

[0050] Based on the above embodiment, in another embodiment of the present invention, a capture system for treating carbon dioxide in flue gas is introduced.

[0051] The capture unit 100 is further provided with an absorption tower 160 , which is connected in parallel with the gas-liquid mass transfer device 110 and is used in rotation with the gas-liquid mass transfer device 110 during maintenance. The rich liquid outlet at the bottom of the absorption tower 160 is connected to the heat exchange circuit 140 .

[0052] The flue gas is compressed by the fan 171 and sent to the water scrubber 170. The scrubbed flue gas is sent to the rotating packed bed or the standby decarbonization absorption tower 160. The rich liquid after absorbing carbon dioxide enters the regeneration tower 120, where the rich liquid is desorbed, releasing carbon dioxide to become lean liquid, and then refluxes to the rotating packed bed or the absorption tower 160.

[0053] The high-gravity rotating packed bed simulates the high-gravity environment by generating a strong centrifugal field through the high-speed rotating bed. In the high-gravity environment, two-phase materials such as gas-liquid, liquid-liquid and liquid-solid flow and contact in porous media or pores. The huge shear force tears the liquid into liquid films, liquid filaments and droplets at the micron to nanometer level. The micro-mixing and mass transfer process is greatly enhanced. The production efficiency per unit equipment volume is improved by 1~2 orders of magnitude compared with traditional tower equipment.

[0054] Based on the above embodiment, in another embodiment of the present invention, a capture system for treating carbon dioxide in flue gas is introduced.

[0055] The capture system also includes a water scrubber 170. The gas outlet at the upper end of the water scrubber 170 is connected to the gas inlet of the gas-liquid mass transfer device 110. The flue gas first enters the water scrubber 170, undergoes dust removal and cooling treatment, and then enters the gas-liquid mass transfer device 110 for decarbonization treatment.

[0056] The capture system of the present invention can achieve a high standard of more than 90% carbon dioxide removal rate and more than 99% purity of the output carbon dioxide in flue gas with a low carbon dioxide concentration of about 3% (volume fraction).

[0057] Based on the above embodiment, in another embodiment of the present invention, a capture system for treating carbon dioxide in flue gas is introduced.

[0058] It also includes a liquid separator tower 180, one end of which is connected to the gas outlet of the gas-liquid mass transfer device 110. The bottom end of the liquid separator tower 180 is connected to the rich liquid buffer tank 131, and is used to send the absorbent condensed from the flue gas after decarbonization into the rich liquid buffer tank 131.

[0059] The decarbonized flue gas enters the liquid separation tank tower 180 for cooling, and the solution carried by the flue gas is condensed and liquefied and transported to the rich liquid buffer tank 131 .

[0060] The flue gas released by the power plant is compressed by the fan 171 and enters the water scrubber 170. The water scrubber 170 is connected to the rotating packed bed or the absorption tower 160. The absorption tower 160 is used as an alternative decarbonization device. The rotating packed bed and the absorption tower 160 are both connected to the liquid separator tower 180.

[0061] like Figure 1 As shown, a reboiler 121 connected to the regeneration tower 120 through a pipeline is also provided at the bottom of the regeneration tower 120. The lean liquid can flow from the regeneration tower 120 to the reboiler 121. After being heated by steam in the reboiler 121, the lean liquid refluxes into the regeneration tower 120, realizing the internal circulation of the lean liquid in the regeneration tower 120.

[0062] A carbon dioxide post-processing unit is also provided in the capture unit 100. The carbon dioxide post-processing unit includes a carbon dioxide cooler 102, a carbon dioxide separator 101 and a reflux pump connected in sequence. The carbon dioxide cooler 102 is connected to the carbon dioxide and rich liquid heat exchanger 142. The discharge end of the reflux pump is connected to the regeneration tower 120. The carbon dioxide separator 101 is connected to the carbon dioxide buffer tank 201 of the liquefaction unit 200.

[0063] A carbon dioxide and rich liquid heat exchanger 142 is arranged in series between the regeneration tower 120 and the carbon dioxide post-processing unit. The absorbent used to capture carbon dioxide is desorbed from rich liquid to lean liquid in the regeneration tower 120. Then, the lean liquid flows out from the outlet at the bottom of the regeneration tower 120. The lean liquid first flows through the lean-rich liquid heat exchanger 141, then enters the filter assembly 150, and after being filtered, flows back to the gas-liquid mass transfer device 110, completing a cycle of absorbing carbon dioxide and desorbing carbon dioxide by the absorbent.

[0064] In this embodiment, by adopting a split multi-stage heat exchange process for the rich liquid, the waste heat of the reboiler 121 is better utilized, and the rich liquid temperature at the inlet of the regeneration tower 120 is increased from 98°C to above 105°C, thereby reducing the heat load of the reboiler 121, thereby improving the utilization efficiency of the regeneration tower 120 for the waste heat of the lean liquid and carbon dioxide gas, and reducing the heat consumption.

[0065] On the other hand, in the following embodiments of the present invention, a process for treating carbon dioxide in flue gas is introduced, which is implemented by the capture system described in any of the above embodiments.

[0066] The process for treating carbon dioxide in flue gas includes the following steps: S1, pre-treating the flue gas, removing dust from the flue gas, and cooling the flue gas to below 40°C; S2, capturing the carbon dioxide in the pre-treated flue gas, and then discharging the decarbonized flue gas; S3, liquefying the carbon dioxide and storing it.

[0067] Specifically, the rich liquid is desorbed in the regeneration tower 120, and the generated carbon dioxide is transported to the liquefaction unit 200. First, it is compressed by the compression module 210, then it is sent to the drying module 220 for drying, and finally, it enters the liquefaction module 230, where it is liquefied and stored.

[0068] Furthermore, the capturing of carbon dioxide in the flue gas after pretreatment specifically includes: conveying the pretreated flue gas to the gas-liquid mass transfer device 110, allowing the flue gas to enter the bottom of the gas-liquid mass transfer device 110 under a slightly positive pressure, adding a solution for absorbing and desorbing carbon dioxide from the top of the gas-liquid mass transfer device 110, allowing the solution to contact the flue gas in reverse to absorb the carbon dioxide in the flue gas to form a rich liquid, and then conveying the rich liquid to the regeneration tower 120, so that the rich liquid releases carbon dioxide in the regeneration tower 120.

[0069] After that, the carbon dioxide is transported to the carbon dioxide tower liquid separator 101. The carbon dioxide liquid separator 101 is connected to the carbon dioxide buffer tank 201 of the liquefaction unit 200. Furthermore, the carbon dioxide is transported to the liquefaction unit 200, and the liquefaction unit 200 compresses, dries and liquefies the carbon dioxide.

[0070] like Figure 2 As shown, the liquefaction unit 200 includes a compression module 210, a drying module 220 and a liquefaction module 230 which are sequentially connected and arranged.

[0071] The compression module 210 includes a primary compressor 211, a primary cooler 212, a primary liquid separator 213, a secondary compressor 214, a secondary cooler 215, a secondary liquid separator 216, a tertiary compressor 217, a tertiary cooler 218, and a tertiary liquid separator 219 which are connected in sequence.

[0072] The drying module 220 includes a first drying tower 221, a second drying tower 222, an electric heater 223, a cooler 224, and a regeneration gas separation tank 225. The liquefaction module 230 is disposed downstream of the drying module 220.

[0073] The liquefaction module 230 includes a first liquefier 231, a second liquefier 232, a front liquid separator 233, a rear liquid separator 234, and a carbon dioxide storage tank 235. The front liquid separator 233 is connected to both the first liquefier 231 and the second liquefier 232. One end of the rear liquid separator 234 is connected to the first liquefier 231, and the other end is connected to the carbon dioxide storage tank.

[0074] During the operation of the capture system, the carbon dioxide in the flue gas is processed by the capture unit 100 to form carbon dioxide gas with a concentration of more than 94.5%.

[0075] The carbon dioxide gas is then processed by the liquefaction unit 200 and compressed three times by the compression module 210 to compress the carbon dioxide gas from normal pressure to 2.4 MPa.g. Then, the compressed carbon dioxide gas is transported to the drying module 220.

[0076] The compressed carbon dioxide gas enters the PTSA system. The PTSA system consists of a first drying tower 221, a second drying tower 222, an electric heater 223, a cooler 224 and a regeneration gas separator 225. Among them, one of the two drying towers is working and the other is regenerating. Part of the carbon dioxide gas is taken out from the front of the drying tower, heated by the electric heater 223 and sent to the drying tower to remove moisture from the packing in the drying tower and regenerate the packing. The packing regeneration temperature is 250°C. The regeneration gas of carbon dioxide used to remove moisture from the packing in the drying tower enters the regeneration gas separator 225 after cooling, and then enters the drying tower, and the cycle is repeated.

[0077] The dried carbon dioxide gas is liquefied in the liquefaction module 230 through medium-temperature and low-temperature two-stage liquefaction treatments in the first liquefier 231 and the second liquefier 232 , and is cooled to -25°C. After liquefaction, it is stored in the carbon dioxide storage tank 235 .

[0078] The Freon refrigeration unit 202 provides cooling liquid to the first liquefier 231 and the second liquefier 232 .

[0079] 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A capture system for treating carbon dioxide in flue gas, characterized in that: include: The capture unit (100) is provided with a gas-liquid mass transfer device (110), a regeneration tower (120), and a solution circulating between the gas-liquid mass transfer device (110) and the regeneration tower (120), and is used for absorbing and desorbing carbon dioxide; a liquefaction unit (200), which is in communication with the regeneration tower (120) and is used to compress, dry and liquefy the carbon dioxide discharged from the regeneration tower (120); The solution has two states: absorbing carbon dioxide in the gas-liquid mass transfer device (110) to form a rich liquid, and desorbing carbon dioxide in the regeneration tower (120) to form a lean liquid; The capture unit (100) is provided with a process module (130) for treating a solution, and the gas-liquid mass transfer device (110) is connected to the regeneration tower (120) via the process module (130).

2. The capture system for treating carbon dioxide in flue gas according to claim 1, characterized in that: The process module (130) comprises: a rich liquid buffer tank (131), which is arranged on a loop for conveying rich liquid from the gas-liquid mass transfer device (110) to the regeneration tower (120), and is used for screening out semi-lean liquid that has insufficiently absorbed carbon dioxide from the rich liquid and returning it to the gas-liquid mass transfer device (110).

3. The capture system for treating carbon dioxide in flue gas according to claim 2, characterized in that: The process module (130) comprises: a heat exchange circuit (140) arranged between the rich liquid buffer tank (131) and the regeneration tower (120); The heat exchange circuit (140) has two parallel branches, one branch is provided with a lean and rich liquid heat exchanger (141), and the other branch is provided with a carbon dioxide and rich liquid heat exchanger (142) and a solution heat exchanger (143), which are used to perform flow diversion and multi-stage heat exchange treatment on the rich liquid.

4. The capture system for treating carbon dioxide in flue gas according to claim 3, characterized in that: The process module (130) comprises: a filtering component (150) arranged on a loop for conveying lean liquid from the regeneration tower (120) to the gas-liquid mass transfer device (110), and used for filtering the lean liquid.

5. The capture system for treating carbon dioxide in flue gas according to claim 4, characterized in that: The filter assembly (150) comprises a particle filter (151), an activated carbon filter (152), and a membrane filter (153) which are sequentially connected in series.

6. The capture system for treating carbon dioxide in flue gas according to any one of claims 1 to 5, characterized in that: The capture unit (100) is further provided with an absorption tower (160), and the absorption tower (160) is connected in parallel with the gas-liquid mass transfer device (110) and is used in rotation with the gas-liquid mass transfer device (110) during maintenance.

7. The capture system for treating carbon dioxide in flue gas according to any one of claims 1 to 5, characterized in that: It also includes a water scrubber (170), wherein a gas outlet at the upper end of the water scrubber (170) is connected to a gas inlet of the gas-liquid mass transfer device (110); the flue gas first enters the water scrubber (170), undergoes dust removal and cooling treatment, and then enters the gas-liquid mass transfer device (110) for decarbonization treatment.

8. The capture system for treating carbon dioxide in flue gas according to claim 2, characterized in that: It also includes a liquid separation tank tower (180), one end of the liquid separation tank tower (180) is connected to the gas outlet of the gas-liquid mass transfer device (110), and the bottom end of the liquid separation tank tower (180) is connected to the rich liquid buffer tank (131); The decarbonized flue gas enters the liquid separation tank tower (180) for cooling, and the solution carried by the flue gas is condensed and liquefied and transported to the rich liquid buffer tank (131).

9. A process for treating carbon dioxide in flue gas, characterized in that: The capture system for treating carbon dioxide in flue gas according to any one of claims 1 to 8 is implemented, comprising the following steps: S1, pre-treating the flue gas, removing dust from the flue gas, and cooling the flue gas to below 40° C.; S2, capturing carbon dioxide in the pre-treated flue gas, and then discharging the decarbonized flue gas; S3. The carbon dioxide is liquefied and then stored.

10. The process for treating carbon dioxide in flue gas according to claim 9, characterized in that: The capturing of carbon dioxide in the pre-treated flue gas comprises: The pretreated flue gas is transported to the gas-liquid mass transfer device (110), so that the flue gas enters the bottom of the gas-liquid mass transfer device (110) under a slightly positive pressure, and a solution for absorbing and desorbing carbon dioxide is added from the top of the gas-liquid mass transfer device (110), so that the solution and the flue gas are in reverse contact to absorb the carbon dioxide in the flue gas to form a rich liquid, and then the rich liquid is transported to the regeneration tower (120), so that the rich liquid releases carbon dioxide in the regeneration tower (120).

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