A flue gas carbon dioxide capture and purification system and its operation method

Abstract

This invention relates to a flue gas carbon dioxide capture and purification system and its operation method, comprising a flue gas pretreatment unit, a carbon dioxide absorption unit, a carbon dioxide regeneration unit, and a carbon dioxide post-treatment unit connected in sequence. The carbon dioxide regeneration unit includes a decarbonization device and a first heating module, a second heating module, and a third heating module connected to the decarbonization device. The first heating module is activated when the plant's zero-discharge wastewater system is running; the second heating module is activated when the plant's zero-discharge wastewater system is shut down and during non-off-peak electricity hours; and the third heating module is activated when the plant's zero-discharge wastewater system is shut down and during off-peak electricity hours. This system can flexibly switch the three heating modules according to different time periods to use the optimal heating method at any given time. This significantly reduces high-cost electricity consumption and lowers system operating costs. It also utilizes the waste heat from flue gas that might otherwise be wasted in thermal power plants for system operation, improving the energy utilization rate of thermal power plants.

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 and purification system and its operation method. Background Technology

[0002] Currently, carbon dioxide is one of the main greenhouse gases contributing to global warming, accounting for up to 55% of the greenhouse effect. Coal-fired power plants are the largest emitters of carbon dioxide, and effectively capturing carbon dioxide from flue gas from these plants is an urgent problem to be solved. Flue gas carbon dioxide capture technologies mainly include chemical absorption, physical adsorption, and membrane separation. Among these, chemical absorption is widely used due to its low operating pressure and high capture efficiency. In the traditional chemical absorption process, the outlet flue gas is first pretreated and cooled before entering the absorption tower to contact the absorbent liquid. The carbon dioxide in the outlet flue gas is absorbed by the absorbent liquid, forming a rich liquid that flows out from the bottom of the absorption tower. The decarbonized flue gas is discharged from the top of the absorption tower into the chimney. The rich liquid passes through a heat exchanger and is heated before entering the top of the regeneration tower. After being heated in the regeneration tower, desorption is completed. The desorbed carbon dioxide gas is collected, and the lean liquid separated by desorption is returned to the absorption tower for reuse after heat recovery through a heat exchanger.

[0003] However, in the above-mentioned traditional chemical process, the desorption of carbon dioxide in the regeneration tower is a thermally driven process. Usually, a decarbonization device such as a reboiler is installed at the bottom of the desorption tower to heat the rich liquid output from the regeneration tower. The decarbonization device often consumes a lot of electrical energy during operation, resulting in a significant increase in system energy consumption and operating costs. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a flue gas carbon dioxide capture and purification system and its operation method. This system can be linked to the zero-discharge system for wastewater in thermal power plants, enabling the system to flexibly switch heating modes according to different time periods, thereby minimizing system operating costs. Furthermore, the use of flue gas heat exchange instead of electric heating can significantly reduce the high-cost electricity consumption required for system operation and also enable the recycling and reuse of waste resources.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A flue gas carbon dioxide capture and purification system is connected to the plant's wastewater zero-discharge system and boiler denitrification device, including a flue gas pretreatment unit, a carbon dioxide absorption unit, a carbon dioxide regeneration unit and a carbon dioxide post-treatment unit connected in sequence.

[0007] The absorbent liquid of the carbon dioxide absorption unit absorbs carbon dioxide from the flue gas to form a rich liquid.

[0008] The carbon dioxide regeneration unit is used to heat the rich liquid and desorb carbon dioxide, which is then discharged into the carbon dioxide post-treatment unit. The carbon dioxide regeneration unit includes a decarbonization device and three heating modules connected to the decarbonization device. The heating modules include a first heating module, a second heating module, and a third heating module.

[0009] The first heating module uses the outlet flue gas output from the wastewater bypass evaporation tower of the plant's zero wastewater discharge system to heat the decarbonization device. The first heating module is turned on when the plant's zero wastewater discharge system is running.

[0010] The second heating module draws high-temperature flue gas from the outlet of the denitrification device of the boiler in the plant to heat the decarbonization device. The second heating module is turned on when the plant's wastewater zero-discharge system is shut down and during non-off-peak electricity hours.

[0011] The third heating module uses off-peak electricity to heat the decarbonization device. The third heating module is turned on during off-peak electricity hours when the plant's zero wastewater discharge system is shut down.

[0012] Furthermore, the first heating module includes a switchable first pipe and a second pipe. The inlet end of the first pipe is connected to the outlet end of the boiler denitrification device in the plant, the outlet end of the first pipe is connected to the inlet end of the wastewater bypass evaporation tower in the plant, the inlet end of the second pipe is connected to the outlet end of the wastewater bypass evaporation tower in the plant, and the outlet end of the second pipe is connected to the decarbonization device.

[0013] The second pipe is equipped with an ash removal device.

[0014] Furthermore, the second heating module includes a switchable third pipe, the inlet end of which is connected to the outlet end of the denitrification device of the boiler in the plant, and the outlet end of which is connected to the decarbonization device.

[0015] The third pipe is equipped with an ash removal device.

[0016] Furthermore, the decarbonization device includes a lean liquor output end. The lean liquor generated after the decarbonization device heats the rich liquor is discharged through the lean liquor output end. A lean liquor thermometer is provided on the lean liquor output end to detect whether the lean liquor temperature is within a set value. Both the first heating module and the second heating module are connected to a diversion pipe.

[0017] When the lean liquor temperature is lower than the set value, the second heating module is turned on to assist in heating the decarbonization device; when the lean liquor temperature is higher than the set value, the diversion pipe is turned on.

[0018] Furthermore, the carbon dioxide post-treatment unit includes at least two dehydration towers for switching use to continuously dehydrate the carbon dioxide from the carbon dioxide post-treatment unit. The bottom of the dehydration tower is connected to a heating component, which provides hot air to heat the dehydration tower after it becomes saturated with water, thereby desorbing water and regenerating it.

[0019] The heating assembly includes an air preheater and a first heating assembly and a second heating assembly connected to the air preheater.

[0020] The first heating component uses the flue gas discharged after heating the decarbonization device to heat the air in the air preheater. The first heating component is turned on when the first heating module and / or the second heating module are running.

[0021] The second heating component uses off-peak electricity to heat the air preheater.

[0022] Furthermore, a hot air thermometer is installed on the pipe connecting the air preheater and the dehydration tower to detect whether the temperature of the hot air output from the air preheater is within the set value range. The air preheater is also connected to a valley electricity storage device.

[0023] When the hot air temperature is lower than the set value, the off-peak electricity storage device is turned on to assist in heating the air preheater.

[0024] When the hot air temperature is higher than the set value, the flow rate of the first heating component is reduced.

[0025] Furthermore, the flue gas pretreatment unit includes a pretreatment tower, the inlet end of which is connected to the flue gas outlet of the desulfurization tower in the plant. The pretreatment tower includes an alkali input end, an alkali output end, a first spray end, and a first industrial water input end. The first spray end includes a first demister and a first nozzle.

[0026] The alkali output end is sequentially connected to the first circulating pump, the alkali input end, the first heat exchanger and the first nozzle to form an alkali delivery path;

[0027] The pretreatment tower is also equipped with a pH meter to monitor in real time whether the pH value in the pretreatment tower is at the preset value. The alkali input terminal is connected to the alkali tank and is used to add alkali when the pH value in the pretreatment tower is lower than the preset value.

[0028] The pretreatment tower is also equipped with a level gauge to monitor in real time whether the water level in the pretreatment tower is at a preset value. The first industrial water input terminal is connected to the industrial water tank and is used to replenish industrial water when the water level in the pretreatment tower is lower than the set value.

[0029] Furthermore, the carbon dioxide absorption unit includes an absorption tower and a scrubbing tower. The absorption tower is connected to the scrubbing tower. The absorption tower is equipped with an absorbent liquid inside to adsorb carbon dioxide in the flue gas to form a rich liquid and decarbonized flue gas. The scrubbing tower is used to remove the absorbent liquid carried on the surface of the decarbonized flue gas from the absorption tower.

[0030] The scrubbing tower includes a second industrial water inlet, a first industrial water outlet, a second spray outlet, a low-concentration absorbent outlet, and a decarbonized flue gas outlet. The second spray outlet includes a second demister and a second nozzle.

[0031] The second industrial water inlet is connected to the industrial water tank;

[0032] The second industrial water inlet is connected sequentially to the second nozzle, the second industrial water outlet, the second circulating pump, and the second nozzle to form an industrial water scrubbing air path;

[0033] The low-concentration absorbent output is connected to the absorption tower for reuse of the low-concentration absorbent.

[0034] The decarbonized flue gas output end is connected to the chimney.

[0035] To achieve the above objectives, the present invention also employs the following technical solution:

[0036] An operating method for a flue gas carbon dioxide capture and purification system, applicable to any of the flue gas carbon dioxide capture and purification systems described above, includes the following steps:

[0037] Step S1: After the flue gas is treated by the flue gas pretreatment unit to remove acidic gases and cool down, it enters the carbon dioxide absorption unit and comes into countercurrent contact with the absorbent liquid to form a rich liquid. The rich liquid enters the decarbonization device after heat exchange.

[0038] Step S2: Determine whether the plant's zero-discharge wastewater system is operating during this time period;

[0039] If running, switch the first heating module to heat the decarbonization device;

[0040] If it does not run, determine whether this time period is a low-electricity period;

[0041] If so, switch the third heating module to heat the decarbonization device;

[0042] If not, switch to the second heating module to heat the decarbonization device;

[0043] Step S3: After heating and desorption, the rich solution yields carbon dioxide and a lean solution. The carbon dioxide is compressed and then enters the carbon dioxide post-treatment unit for dehydration and impurity removal to obtain high-purity carbon dioxide. The lean solution is returned to the carbon dioxide absorption unit for reuse.

[0044] In summary, compared with the prior art, the present invention has at least the following beneficial effects:

[0045] This invention relates to a flue gas carbon dioxide capture and purification system and its operating method. The system is connected to an in-plant wastewater zero-discharge system and a boiler denitrification device, and includes a flue gas pretreatment unit, a carbon dioxide absorption unit, a carbon dioxide regeneration unit, and a carbon dioxide post-treatment unit connected in sequence. The absorbent in the carbon dioxide absorption unit absorbs carbon dioxide from the flue gas to form a rich liquid. The carbon dioxide regeneration unit heats the rich liquid and desorbs carbon dioxide, which is then discharged into the carbon dioxide post-treatment unit. The carbon dioxide regeneration unit includes a decarbonization device and three heating modules connected to the decarbonization device. Each heating module includes a first heating module, a second heating module, and a third heating module. The first heating module uses the outlet flue gas from the wastewater bypass evaporator of the in-plant wastewater zero-discharge system to heat the decarbonization device, and this module is activated when the in-plant wastewater zero-discharge system is running. The second heating module draws high-temperature flue gas from the outlet of the in-plant boiler denitrification device to heat the decarbonization device, and this module is activated when the in-plant wastewater zero-discharge system is shut down and during non-off-peak electricity hours. The third heating module uses off-peak electricity to heat the decarbonization device, and this module is activated when the in-plant wastewater zero-discharge system is shut down and during off-peak electricity hours. By linking the flue gas carbon dioxide capture and purification system with the zero-discharge wastewater system in the thermal power plant, this system can flexibly switch the operation of the three heating modules according to different time periods, using waste flue gas for heat exchange or using off-peak electricity for heating. This allows the system to use the heating method that minimizes the system's operating costs during any given time period to heat the decarbonization device. This not only significantly reduces the high-cost electricity consumption required for system operation and lowers system operating costs, but also enables the effective utilization of resources within the thermal power plant. By using the waste heat from the flue gas that might otherwise be wasted in the thermal power plant for heating in the carbon dioxide regeneration process, electricity consumption is reduced and the energy utilization rate of the thermal power plant is improved. Attached Figure Description

[0046] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0047] Figure 1 This is a schematic diagram of a flue gas carbon dioxide capture and purification system provided in one embodiment of the present invention.

[0048] Figure 2This is a schematic diagram of the structure of a carbon dioxide regeneration unit provided in one embodiment of the present invention.

[0049] Figure 3 This is a schematic diagram of the structure of a carbon dioxide after-treatment unit provided in one embodiment of the present invention.

[0050] Figure 4 This is a schematic diagram of the structure of a flue gas pretreatment unit provided in one embodiment of the present invention.

[0051] Figure 5 This is a schematic diagram of the structure of a carbon dioxide absorption unit provided in one embodiment of the present invention.

[0052] Explanation of reference numerals in the attached figures:

[0053] 1. Flue gas pretreatment unit; 11. Pretreatment tower; 111. Alkali inlet; 112. Alkali outlet; 113. First industrial water inlet; 114. First demister; 115. First nozzle; 116. First circulating pump; 117. pH meter; 118. Flue gas outlet; 12. First heat exchanger; 13. Alkali tank; 131. Alkali pump; 14. Level gauge;

[0054] 2. Carbon dioxide absorption unit; 21. Absorption tower; 211. Flue gas inlet; 212. Rich liquid outlet; 213. Absorbent liquid outlet; 214. Decarbonized flue gas outlet; 215. Third demister; 216. Third nozzle; 217. Second circulating pump; 22. Gas scrubbing tower; 221. Second industrial water inlet; 222. First industrial water outlet; 223. Low-concentration absorbent liquid outlet; 224. Decarbonized flue gas outlet; 225. Second demister; 226. Second nozzle; 23. Second heat exchanger; 24. Third heat exchanger;

[0055] 3. Carbon dioxide regeneration unit; 31. Decarbonization device; 311. Lean liquor output end; 3111. Lean liquor thermometer; 32. First heating module; 321. First pipeline; 322. Second pipeline; 33. Second heating module; 331. Third pipeline; 34. Ash removal device; 35. Diversion pipeline; 36. Regeneration tower; 361. Rich liquor input end; 362. Rich liquor outlet end; 363. Third carbon dioxide input end; 364. Third carbon dioxide output end; 37. Compressor;

[0056] 4. Carbon dioxide post-treatment unit; 41. Dehydration tower; 411. First carbon dioxide input end; 412. Packing material; 413. First carbon dioxide output end; 414. Exhaust port; 42. Heating assembly; 421. Air preheater; 422. First heating assembly; 4221. Fourth pipeline; 423. Air booster fan; 43. Hot air thermometer; 44. Off-peak electricity storage device; 45. Adsorption tower; 451. Second carbon dioxide input end; 452. Second carbon dioxide output end;

[0057] 5. Zero-discharge system for wastewater within the plant; 51. Denitrification unit; 52. Wastewater bypass evaporation tower;

[0058] 6. Industrial water tanks. Detailed Implementation

[0059] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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 the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0061] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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.

[0062] In the operation of thermal power plants, multiple systems typically operate in tandem. Due to environmental policy requirements, achieving zero wastewater discharge within the plant has become an inevitable trend. Currently, the bypass evaporation crystallization process is proving effective. This system extracts high-temperature flue gas (350-380℃) from the denitrification unit outlet and brings it counter-currently to contact atomized high-salt wastewater in a bypass evaporation tower. The high-temperature flue gas causes the wastewater to evaporate and crystallize inside the tower. The outlet flue gas temperature of the bypass evaporation tower is 180-220℃. This waste heat flue gas is typically directly treated by the dust removal system before being discharged, failing to effectively utilize the waste heat of this part of the flue gas, increasing energy consumption in the thermal power plant, and hindering the overall efficiency improvement. Therefore, this invention combines the carbon dioxide capture and purification system within the thermal power plant with the zero wastewater discharge system, effectively utilizing the flue gas temperature of the zero wastewater discharge system and reducing the energy consumption and operating costs of the carbon dioxide capture and purification system.

[0063] As attached Figure 1As shown, the present invention provides a flue gas carbon dioxide capture and purification system, comprising a flue gas pretreatment unit 1, a carbon dioxide absorption unit 2, a carbon dioxide regeneration unit 3, and a carbon dioxide post-treatment unit 4 connected in sequence. The flue gas pretreatment unit 1 is connected to the flue gas outlet of the desulfurization tower in the site and is used to remove acidic gases from the flue gas, while also reducing the flue gas temperature. The pretreated flue gas enters the carbon dioxide absorption unit 2 from the bottom and comes into countercurrent contact with the absorbent liquid stored at the bottom of the unit. The absorbent liquid that has absorbed carbon dioxide from the flue gas is used as rich liquid and enters the carbon dioxide regeneration unit 3. The carbon dioxide regeneration unit 3 is used to heat the rich liquid and desorb the carbon dioxide from the rich liquid, and discharge it into the carbon dioxide post-treatment unit 4. The rich liquid from which carbon dioxide has been desorbed forms a lean liquid and is returned to the carbon dioxide absorption unit 2 for reuse. The carbon dioxide regeneration unit 3 includes a decarbonization device 31 and three heating modules connected to the decarbonization device 31. The heating modules include a first heating module 32, a second heating module 33, and a third heating module. The first heating module 32 is activated when the plant's zero-discharge wastewater system 5 is running. At this time, the wastewater bypass evaporator 52 is operating normally, and the first heating module 32 uses the outlet flue gas output from the wastewater bypass evaporator 52 to heat the decarbonization device 31. The second heating module 33 is activated when the plant's zero-discharge wastewater system 5 is shut down and during non-off-peak electricity hours. At this time, the wastewater bypass evaporator 52 is shut down, but the boiler's denitrification device 51 is still operating. The high-temperature flue gas from the denitrification unit 51 of the boiler in the plant is heated and decarbonized by the decarbonization unit 31. It is worth noting that, considering that the process of extracting flue gas inevitably involves a certain amount of energy consumption, the flue gas carbon dioxide capture and purification system will prioritize the use of the first heating module 32 to meet the heating requirements. Therefore, the second heating module 33 will be started when the first heating module 32 cannot provide a heat source and during non-off-peak electricity periods. The third heating module will be started when the plant's wastewater zero-discharge system is shut down and during off-peak electricity periods. The third heating module uses off-peak electricity to heat the decarbonization unit 31, making full use of the low-cost off-peak electricity resources, significantly reducing heating costs, and improving the economic efficiency of the entire flue gas carbon dioxide capture and purification system. By flexibly switching the operation of the three heating modules according to different time periods, using waste flue gas for heat exchange or using off-peak electricity for heating, this system can use the heating method that minimizes the system's operating cost in any given time period to heat the decarbonization device 31 to desorb the rich liquid and form carbon dioxide. This not only significantly reduces the high-cost electricity consumption required for system operation and lowers system operating costs, but also enables the effective utilization of resources within the thermal power plant. By using the waste heat of flue gas that might otherwise be wasted in the thermal power plant for heating in the carbon dioxide regeneration process, electricity consumption is reduced and the energy utilization rate of the thermal power plant is improved.

[0064] It is worth noting that some thermal power plants do not have a zero-discharge wastewater system 5, but they must have a denitrification device 51 installed in the plant. These thermal power plants can use the second heating module 33 of this system to extract high-temperature flue gas from the outlet flue of the denitrification device 51 to heat the decarbonization device 31 during off-peak hours. During off-peak hours, the third heating module is still used for heating. The two heating modes can be switched to reduce the energy loss and operating cost of the flue gas carbon dioxide capture and purification system.

[0065] In some embodiments of the present invention, as shown in the appendix Figure 2 As shown, the first heating module 32 includes a switchable first pipe 321 and a second pipe 322. The inlet end of the first pipe 321 is connected to the outlet end of the boiler denitrification device 51 in the plant, and the outlet end of the first pipe 321 is connected to the inlet end of the wastewater bypass evaporation tower 52 in the plant. The first pipe 321 is used to guide the high-temperature flue gas in the outlet flue of the denitrification device 51 to the wastewater bypass evaporation tower 52, using the high-temperature flue gas to promote the evaporation and crystallization of the wastewater in the evaporation tower, thereby achieving preliminary treatment and resource recovery of the wastewater. The inlet end of the second pipe 322 is connected to the outlet end of the wastewater bypass evaporation tower 52 in the plant, and the outlet end of the second pipe 322 is connected to the decarbonization device 31. The second pipe 322 is used to introduce the outlet flue gas flowing out of the wastewater bypass evaporation tower 52 into the decarbonization device 31, heat the decarbonization device 31, and then discharge it through the decarbonization device 31 to the subsequent flue gas treatment system of the wastewater zero discharge system 5. Furthermore, since the flue gas discharged from the wastewater bypass evaporator 52 is untreated, there may be dust and other impurities in the flue gas. In order to prevent impurities from damaging the internal components of the decarbonization device 31 or clogging the pipes, an ash removal device 34 is installed on the second pipe 322 to intercept dust and ensure the reliability of the system operation.

[0066] In some embodiments of the present invention, the second heating module 33 includes a switchable third pipe 331. The inlet end of the third pipe 331 is connected to the outlet end of the denitrification device 51 in the plant, and the outlet end of the third pipe 331 is connected to the decarbonization device 31. When the first heating module 32 cannot provide a heat source and it is outside of off-peak electricity hours, or when the thermal power plant does not have a zero-discharge wastewater system and it is outside of off-peak electricity hours, the third pipe 331 will be opened, allowing the high-temperature flue gas from the outlet of the denitrification device 51 to be directly transmitted to the decarbonization device 31 through the third pipe 331. After heating the decarbonization device 31, the gas is discharged through the decarbonization device 31 into the subsequent flue gas treatment system of the zero-discharge wastewater system 5. Similarly, the third pipe 331 is equipped with an ash removal device 34 to intercept dust to prevent impurities from damaging the internal components of the decarbonization device 31 or clogging the pipe.

[0067] It is worth noting that the second pipe 322 of the first heating module 32 and the third pipe 331 of the second heating module 33 have a certain degree of flexibility in layout. Their rear ends can be merged, and the ash removal device 34 is set in the merging part to save space and facilitate system installation; or they can be set apart and lead to the decarbonization device 31 independently, with the ash removal device 34 set on the second pipe 322 and the third pipe 331 respectively, to remove ash according to the flue gas temperature in different pipes.

[0068] In some embodiments of the present invention, the decarbonization device 31 includes a lean liquor output terminal 311. During its operation, the lean liquor formed after the decarbonization device 31 heats the rich liquor is transported to the carbon dioxide absorption unit 2 for reuse via the lean liquor output terminal 311. In this reuse process, the lean liquor first passes through the second heat exchanger 23, where it exchanges heat with the rich liquor output from the carbon dioxide absorption unit 2. This allows the rich liquor to absorb the heat carried by the lean liquor, thereby raising its own temperature before entering the carbon dioxide regeneration unit 3, reducing the energy consumption and heating time used by the decarbonization device 31 when heating the rich liquor. Therefore, in order to accurately control the output temperature of the lean liquor, a lean liquor thermometer 3111 is provided on the lean liquor output terminal 311 to detect whether the lean liquor temperature is between the set value of 130-140°C.

[0069] Specifically, when the lean liquid temperature detected by the lean liquid thermometer 3111 is lower than the set range of 130-140℃, this situation may occur when the first heating module 32 is used for heating. Since the temperature is below the standard, it will affect the efficiency of heat exchange between the lean liquid and the rich liquid in the carbon dioxide absorption unit 2, as well as the stability of the system. In this case, the second heating module 33 can be opened to assist in heating the decarbonization device 31 until the lean liquid temperature equals the set value of 130-140℃, at which point the second heating module 33 can be closed. This ensures a suitable lean liquid temperature while avoiding energy loss caused by excessive extraction of high-temperature flue gas from the outlet of the denitrification device 51. Furthermore, both the first heating module 32 and the second heating module 33 are connected to a diversion pipe 35. When the lean liquid temperature detected by the lean liquid thermometer 3111 is higher than the set value of 130-140℃, this situation may occur when either the first heating module 32 or the second heating module 33 is used for heating. In this case, the diversion pipe 35 can be opened to divert the flue gas to the subsequent flue gas treatment system of the zero-discharge wastewater system, thereby reducing the lean liquid temperature to the set range.

[0070] In some embodiments of the present invention, the carbon dioxide regeneration unit 3 further includes a regeneration tower 36, which includes a rich liquid input end 361, a fourth spray end, a rich liquid outlet end 362, a third carbon dioxide input end 363, and a third carbon dioxide output end 364. The rich liquid input end 361 is connected to the carbon dioxide absorption unit 2, and the rich liquid outlet end 362 is connected to the decarbonization device 31 to input rich liquid for desorption. The desorbed carbon dioxide is transported to the third carbon dioxide input end 363 through the decarbonization device 31, and enters the carbon dioxide post-treatment unit 4 after being compressed by the heat exchanger and compressor 37 from the third carbon dioxide output end 364.

[0071] In some embodiments of the present invention, since the carbon dioxide output from the regeneration tower 36 is obtained by high-temperature desorption of the rich liquid from the decarbonization device 31, the obtained carbon dioxide itself carries a certain amount of water vapor. Therefore, the carbon dioxide post-treatment unit 4 is provided with a dehydration tower 41 to dry the carbon dioxide. The dehydration tower 41 includes a first carbon dioxide input end 411 at the bottom, packing material 412 inside, a first carbon dioxide output end 413 at the top, and an vent 414 communicating with the atmosphere for discharging moisture when the packing material 412 is heated. The first carbon dioxide input end 411 is connected to the packing material 412 and the first carbon dioxide output end 413 in sequence to form a carbon dioxide dehydration path. Furthermore, the carbon dioxide post-treatment unit 4 includes at least two dehydration towers 41 for switching between them to continuously dehydrate the carbon dioxide. The bottom of the dehydration tower 41 is connected to a heating assembly 42, which provides hot air to heat the packing material 412 inside one of the dehydration towers after it has absorbed water to saturation, thereby desorbing water and regenerating it. When one of the dehydration towers 41 becomes saturated with water, the switching process is as follows: First, carbon dioxide is stopped from entering the currently saturated dehydration tower 41. Instead, carbon dioxide is introduced into the standby dehydration tower 41'. Then, the heating component 42 is turned on to heat the currently stopped dehydration tower 41. Under the heating effect, the water originally absorbed by the packing 412 is gradually converted into water vapor and discharged from the vent 414. As the water is removed, the dehydration tower 41 is regenerated, restoring its water absorption capacity, and can then be put back into use. When the standby dehydration tower 41' becomes saturated with water after running for a period of time, the above steps are repeated to heat and regenerate the dehydration tower 41'. At least two dehydration towers are switched between operation, in a continuous cycle. By using at least two dehydration towers and following this uninterrupted switching operation mode, the need to suspend the operation of other units in the system when the dehydration tower 41 becomes saturated during regeneration is effectively avoided. This effectively improves the operating efficiency of the system and ensures that the entire carbon dioxide capture and purification system can operate stably for a long period of time.

[0072] Furthermore, the heating assembly 42 includes an air preheater 421 and a first heating assembly 422 and a second heating assembly connected to the air preheater 421. The air preheater 421 introduces air through an air booster fan 423 and heats the air through the first heating assembly 422 or the second heating assembly. The hot air enters the dehydration tower 41 through the bottom of the dehydration tower 41 to regenerate the dehydration tower 41. The first heating component 422 uses the flue gas discharged from the decarbonization device 31 to heat the air in the air preheater 421. The first heating component 422 includes a switchable fourth pipe 4221, which is a branch of the pipeline between the decarbonization device 31 and the subsequent flue gas treatment system of the zero-discharge wastewater system 5. When the first heating module 32 and / or the second heating module 33 are in operation, the first heating component 422 is activated, allowing the still relatively hot flue gas discharged from the decarbonization device 31 to flow into the air preheater 421 through the fourth pipe 4221. The residual heat of the flue gas is used to raise the air temperature, further realizing the effective utilization of residual heat resources and improving the energy efficiency of the entire system. The second heating component uses off-peak electricity to heat the air preheater 421 during the operation period of the third heating module. This heating method, which flexibly switches according to the operating period of different heating modules, combined with the operation mode of the carbon dioxide regeneration unit 3 during system operation, can meet the heat required for the regeneration of the dehydration tower 41 while minimizing system operating costs and energy consumption.

[0073] In some embodiments of the present invention, since the packing 412 in the dehydration tower has a suitable regeneration temperature range, if the hot air temperature is too high, the packing 412 may deform or age, thus affecting the performance or lifespan of the packing 412. If the hot air temperature is too low, the moisture in the packing 412 will not be completely extracted, resulting in poor regeneration effect. In order to keep the packing 412 at a suitable temperature, it is necessary to accurately control the temperature of the hot air entering the dehydration tower 41. Therefore, a hot air thermometer 43 is installed on the pipe connecting the air preheater 421 and the dehydration tower 41 to detect whether the temperature of the hot air output from the air preheater 421 is between the set value of 120-150°C.

[0074] Specifically, the air preheater 421 is also connected to a rural electricity storage device 44. When the hot air temperature detected by the hot air thermometer 43 is lower than the set value of 120-150℃, this situation may occur when the first heating component 422 is used for heating. At this time, it is a non-rural electricity period. The rural electricity storage device 44 is turned on to assist in heating the air preheater 421 until the hot air is equal to the set value of 120-150℃, and then the rural electricity storage device 44 is turned off. This ensures that the hot air temperature is suitable while avoiding energy loss caused by overheating the hot air in the air preheater 421 and avoiding the impact on the performance of the packing 412 due to excessively high hot air temperature. When the hot air temperature detected by the hot air thermometer 43 is higher than the set value of 120-150℃, this situation may also occur when the first heating component 422 is used for heating. At this time, the flue gas flow rate entering the first heating component 422 can be reduced or the pipeline between the decarbonization device 31 and the subsequent flue gas treatment system of the wastewater zero discharge system 5 can be opened to divert the flue gas and reduce the hot air temperature to the set range.

[0075] In some embodiments of the present invention, in order to further depurify the dehydrated carbon dioxide to obtain high-purity carbon dioxide, the carbon dioxide post-treatment unit 4 further includes an adsorption tower 45. The adsorption tower 45 is connected to the dehydration tower 41. The adsorption tower 45 includes a second carbon dioxide input end 451 disposed at the bottom, an adsorbent material disposed inside, and a second carbon dioxide output end 452 disposed at the top. The second carbon dioxide input end 451 is connected to the first carbon dioxide output end 413 to receive the dehydrated carbon dioxide. The second carbon dioxide input end 451 is connected to the adsorbent material and the second carbon dioxide output end 452 in sequence to form a carbon dioxide depurification path. The carbon dioxide discharged through the second carbon dioxide output end 452 is high-purity carbon dioxide. High-purity carbon dioxide can be used in subsequent applications such as chemical production and food processing where the purity of carbon dioxide is required.

[0076] In some embodiments of the present invention, the flue gas pretreatment unit 1 includes a pretreatment tower 11. The inlet end of the pretreatment tower 11 is connected to the flue gas outlet of the desulfurization tower in the plant. The pretreatment tower 11 includes an alkali input end 111, an alkali output end 112, a first spray end, a first industrial water input end 113, and a flue gas outlet end 118. The flue gas outlet end 118 is connected to the bottom of the carbon dioxide absorption unit 2. The flue gas enters the pretreatment tower 11 and is treated by alkali solution to remove acidic gases and cool down. The pretreated flue gas enters the carbon dioxide absorption unit 2 through the flue gas outlet end 118 and comes into countercurrent contact with the absorbent liquid. The first spray end includes a first demister 114 and a first nozzle 115. The first demister 114 is used to remove the mist droplets carried by the flue gas after the alkali spraying and other treatment processes, to prevent the mist droplets from affecting the subsequent flue gas treatment effect or damaging the subsequent equipment. The alkali output end 112 is connected in sequence to the first circulating pump 116, the alkali input end 111, the first heat exchanger 12 and the first nozzle 115 to form an alkali delivery path, so that the alkali continuously circulates and enhances the mass transfer effect between the alkali and the flue gas, so as to more effectively remove acidic gases from the flue gas.

[0077] Furthermore, a pH meter 117 is also installed on the pretreatment tower 11 to monitor in real time whether the pH value inside the pretreatment tower 11 is within the preset value of pH = 8-9. The alkali input terminal 111 is connected to the alkali tank 13. When the pH value of the alkali solution in the pretreatment tower 11 detected by the pH meter 117 is less than 8-9, the ability to absorb acidic gases in the flue gas will be affected due to insufficient alkalinity. At this time, the alkali pump 131 is turned on to draw alkali solution from the alkali tank 13 into the pretreatment tower 11 to replenish the alkali solution and restore the pH value of the alkali solution to a suitable range. As the alkali solution is continuously consumed, the liquid level of the alkali solution will drop. When the liquid level is too low, the mass transfer and reaction effect between the alkali solution and the flue gas will be unsatisfactory, resulting in insufficient contact between the alkali solution and the flue gas. This further leads to the inability to effectively remove acidic gases in the flue gas, affecting the effect of the pretreatment step. Therefore, a level gauge is also installed on the pretreatment tower 11 to monitor in real time whether the water level inside the pretreatment tower 11 is within the preset range. The first industrial water inlet 113 of the pretreatment tower 11 is connected to the industrial water tank 6. When the level gauge 14 detects that the liquid level is too low, industrial water is added to the pretreatment tower 11 to keep the liquid level in the pretreatment tower 11 stable and ensure the normal operation of the pretreatment tower 11.

[0078] In some embodiments of the present invention, the carbon dioxide absorption unit 2 includes an absorption tower 21, which includes a flue gas inlet end 211, a rich liquid outlet end 212, an absorbent liquid outlet end 213, a third spray end, and a decarbonized flue gas outlet end 214 disposed at the bottom. The flue gas inlet end 211 is connected to the flue gas outlet end 118 of the pretreatment tower 11, and the rich liquid outlet end 212 is connected to the carbon dioxide regeneration unit 3. The pretreated flue gas enters the absorption tower 21 through the flue gas inlet end 211 and comes into countercurrent contact with the absorbent liquid in the absorption tower 21. The absorbent liquid absorbs the carbon dioxide in the flue gas and is discharged from the rich liquid outlet end 212 as rich liquid. It then passes through the third heat exchanger 24 to exchange heat with high-temperature carbon dioxide and the second heat exchanger 23 to exchange heat with high-temperature lean liquid, and then enters the regeneration tower 36. The flue gas with carbon dioxide removed is discharged from the decarbonized flue gas outlet end 214 at the top of the absorption tower 21. Preferably, the absorption tower 21 is provided with a second circulation pump 217. The third spray end includes a third demister 215 and a third nozzle 216. The third demister 215 is used to reduce the absorbent content carried on the surface of the decarbonized flue gas, thereby reducing absorbent waste. The absorbent output end 213 is connected in sequence to the second circulating pump 217 and the third nozzle 216 to form an absorbent mass transfer path, enhancing the mass transfer effect between the absorbent and carbon dioxide, improving the carbon dioxide absorption rate, and also helping to improve the treatment efficiency of the absorption tower 21.

[0079] In some embodiments of the present invention, the third demister 215 alone cannot completely remove the amount of absorbent carried by the decarbonized flue gas. Therefore, the carbon dioxide absorption unit 2 of this system is further equipped with a scrubbing tower 22 to further remove the absorbent from the surface of the decarbonized flue gas. The scrubbing tower 22 is connected to the decarbonized flue gas outlet 214 of the absorption tower 21. The scrubbing tower 22 includes a second industrial water inlet 221, a first industrial water outlet 222, a second spray end, a low-concentration absorbent outlet 223, and a decarbonized flue gas outlet 224. The second spray end includes a second demister 225 and a second nozzle 226. The second industrial water inlet 221 is connected to the industrial water tank 6. The absorbent is further removed by the scrubbing of the gas with industrial water. The second industrial water inlet 221 is connected in sequence to the second nozzle 226, the first industrial water outlet 222, the second circulation pump 217, and the second nozzle 226 to form a circulation path, thus forming an industrial water scrubbing gas path. Furthermore, the washed-off absorbent mixes with the industrial water at the bottom of the scrubbing tower 22 to form a low-concentration absorbent. The low-concentration absorbent outlet 223 is connected to the absorbent mass transfer path of the absorption tower 21, allowing the low-concentration absorbent to be reused in the absorption tower 21, effectively reducing operating costs and losses. The decarbonized flue gas outlet 214 is connected to the chimney, and the decarbonized flue gas, after the absorbent has been thoroughly removed, is discharged from the top of the scrubbing tower 22 into the chimney of the thermal power plant.

[0080] In addition to the above-mentioned flue gas carbon dioxide capture and purification system, the present invention also provides an operating method applicable to the above-mentioned flue gas carbon dioxide capture and purification system, and the operating method of the flue gas carbon dioxide capture and purification system can be referred to in correspondence with the above-mentioned flue gas carbon dioxide capture and purification system.

[0081] A method for operating a flue gas carbon dioxide capture and purification system includes the following steps:

[0082] Step S1: After the flue gas is treated by the flue gas pretreatment unit 1 to remove acidic gases and cool down, it enters the carbon dioxide absorption unit 2 and comes into countercurrent contact with the absorbent liquid to form a rich liquid. The rich liquid enters the decarbonization device 31 after heat exchange.

[0083] Step S2: Determine whether the factory's zero-discharge wastewater system 5 is operating during this time period;

[0084] If running, switch the first heating module 32 to heat the decarbonization device 31;

[0085] If it does not run, determine whether this time period is a low-electricity period;

[0086] If so, switch to the third heating module to heat the decarburization device 31;

[0087] If not, switch the second heating module 33 to heat the decarburization device 31;

[0088] Step S3: After heating and desorption, the rich solution yields carbon dioxide and the lean solution. The carbon dioxide is compressed and then enters the carbon dioxide post-treatment unit 4 for dehydration and impurity removal to obtain high-purity carbon dioxide. The lean solution is returned to the carbon dioxide absorption unit 2 for reuse.

[0089] It is worth noting that if some thermal power plants do not have a zero-discharge wastewater system 5, the energy consumption and operating cost of the flue gas carbon dioxide capture and purification system can be flexibly modified in step S2. In this case, step S2 is: determine whether this time period is a peak electricity period.

[0090] If so, switch to the third heating module to heat the decarburization device 31;

[0091] If not, switch the second heating module 33 to heat the decarburization device 31.

[0092] As attached Figure 1-5As shown, the specific operation mode of all embodiments of the flue gas carbon dioxide capture and purification system of this invention is as follows: First, the flue gas is discharged from the flue gas outlet of the desulfurization tower in the plant and enters the pretreatment tower 11. The acidic gases are removed and the temperature is lowered by the alkaline solution in the pretreatment tower 11. During this process, the pH value and liquid level of the alkaline solution in the tower need to be continuously balanced. The treated flue gas is discharged into the absorption tower 21 through the pretreatment tower 11. The decarbonized flue gas, after the removal of carbon dioxide, is input from the absorption tower 21 into the scrubbing tower 22 for the removal of the surface absorbent liquid of the decarbonized flue gas. The decarbonized flue gas after scrubbing is discharged into the chimney in the plant. The low-concentration absorbent liquid washed off is reused in the absorption tower 21. The absorbent liquid absorbs the carbon dioxide in the flue gas and is discharged from the absorption tower 21 as a rich liquid. After heat exchange, it is input into the regeneration tower 36 and then transported to the decarbonization device 31 by the regeneration tower 36. Different heating modules are switched according to different time periods for heating. The decarbonization device 31 operates by switching to the first heating module 32 during the period when the plant's zero-discharge wastewater system 5 is running, switching to the second heating module 33 during the period when the plant's zero-discharge wastewater system 5 is not running and there is no off-peak electricity, and switching to the third heating module during the period when the plant's zero-discharge wastewater system 5 is not running and there is no off-peak electricity. After being heated by the decarbonization device 31, the rich liquor is desorbed to obtain desorbed carbon dioxide and lean liquor with carbon dioxide removed. The high-temperature lean liquor is transported back to the absorption tower 21 for reuse through the decarbonization device 31, and heat is exchanged with the undesorbed rich liquor during the transportation process. The carbon dioxide is transported back to the regeneration tower 36 through the decarbonization device 31 and discharged through the regeneration tower 36. After heat exchange and compression with the undesorbed rich liquor, it enters the dehydration tower 41 to remove water vapor. The dehydrated carbon dioxide enters the adsorption tower 45 for further impurity removal to obtain high-purity carbon dioxide. This operating method can continuously capture and purify high-purity carbon dioxide, always using the method with the lowest operating cost and energy consumption, and the resources in each link can be recycled, effectively reducing operating costs.

[0093] In addition, the system includes a regeneration step for dehydration tower 41: First, carbon dioxide is stopped from entering the currently saturated dehydration tower 41. Instead, carbon dioxide is introduced into the standby dehydration tower 41'. Then, the heating component 42 is turned on to heat the currently stopped dehydration tower 41. Under the heating action, the water absorbed by the packing 412 is gradually converted into water vapor and discharged. As the water is removed, the dehydration tower 41 is regenerated, restoring its water absorption capacity, and can then be put into use again. When the standby dehydration tower 41' becomes saturated after running for a period of time, the above steps are repeated to heat and regenerate the dehydration tower 41'. At least two dehydration towers are switched between operation and used in a cyclical manner. This avoids the need to suspend the operation of other units in the system when the dehydration tower 41 is saturated during regeneration, effectively improving the operating efficiency of the system and ensuring that the entire carbon dioxide capture and purification system can operate stably for a long time.

[0094] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A flue gas carbon dioxide capture and purification system, connected to an in-plant wastewater zero-discharge system and an in-plant denitrification device, characterized in that, It includes a flue gas pretreatment unit, a carbon dioxide absorption unit, a carbon dioxide regeneration unit, and a carbon dioxide posttreatment unit connected in sequence. The absorbent liquid of the carbon dioxide absorption unit absorbs carbon dioxide from the flue gas to form a rich liquid. The carbon dioxide regeneration unit is used to heat the rich liquid and desorb carbon dioxide, which is then discharged into the carbon dioxide post-treatment unit. The carbon dioxide regeneration unit includes a decarbonization device and three heating modules connected to the decarbonization device. The heating modules include a first heating module, a second heating module, and a third heating module. The first heating module uses the outlet flue gas output from the wastewater bypass evaporation tower of the plant's zero wastewater discharge system to heat the decarbonization device. The first heating module is turned on when the plant's zero wastewater discharge system is running. The second heating module draws high-temperature flue gas from the outlet of the denitrification device of the boiler in the plant to heat the decarbonization device. The second heating module is turned on when the plant's wastewater zero-discharge system is shut down and during non-off-peak electricity hours. The third heating module uses off-peak electricity to heat the decarbonization device. The third heating module is turned on during off-peak electricity hours when the plant's zero wastewater discharge system is shut down.

2. The flue gas carbon dioxide capture and purification system as described in claim 1, characterized in that, The first heating module includes a switchable first pipe and a second pipe. The inlet end of the first pipe is connected to the outlet end of the boiler denitrification device in the plant. The outlet end of the first pipe is connected to the inlet end of the wastewater bypass evaporation tower in the plant. The inlet end of the second pipe is connected to the outlet end of the wastewater bypass evaporation tower in the plant. The outlet end of the second pipe is connected to the decarbonization device. The second pipe is equipped with an ash removal device.

3. The flue gas carbon dioxide capture and purification system as described in claim 1, characterized in that, The second heating module includes a switchable third pipe, the inlet end of which is connected to the outlet end of the denitrification device of the boiler in the plant, and the outlet end of which is connected to the decarbonization device. The third pipe is equipped with an ash removal device.

4. The flue gas carbon dioxide capture and purification system as described in claim 1, characterized in that, The decarbonization device includes a lean liquor output end. The lean liquor generated after heating the rich liquor is discharged through the lean liquor output end. A lean liquor thermometer is installed on the lean liquor output end to detect whether the lean liquor temperature is within a set value. The first heating module and the second heating module are both connected to a diversion pipe. When the lean liquor temperature is lower than the set value, the second heating module is turned on to assist in heating the decarbonization device; when the lean liquor temperature is higher than the set value, the diversion pipe is turned on.

5. The flue gas carbon dioxide capture and purification system as described in claim 1, characterized in that, The carbon dioxide post-treatment unit includes at least two dehydration towers for switching use to continuously dehydrate the carbon dioxide from the carbon dioxide post-treatment unit. The bottom of the dehydration tower is connected to a heating component, which provides hot air to heat the dehydration tower after it becomes saturated with water, thereby desorbing water and regenerating it. The heating assembly includes an air preheater and a first heating assembly and a second heating assembly connected to the air preheater. The first heating component uses the flue gas discharged after heating the decarbonization device to heat the air in the air preheater. The first heating component is turned on when the first heating module and / or the second heating module are running. The second heating component uses off-peak electricity to heat the air preheater.

6. The flue gas carbon dioxide capture and purification system as described in claim 5, characterized in that, A hot air thermometer is installed on the pipe connecting the air preheater and the dehydration tower to detect whether the temperature of the hot air output from the air preheater is within the set value. The air preheater is also connected to a valley electricity storage device. When the hot air temperature is lower than the set value, the off-peak electricity storage device is turned on to assist in heating the air preheater. When the hot air temperature is higher than the set value, the flow rate of the first heating component is reduced.

7. The flue gas carbon dioxide capture and purification system as described in claim 1, characterized in that, The flue gas pretreatment unit includes a pretreatment tower, the inlet of which is connected to the flue gas outlet of the desulfurization tower in the plant. The pretreatment tower includes an alkali input end, an alkali output end, a first spray end, and a first industrial water input end. The first spray end includes a first demister and a first nozzle. The alkali output end is sequentially connected to the first circulating pump, the alkali input end, the first heat exchanger and the first nozzle to form an alkali delivery path; The pretreatment tower is also equipped with a pH meter to monitor in real time whether the pH value in the pretreatment tower is at the preset value. The alkali input terminal is connected to the alkali tank and is used to add alkali when the pH value in the pretreatment tower is lower than the preset value. The pretreatment tower is also equipped with a level gauge to monitor in real time whether the water level in the pretreatment tower is at a preset value. The first industrial water input terminal is connected to the industrial water tank and is used to replenish industrial water when the water level in the pretreatment tower is lower than the set value.

8. The flue gas carbon dioxide capture and purification system as described in claim 1, characterized in that, The carbon dioxide absorption unit includes an absorption tower and a scrubbing tower. The absorption tower is connected to the scrubbing tower. The absorption tower is equipped with an absorbent liquid inside to adsorb carbon dioxide in the flue gas to form a rich liquid and decarbonized flue gas. The scrubbing tower is used to remove the absorbent liquid carried on the surface of the decarbonized flue gas from the absorption tower. The scrubbing tower includes a second industrial water inlet, a first industrial water outlet, a second spray outlet, a low-concentration absorbent outlet, and a decarbonized flue gas outlet. The second spray outlet includes a second demister and a second nozzle. The second industrial water inlet is connected to the industrial water tank; The second industrial water inlet is connected sequentially to the second nozzle, the first industrial water outlet, the second circulating pump, and the second nozzle to form an industrial water scrubbing air path; The low-concentration absorbent output is connected to the absorption tower for reuse of the low-concentration absorbent. The decarbonized flue gas output end is connected to the chimney.

9. A method for operating a flue gas carbon dioxide capture and purification system, applicable to the flue gas carbon dioxide capture and purification system according to any one of claims 1-6, characterized in that, Includes the following steps: Step S1: After the flue gas is treated by the flue gas pretreatment unit to remove acidic gases and cool down, it enters the carbon dioxide absorption unit and comes into countercurrent contact with the absorbent liquid to form a rich liquid. The rich liquid enters the decarbonization device after heat exchange. Step S2: Determine whether the plant's zero-discharge wastewater system is operating during this time period; If running, switch the first heating module to heat the decarbonization device; If it does not run, determine whether this time period is a low-electricity period; If so, switch the third heating module to heat the decarbonization device; If not, switch to the second heating module to heat the decarbonization device; Step S3: After heating and desorption, the rich solution yields carbon dioxide and a lean solution. The carbon dioxide is compressed and then enters the carbon dioxide post-treatment unit for dehydration and impurity removal to obtain high-purity carbon dioxide. The lean solution is returned to the carbon dioxide absorption unit for reuse.

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