CO2 capture and compression integrated system and method based on high-pressure ammonia evaporative cooling

Abstract

The invention discloses a CO2 capture and compression integrated system and method based on high-pressure ammonia evaporative cooling. The CO2 trapping and compressing integrated system provided by the invention comprises a CO2 multi-stage compressor unit and an ammonia multi-stage flash evaporation cooling system, flue gas discharged by a boiler is conveyed to the CO2 capturing unit, and CO2 gas separated by the CO2 capturing unit is conveyed to the CO2 multi-stage compressor unit to be compressed stage by stage; the CO2 multi-stage compressor unit comprises multiple stages of CO2 compressors connected in series, and an interstage cooler is arranged between every two adjacent stages of CO2 compressors. The ammonia multi-stage flash evaporation cooling system comprises a liquid ammonia storage tank and a pump set and is communicated with multiple stages of flash evaporation tanks which are connected in series, and each stage of flash evaporation tank is communicated with the corresponding stage of interstage cooler; the final-stage flash tank is sequentially communicated with an ammonia gas compressor and a flue gas waste heat heater, the flue gas waste heat heater is communicated with the boiler, and the pressurized and heated ammonia gas is sent back to the boiler for blending combustion.

Description

Technical Field

[0001] This application belongs to the field of flue gas treatment technology, specifically relating to an integrated CO2 capture and compression system and method based on high-pressure ammonia evaporation cooling. Background Technology

[0002] Coal-fired power plants are accelerating the development of two key technologies: ammonia-blended combustion and post-combustion carbon dioxide capture, utilization, and storage (CCUS). Ammonia-blended combustion reduces carbon emissions at the source by incorporating zero-carbon ammonia fuel into the boiler; CCUS technology separates CO2 from flue gas and then compresses it through multiple stages to a supercritical state for transport and storage. In current engineering practice, these two technologies are usually operated as independent subsystems: ammonia fuel needs to be pressurized and pumped from a liquid ammonia storage tank, evaporated stage by stage, and superheated by waste heat from the flue gas before being sent into the furnace; while the CO2 compression process relies on traditional cooling methods—mostly open-loop circulating water cooling or air cooling systems—to cool the high-temperature CO2 after each stage of compression to meet the inlet temperature requirements of the next stage of compression. This type of cooling system has a mature structure and simple control, and has been applied in several demonstration projects.

[0003] However, the aforementioned conventional technical routes suffer from significant energy efficiency synergy deficiencies: on the one hand, high-pressure liquid ammonia requires substantial heat absorption during evaporation into gaseous fuel, and this cold energy currently relies entirely on external heat sources (such as flue gas) and is not effectively recovered and utilized; on the other hand, the multi-stage compression process of CO2 generates a large amount of compression heat, which must be carried away by external cooling media, resulting in high power consumption, high water consumption, or significant susceptibility to ambient temperature in the cooling system. The two technologies are naturally complementary in terms of energy flow: ammonia evaporation is an endothermic process, while CO2 compression is an exothermic process; however, existing technologies have not yet established a direct thermodynamic coupling mechanism between them, resulting in insufficient energy cascade utilization and low overall system net efficiency, thus hindering the large-scale commercial application of ammonia-blended + CCUS combined technology in thermal power plants. Therefore, there is an urgent need for an integrated system and method that can deeply couple the cold energy from ammonia fuel preparation with the heat energy from CO2 compression, achieving synergistic energy transfer within the system. Summary of the Invention

[0004] To address the problems of low system efficiency and high resource consumption caused by the independent operation of existing ammonia-blended combustion and CCUS systems, this invention proposes an integrated CO2 capture and compression system and method based on high-pressure ammonia evaporation cooling.

[0005] To achieve the above objectives, this application provides the following technical solution: This invention provides an integrated CO2 capture and compression system based on high-pressure ammonia evaporation cooling, including a CO2 multi-stage compressor unit and an ammonia multi-stage flash cooling system; The flue gas discharged from the boiler is sent to the CO2 capture unit. The CO2 gas separated by the CO2 capture unit is sent to the CO2 multi-stage compressor unit for compression stage by stage. The compressed CO2 is then absorbed or stored. The CO2 multi-stage compressor unit includes multiple CO2 compressors connected in series, and an interstage cooler is installed between adjacent CO2 compressor stages. The ammonia multi-stage flash cooling system includes a liquid ammonia storage tank and a pump set. The liquid ammonia storage tank and pump set are connected to a series of flash tanks. Each flash tank is connected to the corresponding CO2 compression stage cooler in the CO2 multi-stage compressor unit. The low-temperature two-phase ammonia flow generated by the flash tank is sent to the corresponding connected cooler, where it undergoes direct contact heat exchange with the compressed high-temperature CO2 gas. The final flash tank is connected in sequence to the ammonia compressor and the flue gas waste heat heater. The flue gas waste heat heater is connected to the boiler, which sends the pressurized and heated ammonia gas back to the boiler for co-firing.

[0006] Furthermore, the CO2 compression interstage cooler adopts a shell-and-tube heat exchange structure, with the ammonia-side medium flowing through the tubes and the CO2-side medium flowing through the shell, and the shell design pressure is not less than 4.0 MPa.

[0007] Furthermore, the heat source of the flue gas waste heat heater is taken from the bypass flue gas of the boiler, and its flue gas inlet temperature is 280~420°C and its outlet temperature is not lower than 150°C.

[0008] This invention also provides a CO2 capture and compression method based on high-pressure ammonia evaporation cooling, which uses the above-mentioned integrated CO2 capture and compression system based on high-pressure ammonia evaporation cooling to capture and compress CO2, including the following steps: The flue gas discharged from the boiler enters the CO2 capture unit and is separated to obtain low-pressure CO2 gas; Low-pressure CO2 gas is fed into a CO2 multi-stage compressor unit for step-by-step compression. After each stage of compression, the high-temperature CO2 gas is introduced into the corresponding CO2 compression interstage cooler, while the low-temperature two-phase ammonia stream from the corresponding stage flash tank is sent into the same stage CO2 compression interstage cooler to achieve CO2 cooling through direct contact heat exchange. After the ammonia gas from each stage of the CO2 compression interstage cooler has completed heat exchange, it is collected, pressurized by the ammonia compressor, and sent to the flue gas waste heat heater to be heated to the temperature and pressure required for combustion. The heated, high-temperature, high-pressure gaseous ammonia is fed into the boiler as fuel to participate in co-firing, thus completing the closed-loop ammonia cycle.

[0009] Furthermore, the temperature of the low-temperature two-phase ammonia flow generated by each stage of the flash tank decreases sequentially, with the temperature difference between adjacent flash tanks being 15~30℃.

[0010] Furthermore, the temperature of the low-temperature two-phase ammonia flow generated by the final flash tank is -30 to -10℃.

[0011] Furthermore, the temperature difference between the low-temperature two-phase ammonia flow generated by each stage of flash evaporation and the corresponding stage CO2 compression outlet temperature is controlled within the range of 20~60℃.

[0012] Furthermore, the heat source of the flue gas waste heat heater is taken from the bypass flue gas of the boiler. By adjusting the flow rate of the bypass flue gas of the boiler, the outlet ammonia temperature of the flue gas waste heat heater is controlled to be 400~550℃, the pressure to be 2.5~4.0MPa, and the superheat to be 50~100℃.

[0013] Furthermore, the inlet flow rate and outlet temperature of each stage of the CO2 compressor are monitored in real time, and the compression heat load of each stage is calculated; the liquid ammonia supply flow rate of the corresponding stage ammonia flash evaporation system is adjusted synchronously to maintain a dynamic balance between the heat absorbed by ammonia evaporation and the heat released by CO2 compression.

[0014] Furthermore, during system start-up, shutdown, or sudden changes in operating conditions: when the CO2 capture load decreases to 70% or below the rated load, the liquid ammonia supply and ammonia compressor speed are reduced proportionally.

[0015] Compared with the prior art, the beneficial effects of this application are as follows: The CO2 capture and compression integrated system (ACCC) proposed in this invention achieves synergistic optimization of two high-energy-consuming processes—ammonia-blended fuel preparation and CO2 capture and compression—through a deep coupling design of a multi-stage CO2 compressor unit and a multi-stage ammonia flash cooling system. This system utilizes the low-temperature two-phase ammonia flow generated by multi-stage ammonia flash evaporation to directly exchange heat with the exothermic CO2 compression, transforming ammonia gasification from an energy-consuming unit into a CO2 cooling capacity unit. This avoids the additional power consumption of the cooling system, significantly reducing CCUS energy consumption and improving the net power generation efficiency of the power plant. Furthermore, by replacing the traditional cooling water system with ammonia, water consumption and water treatment costs are reduced, making it suitable for power plants in water-scarce or air-cooled, inefficient regions. Simultaneously, it operates stably and reliably; the closed-loop ammonia cycle system is unaffected by ambient temperature, ensuring stable and efficient unit output under various operating conditions, including high temperatures in summer, comprehensively improving the overall economic efficiency and operational reliability of ammonia-blended thermal power plants.

[0016] The CO2 compression method provided by this invention directly matches the heat absorption of ammonia gasification with the heat release of CO2 compression, transforming ammonia gasification from an energy-consuming process into a highly efficient cooling unit. This avoids the high power consumption of additional cooling systems, significantly reduces CCUS energy consumption, and improves the net efficiency of the power plant. Simultaneously, replacing traditional cooling water with ammonia drastically reduces water consumption and water treatment costs, making it suitable for water-scarce regions. Furthermore, the closed-loop ammonia circulation design is unaffected by ambient temperature, ensuring stable output under all operating conditions, including high summer temperatures, comprehensively improving the overall economic efficiency and operational reliability of ammonia-blended thermal power plants. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of a premixed chemical mixture production line provided by the present invention; In the diagram: 1. Boiler; 2. CO2 capture unit; 3. First-stage CO2 compressor; 4. First-stage CO2 compression interstage cooler; 5. Second-stage CO2 compressor; 6. Second-stage CO2 compression cooler; 7. Third-stage CO2 compressor; 8. Liquid ammonia storage tank and pump set; 9. First-stage ammonia flash tank; 10. Second-stage ammonia flash tank; 11. Ammonia compressor; 12. Flue gas waste heat heater. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can typically be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] In the description of the embodiments of this application, it should be noted that if terms such as "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0023] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0024] In the description of the embodiments of this application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" 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 application according to the specific circumstances.

[0025] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. It should be noted that similar reference numerals and letters in the following drawings indicate similar items; therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0026] Ammonia-blended combustion and post-combustion carbon dioxide capture, utilization, and storage (CCUS) are the core technologies for achieving this goal. The former directly reduces CO2 generation by using ammonia as a zero-carbon fuel, while the latter is responsible for processing the generated CO2. However, both face energy consumption challenges in practical engineering applications: in ammonia-blended combustion, ammonia evaporates from a high-pressure liquid state and is superheated to a gaseous state for use as fuel; in CCUS, the post-combustion CO2 capture system has high energy consumption penalties. The step of compressing the captured low-pressure CO2 to a high-pressure liquid or supercritical state is not only energy-intensive, but the cooling system for the compression heat generation also consumes a large amount of electricity and water resources. Therefore, how to reduce the energy consumption of these two steps and achieve efficient integration of the two technologies has become a key technical challenge for the low-carbon transformation of thermal power plants.

[0027] Based on this, the present invention provides an integrated CO2 capture and compression system based on high-pressure ammonia evaporation cooling, including a CO2 multi-stage compressor unit and an ammonia multi-stage flash evaporation cooling system. The flue gas discharged from boiler 1 is sent to CO2 capture unit 2. The CO2 gas separated by CO2 capture unit 2 is sent to CO2 multi-stage compressor unit for compression stage by stage. The compressed CO2 is absorbed or stored. CO2 multi-stage compressor unit includes multiple CO2 compressors connected in series. CO2 interstage cooler is set between two adjacent CO2 compressor stages. The ammonia multi-stage flash cooling system includes a liquid ammonia storage tank and pump group 8. The liquid ammonia storage tank and pump group 8 are connected to a multi-stage series flash tank. Each stage of the ammonia flash tank is connected to the corresponding stage of the CO2 compression interstage cooler in the CO2 multi-stage compressor group. The low-temperature two-phase ammonia flow generated by the ammonia flash tank is sent to the corresponding connected cooler, where it undergoes direct contact heat exchange with the compressed high-temperature CO2 gas. The final stage flash tank is connected in sequence to the ammonia compressor 11 and the flue gas waste heat heater 12. The flue gas waste heat heater 12 is connected to the boiler 1, which sends the pressurized and heated ammonia gas back to the boiler 1 for co-firing.

[0028] The system of this invention includes a multi-stage CO2 compressor unit and a multi-stage ammonia flash cooling system. This invention directly couples the endothermic demand of ammonia fuel gasification with the exothermic process of CO2 compression, achieving synergistic energy transfer and utilization within the system. This reduces the significant power consumption caused by additional cooling systems and improves the net power generation efficiency of power plants after implementing CCUS (Cooled-Off System). Using ammonia as the primary cooling medium, this system replaces traditional cooling water systems in CCUS systems, reducing water treatment costs and making it particularly suitable for thermal power plants in water-scarce or air-cooled regions with low efficiency. The closed-loop system is almost unaffected by ambient temperature. Compared to air-cooled or humidified cooling systems, whose efficiency drops significantly in high summer temperatures, this invention ensures that the unit maintains stable and efficient output under various climatic conditions, especially during peak summer electricity demand.

[0029] In some specific embodiments, the CO2 compression interstage cooler adopts a shell-and-tube heat exchange structure, specifically a vertical fixed tube sheet heat exchanger; the ammonia-side medium flows through the tubes and the CO2-side medium flows through the shell, with a shell design pressure of not less than 4.0 MPa.

[0030] The ammonia flash tank in this integrated CO2 capture and compression system is equipped with an ammonia supply flow regulating valve at the inlet. A flow meter is installed at the inlet of the CO2 compressor, and temperature sensors are installed at the outlets of each stage of the CO2 compressor and the ammonia flash tank. The control system calculates the liquid ammonia supply flow based on the real-time collected CO2 compression heat load from the flow rate and temperature rise, so that the deviation between the heat absorbed by ammonia evaporation and the heat released by CO2 compression is controlled within ±5%, maintaining stable energy matching.

[0031] In some specific embodiments, the heat source of the flue gas waste heat heater 12 is taken from the bypass flue gas of the boiler 1, and its flue gas inlet temperature is 280~420°C and its outlet temperature is not lower than 150°C.

[0032] The CO2 multistage compressor unit has 2, 3, or 4 stages or more, configured according to the final pressure requirements. The number of flash stages of the ammonia multistage flash cooling subsystem strictly corresponds to the number of stages. For each additional compression stage, an additional ammonia flash tank is added, and a corresponding CO2 compression interstage cooler is configured.

[0033] The present invention also provides a CO2 capture and compression system based on high-pressure ammonia evaporation cooling, comprising the following steps: The flue gas discharged from boiler 1 enters CO2 capture unit 2 and is separated to obtain low-pressure CO2 gas; Low-pressure CO2 gas is fed into a CO2 multi-stage compressor unit for step-by-step compression. After each stage of compression, the high-temperature CO2 gas is introduced into the corresponding CO2 compression interstage cooler, while the low-temperature two-phase ammonia stream from the corresponding stage flash tank is sent into the same stage CO2 compression interstage cooler to achieve CO2 cooling through direct contact heat exchange. After the ammonia gas from each stage of the CO2 compression interstage cooler has completed heat exchange, it is collected, pressurized by the ammonia compressor, and sent to the flue gas waste heat heater to be heated to the temperature and pressure required for combustion. The heated, high-temperature, high-pressure gaseous ammonia is fed into boiler 1 as fuel to participate in co-firing, thus completing the closed-loop ammonia cycle.

[0034] In some specific embodiments, the temperature of the low-temperature two-phase ammonia flow generated by each stage of the flash tank decreases sequentially, the temperature difference between two adjacent flash tanks is 15~30℃, and the temperature of the low-temperature two-phase ammonia flow generated by the last stage flash tank is -30~-10℃, so as to balance the low-temperature cooling efficiency and the antifreeze safety of the ammonia system.

[0035] In some specific embodiments, the temperature difference between the low-temperature two-phase ammonia flow generated by each stage of flash evaporation and the corresponding stage CO2 compression outlet temperature is controlled within the range of 20~60℃ to ensure efficient heat transfer and low heat loss.

[0036] In some specific embodiments, by adjusting the bypass flue gas flow rate of boiler 1, the ammonia temperature at the outlet of flue gas waste heat heater 12 is controlled to be 400~550℃, the pressure to be 2.5~4.0MPa, and the superheat to be 50~100℃, so as to prevent condensation or liquid hammer during the transportation process.

[0037] In some specific embodiments, the inlet flow rate and outlet temperature of each stage of the CO2 compressor are monitored in real time, and the compression heat load of each stage is calculated; the liquid ammonia supply flow rate of the corresponding stage ammonia flash evaporation system is adjusted synchronously to maintain a dynamic balance between the heat absorbed by ammonia evaporation and the heat released by CO2 compression.

[0038] In some specific embodiments, during system start-up, shutdown, or sudden changes in operating conditions: when the CO2 capture load decreases to 70% or below the rated load, the liquid ammonia supply and ammonia compressor speed are simultaneously reduced proportionally. This mechanism enhances the system's disturbance immunity and intrinsic safety.

[0039] Example like Figure 1 As shown, the CO2 capture and compression integrated system based on high-pressure ammonia evaporation cooling includes a conventional boiler 1, a CO2 capture unit 2, a CO2 multi-stage compressor unit, and an ammonia multi-stage flash cooling system.

[0040] The flue gas discharged from boiler 1 enters CO2 capture unit 2, where the separated low-pressure CO2 gas is sent to a CO2 multi-stage compressor unit. The CO2 multi-stage compressor unit includes a first-stage CO2 compressor 3, a first-stage CO2 compressor cooler 4, a second-stage CO2 compressor 5, a second-stage CO2 compressor cooler 6, and a third-stage CO2 compressor 7 connected in series, which absorb or store the high-concentration CO2 output from CO2 capture unit 2 and third-stage CO2 compressor 7.

[0041] The ammonia multi-stage flash cooling system includes a liquid ammonia storage tank and pump set 8, which are connected in sequence to a primary ammonia flash tank 9, a secondary ammonia flash tank 10, an ammonia compressor 11, and a flue gas waste heat heater 12. The primary ammonia flash tank 9 is connected to a primary CO2 compressor cooler 4. The secondary ammonia flash tank 10 is connected to a secondary CO2 compressor cooler 6. The flue gas waste heat heater 12 is connected to a boiler 1, and the pressurized and heated ammonia gas is sent back to the boiler 1 for co-firing. The heat source of the flue gas waste heat heater 12 is taken from the bypass flue gas of the boiler 1.

[0042] The CO2 capture and compression integrated system of this invention consists of a conventional boiler 1, a CO2 capture unit 2, and the core of this invention, an integrated CO2 capture and compression unit utilizing high-pressure ammonia evaporation cooling. Internally, it comprises two subsystems: a multi-stage CO2 compressor unit and a multi-stage ammonia flash cooling system. Flue gas discharged from boiler 1 enters CO2 capture unit 2, and the separated low-pressure CO2 gas is sent to the ACCC integrated unit.

[0043] Low-pressure CO2 gas sequentially enters a compressor unit consisting of a first-stage CO2 compressor 3, a second-stage CO2 compressor 5, and a third-stage CO2 compressor 7 connected in series. After each stage of compression, the high-temperature CO2 gas enters the corresponding first-stage CO2 compressor cooler 4 and second-stage CO2 compressor cooler 6 for cooling before entering the next stage of compression.

[0044] The multi-stage ammonia flash cooling system delivers high-pressure liquid ammonia from the liquid ammonia storage tank / pump unit 8 to the first-stage ammonia flash tank 9 for depressurized flash evaporation, producing low-temperature gas-liquid two-phase ammonia. This low-temperature two-phase ammonia is then sent to the first-stage CO2 compressor cooler 4, where its evaporation process absorbs the heat from the CO2 after the first-stage compression, achieving efficient cooling of the CO2. The two-phase ammonia exiting the first-stage CO2 compressor cooler 4 is sent to the second-stage ammonia flash tank 10 for secondary flash evaporation, further reducing its temperature. This even lower-temperature two-phase ammonia is then sent to the second-stage CO2 compressor cooler 6 to cool the CO2 after the second-stage compression. This process can be multi-stage series connection depending on the number of compressor stages, achieving cascaded utilization of cold energy.

[0045] After multi-stage flash cooling, the vaporized low-temperature, low-pressure ammonia gas collects from the top of the primary ammonia flash tank 9 and the secondary ammonia flash tank 10, and enters an ammonia compressor 11 for pressurization. The pressurized ammonia gas then enters the flue gas waste heat heater 12, where it undergoes final superheating using bypass flue gas drawn from boiler 1. The prepared high-temperature, high-pressure fuel ammonia is then returned to boiler 1 for co-firing, completing the entire cycle.

[0046] When this system is used in power plants with ammonia-blended combustion and CCUS function activated, its operation is automated and integrated with the main process.

[0047] When the unit is operating stably under ammonia-blended conditions and the CO2 capture unit is in operation, the CO2 capture and compression integrated system (ACCC) based on high-pressure ammonia evaporation cooling will start simultaneously. The CO2 gas separated from the capture unit enters the first stage of the CO2 compressor for compression. At the same time, the liquid ammonia supply valve of the multi-stage flash cooling system opens, and high-pressure liquid ammonia from the liquid ammonia storage tank begins to enter the cooling process of the first-stage ammonia flash tank and interstage cooler. Thereafter, CO2 and ammonia complete the subsequent compression and cooling processes stage by stage, synchronously, along their respective paths. The flow rate and pressure of the entire system are regulated by the control system to ensure a dynamic balance between the ammonia evaporation rate and the CO2 cooling demand.

[0048] During system operation, the ammonia compressor and flue gas waste heat heater continuously operate, converting the low-temperature spent ammonia, which has completed its cooling task, into high-quality fuel ammonia that meets combustion requirements, and stably sending it back to the boiler. During system start-up, shutdown, or operational condition adjustments, the control system executes complex linkage logic. When reducing the CCUS load, the flow rate of the CO2 compressor and the liquid ammonia flow rate of the ammonia flash system are simultaneously reduced to maintain energy matching. In emergencies, such as a CO2 compressor trip, the ammonia flash system will immediately shut down and redirect the ammonia in the pipeline to the recovery system, ensuring system safety.

[0049] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation methods of this application. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this application are within the protection scope of the claims of this application pending approval.

Claims

1. An integrated CO2 capture and compression system based on high-pressure ammonia evaporation cooling, characterized in that, This includes a CO2 multi-stage compressor unit and an ammonia multi-stage flash cooling system; The flue gas discharged from the boiler (1) is transported to the CO2 capture unit (2). The CO2 gas separated by the CO2 capture unit (2) is transported to the CO2 multi-stage compressor unit for compression stage by stage. The compressed CO2 is absorbed or stored. The CO2 multi-stage compressor unit includes a multi-stage CO2 compressor connected in series. A CO2 compression stage cooler is set between two adjacent CO2 compressor stages. The ammonia multi-stage flash cooling system includes a liquid ammonia storage tank and a pump group (8). The liquid ammonia storage tank and the pump group (8) are connected to a multi-stage series flash tank. Each stage flash tank is connected to the corresponding stage CO2 compression interstage cooler in the CO2 multi-stage compressor group. The low-temperature two-phase ammonia flow generated by the flash tank is sent to the corresponding connected cooler and undergoes direct contact heat exchange with the compressed high-temperature CO2 gas in the cooler. The final stage flash tank is connected to the ammonia compressor (11) and the flue gas waste heat heater (12) in sequence. The flue gas waste heat heater (12) is connected to the boiler (1) and sends the pressurized and heated ammonia gas back to the boiler (1) for co-firing.

2. The integrated CO2 capture and compression system based on high-pressure ammonia evaporation cooling according to claim 1, characterized in that, The CO2 compression interstage cooler adopts a shell-and-tube heat exchange structure, with the ammonia-side medium flowing through the tubes and the CO2-side medium flowing through the shell. The shell design pressure is not less than 4.0 MPa.

3. The integrated CO2 capture and compression system based on high-pressure ammonia evaporation cooling according to claim 1, characterized in that, The heat source of the flue gas waste heat heater (12) is taken from the bypass flue gas of the boiler (1), and its flue gas inlet temperature is 280~420°C and its outlet temperature is not lower than 150°C.

4. A method for CO2 capture and compression based on high-pressure ammonia evaporation cooling, characterized in that, The CO2 capture and compression using the integrated CO2 capture and compression system based on high-pressure ammonia evaporation cooling as described in any one of claims 1-3 includes the following steps: The flue gas discharged from the boiler (1) enters the CO2 capture unit (2) and is separated to obtain low-pressure CO2 gas; Low-pressure CO2 gas is fed into a CO2 multi-stage compressor unit for step-by-step compression. After each stage of compression, the high-temperature CO2 gas is introduced into the corresponding CO2 compression interstage cooler, while the low-temperature two-phase ammonia stream from the corresponding stage flash tank is sent into the same stage CO2 compression interstage cooler to achieve CO2 cooling through direct contact heat exchange. After the ammonia gas from each stage of the CO2 compression interstage cooler has completed heat exchange, it is collected, pressurized by the ammonia compressor, and sent to the flue gas waste heat heater (12) to be heated to the temperature and pressure required for combustion. The heated high-temperature and high-pressure gaseous ammonia is fed into the boiler (1) as fuel to participate in co-firing and complete the closed ammonia cycle.

5. The CO2 capture and compression method based on high-pressure ammonia evaporation cooling according to claim 4, characterized in that, The temperature of the low-temperature two-phase ammonia flow generated by each flash tank decreases sequentially, and the temperature difference between adjacent flash tanks is 15~30℃.

6. The CO2 capture and compression method based on high-pressure ammonia evaporation cooling according to claim 5, characterized in that, The low-temperature two-phase ammonia flow generated by the final flash tank has a temperature of -30 to -10℃.

7. The CO2 capture and compression method based on high-pressure ammonia evaporation cooling according to claim 4, characterized in that, The temperature difference between the low-temperature two-phase ammonia flow generated by each stage of flash evaporation and the corresponding stage CO2 compression outlet temperature is controlled within the range of 20~60℃.

8. The CO2 capture and compression method based on high-pressure ammonia evaporation cooling according to claim 4, characterized in that, The heat source of the flue gas waste heat heater (12) is taken from the bypass flue gas of the boiler (1). By adjusting the flow rate of the bypass flue gas of the boiler (1), the outlet ammonia temperature of the flue gas waste heat heater (12) is controlled to be 400~550℃, the pressure is 2.5~4.0MPa, and the superheat is 50~100℃.

9. The CO2 capture and compression method based on high-pressure ammonia evaporation cooling according to claim 4, characterized in that, Real-time monitoring of the inlet flow rate and outlet temperature of each stage of the CO2 compressor, and calculation of the compression heat load of each stage; synchronous adjustment of the liquid ammonia supply flow rate of the corresponding stage ammonia flash evaporation system to maintain a dynamic balance between the heat absorbed by ammonia evaporation and the heat released by CO2 compression.

10. The CO2 capture and compression method based on high-pressure ammonia evaporation cooling according to claim 4, characterized in that, When the system starts up or stops or the operating conditions change abruptly: when the CO2 capture load drops to 70% or below the rated load, the liquid ammonia supply and the ammonia compressor speed are reduced proportionally.

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