Carbon dioxide capture and carbon dioxide compression energy coupling system

Abstract

The utility model relates to the technical field of carbon capture and energy conservation, and discloses an energy coupling system for carbon dioxide capture and carbon dioxide compression. The system comprises a regeneration tower, a multi-stage compression unit and a multi-stage heat exchange unit, each stage of compression unit in the multi-stage compression unit is provided with a carbon dioxide compression device and a multi-stream heat exchanger, and the multi-stream heat exchanger is internally provided with a high-temperature section heat exchange area and a low-temperature section heat exchange area. The multi-stage heat exchange unit comprises a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a first compression device, a second compression device and a first reboiler. According to the system, the steam production energy consumption is reduced, and the carbon capture operation cost is lower.

Description

Technical Field

[0001] This utility model relates to the field of carbon capture and energy-saving technology, specifically to an energy coupling system for carbon dioxide capture and carbon dioxide compression. Background Technology

[0002] CO2 amine capture and liquefaction technology is an important component of carbon capture. The main problem at present is the high energy consumption and operating cost of CO2 capture and liquefaction. How to reduce the energy consumption and operating cost of CO2 capture and liquefaction has always been a hot topic in carbon capture research.

[0003] Currently, CO2 capture and CO2 liquefaction are usually designed as two independent sections. Apart from the direct supply of process materials, energy use is relatively independent, and energy-saving solutions are usually studied independently. For the CO2 capture section, reducing the energy consumption of the regeneration tower mainly involves exploring within this section, mainly through upgrading and utilizing the waste heat at the top of the tower or deep heat exchange of the waste heat at the bottom of the tower. However, it is becoming increasingly difficult to further reduce the steam consumption at the bottom of the regeneration tower.

[0004] In existing technologies, the compressors in CO2 liquefaction stages typically employ multi-stage compression. After compression, the gas temperature is approximately 100–130°C. It is then cooled to 40°C by circulating water via an interstage cooler before entering the next stage. This process of compression and cooling continues until the set pressure is reached. The heat generated during this process is not recovered, and the CO2 liquefaction stage requires a large amount of circulating water for cooling, resulting in both heat loss during compression and high energy consumption. Therefore, the need to further reduce liquefaction energy consumption is becoming increasingly urgent. Utility Model Content

[0005] The purpose of this invention is to overcome the problems of high steam consumption at the bottom of the regeneration tower and high operating energy consumption in existing carbon capture processes, as well as high compression heat loss and circulating water consumption in the CO2 liquefaction section. This invention provides an energy coupling system for carbon dioxide capture and compression. The system described in this invention recovers all compression heat in the carbon dioxide liquefaction process through multi-stage heat exchange, and generates steam from the recovered heat. This steam is then supplied to the regeneration tower, significantly reducing the amount of external steam required for the regeneration tower, and resulting in lower steam production energy consumption and operating costs, thus reducing the energy consumption per ton of CO2 regeneration.

[0006] To achieve the above objectives, this utility model provides an energy coupling system for carbon dioxide capture and compression. The system includes a regeneration tower, a multi-stage compression unit, and a multi-stage heat exchange unit. Each stage of the multi-stage compression unit is equipped with a carbon dioxide compression device and a multi-stream heat exchanger. The multi-stream heat exchanger is provided with a high-temperature heat exchange zone and a low-temperature heat exchange zone. The multi-stage heat exchange unit includes a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a first compression device, a second compression device, and a first reboiler.

[0007] The CO2 gas from the top of the regeneration tower is compressed in the multi-stage compression unit in sequence. In each compression unit, the CO2 gas compressed by the carbon dioxide compression device first exchanges heat with the first high-temperature cooling water in the high-temperature section of the multi-stream heat exchanger, and then exchanges heat with the low-temperature cooling water in the low-temperature section of the multi-stream heat exchanger.

[0008] After heat exchange, the low-temperature cooling water and the liquid low-temperature working fluid exchange heat in the first heat exchanger, causing the liquid low-temperature working fluid to absorb heat and evaporate into a gaseous state. The low-temperature cooling water is then cooled down and recycled.

[0009] The gaseous cryogenic working fluid is first compressed in the first compression device, and then exchanged with the second high-temperature cooling water in the second heat exchanger, so that the gaseous cryogenic working fluid is condensed into a liquid state and recycled.

[0010] The high-temperature cooling water formed by the merging of the first and second high-temperature cooling waters after heat exchange is exchanged with the liquid high-temperature working fluid in the third heat exchanger. The liquid high-temperature working fluid absorbs heat and evaporates into a gaseous state. The merged high-temperature cooling water is cooled down and split into the first and second high-temperature cooling waters for recycling.

[0011] The gaseous high-temperature working fluid is first compressed in the second compression device, and then exchanged with the steam condensate in the fourth heat exchanger, so that the steam condensate absorbs and evaporates into steam, and the gaseous high-temperature working fluid is condensed into liquid and recycled.

[0012] In the first reboiler, the steam is used to heat the solution at the bottom of the regeneration tower, so that the solution absorbs heat and reboils. The reboiled solution is returned to the regeneration tower for desorption and regeneration to obtain regenerated lean liquid and CO2 gas. The steam is condensed into steam condensate and recycled.

[0013] Preferably, the system further includes a first throttling expansion device for throttling and expanding the liquid cryogenic working fluid obtained after heat exchange in the second heat exchanger, and then recycling the liquid cryogenic working fluid.

[0014] Preferably, the second compression device is provided with an intermediate air inlet, and the system further includes a second throttling expansion device and a first gas-liquid separation device. The second throttling expansion device is used to throttle and expand the high-temperature liquid working fluid obtained after heat exchange in the fourth heat exchanger, and the material from the second throttling expansion device is subjected to gas-liquid separation in the first gas-liquid separation device. The separated gas phase working fluid is transported to the second compression device through the intermediate air inlet for air replenishment, and the separated liquid phase working fluid is returned to the third heat exchanger for recycling.

[0015] Preferably, the system further includes a third throttling expansion device for throttling and expanding the liquid working fluid from the first gas-liquid separation device for recycling.

[0016] This utility model has the following beneficial effects:

[0017] (1) The system described in this utility model adopts a two-stage cascade recovery technology to fully recover the compression heat generated in the CO2 liquefaction section. Based on the cascade utilization of compression heat and the principle of reverse Carnot cycle steam generation, a multi-stream high-efficiency heat exchange system is used to replace the original interstage cooler. The compression heat is divided into high-temperature section and low-temperature section heat. High-temperature cooling water and low-temperature cooling water are matched respectively to exchange heat with the high-temperature section heat and the low-temperature section heat. High-temperature hot water is produced by water exchange in two parallel ways. Then, the obtained high-temperature hot water is exchanged with high-temperature working fluid to evaporate the high-temperature working fluid into a gaseous state. Then, the gaseous high-temperature working fluid is compressed and exchanged with steam condensate to evaporate the steam condensate into a gaseous state. Steam is produced through the reverse Carnot cycle of the high-temperature working fluid. The obtained steam is then directly supplied to the regeneration tower to heat the solution at the bottom of the regeneration tower. The heated solution is returned to the regeneration tower for desorption and regeneration to obtain regenerated lean liquid and carbon dioxide. At the same time, the steam after heat exchange is condensed to obtain condensate and continues to be returned to the system for recycling to produce steam. The method described in this invention realizes the full recovery of the compression heat of the CO2 compression section and further utilizes this heat to produce steam for carbon capture in the rich liquid reboiling process. This not only achieves the effect of recovering and reusing the compression heat of the CO2 compression section, but also reduces the energy consumption and water consumption of the CO2 liquefaction section.

[0018] (2) The system described in this invention efficiently recovers the compression heat of the CO2 liquefaction section, further generates steam from the recovered heat, and exchanges the steam with the solution from the regeneration tower, allowing the solution to desorb and regenerate to obtain regenerated lean liquor. This significantly reduces the external steam supply required during carbon capture, further lowering the operating cost of carbon capture, optimizing the overall energy efficiency of carbon capture, and exhibiting significant energy-saving effects. Furthermore, the thermal efficiency of the steam produced by the method described in this invention is higher than that of traditional steam generation methods, such as boilers or electric heating, further reducing energy consumption.

[0019] (3) The system described in this utility model further optimizes the steam generation efficiency through the reverse Carnot cycle of the high-temperature working fluid and the control of the throttling expansion valve. The steam generation process is more stable and efficient, ensuring the continuous supply of steam, guaranteeing the stable regeneration of the rich liquid during the carbon capture process, and maintaining the stable operation of the carbon capture process. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the energy coupling system for carbon dioxide capture and compression.

[0021] Explanation of reference numerals in the attached figures

[0022] 1. Regeneration tower; 2. Carbon dioxide compression unit;

[0023] 3. Multi-stream heat exchanger; 3A high-temperature heat exchange zone;

[0024] 3B Low-temperature heat exchange zone; 4 Second gas-liquid separation device;

[0025] 5. Low-temperature cooling water circulating pump; 6. First heat exchanger;

[0026] 7 First compression unit; 8 Second heat exchanger;

[0027] 9. First throttling expansion device; 10. High-temperature cooling water circulating pump;

[0028] 11. Third heat exchanger; 12. Second compression unit;

[0029] 13 Fourth heat exchanger; 14 Second throttling expansion device;

[0030] 15 First gas-liquid separation device; 16 Third throttling expansion device;

[0031] 17 First reboiler; 18 Steam condensate circulation pump;

[0032] 19 Second reboiler; 20 Reflux pump;

[0033] 21. Third gas-liquid separation device; 22. Cooling device. Detailed Implementation

[0034] The specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of this utility model.

[0035] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0036] In existing carbon capture processes, the absorbent liquid in the absorption tower, after absorbing carbon dioxide, needs to be transported to a regeneration tower for heating and desorption regeneration to obtain a regenerated lean solution (absorbent liquid) for treating the carbon-containing gas to be captured. Therefore, the regeneration tower in the carbon capture system requires a large amount of high-temperature steam to heat the solution at the bottom of the tower to promote desorption and regeneration, significantly increasing the operating cost and energy consumption of the carbon capture system. Simultaneously, the carbon dioxide obtained from the desorption and regeneration of the solution in the regeneration tower is transported to the CO2 liquefaction section for liquefaction treatment. The CO2 liquefaction section typically requires multi-stage compression, and a circulating water cooler is installed between each compression stage to cool the compressed gas. This consumes a large amount of circulating cooling water and also results in significant energy waste. Understandably, in this invention, the solution at the bottom of the regeneration tower 1 is the solution after absorbing carbon dioxide. Reboiling this solution and then desorbing it yields a regenerated lean solution, i.e., the regenerated absorbent liquid.

[0037] Based on this, the present invention provides an energy coupling system for carbon dioxide capture and compression, the process flow diagram of which can be found in conjunction with the above. Figure 1 The system includes a regeneration tower 1, a multi-stage compression unit, and a multi-stage heat exchange unit.

[0038] Each stage of the multi-stage compression unit is equipped with a carbon dioxide compression device 2 and a multi-stream heat exchanger 3. The multi-stream heat exchanger 3 is provided with a high-temperature heat exchange zone 3A and a low-temperature heat exchange zone 3B. The high-temperature heat exchange zone 3A is used to exchange heat between the compressed CO2 gas and the first high-temperature cooling water for a primary heat exchange, and the low-temperature heat exchange zone 3B is used to exchange heat between the CO2 gas and the low-temperature cooling water for a secondary heat exchange, so as to completely recover the heat of the compressed CO2 gas.

[0039] In a specific embodiment, the multi-stage compression unit also includes a second gas-liquid separation device 4, which is used to separate the CO2 after heat exchange in the multi-stream heat exchanger 3. The separated CO2 gas is then transported to the carbon dioxide compression device 2 of the next stage compression unit for compression processing.

[0040] Specifically, the CO2 gas from the top of the regeneration tower 1 is compressed in multiple stages in the multi-stage compression unit. In each compression unit, the CO2 gas compressed by the carbon dioxide compression device first exchanges heat with the first high-temperature cooling water in the high-temperature heat exchange zone 3A of the multi-stream heat exchanger 3, and then exchanges heat with the low-temperature cooling water in the low-temperature heat exchange zone 3B of the multi-stream heat exchanger 3. The CO2 gas after heat exchange is sent to the second gas-liquid separation device 4 for gas-liquid separation. After being pressurized in the multi-stage compression unit, the CO2 gas is sent to the next stage for further processing.

[0041] In one specific embodiment, in the high-temperature section heat exchange zone 3A of the multi-stream heat exchanger 3, the temperature of the first high-temperature cooling water used for heat exchange is 60-70°C, and the temperature of the first high-temperature cooling water after heat exchange is 70-80°C; in the low-temperature section heat exchange zone 3B of the multi-stream heat exchanger 3, the temperature of the low-temperature cooling water used for heat exchange is 30-35°C, and the temperature of the low-temperature cooling water after heat exchange is 40-50°C.

[0042] In the system described in this utility model, the multi-stage heat exchange unit includes a first heat exchanger 6, a second heat exchanger 8, a third heat exchanger 11, a fourth heat exchanger 13, a first compression device 7, a second compression device 12, and a first reboiler 17.

[0043] Specifically, the first heat exchanger 6 is used to exchange heat between the low-temperature cooling water after heat exchange from the low-temperature section heat exchange zone 3B of the multi-stream heat exchanger 3 and the liquid low-temperature working fluid. The liquid low-temperature working fluid absorbs heat and evaporates into a gaseous low-temperature working fluid. The temperature of the low-temperature cooling water after heat exchange decreases and it is returned to the low-temperature section heat exchange zone 3B of the multi-stream heat exchanger 3 for recycling.

[0044] In a more specific embodiment, the low-temperature cooling water after heat exchange in the low-temperature section heat exchange zone 3B of the multi-stream heat exchanger 3 in each stage of the compression unit of the system is combined and then transported to the first heat exchanger 6 to exchange heat with the liquid low-temperature working fluid. After the low-temperature cooling water is cooled down by heat exchange, it is divided into n streams and transported to the low-temperature section heat exchange zone 3B of the multi-stream heat exchanger 3 in each stage of the compression unit for recycling.

[0045] In a specific implementation, the multi-stage heat exchange unit further includes a low-temperature cooling water circulation pump 5, used to transport the low-temperature cooling water after heat exchange and cooling. The low-temperature cooling water after heat exchange and cooling is divided into n streams and correspondingly transported to the low-temperature section heat exchange zone 3B of the multi-stream heat exchanger 3 in each stage compression unit. Specifically, the low-temperature cooling water after heat exchange and cooling returns to the inlet of the low-temperature cooling water circulation pump 5 and is then transported to the low-temperature section heat exchange zone 3B for recycling.

[0046] Specifically, the first compression device 7 is used to compress the gaseous cryogenic working fluid from the first heat exchanger 6 and pressurize the gaseous cryogenic working fluid to a set pressure.

[0047] Specifically, the second heat exchanger 8 is used to exchange heat between the gaseous low-temperature working fluid from the first compression device 7 and the second high-temperature cooling water. After the heat exchange, the temperature of the second high-temperature cooling water increases, and the gaseous low-temperature working fluid releases heat and condenses into a liquid low-temperature working fluid.

[0048] The system described in this utility model also includes a first throttling expansion device 9, which is used to throttle and expand the liquid cryogenic working fluid obtained after heat exchange in the second heat exchanger 8, reduce the pressure to a set value through throttling, and then return it to the first heat exchanger 6 for recycling.

[0049] The system of this invention also includes a high-temperature cooling water circulation pump 10, used to pressurize the high-temperature cooling water. The pressurized high-temperature cooling water is then divided into a first high-temperature cooling water and a second high-temperature cooling water. The first high-temperature cooling water returns to the high-temperature heat exchange zone 3A of the multi-stream heat exchanger 3 to exchange heat once with the compressed CO2 gas. The second high-temperature cooling water returns to the second heat exchanger 8 to exchange heat with the gaseous cryogenic working fluid from the first compression device 7.

[0050] Specifically, the third heat exchanger 11 is used to exchange heat between the first and second high-temperature cooling water (after heat exchange) and the liquid high-temperature working fluid. The cooled high-temperature cooling water is returned to the high-temperature cooling water circulation pump 10, which then pressurizes the high-temperature cooling water. The pressurized high-temperature cooling water is then divided into a first high-temperature cooling water and a second high-temperature cooling water for circulation. Specifically, the first high-temperature cooling water is returned to the high-temperature section heat exchange zone 3A of the multi-stream heat exchanger 3 for circulation, and the second high-temperature cooling water is returned to the second heat exchanger 8 for circulation. The liquid high-temperature working fluid absorbs heat and evaporates into a gaseous high-temperature working fluid in the third heat exchanger 11, and is then transported to the fourth heat exchanger 13 for heat exchange.

[0051] In a more specific embodiment, the first high-temperature cooling water after heat exchange in the high-temperature section heat exchange zone 3A of the multi-stream heat exchanger 3 in each stage of the system merges with the second high-temperature cooling water after heat exchange to obtain high-temperature cooling water. This high-temperature cooling water is then transported to the third heat exchanger 11 to exchange heat with the liquid high-temperature working fluid. Furthermore, the first high-temperature cooling water obtained after heat exchange and cooling is also divided into n streams during recycling, and correspondingly transported to the high-temperature section heat exchange zone 3A of the multi-stream heat exchanger 3 in each stage of the compression unit to exchange heat with the compressed CO2 gas.

[0052] Specifically, the second compression device 12 is used to compress the gaseous high-temperature working fluid and then transport it to the fourth heat exchanger 13 for heat exchange. Preferably, the second compression device 12 is provided with an intermediate gas supply port for supplying gas from the outside to the second compression device to replenish it, thereby reducing the energy consumption of the second compression device.

[0053] Specifically, the fourth heat exchanger 13 is used to exchange heat between the compressed gaseous high-temperature working fluid from the second compression device 12 and the steam condensate. After the heat exchange, the gaseous high-temperature working fluid releases heat and condenses into a liquid high-temperature working fluid, while the steam condensate absorbs heat and evaporates into steam.

[0054] In a preferred embodiment, the system further includes a second throttling expansion device 14, used to throttle and expand the high-temperature liquid working fluid obtained after heat exchange and condensation in the fourth heat exchanger 13, and reduce the pressure to a set value through throttling.

[0055] In a preferred embodiment, the system further includes a first gas-liquid separation device 15, used to separate the material from the second throttling expansion device 14 into gas and liquid phases. The separated gas phase working fluid (i.e., gaseous high-temperature working fluid) is transported to the second compression device 12 through an intermediate gas inlet for gas replenishment. The separated liquid phase working fluid (i.e., liquid high-temperature working fluid) is recycled.

[0056] In a further preferred embodiment, the system further includes a third throttling expansion device 16, used to throttle and expand the liquid working fluid separated from the first gas-liquid separation device 15, reduce its pressure to a set value, and then transport it to the third heat exchanger 11 for recycling.

[0057] Specifically, the first reboiler 17 is used to exchange heat between the steam from the fourth heat exchanger 13 and the solution at the bottom of the regeneration tower 1. The steam heats the solution at the bottom of the regeneration tower 1, causing it to reboil. After absorbing heat, the solution partially vaporizes and then returns to the regeneration tower 1 for desorption and regeneration to obtain regenerated lean liquor and CO2 gas. This completes the reboiling heating of the bottom stream of the regeneration tower 1, ultimately reducing the steam consumption of the reboiler originally installed in the carbon capture system for heating the rich liquor. The regenerated lean liquor is then transported to the absorption tower for treatment of the carbon-containing gas.

[0058] More specifically, the steam that has undergone heat exchange in the first reboiler 17 releases heat, re-condenses into steam condensate, and returns to the fourth heat exchanger 13 for recycling.

[0059] In the system described in this utility model, a steam condensate circulation pump 18 is also provided between the fourth heat exchanger 13 and the first reboiler 17 for transporting steam condensate to the fourth heat exchanger 13 for heat exchange.

[0060] In a specific embodiment, the steam condensate obtained after heat exchange and condensation in the first reboiler 17 is returned to the steam condensate circulation pump 18, and then pressurized by the steam condensate circulation pump 18 before being returned to the fourth heat exchanger 13 for recycling.

[0061] In the system described in this utility model, the system further includes a second reboiler 19 connected to the regeneration tower 1, which is used to heat the solution at the bottom of the regeneration tower 1 with steam from the outside.

[0062] In one specific embodiment, the system further includes a reflux pump 20, a third gas-liquid separator 21, and a cooling device 22. The CO2 gas obtained by desorption of the rich liquid in the regeneration tower 1 is discharged through the top of the regeneration tower 1, then first transported to the cooling device 22 for cooling, and then transported to the third gas-liquid separator 21 for separation. The separated gas (i.e., CO2 gas) is transported to the carbon dioxide compression device 2 of the multi-stage compression unit for compression, and the separated liquid (i.e., lean liquid) is returned to the regeneration tower 1 via the reflux pump 20 for recycling.

[0063] In one specific embodiment, the bottom temperature of the regeneration tower 1 is in the range of 100–130°C.

[0064] In the system described in this utility model, the heat of compression in the CO2 liquefaction section is recovered in a stepwise manner to produce steam with a pressure of 0.2 to 0.3 MPa and a temperature of 130 to 145°C. The produced steam is directly supplied to the regeneration tower 1 of the carbon capture system for heating, thereby reducing the energy consumption of the regeneration tower.

[0065] In the system described in this invention, based on the principles of cascaded utilization of compression heat and two-stage reverse Carnot cycle steam generation, a multi-stream heat exchange system replaces the original interstage cooler in the carbon dioxide liquefaction section. The compression heat of carbon dioxide is divided into a high-temperature section and a low-temperature section. High-temperature cooling water and low-temperature cooling water are then respectively matched to exchange heat with the carbon dioxide gas in the high-temperature section and the carbon dioxide gas in the low-temperature section. A high-temperature heat source is generated through a two-way parallel connection. This high-temperature heat source then exchanges heat with a high-temperature working fluid, and through a reverse Carnot cycle, it exchanges heat with the steam condensate, causing the steam condensate to evaporate and produce steam. The obtained steam is directly supplied to the regeneration tower for heating. The steam after heat exchange is condensed to obtain steam condensate, which is then returned to the system for steam production. This achieves full recovery of CO2 compression heat for steam production, reduces the energy consumption of the carbon capture regeneration tower, saves circulating water used for compression heat cooling, and produces steam to meet the heating needs of the regeneration tower. This not only reduces the amount of external steam supply to the carbon capture process, but also further realizes the coupling between the compression heat of the carbon dioxide liquefaction section and carbon capture, that is, the full recovery of the compression heat of the carbon dioxide liquefaction section, while also reducing the energy consumption and operating costs of the carbon capture process.

[0066] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto.

[0067] Adopting such Figure 1 The energy coupling system for carbon dioxide capture and compression shown is operated in the following embodiment. The multi-stage compression unit of the system contains four carbon dioxide compression devices 2, four multi-stream heat exchangers 3, and four second gas-liquid separation devices 4. That is, CO2 gas from the top of the regeneration tower 1 is compressed and liquefied in four stages in the multi-stage compression unit.

[0068] The system operation process is as follows:

[0069] The CO2 gas from the top of the regeneration tower 1 is compressed in multiple stages in the multi-stage compression unit. In each compression unit, the CO2 gas compressed by the carbon dioxide compression device 2 first exchanges heat with the first high-temperature cooling water in the high-temperature heat exchange zone 3A of the multi-stream heat exchanger 3, and then exchanges heat with the low-temperature cooling water in the low-temperature heat exchange zone 3B of the multi-stream heat exchanger 3. The CO2 gas after heat exchange is sent to the second gas-liquid separation device 4 for gas-liquid separation. The separated CO2 gas is then sent to the carbon dioxide compression device 2 of the next stage compression unit for compression.

[0070] The low-temperature cooling water from the low-temperature section heat exchange zone 3B of the multi-stream heat exchanger 3 exchanges heat with the liquid low-temperature working fluid in the first heat exchanger 6. The liquid low-temperature working fluid absorbs heat and evaporates into a gaseous low-temperature working fluid. The temperature of the low-temperature cooling water decreases after heat exchange and is returned to the low-temperature section heat exchange zone 3B of the multi-stream heat exchanger 3 by the low-temperature cooling water circulation pump 5 for recycling.

[0071] The gaseous cryogenic working fluid is first compressed in the first compression device 7, and then exchanged heat with the second high-temperature cooling water in the second heat exchanger 8. The gaseous cryogenic working fluid releases heat and condenses into a liquid cryogenic working fluid, which is then transported to the first throttling expansion device 9 for throttling expansion. After throttling and depressurization to the set value, it is then returned to the first heat exchanger 6 for recycling.

[0072] The high-temperature cooling water formed by the merging of the first and second high-temperature cooling waters after heat exchange, and the liquid high-temperature working fluid exchange heat in the third heat exchanger 11. The liquid high-temperature working fluid absorbs heat and evaporates into a gaseous high-temperature working fluid. At the same time, the high-temperature cooling water that has cooled down after heat exchange returns to the high-temperature cooling water circulation pump 10. Then, the high-temperature cooling water circulation pump 10 pressurizes the cooled high-temperature cooling water and then splits it into the first high-temperature cooling water and the second high-temperature cooling water. The first high-temperature cooling water obtained by splitting returns to the high-temperature section heat exchange zone 3A of the multi-stream heat exchanger 3 for recycling, and the second high-temperature cooling water obtained by splitting returns to the second heat exchanger 8 for recycling.

[0073] The gaseous high-temperature working fluid is first compressed in the second compression device 12, and then exchanged heat with the steam condensate in the fourth heat exchanger 13. The steam condensate absorbs and evaporates into steam, and the gaseous high-temperature working fluid releases heat and condenses into a liquid high-temperature working fluid. The condensed liquid high-temperature working fluid is then transported to the second throttling expansion device 14 for throttling expansion. After throttling and depressurization to a set value, the resulting material is transported to the first gas-liquid separation device 15 for gas-liquid separation. The separated gaseous working fluid (i.e., the gaseous high-temperature working fluid) is transported to the second compression device 12 through the intermediate air inlet provided on the second compression device 12 for air replenishment. The separated liquid working fluid is transported to the third throttling expansion device 16 for throttling expansion. After throttling and depressurization to a set value, it is then transported to the third heat exchanger 11 for recycling.

[0074] The steam obtained from the heat exchange in the fourth heat exchanger 13 is transported to the first reboiler 17 to exchange heat with the solution at the bottom of the regeneration tower 1. After absorbing heat, the solution at the bottom of the regeneration tower 1 partially vaporizes and reboiles. The reboiled solution is returned to the regeneration tower 1 for desorption and regeneration to obtain regenerated lean liquid and CO2 gas. At the same time, the steam is condensed into steam condensate and returned to the fourth heat exchanger 13 for recycling.

[0075] The CO2 gas obtained in the regeneration tower 1 is discharged through the top of the tower, and then first sent to the cooling device 22 for cooling, and then sent to the third gas-liquid separator 21 for separation. The separated gas (i.e., CO2 gas) is sent to the carbon dioxide compressor 2 of the multi-stage compression unit for compression, and the separated liquid (i.e. lean liquid) is returned to the regeneration tower 1 through the reflux pump 20 for recycling.

[0076] Example 1

[0077] The CO2 gas (temperature 35°C) at the top of the regeneration tower 1 is compressed in multiple stages. After each stage of compression, the compressed CO2 gas (temperature 110°C) is first exchanged with the first high-temperature cooling water (demineralized water, temperature 65°C) and then exchanged with the low-temperature cooling water (demineralized water, temperature 35°C). The CO2 gas after heat exchange is separated into gas and liquid. The separated CO2 gas is then sent to the next stage compression unit for further compression.

[0078] The low-temperature cooling water (temperature of 45°C) after heat exchange is exchanged with the liquid low-temperature working fluid (1,1,1,2-tetrafluoroethane). The liquid low-temperature working fluid absorbs heat and evaporates into a gaseous low-temperature working fluid. The temperature of the low-temperature cooling water after heat exchange decreases and it is returned for recycling.

[0079] The gaseous cryogenic working fluid is first compressed, and then exchanged heat with the second high-temperature cooling water (demineralized water, temperature 65°C). The gaseous cryogenic working fluid releases heat and condenses into a liquid cryogenic working fluid. Then it undergoes throttling expansion, and after throttling and pressure reduction to the set value, it is returned and recycled.

[0080] The high-temperature cooling water formed by the combination of the first high-temperature cooling water (temperature of 75°C) and the second high-temperature cooling water after heat exchange exchanges heat with the liquid high-temperature working fluid (1,1,1,3,3-pentafluoropropane). The liquid high-temperature working fluid absorbs heat and evaporates into a gaseous high-temperature working fluid. At the same time, the high-temperature cooling water that has cooled down after heat exchange is divided into the first high-temperature cooling water and the second high-temperature cooling water for recycling.

[0081] The gaseous high-temperature working fluid is first compressed, and then exchanged heat with the steam condensate. The steam condensate absorbs and evaporates into steam, and the gaseous high-temperature working fluid releases heat and condenses into a liquid high-temperature working fluid. Then, the condensed liquid high-temperature working fluid undergoes a first throttling expansion, and the pressure is reduced to a set value. The resulting material is then subjected to gas-liquid separation. The separated gaseous working fluid (i.e., the gaseous high-temperature working fluid) is used to replenish the gaseous high-temperature working fluid during the compression process. The resulting liquid working fluid undergoes a second throttling expansion and is then recycled.

[0082] The steam obtained from the heat exchange is exchanged with the solution at the bottom of the regeneration tower 1. The solution at the bottom of the regeneration tower 1 absorbs heat and then boils again. After boiling again, it is returned to the regeneration tower 1 for desorption and regeneration to obtain regenerated lean liquid and CO2 gas. At the same time, the steam is condensed into steam condensate and returned for recycling.

[0083] The CO2 gas obtained in the regeneration tower 1 is discharged through the top of the tower, then cooled, and then separated into gas and liquid. The separated gas (i.e., CO2 gas) is compressed in multiple stages, and the separated liquid (i.e. lean liquid) is returned to the regeneration tower 1 for recycling.

[0084] The energy consumption of the regeneration tower during the carbon capture process in the system described in Example 1 is compared with the energy consumption of the regeneration tower without the steam supply system described in this utility model. The results are shown in Table 1.

[0085] Table 1

[0086] project unit Before direct steam supply After direct steam supply Difference Reduction rate Regeneration tower heat load kW 98006.9 82305.9 15701.0 16.0％ External steam usage t / h 158.1 132.5 25.6 16.2％ Increased power consumption kW 0.0 5441.0 -5441.0 / <![CDATA[CO2 production]]> t / h 125.0 125.0 0.0 0.0 <![CDATA[Converted tons of CO2 regeneration energy consumption]]> <![CDATA[GJ / tCO2]]> 2.82 2.53 0.30 10.5％

[0087] Example 2

[0088] The CO2 gas (temperature 40°C) at the top of the regeneration tower 1 is compressed in multiple stages. After each stage of compression, the compressed CO2 gas (temperature 120°C) is first exchanged with the first high-temperature cooling water (demineralized water, temperature 70°C) and then exchanged with the low-temperature cooling water (demineralized water, temperature 30°C). The CO2 gas after heat exchange is separated into gas and liquid. The separated CO2 gas is then sent to the next stage compression unit for further compression.

[0089] The low-temperature cooling water (temperature 40°C) after heat exchange is exchanged with the liquid low-temperature working fluid (trans-1-chloro-3,3,3-trifluoropropylene). The liquid low-temperature working fluid absorbs heat and evaporates into a gaseous low-temperature working fluid. The temperature of the low-temperature cooling water after heat exchange decreases and it is returned for recycling.

[0090] The gaseous cryogenic working fluid is first compressed, and then exchanged heat with the second high-temperature cooling water (demineralized water, temperature 70°C). The gaseous cryogenic working fluid releases heat and condenses into a liquid cryogenic working fluid. Then it undergoes throttling expansion, and after throttling and depressurization to the set value, it is returned and recycled.

[0091] The high-temperature cooling water formed by the combination of the first high-temperature cooling water (temperature of 75°C) and the second high-temperature cooling water after heat exchange exchanges heat with the liquid high-temperature working fluid (trans-1-chloro-3,3,3-trifluoropropylene). The liquid high-temperature working fluid absorbs heat and evaporates into a gaseous high-temperature working fluid. At the same time, the high-temperature cooling water that has cooled down after heat exchange is divided into the first high-temperature cooling water and the second high-temperature cooling water for recycling.

[0092] The gaseous high-temperature working fluid is first compressed, and then exchanged heat with the steam condensate. The steam condensate absorbs and evaporates into steam, and the gaseous high-temperature working fluid releases heat and condenses into a liquid high-temperature working fluid. Then, the condensed liquid high-temperature working fluid undergoes a first throttling expansion, and the pressure is reduced to a set value. The resulting material is then subjected to gas-liquid separation. The separated gaseous working fluid (i.e., the gaseous high-temperature working fluid) is used to replenish the gaseous high-temperature working fluid during the compression process. The resulting liquid working fluid undergoes a second throttling expansion and is then recycled.

[0093] The steam obtained from the heat exchange is exchanged with the solution at the bottom of the regeneration tower 1. The solution at the bottom of the regeneration tower 1 absorbs heat and then boils again. After boiling again, it is returned to the regeneration tower 1 for desorption and regeneration to obtain regenerated lean liquid and CO2 gas. At the same time, the steam is condensed into steam condensate and returned for recycling.

[0094] The CO2 gas obtained in the regeneration tower 1 is discharged through the top of the tower, then cooled, and then separated into gas and liquid. The separated gas (i.e., CO2 gas) is compressed in multiple stages, and the separated liquid (i.e. lean liquid) is returned to the regeneration tower 1 for recycling.

[0095] The energy consumption of the regeneration tower during the carbon capture process in the system described in Example 2 is compared with the energy consumption of the regeneration tower without the steam supply system described in this utility model. The results are shown in Table 2.

[0096] Table 2

[0097] project unit Before direct steam supply After direct steam supply Difference Reduction rate Regeneration tower heat load kW 98006.9 82325.8 15681.1 16％ External steam usage t / h 158.1 133 25.1 15.9％ Increased power consumption kW 0.0 5169.0 -5169.0 / <![CDATA[CO2 production]]> t / h 125.0 125 0.0 0.0 <![CDATA[Converted tons of CO2 regeneration energy consumption]]> <![CDATA[GJ / tCO2]]> 2.82 2.528 0.29 10.4％

[0098] Example 3

[0099] The CO2 gas (temperature 35°C) at the top of the regeneration tower 1 is compressed in multiple stages. After each stage of compression, the compressed CO2 gas (temperature 115°C) is first exchanged with the first high-temperature cooling water (demineralized water, temperature 70°C) and then exchanged with the low-temperature cooling water (demineralized water, temperature 33°C). The CO2 gas after heat exchange is then separated into gas and liquid. The separated CO2 gas is then sent to the next stage compression unit for further compression.

[0100] The low-temperature cooling water (temperature of 45°C) after heat exchange is exchanged with the liquid low-temperature working fluid (1,1,1,2-tetrafluoroethane). The liquid low-temperature working fluid absorbs heat and evaporates into a gaseous low-temperature working fluid. The temperature of the low-temperature cooling water after heat exchange decreases and it is returned for recycling.

[0101] The gaseous cryogenic working fluid is first compressed, and then exchanged heat with the second high-temperature cooling water (demineralized water, temperature 70°C). The gaseous cryogenic working fluid releases heat and condenses into a liquid cryogenic working fluid. Then it undergoes throttling expansion, and after throttling and depressurization to the set value, it is returned and recycled.

[0102] The high-temperature cooling water formed by the combination of the first high-temperature cooling water (temperature of 80°C) and the second high-temperature cooling water after heat exchange exchanges heat with the liquid high-temperature working fluid (trans-1-chloro-3,3,3-trifluoropropylene). The liquid high-temperature working fluid absorbs heat and evaporates into a gaseous high-temperature working fluid. At the same time, the high-temperature cooling water that has cooled down after heat exchange is divided into the first high-temperature cooling water and the second high-temperature cooling water for recycling.

[0103] The gaseous high-temperature working fluid is first compressed, and then exchanged heat with the steam condensate. The steam condensate absorbs and evaporates into steam, and the gaseous high-temperature working fluid releases heat and condenses into a liquid high-temperature working fluid. Then, the condensed liquid high-temperature working fluid undergoes a first throttling expansion, and the pressure is reduced to a set value. The resulting material is then subjected to gas-liquid separation. The separated gaseous working fluid (i.e., the gaseous high-temperature working fluid) is used to replenish the gaseous high-temperature working fluid during the compression process. The resulting liquid working fluid undergoes a second throttling expansion and is then recycled.

[0104] The steam obtained from the heat exchange is exchanged with the solution at the bottom of the regeneration tower 1. The solution at the bottom of the regeneration tower 1 absorbs heat and then boils again. After boiling again, it is returned to the regeneration tower 1 for desorption and regeneration to obtain regenerated lean liquid and CO2 gas. At the same time, the steam is condensed into steam condensate and returned for recycling.

[0105] The CO2 gas obtained in the regeneration tower 1 is discharged through the top of the tower, then cooled, and then separated into gas and liquid. The separated gas (i.e., CO2 gas) is compressed in multiple stages, and the separated liquid (i.e. lean liquid) is returned to the regeneration tower 1 for recycling.

[0106] The energy consumption of the regeneration tower during the carbon capture process in the system described in Example 3 is compared with the energy consumption of the regeneration tower without the steam supply system described in this utility model. The results are shown in Table 3.

[0107] Table 3

[0108] project unit Before direct steam supply After direct steam supply Difference Reduction rate Regeneration tower heat load kW 98006.9 82007 16000.2 16.3％ External steam usage t / h 158.1 132.3 25.8 16.3％ Increased power consumption kW 0.0 5713.1 -5713.1 / <![CDATA[CO2 production]]> t / h 125.0 125 0.0 0.0 <![CDATA[Converted tons of CO2 regeneration energy consumption]]> <![CDATA[GJ / tCO2]]> 2.82 2.526 0.29 10.4％

[0109] Example 4

[0110] The method described in Example 1 is implemented, except that the inlet temperature of the first high-temperature cooling water and the second high-temperature cooling water is 60°C, and the return temperature of the first high-temperature cooling water and the second high-temperature cooling water is 70°C; the inlet temperature of the low-temperature cooling water is 30°C, and the return temperature is 40°C.

[0111] The energy consumption of the regeneration tower during the carbon capture process in the system described in Example 4 is compared with the energy consumption of the regeneration tower without the steam supply system described in this utility model. The results are shown in Table 4.

[0112] Table 4

[0113] project unit Before direct steam supply After direct steam supply Difference Reduction rate Regeneration tower heat load kW 98006.9 81588 16419.2 16.8％ External steam usage t / h 158.1 131.6 26.5 16.8％ Increased power consumption kW 0.0 6093.9 -6093.9 / <![CDATA[CO2 production]]> t / h 125.0 125 0.0 0.0 <![CDATA[Converted tons of CO2 regeneration energy consumption]]> <![CDATA[GJ / tCO2]]> 2.82 2.525 0.29 10.5％

[0114] Example 5

[0115] The method described in Example 1 is implemented, except that the inlet temperature of the first high-temperature cooling water and the second high-temperature cooling water is 60°C, and the return temperature of the first high-temperature cooling water and the second high-temperature cooling water is 70°C; the inlet temperature of the low-temperature cooling water is 48°C, and the return temperature is 53°C.

[0116] The energy consumption of the regeneration tower during the carbon capture process in the system described in Example 5 is compared with the energy consumption of the regeneration tower without the steam supply system described in this utility model. The results are shown in Table 5.

[0117] Table 5

[0118] project unit Before direct steam supply After direct steam supply Difference Reduction rate Regeneration tower heat load kW 98006.9 82785 15222.2 15.5％ External steam usage t / h 158.1 133.5 24.6 15.5％ Increased power consumption kW 0.0 5005.7 -5005.7 / <![CDATA[CO2 production]]> t / h 125.0 125 0.0 0.0 <![CDATA[Converted tons of CO2 regeneration energy consumption]]> <![CDATA[GJ / tCO2]]> 2.82 2.544 0.276 9.8％

[0119] According to the data in Tables 1-5, the system described in this invention can recover all the compression heat between the compressor stages in the carbon dioxide liquefaction section. The circulating water in the interstage cooler set in the prior art can be shut down. Furthermore, the system described in this invention can produce a large amount of steam. After the system described in this invention supplies steam to the carbon capture and regeneration tower, the regeneration energy consumption of the carbon capture and regeneration tower is reduced, resulting in significant energy-saving benefits.

[0120] The preferred embodiments of this utility model have been described in detail above; however, this utility model is not limited thereto. Within the scope of the technical concept of this utility model, various simple modifications can be made to the technical solution of this utility model, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed by this utility model and are all within the protection scope of this utility model.

Claims

1. An energy coupling system for carbon dioxide capture and carbon dioxide compression, characterized by, The system includes a regeneration tower (1), a multi-stage compression unit and a multi-stage heat exchange unit. Each stage of the multi-stage compression unit is equipped with a carbon dioxide compression device (2) and a multi-stream heat exchanger (3). The multi-stream heat exchanger is provided with a high-temperature heat exchange zone (3A) and a low-temperature heat exchange zone (3B). The multi-stage heat exchange unit includes a first heat exchanger (6), a second heat exchanger (8), a third heat exchanger (11), a fourth heat exchanger (13), a first compression device (7), a second compression device (12), and a first reboiler (17). The CO2 gas from the top of the regeneration tower (1) is compressed in the multi-stage compression unit in sequence. In each compression unit, the CO2 gas compressed by the carbon dioxide compression device (2) first exchanges heat with the first high temperature cooling water in the high temperature section heat exchange zone (3A) of the multi-stream heat exchanger, and then exchanges heat with the low temperature cooling water in the low temperature section heat exchange zone (3B) of the multi-stream heat exchanger. The low-temperature cooling water after heat exchange and the liquid low-temperature working fluid exchange heat in the first heat exchanger (6), so that the liquid low-temperature working fluid absorbs heat and evaporates into gas, and the low-temperature cooling water is cooled down and recycled. The gaseous low-temperature working fluid is first compressed in the first compression device (7), and then exchanged with the second high-temperature cooling water in the second heat exchanger (8) to condense the gaseous low-temperature working fluid into a liquid state and recycle it. The high-temperature cooling water formed by the merging of the first high-temperature cooling water and the second high-temperature cooling water after heat exchange is exchanged with the liquid high-temperature working fluid in the third heat exchanger (11), so that the liquid high-temperature working fluid absorbs heat and evaporates into gas, and the merged high-temperature cooling water is cooled down and split into the first high-temperature cooling water and the second high-temperature cooling water for recycling. The gaseous high-temperature working fluid is first compressed in the second compression device (12), and then exchanged with the steam condensate in the fourth heat exchanger (13), so that the steam condensate is absorbed and evaporated into steam, and the gaseous high-temperature working fluid is condensed into liquid and recycled. In the first reboiler (17), the steam is used to heat the solution at the bottom of the regeneration tower (1), so that the solution absorbs heat and reboils. The reboiled solution is returned to the regeneration tower (1) for desorption and regeneration to obtain regenerated lean liquid and CO2 gas, so that the steam is condensed into steam condensate and recycled.

2. The system of claim 1, wherein, The system also includes a first throttling expansion device (9) for throttling and expanding the liquid cryogenic working fluid obtained after heat exchange in the second heat exchanger (8), and then returning the liquid cryogenic working fluid to the first heat exchanger (6) for recycling.

3. The system of claim 1 or 2, wherein, The second compression device (12) is provided with an intermediate gas supply port. The system also includes a second throttling expansion device (14) and a first gas-liquid separation device (15). The second throttling expansion device (14) is used to throttle and expand the high-temperature liquid working fluid obtained after heat exchange in the fourth heat exchanger (13). The material from the second throttling expansion device (14) is separated into gas and liquid in the first gas-liquid separation device (15). The separated gas phase working fluid is transported to the second compression device (12) through the intermediate gas supply port for gas replenishment. The separated liquid phase working fluid is returned to the third heat exchanger (11) for recycling.

4. The system of claim 3, wherein, The system also includes a third throttling expansion device (16) for throttling and expanding the liquid working fluid from the first gas-liquid separation device (15) and then returning it to the third heat exchanger (11) for recycling.

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