A CO2 cold energy recovery and utilization system based on deep-sea storage

Abstract

The application belongs to the technical field of ships, and provides a CO2 cold energy recovery and utilization system based on a deep-sea storage mode, which comprises a CO2 cold energy recovery system, a CO2 cold energy utilization system and a glycol loading and unloading system. The application ingeniously utilizes the space of the "corners and corners" of a ship, and directly stores glycol in the space between the outer surface of a CO2 storage tank and the cargo hold bulkhead in the cargo hold of the ship. When CO2 is stored in the deep sea, the glycol aqueous solution is used for heat exchange with CO2 to recover cold energy, and the glycol aqueous solution after heat exchange is transported to land, so that the cold energy is utilized in the process of liquefying CO2, and waste of cold energy is avoided. Meanwhile, when the CO2 transport ship sails empty, the glycol is used as ballast water, so that the steps of adding and discharging ballast water are omitted, and the low-temperature glycol in the cargo hold enables the CO2 storage tank to continuously maintain a low temperature, so that the CO2 storage tank does not need to be pre-cooled when CO2 is added subsequently, and the transportation efficiency of CO2 and the efficiency of ship berthing operation are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of marine technology, specifically relating to a CO2 cold energy recovery and utilization system based on deep-sea storage. Background Technology

[0002] With increasing global emphasis on reducing greenhouse gas emissions, carbon capture and storage (CFS) technology has become a key means to achieve carbon reduction goals. CFS refers to capturing CO2 and transporting it to a specific location for storage. Storage methods include marine storage, geological storage, and biological storage. Among these, deep-sea storage has advantages such as large carbon storage capacity, stable storage, and low leakage risk, thus showing great development potential. In deep-sea CO2 storage, CO2 transport ships are the primary means of achieving this method because the transportation of CO2 to the storage site involves maritime transport.

[0003] To increase CO2 transport capacity, a semi-cooled, semi-pressurized method is typically used to store CO2 in liquid form in C-type tanks on ships. These C-type tanks are insulated, corrosion-resistant, and have a certain pressure-bearing capacity. The semi-cooled, semi-pressurized storage method requires the temperature inside the C-type tank to be controlled between -50℃ and -20℃, and the pressure between 0.7MPa and 2.1MPa. However, the shape of the C-type tank differs significantly from the geometry of the ship's cargo hold. When C-type tanks are placed inside the hold, a large amount of unusable space is created between the tanks and the hold walls, and between tanks themselves, resulting in a severe "undercapacity" phenomenon. This indicates that although the ship's hold has a large total volume, the incompatibility between the tanks and the cargo hold's shape leads to a significant reduction in space utilization.

[0004] In deep-sea CO2 storage operations, the storage sites are typically located at depths of approximately 1000 meters on the seabed. Due to the high pressure in this area, the liquid CO2 needs to be pressurized before storage to ensure its smooth transport to the seabed storage area. Because the temperature rise of the liquid after pressurization is very small, the pressurized liquid CO2 still retains a significant amount of cold energy. Furthermore, there is a large temperature difference between the storage temperature of CO2 on board (-50℃ to -20℃) and the storage temperature (approximately 4℃ at a depth of 1000 meters). Therefore, a considerable amount of cold energy is released during CO2 storage, which is not utilized, resulting in wasted cold energy. To reduce transportation costs due to distance between the offshore storage site and the land-based CO2 receiving station, most offshore storage sites are located relatively close to the land-based receiving station, with ships able to travel from the receiving station to the offshore storage site in approximately 1-2 days. This provides an opportunity to recover the cold energy of CO2 for utilization on land.

[0005] Ethylene glycol aqueous solution (hereinafter referred to as ethylene glycol) is a mainstream antifreeze heat transfer medium in the industrial field, possessing both excellent low-temperature resistance and stable heat transfer performance. Ethylene glycol is miscible with water in any proportion, and its freezing point can be reduced to -40°C by adjusting the concentration from 30% to 60%. Therefore, ethylene glycol aqueous solution is a widely used heat exchange medium in the current industrial field.

[0006] Since CO2 produced by factories is typically captured and transported to receiving stations in gaseous form via pipelines, it needs to be liquefied at the receiving station to meet the requirements of semi-cooled and semi-pressurized transportation. The liquefied CO2 is then transported by CO2 transport ships to offshore storage points for storage. Due to the low temperature of liquid CO2 and the large amount of CO2 emitted by factories, the liquefaction process suffers from high energy consumption and high costs.

[0007] Based on the above problems, if a CO2 cold energy recovery and utilization system based on deep-sea storage could be proposed, where ethylene glycol is directly stored in the ship's cargo hold, and during deep-sea storage, heat exchange between ethylene glycol and CO2 is used to recover cold energy, and then the system is transported to a receiving station for cold energy utilization, it would not only fully recover and utilize the cold energy of CO2, but also cleverly utilize ethylene glycol as ballast water, eliminating the steps of adding and discharging ballast water when the ship is empty, thus improving the ship's transportation efficiency and demonstrating great innovation. Summary of the Invention

[0008] The purpose of this invention is to address the problem of CO2 cold energy recovery and utilization during seabed storage, and to propose a CO2 cold energy recovery and utilization system based on deep-sea storage. The system includes a CO2 cold energy recovery system, a CO2 cold energy utilization system, and an ethylene glycol loading and unloading system.

[0009] The CO2 cold energy recovery system includes: a CO2 transport ship, a CO2 storage tank, a port forward compartment, a starboard forward compartment, a port aft compartment, a starboard aft compartment, a CO2 pump, a CO2 valve, a booster pump, a heat exchanger, an ethylene glycol pump, an ethylene glycol outlet valve, a buffer tank, an ethylene glycol inlet valve, a barge pump, and a buffer valve.

[0010] The CO2 cold energy utilization system includes: a primary compressor, a shut-off valve, a secondary compressor, a primary heat exchanger, a secondary heat exchanger, a refrigeration system, a CO2 receiving tank, a CO2 transfer pump, a CO2 outlet, a CO2 inlet, a CO2 inlet valve, and a CO2 storage tank.

[0011] The ethylene glycol loading and unloading system includes: a CO2 carrier, a port forward hold, a starboard forward hold, a port aft hold, a starboard aft hold, an ethylene glycol pump, an unloading valve, port I, port II, an ethylene glycol receiving tank, a supply pump, an ethylene glycol storage tank, an ethylene glycol transfer pump, port III, port IV, and a filling valve.

[0012] Furthermore, the CO2 transport ship defined in this invention is provided with two sets of cargo holds from bow to stern. Each set of cargo holds consists of a single cargo hold symmetrically located on the port and starboard sides of the ship. The cargo hold near the bow and on the port side is the port forward cargo hold, the cargo hold near the bow and on the starboard side is the starboard forward cargo hold, the cargo hold near the stern and on the port side is the port aft cargo hold, and the cargo hold near the stern and on the starboard side is the starboard aft cargo hold.

[0013] In the CO2 cold energy recovery system, a CO2 storage tank is installed in each of the left front compartment, right front compartment, left rear compartment, and right rear compartment. The CO2 pump is located inside the CO2 storage tank and at the bottom, and is connected sequentially to a CO2 valve, a booster pump, and the cold flow inlet of the heat exchanger via pipelines. An ethylene glycol pump is installed at the bottom of each of the left front compartment, right front compartment, left rear compartment, and right rear compartment. The ethylene glycol pump is connected sequentially to an ethylene glycol outlet valve and the hot flow inlet of the heat exchanger via pipelines. The hot flow outlet of the heat exchanger is connected to the buffer compartment, left front compartment, right front compartment, and left rear compartment via pipelines, and each compartment has an ethylene glycol inlet valve on the pipeline connecting to the heat flow outlet of the heat exchanger. The transfer pump is located at the bottom of the buffer compartment and is connected sequentially to the buffer valve and the right rear compartment via pipelines.

[0014] In the CO2 cold energy utilization system, the factory is connected to the primary compressor via pipelines. The primary compressor is connected in sequence via pipelines to the shut-off valve, the secondary compressor, the primary heat exchanger, the secondary heat exchanger, the refrigeration system, and the CO2 receiving tank. The CO2 delivery pump is located inside the CO2 receiving tank and is connected to the CO2 outlet via pipelines. The CO2 inlet is connected in sequence via pipelines to the CO2 inlet valve and the CO2 storage tank.

[0015] In the ethylene glycol loading and unloading system, an ethylene glycol pump is installed at the bottom of each of the left forward, right forward, left aft, and right aft compartments. The ethylene glycol pumps are connected to the unloading valve and port I in sequence via pipelines. Port II is connected to the ethylene glycol receiving tank via pipelines. The supply pump is located in the ethylene glycol receiving tank and is connected to the secondary heat exchanger and ethylene glycol storage tank in sequence via pipelines. The ethylene glycol transfer pump is located in the ethylene glycol storage tank and is connected to port III via pipelines. Port IV is connected to the left forward, right forward, left aft, and right aft compartments via pipelines, and a filling valve is installed on the pipeline connecting port IV to each compartment.

[0016] Furthermore, the CO2 valve, ethylene glycol outlet valve, ethylene glycol inlet valve, buffer valve, shut-off valve, CO2 inlet valve, unloading valve, and filling valve are all initially in a closed state before performing any operation.

[0017] When the CO2 transport ship sails to the vicinity of the offshore storage point, it first undergoes mooring: the CO2 transport ship is secured to a fixed anchor point with cables. After mooring is completed, it is stored in deep sea, at which point the cold energy of the CO2 is recovered. The cold energy recovery process consists of four stages:

[0018] The first process involves heat exchange between CO2 in the left forward compartment and ethylene glycol in the right forward compartment. Specifically: the CO2 valve connected to the left forward compartment is opened, and the CO2 pump transports the CO2 from the left forward compartment through pipelines to the booster pump for pressurization. The pressurized CO2 then enters the heat exchanger. Simultaneously, the ethylene glycol outlet valve connected to the right forward compartment and the ethylene glycol inlet valve connected to the buffer tank are opened. The ethylene glycol pump transports the ethylene glycol from the right forward compartment through pipelines to the heat exchanger to exchange heat with the CO2. The resulting low-temperature ethylene glycol is then transported through pipelines and the ethylene glycol inlet valve to the buffer tank, while the CO2 after heat exchange is directly injected into the seabed for storage. After the heat exchange is complete, the CO2 valve connected to the left forward compartment, the ethylene glycol outlet valve connected to the right forward compartment, and the ethylene glycol inlet valve connected to the buffer tank are closed. At this point, the first process ends, and the second process begins.

[0019] The second process involves heat exchange between CO2 in the right forward compartment and ethylene glycol in the left forward compartment. Specifically: the CO2 valve connected to the right forward compartment is opened, and the CO2 pump in the right forward compartment pipes CO2 to a booster pump for pressurization. The pressurized CO2 then enters the heat exchanger. Simultaneously, the ethylene glycol outlet valve connected to the left forward compartment and the ethylene glycol inlet valve connected to the right forward compartment are opened. The ethylene glycol pump pipes ethylene glycol from the left forward compartment to the heat exchanger to exchange heat with the CO2. The resulting low-temperature ethylene glycol is piped to the right forward compartment through the ethylene glycol inlet valve, while the CO2 after heat exchange is directly injected into the seabed for storage. After the heat exchange is complete, the CO2 valve connected to the right forward compartment, the ethylene glycol outlet valve connected to the left forward compartment, and the ethylene glycol inlet valve connected to the right forward compartment are closed. At this point, the second process ends, and the third process begins.

[0020] The third process involves heat exchange between CO2 in the right aft compartment and ethylene glycol in the left aft compartment. Specifically: the CO2 valve connected to the right aft compartment is opened, and the CO2 pump in the right aft compartment pipes CO2 to a booster pump for pressurization. The pressurized CO2 then enters the heat exchanger. Simultaneously, the ethylene glycol outlet valve connected to the left aft compartment and the ethylene glycol inlet valve connected to the left forward compartment are opened. The ethylene glycol pump pipes ethylene glycol from the left aft compartment to the heat exchanger to exchange heat with the CO2. The resulting low-temperature ethylene glycol is piped to the left forward compartment via the ethylene glycol inlet valve, while the CO2 after heat exchange is directly injected into the seabed for storage. After the heat exchange is complete, the CO2 valve connected to the right aft compartment and the ethylene glycol outlet valve connected to the left aft compartment are closed. The ethylene glycol inlet valve connected to the left forward compartment is then closed. At this point, the third process ends, and the fourth process begins.

[0021] The fourth process involves heat exchange between CO2 in the left aft compartment and ethylene glycol in the right aft compartment. Specifically: the CO2 valve connected to the left aft compartment is opened, and the CO2 pump in the left aft compartment pipes CO2 to a booster pump for pressurization. The pressurized CO2 then enters the heat exchanger. Simultaneously, the ethylene glycol outlet valve connected to the right aft compartment and the ethylene glycol inlet valve connected to the left aft compartment are opened. The ethylene glycol pump pipes ethylene glycol from the right aft compartment to the heat exchanger to exchange heat with the CO2. The resulting low-temperature ethylene glycol is piped to the left aft compartment through the ethylene glycol inlet valve, while the CO2, after heat exchange, is directly injected into the seabed for storage. After the heat exchange is complete, the CO2 valve connected to the left aft compartment and the ethylene glycol outlet valve connected to the right aft compartment are closed. The ethylene glycol inlet valve connected to the left aft compartment is then closed. At this point, the fourth process ends. To ensure the balance of ethylene glycol in the cargo hold when the ship is sailing empty, after the heat exchange of ethylene glycol in the right aft hold is completed, the buffer valve is opened, and the barge pump in the buffer hold transports low-temperature ethylene glycol to the right aft hold through pipelines. When all the low-temperature ethylene glycol in the buffer hold has been transported to the right aft hold, the buffer valve is closed. At this time, all CO2 is sealed and the cold energy recovery process ends.

[0022] Since the lower the temperature of liquid CO2, the lower its saturation pressure, the design pressure of the CO2 receiving tank and CO2 storage tank can be correspondingly reduced when the temperature of liquid CO2 is low. Furthermore, lower-strength materials can be selected for the tank body during the ship design phase. Therefore, to reduce the design pressure of the CO2 receiving tank and CO2 storage tank, the CO2 storage tank of this invention is designed with a storage temperature of -46℃ (saturation pressure of 0.8 MPa). The following calculations are performed on the cold energy released by CO2 and the cold energy absorbed by ethylene glycol to determine the mass ratio of ethylene glycol to CO2 in the tank. The formula is as follows:

[0023]

[0024] In the formula: —The total heat released by CO2 during temperature changes, in kW;

[0025] —Heat exchange efficiency of the heat exchanger =0.9;

[0026] —Specific heat capacity of CO2 J / (kg·K);

[0027] —Total mass of CO2, kg;

[0028] —The temperature difference of CO2 before and after heat exchange, in K;

[0029]

[0030] In the formula: —The total heat absorbed by ethylene glycol during temperature change, in kW;

[0031] —Specific heat capacity of ethylene glycol J / (kg·K);

[0032] —Total mass of ethylene glycol, kg;

[0033] —Temperature difference of ethylene glycol before and after heat exchange, K;

[0034] Through theoretical calculations and numerical calculations using the engineering software Aspen HYSYS, it was ultimately shown that when the mass ratio of ethylene glycol to CO2... At that temperature, the cold released by CO2 can be completely absorbed by ethylene glycol; therefore, the mass ratio of ethylene glycol to CO2 carried by a CO2 transport ship must be at least 0.67. This is based on the density of CO2 at -46℃. The saturation pressure is 0.8 MPa, and the density of a 50% ethylene glycol aqueous solution is... The volume ratio of ethylene glycol to CO2 can be calculated. Therefore, in a single cargo hold containing a CO2 storage tank, the ratio of the volume of the cargo hold containing ethylene glycol (the space between the tank and the bulkhead) to the volume of the CO2 storage tank is at least 0.72, and the volume of the buffer tank is equal to the volume of ethylene glycol in a single cargo hold.

[0035] After the CO2 seabed storage is completed, the CO2 transport ship, carrying the cooled ethylene glycol after heat exchange, sails back to the receiving station. Once the ship is docked, loading and unloading, as well as the utilization of the cold energy, are completed at the receiving station. The unloading of ethylene glycol begins as follows: Connecting Port I and Port II, opening the unloading valve, and the ethylene glycol pump sequentially transports ethylene glycol from the port forward, starboard forward, port aft, and starboard aft tanks through pipelines via Port I and Port II to the ethylene glycol receiving tank. Once the ethylene glycol unloading is complete, the unloading valve is closed, and Port I and Port II are disconnected.

[0036] Because CO2 carriers store low-temperature ethylene glycol during their return voyage to the receiving station, the steps of refueling and discharging ballast water are eliminated when sailing empty. Loading and unloading operations can be carried out directly after the ship arrives at the receiving station, simplifying the berthing process, shortening the berthing cycle, and improving the efficiency of ship operations when berthing.

[0037] After the ethylene glycol is unloaded, the ship's ethylene glycol loading proceeds. To improve the efficiency of ethylene glycol loading, the ship's ethylene glycol loading begins immediately after the ethylene glycol in the port forward hold is unloaded. The ethylene glycol loading process and the CO2 loading process can be carried out simultaneously or separately. To save time and improve the efficiency of operations when the ship is berthed, this invention loads ethylene glycol and CO2 simultaneously.

[0038] The ethylene glycol loading process is as follows: Connect ports III and IV, open the filling valve, and the ethylene glycol transfer pump will sequentially transfer the ethylene glycol from the storage tank to the port forward, starboard forward, port aft, and starboard aft compartments of the CO2 carrier via pipelines. After loading is complete, close the filling valve and disconnect ports III and IV.

[0039] After CO2 storage is completed, the temperature inside the CO2 storage tank remains low. During the CO2 transport ship's return journey from the offshore storage point to the receiving terminal, the low-temperature ethylene glycol stored in the cargo hold, combined with the insulation layer on the outside of the CO2 storage tank, significantly reduces heat loss from the tank, maintaining a low temperature. Furthermore, to minimize transportation costs associated with the distance to the offshore storage point, most of these points are relatively close to land, typically reaching the destination in 1-2 days. Therefore, when the ship returns to the receiving terminal, the CO2 storage tank remains at a low temperature. At this point, no pre-cooling is required before loading CO2; the loading operation can proceed directly.

[0040] The CO2 loading process is as follows: Connect the CO2 outlet and CO2 inlet, open the CO2 inlet valve, and the CO2 transfer pump will transport the liquid CO2 in the CO2 receiving tank to the CO2 storage tank through pipeline. After the CO2 loading is completed, close the CO2 inlet valve and disconnect the CO2 outlet and CO2 inlet.

[0041] When the CO2 captured by the factory needs to be transported to the receiving station for liquefaction, cold energy is utilized. The process is as follows: The shut-off valve is opened, and the gaseous CO2 produced by the factory passes through the shut-off valve, the primary compressor, and the secondary compressor via pipelines to the primary heat exchanger. In the primary heat exchanger, CO2 undergoes preliminary heat exchange with seawater. The gaseous CO2 after preliminary heat exchange then enters the secondary heat exchanger via pipelines. Simultaneously, a supply pump transports ethylene glycol from the ethylene glycol receiving tank to the secondary heat exchanger via pipelines. In the secondary heat exchanger, ethylene glycol exchanges heat with gaseous CO2. The ethylene glycol after heat exchange is then transported to the ethylene glycol storage tank via pipelines. Meanwhile, the CO2 after heat exchange enters the refrigeration system for cooling. The resulting liquid CO2 is then transported to the CO2 receiving tank for storage via pipelines.

[0042] Beneficial effects of the invention

[0043] 1. This invention recovers the cold energy of CO2 stored on the seabed through ethylene glycol heat exchange, and uses the cold energy for CO2 liquefaction at the receiving station. This not only recovers the cold energy of CO2 and avoids its waste, but also makes full use of the cold energy of CO2, significantly reducing the power consumption and cost of CO2 liquefaction.

[0044] 2. In the process of a CO2 transport ship returning to the receiving station, the present invention provides a solution where the ship's hold contains low-temperature ethylene glycol, eliminating the need for refueling and draining ballast water during empty voyages. This allows for direct CO2 loading operations upon arrival at the receiving station, improving the efficiency of operations when the ship is berthed.

[0045] 3. This invention directly stores ethylene glycol in the space between the outer surface of the CO2 storage tank and the bulkhead of the ship's cargo hold, cleverly utilizing the ship's "nook and cranny" space. Simultaneously, when the CO2 transport ship returns to the receiving station, the low-temperature ethylene glycol in the cargo hold keeps the CO2 storage tank at a consistently low temperature. Therefore, when refilling CO2 subsequently, the CO2 storage tank does not require pre-cooling, thus simplifying the CO2 loading and unloading process and improving CO2 transportation efficiency. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of CO2 cold energy recovery.

[0047] Figure 2 This is a schematic diagram of CO2 cold energy utilization;

[0048] Figure 3 System diagram;

[0049] Figure 4 A schematic diagram of a CO2 transport ship;

[0050] Figure 5 A schematic diagram showing the location of a deep-sea CO2 storage transport ship;

[0051] In the attached diagram: 1. CO2 transport ship; 2. CO2 storage tank; 3. Port forward hold; 4. Starboard forward hold; 5. Port aft hold; 6. Starboard aft hold; 7. CO2 pump; 8. CO2 valve; 9. Booster pump; 10. Heat exchanger; 11. Ethylene glycol pump; 12. Ethylene glycol outlet valve; 13. Buffer tank; 14. Ethylene glycol inlet valve; 15. Transfer pump; 16. Buffer valve; 17. Primary compressor; 18. Shut-off valve; 19. Secondary compressor; 20. 21. Primary heat exchanger; 22. Secondary heat exchanger; 23. Refrigeration system; 24. CO2 receiving tank; 25. CO2 transfer pump; 26. CO2 outlet; 27. CO2 inlet; 28. CO2 inlet valve; 29. ​​Unloading valve; 30. I port; 31. II port; 32. Ethylene glycol receiving tank; 33. Supply pump; 34. Ethylene glycol storage tank; 35. Ethylene glycol transfer pump; 36. III port; 37. IV port; 38. Filling valve. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0053] A CO2 cold energy recovery and utilization system based on deep-sea storage, comprising a CO2 cold energy recovery system, a CO2 cold energy utilization system, and an ethylene glycol loading and unloading system.

[0054] The CO2 cold energy recovery system includes: a CO2 transport ship 1, a CO2 storage tank 2, a left forward compartment 3, a right forward compartment 4, a left aft compartment 5, a right aft compartment 6, a CO2 pump 7, a CO2 valve 8, a booster pump 9, a heat exchanger 10, an ethylene glycol pump 11, an ethylene glycol outlet valve 12, a buffer tank 13, an ethylene glycol inlet valve 14, a barge pump 15, and a buffer valve 16.

[0055] The CO2 cold energy utilization system includes: a primary compressor 17, a shut-off valve 18, a secondary compressor 19, a primary heat exchanger 20, a secondary heat exchanger 21, a refrigeration system 22, a CO2 receiving tank 23, a CO2 transfer pump 24, a CO2 outlet 25, a CO2 inlet 26, a CO2 inlet valve 27, and a CO2 storage tank 2.

[0056] The ethylene glycol loading and unloading system includes: CO2 carrier 1, port forward hold 3, starboard forward hold 4, port aft hold 5, starboard aft hold 6, ethylene glycol pump 11, unloading valve 28, I port 29, II port 30, ethylene glycol receiving tank 31, supply pump 32, ethylene glycol storage tank 33, ethylene glycol transfer pump 34, III port 35, IV port 36, and filling valve 37.

[0057] In the CO2 cold energy recovery system, a CO2 storage tank 2 is installed in each of the left front compartment 3, right front compartment 4, left rear compartment 5, and right rear compartment 6. A CO2 pump 7 is located inside the CO2 storage tank 2 and at the bottom, and is connected sequentially to a CO2 valve 8, a booster pump 9, and the cold flow inlet of a heat exchanger 10 via pipes. An ethylene glycol pump 11 is installed at the bottom of each of the left front compartment 3, right front compartment 4, left rear compartment 5, and right rear compartment 6. The ethylene glycol pump 11 is connected sequentially to an ethylene glycol outlet valve 12 and the hot flow inlet of the heat exchanger 10 via pipes. The hot flow outlet of the heat exchanger 10 is connected to a buffer compartment 13, left front compartment 3, right front compartment 4, and left rear compartment 5 via pipes, and each compartment is connected to the hot flow outlet of the heat exchanger 10 via an ethylene glycol inlet valve 14. A transfer pump 15 is located at the bottom of the buffer compartment 13 and is connected sequentially to a buffer valve 16 and the right rear compartment 6 via pipes.

[0058] In the CO2 cold energy utilization system, the factory is connected to the primary compressor 17 via pipelines. The primary compressor 17 is connected in sequence via pipelines to the shut-off valve 18, the secondary compressor 19, the primary heat exchanger 20, the secondary heat exchanger 21, the refrigeration system 22, and the CO2 receiving tank 23. The CO2 delivery pump 24 is located inside the CO2 receiving tank 23 and is connected to the CO2 outlet 25 via pipelines. The CO2 inlet 26 is connected in sequence via pipelines to the CO2 inlet valve 27 and the CO2 storage tank 2. Both the CO2 receiving tank 23 and the CO2 storage tank 2 are C-type tanks and are equipped with insulation layers.

[0059] In the ethylene glycol loading and unloading system, an ethylene glycol pump 11 is installed at the bottom of each of the left front compartment 3, right front compartment 4, left rear compartment 5, and right rear compartment 6. The ethylene glycol pump 11 is connected to the unloading valve 28 and port I 29 in sequence through pipelines. Port II 30 is connected to the ethylene glycol receiving tank 31 in sequence through pipelines. The supply pump 32 is located in the ethylene glycol receiving tank 31 and is connected to the secondary heat exchanger 21 and the ethylene glycol storage tank 33 in sequence through pipelines. The ethylene glycol transfer pump 34 is located in the ethylene glycol storage tank 33 and is connected to port III 35 in sequence through pipelines. Port IV 36 is connected to the left front compartment 3, right front compartment 4, left rear compartment 5, and right rear compartment 6 in sequence through pipelines, and a filling valve 37 is installed on the pipeline connecting port IV 36 to each compartment.

[0060] Furthermore, the CO2 transport ship 1 defined in this invention is provided with two sets of cargo holds from bow to stern. Each set of cargo holds consists of a single cargo hold symmetrically located on the port and starboard sides of the ship. The cargo hold near the bow and on the port side is the port forward hold 3, the cargo hold near the bow and on the starboard side is the starboard forward hold 4, the cargo hold near the stern and on the port side is the port aft hold 5, and the cargo hold near the stern and on the starboard side is the starboard aft hold 6.

[0061] Furthermore, the ethylene glycol receiving tank 31 and ethylene glycol storage tank 33 defined in this invention contain a certain amount of ethylene glycol, ensuring that low-temperature ethylene glycol still participates in the CO2 liquefaction process when the CO2 transport ship 1 leaves the receiving station.

[0062] Furthermore, the CO2 valve 8, ethylene glycol outlet valve 12, ethylene glycol inlet valve 14, buffer valve 16, shut-off valve 18, CO2 inlet valve 27, unloading valve 28, and filling valve 37 are all initially closed before any operation is performed.

[0063] When CO2 transport ship 1 sails to the sea storage point (e.g. Figure 5 When in the vicinity of the waters shown, mooring operations will be carried out first. CO2 transport ship 1 will be secured to a fixed anchor point (as shown) by cables. Figure 5 As shown), after mooring is completed, the CO2 is stored in the deep sea. At this time, the cold energy of CO2 is recovered. The cold energy recovery process consists of four steps:

[0064] The first process involves heat exchange between CO2 in the left forward compartment 3 and ethylene glycol in the right forward compartment 4. Specifically, the CO2 valve 8 connected to the left forward compartment 3 is opened, and the CO2 pump 7 in the left forward compartment 3 pumps CO2 through a pipeline to the booster pump 9 for pressurization. The pressurized CO2 is then pumped through a pipeline to the heat exchanger 10. Simultaneously, the ethylene glycol outlet valve 12 connected to the right forward compartment 4 and the ethylene glycol inlet valve 14 connected to the buffer tank 13 are opened. The ethylene glycol pump 11 pumps ethylene glycol from the right forward compartment 4 through a pipeline to the heat exchanger 10 to exchange heat with the CO2. The resulting low-temperature ethylene glycol is then pumped through a pipeline to the buffer tank 13, while the CO2 is directly injected into the seabed for storage. Figure 5 The injection port in the middle injects into the deep sea. After heat exchange is completed, the CO2 valve 8 connected to the left front compartment 3, the ethylene glycol outlet valve 12 connected to the right front compartment 4, and the ethylene glycol inlet valve 14 connected to the buffer compartment 13 are closed. At this time, the first process ends and the second process begins.

[0065] The second process involves heat exchange between CO2 in the right forward compartment 4 and ethylene glycol in the left forward compartment 3. Specifically, CO2 valve 8, connected to the right forward compartment 4, is opened. CO2 pump 7 in the right forward compartment 4 then pumps CO2 through a pipeline to booster pump 9 for pressurization. The pressurized CO2 is then pumped through a pipeline to heat exchanger 10. Simultaneously, ethylene glycol outlet valve 12, connected to the left forward compartment 3, and ethylene glycol inlet valve 14, connected to the right forward compartment 4, are opened. Ethylene glycol pump 11 pumps ethylene glycol from the left forward compartment 3 through a pipeline to heat exchanger 10 to exchange heat with CO2. The resulting low-temperature ethylene glycol is then pumped through a pipeline to the right forward compartment 4, while the CO2 is directly injected into the seabed for storage. Figure 5The injection port in the middle injects into the deep sea. After heat exchange is completed, the CO2 valve 8 connected to the right front compartment 4, the ethylene glycol outlet valve 12 connected to the left front compartment 3, and the ethylene glycol inlet valve 14 connected to the right front compartment 4 are closed. At this time, the second process ends and the third process begins.

[0066] The third process involves heat exchange between CO2 in the right aft compartment 6 and ethylene glycol in the left aft compartment 5. Specifically, CO2 valve 8, connected to the right aft compartment 6, is opened. CO2 pump 7 in the right aft compartment 6 then pipes CO2 to booster pump 9 for pressurization. The pressurized CO2 is then piped to heat exchanger 10. Simultaneously, ethylene glycol outlet valve 12, connected to the left aft compartment 5, and ethylene glycol inlet valve 14, connected to the left forward compartment 3, are opened. Ethylene glycol pump 11 then pipes ethylene glycol from the left aft compartment 5 to heat exchanger 10 to exchange heat with CO2. The resulting low-temperature ethylene glycol is piped to the left forward compartment 3, while the CO2 is directly injected into the seabed for storage. Figure 5 The injection port in the middle injects into the deep sea. After heat exchange is completed, the CO2 valve 8 connected to the right aft compartment 6 and the ethylene glycol outlet valve 12 connected to the left aft compartment 5 are closed. The ethylene glycol inlet valve 14 connected to the left front compartment 3 is closed. At this point, the third process ends and the fourth process begins.

[0067] The fourth process involves heat exchange between CO2 in the left aft compartment 5 and ethylene glycol in the right aft compartment 6. Specifically, the CO2 valve 8 connected to the left aft compartment 5 is opened, and the CO2 pump 7 in the left aft compartment 5 pumps CO2 through a pipeline to the booster pump 9 for pressurization. The pressurized CO2 is then pumped through a pipeline to the heat exchanger 10. Simultaneously, the ethylene glycol outlet valve 12 connected to the right aft compartment 6 and the ethylene glycol inlet valve 14 connected to the left aft compartment 5 are opened. The ethylene glycol pump 11 pumps ethylene glycol from the right aft compartment 6 through a pipeline to the heat exchanger 10 to exchange heat with the CO2. The resulting low-temperature ethylene glycol is then pumped through a pipeline to the left aft compartment 5, while the CO2 will be directly injected into the seabed for storage. Figure 5 The injection port in the middle injects into the deep sea. After heat exchange is completed, the CO2 valve 8 connected to the left aft compartment 5 and the ethylene glycol outlet valve 12 connected to the right aft compartment 6 are closed. The ethylene glycol inlet valve 14 connected to the left aft compartment 5 is closed, at which point the fourth process ends. In order to ensure the load balance of ethylene glycol in the cargo hold when the ship is sailing empty, after the ethylene glycol heat exchange in the right aft compartment 6 is completed, the buffer valve 16 connected to the buffer tank 13 is opened, and the barge pump 15 in the buffer tank 13 transports the low-temperature ethylene glycol to the right aft compartment 6 through pipeline. When all the low-temperature ethylene glycol in the buffer tank 13 has been transported to the right aft compartment 6, the buffer valve 16 is closed. At this point, all CO2 is sealed, and the cold energy recovery process ends.

[0068] Since the lower the temperature of liquid CO2, the lower its saturation pressure, the design pressure of CO2 receiving tank 23 and CO2 storage tank 2 can be correspondingly reduced when the temperature of liquid CO2 is low. Furthermore, materials with lower strength can be selected for tank construction during the ship design phase. Therefore, to reduce the design pressure of CO2 receiving tank 23 and CO2 storage tank 2, the CO2 storage tank 2 of this invention is designed to have a storage temperature of -46℃ (saturation pressure of 0.8 MPa). The following calculations are performed on the cold energy released by CO2 and the cold energy absorbed by ethylene glycol, calculating the mass ratio of ethylene glycol to CO2 in the tank. The formula is as follows:

[0069]

[0070] In the formula: —The total heat released by CO2 during temperature changes, in kW;

[0071] —Heat exchange efficiency of the heat exchanger =0.9;

[0072] —Specific heat capacity of CO2 J / (kg·K);

[0073] —Total mass of CO2, kg;

[0074] —The temperature difference of CO2 before and after heat exchange, in K;

[0075]

[0076] In the formula: —The total heat absorbed by ethylene glycol during temperature change, in kW;

[0077] —Specific heat capacity of ethylene glycol J / (kg·K);

[0078] —Total mass of ethylene glycol, kg;

[0079] —Temperature difference of ethylene glycol before and after heat exchange, K;

[0080] Through theoretical calculations and numerical calculations using the engineering software Aspen HYSYS, it was ultimately shown that when the mass ratio of ethylene glycol to CO2... At that time, the cold energy released by CO2 can be completely absorbed by ethylene glycol; therefore, the mass ratio of ethylene glycol to CO2 carried by CO2 transport ship 1 is at least 0.67. Based on the density of CO2 at -46℃... The saturation pressure is 0.8 MPa, and the density of a 50% ethylene glycol aqueous solution is... The volume ratio of ethylene glycol to CO2 can be calculated. Therefore, in a single cargo hold containing CO2 storage tank 2, the ratio of the cargo hold volume containing ethylene glycol (the space between the tank and the bulkhead) to the volume of CO2 storage tank 2 is at least 0.72, and the volume of the buffer tank 13 is equal to the volume of ethylene glycol in a single cargo hold.

[0081] After the CO2 seabed storage is completed, CO2 transport ship 1, carrying the cooled ethylene glycol after heat exchange, sails back to the receiving station. Upon docking, loading and unloading, as well as the utilization of cold energy, are completed at the receiving station. First, the ethylene glycol is unloaded as follows: Connect port I 29 to port II 30, open the unloading valve 28 connected to the port forward compartment 3, and the ethylene glycol pump 11 in the port forward compartment 3 unloads the ethylene glycol through pipelines via port I 29 and port II 30 to the ethylene glycol receiving tank 31. After the ethylene glycol in the port forward compartment 3 is unloaded, the unloading valve 28 connected to the port forward compartment 3 is closed, and the unloading valve 28 connected to the starboard forward compartment 4 is opened. The ethylene glycol pump 11 in the starboard forward compartment 4 unloads the ethylene glycol through pipelines via port I 29 and port II 30 to the ethylene glycol receiving tank 31. After the ethylene glycol in the right forward compartment 4 is unloaded, the unloading valve 28 connected to the right forward compartment 4 is closed, and the unloading valve 28 connected to the left aft compartment 5 is opened. The ethylene glycol pump 11 in the left aft compartment 5 unloads the ethylene glycol through pipelines via port I 29 and port II 30 to the ethylene glycol receiving tank 31. After the ethylene glycol in the left aft compartment 5 is unloaded, the unloading valve 28 connected to the left aft compartment 5 is closed, and the unloading valve 28 connected to the right aft compartment 6 is opened. The ethylene glycol pump 11 in the right aft compartment 6 unloads the ethylene glycol through pipelines via port I 29 and port II 30 to the ethylene glycol receiving tank 31. After the ethylene glycol in the right aft compartment 6 is unloaded, the unloading valve 28 connected to the right aft compartment 6 is closed, and port I 29 and port II 30 are disconnected. At this point, the ethylene glycol unloading process is complete.

[0082] Because the CO2 transport ship 1 stores cryogenic ethylene glycol during its return voyage to the receiving station, the steps of refueling and discharging ballast water are omitted during empty voyages. After the ethylene glycol is unloaded, the ship is loaded. To improve the efficiency of ethylene glycol loading, the loading of ethylene glycol into the ship is carried out directly after the ethylene glycol in the port forward hold 3 is unloaded. The loading process of ethylene glycol and CO2 can be carried out simultaneously or separately. To save time and improve the efficiency of operations when the ship is berthed, this invention loads ethylene glycol and CO2 simultaneously.

[0083] The ethylene glycol loading process is as follows: Connect port III 35 and port IV 36. After connection, open the filling valve 37 connected to the port forward compartment 3. The ethylene glycol transfer pump 34 will transport the heat-exchanged ethylene glycol through pipelines via port III 35, port IV 36, and filling valve 37 to the port forward compartment 3 of the CO2 transport ship 1. The ethylene glycol filling process in the starboard forward compartment 4, port port aft compartment 5, and starboard aft compartment 6 is the same as the above process. After the ethylene glycol loading is completed, close the filling valve 37 and disconnect port III 35 and port IV 36.

[0084] After CO2 storage is completed, the temperature inside CO2 storage tank 2 remains low. During the return journey of CO2 transport ship 1 from the offshore storage point to the receiving station, the low-temperature ethylene glycol stored in the cargo hold, combined with the external insulation layer of CO2 storage tank 2, significantly reduces heat loss, maintaining a consistently low temperature. Furthermore, to minimize transportation costs associated with the distance to the offshore storage point, most of these points are relatively close to land, typically reaching the destination in 1-2 days. Therefore, when the ship returns to the receiving station, CO2 storage tank 2 remains at a low temperature. At this point, CO2 loading can proceed directly without pre-cooling.

[0085] The CO2 loading process is as follows: Connect CO2 outlet 25 and CO2 inlet 26. After connection, open CO2 inlet valve 27. CO2 transfer pump 24 transports liquid CO2 from the tank through pipelines via CO2 outlet 25, CO2 inlet 26, and CO2 inlet valve 27 to CO2 storage tank 2 of CO2 transport ship 1. After CO2 loading is completed, close CO2 inlet valve 27 and disconnect CO2 outlet 25 and CO2 inlet 26.

[0086] Typically factories (such as Figure 2(As shown) The plants are distributed in different areas, and each plant is far from the receiving station. The plants capture gaseous CO2 from the waste gas they produce. The captured gaseous CO2 needs to be transported to the receiving station for liquefaction through pipelines, and the amount of CO2 captured by the plants is dynamic. When the CO2 captured by the plants needs to be transported to the receiving station for liquefaction, cold energy is utilized at this time. The process is as follows: the shut-off valve 18 is opened, and the gaseous CO2 produced by the plants is sent to the first-stage compressor 17 for initial pressurization through pipelines. The initially pressurized gaseous CO2 is then sent to the second-stage compressor 19 for further pressurization through pipelines. The pressurized high-pressure gaseous CO2 is then sent to the first-stage heat exchanger 20 through pipelines to exchange heat with seawater. The gaseous CO2 after initial heat exchange enters the second-stage heat exchanger 21 through pipelines. At the same time, the supply pump 32 transports the low-temperature ethylene glycol in the ethylene glycol receiving tank 31 through pipelines to the second-stage heat exchanger 21, where it exchanges heat with the gaseous CO2. The heat-exchanged ethylene glycol is then transported to the ethylene glycol storage tank 33 through pipelines. The CO2 after heat exchange is transported through pipelines to the refrigeration system 22 for cooling, and the resulting liquid CO2 is transported through pipelines to the CO2 receiving tank 23 for storage.

[0087] Since the amount of CO2 captured by the factory is dynamic, the ethylene glycol supply pump 32 in the receiving tank 31 controls the amount of ethylene glycol supplied according to the amount of CO2 captured. When the amount of CO2 captured by the factory is large, the amount of ethylene glycol consumed in the receiving tank 31 is also large; when the amount of CO2 captured by the factory is small, the amount of ethylene glycol consumed in the receiving tank 31 is correspondingly reduced; when the factory does not supply CO2, the ethylene glycol is directly stored in the receiving tank 31. Therefore, the receiving tank 31 has a good buffering effect.

[0088] In deep-sea CO2 sequestration operations, the sequestration point is typically located at a depth of approximately 1000 meters on the seabed. Due to the high pressure in this area, the liquid CO2 needs to be pressurized before sequestration to ensure its smooth transport to the seabed storage area. However, the temperature rise of the liquid after pressurization is very small, meaning the pressurized liquid CO2 still retains significant cold energy. Furthermore, there is a large temperature difference between the CO2 storage temperature on the ship (-50℃ to -20℃) and the temperature during sequestration (the temperature at a depth of 1000 meters is approximately 4℃). Therefore, a considerable amount of cold energy is released during CO2 sequestration, resulting in energy waste. In deep-sea sequestration, ethylene glycol is used to exchange heat with CO2 for cold energy recovery. The heated ethylene glycol is then transported back to the receiving station for cold energy utilization, while the CO2 is injected into the seabed for sequestration.

[0089] This invention cleverly utilizes the space between the cargo hold and the CO2 storage tank 2, storing ethylene glycol directly in the space between the outer surface of the CO2 storage tank 2 and the cargo hold wall. This ingenious use of the ship's "nook and cranny" space not only eliminates the need to increase the ship's hull size for loading ethylene glycol during the ship design phase, but also eliminates the design requirement for ballast tanks. When the ship is sailing empty, the steps of adding and discharging ballast water are eliminated, allowing the ship to directly carry out loading and unloading operations after arriving at the receiving station, thus improving the efficiency of operations when the ship is berthed.

[0090] Because the CO2 storage temperature on the ship in this invention is -46℃ (saturation pressure of 0.8 MPa), the temperature inside CO2 storage tank 2 remains low after CO2 sealing is completed. During the return journey of the CO2 transport ship 1 from the offshore sealing point to the receiving station, the presence of -25℃ low-temperature ethylene glycol in the cargo hold minimizes the temperature difference between the interior of CO2 storage tank 2 and the cargo hold. Furthermore, CO2 storage tank 2 is a C-type tank with an external insulation layer, resulting in minimal heat loss and maintaining a low temperature. To reduce transportation costs due to distance between the offshore sealing point and the land-based CO2 receiving station, most offshore sealing points are relatively close to the land-based receiving station, typically taking 1-2 days for a ship to reach the offshore sealing point. Therefore, when the ship arrives at the receiving station, the temperature inside CO2 storage tank 2 is still low. At this point, CO2 refueling does not require pre-cooling of CO2 storage tank 2, simplifying the CO2 loading and unloading process, improving CO2 transportation efficiency, and demonstrating significant innovation.

[0091] The tank capacity ratio, design pressure of CO2 storage tank 2, and material selection parameters in this embodiment are all designed for liquid CO2 at -46℃ (saturation pressure of 0.8 MPa). The system of this invention is still applicable to liquid CO2 between -50℃ and -20℃; specific parameters are calculated based on the selected temperature. For example, for liquid CO2 at -30℃, the design pressure of the selected CO2 storage tank 2 is 1.7 MPa, allowing for a reduction in the insulation layer thickness, and the CO2 storage tank 2 requires the use of higher-strength materials. In summary, for higher-temperature liquid CO2, the design pressure of CO2 storage tank 2 is higher, requiring the selection of high-strength materials, and the insulation layer thickness can be appropriately reduced; while for lower-temperature liquid CO2, the design pressure of CO2 storage tank 2 is lower, requiring the selection of lower-strength materials, and the insulation layer thickness can be appropriately increased.

[0092] The above description is merely a preferred embodiment of the present invention. The specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A CO2 cold energy recovery and utilization system based on a deep-sea sequestration mode, characterized in that: This system includes a CO2 cold energy recovery system, a CO2 cold energy utilization system, and an ethylene glycol loading and unloading system. The CO2 cold energy recovery system includes: a CO2 transport ship (1), a CO2 storage tank (2), a port forward compartment (3), a starboard forward compartment (4), a port aft compartment (5), a starboard aft compartment (6), a CO2 pump (7), a CO2 valve (8), a booster pump (9), a heat exchanger (10), an ethylene glycol pump (11), an ethylene glycol outlet valve (12), a buffer tank (13), an ethylene glycol inlet valve (14), a barge pump (15), and a buffer valve (16). A CO2 storage tank (2) is installed in each of the left front compartment (3), right front compartment (4), left rear compartment (5), and right rear compartment (6); the CO2 pump (7) is connected to the CO2 valve (8), booster pump (9), and heat exchanger (10) in sequence via pipelines; an ethylene glycol pump (11) is installed at the bottom of each of the left front compartment (3), right front compartment (4), left rear compartment (5), and right rear compartment (6), and the ethylene glycol pump (11) is connected to the ethylene glycol outlet valve (12) and heat exchanger (10) in sequence via pipelines; the heat exchanger (10) is connected to the buffer compartment (13), left front compartment (3), right front compartment (4), and left rear compartment (5) in sequence via pipelines, and an ethylene glycol inlet valve (14) is installed on the pipeline connecting each compartment to the heat exchanger (10); the transfer pump (15) is connected to the buffer valve (16) and right rear compartment (6) in sequence via pipelines. The CO2 cold energy utilization system includes: a primary compressor (17), a shut-off valve (18), a secondary compressor (19), a primary heat exchanger (20), a secondary heat exchanger (21), a refrigeration system (22), a CO2 receiving tank (23), a CO2 transfer pump (24), a CO2 outlet (25), a CO2 inlet (26), a CO2 inlet valve (27), and a CO2 storage tank (2). The factory is connected to the primary compressor (17) via pipelines. The primary compressor (17) is connected in sequence via pipelines to the shut-off valve (18), the secondary compressor (19), the primary heat exchanger (20), the secondary heat exchanger (21), the refrigeration system (22), and the CO2 receiving tank (23). The CO2 transfer pump (24) is located inside the CO2 receiving tank (23) and is connected to the CO2 outlet (25) via pipelines. The CO2 inlet (26) is connected in sequence via pipelines to the CO2 inlet valve (27) and the CO2 storage tank (2). When storing CO2 in the deep sea, in order to maintain the balance of the CO2 transport ship (1), when storing CO2 in the port forward compartment (3), ethylene glycol in the starboard forward compartment (4) is used to exchange heat with CO2; when storing CO2 in the starboard forward compartment (4), ethylene glycol in the port forward compartment (3) is used to exchange heat with CO2; when storing CO2 in the starboard aft compartment (6), ethylene glycol in the port aft compartment (5) is used to exchange heat with CO2; when storing CO2 in the port aft compartment (5), ethylene glycol in the port aft compartment (6) is used to exchange heat with CO2.

2. The CO2 cold energy recovery and utilization system based on deep-sea sequestration according to claim 1, characterized in that: The design temperature of the CO2 storage tank (2) and the CO2 receiving tank (23) is -46℃.

3. The CO2 cold energy recovery and utilization system based on deep-sea storage as described in claim 1, characterized in that: The cooling capacity released by CO2 and the cooling capacity absorbed by ethylene glycol are calculated to determine the mass ratio of ethylene glycol to CO2 in the chamber. The formula is as follows: In the formula: —The total heat released by CO2 during temperature changes, in kW; —Heat exchange efficiency of the heat exchanger =0.9; —Specific heat capacity of CO2 ; —Total mass of CO2, kg; —The temperature difference of CO2 before and after heat exchange, in K; In the formula: —The total heat absorbed by ethylene glycol during temperature change, in kW; —Specific heat capacity of ethylene glycol ; —Total mass of ethylene glycol, kg; —Temperature difference of ethylene glycol before and after heat exchange, K; From the formula and This indicates that when the mass ratio of ethylene glycol to CO2... At that time, the cold energy released by CO2 can be completely absorbed by ethylene glycol, that is, the mass ratio of ethylene glycol to CO2 carried by the CO2 transport ship (1) is... Density of CO2 at -46℃ The saturation pressure is 0.8 MPa, and the density of a 50% ethylene glycol aqueous solution is... The volume ratio of ethylene glycol to CO2 was calculated. That is, in a single cargo hold containing CO2 storage tank (2), the ratio of the volume of the cargo hold containing ethylene glycol to the volume of CO2 storage tank (2). The volume of the buffer compartment (13) is equal to the volume of ethylene glycol in a single cargo hold.

4. A CO2 cold energy recovery and utilization system based on deep-sea storage as described in claim 1, characterized in that: The CO2 transport ship (1) has two sets of cargo holds from bow to stern. Each set of cargo holds consists of a single cargo hold symmetrically located on the port and starboard sides of the ship. The cargo hold near the bow and on the port side is the port forward cargo hold (3), the cargo hold near the bow and on the starboard side is the starboard forward cargo hold (4), the cargo hold near the stern and on the port side is the port aft cargo hold (5), and the cargo hold near the stern and on the starboard side is the starboard aft cargo hold (6).

5. A CO2 cold energy recovery and utilization system based on deep-sea storage as described in claim 1, characterized in that: Ethylene glycol is stored in the left front compartment (3), right front compartment (4), left rear compartment (5), and right rear compartment (6), and the CO2 storage tank (2) is immersed in ethylene glycol.

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