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

Abstract

The invention 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 an ethylene glycol loading and unloading system. The space of the corner of the ship is ingeniously utilized, ethylene glycol is directly stored in the space between the outer surface of the CO2 storage tank in the cargo hold of the ship and the wall of the cargo hold, when CO2 is sealed in the deep sea, cold energy is recycled through heat exchange between the ethylene glycol aqueous solution and CO2, the ethylene glycol aqueous solution obtained after heat exchange is transported to the land, and the CO2 is stored in the cargo hold of the ship. The cold energy is utilized in the process of liquefying CO2, so that the waste of the cold energy is avoided. Meanwhile, when the CO2 transport ship sails in a no-load mode, ethylene glycol serves as ballast water, the steps of filling and discharging the ballast water are omitted, the low-temperature ethylene glycol in the cabin enables the interior of the CO2 storage tank to be continuously kept at the low temperature, the CO2 storage tank does not need to be pre-cooled during follow-up CO2 filling, and the CO2 transport efficiency and the operation efficiency during ship berthing are greatly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ships, and particularly relates to a CO2 cold energy recovery and utilization system based on a deep-sea storage mode. BACKGROUND

[0002] With the global emphasis on reducing greenhouse gas emissions, carbon capture and storage technology has become one of the key means of carbon emission reduction. Carbon capture and storage technology refers to the process of capturing CO2 and transporting it to a specific place for storage. The storage methods include ocean storage, geological storage, biological storage, etc. Among them, deep-sea storage has the advantages of large carbon storage capacity, stable storage and low leakage risk, and therefore has a good development prospect. In the process of deep-sea CO2 storage, CO2 is transported to the storage site by sea, so the CO2 transport ship is the main means to realize this mode.

[0003] In order to increase the transportation capacity of CO2, the semi-cold and semi-pressure mode is usually used to store CO2 in liquid form in the C-type tank on the ship. The C-type tank is a storage tank with a thermal insulation layer, corrosion resistance and certain pressure bearing capacity. The semi-cold and semi-pressure storage mode requires the temperature in the C-type tank to be controlled between-50℃ and-20℃, and the pressure to be controlled between 0.7MPa and 2.1MPa. However, there is a significant difference between the shape of the C-type tank and the geometric structure of the ship cargo hold. When the C-type tank is arranged inside the ship hold, a large amount of gap space cannot be utilized between the C-type tank and the ship hold bulkhead, and between the tank body and the tank body, resulting in a serious "loss of hold" phenomenon. This indicates that although the ship hold has a large total volume, the space utilization rate of the ship hold is greatly reduced due to the incompatibility of the shapes between the two.

[0004] In the deep-sea CO2 storage operation, the offshore storage point is usually an area about 1000m below the sea surface. Since the pressure in this area is high, the liquid CO2 needs to be pressurized before storage to ensure that the CO2 is smoothly transported to the seabed storage area for storage. Since the temperature of the pressurized liquid rises very little, the pressurized liquid CO2 still has a large amount of cold energy. In addition, there is a large temperature difference between the storage temperature of CO2 on the ship (-50℃ to-20℃) and the storage temperature (-4℃ at 1000m below the sea surface), so a large amount of cold energy will be released during the CO2 storage process, and this part of the cold energy cannot be utilized, resulting in waste of cold energy. In order to reduce the transportation cost between the offshore storage point and the land CO2 receiving station due to the distance, most offshore storage points are close to the land receiving station, and the ship can reach the offshore storage point in about 1-2 days from the receiving station, which provides an opportunity for the utilization of the cold energy of the recovered CO2 on land.

[0005] As the mainstream antifreeze heat conducting medium in the industrial field, ethylene glycol aqueous solution (ethylene glycol for short) has excellent low temperature resistance and stable heat transfer performance. Ethylene glycol can be miscible with water in any proportion, and the freezing point can be as low as-40 DEG C by adjusting the concentration to 30%-60%, so ethylene glycol aqueous solution is a widely used heat transfer medium in the current industrial field.

[0006] Since the CO2 generated by the factory is usually transported to the receiving station in gaseous form through the pipeline after capture, in order to meet the semi-cold and semi-pressure transportation requirements, the gaseous CO2 needs to be liquefied at the receiving station, and the liquefied CO2 is transported to the offshore storage point by the CO2 transport ship for storage. Since the temperature of the liquid CO2 is low, and the amount of CO2 discharged by the factory is large, there are problems of high power consumption and high cost of liquefied CO2 in the liquefaction process.

[0007] Based on the above problems, if a CO2 cold energy recovery and utilization system based on the deep sea storage mode can be proposed, ethylene glycol is directly stored in the cargo hold of the ship, when deep sea storage is performed, the cold energy is recovered by using the heat exchange between ethylene glycol and CO2, and then transported to the receiving station for cold energy utilization, so that the cold energy of CO2 is fully recovered and utilized, and ethylene glycol is ingeniously used as ballast water, so that the steps of filling and discharging ballast water during empty sailing of the ship are saved, and the transportation efficiency of the ship is improved, which has good innovation. SUMMARY

[0008] The purpose of the present application is to solve the problem of recovery and utilization of CO2 cold energy during submarine storage, and a CO2 cold energy recovery and utilization system based on the deep sea storage mode is proposed, which comprises 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 comprises a CO2 transport ship, a CO2 storage tank, a left front cabin, a right front cabin, a left rear cabin, a right rear cabin, a CO2 pump, a CO2 valve, a booster pump, a heat exchanger, an ethylene glycol pump, an ethylene glycol outlet valve, a buffer cabin, an ethylene glycol inlet valve, a transfer pump and a buffer valve.

[0010] The CO2 cold energy utilization system comprises a primary compressor, a stop valve, a secondary compressor, a primary heat exchanger, a secondary heat exchanger, a refrigeration system, a CO2 receiving tank, a CO2 delivery pump, a CO2 outlet, a CO2 inlet, a CO2 inlet valve and a CO2 storage tank.

[0011] The ethylene glycol loading and unloading system comprises a CO2 transport ship, a left front cabin, a right front cabin, a left rear cabin, a right rear cabin, an ethylene glycol pump, an unloading valve, an I interface, a II interface, an ethylene glycol receiving tank, a supply pump, an ethylene glycol storage tank, an ethylene glycol delivery pump, a III interface, a IV interface and a filling valve.

[0012] Further, the CO2 transport ship defined by the present application is provided with two groups of cabins from the bow to the stern, each group of cabins is composed of a single cargo cabin symmetrically arranged at the left and right sides of the ship, wherein the cargo cabin near the bow and the left side is the left front cabin, the cargo cabin near the bow and the right side is the right front cabin, the cargo cabin near the stern and the left side is the left rear cabin, and the cargo cabin near the stern and the right side is the right rear cabin.

[0013] In the CO2 cold energy recovery system, a CO2 storage tank is arranged in each of the left front cabin, the right front cabin, the left rear cabin and the right rear cabin; the CO2 pump is located in the CO2 storage tank and is arranged at the bottom, and is connected with the CO2 valve, the booster pump and the cold flow inlet of the heat exchanger in sequence through pipelines; a glycol pump is arranged at the bottom of each of the left front cabin, the right front cabin, the left rear cabin and the right rear cabin, and the glycol pump is connected with the glycol outlet valve and the hot flow inlet of the heat exchanger in sequence through pipelines, the hot flow outlet of the heat exchanger is connected with the buffer cabin, the left front cabin, the right front cabin and the left rear cabin in sequence through pipelines, and a glycol inlet valve is arranged on the pipeline connected with the heat exchanger hot flow outlet of each cabin. The transfer pump is located at the bottom of the buffer cabin and is connected with the buffer valve and the right rear cabin in sequence through pipelines.

[0014] In the CO2 cold energy utilization system, the factory is connected with the primary compressor through pipelines, the primary compressor is connected with the stop valve, the secondary compressor, the primary heat exchanger, the secondary heat exchanger, the refrigeration system and the CO2 receiving tank in sequence through pipelines; the CO2 delivery pump is located in the CO2 receiving tank and is connected with the CO2 outlet through pipelines; the CO2 inlet is connected with the CO2 inlet valve and the CO2 storage tank in sequence through pipelines.

[0015] In the glycol loading and unloading system, a glycol pump is arranged at the bottom of each of the left front cabin, the right front cabin, the left rear cabin and the right rear cabin, and the glycol pump is connected with the unloading valve and the I interface in sequence through pipelines; the II interface is connected with the glycol receiving tank through pipelines; the supply pump is located in the glycol receiving tank and is connected with the secondary heat exchanger and the glycol storage tank in sequence through pipelines; the glycol delivery pump is located in the glycol storage tank and is connected with the III interface through pipelines; the IV interface is connected with the left front cabin, the right front cabin, the left rear cabin and the right rear cabin in sequence through pipelines, and a filling valve is arranged on the pipeline connected with each cabin of the IV interface.

[0016] Further, the CO2 valve, the glycol outlet valve, the glycol inlet valve, the buffer valve, the stop valve, the CO2 inlet valve, the unloading valve and the filling valve are all in the closed state before any operation is performed.

[0017] When the CO2 transport ship sails to the sea area near the offshore storage point, mooring work is first performed: the CO2 transport ship is fixed to the fixed anchor point through a cable. After the mooring work is completed, deep-sea storage is performed, at this time, the cold energy of CO2 is recovered, and the cold energy recovery process is divided into four processes:

[0018] The first process is the heat exchange between CO2 in the left front tank and ethylene glycol in the right front tank. The specific process is as follows: open the CO2 valve connected with the left front tank, the CO2 pump in the left front tank transports CO2 through the pipeline to the booster pump for pressurization, and the pressurized CO2 enters the heat exchanger. At the same time, open the ethylene glycol outlet valve connected with the right front tank, open the ethylene glycol inlet valve connected with the buffer tank, and the ethylene glycol pump in the right front tank transports ethylene glycol through the pipeline to the heat exchanger for heat exchange with CO2. The low-temperature ethylene glycol formed after heat exchange is transported to the buffer tank through the ethylene glycol inlet valve, and the heat-exchanged CO2 is directly injected into the seabed for storage through the injection port. After the heat exchange is completed, the CO2 valve connected with the left front tank, the ethylene glycol outlet valve connected with the right front tank, and the ethylene glycol inlet valve connected with the buffer tank are closed. At this time, the first process ends, and the second process begins.

[0019] The second process is the heat exchange between CO2 in the right front tank and ethylene glycol in the left front tank. The specific process is as follows: open the CO2 valve connected with the right front tank, the CO2 pump in the right front tank transports CO2 through the pipeline to the booster pump for pressurization, and the pressurized CO2 enters the heat exchanger. At the same time, open the ethylene glycol outlet valve connected with the left front tank, open the ethylene glycol inlet valve connected with the right front tank, and the ethylene glycol pump in the left front tank transports ethylene glycol through the pipeline to the heat exchanger for heat exchange with CO2. The low-temperature ethylene glycol formed after heat exchange is transported to the right front tank through the ethylene glycol inlet valve, and the heat-exchanged CO2 is directly injected into the seabed for storage through the injection port. After the heat exchange is completed, the CO2 valve connected with the right front tank, the ethylene glycol outlet valve connected with the left front tank, and the ethylene glycol inlet valve connected with the right front tank are closed. At this time, the second process ends, and the third process begins.

[0020] The third process is the heat exchange between CO2 in the right rear tank and ethylene glycol in the left rear tank. The specific process is as follows: open the CO2 valve connected with the right rear tank, the CO2 pump in the right rear tank transports CO2 through the pipeline to the booster pump for pressurization, and the pressurized CO2 enters the heat exchanger. At the same time, open the ethylene glycol outlet valve connected with the left rear tank, open the ethylene glycol inlet valve connected with the left front tank, and the ethylene glycol pump in the left rear tank transports ethylene glycol through the pipeline to the heat exchanger for heat exchange with CO2. The low-temperature ethylene glycol formed after heat exchange is transported to the left front tank through the ethylene glycol inlet valve, and the heat-exchanged CO2 is directly injected into the seabed for storage through the injection port. After the heat exchange is completed, the CO2 valve connected with the right rear tank, the ethylene glycol outlet valve connected with the left rear tank, and the ethylene glycol inlet valve connected with the left front tank are closed. At this time, the third process ends, and the fourth process begins.

[0021] The fourth process is heat exchange between CO2 in the left rear cabin and ethylene glycol in the right rear cabin, and the specific process is: opening the CO2 valve connected with the left rear cabin, the CO2 pump in the left rear cabin conveying CO2 through the pipeline to the booster pump for pressurization, and the pressurized CO2 entering the heat exchanger. At the same time, the ethylene glycol outlet valve connected with the right rear cabin is opened, the ethylene glycol inlet valve connected with the left rear cabin is opened, the ethylene glycol pump conveying the ethylene glycol in the right rear cabin through the pipeline to the heat exchanger for heat exchange with CO2, the low-temperature ethylene glycol formed after heat exchange is conveyed to the left rear cabin through the ethylene glycol inlet valve, and the heat-exchanged CO2 is directly injected into the seabed for storage through the injection port, and the CO2 valve connected with the left rear cabin, the ethylene glycol outlet valve connected with the right rear cabin and the ethylene glycol inlet valve connected with the left rear cabin are closed after heat exchange is completed. At this time, the fourth process is completed. In order to ensure the balance of the ethylene glycol ship body in the cargo cabin when the ship sails empty, after the ethylene glycol heat exchange in the right rear cabin is completed, the buffer valve is opened, and the low-temperature ethylene glycol in the buffer cabin is conveyed to the right rear cabin through the pipeline by the barge pump, and when the low-temperature ethylene glycol in the buffer cabin is completely conveyed to the right rear cabin, the buffer valve is closed, at this time, all CO2 storage is completed, and the cold energy recovery process is completed.

[0022] Since the lower the temperature of liquid CO2, the lower the saturation pressure, when the temperature of liquid CO2 is low, the design pressure of the CO2 receiving tank and the CO2 storage tank can also be correspondingly reduced, and the tank body can be made of low-strength material in the ship design stage. Therefore, in order to reduce the design pressure of the CO2 receiving tank and the CO2 storage tank, the storage temperature of the CO2 storage tank designed by the application is-46℃ (the saturation pressure is 0.8Mpa), and the cold energy released by CO2 and the cold energy absorbed by ethylene glycol are calculated below, and the mass ratio of ethylene glycol and CO2 in the cabin is calculated, and the formula is:

[0023]

[0024] In the formula: total heat released by CO2 during temperature change, kW;

[0025] heat exchange efficiency of heat exchanger, =0.9;

[0026] specific heat capacity of CO2, J / (kg·K);

[0027] total mass of CO2, kg;

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

[0029]

[0030] wherein: - the total heat absorbed by the ethylene glycol during the temperature change, kW;

[0031] - the specific heat capacity of the ethylene glycol, J / (kg·K);

[0032] - the total mass of the ethylene glycol, kg;

[0033] - the temperature difference of the ethylene glycol before and after heat exchange, K;

[0034] Theoretical calculation and numerical calculation by the engineering software Aspen HYSYS show that when the mass ratio of ethylene glycol to CO2 is 0.67, the cold energy released by CO2 can be completely absorbed by ethylene glycol. Therefore, the mass ratio of ethylene glycol to CO2 carried by the CO2 transport ship is at least 0.67. According to the density of CO2 at -46℃ , the saturated pressure is 0.8 MPa, and the density of 50% ethylene glycol aqueous solution is , the volume ratio of ethylene glycol to CO2 can be calculated as . Therefore, in a single cargo hold equipped with a CO2 storage tank, the ratio of the cargo hold volume (the space between the tank body and the hold wall) containing ethylene glycol to the volume of the CO2 storage tank is at least 0.72, and the cargo hold volume in the buffer tank is equal to the cargo hold volume of ethylene glycol in the single cargo hold. When the CO2 seabed storage is completed, the CO2 transport ship carrying the low-temperature ethylene glycol after heat exchange sails back to the receiving station. After the ship docks at the receiving station, the ship's loading and unloading and the utilization of cold energy are completed at the receiving station. First, unload the ethylene glycol: connect interface I and interface II, open the unloading valve, and the ethylene glycol pump will transport the ethylene glycol in the left front hold, right front hold, left rear hold, and right rear hold through the pipeline in sequence through interface I, interface II to the ethylene glycol receiving tank. When the ethylene glycol unloading is completed, close the unloading valve and disconnect interface I and interface II.

[0035] Since the CO2 transport ship stores low-temperature ethylene glycol during the return journey to the receiving station, the process of filling and discharging ballast water is omitted during the empty sailing, and the ship's loading and unloading operations can be directly carried out after the ship arrives at the receiving station, simplifying the docking process, shortening the docking period, and improving the efficiency of the ship's operation during docking.

[0036]

[0037] ​When the unloading of the ethylene glycol is completed, the loading of the ship is carried out, in order to improve the efficiency of the loading of the ethylene glycol of the ship, when the unloading of the ethylene glycol in the left front cabin is completed, the loading of the ethylene glycol of the ship is directly carried out. The loading process of the ethylene glycol and the loading process of the CO2 can be carried out simultaneously or separately, in order to save time and improve the efficiency of the operation when the ship is berthed, the loading of the ethylene glycol and the loading of the CO2 are carried out simultaneously.

[0038] The loading process of the ethylene glycol is as follows: the III interface and the IV interface are connected, the filling valve is opened, and the ethylene glycol conveying pump sequentially conveys the ethylene glycol in the ethylene glycol storage tank to the left front cabin, the right front cabin, the left rear cabin and the right rear cabin of the CO2 transport ship through the pipeline. After the loading of the ethylene glycol is completed, the filling valve is closed, and the III interface and the IV interface are disconnected.

[0039] When the CO2 storage is completed, the temperature in the CO2 storage tank is still relatively low. During the return of the CO2 transport ship from the offshore storage point to the receiving station, on the one hand, the low-temperature ethylene glycol stored in the cargo cabin and the heat preservation layer outside the CO2 storage tank jointly act to greatly reduce the heat loss in the CO2 storage tank, so that it can continuously maintain a low temperature; on the other hand, in order to reduce the transportation cost due to the distance to the offshore storage point, most offshore storage points are relatively close to the land, and usually the ship can arrive after traveling for 1-2 days. Therefore, when the ship returns to the receiving station, the CO2 storage tank still maintains a low temperature, and when the CO2 is filled, the CO2 storage tank does not need to be pre-cooled and can directly carry out the loading operation of the CO2.

[0040] The loading process of the CO2 is as follows: the CO2 outlet and the CO2 inlet are connected, the CO2 inlet valve is opened, and the CO2 conveying pump conveys the liquid CO2 in the CO2 receiving tank to the CO2 storage tank through the pipeline. When the loading of the CO2 is completed, the CO2 inlet valve is closed, and the CO2 outlet and the CO2 inlet are disconnected.

[0041] When the CO2 captured by the factory needs to be transported to the receiving station for liquefaction, the cold energy utilization is carried out at this time, and the process is as follows: the stop valve is opened, the gaseous CO2 generated by the factory is sequentially sent to the primary heat exchanger through the pipeline after passing through the stop valve, the primary compressor and the secondary compressor, and the CO2 in the primary heat exchanger is preliminarily heat-exchanged with seawater. The gaseous CO2 preliminarily heat-exchanged passes through the pipeline into the secondary heat exchanger. At the same time, the supply pump conveys the ethylene glycol in the ethylene glycol receiving tank to the secondary heat exchanger through the pipeline, and the ethylene glycol in the secondary heat exchanger is heat-exchanged with the gaseous CO2. The heat-exchanged ethylene glycol is conveyed to the ethylene glycol storage tank through the pipeline, and at the same time, the heat-exchanged CO2 enters the refrigeration system through the pipeline for refrigeration. The liquid CO2 formed after the refrigeration is conveyed to the CO2 receiving tank for storage through the pipeline.

[0042] Advantages of the present application

[0043] 1. The application recovers the cold energy of CO2 stored in the seabed by glycol heat exchange, and uses the cold energy for liquefying CO2 in the receiving station, which recovers the cold energy of CO2, avoids waste of cold energy, fully utilizes the cold energy of CO2, and significantly reduces the power consumption and cost of liquefying CO2.

[0044] 2. The application stores low-temperature glycol in the cabin of the CO2 transport ship during the voyage of the CO2 transport ship returning to the receiving station, which eliminates the need for filling and discharging ballast water during the empty voyage, and directly carries out the CO2 loading operation after the ship arrives at the receiving station, thereby improving the operation efficiency when the ship is berthed.

[0045] 3. The application directly stores glycol in the space between the outer surface of the CO2 storage tank and the cargo hold bulkhead of the ship cargo hold, which ingeniously utilizes the space of the "corners and corners" of the ship. At the same time, when the CO2 transport ship returns to the receiving station, the low-temperature glycol in the cargo hold continuously maintains a low temperature for the CO2 storage tank, and the CO2 storage tank does not need to be pre-cooled when refilling CO2 again, which simplifies the CO2 loading and unloading process and improves the CO2 transportation efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a schematic diagram for CO2 cold energy recovery;

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

[0048] Figure 3 is a system diagram;

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

[0050] Figure 5 is a schematic diagram of a deep-sea CO2 storage transport ship position;

[0051] In the drawing: 1. CO2 transport ship; 2. CO2 storage tank; 3. left front cabin; 4. right front cabin; 5. left rear cabin; 6. right rear cabin; 7. CO2 pump; 8. CO2 valve; 9. booster pump; 10. heat exchanger; 11. ethylene glycol pump; 12. ethylene glycol outlet valve; 13. buffer cabin; 14. ethylene glycol inlet valve; 15. transfer pump; 16. buffer valve; 17. primary compressor; 18. stop valve; 19. secondary compressor; 20. primary heat exchanger; 21. secondary heat exchanger; 22. refrigeration system; 23. CO2 receiving tank; 24. CO2 delivery pump; 25. CO2 outlet; 26. CO2 inlet; 27. CO2 inlet valve; 28. unloading valve; 29. I interface; 30. II interface; 31. ethylene glycol receiving tank; 32. supply pump; 33. ethylene glycol storage tank; 34. ethylene glycol delivery pump; 35. III interface; 36. IV interface; 37. filling valve. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples.

[0053] A CO2 cold energy recovery and utilization system based on a deep-sea storage mode, 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 comprises a CO2 transport ship 1, a CO2 storage tank 2, a left front cabin 3, a right front cabin 4, a left rear cabin 5, a right rear cabin 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 cabin 13, an ethylene glycol inlet valve 14, a transfer pump 15 and a buffer valve 16.

[0055] The CO2 cold energy utilization system comprises a primary compressor 17, a stop 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 delivery pump 24, a CO2 outlet 25, a CO2 inlet 26, a CO2 inlet valve 27 and the CO2 storage tank 2.

[0056] The ethylene glycol loading and unloading system comprises the CO2 transport ship 1, the left front cabin 3, the right front cabin 4, the left rear cabin 5, the right rear cabin 6, the ethylene glycol pump 11, an unloading valve 28, an I interface 29, an II interface 30, an ethylene glycol receiving tank 31, a supply pump 32, an ethylene glycol storage tank 33, an ethylene glycol delivery pump 34, an III interface 35, an IV interface 36 and a filling valve 37.

[0057] In the CO2 cold energy recovery system, a CO2 storage tank 2 is arranged in each of the left front cabin 3, the right front cabin 4, the left rear cabin 5 and the right rear cabin 6; the CO2 pump 7 is arranged in the CO2 storage tank 2 and located at the bottom, and is connected with the CO2 valve 8, the booster pump 9 and the cold flow inlet of the heat exchanger 10 in sequence through pipelines; a glycol pump 11 is arranged at the bottom of each of the left front cabin 3, the right front cabin 4, the left rear cabin 5 and the right rear cabin 6, and the glycol pump 11 is connected with the glycol outlet valve 12 and the hot flow inlet of the heat exchanger 10 in sequence through pipelines, the hot flow outlet of the heat exchanger 10 is connected with the buffer cabin 13, the left front cabin 3, the right front cabin 4 and the left rear cabin 5 through pipelines respectively, and a glycol inlet valve 14 is arranged on the pipeline connected with the heat exchanger 10 of each cabin respectively. The transfer pump 15 is arranged at the bottom of the buffer cabin 13 and is connected with the buffer valve 16 and the right rear cabin 6 in sequence through pipelines.

[0058] In the CO2 cold energy utilization system, the factory is connected with the primary compressor 17 through pipelines, the primary compressor 17 is connected with the stop 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 in sequence through pipelines; the CO2 delivery pump 24 is arranged in the CO2 receiving tank 23 and is connected with the CO2 outlet 25 through pipelines; the CO2 inlet 26 is connected with the CO2 inlet valve 27 and the CO2 storage tank 2 in sequence through pipelines; wherein the CO2 receiving tank 23 and the CO2 storage tank 2 are both C-shaped tanks and are provided with thermal insulation layers.

[0059] In the glycol loading and unloading system, a glycol pump 11 is arranged at the bottom of each of the left front cabin 3, the right front cabin 4, the left rear cabin 5 and the right rear cabin 6, and the glycol pump 11 is connected with the unloading valve 28 and the I interface 29 in sequence through pipelines; the II interface 30 is connected with the glycol receiving tank 31 through pipelines; the supply pump 32 is arranged in the glycol receiving tank 31 and is connected with the secondary heat exchanger 21 and the glycol storage tank 33 in sequence through pipelines; the glycol delivery pump 34 is arranged in the glycol storage tank 33 and is connected with the III interface 35 through pipelines; the IV interface 36 is connected with the left front cabin 3, the right front cabin 4, the left rear cabin 5 and the right rear cabin 6 respectively through pipelines, and a filling valve 37 is arranged on the pipeline connected with each cabin of the IV interface 36 respectively.

[0060] Further, the CO2 transport ship 1 defined in the present application is provided with two groups of cabins from the bow to the stern, each group of cabins is composed of a single cargo cabin symmetrically arranged at the left and right sides of the ship, wherein the cargo cabin close to the bow and at the left side is the left front cabin 3, the cargo cabin close to the bow and at the right side is the right front cabin 4, the cargo cabin close to the stern and at the left side is the left rear cabin 5, and the cargo cabin close to the stern and at the right side is the right rear cabin 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 2 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 deep-sea storage, 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 through 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), and the ethylene glycol pump (11) is connected to the ethylene glycol outlet valve (12) and heat exchanger (10) in sequence through pipes; 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 through pipes, and an ethylene glycol inlet valve (14) is installed on the pipe 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 through pipes.

2. The CO2 cold energy recovery and utilization system based on deep-sea storage as described in claim 1, characterized in that: 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 first-stage compressor (17) via a pipeline. The first-stage compressor (17) is connected in sequence to the shut-off valve (18), the second-stage compressor (19), the first-stage heat exchanger (20), the second-stage heat exchanger (21), the refrigeration system (22), and the CO2 receiving tank (23) via a pipeline. The CO2 delivery pump (24) is located inside the CO2 receiving tank (23) and is connected to the CO2 outlet (25) via a pipeline. The CO2 inlet (26) is connected in sequence to the CO2 inlet valve (27) and the CO2 storage tank (2) via a pipeline.

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

4. A CO2 cold energy recovery and utilization system based on deep-sea storage as described in claim 3, characterized in that: This invention calculates the cooling capacity released by CO2 and the cooling capacity absorbed by ethylene glycol, and calculates 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 J / (kg·K); —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 J / (kg·K); —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... 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 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.

5. 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) defined in this invention has two sets of cabins from bow to stern. Each set of cabins consists of a single cargo hold symmetrically located on the port and starboard sides of the ship. The cabin near the bow and on the port side is the port forward cabin (3), the cabin near the bow and on the starboard side is the starboard forward cabin (4), the cabin near the stern and on the port side is the port aft cabin (5), and the cabin near the stern and on the starboard side is the starboard aft cabin (6).

6. 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.

7. A CO2 cold energy recovery and utilization system based on deep-sea storage as described in claim 1, characterized in that: 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.

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